Adding upstream version 124.0.1.upstream/124.0.1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

207 files changed, 81182 insertions, 0 deletions

diff --git a/widget/windows/AudioSession.cpp b/widget/windows/AudioSession.cpp
new file mode 100644
index 0000000000..c14278f56c
--- /dev/null
+++ b/widget/windows/AudioSession.cpp
@@ -0,0 +1,346 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <atomic>
+#include <audiopolicy.h>
+#include <windows.h>
+#include <mmdeviceapi.h>
+
+#include "mozilla/ClearOnShutdown.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/ScopeExit.h"
+#include "mozilla/StaticPtr.h"
+#include "nsIStringBundle.h"
+
+#include "nsCOMPtr.h"
+#include "nsID.h"
+#include "nsServiceManagerUtils.h"
+#include "nsString.h"
+#include "nsThreadUtils.h"
+#include "nsXULAppAPI.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/mscom/AgileReference.h"
+#include "mozilla/mscom/Utils.h"
+#include "mozilla/Mutex.h"
+#include "mozilla/WindowsVersion.h"
+
+namespace mozilla {
+namespace widget {
+
+/*
+ * To take advantage of what Vista+ have to offer with respect to audio,
+ * we need to maintain an audio session.  This class wraps IAudioSessionControl
+ * and implements IAudioSessionEvents (for callbacks from Windows)
+ */
+class AudioSession final : public IAudioSessionEvents {
+ public:
+  AudioSession();
+
+  static AudioSession* GetSingleton();
+
+  // COM IUnknown
+  STDMETHODIMP_(ULONG) AddRef();
+  STDMETHODIMP QueryInterface(REFIID, void**);
+  STDMETHODIMP_(ULONG) Release();
+
+  // IAudioSessionEvents
+  STDMETHODIMP OnChannelVolumeChanged(DWORD aChannelCount,
+                                      float aChannelVolumeArray[],
+                                      DWORD aChangedChannel, LPCGUID aContext);
+  STDMETHODIMP OnDisplayNameChanged(LPCWSTR aDisplayName, LPCGUID aContext);
+  STDMETHODIMP OnGroupingParamChanged(LPCGUID aGroupingParam, LPCGUID aContext);
+  STDMETHODIMP OnIconPathChanged(LPCWSTR aIconPath, LPCGUID aContext);
+  STDMETHODIMP OnSessionDisconnected(AudioSessionDisconnectReason aReason);
+  STDMETHODIMP OnSimpleVolumeChanged(float aVolume, BOOL aMute,
+                                     LPCGUID aContext);
+  STDMETHODIMP OnStateChanged(AudioSessionState aState);
+
+  void Start();
+  void Stop(bool shouldRestart = false);
+
+  nsresult GetSessionData(nsID& aID, nsString& aSessionName,
+                          nsString& aIconPath);
+  nsresult SetSessionData(const nsID& aID, const nsString& aSessionName,
+                          const nsString& aIconPath);
+
+ private:
+  ~AudioSession() = default;
+
+  void StopInternal(const MutexAutoLock& aProofOfLock,
+                    bool shouldRestart = false);
+
+ protected:
+  RefPtr<IAudioSessionControl> mAudioSessionControl;
+  nsString mDisplayName;
+  nsString mIconPath;
+  nsID mSessionGroupingParameter;
+  // Guards the IAudioSessionControl
+  mozilla::Mutex mMutex MOZ_UNANNOTATED;
+
+  ThreadSafeAutoRefCnt mRefCnt;
+  NS_DECL_OWNINGTHREAD
+};
+
+StaticRefPtr<AudioSession> sService;
+
+void StartAudioSession() {
+  MOZ_ASSERT(NS_IsMainThread());
+  MOZ_ASSERT(!sService);
+  sService = new AudioSession();
+
+  // Destroy AudioSession only after any background task threads have been
+  // stopped or abandoned.
+  ClearOnShutdown(&sService, ShutdownPhase::XPCOMShutdownFinal);
+
+  NS_DispatchBackgroundTask(
+      NS_NewCancelableRunnableFunction("StartAudioSession", []() -> void {
+        MOZ_ASSERT(AudioSession::GetSingleton(),
+                   "AudioSession should outlive background threads");
+        AudioSession::GetSingleton()->Start();
+      }));
+}
+
+void StopAudioSession() {
+  MOZ_ASSERT(NS_IsMainThread());
+  MOZ_ASSERT(sService);
+  NS_DispatchBackgroundTask(
+      NS_NewRunnableFunction("StopAudioSession", []() -> void {
+        MOZ_ASSERT(AudioSession::GetSingleton(),
+                   "AudioSession should outlive background threads");
+        AudioSession::GetSingleton()->Stop();
+      }));
+}
+
+AudioSession* AudioSession::GetSingleton() {
+  MOZ_ASSERT(mscom::IsCurrentThreadMTA());
+  return sService;
+}
+
+// It appears Windows will use us on a background thread ...
+NS_IMPL_ADDREF(AudioSession)
+NS_IMPL_RELEASE(AudioSession)
+
+STDMETHODIMP
+AudioSession::QueryInterface(REFIID iid, void** ppv) {
+  const IID IID_IAudioSessionEvents = __uuidof(IAudioSessionEvents);
+  if ((IID_IUnknown == iid) || (IID_IAudioSessionEvents == iid)) {
+    *ppv = static_cast<IAudioSessionEvents*>(this);
+    AddRef();
+    return S_OK;
+  }
+
+  return E_NOINTERFACE;
+}
+
+AudioSession::AudioSession() : mMutex("AudioSessionControl") {
+  // This func must be run on the main thread as
+  // nsStringBundle is not thread safe otherwise
+  MOZ_ASSERT(NS_IsMainThread());
+
+  MOZ_ASSERT(XRE_IsParentProcess(),
+             "Should only get here in a chrome process!");
+
+  nsCOMPtr<nsIStringBundleService> bundleService =
+      do_GetService(NS_STRINGBUNDLE_CONTRACTID);
+  MOZ_ASSERT(bundleService);
+
+  nsCOMPtr<nsIStringBundle> bundle;
+  bundleService->CreateBundle("chrome://branding/locale/brand.properties",
+                              getter_AddRefs(bundle));
+  MOZ_ASSERT(bundle);
+  bundle->GetStringFromName("brandFullName", mDisplayName);
+
+  wchar_t* buffer;
+  mIconPath.GetMutableData(&buffer, MAX_PATH);
+  ::GetModuleFileNameW(nullptr, buffer, MAX_PATH);
+
+  [[maybe_unused]] nsresult rv =
+      nsID::GenerateUUIDInPlace(mSessionGroupingParameter);
+  MOZ_ASSERT(rv == NS_OK);
+}
+
+// Once we are started Windows will hold a reference to us through our
+// IAudioSessionEvents interface that will keep us alive until the appshell
+// calls Stop.
+void AudioSession::Start() {
+  MOZ_ASSERT(mscom::IsCurrentThreadMTA());
+
+  const CLSID CLSID_MMDeviceEnumerator = __uuidof(MMDeviceEnumerator);
+  const IID IID_IMMDeviceEnumerator = __uuidof(IMMDeviceEnumerator);
+  const IID IID_IAudioSessionManager = __uuidof(IAudioSessionManager);
+
+  MutexAutoLock lock(mMutex);
+  MOZ_ASSERT(!mAudioSessionControl);
+  MOZ_ASSERT(!mDisplayName.IsEmpty() || !mIconPath.IsEmpty(),
+             "Should never happen ...");
+
+  auto scopeExit = MakeScopeExit([&] { StopInternal(lock); });
+
+  RefPtr<IMMDeviceEnumerator> enumerator;
+  HRESULT hr =
+      ::CoCreateInstance(CLSID_MMDeviceEnumerator, nullptr, CLSCTX_ALL,
+                         IID_IMMDeviceEnumerator, getter_AddRefs(enumerator));
+  if (FAILED(hr)) {
+    return;
+  }
+
+  RefPtr<IMMDevice> device;
+  hr = enumerator->GetDefaultAudioEndpoint(
+      EDataFlow::eRender, ERole::eMultimedia, getter_AddRefs(device));
+  if (FAILED(hr)) {
+    return;
+  }
+
+  RefPtr<IAudioSessionManager> manager;
+  hr = device->Activate(IID_IAudioSessionManager, CLSCTX_ALL, nullptr,
+                        getter_AddRefs(manager));
+  if (FAILED(hr)) {
+    return;
+  }
+
+  hr = manager->GetAudioSessionControl(&GUID_NULL, 0,
+                                       getter_AddRefs(mAudioSessionControl));
+
+  if (FAILED(hr) || !mAudioSessionControl) {
+    return;
+  }
+
+  // Increments refcount of 'this'.
+  hr = mAudioSessionControl->RegisterAudioSessionNotification(this);
+  if (FAILED(hr)) {
+    return;
+  }
+
+  hr = mAudioSessionControl->SetGroupingParam(
+      (LPGUID) & (mSessionGroupingParameter), nullptr);
+  if (FAILED(hr)) {
+    return;
+  }
+
+  hr = mAudioSessionControl->SetDisplayName(mDisplayName.get(), nullptr);
+  if (FAILED(hr)) {
+    return;
+  }
+
+  hr = mAudioSessionControl->SetIconPath(mIconPath.get(), nullptr);
+  if (FAILED(hr)) {
+    return;
+  }
+
+  scopeExit.release();
+}
+
+void AudioSession::Stop(bool shouldRestart) {
+  MOZ_ASSERT(mscom::IsCurrentThreadMTA());
+
+  MutexAutoLock lock(mMutex);
+  StopInternal(lock, shouldRestart);
+}
+
+void AudioSession::StopInternal(const MutexAutoLock& aProofOfLock,
+                                bool shouldRestart) {
+  if (!mAudioSessionControl) {
+    return;
+  }
+
+  // Decrement refcount of 'this'
+  mAudioSessionControl->UnregisterAudioSessionNotification(this);
+
+  // Deleting the IAudioSessionControl COM object requires the STA/main thread.
+  // Audio code may concurrently be running on the main thread and it may
+  // block waiting for this to complete, creating deadlock.  So we destroy the
+  // IAudioSessionControl on the main thread instead.  In order to do that, we
+  // need to marshall the object to the main thread's apartment with an
+  // AgileReference.
+  mscom::AgileReference agileAsc(mAudioSessionControl);
+  mAudioSessionControl = nullptr;
+  NS_DispatchToMainThread(NS_NewRunnableFunction(
+      "FreeAudioSession",
+      [agileAsc = std::move(agileAsc), shouldRestart]() mutable {
+        // Now release the AgileReference which holds our only reference to the
+        // IAudioSessionControl, then maybe restart.
+        agileAsc = nullptr;
+        if (shouldRestart) {
+          NS_DispatchBackgroundTask(
+              NS_NewCancelableRunnableFunction("RestartAudioSession", [] {
+                AudioSession* as = AudioSession::GetSingleton();
+                MOZ_ASSERT(as);
+                as->Start();
+              }));
+        }
+      }));
+}
+
+void CopynsID(nsID& lhs, const nsID& rhs) {
+  lhs.m0 = rhs.m0;
+  lhs.m1 = rhs.m1;
+  lhs.m2 = rhs.m2;
+  for (int i = 0; i < 8; i++) {
+    lhs.m3[i] = rhs.m3[i];
+  }
+}
+
+nsresult AudioSession::GetSessionData(nsID& aID, nsString& aSessionName,
+                                      nsString& aIconPath) {
+  CopynsID(aID, mSessionGroupingParameter);
+  aSessionName = mDisplayName;
+  aIconPath = mIconPath;
+
+  return NS_OK;
+}
+
+nsresult AudioSession::SetSessionData(const nsID& aID,
+                                      const nsString& aSessionName,
+                                      const nsString& aIconPath) {
+  MOZ_ASSERT(!XRE_IsParentProcess(),
+             "Should never get here in a chrome process!");
+  CopynsID(mSessionGroupingParameter, aID);
+  mDisplayName = aSessionName;
+  mIconPath = aIconPath;
+  return NS_OK;
+}
+
+STDMETHODIMP
+AudioSession::OnChannelVolumeChanged(DWORD aChannelCount,
+                                     float aChannelVolumeArray[],
+                                     DWORD aChangedChannel, LPCGUID aContext) {
+  return S_OK;  // NOOP
+}
+
+STDMETHODIMP
+AudioSession::OnDisplayNameChanged(LPCWSTR aDisplayName, LPCGUID aContext) {
+  return S_OK;  // NOOP
+}
+
+STDMETHODIMP
+AudioSession::OnGroupingParamChanged(LPCGUID aGroupingParam, LPCGUID aContext) {
+  return S_OK;  // NOOP
+}
+
+STDMETHODIMP
+AudioSession::OnIconPathChanged(LPCWSTR aIconPath, LPCGUID aContext) {
+  return S_OK;  // NOOP
+}
+
+STDMETHODIMP
+AudioSession::OnSessionDisconnected(AudioSessionDisconnectReason aReason) {
+  Stop(true /* shouldRestart */);
+  return S_OK;
+}
+
+STDMETHODIMP
+AudioSession::OnSimpleVolumeChanged(float aVolume, BOOL aMute,
+                                    LPCGUID aContext) {
+  return S_OK;  // NOOP
+}
+
+STDMETHODIMP
+AudioSession::OnStateChanged(AudioSessionState aState) {
+  return S_OK;  // NOOP
+}
+
+}  // namespace widget
+}  // namespace mozilla
diff --git a/widget/windows/AudioSession.h b/widget/windows/AudioSession.h
new file mode 100644
index 0000000000..612a5e209b
--- /dev/null
+++ b/widget/windows/AudioSession.h
@@ -0,0 +1,19 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsString.h"
+
+namespace mozilla {
+namespace widget {
+
+// Start the audio session in the current process
+void StartAudioSession();
+
+// Stop the audio session in the current process
+void StopAudioSession();
+
+}  // namespace widget
+}  // namespace mozilla
diff --git a/widget/windows/CheckInvariantWrapper.h b/widget/windows/CheckInvariantWrapper.h
new file mode 100644
index 0000000000..da6024ec21
--- /dev/null
+++ b/widget/windows/CheckInvariantWrapper.h
@@ -0,0 +1,78 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// A wrapper that uses RAII to ensure that a class invariant is checked
+// before and after any public function is called
+
+#ifndef CHECKINVARIANTWRAPPER_H_
+#define CHECKINVARIANTWRAPPER_H_
+
+#include "mozilla/Attributes.h"
+#include <utility>
+
+namespace mozilla {
+
+//
+// Wraps an object of type T and allows access to its public API by
+// deferencing it using the pointer syntax "->".
+//
+// Using that operator will return a temporary RAII object that
+// calls a method named "CheckInvariant" in its constructor, calls the
+// requested method, and then calls "CheckInvariant" again in its
+// destructor.
+//
+// The only thing your class requires is a method with the following signature:
+//
+// void CheckInvariant() const;
+//
+template <typename T>
+class CheckInvariantWrapper {
+ public:
+  class Wrapper {
+   public:
+    explicit Wrapper(T& aObject) : mObject(aObject) {
+      mObject.CheckInvariant();
+    }
+    ~Wrapper() { mObject.CheckInvariant(); }
+
+    T* operator->() { return &mObject; }
+
+   private:
+    T& mObject;
+  };
+
+  class ConstWrapper {
+   public:
+    explicit ConstWrapper(const T& aObject) : mObject(aObject) {
+      mObject.CheckInvariant();
+    }
+    ~ConstWrapper() { mObject.CheckInvariant(); }
+
+    const T* operator->() const { return &mObject; }
+
+   private:
+    const T& mObject;
+  };
+
+  CheckInvariantWrapper() = default;
+
+  MOZ_IMPLICIT CheckInvariantWrapper(T aObject) : mObject(std::move(aObject)) {}
+
+  template <typename... Args>
+  explicit CheckInvariantWrapper(std::in_place_t, Args&&... args)
+      : mObject(std::forward<Args>(args)...) {}
+
+  const ConstWrapper operator->() const { return ConstWrapper(mObject); }
+
+  Wrapper operator->() { return Wrapper(mObject); }
+
+ private:
+  T mObject;
+};
+
+}  // namespace mozilla
+
+#endif  // CHECKINVARIANTWRAPPER_H_
diff --git a/widget/windows/CompositorWidgetChild.cpp b/widget/windows/CompositorWidgetChild.cpp
new file mode 100644
index 0000000000..b294efef51
--- /dev/null
+++ b/widget/windows/CompositorWidgetChild.cpp
@@ -0,0 +1,114 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "CompositorWidgetChild.h"
+#include "mozilla/Unused.h"
+#include "mozilla/gfx/Logging.h"
+#include "mozilla/widget/CompositorWidgetVsyncObserver.h"
+#include "mozilla/widget/PlatformWidgetTypes.h"
+#include "nsBaseWidget.h"
+#include "VsyncDispatcher.h"
+#include "gfxPlatform.h"
+#include "RemoteBackbuffer.h"
+
+namespace mozilla {
+namespace widget {
+
+CompositorWidgetChild::CompositorWidgetChild(
+    RefPtr<CompositorVsyncDispatcher> aVsyncDispatcher,
+    RefPtr<CompositorWidgetVsyncObserver> aVsyncObserver,
+    const CompositorWidgetInitData& aInitData)
+    : mVsyncDispatcher(aVsyncDispatcher),
+      mVsyncObserver(aVsyncObserver),
+      mCompositorWnd(nullptr),
+      mWnd(reinterpret_cast<HWND>(
+          aInitData.get_WinCompositorWidgetInitData().hWnd())),
+      mTransparencyMode(
+          aInitData.get_WinCompositorWidgetInitData().transparencyMode()),
+      mRemoteBackbufferProvider() {
+  MOZ_ASSERT(XRE_IsParentProcess());
+  MOZ_ASSERT(!gfxPlatform::IsHeadless());
+  MOZ_ASSERT(mWnd && ::IsWindow(mWnd));
+}
+
+CompositorWidgetChild::~CompositorWidgetChild() {}
+
+bool CompositorWidgetChild::Initialize() {
+  mRemoteBackbufferProvider = std::make_unique<remote_backbuffer::Provider>();
+  if (!mRemoteBackbufferProvider->Initialize(mWnd, OtherPid(),
+                                             mTransparencyMode)) {
+    return false;
+  }
+
+  auto maybeRemoteHandles = mRemoteBackbufferProvider->CreateRemoteHandles();
+  if (!maybeRemoteHandles) {
+    return false;
+  }
+
+  Unused << SendInitialize(*maybeRemoteHandles);
+
+  return true;
+}
+
+void CompositorWidgetChild::EnterPresentLock() {
+  Unused << SendEnterPresentLock();
+}
+
+void CompositorWidgetChild::LeavePresentLock() {
+  Unused << SendLeavePresentLock();
+}
+
+void CompositorWidgetChild::OnDestroyWindow() {}
+
+bool CompositorWidgetChild::OnWindowResize(const LayoutDeviceIntSize& aSize) {
+  return true;
+}
+
+void CompositorWidgetChild::OnWindowModeChange(nsSizeMode aSizeMode) {}
+
+void CompositorWidgetChild::UpdateTransparency(TransparencyMode aMode) {
+  mTransparencyMode = aMode;
+  mRemoteBackbufferProvider->UpdateTransparencyMode(aMode);
+  Unused << SendUpdateTransparency(aMode);
+}
+
+void CompositorWidgetChild::NotifyVisibilityUpdated(nsSizeMode aSizeMode,
+                                                    bool aIsFullyOccluded) {
+  Unused << SendNotifyVisibilityUpdated(aSizeMode, aIsFullyOccluded);
+};
+
+void CompositorWidgetChild::ClearTransparentWindow() {
+  Unused << SendClearTransparentWindow();
+}
+
+mozilla::ipc::IPCResult CompositorWidgetChild::RecvObserveVsync() {
+  mVsyncDispatcher->SetCompositorVsyncObserver(mVsyncObserver);
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult CompositorWidgetChild::RecvUnobserveVsync() {
+  mVsyncDispatcher->SetCompositorVsyncObserver(nullptr);
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult CompositorWidgetChild::RecvUpdateCompositorWnd(
+    const WindowsHandle& aCompositorWnd, const WindowsHandle& aParentWnd,
+    UpdateCompositorWndResolver&& aResolve) {
+  HWND parentWnd = reinterpret_cast<HWND>(aParentWnd);
+  if (mWnd == parentWnd) {
+    mCompositorWnd = reinterpret_cast<HWND>(aCompositorWnd);
+    ::SetParent(mCompositorWnd, mWnd);
+    aResolve(true);
+  } else {
+    aResolve(false);
+    gfxCriticalNote << "Parent winow does not match";
+    MOZ_ASSERT_UNREACHABLE("unexpected to happen");
+  }
+
+  return IPC_OK();
+}
+
+}  // namespace widget
+}  // namespace mozilla
diff --git a/widget/windows/CompositorWidgetChild.h b/widget/windows/CompositorWidgetChild.h
new file mode 100644
index 0000000000..bec8ead98e
--- /dev/null
+++ b/widget/windows/CompositorWidgetChild.h
@@ -0,0 +1,62 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef widget_windows_CompositorWidgetChild_h
+#define widget_windows_CompositorWidgetChild_h
+
+#include "WinCompositorWidget.h"
+#include "mozilla/widget/PCompositorWidgetChild.h"
+#include "mozilla/widget/CompositorWidgetVsyncObserver.h"
+
+namespace mozilla {
+class CompositorVsyncDispatcher;
+
+namespace widget {
+
+namespace remote_backbuffer {
+class Provider;
+}
+
+class CompositorWidgetChild final : public PCompositorWidgetChild,
+                                    public PlatformCompositorWidgetDelegate {
+ public:
+  CompositorWidgetChild(RefPtr<CompositorVsyncDispatcher> aVsyncDispatcher,
+                        RefPtr<CompositorWidgetVsyncObserver> aVsyncObserver,
+                        const CompositorWidgetInitData& aInitData);
+  ~CompositorWidgetChild() override;
+
+  bool Initialize();
+
+  void EnterPresentLock() override;
+  void LeavePresentLock() override;
+  void OnDestroyWindow() override;
+  bool OnWindowResize(const LayoutDeviceIntSize& aSize) override;
+  void OnWindowModeChange(nsSizeMode aSizeMode) override;
+  void UpdateTransparency(TransparencyMode aMode) override;
+  void NotifyVisibilityUpdated(nsSizeMode aSizeMode,
+                               bool aIsFullyOccluded) override;
+  void ClearTransparentWindow() override;
+
+  mozilla::ipc::IPCResult RecvObserveVsync() override;
+  mozilla::ipc::IPCResult RecvUnobserveVsync() override;
+  mozilla::ipc::IPCResult RecvUpdateCompositorWnd(
+      const WindowsHandle& aCompositorWnd, const WindowsHandle& aParentWnd,
+      UpdateCompositorWndResolver&& aResolve) override;
+
+ private:
+  RefPtr<CompositorVsyncDispatcher> mVsyncDispatcher;
+  RefPtr<CompositorWidgetVsyncObserver> mVsyncObserver;
+  HWND mCompositorWnd;
+
+  HWND mWnd;
+  TransparencyMode mTransparencyMode;
+
+  std::unique_ptr<remote_backbuffer::Provider> mRemoteBackbufferProvider;
+};
+
+}  // namespace widget
+}  // namespace mozilla
+
+#endif  // widget_windows_CompositorWidgetChild_h
diff --git a/widget/windows/CompositorWidgetParent.cpp b/widget/windows/CompositorWidgetParent.cpp
new file mode 100644
index 0000000000..b25d30d9d5
--- /dev/null
+++ b/widget/windows/CompositorWidgetParent.cpp
@@ -0,0 +1,232 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+#include "CompositorWidgetParent.h"
+
+#include "mozilla/Unused.h"
+#include "mozilla/StaticPrefs_layers.h"
+#include "mozilla/gfx/DeviceManagerDx.h"
+#include "mozilla/gfx/Point.h"
+#include "mozilla/layers/Compositor.h"
+#include "mozilla/layers/CompositorBridgeParent.h"
+#include "mozilla/layers/CompositorThread.h"
+#include "mozilla/webrender/RenderThread.h"
+#include "mozilla/widget/PlatformWidgetTypes.h"
+#include "nsWindow.h"
+#include "VsyncDispatcher.h"
+#include "WinCompositorWindowThread.h"
+#include "VRShMem.h"
+#include "RemoteBackbuffer.h"
+
+#include <ddraw.h>
+
+namespace mozilla {
+namespace widget {
+
+using namespace mozilla::gfx;
+using namespace mozilla;
+
+CompositorWidgetParent::CompositorWidgetParent(
+    const CompositorWidgetInitData& aInitData,
+    const layers::CompositorOptions& aOptions)
+    : WinCompositorWidget(aInitData.get_WinCompositorWidgetInitData(),
+                          aOptions),
+      mWnd(reinterpret_cast<HWND>(
+          aInitData.get_WinCompositorWidgetInitData().hWnd())),
+      mTransparencyMode(uint32_t(
+          aInitData.get_WinCompositorWidgetInitData().transparencyMode())),
+      mSizeMode(nsSizeMode_Normal),
+      mIsFullyOccluded(false),
+      mRemoteBackbufferClient() {
+  MOZ_ASSERT(XRE_GetProcessType() == GeckoProcessType_GPU);
+  MOZ_ASSERT(mWnd && ::IsWindow(mWnd));
+}
+
+CompositorWidgetParent::~CompositorWidgetParent() {}
+
+bool CompositorWidgetParent::Initialize(
+    const RemoteBackbufferHandles& aRemoteHandles) {
+  mRemoteBackbufferClient = std::make_unique<remote_backbuffer::Client>();
+  if (!mRemoteBackbufferClient->Initialize(aRemoteHandles)) {
+    return false;
+  }
+
+  return true;
+}
+
+bool CompositorWidgetParent::PreRender(WidgetRenderingContext* aContext) {
+  // This can block waiting for WM_SETTEXT to finish
+  // Using PreRender is unnecessarily pessimistic because
+  // we technically only need to block during the present call
+  // not all of compositor rendering
+  mPresentLock.Enter();
+  return true;
+}
+
+void CompositorWidgetParent::PostRender(WidgetRenderingContext* aContext) {
+  mPresentLock.Leave();
+}
+
+LayoutDeviceIntSize CompositorWidgetParent::GetClientSize() {
+  RECT r;
+  if (!::GetClientRect(mWnd, &r)) {
+    return LayoutDeviceIntSize();
+  }
+  return LayoutDeviceIntSize(r.right - r.left, r.bottom - r.top);
+}
+
+already_AddRefed<gfx::DrawTarget>
+CompositorWidgetParent::StartRemoteDrawingInRegion(
+    const LayoutDeviceIntRegion& aInvalidRegion,
+    layers::BufferMode* aBufferMode) {
+  MOZ_ASSERT(mRemoteBackbufferClient);
+  MOZ_ASSERT(aBufferMode);
+
+  // Because we use remote backbuffering, there is no need to use a local
+  // backbuffer too.
+  (*aBufferMode) = layers::BufferMode::BUFFER_NONE;
+
+  return mRemoteBackbufferClient->BorrowDrawTarget();
+}
+
+void CompositorWidgetParent::EndRemoteDrawingInRegion(
+    gfx::DrawTarget* aDrawTarget, const LayoutDeviceIntRegion& aInvalidRegion) {
+  Unused << mRemoteBackbufferClient->PresentDrawTarget(
+      aInvalidRegion.ToUnknownRegion());
+}
+
+bool CompositorWidgetParent::NeedsToDeferEndRemoteDrawing() { return false; }
+
+already_AddRefed<gfx::DrawTarget>
+CompositorWidgetParent::GetBackBufferDrawTarget(gfx::DrawTarget* aScreenTarget,
+                                                const gfx::IntRect& aRect,
+                                                bool* aOutIsCleared) {
+  MOZ_CRASH(
+      "Unexpected call to GetBackBufferDrawTarget() with remote "
+      "backbuffering in use");
+}
+
+already_AddRefed<gfx::SourceSurface>
+CompositorWidgetParent::EndBackBufferDrawing() {
+  MOZ_CRASH(
+      "Unexpected call to EndBackBufferDrawing() with remote "
+      "backbuffering in use");
+}
+
+bool CompositorWidgetParent::InitCompositor(layers::Compositor* aCompositor) {
+  return true;
+}
+
+bool CompositorWidgetParent::IsHidden() const { return ::IsIconic(mWnd); }
+
+mozilla::ipc::IPCResult CompositorWidgetParent::RecvInitialize(
+    const RemoteBackbufferHandles& aRemoteHandles) {
+  Unused << Initialize(aRemoteHandles);
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult CompositorWidgetParent::RecvEnterPresentLock() {
+  mPresentLock.Enter();
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult CompositorWidgetParent::RecvLeavePresentLock() {
+  mPresentLock.Leave();
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult CompositorWidgetParent::RecvUpdateTransparency(
+    const TransparencyMode& aMode) {
+  mTransparencyMode = uint32_t(aMode);
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult CompositorWidgetParent::RecvNotifyVisibilityUpdated(
+    const nsSizeMode& aSizeMode, const bool& aIsFullyOccluded) {
+  mSizeMode = aSizeMode;
+  mIsFullyOccluded = aIsFullyOccluded;
+  return IPC_OK();
+}
+
+nsSizeMode CompositorWidgetParent::CompositorWidgetParent::GetWindowSizeMode()
+    const {
+  nsSizeMode sizeMode = mSizeMode;
+  return sizeMode;
+}
+
+bool CompositorWidgetParent::CompositorWidgetParent::GetWindowIsFullyOccluded()
+    const {
+  bool isFullyOccluded = mIsFullyOccluded;
+  return isFullyOccluded;
+}
+
+mozilla::ipc::IPCResult CompositorWidgetParent::RecvClearTransparentWindow() {
+  gfx::CriticalSectionAutoEnter lock(&mPresentLock);
+
+  RefPtr<DrawTarget> drawTarget = mRemoteBackbufferClient->BorrowDrawTarget();
+  if (!drawTarget) {
+    return IPC_OK();
+  }
+
+  IntSize size = drawTarget->GetSize();
+  if (size.IsEmpty()) {
+    return IPC_OK();
+  }
+
+  drawTarget->ClearRect(Rect(0, 0, size.width, size.height));
+
+  Unused << mRemoteBackbufferClient->PresentDrawTarget(
+      IntRect(0, 0, size.width, size.height));
+
+  return IPC_OK();
+}
+
+nsIWidget* CompositorWidgetParent::RealWidget() { return nullptr; }
+
+void CompositorWidgetParent::ObserveVsync(VsyncObserver* aObserver) {
+  if (aObserver) {
+    Unused << SendObserveVsync();
+  } else {
+    Unused << SendUnobserveVsync();
+  }
+  mVsyncObserver = aObserver;
+}
+
+RefPtr<VsyncObserver> CompositorWidgetParent::GetVsyncObserver() const {
+  MOZ_ASSERT(XRE_GetProcessType() == GeckoProcessType_GPU);
+  return mVsyncObserver;
+}
+
+void CompositorWidgetParent::UpdateCompositorWnd(const HWND aCompositorWnd,
+                                                 const HWND aParentWnd) {
+  MOZ_ASSERT(layers::CompositorThreadHolder::IsInCompositorThread());
+  MOZ_ASSERT(mRootLayerTreeID.isSome());
+
+  RefPtr<CompositorWidgetParent> self = this;
+  SendUpdateCompositorWnd(reinterpret_cast<WindowsHandle>(aCompositorWnd),
+                          reinterpret_cast<WindowsHandle>(aParentWnd))
+      ->Then(
+          layers::CompositorThread(), __func__,
+          [self](const bool& aSuccess) {
+            if (aSuccess && self->mRootLayerTreeID.isSome() &&
+                layers::CompositorThreadHolder::IsActive()) {
+              self->mSetParentCompleted = true;
+              // Schedule composition after ::SetParent() call in parent
+              // process.
+              layers::CompositorBridgeParent::ScheduleForcedComposition(
+                  self->mRootLayerTreeID.ref(), wr::RenderReasons::WIDGET);
+            }
+          },
+          [self](const mozilla::ipc::ResponseRejectReason&) {});
+}
+
+void CompositorWidgetParent::SetRootLayerTreeID(
+    const layers::LayersId& aRootLayerTreeId) {
+  mRootLayerTreeID = Some(aRootLayerTreeId);
+}
+
+void CompositorWidgetParent::ActorDestroy(ActorDestroyReason aWhy) {}
+
+}  // namespace widget
+}  // namespace mozilla
diff --git a/widget/windows/CompositorWidgetParent.h b/widget/windows/CompositorWidgetParent.h
new file mode 100644
index 0000000000..0f91fa7ccb
--- /dev/null
+++ b/widget/windows/CompositorWidgetParent.h
@@ -0,0 +1,92 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef widget_windows_CompositorWidgetParent_h
+#define widget_windows_CompositorWidgetParent_h
+
+#include "WinCompositorWidget.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/widget/PCompositorWidgetParent.h"
+
+namespace mozilla {
+namespace widget {
+
+enum class TransparencyMode : uint8_t;
+
+namespace remote_backbuffer {
+class Client;
+}
+
+class CompositorWidgetParent final : public PCompositorWidgetParent,
+                                     public WinCompositorWidget {
+ public:
+  explicit CompositorWidgetParent(const CompositorWidgetInitData& aInitData,
+                                  const layers::CompositorOptions& aOptions);
+  ~CompositorWidgetParent() override;
+
+  bool Initialize(const RemoteBackbufferHandles& aRemoteHandles);
+
+  bool PreRender(WidgetRenderingContext*) override;
+  void PostRender(WidgetRenderingContext*) override;
+  already_AddRefed<gfx::DrawTarget> StartRemoteDrawingInRegion(
+      const LayoutDeviceIntRegion& aInvalidRegion,
+      layers::BufferMode* aBufferMode) override;
+  void EndRemoteDrawingInRegion(
+      gfx::DrawTarget* aDrawTarget,
+      const LayoutDeviceIntRegion& aInvalidRegion) override;
+  bool NeedsToDeferEndRemoteDrawing() override;
+  LayoutDeviceIntSize GetClientSize() override;
+  already_AddRefed<gfx::DrawTarget> GetBackBufferDrawTarget(
+      gfx::DrawTarget* aScreenTarget, const gfx::IntRect& aRect,
+      bool* aOutIsCleared) override;
+  already_AddRefed<gfx::SourceSurface> EndBackBufferDrawing() override;
+  bool InitCompositor(layers::Compositor* aCompositor) override;
+  bool IsHidden() const override;
+
+  nsSizeMode GetWindowSizeMode() const override;
+  bool GetWindowIsFullyOccluded() const override;
+
+  mozilla::ipc::IPCResult RecvInitialize(
+      const RemoteBackbufferHandles& aRemoteHandles) override;
+  mozilla::ipc::IPCResult RecvEnterPresentLock() override;
+  mozilla::ipc::IPCResult RecvLeavePresentLock() override;
+  mozilla::ipc::IPCResult RecvUpdateTransparency(
+      const TransparencyMode& aMode) override;
+  mozilla::ipc::IPCResult RecvNotifyVisibilityUpdated(
+      const nsSizeMode& aSizeMode, const bool& aIsFullyOccluded) override;
+  mozilla::ipc::IPCResult RecvClearTransparentWindow() override;
+  void ActorDestroy(ActorDestroyReason aWhy) override;
+
+  nsIWidget* RealWidget() override;
+  void ObserveVsync(VsyncObserver* aObserver) override;
+  RefPtr<VsyncObserver> GetVsyncObserver() const override;
+
+  // PlatformCompositorWidgetDelegate Overrides
+  void UpdateCompositorWnd(const HWND aCompositorWnd,
+                           const HWND aParentWnd) override;
+  void SetRootLayerTreeID(const layers::LayersId& aRootLayerTreeId) override;
+
+ private:
+  RefPtr<VsyncObserver> mVsyncObserver;
+  Maybe<layers::LayersId> mRootLayerTreeID;
+
+  HWND mWnd;
+
+  gfx::CriticalSection mPresentLock;
+
+  // Transparency handling.
+  mozilla::Atomic<uint32_t, MemoryOrdering::Relaxed> mTransparencyMode;
+
+  // Visibility handling.
+  mozilla::Atomic<nsSizeMode, MemoryOrdering::Relaxed> mSizeMode;
+  mozilla::Atomic<bool, MemoryOrdering::Relaxed> mIsFullyOccluded;
+
+  std::unique_ptr<remote_backbuffer::Client> mRemoteBackbufferClient;
+};
+
+}  // namespace widget
+}  // namespace mozilla
+
+#endif  // widget_windows_CompositorWidgetParent_h
diff --git a/widget/windows/DirectManipulationOwner.cpp b/widget/windows/DirectManipulationOwner.cpp
new file mode 100644
index 0000000000..569dd4e189
--- /dev/null
+++ b/widget/windows/DirectManipulationOwner.cpp
@@ -0,0 +1,722 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "DirectManipulationOwner.h"
+#include "nsWindow.h"
+#include "WinModifierKeyState.h"
+#include "InputData.h"
+#include "mozilla/StaticPrefs_apz.h"
+#include "mozilla/SwipeTracker.h"
+#include "mozilla/TimeStamp.h"
+#include "mozilla/VsyncDispatcher.h"
+
+#include "directmanipulation.h"
+
+namespace mozilla {
+namespace widget {
+
+class DManipEventHandler : public IDirectManipulationViewportEventHandler,
+                           public IDirectManipulationInteractionEventHandler {
+ public:
+  typedef mozilla::LayoutDeviceIntRect LayoutDeviceIntRect;
+
+  friend class DirectManipulationOwner;
+
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(DManipEventHandler)
+
+  STDMETHODIMP QueryInterface(REFIID, void**) override;
+
+  friend class DirectManipulationOwner;
+
+  explicit DManipEventHandler(nsWindow* aWindow,
+                              DirectManipulationOwner* aOwner,
+                              const LayoutDeviceIntRect& aBounds);
+
+  HRESULT STDMETHODCALLTYPE OnViewportStatusChanged(
+      IDirectManipulationViewport* viewport, DIRECTMANIPULATION_STATUS current,
+      DIRECTMANIPULATION_STATUS previous) override;
+
+  HRESULT STDMETHODCALLTYPE
+  OnViewportUpdated(IDirectManipulationViewport* viewport) override;
+
+  HRESULT STDMETHODCALLTYPE
+  OnContentUpdated(IDirectManipulationViewport* viewport,
+                   IDirectManipulationContent* content) override;
+
+  HRESULT STDMETHODCALLTYPE
+  OnInteraction(IDirectManipulationViewport2* viewport,
+                DIRECTMANIPULATION_INTERACTION_TYPE interaction) override;
+
+  void Update();
+
+  class VObserver final : public mozilla::VsyncObserver {
+    NS_INLINE_DECL_THREADSAFE_REFCOUNTING(DManipEventHandler::VObserver,
+                                          override)
+
+   public:
+    void NotifyVsync(const mozilla::VsyncEvent& aVsync) override {
+      if (mOwner) {
+        mOwner->Update();
+      }
+    }
+    explicit VObserver(DManipEventHandler* aOwner) : mOwner(aOwner) {}
+
+    void ClearOwner() { mOwner = nullptr; }
+
+   private:
+    virtual ~VObserver() {}
+    DManipEventHandler* mOwner;
+  };
+
+  enum class State { eNone, ePanning, eInertia, ePinching };
+  void TransitionToState(State aNewState);
+
+  enum class Phase { eStart, eMiddle, eEnd };
+  // Return value indicates if we sent an event or not and hence if we should
+  // update mLastScale. (We only want to send pinch events if the computed
+  // deltaY for the corresponding WidgetWheelEvent would be non-zero.)
+  bool SendPinch(Phase aPhase, float aScale);
+  void SendPan(Phase aPhase, float x, float y, bool aIsInertia);
+  static void SendPanCommon(nsWindow* aWindow, Phase aPhase,
+                            ScreenPoint aPosition, double aDeltaX,
+                            double aDeltaY, Modifiers aMods, bool aIsInertia);
+
+  static void SynthesizeNativeTouchpadPan(
+      nsWindow* aWindow, nsIWidget::TouchpadGesturePhase aEventPhase,
+      LayoutDeviceIntPoint aPoint, double aDeltaX, double aDeltaY,
+      int32_t aModifierFlags);
+
+ private:
+  virtual ~DManipEventHandler() = default;
+
+  nsWindow* mWindow;
+  DirectManipulationOwner* mOwner;
+  RefPtr<VObserver> mObserver;
+  float mLastScale;
+  float mLastXOffset;
+  float mLastYOffset;
+  LayoutDeviceIntRect mBounds;
+  bool mShouldSendPanStart;
+  bool mShouldSendPinchStart;
+  State mState = State::eNone;
+};
+
+DManipEventHandler::DManipEventHandler(nsWindow* aWindow,
+                                       DirectManipulationOwner* aOwner,
+                                       const LayoutDeviceIntRect& aBounds)
+    : mWindow(aWindow),
+      mOwner(aOwner),
+      mLastScale(1.f),
+      mLastXOffset(0.f),
+      mLastYOffset(0.f),
+      mBounds(aBounds),
+      mShouldSendPanStart(false),
+      mShouldSendPinchStart(false) {}
+
+STDMETHODIMP
+DManipEventHandler::QueryInterface(REFIID iid, void** ppv) {
+  const IID IID_IDirectManipulationViewportEventHandler =
+      __uuidof(IDirectManipulationViewportEventHandler);
+  const IID IID_IDirectManipulationInteractionEventHandler =
+      __uuidof(IDirectManipulationInteractionEventHandler);
+
+  if ((IID_IUnknown == iid) ||
+      (IID_IDirectManipulationViewportEventHandler == iid)) {
+    *ppv = static_cast<IDirectManipulationViewportEventHandler*>(this);
+    AddRef();
+    return S_OK;
+  }
+  if (IID_IDirectManipulationInteractionEventHandler == iid) {
+    *ppv = static_cast<IDirectManipulationInteractionEventHandler*>(this);
+    AddRef();
+    return S_OK;
+  }
+
+  return E_NOINTERFACE;
+}
+
+HRESULT
+DManipEventHandler::OnViewportStatusChanged(
+    IDirectManipulationViewport* viewport, DIRECTMANIPULATION_STATUS current,
+    DIRECTMANIPULATION_STATUS previous) {
+  if (current == previous) {
+    return S_OK;
+  }
+
+  if (current == DIRECTMANIPULATION_INERTIA) {
+    if (previous != DIRECTMANIPULATION_RUNNING || mState != State::ePanning) {
+      // xxx transition to none?
+      return S_OK;
+    }
+
+    TransitionToState(State::eInertia);
+  }
+
+  if (current == DIRECTMANIPULATION_RUNNING) {
+    // INERTIA -> RUNNING, should start a new sequence.
+    if (previous == DIRECTMANIPULATION_INERTIA) {
+      TransitionToState(State::eNone);
+    }
+  }
+
+  if (current != DIRECTMANIPULATION_ENABLED &&
+      current != DIRECTMANIPULATION_READY) {
+    return S_OK;
+  }
+
+  // A session has ended, reset the transform.
+  if (mLastScale != 1.f || mLastXOffset != 0.f || mLastYOffset != 0.f) {
+    HRESULT hr =
+        viewport->ZoomToRect(0, 0, mBounds.width, mBounds.height, false);
+    if (!SUCCEEDED(hr)) {
+      NS_WARNING("ZoomToRect failed");
+    }
+  }
+  mLastScale = 1.f;
+  mLastXOffset = 0.f;
+  mLastYOffset = 0.f;
+
+  TransitionToState(State::eNone);
+
+  return S_OK;
+}
+
+HRESULT
+DManipEventHandler::OnViewportUpdated(IDirectManipulationViewport* viewport) {
+  return S_OK;
+}
+
+void DManipEventHandler::TransitionToState(State aNewState) {
+  if (mState == aNewState) {
+    return;
+  }
+
+  State prevState = mState;
+  mState = aNewState;
+
+  // End the previous sequence.
+  switch (prevState) {
+    case State::ePanning: {
+      // ePanning -> *: PanEnd
+      SendPan(Phase::eEnd, 0.f, 0.f, false);
+      break;
+    }
+    case State::eInertia: {
+      // eInertia -> *: MomentumEnd
+      SendPan(Phase::eEnd, 0.f, 0.f, true);
+      break;
+    }
+    case State::ePinching: {
+      MOZ_ASSERT(aNewState == State::eNone);
+      // ePinching -> eNone: PinchEnd. ePinching should only transition to
+      // eNone.
+      // Only send a pinch end if we sent a pinch start.
+      if (!mShouldSendPinchStart) {
+        SendPinch(Phase::eEnd, 0.f);
+      }
+      mShouldSendPinchStart = false;
+      break;
+    }
+    case State::eNone: {
+      // eNone -> *: no cleanup is needed.
+      break;
+    }
+    default:
+      MOZ_ASSERT(false);
+  }
+
+  // Start the new sequence.
+  switch (aNewState) {
+    case State::ePanning: {
+      // eInertia, eNone -> ePanning: PanStart.
+      // We're being called from OnContentUpdated, it has the coords we need to
+      // pass to SendPan(Phase::eStart), so set mShouldSendPanStart and when we
+      // return OnContentUpdated will check it and call SendPan(Phase::eStart).
+      mShouldSendPanStart = true;
+      break;
+    }
+    case State::eInertia: {
+      // Only ePanning can transition to eInertia.
+      MOZ_ASSERT(prevState == State::ePanning);
+      SendPan(Phase::eStart, 0.f, 0.f, true);
+      break;
+    }
+    case State::ePinching: {
+      // * -> ePinching: PinchStart.
+      // Pinch gesture may begin with some scroll events.
+      // We're being called from OnContentUpdated, it has the scale we need to
+      // pass to SendPinch(Phase::eStart), so set mShouldSendPinchStart and when
+      // we return OnContentUpdated will check it and call
+      // SendPinch(Phase::eStart).
+      mShouldSendPinchStart = true;
+      break;
+    }
+    case State::eNone: {
+      // * -> eNone: only cleanup is needed.
+      break;
+    }
+    default:
+      MOZ_ASSERT(false);
+  }
+}
+
+HRESULT
+DManipEventHandler::OnContentUpdated(IDirectManipulationViewport* viewport,
+                                     IDirectManipulationContent* content) {
+  float transform[6];
+  HRESULT hr = content->GetContentTransform(transform, ARRAYSIZE(transform));
+  if (!SUCCEEDED(hr)) {
+    NS_WARNING("GetContentTransform failed");
+    return S_OK;
+  }
+
+  float scale = transform[0];
+  float xoffset = transform[4];
+  float yoffset = transform[5];
+
+  // Not different from last time.
+  if (FuzzyEqualsMultiplicative(scale, mLastScale) && xoffset == mLastXOffset &&
+      yoffset == mLastYOffset) {
+    return S_OK;
+  }
+
+  // Consider this is a Scroll when scale factor equals 1.0.
+  if (FuzzyEqualsMultiplicative(scale, 1.f)) {
+    if (mState == State::eNone) {
+      TransitionToState(State::ePanning);
+    }
+  } else {
+    // Pinch gesture may begin with some scroll events.
+    TransitionToState(State::ePinching);
+  }
+
+  if (mState == State::ePanning || mState == State::eInertia) {
+    // Accumulate the offset (by not updating mLastX/YOffset) until we have at
+    // least one pixel.
+    float dx = std::abs(mLastXOffset - xoffset);
+    float dy = std::abs(mLastYOffset - yoffset);
+    if (dx < 1.f && dy < 1.f) {
+      return S_OK;
+    }
+  }
+
+  bool updateLastScale = true;
+  if (mState == State::ePanning) {
+    if (mShouldSendPanStart) {
+      SendPan(Phase::eStart, mLastXOffset - xoffset, mLastYOffset - yoffset,
+              false);
+      mShouldSendPanStart = false;
+    } else {
+      SendPan(Phase::eMiddle, mLastXOffset - xoffset, mLastYOffset - yoffset,
+              false);
+    }
+  } else if (mState == State::eInertia) {
+    SendPan(Phase::eMiddle, mLastXOffset - xoffset, mLastYOffset - yoffset,
+            true);
+  } else if (mState == State::ePinching) {
+    if (mShouldSendPinchStart) {
+      updateLastScale = SendPinch(Phase::eStart, scale);
+      // Only clear mShouldSendPinchStart if we actually sent the event
+      // (updateLastScale tells us if we sent an event).
+      if (updateLastScale) {
+        mShouldSendPinchStart = false;
+      }
+    } else {
+      updateLastScale = SendPinch(Phase::eMiddle, scale);
+    }
+  }
+
+  if (updateLastScale) {
+    mLastScale = scale;
+  }
+  mLastXOffset = xoffset;
+  mLastYOffset = yoffset;
+
+  return S_OK;
+}
+
+HRESULT
+DManipEventHandler::OnInteraction(
+    IDirectManipulationViewport2* viewport,
+    DIRECTMANIPULATION_INTERACTION_TYPE interaction) {
+  if (interaction == DIRECTMANIPULATION_INTERACTION_BEGIN) {
+    if (!mObserver) {
+      mObserver = new VObserver(this);
+    }
+
+    gfxWindowsPlatform::GetPlatform()
+        ->GetGlobalVsyncDispatcher()
+        ->AddMainThreadObserver(mObserver);
+  }
+
+  if (mObserver && interaction == DIRECTMANIPULATION_INTERACTION_END) {
+    gfxWindowsPlatform::GetPlatform()
+        ->GetGlobalVsyncDispatcher()
+        ->RemoveMainThreadObserver(mObserver);
+  }
+
+  return S_OK;
+}
+
+void DManipEventHandler::Update() {
+  if (mOwner) {
+    mOwner->Update();
+  }
+}
+
+void DirectManipulationOwner::Update() {
+  if (mDmUpdateManager) {
+    mDmUpdateManager->Update(nullptr);
+  }
+}
+
+DirectManipulationOwner::DirectManipulationOwner(nsWindow* aWindow)
+    : mWindow(aWindow) {}
+
+DirectManipulationOwner::~DirectManipulationOwner() { Destroy(); }
+
+bool DManipEventHandler::SendPinch(Phase aPhase, float aScale) {
+  if (!mWindow) {
+    return false;
+  }
+
+  if (aScale == mLastScale && aPhase != Phase::eEnd) {
+    return false;
+  }
+
+  PinchGestureInput::PinchGestureType pinchGestureType =
+      PinchGestureInput::PINCHGESTURE_SCALE;
+  switch (aPhase) {
+    case Phase::eStart:
+      pinchGestureType = PinchGestureInput::PINCHGESTURE_START;
+      break;
+    case Phase::eMiddle:
+      pinchGestureType = PinchGestureInput::PINCHGESTURE_SCALE;
+      break;
+    case Phase::eEnd:
+      pinchGestureType = PinchGestureInput::PINCHGESTURE_END;
+      break;
+    default:
+      MOZ_ASSERT_UNREACHABLE("handle all enum values");
+  }
+
+  TimeStamp eventTimeStamp = TimeStamp::Now();
+
+  ModifierKeyState modifierKeyState;
+  Modifiers mods = modifierKeyState.GetModifiers();
+
+  ExternalPoint screenOffset = ViewAs<ExternalPixel>(
+      mWindow->WidgetToScreenOffset(),
+      PixelCastJustification::LayoutDeviceIsScreenForUntransformedEvent);
+
+  POINT cursor_pos;
+  ::GetCursorPos(&cursor_pos);
+  HWND wnd = static_cast<HWND>(mWindow->GetNativeData(NS_NATIVE_WINDOW));
+  ::ScreenToClient(wnd, &cursor_pos);
+  ScreenPoint position = {(float)cursor_pos.x, (float)cursor_pos.y};
+
+  PinchGestureInput event{pinchGestureType,
+                          PinchGestureInput::TRACKPAD,
+                          eventTimeStamp,
+                          screenOffset,
+                          position,
+                          100.0 * ((aPhase == Phase::eEnd) ? 1.f : aScale),
+                          100.0 * ((aPhase == Phase::eEnd) ? 1.f : mLastScale),
+                          mods};
+
+  if (!event.SetLineOrPageDeltaY(mWindow)) {
+    return false;
+  }
+
+  mWindow->SendAnAPZEvent(event);
+
+  return true;
+}
+
+void DManipEventHandler::SendPan(Phase aPhase, float x, float y,
+                                 bool aIsInertia) {
+  if (!mWindow) {
+    return;
+  }
+
+  ModifierKeyState modifierKeyState;
+  Modifiers mods = modifierKeyState.GetModifiers();
+
+  POINT cursor_pos;
+  ::GetCursorPos(&cursor_pos);
+  HWND wnd = static_cast<HWND>(mWindow->GetNativeData(NS_NATIVE_WINDOW));
+  ::ScreenToClient(wnd, &cursor_pos);
+  ScreenPoint position = {(float)cursor_pos.x, (float)cursor_pos.y};
+
+  SendPanCommon(mWindow, aPhase, position, x, y, mods, aIsInertia);
+}
+
+/* static */
+void DManipEventHandler::SendPanCommon(nsWindow* aWindow, Phase aPhase,
+                                       ScreenPoint aPosition, double aDeltaX,
+                                       double aDeltaY, Modifiers aMods,
+                                       bool aIsInertia) {
+  if (!aWindow) {
+    return;
+  }
+
+  PanGestureInput::PanGestureType panGestureType =
+      PanGestureInput::PANGESTURE_PAN;
+  if (aIsInertia) {
+    switch (aPhase) {
+      case Phase::eStart:
+        panGestureType = PanGestureInput::PANGESTURE_MOMENTUMSTART;
+        break;
+      case Phase::eMiddle:
+        panGestureType = PanGestureInput::PANGESTURE_MOMENTUMPAN;
+        break;
+      case Phase::eEnd:
+        panGestureType = PanGestureInput::PANGESTURE_MOMENTUMEND;
+        break;
+      default:
+        MOZ_ASSERT_UNREACHABLE("handle all enum values");
+    }
+  } else {
+    switch (aPhase) {
+      case Phase::eStart:
+        panGestureType = PanGestureInput::PANGESTURE_START;
+        break;
+      case Phase::eMiddle:
+        panGestureType = PanGestureInput::PANGESTURE_PAN;
+        break;
+      case Phase::eEnd:
+        panGestureType = PanGestureInput::PANGESTURE_END;
+        break;
+      default:
+        MOZ_ASSERT_UNREACHABLE("handle all enum values");
+    }
+  }
+
+  TimeStamp eventTimeStamp = TimeStamp::Now();
+
+  PanGestureInput event{panGestureType, eventTimeStamp, aPosition,
+                        ScreenPoint(aDeltaX, aDeltaY), aMods};
+
+  aWindow->SendAnAPZEvent(event);
+}
+
+void DirectManipulationOwner::Init(const LayoutDeviceIntRect& aBounds) {
+  HRESULT hr = CoCreateInstance(
+      CLSID_DirectManipulationManager, nullptr, CLSCTX_INPROC_SERVER,
+      IID_IDirectManipulationManager, getter_AddRefs(mDmManager));
+  if (!SUCCEEDED(hr)) {
+    NS_WARNING("CoCreateInstance(CLSID_DirectManipulationManager failed");
+    mDmManager = nullptr;
+    return;
+  }
+
+  hr = mDmManager->GetUpdateManager(IID_IDirectManipulationUpdateManager,
+                                    getter_AddRefs(mDmUpdateManager));
+  if (!SUCCEEDED(hr)) {
+    NS_WARNING("GetUpdateManager failed");
+    mDmManager = nullptr;
+    mDmUpdateManager = nullptr;
+    return;
+  }
+
+  HWND wnd = static_cast<HWND>(mWindow->GetNativeData(NS_NATIVE_WINDOW));
+
+  hr = mDmManager->CreateViewport(nullptr, wnd, IID_IDirectManipulationViewport,
+                                  getter_AddRefs(mDmViewport));
+  if (!SUCCEEDED(hr)) {
+    NS_WARNING("CreateViewport failed");
+    mDmManager = nullptr;
+    mDmUpdateManager = nullptr;
+    mDmViewport = nullptr;
+    return;
+  }
+
+  DIRECTMANIPULATION_CONFIGURATION configuration =
+      DIRECTMANIPULATION_CONFIGURATION_INTERACTION |
+      DIRECTMANIPULATION_CONFIGURATION_TRANSLATION_X |
+      DIRECTMANIPULATION_CONFIGURATION_TRANSLATION_Y |
+      DIRECTMANIPULATION_CONFIGURATION_TRANSLATION_INERTIA |
+      DIRECTMANIPULATION_CONFIGURATION_RAILS_X |
+      DIRECTMANIPULATION_CONFIGURATION_RAILS_Y;
+  if (StaticPrefs::apz_allow_zooming()) {
+    configuration |= DIRECTMANIPULATION_CONFIGURATION_SCALING;
+  }
+
+  hr = mDmViewport->ActivateConfiguration(configuration);
+  if (!SUCCEEDED(hr)) {
+    NS_WARNING("ActivateConfiguration failed");
+    mDmManager = nullptr;
+    mDmUpdateManager = nullptr;
+    mDmViewport = nullptr;
+    return;
+  }
+
+  hr = mDmViewport->SetViewportOptions(
+      DIRECTMANIPULATION_VIEWPORT_OPTIONS_MANUALUPDATE);
+  if (!SUCCEEDED(hr)) {
+    NS_WARNING("SetViewportOptions failed");
+    mDmManager = nullptr;
+    mDmUpdateManager = nullptr;
+    mDmViewport = nullptr;
+    return;
+  }
+
+  mDmHandler = new DManipEventHandler(mWindow, this, aBounds);
+
+  hr = mDmViewport->AddEventHandler(wnd, mDmHandler.get(),
+                                    &mDmViewportHandlerCookie);
+  if (!SUCCEEDED(hr)) {
+    NS_WARNING("AddEventHandler failed");
+    mDmManager = nullptr;
+    mDmUpdateManager = nullptr;
+    mDmViewport = nullptr;
+    mDmHandler = nullptr;
+    return;
+  }
+
+  RECT rect = {0, 0, aBounds.Width(), aBounds.Height()};
+  hr = mDmViewport->SetViewportRect(&rect);
+  if (!SUCCEEDED(hr)) {
+    NS_WARNING("SetViewportRect failed");
+    mDmManager = nullptr;
+    mDmUpdateManager = nullptr;
+    mDmViewport = nullptr;
+    mDmHandler = nullptr;
+    return;
+  }
+
+  hr = mDmManager->Activate(wnd);
+  if (!SUCCEEDED(hr)) {
+    NS_WARNING("manager Activate failed");
+    mDmManager = nullptr;
+    mDmUpdateManager = nullptr;
+    mDmViewport = nullptr;
+    mDmHandler = nullptr;
+    return;
+  }
+
+  hr = mDmViewport->Enable();
+  if (!SUCCEEDED(hr)) {
+    NS_WARNING("mDmViewport->Enable failed");
+    mDmManager = nullptr;
+    mDmUpdateManager = nullptr;
+    mDmViewport = nullptr;
+    mDmHandler = nullptr;
+    return;
+  }
+
+  hr = mDmUpdateManager->Update(nullptr);
+  if (!SUCCEEDED(hr)) {
+    NS_WARNING("mDmUpdateManager->Update failed");
+    mDmManager = nullptr;
+    mDmUpdateManager = nullptr;
+    mDmViewport = nullptr;
+    mDmHandler = nullptr;
+    return;
+  }
+}
+
+void DirectManipulationOwner::ResizeViewport(
+    const LayoutDeviceIntRect& aBounds) {
+  if (mDmHandler) {
+    mDmHandler->mBounds = aBounds;
+  }
+
+  if (mDmViewport) {
+    RECT rect = {0, 0, aBounds.Width(), aBounds.Height()};
+    HRESULT hr = mDmViewport->SetViewportRect(&rect);
+    if (!SUCCEEDED(hr)) {
+      NS_WARNING("SetViewportRect failed");
+    }
+  }
+}
+
+void DirectManipulationOwner::Destroy() {
+  if (mDmHandler) {
+    mDmHandler->mWindow = nullptr;
+    mDmHandler->mOwner = nullptr;
+    if (mDmHandler->mObserver) {
+      gfxWindowsPlatform::GetPlatform()
+          ->GetGlobalVsyncDispatcher()
+          ->RemoveMainThreadObserver(mDmHandler->mObserver);
+      mDmHandler->mObserver->ClearOwner();
+      mDmHandler->mObserver = nullptr;
+    }
+  }
+
+  HRESULT hr;
+  if (mDmViewport) {
+    hr = mDmViewport->Stop();
+    if (!SUCCEEDED(hr)) {
+      NS_WARNING("mDmViewport->Stop() failed");
+    }
+
+    hr = mDmViewport->Disable();
+    if (!SUCCEEDED(hr)) {
+      NS_WARNING("mDmViewport->Disable() failed");
+    }
+
+    hr = mDmViewport->RemoveEventHandler(mDmViewportHandlerCookie);
+    if (!SUCCEEDED(hr)) {
+      NS_WARNING("mDmViewport->RemoveEventHandler() failed");
+    }
+
+    hr = mDmViewport->Abandon();
+    if (!SUCCEEDED(hr)) {
+      NS_WARNING("mDmViewport->Abandon() failed");
+    }
+  }
+
+  if (mWindow) {
+    HWND wnd = static_cast<HWND>(mWindow->GetNativeData(NS_NATIVE_WINDOW));
+
+    if (mDmManager) {
+      hr = mDmManager->Deactivate(wnd);
+      if (!SUCCEEDED(hr)) {
+        NS_WARNING("mDmManager->Deactivate() failed");
+      }
+    }
+  }
+
+  mDmHandler = nullptr;
+  mDmViewport = nullptr;
+  mDmUpdateManager = nullptr;
+  mDmManager = nullptr;
+  mWindow = nullptr;
+}
+
+void DirectManipulationOwner::SetContact(UINT aContactId) {
+  if (mDmViewport) {
+    mDmViewport->SetContact(aContactId);
+  }
+}
+
+/*static  */ void DirectManipulationOwner::SynthesizeNativeTouchpadPan(
+    nsWindow* aWindow, nsIWidget::TouchpadGesturePhase aEventPhase,
+    LayoutDeviceIntPoint aPoint, double aDeltaX, double aDeltaY,
+    int32_t aModifierFlags) {
+  DManipEventHandler::SynthesizeNativeTouchpadPan(
+      aWindow, aEventPhase, aPoint, aDeltaX, aDeltaY, aModifierFlags);
+}
+
+/*static  */ void DManipEventHandler::SynthesizeNativeTouchpadPan(
+    nsWindow* aWindow, nsIWidget::TouchpadGesturePhase aEventPhase,
+    LayoutDeviceIntPoint aPoint, double aDeltaX, double aDeltaY,
+    int32_t aModifierFlags) {
+  ScreenPoint position = {(float)aPoint.x, (float)aPoint.y};
+  Phase phase = Phase::eStart;
+  if (aEventPhase == nsIWidget::PHASE_UPDATE) {
+    phase = Phase::eMiddle;
+  }
+
+  if (aEventPhase == nsIWidget::PHASE_END) {
+    phase = Phase::eEnd;
+  }
+  SendPanCommon(aWindow, phase, position, aDeltaX, aDeltaY, aModifierFlags,
+                /* aIsInertia = */ false);
+}
+
+}  // namespace widget
+}  // namespace mozilla
diff --git a/widget/windows/DirectManipulationOwner.h b/widget/windows/DirectManipulationOwner.h
new file mode 100644
index 0000000000..b4d5877d70
--- /dev/null
+++ b/widget/windows/DirectManipulationOwner.h
@@ -0,0 +1,54 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef DirectManipulationOwner_h__
+#define DirectManipulationOwner_h__
+
+#include <windows.h>
+#include "Units.h"
+#include "nsIWidget.h"  // for TouchpadGesturePhase
+
+class nsWindow;
+class IDirectManipulationManager;
+class IDirectManipulationUpdateManager;
+class IDirectManipulationViewport;
+
+namespace mozilla {
+namespace widget {
+
+class DManipEventHandler;
+
+class DirectManipulationOwner {
+ public:
+  typedef mozilla::LayoutDeviceIntRect LayoutDeviceIntRect;
+
+  explicit DirectManipulationOwner(nsWindow* aWindow);
+  ~DirectManipulationOwner();
+  void Init(const LayoutDeviceIntRect& aBounds);
+  void ResizeViewport(const LayoutDeviceIntRect& aBounds);
+  void Destroy();
+
+  void SetContact(UINT aContactId);
+
+  void Update();
+
+  static void SynthesizeNativeTouchpadPan(
+      nsWindow* aWindow, nsIWidget::TouchpadGesturePhase aEventPhase,
+      LayoutDeviceIntPoint aPoint, double aDeltaX, double aDeltaY,
+      int32_t aModifierFlags);
+
+ private:
+  nsWindow* mWindow;
+  DWORD mDmViewportHandlerCookie;
+  RefPtr<IDirectManipulationManager> mDmManager;
+  RefPtr<IDirectManipulationUpdateManager> mDmUpdateManager;
+  RefPtr<IDirectManipulationViewport> mDmViewport;
+  RefPtr<DManipEventHandler> mDmHandler;
+};
+
+}  // namespace widget
+}  // namespace mozilla
+
+#endif  // #ifndef DirectManipulationOwner_h__
diff --git a/widget/windows/GfxInfo.cpp b/widget/windows/GfxInfo.cpp
new file mode 100644
index 0000000000..6f033785f5
--- /dev/null
+++ b/widget/windows/GfxInfo.cpp
@@ -0,0 +1,2082 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "GfxInfo.h"
+
+#include "gfxConfig.h"
+#include "GfxDriverInfo.h"
+#include "gfxWindowsPlatform.h"
+#include "jsapi.h"
+#include "js/PropertyAndElement.h"  // JS_SetElement, JS_SetProperty
+#include "nsExceptionHandler.h"
+#include "nsPrintfCString.h"
+#include "nsUnicharUtils.h"
+#include "prenv.h"
+#include "prprf.h"
+#include "xpcpublic.h"
+
+#include "mozilla/Components.h"
+#include "mozilla/Preferences.h"
+#include "mozilla/gfx/DeviceManagerDx.h"
+#include "mozilla/gfx/Logging.h"
+#include "mozilla/SSE.h"
+#include "mozilla/ArrayUtils.h"
+#include "mozilla/WindowsProcessMitigations.h"
+
+#include <intrin.h>
+#include <windows.h>
+#include <devguid.h>   // for GUID_DEVCLASS_BATTERY
+#include <setupapi.h>  // for SetupDi*
+#include <winioctl.h>  // for IOCTL_*
+#include <batclass.h>  // for BATTERY_*
+
+using namespace mozilla;
+using namespace mozilla::gfx;
+using namespace mozilla::widget;
+
+#ifdef DEBUG
+NS_IMPL_ISUPPORTS_INHERITED(GfxInfo, GfxInfoBase, nsIGfxInfoDebug)
+#endif
+
+static void AssertNotWin32kLockdown() {
+  // Check that we are not in Win32k lockdown
+  MOZ_DIAGNOSTIC_ASSERT(!IsWin32kLockedDown(),
+                        "Invalid Windows GfxInfo API with Win32k lockdown");
+}
+
+/* GetD2DEnabled and GetDwriteEnabled shouldn't be called until after
+ * gfxPlatform initialization has occurred because they depend on it for
+ * information. (See bug 591561) */
+nsresult GfxInfo::GetD2DEnabled(bool* aEnabled) {
+  // Telemetry queries this during XPCOM initialization, and there's no
+  // gfxPlatform by then. Just bail out if gfxPlatform isn't initialized.
+  if (!gfxPlatform::Initialized()) {
+    *aEnabled = false;
+    return NS_OK;
+  }
+
+  // We check gfxConfig rather than the actual render mode, since the UI
+  // process does not use Direct2D if the GPU process is enabled. However,
+  // content processes can still use Direct2D.
+  *aEnabled = gfx::gfxConfig::IsEnabled(gfx::Feature::DIRECT2D);
+  return NS_OK;
+}
+
+nsresult GfxInfo::GetDWriteEnabled(bool* aEnabled) {
+  *aEnabled = gfxWindowsPlatform::GetPlatform()->DWriteEnabled();
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+GfxInfo::GetDWriteVersion(nsAString& aDwriteVersion) {
+  gfxWindowsPlatform::GetDLLVersion(L"dwrite.dll", aDwriteVersion);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+GfxInfo::GetHasBattery(bool* aHasBattery) {
+  AssertNotWin32kLockdown();
+
+  *aHasBattery = mHasBattery;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+GfxInfo::GetEmbeddedInFirefoxReality(bool* aEmbeddedInFirefoxReality) {
+  *aEmbeddedInFirefoxReality = gfxVars::FxREmbedded();
+  return NS_OK;
+}
+
+#define PIXEL_STRUCT_RGB 1
+#define PIXEL_STRUCT_BGR 2
+
+NS_IMETHODIMP
+GfxInfo::GetCleartypeParameters(nsAString& aCleartypeParams) {
+  nsTArray<ClearTypeParameterInfo> clearTypeParams;
+
+  gfxWindowsPlatform::GetPlatform()->GetCleartypeParams(clearTypeParams);
+  uint32_t d, numDisplays = clearTypeParams.Length();
+  bool displayNames = (numDisplays > 1);
+  bool foundData = false;
+  nsString outStr;
+
+  for (d = 0; d < numDisplays; d++) {
+    ClearTypeParameterInfo& params = clearTypeParams[d];
+
+    if (displayNames) {
+      outStr.AppendPrintf(
+          "%S [ ", static_cast<const wchar_t*>(params.displayName.get()));
+    }
+
+    if (params.gamma >= 0) {
+      foundData = true;
+      outStr.AppendPrintf("Gamma: %.4g ", params.gamma / 1000.0);
+    }
+
+    if (params.pixelStructure >= 0) {
+      foundData = true;
+      if (params.pixelStructure == PIXEL_STRUCT_RGB ||
+          params.pixelStructure == PIXEL_STRUCT_BGR) {
+        outStr.AppendPrintf(
+            "Pixel Structure: %s ",
+            (params.pixelStructure == PIXEL_STRUCT_RGB ? "RGB" : "BGR"));
+      } else {
+        outStr.AppendPrintf("Pixel Structure: %d ", params.pixelStructure);
+      }
+    }
+
+    if (params.clearTypeLevel >= 0) {
+      foundData = true;
+      outStr.AppendPrintf("ClearType Level: %d ", params.clearTypeLevel);
+    }
+
+    if (params.enhancedContrast >= 0) {
+      foundData = true;
+      outStr.AppendPrintf("Enhanced Contrast: %d ", params.enhancedContrast);
+    }
+
+    if (displayNames) {
+      outStr.Append(u"] ");
+    }
+  }
+
+  if (foundData) {
+    aCleartypeParams.Assign(outStr);
+    return NS_OK;
+  }
+  return NS_ERROR_FAILURE;
+}
+
+NS_IMETHODIMP
+GfxInfo::GetWindowProtocol(nsAString& aWindowProtocol) {
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP
+GfxInfo::GetTestType(nsAString& aTestType) { return NS_ERROR_NOT_IMPLEMENTED; }
+
+static nsresult GetKeyValue(const WCHAR* keyLocation, const WCHAR* keyName,
+                            uint32_t& destValue, int type) {
+  MOZ_ASSERT(type == REG_DWORD || type == REG_QWORD);
+  HKEY key;
+  DWORD dwcbData;
+  DWORD dValue;
+  DWORD resultType;
+  LONG result;
+  nsresult retval = NS_OK;
+
+  result =
+      RegOpenKeyExW(HKEY_LOCAL_MACHINE, keyLocation, 0, KEY_QUERY_VALUE, &key);
+  if (result != ERROR_SUCCESS) {
+    return NS_ERROR_FAILURE;
+  }
+
+  switch (type) {
+    case REG_DWORD: {
+      // We only use this for vram size
+      dwcbData = sizeof(dValue);
+      result = RegQueryValueExW(key, keyName, nullptr, &resultType,
+                                (LPBYTE)&dValue, &dwcbData);
+      if (result == ERROR_SUCCESS && resultType == REG_DWORD) {
+        destValue = (uint32_t)(dValue / 1024 / 1024);
+      } else {
+        retval = NS_ERROR_FAILURE;
+      }
+      break;
+    }
+    case REG_QWORD: {
+      // We only use this for vram size
+      LONGLONG qValue;
+      dwcbData = sizeof(qValue);
+      result = RegQueryValueExW(key, keyName, nullptr, &resultType,
+                                (LPBYTE)&qValue, &dwcbData);
+      if (result == ERROR_SUCCESS && resultType == REG_QWORD) {
+        destValue = (uint32_t)(qValue / 1024 / 1024);
+      } else {
+        retval = NS_ERROR_FAILURE;
+      }
+      break;
+    }
+  }
+  RegCloseKey(key);
+
+  return retval;
+}
+
+static nsresult GetKeyValue(const WCHAR* keyLocation, const WCHAR* keyName,
+                            nsAString& destString, int type) {
+  MOZ_ASSERT(type == REG_MULTI_SZ);
+
+  HKEY key;
+  DWORD dwcbData;
+  DWORD resultType;
+  LONG result;
+  nsresult retval = NS_OK;
+
+  result =
+      RegOpenKeyExW(HKEY_LOCAL_MACHINE, keyLocation, 0, KEY_QUERY_VALUE, &key);
+  if (result != ERROR_SUCCESS) {
+    return NS_ERROR_FAILURE;
+  }
+
+  // A chain of null-separated strings; we convert the nulls to spaces
+  WCHAR wCharValue[1024];
+  dwcbData = sizeof(wCharValue);
+
+  result = RegQueryValueExW(key, keyName, nullptr, &resultType,
+                            (LPBYTE)wCharValue, &dwcbData);
+  if (result == ERROR_SUCCESS && resultType == REG_MULTI_SZ) {
+    // This bit here could probably be cleaner.
+    bool isValid = false;
+
+    DWORD strLen = dwcbData / sizeof(wCharValue[0]);
+    for (DWORD i = 0; i < strLen; i++) {
+      if (wCharValue[i] == '\0') {
+        if (i < strLen - 1 && wCharValue[i + 1] == '\0') {
+          isValid = true;
+          break;
+        } else {
+          wCharValue[i] = ' ';
+        }
+      }
+    }
+
+    // ensure wCharValue is null terminated
+    wCharValue[strLen - 1] = '\0';
+
+    if (isValid) destString = wCharValue;
+
+  } else {
+    retval = NS_ERROR_FAILURE;
+  }
+
+  RegCloseKey(key);
+
+  return retval;
+}
+
+static nsresult GetKeyValues(const WCHAR* keyLocation, const WCHAR* keyName,
+                             nsTArray<nsString>& destStrings) {
+  // First ask for the size of the value
+  DWORD size;
+  LONG rv = RegGetValueW(HKEY_LOCAL_MACHINE, keyLocation, keyName,
+                         RRF_RT_REG_MULTI_SZ, nullptr, nullptr, &size);
+  if (rv != ERROR_SUCCESS) {
+    return NS_ERROR_FAILURE;
+  }
+
+  // Create a buffer with the proper size and retrieve the value
+  WCHAR* wCharValue = new WCHAR[size / sizeof(WCHAR)];
+  rv = RegGetValueW(HKEY_LOCAL_MACHINE, keyLocation, keyName,
+                    RRF_RT_REG_MULTI_SZ, nullptr, (LPBYTE)wCharValue, &size);
+  if (rv != ERROR_SUCCESS) {
+    delete[] wCharValue;
+    return NS_ERROR_FAILURE;
+  }
+
+  // The value is a sequence of null-terminated strings, usually terminated by
+  // an empty string (\0). RegGetValue ensures that the value is properly
+  // terminated with a null character.
+  DWORD i = 0;
+  DWORD strLen = size / sizeof(WCHAR);
+  while (i < strLen) {
+    nsString value(wCharValue + i);
+    if (!value.IsEmpty()) {
+      destStrings.AppendElement(value);
+    }
+    i += value.Length() + 1;
+  }
+  delete[] wCharValue;
+
+  return NS_OK;
+}
+
+// The device ID is a string like PCI\VEN_15AD&DEV_0405&SUBSYS_040515AD
+// this function is used to extract the id's out of it
+uint32_t ParseIDFromDeviceID(const nsAString& key, const nsAString& prefix,
+                             int length) {
+  nsAutoString id(key);
+  ToUpperCase(id);
+  int32_t start = id.Find(prefix);
+  if (start != -1) {
+    id.Cut(0, start + prefix.Length());
+    id.Truncate(length);
+  }
+  if (id.Equals(L"QCOM", nsCaseInsensitiveStringComparator)) {
+    // String format assumptions are broken, so use a Qualcomm PCI Vendor ID
+    // for now. See also GfxDriverInfo::GetDeviceVendor.
+    return 0x5143;
+  }
+  nsresult err;
+  return id.ToInteger(&err, 16);
+}
+
+// OS version in 16.16 major/minor form
+// based on http://msdn.microsoft.com/en-us/library/ms724834(VS.85).aspx
+enum {
+  kWindowsUnknown = 0,
+  kWindows7 = 0x60001,
+  kWindows8 = 0x60002,
+  kWindows8_1 = 0x60003,
+  kWindows10 = 0xA0000
+};
+
+static bool HasBattery() {
+  // Helper classes to manage lifetimes of Windows structs.
+  class MOZ_STACK_CLASS HDevInfoHolder final {
+   public:
+    explicit HDevInfoHolder(HDEVINFO aHandle) : mHandle(aHandle) {}
+
+    ~HDevInfoHolder() { ::SetupDiDestroyDeviceInfoList(mHandle); }
+
+   private:
+    HDEVINFO mHandle;
+  };
+
+  class MOZ_STACK_CLASS HandleHolder final {
+   public:
+    explicit HandleHolder(HANDLE aHandle) : mHandle(aHandle) {}
+
+    ~HandleHolder() { ::CloseHandle(mHandle); }
+
+   private:
+    HANDLE mHandle;
+  };
+
+  HDEVINFO hdev =
+      ::SetupDiGetClassDevs(&GUID_DEVCLASS_BATTERY, nullptr, nullptr,
+                            DIGCF_PRESENT | DIGCF_DEVICEINTERFACE);
+  if (hdev == INVALID_HANDLE_VALUE) {
+    return true;
+  }
+
+  HDevInfoHolder hdevHolder(hdev);
+
+  DWORD i = 0;
+  SP_DEVICE_INTERFACE_DATA did = {0};
+  did.cbSize = sizeof(did);
+
+  while (::SetupDiEnumDeviceInterfaces(hdev, nullptr, &GUID_DEVCLASS_BATTERY, i,
+                                       &did)) {
+    DWORD bufferSize = 0;
+    ::SetupDiGetDeviceInterfaceDetail(hdev, &did, nullptr, 0, &bufferSize,
+                                      nullptr);
+    if (::GetLastError() != ERROR_INSUFFICIENT_BUFFER) {
+      return true;
+    }
+
+    UniquePtr<uint8_t[]> buffer(new (std::nothrow) uint8_t[bufferSize]);
+    if (!buffer) {
+      return true;
+    }
+
+    PSP_DEVICE_INTERFACE_DETAIL_DATA pdidd =
+        reinterpret_cast<PSP_DEVICE_INTERFACE_DETAIL_DATA>(buffer.get());
+    pdidd->cbSize = sizeof(*pdidd);
+    if (!::SetupDiGetDeviceInterfaceDetail(hdev, &did, pdidd, bufferSize,
+                                           &bufferSize, nullptr)) {
+      return true;
+    }
+
+    HANDLE hbat = ::CreateFile(pdidd->DevicePath, GENERIC_READ | GENERIC_WRITE,
+                               FILE_SHARE_READ | FILE_SHARE_WRITE, nullptr,
+                               OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, nullptr);
+    if (hbat == INVALID_HANDLE_VALUE) {
+      return true;
+    }
+
+    HandleHolder hbatHolder(hbat);
+
+    BATTERY_QUERY_INFORMATION bqi = {0};
+    DWORD dwWait = 0;
+    DWORD dwOut;
+
+    // We need the tag to query the information below.
+    if (!::DeviceIoControl(hbat, IOCTL_BATTERY_QUERY_TAG, &dwWait,
+                           sizeof(dwWait), &bqi.BatteryTag,
+                           sizeof(bqi.BatteryTag), &dwOut, nullptr) ||
+        !bqi.BatteryTag) {
+      return true;
+    }
+
+    BATTERY_INFORMATION bi = {0};
+    bqi.InformationLevel = BatteryInformation;
+
+    if (!::DeviceIoControl(hbat, IOCTL_BATTERY_QUERY_INFORMATION, &bqi,
+                           sizeof(bqi), &bi, sizeof(bi), &dwOut, nullptr)) {
+      return true;
+    }
+
+    // If a battery intended for general use (i.e. system use) is not a UPS
+    // (i.e. short term), then we know for certain we have a battery.
+    if ((bi.Capabilities & BATTERY_SYSTEM_BATTERY) &&
+        !(bi.Capabilities & BATTERY_IS_SHORT_TERM)) {
+      return true;
+    }
+
+    // Otherwise we check the next battery.
+    ++i;
+  }
+
+  // If we fail to enumerate because there are no more batteries to check, then
+  // we can safely say there are indeed no system batteries.
+  return ::GetLastError() != ERROR_NO_MORE_ITEMS;
+}
+
+/* Other interesting places for info:
+ *   IDXGIAdapter::GetDesc()
+ *   IDirectDraw7::GetAvailableVidMem()
+ *   e->GetAvailableTextureMem()
+ * */
+
+#define DEVICE_KEY_PREFIX L"\\Registry\\Machine\\"
+nsresult GfxInfo::Init() {
+  nsresult rv = GfxInfoBase::Init();
+
+  // If we are locked down in a content process, we can't call any of the
+  // Win32k APIs below. Any method that accesses members of this class should
+  // assert that it's not used in content
+  if (IsWin32kLockedDown()) {
+    return rv;
+  }
+
+  mHasBattery = HasBattery();
+
+  DISPLAY_DEVICEW displayDevice;
+  displayDevice.cb = sizeof(displayDevice);
+  int deviceIndex = 0;
+
+  const char* spoofedWindowsVersion =
+      PR_GetEnv("MOZ_GFX_SPOOF_WINDOWS_VERSION");
+  if (spoofedWindowsVersion) {
+    PR_sscanf(spoofedWindowsVersion, "%x,%u", &mWindowsVersion,
+              &mWindowsBuildNumber);
+  } else {
+    OSVERSIONINFO vinfo;
+    vinfo.dwOSVersionInfoSize = sizeof(vinfo);
+#ifdef _MSC_VER
+#  pragma warning(push)
+#  pragma warning(disable : 4996)
+#endif
+    if (!GetVersionEx(&vinfo)) {
+#ifdef _MSC_VER
+#  pragma warning(pop)
+#endif
+      mWindowsVersion = kWindowsUnknown;
+    } else {
+      mWindowsVersion =
+          int32_t(vinfo.dwMajorVersion << 16) + vinfo.dwMinorVersion;
+      mWindowsBuildNumber = vinfo.dwBuildNumber;
+    }
+  }
+
+  mDeviceKeyDebug = u"PrimarySearch"_ns;
+
+  while (EnumDisplayDevicesW(nullptr, deviceIndex, &displayDevice, 0)) {
+    if (displayDevice.StateFlags & DISPLAY_DEVICE_PRIMARY_DEVICE) {
+      mDeviceKeyDebug = u"NullSearch"_ns;
+      break;
+    }
+    deviceIndex++;
+  }
+
+  // make sure the string is nullptr terminated
+  if (wcsnlen(displayDevice.DeviceKey, ArrayLength(displayDevice.DeviceKey)) ==
+      ArrayLength(displayDevice.DeviceKey)) {
+    // we did not find a nullptr
+    return rv;
+  }
+
+  mDeviceKeyDebug = displayDevice.DeviceKey;
+
+  /* DeviceKey is "reserved" according to MSDN so we'll be careful with it */
+  /* check that DeviceKey begins with DEVICE_KEY_PREFIX */
+  /* some systems have a DeviceKey starting with \REGISTRY\Machine\ so we need
+   * to compare case insenstively */
+  /* If the device key is empty, we are most likely in a remote desktop
+   * environment. In this case we set the devicekey to an empty string so
+   * it can be handled later.
+   */
+  if (displayDevice.DeviceKey[0] != '\0') {
+    if (_wcsnicmp(displayDevice.DeviceKey, DEVICE_KEY_PREFIX,
+                  ArrayLength(DEVICE_KEY_PREFIX) - 1) != 0) {
+      return rv;
+    }
+
+    // chop off DEVICE_KEY_PREFIX
+    mDeviceKey[0] =
+        displayDevice.DeviceKey + ArrayLength(DEVICE_KEY_PREFIX) - 1;
+  } else {
+    mDeviceKey[0].Truncate();
+  }
+
+  mDeviceID[0] = displayDevice.DeviceID;
+  mDeviceString[0] = displayDevice.DeviceString;
+
+  // On Windows 8 and Server 2012 hosts, we want to not block RDP
+  // sessions from attempting hardware acceleration.  RemoteFX
+  // provides features and functionaltiy that can give a good D3D10 +
+  // D2D + DirectWrite experience emulated via a software GPU.
+  //
+  // Unfortunately, the Device ID is nullptr, and we can't enumerate
+  // it using the setup infrastructure (SetupDiGetClassDevsW below
+  // will return INVALID_HANDLE_VALUE).
+  UINT flags = DIGCF_PRESENT | DIGCF_PROFILE | DIGCF_ALLCLASSES;
+  if (mWindowsVersion >= kWindows8 && mDeviceID[0].Length() == 0 &&
+      mDeviceString[0].EqualsLiteral("RDPUDD Chained DD")) {
+    WCHAR sysdir[255];
+    UINT len = GetSystemDirectory(sysdir, sizeof(sysdir));
+    if (len < sizeof(sysdir)) {
+      nsString rdpudd(sysdir);
+      rdpudd.AppendLiteral("\\rdpudd.dll");
+      gfxWindowsPlatform::GetDLLVersion(rdpudd.BeginReading(),
+                                        mDriverVersion[0]);
+      mDriverDate[0].AssignLiteral("01-01-1970");
+
+      // 0x1414 is Microsoft; 0xfefe is an invented (and unused) code
+      mDeviceID[0].AssignLiteral("PCI\\VEN_1414&DEV_FEFE&SUBSYS_00000000");
+      flags |= DIGCF_DEVICEINTERFACE;
+    }
+  }
+
+  /* create a device information set composed of the current display device */
+  HDEVINFO devinfo =
+      SetupDiGetClassDevsW(nullptr, mDeviceID[0].get(), nullptr, flags);
+
+  if (devinfo != INVALID_HANDLE_VALUE) {
+    HKEY key;
+    LONG result;
+    WCHAR value[255];
+    DWORD dwcbData;
+    SP_DEVINFO_DATA devinfoData;
+    DWORD memberIndex = 0;
+
+    devinfoData.cbSize = sizeof(devinfoData);
+    constexpr auto driverKeyPre =
+        u"System\\CurrentControlSet\\Control\\Class\\"_ns;
+    /* enumerate device information elements in the device information set */
+    while (SetupDiEnumDeviceInfo(devinfo, memberIndex++, &devinfoData)) {
+      /* get a string that identifies the device's driver key */
+      if (SetupDiGetDeviceRegistryPropertyW(devinfo, &devinfoData, SPDRP_DRIVER,
+                                            nullptr, (PBYTE)value,
+                                            sizeof(value), nullptr)) {
+        nsAutoString driverKey(driverKeyPre);
+        driverKey += value;
+        result = RegOpenKeyExW(HKEY_LOCAL_MACHINE, driverKey.get(), 0,
+                               KEY_QUERY_VALUE, &key);
+        if (result == ERROR_SUCCESS) {
+          /* we've found the driver we're looking for */
+          dwcbData = sizeof(value);
+          result = RegQueryValueExW(key, L"DriverVersion", nullptr, nullptr,
+                                    (LPBYTE)value, &dwcbData);
+          if (result == ERROR_SUCCESS) {
+            mDriverVersion[0] = value;
+          } else {
+            // If the entry wasn't found, assume the worst (0.0.0.0).
+            mDriverVersion[0].AssignLiteral("0.0.0.0");
+          }
+          dwcbData = sizeof(value);
+          result = RegQueryValueExW(key, L"DriverDate", nullptr, nullptr,
+                                    (LPBYTE)value, &dwcbData);
+          if (result == ERROR_SUCCESS) {
+            mDriverDate[0] = value;
+          } else {
+            // Again, assume the worst
+            mDriverDate[0].AssignLiteral("01-01-1970");
+          }
+          RegCloseKey(key);
+          break;
+        }
+      }
+    }
+
+    SetupDiDestroyDeviceInfoList(devinfo);
+  }
+
+  // It is convenient to have these as integers
+  uint32_t adapterVendorID[2] = {0, 0};
+  uint32_t adapterDeviceID[2] = {0, 0};
+  uint32_t adapterSubsysID[2] = {0, 0};
+
+  adapterVendorID[0] = ParseIDFromDeviceID(mDeviceID[0], u"VEN_"_ns, 4);
+  adapterDeviceID[0] = ParseIDFromDeviceID(mDeviceID[0], u"&DEV_"_ns, 4);
+  adapterSubsysID[0] = ParseIDFromDeviceID(mDeviceID[0], u"&SUBSYS_"_ns, 8);
+
+  // Sometimes we don't get the valid device using this method.  For now,
+  // allow zero vendor or device as valid, as long as the other value is
+  // non-zero.
+  bool foundValidDevice = (adapterVendorID[0] != 0 || adapterDeviceID[0] != 0);
+
+  // We now check for second display adapter.  If we didn't find the valid
+  // device using the original approach, we will try the alternative.
+
+  // Device interface class for display adapters.
+  CLSID GUID_DISPLAY_DEVICE_ARRIVAL;
+  HRESULT hresult = CLSIDFromString(L"{1CA05180-A699-450A-9A0C-DE4FBE3DDD89}",
+                                    &GUID_DISPLAY_DEVICE_ARRIVAL);
+  if (hresult == NOERROR) {
+    devinfo =
+        SetupDiGetClassDevsW(&GUID_DISPLAY_DEVICE_ARRIVAL, nullptr, nullptr,
+                             DIGCF_PRESENT | DIGCF_INTERFACEDEVICE);
+
+    if (devinfo != INVALID_HANDLE_VALUE) {
+      HKEY key;
+      LONG result;
+      WCHAR value[255];
+      DWORD dwcbData;
+      SP_DEVINFO_DATA devinfoData;
+      DWORD memberIndex = 0;
+      devinfoData.cbSize = sizeof(devinfoData);
+
+      nsAutoString adapterDriver2;
+      nsAutoString deviceID2;
+      nsAutoString driverVersion2;
+      nsAutoString driverDate2;
+
+      constexpr auto driverKeyPre =
+          u"System\\CurrentControlSet\\Control\\Class\\"_ns;
+      /* enumerate device information elements in the device information set */
+      while (SetupDiEnumDeviceInfo(devinfo, memberIndex++, &devinfoData)) {
+        /* get a string that identifies the device's driver key */
+        if (SetupDiGetDeviceRegistryPropertyW(
+                devinfo, &devinfoData, SPDRP_DRIVER, nullptr, (PBYTE)value,
+                sizeof(value), nullptr)) {
+          nsAutoString driverKey2(driverKeyPre);
+          driverKey2 += value;
+          result = RegOpenKeyExW(HKEY_LOCAL_MACHINE, driverKey2.get(), 0,
+                                 KEY_QUERY_VALUE, &key);
+          if (result == ERROR_SUCCESS) {
+            dwcbData = sizeof(value);
+            result = RegQueryValueExW(key, L"MatchingDeviceId", nullptr,
+                                      nullptr, (LPBYTE)value, &dwcbData);
+            if (result != ERROR_SUCCESS) {
+              continue;
+            }
+            deviceID2 = value;
+            adapterVendorID[1] = ParseIDFromDeviceID(deviceID2, u"VEN_"_ns, 4);
+            adapterDeviceID[1] = ParseIDFromDeviceID(deviceID2, u"&DEV_"_ns, 4);
+            // Skip the devices we already considered, as well as any
+            // "zero" ones.
+            if ((adapterVendorID[0] == adapterVendorID[1] &&
+                 adapterDeviceID[0] == adapterDeviceID[1]) ||
+                (adapterVendorID[1] == 0 && adapterDeviceID[1] == 0)) {
+              RegCloseKey(key);
+              continue;
+            }
+
+            // If this device is missing driver information, it is unlikely to
+            // be a real display adapter.
+            if (NS_FAILED(GetKeyValue(driverKey2.get(),
+                                      L"InstalledDisplayDrivers",
+                                      adapterDriver2, REG_MULTI_SZ))) {
+              RegCloseKey(key);
+              continue;
+            }
+            dwcbData = sizeof(value);
+            result = RegQueryValueExW(key, L"DriverVersion", nullptr, nullptr,
+                                      (LPBYTE)value, &dwcbData);
+            if (result != ERROR_SUCCESS) {
+              RegCloseKey(key);
+              continue;
+            }
+            driverVersion2 = value;
+            dwcbData = sizeof(value);
+            result = RegQueryValueExW(key, L"DriverDate", nullptr, nullptr,
+                                      (LPBYTE)value, &dwcbData);
+            if (result != ERROR_SUCCESS) {
+              RegCloseKey(key);
+              continue;
+            }
+            driverDate2 = value;
+            dwcbData = sizeof(value);
+            result = RegQueryValueExW(key, L"Device Description", nullptr,
+                                      nullptr, (LPBYTE)value, &dwcbData);
+            if (result != ERROR_SUCCESS) {
+              dwcbData = sizeof(value);
+              result = RegQueryValueExW(key, L"DriverDesc", nullptr, nullptr,
+                                        (LPBYTE)value, &dwcbData);
+            }
+            RegCloseKey(key);
+            if (result == ERROR_SUCCESS) {
+              // If we didn't find a valid device with the original method
+              // take this one, and continue looking for the second GPU.
+              if (!foundValidDevice) {
+                foundValidDevice = true;
+                adapterVendorID[0] = adapterVendorID[1];
+                adapterDeviceID[0] = adapterDeviceID[1];
+                mDeviceString[0] = value;
+                mDeviceID[0] = deviceID2;
+                mDeviceKey[0] = driverKey2;
+                mDriverVersion[0] = driverVersion2;
+                mDriverDate[0] = driverDate2;
+                adapterSubsysID[0] =
+                    ParseIDFromDeviceID(mDeviceID[0], u"&SUBSYS_"_ns, 8);
+                continue;
+              }
+
+              mHasDualGPU = true;
+              mDeviceString[1] = value;
+              mDeviceID[1] = deviceID2;
+              mDeviceKey[1] = driverKey2;
+              mDriverVersion[1] = driverVersion2;
+              mDriverDate[1] = driverDate2;
+              adapterSubsysID[1] =
+                  ParseIDFromDeviceID(mDeviceID[1], u"&SUBSYS_"_ns, 8);
+              mAdapterVendorID[1].AppendPrintf("0x%04x", adapterVendorID[1]);
+              mAdapterDeviceID[1].AppendPrintf("0x%04x", adapterDeviceID[1]);
+              mAdapterSubsysID[1].AppendPrintf("%08x", adapterSubsysID[1]);
+              break;
+            }
+          }
+        }
+      }
+
+      SetupDiDestroyDeviceInfoList(devinfo);
+    }
+  }
+
+  mAdapterVendorID[0].AppendPrintf("0x%04x", adapterVendorID[0]);
+  mAdapterDeviceID[0].AppendPrintf("0x%04x", adapterDeviceID[0]);
+  mAdapterSubsysID[0].AppendPrintf("%08x", adapterSubsysID[0]);
+
+  // Sometimes, the enumeration is not quite right and the two adapters
+  // end up being swapped.  Actually enumerate the adapters that come
+  // back from the DXGI factory to check, and tag the second as active
+  // if found.
+  if (mHasDualGPU) {
+    nsModuleHandle dxgiModule(LoadLibrarySystem32(L"dxgi.dll"));
+    decltype(CreateDXGIFactory)* createDXGIFactory =
+        (decltype(CreateDXGIFactory)*)GetProcAddress(dxgiModule,
+                                                     "CreateDXGIFactory");
+
+    if (createDXGIFactory) {
+      RefPtr<IDXGIFactory> factory = nullptr;
+      createDXGIFactory(__uuidof(IDXGIFactory), (void**)(&factory));
+      if (factory) {
+        RefPtr<IDXGIAdapter> adapter;
+        if (SUCCEEDED(factory->EnumAdapters(0, getter_AddRefs(adapter)))) {
+          DXGI_ADAPTER_DESC desc;
+          PodZero(&desc);
+          if (SUCCEEDED(adapter->GetDesc(&desc))) {
+            if (desc.VendorId != adapterVendorID[0] &&
+                desc.DeviceId != adapterDeviceID[0] &&
+                desc.VendorId == adapterVendorID[1] &&
+                desc.DeviceId == adapterDeviceID[1]) {
+              mActiveGPUIndex = 1;
+            }
+          }
+        }
+      }
+    }
+  }
+
+  mHasDriverVersionMismatch = false;
+  if (mAdapterVendorID[mActiveGPUIndex] ==
+      GfxDriverInfo::GetDeviceVendor(DeviceVendor::Intel)) {
+    // we've had big crashers (bugs 590373 and 595364) apparently correlated
+    // with bad Intel driver installations where the DriverVersion reported
+    // by the registry was not the version of the DLL.
+
+    // Note that these start without the .dll extension but eventually gain it.
+    bool is64bitApp = sizeof(void*) == 8;
+    nsAutoString dllFileName(is64bitApp ? u"igd10umd64" : u"igd10umd32");
+    nsAutoString dllFileName2(is64bitApp ? u"igd10iumd64" : u"igd10iumd32");
+
+    nsString dllVersion, dllVersion2;
+    uint64_t dllNumericVersion = 0, dllNumericVersion2 = 0,
+             driverNumericVersion = 0, knownSafeMismatchVersion = 0;
+
+    // Only parse the DLL version for those found in the driver list
+    nsAutoString eligibleDLLs;
+    if (NS_SUCCEEDED(GetAdapterDriver(eligibleDLLs))) {
+      if (FindInReadable(dllFileName, eligibleDLLs)) {
+        dllFileName += u".dll"_ns;
+        gfxWindowsPlatform::GetDLLVersion(dllFileName.get(), dllVersion);
+        ParseDriverVersion(dllVersion, &dllNumericVersion);
+      }
+      if (FindInReadable(dllFileName2, eligibleDLLs)) {
+        dllFileName2 += u".dll"_ns;
+        gfxWindowsPlatform::GetDLLVersion(dllFileName2.get(), dllVersion2);
+        ParseDriverVersion(dllVersion2, &dllNumericVersion2);
+      }
+    }
+
+    // Sometimes the DLL is not in the System32 nor SysWOW64 directories. But
+    // UserModeDriverName (or UserModeDriverNameWow, if available) might provide
+    // the full path to the DLL in some DriverStore FileRepository.
+    if (dllNumericVersion == 0 && dllNumericVersion2 == 0) {
+      nsTArray<nsString> eligibleDLLpaths;
+      const WCHAR* keyLocation = mDeviceKey[mActiveGPUIndex].get();
+      GetKeyValues(keyLocation, L"UserModeDriverName", eligibleDLLpaths);
+      GetKeyValues(keyLocation, L"UserModeDriverNameWow", eligibleDLLpaths);
+      size_t length = eligibleDLLpaths.Length();
+      for (size_t i = 0;
+           i < length && dllNumericVersion == 0 && dllNumericVersion2 == 0;
+           ++i) {
+        if (FindInReadable(dllFileName, eligibleDLLpaths[i])) {
+          gfxWindowsPlatform::GetDLLVersion(eligibleDLLpaths[i].get(),
+                                            dllVersion);
+          ParseDriverVersion(dllVersion, &dllNumericVersion);
+        } else if (FindInReadable(dllFileName2, eligibleDLLpaths[i])) {
+          gfxWindowsPlatform::GetDLLVersion(eligibleDLLpaths[i].get(),
+                                            dllVersion2);
+          ParseDriverVersion(dllVersion2, &dllNumericVersion2);
+        }
+      }
+    }
+
+    ParseDriverVersion(mDriverVersion[mActiveGPUIndex], &driverNumericVersion);
+    ParseDriverVersion(u"9.17.10.0"_ns, &knownSafeMismatchVersion);
+
+    // If there's a driver version mismatch, consider this harmful only when
+    // the driver version is less than knownSafeMismatchVersion.  See the
+    // above comment about crashes with old mismatches.  If the GetDllVersion
+    // call fails, we are not calling it a mismatch.
+    if ((dllNumericVersion != 0 && dllNumericVersion != driverNumericVersion) ||
+        (dllNumericVersion2 != 0 &&
+         dllNumericVersion2 != driverNumericVersion)) {
+      if (driverNumericVersion < knownSafeMismatchVersion ||
+          std::max(dllNumericVersion, dllNumericVersion2) <
+              knownSafeMismatchVersion) {
+        mHasDriverVersionMismatch = true;
+        gfxCriticalNoteOnce
+            << "Mismatched driver versions between the registry "
+            << NS_ConvertUTF16toUTF8(mDriverVersion[mActiveGPUIndex]).get()
+            << " and DLL(s) " << NS_ConvertUTF16toUTF8(dllVersion).get() << ", "
+            << NS_ConvertUTF16toUTF8(dllVersion2).get() << " reported.";
+      }
+    } else if (dllNumericVersion == 0 && dllNumericVersion2 == 0) {
+      // Leave it as an asserting error for now, to see if we can find
+      // a system that exhibits this kind of a problem internally.
+      gfxCriticalErrorOnce()
+          << "Potential driver version mismatch ignored due to missing DLLs "
+          << NS_ConvertUTF16toUTF8(dllFileName).get()
+          << " v=" << NS_ConvertUTF16toUTF8(dllVersion).get() << " and "
+          << NS_ConvertUTF16toUTF8(dllFileName2).get()
+          << " v=" << NS_ConvertUTF16toUTF8(dllVersion2).get();
+    }
+  }
+
+  const char* spoofedDriverVersionString =
+      PR_GetEnv("MOZ_GFX_SPOOF_DRIVER_VERSION");
+  if (spoofedDriverVersionString) {
+    mDriverVersion[mActiveGPUIndex].AssignASCII(spoofedDriverVersionString);
+  }
+
+  const char* spoofedVendor = PR_GetEnv("MOZ_GFX_SPOOF_VENDOR_ID");
+  if (spoofedVendor) {
+    mAdapterVendorID[mActiveGPUIndex].AssignASCII(spoofedVendor);
+  }
+
+  const char* spoofedDevice = PR_GetEnv("MOZ_GFX_SPOOF_DEVICE_ID");
+  if (spoofedDevice) {
+    mAdapterDeviceID[mActiveGPUIndex].AssignASCII(spoofedDevice);
+  }
+
+  AddCrashReportAnnotations();
+
+  return rv;
+}
+
+NS_IMETHODIMP
+GfxInfo::GetAdapterDescription(nsAString& aAdapterDescription) {
+  AssertNotWin32kLockdown();
+
+  aAdapterDescription = mDeviceString[mActiveGPUIndex];
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+GfxInfo::GetAdapterDescription2(nsAString& aAdapterDescription) {
+  AssertNotWin32kLockdown();
+
+  aAdapterDescription = mDeviceString[1 - mActiveGPUIndex];
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+GfxInfo::GetAdapterRAM(uint32_t* aAdapterRAM) {
+  AssertNotWin32kLockdown();
+
+  uint32_t result = 0;
+  if (NS_FAILED(GetKeyValue(mDeviceKey[mActiveGPUIndex].get(),
+                            L"HardwareInformation.qwMemorySize", result,
+                            REG_QWORD)) ||
+      result == 0) {
+    if (NS_FAILED(GetKeyValue(mDeviceKey[mActiveGPUIndex].get(),
+                              L"HardwareInformation.MemorySize", result,
+                              REG_DWORD))) {
+      result = 0;
+    }
+  }
+  *aAdapterRAM = result;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+GfxInfo::GetAdapterRAM2(uint32_t* aAdapterRAM) {
+  AssertNotWin32kLockdown();
+
+  uint32_t result = 0;
+  if (mHasDualGPU) {
+    if (NS_FAILED(GetKeyValue(mDeviceKey[1 - mActiveGPUIndex].get(),
+                              L"HardwareInformation.qwMemorySize", result,
+                              REG_QWORD)) ||
+        result == 0) {
+      if (NS_FAILED(GetKeyValue(mDeviceKey[1 - mActiveGPUIndex].get(),
+                                L"HardwareInformation.MemorySize", result,
+                                REG_DWORD))) {
+        result = 0;
+      }
+    }
+  }
+  *aAdapterRAM = result;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+GfxInfo::GetAdapterDriver(nsAString& aAdapterDriver) {
+  AssertNotWin32kLockdown();
+
+  if (NS_FAILED(GetKeyValue(mDeviceKey[mActiveGPUIndex].get(),
+                            L"InstalledDisplayDrivers", aAdapterDriver,
+                            REG_MULTI_SZ)))
+    aAdapterDriver = L"Unknown";
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+GfxInfo::GetAdapterDriver2(nsAString& aAdapterDriver) {
+  AssertNotWin32kLockdown();
+
+  if (!mHasDualGPU) {
+    aAdapterDriver.Truncate();
+  } else if (NS_FAILED(GetKeyValue(mDeviceKey[1 - mActiveGPUIndex].get(),
+                                   L"InstalledDisplayDrivers", aAdapterDriver,
+                                   REG_MULTI_SZ))) {
+    aAdapterDriver = L"Unknown";
+  }
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+GfxInfo::GetAdapterDriverVendor(nsAString& aAdapterDriverVendor) {
+  aAdapterDriverVendor.Truncate();
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+GfxInfo::GetAdapterDriverVersion(nsAString& aAdapterDriverVersion) {
+  AssertNotWin32kLockdown();
+
+  aAdapterDriverVersion = mDriverVersion[mActiveGPUIndex];
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+GfxInfo::GetAdapterDriverDate(nsAString& aAdapterDriverDate) {
+  AssertNotWin32kLockdown();
+
+  aAdapterDriverDate = mDriverDate[mActiveGPUIndex];
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+GfxInfo::GetAdapterDriverVendor2(nsAString& aAdapterDriverVendor) {
+  aAdapterDriverVendor.Truncate();
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+GfxInfo::GetAdapterDriverVersion2(nsAString& aAdapterDriverVersion) {
+  AssertNotWin32kLockdown();
+
+  aAdapterDriverVersion = mDriverVersion[1 - mActiveGPUIndex];
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+GfxInfo::GetAdapterDriverDate2(nsAString& aAdapterDriverDate) {
+  AssertNotWin32kLockdown();
+
+  aAdapterDriverDate = mDriverDate[1 - mActiveGPUIndex];
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+GfxInfo::GetAdapterVendorID(nsAString& aAdapterVendorID) {
+  AssertNotWin32kLockdown();
+
+  aAdapterVendorID = mAdapterVendorID[mActiveGPUIndex];
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+GfxInfo::GetAdapterVendorID2(nsAString& aAdapterVendorID) {
+  AssertNotWin32kLockdown();
+
+  aAdapterVendorID = mAdapterVendorID[1 - mActiveGPUIndex];
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+GfxInfo::GetAdapterDeviceID(nsAString& aAdapterDeviceID) {
+  AssertNotWin32kLockdown();
+
+  aAdapterDeviceID = mAdapterDeviceID[mActiveGPUIndex];
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+GfxInfo::GetAdapterDeviceID2(nsAString& aAdapterDeviceID) {
+  AssertNotWin32kLockdown();
+
+  aAdapterDeviceID = mAdapterDeviceID[1 - mActiveGPUIndex];
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+GfxInfo::GetAdapterSubsysID(nsAString& aAdapterSubsysID) {
+  AssertNotWin32kLockdown();
+
+  aAdapterSubsysID = mAdapterSubsysID[mActiveGPUIndex];
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+GfxInfo::GetAdapterSubsysID2(nsAString& aAdapterSubsysID) {
+  AssertNotWin32kLockdown();
+
+  aAdapterSubsysID = mAdapterSubsysID[1 - mActiveGPUIndex];
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+GfxInfo::GetIsGPU2Active(bool* aIsGPU2Active) {
+  // This is never the case, as the active GPU ends up being
+  // the first one.  It should probably be removed.
+  *aIsGPU2Active = false;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+GfxInfo::GetDrmRenderDevice(nsACString& aDrmRenderDevice) {
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+/* Cisco's VPN software can cause corruption of the floating point state.
+ * Make a note of this in our crash reports so that some weird crashes
+ * make more sense */
+static void CheckForCiscoVPN() {
+  LONG result;
+  HKEY key;
+  /* This will give false positives, but hopefully no false negatives */
+  result =
+      RegOpenKeyExW(HKEY_LOCAL_MACHINE, L"Software\\Cisco Systems\\VPN Client",
+                    0, KEY_QUERY_VALUE, &key);
+  if (result == ERROR_SUCCESS) {
+    RegCloseKey(key);
+    CrashReporter::AppendAppNotesToCrashReport("Cisco VPN\n"_ns);
+  }
+}
+
+void GfxInfo::AddCrashReportAnnotations() {
+  AssertNotWin32kLockdown();
+
+  CheckForCiscoVPN();
+
+  if (mHasDriverVersionMismatch) {
+    CrashReporter::AppendAppNotesToCrashReport("DriverVersionMismatch\n"_ns);
+  }
+
+  nsString deviceID, vendorID, driverVersion, subsysID;
+  nsCString narrowDeviceID, narrowVendorID, narrowDriverVersion, narrowSubsysID;
+
+  GetAdapterDeviceID(deviceID);
+  CopyUTF16toUTF8(deviceID, narrowDeviceID);
+  GetAdapterVendorID(vendorID);
+  CopyUTF16toUTF8(vendorID, narrowVendorID);
+  GetAdapterDriverVersion(driverVersion);
+  CopyUTF16toUTF8(driverVersion, narrowDriverVersion);
+  GetAdapterSubsysID(subsysID);
+  CopyUTF16toUTF8(subsysID, narrowSubsysID);
+
+  CrashReporter::AnnotateCrashReport(CrashReporter::Annotation::AdapterVendorID,
+                                     narrowVendorID);
+  CrashReporter::AnnotateCrashReport(CrashReporter::Annotation::AdapterDeviceID,
+                                     narrowDeviceID);
+  CrashReporter::AnnotateCrashReport(
+      CrashReporter::Annotation::AdapterDriverVersion, narrowDriverVersion);
+  CrashReporter::AnnotateCrashReport(CrashReporter::Annotation::AdapterSubsysID,
+                                     narrowSubsysID);
+
+  /* Add an App Note, this contains extra information. */
+  nsAutoCString note;
+
+  // TODO: We should probably convert this into a proper annotation
+  if (vendorID == GfxDriverInfo::GetDeviceVendor(DeviceVendor::All)) {
+    /* if we didn't find a valid vendorID lets append the mDeviceID string to
+     * try to find out why */
+    LossyAppendUTF16toASCII(mDeviceID[mActiveGPUIndex], note);
+    note.AppendLiteral(", ");
+    LossyAppendUTF16toASCII(mDeviceKeyDebug, note);
+  }
+  note.AppendLiteral("\n");
+
+  if (mHasDualGPU) {
+    nsString deviceID2, vendorID2, subsysID2;
+    nsAutoString adapterDriverVersionString2;
+    nsCString narrowDeviceID2, narrowVendorID2, narrowSubsysID2;
+
+    // Make a slight difference between the two cases so that we
+    // can see it in the crash reports.  It may come in handy.
+    if (mActiveGPUIndex == 1) {
+      note.AppendLiteral("Has dual GPUs. GPU-#2: ");
+    } else {
+      note.AppendLiteral("Has dual GPUs. GPU #2: ");
+    }
+    GetAdapterDeviceID2(deviceID2);
+    CopyUTF16toUTF8(deviceID2, narrowDeviceID2);
+    GetAdapterVendorID2(vendorID2);
+    CopyUTF16toUTF8(vendorID2, narrowVendorID2);
+    GetAdapterDriverVersion2(adapterDriverVersionString2);
+    GetAdapterSubsysID(subsysID2);
+    CopyUTF16toUTF8(subsysID2, narrowSubsysID2);
+    note.AppendLiteral("AdapterVendorID2: ");
+    note.Append(narrowVendorID2);
+    note.AppendLiteral(", AdapterDeviceID2: ");
+    note.Append(narrowDeviceID2);
+    note.AppendLiteral(", AdapterSubsysID2: ");
+    note.Append(narrowSubsysID2);
+    note.AppendLiteral(", AdapterDriverVersion2: ");
+    note.Append(NS_LossyConvertUTF16toASCII(adapterDriverVersionString2));
+  }
+  CrashReporter::AppendAppNotesToCrashReport(note);
+}
+
+static OperatingSystem WindowsVersionToOperatingSystem(
+    int32_t aWindowsVersion) {
+  switch (aWindowsVersion) {
+    case kWindows7:
+      return OperatingSystem::Windows7;
+    case kWindows8:
+      return OperatingSystem::Windows8;
+    case kWindows8_1:
+      return OperatingSystem::Windows8_1;
+    case kWindows10:
+      return OperatingSystem::Windows10;
+    case kWindowsUnknown:
+    default:
+      return OperatingSystem::Unknown;
+  }
+}
+
+// Return true if the CPU supports AVX, but the operating system does not.
+#if defined(_M_X64)
+static inline bool DetectBrokenAVX() {
+  int regs[4];
+  __cpuid(regs, 0);
+  if (regs[0] == 0) {
+    // Level not supported.
+    return false;
+  }
+
+  __cpuid(regs, 1);
+
+  const unsigned AVX = 1u << 28;
+  const unsigned XSAVE = 1u << 26;
+  if ((regs[2] & (AVX | XSAVE)) != (AVX | XSAVE)) {
+    // AVX is not supported on this CPU.
+    return false;
+  }
+
+  const unsigned OSXSAVE = 1u << 27;
+  if ((regs[2] & OSXSAVE) != OSXSAVE) {
+    // AVX is supported, but the OS didn't enable it.
+    // This can be forced via bcdedit /set xsavedisable 1.
+    return true;
+  }
+
+  const unsigned AVX_CTRL_BITS = (1 << 1) | (1 << 2);
+  return (xgetbv(0) & AVX_CTRL_BITS) != AVX_CTRL_BITS;
+}
+#endif
+
+const nsTArray<GfxDriverInfo>& GfxInfo::GetGfxDriverInfo() {
+  if (!sDriverInfo->Length()) {
+    /*
+     * It should be noted here that more specialized rules on certain features
+     * should be inserted -before- more generalized restriction. As the first
+     * match for feature/OS/device found in the list will be used for the final
+     * blocklisting call.
+     */
+
+    /*
+     * NVIDIA entries
+     */
+    /*
+     * The last 5 digit of the NVIDIA driver version maps to the version that
+     * NVIDIA uses. The minor version (15, 16, 17) corresponds roughtly to the
+     * OS (Vista, Win7, Win7) but they show up in smaller numbers across all
+     * OS versions (perhaps due to OS upgrades). So we want to support
+     * October 2009+ drivers across all these minor versions.
+     *
+     * 187.45 (late October 2009) and earlier contain a bug which can cause us
+     * to crash on shutdown.
+     */
+    APPEND_TO_DRIVER_BLOCKLIST(
+        OperatingSystem::Windows7, DeviceFamily::NvidiaAll,
+        GfxDriverInfo::optionalFeatures,
+        nsIGfxInfo::FEATURE_BLOCKED_DRIVER_VERSION, DRIVER_LESS_THAN_OR_EQUAL,
+        V(8, 15, 11, 8745), "FEATURE_FAILURE_NV_W7_15",
+        "nVidia driver > 187.45");
+    APPEND_TO_DRIVER_BLOCKLIST_RANGE(
+        OperatingSystem::Windows7, DeviceFamily::NvidiaAll,
+        GfxDriverInfo::optionalFeatures,
+        nsIGfxInfo::FEATURE_BLOCKED_DRIVER_VERSION,
+        DRIVER_BETWEEN_INCLUSIVE_START, V(8, 16, 10, 0000), V(8, 16, 11, 8745),
+        "FEATURE_FAILURE_NV_W7_16", "nVidia driver > 187.45");
+    // Telemetry doesn't show any driver in this range so it might not even be
+    // required.
+    APPEND_TO_DRIVER_BLOCKLIST_RANGE(
+        OperatingSystem::Windows7, DeviceFamily::NvidiaAll,
+        GfxDriverInfo::optionalFeatures,
+        nsIGfxInfo::FEATURE_BLOCKED_DRIVER_VERSION,
+        DRIVER_BETWEEN_INCLUSIVE_START, V(8, 17, 10, 0000), V(8, 17, 11, 8745),
+        "FEATURE_FAILURE_NV_W7_17", "nVidia driver > 187.45");
+
+    /*
+     * AMD/ATI entries. 8.56.1.15 is the driver that shipped with Windows 7 RTM
+     */
+    APPEND_TO_DRIVER_BLOCKLIST(OperatingSystem::Windows, DeviceFamily::AtiAll,
+                               GfxDriverInfo::optionalFeatures,
+                               nsIGfxInfo::FEATURE_BLOCKED_DRIVER_VERSION,
+                               DRIVER_LESS_THAN, V(8, 56, 1, 15),
+                               "FEATURE_FAILURE_AMD1", "8.56.1.15");
+
+    // Bug 1099252
+    APPEND_TO_DRIVER_BLOCKLIST2(OperatingSystem::Windows7, DeviceFamily::AtiAll,
+                                GfxDriverInfo::optionalFeatures,
+                                nsIGfxInfo::FEATURE_BLOCKED_DRIVER_VERSION,
+                                DRIVER_EQUAL, V(8, 832, 0, 0),
+                                "FEATURE_FAILURE_BUG_1099252");
+
+    // Bug 1118695
+    APPEND_TO_DRIVER_BLOCKLIST2(OperatingSystem::Windows7, DeviceFamily::AtiAll,
+                                GfxDriverInfo::optionalFeatures,
+                                nsIGfxInfo::FEATURE_BLOCKED_DRIVER_VERSION,
+                                DRIVER_EQUAL, V(8, 783, 2, 2000),
+                                "FEATURE_FAILURE_BUG_1118695");
+
+    // Bug 1587155
+    //
+    // There are a several reports of strange rendering corruptions with this
+    // driver version, with and without webrender. We weren't able to
+    // reproduce these problems, but the users were able to update their
+    // drivers and it went away. So just to be safe, let's blocklist all
+    // gpu use with this particular (very old) driver, restricted
+    // to Win10 since we only have reports from that platform.
+    APPEND_TO_DRIVER_BLOCKLIST2(
+        OperatingSystem::Windows10, DeviceFamily::AtiAll,
+        GfxDriverInfo::optionalFeatures,
+        nsIGfxInfo::FEATURE_BLOCKED_DRIVER_VERSION, DRIVER_EQUAL,
+        V(22, 19, 162, 4), "FEATURE_FAILURE_BUG_1587155");
+
+    // Bug 1829487 - Work around a gen6 driver bug that miscompiles shaders
+    // resulting
+    //               in black squares. Disabling shader optimization pass
+    //               appears to work around this for now.
+    APPEND_TO_DRIVER_BLOCKLIST2(
+        OperatingSystem::Windows, DeviceFamily::IntelSandyBridge,
+        nsIGfxInfo::FEATURE_WEBRENDER_OPTIMIZED_SHADERS,
+        nsIGfxInfo::FEATURE_BLOCKED_DEVICE, DRIVER_LESS_THAN,
+        GfxDriverInfo::allDriverVersions, "FEATURE_FAILURE_BUG_1829487");
+
+    // Bug 1198815
+    APPEND_TO_DRIVER_BLOCKLIST_RANGE(
+        OperatingSystem::Windows, DeviceFamily::AtiAll,
+        nsIGfxInfo::FEATURE_HARDWARE_VIDEO_DECODING,
+        nsIGfxInfo::FEATURE_BLOCKED_DRIVER_VERSION, DRIVER_BETWEEN_INCLUSIVE,
+        V(15, 200, 0, 0), V(15, 200, 1062, 1004), "FEATURE_FAILURE_BUG_1198815",
+        "15.200.0.0-15.200.1062.1004");
+
+    // Bug 1267970
+    APPEND_TO_DRIVER_BLOCKLIST_RANGE(
+        OperatingSystem::Windows10, DeviceFamily::AtiAll,
+        nsIGfxInfo::FEATURE_HARDWARE_VIDEO_DECODING,
+        nsIGfxInfo::FEATURE_BLOCKED_DRIVER_VERSION, DRIVER_BETWEEN_INCLUSIVE,
+        V(15, 200, 0, 0), V(15, 301, 2301, 1002), "FEATURE_FAILURE_BUG_1267970",
+        "15.200.0.0-15.301.2301.1002");
+    APPEND_TO_DRIVER_BLOCKLIST_RANGE(
+        OperatingSystem::Windows10, DeviceFamily::AtiAll,
+        nsIGfxInfo::FEATURE_HARDWARE_VIDEO_DECODING,
+        nsIGfxInfo::FEATURE_BLOCKED_DRIVER_VERSION, DRIVER_BETWEEN_INCLUSIVE,
+        V(16, 100, 0, 0), V(16, 300, 2311, 0), "FEATURE_FAILURE_BUG_1267970",
+        "16.100.0.0-16.300.2311.0");
+
+    /*
+     * Bug 783517 - crashes in AMD driver on Windows 8
+     */
+    APPEND_TO_DRIVER_BLOCKLIST_RANGE(
+        OperatingSystem::Windows8, DeviceFamily::AtiAll,
+        GfxDriverInfo::optionalFeatures,
+        nsIGfxInfo::FEATURE_BLOCKED_DRIVER_VERSION,
+        DRIVER_BETWEEN_INCLUSIVE_START, V(8, 982, 0, 0), V(8, 983, 0, 0),
+        "FEATURE_FAILURE_BUG_783517_AMD", "!= 8.982.*.*");
+
+    /*
+     *  Bug 1599981 - crashes in AMD driver on Windows 10
+     */
+    APPEND_TO_DRIVER_BLOCKLIST2(
+        OperatingSystem::Windows10, DeviceFamily::RadeonCaicos,
+        nsIGfxInfo::FEATURE_DIRECT3D_11_LAYERS,
+        nsIGfxInfo::FEATURE_BLOCKED_DRIVER_VERSION, DRIVER_LESS_THAN,
+        V(15, 301, 1901, 0), "FEATURE_FAILURE_BUG_1599981");
+
+    /* OpenGL on any ATI/AMD hardware is discouraged
+     * See:
+     *  bug 619773 - WebGL: Crash with blue screen : "NMI: Parity Check / Memory
+     * Parity Error" bugs 584403, 584404, 620924 - crashes in atioglxx
+     *  + many complaints about incorrect rendering
+     */
+    APPEND_TO_DRIVER_BLOCKLIST2(
+        OperatingSystem::Windows, DeviceFamily::AtiAll,
+        nsIGfxInfo::FEATURE_OPENGL_LAYERS, nsIGfxInfo::FEATURE_DISCOURAGED,
+        DRIVER_LESS_THAN, GfxDriverInfo::allDriverVersions,
+        "FEATURE_FAILURE_OGL_ATI_DIS");
+
+/*
+ * Intel entries
+ */
+
+/* The driver versions used here come from bug 594877. They might not
+ * be particularly relevant anymore.
+ */
+#define IMPLEMENT_INTEL_DRIVER_BLOCKLIST(winVer, devFamily, driverVer, ruleId) \
+  APPEND_TO_DRIVER_BLOCKLIST2(winVer, devFamily,                               \
+                              GfxDriverInfo::optionalFeatures,                 \
+                              nsIGfxInfo::FEATURE_BLOCKED_DRIVER_VERSION,      \
+                              DRIVER_LESS_THAN, driverVer, ruleId)
+
+#define IMPLEMENT_INTEL_DRIVER_BLOCKLIST_D2D(winVer, devFamily, driverVer,     \
+                                             ruleId)                           \
+  APPEND_TO_DRIVER_BLOCKLIST2(winVer, devFamily, nsIGfxInfo::FEATURE_DIRECT2D, \
+                              nsIGfxInfo::FEATURE_BLOCKED_DRIVER_VERSION,      \
+                              DRIVER_BUILD_ID_LESS_THAN, driverVer, ruleId)
+
+    IMPLEMENT_INTEL_DRIVER_BLOCKLIST_D2D(OperatingSystem::Windows7,
+                                         DeviceFamily::IntelGMA500, 2026,
+                                         "FEATURE_FAILURE_594877_7");
+    IMPLEMENT_INTEL_DRIVER_BLOCKLIST_D2D(
+        OperatingSystem::Windows7, DeviceFamily::IntelGMA900,
+        GfxDriverInfo::allDriverVersions, "FEATURE_FAILURE_594877_8");
+    IMPLEMENT_INTEL_DRIVER_BLOCKLIST_D2D(OperatingSystem::Windows7,
+                                         DeviceFamily::IntelGMA950, 1930,
+                                         "FEATURE_FAILURE_594877_9");
+    IMPLEMENT_INTEL_DRIVER_BLOCKLIST_D2D(OperatingSystem::Windows7,
+                                         DeviceFamily::IntelGMA3150, 2117,
+                                         "FEATURE_FAILURE_594877_10");
+    IMPLEMENT_INTEL_DRIVER_BLOCKLIST_D2D(OperatingSystem::Windows7,
+                                         DeviceFamily::IntelGMAX3000, 1930,
+                                         "FEATURE_FAILURE_594877_11");
+    IMPLEMENT_INTEL_DRIVER_BLOCKLIST_D2D(
+        OperatingSystem::Windows7, DeviceFamily::IntelHDGraphicsToSandyBridge,
+        2202, "FEATURE_FAILURE_594877_12");
+
+    /* Disable Direct2D on Intel GMAX4500 devices because of rendering
+     * corruption discovered in bug 1180379. These seems to affect even the most
+     * recent drivers. We're black listing all of the devices to be safe even
+     * though we've only confirmed the issue on the G45
+     */
+    APPEND_TO_DRIVER_BLOCKLIST2(
+        OperatingSystem::Windows, DeviceFamily::IntelGMAX4500HD,
+        nsIGfxInfo::FEATURE_DIRECT2D, nsIGfxInfo::FEATURE_BLOCKED_DEVICE,
+        DRIVER_LESS_THAN, GfxDriverInfo::allDriverVersions,
+        "FEATURE_FAILURE_1180379");
+
+    IMPLEMENT_INTEL_DRIVER_BLOCKLIST(
+        OperatingSystem::Windows7, DeviceFamily::IntelGMA500, V(5, 0, 0, 2026),
+        "FEATURE_FAILURE_INTEL_16");
+    IMPLEMENT_INTEL_DRIVER_BLOCKLIST(
+        OperatingSystem::Windows7, DeviceFamily::IntelGMA900,
+        GfxDriverInfo::allDriverVersions, "FEATURE_FAILURE_INTEL_17");
+    IMPLEMENT_INTEL_DRIVER_BLOCKLIST(
+        OperatingSystem::Windows7, DeviceFamily::IntelGMA950,
+        V(8, 15, 10, 1930), "FEATURE_FAILURE_INTEL_18");
+    IMPLEMENT_INTEL_DRIVER_BLOCKLIST(
+        OperatingSystem::Windows7, DeviceFamily::IntelGMA3150,
+        V(8, 14, 10, 1972), "FEATURE_FAILURE_INTEL_19");
+    IMPLEMENT_INTEL_DRIVER_BLOCKLIST(
+        OperatingSystem::Windows7, DeviceFamily::IntelGMAX3000,
+        V(7, 15, 10, 1666), "FEATURE_FAILURE_INTEL_20");
+    IMPLEMENT_INTEL_DRIVER_BLOCKLIST(
+        OperatingSystem::Windows7, DeviceFamily::IntelGMAX4500HD,
+        V(7, 15, 10, 1666), "FEATURE_FAILURE_INTEL_21");
+    IMPLEMENT_INTEL_DRIVER_BLOCKLIST(
+        OperatingSystem::Windows7, DeviceFamily::IntelHDGraphicsToSandyBridge,
+        V(7, 15, 10, 1666), "FEATURE_FAILURE_INTEL_22");
+
+    // Bug 1074378
+    APPEND_TO_DRIVER_BLOCKLIST(
+        OperatingSystem::Windows7, DeviceFamily::IntelGMAX4500HD,
+        GfxDriverInfo::optionalFeatures,
+        nsIGfxInfo::FEATURE_BLOCKED_DRIVER_VERSION, DRIVER_EQUAL,
+        V(8, 15, 10, 1749), "FEATURE_FAILURE_BUG_1074378_1", "8.15.10.2342");
+    APPEND_TO_DRIVER_BLOCKLIST(
+        OperatingSystem::Windows7, DeviceFamily::IntelHDGraphicsToSandyBridge,
+        GfxDriverInfo::optionalFeatures,
+        nsIGfxInfo::FEATURE_BLOCKED_DRIVER_VERSION, DRIVER_EQUAL,
+        V(8, 15, 10, 1749), "FEATURE_FAILURE_BUG_1074378_2", "8.15.10.2342");
+
+    /* OpenGL on any Intel hardware is discouraged */
+    APPEND_TO_DRIVER_BLOCKLIST2(
+        OperatingSystem::Windows, DeviceFamily::IntelAll,
+        nsIGfxInfo::FEATURE_OPENGL_LAYERS, nsIGfxInfo::FEATURE_DISCOURAGED,
+        DRIVER_LESS_THAN, GfxDriverInfo::allDriverVersions,
+        "FEATURE_FAILURE_INTEL_OGL_DIS");
+
+    /**
+     * Disable acceleration on Intel HD 3000 for graphics drivers
+     * <= 8.15.10.2321. See bug 1018278 and bug 1060736.
+     */
+    APPEND_TO_DRIVER_BLOCKLIST(OperatingSystem::Windows,
+                               DeviceFamily::IntelSandyBridge,
+                               GfxDriverInfo::optionalFeatures,
+                               nsIGfxInfo::FEATURE_BLOCKED_DRIVER_VERSION,
+                               DRIVER_BUILD_ID_LESS_THAN_OR_EQUAL, 2321,
+                               "FEATURE_FAILURE_BUG_1018278", "X.X.X.2342");
+
+    /**
+     * Disable D2D on Win7 on Intel Haswell for graphics drivers build id <=
+     * 4578. See bug 1432610
+     */
+    APPEND_TO_DRIVER_BLOCKLIST2(OperatingSystem::Windows7,
+                                DeviceFamily::IntelHaswell,
+                                nsIGfxInfo::FEATURE_DIRECT2D,
+                                nsIGfxInfo::FEATURE_BLOCKED_DRIVER_VERSION,
+                                DRIVER_BUILD_ID_LESS_THAN_OR_EQUAL, 4578,
+                                "FEATURE_FAILURE_BUG_1432610");
+    /**
+     * Disable VP8 HW decoding on Windows 8.1 on Intel Haswel and a certain
+     * driver version. See bug 1760464 comment 6 and bug 1761332.
+     */
+    APPEND_TO_DRIVER_BLOCKLIST2(
+        OperatingSystem::Windows8_1, DeviceFamily::IntelHaswell,
+        nsIGfxInfo::FEATURE_VP8_HW_DECODE, nsIGfxInfo::FEATURE_BLOCKED_DEVICE,
+        DRIVER_LESS_THAN, GfxDriverInfo::allDriverVersions,
+        "FEATURE_FAILURE_BUG_1760464");
+
+    APPEND_TO_DRIVER_BLOCKLIST2(
+        OperatingSystem::Windows8_1, DeviceFamily::IntelAll,
+        nsIGfxInfo::FEATURE_VP8_HW_DECODE, nsIGfxInfo::FEATURE_BLOCKED_DEVICE,
+        DRIVER_EQUAL, V(10, 18, 14, 4264), "FEATURE_FAILURE_BUG_1761332");
+
+    /* Disable D2D on Win7 on Intel HD Graphics on driver <= 8.15.10.2302
+     * See bug 806786
+     */
+    APPEND_TO_DRIVER_BLOCKLIST2(
+        OperatingSystem::Windows7, DeviceFamily::IntelMobileHDGraphics,
+        nsIGfxInfo::FEATURE_DIRECT2D,
+        nsIGfxInfo::FEATURE_BLOCKED_DRIVER_VERSION, DRIVER_LESS_THAN_OR_EQUAL,
+        V(8, 15, 10, 2302), "FEATURE_FAILURE_BUG_806786");
+
+    /* Disable D2D on Win8 on Intel HD Graphics on driver <= 8.15.10.2302
+     * See bug 804144 and 863683
+     */
+    APPEND_TO_DRIVER_BLOCKLIST2(
+        OperatingSystem::Windows8, DeviceFamily::IntelMobileHDGraphics,
+        nsIGfxInfo::FEATURE_DIRECT2D,
+        nsIGfxInfo::FEATURE_BLOCKED_DRIVER_VERSION, DRIVER_LESS_THAN_OR_EQUAL,
+        V(8, 15, 10, 2302), "FEATURE_FAILURE_BUG_804144");
+
+    /* Disable D2D on Win7 on Intel HD Graphics on driver == 8.15.10.2418
+     * See bug 1433790
+     */
+    APPEND_TO_DRIVER_BLOCKLIST2(
+        OperatingSystem::Windows7, DeviceFamily::IntelHDGraphicsToSandyBridge,
+        nsIGfxInfo::FEATURE_DIRECT2D,
+        nsIGfxInfo::FEATURE_BLOCKED_DRIVER_VERSION, DRIVER_EQUAL,
+        V(8, 15, 10, 2418), "FEATURE_FAILURE_BUG_1433790");
+
+    /* Disable D3D11 layers on Intel G41 express graphics and Intel GM965, Intel
+     * X3100, for causing device resets. See bug 1116812.
+     */
+    APPEND_TO_DRIVER_BLOCKLIST2(
+        OperatingSystem::Windows, DeviceFamily::Bug1116812,
+        nsIGfxInfo::FEATURE_DIRECT3D_11_LAYERS,
+        nsIGfxInfo::FEATURE_BLOCKED_DEVICE, DRIVER_LESS_THAN,
+        GfxDriverInfo::allDriverVersions, "FEATURE_FAILURE_BUG_1116812");
+
+    /* Disable D3D11 layers on Intel GMA 3150 for failing to allocate a shared
+     * handle for textures. See bug 1207665. Additionally block D2D so we don't
+     * accidentally use WARP.
+     */
+    APPEND_TO_DRIVER_BLOCKLIST2(
+        OperatingSystem::Windows, DeviceFamily::Bug1207665,
+        nsIGfxInfo::FEATURE_DIRECT3D_11_LAYERS,
+        nsIGfxInfo::FEATURE_BLOCKED_DEVICE, DRIVER_LESS_THAN,
+        GfxDriverInfo::allDriverVersions, "FEATURE_FAILURE_BUG_1207665_1");
+    APPEND_TO_DRIVER_BLOCKLIST2(
+        OperatingSystem::Windows, DeviceFamily::Bug1207665,
+        nsIGfxInfo::FEATURE_DIRECT2D, nsIGfxInfo::FEATURE_BLOCKED_DEVICE,
+        DRIVER_LESS_THAN, GfxDriverInfo::allDriverVersions,
+        "FEATURE_FAILURE_BUG_1207665_2");
+
+    APPEND_TO_DRIVER_BLOCKLIST2(
+        OperatingSystem::Windows10, DeviceFamily::QualcommAll,
+        nsIGfxInfo::FEATURE_DIRECT2D,
+        nsIGfxInfo::FEATURE_BLOCKED_DRIVER_VERSION, DRIVER_LESS_THAN,
+        GfxDriverInfo::allDriverVersions, "FEATURE_FAILURE_QUALCOMM");
+
+    // Bug 1548410. Disable hardware accelerated video decoding on
+    // Qualcomm drivers used on Windows on ARM64 which are known to
+    // cause BSOD's and output suprious green frames while decoding video.
+    // Bug 1592826 expands the blocklist.
+    APPEND_TO_DRIVER_BLOCKLIST2(
+        OperatingSystem::Windows10, DeviceFamily::QualcommAll,
+        nsIGfxInfo::FEATURE_HARDWARE_VIDEO_DECODING,
+        nsIGfxInfo::FEATURE_BLOCKED_DRIVER_VERSION, DRIVER_LESS_THAN_OR_EQUAL,
+        V(25, 18, 10440, 0), "FEATURE_FAILURE_BUG_1592826");
+
+    /* Disable D2D on AMD Catalyst 14.4 until 14.6
+     * See bug 984488
+     */
+    APPEND_TO_DRIVER_BLOCKLIST_RANGE(
+        OperatingSystem::Windows, DeviceFamily::AtiAll,
+        nsIGfxInfo::FEATURE_DIRECT2D,
+        nsIGfxInfo::FEATURE_BLOCKED_DRIVER_VERSION,
+        DRIVER_BETWEEN_INCLUSIVE_START, V(14, 1, 0, 0), V(14, 2, 0, 0),
+        "FEATURE_FAILURE_BUG_984488_1", "ATI Catalyst 14.6+");
+
+    /* Disable D3D9 layers on NVIDIA 6100/6150/6200 series due to glitches
+     * whilst scrolling. See bugs: 612007, 644787 & 645872.
+     */
+    APPEND_TO_DRIVER_BLOCKLIST2(
+        OperatingSystem::Windows, DeviceFamily::NvidiaBlockD3D9Layers,
+        nsIGfxInfo::FEATURE_DIRECT3D_9_LAYERS,
+        nsIGfxInfo::FEATURE_BLOCKED_DEVICE, DRIVER_LESS_THAN,
+        GfxDriverInfo::allDriverVersions, "FEATURE_FAILURE_BUG_612007");
+
+    /* Microsoft RemoteFX; blocked less than 6.2.0.0 */
+    APPEND_TO_DRIVER_BLOCKLIST(
+        OperatingSystem::Windows, DeviceFamily::MicrosoftAll,
+        GfxDriverInfo::optionalFeatures,
+        nsIGfxInfo::FEATURE_BLOCKED_DRIVER_VERSION, DRIVER_LESS_THAN,
+        V(6, 2, 0, 0), "< 6.2.0.0", "FEATURE_FAILURE_REMOTE_FX");
+
+    /* Bug 1008759: Optimus (NVidia) crash.  Disable D2D on NV 310M. */
+    APPEND_TO_DRIVER_BLOCKLIST2(
+        OperatingSystem::Windows, DeviceFamily::Nvidia310M,
+        nsIGfxInfo::FEATURE_DIRECT2D, nsIGfxInfo::FEATURE_BLOCKED_DEVICE,
+        DRIVER_LESS_THAN, GfxDriverInfo::allDriverVersions,
+        "FEATURE_FAILURE_BUG_1008759");
+
+    /* Bug 1139503: DXVA crashes with ATI cards on windows 10. */
+    APPEND_TO_DRIVER_BLOCKLIST2(
+        OperatingSystem::Windows10, DeviceFamily::AtiAll,
+        nsIGfxInfo::FEATURE_HARDWARE_VIDEO_DECODING,
+        nsIGfxInfo::FEATURE_BLOCKED_DRIVER_VERSION, DRIVER_EQUAL,
+        V(15, 200, 1006, 0), "FEATURE_FAILURE_BUG_1139503");
+
+    /* Bug 1213107: D3D9 crashes with ATI cards on Windows 7. */
+    APPEND_TO_DRIVER_BLOCKLIST_RANGE(
+        OperatingSystem::Windows7, DeviceFamily::AtiAll,
+        nsIGfxInfo::FEATURE_HARDWARE_VIDEO_DECODING,
+        nsIGfxInfo::FEATURE_BLOCKED_DRIVER_VERSION, DRIVER_BETWEEN_INCLUSIVE,
+        V(8, 861, 0, 0), V(8, 862, 6, 5000), "FEATURE_FAILURE_BUG_1213107_1",
+        "Radeon driver > 8.862.6.5000");
+    APPEND_TO_DRIVER_BLOCKLIST_RANGE(
+        OperatingSystem::Windows7, DeviceFamily::AtiAll,
+        nsIGfxInfo::FEATURE_WEBGL_ANGLE,
+        nsIGfxInfo::FEATURE_BLOCKED_DRIVER_VERSION, DRIVER_BETWEEN_INCLUSIVE,
+        V(8, 861, 0, 0), V(8, 862, 6, 5000), "FEATURE_FAILURE_BUG_1213107_2",
+        "Radeon driver > 8.862.6.5000");
+
+    /* This may not be needed at all */
+    APPEND_TO_DRIVER_BLOCKLIST2(
+        OperatingSystem::Windows7, DeviceFamily::Bug1155608,
+        nsIGfxInfo::FEATURE_HARDWARE_VIDEO_DECODING,
+        nsIGfxInfo::FEATURE_BLOCKED_DRIVER_VERSION, DRIVER_LESS_THAN,
+        V(8, 15, 10, 2869), "FEATURE_FAILURE_INTEL_W7_HW_DECODING");
+
+    /* Bug 1203199/1092166: DXVA startup crashes on some intel drivers. */
+    APPEND_TO_DRIVER_BLOCKLIST_RANGE(
+        OperatingSystem::Windows, DeviceFamily::IntelAll,
+        nsIGfxInfo::FEATURE_HARDWARE_VIDEO_DECODING,
+        nsIGfxInfo::FEATURE_BLOCKED_DRIVER_VERSION, DRIVER_BETWEEN_INCLUSIVE,
+        V(9, 17, 10, 0), V(9, 17, 10, 2849), "FEATURE_FAILURE_BUG_1203199_1",
+        "Intel driver > 9.17.10.2849");
+
+    APPEND_TO_DRIVER_BLOCKLIST2(
+        OperatingSystem::Windows, DeviceFamily::Nvidia8800GTS,
+        nsIGfxInfo::FEATURE_HARDWARE_VIDEO_DECODING,
+        nsIGfxInfo::FEATURE_BLOCKED_DRIVER_VERSION, DRIVER_EQUAL,
+        V(9, 18, 13, 4052), "FEATURE_FAILURE_BUG_1203199_2");
+
+    /* Bug 1137716: XXX this should really check for the matching Intel piece as
+     * well. Unfortunately, we don't have the infrastructure to do that */
+    APPEND_TO_DRIVER_BLOCKLIST_RANGE_GPU2(
+        OperatingSystem::Windows7, DeviceFamily::Bug1137716,
+        GfxDriverInfo::optionalFeatures,
+        nsIGfxInfo::FEATURE_BLOCKED_DRIVER_VERSION, DRIVER_BETWEEN_INCLUSIVE,
+        V(8, 17, 12, 5730), V(8, 17, 12, 6901), "FEATURE_FAILURE_BUG_1137716",
+        "Nvidia driver > 8.17.12.6901");
+
+    /* Bug 1336710: Crash in rx::Blit9::initialize. */
+    APPEND_TO_DRIVER_BLOCKLIST2(
+        OperatingSystem::WindowsXP, DeviceFamily::IntelGMAX4500HD,
+        nsIGfxInfo::FEATURE_WEBGL_ANGLE, nsIGfxInfo::FEATURE_BLOCKED_DEVICE,
+        DRIVER_LESS_THAN, GfxDriverInfo::allDriverVersions,
+        "FEATURE_FAILURE_BUG_1336710");
+
+    APPEND_TO_DRIVER_BLOCKLIST2(
+        OperatingSystem::WindowsXP, DeviceFamily::IntelHDGraphicsToSandyBridge,
+        nsIGfxInfo::FEATURE_WEBGL_ANGLE, nsIGfxInfo::FEATURE_BLOCKED_DEVICE,
+        DRIVER_LESS_THAN, GfxDriverInfo::allDriverVersions,
+        "FEATURE_FAILURE_BUG_1336710");
+
+    /* Bug 1304360: Graphical artifacts with D3D9 on Windows 7. */
+    APPEND_TO_DRIVER_BLOCKLIST2(OperatingSystem::Windows7,
+                                DeviceFamily::IntelGMAX3000,
+                                nsIGfxInfo::FEATURE_DIRECT3D_9_LAYERS,
+                                nsIGfxInfo::FEATURE_BLOCKED_DRIVER_VERSION,
+                                DRIVER_BUILD_ID_LESS_THAN_OR_EQUAL, 1749,
+                                "FEATURE_FAILURE_INTEL_W7_D3D9_LAYERS");
+
+    /* Bug 1717519/1717911: Crashes while drawing with swgl.
+     * Reproducible but not investigated yet.*/
+    APPEND_TO_DRIVER_BLOCKLIST_RANGE(
+        OperatingSystem::Windows, DeviceFamily::IntelAll,
+        nsIGfxInfo::FEATURE_DIRECT3D_11_LAYERS,
+        nsIGfxInfo::FEATURE_BLOCKED_DRIVER_VERSION, DRIVER_BETWEEN_INCLUSIVE,
+        V(8, 15, 10, 2125), V(8, 15, 10, 2141), "FEATURE_FAILURE_BUG_1717911",
+        "Intel driver > 8.15.10.2141");
+
+#if defined(_M_X64)
+    if (DetectBrokenAVX()) {
+      APPEND_TO_DRIVER_BLOCKLIST2(
+          OperatingSystem::Windows7, DeviceFamily::IntelAll,
+          nsIGfxInfo::FEATURE_DIRECT3D_11_LAYERS,
+          nsIGfxInfo::FEATURE_BLOCKED_DRIVER_VERSION, DRIVER_LESS_THAN,
+          GfxDriverInfo::allDriverVersions, "FEATURE_FAILURE_BUG_1403353");
+    }
+#endif
+
+    ////////////////////////////////////
+    // WebGL
+
+    // Older than 5-15-2016
+    APPEND_TO_DRIVER_BLOCKLIST2(
+        OperatingSystem::Windows, DeviceFamily::AtiAll,
+        nsIGfxInfo::FEATURE_WEBGL_OPENGL, nsIGfxInfo::FEATURE_DISCOURAGED,
+        DRIVER_LESS_THAN, V(16, 200, 1010, 1002), "WEBGL_NATIVE_GL_OLD_AMD");
+
+    // Older than 11-18-2015
+    APPEND_TO_DRIVER_BLOCKLIST2(
+        OperatingSystem::Windows, DeviceFamily::IntelAll,
+        nsIGfxInfo::FEATURE_WEBGL_OPENGL, nsIGfxInfo::FEATURE_DISCOURAGED,
+        DRIVER_BUILD_ID_LESS_THAN, 4331, "WEBGL_NATIVE_GL_OLD_INTEL");
+
+    // Older than 2-23-2016
+    APPEND_TO_DRIVER_BLOCKLIST2(
+        OperatingSystem::Windows, DeviceFamily::NvidiaAll,
+        nsIGfxInfo::FEATURE_WEBGL_OPENGL, nsIGfxInfo::FEATURE_DISCOURAGED,
+        DRIVER_LESS_THAN, V(10, 18, 13, 6200), "WEBGL_NATIVE_GL_OLD_NVIDIA");
+
+    ////////////////////////////////////
+    // FEATURE_DX_INTEROP2
+
+    // All AMD.
+    APPEND_TO_DRIVER_BLOCKLIST2(
+        OperatingSystem::Windows, DeviceFamily::AtiAll,
+        nsIGfxInfo::FEATURE_DX_INTEROP2,
+        nsIGfxInfo::FEATURE_BLOCKED_DRIVER_VERSION, DRIVER_LESS_THAN,
+        GfxDriverInfo::allDriverVersions, "DX_INTEROP2_AMD_CRASH");
+
+    ////////////////////////////////////
+    // FEATURE_D3D11_KEYED_MUTEX
+
+    // bug 1359416
+    APPEND_TO_DRIVER_BLOCKLIST2(
+        OperatingSystem::Windows, DeviceFamily::IntelHDGraphicsToSandyBridge,
+        nsIGfxInfo::FEATURE_D3D11_KEYED_MUTEX,
+        nsIGfxInfo::FEATURE_BLOCKED_DEVICE, DRIVER_LESS_THAN,
+        GfxDriverInfo::allDriverVersions, "FEATURE_FAILURE_BUG_1359416");
+
+    // Bug 1447141, for causing device creation crashes.
+    APPEND_TO_DRIVER_BLOCKLIST2(
+        OperatingSystem::Windows7, DeviceFamily::Bug1447141,
+        GfxDriverInfo::optionalFeatures, nsIGfxInfo::FEATURE_BLOCKED_DEVICE,
+        DRIVER_EQUAL, V(15, 201, 2201, 0), "FEATURE_FAILURE_BUG_1447141_1");
+    APPEND_TO_DRIVER_BLOCKLIST2(
+        OperatingSystem::Windows7, DeviceFamily::Bug1447141,
+        GfxDriverInfo::optionalFeatures, nsIGfxInfo::FEATURE_BLOCKED_DEVICE,
+        DRIVER_EQUAL, V(15, 201, 1701, 0), "FEATURE_FAILURE_BUG_1447141_1");
+
+    // bug 1457758
+    APPEND_TO_DRIVER_BLOCKLIST2(
+        OperatingSystem::Windows, DeviceFamily::NvidiaAll,
+        GfxDriverInfo::optionalFeatures, nsIGfxInfo::FEATURE_BLOCKED_DEVICE,
+        DRIVER_EQUAL, V(24, 21, 13, 9731), "FEATURE_FAILURE_BUG_1457758");
+
+    ////////////////////////////////////
+    // FEATURE_DX_NV12
+
+    // Bug 1437334
+    APPEND_TO_DRIVER_BLOCKLIST2(
+        OperatingSystem::Windows, DeviceFamily::IntelHDGraphicsToSandyBridge,
+        nsIGfxInfo::FEATURE_DX_NV12, nsIGfxInfo::FEATURE_BLOCKED_DRIVER_VERSION,
+        DRIVER_BUILD_ID_LESS_THAN_OR_EQUAL, 4459,
+        "FEATURE_BLOCKED_DRIVER_VERSION");
+
+    ////////////////////////////////////
+    // FEATURE_DX_P010
+
+    APPEND_TO_DRIVER_BLOCKLIST2(
+        OperatingSystem::Windows, DeviceFamily::NvidiaAll,
+        nsIGfxInfo::FEATURE_DX_P010, nsIGfxInfo::FEATURE_BLOCKED_DEVICE,
+        DRIVER_LESS_THAN, GfxDriverInfo::allDriverVersions,
+        "FEATURE_UNQUALIFIED_P010_NVIDIA");
+
+    ////////////////////////////////////
+    // FEATURE_VIDEO_OVERLAY - ALLOWLIST
+#ifdef EARLY_BETA_OR_EARLIER
+    APPEND_TO_DRIVER_BLOCKLIST2(
+        OperatingSystem::Windows, DeviceFamily::All,
+        nsIGfxInfo::FEATURE_VIDEO_OVERLAY, nsIGfxInfo::FEATURE_ALLOW_ALWAYS,
+        DRIVER_COMPARISON_IGNORED, V(0, 0, 0, 0), "FEATURE_ROLLOUT_ALL");
+#else
+    APPEND_TO_DRIVER_BLOCKLIST2(
+        OperatingSystem::Windows, DeviceFamily::IntelAll,
+        nsIGfxInfo::FEATURE_VIDEO_OVERLAY, nsIGfxInfo::FEATURE_ALLOW_ALWAYS,
+        DRIVER_COMPARISON_IGNORED, V(0, 0, 0, 0), "FEATURE_ROLLOUT_INTEL");
+    APPEND_TO_DRIVER_BLOCKLIST2(
+        OperatingSystem::Windows, DeviceFamily::NvidiaAll,
+        nsIGfxInfo::FEATURE_VIDEO_OVERLAY, nsIGfxInfo::FEATURE_ALLOW_ALWAYS,
+        DRIVER_COMPARISON_IGNORED, V(0, 0, 0, 0), "FEATURE_ROLLOUT_NVIDIA");
+#endif
+
+    ////////////////////////////////////
+    // FEATURE_HW_DECODED_VIDEO_ZERO_COPY
+
+    APPEND_TO_DRIVER_BLOCKLIST_RANGE(
+        OperatingSystem::Windows10, DeviceFamily::IntelSkylake,
+        nsIGfxInfo::FEATURE_HW_DECODED_VIDEO_ZERO_COPY,
+        nsIGfxInfo::FEATURE_BLOCKED_DRIVER_VERSION, DRIVER_BETWEEN_INCLUSIVE,
+        V(20, 19, 15, 4285), V(20, 19, 15, 4390), "FEATURE_FAILURE_BUG_1763280",
+        "Intel driver 20.19.15.*");
+
+    APPEND_TO_DRIVER_BLOCKLIST_RANGE(
+        OperatingSystem::Windows10, DeviceFamily::IntelSkylake,
+        nsIGfxInfo::FEATURE_HW_DECODED_VIDEO_ZERO_COPY,
+        nsIGfxInfo::FEATURE_BLOCKED_DRIVER_VERSION, DRIVER_BETWEEN_INCLUSIVE,
+        V(10, 18, 15, 4256), V(10, 18, 15, 4293), "FEATURE_FAILURE_BUG_1763280",
+        "Intel driver 10.18.15.*");
+
+    APPEND_TO_DRIVER_BLOCKLIST2(
+        OperatingSystem::Windows10, DeviceFamily::IntelKabyLake,
+        nsIGfxInfo::FEATURE_HW_DECODED_VIDEO_ZERO_COPY,
+        nsIGfxInfo::FEATURE_BLOCKED_DRIVER_VERSION, DRIVER_LESS_THAN,
+        GfxDriverInfo::allDriverVersions, "FEATURE_FAILURE_BUG_1802357");
+
+    APPEND_TO_DRIVER_BLOCKLIST2(
+        OperatingSystem::Windows, DeviceFamily::NvidiaAll,
+        nsIGfxInfo::FEATURE_HW_DECODED_VIDEO_ZERO_COPY,
+        nsIGfxInfo::FEATURE_BLOCKED_DRIVER_VERSION, DRIVER_LESS_THAN,
+        V(21, 21, 13, 7576), "FEATURE_FAILURE_BUG_1767212");
+
+    APPEND_TO_DRIVER_BLOCKLIST2(OperatingSystem::Windows, DeviceFamily::AtiAll,
+                                nsIGfxInfo::FEATURE_HW_DECODED_VIDEO_ZERO_COPY,
+                                nsIGfxInfo::FEATURE_BLOCKED_DRIVER_VERSION,
+                                DRIVER_LESS_THAN, V(23, 20, 826, 5120),
+                                "FEATURE_FAILURE_BUG_1767212");
+
+    APPEND_TO_DRIVER_BLOCKLIST2(
+        OperatingSystem::Windows, DeviceFamily::RadeonBlockZeroVideoCopy,
+        nsIGfxInfo::FEATURE_HW_DECODED_VIDEO_ZERO_COPY,
+        nsIGfxInfo::FEATURE_BLOCKED_DRIVER_VERSION, DRIVER_LESS_THAN,
+        V(26, 20, 15000, 37), "FEATURE_FAILURE_BUG_1767212");
+
+    ////////////////////////////////////
+    // FEATURE_HW_DECODED_VIDEO_ZERO_COPY - ALLOWLIST
+
+    // XXX ZeroCopyNV12Texture is disabled with non-intel GPUs for now.
+    // See Bug 1798242
+    APPEND_TO_DRIVER_BLOCKLIST2(
+        OperatingSystem::Windows, DeviceFamily::IntelAll,
+        nsIGfxInfo::FEATURE_HW_DECODED_VIDEO_ZERO_COPY,
+        nsIGfxInfo::FEATURE_ALLOW_ALWAYS, DRIVER_COMPARISON_IGNORED,
+        V(0, 0, 0, 0), "FEATURE_ROLLOUT_ALL");
+
+    ////////////////////////////////////
+    // FEATURE_REUSE_DECODER_DEVICE
+
+    APPEND_TO_DRIVER_BLOCKLIST_RANGE(
+        OperatingSystem::Windows10, DeviceFamily::IntelSkylake,
+        nsIGfxInfo::FEATURE_REUSE_DECODER_DEVICE,
+        nsIGfxInfo::FEATURE_BLOCKED_DRIVER_VERSION, DRIVER_BETWEEN_INCLUSIVE,
+        V(20, 19, 15, 4285), V(20, 19, 15, 4390), "FEATURE_FAILURE_BUG_1833809",
+        "Intel driver 20.19.15.*");
+
+    APPEND_TO_DRIVER_BLOCKLIST_RANGE(
+        OperatingSystem::Windows10, DeviceFamily::IntelSkylake,
+        nsIGfxInfo::FEATURE_REUSE_DECODER_DEVICE,
+        nsIGfxInfo::FEATURE_BLOCKED_DRIVER_VERSION, DRIVER_BETWEEN_INCLUSIVE,
+        V(10, 18, 15, 4256), V(10, 18, 15, 4293), "FEATURE_FAILURE_BUG_1833809",
+        "Intel driver 10.18.15.*");
+
+    ////////////////////////////////////
+    // FEATURE_WEBRENDER
+    // Block 8.56.1.15/16
+    APPEND_TO_DRIVER_BLOCKLIST2(OperatingSystem::Windows, DeviceFamily::AtiAll,
+                                nsIGfxInfo::FEATURE_WEBRENDER,
+                                nsIGfxInfo::FEATURE_BLOCKED_DRIVER_VERSION,
+                                DRIVER_LESS_THAN_OR_EQUAL, V(8, 56, 1, 16),
+                                "CRASHY_DRIVERS_BUG_1678808");
+
+    // Shader compilation startup crashes with WebRender on Windows 7.
+    APPEND_TO_DRIVER_BLOCKLIST_RANGE(
+        OperatingSystem::Windows7, DeviceFamily::NvidiaAll,
+        nsIGfxInfo::FEATURE_WEBRENDER,
+        nsIGfxInfo::FEATURE_BLOCKED_DRIVER_VERSION, DRIVER_BETWEEN_INCLUSIVE,
+        V(8, 17, 12, 8019), V(8, 17, 12, 8026), "FEATURE_FAILURE_BUG_1709629",
+        "nVidia driver > 280.26");
+
+    APPEND_TO_DRIVER_BLOCKLIST2(
+        OperatingSystem::Windows, DeviceFamily::IntelWebRenderBlocked,
+        nsIGfxInfo::FEATURE_WEBRENDER, nsIGfxInfo::FEATURE_BLOCKED_DEVICE,
+        DRIVER_LESS_THAN, GfxDriverInfo::allDriverVersions,
+        "INTEL_DEVICE_GEN5_OR_OLDER");
+
+    APPEND_TO_DRIVER_BLOCKLIST2(
+        OperatingSystem::Windows, DeviceFamily::NvidiaWebRenderBlocked,
+        nsIGfxInfo::FEATURE_WEBRENDER, nsIGfxInfo::FEATURE_BLOCKED_DEVICE,
+        DRIVER_LESS_THAN, GfxDriverInfo::allDriverVersions, "EARLY_NVIDIA");
+
+    ////////////////////////////////////
+    // FEATURE_WEBRENDER_COMPOSITOR
+
+#ifndef EARLY_BETA_OR_EARLIER
+    // See also bug 1616874
+    APPEND_TO_DRIVER_BLOCKLIST2(
+        OperatingSystem::Windows, DeviceFamily::IntelAll,
+        nsIGfxInfo::FEATURE_WEBRENDER_COMPOSITOR,
+        nsIGfxInfo::FEATURE_BLOCKED_DEVICE, DRIVER_EQUAL, V(24, 20, 100, 6293),
+        "FEATURE_FAILURE_BUG_1602511");
+
+    APPEND_TO_DRIVER_BLOCKLIST2(OperatingSystem::Windows, DeviceFamily::AtiAll,
+                                nsIGfxInfo::FEATURE_WEBRENDER_COMPOSITOR,
+                                nsIGfxInfo::FEATURE_BLOCKED_DEVICE,
+                                DRIVER_LESS_THAN_OR_EQUAL, V(8, 17, 10, 1129),
+                                "FEATURE_FAILURE_CHROME_BUG_800950");
+#endif
+
+    // WebRender is unable to use scissored clears in some cases
+    APPEND_TO_DRIVER_BLOCKLIST2(
+        OperatingSystem::Windows, DeviceFamily::IntelAll,
+        nsIGfxInfo::FEATURE_WEBRENDER_SCISSORED_CACHE_CLEARS,
+        nsIGfxInfo::FEATURE_BLOCKED_DEVICE, DRIVER_COMPARISON_IGNORED,
+        V(0, 0, 0, 0), "FEATURE_FAILURE_BUG_1603515");
+
+    ////////////////////////////////////
+    // FEATURE_BACKDROP_FILTER
+
+    // Backdrop filter crashes the driver. See bug 1785366 and bug 1784093.
+    APPEND_TO_DRIVER_BLOCKLIST_RANGE(
+        OperatingSystem::Windows, DeviceFamily::IntelHDGraphicsToIvyBridge,
+        nsIGfxInfo::FEATURE_BACKDROP_FILTER,
+        nsIGfxInfo::FEATURE_BLOCKED_DRIVER_VERSION, DRIVER_BETWEEN_EXCLUSIVE,
+        V(8, 15, 10, 2879), V(10, 18, 10, 4425), "FEATURE_FAILURE_BUG_1785366",
+        "Intel driver >= 10.18.10.4425");
+  }
+  return *sDriverInfo;
+}
+
+OperatingSystem GfxInfo::GetOperatingSystem() {
+  return WindowsVersionToOperatingSystem(mWindowsVersion);
+}
+
+nsresult GfxInfo::GetFeatureStatusImpl(
+    int32_t aFeature, int32_t* aStatus, nsAString& aSuggestedDriverVersion,
+    const nsTArray<GfxDriverInfo>& aDriverInfo, nsACString& aFailureId,
+    OperatingSystem* aOS /* = nullptr */) {
+  AssertNotWin32kLockdown();
+
+  NS_ENSURE_ARG_POINTER(aStatus);
+  aSuggestedDriverVersion.SetIsVoid(true);
+  OperatingSystem os = WindowsVersionToOperatingSystem(mWindowsVersion);
+  *aStatus = nsIGfxInfo::FEATURE_STATUS_UNKNOWN;
+  if (aOS) *aOS = os;
+
+  if (sShutdownOccurred) {
+    return NS_OK;
+  }
+
+  // Don't evaluate special cases if we're checking the downloaded blocklist.
+  if (!aDriverInfo.Length()) {
+    nsAutoString adapterVendorID;
+    nsAutoString adapterDeviceID;
+    nsAutoString adapterDriverVersionString;
+    if (NS_FAILED(GetAdapterVendorID(adapterVendorID)) ||
+        NS_FAILED(GetAdapterDeviceID(adapterDeviceID)) ||
+        NS_FAILED(GetAdapterDriverVersion(adapterDriverVersionString))) {
+      if (OnlyAllowFeatureOnKnownConfig(aFeature)) {
+        aFailureId = "FEATURE_FAILURE_GET_ADAPTER";
+        *aStatus = FEATURE_BLOCKED_DEVICE;
+      } else {
+        *aStatus = FEATURE_STATUS_OK;
+      }
+      return NS_OK;
+    }
+
+    if (OnlyAllowFeatureOnKnownConfig(aFeature) &&
+        !adapterVendorID.Equals(
+            GfxDriverInfo::GetDeviceVendor(DeviceVendor::Intel),
+            nsCaseInsensitiveStringComparator) &&
+        !adapterVendorID.Equals(
+            GfxDriverInfo::GetDeviceVendor(DeviceVendor::NVIDIA),
+            nsCaseInsensitiveStringComparator) &&
+        !adapterVendorID.Equals(
+            GfxDriverInfo::GetDeviceVendor(DeviceVendor::ATI),
+            nsCaseInsensitiveStringComparator) &&
+        !adapterVendorID.Equals(
+            GfxDriverInfo::GetDeviceVendor(DeviceVendor::Microsoft),
+            nsCaseInsensitiveStringComparator) &&
+        !adapterVendorID.Equals(
+            GfxDriverInfo::GetDeviceVendor(DeviceVendor::Parallels),
+            nsCaseInsensitiveStringComparator) &&
+        !adapterVendorID.Equals(
+            GfxDriverInfo::GetDeviceVendor(DeviceVendor::Qualcomm),
+            nsCaseInsensitiveStringComparator) &&
+        // FIXME - these special hex values are currently used in xpcshell tests
+        // introduced by bug 625160 patch 8/8. Maybe these tests need to be
+        // adjusted now that we're only whitelisting intel/ati/nvidia.
+        !adapterVendorID.LowerCaseEqualsLiteral("0xabcd") &&
+        !adapterVendorID.LowerCaseEqualsLiteral("0xdcba") &&
+        !adapterVendorID.LowerCaseEqualsLiteral("0xabab") &&
+        !adapterVendorID.LowerCaseEqualsLiteral("0xdcdc")) {
+      if (adapterVendorID.Equals(
+              GfxDriverInfo::GetDeviceVendor(DeviceVendor::MicrosoftHyperV),
+              nsCaseInsensitiveStringComparator) ||
+          adapterVendorID.Equals(
+              GfxDriverInfo::GetDeviceVendor(DeviceVendor::VMWare),
+              nsCaseInsensitiveStringComparator) ||
+          adapterVendorID.Equals(
+              GfxDriverInfo::GetDeviceVendor(DeviceVendor::VirtualBox),
+              nsCaseInsensitiveStringComparator)) {
+        aFailureId = "FEATURE_FAILURE_VM_VENDOR";
+      } else if (adapterVendorID.Equals(GfxDriverInfo::GetDeviceVendor(
+                                            DeviceVendor::MicrosoftBasic),
+                                        nsCaseInsensitiveStringComparator)) {
+        aFailureId = "FEATURE_FAILURE_MICROSOFT_BASIC_VENDOR";
+      } else if (adapterVendorID.IsEmpty()) {
+        aFailureId = "FEATURE_FAILURE_EMPTY_DEVICE_VENDOR";
+      } else {
+        aFailureId = "FEATURE_FAILURE_UNKNOWN_DEVICE_VENDOR";
+      }
+      *aStatus = FEATURE_BLOCKED_DEVICE;
+      return NS_OK;
+    }
+
+    if (adapterDriverVersionString.Length() == 0) {
+      if (OnlyAllowFeatureOnKnownConfig(aFeature)) {
+        aFailureId = "FEATURE_FAILURE_EMPTY_DRIVER_VERSION";
+        *aStatus = FEATURE_BLOCKED_DRIVER_VERSION;
+      } else {
+        *aStatus = FEATURE_STATUS_OK;
+      }
+      return NS_OK;
+    }
+
+    uint64_t driverVersion;
+    if (!ParseDriverVersion(adapterDriverVersionString, &driverVersion)) {
+      if (OnlyAllowFeatureOnKnownConfig(aFeature)) {
+        aFailureId = "FEATURE_FAILURE_PARSE_DRIVER";
+        *aStatus = FEATURE_BLOCKED_DRIVER_VERSION;
+      } else {
+        *aStatus = FEATURE_STATUS_OK;
+      }
+      return NS_OK;
+    }
+  }
+
+  return GfxInfoBase::GetFeatureStatusImpl(
+      aFeature, aStatus, aSuggestedDriverVersion, aDriverInfo, aFailureId, &os);
+}
+
+void GfxInfo::DescribeFeatures(JSContext* aCx, JS::Handle<JSObject*> aObj) {
+  // Add the platform neutral features
+  GfxInfoBase::DescribeFeatures(aCx, aObj);
+
+  JS::Rooted<JSObject*> obj(aCx);
+
+  gfx::FeatureState& d3d11 = gfxConfig::GetFeature(Feature::D3D11_COMPOSITING);
+  if (!InitFeatureObject(aCx, aObj, "d3d11", d3d11, &obj)) {
+    return;
+  }
+  if (d3d11.GetValue() == gfx::FeatureStatus::Available) {
+    DeviceManagerDx* dm = DeviceManagerDx::Get();
+    JS::Rooted<JS::Value> val(aCx,
+                              JS::Int32Value(dm->GetCompositorFeatureLevel()));
+    JS_SetProperty(aCx, obj, "version", val);
+
+    val = JS::BooleanValue(dm->IsWARP());
+    JS_SetProperty(aCx, obj, "warp", val);
+
+    val = JS::BooleanValue(dm->TextureSharingWorks());
+    JS_SetProperty(aCx, obj, "textureSharing", val);
+
+    bool blocklisted = false;
+    if (nsCOMPtr<nsIGfxInfo> gfxInfo = components::GfxInfo::Service()) {
+      int32_t status;
+      nsCString discardFailureId;
+      if (SUCCEEDED(
+              gfxInfo->GetFeatureStatus(nsIGfxInfo::FEATURE_DIRECT3D_11_LAYERS,
+                                        discardFailureId, &status))) {
+        blocklisted = (status != nsIGfxInfo::FEATURE_STATUS_OK);
+      }
+    }
+
+    val = JS::BooleanValue(blocklisted);
+    JS_SetProperty(aCx, obj, "blocklisted", val);
+  }
+
+  gfx::FeatureState& d2d = gfxConfig::GetFeature(Feature::DIRECT2D);
+  if (!InitFeatureObject(aCx, aObj, "d2d", d2d, &obj)) {
+    return;
+  }
+  {
+    const char* version = "1.1";
+    JS::Rooted<JSString*> str(aCx, JS_NewStringCopyZ(aCx, version));
+    JS::Rooted<JS::Value> val(aCx, JS::StringValue(str));
+    JS_SetProperty(aCx, obj, "version", val);
+  }
+}
+
+#ifdef DEBUG
+
+// Implement nsIGfxInfoDebug
+
+NS_IMETHODIMP GfxInfo::SpoofVendorID(const nsAString& aVendorID) {
+  mAdapterVendorID[mActiveGPUIndex] = aVendorID;
+  return NS_OK;
+}
+
+NS_IMETHODIMP GfxInfo::SpoofDeviceID(const nsAString& aDeviceID) {
+  mAdapterDeviceID[mActiveGPUIndex] = aDeviceID;
+  return NS_OK;
+}
+
+NS_IMETHODIMP GfxInfo::SpoofDriverVersion(const nsAString& aDriverVersion) {
+  mDriverVersion[mActiveGPUIndex] = aDriverVersion;
+  return NS_OK;
+}
+
+NS_IMETHODIMP GfxInfo::SpoofOSVersion(uint32_t aVersion) {
+  mWindowsVersion = aVersion;
+  return NS_OK;
+}
+
+#endif
diff --git a/widget/windows/GfxInfo.h b/widget/windows/GfxInfo.h
new file mode 100644
index 0000000000..f2549afa4e
--- /dev/null
+++ b/widget/windows/GfxInfo.h
@@ -0,0 +1,105 @@
+/* vim: se cin sw=2 ts=2 et : */
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef WIDGET_WINDOWS_GFXINFO_H_
+#define WIDGET_WINDOWS_GFXINFO_H_
+
+#include "GfxInfoBase.h"
+
+namespace mozilla::widget {
+
+class GfxInfo : public GfxInfoBase {
+ public:
+  using GfxInfoBase::GetFeatureStatus;
+  using GfxInfoBase::GetFeatureSuggestedDriverVersion;
+
+  GfxInfo() = default;
+  nsresult Init() override;
+
+  // We only declare the subset of nsIGfxInfo that we actually implement. The
+  // rest is brought forward from GfxInfoBase.
+  NS_IMETHOD GetD2DEnabled(bool* aD2DEnabled) override;
+  NS_IMETHOD GetDWriteEnabled(bool* aDWriteEnabled) override;
+  NS_IMETHOD GetDWriteVersion(nsAString& aDwriteVersion) override;
+  NS_IMETHOD GetEmbeddedInFirefoxReality(
+      bool* aEmbeddedInFirefoxReality) override;
+  NS_IMETHOD GetHasBattery(bool* aHasBattery) override;
+  NS_IMETHOD GetCleartypeParameters(nsAString& aCleartypeParams) override;
+  NS_IMETHOD GetWindowProtocol(nsAString& aWindowProtocol) override;
+  NS_IMETHOD GetTestType(nsAString& aTestType) override;
+  NS_IMETHOD GetAdapterDescription(nsAString& aAdapterDescription) override;
+  NS_IMETHOD GetAdapterDriver(nsAString& aAdapterDriver) override;
+  NS_IMETHOD GetAdapterVendorID(nsAString& aAdapterVendorID) override;
+  NS_IMETHOD GetAdapterDeviceID(nsAString& aAdapterDeviceID) override;
+  NS_IMETHOD GetAdapterSubsysID(nsAString& aAdapterSubsysID) override;
+  NS_IMETHOD GetAdapterRAM(uint32_t* aAdapterRAM) override;
+  NS_IMETHOD GetAdapterDriverVendor(nsAString& aAdapterDriverVendor) override;
+  NS_IMETHOD GetAdapterDriverVersion(nsAString& aAdapterDriverVersion) override;
+  NS_IMETHOD GetAdapterDriverDate(nsAString& aAdapterDriverDate) override;
+  NS_IMETHOD GetAdapterDescription2(nsAString& aAdapterDescription) override;
+  NS_IMETHOD GetAdapterDriver2(nsAString& aAdapterDriver) override;
+  NS_IMETHOD GetAdapterVendorID2(nsAString& aAdapterVendorID) override;
+  NS_IMETHOD GetAdapterDeviceID2(nsAString& aAdapterDeviceID) override;
+  NS_IMETHOD GetAdapterSubsysID2(nsAString& aAdapterSubsysID) override;
+  NS_IMETHOD GetAdapterRAM2(uint32_t* aAdapterRAM) override;
+  NS_IMETHOD GetAdapterDriverVendor2(nsAString& aAdapterDriverVendor) override;
+  NS_IMETHOD GetAdapterDriverVersion2(
+      nsAString& aAdapterDriverVersion) override;
+  NS_IMETHOD GetAdapterDriverDate2(nsAString& aAdapterDriverDate) override;
+  NS_IMETHOD GetIsGPU2Active(bool* aIsGPU2Active) override;
+  NS_IMETHOD GetDrmRenderDevice(nsACString& aDrmRenderDevice) override;
+
+  uint32_t OperatingSystemVersion() override { return mWindowsVersion; }
+  uint32_t OperatingSystemBuild() override { return mWindowsBuildNumber; }
+
+#ifdef DEBUG
+  NS_DECL_ISUPPORTS_INHERITED
+  NS_DECL_NSIGFXINFODEBUG
+#endif
+
+ private:
+  ~GfxInfo() = default;
+
+  // Disallow copy/move
+  GfxInfo(const GfxInfo&) = delete;
+  GfxInfo& operator=(const GfxInfo&) = delete;
+  GfxInfo(GfxInfo&&) = delete;
+  GfxInfo& operator=(GfxInfo&&) = delete;
+
+  OperatingSystem GetOperatingSystem() override;
+
+  nsresult GetFeatureStatusImpl(int32_t aFeature, int32_t* aStatus,
+                                nsAString& aSuggestedDriverVersion,
+                                const nsTArray<GfxDriverInfo>& aDriverInfo,
+                                nsACString& aFailureId,
+                                OperatingSystem* aOS = nullptr) override;
+  const nsTArray<GfxDriverInfo>& GetGfxDriverInfo() override;
+
+  void DescribeFeatures(JSContext* cx, JS::Handle<JSObject*> aOut) override;
+
+  void AddCrashReportAnnotations();
+
+  nsString mDeviceString[2];
+  nsString mDeviceID[2];
+  nsString mDriverVersion[2];
+  nsString mDriverDate[2];
+  nsString mDeviceKey[2];
+  nsString mDeviceKeyDebug;
+  nsString mAdapterVendorID[2];
+  nsString mAdapterDeviceID[2];
+  nsString mAdapterSubsysID[2];
+  uint32_t mWindowsVersion = 0;
+  uint32_t mWindowsBuildNumber = 0;
+  uint32_t mActiveGPUIndex = 0;  // This must be 0 or 1
+  bool mHasDualGPU = false;
+  bool mHasDriverVersionMismatch = false;
+  bool mHasBattery = false;
+};
+
+}  // namespace mozilla::widget
+
+#endif  // WIDGET_WINDOWS_GFXINFO_H_
diff --git a/widget/windows/IEnumFE.cpp b/widget/windows/IEnumFE.cpp
new file mode 100644
index 0000000000..8fe7138609
--- /dev/null
+++ b/widget/windows/IEnumFE.cpp
@@ -0,0 +1,139 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "IEnumFE.h"
+#include "nsAlgorithm.h"
+#include <algorithm>
+
+CEnumFormatEtc::CEnumFormatEtc() : mRefCnt(0), mCurrentIdx(0) {}
+
+// Constructor used by Clone()
+CEnumFormatEtc::CEnumFormatEtc(nsTArray<FormatEtc>& aArray)
+    : mRefCnt(0), mCurrentIdx(0) {
+  // a deep copy, calls FormatEtc's copy constructor on each
+  mFormatList.AppendElements(aArray);
+}
+
+CEnumFormatEtc::~CEnumFormatEtc() {}
+
+/* IUnknown impl. */
+
+STDMETHODIMP
+CEnumFormatEtc::QueryInterface(REFIID riid, LPVOID* ppv) {
+  *ppv = nullptr;
+
+  if (IsEqualIID(riid, IID_IUnknown) || IsEqualIID(riid, IID_IEnumFORMATETC))
+    *ppv = (LPVOID)this;
+
+  if (*ppv == nullptr) return E_NOINTERFACE;
+
+  // AddRef any interface we'll return.
+  ((LPUNKNOWN)*ppv)->AddRef();
+  return S_OK;
+}
+
+STDMETHODIMP_(ULONG)
+CEnumFormatEtc::AddRef() {
+  ++mRefCnt;
+  NS_LOG_ADDREF(this, mRefCnt, "CEnumFormatEtc", sizeof(*this));
+  return mRefCnt;
+}
+
+STDMETHODIMP_(ULONG)
+CEnumFormatEtc::Release() {
+  uint32_t refReturn;
+
+  refReturn = --mRefCnt;
+  NS_LOG_RELEASE(this, mRefCnt, "CEnumFormatEtc");
+
+  if (mRefCnt == 0) delete this;
+
+  return refReturn;
+}
+
+/* IEnumFORMATETC impl. */
+
+STDMETHODIMP
+CEnumFormatEtc::Next(ULONG aMaxToFetch, FORMATETC* aResult,
+                     ULONG* aNumFetched) {
+  // If the method retrieves the number of items requested, the return
+  // value is S_OK. Otherwise, it is S_FALSE.
+
+  if (aNumFetched) *aNumFetched = 0;
+
+  // aNumFetched can be null if aMaxToFetch is 1
+  if (!aNumFetched && aMaxToFetch > 1) return S_FALSE;
+
+  if (!aResult) return S_FALSE;
+
+  // We're done walking the list
+  if (mCurrentIdx >= mFormatList.Length()) return S_FALSE;
+
+  uint32_t left = mFormatList.Length() - mCurrentIdx;
+
+  if (!aMaxToFetch) return S_FALSE;
+
+  uint32_t count = std::min(static_cast<uint32_t>(aMaxToFetch), left);
+
+  uint32_t idx = 0;
+  while (count > 0) {
+    // Copy out to aResult
+    mFormatList[mCurrentIdx++].CopyOut(&aResult[idx++]);
+    count--;
+  }
+
+  if (aNumFetched) *aNumFetched = idx;
+
+  return S_OK;
+}
+
+STDMETHODIMP
+CEnumFormatEtc::Skip(ULONG aSkipNum) {
+  // If the method skips the number of items requested, the return value is
+  // S_OK. Otherwise, it is S_FALSE.
+
+  if ((mCurrentIdx + aSkipNum) >= mFormatList.Length()) return S_FALSE;
+
+  mCurrentIdx += aSkipNum;
+
+  return S_OK;
+}
+
+STDMETHODIMP
+CEnumFormatEtc::Reset(void) {
+  mCurrentIdx = 0;
+  return S_OK;
+}
+
+STDMETHODIMP
+CEnumFormatEtc::Clone(LPENUMFORMATETC* aResult) {
+  // Must return a new IEnumFORMATETC interface with the same iterative state.
+
+  if (!aResult) return E_INVALIDARG;
+
+  CEnumFormatEtc* pEnumObj = new CEnumFormatEtc(mFormatList);
+
+  if (!pEnumObj) return E_OUTOFMEMORY;
+
+  pEnumObj->AddRef();
+  pEnumObj->SetIndex(mCurrentIdx);
+
+  *aResult = pEnumObj;
+
+  return S_OK;
+}
+
+/* utils */
+
+void CEnumFormatEtc::AddFormatEtc(LPFORMATETC aFormat) {
+  if (!aFormat) return;
+  FormatEtc* etc = mFormatList.AppendElement();
+  // Make a copy of aFormat
+  if (etc) etc->CopyIn(aFormat);
+}
+
+/* private */
+
+void CEnumFormatEtc::SetIndex(uint32_t aIdx) { mCurrentIdx = aIdx; }
diff --git a/widget/windows/IEnumFE.h b/widget/windows/IEnumFE.h
new file mode 100644
index 0000000000..b8cb6ad9d0
--- /dev/null
+++ b/widget/windows/IEnumFE.h
@@ -0,0 +1,88 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef IEnumeFE_h__
+#define IEnumeFE_h__
+
+/*
+ * CEnumFormatEtc - implements IEnumFORMATETC
+ */
+
+#include <ole2.h>
+
+#include "nsTArray.h"
+#include "mozilla/Attributes.h"
+
+// FORMATETC container
+class FormatEtc {
+ public:
+  FormatEtc() { memset(&mFormat, 0, sizeof(FORMATETC)); }
+  FormatEtc(const FormatEtc& copy) { CopyIn(&copy.mFormat); }
+  ~FormatEtc() {
+    if (mFormat.ptd) CoTaskMemFree(mFormat.ptd);
+  }
+
+  void CopyIn(const FORMATETC* aSrc) {
+    if (!aSrc) {
+      memset(&mFormat, 0, sizeof(FORMATETC));
+      return;
+    }
+    mFormat = *aSrc;
+    if (aSrc->ptd) {
+      mFormat.ptd = (DVTARGETDEVICE*)CoTaskMemAlloc(sizeof(DVTARGETDEVICE));
+      *(mFormat.ptd) = *(aSrc->ptd);
+    }
+  }
+
+  void CopyOut(LPFORMATETC aDest) {
+    if (!aDest) return;
+    *aDest = mFormat;
+    if (mFormat.ptd) {
+      aDest->ptd = (DVTARGETDEVICE*)CoTaskMemAlloc(sizeof(DVTARGETDEVICE));
+      *(aDest->ptd) = *(mFormat.ptd);
+    }
+  }
+
+ private:
+  FORMATETC mFormat;
+};
+
+/*
+ * CEnumFormatEtc is created within IDataObject::EnumFormatEtc. This object
+ * lives on its own, that is, QueryInterface only knows IUnknown and
+ * IEnumFormatEtc, nothing more.  We still use an outer unknown for reference
+ * counting, because as long as this enumerator lives, the data object should
+ * live, thereby keeping the application up.
+ */
+
+class CEnumFormatEtc final : public IEnumFORMATETC {
+ public:
+  explicit CEnumFormatEtc(nsTArray<FormatEtc>& aArray);
+  CEnumFormatEtc();
+  ~CEnumFormatEtc();
+
+  // IUnknown impl.
+  STDMETHODIMP QueryInterface(REFIID riid, LPVOID* ppv);
+  STDMETHODIMP_(ULONG) AddRef();
+  STDMETHODIMP_(ULONG) Release();
+
+  // IEnumFORMATETC impl.
+  STDMETHODIMP Next(ULONG aMaxToFetch, FORMATETC* aResult, ULONG* aNumFetched);
+  STDMETHODIMP Skip(ULONG aSkipNum);
+  STDMETHODIMP Reset();
+  STDMETHODIMP Clone(LPENUMFORMATETC* aResult);  // Addrefs
+
+  // Utils
+  void AddFormatEtc(LPFORMATETC aFormat);
+
+ private:
+  nsTArray<FormatEtc> mFormatList;  // Formats
+  ULONG mRefCnt;                    // Object reference count
+  ULONG mCurrentIdx;                // Current element
+
+  void SetIndex(uint32_t aIdx);
+};
+
+#endif  //_IENUMFE_H_
diff --git a/widget/windows/IMMHandler.cpp b/widget/windows/IMMHandler.cpp
new file mode 100644
index 0000000000..2f64f93922
--- /dev/null
+++ b/widget/windows/IMMHandler.cpp
@@ -0,0 +1,2408 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:set ts=2 sts=2 sw=2 et cin: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/Logging.h"
+
+#include "IMMHandler.h"
+#include "nsWindow.h"
+#include "nsWindowDefs.h"
+#include "WinIMEHandler.h"
+#include "WinUtils.h"
+#include "KeyboardLayout.h"
+#include <algorithm>
+
+#include "mozilla/CheckedInt.h"
+#include "mozilla/MiscEvents.h"
+#include "mozilla/TextEvents.h"
+#include "mozilla/ToString.h"
+
+#ifndef IME_PROP_ACCEPT_WIDE_VKEY
+#  define IME_PROP_ACCEPT_WIDE_VKEY 0x20
+#endif
+
+//-------------------------------------------------------------------------
+//
+// from
+// http://download.microsoft.com/download/6/0/9/60908e9e-d2c1-47db-98f6-216af76a235f/msime.h
+// The document for this has been removed from MSDN...
+//
+//-------------------------------------------------------------------------
+
+#define RWM_MOUSE TEXT("MSIMEMouseOperation")
+
+#define IMEMOUSE_NONE 0x00  // no mouse button was pushed
+#define IMEMOUSE_LDOWN 0x01
+#define IMEMOUSE_RDOWN 0x02
+#define IMEMOUSE_MDOWN 0x04
+#define IMEMOUSE_WUP 0x10    // wheel up
+#define IMEMOUSE_WDOWN 0x20  // wheel down
+
+// For collecting other people's log, tell `MOZ_LOG=IMEHandler:4,sync`
+// rather than `MOZ_LOG=IMEHandler:5,sync` since using `5` may create too
+// big file.
+// Therefore you shouldn't use `LogLevel::Verbose` for logging usual behavior.
+extern mozilla::LazyLogModule gIMELog;
+
+static const char* GetBoolName(bool aBool) { return aBool ? "true" : "false"; }
+
+static void HandleSeparator(nsACString& aDesc) {
+  if (!aDesc.IsEmpty()) {
+    aDesc.AppendLiteral(" | ");
+  }
+}
+
+class GetIMEGeneralPropertyName : public nsAutoCString {
+ public:
+  explicit GetIMEGeneralPropertyName(DWORD aFlags) {
+    if (!aFlags) {
+      AppendLiteral("no flags");
+      return;
+    }
+    if (aFlags & IME_PROP_AT_CARET) {
+      AppendLiteral("IME_PROP_AT_CARET");
+    }
+    if (aFlags & IME_PROP_SPECIAL_UI) {
+      HandleSeparator(*this);
+      AppendLiteral("IME_PROP_SPECIAL_UI");
+    }
+    if (aFlags & IME_PROP_CANDLIST_START_FROM_1) {
+      HandleSeparator(*this);
+      AppendLiteral("IME_PROP_CANDLIST_START_FROM_1");
+    }
+    if (aFlags & IME_PROP_UNICODE) {
+      HandleSeparator(*this);
+      AppendLiteral("IME_PROP_UNICODE");
+    }
+    if (aFlags & IME_PROP_COMPLETE_ON_UNSELECT) {
+      HandleSeparator(*this);
+      AppendLiteral("IME_PROP_COMPLETE_ON_UNSELECT");
+    }
+    if (aFlags & IME_PROP_ACCEPT_WIDE_VKEY) {
+      HandleSeparator(*this);
+      AppendLiteral("IME_PROP_ACCEPT_WIDE_VKEY");
+    }
+  }
+  virtual ~GetIMEGeneralPropertyName() {}
+};
+
+class GetIMEUIPropertyName : public nsAutoCString {
+ public:
+  explicit GetIMEUIPropertyName(DWORD aFlags) {
+    if (!aFlags) {
+      AppendLiteral("no flags");
+      return;
+    }
+    if (aFlags & UI_CAP_2700) {
+      AppendLiteral("UI_CAP_2700");
+    }
+    if (aFlags & UI_CAP_ROT90) {
+      HandleSeparator(*this);
+      AppendLiteral("UI_CAP_ROT90");
+    }
+    if (aFlags & UI_CAP_ROTANY) {
+      HandleSeparator(*this);
+      AppendLiteral("UI_CAP_ROTANY");
+    }
+  }
+  virtual ~GetIMEUIPropertyName() {}
+};
+
+class GetReconvertStringLog : public nsAutoCString {
+ public:
+  explicit GetReconvertStringLog(RECONVERTSTRING* aReconv) {
+    AssignLiteral("{ dwSize=");
+    AppendInt(static_cast<uint32_t>(aReconv->dwSize));
+    AppendLiteral(", dwVersion=");
+    AppendInt(static_cast<uint32_t>(aReconv->dwVersion));
+    AppendLiteral(", dwStrLen=");
+    AppendInt(static_cast<uint32_t>(aReconv->dwStrLen));
+    AppendLiteral(", dwStrOffset=");
+    AppendInt(static_cast<uint32_t>(aReconv->dwStrOffset));
+    AppendLiteral(", dwCompStrLen=");
+    AppendInt(static_cast<uint32_t>(aReconv->dwCompStrLen));
+    AppendLiteral(", dwCompStrOffset=");
+    AppendInt(static_cast<uint32_t>(aReconv->dwCompStrOffset));
+    AppendLiteral(", dwTargetStrLen=");
+    AppendInt(static_cast<uint32_t>(aReconv->dwTargetStrLen));
+    AppendLiteral(", dwTargetStrOffset=");
+    AppendInt(static_cast<uint32_t>(aReconv->dwTargetStrOffset));
+    AppendLiteral(", result str=\"");
+    if (aReconv->dwStrLen) {
+      char16_t* strStart = reinterpret_cast<char16_t*>(
+          reinterpret_cast<char*>(aReconv) + aReconv->dwStrOffset);
+      nsDependentString str(strStart, aReconv->dwStrLen);
+      Append(NS_ConvertUTF16toUTF8(str));
+    }
+    AppendLiteral("\" }");
+  }
+  virtual ~GetReconvertStringLog() {}
+};
+
+namespace mozilla {
+namespace widget {
+
+static IMMHandler* gIMMHandler = nullptr;
+
+/******************************************************************************
+ * IMEContext
+ ******************************************************************************/
+
+IMEContext::IMEContext(HWND aWnd) : mWnd(aWnd), mIMC(::ImmGetContext(aWnd)) {}
+
+IMEContext::IMEContext(nsWindow* aWindowBase)
+    : mWnd(aWindowBase->GetWindowHandle()),
+      mIMC(::ImmGetContext(aWindowBase->GetWindowHandle())) {}
+
+void IMEContext::Init(HWND aWnd) {
+  Clear();
+  mWnd = aWnd;
+  mIMC = ::ImmGetContext(mWnd);
+}
+
+void IMEContext::Init(nsWindow* aWindowBase) {
+  Init(aWindowBase->GetWindowHandle());
+}
+
+void IMEContext::Clear() {
+  if (mWnd && mIMC) {
+    ::ImmReleaseContext(mWnd, mIMC);
+  }
+  mWnd = nullptr;
+  mIMC = nullptr;
+}
+
+/******************************************************************************
+ * IMMHandler
+ ******************************************************************************/
+
+static UINT sWM_MSIME_MOUSE = 0;  // mouse message for MSIME 98/2000
+
+WritingMode IMMHandler::sWritingModeOfCompositionFont;
+nsString IMMHandler::sIMEName;
+UINT IMMHandler::sCodePage = 0;
+DWORD IMMHandler::sIMEProperty = 0;
+DWORD IMMHandler::sIMEUIProperty = 0;
+bool IMMHandler::sAssumeVerticalWritingModeNotSupported = false;
+bool IMMHandler::sHasFocus = false;
+
+#define IMPL_IS_IME_ACTIVE(aReadableName, aActualName) \
+  bool IMMHandler::Is##aReadableName##Active() {       \
+    return sIMEName.Equals(aActualName);               \
+  }
+
+IMPL_IS_IME_ACTIVE(ATOK2006, u"ATOK 2006")
+IMPL_IS_IME_ACTIVE(ATOK2007, u"ATOK 2007")
+IMPL_IS_IME_ACTIVE(ATOK2008, u"ATOK 2008")
+IMPL_IS_IME_ACTIVE(ATOK2009, u"ATOK 2009")
+IMPL_IS_IME_ACTIVE(ATOK2010, u"ATOK 2010")
+// NOTE: Even on Windows for en-US, the name of Google Japanese Input is
+//       written in Japanese.
+IMPL_IS_IME_ACTIVE(GoogleJapaneseInput,
+                   u"Google \x65E5\x672C\x8A9E\x5165\x529B "
+                   u"IMM32 \x30E2\x30B8\x30E5\x30FC\x30EB")
+IMPL_IS_IME_ACTIVE(Japanist2003, u"Japanist 2003")
+
+#undef IMPL_IS_IME_ACTIVE
+
+// static
+bool IMMHandler::IsActiveIMEInBlockList() {
+  if (sIMEName.IsEmpty()) {
+    return false;
+  }
+#ifdef _WIN64
+  // ATOK started to be TIP of TSF since 2011.  Older than it, i.e., ATOK 2010
+  // and earlier have a lot of problems even for daily use.  Perhaps, the
+  // reason is Win 8 has a lot of changes around IMM-IME support and TSF,
+  // and ATOK 2010 is released earlier than Win 8.
+  // ATOK 2006 crashes while converting a word with candidate window.
+  // ATOK 2007 doesn't paint and resize suggest window and candidate window
+  // correctly (showing white window or too big window).
+  // ATOK 2008 and ATOK 2009 crash when user just opens their open state.
+  // ATOK 2010 isn't installable newly on Win 7 or later, but we have a lot of
+  // crash reports.
+  if ((IsATOK2006Active() || IsATOK2007Active() || IsATOK2008Active() ||
+       IsATOK2009Active() || IsATOK2010Active())) {
+    return true;
+  }
+#endif  // #ifdef _WIN64
+  return false;
+}
+
+// static
+void IMMHandler::EnsureHandlerInstance() {
+  if (!gIMMHandler) {
+    gIMMHandler = new IMMHandler();
+  }
+}
+
+// static
+void IMMHandler::Initialize() {
+  if (!sWM_MSIME_MOUSE) {
+    sWM_MSIME_MOUSE = ::RegisterWindowMessage(RWM_MOUSE);
+  }
+  sAssumeVerticalWritingModeNotSupported = Preferences::GetBool(
+      "intl.imm.vertical_writing.always_assume_not_supported", false);
+  InitKeyboardLayout(nullptr, ::GetKeyboardLayout(0));
+}
+
+// static
+void IMMHandler::Terminate() {
+  if (!gIMMHandler) return;
+  delete gIMMHandler;
+  gIMMHandler = nullptr;
+}
+
+// static
+bool IMMHandler::IsComposingOnOurEditor() {
+  return gIMMHandler && gIMMHandler->mIsComposing;
+}
+
+// static
+bool IMMHandler::IsComposingWindow(nsWindow* aWindow) {
+  return gIMMHandler && gIMMHandler->mComposingWindow == aWindow;
+}
+
+// static
+bool IMMHandler::IsTopLevelWindowOfComposition(nsWindow* aWindow) {
+  if (!gIMMHandler || !gIMMHandler->mComposingWindow) {
+    return false;
+  }
+  HWND wnd = gIMMHandler->mComposingWindow->GetWindowHandle();
+  return WinUtils::GetTopLevelHWND(wnd, true) == aWindow->GetWindowHandle();
+}
+
+// static
+bool IMMHandler::ShouldDrawCompositionStringOurselves() {
+  // If current IME has special UI or its composition window should not
+  // positioned to caret position, we should now draw composition string
+  // ourselves.
+  return !(sIMEProperty & IME_PROP_SPECIAL_UI) &&
+         (sIMEProperty & IME_PROP_AT_CARET);
+}
+
+// static
+bool IMMHandler::IsVerticalWritingSupported() {
+  // Even if IME claims that they support vertical writing mode but it may not
+  // support vertical writing mode for its candidate window.
+  if (sAssumeVerticalWritingModeNotSupported) {
+    return false;
+  }
+  // Google Japanese Input doesn't support vertical writing mode.  We should
+  // return false if it's active IME.
+  if (IsGoogleJapaneseInputActive()) {
+    return false;
+  }
+  return !!(sIMEUIProperty & (UI_CAP_2700 | UI_CAP_ROT90 | UI_CAP_ROTANY));
+}
+
+// static
+void IMMHandler::InitKeyboardLayout(nsWindow* aWindow, HKL aKeyboardLayout) {
+  UINT IMENameLength = ::ImmGetDescriptionW(aKeyboardLayout, nullptr, 0);
+  if (IMENameLength) {
+    // Add room for the terminating null character
+    sIMEName.SetLength(++IMENameLength);
+    IMENameLength =
+        ::ImmGetDescriptionW(aKeyboardLayout, sIMEName.get(), IMENameLength);
+    // Adjust the length to ignore the terminating null character
+    sIMEName.SetLength(IMENameLength);
+  } else {
+    sIMEName.Truncate();
+  }
+
+  WORD langID = LOWORD(aKeyboardLayout);
+  ::GetLocaleInfoW(MAKELCID(langID, SORT_DEFAULT),
+                   LOCALE_IDEFAULTANSICODEPAGE | LOCALE_RETURN_NUMBER,
+                   (PWSTR)&sCodePage, sizeof(sCodePage) / sizeof(WCHAR));
+  sIMEProperty = ::ImmGetProperty(aKeyboardLayout, IGP_PROPERTY);
+  sIMEUIProperty = ::ImmGetProperty(aKeyboardLayout, IGP_UI);
+
+  // If active IME is a TIP of TSF, we cannot retrieve the name with IMM32 API.
+  // For hacking some bugs of some TIP, we should set an IME name from the
+  // pref.
+  if (sCodePage == 932 && sIMEName.IsEmpty()) {
+    Preferences::GetString("intl.imm.japanese.assume_active_tip_name_as",
+                           sIMEName);
+  }
+
+  // Whether the IME supports vertical writing mode might be changed or
+  // some IMEs may need specific font for their UI.  Therefore, we should
+  // update composition font forcibly here.
+  if (aWindow) {
+    MaybeAdjustCompositionFont(aWindow, sWritingModeOfCompositionFont, true);
+  }
+
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("IMMHandler::InitKeyboardLayout, aKeyboardLayout=%p (\"%s\"), "
+           "sCodePage=%u, sIMEProperty=%s, sIMEUIProperty=%s",
+           aKeyboardLayout, NS_ConvertUTF16toUTF8(sIMEName).get(), sCodePage,
+           GetIMEGeneralPropertyName(sIMEProperty).get(),
+           GetIMEUIPropertyName(sIMEUIProperty).get()));
+}
+
+// static
+UINT IMMHandler::GetKeyboardCodePage() { return sCodePage; }
+
+// static
+IMENotificationRequests IMMHandler::GetIMENotificationRequests() {
+  return IMENotificationRequests(
+      IMENotificationRequests::NOTIFY_POSITION_CHANGE |
+      IMENotificationRequests::NOTIFY_MOUSE_BUTTON_EVENT_ON_CHAR);
+}
+
+// used for checking the lParam of WM_IME_COMPOSITION
+#define IS_COMPOSING_LPARAM(lParam) \
+  ((lParam) & (GCS_COMPSTR | GCS_COMPATTR | GCS_COMPCLAUSE | GCS_CURSORPOS))
+#define IS_COMMITTING_LPARAM(lParam) ((lParam) & GCS_RESULTSTR)
+// Some IMEs (e.g., the standard IME for Korean) don't have caret position,
+// then, we should not set caret position to compositionchange event.
+#define NO_IME_CARET -1
+
+IMMHandler::IMMHandler()
+    : mComposingWindow(nullptr),
+      mCursorPosition(NO_IME_CARET),
+      mCompositionStart(0),
+      mIsComposing(false) {
+  MOZ_LOG(gIMELog, LogLevel::Debug, ("IMMHandler::IMMHandler is created"));
+}
+
+IMMHandler::~IMMHandler() {
+  if (mIsComposing) {
+    MOZ_LOG(
+        gIMELog, LogLevel::Error,
+        ("  IMMHandler::~IMMHandler, ERROR, the instance is still composing"));
+  }
+  MOZ_LOG(gIMELog, LogLevel::Debug, ("IMMHandler::IMMHandler is destroyed"));
+}
+
+nsresult IMMHandler::EnsureClauseArray(int32_t aCount) {
+  NS_ENSURE_ARG_MIN(aCount, 0);
+  mClauseArray.SetCapacity(aCount + 32);
+  return NS_OK;
+}
+
+nsresult IMMHandler::EnsureAttributeArray(int32_t aCount) {
+  NS_ENSURE_ARG_MIN(aCount, 0);
+  mAttributeArray.SetCapacity(aCount + 64);
+  return NS_OK;
+}
+
+// static
+void IMMHandler::CommitComposition(nsWindow* aWindow, bool aForce) {
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("IMMHandler::CommitComposition, aForce=%s, aWindow=%p, hWnd=%p, "
+           "mComposingWindow=%p%s",
+           GetBoolName(aForce), aWindow, aWindow->GetWindowHandle(),
+           gIMMHandler ? gIMMHandler->mComposingWindow : nullptr,
+           gIMMHandler && gIMMHandler->mComposingWindow
+               ? IsComposingOnOurEditor() ? " (composing on editor)"
+                                          : " (composing on plug-in)"
+               : ""));
+  if (!aForce && !IsComposingWindow(aWindow)) {
+    return;
+  }
+
+  IMEContext context(aWindow);
+  bool associated = context.AssociateDefaultContext();
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("  IMMHandler::CommitComposition, associated=%s",
+           GetBoolName(associated)));
+
+  if (context.IsValid()) {
+    ::ImmNotifyIME(context.get(), NI_COMPOSITIONSTR, CPS_COMPLETE, 0);
+    ::ImmNotifyIME(context.get(), NI_COMPOSITIONSTR, CPS_CANCEL, 0);
+  }
+
+  if (associated) {
+    context.Disassociate();
+  }
+}
+
+// static
+void IMMHandler::CancelComposition(nsWindow* aWindow, bool aForce) {
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("IMMHandler::CancelComposition, aForce=%s, aWindow=%p, hWnd=%p, "
+           "mComposingWindow=%p%s",
+           GetBoolName(aForce), aWindow, aWindow->GetWindowHandle(),
+           gIMMHandler ? gIMMHandler->mComposingWindow : nullptr,
+           gIMMHandler && gIMMHandler->mComposingWindow
+               ? IsComposingOnOurEditor() ? " (composing on editor)"
+                                          : " (composing on plug-in)"
+               : ""));
+  if (!aForce && !IsComposingWindow(aWindow)) {
+    return;
+  }
+
+  IMEContext context(aWindow);
+  bool associated = context.AssociateDefaultContext();
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("  IMMHandler::CancelComposition, associated=%s",
+           GetBoolName(associated)));
+
+  if (context.IsValid()) {
+    ::ImmNotifyIME(context.get(), NI_COMPOSITIONSTR, CPS_CANCEL, 0);
+  }
+
+  if (associated) {
+    context.Disassociate();
+  }
+}
+
+// static
+void IMMHandler::OnFocusChange(bool aFocus, nsWindow* aWindow) {
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("IMMHandler::OnFocusChange(aFocus=%s, aWindow=%p), sHasFocus=%s, "
+           "IsComposingWindow(aWindow)=%s, aWindow->Destroyed()=%s",
+           GetBoolName(aFocus), aWindow, GetBoolName(sHasFocus),
+           GetBoolName(IsComposingWindow(aWindow)),
+           GetBoolName(aWindow->Destroyed())));
+
+  if (!aFocus) {
+    IMEHandler::MaybeDestroyNativeCaret();
+    if (IsComposingWindow(aWindow) && aWindow->Destroyed()) {
+      CancelComposition(aWindow);
+    }
+  }
+  if (gIMMHandler) {
+    gIMMHandler->mContentSelection.reset();
+  }
+  sHasFocus = aFocus;
+}
+
+// static
+void IMMHandler::OnUpdateComposition(nsWindow* aWindow) {
+  if (!gIMMHandler) {
+    return;
+  }
+
+  IMEContext context(aWindow);
+  gIMMHandler->SetIMERelatedWindowsPos(aWindow, context);
+}
+
+// static
+void IMMHandler::OnSelectionChange(nsWindow* aWindow,
+                                   const IMENotification& aIMENotification,
+                                   bool aIsIMMActive) {
+  if (!aIMENotification.mSelectionChangeData.mCausedByComposition &&
+      aIsIMMActive) {
+    MaybeAdjustCompositionFont(
+        aWindow, aIMENotification.mSelectionChangeData.GetWritingMode());
+  }
+  // MaybeAdjustCompositionFont() may create gIMMHandler.  So, check it
+  // after a call of MaybeAdjustCompositionFont().
+  if (gIMMHandler) {
+    gIMMHandler->mContentSelection =
+        Some(ContentSelection(aIMENotification.mSelectionChangeData));
+  }
+}
+
+// static
+void IMMHandler::MaybeAdjustCompositionFont(nsWindow* aWindow,
+                                            const WritingMode& aWritingMode,
+                                            bool aForceUpdate) {
+  switch (sCodePage) {
+    case 932:  // Japanese Shift-JIS
+    case 936:  // Simlified Chinese GBK
+    case 949:  // Korean
+    case 950:  // Traditional Chinese Big5
+      EnsureHandlerInstance();
+      break;
+    default:
+      // If there is no instance of nsIMM32Hander, we shouldn't waste footprint.
+      if (!gIMMHandler) {
+        return;
+      }
+  }
+
+  // Like Navi-Bar of ATOK, some IMEs may require proper composition font even
+  // before sending WM_IME_STARTCOMPOSITION.
+  IMEContext context(aWindow);
+  gIMMHandler->AdjustCompositionFont(aWindow, context, aWritingMode,
+                                     aForceUpdate);
+}
+
+// static
+bool IMMHandler::ProcessInputLangChangeMessage(nsWindow* aWindow, WPARAM wParam,
+                                               LPARAM lParam,
+                                               MSGResult& aResult) {
+  aResult.mResult = 0;
+  aResult.mConsumed = false;
+  // We don't need to create the instance of the handler here.
+  if (gIMMHandler) {
+    gIMMHandler->OnInputLangChange(aWindow, wParam, lParam, aResult);
+  }
+  InitKeyboardLayout(aWindow, reinterpret_cast<HKL>(lParam));
+  // We can release the instance here, because the instance may be never
+  // used. E.g., the new keyboard layout may not use IME, or it may use TSF.
+  Terminate();
+  // Don't return as "processed", the messages should be processed on nsWindow
+  // too.
+  return false;
+}
+
+// static
+bool IMMHandler::ProcessMessage(nsWindow* aWindow, UINT msg, WPARAM& wParam,
+                                LPARAM& lParam, MSGResult& aResult) {
+  // XXX We store the composing window in mComposingWindow.  If IME messages are
+  // sent to different window, we should commit the old transaction.  And also
+  // if the new window handle is not focused, probably, we should not start
+  // the composition, however, such case should not be, it's just bad scenario.
+
+  aResult.mResult = 0;
+  switch (msg) {
+    case WM_INPUTLANGCHANGE:
+      return ProcessInputLangChangeMessage(aWindow, wParam, lParam, aResult);
+    case WM_IME_STARTCOMPOSITION:
+      EnsureHandlerInstance();
+      return gIMMHandler->OnIMEStartComposition(aWindow, aResult);
+    case WM_IME_COMPOSITION:
+      EnsureHandlerInstance();
+      return gIMMHandler->OnIMEComposition(aWindow, wParam, lParam, aResult);
+    case WM_IME_ENDCOMPOSITION:
+      EnsureHandlerInstance();
+      return gIMMHandler->OnIMEEndComposition(aWindow, aResult);
+    case WM_IME_CHAR:
+      return OnIMEChar(aWindow, wParam, lParam, aResult);
+    case WM_IME_NOTIFY:
+      return OnIMENotify(aWindow, wParam, lParam, aResult);
+    case WM_IME_REQUEST:
+      EnsureHandlerInstance();
+      return gIMMHandler->OnIMERequest(aWindow, wParam, lParam, aResult);
+    case WM_IME_SELECT:
+      return OnIMESelect(aWindow, wParam, lParam, aResult);
+    case WM_IME_SETCONTEXT:
+      return OnIMESetContext(aWindow, wParam, lParam, aResult);
+    case WM_KEYDOWN:
+      return OnKeyDownEvent(aWindow, wParam, lParam, aResult);
+    case WM_CHAR:
+      if (!gIMMHandler) {
+        return false;
+      }
+      return gIMMHandler->OnChar(aWindow, wParam, lParam, aResult);
+    default:
+      return false;
+  };
+}
+
+/****************************************************************************
+ * message handlers
+ ****************************************************************************/
+
+void IMMHandler::OnInputLangChange(nsWindow* aWindow, WPARAM wParam,
+                                   LPARAM lParam, MSGResult& aResult) {
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("IMMHandler::OnInputLangChange, hWnd=%p, wParam=%08zx, "
+           "lParam=%08" PRIxLPTR,
+           aWindow->GetWindowHandle(), wParam, lParam));
+
+  aWindow->NotifyIME(REQUEST_TO_COMMIT_COMPOSITION);
+  NS_ASSERTION(!mIsComposing, "ResetInputState failed");
+
+  if (mIsComposing) {
+    HandleEndComposition(aWindow);
+  }
+
+  aResult.mConsumed = false;
+}
+
+bool IMMHandler::OnIMEStartComposition(nsWindow* aWindow, MSGResult& aResult) {
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("IMMHandler::OnIMEStartComposition, hWnd=%p, mIsComposing=%s",
+           aWindow->GetWindowHandle(), GetBoolName(mIsComposing)));
+  aResult.mConsumed = ShouldDrawCompositionStringOurselves();
+  if (mIsComposing) {
+    NS_WARNING("Composition has been already started");
+    return true;
+  }
+
+  IMEContext context(aWindow);
+  HandleStartComposition(aWindow, context);
+  return true;
+}
+
+bool IMMHandler::OnIMEComposition(nsWindow* aWindow, WPARAM wParam,
+                                  LPARAM lParam, MSGResult& aResult) {
+  MOZ_LOG(
+      gIMELog, LogLevel::Info,
+      ("IMMHandler::OnIMEComposition, hWnd=%p, lParam=%08" PRIxLPTR
+       ", mIsComposing=%s, "
+       "GCS_RESULTSTR=%s, GCS_COMPSTR=%s, GCS_COMPATTR=%s, GCS_COMPCLAUSE=%s, "
+       "GCS_CURSORPOS=%s,",
+       aWindow->GetWindowHandle(), lParam, GetBoolName(mIsComposing),
+       GetBoolName(lParam & GCS_RESULTSTR), GetBoolName(lParam & GCS_COMPSTR),
+       GetBoolName(lParam & GCS_COMPATTR), GetBoolName(lParam & GCS_COMPCLAUSE),
+       GetBoolName(lParam & GCS_CURSORPOS)));
+
+  IMEContext context(aWindow);
+  aResult.mConsumed = HandleComposition(aWindow, context, lParam);
+  return true;
+}
+
+bool IMMHandler::OnIMEEndComposition(nsWindow* aWindow, MSGResult& aResult) {
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("IMMHandler::OnIMEEndComposition, hWnd=%p, mIsComposing=%s",
+           aWindow->GetWindowHandle(), GetBoolName(mIsComposing)));
+
+  aResult.mConsumed = ShouldDrawCompositionStringOurselves();
+  if (!mIsComposing) {
+    return true;
+  }
+
+  // Korean IME posts WM_IME_ENDCOMPOSITION first when we hit space during
+  // composition. Then, we should ignore the message and commit the composition
+  // string at following WM_IME_COMPOSITION.
+  MSG compositionMsg;
+  if (WinUtils::PeekMessage(&compositionMsg, aWindow->GetWindowHandle(),
+                            WM_IME_STARTCOMPOSITION, WM_IME_COMPOSITION,
+                            PM_NOREMOVE) &&
+      compositionMsg.message == WM_IME_COMPOSITION &&
+      IS_COMMITTING_LPARAM(compositionMsg.lParam)) {
+    MOZ_LOG(gIMELog, LogLevel::Info,
+            ("  IMMHandler::OnIMEEndComposition, WM_IME_ENDCOMPOSITION is "
+             "followed by WM_IME_COMPOSITION, ignoring the message..."));
+    return true;
+  }
+
+  // Otherwise, e.g., ChangJie doesn't post WM_IME_COMPOSITION before
+  // WM_IME_ENDCOMPOSITION when composition string becomes empty.
+  // Then, we should dispatch a compositionupdate event, a compositionchange
+  // event and a compositionend event.
+  // XXX Shouldn't we dispatch the compositionchange event with actual or
+  //     latest composition string?
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("  IMMHandler::OnIMEEndComposition, mCompositionString=\"%s\"%s",
+           NS_ConvertUTF16toUTF8(mCompositionString).get(),
+           mCompositionString.IsEmpty() ? "" : ", but canceling it..."));
+
+  HandleEndComposition(aWindow, &EmptyString());
+
+  return true;
+}
+
+// static
+bool IMMHandler::OnIMEChar(nsWindow* aWindow, WPARAM wParam, LPARAM lParam,
+                           MSGResult& aResult) {
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("IMMHandler::OnIMEChar, hWnd=%p, char=%08zx",
+           aWindow->GetWindowHandle(), wParam));
+
+  // We don't need to fire any compositionchange events from here. This method
+  // will be called when the composition string of the current IME is not drawn
+  // by us and some characters are committed. In that case, the committed
+  // string was processed in nsWindow::OnIMEComposition already.
+
+  // We need to consume the message so that Windows don't send two WM_CHAR msgs
+  aResult.mConsumed = true;
+  return true;
+}
+
+// static
+bool IMMHandler::OnIMECompositionFull(nsWindow* aWindow, MSGResult& aResult) {
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("IMMHandler::OnIMECompositionFull, hWnd=%p",
+           aWindow->GetWindowHandle()));
+
+  // not implement yet
+  aResult.mConsumed = false;
+  return true;
+}
+
+// static
+bool IMMHandler::OnIMENotify(nsWindow* aWindow, WPARAM wParam, LPARAM lParam,
+                             MSGResult& aResult) {
+  switch (wParam) {
+    case IMN_CHANGECANDIDATE:
+      MOZ_LOG(gIMELog, LogLevel::Info,
+              ("IMMHandler::OnIMENotify, hWnd=%p, IMN_CHANGECANDIDATE, "
+               "lParam=%08" PRIxLPTR,
+               aWindow->GetWindowHandle(), lParam));
+      break;
+    case IMN_CLOSECANDIDATE:
+      MOZ_LOG(gIMELog, LogLevel::Info,
+              ("IMMHandler::OnIMENotify, hWnd=%p, IMN_CLOSECANDIDATE, "
+               "lParam=%08" PRIxLPTR,
+               aWindow->GetWindowHandle(), lParam));
+      break;
+    case IMN_CLOSESTATUSWINDOW:
+      MOZ_LOG(gIMELog, LogLevel::Info,
+              ("IMMHandler::OnIMENotify, hWnd=%p, IMN_CLOSESTATUSWINDOW",
+               aWindow->GetWindowHandle()));
+      break;
+    case IMN_GUIDELINE:
+      MOZ_LOG(gIMELog, LogLevel::Info,
+              ("IMMHandler::OnIMENotify, hWnd=%p, IMN_GUIDELINE",
+               aWindow->GetWindowHandle()));
+      break;
+    case IMN_OPENCANDIDATE:
+      MOZ_LOG(gIMELog, LogLevel::Info,
+              ("IMMHandler::OnIMENotify, hWnd=%p, IMN_OPENCANDIDATE, "
+               "lParam=%08" PRIxLPTR,
+               aWindow->GetWindowHandle(), lParam));
+      break;
+    case IMN_OPENSTATUSWINDOW:
+      MOZ_LOG(gIMELog, LogLevel::Info,
+              ("IMMHandler::OnIMENotify, hWnd=%p, IMN_OPENSTATUSWINDOW",
+               aWindow->GetWindowHandle()));
+      break;
+    case IMN_SETCANDIDATEPOS:
+      MOZ_LOG(gIMELog, LogLevel::Info,
+              ("IMMHandler::OnIMENotify, hWnd=%p, IMN_SETCANDIDATEPOS, "
+               "lParam=%08" PRIxLPTR,
+               aWindow->GetWindowHandle(), lParam));
+      break;
+    case IMN_SETCOMPOSITIONFONT:
+      MOZ_LOG(gIMELog, LogLevel::Info,
+              ("IMMHandler::OnIMENotify, hWnd=%p, IMN_SETCOMPOSITIONFONT",
+               aWindow->GetWindowHandle()));
+      break;
+    case IMN_SETCOMPOSITIONWINDOW:
+      MOZ_LOG(gIMELog, LogLevel::Info,
+              ("IMMHandler::OnIMENotify, hWnd=%p, IMN_SETCOMPOSITIONWINDOW",
+               aWindow->GetWindowHandle()));
+      break;
+    case IMN_SETCONVERSIONMODE:
+      MOZ_LOG(gIMELog, LogLevel::Info,
+              ("IMMHandler::OnIMENotify, hWnd=%p, IMN_SETCONVERSIONMODE",
+               aWindow->GetWindowHandle()));
+      break;
+    case IMN_SETOPENSTATUS:
+      MOZ_LOG(gIMELog, LogLevel::Info,
+              ("IMMHandler::OnIMENotify, hWnd=%p, IMN_SETOPENSTATUS",
+               aWindow->GetWindowHandle()));
+      break;
+    case IMN_SETSENTENCEMODE:
+      MOZ_LOG(gIMELog, LogLevel::Info,
+              ("IMMHandler::OnIMENotify, hWnd=%p, IMN_SETSENTENCEMODE",
+               aWindow->GetWindowHandle()));
+      break;
+    case IMN_SETSTATUSWINDOWPOS:
+      MOZ_LOG(gIMELog, LogLevel::Info,
+              ("IMMHandler::OnIMENotify, hWnd=%p, IMN_SETSTATUSWINDOWPOS",
+               aWindow->GetWindowHandle()));
+      break;
+    case IMN_PRIVATE:
+      MOZ_LOG(gIMELog, LogLevel::Info,
+              ("IMMHandler::OnIMENotify, hWnd=%p, IMN_PRIVATE",
+               aWindow->GetWindowHandle()));
+      break;
+  }
+
+  // not implement yet
+  aResult.mConsumed = false;
+  return true;
+}
+
+bool IMMHandler::OnIMERequest(nsWindow* aWindow, WPARAM wParam, LPARAM lParam,
+                              MSGResult& aResult) {
+  switch (wParam) {
+    case IMR_RECONVERTSTRING:
+      MOZ_LOG(gIMELog, LogLevel::Info,
+              ("IMMHandler::OnIMERequest, hWnd=%p, IMR_RECONVERTSTRING",
+               aWindow->GetWindowHandle()));
+      aResult.mConsumed = HandleReconvert(aWindow, lParam, &aResult.mResult);
+      return true;
+    case IMR_QUERYCHARPOSITION:
+      MOZ_LOG(gIMELog, LogLevel::Info,
+              ("IMMHandler::OnIMERequest, hWnd=%p, IMR_QUERYCHARPOSITION",
+               aWindow->GetWindowHandle()));
+      aResult.mConsumed =
+          HandleQueryCharPosition(aWindow, lParam, &aResult.mResult);
+      return true;
+    case IMR_DOCUMENTFEED:
+      MOZ_LOG(gIMELog, LogLevel::Info,
+              ("IMMHandler::OnIMERequest, hWnd=%p, IMR_DOCUMENTFEED",
+               aWindow->GetWindowHandle()));
+      aResult.mConsumed = HandleDocumentFeed(aWindow, lParam, &aResult.mResult);
+      return true;
+    default:
+      MOZ_LOG(gIMELog, LogLevel::Info,
+              ("IMMHandler::OnIMERequest, hWnd=%p, wParam=%08zx",
+               aWindow->GetWindowHandle(), wParam));
+      aResult.mConsumed = false;
+      return true;
+  }
+}
+
+// static
+bool IMMHandler::OnIMESelect(nsWindow* aWindow, WPARAM wParam, LPARAM lParam,
+                             MSGResult& aResult) {
+  MOZ_LOG(
+      gIMELog, LogLevel::Info,
+      ("IMMHandler::OnIMESelect, hWnd=%p, wParam=%08zx, lParam=%08" PRIxLPTR,
+       aWindow->GetWindowHandle(), wParam, lParam));
+
+  // not implement yet
+  aResult.mConsumed = false;
+  return true;
+}
+
+// static
+bool IMMHandler::OnIMESetContext(nsWindow* aWindow, WPARAM wParam,
+                                 LPARAM lParam, MSGResult& aResult) {
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("IMMHandler::OnIMESetContext, hWnd=%p, %s, lParam=%08" PRIxLPTR,
+           aWindow->GetWindowHandle(), wParam ? "Active" : "Deactive", lParam));
+
+  aResult.mConsumed = false;
+
+  // NOTE: If the aWindow is top level window of the composing window because
+  // when a window on deactive window gets focus, WM_IME_SETCONTEXT (wParam is
+  // TRUE) is sent to the top level window first.  After that,
+  // WM_IME_SETCONTEXT (wParam is FALSE) is sent to the top level window.
+  // Finally, WM_IME_SETCONTEXT (wParam is TRUE) is sent to the focused window.
+  // The top level window never becomes composing window, so, we can ignore
+  // the WM_IME_SETCONTEXT on the top level window.
+  if (IsTopLevelWindowOfComposition(aWindow)) {
+    MOZ_LOG(gIMELog, LogLevel::Info,
+            ("  IMMHandler::OnIMESetContext, hWnd=%p is top level window",
+             aWindow->GetWindowHandle()));
+    return true;
+  }
+
+  // When IME context is activating on another window,
+  // we should commit the old composition on the old window.
+  bool cancelComposition = false;
+  if (wParam && gIMMHandler) {
+    cancelComposition = gIMMHandler->CommitCompositionOnPreviousWindow(aWindow);
+  }
+
+  if (wParam && (lParam & ISC_SHOWUICOMPOSITIONWINDOW) &&
+      ShouldDrawCompositionStringOurselves()) {
+    MOZ_LOG(gIMELog, LogLevel::Info,
+            ("  IMMHandler::OnIMESetContext, ISC_SHOWUICOMPOSITIONWINDOW is "
+             "removed"));
+    lParam &= ~ISC_SHOWUICOMPOSITIONWINDOW;
+  }
+
+  // We should sent WM_IME_SETCONTEXT to the DefWndProc here because the
+  // ancestor windows shouldn't receive this message.  If they receive the
+  // message, we cannot know whether which window is the target of the message.
+  aResult.mResult = ::DefWindowProc(aWindow->GetWindowHandle(),
+                                    WM_IME_SETCONTEXT, wParam, lParam);
+
+  // Cancel composition on the new window if we committed our composition on
+  // another window.
+  if (cancelComposition) {
+    CancelComposition(aWindow, true);
+  }
+
+  aResult.mConsumed = true;
+  return true;
+}
+
+bool IMMHandler::OnChar(nsWindow* aWindow, WPARAM wParam, LPARAM lParam,
+                        MSGResult& aResult) {
+  // The return value must be same as aResult.mConsumed because only when we
+  // consume the message, the caller shouldn't do anything anymore but
+  // otherwise, the caller should handle the message.
+  aResult.mConsumed = false;
+  if (IsIMECharRecordsEmpty()) {
+    return aResult.mConsumed;
+  }
+  WPARAM recWParam;
+  LPARAM recLParam;
+  DequeueIMECharRecords(recWParam, recLParam);
+  MOZ_LOG(
+      gIMELog, LogLevel::Info,
+      ("IMMHandler::OnChar, aWindow=%p, wParam=%08zx, lParam=%08" PRIxLPTR ", "
+       "recorded: wParam=%08zx, lParam=%08" PRIxLPTR,
+       aWindow->GetWindowHandle(), wParam, lParam, recWParam, recLParam));
+  // If an unexpected char message comes, we should reset the records,
+  // of course, this shouldn't happen.
+  if (recWParam != wParam || recLParam != lParam) {
+    ResetIMECharRecords();
+    return aResult.mConsumed;
+  }
+  // Eat the char message which is caused by WM_IME_CHAR because we should
+  // have processed the IME messages, so, this message could be come from
+  // a windowless plug-in.
+  aResult.mConsumed = true;
+  return aResult.mConsumed;
+}
+
+/****************************************************************************
+ * others
+ ****************************************************************************/
+
+TextEventDispatcher* IMMHandler::GetTextEventDispatcherFor(nsWindow* aWindow) {
+  return aWindow == mComposingWindow && mDispatcher
+             ? mDispatcher.get()
+             : aWindow->GetTextEventDispatcher();
+}
+
+void IMMHandler::HandleStartComposition(nsWindow* aWindow,
+                                        const IMEContext& aContext) {
+  MOZ_ASSERT(!mIsComposing,
+             "HandleStartComposition is called but mIsComposing is TRUE");
+
+  const Maybe<ContentSelection>& contentSelection =
+      GetContentSelectionWithQueryIfNothing(aWindow);
+  if (contentSelection.isNothing()) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("  IMMHandler::HandleStartComposition, FAILED, due to "
+             "Selection::GetContentSelectionWithQueryIfNothing() failure"));
+    return;
+  }
+  if (!contentSelection->HasRange()) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("  IMMHandler::HandleStartComposition, FAILED, due to "
+             "there is no selection"));
+    return;
+  }
+
+  AdjustCompositionFont(aWindow, aContext, contentSelection->WritingModeRef());
+
+  mCompositionStart = contentSelection->OffsetAndDataRef().StartOffset();
+  mCursorPosition = NO_IME_CARET;
+
+  RefPtr<TextEventDispatcher> dispatcher = GetTextEventDispatcherFor(aWindow);
+  nsresult rv = dispatcher->BeginNativeInputTransaction();
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("  IMMHandler::HandleStartComposition, FAILED due to "
+             "TextEventDispatcher::BeginNativeInputTransaction() failure"));
+    return;
+  }
+  WidgetEventTime eventTime = aWindow->CurrentMessageWidgetEventTime();
+  nsEventStatus status;
+  rv = dispatcher->StartComposition(status, &eventTime);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("  IMMHandler::HandleStartComposition, FAILED, due to "
+             "TextEventDispatcher::StartComposition() failure"));
+    return;
+  }
+
+  mIsComposing = true;
+  mComposingWindow = aWindow;
+  mDispatcher = dispatcher;
+
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("IMMHandler::HandleStartComposition, START composition, "
+           "mCompositionStart=%u",
+           mCompositionStart));
+}
+
+bool IMMHandler::HandleComposition(nsWindow* aWindow,
+                                   const IMEContext& aContext, LPARAM lParam) {
+  // for bug #60050
+  // MS-IME 95/97/98/2000 may send WM_IME_COMPOSITION with non-conversion
+  // mode before it send WM_IME_STARTCOMPOSITION.
+  // However, ATOK sends a WM_IME_COMPOSITION before WM_IME_STARTCOMPOSITION,
+  // and if we access ATOK via some APIs, ATOK will sometimes fail to
+  // initialize its state.  If WM_IME_STARTCOMPOSITION is already in the
+  // message queue, we should ignore the strange WM_IME_COMPOSITION message and
+  // skip to the next.  So, we should look for next composition message
+  // (WM_IME_STARTCOMPOSITION or WM_IME_ENDCOMPOSITION or WM_IME_COMPOSITION),
+  // and if it's WM_IME_STARTCOMPOSITION, and one more next composition message
+  // is WM_IME_COMPOSITION, current IME is ATOK, probably.  Otherwise, we
+  // should start composition forcibly.
+  if (!mIsComposing) {
+    MSG msg1, msg2;
+    HWND wnd = aWindow->GetWindowHandle();
+    if (WinUtils::PeekMessage(&msg1, wnd, WM_IME_STARTCOMPOSITION,
+                              WM_IME_COMPOSITION, PM_NOREMOVE) &&
+        msg1.message == WM_IME_STARTCOMPOSITION &&
+        WinUtils::PeekMessage(&msg2, wnd, WM_IME_ENDCOMPOSITION,
+                              WM_IME_COMPOSITION, PM_NOREMOVE) &&
+        msg2.message == WM_IME_COMPOSITION) {
+      MOZ_LOG(gIMELog, LogLevel::Info,
+              ("IMMHandler::HandleComposition, Ignores due to find a "
+               "WM_IME_STARTCOMPOSITION"));
+      return ShouldDrawCompositionStringOurselves();
+    }
+  }
+
+  bool startCompositionMessageHasBeenSent = mIsComposing;
+
+  //
+  // This catches a fixed result
+  //
+  if (IS_COMMITTING_LPARAM(lParam)) {
+    if (!mIsComposing) {
+      HandleStartComposition(aWindow, aContext);
+    }
+
+    GetCompositionString(aContext, GCS_RESULTSTR, mCompositionString);
+
+    MOZ_LOG(gIMELog, LogLevel::Info,
+            ("IMMHandler::HandleComposition, GCS_RESULTSTR"));
+
+    HandleEndComposition(aWindow, &mCompositionString);
+
+    if (!IS_COMPOSING_LPARAM(lParam)) {
+      return ShouldDrawCompositionStringOurselves();
+    }
+  }
+
+  //
+  // This provides us with a composition string
+  //
+  if (!mIsComposing) {
+    HandleStartComposition(aWindow, aContext);
+  }
+
+  //--------------------------------------------------------
+  // 1. Get GCS_COMPSTR
+  //--------------------------------------------------------
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("IMMHandler::HandleComposition, GCS_COMPSTR"));
+
+  nsAutoString previousCompositionString(mCompositionString);
+  GetCompositionString(aContext, GCS_COMPSTR, mCompositionString);
+
+  if (!IS_COMPOSING_LPARAM(lParam)) {
+    MOZ_LOG(
+        gIMELog, LogLevel::Info,
+        ("  IMMHandler::HandleComposition, lParam doesn't indicate composing, "
+         "mCompositionString=\"%s\", previousCompositionString=\"%s\"",
+         NS_ConvertUTF16toUTF8(mCompositionString).get(),
+         NS_ConvertUTF16toUTF8(previousCompositionString).get()));
+
+    // If composition string isn't changed, we can trust the lParam.
+    // So, we need to do nothing.
+    if (previousCompositionString == mCompositionString) {
+      return ShouldDrawCompositionStringOurselves();
+    }
+
+    // IME may send WM_IME_COMPOSITION without composing lParam values
+    // when composition string becomes empty (e.g., using Backspace key).
+    // If composition string is empty, we should dispatch a compositionchange
+    // event with empty string and clear the clause information.
+    if (mCompositionString.IsEmpty()) {
+      mClauseArray.Clear();
+      mAttributeArray.Clear();
+      mCursorPosition = 0;
+      DispatchCompositionChangeEvent(aWindow, aContext);
+      return ShouldDrawCompositionStringOurselves();
+    }
+
+    // Otherwise, we cannot trust the lParam value.  We might need to
+    // dispatch compositionchange event with the latest composition string
+    // information.
+  }
+
+  // See https://bugzilla.mozilla.org/show_bug.cgi?id=296339
+  if (mCompositionString.IsEmpty() && !startCompositionMessageHasBeenSent) {
+    // In this case, maybe, the sender is MSPinYin. That sends *only*
+    // WM_IME_COMPOSITION with GCS_COMP* and GCS_RESULT* when
+    // user inputted the Chinese full stop. So, that doesn't send
+    // WM_IME_STARTCOMPOSITION and WM_IME_ENDCOMPOSITION.
+    // If WM_IME_STARTCOMPOSITION was not sent and the composition
+    // string is null (it indicates the composition transaction ended),
+    // WM_IME_ENDCOMPOSITION may not be sent. If so, we cannot run
+    // HandleEndComposition() in other place.
+    MOZ_LOG(gIMELog, LogLevel::Info,
+            ("    IMMHandler::HandleComposition, Aborting GCS_COMPSTR"));
+    HandleEndComposition(aWindow);
+    return IS_COMMITTING_LPARAM(lParam);
+  }
+
+  //--------------------------------------------------------
+  // 2. Get GCS_COMPCLAUSE
+  //--------------------------------------------------------
+  long clauseArrayLength =
+      ::ImmGetCompositionStringW(aContext.get(), GCS_COMPCLAUSE, nullptr, 0);
+  clauseArrayLength /= sizeof(uint32_t);
+
+  if (clauseArrayLength > 0) {
+    nsresult rv = EnsureClauseArray(clauseArrayLength);
+    NS_ENSURE_SUCCESS(rv, false);
+
+    // Intelligent ABC IME (Simplified Chinese IME, the code page is 936)
+    // will crash in ImmGetCompositionStringW for GCS_COMPCLAUSE (bug 424663).
+    // See comment 35 of the bug for the detail. Therefore, we should use A
+    // API for it, however, we should not kill Unicode support on all IMEs.
+    bool useA_API = !(sIMEProperty & IME_PROP_UNICODE);
+
+    MOZ_LOG(gIMELog, LogLevel::Info,
+            ("  IMMHandler::HandleComposition, GCS_COMPCLAUSE, useA_API=%s",
+             useA_API ? "TRUE" : "FALSE"));
+
+    long clauseArrayLength2 =
+        useA_API ? ::ImmGetCompositionStringA(
+                       aContext.get(), GCS_COMPCLAUSE, mClauseArray.Elements(),
+                       mClauseArray.Capacity() * sizeof(uint32_t))
+                 : ::ImmGetCompositionStringW(
+                       aContext.get(), GCS_COMPCLAUSE, mClauseArray.Elements(),
+                       mClauseArray.Capacity() * sizeof(uint32_t));
+    clauseArrayLength2 /= sizeof(uint32_t);
+
+    if (clauseArrayLength != clauseArrayLength2) {
+      MOZ_LOG(gIMELog, LogLevel::Info,
+              ("    IMMHandler::HandleComposition, GCS_COMPCLAUSE, "
+               "clauseArrayLength=%ld but clauseArrayLength2=%ld",
+               clauseArrayLength, clauseArrayLength2));
+      if (clauseArrayLength > clauseArrayLength2)
+        clauseArrayLength = clauseArrayLength2;
+    }
+
+    if (useA_API && clauseArrayLength > 0) {
+      // Convert each values of sIMECompClauseArray. The values mean offset of
+      // the clauses in ANSI string. But we need the values in Unicode string.
+      nsAutoCString compANSIStr;
+      if (ConvertToANSIString(mCompositionString, GetKeyboardCodePage(),
+                              compANSIStr)) {
+        uint32_t maxlen = compANSIStr.Length();
+        mClauseArray.SetLength(clauseArrayLength);
+        mClauseArray[0] = 0;  // first value must be 0
+        for (int32_t i = 1; i < clauseArrayLength; i++) {
+          uint32_t len = std::min(mClauseArray[i], maxlen);
+          mClauseArray[i] =
+              ::MultiByteToWideChar(GetKeyboardCodePage(), MB_PRECOMPOSED,
+                                    (LPCSTR)compANSIStr.get(), len, nullptr, 0);
+        }
+      }
+    }
+  }
+  // compClauseArrayLength may be negative. I.e., ImmGetCompositionStringW
+  // may return an error code.
+  mClauseArray.SetLength(std::max<long>(0, clauseArrayLength));
+
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("  IMMHandler::HandleComposition, GCS_COMPCLAUSE, mClauseLength=%zu",
+           mClauseArray.Length()));
+
+  //--------------------------------------------------------
+  // 3. Get GCS_COMPATTR
+  //--------------------------------------------------------
+  // This provides us with the attribute string necessary
+  // for doing hiliting
+  long attrArrayLength =
+      ::ImmGetCompositionStringW(aContext.get(), GCS_COMPATTR, nullptr, 0);
+  attrArrayLength /= sizeof(uint8_t);
+
+  if (attrArrayLength > 0) {
+    nsresult rv = EnsureAttributeArray(attrArrayLength);
+    NS_ENSURE_SUCCESS(rv, false);
+    attrArrayLength = ::ImmGetCompositionStringW(
+        aContext.get(), GCS_COMPATTR, mAttributeArray.Elements(),
+        mAttributeArray.Capacity() * sizeof(uint8_t));
+  }
+
+  // attrStrLen may be negative. I.e., ImmGetCompositionStringW may return an
+  // error code.
+  mAttributeArray.SetLength(std::max<long>(0, attrArrayLength));
+
+  MOZ_LOG(
+      gIMELog, LogLevel::Info,
+      ("  IMMHandler::HandleComposition, GCS_COMPATTR, mAttributeLength=%zu",
+       mAttributeArray.Length()));
+
+  //--------------------------------------------------------
+  // 4. Get GCS_CURSOPOS
+  //--------------------------------------------------------
+  // Some IMEs (e.g., the standard IME for Korean) don't have caret position.
+  if (lParam & GCS_CURSORPOS) {
+    mCursorPosition =
+        ::ImmGetCompositionStringW(aContext.get(), GCS_CURSORPOS, nullptr, 0);
+    if (mCursorPosition < 0) {
+      mCursorPosition = NO_IME_CARET;  // The result is error
+    }
+  } else {
+    mCursorPosition = NO_IME_CARET;
+  }
+
+  NS_ASSERTION(mCursorPosition <= (long)mCompositionString.Length(),
+               "illegal pos");
+
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("  IMMHandler::HandleComposition, GCS_CURSORPOS, mCursorPosition=%d",
+           mCursorPosition));
+
+  //--------------------------------------------------------
+  // 5. Send the compositionchange event
+  //--------------------------------------------------------
+  DispatchCompositionChangeEvent(aWindow, aContext);
+
+  return ShouldDrawCompositionStringOurselves();
+}
+
+void IMMHandler::HandleEndComposition(nsWindow* aWindow,
+                                      const nsAString* aCommitString) {
+  MOZ_ASSERT(mIsComposing,
+             "HandleEndComposition is called but mIsComposing is FALSE");
+
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("IMMHandler::HandleEndComposition(aWindow=0x%p, aCommitString=0x%p "
+           "(\"%s\"))",
+           aWindow, aCommitString,
+           aCommitString ? NS_ConvertUTF16toUTF8(*aCommitString).get() : ""));
+
+  IMEHandler::MaybeDestroyNativeCaret();
+
+  RefPtr<TextEventDispatcher> dispatcher = GetTextEventDispatcherFor(aWindow);
+  nsresult rv = dispatcher->BeginNativeInputTransaction();
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("  IMMHandler::HandleEndComposition, FAILED due to "
+             "TextEventDispatcher::BeginNativeInputTransaction() failure"));
+    return;
+  }
+  WidgetEventTime eventTime = aWindow->CurrentMessageWidgetEventTime();
+  nsEventStatus status;
+  rv = dispatcher->CommitComposition(status, aCommitString, &eventTime);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("  IMMHandler::HandleStartComposition, FAILED, due to "
+             "TextEventDispatcher::CommitComposition() failure"));
+    return;
+  }
+  mIsComposing = false;
+  // XXX aWindow and mComposingWindow are always same??
+  mComposingWindow = nullptr;
+  mDispatcher = nullptr;
+}
+
+bool IMMHandler::HandleReconvert(nsWindow* aWindow, LPARAM lParam,
+                                 LRESULT* oResult) {
+  *oResult = 0;
+  RECONVERTSTRING* pReconv = reinterpret_cast<RECONVERTSTRING*>(lParam);
+
+  const Maybe<ContentSelection>& contentSelection =
+      GetContentSelectionWithQueryIfNothing(aWindow);
+  if (contentSelection.isNothing()) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("IMMHandler::HandleReconvert, FAILED, due to "
+             "Selection::GetContentSelectionWithQueryIfNothing() failure"));
+    return false;
+  }
+
+  const uint32_t len = contentSelection->HasRange()
+                           ? contentSelection->OffsetAndDataRef().Length()
+                           : 0u;
+  uint32_t needSize = sizeof(RECONVERTSTRING) + len * sizeof(WCHAR);
+
+  if (!pReconv) {
+    // Return need size to reconvert.
+    if (len == 0) {
+      MOZ_LOG(gIMELog, LogLevel::Error,
+              ("IMMHandler::HandleReconvert, There are not selected text"));
+      return false;
+    }
+    *oResult = needSize;
+    MOZ_LOG(gIMELog, LogLevel::Info,
+            ("IMMHandler::HandleReconvert, succeeded, result=%" PRIdLPTR,
+             *oResult));
+    return true;
+  }
+
+  if (pReconv->dwSize < needSize) {
+    MOZ_LOG(gIMELog, LogLevel::Info,
+            ("IMMHandler::HandleReconvert, FAILED, pReconv->dwSize=%ld, "
+             "needSize=%u",
+             pReconv->dwSize, needSize));
+    return false;
+  }
+
+  *oResult = needSize;
+
+  // Fill reconvert struct
+  pReconv->dwVersion = 0;
+  pReconv->dwStrLen = len;
+  pReconv->dwStrOffset = sizeof(RECONVERTSTRING);
+  pReconv->dwCompStrLen = len;
+  pReconv->dwCompStrOffset = 0;
+  pReconv->dwTargetStrLen = len;
+  pReconv->dwTargetStrOffset = 0;
+
+  if (len) {
+    ::CopyMemory(reinterpret_cast<LPVOID>(lParam + sizeof(RECONVERTSTRING)),
+                 contentSelection->OffsetAndDataRef().DataRef().get(),
+                 len * sizeof(WCHAR));
+  }
+
+  MOZ_LOG(
+      gIMELog, LogLevel::Info,
+      ("IMMHandler::HandleReconvert, SUCCEEDED, pReconv=%s, result=%" PRIdLPTR,
+       GetReconvertStringLog(pReconv).get(), *oResult));
+
+  return true;
+}
+
+bool IMMHandler::HandleQueryCharPosition(nsWindow* aWindow, LPARAM lParam,
+                                         LRESULT* oResult) {
+  uint32_t len = mIsComposing ? mCompositionString.Length() : 0;
+  *oResult = false;
+  IMECHARPOSITION* pCharPosition = reinterpret_cast<IMECHARPOSITION*>(lParam);
+  if (!pCharPosition) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("IMMHandler::HandleQueryCharPosition, FAILED, due to "
+             "pCharPosition is null"));
+    return false;
+  }
+  if (pCharPosition->dwSize < sizeof(IMECHARPOSITION)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("IMMHandler::HandleReconvert, FAILED, pCharPosition->dwSize=%lu, "
+             "sizeof(IMECHARPOSITION)=%zu",
+             pCharPosition->dwSize, sizeof(IMECHARPOSITION)));
+    return false;
+  }
+  if (::GetFocus() != aWindow->GetWindowHandle()) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("IMMHandler::HandleReconvert, FAILED, ::GetFocus()=%p, "
+             "OurWindowHandle=%p",
+             ::GetFocus(), aWindow->GetWindowHandle()));
+    return false;
+  }
+  if (pCharPosition->dwCharPos > len) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("IMMHandler::HandleQueryCharPosition, FAILED, "
+             "pCharPosition->dwCharPos=%ld, len=%u",
+             pCharPosition->dwCharPos, len));
+    return false;
+  }
+
+  LayoutDeviceIntRect r;
+  bool ret =
+      GetCharacterRectOfSelectedTextAt(aWindow, pCharPosition->dwCharPos, r);
+  NS_ENSURE_TRUE(ret, false);
+
+  LayoutDeviceIntRect screenRect;
+  // We always need top level window that is owner window of the popup window
+  // even if the content of the popup window has focus.
+  ResolveIMECaretPos(aWindow->GetTopLevelWindow(false), r, nullptr, screenRect);
+
+  // XXX This might need to check writing mode.  However, MSDN doesn't explain
+  //     how to set the values in vertical writing mode. Additionally, IME
+  //     doesn't work well with top-left of the character (this is explicitly
+  //     documented) and its horizontal width.  So, it might be better to set
+  //     top-right corner of the character and horizontal width, but we're not
+  //     sure if it doesn't cause any problems with a lot of IMEs...
+  pCharPosition->pt.x = screenRect.X();
+  pCharPosition->pt.y = screenRect.Y();
+
+  pCharPosition->cLineHeight = r.Height();
+
+  WidgetQueryContentEvent queryEditorRectEvent(true, eQueryEditorRect, aWindow);
+  aWindow->InitEvent(queryEditorRectEvent);
+  DispatchEvent(aWindow, queryEditorRectEvent);
+  if (NS_WARN_IF(queryEditorRectEvent.Failed())) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("  IMMHandler::HandleQueryCharPosition, eQueryEditorRect failed"));
+    ::GetWindowRect(aWindow->GetWindowHandle(), &pCharPosition->rcDocument);
+  } else {
+    LayoutDeviceIntRect editorRectInWindow = queryEditorRectEvent.mReply->mRect;
+    nsWindow* window = !!queryEditorRectEvent.mReply->mFocusedWidget
+                           ? static_cast<nsWindow*>(
+                                 queryEditorRectEvent.mReply->mFocusedWidget)
+                           : aWindow;
+    LayoutDeviceIntRect editorRectInScreen;
+    ResolveIMECaretPos(window, editorRectInWindow, nullptr, editorRectInScreen);
+    ::SetRect(&pCharPosition->rcDocument, editorRectInScreen.X(),
+              editorRectInScreen.Y(), editorRectInScreen.XMost(),
+              editorRectInScreen.YMost());
+  }
+
+  *oResult = TRUE;
+
+  MOZ_LOG(
+      gIMELog, LogLevel::Info,
+      ("IMMHandler::HandleQueryCharPosition, SUCCEEDED, pCharPosition={ "
+       "pt={ x=%ld, y=%ld }, cLineHeight=%d, rcDocument={ left=%ld, top=%ld, "
+       "right=%ld, bottom=%ld } }",
+       pCharPosition->pt.x, pCharPosition->pt.y, pCharPosition->cLineHeight,
+       pCharPosition->rcDocument.left, pCharPosition->rcDocument.top,
+       pCharPosition->rcDocument.right, pCharPosition->rcDocument.bottom));
+  return true;
+}
+
+bool IMMHandler::HandleDocumentFeed(nsWindow* aWindow, LPARAM lParam,
+                                    LRESULT* oResult) {
+  *oResult = 0;
+  RECONVERTSTRING* pReconv = reinterpret_cast<RECONVERTSTRING*>(lParam);
+
+  LayoutDeviceIntPoint point(0, 0);
+
+  bool hasCompositionString =
+      mIsComposing && ShouldDrawCompositionStringOurselves();
+
+  int32_t targetOffset, targetLength;
+  if (!hasCompositionString) {
+    const Maybe<ContentSelection>& contentSelection =
+        GetContentSelectionWithQueryIfNothing(aWindow);
+    if (contentSelection.isNothing()) {
+      MOZ_LOG(gIMELog, LogLevel::Error,
+              ("IMMHandler::HandleDocumentFeed, FAILED, due to "
+               "Selection::GetContentSelectionWithQueryIfNothing() failure"));
+      return false;
+    }
+    if (contentSelection->HasRange()) {
+      targetOffset = static_cast<int32_t>(
+          contentSelection->OffsetAndDataRef().StartOffset());
+      targetLength =
+          static_cast<int32_t>(contentSelection->OffsetAndDataRef().Length());
+    } else {
+      // If there is no selection range, let's return all text in the editor.
+      targetOffset = 0;
+      targetLength = INT32_MAX;
+    }
+  } else {
+    targetOffset = int32_t(mCompositionStart);
+    targetLength = int32_t(mCompositionString.Length());
+  }
+
+  // XXX nsString::Find and nsString::RFind take int32_t for offset, so,
+  //     we cannot support this message when the current offset is larger than
+  //     INT32_MAX.
+  if (targetOffset < 0 || targetLength < 0 || targetOffset + targetLength < 0) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("IMMHandler::HandleDocumentFeed, FAILED, "
+             "due to the selection is out of range"));
+    return false;
+  }
+
+  // Get all contents of the focused editor.
+  WidgetQueryContentEvent queryTextContentEvent(true, eQueryTextContent,
+                                                aWindow);
+  queryTextContentEvent.InitForQueryTextContent(0, UINT32_MAX);
+  aWindow->InitEvent(queryTextContentEvent, &point);
+  DispatchEvent(aWindow, queryTextContentEvent);
+  if (NS_WARN_IF(queryTextContentEvent.Failed())) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("IMMHandler::HandleDocumentFeed, FAILED, "
+             "due to eQueryTextContent failure"));
+    return false;
+  }
+
+  nsAutoString str(queryTextContentEvent.mReply->DataRef());
+  if (targetOffset > static_cast<int32_t>(str.Length())) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("  IMMHandler::HandleDocumentFeed, FAILED, "
+             "due to the caret offset is invalid"));
+    return false;
+  }
+
+  // Get the focused paragraph, we decide that it starts from the previous CRLF
+  // (or start of the editor) to the next one (or the end of the editor).
+  int32_t paragraphStart = 0;
+  if (targetOffset > 0) {
+    paragraphStart = Substring(str, 0, targetOffset).RFind(u"\n") + 1;
+  }
+  int32_t paragraphEnd = str.Find(u"\r", targetOffset + targetLength);
+  if (paragraphEnd < 0) {
+    paragraphEnd = str.Length();
+  }
+  nsDependentSubstring paragraph(str, paragraphStart,
+                                 paragraphEnd - paragraphStart);
+
+  uint32_t len = paragraph.Length();
+  uint32_t needSize = sizeof(RECONVERTSTRING) + len * sizeof(WCHAR);
+
+  if (!pReconv) {
+    *oResult = needSize;
+    MOZ_LOG(gIMELog, LogLevel::Info,
+            ("IMMHandler::HandleDocumentFeed, succeeded, result=%" PRIdLPTR,
+             *oResult));
+    return true;
+  }
+
+  if (pReconv->dwSize < needSize) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("IMMHandler::HandleDocumentFeed, FAILED, "
+             "pReconv->dwSize=%ld, needSize=%u",
+             pReconv->dwSize, needSize));
+    return false;
+  }
+
+  // Fill reconvert struct
+  pReconv->dwVersion = 0;
+  pReconv->dwStrLen = len;
+  pReconv->dwStrOffset = sizeof(RECONVERTSTRING);
+  if (hasCompositionString) {
+    pReconv->dwCompStrLen = targetLength;
+    pReconv->dwCompStrOffset = (targetOffset - paragraphStart) * sizeof(WCHAR);
+    // Set composition target clause information
+    uint32_t offset, length;
+    if (!GetTargetClauseRange(&offset, &length)) {
+      MOZ_LOG(gIMELog, LogLevel::Error,
+              ("IMMHandler::HandleDocumentFeed, FAILED, "
+               "due to IMMHandler::GetTargetClauseRange() failure"));
+      return false;
+    }
+    pReconv->dwTargetStrLen = length;
+    pReconv->dwTargetStrOffset = (offset - paragraphStart) * sizeof(WCHAR);
+  } else {
+    pReconv->dwTargetStrLen = targetLength;
+    pReconv->dwTargetStrOffset =
+        (targetOffset - paragraphStart) * sizeof(WCHAR);
+    // There is no composition string, so, the length is zero but we should
+    // set the cursor offset to the composition str offset.
+    pReconv->dwCompStrLen = 0;
+    pReconv->dwCompStrOffset = pReconv->dwTargetStrOffset;
+  }
+
+  *oResult = needSize;
+  ::CopyMemory(reinterpret_cast<LPVOID>(lParam + sizeof(RECONVERTSTRING)),
+               paragraph.BeginReading(), len * sizeof(WCHAR));
+
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("IMMHandler::HandleDocumentFeed, SUCCEEDED, pReconv=%s, "
+           "result=%" PRIdLPTR,
+           GetReconvertStringLog(pReconv).get(), *oResult));
+
+  return true;
+}
+
+bool IMMHandler::CommitCompositionOnPreviousWindow(nsWindow* aWindow) {
+  if (!mComposingWindow || mComposingWindow == aWindow) {
+    return false;
+  }
+
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("IMMHandler::CommitCompositionOnPreviousWindow, mIsComposing=%s",
+           GetBoolName(mIsComposing)));
+
+  // If we have composition, we should dispatch composition events internally.
+  if (mIsComposing) {
+    IMEContext context(mComposingWindow);
+    NS_ASSERTION(context.IsValid(), "IME context must be valid");
+
+    HandleEndComposition(mComposingWindow);
+    return true;
+  }
+
+  return false;
+}
+
+static TextRangeType PlatformToNSAttr(uint8_t aAttr) {
+  switch (aAttr) {
+    case ATTR_INPUT_ERROR:
+    // case ATTR_FIXEDCONVERTED:
+    case ATTR_INPUT:
+      return TextRangeType::eRawClause;
+    case ATTR_CONVERTED:
+      return TextRangeType::eConvertedClause;
+    case ATTR_TARGET_NOTCONVERTED:
+      return TextRangeType::eSelectedRawClause;
+    case ATTR_TARGET_CONVERTED:
+      return TextRangeType::eSelectedClause;
+    default:
+      NS_ASSERTION(false, "unknown attribute");
+      return TextRangeType::eCaret;
+  }
+}
+
+// static
+void IMMHandler::DispatchEvent(nsWindow* aWindow, WidgetGUIEvent& aEvent) {
+  MOZ_LOG(
+      gIMELog, LogLevel::Info,
+      ("IMMHandler::DispatchEvent(aWindow=0x%p, aEvent={ mMessage=%s }, "
+       "aWindow->Destroyed()=%s",
+       aWindow, ToChar(aEvent.mMessage), GetBoolName(aWindow->Destroyed())));
+
+  if (aWindow->Destroyed()) {
+    return;
+  }
+
+  aWindow->DispatchWindowEvent(aEvent);
+}
+
+void IMMHandler::DispatchCompositionChangeEvent(nsWindow* aWindow,
+                                                const IMEContext& aContext) {
+  NS_ASSERTION(mIsComposing, "conflict state");
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("IMMHandler::DispatchCompositionChangeEvent"));
+
+  // If we don't need to draw composition string ourselves, we don't need to
+  // fire compositionchange event during composing.
+  if (!ShouldDrawCompositionStringOurselves()) {
+    // But we need to adjust composition window pos and native caret pos, here.
+    SetIMERelatedWindowsPos(aWindow, aContext);
+    return;
+  }
+
+  RefPtr<nsWindow> kungFuDeathGrip(aWindow);
+  RefPtr<TextEventDispatcher> dispatcher = GetTextEventDispatcherFor(aWindow);
+  nsresult rv = dispatcher->BeginNativeInputTransaction();
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("  IMMHandler::DispatchCompositionChangeEvent, FAILED due to "
+             "TextEventDispatcher::BeginNativeInputTransaction() failure"));
+    return;
+  }
+
+  // NOTE: Calling SetIMERelatedWindowsPos() from this method will be failure
+  //       in e10s mode.  compositionchange event will notify this of
+  //       NOTIFY_IME_OF_COMPOSITION_EVENT_HANDLED, then
+  //       SetIMERelatedWindowsPos() will be called.
+
+  // XXX Sogou (Simplified Chinese IME) returns contradictory values:
+  //     The cursor position is actual cursor position. However, other values
+  //     (composition string and attributes) are empty.
+
+  if (mCompositionString.IsEmpty()) {
+    // Don't append clause information if composition string is empty.
+  } else if (mClauseArray.IsEmpty()) {
+    // Some IMEs don't return clause array information, then, we assume that
+    // all characters in the composition string are in one clause.
+    MOZ_LOG(gIMELog, LogLevel::Info,
+            ("  IMMHandler::DispatchCompositionChangeEvent, "
+             "mClauseArray.Length()=0"));
+    rv = dispatcher->SetPendingComposition(mCompositionString, nullptr);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      MOZ_LOG(gIMELog, LogLevel::Error,
+              ("  IMMHandler::DispatchCompositionChangeEvent, FAILED due to"
+               "TextEventDispatcher::SetPendingComposition() failure"));
+      return;
+    }
+  } else {
+    // iterate over the attributes
+    rv = dispatcher->SetPendingCompositionString(mCompositionString);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      MOZ_LOG(gIMELog, LogLevel::Error,
+              ("  IMMHandler::DispatchCompositionChangeEvent, FAILED due to"
+               "TextEventDispatcher::SetPendingCompositionString() failure"));
+      return;
+    }
+    uint32_t lastOffset = 0;
+    for (uint32_t i = 0; i < mClauseArray.Length() - 1; i++) {
+      uint32_t current = mClauseArray[i + 1];
+      if (current > mCompositionString.Length()) {
+        MOZ_LOG(gIMELog, LogLevel::Info,
+                ("  IMMHandler::DispatchCompositionChangeEvent, "
+                 "mClauseArray[%u]=%u. "
+                 "This is larger than mCompositionString.Length()=%zu",
+                 i + 1, current, mCompositionString.Length()));
+        current = int32_t(mCompositionString.Length());
+      }
+
+      uint32_t length = current - lastOffset;
+      if (NS_WARN_IF(lastOffset >= mAttributeArray.Length())) {
+        MOZ_LOG(gIMELog, LogLevel::Error,
+                ("  IMMHandler::DispatchCompositionChangeEvent, FAILED due to "
+                 "invalid data of mClauseArray or mAttributeArray"));
+        return;
+      }
+      TextRangeType textRangeType =
+          PlatformToNSAttr(mAttributeArray[lastOffset]);
+      rv = dispatcher->AppendClauseToPendingComposition(length, textRangeType);
+      if (NS_WARN_IF(NS_FAILED(rv))) {
+        MOZ_LOG(gIMELog, LogLevel::Error,
+                ("  IMMHandler::DispatchCompositionChangeEvent, FAILED due to"
+                 "TextEventDispatcher::AppendClauseToPendingComposition() "
+                 "failure"));
+        return;
+      }
+
+      lastOffset = current;
+
+      MOZ_LOG(gIMELog, LogLevel::Info,
+              ("  IMMHandler::DispatchCompositionChangeEvent, index=%u, "
+               "rangeType=%s, range length=%u",
+               i, ToChar(textRangeType), length));
+    }
+  }
+
+  if (mCursorPosition == NO_IME_CARET) {
+    MOZ_LOG(gIMELog, LogLevel::Info,
+            ("  IMMHandler::DispatchCompositionChangeEvent, no caret"));
+  } else {
+    uint32_t cursor = static_cast<uint32_t>(mCursorPosition);
+    if (cursor > mCompositionString.Length()) {
+      MOZ_LOG(gIMELog, LogLevel::Info,
+              ("  IMMHandler::CreateTextRangeArray, mCursorPosition=%d. "
+               "This is larger than mCompositionString.Length()=%zu",
+               mCursorPosition, mCompositionString.Length()));
+      cursor = mCompositionString.Length();
+    }
+
+    // If caret is in the target clause, the target clause will be painted as
+    // normal selection range.  Since caret shouldn't be in selection range on
+    // Windows, we shouldn't append caret range in such case.
+    const TextRangeArray* clauses = dispatcher->GetPendingCompositionClauses();
+    const TextRange* targetClause =
+        clauses ? clauses->GetTargetClause() : nullptr;
+    if (targetClause && cursor >= targetClause->mStartOffset &&
+        cursor <= targetClause->mEndOffset) {
+      // Forget the caret position specified by IME since Gecko's caret position
+      // will be at the end of composition string.
+      mCursorPosition = NO_IME_CARET;
+      MOZ_LOG(gIMELog, LogLevel::Info,
+              ("  IMMHandler::CreateTextRangeArray, no caret due to it's in "
+               "the target clause, now, mCursorPosition is NO_IME_CARET"));
+    }
+
+    if (mCursorPosition != NO_IME_CARET) {
+      rv = dispatcher->SetCaretInPendingComposition(cursor, 0);
+      if (NS_WARN_IF(NS_FAILED(rv))) {
+        MOZ_LOG(
+            gIMELog, LogLevel::Error,
+            ("  IMMHandler::DispatchCompositionChangeEvent, FAILED due to"
+             "TextEventDispatcher::SetCaretInPendingComposition() failure"));
+        return;
+      }
+    }
+  }
+
+  WidgetEventTime eventTime = aWindow->CurrentMessageWidgetEventTime();
+  nsEventStatus status;
+  rv = dispatcher->FlushPendingComposition(status, &eventTime);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("  IMMHandler::DispatchCompositionChangeEvent, FAILED due to"
+             "TextEventDispatcher::FlushPendingComposition() failure"));
+    return;
+  }
+}
+
+void IMMHandler::GetCompositionString(const IMEContext& aContext, DWORD aIndex,
+                                      nsAString& aCompositionString) const {
+  aCompositionString.Truncate();
+
+  // Retrieve the size of the required output buffer.
+  long lRtn = ::ImmGetCompositionStringW(aContext.get(), aIndex, nullptr, 0);
+  if (lRtn < 0 || !aCompositionString.SetLength((lRtn / sizeof(WCHAR)) + 1,
+                                                mozilla::fallible)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("IMMHandler::GetCompositionString, FAILED, due to OOM"));
+    return;  // Error or out of memory.
+  }
+
+  // Actually retrieve the composition string information.
+  lRtn = ::ImmGetCompositionStringW(aContext.get(), aIndex,
+                                    (LPVOID)aCompositionString.BeginWriting(),
+                                    lRtn + sizeof(WCHAR));
+  aCompositionString.SetLength(lRtn / sizeof(WCHAR));
+
+  MOZ_LOG(
+      gIMELog, LogLevel::Info,
+      ("IMMHandler::GetCompositionString, succeeded, aCompositionString=\"%s\"",
+       NS_ConvertUTF16toUTF8(aCompositionString).get()));
+}
+
+bool IMMHandler::GetTargetClauseRange(uint32_t* aOffset, uint32_t* aLength) {
+  NS_ENSURE_TRUE(aOffset, false);
+  NS_ENSURE_TRUE(mIsComposing, false);
+  NS_ENSURE_TRUE(ShouldDrawCompositionStringOurselves(), false);
+
+  bool found = false;
+  *aOffset = mCompositionStart;
+  for (uint32_t i = 0; i < mAttributeArray.Length(); i++) {
+    if (mAttributeArray[i] == ATTR_TARGET_NOTCONVERTED ||
+        mAttributeArray[i] == ATTR_TARGET_CONVERTED) {
+      *aOffset = mCompositionStart + i;
+      found = true;
+      break;
+    }
+  }
+
+  if (!aLength) {
+    return true;
+  }
+
+  if (!found) {
+    // The all composition string is targetted when there is no ATTR_TARGET_*
+    // clause. E.g., there is only ATTR_INPUT
+    *aLength = mCompositionString.Length();
+    return true;
+  }
+
+  uint32_t offsetInComposition = *aOffset - mCompositionStart;
+  *aLength = mCompositionString.Length() - offsetInComposition;
+  for (uint32_t i = offsetInComposition; i < mAttributeArray.Length(); i++) {
+    if (mAttributeArray[i] != ATTR_TARGET_NOTCONVERTED &&
+        mAttributeArray[i] != ATTR_TARGET_CONVERTED) {
+      *aLength = i - offsetInComposition;
+      break;
+    }
+  }
+  return true;
+}
+
+bool IMMHandler::ConvertToANSIString(const nsString& aStr, UINT aCodePage,
+                                     nsACString& aANSIStr) {
+  int len = ::WideCharToMultiByte(aCodePage, 0, (LPCWSTR)aStr.get(),
+                                  aStr.Length(), nullptr, 0, nullptr, nullptr);
+  NS_ENSURE_TRUE(len >= 0, false);
+
+  if (!aANSIStr.SetLength(len, mozilla::fallible)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("IMMHandler::ConvertToANSIString, FAILED, due to OOM"));
+    return false;
+  }
+  ::WideCharToMultiByte(aCodePage, 0, (LPCWSTR)aStr.get(), aStr.Length(),
+                        (LPSTR)aANSIStr.BeginWriting(), len, nullptr, nullptr);
+  return true;
+}
+
+bool IMMHandler::GetCharacterRectOfSelectedTextAt(
+    nsWindow* aWindow, uint32_t aOffset, LayoutDeviceIntRect& aCharRect,
+    WritingMode* aWritingMode) {
+  LayoutDeviceIntPoint point(0, 0);
+
+  const Maybe<ContentSelection>& contentSelection =
+      GetContentSelectionWithQueryIfNothing(aWindow);
+  if (contentSelection.isNothing()) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("IMMHandler::GetCharacterRectOfSelectedTextAt, FAILED, due to "
+             "Selection::GetContentSelectionWithQueryIfNothing() failure"));
+    return false;
+  }
+
+  // If there is neither a selection range nor composition string, cannot return
+  // character rect, of course.
+  if (!contentSelection->HasRange() && !mIsComposing) {
+    MOZ_LOG(gIMELog, LogLevel::Warning,
+            ("IMMHandler::GetCharacterRectOfSelectedTextAt, FAILED, due to "
+             "there is neither a selection range nor composition string"));
+    return false;
+  }
+
+  // If the offset is larger than the end of composition string or selected
+  // string, we should return false since such case must be a bug of the caller
+  // or the active IME.  If it's an IME's bug, we need to set targetLength to
+  // aOffset.
+  const uint32_t targetLength =
+      mIsComposing ? mCompositionString.Length()
+                   : contentSelection->OffsetAndDataRef().Length();
+  if (NS_WARN_IF(aOffset > targetLength)) {
+    MOZ_LOG(
+        gIMELog, LogLevel::Error,
+        ("IMMHandler::GetCharacterRectOfSelectedTextAt, FAILED, due to "
+         "aOffset is too large (aOffset=%u, targetLength=%u, mIsComposing=%s)",
+         aOffset, targetLength, GetBoolName(mIsComposing)));
+    return false;
+  }
+
+  // If there is caret, we might be able to use caret rect.
+  uint32_t caretOffset = UINT32_MAX;
+  // There is a caret only when the normal selection is collapsed.
+  if (contentSelection.isNothing() ||
+      contentSelection->OffsetAndDataRef().IsDataEmpty()) {
+    if (mIsComposing) {
+      // If it's composing, mCursorPosition is the offset to caret in
+      // the composition string.
+      if (mCursorPosition != NO_IME_CARET) {
+        MOZ_ASSERT(mCursorPosition >= 0);
+        caretOffset = mCursorPosition;
+      } else if (!ShouldDrawCompositionStringOurselves() ||
+                 mCompositionString.IsEmpty()) {
+        // Otherwise, if there is no composition string, we should assume that
+        // there is a caret at the start of composition string.
+        caretOffset = 0;
+      }
+    } else {
+      // If there is no composition, the selection offset is the caret offset.
+      caretOffset = 0;
+    }
+  }
+
+  // If there is a caret and retrieving offset is same as the caret offset,
+  // we should use the caret rect.
+  if (aOffset != caretOffset) {
+    WidgetQueryContentEvent queryTextRectEvent(true, eQueryTextRect, aWindow);
+    WidgetQueryContentEvent::Options options;
+    options.mRelativeToInsertionPoint = true;
+    queryTextRectEvent.InitForQueryTextRect(aOffset, 1, options);
+    aWindow->InitEvent(queryTextRectEvent, &point);
+    DispatchEvent(aWindow, queryTextRectEvent);
+    if (queryTextRectEvent.Succeeded()) {
+      aCharRect = queryTextRectEvent.mReply->mRect;
+      if (aWritingMode) {
+        *aWritingMode = queryTextRectEvent.mReply->WritingModeRef();
+      }
+      MOZ_LOG(
+          gIMELog, LogLevel::Debug,
+          ("IMMHandler::GetCharacterRectOfSelectedTextAt, Succeeded, "
+           "aOffset=%u, aCharRect={ x: %d, y: %d, width: %d, height: %d }, "
+           "queryTextRectEvent={ mReply=%s }",
+           aOffset, aCharRect.X(), aCharRect.Y(), aCharRect.Width(),
+           aCharRect.Height(), ToString(queryTextRectEvent.mReply).c_str()));
+      return true;
+    }
+  }
+
+  return GetCaretRect(aWindow, aCharRect, aWritingMode);
+}
+
+bool IMMHandler::GetCaretRect(nsWindow* aWindow,
+                              LayoutDeviceIntRect& aCaretRect,
+                              WritingMode* aWritingMode) {
+  LayoutDeviceIntPoint point(0, 0);
+
+  WidgetQueryContentEvent queryCaretRectEvent(true, eQueryCaretRect, aWindow);
+  WidgetQueryContentEvent::Options options;
+  options.mRelativeToInsertionPoint = true;
+  queryCaretRectEvent.InitForQueryCaretRect(0, options);
+  aWindow->InitEvent(queryCaretRectEvent, &point);
+  DispatchEvent(aWindow, queryCaretRectEvent);
+  if (queryCaretRectEvent.Failed()) {
+    MOZ_LOG(
+        gIMELog, LogLevel::Info,
+        ("IMMHandler::GetCaretRect, FAILED, due to eQueryCaretRect failure"));
+    return false;
+  }
+  aCaretRect = queryCaretRectEvent.mReply->mRect;
+  if (aWritingMode) {
+    *aWritingMode = queryCaretRectEvent.mReply->WritingModeRef();
+  }
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("IMMHandler::GetCaretRect, SUCCEEDED, "
+           "aCaretRect={ x: %d, y: %d, width: %d, height: %d }, "
+           "queryCaretRectEvent={ mReply=%s }",
+           aCaretRect.X(), aCaretRect.Y(), aCaretRect.Width(),
+           aCaretRect.Height(), ToString(queryCaretRectEvent.mReply).c_str()));
+  return true;
+}
+
+bool IMMHandler::SetIMERelatedWindowsPos(nsWindow* aWindow,
+                                         const IMEContext& aContext) {
+  // Get first character rect of current a normal selected text or a composing
+  // string.
+  WritingMode writingMode;
+  LayoutDeviceIntRect firstSelectedCharRectRelativeToWindow;
+  bool ret = GetCharacterRectOfSelectedTextAt(
+      aWindow, 0, firstSelectedCharRectRelativeToWindow, &writingMode);
+  NS_ENSURE_TRUE(ret, false);
+  nsWindow* toplevelWindow = aWindow->GetTopLevelWindow(false);
+  LayoutDeviceIntRect firstSelectedCharRect;
+  ResolveIMECaretPos(toplevelWindow, firstSelectedCharRectRelativeToWindow,
+                     aWindow, firstSelectedCharRect);
+
+  // Set native caret size/position to our caret. Some IMEs honor it. E.g.,
+  // "Intelligent ABC" (Simplified Chinese) and "MS PinYin 3.0" (Simplified
+  // Chinese) on XP.  But if a11y module is handling native caret, we shouldn't
+  // touch it.
+  if (!IMEHandler::IsA11yHandlingNativeCaret()) {
+    LayoutDeviceIntRect caretRect(firstSelectedCharRect),
+        caretRectRelativeToWindow;
+    if (GetCaretRect(aWindow, caretRectRelativeToWindow)) {
+      ResolveIMECaretPos(toplevelWindow, caretRectRelativeToWindow, aWindow,
+                         caretRect);
+    } else {
+      NS_WARNING("failed to get caret rect");
+      caretRect.SetWidth(1);
+    }
+    IMEHandler::CreateNativeCaret(aWindow, caretRect);
+  }
+
+  if (ShouldDrawCompositionStringOurselves()) {
+    MOZ_LOG(gIMELog, LogLevel::Info,
+            ("IMMHandler::SetIMERelatedWindowsPos, Set candidate window"));
+
+    // Get a rect of first character in current target in composition string.
+    LayoutDeviceIntRect firstTargetCharRect, lastTargetCharRect;
+    if (mIsComposing && !mCompositionString.IsEmpty()) {
+      // If there are no targetted selection, we should use it's first character
+      // rect instead.
+      uint32_t offset, length;
+      if (!GetTargetClauseRange(&offset, &length)) {
+        MOZ_LOG(gIMELog, LogLevel::Error,
+                ("  IMMHandler::SetIMERelatedWindowsPos, FAILED, due to "
+                 "GetTargetClauseRange() failure"));
+        return false;
+      }
+      ret =
+          GetCharacterRectOfSelectedTextAt(aWindow, offset - mCompositionStart,
+                                           firstTargetCharRect, &writingMode);
+      NS_ENSURE_TRUE(ret, false);
+      if (length) {
+        ret = GetCharacterRectOfSelectedTextAt(
+            aWindow, offset + length - 1 - mCompositionStart,
+            lastTargetCharRect);
+        NS_ENSURE_TRUE(ret, false);
+      } else {
+        lastTargetCharRect = firstTargetCharRect;
+      }
+    } else {
+      // If there are no composition string, we should use a first character
+      // rect.
+      ret = GetCharacterRectOfSelectedTextAt(aWindow, 0, firstTargetCharRect,
+                                             &writingMode);
+      NS_ENSURE_TRUE(ret, false);
+      lastTargetCharRect = firstTargetCharRect;
+    }
+    ResolveIMECaretPos(toplevelWindow, firstTargetCharRect, aWindow,
+                       firstTargetCharRect);
+    ResolveIMECaretPos(toplevelWindow, lastTargetCharRect, aWindow,
+                       lastTargetCharRect);
+    LayoutDeviceIntRect targetClauseRect;
+    targetClauseRect.UnionRect(firstTargetCharRect, lastTargetCharRect);
+
+    // Move the candidate window to proper position from the target clause as
+    // far as possible.
+    CANDIDATEFORM candForm;
+    candForm.dwIndex = 0;
+    if (!writingMode.IsVertical() || IsVerticalWritingSupported()) {
+      candForm.dwStyle = CFS_EXCLUDE;
+      // Candidate window shouldn't overlap the target clause in any writing
+      // mode.
+      candForm.rcArea.left = targetClauseRect.X();
+      candForm.rcArea.right = targetClauseRect.XMost();
+      candForm.rcArea.top = targetClauseRect.Y();
+      candForm.rcArea.bottom = targetClauseRect.YMost();
+      if (!writingMode.IsVertical()) {
+        // In horizontal layout, current point of interest should be top-left
+        // of the first character.
+        candForm.ptCurrentPos.x = firstTargetCharRect.X();
+        candForm.ptCurrentPos.y = firstTargetCharRect.Y();
+      } else if (writingMode.IsVerticalRL()) {
+        // In vertical layout (RL), candidate window should be positioned right
+        // side of target clause.  However, we don't set vertical writing font
+        // to the IME.  Therefore, the candidate window may be positioned
+        // bottom-left of target clause rect with these information.
+        candForm.ptCurrentPos.x = targetClauseRect.X();
+        candForm.ptCurrentPos.y = targetClauseRect.Y();
+      } else {
+        MOZ_ASSERT(writingMode.IsVerticalLR(), "Did we miss some causes?");
+        // In vertical layout (LR), candidate window should be poisitioned left
+        // side of target clause.  Although, we don't set vertical writing font
+        // to the IME, the candidate window may be positioned bottom-right of
+        // the target clause rect with these information.
+        candForm.ptCurrentPos.x = targetClauseRect.XMost();
+        candForm.ptCurrentPos.y = targetClauseRect.Y();
+      }
+    } else {
+      // If vertical writing is not supported by IME, let's set candidate
+      // window position to the bottom-left of the target clause because
+      // the position must be the safest position to prevent the candidate
+      // window to overlap with the target clause.
+      candForm.dwStyle = CFS_CANDIDATEPOS;
+      candForm.ptCurrentPos.x = targetClauseRect.X();
+      candForm.ptCurrentPos.y = targetClauseRect.YMost();
+    }
+    MOZ_LOG(gIMELog, LogLevel::Info,
+            ("  IMMHandler::SetIMERelatedWindowsPos, Calling "
+             "ImmSetCandidateWindow()... ptCurrentPos={ x=%ld, y=%ld }, "
+             "rcArea={ left=%ld, top=%ld, right=%ld, bottom=%ld }, "
+             "writingMode=%s",
+             candForm.ptCurrentPos.x, candForm.ptCurrentPos.y,
+             candForm.rcArea.left, candForm.rcArea.top, candForm.rcArea.right,
+             candForm.rcArea.bottom, ToString(writingMode).c_str()));
+    ::ImmSetCandidateWindow(aContext.get(), &candForm);
+  } else {
+    MOZ_LOG(gIMELog, LogLevel::Info,
+            ("IMMHandler::SetIMERelatedWindowsPos, Set composition window"));
+
+    // Move the composition window to caret position (if selected some
+    // characters, we should use first character rect of them).
+    // And in this mode, IME adjusts the candidate window position
+    // automatically. So, we don't need to set it.
+    COMPOSITIONFORM compForm;
+    compForm.dwStyle = CFS_POINT;
+    compForm.ptCurrentPos.x = !writingMode.IsVerticalLR()
+                                  ? firstSelectedCharRect.X()
+                                  : firstSelectedCharRect.XMost();
+    compForm.ptCurrentPos.y = firstSelectedCharRect.Y();
+    ::ImmSetCompositionWindow(aContext.get(), &compForm);
+  }
+
+  return true;
+}
+
+void IMMHandler::ResolveIMECaretPos(nsIWidget* aReferenceWidget,
+                                    LayoutDeviceIntRect& aCursorRect,
+                                    nsIWidget* aNewOriginWidget,
+                                    LayoutDeviceIntRect& aOutRect) {
+  aOutRect = aCursorRect;
+
+  if (aReferenceWidget == aNewOriginWidget) return;
+
+  if (aReferenceWidget)
+    aOutRect.MoveBy(aReferenceWidget->WidgetToScreenOffset());
+
+  if (aNewOriginWidget)
+    aOutRect.MoveBy(-aNewOriginWidget->WidgetToScreenOffset());
+}
+
+static void SetHorizontalFontToLogFont(const nsAString& aFontFace,
+                                       LOGFONTW& aLogFont) {
+  aLogFont.lfEscapement = aLogFont.lfOrientation = 0;
+  if (NS_WARN_IF(aFontFace.Length() > LF_FACESIZE - 1)) {
+    memcpy(aLogFont.lfFaceName, L"System", sizeof(L"System"));
+    return;
+  }
+  memcpy(aLogFont.lfFaceName, aFontFace.BeginReading(),
+         aFontFace.Length() * sizeof(wchar_t));
+  aLogFont.lfFaceName[aFontFace.Length()] = 0;
+}
+
+static void SetVerticalFontToLogFont(const nsAString& aFontFace,
+                                     LOGFONTW& aLogFont) {
+  aLogFont.lfEscapement = aLogFont.lfOrientation = 2700;
+  if (NS_WARN_IF(aFontFace.Length() > LF_FACESIZE - 2)) {
+    memcpy(aLogFont.lfFaceName, L"@System", sizeof(L"@System"));
+    return;
+  }
+  aLogFont.lfFaceName[0] = '@';
+  memcpy(&aLogFont.lfFaceName[1], aFontFace.BeginReading(),
+         aFontFace.Length() * sizeof(wchar_t));
+  aLogFont.lfFaceName[aFontFace.Length() + 1] = 0;
+}
+
+void IMMHandler::AdjustCompositionFont(nsWindow* aWindow,
+                                       const IMEContext& aContext,
+                                       const WritingMode& aWritingMode,
+                                       bool aForceUpdate) {
+  // An instance of IMMHandler is destroyed when active IME is changed.
+  // Therefore, we need to store the information which are set to the IM
+  // context to static variables since IM context is never recreated.
+  static bool sCompositionFontsInitialized = false;
+  static nsString sCompositionFont;
+  static bool sCompositionFontPrefDone = false;
+  if (!sCompositionFontPrefDone) {
+    sCompositionFontPrefDone = true;
+    Preferences::GetString("intl.imm.composition_font", sCompositionFont);
+  }
+
+  // If composition font is customized by pref, we need to modify the
+  // composition font of the IME context at first time even if the writing mode
+  // is horizontal.
+  bool setCompositionFontForcibly =
+      aForceUpdate ||
+      (!sCompositionFontsInitialized && !sCompositionFont.IsEmpty());
+
+  static WritingMode sCurrentWritingMode;
+  static nsString sCurrentIMEName;
+  if (!setCompositionFontForcibly &&
+      sWritingModeOfCompositionFont == aWritingMode &&
+      sCurrentIMEName == sIMEName) {
+    // Nothing to do if writing mode isn't being changed.
+    return;
+  }
+
+  // Decide composition fonts for both horizontal writing mode and vertical
+  // writing mode.  If the font isn't specified by the pref, use default
+  // font which is already set to the IM context.  And also in vertical writing
+  // mode, insert '@' to the start of the font.
+  if (!sCompositionFontsInitialized) {
+    sCompositionFontsInitialized = true;
+    // sCompositionFontH must not start with '@' and its length is less than
+    // LF_FACESIZE since it needs to end with null terminating character.
+    if (sCompositionFont.IsEmpty() ||
+        sCompositionFont.Length() > LF_FACESIZE - 1 ||
+        sCompositionFont[0] == '@') {
+      LOGFONTW defaultLogFont;
+      if (NS_WARN_IF(
+              !::ImmGetCompositionFont(aContext.get(), &defaultLogFont))) {
+        MOZ_LOG(
+            gIMELog, LogLevel::Error,
+            ("  IMMHandler::AdjustCompositionFont, ::ImmGetCompositionFont() "
+             "failed"));
+        sCompositionFont.AssignLiteral("System");
+      } else {
+        // The font face is typically, "System".
+        sCompositionFont.Assign(defaultLogFont.lfFaceName);
+      }
+    }
+
+    MOZ_LOG(gIMELog, LogLevel::Info,
+            ("  IMMHandler::AdjustCompositionFont, sCompositionFont=\"%s\" is "
+             "initialized",
+             NS_ConvertUTF16toUTF8(sCompositionFont).get()));
+  }
+
+  static nsString sCompositionFontForJapanist2003;
+  if (IsJapanist2003Active() && sCompositionFontForJapanist2003.IsEmpty()) {
+    const char* kCompositionFontForJapanist2003 =
+        "intl.imm.composition_font.japanist_2003";
+    Preferences::GetString(kCompositionFontForJapanist2003,
+                           sCompositionFontForJapanist2003);
+    // If the font name is not specified properly, let's use
+    // "MS PGothic" instead.
+    if (sCompositionFontForJapanist2003.IsEmpty() ||
+        sCompositionFontForJapanist2003.Length() > LF_FACESIZE - 2 ||
+        sCompositionFontForJapanist2003[0] == '@') {
+      sCompositionFontForJapanist2003.AssignLiteral("MS PGothic");
+    }
+  }
+
+  sWritingModeOfCompositionFont = aWritingMode;
+  sCurrentIMEName = sIMEName;
+
+  LOGFONTW logFont;
+  memset(&logFont, 0, sizeof(logFont));
+  if (!::ImmGetCompositionFont(aContext.get(), &logFont)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("  IMMHandler::AdjustCompositionFont, ::ImmGetCompositionFont() "
+             "failed"));
+    logFont.lfFaceName[0] = 0;
+  }
+  // Need to reset some information which should be recomputed with new font.
+  logFont.lfWidth = 0;
+  logFont.lfWeight = FW_DONTCARE;
+  logFont.lfOutPrecision = OUT_DEFAULT_PRECIS;
+  logFont.lfClipPrecision = CLIP_DEFAULT_PRECIS;
+  logFont.lfPitchAndFamily = DEFAULT_PITCH;
+
+  if (aWritingMode.IsVertical() && IsVerticalWritingSupported()) {
+    SetVerticalFontToLogFont(IsJapanist2003Active()
+                                 ? sCompositionFontForJapanist2003
+                                 : sCompositionFont,
+                             logFont);
+  } else {
+    SetHorizontalFontToLogFont(IsJapanist2003Active()
+                                   ? sCompositionFontForJapanist2003
+                                   : sCompositionFont,
+                               logFont);
+  }
+  MOZ_LOG(gIMELog, LogLevel::Warning,
+          ("  IMMHandler::AdjustCompositionFont, calling "
+           "::ImmSetCompositionFont(\"%s\")",
+           NS_ConvertUTF16toUTF8(nsDependentString(logFont.lfFaceName)).get()));
+  ::ImmSetCompositionFontW(aContext.get(), &logFont);
+}
+
+// static
+nsresult IMMHandler::OnMouseButtonEvent(
+    nsWindow* aWindow, const IMENotification& aIMENotification) {
+  // We don't need to create the instance of the handler here.
+  if (!gIMMHandler) {
+    return NS_OK;
+  }
+
+  if (!sWM_MSIME_MOUSE || !IsComposingOnOurEditor() ||
+      !ShouldDrawCompositionStringOurselves()) {
+    return NS_OK;
+  }
+
+  // We need to handle only mousedown event.
+  if (aIMENotification.mMouseButtonEventData.mEventMessage != eMouseDown) {
+    return NS_OK;
+  }
+
+  // If the character under the cursor is not in the composition string,
+  // we don't need to notify IME of it.
+  uint32_t compositionStart = gIMMHandler->mCompositionStart;
+  uint32_t compositionEnd =
+      compositionStart + gIMMHandler->mCompositionString.Length();
+  if (aIMENotification.mMouseButtonEventData.mOffset < compositionStart ||
+      aIMENotification.mMouseButtonEventData.mOffset >= compositionEnd) {
+    return NS_OK;
+  }
+
+  BYTE button;
+  switch (aIMENotification.mMouseButtonEventData.mButton) {
+    case MouseButton::ePrimary:
+      button = IMEMOUSE_LDOWN;
+      break;
+    case MouseButton::eMiddle:
+      button = IMEMOUSE_MDOWN;
+      break;
+    case MouseButton::eSecondary:
+      button = IMEMOUSE_RDOWN;
+      break;
+    default:
+      return NS_OK;
+  }
+
+  // calcurate positioning and offset
+  // char :            JCH1|JCH2|JCH3
+  // offset:           0011 1122 2233
+  // positioning:      2301 2301 2301
+  LayoutDeviceIntPoint cursorPos =
+      aIMENotification.mMouseButtonEventData.mCursorPos;
+  LayoutDeviceIntRect charRect =
+      aIMENotification.mMouseButtonEventData.mCharRect;
+  int32_t cursorXInChar = cursorPos.x - charRect.X();
+  // The event might hit to zero-width character, see bug 694913.
+  // The reason might be:
+  // * There are some zero-width characters are actually.
+  // * font-size is specified zero.
+  // But nobody reproduced this bug actually...
+  // We should assume that user clicked on right most of the zero-width
+  // character in such case.
+  int positioning = 1;
+  if (charRect.Width() > 0) {
+    positioning = cursorXInChar * 4 / charRect.Width();
+    positioning = (positioning + 2) % 4;
+  }
+
+  int offset =
+      aIMENotification.mMouseButtonEventData.mOffset - compositionStart;
+  if (positioning < 2) {
+    offset++;
+  }
+
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("IMMHandler::OnMouseButtonEvent, x,y=%d,%d, offset=%d, "
+           "positioning=%d",
+           cursorPos.x.value, cursorPos.y.value, offset, positioning));
+
+  // send MS_MSIME_MOUSE message to default IME window.
+  HWND imeWnd = ::ImmGetDefaultIMEWnd(aWindow->GetWindowHandle());
+  IMEContext context(aWindow);
+  if (::SendMessageW(imeWnd, sWM_MSIME_MOUSE,
+                     MAKELONG(MAKEWORD(button, positioning), offset),
+                     (LPARAM)context.get()) == 1) {
+    return NS_SUCCESS_EVENT_CONSUMED;
+  }
+  return NS_OK;
+}
+
+// static
+bool IMMHandler::OnKeyDownEvent(nsWindow* aWindow, WPARAM wParam, LPARAM lParam,
+                                MSGResult& aResult) {
+  MOZ_LOG(
+      gIMELog, LogLevel::Info,
+      ("IMMHandler::OnKeyDownEvent, hWnd=%p, wParam=%08zx, lParam=%08" PRIxLPTR,
+       aWindow->GetWindowHandle(), wParam, lParam));
+  aResult.mConsumed = false;
+  switch (wParam) {
+    case VK_TAB:
+    case VK_PRIOR:
+    case VK_NEXT:
+    case VK_END:
+    case VK_HOME:
+    case VK_LEFT:
+    case VK_UP:
+    case VK_RIGHT:
+    case VK_DOWN:
+    case VK_RETURN:
+      // If IME didn't process the key message (the virtual key code wasn't
+      // converted to VK_PROCESSKEY), and the virtual key code event causes
+      // moving caret or editing text with keeping composing state, we should
+      // cancel the composition here because we cannot support moving
+      // composition string with DOM events (IE also cancels the composition
+      // in same cases).  Then, this event will be dispatched.
+      if (IsComposingOnOurEditor()) {
+        // NOTE: We don't need to cancel the composition on another window.
+        CancelComposition(aWindow, false);
+      }
+      return false;
+    default:
+      return false;
+  }
+}
+
+Maybe<ContentSelection> IMMHandler::QueryContentSelection(nsWindow* aWindow) {
+  WidgetQueryContentEvent querySelectedTextEvent(true, eQuerySelectedText,
+                                                 aWindow);
+  LayoutDeviceIntPoint point(0, 0);
+  aWindow->InitEvent(querySelectedTextEvent, &point);
+  DispatchEvent(aWindow, querySelectedTextEvent);
+  if (NS_WARN_IF(querySelectedTextEvent.Failed())) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("  IMMHandler::Selection::Init, FAILED, due to eQuerySelectedText "
+             "failure"));
+    return Nothing();
+  }
+  // If the window is destroyed during querying selected text, we shouldn't
+  // do anymore.
+  if (aWindow->Destroyed()) {
+    MOZ_LOG(
+        gIMELog, LogLevel::Error,
+        ("  IMMHandler::Selection::Init, FAILED, due to the widget destroyed"));
+    return Nothing();
+  }
+
+  ContentSelection contentSelection(querySelectedTextEvent);
+
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("IMMHandler::Selection::Init, querySelectedTextEvent={ mReply=%s }",
+           ToString(querySelectedTextEvent.mReply).c_str()));
+
+  if (contentSelection.HasRange() &&
+      !contentSelection.OffsetAndDataRef().IsValid()) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("  IMMHandler::Selection::Init, FAILED, due to invalid range"));
+    return Nothing();
+  }
+  return Some(contentSelection);
+}
+
+}  // namespace widget
+}  // namespace mozilla
diff --git a/widget/windows/IMMHandler.h b/widget/windows/IMMHandler.h
new file mode 100644
index 0000000000..e012541fae
--- /dev/null
+++ b/widget/windows/IMMHandler.h
@@ -0,0 +1,427 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef IMMHandler_h_
+#define IMMHandler_h_
+
+#include "mozilla/ContentData.h"
+#include "mozilla/EventForwards.h"
+#include "mozilla/TextEventDispatcher.h"
+#include "mozilla/WritingModes.h"
+
+#include "windef.h"
+#include "winnetwk.h"
+#include "npapi.h"
+
+#include "nsCOMPtr.h"
+#include "nsIWidget.h"
+#include "nsRect.h"
+#include "nsString.h"
+#include "nsTArray.h"
+
+#include <windows.h>
+
+class nsWindow;
+
+namespace mozilla {
+namespace widget {
+
+struct MSGResult;
+
+class IMEContext final {
+ public:
+  IMEContext() : mWnd(nullptr), mIMC(nullptr) {}
+
+  explicit IMEContext(HWND aWnd);
+  explicit IMEContext(nsWindow* aWindowBase);
+
+  ~IMEContext() { Clear(); }
+
+  HIMC get() const { return mIMC; }
+
+  void Init(HWND aWnd);
+  void Init(nsWindow* aWindowBase);
+  void Clear();
+
+  bool IsValid() const { return !!mIMC; }
+
+  void SetOpenState(bool aOpen) const {
+    if (!mIMC) {
+      return;
+    }
+    ::ImmSetOpenStatus(mIMC, aOpen);
+  }
+
+  bool GetOpenState() const {
+    if (!mIMC) {
+      return false;
+    }
+    return (::ImmGetOpenStatus(mIMC) != FALSE);
+  }
+
+  bool AssociateDefaultContext() {
+    // We assume that there is only default IMC, no new IMC has been created.
+    if (mIMC) {
+      return false;
+    }
+    if (!::ImmAssociateContextEx(mWnd, nullptr, IACE_DEFAULT)) {
+      return false;
+    }
+    mIMC = ::ImmGetContext(mWnd);
+    return (mIMC != nullptr);
+  }
+
+  bool Disassociate() {
+    if (!mIMC) {
+      return false;
+    }
+    if (!::ImmAssociateContextEx(mWnd, nullptr, 0)) {
+      return false;
+    }
+    ::ImmReleaseContext(mWnd, mIMC);
+    mIMC = nullptr;
+    return true;
+  }
+
+ protected:
+  IMEContext(const IMEContext& aOther) { MOZ_CRASH("Don't copy IMEContext"); }
+
+  HWND mWnd;
+  HIMC mIMC;
+};
+
+class IMMHandler final {
+ public:
+  static void Initialize();
+  static void Terminate();
+
+  // If Process*() returns true, the caller shouldn't do anything anymore.
+  static bool ProcessMessage(nsWindow* aWindow, UINT msg, WPARAM& wParam,
+                             LPARAM& lParam, MSGResult& aResult);
+  static bool IsComposing() { return IsComposingOnOurEditor(); }
+  static bool IsComposingOn(nsWindow* aWindow) {
+    return IsComposing() && IsComposingWindow(aWindow);
+  }
+
+#ifdef DEBUG
+  /**
+   * IsIMEAvailable() returns TRUE when current keyboard layout has IME.
+   * Otherwise, FALSE.
+   */
+  static bool IsIMEAvailable() { return !!::ImmIsIME(::GetKeyboardLayout(0)); }
+#endif
+
+  // If aForce is TRUE, these methods doesn't check whether we have composition
+  // or not.  If you don't set it to TRUE, these method doesn't commit/cancel
+  // the composition on uexpected window.
+  static void CommitComposition(nsWindow* aWindow, bool aForce = false);
+  static void CancelComposition(nsWindow* aWindow, bool aForce = false);
+  static void OnFocusChange(bool aFocus, nsWindow* aWindow);
+  static void OnUpdateComposition(nsWindow* aWindow);
+  static void OnSelectionChange(nsWindow* aWindow,
+                                const IMENotification& aIMENotification,
+                                bool aIsIMMActive);
+
+  static IMENotificationRequests GetIMENotificationRequests();
+
+  // Returns NS_SUCCESS_EVENT_CONSUMED if the mouse button event is consumed by
+  // IME.  Otherwise, NS_OK.
+  static nsresult OnMouseButtonEvent(nsWindow* aWindow,
+                                     const IMENotification& aIMENotification);
+
+#define DECL_IS_IME_ACTIVE(aReadableName) \
+  static bool Is##aReadableName##Active();
+
+  // Japanese IMEs
+  DECL_IS_IME_ACTIVE(ATOK2006)
+  DECL_IS_IME_ACTIVE(ATOK2007)
+  DECL_IS_IME_ACTIVE(ATOK2008)
+  DECL_IS_IME_ACTIVE(ATOK2009)
+  DECL_IS_IME_ACTIVE(ATOK2010)
+  DECL_IS_IME_ACTIVE(GoogleJapaneseInput)
+  DECL_IS_IME_ACTIVE(Japanist2003)
+
+#undef DECL_IS_IME_ACTIVE
+
+  /**
+   * IsActiveIMEInBlockList() returns true if we know active keyboard layout's
+   * IME has some crash bugs or something which make some damage to us.  When
+   * this returns true, IMC shouldn't be associated with any windows.
+   */
+  static bool IsActiveIMEInBlockList();
+
+ protected:
+  static void EnsureHandlerInstance();
+
+  static bool IsComposingOnOurEditor();
+  static bool IsComposingWindow(nsWindow* aWindow);
+
+  static bool ShouldDrawCompositionStringOurselves();
+  static bool IsVerticalWritingSupported();
+  // aWindow can be nullptr if it's called without receiving WM_INPUTLANGCHANGE.
+  static void InitKeyboardLayout(nsWindow* aWindow, HKL aKeyboardLayout);
+  static UINT GetKeyboardCodePage();
+
+  /**
+   * Checks whether the window is top level window of the composing window.
+   * In this method, the top level window means in all windows, not only in all
+   * OUR windows.  I.e., if the aWindow is embedded, this always returns FALSE.
+   */
+  static bool IsTopLevelWindowOfComposition(nsWindow* aWindow);
+
+  static bool ProcessInputLangChangeMessage(nsWindow* aWindow, WPARAM wParam,
+                                            LPARAM lParam, MSGResult& aResult);
+
+  IMMHandler();
+  ~IMMHandler();
+
+  // On*() methods return true if the caller of message handler shouldn't do
+  // anything anymore.  Otherwise, false.
+  static bool OnKeyDownEvent(nsWindow* aWindow, WPARAM wParam, LPARAM lParam,
+                             MSGResult& aResult);
+
+  bool OnIMEStartComposition(nsWindow* aWindow, MSGResult& aResult);
+  bool OnIMEComposition(nsWindow* aWindow, WPARAM wParam, LPARAM lParam,
+                        MSGResult& aResult);
+  bool OnIMEEndComposition(nsWindow* aWindow, MSGResult& aResult);
+  bool OnIMERequest(nsWindow* aWindow, WPARAM wParam, LPARAM lParam,
+                    MSGResult& aResult);
+  bool OnChar(nsWindow* aWindow, WPARAM wParam, LPARAM lParam,
+              MSGResult& aResult);
+  void OnInputLangChange(nsWindow* aWindow, WPARAM wParam, LPARAM lParam,
+                         MSGResult& aResult);
+
+  // These message handlers don't use instance members, we should not create
+  // the instance by the messages.  So, they should be static.
+  static bool OnIMEChar(nsWindow* aWindow, WPARAM wParam, LPARAM lParam,
+                        MSGResult& aResult);
+  static bool OnIMESetContext(nsWindow* aWindow, WPARAM wParam, LPARAM lParam,
+                              MSGResult& aResult);
+  static bool OnIMECompositionFull(nsWindow* aWindow, MSGResult& aResult);
+  static bool OnIMENotify(nsWindow* aWindow, WPARAM wParam, LPARAM lParam,
+                          MSGResult& aResult);
+  static bool OnIMESelect(nsWindow* aWindow, WPARAM wParam, LPARAM lParam,
+                          MSGResult& aResult);
+
+  // The result of Handle* method mean "Processed" when it's TRUE.
+  void HandleStartComposition(nsWindow* aWindow, const IMEContext& aContext);
+  bool HandleComposition(nsWindow* aWindow, const IMEContext& aContext,
+                         LPARAM lParam);
+  // If aCommitString is null, this commits composition with the latest
+  // dispatched data.  Otherwise, commits composition with the value.
+  void HandleEndComposition(nsWindow* aWindow,
+                            const nsAString* aCommitString = nullptr);
+  bool HandleReconvert(nsWindow* aWindow, LPARAM lParam, LRESULT* oResult);
+  bool HandleQueryCharPosition(nsWindow* aWindow, LPARAM lParam,
+                               LRESULT* oResult);
+  bool HandleDocumentFeed(nsWindow* aWindow, LPARAM lParam, LRESULT* oResult);
+
+  /**
+   *  When a window's IME context is activating but we have composition on
+   *  another window, we should commit our composition because IME context is
+   *  shared by all our windows (including plug-ins).
+   *  @param aWindow is a new activated window.
+   *  If aWindow is our composing window, this method does nothing.
+   *  Otherwise, this commits the composition on the previous window.
+   *  If this method did commit a composition, this returns TRUE.
+   */
+  bool CommitCompositionOnPreviousWindow(nsWindow* aWindow);
+
+  /**
+   *  ResolveIMECaretPos
+   *  Convert the caret rect of a composition event to another widget's
+   *  coordinate system.
+   *
+   *  @param aReferenceWidget The origin widget of aCursorRect.
+   *                          Typically, this is mReferenceWidget of the
+   *                          composing events. If the aCursorRect is in screen
+   *                          coordinates, set nullptr.
+   *  @param aCursorRect      The cursor rect.
+   *  @param aNewOriginWidget aOutRect will be in this widget's coordinates. If
+   *                          this is nullptr, aOutRect will be in screen
+   *                          coordinates.
+   *  @param aOutRect         The converted cursor rect.
+   */
+  void ResolveIMECaretPos(nsIWidget* aReferenceWidget,
+                          mozilla::LayoutDeviceIntRect& aCursorRect,
+                          nsIWidget* aNewOriginWidget,
+                          mozilla::LayoutDeviceIntRect& aOutRect);
+
+  bool ConvertToANSIString(const nsString& aStr, UINT aCodePage,
+                           nsACString& aANSIStr);
+
+  bool SetIMERelatedWindowsPos(nsWindow* aWindow, const IMEContext& aContext);
+  /**
+   * GetCharacterRectOfSelectedTextAt() returns character rect of the offset
+   * from the selection start or the start of composition string if there is
+   * a composition.
+   *
+   * @param aWindow         The window which has focus.
+   * @param aOffset         Offset from the selection start or the start of
+   *                        composition string when there is a composition.
+   *                        This must be in the selection range or
+   *                        the composition string.
+   * @param aCharRect       The result.
+   * @param aWritingMode    The writing mode of current selection.  When this
+   *                        is nullptr, this assumes that the selection is in
+   *                        horizontal writing mode.
+   * @return                true if this succeeded to retrieve the rect.
+   *                        Otherwise, false.
+   */
+  bool GetCharacterRectOfSelectedTextAt(
+      nsWindow* aWindow, uint32_t aOffset,
+      mozilla::LayoutDeviceIntRect& aCharRect,
+      mozilla::WritingMode* aWritingMode = nullptr);
+  /**
+   * GetCaretRect() returns caret rect at current selection start.
+   *
+   * @param aWindow         The window which has focus.
+   * @param aCaretRect      The result.
+   * @param aWritingMode    The writing mode of current selection.  When this
+   *                        is nullptr, this assumes that the selection is in
+   *                        horizontal writing mode.
+   * @return                true if this succeeded to retrieve the rect.
+   *                        Otherwise, false.
+   */
+  bool GetCaretRect(nsWindow* aWindow, mozilla::LayoutDeviceIntRect& aCaretRect,
+                    mozilla::WritingMode* aWritingMode = nullptr);
+  void GetCompositionString(const IMEContext& aContext, DWORD aIndex,
+                            nsAString& aCompositionString) const;
+
+  /**
+   * AdjustCompositionFont() makes IME vertical writing mode if it's supported.
+   * If aForceUpdate is true, it will update composition font even if writing
+   * mode isn't being changed.
+   */
+  void AdjustCompositionFont(nsWindow* aWindow, const IMEContext& aContext,
+                             const mozilla::WritingMode& aWritingMode,
+                             bool aForceUpdate = false);
+
+  /**
+   * MaybeAdjustCompositionFont() calls AdjustCompositionFont() when the
+   * locale of active IME is CJK.  Note that this creates an instance even
+   * when there is no composition but the locale is CJK.
+   */
+  static void MaybeAdjustCompositionFont(
+      nsWindow* aWindow, const mozilla::WritingMode& aWritingMode,
+      bool aForceUpdate = false);
+
+  /**
+   *  Get the current target clause of composition string.
+   *  If there are one or more characters whose attribute is ATTR_TARGET_*,
+   *  this returns the first character's offset and its length.
+   *  Otherwise, e.g., the all characters are ATTR_INPUT, this returns
+   *  the composition string range because the all is the current target.
+   *
+   *  aLength can be null (default), but aOffset must not be null.
+   *
+   *  The aOffset value is offset in the contents.  So, when you need offset
+   *  in the composition string, you need to subtract mCompositionStart from it.
+   */
+  bool GetTargetClauseRange(uint32_t* aOffset, uint32_t* aLength = nullptr);
+
+  /**
+   * DispatchEvent() dispatches aEvent if aWidget hasn't been destroyed yet.
+   */
+  static void DispatchEvent(nsWindow* aWindow, WidgetGUIEvent& aEvent);
+
+  /**
+   * DispatchCompositionChangeEvent() dispatches eCompositionChange event
+   * with clause information (it'll be retrieved by CreateTextRangeArray()).
+   * I.e., this should be called only during composing.  If a composition is
+   * being committed, only HandleCompositionEnd() should be called.
+   *
+   * @param aWindow     The window which has the composition.
+   * @param aContext    Native IME context which has the composition.
+   */
+  void DispatchCompositionChangeEvent(nsWindow* aWindow,
+                                      const IMEContext& aContext);
+
+  nsresult EnsureClauseArray(int32_t aCount);
+  nsresult EnsureAttributeArray(int32_t aCount);
+
+  /**
+   * When WM_IME_CHAR is received and passed to DefWindowProc, we need to
+   * record the messages.  In other words, we should record the messages
+   * when we receive WM_IME_CHAR on windowless plug-in (if we have focus,
+   * we always eat them).  When focus is moved from a windowless plug-in to
+   * our window during composition, WM_IME_CHAR messages were received when
+   * the plug-in has focus.  However, WM_CHAR messages are received after the
+   * plug-in lost focus.  So, we need to ignore the WM_CHAR messages because
+   * they make unexpected text input events on us.
+   */
+  nsTArray<MSG> mPassedIMEChar;
+
+  bool IsIMECharRecordsEmpty() { return mPassedIMEChar.IsEmpty(); }
+  void ResetIMECharRecords() { mPassedIMEChar.Clear(); }
+  void DequeueIMECharRecords(WPARAM& wParam, LPARAM& lParam) {
+    MSG msg = mPassedIMEChar.ElementAt(0);
+    wParam = msg.wParam;
+    lParam = msg.lParam;
+    mPassedIMEChar.RemoveElementAt(0);
+  }
+  void EnqueueIMECharRecords(WPARAM wParam, LPARAM lParam) {
+    MSG msg;
+    msg.wParam = wParam;
+    msg.lParam = lParam;
+    mPassedIMEChar.AppendElement(msg);
+  }
+
+  TextEventDispatcher* GetTextEventDispatcherFor(nsWindow* aWindow);
+
+  nsWindow* mComposingWindow;
+  RefPtr<TextEventDispatcher> mDispatcher;
+  nsString mCompositionString;
+  nsTArray<uint32_t> mClauseArray;
+  nsTArray<uint8_t> mAttributeArray;
+
+  int32_t mCursorPosition;
+  uint32_t mCompositionStart;
+
+  // mContentSelection stores the latest selection data only when sHasFocus is
+  // true. Don't access mContentSelection directly.  You should use
+  // GetContentSelectionWithQueryIfNothing() for getting proper state.
+  Maybe<ContentSelection> mContentSelection;
+
+  const Maybe<ContentSelection>& GetContentSelectionWithQueryIfNothing(
+      nsWindow* aWindow) {
+    // When IME has focus, mContentSelection is automatically updated by
+    // NOTIFY_IME_OF_SELECTION_CHANGE.
+    if (sHasFocus) {
+      if (mContentSelection.isNothing()) {
+        // But if this is the first access of mContentSelection, we need to
+        // query selection now.
+        mContentSelection = QueryContentSelection(aWindow);
+      }
+      return mContentSelection;
+    }
+    // Otherwise, i.e., While IME doesn't have focus, we cannot observe
+    // selection changes.  So, in such case, we need to query selection
+    // when it's necessary.
+    static Maybe<ContentSelection> sTempContentSelection;
+    sTempContentSelection = QueryContentSelection(aWindow);
+    return sTempContentSelection;
+  }
+
+  /**
+   * Query content selection on aWindow with WidgetQueryContent event.
+   */
+  static Maybe<ContentSelection> QueryContentSelection(nsWindow* aWindow);
+
+  bool mIsComposing;
+
+  static mozilla::WritingMode sWritingModeOfCompositionFont;
+  static nsString sIMEName;
+  static UINT sCodePage;
+  static DWORD sIMEProperty;
+  static DWORD sIMEUIProperty;
+  static bool sAssumeVerticalWritingModeNotSupported;
+  static bool sHasFocus;
+};
+
+}  // namespace widget
+}  // namespace mozilla
+
+#endif  // IMMHandler_h_
diff --git a/widget/windows/InProcessWinCompositorWidget.cpp b/widget/windows/InProcessWinCompositorWidget.cpp
new file mode 100644
index 0000000000..de491b734b
--- /dev/null
+++ b/widget/windows/InProcessWinCompositorWidget.cpp
@@ -0,0 +1,368 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "InProcessWinCompositorWidget.h"
+
+#include "mozilla/StaticPrefs_layers.h"
+#include "mozilla/gfx/DeviceManagerDx.h"
+#include "mozilla/gfx/Point.h"
+#include "mozilla/layers/Compositor.h"
+#include "mozilla/layers/CompositorThread.h"
+#include "mozilla/webrender/RenderThread.h"
+#include "mozilla/widget/PlatformWidgetTypes.h"
+#include "gfxPlatform.h"
+#include "HeadlessCompositorWidget.h"
+#include "HeadlessWidget.h"
+#include "nsIWidget.h"
+#include "nsWindow.h"
+#include "VsyncDispatcher.h"
+#include "WinCompositorWindowThread.h"
+#include "VRShMem.h"
+
+#include <ddraw.h>
+
+namespace mozilla::widget {
+
+using namespace mozilla::gfx;
+using namespace mozilla;
+
+/* static */
+RefPtr<CompositorWidget> CompositorWidget::CreateLocal(
+    const CompositorWidgetInitData& aInitData,
+    const layers::CompositorOptions& aOptions, nsIWidget* aWidget) {
+  if (aInitData.type() ==
+      CompositorWidgetInitData::THeadlessCompositorWidgetInitData) {
+    return new HeadlessCompositorWidget(
+        aInitData.get_HeadlessCompositorWidgetInitData(), aOptions,
+        static_cast<HeadlessWidget*>(aWidget));
+  } else {
+    return new InProcessWinCompositorWidget(
+        aInitData.get_WinCompositorWidgetInitData(), aOptions,
+        static_cast<nsWindow*>(aWidget));
+  }
+}
+
+InProcessWinCompositorWidget::InProcessWinCompositorWidget(
+    const WinCompositorWidgetInitData& aInitData,
+    const layers::CompositorOptions& aOptions, nsWindow* aWindow)
+    : WinCompositorWidget(aInitData, aOptions),
+      mWindow(aWindow),
+      mWnd(reinterpret_cast<HWND>(aInitData.hWnd())),
+      mTransparentSurfaceLock("mTransparentSurfaceLock"),
+      mTransparencyMode(uint32_t(aInitData.transparencyMode())),
+      mMemoryDC(nullptr),
+      mCompositeDC(nullptr),
+      mLockedBackBufferData(nullptr) {
+  MOZ_ASSERT(mWindow);
+  MOZ_ASSERT(mWnd && ::IsWindow(mWnd));
+
+  // mNotDeferEndRemoteDrawing is set on the main thread during init,
+  // but is only accessed after on the compositor thread.
+  mNotDeferEndRemoteDrawing =
+      StaticPrefs::layers_offmainthreadcomposition_frame_rate() == 0 ||
+      gfxPlatform::IsInLayoutAsapMode() || gfxPlatform::ForceSoftwareVsync();
+}
+
+void InProcessWinCompositorWidget::OnDestroyWindow() {
+  gfx::CriticalSectionAutoEnter presentLock(&mPresentLock);
+  MutexAutoLock lock(mTransparentSurfaceLock);
+  mTransparentSurface = nullptr;
+  mMemoryDC = nullptr;
+}
+
+bool InProcessWinCompositorWidget::OnWindowResize(
+    const LayoutDeviceIntSize& aSize) {
+  return true;
+}
+
+void InProcessWinCompositorWidget::OnWindowModeChange(nsSizeMode aSizeMode) {}
+
+bool InProcessWinCompositorWidget::PreRender(WidgetRenderingContext* aContext) {
+  // This can block waiting for WM_SETTEXT to finish
+  // Using PreRender is unnecessarily pessimistic because
+  // we technically only need to block during the present call
+  // not all of compositor rendering
+  mPresentLock.Enter();
+  return true;
+}
+
+void InProcessWinCompositorWidget::PostRender(
+    WidgetRenderingContext* aContext) {
+  mPresentLock.Leave();
+}
+
+LayoutDeviceIntSize InProcessWinCompositorWidget::GetClientSize() {
+  RECT r;
+  if (!::GetClientRect(mWnd, &r)) {
+    return LayoutDeviceIntSize();
+  }
+  return LayoutDeviceIntSize(r.right - r.left, r.bottom - r.top);
+}
+
+already_AddRefed<gfx::DrawTarget>
+InProcessWinCompositorWidget::StartRemoteDrawing() {
+  MutexAutoLock lock(mTransparentSurfaceLock);
+
+  MOZ_ASSERT(!mCompositeDC);
+
+  RefPtr<gfxASurface> surf;
+  if (TransparencyModeIs(TransparencyMode::Transparent)) {
+    surf = EnsureTransparentSurface();
+  }
+
+  // Must call this after EnsureTransparentSurface(), since it could update
+  // the DC.
+  HDC dc = GetWindowSurface();
+  if (!surf) {
+    if (!dc) {
+      return nullptr;
+    }
+    uint32_t flags = TransparencyModeIs(TransparencyMode::Opaque)
+                         ? 0
+                         : gfxWindowsSurface::FLAG_IS_TRANSPARENT;
+    surf = new gfxWindowsSurface(dc, flags);
+  }
+
+  IntSize size = surf->GetSize();
+  if (size.width <= 0 || size.height <= 0) {
+    if (dc) {
+      FreeWindowSurface(dc);
+    }
+    return nullptr;
+  }
+
+  RefPtr<DrawTarget> dt =
+      mozilla::gfx::Factory::CreateDrawTargetForCairoSurface(
+          surf->CairoSurface(), size);
+  if (dt) {
+    mCompositeDC = dc;
+  } else {
+    FreeWindowSurface(dc);
+  }
+
+  return dt.forget();
+}
+
+void InProcessWinCompositorWidget::EndRemoteDrawing() {
+  MOZ_ASSERT(!mLockedBackBufferData);
+
+  if (TransparencyModeIs(TransparencyMode::Transparent)) {
+    MOZ_ASSERT(mTransparentSurface);
+    RedrawTransparentWindow();
+  }
+  if (mCompositeDC) {
+    FreeWindowSurface(mCompositeDC);
+  }
+  mCompositeDC = nullptr;
+}
+
+bool InProcessWinCompositorWidget::NeedsToDeferEndRemoteDrawing() {
+  if (mNotDeferEndRemoteDrawing) {
+    return false;
+  }
+
+  IDirectDraw7* ddraw = DeviceManagerDx::Get()->GetDirectDraw();
+  if (!ddraw) {
+    return false;
+  }
+
+  DWORD scanLine = 0;
+  int height = ::GetSystemMetrics(SM_CYSCREEN);
+  HRESULT ret = ddraw->GetScanLine(&scanLine);
+  if (ret == DDERR_VERTICALBLANKINPROGRESS) {
+    scanLine = 0;
+  } else if (ret != DD_OK) {
+    return false;
+  }
+
+  // Check if there is a risk of tearing with GDI.
+  if (static_cast<int>(scanLine) > height / 2) {
+    // No need to defer.
+    return false;
+  }
+
+  return true;
+}
+
+already_AddRefed<gfx::DrawTarget>
+InProcessWinCompositorWidget::GetBackBufferDrawTarget(
+    gfx::DrawTarget* aScreenTarget, const gfx::IntRect& aRect,
+    bool* aOutIsCleared) {
+  MOZ_ASSERT(!mLockedBackBufferData);
+
+  RefPtr<gfx::DrawTarget> target = CompositorWidget::GetBackBufferDrawTarget(
+      aScreenTarget, aRect, aOutIsCleared);
+  if (!target) {
+    return nullptr;
+  }
+
+  MOZ_ASSERT(target->GetBackendType() == BackendType::CAIRO);
+
+  uint8_t* destData;
+  IntSize destSize;
+  int32_t destStride;
+  SurfaceFormat destFormat;
+  if (!target->LockBits(&destData, &destSize, &destStride, &destFormat)) {
+    // LockBits is not supported. Use original DrawTarget.
+    return target.forget();
+  }
+
+  RefPtr<gfx::DrawTarget> dataTarget = Factory::CreateDrawTargetForData(
+      BackendType::CAIRO, destData, destSize, destStride, destFormat);
+  mLockedBackBufferData = destData;
+
+  return dataTarget.forget();
+}
+
+already_AddRefed<gfx::SourceSurface>
+InProcessWinCompositorWidget::EndBackBufferDrawing() {
+  if (mLockedBackBufferData) {
+    MOZ_ASSERT(mLastBackBuffer);
+    mLastBackBuffer->ReleaseBits(mLockedBackBufferData);
+    mLockedBackBufferData = nullptr;
+  }
+  return CompositorWidget::EndBackBufferDrawing();
+}
+
+bool InProcessWinCompositorWidget::InitCompositor(
+    layers::Compositor* aCompositor) {
+  return true;
+}
+
+void InProcessWinCompositorWidget::EnterPresentLock() { mPresentLock.Enter(); }
+
+void InProcessWinCompositorWidget::LeavePresentLock() { mPresentLock.Leave(); }
+
+RefPtr<gfxASurface> InProcessWinCompositorWidget::EnsureTransparentSurface() {
+  mTransparentSurfaceLock.AssertCurrentThreadOwns();
+  MOZ_ASSERT(TransparencyModeIs(TransparencyMode::Transparent));
+
+  IntSize size = GetClientSize().ToUnknownSize();
+  if (!mTransparentSurface || mTransparentSurface->GetSize() != size) {
+    mTransparentSurface = nullptr;
+    mMemoryDC = nullptr;
+    CreateTransparentSurface(size);
+  }
+
+  RefPtr<gfxASurface> surface = mTransparentSurface;
+  return surface.forget();
+}
+
+void InProcessWinCompositorWidget::CreateTransparentSurface(
+    const gfx::IntSize& aSize) {
+  mTransparentSurfaceLock.AssertCurrentThreadOwns();
+  MOZ_ASSERT(!mTransparentSurface && !mMemoryDC);
+  RefPtr<gfxWindowsSurface> surface =
+      new gfxWindowsSurface(aSize, SurfaceFormat::A8R8G8B8_UINT32);
+  mTransparentSurface = surface;
+  mMemoryDC = surface->GetDC();
+}
+
+void InProcessWinCompositorWidget::UpdateTransparency(TransparencyMode aMode) {
+  gfx::CriticalSectionAutoEnter presentLock(&mPresentLock);
+  MutexAutoLock lock(mTransparentSurfaceLock);
+  if (TransparencyModeIs(aMode)) {
+    return;
+  }
+
+  mTransparencyMode = uint32_t(aMode);
+  mTransparentSurface = nullptr;
+  mMemoryDC = nullptr;
+
+  if (aMode == TransparencyMode::Transparent) {
+    EnsureTransparentSurface();
+  }
+}
+
+void InProcessWinCompositorWidget::NotifyVisibilityUpdated(
+    nsSizeMode aSizeMode, bool aIsFullyOccluded) {
+  mSizeMode = aSizeMode;
+  mIsFullyOccluded = aIsFullyOccluded;
+}
+
+nsSizeMode InProcessWinCompositorWidget::GetWindowSizeMode() const {
+  nsSizeMode sizeMode = mSizeMode;
+  return sizeMode;
+}
+
+bool InProcessWinCompositorWidget::GetWindowIsFullyOccluded() const {
+  bool isFullyOccluded = mIsFullyOccluded;
+  return isFullyOccluded;
+}
+
+void InProcessWinCompositorWidget::ClearTransparentWindow() {
+  gfx::CriticalSectionAutoEnter presentLock(&mPresentLock);
+  MutexAutoLock lock(mTransparentSurfaceLock);
+  if (!mTransparentSurface) {
+    return;
+  }
+
+  EnsureTransparentSurface();
+
+  IntSize size = mTransparentSurface->GetSize();
+  if (!size.IsEmpty()) {
+    RefPtr<DrawTarget> drawTarget =
+        gfxPlatform::CreateDrawTargetForSurface(mTransparentSurface, size);
+    if (!drawTarget) {
+      return;
+    }
+    drawTarget->ClearRect(Rect(0, 0, size.width, size.height));
+    RedrawTransparentWindow();
+  }
+}
+
+bool InProcessWinCompositorWidget::RedrawTransparentWindow() {
+  MOZ_ASSERT(TransparencyModeIs(TransparencyMode::Transparent));
+
+  LayoutDeviceIntSize size = GetClientSize();
+
+  ::GdiFlush();
+
+  BLENDFUNCTION bf = {AC_SRC_OVER, 0, 255, AC_SRC_ALPHA};
+  SIZE winSize = {size.width, size.height};
+  POINT srcPos = {0, 0};
+  HWND hWnd = WinUtils::GetTopLevelHWND(mWnd, true);
+  RECT winRect;
+  ::GetWindowRect(hWnd, &winRect);
+
+  // perform the alpha blend
+  return !!::UpdateLayeredWindow(hWnd, nullptr, (POINT*)&winRect, &winSize,
+                                 mMemoryDC, &srcPos, 0, &bf, ULW_ALPHA);
+}
+
+HDC InProcessWinCompositorWidget::GetWindowSurface() {
+  return TransparencyModeIs(TransparencyMode::Transparent) ? mMemoryDC
+                                                           : ::GetDC(mWnd);
+}
+
+void InProcessWinCompositorWidget::FreeWindowSurface(HDC dc) {
+  if (!TransparencyModeIs(TransparencyMode::Transparent)) {
+    ::ReleaseDC(mWnd, dc);
+  }
+}
+
+bool InProcessWinCompositorWidget::IsHidden() const { return ::IsIconic(mWnd); }
+
+nsIWidget* InProcessWinCompositorWidget::RealWidget() { return mWindow; }
+
+void InProcessWinCompositorWidget::ObserveVsync(VsyncObserver* aObserver) {
+  if (RefPtr<CompositorVsyncDispatcher> cvd =
+          mWindow->GetCompositorVsyncDispatcher()) {
+    cvd->SetCompositorVsyncObserver(aObserver);
+  }
+}
+
+void InProcessWinCompositorWidget::UpdateCompositorWnd(
+    const HWND aCompositorWnd, const HWND aParentWnd) {
+  MOZ_ASSERT(layers::CompositorThreadHolder::IsInCompositorThread());
+  MOZ_ASSERT(aCompositorWnd && aParentWnd);
+  MOZ_ASSERT(aParentWnd == mWnd);
+
+  // Since we're in the parent process anyway, we can just call SetParent
+  // directly.
+  ::SetParent(aCompositorWnd, aParentWnd);
+  mSetParentCompleted = true;
+}
+}  // namespace mozilla::widget
diff --git a/widget/windows/InProcessWinCompositorWidget.h b/widget/windows/InProcessWinCompositorWidget.h
new file mode 100644
index 0000000000..e287204461
--- /dev/null
+++ b/widget/windows/InProcessWinCompositorWidget.h
@@ -0,0 +1,111 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef widget_windows_InProcessWinCompositorWidget_h
+#define widget_windows_InProcessWinCompositorWidget_h
+
+#include "WinCompositorWidget.h"
+
+class nsWindow;
+class gfxASurface;
+
+namespace mozilla::widget {
+
+// This is the Windows-specific implementation of CompositorWidget. For
+// the most part it only requires an HWND, however it maintains extra state
+// for transparent windows, as well as for synchronizing WM_SETTEXT messages
+// with the compositor.
+class InProcessWinCompositorWidget final
+    : public WinCompositorWidget,
+      public PlatformCompositorWidgetDelegate {
+ public:
+  InProcessWinCompositorWidget(const WinCompositorWidgetInitData& aInitData,
+                               const layers::CompositorOptions& aOptions,
+                               nsWindow* aWindow);
+
+  bool PreRender(WidgetRenderingContext*) override;
+  void PostRender(WidgetRenderingContext*) override;
+  already_AddRefed<gfx::DrawTarget> StartRemoteDrawing() override;
+  void EndRemoteDrawing() override;
+  bool NeedsToDeferEndRemoteDrawing() override;
+  LayoutDeviceIntSize GetClientSize() override;
+  already_AddRefed<gfx::DrawTarget> GetBackBufferDrawTarget(
+      gfx::DrawTarget* aScreenTarget, const gfx::IntRect& aRect,
+      bool* aOutIsCleared) override;
+  already_AddRefed<gfx::SourceSurface> EndBackBufferDrawing() override;
+  bool InitCompositor(layers::Compositor* aCompositor) override;
+  CompositorWidgetDelegate* AsDelegate() override { return this; }
+  bool IsHidden() const override;
+
+  // PlatformCompositorWidgetDelegate Overrides
+
+  void EnterPresentLock() override;
+  void LeavePresentLock() override;
+  void OnDestroyWindow() override;
+  bool OnWindowResize(const LayoutDeviceIntSize& aSize) override;
+  void OnWindowModeChange(nsSizeMode aSizeMode) override;
+  void UpdateTransparency(TransparencyMode aMode) override;
+  void NotifyVisibilityUpdated(nsSizeMode aSizeMode,
+                               bool aIsFullyOccluded) override;
+  void ClearTransparentWindow() override;
+
+  bool RedrawTransparentWindow();
+
+  // Ensure that a transparent surface exists, then return it.
+  RefPtr<gfxASurface> EnsureTransparentSurface();
+
+  HDC GetTransparentDC() const { return mMemoryDC; }
+
+  mozilla::Mutex& GetTransparentSurfaceLock() {
+    return mTransparentSurfaceLock;
+  }
+
+  nsSizeMode GetWindowSizeMode() const override;
+  bool GetWindowIsFullyOccluded() const override;
+
+  void ObserveVsync(VsyncObserver* aObserver) override;
+  nsIWidget* RealWidget() override;
+
+  void UpdateCompositorWnd(const HWND aCompositorWnd,
+                           const HWND aParentWnd) override;
+  void SetRootLayerTreeID(const layers::LayersId& aRootLayerTreeId) override {}
+
+ private:
+  HDC GetWindowSurface();
+  void FreeWindowSurface(HDC dc);
+
+  void CreateTransparentSurface(const gfx::IntSize& aSize);
+
+  nsWindow* mWindow;
+
+  HWND mWnd;
+
+  gfx::CriticalSection mPresentLock;
+
+  // Transparency handling.
+  mozilla::Mutex mTransparentSurfaceLock MOZ_UNANNOTATED;
+  mozilla::Atomic<uint32_t, MemoryOrdering::Relaxed> mTransparencyMode;
+
+  bool TransparencyModeIs(TransparencyMode aMode) const {
+    return TransparencyMode(uint32_t(mTransparencyMode)) == aMode;
+  }
+
+  // Visibility handling.
+  mozilla::Atomic<nsSizeMode, MemoryOrdering::Relaxed> mSizeMode;
+  mozilla::Atomic<bool, MemoryOrdering::Relaxed> mIsFullyOccluded;
+
+  RefPtr<gfxASurface> mTransparentSurface;
+  HDC mMemoryDC;
+  HDC mCompositeDC;
+
+  // Locked back buffer of BasicCompositor
+  uint8_t* mLockedBackBufferData;
+
+  bool mNotDeferEndRemoteDrawing;
+};
+
+}  // namespace mozilla::widget
+
+#endif  // widget_windows_InProcessWinCompositorWidget_h
diff --git a/widget/windows/InputDeviceUtils.cpp b/widget/windows/InputDeviceUtils.cpp
new file mode 100644
index 0000000000..3636b93d6a
--- /dev/null
+++ b/widget/windows/InputDeviceUtils.cpp
@@ -0,0 +1,61 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:set ts=2 sts=2 sw=2 et cin: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "InputDeviceUtils.h"
+
+#define INITGUID
+#include <dbt.h>
+#include <hidclass.h>
+#include <ntddmou.h>
+#include <setupapi.h>
+
+namespace mozilla {
+namespace widget {
+
+HDEVNOTIFY
+InputDeviceUtils::RegisterNotification(HWND aHwnd) {
+  DEV_BROADCAST_DEVICEINTERFACE filter = {};
+
+  filter.dbcc_size = sizeof(DEV_BROADCAST_DEVICEINTERFACE);
+  filter.dbcc_devicetype = DBT_DEVTYP_DEVICEINTERFACE;
+  // Some touchsreen devices are not GUID_DEVINTERFACE_MOUSE, so here we use
+  // GUID_DEVINTERFACE_HID instead.
+  filter.dbcc_classguid = GUID_DEVINTERFACE_HID;
+  return RegisterDeviceNotification(aHwnd, &filter,
+                                    DEVICE_NOTIFY_WINDOW_HANDLE);
+}
+
+void InputDeviceUtils::UnregisterNotification(HDEVNOTIFY aHandle) {
+  if (!aHandle) {
+    return;
+  }
+  UnregisterDeviceNotification(aHandle);
+}
+
+DWORD
+InputDeviceUtils::CountMouseDevices() {
+  HDEVINFO hdev =
+      SetupDiGetClassDevs(&GUID_DEVINTERFACE_MOUSE, nullptr, nullptr,
+                          DIGCF_DEVICEINTERFACE | DIGCF_PRESENT);
+  if (hdev == INVALID_HANDLE_VALUE) {
+    return 0;
+  }
+
+  DWORD count = 0;
+  SP_INTERFACE_DEVICE_DATA info = {};
+  info.cbSize = sizeof(SP_INTERFACE_DEVICE_DATA);
+  while (SetupDiEnumDeviceInterfaces(hdev, nullptr, &GUID_DEVINTERFACE_MOUSE,
+                                     count, &info)) {
+    if (info.Flags & SPINT_ACTIVE) {
+      count++;
+    }
+  }
+  SetupDiDestroyDeviceInfoList(hdev);
+  return count;
+}
+
+}  // namespace widget
+}  // namespace mozilla
diff --git a/widget/windows/InputDeviceUtils.h b/widget/windows/InputDeviceUtils.h
new file mode 100644
index 0000000000..d16698a03a
--- /dev/null
+++ b/widget/windows/InputDeviceUtils.h
@@ -0,0 +1,26 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:set ts=2 sts=2 sw=2 et cin: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_widget_InputDeviceUtils_h__
+#define mozilla_widget_InputDeviceUtils_h__
+
+#include <windows.h>
+
+namespace mozilla {
+namespace widget {
+
+class InputDeviceUtils {
+ public:
+  static HDEVNOTIFY RegisterNotification(HWND aHwnd);
+  static void UnregisterNotification(HDEVNOTIFY aHandle);
+
+  // Returns the number of mouse type devices connected to this system.
+  static DWORD CountMouseDevices();
+};
+
+}  // namespace widget
+}  // namespace mozilla
+#endif  // mozilla_widget_InputDeviceUtils_h__
diff --git a/widget/windows/JumpListBuilder.cpp b/widget/windows/JumpListBuilder.cpp
new file mode 100644
index 0000000000..80b1c29aa7
--- /dev/null
+++ b/widget/windows/JumpListBuilder.cpp
@@ -0,0 +1,818 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <windows.h>
+#include <shobjidl.h>
+#include <propkey.h>
+#include <propvarutil.h>
+#include <shellapi.h>
+#include "JumpListBuilder.h"
+#include "mozilla/Preferences.h"
+#include "mozilla/dom/Promise.h"
+#include "mozilla/dom/WindowsJumpListShortcutDescriptionBinding.h"
+#include "mozilla/mscom/EnsureMTA.h"
+#include "nsIFile.h"
+#include "nsIObserverService.h"
+#include "nsServiceManagerUtils.h"
+#include "WinUtils.h"
+
+using mozilla::dom::Promise;
+using mozilla::dom::WindowsJumpListShortcutDescription;
+
+namespace mozilla {
+namespace widget {
+
+NS_IMPL_ISUPPORTS(JumpListBuilder, nsIJumpListBuilder, nsIObserver)
+
+#define TOPIC_PROFILE_BEFORE_CHANGE "profile-before-change"
+#define TOPIC_CLEAR_PRIVATE_DATA "clear-private-data"
+
+// The amount of time, in milliseconds, that our IO thread will stay alive after
+// the last event it processes.
+#define DEFAULT_THREAD_TIMEOUT_MS 30000
+
+const char kPrefTaskbarEnabled[] = "browser.taskbar.lists.enabled";
+
+/**
+ * A wrapper around a ICustomDestinationList that implements the JumpListBackend
+ * interface. This is an implementation of JumpListBackend that actually causes
+ * items to appear in a Windows jump list.
+ */
+class NativeJumpListBackend : public JumpListBackend {
+  // We use NS_INLINE_DECL_REFCOUNTING_ONEVENTTARGET because this
+  // class might be destroyed on a different thread than the one it
+  // was created on, since it's maintained by a LazyIdleThread.
+  //
+  // This is a workaround for bug 1648031.
+  NS_INLINE_DECL_REFCOUNTING_ONEVENTTARGET(JumpListBackend, override)
+
+  NativeJumpListBackend() {
+    MOZ_ASSERT(!NS_IsMainThread());
+
+    mscom::EnsureMTA([&]() {
+      RefPtr<ICustomDestinationList> destList;
+      HRESULT hr = ::CoCreateInstance(
+          CLSID_DestinationList, nullptr, CLSCTX_INPROC_SERVER,
+          IID_ICustomDestinationList, getter_AddRefs(destList));
+      if (FAILED(hr)) {
+        return;
+      }
+
+      mWindowsDestList = destList;
+    });
+  }
+
+  virtual bool IsAvailable() override {
+    MOZ_ASSERT(!NS_IsMainThread());
+    return mWindowsDestList != nullptr;
+  }
+
+  virtual HRESULT SetAppID(LPCWSTR pszAppID) override {
+    MOZ_ASSERT(!NS_IsMainThread());
+    MOZ_ASSERT(mWindowsDestList);
+
+    return mWindowsDestList->SetAppID(pszAppID);
+  }
+
+  virtual HRESULT BeginList(UINT* pcMinSlots, REFIID riid,
+                            void** ppv) override {
+    MOZ_ASSERT(!NS_IsMainThread());
+    MOZ_ASSERT(mWindowsDestList);
+
+    return mWindowsDestList->BeginList(pcMinSlots, riid, ppv);
+  }
+
+  virtual HRESULT AddUserTasks(IObjectArray* poa) override {
+    MOZ_ASSERT(!NS_IsMainThread());
+    MOZ_ASSERT(mWindowsDestList);
+
+    return mWindowsDestList->AddUserTasks(poa);
+  }
+
+  virtual HRESULT AppendCategory(LPCWSTR pszCategory,
+                                 IObjectArray* poa) override {
+    MOZ_ASSERT(!NS_IsMainThread());
+    MOZ_ASSERT(mWindowsDestList);
+
+    return mWindowsDestList->AppendCategory(pszCategory, poa);
+  }
+
+  virtual HRESULT CommitList() override {
+    MOZ_ASSERT(!NS_IsMainThread());
+    MOZ_ASSERT(mWindowsDestList);
+
+    return mWindowsDestList->CommitList();
+  }
+
+  virtual HRESULT AbortList() override {
+    MOZ_ASSERT(!NS_IsMainThread());
+    MOZ_ASSERT(mWindowsDestList);
+
+    return mWindowsDestList->AbortList();
+  }
+
+  virtual HRESULT DeleteList(LPCWSTR pszAppID) override {
+    MOZ_ASSERT(!NS_IsMainThread());
+    MOZ_ASSERT(mWindowsDestList);
+
+    return mWindowsDestList->DeleteList(pszAppID);
+  }
+
+  virtual HRESULT AppendKnownCategory(KNOWNDESTCATEGORY category) override {
+    MOZ_ASSERT(!NS_IsMainThread());
+    MOZ_ASSERT(mWindowsDestList);
+
+    return mWindowsDestList->AppendKnownCategory(category);
+  }
+
+ protected:
+  virtual ~NativeJumpListBackend() override{};
+
+ private:
+  RefPtr<ICustomDestinationList> mWindowsDestList;
+};
+
+JumpListBuilder::JumpListBuilder(const nsAString& aAppUserModelId,
+                                 RefPtr<JumpListBackend> aTestingBackend) {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  mAppUserModelId.Assign(aAppUserModelId);
+
+  Preferences::AddStrongObserver(this, kPrefTaskbarEnabled);
+
+  // Make a lazy thread for any IO.
+  mIOThread = new LazyIdleThread(DEFAULT_THREAD_TIMEOUT_MS, "Jump List",
+                                 LazyIdleThread::ManualShutdown);
+
+  nsCOMPtr<nsIObserverService> observerService =
+      do_GetService("@mozilla.org/observer-service;1");
+  if (observerService) {
+    observerService->AddObserver(this, TOPIC_PROFILE_BEFORE_CHANGE, false);
+    observerService->AddObserver(this, TOPIC_CLEAR_PRIVATE_DATA, false);
+  }
+
+  nsCOMPtr<nsIRunnable> runnable;
+
+  if (aTestingBackend) {
+    // Dispatch a task that hands a reference to the testing backend
+    // to the background thread. The testing backend was probably
+    // constructed on the main thread, and is responsible for doing
+    // any locking as well as cleanup.
+    runnable = NewRunnableMethod<RefPtr<JumpListBackend>>(
+        "SetupTestingBackend", this, &JumpListBuilder::DoSetupTestingBackend,
+        aTestingBackend);
+
+  } else {
+    // Dispatch a task that constructs the native jump list backend.
+    runnable = NewRunnableMethod("SetupBackend", this,
+                                 &JumpListBuilder::DoSetupBackend);
+  }
+
+  mIOThread->Dispatch(runnable, NS_DISPATCH_NORMAL);
+
+  // MSIX packages explicitly do not support setting the appid from within
+  // the app, as it is set in the package manifest instead.
+  if (!mozilla::widget::WinUtils::HasPackageIdentity()) {
+    mIOThread->Dispatch(
+        NewRunnableMethod<nsString>(
+            "SetAppID", this, &JumpListBuilder::DoSetAppID, aAppUserModelId),
+        NS_DISPATCH_NORMAL);
+  }
+}
+
+JumpListBuilder::~JumpListBuilder() {
+  Preferences::RemoveObserver(this, kPrefTaskbarEnabled);
+}
+
+void JumpListBuilder::DoSetupTestingBackend(
+    RefPtr<JumpListBackend> aTestingBackend) {
+  MOZ_ASSERT(!NS_IsMainThread());
+  mJumpListBackend = aTestingBackend;
+}
+
+void JumpListBuilder::DoSetupBackend() {
+  MOZ_ASSERT(!NS_IsMainThread());
+  MOZ_ASSERT(!mJumpListBackend);
+  mJumpListBackend = new NativeJumpListBackend();
+}
+
+void JumpListBuilder::DoShutdownBackend() {
+  MOZ_ASSERT(!NS_IsMainThread());
+  mJumpListBackend = nullptr;
+}
+
+void JumpListBuilder::DoSetAppID(nsString aAppUserModelID) {
+  MOZ_ASSERT(!NS_IsMainThread());
+  MOZ_ASSERT(mJumpListBackend);
+  mJumpListBackend->SetAppID(aAppUserModelID.get());
+}
+
+NS_IMETHODIMP
+JumpListBuilder::ObtainAndCacheFavicon(nsIURI* aFaviconURI,
+                                       nsAString& aCachedIconPath) {
+  MOZ_ASSERT(NS_IsMainThread());
+  nsString iconFilePath;
+  nsresult rv = mozilla::widget::FaviconHelper::ObtainCachedIconFile(
+      aFaviconURI, iconFilePath, mIOThread, false);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  aCachedIconPath = iconFilePath;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+JumpListBuilder::IsAvailable(JSContext* aCx, Promise** aPromise) {
+  MOZ_ASSERT(NS_IsMainThread());
+  MOZ_ASSERT(aPromise);
+  MOZ_ASSERT(mIOThread);
+
+  ErrorResult result;
+  RefPtr<Promise> promise =
+      Promise::Create(xpc::CurrentNativeGlobal(aCx), result);
+
+  if (MOZ_UNLIKELY(result.Failed())) {
+    return result.StealNSResult();
+  }
+
+  nsMainThreadPtrHandle<Promise> promiseHolder(
+      new nsMainThreadPtrHolder<Promise>("JumpListBuilder::IsAvailable promise",
+                                         promise));
+
+  nsCOMPtr<nsIRunnable> runnable =
+      NewRunnableMethod<nsMainThreadPtrHandle<Promise>>(
+          "IsAvailable", this, &JumpListBuilder::DoIsAvailable,
+          std::move(promiseHolder));
+  nsresult rv = mIOThread->Dispatch(runnable, NS_DISPATCH_NORMAL);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  promise.forget(aPromise);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+JumpListBuilder::CheckForRemovals(JSContext* aCx, Promise** aPromise) {
+  MOZ_ASSERT(NS_IsMainThread());
+  MOZ_ASSERT(aPromise);
+  MOZ_ASSERT(mIOThread);
+
+  ErrorResult result;
+  RefPtr<Promise> promise =
+      Promise::Create(xpc::CurrentNativeGlobal(aCx), result);
+
+  if (MOZ_UNLIKELY(result.Failed())) {
+    return result.StealNSResult();
+  }
+
+  nsMainThreadPtrHandle<Promise> promiseHolder(
+      new nsMainThreadPtrHolder<Promise>(
+          "JumpListBuilder::CheckForRemovals promise", promise));
+
+  nsCOMPtr<nsIRunnable> runnable =
+      NewRunnableMethod<nsMainThreadPtrHandle<Promise>>(
+          "CheckForRemovals", this, &JumpListBuilder::DoCheckForRemovals,
+          std::move(promiseHolder));
+
+  nsresult rv = mIOThread->Dispatch(runnable, NS_DISPATCH_NORMAL);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  promise.forget(aPromise);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+JumpListBuilder::PopulateJumpList(
+    const nsTArray<JS::Value>& aTaskDescriptions, const nsAString& aCustomTitle,
+    const nsTArray<JS::Value>& aCustomDescriptions, JSContext* aCx,
+    Promise** aPromise) {
+  MOZ_ASSERT(NS_IsMainThread());
+  MOZ_ASSERT(aPromise);
+  MOZ_ASSERT(mIOThread);
+
+  if (aCustomDescriptions.Length() && aCustomTitle.IsEmpty()) {
+    return NS_ERROR_INVALID_ARG;
+  }
+
+  // Get rid of the old icons
+  nsCOMPtr<nsIRunnable> event =
+      new mozilla::widget::AsyncDeleteAllFaviconsFromDisk(true);
+  mIOThread->Dispatch(event, NS_DISPATCH_NORMAL);
+
+  nsTArray<WindowsJumpListShortcutDescription> taskDescs;
+  for (auto& jsval : aTaskDescriptions) {
+    JS::Rooted<JS::Value> rootedVal(aCx);
+    if (NS_WARN_IF(!dom::ToJSValue(aCx, jsval, &rootedVal))) {
+      return NS_ERROR_INVALID_ARG;
+    }
+
+    WindowsJumpListShortcutDescription desc;
+    if (!desc.Init(aCx, rootedVal)) {
+      return NS_ERROR_INVALID_ARG;
+    }
+
+    taskDescs.AppendElement(std::move(desc));
+  }
+
+  nsTArray<WindowsJumpListShortcutDescription> customDescs;
+  for (auto& jsval : aCustomDescriptions) {
+    JS::Rooted<JS::Value> rootedVal(aCx);
+    if (NS_WARN_IF(!dom::ToJSValue(aCx, jsval, &rootedVal))) {
+      return NS_ERROR_INVALID_ARG;
+    }
+
+    WindowsJumpListShortcutDescription desc;
+    if (!desc.Init(aCx, rootedVal)) {
+      return NS_ERROR_INVALID_ARG;
+    }
+
+    customDescs.AppendElement(std::move(desc));
+  }
+
+  ErrorResult result;
+  RefPtr<Promise> promise =
+      Promise::Create(xpc::CurrentNativeGlobal(aCx), result);
+
+  if (MOZ_UNLIKELY(result.Failed())) {
+    return result.StealNSResult();
+  }
+
+  nsMainThreadPtrHandle<Promise> promiseHolder(
+      new nsMainThreadPtrHolder<Promise>(
+          "JumpListBuilder::PopulateJumpList promise", promise));
+
+  nsCOMPtr<nsIRunnable> runnable = NewRunnableMethod<
+      StoreCopyPassByRRef<nsTArray<WindowsJumpListShortcutDescription>>,
+      nsString,
+      StoreCopyPassByRRef<nsTArray<WindowsJumpListShortcutDescription>>,
+      nsMainThreadPtrHandle<Promise>>(
+      "PopulateJumpList", this, &JumpListBuilder::DoPopulateJumpList,
+      std::move(taskDescs), aCustomTitle, std::move(customDescs),
+      std::move(promiseHolder));
+  nsresult rv = mIOThread->Dispatch(runnable, NS_DISPATCH_NORMAL);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  promise.forget(aPromise);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+JumpListBuilder::ClearJumpList(JSContext* aCx, Promise** aPromise) {
+  MOZ_ASSERT(NS_IsMainThread());
+  MOZ_ASSERT(aPromise);
+  MOZ_ASSERT(mIOThread);
+
+  ErrorResult result;
+  RefPtr<Promise> promise =
+      Promise::Create(xpc::CurrentNativeGlobal(aCx), result);
+
+  if (MOZ_UNLIKELY(result.Failed())) {
+    return result.StealNSResult();
+  }
+
+  nsMainThreadPtrHandle<Promise> promiseHolder(
+      new nsMainThreadPtrHolder<Promise>(
+          "JumpListBuilder::ClearJumpList promise", promise));
+
+  nsCOMPtr<nsIRunnable> runnable =
+      NewRunnableMethod<nsMainThreadPtrHandle<Promise>>(
+          "ClearJumpList", this, &JumpListBuilder::DoClearJumpList,
+          std::move(promiseHolder));
+  nsresult rv = mIOThread->Dispatch(runnable, NS_DISPATCH_NORMAL);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  promise.forget(aPromise);
+  return NS_OK;
+}
+
+void JumpListBuilder::DoIsAvailable(
+    const nsMainThreadPtrHandle<Promise>& aPromiseHolder) {
+  MOZ_ASSERT(!NS_IsMainThread());
+  MOZ_ASSERT(aPromiseHolder);
+
+  if (!mJumpListBackend) {
+    NS_DispatchToMainThread(NS_NewRunnableFunction(
+        "DoIsAvailable", [promiseHolder = std::move(aPromiseHolder)]() {
+          promiseHolder.get()->MaybeResolve(false);
+        }));
+    return;
+  }
+
+  bool isAvailable = mJumpListBackend->IsAvailable();
+
+  NS_DispatchToMainThread(NS_NewRunnableFunction(
+      "DoIsAvailable",
+      [promiseHolder = std::move(aPromiseHolder), isAvailable]() {
+        promiseHolder.get()->MaybeResolve(isAvailable);
+      }));
+}
+
+void JumpListBuilder::DoCheckForRemovals(
+    const nsMainThreadPtrHandle<Promise>& aPromiseHolder) {
+  MOZ_ASSERT(!NS_IsMainThread());
+  MOZ_ASSERT(aPromiseHolder);
+
+  nsresult rv = NS_ERROR_UNEXPECTED;
+
+  auto errorHandler = MakeScopeExit([&aPromiseHolder, &rv]() {
+    NS_DispatchToMainThread(NS_NewRunnableFunction(
+        "DoCheckForRemovals",
+        [promiseHolder = std::move(aPromiseHolder), rv]() {
+          promiseHolder.get()->MaybeReject(rv);
+        }));
+  });
+
+  MOZ_ASSERT(mJumpListBackend);
+  if (!mJumpListBackend) {
+    return;
+  }
+
+  // Abort any ongoing list building that might not have been committed,
+  // otherwise BeginList will give us problems.
+  Unused << mJumpListBackend->AbortList();
+
+  nsTArray<nsString> urisToRemove;
+  RefPtr<IObjectArray> objArray;
+  uint32_t maxItems = 0;
+
+  HRESULT hr = mJumpListBackend->BeginList(
+      &maxItems,
+      IID_PPV_ARGS(static_cast<IObjectArray**>(getter_AddRefs(objArray))));
+
+  if (FAILED(hr)) {
+    rv = NS_ERROR_UNEXPECTED;
+    return;
+  }
+
+  RemoveIconCacheAndGetJumplistShortcutURIs(objArray, urisToRemove);
+
+  // We began a list in order to get the removals, which we can now abort.
+  Unused << mJumpListBackend->AbortList();
+
+  errorHandler.release();
+
+  NS_DispatchToMainThread(NS_NewRunnableFunction(
+      "DoCheckForRemovals", [urisToRemove = std::move(urisToRemove),
+                             promiseHolder = std::move(aPromiseHolder)]() {
+        promiseHolder.get()->MaybeResolve(urisToRemove);
+      }));
+}
+
+void JumpListBuilder::DoPopulateJumpList(
+    const nsTArray<WindowsJumpListShortcutDescription>&& aTaskDescriptions,
+    const nsAString& aCustomTitle,
+    const nsTArray<WindowsJumpListShortcutDescription>&& aCustomDescriptions,
+    const nsMainThreadPtrHandle<Promise>& aPromiseHolder) {
+  MOZ_ASSERT(!NS_IsMainThread());
+  MOZ_ASSERT(aPromiseHolder);
+
+  nsresult rv = NS_ERROR_UNEXPECTED;
+
+  auto errorHandler = MakeScopeExit([&aPromiseHolder, &rv]() {
+    NS_DispatchToMainThread(NS_NewRunnableFunction(
+        "DoPopulateJumpList",
+        [promiseHolder = std::move(aPromiseHolder), rv]() {
+          promiseHolder.get()->MaybeReject(rv);
+        }));
+  });
+
+  MOZ_ASSERT(mJumpListBackend);
+  if (!mJumpListBackend) {
+    return;
+  }
+
+  // Abort any ongoing list building that might not have been committed,
+  // otherwise BeginList will give us problems.
+  Unused << mJumpListBackend->AbortList();
+
+  nsTArray<nsString> urisToRemove;
+  RefPtr<IObjectArray> objArray;
+  uint32_t maxItems = 0;
+
+  HRESULT hr = mJumpListBackend->BeginList(
+      &maxItems,
+      IID_PPV_ARGS(static_cast<IObjectArray**>(getter_AddRefs(objArray))));
+
+  if (FAILED(hr)) {
+    rv = NS_ERROR_UNEXPECTED;
+    return;
+  }
+
+  if (urisToRemove.Length()) {
+    // It'd be nice if we could return a more descriptive error here so that
+    // the caller knows that they should have called checkForRemovals first.
+    rv = NS_ERROR_UNEXPECTED;
+    return;
+  }
+
+  if (aTaskDescriptions.Length()) {
+    RefPtr<IObjectCollection> taskCollection;
+    hr = CoCreateInstance(CLSID_EnumerableObjectCollection, nullptr,
+                          CLSCTX_INPROC_SERVER, IID_IObjectCollection,
+                          getter_AddRefs(taskCollection));
+    if (FAILED(hr)) {
+      rv = NS_ERROR_UNEXPECTED;
+      return;
+    }
+
+    // Start by building the task list
+    for (auto& desc : aTaskDescriptions) {
+      // These should all be ShellLinks
+      RefPtr<IShellLinkW> link;
+      rv = GetShellLinkFromDescription(desc, link);
+      if (NS_FAILED(rv)) {
+        // Let the errorHandler deal with this.
+        return;
+      }
+      taskCollection->AddObject(link);
+    }
+
+    RefPtr<IObjectArray> pTaskArray;
+    hr = taskCollection->QueryInterface(IID_IObjectArray,
+                                        getter_AddRefs(pTaskArray));
+
+    if (FAILED(hr)) {
+      rv = NS_ERROR_UNEXPECTED;
+      return;
+    }
+
+    hr = mJumpListBackend->AddUserTasks(pTaskArray);
+
+    if (FAILED(hr)) {
+      rv = NS_ERROR_FAILURE;
+      return;
+    }
+  }
+
+  if (aCustomDescriptions.Length()) {
+    // Then build the custom list
+    RefPtr<IObjectCollection> customCollection;
+    hr = CoCreateInstance(CLSID_EnumerableObjectCollection, nullptr,
+                          CLSCTX_INPROC_SERVER, IID_IObjectCollection,
+                          getter_AddRefs(customCollection));
+    if (FAILED(hr)) {
+      rv = NS_ERROR_UNEXPECTED;
+      return;
+    }
+
+    for (auto& desc : aCustomDescriptions) {
+      // These should all be ShellLinks
+      RefPtr<IShellLinkW> link;
+      rv = GetShellLinkFromDescription(desc, link);
+      if (NS_FAILED(rv)) {
+        // Let the errorHandler deal with this.
+        return;
+      }
+      customCollection->AddObject(link);
+    }
+
+    RefPtr<IObjectArray> pCustomArray;
+    hr = customCollection->QueryInterface(IID_IObjectArray,
+                                          getter_AddRefs(pCustomArray));
+    if (FAILED(hr)) {
+      rv = NS_ERROR_UNEXPECTED;
+      return;
+    }
+
+    hr = mJumpListBackend->AppendCategory(
+        reinterpret_cast<const wchar_t*>(aCustomTitle.BeginReading()),
+        pCustomArray);
+
+    if (FAILED(hr)) {
+      rv = NS_ERROR_UNEXPECTED;
+      return;
+    }
+  }
+
+  hr = mJumpListBackend->CommitList();
+  if (FAILED(hr)) {
+    rv = NS_ERROR_FAILURE;
+    return;
+  }
+
+  errorHandler.release();
+
+  NS_DispatchToMainThread(NS_NewRunnableFunction(
+      "DoPopulateJumpList", [promiseHolder = std::move(aPromiseHolder)]() {
+        promiseHolder.get()->MaybeResolveWithUndefined();
+      }));
+}
+
+void JumpListBuilder::DoClearJumpList(
+    const nsMainThreadPtrHandle<Promise>& aPromiseHolder) {
+  MOZ_ASSERT(!NS_IsMainThread());
+  MOZ_ASSERT(aPromiseHolder);
+
+  if (!mJumpListBackend) {
+    NS_DispatchToMainThread(NS_NewRunnableFunction(
+        "DoClearJumpList", [promiseHolder = std::move(aPromiseHolder)]() {
+          promiseHolder.get()->MaybeReject(NS_ERROR_UNEXPECTED);
+        }));
+    return;
+  }
+
+  if (SUCCEEDED(mJumpListBackend->DeleteList(mAppUserModelId.get()))) {
+    NS_DispatchToMainThread(NS_NewRunnableFunction(
+        "DoClearJumpList", [promiseHolder = std::move(aPromiseHolder)]() {
+          promiseHolder.get()->MaybeResolveWithUndefined();
+        }));
+  } else {
+    NS_DispatchToMainThread(NS_NewRunnableFunction(
+        "DoClearJumpList", [promiseHolder = std::move(aPromiseHolder)]() {
+          promiseHolder.get()->MaybeReject(NS_ERROR_FAILURE);
+        }));
+  }
+}
+
+// RemoveIconCacheAndGetJumplistShortcutURIs - does multiple things to
+// avoid unnecessary extra XPCOM incantations. For each object in the input
+// array,  if it's an IShellLinkW, this deletes the cached icon and adds the
+// url param to a list of URLs to be removed from the places database.
+void JumpListBuilder::RemoveIconCacheAndGetJumplistShortcutURIs(
+    IObjectArray* aObjArray, nsTArray<nsString>& aURISpecs) {
+  MOZ_ASSERT(!NS_IsMainThread());
+
+  // Early return here just in case some versions of Windows don't populate this
+  if (!aObjArray) {
+    return;
+  }
+
+  uint32_t count = 0;
+  aObjArray->GetCount(&count);
+
+  for (uint32_t idx = 0; idx < count; idx++) {
+    RefPtr<IShellLinkW> pLink;
+
+    if (FAILED(aObjArray->GetAt(idx, IID_IShellLinkW,
+                                static_cast<void**>(getter_AddRefs(pLink))))) {
+      continue;
+    }
+
+    wchar_t buf[MAX_PATH];
+    HRESULT hres = pLink->GetArguments(buf, MAX_PATH);
+    if (SUCCEEDED(hres)) {
+      LPWSTR* arglist;
+      int32_t numArgs;
+
+      arglist = ::CommandLineToArgvW(buf, &numArgs);
+      if (arglist && numArgs > 0) {
+        nsString spec(arglist[0]);
+        aURISpecs.AppendElement(std::move(spec));
+        ::LocalFree(arglist);
+      }
+    }
+
+    int iconIdx = 0;
+    hres = pLink->GetIconLocation(buf, MAX_PATH, &iconIdx);
+    if (SUCCEEDED(hres)) {
+      nsDependentString spec(buf);
+      DeleteIconFromDisk(spec);
+    }
+  }
+}
+
+void JumpListBuilder::DeleteIconFromDisk(const nsAString& aPath) {
+  MOZ_ASSERT(!NS_IsMainThread());
+
+  // Check that we aren't deleting some arbitrary file that is not an icon
+  if (StringTail(aPath, 4).LowerCaseEqualsASCII(".ico")) {
+    // Construct the parent path of the passed in path
+    nsCOMPtr<nsIFile> icoFile;
+    nsresult rv = NS_NewLocalFile(aPath, true, getter_AddRefs(icoFile));
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return;
+    }
+
+    icoFile->Remove(false);
+  }
+}
+
+// Converts a WindowsJumpListShortcutDescription into a IShellLinkW
+nsresult JumpListBuilder::GetShellLinkFromDescription(
+    const WindowsJumpListShortcutDescription& aDesc,
+    RefPtr<IShellLinkW>& aShellLink) {
+  MOZ_ASSERT(!NS_IsMainThread());
+
+  HRESULT hr;
+  IShellLinkW* psl;
+
+  // Shell links:
+  // http://msdn.microsoft.com/en-us/library/bb776891(VS.85).aspx
+  // http://msdn.microsoft.com/en-us/library/bb774950(VS.85).aspx
+
+  // Create a IShellLink
+  hr = CoCreateInstance(CLSID_ShellLink, nullptr, CLSCTX_INPROC_SERVER,
+                        IID_IShellLinkW, (LPVOID*)&psl);
+  if (FAILED(hr)) {
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  // Store the title of the app
+  if (!aDesc.mTitle.IsEmpty()) {
+    IPropertyStore* pPropStore = nullptr;
+    hr = psl->QueryInterface(IID_IPropertyStore, (LPVOID*)&pPropStore);
+    if (FAILED(hr)) {
+      return NS_ERROR_UNEXPECTED;
+    }
+
+    PROPVARIANT pv;
+    ::InitPropVariantFromString(aDesc.mTitle.get(), &pv);
+
+    pPropStore->SetValue(PKEY_Title, pv);
+    pPropStore->Commit();
+    pPropStore->Release();
+
+    PropVariantClear(&pv);
+  }
+
+  // Store the rest of the params
+  hr = psl->SetPath(aDesc.mPath.get());
+
+  // According to the documentation at [1], the maximum description length is
+  // INFOTIPSIZE, so we copy the const string from the description into a buffer
+  // of that maximum size. However, testing reveals that INFOTIPSIZE is still
+  // sometimes too large. MAX_PATH seems to work instead.
+  //
+  // We truncate to MAX_PATH - 1, since nsAutoString's don't include the null
+  // character in their capacity calculations, but the string for IShellLinkW
+  // description does. So by truncating to MAX_PATH - 1, the full contents of
+  // the truncated nsAutoString will be copied into the IShellLink description
+  // buffer.
+  //
+  // [1]:
+  // https://learn.microsoft.com/en-us/windows/win32/api/shobjidl_core/nf-shobjidl_core-ishelllinka-setdescription
+  nsAutoString descriptionCopy(aDesc.mDescription.get());
+  if (descriptionCopy.Length() >= MAX_PATH) {
+    descriptionCopy.Truncate(MAX_PATH - 1);
+  }
+
+  hr = psl->SetDescription(descriptionCopy.get());
+
+  if (aDesc.mArguments.WasPassed() && !aDesc.mArguments.Value().IsEmpty()) {
+    hr = psl->SetArguments(aDesc.mArguments.Value().get());
+  } else {
+    hr = psl->SetArguments(L"");
+  }
+
+  // Set up the fallback icon in the event that a valid icon URI has
+  // not been supplied.
+  hr = psl->SetIconLocation(aDesc.mPath.get(), aDesc.mFallbackIconIndex);
+
+  if (aDesc.mIconPath.WasPassed() && !aDesc.mIconPath.Value().IsEmpty()) {
+    // Always use the first icon in the ICO file, as our encoded icon only has 1
+    // resource
+    hr = psl->SetIconLocation(aDesc.mIconPath.Value().get(), 0);
+  }
+
+  aShellLink = dont_AddRef(psl);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+JumpListBuilder::Observe(nsISupports* aSubject, const char* aTopic,
+                         const char16_t* aData) {
+  MOZ_ASSERT(NS_IsMainThread());
+  NS_ENSURE_ARG_POINTER(aTopic);
+  if (strcmp(aTopic, TOPIC_PROFILE_BEFORE_CHANGE) == 0) {
+    nsCOMPtr<nsIObserverService> observerService =
+        do_GetService("@mozilla.org/observer-service;1");
+    if (observerService) {
+      observerService->RemoveObserver(this, TOPIC_PROFILE_BEFORE_CHANGE);
+      observerService->RemoveObserver(this, TOPIC_CLEAR_PRIVATE_DATA);
+    }
+
+    mIOThread->Dispatch(NewRunnableMethod("ShutdownBackend", this,
+                                          &JumpListBuilder::DoShutdownBackend),
+                        NS_DISPATCH_NORMAL);
+
+    mIOThread->Shutdown();
+  } else if (strcmp(aTopic, "nsPref:changed") == 0 &&
+             nsDependentString(aData).EqualsASCII(kPrefTaskbarEnabled)) {
+    bool enabled = Preferences::GetBool(kPrefTaskbarEnabled, true);
+    if (!enabled) {
+      nsCOMPtr<nsIRunnable> event =
+          new mozilla::widget::AsyncDeleteAllFaviconsFromDisk();
+      mIOThread->Dispatch(event, NS_DISPATCH_NORMAL);
+    }
+  } else if (strcmp(aTopic, TOPIC_CLEAR_PRIVATE_DATA) == 0) {
+    // Delete JumpListCache icons from Disk, if any.
+    nsCOMPtr<nsIRunnable> event =
+        new mozilla::widget::AsyncDeleteAllFaviconsFromDisk(false);
+    mIOThread->Dispatch(event, NS_DISPATCH_NORMAL);
+  }
+  return NS_OK;
+}
+
+}  // namespace widget
+}  // namespace mozilla
diff --git a/widget/windows/JumpListBuilder.h b/widget/windows/JumpListBuilder.h
new file mode 100644
index 0000000000..e228669f11
--- /dev/null
+++ b/widget/windows/JumpListBuilder.h
@@ -0,0 +1,102 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef __JumpListBuilder_h__
+#define __JumpListBuilder_h__
+
+#include "nsIJumpListBuilder.h"
+
+#include "nsIObserver.h"
+#include "nsProxyRelease.h"
+#include "mozilla/LazyIdleThread.h"
+
+namespace mozilla {
+
+namespace dom {
+struct WindowsJumpListShortcutDescription;
+}  // namespace dom
+
+namespace widget {
+
+/**
+ * This is an abstract class for a backend to write to the Windows Jump List.
+ *
+ * It has a 1-to-1 method mapping with ICustomDestinationList. The abtract
+ * class allows us to implement a "fake" backend for automated testing.
+ */
+class JumpListBackend {
+  NS_INLINE_DECL_PURE_VIRTUAL_REFCOUNTING
+
+  virtual bool IsAvailable() = 0;
+
+  virtual HRESULT SetAppID(LPCWSTR pszAppID) = 0;
+  virtual HRESULT BeginList(UINT* pcMinSlots, REFIID riid, void** ppv) = 0;
+  virtual HRESULT AddUserTasks(IObjectArray* poa) = 0;
+  virtual HRESULT AppendCategory(LPCWSTR pszCategory, IObjectArray* poa) = 0;
+  virtual HRESULT CommitList() = 0;
+  virtual HRESULT AbortList() = 0;
+  virtual HRESULT DeleteList(LPCWSTR pszAppID) = 0;
+  virtual HRESULT AppendKnownCategory(KNOWNDESTCATEGORY category) = 0;
+
+ protected:
+  virtual ~JumpListBackend() {}
+};
+
+/**
+ * JumpListBuilder is a component that can be used to manage the Windows
+ * Jump List off of the main thread.
+ */
+class JumpListBuilder : public nsIJumpListBuilder, public nsIObserver {
+  virtual ~JumpListBuilder();
+
+ public:
+  NS_DECL_THREADSAFE_ISUPPORTS
+  NS_DECL_NSIJUMPLISTBUILDER
+  NS_DECL_NSIOBSERVER
+
+  explicit JumpListBuilder(const nsAString& aAppUserModelId,
+                           RefPtr<JumpListBackend> aTestingBackend = nullptr);
+
+ private:
+  // These all run on the lazy helper thread.
+  void DoSetupBackend();
+  void DoSetupTestingBackend(RefPtr<JumpListBackend> aTestingBackend);
+  void DoShutdownBackend();
+  void DoSetAppID(nsString aAppUserModelID);
+  void DoIsAvailable(const nsMainThreadPtrHandle<dom::Promise>& aPromiseHolder);
+  void DoCheckForRemovals(
+      const nsMainThreadPtrHandle<dom::Promise>& aPromiseHolder);
+  void DoPopulateJumpList(
+      const nsTArray<dom::WindowsJumpListShortcutDescription>&&
+          aTaskDescriptions,
+      const nsAString& aCustomTitle,
+      const nsTArray<dom::WindowsJumpListShortcutDescription>&&
+          aCustomDescriptions,
+      const nsMainThreadPtrHandle<dom::Promise>& aPromiseHolder);
+  void DoClearJumpList(
+      const nsMainThreadPtrHandle<dom::Promise>& aPromiseHolder);
+  void RemoveIconCacheAndGetJumplistShortcutURIs(IObjectArray* aObjArray,
+                                                 nsTArray<nsString>& aURISpecs);
+  void DeleteIconFromDisk(const nsAString& aPath);
+  nsresult GetShellLinkFromDescription(
+      const dom::WindowsJumpListShortcutDescription& aDesc,
+      RefPtr<IShellLinkW>& aShellLink);
+
+  // This is written to once during construction on the main thread before the
+  // lazy helper thread is created. After that, the lazy helper thread might
+  // read from it.
+  nsString mAppUserModelId;
+
+  // This is only accessed by the lazy helper thread.
+  RefPtr<JumpListBackend> mJumpListBackend;
+
+  // This is only accessed by the main thread.
+  RefPtr<LazyIdleThread> mIOThread;
+};
+
+}  // namespace widget
+}  // namespace mozilla
+
+#endif /* __JumpListBuilder_h__ */
diff --git a/widget/windows/KeyboardLayout.cpp b/widget/windows/KeyboardLayout.cpp
new file mode 100644
index 0000000000..3b59aa9319
--- /dev/null
+++ b/widget/windows/KeyboardLayout.cpp
@@ -0,0 +1,5442 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/Logging.h"
+
+#include "mozilla/ArrayUtils.h"
+#include "mozilla/AutoRestore.h"
+#include "mozilla/MouseEvents.h"
+#include "mozilla/MiscEvents.h"
+#include "mozilla/StaticPrefs_ui.h"
+#include "mozilla/TextEvents.h"
+#include "mozilla/widget/WinRegistry.h"
+
+#include "nsExceptionHandler.h"
+#include "nsGkAtoms.h"
+#include "nsIUserIdleServiceInternal.h"
+#include "nsIWindowsRegKey.h"
+#include "nsPrintfCString.h"
+#include "nsReadableUtils.h"
+#include "nsServiceManagerUtils.h"
+#include "nsTArray.h"
+#include "nsUnicharUtils.h"
+#include "nsWindowDbg.h"
+
+#include "KeyboardLayout.h"
+#include "WidgetUtils.h"
+#include "WinUtils.h"
+
+#include "npapi.h"
+
+#include <windows.h>
+#include <winnls.h>
+#include <winuser.h>
+#include <algorithm>
+
+#ifndef WINABLEAPI
+#  include <winable.h>
+#endif
+
+// For collecting other people's log, tell them `MOZ_LOG=KeyboardHandler:4,sync`
+// rather than `MOZ_LOG=KeyboardHandler:5,sync` since using `5` may create too
+// big file.
+// Therefore you shouldn't use `LogLevel::Verbose` for logging usual behavior.
+mozilla::LazyLogModule gKeyLog("KeyboardHandler");
+
+namespace mozilla {
+namespace widget {
+
+static const char* const kVirtualKeyName[] = {
+    "NULL",
+    "VK_LBUTTON",
+    "VK_RBUTTON",
+    "VK_CANCEL",
+    "VK_MBUTTON",
+    "VK_XBUTTON1",
+    "VK_XBUTTON2",
+    "0x07",
+    "VK_BACK",
+    "VK_TAB",
+    "0x0A",
+    "0x0B",
+    "VK_CLEAR",
+    "VK_RETURN",
+    "0x0E",
+    "0x0F",
+
+    "VK_SHIFT",
+    "VK_CONTROL",
+    "VK_MENU",
+    "VK_PAUSE",
+    "VK_CAPITAL",
+    "VK_KANA, VK_HANGUL",
+    "0x16",
+    "VK_JUNJA",
+    "VK_FINAL",
+    "VK_HANJA, VK_KANJI",
+    "0x1A",
+    "VK_ESCAPE",
+    "VK_CONVERT",
+    "VK_NONCONVERT",
+    "VK_ACCEPT",
+    "VK_MODECHANGE",
+
+    "VK_SPACE",
+    "VK_PRIOR",
+    "VK_NEXT",
+    "VK_END",
+    "VK_HOME",
+    "VK_LEFT",
+    "VK_UP",
+    "VK_RIGHT",
+    "VK_DOWN",
+    "VK_SELECT",
+    "VK_PRINT",
+    "VK_EXECUTE",
+    "VK_SNAPSHOT",
+    "VK_INSERT",
+    "VK_DELETE",
+    "VK_HELP",
+
+    "VK_0",
+    "VK_1",
+    "VK_2",
+    "VK_3",
+    "VK_4",
+    "VK_5",
+    "VK_6",
+    "VK_7",
+    "VK_8",
+    "VK_9",
+    "0x3A",
+    "0x3B",
+    "0x3C",
+    "0x3D",
+    "0x3E",
+    "0x3F",
+
+    "0x40",
+    "VK_A",
+    "VK_B",
+    "VK_C",
+    "VK_D",
+    "VK_E",
+    "VK_F",
+    "VK_G",
+    "VK_H",
+    "VK_I",
+    "VK_J",
+    "VK_K",
+    "VK_L",
+    "VK_M",
+    "VK_N",
+    "VK_O",
+
+    "VK_P",
+    "VK_Q",
+    "VK_R",
+    "VK_S",
+    "VK_T",
+    "VK_U",
+    "VK_V",
+    "VK_W",
+    "VK_X",
+    "VK_Y",
+    "VK_Z",
+    "VK_LWIN",
+    "VK_RWIN",
+    "VK_APPS",
+    "0x5E",
+    "VK_SLEEP",
+
+    "VK_NUMPAD0",
+    "VK_NUMPAD1",
+    "VK_NUMPAD2",
+    "VK_NUMPAD3",
+    "VK_NUMPAD4",
+    "VK_NUMPAD5",
+    "VK_NUMPAD6",
+    "VK_NUMPAD7",
+    "VK_NUMPAD8",
+    "VK_NUMPAD9",
+    "VK_MULTIPLY",
+    "VK_ADD",
+    "VK_SEPARATOR",
+    "VK_SUBTRACT",
+    "VK_DECIMAL",
+    "VK_DIVIDE",
+
+    "VK_F1",
+    "VK_F2",
+    "VK_F3",
+    "VK_F4",
+    "VK_F5",
+    "VK_F6",
+    "VK_F7",
+    "VK_F8",
+    "VK_F9",
+    "VK_F10",
+    "VK_F11",
+    "VK_F12",
+    "VK_F13",
+    "VK_F14",
+    "VK_F15",
+    "VK_F16",
+
+    "VK_F17",
+    "VK_F18",
+    "VK_F19",
+    "VK_F20",
+    "VK_F21",
+    "VK_F22",
+    "VK_F23",
+    "VK_F24",
+    "0x88",
+    "0x89",
+    "0x8A",
+    "0x8B",
+    "0x8C",
+    "0x8D",
+    "0x8E",
+    "0x8F",
+
+    "VK_NUMLOCK",
+    "VK_SCROLL",
+    "VK_OEM_NEC_EQUAL, VK_OEM_FJ_JISHO",
+    "VK_OEM_FJ_MASSHOU",
+    "VK_OEM_FJ_TOUROKU",
+    "VK_OEM_FJ_LOYA",
+    "VK_OEM_FJ_ROYA",
+    "0x97",
+    "0x98",
+    "0x99",
+    "0x9A",
+    "0x9B",
+    "0x9C",
+    "0x9D",
+    "0x9E",
+    "0x9F",
+
+    "VK_LSHIFT",
+    "VK_RSHIFT",
+    "VK_LCONTROL",
+    "VK_RCONTROL",
+    "VK_LMENU",
+    "VK_RMENU",
+    "VK_BROWSER_BACK",
+    "VK_BROWSER_FORWARD",
+    "VK_BROWSER_REFRESH",
+    "VK_BROWSER_STOP",
+    "VK_BROWSER_SEARCH",
+    "VK_BROWSER_FAVORITES",
+    "VK_BROWSER_HOME",
+    "VK_VOLUME_MUTE",
+    "VK_VOLUME_DOWN",
+    "VK_VOLUME_UP",
+
+    "VK_MEDIA_NEXT_TRACK",
+    "VK_MEDIA_PREV_TRACK",
+    "VK_MEDIA_STOP",
+    "VK_MEDIA_PLAY_PAUSE",
+    "VK_LAUNCH_MAIL",
+    "VK_LAUNCH_MEDIA_SELECT",
+    "VK_LAUNCH_APP1",
+    "VK_LAUNCH_APP2",
+    "0xB8",
+    "0xB9",
+    "VK_OEM_1",
+    "VK_OEM_PLUS",
+    "VK_OEM_COMMA",
+    "VK_OEM_MINUS",
+    "VK_OEM_PERIOD",
+    "VK_OEM_2",
+
+    "VK_OEM_3",
+    "VK_ABNT_C1",
+    "VK_ABNT_C2",
+    "0xC3",
+    "0xC4",
+    "0xC5",
+    "0xC6",
+    "0xC7",
+    "0xC8",
+    "0xC9",
+    "0xCA",
+    "0xCB",
+    "0xCC",
+    "0xCD",
+    "0xCE",
+    "0xCF",
+
+    "0xD0",
+    "0xD1",
+    "0xD2",
+    "0xD3",
+    "0xD4",
+    "0xD5",
+    "0xD6",
+    "0xD7",
+    "0xD8",
+    "0xD9",
+    "0xDA",
+    "VK_OEM_4",
+    "VK_OEM_5",
+    "VK_OEM_6",
+    "VK_OEM_7",
+    "VK_OEM_8",
+
+    "0xE0",
+    "VK_OEM_AX",
+    "VK_OEM_102",
+    "VK_ICO_HELP",
+    "VK_ICO_00",
+    "VK_PROCESSKEY",
+    "VK_ICO_CLEAR",
+    "VK_PACKET",
+    "0xE8",
+    "VK_OEM_RESET",
+    "VK_OEM_JUMP",
+    "VK_OEM_PA1",
+    "VK_OEM_PA2",
+    "VK_OEM_PA3",
+    "VK_OEM_WSCTRL",
+    "VK_OEM_CUSEL",
+
+    "VK_OEM_ATTN",
+    "VK_OEM_FINISH",
+    "VK_OEM_COPY",
+    "VK_OEM_AUTO",
+    "VK_OEM_ENLW",
+    "VK_OEM_BACKTAB",
+    "VK_ATTN",
+    "VK_CRSEL",
+    "VK_EXSEL",
+    "VK_EREOF",
+    "VK_PLAY",
+    "VK_ZOOM",
+    "VK_NONAME",
+    "VK_PA1",
+    "VK_OEM_CLEAR",
+    "0xFF"};
+
+static_assert(sizeof(kVirtualKeyName) / sizeof(const char*) == 0x100,
+              "The virtual key name must be defined just 256 keys");
+
+static const char* GetBoolName(bool aBool) { return aBool ? "true" : "false"; }
+
+static const nsCString GetCharacterCodeName(WPARAM aCharCode) {
+  switch (aCharCode) {
+    case 0x0000:
+      return "NULL (0x0000)"_ns;
+    case 0x0008:
+      return "BACKSPACE (0x0008)"_ns;
+    case 0x0009:
+      return "CHARACTER TABULATION (0x0009)"_ns;
+    case 0x000A:
+      return "LINE FEED (0x000A)"_ns;
+    case 0x000B:
+      return "LINE TABULATION (0x000B)"_ns;
+    case 0x000C:
+      return "FORM FEED (0x000C)"_ns;
+    case 0x000D:
+      return "CARRIAGE RETURN (0x000D)"_ns;
+    case 0x0018:
+      return "CANCEL (0x0018)"_ns;
+    case 0x001B:
+      return "ESCAPE (0x001B)"_ns;
+    case 0x0020:
+      return "SPACE (0x0020)"_ns;
+    case 0x007F:
+      return "DELETE (0x007F)"_ns;
+    case 0x00A0:
+      return "NO-BREAK SPACE (0x00A0)"_ns;
+    case 0x00AD:
+      return "SOFT HYPHEN (0x00AD)"_ns;
+    case 0x2000:
+      return "EN QUAD (0x2000)"_ns;
+    case 0x2001:
+      return "EM QUAD (0x2001)"_ns;
+    case 0x2002:
+      return "EN SPACE (0x2002)"_ns;
+    case 0x2003:
+      return "EM SPACE (0x2003)"_ns;
+    case 0x2004:
+      return "THREE-PER-EM SPACE (0x2004)"_ns;
+    case 0x2005:
+      return "FOUR-PER-EM SPACE (0x2005)"_ns;
+    case 0x2006:
+      return "SIX-PER-EM SPACE (0x2006)"_ns;
+    case 0x2007:
+      return "FIGURE SPACE (0x2007)"_ns;
+    case 0x2008:
+      return "PUNCTUATION SPACE (0x2008)"_ns;
+    case 0x2009:
+      return "THIN SPACE (0x2009)"_ns;
+    case 0x200A:
+      return "HAIR SPACE (0x200A)"_ns;
+    case 0x200B:
+      return "ZERO WIDTH SPACE (0x200B)"_ns;
+    case 0x200C:
+      return "ZERO WIDTH NON-JOINER (0x200C)"_ns;
+    case 0x200D:
+      return "ZERO WIDTH JOINER (0x200D)"_ns;
+    case 0x200E:
+      return "LEFT-TO-RIGHT MARK (0x200E)"_ns;
+    case 0x200F:
+      return "RIGHT-TO-LEFT MARK (0x200F)"_ns;
+    case 0x2029:
+      return "PARAGRAPH SEPARATOR (0x2029)"_ns;
+    case 0x202A:
+      return "LEFT-TO-RIGHT EMBEDDING (0x202A)"_ns;
+    case 0x202B:
+      return "RIGHT-TO-LEFT EMBEDDING (0x202B)"_ns;
+    case 0x202D:
+      return "LEFT-TO-RIGHT OVERRIDE (0x202D)"_ns;
+    case 0x202E:
+      return "RIGHT-TO-LEFT OVERRIDE (0x202E)"_ns;
+    case 0x202F:
+      return "NARROW NO-BREAK SPACE (0x202F)"_ns;
+    case 0x205F:
+      return "MEDIUM MATHEMATICAL SPACE (0x205F)"_ns;
+    case 0x2060:
+      return "WORD JOINER (0x2060)"_ns;
+    case 0x2066:
+      return "LEFT-TO-RIGHT ISOLATE (0x2066)"_ns;
+    case 0x2067:
+      return "RIGHT-TO-LEFT ISOLATE (0x2067)"_ns;
+    case 0x3000:
+      return "IDEOGRAPHIC SPACE (0x3000)"_ns;
+    case 0xFEFF:
+      return "ZERO WIDTH NO-BREAK SPACE (0xFEFF)"_ns;
+    default: {
+      if (aCharCode < ' ' || (aCharCode >= 0x80 && aCharCode < 0xA0)) {
+        return nsPrintfCString("control (0x%04zX)", aCharCode);
+      }
+      if (NS_IS_HIGH_SURROGATE(aCharCode)) {
+        return nsPrintfCString("high surrogate (0x%04zX)", aCharCode);
+      }
+      if (NS_IS_LOW_SURROGATE(aCharCode)) {
+        return nsPrintfCString("low surrogate (0x%04zX)", aCharCode);
+      }
+      return IS_IN_BMP(aCharCode)
+                 ? nsPrintfCString(
+                       "'%s' (0x%04zX)",
+                       NS_ConvertUTF16toUTF8(nsAutoString(aCharCode)).get(),
+                       aCharCode)
+                 : nsPrintfCString(
+                       "'%s' (0x%08zX)",
+                       NS_ConvertUTF16toUTF8(nsAutoString(aCharCode)).get(),
+                       aCharCode);
+    }
+  }
+}
+
+static const nsCString GetKeyLocationName(uint32_t aLocation) {
+  switch (aLocation) {
+    case eKeyLocationLeft:
+      return "KEY_LOCATION_LEFT"_ns;
+    case eKeyLocationRight:
+      return "KEY_LOCATION_RIGHT"_ns;
+    case eKeyLocationStandard:
+      return "KEY_LOCATION_STANDARD"_ns;
+    case eKeyLocationNumpad:
+      return "KEY_LOCATION_NUMPAD"_ns;
+    default:
+      return nsPrintfCString("Unknown (0x%04X)", aLocation);
+  }
+}
+
+static const nsCString GetCharacterCodeNames(const char16_t* aChars,
+                                             uint32_t aLength) {
+  if (!aLength) {
+    return ""_ns;
+  }
+  nsCString result;
+  result.AssignLiteral("\"");
+  StringJoinAppend(result, ", "_ns, Span{aChars, aLength},
+                   [](nsACString& dest, const char16_t charValue) {
+                     dest.Append(GetCharacterCodeName(charValue));
+                   });
+  result.AppendLiteral("\"");
+  return result;
+}
+
+static const nsCString GetCharacterCodeNames(
+    const UniCharsAndModifiers& aUniCharsAndModifiers) {
+  if (aUniCharsAndModifiers.IsEmpty()) {
+    return ""_ns;
+  }
+  nsCString result;
+  result.AssignLiteral("\"");
+  StringJoinAppend(result, ", "_ns, Span{aUniCharsAndModifiers.ToString()},
+                   [](nsACString& dest, const char16_t charValue) {
+                     dest.Append(GetCharacterCodeName(charValue));
+                   });
+  result.AppendLiteral("\"");
+  return result;
+}
+
+class MOZ_STACK_CLASS GetShiftStateName final : public nsAutoCString {
+ public:
+  explicit GetShiftStateName(VirtualKey::ShiftState aShiftState) {
+    if (!aShiftState) {
+      AssignLiteral("none");
+      return;
+    }
+    if (aShiftState & VirtualKey::STATE_SHIFT) {
+      AssignLiteral("Shift");
+      aShiftState &= ~VirtualKey::STATE_SHIFT;
+    }
+    if (aShiftState & VirtualKey::STATE_CONTROL) {
+      MaybeAppendSeparator();
+      AssignLiteral("Ctrl");
+      aShiftState &= ~VirtualKey::STATE_CONTROL;
+    }
+    if (aShiftState & VirtualKey::STATE_ALT) {
+      MaybeAppendSeparator();
+      AssignLiteral("Alt");
+      aShiftState &= ~VirtualKey::STATE_ALT;
+    }
+    if (aShiftState & VirtualKey::STATE_CAPSLOCK) {
+      MaybeAppendSeparator();
+      AssignLiteral("CapsLock");
+      aShiftState &= ~VirtualKey::STATE_CAPSLOCK;
+    }
+    MOZ_ASSERT(!aShiftState);
+  }
+
+ private:
+  void MaybeAppendSeparator() {
+    if (!IsEmpty()) {
+      AppendLiteral(" | ");
+    }
+  }
+};
+
+static const nsCString GetMessageName(UINT aMessage) {
+  switch (aMessage) {
+    case WM_NULL:
+      return "WM_NULL"_ns;
+    case WM_KEYDOWN:
+      return "WM_KEYDOWN"_ns;
+    case WM_KEYUP:
+      return "WM_KEYUP"_ns;
+    case WM_SYSKEYDOWN:
+      return "WM_SYSKEYDOWN"_ns;
+    case WM_SYSKEYUP:
+      return "WM_SYSKEYUP"_ns;
+    case WM_CHAR:
+      return "WM_CHAR"_ns;
+    case WM_UNICHAR:
+      return "WM_UNICHAR"_ns;
+    case WM_SYSCHAR:
+      return "WM_SYSCHAR"_ns;
+    case WM_DEADCHAR:
+      return "WM_DEADCHAR"_ns;
+    case WM_SYSDEADCHAR:
+      return "WM_SYSDEADCHAR"_ns;
+    case WM_APPCOMMAND:
+      return "WM_APPCOMMAND"_ns;
+    case WM_QUIT:
+      return "WM_QUIT"_ns;
+    default:
+      return nsPrintfCString("Unknown Message (0x%04X)", aMessage);
+  }
+}
+
+static const nsCString GetVirtualKeyCodeName(WPARAM aVK) {
+  if (aVK >= ArrayLength(kVirtualKeyName)) {
+    return nsPrintfCString("Invalid (0x%08zX)", aVK);
+  }
+  return nsCString(kVirtualKeyName[aVK]);
+}
+
+static const nsCString GetAppCommandName(WPARAM aCommand) {
+  switch (aCommand) {
+    case APPCOMMAND_BASS_BOOST:
+      return "APPCOMMAND_BASS_BOOST"_ns;
+    case APPCOMMAND_BASS_DOWN:
+      return "APPCOMMAND_BASS_DOWN"_ns;
+    case APPCOMMAND_BASS_UP:
+      return "APPCOMMAND_BASS_UP"_ns;
+    case APPCOMMAND_BROWSER_BACKWARD:
+      return "APPCOMMAND_BROWSER_BACKWARD"_ns;
+    case APPCOMMAND_BROWSER_FAVORITES:
+      return "APPCOMMAND_BROWSER_FAVORITES"_ns;
+    case APPCOMMAND_BROWSER_FORWARD:
+      return "APPCOMMAND_BROWSER_FORWARD"_ns;
+    case APPCOMMAND_BROWSER_HOME:
+      return "APPCOMMAND_BROWSER_HOME"_ns;
+    case APPCOMMAND_BROWSER_REFRESH:
+      return "APPCOMMAND_BROWSER_REFRESH"_ns;
+    case APPCOMMAND_BROWSER_SEARCH:
+      return "APPCOMMAND_BROWSER_SEARCH"_ns;
+    case APPCOMMAND_BROWSER_STOP:
+      return "APPCOMMAND_BROWSER_STOP"_ns;
+    case APPCOMMAND_CLOSE:
+      return "APPCOMMAND_CLOSE"_ns;
+    case APPCOMMAND_COPY:
+      return "APPCOMMAND_COPY"_ns;
+    case APPCOMMAND_CORRECTION_LIST:
+      return "APPCOMMAND_CORRECTION_LIST"_ns;
+    case APPCOMMAND_CUT:
+      return "APPCOMMAND_CUT"_ns;
+    case APPCOMMAND_DICTATE_OR_COMMAND_CONTROL_TOGGLE:
+      return "APPCOMMAND_DICTATE_OR_COMMAND_CONTROL_TOGGLE"_ns;
+    case APPCOMMAND_FIND:
+      return "APPCOMMAND_FIND"_ns;
+    case APPCOMMAND_FORWARD_MAIL:
+      return "APPCOMMAND_FORWARD_MAIL"_ns;
+    case APPCOMMAND_HELP:
+      return "APPCOMMAND_HELP"_ns;
+    case APPCOMMAND_LAUNCH_APP1:
+      return "APPCOMMAND_LAUNCH_APP1"_ns;
+    case APPCOMMAND_LAUNCH_APP2:
+      return "APPCOMMAND_LAUNCH_APP2"_ns;
+    case APPCOMMAND_LAUNCH_MAIL:
+      return "APPCOMMAND_LAUNCH_MAIL"_ns;
+    case APPCOMMAND_LAUNCH_MEDIA_SELECT:
+      return "APPCOMMAND_LAUNCH_MEDIA_SELECT"_ns;
+    case APPCOMMAND_MEDIA_CHANNEL_DOWN:
+      return "APPCOMMAND_MEDIA_CHANNEL_DOWN"_ns;
+    case APPCOMMAND_MEDIA_CHANNEL_UP:
+      return "APPCOMMAND_MEDIA_CHANNEL_UP"_ns;
+    case APPCOMMAND_MEDIA_FAST_FORWARD:
+      return "APPCOMMAND_MEDIA_FAST_FORWARD"_ns;
+    case APPCOMMAND_MEDIA_NEXTTRACK:
+      return "APPCOMMAND_MEDIA_NEXTTRACK"_ns;
+    case APPCOMMAND_MEDIA_PAUSE:
+      return "APPCOMMAND_MEDIA_PAUSE"_ns;
+    case APPCOMMAND_MEDIA_PLAY:
+      return "APPCOMMAND_MEDIA_PLAY"_ns;
+    case APPCOMMAND_MEDIA_PLAY_PAUSE:
+      return "APPCOMMAND_MEDIA_PLAY_PAUSE"_ns;
+    case APPCOMMAND_MEDIA_PREVIOUSTRACK:
+      return "APPCOMMAND_MEDIA_PREVIOUSTRACK"_ns;
+    case APPCOMMAND_MEDIA_RECORD:
+      return "APPCOMMAND_MEDIA_RECORD"_ns;
+    case APPCOMMAND_MEDIA_REWIND:
+      return "APPCOMMAND_MEDIA_REWIND"_ns;
+    case APPCOMMAND_MEDIA_STOP:
+      return "APPCOMMAND_MEDIA_STOP"_ns;
+    case APPCOMMAND_MIC_ON_OFF_TOGGLE:
+      return "APPCOMMAND_MIC_ON_OFF_TOGGLE"_ns;
+    case APPCOMMAND_MICROPHONE_VOLUME_DOWN:
+      return "APPCOMMAND_MICROPHONE_VOLUME_DOWN"_ns;
+    case APPCOMMAND_MICROPHONE_VOLUME_MUTE:
+      return "APPCOMMAND_MICROPHONE_VOLUME_MUTE"_ns;
+    case APPCOMMAND_MICROPHONE_VOLUME_UP:
+      return "APPCOMMAND_MICROPHONE_VOLUME_UP"_ns;
+    case APPCOMMAND_NEW:
+      return "APPCOMMAND_NEW"_ns;
+    case APPCOMMAND_OPEN:
+      return "APPCOMMAND_OPEN"_ns;
+    case APPCOMMAND_PASTE:
+      return "APPCOMMAND_PASTE"_ns;
+    case APPCOMMAND_PRINT:
+      return "APPCOMMAND_PRINT"_ns;
+    case APPCOMMAND_REDO:
+      return "APPCOMMAND_REDO"_ns;
+    case APPCOMMAND_REPLY_TO_MAIL:
+      return "APPCOMMAND_REPLY_TO_MAIL"_ns;
+    case APPCOMMAND_SAVE:
+      return "APPCOMMAND_SAVE"_ns;
+    case APPCOMMAND_SEND_MAIL:
+      return "APPCOMMAND_SEND_MAIL"_ns;
+    case APPCOMMAND_SPELL_CHECK:
+      return "APPCOMMAND_SPELL_CHECK"_ns;
+    case APPCOMMAND_TREBLE_DOWN:
+      return "APPCOMMAND_TREBLE_DOWN"_ns;
+    case APPCOMMAND_TREBLE_UP:
+      return "APPCOMMAND_TREBLE_UP"_ns;
+    case APPCOMMAND_UNDO:
+      return "APPCOMMAND_UNDO"_ns;
+    case APPCOMMAND_VOLUME_DOWN:
+      return "APPCOMMAND_VOLUME_DOWN"_ns;
+    case APPCOMMAND_VOLUME_MUTE:
+      return "APPCOMMAND_VOLUME_MUTE"_ns;
+    case APPCOMMAND_VOLUME_UP:
+      return "APPCOMMAND_VOLUME_UP"_ns;
+    default:
+      return nsPrintfCString("Unknown app command (0x%08zX)", aCommand);
+  }
+}
+
+static const nsCString GetAppCommandDeviceName(LPARAM aDevice) {
+  switch (aDevice) {
+    case FAPPCOMMAND_KEY:
+      return "FAPPCOMMAND_KEY"_ns;
+    case FAPPCOMMAND_MOUSE:
+      return "FAPPCOMMAND_MOUSE"_ns;
+    case FAPPCOMMAND_OEM:
+      return "FAPPCOMMAND_OEM"_ns;
+    default:
+      return nsPrintfCString("Unknown app command device (0x%04" PRIXLPTR ")",
+                             aDevice);
+  }
+};
+
+class MOZ_STACK_CLASS GetAppCommandKeysName final : public nsAutoCString {
+ public:
+  explicit GetAppCommandKeysName(WPARAM aKeys) {
+    if (aKeys & MK_CONTROL) {
+      AppendLiteral("MK_CONTROL");
+      aKeys &= ~MK_CONTROL;
+    }
+    if (aKeys & MK_LBUTTON) {
+      MaybeAppendSeparator();
+      AppendLiteral("MK_LBUTTON");
+      aKeys &= ~MK_LBUTTON;
+    }
+    if (aKeys & MK_MBUTTON) {
+      MaybeAppendSeparator();
+      AppendLiteral("MK_MBUTTON");
+      aKeys &= ~MK_MBUTTON;
+    }
+    if (aKeys & MK_RBUTTON) {
+      MaybeAppendSeparator();
+      AppendLiteral("MK_RBUTTON");
+      aKeys &= ~MK_RBUTTON;
+    }
+    if (aKeys & MK_SHIFT) {
+      MaybeAppendSeparator();
+      AppendLiteral("MK_SHIFT");
+      aKeys &= ~MK_SHIFT;
+    }
+    if (aKeys & MK_XBUTTON1) {
+      MaybeAppendSeparator();
+      AppendLiteral("MK_XBUTTON1");
+      aKeys &= ~MK_XBUTTON1;
+    }
+    if (aKeys & MK_XBUTTON2) {
+      MaybeAppendSeparator();
+      AppendLiteral("MK_XBUTTON2");
+      aKeys &= ~MK_XBUTTON2;
+    }
+    if (aKeys) {
+      MaybeAppendSeparator();
+      AppendPrintf("Unknown Flags (0x%04zX)", aKeys);
+    }
+    if (IsEmpty()) {
+      AssignLiteral("none (0x0000)");
+    }
+  }
+
+ private:
+  void MaybeAppendSeparator() {
+    if (!IsEmpty()) {
+      AppendLiteral(" | ");
+    }
+  }
+};
+
+static const nsCString ToString(const MSG& aMSG) {
+  nsCString result;
+  result.AssignLiteral("{ message=");
+  result.Append(GetMessageName(aMSG.message).get());
+  result.AppendLiteral(", ");
+  switch (aMSG.message) {
+    case WM_KEYDOWN:
+    case WM_KEYUP:
+    case WM_SYSKEYDOWN:
+    case WM_SYSKEYUP:
+      result.AppendPrintf(
+          "virtual keycode=%s, repeat count=%" PRIdLPTR
+          ", "
+          "scancode=0x%02X, extended key=%s, "
+          "context code=%s, previous key state=%s, "
+          "transition state=%s",
+          GetVirtualKeyCodeName(aMSG.wParam).get(), aMSG.lParam & 0xFFFF,
+          WinUtils::GetScanCode(aMSG.lParam),
+          GetBoolName(WinUtils::IsExtendedScanCode(aMSG.lParam)),
+          GetBoolName((aMSG.lParam & (1 << 29)) != 0),
+          GetBoolName((aMSG.lParam & (1 << 30)) != 0),
+          GetBoolName((aMSG.lParam & (1 << 31)) != 0));
+      break;
+    case WM_CHAR:
+    case WM_DEADCHAR:
+    case WM_SYSCHAR:
+    case WM_SYSDEADCHAR:
+      result.AppendPrintf(
+          "character code=%s, repeat count=%" PRIdLPTR
+          ", "
+          "scancode=0x%02X, extended key=%s, "
+          "context code=%s, previous key state=%s, "
+          "transition state=%s",
+          GetCharacterCodeName(aMSG.wParam).get(), aMSG.lParam & 0xFFFF,
+          WinUtils::GetScanCode(aMSG.lParam),
+          GetBoolName(WinUtils::IsExtendedScanCode(aMSG.lParam)),
+          GetBoolName((aMSG.lParam & (1 << 29)) != 0),
+          GetBoolName((aMSG.lParam & (1 << 30)) != 0),
+          GetBoolName((aMSG.lParam & (1 << 31)) != 0));
+      break;
+    case WM_APPCOMMAND:
+      result.AppendPrintf(
+          "window handle=0x%zx, app command=%s, device=%s, dwKeys=%s",
+          aMSG.wParam,
+          GetAppCommandName(GET_APPCOMMAND_LPARAM(aMSG.lParam)).get(),
+          GetAppCommandDeviceName(GET_DEVICE_LPARAM(aMSG.lParam)).get(),
+          GetAppCommandKeysName(GET_KEYSTATE_LPARAM(aMSG.lParam)).get());
+      break;
+    default:
+      result.AppendPrintf("wParam=%zu, lParam=%" PRIdLPTR, aMSG.wParam,
+                          aMSG.lParam);
+      break;
+  }
+  result.AppendPrintf(", hwnd=0x%p", aMSG.hwnd);
+  return result;
+}
+
+static const nsCString ToString(
+    const UniCharsAndModifiers& aUniCharsAndModifiers) {
+  if (aUniCharsAndModifiers.IsEmpty()) {
+    return "{}"_ns;
+  }
+  nsCString result;
+  result.AssignLiteral("{ ");
+  result.Append(GetCharacterCodeName(aUniCharsAndModifiers.CharAt(0)));
+  for (size_t i = 1; i < aUniCharsAndModifiers.Length(); ++i) {
+    if (aUniCharsAndModifiers.ModifiersAt(i - 1) !=
+        aUniCharsAndModifiers.ModifiersAt(i)) {
+      result.AppendLiteral(" [");
+      result.Append(GetModifiersName(aUniCharsAndModifiers.ModifiersAt(0)));
+      result.AppendLiteral("]");
+    }
+    result.AppendLiteral(", ");
+    result.Append(GetCharacterCodeName(aUniCharsAndModifiers.CharAt(i)));
+  }
+  result.AppendLiteral(" [");
+  uint32_t lastIndex = aUniCharsAndModifiers.Length() - 1;
+  result.Append(GetModifiersName(aUniCharsAndModifiers.ModifiersAt(lastIndex)));
+  result.AppendLiteral("] }");
+  return result;
+}
+
+const nsCString ToString(const ModifierKeyState& aModifierKeyState) {
+  nsCString result;
+  result.AssignLiteral("{ ");
+  result.Append(GetModifiersName(aModifierKeyState.GetModifiers()).get());
+  result.AppendLiteral(" }");
+  return result;
+}
+
+// Unique id counter associated with a keydown / keypress events. Used in
+// identifing keypress events for removal from async event dispatch queue
+// in metrofx after preventDefault is called on keydown events.
+static uint32_t sUniqueKeyEventId = 0;
+
+/*****************************************************************************
+ * mozilla::widget::ModifierKeyState
+ *****************************************************************************/
+
+ModifierKeyState::ModifierKeyState() { Update(); }
+
+ModifierKeyState::ModifierKeyState(Modifiers aModifiers)
+    : mModifiers(aModifiers) {
+  MOZ_ASSERT(!(mModifiers & MODIFIER_ALTGRAPH) || (!IsControl() && !IsAlt()),
+             "Neither MODIFIER_CONTROL nor MODIFIER_ALT should be set "
+             "if MODIFIER_ALTGRAPH is set");
+}
+
+void ModifierKeyState::Update() {
+  mModifiers = 0;
+  if (IS_VK_DOWN(VK_SHIFT)) {
+    mModifiers |= MODIFIER_SHIFT;
+  }
+  // If AltGr key (i.e., VK_RMENU on some keyboard layout) is pressed, only
+  // MODIFIER_ALTGRAPH should be set.  Otherwise, i.e., if both Ctrl and Alt
+  // keys are pressed to emulate AltGr key, MODIFIER_CONTROL and MODIFIER_ALT
+  // keys should be set separately.
+  if (IS_VK_DOWN(VK_RMENU) && KeyboardLayout::GetInstance()->HasAltGr()) {
+    mModifiers |= MODIFIER_ALTGRAPH;
+  } else {
+    if (IS_VK_DOWN(VK_CONTROL)) {
+      mModifiers |= MODIFIER_CONTROL;
+    }
+    if (IS_VK_DOWN(VK_MENU)) {
+      mModifiers |= MODIFIER_ALT;
+    }
+  }
+  if (IS_VK_DOWN(VK_LWIN) || IS_VK_DOWN(VK_RWIN)) {
+    mModifiers |= MODIFIER_META;
+  }
+  if (::GetKeyState(VK_CAPITAL) & 1) {
+    mModifiers |= MODIFIER_CAPSLOCK;
+  }
+  if (::GetKeyState(VK_NUMLOCK) & 1) {
+    mModifiers |= MODIFIER_NUMLOCK;
+  }
+  if (::GetKeyState(VK_SCROLL) & 1) {
+    mModifiers |= MODIFIER_SCROLLLOCK;
+  }
+}
+
+void ModifierKeyState::Unset(Modifiers aRemovingModifiers) {
+  mModifiers &= ~aRemovingModifiers;
+}
+
+void ModifierKeyState::Set(Modifiers aAddingModifiers) {
+  mModifiers |= aAddingModifiers;
+  MOZ_ASSERT(!(mModifiers & MODIFIER_ALTGRAPH) || (!IsControl() && !IsAlt()),
+             "Neither MODIFIER_CONTROL nor MODIFIER_ALT should be set "
+             "if MODIFIER_ALTGRAPH is set");
+}
+
+void ModifierKeyState::InitInputEvent(WidgetInputEvent& aInputEvent) const {
+  aInputEvent.mModifiers = mModifiers;
+
+  switch (aInputEvent.mClass) {
+    case eMouseEventClass:
+    case eMouseScrollEventClass:
+    case eWheelEventClass:
+    case eDragEventClass:
+    case eSimpleGestureEventClass:
+      InitMouseEvent(aInputEvent);
+      break;
+    default:
+      break;
+  }
+}
+
+void ModifierKeyState::InitMouseEvent(WidgetInputEvent& aMouseEvent) const {
+  NS_ASSERTION(aMouseEvent.mClass == eMouseEventClass ||
+                   aMouseEvent.mClass == eWheelEventClass ||
+                   aMouseEvent.mClass == eDragEventClass ||
+                   aMouseEvent.mClass == eSimpleGestureEventClass,
+               "called with non-mouse event");
+
+  WidgetMouseEventBase& mouseEvent = *aMouseEvent.AsMouseEventBase();
+  mouseEvent.mButtons = 0;
+  if (::GetKeyState(VK_LBUTTON) < 0) {
+    mouseEvent.mButtons |= MouseButtonsFlag::ePrimaryFlag;
+  }
+  if (::GetKeyState(VK_RBUTTON) < 0) {
+    mouseEvent.mButtons |= MouseButtonsFlag::eSecondaryFlag;
+  }
+  if (::GetKeyState(VK_MBUTTON) < 0) {
+    mouseEvent.mButtons |= MouseButtonsFlag::eMiddleFlag;
+  }
+  if (::GetKeyState(VK_XBUTTON1) < 0) {
+    mouseEvent.mButtons |= MouseButtonsFlag::e4thFlag;
+  }
+  if (::GetKeyState(VK_XBUTTON2) < 0) {
+    mouseEvent.mButtons |= MouseButtonsFlag::e5thFlag;
+  }
+}
+
+bool ModifierKeyState::IsShift() const {
+  return (mModifiers & MODIFIER_SHIFT) != 0;
+}
+
+bool ModifierKeyState::IsControl() const {
+  return (mModifiers & MODIFIER_CONTROL) != 0;
+}
+
+bool ModifierKeyState::IsAlt() const {
+  return (mModifiers & MODIFIER_ALT) != 0;
+}
+
+bool ModifierKeyState::IsWin() const {
+  return (mModifiers & MODIFIER_META) != 0;
+}
+
+bool ModifierKeyState::MaybeMatchShortcutKey() const {
+  // If Windows key is pressed, even if both Ctrl key and Alt key are pressed,
+  // it's possible to match a shortcut key.
+  if (IsWin()) {
+    return true;
+  }
+  // Otherwise, when both Ctrl key and Alt key are pressed, it shouldn't be
+  // a shortcut key for Windows since it means pressing AltGr key on
+  // some keyboard layouts.
+  if (IsControl() ^ IsAlt()) {
+    return true;
+  }
+  // If no modifier key is active except a lockable modifier nor Shift key,
+  // the key shouldn't match any shortcut keys (there are Space and
+  // Shift+Space, though, let's ignore these special case...).
+  return false;
+}
+
+bool ModifierKeyState::IsCapsLocked() const {
+  return (mModifiers & MODIFIER_CAPSLOCK) != 0;
+}
+
+bool ModifierKeyState::IsNumLocked() const {
+  return (mModifiers & MODIFIER_NUMLOCK) != 0;
+}
+
+bool ModifierKeyState::IsScrollLocked() const {
+  return (mModifiers & MODIFIER_SCROLLLOCK) != 0;
+}
+
+/*****************************************************************************
+ * mozilla::widget::UniCharsAndModifiers
+ *****************************************************************************/
+
+void UniCharsAndModifiers::Append(char16_t aUniChar, Modifiers aModifiers) {
+  mChars.Append(aUniChar);
+  mModifiers.AppendElement(aModifiers);
+}
+
+void UniCharsAndModifiers::FillModifiers(Modifiers aModifiers) {
+  for (size_t i = 0; i < Length(); i++) {
+    mModifiers[i] = aModifiers;
+  }
+}
+
+void UniCharsAndModifiers::OverwriteModifiersIfBeginsWith(
+    const UniCharsAndModifiers& aOther) {
+  if (!BeginsWith(aOther)) {
+    return;
+  }
+  for (size_t i = 0; i < aOther.Length(); ++i) {
+    mModifiers[i] = aOther.mModifiers[i];
+  }
+}
+
+bool UniCharsAndModifiers::UniCharsEqual(
+    const UniCharsAndModifiers& aOther) const {
+  return mChars.Equals(aOther.mChars);
+}
+
+bool UniCharsAndModifiers::UniCharsCaseInsensitiveEqual(
+    const UniCharsAndModifiers& aOther) const {
+  return mChars.Equals(aOther.mChars, nsCaseInsensitiveStringComparator);
+}
+
+bool UniCharsAndModifiers::BeginsWith(
+    const UniCharsAndModifiers& aOther) const {
+  return StringBeginsWith(mChars, aOther.mChars);
+}
+
+UniCharsAndModifiers& UniCharsAndModifiers::operator+=(
+    const UniCharsAndModifiers& aOther) {
+  mChars.Append(aOther.mChars);
+  mModifiers.AppendElements(aOther.mModifiers);
+  return *this;
+}
+
+UniCharsAndModifiers UniCharsAndModifiers::operator+(
+    const UniCharsAndModifiers& aOther) const {
+  UniCharsAndModifiers result(*this);
+  result += aOther;
+  return result;
+}
+
+/*****************************************************************************
+ * mozilla::widget::VirtualKey
+ *****************************************************************************/
+
+// static
+VirtualKey::ShiftState VirtualKey::ModifiersToShiftState(Modifiers aModifiers) {
+  ShiftState state = 0;
+  if (aModifiers & MODIFIER_SHIFT) {
+    state |= STATE_SHIFT;
+  }
+  if (aModifiers & MODIFIER_ALTGRAPH) {
+    state |= STATE_ALTGRAPH;
+  } else {
+    if (aModifiers & MODIFIER_CONTROL) {
+      state |= STATE_CONTROL;
+    }
+    if (aModifiers & MODIFIER_ALT) {
+      state |= STATE_ALT;
+    }
+  }
+  if (aModifiers & MODIFIER_CAPSLOCK) {
+    state |= STATE_CAPSLOCK;
+  }
+  return state;
+}
+
+// static
+Modifiers VirtualKey::ShiftStateToModifiers(ShiftState aShiftState) {
+  Modifiers modifiers = 0;
+  if (aShiftState & STATE_SHIFT) {
+    modifiers |= MODIFIER_SHIFT;
+  }
+  if (aShiftState & STATE_ALTGRAPH) {
+    modifiers |= MODIFIER_ALTGRAPH;
+  } else {
+    if (aShiftState & STATE_CONTROL) {
+      modifiers |= MODIFIER_CONTROL;
+    }
+    if (aShiftState & STATE_ALT) {
+      modifiers |= MODIFIER_ALT;
+    }
+  }
+  if (aShiftState & STATE_CAPSLOCK) {
+    modifiers |= MODIFIER_CAPSLOCK;
+  }
+  return modifiers;
+}
+
+const DeadKeyTable* VirtualKey::MatchingDeadKeyTable(
+    const DeadKeyEntry* aDeadKeyArray, uint32_t aEntries) const {
+  if (!mIsDeadKey) {
+    return nullptr;
+  }
+
+  for (ShiftState shiftState = 0; shiftState < 16; shiftState++) {
+    if (!IsDeadKey(shiftState)) {
+      continue;
+    }
+    const DeadKeyTable* dkt = mShiftStates[shiftState].DeadKey.Table;
+    if (dkt && dkt->IsEqual(aDeadKeyArray, aEntries)) {
+      return dkt;
+    }
+  }
+
+  return nullptr;
+}
+
+void VirtualKey::SetNormalChars(ShiftState aShiftState, const char16_t* aChars,
+                                uint32_t aNumOfChars) {
+  MOZ_ASSERT(aShiftState == ToShiftStateIndex(aShiftState));
+
+  SetDeadKey(aShiftState, false);
+
+  for (uint32_t index = 0; index < aNumOfChars; index++) {
+    // Ignore legacy non-printable control characters
+    mShiftStates[aShiftState].Normal.Chars[index] =
+        (aChars[index] >= 0x20) ? aChars[index] : 0;
+  }
+
+  uint32_t len = ArrayLength(mShiftStates[aShiftState].Normal.Chars);
+  for (uint32_t index = aNumOfChars; index < len; index++) {
+    mShiftStates[aShiftState].Normal.Chars[index] = 0;
+  }
+}
+
+void VirtualKey::SetDeadChar(ShiftState aShiftState, char16_t aDeadChar) {
+  MOZ_ASSERT(aShiftState == ToShiftStateIndex(aShiftState));
+
+  SetDeadKey(aShiftState, true);
+
+  mShiftStates[aShiftState].DeadKey.DeadChar = aDeadChar;
+  mShiftStates[aShiftState].DeadKey.Table = nullptr;
+}
+
+UniCharsAndModifiers VirtualKey::GetUniChars(ShiftState aShiftState) const {
+  UniCharsAndModifiers result = GetNativeUniChars(aShiftState);
+
+  const uint8_t kShiftStateIndex = ToShiftStateIndex(aShiftState);
+  if (!(kShiftStateIndex & STATE_CONTROL_ALT)) {
+    // If neither Alt nor Ctrl key is pressed, just return stored data
+    // for the key.
+    return result;
+  }
+
+  if (result.IsEmpty()) {
+    // If Alt and/or Control are pressed and the key produces no
+    // character, return characters which is produced by the key without
+    // Alt and Control, and return given modifiers as is.
+    result = GetNativeUniChars(kShiftStateIndex & ~STATE_CONTROL_ALT);
+    result.FillModifiers(ShiftStateToModifiers(aShiftState));
+    return result;
+  }
+
+  if (IsAltGrIndex(kShiftStateIndex)) {
+    // If AltGr or both Ctrl and Alt are pressed and the key produces
+    // character(s), we need to clear MODIFIER_ALT and MODIFIER_CONTROL
+    // since TextEditor won't handle eKeyPress event whose mModifiers
+    // has MODIFIER_ALT or MODIFIER_CONTROL.  Additionally, we need to
+    // use MODIFIER_ALTGRAPH when a key produces character(s) with
+    // AltGr or both Ctrl and Alt on Windows.  See following spec issue:
+    // <https://github.com/w3c/uievents/issues/147>
+    Modifiers finalModifiers = ShiftStateToModifiers(aShiftState);
+    finalModifiers &= ~(MODIFIER_ALT | MODIFIER_CONTROL);
+    finalModifiers |= MODIFIER_ALTGRAPH;
+    result.FillModifiers(finalModifiers);
+    return result;
+  }
+
+  // Otherwise, i.e., Alt or Ctrl is pressed and it produces character(s),
+  // check if different character(s) is produced by the key without Alt/Ctrl.
+  // If it produces different character, we need to consume the Alt and
+  // Ctrl modifier for TextEditor.  Otherwise, the key does not produces the
+  // character actually.  So, keep setting Alt and Ctrl modifiers.
+  UniCharsAndModifiers unmodifiedReslt =
+      GetNativeUniChars(kShiftStateIndex & ~STATE_CONTROL_ALT);
+  if (!result.UniCharsEqual(unmodifiedReslt)) {
+    Modifiers finalModifiers = ShiftStateToModifiers(aShiftState);
+    finalModifiers &= ~(MODIFIER_ALT | MODIFIER_CONTROL);
+    result.FillModifiers(finalModifiers);
+  }
+  return result;
+}
+
+UniCharsAndModifiers VirtualKey::GetNativeUniChars(
+    ShiftState aShiftState) const {
+  const uint8_t kShiftStateIndex = ToShiftStateIndex(aShiftState);
+  UniCharsAndModifiers result;
+  Modifiers modifiers = ShiftStateToModifiers(aShiftState);
+  if (IsDeadKey(aShiftState)) {
+    result.Append(mShiftStates[kShiftStateIndex].DeadKey.DeadChar, modifiers);
+    return result;
+  }
+
+  uint32_t len = ArrayLength(mShiftStates[kShiftStateIndex].Normal.Chars);
+  for (uint32_t i = 0;
+       i < len && mShiftStates[kShiftStateIndex].Normal.Chars[i]; i++) {
+    result.Append(mShiftStates[kShiftStateIndex].Normal.Chars[i], modifiers);
+  }
+  return result;
+}
+
+// static
+void VirtualKey::FillKbdState(PBYTE aKbdState, const ShiftState aShiftState) {
+  if (aShiftState & STATE_SHIFT) {
+    aKbdState[VK_SHIFT] |= 0x80;
+  } else {
+    aKbdState[VK_SHIFT] &= ~0x80;
+    aKbdState[VK_LSHIFT] &= ~0x80;
+    aKbdState[VK_RSHIFT] &= ~0x80;
+  }
+
+  if (aShiftState & STATE_ALTGRAPH) {
+    aKbdState[VK_CONTROL] |= 0x80;
+    aKbdState[VK_LCONTROL] |= 0x80;
+    aKbdState[VK_RCONTROL] &= ~0x80;
+    aKbdState[VK_MENU] |= 0x80;
+    aKbdState[VK_LMENU] &= ~0x80;
+    aKbdState[VK_RMENU] |= 0x80;
+  } else {
+    if (aShiftState & STATE_CONTROL) {
+      aKbdState[VK_CONTROL] |= 0x80;
+    } else {
+      aKbdState[VK_CONTROL] &= ~0x80;
+      aKbdState[VK_LCONTROL] &= ~0x80;
+      aKbdState[VK_RCONTROL] &= ~0x80;
+    }
+
+    if (aShiftState & STATE_ALT) {
+      aKbdState[VK_MENU] |= 0x80;
+    } else {
+      aKbdState[VK_MENU] &= ~0x80;
+      aKbdState[VK_LMENU] &= ~0x80;
+      aKbdState[VK_RMENU] &= ~0x80;
+    }
+  }
+
+  if (aShiftState & STATE_CAPSLOCK) {
+    aKbdState[VK_CAPITAL] |= 0x01;
+  } else {
+    aKbdState[VK_CAPITAL] &= ~0x01;
+  }
+}
+
+/*****************************************************************************
+ * mozilla::widget::NativeKey
+ *****************************************************************************/
+
+uint8_t NativeKey::sDispatchedKeyOfAppCommand = 0;
+NativeKey* NativeKey::sLatestInstance = nullptr;
+const MSG NativeKey::sEmptyMSG = {};
+MSG NativeKey::sLastKeyOrCharMSG = {};
+MSG NativeKey::sLastKeyMSG = {};
+char16_t NativeKey::sPendingHighSurrogate = 0;
+
+NativeKey::NativeKey(nsWindow* aWidget, const MSG& aMessage,
+                     const ModifierKeyState& aModKeyState,
+                     HKL aOverrideKeyboardLayout,
+                     nsTArray<FakeCharMsg>* aFakeCharMsgs)
+    : mLastInstance(sLatestInstance),
+      mRemovingMsg(sEmptyMSG),
+      mReceivedMsg(sEmptyMSG),
+      mWidget(aWidget),
+      mDispatcher(aWidget->GetTextEventDispatcher()),
+      mMsg(aMessage),
+      mFocusedWndBeforeDispatch(::GetFocus()),
+      mDOMKeyCode(0),
+      mKeyNameIndex(KEY_NAME_INDEX_Unidentified),
+      mCodeNameIndex(CODE_NAME_INDEX_UNKNOWN),
+      mModKeyState(aModKeyState),
+      mVirtualKeyCode(0),
+      mOriginalVirtualKeyCode(0),
+      mShiftedLatinChar(0),
+      mUnshiftedLatinChar(0),
+      mScanCode(0),
+      mIsExtended(false),
+      mIsRepeat(false),
+      mIsDeadKey(false),
+      mIsPrintableKey(false),
+      mIsSkippableInRemoteProcess(false),
+      mCharMessageHasGone(false),
+      mCanIgnoreModifierStateAtKeyPress(true),
+      mFakeCharMsgs(aFakeCharMsgs && aFakeCharMsgs->Length() ? aFakeCharMsgs
+                                                             : nullptr) {
+  MOZ_LOG(gKeyLog, LogLevel::Info,
+          ("%p NativeKey::NativeKey(aWidget=0x%p { GetWindowHandle()=0x%p }, "
+           "aMessage=%s, aModKeyState=%s), sLatestInstance=0x%p",
+           this, aWidget, aWidget->GetWindowHandle(), ToString(aMessage).get(),
+           ToString(aModKeyState).get(), sLatestInstance));
+
+  MOZ_ASSERT(aWidget);
+  MOZ_ASSERT(mDispatcher);
+  sLatestInstance = this;
+  KeyboardLayout* keyboardLayout = KeyboardLayout::GetInstance();
+  mKeyboardLayout = KeyboardLayout::GetLayout();
+  if (aOverrideKeyboardLayout && mKeyboardLayout != aOverrideKeyboardLayout) {
+    keyboardLayout->OverrideLayout(aOverrideKeyboardLayout);
+    mKeyboardLayout = keyboardLayout->GetLoadedLayout();
+    MOZ_ASSERT(mKeyboardLayout == aOverrideKeyboardLayout);
+    mIsOverridingKeyboardLayout = true;
+  } else {
+    mIsOverridingKeyboardLayout = false;
+    sLastKeyOrCharMSG = aMessage;
+  }
+
+  if (mMsg.message == WM_APPCOMMAND) {
+    InitWithAppCommand();
+  } else {
+    InitWithKeyOrChar();
+  }
+
+  MOZ_LOG(gKeyLog, LogLevel::Info,
+          ("%p   NativeKey::NativeKey(), mKeyboardLayout=0x%p, "
+           "mFocusedWndBeforeDispatch=0x%p, mDOMKeyCode=%s, "
+           "mKeyNameIndex=%s, mCodeNameIndex=%s, mModKeyState=%s, "
+           "mVirtualKeyCode=%s, mOriginalVirtualKeyCode=%s, "
+           "mCommittedCharsAndModifiers=%s, mInputtingStringAndModifiers=%s, "
+           "mShiftedString=%s, mUnshiftedString=%s, mShiftedLatinChar=%s, "
+           "mUnshiftedLatinChar=%s, mScanCode=0x%04X, mIsExtended=%s, "
+           "mIsRepeat=%s, mIsDeadKey=%s, mIsPrintableKey=%s, "
+           "mIsSkippableInRemoteProcess=%s, mCharMessageHasGone=%s, "
+           "mIsOverridingKeyboardLayout=%s",
+           this, mKeyboardLayout, mFocusedWndBeforeDispatch,
+           GetDOMKeyCodeName(mDOMKeyCode).get(), ToString(mKeyNameIndex).get(),
+           ToString(mCodeNameIndex).get(), ToString(mModKeyState).get(),
+           GetVirtualKeyCodeName(mVirtualKeyCode).get(),
+           GetVirtualKeyCodeName(mOriginalVirtualKeyCode).get(),
+           ToString(mCommittedCharsAndModifiers).get(),
+           ToString(mInputtingStringAndModifiers).get(),
+           ToString(mShiftedString).get(), ToString(mUnshiftedString).get(),
+           GetCharacterCodeName(mShiftedLatinChar).get(),
+           GetCharacterCodeName(mUnshiftedLatinChar).get(), mScanCode,
+           GetBoolName(mIsExtended), GetBoolName(mIsRepeat),
+           GetBoolName(mIsDeadKey), GetBoolName(mIsPrintableKey),
+           GetBoolName(mIsSkippableInRemoteProcess),
+           GetBoolName(mCharMessageHasGone),
+           GetBoolName(mIsOverridingKeyboardLayout)));
+}
+
+void NativeKey::InitIsSkippableForKeyOrChar(const MSG& aLastKeyMSG) {
+  mIsSkippableInRemoteProcess = false;
+
+  if (!mIsRepeat) {
+    // If the message is not repeated key message, the event should be always
+    // handled in remote process even if it's too old.
+    return;
+  }
+
+  // Keyboard utilities may send us some generated messages and such messages
+  // may be marked as "repeated", e.g., SendInput() calls with
+  // KEYEVENTF_UNICODE but without KEYEVENTF_KEYUP.   However, key sequence
+  // comes from such utilities may be really important.  For example, utilities
+  // may send WM_KEYDOWN for VK_BACK to remove previous character and send
+  // WM_KEYDOWN for VK_PACKET to insert a composite character.  Therefore, we
+  // should check if current message and previous key message are caused by
+  // same physical key.  If not, the message may be generated by such
+  // utility.
+  // XXX With this approach, if VK_BACK messages are generated with known
+  //     scancode, we cannot distinguish whether coming VK_BACK message is
+  //     actually repeated by the auto-repeat feature.  Currently, we need
+  //     this hack only for "SinhalaTamil IME" and fortunately, it generates
+  //     VK_BACK messages with odd scancode.  So, we don't need to handle
+  //     VK_BACK specially at least for now.
+
+  if (mCodeNameIndex == CODE_NAME_INDEX_UNKNOWN) {
+    // If current event is not caused by physical key operation, it may be
+    // caused by a keyboard utility.  If so, the event shouldn't be ignored by
+    // BrowserChild since it want to insert the character, delete a character or
+    // move caret.
+    return;
+  }
+
+  if (mOriginalVirtualKeyCode == VK_PACKET) {
+    // If the message is VK_PACKET, that means that a keyboard utility
+    // tries to insert a character.
+    return;
+  }
+
+  switch (mMsg.message) {
+    case WM_KEYDOWN:
+    case WM_SYSKEYDOWN:
+    case WM_CHAR:
+    case WM_SYSCHAR:
+    case WM_DEADCHAR:
+    case WM_SYSDEADCHAR:
+      // However, some keyboard layouts may send some keyboard messages with
+      // activating the bit.  If we dispatch repeated keyboard events, they
+      // may be ignored by BrowserChild due to performance reason.  So, we need
+      // to check if actually a physical key is repeated by the auto-repeat
+      // feature.
+      switch (aLastKeyMSG.message) {
+        case WM_KEYDOWN:
+        case WM_SYSKEYDOWN:
+          if (aLastKeyMSG.wParam == VK_PACKET) {
+            // If the last message was VK_PACKET, that means that a keyboard
+            // utility tried to insert a character.  So, current message is
+            // not repeated key event of the previous event.
+            return;
+          }
+          // Let's check whether current message and previous message are
+          // caused by same physical key.
+          mIsSkippableInRemoteProcess =
+              mScanCode == WinUtils::GetScanCode(aLastKeyMSG.lParam) &&
+              mIsExtended == WinUtils::IsExtendedScanCode(aLastKeyMSG.lParam);
+          return;
+        default:
+          // If previous message is not a keydown, this must not be generated
+          // by the auto-repeat feature.
+          return;
+      }
+    case WM_APPCOMMAND:
+      MOZ_ASSERT_UNREACHABLE(
+          "WM_APPCOMMAND should be handled in "
+          "InitWithAppCommand()");
+      return;
+    default:
+      // keyup message shouldn't be repeated by the auto-repeat feature.
+      return;
+  }
+}
+
+void NativeKey::InitWithKeyOrChar() {
+  MSG lastKeyMSG = sLastKeyMSG;
+  char16_t pendingHighSurrogate = sPendingHighSurrogate;
+  mScanCode = WinUtils::GetScanCode(mMsg.lParam);
+  mIsExtended = WinUtils::IsExtendedScanCode(mMsg.lParam);
+  switch (mMsg.message) {
+    case WM_KEYDOWN:
+    case WM_SYSKEYDOWN:
+      sPendingHighSurrogate = 0;
+      [[fallthrough]];
+    case WM_KEYUP:
+    case WM_SYSKEYUP: {
+      // Modify sLastKeyMSG now since retrieving following char messages may
+      // cause sending another key message if odd tool hooks GetMessage(),
+      // PeekMessage().
+      sLastKeyMSG = mMsg;
+
+      // Note that we don't need to compute raw virtual keycode here even when
+      // it's VK_PROCESS (i.e., already handled by IME) because we need to
+      // export it as DOM_VK_PROCESS and KEY_NAME_INDEX_Process.
+      mOriginalVirtualKeyCode = static_cast<uint8_t>(mMsg.wParam);
+
+      // If the key message is sent from other application like a11y tools, the
+      // scancode value might not be set proper value.  Then, probably the value
+      // is 0.
+      // NOTE: If the virtual keycode can be caused by both non-extended key
+      //       and extended key, the API returns the non-extended key's
+      //       scancode.  E.g., VK_LEFT causes "4" key on numpad.
+      if (!mScanCode && mOriginalVirtualKeyCode != VK_PACKET) {
+        uint16_t scanCodeEx = ComputeScanCodeExFromVirtualKeyCode(mMsg.wParam);
+        if (scanCodeEx) {
+          mScanCode = static_cast<uint8_t>(scanCodeEx & 0xFF);
+          uint8_t extended = static_cast<uint8_t>((scanCodeEx & 0xFF00) >> 8);
+          mIsExtended = (extended == 0xE0) || (extended == 0xE1);
+        }
+      }
+
+      // Most keys are not distinguished as left or right keys.
+      bool isLeftRightDistinguishedKey = false;
+
+      // mOriginalVirtualKeyCode must not distinguish left or right of
+      // Shift, Control or Alt.
+      switch (mOriginalVirtualKeyCode) {
+        case VK_SHIFT:
+        case VK_CONTROL:
+        case VK_MENU:
+          isLeftRightDistinguishedKey = true;
+          break;
+        case VK_LSHIFT:
+        case VK_RSHIFT:
+          mVirtualKeyCode = mOriginalVirtualKeyCode;
+          mOriginalVirtualKeyCode = VK_SHIFT;
+          isLeftRightDistinguishedKey = true;
+          break;
+        case VK_LCONTROL:
+        case VK_RCONTROL:
+          mVirtualKeyCode = mOriginalVirtualKeyCode;
+          mOriginalVirtualKeyCode = VK_CONTROL;
+          isLeftRightDistinguishedKey = true;
+          break;
+        case VK_LMENU:
+        case VK_RMENU:
+          mVirtualKeyCode = mOriginalVirtualKeyCode;
+          mOriginalVirtualKeyCode = VK_MENU;
+          isLeftRightDistinguishedKey = true;
+          break;
+      }
+
+      // If virtual keycode (left-right distinguished keycode) is already
+      // computed, we don't need to do anymore.
+      if (mVirtualKeyCode) {
+        break;
+      }
+
+      // If the keycode doesn't have LR distinguished keycode, we just set
+      // mOriginalVirtualKeyCode to mVirtualKeyCode.  Note that don't compute
+      // it from MapVirtualKeyEx() because the scan code might be wrong if
+      // the message is sent/posted by other application.  Then, we will compute
+      // unexpected keycode from the scan code.
+      if (!isLeftRightDistinguishedKey) {
+        break;
+      }
+
+      NS_ASSERTION(!mVirtualKeyCode,
+                   "mVirtualKeyCode has been computed already");
+
+      // Otherwise, compute the virtual keycode with MapVirtualKeyEx().
+      mVirtualKeyCode = ComputeVirtualKeyCodeFromScanCodeEx();
+
+      // Following code shouldn't be used now because we compute scancode value
+      // if we detect that the sender doesn't set proper scancode.
+      // However, the detection might fail. Therefore, let's keep using this.
+      switch (mOriginalVirtualKeyCode) {
+        case VK_CONTROL:
+          if (mVirtualKeyCode != VK_LCONTROL &&
+              mVirtualKeyCode != VK_RCONTROL) {
+            mVirtualKeyCode = mIsExtended ? VK_RCONTROL : VK_LCONTROL;
+          }
+          break;
+        case VK_MENU:
+          if (mVirtualKeyCode != VK_LMENU && mVirtualKeyCode != VK_RMENU) {
+            mVirtualKeyCode = mIsExtended ? VK_RMENU : VK_LMENU;
+          }
+          break;
+        case VK_SHIFT:
+          if (mVirtualKeyCode != VK_LSHIFT && mVirtualKeyCode != VK_RSHIFT) {
+            // Neither left shift nor right shift is an extended key,
+            // let's use VK_LSHIFT for unknown mapping.
+            mVirtualKeyCode = VK_LSHIFT;
+          }
+          break;
+        default:
+          MOZ_CRASH("Unsupported mOriginalVirtualKeyCode");
+      }
+      break;
+    }
+    case WM_CHAR:
+    case WM_UNICHAR:
+    case WM_SYSCHAR:
+      sPendingHighSurrogate = 0;
+      // If there is another instance and it is trying to remove a char message
+      // from the queue, this message should be handled in the old instance.
+      if (IsAnotherInstanceRemovingCharMessage()) {
+        // XXX Do we need to make mReceivedMsg an array?
+        MOZ_ASSERT(IsEmptyMSG(mLastInstance->mReceivedMsg));
+        MOZ_LOG(
+            gKeyLog, LogLevel::Warning,
+            ("%p   NativeKey::InitWithKeyOrChar(), WARNING, detecting another "
+             "instance is trying to remove a char message, so, this instance "
+             "should do nothing, mLastInstance=0x%p, mRemovingMsg=%s, "
+             "mReceivedMsg=%s",
+             this, mLastInstance, ToString(mLastInstance->mRemovingMsg).get(),
+             ToString(mLastInstance->mReceivedMsg).get()));
+        mLastInstance->mReceivedMsg = mMsg;
+        return;
+      }
+
+      // NOTE: If other applications like a11y tools sends WM_*CHAR without
+      //       scancode, we cannot compute virtual keycode.  I.e., with such
+      //       applications, we cannot generate proper KeyboardEvent.code value.
+
+      mVirtualKeyCode = mOriginalVirtualKeyCode =
+          ComputeVirtualKeyCodeFromScanCodeEx();
+      NS_ASSERTION(mVirtualKeyCode, "Failed to compute virtual keycode");
+      break;
+    default: {
+      MOZ_CRASH_UNSAFE_PRINTF("Unsupported message: 0x%04X", mMsg.message);
+      break;
+    }
+  }
+
+  if (!mVirtualKeyCode) {
+    mVirtualKeyCode = mOriginalVirtualKeyCode;
+  }
+
+  KeyboardLayout* keyboardLayout = KeyboardLayout::GetInstance();
+  mDOMKeyCode =
+      keyboardLayout->ConvertNativeKeyCodeToDOMKeyCode(mVirtualKeyCode);
+  // Be aware, keyboard utilities can change non-printable keys to printable
+  // keys.  In such case, we should make the key value as a printable key.
+  // FYI: IsFollowedByPrintableCharMessage() returns true only when it's
+  //      handling a keydown message.
+  mKeyNameIndex =
+      IsFollowedByPrintableCharMessage()
+          ? KEY_NAME_INDEX_USE_STRING
+          : keyboardLayout->ConvertNativeKeyCodeToKeyNameIndex(mVirtualKeyCode);
+  mCodeNameIndex = KeyboardLayout::ConvertScanCodeToCodeNameIndex(
+      GetScanCodeWithExtendedFlag());
+
+  // If next message of WM_(SYS)KEYDOWN is WM_*CHAR message and the key
+  // combination is not reserved by the system, let's consume it now.
+  // TODO: We cannot initialize mCommittedCharsAndModifiers for VK_PACKET
+  //       if the message is WM_KEYUP because we don't have preceding
+  //       WM_CHAR message.
+  // TODO: Like Edge, we shouldn't dispatch two sets of keyboard events
+  //       for a Unicode character in non-BMP because its key value looks
+  //       broken and not good thing for our editor if only one keydown or
+  //       keypress event's default is prevented.  I guess, we should store
+  //       key message information globally and we should wait following
+  //       WM_KEYDOWN if following WM_CHAR is a part of a Unicode character.
+  if ((mMsg.message == WM_KEYDOWN || mMsg.message == WM_SYSKEYDOWN) &&
+      !IsReservedBySystem()) {
+    MSG charMsg;
+    while (GetFollowingCharMessage(charMsg)) {
+      // Although, got message shouldn't be WM_NULL in desktop apps,
+      // we should keep checking this.  FYI: This was added for Metrofox.
+      if (charMsg.message == WM_NULL) {
+        continue;
+      }
+      MOZ_LOG(gKeyLog, LogLevel::Info,
+              ("%p   NativeKey::InitWithKeyOrChar(), removed char message, %s",
+               this, ToString(charMsg).get()));
+      Unused << NS_WARN_IF(charMsg.hwnd != mMsg.hwnd);
+      mFollowingCharMsgs.AppendElement(charMsg);
+    }
+    if (mFollowingCharMsgs.Length() == 1) {
+      // If we receive a keydown message for a high-surrogate, a low-surrogate
+      // keydown message **will** and should follow it.  We cannot translate the
+      // following WM_KEYDOWN message for the low-surrogate right now since
+      // it's not yet queued into the message queue yet.  Therefore, we need to
+      // wait next one to dispatch keypress event with setting its `.key` value
+      // to a surrogate pair rather than setting it to a lone surrogate.
+      // FYI: This may happen with typing a non-BMP character on the touch
+      // keyboard on Windows 10 or later except when an IME is installed. (If
+      // IME is installed, composition is used instead.)
+      if (IS_HIGH_SURROGATE(mFollowingCharMsgs[0].wParam)) {
+        if (pendingHighSurrogate) {
+          MOZ_LOG(gKeyLog, LogLevel::Warning,
+                  ("%p   NativeKey::InitWithKeyOrChar(), there is pending "
+                   "high surrogate input, but received another high surrogate "
+                   "input.  The previous one is discarded",
+                   this));
+        }
+        sPendingHighSurrogate = mFollowingCharMsgs[0].wParam;
+        mFollowingCharMsgs.Clear();
+      } else if (IS_LOW_SURROGATE(mFollowingCharMsgs[0].wParam)) {
+        // If we stopped dispathing a keypress event for a preceding
+        // high-surrogate, treat this keydown (for a low-surrogate) as
+        // introducing both the high surrogate and the low surrogate.
+        if (pendingHighSurrogate) {
+          MSG charMsg = mFollowingCharMsgs[0];
+          mFollowingCharMsgs[0].wParam = pendingHighSurrogate;
+          mFollowingCharMsgs.AppendElement(std::move(charMsg));
+        } else {
+          MOZ_LOG(
+              gKeyLog, LogLevel::Warning,
+              ("%p   NativeKey::InitWithKeyOrChar(), there is no pending high "
+               "surrogate input, but received lone low surrogate input",
+               this));
+        }
+      } else {
+        MOZ_LOG(gKeyLog, LogLevel::Warning,
+                ("%p   NativeKey::InitWithKeyOrChar(), there is pending "
+                 "high surrogate input, but received non-surrogate input.  "
+                 "The high surrogate input is discarded",
+                 this));
+      }
+    } else if (!mFollowingCharMsgs.IsEmpty()) {
+      MOZ_LOG(gKeyLog, LogLevel::Warning,
+              ("%p   NativeKey::InitWithKeyOrChar(), there is pending "
+               "high surrogate input, but received 2 or more character input.  "
+               "The high surrogate input is discarded",
+               this));
+    }
+  }
+
+  keyboardLayout->InitNativeKey(*this);
+
+  // Now, we can know if the key produces character(s) or a dead key with
+  // AltGraph modifier.  When user emulates AltGr key press with pressing
+  // both Ctrl and Alt and the key produces character(s) or a dead key, we
+  // need to replace Control and Alt state with AltGraph if the keyboard
+  // layout has AltGr key.
+  // Note that if Ctrl and/or Alt are pressed (not to emulate to press AltGr),
+  // we need to set actual modifiers to eKeyDown and eKeyUp.
+  if (MaybeEmulatingAltGraph() &&
+      (mCommittedCharsAndModifiers.IsProducingCharsWithAltGr() ||
+       mKeyNameIndex == KEY_NAME_INDEX_Dead)) {
+    mModKeyState.Unset(MODIFIER_CONTROL | MODIFIER_ALT);
+    mModKeyState.Set(MODIFIER_ALTGRAPH);
+  }
+
+  mIsDeadKey =
+      (IsFollowedByDeadCharMessage() ||
+       keyboardLayout->IsDeadKey(mOriginalVirtualKeyCode, mModKeyState));
+  mIsPrintableKey = mKeyNameIndex == KEY_NAME_INDEX_USE_STRING ||
+                    KeyboardLayout::IsPrintableCharKey(mOriginalVirtualKeyCode);
+  // The repeat count in mMsg.lParam isn't useful to check whether the event
+  // is caused by the auto-repeat feature because it's not incremented even
+  // if it's repeated twice or more (i.e., always 1).  Therefore, we need to
+  // check previous key state (31th bit) instead.  If it's 1, the key was down
+  // before the message was sent.
+  mIsRepeat = (mMsg.lParam & (1 << 30)) != 0;
+  InitIsSkippableForKeyOrChar(lastKeyMSG);
+
+  if (IsKeyDownMessage()) {
+    // Compute some strings which may be inputted by the key with various
+    // modifier state if this key event won't cause text input actually.
+    // They will be used for setting mAlternativeCharCodes in the callback
+    // method which will be called by TextEventDispatcher.
+    if (!IsFollowedByPrintableCharMessage()) {
+      ComputeInputtingStringWithKeyboardLayout();
+    }
+    // Remove odd char messages if there are.
+    RemoveFollowingOddCharMessages();
+  }
+}
+
+void NativeKey::InitCommittedCharsAndModifiersWithFollowingCharMessages() {
+  mCommittedCharsAndModifiers.Clear();
+  // This should cause inputting text in focused editor.  However, it
+  // ignores keypress events whose altKey or ctrlKey is true.
+  // Therefore, we need to remove these modifier state here.
+  Modifiers modifiers = mModKeyState.GetModifiers();
+  if (IsFollowedByPrintableCharMessage()) {
+    modifiers &= ~(MODIFIER_ALT | MODIFIER_CONTROL);
+    if (MaybeEmulatingAltGraph()) {
+      modifiers |= MODIFIER_ALTGRAPH;
+    }
+  }
+  // NOTE: This method assumes that WM_CHAR and WM_SYSCHAR are never retrieved
+  //       at same time.
+  for (size_t i = 0; i < mFollowingCharMsgs.Length(); ++i) {
+    // Ignore non-printable char messages.
+    if (!IsPrintableCharOrSysCharMessage(mFollowingCharMsgs[i])) {
+      continue;
+    }
+    char16_t ch = static_cast<char16_t>(mFollowingCharMsgs[i].wParam);
+    mCommittedCharsAndModifiers.Append(ch, modifiers);
+  }
+}
+
+NativeKey::~NativeKey() {
+  MOZ_LOG(gKeyLog, LogLevel::Debug,
+          ("%p   NativeKey::~NativeKey(), destroyed", this));
+  if (mIsOverridingKeyboardLayout) {
+    KeyboardLayout* keyboardLayout = KeyboardLayout::GetInstance();
+    keyboardLayout->RestoreLayout();
+  }
+  sLatestInstance = mLastInstance;
+}
+
+void NativeKey::InitWithAppCommand() {
+  if (GET_DEVICE_LPARAM(mMsg.lParam) != FAPPCOMMAND_KEY) {
+    return;
+  }
+
+  uint32_t appCommand = GET_APPCOMMAND_LPARAM(mMsg.lParam);
+  switch (GET_APPCOMMAND_LPARAM(mMsg.lParam)) {
+#undef NS_APPCOMMAND_TO_DOM_KEY_NAME_INDEX
+#define NS_APPCOMMAND_TO_DOM_KEY_NAME_INDEX(aAppCommand, aKeyNameIndex) \
+  case aAppCommand:                                                     \
+    mKeyNameIndex = aKeyNameIndex;                                      \
+    break;
+
+#include "NativeKeyToDOMKeyName.h"
+
+#undef NS_APPCOMMAND_TO_DOM_KEY_NAME_INDEX
+
+    default:
+      mKeyNameIndex = KEY_NAME_INDEX_Unidentified;
+  }
+
+  // Guess the virtual keycode which caused this message.
+  switch (appCommand) {
+    case APPCOMMAND_BROWSER_BACKWARD:
+      mVirtualKeyCode = mOriginalVirtualKeyCode = VK_BROWSER_BACK;
+      break;
+    case APPCOMMAND_BROWSER_FORWARD:
+      mVirtualKeyCode = mOriginalVirtualKeyCode = VK_BROWSER_FORWARD;
+      break;
+    case APPCOMMAND_BROWSER_REFRESH:
+      mVirtualKeyCode = mOriginalVirtualKeyCode = VK_BROWSER_REFRESH;
+      break;
+    case APPCOMMAND_BROWSER_STOP:
+      mVirtualKeyCode = mOriginalVirtualKeyCode = VK_BROWSER_STOP;
+      break;
+    case APPCOMMAND_BROWSER_SEARCH:
+      mVirtualKeyCode = mOriginalVirtualKeyCode = VK_BROWSER_SEARCH;
+      break;
+    case APPCOMMAND_BROWSER_FAVORITES:
+      mVirtualKeyCode = mOriginalVirtualKeyCode = VK_BROWSER_FAVORITES;
+      break;
+    case APPCOMMAND_BROWSER_HOME:
+      mVirtualKeyCode = mOriginalVirtualKeyCode = VK_BROWSER_HOME;
+      break;
+    case APPCOMMAND_VOLUME_MUTE:
+      mVirtualKeyCode = mOriginalVirtualKeyCode = VK_VOLUME_MUTE;
+      break;
+    case APPCOMMAND_VOLUME_DOWN:
+      mVirtualKeyCode = mOriginalVirtualKeyCode = VK_VOLUME_DOWN;
+      break;
+    case APPCOMMAND_VOLUME_UP:
+      mVirtualKeyCode = mOriginalVirtualKeyCode = VK_VOLUME_UP;
+      break;
+    case APPCOMMAND_MEDIA_NEXTTRACK:
+      mVirtualKeyCode = mOriginalVirtualKeyCode = VK_MEDIA_NEXT_TRACK;
+      break;
+    case APPCOMMAND_MEDIA_PREVIOUSTRACK:
+      mVirtualKeyCode = mOriginalVirtualKeyCode = VK_MEDIA_PREV_TRACK;
+      break;
+    case APPCOMMAND_MEDIA_STOP:
+      mVirtualKeyCode = mOriginalVirtualKeyCode = VK_MEDIA_STOP;
+      break;
+    case APPCOMMAND_MEDIA_PLAY_PAUSE:
+      mVirtualKeyCode = mOriginalVirtualKeyCode = VK_MEDIA_PLAY_PAUSE;
+      break;
+    case APPCOMMAND_LAUNCH_MAIL:
+      mVirtualKeyCode = mOriginalVirtualKeyCode = VK_LAUNCH_MAIL;
+      break;
+    case APPCOMMAND_LAUNCH_MEDIA_SELECT:
+      mVirtualKeyCode = mOriginalVirtualKeyCode = VK_LAUNCH_MEDIA_SELECT;
+      break;
+    case APPCOMMAND_LAUNCH_APP1:
+      mVirtualKeyCode = mOriginalVirtualKeyCode = VK_LAUNCH_APP1;
+      break;
+    case APPCOMMAND_LAUNCH_APP2:
+      mVirtualKeyCode = mOriginalVirtualKeyCode = VK_LAUNCH_APP2;
+      break;
+    default:
+      return;
+  }
+
+  uint16_t scanCodeEx = ComputeScanCodeExFromVirtualKeyCode(mVirtualKeyCode);
+  mScanCode = static_cast<uint8_t>(scanCodeEx & 0xFF);
+  uint8_t extended = static_cast<uint8_t>((scanCodeEx & 0xFF00) >> 8);
+  mIsExtended = (extended == 0xE0) || (extended == 0xE1);
+  mDOMKeyCode = KeyboardLayout::GetInstance()->ConvertNativeKeyCodeToDOMKeyCode(
+      mOriginalVirtualKeyCode);
+  mCodeNameIndex = KeyboardLayout::ConvertScanCodeToCodeNameIndex(
+      GetScanCodeWithExtendedFlag());
+  // If we can map the WM_APPCOMMAND to a virtual keycode, we can trust
+  // the result of GetKeyboardState().  Otherwise, we dispatch both
+  // keydown and keyup events from WM_APPCOMMAND handler.  Therefore,
+  // even if WM_APPCOMMAND is caused by auto key repeat, web apps receive
+  // a pair of DOM keydown and keyup events.  I.e., KeyboardEvent.repeat
+  // should be never true of such keys.
+  // XXX Isn't the key state always true?  If the key press caused this
+  //     WM_APPCOMMAND, that means it's pressed at that time.
+  if (mVirtualKeyCode) {
+    BYTE kbdState[256];
+    memset(kbdState, 0, sizeof(kbdState));
+    ::GetKeyboardState(kbdState);
+    mIsSkippableInRemoteProcess = mIsRepeat = !!kbdState[mVirtualKeyCode];
+  }
+}
+
+bool NativeKey::MaybeEmulatingAltGraph() const {
+  return IsControl() && IsAlt() && KeyboardLayout::GetInstance()->HasAltGr();
+}
+
+// static
+bool NativeKey::IsControlChar(char16_t aChar) {
+  static const char16_t U_SPACE = 0x20;
+  static const char16_t U_DELETE = 0x7F;
+  return aChar < U_SPACE || aChar == U_DELETE;
+}
+
+bool NativeKey::IsFollowedByDeadCharMessage() const {
+  if (mFollowingCharMsgs.IsEmpty()) {
+    return false;
+  }
+  return IsDeadCharMessage(mFollowingCharMsgs[0]);
+}
+
+bool NativeKey::IsFollowedByPrintableCharMessage() const {
+  for (size_t i = 0; i < mFollowingCharMsgs.Length(); ++i) {
+    if (IsPrintableCharMessage(mFollowingCharMsgs[i])) {
+      return true;
+    }
+  }
+  return false;
+}
+
+bool NativeKey::IsFollowedByPrintableCharOrSysCharMessage() const {
+  for (size_t i = 0; i < mFollowingCharMsgs.Length(); ++i) {
+    if (IsPrintableCharOrSysCharMessage(mFollowingCharMsgs[i])) {
+      return true;
+    }
+  }
+  return false;
+}
+
+bool NativeKey::IsReservedBySystem() const {
+  // Alt+Space key is handled by OS, we shouldn't touch it.
+  if (mModKeyState.IsAlt() && !mModKeyState.IsControl() &&
+      mVirtualKeyCode == VK_SPACE) {
+    return true;
+  }
+
+  // XXX How about Alt+F4? We receive WM_SYSKEYDOWN for F4 before closing the
+  //     window.  Although, we don't prevent to close the window but the key
+  //     event shouldn't be exposed to the web.
+
+  return false;
+}
+
+bool NativeKey::IsIMEDoingKakuteiUndo() const {
+  // Following message pattern is caused by "Kakutei-Undo" of ATOK or WXG:
+  // ---------------------------------------------------------------------------
+  // WM_KEYDOWN              * n (wParam = VK_BACK, lParam = 0x1)
+  // WM_KEYUP                * 1 (wParam = VK_BACK, lParam = 0xC0000001) # ATOK
+  // WM_IME_STARTCOMPOSITION * 1 (wParam = 0x0, lParam = 0x0)
+  // WM_IME_COMPOSITION      * 1 (wParam = 0x0, lParam = 0x1BF)
+  // WM_CHAR                 * n (wParam = VK_BACK, lParam = 0x1)
+  // WM_KEYUP                * 1 (wParam = VK_BACK, lParam = 0xC00E0001)
+  // ---------------------------------------------------------------------------
+  // This doesn't match usual key message pattern such as:
+  //   WM_KEYDOWN -> WM_CHAR -> WM_KEYDOWN -> WM_CHAR -> ... -> WM_KEYUP
+  // See following bugs for the detail.
+  // https://bugzilla.mozilla.gr.jp/show_bug.cgi?id=2885 (written in Japanese)
+  // https://bugzilla.mozilla.org/show_bug.cgi?id=194559 (written in English)
+  MSG startCompositionMsg, compositionMsg, charMsg;
+  return WinUtils::PeekMessage(&startCompositionMsg, mMsg.hwnd,
+                               WM_IME_STARTCOMPOSITION, WM_IME_STARTCOMPOSITION,
+                               PM_NOREMOVE | PM_NOYIELD) &&
+         WinUtils::PeekMessage(&compositionMsg, mMsg.hwnd, WM_IME_COMPOSITION,
+                               WM_IME_COMPOSITION, PM_NOREMOVE | PM_NOYIELD) &&
+         WinUtils::PeekMessage(&charMsg, mMsg.hwnd, WM_CHAR, WM_CHAR,
+                               PM_NOREMOVE | PM_NOYIELD) &&
+         startCompositionMsg.wParam == 0x0 &&
+         startCompositionMsg.lParam == 0x0 && compositionMsg.wParam == 0x0 &&
+         compositionMsg.lParam == 0x1BF && charMsg.wParam == VK_BACK &&
+         charMsg.lParam == 0x1 &&
+         startCompositionMsg.time <= compositionMsg.time &&
+         compositionMsg.time <= charMsg.time;
+}
+
+void NativeKey::RemoveFollowingOddCharMessages() {
+  MOZ_ASSERT(IsKeyDownMessage());
+
+  // If the keydown message is synthesized for automated tests, there is
+  // nothing to do here.
+  if (mFakeCharMsgs) {
+    return;
+  }
+
+  // If there are some following char messages before another key message,
+  // there is nothing to do here.
+  if (!mFollowingCharMsgs.IsEmpty()) {
+    return;
+  }
+
+  // If the handling key isn't Backspace, there is nothing to do here.
+  if (mOriginalVirtualKeyCode != VK_BACK) {
+    return;
+  }
+
+  // If we don't see the odd message pattern, there is nothing to do here.
+  if (!IsIMEDoingKakuteiUndo()) {
+    return;
+  }
+
+  // Otherwise, we need to remove odd WM_CHAR messages for ATOK or WXG (both
+  // of them are Japanese IME).
+  MSG msg;
+  while (WinUtils::PeekMessage(&msg, mMsg.hwnd, WM_CHAR, WM_CHAR,
+                               PM_REMOVE | PM_NOYIELD)) {
+    if (msg.message != WM_CHAR) {
+      MOZ_RELEASE_ASSERT(msg.message == WM_NULL,
+                         "Unexpected message was removed");
+      continue;
+    }
+    MOZ_LOG(
+        gKeyLog, LogLevel::Info,
+        ("%p   NativeKey::RemoveFollowingOddCharMessages(), removed odd char "
+         "message, %s",
+         this, ToString(msg).get()));
+    mRemovedOddCharMsgs.AppendElement(msg);
+  }
+}
+
+UINT NativeKey::GetScanCodeWithExtendedFlag() const {
+  if (!mIsExtended) {
+    return mScanCode;
+  }
+  return (0xE000 | mScanCode);
+}
+
+uint32_t NativeKey::GetKeyLocation() const {
+  switch (mVirtualKeyCode) {
+    case VK_LSHIFT:
+    case VK_LCONTROL:
+    case VK_LMENU:
+    case VK_LWIN:
+      return eKeyLocationLeft;
+
+    case VK_RSHIFT:
+    case VK_RCONTROL:
+    case VK_RMENU:
+    case VK_RWIN:
+      return eKeyLocationRight;
+
+    case VK_RETURN:
+      // XXX This code assumes that all keyboard drivers use same mapping.
+      return !mIsExtended ? eKeyLocationStandard : eKeyLocationNumpad;
+
+    case VK_INSERT:
+    case VK_DELETE:
+    case VK_END:
+    case VK_DOWN:
+    case VK_NEXT:
+    case VK_LEFT:
+    case VK_CLEAR:
+    case VK_RIGHT:
+    case VK_HOME:
+    case VK_UP:
+    case VK_PRIOR:
+      // XXX This code assumes that all keyboard drivers use same mapping.
+      return mIsExtended ? eKeyLocationStandard : eKeyLocationNumpad;
+
+    // NumLock key isn't included due to IE9's behavior.
+    case VK_NUMPAD0:
+    case VK_NUMPAD1:
+    case VK_NUMPAD2:
+    case VK_NUMPAD3:
+    case VK_NUMPAD4:
+    case VK_NUMPAD5:
+    case VK_NUMPAD6:
+    case VK_NUMPAD7:
+    case VK_NUMPAD8:
+    case VK_NUMPAD9:
+    case VK_DECIMAL:
+    case VK_DIVIDE:
+    case VK_MULTIPLY:
+    case VK_SUBTRACT:
+    case VK_ADD:
+    // Separator key of Brazilian keyboard or JIS keyboard for Mac
+    case VK_ABNT_C2:
+      return eKeyLocationNumpad;
+
+    case VK_SHIFT:
+    case VK_CONTROL:
+    case VK_MENU:
+      NS_WARNING("Failed to decide the key location?");
+      [[fallthrough]];
+
+    default:
+      return eKeyLocationStandard;
+  }
+}
+
+uint8_t NativeKey::ComputeVirtualKeyCodeFromScanCode() const {
+  return static_cast<uint8_t>(
+      ::MapVirtualKeyEx(mScanCode, MAPVK_VSC_TO_VK, mKeyboardLayout));
+}
+
+uint8_t NativeKey::ComputeVirtualKeyCodeFromScanCodeEx() const {
+  // MapVirtualKeyEx() has been improved for supporting extended keys since
+  // Vista.  When we call it for mapping a scancode of an extended key and
+  // a virtual keycode, we need to add 0xE000 to the scancode.
+  return static_cast<uint8_t>(::MapVirtualKeyEx(
+      GetScanCodeWithExtendedFlag(), MAPVK_VSC_TO_VK_EX, mKeyboardLayout));
+}
+
+uint16_t NativeKey::ComputeScanCodeExFromVirtualKeyCode(
+    UINT aVirtualKeyCode) const {
+  return static_cast<uint16_t>(
+      ::MapVirtualKeyEx(aVirtualKeyCode, MAPVK_VK_TO_VSC_EX, mKeyboardLayout));
+}
+
+char16_t NativeKey::ComputeUnicharFromScanCode() const {
+  return static_cast<char16_t>(::MapVirtualKeyEx(
+      ComputeVirtualKeyCodeFromScanCode(), MAPVK_VK_TO_CHAR, mKeyboardLayout));
+}
+
+nsEventStatus NativeKey::InitKeyEvent(WidgetKeyboardEvent& aKeyEvent) const {
+  return InitKeyEvent(aKeyEvent, mModKeyState);
+}
+
+nsEventStatus NativeKey::InitKeyEvent(
+    WidgetKeyboardEvent& aKeyEvent,
+    const ModifierKeyState& aModKeyState) const {
+  if (mWidget->Destroyed()) {
+    MOZ_CRASH("NativeKey tries to dispatch a key event on destroyed widget");
+  }
+
+  LayoutDeviceIntPoint point(0, 0);
+  mWidget->InitEvent(aKeyEvent, &point);
+
+  switch (aKeyEvent.mMessage) {
+    case eKeyDown:
+      // If it was followed by a char message but it was consumed by somebody,
+      // we should mark it as consumed because somebody must have handled it
+      // and we should prevent to do "double action" for the key operation.
+      // However, for compatibility with older version and other browsers,
+      // we should dispatch the events even in the web content.
+      if (mCharMessageHasGone) {
+        aKeyEvent.PreventDefaultBeforeDispatch(CrossProcessForwarding::eAllow);
+      }
+      aKeyEvent.mKeyCode = mDOMKeyCode;
+      // Unique id for this keydown event and its associated keypress.
+      sUniqueKeyEventId++;
+      aKeyEvent.mUniqueId = sUniqueKeyEventId;
+      break;
+    case eKeyUp:
+      aKeyEvent.mKeyCode = mDOMKeyCode;
+      // Set defaultPrevented of the key event if the VK_MENU is not a system
+      // key release, so that the menu bar does not trigger.  This helps avoid
+      // triggering the menu bar for ALT key accelerators used in assistive
+      // technologies such as Window-Eyes and ZoomText or for switching open
+      // state of IME.  On the other hand, we should dispatch the events even
+      // in the web content for compatibility with older version and other
+      // browsers.
+      if (mOriginalVirtualKeyCode == VK_MENU && mMsg.message != WM_SYSKEYUP) {
+        aKeyEvent.PreventDefaultBeforeDispatch(CrossProcessForwarding::eAllow);
+      }
+      break;
+    case eKeyPress:
+      MOZ_ASSERT(!mCharMessageHasGone,
+                 "If following char message was consumed by somebody, "
+                 "keydown event should be consumed above");
+      aKeyEvent.mUniqueId = sUniqueKeyEventId;
+      break;
+    default:
+      MOZ_CRASH("Invalid event message");
+  }
+
+  aKeyEvent.mIsRepeat = mIsRepeat;
+  aKeyEvent.mMaybeSkippableInRemoteProcess = mIsSkippableInRemoteProcess;
+  aKeyEvent.mKeyNameIndex = mKeyNameIndex;
+  if (mKeyNameIndex == KEY_NAME_INDEX_USE_STRING) {
+    aKeyEvent.mKeyValue = mCommittedCharsAndModifiers.ToString();
+  }
+  aKeyEvent.mCodeNameIndex = mCodeNameIndex;
+  MOZ_ASSERT(mCodeNameIndex != CODE_NAME_INDEX_USE_STRING);
+  aKeyEvent.mLocation = GetKeyLocation();
+  aModKeyState.InitInputEvent(aKeyEvent);
+
+  KeyboardLayout::NotifyIdleServiceOfUserActivity();
+
+  MOZ_LOG(
+      gKeyLog, LogLevel::Info,
+      ("%p   NativeKey::InitKeyEvent(), initialized, aKeyEvent={ "
+       "mMessage=%s, mKeyNameIndex=%s, mKeyValue=\"%s\", mCodeNameIndex=%s, "
+       "mKeyCode=%s, mLocation=%s, mModifiers=%s, DefaultPrevented()=%s }",
+       this, ToChar(aKeyEvent.mMessage),
+       ToString(aKeyEvent.mKeyNameIndex).get(),
+       NS_ConvertUTF16toUTF8(aKeyEvent.mKeyValue).get(),
+       ToString(aKeyEvent.mCodeNameIndex).get(),
+       GetDOMKeyCodeName(aKeyEvent.mKeyCode).get(),
+       GetKeyLocationName(aKeyEvent.mLocation).get(),
+       GetModifiersName(aKeyEvent.mModifiers).get(),
+       GetBoolName(aKeyEvent.DefaultPrevented())));
+
+  return aKeyEvent.DefaultPrevented() ? nsEventStatus_eConsumeNoDefault
+                                      : nsEventStatus_eIgnore;
+}
+
+bool NativeKey::DispatchCommandEvent(uint32_t aEventCommand) const {
+  RefPtr<nsAtom> command;
+  switch (aEventCommand) {
+    case APPCOMMAND_BROWSER_BACKWARD:
+      command = nsGkAtoms::Back;
+      break;
+    case APPCOMMAND_BROWSER_FORWARD:
+      command = nsGkAtoms::Forward;
+      break;
+    case APPCOMMAND_BROWSER_REFRESH:
+      command = nsGkAtoms::Reload;
+      break;
+    case APPCOMMAND_BROWSER_STOP:
+      command = nsGkAtoms::Stop;
+      break;
+    case APPCOMMAND_BROWSER_SEARCH:
+      command = nsGkAtoms::Search;
+      break;
+    case APPCOMMAND_BROWSER_FAVORITES:
+      command = nsGkAtoms::Bookmarks;
+      break;
+    case APPCOMMAND_BROWSER_HOME:
+      command = nsGkAtoms::Home;
+      break;
+    case APPCOMMAND_CLOSE:
+      command = nsGkAtoms::Close;
+      break;
+    case APPCOMMAND_FIND:
+      command = nsGkAtoms::Find;
+      break;
+    case APPCOMMAND_HELP:
+      command = nsGkAtoms::Help;
+      break;
+    case APPCOMMAND_NEW:
+      command = nsGkAtoms::New;
+      break;
+    case APPCOMMAND_OPEN:
+      command = nsGkAtoms::Open;
+      break;
+    case APPCOMMAND_PRINT:
+      command = nsGkAtoms::Print;
+      break;
+    case APPCOMMAND_SAVE:
+      command = nsGkAtoms::Save;
+      break;
+    case APPCOMMAND_FORWARD_MAIL:
+      command = nsGkAtoms::ForwardMail;
+      break;
+    case APPCOMMAND_REPLY_TO_MAIL:
+      command = nsGkAtoms::ReplyToMail;
+      break;
+    case APPCOMMAND_SEND_MAIL:
+      command = nsGkAtoms::SendMail;
+      break;
+    case APPCOMMAND_MEDIA_NEXTTRACK:
+      command = nsGkAtoms::NextTrack;
+      break;
+    case APPCOMMAND_MEDIA_PREVIOUSTRACK:
+      command = nsGkAtoms::PreviousTrack;
+      break;
+    case APPCOMMAND_MEDIA_STOP:
+      command = nsGkAtoms::MediaStop;
+      break;
+    case APPCOMMAND_MEDIA_PLAY_PAUSE:
+      command = nsGkAtoms::PlayPause;
+      break;
+    default:
+      MOZ_LOG(
+          gKeyLog, LogLevel::Info,
+          ("%p   NativeKey::DispatchCommandEvent(), doesn't dispatch command "
+           "event",
+           this));
+      return false;
+  }
+  WidgetCommandEvent appCommandEvent(true, command, mWidget);
+
+  mWidget->InitEvent(appCommandEvent);
+  MOZ_LOG(gKeyLog, LogLevel::Info,
+          ("%p   NativeKey::DispatchCommandEvent(), dispatching "
+           "%s app command event...",
+           this, nsAtomCString(command).get()));
+  bool ok =
+      mWidget->DispatchWindowEvent(appCommandEvent) || mWidget->Destroyed();
+  MOZ_LOG(
+      gKeyLog, LogLevel::Info,
+      ("%p   NativeKey::DispatchCommandEvent(), dispatched app command event, "
+       "result=%s, mWidget->Destroyed()=%s",
+       this, GetBoolName(ok), GetBoolName(mWidget->Destroyed())));
+  return ok;
+}
+
+bool NativeKey::HandleAppCommandMessage() const {
+  // If the widget has gone, we should do nothing.
+  if (mWidget->Destroyed()) {
+    MOZ_LOG(gKeyLog, LogLevel::Warning,
+            ("%p   NativeKey::HandleAppCommandMessage(), WARNING, not handled "
+             "due to "
+             "destroyed the widget",
+             this));
+    return false;
+  }
+
+  // NOTE: Typical behavior of WM_APPCOMMAND caused by key is, WM_APPCOMMAND
+  //       message is _sent_ first.  Then, the DefaultWndProc will _post_
+  //       WM_KEYDOWN message and WM_KEYUP message if the keycode for the
+  //       command is available (i.e., mVirtualKeyCode is not 0).
+
+  // NOTE: IntelliType (Microsoft's keyboard utility software) always consumes
+  //       WM_KEYDOWN and WM_KEYUP.
+
+  // Let's dispatch keydown message before our chrome handles the command
+  // when the message is caused by a keypress.  This behavior makes handling
+  // WM_APPCOMMAND be a default action of the keydown event.  This means that
+  // web applications can handle multimedia keys and prevent our default action.
+  // This allow web applications to provide better UX for multimedia keyboard
+  // users.
+  bool dispatchKeyEvent = (GET_DEVICE_LPARAM(mMsg.lParam) == FAPPCOMMAND_KEY);
+  if (dispatchKeyEvent) {
+    // If a plug-in window has focus but it didn't consume the message, our
+    // window receive WM_APPCOMMAND message.  In this case, we shouldn't
+    // dispatch KeyboardEvents because an event handler may access the
+    // plug-in process synchronously.
+    dispatchKeyEvent =
+        WinUtils::IsOurProcessWindow(reinterpret_cast<HWND>(mMsg.wParam));
+  }
+
+  bool consumed = false;
+
+  if (dispatchKeyEvent) {
+    nsresult rv = mDispatcher->BeginNativeInputTransaction();
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      MOZ_LOG(gKeyLog, LogLevel::Error,
+              ("%p   NativeKey::HandleAppCommandMessage(), FAILED due to "
+               "BeginNativeInputTransaction() failure",
+               this));
+      return true;
+    }
+    MOZ_LOG(gKeyLog, LogLevel::Info,
+            ("%p   NativeKey::HandleAppCommandMessage(), initializing keydown "
+             "event...",
+             this));
+    WidgetKeyboardEvent keydownEvent(true, eKeyDown, mWidget);
+    nsEventStatus status = InitKeyEvent(keydownEvent, mModKeyState);
+    MOZ_LOG(gKeyLog, LogLevel::Info,
+            ("%p   NativeKey::HandleAppCommandMessage(), tries to dispatch "
+             "keydown event...",
+             this));
+    // NOTE: If the keydown event is consumed by web contents, we shouldn't
+    //       continue to handle the command.
+    if (!mDispatcher->DispatchKeyboardEvent(eKeyDown, keydownEvent, status,
+                                            const_cast<NativeKey*>(this))) {
+      MOZ_LOG(gKeyLog, LogLevel::Info,
+              ("%p   NativeKey::HandleAppCommandMessage(), keydown event isn't "
+               "dispatched",
+               this));
+      // If keyboard event wasn't fired, there must be composition.
+      // So, we don't need to dispatch a command event.
+      return true;
+    }
+    consumed = status == nsEventStatus_eConsumeNoDefault;
+    MOZ_LOG(gKeyLog, LogLevel::Info,
+            ("%p   NativeKey::HandleAppCommandMessage(), keydown event was "
+             "dispatched, consumed=%s",
+             this, GetBoolName(consumed)));
+    sDispatchedKeyOfAppCommand = mVirtualKeyCode;
+    if (mWidget->Destroyed()) {
+      MOZ_LOG(
+          gKeyLog, LogLevel::Info,
+          ("%p   NativeKey::HandleAppCommandMessage(), keydown event caused "
+           "destroying the widget",
+           this));
+      return true;
+    }
+  }
+
+  // Dispatch a command event or a content command event if the command is
+  // supported.
+  if (!consumed) {
+    uint32_t appCommand = GET_APPCOMMAND_LPARAM(mMsg.lParam);
+    EventMessage contentCommandMessage = eVoidEvent;
+    switch (appCommand) {
+      case APPCOMMAND_BROWSER_BACKWARD:
+      case APPCOMMAND_BROWSER_FORWARD:
+      case APPCOMMAND_BROWSER_REFRESH:
+      case APPCOMMAND_BROWSER_STOP:
+      case APPCOMMAND_BROWSER_SEARCH:
+      case APPCOMMAND_BROWSER_FAVORITES:
+      case APPCOMMAND_BROWSER_HOME:
+      case APPCOMMAND_CLOSE:
+      case APPCOMMAND_FIND:
+      case APPCOMMAND_HELP:
+      case APPCOMMAND_NEW:
+      case APPCOMMAND_OPEN:
+      case APPCOMMAND_PRINT:
+      case APPCOMMAND_SAVE:
+      case APPCOMMAND_FORWARD_MAIL:
+      case APPCOMMAND_REPLY_TO_MAIL:
+      case APPCOMMAND_SEND_MAIL:
+      case APPCOMMAND_MEDIA_NEXTTRACK:
+      case APPCOMMAND_MEDIA_PREVIOUSTRACK:
+      case APPCOMMAND_MEDIA_STOP:
+      case APPCOMMAND_MEDIA_PLAY_PAUSE:
+        // We shouldn't consume the message always because if we don't handle
+        // the message, the sender (typically, utility of keyboard or mouse)
+        // may send other key messages which indicate well known shortcut key.
+        consumed = DispatchCommandEvent(appCommand);
+        break;
+
+      // Use content command for following commands:
+      case APPCOMMAND_COPY:
+        contentCommandMessage = eContentCommandCopy;
+        break;
+      case APPCOMMAND_CUT:
+        contentCommandMessage = eContentCommandCut;
+        break;
+      case APPCOMMAND_PASTE:
+        contentCommandMessage = eContentCommandPaste;
+        break;
+      case APPCOMMAND_REDO:
+        contentCommandMessage = eContentCommandRedo;
+        break;
+      case APPCOMMAND_UNDO:
+        contentCommandMessage = eContentCommandUndo;
+        break;
+    }
+
+    if (contentCommandMessage) {
+      MOZ_ASSERT(!mWidget->Destroyed());
+      WidgetContentCommandEvent contentCommandEvent(true, contentCommandMessage,
+                                                    mWidget);
+      MOZ_LOG(
+          gKeyLog, LogLevel::Info,
+          ("%p   NativeKey::HandleAppCommandMessage(), dispatching %s event...",
+           this, ToChar(contentCommandMessage)));
+      mWidget->DispatchWindowEvent(contentCommandEvent);
+      MOZ_LOG(gKeyLog, LogLevel::Info,
+              ("%p   NativeKey::HandleAppCommandMessage(), dispatched %s event",
+               this, ToChar(contentCommandMessage)));
+      consumed = true;
+
+      if (mWidget->Destroyed()) {
+        MOZ_LOG(gKeyLog, LogLevel::Info,
+                ("%p   NativeKey::HandleAppCommandMessage(), %s event caused "
+                 "destroying the widget",
+                 this, ToChar(contentCommandMessage)));
+        return true;
+      }
+    } else {
+      MOZ_LOG(gKeyLog, LogLevel::Info,
+              ("%p   NativeKey::HandleAppCommandMessage(), doesn't dispatch "
+               "content "
+               "command event",
+               this));
+    }
+  }
+
+  // Dispatch a keyup event if the command is caused by pressing a key and
+  // the key isn't mapped to a virtual keycode.
+  if (dispatchKeyEvent && !mVirtualKeyCode) {
+    MOZ_ASSERT(!mWidget->Destroyed());
+    nsresult rv = mDispatcher->BeginNativeInputTransaction();
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      MOZ_LOG(gKeyLog, LogLevel::Error,
+              ("%p   NativeKey::HandleAppCommandMessage(), FAILED due to "
+               "BeginNativeInputTransaction() failure",
+               this));
+      return true;
+    }
+    MOZ_LOG(gKeyLog, LogLevel::Info,
+            ("%p   NativeKey::HandleAppCommandMessage(), initializing keyup "
+             "event...",
+             this));
+    WidgetKeyboardEvent keyupEvent(true, eKeyUp, mWidget);
+    nsEventStatus status = InitKeyEvent(keyupEvent, mModKeyState);
+    MOZ_LOG(gKeyLog, LogLevel::Info,
+            ("%p   NativeKey::HandleAppCommandMessage(), dispatching keyup "
+             "event...",
+             this));
+    // NOTE: Ignore if the keyup event is consumed because keyup event
+    //       represents just a physical key event state change.
+    mDispatcher->DispatchKeyboardEvent(eKeyUp, keyupEvent, status,
+                                       const_cast<NativeKey*>(this));
+    MOZ_LOG(
+        gKeyLog, LogLevel::Info,
+        ("%p   NativeKey::HandleAppCommandMessage(), dispatched keyup event",
+         this));
+    if (mWidget->Destroyed()) {
+      MOZ_LOG(gKeyLog, LogLevel::Info,
+              ("%p   NativeKey::HandleAppCommandMessage(), keyup event caused "
+               "destroying the widget",
+               this));
+      return true;
+    }
+  }
+
+  return consumed;
+}
+
+bool NativeKey::HandleKeyDownMessage(bool* aEventDispatched) const {
+  MOZ_ASSERT(IsKeyDownMessage());
+
+  if (aEventDispatched) {
+    *aEventDispatched = false;
+  }
+
+  if (sDispatchedKeyOfAppCommand &&
+      sDispatchedKeyOfAppCommand == mOriginalVirtualKeyCode) {
+    // The multimedia key event has already been dispatch from
+    // HandleAppCommandMessage().
+    sDispatchedKeyOfAppCommand = 0;
+    MOZ_LOG(gKeyLog, LogLevel::Info,
+            ("%p   NativeKey::HandleKeyDownMessage(), doesn't dispatch keydown "
+             "event due to already dispatched from HandleAppCommandMessage(), ",
+             this));
+    if (RedirectedKeyDownMessageManager::IsRedirectedMessage(mMsg)) {
+      RedirectedKeyDownMessageManager::Forget();
+    }
+    return true;
+  }
+
+  if (IsReservedBySystem()) {
+    MOZ_LOG(gKeyLog, LogLevel::Info,
+            ("%p   NativeKey::HandleKeyDownMessage(), doesn't dispatch keydown "
+             "event because the key combination is reserved by the system",
+             this));
+    if (RedirectedKeyDownMessageManager::IsRedirectedMessage(mMsg)) {
+      RedirectedKeyDownMessageManager::Forget();
+    }
+    return false;
+  }
+
+  if (sPendingHighSurrogate) {
+    MOZ_LOG(gKeyLog, LogLevel::Info,
+            ("%p   NativeKey::HandleKeyDownMessage(), doesn't dispatch keydown "
+             "event because the key introduced only a high surrotate, so we "
+             "should wait the following low surrogate input",
+             this));
+    if (RedirectedKeyDownMessageManager::IsRedirectedMessage(mMsg)) {
+      RedirectedKeyDownMessageManager::Forget();
+    }
+    return false;
+  }
+
+  // If the widget has gone, we should do nothing.
+  if (mWidget->Destroyed()) {
+    MOZ_LOG(
+        gKeyLog, LogLevel::Warning,
+        ("%p   NativeKey::HandleKeyDownMessage(), WARNING, not handled due to "
+         "destroyed the widget",
+         this));
+    if (RedirectedKeyDownMessageManager::IsRedirectedMessage(mMsg)) {
+      RedirectedKeyDownMessageManager::Forget();
+    }
+    return false;
+  }
+
+  bool defaultPrevented = false;
+  if (mFakeCharMsgs ||
+      !RedirectedKeyDownMessageManager::IsRedirectedMessage(mMsg)) {
+    nsresult rv = mDispatcher->BeginNativeInputTransaction();
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      MOZ_LOG(gKeyLog, LogLevel::Error,
+              ("%p   NativeKey::HandleKeyDownMessage(), FAILED due to "
+               "BeginNativeInputTransaction() failure",
+               this));
+      return true;
+    }
+
+    bool isIMEEnabled = WinUtils::IsIMEEnabled(mWidget->GetInputContext());
+
+    MOZ_LOG(gKeyLog, LogLevel::Debug,
+            ("%p   NativeKey::HandleKeyDownMessage(), initializing keydown "
+             "event...",
+             this));
+
+    WidgetKeyboardEvent keydownEvent(true, eKeyDown, mWidget);
+    nsEventStatus status = InitKeyEvent(keydownEvent, mModKeyState);
+    MOZ_LOG(
+        gKeyLog, LogLevel::Info,
+        ("%p   NativeKey::HandleKeyDownMessage(), dispatching keydown event...",
+         this));
+    bool dispatched = mDispatcher->DispatchKeyboardEvent(
+        eKeyDown, keydownEvent, status, const_cast<NativeKey*>(this));
+    if (aEventDispatched) {
+      *aEventDispatched = dispatched;
+    }
+    if (!dispatched) {
+      // If the keydown event wasn't fired, there must be composition.
+      // we don't need to do anything anymore.
+      MOZ_LOG(
+          gKeyLog, LogLevel::Info,
+          ("%p   NativeKey::HandleKeyDownMessage(), doesn't dispatch keypress "
+           "event(s) because keydown event isn't dispatched actually",
+           this));
+      return false;
+    }
+    defaultPrevented = status == nsEventStatus_eConsumeNoDefault;
+
+    if (mWidget->Destroyed() || IsFocusedWindowChanged()) {
+      MOZ_LOG(gKeyLog, LogLevel::Info,
+              ("%p   NativeKey::HandleKeyDownMessage(), keydown event caused "
+               "destroying the widget",
+               this));
+      return true;
+    }
+
+    MOZ_LOG(
+        gKeyLog, LogLevel::Info,
+        ("%p   NativeKey::HandleKeyDownMessage(), dispatched keydown event, "
+         "dispatched=%s, defaultPrevented=%s",
+         this, GetBoolName(dispatched), GetBoolName(defaultPrevented)));
+
+    // If IMC wasn't associated to the window but is associated it now (i.e.,
+    // focus is moved from a non-editable editor to an editor by keydown
+    // event handler), WM_CHAR and WM_SYSCHAR shouldn't cause first character
+    // inputting if IME is opened.  But then, we should redirect the native
+    // keydown message to IME.
+    // However, note that if focus has been already moved to another
+    // application, we shouldn't redirect the message to it because the keydown
+    // message is processed by us, so, nobody shouldn't process it.
+    HWND focusedWnd = ::GetFocus();
+    if (!defaultPrevented && !mFakeCharMsgs && focusedWnd && !isIMEEnabled &&
+        WinUtils::IsIMEEnabled(mWidget->GetInputContext())) {
+      RedirectedKeyDownMessageManager::RemoveNextCharMessage(focusedWnd);
+
+      INPUT keyinput;
+      keyinput.type = INPUT_KEYBOARD;
+      keyinput.ki.wVk = mOriginalVirtualKeyCode;
+      keyinput.ki.wScan = mScanCode;
+      keyinput.ki.dwFlags = KEYEVENTF_SCANCODE;
+      if (mIsExtended) {
+        keyinput.ki.dwFlags |= KEYEVENTF_EXTENDEDKEY;
+      }
+      keyinput.ki.time = 0;
+      keyinput.ki.dwExtraInfo = 0;
+
+      RedirectedKeyDownMessageManager::WillRedirect(mMsg, defaultPrevented);
+
+      MOZ_LOG(gKeyLog, LogLevel::Info,
+              ("%p   NativeKey::HandleKeyDownMessage(), redirecting %s...",
+               this, ToString(mMsg).get()));
+
+      ::SendInput(1, &keyinput, sizeof(keyinput));
+
+      MOZ_LOG(gKeyLog, LogLevel::Info,
+              ("%p   NativeKey::HandleKeyDownMessage(), redirected %s", this,
+               ToString(mMsg).get()));
+
+      // Return here.  We shouldn't dispatch keypress event for this WM_KEYDOWN.
+      // If it's needed, it will be dispatched after next (redirected)
+      // WM_KEYDOWN.
+      return true;
+    }
+  } else {
+    MOZ_LOG(gKeyLog, LogLevel::Info,
+            ("%p   NativeKey::HandleKeyDownMessage(), received a redirected %s",
+             this, ToString(mMsg).get()));
+
+    defaultPrevented = RedirectedKeyDownMessageManager::DefaultPrevented();
+    // If this is redirected keydown message, we have dispatched the keydown
+    // event already.
+    if (aEventDispatched) {
+      *aEventDispatched = true;
+    }
+  }
+
+  RedirectedKeyDownMessageManager::Forget();
+
+  MOZ_ASSERT(!mWidget->Destroyed());
+
+  // If the key was processed by IME and didn't cause WM_(SYS)CHAR messages, we
+  // shouldn't dispatch keypress event.
+  if (mOriginalVirtualKeyCode == VK_PROCESSKEY &&
+      !IsFollowedByPrintableCharOrSysCharMessage()) {
+    MOZ_LOG(gKeyLog, LogLevel::Info,
+            ("%p   NativeKey::HandleKeyDownMessage(), not dispatching keypress "
+             "event because the key was already handled by IME, "
+             "defaultPrevented=%s",
+             this, GetBoolName(defaultPrevented)));
+    return defaultPrevented;
+  }
+
+  if (defaultPrevented) {
+    MOZ_LOG(gKeyLog, LogLevel::Info,
+            ("%p   NativeKey::HandleKeyDownMessage(), not dispatching keypress "
+             "event because preceding keydown event was consumed",
+             this));
+    return true;
+  }
+
+  MOZ_ASSERT(!mCharMessageHasGone,
+             "If following char message was consumed by somebody, "
+             "keydown event should have been consumed before dispatch");
+
+  // If mCommittedCharsAndModifiers was initialized with following char
+  // messages, we should dispatch keypress events with its information.
+  if (IsFollowedByPrintableCharOrSysCharMessage()) {
+    MOZ_LOG(gKeyLog, LogLevel::Info,
+            ("%p   NativeKey::HandleKeyDownMessage(), tries to be dispatching "
+             "keypress events with retrieved char messages...",
+             this));
+    return DispatchKeyPressEventsWithRetrievedCharMessages();
+  }
+
+  // If we won't be getting a WM_CHAR, WM_SYSCHAR or WM_DEADCHAR, synthesize a
+  // keypress for almost all keys
+  if (NeedsToHandleWithoutFollowingCharMessages()) {
+    MOZ_LOG(gKeyLog, LogLevel::Info,
+            ("%p   NativeKey::HandleKeyDownMessage(), tries to be dispatching "
+             "keypress events...",
+             this));
+    return DispatchKeyPressEventsWithoutCharMessage();
+  }
+
+  // If WM_KEYDOWN of VK_PACKET isn't followed by WM_CHAR, we don't need to
+  // dispatch keypress events.
+  if (mVirtualKeyCode == VK_PACKET) {
+    MOZ_LOG(gKeyLog, LogLevel::Info,
+            ("%p   NativeKey::HandleKeyDownMessage(), not dispatching keypress "
+             "event "
+             "because the key is VK_PACKET and there are no char messages",
+             this));
+    return false;
+  }
+
+  if (!mModKeyState.IsControl() && !mModKeyState.IsAlt() &&
+      !mModKeyState.IsWin() && mIsPrintableKey) {
+    // If this is simple KeyDown event but next message is not WM_CHAR,
+    // this event may not input text, so we should ignore this event.
+    // See bug 314130.
+    MOZ_LOG(gKeyLog, LogLevel::Info,
+            ("%p   NativeKey::HandleKeyDownMessage(), not dispatching keypress "
+             "event "
+             "because the key event is simple printable key's event but not "
+             "followed "
+             "by char messages",
+             this));
+    return false;
+  }
+
+  if (mIsDeadKey) {
+    MOZ_LOG(gKeyLog, LogLevel::Info,
+            ("%p   NativeKey::HandleKeyDownMessage(), not dispatching keypress "
+             "event "
+             "because the key is a dead key and not followed by char messages",
+             this));
+    return false;
+  }
+
+  MOZ_LOG(gKeyLog, LogLevel::Info,
+          ("%p   NativeKey::HandleKeyDownMessage(), tries to be dispatching "
+           "keypress events due to no following char messages...",
+           this));
+  return DispatchKeyPressEventsWithoutCharMessage();
+}
+
+bool NativeKey::HandleCharMessage(bool* aEventDispatched) const {
+  MOZ_ASSERT(IsCharOrSysCharMessage(mMsg));
+  return HandleCharMessage(mMsg, aEventDispatched);
+}
+
+bool NativeKey::HandleCharMessage(const MSG& aCharMsg,
+                                  bool* aEventDispatched) const {
+  MOZ_ASSERT(IsKeyDownMessage() || IsCharOrSysCharMessage(mMsg));
+  MOZ_ASSERT(IsCharOrSysCharMessage(aCharMsg.message));
+
+  if (aEventDispatched) {
+    *aEventDispatched = false;
+  }
+
+  if ((IsCharOrSysCharMessage(mMsg) || IsEnterKeyPressCharMessage(mMsg)) &&
+      IsAnotherInstanceRemovingCharMessage()) {
+    MOZ_LOG(
+        gKeyLog, LogLevel::Warning,
+        ("%p   NativeKey::HandleCharMessage(), WARNING, does nothing because "
+         "the message should be handled in another instance removing this "
+         "message",
+         this));
+    // Consume this for now because it will be handled by another instance.
+    return true;
+  }
+
+  // If the key combinations is reserved by the system, we shouldn't dispatch
+  // eKeyPress event for it and passes the message to next wndproc.
+  if (IsReservedBySystem()) {
+    MOZ_LOG(gKeyLog, LogLevel::Info,
+            ("%p   NativeKey::HandleCharMessage(), doesn't dispatch keypress "
+             "event because the key combination is reserved by the system",
+             this));
+    return false;
+  }
+
+  // If the widget has gone, we should do nothing.
+  if (mWidget->Destroyed()) {
+    MOZ_LOG(gKeyLog, LogLevel::Warning,
+            ("%p   NativeKey::HandleCharMessage(), WARNING, not handled due to "
+             "destroyed the widget",
+             this));
+    return false;
+  }
+
+  // When a control key is inputted by a key, it should be handled without
+  // WM_*CHAR messages at receiving WM_*KEYDOWN message.  So, when we receive
+  // WM_*CHAR message directly, we see a control character here.
+  // Note that when the char is '\r', it means that the char message should
+  // cause "Enter" keypress event for inserting a line break.
+  if (IsControlCharMessage(aCharMsg) && !IsEnterKeyPressCharMessage(aCharMsg)) {
+    // In this case, we don't need to dispatch eKeyPress event because:
+    // 1. We're the only browser which dispatches "keypress" event for
+    //    non-printable characters (Although, both Chrome and Edge dispatch
+    //    "keypress" event for some keys accidentally.  For example, "IntlRo"
+    //    key with Ctrl of Japanese keyboard layout).
+    // 2. Currently, we may handle shortcut keys with "keydown" event if
+    //    it's reserved or something.  So, we shouldn't dispatch "keypress"
+    //    event without it.
+    // Note that this does NOT mean we stop dispatching eKeyPress event for
+    // key presses causes a control character when Ctrl is pressed.  In such
+    // case, DispatchKeyPressEventsWithoutCharMessage() dispatches eKeyPress
+    // instead of this method.
+    MOZ_LOG(
+        gKeyLog, LogLevel::Info,
+        ("%p   NativeKey::HandleCharMessage(), doesn't dispatch keypress "
+         "event because received a control character input without WM_KEYDOWN",
+         this));
+    return false;
+  }
+
+  // XXXmnakano I think that if mMsg is WM_CHAR, i.e., it comes without
+  //            preceding WM_KEYDOWN, we should should dispatch composition
+  //            events instead of eKeyPress because they are not caused by
+  //            actual keyboard operation.
+
+  // First, handle normal text input or non-printable key case here.
+  WidgetKeyboardEvent keypressEvent(true, eKeyPress, mWidget);
+  if (IsEnterKeyPressCharMessage(aCharMsg)) {
+    keypressEvent.mKeyCode = NS_VK_RETURN;
+  } else {
+    keypressEvent.mCharCode = static_cast<uint32_t>(aCharMsg.wParam);
+  }
+  nsresult rv = mDispatcher->BeginNativeInputTransaction();
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    MOZ_LOG(gKeyLog, LogLevel::Error,
+            ("%p   NativeKey::HandleCharMessage(), FAILED due to "
+             "BeginNativeInputTransaction() failure",
+             this));
+    return true;
+  }
+
+  MOZ_LOG(gKeyLog, LogLevel::Debug,
+          ("%p   NativeKey::HandleCharMessage(), initializing keypress "
+           "event...",
+           this));
+
+  ModifierKeyState modKeyState(mModKeyState);
+  // When AltGr is pressed, both Alt and Ctrl are active.  However, when they
+  // are active, TextEditor won't treat the keypress event as inputting a
+  // character.  Therefore, when AltGr is pressed and the key tries to input
+  // a character, let's set them to false.
+  if (modKeyState.IsControl() && modKeyState.IsAlt() &&
+      IsPrintableCharMessage(aCharMsg)) {
+    modKeyState.Unset(MODIFIER_ALT | MODIFIER_CONTROL);
+  }
+  nsEventStatus status = InitKeyEvent(keypressEvent, modKeyState);
+  MOZ_LOG(gKeyLog, LogLevel::Info,
+          ("%p   NativeKey::HandleCharMessage(), dispatching keypress event...",
+           this));
+  bool dispatched = mDispatcher->MaybeDispatchKeypressEvents(
+      keypressEvent, status, const_cast<NativeKey*>(this));
+  if (aEventDispatched) {
+    *aEventDispatched = dispatched;
+  }
+  if (mWidget->Destroyed()) {
+    MOZ_LOG(gKeyLog, LogLevel::Info,
+            ("%p   NativeKey::HandleCharMessage(), keypress event caused "
+             "destroying the widget",
+             this));
+    return true;
+  }
+  bool consumed = status == nsEventStatus_eConsumeNoDefault;
+  MOZ_LOG(gKeyLog, LogLevel::Info,
+          ("%p   NativeKey::HandleCharMessage(), dispatched keypress event, "
+           "dispatched=%s, consumed=%s",
+           this, GetBoolName(dispatched), GetBoolName(consumed)));
+  return consumed;
+}
+
+bool NativeKey::HandleKeyUpMessage(bool* aEventDispatched) const {
+  MOZ_ASSERT(IsKeyUpMessage());
+
+  if (aEventDispatched) {
+    *aEventDispatched = false;
+  }
+
+  // If the key combinations is reserved by the system, we shouldn't dispatch
+  // eKeyUp event for it and passes the message to next wndproc.
+  if (IsReservedBySystem()) {
+    MOZ_LOG(gKeyLog, LogLevel::Info,
+            ("%p   NativeKey::HandleKeyUpMessage(), doesn't dispatch keyup "
+             "event because the key combination is reserved by the system",
+             this));
+    return false;
+  }
+
+  if (sPendingHighSurrogate) {
+    MOZ_LOG(gKeyLog, LogLevel::Info,
+            ("%p   NativeKey::HandleKeyUpMessage(), doesn't dispatch keyup "
+             "event because the key introduced only a high surrotate, so we "
+             "should wait the following low surrogate input",
+             this));
+    return false;
+  }
+
+  // If the widget has gone, we should do nothing.
+  if (mWidget->Destroyed()) {
+    MOZ_LOG(
+        gKeyLog, LogLevel::Warning,
+        ("%p   NativeKey::HandleKeyUpMessage(), WARNING, not handled due to "
+         "destroyed the widget",
+         this));
+    return false;
+  }
+
+  nsresult rv = mDispatcher->BeginNativeInputTransaction();
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    MOZ_LOG(gKeyLog, LogLevel::Error,
+            ("%p   NativeKey::HandleKeyUpMessage(), FAILED due to "
+             "BeginNativeInputTransaction() failure",
+             this));
+    return true;
+  }
+
+  MOZ_LOG(gKeyLog, LogLevel::Debug,
+          ("%p   NativeKey::HandleKeyUpMessage(), initializing keyup event...",
+           this));
+  WidgetKeyboardEvent keyupEvent(true, eKeyUp, mWidget);
+  nsEventStatus status = InitKeyEvent(keyupEvent, mModKeyState);
+  MOZ_LOG(gKeyLog, LogLevel::Info,
+          ("%p   NativeKey::HandleKeyUpMessage(), dispatching keyup event...",
+           this));
+  bool dispatched = mDispatcher->DispatchKeyboardEvent(
+      eKeyUp, keyupEvent, status, const_cast<NativeKey*>(this));
+  if (aEventDispatched) {
+    *aEventDispatched = dispatched;
+  }
+  if (mWidget->Destroyed()) {
+    MOZ_LOG(gKeyLog, LogLevel::Info,
+            ("%p   NativeKey::HandleKeyUpMessage(), keyup event caused "
+             "destroying the widget",
+             this));
+    return true;
+  }
+  bool consumed = status == nsEventStatus_eConsumeNoDefault;
+  MOZ_LOG(gKeyLog, LogLevel::Info,
+          ("%p   NativeKey::HandleKeyUpMessage(), dispatched keyup event, "
+           "dispatched=%s, consumed=%s",
+           this, GetBoolName(dispatched), GetBoolName(consumed)));
+  return consumed;
+}
+
+bool NativeKey::NeedsToHandleWithoutFollowingCharMessages() const {
+  MOZ_ASSERT(IsKeyDownMessage());
+
+  // If the key combination is reserved by the system, the caller shouldn't
+  // do anything with following WM_*CHAR messages.  So, let's return true here.
+  if (IsReservedBySystem()) {
+    return true;
+  }
+
+  // If the keydown message is generated for inputting some Unicode characters
+  // via SendInput() API, we need to handle it only with WM_*CHAR messages.
+  if (mVirtualKeyCode == VK_PACKET) {
+    return false;
+  }
+
+  // If following char message is for a control character, it should be handled
+  // without WM_CHAR message.  This is typically Ctrl + [a-z].
+  if (mFollowingCharMsgs.Length() == 1 &&
+      IsControlCharMessage(mFollowingCharMsgs[0])) {
+    return true;
+  }
+
+  // If keydown message is followed by WM_CHAR or WM_SYSCHAR whose wParam isn't
+  // a control character, we should dispatch keypress event with the char
+  // message even with any modifier state.
+  if (IsFollowedByPrintableCharOrSysCharMessage()) {
+    return false;
+  }
+
+  // If any modifier keys which may cause printable keys becoming non-printable
+  // are not pressed, we don't need special handling for the key.
+  // Note that if the key does not produce a character with AltGr and when
+  // AltGr key is pressed, we don't need to dispatch eKeyPress event for it
+  // because AltGr shouldn't be used for a modifier for a shortcut without
+  // Ctrl, Alt or Win.  That means that we should treat it in same path for
+  // Shift key.
+  if (!mModKeyState.IsControl() && !mModKeyState.IsAlt() &&
+      !mModKeyState.IsWin()) {
+    return false;
+  }
+
+  // If the key event causes dead key event, we don't need to dispatch keypress
+  // event.
+  if (mIsDeadKey && mCommittedCharsAndModifiers.IsEmpty()) {
+    return false;
+  }
+
+  // Even if the key is a printable key, it might cause non-printable character
+  // input with modifier key(s).
+  return mIsPrintableKey;
+}
+
+static nsCString GetResultOfInSendMessageEx() {
+  DWORD ret = ::InSendMessageEx(nullptr);
+  if (!ret) {
+    return "ISMEX_NOSEND"_ns;
+  }
+  nsCString result;
+  if (ret & ISMEX_CALLBACK) {
+    result = "ISMEX_CALLBACK";
+  }
+  if (ret & ISMEX_NOTIFY) {
+    if (!result.IsEmpty()) {
+      result += " | ";
+    }
+    result += "ISMEX_NOTIFY";
+  }
+  if (ret & ISMEX_REPLIED) {
+    if (!result.IsEmpty()) {
+      result += " | ";
+    }
+    result += "ISMEX_REPLIED";
+  }
+  if (ret & ISMEX_SEND) {
+    if (!result.IsEmpty()) {
+      result += " | ";
+    }
+    result += "ISMEX_SEND";
+  }
+  return result;
+}
+
+bool NativeKey::MayBeSameCharMessage(const MSG& aCharMsg1,
+                                     const MSG& aCharMsg2) const {
+  // NOTE: Although, we don't know when this case occurs, the scan code value
+  //       in lParam may be changed from 0 to something.  The changed value
+  //       is different from the scan code of handling keydown message.
+  static const LPARAM kScanCodeMask = 0x00FF0000;
+  return aCharMsg1.message == aCharMsg2.message &&
+         aCharMsg1.wParam == aCharMsg2.wParam &&
+         (aCharMsg1.lParam & ~kScanCodeMask) ==
+             (aCharMsg2.lParam & ~kScanCodeMask);
+}
+
+bool NativeKey::IsSamePhysicalKeyMessage(const MSG& aKeyOrCharMsg1,
+                                         const MSG& aKeyOrCharMsg2) const {
+  if (NS_WARN_IF(aKeyOrCharMsg1.message < WM_KEYFIRST) ||
+      NS_WARN_IF(aKeyOrCharMsg1.message > WM_KEYLAST) ||
+      NS_WARN_IF(aKeyOrCharMsg2.message < WM_KEYFIRST) ||
+      NS_WARN_IF(aKeyOrCharMsg2.message > WM_KEYLAST)) {
+    return false;
+  }
+  return WinUtils::GetScanCode(aKeyOrCharMsg1.lParam) ==
+             WinUtils::GetScanCode(aKeyOrCharMsg2.lParam) &&
+         WinUtils::IsExtendedScanCode(aKeyOrCharMsg1.lParam) ==
+             WinUtils::IsExtendedScanCode(aKeyOrCharMsg2.lParam);
+}
+
+bool NativeKey::GetFollowingCharMessage(MSG& aCharMsg) {
+  MOZ_ASSERT(IsKeyDownMessage());
+
+  aCharMsg.message = WM_NULL;
+
+  if (mFakeCharMsgs) {
+    for (size_t i = 0; i < mFakeCharMsgs->Length(); i++) {
+      FakeCharMsg& fakeCharMsg = mFakeCharMsgs->ElementAt(i);
+      if (fakeCharMsg.mConsumed) {
+        continue;
+      }
+      MSG charMsg = fakeCharMsg.GetCharMsg(mMsg.hwnd);
+      fakeCharMsg.mConsumed = true;
+      if (!IsCharMessage(charMsg)) {
+        return false;
+      }
+      aCharMsg = charMsg;
+      return true;
+    }
+    return false;
+  }
+
+  // If next key message is not char message, we should give up to find a
+  // related char message for the handling keydown event for now.
+  // Note that it's possible other applications may send other key message
+  // after we call TranslateMessage(). That may cause PeekMessage() failing
+  // to get char message for the handling keydown message.
+  MSG nextKeyMsg;
+  if (!WinUtils::PeekMessage(&nextKeyMsg, mMsg.hwnd, WM_KEYFIRST, WM_KEYLAST,
+                             PM_NOREMOVE | PM_NOYIELD) ||
+      !IsCharMessage(nextKeyMsg)) {
+    MOZ_LOG(gKeyLog, LogLevel::Debug,
+            ("%p   NativeKey::GetFollowingCharMessage(), there are no char "
+             "messages",
+             this));
+    return false;
+  }
+  const MSG kFoundCharMsg = nextKeyMsg;
+
+  AutoRestore<MSG> saveLastRemovingMsg(mRemovingMsg);
+  mRemovingMsg = nextKeyMsg;
+
+  mReceivedMsg = sEmptyMSG;
+  AutoRestore<MSG> ensureToClearRecivedMsg(mReceivedMsg);
+
+  // On Metrofox, PeekMessage() sometimes returns WM_NULL even if we specify
+  // the message range.  So, if it returns WM_NULL, we should retry to get
+  // the following char message it was found above.
+  for (uint32_t i = 0; i < 50; i++) {
+    MSG removedMsg, nextKeyMsgInAllWindows;
+    bool doCrash = false;
+    if (!WinUtils::PeekMessage(&removedMsg, mMsg.hwnd, nextKeyMsg.message,
+                               nextKeyMsg.message, PM_REMOVE | PM_NOYIELD)) {
+      // We meets unexpected case.  We should collect the message queue state
+      // and crash for reporting the bug.
+      doCrash = true;
+
+      // If another instance was created for the removing message during trying
+      // to remove a char message, the instance didn't handle it for preventing
+      // recursive handling.  So, let's handle it in this instance.
+      if (!IsEmptyMSG(mReceivedMsg)) {
+        // If focus is moved to different window, we shouldn't handle it on
+        // the widget.  Let's discard it for now.
+        if (mReceivedMsg.hwnd != nextKeyMsg.hwnd) {
+          MOZ_LOG(
+              gKeyLog, LogLevel::Warning,
+              ("%p   NativeKey::GetFollowingCharMessage(), WARNING, received a "
+               "char message during removing it from the queue, but it's for "
+               "different window, mReceivedMsg=%s, nextKeyMsg=%s, "
+               "kFoundCharMsg=%s",
+               this, ToString(mReceivedMsg).get(), ToString(nextKeyMsg).get(),
+               ToString(kFoundCharMsg).get()));
+          // There might still exist char messages, the loop of calling
+          // this method should be continued.
+          aCharMsg.message = WM_NULL;
+          return true;
+        }
+        // Even if the received message is different from what we tried to
+        // remove from the queue, let's take the received message as a part of
+        // the result of this key sequence.
+        if (mReceivedMsg.message != nextKeyMsg.message ||
+            mReceivedMsg.wParam != nextKeyMsg.wParam ||
+            mReceivedMsg.lParam != nextKeyMsg.lParam) {
+          MOZ_LOG(
+              gKeyLog, LogLevel::Warning,
+              ("%p   NativeKey::GetFollowingCharMessage(), WARNING, received a "
+               "char message during removing it from the queue, but it's "
+               "differnt from what trying to remove from the queue, "
+               "aCharMsg=%s, nextKeyMsg=%s, kFoundCharMsg=%s",
+               this, ToString(mReceivedMsg).get(), ToString(nextKeyMsg).get(),
+               ToString(kFoundCharMsg).get()));
+        } else {
+          MOZ_LOG(
+              gKeyLog, LogLevel::Debug,
+              ("%p   NativeKey::GetFollowingCharMessage(), succeeded to "
+               "retrieve next char message via another instance, aCharMsg=%s, "
+               "kFoundCharMsg=%s",
+               this, ToString(mReceivedMsg).get(),
+               ToString(kFoundCharMsg).get()));
+        }
+        aCharMsg = mReceivedMsg;
+        return true;
+      }
+
+      // The char message is redirected to different thread's window by focus
+      // move or something or just cancelled by external application.
+      if (!WinUtils::PeekMessage(&nextKeyMsgInAllWindows, 0, WM_KEYFIRST,
+                                 WM_KEYLAST, PM_NOREMOVE | PM_NOYIELD)) {
+        MOZ_LOG(
+            gKeyLog, LogLevel::Warning,
+            ("%p   NativeKey::GetFollowingCharMessage(), WARNING, failed to "
+             "remove a char message, but it's already gone from all message "
+             "queues, nextKeyMsg=%s, kFoundCharMsg=%s",
+             this, ToString(nextKeyMsg).get(), ToString(kFoundCharMsg).get()));
+        return true;  // XXX should return false in this case
+      }
+      // The next key message is redirected to different window created by our
+      // thread, we should do nothing because we must not have focus.
+      if (nextKeyMsgInAllWindows.hwnd != mMsg.hwnd) {
+        aCharMsg = nextKeyMsgInAllWindows;
+        MOZ_LOG(
+            gKeyLog, LogLevel::Warning,
+            ("%p   NativeKey::GetFollowingCharMessage(), WARNING, failed to "
+             "remove a char message, but found in another message queue, "
+             "nextKeyMsgInAllWindows=%s, nextKeyMsg=%s, kFoundCharMsg=%s",
+             this, ToString(nextKeyMsgInAllWindows).get(),
+             ToString(nextKeyMsg).get(), ToString(kFoundCharMsg).get()));
+        return true;
+      }
+      // If next key message becomes non-char message, this key operation
+      // may have already been consumed or canceled.
+      if (!IsCharMessage(nextKeyMsgInAllWindows)) {
+        MOZ_LOG(
+            gKeyLog, LogLevel::Warning,
+            ("%p   NativeKey::GetFollowingCharMessage(), WARNING, failed to "
+             "remove a char message and next key message becomes non-char "
+             "message, nextKeyMsgInAllWindows=%s, nextKeyMsg=%s, "
+             "kFoundCharMsg=%s",
+             this, ToString(nextKeyMsgInAllWindows).get(),
+             ToString(nextKeyMsg).get(), ToString(kFoundCharMsg).get()));
+        MOZ_ASSERT(!mCharMessageHasGone);
+        mFollowingCharMsgs.Clear();
+        mCharMessageHasGone = true;
+        return false;
+      }
+      // If next key message is still a char message but different key message,
+      // we should treat current key operation is consumed or canceled and
+      // next char message should be handled as an orphan char message later.
+      if (!IsSamePhysicalKeyMessage(nextKeyMsgInAllWindows, kFoundCharMsg)) {
+        MOZ_LOG(
+            gKeyLog, LogLevel::Warning,
+            ("%p   NativeKey::GetFollowingCharMessage(), WARNING, failed to "
+             "remove a char message and next key message becomes differnt "
+             "key's "
+             "char message, nextKeyMsgInAllWindows=%s, nextKeyMsg=%s, "
+             "kFoundCharMsg=%s",
+             this, ToString(nextKeyMsgInAllWindows).get(),
+             ToString(nextKeyMsg).get(), ToString(kFoundCharMsg).get()));
+        MOZ_ASSERT(!mCharMessageHasGone);
+        mFollowingCharMsgs.Clear();
+        mCharMessageHasGone = true;
+        return false;
+      }
+      // If next key message is still a char message but the message is changed,
+      // we should retry to remove the new message with PeekMessage() again.
+      if (nextKeyMsgInAllWindows.message != nextKeyMsg.message) {
+        MOZ_LOG(
+            gKeyLog, LogLevel::Warning,
+            ("%p   NativeKey::GetFollowingCharMessage(), WARNING, failed to "
+             "remove a char message due to message change, let's retry to "
+             "remove the message with newly found char message, "
+             "nextKeyMsgInAllWindows=%s, nextKeyMsg=%s, kFoundCharMsg=%s",
+             this, ToString(nextKeyMsgInAllWindows).get(),
+             ToString(nextKeyMsg).get(), ToString(kFoundCharMsg).get()));
+        nextKeyMsg = nextKeyMsgInAllWindows;
+        continue;
+      }
+      // If there is still existing a char message caused by same physical key
+      // in the queue but PeekMessage(PM_REMOVE) failed to remove it from the
+      // queue, it might be possible that the odd keyboard layout or utility
+      // hooks only PeekMessage(PM_NOREMOVE) and GetMessage().  So, let's try
+      // remove the char message with GetMessage() again.
+      // FYI: The wParam might be different from the found message, but it's
+      //      okay because we assume that odd keyboard layouts return actual
+      //      inputting character at removing the char message.
+      if (WinUtils::GetMessage(&removedMsg, mMsg.hwnd, nextKeyMsg.message,
+                               nextKeyMsg.message)) {
+        MOZ_LOG(
+            gKeyLog, LogLevel::Warning,
+            ("%p   NativeKey::GetFollowingCharMessage(), WARNING, failed to "
+             "remove a char message, but succeeded with GetMessage(), "
+             "removedMsg=%s, kFoundCharMsg=%s",
+             this, ToString(removedMsg).get(), ToString(kFoundCharMsg).get()));
+        // Cancel to crash, but we need to check the removed message value.
+        doCrash = false;
+      }
+      // If we've already removed some WM_NULL messages from the queue and
+      // the found message has already gone from the queue, let's treat the key
+      // as inputting no characters and already consumed.
+      else if (i > 0) {
+        MOZ_LOG(
+            gKeyLog, LogLevel::Warning,
+            ("%p   NativeKey::GetFollowingCharMessage(), WARNING, failed to "
+             "remove a char message, but removed %d WM_NULL messages",
+             this, i));
+        // If the key is a printable key or a control key but tried to input
+        // a character, mark mCharMessageHasGone true for handling the keydown
+        // event as inputting empty string.
+        MOZ_ASSERT(!mCharMessageHasGone);
+        mFollowingCharMsgs.Clear();
+        mCharMessageHasGone = true;
+        return false;
+      }
+      MOZ_LOG(gKeyLog, LogLevel::Error,
+              ("%p   NativeKey::GetFollowingCharMessage(), FAILED, lost target "
+               "message to remove, nextKeyMsg=%s",
+               this, ToString(nextKeyMsg).get()));
+    }
+
+    if (doCrash) {
+      nsPrintfCString info(
+          "\nPeekMessage() failed to remove char message! "
+          "\nActive keyboard layout=0x%p (%s), "
+          "\nHandling message: %s, InSendMessageEx()=%s, "
+          "\nFound message: %s, "
+          "\nWM_NULL has been removed: %d, "
+          "\nNext key message in all windows: %s, "
+          "time=%ld, ",
+          KeyboardLayout::GetInstance()->GetLoadedLayout(),
+          KeyboardLayout::GetInstance()->GetLoadedLayoutName().get(),
+          ToString(mMsg).get(), GetResultOfInSendMessageEx().get(),
+          ToString(kFoundCharMsg).get(), i,
+          ToString(nextKeyMsgInAllWindows).get(), nextKeyMsgInAllWindows.time);
+      CrashReporter::AppendAppNotesToCrashReport(info);
+      MSG nextMsg;
+      if (WinUtils::PeekMessage(&nextMsg, 0, 0, 0, PM_NOREMOVE | PM_NOYIELD)) {
+        nsPrintfCString info("\nNext message in all windows: %s, time=%ld",
+                             ToString(nextMsg).get(), nextMsg.time);
+        CrashReporter::AppendAppNotesToCrashReport(info);
+      } else {
+        CrashReporter::AppendAppNotesToCrashReport(
+            "\nThere is no message in any window"_ns);
+      }
+
+      MOZ_CRASH("We lost the following char message");
+    }
+
+    // We're still not sure why ::PeekMessage() may return WM_NULL even with
+    // its first message and its last message are same message.  However,
+    // at developing Metrofox, we met this case even with usual keyboard
+    // layouts.  So, it might be possible in desktop application or it really
+    // occurs with some odd keyboard layouts which perhaps hook API.
+    if (removedMsg.message == WM_NULL) {
+      MOZ_LOG(gKeyLog, LogLevel::Warning,
+              ("%p   NativeKey::GetFollowingCharMessage(), WARNING, failed to "
+               "remove a char message, instead, removed WM_NULL message, "
+               "removedMsg=%s",
+               this, ToString(removedMsg).get()));
+      // Check if there is the message which we're trying to remove.
+      MSG newNextKeyMsg;
+      if (!WinUtils::PeekMessage(&newNextKeyMsg, mMsg.hwnd, WM_KEYFIRST,
+                                 WM_KEYLAST, PM_NOREMOVE | PM_NOYIELD)) {
+        // If there is no key message, we should mark this keydown as consumed
+        // because the key operation may have already been handled or canceled.
+        MOZ_LOG(
+            gKeyLog, LogLevel::Warning,
+            ("%p   NativeKey::GetFollowingCharMessage(), WARNING, failed to "
+             "remove a char message because it's gone during removing it from "
+             "the queue, nextKeyMsg=%s, kFoundCharMsg=%s",
+             this, ToString(nextKeyMsg).get(), ToString(kFoundCharMsg).get()));
+        MOZ_ASSERT(!mCharMessageHasGone);
+        mFollowingCharMsgs.Clear();
+        mCharMessageHasGone = true;
+        return false;
+      }
+      if (!IsCharMessage(newNextKeyMsg)) {
+        // If next key message becomes a non-char message, we should mark this
+        // keydown as consumed because the key operation may have already been
+        // handled or canceled.
+        MOZ_LOG(
+            gKeyLog, LogLevel::Warning,
+            ("%p   NativeKey::GetFollowingCharMessage(), WARNING, failed to "
+             "remove a char message because it's gone during removing it from "
+             "the queue, nextKeyMsg=%s, newNextKeyMsg=%s, kFoundCharMsg=%s",
+             this, ToString(nextKeyMsg).get(), ToString(newNextKeyMsg).get(),
+             ToString(kFoundCharMsg).get()));
+        MOZ_ASSERT(!mCharMessageHasGone);
+        mFollowingCharMsgs.Clear();
+        mCharMessageHasGone = true;
+        return false;
+      }
+      MOZ_LOG(
+          gKeyLog, LogLevel::Debug,
+          ("%p   NativeKey::GetFollowingCharMessage(), there is the message "
+           "which is being tried to be removed from the queue, trying again...",
+           this));
+      continue;
+    }
+
+    // Typically, this case occurs with WM_DEADCHAR.  If the removed message's
+    // wParam becomes 0, that means that the key event shouldn't cause text
+    // input.  So, let's ignore the strange char message.
+    if (removedMsg.message == nextKeyMsg.message && !removedMsg.wParam) {
+      MOZ_LOG(
+          gKeyLog, LogLevel::Warning,
+          ("%p   NativeKey::GetFollowingCharMessage(), WARNING, succeeded to "
+           "remove a char message, but the removed message's wParam is 0, "
+           "removedMsg=%s",
+           this, ToString(removedMsg).get()));
+      return false;
+    }
+
+    // This is normal case.
+    if (MayBeSameCharMessage(removedMsg, nextKeyMsg)) {
+      aCharMsg = removedMsg;
+      MOZ_LOG(
+          gKeyLog, LogLevel::Debug,
+          ("%p   NativeKey::GetFollowingCharMessage(), succeeded to retrieve "
+           "next char message, aCharMsg=%s",
+           this, ToString(aCharMsg).get()));
+      return true;
+    }
+
+    // Even if removed message is different char message from the found char
+    // message, when the scan code is same, we can assume that the message
+    // is overwritten by somebody who hooks API.  See bug 1336028 comment 0 for
+    // the possible scenarios.
+    if (IsCharMessage(removedMsg) &&
+        IsSamePhysicalKeyMessage(removedMsg, nextKeyMsg)) {
+      aCharMsg = removedMsg;
+      MOZ_LOG(
+          gKeyLog, LogLevel::Warning,
+          ("%p   NativeKey::GetFollowingCharMessage(), WARNING, succeeded to "
+           "remove a char message, but the removed message was changed from "
+           "the found message except their scancode, aCharMsg=%s, "
+           "nextKeyMsg=%s, kFoundCharMsg=%s",
+           this, ToString(aCharMsg).get(), ToString(nextKeyMsg).get(),
+           ToString(kFoundCharMsg).get()));
+      return true;
+    }
+
+    // When found message's wParam is 0 and its scancode is 0xFF, we may remove
+    // usual char message actually.  In such case, we should use the removed
+    // char message.
+    if (IsCharMessage(removedMsg) && !nextKeyMsg.wParam &&
+        WinUtils::GetScanCode(nextKeyMsg.lParam) == 0xFF) {
+      aCharMsg = removedMsg;
+      MOZ_LOG(
+          gKeyLog, LogLevel::Warning,
+          ("%p   NativeKey::GetFollowingCharMessage(), WARNING, succeeded to "
+           "remove a char message, but the removed message was changed from "
+           "the found message but the found message was odd, so, ignoring the "
+           "odd found message and respecting the removed message, aCharMsg=%s, "
+           "nextKeyMsg=%s, kFoundCharMsg=%s",
+           this, ToString(aCharMsg).get(), ToString(nextKeyMsg).get(),
+           ToString(kFoundCharMsg).get()));
+      return true;
+    }
+
+    // NOTE: Although, we don't know when this case occurs, the scan code value
+    //       in lParam may be changed from 0 to something.  The changed value
+    //       is different from the scan code of handling keydown message.
+    MOZ_LOG(
+        gKeyLog, LogLevel::Error,
+        ("%p   NativeKey::GetFollowingCharMessage(), FAILED, removed message "
+         "is really different from what we have already found, removedMsg=%s, "
+         "nextKeyMsg=%s, kFoundCharMsg=%s",
+         this, ToString(removedMsg).get(), ToString(nextKeyMsg).get(),
+         ToString(kFoundCharMsg).get()));
+    nsPrintfCString info(
+        "\nPeekMessage() removed unexpcted char message! "
+        "\nActive keyboard layout=0x%p (%s), "
+        "\nHandling message: %s, InSendMessageEx()=%s, "
+        "\nFound message: %s, "
+        "\nRemoved message: %s, ",
+        KeyboardLayout::GetInstance()->GetLoadedLayout(),
+        KeyboardLayout::GetInstance()->GetLoadedLayoutName().get(),
+        ToString(mMsg).get(), GetResultOfInSendMessageEx().get(),
+        ToString(kFoundCharMsg).get(), ToString(removedMsg).get());
+    CrashReporter::AppendAppNotesToCrashReport(info);
+    // What's the next key message?
+    MSG nextKeyMsgAfter;
+    if (WinUtils::PeekMessage(&nextKeyMsgAfter, mMsg.hwnd, WM_KEYFIRST,
+                              WM_KEYLAST, PM_NOREMOVE | PM_NOYIELD)) {
+      nsPrintfCString info(
+          "\nNext key message after unexpected char message "
+          "removed: %s, ",
+          ToString(nextKeyMsgAfter).get());
+      CrashReporter::AppendAppNotesToCrashReport(info);
+    } else {
+      CrashReporter::AppendAppNotesToCrashReport(
+          nsLiteralCString("\nThere is no key message after unexpected char "
+                           "message removed, "));
+    }
+    // Another window has a key message?
+    if (WinUtils::PeekMessage(&nextKeyMsgInAllWindows, 0, WM_KEYFIRST,
+                              WM_KEYLAST, PM_NOREMOVE | PM_NOYIELD)) {
+      nsPrintfCString info("\nNext key message in all windows: %s.",
+                           ToString(nextKeyMsgInAllWindows).get());
+      CrashReporter::AppendAppNotesToCrashReport(info);
+    } else {
+      CrashReporter::AppendAppNotesToCrashReport(
+          "\nThere is no key message in any windows."_ns);
+    }
+
+    MOZ_CRASH("PeekMessage() removed unexpected message");
+  }
+  MOZ_LOG(
+      gKeyLog, LogLevel::Error,
+      ("%p   NativeKey::GetFollowingCharMessage(), FAILED, removed messages "
+       "are all WM_NULL, nextKeyMsg=%s",
+       this, ToString(nextKeyMsg).get()));
+  nsPrintfCString info(
+      "\nWe lost following char message! "
+      "\nActive keyboard layout=0x%p (%s), "
+      "\nHandling message: %s, InSendMessageEx()=%s, \n"
+      "Found message: %s, removed a lot of WM_NULL",
+      KeyboardLayout::GetInstance()->GetLoadedLayout(),
+      KeyboardLayout::GetInstance()->GetLoadedLayoutName().get(),
+      ToString(mMsg).get(), GetResultOfInSendMessageEx().get(),
+      ToString(kFoundCharMsg).get());
+  CrashReporter::AppendAppNotesToCrashReport(info);
+  MOZ_CRASH("We lost the following char message");
+  return false;
+}
+
+void NativeKey::ComputeInputtingStringWithKeyboardLayout() {
+  KeyboardLayout* keyboardLayout = KeyboardLayout::GetInstance();
+
+  if (KeyboardLayout::IsPrintableCharKey(mVirtualKeyCode) ||
+      mCharMessageHasGone) {
+    mInputtingStringAndModifiers = mCommittedCharsAndModifiers;
+  } else {
+    mInputtingStringAndModifiers.Clear();
+  }
+  mShiftedString.Clear();
+  mUnshiftedString.Clear();
+  mShiftedLatinChar = mUnshiftedLatinChar = 0;
+
+  // XXX How about when Win key is pressed?
+  if (!mModKeyState.IsControl() && !mModKeyState.IsAlt()) {
+    return;
+  }
+
+  // If user is inputting a Unicode character with typing Alt + Numpad
+  // keys, we shouldn't set alternative key codes because the key event
+  // shouldn't match with a mnemonic.  However, we should set only
+  // mUnshiftedString for keeping traditional behavior at WM_SYSKEYDOWN.
+  // FYI: I guess that it's okay that mUnshiftedString stays empty.  So,
+  //      if its value breaks something, you must be able to just return here.
+  if (MaybeTypingUnicodeScalarValue()) {
+    if (!mCommittedCharsAndModifiers.IsEmpty()) {
+      MOZ_ASSERT(mMsg.message == WM_SYSKEYDOWN);
+      char16_t num = mCommittedCharsAndModifiers.CharAt(0);
+      MOZ_ASSERT(num >= '0' && num <= '9');
+      mUnshiftedString.Append(num, MODIFIER_NONE);
+      return;
+    }
+    // If user presses a function key without NumLock or 3rd party utility
+    // synthesizes a function key on numpad, we should handle it as-is because
+    // the user's intention may be performing `Alt` + foo.
+    MOZ_ASSERT(!KeyboardLayout::IsPrintableCharKey(mVirtualKeyCode));
+    return;
+  }
+
+  ModifierKeyState capsLockState(mModKeyState.GetModifiers() &
+                                 MODIFIER_CAPSLOCK);
+
+  mUnshiftedString =
+      keyboardLayout->GetUniCharsAndModifiers(mVirtualKeyCode, capsLockState);
+  capsLockState.Set(MODIFIER_SHIFT);
+  mShiftedString =
+      keyboardLayout->GetUniCharsAndModifiers(mVirtualKeyCode, capsLockState);
+
+  // The current keyboard cannot input alphabets or numerics,
+  // we should append them for Shortcut/Access keys.
+  // E.g., for Cyrillic keyboard layout.
+  capsLockState.Unset(MODIFIER_SHIFT);
+  WidgetUtils::GetLatinCharCodeForKeyCode(
+      mDOMKeyCode, capsLockState.GetModifiers(), &mUnshiftedLatinChar,
+      &mShiftedLatinChar);
+
+  // If the mShiftedLatinChar isn't 0, the key code is NS_VK_[A-Z].
+  if (mShiftedLatinChar) {
+    // If the produced characters of the key on current keyboard layout
+    // are same as computed Latin characters, we shouldn't append the
+    // Latin characters to alternativeCharCode.
+    if (mUnshiftedLatinChar == mUnshiftedString.CharAt(0) &&
+        mShiftedLatinChar == mShiftedString.CharAt(0)) {
+      mShiftedLatinChar = mUnshiftedLatinChar = 0;
+    }
+  } else if (mUnshiftedLatinChar) {
+    // If the mShiftedLatinChar is 0, the mKeyCode doesn't produce
+    // alphabet character.  At that time, the character may be produced
+    // with Shift key.  E.g., on French keyboard layout, NS_VK_PERCENT
+    // key produces LATIN SMALL LETTER U WITH GRAVE (U+00F9) without
+    // Shift key but with Shift key, it produces '%'.
+    // If the mUnshiftedLatinChar is produced by the key on current
+    // keyboard layout, we shouldn't append it to alternativeCharCode.
+    if (mUnshiftedLatinChar == mUnshiftedString.CharAt(0) ||
+        mUnshiftedLatinChar == mShiftedString.CharAt(0)) {
+      mUnshiftedLatinChar = 0;
+    }
+  }
+
+  if (!mModKeyState.IsControl()) {
+    return;
+  }
+
+  // If the mCharCode is not ASCII character, we should replace the
+  // mCharCode with ASCII character only when Ctrl is pressed.
+  // But don't replace the mCharCode when the mCharCode is not same as
+  // unmodified characters. In such case, Ctrl is sometimes used for a
+  // part of character inputting key combination like Shift.
+  uint32_t ch =
+      mModKeyState.IsShift() ? mShiftedLatinChar : mUnshiftedLatinChar;
+  if (!ch) {
+    return;
+  }
+  if (mInputtingStringAndModifiers.IsEmpty() ||
+      mInputtingStringAndModifiers.UniCharsCaseInsensitiveEqual(
+          mModKeyState.IsShift() ? mShiftedString : mUnshiftedString)) {
+    mInputtingStringAndModifiers.Clear();
+    mInputtingStringAndModifiers.Append(ch, mModKeyState.GetModifiers());
+  }
+}
+
+bool NativeKey::DispatchKeyPressEventsWithRetrievedCharMessages() const {
+  MOZ_ASSERT(IsKeyDownMessage());
+  MOZ_ASSERT(IsFollowedByPrintableCharOrSysCharMessage());
+  MOZ_ASSERT(!mWidget->Destroyed());
+
+  nsresult rv = mDispatcher->BeginNativeInputTransaction();
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    MOZ_LOG(
+        gKeyLog, LogLevel::Error,
+        ("%p   NativeKey::DispatchKeyPressEventsWithRetrievedCharMessages(), "
+         "FAILED due to BeginNativeInputTransaction() failure",
+         this));
+    return true;
+  }
+  WidgetKeyboardEvent keypressEvent(true, eKeyPress, mWidget);
+  MOZ_LOG(gKeyLog, LogLevel::Debug,
+          ("%p   NativeKey::DispatchKeyPressEventsWithRetrievedCharMessages(), "
+           "initializing keypress event...",
+           this));
+  ModifierKeyState modKeyState(mModKeyState);
+  if (mCanIgnoreModifierStateAtKeyPress && IsFollowedByPrintableCharMessage()) {
+    // If eKeyPress event should cause inputting text in focused editor,
+    // we need to remove Alt and Ctrl state.
+    modKeyState.Unset(MODIFIER_ALT | MODIFIER_CONTROL);
+  }
+  // We don't need to send char message here if there are two or more retrieved
+  // messages because we need to set each message to each eKeyPress event.
+  bool needsCallback = mFollowingCharMsgs.Length() > 1;
+  nsEventStatus status = InitKeyEvent(keypressEvent, modKeyState);
+  MOZ_LOG(gKeyLog, LogLevel::Info,
+          ("%p   NativeKey::DispatchKeyPressEventsWithRetrievedCharMessages(), "
+           "dispatching keypress event(s)...",
+           this));
+  bool dispatched = mDispatcher->MaybeDispatchKeypressEvents(
+      keypressEvent, status, const_cast<NativeKey*>(this), needsCallback);
+  if (mWidget->Destroyed()) {
+    MOZ_LOG(
+        gKeyLog, LogLevel::Info,
+        ("%p   NativeKey::DispatchKeyPressEventsWithRetrievedCharMessages(), "
+         "keypress event(s) caused destroying the widget",
+         this));
+    return true;
+  }
+  bool consumed = status == nsEventStatus_eConsumeNoDefault;
+  MOZ_LOG(gKeyLog, LogLevel::Info,
+          ("%p   NativeKey::DispatchKeyPressEventsWithRetrievedCharMessages(), "
+           "dispatched keypress event(s), dispatched=%s, consumed=%s",
+           this, GetBoolName(dispatched), GetBoolName(consumed)));
+  return consumed;
+}
+
+bool NativeKey::DispatchKeyPressEventsWithoutCharMessage() const {
+  MOZ_ASSERT(IsKeyDownMessage());
+  MOZ_ASSERT(!mIsDeadKey || !mCommittedCharsAndModifiers.IsEmpty());
+  MOZ_ASSERT(!mWidget->Destroyed());
+
+  nsresult rv = mDispatcher->BeginNativeInputTransaction();
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    MOZ_LOG(gKeyLog, LogLevel::Error,
+            ("%p   NativeKey::DispatchKeyPressEventsWithoutCharMessage(), "
+             "FAILED due "
+             "to BeginNativeInputTransaction() failure",
+             this));
+    return true;
+  }
+
+  WidgetKeyboardEvent keypressEvent(true, eKeyPress, mWidget);
+  if (mInputtingStringAndModifiers.IsEmpty() && mShiftedString.IsEmpty() &&
+      mUnshiftedString.IsEmpty()) {
+    keypressEvent.mKeyCode = mDOMKeyCode;
+  }
+  MOZ_LOG(gKeyLog, LogLevel::Debug,
+          ("%p   NativeKey::DispatchKeyPressEventsWithoutCharMessage(), "
+           "initializing "
+           "keypress event...",
+           this));
+  nsEventStatus status = InitKeyEvent(keypressEvent, mModKeyState);
+  MOZ_LOG(gKeyLog, LogLevel::Info,
+          ("%p   NativeKey::DispatchKeyPressEventsWithoutCharMessage(), "
+           "dispatching "
+           "keypress event(s)...",
+           this));
+  bool dispatched = mDispatcher->MaybeDispatchKeypressEvents(
+      keypressEvent, status, const_cast<NativeKey*>(this));
+  if (mWidget->Destroyed()) {
+    MOZ_LOG(gKeyLog, LogLevel::Info,
+            ("%p   NativeKey::DispatchKeyPressEventsWithoutCharMessage(), "
+             "keypress event(s) caused destroying the widget",
+             this));
+    return true;
+  }
+  bool consumed = status == nsEventStatus_eConsumeNoDefault;
+  MOZ_LOG(
+      gKeyLog, LogLevel::Info,
+      ("%p   NativeKey::DispatchKeyPressEventsWithoutCharMessage(), dispatched "
+       "keypress event(s), dispatched=%s, consumed=%s",
+       this, GetBoolName(dispatched), GetBoolName(consumed)));
+  return consumed;
+}
+
+void NativeKey::WillDispatchKeyboardEvent(WidgetKeyboardEvent& aKeyboardEvent,
+                                          uint32_t aIndex) {
+  // If it's an eKeyPress event and it's generated from retrieved char message,
+  // we need to set raw message information for plugins.
+  if (aKeyboardEvent.mMessage == eKeyPress &&
+      IsFollowedByPrintableCharOrSysCharMessage()) {
+    MOZ_RELEASE_ASSERT(aIndex < mCommittedCharsAndModifiers.Length());
+    uint32_t foundPrintableCharMessages = 0;
+    for (size_t i = 0; i < mFollowingCharMsgs.Length(); ++i) {
+      if (!IsPrintableCharOrSysCharMessage(mFollowingCharMsgs[i])) {
+        // XXX Should we dispatch a plugin event for WM_*DEADCHAR messages and
+        //     WM_CHAR with a control character here?  But we're not sure
+        //     how can we create such message queue (i.e., WM_CHAR or
+        //     WM_SYSCHAR with a printable character and such message are
+        //     generated by a keydown).  So, let's ignore such case until
+        //     we'd get some bug reports.
+        MOZ_LOG(gKeyLog, LogLevel::Warning,
+                ("%p   NativeKey::WillDispatchKeyboardEvent(), WARNING, "
+                 "ignoring %zuth message due to non-printable char message, %s",
+                 this, i + 1, ToString(mFollowingCharMsgs[i]).get()));
+        continue;
+      }
+      if (foundPrintableCharMessages++ == aIndex) {
+        // Found message which caused the eKeyPress event.
+        break;
+      }
+    }
+    // Set modifier state from mCommittedCharsAndModifiers because some of them
+    // might be different.  For example, Shift key was pressed at inputting
+    // dead char but Shift key was released before inputting next character.
+    if (mCanIgnoreModifierStateAtKeyPress) {
+      ModifierKeyState modKeyState(mModKeyState);
+      modKeyState.Unset(MODIFIER_SHIFT | MODIFIER_CONTROL | MODIFIER_ALT |
+                        MODIFIER_ALTGRAPH | MODIFIER_CAPSLOCK);
+      modKeyState.Set(mCommittedCharsAndModifiers.ModifiersAt(aIndex));
+      modKeyState.InitInputEvent(aKeyboardEvent);
+      MOZ_LOG(gKeyLog, LogLevel::Info,
+              ("%p   NativeKey::WillDispatchKeyboardEvent(), "
+               "setting %uth modifier state to %s",
+               this, aIndex + 1, ToString(modKeyState).get()));
+    }
+  }
+  size_t longestLength =
+      std::max(mInputtingStringAndModifiers.Length(),
+               std::max(mShiftedString.Length(), mUnshiftedString.Length()));
+  size_t skipUniChars = longestLength - mInputtingStringAndModifiers.Length();
+  size_t skipShiftedChars = longestLength - mShiftedString.Length();
+  size_t skipUnshiftedChars = longestLength - mUnshiftedString.Length();
+  if (aIndex >= longestLength) {
+    MOZ_LOG(
+        gKeyLog, LogLevel::Info,
+        ("%p   NativeKey::WillDispatchKeyboardEvent(), does nothing for %uth "
+         "%s event",
+         this, aIndex + 1, ToChar(aKeyboardEvent.mMessage)));
+    return;
+  }
+
+  // Check if aKeyboardEvent is the last event for a key press.
+  // So, if it's not an eKeyPress event, it's always the last event.
+  // Otherwise, check if the index is the last character of
+  // mCommittedCharsAndModifiers.
+  bool isLastIndex = aKeyboardEvent.mMessage != eKeyPress ||
+                     mCommittedCharsAndModifiers.IsEmpty() ||
+                     mCommittedCharsAndModifiers.Length() - 1 == aIndex;
+
+  nsTArray<AlternativeCharCode>& altArray =
+      aKeyboardEvent.mAlternativeCharCodes;
+
+  // Set charCode and adjust modifier state for every eKeyPress event.
+  // This is not necessary for the other keyboard events because the other
+  // keyboard events shouldn't have non-zero charCode value and should have
+  // current modifier state.
+  if (aKeyboardEvent.mMessage == eKeyPress && skipUniChars <= aIndex) {
+    // XXX Modifying modifier state of aKeyboardEvent is illegal, but no way
+    //     to set different modifier state per keypress event except this
+    //     hack.  Note that ideally, dead key should cause composition events
+    //     instead of keypress events, though.
+    if (aIndex - skipUniChars < mInputtingStringAndModifiers.Length()) {
+      ModifierKeyState modKeyState(mModKeyState);
+      // If key in combination with Alt and/or Ctrl produces a different
+      // character than without them then do not report these flags
+      // because it is separate keyboard layout shift state. If dead-key
+      // and base character does not produce a valid composite character
+      // then both produced dead-key character and following base
+      // character may have different modifier flags, too.
+      modKeyState.Unset(MODIFIER_SHIFT | MODIFIER_CONTROL | MODIFIER_ALT |
+                        MODIFIER_ALTGRAPH | MODIFIER_CAPSLOCK);
+      modKeyState.Set(
+          mInputtingStringAndModifiers.ModifiersAt(aIndex - skipUniChars));
+      modKeyState.InitInputEvent(aKeyboardEvent);
+      MOZ_LOG(gKeyLog, LogLevel::Info,
+              ("%p   NativeKey::WillDispatchKeyboardEvent(), "
+               "setting %uth modifier state to %s",
+               this, aIndex + 1, ToString(modKeyState).get()));
+    }
+    uint16_t uniChar =
+        mInputtingStringAndModifiers.CharAt(aIndex - skipUniChars);
+
+    // The mCharCode was set from mKeyValue. However, for example, when Ctrl key
+    // is pressed, its value should indicate an ASCII character for backward
+    // compatibility rather than inputting character without the modifiers.
+    // Therefore, we need to modify mCharCode value here.
+    aKeyboardEvent.SetCharCode(uniChar);
+    MOZ_LOG(gKeyLog, LogLevel::Info,
+            ("%p   NativeKey::WillDispatchKeyboardEvent(), "
+             "setting %uth charCode to %s",
+             this, aIndex + 1, GetCharacterCodeName(uniChar).get()));
+  }
+
+  // We need to append alterntaive charCode values:
+  //   - if the event is eKeyPress, we need to append for the index because
+  //     eKeyPress event is dispatched for every character inputted by a
+  //     key press.
+  //   - if the event is not eKeyPress, we need to append for all characters
+  //     inputted by the key press because the other keyboard events (e.g.,
+  //     eKeyDown are eKeyUp) are fired only once for a key press.
+  size_t count;
+  if (aKeyboardEvent.mMessage == eKeyPress) {
+    // Basically, append alternative charCode values only for the index.
+    count = 1;
+    // However, if it's the last eKeyPress event but different shift state
+    // can input longer string, the last eKeyPress event should have all
+    // remaining alternative charCode values.
+    if (isLastIndex) {
+      count = longestLength - aIndex;
+    }
+  } else {
+    count = longestLength;
+  }
+  for (size_t i = 0; i < count; ++i) {
+    uint16_t shiftedChar = 0, unshiftedChar = 0;
+    if (skipShiftedChars <= aIndex + i) {
+      shiftedChar = mShiftedString.CharAt(aIndex + i - skipShiftedChars);
+    }
+    if (skipUnshiftedChars <= aIndex + i) {
+      unshiftedChar = mUnshiftedString.CharAt(aIndex + i - skipUnshiftedChars);
+    }
+
+    if (shiftedChar || unshiftedChar) {
+      AlternativeCharCode chars(unshiftedChar, shiftedChar);
+      altArray.AppendElement(chars);
+    }
+
+    if (!isLastIndex) {
+      continue;
+    }
+
+    if (mUnshiftedLatinChar || mShiftedLatinChar) {
+      AlternativeCharCode chars(mUnshiftedLatinChar, mShiftedLatinChar);
+      altArray.AppendElement(chars);
+    }
+
+    // Typically, following virtual keycodes are used for a key which can
+    // input the character.  However, these keycodes are also used for
+    // other keys on some keyboard layout.  E.g., in spite of Shift+'1'
+    // inputs '+' on Thai keyboard layout, a key which is at '=/+'
+    // key on ANSI keyboard layout is VK_OEM_PLUS.  Native applications
+    // handle it as '+' key if Ctrl key is pressed.
+    char16_t charForOEMKeyCode = 0;
+    switch (mVirtualKeyCode) {
+      case VK_OEM_PLUS:
+        charForOEMKeyCode = '+';
+        break;
+      case VK_OEM_COMMA:
+        charForOEMKeyCode = ',';
+        break;
+      case VK_OEM_MINUS:
+        charForOEMKeyCode = '-';
+        break;
+      case VK_OEM_PERIOD:
+        charForOEMKeyCode = '.';
+        break;
+    }
+    if (charForOEMKeyCode && charForOEMKeyCode != mUnshiftedString.CharAt(0) &&
+        charForOEMKeyCode != mShiftedString.CharAt(0) &&
+        charForOEMKeyCode != mUnshiftedLatinChar &&
+        charForOEMKeyCode != mShiftedLatinChar) {
+      AlternativeCharCode OEMChars(charForOEMKeyCode, charForOEMKeyCode);
+      altArray.AppendElement(OEMChars);
+    }
+  }
+}
+
+/*****************************************************************************
+ * mozilla::widget::KeyboardLayout
+ *****************************************************************************/
+
+KeyboardLayout* KeyboardLayout::sInstance = nullptr;
+StaticRefPtr<nsIUserIdleServiceInternal> KeyboardLayout::sIdleService;
+
+// static
+KeyboardLayout* KeyboardLayout::GetInstance() {
+  if (!sInstance) {
+    sInstance = new KeyboardLayout();
+  }
+  return sInstance;
+}
+
+// static
+void KeyboardLayout::Shutdown() {
+  delete sInstance;
+  sInstance = nullptr;
+  sIdleService = nullptr;
+}
+
+// static
+void KeyboardLayout::NotifyIdleServiceOfUserActivity() {
+  if (!sIdleService) {
+    sIdleService = nsCOMPtr<nsIUserIdleServiceInternal>(
+                       do_GetService("@mozilla.org/widget/useridleservice;1"))
+                       .forget();
+    if (NS_WARN_IF(!sIdleService)) {
+      return;
+    }
+  }
+  sIdleService->ResetIdleTimeOut(0);
+}
+
+KeyboardLayout::KeyboardLayout() {
+  mDeadKeyTableListHead = nullptr;
+  // A dead key sequence should be made from up to 5 keys.  Therefore, 4 is
+  // enough and makes sense because the item is uint8_t.
+  // (Although, even if it's possible to be 6 keys or more in a sequence,
+  // this array will be re-allocated).
+  mActiveDeadKeys.SetCapacity(4);
+  mDeadKeyShiftStates.SetCapacity(4);
+
+  // If we put it off to load active keyboard layout when first needed, we need
+  // to load it at instanciation.  That makes us save the cost of a call of
+  // GetKeyboardLayout() API.
+  if (StaticPrefs::ui_key_layout_load_when_first_needed()) {
+    OnLayoutChange(::GetKeyboardLayout(0));
+  }
+}
+
+KeyboardLayout::~KeyboardLayout() { ReleaseDeadKeyTables(); }
+
+bool KeyboardLayout::IsPrintableCharKey(uint8_t aVirtualKey) {
+  return GetKeyIndex(aVirtualKey) >= 0;
+}
+
+WORD KeyboardLayout::ComputeScanCodeForVirtualKeyCode(
+    uint8_t aVirtualKeyCode) const {
+  return static_cast<WORD>(::MapVirtualKeyEx(aVirtualKeyCode, MAPVK_VK_TO_VSC,
+                                             KeyboardLayout::GetLayout()));
+}
+
+bool KeyboardLayout::IsDeadKey(uint8_t aVirtualKey,
+                               const ModifierKeyState& aModKeyState) const {
+  int32_t virtualKeyIndex = GetKeyIndex(aVirtualKey);
+
+  // XXX KeyboardLayout class doesn't support unusual keyboard layout which
+  //     maps some function keys as dead keys.
+  if (virtualKeyIndex < 0) {
+    return false;
+  }
+
+  return mVirtualKeys[virtualKeyIndex].IsDeadKey(
+      VirtualKey::ModifiersToShiftState(aModKeyState.GetModifiers()));
+}
+
+bool KeyboardLayout::IsSysKey(uint8_t aVirtualKey,
+                              const ModifierKeyState& aModKeyState) const {
+  // If Alt key is not pressed, it's never a system key combination.
+  // Additionally, if Ctrl key is pressed, it's never a system key combination
+  // too.
+  // FYI: Windows logo key state won't affect if it's a system key.
+  if (!aModKeyState.IsAlt() || aModKeyState.IsControl()) {
+    return false;
+  }
+
+  int32_t virtualKeyIndex = GetKeyIndex(aVirtualKey);
+  if (virtualKeyIndex < 0) {
+    return true;
+  }
+
+  UniCharsAndModifiers inputCharsAndModifiers =
+      GetUniCharsAndModifiers(aVirtualKey, aModKeyState);
+  if (inputCharsAndModifiers.IsEmpty()) {
+    return true;
+  }
+
+  // If the Alt key state isn't consumed, that means that the key with Alt
+  // doesn't cause text input.  So, the combination is a system key.
+  return !!(inputCharsAndModifiers.ModifiersAt(0) & MODIFIER_ALT);
+}
+
+void KeyboardLayout::InitNativeKey(NativeKey& aNativeKey) {
+  if (mIsPendingToRestoreKeyboardLayout) {
+    LoadLayout(::GetKeyboardLayout(0));
+  }
+
+  // If the aNativeKey is initialized with WM_CHAR, the key information
+  // should be discarded because mKeyValue should have the string to be
+  // inputted.
+  if (aNativeKey.mMsg.message == WM_CHAR) {
+    char16_t ch = static_cast<char16_t>(aNativeKey.mMsg.wParam);
+    // But don't set key value as printable key if the character is a control
+    // character such as 0x0D at pressing Enter key.
+    if (!NativeKey::IsControlChar(ch)) {
+      aNativeKey.mKeyNameIndex = KEY_NAME_INDEX_USE_STRING;
+      Modifiers modifiers =
+          aNativeKey.GetModifiers() & ~(MODIFIER_ALT | MODIFIER_CONTROL);
+      aNativeKey.mCommittedCharsAndModifiers.Append(ch, modifiers);
+      return;
+    }
+  }
+
+  // If the aNativeKey is in a sequence to input a Unicode character with
+  // Alt + numpad keys, we should just set the number as the inputting charcter.
+  // Note that we should compute the key value from the virtual key code
+  // because they may be mapped to alphabets, but they should be treated as
+  // Alt + [0-9] even by web apps.
+  // However, we shouldn't touch the key value if given virtual key code is
+  // not a printable key because it may be synthesized by 3rd party utility
+  // or just NumLock is unlocked and user tries to use shortcut key.  In the
+  // latter case, we cannot solve the conflict issue with Alt+foo shortcut key
+  // and inputting a Unicode scalar value like reported to bug 1606655, though,
+  // I have no better idea.  Perhaps, `Alt` shouldn't be used for shortcut key
+  // combination on Windows.
+  if (aNativeKey.MaybeTypingUnicodeScalarValue() &&
+      KeyboardLayout::IsPrintableCharKey(aNativeKey.mVirtualKeyCode)) {
+    // If the key code value is mapped to a Numpad key, let's compute the key
+    // value with it.  This is same behavior as Chrome.  In strictly speaking,
+    // I think that the else block's computation is better because it seems
+    // that Windows does not refer virtual key code value, but we should avoid
+    // web-compat issues.
+    char16_t num = '0';
+    if (aNativeKey.mVirtualKeyCode >= VK_NUMPAD0 &&
+        aNativeKey.mVirtualKeyCode <= VK_NUMPAD9) {
+      num = '0' + aNativeKey.mVirtualKeyCode - VK_NUMPAD0;
+    }
+    // Otherwise, let's use fake key value for making never match with
+    // mnemonic.
+    else {
+      switch (aNativeKey.mScanCode) {
+        case 0x0052:  // Numpad0
+          num = '0';
+          break;
+        case 0x004F:  // Numpad1
+          num = '1';
+          break;
+        case 0x0050:  // Numpad2
+          num = '2';
+          break;
+        case 0x0051:  // Numpad3
+          num = '3';
+          break;
+        case 0x004B:  // Numpad4
+          num = '4';
+          break;
+        case 0x004C:  // Numpad5
+          num = '5';
+          break;
+        case 0x004D:  // Numpad6
+          num = '6';
+          break;
+        case 0x0047:  // Numpad7
+          num = '7';
+          break;
+        case 0x0048:  // Numpad8
+          num = '8';
+          break;
+        case 0x0049:  // Numpad9
+          num = '9';
+          break;
+        default:
+          MOZ_ASSERT_UNREACHABLE(
+              "IsTypingUnicodeScalarValue() must have returned true for wrong "
+              "scancode");
+          break;
+      }
+    }
+    aNativeKey.mCommittedCharsAndModifiers.Append(num,
+                                                  aNativeKey.GetModifiers());
+    aNativeKey.mKeyNameIndex = KEY_NAME_INDEX_USE_STRING;
+    return;
+  }
+
+  // When it's followed by non-dead char message(s) for printable character(s),
+  // aNativeKey should dispatch eKeyPress events for them rather than
+  // information from keyboard layout because respecting WM_(SYS)CHAR messages
+  // guarantees that we can always input characters which is expected by
+  // the user even if the user uses odd keyboard layout.
+  // Or, when it was followed by non-dead char message for a printable character
+  // but it's gone at removing the message from the queue, let's treat it
+  // as a key inputting empty string.
+  if (aNativeKey.IsFollowedByPrintableCharOrSysCharMessage() ||
+      aNativeKey.mCharMessageHasGone) {
+    MOZ_ASSERT(!aNativeKey.IsCharMessage(aNativeKey.mMsg));
+    if (aNativeKey.IsFollowedByPrintableCharOrSysCharMessage()) {
+      // Initialize mCommittedCharsAndModifiers with following char messages.
+      aNativeKey.InitCommittedCharsAndModifiersWithFollowingCharMessages();
+      MOZ_ASSERT(!aNativeKey.mCommittedCharsAndModifiers.IsEmpty());
+
+      // Currently, we are doing a ugly hack to keypress events to cause
+      // inputting character even if Ctrl or Alt key is pressed, that is, we
+      // remove Ctrl and Alt modifier state from keypress event.  However, for
+      // example, Ctrl+Space which causes ' ' of WM_CHAR message never causes
+      // keypress event whose ctrlKey is true.  For preventing this problem,
+      // we should mark as not removable if Ctrl or Alt key does not cause
+      // changing inputting character.
+      if (IsPrintableCharKey(aNativeKey.mOriginalVirtualKeyCode) &&
+          (aNativeKey.IsControl() ^ aNativeKey.IsAlt())) {
+        ModifierKeyState state = aNativeKey.ModifierKeyStateRef();
+        state.Unset(MODIFIER_ALT | MODIFIER_CONTROL);
+        UniCharsAndModifiers charsWithoutModifier =
+            GetUniCharsAndModifiers(aNativeKey.GenericVirtualKeyCode(), state);
+        aNativeKey.mCanIgnoreModifierStateAtKeyPress =
+            !charsWithoutModifier.UniCharsEqual(
+                aNativeKey.mCommittedCharsAndModifiers);
+      }
+    } else {
+      aNativeKey.mCommittedCharsAndModifiers.Clear();
+    }
+    aNativeKey.mKeyNameIndex = KEY_NAME_INDEX_USE_STRING;
+
+    // If it's not in dead key sequence, we don't need to do anymore here.
+    if (!IsInDeadKeySequence()) {
+      return;
+    }
+
+    // If it's in dead key sequence and dead char is inputted as is, we need to
+    // set the previous modifier state which is stored when preceding dead key
+    // is pressed.
+    UniCharsAndModifiers deadChars = GetDeadUniCharsAndModifiers();
+    aNativeKey.mCommittedCharsAndModifiers.OverwriteModifiersIfBeginsWith(
+        deadChars);
+    // Finish the dead key sequence.
+    DeactivateDeadKeyState();
+    return;
+  }
+
+  // If it's a dead key, aNativeKey will be initialized by
+  // MaybeInitNativeKeyAsDeadKey().
+  if (MaybeInitNativeKeyAsDeadKey(aNativeKey)) {
+    return;
+  }
+
+  // If the key is not a usual printable key, KeyboardLayout class assume that
+  // it's not cause dead char nor printable char.  Therefore, there are nothing
+  // to do here fore such keys (e.g., function keys).
+  // However, this should keep dead key state even if non-printable key is
+  // pressed during a dead key sequence.
+  if (!IsPrintableCharKey(aNativeKey.mOriginalVirtualKeyCode)) {
+    return;
+  }
+
+  MOZ_ASSERT(aNativeKey.mOriginalVirtualKeyCode != VK_PACKET,
+             "At handling VK_PACKET, we shouldn't refer keyboard layout");
+  MOZ_ASSERT(
+      aNativeKey.mKeyNameIndex == KEY_NAME_INDEX_USE_STRING,
+      "Printable key's key name index must be KEY_NAME_INDEX_USE_STRING");
+
+  // If it's in dead key handling and the pressed key causes a composite
+  // character, aNativeKey will be initialized by
+  // MaybeInitNativeKeyWithCompositeChar().
+  if (MaybeInitNativeKeyWithCompositeChar(aNativeKey)) {
+    return;
+  }
+
+  UniCharsAndModifiers baseChars = GetUniCharsAndModifiers(aNativeKey);
+
+  // If the key press isn't related to any dead keys, initialize aNativeKey
+  // with the characters which should be caused by the key.
+  if (!IsInDeadKeySequence()) {
+    aNativeKey.mCommittedCharsAndModifiers = baseChars;
+    return;
+  }
+
+  // If the key doesn't cause a composite character with preceding dead key,
+  // initialize aNativeKey with the dead-key character followed by current
+  // key's character.
+  UniCharsAndModifiers deadChars = GetDeadUniCharsAndModifiers();
+  aNativeKey.mCommittedCharsAndModifiers = deadChars + baseChars;
+  if (aNativeKey.IsKeyDownMessage()) {
+    DeactivateDeadKeyState();
+  }
+}
+
+bool KeyboardLayout::MaybeInitNativeKeyAsDeadKey(NativeKey& aNativeKey) {
+  // Only when it's not in dead key sequence, we can trust IsDeadKey() result.
+  if (!IsInDeadKeySequence() && !IsDeadKey(aNativeKey)) {
+    return false;
+  }
+
+  // When keydown message is followed by a dead char message, it should be
+  // initialized as dead key.
+  bool isDeadKeyDownEvent =
+      aNativeKey.IsKeyDownMessage() && aNativeKey.IsFollowedByDeadCharMessage();
+
+  // When keyup message is received, let's check if it's one of preceding
+  // dead keys because keydown message order and keyup message order may be
+  // different.
+  bool isDeadKeyUpEvent =
+      !aNativeKey.IsKeyDownMessage() &&
+      mActiveDeadKeys.Contains(aNativeKey.GenericVirtualKeyCode());
+
+  if (isDeadKeyDownEvent || isDeadKeyUpEvent) {
+    ActivateDeadKeyState(aNativeKey);
+    // Any dead key events don't generate characters.  So, a dead key should
+    // cause only keydown event and keyup event whose KeyboardEvent.key
+    // values are "Dead".
+    aNativeKey.mCommittedCharsAndModifiers.Clear();
+    aNativeKey.mKeyNameIndex = KEY_NAME_INDEX_Dead;
+    return true;
+  }
+
+  // At keydown message handling, we need to forget the first dead key
+  // because there is no guarantee coming WM_KEYUP for the second dead
+  // key before next WM_KEYDOWN.  E.g., due to auto key repeat or pressing
+  // another dead key before releasing current key.  Therefore, we can
+  // set only a character for current key for keyup event.
+  if (!IsInDeadKeySequence()) {
+    aNativeKey.mCommittedCharsAndModifiers =
+        GetUniCharsAndModifiers(aNativeKey);
+    return true;
+  }
+
+  // When non-printable key event comes during a dead key sequence, that must
+  // be a modifier key event.  So, such events shouldn't be handled as a part
+  // of the dead key sequence.
+  if (!IsDeadKey(aNativeKey)) {
+    return false;
+  }
+
+  // FYI: Following code may run when the user doesn't input text actually
+  //      but the key sequence is a dead key sequence.  For example,
+  //      ` -> Ctrl+` with Spanish keyboard layout.  Let's keep using this
+  //      complicated code for now because this runs really rarely.
+
+  // Dead key followed by another dead key may cause a composed character
+  // (e.g., "Russian - Mnemonic" keyboard layout's 's' -> 'c').
+  if (MaybeInitNativeKeyWithCompositeChar(aNativeKey)) {
+    return true;
+  }
+
+  // Otherwise, dead key followed by another dead key causes inputting both
+  // character.
+  UniCharsAndModifiers prevDeadChars = GetDeadUniCharsAndModifiers();
+  UniCharsAndModifiers newChars = GetUniCharsAndModifiers(aNativeKey);
+  // But keypress events should be fired for each committed character.
+  aNativeKey.mCommittedCharsAndModifiers = prevDeadChars + newChars;
+  if (aNativeKey.IsKeyDownMessage()) {
+    DeactivateDeadKeyState();
+  }
+  return true;
+}
+
+bool KeyboardLayout::MaybeInitNativeKeyWithCompositeChar(
+    NativeKey& aNativeKey) {
+  if (!IsInDeadKeySequence()) {
+    return false;
+  }
+
+  if (NS_WARN_IF(!IsPrintableCharKey(aNativeKey.mOriginalVirtualKeyCode))) {
+    return false;
+  }
+
+  UniCharsAndModifiers baseChars = GetUniCharsAndModifiers(aNativeKey);
+  if (baseChars.IsEmpty() || !baseChars.CharAt(0)) {
+    return false;
+  }
+
+  char16_t compositeChar = GetCompositeChar(baseChars.CharAt(0));
+  if (!compositeChar) {
+    return false;
+  }
+
+  // Active dead-key and base character does produce exactly one composite
+  // character.
+  aNativeKey.mCommittedCharsAndModifiers.Append(compositeChar,
+                                                baseChars.ModifiersAt(0));
+  if (aNativeKey.IsKeyDownMessage()) {
+    DeactivateDeadKeyState();
+  }
+  return true;
+}
+
+UniCharsAndModifiers KeyboardLayout::GetUniCharsAndModifiers(
+    uint8_t aVirtualKey, VirtualKey::ShiftState aShiftState) const {
+  UniCharsAndModifiers result;
+  int32_t key = GetKeyIndex(aVirtualKey);
+  if (key < 0) {
+    return result;
+  }
+  return mVirtualKeys[key].GetUniChars(aShiftState);
+}
+
+UniCharsAndModifiers KeyboardLayout::GetDeadUniCharsAndModifiers() const {
+  MOZ_RELEASE_ASSERT(mActiveDeadKeys.Length() == mDeadKeyShiftStates.Length());
+
+  if (NS_WARN_IF(mActiveDeadKeys.IsEmpty())) {
+    return UniCharsAndModifiers();
+  }
+
+  UniCharsAndModifiers result;
+  for (size_t i = 0; i < mActiveDeadKeys.Length(); ++i) {
+    result +=
+        GetUniCharsAndModifiers(mActiveDeadKeys[i], mDeadKeyShiftStates[i]);
+  }
+  return result;
+}
+
+char16_t KeyboardLayout::GetCompositeChar(char16_t aBaseChar) const {
+  if (NS_WARN_IF(mActiveDeadKeys.IsEmpty())) {
+    return 0;
+  }
+  // XXX Currently, we don't support computing a composite character with
+  //     two or more dead keys since it needs big table for supporting
+  //     long chained dead keys.  However, this should be a minor bug
+  //     because this runs only when the latest keydown event does not cause
+  //     WM_(SYS)CHAR messages.  So, when user wants to input a character,
+  //     this path never runs.
+  if (mActiveDeadKeys.Length() > 1) {
+    return 0;
+  }
+  int32_t key = GetKeyIndex(mActiveDeadKeys[0]);
+  if (key < 0) {
+    return 0;
+  }
+  return mVirtualKeys[key].GetCompositeChar(mDeadKeyShiftStates[0], aBaseChar);
+}
+
+static bool IsValidKeyboardLayoutsChild(const nsAString& aChildName) {
+  if (aChildName.Length() != 8) {
+    return false;
+  }
+  for (size_t i = 0; i < aChildName.Length(); i++) {
+    if ((aChildName[i] >= '0' && aChildName[i] <= '9') ||
+        (aChildName[i] >= 'a' && aChildName[i] <= 'f') ||
+        (aChildName[i] >= 'A' && aChildName[i] <= 'F')) {
+      continue;
+    }
+    return false;
+  }
+  return true;
+}
+
+// static
+nsCString KeyboardLayout::GetLayoutName(HKL aLayout) {
+  constexpr auto kKeyboardLayouts =
+      u"SYSTEM\\CurrentControlSet\\Control\\Keyboard Layouts\\"_ns;
+  uint16_t language = reinterpret_cast<uintptr_t>(aLayout) & 0xFFFF;
+  uint16_t layout = (reinterpret_cast<uintptr_t>(aLayout) >> 16) & 0xFFFF;
+  // If the layout is less than 0xA000XXXX (normal keyboard layout for the
+  // language) or 0xEYYYXXXX (IMM-IME), we can retrieve its name simply.
+  if (layout < 0xA000 || (layout & 0xF000) == 0xE000) {
+    nsAutoString key(kKeyboardLayouts);
+    key.AppendPrintf("%08" PRIXPTR, layout < 0xA000
+                                        ? layout
+                                        : reinterpret_cast<uintptr_t>(aLayout));
+    wchar_t buf[256];
+    if (NS_WARN_IF(!WinRegistry::GetString(
+            HKEY_LOCAL_MACHINE, key, u"Layout Text"_ns, buf,
+            WinRegistry::kLegacyWinUtilsStringFlags))) {
+      return "No name or too long name"_ns;
+    }
+    return NS_ConvertUTF16toUTF8(buf);
+  }
+
+  if (NS_WARN_IF((layout & 0xF000) != 0xF000)) {
+    nsCString result;
+    result.AppendPrintf("Odd HKL: 0x%08" PRIXPTR,
+                        reinterpret_cast<uintptr_t>(aLayout));
+    return result;
+  }
+
+  // Otherwise, we need to walk the registry under "Keyboard Layouts".
+  WinRegistry::Key regKey(HKEY_LOCAL_MACHINE, kKeyboardLayouts,
+                          WinRegistry::KeyMode::Read);
+  if (NS_WARN_IF(!regKey)) {
+    return ""_ns;
+  }
+  uint32_t childCount = regKey.GetChildCount();
+  if (NS_WARN_IF(!childCount)) {
+    return ""_ns;
+  }
+  for (uint32_t i = 0; i < childCount; i++) {
+    nsAutoString childName;
+    if (NS_WARN_IF(!regKey.GetChildName(i, childName)) ||
+        !IsValidKeyboardLayoutsChild(childName)) {
+      continue;
+    }
+    nsresult rv = NS_OK;
+    uint32_t childNum = static_cast<uint32_t>(childName.ToInteger64(&rv, 16));
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      continue;
+    }
+    // Ignore normal keyboard layouts for each language.
+    if (childNum <= 0xFFFF) {
+      continue;
+    }
+    // If it doesn't start with 'A' nor 'a', language should be matched.
+    if ((childNum & 0xFFFF) != language &&
+        (childNum & 0xF0000000) != 0xA0000000) {
+      continue;
+    }
+    // Then, the child should have "Layout Id" which is "YYY" of 0xFYYYXXXX.
+    nsAutoString key(kKeyboardLayouts);
+    key += childName;
+    WinRegistry::Key regKey(HKEY_LOCAL_MACHINE, key,
+                            WinRegistry::KeyMode::QueryValue);
+    if (NS_WARN_IF(!regKey)) {
+      continue;
+    }
+    wchar_t buf[256];
+    if (NS_WARN_IF(!regKey.GetValueAsString(
+            u"Layout Id"_ns, buf, WinRegistry::kLegacyWinUtilsStringFlags))) {
+      continue;
+    }
+    uint16_t layoutId = wcstol(buf, nullptr, 16);
+    if (layoutId != (layout & 0x0FFF)) {
+      continue;
+    }
+    if (NS_WARN_IF(!regKey.GetValueAsString(
+            u"Layout Text"_ns, buf, WinRegistry::kLegacyWinUtilsStringFlags))) {
+      continue;
+    }
+    return NS_ConvertUTF16toUTF8(buf);
+  }
+  return ""_ns;
+}
+
+void KeyboardLayout::LoadLayout(HKL aLayout) {
+  mIsPendingToRestoreKeyboardLayout = false;
+
+  if (mKeyboardLayout == aLayout) {
+    return;
+  }
+
+  mKeyboardLayout = aLayout;
+  mHasAltGr = false;
+
+  MOZ_LOG(gKeyLog, LogLevel::Info,
+          ("KeyboardLayout::LoadLayout(aLayout=0x%p (%s))", aLayout,
+           GetLayoutName(aLayout).get()));
+
+  BYTE kbdState[256];
+  memset(kbdState, 0, sizeof(kbdState));
+
+  BYTE originalKbdState[256];
+  // Bitfield with all shift states that have at least one dead-key.
+  uint16_t shiftStatesWithDeadKeys = 0;
+  // Bitfield with all shift states that produce any possible dead-key base
+  // characters.
+  uint16_t shiftStatesWithBaseChars = 0;
+
+  mActiveDeadKeys.Clear();
+  mDeadKeyShiftStates.Clear();
+
+  ReleaseDeadKeyTables();
+
+  ::GetKeyboardState(originalKbdState);
+
+  // For each shift state gather all printable characters that are produced
+  // for normal case when no any dead-key is active.
+
+  for (VirtualKey::ShiftState shiftState = 0; shiftState < 16; shiftState++) {
+    VirtualKey::FillKbdState(kbdState, shiftState);
+    bool isAltGr = VirtualKey::IsAltGrIndex(shiftState);
+    for (uint32_t virtualKey = 0; virtualKey < 256; virtualKey++) {
+      int32_t vki = GetKeyIndex(virtualKey);
+      if (vki < 0) {
+        continue;
+      }
+      NS_ASSERTION(uint32_t(vki) < ArrayLength(mVirtualKeys), "invalid index");
+      char16_t uniChars[5];
+      int32_t ret = ::ToUnicodeEx(virtualKey, 0, kbdState, (LPWSTR)uniChars,
+                                  ArrayLength(uniChars), 0, mKeyboardLayout);
+      // dead-key
+      if (ret < 0) {
+        shiftStatesWithDeadKeys |= (1 << shiftState);
+        // Repeat dead-key to deactivate it and get its character
+        // representation.
+        char16_t deadChar[2];
+        ret = ::ToUnicodeEx(virtualKey, 0, kbdState, (LPWSTR)deadChar,
+                            ArrayLength(deadChar), 0, mKeyboardLayout);
+        NS_ASSERTION(ret == 2, "Expecting twice repeated dead-key character");
+        mVirtualKeys[vki].SetDeadChar(shiftState, deadChar[0]);
+
+        MOZ_LOG(gKeyLog, LogLevel::Verbose,
+                ("  %s (%d): DeadChar(%s, %s) (ret=%d)",
+                 kVirtualKeyName[virtualKey], vki,
+                 GetShiftStateName(shiftState).get(),
+                 GetCharacterCodeNames(deadChar, 1).get(), ret));
+      } else {
+        if (ret == 1) {
+          // dead-key can pair only with exactly one base character.
+          shiftStatesWithBaseChars |= (1 << shiftState);
+        }
+        mVirtualKeys[vki].SetNormalChars(shiftState, uniChars, ret);
+        MOZ_LOG(gKeyLog, LogLevel::Verbose,
+                ("  %s (%d): NormalChar(%s, %s) (ret=%d)",
+                 kVirtualKeyName[virtualKey], vki,
+                 GetShiftStateName(shiftState).get(),
+                 GetCharacterCodeNames(uniChars, ret).get(), ret));
+      }
+
+      // If the key inputs at least one character with AltGr modifier,
+      // check if AltGr changes inputting character.  If it does, mark
+      // this keyboard layout has AltGr modifier actually.
+      if (!mHasAltGr && ret > 0 && isAltGr &&
+          mVirtualKeys[vki].IsChangedByAltGr(shiftState)) {
+        mHasAltGr = true;
+        MOZ_LOG(gKeyLog, LogLevel::Info,
+                ("  Found a key (%s) changed by AltGr: %s -> %s (%s) (ret=%d)",
+                 kVirtualKeyName[virtualKey],
+                 GetCharacterCodeNames(
+                     mVirtualKeys[vki].GetNativeUniChars(
+                         shiftState - VirtualKey::ShiftStateIndex::eAltGr))
+                     .get(),
+                 GetCharacterCodeNames(
+                     mVirtualKeys[vki].GetNativeUniChars(shiftState))
+                     .get(),
+                 GetShiftStateName(shiftState).get(), ret));
+      }
+    }
+  }
+
+  // Now process each dead-key to find all its base characters and resulting
+  // composite characters.
+  for (VirtualKey::ShiftState shiftState = 0; shiftState < 16; shiftState++) {
+    if (!(shiftStatesWithDeadKeys & (1 << shiftState))) {
+      continue;
+    }
+
+    VirtualKey::FillKbdState(kbdState, shiftState);
+
+    for (uint32_t virtualKey = 0; virtualKey < 256; virtualKey++) {
+      int32_t vki = GetKeyIndex(virtualKey);
+      if (vki >= 0 && mVirtualKeys[vki].IsDeadKey(shiftState)) {
+        AutoTArray<DeadKeyEntry, 256> deadKeyArray;
+        uint32_t n = GetDeadKeyCombinations(
+            virtualKey, kbdState, shiftStatesWithBaseChars, deadKeyArray);
+        const DeadKeyTable* dkt =
+            mVirtualKeys[vki].MatchingDeadKeyTable(deadKeyArray.Elements(), n);
+        if (!dkt) {
+          dkt = AddDeadKeyTable(deadKeyArray.Elements(), n);
+        }
+        mVirtualKeys[vki].AttachDeadKeyTable(shiftState, dkt);
+      }
+    }
+  }
+
+  ::SetKeyboardState(originalKbdState);
+
+  if (MOZ_LOG_TEST(gKeyLog, LogLevel::Verbose)) {
+    static const UINT kExtendedScanCode[] = {0x0000, 0xE000};
+    static const UINT kMapType = MAPVK_VSC_TO_VK_EX;
+    MOZ_LOG(gKeyLog, LogLevel::Verbose,
+            ("Logging virtual keycode values for scancode (0x%p)...",
+             mKeyboardLayout));
+    for (uint32_t i = 0; i < ArrayLength(kExtendedScanCode); i++) {
+      for (uint32_t j = 1; j <= 0xFF; j++) {
+        UINT scanCode = kExtendedScanCode[i] + j;
+        UINT virtualKeyCode =
+            ::MapVirtualKeyEx(scanCode, kMapType, mKeyboardLayout);
+        MOZ_LOG(gKeyLog, LogLevel::Verbose,
+                ("0x%04X, %s", scanCode, kVirtualKeyName[virtualKeyCode]));
+      }
+    }
+  }
+
+  MOZ_LOG(gKeyLog, LogLevel::Info,
+          ("  AltGr key is %s in %s", mHasAltGr ? "found" : "not found",
+           GetLayoutName(aLayout).get()));
+}
+
+inline int32_t KeyboardLayout::GetKeyIndex(uint8_t aVirtualKey) {
+  // Currently these 68 (NS_NUM_OF_KEYS) virtual keys are assumed
+  // to produce visible representation:
+  // 0x20 - VK_SPACE          ' '
+  // 0x30..0x39               '0'..'9'
+  // 0x41..0x5A               'A'..'Z'
+  // 0x60..0x69               '0'..'9' on numpad
+  // 0x6A - VK_MULTIPLY       '*' on numpad
+  // 0x6B - VK_ADD            '+' on numpad
+  // 0x6D - VK_SUBTRACT       '-' on numpad
+  // 0x6E - VK_DECIMAL        '.' on numpad
+  // 0x6F - VK_DIVIDE         '/' on numpad
+  // 0x6E - VK_DECIMAL        '.'
+  // 0xBA - VK_OEM_1          ';:' for US
+  // 0xBB - VK_OEM_PLUS       '+' any country
+  // 0xBC - VK_OEM_COMMA      ',' any country
+  // 0xBD - VK_OEM_MINUS      '-' any country
+  // 0xBE - VK_OEM_PERIOD     '.' any country
+  // 0xBF - VK_OEM_2          '/?' for US
+  // 0xC0 - VK_OEM_3          '`~' for US
+  // 0xC1 - VK_ABNT_C1        '/?' for Brazilian
+  // 0xC2 - VK_ABNT_C2        separator key on numpad (Brazilian or JIS for Mac)
+  // 0xDB - VK_OEM_4          '[{' for US
+  // 0xDC - VK_OEM_5          '\|' for US
+  // 0xDD - VK_OEM_6          ']}' for US
+  // 0xDE - VK_OEM_7          ''"' for US
+  // 0xDF - VK_OEM_8
+  // 0xE1 - no name
+  // 0xE2 - VK_OEM_102        '\_' for JIS
+  // 0xE3 - no name
+  // 0xE4 - no name
+
+  static const int8_t xlat[256] = {
+      // 0   1   2   3   4   5   6   7   8   9   A   B   C   D   E   F
+      //-----------------------------------------------------------------------
+      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,  // 00
+      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,  // 10
+      0,  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,  // 20
+      1,  2,  3,  4,  5,  6,  7,  8,  9,  10, -1, -1, -1, -1, -1, -1,  // 30
+      -1, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,  // 40
+      26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, -1, -1, -1, -1, -1,  // 50
+      37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, -1, 49, 50, 51,  // 60
+      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,  // 70
+      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,  // 80
+      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,  // 90
+      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,  // A0
+      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 52, 53, 54, 55, 56, 57,  // B0
+      58, 59, 60, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,  // C0
+      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 61, 62, 63, 64, 65,  // D0
+      -1, 66, 67, 68, 69, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,  // E0
+      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1   // F0
+  };
+
+  return xlat[aVirtualKey];
+}
+
+const DeadKeyTable* KeyboardLayout::AddDeadKeyTable(
+    const DeadKeyEntry* aDeadKeyArray, uint32_t aEntries) {
+  DeadKeyTableListEntry* next = mDeadKeyTableListHead;
+
+  const size_t bytes = offsetof(DeadKeyTableListEntry, data) +
+                       DeadKeyTable::SizeInBytes(aEntries);
+  uint8_t* p = new uint8_t[bytes];
+
+  mDeadKeyTableListHead = reinterpret_cast<DeadKeyTableListEntry*>(p);
+  mDeadKeyTableListHead->next = next;
+
+  DeadKeyTable* dkt =
+      reinterpret_cast<DeadKeyTable*>(mDeadKeyTableListHead->data);
+
+  dkt->Init(aDeadKeyArray, aEntries);
+
+  return dkt;
+}
+
+void KeyboardLayout::ReleaseDeadKeyTables() {
+  while (mDeadKeyTableListHead) {
+    uint8_t* p = reinterpret_cast<uint8_t*>(mDeadKeyTableListHead);
+    mDeadKeyTableListHead = mDeadKeyTableListHead->next;
+
+    delete[] p;
+  }
+}
+
+bool KeyboardLayout::EnsureDeadKeyActive(bool aIsActive, uint8_t aDeadKey,
+                                         const PBYTE aDeadKeyKbdState) {
+  int32_t ret;
+  do {
+    char16_t dummyChars[5];
+    ret =
+        ::ToUnicodeEx(aDeadKey, 0, (PBYTE)aDeadKeyKbdState, (LPWSTR)dummyChars,
+                      ArrayLength(dummyChars), 0, mKeyboardLayout);
+    // returned values:
+    // <0 - Dead key state is active. The keyboard driver will wait for next
+    //      character.
+    //  1 - Previous pressed key was a valid base character that produced
+    //      exactly one composite character.
+    // >1 - Previous pressed key does not produce any composite characters.
+    //      Return dead-key character followed by base character(s).
+  } while ((ret < 0) != aIsActive);
+
+  return (ret < 0);
+}
+
+void KeyboardLayout::ActivateDeadKeyState(const NativeKey& aNativeKey) {
+  // Dead-key state should be activated at keydown.
+  if (!aNativeKey.IsKeyDownMessage()) {
+    return;
+  }
+
+  mActiveDeadKeys.AppendElement(aNativeKey.mOriginalVirtualKeyCode);
+  mDeadKeyShiftStates.AppendElement(aNativeKey.GetShiftState());
+}
+
+void KeyboardLayout::DeactivateDeadKeyState() {
+  if (mActiveDeadKeys.IsEmpty()) {
+    return;
+  }
+
+  BYTE kbdState[256];
+  memset(kbdState, 0, sizeof(kbdState));
+
+  // Assume that the last dead key can finish dead key sequence.
+  VirtualKey::FillKbdState(kbdState, mDeadKeyShiftStates.LastElement());
+  EnsureDeadKeyActive(false, mActiveDeadKeys.LastElement(), kbdState);
+  mActiveDeadKeys.Clear();
+  mDeadKeyShiftStates.Clear();
+}
+
+bool KeyboardLayout::AddDeadKeyEntry(char16_t aBaseChar,
+                                     char16_t aCompositeChar,
+                                     nsTArray<DeadKeyEntry>& aDeadKeyArray) {
+  auto dke = DeadKeyEntry(aBaseChar, aCompositeChar);
+  for (uint32_t index = 0; index < aDeadKeyArray.Length(); index++) {
+    if (aDeadKeyArray[index] == dke) {
+      return false;
+    }
+  }
+
+  aDeadKeyArray.AppendElement(dke);
+
+  return true;
+}
+
+uint32_t KeyboardLayout::GetDeadKeyCombinations(
+    uint8_t aDeadKey, const PBYTE aDeadKeyKbdState,
+    uint16_t aShiftStatesWithBaseChars, nsTArray<DeadKeyEntry>& aDeadKeyArray) {
+  bool deadKeyActive = false;
+  uint32_t entries = 0;
+  BYTE kbdState[256];
+  memset(kbdState, 0, sizeof(kbdState));
+
+  for (uint32_t shiftState = 0; shiftState < 16; shiftState++) {
+    if (!(aShiftStatesWithBaseChars & (1 << shiftState))) {
+      continue;
+    }
+
+    VirtualKey::FillKbdState(kbdState, shiftState);
+
+    for (uint32_t virtualKey = 0; virtualKey < 256; virtualKey++) {
+      int32_t vki = GetKeyIndex(virtualKey);
+      // Dead-key can pair only with such key that produces exactly one base
+      // character.
+      if (vki >= 0 &&
+          mVirtualKeys[vki].GetNativeUniChars(shiftState).Length() == 1) {
+        // Ensure dead-key is in active state, when it swallows entered
+        // character and waits for the next pressed key.
+        if (!deadKeyActive) {
+          deadKeyActive = EnsureDeadKeyActive(true, aDeadKey, aDeadKeyKbdState);
+        }
+
+        // Depending on the character the followed the dead-key, the keyboard
+        // driver can produce one composite character, or a dead-key character
+        // followed by a second character.
+        char16_t compositeChars[5];
+        int32_t ret =
+            ::ToUnicodeEx(virtualKey, 0, kbdState, (LPWSTR)compositeChars,
+                          ArrayLength(compositeChars), 0, mKeyboardLayout);
+        switch (ret) {
+          case 0:
+            // This key combination does not produce any characters. The
+            // dead-key is still in active state.
+            break;
+          case 1: {
+            char16_t baseChars[5];
+            ret = ::ToUnicodeEx(virtualKey, 0, kbdState, (LPWSTR)baseChars,
+                                ArrayLength(baseChars), 0, mKeyboardLayout);
+            if (entries < aDeadKeyArray.Capacity()) {
+              switch (ret) {
+                case 1:
+                  // Exactly one composite character produced. Now, when
+                  // dead-key is not active, repeat the last character one more
+                  // time to determine the base character.
+                  if (AddDeadKeyEntry(baseChars[0], compositeChars[0],
+                                      aDeadKeyArray)) {
+                    entries++;
+                  }
+                  deadKeyActive = false;
+                  break;
+                case -1: {
+                  // If pressing another dead-key produces different character,
+                  // we should register the dead-key entry with first character
+                  // produced by current key.
+
+                  // First inactivate the dead-key state completely.
+                  deadKeyActive =
+                      EnsureDeadKeyActive(false, aDeadKey, aDeadKeyKbdState);
+                  if (NS_WARN_IF(deadKeyActive)) {
+                    MOZ_LOG(gKeyLog, LogLevel::Error,
+                            ("  failed to deactivating the dead-key state..."));
+                    break;
+                  }
+                  for (int32_t i = 0; i < 5; ++i) {
+                    ret = ::ToUnicodeEx(
+                        virtualKey, 0, kbdState, (LPWSTR)baseChars,
+                        ArrayLength(baseChars), 0, mKeyboardLayout);
+                    if (ret >= 0) {
+                      break;
+                    }
+                  }
+                  if (ret > 0 &&
+                      AddDeadKeyEntry(baseChars[0], compositeChars[0],
+                                      aDeadKeyArray)) {
+                    entries++;
+                  }
+                  // Inactivate dead-key state for current virtual keycode.
+                  EnsureDeadKeyActive(false, virtualKey, kbdState);
+                  break;
+                }
+                default:
+                  NS_WARNING("File a bug for this dead-key handling!");
+                  deadKeyActive = false;
+                  break;
+              }
+            }
+            MOZ_LOG(
+                gKeyLog, LogLevel::Verbose,
+                ("  %s -> %s (%d): DeadKeyEntry(%s, %s) (ret=%d)",
+                 kVirtualKeyName[aDeadKey], kVirtualKeyName[virtualKey], vki,
+                 GetCharacterCodeNames(compositeChars, 1).get(),
+                 ret <= 0
+                     ? "''"
+                     : GetCharacterCodeNames(baseChars, std::min(ret, 5)).get(),
+                 ret));
+            break;
+          }
+          default:
+            // 1. Unexpected dead-key. Dead-key chaining is not supported.
+            // 2. More than one character generated. This is not a valid
+            //    dead-key and base character combination.
+            deadKeyActive = false;
+            MOZ_LOG(
+                gKeyLog, LogLevel::Verbose,
+                ("  %s -> %s (%d): Unsupport dead key type(%s) (ret=%d)",
+                 kVirtualKeyName[aDeadKey], kVirtualKeyName[virtualKey], vki,
+                 ret <= 0
+                     ? "''"
+                     : GetCharacterCodeNames(compositeChars, std::min(ret, 5))
+                           .get(),
+                 ret));
+            break;
+        }
+      }
+    }
+  }
+
+  if (deadKeyActive) {
+    deadKeyActive = EnsureDeadKeyActive(false, aDeadKey, aDeadKeyKbdState);
+  }
+
+  aDeadKeyArray.Sort();
+
+  return entries;
+}
+
+uint32_t KeyboardLayout::ConvertNativeKeyCodeToDOMKeyCode(
+    UINT aNativeKeyCode) const {
+  // Alphabet or Numeric or Numpad or Function keys
+  if ((aNativeKeyCode >= 0x30 && aNativeKeyCode <= 0x39) ||
+      (aNativeKeyCode >= 0x41 && aNativeKeyCode <= 0x5A) ||
+      (aNativeKeyCode >= 0x60 && aNativeKeyCode <= 0x87)) {
+    return static_cast<uint32_t>(aNativeKeyCode);
+  }
+  switch (aNativeKeyCode) {
+    // Following keycodes are same as our DOM keycodes
+    case VK_CANCEL:
+    case VK_BACK:
+    case VK_TAB:
+    case VK_CLEAR:
+    case VK_RETURN:
+    case VK_SHIFT:
+    case VK_CONTROL:
+    case VK_MENU:  // Alt
+    case VK_PAUSE:
+    case VK_CAPITAL:  // CAPS LOCK
+    case VK_KANA:     // same as VK_HANGUL
+    case VK_JUNJA:
+    case VK_FINAL:
+    case VK_HANJA:  // same as VK_KANJI
+    case VK_ESCAPE:
+    case VK_CONVERT:
+    case VK_NONCONVERT:
+    case VK_ACCEPT:
+    case VK_MODECHANGE:
+    case VK_SPACE:
+    case VK_PRIOR:  // PAGE UP
+    case VK_NEXT:   // PAGE DOWN
+    case VK_END:
+    case VK_HOME:
+    case VK_LEFT:
+    case VK_UP:
+    case VK_RIGHT:
+    case VK_DOWN:
+    case VK_SELECT:
+    case VK_PRINT:
+    case VK_EXECUTE:
+    case VK_SNAPSHOT:
+    case VK_INSERT:
+    case VK_DELETE:
+    case VK_APPS:  // Context Menu
+    case VK_SLEEP:
+    case VK_NUMLOCK:
+    case VK_SCROLL:  // SCROLL LOCK
+    case VK_ATTN:    // Attension key of IBM midrange computers, e.g., AS/400
+    case VK_CRSEL:   // Cursor Selection
+    case VK_EXSEL:   // Extend Selection
+    case VK_EREOF:   // Erase EOF key of IBM 3270 keyboard layout
+    case VK_PLAY:
+    case VK_ZOOM:
+    case VK_PA1:  // PA1 key of IBM 3270 keyboard layout
+      return uint32_t(aNativeKeyCode);
+
+    case VK_HELP:
+      return NS_VK_HELP;
+
+    // Windows key should be mapped to a Win keycode
+    // They should be able to be distinguished by DOM3 KeyboardEvent.location
+    case VK_LWIN:
+    case VK_RWIN:
+      return NS_VK_WIN;
+
+    case VK_VOLUME_MUTE:
+      return NS_VK_VOLUME_MUTE;
+    case VK_VOLUME_DOWN:
+      return NS_VK_VOLUME_DOWN;
+    case VK_VOLUME_UP:
+      return NS_VK_VOLUME_UP;
+
+    case VK_LSHIFT:
+    case VK_RSHIFT:
+      return NS_VK_SHIFT;
+
+    case VK_LCONTROL:
+    case VK_RCONTROL:
+      return NS_VK_CONTROL;
+
+    // Note that even if the key is AltGr, we should return NS_VK_ALT for
+    // compatibility with both older Gecko and the other browsers.
+    case VK_LMENU:
+    case VK_RMENU:
+      return NS_VK_ALT;
+
+    // Following keycodes are not defined in our DOM keycodes.
+    case VK_BROWSER_BACK:
+    case VK_BROWSER_FORWARD:
+    case VK_BROWSER_REFRESH:
+    case VK_BROWSER_STOP:
+    case VK_BROWSER_SEARCH:
+    case VK_BROWSER_FAVORITES:
+    case VK_BROWSER_HOME:
+    case VK_MEDIA_NEXT_TRACK:
+    case VK_MEDIA_PREV_TRACK:
+    case VK_MEDIA_STOP:
+    case VK_MEDIA_PLAY_PAUSE:
+    case VK_LAUNCH_MAIL:
+    case VK_LAUNCH_MEDIA_SELECT:
+    case VK_LAUNCH_APP1:
+    case VK_LAUNCH_APP2:
+      return 0;
+
+    // Following OEM specific virtual keycodes should pass through DOM keyCode
+    // for compatibility with the other browsers on Windows.
+
+    // Following OEM specific virtual keycodes are defined for Fujitsu/OASYS.
+    case VK_OEM_FJ_JISHO:
+    case VK_OEM_FJ_MASSHOU:
+    case VK_OEM_FJ_TOUROKU:
+    case VK_OEM_FJ_LOYA:
+    case VK_OEM_FJ_ROYA:
+    // Not sure what means "ICO".
+    case VK_ICO_HELP:
+    case VK_ICO_00:
+    case VK_ICO_CLEAR:
+    // Following OEM specific virtual keycodes are defined for Nokia/Ericsson.
+    case VK_OEM_RESET:
+    case VK_OEM_JUMP:
+    case VK_OEM_PA1:
+    case VK_OEM_PA2:
+    case VK_OEM_PA3:
+    case VK_OEM_WSCTRL:
+    case VK_OEM_CUSEL:
+    case VK_OEM_ATTN:
+    case VK_OEM_FINISH:
+    case VK_OEM_COPY:
+    case VK_OEM_AUTO:
+    case VK_OEM_ENLW:
+    case VK_OEM_BACKTAB:
+    // VK_OEM_CLEAR is defined as not OEM specific, but let's pass though
+    // DOM keyCode like other OEM specific virtual keycodes.
+    case VK_OEM_CLEAR:
+      return uint32_t(aNativeKeyCode);
+
+    // 0xE1 is an OEM specific virtual keycode. However, the value is already
+    // used in our DOM keyCode for AltGr on Linux. So, this virtual keycode
+    // cannot pass through DOM keyCode.
+    case 0xE1:
+      return 0;
+
+    // Following keycodes are OEM keys which are keycodes for non-alphabet and
+    // non-numeric keys, we should compute each keycode of them from unshifted
+    // character which is inputted by each key.  But if the unshifted character
+    // is not an ASCII character but shifted character is an ASCII character,
+    // we should refer it.
+    case VK_OEM_1:
+    case VK_OEM_PLUS:
+    case VK_OEM_COMMA:
+    case VK_OEM_MINUS:
+    case VK_OEM_PERIOD:
+    case VK_OEM_2:
+    case VK_OEM_3:
+    case VK_OEM_4:
+    case VK_OEM_5:
+    case VK_OEM_6:
+    case VK_OEM_7:
+    case VK_OEM_8:
+    case VK_OEM_102:
+    case VK_ABNT_C1: {
+      NS_ASSERTION(IsPrintableCharKey(aNativeKeyCode),
+                   "The key must be printable");
+      ModifierKeyState modKeyState(0);
+      UniCharsAndModifiers uniChars =
+          GetUniCharsAndModifiers(aNativeKeyCode, modKeyState);
+      if (uniChars.Length() != 1 || uniChars.CharAt(0) < ' ' ||
+          uniChars.CharAt(0) > 0x7F) {
+        modKeyState.Set(MODIFIER_SHIFT);
+        uniChars = GetUniCharsAndModifiers(aNativeKeyCode, modKeyState);
+        if (uniChars.Length() != 1 || uniChars.CharAt(0) < ' ' ||
+            uniChars.CharAt(0) > 0x7F) {
+          // In this case, we've returned 0 in this case for long time because
+          // we decided that we should avoid setting same keyCode value to 2 or
+          // more keys since active keyboard layout may have a key to input the
+          // punctuation with different key.  However, setting keyCode to 0
+          // makes some web applications which are aware of neither
+          // KeyboardEvent.key nor KeyboardEvent.code not work with Firefox
+          // when user selects non-ASCII capable keyboard layout such as
+          // Russian and Thai layout.  So, let's decide keyCode value with
+          // major keyboard layout's key which causes the OEM keycode.
+          // Actually, this maps same keyCode value to 2 keys on Russian
+          // keyboard layout.  "Period" key causes VK_OEM_PERIOD but inputs
+          // Yu of Cyrillic and "Slash" key causes VK_OEM_2 (same as US
+          // keyboard layout) but inputs "." (period of ASCII).  Therefore,
+          // we return DOM_VK_PERIOD which is same as VK_OEM_PERIOD for
+          // "Period" key.  On the other hand, we use same keyCode value for
+          // "Slash" key too because it inputs ".".
+          CodeNameIndex code;
+          switch (aNativeKeyCode) {
+            case VK_OEM_1:
+              code = CODE_NAME_INDEX_Semicolon;
+              break;
+            case VK_OEM_PLUS:
+              code = CODE_NAME_INDEX_Equal;
+              break;
+            case VK_OEM_COMMA:
+              code = CODE_NAME_INDEX_Comma;
+              break;
+            case VK_OEM_MINUS:
+              code = CODE_NAME_INDEX_Minus;
+              break;
+            case VK_OEM_PERIOD:
+              code = CODE_NAME_INDEX_Period;
+              break;
+            case VK_OEM_2:
+              code = CODE_NAME_INDEX_Slash;
+              break;
+            case VK_OEM_3:
+              code = CODE_NAME_INDEX_Backquote;
+              break;
+            case VK_OEM_4:
+              code = CODE_NAME_INDEX_BracketLeft;
+              break;
+            case VK_OEM_5:
+              code = CODE_NAME_INDEX_Backslash;
+              break;
+            case VK_OEM_6:
+              code = CODE_NAME_INDEX_BracketRight;
+              break;
+            case VK_OEM_7:
+              code = CODE_NAME_INDEX_Quote;
+              break;
+            case VK_OEM_8:
+              // Use keyCode value for "Backquote" key on UK keyboard layout.
+              code = CODE_NAME_INDEX_Backquote;
+              break;
+            case VK_OEM_102:
+              // Use keyCode value for "IntlBackslash" key.
+              code = CODE_NAME_INDEX_IntlBackslash;
+              break;
+            case VK_ABNT_C1:  // "/" of ABNT.
+              // Use keyCode value for "IntlBackslash" key on ABNT keyboard
+              // layout.
+              code = CODE_NAME_INDEX_IntlBackslash;
+              break;
+            default:
+              MOZ_ASSERT_UNREACHABLE("Handle all OEM keycode values");
+              return 0;
+          }
+          return WidgetKeyboardEvent::GetFallbackKeyCodeOfPunctuationKey(code);
+        }
+      }
+      return WidgetUtils::ComputeKeyCodeFromChar(uniChars.CharAt(0));
+    }
+
+    // IE sets 0xC2 to the DOM keyCode for VK_ABNT_C2.  However, we're already
+    // using NS_VK_SEPARATOR for the separator key on Mac and Linux.  Therefore,
+    // We should keep consistency between Gecko on all platforms rather than
+    // with other browsers since a lot of keyCode values are already different
+    // between browsers.
+    case VK_ABNT_C2:
+      return NS_VK_SEPARATOR;
+
+    // VK_PROCESSKEY means IME already consumed the key event.
+    case VK_PROCESSKEY:
+      return NS_VK_PROCESSKEY;
+    // VK_PACKET is generated by SendInput() API, we don't need to
+    // care this message as key event.
+    case VK_PACKET:
+      return 0;
+    // If a key is not mapped to a virtual keycode, 0xFF is used.
+    case 0xFF:
+      NS_WARNING("The key is failed to be converted to a virtual keycode");
+      return 0;
+  }
+#ifdef DEBUG
+  nsPrintfCString warning(
+      "Unknown virtual keycode (0x%08X), please check the "
+      "latest MSDN document, there may be some new "
+      "keycodes we've never known.",
+      aNativeKeyCode);
+  NS_WARNING(warning.get());
+#endif
+  return 0;
+}
+
+KeyNameIndex KeyboardLayout::ConvertNativeKeyCodeToKeyNameIndex(
+    uint8_t aVirtualKey) const {
+  if (IsPrintableCharKey(aVirtualKey) || aVirtualKey == VK_PACKET) {
+    return KEY_NAME_INDEX_USE_STRING;
+  }
+
+  // If the keyboard layout has AltGr and AltRight key is pressed,
+  // return AltGraph.
+  if (aVirtualKey == VK_RMENU && HasAltGr()) {
+    return KEY_NAME_INDEX_AltGraph;
+  }
+
+  switch (aVirtualKey) {
+#undef NS_NATIVE_KEY_TO_DOM_KEY_NAME_INDEX
+#define NS_NATIVE_KEY_TO_DOM_KEY_NAME_INDEX(aNativeKey, aKeyNameIndex) \
+  case aNativeKey:                                                     \
+    return aKeyNameIndex;
+
+#include "NativeKeyToDOMKeyName.h"
+
+#undef NS_NATIVE_KEY_TO_DOM_KEY_NAME_INDEX
+
+    default:
+      break;
+  }
+
+  HKL layout = KeyboardLayout::GetLayout();
+  WORD langID = LOWORD(static_cast<HKL>(layout));
+  WORD primaryLangID = PRIMARYLANGID(langID);
+
+  if (primaryLangID == LANG_JAPANESE) {
+    switch (aVirtualKey) {
+#undef NS_JAPANESE_NATIVE_KEY_TO_DOM_KEY_NAME_INDEX
+#define NS_JAPANESE_NATIVE_KEY_TO_DOM_KEY_NAME_INDEX(aNativeKey,    \
+                                                     aKeyNameIndex) \
+  case aNativeKey:                                                  \
+    return aKeyNameIndex;
+
+#include "NativeKeyToDOMKeyName.h"
+
+#undef NS_JAPANESE_NATIVE_KEY_TO_DOM_KEY_NAME_INDEX
+
+      default:
+        break;
+    }
+  } else if (primaryLangID == LANG_KOREAN) {
+    switch (aVirtualKey) {
+#undef NS_KOREAN_NATIVE_KEY_TO_DOM_KEY_NAME_INDEX
+#define NS_KOREAN_NATIVE_KEY_TO_DOM_KEY_NAME_INDEX(aNativeKey, aKeyNameIndex) \
+  case aNativeKey:                                                            \
+    return aKeyNameIndex;
+
+#include "NativeKeyToDOMKeyName.h"
+
+#undef NS_KOREAN_NATIVE_KEY_TO_DOM_KEY_NAME_INDEX
+
+      default:
+        return KEY_NAME_INDEX_Unidentified;
+    }
+  }
+
+  switch (aVirtualKey) {
+#undef NS_OTHER_NATIVE_KEY_TO_DOM_KEY_NAME_INDEX
+#define NS_OTHER_NATIVE_KEY_TO_DOM_KEY_NAME_INDEX(aNativeKey, aKeyNameIndex) \
+  case aNativeKey:                                                           \
+    return aKeyNameIndex;
+
+#include "NativeKeyToDOMKeyName.h"
+
+#undef NS_OTHER_NATIVE_KEY_TO_DOM_KEY_NAME_INDEX
+
+    default:
+      return KEY_NAME_INDEX_Unidentified;
+  }
+}
+
+// static
+CodeNameIndex KeyboardLayout::ConvertScanCodeToCodeNameIndex(UINT aScanCode) {
+  switch (aScanCode) {
+#define NS_NATIVE_KEY_TO_DOM_CODE_NAME_INDEX(aNativeKey, aCodeNameIndex) \
+  case aNativeKey:                                                       \
+    return aCodeNameIndex;
+
+#include "NativeKeyToDOMCodeName.h"
+
+#undef NS_NATIVE_KEY_TO_DOM_CODE_NAME_INDEX
+
+    default:
+      return CODE_NAME_INDEX_UNKNOWN;
+  }
+}
+
+nsresult KeyboardLayout::SynthesizeNativeKeyEvent(
+    nsWindow* aWidget, int32_t aNativeKeyboardLayout, int32_t aNativeKeyCode,
+    uint32_t aModifierFlags, const nsAString& aCharacters,
+    const nsAString& aUnmodifiedCharacters) {
+  UINT keyboardLayoutListCount = ::GetKeyboardLayoutList(0, nullptr);
+  NS_ASSERTION(keyboardLayoutListCount > 0,
+               "One keyboard layout must be installed at least");
+  HKL keyboardLayoutListBuff[50];
+  HKL* keyboardLayoutList = keyboardLayoutListCount < 50
+                                ? keyboardLayoutListBuff
+                                : new HKL[keyboardLayoutListCount];
+  keyboardLayoutListCount =
+      ::GetKeyboardLayoutList(keyboardLayoutListCount, keyboardLayoutList);
+  NS_ASSERTION(keyboardLayoutListCount > 0,
+               "Failed to get all keyboard layouts installed on the system");
+
+  nsPrintfCString layoutName("%08x", aNativeKeyboardLayout);
+  HKL loadedLayout = LoadKeyboardLayoutA(layoutName.get(), KLF_NOTELLSHELL);
+  if (loadedLayout == nullptr) {
+    if (keyboardLayoutListBuff != keyboardLayoutList) {
+      delete[] keyboardLayoutList;
+    }
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  // Setup clean key state and load desired layout
+  BYTE originalKbdState[256];
+  ::GetKeyboardState(originalKbdState);
+  BYTE kbdState[256];
+  memset(kbdState, 0, sizeof(kbdState));
+  // This changes the state of the keyboard for the current thread only,
+  // and we'll restore it soon, so this should be OK.
+  ::SetKeyboardState(kbdState);
+
+  OverrideLayout(loadedLayout);
+
+  bool isAltGrKeyPress = false;
+  if (aModifierFlags & nsIWidget::ALTGRAPH) {
+    if (!HasAltGr()) {
+      return NS_ERROR_INVALID_ARG;
+    }
+    // AltGr emulates ControlLeft key press and AltRight key press.
+    // So, we should remove those flags from aModifierFlags before
+    // calling WinUtils::SetupKeyModifiersSequence() to create correct
+    // key sequence.
+    // FYI: We don't support both ControlLeft and AltRight (AltGr) are
+    //      pressed at the same time unless synthesizing key is
+    //      VK_LCONTROL.
+    aModifierFlags &= ~(nsIWidget::CTRL_L | nsIWidget::ALT_R);
+  }
+
+  uint8_t argumentKeySpecific = 0;
+  switch (aNativeKeyCode & 0xFF) {
+    case VK_SHIFT:
+      aModifierFlags &= ~(nsIWidget::SHIFT_L | nsIWidget::SHIFT_R);
+      argumentKeySpecific = VK_LSHIFT;
+      break;
+    case VK_LSHIFT:
+      aModifierFlags &= ~nsIWidget::SHIFT_L;
+      argumentKeySpecific = aNativeKeyCode & 0xFF;
+      aNativeKeyCode = (aNativeKeyCode & 0xFFFF0000) | VK_SHIFT;
+      break;
+    case VK_RSHIFT:
+      aModifierFlags &= ~nsIWidget::SHIFT_R;
+      argumentKeySpecific = aNativeKeyCode & 0xFF;
+      aNativeKeyCode = (aNativeKeyCode & 0xFFFF0000) | VK_SHIFT;
+      break;
+    case VK_CONTROL:
+      aModifierFlags &= ~(nsIWidget::CTRL_L | nsIWidget::CTRL_R);
+      argumentKeySpecific = VK_LCONTROL;
+      break;
+    case VK_LCONTROL:
+      aModifierFlags &= ~nsIWidget::CTRL_L;
+      argumentKeySpecific = aNativeKeyCode & 0xFF;
+      aNativeKeyCode = (aNativeKeyCode & 0xFFFF0000) | VK_CONTROL;
+      break;
+    case VK_RCONTROL:
+      aModifierFlags &= ~nsIWidget::CTRL_R;
+      argumentKeySpecific = aNativeKeyCode & 0xFF;
+      aNativeKeyCode = (aNativeKeyCode & 0xFFFF0000) | VK_CONTROL;
+      break;
+    case VK_MENU:
+      aModifierFlags &= ~(nsIWidget::ALT_L | nsIWidget::ALT_R);
+      argumentKeySpecific = VK_LMENU;
+      break;
+    case VK_LMENU:
+      aModifierFlags &= ~nsIWidget::ALT_L;
+      argumentKeySpecific = aNativeKeyCode & 0xFF;
+      aNativeKeyCode = (aNativeKeyCode & 0xFFFF0000) | VK_MENU;
+      break;
+    case VK_RMENU:
+      aModifierFlags &= ~(nsIWidget::ALT_R | nsIWidget::ALTGRAPH);
+      argumentKeySpecific = aNativeKeyCode & 0xFF;
+      aNativeKeyCode = (aNativeKeyCode & 0xFFFF0000) | VK_MENU;
+      // If AltRight key is AltGr in the keyboard layout, let's use
+      // SetupKeyModifiersSequence() to emulate the native behavior
+      // since the same event order between keydown and keyup makes
+      // the following code complicated.
+      if (HasAltGr()) {
+        isAltGrKeyPress = true;
+        aModifierFlags &= ~nsIWidget::CTRL_L;
+        aModifierFlags |= nsIWidget::ALTGRAPH;
+      }
+      break;
+    case VK_CAPITAL:
+      aModifierFlags &= ~nsIWidget::CAPS_LOCK;
+      argumentKeySpecific = VK_CAPITAL;
+      break;
+    case VK_NUMLOCK:
+      aModifierFlags &= ~nsIWidget::NUM_LOCK;
+      argumentKeySpecific = VK_NUMLOCK;
+      break;
+  }
+
+  AutoTArray<KeyPair, 10> keySequence;
+  WinUtils::SetupKeyModifiersSequence(&keySequence, aModifierFlags, WM_KEYDOWN);
+  if (!isAltGrKeyPress) {
+    keySequence.AppendElement(KeyPair(aNativeKeyCode, argumentKeySpecific));
+  }
+
+  // Simulate the pressing of each modifier key and then the real key
+  // FYI: Each NativeKey instance here doesn't need to override keyboard layout
+  //      since this method overrides and restores the keyboard layout.
+  for (uint32_t i = 0; i < keySequence.Length(); ++i) {
+    uint8_t key = keySequence[i].mGeneral;
+    uint8_t keySpecific = keySequence[i].mSpecific;
+    uint16_t scanCode = keySequence[i].mScanCode;
+    kbdState[key] = 0x81;  // key is down and toggled on if appropriate
+    if (keySpecific) {
+      kbdState[keySpecific] = 0x81;
+    }
+    ::SetKeyboardState(kbdState);
+    ModifierKeyState modKeyState;
+    // If scan code isn't specified explicitly, let's compute it with current
+    // keyboard layout.
+    if (!scanCode) {
+      scanCode =
+          ComputeScanCodeForVirtualKeyCode(keySpecific ? keySpecific : key);
+    }
+    LPARAM lParam = static_cast<LPARAM>(scanCode << 16);
+    // If the scan code is for an extended key, set extended key flag.
+    if ((scanCode & 0xFF00) == 0xE000) {
+      lParam |= 0x1000000;
+    }
+    // When AltGr key is pressed, both ControlLeft and AltRight cause
+    // WM_KEYDOWN messages.
+    bool makeSysKeyMsg =
+        !(aModifierFlags & nsIWidget::ALTGRAPH) && IsSysKey(key, modKeyState);
+    MSG keyDownMsg =
+        WinUtils::InitMSG(makeSysKeyMsg ? WM_SYSKEYDOWN : WM_KEYDOWN, key,
+                          lParam, aWidget->GetWindowHandle());
+    if (i == keySequence.Length() - 1) {
+      bool makeDeadCharMsg =
+          (IsDeadKey(key, modKeyState) && aCharacters.IsEmpty());
+      nsAutoString chars(aCharacters);
+      if (makeDeadCharMsg) {
+        UniCharsAndModifiers deadChars =
+            GetUniCharsAndModifiers(key, modKeyState);
+        chars = deadChars.ToString();
+        NS_ASSERTION(chars.Length() == 1,
+                     "Dead char must be only one character");
+      }
+      if (chars.IsEmpty()) {
+        NativeKey nativeKey(aWidget, keyDownMsg, modKeyState);
+        nativeKey.HandleKeyDownMessage();
+      } else {
+        AutoTArray<NativeKey::FakeCharMsg, 10> fakeCharMsgs;
+        for (uint32_t j = 0; j < chars.Length(); j++) {
+          NativeKey::FakeCharMsg* fakeCharMsg = fakeCharMsgs.AppendElement();
+          fakeCharMsg->mCharCode = chars.CharAt(j);
+          fakeCharMsg->mScanCode = scanCode;
+          fakeCharMsg->mIsSysKey = makeSysKeyMsg;
+          fakeCharMsg->mIsDeadKey = makeDeadCharMsg;
+        }
+        NativeKey nativeKey(aWidget, keyDownMsg, modKeyState, 0, &fakeCharMsgs);
+        bool dispatched;
+        nativeKey.HandleKeyDownMessage(&dispatched);
+        // If some char messages are not consumed, let's emulate the widget
+        // receiving the message directly.
+        for (uint32_t j = 1; j < fakeCharMsgs.Length(); j++) {
+          if (fakeCharMsgs[j].mConsumed) {
+            continue;
+          }
+          MSG charMsg = fakeCharMsgs[j].GetCharMsg(aWidget->GetWindowHandle());
+          NativeKey nativeKey(aWidget, charMsg, modKeyState);
+          nativeKey.HandleCharMessage(charMsg);
+        }
+      }
+    } else {
+      NativeKey nativeKey(aWidget, keyDownMsg, modKeyState);
+      nativeKey.HandleKeyDownMessage();
+    }
+  }
+
+  keySequence.Clear();
+  if (!isAltGrKeyPress) {
+    keySequence.AppendElement(KeyPair(aNativeKeyCode, argumentKeySpecific));
+  }
+  WinUtils::SetupKeyModifiersSequence(&keySequence, aModifierFlags, WM_KEYUP);
+  for (uint32_t i = 0; i < keySequence.Length(); ++i) {
+    uint8_t key = keySequence[i].mGeneral;
+    uint8_t keySpecific = keySequence[i].mSpecific;
+    uint16_t scanCode = keySequence[i].mScanCode;
+    kbdState[key] = 0;  // key is up and toggled off if appropriate
+    if (keySpecific) {
+      kbdState[keySpecific] = 0;
+    }
+    ::SetKeyboardState(kbdState);
+    ModifierKeyState modKeyState;
+    // If scan code isn't specified explicitly, let's compute it with current
+    // keyboard layout.
+    if (!scanCode) {
+      scanCode =
+          ComputeScanCodeForVirtualKeyCode(keySpecific ? keySpecific : key);
+    }
+    LPARAM lParam = static_cast<LPARAM>(scanCode << 16);
+    // If the scan code is for an extended key, set extended key flag.
+    if ((scanCode & 0xFF00) == 0xE000) {
+      lParam |= 0x1000000;
+    }
+    // Don't use WM_SYSKEYUP for Alt keyup.
+    // NOTE: When AltGr was pressed, ControlLeft causes WM_SYSKEYUP normally.
+    bool makeSysKeyMsg = IsSysKey(key, modKeyState) && key != VK_MENU;
+    MSG keyUpMsg = WinUtils::InitMSG(makeSysKeyMsg ? WM_SYSKEYUP : WM_KEYUP,
+                                     key, lParam, aWidget->GetWindowHandle());
+    NativeKey nativeKey(aWidget, keyUpMsg, modKeyState);
+    nativeKey.HandleKeyUpMessage();
+  }
+
+  // Restore old key state and layout
+  ::SetKeyboardState(originalKbdState);
+  RestoreLayout();
+
+  // Don't unload the layout if it's installed actually.
+  for (uint32_t i = 0; i < keyboardLayoutListCount; i++) {
+    if (keyboardLayoutList[i] == loadedLayout) {
+      loadedLayout = 0;
+      break;
+    }
+  }
+  if (keyboardLayoutListBuff != keyboardLayoutList) {
+    delete[] keyboardLayoutList;
+  }
+  if (loadedLayout) {
+    ::UnloadKeyboardLayout(loadedLayout);
+  }
+  return NS_OK;
+}
+
+/*****************************************************************************
+ * mozilla::widget::DeadKeyTable
+ *****************************************************************************/
+
+char16_t DeadKeyTable::GetCompositeChar(char16_t aBaseChar) const {
+  // Dead-key table is sorted by BaseChar in ascending order.
+  // Usually they are too small to use binary search.
+
+  for (uint32_t index = 0; index < mEntries; index++) {
+    if (mTable[index].BaseChar == aBaseChar) {
+      return mTable[index].CompositeChar;
+    }
+    if (mTable[index].BaseChar > aBaseChar) {
+      break;
+    }
+  }
+
+  return 0;
+}
+
+/*****************************************************************************
+ * mozilla::widget::RedirectedKeyDownMessage
+ *****************************************************************************/
+
+MSG RedirectedKeyDownMessageManager::sRedirectedKeyDownMsg;
+bool RedirectedKeyDownMessageManager::sDefaultPreventedOfRedirectedMsg = false;
+
+// static
+bool RedirectedKeyDownMessageManager::IsRedirectedMessage(const MSG& aMsg) {
+  return (aMsg.message == WM_KEYDOWN || aMsg.message == WM_SYSKEYDOWN) &&
+         (sRedirectedKeyDownMsg.message == aMsg.message &&
+          WinUtils::GetScanCode(sRedirectedKeyDownMsg.lParam) ==
+              WinUtils::GetScanCode(aMsg.lParam));
+}
+
+// static
+void RedirectedKeyDownMessageManager::RemoveNextCharMessage(HWND aWnd) {
+  MSG msg;
+  if (WinUtils::PeekMessage(&msg, aWnd, WM_KEYFIRST, WM_KEYLAST,
+                            PM_NOREMOVE | PM_NOYIELD) &&
+      (msg.message == WM_CHAR || msg.message == WM_SYSCHAR)) {
+    WinUtils::PeekMessage(&msg, aWnd, msg.message, msg.message,
+                          PM_REMOVE | PM_NOYIELD);
+  }
+}
+
+}  // namespace widget
+}  // namespace mozilla
diff --git a/widget/windows/KeyboardLayout.h b/widget/windows/KeyboardLayout.h
new file mode 100644
index 0000000000..5d430dbea0
--- /dev/null
+++ b/widget/windows/KeyboardLayout.h
@@ -0,0 +1,1156 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef KeyboardLayout_h__
+#define KeyboardLayout_h__
+
+#include "mozilla/RefPtr.h"
+#include "nscore.h"
+#include "nsString.h"
+#include "nsTArray.h"
+#include "nsWindow.h"
+#include "nsWindowDefs.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/EventForwards.h"
+#include "mozilla/StaticPtr.h"
+#include "mozilla/TextEventDispatcher.h"
+#include "mozilla/widget/WinMessages.h"
+#include "mozilla/widget/WinModifierKeyState.h"
+#include <windows.h>
+
+#define NS_NUM_OF_KEYS 70
+
+#define VK_OEM_1 0xBA     // ';:' for US
+#define VK_OEM_PLUS 0xBB  // '+' any country
+#define VK_OEM_COMMA 0xBC
+#define VK_OEM_MINUS 0xBD  // '-' any country
+#define VK_OEM_PERIOD 0xBE
+#define VK_OEM_2 0xBF
+#define VK_OEM_3 0xC0
+// '/?' for Brazilian (ABNT)
+#define VK_ABNT_C1 0xC1
+// Separator in Numpad for Brazilian (ABNT) or JIS keyboard for Mac.
+#define VK_ABNT_C2 0xC2
+#define VK_OEM_4 0xDB
+#define VK_OEM_5 0xDC
+#define VK_OEM_6 0xDD
+#define VK_OEM_7 0xDE
+#define VK_OEM_8 0xDF
+#define VK_OEM_102 0xE2
+#define VK_OEM_CLEAR 0xFE
+
+class nsIUserIdleServiceInternal;
+
+namespace mozilla {
+namespace widget {
+
+enum ScanCode : uint16_t {
+  eCapsLock = 0x003A,
+  eNumLock = 0xE045,
+  eShiftLeft = 0x002A,
+  eShiftRight = 0x0036,
+  eControlLeft = 0x001D,
+  eControlRight = 0xE01D,
+  eAltLeft = 0x0038,
+  eAltRight = 0xE038,
+};
+
+// 0: nsIWidget's native modifier flag
+// 1: Virtual keycode which does not distinguish whether left or right location.
+// 2: Virtual keycode which distinguishes whether left or right location.
+// 3: Scan code.
+static const uint32_t sModifierKeyMap[][4] = {
+    {nsIWidget::CAPS_LOCK, VK_CAPITAL, 0, ScanCode::eCapsLock},
+    {nsIWidget::NUM_LOCK, VK_NUMLOCK, 0, ScanCode::eNumLock},
+    {nsIWidget::SHIFT_L, VK_SHIFT, VK_LSHIFT, ScanCode::eShiftLeft},
+    {nsIWidget::SHIFT_R, VK_SHIFT, VK_RSHIFT, ScanCode::eShiftRight},
+    {nsIWidget::CTRL_L, VK_CONTROL, VK_LCONTROL, ScanCode::eControlLeft},
+    {nsIWidget::CTRL_R, VK_CONTROL, VK_RCONTROL, ScanCode::eControlRight},
+    {nsIWidget::ALT_L, VK_MENU, VK_LMENU, ScanCode::eAltLeft},
+    {nsIWidget::ALT_R, VK_MENU, VK_RMENU, ScanCode::eAltRight}};
+
+class KeyboardLayout;
+
+class MOZ_STACK_CLASS UniCharsAndModifiers final {
+ public:
+  UniCharsAndModifiers() {}
+  UniCharsAndModifiers operator+(const UniCharsAndModifiers& aOther) const;
+  UniCharsAndModifiers& operator+=(const UniCharsAndModifiers& aOther);
+
+  /**
+   * Append a pair of unicode character and the final modifier.
+   */
+  void Append(char16_t aUniChar, Modifiers aModifiers);
+  void Clear() {
+    mChars.Truncate();
+    mModifiers.Clear();
+  }
+  bool IsEmpty() const {
+    MOZ_ASSERT(mChars.Length() == mModifiers.Length());
+    return mChars.IsEmpty();
+  }
+
+  char16_t CharAt(size_t aIndex) const {
+    MOZ_ASSERT(aIndex < Length());
+    return mChars[aIndex];
+  }
+  Modifiers ModifiersAt(size_t aIndex) const {
+    MOZ_ASSERT(aIndex < Length());
+    return mModifiers[aIndex];
+  }
+  size_t Length() const {
+    MOZ_ASSERT(mChars.Length() == mModifiers.Length());
+    return mChars.Length();
+  }
+
+  bool IsProducingCharsWithAltGr() const {
+    return !IsEmpty() && (ModifiersAt(0) & MODIFIER_ALTGRAPH) != 0;
+  }
+
+  void FillModifiers(Modifiers aModifiers);
+  /**
+   * OverwriteModifiersIfBeginsWith() assigns mModifiers with aOther between
+   * [0] and [aOther.mLength - 1] only when mChars begins with aOther.mChars.
+   */
+  void OverwriteModifiersIfBeginsWith(const UniCharsAndModifiers& aOther);
+
+  bool UniCharsEqual(const UniCharsAndModifiers& aOther) const;
+  bool UniCharsCaseInsensitiveEqual(const UniCharsAndModifiers& aOther) const;
+  bool BeginsWith(const UniCharsAndModifiers& aOther) const;
+
+  const nsString& ToString() const { return mChars; }
+
+ private:
+  nsAutoString mChars;
+  // 5 is enough number for normal keyboard layout handling.  On Windows,
+  // a dead key sequence may cause inputting up to 5 characters per key press.
+  CopyableAutoTArray<Modifiers, 5> mModifiers;
+};
+
+struct DeadKeyEntry {
+  char16_t BaseChar;
+  char16_t CompositeChar;
+
+  DeadKeyEntry(char16_t aBaseChar, char16_t aCompositeChar)
+      : BaseChar(aBaseChar), CompositeChar(aCompositeChar) {}
+
+  bool operator<(const DeadKeyEntry& aOther) const {
+    return this->BaseChar < aOther.BaseChar;
+  }
+
+  bool operator==(const DeadKeyEntry& aOther) const {
+    return this->BaseChar == aOther.BaseChar;
+  }
+};
+
+class DeadKeyTable {
+  friend class KeyboardLayout;
+
+  uint16_t mEntries;
+  // KeyboardLayout::AddDeadKeyTable() will allocate as many entries as
+  // required.  It is the only way to create new DeadKeyTable instances.
+  DeadKeyEntry mTable[1];
+
+  void Init(const DeadKeyEntry* aDeadKeyArray, uint32_t aEntries) {
+    mEntries = aEntries;
+    memcpy(mTable, aDeadKeyArray, aEntries * sizeof(DeadKeyEntry));
+  }
+
+  static uint32_t SizeInBytes(uint32_t aEntries) {
+    return offsetof(DeadKeyTable, mTable) + aEntries * sizeof(DeadKeyEntry);
+  }
+
+ public:
+  uint32_t Entries() const { return mEntries; }
+
+  bool IsEqual(const DeadKeyEntry* aDeadKeyArray, uint32_t aEntries) const {
+    return (mEntries == aEntries &&
+            !memcmp(mTable, aDeadKeyArray, aEntries * sizeof(DeadKeyEntry)));
+  }
+
+  char16_t GetCompositeChar(char16_t aBaseChar) const;
+};
+
+class VirtualKey {
+ public:
+  enum ShiftStateIndex : uint8_t {
+    //  0 - Normal
+    eNormal = 0,
+    //  1 - Shift
+    eShift,
+    //  2 - Control
+    eControl,
+    //  3 - Control + Shift
+    eControlShift,
+    //  4 - Alt
+    eAlt,
+    //  5 - Alt + Shift
+    eAltShift,
+    //  6 - Alt + Control (AltGr)
+    eAltGr,
+    //  7 - Alt + Control + Shift (AltGr + Shift)
+    eAltGrShift,
+    //  8 - CapsLock
+    eWithCapsLock,
+    //  9 - CapsLock + Shift
+    eShiftWithCapsLock,
+    // 10 - CapsLock + Control
+    eControlWithCapsLock,
+    // 11 - CapsLock + Control + Shift
+    eControlShiftWithCapsLock,
+    // 12 - CapsLock + Alt
+    eAltWithCapsLock,
+    // 13 - CapsLock + Alt + Shift
+    eAltShiftWithCapsLock,
+    // 14 - CapsLock + Alt + Control (CapsLock + AltGr)
+    eAltGrWithCapsLock,
+    // 15 - CapsLock + Alt + Control + Shift (CapsLock + AltGr + Shift)
+    eAltGrShiftWithCapsLock,
+  };
+
+  enum ShiftStateFlag {
+    STATE_SHIFT = 0x01,
+    STATE_CONTROL = 0x02,
+    STATE_ALT = 0x04,
+    STATE_CAPSLOCK = 0x08,
+    // ShiftState needs to have AltGr state separately since this is necessary
+    // for lossless conversion with Modifiers.
+    STATE_ALTGRAPH = 0x80,
+    // Useful to remove or check Ctrl and Alt flags.
+    STATE_CONTROL_ALT = STATE_CONTROL | STATE_ALT,
+  };
+
+  typedef uint8_t ShiftState;
+
+  static ShiftState ModifiersToShiftState(Modifiers aModifiers);
+  static ShiftState ModifierKeyStateToShiftState(
+      const ModifierKeyState& aModKeyState) {
+    return ModifiersToShiftState(aModKeyState.GetModifiers());
+  }
+  static Modifiers ShiftStateToModifiers(ShiftState aShiftState);
+  static bool IsAltGrIndex(uint8_t aIndex) {
+    return (aIndex & STATE_CONTROL_ALT) == STATE_CONTROL_ALT;
+  }
+
+ private:
+  union KeyShiftState {
+    struct {
+      char16_t Chars[4];
+    } Normal;
+    struct {
+      const DeadKeyTable* Table;
+      char16_t DeadChar;
+    } DeadKey;
+  };
+
+  KeyShiftState mShiftStates[16];
+  uint16_t mIsDeadKey;
+
+  static uint8_t ToShiftStateIndex(ShiftState aShiftState) {
+    if (!(aShiftState & STATE_ALTGRAPH)) {
+      MOZ_ASSERT(aShiftState <= eAltGrShiftWithCapsLock);
+      return static_cast<uint8_t>(aShiftState);
+    }
+    uint8_t index = aShiftState & ~STATE_ALTGRAPH;
+    index |= (STATE_ALT | STATE_CONTROL);
+    MOZ_ASSERT(index <= eAltGrShiftWithCapsLock);
+    return index;
+  }
+
+  void SetDeadKey(ShiftState aShiftState, bool aIsDeadKey) {
+    if (aIsDeadKey) {
+      mIsDeadKey |= 1 << ToShiftStateIndex(aShiftState);
+    } else {
+      mIsDeadKey &= ~(1 << ToShiftStateIndex(aShiftState));
+    }
+  }
+
+ public:
+  static void FillKbdState(PBYTE aKbdState, const ShiftState aShiftState);
+
+  bool IsDeadKey(ShiftState aShiftState) const {
+    return (mIsDeadKey & (1 << ToShiftStateIndex(aShiftState))) != 0;
+  }
+
+  /**
+   * IsChangedByAltGr() is useful to check if a key with AltGr produces
+   * different character(s) from the key without AltGr.
+   * Note that this is designed for checking if a keyboard layout has AltGr
+   * key.  So, this result may not exactly correct for the key since it's
+   * okay to fails in some edge cases when we check all keys which produce
+   * character(s) in a layout.
+   */
+  bool IsChangedByAltGr(ShiftState aShiftState) const {
+    MOZ_ASSERT(aShiftState == ToShiftStateIndex(aShiftState));
+    MOZ_ASSERT(IsAltGrIndex(aShiftState));
+    MOZ_ASSERT(IsDeadKey(aShiftState) ||
+               mShiftStates[aShiftState].Normal.Chars[0]);
+    const ShiftState kShiftStateWithoutAltGr =
+        aShiftState - ShiftStateIndex::eAltGr;
+    if (IsDeadKey(aShiftState) != IsDeadKey(kShiftStateWithoutAltGr)) {
+      return false;
+    }
+    if (IsDeadKey(aShiftState)) {
+      return mShiftStates[aShiftState].DeadKey.DeadChar !=
+             mShiftStates[kShiftStateWithoutAltGr].DeadKey.DeadChar;
+    }
+    for (size_t i = 0; i < 4; i++) {
+      if (mShiftStates[aShiftState].Normal.Chars[i] !=
+          mShiftStates[kShiftStateWithoutAltGr].Normal.Chars[i]) {
+        return true;
+      }
+      if (!mShiftStates[aShiftState].Normal.Chars[i] &&
+          !mShiftStates[kShiftStateWithoutAltGr].Normal.Chars[i]) {
+        return false;
+      }
+    }
+    return false;
+  }
+
+  void AttachDeadKeyTable(ShiftState aShiftState,
+                          const DeadKeyTable* aDeadKeyTable) {
+    MOZ_ASSERT(aShiftState == ToShiftStateIndex(aShiftState));
+    mShiftStates[aShiftState].DeadKey.Table = aDeadKeyTable;
+  }
+
+  void SetNormalChars(ShiftState aShiftState, const char16_t* aChars,
+                      uint32_t aNumOfChars);
+  void SetDeadChar(ShiftState aShiftState, char16_t aDeadChar);
+  const DeadKeyTable* MatchingDeadKeyTable(const DeadKeyEntry* aDeadKeyArray,
+                                           uint32_t aEntries) const;
+  inline char16_t GetCompositeChar(ShiftState aShiftState,
+                                   char16_t aBaseChar) const {
+    return mShiftStates[ToShiftStateIndex(aShiftState)]
+        .DeadKey.Table->GetCompositeChar(aBaseChar);
+  }
+
+  char16_t GetCompositeChar(const ModifierKeyState& aModKeyState,
+                            char16_t aBaseChar) const {
+    return GetCompositeChar(ModifierKeyStateToShiftState(aModKeyState),
+                            aBaseChar);
+  }
+
+  /**
+   * GetNativeUniChars() returns character(s) which is produced by the
+   * key with given modifiers.  This does NOT return proper MODIFIER_ALTGRAPH
+   * state because this is raw accessor of the database of this key.
+   */
+  UniCharsAndModifiers GetNativeUniChars(ShiftState aShiftState) const;
+  UniCharsAndModifiers GetNativeUniChars(
+      const ModifierKeyState& aModKeyState) const {
+    return GetNativeUniChars(ModifierKeyStateToShiftState(aModKeyState));
+  }
+
+  /**
+   * GetUniChars() returns characters and modifiers which are not consumed
+   * to input the character.
+   * For example, if you specify Ctrl key but the key produces no character
+   * with Ctrl, this returns character(s) which is produced by the key
+   * without Ctrl.  So, the result is useful to decide KeyboardEvent.key
+   * value.
+   * Another example is, if you specify Ctrl key and the key produces
+   * different character(s) from the case without Ctrl key, this returns
+   * the character(s) *without* MODIFIER_CONTROL.  This modifier information
+   * is useful for eKeyPress since TextEditor does not treat eKeyPress events
+   * whose modifier includes MODIFIER_ALT and/or MODIFIER_CONTROL.
+   *
+   * @param aShiftState         Modifiers which you want to retrieve
+   *                            KeyboardEvent.key value for the key with.
+   *                            If AltGr key is pressed, this should include
+   *                            STATE_ALTGRAPH and should NOT include
+   *                            STATE_ALT nor STATE_CONTROL.
+   *                            If both Alt and Ctrl are pressed to emulate
+   *                            AltGr, this should include both STATE_ALT and
+   *                            STATE_CONTROL but should NOT include
+   *                            MODIFIER_ALTGRAPH.
+   *                            Then, this returns proper modifiers when
+   *                            this key produces no character with AltGr.
+   */
+  UniCharsAndModifiers GetUniChars(ShiftState aShiftState) const;
+  UniCharsAndModifiers GetUniChars(const ModifierKeyState& aModKeyState) const {
+    return GetUniChars(ModifierKeyStateToShiftState(aModKeyState));
+  }
+};
+
+class MOZ_STACK_CLASS NativeKey final {
+  friend class KeyboardLayout;
+
+ public:
+  struct FakeCharMsg {
+    UINT mCharCode;
+    UINT mScanCode;
+    bool mIsSysKey;
+    bool mIsDeadKey;
+    bool mConsumed;
+
+    FakeCharMsg()
+        : mCharCode(0),
+          mScanCode(0),
+          mIsSysKey(false),
+          mIsDeadKey(false),
+          mConsumed(false) {}
+
+    MSG GetCharMsg(HWND aWnd) const {
+      MSG msg;
+      msg.hwnd = aWnd;
+      msg.message = mIsDeadKey && mIsSysKey ? WM_SYSDEADCHAR
+                    : mIsDeadKey            ? WM_DEADCHAR
+                    : mIsSysKey             ? WM_SYSCHAR
+                                            : WM_CHAR;
+      msg.wParam = static_cast<WPARAM>(mCharCode);
+      msg.lParam = static_cast<LPARAM>(mScanCode << 16);
+      msg.time = 0;
+      msg.pt.x = msg.pt.y = 0;
+      return msg;
+    }
+  };
+
+  NativeKey(nsWindow* aWidget, const MSG& aMessage,
+            const ModifierKeyState& aModKeyState,
+            HKL aOverrideKeyboardLayout = 0,
+            nsTArray<FakeCharMsg>* aFakeCharMsgs = nullptr);
+
+  ~NativeKey();
+
+  /**
+   * Handle WM_KEYDOWN message or WM_SYSKEYDOWN message.  The instance must be
+   * initialized with WM_KEYDOWN or WM_SYSKEYDOWN.
+   * Returns true if dispatched keydown event or keypress event is consumed.
+   * Otherwise, false.
+   */
+  bool HandleKeyDownMessage(bool* aEventDispatched = nullptr) const;
+
+  /**
+   * Handles WM_CHAR message or WM_SYSCHAR message.  The instance must be
+   * initialized with them.
+   * Returns true if dispatched keypress event is consumed.  Otherwise, false.
+   */
+  bool HandleCharMessage(bool* aEventDispatched = nullptr) const;
+
+  /**
+   * Handles keyup message.  Returns true if the event is consumed.
+   * Otherwise, false.
+   */
+  bool HandleKeyUpMessage(bool* aEventDispatched = nullptr) const;
+
+  /**
+   * Handles WM_APPCOMMAND message.  Returns true if the event is consumed.
+   * Otherwise, false.
+   */
+  bool HandleAppCommandMessage() const;
+
+  /**
+   * Callback of TextEventDispatcherListener::WillDispatchKeyboardEvent().
+   * This method sets alternative char codes of aKeyboardEvent.
+   */
+  void WillDispatchKeyboardEvent(WidgetKeyboardEvent& aKeyboardEvent,
+                                 uint32_t aIndex);
+
+  /**
+   * Returns true if aChar is a control character which shouldn't be inputted
+   * into focused text editor.
+   */
+  static bool IsControlChar(char16_t aChar);
+
+  bool IsShift() const { return mModKeyState.IsShift(); }
+  bool IsControl() const { return mModKeyState.IsControl(); }
+  bool IsAlt() const { return mModKeyState.IsAlt(); }
+  bool MaybeEmulatingAltGraph() const;
+  Modifiers GetModifiers() const { return mModKeyState.GetModifiers(); }
+  const ModifierKeyState& ModifierKeyStateRef() const { return mModKeyState; }
+  VirtualKey::ShiftState GetShiftState() const {
+    return VirtualKey::ModifierKeyStateToShiftState(mModKeyState);
+  }
+
+  /**
+   * GenericVirtualKeyCode() returns virtual keycode which cannot distinguish
+   * position of modifier keys.  E.g., VK_CONTROL for both ControlLeft and
+   * ControlRight.
+   */
+  uint8_t GenericVirtualKeyCode() const { return mOriginalVirtualKeyCode; }
+
+  /**
+   * SpecificVirtualKeyCode() returns virtual keycode which can distinguish
+   * position of modifier keys.  E.g., returns VK_LCONTROL or VK_RCONTROL
+   * instead of VK_CONTROL.  If the key message is synthesized with not
+   * enough information, this prefers left position's keycode.
+   */
+  uint8_t SpecificVirtualKeyCode() const { return mVirtualKeyCode; }
+
+ private:
+  NativeKey* mLastInstance;
+  // mRemovingMsg is set at removing a char message from
+  // GetFollowingCharMessage().
+  MSG mRemovingMsg;
+  // mReceivedMsg is set when another instance starts to handle the message
+  // unexpectedly.
+  MSG mReceivedMsg;
+  RefPtr<nsWindow> mWidget;
+  RefPtr<TextEventDispatcher> mDispatcher;
+  HKL mKeyboardLayout;
+  MSG mMsg;
+  // mFollowingCharMsgs stores WM_CHAR, WM_SYSCHAR, WM_DEADCHAR or
+  // WM_SYSDEADCHAR message which follows WM_KEYDOWN.
+  // Note that the stored messaged are already removed from the queue.
+  // FYI: 5 is enough number for usual keyboard layout handling.  On Windows,
+  // a dead key sequence may cause inputting up to 5 characters per key press.
+  AutoTArray<MSG, 5> mFollowingCharMsgs;
+  // mRemovedOddCharMsgs stores WM_CHAR messages which are caused by ATOK or
+  // WXG (they are Japanese IME) when the user tries to do "Kakutei-undo"
+  // (it means "undo the last commit").
+  nsTArray<MSG> mRemovedOddCharMsgs;
+  // If dispatching eKeyDown or eKeyPress event causes focus change,
+  // the instance shouldn't handle remaning char messages.  For checking it,
+  // this should store first focused window.
+  HWND mFocusedWndBeforeDispatch;
+
+  uint32_t mDOMKeyCode;
+  KeyNameIndex mKeyNameIndex;
+  CodeNameIndex mCodeNameIndex;
+
+  ModifierKeyState mModKeyState;
+
+  // mVirtualKeyCode distinguishes left key or right key of modifier key.
+  uint8_t mVirtualKeyCode;
+  // mOriginalVirtualKeyCode doesn't distinguish left key or right key of
+  // modifier key.  However, if the given keycode is VK_PROCESS, it's resolved
+  // to a keycode before it's handled by IME.
+  uint8_t mOriginalVirtualKeyCode;
+
+  // mCommittedChars indicates the inputted characters which is committed by
+  // the key.  If dead key fail to composite a character, mCommittedChars
+  // indicates both the dead characters and the base characters.
+  UniCharsAndModifiers mCommittedCharsAndModifiers;
+
+  // Following strings are computed by
+  // ComputeInputtingStringWithKeyboardLayout() which is typically called
+  // before dispatching keydown event.
+  // mInputtingStringAndModifiers's string is the string to be
+  // inputted into the focused editor and its modifier state is proper
+  // modifier state for inputting the string into the editor.
+  UniCharsAndModifiers mInputtingStringAndModifiers;
+  // mShiftedString is the string to be inputted into the editor with
+  // current modifier state with active shift state.
+  UniCharsAndModifiers mShiftedString;
+  // mUnshiftedString is the string to be inputted into the editor with
+  // current modifier state without shift state.
+  UniCharsAndModifiers mUnshiftedString;
+  // Following integers are computed by
+  // ComputeInputtingStringWithKeyboardLayout() which is typically called
+  // before dispatching keydown event.  The meaning of these values is same
+  // as charCode.
+  uint32_t mShiftedLatinChar;
+  uint32_t mUnshiftedLatinChar;
+
+  WORD mScanCode;
+  bool mIsExtended;
+  // mIsRepeat is true if the key message is caused by the auto-repeat
+  // feature.
+  bool mIsRepeat;
+  bool mIsDeadKey;
+  // mIsPrintableKey is true if the key may be a printable key without
+  // any modifier keys.  Otherwise, false.
+  // Please note that the event may not cause any text input even if this
+  // is true.  E.g., it might be dead key state or Ctrl key may be pressed.
+  bool mIsPrintableKey;
+  // mIsSkippableInRemoteProcess is false if the key event shouldn't be
+  // skipped in the remote process even if it's too old event.
+  bool mIsSkippableInRemoteProcess;
+  // mCharMessageHasGone is true if the message is a keydown message and
+  // it's followed by at least one char message but it's gone at removing
+  // from the queue.  This could occur if PeekMessage() or something is
+  // hooked by odd tool.
+  bool mCharMessageHasGone;
+  // mIsOverridingKeyboardLayout is true if the instance temporarily overriding
+  // keyboard layout with specified by the constructor.
+  bool mIsOverridingKeyboardLayout;
+  // mCanIgnoreModifierStateAtKeyPress is true if it's allowed to remove
+  // Ctrl or Alt modifier state at dispatching eKeyPress.
+  bool mCanIgnoreModifierStateAtKeyPress;
+
+  nsTArray<FakeCharMsg>* mFakeCharMsgs;
+
+  // When a keydown event is dispatched at handling WM_APPCOMMAND, the computed
+  // virtual keycode is set to this.  Even if we consume WM_APPCOMMAND message,
+  // Windows may send WM_KEYDOWN and WM_KEYUP message for them.
+  // At that time, we should not dispatch key events for them.
+  static uint8_t sDispatchedKeyOfAppCommand;
+
+  NativeKey() {
+    MOZ_CRASH("The default constructor of NativeKey isn't available");
+  }
+
+  void InitWithAppCommand();
+  void InitWithKeyOrChar();
+
+  /**
+   * InitIsSkippableForKeyOrChar() initializes mIsSkippableInRemoteProcess with
+   * mIsRepeat and previous key message information.  So, this must be called
+   * after mIsRepeat is initialized.
+   */
+  void InitIsSkippableForKeyOrChar(const MSG& aLastKeyMSG);
+
+  /**
+   * InitCommittedCharsAndModifiersWithFollowingCharMessages() initializes
+   * mCommittedCharsAndModifiers with mFollowingCharMsgs and mModKeyState.
+   * If mFollowingCharMsgs includes non-printable char messages, they are
+   * ignored (skipped).
+   */
+  void InitCommittedCharsAndModifiersWithFollowingCharMessages();
+
+  UINT GetScanCodeWithExtendedFlag() const;
+
+  // The result is one of eKeyLocation*.
+  uint32_t GetKeyLocation() const;
+
+  /**
+   * RemoveFollowingOddCharMessages() removes odd WM_CHAR messages from the
+   * queue when IsIMEDoingKakuteiUndo() returns true.
+   */
+  void RemoveFollowingOddCharMessages();
+
+  /**
+   * "Kakutei-Undo" of ATOK or WXG (both of them are Japanese IME) causes
+   * strange WM_KEYDOWN/WM_KEYUP/WM_CHAR message pattern.  So, when this
+   * returns true, the caller needs to be careful for processing the messages.
+   */
+  bool IsIMEDoingKakuteiUndo() const;
+
+  /**
+   * This returns true if user types a number key in numpad with Alt key
+   * to input a Unicode character from its scalar value.
+   * Note that inputting Unicode scalar value is available without NumLock.
+   * Therefore, this returns true even if user presses a function key on
+   * numpad without NumLock, but that may be intended to perform a shortcut
+   * key like Alt + Home.
+   */
+  bool MaybeTypingUnicodeScalarValue() const {
+    return !mIsExtended && IsSysKeyDownOrKeyUpMessage() && IsAlt() &&
+           !IsControl() && !IsShift() &&
+           ((mScanCode >= 0x004F && mScanCode <= 0x0052) ||  // Numpad0-3
+            (mScanCode >= 0x004B && mScanCode <= 0x004D) ||  // Numpad4-6
+            (mScanCode >= 0x0047 && mScanCode <= 0x0049));   // Numpad7-9
+  }
+
+  bool IsKeyDownMessage() const {
+    return mMsg.message == WM_KEYDOWN || mMsg.message == WM_SYSKEYDOWN;
+  }
+  bool IsKeyUpMessage() const {
+    return mMsg.message == WM_KEYUP || mMsg.message == WM_SYSKEYUP;
+  }
+  bool IsSysKeyDownOrKeyUpMessage() const {
+    return mMsg.message == WM_SYSKEYDOWN || mMsg.message == WM_SYSKEYUP;
+  }
+  bool IsCharOrSysCharMessage(const MSG& aMSG) const {
+    return IsCharOrSysCharMessage(aMSG.message);
+  }
+  bool IsCharOrSysCharMessage(UINT aMessage) const {
+    return (aMessage == WM_CHAR || aMessage == WM_SYSCHAR);
+  }
+  bool IsCharMessage(const MSG& aMSG) const {
+    return IsCharMessage(aMSG.message);
+  }
+  bool IsCharMessage(UINT aMessage) const {
+    return (IsCharOrSysCharMessage(aMessage) || IsDeadCharMessage(aMessage));
+  }
+  bool IsDeadCharMessage(const MSG& aMSG) const {
+    return IsDeadCharMessage(aMSG.message);
+  }
+  bool IsDeadCharMessage(UINT aMessage) const {
+    return (aMessage == WM_DEADCHAR || aMessage == WM_SYSDEADCHAR);
+  }
+  bool IsSysCharMessage(const MSG& aMSG) const {
+    return IsSysCharMessage(aMSG.message);
+  }
+  bool IsSysCharMessage(UINT aMessage) const {
+    return (aMessage == WM_SYSCHAR || aMessage == WM_SYSDEADCHAR);
+  }
+  bool MayBeSameCharMessage(const MSG& aCharMsg1, const MSG& aCharMsg2) const;
+  bool IsSamePhysicalKeyMessage(const MSG& aKeyOrCharMsg1,
+                                const MSG& aKeyOrCharMsg2) const;
+  bool IsFollowedByPrintableCharMessage() const;
+  bool IsFollowedByPrintableCharOrSysCharMessage() const;
+  bool IsFollowedByDeadCharMessage() const;
+  bool IsPrintableCharMessage(const MSG& aMSG) const {
+    return aMSG.message == WM_CHAR &&
+           !IsControlChar(static_cast<char16_t>(aMSG.wParam));
+  }
+  bool IsEnterKeyPressCharMessage(const MSG& aMSG) const {
+    return aMSG.message == WM_CHAR && aMSG.wParam == '\r';
+  }
+  bool IsPrintableCharOrSysCharMessage(const MSG& aMSG) const {
+    return IsCharOrSysCharMessage(aMSG) &&
+           !IsControlChar(static_cast<char16_t>(aMSG.wParam));
+  }
+  bool IsControlCharMessage(const MSG& aMSG) const {
+    return IsCharMessage(aMSG.message) &&
+           IsControlChar(static_cast<char16_t>(aMSG.wParam));
+  }
+
+  /**
+   * IsReservedBySystem() returns true if the key combination is reserved by
+   * the system.  Even if it's consumed by web apps, the message should be
+   * sent to next wndproc.
+   */
+  bool IsReservedBySystem() const;
+
+  /**
+   * GetFollowingCharMessage() returns following char message of handling
+   * keydown event.  If the message is found, this method returns true.
+   * Otherwise, returns false.
+   *
+   * WARNING: Even if this returns true, aCharMsg may be WM_NULL or its
+   *          hwnd may be different window.
+   */
+  bool GetFollowingCharMessage(MSG& aCharMsg);
+
+  /**
+   * Wraps MapVirtualKeyEx() with MAPVK_VSC_TO_VK.
+   */
+  uint8_t ComputeVirtualKeyCodeFromScanCode() const;
+
+  /**
+   * Wraps MapVirtualKeyEx() with MAPVK_VSC_TO_VK_EX.
+   */
+  uint8_t ComputeVirtualKeyCodeFromScanCodeEx() const;
+
+  /**
+   * Wraps MapVirtualKeyEx() with MAPVK_VK_TO_VSC_EX or MAPVK_VK_TO_VSC.
+   */
+  uint16_t ComputeScanCodeExFromVirtualKeyCode(UINT aVirtualKeyCode) const;
+
+  /**
+   * Wraps MapVirtualKeyEx() with MAPVK_VSC_TO_VK and MAPVK_VK_TO_CHAR.
+   */
+  char16_t ComputeUnicharFromScanCode() const;
+
+  /**
+   * Initializes the aKeyEvent with the information stored in the instance.
+   */
+  nsEventStatus InitKeyEvent(WidgetKeyboardEvent& aKeyEvent,
+                             const ModifierKeyState& aModKeyState) const;
+  nsEventStatus InitKeyEvent(WidgetKeyboardEvent& aKeyEvent) const;
+
+  /**
+   * Dispatches a command event for aEventCommand.
+   * Returns true if the event is consumed.  Otherwise, false.
+   */
+  bool DispatchCommandEvent(uint32_t aEventCommand) const;
+
+  /**
+   * DispatchKeyPressEventsWithRetrievedCharMessages() dispatches keypress
+   * event(s) with retrieved char messages.
+   */
+  bool DispatchKeyPressEventsWithRetrievedCharMessages() const;
+
+  /**
+   * DispatchKeyPressEventsWithoutCharMessage() dispatches keypress event(s)
+   * without char messages.  So, this should be used only when there are no
+   * following char messages.
+   */
+  bool DispatchKeyPressEventsWithoutCharMessage() const;
+
+  /**
+   * Checkes whether the key event down message is handled without following
+   * WM_CHAR messages.  For example, if following WM_CHAR message indicates
+   * control character input, the WM_CHAR message is unclear whether it's
+   * caused by a printable key with Ctrl or just a function key such as Enter
+   * or Backspace.
+   */
+  bool NeedsToHandleWithoutFollowingCharMessages() const;
+
+  /**
+   * ComputeInputtingStringWithKeyboardLayout() computes string to be inputted
+   * with the key and the modifier state, without shift state and with shift
+   * state.
+   */
+  void ComputeInputtingStringWithKeyboardLayout();
+
+  /**
+   * IsFocusedWindowChanged() returns true if focused window is changed
+   * after the instance is created.
+   */
+  bool IsFocusedWindowChanged() const {
+    return mFocusedWndBeforeDispatch != ::GetFocus();
+  }
+
+  /**
+   * Handles WM_CHAR message or WM_SYSCHAR message.  The instance must be
+   * initialized with WM_KEYDOWN, WM_SYSKEYDOWN or them.
+   * Returns true if dispatched keypress event is consumed.  Otherwise, false.
+   */
+  bool HandleCharMessage(const MSG& aCharMsg,
+                         bool* aEventDispatched = nullptr) const;
+
+  // Calls of PeekMessage() from NativeKey might cause nested message handling
+  // due to (perhaps) odd API hook.  NativeKey should do nothing if given
+  // message is tried to be retrieved by another instance.
+
+  /**
+   * sLatestInstacne is a pointer to the newest instance of NativeKey which is
+   * handling a key or char message(s).
+   */
+  static NativeKey* sLatestInstance;
+
+  static const MSG sEmptyMSG;
+
+  static MSG sLastKeyOrCharMSG;
+
+  static MSG sLastKeyMSG;
+
+  // Set to non-zero if we receive a WM_KEYDOWN message which introduces only
+  // a high surrogate.  Then, it'll be cleared when next keydown or char message
+  // is received.
+  static char16_t sPendingHighSurrogate;
+
+  static bool IsEmptyMSG(const MSG& aMSG) {
+    return !memcmp(&aMSG, &sEmptyMSG, sizeof(MSG));
+  }
+
+  bool IsAnotherInstanceRemovingCharMessage() const {
+    return mLastInstance && !IsEmptyMSG(mLastInstance->mRemovingMsg);
+  }
+
+ public:
+  /**
+   * Returns last key or char MSG.  If no MSG has been received yet, the result
+   * is empty MSG (i.e., .message is WM_NULL).
+   */
+  static const MSG& LastKeyOrCharMSG() { return sLastKeyOrCharMSG; }
+};
+
+class KeyboardLayout {
+ public:
+  static KeyboardLayout* GetInstance();
+  static void Shutdown();
+
+  /**
+   * GetLayout() returns a keyboard layout which has already been loaded in the
+   * singleton instance or active keyboard layout.
+   */
+  static HKL GetLayout() {
+    if (!sInstance || sInstance->mIsPendingToRestoreKeyboardLayout) {
+      return ::GetKeyboardLayout(0);
+    }
+    return sInstance->mKeyboardLayout;
+  }
+
+  /**
+   * GetLoadedLayout() returns a keyboard layout which was loaded in the
+   * singleton instance.  This may be different from the active keyboard layout
+   * on the system if we override the keyboard layout for synthesizing native
+   * key events for tests.
+   */
+  HKL GetLoadedLayout() { return mKeyboardLayout; }
+
+  /**
+   * GetLoadedLayoutName() returns the name of the loaded keyboard layout in the
+   * singleton instance.
+   */
+  nsCString GetLoadedLayoutName() {
+    return KeyboardLayout::GetLayoutName(mKeyboardLayout);
+  }
+
+  static void NotifyIdleServiceOfUserActivity();
+
+  static bool IsPrintableCharKey(uint8_t aVirtualKey);
+
+  /**
+   * HasAltGr() returns true if the keyboard layout's AltRight key is AltGr
+   * key.
+   */
+  bool HasAltGr() const { return mHasAltGr; }
+
+  /**
+   * IsDeadKey() returns true if aVirtualKey is a dead key with aModKeyState.
+   * This method isn't stateful.
+   */
+  bool IsDeadKey(uint8_t aVirtualKey,
+                 const ModifierKeyState& aModKeyState) const;
+  bool IsDeadKey(const NativeKey& aNativeKey) const {
+    return IsDeadKey(aNativeKey.GenericVirtualKeyCode(),
+                     aNativeKey.ModifierKeyStateRef());
+  }
+
+  /**
+   * IsInDeadKeySequence() returns true when it's in a dead key sequence.
+   * It starts when a dead key is down and ends when another key down causes
+   * inactivating the dead key state.
+   */
+  bool IsInDeadKeySequence() const { return !mActiveDeadKeys.IsEmpty(); }
+
+  /**
+   * IsSysKey() returns true if aVirtualKey with aModKeyState causes WM_SYSKEY*
+   * or WM_SYS*CHAR messages.
+   */
+  bool IsSysKey(uint8_t aVirtualKey,
+                const ModifierKeyState& aModKeyState) const;
+  bool IsSysKey(const NativeKey& aNativeKey) const {
+    return IsSysKey(aNativeKey.GenericVirtualKeyCode(),
+                    aNativeKey.ModifierKeyStateRef());
+  }
+
+  /**
+   * GetUniCharsAndModifiers() returns characters which are inputted by
+   * aVirtualKey with aModKeyState.  This method isn't stateful.
+   * Note that if the combination causes text input, the result's Ctrl and
+   * Alt key state are never active.
+   */
+  UniCharsAndModifiers GetUniCharsAndModifiers(
+      uint8_t aVirtualKey, const ModifierKeyState& aModKeyState) const {
+    VirtualKey::ShiftState shiftState =
+        VirtualKey::ModifierKeyStateToShiftState(aModKeyState);
+    return GetUniCharsAndModifiers(aVirtualKey, shiftState);
+  }
+  UniCharsAndModifiers GetUniCharsAndModifiers(
+      const NativeKey& aNativeKey) const {
+    return GetUniCharsAndModifiers(aNativeKey.GenericVirtualKeyCode(),
+                                   aNativeKey.GetShiftState());
+  }
+
+  /**
+   * OnLayoutChange() must be called before the first keydown message is
+   * received.  LoadLayout() changes the keyboard state, that causes breaking
+   * dead key state.  Therefore, we need to load the layout before the first
+   * keydown message.
+   */
+  void OnLayoutChange(HKL aKeyboardLayout) {
+    MOZ_ASSERT(!mIsOverridden);
+    LoadLayout(aKeyboardLayout);
+  }
+
+  /**
+   * OverrideLayout() loads the specified keyboard layout.
+   */
+  void OverrideLayout(HKL aLayout) {
+    mIsOverridden = true;
+    LoadLayout(aLayout);
+  }
+
+  /**
+   * RestoreLayout() loads the current keyboard layout of the thread.
+   */
+  void RestoreLayout() {
+    mIsOverridden = false;
+    mIsPendingToRestoreKeyboardLayout = true;
+  }
+
+  uint32_t ConvertNativeKeyCodeToDOMKeyCode(UINT aNativeKeyCode) const;
+
+  /**
+   * ConvertNativeKeyCodeToKeyNameIndex() returns KeyNameIndex value for
+   * non-printable keys (except some special keys like space key).
+   */
+  KeyNameIndex ConvertNativeKeyCodeToKeyNameIndex(uint8_t aVirtualKey) const;
+
+  /**
+   * ConvertScanCodeToCodeNameIndex() returns CodeNameIndex value for
+   * the given scan code.  aScanCode can be over 0xE000 since this method
+   * doesn't use Windows API.
+   */
+  static CodeNameIndex ConvertScanCodeToCodeNameIndex(UINT aScanCode);
+
+  /**
+   * This wraps MapVirtualKeyEx() API with MAPVK_VK_TO_VSC.
+   */
+  WORD ComputeScanCodeForVirtualKeyCode(uint8_t aVirtualKeyCode) const;
+
+  /**
+   * Implementation of nsIWidget::SynthesizeNativeKeyEvent().
+   */
+  nsresult SynthesizeNativeKeyEvent(nsWindow* aWidget,
+                                    int32_t aNativeKeyboardLayout,
+                                    int32_t aNativeKeyCode,
+                                    uint32_t aModifierFlags,
+                                    const nsAString& aCharacters,
+                                    const nsAString& aUnmodifiedCharacters);
+
+ private:
+  KeyboardLayout();
+  ~KeyboardLayout();
+
+  static KeyboardLayout* sInstance;
+  static StaticRefPtr<nsIUserIdleServiceInternal> sIdleService;
+
+  struct DeadKeyTableListEntry {
+    DeadKeyTableListEntry* next;
+    uint8_t data[1];
+  };
+
+  HKL mKeyboardLayout = nullptr;
+
+  VirtualKey mVirtualKeys[NS_NUM_OF_KEYS] = {};
+  DeadKeyTableListEntry* mDeadKeyTableListHead = nullptr;
+  // When mActiveDeadKeys is empty, it's not in dead key sequence.
+  // Otherwise, it contains virtual keycodes which are pressed in current
+  // dead key sequence.
+  nsTArray<uint8_t> mActiveDeadKeys;
+  // mDeadKeyShiftStates is always same length as mActiveDeadKeys.
+  // This stores shift states at pressing each dead key stored in
+  // mActiveDeadKeys.
+  nsTArray<VirtualKey::ShiftState> mDeadKeyShiftStates;
+
+  bool mIsOverridden = false;
+  bool mIsPendingToRestoreKeyboardLayout = false;
+  bool mHasAltGr = false;
+
+  static inline int32_t GetKeyIndex(uint8_t aVirtualKey);
+  static bool AddDeadKeyEntry(char16_t aBaseChar, char16_t aCompositeChar,
+                              nsTArray<DeadKeyEntry>& aDeadKeyArray);
+  bool EnsureDeadKeyActive(bool aIsActive, uint8_t aDeadKey,
+                           const PBYTE aDeadKeyKbdState);
+  uint32_t GetDeadKeyCombinations(uint8_t aDeadKey,
+                                  const PBYTE aDeadKeyKbdState,
+                                  uint16_t aShiftStatesWithBaseChars,
+                                  nsTArray<DeadKeyEntry>& aDeadKeyArray);
+  /**
+   * Activates or deactivates dead key state.
+   */
+  void ActivateDeadKeyState(const NativeKey& aNativeKey);
+  void DeactivateDeadKeyState();
+
+  const DeadKeyTable* AddDeadKeyTable(const DeadKeyEntry* aDeadKeyArray,
+                                      uint32_t aEntries);
+  void ReleaseDeadKeyTables();
+
+  /**
+   * Loads the specified keyboard layout. This method always clear the dead key
+   * state.
+   */
+  void LoadLayout(HKL aLayout);
+
+  /**
+   * Gets the keyboard layout name of aLayout.  Be careful, this may be too
+   * slow to call at handling user input.
+   */
+  static nsCString GetLayoutName(HKL aLayout);
+
+  /**
+   * InitNativeKey() must be called when actually widget receives WM_KEYDOWN or
+   * WM_KEYUP.  This method is stateful.  This saves current dead key state at
+   * WM_KEYDOWN.  Additionally, computes current inputted character(s) and set
+   * them to the aNativeKey.
+   */
+  void InitNativeKey(NativeKey& aNativeKey);
+
+  /**
+   * MaybeInitNativeKeyAsDeadKey() initializes aNativeKey only when aNativeKey
+   * is a dead key's event.
+   * When it's not in a dead key sequence, this activates the dead key state.
+   * When it's in a dead key sequence, this initializes aNativeKey with a
+   * composite character or a preceding dead char and a dead char which should
+   * be caused by aNativeKey.
+   * Returns true when this initializes aNativeKey.  Otherwise, false.
+   */
+  bool MaybeInitNativeKeyAsDeadKey(NativeKey& aNativeKey);
+
+  /**
+   * MaybeInitNativeKeyWithCompositeChar() may initialize aNativeKey with
+   * proper composite character when dead key produces a composite character.
+   * Otherwise, just returns false.
+   */
+  bool MaybeInitNativeKeyWithCompositeChar(NativeKey& aNativeKey);
+
+  /**
+   * See the comment of GetUniCharsAndModifiers() below.
+   */
+  UniCharsAndModifiers GetUniCharsAndModifiers(
+      uint8_t aVirtualKey, VirtualKey::ShiftState aShiftState) const;
+
+  /**
+   * GetDeadUniCharsAndModifiers() returns dead chars which are stored in
+   * current dead key sequence.  So, this is stateful.
+   */
+  UniCharsAndModifiers GetDeadUniCharsAndModifiers() const;
+
+  /**
+   * GetCompositeChar() returns a composite character with dead character
+   * caused by mActiveDeadKeys, mDeadKeyShiftStates and a base character
+   * (aBaseChar).
+   * If the combination of the dead character and the base character doesn't
+   * cause a composite character, this returns 0.
+   */
+  char16_t GetCompositeChar(char16_t aBaseChar) const;
+
+  // NativeKey class should access InitNativeKey() directly, but it shouldn't
+  // be available outside of NativeKey.  So, let's make NativeKey a friend
+  // class of this.
+  friend class NativeKey;
+};
+
+class RedirectedKeyDownMessageManager {
+ public:
+  /*
+   * If a window receives WM_KEYDOWN message or WM_SYSKEYDOWM message which is
+   * a redirected message, NativeKey::DispatchKeyDownAndKeyPressEvent()
+   * prevents to dispatch eKeyDown event because it has been dispatched
+   * before the message was redirected.  However, in some cases, WM_*KEYDOWN
+   * message handler may not handle actually.  Then, the message handler needs
+   * to forget the redirected message and remove WM_CHAR message or WM_SYSCHAR
+   * message for the redirected keydown message.  AutoFlusher class is a helper
+   * class for doing it.  This must be created in the stack.
+   */
+  class MOZ_STACK_CLASS AutoFlusher final {
+   public:
+    AutoFlusher(nsWindow* aWidget, const MSG& aMsg)
+        : mCancel(!RedirectedKeyDownMessageManager::IsRedirectedMessage(aMsg)),
+          mWidget(aWidget),
+          mMsg(aMsg) {}
+
+    ~AutoFlusher() {
+      if (mCancel) {
+        return;
+      }
+      // Prevent unnecessary keypress event
+      if (!mWidget->Destroyed()) {
+        RedirectedKeyDownMessageManager::RemoveNextCharMessage(mMsg.hwnd);
+      }
+      // Foreget the redirected message
+      RedirectedKeyDownMessageManager::Forget();
+    }
+
+    void Cancel() { mCancel = true; }
+
+   private:
+    bool mCancel;
+    RefPtr<nsWindow> mWidget;
+    const MSG& mMsg;
+  };
+
+  static void WillRedirect(const MSG& aMsg, bool aDefualtPrevented) {
+    sRedirectedKeyDownMsg = aMsg;
+    sDefaultPreventedOfRedirectedMsg = aDefualtPrevented;
+  }
+
+  static void Forget() { sRedirectedKeyDownMsg.message = WM_NULL; }
+
+  static void PreventDefault() { sDefaultPreventedOfRedirectedMsg = true; }
+  static bool DefaultPrevented() { return sDefaultPreventedOfRedirectedMsg; }
+
+  static bool IsRedirectedMessage(const MSG& aMsg);
+
+  /**
+   * RemoveNextCharMessage() should be called by WM_KEYDOWN or WM_SYSKEYDOWM
+   * message handler.  If there is no WM_(SYS)CHAR message for it, this
+   * method does nothing.
+   * NOTE: WM_(SYS)CHAR message is posted by TranslateMessage() API which is
+   * called in message loop.  So, WM_(SYS)KEYDOWN message should have
+   * WM_(SYS)CHAR message in the queue if the keydown event causes character
+   * input.
+   */
+  static void RemoveNextCharMessage(HWND aWnd);
+
+ private:
+  // sRedirectedKeyDownMsg is WM_KEYDOWN message or WM_SYSKEYDOWN message which
+  // is reirected with SendInput() API by
+  // widget::NativeKey::DispatchKeyDownAndKeyPressEvent()
+  static MSG sRedirectedKeyDownMsg;
+  static bool sDefaultPreventedOfRedirectedMsg;
+};
+
+}  // namespace widget
+}  // namespace mozilla
+
+#endif
diff --git a/widget/windows/LSPAnnotator.cpp b/widget/windows/LSPAnnotator.cpp
new file mode 100644
index 0000000000..ab3a768d66
--- /dev/null
+++ b/widget/windows/LSPAnnotator.cpp
@@ -0,0 +1,135 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/**
+ * LSPs are evil little bits of code that are allowed to inject into our
+ * networking stack by Windows.  Once they have wormed into our process
+ * they gnaw at our innards until we crash.  Here we force the buggers
+ * into the light by recording them in our crash information.
+ * We do the enumeration on a thread because I'm concerned about startup perf
+ * on machines with several LSPs.
+ */
+
+#include "nsICrashReporter.h"
+#include "nsISupportsImpl.h"
+#include "nsServiceManagerUtils.h"
+#include "nsThreadUtils.h"
+#include "nsQueryObject.h"
+#include "nsWindowsHelpers.h"
+#include <windows.h>
+#include <rpc.h>
+#include <ws2spi.h>
+
+namespace mozilla {
+namespace crashreporter {
+
+class LSPAnnotationGatherer : public Runnable {
+  ~LSPAnnotationGatherer() {}
+
+ public:
+  LSPAnnotationGatherer() : Runnable("crashreporter::LSPAnnotationGatherer") {}
+  NS_DECL_NSIRUNNABLE
+
+  void Annotate();
+  nsCString mString;
+};
+
+void LSPAnnotationGatherer::Annotate() {
+  nsCOMPtr<nsICrashReporter> cr =
+      do_GetService("@mozilla.org/toolkit/crash-reporter;1");
+  bool enabled;
+  if (cr && NS_SUCCEEDED(cr->GetCrashReporterEnabled(&enabled)) && enabled) {
+    cr->AnnotateCrashReport("Winsock_LSP"_ns, mString);
+  }
+}
+
+NS_IMETHODIMP
+LSPAnnotationGatherer::Run() {
+  DWORD size = 0;
+  int err;
+  // Get the size of the buffer we need
+  if (SOCKET_ERROR != WSCEnumProtocols(nullptr, nullptr, &size, &err) ||
+      err != WSAENOBUFS) {
+    // Er, what?
+    MOZ_ASSERT_UNREACHABLE(
+        "WSCEnumProtocols succeeded when it should have "
+        "failed");
+    return NS_ERROR_FAILURE;
+  }
+
+  auto byteArray = MakeUnique<char[]>(size);
+  WSAPROTOCOL_INFOW* providers =
+      reinterpret_cast<WSAPROTOCOL_INFOW*>(byteArray.get());
+
+  int n = WSCEnumProtocols(nullptr, providers, &size, &err);
+  if (n == SOCKET_ERROR) {
+    // Lame. We provided the right size buffer; we'll just give up now.
+    NS_WARNING("Could not get LSP list");
+    return NS_ERROR_FAILURE;
+  }
+
+  nsCString str;
+  for (int i = 0; i < n; i++) {
+    AppendUTF16toUTF8(nsDependentString(providers[i].szProtocol), str);
+    str.AppendLiteral(" : ");
+    str.AppendInt(providers[i].iVersion);
+    str.AppendLiteral(" : ");
+    str.AppendInt(providers[i].iAddressFamily);
+    str.AppendLiteral(" : ");
+    str.AppendInt(providers[i].iSocketType);
+    str.AppendLiteral(" : ");
+    str.AppendInt(providers[i].iProtocol);
+    str.AppendLiteral(" : ");
+    str.AppendPrintf("0x%lx", providers[i].dwServiceFlags1);
+    str.AppendLiteral(" : ");
+    str.AppendPrintf("0x%lx", providers[i].dwProviderFlags);
+    str.AppendLiteral(" : ");
+
+    wchar_t path[MAX_PATH];
+    int pathLen = MAX_PATH;
+    if (!WSCGetProviderPath(&providers[i].ProviderId, path, &pathLen, &err)) {
+      AppendUTF16toUTF8(nsDependentString(path), str);
+    }
+
+    str.AppendLiteral(" : ");
+    // Call WSCGetProviderInfo to obtain the category flags for this provider.
+    // When present, these flags inform Windows as to which order to chain the
+    // providers.
+    DWORD categoryInfo;
+    size_t categoryInfoSize = sizeof(categoryInfo);
+    if (!WSCGetProviderInfo(&providers[i].ProviderId, ProviderInfoLspCategories,
+                            (PBYTE)&categoryInfo, &categoryInfoSize, 0, &err)) {
+      str.AppendPrintf("0x%lx", categoryInfo);
+    }
+
+    str.AppendLiteral(" : ");
+    if (providers[i].ProtocolChain.ChainLen <= BASE_PROTOCOL) {
+      // If we're dealing with a catalog entry that identifies an individual
+      // base or layer provider, log its provider GUID.
+      RPC_CSTR provIdStr = nullptr;
+      if (UuidToStringA(&providers[i].ProviderId, &provIdStr) == RPC_S_OK) {
+        str.Append(reinterpret_cast<char*>(provIdStr));
+        RpcStringFreeA(&provIdStr);
+      }
+    }
+
+    if (i + 1 != n) {
+      str.AppendLiteral(" \n ");
+    }
+  }
+
+  mString = str;
+  NS_DispatchToMainThread(
+      NewRunnableMethod("crashreporter::LSPAnnotationGatherer::Annotate", this,
+                        &LSPAnnotationGatherer::Annotate));
+  return NS_OK;
+}
+
+void LSPAnnotate() {
+  nsCOMPtr<nsIRunnable> runnable(new LSPAnnotationGatherer());
+  NS_DispatchBackgroundTask(runnable.forget());
+}
+
+}  // namespace crashreporter
+}  // namespace mozilla
diff --git a/widget/windows/LegacyJumpListBuilder.cpp b/widget/windows/LegacyJumpListBuilder.cpp
new file mode 100644
index 0000000000..fbfe10f64b
--- /dev/null
+++ b/widget/windows/LegacyJumpListBuilder.cpp
@@ -0,0 +1,647 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "LegacyJumpListBuilder.h"
+
+#include "nsError.h"
+#include "nsCOMPtr.h"
+#include "nsServiceManagerUtils.h"
+#include "nsString.h"
+#include "nsArrayUtils.h"
+#include "nsWidgetsCID.h"
+#include "WinTaskbar.h"
+#include "nsDirectoryServiceUtils.h"
+#include "mozilla/Preferences.h"
+#include "nsStringStream.h"
+#include "nsThreadUtils.h"
+#include "mozilla/LazyIdleThread.h"
+#include "nsIObserverService.h"
+#include "mozilla/ScopeExit.h"
+#include "mozilla/Unused.h"
+#include "mozilla/dom/Promise.h"
+#include "mozilla/mscom/ApartmentRegion.h"
+#include "mozilla/mscom/EnsureMTA.h"
+
+#include <shellapi.h>
+#include "WinUtils.h"
+
+using mozilla::dom::Promise;
+
+// The amount of time, in milliseconds, that our IO thread will stay alive after
+// the last event it processes.
+#define DEFAULT_THREAD_TIMEOUT_MS 30000
+
+namespace mozilla {
+namespace widget {
+
+// defined in WinTaskbar.cpp
+extern const wchar_t* gMozillaJumpListIDGeneric;
+
+Atomic<bool> LegacyJumpListBuilder::sBuildingList(false);
+const char kPrefTaskbarEnabled[] = "browser.taskbar.lists.enabled";
+
+NS_IMPL_ISUPPORTS(LegacyJumpListBuilder, nsILegacyJumpListBuilder, nsIObserver)
+#define TOPIC_PROFILE_BEFORE_CHANGE "profile-before-change"
+#define TOPIC_CLEAR_PRIVATE_DATA "clear-private-data"
+
+namespace detail {
+
+class DoneCommitListBuildCallback final : public nsIRunnable {
+  NS_DECL_THREADSAFE_ISUPPORTS
+
+ public:
+  DoneCommitListBuildCallback(nsILegacyJumpListCommittedCallback* aCallback,
+                              LegacyJumpListBuilder* aBuilder)
+      : mCallback(aCallback), mBuilder(aBuilder), mResult(false) {}
+
+  NS_IMETHOD Run() override {
+    MOZ_ASSERT(NS_IsMainThread());
+    if (mCallback) {
+      Unused << mCallback->Done(mResult);
+    }
+    // Ensure we are releasing on the main thread.
+    Destroy();
+    return NS_OK;
+  }
+
+  void SetResult(bool aResult) { mResult = aResult; }
+
+ private:
+  ~DoneCommitListBuildCallback() {
+    // Destructor does not always call on the main thread.
+    MOZ_ASSERT(!mCallback);
+    MOZ_ASSERT(!mBuilder);
+  }
+
+  void Destroy() {
+    MOZ_ASSERT(NS_IsMainThread());
+    mCallback = nullptr;
+    mBuilder = nullptr;
+  }
+
+  // These two references MUST be released on the main thread.
+  RefPtr<nsILegacyJumpListCommittedCallback> mCallback;
+  RefPtr<LegacyJumpListBuilder> mBuilder;
+  bool mResult;
+};
+
+NS_IMPL_ISUPPORTS(DoneCommitListBuildCallback, nsIRunnable);
+
+}  // namespace detail
+
+LegacyJumpListBuilder::LegacyJumpListBuilder()
+    : mMaxItems(0),
+      mHasCommit(false),
+      mMonitor("LegacyJumpListBuilderMonitor") {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  // Instantiate mJumpListMgr in the multithreaded apartment so that proxied
+  // calls on that object do not need to interact with the main thread's message
+  // pump.
+  mscom::EnsureMTA([&]() {
+    RefPtr<ICustomDestinationList> jumpListMgr;
+    HRESULT hr = ::CoCreateInstance(
+        CLSID_DestinationList, nullptr, CLSCTX_INPROC_SERVER,
+        IID_ICustomDestinationList, getter_AddRefs(jumpListMgr));
+    if (FAILED(hr)) {
+      return;
+    }
+
+    ReentrantMonitorAutoEnter lock(mMonitor);
+    // Since we are accessing mJumpListMgr across different threads
+    // (ie, different apartments), mJumpListMgr must be an agile reference.
+    mJumpListMgr = mscom::AgileReference(jumpListMgr);
+  });
+
+  if (!mJumpListMgr) {
+    return;
+  }
+
+  // Make a lazy thread for any IO
+  mIOThread = new LazyIdleThread(DEFAULT_THREAD_TIMEOUT_MS, "Jump List",
+                                 LazyIdleThread::ManualShutdown);
+  Preferences::AddStrongObserver(this, kPrefTaskbarEnabled);
+
+  nsCOMPtr<nsIObserverService> observerService =
+      do_GetService("@mozilla.org/observer-service;1");
+  if (observerService) {
+    observerService->AddObserver(this, TOPIC_PROFILE_BEFORE_CHANGE, false);
+    observerService->AddObserver(this, TOPIC_CLEAR_PRIVATE_DATA, false);
+  }
+}
+
+LegacyJumpListBuilder::~LegacyJumpListBuilder() {
+  Preferences::RemoveObserver(this, kPrefTaskbarEnabled);
+}
+
+NS_IMETHODIMP LegacyJumpListBuilder::SetAppUserModelID(
+    const nsAString& aAppUserModelId) {
+  ReentrantMonitorAutoEnter lock(mMonitor);
+  if (!mJumpListMgr) return NS_ERROR_NOT_AVAILABLE;
+
+  RefPtr<ICustomDestinationList> jumpListMgr = mJumpListMgr.Resolve();
+  if (!jumpListMgr) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  mAppUserModelId.Assign(aAppUserModelId);
+  // MSIX packages explicitly do not support setting the appid from within
+  // the app, as it is set in the package manifest instead.
+  if (!mozilla::widget::WinUtils::HasPackageIdentity()) {
+    jumpListMgr->SetAppID(mAppUserModelId.get());
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP LegacyJumpListBuilder::GetAvailable(int16_t* aAvailable) {
+  *aAvailable = false;
+
+  ReentrantMonitorAutoEnter lock(mMonitor);
+  if (mJumpListMgr) *aAvailable = true;
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP LegacyJumpListBuilder::GetIsListCommitted(bool* aCommit) {
+  *aCommit = mHasCommit;
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP LegacyJumpListBuilder::GetMaxListItems(int16_t* aMaxItems) {
+  ReentrantMonitorAutoEnter lock(mMonitor);
+  if (!mJumpListMgr) return NS_ERROR_NOT_AVAILABLE;
+
+  *aMaxItems = 0;
+
+  if (sBuildingList) {
+    *aMaxItems = mMaxItems;
+    return NS_OK;
+  }
+
+  RefPtr<ICustomDestinationList> jumpListMgr = mJumpListMgr.Resolve();
+  if (!jumpListMgr) {
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  IObjectArray* objArray;
+  if (SUCCEEDED(jumpListMgr->BeginList(&mMaxItems, IID_PPV_ARGS(&objArray)))) {
+    *aMaxItems = mMaxItems;
+
+    if (objArray) objArray->Release();
+
+    jumpListMgr->AbortList();
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP LegacyJumpListBuilder::InitListBuild(JSContext* aCx,
+                                                   Promise** aPromise) {
+  ReentrantMonitorAutoEnter lock(mMonitor);
+  if (!mJumpListMgr) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  nsIGlobalObject* globalObject = xpc::CurrentNativeGlobal(aCx);
+  if (NS_WARN_IF(!globalObject)) {
+    return NS_ERROR_FAILURE;
+  }
+
+  ErrorResult result;
+  RefPtr<Promise> promise = Promise::Create(globalObject, result);
+  if (NS_WARN_IF(result.Failed())) {
+    return result.StealNSResult();
+  }
+
+  nsCOMPtr<nsIRunnable> runnable =
+      NewRunnableMethod<StoreCopyPassByRRef<RefPtr<Promise>>>(
+          "InitListBuild", this, &LegacyJumpListBuilder::DoInitListBuild,
+          promise);
+  nsresult rv = mIOThread->Dispatch(runnable, NS_DISPATCH_NORMAL);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+
+  promise.forget(aPromise);
+  return NS_OK;
+}
+
+void LegacyJumpListBuilder::DoInitListBuild(RefPtr<Promise>&& aPromise) {
+  // Since we're invoking COM interfaces to talk to the shell on a background
+  // thread, we need to be running inside a multithreaded apartment.
+  mscom::MTARegion mta;
+  MOZ_ASSERT(mta.IsValid());
+
+  ReentrantMonitorAutoEnter lock(mMonitor);
+  MOZ_ASSERT(mJumpListMgr);
+
+  if (sBuildingList) {
+    AbortListBuild();
+  }
+
+  HRESULT hr = E_UNEXPECTED;
+  auto errorHandler = MakeScopeExit([&aPromise, &hr]() {
+    if (SUCCEEDED(hr)) {
+      return;
+    }
+
+    NS_DispatchToMainThread(NS_NewRunnableFunction(
+        "InitListBuildReject", [promise = std::move(aPromise)]() {
+          promise->MaybeReject(NS_ERROR_FAILURE);
+        }));
+  });
+
+  RefPtr<ICustomDestinationList> jumpListMgr = mJumpListMgr.Resolve();
+  if (!jumpListMgr) {
+    return;
+  }
+
+  nsTArray<nsString> urisToRemove;
+  RefPtr<IObjectArray> objArray;
+  hr = jumpListMgr->BeginList(
+      &mMaxItems,
+      IID_PPV_ARGS(static_cast<IObjectArray**>(getter_AddRefs(objArray))));
+  if (FAILED(hr)) {
+    return;
+  }
+
+  // The returned objArray of removed items are for manually removed items.
+  // This does not return items which are removed because they were previously
+  // part of the jump list but are no longer part of the jump list.
+  sBuildingList = true;
+  RemoveIconCacheAndGetJumplistShortcutURIs(objArray, urisToRemove);
+
+  NS_DispatchToMainThread(NS_NewRunnableFunction(
+      "InitListBuildResolve", [urisToRemove = std::move(urisToRemove),
+                               promise = std::move(aPromise)]() {
+        promise->MaybeResolve(urisToRemove);
+      }));
+}
+
+// Ensures that we have no old ICO files left in the jump list cache
+nsresult LegacyJumpListBuilder::RemoveIconCacheForAllItems() {
+  // Construct the path of our jump list cache
+  nsCOMPtr<nsIFile> jumpListCacheDir;
+  nsresult rv =
+      NS_GetSpecialDirectory("ProfLDS", getter_AddRefs(jumpListCacheDir));
+  NS_ENSURE_SUCCESS(rv, rv);
+  rv = jumpListCacheDir->AppendNative(
+      nsDependentCString(mozilla::widget::FaviconHelper::kJumpListCacheDir));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsCOMPtr<nsIDirectoryEnumerator> entries;
+  rv = jumpListCacheDir->GetDirectoryEntries(getter_AddRefs(entries));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // Loop through each directory entry and remove all ICO files found
+  do {
+    nsCOMPtr<nsIFile> currFile;
+    if (NS_FAILED(entries->GetNextFile(getter_AddRefs(currFile))) || !currFile)
+      break;
+
+    nsAutoString path;
+    if (NS_FAILED(currFile->GetPath(path))) continue;
+
+    if (StringTail(path, 4).LowerCaseEqualsASCII(".ico")) {
+      // Check if the cached ICO file exists
+      bool exists;
+      if (NS_FAILED(currFile->Exists(&exists)) || !exists) continue;
+
+      // We found an ICO file that exists, so we should remove it
+      currFile->Remove(false);
+    }
+  } while (true);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP LegacyJumpListBuilder::AddListToBuild(int16_t aCatType,
+                                                    nsIArray* items,
+                                                    const nsAString& catName,
+                                                    bool* _retval) {
+  nsresult rv;
+
+  *_retval = false;
+
+  ReentrantMonitorAutoEnter lock(mMonitor);
+  if (!mJumpListMgr) return NS_ERROR_NOT_AVAILABLE;
+
+  RefPtr<ICustomDestinationList> jumpListMgr = mJumpListMgr.Resolve();
+  if (!jumpListMgr) {
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  switch (aCatType) {
+    case nsILegacyJumpListBuilder::JUMPLIST_CATEGORY_TASKS: {
+      NS_ENSURE_ARG_POINTER(items);
+
+      HRESULT hr;
+      RefPtr<IObjectCollection> collection;
+      hr = CoCreateInstance(CLSID_EnumerableObjectCollection, nullptr,
+                            CLSCTX_INPROC_SERVER, IID_IObjectCollection,
+                            getter_AddRefs(collection));
+      if (FAILED(hr)) return NS_ERROR_UNEXPECTED;
+
+      // Build the list
+      uint32_t length;
+      items->GetLength(&length);
+      for (uint32_t i = 0; i < length; ++i) {
+        nsCOMPtr<nsILegacyJumpListItem> item = do_QueryElementAt(items, i);
+        if (!item) continue;
+        // Check for separators
+        if (IsSeparator(item)) {
+          RefPtr<IShellLinkW> link;
+          rv = LegacyJumpListSeparator::GetSeparator(link);
+          if (NS_FAILED(rv)) return rv;
+          collection->AddObject(link);
+          continue;
+        }
+        // These should all be ShellLinks
+        RefPtr<IShellLinkW> link;
+        rv = LegacyJumpListShortcut::GetShellLink(item, link, mIOThread);
+        if (NS_FAILED(rv)) return rv;
+        collection->AddObject(link);
+      }
+
+      // We need IObjectArray to submit
+      RefPtr<IObjectArray> pArray;
+      hr = collection->QueryInterface(IID_IObjectArray, getter_AddRefs(pArray));
+      if (FAILED(hr)) return NS_ERROR_UNEXPECTED;
+
+      // Add the tasks
+      hr = jumpListMgr->AddUserTasks(pArray);
+      if (SUCCEEDED(hr)) *_retval = true;
+      return NS_OK;
+    } break;
+    case nsILegacyJumpListBuilder::JUMPLIST_CATEGORY_RECENT: {
+      if (SUCCEEDED(jumpListMgr->AppendKnownCategory(KDC_RECENT)))
+        *_retval = true;
+      return NS_OK;
+    } break;
+    case nsILegacyJumpListBuilder::JUMPLIST_CATEGORY_FREQUENT: {
+      if (SUCCEEDED(jumpListMgr->AppendKnownCategory(KDC_FREQUENT)))
+        *_retval = true;
+      return NS_OK;
+    } break;
+    case nsILegacyJumpListBuilder::JUMPLIST_CATEGORY_CUSTOMLIST: {
+      NS_ENSURE_ARG_POINTER(items);
+
+      if (catName.IsEmpty()) return NS_ERROR_INVALID_ARG;
+
+      HRESULT hr;
+      RefPtr<IObjectCollection> collection;
+      hr = CoCreateInstance(CLSID_EnumerableObjectCollection, nullptr,
+                            CLSCTX_INPROC_SERVER, IID_IObjectCollection,
+                            getter_AddRefs(collection));
+      if (FAILED(hr)) return NS_ERROR_UNEXPECTED;
+
+      uint32_t length;
+      items->GetLength(&length);
+      for (uint32_t i = 0; i < length; ++i) {
+        nsCOMPtr<nsILegacyJumpListItem> item = do_QueryElementAt(items, i);
+        if (!item) continue;
+        int16_t type;
+        if (NS_FAILED(item->GetType(&type))) continue;
+        switch (type) {
+          case nsILegacyJumpListItem::JUMPLIST_ITEM_SEPARATOR: {
+            RefPtr<IShellLinkW> shellItem;
+            rv = LegacyJumpListSeparator::GetSeparator(shellItem);
+            if (NS_FAILED(rv)) return rv;
+            collection->AddObject(shellItem);
+          } break;
+          case nsILegacyJumpListItem::JUMPLIST_ITEM_LINK: {
+            RefPtr<IShellItem2> shellItem;
+            rv = LegacyJumpListLink::GetShellItem(item, shellItem);
+            if (NS_FAILED(rv)) return rv;
+            collection->AddObject(shellItem);
+          } break;
+          case nsILegacyJumpListItem::JUMPLIST_ITEM_SHORTCUT: {
+            RefPtr<IShellLinkW> shellItem;
+            rv = LegacyJumpListShortcut::GetShellLink(item, shellItem,
+                                                      mIOThread);
+            if (NS_FAILED(rv)) return rv;
+            collection->AddObject(shellItem);
+          } break;
+        }
+      }
+
+      // We need IObjectArray to submit
+      RefPtr<IObjectArray> pArray;
+      hr = collection->QueryInterface(IID_IObjectArray, (LPVOID*)&pArray);
+      if (FAILED(hr)) return NS_ERROR_UNEXPECTED;
+
+      // Add the tasks
+      hr = jumpListMgr->AppendCategory(
+          reinterpret_cast<const wchar_t*>(catName.BeginReading()), pArray);
+      if (SUCCEEDED(hr)) *_retval = true;
+
+      // Get rid of the old icons
+      nsCOMPtr<nsIRunnable> event =
+          new mozilla::widget::AsyncDeleteAllFaviconsFromDisk(true);
+      mIOThread->Dispatch(event, NS_DISPATCH_NORMAL);
+
+      return NS_OK;
+    } break;
+  }
+  return NS_OK;
+}
+
+NS_IMETHODIMP LegacyJumpListBuilder::AbortListBuild() {
+  ReentrantMonitorAutoEnter lock(mMonitor);
+  if (!mJumpListMgr) return NS_ERROR_NOT_AVAILABLE;
+
+  RefPtr<ICustomDestinationList> jumpListMgr = mJumpListMgr.Resolve();
+  if (!jumpListMgr) {
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  jumpListMgr->AbortList();
+  sBuildingList = false;
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP LegacyJumpListBuilder::CommitListBuild(
+    nsILegacyJumpListCommittedCallback* aCallback) {
+  ReentrantMonitorAutoEnter lock(mMonitor);
+  if (!mJumpListMgr) return NS_ERROR_NOT_AVAILABLE;
+
+  // Also holds a strong reference to this to prevent use-after-free.
+  RefPtr<detail::DoneCommitListBuildCallback> callback =
+      new detail::DoneCommitListBuildCallback(aCallback, this);
+
+  // The builder has a strong reference in the callback already, so we do not
+  // need to do it for this runnable again.
+  RefPtr<nsIRunnable> event =
+      NewNonOwningRunnableMethod<RefPtr<detail::DoneCommitListBuildCallback>>(
+          "LegacyJumpListBuilder::DoCommitListBuild", this,
+          &LegacyJumpListBuilder::DoCommitListBuild, std::move(callback));
+  Unused << mIOThread->Dispatch(event, NS_DISPATCH_NORMAL);
+
+  return NS_OK;
+}
+
+void LegacyJumpListBuilder::DoCommitListBuild(
+    RefPtr<detail::DoneCommitListBuildCallback> aCallback) {
+  // Since we're invoking COM interfaces to talk to the shell on a background
+  // thread, we need to be running inside a multithreaded apartment.
+  mscom::MTARegion mta;
+  MOZ_ASSERT(mta.IsValid());
+
+  ReentrantMonitorAutoEnter lock(mMonitor);
+  MOZ_ASSERT(mJumpListMgr);
+  MOZ_ASSERT(aCallback);
+
+  HRESULT hr = E_UNEXPECTED;
+  auto onExit = MakeScopeExit([&hr, &aCallback]() {
+    // XXX We might want some specific error data here.
+    aCallback->SetResult(SUCCEEDED(hr));
+    Unused << NS_DispatchToMainThread(aCallback);
+  });
+
+  RefPtr<ICustomDestinationList> jumpListMgr = mJumpListMgr.Resolve();
+  if (!jumpListMgr) {
+    return;
+  }
+
+  hr = jumpListMgr->CommitList();
+  sBuildingList = false;
+
+  if (SUCCEEDED(hr)) {
+    mHasCommit = true;
+  }
+}
+
+NS_IMETHODIMP LegacyJumpListBuilder::DeleteActiveList(bool* _retval) {
+  *_retval = false;
+
+  ReentrantMonitorAutoEnter lock(mMonitor);
+  if (!mJumpListMgr) return NS_ERROR_NOT_AVAILABLE;
+
+  if (sBuildingList) {
+    AbortListBuild();
+  }
+
+  RefPtr<ICustomDestinationList> jumpListMgr = mJumpListMgr.Resolve();
+  if (!jumpListMgr) {
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  if (SUCCEEDED(jumpListMgr->DeleteList(mAppUserModelId.get()))) {
+    *_retval = true;
+  }
+
+  return NS_OK;
+}
+
+/* internal */
+
+bool LegacyJumpListBuilder::IsSeparator(nsCOMPtr<nsILegacyJumpListItem>& item) {
+  int16_t type;
+  item->GetType(&type);
+  if (NS_FAILED(item->GetType(&type))) return false;
+
+  if (type == nsILegacyJumpListItem::JUMPLIST_ITEM_SEPARATOR) return true;
+  return false;
+}
+
+// RemoveIconCacheAndGetJumplistShortcutURIs - does multiple things to
+// avoid unnecessary extra XPCOM incantations. For each object in the input
+// array,  if it's an IShellLinkW, this deletes the cached icon and adds the
+// url param to a list of URLs to be removed from the places database.
+void LegacyJumpListBuilder::RemoveIconCacheAndGetJumplistShortcutURIs(
+    IObjectArray* aObjArray, nsTArray<nsString>& aURISpecs) {
+  MOZ_ASSERT(!NS_IsMainThread());
+
+  // Early return here just in case some versions of Windows don't populate this
+  if (!aObjArray) {
+    return;
+  }
+
+  uint32_t count = 0;
+  aObjArray->GetCount(&count);
+
+  for (uint32_t idx = 0; idx < count; idx++) {
+    RefPtr<IShellLinkW> pLink;
+
+    if (FAILED(aObjArray->GetAt(idx, IID_IShellLinkW,
+                                static_cast<void**>(getter_AddRefs(pLink))))) {
+      continue;
+    }
+
+    wchar_t buf[MAX_PATH];
+    HRESULT hres = pLink->GetArguments(buf, MAX_PATH);
+    if (SUCCEEDED(hres)) {
+      LPWSTR* arglist;
+      int32_t numArgs;
+
+      arglist = ::CommandLineToArgvW(buf, &numArgs);
+      if (arglist && numArgs > 0) {
+        nsString spec(arglist[0]);
+        aURISpecs.AppendElement(std::move(spec));
+        ::LocalFree(arglist);
+      }
+    }
+
+    int iconIdx = 0;
+    hres = pLink->GetIconLocation(buf, MAX_PATH, &iconIdx);
+    if (SUCCEEDED(hres)) {
+      nsDependentString spec(buf);
+      DeleteIconFromDisk(spec);
+    }
+  }
+}
+
+void LegacyJumpListBuilder::DeleteIconFromDisk(const nsAString& aPath) {
+  MOZ_ASSERT(!NS_IsMainThread());
+
+  // Check that we aren't deleting some arbitrary file that is not an icon
+  if (StringTail(aPath, 4).LowerCaseEqualsASCII(".ico")) {
+    // Construct the parent path of the passed in path
+    nsCOMPtr<nsIFile> icoFile;
+    nsresult rv = NS_NewLocalFile(aPath, true, getter_AddRefs(icoFile));
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return;
+    }
+
+    icoFile->Remove(false);
+  }
+}
+
+NS_IMETHODIMP LegacyJumpListBuilder::Observe(nsISupports* aSubject,
+                                             const char* aTopic,
+                                             const char16_t* aData) {
+  NS_ENSURE_ARG_POINTER(aTopic);
+  if (strcmp(aTopic, TOPIC_PROFILE_BEFORE_CHANGE) == 0) {
+    nsCOMPtr<nsIObserverService> observerService =
+        do_GetService("@mozilla.org/observer-service;1");
+    if (observerService) {
+      observerService->RemoveObserver(this, TOPIC_PROFILE_BEFORE_CHANGE);
+    }
+    mIOThread->Shutdown();
+    // Clear out mJumpListMgr, as MSCOM services won't be available soon.
+    ReentrantMonitorAutoEnter lock(mMonitor);
+    mJumpListMgr = nullptr;
+  } else if (strcmp(aTopic, "nsPref:changed") == 0 &&
+             nsDependentString(aData).EqualsASCII(kPrefTaskbarEnabled)) {
+    bool enabled = Preferences::GetBool(kPrefTaskbarEnabled, true);
+    if (!enabled) {
+      nsCOMPtr<nsIRunnable> event =
+          new mozilla::widget::AsyncDeleteAllFaviconsFromDisk();
+      mIOThread->Dispatch(event, NS_DISPATCH_NORMAL);
+    }
+  } else if (strcmp(aTopic, TOPIC_CLEAR_PRIVATE_DATA) == 0) {
+    // Delete JumpListCache icons from Disk, if any.
+    nsCOMPtr<nsIRunnable> event =
+        new mozilla::widget::AsyncDeleteAllFaviconsFromDisk(false);
+    mIOThread->Dispatch(event, NS_DISPATCH_NORMAL);
+  }
+  return NS_OK;
+}
+
+}  // namespace widget
+}  // namespace mozilla
diff --git a/widget/windows/LegacyJumpListBuilder.h b/widget/windows/LegacyJumpListBuilder.h
new file mode 100644
index 0000000000..1d96773c47
--- /dev/null
+++ b/widget/windows/LegacyJumpListBuilder.h
@@ -0,0 +1,71 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef __LegacyJumpListBuilder_h__
+#define __LegacyJumpListBuilder_h__
+
+#include <windows.h>
+
+// Needed for various com interfaces
+#include <shobjidl.h>
+#undef LogSeverity  // SetupAPI.h #defines this as DWORD
+
+#include "nsString.h"
+
+#include "nsILegacyJumpListBuilder.h"
+#include "nsILegacyJumpListItem.h"
+#include "LegacyJumpListItem.h"
+#include "nsIObserver.h"
+#include "nsTArray.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/LazyIdleThread.h"
+#include "mozilla/mscom/AgileReference.h"
+#include "mozilla/ReentrantMonitor.h"
+
+namespace mozilla {
+namespace widget {
+
+namespace detail {
+class DoneCommitListBuildCallback;
+}  // namespace detail
+
+class LegacyJumpListBuilder : public nsILegacyJumpListBuilder,
+                              public nsIObserver {
+  virtual ~LegacyJumpListBuilder();
+
+ public:
+  NS_DECL_THREADSAFE_ISUPPORTS
+  NS_DECL_NSILEGACYJUMPLISTBUILDER
+  NS_DECL_NSIOBSERVER
+
+  LegacyJumpListBuilder();
+
+ protected:
+  static Atomic<bool> sBuildingList;
+
+ private:
+  mscom::AgileReference<ICustomDestinationList> mJumpListMgr
+      MOZ_GUARDED_BY(mMonitor);
+  uint32_t mMaxItems MOZ_GUARDED_BY(mMonitor);
+  bool mHasCommit;
+  RefPtr<LazyIdleThread> mIOThread;
+  ReentrantMonitor mMonitor;
+  nsString mAppUserModelId;
+
+  bool IsSeparator(nsCOMPtr<nsILegacyJumpListItem>& item);
+  void RemoveIconCacheAndGetJumplistShortcutURIs(IObjectArray* aObjArray,
+                                                 nsTArray<nsString>& aURISpecs);
+  void DeleteIconFromDisk(const nsAString& aPath);
+  nsresult RemoveIconCacheForAllItems();
+  void DoCommitListBuild(RefPtr<detail::DoneCommitListBuildCallback> aCallback);
+  void DoInitListBuild(RefPtr<dom::Promise>&& aPromise);
+
+  friend class WinTaskbar;
+};
+
+}  // namespace widget
+}  // namespace mozilla
+
+#endif /* __LegacyJumpListBuilder_h__ */
diff --git a/widget/windows/LegacyJumpListItem.cpp b/widget/windows/LegacyJumpListItem.cpp
new file mode 100644
index 0000000000..3ffddf11f9
--- /dev/null
+++ b/widget/windows/LegacyJumpListItem.cpp
@@ -0,0 +1,559 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "LegacyJumpListItem.h"
+
+#include <shellapi.h>
+#include <propvarutil.h>
+#include <propkey.h>
+
+#include "nsIFile.h"
+#include "nsNetUtil.h"
+#include "nsCRT.h"
+#include "nsNetCID.h"
+#include "nsCExternalHandlerService.h"
+#include "nsComponentManagerUtils.h"
+#include "nsCycleCollectionParticipant.h"
+#include "mozilla/Preferences.h"
+#include "LegacyJumpListBuilder.h"
+#include "WinUtils.h"
+
+namespace mozilla {
+namespace widget {
+
+// ISUPPORTS Impl's
+NS_IMPL_ISUPPORTS(LegacyJumpListItem, nsILegacyJumpListItem)
+
+NS_INTERFACE_MAP_BEGIN(LegacyJumpListSeparator)
+  NS_INTERFACE_MAP_ENTRY(nsILegacyJumpListSeparator)
+  NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsILegacyJumpListItem,
+                                   LegacyJumpListItemBase)
+  NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsISupports, LegacyJumpListItemBase)
+NS_INTERFACE_MAP_END
+NS_IMPL_ADDREF(LegacyJumpListSeparator)
+NS_IMPL_RELEASE(LegacyJumpListSeparator)
+
+NS_INTERFACE_MAP_BEGIN(LegacyJumpListLink)
+  NS_INTERFACE_MAP_ENTRY(nsILegacyJumpListLink)
+  NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsILegacyJumpListItem,
+                                   LegacyJumpListItemBase)
+  NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsISupports, LegacyJumpListItemBase)
+NS_INTERFACE_MAP_END
+NS_IMPL_ADDREF(LegacyJumpListLink)
+NS_IMPL_RELEASE(LegacyJumpListLink)
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(LegacyJumpListShortcut)
+  NS_INTERFACE_MAP_ENTRY(nsILegacyJumpListShortcut)
+  NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsILegacyJumpListItem,
+                                   LegacyJumpListItemBase)
+  NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsISupports, nsILegacyJumpListShortcut)
+NS_INTERFACE_MAP_END
+NS_IMPL_CYCLE_COLLECTING_ADDREF(LegacyJumpListShortcut)
+NS_IMPL_CYCLE_COLLECTING_RELEASE(LegacyJumpListShortcut)
+NS_IMPL_CYCLE_COLLECTION(LegacyJumpListShortcut, mHandlerApp)
+
+NS_IMETHODIMP LegacyJumpListItemBase::GetType(int16_t* aType) {
+  NS_ENSURE_ARG_POINTER(aType);
+
+  *aType = mItemType;
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP LegacyJumpListItemBase::Equals(nsILegacyJumpListItem* aItem,
+                                             bool* aResult) {
+  NS_ENSURE_ARG_POINTER(aItem);
+
+  *aResult = false;
+
+  int16_t theType = nsILegacyJumpListItem::JUMPLIST_ITEM_EMPTY;
+  if (NS_FAILED(aItem->GetType(&theType))) return NS_OK;
+
+  // Make sure the types match.
+  if (Type() != theType) return NS_OK;
+
+  *aResult = true;
+
+  return NS_OK;
+}
+
+/* link impl. */
+
+NS_IMETHODIMP LegacyJumpListLink::GetUri(nsIURI** aURI) {
+  NS_IF_ADDREF(*aURI = mURI);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP LegacyJumpListLink::SetUri(nsIURI* aURI) {
+  mURI = aURI;
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP LegacyJumpListLink::SetUriTitle(const nsAString& aUriTitle) {
+  mUriTitle.Assign(aUriTitle);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP LegacyJumpListLink::GetUriTitle(nsAString& aUriTitle) {
+  aUriTitle.Assign(mUriTitle);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP LegacyJumpListLink::Equals(nsILegacyJumpListItem* aItem,
+                                         bool* aResult) {
+  NS_ENSURE_ARG_POINTER(aItem);
+
+  nsresult rv;
+
+  *aResult = false;
+
+  int16_t theType = nsILegacyJumpListItem::JUMPLIST_ITEM_EMPTY;
+  if (NS_FAILED(aItem->GetType(&theType))) return NS_OK;
+
+  // Make sure the types match.
+  if (Type() != theType) return NS_OK;
+
+  nsCOMPtr<nsILegacyJumpListLink> link = do_QueryInterface(aItem, &rv);
+  if (NS_FAILED(rv)) return rv;
+
+  // Check the titles
+  nsAutoString title;
+  link->GetUriTitle(title);
+  if (!mUriTitle.Equals(title)) return NS_OK;
+
+  // Call the internal object's equals() method to check.
+  nsCOMPtr<nsIURI> theUri;
+  bool equals = false;
+  if (NS_SUCCEEDED(link->GetUri(getter_AddRefs(theUri)))) {
+    if (!theUri) {
+      if (!mURI) *aResult = true;
+      return NS_OK;
+    }
+    if (NS_SUCCEEDED(theUri->Equals(mURI, &equals)) && equals) {
+      *aResult = true;
+    }
+  }
+
+  return NS_OK;
+}
+
+/* shortcut impl. */
+
+NS_IMETHODIMP LegacyJumpListShortcut::GetApp(nsILocalHandlerApp** aApp) {
+  NS_IF_ADDREF(*aApp = mHandlerApp);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP LegacyJumpListShortcut::SetApp(nsILocalHandlerApp* aApp) {
+  mHandlerApp = aApp;
+  return NS_OK;
+}
+
+NS_IMETHODIMP LegacyJumpListShortcut::GetIconIndex(int32_t* aIconIndex) {
+  NS_ENSURE_ARG_POINTER(aIconIndex);
+
+  *aIconIndex = mIconIndex;
+  return NS_OK;
+}
+
+NS_IMETHODIMP LegacyJumpListShortcut::SetIconIndex(int32_t aIconIndex) {
+  mIconIndex = aIconIndex;
+  return NS_OK;
+}
+
+NS_IMETHODIMP LegacyJumpListShortcut::GetFaviconPageUri(
+    nsIURI** aFaviconPageURI) {
+  NS_IF_ADDREF(*aFaviconPageURI = mFaviconPageURI);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP LegacyJumpListShortcut::SetFaviconPageUri(
+    nsIURI* aFaviconPageURI) {
+  mFaviconPageURI = aFaviconPageURI;
+  return NS_OK;
+}
+
+NS_IMETHODIMP LegacyJumpListShortcut::Equals(nsILegacyJumpListItem* aItem,
+                                             bool* aResult) {
+  NS_ENSURE_ARG_POINTER(aItem);
+
+  nsresult rv;
+
+  *aResult = false;
+
+  int16_t theType = nsILegacyJumpListItem::JUMPLIST_ITEM_EMPTY;
+  if (NS_FAILED(aItem->GetType(&theType))) return NS_OK;
+
+  // Make sure the types match.
+  if (Type() != theType) return NS_OK;
+
+  nsCOMPtr<nsILegacyJumpListShortcut> shortcut = do_QueryInterface(aItem, &rv);
+  if (NS_FAILED(rv)) return rv;
+
+  // Check the icon index
+  // int32_t idx;
+  // shortcut->GetIconIndex(&idx);
+  // if (mIconIndex != idx)
+  //  return NS_OK;
+  // No need to check the icon page URI either
+
+  // Call the internal object's equals() method to check.
+  nsCOMPtr<nsILocalHandlerApp> theApp;
+  bool equals = false;
+  if (NS_SUCCEEDED(shortcut->GetApp(getter_AddRefs(theApp)))) {
+    if (!theApp) {
+      if (!mHandlerApp) *aResult = true;
+      return NS_OK;
+    }
+    if (NS_SUCCEEDED(theApp->Equals(mHandlerApp, &equals)) && equals) {
+      *aResult = true;
+    }
+  }
+
+  return NS_OK;
+}
+
+/* internal helpers */
+
+// (static) Creates a ShellLink that encapsulate a separator.
+nsresult LegacyJumpListSeparator::GetSeparator(
+    RefPtr<IShellLinkW>& aShellLink) {
+  HRESULT hr;
+  IShellLinkW* psl;
+
+  // Create a IShellLink.
+  hr = CoCreateInstance(CLSID_ShellLink, nullptr, CLSCTX_INPROC_SERVER,
+                        IID_IShellLinkW, (LPVOID*)&psl);
+  if (FAILED(hr)) return NS_ERROR_UNEXPECTED;
+
+  IPropertyStore* pPropStore = nullptr;
+  hr = psl->QueryInterface(IID_IPropertyStore, (LPVOID*)&pPropStore);
+  if (FAILED(hr)) return NS_ERROR_UNEXPECTED;
+
+  PROPVARIANT pv;
+  InitPropVariantFromBoolean(TRUE, &pv);
+
+  pPropStore->SetValue(PKEY_AppUserModel_IsDestListSeparator, pv);
+  pPropStore->Commit();
+  pPropStore->Release();
+
+  PropVariantClear(&pv);
+
+  aShellLink = dont_AddRef(psl);
+
+  return NS_OK;
+}
+
+// (static) Creates a ShellLink that encapsulate a shortcut to local apps.
+nsresult LegacyJumpListShortcut::GetShellLink(
+    nsCOMPtr<nsILegacyJumpListItem>& item, RefPtr<IShellLinkW>& aShellLink,
+    RefPtr<LazyIdleThread>& aIOThread) {
+  HRESULT hr;
+  IShellLinkW* psl;
+  nsresult rv;
+
+  // Shell links:
+  // http://msdn.microsoft.com/en-us/library/bb776891(VS.85).aspx
+  // http://msdn.microsoft.com/en-us/library/bb774950(VS.85).aspx
+
+  int16_t type;
+  if (NS_FAILED(item->GetType(&type))) return NS_ERROR_INVALID_ARG;
+
+  if (type != nsILegacyJumpListItem::JUMPLIST_ITEM_SHORTCUT)
+    return NS_ERROR_INVALID_ARG;
+
+  nsCOMPtr<nsILegacyJumpListShortcut> shortcut = do_QueryInterface(item, &rv);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsCOMPtr<nsILocalHandlerApp> handlerApp;
+  rv = shortcut->GetApp(getter_AddRefs(handlerApp));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // Create a IShellLink
+  hr = CoCreateInstance(CLSID_ShellLink, nullptr, CLSCTX_INPROC_SERVER,
+                        IID_IShellLinkW, (LPVOID*)&psl);
+  if (FAILED(hr)) return NS_ERROR_UNEXPECTED;
+
+  // Retrieve the app path, title, description and optional command line args.
+  nsAutoString appPath, appTitle, appDescription, appArgs;
+  int32_t appIconIndex = 0;
+
+  // Path
+  nsCOMPtr<nsIFile> executable;
+  handlerApp->GetExecutable(getter_AddRefs(executable));
+
+  rv = executable->GetPath(appPath);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // Command line parameters
+  uint32_t count = 0;
+  handlerApp->GetParameterCount(&count);
+  for (uint32_t idx = 0; idx < count; idx++) {
+    if (idx > 0) appArgs.Append(' ');
+    nsAutoString param;
+    rv = handlerApp->GetParameter(idx, param);
+    if (NS_FAILED(rv)) return rv;
+    appArgs.Append(param);
+  }
+
+  handlerApp->GetName(appTitle);
+  handlerApp->GetDetailedDescription(appDescription);
+
+  bool useUriIcon = false;   // if we want to use the URI icon
+  bool usedUriIcon = false;  // if we did use the URI icon
+  shortcut->GetIconIndex(&appIconIndex);
+
+  nsCOMPtr<nsIURI> iconUri;
+  rv = shortcut->GetFaviconPageUri(getter_AddRefs(iconUri));
+  if (NS_SUCCEEDED(rv) && iconUri) {
+    useUriIcon = true;
+  }
+
+  // Store the title of the app
+  if (appTitle.Length() > 0) {
+    IPropertyStore* pPropStore = nullptr;
+    hr = psl->QueryInterface(IID_IPropertyStore, (LPVOID*)&pPropStore);
+    if (FAILED(hr)) return NS_ERROR_UNEXPECTED;
+
+    PROPVARIANT pv;
+    InitPropVariantFromString(appTitle.get(), &pv);
+
+    pPropStore->SetValue(PKEY_Title, pv);
+    pPropStore->Commit();
+    pPropStore->Release();
+
+    PropVariantClear(&pv);
+  }
+
+  // Store the rest of the params
+  psl->SetPath(appPath.get());
+  psl->SetDescription(appDescription.get());
+  psl->SetArguments(appArgs.get());
+
+  if (useUriIcon) {
+    nsString icoFilePath;
+    rv = mozilla::widget::FaviconHelper::ObtainCachedIconFile(
+        iconUri, icoFilePath, aIOThread, false);
+    if (NS_SUCCEEDED(rv)) {
+      // Always use the first icon in the ICO file
+      // our encoded icon only has 1 resource
+      psl->SetIconLocation(icoFilePath.get(), 0);
+      usedUriIcon = true;
+    }
+  }
+
+  // We didn't use an ICO via URI so fall back to the app icon
+  if (!usedUriIcon) {
+    psl->SetIconLocation(appPath.get(), appIconIndex);
+  }
+
+  aShellLink = dont_AddRef(psl);
+
+  return NS_OK;
+}
+
+// If successful fills in the aSame parameter
+// aSame will be true if the path is in our icon cache
+static nsresult IsPathInOurIconCache(
+    nsCOMPtr<nsILegacyJumpListShortcut>& aShortcut, wchar_t* aPath,
+    bool* aSame) {
+  NS_ENSURE_ARG_POINTER(aPath);
+  NS_ENSURE_ARG_POINTER(aSame);
+
+  *aSame = false;
+
+  // Construct the path of our jump list cache
+  nsCOMPtr<nsIFile> jumpListCache;
+  nsresult rv =
+      NS_GetSpecialDirectory("ProfLDS", getter_AddRefs(jumpListCache));
+  NS_ENSURE_SUCCESS(rv, rv);
+  rv = jumpListCache->AppendNative(
+      nsDependentCString(FaviconHelper::kJumpListCacheDir));
+  NS_ENSURE_SUCCESS(rv, rv);
+  nsAutoString jumpListCachePath;
+  rv = jumpListCache->GetPath(jumpListCachePath);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // Construct the parent path of the passed in path
+  nsCOMPtr<nsIFile> passedInFile =
+      do_CreateInstance("@mozilla.org/file/local;1");
+  NS_ENSURE_TRUE(passedInFile, NS_ERROR_FAILURE);
+  nsAutoString passedInPath(aPath);
+  rv = passedInFile->InitWithPath(passedInPath);
+  nsCOMPtr<nsIFile> passedInParentFile;
+  passedInFile->GetParent(getter_AddRefs(passedInParentFile));
+  nsAutoString passedInParentPath;
+  rv = jumpListCache->GetPath(passedInParentPath);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  *aSame = jumpListCachePath.Equals(passedInParentPath);
+  return NS_OK;
+}
+
+// (static) For a given IShellLink, create and return a populated
+// nsILegacyJumpListShortcut.
+nsresult LegacyJumpListShortcut::GetJumpListShortcut(
+    IShellLinkW* pLink, nsCOMPtr<nsILegacyJumpListShortcut>& aShortcut) {
+  NS_ENSURE_ARG_POINTER(pLink);
+
+  nsresult rv;
+  HRESULT hres;
+
+  nsCOMPtr<nsILocalHandlerApp> handlerApp =
+      do_CreateInstance(NS_LOCALHANDLERAPP_CONTRACTID, &rv);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  wchar_t buf[MAX_PATH];
+
+  // Path
+  hres = pLink->GetPath(buf, MAX_PATH, nullptr, SLGP_UNCPRIORITY);
+  if (FAILED(hres)) return NS_ERROR_INVALID_ARG;
+
+  nsCOMPtr<nsIFile> file;
+  nsDependentString filepath(buf);
+  rv = NS_NewLocalFile(filepath, false, getter_AddRefs(file));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  rv = handlerApp->SetExecutable(file);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // Parameters
+  hres = pLink->GetArguments(buf, MAX_PATH);
+  if (SUCCEEDED(hres)) {
+    LPWSTR* arglist;
+    int32_t numArgs;
+    int32_t idx;
+
+    arglist = ::CommandLineToArgvW(buf, &numArgs);
+    if (arglist) {
+      for (idx = 0; idx < numArgs; idx++) {
+        // szArglist[i] is null terminated
+        nsDependentString arg(arglist[idx]);
+        handlerApp->AppendParameter(arg);
+      }
+      ::LocalFree(arglist);
+    }
+  }
+
+  rv = aShortcut->SetApp(handlerApp);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // Icon index or file location
+  int iconIdx = 0;
+  hres = pLink->GetIconLocation(buf, MAX_PATH, &iconIdx);
+  if (SUCCEEDED(hres)) {
+    // XXX How do we handle converting local files to images here? Do we need
+    // to?
+    aShortcut->SetIconIndex(iconIdx);
+
+    // Obtain the local profile directory and construct the output icon file
+    // path We only set the Icon Uri if we're sure it was from our icon cache.
+    bool isInOurCache;
+    if (NS_SUCCEEDED(IsPathInOurIconCache(aShortcut, buf, &isInOurCache)) &&
+        isInOurCache) {
+      nsCOMPtr<nsIURI> iconUri;
+      nsAutoString path(buf);
+      rv = NS_NewURI(getter_AddRefs(iconUri), path);
+      if (NS_SUCCEEDED(rv)) {
+        aShortcut->SetFaviconPageUri(iconUri);
+      }
+    }
+  }
+
+  // Do we need the title and description? Probably not since handler app
+  // doesn't compare these in equals.
+
+  return NS_OK;
+}
+
+// (static) ShellItems are used to encapsulate links to things. We currently
+// only support URI links, but more support could be added, such as local file
+// and directory links.
+nsresult LegacyJumpListLink::GetShellItem(nsCOMPtr<nsILegacyJumpListItem>& item,
+                                          RefPtr<IShellItem2>& aShellItem) {
+  IShellItem2* psi = nullptr;
+  nsresult rv;
+
+  int16_t type;
+  if (NS_FAILED(item->GetType(&type))) return NS_ERROR_INVALID_ARG;
+
+  if (type != nsILegacyJumpListItem::JUMPLIST_ITEM_LINK)
+    return NS_ERROR_INVALID_ARG;
+
+  nsCOMPtr<nsILegacyJumpListLink> link = do_QueryInterface(item, &rv);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsCOMPtr<nsIURI> uri;
+  rv = link->GetUri(getter_AddRefs(uri));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsAutoCString spec;
+  rv = uri->GetSpec(spec);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // Create the IShellItem
+  if (FAILED(SHCreateItemFromParsingName(NS_ConvertASCIItoUTF16(spec).get(),
+                                         nullptr, IID_PPV_ARGS(&psi)))) {
+    return NS_ERROR_INVALID_ARG;
+  }
+
+  // Set the title
+  nsAutoString linkTitle;
+  link->GetUriTitle(linkTitle);
+
+  IPropertyStore* pPropStore = nullptr;
+  HRESULT hres = psi->GetPropertyStore(GPS_DEFAULT, IID_IPropertyStore,
+                                       (void**)&pPropStore);
+  if (FAILED(hres)) return NS_ERROR_UNEXPECTED;
+
+  PROPVARIANT pv;
+  InitPropVariantFromString(linkTitle.get(), &pv);
+
+  // May fail due to shell item access permissions.
+  pPropStore->SetValue(PKEY_ItemName, pv);
+  pPropStore->Commit();
+  pPropStore->Release();
+
+  PropVariantClear(&pv);
+
+  aShellItem = dont_AddRef(psi);
+
+  return NS_OK;
+}
+
+// (static) For a given IShellItem, create and return a populated
+// nsILegacyJumpListLink.
+nsresult LegacyJumpListLink::GetJumpListLink(
+    IShellItem* pItem, nsCOMPtr<nsILegacyJumpListLink>& aLink) {
+  NS_ENSURE_ARG_POINTER(pItem);
+
+  // We assume for now these are URI links, but through properties we could
+  // query and create other types.
+  nsresult rv;
+  LPWSTR lpstrName = nullptr;
+
+  if (SUCCEEDED(pItem->GetDisplayName(SIGDN_URL, &lpstrName))) {
+    nsCOMPtr<nsIURI> uri;
+    nsAutoString spec(lpstrName);
+
+    rv = NS_NewURI(getter_AddRefs(uri), NS_ConvertUTF16toUTF8(spec));
+    if (NS_FAILED(rv)) return NS_ERROR_INVALID_ARG;
+
+    aLink->SetUri(uri);
+
+    ::CoTaskMemFree(lpstrName);
+  }
+
+  return NS_OK;
+}
+
+}  // namespace widget
+}  // namespace mozilla
diff --git a/widget/windows/LegacyJumpListItem.h b/widget/windows/LegacyJumpListItem.h
new file mode 100644
index 0000000000..bcef82d349
--- /dev/null
+++ b/widget/windows/LegacyJumpListItem.h
@@ -0,0 +1,133 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef __LegacyJumpListItem_h__
+#define __LegacyJumpListItem_h__
+
+#include <windows.h>
+#include <shobjidl.h>
+#undef LogSeverity  // SetupAPI.h #defines this as DWORD
+
+#include "mozilla/RefPtr.h"
+#include "mozilla/LazyIdleThread.h"
+#include "nsILegacyJumpListItem.h"  // defines nsILegacyJumpListItem
+#include "nsIMIMEInfo.h"            // defines nsILocalHandlerApp
+#include "nsTArray.h"
+#include "nsCOMPtr.h"
+#include "nsIURI.h"
+#include "nsICryptoHash.h"
+#include "nsString.h"
+#include "nsCycleCollectionParticipant.h"
+
+class nsIThread;
+
+namespace mozilla {
+namespace widget {
+
+class LegacyJumpListItemBase : public nsILegacyJumpListItem {
+ public:
+  LegacyJumpListItemBase()
+      : mItemType(nsILegacyJumpListItem::JUMPLIST_ITEM_EMPTY) {}
+
+  explicit LegacyJumpListItemBase(int32_t type) : mItemType(type) {}
+
+  NS_DECL_NSILEGACYJUMPLISTITEM
+
+  static const char kJumpListCacheDir[];
+
+ protected:
+  virtual ~LegacyJumpListItemBase() {}
+
+  short Type() { return mItemType; }
+  short mItemType;
+};
+
+class LegacyJumpListItem : public LegacyJumpListItemBase {
+  ~LegacyJumpListItem() {}
+
+ public:
+  using LegacyJumpListItemBase::LegacyJumpListItemBase;
+
+  NS_DECL_ISUPPORTS
+};
+
+class LegacyJumpListSeparator : public LegacyJumpListItemBase,
+                                public nsILegacyJumpListSeparator {
+  ~LegacyJumpListSeparator() {}
+
+ public:
+  LegacyJumpListSeparator()
+      : LegacyJumpListItemBase(nsILegacyJumpListItem::JUMPLIST_ITEM_SEPARATOR) {
+  }
+
+  NS_DECL_ISUPPORTS
+  NS_FORWARD_NSILEGACYJUMPLISTITEM(LegacyJumpListItemBase::)
+
+  static nsresult GetSeparator(RefPtr<IShellLinkW>& aShellLink);
+};
+
+class LegacyJumpListLink : public LegacyJumpListItemBase,
+                           public nsILegacyJumpListLink {
+  ~LegacyJumpListLink() {}
+
+ public:
+  LegacyJumpListLink()
+      : LegacyJumpListItemBase(nsILegacyJumpListItem::JUMPLIST_ITEM_LINK) {}
+
+  NS_DECL_ISUPPORTS
+  NS_IMETHOD GetType(int16_t* aType) override {
+    return LegacyJumpListItemBase::GetType(aType);
+  }
+  NS_IMETHOD Equals(nsILegacyJumpListItem* item, bool* _retval) override;
+  NS_DECL_NSILEGACYJUMPLISTLINK
+
+  static nsresult GetShellItem(nsCOMPtr<nsILegacyJumpListItem>& item,
+                               RefPtr<IShellItem2>& aShellItem);
+  static nsresult GetJumpListLink(IShellItem* pItem,
+                                  nsCOMPtr<nsILegacyJumpListLink>& aLink);
+
+ protected:
+  nsString mUriTitle;
+  nsCOMPtr<nsIURI> mURI;
+  nsCOMPtr<nsICryptoHash> mCryptoHash;
+};
+
+class LegacyJumpListShortcut : public LegacyJumpListItemBase,
+                               public nsILegacyJumpListShortcut {
+  ~LegacyJumpListShortcut() {}
+
+ public:
+  LegacyJumpListShortcut()
+      : LegacyJumpListItemBase(nsILegacyJumpListItem::JUMPLIST_ITEM_SHORTCUT) {}
+
+  NS_DECL_CYCLE_COLLECTING_ISUPPORTS
+  NS_DECL_CYCLE_COLLECTION_CLASS_AMBIGUOUS(LegacyJumpListShortcut,
+                                           LegacyJumpListItemBase)
+  NS_IMETHOD GetType(int16_t* aType) override {
+    return LegacyJumpListItemBase::GetType(aType);
+  }
+  NS_IMETHOD Equals(nsILegacyJumpListItem* item, bool* _retval) override;
+  NS_DECL_NSILEGACYJUMPLISTSHORTCUT
+
+  static nsresult GetShellLink(nsCOMPtr<nsILegacyJumpListItem>& item,
+                               RefPtr<IShellLinkW>& aShellLink,
+                               RefPtr<LazyIdleThread>& aIOThread);
+  static nsresult GetJumpListShortcut(
+      IShellLinkW* pLink, nsCOMPtr<nsILegacyJumpListShortcut>& aShortcut);
+  static nsresult GetOutputIconPath(nsCOMPtr<nsIURI> aFaviconPageURI,
+                                    nsCOMPtr<nsIFile>& aICOFile);
+
+ protected:
+  int32_t mIconIndex;
+  nsCOMPtr<nsIURI> mFaviconPageURI;
+  nsCOMPtr<nsILocalHandlerApp> mHandlerApp;
+
+  bool ExecutableExists(nsCOMPtr<nsILocalHandlerApp>& handlerApp);
+};
+
+}  // namespace widget
+}  // namespace mozilla
+
+#endif /* __LegacyJumpListItem_h__ */
diff --git a/widget/windows/MediaKeysEventSourceFactory.cpp b/widget/windows/MediaKeysEventSourceFactory.cpp
new file mode 100644
index 0000000000..525aab19c6
--- /dev/null
+++ b/widget/windows/MediaKeysEventSourceFactory.cpp
@@ -0,0 +1,20 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "MediaKeysEventSourceFactory.h"
+#include "WindowsSMTCProvider.h"
+
+namespace mozilla {
+namespace widget {
+
+mozilla::dom::MediaControlKeySource* CreateMediaControlKeySource() {
+#ifndef __MINGW32__
+  return new WindowsSMTCProvider();
+#else
+  return nullptr;  // MinGW doesn't support the required Windows 8.1+ APIs
+#endif
+}
+
+}  // namespace widget
+}  // namespace mozilla
diff --git a/widget/windows/OSKInputPaneManager.cpp b/widget/windows/OSKInputPaneManager.cpp
new file mode 100644
index 0000000000..293a84cd28
--- /dev/null
+++ b/widget/windows/OSKInputPaneManager.cpp
@@ -0,0 +1,101 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:set ts=2 sts=2 sw=2 et cin: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#define NTDDI_VERSION NTDDI_WIN10_RS1
+
+#include "OSKInputPaneManager.h"
+#include "nsDebug.h"
+
+#ifndef __MINGW32__
+#  include <inputpaneinterop.h>
+#  include <windows.ui.viewmanagement.h>
+#  include <wrl.h>
+
+using namespace ABI::Windows::UI::ViewManagement;
+using namespace Microsoft::WRL;
+using namespace Microsoft::WRL::Wrappers;
+#endif
+
+namespace mozilla {
+namespace widget {
+
+#ifndef __MINGW32__
+static ComPtr<IInputPane2> GetInputPane(HWND aHwnd) {
+  ComPtr<IInputPaneInterop> inputPaneInterop;
+  HRESULT hr = RoGetActivationFactory(
+      HStringReference(RuntimeClass_Windows_UI_ViewManagement_InputPane).Get(),
+      IID_PPV_ARGS(&inputPaneInterop));
+  if (NS_WARN_IF(FAILED(hr))) {
+    return nullptr;
+  }
+
+  ComPtr<IInputPane> inputPane;
+  hr = inputPaneInterop->GetForWindow(aHwnd, IID_PPV_ARGS(&inputPane));
+  if (NS_WARN_IF(FAILED(hr))) {
+    return nullptr;
+  }
+
+  ComPtr<IInputPane2> inputPane2;
+  inputPane.As(&inputPane2);
+  return inputPane2;
+}
+
+#  ifdef DEBUG
+static bool IsInputPaneVisible(ComPtr<IInputPane2>& aInputPane2) {
+  ComPtr<IInputPaneControl> inputPaneControl;
+  aInputPane2.As(&inputPaneControl);
+  if (NS_WARN_IF(!inputPaneControl)) {
+    return false;
+  }
+  boolean visible = false;
+  inputPaneControl->get_Visible(&visible);
+  return visible;
+}
+
+static bool IsForegroundApp() {
+  HWND foregroundWnd = ::GetForegroundWindow();
+  if (!foregroundWnd) {
+    return false;
+  }
+  DWORD pid;
+  ::GetWindowThreadProcessId(foregroundWnd, &pid);
+  return pid == ::GetCurrentProcessId();
+}
+#  endif
+#endif
+
+// static
+void OSKInputPaneManager::ShowOnScreenKeyboard(HWND aWnd) {
+#ifndef __MINGW32__
+  ComPtr<IInputPane2> inputPane2 = GetInputPane(aWnd);
+  if (!inputPane2) {
+    return;
+  }
+  boolean result;
+  inputPane2->TryShow(&result);
+  NS_WARNING_ASSERTION(
+      result || !IsForegroundApp() || IsInputPaneVisible(inputPane2),
+      "IInputPane2::TryShow is failure");
+#endif
+}
+
+// static
+void OSKInputPaneManager::DismissOnScreenKeyboard(HWND aWnd) {
+#ifndef __MINGW32__
+  ComPtr<IInputPane2> inputPane2 = GetInputPane(aWnd);
+  if (!inputPane2) {
+    return;
+  }
+  boolean result;
+  inputPane2->TryHide(&result);
+  NS_WARNING_ASSERTION(
+      result || !IsForegroundApp() || !IsInputPaneVisible(inputPane2),
+      "IInputPane2::TryHide is failure");
+#endif
+}
+
+}  // namespace widget
+}  // namespace mozilla
diff --git a/widget/windows/OSKInputPaneManager.h b/widget/windows/OSKInputPaneManager.h
new file mode 100644
index 0000000000..421a5f1e02
--- /dev/null
+++ b/widget/windows/OSKInputPaneManager.h
@@ -0,0 +1,24 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:set ts=2 sts=2 sw=2 et cin: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_widget_OSKInputPaneManager_h
+#define mozilla_widget_OSKInputPaneManager_h
+
+#include <windows.h>
+
+namespace mozilla {
+namespace widget {
+
+class OSKInputPaneManager final {
+ public:
+  static void ShowOnScreenKeyboard(HWND aHwnd);
+  static void DismissOnScreenKeyboard(HWND aHwnd);
+};
+
+}  // namespace widget
+}  // namespace mozilla
+
+#endif  // mozilla_widget_OSKInputPaneManager_h
diff --git a/widget/windows/OSKTabTipManager.cpp b/widget/windows/OSKTabTipManager.cpp
new file mode 100644
index 0000000000..b7b06c08d1
--- /dev/null
+++ b/widget/windows/OSKTabTipManager.cpp
@@ -0,0 +1,112 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "OSKTabTipManager.h"
+
+#include "mozilla/Preferences.h"
+#include "nsDebug.h"
+#include "mozilla/widget/WinRegistry.h"
+
+#include <shellapi.h>
+#include <shlobj.h>
+#include <windows.h>
+
+namespace mozilla {
+namespace widget {
+
+/**
+ * Get the HWND for the on-screen keyboard, if it's up. Only
+ * allowed for Windows 8 and higher.
+ */
+static HWND GetOnScreenKeyboardWindow() {
+  const wchar_t kOSKClassName[] = L"IPTip_Main_Window";
+  HWND osk = ::FindWindowW(kOSKClassName, nullptr);
+  if (::IsWindow(osk) && ::IsWindowEnabled(osk) && ::IsWindowVisible(osk)) {
+    return osk;
+  }
+  return nullptr;
+}
+
+// static
+void OSKTabTipManager::ShowOnScreenKeyboard() {
+  const char* kOskPathPrefName = "ui.osk.on_screen_keyboard_path";
+
+  if (GetOnScreenKeyboardWindow()) {
+    return;
+  }
+
+  nsAutoString cachedPath;
+  nsresult result = Preferences::GetString(kOskPathPrefName, cachedPath);
+  if (NS_FAILED(result) || cachedPath.IsEmpty()) {
+    wchar_t path[MAX_PATH];
+    // The path to TabTip.exe is defined at the following registry key.
+    // This is pulled out of the 64-bit registry hive directly.
+    constexpr auto kRegKeyName =
+        u"Software\\Classes\\CLSID\\{054AAE20-4BEA-4347-8A35-64A533254A9D}\\LocalServer32"_ns;
+    if (!WinRegistry::GetString(HKEY_LOCAL_MACHINE, kRegKeyName, u""_ns, path,
+                                WinRegistry::kLegacyWinUtilsStringFlags)) {
+      return;
+    }
+
+    std::wstring wstrpath(path);
+    // The path provided by the registry will often contain
+    // %CommonProgramFiles%, which will need to be replaced if it is present.
+    size_t commonProgramFilesOffset = wstrpath.find(L"%CommonProgramFiles%");
+    if (commonProgramFilesOffset != std::wstring::npos) {
+      // The path read from the registry contains the %CommonProgramFiles%
+      // environment variable prefix. On 64 bit Windows the
+      // SHGetKnownFolderPath function returns the common program files path
+      // with the X86 suffix for the FOLDERID_ProgramFilesCommon value.
+      // To get the correct path to TabTip.exe we first read the environment
+      // variable CommonProgramW6432 which points to the desired common
+      // files path. Failing that we fallback to the SHGetKnownFolderPath API.
+      // We then replace the %CommonProgramFiles% value with the actual common
+      // files path found in the process.
+      std::wstring commonProgramFilesPath;
+      std::vector<wchar_t> commonProgramFilesPathW6432;
+      DWORD bufferSize =
+          ::GetEnvironmentVariableW(L"CommonProgramW6432", nullptr, 0);
+      if (bufferSize) {
+        commonProgramFilesPathW6432.resize(bufferSize);
+        ::GetEnvironmentVariableW(L"CommonProgramW6432",
+                                  commonProgramFilesPathW6432.data(),
+                                  bufferSize);
+        commonProgramFilesPath =
+            std::wstring(commonProgramFilesPathW6432.data());
+      } else {
+        PWSTR path = nullptr;
+        HRESULT hres = SHGetKnownFolderPath(FOLDERID_ProgramFilesCommon, 0,
+                                            nullptr, &path);
+        if (FAILED(hres) || !path) {
+          return;
+        }
+        commonProgramFilesPath =
+            static_cast<const wchar_t*>(nsDependentString(path).get());
+        ::CoTaskMemFree(path);
+      }
+      wstrpath.replace(commonProgramFilesOffset,
+                       wcslen(L"%CommonProgramFiles%"), commonProgramFilesPath);
+    }
+
+    cachedPath.Assign(wstrpath.data());
+    Preferences::SetString(kOskPathPrefName, cachedPath);
+  }
+
+  const char16_t* cachedPathPtr;
+  cachedPath.GetData(&cachedPathPtr);
+  ShellExecuteW(nullptr, L"", char16ptr_t(cachedPathPtr), nullptr, nullptr,
+                SW_SHOW);
+}
+
+// static
+void OSKTabTipManager::DismissOnScreenKeyboard() {
+  HWND osk = GetOnScreenKeyboardWindow();
+  if (osk) {
+    ::PostMessage(osk, WM_SYSCOMMAND, SC_CLOSE, 0);
+  }
+}
+
+}  // namespace widget
+}  // namespace mozilla
diff --git a/widget/windows/OSKTabTipManager.h b/widget/windows/OSKTabTipManager.h
new file mode 100644
index 0000000000..231403375b
--- /dev/null
+++ b/widget/windows/OSKTabTipManager.h
@@ -0,0 +1,22 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:set ts=2 sts=2 sw=2 et cin: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef OSKTabTipManager_h
+#define OSKTabTipManager_h
+
+namespace mozilla {
+namespace widget {
+
+class OSKTabTipManager final {
+ public:
+  static void ShowOnScreenKeyboard();
+  static void DismissOnScreenKeyboard();
+};
+
+}  // namespace widget
+}  // namespace mozilla
+
+#endif  // OSKTabTipManager_h
diff --git a/widget/windows/OSKVRManager.cpp b/widget/windows/OSKVRManager.cpp
new file mode 100644
index 0000000000..158a0f3561
--- /dev/null
+++ b/widget/windows/OSKVRManager.cpp
@@ -0,0 +1,35 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:set ts=2 sts=2 sw=2 et cin: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "OSKVRManager.h"
+
+#include "FxRWindowManager.h"
+#include "VRShMem.h"
+#include "moz_external_vr.h"
+
+namespace mozilla {
+namespace widget {
+
+// static
+void OSKVRManager::ShowOnScreenKeyboard() {
+#ifdef NIGHTLY_BUILD
+  mozilla::gfx::VRShMem shmem(nullptr, true /*aRequiresMutex*/);
+  shmem.SendIMEState(FxRWindowManager::GetInstance()->GetWindowID(),
+                     mozilla::gfx::VRFxEventState::FOCUS);
+#endif  // NIGHTLY_BUILD
+}
+
+// static
+void OSKVRManager::DismissOnScreenKeyboard() {
+#ifdef NIGHTLY_BUILD
+  mozilla::gfx::VRShMem shmem(nullptr, true /*aRequiresMutex*/);
+  shmem.SendIMEState(FxRWindowManager::GetInstance()->GetWindowID(),
+                     mozilla::gfx::VRFxEventState::BLUR);
+#endif  // NIGHTLY_BUILD
+}
+
+}  // namespace widget
+}  // namespace mozilla
diff --git a/widget/windows/OSKVRManager.h b/widget/windows/OSKVRManager.h
new file mode 100644
index 0000000000..7c5a1afa07
--- /dev/null
+++ b/widget/windows/OSKVRManager.h
@@ -0,0 +1,22 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:set ts=2 sts=2 sw=2 et cin: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef OSKVRManager_h
+#define OSKVRManager_h
+
+namespace mozilla {
+namespace widget {
+
+class OSKVRManager final {
+ public:
+  static void ShowOnScreenKeyboard();
+  static void DismissOnScreenKeyboard();
+};
+
+}  // namespace widget
+}  // namespace mozilla
+
+#endif  // OSKVRManager_h
diff --git a/widget/windows/PCompositorWidget.ipdl b/widget/windows/PCompositorWidget.ipdl
new file mode 100644
index 0000000000..89ea575a47
--- /dev/null
+++ b/widget/windows/PCompositorWidget.ipdl
@@ -0,0 +1,49 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=99: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+include protocol PCompositorBridge;
+
+include "mozilla/dom/TabMessageUtils.h";
+include "mozilla/widget/WidgetMessageUtils.h";
+
+using mozilla::gfx::IntSize from "mozilla/gfx/Point.h";
+using mozilla::WindowsHandle from "mozilla/ipc/IPCTypes.h";
+using mozilla::widget::TransparencyMode from "nsIWidget.h";
+using nsSizeMode from "nsIWidget.h";
+
+namespace mozilla {
+namespace widget {
+
+struct RemoteBackbufferHandles {
+  FileDescriptor fileMapping;
+  FileDescriptor requestReadyEvent;
+  FileDescriptor responseReadyEvent;
+};
+
+[ManualDealloc, ChildImpl=virtual, ParentImpl=virtual]
+sync protocol PCompositorWidget
+{
+  manager PCompositorBridge;
+
+parent:
+  sync Initialize(RemoteBackbufferHandles aRemoteHandles);
+  
+  sync EnterPresentLock();
+  sync LeavePresentLock();
+  async UpdateTransparency(TransparencyMode aMode);
+  async NotifyVisibilityUpdated(nsSizeMode aSizeMode, bool aIsFullyOccluded);
+  sync ClearTransparentWindow();
+  async __delete__();
+
+child:
+  async ObserveVsync();
+  async UnobserveVsync();
+  async UpdateCompositorWnd(WindowsHandle aCompositorWnd, WindowsHandle aParentWnd)
+    returns (bool success);
+};
+
+} // namespace widget
+} // namespace mozilla
diff --git a/widget/windows/PlatformWidgetTypes.ipdlh b/widget/windows/PlatformWidgetTypes.ipdlh
new file mode 100644
index 0000000000..67dd92b802
--- /dev/null
+++ b/widget/windows/PlatformWidgetTypes.ipdlh
@@ -0,0 +1,34 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=99: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+include "mozilla/dom/TabMessageUtils.h";
+include "mozilla/widget/WidgetMessageUtils.h";
+
+include HeadlessWidgetTypes;
+
+using mozilla::WindowsHandle from "mozilla/ipc/IPCTypes.h";
+using nsSizeMode from "nsIWidgetListener.h";
+using mozilla::widget::TransparencyMode from "nsIWidget.h";
+
+namespace mozilla {
+namespace widget {
+
+struct WinCompositorWidgetInitData
+{
+  WindowsHandle hWnd;
+  uintptr_t widgetKey;
+  TransparencyMode transparencyMode;
+  nsSizeMode sizeMode;
+};
+
+union CompositorWidgetInitData
+{
+  WinCompositorWidgetInitData;
+  HeadlessCompositorWidgetInitData;
+};
+
+} // namespace widget
+} // namespace mozilla
diff --git a/widget/windows/RemoteBackbuffer.cpp b/widget/windows/RemoteBackbuffer.cpp
new file mode 100644
index 0000000000..56a8bae0fe
--- /dev/null
+++ b/widget/windows/RemoteBackbuffer.cpp
@@ -0,0 +1,713 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "RemoteBackbuffer.h"
+#include "GeckoProfiler.h"
+#include "nsThreadUtils.h"
+#include "mozilla/Span.h"
+#include "mozilla/gfx/Point.h"
+#include "WinUtils.h"
+#include <algorithm>
+#include <type_traits>
+
+namespace mozilla {
+namespace widget {
+namespace remote_backbuffer {
+
+// This number can be adjusted as a time-memory tradeoff
+constexpr uint8_t kMaxDirtyRects = 8;
+
+struct IpcSafeRect {
+  explicit IpcSafeRect(const gfx::IntRect& aRect)
+      : x(aRect.x), y(aRect.y), width(aRect.width), height(aRect.height) {}
+  int32_t x;
+  int32_t y;
+  int32_t width;
+  int32_t height;
+};
+
+enum class ResponseResult {
+  Unknown,
+  Error,
+  BorrowSuccess,
+  BorrowSameBuffer,
+  PresentSuccess
+};
+
+enum class SharedDataType {
+  BorrowRequest,
+  BorrowRequestAllowSameBuffer,
+  BorrowResponse,
+  PresentRequest,
+  PresentResponse
+};
+
+struct BorrowResponseData {
+  ResponseResult result;
+  int32_t width;
+  int32_t height;
+  HANDLE fileMapping;
+};
+
+struct PresentRequestData {
+  uint8_t lenDirtyRects;
+  IpcSafeRect dirtyRects[kMaxDirtyRects];
+};
+
+struct PresentResponseData {
+  ResponseResult result;
+};
+
+struct SharedData {
+  SharedDataType dataType;
+  union {
+    BorrowResponseData borrowResponse;
+    PresentRequestData presentRequest;
+    PresentResponseData presentResponse;
+  } data;
+};
+
+static_assert(std::is_trivially_copyable<SharedData>::value &&
+                  std::is_standard_layout<SharedData>::value,
+              "SharedData must be safe to pass over IPC boundaries");
+
+class SharedImage {
+ public:
+  SharedImage()
+      : mWidth(0), mHeight(0), mFileMapping(nullptr), mPixelData(nullptr) {}
+
+  ~SharedImage() {
+    if (mPixelData) {
+      MOZ_ALWAYS_TRUE(::UnmapViewOfFile(mPixelData));
+    }
+
+    if (mFileMapping) {
+      MOZ_ALWAYS_TRUE(::CloseHandle(mFileMapping));
+    }
+  }
+
+  bool Initialize(int32_t aWidth, int32_t aHeight) {
+    MOZ_ASSERT(aWidth > 0);
+    MOZ_ASSERT(aHeight > 0);
+
+    mWidth = aWidth;
+    mHeight = aHeight;
+
+    DWORD bufferSize = static_cast<DWORD>(mHeight * GetStride());
+
+    mFileMapping = ::CreateFileMappingW(
+        INVALID_HANDLE_VALUE, nullptr /*secattr*/, PAGE_READWRITE,
+        0 /*sizeHigh*/, bufferSize, nullptr /*name*/);
+    if (!mFileMapping) {
+      return false;
+    }
+
+    void* mappedFilePtr =
+        ::MapViewOfFile(mFileMapping, FILE_MAP_ALL_ACCESS, 0 /*offsetHigh*/,
+                        0 /*offsetLow*/, 0 /*bytesToMap*/);
+    if (!mappedFilePtr) {
+      return false;
+    }
+
+    mPixelData = reinterpret_cast<unsigned char*>(mappedFilePtr);
+
+    return true;
+  }
+
+  bool InitializeRemote(int32_t aWidth, int32_t aHeight, HANDLE aFileMapping) {
+    MOZ_ASSERT(aWidth > 0);
+    MOZ_ASSERT(aHeight > 0);
+    MOZ_ASSERT(aFileMapping);
+
+    mWidth = aWidth;
+    mHeight = aHeight;
+    mFileMapping = aFileMapping;
+
+    void* mappedFilePtr =
+        ::MapViewOfFile(mFileMapping, FILE_MAP_ALL_ACCESS, 0 /*offsetHigh*/,
+                        0 /*offsetLow*/, 0 /*bytesToMap*/);
+    if (!mappedFilePtr) {
+      return false;
+    }
+
+    mPixelData = reinterpret_cast<unsigned char*>(mappedFilePtr);
+
+    return true;
+  }
+
+  HBITMAP CreateDIBSection() {
+    BITMAPINFO bitmapInfo = {};
+    bitmapInfo.bmiHeader.biSize = sizeof(bitmapInfo.bmiHeader);
+    bitmapInfo.bmiHeader.biWidth = mWidth;
+    bitmapInfo.bmiHeader.biHeight = -mHeight;
+    bitmapInfo.bmiHeader.biPlanes = 1;
+    bitmapInfo.bmiHeader.biBitCount = 32;
+    bitmapInfo.bmiHeader.biCompression = BI_RGB;
+    void* dummy = nullptr;
+    return ::CreateDIBSection(nullptr /*paletteDC*/, &bitmapInfo,
+                              DIB_RGB_COLORS, &dummy, mFileMapping,
+                              0 /*offset*/);
+  }
+
+  HANDLE CreateRemoteFileMapping(HANDLE aTargetProcess) {
+    MOZ_ASSERT(aTargetProcess);
+
+    HANDLE fileMapping = nullptr;
+    if (!::DuplicateHandle(GetCurrentProcess(), mFileMapping, aTargetProcess,
+                           &fileMapping, 0 /*desiredAccess*/,
+                           FALSE /*inheritHandle*/, DUPLICATE_SAME_ACCESS)) {
+      return nullptr;
+    }
+    return fileMapping;
+  }
+
+  already_AddRefed<gfx::DrawTarget> CreateDrawTarget() {
+    return gfx::Factory::CreateDrawTargetForData(
+        gfx::BackendType::CAIRO, mPixelData, gfx::IntSize(mWidth, mHeight),
+        GetStride(), gfx::SurfaceFormat::B8G8R8A8);
+  }
+
+  void CopyPixelsFrom(const SharedImage& other) {
+    const unsigned char* src = other.mPixelData;
+    unsigned char* dst = mPixelData;
+
+    int32_t width = std::min(mWidth, other.mWidth);
+    int32_t height = std::min(mHeight, other.mHeight);
+
+    for (int32_t row = 0; row < height; ++row) {
+      memcpy(dst, src, static_cast<uint32_t>(width * kBytesPerPixel));
+      src += other.GetStride();
+      dst += GetStride();
+    }
+  }
+
+  int32_t GetWidth() { return mWidth; }
+
+  int32_t GetHeight() { return mHeight; }
+
+  SharedImage(const SharedImage&) = delete;
+  SharedImage(SharedImage&&) = delete;
+  SharedImage& operator=(const SharedImage&) = delete;
+  SharedImage& operator=(SharedImage&&) = delete;
+
+ private:
+  static constexpr int32_t kBytesPerPixel = 4;
+
+  int32_t GetStride() const {
+    // DIB requires 32-bit row alignment
+    return (((mWidth * kBytesPerPixel) + 3) / 4) * 4;
+  }
+
+  int32_t mWidth;
+  int32_t mHeight;
+  HANDLE mFileMapping;
+  unsigned char* mPixelData;
+};
+
+class PresentableSharedImage {
+ public:
+  PresentableSharedImage()
+      : mSharedImage(),
+        mDeviceContext(nullptr),
+        mDIBSection(nullptr),
+        mSavedObject(nullptr) {}
+
+  ~PresentableSharedImage() {
+    if (mSavedObject) {
+      MOZ_ALWAYS_TRUE(::SelectObject(mDeviceContext, mSavedObject));
+    }
+
+    if (mDIBSection) {
+      MOZ_ALWAYS_TRUE(::DeleteObject(mDIBSection));
+    }
+
+    if (mDeviceContext) {
+      MOZ_ALWAYS_TRUE(::DeleteDC(mDeviceContext));
+    }
+  }
+
+  bool Initialize(int32_t aWidth, int32_t aHeight) {
+    if (!mSharedImage.Initialize(aWidth, aHeight)) {
+      return false;
+    }
+
+    mDeviceContext = ::CreateCompatibleDC(nullptr);
+    if (!mDeviceContext) {
+      return false;
+    }
+
+    mDIBSection = mSharedImage.CreateDIBSection();
+    if (!mDIBSection) {
+      return false;
+    }
+
+    mSavedObject = ::SelectObject(mDeviceContext, mDIBSection);
+    if (!mSavedObject) {
+      return false;
+    }
+
+    return true;
+  }
+
+  bool PresentToWindow(HWND aWindowHandle, TransparencyMode aTransparencyMode,
+                       Span<const IpcSafeRect> aDirtyRects) {
+    if (aTransparencyMode == TransparencyMode::Transparent) {
+      // If our window is a child window or a child-of-a-child, the window
+      // that needs to be updated is the top level ancestor of the tree
+      HWND topLevelWindow = WinUtils::GetTopLevelHWND(aWindowHandle, true);
+      MOZ_ASSERT(::GetWindowLongPtr(topLevelWindow, GWL_EXSTYLE) &
+                 WS_EX_LAYERED);
+
+      BLENDFUNCTION bf = {AC_SRC_OVER, 0, 255, AC_SRC_ALPHA};
+      POINT srcPos = {0, 0};
+      RECT clientRect = {};
+      if (!::GetClientRect(aWindowHandle, &clientRect)) {
+        return false;
+      }
+      MOZ_ASSERT(clientRect.left == 0);
+      MOZ_ASSERT(clientRect.top == 0);
+      int32_t width = clientRect.right;
+      int32_t height = clientRect.bottom;
+      SIZE winSize = {width, height};
+      // Window resize could cause the client area to be different than
+      // mSharedImage's size. If the client area doesn't match,
+      // PresentToWindow() returns false without calling UpdateLayeredWindow().
+      // Another call to UpdateLayeredWindow() will follow shortly, since the
+      // resize will eventually force the backbuffer to repaint itself again.
+      // When client area is larger than mSharedImage's size,
+      // UpdateLayeredWindow() draws the window completely invisible. But it
+      // does not return false.
+      if (width != mSharedImage.GetWidth() ||
+          height != mSharedImage.GetHeight()) {
+        return false;
+      }
+
+      return !!::UpdateLayeredWindow(
+          topLevelWindow, nullptr /*paletteDC*/, nullptr /*newPos*/, &winSize,
+          mDeviceContext, &srcPos, 0 /*colorKey*/, &bf, ULW_ALPHA);
+    }
+
+    gfx::IntRect sharedImageRect{0, 0, mSharedImage.GetWidth(),
+                                 mSharedImage.GetHeight()};
+
+    bool result = true;
+
+    HDC windowDC = ::GetDC(aWindowHandle);
+    if (!windowDC) {
+      return false;
+    }
+
+    for (auto& ipcDirtyRect : aDirtyRects) {
+      gfx::IntRect dirtyRect{ipcDirtyRect.x, ipcDirtyRect.y, ipcDirtyRect.width,
+                             ipcDirtyRect.height};
+      gfx::IntRect bltRect = dirtyRect.Intersect(sharedImageRect);
+
+      if (!::BitBlt(windowDC, bltRect.x /*dstX*/, bltRect.y /*dstY*/,
+                    bltRect.width, bltRect.height, mDeviceContext,
+                    bltRect.x /*srcX*/, bltRect.y /*srcY*/, SRCCOPY)) {
+        result = false;
+        break;
+      }
+    }
+
+    MOZ_ALWAYS_TRUE(::ReleaseDC(aWindowHandle, windowDC));
+
+    return result;
+  }
+
+  HANDLE CreateRemoteFileMapping(HANDLE aTargetProcess) {
+    return mSharedImage.CreateRemoteFileMapping(aTargetProcess);
+  }
+
+  already_AddRefed<gfx::DrawTarget> CreateDrawTarget() {
+    return mSharedImage.CreateDrawTarget();
+  }
+
+  void CopyPixelsFrom(const PresentableSharedImage& other) {
+    mSharedImage.CopyPixelsFrom(other.mSharedImage);
+  }
+
+  int32_t GetWidth() { return mSharedImage.GetWidth(); }
+
+  int32_t GetHeight() { return mSharedImage.GetHeight(); }
+
+  PresentableSharedImage(const PresentableSharedImage&) = delete;
+  PresentableSharedImage(PresentableSharedImage&&) = delete;
+  PresentableSharedImage& operator=(const PresentableSharedImage&) = delete;
+  PresentableSharedImage& operator=(PresentableSharedImage&&) = delete;
+
+ private:
+  SharedImage mSharedImage;
+  HDC mDeviceContext;
+  HBITMAP mDIBSection;
+  HGDIOBJ mSavedObject;
+};
+
+Provider::Provider()
+    : mWindowHandle(nullptr),
+      mTargetProcess(nullptr),
+      mFileMapping(nullptr),
+      mRequestReadyEvent(nullptr),
+      mResponseReadyEvent(nullptr),
+      mSharedDataPtr(nullptr),
+      mStopServiceThread(false),
+      mServiceThread(nullptr),
+      mBackbuffer() {}
+
+Provider::~Provider() {
+  mBackbuffer.reset();
+
+  if (mServiceThread) {
+    mStopServiceThread = true;
+    MOZ_ALWAYS_TRUE(::SetEvent(mRequestReadyEvent));
+    MOZ_ALWAYS_TRUE(PR_JoinThread(mServiceThread) == PR_SUCCESS);
+  }
+
+  if (mSharedDataPtr) {
+    MOZ_ALWAYS_TRUE(::UnmapViewOfFile(mSharedDataPtr));
+  }
+
+  if (mResponseReadyEvent) {
+    MOZ_ALWAYS_TRUE(::CloseHandle(mResponseReadyEvent));
+  }
+
+  if (mRequestReadyEvent) {
+    MOZ_ALWAYS_TRUE(::CloseHandle(mRequestReadyEvent));
+  }
+
+  if (mFileMapping) {
+    MOZ_ALWAYS_TRUE(::CloseHandle(mFileMapping));
+  }
+
+  if (mTargetProcess) {
+    MOZ_ALWAYS_TRUE(::CloseHandle(mTargetProcess));
+  }
+}
+
+bool Provider::Initialize(HWND aWindowHandle, DWORD aTargetProcessId,
+                          TransparencyMode aTransparencyMode) {
+  MOZ_ASSERT(aWindowHandle);
+  MOZ_ASSERT(aTargetProcessId);
+
+  mWindowHandle = aWindowHandle;
+
+  mTargetProcess = ::OpenProcess(PROCESS_DUP_HANDLE, FALSE /*inheritHandle*/,
+                                 aTargetProcessId);
+  if (!mTargetProcess) {
+    return false;
+  }
+
+  mFileMapping = ::CreateFileMappingW(
+      INVALID_HANDLE_VALUE, nullptr /*secattr*/, PAGE_READWRITE, 0 /*sizeHigh*/,
+      static_cast<DWORD>(sizeof(SharedData)), nullptr /*name*/);
+  if (!mFileMapping) {
+    return false;
+  }
+
+  mRequestReadyEvent =
+      ::CreateEventW(nullptr /*secattr*/, FALSE /*manualReset*/,
+                     FALSE /*initialState*/, nullptr /*name*/);
+  if (!mRequestReadyEvent) {
+    return false;
+  }
+
+  mResponseReadyEvent =
+      ::CreateEventW(nullptr /*secattr*/, FALSE /*manualReset*/,
+                     FALSE /*initialState*/, nullptr /*name*/);
+  if (!mResponseReadyEvent) {
+    return false;
+  }
+
+  void* mappedFilePtr =
+      ::MapViewOfFile(mFileMapping, FILE_MAP_ALL_ACCESS, 0 /*offsetHigh*/,
+                      0 /*offsetLow*/, 0 /*bytesToMap*/);
+  if (!mappedFilePtr) {
+    return false;
+  }
+
+  mSharedDataPtr = reinterpret_cast<SharedData*>(mappedFilePtr);
+
+  mStopServiceThread = false;
+
+  // Use a raw NSPR OS-level thread here instead of nsThread because we are
+  // performing low-level synchronization across processes using Win32 Events,
+  // and nsThread is designed around an incompatible "in-process task queue"
+  // model
+  mServiceThread = PR_CreateThread(
+      PR_USER_THREAD, [](void* p) { static_cast<Provider*>(p)->ThreadMain(); },
+      this, PR_PRIORITY_NORMAL, PR_GLOBAL_THREAD, PR_JOINABLE_THREAD,
+      0 /*default stack size*/);
+  if (!mServiceThread) {
+    return false;
+  }
+
+  mTransparencyMode = uint32_t(aTransparencyMode);
+
+  return true;
+}
+
+Maybe<RemoteBackbufferHandles> Provider::CreateRemoteHandles() {
+  return Some(
+      RemoteBackbufferHandles(ipc::FileDescriptor(mFileMapping),
+                              ipc::FileDescriptor(mRequestReadyEvent),
+                              ipc::FileDescriptor(mResponseReadyEvent)));
+}
+
+void Provider::UpdateTransparencyMode(TransparencyMode aTransparencyMode) {
+  mTransparencyMode = uint32_t(aTransparencyMode);
+}
+
+void Provider::ThreadMain() {
+  AUTO_PROFILER_REGISTER_THREAD("RemoteBackbuffer");
+  NS_SetCurrentThreadName("RemoteBackbuffer");
+
+  while (true) {
+    {
+      AUTO_PROFILER_THREAD_SLEEP;
+      MOZ_ALWAYS_TRUE(::WaitForSingleObject(mRequestReadyEvent, INFINITE) ==
+                      WAIT_OBJECT_0);
+    }
+
+    if (mStopServiceThread) {
+      break;
+    }
+
+    switch (mSharedDataPtr->dataType) {
+      case SharedDataType::BorrowRequest:
+      case SharedDataType::BorrowRequestAllowSameBuffer: {
+        BorrowResponseData responseData = {};
+
+        HandleBorrowRequest(&responseData,
+                            mSharedDataPtr->dataType ==
+                                SharedDataType::BorrowRequestAllowSameBuffer);
+
+        mSharedDataPtr->dataType = SharedDataType::BorrowResponse;
+        mSharedDataPtr->data.borrowResponse = responseData;
+
+        MOZ_ALWAYS_TRUE(::SetEvent(mResponseReadyEvent));
+
+        break;
+      }
+      case SharedDataType::PresentRequest: {
+        PresentRequestData requestData = mSharedDataPtr->data.presentRequest;
+        PresentResponseData responseData = {};
+
+        HandlePresentRequest(requestData, &responseData);
+
+        mSharedDataPtr->dataType = SharedDataType::PresentResponse;
+        mSharedDataPtr->data.presentResponse = responseData;
+
+        MOZ_ALWAYS_TRUE(::SetEvent(mResponseReadyEvent));
+
+        break;
+      }
+      default:
+        break;
+    };
+  }
+}
+
+void Provider::HandleBorrowRequest(BorrowResponseData* aResponseData,
+                                   bool aAllowSameBuffer) {
+  MOZ_ASSERT(aResponseData);
+
+  aResponseData->result = ResponseResult::Error;
+
+  RECT clientRect = {};
+  if (!::GetClientRect(mWindowHandle, &clientRect)) {
+    return;
+  }
+
+  MOZ_ASSERT(clientRect.left == 0);
+  MOZ_ASSERT(clientRect.top == 0);
+
+  int32_t width = clientRect.right ? clientRect.right : 1;
+  int32_t height = clientRect.bottom ? clientRect.bottom : 1;
+
+  bool needNewBackbuffer = !aAllowSameBuffer || !mBackbuffer ||
+                           (mBackbuffer->GetWidth() != width) ||
+                           (mBackbuffer->GetHeight() != height);
+
+  if (!needNewBackbuffer) {
+    aResponseData->result = ResponseResult::BorrowSameBuffer;
+    return;
+  }
+
+  auto newBackbuffer = std::make_unique<PresentableSharedImage>();
+  if (!newBackbuffer->Initialize(width, height)) {
+    return;
+  }
+
+  // Preserve the contents of the old backbuffer (if it exists)
+  if (mBackbuffer) {
+    newBackbuffer->CopyPixelsFrom(*mBackbuffer);
+    mBackbuffer.reset();
+  }
+
+  HANDLE remoteFileMapping =
+      newBackbuffer->CreateRemoteFileMapping(mTargetProcess);
+  if (!remoteFileMapping) {
+    return;
+  }
+
+  aResponseData->result = ResponseResult::BorrowSuccess;
+  aResponseData->width = width;
+  aResponseData->height = height;
+  aResponseData->fileMapping = remoteFileMapping;
+
+  mBackbuffer = std::move(newBackbuffer);
+}
+
+void Provider::HandlePresentRequest(const PresentRequestData& aRequestData,
+                                    PresentResponseData* aResponseData) {
+  MOZ_ASSERT(aResponseData);
+
+  Span rectSpan(aRequestData.dirtyRects, kMaxDirtyRects);
+
+  aResponseData->result = ResponseResult::Error;
+
+  if (!mBackbuffer) {
+    return;
+  }
+
+  if (!mBackbuffer->PresentToWindow(
+          mWindowHandle, GetTransparencyMode(),
+          rectSpan.First(aRequestData.lenDirtyRects))) {
+    return;
+  }
+
+  aResponseData->result = ResponseResult::PresentSuccess;
+}
+
+Client::Client()
+    : mFileMapping(nullptr),
+      mRequestReadyEvent(nullptr),
+      mResponseReadyEvent(nullptr),
+      mSharedDataPtr(nullptr),
+      mBackbuffer() {}
+
+Client::~Client() {
+  mBackbuffer.reset();
+
+  if (mSharedDataPtr) {
+    MOZ_ALWAYS_TRUE(::UnmapViewOfFile(mSharedDataPtr));
+  }
+
+  if (mResponseReadyEvent) {
+    MOZ_ALWAYS_TRUE(::CloseHandle(mResponseReadyEvent));
+  }
+
+  if (mRequestReadyEvent) {
+    MOZ_ALWAYS_TRUE(::CloseHandle(mRequestReadyEvent));
+  }
+
+  if (mFileMapping) {
+    MOZ_ALWAYS_TRUE(::CloseHandle(mFileMapping));
+  }
+}
+
+bool Client::Initialize(const RemoteBackbufferHandles& aRemoteHandles) {
+  MOZ_ASSERT(aRemoteHandles.fileMapping().IsValid());
+  MOZ_ASSERT(aRemoteHandles.requestReadyEvent().IsValid());
+  MOZ_ASSERT(aRemoteHandles.responseReadyEvent().IsValid());
+
+  // FIXME: Due to PCompositorWidget using virtual Recv methods,
+  // RemoteBackbufferHandles is passed by const reference, and cannot have its
+  // signature customized, meaning that we need to clone the handles here.
+  //
+  // Once PCompositorWidget is migrated to use direct call semantics, the
+  // signature can be changed to accept RemoteBackbufferHandles by rvalue
+  // reference or value, and the DuplicateHandle calls here can be avoided.
+  mFileMapping = aRemoteHandles.fileMapping().ClonePlatformHandle().release();
+  mRequestReadyEvent =
+      aRemoteHandles.requestReadyEvent().ClonePlatformHandle().release();
+  mResponseReadyEvent =
+      aRemoteHandles.responseReadyEvent().ClonePlatformHandle().release();
+
+  void* mappedFilePtr =
+      ::MapViewOfFile(mFileMapping, FILE_MAP_ALL_ACCESS, 0 /*offsetHigh*/,
+                      0 /*offsetLow*/, 0 /*bytesToMap*/);
+  if (!mappedFilePtr) {
+    return false;
+  }
+
+  mSharedDataPtr = reinterpret_cast<SharedData*>(mappedFilePtr);
+
+  return true;
+}
+
+already_AddRefed<gfx::DrawTarget> Client::BorrowDrawTarget() {
+  mSharedDataPtr->dataType = mBackbuffer
+                                 ? SharedDataType::BorrowRequestAllowSameBuffer
+                                 : SharedDataType::BorrowRequest;
+
+  MOZ_ALWAYS_TRUE(::SetEvent(mRequestReadyEvent));
+  MOZ_ALWAYS_TRUE(::WaitForSingleObject(mResponseReadyEvent, INFINITE) ==
+                  WAIT_OBJECT_0);
+
+  if (mSharedDataPtr->dataType != SharedDataType::BorrowResponse) {
+    return nullptr;
+  }
+
+  BorrowResponseData responseData = mSharedDataPtr->data.borrowResponse;
+
+  if ((responseData.result != ResponseResult::BorrowSameBuffer) &&
+      (responseData.result != ResponseResult::BorrowSuccess)) {
+    return nullptr;
+  }
+
+  if (responseData.result == ResponseResult::BorrowSuccess) {
+    mBackbuffer.reset();
+
+    auto newBackbuffer = std::make_unique<SharedImage>();
+    if (!newBackbuffer->InitializeRemote(responseData.width,
+                                         responseData.height,
+                                         responseData.fileMapping)) {
+      return nullptr;
+    }
+
+    mBackbuffer = std::move(newBackbuffer);
+  }
+
+  MOZ_ASSERT(mBackbuffer);
+
+  return mBackbuffer->CreateDrawTarget();
+}
+
+bool Client::PresentDrawTarget(gfx::IntRegion aDirtyRegion) {
+  mSharedDataPtr->dataType = SharedDataType::PresentRequest;
+
+  // Simplify the region until it has <= kMaxDirtyRects
+  aDirtyRegion.SimplifyOutward(kMaxDirtyRects);
+
+  Span rectSpan(mSharedDataPtr->data.presentRequest.dirtyRects, kMaxDirtyRects);
+
+  uint8_t rectIndex = 0;
+  for (auto iter = aDirtyRegion.RectIter(); !iter.Done(); iter.Next()) {
+    rectSpan[rectIndex] = IpcSafeRect(iter.Get());
+    ++rectIndex;
+  }
+
+  mSharedDataPtr->data.presentRequest.lenDirtyRects = rectIndex;
+
+  MOZ_ALWAYS_TRUE(::SetEvent(mRequestReadyEvent));
+  MOZ_ALWAYS_TRUE(::WaitForSingleObject(mResponseReadyEvent, INFINITE) ==
+                  WAIT_OBJECT_0);
+
+  if (mSharedDataPtr->dataType != SharedDataType::PresentResponse) {
+    return false;
+  }
+
+  if (mSharedDataPtr->data.presentResponse.result !=
+      ResponseResult::PresentSuccess) {
+    return false;
+  }
+
+  return true;
+}
+
+}  // namespace remote_backbuffer
+}  // namespace widget
+}  // namespace mozilla
diff --git a/widget/windows/RemoteBackbuffer.h b/widget/windows/RemoteBackbuffer.h
new file mode 100644
index 0000000000..5899e80984
--- /dev/null
+++ b/widget/windows/RemoteBackbuffer.h
@@ -0,0 +1,95 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef widget_windows_RemoteBackbuffer_h
+#define widget_windows_RemoteBackbuffer_h
+
+#include "nsIWidget.h"
+#include "mozilla/widget/PCompositorWidgetParent.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/gfx/2D.h"
+#include "prthread.h"
+#include <windows.h>
+
+namespace mozilla {
+namespace widget {
+namespace remote_backbuffer {
+
+struct IpcRect;
+struct SharedData;
+struct BorrowResponseData;
+struct PresentRequestData;
+struct PresentResponseData;
+class SharedImage;
+class PresentableSharedImage;
+
+class Provider {
+ public:
+  Provider();
+  ~Provider();
+
+  bool Initialize(HWND aWindowHandle, DWORD aTargetProcessId,
+                  TransparencyMode aTransparencyMode);
+
+  Maybe<RemoteBackbufferHandles> CreateRemoteHandles();
+
+  void UpdateTransparencyMode(TransparencyMode aTransparencyMode);
+
+  Provider(const Provider&) = delete;
+  Provider(Provider&&) = delete;
+  Provider& operator=(const Provider&) = delete;
+  Provider& operator=(Provider&&) = delete;
+
+ private:
+  void ThreadMain();
+
+  void HandleBorrowRequest(BorrowResponseData* aResponseData,
+                           bool aAllowSameBuffer);
+  void HandlePresentRequest(const PresentRequestData& aRequestData,
+                            PresentResponseData* aResponseData);
+
+  HWND mWindowHandle;
+  HANDLE mTargetProcess;
+  HANDLE mFileMapping;
+  HANDLE mRequestReadyEvent;
+  HANDLE mResponseReadyEvent;
+  SharedData* mSharedDataPtr;
+  bool mStopServiceThread;
+  PRThread* mServiceThread;
+  std::unique_ptr<PresentableSharedImage> mBackbuffer;
+  mozilla::Atomic<uint32_t, MemoryOrdering::Relaxed> mTransparencyMode;
+  TransparencyMode GetTransparencyMode() const {
+    return TransparencyMode(uint32_t(mTransparencyMode));
+  }
+};
+
+class Client {
+ public:
+  Client();
+  ~Client();
+
+  bool Initialize(const RemoteBackbufferHandles& aRemoteHandles);
+
+  already_AddRefed<gfx::DrawTarget> BorrowDrawTarget();
+  bool PresentDrawTarget(gfx::IntRegion aDirtyRegion);
+
+  Client(const Client&) = delete;
+  Client(Client&&) = delete;
+  Client& operator=(const Client&) = delete;
+  Client& operator=(Client&&) = delete;
+
+ private:
+  HANDLE mFileMapping;
+  HANDLE mRequestReadyEvent;
+  HANDLE mResponseReadyEvent;
+  SharedData* mSharedDataPtr;
+  std::unique_ptr<SharedImage> mBackbuffer;
+};
+
+}  // namespace remote_backbuffer
+}  // namespace widget
+}  // namespace mozilla
+
+#endif  // widget_windows_RemoteBackbuffer_h
diff --git a/widget/windows/ScreenHelperWin.cpp b/widget/windows/ScreenHelperWin.cpp
new file mode 100644
index 0000000000..8a0ec3b608
--- /dev/null
+++ b/widget/windows/ScreenHelperWin.cpp
@@ -0,0 +1,157 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "ScreenHelperWin.h"
+
+#include "mozilla/Logging.h"
+#include "nsTArray.h"
+#include "WinUtils.h"
+
+static mozilla::LazyLogModule sScreenLog("WidgetScreen");
+
+namespace mozilla {
+namespace widget {
+
+static void GetDisplayInfo(const char16ptr_t aName,
+                           hal::ScreenOrientation& aOrientation,
+                           uint16_t& aAngle, bool& aIsPseudoDisplay,
+                           uint32_t& aRefreshRate) {
+  DISPLAY_DEVICEW displayDevice = {.cb = sizeof(DISPLAY_DEVICEW)};
+
+  // XXX Is the pseudodisplay status really useful?
+  aIsPseudoDisplay =
+      EnumDisplayDevicesW(aName, 0, &displayDevice, 0) &&
+      (displayDevice.StateFlags & DISPLAY_DEVICE_MIRRORING_DRIVER);
+
+  DEVMODEW mode = {.dmSize = sizeof(DEVMODEW)};
+  if (!EnumDisplaySettingsW(aName, ENUM_CURRENT_SETTINGS, &mode)) {
+    return;
+  }
+  MOZ_ASSERT(mode.dmFields & DM_DISPLAYORIENTATION);
+
+  aRefreshRate = mode.dmDisplayFrequency;
+
+  // conver to default/natural size
+  if (mode.dmDisplayOrientation == DMDO_90 ||
+      mode.dmDisplayOrientation == DMDO_270) {
+    DWORD temp = mode.dmPelsHeight;
+    mode.dmPelsHeight = mode.dmPelsWidth;
+    mode.dmPelsWidth = temp;
+  }
+
+  bool defaultIsLandscape = mode.dmPelsWidth >= mode.dmPelsHeight;
+  switch (mode.dmDisplayOrientation) {
+    case DMDO_DEFAULT:
+      aOrientation = defaultIsLandscape
+                         ? hal::ScreenOrientation::LandscapePrimary
+                         : hal::ScreenOrientation::PortraitPrimary;
+      aAngle = 0;
+      break;
+    case DMDO_90:
+      aOrientation = defaultIsLandscape
+                         ? hal::ScreenOrientation::PortraitPrimary
+                         : hal::ScreenOrientation::LandscapeSecondary;
+      aAngle = 270;
+      break;
+    case DMDO_180:
+      aOrientation = defaultIsLandscape
+                         ? hal::ScreenOrientation::LandscapeSecondary
+                         : hal::ScreenOrientation::PortraitSecondary;
+      aAngle = 180;
+      break;
+    case DMDO_270:
+      aOrientation = defaultIsLandscape
+                         ? hal::ScreenOrientation::PortraitSecondary
+                         : hal::ScreenOrientation::LandscapePrimary;
+      aAngle = 90;
+      break;
+    default:
+      MOZ_ASSERT_UNREACHABLE("Unexpected angle");
+      break;
+  }
+}
+
+BOOL CALLBACK CollectMonitors(HMONITOR aMon, HDC, LPRECT, LPARAM ioParam) {
+  auto screens = reinterpret_cast<nsTArray<RefPtr<Screen>>*>(ioParam);
+  BOOL success = FALSE;
+  MONITORINFOEX info;
+  info.cbSize = sizeof(MONITORINFOEX);
+  success = ::GetMonitorInfoW(aMon, &info);
+  if (!success) {
+    MOZ_LOG(sScreenLog, LogLevel::Error, ("GetMonitorInfoW failed"));
+    return TRUE;  // continue the enumeration
+  }
+
+  double scale = WinUtils::LogToPhysFactor(aMon);
+  DesktopToLayoutDeviceScale contentsScaleFactor;
+  if (WinUtils::IsPerMonitorDPIAware()) {
+    contentsScaleFactor.scale = 1.0;
+  } else {
+    contentsScaleFactor.scale = scale;
+  }
+  CSSToLayoutDeviceScale defaultCssScaleFactor(scale);
+  LayoutDeviceIntRect rect(info.rcMonitor.left, info.rcMonitor.top,
+                           info.rcMonitor.right - info.rcMonitor.left,
+                           info.rcMonitor.bottom - info.rcMonitor.top);
+  LayoutDeviceIntRect availRect(info.rcWork.left, info.rcWork.top,
+                                info.rcWork.right - info.rcWork.left,
+                                info.rcWork.bottom - info.rcWork.top);
+
+  HDC hDC = CreateDC(nullptr, info.szDevice, nullptr, nullptr);
+  if (!hDC) {
+    MOZ_LOG(sScreenLog, LogLevel::Error, ("CollectMonitors CreateDC failed"));
+    return TRUE;
+  }
+  uint32_t pixelDepth = ::GetDeviceCaps(hDC, BITSPIXEL);
+  DeleteDC(hDC);
+  if (pixelDepth == 32) {
+    // If a device uses 32 bits per pixel, it's still only using 8 bits
+    // per color component, which is what our callers want to know.
+    // (Some devices report 32 and some devices report 24.)
+    pixelDepth = 24;
+  }
+
+  float dpi = WinUtils::MonitorDPI(aMon);
+
+  auto orientation = hal::ScreenOrientation::None;
+  uint16_t angle = 0;
+  bool isPseudoDisplay = false;
+  uint32_t refreshRate = 0;
+  GetDisplayInfo(info.szDevice, orientation, angle, isPseudoDisplay,
+                 refreshRate);
+
+  MOZ_LOG(sScreenLog, LogLevel::Debug,
+          ("New screen [%s (%s) %d %u %f %f %f %d %d %d]",
+           ToString(rect).c_str(), ToString(availRect).c_str(), pixelDepth,
+           refreshRate, contentsScaleFactor.scale, defaultCssScaleFactor.scale,
+           dpi, isPseudoDisplay, uint32_t(orientation), angle));
+  auto screen = MakeRefPtr<Screen>(
+      rect, availRect, pixelDepth, pixelDepth, refreshRate, contentsScaleFactor,
+      defaultCssScaleFactor, dpi, Screen::IsPseudoDisplay(isPseudoDisplay),
+      orientation, angle);
+  if (info.dwFlags & MONITORINFOF_PRIMARY) {
+    // The primary monitor must be the first element of the screen list.
+    screens->InsertElementAt(0, std::move(screen));
+  } else {
+    screens->AppendElement(std::move(screen));
+  }
+  return TRUE;
+}
+
+void ScreenHelperWin::RefreshScreens() {
+  MOZ_LOG(sScreenLog, LogLevel::Debug, ("Refreshing screens"));
+
+  AutoTArray<RefPtr<Screen>, 4> screens;
+  BOOL result = ::EnumDisplayMonitors(
+      nullptr, nullptr, (MONITORENUMPROC)CollectMonitors, (LPARAM)&screens);
+  if (!result) {
+    NS_WARNING("Unable to EnumDisplayMonitors");
+  }
+  ScreenManager::Refresh(std::move(screens));
+}
+
+}  // namespace widget
+}  // namespace mozilla
diff --git a/widget/windows/ScreenHelperWin.h b/widget/windows/ScreenHelperWin.h
new file mode 100644
index 0000000000..275014232a
--- /dev/null
+++ b/widget/windows/ScreenHelperWin.h
@@ -0,0 +1,26 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_widget_windows_ScreenHelperWin_h
+#define mozilla_widget_windows_ScreenHelperWin_h
+
+#include "mozilla/widget/ScreenManager.h"
+
+namespace mozilla {
+namespace widget {
+
+class ScreenHelperWin final : public ScreenManager::Helper {
+ public:
+  ScreenHelperWin(){};
+  ~ScreenHelperWin() override {}
+
+  static void RefreshScreens();
+};
+
+}  // namespace widget
+}  // namespace mozilla
+
+#endif  // mozilla_widget_windows_ScreenHelperWin_h
diff --git a/widget/windows/ShellHeaderOnlyUtils.h b/widget/windows/ShellHeaderOnlyUtils.h
new file mode 100644
index 0000000000..ea95077fb3
--- /dev/null
+++ b/widget/windows/ShellHeaderOnlyUtils.h
@@ -0,0 +1,183 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_ShellHeaderOnlyUtils_h
+#define mozilla_ShellHeaderOnlyUtils_h
+
+#if defined(LIBXUL) && !defined(UNICODE)
+#  error \
+      "UNICODE not set - must be set to prevent compile failure in `comdef.h` due to us deleting `FormatMessage` when absent."
+#endif
+
+#include "mozilla/WinHeaderOnlyUtils.h"
+
+#include <objbase.h>
+
+#include <exdisp.h>
+#include <shldisp.h>
+#include <shlobj.h>
+#include <shlwapi.h>
+#include <shobjidl.h>
+#include <shtypes.h>
+// NB: include this after shldisp.h so its macros do not conflict with COM
+// interfaces defined by shldisp.h
+#include <shellapi.h>
+#include <type_traits>
+
+#include <comdef.h>
+#include <comutil.h>
+
+#include "mozilla/RefPtr.h"
+#include "mozilla/UniquePtr.h"
+
+namespace mozilla {
+
+/**
+ * Ask the current user's Desktop to ShellExecute on our behalf, thus causing
+ * the resulting launched process to inherit its security priviliges from
+ * Explorer instead of our process.
+ *
+ * This is useful in two scenarios, in particular:
+ *   * We are running as an elevated user and we want to start something as the
+ *     "normal" user;
+ *   * We are starting a process that is incompatible with our process's
+ *     process mitigation policies. By delegating to Explorer, the child process
+ *     will not be affected by our process mitigations.
+ *
+ * Since this communication happens over DCOM, Explorer's COM DACL governs
+ * whether or not we can execute against it, thus avoiding privilege escalation.
+ */
+inline LauncherVoidResult ShellExecuteByExplorer(const _bstr_t& aPath,
+                                                 const _variant_t& aArgs,
+                                                 const _variant_t& aVerb,
+                                                 const _variant_t& aWorkingDir,
+                                                 const _variant_t& aShowCmd) {
+  // NB: Explorer may be a local server, not an inproc server
+  RefPtr<IShellWindows> shellWindows;
+  HRESULT hr = ::CoCreateInstance(
+      CLSID_ShellWindows, nullptr, CLSCTX_INPROC_SERVER | CLSCTX_LOCAL_SERVER,
+      IID_IShellWindows, getter_AddRefs(shellWindows));
+  if (FAILED(hr)) {
+    return LAUNCHER_ERROR_FROM_HRESULT(hr);
+  }
+
+  // 1. Find the shell view for the desktop.
+  _variant_t loc(int(CSIDL_DESKTOP));
+  _variant_t empty;
+  long hwnd;
+  RefPtr<IDispatch> dispDesktop;
+  hr = shellWindows->FindWindowSW(&loc, &empty, SWC_DESKTOP, &hwnd,
+                                  SWFO_NEEDDISPATCH,
+                                  getter_AddRefs(dispDesktop));
+  if (FAILED(hr)) {
+    return LAUNCHER_ERROR_FROM_HRESULT(hr);
+  }
+
+  if (hr == S_FALSE) {
+    // The call succeeded but the window was not found.
+    return LAUNCHER_ERROR_FROM_WIN32(ERROR_NOT_FOUND);
+  }
+
+  RefPtr<IServiceProvider> servProv;
+  hr = dispDesktop->QueryInterface(IID_IServiceProvider,
+                                   getter_AddRefs(servProv));
+  if (FAILED(hr)) {
+    return LAUNCHER_ERROR_FROM_HRESULT(hr);
+  }
+
+  RefPtr<IShellBrowser> browser;
+  hr = servProv->QueryService(SID_STopLevelBrowser, IID_IShellBrowser,
+                              getter_AddRefs(browser));
+  if (FAILED(hr)) {
+    return LAUNCHER_ERROR_FROM_HRESULT(hr);
+  }
+
+  RefPtr<IShellView> activeShellView;
+  hr = browser->QueryActiveShellView(getter_AddRefs(activeShellView));
+  if (FAILED(hr)) {
+    return LAUNCHER_ERROR_FROM_HRESULT(hr);
+  }
+
+  // 2. Get the automation object for the desktop.
+  RefPtr<IDispatch> dispView;
+  hr = activeShellView->GetItemObject(SVGIO_BACKGROUND, IID_IDispatch,
+                                      getter_AddRefs(dispView));
+  if (FAILED(hr)) {
+    return LAUNCHER_ERROR_FROM_HRESULT(hr);
+  }
+
+  RefPtr<IShellFolderViewDual> folderView;
+  hr = dispView->QueryInterface(IID_IShellFolderViewDual,
+                                getter_AddRefs(folderView));
+  if (FAILED(hr)) {
+    return LAUNCHER_ERROR_FROM_HRESULT(hr);
+  }
+
+  // 3. Get the interface to IShellDispatch2
+  RefPtr<IDispatch> dispShell;
+  hr = folderView->get_Application(getter_AddRefs(dispShell));
+  if (FAILED(hr)) {
+    return LAUNCHER_ERROR_FROM_HRESULT(hr);
+  }
+
+  RefPtr<IShellDispatch2> shellDisp;
+  hr =
+      dispShell->QueryInterface(IID_IShellDispatch2, getter_AddRefs(shellDisp));
+  if (FAILED(hr)) {
+    return LAUNCHER_ERROR_FROM_HRESULT(hr);
+  }
+
+  // Passing the foreground privilege so that the shell can launch an
+  // application in the foreground.  This fails with E_ACCESSDENIED if the
+  // current window is shown in the background.  We keep a soft assert for
+  // the other failures to investigate how it happened.
+  hr = ::CoAllowSetForegroundWindow(shellDisp, nullptr);
+  MOZ_ASSERT(SUCCEEDED(hr) || hr == E_ACCESSDENIED);
+
+  // shellapi.h macros interfere with the correct naming of the method being
+  // called on IShellDispatch2. Temporarily remove that definition.
+#if defined(ShellExecute)
+#  define MOZ_REDEFINE_SHELLEXECUTE
+#  undef ShellExecute
+#endif  // defined(ShellExecute)
+
+  // 4. Now call IShellDispatch2::ShellExecute to ask Explorer to execute.
+  hr = shellDisp->ShellExecute(aPath, aArgs, aWorkingDir, aVerb, aShowCmd);
+  if (FAILED(hr)) {
+    return LAUNCHER_ERROR_FROM_HRESULT(hr);
+  }
+
+  // Restore the macro that was removed prior to IShellDispatch2::ShellExecute
+#if defined(MOZ_REDEFINE_SHELLEXECUTE)
+#  if defined(UNICODE)
+#    define ShellExecute ShellExecuteW
+#  else
+#    define ShellExecute ShellExecuteA
+#  endif
+#  undef MOZ_REDEFINE_SHELLEXECUTE
+#endif  // defined(MOZ_REDEFINE_SHELLEXECUTE)
+
+  return Ok();
+}
+
+using UniqueAbsolutePidl =
+    UniquePtr<std::remove_pointer_t<PIDLIST_ABSOLUTE>, CoTaskMemFreeDeleter>;
+
+inline LauncherResult<UniqueAbsolutePidl> ShellParseDisplayName(
+    const wchar_t* aPath) {
+  PIDLIST_ABSOLUTE rawAbsPidl = nullptr;
+  SFGAOF sfgao;
+  HRESULT hr = ::SHParseDisplayName(aPath, nullptr, &rawAbsPidl, 0, &sfgao);
+  if (FAILED(hr)) {
+    return LAUNCHER_ERROR_FROM_HRESULT(hr);
+  }
+
+  return UniqueAbsolutePidl(rawAbsPidl);
+}
+
+}  // namespace mozilla
+
+#endif  // mozilla_ShellHeaderOnlyUtils_h
diff --git a/widget/windows/SystemStatusBar.cpp b/widget/windows/SystemStatusBar.cpp
new file mode 100644
index 0000000000..6cc5668bbe
--- /dev/null
+++ b/widget/windows/SystemStatusBar.cpp
@@ -0,0 +1,339 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:set ts=2 sts=2 sw=2 et cin: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <strsafe.h>
+#include "SystemStatusBar.h"
+
+#include "mozilla/dom/Document.h"
+#include "mozilla/dom/Element.h"
+#include "mozilla/ClearOnShutdown.h"
+#include "mozilla/EventDispatcher.h"
+#include "mozilla/LinkedList.h"
+#include "mozilla/StaticPtr.h"
+#include "mozilla/widget/IconLoader.h"
+#include "mozilla/dom/XULButtonElement.h"
+#include "nsComputedDOMStyle.h"
+#include "nsIContentPolicy.h"
+#include "nsISupports.h"
+#include "nsMenuPopupFrame.h"
+#include "nsXULPopupManager.h"
+#include "nsIDocShell.h"
+#include "nsDocShell.h"
+#include "nsWindowGfx.h"
+
+#include "shellapi.h"
+
+namespace mozilla::widget {
+
+using mozilla::LinkedListElement;
+using mozilla::dom::Element;
+
+class StatusBarEntry final : public LinkedListElement<RefPtr<StatusBarEntry>>,
+                             public IconLoader::Listener,
+                             public nsISupports {
+ public:
+  explicit StatusBarEntry(Element* aMenu);
+  NS_DECL_CYCLE_COLLECTING_ISUPPORTS
+  NS_DECL_CYCLE_COLLECTION_CLASS(StatusBarEntry)
+  nsresult Init();
+  void Destroy();
+
+  MOZ_CAN_RUN_SCRIPT LRESULT OnMessage(HWND hWnd, UINT msg, WPARAM wp,
+                                       LPARAM lp);
+  const Element* GetMenu() { return mMenu; };
+
+  nsresult OnComplete(imgIContainer* aImage) override;
+
+ private:
+  ~StatusBarEntry();
+  RefPtr<mozilla::widget::IconLoader> mIconLoader;
+  // Effectively const but is cycle collected
+  MOZ_KNOWN_LIVE RefPtr<Element> mMenu;
+  NOTIFYICONDATAW mIconData;
+  boolean mInitted;
+};
+
+NS_IMPL_CYCLE_COLLECTION_CLASS(StatusBarEntry)
+
+NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(StatusBarEntry)
+  tmp->Destroy();
+NS_IMPL_CYCLE_COLLECTION_UNLINK_END
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(StatusBarEntry)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mIconLoader)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mMenu)
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(StatusBarEntry)
+  NS_INTERFACE_MAP_ENTRY(nsISupports)
+NS_INTERFACE_MAP_END
+
+NS_IMPL_CYCLE_COLLECTING_ADDREF(StatusBarEntry)
+NS_IMPL_CYCLE_COLLECTING_RELEASE(StatusBarEntry)
+
+StatusBarEntry::StatusBarEntry(Element* aMenu) : mMenu(aMenu), mInitted(false) {
+  mIconData = {/* cbSize */ sizeof(NOTIFYICONDATA),
+               /* hWnd */ 0,
+               /* uID */ 2,
+               /* uFlags */ NIF_ICON | NIF_MESSAGE | NIF_TIP | NIF_SHOWTIP,
+               /* uCallbackMessage */ WM_USER,
+               /* hIcon */ 0,
+               /* szTip */ L"",  // This is updated in Init()
+               /* dwState */ 0,
+               /* dwStateMask */ 0,
+               /* szInfo */ L"",
+               /* uVersion */ {NOTIFYICON_VERSION_4},
+               /* szInfoTitle */ L"",
+               /* dwInfoFlags */ 0};
+  MOZ_ASSERT(mMenu);
+}
+
+StatusBarEntry::~StatusBarEntry() {
+  if (!mInitted) {
+    return;
+  }
+  Destroy();
+  ::Shell_NotifyIconW(NIM_DELETE, &mIconData);
+  VERIFY(::DestroyWindow(mIconData.hWnd));
+}
+
+void StatusBarEntry::Destroy() {
+  if (mIconLoader) {
+    mIconLoader->Destroy();
+    mIconLoader = nullptr;
+  }
+}
+
+nsresult StatusBarEntry::Init() {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  // First, look at the content node's "image" attribute.
+  nsAutoString imageURIString;
+  bool hasImageAttr = mMenu->GetAttr(nsGkAtoms::image, imageURIString);
+
+  nsresult rv;
+  nsCOMPtr<nsIURI> iconURI;
+  if (!hasImageAttr) {
+    // If the content node has no "image" attribute, get the
+    // "list-style-image" property from CSS.
+    RefPtr<mozilla::dom::Document> document = mMenu->GetComposedDoc();
+    if (!document) {
+      return NS_ERROR_FAILURE;
+    }
+
+    RefPtr<const ComputedStyle> sc =
+        nsComputedDOMStyle::GetComputedStyle(mMenu);
+    if (!sc) {
+      return NS_ERROR_FAILURE;
+    }
+
+    iconURI = sc->StyleList()->GetListStyleImageURI();
+  } else {
+    uint64_t dummy = 0;
+    nsContentPolicyType policyType;
+    nsCOMPtr<nsIPrincipal> triggeringPrincipal = mMenu->NodePrincipal();
+    nsContentUtils::GetContentPolicyTypeForUIImageLoading(
+        mMenu, getter_AddRefs(triggeringPrincipal), policyType, &dummy);
+    if (policyType != nsIContentPolicy::TYPE_INTERNAL_IMAGE) {
+      return NS_ERROR_ILLEGAL_VALUE;
+    }
+
+    // If this menu item shouldn't have an icon, the string will be empty,
+    // and NS_NewURI will fail.
+    rv = NS_NewURI(getter_AddRefs(iconURI), imageURIString);
+    if (NS_FAILED(rv)) return rv;
+  }
+
+  mIconLoader = new IconLoader(this);
+
+  if (iconURI) {
+    rv = mIconLoader->LoadIcon(iconURI, mMenu);
+  }
+
+  HWND iconWindow;
+  NS_ENSURE_TRUE(iconWindow = ::CreateWindowExW(
+                     /* extended style */ 0,
+                     /* className */ L"IconWindowClass",
+                     /* title */ 0,
+                     /* style */ WS_CAPTION,
+                     /* x, y, cx, cy */ 0, 0, 0, 0,
+                     /* parent */ 0,
+                     /* menu */ 0,
+                     /* instance */ 0,
+                     /* create struct */ 0),
+                 NS_ERROR_FAILURE);
+  ::SetWindowLongPtr(iconWindow, GWLP_USERDATA, (LONG_PTR)this);
+
+  mIconData.hWnd = iconWindow;
+  mIconData.hIcon = ::LoadIcon(::GetModuleHandle(NULL), IDI_APPLICATION);
+
+  nsAutoString labelAttr;
+  mMenu->GetAttr(nsGkAtoms::label, labelAttr);
+  const nsString& label = PromiseFlatString(labelAttr);
+
+  size_t destLength = sizeof mIconData.szTip / (sizeof mIconData.szTip[0]);
+  wchar_t* tooltip = &(mIconData.szTip[0]);
+  ::StringCchCopyNW(tooltip, destLength, label.get(), label.Length());
+
+  ::Shell_NotifyIconW(NIM_ADD, &mIconData);
+  ::Shell_NotifyIconW(NIM_SETVERSION, &mIconData);
+
+  mInitted = true;
+  return NS_OK;
+}
+
+nsresult StatusBarEntry::OnComplete(imgIContainer* aImage) {
+  NS_ENSURE_ARG_POINTER(aImage);
+
+  RefPtr<StatusBarEntry> kungFuDeathGrip = this;
+
+  nsresult rv = nsWindowGfx::CreateIcon(
+      aImage, false, LayoutDeviceIntPoint(),
+      nsWindowGfx::GetIconMetrics(nsWindowGfx::kRegularIcon), &mIconData.hIcon);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  ::Shell_NotifyIconW(NIM_MODIFY, &mIconData);
+
+  if (mIconData.hIcon) {
+    ::DestroyIcon(mIconData.hIcon);
+    mIconData.hIcon = nullptr;
+  }
+
+  // To simplify things, we won't react to CSS changes to update the icon
+  // with this implementation. We can get rid of the IconLoader at this point.
+  mIconLoader->Destroy();
+  mIconLoader = nullptr;
+  return NS_OK;
+}
+
+LRESULT StatusBarEntry::OnMessage(HWND hWnd, UINT msg, WPARAM wp, LPARAM lp) {
+  if (msg == WM_USER &&
+      (LOWORD(lp) == NIN_SELECT || LOWORD(lp) == NIN_KEYSELECT ||
+       LOWORD(lp) == WM_CONTEXTMENU)) {
+    auto* menu = dom::XULButtonElement::FromNode(mMenu);
+    if (!menu) {
+      return TRUE;
+    }
+
+    nsMenuPopupFrame* popupFrame = menu->GetMenuPopup(FlushType::None);
+    if (NS_WARN_IF(!popupFrame)) {
+      return TRUE;
+    }
+
+    nsIWidget* widget = popupFrame->GetNearestWidget();
+    MOZ_DIAGNOSTIC_ASSERT(widget);
+    if (!widget) {
+      return TRUE;
+    }
+
+    HWND win = static_cast<HWND>(widget->GetNativeData(NS_NATIVE_WINDOW));
+    MOZ_DIAGNOSTIC_ASSERT(win);
+    if (!win) {
+      return TRUE;
+    }
+
+    if (LOWORD(lp) == NIN_KEYSELECT && ::GetForegroundWindow() == win) {
+      // When enter is pressed on the icon, the shell sends two NIN_KEYSELECT
+      // notifications. This might cause us to open two windows. To work around
+      // this, if we're already the foreground window (which happens below),
+      // ignore this notification.
+      return TRUE;
+    }
+
+    if (LOWORD(lp) != WM_CONTEXTMENU &&
+        mMenu->HasAttr(nsGkAtoms::contextmenu)) {
+      ::SetForegroundWindow(win);
+      nsEventStatus status = nsEventStatus_eIgnore;
+      WidgetMouseEvent event(true, eXULSystemStatusBarClick, nullptr,
+                             WidgetMouseEvent::eReal);
+      RefPtr<nsPresContext> presContext = popupFrame->PresContext();
+      EventDispatcher::Dispatch(mMenu, presContext, &event, nullptr, &status);
+      return DefWindowProc(hWnd, msg, wp, lp);
+    }
+
+    nsPresContext* pc = popupFrame->PresContext();
+    const CSSIntPoint point = gfx::RoundedToInt(
+        LayoutDeviceIntPoint(GET_X_LPARAM(wp), GET_Y_LPARAM(wp)) /
+        pc->CSSToDevPixelScale());
+
+    // The menu that is being opened is a Gecko <xul:menu>, and the popup code
+    // that manages it expects that the window that the <xul:menu> belongs to
+    // will be in the foreground when it opens. If we don't do this, then if the
+    // icon is clicked when the window is _not_ in the foreground, then the
+    // opened menu will not be keyboard focusable, nor will it close on its own
+    // if the user clicks away from the menu (at least, not until the user
+    // focuses any window in the parent process).
+    ::SetForegroundWindow(win);
+    nsXULPopupManager* pm = nsXULPopupManager::GetInstance();
+    pm->ShowPopupAtScreen(popupFrame->GetContent()->AsElement(), point.x,
+                          point.y, false, nullptr);
+  }
+
+  return DefWindowProc(hWnd, msg, wp, lp);
+}
+
+NS_IMPL_ISUPPORTS(SystemStatusBar, nsISystemStatusBar)
+
+MOZ_CAN_RUN_SCRIPT static LRESULT CALLBACK WindowProc(HWND hWnd, UINT msg,
+                                                      WPARAM wp, LPARAM lp) {
+  if (RefPtr<StatusBarEntry> entry =
+          (StatusBarEntry*)GetWindowLongPtr(hWnd, GWLP_USERDATA)) {
+    return entry->OnMessage(hWnd, msg, wp, lp);
+  }
+  return TRUE;
+}
+
+static StaticRefPtr<SystemStatusBar> sSingleton;
+
+SystemStatusBar& SystemStatusBar::GetSingleton() {
+  if (!sSingleton) {
+    sSingleton = new SystemStatusBar();
+    ClearOnShutdown(&sSingleton);
+  }
+  return *sSingleton;
+}
+
+already_AddRefed<SystemStatusBar> SystemStatusBar::GetAddRefedSingleton() {
+  RefPtr<SystemStatusBar> sm = &GetSingleton();
+  return sm.forget();
+}
+
+nsresult SystemStatusBar::Init() {
+  WNDCLASS classStruct = {/* style */ 0,
+                          /* lpfnWndProc */ &WindowProc,
+                          /* cbClsExtra */ 0,
+                          /* cbWndExtra */ 0,
+                          /* hInstance */ 0,
+                          /* hIcon */ 0,
+                          /* hCursor */ 0,
+                          /* hbrBackground */ 0,
+                          /* lpszMenuName */ 0,
+                          /* lpszClassName */ L"IconWindowClass"};
+  NS_ENSURE_TRUE(::RegisterClass(&classStruct), NS_ERROR_FAILURE);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+SystemStatusBar::AddItem(Element* aElement) {
+  RefPtr<StatusBarEntry> entry = new StatusBarEntry(aElement);
+  nsresult rv = entry->Init();
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  mStatusBarEntries.insertBack(entry);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+SystemStatusBar::RemoveItem(Element* aElement) {
+  for (StatusBarEntry* entry : mStatusBarEntries) {
+    if (entry->GetMenu() == aElement) {
+      entry->removeFrom(mStatusBarEntries);
+      return NS_OK;
+    }
+  }
+  return NS_ERROR_NOT_AVAILABLE;
+}
+
+}  // namespace mozilla::widget
diff --git a/widget/windows/SystemStatusBar.h b/widget/windows/SystemStatusBar.h
new file mode 100644
index 0000000000..6afafd9d80
--- /dev/null
+++ b/widget/windows/SystemStatusBar.h
@@ -0,0 +1,33 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef widget_windows_SystemStatusBar_h
+#define widget_windows_SystemStatusBar_h
+
+#include "nsISystemStatusBar.h"
+#include "mozilla/LinkedList.h"
+
+namespace mozilla::widget {
+class StatusBarEntry;
+
+class SystemStatusBar final : public nsISystemStatusBar {
+ public:
+  explicit SystemStatusBar() = default;
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSISYSTEMSTATUSBAR
+
+  static SystemStatusBar& GetSingleton();
+  static already_AddRefed<SystemStatusBar> GetAddRefedSingleton();
+
+  nsresult Init();
+
+ private:
+  ~SystemStatusBar() = default;
+  mozilla::LinkedList<RefPtr<StatusBarEntry>> mStatusBarEntries;
+};
+
+}  // namespace mozilla::widget
+
+#endif  // widget_windows_SystemStatusBar_h
diff --git a/widget/windows/TSFTextStore.cpp b/widget/windows/TSFTextStore.cpp
new file mode 100644
index 0000000000..b3e3a164ae
--- /dev/null
+++ b/widget/windows/TSFTextStore.cpp
@@ -0,0 +1,7513 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#define INPUTSCOPE_INIT_GUID
+#define TEXTATTRS_INIT_GUID
+#include "TSFTextStore.h"
+
+#include <algorithm>
+#include <comutil.h>  // for _bstr_t
+#include <oleauto.h>  // for SysAllocString
+#include <olectl.h>
+#include "nscore.h"
+
+#include "IMMHandler.h"
+#include "KeyboardLayout.h"
+#include "WinIMEHandler.h"
+#include "WinUtils.h"
+#include "mozilla/AutoRestore.h"
+#include "mozilla/Logging.h"
+#include "mozilla/StaticPrefs_intl.h"
+#include "mozilla/Telemetry.h"
+#include "mozilla/TextEventDispatcher.h"
+#include "mozilla/TextEvents.h"
+#include "mozilla/ToString.h"
+#include "mozilla/WindowsVersion.h"
+#include "mozilla/widget/WinRegistry.h"
+#include "nsWindow.h"
+#include "nsPrintfCString.h"
+
+// For collecting other people's log, tell `MOZ_LOG=IMEHandler:4,sync`
+// rather than `MOZ_LOG=IMEHandler:5,sync` since using `5` may create too
+// big file.
+// Therefore you shouldn't use `LogLevel::Verbose` for logging usual behavior.
+mozilla::LazyLogModule gIMELog("IMEHandler");
+
+// TODO: GUID_PROP_URL has not been declared in the SDK yet.  We should drop the
+//       `s` prefix after it's released by a new SDK and define it with #if.
+static const GUID sGUID_PROP_URL = {
+    0xd5138268,
+    0xa1bf,
+    0x4308,
+    {0xbc, 0xbf, 0x2e, 0x73, 0x93, 0x98, 0xe2, 0x34}};
+
+namespace mozilla {
+namespace widget {
+
+/**
+ * TSF related code should log its behavior even on release build especially
+ * in the interface methods.
+ *
+ * In interface methods, use LogLevel::Info.
+ * In internal methods, use LogLevel::Debug for logging normal behavior.
+ * For logging error, use LogLevel::Error.
+ *
+ * When an instance method is called, start with following text:
+ *   "0x%p TSFFoo::Bar(", the 0x%p should be the "this" of the nsFoo.
+ * after that, start with:
+ *   "0x%p   TSFFoo::Bar("
+ * In an internal method, start with following text:
+ *   "0x%p   TSFFoo::Bar("
+ * When a static method is called, start with following text:
+ *   "TSFFoo::Bar("
+ */
+
+enum class TextInputProcessorID {
+  // Internal use only.  This won't be returned by TSFStaticSink::ActiveTIP().
+  eNotComputed,
+
+  // Not a TIP.  E.g., simple keyboard layout or IMM-IME.
+  eNone,
+
+  // Used for other TIPs, i.e., any TIPs which we don't support specifically.
+  eUnknown,
+
+  // TIP for Japanese.
+  eMicrosoftIMEForJapanese,
+  eMicrosoftOfficeIME2010ForJapanese,
+  eGoogleJapaneseInput,
+  eATOK2011,
+  eATOK2012,
+  eATOK2013,
+  eATOK2014,
+  eATOK2015,
+  eATOK2016,
+  eATOKUnknown,
+  eJapanist10,
+
+  // TIP for Traditional Chinese.
+  eMicrosoftBopomofo,
+  eMicrosoftChangJie,
+  eMicrosoftPhonetic,
+  eMicrosoftQuick,
+  eMicrosoftNewChangJie,
+  eMicrosoftNewPhonetic,
+  eMicrosoftNewQuick,
+  eFreeChangJie,
+
+  // TIP for Simplified Chinese.
+  eMicrosoftPinyin,
+  eMicrosoftPinyinNewExperienceInputStyle,
+  eMicrosoftWubi,
+
+  // TIP for Korean.
+  eMicrosoftIMEForKorean,
+  eMicrosoftOldHangul,
+
+  // Keyman Desktop, which can install various language keyboards.
+  eKeymanDesktop,
+};
+
+static const char* GetBoolName(bool aBool) { return aBool ? "true" : "false"; }
+
+static void HandleSeparator(nsCString& aDesc) {
+  if (!aDesc.IsEmpty()) {
+    aDesc.AppendLiteral(" | ");
+  }
+}
+
+static const nsCString GetFindFlagName(DWORD aFindFlag) {
+  nsCString description;
+  if (!aFindFlag) {
+    description.AppendLiteral("no flags (0)");
+    return description;
+  }
+  if (aFindFlag & TS_ATTR_FIND_BACKWARDS) {
+    description.AppendLiteral("TS_ATTR_FIND_BACKWARDS");
+  }
+  if (aFindFlag & TS_ATTR_FIND_WANT_OFFSET) {
+    HandleSeparator(description);
+    description.AppendLiteral("TS_ATTR_FIND_WANT_OFFSET");
+  }
+  if (aFindFlag & TS_ATTR_FIND_UPDATESTART) {
+    HandleSeparator(description);
+    description.AppendLiteral("TS_ATTR_FIND_UPDATESTART");
+  }
+  if (aFindFlag & TS_ATTR_FIND_WANT_VALUE) {
+    HandleSeparator(description);
+    description.AppendLiteral("TS_ATTR_FIND_WANT_VALUE");
+  }
+  if (aFindFlag & TS_ATTR_FIND_WANT_END) {
+    HandleSeparator(description);
+    description.AppendLiteral("TS_ATTR_FIND_WANT_END");
+  }
+  if (aFindFlag & TS_ATTR_FIND_HIDDEN) {
+    HandleSeparator(description);
+    description.AppendLiteral("TS_ATTR_FIND_HIDDEN");
+  }
+  if (description.IsEmpty()) {
+    description.AppendLiteral("Unknown (");
+    description.AppendInt(static_cast<uint32_t>(aFindFlag));
+    description.Append(')');
+  }
+  return description;
+}
+
+class GetACPFromPointFlagName : public nsAutoCString {
+ public:
+  explicit GetACPFromPointFlagName(DWORD aFlags) {
+    if (!aFlags) {
+      AppendLiteral("no flags (0)");
+      return;
+    }
+    if (aFlags & GXFPF_ROUND_NEAREST) {
+      AppendLiteral("GXFPF_ROUND_NEAREST");
+      aFlags &= ~GXFPF_ROUND_NEAREST;
+    }
+    if (aFlags & GXFPF_NEAREST) {
+      HandleSeparator(*this);
+      AppendLiteral("GXFPF_NEAREST");
+      aFlags &= ~GXFPF_NEAREST;
+    }
+    if (aFlags) {
+      HandleSeparator(*this);
+      AppendLiteral("Unknown(");
+      AppendInt(static_cast<uint32_t>(aFlags));
+      Append(')');
+    }
+  }
+  virtual ~GetACPFromPointFlagName() {}
+};
+
+static const char* GetFocusChangeName(
+    InputContextAction::FocusChange aFocusChange) {
+  switch (aFocusChange) {
+    case InputContextAction::FOCUS_NOT_CHANGED:
+      return "FOCUS_NOT_CHANGED";
+    case InputContextAction::GOT_FOCUS:
+      return "GOT_FOCUS";
+    case InputContextAction::LOST_FOCUS:
+      return "LOST_FOCUS";
+    case InputContextAction::MENU_GOT_PSEUDO_FOCUS:
+      return "MENU_GOT_PSEUDO_FOCUS";
+    case InputContextAction::MENU_LOST_PSEUDO_FOCUS:
+      return "MENU_LOST_PSEUDO_FOCUS";
+    case InputContextAction::WIDGET_CREATED:
+      return "WIDGET_CREATED";
+    default:
+      return "Unknown";
+  }
+}
+
+static nsCString GetCLSIDNameStr(REFCLSID aCLSID) {
+  LPOLESTR str = nullptr;
+  HRESULT hr = ::StringFromCLSID(aCLSID, &str);
+  if (FAILED(hr) || !str || !str[0]) {
+    return ""_ns;
+  }
+
+  nsCString result;
+  result = NS_ConvertUTF16toUTF8(str);
+  ::CoTaskMemFree(str);
+  return result;
+}
+
+static nsCString GetGUIDNameStr(REFGUID aGUID) {
+  OLECHAR str[40];
+  int len = ::StringFromGUID2(aGUID, str, ArrayLength(str));
+  if (!len || !str[0]) {
+    return ""_ns;
+  }
+
+  return NS_ConvertUTF16toUTF8(str);
+}
+
+static nsCString GetGUIDNameStrWithTable(REFGUID aGUID) {
+#define RETURN_GUID_NAME(aNamedGUID)      \
+  if (IsEqualGUID(aGUID, aNamedGUID)) {   \
+    return nsLiteralCString(#aNamedGUID); \
+  }
+
+  RETURN_GUID_NAME(GUID_PROP_INPUTSCOPE)
+  RETURN_GUID_NAME(sGUID_PROP_URL)
+  RETURN_GUID_NAME(TSATTRID_OTHERS)
+  RETURN_GUID_NAME(TSATTRID_Font)
+  RETURN_GUID_NAME(TSATTRID_Font_FaceName)
+  RETURN_GUID_NAME(TSATTRID_Font_SizePts)
+  RETURN_GUID_NAME(TSATTRID_Font_Style)
+  RETURN_GUID_NAME(TSATTRID_Font_Style_Bold)
+  RETURN_GUID_NAME(TSATTRID_Font_Style_Italic)
+  RETURN_GUID_NAME(TSATTRID_Font_Style_SmallCaps)
+  RETURN_GUID_NAME(TSATTRID_Font_Style_Capitalize)
+  RETURN_GUID_NAME(TSATTRID_Font_Style_Uppercase)
+  RETURN_GUID_NAME(TSATTRID_Font_Style_Lowercase)
+  RETURN_GUID_NAME(TSATTRID_Font_Style_Animation)
+  RETURN_GUID_NAME(TSATTRID_Font_Style_Animation_LasVegasLights)
+  RETURN_GUID_NAME(TSATTRID_Font_Style_Animation_BlinkingBackground)
+  RETURN_GUID_NAME(TSATTRID_Font_Style_Animation_SparkleText)
+  RETURN_GUID_NAME(TSATTRID_Font_Style_Animation_MarchingBlackAnts)
+  RETURN_GUID_NAME(TSATTRID_Font_Style_Animation_MarchingRedAnts)
+  RETURN_GUID_NAME(TSATTRID_Font_Style_Animation_Shimmer)
+  RETURN_GUID_NAME(TSATTRID_Font_Style_Animation_WipeDown)
+  RETURN_GUID_NAME(TSATTRID_Font_Style_Animation_WipeRight)
+  RETURN_GUID_NAME(TSATTRID_Font_Style_Emboss)
+  RETURN_GUID_NAME(TSATTRID_Font_Style_Engrave)
+  RETURN_GUID_NAME(TSATTRID_Font_Style_Hidden)
+  RETURN_GUID_NAME(TSATTRID_Font_Style_Kerning)
+  RETURN_GUID_NAME(TSATTRID_Font_Style_Outlined)
+  RETURN_GUID_NAME(TSATTRID_Font_Style_Position)
+  RETURN_GUID_NAME(TSATTRID_Font_Style_Protected)
+  RETURN_GUID_NAME(TSATTRID_Font_Style_Shadow)
+  RETURN_GUID_NAME(TSATTRID_Font_Style_Spacing)
+  RETURN_GUID_NAME(TSATTRID_Font_Style_Weight)
+  RETURN_GUID_NAME(TSATTRID_Font_Style_Height)
+  RETURN_GUID_NAME(TSATTRID_Font_Style_Underline)
+  RETURN_GUID_NAME(TSATTRID_Font_Style_Underline_Single)
+  RETURN_GUID_NAME(TSATTRID_Font_Style_Underline_Double)
+  RETURN_GUID_NAME(TSATTRID_Font_Style_Strikethrough)
+  RETURN_GUID_NAME(TSATTRID_Font_Style_Strikethrough_Single)
+  RETURN_GUID_NAME(TSATTRID_Font_Style_Strikethrough_Double)
+  RETURN_GUID_NAME(TSATTRID_Font_Style_Overline)
+  RETURN_GUID_NAME(TSATTRID_Font_Style_Overline_Single)
+  RETURN_GUID_NAME(TSATTRID_Font_Style_Overline_Double)
+  RETURN_GUID_NAME(TSATTRID_Font_Style_Blink)
+  RETURN_GUID_NAME(TSATTRID_Font_Style_Subscript)
+  RETURN_GUID_NAME(TSATTRID_Font_Style_Superscript)
+  RETURN_GUID_NAME(TSATTRID_Font_Style_Color)
+  RETURN_GUID_NAME(TSATTRID_Font_Style_BackgroundColor)
+  RETURN_GUID_NAME(TSATTRID_Text)
+  RETURN_GUID_NAME(TSATTRID_Text_VerticalWriting)
+  RETURN_GUID_NAME(TSATTRID_Text_RightToLeft)
+  RETURN_GUID_NAME(TSATTRID_Text_Orientation)
+  RETURN_GUID_NAME(TSATTRID_Text_Language)
+  RETURN_GUID_NAME(TSATTRID_Text_ReadOnly)
+  RETURN_GUID_NAME(TSATTRID_Text_EmbeddedObject)
+  RETURN_GUID_NAME(TSATTRID_Text_Alignment)
+  RETURN_GUID_NAME(TSATTRID_Text_Alignment_Left)
+  RETURN_GUID_NAME(TSATTRID_Text_Alignment_Right)
+  RETURN_GUID_NAME(TSATTRID_Text_Alignment_Center)
+  RETURN_GUID_NAME(TSATTRID_Text_Alignment_Justify)
+  RETURN_GUID_NAME(TSATTRID_Text_Link)
+  RETURN_GUID_NAME(TSATTRID_Text_Hyphenation)
+  RETURN_GUID_NAME(TSATTRID_Text_Para)
+  RETURN_GUID_NAME(TSATTRID_Text_Para_FirstLineIndent)
+  RETURN_GUID_NAME(TSATTRID_Text_Para_LeftIndent)
+  RETURN_GUID_NAME(TSATTRID_Text_Para_RightIndent)
+  RETURN_GUID_NAME(TSATTRID_Text_Para_SpaceAfter)
+  RETURN_GUID_NAME(TSATTRID_Text_Para_SpaceBefore)
+  RETURN_GUID_NAME(TSATTRID_Text_Para_LineSpacing)
+  RETURN_GUID_NAME(TSATTRID_Text_Para_LineSpacing_Single)
+  RETURN_GUID_NAME(TSATTRID_Text_Para_LineSpacing_OnePtFive)
+  RETURN_GUID_NAME(TSATTRID_Text_Para_LineSpacing_Double)
+  RETURN_GUID_NAME(TSATTRID_Text_Para_LineSpacing_AtLeast)
+  RETURN_GUID_NAME(TSATTRID_Text_Para_LineSpacing_Exactly)
+  RETURN_GUID_NAME(TSATTRID_Text_Para_LineSpacing_Multiple)
+  RETURN_GUID_NAME(TSATTRID_List)
+  RETURN_GUID_NAME(TSATTRID_List_LevelIndel)
+  RETURN_GUID_NAME(TSATTRID_List_Type)
+  RETURN_GUID_NAME(TSATTRID_List_Type_Bullet)
+  RETURN_GUID_NAME(TSATTRID_List_Type_Arabic)
+  RETURN_GUID_NAME(TSATTRID_List_Type_LowerLetter)
+  RETURN_GUID_NAME(TSATTRID_List_Type_UpperLetter)
+  RETURN_GUID_NAME(TSATTRID_List_Type_LowerRoman)
+  RETURN_GUID_NAME(TSATTRID_List_Type_UpperRoman)
+  RETURN_GUID_NAME(TSATTRID_App)
+  RETURN_GUID_NAME(TSATTRID_App_IncorrectSpelling)
+  RETURN_GUID_NAME(TSATTRID_App_IncorrectGrammar)
+
+#undef RETURN_GUID_NAME
+
+  return GetGUIDNameStr(aGUID);
+}
+
+static nsCString GetRIIDNameStr(REFIID aRIID) {
+  LPOLESTR str = nullptr;
+  HRESULT hr = ::StringFromIID(aRIID, &str);
+  if (FAILED(hr) || !str || !str[0]) {
+    return ""_ns;
+  }
+
+  nsAutoString key(L"Interface\\");
+  key += str;
+
+  nsCString result;
+  wchar_t buf[256];
+  if (WinRegistry::GetString(HKEY_CLASSES_ROOT, key, u""_ns, buf,
+                             WinRegistry::kLegacyWinUtilsStringFlags)) {
+    result = NS_ConvertUTF16toUTF8(buf);
+  } else {
+    result = NS_ConvertUTF16toUTF8(str);
+  }
+
+  ::CoTaskMemFree(str);
+  return result;
+}
+
+static const char* GetCommonReturnValueName(HRESULT aResult) {
+  switch (aResult) {
+    case S_OK:
+      return "S_OK";
+    case E_ABORT:
+      return "E_ABORT";
+    case E_ACCESSDENIED:
+      return "E_ACCESSDENIED";
+    case E_FAIL:
+      return "E_FAIL";
+    case E_HANDLE:
+      return "E_HANDLE";
+    case E_INVALIDARG:
+      return "E_INVALIDARG";
+    case E_NOINTERFACE:
+      return "E_NOINTERFACE";
+    case E_NOTIMPL:
+      return "E_NOTIMPL";
+    case E_OUTOFMEMORY:
+      return "E_OUTOFMEMORY";
+    case E_POINTER:
+      return "E_POINTER";
+    case E_UNEXPECTED:
+      return "E_UNEXPECTED";
+    default:
+      return SUCCEEDED(aResult) ? "Succeeded" : "Failed";
+  }
+}
+
+static const char* GetTextStoreReturnValueName(HRESULT aResult) {
+  switch (aResult) {
+    case TS_E_FORMAT:
+      return "TS_E_FORMAT";
+    case TS_E_INVALIDPOINT:
+      return "TS_E_INVALIDPOINT";
+    case TS_E_INVALIDPOS:
+      return "TS_E_INVALIDPOS";
+    case TS_E_NOINTERFACE:
+      return "TS_E_NOINTERFACE";
+    case TS_E_NOLAYOUT:
+      return "TS_E_NOLAYOUT";
+    case TS_E_NOLOCK:
+      return "TS_E_NOLOCK";
+    case TS_E_NOOBJECT:
+      return "TS_E_NOOBJECT";
+    case TS_E_NOSELECTION:
+      return "TS_E_NOSELECTION";
+    case TS_E_NOSERVICE:
+      return "TS_E_NOSERVICE";
+    case TS_E_READONLY:
+      return "TS_E_READONLY";
+    case TS_E_SYNCHRONOUS:
+      return "TS_E_SYNCHRONOUS";
+    case TS_S_ASYNC:
+      return "TS_S_ASYNC";
+    default:
+      return GetCommonReturnValueName(aResult);
+  }
+}
+
+static const nsCString GetSinkMaskNameStr(DWORD aSinkMask) {
+  nsCString description;
+  if (aSinkMask & TS_AS_TEXT_CHANGE) {
+    description.AppendLiteral("TS_AS_TEXT_CHANGE");
+  }
+  if (aSinkMask & TS_AS_SEL_CHANGE) {
+    HandleSeparator(description);
+    description.AppendLiteral("TS_AS_SEL_CHANGE");
+  }
+  if (aSinkMask & TS_AS_LAYOUT_CHANGE) {
+    HandleSeparator(description);
+    description.AppendLiteral("TS_AS_LAYOUT_CHANGE");
+  }
+  if (aSinkMask & TS_AS_ATTR_CHANGE) {
+    HandleSeparator(description);
+    description.AppendLiteral("TS_AS_ATTR_CHANGE");
+  }
+  if (aSinkMask & TS_AS_STATUS_CHANGE) {
+    HandleSeparator(description);
+    description.AppendLiteral("TS_AS_STATUS_CHANGE");
+  }
+  if (description.IsEmpty()) {
+    description.AppendLiteral("not-specified");
+  }
+  return description;
+}
+
+static const nsCString GetLockFlagNameStr(DWORD aLockFlags) {
+  nsCString description;
+  if ((aLockFlags & TS_LF_READWRITE) == TS_LF_READWRITE) {
+    description.AppendLiteral("TS_LF_READWRITE");
+  } else if (aLockFlags & TS_LF_READ) {
+    description.AppendLiteral("TS_LF_READ");
+  }
+  if (aLockFlags & TS_LF_SYNC) {
+    if (!description.IsEmpty()) {
+      description.AppendLiteral(" | ");
+    }
+    description.AppendLiteral("TS_LF_SYNC");
+  }
+  if (description.IsEmpty()) {
+    description.AppendLiteral("not-specified");
+  }
+  return description;
+}
+
+static const char* GetTextRunTypeName(TsRunType aRunType) {
+  switch (aRunType) {
+    case TS_RT_PLAIN:
+      return "TS_RT_PLAIN";
+    case TS_RT_HIDDEN:
+      return "TS_RT_HIDDEN";
+    case TS_RT_OPAQUE:
+      return "TS_RT_OPAQUE";
+    default:
+      return "Unknown";
+  }
+}
+
+static nsCString GetColorName(const TF_DA_COLOR& aColor) {
+  switch (aColor.type) {
+    case TF_CT_NONE:
+      return "TF_CT_NONE"_ns;
+    case TF_CT_SYSCOLOR:
+      return nsPrintfCString("TF_CT_SYSCOLOR, nIndex:0x%08X",
+                             static_cast<int32_t>(aColor.nIndex));
+    case TF_CT_COLORREF:
+      return nsPrintfCString("TF_CT_COLORREF, cr:0x%08X",
+                             static_cast<int32_t>(aColor.cr));
+      break;
+    default:
+      return nsPrintfCString("Unknown(%08X)",
+                             static_cast<int32_t>(aColor.type));
+  }
+}
+
+static nsCString GetLineStyleName(TF_DA_LINESTYLE aLineStyle) {
+  switch (aLineStyle) {
+    case TF_LS_NONE:
+      return "TF_LS_NONE"_ns;
+    case TF_LS_SOLID:
+      return "TF_LS_SOLID"_ns;
+    case TF_LS_DOT:
+      return "TF_LS_DOT"_ns;
+    case TF_LS_DASH:
+      return "TF_LS_DASH"_ns;
+    case TF_LS_SQUIGGLE:
+      return "TF_LS_SQUIGGLE"_ns;
+    default: {
+      return nsPrintfCString("Unknown(%08X)", static_cast<int32_t>(aLineStyle));
+    }
+  }
+}
+
+static nsCString GetClauseAttrName(TF_DA_ATTR_INFO aAttr) {
+  switch (aAttr) {
+    case TF_ATTR_INPUT:
+      return "TF_ATTR_INPUT"_ns;
+    case TF_ATTR_TARGET_CONVERTED:
+      return "TF_ATTR_TARGET_CONVERTED"_ns;
+    case TF_ATTR_CONVERTED:
+      return "TF_ATTR_CONVERTED"_ns;
+    case TF_ATTR_TARGET_NOTCONVERTED:
+      return "TF_ATTR_TARGET_NOTCONVERTED"_ns;
+    case TF_ATTR_INPUT_ERROR:
+      return "TF_ATTR_INPUT_ERROR"_ns;
+    case TF_ATTR_FIXEDCONVERTED:
+      return "TF_ATTR_FIXEDCONVERTED"_ns;
+    case TF_ATTR_OTHER:
+      return "TF_ATTR_OTHER"_ns;
+    default: {
+      return nsPrintfCString("Unknown(%08X)", static_cast<int32_t>(aAttr));
+    }
+  }
+}
+
+static nsCString GetDisplayAttrStr(const TF_DISPLAYATTRIBUTE& aDispAttr) {
+  nsCString str;
+  str = "crText:{ ";
+  str += GetColorName(aDispAttr.crText);
+  str += " }, crBk:{ ";
+  str += GetColorName(aDispAttr.crBk);
+  str += " }, lsStyle: ";
+  str += GetLineStyleName(aDispAttr.lsStyle);
+  str += ", fBoldLine: ";
+  str += GetBoolName(aDispAttr.fBoldLine);
+  str += ", crLine:{ ";
+  str += GetColorName(aDispAttr.crLine);
+  str += " }, bAttr: ";
+  str += GetClauseAttrName(aDispAttr.bAttr);
+  return str;
+}
+
+static const char* GetMouseButtonName(int16_t aButton) {
+  switch (aButton) {
+    case MouseButton::ePrimary:
+      return "LeftButton";
+    case MouseButton::eMiddle:
+      return "MiddleButton";
+    case MouseButton::eSecondary:
+      return "RightButton";
+    default:
+      return "UnknownButton";
+  }
+}
+
+#define ADD_SEPARATOR_IF_NECESSARY(aStr) \
+  if (!aStr.IsEmpty()) {                 \
+    aStr.AppendLiteral(", ");            \
+  }
+
+static nsCString GetMouseButtonsName(int16_t aButtons) {
+  if (!aButtons) {
+    return "no buttons"_ns;
+  }
+  nsCString names;
+  if (aButtons & MouseButtonsFlag::ePrimaryFlag) {
+    names = "LeftButton";
+  }
+  if (aButtons & MouseButtonsFlag::eSecondaryFlag) {
+    ADD_SEPARATOR_IF_NECESSARY(names);
+    names += "RightButton";
+  }
+  if (aButtons & MouseButtonsFlag::eMiddleFlag) {
+    ADD_SEPARATOR_IF_NECESSARY(names);
+    names += "MiddleButton";
+  }
+  if (aButtons & MouseButtonsFlag::e4thFlag) {
+    ADD_SEPARATOR_IF_NECESSARY(names);
+    names += "4thButton";
+  }
+  if (aButtons & MouseButtonsFlag::e5thFlag) {
+    ADD_SEPARATOR_IF_NECESSARY(names);
+    names += "5thButton";
+  }
+  return names;
+}
+
+static nsCString GetModifiersName(Modifiers aModifiers) {
+  if (aModifiers == MODIFIER_NONE) {
+    return "no modifiers"_ns;
+  }
+  nsCString names;
+  if (aModifiers & MODIFIER_ALT) {
+    names = NS_DOM_KEYNAME_ALT;
+  }
+  if (aModifiers & MODIFIER_ALTGRAPH) {
+    ADD_SEPARATOR_IF_NECESSARY(names);
+    names += NS_DOM_KEYNAME_ALTGRAPH;
+  }
+  if (aModifiers & MODIFIER_CAPSLOCK) {
+    ADD_SEPARATOR_IF_NECESSARY(names);
+    names += NS_DOM_KEYNAME_CAPSLOCK;
+  }
+  if (aModifiers & MODIFIER_CONTROL) {
+    ADD_SEPARATOR_IF_NECESSARY(names);
+    names += NS_DOM_KEYNAME_CONTROL;
+  }
+  if (aModifiers & MODIFIER_FN) {
+    ADD_SEPARATOR_IF_NECESSARY(names);
+    names += NS_DOM_KEYNAME_FN;
+  }
+  if (aModifiers & MODIFIER_FNLOCK) {
+    ADD_SEPARATOR_IF_NECESSARY(names);
+    names += NS_DOM_KEYNAME_FNLOCK;
+  }
+  if (aModifiers & MODIFIER_META) {
+    ADD_SEPARATOR_IF_NECESSARY(names);
+    names += NS_DOM_KEYNAME_META;
+  }
+  if (aModifiers & MODIFIER_NUMLOCK) {
+    ADD_SEPARATOR_IF_NECESSARY(names);
+    names += NS_DOM_KEYNAME_NUMLOCK;
+  }
+  if (aModifiers & MODIFIER_SCROLLLOCK) {
+    ADD_SEPARATOR_IF_NECESSARY(names);
+    names += NS_DOM_KEYNAME_SCROLLLOCK;
+  }
+  if (aModifiers & MODIFIER_SHIFT) {
+    ADD_SEPARATOR_IF_NECESSARY(names);
+    names += NS_DOM_KEYNAME_SHIFT;
+  }
+  if (aModifiers & MODIFIER_SYMBOL) {
+    ADD_SEPARATOR_IF_NECESSARY(names);
+    names += NS_DOM_KEYNAME_SYMBOL;
+  }
+  if (aModifiers & MODIFIER_SYMBOLLOCK) {
+    ADD_SEPARATOR_IF_NECESSARY(names);
+    names += NS_DOM_KEYNAME_SYMBOLLOCK;
+  }
+  return names;
+}
+
+class GetWritingModeName : public nsAutoCString {
+ public:
+  explicit GetWritingModeName(const WritingMode& aWritingMode) {
+    if (!aWritingMode.IsVertical()) {
+      AssignLiteral("Horizontal");
+      return;
+    }
+    if (aWritingMode.IsVerticalLR()) {
+      AssignLiteral("Vertical (LR)");
+      return;
+    }
+    AssignLiteral("Vertical (RL)");
+  }
+  virtual ~GetWritingModeName() {}
+};
+
+class GetEscapedUTF8String final : public NS_ConvertUTF16toUTF8 {
+ public:
+  explicit GetEscapedUTF8String(const nsAString& aString)
+      : NS_ConvertUTF16toUTF8(aString) {
+    Escape();
+  }
+  explicit GetEscapedUTF8String(const char16ptr_t aString)
+      : NS_ConvertUTF16toUTF8(aString) {
+    Escape();
+  }
+  GetEscapedUTF8String(const char16ptr_t aString, uint32_t aLength)
+      : NS_ConvertUTF16toUTF8(aString, aLength) {
+    Escape();
+  }
+
+ private:
+  void Escape() {
+    ReplaceSubstring("\r", "\\r");
+    ReplaceSubstring("\n", "\\n");
+    ReplaceSubstring("\t", "\\t");
+  }
+};
+
+class GetInputScopeString : public nsAutoCString {
+ public:
+  explicit GetInputScopeString(const nsTArray<InputScope>& aList) {
+    for (InputScope inputScope : aList) {
+      if (!IsEmpty()) {
+        AppendLiteral(", ");
+      }
+      switch (inputScope) {
+        case IS_DEFAULT:
+          AppendLiteral("IS_DEFAULT");
+          break;
+        case IS_URL:
+          AppendLiteral("IS_URL");
+          break;
+        case IS_FILE_FULLFILEPATH:
+          AppendLiteral("IS_FILE_FULLFILEPATH");
+          break;
+        case IS_FILE_FILENAME:
+          AppendLiteral("IS_FILE_FILENAME");
+          break;
+        case IS_EMAIL_USERNAME:
+          AppendLiteral("IS_EMAIL_USERNAME");
+          break;
+        case IS_EMAIL_SMTPEMAILADDRESS:
+          AppendLiteral("IS_EMAIL_SMTPEMAILADDRESS");
+          break;
+        case IS_LOGINNAME:
+          AppendLiteral("IS_LOGINNAME");
+          break;
+        case IS_PERSONALNAME_FULLNAME:
+          AppendLiteral("IS_PERSONALNAME_FULLNAME");
+          break;
+        case IS_PERSONALNAME_PREFIX:
+          AppendLiteral("IS_PERSONALNAME_PREFIX");
+          break;
+        case IS_PERSONALNAME_GIVENNAME:
+          AppendLiteral("IS_PERSONALNAME_GIVENNAME");
+          break;
+        case IS_PERSONALNAME_MIDDLENAME:
+          AppendLiteral("IS_PERSONALNAME_MIDDLENAME");
+          break;
+        case IS_PERSONALNAME_SURNAME:
+          AppendLiteral("IS_PERSONALNAME_SURNAME");
+          break;
+        case IS_PERSONALNAME_SUFFIX:
+          AppendLiteral("IS_PERSONALNAME_SUFFIX");
+          break;
+        case IS_ADDRESS_FULLPOSTALADDRESS:
+          AppendLiteral("IS_ADDRESS_FULLPOSTALADDRESS");
+          break;
+        case IS_ADDRESS_POSTALCODE:
+          AppendLiteral("IS_ADDRESS_POSTALCODE");
+          break;
+        case IS_ADDRESS_STREET:
+          AppendLiteral("IS_ADDRESS_STREET");
+          break;
+        case IS_ADDRESS_STATEORPROVINCE:
+          AppendLiteral("IS_ADDRESS_STATEORPROVINCE");
+          break;
+        case IS_ADDRESS_CITY:
+          AppendLiteral("IS_ADDRESS_CITY");
+          break;
+        case IS_ADDRESS_COUNTRYNAME:
+          AppendLiteral("IS_ADDRESS_COUNTRYNAME");
+          break;
+        case IS_ADDRESS_COUNTRYSHORTNAME:
+          AppendLiteral("IS_ADDRESS_COUNTRYSHORTNAME");
+          break;
+        case IS_CURRENCY_AMOUNTANDSYMBOL:
+          AppendLiteral("IS_CURRENCY_AMOUNTANDSYMBOL");
+          break;
+        case IS_CURRENCY_AMOUNT:
+          AppendLiteral("IS_CURRENCY_AMOUNT");
+          break;
+        case IS_DATE_FULLDATE:
+          AppendLiteral("IS_DATE_FULLDATE");
+          break;
+        case IS_DATE_MONTH:
+          AppendLiteral("IS_DATE_MONTH");
+          break;
+        case IS_DATE_DAY:
+          AppendLiteral("IS_DATE_DAY");
+          break;
+        case IS_DATE_YEAR:
+          AppendLiteral("IS_DATE_YEAR");
+          break;
+        case IS_DATE_MONTHNAME:
+          AppendLiteral("IS_DATE_MONTHNAME");
+          break;
+        case IS_DATE_DAYNAME:
+          AppendLiteral("IS_DATE_DAYNAME");
+          break;
+        case IS_DIGITS:
+          AppendLiteral("IS_DIGITS");
+          break;
+        case IS_NUMBER:
+          AppendLiteral("IS_NUMBER");
+          break;
+        case IS_ONECHAR:
+          AppendLiteral("IS_ONECHAR");
+          break;
+        case IS_PASSWORD:
+          AppendLiteral("IS_PASSWORD");
+          break;
+        case IS_TELEPHONE_FULLTELEPHONENUMBER:
+          AppendLiteral("IS_TELEPHONE_FULLTELEPHONENUMBER");
+          break;
+        case IS_TELEPHONE_COUNTRYCODE:
+          AppendLiteral("IS_TELEPHONE_COUNTRYCODE");
+          break;
+        case IS_TELEPHONE_AREACODE:
+          AppendLiteral("IS_TELEPHONE_AREACODE");
+          break;
+        case IS_TELEPHONE_LOCALNUMBER:
+          AppendLiteral("IS_TELEPHONE_LOCALNUMBER");
+          break;
+        case IS_TIME_FULLTIME:
+          AppendLiteral("IS_TIME_FULLTIME");
+          break;
+        case IS_TIME_HOUR:
+          AppendLiteral("IS_TIME_HOUR");
+          break;
+        case IS_TIME_MINORSEC:
+          AppendLiteral("IS_TIME_MINORSEC");
+          break;
+        case IS_NUMBER_FULLWIDTH:
+          AppendLiteral("IS_NUMBER_FULLWIDTH");
+          break;
+        case IS_ALPHANUMERIC_HALFWIDTH:
+          AppendLiteral("IS_ALPHANUMERIC_HALFWIDTH");
+          break;
+        case IS_ALPHANUMERIC_FULLWIDTH:
+          AppendLiteral("IS_ALPHANUMERIC_FULLWIDTH");
+          break;
+        case IS_CURRENCY_CHINESE:
+          AppendLiteral("IS_CURRENCY_CHINESE");
+          break;
+        case IS_BOPOMOFO:
+          AppendLiteral("IS_BOPOMOFO");
+          break;
+        case IS_HIRAGANA:
+          AppendLiteral("IS_HIRAGANA");
+          break;
+        case IS_KATAKANA_HALFWIDTH:
+          AppendLiteral("IS_KATAKANA_HALFWIDTH");
+          break;
+        case IS_KATAKANA_FULLWIDTH:
+          AppendLiteral("IS_KATAKANA_FULLWIDTH");
+          break;
+        case IS_HANJA:
+          AppendLiteral("IS_HANJA");
+          break;
+        case IS_PHRASELIST:
+          AppendLiteral("IS_PHRASELIST");
+          break;
+        case IS_REGULAREXPRESSION:
+          AppendLiteral("IS_REGULAREXPRESSION");
+          break;
+        case IS_SRGS:
+          AppendLiteral("IS_SRGS");
+          break;
+        case IS_XML:
+          AppendLiteral("IS_XML");
+          break;
+        case IS_PRIVATE:
+          AppendLiteral("IS_PRIVATE");
+          break;
+        default:
+          AppendPrintf("Unknown Value(%d)", inputScope);
+          break;
+      }
+    }
+  }
+};
+
+/******************************************************************/
+/* InputScopeImpl                                                 */
+/******************************************************************/
+
+class InputScopeImpl final : public ITfInputScope {
+  ~InputScopeImpl() {}
+
+ public:
+  explicit InputScopeImpl(const nsTArray<InputScope>& aList)
+      : mInputScopes(aList.Clone()) {
+    MOZ_LOG(
+        gIMELog, LogLevel::Info,
+        ("0x%p InputScopeImpl(%s)", this, GetInputScopeString(aList).get()));
+  }
+
+  NS_INLINE_DECL_IUNKNOWN_REFCOUNTING(InputScopeImpl)
+
+  STDMETHODIMP QueryInterface(REFIID riid, void** ppv) {
+    *ppv = nullptr;
+    if ((IID_IUnknown == riid) || (IID_ITfInputScope == riid)) {
+      *ppv = static_cast<ITfInputScope*>(this);
+    }
+    if (*ppv) {
+      AddRef();
+      return S_OK;
+    }
+    return E_NOINTERFACE;
+  }
+
+  STDMETHODIMP GetInputScopes(InputScope** pprgInputScopes, UINT* pcCount) {
+    uint32_t count = (mInputScopes.IsEmpty() ? 1 : mInputScopes.Length());
+
+    InputScope* pScope =
+        (InputScope*)CoTaskMemAlloc(sizeof(InputScope) * count);
+    NS_ENSURE_TRUE(pScope, E_OUTOFMEMORY);
+
+    if (mInputScopes.IsEmpty()) {
+      *pScope = IS_DEFAULT;
+      *pcCount = 1;
+      *pprgInputScopes = pScope;
+      return S_OK;
+    }
+
+    *pcCount = 0;
+
+    for (uint32_t idx = 0; idx < count; idx++) {
+      *(pScope + idx) = mInputScopes[idx];
+      (*pcCount)++;
+    }
+
+    *pprgInputScopes = pScope;
+    return S_OK;
+  }
+
+  STDMETHODIMP GetPhrase(BSTR** ppbstrPhrases, UINT* pcCount) {
+    return E_NOTIMPL;
+  }
+  STDMETHODIMP GetRegularExpression(BSTR* pbstrRegExp) { return E_NOTIMPL; }
+  STDMETHODIMP GetSRGS(BSTR* pbstrSRGS) { return E_NOTIMPL; }
+  STDMETHODIMP GetXML(BSTR* pbstrXML) { return E_NOTIMPL; }
+
+ private:
+  nsTArray<InputScope> mInputScopes;
+};
+
+/******************************************************************/
+/* TSFStaticSink                                                  */
+/******************************************************************/
+
+class TSFStaticSink final : public ITfInputProcessorProfileActivationSink {
+ public:
+  static TSFStaticSink* GetInstance() {
+    if (!sInstance) {
+      RefPtr<ITfThreadMgr> threadMgr = TSFTextStore::GetThreadMgr();
+      if (NS_WARN_IF(!threadMgr)) {
+        MOZ_LOG(
+            gIMELog, LogLevel::Error,
+            ("TSFStaticSink::GetInstance() FAILED to initialize TSFStaticSink "
+             "instance due to no ThreadMgr instance"));
+        return nullptr;
+      }
+      RefPtr<ITfInputProcessorProfiles> inputProcessorProfiles =
+          TSFTextStore::GetInputProcessorProfiles();
+      if (NS_WARN_IF(!inputProcessorProfiles)) {
+        MOZ_LOG(
+            gIMELog, LogLevel::Error,
+            ("TSFStaticSink::GetInstance() FAILED to initialize TSFStaticSink "
+             "instance due to no InputProcessorProfiles instance"));
+        return nullptr;
+      }
+      RefPtr<TSFStaticSink> staticSink = new TSFStaticSink();
+      if (NS_WARN_IF(!staticSink->Init(threadMgr, inputProcessorProfiles))) {
+        staticSink->Destroy();
+        MOZ_LOG(
+            gIMELog, LogLevel::Error,
+            ("TSFStaticSink::GetInstance() FAILED to initialize TSFStaticSink "
+             "instance"));
+        return nullptr;
+      }
+      sInstance = staticSink.forget();
+    }
+    return sInstance;
+  }
+
+  static void Shutdown() {
+    if (sInstance) {
+      sInstance->Destroy();
+      sInstance = nullptr;
+    }
+  }
+
+  bool Init(ITfThreadMgr* aThreadMgr,
+            ITfInputProcessorProfiles* aInputProcessorProfiles);
+  STDMETHODIMP QueryInterface(REFIID riid, void** ppv) {
+    *ppv = nullptr;
+    if (IID_IUnknown == riid ||
+        IID_ITfInputProcessorProfileActivationSink == riid) {
+      *ppv = static_cast<ITfInputProcessorProfileActivationSink*>(this);
+    }
+    if (*ppv) {
+      AddRef();
+      return S_OK;
+    }
+    return E_NOINTERFACE;
+  }
+
+  NS_INLINE_DECL_IUNKNOWN_REFCOUNTING(TSFStaticSink)
+
+  const nsString& GetActiveTIPKeyboardDescription() const {
+    return mActiveTIPKeyboardDescription;
+  }
+
+  static bool IsIMM_IMEActive() {
+    // Use IMM API until TSFStaticSink starts to work.
+    if (!sInstance || !sInstance->EnsureInitActiveTIPKeyboard()) {
+      return IsIMM_IME(::GetKeyboardLayout(0));
+    }
+    return sInstance->mIsIMM_IME;
+  }
+
+  static bool IsIMM_IME(HKL aHKL) {
+    return (::ImmGetIMEFileNameW(aHKL, nullptr, 0) > 0);
+  }
+
+  static bool IsTraditionalChinese() {
+    EnsureInstance();
+    return sInstance && sInstance->IsTraditionalChineseInternal();
+  }
+  static bool IsSimplifiedChinese() {
+    EnsureInstance();
+    return sInstance && sInstance->IsSimplifiedChineseInternal();
+  }
+  static bool IsJapanese() {
+    EnsureInstance();
+    return sInstance && sInstance->IsJapaneseInternal();
+  }
+  static bool IsKorean() {
+    EnsureInstance();
+    return sInstance && sInstance->IsKoreanInternal();
+  }
+
+  /**
+   * ActiveTIP() returns an ID for currently active TIP.
+   * Please note that this method is expensive due to needs a lot of GUID
+   * comparations if active language ID is one of CJKT.  If you need to
+   * check TIPs for a specific language, you should check current language
+   * first.
+   */
+  static TextInputProcessorID ActiveTIP() {
+    EnsureInstance();
+    if (!sInstance || !sInstance->EnsureInitActiveTIPKeyboard()) {
+      return TextInputProcessorID::eUnknown;
+    }
+    sInstance->ComputeActiveTextInputProcessor();
+    if (NS_WARN_IF(sInstance->mActiveTIP ==
+                   TextInputProcessorID::eNotComputed)) {
+      return TextInputProcessorID::eUnknown;
+    }
+    return sInstance->mActiveTIP;
+  }
+
+  static bool GetActiveTIPNameForTelemetry(nsAString& aName) {
+    if (!sInstance || !sInstance->EnsureInitActiveTIPKeyboard()) {
+      return false;
+    }
+    if (sInstance->mActiveTIPGUID == GUID_NULL) {
+      aName.Truncate();
+      aName.AppendPrintf("0x%04X", sInstance->mLangID);
+      return true;
+    }
+    // key should be "LocaleID|Description".  Although GUID of the
+    // profile is unique key since description may be localized for system
+    // language, unfortunately, it's too long to record as key with its
+    // description.  Therefore, we should record only the description with
+    // LocaleID because Microsoft IME may not include language information.
+    // 72 is kMaximumKeyStringLength in TelemetryScalar.cpp
+    aName.Truncate();
+    aName.AppendPrintf("0x%04X|", sInstance->mLangID);
+    nsAutoString description;
+    description.Assign(sInstance->mActiveTIPKeyboardDescription);
+    static const uint32_t kMaxDescriptionLength = 72 - aName.Length();
+    if (description.Length() > kMaxDescriptionLength) {
+      if (NS_IS_LOW_SURROGATE(description[kMaxDescriptionLength - 1]) &&
+          NS_IS_HIGH_SURROGATE(description[kMaxDescriptionLength - 2])) {
+        description.Truncate(kMaxDescriptionLength - 2);
+      } else {
+        description.Truncate(kMaxDescriptionLength - 1);
+      }
+      // U+2026 is "..."
+      description.Append(char16_t(0x2026));
+    }
+    aName.Append(description);
+    return true;
+  }
+
+  static bool IsMSChangJieOrMSQuickActive() {
+    // ActiveTIP() is expensive if it hasn't computed active TIP yet.
+    // For avoiding unnecessary computation, we should check if the language
+    // for current TIP is Traditional Chinese.
+    if (!IsTraditionalChinese()) {
+      return false;
+    }
+    switch (ActiveTIP()) {
+      case TextInputProcessorID::eMicrosoftChangJie:
+      case TextInputProcessorID::eMicrosoftQuick:
+        return true;
+      default:
+        return false;
+    }
+  }
+
+  static bool IsMSPinyinOrMSWubiActive() {
+    // ActiveTIP() is expensive if it hasn't computed active TIP yet.
+    // For avoiding unnecessary computation, we should check if the language
+    // for current TIP is Simplified Chinese.
+    if (!IsSimplifiedChinese()) {
+      return false;
+    }
+    switch (ActiveTIP()) {
+      case TextInputProcessorID::eMicrosoftPinyin:
+      case TextInputProcessorID::eMicrosoftWubi:
+        return true;
+      default:
+        return false;
+    }
+  }
+
+  static bool IsMSJapaneseIMEActive() {
+    // ActiveTIP() is expensive if it hasn't computed active TIP yet.
+    // For avoiding unnecessary computation, we should check if the language
+    // for current TIP is Japanese.
+    if (!IsJapanese()) {
+      return false;
+    }
+    return ActiveTIP() == TextInputProcessorID::eMicrosoftIMEForJapanese;
+  }
+
+  static bool IsGoogleJapaneseInputActive() {
+    // ActiveTIP() is expensive if it hasn't computed active TIP yet.
+    // For avoiding unnecessary computation, we should check if the language
+    // for current TIP is Japanese.
+    if (!IsJapanese()) {
+      return false;
+    }
+    return ActiveTIP() == TextInputProcessorID::eGoogleJapaneseInput;
+  }
+
+  static bool IsATOKActive() {
+    // ActiveTIP() is expensive if it hasn't computed active TIP yet.
+    // For avoiding unnecessary computation, we should check if active TIP is
+    // ATOK first since it's cheaper.
+    return IsJapanese() && sInstance->IsATOKActiveInternal();
+  }
+
+  // Note that ATOK 2011 - 2016 refers native caret position for deciding its
+  // popup window position.
+  static bool IsATOKReferringNativeCaretActive() {
+    // ActiveTIP() is expensive if it hasn't computed active TIP yet.
+    // For avoiding unnecessary computation, we should check if active TIP is
+    // ATOK first since it's cheaper.
+    if (!IsJapanese() || !sInstance->IsATOKActiveInternal()) {
+      return false;
+    }
+    switch (ActiveTIP()) {
+      case TextInputProcessorID::eATOK2011:
+      case TextInputProcessorID::eATOK2012:
+      case TextInputProcessorID::eATOK2013:
+      case TextInputProcessorID::eATOK2014:
+      case TextInputProcessorID::eATOK2015:
+        return true;
+      default:
+        return false;
+    }
+  }
+
+ private:
+  static void EnsureInstance() {
+    if (!sInstance) {
+      RefPtr<TSFStaticSink> staticSink = GetInstance();
+      Unused << staticSink;
+    }
+  }
+
+  bool IsTraditionalChineseInternal() const { return mLangID == 0x0404; }
+  bool IsSimplifiedChineseInternal() const { return mLangID == 0x0804; }
+  bool IsJapaneseInternal() const { return mLangID == 0x0411; }
+  bool IsKoreanInternal() const { return mLangID == 0x0412; }
+
+  bool IsATOKActiveInternal() {
+    EnsureInitActiveTIPKeyboard();
+    // FYI: Name of packaged ATOK includes the release year like "ATOK 2015".
+    //      Name of ATOK Passport (subscription) equals "ATOK".
+    return StringBeginsWith(mActiveTIPKeyboardDescription, u"ATOK "_ns) ||
+           mActiveTIPKeyboardDescription.EqualsLiteral("ATOK");
+  }
+
+  void ComputeActiveTextInputProcessor() {
+    if (mActiveTIP != TextInputProcessorID::eNotComputed) {
+      return;
+    }
+
+    if (mActiveTIPGUID == GUID_NULL) {
+      mActiveTIP = TextInputProcessorID::eNone;
+      return;
+    }
+
+    // Comparing GUID is slow. So, we should use language information to
+    // reduce the comparing cost for TIP which is not we do not support
+    // specifically since they are always compared with all supported TIPs.
+    switch (mLangID) {
+      case 0x0404:
+        mActiveTIP = ComputeActiveTIPAsTraditionalChinese();
+        break;
+      case 0x0411:
+        mActiveTIP = ComputeActiveTIPAsJapanese();
+        break;
+      case 0x0412:
+        mActiveTIP = ComputeActiveTIPAsKorean();
+        break;
+      case 0x0804:
+        mActiveTIP = ComputeActiveTIPAsSimplifiedChinese();
+        break;
+      default:
+        mActiveTIP = TextInputProcessorID::eUnknown;
+        break;
+    }
+    // Special case for Keyman Desktop, it is available for any languages.
+    // Therefore, we need to check it only if we don't know the active TIP.
+    if (mActiveTIP != TextInputProcessorID::eUnknown) {
+      return;
+    }
+
+    // Note that keyboard layouts for Keyman assign its GUID on install
+    // randomly, but CLSID is constant in any environments.
+    // https://bugzilla.mozilla.org/show_bug.cgi?id=1670834#c7
+    // https://github.com/keymanapp/keyman/blob/318c73a9e1d571d942837ff9964590626e5bd5aa/windows/src/engine/kmtip/globals.cpp#L37
+    // {FE0420F1-38D1-4B4C-96BF-E7E20A74CFB7}
+    static constexpr CLSID kKeymanDesktop_CLSID = {
+        0xFE0420F1,
+        0x38D1,
+        0x4B4C,
+        {0x96, 0xBF, 0xE7, 0xE2, 0x0A, 0x74, 0xCF, 0xB7}};
+    if (mActiveTIPCLSID == kKeymanDesktop_CLSID) {
+      mActiveTIP = TextInputProcessorID::eKeymanDesktop;
+    }
+  }
+
+  TextInputProcessorID ComputeActiveTIPAsJapanese() {
+    // {A76C93D9-5523-4E90-AAFA-4DB112F9AC76} (Win7, Win8.1, Win10)
+    static constexpr GUID kMicrosoftIMEForJapaneseGUID = {
+        0xA76C93D9,
+        0x5523,
+        0x4E90,
+        {0xAA, 0xFA, 0x4D, 0xB1, 0x12, 0xF9, 0xAC, 0x76}};
+    if (mActiveTIPGUID == kMicrosoftIMEForJapaneseGUID) {
+      return TextInputProcessorID::eMicrosoftIMEForJapanese;
+    }
+    // {54EDCC94-1524-4BB1-9FB7-7BABE4F4CA64}
+    static constexpr GUID kMicrosoftOfficeIME2010ForJapaneseGUID = {
+        0x54EDCC94,
+        0x1524,
+        0x4BB1,
+        {0x9F, 0xB7, 0x7B, 0xAB, 0xE4, 0xF4, 0xCA, 0x64}};
+    if (mActiveTIPGUID == kMicrosoftOfficeIME2010ForJapaneseGUID) {
+      return TextInputProcessorID::eMicrosoftOfficeIME2010ForJapanese;
+    }
+    // {773EB24E-CA1D-4B1B-B420-FA985BB0B80D}
+    static constexpr GUID kGoogleJapaneseInputGUID = {
+        0x773EB24E,
+        0xCA1D,
+        0x4B1B,
+        {0xB4, 0x20, 0xFA, 0x98, 0x5B, 0xB0, 0xB8, 0x0D}};
+    if (mActiveTIPGUID == kGoogleJapaneseInputGUID) {
+      return TextInputProcessorID::eGoogleJapaneseInput;
+    }
+    // {F9C24A5C-8A53-499D-9572-93B2FF582115}
+    static const GUID kATOK2011GUID = {
+        0xF9C24A5C,
+        0x8A53,
+        0x499D,
+        {0x95, 0x72, 0x93, 0xB2, 0xFF, 0x58, 0x21, 0x15}};
+    if (mActiveTIPGUID == kATOK2011GUID) {
+      return TextInputProcessorID::eATOK2011;
+    }
+    // {1DE01562-F445-401B-B6C3-E5B18DB79461}
+    static constexpr GUID kATOK2012GUID = {
+        0x1DE01562,
+        0xF445,
+        0x401B,
+        {0xB6, 0xC3, 0xE5, 0xB1, 0x8D, 0xB7, 0x94, 0x61}};
+    if (mActiveTIPGUID == kATOK2012GUID) {
+      return TextInputProcessorID::eATOK2012;
+    }
+    // {3C4DB511-189A-4168-B6EA-BFD0B4C85615}
+    static constexpr GUID kATOK2013GUID = {
+        0x3C4DB511,
+        0x189A,
+        0x4168,
+        {0xB6, 0xEA, 0xBF, 0xD0, 0xB4, 0xC8, 0x56, 0x15}};
+    if (mActiveTIPGUID == kATOK2013GUID) {
+      return TextInputProcessorID::eATOK2013;
+    }
+    // {4EF33B79-6AA9-4271-B4BF-9321C279381B}
+    static constexpr GUID kATOK2014GUID = {
+        0x4EF33B79,
+        0x6AA9,
+        0x4271,
+        {0xB4, 0xBF, 0x93, 0x21, 0xC2, 0x79, 0x38, 0x1B}};
+    if (mActiveTIPGUID == kATOK2014GUID) {
+      return TextInputProcessorID::eATOK2014;
+    }
+    // {EAB4DC00-CE2E-483D-A86A-E6B99DA9599A}
+    static constexpr GUID kATOK2015GUID = {
+        0xEAB4DC00,
+        0xCE2E,
+        0x483D,
+        {0xA8, 0x6A, 0xE6, 0xB9, 0x9D, 0xA9, 0x59, 0x9A}};
+    if (mActiveTIPGUID == kATOK2015GUID) {
+      return TextInputProcessorID::eATOK2015;
+    }
+    // {0B557B4C-5740-4110-A60A-1493FA10BF2B}
+    static constexpr GUID kATOK2016GUID = {
+        0x0B557B4C,
+        0x5740,
+        0x4110,
+        {0xA6, 0x0A, 0x14, 0x93, 0xFA, 0x10, 0xBF, 0x2B}};
+    if (mActiveTIPGUID == kATOK2016GUID) {
+      return TextInputProcessorID::eATOK2016;
+    }
+
+    // * ATOK 2017
+    //   - {6DBFD8F5-701D-11E6-920F-782BCBA6348F}
+    // * ATOK Passport (confirmed with version 31.1.2)
+    //   - {A38F2FD9-7199-45E1-841C-BE0313D8052F}
+
+    if (IsATOKActiveInternal()) {
+      return TextInputProcessorID::eATOKUnknown;
+    }
+
+    // {E6D66705-1EDA-4373-8D01-1D0CB2D054C7}
+    static constexpr GUID kJapanist10GUID = {
+        0xE6D66705,
+        0x1EDA,
+        0x4373,
+        {0x8D, 0x01, 0x1D, 0x0C, 0xB2, 0xD0, 0x54, 0xC7}};
+    if (mActiveTIPGUID == kJapanist10GUID) {
+      return TextInputProcessorID::eJapanist10;
+    }
+
+    return TextInputProcessorID::eUnknown;
+  }
+
+  TextInputProcessorID ComputeActiveTIPAsTraditionalChinese() {
+    // {B2F9C502-1742-11D4-9790-0080C882687E} (Win8.1, Win10)
+    static constexpr GUID kMicrosoftBopomofoGUID = {
+        0xB2F9C502,
+        0x1742,
+        0x11D4,
+        {0x97, 0x90, 0x00, 0x80, 0xC8, 0x82, 0x68, 0x7E}};
+    if (mActiveTIPGUID == kMicrosoftBopomofoGUID) {
+      return TextInputProcessorID::eMicrosoftBopomofo;
+    }
+    // {4BDF9F03-C7D3-11D4-B2AB-0080C882687E} (Win7, Win8.1, Win10)
+    static const GUID kMicrosoftChangJieGUID = {
+        0x4BDF9F03,
+        0xC7D3,
+        0x11D4,
+        {0xB2, 0xAB, 0x00, 0x80, 0xC8, 0x82, 0x68, 0x7E}};
+    if (mActiveTIPGUID == kMicrosoftChangJieGUID) {
+      return TextInputProcessorID::eMicrosoftChangJie;
+    }
+    // {761309DE-317A-11D4-9B5D-0080C882687E} (Win7)
+    static constexpr GUID kMicrosoftPhoneticGUID = {
+        0x761309DE,
+        0x317A,
+        0x11D4,
+        {0x9B, 0x5D, 0x00, 0x80, 0xC8, 0x82, 0x68, 0x7E}};
+    if (mActiveTIPGUID == kMicrosoftPhoneticGUID) {
+      return TextInputProcessorID::eMicrosoftPhonetic;
+    }
+    // {6024B45F-5C54-11D4-B921-0080C882687E} (Win7, Win8.1, Win10)
+    static constexpr GUID kMicrosoftQuickGUID = {
+        0x6024B45F,
+        0x5C54,
+        0x11D4,
+        {0xB9, 0x21, 0x00, 0x80, 0xC8, 0x82, 0x68, 0x7E}};
+    if (mActiveTIPGUID == kMicrosoftQuickGUID) {
+      return TextInputProcessorID::eMicrosoftQuick;
+    }
+    // {F3BA907A-6C7E-11D4-97FA-0080C882687E} (Win7)
+    static constexpr GUID kMicrosoftNewChangJieGUID = {
+        0xF3BA907A,
+        0x6C7E,
+        0x11D4,
+        {0x97, 0xFA, 0x00, 0x80, 0xC8, 0x82, 0x68, 0x7E}};
+    if (mActiveTIPGUID == kMicrosoftNewChangJieGUID) {
+      return TextInputProcessorID::eMicrosoftNewChangJie;
+    }
+    // {B2F9C502-1742-11D4-9790-0080C882687E} (Win7)
+    static constexpr GUID kMicrosoftNewPhoneticGUID = {
+        0xB2F9C502,
+        0x1742,
+        0x11D4,
+        {0x97, 0x90, 0x00, 0x80, 0xC8, 0x82, 0x68, 0x7E}};
+    if (mActiveTIPGUID == kMicrosoftNewPhoneticGUID) {
+      return TextInputProcessorID::eMicrosoftNewPhonetic;
+    }
+    // {0B883BA0-C1C7-11D4-87F9-0080C882687E} (Win7)
+    static constexpr GUID kMicrosoftNewQuickGUID = {
+        0x0B883BA0,
+        0xC1C7,
+        0x11D4,
+        {0x87, 0xF9, 0x00, 0x80, 0xC8, 0x82, 0x68, 0x7E}};
+    if (mActiveTIPGUID == kMicrosoftNewQuickGUID) {
+      return TextInputProcessorID::eMicrosoftNewQuick;
+    }
+
+    // NOTE: There are some other Traditional Chinese TIPs installed in Windows:
+    // * Chinese Traditional Array (version 6.0)
+    //   - {D38EFF65-AA46-4FD5-91A7-67845FB02F5B} (Win7, Win8.1)
+    // * Chinese Traditional DaYi (version 6.0)
+    //   - {037B2C25-480C-4D7F-B027-D6CA6B69788A} (Win7, Win8.1)
+
+    // {B58630B5-0ED3-4335-BBC9-E77BBCB43CAD}
+    static const GUID kFreeChangJieGUID = {
+        0xB58630B5,
+        0x0ED3,
+        0x4335,
+        {0xBB, 0xC9, 0xE7, 0x7B, 0xBC, 0xB4, 0x3C, 0xAD}};
+    if (mActiveTIPGUID == kFreeChangJieGUID) {
+      return TextInputProcessorID::eFreeChangJie;
+    }
+
+    return TextInputProcessorID::eUnknown;
+  }
+
+  TextInputProcessorID ComputeActiveTIPAsSimplifiedChinese() {
+    // FYI: This matches with neither "Microsoft Pinyin ABC Input Style" nor
+    //      "Microsoft Pinyin New Experience Input Style" on Win7.
+    // {FA550B04-5AD7-411F-A5AC-CA038EC515D7} (Win8.1, Win10)
+    static constexpr GUID kMicrosoftPinyinGUID = {
+        0xFA550B04,
+        0x5AD7,
+        0x411F,
+        {0xA5, 0xAC, 0xCA, 0x03, 0x8E, 0xC5, 0x15, 0xD7}};
+    if (mActiveTIPGUID == kMicrosoftPinyinGUID) {
+      return TextInputProcessorID::eMicrosoftPinyin;
+    }
+
+    // {F3BA9077-6C7E-11D4-97FA-0080C882687E} (Win7)
+    static constexpr GUID kMicrosoftPinyinNewExperienceInputStyleGUID = {
+        0xF3BA9077,
+        0x6C7E,
+        0x11D4,
+        {0x97, 0xFA, 0x00, 0x80, 0xC8, 0x82, 0x68, 0x7E}};
+    if (mActiveTIPGUID == kMicrosoftPinyinNewExperienceInputStyleGUID) {
+      return TextInputProcessorID::eMicrosoftPinyinNewExperienceInputStyle;
+    }
+    // {82590C13-F4DD-44F4-BA1D-8667246FDF8E} (Win8.1, Win10)
+    static constexpr GUID kMicrosoftWubiGUID = {
+        0x82590C13,
+        0xF4DD,
+        0x44F4,
+        {0xBA, 0x1D, 0x86, 0x67, 0x24, 0x6F, 0xDF, 0x8E}};
+    if (mActiveTIPGUID == kMicrosoftWubiGUID) {
+      return TextInputProcessorID::eMicrosoftWubi;
+    }
+    // NOTE: There are some other Simplified Chinese TIPs installed in Windows:
+    // * Chinese Simplified QuanPin (version 6.0)
+    //   - {54FC610E-6ABD-4685-9DDD-A130BDF1B170} (Win8.1)
+    // * Chinese Simplified ZhengMa (version 6.0)
+    //   - {733B4D81-3BC3-4132-B91A-E9CDD5E2BFC9} (Win8.1)
+    // * Chinese Simplified ShuangPin (version 6.0)
+    //   - {EF63706D-31C4-490E-9DBB-BD150ADC454B} (Win8.1)
+    // * Microsoft Pinyin ABC Input Style
+    //   - {FCA121D2-8C6D-41FB-B2DE-A2AD110D4820} (Win7)
+    return TextInputProcessorID::eUnknown;
+  }
+
+  TextInputProcessorID ComputeActiveTIPAsKorean() {
+    // {B5FE1F02-D5F2-4445-9C03-C568F23C99A1} (Win7, Win8.1, Win10)
+    static constexpr GUID kMicrosoftIMEForKoreanGUID = {
+        0xB5FE1F02,
+        0xD5F2,
+        0x4445,
+        {0x9C, 0x03, 0xC5, 0x68, 0xF2, 0x3C, 0x99, 0xA1}};
+    if (mActiveTIPGUID == kMicrosoftIMEForKoreanGUID) {
+      return TextInputProcessorID::eMicrosoftIMEForKorean;
+    }
+    // {B60AF051-257A-46BC-B9D3-84DAD819BAFB} (Win8.1, Win10)
+    static constexpr GUID kMicrosoftOldHangulGUID = {
+        0xB60AF051,
+        0x257A,
+        0x46BC,
+        {0xB9, 0xD3, 0x84, 0xDA, 0xD8, 0x19, 0xBA, 0xFB}};
+    if (mActiveTIPGUID == kMicrosoftOldHangulGUID) {
+      return TextInputProcessorID::eMicrosoftOldHangul;
+    }
+
+    // NOTE: There is the other Korean TIP installed in Windows:
+    // * Microsoft IME 2010
+    //   - {48878C45-93F9-4aaf-A6A1-272CD863C4F5} (Win7)
+
+    return TextInputProcessorID::eUnknown;
+  }
+
+ public:  // ITfInputProcessorProfileActivationSink
+  STDMETHODIMP OnActivated(DWORD, LANGID, REFCLSID, REFGUID, REFGUID, HKL,
+                           DWORD);
+
+ private:
+  TSFStaticSink();
+  virtual ~TSFStaticSink() {}
+
+  bool EnsureInitActiveTIPKeyboard();
+
+  void Destroy();
+
+  void GetTIPDescription(REFCLSID aTextService, LANGID aLangID,
+                         REFGUID aProfile, nsAString& aDescription);
+  bool IsTIPCategoryKeyboard(REFCLSID aTextService, LANGID aLangID,
+                             REFGUID aProfile);
+
+  TextInputProcessorID mActiveTIP;
+
+  // Cookie of installing ITfInputProcessorProfileActivationSink
+  DWORD mIPProfileCookie;
+
+  LANGID mLangID;
+
+  // True if current IME is implemented with IMM.
+  bool mIsIMM_IME;
+  // True if OnActivated() is already called
+  bool mOnActivatedCalled;
+
+  RefPtr<ITfThreadMgr> mThreadMgr;
+  RefPtr<ITfInputProcessorProfiles> mInputProcessorProfiles;
+
+  // Active TIP keyboard's description.  If active language profile isn't TIP,
+  // i.e., IMM-IME or just a keyboard layout, this is empty.
+  nsString mActiveTIPKeyboardDescription;
+
+  // Active TIP's GUID and CLSID
+  GUID mActiveTIPGUID;
+  CLSID mActiveTIPCLSID;
+
+  static StaticRefPtr<TSFStaticSink> sInstance;
+};
+
+StaticRefPtr<TSFStaticSink> TSFStaticSink::sInstance;
+
+TSFStaticSink::TSFStaticSink()
+    : mActiveTIP(TextInputProcessorID::eNotComputed),
+      mIPProfileCookie(TF_INVALID_COOKIE),
+      mLangID(0),
+      mIsIMM_IME(false),
+      mOnActivatedCalled(false),
+      mActiveTIPGUID(GUID_NULL) {}
+
+bool TSFStaticSink::Init(ITfThreadMgr* aThreadMgr,
+                         ITfInputProcessorProfiles* aInputProcessorProfiles) {
+  MOZ_ASSERT(!mThreadMgr && !mInputProcessorProfiles,
+             "TSFStaticSink::Init() must be called only once");
+
+  mThreadMgr = aThreadMgr;
+  mInputProcessorProfiles = aInputProcessorProfiles;
+
+  RefPtr<ITfSource> source;
+  HRESULT hr =
+      mThreadMgr->QueryInterface(IID_ITfSource, getter_AddRefs(source));
+  if (FAILED(hr)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p TSFStaticSink::Init() FAILED to get ITfSource "
+             "instance (0x%08lX)",
+             this, hr));
+    return false;
+  }
+
+  // NOTE: On Vista or later, Windows let us know activate IME changed only
+  //       with ITfInputProcessorProfileActivationSink.
+  hr = source->AdviseSink(
+      IID_ITfInputProcessorProfileActivationSink,
+      static_cast<ITfInputProcessorProfileActivationSink*>(this),
+      &mIPProfileCookie);
+  if (FAILED(hr) || mIPProfileCookie == TF_INVALID_COOKIE) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p TSFStaticSink::Init() FAILED to install "
+             "ITfInputProcessorProfileActivationSink (0x%08lX)",
+             this, hr));
+    return false;
+  }
+
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p TSFStaticSink::Init(), "
+           "mIPProfileCookie=0x%08lX",
+           this, mIPProfileCookie));
+  return true;
+}
+
+void TSFStaticSink::Destroy() {
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p TSFStaticSink::Shutdown() "
+           "mIPProfileCookie=0x%08lX",
+           this, mIPProfileCookie));
+
+  if (mIPProfileCookie != TF_INVALID_COOKIE) {
+    RefPtr<ITfSource> source;
+    HRESULT hr =
+        mThreadMgr->QueryInterface(IID_ITfSource, getter_AddRefs(source));
+    if (FAILED(hr)) {
+      MOZ_LOG(gIMELog, LogLevel::Error,
+              ("0x%p   TSFStaticSink::Shutdown() FAILED to get "
+               "ITfSource instance (0x%08lX)",
+               this, hr));
+    } else {
+      hr = source->UnadviseSink(mIPProfileCookie);
+      if (FAILED(hr)) {
+        MOZ_LOG(gIMELog, LogLevel::Error,
+                ("0x%p   TSFTextStore::Shutdown() FAILED to uninstall "
+                 "ITfInputProcessorProfileActivationSink (0x%08lX)",
+                 this, hr));
+      }
+    }
+  }
+
+  mThreadMgr = nullptr;
+  mInputProcessorProfiles = nullptr;
+}
+
+STDMETHODIMP
+TSFStaticSink::OnActivated(DWORD dwProfileType, LANGID langid, REFCLSID rclsid,
+                           REFGUID catid, REFGUID guidProfile, HKL hkl,
+                           DWORD dwFlags) {
+  if ((dwFlags & TF_IPSINK_FLAG_ACTIVE) &&
+      (dwProfileType == TF_PROFILETYPE_KEYBOARDLAYOUT ||
+       catid == GUID_TFCAT_TIP_KEYBOARD)) {
+    mOnActivatedCalled = true;
+    mActiveTIP = TextInputProcessorID::eNotComputed;
+    mActiveTIPGUID = guidProfile;
+    mActiveTIPCLSID = rclsid;
+    mLangID = langid & 0xFFFF;
+    mIsIMM_IME = IsIMM_IME(hkl);
+    GetTIPDescription(rclsid, langid, guidProfile,
+                      mActiveTIPKeyboardDescription);
+    if (mActiveTIPGUID != GUID_NULL) {
+      // key should be "LocaleID|Description".  Although GUID of the
+      // profile is unique key since description may be localized for system
+      // language, unfortunately, it's too long to record as key with its
+      // description.  Therefore, we should record only the description with
+      // LocaleID because Microsoft IME may not include language information.
+      // 72 is kMaximumKeyStringLength in TelemetryScalar.cpp
+      nsAutoString key;
+      TSFStaticSink::GetActiveTIPNameForTelemetry(key);
+      Telemetry::ScalarSet(Telemetry::ScalarID::WIDGET_IME_NAME_ON_WINDOWS, key,
+                           true);
+    }
+    // Notify IMEHandler of changing active keyboard layout.
+    IMEHandler::OnKeyboardLayoutChanged();
+  }
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p TSFStaticSink::OnActivated(dwProfileType=%s (0x%08lX), "
+           "langid=0x%08X, rclsid=%s, catid=%s, guidProfile=%s, hkl=0x%p, "
+           "dwFlags=0x%08lX (TF_IPSINK_FLAG_ACTIVE: %s)), mIsIMM_IME=%s, "
+           "mActiveTIPDescription=\"%s\"",
+           this,
+           dwProfileType == TF_PROFILETYPE_INPUTPROCESSOR
+               ? "TF_PROFILETYPE_INPUTPROCESSOR"
+           : dwProfileType == TF_PROFILETYPE_KEYBOARDLAYOUT
+               ? "TF_PROFILETYPE_KEYBOARDLAYOUT"
+               : "Unknown",
+           dwProfileType, langid, GetCLSIDNameStr(rclsid).get(),
+           GetGUIDNameStr(catid).get(), GetGUIDNameStr(guidProfile).get(), hkl,
+           dwFlags, GetBoolName(dwFlags & TF_IPSINK_FLAG_ACTIVE),
+           GetBoolName(mIsIMM_IME),
+           NS_ConvertUTF16toUTF8(mActiveTIPKeyboardDescription).get()));
+  return S_OK;
+}
+
+bool TSFStaticSink::EnsureInitActiveTIPKeyboard() {
+  if (mOnActivatedCalled) {
+    return true;
+  }
+
+  RefPtr<ITfInputProcessorProfileMgr> profileMgr;
+  HRESULT hr = mInputProcessorProfiles->QueryInterface(
+      IID_ITfInputProcessorProfileMgr, getter_AddRefs(profileMgr));
+  if (FAILED(hr) || !profileMgr) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFStaticSink::EnsureInitActiveLanguageProfile(), FAILED "
+             "to get input processor profile manager, hr=0x%08lX",
+             this, hr));
+    return false;
+  }
+
+  TF_INPUTPROCESSORPROFILE profile;
+  hr = profileMgr->GetActiveProfile(GUID_TFCAT_TIP_KEYBOARD, &profile);
+  if (hr == S_FALSE) {
+    MOZ_LOG(gIMELog, LogLevel::Info,
+            ("0x%p   TSFStaticSink::EnsureInitActiveLanguageProfile(), FAILED "
+             "to get active keyboard layout profile due to no active profile, "
+             "hr=0x%08lX",
+             this, hr));
+    // XXX Should we call OnActivated() with arguments like non-TIP in this
+    //     case?
+    return false;
+  }
+  if (FAILED(hr)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFStaticSink::EnsureInitActiveLanguageProfile(), FAILED "
+             "to get active TIP keyboard, hr=0x%08lX",
+             this, hr));
+    return false;
+  }
+
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p   TSFStaticSink::EnsureInitActiveLanguageProfile(), "
+           "calling OnActivated() manually...",
+           this));
+  OnActivated(profile.dwProfileType, profile.langid, profile.clsid,
+              profile.catid, profile.guidProfile, ::GetKeyboardLayout(0),
+              TF_IPSINK_FLAG_ACTIVE);
+  return true;
+}
+
+void TSFStaticSink::GetTIPDescription(REFCLSID aTextService, LANGID aLangID,
+                                      REFGUID aProfile,
+                                      nsAString& aDescription) {
+  aDescription.Truncate();
+
+  if (aTextService == CLSID_NULL || aProfile == GUID_NULL) {
+    return;
+  }
+
+  BSTR description = nullptr;
+  HRESULT hr = mInputProcessorProfiles->GetLanguageProfileDescription(
+      aTextService, aLangID, aProfile, &description);
+  if (FAILED(hr)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFStaticSink::InitActiveTIPDescription() FAILED "
+             "due to GetLanguageProfileDescription() failure, hr=0x%08lX",
+             this, hr));
+    return;
+  }
+
+  if (description && description[0]) {
+    aDescription.Assign(description);
+  }
+  ::SysFreeString(description);
+}
+
+bool TSFStaticSink::IsTIPCategoryKeyboard(REFCLSID aTextService, LANGID aLangID,
+                                          REFGUID aProfile) {
+  if (aTextService == CLSID_NULL || aProfile == GUID_NULL) {
+    return false;
+  }
+
+  RefPtr<IEnumTfLanguageProfiles> enumLangProfiles;
+  HRESULT hr = mInputProcessorProfiles->EnumLanguageProfiles(
+      aLangID, getter_AddRefs(enumLangProfiles));
+  if (FAILED(hr) || !enumLangProfiles) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFStaticSink::IsTIPCategoryKeyboard(), FAILED "
+             "to get language profiles enumerator, hr=0x%08lX",
+             this, hr));
+    return false;
+  }
+
+  TF_LANGUAGEPROFILE profile;
+  ULONG fetch = 0;
+  while (SUCCEEDED(enumLangProfiles->Next(1, &profile, &fetch)) && fetch) {
+    // XXX We're not sure a profile is registered with two or more categories.
+    if (profile.clsid == aTextService && profile.guidProfile == aProfile &&
+        profile.catid == GUID_TFCAT_TIP_KEYBOARD) {
+      return true;
+    }
+  }
+  return false;
+}
+
+/******************************************************************/
+/* TSFTextStore                                                   */
+/******************************************************************/
+
+StaticRefPtr<ITfThreadMgr> TSFTextStore::sThreadMgr;
+StaticRefPtr<ITfMessagePump> TSFTextStore::sMessagePump;
+StaticRefPtr<ITfKeystrokeMgr> TSFTextStore::sKeystrokeMgr;
+StaticRefPtr<ITfDisplayAttributeMgr> TSFTextStore::sDisplayAttrMgr;
+StaticRefPtr<ITfCategoryMgr> TSFTextStore::sCategoryMgr;
+StaticRefPtr<ITfCompartment> TSFTextStore::sCompartmentForOpenClose;
+StaticRefPtr<ITfDocumentMgr> TSFTextStore::sDisabledDocumentMgr;
+StaticRefPtr<ITfContext> TSFTextStore::sDisabledContext;
+StaticRefPtr<ITfInputProcessorProfiles> TSFTextStore::sInputProcessorProfiles;
+StaticRefPtr<TSFTextStore> TSFTextStore::sEnabledTextStore;
+const MSG* TSFTextStore::sHandlingKeyMsg = nullptr;
+DWORD TSFTextStore::sClientId = 0;
+bool TSFTextStore::sIsKeyboardEventDispatched = false;
+
+#define TEXTSTORE_DEFAULT_VIEW (1)
+
+TSFTextStore::TSFTextStore()
+    : mEditCookie(0),
+      mSinkMask(0),
+      mLock(0),
+      mLockQueued(0),
+      mHandlingKeyMessage(0) {
+  // We hope that 5 or more actions don't occur at once.
+  mPendingActions.SetCapacity(5);
+
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p TSFTextStore::TSFTextStore() SUCCEEDED", this));
+}
+
+TSFTextStore::~TSFTextStore() {
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p TSFTextStore instance is destroyed", this));
+}
+
+bool TSFTextStore::Init(nsWindow* aWidget, const InputContext& aContext) {
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p TSFTextStore::Init(aWidget=0x%p)", this, aWidget));
+
+  if (NS_WARN_IF(!aWidget) || NS_WARN_IF(aWidget->Destroyed())) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::Init() FAILED due to being initialized with "
+             "destroyed widget",
+             this));
+    return false;
+  }
+
+  if (mDocumentMgr) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::Init() FAILED due to already initialized",
+             this));
+    return false;
+  }
+
+  mWidget = aWidget;
+  if (NS_WARN_IF(!mWidget)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::Init() FAILED "
+             "due to aWidget is nullptr ",
+             this));
+    return false;
+  }
+  mDispatcher = mWidget->GetTextEventDispatcher();
+  if (NS_WARN_IF(!mDispatcher)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::Init() FAILED "
+             "due to aWidget->GetTextEventDispatcher() failure",
+             this));
+    return false;
+  }
+
+  mInPrivateBrowsing = aContext.mInPrivateBrowsing;
+  SetInputScope(aContext.mHTMLInputType, aContext.mHTMLInputMode);
+
+  if (aContext.mURI) {
+    // We don't need the document URL if it fails, let's ignore the error.
+    nsAutoCString spec;
+    if (NS_SUCCEEDED(aContext.mURI->GetSpec(spec))) {
+      CopyUTF8toUTF16(spec, mDocumentURL);
+    }
+  }
+
+  // Create document manager
+  RefPtr<ITfThreadMgr> threadMgr = sThreadMgr;
+  RefPtr<ITfDocumentMgr> documentMgr;
+  HRESULT hr = threadMgr->CreateDocumentMgr(getter_AddRefs(documentMgr));
+  if (NS_WARN_IF(FAILED(hr))) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::Init() FAILED to create ITfDocumentMgr "
+             "(0x%08lX)",
+             this, hr));
+    return false;
+  }
+  if (NS_WARN_IF(mDestroyed)) {
+    MOZ_LOG(
+        gIMELog, LogLevel::Error,
+        ("0x%p   TSFTextStore::Init() FAILED to create ITfDocumentMgr due to "
+         "TextStore being destroyed during calling "
+         "ITfThreadMgr::CreateDocumentMgr()",
+         this));
+    return false;
+  }
+  // Create context and add it to document manager
+  RefPtr<ITfContext> context;
+  hr = documentMgr->CreateContext(sClientId, 0,
+                                  static_cast<ITextStoreACP*>(this),
+                                  getter_AddRefs(context), &mEditCookie);
+  if (NS_WARN_IF(FAILED(hr))) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::Init() FAILED to create the context "
+             "(0x%08lX)",
+             this, hr));
+    return false;
+  }
+  if (NS_WARN_IF(mDestroyed)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::Init() FAILED to create ITfContext due to "
+             "TextStore being destroyed during calling "
+             "ITfDocumentMgr::CreateContext()",
+             this));
+    return false;
+  }
+
+  hr = documentMgr->Push(context);
+  if (NS_WARN_IF(FAILED(hr))) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::Init() FAILED to push the context (0x%08lX)",
+             this, hr));
+    return false;
+  }
+  if (NS_WARN_IF(mDestroyed)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::Init() FAILED to create ITfContext due to "
+             "TextStore being destroyed during calling ITfDocumentMgr::Push()",
+             this));
+    documentMgr->Pop(TF_POPF_ALL);
+    return false;
+  }
+
+  mDocumentMgr = documentMgr;
+  mContext = context;
+
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p   TSFTextStore::Init() succeeded: "
+           "mDocumentMgr=0x%p, mContext=0x%p, mEditCookie=0x%08lX",
+           this, mDocumentMgr.get(), mContext.get(), mEditCookie));
+
+  return true;
+}
+
+void TSFTextStore::Destroy() {
+  if (mBeingDestroyed) {
+    return;
+  }
+
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p TSFTextStore::Destroy(), mLock=%s, "
+           "mComposition=%s, mHandlingKeyMessage=%u",
+           this, GetLockFlagNameStr(mLock).get(),
+           ToString(mComposition).c_str(), mHandlingKeyMessage));
+
+  mDestroyed = true;
+
+  // Destroy native caret first because it's not directly related to TSF and
+  // there may be another textstore which gets focus.  So, we should avoid
+  // to destroy caret after the new one recreates caret.
+  IMEHandler::MaybeDestroyNativeCaret();
+
+  if (mLock) {
+    mPendingDestroy = true;
+    return;
+  }
+
+  AutoRestore<bool> savedBeingDestroyed(mBeingDestroyed);
+  mBeingDestroyed = true;
+
+  // If there is composition, TSF keeps the composition even after the text
+  // store destroyed.  So, we should clear the composition here.
+  if (mComposition.isSome()) {
+    CommitCompositionInternal(false);
+  }
+
+  if (mSink) {
+    MOZ_LOG(gIMELog, LogLevel::Debug,
+            ("0x%p   TSFTextStore::Destroy(), calling "
+             "ITextStoreACPSink::OnLayoutChange(TS_LC_DESTROY)...",
+             this));
+    RefPtr<ITextStoreACPSink> sink = mSink;
+    sink->OnLayoutChange(TS_LC_DESTROY, TEXTSTORE_DEFAULT_VIEW);
+  }
+
+  // If this is called during handling a keydown or keyup message, we should
+  // put off to release TSF objects until it completely finishes since
+  // MS-IME for Japanese refers some objects without grabbing them.
+  if (!mHandlingKeyMessage) {
+    ReleaseTSFObjects();
+  }
+
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p   TSFTextStore::Destroy() succeeded", this));
+}
+
+void TSFTextStore::ReleaseTSFObjects() {
+  MOZ_ASSERT(!mHandlingKeyMessage);
+
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p TSFTextStore::ReleaseTSFObjects()", this));
+
+  mDocumentURL.Truncate();
+  mContext = nullptr;
+  if (mDocumentMgr) {
+    RefPtr<ITfDocumentMgr> documentMgr = mDocumentMgr.forget();
+    documentMgr->Pop(TF_POPF_ALL);
+  }
+  mSink = nullptr;
+  mWidget = nullptr;
+  mDispatcher = nullptr;
+
+  if (!mMouseTrackers.IsEmpty()) {
+    MOZ_LOG(gIMELog, LogLevel::Debug,
+            ("0x%p   TSFTextStore::ReleaseTSFObjects(), "
+             "removing a mouse tracker...",
+             this));
+    mMouseTrackers.Clear();
+  }
+
+  MOZ_LOG(gIMELog, LogLevel::Debug,
+          ("0x%p   TSFTextStore::ReleaseTSFObjects() completed", this));
+}
+
+STDMETHODIMP
+TSFTextStore::QueryInterface(REFIID riid, void** ppv) {
+  *ppv = nullptr;
+  if ((IID_IUnknown == riid) || (IID_ITextStoreACP == riid)) {
+    *ppv = static_cast<ITextStoreACP*>(this);
+  } else if (IID_ITfContextOwnerCompositionSink == riid) {
+    *ppv = static_cast<ITfContextOwnerCompositionSink*>(this);
+  } else if (IID_ITfMouseTrackerACP == riid) {
+    *ppv = static_cast<ITfMouseTrackerACP*>(this);
+  }
+  if (*ppv) {
+    AddRef();
+    return S_OK;
+  }
+
+  MOZ_LOG(gIMELog, LogLevel::Error,
+          ("0x%p TSFTextStore::QueryInterface() FAILED, riid=%s", this,
+           GetRIIDNameStr(riid).get()));
+  return E_NOINTERFACE;
+}
+
+STDMETHODIMP
+TSFTextStore::AdviseSink(REFIID riid, IUnknown* punk, DWORD dwMask) {
+  MOZ_LOG(
+      gIMELog, LogLevel::Info,
+      ("0x%p TSFTextStore::AdviseSink(riid=%s, punk=0x%p, dwMask=%s), "
+       "mSink=0x%p, mSinkMask=%s",
+       this, GetRIIDNameStr(riid).get(), punk, GetSinkMaskNameStr(dwMask).get(),
+       mSink.get(), GetSinkMaskNameStr(mSinkMask).get()));
+
+  if (!punk) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::AdviseSink() FAILED due to the null punk",
+             this));
+    return E_UNEXPECTED;
+  }
+
+  if (IID_ITextStoreACPSink != riid) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::AdviseSink() FAILED due to "
+             "unsupported interface",
+             this));
+    return E_INVALIDARG;  // means unsupported interface.
+  }
+
+  if (!mSink) {
+    // Install sink
+    punk->QueryInterface(IID_ITextStoreACPSink, getter_AddRefs(mSink));
+    if (!mSink) {
+      MOZ_LOG(gIMELog, LogLevel::Error,
+              ("0x%p   TSFTextStore::AdviseSink() FAILED due to "
+               "punk not having the interface",
+               this));
+      return E_UNEXPECTED;
+    }
+  } else {
+    // If sink is already installed we check to see if they are the same
+    // Get IUnknown from both sides for comparison
+    RefPtr<IUnknown> comparison1, comparison2;
+    punk->QueryInterface(IID_IUnknown, getter_AddRefs(comparison1));
+    mSink->QueryInterface(IID_IUnknown, getter_AddRefs(comparison2));
+    if (comparison1 != comparison2) {
+      MOZ_LOG(gIMELog, LogLevel::Error,
+              ("0x%p   TSFTextStore::AdviseSink() FAILED due to "
+               "the sink being different from the stored sink",
+               this));
+      return CONNECT_E_ADVISELIMIT;
+    }
+  }
+  // Update mask either for a new sink or an existing sink
+  mSinkMask = dwMask;
+  return S_OK;
+}
+
+STDMETHODIMP
+TSFTextStore::UnadviseSink(IUnknown* punk) {
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p TSFTextStore::UnadviseSink(punk=0x%p), mSink=0x%p", this, punk,
+           mSink.get()));
+
+  if (!punk) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::UnadviseSink() FAILED due to the null punk",
+             this));
+    return E_INVALIDARG;
+  }
+  if (!mSink) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::UnadviseSink() FAILED due to "
+             "any sink not stored",
+             this));
+    return CONNECT_E_NOCONNECTION;
+  }
+  // Get IUnknown from both sides for comparison
+  RefPtr<IUnknown> comparison1, comparison2;
+  punk->QueryInterface(IID_IUnknown, getter_AddRefs(comparison1));
+  mSink->QueryInterface(IID_IUnknown, getter_AddRefs(comparison2));
+  // Unadvise only if sinks are the same
+  if (comparison1 != comparison2) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::UnadviseSink() FAILED due to "
+             "the sink being different from the stored sink",
+             this));
+    return CONNECT_E_NOCONNECTION;
+  }
+  mSink = nullptr;
+  mSinkMask = 0;
+  return S_OK;
+}
+
+STDMETHODIMP
+TSFTextStore::RequestLock(DWORD dwLockFlags, HRESULT* phrSession) {
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p TSFTextStore::RequestLock(dwLockFlags=%s, phrSession=0x%p), "
+           "mLock=%s, mDestroyed=%s",
+           this, GetLockFlagNameStr(dwLockFlags).get(), phrSession,
+           GetLockFlagNameStr(mLock).get(), GetBoolName(mDestroyed)));
+
+  if (!mSink) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::RequestLock() FAILED due to "
+             "any sink not stored",
+             this));
+    return E_FAIL;
+  }
+  if (mDestroyed &&
+      (mContentForTSF.isNothing() || mSelectionForTSF.isNothing())) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::RequestLock() FAILED due to "
+             "being destroyed and no information of the contents",
+             this));
+    return E_FAIL;
+  }
+  if (!phrSession) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::RequestLock() FAILED due to "
+             "null phrSession",
+             this));
+    return E_INVALIDARG;
+  }
+
+  if (!mLock) {
+    // put on lock
+    mLock = dwLockFlags & (~TS_LF_SYNC);
+    MOZ_LOG(
+        gIMELog, LogLevel::Info,
+        ("0x%p   Locking (%s) >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>"
+         ">>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>",
+         this, GetLockFlagNameStr(mLock).get()));
+    // Don't release this instance during this lock because this is called by
+    // TSF but they don't grab us during this call.
+    RefPtr<TSFTextStore> kungFuDeathGrip(this);
+    RefPtr<ITextStoreACPSink> sink = mSink;
+    *phrSession = sink->OnLockGranted(mLock);
+    MOZ_LOG(
+        gIMELog, LogLevel::Info,
+        ("0x%p   Unlocked (%s) <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<"
+         "<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<",
+         this, GetLockFlagNameStr(mLock).get()));
+    DidLockGranted();
+    while (mLockQueued) {
+      mLock = mLockQueued;
+      mLockQueued = 0;
+      MOZ_LOG(gIMELog, LogLevel::Info,
+              ("0x%p   Locking for the request in the queue (%s) >>>>>>>>>>>>>>"
+               ">>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>"
+               ">>>>>",
+               this, GetLockFlagNameStr(mLock).get()));
+      sink->OnLockGranted(mLock);
+      MOZ_LOG(gIMELog, LogLevel::Info,
+              ("0x%p   Unlocked (%s) <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<"
+               "<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<"
+               "<<<<<",
+               this, GetLockFlagNameStr(mLock).get()));
+      DidLockGranted();
+    }
+
+    // The document is now completely unlocked.
+    mLock = 0;
+
+    MaybeFlushPendingNotifications();
+
+    MOZ_LOG(gIMELog, LogLevel::Info,
+            ("0x%p   TSFTextStore::RequestLock() succeeded: *phrSession=%s",
+             this, GetTextStoreReturnValueName(*phrSession)));
+    return S_OK;
+  }
+
+  // only time when reentrant lock is allowed is when caller holds a
+  // read-only lock and is requesting an async write lock
+  if (IsReadLocked() && !IsReadWriteLocked() && IsReadWriteLock(dwLockFlags) &&
+      !(dwLockFlags & TS_LF_SYNC)) {
+    *phrSession = TS_S_ASYNC;
+    mLockQueued = dwLockFlags & (~TS_LF_SYNC);
+
+    MOZ_LOG(gIMELog, LogLevel::Info,
+            ("0x%p   TSFTextStore::RequestLock() stores the request in the "
+             "queue, *phrSession=TS_S_ASYNC",
+             this));
+    return S_OK;
+  }
+
+  // no more locks allowed
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p   TSFTextStore::RequestLock() didn't allow to lock, "
+           "*phrSession=TS_E_SYNCHRONOUS",
+           this));
+  *phrSession = TS_E_SYNCHRONOUS;
+  return E_FAIL;
+}
+
+void TSFTextStore::DidLockGranted() {
+  if (IsReadWriteLocked()) {
+    // FreeCJ (TIP for Traditional Chinese) calls SetSelection() to set caret
+    // to the start of composition string and insert a full width space for
+    // a placeholder with a call of SetText().  After that, it calls
+    // OnUpdateComposition() without new range.  Therefore, let's record the
+    // composition update information here.
+    CompleteLastActionIfStillIncomplete();
+
+    FlushPendingActions();
+  }
+
+  // If the widget has gone, we don't need to notify anything.
+  if (mDestroyed || !mWidget || mWidget->Destroyed()) {
+    mPendingSelectionChangeData.reset();
+    mHasReturnedNoLayoutError = false;
+  }
+}
+
+void TSFTextStore::DispatchEvent(WidgetGUIEvent& aEvent) {
+  if (NS_WARN_IF(!mWidget) || NS_WARN_IF(mWidget->Destroyed())) {
+    return;
+  }
+  // If the event isn't a query content event, the event may be handled
+  // asynchronously.  So, we should put off to answer from GetTextExt() etc.
+  if (!aEvent.AsQueryContentEvent()) {
+    mDeferNotifyingTSFUntilNextUpdate = true;
+  }
+  mWidget->DispatchWindowEvent(aEvent);
+}
+
+void TSFTextStore::FlushPendingActions() {
+  if (!mWidget || mWidget->Destroyed()) {
+    // Note that don't clear mContentForTSF because TIP may try to commit
+    // composition with a document lock.  In such case, TSFTextStore needs to
+    // behave as expected by TIP.
+    mPendingActions.Clear();
+    mPendingSelectionChangeData.reset();
+    mHasReturnedNoLayoutError = false;
+    return;
+  }
+
+  // Some TIP may request lock but does nothing during the lock.  In such case,
+  // this should do nothing.  For example, when MS-IME for Japanese is active
+  // and we're inactivating, this case occurs and causes different behavior
+  // from the other TIPs.
+  if (mPendingActions.IsEmpty()) {
+    return;
+  }
+
+  RefPtr<nsWindow> widget(mWidget);
+  nsresult rv = mDispatcher->BeginNativeInputTransaction();
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::FlushPendingActions() "
+             "FAILED due to BeginNativeInputTransaction() failure",
+             this));
+    return;
+  }
+  for (uint32_t i = 0; i < mPendingActions.Length(); i++) {
+    PendingAction& action = mPendingActions[i];
+    switch (action.mType) {
+      case PendingAction::Type::eKeyboardEvent:
+        if (mDestroyed) {
+          MOZ_LOG(
+              gIMELog, LogLevel::Warning,
+              ("0x%p   TSFTextStore::FlushPendingActions() "
+               "IGNORED pending KeyboardEvent(%s) due to already destroyed",
+               this,
+               action.mKeyMsg.message == WM_KEYDOWN ? "eKeyDown" : "eKeyUp"));
+        }
+        MOZ_DIAGNOSTIC_ASSERT(action.mKeyMsg.message == WM_KEYDOWN ||
+                              action.mKeyMsg.message == WM_KEYUP);
+        DispatchKeyboardEventAsProcessedByIME(action.mKeyMsg);
+        if (!widget || widget->Destroyed()) {
+          break;
+        }
+        break;
+      case PendingAction::Type::eCompositionStart: {
+        MOZ_LOG(gIMELog, LogLevel::Debug,
+                ("0x%p   TSFTextStore::FlushPendingActions() "
+                 "flushing Type::eCompositionStart={ mSelectionStart=%ld, "
+                 "mSelectionLength=%ld }, mDestroyed=%s",
+                 this, action.mSelectionStart, action.mSelectionLength,
+                 GetBoolName(mDestroyed)));
+
+        if (mDestroyed) {
+          MOZ_LOG(gIMELog, LogLevel::Warning,
+                  ("0x%p   TSFTextStore::FlushPendingActions() "
+                   "IGNORED pending compositionstart due to already destroyed",
+                   this));
+          break;
+        }
+
+        if (action.mAdjustSelection) {
+          // Select composition range so the new composition replaces the range
+          WidgetSelectionEvent selectionSet(true, eSetSelection, widget);
+          widget->InitEvent(selectionSet);
+          selectionSet.mOffset = static_cast<uint32_t>(action.mSelectionStart);
+          selectionSet.mLength = static_cast<uint32_t>(action.mSelectionLength);
+          selectionSet.mReversed = false;
+          selectionSet.mExpandToClusterBoundary =
+              TSFStaticSink::ActiveTIP() !=
+                  TextInputProcessorID::eKeymanDesktop &&
+              StaticPrefs::
+                  intl_tsf_hack_extend_setting_selection_range_to_cluster_boundaries();
+          DispatchEvent(selectionSet);
+          if (!selectionSet.mSucceeded) {
+            MOZ_LOG(gIMELog, LogLevel::Error,
+                    ("0x%p   TSFTextStore::FlushPendingActions() "
+                     "FAILED due to eSetSelection failure",
+                     this));
+            break;
+          }
+        }
+
+        // eCompositionStart always causes
+        // NOTIFY_IME_OF_COMPOSITION_EVENT_HANDLED.  Therefore, we should
+        // wait to clear mContentForTSF until it's notified.
+        mDeferClearingContentForTSF = true;
+
+        MOZ_LOG(gIMELog, LogLevel::Debug,
+                ("0x%p   TSFTextStore::FlushPendingActions() "
+                 "dispatching compositionstart event...",
+                 this));
+        WidgetEventTime eventTime = widget->CurrentMessageWidgetEventTime();
+        nsEventStatus status;
+        rv = mDispatcher->StartComposition(status, &eventTime);
+        if (NS_WARN_IF(NS_FAILED(rv))) {
+          MOZ_LOG(gIMELog, LogLevel::Error,
+                  ("0x%p   TSFTextStore::FlushPendingActions() "
+                   "FAILED to dispatch compositionstart event, "
+                   "IsHandlingCompositionInContent()=%s",
+                   this, GetBoolName(IsHandlingCompositionInContent())));
+          // XXX Is this right? If there is a composition in content,
+          //     shouldn't we wait NOTIFY_IME_OF_COMPOSITION_EVENT_HANDLED?
+          mDeferClearingContentForTSF = !IsHandlingCompositionInContent();
+        }
+        if (!widget || widget->Destroyed()) {
+          break;
+        }
+        break;
+      }
+      case PendingAction::Type::eCompositionUpdate: {
+        MOZ_LOG(gIMELog, LogLevel::Debug,
+                ("0x%p   TSFTextStore::FlushPendingActions() "
+                 "flushing Type::eCompositionUpdate={ mData=\"%s\", "
+                 "mRanges=0x%p, mRanges->Length()=%zu }",
+                 this, GetEscapedUTF8String(action.mData).get(),
+                 action.mRanges.get(),
+                 action.mRanges ? action.mRanges->Length() : 0));
+
+        // eCompositionChange causes a DOM text event, the IME will be notified
+        // of NOTIFY_IME_OF_COMPOSITION_EVENT_HANDLED.  In this case, we
+        // should not clear mContentForTSF until we notify the IME of the
+        // composition update.
+        mDeferClearingContentForTSF = true;
+
+        rv = mDispatcher->SetPendingComposition(action.mData, action.mRanges);
+        if (NS_WARN_IF(NS_FAILED(rv))) {
+          MOZ_LOG(gIMELog, LogLevel::Error,
+                  ("0x%p   TSFTextStore::FlushPendingActions() "
+                   "FAILED to setting pending composition... "
+                   "IsHandlingCompositionInContent()=%s",
+                   this, GetBoolName(IsHandlingCompositionInContent())));
+          // XXX Is this right? If there is a composition in content,
+          //     shouldn't we wait NOTIFY_IME_OF_COMPOSITION_EVENT_HANDLED?
+          mDeferClearingContentForTSF = !IsHandlingCompositionInContent();
+        } else {
+          MOZ_LOG(gIMELog, LogLevel::Debug,
+                  ("0x%p   TSFTextStore::FlushPendingActions() "
+                   "dispatching compositionchange event...",
+                   this));
+          WidgetEventTime eventTime = widget->CurrentMessageWidgetEventTime();
+          nsEventStatus status;
+          rv = mDispatcher->FlushPendingComposition(status, &eventTime);
+          if (NS_WARN_IF(NS_FAILED(rv))) {
+            MOZ_LOG(gIMELog, LogLevel::Error,
+                    ("0x%p   TSFTextStore::FlushPendingActions() "
+                     "FAILED to dispatch compositionchange event, "
+                     "IsHandlingCompositionInContent()=%s",
+                     this, GetBoolName(IsHandlingCompositionInContent())));
+            // XXX Is this right? If there is a composition in content,
+            //     shouldn't we wait NOTIFY_IME_OF_COMPOSITION_EVENT_HANDLED?
+            mDeferClearingContentForTSF = !IsHandlingCompositionInContent();
+          }
+          // Be aware, the mWidget might already have been destroyed.
+        }
+        break;
+      }
+      case PendingAction::Type::eCompositionEnd: {
+        MOZ_LOG(gIMELog, LogLevel::Debug,
+                ("0x%p   TSFTextStore::FlushPendingActions() "
+                 "flushing Type::eCompositionEnd={ mData=\"%s\" }",
+                 this, GetEscapedUTF8String(action.mData).get()));
+
+        // Dispatching eCompositionCommit causes a DOM text event, then,
+        // the IME will be notified of NOTIFY_IME_OF_COMPOSITION_EVENT_HANDLED
+        // when focused content actually handles the event.  For example,
+        // when focused content is in a remote process, it's sent when
+        // all dispatched composition events have been handled in the remote
+        // process.  So, until then, we don't have newer content information.
+        // Therefore, we need to put off to clear mContentForTSF.
+        mDeferClearingContentForTSF = true;
+
+        MOZ_LOG(gIMELog, LogLevel::Debug,
+                ("0x%p   TSFTextStore::FlushPendingActions(), "
+                 "dispatching compositioncommit event...",
+                 this));
+        WidgetEventTime eventTime = widget->CurrentMessageWidgetEventTime();
+        nsEventStatus status;
+        rv = mDispatcher->CommitComposition(status, &action.mData, &eventTime);
+        if (NS_WARN_IF(NS_FAILED(rv))) {
+          MOZ_LOG(gIMELog, LogLevel::Error,
+                  ("0x%p   TSFTextStore::FlushPendingActions() "
+                   "FAILED to dispatch compositioncommit event, "
+                   "IsHandlingCompositionInContent()=%s",
+                   this, GetBoolName(IsHandlingCompositionInContent())));
+          // XXX Is this right? If there is a composition in content,
+          //     shouldn't we wait NOTIFY_IME_OF_COMPOSITION_EVENT_HANDLED?
+          mDeferClearingContentForTSF = !IsHandlingCompositionInContent();
+        }
+        break;
+      }
+      case PendingAction::Type::eSetSelection: {
+        MOZ_LOG(
+            gIMELog, LogLevel::Debug,
+            ("0x%p   TSFTextStore::FlushPendingActions() "
+             "flushing Type::eSetSelection={ mSelectionStart=%ld, "
+             "mSelectionLength=%ld, mSelectionReversed=%s }, "
+             "mDestroyed=%s",
+             this, action.mSelectionStart, action.mSelectionLength,
+             GetBoolName(action.mSelectionReversed), GetBoolName(mDestroyed)));
+
+        if (mDestroyed) {
+          MOZ_LOG(gIMELog, LogLevel::Warning,
+                  ("0x%p   TSFTextStore::FlushPendingActions() "
+                   "IGNORED pending selectionset due to already destroyed",
+                   this));
+          break;
+        }
+
+        WidgetSelectionEvent selectionSet(true, eSetSelection, widget);
+        selectionSet.mOffset = static_cast<uint32_t>(action.mSelectionStart);
+        selectionSet.mLength = static_cast<uint32_t>(action.mSelectionLength);
+        selectionSet.mReversed = action.mSelectionReversed;
+        selectionSet.mExpandToClusterBoundary =
+            TSFStaticSink::ActiveTIP() !=
+                TextInputProcessorID::eKeymanDesktop &&
+            StaticPrefs::
+                intl_tsf_hack_extend_setting_selection_range_to_cluster_boundaries();
+        DispatchEvent(selectionSet);
+        if (!selectionSet.mSucceeded) {
+          MOZ_LOG(gIMELog, LogLevel::Error,
+                  ("0x%p   TSFTextStore::FlushPendingActions() "
+                   "FAILED due to eSetSelection failure",
+                   this));
+          break;
+        }
+        break;
+      }
+      default:
+        MOZ_CRASH("unexpected action type");
+    }
+
+    if (widget && !widget->Destroyed()) {
+      continue;
+    }
+
+    MOZ_LOG(gIMELog, LogLevel::Info,
+            ("0x%p   TSFTextStore::FlushPendingActions(), "
+             "qutting since the mWidget has gone",
+             this));
+    break;
+  }
+  mPendingActions.Clear();
+}
+
+void TSFTextStore::MaybeFlushPendingNotifications() {
+  if (mDeferNotifyingTSF) {
+    MOZ_LOG(gIMELog, LogLevel::Debug,
+            ("0x%p   TSFTextStore::MaybeFlushPendingNotifications(), "
+             "putting off flushing pending notifications due to initializing "
+             "something...",
+             this));
+    return;
+  }
+
+  if (IsReadLocked()) {
+    MOZ_LOG(gIMELog, LogLevel::Debug,
+            ("0x%p   TSFTextStore::MaybeFlushPendingNotifications(), "
+             "putting off flushing pending notifications due to being the "
+             "document locked...",
+             this));
+    return;
+  }
+
+  if (mDeferCommittingComposition) {
+    MOZ_LOG(gIMELog, LogLevel::Info,
+            ("0x%p   TSFTextStore::MaybeFlushPendingNotifications(), "
+             "calling TSFTextStore::CommitCompositionInternal(false)...",
+             this));
+    mDeferCommittingComposition = mDeferCancellingComposition = false;
+    CommitCompositionInternal(false);
+  } else if (mDeferCancellingComposition) {
+    MOZ_LOG(gIMELog, LogLevel::Info,
+            ("0x%p   TSFTextStore::MaybeFlushPendingNotifications(), "
+             "calling TSFTextStore::CommitCompositionInternal(true)...",
+             this));
+    mDeferCommittingComposition = mDeferCancellingComposition = false;
+    CommitCompositionInternal(true);
+  }
+
+  if (mDeferNotifyingTSFUntilNextUpdate) {
+    MOZ_LOG(gIMELog, LogLevel::Debug,
+            ("0x%p   TSFTextStore::MaybeFlushPendingNotifications(), "
+             "putting off flushing pending notifications due to being "
+             "dispatching events...",
+             this));
+    return;
+  }
+
+  if (mPendingDestroy) {
+    Destroy();
+    return;
+  }
+
+  if (mDestroyed) {
+    // If it's already been destroyed completely, this shouldn't notify TSF of
+    // anything anymore.
+    MOZ_LOG(gIMELog, LogLevel::Debug,
+            ("0x%p   TSFTextStore::MaybeFlushPendingNotifications(), "
+             "does nothing because this has already destroyed completely...",
+             this));
+    return;
+  }
+
+  if (!mDeferClearingContentForTSF && mContentForTSF.isSome()) {
+    mContentForTSF.reset();
+    MOZ_LOG(gIMELog, LogLevel::Debug,
+            ("0x%p   TSFTextStore::MaybeFlushPendingNotifications(), "
+             "mContentForTSF is set to `Nothing`",
+             this));
+  }
+
+  // When there is no cached content, we can sync actual contents and TSF/TIP
+  // expecting contents.
+  RefPtr<TSFTextStore> kungFuDeathGrip = this;
+  Unused << kungFuDeathGrip;
+  if (mContentForTSF.isNothing()) {
+    if (mPendingTextChangeData.IsValid()) {
+      MOZ_LOG(gIMELog, LogLevel::Info,
+              ("0x%p   TSFTextStore::MaybeFlushPendingNotifications(), "
+               "calling TSFTextStore::NotifyTSFOfTextChange()...",
+               this));
+      NotifyTSFOfTextChange();
+    }
+    if (mPendingSelectionChangeData.isSome()) {
+      MOZ_LOG(gIMELog, LogLevel::Info,
+              ("0x%p   TSFTextStore::MaybeFlushPendingNotifications(), "
+               "calling TSFTextStore::NotifyTSFOfSelectionChange()...",
+               this));
+      NotifyTSFOfSelectionChange();
+    }
+  }
+
+  if (mHasReturnedNoLayoutError) {
+    MOZ_LOG(gIMELog, LogLevel::Info,
+            ("0x%p   TSFTextStore::MaybeFlushPendingNotifications(), "
+             "calling TSFTextStore::NotifyTSFOfLayoutChange()...",
+             this));
+    NotifyTSFOfLayoutChange();
+  }
+}
+
+void TSFTextStore::MaybeDispatchKeyboardEventAsProcessedByIME() {
+  // If we've already been destroyed, we cannot do anything.
+  if (mDestroyed) {
+    MOZ_LOG(
+        gIMELog, LogLevel::Debug,
+        ("0x%p   TSFTextStore::MaybeDispatchKeyboardEventAsProcessedByIME(), "
+         "does nothing because it's already been destroyed",
+         this));
+    return;
+  }
+
+  // If we're not handling key message or we've already dispatched a keyboard
+  // event for the handling key message, we should do nothing anymore.
+  if (!sHandlingKeyMsg || sIsKeyboardEventDispatched) {
+    MOZ_LOG(
+        gIMELog, LogLevel::Debug,
+        ("0x%p   TSFTextStore::MaybeDispatchKeyboardEventAsProcessedByIME(), "
+         "does nothing because not necessary to dispatch keyboard event",
+         this));
+    return;
+  }
+
+  sIsKeyboardEventDispatched = true;
+  // If the document is locked, just adding the task to dispatching an event
+  // to the queue.
+  if (IsReadLocked()) {
+    MOZ_LOG(
+        gIMELog, LogLevel::Debug,
+        ("0x%p   TSFTextStore::MaybeDispatchKeyboardEventAsProcessedByIME(), "
+         "adding to dispatch a keyboard event into the queue...",
+         this));
+    PendingAction* action = mPendingActions.AppendElement();
+    action->mType = PendingAction::Type::eKeyboardEvent;
+    memcpy(&action->mKeyMsg, sHandlingKeyMsg, sizeof(MSG));
+    return;
+  }
+
+  // Otherwise, dispatch a keyboard event.
+  MOZ_LOG(gIMELog, LogLevel::Debug,
+          ("0x%p   TSFTextStore::MaybeDispatchKeyboardEventAsProcessedByIME(), "
+           "trying to dispatch a keyboard event...",
+           this));
+  DispatchKeyboardEventAsProcessedByIME(*sHandlingKeyMsg);
+}
+
+void TSFTextStore::DispatchKeyboardEventAsProcessedByIME(const MSG& aMsg) {
+  MOZ_ASSERT(mWidget);
+  MOZ_ASSERT(!mWidget->Destroyed());
+  MOZ_ASSERT(!mDestroyed);
+
+  ModifierKeyState modKeyState;
+  MSG msg(aMsg);
+  msg.wParam = VK_PROCESSKEY;
+  NativeKey nativeKey(mWidget, msg, modKeyState);
+  switch (aMsg.message) {
+    case WM_KEYDOWN:
+      MOZ_LOG(gIMELog, LogLevel::Debug,
+              ("0x%p   TSFTextStore::DispatchKeyboardEventAsProcessedByIME(), "
+               "dispatching an eKeyDown event...",
+               this));
+      nativeKey.HandleKeyDownMessage();
+      break;
+    case WM_KEYUP:
+      MOZ_LOG(gIMELog, LogLevel::Debug,
+              ("0x%p   TSFTextStore::DispatchKeyboardEventAsProcessedByIME(), "
+               "dispatching an eKeyUp event...",
+               this));
+      nativeKey.HandleKeyUpMessage();
+      break;
+    default:
+      MOZ_LOG(gIMELog, LogLevel::Error,
+              ("0x%p   TSFTextStore::DispatchKeyboardEventAsProcessedByIME(), "
+               "ERROR, it doesn't handle the message",
+               this));
+      break;
+  }
+}
+
+STDMETHODIMP
+TSFTextStore::GetStatus(TS_STATUS* pdcs) {
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p TSFTextStore::GetStatus(pdcs=0x%p)", this, pdcs));
+
+  if (!pdcs) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::GetStatus() FAILED due to null pdcs", this));
+    return E_INVALIDARG;
+  }
+  // We manage on-screen keyboard by own.
+  pdcs->dwDynamicFlags = TS_SD_INPUTPANEMANUALDISPLAYENABLE;
+  // we use a "flat" text model for TSF support so no hidden text
+  pdcs->dwStaticFlags = TS_SS_NOHIDDENTEXT;
+  return S_OK;
+}
+
+STDMETHODIMP
+TSFTextStore::QueryInsert(LONG acpTestStart, LONG acpTestEnd, ULONG cch,
+                          LONG* pacpResultStart, LONG* pacpResultEnd) {
+  MOZ_LOG(
+      gIMELog, LogLevel::Info,
+      ("0x%p TSFTextStore::QueryInsert(acpTestStart=%ld, "
+       "acpTestEnd=%ld, cch=%lu, pacpResultStart=0x%p, pacpResultEnd=0x%p)",
+       this, acpTestStart, acpTestEnd, cch, pacpResultStart, pacpResultEnd));
+
+  if (!pacpResultStart || !pacpResultEnd) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::QueryInsert() FAILED due to "
+             "the null argument",
+             this));
+    return E_INVALIDARG;
+  }
+
+  if (acpTestStart < 0 || acpTestStart > acpTestEnd) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::QueryInsert() FAILED due to "
+             "wrong argument",
+             this));
+    return E_INVALIDARG;
+  }
+
+  // XXX need to adjust to cluster boundary
+  // Assume we are given good offsets for now
+  if (mComposition.isNothing() &&
+      ((StaticPrefs::
+            intl_tsf_hack_ms_traditional_chinese_query_insert_result() &&
+        TSFStaticSink::IsMSChangJieOrMSQuickActive()) ||
+       (StaticPrefs::
+            intl_tsf_hack_ms_simplified_chinese_query_insert_result() &&
+        TSFStaticSink::IsMSPinyinOrMSWubiActive()))) {
+    MOZ_LOG(gIMELog, LogLevel::Warning,
+            ("0x%p   TSFTextStore::QueryInsert() WARNING using different "
+             "result for the TIP",
+             this));
+    // Chinese TIPs of Microsoft assume that QueryInsert() returns selected
+    // range which should be removed.
+    *pacpResultStart = acpTestStart;
+    *pacpResultEnd = acpTestEnd;
+  } else {
+    *pacpResultStart = acpTestStart;
+    *pacpResultEnd = acpTestStart + cch;
+  }
+
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p  TSFTextStore::QueryInsert() succeeded: "
+           "*pacpResultStart=%ld, *pacpResultEnd=%ld)",
+           this, *pacpResultStart, *pacpResultEnd));
+  return S_OK;
+}
+
+STDMETHODIMP
+TSFTextStore::GetSelection(ULONG ulIndex, ULONG ulCount,
+                           TS_SELECTION_ACP* pSelection, ULONG* pcFetched) {
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p TSFTextStore::GetSelection(ulIndex=%lu, ulCount=%lu, "
+           "pSelection=0x%p, pcFetched=0x%p)",
+           this, ulIndex, ulCount, pSelection, pcFetched));
+
+  if (!IsReadLocked()) {
+    MOZ_LOG(
+        gIMELog, LogLevel::Error,
+        ("0x%p   TSFTextStore::GetSelection() FAILED due to not locked", this));
+    return TS_E_NOLOCK;
+  }
+  if (!ulCount || !pSelection || !pcFetched) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::GetSelection() FAILED due to "
+             "null argument",
+             this));
+    return E_INVALIDARG;
+  }
+
+  *pcFetched = 0;
+
+  if (ulIndex != static_cast<ULONG>(TS_DEFAULT_SELECTION) && ulIndex != 0) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::GetSelection() FAILED due to "
+             "unsupported selection",
+             this));
+    return TS_E_NOSELECTION;
+  }
+
+  Maybe<Selection>& selectionForTSF = SelectionForTSF();
+  if (selectionForTSF.isNothing()) {
+    if (DoNotReturnErrorFromGetSelection()) {
+      *pSelection = Selection::EmptyACP();
+      *pcFetched = 1;
+      MOZ_LOG(
+          gIMELog, LogLevel::Info,
+          ("0x%p   TSFTextStore::GetSelection() returns fake selection range "
+           "for avoiding a crash in TSF, *pSelection=%s",
+           this, mozilla::ToString(*pSelection).c_str()));
+      return S_OK;
+    }
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::GetSelection() FAILED due to "
+             "SelectionForTSF() failure",
+             this));
+    return E_FAIL;
+  }
+  if (!selectionForTSF->HasRange()) {
+    *pSelection = Selection::EmptyACP();
+    *pcFetched = 0;
+    return TS_E_NOSELECTION;
+  }
+  *pSelection = selectionForTSF->ACPRef();
+  *pcFetched = 1;
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p   TSFTextStore::GetSelection() succeeded, *pSelection=%s",
+           this, mozilla::ToString(*pSelection).c_str()));
+  return S_OK;
+}
+
+// static
+bool TSFTextStore::DoNotReturnErrorFromGetSelection() {
+  // There is a crash bug of TSF if we return error from GetSelection().
+  // That was introduced in Anniversary Update (build 14393, see bug 1312302)
+  // TODO: We should avoid to run this hack on fixed builds.  When we get
+  //       exact build number, we should get back here.
+  static bool sTSFMayCrashIfGetSelectionReturnsError =
+      IsWin10AnniversaryUpdateOrLater();
+  return sTSFMayCrashIfGetSelectionReturnsError;
+}
+
+Maybe<TSFTextStore::Content>& TSFTextStore::ContentForTSF() {
+  // This should be called when the document is locked or the content hasn't
+  // been abandoned yet.
+  if (NS_WARN_IF(!IsReadLocked() && mContentForTSF.isNothing())) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::ContentForTSF(), FAILED, due to "
+             "called wrong timing, IsReadLocked()=%s, mContentForTSF=Nothing",
+             this, GetBoolName(IsReadLocked())));
+    return mContentForTSF;
+  }
+
+  Maybe<Selection>& selectionForTSF = SelectionForTSF();
+  if (selectionForTSF.isNothing()) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::ContentForTSF(), FAILED, due to "
+             "SelectionForTSF() failure",
+             this));
+    mContentForTSF.reset();
+    return mContentForTSF;
+  }
+
+  if (mContentForTSF.isNothing()) {
+    MOZ_DIAGNOSTIC_ASSERT(
+        !mIsInitializingContentForTSF,
+        "TSFTextStore::ContentForTSF() shouldn't be called recursively");
+
+    AutoNotifyingTSFBatch deferNotifyingTSF(*this);
+    AutoRestore<bool> saveInitializingContetTSF(mIsInitializingContentForTSF);
+    mIsInitializingContentForTSF = true;
+
+    nsString text;  // Don't use auto string for avoiding to copy long string.
+    if (NS_WARN_IF(!GetCurrentText(text))) {
+      MOZ_LOG(gIMELog, LogLevel::Error,
+              ("0x%p   TSFTextStore::ContentForTSF(), FAILED, due to "
+               "GetCurrentText() failure",
+               this));
+      return mContentForTSF;
+    }
+
+    MOZ_DIAGNOSTIC_ASSERT(mContentForTSF.isNothing(),
+                          "How was it initialized recursively?");
+    mContentForTSF.reset();  // For avoiding crash in release channel
+    mContentForTSF.emplace(*this, text);
+    // Basically, the cached content which is expected by TSF/TIP should be
+    // cleared after active composition is committed or the document lock is
+    // unlocked.  However, in e10s mode, content will be modified
+    // asynchronously.  In such case, mDeferClearingContentForTSF may be
+    // true until whole dispatched events are handled by the focused editor.
+    mDeferClearingContentForTSF = false;
+  }
+
+  MOZ_LOG(gIMELog, LogLevel::Debug,
+          ("0x%p   TSFTextStore::ContentForTSF(): mContentForTSF=%s", this,
+           mozilla::ToString(mContentForTSF).c_str()));
+
+  return mContentForTSF;
+}
+
+bool TSFTextStore::CanAccessActualContentDirectly() const {
+  if (mContentForTSF.isNothing() || mSelectionForTSF.isNothing()) {
+    return true;
+  }
+
+  // If the cached content has been changed by something except composition,
+  // the content cache may be different from actual content.
+  if (mPendingTextChangeData.IsValid() &&
+      !mPendingTextChangeData.mCausedOnlyByComposition) {
+    return false;
+  }
+
+  // If the cached selection isn't changed, cached content and actual content
+  // should be same.
+  if (mPendingSelectionChangeData.isNothing()) {
+    return true;
+  }
+
+  return mSelectionForTSF->EqualsExceptDirection(*mPendingSelectionChangeData);
+}
+
+bool TSFTextStore::GetCurrentText(nsAString& aTextContent) {
+  if (mContentForTSF.isSome()) {
+    aTextContent = mContentForTSF->TextRef();
+    return true;
+  }
+
+  MOZ_ASSERT(!mDestroyed);
+  MOZ_ASSERT(mWidget && !mWidget->Destroyed());
+
+  MOZ_LOG(gIMELog, LogLevel::Debug,
+          ("0x%p   TSFTextStore::GetCurrentText(): "
+           "retrieving text from the content...",
+           this));
+
+  WidgetQueryContentEvent queryTextContentEvent(true, eQueryTextContent,
+                                                mWidget);
+  queryTextContentEvent.InitForQueryTextContent(0, UINT32_MAX);
+  mWidget->InitEvent(queryTextContentEvent);
+  DispatchEvent(queryTextContentEvent);
+  if (NS_WARN_IF(queryTextContentEvent.Failed())) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::GetCurrentText(), FAILED, due to "
+             "eQueryTextContent failure",
+             this));
+    aTextContent.Truncate();
+    return false;
+  }
+
+  aTextContent = queryTextContentEvent.mReply->DataRef();
+  return true;
+}
+
+Maybe<TSFTextStore::Selection>& TSFTextStore::SelectionForTSF() {
+  if (mSelectionForTSF.isNothing()) {
+    MOZ_ASSERT(!mDestroyed);
+    // If the window has never been available, we should crash since working
+    // with broken values may make TIP confused.
+    if (!mWidget || mWidget->Destroyed()) {
+      MOZ_ASSERT_UNREACHABLE("There should be non-destroyed widget");
+    }
+
+    MOZ_DIAGNOSTIC_ASSERT(
+        !mIsInitializingSelectionForTSF,
+        "TSFTextStore::SelectionForTSF() shouldn't be called recursively");
+
+    AutoNotifyingTSFBatch deferNotifyingTSF(*this);
+    AutoRestore<bool> saveInitializingSelectionForTSF(
+        mIsInitializingSelectionForTSF);
+    mIsInitializingSelectionForTSF = true;
+
+    WidgetQueryContentEvent querySelectedTextEvent(true, eQuerySelectedText,
+                                                   mWidget);
+    mWidget->InitEvent(querySelectedTextEvent);
+    DispatchEvent(querySelectedTextEvent);
+    if (NS_WARN_IF(querySelectedTextEvent.Failed())) {
+      return mSelectionForTSF;
+    }
+    MOZ_DIAGNOSTIC_ASSERT(mSelectionForTSF.isNothing(),
+                          "How was it initialized recursively?");
+    mSelectionForTSF = Some(Selection(querySelectedTextEvent));
+  }
+
+  MOZ_LOG(gIMELog, LogLevel::Debug,
+          ("0x%p   TSFTextStore::SelectionForTSF() succeeded, "
+           "mSelectionForTSF=%s",
+           this, ToString(mSelectionForTSF).c_str()));
+
+  return mSelectionForTSF;
+}
+
+static HRESULT GetRangeExtent(ITfRange* aRange, LONG* aStart, LONG* aLength) {
+  RefPtr<ITfRangeACP> rangeACP;
+  aRange->QueryInterface(IID_ITfRangeACP, getter_AddRefs(rangeACP));
+  NS_ENSURE_TRUE(rangeACP, E_FAIL);
+  return rangeACP->GetExtent(aStart, aLength);
+}
+
+static TextRangeType GetGeckoSelectionValue(TF_DISPLAYATTRIBUTE& aDisplayAttr) {
+  switch (aDisplayAttr.bAttr) {
+    case TF_ATTR_TARGET_CONVERTED:
+      return TextRangeType::eSelectedClause;
+    case TF_ATTR_CONVERTED:
+      return TextRangeType::eConvertedClause;
+    case TF_ATTR_TARGET_NOTCONVERTED:
+      return TextRangeType::eSelectedRawClause;
+    default:
+      return TextRangeType::eRawClause;
+  }
+}
+
+HRESULT
+TSFTextStore::GetDisplayAttribute(ITfProperty* aAttrProperty, ITfRange* aRange,
+                                  TF_DISPLAYATTRIBUTE* aResult) {
+  NS_ENSURE_TRUE(aAttrProperty, E_FAIL);
+  NS_ENSURE_TRUE(aRange, E_FAIL);
+  NS_ENSURE_TRUE(aResult, E_FAIL);
+
+  HRESULT hr;
+
+  if (MOZ_LOG_TEST(gIMELog, LogLevel::Debug)) {
+    LONG start = 0, length = 0;
+    hr = GetRangeExtent(aRange, &start, &length);
+    MOZ_LOG(gIMELog, LogLevel::Debug,
+            ("0x%p   TSFTextStore::GetDisplayAttribute(): "
+             "GetDisplayAttribute range=%ld-%ld (hr=%s)",
+             this, start - mComposition->StartOffset(),
+             start - mComposition->StartOffset() + length,
+             GetCommonReturnValueName(hr)));
+  }
+
+  VARIANT propValue;
+  ::VariantInit(&propValue);
+  hr = aAttrProperty->GetValue(TfEditCookie(mEditCookie), aRange, &propValue);
+  if (FAILED(hr)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::GetDisplayAttribute() FAILED due to "
+             "ITfProperty::GetValue() failed",
+             this));
+    return hr;
+  }
+  if (VT_I4 != propValue.vt) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::GetDisplayAttribute() FAILED due to "
+             "ITfProperty::GetValue() returns non-VT_I4 value",
+             this));
+    ::VariantClear(&propValue);
+    return E_FAIL;
+  }
+
+  RefPtr<ITfCategoryMgr> categoryMgr = GetCategoryMgr();
+  if (NS_WARN_IF(!categoryMgr)) {
+    return E_FAIL;
+  }
+  GUID guid;
+  hr = categoryMgr->GetGUID(DWORD(propValue.lVal), &guid);
+  ::VariantClear(&propValue);
+  if (FAILED(hr)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::GetDisplayAttribute() FAILED due to "
+             "ITfCategoryMgr::GetGUID() failed",
+             this));
+    return hr;
+  }
+
+  RefPtr<ITfDisplayAttributeMgr> displayAttrMgr = GetDisplayAttributeMgr();
+  if (NS_WARN_IF(!displayAttrMgr)) {
+    return E_FAIL;
+  }
+  RefPtr<ITfDisplayAttributeInfo> info;
+  hr = displayAttrMgr->GetDisplayAttributeInfo(guid, getter_AddRefs(info),
+                                               nullptr);
+  if (FAILED(hr) || !info) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::GetDisplayAttribute() FAILED due to "
+             "ITfDisplayAttributeMgr::GetDisplayAttributeInfo() failed",
+             this));
+    return hr;
+  }
+
+  hr = info->GetAttributeInfo(aResult);
+  if (FAILED(hr)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::GetDisplayAttribute() FAILED due to "
+             "ITfDisplayAttributeInfo::GetAttributeInfo() failed",
+             this));
+    return hr;
+  }
+
+  MOZ_LOG(gIMELog, LogLevel::Debug,
+          ("0x%p   TSFTextStore::GetDisplayAttribute() succeeded: "
+           "Result={ %s }",
+           this, GetDisplayAttrStr(*aResult).get()));
+  return S_OK;
+}
+
+HRESULT
+TSFTextStore::RestartCompositionIfNecessary(ITfRange* aRangeNew) {
+  MOZ_LOG(gIMELog, LogLevel::Debug,
+          ("0x%p   TSFTextStore::RestartCompositionIfNecessary("
+           "aRangeNew=0x%p), mComposition=%s",
+           this, aRangeNew, ToString(mComposition).c_str()));
+
+  if (mComposition.isNothing()) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::RestartCompositionIfNecessary() FAILED "
+             "due to no composition view",
+             this));
+    return E_FAIL;
+  }
+
+  HRESULT hr;
+  RefPtr<ITfCompositionView> pComposition(mComposition->GetView());
+  RefPtr<ITfRange> composingRange(aRangeNew);
+  if (!composingRange) {
+    hr = pComposition->GetRange(getter_AddRefs(composingRange));
+    if (FAILED(hr)) {
+      MOZ_LOG(gIMELog, LogLevel::Error,
+              ("0x%p   TSFTextStore::RestartCompositionIfNecessary() "
+               "FAILED due to pComposition->GetRange() failure",
+               this));
+      return hr;
+    }
+  }
+
+  // Get starting offset of the composition
+  LONG compStart = 0, compLength = 0;
+  hr = GetRangeExtent(composingRange, &compStart, &compLength);
+  if (FAILED(hr)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::RestartCompositionIfNecessary() FAILED "
+             "due to GetRangeExtent() failure",
+             this));
+    return hr;
+  }
+
+  if (mComposition->StartOffset() == compStart &&
+      mComposition->Length() == compLength) {
+    return S_OK;
+  }
+
+  MOZ_LOG(gIMELog, LogLevel::Debug,
+          ("0x%p   TSFTextStore::RestartCompositionIfNecessary(), "
+           "restaring composition because of compostion range is changed "
+           "(range=%ld-%ld, mComposition=%s)",
+           this, compStart, compStart + compLength,
+           ToString(mComposition).c_str()));
+
+  // If the queried composition length is different from the length
+  // of our composition string, OnUpdateComposition is being called
+  // because a part of the original composition was committed.
+  hr = RestartComposition(*mComposition, pComposition, composingRange);
+  if (FAILED(hr)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::RestartCompositionIfNecessary() "
+             "FAILED due to RestartComposition() failure",
+             this));
+    return hr;
+  }
+
+  MOZ_LOG(
+      gIMELog, LogLevel::Debug,
+      ("0x%p   TSFTextStore::RestartCompositionIfNecessary() succeeded", this));
+  return S_OK;
+}
+
+HRESULT TSFTextStore::RestartComposition(Composition& aCurrentComposition,
+                                         ITfCompositionView* aCompositionView,
+                                         ITfRange* aNewRange) {
+  Maybe<Selection>& selectionForTSF = SelectionForTSF();
+
+  LONG newStart, newLength;
+  HRESULT hr = GetRangeExtent(aNewRange, &newStart, &newLength);
+  LONG newEnd = newStart + newLength;
+
+  if (selectionForTSF.isNothing()) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::RestartComposition() FAILED "
+             "due to SelectionForTSF() failure",
+             this));
+    return E_FAIL;
+  }
+
+  if (FAILED(hr)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::RestartComposition() FAILED "
+             "due to GetRangeExtent() failure",
+             this));
+    return hr;
+  }
+
+  // If the new range has no overlap with the crrent range, we just commit
+  // the composition and restart new composition with the new range but
+  // current selection range should be preserved.
+  if (newStart >= aCurrentComposition.EndOffset() ||
+      newEnd <= aCurrentComposition.StartOffset()) {
+    RecordCompositionEndAction();
+    RecordCompositionStartAction(aCompositionView, newStart, newLength, true);
+    return S_OK;
+  }
+
+  MOZ_LOG(gIMELog, LogLevel::Debug,
+          ("0x%p   TSFTextStore::RestartComposition(aCompositionView=0x%p, "
+           "aNewRange=0x%p { newStart=%ld, newLength=%ld }), "
+           "aCurrentComposition=%s, "
+           "selectionForTSF=%s",
+           this, aCompositionView, aNewRange, newStart, newLength,
+           ToString(aCurrentComposition).c_str(),
+           ToString(selectionForTSF).c_str()));
+
+  // If the new range has an overlap with the current one, we should not commit
+  // the whole current range to avoid creating an odd undo transaction.
+  // I.e., the overlapped range which is being composed should not appear in
+  // undo transaction.
+
+  // Backup current composition data and selection data.
+  Composition oldComposition = aCurrentComposition;
+  Selection oldSelection = *selectionForTSF;
+
+  // Commit only the part of composition.
+  LONG keepComposingStartOffset =
+      std::max(oldComposition.StartOffset(), newStart);
+  LONG keepComposingEndOffset = std::min(oldComposition.EndOffset(), newEnd);
+  MOZ_ASSERT(
+      keepComposingStartOffset <= keepComposingEndOffset,
+      "Why keepComposingEndOffset is smaller than keepComposingStartOffset?");
+  LONG keepComposingLength = keepComposingEndOffset - keepComposingStartOffset;
+  // Remove the overlapped part from the commit string.
+  nsAutoString commitString(oldComposition.DataRef());
+  commitString.Cut(keepComposingStartOffset - oldComposition.StartOffset(),
+                   keepComposingLength);
+  // Update the composition string.
+  Maybe<Content>& contentForTSF = ContentForTSF();
+  if (contentForTSF.isNothing()) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::RestartComposition() FAILED "
+             "due to ContentForTSF() failure",
+             this));
+    return E_FAIL;
+  }
+  contentForTSF->ReplaceTextWith(oldComposition.StartOffset(),
+                                 oldComposition.Length(), commitString);
+  MOZ_ASSERT(mComposition.isSome());
+  // Record a compositionupdate action for commit the part of composing string.
+  PendingAction* action = LastOrNewPendingCompositionUpdate();
+  if (mComposition.isSome()) {
+    action->mData = mComposition->DataRef();
+  }
+  action->mRanges->Clear();
+  // Note that we shouldn't append ranges when composition string
+  // is empty because it may cause TextComposition confused.
+  if (!action->mData.IsEmpty()) {
+    TextRange caretRange;
+    caretRange.mStartOffset = caretRange.mEndOffset = static_cast<uint32_t>(
+        oldComposition.StartOffset() + commitString.Length());
+    caretRange.mRangeType = TextRangeType::eCaret;
+    action->mRanges->AppendElement(caretRange);
+  }
+  action->mIncomplete = false;
+
+  // Record compositionend action.
+  RecordCompositionEndAction();
+
+  // Record compositionstart action only with the new start since this method
+  // hasn't restored composing string yet.
+  RecordCompositionStartAction(aCompositionView, newStart, 0, false);
+
+  // Restore the latest text content and selection.
+  contentForTSF->ReplaceSelectedTextWith(nsDependentSubstring(
+      oldComposition.DataRef(),
+      keepComposingStartOffset - oldComposition.StartOffset(),
+      keepComposingLength));
+  selectionForTSF = Some(oldSelection);
+
+  MOZ_LOG(gIMELog, LogLevel::Debug,
+          ("0x%p   TSFTextStore::RestartComposition() succeeded, "
+           "mComposition=%s, selectionForTSF=%s",
+           this, ToString(mComposition).c_str(),
+           ToString(selectionForTSF).c_str()));
+
+  return S_OK;
+}
+
+static bool GetColor(const TF_DA_COLOR& aTSFColor, nscolor& aResult) {
+  switch (aTSFColor.type) {
+    case TF_CT_SYSCOLOR: {
+      DWORD sysColor = ::GetSysColor(aTSFColor.nIndex);
+      aResult =
+          NS_RGB(GetRValue(sysColor), GetGValue(sysColor), GetBValue(sysColor));
+      return true;
+    }
+    case TF_CT_COLORREF:
+      aResult = NS_RGB(GetRValue(aTSFColor.cr), GetGValue(aTSFColor.cr),
+                       GetBValue(aTSFColor.cr));
+      return true;
+    case TF_CT_NONE:
+    default:
+      return false;
+  }
+}
+
+static bool GetLineStyle(TF_DA_LINESTYLE aTSFLineStyle,
+                         TextRangeStyle::LineStyle& aTextRangeLineStyle) {
+  switch (aTSFLineStyle) {
+    case TF_LS_NONE:
+      aTextRangeLineStyle = TextRangeStyle::LineStyle::None;
+      return true;
+    case TF_LS_SOLID:
+      aTextRangeLineStyle = TextRangeStyle::LineStyle::Solid;
+      return true;
+    case TF_LS_DOT:
+      aTextRangeLineStyle = TextRangeStyle::LineStyle::Dotted;
+      return true;
+    case TF_LS_DASH:
+      aTextRangeLineStyle = TextRangeStyle::LineStyle::Dashed;
+      return true;
+    case TF_LS_SQUIGGLE:
+      aTextRangeLineStyle = TextRangeStyle::LineStyle::Wavy;
+      return true;
+    default:
+      return false;
+  }
+}
+
+HRESULT
+TSFTextStore::RecordCompositionUpdateAction() {
+  MOZ_LOG(
+      gIMELog, LogLevel::Debug,
+      ("0x%p   TSFTextStore::RecordCompositionUpdateAction(), mComposition=%s",
+       this, ToString(mComposition).c_str()));
+
+  if (mComposition.isNothing()) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::RecordCompositionUpdateAction() FAILED "
+             "due to no composition view",
+             this));
+    return E_FAIL;
+  }
+
+  // Getting display attributes is *really* complicated!
+  // We first get the context and the property objects to query for
+  // attributes, but since a big range can have a variety of values for
+  // the attribute, we have to find out all the ranges that have distinct
+  // attribute values. Then we query for what the value represents through
+  // the display attribute manager and translate that to TextRange to be
+  // sent in eCompositionChange
+
+  RefPtr<ITfProperty> attrPropetry;
+  HRESULT hr =
+      mContext->GetProperty(GUID_PROP_ATTRIBUTE, getter_AddRefs(attrPropetry));
+  if (FAILED(hr) || !attrPropetry) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::RecordCompositionUpdateAction() FAILED "
+             "due to mContext->GetProperty() failure",
+             this));
+    return FAILED(hr) ? hr : E_FAIL;
+  }
+
+  RefPtr<ITfRange> composingRange;
+  hr = mComposition->GetView()->GetRange(getter_AddRefs(composingRange));
+  if (FAILED(hr)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::RecordCompositionUpdateAction() "
+             "FAILED due to mComposition->GetView()->GetRange() failure",
+             this));
+    return hr;
+  }
+
+  RefPtr<IEnumTfRanges> enumRanges;
+  hr = attrPropetry->EnumRanges(TfEditCookie(mEditCookie),
+                                getter_AddRefs(enumRanges), composingRange);
+  if (FAILED(hr) || !enumRanges) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::RecordCompositionUpdateAction() FAILED "
+             "due to attrPropetry->EnumRanges() failure",
+             this));
+    return FAILED(hr) ? hr : E_FAIL;
+  }
+
+  // First, put the log of content and selection here.
+  Maybe<Selection>& selectionForTSF = SelectionForTSF();
+  if (selectionForTSF.isNothing()) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::RecordCompositionUpdateAction() FAILED "
+             "due to SelectionForTSF() failure",
+             this));
+    return E_FAIL;
+  }
+
+  PendingAction* action = LastOrNewPendingCompositionUpdate();
+  action->mData = mComposition->DataRef();
+  // The ranges might already have been initialized, however, if this is
+  // called again, that means we need to overwrite the ranges with current
+  // information.
+  action->mRanges->Clear();
+
+  // Note that we shouldn't append ranges when composition string
+  // is empty because it may cause TextComposition confused.
+  if (!action->mData.IsEmpty()) {
+    TextRange newRange;
+    // No matter if we have display attribute info or not,
+    // we always pass in at least one range to eCompositionChange
+    newRange.mStartOffset = 0;
+    newRange.mEndOffset = action->mData.Length();
+    newRange.mRangeType = TextRangeType::eRawClause;
+    action->mRanges->AppendElement(newRange);
+
+    RefPtr<ITfRange> range;
+    while (enumRanges->Next(1, getter_AddRefs(range), nullptr) == S_OK) {
+      if (NS_WARN_IF(!range)) {
+        break;
+      }
+
+      LONG rangeStart = 0, rangeLength = 0;
+      if (FAILED(GetRangeExtent(range, &rangeStart, &rangeLength))) {
+        continue;
+      }
+      // The range may include out of composition string.  We should ignore
+      // outside of the composition string.
+      LONG start = std::min(std::max(rangeStart, mComposition->StartOffset()),
+                            mComposition->EndOffset());
+      LONG end = std::max(
+          std::min(rangeStart + rangeLength, mComposition->EndOffset()),
+          mComposition->StartOffset());
+      LONG length = end - start;
+      if (length < 0) {
+        MOZ_LOG(gIMELog, LogLevel::Error,
+                ("0x%p   TSFTextStore::RecordCompositionUpdateAction() "
+                 "ignores invalid range (%ld-%ld)",
+                 this, rangeStart - mComposition->StartOffset(),
+                 rangeStart - mComposition->StartOffset() + rangeLength));
+        continue;
+      }
+      if (!length) {
+        MOZ_LOG(gIMELog, LogLevel::Debug,
+                ("0x%p   TSFTextStore::RecordCompositionUpdateAction() "
+                 "ignores a range due to outside of the composition or empty "
+                 "(%ld-%ld)",
+                 this, rangeStart - mComposition->StartOffset(),
+                 rangeStart - mComposition->StartOffset() + rangeLength));
+        continue;
+      }
+
+      TextRange newRange;
+      newRange.mStartOffset =
+          static_cast<uint32_t>(start - mComposition->StartOffset());
+      // The end of the last range in the array is
+      // always kept at the end of composition
+      newRange.mEndOffset = mComposition->Length();
+
+      TF_DISPLAYATTRIBUTE attr;
+      hr = GetDisplayAttribute(attrPropetry, range, &attr);
+      if (FAILED(hr)) {
+        newRange.mRangeType = TextRangeType::eRawClause;
+      } else {
+        newRange.mRangeType = GetGeckoSelectionValue(attr);
+        if (GetColor(attr.crText, newRange.mRangeStyle.mForegroundColor)) {
+          newRange.mRangeStyle.mDefinedStyles |=
+              TextRangeStyle::DEFINED_FOREGROUND_COLOR;
+        }
+        if (GetColor(attr.crBk, newRange.mRangeStyle.mBackgroundColor)) {
+          newRange.mRangeStyle.mDefinedStyles |=
+              TextRangeStyle::DEFINED_BACKGROUND_COLOR;
+        }
+        if (GetColor(attr.crLine, newRange.mRangeStyle.mUnderlineColor)) {
+          newRange.mRangeStyle.mDefinedStyles |=
+              TextRangeStyle::DEFINED_UNDERLINE_COLOR;
+        }
+        if (GetLineStyle(attr.lsStyle, newRange.mRangeStyle.mLineStyle)) {
+          newRange.mRangeStyle.mDefinedStyles |=
+              TextRangeStyle::DEFINED_LINESTYLE;
+          newRange.mRangeStyle.mIsBoldLine = attr.fBoldLine != 0;
+        }
+      }
+
+      TextRange& lastRange = action->mRanges->LastElement();
+      if (lastRange.mStartOffset == newRange.mStartOffset) {
+        // Replace range if last range is the same as this one
+        // So that ranges don't overlap and confuse the editor
+        lastRange = newRange;
+      } else {
+        lastRange.mEndOffset = newRange.mStartOffset;
+        action->mRanges->AppendElement(newRange);
+      }
+    }
+
+    // We need to hack for Korean Input System which is Korean standard TIP.
+    // It sets no change style to IME selection (the selection is always only
+    // one).  So, the composition string looks like normal (or committed)
+    // string.  At this time, current selection range is same as the
+    // composition string range.  Other applications set a wide caret which
+    // covers the composition string,  however, Gecko doesn't support the wide
+    // caret drawing now (Gecko doesn't support XOR drawing), unfortunately.
+    // For now, we should change the range style to undefined.
+    if (!selectionForTSF->Collapsed() && action->mRanges->Length() == 1) {
+      TextRange& range = action->mRanges->ElementAt(0);
+      LONG start = selectionForTSF->MinOffset();
+      LONG end = selectionForTSF->MaxOffset();
+      if (static_cast<LONG>(range.mStartOffset) ==
+              start - mComposition->StartOffset() &&
+          static_cast<LONG>(range.mEndOffset) ==
+              end - mComposition->StartOffset() &&
+          range.mRangeStyle.IsNoChangeStyle()) {
+        range.mRangeStyle.Clear();
+        // The looks of selected type is better than others.
+        range.mRangeType = TextRangeType::eSelectedRawClause;
+      }
+    }
+
+    // The caret position has to be collapsed.
+    uint32_t caretPosition = static_cast<uint32_t>(
+        selectionForTSF->HasRange()
+            ? selectionForTSF->MaxOffset() - mComposition->StartOffset()
+            : mComposition->StartOffset());
+
+    // If caret is in the target clause and it doesn't have specific style,
+    // the target clause will be painted as normal selection range.  Since
+    // caret shouldn't be in selection range on Windows, we shouldn't append
+    // caret range in such case.
+    const TextRange* targetClause = action->mRanges->GetTargetClause();
+    if (!targetClause || targetClause->mRangeStyle.IsDefined() ||
+        caretPosition < targetClause->mStartOffset ||
+        caretPosition > targetClause->mEndOffset) {
+      TextRange caretRange;
+      caretRange.mStartOffset = caretRange.mEndOffset = caretPosition;
+      caretRange.mRangeType = TextRangeType::eCaret;
+      action->mRanges->AppendElement(caretRange);
+    }
+  }
+
+  action->mIncomplete = false;
+
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p   TSFTextStore::RecordCompositionUpdateAction() "
+           "succeeded",
+           this));
+
+  return S_OK;
+}
+
+HRESULT
+TSFTextStore::SetSelectionInternal(const TS_SELECTION_ACP* pSelection,
+                                   bool aDispatchCompositionChangeEvent) {
+  MOZ_LOG(
+      gIMELog, LogLevel::Debug,
+      ("0x%p   TSFTextStore::SetSelectionInternal(pSelection=%s, "
+       "aDispatchCompositionChangeEvent=%s), mComposition=%s",
+       this, pSelection ? mozilla::ToString(*pSelection).c_str() : "nullptr",
+       GetBoolName(aDispatchCompositionChangeEvent),
+       ToString(mComposition).c_str()));
+
+  MOZ_ASSERT(IsReadWriteLocked());
+
+  Maybe<Selection>& selectionForTSF = SelectionForTSF();
+  if (selectionForTSF.isNothing()) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::SetSelectionInternal() FAILED due to "
+             "SelectionForTSF() failure",
+             this));
+    return E_FAIL;
+  }
+
+  MaybeDispatchKeyboardEventAsProcessedByIME();
+  if (mDestroyed) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::SetSelectionInternal() FAILED due to "
+             "destroyed during dispatching a keyboard event",
+             this));
+    return E_FAIL;
+  }
+
+  // If actually the range is not changing, we should do nothing.
+  // Perhaps, we can ignore the difference change because it must not be
+  // important for following edit.
+  if (selectionForTSF->EqualsExceptDirection(*pSelection)) {
+    MOZ_LOG(gIMELog, LogLevel::Warning,
+            ("0x%p   TSFTextStore::SetSelectionInternal() Succeeded but "
+             "did nothing because the selection range isn't changing",
+             this));
+    selectionForTSF->SetSelection(*pSelection);
+    return S_OK;
+  }
+
+  if (mComposition.isSome()) {
+    if (aDispatchCompositionChangeEvent) {
+      HRESULT hr = RestartCompositionIfNecessary();
+      if (FAILED(hr)) {
+        MOZ_LOG(gIMELog, LogLevel::Error,
+                ("0x%p   TSFTextStore::SetSelectionInternal() FAILED due to "
+                 "RestartCompositionIfNecessary() failure",
+                 this));
+        return hr;
+      }
+    }
+    if (pSelection->acpStart < mComposition->StartOffset() ||
+        pSelection->acpEnd > mComposition->EndOffset()) {
+      MOZ_LOG(gIMELog, LogLevel::Error,
+              ("0x%p   TSFTextStore::SetSelectionInternal() FAILED due to "
+               "the selection being out of the composition string",
+               this));
+      return TS_E_INVALIDPOS;
+    }
+    // Emulate selection during compositions
+    selectionForTSF->SetSelection(*pSelection);
+    if (aDispatchCompositionChangeEvent) {
+      HRESULT hr = RecordCompositionUpdateAction();
+      if (FAILED(hr)) {
+        MOZ_LOG(gIMELog, LogLevel::Error,
+                ("0x%p   TSFTextStore::SetSelectionInternal() FAILED due to "
+                 "RecordCompositionUpdateAction() failure",
+                 this));
+        return hr;
+      }
+    }
+    return S_OK;
+  }
+
+  TS_SELECTION_ACP selectionInContent(*pSelection);
+
+  // If mContentForTSF caches old contents which is now different from
+  // actual contents, we need some complicated hack here...
+  // Note that this hack assumes that this is used for reconversion.
+  if (mContentForTSF.isSome() && mPendingTextChangeData.IsValid() &&
+      !mPendingTextChangeData.mCausedOnlyByComposition) {
+    uint32_t startOffset = static_cast<uint32_t>(selectionInContent.acpStart);
+    uint32_t endOffset = static_cast<uint32_t>(selectionInContent.acpEnd);
+    if (mPendingTextChangeData.mStartOffset >= endOffset) {
+      // Setting selection before any changed ranges is fine.
+    } else if (mPendingTextChangeData.mRemovedEndOffset <= startOffset) {
+      // Setting selection after removed range is fine with following
+      // adjustment.
+      selectionInContent.acpStart += mPendingTextChangeData.Difference();
+      selectionInContent.acpEnd += mPendingTextChangeData.Difference();
+    } else if (startOffset == endOffset) {
+      // Moving caret position may be fine in most cases even if the insertion
+      // point has already gone but in this case, composition will be inserted
+      // to unexpected position, though.
+      // It seems that moving caret into middle of the new text is odd.
+      // Perhaps, end of it is expected by users in most cases.
+      selectionInContent.acpStart = mPendingTextChangeData.mAddedEndOffset;
+      selectionInContent.acpEnd = selectionInContent.acpStart;
+    } else {
+      // Otherwise, i.e., setting range has already gone, we cannot set
+      // selection properly.
+      MOZ_LOG(gIMELog, LogLevel::Error,
+              ("0x%p   TSFTextStore::SetSelectionInternal() FAILED due to "
+               "there is unknown content change",
+               this));
+      return E_FAIL;
+    }
+  }
+
+  CompleteLastActionIfStillIncomplete();
+  PendingAction* action = mPendingActions.AppendElement();
+  action->mType = PendingAction::Type::eSetSelection;
+  action->mSelectionStart = selectionInContent.acpStart;
+  action->mSelectionLength =
+      selectionInContent.acpEnd - selectionInContent.acpStart;
+  action->mSelectionReversed = (selectionInContent.style.ase == TS_AE_START);
+
+  // Use TSF specified selection for updating mSelectionForTSF.
+  selectionForTSF->SetSelection(*pSelection);
+
+  return S_OK;
+}
+
+STDMETHODIMP
+TSFTextStore::SetSelection(ULONG ulCount, const TS_SELECTION_ACP* pSelection) {
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p TSFTextStore::SetSelection(ulCount=%lu, pSelection=%s }), "
+           "mComposition=%s",
+           this, ulCount,
+           pSelection ? mozilla::ToString(pSelection).c_str() : "nullptr",
+           ToString(mComposition).c_str()));
+
+  if (!IsReadWriteLocked()) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::SetSelection() FAILED due to "
+             "not locked (read-write)",
+             this));
+    return TS_E_NOLOCK;
+  }
+  if (ulCount != 1) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::SetSelection() FAILED due to "
+             "trying setting multiple selection",
+             this));
+    return E_INVALIDARG;
+  }
+  if (!pSelection) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::SetSelection() FAILED due to "
+             "null argument",
+             this));
+    return E_INVALIDARG;
+  }
+
+  HRESULT hr = SetSelectionInternal(pSelection, true);
+  if (FAILED(hr)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::SetSelection() FAILED due to "
+             "SetSelectionInternal() failure",
+             this));
+  } else {
+    MOZ_LOG(gIMELog, LogLevel::Info,
+            ("0x%p   TSFTextStore::SetSelection() succeeded", this));
+  }
+  return hr;
+}
+
+STDMETHODIMP
+TSFTextStore::GetText(LONG acpStart, LONG acpEnd, WCHAR* pchPlain,
+                      ULONG cchPlainReq, ULONG* pcchPlainOut,
+                      TS_RUNINFO* prgRunInfo, ULONG ulRunInfoReq,
+                      ULONG* pulRunInfoOut, LONG* pacpNext) {
+  MOZ_LOG(
+      gIMELog, LogLevel::Info,
+      ("0x%p TSFTextStore::GetText(acpStart=%ld, acpEnd=%ld, pchPlain=0x%p, "
+       "cchPlainReq=%lu, pcchPlainOut=0x%p, prgRunInfo=0x%p, ulRunInfoReq=%lu, "
+       "pulRunInfoOut=0x%p, pacpNext=0x%p), mComposition=%s",
+       this, acpStart, acpEnd, pchPlain, cchPlainReq, pcchPlainOut, prgRunInfo,
+       ulRunInfoReq, pulRunInfoOut, pacpNext, ToString(mComposition).c_str()));
+
+  if (!IsReadLocked()) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::GetText() FAILED due to "
+             "not locked (read)",
+             this));
+    return TS_E_NOLOCK;
+  }
+
+  if (!pcchPlainOut || (!pchPlain && !prgRunInfo) ||
+      !cchPlainReq != !pchPlain || !ulRunInfoReq != !prgRunInfo) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::GetText() FAILED due to "
+             "invalid argument",
+             this));
+    return E_INVALIDARG;
+  }
+
+  if (acpStart < 0 || acpEnd < -1 || (acpEnd != -1 && acpStart > acpEnd)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::GetText() FAILED due to "
+             "invalid position",
+             this));
+    return TS_E_INVALIDPOS;
+  }
+
+  // Making sure to null-terminate string just to be on the safe side
+  *pcchPlainOut = 0;
+  if (pchPlain && cchPlainReq) *pchPlain = 0;
+  if (pulRunInfoOut) *pulRunInfoOut = 0;
+  if (pacpNext) *pacpNext = acpStart;
+  if (prgRunInfo && ulRunInfoReq) {
+    prgRunInfo->uCount = 0;
+    prgRunInfo->type = TS_RT_PLAIN;
+  }
+
+  Maybe<Content>& contentForTSF = ContentForTSF();
+  if (contentForTSF.isNothing()) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::GetText() FAILED due to "
+             "ContentForTSF() failure",
+             this));
+    return E_FAIL;
+  }
+  if (contentForTSF->TextRef().Length() < static_cast<uint32_t>(acpStart)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::GetText() FAILED due to "
+             "acpStart is larger offset than the actual text length",
+             this));
+    return TS_E_INVALIDPOS;
+  }
+  if (acpEnd != -1 &&
+      contentForTSF->TextRef().Length() < static_cast<uint32_t>(acpEnd)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::GetText() FAILED due to "
+             "acpEnd is larger offset than the actual text length",
+             this));
+    return TS_E_INVALIDPOS;
+  }
+  uint32_t length = (acpEnd == -1) ? contentForTSF->TextRef().Length() -
+                                         static_cast<uint32_t>(acpStart)
+                                   : static_cast<uint32_t>(acpEnd - acpStart);
+  if (cchPlainReq && cchPlainReq - 1 < length) {
+    length = cchPlainReq - 1;
+  }
+  if (length) {
+    if (pchPlain && cchPlainReq) {
+      const char16_t* startChar =
+          contentForTSF->TextRef().BeginReading() + acpStart;
+      memcpy(pchPlain, startChar, length * sizeof(*pchPlain));
+      pchPlain[length] = 0;
+      *pcchPlainOut = length;
+    }
+    if (prgRunInfo && ulRunInfoReq) {
+      prgRunInfo->uCount = length;
+      prgRunInfo->type = TS_RT_PLAIN;
+      if (pulRunInfoOut) *pulRunInfoOut = 1;
+    }
+    if (pacpNext) *pacpNext = acpStart + length;
+  }
+
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p   TSFTextStore::GetText() succeeded: pcchPlainOut=0x%p, "
+           "*prgRunInfo={ uCount=%lu, type=%s }, *pulRunInfoOut=%lu, "
+           "*pacpNext=%ld)",
+           this, pcchPlainOut, prgRunInfo ? prgRunInfo->uCount : 0,
+           prgRunInfo ? GetTextRunTypeName(prgRunInfo->type) : "N/A",
+           pulRunInfoOut ? *pulRunInfoOut : 0, pacpNext ? *pacpNext : 0));
+  return S_OK;
+}
+
+STDMETHODIMP
+TSFTextStore::SetText(DWORD dwFlags, LONG acpStart, LONG acpEnd,
+                      const WCHAR* pchText, ULONG cch, TS_TEXTCHANGE* pChange) {
+  MOZ_LOG(
+      gIMELog, LogLevel::Info,
+      ("0x%p TSFTextStore::SetText(dwFlags=%s, acpStart=%ld, acpEnd=%ld, "
+       "pchText=0x%p \"%s\", cch=%lu, pChange=0x%p), mComposition=%s",
+       this, dwFlags == TS_ST_CORRECTION ? "TS_ST_CORRECTION" : "not-specified",
+       acpStart, acpEnd, pchText,
+       pchText && cch ? GetEscapedUTF8String(pchText, cch).get() : "", cch,
+       pChange, ToString(mComposition).c_str()));
+
+  // Per SDK documentation, and since we don't have better
+  // ways to do this, this method acts as a helper to
+  // call SetSelection followed by InsertTextAtSelection
+  if (!IsReadWriteLocked()) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::SetText() FAILED due to "
+             "not locked (read)",
+             this));
+    return TS_E_NOLOCK;
+  }
+
+  TS_SELECTION_ACP selection;
+  selection.acpStart = acpStart;
+  selection.acpEnd = acpEnd;
+  selection.style.ase = TS_AE_END;
+  selection.style.fInterimChar = 0;
+  // Set selection to desired range
+  HRESULT hr = SetSelectionInternal(&selection);
+  if (FAILED(hr)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::SetText() FAILED due to "
+             "SetSelectionInternal() failure",
+             this));
+    return hr;
+  }
+  // Replace just selected text
+  if (!InsertTextAtSelectionInternal(nsDependentSubstring(pchText, cch),
+                                     pChange)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::SetText() FAILED due to "
+             "InsertTextAtSelectionInternal() failure",
+             this));
+    return E_FAIL;
+  }
+
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p   TSFTextStore::SetText() succeeded: pChange={ "
+           "acpStart=%ld, acpOldEnd=%ld, acpNewEnd=%ld }",
+           this, pChange ? pChange->acpStart : 0,
+           pChange ? pChange->acpOldEnd : 0, pChange ? pChange->acpNewEnd : 0));
+  return S_OK;
+}
+
+STDMETHODIMP
+TSFTextStore::GetFormattedText(LONG acpStart, LONG acpEnd,
+                               IDataObject** ppDataObject) {
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p TSFTextStore::GetFormattedText() called "
+           "but not supported (E_NOTIMPL)",
+           this));
+
+  // no support for formatted text
+  return E_NOTIMPL;
+}
+
+STDMETHODIMP
+TSFTextStore::GetEmbedded(LONG acpPos, REFGUID rguidService, REFIID riid,
+                          IUnknown** ppunk) {
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p TSFTextStore::GetEmbedded() called "
+           "but not supported (E_NOTIMPL)",
+           this));
+
+  // embedded objects are not supported
+  return E_NOTIMPL;
+}
+
+STDMETHODIMP
+TSFTextStore::QueryInsertEmbedded(const GUID* pguidService,
+                                  const FORMATETC* pFormatEtc,
+                                  BOOL* pfInsertable) {
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p TSFTextStore::QueryInsertEmbedded() called "
+           "but not supported, *pfInsertable=FALSE (S_OK)",
+           this));
+
+  // embedded objects are not supported
+  *pfInsertable = FALSE;
+  return S_OK;
+}
+
+STDMETHODIMP
+TSFTextStore::InsertEmbedded(DWORD dwFlags, LONG acpStart, LONG acpEnd,
+                             IDataObject* pDataObject, TS_TEXTCHANGE* pChange) {
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p TSFTextStore::InsertEmbedded() called "
+           "but not supported (E_NOTIMPL)",
+           this));
+
+  // embedded objects are not supported
+  return E_NOTIMPL;
+}
+
+// static
+bool TSFTextStore::ShouldSetInputScopeOfURLBarToDefault() {
+  // FYI: Google Japanese Input may be an IMM-IME.  If it's installed on
+  //      Win7, it's always IMM-IME.  Otherwise, basically, it's a TIP.
+  //      However, if it's installed on Win7 and has not been updated yet
+  //      after the OS is upgraded to Win8 or later, it's still an IMM-IME.
+  //      Therefore, we also need to check with IMMHandler here.
+  if (!StaticPrefs::intl_ime_hack_set_input_scope_of_url_bar_to_default()) {
+    return false;
+  }
+
+  if (IMMHandler::IsGoogleJapaneseInputActive()) {
+    return true;
+  }
+
+  switch (TSFStaticSink::ActiveTIP()) {
+    case TextInputProcessorID::eMicrosoftIMEForJapanese:
+    case TextInputProcessorID::eGoogleJapaneseInput:
+    case TextInputProcessorID::eMicrosoftBopomofo:
+    case TextInputProcessorID::eMicrosoftChangJie:
+    case TextInputProcessorID::eMicrosoftPhonetic:
+    case TextInputProcessorID::eMicrosoftQuick:
+    case TextInputProcessorID::eMicrosoftNewChangJie:
+    case TextInputProcessorID::eMicrosoftNewPhonetic:
+    case TextInputProcessorID::eMicrosoftNewQuick:
+    case TextInputProcessorID::eMicrosoftPinyin:
+    case TextInputProcessorID::eMicrosoftPinyinNewExperienceInputStyle:
+    case TextInputProcessorID::eMicrosoftOldHangul:
+    case TextInputProcessorID::eMicrosoftWubi:
+    case TextInputProcessorID::eMicrosoftIMEForKorean:
+      return true;
+    default:
+      return false;
+  }
+}
+
+void TSFTextStore::SetInputScope(const nsString& aHTMLInputType,
+                                 const nsString& aHTMLInputMode) {
+  mInputScopes.Clear();
+
+  // IME may refer only first input scope, but we will append inputmode's
+  // input scopes too like Chrome since IME may refer it.
+  IMEHandler::AppendInputScopeFromType(aHTMLInputType, mInputScopes);
+  IMEHandler::AppendInputScopeFromInputMode(aHTMLInputMode, mInputScopes);
+
+  if (mInPrivateBrowsing) {
+    mInputScopes.AppendElement(IS_PRIVATE);
+  }
+}
+
+int32_t TSFTextStore::GetRequestedAttrIndex(const TS_ATTRID& aAttrID) {
+  if (IsEqualGUID(aAttrID, GUID_PROP_INPUTSCOPE)) {
+    return eInputScope;
+  }
+  if (IsEqualGUID(aAttrID, sGUID_PROP_URL)) {
+    return eDocumentURL;
+  }
+  if (IsEqualGUID(aAttrID, TSATTRID_Text_VerticalWriting)) {
+    return eTextVerticalWriting;
+  }
+  if (IsEqualGUID(aAttrID, TSATTRID_Text_Orientation)) {
+    return eTextOrientation;
+  }
+  return eNotSupported;
+}
+
+TS_ATTRID
+TSFTextStore::GetAttrID(int32_t aIndex) {
+  switch (aIndex) {
+    case eInputScope:
+      return GUID_PROP_INPUTSCOPE;
+    case eDocumentURL:
+      return sGUID_PROP_URL;
+    case eTextVerticalWriting:
+      return TSATTRID_Text_VerticalWriting;
+    case eTextOrientation:
+      return TSATTRID_Text_Orientation;
+    default:
+      MOZ_CRASH("Invalid index? Or not implemented yet?");
+      return GUID_NULL;
+  }
+}
+
+HRESULT
+TSFTextStore::HandleRequestAttrs(DWORD aFlags, ULONG aFilterCount,
+                                 const TS_ATTRID* aFilterAttrs) {
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p TSFTextStore::HandleRequestAttrs(aFlags=%s, "
+           "aFilterCount=%lu)",
+           this, GetFindFlagName(aFlags).get(), aFilterCount));
+
+  // This is a little weird! RequestSupportedAttrs gives us advanced notice
+  // of a support query via RetrieveRequestedAttrs for a specific attribute.
+  // RetrieveRequestedAttrs needs to return valid data for all attributes we
+  // support, but the text service will only want the input scope object
+  // returned in RetrieveRequestedAttrs if the dwFlags passed in here contains
+  // TS_ATTR_FIND_WANT_VALUE.
+  for (int32_t i = 0; i < NUM_OF_SUPPORTED_ATTRS; i++) {
+    mRequestedAttrs[i] = false;
+  }
+  mRequestedAttrValues = !!(aFlags & TS_ATTR_FIND_WANT_VALUE);
+
+  for (uint32_t i = 0; i < aFilterCount; i++) {
+    MOZ_LOG(gIMELog, LogLevel::Info,
+            ("0x%p   TSFTextStore::HandleRequestAttrs(), "
+             "requested attr=%s",
+             this, GetGUIDNameStrWithTable(aFilterAttrs[i]).get()));
+    int32_t index = GetRequestedAttrIndex(aFilterAttrs[i]);
+    if (index != eNotSupported) {
+      mRequestedAttrs[index] = true;
+    }
+  }
+  return S_OK;
+}
+
+STDMETHODIMP
+TSFTextStore::RequestSupportedAttrs(DWORD dwFlags, ULONG cFilterAttrs,
+                                    const TS_ATTRID* paFilterAttrs) {
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p TSFTextStore::RequestSupportedAttrs(dwFlags=%s, "
+           "cFilterAttrs=%lu)",
+           this, GetFindFlagName(dwFlags).get(), cFilterAttrs));
+
+  return HandleRequestAttrs(dwFlags, cFilterAttrs, paFilterAttrs);
+}
+
+STDMETHODIMP
+TSFTextStore::RequestAttrsAtPosition(LONG acpPos, ULONG cFilterAttrs,
+                                     const TS_ATTRID* paFilterAttrs,
+                                     DWORD dwFlags) {
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p TSFTextStore::RequestAttrsAtPosition(acpPos=%ld, "
+           "cFilterAttrs=%lu, dwFlags=%s)",
+           this, acpPos, cFilterAttrs, GetFindFlagName(dwFlags).get()));
+
+  return HandleRequestAttrs(dwFlags | TS_ATTR_FIND_WANT_VALUE, cFilterAttrs,
+                            paFilterAttrs);
+}
+
+STDMETHODIMP
+TSFTextStore::RequestAttrsTransitioningAtPosition(LONG acpPos,
+                                                  ULONG cFilterAttrs,
+                                                  const TS_ATTRID* paFilterAttr,
+                                                  DWORD dwFlags) {
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p TSFTextStore::RequestAttrsTransitioningAtPosition("
+           "acpPos=%ld, cFilterAttrs=%lu, dwFlags=%s) called but not supported "
+           "(S_OK)",
+           this, acpPos, cFilterAttrs, GetFindFlagName(dwFlags).get()));
+
+  // no per character attributes defined
+  return S_OK;
+}
+
+STDMETHODIMP
+TSFTextStore::FindNextAttrTransition(LONG acpStart, LONG acpHalt,
+                                     ULONG cFilterAttrs,
+                                     const TS_ATTRID* paFilterAttrs,
+                                     DWORD dwFlags, LONG* pacpNext,
+                                     BOOL* pfFound, LONG* plFoundOffset) {
+  if (!pacpNext || !pfFound || !plFoundOffset) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("  0x%p TSFTextStore::FindNextAttrTransition() FAILED due to "
+             "null argument",
+             this));
+    return E_INVALIDARG;
+  }
+
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p   TSFTextStore::FindNextAttrTransition() called "
+           "but not supported (S_OK)",
+           this));
+
+  // no per character attributes defined
+  *pacpNext = *plFoundOffset = acpHalt;
+  *pfFound = FALSE;
+  return S_OK;
+}
+
+// To test the document URL result, define this to out put it to the stdout
+// #define DEBUG_PRINT_DOCUMENT_URL
+
+STDMETHODIMP
+TSFTextStore::RetrieveRequestedAttrs(ULONG ulCount, TS_ATTRVAL* paAttrVals,
+                                     ULONG* pcFetched) {
+  if (!pcFetched || !paAttrVals) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p TSFTextStore::RetrieveRequestedAttrs() FAILED due to "
+             "null argument",
+             this));
+    return E_INVALIDARG;
+  }
+
+  ULONG expectedCount = 0;
+  for (int32_t i = 0; i < NUM_OF_SUPPORTED_ATTRS; i++) {
+    if (mRequestedAttrs[i]) {
+      expectedCount++;
+    }
+  }
+  if (ulCount < expectedCount) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p TSFTextStore::RetrieveRequestedAttrs() FAILED due to "
+             "not enough count ulCount=%lu, expectedCount=%lu",
+             this, ulCount, expectedCount));
+    return E_INVALIDARG;
+  }
+
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p TSFTextStore::RetrieveRequestedAttrs() called "
+           "ulCount=%lu, mRequestedAttrValues=%s",
+           this, ulCount, GetBoolName(mRequestedAttrValues)));
+
+  auto GetExposingURL = [&]() -> BSTR {
+    const bool allowed =
+        StaticPrefs::intl_tsf_expose_url_allowed() &&
+        (!mInPrivateBrowsing ||
+         StaticPrefs::intl_tsf_expose_url_in_private_browsing_allowed());
+    if (!allowed || mDocumentURL.IsEmpty()) {
+      BSTR emptyString = ::SysAllocString(L"");
+      MOZ_ASSERT(
+          emptyString,
+          "We need to return valid BSTR pointer to notify TSF of supporting it "
+          "with a pointer to empty string");
+      return emptyString;
+    }
+    return ::SysAllocString(mDocumentURL.get());
+  };
+
+#ifdef DEBUG_PRINT_DOCUMENT_URL
+  {
+    BSTR exposingURL = GetExposingURL();
+    printf("TSFTextStore::RetrieveRequestedAttrs: DocumentURL=\"%s\"\n",
+           NS_ConvertUTF16toUTF8(static_cast<char16ptr_t>(_bstr_t(exposingURL)))
+               .get());
+    ::SysFreeString(exposingURL);
+  }
+#endif  // #ifdef DEBUG_PRINT_DOCUMENT_URL
+
+  int32_t count = 0;
+  for (int32_t i = 0; i < NUM_OF_SUPPORTED_ATTRS; i++) {
+    if (!mRequestedAttrs[i]) {
+      continue;
+    }
+    mRequestedAttrs[i] = false;
+
+    TS_ATTRID attrID = GetAttrID(i);
+
+    MOZ_LOG(gIMELog, LogLevel::Info,
+            ("0x%p   TSFTextStore::RetrieveRequestedAttrs() for %s", this,
+             GetGUIDNameStrWithTable(attrID).get()));
+
+    paAttrVals[count].idAttr = attrID;
+    paAttrVals[count].dwOverlapId = 0;
+
+    if (!mRequestedAttrValues) {
+      paAttrVals[count].varValue.vt = VT_EMPTY;
+    } else {
+      switch (i) {
+        case eInputScope: {
+          paAttrVals[count].varValue.vt = VT_UNKNOWN;
+          RefPtr<IUnknown> inputScope = new InputScopeImpl(mInputScopes);
+          paAttrVals[count].varValue.punkVal = inputScope.forget().take();
+          break;
+        }
+        case eDocumentURL: {
+          paAttrVals[count].varValue.vt = VT_BSTR;
+          paAttrVals[count].varValue.bstrVal = GetExposingURL();
+          break;
+        }
+        case eTextVerticalWriting: {
+          Maybe<Selection>& selectionForTSF = SelectionForTSF();
+          paAttrVals[count].varValue.vt = VT_BOOL;
+          paAttrVals[count].varValue.boolVal =
+              selectionForTSF.isSome() &&
+                      selectionForTSF->WritingModeRef().IsVertical()
+                  ? VARIANT_TRUE
+                  : VARIANT_FALSE;
+          break;
+        }
+        case eTextOrientation: {
+          Maybe<Selection>& selectionForTSF = SelectionForTSF();
+          paAttrVals[count].varValue.vt = VT_I4;
+          paAttrVals[count].varValue.lVal =
+              selectionForTSF.isSome() &&
+                      selectionForTSF->WritingModeRef().IsVertical()
+                  ? 2700
+                  : 0;
+          break;
+        }
+        default:
+          MOZ_CRASH("Invalid index? Or not implemented yet?");
+          break;
+      }
+    }
+    count++;
+  }
+
+  mRequestedAttrValues = false;
+
+  if (count) {
+    *pcFetched = count;
+    return S_OK;
+  }
+
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p   TSFTextStore::RetrieveRequestedAttrs() called "
+           "for unknown TS_ATTRVAL, *pcFetched=0 (S_OK)",
+           this));
+
+  paAttrVals->dwOverlapId = 0;
+  paAttrVals->varValue.vt = VT_EMPTY;
+  *pcFetched = 0;
+  return S_OK;
+}
+
+#undef DEBUG_PRINT_DOCUMENT_URL
+
+STDMETHODIMP
+TSFTextStore::GetEndACP(LONG* pacp) {
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p TSFTextStore::GetEndACP(pacp=0x%p)", this, pacp));
+
+  if (!IsReadLocked()) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::GetEndACP() FAILED due to "
+             "not locked (read)",
+             this));
+    return TS_E_NOLOCK;
+  }
+
+  if (!pacp) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::GetEndACP() FAILED due to "
+             "null argument",
+             this));
+    return E_INVALIDARG;
+  }
+
+  Maybe<Content>& contentForTSF = ContentForTSF();
+  if (contentForTSF.isNothing()) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::GetEndACP() FAILED due to "
+             "ContentForTSF() failure",
+             this));
+    return E_FAIL;
+  }
+  *pacp = static_cast<LONG>(contentForTSF->TextRef().Length());
+  return S_OK;
+}
+
+STDMETHODIMP
+TSFTextStore::GetActiveView(TsViewCookie* pvcView) {
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p TSFTextStore::GetActiveView(pvcView=0x%p)", this, pvcView));
+
+  if (!pvcView) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::GetActiveView() FAILED due to "
+             "null argument",
+             this));
+    return E_INVALIDARG;
+  }
+
+  *pvcView = TEXTSTORE_DEFAULT_VIEW;
+
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p   TSFTextStore::GetActiveView() succeeded: *pvcView=%ld", this,
+           *pvcView));
+  return S_OK;
+}
+
+STDMETHODIMP
+TSFTextStore::GetACPFromPoint(TsViewCookie vcView, const POINT* pt,
+                              DWORD dwFlags, LONG* pacp) {
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p TSFTextStore::GetACPFromPoint(pvcView=%ld, pt=%p (x=%ld, "
+           "y=%ld), dwFlags=%s, pacp=%p, mDeferNotifyingTSFUntilNextUpdate=%s, "
+           "mWaitingQueryLayout=%s",
+           this, vcView, pt, pt ? pt->x : 0, pt ? pt->y : 0,
+           GetACPFromPointFlagName(dwFlags).get(), pacp,
+           GetBoolName(mDeferNotifyingTSFUntilNextUpdate),
+           GetBoolName(mWaitingQueryLayout)));
+
+  if (!IsReadLocked()) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::GetACPFromPoint() FAILED due to "
+             "not locked (read)",
+             this));
+    return TS_E_NOLOCK;
+  }
+
+  if (vcView != TEXTSTORE_DEFAULT_VIEW) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::GetACPFromPoint() FAILED due to "
+             "called with invalid view",
+             this));
+    return E_INVALIDARG;
+  }
+
+  if (!pt) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::GetACPFromPoint() FAILED due to "
+             "null pt",
+             this));
+    return E_INVALIDARG;
+  }
+
+  if (!pacp) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::GetACPFromPoint() FAILED due to "
+             "null pacp",
+             this));
+    return E_INVALIDARG;
+  }
+
+  mWaitingQueryLayout = false;
+
+  if (mDestroyed ||
+      (mContentForTSF.isSome() && mContentForTSF->IsLayoutChanged())) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::GetACPFromPoint() returned "
+             "TS_E_NOLAYOUT",
+             this));
+    mHasReturnedNoLayoutError = true;
+    return TS_E_NOLAYOUT;
+  }
+
+  LayoutDeviceIntPoint ourPt(pt->x, pt->y);
+  // Convert to widget relative coordinates from screen's.
+  ourPt -= mWidget->WidgetToScreenOffset();
+
+  // NOTE: Don't check if the point is in the widget since the point can be
+  //       outside of the widget if focused editor is in a XUL <panel>.
+
+  WidgetQueryContentEvent queryCharAtPointEvent(true, eQueryCharacterAtPoint,
+                                                mWidget);
+  mWidget->InitEvent(queryCharAtPointEvent, &ourPt);
+
+  // FYI: WidgetQueryContentEvent may cause flushing pending layout and it
+  //      may cause focus change or something.
+  RefPtr<TSFTextStore> kungFuDeathGrip(this);
+  DispatchEvent(queryCharAtPointEvent);
+  if (!mWidget || mWidget->Destroyed()) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::GetACPFromPoint() FAILED due to "
+             "mWidget was destroyed during eQueryCharacterAtPoint",
+             this));
+    return E_FAIL;
+  }
+
+  MOZ_LOG(gIMELog, LogLevel::Debug,
+          ("0x%p   TSFTextStore::GetACPFromPoint(), queryCharAtPointEvent={ "
+           "mReply=%s }",
+           this, ToString(queryCharAtPointEvent.mReply).c_str()));
+
+  if (NS_WARN_IF(queryCharAtPointEvent.Failed())) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::GetACPFromPoint() FAILED due to "
+             "eQueryCharacterAtPoint failure",
+             this));
+    return E_FAIL;
+  }
+
+  // If dwFlags isn't set and the point isn't in any character's bounding box,
+  // we should return TS_E_INVALIDPOINT.
+  if (!(dwFlags & GXFPF_NEAREST) && queryCharAtPointEvent.DidNotFindChar()) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::GetACPFromPoint() FAILED due to the "
+             "point contained by no bounding box",
+             this));
+    return TS_E_INVALIDPOINT;
+  }
+
+  // Although, we're not sure if mTentativeCaretOffset becomes NOT_FOUND,
+  // let's assume that there is no content in such case.
+  NS_WARNING_ASSERTION(queryCharAtPointEvent.DidNotFindTentativeCaretOffset(),
+                       "Tentative caret offset was not found");
+
+  uint32_t offset;
+
+  // If dwFlags includes GXFPF_ROUND_NEAREST, we should return tentative
+  // caret offset (MSDN calls it "range position").
+  if (dwFlags & GXFPF_ROUND_NEAREST) {
+    offset = queryCharAtPointEvent.mReply->mTentativeCaretOffset.valueOr(0);
+  } else if (queryCharAtPointEvent.FoundChar()) {
+    // Otherwise, we should return character offset whose bounding box contains
+    // the point.
+    offset = queryCharAtPointEvent.mReply->StartOffset();
+  } else {
+    // If the point isn't in any character's bounding box but we need to return
+    // the nearest character from the point, we should *guess* the character
+    // offset since there is no inexpensive API to check it strictly.
+    // XXX If we retrieve 2 bounding boxes, one is before the offset and
+    //     the other is after the offset, we could resolve the offset.
+    //     However, dispatching 2 eQueryTextRect may be expensive.
+
+    // So, use tentative offset for now.
+    offset = queryCharAtPointEvent.mReply->mTentativeCaretOffset.valueOr(0);
+
+    // However, if it's after the last character, we need to decrement the
+    // offset.
+    Maybe<Content>& contentForTSF = ContentForTSF();
+    if (contentForTSF.isNothing()) {
+      MOZ_LOG(gIMELog, LogLevel::Error,
+              ("0x%p   TSFTextStore::GetACPFromPoint() FAILED due to "
+               "ContentForTSF() failure",
+               this));
+      return E_FAIL;
+    }
+    if (contentForTSF->TextRef().Length() <= offset) {
+      // If the tentative caret is after the last character, let's return
+      // the last character's offset.
+      offset = contentForTSF->TextRef().Length() - 1;
+    }
+  }
+
+  if (NS_WARN_IF(offset > LONG_MAX)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::GetACPFromPoint() FAILED due to out of "
+             "range of the result",
+             this));
+    return TS_E_INVALIDPOINT;
+  }
+
+  *pacp = static_cast<LONG>(offset);
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p   TSFTextStore::GetACPFromPoint() succeeded: *pacp=%ld", this,
+           *pacp));
+  return S_OK;
+}
+
+STDMETHODIMP
+TSFTextStore::GetTextExt(TsViewCookie vcView, LONG acpStart, LONG acpEnd,
+                         RECT* prc, BOOL* pfClipped) {
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p TSFTextStore::GetTextExt(vcView=%ld, "
+           "acpStart=%ld, acpEnd=%ld, prc=0x%p, pfClipped=0x%p), "
+           "IsHandlingCompositionInParent()=%s, "
+           "IsHandlingCompositionInContent()=%s, mContentForTSF=%s, "
+           "mSelectionForTSF=%s, mComposition=%s, "
+           "mDeferNotifyingTSFUntilNextUpdate=%s, mWaitingQueryLayout=%s, "
+           "IMEHandler::IsA11yHandlingNativeCaret()=%s",
+           this, vcView, acpStart, acpEnd, prc, pfClipped,
+           GetBoolName(IsHandlingCompositionInParent()),
+           GetBoolName(IsHandlingCompositionInContent()),
+           mozilla::ToString(mContentForTSF).c_str(),
+           ToString(mSelectionForTSF).c_str(), ToString(mComposition).c_str(),
+           GetBoolName(mDeferNotifyingTSFUntilNextUpdate),
+           GetBoolName(mWaitingQueryLayout),
+           GetBoolName(IMEHandler::IsA11yHandlingNativeCaret())));
+
+  if (!IsReadLocked()) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::GetTextExt() FAILED due to "
+             "not locked (read)",
+             this));
+    return TS_E_NOLOCK;
+  }
+
+  if (vcView != TEXTSTORE_DEFAULT_VIEW) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::GetTextExt() FAILED due to "
+             "called with invalid view",
+             this));
+    return E_INVALIDARG;
+  }
+
+  if (!prc || !pfClipped) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::GetTextExt() FAILED due to "
+             "null argument",
+             this));
+    return E_INVALIDARG;
+  }
+
+  // According to MSDN, ITextStoreACP::GetTextExt() should return
+  // TS_E_INVALIDARG when acpStart and acpEnd are same (i.e., collapsed range).
+  // https://msdn.microsoft.com/en-us/library/windows/desktop/ms538435(v=vs.85).aspx
+  // > TS_E_INVALIDARG: The specified start and end character positions are
+  // >                  equal.
+  // However, some TIPs (including Microsoft's Chinese TIPs!) call this with
+  // collapsed range and if we return TS_E_INVALIDARG, they stops showing their
+  // owning window or shows it but odd position.  So, we should just return
+  // error only when acpStart and/or acpEnd are really odd.
+
+  if (acpStart < 0 || acpEnd < acpStart) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::GetTextExt() FAILED due to "
+             "invalid position",
+             this));
+    return TS_E_INVALIDPOS;
+  }
+
+  mWaitingQueryLayout = false;
+
+  if (IsHandlingCompositionInContent() && mContentForTSF.isSome() &&
+      mContentForTSF->HasOrHadComposition() &&
+      mContentForTSF->IsLayoutChanged() &&
+      mContentForTSF->MinModifiedOffset().value() >
+          static_cast<uint32_t>(LONG_MAX)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::GetTextExt(), FAILED due to the text "
+             "is too big for TSF (cannot treat modified offset as LONG), "
+             "mContentForTSF=%s",
+             this, ToString(mContentForTSF).c_str()));
+    return E_FAIL;
+  }
+
+  // At Windows 10 build 17643 (an insider preview for RS5), Microsoft fixed
+  // the bug of TS_E_NOLAYOUT (even when we returned TS_E_NOLAYOUT, TSF
+  // returned E_FAIL to TIP).  However, until we drop to support older Windows
+  // and all TIPs are aware of TS_E_NOLAYOUT result, we need to keep returning
+  // S_OK and available rectangle only for them.
+  if (!MaybeHackNoErrorLayoutBugs(acpStart, acpEnd) &&
+      mContentForTSF.isSome() && mContentForTSF->IsLayoutChangedAt(acpEnd)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::GetTextExt() returned TS_E_NOLAYOUT "
+             "(acpEnd=%ld)",
+             this, acpEnd));
+    mHasReturnedNoLayoutError = true;
+    return TS_E_NOLAYOUT;
+  }
+
+  if (mDestroyed) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::GetTextExt() returned TS_E_NOLAYOUT "
+             "(acpEnd=%ld) because this has already been destroyed",
+             this, acpEnd));
+    mHasReturnedNoLayoutError = true;
+    return TS_E_NOLAYOUT;
+  }
+
+  // use eQueryTextRect to get rect in system, screen coordinates
+  WidgetQueryContentEvent queryTextRectEvent(true, eQueryTextRect, mWidget);
+  mWidget->InitEvent(queryTextRectEvent);
+
+  WidgetQueryContentEvent::Options options;
+  int64_t startOffset = acpStart;
+  if (mComposition.isSome()) {
+    // If there is a composition, TSF must want character rects related to
+    // the composition.  Therefore, we should use insertion point relative
+    // query because the composition might be at different position from
+    // the position where TSFTextStore believes it at.
+    options.mRelativeToInsertionPoint = true;
+    startOffset -= mComposition->StartOffset();
+  } else if (IsHandlingCompositionInParent() && mContentForTSF.isSome() &&
+             mContentForTSF->HasOrHadComposition()) {
+    // If there was a composition and its commit event hasn't been dispatched
+    // yet, ContentCacheInParent is still open for relative offset query from
+    // the latest composition.
+    options.mRelativeToInsertionPoint = true;
+    startOffset -= mContentForTSF->LatestCompositionRange()->StartOffset();
+  } else if (!CanAccessActualContentDirectly() &&
+             mSelectionForTSF->HasRange()) {
+    // If TSF/TIP cannot access actual content directly, there may be pending
+    // text and/or selection changes which have not been notified TSF yet.
+    // Therefore, we should use relative to insertion point query since
+    // TSF/TIP computes the offset from the cached selection.
+    options.mRelativeToInsertionPoint = true;
+    startOffset -= mSelectionForTSF->StartOffset();
+  }
+  // ContentEventHandler and ContentCache return actual caret rect when
+  // the queried range is collapsed and selection is collapsed at the
+  // queried range.  Then, its height (in horizontal layout, width in vertical
+  // layout) may be different from actual font height of the line.  In such
+  // case, users see "dancing" of candidate or suggest window of TIP.
+  // For preventing it, we should query text rect with at least 1 length.
+  uint32_t length = std::max(static_cast<int32_t>(acpEnd - acpStart), 1);
+  queryTextRectEvent.InitForQueryTextRect(startOffset, length, options);
+
+  DispatchEvent(queryTextRectEvent);
+  if (NS_WARN_IF(queryTextRectEvent.Failed())) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::GetTextExt() FAILED due to "
+             "eQueryTextRect failure",
+             this));
+    return TS_E_INVALIDPOS;  // but unexpected failure, maybe.
+  }
+
+  // IMEs don't like empty rects, fix here
+  if (queryTextRectEvent.mReply->mRect.Width() <= 0) {
+    queryTextRectEvent.mReply->mRect.SetWidth(1);
+  }
+  if (queryTextRectEvent.mReply->mRect.Height() <= 0) {
+    queryTextRectEvent.mReply->mRect.SetHeight(1);
+  }
+
+  // convert to unclipped screen rect
+  nsWindow* refWindow =
+      static_cast<nsWindow*>(!!queryTextRectEvent.mReply->mFocusedWidget
+                                 ? queryTextRectEvent.mReply->mFocusedWidget
+                                 : static_cast<nsIWidget*>(mWidget.get()));
+  // Result rect is in top level widget coordinates
+  refWindow = refWindow->GetTopLevelWindow(false);
+  if (!refWindow) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::GetTextExt() FAILED due to "
+             "no top level window",
+             this));
+    return E_FAIL;
+  }
+
+  queryTextRectEvent.mReply->mRect.MoveBy(refWindow->WidgetToScreenOffset());
+
+  // get bounding screen rect to test for clipping
+  if (!GetScreenExtInternal(*prc)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::GetTextExt() FAILED due to "
+             "GetScreenExtInternal() failure",
+             this));
+    return E_FAIL;
+  }
+
+  // clip text rect to bounding rect
+  RECT textRect;
+  ::SetRect(&textRect, queryTextRectEvent.mReply->mRect.X(),
+            queryTextRectEvent.mReply->mRect.Y(),
+            queryTextRectEvent.mReply->mRect.XMost(),
+            queryTextRectEvent.mReply->mRect.YMost());
+  if (!::IntersectRect(prc, prc, &textRect))
+    // Text is not visible
+    ::SetRectEmpty(prc);
+
+  // not equal if text rect was clipped
+  *pfClipped = !::EqualRect(prc, &textRect);
+
+  // ATOK 2011 - 2016 refers native caret position and size on windows whose
+  // class name is one of Mozilla's windows for deciding candidate window
+  // position.  Additionally, ATOK 2015 and earlier behaves really odd when
+  // we don't create native caret.  Therefore, we need to create native caret
+  // only when ATOK 2011 - 2015 is active (i.e., not necessary for ATOK 2016).
+  // However, if a11y module is handling native caret, we shouldn't touch it.
+  // Note that ATOK must require the latest information of the caret.  So,
+  // even if we'll create native caret later, we need to creat it here with
+  // current information.
+  if (!IMEHandler::IsA11yHandlingNativeCaret() &&
+      StaticPrefs::intl_tsf_hack_atok_create_native_caret() &&
+      TSFStaticSink::IsATOKReferringNativeCaretActive() &&
+      mComposition.isSome() &&
+      mComposition->IsOffsetInRangeOrEndOffset(acpStart) &&
+      mComposition->IsOffsetInRangeOrEndOffset(acpEnd)) {
+    CreateNativeCaret();
+  }
+
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p   TSFTextStore::GetTextExt() succeeded: "
+           "*prc={ left=%ld, top=%ld, right=%ld, bottom=%ld }, *pfClipped=%s",
+           this, prc->left, prc->top, prc->right, prc->bottom,
+           GetBoolName(*pfClipped)));
+
+  return S_OK;
+}
+
+bool TSFTextStore::MaybeHackNoErrorLayoutBugs(LONG& aACPStart, LONG& aACPEnd) {
+  // When ITextStoreACP::GetTextExt() returns TS_E_NOLAYOUT, TSF returns E_FAIL
+  // to its caller (typically, active TIP).  Then, most TIPs abort current job
+  // or treat such application as non-GUI apps.  E.g., some of them give up
+  // showing candidate window, some others show candidate window at top-left of
+  // the screen.  For avoiding this issue, when there is composition (until
+  // composition is actually committed in remote content), we should not
+  // return TS_E_NOLAYOUT error for TIPs whose some features are broken by
+  // this issue.
+  // Note that ideally, this issue should be avoided by each TIP since this
+  // won't be fixed at least on non-latest Windows.  Actually, Google Japanese
+  // Input (based on Mozc) does it.  When GetTextExt() returns E_FAIL, TIPs
+  // should try to check result of GetRangeFromPoint() because TSF returns
+  // TS_E_NOLAYOUT correctly in this case. See:
+  // https://github.com/google/mozc/blob/6b878e31fb6ac4347dc9dfd8ccc1080fe718479f/src/win32/tip/tip_range_util.cc#L237-L257
+
+  if (!IsHandlingCompositionInContent() || mContentForTSF.isNothing() ||
+      !mContentForTSF->HasOrHadComposition() ||
+      !mContentForTSF->IsLayoutChangedAt(aACPEnd)) {
+    return false;
+  }
+
+  MOZ_ASSERT(mComposition.isNothing() ||
+             mComposition->StartOffset() ==
+                 mContentForTSF->LatestCompositionRange()->StartOffset());
+  MOZ_ASSERT(mComposition.isNothing() ||
+             mComposition->EndOffset() ==
+                 mContentForTSF->LatestCompositionRange()->EndOffset());
+
+  // If TSF does not have the bug, we need to hack only with a few TIPs.
+  static const bool sAlllowToStopHackingIfFine =
+      IsWindows10BuildOrLater(17643) &&
+      StaticPrefs::
+          intl_tsf_hack_allow_to_stop_hacking_on_build_17643_or_later();
+
+  // We need to compute active TIP now.  This may take a couple of milliseconds,
+  // however, it'll be cached, so, must be faster than check active TIP every
+  // GetTextExt() calls.
+  const Maybe<Selection>& selectionForTSF = SelectionForTSF();
+  switch (TSFStaticSink::ActiveTIP()) {
+    // MS IME for Japanese doesn't support asynchronous handling at deciding
+    // its suggest list window position.  The feature was implemented
+    // starting from Windows 8.  And also we may meet same trouble in e10s
+    // mode on Win7.  So, we should never return TS_E_NOLAYOUT to MS IME for
+    // Japanese.
+    case TextInputProcessorID::eMicrosoftIMEForJapanese:
+      // Basically, MS-IME tries to retrieve whole composition string rect
+      // at deciding suggest window immediately after unlocking the document.
+      // However, in e10s mode, the content hasn't updated yet in most cases.
+      // Therefore, if the first character at the retrieving range rect is
+      // available, we should use it as the result.
+      // Note that according to bug 1609675, MS-IME for Japanese itself does
+      // not handle TS_E_NOLAYOUT correctly at least on Build 18363.657 (1909).
+      if (StaticPrefs::
+              intl_tsf_hack_ms_japanese_ime_do_not_return_no_layout_error_at_first_char() &&
+          aACPStart < aACPEnd) {
+        aACPEnd = aACPStart;
+        break;
+      }
+      if (sAlllowToStopHackingIfFine) {
+        return false;
+      }
+      // Although, the condition is not clear, MS-IME sometimes retrieves the
+      // caret rect immediately after modifying the composition string but
+      // before unlocking the document.  In such case, we should return the
+      // nearest character rect.
+      // (Let's return true if there is no selection which must be not expected
+      // by MS-IME nor TSF.)
+      if (StaticPrefs::
+              intl_tsf_hack_ms_japanese_ime_do_not_return_no_layout_error_at_caret() &&
+          aACPStart == aACPEnd && selectionForTSF.isSome() &&
+          (!selectionForTSF->HasRange() ||
+           (selectionForTSF->Collapsed() &&
+            selectionForTSF->EndOffset() == aACPEnd))) {
+        int32_t minOffsetOfLayoutChanged =
+            static_cast<int32_t>(mContentForTSF->MinModifiedOffset().value());
+        aACPEnd = aACPStart = std::max(minOffsetOfLayoutChanged - 1, 0);
+      } else {
+        return false;
+      }
+      break;
+    // The bug of Microsoft Office IME 2010 for Japanese is similar to
+    // MS-IME for Win 8.1 and Win 10.  Newer version of MS Office IME is not
+    // released yet.  So, we can hack it without prefs  because there must be
+    // no developers who want to disable this hack for tests.
+    // XXX We have not tested with Microsoft Office IME 2010 since it's
+    //     installable only with Win7 and Win8 (i.e., cannot install Win8.1
+    //     and Win10), and requires upgrade to Win10.
+    case TextInputProcessorID::eMicrosoftOfficeIME2010ForJapanese:
+      // Basically, MS-IME tries to retrieve whole composition string rect
+      // at deciding suggest window immediately after unlocking the document.
+      // However, in e10s mode, the content hasn't updated yet in most cases.
+      // Therefore, if the first character at the retrieving range rect is
+      // available, we should use it as the result.
+      if (aACPStart < aACPEnd) {
+        aACPEnd = aACPStart;
+      }
+      // Although, the condition is not clear, MS-IME sometimes retrieves the
+      // caret rect immediately after modifying the composition string but
+      // before unlocking the document.  In such case, we should return the
+      // nearest character rect.
+      // (Let's return true if there is no selection which must be not expected
+      // by MS-IME nor TSF.)
+      else if (aACPStart == aACPEnd && selectionForTSF.isSome() &&
+               (!selectionForTSF->HasRange() ||
+                (selectionForTSF->Collapsed() &&
+                 selectionForTSF->EndOffset() == aACPEnd))) {
+        int32_t minOffsetOfLayoutChanged =
+            static_cast<int32_t>(mContentForTSF->MinModifiedOffset().value());
+        aACPEnd = aACPStart = std::max(minOffsetOfLayoutChanged - 1, 0);
+      } else {
+        return false;
+      }
+      break;
+    // ATOK fails to handle TS_E_NOLAYOUT only when it decides the position of
+    // suggest window.  In such case, ATOK tries to query rect of whole or a
+    // part of composition string.
+    // FYI: ATOK changes their implementation around candidate window and
+    //      suggest widget at ATOK 2016.  Therefore, there are some differences
+    //      ATOK 2015 (or older) and ATOK 2016 (or newer).
+    // FYI: ATOK 2017 stops referring our window class name.  I.e., ATOK 2016
+    //      and older may behave differently only on Gecko but this must be
+    //      finished from ATOK 2017.
+    // FYI: For testing with legacy ATOK, we should hack it even if current ATOK
+    //      refers native caret rect on windows whose window class is one of
+    //      Mozilla window classes and we stop creating native caret for ATOK
+    //      because creating native caret causes ATOK refers caret position
+    //      when GetTextExt() returns TS_E_NOLAYOUT.
+    case TextInputProcessorID::eATOK2011:
+    case TextInputProcessorID::eATOK2012:
+    case TextInputProcessorID::eATOK2013:
+    case TextInputProcessorID::eATOK2014:
+    case TextInputProcessorID::eATOK2015:
+      // ATOK 2016 and later may temporarily show candidate window at odd
+      // position when you convert a word quickly (e.g., keep pressing
+      // space bar).  So, on ATOK 2016 or later, we need to keep hacking the
+      // result of GetTextExt().
+      if (sAlllowToStopHackingIfFine) {
+        return false;
+      }
+      // If we'll create native caret where we paint our caret.  Then, ATOK
+      // will refer native caret.  So, we don't need to hack anything in
+      // this case.
+      if (StaticPrefs::intl_tsf_hack_atok_create_native_caret()) {
+        MOZ_ASSERT(TSFStaticSink::IsATOKReferringNativeCaretActive());
+        return false;
+      }
+      [[fallthrough]];
+    case TextInputProcessorID::eATOK2016:
+    case TextInputProcessorID::eATOKUnknown:
+      if (!StaticPrefs::
+              intl_tsf_hack_atok_do_not_return_no_layout_error_of_composition_string()) {
+        return false;
+      }
+      // If the range is in the composition string, we should return rectangle
+      // in it as far as possible.
+      if (!mContentForTSF->LatestCompositionRange()->IsOffsetInRangeOrEndOffset(
+              aACPStart) ||
+          !mContentForTSF->LatestCompositionRange()->IsOffsetInRangeOrEndOffset(
+              aACPEnd)) {
+        return false;
+      }
+      break;
+    // Japanist 10 fails to handle TS_E_NOLAYOUT when it decides the position
+    // of candidate window.  In such case, Japanist shows candidate window at
+    // top-left of the screen.  So, we should return the nearest caret rect
+    // where we know.  This is Japanist's bug.  So, even after build 17643,
+    // we need this hack.
+    case TextInputProcessorID::eJapanist10:
+      if (!StaticPrefs::
+              intl_tsf_hack_japanist10_do_not_return_no_layout_error_of_composition_string()) {
+        return false;
+      }
+      if (!mContentForTSF->LatestCompositionRange()->IsOffsetInRangeOrEndOffset(
+              aACPStart) ||
+          !mContentForTSF->LatestCompositionRange()->IsOffsetInRangeOrEndOffset(
+              aACPEnd)) {
+        return false;
+      }
+      break;
+    // Free ChangJie 2010 doesn't handle ITfContextView::GetTextExt() properly.
+    // This must be caused by the bug of TSF since Free ChangJie works fine on
+    // build 17643 and later.
+    case TextInputProcessorID::eFreeChangJie:
+      if (sAlllowToStopHackingIfFine) {
+        return false;
+      }
+      if (!StaticPrefs::
+              intl_tsf_hack_free_chang_jie_do_not_return_no_layout_error()) {
+        return false;
+      }
+      aACPEnd = mContentForTSF->LatestCompositionRange()->StartOffset();
+      aACPStart = std::min(aACPStart, aACPEnd);
+      break;
+    // Some Traditional Chinese TIPs of Microsoft don't show candidate window
+    // in e10s mode on Win8 or later.
+    case TextInputProcessorID::eMicrosoftQuick:
+      if (sAlllowToStopHackingIfFine) {
+        return false;  // MS Quick works fine with Win10 build 17643.
+      }
+      [[fallthrough]];
+    case TextInputProcessorID::eMicrosoftChangJie:
+      if (!StaticPrefs::
+              intl_tsf_hack_ms_traditional_chinese_do_not_return_no_layout_error()) {
+        return false;
+      }
+      aACPEnd = mContentForTSF->LatestCompositionRange()->StartOffset();
+      aACPStart = std::min(aACPStart, aACPEnd);
+      break;
+    // Some Simplified Chinese TIPs of Microsoft don't show candidate window
+    // in e10s mode on Win8 or later.
+    // FYI: Only Simplified Chinese TIPs of Microsoft still require this hack
+    //      because they sometimes do not show candidate window when we return
+    //      TS_E_NOLAYOUT for first query.  Note that even when they show
+    //      candidate window properly, we return TS_E_NOLAYOUT and following
+    //      log looks same as when they don't show candidate window.  Perhaps,
+    //      there is stateful cause or race in them.
+    case TextInputProcessorID::eMicrosoftPinyin:
+    case TextInputProcessorID::eMicrosoftWubi:
+      if (!StaticPrefs::
+              intl_tsf_hack_ms_simplified_chinese_do_not_return_no_layout_error()) {
+        return false;
+      }
+      aACPEnd = mContentForTSF->LatestCompositionRange()->StartOffset();
+      aACPStart = std::min(aACPStart, aACPEnd);
+      break;
+    default:
+      return false;
+  }
+
+  // If we hack the queried range for active TIP, that means we should not
+  // return TS_E_NOLAYOUT even if hacked offset is still modified.  So, as
+  // far as possible, we should adjust the offset.
+  MOZ_ASSERT(mContentForTSF->IsLayoutChanged());
+  bool collapsed = aACPStart == aACPEnd;
+  // Note that even if all characters in the editor or the composition
+  // string was modified, 0 or start offset of the composition string is
+  // useful because it may return caret rect or old character's rect which
+  // the user still see.  That must be useful information for TIP.
+  int32_t firstModifiedOffset =
+      static_cast<int32_t>(mContentForTSF->MinModifiedOffset().value());
+  LONG lastUnmodifiedOffset = std::max(firstModifiedOffset - 1, 0);
+  if (mContentForTSF->IsLayoutChangedAt(aACPStart)) {
+    if (aACPStart >= mContentForTSF->LatestCompositionRange()->StartOffset()) {
+      // If mContentForTSF has last composition string and current
+      // composition string, we can assume that ContentCacheInParent has
+      // cached rects of composition string at least length of current
+      // composition string.  Otherwise, we can assume that rect for
+      // first character of composition string is stored since it was
+      // selection start or caret position.
+      LONG maxCachedOffset =
+          mContentForTSF->LatestCompositionRange()->EndOffset();
+      if (mContentForTSF->LastComposition().isSome()) {
+        maxCachedOffset = std::min(
+            maxCachedOffset, mContentForTSF->LastComposition()->EndOffset());
+      }
+      aACPStart = std::min(aACPStart, maxCachedOffset);
+    }
+    // Otherwise, we don't know which character rects are cached.  So, we
+    // need to use first unmodified character's rect in this case.  Even
+    // if there is no character, the query event will return caret rect
+    // instead.
+    else {
+      aACPStart = lastUnmodifiedOffset;
+    }
+    MOZ_ASSERT(aACPStart <= aACPEnd);
+  }
+
+  // If TIP requests caret rect with collapsed range, we should keep
+  // collapsing the range.
+  if (collapsed) {
+    aACPEnd = aACPStart;
+  }
+  // Let's set aACPEnd to larger offset of last unmodified offset or
+  // aACPStart which may be the first character offset of the composition
+  // string.  However, some TIPs may want to know the right edge of the
+  // range.  Therefore, if aACPEnd is in composition string and active TIP
+  // doesn't retrieve caret rect (i.e., the range isn't collapsed), we
+  // should keep using the original aACPEnd.  Otherwise, we should set
+  // aACPEnd to larger value of aACPStart and lastUnmodifiedOffset.
+  else if (mContentForTSF->IsLayoutChangedAt(aACPEnd) &&
+           !mContentForTSF->LatestCompositionRange()
+                ->IsOffsetInRangeOrEndOffset(aACPEnd)) {
+    aACPEnd = std::max(aACPStart, lastUnmodifiedOffset);
+  }
+
+  MOZ_LOG(
+      gIMELog, LogLevel::Debug,
+      ("0x%p   TSFTextStore::HackNoErrorLayoutBugs() hacked the queried range "
+       "for not returning TS_E_NOLAYOUT, new values are: "
+       "aACPStart=%ld, aACPEnd=%ld",
+       this, aACPStart, aACPEnd));
+
+  return true;
+}
+
+STDMETHODIMP
+TSFTextStore::GetScreenExt(TsViewCookie vcView, RECT* prc) {
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p TSFTextStore::GetScreenExt(vcView=%ld, prc=0x%p)", this,
+           vcView, prc));
+
+  if (vcView != TEXTSTORE_DEFAULT_VIEW) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::GetScreenExt() FAILED due to "
+             "called with invalid view",
+             this));
+    return E_INVALIDARG;
+  }
+
+  if (!prc) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::GetScreenExt() FAILED due to "
+             "null argument",
+             this));
+    return E_INVALIDARG;
+  }
+
+  if (mDestroyed) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::GetScreenExt() returns empty rect "
+             "due to already destroyed",
+             this));
+    prc->left = prc->top = prc->right = prc->bottom = 0;
+    return S_OK;
+  }
+
+  if (!GetScreenExtInternal(*prc)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::GetScreenExt() FAILED due to "
+             "GetScreenExtInternal() failure",
+             this));
+    return E_FAIL;
+  }
+
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p   TSFTextStore::GetScreenExt() succeeded: "
+           "*prc={ left=%ld, top=%ld, right=%ld, bottom=%ld }",
+           this, prc->left, prc->top, prc->right, prc->bottom));
+  return S_OK;
+}
+
+bool TSFTextStore::GetScreenExtInternal(RECT& aScreenExt) {
+  MOZ_LOG(gIMELog, LogLevel::Debug,
+          ("0x%p   TSFTextStore::GetScreenExtInternal()", this));
+
+  MOZ_ASSERT(!mDestroyed);
+
+  // use NS_QUERY_EDITOR_RECT to get rect in system, screen coordinates
+  WidgetQueryContentEvent queryEditorRectEvent(true, eQueryEditorRect, mWidget);
+  mWidget->InitEvent(queryEditorRectEvent);
+  DispatchEvent(queryEditorRectEvent);
+  if (queryEditorRectEvent.Failed()) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::GetScreenExtInternal() FAILED due to "
+             "eQueryEditorRect failure",
+             this));
+    return false;
+  }
+
+  nsWindow* refWindow =
+      static_cast<nsWindow*>(!!queryEditorRectEvent.mReply->mFocusedWidget
+                                 ? queryEditorRectEvent.mReply->mFocusedWidget
+                                 : static_cast<nsIWidget*>(mWidget.get()));
+  // Result rect is in top level widget coordinates
+  refWindow = refWindow->GetTopLevelWindow(false);
+  if (!refWindow) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::GetScreenExtInternal() FAILED due to "
+             "no top level window",
+             this));
+    return false;
+  }
+
+  LayoutDeviceIntRect boundRect = refWindow->GetClientBounds();
+  boundRect.MoveTo(0, 0);
+
+  // Clip frame rect to window rect
+  boundRect.IntersectRect(queryEditorRectEvent.mReply->mRect, boundRect);
+  if (!boundRect.IsEmpty()) {
+    boundRect.MoveBy(refWindow->WidgetToScreenOffset());
+    ::SetRect(&aScreenExt, boundRect.X(), boundRect.Y(), boundRect.XMost(),
+              boundRect.YMost());
+  } else {
+    ::SetRectEmpty(&aScreenExt);
+  }
+
+  MOZ_LOG(gIMELog, LogLevel::Debug,
+          ("0x%p   TSFTextStore::GetScreenExtInternal() succeeded: "
+           "aScreenExt={ left=%ld, top=%ld, right=%ld, bottom=%ld }",
+           this, aScreenExt.left, aScreenExt.top, aScreenExt.right,
+           aScreenExt.bottom));
+  return true;
+}
+
+STDMETHODIMP
+TSFTextStore::GetWnd(TsViewCookie vcView, HWND* phwnd) {
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p TSFTextStore::GetWnd(vcView=%ld, phwnd=0x%p), "
+           "mWidget=0x%p",
+           this, vcView, phwnd, mWidget.get()));
+
+  if (vcView != TEXTSTORE_DEFAULT_VIEW) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::GetWnd() FAILED due to "
+             "called with invalid view",
+             this));
+    return E_INVALIDARG;
+  }
+
+  if (!phwnd) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::GetScreenExt() FAILED due to "
+             "null argument",
+             this));
+    return E_INVALIDARG;
+  }
+
+  *phwnd = mWidget ? mWidget->GetWindowHandle() : nullptr;
+
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p   TSFTextStore::GetWnd() succeeded: *phwnd=0x%p", this,
+           static_cast<void*>(*phwnd)));
+  return S_OK;
+}
+
+STDMETHODIMP
+TSFTextStore::InsertTextAtSelection(DWORD dwFlags, const WCHAR* pchText,
+                                    ULONG cch, LONG* pacpStart, LONG* pacpEnd,
+                                    TS_TEXTCHANGE* pChange) {
+  MOZ_LOG(
+      gIMELog, LogLevel::Info,
+      ("0x%p TSFTextStore::InsertTextAtSelection(dwFlags=%s, "
+       "pchText=0x%p \"%s\", cch=%lu, pacpStart=0x%p, pacpEnd=0x%p, "
+       "pChange=0x%p), mComposition=%s",
+       this,
+       dwFlags == 0                  ? "0"
+       : dwFlags == TF_IAS_NOQUERY   ? "TF_IAS_NOQUERY"
+       : dwFlags == TF_IAS_QUERYONLY ? "TF_IAS_QUERYONLY"
+                                     : "Unknown",
+       pchText, pchText && cch ? GetEscapedUTF8String(pchText, cch).get() : "",
+       cch, pacpStart, pacpEnd, pChange, ToString(mComposition).c_str()));
+
+  if (cch && !pchText) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::InsertTextAtSelection() FAILED due to "
+             "null pchText",
+             this));
+    return E_INVALIDARG;
+  }
+
+  if (TS_IAS_QUERYONLY == dwFlags) {
+    if (!IsReadLocked()) {
+      MOZ_LOG(gIMELog, LogLevel::Error,
+              ("0x%p   TSFTextStore::InsertTextAtSelection() FAILED due to "
+               "not locked (read)",
+               this));
+      return TS_E_NOLOCK;
+    }
+
+    if (!pacpStart || !pacpEnd) {
+      MOZ_LOG(gIMELog, LogLevel::Error,
+              ("0x%p   TSFTextStore::InsertTextAtSelection() FAILED due to "
+               "null argument",
+               this));
+      return E_INVALIDARG;
+    }
+
+    // Get selection first
+    Maybe<Selection>& selectionForTSF = SelectionForTSF();
+    if (selectionForTSF.isNothing()) {
+      MOZ_LOG(gIMELog, LogLevel::Error,
+              ("0x%p   TSFTextStore::InsertTextAtSelection() FAILED due to "
+               "SelectionForTSF() failure",
+               this));
+      return E_FAIL;
+    }
+
+    // Simulate text insertion
+    if (selectionForTSF->HasRange()) {
+      *pacpStart = selectionForTSF->StartOffset();
+      *pacpEnd = selectionForTSF->EndOffset();
+      if (pChange) {
+        *pChange = TS_TEXTCHANGE{.acpStart = selectionForTSF->StartOffset(),
+                                 .acpOldEnd = selectionForTSF->EndOffset(),
+                                 .acpNewEnd = selectionForTSF->StartOffset() +
+                                              static_cast<LONG>(cch)};
+      }
+    } else {
+      // There is no error code to return "no selection" state from this method.
+      // This means that TSF/TIP should check `GetSelection` result first and
+      // stop using this.  However, this could be called by TIP/TSF if they do
+      // not do so.  Therefore, we should use start of editor instead, but
+      // notify the caller of nothing will be inserted with pChange->acpNewEnd.
+      *pacpStart = *pacpEnd = 0;
+      if (pChange) {
+        *pChange = TS_TEXTCHANGE{.acpStart = 0, .acpOldEnd = 0, .acpNewEnd = 0};
+      }
+    }
+  } else {
+    if (!IsReadWriteLocked()) {
+      MOZ_LOG(gIMELog, LogLevel::Error,
+              ("0x%p   TSFTextStore::InsertTextAtSelection() FAILED due to "
+               "not locked (read-write)",
+               this));
+      return TS_E_NOLOCK;
+    }
+
+    if (!pChange) {
+      MOZ_LOG(gIMELog, LogLevel::Error,
+              ("0x%p   TSFTextStore::InsertTextAtSelection() FAILED due to "
+               "null pChange",
+               this));
+      return E_INVALIDARG;
+    }
+
+    if (TS_IAS_NOQUERY != dwFlags && (!pacpStart || !pacpEnd)) {
+      MOZ_LOG(gIMELog, LogLevel::Error,
+              ("0x%p   TSFTextStore::InsertTextAtSelection() FAILED due to "
+               "null argument",
+               this));
+      return E_INVALIDARG;
+    }
+
+    if (!InsertTextAtSelectionInternal(nsDependentSubstring(pchText, cch),
+                                       pChange)) {
+      MOZ_LOG(gIMELog, LogLevel::Error,
+              ("0x%p   TSFTextStore::InsertTextAtSelection() FAILED due to "
+               "InsertTextAtSelectionInternal() failure",
+               this));
+      return E_FAIL;
+    }
+
+    if (TS_IAS_NOQUERY != dwFlags) {
+      *pacpStart = pChange->acpStart;
+      *pacpEnd = pChange->acpNewEnd;
+    }
+  }
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p   TSFTextStore::InsertTextAtSelection() succeeded: "
+           "*pacpStart=%ld, *pacpEnd=%ld, "
+           "*pChange={ acpStart=%ld, acpOldEnd=%ld, acpNewEnd=%ld })",
+           this, pacpStart ? *pacpStart : 0, pacpEnd ? *pacpEnd : 0,
+           pChange ? pChange->acpStart : 0, pChange ? pChange->acpOldEnd : 0,
+           pChange ? pChange->acpNewEnd : 0));
+  return S_OK;
+}
+
+bool TSFTextStore::InsertTextAtSelectionInternal(const nsAString& aInsertStr,
+                                                 TS_TEXTCHANGE* aTextChange) {
+  MOZ_LOG(gIMELog, LogLevel::Debug,
+          ("0x%p   TSFTextStore::InsertTextAtSelectionInternal("
+           "aInsertStr=\"%s\", aTextChange=0x%p), mComposition=%s",
+           this, GetEscapedUTF8String(aInsertStr).get(), aTextChange,
+           ToString(mComposition).c_str()));
+
+  Maybe<Content>& contentForTSF = ContentForTSF();
+  if (contentForTSF.isNothing()) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::InsertTextAtSelectionInternal() failed "
+             "due to ContentForTSF() failure()",
+             this));
+    return false;
+  }
+
+  MaybeDispatchKeyboardEventAsProcessedByIME();
+  if (mDestroyed) {
+    MOZ_LOG(
+        gIMELog, LogLevel::Error,
+        ("0x%p   TSFTextStore::InsertTextAtSelectionInternal() FAILED due to "
+         "destroyed during dispatching a keyboard event",
+         this));
+    return false;
+  }
+
+  const auto numberOfCRLFs = [&]() -> uint32_t {
+    const auto* str = aInsertStr.BeginReading();
+    uint32_t num = 0;
+    for (uint32_t i = 0; i + 1 < aInsertStr.Length(); i++) {
+      if (str[i] == '\r' && str[i + 1] == '\n') {
+        num++;
+        i++;
+      }
+    }
+    return num;
+  }();
+  if (numberOfCRLFs) {
+    nsAutoString key;
+    if (TSFStaticSink::GetActiveTIPNameForTelemetry(key)) {
+      Telemetry::ScalarSet(
+          Telemetry::ScalarID::WIDGET_IME_NAME_ON_WINDOWS_INSERTED_CRLF, key,
+          true);
+    }
+  }
+
+  TS_SELECTION_ACP oldSelection = contentForTSF->Selection()->ACPRef();
+  if (mComposition.isNothing()) {
+    // Use a temporary composition to contain the text
+    PendingAction* compositionStart = mPendingActions.AppendElements(2);
+    PendingAction* compositionEnd = compositionStart + 1;
+
+    compositionStart->mType = PendingAction::Type::eCompositionStart;
+    compositionStart->mSelectionStart = oldSelection.acpStart;
+    compositionStart->mSelectionLength =
+        oldSelection.acpEnd - oldSelection.acpStart;
+    compositionStart->mAdjustSelection = false;
+
+    compositionEnd->mType = PendingAction::Type::eCompositionEnd;
+    compositionEnd->mData = aInsertStr;
+    compositionEnd->mSelectionStart = compositionStart->mSelectionStart;
+
+    MOZ_LOG(gIMELog, LogLevel::Debug,
+            ("0x%p   TSFTextStore::InsertTextAtSelectionInternal() "
+             "appending pending compositionstart and compositionend... "
+             "PendingCompositionStart={ mSelectionStart=%ld, "
+             "mSelectionLength=%ld }, PendingCompositionEnd={ mData=\"%s\" "
+             "(Length()=%zu), mSelectionStart=%ld }",
+             this, compositionStart->mSelectionStart,
+             compositionStart->mSelectionLength,
+             GetEscapedUTF8String(compositionEnd->mData).get(),
+             compositionEnd->mData.Length(), compositionEnd->mSelectionStart));
+  }
+
+  contentForTSF->ReplaceSelectedTextWith(aInsertStr);
+
+  if (aTextChange) {
+    aTextChange->acpStart = oldSelection.acpStart;
+    aTextChange->acpOldEnd = oldSelection.acpEnd;
+    aTextChange->acpNewEnd = contentForTSF->Selection()->EndOffset();
+  }
+
+  MOZ_LOG(
+      gIMELog, LogLevel::Debug,
+      ("0x%p   TSFTextStore::InsertTextAtSelectionInternal() "
+       "succeeded: mWidget=0x%p, mWidget->Destroyed()=%s, aTextChange={ "
+       "acpStart=%ld, acpOldEnd=%ld, acpNewEnd=%ld }",
+       this, mWidget.get(), GetBoolName(mWidget ? mWidget->Destroyed() : true),
+       aTextChange ? aTextChange->acpStart : 0,
+       aTextChange ? aTextChange->acpOldEnd : 0,
+       aTextChange ? aTextChange->acpNewEnd : 0));
+  return true;
+}
+
+STDMETHODIMP
+TSFTextStore::InsertEmbeddedAtSelection(DWORD dwFlags, IDataObject* pDataObject,
+                                        LONG* pacpStart, LONG* pacpEnd,
+                                        TS_TEXTCHANGE* pChange) {
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p TSFTextStore::InsertEmbeddedAtSelection() called "
+           "but not supported (E_NOTIMPL)",
+           this));
+
+  // embedded objects are not supported
+  return E_NOTIMPL;
+}
+
+HRESULT TSFTextStore::RecordCompositionStartAction(
+    ITfCompositionView* aCompositionView, ITfRange* aRange,
+    bool aPreserveSelection) {
+  MOZ_LOG(gIMELog, LogLevel::Debug,
+          ("0x%p   TSFTextStore::RecordCompositionStartAction("
+           "aCompositionView=0x%p, aRange=0x%p, aPreserveSelection=%s), "
+           "mComposition=%s",
+           this, aCompositionView, aRange, GetBoolName(aPreserveSelection),
+           ToString(mComposition).c_str()));
+
+  LONG start = 0, length = 0;
+  HRESULT hr = GetRangeExtent(aRange, &start, &length);
+  if (FAILED(hr)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::RecordCompositionStartAction() FAILED "
+             "due to GetRangeExtent() failure",
+             this));
+    return hr;
+  }
+
+  return RecordCompositionStartAction(aCompositionView, start, length,
+                                      aPreserveSelection);
+}
+
+HRESULT TSFTextStore::RecordCompositionStartAction(
+    ITfCompositionView* aCompositionView, LONG aStart, LONG aLength,
+    bool aPreserveSelection) {
+  MOZ_LOG(gIMELog, LogLevel::Debug,
+          ("0x%p   TSFTextStore::RecordCompositionStartAction("
+           "aCompositionView=0x%p, aStart=%ld, aLength=%ld, "
+           "aPreserveSelection=%s), "
+           "mComposition=%s",
+           this, aCompositionView, aStart, aLength,
+           GetBoolName(aPreserveSelection), ToString(mComposition).c_str()));
+
+  Maybe<Content>& contentForTSF = ContentForTSF();
+  if (contentForTSF.isNothing()) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::RecordCompositionStartAction() FAILED "
+             "due to ContentForTSF() failure",
+             this));
+    return E_FAIL;
+  }
+
+  MaybeDispatchKeyboardEventAsProcessedByIME();
+  if (mDestroyed) {
+    MOZ_LOG(
+        gIMELog, LogLevel::Error,
+        ("0x%p   TSFTextStore::RecordCompositionStartAction() FAILED due to "
+         "destroyed during dispatching a keyboard event",
+         this));
+    return false;
+  }
+
+  CompleteLastActionIfStillIncomplete();
+
+  // TIP may have inserted text at selection before calling
+  // OnStartComposition().  In this case, we've already created a pending
+  // compositionend.  If new composition replaces all commit string of the
+  // pending compositionend, we should cancel the pending compositionend and
+  // keep the previous composition normally.
+  // On Windows 7, MS-IME for Korean, MS-IME 2010 for Korean and MS Old Hangul
+  // may start composition with calling InsertTextAtSelection() and
+  // OnStartComposition() with this order (bug 1208043).
+  // On Windows 10, MS Pinyin, MS Wubi, MS ChangJie and MS Quick commits
+  // last character and replace it with empty string with new composition
+  // when user removes last character of composition string with Backspace
+  // key (bug 1462257).
+  if (!aPreserveSelection &&
+      IsLastPendingActionCompositionEndAt(aStart, aLength)) {
+    const PendingAction& pendingCompositionEnd = mPendingActions.LastElement();
+    contentForTSF->RestoreCommittedComposition(aCompositionView,
+                                               pendingCompositionEnd);
+    mPendingActions.RemoveLastElement();
+    MOZ_LOG(gIMELog, LogLevel::Info,
+            ("0x%p   TSFTextStore::RecordCompositionStartAction() "
+             "succeeded: restoring the committed string as composing string, "
+             "mComposition=%s, mSelectionForTSF=%s",
+             this, ToString(mComposition).c_str(),
+             ToString(mSelectionForTSF).c_str()));
+    return S_OK;
+  }
+
+  PendingAction* action = mPendingActions.AppendElement();
+  action->mType = PendingAction::Type::eCompositionStart;
+  action->mSelectionStart = aStart;
+  action->mSelectionLength = aLength;
+
+  Maybe<Selection>& selectionForTSF = SelectionForTSF();
+  if (selectionForTSF.isNothing()) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::RecordCompositionStartAction() FAILED "
+             "due to SelectionForTSF() failure",
+             this));
+    action->mAdjustSelection = true;
+  } else if (!selectionForTSF->HasRange()) {
+    // If there is no selection, let's collapse seletion to the insertion point.
+    action->mAdjustSelection = true;
+  } else if (selectionForTSF->MinOffset() != aStart ||
+             selectionForTSF->MaxOffset() != aStart + aLength) {
+    // If new composition range is different from current selection range,
+    // we need to set selection before dispatching compositionstart event.
+    action->mAdjustSelection = true;
+  } else {
+    // We shouldn't dispatch selection set event before dispatching
+    // compositionstart event because it may cause put caret different
+    // position in HTML editor since generated flat text content and offset in
+    // it are lossy data of HTML contents.
+    action->mAdjustSelection = false;
+  }
+
+  contentForTSF->StartComposition(aCompositionView, *action,
+                                  aPreserveSelection);
+  MOZ_ASSERT(mComposition.isSome());
+  action->mData = mComposition->DataRef();
+
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p   TSFTextStore::RecordCompositionStartAction() succeeded: "
+           "mComposition=%s, mSelectionForTSF=%s }",
+           this, ToString(mComposition).c_str(),
+           ToString(mSelectionForTSF).c_str()));
+  return S_OK;
+}
+
+HRESULT
+TSFTextStore::RecordCompositionEndAction() {
+  MOZ_LOG(gIMELog, LogLevel::Debug,
+          ("0x%p   TSFTextStore::RecordCompositionEndAction(), "
+           "mComposition=%s",
+           this, ToString(mComposition).c_str()));
+
+  MOZ_ASSERT(mComposition.isSome());
+
+  if (mComposition.isNothing()) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::RecordCompositionEndAction() FAILED due to "
+             "no composition",
+             this));
+    return false;
+  }
+
+  MaybeDispatchKeyboardEventAsProcessedByIME();
+  if (mDestroyed) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::RecordCompositionEndAction() FAILED due to "
+             "destroyed during dispatching a keyboard event",
+             this));
+    return false;
+  }
+
+  // If we're handling incomplete composition update or already handled
+  // composition update, we can forget them since composition end will send
+  // the latest composition string and it overwrites the composition string
+  // even if we dispatch eCompositionChange event before that.  So, let's
+  // forget all composition updates now.
+  RemoveLastCompositionUpdateActions();
+  PendingAction* action = mPendingActions.AppendElement();
+  action->mType = PendingAction::Type::eCompositionEnd;
+  action->mData = mComposition->DataRef();
+  action->mSelectionStart = mComposition->StartOffset();
+
+  Maybe<Content>& contentForTSF = ContentForTSF();
+  if (contentForTSF.isNothing()) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::RecordCompositionEndAction() FAILED due "
+             "to ContentForTSF() failure",
+             this));
+    return E_FAIL;
+  }
+  contentForTSF->EndComposition(*action);
+
+  // If this composition was restart but the composition doesn't modify
+  // anything, we should remove the pending composition for preventing to
+  // dispatch redundant composition events.
+  for (size_t i = mPendingActions.Length(), j = 1; i > 0; --i, ++j) {
+    PendingAction& pendingAction = mPendingActions[i - 1];
+    if (pendingAction.mType == PendingAction::Type::eCompositionStart) {
+      if (pendingAction.mData != action->mData) {
+        break;
+      }
+      // When only setting selection is necessary, we should append it.
+      if (pendingAction.mAdjustSelection) {
+        LONG selectionStart = pendingAction.mSelectionStart;
+        LONG selectionLength = pendingAction.mSelectionLength;
+
+        PendingAction* setSelection = mPendingActions.AppendElement();
+        setSelection->mType = PendingAction::Type::eSetSelection;
+        setSelection->mSelectionStart = selectionStart;
+        setSelection->mSelectionLength = selectionLength;
+        setSelection->mSelectionReversed = false;
+      }
+      // Remove the redundant pending composition.
+      mPendingActions.RemoveElementsAt(i - 1, j);
+      MOZ_LOG(gIMELog, LogLevel::Info,
+              ("0x%p   TSFTextStore::RecordCompositionEndAction(), "
+               "succeeded, but the composition was canceled due to redundant",
+               this));
+      return S_OK;
+    }
+  }
+
+  MOZ_LOG(
+      gIMELog, LogLevel::Info,
+      ("0x%p   TSFTextStore::RecordCompositionEndAction(), succeeded", this));
+  return S_OK;
+}
+
+STDMETHODIMP
+TSFTextStore::OnStartComposition(ITfCompositionView* pComposition, BOOL* pfOk) {
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p TSFTextStore::OnStartComposition(pComposition=0x%p, "
+           "pfOk=0x%p), mComposition=%s",
+           this, pComposition, pfOk, ToString(mComposition).c_str()));
+
+  AutoPendingActionAndContentFlusher flusher(this);
+
+  *pfOk = FALSE;
+
+  // Only one composition at a time
+  if (mComposition.isSome()) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::OnStartComposition() FAILED due to "
+             "there is another composition already (but returns S_OK)",
+             this));
+    return S_OK;
+  }
+
+  RefPtr<ITfRange> range;
+  HRESULT hr = pComposition->GetRange(getter_AddRefs(range));
+  if (FAILED(hr)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::OnStartComposition() FAILED due to "
+             "pComposition->GetRange() failure",
+             this));
+    return hr;
+  }
+  hr = RecordCompositionStartAction(pComposition, range, false);
+  if (FAILED(hr)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::OnStartComposition() FAILED due to "
+             "RecordCompositionStartAction() failure",
+             this));
+    return hr;
+  }
+
+  *pfOk = TRUE;
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p   TSFTextStore::OnStartComposition() succeeded", this));
+  return S_OK;
+}
+
+STDMETHODIMP
+TSFTextStore::OnUpdateComposition(ITfCompositionView* pComposition,
+                                  ITfRange* pRangeNew) {
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p TSFTextStore::OnUpdateComposition(pComposition=0x%p, "
+           "pRangeNew=0x%p), mComposition=%s",
+           this, pComposition, pRangeNew, ToString(mComposition).c_str()));
+
+  AutoPendingActionAndContentFlusher flusher(this);
+
+  if (!mDocumentMgr || !mContext) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::OnUpdateComposition() FAILED due to "
+             "not ready for the composition",
+             this));
+    return E_UNEXPECTED;
+  }
+  if (mComposition.isNothing()) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::OnUpdateComposition() FAILED due to "
+             "no active composition",
+             this));
+    return E_UNEXPECTED;
+  }
+  if (mComposition->GetView() != pComposition) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::OnUpdateComposition() FAILED due to "
+             "different composition view specified",
+             this));
+    return E_UNEXPECTED;
+  }
+
+  // pRangeNew is null when the update is not complete
+  if (!pRangeNew) {
+    MaybeDispatchKeyboardEventAsProcessedByIME();
+    if (mDestroyed) {
+      MOZ_LOG(gIMELog, LogLevel::Error,
+              ("0x%p   TSFTextStore::OnUpdateComposition() FAILED due to "
+               "destroyed during dispatching a keyboard event",
+               this));
+      return E_FAIL;
+    }
+    PendingAction* action = LastOrNewPendingCompositionUpdate();
+    action->mIncomplete = true;
+    MOZ_LOG(gIMELog, LogLevel::Info,
+            ("0x%p   TSFTextStore::OnUpdateComposition() succeeded but "
+             "not complete",
+             this));
+    return S_OK;
+  }
+
+  HRESULT hr = RestartCompositionIfNecessary(pRangeNew);
+  if (FAILED(hr)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::OnUpdateComposition() FAILED due to "
+             "RestartCompositionIfNecessary() failure",
+             this));
+    return hr;
+  }
+
+  hr = RecordCompositionUpdateAction();
+  if (FAILED(hr)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::OnUpdateComposition() FAILED due to "
+             "RecordCompositionUpdateAction() failure",
+             this));
+    return hr;
+  }
+
+  if (MOZ_LOG_TEST(gIMELog, LogLevel::Info)) {
+    Maybe<Selection>& selectionForTSF = SelectionForTSF();
+    if (selectionForTSF.isNothing()) {
+      MOZ_LOG(gIMELog, LogLevel::Error,
+              ("0x%p   TSFTextStore::OnUpdateComposition() FAILED due to "
+               "SelectionForTSF() failure",
+               this));
+      return S_OK;  // Don't return error only when we're logging.
+    }
+    MOZ_LOG(gIMELog, LogLevel::Info,
+            ("0x%p   TSFTextStore::OnUpdateComposition() succeeded: "
+             "mComposition=%s, SelectionForTSF()=%s",
+             this, ToString(mComposition).c_str(),
+             ToString(selectionForTSF).c_str()));
+  }
+  return S_OK;
+}
+
+STDMETHODIMP
+TSFTextStore::OnEndComposition(ITfCompositionView* pComposition) {
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p TSFTextStore::OnEndComposition(pComposition=0x%p), "
+           "mComposition=%s",
+           this, pComposition, ToString(mComposition).c_str()));
+
+  AutoPendingActionAndContentFlusher flusher(this);
+
+  if (mComposition.isNothing()) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::OnEndComposition() FAILED due to "
+             "no active composition",
+             this));
+    return E_UNEXPECTED;
+  }
+
+  if (mComposition->GetView() != pComposition) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::OnEndComposition() FAILED due to "
+             "different composition view specified",
+             this));
+    return E_UNEXPECTED;
+  }
+
+  HRESULT hr = RecordCompositionEndAction();
+  if (FAILED(hr)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::OnEndComposition() FAILED due to "
+             "RecordCompositionEndAction() failure",
+             this));
+    return hr;
+  }
+
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p   TSFTextStore::OnEndComposition(), succeeded", this));
+  return S_OK;
+}
+
+STDMETHODIMP
+TSFTextStore::AdviseMouseSink(ITfRangeACP* range, ITfMouseSink* pSink,
+                              DWORD* pdwCookie) {
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p TSFTextStore::AdviseMouseSink(range=0x%p, pSink=0x%p, "
+           "pdwCookie=0x%p)",
+           this, range, pSink, pdwCookie));
+
+  if (!pdwCookie) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::AdviseMouseSink() FAILED due to the "
+             "pdwCookie is null",
+             this));
+    return E_INVALIDARG;
+  }
+  // Initialize the result with invalid cookie for safety.
+  *pdwCookie = MouseTracker::kInvalidCookie;
+
+  if (!range) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::AdviseMouseSink() FAILED due to the "
+             "range is null",
+             this));
+    return E_INVALIDARG;
+  }
+  if (!pSink) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::AdviseMouseSink() FAILED due to the "
+             "pSink is null",
+             this));
+    return E_INVALIDARG;
+  }
+
+  // Looking for an unusing tracker.
+  MouseTracker* tracker = nullptr;
+  for (size_t i = 0; i < mMouseTrackers.Length(); i++) {
+    if (mMouseTrackers[i].IsUsing()) {
+      continue;
+    }
+    tracker = &mMouseTrackers[i];
+  }
+  // If there is no unusing tracker, create new one.
+  // XXX Should we make limitation of the number of installs?
+  if (!tracker) {
+    tracker = mMouseTrackers.AppendElement();
+    HRESULT hr = tracker->Init(this);
+    if (FAILED(hr)) {
+      MOZ_LOG(gIMELog, LogLevel::Error,
+              ("0x%p   TSFTextStore::AdviseMouseSink() FAILED due to "
+               "failure of MouseTracker::Init()",
+               this));
+      return hr;
+    }
+  }
+  HRESULT hr = tracker->AdviseSink(this, range, pSink);
+  if (FAILED(hr)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::AdviseMouseSink() FAILED due to failure "
+             "of MouseTracker::Init()",
+             this));
+    return hr;
+  }
+  *pdwCookie = tracker->Cookie();
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p   TSFTextStore::AdviseMouseSink(), succeeded, "
+           "*pdwCookie=%ld",
+           this, *pdwCookie));
+  return S_OK;
+}
+
+STDMETHODIMP
+TSFTextStore::UnadviseMouseSink(DWORD dwCookie) {
+  MOZ_LOG(
+      gIMELog, LogLevel::Info,
+      ("0x%p TSFTextStore::UnadviseMouseSink(dwCookie=%ld)", this, dwCookie));
+  if (dwCookie == MouseTracker::kInvalidCookie) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::UnadviseMouseSink() FAILED due to "
+             "the cookie is invalid value",
+             this));
+    return E_INVALIDARG;
+  }
+  // The cookie value must be an index of mMouseTrackers.
+  // We can use this shortcut for now.
+  if (static_cast<size_t>(dwCookie) >= mMouseTrackers.Length()) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::UnadviseMouseSink() FAILED due to "
+             "the cookie is too large value",
+             this));
+    return E_INVALIDARG;
+  }
+  MouseTracker& tracker = mMouseTrackers[dwCookie];
+  if (!tracker.IsUsing()) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::UnadviseMouseSink() FAILED due to "
+             "the found tracker uninstalled already",
+             this));
+    return E_INVALIDARG;
+  }
+  tracker.UnadviseSink();
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p   TSFTextStore::UnadviseMouseSink(), succeeded", this));
+  return S_OK;
+}
+
+// static
+nsresult TSFTextStore::OnFocusChange(bool aGotFocus, nsWindow* aFocusedWidget,
+                                     const InputContext& aContext) {
+  MOZ_LOG(gIMELog, LogLevel::Debug,
+          ("  TSFTextStore::OnFocusChange(aGotFocus=%s, "
+           "aFocusedWidget=0x%p, aContext=%s), "
+           "sThreadMgr=0x%p, sEnabledTextStore=0x%p",
+           GetBoolName(aGotFocus), aFocusedWidget,
+           mozilla::ToString(aContext).c_str(), sThreadMgr.get(),
+           sEnabledTextStore.get()));
+
+  if (NS_WARN_IF(!IsInTSFMode())) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  RefPtr<ITfDocumentMgr> prevFocusedDocumentMgr;
+  bool hasFocus = ThinksHavingFocus();
+  RefPtr<TSFTextStore> oldTextStore = sEnabledTextStore.forget();
+
+  // If currently oldTextStore still has focus, notifies TSF of losing focus.
+  if (hasFocus) {
+    RefPtr<ITfThreadMgr> threadMgr = sThreadMgr;
+    DebugOnly<HRESULT> hr = threadMgr->AssociateFocus(
+        oldTextStore->mWidget->GetWindowHandle(), nullptr,
+        getter_AddRefs(prevFocusedDocumentMgr));
+    NS_ASSERTION(SUCCEEDED(hr), "Disassociating focus failed");
+    NS_ASSERTION(prevFocusedDocumentMgr == oldTextStore->mDocumentMgr,
+                 "different documentMgr has been associated with the window");
+  }
+
+  // Even if there was a focused TextStore, we won't use it with new focused
+  // editor.  So, release it now.
+  if (oldTextStore) {
+    oldTextStore->Destroy();
+  }
+
+  if (NS_WARN_IF(!sThreadMgr)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("  TSFTextStore::OnFocusChange() FAILED, due to "
+             "sThreadMgr being destroyed during calling "
+             "ITfThreadMgr::AssociateFocus()"));
+    return NS_ERROR_FAILURE;
+  }
+  if (NS_WARN_IF(sEnabledTextStore)) {
+    MOZ_LOG(
+        gIMELog, LogLevel::Error,
+        ("  TSFTextStore::OnFocusChange() FAILED, due to "
+         "nested event handling has created another focused TextStore during "
+         "calling ITfThreadMgr::AssociateFocus()"));
+    return NS_ERROR_FAILURE;
+  }
+
+  // If this is a notification of blur, move focus to the dummy document
+  // manager.
+  if (!aGotFocus || !aContext.mIMEState.IsEditable()) {
+    RefPtr<ITfThreadMgr> threadMgr = sThreadMgr;
+    RefPtr<ITfDocumentMgr> disabledDocumentMgr = sDisabledDocumentMgr;
+    HRESULT hr = threadMgr->SetFocus(disabledDocumentMgr);
+    if (NS_WARN_IF(FAILED(hr))) {
+      MOZ_LOG(gIMELog, LogLevel::Error,
+              ("  TSFTextStore::OnFocusChange() FAILED due to "
+               "ITfThreadMgr::SetFocus() failure"));
+      return NS_ERROR_FAILURE;
+    }
+    return NS_OK;
+  }
+
+  // If an editor is getting focus, create new TextStore and set focus.
+  if (NS_WARN_IF(!CreateAndSetFocus(aFocusedWidget, aContext))) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("  TSFTextStore::OnFocusChange() FAILED due to "
+             "ITfThreadMgr::CreateAndSetFocus() failure"));
+    return NS_ERROR_FAILURE;
+  }
+  return NS_OK;
+}
+
+// static
+void TSFTextStore::EnsureToDestroyAndReleaseEnabledTextStoreIf(
+    RefPtr<TSFTextStore>& aTextStore) {
+  aTextStore->Destroy();
+  if (sEnabledTextStore == aTextStore) {
+    sEnabledTextStore = nullptr;
+  }
+  aTextStore = nullptr;
+}
+
+// static
+bool TSFTextStore::CreateAndSetFocus(nsWindow* aFocusedWidget,
+                                     const InputContext& aContext) {
+  // TSF might do something which causes that we need to access static methods
+  // of TSFTextStore.  At that time, sEnabledTextStore may be necessary.
+  // So, we should set sEnabledTextStore directly.
+  RefPtr<TSFTextStore> textStore = new TSFTextStore();
+  sEnabledTextStore = textStore;
+  if (NS_WARN_IF(!textStore->Init(aFocusedWidget, aContext))) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("  TSFTextStore::CreateAndSetFocus() FAILED due to "
+             "TSFTextStore::Init() failure"));
+    EnsureToDestroyAndReleaseEnabledTextStoreIf(textStore);
+    return false;
+  }
+  RefPtr<ITfDocumentMgr> newDocMgr = textStore->mDocumentMgr;
+  if (NS_WARN_IF(!newDocMgr)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("  TSFTextStore::CreateAndSetFocus() FAILED due to "
+             "invalid TSFTextStore::mDocumentMgr"));
+    EnsureToDestroyAndReleaseEnabledTextStoreIf(textStore);
+    return false;
+  }
+  if (aContext.mIMEState.mEnabled == IMEEnabled::Password) {
+    MarkContextAsKeyboardDisabled(textStore->mContext);
+    RefPtr<ITfContext> topContext;
+    newDocMgr->GetTop(getter_AddRefs(topContext));
+    if (topContext && topContext != textStore->mContext) {
+      MarkContextAsKeyboardDisabled(topContext);
+    }
+  }
+
+  HRESULT hr;
+  RefPtr<ITfThreadMgr> threadMgr = sThreadMgr;
+  hr = threadMgr->SetFocus(newDocMgr);
+
+  if (NS_WARN_IF(FAILED(hr))) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("  TSFTextStore::CreateAndSetFocus() FAILED due to "
+             "ITfTheadMgr::SetFocus() failure"));
+    EnsureToDestroyAndReleaseEnabledTextStoreIf(textStore);
+    return false;
+  }
+  if (NS_WARN_IF(!sThreadMgr)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("  TSFTextStore::CreateAndSetFocus() FAILED due to "
+             "sThreadMgr being destroyed during calling "
+             "ITfTheadMgr::SetFocus()"));
+    EnsureToDestroyAndReleaseEnabledTextStoreIf(textStore);
+    return false;
+  }
+  if (NS_WARN_IF(sEnabledTextStore != textStore)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("  TSFTextStore::CreateAndSetFocus() FAILED due to "
+             "creating TextStore has lost focus during calling "
+             "ITfThreadMgr::SetFocus()"));
+    EnsureToDestroyAndReleaseEnabledTextStoreIf(textStore);
+    return false;
+  }
+
+  // Use AssociateFocus() for ensuring that any native focus event
+  // never steal focus from our documentMgr.
+  RefPtr<ITfDocumentMgr> prevFocusedDocumentMgr;
+  hr = threadMgr->AssociateFocus(aFocusedWidget->GetWindowHandle(), newDocMgr,
+                                 getter_AddRefs(prevFocusedDocumentMgr));
+  if (NS_WARN_IF(FAILED(hr))) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("  TSFTextStore::CreateAndSetFocus() FAILED due to "
+             "ITfTheadMgr::AssociateFocus() failure"));
+    EnsureToDestroyAndReleaseEnabledTextStoreIf(textStore);
+    return false;
+  }
+  if (NS_WARN_IF(!sThreadMgr)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("  TSFTextStore::CreateAndSetFocus() FAILED due to "
+             "sThreadMgr being destroyed during calling "
+             "ITfTheadMgr::AssociateFocus()"));
+    EnsureToDestroyAndReleaseEnabledTextStoreIf(textStore);
+    return false;
+  }
+  if (NS_WARN_IF(sEnabledTextStore != textStore)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("  TSFTextStore::CreateAndSetFocus() FAILED due to "
+             "creating TextStore has lost focus during calling "
+             "ITfTheadMgr::AssociateFocus()"));
+    EnsureToDestroyAndReleaseEnabledTextStoreIf(textStore);
+    return false;
+  }
+
+  if (textStore->mSink) {
+    MOZ_LOG(gIMELog, LogLevel::Info,
+            ("  TSFTextStore::CreateAndSetFocus(), calling "
+             "ITextStoreACPSink::OnLayoutChange(TS_LC_CREATE) for 0x%p...",
+             textStore.get()));
+    RefPtr<ITextStoreACPSink> sink = textStore->mSink;
+    sink->OnLayoutChange(TS_LC_CREATE, TEXTSTORE_DEFAULT_VIEW);
+    if (NS_WARN_IF(sEnabledTextStore != textStore)) {
+      MOZ_LOG(gIMELog, LogLevel::Error,
+              ("  TSFTextStore::CreateAndSetFocus() FAILED due to "
+               "creating TextStore has lost focus during calling "
+               "ITextStoreACPSink::OnLayoutChange(TS_LC_CREATE)"));
+      EnsureToDestroyAndReleaseEnabledTextStoreIf(textStore);
+      return false;
+    }
+  }
+  return true;
+}
+
+// static
+IMENotificationRequests TSFTextStore::GetIMENotificationRequests() {
+  if (!sEnabledTextStore || NS_WARN_IF(!sEnabledTextStore->mDocumentMgr)) {
+    // If there is no active text store, we don't need any notifications
+    // since there is no sink which needs notifications.
+    return IMENotificationRequests();
+  }
+
+  // Otherwise, requests all notifications since even if some of them may not
+  // be required by the sink of active TIP, active TIP may be changed and
+  // other TIPs may need all notifications.
+  // Note that Windows temporarily steal focus from active window if the main
+  // process which created the window becomes busy.  In this case, we shouldn't
+  // commit composition since user may want to continue to compose the
+  // composition after becoming not busy.  Therefore, we need notifications
+  // even during deactive.
+  // Be aware, we don't need to check actual focused text store.  For example,
+  // MS-IME for Japanese handles focus messages by themselves and sets focused
+  // text store to nullptr when the process is being inactivated.  However,
+  // we still need to reuse sEnabledTextStore if the process is activated and
+  // focused element isn't changed.  Therefore, if sEnabledTextStore isn't
+  // nullptr, we need to keep notifying the sink even when it is not focused
+  // text store for the thread manager.
+  return IMENotificationRequests(
+      IMENotificationRequests::NOTIFY_TEXT_CHANGE |
+      IMENotificationRequests::NOTIFY_POSITION_CHANGE |
+      IMENotificationRequests::NOTIFY_MOUSE_BUTTON_EVENT_ON_CHAR |
+      IMENotificationRequests::NOTIFY_DURING_DEACTIVE);
+}
+
+nsresult TSFTextStore::OnTextChangeInternal(
+    const IMENotification& aIMENotification) {
+  const TextChangeDataBase& textChangeData = aIMENotification.mTextChangeData;
+
+  MOZ_LOG(gIMELog, LogLevel::Debug,
+          ("0x%p   TSFTextStore::OnTextChangeInternal(aIMENotification={ "
+           "mMessage=0x%08X, mTextChangeData=%s }), "
+           "mDestroyed=%s, mSink=0x%p, mSinkMask=%s, "
+           "mComposition=%s",
+           this, aIMENotification.mMessage,
+           mozilla::ToString(textChangeData).c_str(), GetBoolName(mDestroyed),
+           mSink.get(), GetSinkMaskNameStr(mSinkMask).get(),
+           ToString(mComposition).c_str()));
+
+  if (mDestroyed) {
+    // If this instance is already destroyed, we shouldn't notify TSF of any
+    // changes.
+    return NS_OK;
+  }
+
+  mDeferNotifyingTSFUntilNextUpdate = false;
+
+  // Different from selection change, we don't modify anything with text
+  // change data.  Therefore, if neither TSF not TIP wants text change
+  // notifications, we don't need to store the changes.
+  if (!mSink || !(mSinkMask & TS_AS_TEXT_CHANGE)) {
+    return NS_OK;
+  }
+
+  // Merge any text change data even if it's caused by composition.
+  mPendingTextChangeData.MergeWith(textChangeData);
+
+  MaybeFlushPendingNotifications();
+
+  return NS_OK;
+}
+
+void TSFTextStore::NotifyTSFOfTextChange() {
+  MOZ_ASSERT(!mDestroyed);
+  MOZ_ASSERT(!IsReadLocked());
+  MOZ_ASSERT(mComposition.isNothing());
+  MOZ_ASSERT(mPendingTextChangeData.IsValid());
+
+  // If the text changes are caused only by composition, we don't need to
+  // notify TSF of the text changes.
+  if (mPendingTextChangeData.mCausedOnlyByComposition) {
+    mPendingTextChangeData.Clear();
+    return;
+  }
+
+  // First, forget cached selection.
+  mSelectionForTSF.reset();
+
+  // For making it safer, we should check if there is a valid sink to receive
+  // text change notification.
+  if (NS_WARN_IF(!mSink) || NS_WARN_IF(!(mSinkMask & TS_AS_TEXT_CHANGE))) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::NotifyTSFOfTextChange() FAILED due to "
+             "mSink is not ready to call ITextStoreACPSink::OnTextChange()...",
+             this));
+    mPendingTextChangeData.Clear();
+    return;
+  }
+
+  if (NS_WARN_IF(!mPendingTextChangeData.IsInInt32Range())) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::NotifyTSFOfTextChange() FAILED due to "
+             "offset is too big for calling "
+             "ITextStoreACPSink::OnTextChange()...",
+             this));
+    mPendingTextChangeData.Clear();
+    return;
+  }
+
+  TS_TEXTCHANGE textChange;
+  textChange.acpStart = static_cast<LONG>(mPendingTextChangeData.mStartOffset);
+  textChange.acpOldEnd =
+      static_cast<LONG>(mPendingTextChangeData.mRemovedEndOffset);
+  textChange.acpNewEnd =
+      static_cast<LONG>(mPendingTextChangeData.mAddedEndOffset);
+  mPendingTextChangeData.Clear();
+
+  MOZ_LOG(
+      gIMELog, LogLevel::Info,
+      ("0x%p   TSFTextStore::NotifyTSFOfTextChange(), calling "
+       "ITextStoreACPSink::OnTextChange(0, { acpStart=%ld, acpOldEnd=%ld, "
+       "acpNewEnd=%ld })...",
+       this, textChange.acpStart, textChange.acpOldEnd, textChange.acpNewEnd));
+  RefPtr<ITextStoreACPSink> sink = mSink;
+  sink->OnTextChange(0, &textChange);
+}
+
+nsresult TSFTextStore::OnSelectionChangeInternal(
+    const IMENotification& aIMENotification) {
+  const SelectionChangeDataBase& selectionChangeData =
+      aIMENotification.mSelectionChangeData;
+  MOZ_LOG(gIMELog, LogLevel::Debug,
+          ("0x%p   TSFTextStore::OnSelectionChangeInternal("
+           "aIMENotification={ mSelectionChangeData=%s }), mDestroyed=%s, "
+           "mSink=0x%p, mSinkMask=%s, mIsRecordingActionsWithoutLock=%s, "
+           "mComposition=%s",
+           this, mozilla::ToString(selectionChangeData).c_str(),
+           GetBoolName(mDestroyed), mSink.get(),
+           GetSinkMaskNameStr(mSinkMask).get(),
+           GetBoolName(mIsRecordingActionsWithoutLock),
+           ToString(mComposition).c_str()));
+
+  if (mDestroyed) {
+    // If this instance is already destroyed, we shouldn't notify TSF of any
+    // changes.
+    return NS_OK;
+  }
+
+  mDeferNotifyingTSFUntilNextUpdate = false;
+
+  // Assign the new selection change data to the pending selection change data
+  // because only the latest selection data is necessary.
+  // Note that this is necessary to update mSelectionForTSF.  Therefore, even if
+  // neither TSF nor TIP wants selection change notifications, we need to
+  // store the selection information.
+  mPendingSelectionChangeData = Some(selectionChangeData);
+
+  // Flush remaining pending notifications here if it's possible.
+  MaybeFlushPendingNotifications();
+
+  // If we're available, we should create native caret instead of IMEHandler
+  // because we may have some cache to do it.
+  // Note that if we have composition, we'll notified composition-updated
+  // later so that we don't need to create native caret in such case.
+  if (!IsHandlingCompositionInContent() &&
+      IMEHandler::NeedsToCreateNativeCaret()) {
+    CreateNativeCaret();
+  }
+
+  return NS_OK;
+}
+
+void TSFTextStore::NotifyTSFOfSelectionChange() {
+  MOZ_ASSERT(!mDestroyed);
+  MOZ_ASSERT(!IsReadLocked());
+  MOZ_ASSERT(mComposition.isNothing());
+  MOZ_ASSERT(mPendingSelectionChangeData.isSome());
+
+  // If selection range isn't actually changed, we don't need to notify TSF
+  // of this selection change.
+  if (mSelectionForTSF.isNothing()) {
+    MOZ_DIAGNOSTIC_ASSERT(!mIsInitializingSelectionForTSF,
+                          "While mSelectionForTSF is being initialized, this "
+                          "should not be called");
+    mSelectionForTSF.emplace(*mPendingSelectionChangeData);
+  } else if (!mSelectionForTSF->SetSelection(*mPendingSelectionChangeData)) {
+    mPendingSelectionChangeData.reset();
+    MOZ_LOG(gIMELog, LogLevel::Debug,
+            ("0x%p   TSFTextStore::NotifyTSFOfSelectionChange(), "
+             "selection isn't actually changed.",
+             this));
+    return;
+  }
+
+  mPendingSelectionChangeData.reset();
+
+  if (!mSink || !(mSinkMask & TS_AS_SEL_CHANGE)) {
+    return;
+  }
+
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p   TSFTextStore::NotifyTSFOfSelectionChange(), calling "
+           "ITextStoreACPSink::OnSelectionChange()...",
+           this));
+  RefPtr<ITextStoreACPSink> sink = mSink;
+  sink->OnSelectionChange();
+}
+
+nsresult TSFTextStore::OnLayoutChangeInternal() {
+  if (mDestroyed) {
+    // If this instance is already destroyed, we shouldn't notify TSF of any
+    // changes.
+    return NS_OK;
+  }
+
+  NS_ENSURE_TRUE(mContext, NS_ERROR_FAILURE);
+  NS_ENSURE_TRUE(mSink, NS_ERROR_FAILURE);
+
+  mDeferNotifyingTSFUntilNextUpdate = false;
+
+  nsresult rv = NS_OK;
+
+  // We need to notify TSF of layout change even if the document is locked.
+  // So, don't use MaybeFlushPendingNotifications() for flushing pending
+  // layout change.
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p   TSFTextStore::OnLayoutChangeInternal(), calling "
+           "NotifyTSFOfLayoutChange()...",
+           this));
+  if (NS_WARN_IF(!NotifyTSFOfLayoutChange())) {
+    rv = NS_ERROR_FAILURE;
+  }
+
+  MOZ_LOG(gIMELog, LogLevel::Debug,
+          ("0x%p   TSFTextStore::OnLayoutChangeInternal(), calling "
+           "MaybeFlushPendingNotifications()...",
+           this));
+  MaybeFlushPendingNotifications();
+
+  return rv;
+}
+
+bool TSFTextStore::NotifyTSFOfLayoutChange() {
+  MOZ_ASSERT(!mDestroyed);
+
+  // If we're waiting a query of layout information from TIP, it means that
+  // we've returned TS_E_NOLAYOUT error.
+  bool returnedNoLayoutError = mHasReturnedNoLayoutError || mWaitingQueryLayout;
+
+  // If we returned TS_E_NOLAYOUT, TIP should query the computed layout again.
+  mWaitingQueryLayout = returnedNoLayoutError;
+
+  // For avoiding to call this method again at unlocking the document during
+  // calls of OnLayoutChange(), reset mHasReturnedNoLayoutError.
+  mHasReturnedNoLayoutError = false;
+
+  // Now, layout has been computed.  We should notify mContentForTSF for
+  // making GetTextExt() and GetACPFromPoint() not return TS_E_NOLAYOUT.
+  if (mContentForTSF.isSome()) {
+    mContentForTSF->OnLayoutChanged();
+  }
+
+  if (IMEHandler::NeedsToCreateNativeCaret()) {
+    // If we're available, we should create native caret instead of IMEHandler
+    // because we may have some cache to do it.
+    CreateNativeCaret();
+  } else {
+    // Now, the caret position is different from ours.  Destroy the native caret
+    // if we've create it only for GetTextExt().
+    IMEHandler::MaybeDestroyNativeCaret();
+  }
+
+  // This method should return true if either way succeeds.
+  bool ret = true;
+
+  if (mSink) {
+    MOZ_LOG(gIMELog, LogLevel::Info,
+            ("0x%p   TSFTextStore::NotifyTSFOfLayoutChange(), "
+             "calling ITextStoreACPSink::OnLayoutChange()...",
+             this));
+    RefPtr<ITextStoreACPSink> sink = mSink;
+    HRESULT hr = sink->OnLayoutChange(TS_LC_CHANGE, TEXTSTORE_DEFAULT_VIEW);
+    MOZ_LOG(gIMELog, LogLevel::Info,
+            ("0x%p   TSFTextStore::NotifyTSFOfLayoutChange(), "
+             "called ITextStoreACPSink::OnLayoutChange()",
+             this));
+    ret = SUCCEEDED(hr);
+  }
+
+  // The layout change caused by composition string change should cause
+  // calling ITfContextOwnerServices::OnLayoutChange() too.
+  if (returnedNoLayoutError && mContext) {
+    RefPtr<ITfContextOwnerServices> service;
+    mContext->QueryInterface(IID_ITfContextOwnerServices,
+                             getter_AddRefs(service));
+    if (service) {
+      MOZ_LOG(gIMELog, LogLevel::Info,
+              ("0x%p   TSFTextStore::NotifyTSFOfLayoutChange(), "
+               "calling ITfContextOwnerServices::OnLayoutChange()...",
+               this));
+      HRESULT hr = service->OnLayoutChange();
+      ret = ret && SUCCEEDED(hr);
+      MOZ_LOG(gIMELog, LogLevel::Info,
+              ("0x%p   TSFTextStore::NotifyTSFOfLayoutChange(), "
+               "called ITfContextOwnerServices::OnLayoutChange()",
+               this));
+    }
+  }
+
+  if (!mWidget || mWidget->Destroyed()) {
+    MOZ_LOG(gIMELog, LogLevel::Info,
+            ("0x%p   TSFTextStore::NotifyTSFOfLayoutChange(), "
+             "the widget is destroyed during calling OnLayoutChange()",
+             this));
+    return ret;
+  }
+
+  if (mDestroyed) {
+    MOZ_LOG(gIMELog, LogLevel::Info,
+            ("0x%p   TSFTextStore::NotifyTSFOfLayoutChange(), "
+             "the TSFTextStore instance is destroyed during calling "
+             "OnLayoutChange()",
+             this));
+    return ret;
+  }
+
+  // If we returned TS_E_NOLAYOUT again, we need another call of
+  // OnLayoutChange() later.  So, let's wait a query from TIP.
+  if (mHasReturnedNoLayoutError) {
+    mWaitingQueryLayout = true;
+  }
+
+  if (!mWaitingQueryLayout) {
+    MOZ_LOG(gIMELog, LogLevel::Info,
+            ("0x%p   TSFTextStore::NotifyTSFOfLayoutChange(), "
+             "succeeded notifying TIP of our layout change",
+             this));
+    return ret;
+  }
+
+  // If we believe that TIP needs to retry to retrieve our layout information
+  // later, we should call it with ::PostMessage() hack.
+  MOZ_LOG(gIMELog, LogLevel::Debug,
+          ("0x%p   TSFTextStore::NotifyTSFOfLayoutChange(), "
+           "posing  MOZ_WM_NOTIY_TSF_OF_LAYOUT_CHANGE for calling "
+           "OnLayoutChange() again...",
+           this));
+  ::PostMessage(mWidget->GetWindowHandle(), MOZ_WM_NOTIY_TSF_OF_LAYOUT_CHANGE,
+                reinterpret_cast<WPARAM>(this), 0);
+
+  return true;
+}
+
+void TSFTextStore::NotifyTSFOfLayoutChangeAgain() {
+  // Don't notify TSF of layout change after destroyed.
+  if (mDestroyed) {
+    mWaitingQueryLayout = false;
+    return;
+  }
+
+  // Before preforming this method, TIP has accessed our layout information by
+  // itself.  In such case, we don't need to call OnLayoutChange() anymore.
+  if (!mWaitingQueryLayout) {
+    return;
+  }
+
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("0x%p   TSFTextStore::NotifyTSFOfLayoutChangeAgain(), "
+           "calling NotifyTSFOfLayoutChange()...",
+           this));
+  NotifyTSFOfLayoutChange();
+
+  // If TIP didn't retrieved our layout information during a call of
+  // NotifyTSFOfLayoutChange(), it means that the TIP already gave up to
+  // retry to retrieve layout information or doesn't necessary it anymore.
+  // But don't forget that the call may have caused returning TS_E_NOLAYOUT
+  // error again.  In such case we still need to call OnLayoutChange() later.
+  if (!mHasReturnedNoLayoutError && mWaitingQueryLayout) {
+    mWaitingQueryLayout = false;
+    MOZ_LOG(gIMELog, LogLevel::Warning,
+            ("0x%p   TSFTextStore::NotifyTSFOfLayoutChangeAgain(), "
+             "called NotifyTSFOfLayoutChange() but TIP didn't retry to "
+             "retrieve the layout information",
+             this));
+  } else {
+    MOZ_LOG(gIMELog, LogLevel::Info,
+            ("0x%p   TSFTextStore::NotifyTSFOfLayoutChangeAgain(), "
+             "called NotifyTSFOfLayoutChange()",
+             this));
+  }
+}
+
+nsresult TSFTextStore::OnUpdateCompositionInternal() {
+  MOZ_LOG(gIMELog, LogLevel::Debug,
+          ("0x%p   TSFTextStore::OnUpdateCompositionInternal(), "
+           "mDestroyed=%s, mDeferNotifyingTSFUntilNextUpdate=%s",
+           this, GetBoolName(mDestroyed),
+           GetBoolName(mDeferNotifyingTSFUntilNextUpdate)));
+
+  // There are nothing to do after destroyed.
+  if (mDestroyed) {
+    return NS_OK;
+  }
+
+  // Update cached data now because all pending events have been handled now.
+  if (mContentForTSF.isSome()) {
+    mContentForTSF->OnCompositionEventsHandled();
+  }
+
+  // If composition is completely finished both in TSF/TIP and the focused
+  // editor which may be in a remote process, we can clear the cache and don't
+  // have it until starting next composition.
+  if (mComposition.isNothing() && !IsHandlingCompositionInContent()) {
+    mDeferClearingContentForTSF = false;
+  }
+  mDeferNotifyingTSFUntilNextUpdate = false;
+  MaybeFlushPendingNotifications();
+
+  // If we're available, we should create native caret instead of IMEHandler
+  // because we may have some cache to do it.
+  if (IMEHandler::NeedsToCreateNativeCaret()) {
+    CreateNativeCaret();
+  }
+
+  return NS_OK;
+}
+
+nsresult TSFTextStore::OnMouseButtonEventInternal(
+    const IMENotification& aIMENotification) {
+  if (mDestroyed) {
+    // If this instance is already destroyed, we shouldn't notify TSF of any
+    // events.
+    return NS_OK;
+  }
+
+  if (mMouseTrackers.IsEmpty()) {
+    return NS_OK;
+  }
+
+  MOZ_LOG(gIMELog, LogLevel::Debug,
+          ("0x%p   TSFTextStore::OnMouseButtonEventInternal("
+           "aIMENotification={ mEventMessage=%s, mOffset=%u, mCursorPos=%s, "
+           "mCharRect=%s, mButton=%s, mButtons=%s, mModifiers=%s })",
+           this, ToChar(aIMENotification.mMouseButtonEventData.mEventMessage),
+           aIMENotification.mMouseButtonEventData.mOffset,
+           ToString(aIMENotification.mMouseButtonEventData.mCursorPos).c_str(),
+           ToString(aIMENotification.mMouseButtonEventData.mCharRect).c_str(),
+           GetMouseButtonName(aIMENotification.mMouseButtonEventData.mButton),
+           GetMouseButtonsName(aIMENotification.mMouseButtonEventData.mButtons)
+               .get(),
+           GetModifiersName(aIMENotification.mMouseButtonEventData.mModifiers)
+               .get()));
+
+  uint32_t offset = aIMENotification.mMouseButtonEventData.mOffset;
+  if (offset > static_cast<uint32_t>(LONG_MAX)) {
+    return NS_OK;
+  }
+  LayoutDeviceIntRect charRect =
+      aIMENotification.mMouseButtonEventData.mCharRect;
+  LayoutDeviceIntPoint cursorPos =
+      aIMENotification.mMouseButtonEventData.mCursorPos;
+  ULONG quadrant = 1;
+  if (charRect.Width() > 0) {
+    int32_t cursorXInChar = cursorPos.x - charRect.X();
+    quadrant = cursorXInChar * 4 / charRect.Width();
+    quadrant = (quadrant + 2) % 4;
+  }
+  ULONG edge = quadrant < 2 ? offset + 1 : offset;
+  DWORD buttonStatus = 0;
+  bool isMouseUp =
+      aIMENotification.mMouseButtonEventData.mEventMessage == eMouseUp;
+  if (!isMouseUp) {
+    switch (aIMENotification.mMouseButtonEventData.mButton) {
+      case MouseButton::ePrimary:
+        buttonStatus = MK_LBUTTON;
+        break;
+      case MouseButton::eMiddle:
+        buttonStatus = MK_MBUTTON;
+        break;
+      case MouseButton::eSecondary:
+        buttonStatus = MK_RBUTTON;
+        break;
+    }
+  }
+  if (aIMENotification.mMouseButtonEventData.mModifiers & MODIFIER_CONTROL) {
+    buttonStatus |= MK_CONTROL;
+  }
+  if (aIMENotification.mMouseButtonEventData.mModifiers & MODIFIER_SHIFT) {
+    buttonStatus |= MK_SHIFT;
+  }
+  for (size_t i = 0; i < mMouseTrackers.Length(); i++) {
+    MouseTracker& tracker = mMouseTrackers[i];
+    if (!tracker.IsUsing() || tracker.Range().isNothing() ||
+        !tracker.Range()->IsOffsetInRange(offset)) {
+      continue;
+    }
+    if (tracker.OnMouseButtonEvent(edge - tracker.Range()->StartOffset(),
+                                   quadrant, buttonStatus)) {
+      return NS_SUCCESS_EVENT_CONSUMED;
+    }
+  }
+  return NS_OK;
+}
+
+void TSFTextStore::CreateNativeCaret() {
+  MOZ_ASSERT(!IMEHandler::IsA11yHandlingNativeCaret());
+
+  IMEHandler::MaybeDestroyNativeCaret();
+
+  // Don't create native caret after destroyed.
+  if (mDestroyed) {
+    return;
+  }
+
+  MOZ_LOG(gIMELog, LogLevel::Debug,
+          ("0x%p   TSFTextStore::CreateNativeCaret(), mComposition=%s", this,
+           ToString(mComposition).c_str()));
+
+  Maybe<Selection>& selectionForTSF = SelectionForTSF();
+  if (MOZ_UNLIKELY(selectionForTSF.isNothing())) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::CreateNativeCaret() FAILED due to "
+             "SelectionForTSF() failure",
+             this));
+    return;
+  }
+  if (!selectionForTSF->HasRange() && mComposition.isNothing()) {
+    // If there is no selection range nor composition, then, we don't have a
+    // good position to show windows of TIP...
+    // XXX It seems that storing last caret rect and using it in this case might
+    // be better?
+    MOZ_LOG(gIMELog, LogLevel::Warning,
+            ("0x%p   TSFTextStore::CreateNativeCaret() couludn't create native "
+             "caret due to no selection range",
+             this));
+    return;
+  }
+
+  WidgetQueryContentEvent queryCaretRectEvent(true, eQueryCaretRect, mWidget);
+  mWidget->InitEvent(queryCaretRectEvent);
+
+  WidgetQueryContentEvent::Options options;
+  // XXX If this is called without composition and the selection isn't
+  //     collapsed, is it OK?
+  int64_t caretOffset = selectionForTSF->HasRange()
+                            ? selectionForTSF->MaxOffset()
+                            : mComposition->StartOffset();
+  if (mComposition.isSome()) {
+    // If there is a composition, use the relative query for deciding caret
+    // position because composition might be different place from that
+    // TSFTextStore assumes.
+    options.mRelativeToInsertionPoint = true;
+    caretOffset -= mComposition->StartOffset();
+  } else if (!CanAccessActualContentDirectly()) {
+    // If TSF/TIP cannot access actual content directly, there may be pending
+    // text and/or selection changes which have not been notified TSF yet.
+    // Therefore, we should use the relative query from start of selection where
+    // TSFTextStore assumes since TSF/TIP computes the offset from our cached
+    // selection.
+    options.mRelativeToInsertionPoint = true;
+    caretOffset -= selectionForTSF->StartOffset();
+  }
+  queryCaretRectEvent.InitForQueryCaretRect(caretOffset, options);
+
+  DispatchEvent(queryCaretRectEvent);
+  if (NS_WARN_IF(queryCaretRectEvent.Failed())) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::CreateNativeCaret() FAILED due to "
+             "eQueryCaretRect failure (offset=%lld)",
+             this, caretOffset));
+    return;
+  }
+
+  if (!IMEHandler::CreateNativeCaret(static_cast<nsWindow*>(mWidget.get()),
+                                     queryCaretRectEvent.mReply->mRect)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::CreateNativeCaret() FAILED due to "
+             "IMEHandler::CreateNativeCaret() failure",
+             this));
+    return;
+  }
+}
+
+void TSFTextStore::CommitCompositionInternal(bool aDiscard) {
+  MOZ_LOG(gIMELog, LogLevel::Debug,
+          ("0x%p   TSFTextStore::CommitCompositionInternal(aDiscard=%s), "
+           "mSink=0x%p, mContext=0x%p, mComposition=%s",
+           this, GetBoolName(aDiscard), mSink.get(), mContext.get(),
+           ToString(mComposition).c_str()));
+
+  // If the document is locked, TSF will fail to commit composition since
+  // TSF needs another document lock.  So, let's put off the request.
+  // Note that TextComposition will commit composition in the focused editor
+  // with the latest composition string for web apps and waits asynchronous
+  // committing messages.  Therefore, we can and need to perform this
+  // asynchronously.
+  if (IsReadLocked()) {
+    if (mDeferCommittingComposition || mDeferCancellingComposition) {
+      MOZ_LOG(gIMELog, LogLevel::Debug,
+              ("0x%p   TSFTextStore::CommitCompositionInternal(), "
+               "does nothing because already called and waiting unlock...",
+               this));
+      return;
+    }
+    if (aDiscard) {
+      mDeferCancellingComposition = true;
+    } else {
+      mDeferCommittingComposition = true;
+    }
+    MOZ_LOG(gIMELog, LogLevel::Debug,
+            ("0x%p   TSFTextStore::CommitCompositionInternal(), "
+             "putting off to request to %s composition after unlocking the "
+             "document",
+             this, aDiscard ? "cancel" : "commit"));
+    return;
+  }
+
+  if (mComposition.isSome() && aDiscard) {
+    LONG endOffset = mComposition->EndOffset();
+    mComposition->SetData(EmptyString());
+    // Note that don't notify TSF of text change after this is destroyed.
+    if (mSink && !mDestroyed) {
+      TS_TEXTCHANGE textChange;
+      textChange.acpStart = mComposition->StartOffset();
+      textChange.acpOldEnd = endOffset;
+      textChange.acpNewEnd = mComposition->StartOffset();
+      MOZ_LOG(gIMELog, LogLevel::Info,
+              ("0x%p   TSFTextStore::CommitCompositionInternal(), calling"
+               "mSink->OnTextChange(0, { acpStart=%ld, acpOldEnd=%ld, "
+               "acpNewEnd=%ld })...",
+               this, textChange.acpStart, textChange.acpOldEnd,
+               textChange.acpNewEnd));
+      RefPtr<ITextStoreACPSink> sink = mSink;
+      sink->OnTextChange(0, &textChange);
+    }
+  }
+  // Terminate two contexts, the base context (mContext) and the top
+  // if the top context is not the same as the base context
+  RefPtr<ITfContext> context = mContext;
+  do {
+    if (context) {
+      RefPtr<ITfContextOwnerCompositionServices> services;
+      context->QueryInterface(IID_ITfContextOwnerCompositionServices,
+                              getter_AddRefs(services));
+      if (services) {
+        MOZ_LOG(gIMELog, LogLevel::Debug,
+                ("0x%p   TSFTextStore::CommitCompositionInternal(), "
+                 "requesting TerminateComposition() for the context 0x%p...",
+                 this, context.get()));
+        services->TerminateComposition(nullptr);
+      }
+    }
+    if (context != mContext) break;
+    if (mDocumentMgr) mDocumentMgr->GetTop(getter_AddRefs(context));
+  } while (context != mContext);
+}
+
+static bool GetCompartment(IUnknown* pUnk, const GUID& aID,
+                           ITfCompartment** aCompartment) {
+  if (!pUnk) return false;
+
+  RefPtr<ITfCompartmentMgr> compMgr;
+  pUnk->QueryInterface(IID_ITfCompartmentMgr, getter_AddRefs(compMgr));
+  if (!compMgr) return false;
+
+  return SUCCEEDED(compMgr->GetCompartment(aID, aCompartment)) &&
+         (*aCompartment) != nullptr;
+}
+
+// static
+void TSFTextStore::SetIMEOpenState(bool aState) {
+  MOZ_LOG(gIMELog, LogLevel::Debug,
+          ("TSFTextStore::SetIMEOpenState(aState=%s)", GetBoolName(aState)));
+
+  if (!sThreadMgr) {
+    return;
+  }
+
+  RefPtr<ITfCompartment> comp = GetCompartmentForOpenClose();
+  if (NS_WARN_IF(!comp)) {
+    MOZ_LOG(gIMELog, LogLevel::Debug,
+            ("  TSFTextStore::SetIMEOpenState() FAILED due to"
+             "no compartment available"));
+    return;
+  }
+
+  VARIANT variant;
+  variant.vt = VT_I4;
+  variant.lVal = aState;
+  HRESULT hr = comp->SetValue(sClientId, &variant);
+  if (NS_WARN_IF(FAILED(hr))) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("  TSFTextStore::SetIMEOpenState() FAILED due to "
+             "ITfCompartment::SetValue() failure, hr=0x%08lX",
+             hr));
+    return;
+  }
+  MOZ_LOG(gIMELog, LogLevel::Debug,
+          ("  TSFTextStore::SetIMEOpenState(), setting "
+           "0x%04lX to GUID_COMPARTMENT_KEYBOARD_OPENCLOSE...",
+           variant.lVal));
+}
+
+// static
+bool TSFTextStore::GetIMEOpenState() {
+  if (!sThreadMgr) {
+    return false;
+  }
+
+  RefPtr<ITfCompartment> comp = GetCompartmentForOpenClose();
+  if (NS_WARN_IF(!comp)) {
+    return false;
+  }
+
+  VARIANT variant;
+  ::VariantInit(&variant);
+  HRESULT hr = comp->GetValue(&variant);
+  if (NS_WARN_IF(FAILED(hr))) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("TSFTextStore::GetIMEOpenState() FAILED due to "
+             "ITfCompartment::GetValue() failure, hr=0x%08lX",
+             hr));
+    return false;
+  }
+  // Until IME is open in this process, the result may be empty.
+  if (variant.vt == VT_EMPTY) {
+    return false;
+  }
+  if (NS_WARN_IF(variant.vt != VT_I4)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("TSFTextStore::GetIMEOpenState() FAILED due to "
+             "invalid result of ITfCompartment::GetValue()"));
+    ::VariantClear(&variant);
+    return false;
+  }
+
+  return variant.lVal != 0;
+}
+
+// static
+void TSFTextStore::SetInputContext(nsWindow* aWidget,
+                                   const InputContext& aContext,
+                                   const InputContextAction& aAction) {
+  MOZ_LOG(gIMELog, LogLevel::Debug,
+          ("TSFTextStore::SetInputContext(aWidget=%p, "
+           "aContext=%s, aAction.mFocusChange=%s), "
+           "sEnabledTextStore(0x%p)={ mWidget=0x%p }, ThinksHavingFocus()=%s",
+           aWidget, mozilla::ToString(aContext).c_str(),
+           GetFocusChangeName(aAction.mFocusChange), sEnabledTextStore.get(),
+           sEnabledTextStore ? sEnabledTextStore->mWidget.get() : nullptr,
+           GetBoolName(ThinksHavingFocus())));
+
+  switch (aAction.mFocusChange) {
+    case InputContextAction::WIDGET_CREATED:
+      // If this is called when the widget is created, there is nothing to do.
+      return;
+    case InputContextAction::FOCUS_NOT_CHANGED:
+    case InputContextAction::MENU_LOST_PSEUDO_FOCUS:
+      if (NS_WARN_IF(!IsInTSFMode())) {
+        return;
+      }
+      // In these cases, `NOTIFY_IME_OF_FOCUS` won't be sent.  Therefore,
+      // we need to reset text store for new state right now.
+      break;
+    default:
+      NS_WARNING_ASSERTION(IsInTSFMode(),
+                           "Why is this called when TSF is disabled?");
+      if (sEnabledTextStore) {
+        RefPtr<TSFTextStore> textStore(sEnabledTextStore);
+        textStore->mInPrivateBrowsing = aContext.mInPrivateBrowsing;
+        textStore->SetInputScope(aContext.mHTMLInputType,
+                                 aContext.mHTMLInputMode);
+        if (aContext.mURI) {
+          nsAutoCString spec;
+          if (NS_SUCCEEDED(aContext.mURI->GetSpec(spec))) {
+            CopyUTF8toUTF16(spec, textStore->mDocumentURL);
+          } else {
+            textStore->mDocumentURL.Truncate();
+          }
+        } else {
+          textStore->mDocumentURL.Truncate();
+        }
+      }
+      return;
+  }
+
+  // If focus isn't actually changed but the enabled state is changed,
+  // emulate the focus move.
+  if (!ThinksHavingFocus() && aContext.mIMEState.IsEditable()) {
+    if (!IMEHandler::GetFocusedWindow()) {
+      MOZ_LOG(gIMELog, LogLevel::Error,
+              ("  TSFTextStore::SetInputContent() gets called to enable IME, "
+               "but IMEHandler has not received focus notification"));
+    } else {
+      MOZ_LOG(gIMELog, LogLevel::Debug,
+              ("  TSFTextStore::SetInputContent() emulates focus for IME "
+               "state change"));
+      OnFocusChange(true, aWidget, aContext);
+    }
+  } else if (ThinksHavingFocus() && !aContext.mIMEState.IsEditable()) {
+    MOZ_LOG(gIMELog, LogLevel::Debug,
+            ("  TSFTextStore::SetInputContent() emulates blur for IME "
+             "state change"));
+    OnFocusChange(false, aWidget, aContext);
+  }
+}
+
+// static
+void TSFTextStore::MarkContextAsKeyboardDisabled(ITfContext* aContext) {
+  VARIANT variant_int4_value1;
+  variant_int4_value1.vt = VT_I4;
+  variant_int4_value1.lVal = 1;
+
+  RefPtr<ITfCompartment> comp;
+  if (!GetCompartment(aContext, GUID_COMPARTMENT_KEYBOARD_DISABLED,
+                      getter_AddRefs(comp))) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("TSFTextStore::MarkContextAsKeyboardDisabled() failed"
+             "aContext=0x%p...",
+             aContext));
+    return;
+  }
+
+  MOZ_LOG(gIMELog, LogLevel::Debug,
+          ("TSFTextStore::MarkContextAsKeyboardDisabled(), setting "
+           "to disable context 0x%p...",
+           aContext));
+  comp->SetValue(sClientId, &variant_int4_value1);
+}
+
+// static
+void TSFTextStore::MarkContextAsEmpty(ITfContext* aContext) {
+  VARIANT variant_int4_value1;
+  variant_int4_value1.vt = VT_I4;
+  variant_int4_value1.lVal = 1;
+
+  RefPtr<ITfCompartment> comp;
+  if (!GetCompartment(aContext, GUID_COMPARTMENT_EMPTYCONTEXT,
+                      getter_AddRefs(comp))) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("TSFTextStore::MarkContextAsEmpty() failed"
+             "aContext=0x%p...",
+             aContext));
+    return;
+  }
+
+  MOZ_LOG(gIMELog, LogLevel::Debug,
+          ("TSFTextStore::MarkContextAsEmpty(), setting "
+           "to mark empty context 0x%p...",
+           aContext));
+  comp->SetValue(sClientId, &variant_int4_value1);
+}
+
+// static
+void TSFTextStore::Initialize() {
+  MOZ_LOG(gIMELog, LogLevel::Info, ("TSFTextStore::Initialize() is called..."));
+
+  if (sThreadMgr) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("  TSFTextStore::Initialize() FAILED due to already initialized"));
+    return;
+  }
+
+  const bool enableTsf = StaticPrefs::intl_tsf_enabled_AtStartup();
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("  TSFTextStore::Initialize(), TSF is %s",
+           enableTsf ? "enabled" : "disabled"));
+  if (!enableTsf) {
+    return;
+  }
+
+  RefPtr<ITfThreadMgr> threadMgr;
+  HRESULT hr =
+      ::CoCreateInstance(CLSID_TF_ThreadMgr, nullptr, CLSCTX_INPROC_SERVER,
+                         IID_ITfThreadMgr, getter_AddRefs(threadMgr));
+  if (FAILED(hr) || !threadMgr) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("  TSFTextStore::Initialize() FAILED to "
+             "create the thread manager, hr=0x%08lX",
+             hr));
+    return;
+  }
+
+  hr = threadMgr->Activate(&sClientId);
+  if (FAILED(hr)) {
+    MOZ_LOG(
+        gIMELog, LogLevel::Error,
+        ("  TSFTextStore::Initialize() FAILED to activate, hr=0x%08lX", hr));
+    return;
+  }
+
+  RefPtr<ITfDocumentMgr> disabledDocumentMgr;
+  hr = threadMgr->CreateDocumentMgr(getter_AddRefs(disabledDocumentMgr));
+  if (FAILED(hr) || !disabledDocumentMgr) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("  TSFTextStore::Initialize() FAILED to create "
+             "a document manager for disabled mode, hr=0x%08lX",
+             hr));
+    return;
+  }
+
+  RefPtr<ITfContext> disabledContext;
+  DWORD editCookie = 0;
+  hr = disabledDocumentMgr->CreateContext(
+      sClientId, 0, nullptr, getter_AddRefs(disabledContext), &editCookie);
+  if (FAILED(hr) || !disabledContext) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("  TSFTextStore::Initialize() FAILED to create "
+             "a context for disabled mode, hr=0x%08lX",
+             hr));
+    return;
+  }
+
+  MarkContextAsKeyboardDisabled(disabledContext);
+  MarkContextAsEmpty(disabledContext);
+
+  sThreadMgr = threadMgr;
+  sDisabledDocumentMgr = disabledDocumentMgr;
+  sDisabledContext = disabledContext;
+
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("  TSFTextStore::Initialize(), sThreadMgr=0x%p, "
+           "sClientId=0x%08lX, sDisabledDocumentMgr=0x%p, sDisabledContext=%p",
+           sThreadMgr.get(), sClientId, sDisabledDocumentMgr.get(),
+           sDisabledContext.get()));
+}
+
+// static
+already_AddRefed<ITfThreadMgr> TSFTextStore::GetThreadMgr() {
+  RefPtr<ITfThreadMgr> threadMgr = sThreadMgr;
+  return threadMgr.forget();
+}
+
+// static
+already_AddRefed<ITfMessagePump> TSFTextStore::GetMessagePump() {
+  static bool sInitialized = false;
+  if (!sThreadMgr) {
+    return nullptr;
+  }
+  if (sMessagePump) {
+    RefPtr<ITfMessagePump> messagePump = sMessagePump;
+    return messagePump.forget();
+  }
+  // If it tried to retrieve ITfMessagePump from sThreadMgr but it failed,
+  // we shouldn't retry it at every message due to performance reason.
+  // Although this shouldn't occur actually.
+  if (sInitialized) {
+    return nullptr;
+  }
+  sInitialized = true;
+
+  RefPtr<ITfMessagePump> messagePump;
+  HRESULT hr = sThreadMgr->QueryInterface(IID_ITfMessagePump,
+                                          getter_AddRefs(messagePump));
+  if (NS_WARN_IF(FAILED(hr)) || NS_WARN_IF(!messagePump)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("TSFTextStore::GetMessagePump() FAILED to "
+             "QI message pump from the thread manager, hr=0x%08lX",
+             hr));
+    return nullptr;
+  }
+  sMessagePump = messagePump;
+  return messagePump.forget();
+}
+
+// static
+already_AddRefed<ITfDisplayAttributeMgr>
+TSFTextStore::GetDisplayAttributeMgr() {
+  RefPtr<ITfDisplayAttributeMgr> displayAttributeMgr;
+  if (sDisplayAttrMgr) {
+    displayAttributeMgr = sDisplayAttrMgr;
+    return displayAttributeMgr.forget();
+  }
+
+  HRESULT hr = ::CoCreateInstance(
+      CLSID_TF_DisplayAttributeMgr, nullptr, CLSCTX_INPROC_SERVER,
+      IID_ITfDisplayAttributeMgr, getter_AddRefs(displayAttributeMgr));
+  if (NS_WARN_IF(FAILED(hr)) || NS_WARN_IF(!displayAttributeMgr)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("TSFTextStore::GetDisplayAttributeMgr() FAILED to create "
+             "a display attribute manager instance, hr=0x%08lX",
+             hr));
+    return nullptr;
+  }
+  sDisplayAttrMgr = displayAttributeMgr;
+  return displayAttributeMgr.forget();
+}
+
+// static
+already_AddRefed<ITfCategoryMgr> TSFTextStore::GetCategoryMgr() {
+  RefPtr<ITfCategoryMgr> categoryMgr;
+  if (sCategoryMgr) {
+    categoryMgr = sCategoryMgr;
+    return categoryMgr.forget();
+  }
+  HRESULT hr =
+      ::CoCreateInstance(CLSID_TF_CategoryMgr, nullptr, CLSCTX_INPROC_SERVER,
+                         IID_ITfCategoryMgr, getter_AddRefs(categoryMgr));
+  if (NS_WARN_IF(FAILED(hr)) || NS_WARN_IF(!categoryMgr)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("TSFTextStore::GetCategoryMgr() FAILED to create "
+             "a category manager instance, hr=0x%08lX",
+             hr));
+    return nullptr;
+  }
+  sCategoryMgr = categoryMgr;
+  return categoryMgr.forget();
+}
+
+// static
+already_AddRefed<ITfCompartment> TSFTextStore::GetCompartmentForOpenClose() {
+  if (sCompartmentForOpenClose) {
+    RefPtr<ITfCompartment> compartment = sCompartmentForOpenClose;
+    return compartment.forget();
+  }
+
+  if (!sThreadMgr) {
+    return nullptr;
+  }
+
+  RefPtr<ITfCompartmentMgr> compartmentMgr;
+  HRESULT hr = sThreadMgr->QueryInterface(IID_ITfCompartmentMgr,
+                                          getter_AddRefs(compartmentMgr));
+  if (NS_WARN_IF(FAILED(hr)) || NS_WARN_IF(!compartmentMgr)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("TSFTextStore::GetCompartmentForOpenClose() FAILED due to"
+             "sThreadMgr not having ITfCompartmentMgr, hr=0x%08lX",
+             hr));
+    return nullptr;
+  }
+
+  RefPtr<ITfCompartment> compartment;
+  hr = compartmentMgr->GetCompartment(GUID_COMPARTMENT_KEYBOARD_OPENCLOSE,
+                                      getter_AddRefs(compartment));
+  if (NS_WARN_IF(FAILED(hr)) || NS_WARN_IF(!compartment)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("TSFTextStore::GetCompartmentForOpenClose() FAILED due to"
+             "ITfCompartmentMgr::GetCompartment() failuere, hr=0x%08lX",
+             hr));
+    return nullptr;
+  }
+
+  sCompartmentForOpenClose = compartment;
+  return compartment.forget();
+}
+
+// static
+already_AddRefed<ITfInputProcessorProfiles>
+TSFTextStore::GetInputProcessorProfiles() {
+  RefPtr<ITfInputProcessorProfiles> inputProcessorProfiles;
+  if (sInputProcessorProfiles) {
+    inputProcessorProfiles = sInputProcessorProfiles;
+    return inputProcessorProfiles.forget();
+  }
+  // XXX MSDN documents that ITfInputProcessorProfiles is available only on
+  //     desktop apps.  However, there is no known way to obtain
+  //     ITfInputProcessorProfileMgr instance without ITfInputProcessorProfiles
+  //     instance.
+  HRESULT hr = ::CoCreateInstance(
+      CLSID_TF_InputProcessorProfiles, nullptr, CLSCTX_INPROC_SERVER,
+      IID_ITfInputProcessorProfiles, getter_AddRefs(inputProcessorProfiles));
+  if (NS_WARN_IF(FAILED(hr)) || NS_WARN_IF(!inputProcessorProfiles)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("TSFTextStore::GetInputProcessorProfiles() FAILED to create input "
+             "processor profiles, hr=0x%08lX",
+             hr));
+    return nullptr;
+  }
+  sInputProcessorProfiles = inputProcessorProfiles;
+  return inputProcessorProfiles.forget();
+}
+
+// static
+void TSFTextStore::Terminate() {
+  MOZ_LOG(gIMELog, LogLevel::Info, ("TSFTextStore::Terminate()"));
+
+  TSFStaticSink::Shutdown();
+
+  sDisplayAttrMgr = nullptr;
+  sCategoryMgr = nullptr;
+  sEnabledTextStore = nullptr;
+  sDisabledDocumentMgr = nullptr;
+  sDisabledContext = nullptr;
+  sCompartmentForOpenClose = nullptr;
+  sInputProcessorProfiles = nullptr;
+  sClientId = 0;
+  if (sThreadMgr) {
+    sThreadMgr->Deactivate();
+    sThreadMgr = nullptr;
+    sMessagePump = nullptr;
+    sKeystrokeMgr = nullptr;
+  }
+}
+
+// static
+bool TSFTextStore::ProcessRawKeyMessage(const MSG& aMsg) {
+  if (!sThreadMgr) {
+    return false;  // not in TSF mode
+  }
+  static bool sInitialized = false;
+  if (!sKeystrokeMgr) {
+    // If it tried to retrieve ITfKeystrokeMgr from sThreadMgr but it failed,
+    // we shouldn't retry it at every keydown nor keyup due to performance
+    // reason.  Although this shouldn't occur actually.
+    if (sInitialized) {
+      return false;
+    }
+    sInitialized = true;
+    RefPtr<ITfKeystrokeMgr> keystrokeMgr;
+    HRESULT hr = sThreadMgr->QueryInterface(IID_ITfKeystrokeMgr,
+                                            getter_AddRefs(keystrokeMgr));
+    if (NS_WARN_IF(FAILED(hr)) || NS_WARN_IF(!keystrokeMgr)) {
+      MOZ_LOG(gIMELog, LogLevel::Error,
+              ("TSFTextStore::ProcessRawKeyMessage() FAILED to "
+               "QI keystroke manager from the thread manager, hr=0x%08lX",
+               hr));
+      return false;
+    }
+    sKeystrokeMgr = keystrokeMgr.forget();
+  }
+
+  if (aMsg.message == WM_KEYDOWN) {
+    RefPtr<TSFTextStore> textStore(sEnabledTextStore);
+    if (textStore) {
+      textStore->OnStartToHandleKeyMessage();
+      if (NS_WARN_IF(textStore != sEnabledTextStore)) {
+        // Let's handle the key message with new focused TSFTextStore.
+        textStore = sEnabledTextStore;
+      }
+    }
+    AutoRestore<const MSG*> savePreviousKeyMsg(sHandlingKeyMsg);
+    AutoRestore<bool> saveKeyEventDispatched(sIsKeyboardEventDispatched);
+    sHandlingKeyMsg = &aMsg;
+    sIsKeyboardEventDispatched = false;
+    BOOL eaten;
+    RefPtr<ITfKeystrokeMgr> keystrokeMgr = sKeystrokeMgr;
+    HRESULT hr = keystrokeMgr->TestKeyDown(aMsg.wParam, aMsg.lParam, &eaten);
+    if (FAILED(hr) || !sKeystrokeMgr || !eaten) {
+      return false;
+    }
+    hr = keystrokeMgr->KeyDown(aMsg.wParam, aMsg.lParam, &eaten);
+    if (textStore) {
+      textStore->OnEndHandlingKeyMessage(!!eaten);
+    }
+    return SUCCEEDED(hr) &&
+           (eaten || !sKeystrokeMgr || sIsKeyboardEventDispatched);
+  }
+  if (aMsg.message == WM_KEYUP) {
+    RefPtr<TSFTextStore> textStore(sEnabledTextStore);
+    if (textStore) {
+      textStore->OnStartToHandleKeyMessage();
+      if (NS_WARN_IF(textStore != sEnabledTextStore)) {
+        // Let's handle the key message with new focused TSFTextStore.
+        textStore = sEnabledTextStore;
+      }
+    }
+    AutoRestore<const MSG*> savePreviousKeyMsg(sHandlingKeyMsg);
+    AutoRestore<bool> saveKeyEventDispatched(sIsKeyboardEventDispatched);
+    sHandlingKeyMsg = &aMsg;
+    sIsKeyboardEventDispatched = false;
+    BOOL eaten;
+    RefPtr<ITfKeystrokeMgr> keystrokeMgr = sKeystrokeMgr;
+    HRESULT hr = keystrokeMgr->TestKeyUp(aMsg.wParam, aMsg.lParam, &eaten);
+    if (FAILED(hr) || !sKeystrokeMgr || !eaten) {
+      return false;
+    }
+    hr = keystrokeMgr->KeyUp(aMsg.wParam, aMsg.lParam, &eaten);
+    if (textStore) {
+      textStore->OnEndHandlingKeyMessage(!!eaten);
+    }
+    return SUCCEEDED(hr) &&
+           (eaten || !sKeystrokeMgr || sIsKeyboardEventDispatched);
+  }
+  return false;
+}
+
+// static
+void TSFTextStore::ProcessMessage(nsWindow* aWindow, UINT aMessage,
+                                  WPARAM& aWParam, LPARAM& aLParam,
+                                  MSGResult& aResult) {
+  switch (aMessage) {
+    case WM_IME_SETCONTEXT:
+      // If a windowless plugin had focus and IME was handled on it, composition
+      // window was set the position.  After that, even in TSF mode, WinXP keeps
+      // to use composition window at the position if the active IME is not
+      // aware TSF.  For avoiding this issue, we need to hide the composition
+      // window here.
+      if (aWParam) {
+        aLParam &= ~ISC_SHOWUICOMPOSITIONWINDOW;
+      }
+      break;
+    case WM_ENTERIDLE:
+      // When an modal dialog such as a file picker is open, composition
+      // should be committed because IME might be used on it.
+      if (!IsComposingOn(aWindow)) {
+        break;
+      }
+      CommitComposition(false);
+      break;
+    case MOZ_WM_NOTIY_TSF_OF_LAYOUT_CHANGE: {
+      TSFTextStore* maybeTextStore = reinterpret_cast<TSFTextStore*>(aWParam);
+      if (maybeTextStore == sEnabledTextStore) {
+        RefPtr<TSFTextStore> textStore(maybeTextStore);
+        textStore->NotifyTSFOfLayoutChangeAgain();
+      }
+      break;
+    }
+  }
+}
+
+// static
+bool TSFTextStore::IsIMM_IMEActive() {
+  return TSFStaticSink::IsIMM_IMEActive();
+}
+
+// static
+bool TSFTextStore::IsMSJapaneseIMEActive() {
+  return TSFStaticSink::IsMSJapaneseIMEActive();
+}
+
+// static
+bool TSFTextStore::IsGoogleJapaneseInputActive() {
+  return TSFStaticSink::IsGoogleJapaneseInputActive();
+}
+
+// static
+bool TSFTextStore::IsATOKActive() { return TSFStaticSink::IsATOKActive(); }
+
+/******************************************************************************
+ *  TSFTextStore::Content
+ *****************************************************************************/
+
+const nsDependentSubstring TSFTextStore::Content::GetSelectedText() const {
+  if (NS_WARN_IF(mSelection.isNothing())) {
+    return nsDependentSubstring();
+  }
+  return GetSubstring(static_cast<uint32_t>(mSelection->StartOffset()),
+                      static_cast<uint32_t>(mSelection->Length()));
+}
+
+const nsDependentSubstring TSFTextStore::Content::GetSubstring(
+    uint32_t aStart, uint32_t aLength) const {
+  return nsDependentSubstring(mText, aStart, aLength);
+}
+
+void TSFTextStore::Content::ReplaceSelectedTextWith(const nsAString& aString) {
+  if (NS_WARN_IF(mSelection.isNothing())) {
+    return;
+  }
+  ReplaceTextWith(mSelection->StartOffset(), mSelection->Length(), aString);
+}
+
+inline uint32_t FirstDifferentCharOffset(const nsAString& aStr1,
+                                         const nsAString& aStr2) {
+  MOZ_ASSERT(aStr1 != aStr2);
+  uint32_t i = 0;
+  uint32_t minLength = std::min(aStr1.Length(), aStr2.Length());
+  for (; i < minLength && aStr1[i] == aStr2[i]; i++) {
+    /* nothing to do */
+  }
+  return i;
+}
+
+void TSFTextStore::Content::ReplaceTextWith(LONG aStart, LONG aLength,
+                                            const nsAString& aReplaceString) {
+  MOZ_ASSERT(aStart >= 0);
+  MOZ_ASSERT(aLength >= 0);
+  const nsDependentSubstring replacedString = GetSubstring(
+      static_cast<uint32_t>(aStart), static_cast<uint32_t>(aLength));
+  if (aReplaceString != replacedString) {
+    uint32_t firstDifferentOffset = mMinModifiedOffset.valueOr(UINT32_MAX);
+    if (mComposition.isSome()) {
+      // Emulate text insertion during compositions, because during a
+      // composition, editor expects the whole composition string to
+      // be sent in eCompositionChange, not just the inserted part.
+      // The actual eCompositionChange will be sent in SetSelection
+      // or OnUpdateComposition.
+      MOZ_ASSERT(aStart >= mComposition->StartOffset());
+      MOZ_ASSERT(aStart + aLength <= mComposition->EndOffset());
+      mComposition->ReplaceData(
+          static_cast<uint32_t>(aStart - mComposition->StartOffset()),
+          static_cast<uint32_t>(aLength), aReplaceString);
+      // TIP may set composition string twice or more times during a document
+      // lock.  Therefore, we should compute the first difference offset with
+      // mLastComposition.
+      if (mLastComposition.isNothing()) {
+        firstDifferentOffset = mComposition->StartOffset();
+      } else if (mComposition->DataRef() != mLastComposition->DataRef()) {
+        firstDifferentOffset =
+            mComposition->StartOffset() +
+            FirstDifferentCharOffset(mComposition->DataRef(),
+                                     mLastComposition->DataRef());
+        // The previous change to the composition string is canceled.
+        if (mMinModifiedOffset.isSome() &&
+            mMinModifiedOffset.value() >=
+                static_cast<uint32_t>(mComposition->StartOffset()) &&
+            mMinModifiedOffset.value() < firstDifferentOffset) {
+          mMinModifiedOffset = Some(firstDifferentOffset);
+        }
+      } else if (mMinModifiedOffset.isSome() &&
+                 mMinModifiedOffset.value() < static_cast<uint32_t>(LONG_MAX) &&
+                 mComposition->IsOffsetInRange(
+                     static_cast<long>(mMinModifiedOffset.value()))) {
+        // The previous change to the composition string is canceled.
+        firstDifferentOffset = mComposition->EndOffset();
+        mMinModifiedOffset = Some(firstDifferentOffset);
+      }
+      mLatestCompositionRange = Some(mComposition->CreateStartAndEndOffsets());
+      MOZ_LOG(
+          gIMELog, LogLevel::Debug,
+          ("0x%p   TSFTextStore::Content::ReplaceTextWith(aStart=%ld, "
+           "aLength=%ld, aReplaceString=\"%s\"), mComposition=%s, "
+           "mLastComposition=%s, mMinModifiedOffset=%s, "
+           "firstDifferentOffset=%u",
+           this, aStart, aLength, GetEscapedUTF8String(aReplaceString).get(),
+           ToString(mComposition).c_str(), ToString(mLastComposition).c_str(),
+           ToString(mMinModifiedOffset).c_str(), firstDifferentOffset));
+    } else {
+      firstDifferentOffset =
+          static_cast<uint32_t>(aStart) +
+          FirstDifferentCharOffset(aReplaceString, replacedString);
+    }
+    mMinModifiedOffset =
+        mMinModifiedOffset.isNothing()
+            ? Some(firstDifferentOffset)
+            : Some(std::min(mMinModifiedOffset.value(), firstDifferentOffset));
+    mText.Replace(static_cast<uint32_t>(aStart), static_cast<uint32_t>(aLength),
+                  aReplaceString);
+  }
+  // Selection should be collapsed at the end of the inserted string.
+  mSelection = Some(TSFTextStore::Selection(static_cast<uint32_t>(aStart) +
+                                            aReplaceString.Length()));
+}
+
+void TSFTextStore::Content::StartComposition(
+    ITfCompositionView* aCompositionView, const PendingAction& aCompStart,
+    bool aPreserveSelection) {
+  MOZ_ASSERT(aCompositionView);
+  MOZ_ASSERT(mComposition.isNothing());
+  MOZ_ASSERT(aCompStart.mType == PendingAction::Type::eCompositionStart);
+
+  mComposition.reset();  // Avoid new crash in the beta and nightly channels.
+  mComposition.emplace(
+      aCompositionView, aCompStart.mSelectionStart,
+      GetSubstring(static_cast<uint32_t>(aCompStart.mSelectionStart),
+                   static_cast<uint32_t>(aCompStart.mSelectionLength)));
+  mLatestCompositionRange = Some(mComposition->CreateStartAndEndOffsets());
+  if (!aPreserveSelection) {
+    // XXX Do we need to set a new writing-mode here when setting a new
+    // selection? Currently, we just preserve the existing value.
+    WritingMode writingMode =
+        mSelection.isNothing() ? WritingMode() : mSelection->WritingModeRef();
+    mSelection = Some(TSFTextStore::Selection(mComposition->StartOffset(),
+                                              mComposition->Length(), false,
+                                              writingMode));
+  }
+}
+
+void TSFTextStore::Content::RestoreCommittedComposition(
+    ITfCompositionView* aCompositionView,
+    const PendingAction& aCanceledCompositionEnd) {
+  MOZ_ASSERT(aCompositionView);
+  MOZ_ASSERT(mComposition.isNothing());
+  MOZ_ASSERT(aCanceledCompositionEnd.mType ==
+             PendingAction::Type::eCompositionEnd);
+  MOZ_ASSERT(
+      GetSubstring(
+          static_cast<uint32_t>(aCanceledCompositionEnd.mSelectionStart),
+          static_cast<uint32_t>(aCanceledCompositionEnd.mData.Length())) ==
+      aCanceledCompositionEnd.mData);
+
+  // Restore the committed string as composing string.
+  mComposition.reset();  // Avoid new crash in the beta and nightly channels.
+  mComposition.emplace(aCompositionView,
+                       aCanceledCompositionEnd.mSelectionStart,
+                       aCanceledCompositionEnd.mData);
+  mLatestCompositionRange = Some(mComposition->CreateStartAndEndOffsets());
+}
+
+void TSFTextStore::Content::EndComposition(const PendingAction& aCompEnd) {
+  MOZ_ASSERT(mComposition.isSome());
+  MOZ_ASSERT(aCompEnd.mType == PendingAction::Type::eCompositionEnd);
+
+  if (mComposition.isNothing()) {
+    return;  // Avoid new crash in the beta and nightly channels.
+  }
+
+  mSelection = Some(TSFTextStore::Selection(mComposition->StartOffset() +
+                                            aCompEnd.mData.Length()));
+  mComposition.reset();
+}
+
+/******************************************************************************
+ *  TSFTextStore::MouseTracker
+ *****************************************************************************/
+
+TSFTextStore::MouseTracker::MouseTracker() : mCookie(kInvalidCookie) {}
+
+HRESULT
+TSFTextStore::MouseTracker::Init(TSFTextStore* aTextStore) {
+  MOZ_LOG(gIMELog, LogLevel::Debug,
+          ("0x%p   TSFTextStore::MouseTracker::Init(aTextStore=0x%p), "
+           "aTextStore->mMouseTrackers.Length()=%zu",
+           this, aTextStore, aTextStore->mMouseTrackers.Length()));
+
+  if (&aTextStore->mMouseTrackers.LastElement() != this) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::MouseTracker::Init() FAILED due to "
+             "this is not the last element of mMouseTrackers",
+             this));
+    return E_FAIL;
+  }
+  if (aTextStore->mMouseTrackers.Length() > kInvalidCookie) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::MouseTracker::Init() FAILED due to "
+             "no new cookie available",
+             this));
+    return E_FAIL;
+  }
+  MOZ_ASSERT(!aTextStore->mMouseTrackers.IsEmpty(),
+             "This instance must be in TSFTextStore::mMouseTrackers");
+  mCookie = static_cast<DWORD>(aTextStore->mMouseTrackers.Length() - 1);
+  return S_OK;
+}
+
+HRESULT
+TSFTextStore::MouseTracker::AdviseSink(TSFTextStore* aTextStore,
+                                       ITfRangeACP* aTextRange,
+                                       ITfMouseSink* aMouseSink) {
+  MOZ_LOG(gIMELog, LogLevel::Debug,
+          ("0x%p   TSFTextStore::MouseTracker::AdviseSink(aTextStore=0x%p, "
+           "aTextRange=0x%p, aMouseSink=0x%p), mCookie=%ld, mSink=0x%p",
+           this, aTextStore, aTextRange, aMouseSink, mCookie, mSink.get()));
+  MOZ_ASSERT(mCookie != kInvalidCookie, "This hasn't been initalized?");
+
+  if (mSink) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::MouseTracker::AdviseMouseSink() FAILED "
+             "due to already being used",
+             this));
+    return E_FAIL;
+  }
+
+  MOZ_ASSERT(mRange.isNothing());
+
+  LONG start = 0, length = 0;
+  HRESULT hr = aTextRange->GetExtent(&start, &length);
+  if (FAILED(hr)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::MouseTracker::AdviseMouseSink() FAILED "
+             "due to failure of ITfRangeACP::GetExtent()",
+             this));
+    return hr;
+  }
+
+  if (start < 0 || length <= 0 || start + length > LONG_MAX) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::MouseTracker::AdviseMouseSink() FAILED "
+             "due to odd result of ITfRangeACP::GetExtent(), "
+             "start=%ld, length=%ld",
+             this, start, length));
+    return E_INVALIDARG;
+  }
+
+  nsAutoString textContent;
+  if (NS_WARN_IF(!aTextStore->GetCurrentText(textContent))) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::MouseTracker::AdviseMouseSink() FAILED "
+             "due to failure of TSFTextStore::GetCurrentText()",
+             this));
+    return E_FAIL;
+  }
+
+  if (textContent.Length() <= static_cast<uint32_t>(start) ||
+      textContent.Length() < static_cast<uint32_t>(start + length)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("0x%p   TSFTextStore::MouseTracker::AdviseMouseSink() FAILED "
+             "due to out of range, start=%ld, length=%ld, "
+             "textContent.Length()=%zu",
+             this, start, length, textContent.Length()));
+    return E_INVALIDARG;
+  }
+
+  mRange.emplace(start, start + length);
+
+  mSink = aMouseSink;
+
+  MOZ_LOG(gIMELog, LogLevel::Debug,
+          ("0x%p   TSFTextStore::MouseTracker::AdviseMouseSink(), "
+           "succeeded, mRange=%s, textContent.Length()=%zu",
+           this, ToString(mRange).c_str(), textContent.Length()));
+  return S_OK;
+}
+
+void TSFTextStore::MouseTracker::UnadviseSink() {
+  MOZ_LOG(gIMELog, LogLevel::Debug,
+          ("0x%p   TSFTextStore::MouseTracker::UnadviseSink(), "
+           "mCookie=%ld, mSink=0x%p, mRange=%s",
+           this, mCookie, mSink.get(), ToString(mRange).c_str()));
+  mSink = nullptr;
+  mRange.reset();
+}
+
+bool TSFTextStore::MouseTracker::OnMouseButtonEvent(ULONG aEdge,
+                                                    ULONG aQuadrant,
+                                                    DWORD aButtonStatus) {
+  MOZ_ASSERT(IsUsing(), "The caller must check before calling OnMouseEvent()");
+
+  BOOL eaten = FALSE;
+  RefPtr<ITfMouseSink> sink = mSink;
+  HRESULT hr = sink->OnMouseEvent(aEdge, aQuadrant, aButtonStatus, &eaten);
+
+  MOZ_LOG(gIMELog, LogLevel::Debug,
+          ("0x%p   TSFTextStore::MouseTracker::OnMouseEvent(aEdge=%ld, "
+           "aQuadrant=%ld, aButtonStatus=0x%08lX), hr=0x%08lX, eaten=%s",
+           this, aEdge, aQuadrant, aButtonStatus, hr, GetBoolName(!!eaten)));
+
+  return SUCCEEDED(hr) && eaten;
+}
+
+#ifdef DEBUG
+// static
+bool TSFTextStore::CurrentKeyboardLayoutHasIME() {
+  RefPtr<ITfInputProcessorProfiles> inputProcessorProfiles =
+      TSFTextStore::GetInputProcessorProfiles();
+  if (!inputProcessorProfiles) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("TSFTextStore::CurrentKeyboardLayoutHasIME() FAILED due to "
+             "there is no input processor profiles instance"));
+    return false;
+  }
+  RefPtr<ITfInputProcessorProfileMgr> profileMgr;
+  HRESULT hr = inputProcessorProfiles->QueryInterface(
+      IID_ITfInputProcessorProfileMgr, getter_AddRefs(profileMgr));
+  if (FAILED(hr) || !profileMgr) {
+    // On Windows Vista or later, ImmIsIME() API always returns true.
+    // If we failed to obtain the profile manager, we cannot know if current
+    // keyboard layout has IME.
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("  TSFTextStore::CurrentKeyboardLayoutHasIME() FAILED to query "
+             "ITfInputProcessorProfileMgr"));
+    return false;
+  }
+
+  TF_INPUTPROCESSORPROFILE profile;
+  hr = profileMgr->GetActiveProfile(GUID_TFCAT_TIP_KEYBOARD, &profile);
+  if (hr == S_FALSE) {
+    return false;  // not found or not active
+  }
+  if (FAILED(hr)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("  TSFTextStore::CurrentKeyboardLayoutHasIME() FAILED to retreive "
+             "active profile"));
+    return false;
+  }
+  return (profile.dwProfileType == TF_PROFILETYPE_INPUTPROCESSOR);
+}
+#endif  // #ifdef DEBUG
+
+}  // namespace widget
+}  // namespace mozilla
diff --git a/widget/windows/TSFTextStore.h b/widget/windows/TSFTextStore.h
new file mode 100644
index 0000000000..17358a488d
--- /dev/null
+++ b/widget/windows/TSFTextStore.h
@@ -0,0 +1,1161 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef TSFTextStore_h_
+#define TSFTextStore_h_
+
+#include "nsCOMPtr.h"
+#include "nsIWidget.h"
+#include "nsString.h"
+#include "nsWindow.h"
+
+#include "WinUtils.h"
+#include "WritingModes.h"
+
+#include "mozilla/Attributes.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/StaticPtr.h"
+#include "mozilla/TextEventDispatcher.h"
+#include "mozilla/TextEvents.h"
+#include "mozilla/TextRange.h"
+#include "mozilla/WindowsVersion.h"
+#include "mozilla/widget/IMEData.h"
+
+#include <msctf.h>
+#include <textstor.h>
+
+// GUID_PROP_INPUTSCOPE is declared in inputscope.h using INIT_GUID.
+// With initguid.h, we get its instance instead of extern declaration.
+#ifdef INPUTSCOPE_INIT_GUID
+#  include <initguid.h>
+#endif
+#ifdef TEXTATTRS_INIT_GUID
+#  include <tsattrs.h>
+#endif
+#include <inputscope.h>
+
+// TSF InputScope, for earlier SDK 8
+#define IS_SEARCH static_cast<InputScope>(50)
+
+struct ITfThreadMgr;
+struct ITfDocumentMgr;
+struct ITfDisplayAttributeMgr;
+struct ITfCategoryMgr;
+class nsWindow;
+
+inline std::ostream& operator<<(std::ostream& aStream,
+                                const TS_SELECTIONSTYLE& aSelectionStyle) {
+  const char* ase = "Unknown";
+  switch (aSelectionStyle.ase) {
+    case TS_AE_START:
+      ase = "TS_AE_START";
+      break;
+    case TS_AE_END:
+      ase = "TS_AE_END";
+      break;
+    case TS_AE_NONE:
+      ase = "TS_AE_NONE";
+      break;
+  }
+  aStream << "{ ase=" << ase << ", fInterimChar="
+          << (aSelectionStyle.fInterimChar ? "TRUE" : "FALSE") << " }";
+  return aStream;
+}
+
+inline std::ostream& operator<<(std::ostream& aStream,
+                                const TS_SELECTION_ACP& aACP) {
+  aStream << "{ acpStart=" << aACP.acpStart << ", acpEnd=" << aACP.acpEnd
+          << ", style=" << mozilla::ToString(aACP.style).c_str() << " }";
+  return aStream;
+}
+
+namespace mozilla {
+namespace widget {
+
+class TSFStaticSink;
+struct MSGResult;
+
+/*
+ * Text Services Framework text store
+ */
+
+class TSFTextStore final : public ITextStoreACP,
+                           public ITfContextOwnerCompositionSink,
+                           public ITfMouseTrackerACP {
+  friend class TSFStaticSink;
+
+ private:
+  typedef IMENotification::SelectionChangeDataBase SelectionChangeDataBase;
+  typedef IMENotification::SelectionChangeData SelectionChangeData;
+  typedef IMENotification::TextChangeDataBase TextChangeDataBase;
+  typedef IMENotification::TextChangeData TextChangeData;
+
+ public: /*IUnknown*/
+  STDMETHODIMP QueryInterface(REFIID, void**);
+
+  NS_INLINE_DECL_IUNKNOWN_REFCOUNTING(TSFTextStore)
+
+ public: /*ITextStoreACP*/
+  STDMETHODIMP AdviseSink(REFIID, IUnknown*, DWORD);
+  STDMETHODIMP UnadviseSink(IUnknown*);
+  STDMETHODIMP RequestLock(DWORD, HRESULT*);
+  STDMETHODIMP GetStatus(TS_STATUS*);
+  STDMETHODIMP QueryInsert(LONG, LONG, ULONG, LONG*, LONG*);
+  STDMETHODIMP GetSelection(ULONG, ULONG, TS_SELECTION_ACP*, ULONG*);
+  STDMETHODIMP SetSelection(ULONG, const TS_SELECTION_ACP*);
+  STDMETHODIMP GetText(LONG, LONG, WCHAR*, ULONG, ULONG*, TS_RUNINFO*, ULONG,
+                       ULONG*, LONG*);
+  STDMETHODIMP SetText(DWORD, LONG, LONG, const WCHAR*, ULONG, TS_TEXTCHANGE*);
+  STDMETHODIMP GetFormattedText(LONG, LONG, IDataObject**);
+  STDMETHODIMP GetEmbedded(LONG, REFGUID, REFIID, IUnknown**);
+  STDMETHODIMP QueryInsertEmbedded(const GUID*, const FORMATETC*, BOOL*);
+  STDMETHODIMP InsertEmbedded(DWORD, LONG, LONG, IDataObject*, TS_TEXTCHANGE*);
+  STDMETHODIMP RequestSupportedAttrs(DWORD, ULONG, const TS_ATTRID*);
+  STDMETHODIMP RequestAttrsAtPosition(LONG, ULONG, const TS_ATTRID*, DWORD);
+  STDMETHODIMP RequestAttrsTransitioningAtPosition(LONG, ULONG,
+                                                   const TS_ATTRID*, DWORD);
+  STDMETHODIMP FindNextAttrTransition(LONG, LONG, ULONG, const TS_ATTRID*,
+                                      DWORD, LONG*, BOOL*, LONG*);
+  STDMETHODIMP RetrieveRequestedAttrs(ULONG, TS_ATTRVAL*, ULONG*);
+  STDMETHODIMP GetEndACP(LONG*);
+  STDMETHODIMP GetActiveView(TsViewCookie*);
+  STDMETHODIMP GetACPFromPoint(TsViewCookie, const POINT*, DWORD, LONG*);
+  STDMETHODIMP GetTextExt(TsViewCookie, LONG, LONG, RECT*, BOOL*);
+  STDMETHODIMP GetScreenExt(TsViewCookie, RECT*);
+  STDMETHODIMP GetWnd(TsViewCookie, HWND*);
+  STDMETHODIMP InsertTextAtSelection(DWORD, const WCHAR*, ULONG, LONG*, LONG*,
+                                     TS_TEXTCHANGE*);
+  STDMETHODIMP InsertEmbeddedAtSelection(DWORD, IDataObject*, LONG*, LONG*,
+                                         TS_TEXTCHANGE*);
+
+ public: /*ITfContextOwnerCompositionSink*/
+  STDMETHODIMP OnStartComposition(ITfCompositionView*, BOOL*);
+  STDMETHODIMP OnUpdateComposition(ITfCompositionView*, ITfRange*);
+  STDMETHODIMP OnEndComposition(ITfCompositionView*);
+
+ public: /*ITfMouseTrackerACP*/
+  STDMETHODIMP AdviseMouseSink(ITfRangeACP*, ITfMouseSink*, DWORD*);
+  STDMETHODIMP UnadviseMouseSink(DWORD);
+
+ public:
+  static void Initialize(void);
+  static void Terminate(void);
+
+  static bool ProcessRawKeyMessage(const MSG& aMsg);
+  static void ProcessMessage(nsWindow* aWindow, UINT aMessage, WPARAM& aWParam,
+                             LPARAM& aLParam, MSGResult& aResult);
+
+  static void SetIMEOpenState(bool);
+  static bool GetIMEOpenState(void);
+
+  static void CommitComposition(bool aDiscard) {
+    NS_ASSERTION(IsInTSFMode(), "Not in TSF mode, shouldn't be called");
+    if (!sEnabledTextStore) {
+      return;
+    }
+    RefPtr<TSFTextStore> textStore(sEnabledTextStore);
+    textStore->CommitCompositionInternal(aDiscard);
+  }
+
+  static void SetInputContext(nsWindow* aWidget, const InputContext& aContext,
+                              const InputContextAction& aAction);
+
+  static nsresult OnFocusChange(bool aGotFocus, nsWindow* aFocusedWidget,
+                                const InputContext& aContext);
+  static nsresult OnTextChange(const IMENotification& aIMENotification) {
+    NS_ASSERTION(IsInTSFMode(), "Not in TSF mode, shouldn't be called");
+    if (!sEnabledTextStore) {
+      return NS_OK;
+    }
+    RefPtr<TSFTextStore> textStore(sEnabledTextStore);
+    return textStore->OnTextChangeInternal(aIMENotification);
+  }
+
+  static nsresult OnSelectionChange(const IMENotification& aIMENotification) {
+    NS_ASSERTION(IsInTSFMode(), "Not in TSF mode, shouldn't be called");
+    if (!sEnabledTextStore) {
+      return NS_OK;
+    }
+    RefPtr<TSFTextStore> textStore(sEnabledTextStore);
+    return textStore->OnSelectionChangeInternal(aIMENotification);
+  }
+
+  static nsresult OnLayoutChange() {
+    NS_ASSERTION(IsInTSFMode(), "Not in TSF mode, shouldn't be called");
+    if (!sEnabledTextStore) {
+      return NS_OK;
+    }
+    RefPtr<TSFTextStore> textStore(sEnabledTextStore);
+    return textStore->OnLayoutChangeInternal();
+  }
+
+  static nsresult OnUpdateComposition() {
+    NS_ASSERTION(IsInTSFMode(), "Not in TSF mode, shouldn't be called");
+    if (!sEnabledTextStore) {
+      return NS_OK;
+    }
+    RefPtr<TSFTextStore> textStore(sEnabledTextStore);
+    return textStore->OnUpdateCompositionInternal();
+  }
+
+  static nsresult OnMouseButtonEvent(const IMENotification& aIMENotification) {
+    NS_ASSERTION(IsInTSFMode(), "Not in TSF mode, shouldn't be called");
+    if (!sEnabledTextStore) {
+      return NS_OK;
+    }
+    RefPtr<TSFTextStore> textStore(sEnabledTextStore);
+    return textStore->OnMouseButtonEventInternal(aIMENotification);
+  }
+
+  static IMENotificationRequests GetIMENotificationRequests();
+
+  // Returns the address of the pointer so that the TSF automatic test can
+  // replace the system object with a custom implementation for testing.
+  // XXX TSF doesn't work now.  Should we remove it?
+  static void* GetNativeData(uint32_t aDataType) {
+    switch (aDataType) {
+      case NS_NATIVE_TSF_THREAD_MGR:
+        Initialize();  // Apply any previous changes
+        return static_cast<void*>(&sThreadMgr);
+      case NS_NATIVE_TSF_CATEGORY_MGR:
+        return static_cast<void*>(&sCategoryMgr);
+      case NS_NATIVE_TSF_DISPLAY_ATTR_MGR:
+        return static_cast<void*>(&sDisplayAttrMgr);
+      default:
+        return nullptr;
+    }
+  }
+
+  static void* GetThreadManager() { return static_cast<void*>(sThreadMgr); }
+
+  static bool ThinksHavingFocus() {
+    return (sEnabledTextStore && sEnabledTextStore->mContext);
+  }
+
+  static bool IsInTSFMode() { return sThreadMgr != nullptr; }
+
+  static bool IsComposing() {
+    return (sEnabledTextStore && sEnabledTextStore->mComposition.isSome());
+  }
+
+  static bool IsComposingOn(nsWindow* aWidget) {
+    return (IsComposing() && sEnabledTextStore->mWidget == aWidget);
+  }
+
+  static nsWindow* GetEnabledWindowBase() {
+    return sEnabledTextStore ? sEnabledTextStore->mWidget.get() : nullptr;
+  }
+
+  /**
+   * Returns true if active keyboard layout is a legacy IMM-IME.
+   */
+  static bool IsIMM_IMEActive();
+
+  /**
+   * Returns true if active TIP is MS-IME for Japanese.
+   */
+  static bool IsMSJapaneseIMEActive();
+
+  /**
+   * Returns true if active TIP is Google Japanese Input.
+   * Note that if Google Japanese Input is installed as an IMM-IME,
+   * this return false even if Google Japanese Input is active.
+   * So, you may need to check IMMHandler::IsGoogleJapaneseInputActive() too.
+   */
+  static bool IsGoogleJapaneseInputActive();
+
+  /**
+   * Returns true if active TIP is ATOK.
+   */
+  static bool IsATOKActive();
+
+  /**
+   * Returns true if active TIP or IME is a black listed one and we should
+   * set input scope of URL bar to IS_DEFAULT rather than IS_URL.
+   */
+  static bool ShouldSetInputScopeOfURLBarToDefault();
+
+  /**
+   * Returns true if TSF may crash if GetSelection() returns E_FAIL.
+   */
+  static bool DoNotReturnErrorFromGetSelection();
+
+#ifdef DEBUG
+  // Returns true when keyboard layout has IME (TIP).
+  static bool CurrentKeyboardLayoutHasIME();
+#endif  // #ifdef DEBUG
+
+ protected:
+  TSFTextStore();
+  ~TSFTextStore();
+
+  static bool CreateAndSetFocus(nsWindow* aFocusedWidget,
+                                const InputContext& aContext);
+  static void EnsureToDestroyAndReleaseEnabledTextStoreIf(
+      RefPtr<TSFTextStore>& aTextStore);
+  static void MarkContextAsKeyboardDisabled(ITfContext* aContext);
+  static void MarkContextAsEmpty(ITfContext* aContext);
+
+  bool Init(nsWindow* aWidget, const InputContext& aContext);
+  void Destroy();
+  void ReleaseTSFObjects();
+
+  bool IsReadLock(DWORD aLock) const {
+    return (TS_LF_READ == (aLock & TS_LF_READ));
+  }
+  bool IsReadWriteLock(DWORD aLock) const {
+    return (TS_LF_READWRITE == (aLock & TS_LF_READWRITE));
+  }
+  bool IsReadLocked() const { return IsReadLock(mLock); }
+  bool IsReadWriteLocked() const { return IsReadWriteLock(mLock); }
+
+  // This is called immediately after a call of OnLockGranted() of mSink.
+  // Note that mLock isn't cleared yet when this is called.
+  void DidLockGranted();
+
+  bool GetScreenExtInternal(RECT& aScreenExt);
+  // If aDispatchCompositionChangeEvent is true, this method will dispatch
+  // compositionchange event if this is called during IME composing.
+  // aDispatchCompositionChangeEvent should be true only when this is called
+  // from SetSelection.  Because otherwise, the compositionchange event should
+  // not be sent from here.
+  HRESULT SetSelectionInternal(const TS_SELECTION_ACP*,
+                               bool aDispatchCompositionChangeEvent = false);
+  bool InsertTextAtSelectionInternal(const nsAString& aInsertStr,
+                                     TS_TEXTCHANGE* aTextChange);
+  void CommitCompositionInternal(bool);
+  HRESULT GetDisplayAttribute(ITfProperty* aProperty, ITfRange* aRange,
+                              TF_DISPLAYATTRIBUTE* aResult);
+  HRESULT RestartCompositionIfNecessary(ITfRange* pRangeNew = nullptr);
+  class Composition;
+  HRESULT RestartComposition(Composition& aCurrentComposition,
+                             ITfCompositionView* aCompositionView,
+                             ITfRange* aNewRange);
+
+  // Following methods record composing action(s) to mPendingActions.
+  // They will be flushed FlushPendingActions().
+  HRESULT RecordCompositionStartAction(ITfCompositionView* aCompositionView,
+                                       ITfRange* aRange,
+                                       bool aPreserveSelection);
+  HRESULT RecordCompositionStartAction(ITfCompositionView* aCompositionView,
+                                       LONG aStart, LONG aLength,
+                                       bool aPreserveSelection);
+  HRESULT RecordCompositionUpdateAction();
+  HRESULT RecordCompositionEndAction();
+
+  // DispatchEvent() dispatches the event and if it may not be handled
+  // synchronously, this makes the instance not notify TSF of pending
+  // notifications until next notification from content.
+  void DispatchEvent(WidgetGUIEvent& aEvent);
+  void OnLayoutInformationAvaliable();
+
+  // FlushPendingActions() performs pending actions recorded in mPendingActions
+  // and clear it.
+  void FlushPendingActions();
+  // MaybeFlushPendingNotifications() performs pending notifications to TSF.
+  void MaybeFlushPendingNotifications();
+
+  nsresult OnTextChangeInternal(const IMENotification& aIMENotification);
+  nsresult OnSelectionChangeInternal(const IMENotification& aIMENotification);
+  nsresult OnMouseButtonEventInternal(const IMENotification& aIMENotification);
+  nsresult OnLayoutChangeInternal();
+  nsresult OnUpdateCompositionInternal();
+
+  // mPendingSelectionChangeData stores selection change data until notifying
+  // TSF of selection change.  If two or more selection changes occur, this
+  // stores the latest selection change data because only it is necessary.
+  Maybe<SelectionChangeData> mPendingSelectionChangeData;
+
+  // mPendingTextChangeData stores one or more text change data until notifying
+  // TSF of text change.  If two or more text changes occur, this merges
+  // every text change data.
+  TextChangeData mPendingTextChangeData;
+
+  void NotifyTSFOfTextChange();
+  void NotifyTSFOfSelectionChange();
+  bool NotifyTSFOfLayoutChange();
+  void NotifyTSFOfLayoutChangeAgain();
+
+  HRESULT HandleRequestAttrs(DWORD aFlags, ULONG aFilterCount,
+                             const TS_ATTRID* aFilterAttrs);
+  void SetInputScope(const nsString& aHTMLInputType,
+                     const nsString& aHTMLInputMode);
+
+  // Creates native caret over our caret.  This method only works on desktop
+  // application.  Otherwise, this does nothing.
+  void CreateNativeCaret();
+  // Destroys native caret if there is.
+  void MaybeDestroyNativeCaret();
+
+  /**
+   * MaybeHackNoErrorLayoutBugs() is a helper method of GetTextExt().  In
+   * strictly speaking, TSF is aware of asynchronous layout computation like us.
+   * However, Windows 10 version 1803 and older (including Windows 8.1 and
+   * older) Windows has a bug which is that the caller of GetTextExt() of TSF
+   * does not return TS_E_NOLAYOUT to TIP as is.  Additionally, even after
+   * fixing this bug, some TIPs are not work well when we return TS_E_NOLAYOUT.
+   * For avoiding this issue, this method checks current Windows version and
+   * active TIP, and if in case we cannot return TS_E_NOLAYOUT, this modifies
+   * aACPStart and aACPEnd to making sure that they are in range of unmodified
+   * characters.
+   *
+   * @param aACPStart   Initial value should be acpStart of GetTextExt().
+   *                    If this method returns true, this may be modified
+   *                    to be in range of unmodified characters.
+   * @param aACPEnd     Initial value should be acpEnd of GetTextExt().
+   *                    If this method returns true, this may be modified
+   *                    to be in range of unmodified characters.
+   *                    And also this may become same as aACPStart.
+   * @return            true if the caller shouldn't return TS_E_NOLAYOUT.
+   *                    In this case, this method modifies aACPStart and/or
+   *                    aASCPEnd to compute rectangle of unmodified characters.
+   *                    false if the caller can return TS_E_NOLAYOUT or
+   *                    we cannot have proper unmodified characters.
+   */
+  bool MaybeHackNoErrorLayoutBugs(LONG& aACPStart, LONG& aACPEnd);
+
+  // Holds the pointer to our current win32 widget
+  RefPtr<nsWindow> mWidget;
+  // mDispatcher is a helper class to dispatch composition events.
+  RefPtr<TextEventDispatcher> mDispatcher;
+  // Document manager for the currently focused editor
+  RefPtr<ITfDocumentMgr> mDocumentMgr;
+  // Edit cookie associated with the current editing context
+  DWORD mEditCookie;
+  // Editing context at the bottom of mDocumentMgr's context stack
+  RefPtr<ITfContext> mContext;
+  // Currently installed notification sink
+  RefPtr<ITextStoreACPSink> mSink;
+  // TS_AS_* mask of what events to notify
+  DWORD mSinkMask;
+  // 0 if not locked, otherwise TS_LF_* indicating the current lock
+  DWORD mLock;
+  // 0 if no lock is queued, otherwise TS_LF_* indicating the queue lock
+  DWORD mLockQueued;
+
+  uint32_t mHandlingKeyMessage;
+  void OnStartToHandleKeyMessage() {
+    // If we're starting to handle another key message during handling a
+    // key message, let's assume that the handling key message is handled by
+    // TIP and it sends another key message for hacking something.
+    // Let's try to dispatch a keyboard event now.
+    // FYI: All callers of this method grab this instance with local variable.
+    //      So, even after calling MaybeDispatchKeyboardEventAsProcessedByIME(),
+    //      we're safe to access any members.
+    if (!mDestroyed && sHandlingKeyMsg && !sIsKeyboardEventDispatched) {
+      MaybeDispatchKeyboardEventAsProcessedByIME();
+    }
+    ++mHandlingKeyMessage;
+  }
+  void OnEndHandlingKeyMessage(bool aIsProcessedByTSF) {
+    // If sHandlingKeyMsg has been handled by TSF or TIP and we're still
+    // alive, but we haven't dispatch keyboard event for it, let's fire it now.
+    // FYI: All callers of this method grab this instance with local variable.
+    //      So, even after calling MaybeDispatchKeyboardEventAsProcessedByIME(),
+    //      we're safe to access any members.
+    if (!mDestroyed && sHandlingKeyMsg && aIsProcessedByTSF &&
+        !sIsKeyboardEventDispatched) {
+      MaybeDispatchKeyboardEventAsProcessedByIME();
+    }
+    MOZ_ASSERT(mHandlingKeyMessage);
+    if (--mHandlingKeyMessage) {
+      return;
+    }
+    // If TSFTextStore instance is destroyed during handling key message(s),
+    // release all TSF objects when all nested key messages have been handled.
+    if (mDestroyed) {
+      ReleaseTSFObjects();
+    }
+  }
+
+  /**
+   * MaybeDispatchKeyboardEventAsProcessedByIME() tries to dispatch eKeyDown
+   * event or eKeyUp event for sHandlingKeyMsg and marking the dispatching
+   * event as "processed by IME".  Note that if the document is locked, this
+   * just adds a pending action into the queue and sets
+   * sIsKeyboardEventDispatched to true.
+   */
+  void MaybeDispatchKeyboardEventAsProcessedByIME();
+
+  /**
+   * DispatchKeyboardEventAsProcessedByIME() dispatches an eKeyDown or
+   * eKeyUp event with NativeKey class and aMsg.
+   */
+  void DispatchKeyboardEventAsProcessedByIME(const MSG& aMsg);
+
+  // Composition class stores a copy of the active composition string.  Only
+  // the data is updated during an InsertTextAtSelection call if we have a
+  // composition.  The data acts as a buffer until OnUpdateComposition is
+  // called and the data is flushed to editor through eCompositionChange.
+  // This allows all changes to be updated in batches to avoid inconsistencies
+  // and artifacts.
+  class Composition final : public OffsetAndData<LONG> {
+   public:
+    explicit Composition(ITfCompositionView* aCompositionView,
+                         LONG aCompositionStartOffset,
+                         const nsAString& aCompositionString)
+        : OffsetAndData<LONG>(aCompositionStartOffset, aCompositionString),
+          mView(aCompositionView) {}
+
+    ITfCompositionView* GetView() const { return mView; }
+
+    friend std::ostream& operator<<(std::ostream& aStream,
+                                    const Composition& aComposition) {
+      aStream << "{ mView=0x" << aComposition.mView.get()
+              << ", OffsetAndData<LONG>="
+              << static_cast<const OffsetAndData<LONG>&>(aComposition) << " }";
+      return aStream;
+    }
+
+   private:
+    RefPtr<ITfCompositionView> const mView;
+  };
+  // While the document is locked, we cannot dispatch any events which cause
+  // DOM events since the DOM events' handlers may modify the locked document.
+  // However, even while the document is locked, TSF may queries us.
+  // For that, TSFTextStore modifies mComposition even while the document is
+  // locked.  With mComposition, query methods can returns the text content
+  // information.
+  Maybe<Composition> mComposition;
+
+  /**
+   * IsHandlingCompositionInParent() returns true if eCompositionStart is
+   * dispatched, but eCompositionCommit(AsIs) is not dispatched.  This means
+   * that if composition is handled in a content process, this status indicates
+   * whether ContentCacheInParent has composition or not.  On the other hand,
+   * if it's handled in the chrome process, this is exactly same as
+   * IsHandlingCompositionInContent().
+   */
+  bool IsHandlingCompositionInParent() const {
+    return mDispatcher && mDispatcher->IsComposing();
+  }
+
+  /**
+   * IsHandlingCompositionInContent() returns true if there is a composition in
+   * the focused editor which may be in a content process.
+   */
+  bool IsHandlingCompositionInContent() const {
+    return mDispatcher && mDispatcher->IsHandlingComposition();
+  }
+
+  class Selection {
+   public:
+    static TS_SELECTION_ACP EmptyACP() {
+      return TS_SELECTION_ACP{
+          .acpStart = 0,
+          .acpEnd = 0,
+          .style = {.ase = TS_AE_NONE, .fInterimChar = FALSE}};
+    }
+
+    bool HasRange() const { return mACP.isSome(); }
+    const TS_SELECTION_ACP& ACPRef() const { return mACP.ref(); }
+
+    explicit Selection(const TS_SELECTION_ACP& aSelection) {
+      SetSelection(aSelection);
+    }
+
+    explicit Selection(uint32_t aOffsetToCollapse) {
+      Collapse(aOffsetToCollapse);
+    }
+
+    explicit Selection(const SelectionChangeDataBase& aSelectionChangeData) {
+      SetSelection(aSelectionChangeData);
+    }
+
+    explicit Selection(const WidgetQueryContentEvent& aQuerySelectionEvent) {
+      SetSelection(aQuerySelectionEvent);
+    }
+
+    Selection(uint32_t aStart, uint32_t aLength, bool aReversed,
+              const WritingMode& aWritingMode) {
+      SetSelection(aStart, aLength, aReversed, aWritingMode);
+    }
+
+    void SetSelection(const TS_SELECTION_ACP& aSelection) {
+      mACP = Some(aSelection);
+      // Selection end must be active in our editor.
+      if (mACP->style.ase != TS_AE_START) {
+        mACP->style.ase = TS_AE_END;
+      }
+      // We're not support interim char selection for now.
+      // XXX Probably, this is necessary for supporting South Asian languages.
+      mACP->style.fInterimChar = FALSE;
+    }
+
+    bool SetSelection(const SelectionChangeDataBase& aSelectionChangeData) {
+      MOZ_ASSERT(aSelectionChangeData.IsInitialized());
+      if (!aSelectionChangeData.HasRange()) {
+        if (mACP.isNothing()) {
+          return false;
+        }
+        mACP.reset();
+        // Let's keep the WritingMode because users don't want to change the UI
+        // of TIP temporarily since no selection case is created only by web
+        // apps, but they or TIP would restore selection at last point later.
+        return true;
+      }
+      return SetSelection(aSelectionChangeData.mOffset,
+                          aSelectionChangeData.Length(),
+                          aSelectionChangeData.mReversed,
+                          aSelectionChangeData.GetWritingMode());
+    }
+
+    bool SetSelection(const WidgetQueryContentEvent& aQuerySelectionEvent) {
+      MOZ_ASSERT(aQuerySelectionEvent.mMessage == eQuerySelectedText);
+      MOZ_ASSERT(aQuerySelectionEvent.Succeeded());
+      if (aQuerySelectionEvent.DidNotFindSelection()) {
+        if (mACP.isNothing()) {
+          return false;
+        }
+        mACP.reset();
+        // Let's keep the WritingMode because users don't want to change the UI
+        // of TIP temporarily since no selection case is created only by web
+        // apps, but they or TIP would restore selection at last point later.
+        return true;
+      }
+      return SetSelection(aQuerySelectionEvent.mReply->StartOffset(),
+                          aQuerySelectionEvent.mReply->DataLength(),
+                          aQuerySelectionEvent.mReply->mReversed,
+                          aQuerySelectionEvent.mReply->WritingModeRef());
+    }
+
+    bool SetSelection(uint32_t aStart, uint32_t aLength, bool aReversed,
+                      const WritingMode& aWritingMode) {
+      const bool changed = mACP.isNothing() ||
+                           mACP->acpStart != static_cast<LONG>(aStart) ||
+                           mACP->acpEnd != static_cast<LONG>(aStart + aLength);
+      mACP = Some(
+          TS_SELECTION_ACP{.acpStart = static_cast<LONG>(aStart),
+                           .acpEnd = static_cast<LONG>(aStart + aLength),
+                           .style = {.ase = aReversed ? TS_AE_START : TS_AE_END,
+                                     .fInterimChar = FALSE}});
+      mWritingMode = aWritingMode;
+
+      return changed;
+    }
+
+    bool Collapsed() const {
+      return mACP.isNothing() || mACP->acpStart == mACP->acpEnd;
+    }
+
+    void Collapse(uint32_t aOffset) {
+      // XXX This does not update the selection's mWritingMode.
+      // If it is ever used to "collapse" to an entirely new location,
+      // we may need to fix that.
+      mACP = Some(
+          TS_SELECTION_ACP{.acpStart = static_cast<LONG>(aOffset),
+                           .acpEnd = static_cast<LONG>(aOffset),
+                           .style = {.ase = TS_AE_END, .fInterimChar = FALSE}});
+    }
+
+    LONG MinOffset() const {
+      MOZ_ASSERT(mACP.isSome());
+      LONG min = std::min(mACP->acpStart, mACP->acpEnd);
+      MOZ_ASSERT(min >= 0);
+      return min;
+    }
+
+    LONG MaxOffset() const {
+      MOZ_ASSERT(mACP.isSome());
+      LONG max = std::max(mACP->acpStart, mACP->acpEnd);
+      MOZ_ASSERT(max >= 0);
+      return max;
+    }
+
+    LONG StartOffset() const {
+      MOZ_ASSERT(mACP.isSome());
+      MOZ_ASSERT(mACP->acpStart >= 0);
+      return mACP->acpStart;
+    }
+
+    LONG EndOffset() const {
+      MOZ_ASSERT(mACP.isSome());
+      MOZ_ASSERT(mACP->acpEnd >= 0);
+      return mACP->acpEnd;
+    }
+
+    LONG Length() const {
+      MOZ_ASSERT_IF(mACP.isSome(), mACP->acpEnd >= mACP->acpStart);
+      return mACP.isSome() ? std::abs(mACP->acpEnd - mACP->acpStart) : 0;
+    }
+
+    bool IsReversed() const {
+      return mACP.isSome() && mACP->style.ase == TS_AE_START;
+    }
+
+    TsActiveSelEnd ActiveSelEnd() const {
+      return mACP.isSome() ? mACP->style.ase : TS_AE_NONE;
+    }
+
+    bool IsInterimChar() const {
+      return mACP.isSome() && mACP->style.fInterimChar != FALSE;
+    }
+
+    const WritingMode& WritingModeRef() const { return mWritingMode; }
+
+    bool EqualsExceptDirection(const TS_SELECTION_ACP& aACP) const {
+      if (mACP.isNothing()) {
+        return false;
+      }
+      if (mACP->style.ase == aACP.style.ase) {
+        return mACP->acpStart == aACP.acpStart && mACP->acpEnd == aACP.acpEnd;
+      }
+      return mACP->acpStart == aACP.acpEnd && mACP->acpEnd == aACP.acpStart;
+    }
+
+    bool EqualsExceptDirection(
+        const SelectionChangeDataBase& aChangedSelection) const {
+      MOZ_ASSERT(aChangedSelection.IsInitialized());
+      if (mACP.isNothing()) {
+        return aChangedSelection.HasRange();
+      }
+      return aChangedSelection.Length() == static_cast<uint32_t>(Length()) &&
+             aChangedSelection.mOffset == static_cast<uint32_t>(StartOffset());
+    }
+
+    friend std::ostream& operator<<(std::ostream& aStream,
+                                    const Selection& aSelection) {
+      aStream << "{ mACP=" << ToString(aSelection.mACP).c_str()
+              << ", mWritingMode=" << ToString(aSelection.mWritingMode).c_str()
+              << ",  Collapsed()="
+              << (aSelection.Collapsed() ? "true" : "false")
+              << ", Length=" << aSelection.Length() << " }";
+      return aStream;
+    }
+
+   private:
+    Maybe<TS_SELECTION_ACP> mACP;  // If Nothing, there is no selection
+    WritingMode mWritingMode;
+  };
+  // Don't access mSelection directly.  Instead, Use SelectionForTSFRef().
+  // This is modified immediately when TSF requests to set selection and not
+  // updated by selection change in content until mContentForTSF is cleared.
+  Maybe<Selection> mSelectionForTSF;
+
+  /**
+   * Get the selection expected by TSF.  If mSelectionForTSF is already valid,
+   * this just return the reference to it.  Otherwise, this initializes it
+   * with eQuerySelectedText.  Please check if the result is valid before
+   * actually using it.
+   * Note that this is also called by ContentForTSF().
+   */
+  Maybe<Selection>& SelectionForTSF();
+
+  struct PendingAction final {
+    enum class Type : uint8_t {
+      eCompositionStart,
+      eCompositionUpdate,
+      eCompositionEnd,
+      eSetSelection,
+      eKeyboardEvent,
+    };
+    Type mType;
+    // For eCompositionStart, eCompositionEnd and eSetSelection
+    LONG mSelectionStart;
+    // For eCompositionStart and eSetSelection
+    LONG mSelectionLength;
+    // For eCompositionStart, eCompositionUpdate and eCompositionEnd
+    nsString mData;
+    // For eCompositionUpdate
+    RefPtr<TextRangeArray> mRanges;
+    // For eKeyboardEvent
+    MSG mKeyMsg;
+    // For eSetSelection
+    bool mSelectionReversed;
+    // For eCompositionUpdate
+    bool mIncomplete;
+    // For eCompositionStart
+    bool mAdjustSelection;
+  };
+  // Items of mPendingActions are appended when TSF tells us to need to dispatch
+  // DOM composition events.  However, we cannot dispatch while the document is
+  // locked because it can cause modifying the locked document.  So, the pending
+  // actions should be performed when document lock is unlocked.
+  nsTArray<PendingAction> mPendingActions;
+
+  PendingAction* LastOrNewPendingCompositionUpdate() {
+    if (!mPendingActions.IsEmpty()) {
+      PendingAction& lastAction = mPendingActions.LastElement();
+      if (lastAction.mType == PendingAction::Type::eCompositionUpdate) {
+        return &lastAction;
+      }
+    }
+    PendingAction* newAction = mPendingActions.AppendElement();
+    newAction->mType = PendingAction::Type::eCompositionUpdate;
+    newAction->mRanges = new TextRangeArray();
+    newAction->mIncomplete = true;
+    return newAction;
+  }
+
+  /**
+   * IsLastPendingActionCompositionEndAt() checks whether the previous pending
+   * action is committing composition whose range starts from aStart and its
+   * length is aLength.  In other words, this checks whether new composition
+   * which will replace same range as previous pending commit can be merged
+   * with the previous composition.
+   *
+   * @param aStart              The inserted offset you expected.
+   * @param aLength             The inserted text length you expected.
+   * @return                    true if the last pending action is
+   *                            eCompositionEnd and it inserted the text
+   *                            between aStart and aStart + aLength.
+   */
+  bool IsLastPendingActionCompositionEndAt(LONG aStart, LONG aLength) const {
+    if (mPendingActions.IsEmpty()) {
+      return false;
+    }
+    const PendingAction& pendingLastAction = mPendingActions.LastElement();
+    return pendingLastAction.mType == PendingAction::Type::eCompositionEnd &&
+           pendingLastAction.mSelectionStart == aStart &&
+           pendingLastAction.mData.Length() == static_cast<ULONG>(aLength);
+  }
+
+  bool IsPendingCompositionUpdateIncomplete() const {
+    if (mPendingActions.IsEmpty()) {
+      return false;
+    }
+    const PendingAction& lastAction = mPendingActions.LastElement();
+    return lastAction.mType == PendingAction::Type::eCompositionUpdate &&
+           lastAction.mIncomplete;
+  }
+
+  void CompleteLastActionIfStillIncomplete() {
+    if (!IsPendingCompositionUpdateIncomplete()) {
+      return;
+    }
+    RecordCompositionUpdateAction();
+  }
+
+  void RemoveLastCompositionUpdateActions() {
+    while (!mPendingActions.IsEmpty()) {
+      const PendingAction& lastAction = mPendingActions.LastElement();
+      if (lastAction.mType != PendingAction::Type::eCompositionUpdate) {
+        break;
+      }
+      mPendingActions.RemoveLastElement();
+    }
+  }
+
+  // When On*Composition() is called without document lock, we need to flush
+  // the recorded actions at quitting the method.
+  // AutoPendingActionAndContentFlusher class is usedful for it.
+  class MOZ_STACK_CLASS AutoPendingActionAndContentFlusher final {
+   public:
+    explicit AutoPendingActionAndContentFlusher(TSFTextStore* aTextStore)
+        : mTextStore(aTextStore) {
+      MOZ_ASSERT(!mTextStore->mIsRecordingActionsWithoutLock);
+      if (!mTextStore->IsReadWriteLocked()) {
+        mTextStore->mIsRecordingActionsWithoutLock = true;
+      }
+    }
+
+    ~AutoPendingActionAndContentFlusher() {
+      if (!mTextStore->mIsRecordingActionsWithoutLock) {
+        return;
+      }
+      mTextStore->FlushPendingActions();
+      mTextStore->mIsRecordingActionsWithoutLock = false;
+    }
+
+   private:
+    AutoPendingActionAndContentFlusher() {}
+
+    RefPtr<TSFTextStore> mTextStore;
+  };
+
+  class Content final {
+   public:
+    Content(TSFTextStore& aTSFTextStore, const nsAString& aText)
+        : mText(aText),
+          mLastComposition(aTSFTextStore.mComposition),
+          mComposition(aTSFTextStore.mComposition),
+          mSelection(aTSFTextStore.mSelectionForTSF) {}
+
+    void OnLayoutChanged() { mMinModifiedOffset.reset(); }
+
+    // OnCompositionEventsHandled() is called when all pending composition
+    // events are handled in the focused content which may be in a remote
+    // process.
+    void OnCompositionEventsHandled() { mLastComposition = mComposition; }
+
+    const nsDependentSubstring GetSelectedText() const;
+    const nsDependentSubstring GetSubstring(uint32_t aStart,
+                                            uint32_t aLength) const;
+    void ReplaceSelectedTextWith(const nsAString& aString);
+    void ReplaceTextWith(LONG aStart, LONG aLength, const nsAString& aString);
+
+    void StartComposition(ITfCompositionView* aCompositionView,
+                          const PendingAction& aCompStart,
+                          bool aPreserveSelection);
+    /**
+     * RestoreCommittedComposition() restores the committed string as
+     * composing string.  If InsertTextAtSelection() or something is called
+     * before a call of OnStartComposition() or previous composition is
+     * committed and new composition is restarted to clean up the commited
+     * string, there is a pending compositionend.  In this case, we need to
+     * cancel the pending compositionend and continue the composition.
+     *
+     * @param aCompositionView          The composition view.
+     * @param aCanceledCompositionEnd   The pending compositionend which is
+     *                                  canceled for restarting the composition.
+     */
+    void RestoreCommittedComposition(
+        ITfCompositionView* aCompositionView,
+        const PendingAction& aCanceledCompositionEnd);
+    void EndComposition(const PendingAction& aCompEnd);
+
+    const nsString& TextRef() const { return mText; }
+    const Maybe<OffsetAndData<LONG>>& LastComposition() const {
+      return mLastComposition;
+    }
+    const Maybe<uint32_t>& MinModifiedOffset() const {
+      return mMinModifiedOffset;
+    }
+    const Maybe<StartAndEndOffsets<LONG>>& LatestCompositionRange() const {
+      return mLatestCompositionRange;
+    }
+
+    // Returns true if layout of the character at the aOffset has not been
+    // calculated.
+    bool IsLayoutChangedAt(uint32_t aOffset) const {
+      return IsLayoutChanged() && (mMinModifiedOffset.value() <= aOffset);
+    }
+    // Returns true if layout of the content has been changed, i.e., the new
+    // layout has not been calculated.
+    bool IsLayoutChanged() const { return mMinModifiedOffset.isSome(); }
+    bool HasOrHadComposition() const {
+      return mLatestCompositionRange.isSome();
+    }
+
+    Maybe<TSFTextStore::Composition>& Composition() { return mComposition; }
+    Maybe<TSFTextStore::Selection>& Selection() { return mSelection; }
+
+    friend std::ostream& operator<<(std::ostream& aStream,
+                                    const Content& aContent) {
+      aStream << "{ mText="
+              << PrintStringDetail(aContent.mText,
+                                   PrintStringDetail::kMaxLengthForEditor)
+                     .get()
+              << ", mLastComposition=" << aContent.mLastComposition
+              << ", mLatestCompositionRange="
+              << aContent.mLatestCompositionRange
+              << ", mMinModifiedOffset=" << aContent.mMinModifiedOffset << " }";
+      return aStream;
+    }
+
+   private:
+    nsString mText;
+
+    // mLastComposition may store the composition string and its start offset
+    // when the document is locked. This is necessary to compute
+    // mMinTextModifiedOffset.
+    Maybe<OffsetAndData<LONG>> mLastComposition;
+
+    Maybe<TSFTextStore::Composition>& mComposition;
+    Maybe<TSFTextStore::Selection>& mSelection;
+
+    // The latest composition's start and end offset.
+    Maybe<StartAndEndOffsets<LONG>> mLatestCompositionRange;
+
+    // The minimum offset of modified part of the text.
+    Maybe<uint32_t> mMinModifiedOffset;
+  };
+  // mContentForTSF is cache of content.  The information is expected by TSF
+  // and TIP.  Therefore, this is useful for answering the query from TSF or
+  // TIP.
+  // This is initialized by ContentForTSF() automatically (therefore, don't
+  // access this member directly except at calling Clear(), IsInitialized(),
+  // IsLayoutChangeAfter() or IsLayoutChanged()).
+  // This is cleared when:
+  //  - When there is no composition, the document is unlocked.
+  //  - When there is a composition, all dispatched events are handled by
+  //    the focused editor which may be in a remote process.
+  // So, if two compositions are created very quickly, this cache may not be
+  // cleared between eCompositionCommit(AsIs) and eCompositionStart.
+  Maybe<Content> mContentForTSF;
+
+  Maybe<Content>& ContentForTSF();
+
+  class MOZ_STACK_CLASS AutoNotifyingTSFBatch final {
+   public:
+    explicit AutoNotifyingTSFBatch(TSFTextStore& aTextStore)
+        : mTextStore(aTextStore), mOldValue(aTextStore.mDeferNotifyingTSF) {
+      mTextStore.mDeferNotifyingTSF = true;
+    }
+    ~AutoNotifyingTSFBatch() {
+      mTextStore.mDeferNotifyingTSF = mOldValue;
+      mTextStore.MaybeFlushPendingNotifications();
+    }
+
+   private:
+    TSFTextStore& mTextStore;
+    bool mOldValue;
+  };
+
+  // CanAccessActualContentDirectly() returns true when TSF/TIP can access
+  // actual content directly.  In other words, mContentForTSF and/or
+  // mSelectionForTSF doesn't cache content or they matches with actual
+  // contents due to no pending text/selection change notifications.
+  bool CanAccessActualContentDirectly() const;
+
+  // While mContentForTSF is valid, this returns the text stored by it.
+  // Otherwise, return the current text content retrieved by eQueryTextContent.
+  bool GetCurrentText(nsAString& aTextContent);
+
+  class MouseTracker final {
+   public:
+    static const DWORD kInvalidCookie = static_cast<DWORD>(-1);
+
+    MouseTracker();
+
+    HRESULT Init(TSFTextStore* aTextStore);
+    HRESULT AdviseSink(TSFTextStore* aTextStore, ITfRangeACP* aTextRange,
+                       ITfMouseSink* aMouseSink);
+    void UnadviseSink();
+
+    bool IsUsing() const { return mSink != nullptr; }
+    DWORD Cookie() const { return mCookie; }
+    bool OnMouseButtonEvent(ULONG aEdge, ULONG aQuadrant, DWORD aButtonStatus);
+    const Maybe<StartAndEndOffsets<LONG>> Range() const { return mRange; }
+
+   private:
+    RefPtr<ITfMouseSink> mSink;
+    Maybe<StartAndEndOffsets<LONG>> mRange;
+    DWORD mCookie;
+  };
+  // mMouseTrackers is an array to store each information of installed
+  // ITfMouseSink instance.
+  nsTArray<MouseTracker> mMouseTrackers;
+
+  // The input scopes for this context, defaults to IS_DEFAULT.
+  nsTArray<InputScope> mInputScopes;
+
+  // The URL cache of the focused document.
+  nsString mDocumentURL;
+
+  // Support retrieving attributes.
+  // TODO: We should support RightToLeft, perhaps.
+  enum {
+    // Used for result of GetRequestedAttrIndex()
+    eNotSupported = -1,
+
+    // Supported attributes
+    eInputScope = 0,
+    eDocumentURL,
+    eTextVerticalWriting,
+    eTextOrientation,
+
+    // Count of the supported attributes
+    NUM_OF_SUPPORTED_ATTRS
+  };
+  bool mRequestedAttrs[NUM_OF_SUPPORTED_ATTRS] = {false};
+
+  int32_t GetRequestedAttrIndex(const TS_ATTRID& aAttrID);
+  TS_ATTRID GetAttrID(int32_t aIndex);
+
+  bool mRequestedAttrValues = false;
+
+  // If edit actions are being recorded without document lock, this is true.
+  // Otherwise, false.
+  bool mIsRecordingActionsWithoutLock = false;
+  // If GetTextExt() or GetACPFromPoint() is called and the layout hasn't been
+  // calculated yet, these methods return TS_E_NOLAYOUT.  At that time,
+  // mHasReturnedNoLayoutError is set to true.
+  bool mHasReturnedNoLayoutError = false;
+  // Before calling ITextStoreACPSink::OnLayoutChange() and
+  // ITfContextOwnerServices::OnLayoutChange(), mWaitingQueryLayout is set to
+  // true.  This is set to  false when GetTextExt() or GetACPFromPoint() is
+  // called.
+  bool mWaitingQueryLayout = false;
+  // During the document is locked, we shouldn't destroy the instance.
+  // If this is true, the instance will be destroyed after unlocked.
+  bool mPendingDestroy = false;
+  // If this is false, MaybeFlushPendingNotifications() will clear the
+  // mContentForTSF.
+  bool mDeferClearingContentForTSF = false;
+  // While the instance is initializing content/selection cache, another
+  // initialization shouldn't run recursively.  Therefore, while the
+  // initialization is running, this is set to true.  Use AutoNotifyingTSFBatch
+  // to set this.
+  bool mDeferNotifyingTSF = false;
+  // While the instance is dispatching events, the event may not be handled
+  // synchronously when remote content has focus.  In the case, we cannot
+  // return the latest layout/content information to TSF/TIP until we get next
+  // update notification from ContentCacheInParent.  For preventing TSF/TIP
+  // retrieves the latest content/layout information while it becomes available,
+  // we should put off notifying TSF of any updates.
+  bool mDeferNotifyingTSFUntilNextUpdate = false;
+  // While the document is locked, committing composition always fails since
+  // TSF needs another document lock for modifying the composition, selection
+  // and etc.  So, committing composition should be performed after the
+  // document is unlocked.
+  bool mDeferCommittingComposition = false;
+  bool mDeferCancellingComposition = false;
+  // Immediately after a call of Destroy(), mDestroyed becomes true.  If this
+  // is true, the instance shouldn't grant any requests from the TIP anymore.
+  bool mDestroyed = false;
+  // While the instance is being destroyed, this is set to true for avoiding
+  // recursive Destroy() calls.
+  bool mBeingDestroyed = false;
+  // Whether we're in the private browsing mode.
+  bool mInPrivateBrowsing = true;
+  // Debug flag to check whether we're initializing mContentForTSF and
+  // mSelectionForTSF.
+  bool mIsInitializingContentForTSF = false;
+  bool mIsInitializingSelectionForTSF = false;
+
+  // TSF thread manager object for the current application
+  static StaticRefPtr<ITfThreadMgr> sThreadMgr;
+  static already_AddRefed<ITfThreadMgr> GetThreadMgr();
+  // sMessagePump is QI'ed from sThreadMgr
+  static StaticRefPtr<ITfMessagePump> sMessagePump;
+
+ public:
+  // Expose GetMessagePump() for WinUtils.
+  static already_AddRefed<ITfMessagePump> GetMessagePump();
+
+ private:
+  // sKeystrokeMgr is QI'ed from sThreadMgr
+  static StaticRefPtr<ITfKeystrokeMgr> sKeystrokeMgr;
+  // TSF display attribute manager
+  static StaticRefPtr<ITfDisplayAttributeMgr> sDisplayAttrMgr;
+  static already_AddRefed<ITfDisplayAttributeMgr> GetDisplayAttributeMgr();
+  // TSF category manager
+  static StaticRefPtr<ITfCategoryMgr> sCategoryMgr;
+  static already_AddRefed<ITfCategoryMgr> GetCategoryMgr();
+  // Compartment for (Get|Set)IMEOpenState()
+  static StaticRefPtr<ITfCompartment> sCompartmentForOpenClose;
+  static already_AddRefed<ITfCompartment> GetCompartmentForOpenClose();
+
+  // Current text store which is managing a keyboard enabled editor (i.e.,
+  // editable editor).  Currently only ONE TSFTextStore instance is ever used,
+  // although Create is called when an editor is focused and Destroy called
+  // when the focused editor is blurred.
+  static StaticRefPtr<TSFTextStore> sEnabledTextStore;
+
+  // For IME (keyboard) disabled state:
+  static StaticRefPtr<ITfDocumentMgr> sDisabledDocumentMgr;
+  static StaticRefPtr<ITfContext> sDisabledContext;
+
+  static StaticRefPtr<ITfInputProcessorProfiles> sInputProcessorProfiles;
+  static already_AddRefed<ITfInputProcessorProfiles>
+  GetInputProcessorProfiles();
+
+  // Handling key message.
+  static const MSG* sHandlingKeyMsg;
+
+  // TSF client ID for the current application
+  static DWORD sClientId;
+
+  // true if an eKeyDown or eKeyUp event for sHandlingKeyMsg has already
+  // been dispatched.
+  static bool sIsKeyboardEventDispatched;
+};
+
+}  // namespace widget
+}  // namespace mozilla
+
+#endif  // #ifndef TSFTextStore_h_
diff --git a/widget/windows/TaskbarPreview.cpp b/widget/windows/TaskbarPreview.cpp
new file mode 100644
index 0000000000..2b958f84c1
--- /dev/null
+++ b/widget/windows/TaskbarPreview.cpp
@@ -0,0 +1,413 @@
+/* vim: se cin sw=2 ts=2 et : */
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "TaskbarPreview.h"
+#include <nsITaskbarPreviewController.h>
+#include <windows.h>
+
+#include <nsError.h>
+#include <nsCOMPtr.h>
+#include <nsIWidget.h>
+#include <nsServiceManagerUtils.h>
+
+#include "nsUXThemeData.h"
+#include "nsWindow.h"
+#include "nsAppShell.h"
+#include "TaskbarPreviewButton.h"
+#include "WinUtils.h"
+
+#include "mozilla/dom/HTMLCanvasElement.h"
+#include "mozilla/gfx/2D.h"
+#include "mozilla/gfx/DataSurfaceHelpers.h"
+#include "mozilla/StaticPrefs_layout.h"
+#include "mozilla/Telemetry.h"
+
+// Defined in dwmapi in a header that needs a higher numbered _WINNT #define
+#ifndef DWM_SIT_DISPLAYFRAME
+#  define DWM_SIT_DISPLAYFRAME 0x1
+#endif
+
+namespace mozilla {
+namespace widget {
+
+///////////////////////////////////////////////////////////////////////////////
+// TaskbarPreview
+
+TaskbarPreview::TaskbarPreview(ITaskbarList4* aTaskbar,
+                               nsITaskbarPreviewController* aController,
+                               HWND aHWND, nsIDocShell* aShell)
+    : mTaskbar(aTaskbar),
+      mController(aController),
+      mWnd(aHWND),
+      mVisible(false),
+      mDocShell(do_GetWeakReference(aShell)) {}
+
+TaskbarPreview::~TaskbarPreview() {
+  // Avoid dangling pointer
+  if (sActivePreview == this) sActivePreview = nullptr;
+
+  // Our subclass should have invoked DetachFromNSWindow already.
+  NS_ASSERTION(
+      !mWnd,
+      "TaskbarPreview::DetachFromNSWindow was not called before destruction");
+
+  // Make sure to release before potentially uninitializing COM
+  mTaskbar = nullptr;
+
+  ::CoUninitialize();
+}
+
+nsresult TaskbarPreview::Init() {
+  // TaskbarPreview may outlive the WinTaskbar that created it
+  if (FAILED(::CoInitialize(nullptr))) {
+    return NS_ERROR_NOT_INITIALIZED;
+  }
+
+  WindowHook* hook = GetWindowHook();
+  if (!hook) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+  return hook->AddMonitor(WM_DESTROY, MainWindowHook, this);
+}
+
+NS_IMETHODIMP
+TaskbarPreview::SetController(nsITaskbarPreviewController* aController) {
+  NS_ENSURE_ARG(aController);
+
+  mController = aController;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+TaskbarPreview::GetController(nsITaskbarPreviewController** aController) {
+  NS_ADDREF(*aController = mController);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+TaskbarPreview::GetTooltip(nsAString& aTooltip) {
+  aTooltip = mTooltip;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+TaskbarPreview::SetTooltip(const nsAString& aTooltip) {
+  mTooltip = aTooltip;
+  return CanMakeTaskbarCalls() ? UpdateTooltip() : NS_OK;
+}
+
+NS_IMETHODIMP
+TaskbarPreview::SetVisible(bool visible) {
+  if (mVisible == visible) return NS_OK;
+  mVisible = visible;
+
+  // If the nsWindow has already been destroyed but the caller is still trying
+  // to use it then just pretend that everything succeeded.  The caller doesn't
+  // actually have a way to detect this since it's the same case as when we
+  // CanMakeTaskbarCalls returns false.
+  if (!IsWindowAvailable()) return NS_OK;
+
+  return visible ? Enable() : Disable();
+}
+
+NS_IMETHODIMP
+TaskbarPreview::GetVisible(bool* visible) {
+  *visible = mVisible;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+TaskbarPreview::SetActive(bool active) {
+  if (active)
+    sActivePreview = this;
+  else if (sActivePreview == this)
+    sActivePreview = nullptr;
+
+  return CanMakeTaskbarCalls() ? ShowActive(active) : NS_OK;
+}
+
+NS_IMETHODIMP
+TaskbarPreview::GetActive(bool* active) {
+  *active = sActivePreview == this;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+TaskbarPreview::Invalidate() {
+  if (!mVisible) return NS_OK;
+
+  HWND previewWindow = PreviewWindow();
+  return FAILED(DwmInvalidateIconicBitmaps(previewWindow)) ? NS_ERROR_FAILURE
+                                                           : NS_OK;
+}
+
+nsresult TaskbarPreview::UpdateTaskbarProperties() {
+  nsresult rv = UpdateTooltip();
+
+  // If we are the active preview and our window is the active window, restore
+  // our active state - otherwise some other non-preview window is now active
+  // and should be displayed as so.
+  if (sActivePreview == this) {
+    if (mWnd == ::GetActiveWindow()) {
+      nsresult rvActive = ShowActive(true);
+      if (NS_FAILED(rvActive)) rv = rvActive;
+    } else {
+      sActivePreview = nullptr;
+    }
+  }
+  return rv;
+}
+
+nsresult TaskbarPreview::Enable() {
+  nsresult rv = NS_OK;
+  if (CanMakeTaskbarCalls()) {
+    rv = UpdateTaskbarProperties();
+  } else if (IsWindowAvailable()) {
+    WindowHook* hook = GetWindowHook();
+    MOZ_ASSERT(hook,
+               "IsWindowAvailable() should have eliminated the null case.");
+    hook->AddMonitor(nsAppShell::GetTaskbarButtonCreatedMessage(),
+                     MainWindowHook, this);
+  }
+  return rv;
+}
+
+nsresult TaskbarPreview::Disable() {
+  if (!IsWindowAvailable()) {
+    // Window is already destroyed
+    return NS_OK;
+  }
+
+  WindowHook* hook = GetWindowHook();
+  MOZ_ASSERT(hook, "IsWindowAvailable() should have eliminated the null case.");
+  (void)hook->RemoveMonitor(nsAppShell::GetTaskbarButtonCreatedMessage(),
+                            MainWindowHook, this);
+
+  return NS_OK;
+}
+
+bool TaskbarPreview::IsWindowAvailable() const {
+  if (mWnd) {
+    nsWindow* win = WinUtils::GetNSWindowPtr(mWnd);
+    if (win && !win->Destroyed()) {
+      return true;
+    }
+  }
+  return false;
+}
+
+void TaskbarPreview::DetachFromNSWindow() {
+  if (WindowHook* hook = GetWindowHook()) {
+    hook->RemoveMonitor(WM_DESTROY, MainWindowHook, this);
+  }
+  mWnd = nullptr;
+}
+
+LRESULT
+TaskbarPreview::WndProc(UINT nMsg, WPARAM wParam, LPARAM lParam) {
+  switch (nMsg) {
+    case WM_DWMSENDICONICTHUMBNAIL: {
+      uint32_t width = HIWORD(lParam);
+      uint32_t height = LOWORD(lParam);
+      float aspectRatio = width / float(height);
+
+      nsresult rv;
+      float preferredAspectRatio;
+      rv = mController->GetThumbnailAspectRatio(&preferredAspectRatio);
+      if (NS_FAILED(rv)) break;
+
+      uint32_t thumbnailWidth = width;
+      uint32_t thumbnailHeight = height;
+
+      if (aspectRatio > preferredAspectRatio) {
+        thumbnailWidth = uint32_t(thumbnailHeight * preferredAspectRatio);
+      } else {
+        thumbnailHeight = uint32_t(thumbnailWidth / preferredAspectRatio);
+      }
+
+      DrawBitmap(thumbnailWidth, thumbnailHeight, false);
+    } break;
+    case WM_DWMSENDICONICLIVEPREVIEWBITMAP: {
+      uint32_t width, height;
+      nsresult rv;
+      rv = mController->GetWidth(&width);
+      if (NS_FAILED(rv)) break;
+      rv = mController->GetHeight(&height);
+      if (NS_FAILED(rv)) break;
+
+      double scale = StaticPrefs::layout_css_devPixelsPerPx();
+      if (scale <= 0.0) {
+        scale = WinUtils::LogToPhysFactor(PreviewWindow());
+      }
+      DrawBitmap(NSToIntRound(scale * width), NSToIntRound(scale * height),
+                 true);
+    } break;
+  }
+  return ::DefWindowProcW(PreviewWindow(), nMsg, wParam, lParam);
+}
+
+bool TaskbarPreview::CanMakeTaskbarCalls() {
+  // If the nsWindow has already been destroyed and we know it but our caller
+  // clearly doesn't so we can't make any calls.
+  if (!mWnd) return false;
+  // Certain functions like SetTabOrder seem to require a visible window. During
+  // window close, the window seems to be hidden before being destroyed.
+  if (!::IsWindowVisible(mWnd)) return false;
+  if (mVisible) {
+    nsWindow* window = WinUtils::GetNSWindowPtr(mWnd);
+    NS_ASSERTION(window, "Could not get nsWindow from HWND");
+    return window ? window->HasTaskbarIconBeenCreated() : false;
+  }
+  return false;
+}
+
+WindowHook* TaskbarPreview::GetWindowHook() {
+  nsWindow* window = WinUtils::GetNSWindowPtr(mWnd);
+  NS_ASSERTION(window, "Cannot use taskbar previews in an embedded context!");
+
+  return window ? &window->GetWindowHook() : nullptr;
+}
+
+void TaskbarPreview::EnableCustomDrawing(HWND aHWND, bool aEnable) {
+  BOOL enabled = aEnable;
+  DwmSetWindowAttribute(aHWND, DWMWA_FORCE_ICONIC_REPRESENTATION, &enabled,
+                        sizeof(enabled));
+
+  DwmSetWindowAttribute(aHWND, DWMWA_HAS_ICONIC_BITMAP, &enabled,
+                        sizeof(enabled));
+}
+
+nsresult TaskbarPreview::UpdateTooltip() {
+  NS_ASSERTION(CanMakeTaskbarCalls() && mVisible,
+               "UpdateTooltip called on invisible tab preview");
+
+  if (FAILED(mTaskbar->SetThumbnailTooltip(PreviewWindow(), mTooltip.get())))
+    return NS_ERROR_FAILURE;
+  return NS_OK;
+}
+
+void TaskbarPreview::DrawBitmap(uint32_t width, uint32_t height,
+                                bool isPreview) {
+  nsresult rv;
+  nsCOMPtr<nsITaskbarPreviewCallback> callback =
+      do_CreateInstance("@mozilla.org/widget/taskbar-preview-callback;1", &rv);
+  if (NS_FAILED(rv)) {
+    return;
+  }
+
+  ((TaskbarPreviewCallback*)callback.get())->SetPreview(this);
+
+  if (isPreview) {
+    ((TaskbarPreviewCallback*)callback.get())->SetIsPreview();
+    mController->RequestPreview(callback);
+  } else {
+    mController->RequestThumbnail(callback, width, height);
+  }
+}
+
+///////////////////////////////////////////////////////////////////////////////
+// TaskbarPreviewCallback
+
+NS_IMPL_ISUPPORTS(TaskbarPreviewCallback, nsITaskbarPreviewCallback)
+
+/* void done (in nsISupports aCanvas, in boolean aDrawBorder); */
+NS_IMETHODIMP
+TaskbarPreviewCallback::Done(nsISupports* aCanvas, bool aDrawBorder) {
+  // We create and destroy TaskbarTabPreviews from front end code in response
+  // to TabOpen and TabClose events. Each TaskbarTabPreview creates and owns a
+  // proxy HWND which it hands to Windows as a tab identifier. When a tab
+  // closes, TaskbarTabPreview Disable() method is called by front end, which
+  // destroys the proxy window and clears mProxyWindow which is the HWND
+  // returned from PreviewWindow(). So, since this is async, we should check to
+  // be sure the tab is still alive before doing all this gfx work and making
+  // dwm calls. To accomplish this we check the result of PreviewWindow().
+  if (!aCanvas || !mPreview || !mPreview->PreviewWindow() ||
+      !mPreview->IsWindowAvailable()) {
+    return NS_ERROR_FAILURE;
+  }
+
+  nsCOMPtr<nsIContent> content(do_QueryInterface(aCanvas));
+  auto canvas = dom::HTMLCanvasElement::FromNodeOrNull(content);
+  if (!canvas) {
+    return NS_ERROR_FAILURE;
+  }
+
+  RefPtr<gfx::SourceSurface> source = canvas->GetSurfaceSnapshot();
+  if (!source) {
+    return NS_ERROR_FAILURE;
+  }
+  RefPtr<gfxWindowsSurface> target = new gfxWindowsSurface(
+      source->GetSize(), gfx::SurfaceFormat::A8R8G8B8_UINT32);
+  if (target->CairoStatus() != CAIRO_STATUS_SUCCESS) {
+    return NS_ERROR_FAILURE;
+  }
+
+  using DataSrcSurf = gfx::DataSourceSurface;
+  RefPtr<DataSrcSurf> srcSurface = source->GetDataSurface();
+  RefPtr<gfxImageSurface> imageSurface = target->GetAsImageSurface();
+  if (!srcSurface || !imageSurface) {
+    return NS_ERROR_FAILURE;
+  }
+
+  if (DataSrcSurf::ScopedMap const sourceMap(srcSurface, DataSrcSurf::READ);
+      sourceMap.IsMapped()) {
+    mozilla::gfx::CopySurfaceDataToPackedArray(
+        sourceMap.GetData(), imageSurface->Data(), srcSurface->GetSize(),
+        sourceMap.GetStride(), BytesPerPixel(srcSurface->GetFormat()));
+  } else if (source->GetSize().IsEmpty()) {
+    // A zero-size source-surface probably shouldn't happen, but is harmless
+    // here. Fall through.
+  } else {
+    return NS_ERROR_FAILURE;
+  }
+
+  HDC hDC = target->GetDC();
+  HBITMAP hBitmap = (HBITMAP)GetCurrentObject(hDC, OBJ_BITMAP);
+
+  DWORD flags = aDrawBorder ? DWM_SIT_DISPLAYFRAME : 0;
+  HRESULT hr;
+  if (!mIsThumbnail) {
+    POINT pptClient = {0, 0};
+    hr = DwmSetIconicLivePreviewBitmap(mPreview->PreviewWindow(), hBitmap,
+                                       &pptClient, flags);
+  } else {
+    hr = DwmSetIconicThumbnail(mPreview->PreviewWindow(), hBitmap, flags);
+  }
+  MOZ_ASSERT(SUCCEEDED(hr));
+  mozilla::Unused << hr;
+  return NS_OK;
+}
+
+/* static */
+bool TaskbarPreview::MainWindowHook(void* aContext, HWND hWnd, UINT nMsg,
+                                    WPARAM wParam, LPARAM lParam,
+                                    LRESULT* aResult) {
+  NS_ASSERTION(nMsg == nsAppShell::GetTaskbarButtonCreatedMessage() ||
+                   nMsg == WM_DESTROY,
+               "Window hook proc called with wrong message");
+  NS_ASSERTION(aContext, "Null context in MainWindowHook");
+  if (!aContext) return false;
+  TaskbarPreview* preview = reinterpret_cast<TaskbarPreview*>(aContext);
+  if (nMsg == WM_DESTROY) {
+    // nsWindow is being destroyed
+    // We can't really do anything at this point including removing hooks
+    return false;
+  } else {
+    nsWindow* window = WinUtils::GetNSWindowPtr(preview->mWnd);
+    if (window) {
+      window->SetHasTaskbarIconBeenCreated();
+
+      if (preview->mVisible) preview->UpdateTaskbarProperties();
+    }
+  }
+  return false;
+}
+
+TaskbarPreview* TaskbarPreview::sActivePreview = nullptr;
+
+}  // namespace widget
+}  // namespace mozilla
diff --git a/widget/windows/TaskbarPreview.h b/widget/windows/TaskbarPreview.h
new file mode 100644
index 0000000000..ca21e3eeb8
--- /dev/null
+++ b/widget/windows/TaskbarPreview.h
@@ -0,0 +1,132 @@
+/* vim: se cin sw=2 ts=2 et : */
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef __mozilla_widget_TaskbarPreview_h__
+#define __mozilla_widget_TaskbarPreview_h__
+
+#include <windows.h>
+#include <shobjidl.h>
+#undef LogSeverity  // SetupAPI.h #defines this as DWORD
+
+#include "mozilla/RefPtr.h"
+#include <nsITaskbarPreview.h>
+#include <nsITaskbarPreviewController.h>
+#include <nsString.h>
+#include <nsIWeakReferenceUtils.h>
+#include <nsIDocShell.h>
+#include "WindowHook.h"
+
+namespace mozilla {
+namespace widget {
+
+class TaskbarPreviewCallback;
+
+class TaskbarPreview : public nsITaskbarPreview {
+ public:
+  TaskbarPreview(ITaskbarList4* aTaskbar,
+                 nsITaskbarPreviewController* aController, HWND aHWND,
+                 nsIDocShell* aShell);
+  virtual nsresult Init();
+
+  friend class TaskbarPreviewCallback;
+
+  NS_DECL_NSITASKBARPREVIEW
+
+ protected:
+  virtual ~TaskbarPreview();
+
+  // Called to update ITaskbarList4 dependent properties
+  virtual nsresult UpdateTaskbarProperties();
+
+  // Invoked when the preview is made visible
+  virtual nsresult Enable();
+  // Invoked when the preview is made invisible
+  virtual nsresult Disable();
+
+  // Detaches this preview from the nsWindow instance it's tied to
+  virtual void DetachFromNSWindow();
+
+  // Determines if the window is available and a destroy has not yet started
+  bool IsWindowAvailable() const;
+
+  // Marks this preview as being active
+  virtual nsresult ShowActive(bool active) = 0;
+  // Gets a reference to the window used to handle the preview messages
+  virtual HWND& PreviewWindow() = 0;
+
+  // Window procedure for the PreviewWindow (hooked for window previews)
+  virtual LRESULT WndProc(UINT nMsg, WPARAM wParam, LPARAM lParam);
+
+  // Returns whether or not the taskbar icon has been created for mWnd The
+  // ITaskbarList4 API requires that we wait until the icon has been created
+  // before we can call its methods.
+  bool CanMakeTaskbarCalls();
+
+  // Gets the WindowHook for the nsWindow
+  WindowHook* GetWindowHook();
+
+  // Enables/disables custom drawing for the given window
+  static void EnableCustomDrawing(HWND aHWND, bool aEnable);
+
+  // MSCOM Taskbar interface
+  RefPtr<ITaskbarList4> mTaskbar;
+  // Controller for this preview
+  nsCOMPtr<nsITaskbarPreviewController> mController;
+  // The HWND to the nsWindow that this object previews
+  HWND mWnd;
+  // Whether or not this preview is visible
+  bool mVisible;
+
+ private:
+  // Called when the tooltip should be updated
+  nsresult UpdateTooltip();
+
+  // Requests the controller to draw into a canvas of the given width and
+  // height. The resulting bitmap is sent to the DWM to display.
+  void DrawBitmap(uint32_t width, uint32_t height, bool isPreview);
+
+  // WindowHook procedure for hooking mWnd
+  static bool MainWindowHook(void* aContext, HWND hWnd, UINT nMsg,
+                             WPARAM wParam, LPARAM lParam, LRESULT* aResult);
+
+  // Docshell corresponding to the <window> the nsWindow contains
+  nsWeakPtr mDocShell;
+  nsString mTooltip;
+
+  // The preview currently marked as active in the taskbar. nullptr if no
+  // preview is active (some other window is).
+  static TaskbarPreview* sActivePreview;
+};
+
+/*
+ * Callback object TaskbarPreview hands to preview controllers when we
+ * request async thumbnail or live preview images. Controllers invoke
+ * this interface once they have aquired the requested image.
+ */
+class TaskbarPreviewCallback : public nsITaskbarPreviewCallback {
+ public:
+  TaskbarPreviewCallback() : mIsThumbnail(true) {}
+
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSITASKBARPREVIEWCALLBACK
+
+  void SetPreview(TaskbarPreview* aPreview) { mPreview = aPreview; }
+
+  void SetIsPreview() { mIsThumbnail = false; }
+
+ protected:
+  virtual ~TaskbarPreviewCallback() {}
+
+ private:
+  RefPtr<TaskbarPreview> mPreview;
+  bool mIsThumbnail;
+};
+
+}  // namespace widget
+}  // namespace mozilla
+
+#endif /* __mozilla_widget_TaskbarPreview_h__ */
diff --git a/widget/windows/TaskbarPreviewButton.cpp b/widget/windows/TaskbarPreviewButton.cpp
new file mode 100644
index 0000000000..abbb1069a9
--- /dev/null
+++ b/widget/windows/TaskbarPreviewButton.cpp
@@ -0,0 +1,137 @@
+/* vim: se cin sw=2 ts=2 et : */
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <windows.h>
+#include <strsafe.h>
+
+#include "TaskbarWindowPreview.h"
+#include "TaskbarPreviewButton.h"
+#include "nsWindowGfx.h"
+#include <imgIContainer.h>
+
+namespace mozilla {
+namespace widget {
+
+NS_IMPL_ISUPPORTS(TaskbarPreviewButton, nsITaskbarPreviewButton,
+                  nsISupportsWeakReference)
+
+TaskbarPreviewButton::TaskbarPreviewButton(TaskbarWindowPreview* preview,
+                                           uint32_t index)
+    : mPreview(preview), mIndex(index) {}
+
+TaskbarPreviewButton::~TaskbarPreviewButton() { SetVisible(false); }
+
+NS_IMETHODIMP
+TaskbarPreviewButton::GetTooltip(nsAString& aTooltip) {
+  aTooltip = mTooltip;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+TaskbarPreviewButton::SetTooltip(const nsAString& aTooltip) {
+  mTooltip = aTooltip;
+  size_t destLength = sizeof Button().szTip / (sizeof Button().szTip[0]);
+  wchar_t* tooltip = &(Button().szTip[0]);
+  StringCchCopyNW(tooltip, destLength, mTooltip.get(), mTooltip.Length());
+  return Update();
+}
+
+NS_IMETHODIMP
+TaskbarPreviewButton::GetDismissOnClick(bool* dismiss) {
+  *dismiss = (Button().dwFlags & THBF_DISMISSONCLICK) == THBF_DISMISSONCLICK;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+TaskbarPreviewButton::SetDismissOnClick(bool dismiss) {
+  if (dismiss)
+    Button().dwFlags |= THBF_DISMISSONCLICK;
+  else
+    Button().dwFlags &= ~THBF_DISMISSONCLICK;
+  return Update();
+}
+
+NS_IMETHODIMP
+TaskbarPreviewButton::GetHasBorder(bool* hasBorder) {
+  *hasBorder = (Button().dwFlags & THBF_NOBACKGROUND) != THBF_NOBACKGROUND;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+TaskbarPreviewButton::SetHasBorder(bool hasBorder) {
+  if (hasBorder)
+    Button().dwFlags &= ~THBF_NOBACKGROUND;
+  else
+    Button().dwFlags |= THBF_NOBACKGROUND;
+  return Update();
+}
+
+NS_IMETHODIMP
+TaskbarPreviewButton::GetDisabled(bool* disabled) {
+  *disabled = (Button().dwFlags & THBF_DISABLED) == THBF_DISABLED;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+TaskbarPreviewButton::SetDisabled(bool disabled) {
+  if (disabled)
+    Button().dwFlags |= THBF_DISABLED;
+  else
+    Button().dwFlags &= ~THBF_DISABLED;
+  return Update();
+}
+
+NS_IMETHODIMP
+TaskbarPreviewButton::GetImage(imgIContainer** img) {
+  if (mImage)
+    NS_ADDREF(*img = mImage);
+  else
+    *img = nullptr;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+TaskbarPreviewButton::SetImage(imgIContainer* img) {
+  if (Button().hIcon) ::DestroyIcon(Button().hIcon);
+  if (img) {
+    nsresult rv;
+    rv = nsWindowGfx::CreateIcon(
+        img, false, LayoutDeviceIntPoint(),
+        nsWindowGfx::GetIconMetrics(nsWindowGfx::kRegularIcon),
+        &Button().hIcon);
+    NS_ENSURE_SUCCESS(rv, rv);
+  } else {
+    Button().hIcon = nullptr;
+  }
+  return Update();
+}
+
+NS_IMETHODIMP
+TaskbarPreviewButton::GetVisible(bool* visible) {
+  *visible = (Button().dwFlags & THBF_HIDDEN) != THBF_HIDDEN;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+TaskbarPreviewButton::SetVisible(bool visible) {
+  if (visible)
+    Button().dwFlags &= ~THBF_HIDDEN;
+  else
+    Button().dwFlags |= THBF_HIDDEN;
+  return Update();
+}
+
+THUMBBUTTON& TaskbarPreviewButton::Button() {
+  return mPreview->mThumbButtons[mIndex];
+}
+
+nsresult TaskbarPreviewButton::Update() {
+  return mPreview->UpdateButton(mIndex);
+}
+
+}  // namespace widget
+}  // namespace mozilla
diff --git a/widget/windows/TaskbarPreviewButton.h b/widget/windows/TaskbarPreviewButton.h
new file mode 100644
index 0000000000..e13b2d6771
--- /dev/null
+++ b/widget/windows/TaskbarPreviewButton.h
@@ -0,0 +1,47 @@
+/* vim: se cin sw=2 ts=2 et : */
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef __mozilla_widget_TaskbarPreviewButton_h__
+#define __mozilla_widget_TaskbarPreviewButton_h__
+
+#include <windows.h>
+#include <shobjidl.h>
+#undef LogSeverity  // SetupAPI.h #defines this as DWORD
+
+#include "mozilla/RefPtr.h"
+#include <nsITaskbarPreviewButton.h>
+#include <nsString.h>
+#include "nsWeakReference.h"
+
+namespace mozilla {
+namespace widget {
+
+class TaskbarWindowPreview;
+class TaskbarPreviewButton : public nsITaskbarPreviewButton,
+                             public nsSupportsWeakReference {
+  virtual ~TaskbarPreviewButton();
+
+ public:
+  TaskbarPreviewButton(TaskbarWindowPreview* preview, uint32_t index);
+
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSITASKBARPREVIEWBUTTON
+
+ private:
+  THUMBBUTTON& Button();
+  nsresult Update();
+
+  RefPtr<TaskbarWindowPreview> mPreview;
+  uint32_t mIndex;
+  nsString mTooltip;
+  nsCOMPtr<imgIContainer> mImage;
+};
+
+}  // namespace widget
+}  // namespace mozilla
+
+#endif /* __mozilla_widget_TaskbarPreviewButton_h__ */
diff --git a/widget/windows/TaskbarTabPreview.cpp b/widget/windows/TaskbarTabPreview.cpp
new file mode 100644
index 0000000000..3421e68ffb
--- /dev/null
+++ b/widget/windows/TaskbarTabPreview.cpp
@@ -0,0 +1,344 @@
+/* vim: se cin sw=2 ts=2 et : */
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "TaskbarTabPreview.h"
+#include "nsWindowGfx.h"
+#include "nsUXThemeData.h"
+#include "WinUtils.h"
+#include <nsITaskbarPreviewController.h>
+
+#define TASKBARPREVIEW_HWNDID L"TaskbarTabPreviewHwnd"
+
+namespace mozilla {
+namespace widget {
+
+NS_IMPL_ISUPPORTS(TaskbarTabPreview, nsITaskbarTabPreview)
+
+const wchar_t* const kWindowClass = L"MozillaTaskbarPreviewClass";
+
+TaskbarTabPreview::TaskbarTabPreview(ITaskbarList4* aTaskbar,
+                                     nsITaskbarPreviewController* aController,
+                                     HWND aHWND, nsIDocShell* aShell)
+    : TaskbarPreview(aTaskbar, aController, aHWND, aShell),
+      mProxyWindow(nullptr),
+      mIcon(nullptr),
+      mRegistered(false) {}
+
+TaskbarTabPreview::~TaskbarTabPreview() {
+  if (mIcon) {
+    ::DestroyIcon(mIcon);
+    mIcon = nullptr;
+  }
+
+  // We need to ensure that proxy window disappears or else Bad Things happen.
+  if (mProxyWindow) Disable();
+
+  NS_ASSERTION(!mProxyWindow, "Taskbar proxy window was not destroyed!");
+
+  if (IsWindowAvailable()) {
+    DetachFromNSWindow();
+  } else {
+    mWnd = nullptr;
+  }
+}
+
+nsresult TaskbarTabPreview::Init() {
+  nsresult rv = TaskbarPreview::Init();
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+
+  WindowHook* hook = GetWindowHook();
+  if (!hook) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  return hook->AddMonitor(WM_WINDOWPOSCHANGED, MainWindowHook, this);
+}
+
+nsresult TaskbarTabPreview::ShowActive(bool active) {
+  NS_ASSERTION(mVisible && CanMakeTaskbarCalls(),
+               "ShowActive called on invisible window or before taskbar calls "
+               "can be made for this window");
+  return FAILED(
+             mTaskbar->SetTabActive(active ? mProxyWindow : nullptr, mWnd, 0))
+             ? NS_ERROR_FAILURE
+             : NS_OK;
+}
+
+HWND& TaskbarTabPreview::PreviewWindow() { return mProxyWindow; }
+
+nativeWindow TaskbarTabPreview::GetHWND() { return mProxyWindow; }
+
+void TaskbarTabPreview::EnsureRegistration() {
+  NS_ASSERTION(mVisible && CanMakeTaskbarCalls(),
+               "EnsureRegistration called when it is not safe to do so");
+
+  (void)UpdateTaskbarProperties();
+}
+
+NS_IMETHODIMP
+TaskbarTabPreview::GetTitle(nsAString& aTitle) {
+  aTitle = mTitle;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+TaskbarTabPreview::SetTitle(const nsAString& aTitle) {
+  mTitle = aTitle;
+  return mVisible ? UpdateTitle() : NS_OK;
+}
+
+NS_IMETHODIMP
+TaskbarTabPreview::SetIcon(imgIContainer* icon) {
+  HICON hIcon = nullptr;
+  if (icon) {
+    nsresult rv;
+    rv = nsWindowGfx::CreateIcon(
+        icon, false, LayoutDeviceIntPoint(),
+        nsWindowGfx::GetIconMetrics(nsWindowGfx::kSmallIcon), &hIcon);
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+
+  if (mIcon) ::DestroyIcon(mIcon);
+  mIcon = hIcon;
+  mIconImage = icon;
+  return mVisible ? UpdateIcon() : NS_OK;
+}
+
+NS_IMETHODIMP
+TaskbarTabPreview::GetIcon(imgIContainer** icon) {
+  NS_IF_ADDREF(*icon = mIconImage);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+TaskbarTabPreview::Move(nsITaskbarTabPreview* aNext) {
+  if (aNext == this) return NS_ERROR_INVALID_ARG;
+  mNext = aNext;
+  return CanMakeTaskbarCalls() ? UpdateNext() : NS_OK;
+}
+
+nsresult TaskbarTabPreview::UpdateTaskbarProperties() {
+  if (mRegistered) return NS_OK;
+
+  if (FAILED(mTaskbar->RegisterTab(mProxyWindow, mWnd)))
+    return NS_ERROR_FAILURE;
+
+  nsresult rv = UpdateNext();
+  NS_ENSURE_SUCCESS(rv, rv);
+  rv = TaskbarPreview::UpdateTaskbarProperties();
+  mRegistered = true;
+  return rv;
+}
+
+LRESULT
+TaskbarTabPreview::WndProc(UINT nMsg, WPARAM wParam, LPARAM lParam) {
+  RefPtr<TaskbarTabPreview> kungFuDeathGrip(this);
+  switch (nMsg) {
+    case WM_CREATE:
+      TaskbarPreview::EnableCustomDrawing(mProxyWindow, true);
+      return 0;
+    case WM_CLOSE:
+      mController->OnClose();
+      return 0;
+    case WM_ACTIVATE:
+      if (LOWORD(wParam) == WA_ACTIVE) {
+        // Activate the tab the user selected then restore the main window,
+        // keeping normal/max window state intact.
+        bool activateWindow;
+        nsresult rv = mController->OnActivate(&activateWindow);
+        if (NS_SUCCEEDED(rv) && activateWindow) {
+          nsWindow* win = WinUtils::GetNSWindowPtr(mWnd);
+          if (win) {
+            nsWindow* parent = win->GetTopLevelWindow(true);
+            if (parent) {
+              parent->Show(true);
+            }
+          }
+        }
+      }
+      return 0;
+    case WM_GETICON:
+      return (LRESULT)mIcon;
+    case WM_SYSCOMMAND:
+      // Send activation events to the top level window and select the proper
+      // tab through the controller.
+      if (wParam == SC_RESTORE || wParam == SC_MAXIMIZE) {
+        bool activateWindow;
+        nsresult rv = mController->OnActivate(&activateWindow);
+        if (NS_SUCCEEDED(rv) && activateWindow) {
+          // Note, restoring an iconic, maximized window here will only
+          // activate the maximized window. This is not a bug, it's default
+          // windows behavior.
+          ::SendMessageW(mWnd, WM_SYSCOMMAND, wParam, lParam);
+        }
+        return 0;
+      }
+      // Forward everything else to the top level window. Do not forward
+      // close since that's intended for the tab. When the preview proxy
+      // closes, we'll close the tab above.
+      return wParam == SC_CLOSE
+                 ? ::DefWindowProcW(mProxyWindow, WM_SYSCOMMAND, wParam, lParam)
+                 : ::SendMessageW(mWnd, WM_SYSCOMMAND, wParam, lParam);
+  }
+  return TaskbarPreview::WndProc(nMsg, wParam, lParam);
+}
+
+/* static */
+LRESULT CALLBACK TaskbarTabPreview::GlobalWndProc(HWND hWnd, UINT nMsg,
+                                                  WPARAM wParam,
+                                                  LPARAM lParam) {
+  TaskbarTabPreview* preview(nullptr);
+  if (nMsg == WM_CREATE) {
+    CREATESTRUCT* cs = reinterpret_cast<CREATESTRUCT*>(lParam);
+    preview = reinterpret_cast<TaskbarTabPreview*>(cs->lpCreateParams);
+    if (!::SetPropW(hWnd, TASKBARPREVIEW_HWNDID, preview))
+      NS_ERROR("Could not associate native window with tab preview");
+    preview->mProxyWindow = hWnd;
+  } else {
+    preview = reinterpret_cast<TaskbarTabPreview*>(
+        ::GetPropW(hWnd, TASKBARPREVIEW_HWNDID));
+    if (nMsg == WM_DESTROY) ::RemovePropW(hWnd, TASKBARPREVIEW_HWNDID);
+  }
+
+  if (preview) return preview->WndProc(nMsg, wParam, lParam);
+  return ::DefWindowProcW(hWnd, nMsg, wParam, lParam);
+}
+
+nsresult TaskbarTabPreview::Enable() {
+  WNDCLASSW wc;
+  HINSTANCE module = GetModuleHandle(nullptr);
+
+  if (!GetClassInfoW(module, kWindowClass, &wc)) {
+    wc.style = 0;
+    wc.lpfnWndProc = GlobalWndProc;
+    wc.cbClsExtra = 0;
+    wc.cbWndExtra = 0;
+    wc.hInstance = module;
+    wc.hIcon = nullptr;
+    wc.hCursor = nullptr;
+    wc.hbrBackground = (HBRUSH) nullptr;
+    wc.lpszMenuName = (LPCWSTR) nullptr;
+    wc.lpszClassName = kWindowClass;
+    RegisterClassW(&wc);
+  }
+  ::CreateWindowW(kWindowClass, L"TaskbarPreviewWindow",
+                  WS_CAPTION | WS_SYSMENU, 0, 0, 200, 60, nullptr, nullptr,
+                  module, this);
+  // GlobalWndProc will set mProxyWindow so that WM_CREATE can have a valid HWND
+  if (!mProxyWindow) return NS_ERROR_INVALID_ARG;
+
+  UpdateProxyWindowStyle();
+
+  nsresult rv = TaskbarPreview::Enable();
+  nsresult rvUpdate;
+  rvUpdate = UpdateTitle();
+  if (NS_FAILED(rvUpdate)) rv = rvUpdate;
+
+  rvUpdate = UpdateIcon();
+  if (NS_FAILED(rvUpdate)) rv = rvUpdate;
+
+  return rv;
+}
+
+nsresult TaskbarTabPreview::Disable() {
+  // TaskbarPreview::Disable assumes that mWnd is valid but this method can be
+  // called when it is null iff the nsWindow has already been destroyed and we
+  // are still visible for some reason during object destruction.
+  if (mWnd) TaskbarPreview::Disable();
+
+  if (FAILED(mTaskbar->UnregisterTab(mProxyWindow))) return NS_ERROR_FAILURE;
+  mRegistered = false;
+
+  // TaskbarPreview::WndProc will set mProxyWindow to null
+  if (!DestroyWindow(mProxyWindow)) return NS_ERROR_FAILURE;
+  mProxyWindow = nullptr;
+  return NS_OK;
+}
+
+void TaskbarTabPreview::DetachFromNSWindow() {
+  (void)SetVisible(false);
+  if (WindowHook* hook = GetWindowHook()) {
+    hook->RemoveMonitor(WM_WINDOWPOSCHANGED, MainWindowHook, this);
+  }
+  TaskbarPreview::DetachFromNSWindow();
+}
+
+/* static */
+bool TaskbarTabPreview::MainWindowHook(void* aContext, HWND hWnd, UINT nMsg,
+                                       WPARAM wParam, LPARAM lParam,
+                                       LRESULT* aResult) {
+  if (nMsg == WM_WINDOWPOSCHANGED) {
+    TaskbarTabPreview* preview = reinterpret_cast<TaskbarTabPreview*>(aContext);
+    WINDOWPOS* pos = reinterpret_cast<WINDOWPOS*>(lParam);
+    if (SWP_FRAMECHANGED == (pos->flags & SWP_FRAMECHANGED))
+      preview->UpdateProxyWindowStyle();
+  } else {
+    MOZ_ASSERT_UNREACHABLE(
+        "Style changed hook fired on non-style changed "
+        "message");
+  }
+  return false;
+}
+
+void TaskbarTabPreview::UpdateProxyWindowStyle() {
+  if (!mProxyWindow) return;
+
+  DWORD minMaxMask = WS_MINIMIZE | WS_MAXIMIZE;
+  DWORD windowStyle = GetWindowLongW(mWnd, GWL_STYLE);
+
+  DWORD proxyStyle = GetWindowLongW(mProxyWindow, GWL_STYLE);
+  proxyStyle &= ~minMaxMask;
+  proxyStyle |= windowStyle & minMaxMask;
+  SetWindowLongW(mProxyWindow, GWL_STYLE, proxyStyle);
+
+  DWORD exStyle =
+      (WS_MAXIMIZE == (windowStyle & WS_MAXIMIZE)) ? WS_EX_TOOLWINDOW : 0;
+  SetWindowLongW(mProxyWindow, GWL_EXSTYLE, exStyle);
+}
+
+nsresult TaskbarTabPreview::UpdateTitle() {
+  NS_ASSERTION(mVisible, "UpdateTitle called on invisible preview");
+
+  if (!::SetWindowTextW(mProxyWindow, mTitle.get())) return NS_ERROR_FAILURE;
+  return NS_OK;
+}
+
+nsresult TaskbarTabPreview::UpdateIcon() {
+  NS_ASSERTION(mVisible, "UpdateIcon called on invisible preview");
+
+  ::SendMessageW(mProxyWindow, WM_SETICON, ICON_SMALL, (LPARAM)mIcon);
+
+  return NS_OK;
+}
+
+nsresult TaskbarTabPreview::UpdateNext() {
+  NS_ASSERTION(CanMakeTaskbarCalls() && mVisible,
+               "UpdateNext called on invisible tab preview");
+  HWND hNext = nullptr;
+  if (mNext) {
+    bool visible;
+    nsresult rv = mNext->GetVisible(&visible);
+
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    // Can only move next to enabled previews
+    if (!visible) return NS_ERROR_FAILURE;
+
+    hNext = (HWND)mNext->GetHWND();
+
+    // hNext must be registered with the taskbar if the call is to succeed
+    mNext->EnsureRegistration();
+  }
+  if (FAILED(mTaskbar->SetTabOrder(mProxyWindow, hNext)))
+    return NS_ERROR_FAILURE;
+  return NS_OK;
+}
+
+}  // namespace widget
+}  // namespace mozilla
diff --git a/widget/windows/TaskbarTabPreview.h b/widget/windows/TaskbarTabPreview.h
new file mode 100644
index 0000000000..9a15760557
--- /dev/null
+++ b/widget/windows/TaskbarTabPreview.h
@@ -0,0 +1,70 @@
+/* vim: se cin sw=2 ts=2 et : */
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef __mozilla_widget_TaskbarTabPreview_h__
+#define __mozilla_widget_TaskbarTabPreview_h__
+
+#include "nsITaskbarTabPreview.h"
+#include "TaskbarPreview.h"
+
+namespace mozilla {
+namespace widget {
+
+class TaskbarTabPreview : public nsITaskbarTabPreview, public TaskbarPreview {
+  virtual ~TaskbarTabPreview();
+
+ public:
+  TaskbarTabPreview(ITaskbarList4* aTaskbar,
+                    nsITaskbarPreviewController* aController, HWND aHWND,
+                    nsIDocShell* aShell);
+  virtual nsresult Init() override;
+
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSITASKBARTABPREVIEW
+  NS_FORWARD_NSITASKBARPREVIEW(TaskbarPreview::)
+
+ private:
+  virtual nsresult ShowActive(bool active);
+  virtual HWND& PreviewWindow();
+  virtual LRESULT WndProc(UINT nMsg, WPARAM wParam, LPARAM lParam);
+  static LRESULT CALLBACK GlobalWndProc(HWND hWnd, UINT nMsg, WPARAM wParam,
+                                        LPARAM lParam);
+
+  virtual nsresult UpdateTaskbarProperties();
+  virtual nsresult Enable();
+  virtual nsresult Disable();
+  virtual void DetachFromNSWindow();
+
+  // WindowHook procedure for hooking mWnd
+  static bool MainWindowHook(void* aContext, HWND hWnd, UINT nMsg,
+                             WPARAM wParam, LPARAM lParam, LRESULT* aResult);
+
+  // Bug 520807 - we need to update the proxy window style based on the main
+  // window's style to workaround a bug with the way the DWM displays the
+  // previews.
+  void UpdateProxyWindowStyle();
+
+  nsresult UpdateTitle();
+  nsresult UpdateIcon();
+  nsresult UpdateNext();
+
+  // Handle to the toplevel proxy window
+  HWND mProxyWindow;
+  nsString mTitle;
+  nsCOMPtr<imgIContainer> mIconImage;
+  // Cached Windows icon of mIconImage
+  HICON mIcon;
+  // Preview that follows this preview in the taskbar (left-to-right order)
+  nsCOMPtr<nsITaskbarTabPreview> mNext;
+  // True if this preview has been registered with the taskbar
+  bool mRegistered;
+};
+
+}  // namespace widget
+}  // namespace mozilla
+
+#endif /* __mozilla_widget_TaskbarTabPreview_h__ */
diff --git a/widget/windows/TaskbarWindowPreview.cpp b/widget/windows/TaskbarWindowPreview.cpp
new file mode 100644
index 0000000000..212278be4a
--- /dev/null
+++ b/widget/windows/TaskbarWindowPreview.cpp
@@ -0,0 +1,326 @@
+/* vim: se cin sw=2 ts=2 et : */
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/ArrayUtils.h"
+
+#include <nsITaskbarPreviewController.h>
+#include "TaskbarWindowPreview.h"
+#include "WindowHook.h"
+#include "nsUXThemeData.h"
+#include "TaskbarPreviewButton.h"
+#include "nsWindow.h"
+#include "nsWindowGfx.h"
+
+namespace mozilla {
+namespace widget {
+
+namespace {
+bool WindowHookProc(void* aContext, HWND hWnd, UINT nMsg, WPARAM wParam,
+                    LPARAM lParam, LRESULT* aResult) {
+  TaskbarWindowPreview* preview =
+      reinterpret_cast<TaskbarWindowPreview*>(aContext);
+  *aResult = preview->WndProc(nMsg, wParam, lParam);
+  return true;
+}
+}  // namespace
+
+NS_IMPL_ISUPPORTS(TaskbarWindowPreview, nsITaskbarWindowPreview,
+                  nsITaskbarProgress, nsITaskbarOverlayIconController,
+                  nsISupportsWeakReference)
+
+/**
+ * These correspond directly to the states defined in nsITaskbarProgress.idl, so
+ * they should be kept in sync.
+ */
+static TBPFLAG sNativeStates[] = {TBPF_NOPROGRESS, TBPF_INDETERMINATE,
+                                  TBPF_NORMAL, TBPF_ERROR, TBPF_PAUSED};
+
+TaskbarWindowPreview::TaskbarWindowPreview(
+    ITaskbarList4* aTaskbar, nsITaskbarPreviewController* aController,
+    HWND aHWND, nsIDocShell* aShell)
+    : TaskbarPreview(aTaskbar, aController, aHWND, aShell),
+      mCustomDrawing(false),
+      mHaveButtons(false),
+      mState(TBPF_NOPROGRESS),
+      mCurrentValue(0),
+      mMaxValue(0),
+      mOverlayIcon(nullptr) {
+  // Window previews are visible by default
+  (void)SetVisible(true);
+
+  memset(mThumbButtons, 0, sizeof mThumbButtons);
+  for (int32_t i = 0; i < nsITaskbarWindowPreview::NUM_TOOLBAR_BUTTONS; i++) {
+    mThumbButtons[i].dwMask = THB_FLAGS | THB_ICON | THB_TOOLTIP;
+    mThumbButtons[i].iId = i;
+    mThumbButtons[i].dwFlags = THBF_HIDDEN;
+  }
+}
+
+TaskbarWindowPreview::~TaskbarWindowPreview() {
+  if (mOverlayIcon) {
+    ::DestroyIcon(mOverlayIcon);
+    mOverlayIcon = nullptr;
+  }
+
+  // We need to clean up a hook associated with the "this" pointer.
+  SetVisible(false);
+
+  if (IsWindowAvailable()) {
+    DetachFromNSWindow();
+  } else {
+    mWnd = nullptr;
+  }
+}
+
+nsresult TaskbarWindowPreview::Init() {
+  nsresult rv = TaskbarPreview::Init();
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+
+  if (CanMakeTaskbarCalls()) {
+    return NS_OK;
+  }
+
+  WindowHook* hook = GetWindowHook();
+  if (!hook) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  return hook->AddMonitor(nsAppShell::GetTaskbarButtonCreatedMessage(),
+                          TaskbarWindowHook, this);
+}
+
+nsresult TaskbarWindowPreview::ShowActive(bool active) {
+  return FAILED(mTaskbar->ActivateTab(active ? mWnd : nullptr))
+             ? NS_ERROR_FAILURE
+             : NS_OK;
+}
+
+HWND& TaskbarWindowPreview::PreviewWindow() { return mWnd; }
+
+nsresult TaskbarWindowPreview::GetButton(uint32_t index,
+                                         nsITaskbarPreviewButton** _retVal) {
+  if (index >= nsITaskbarWindowPreview::NUM_TOOLBAR_BUTTONS)
+    return NS_ERROR_INVALID_ARG;
+
+  nsCOMPtr<nsITaskbarPreviewButton> button(
+      do_QueryReferent(mWeakButtons[index]));
+
+  if (!button) {
+    // Lost reference
+    button = new TaskbarPreviewButton(this, index);
+    if (!button) {
+      return NS_ERROR_OUT_OF_MEMORY;
+    }
+    mWeakButtons[index] = do_GetWeakReference(button);
+  }
+
+  if (!mHaveButtons) {
+    mHaveButtons = true;
+
+    WindowHook* hook = GetWindowHook();
+    if (!hook) {
+      return NS_ERROR_NOT_AVAILABLE;
+    }
+    (void)hook->AddHook(WM_COMMAND, WindowHookProc, this);
+
+    if (mVisible && FAILED(mTaskbar->ThumbBarAddButtons(
+                        mWnd, nsITaskbarWindowPreview::NUM_TOOLBAR_BUTTONS,
+                        mThumbButtons))) {
+      return NS_ERROR_FAILURE;
+    }
+  }
+  button.forget(_retVal);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+TaskbarWindowPreview::SetEnableCustomDrawing(bool aEnable) {
+  if (aEnable == mCustomDrawing) return NS_OK;
+
+  WindowHook* hook = GetWindowHook();
+  if (!hook) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  mCustomDrawing = aEnable;
+  TaskbarPreview::EnableCustomDrawing(mWnd, aEnable);
+
+  if (aEnable) {
+    (void)hook->AddHook(WM_DWMSENDICONICTHUMBNAIL, WindowHookProc, this);
+    (void)hook->AddHook(WM_DWMSENDICONICLIVEPREVIEWBITMAP, WindowHookProc,
+                        this);
+  } else {
+    (void)hook->RemoveHook(WM_DWMSENDICONICLIVEPREVIEWBITMAP, WindowHookProc,
+                           this);
+    (void)hook->RemoveHook(WM_DWMSENDICONICTHUMBNAIL, WindowHookProc, this);
+  }
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+TaskbarWindowPreview::GetEnableCustomDrawing(bool* aEnable) {
+  *aEnable = mCustomDrawing;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+TaskbarWindowPreview::SetProgressState(nsTaskbarProgressState aState,
+                                       uint64_t aCurrentValue,
+                                       uint64_t aMaxValue) {
+  NS_ENSURE_ARG_RANGE(aState, nsTaskbarProgressState(0),
+                      nsTaskbarProgressState(ArrayLength(sNativeStates) - 1));
+
+  TBPFLAG nativeState = sNativeStates[aState];
+  if (nativeState == TBPF_NOPROGRESS || nativeState == TBPF_INDETERMINATE) {
+    NS_ENSURE_TRUE(aCurrentValue == 0, NS_ERROR_INVALID_ARG);
+    NS_ENSURE_TRUE(aMaxValue == 0, NS_ERROR_INVALID_ARG);
+  }
+
+  if (aCurrentValue > aMaxValue) return NS_ERROR_ILLEGAL_VALUE;
+
+  mState = nativeState;
+  mCurrentValue = aCurrentValue;
+  mMaxValue = aMaxValue;
+
+  // Only update if we can
+  return CanMakeTaskbarCalls() ? UpdateTaskbarProgress() : NS_OK;
+}
+
+NS_IMETHODIMP
+TaskbarWindowPreview::SetOverlayIcon(imgIContainer* aStatusIcon,
+                                     const nsAString& aStatusDescription) {
+  nsresult rv;
+  if (aStatusIcon) {
+    // The image shouldn't be animated
+    bool isAnimated;
+    rv = aStatusIcon->GetAnimated(&isAnimated);
+    NS_ENSURE_SUCCESS(rv, rv);
+    NS_ENSURE_FALSE(isAnimated, NS_ERROR_INVALID_ARG);
+  }
+
+  HICON hIcon = nullptr;
+  if (aStatusIcon) {
+    rv = nsWindowGfx::CreateIcon(
+        aStatusIcon, false, LayoutDeviceIntPoint(),
+        nsWindowGfx::GetIconMetrics(nsWindowGfx::kSmallIcon), &hIcon);
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+
+  if (mOverlayIcon) ::DestroyIcon(mOverlayIcon);
+  mOverlayIcon = hIcon;
+  mIconDescription = aStatusDescription;
+
+  // Only update if we can
+  return CanMakeTaskbarCalls() ? UpdateOverlayIcon() : NS_OK;
+}
+
+nsresult TaskbarWindowPreview::UpdateTaskbarProperties() {
+  if (mHaveButtons) {
+    if (FAILED(mTaskbar->ThumbBarAddButtons(
+            mWnd, nsITaskbarWindowPreview::NUM_TOOLBAR_BUTTONS, mThumbButtons)))
+      return NS_ERROR_FAILURE;
+  }
+  nsresult rv = UpdateTaskbarProgress();
+  NS_ENSURE_SUCCESS(rv, rv);
+  rv = UpdateOverlayIcon();
+  NS_ENSURE_SUCCESS(rv, rv);
+  return TaskbarPreview::UpdateTaskbarProperties();
+}
+
+nsresult TaskbarWindowPreview::UpdateTaskbarProgress() {
+  HRESULT hr = mTaskbar->SetProgressState(mWnd, mState);
+  if (SUCCEEDED(hr) && mState != TBPF_NOPROGRESS &&
+      mState != TBPF_INDETERMINATE)
+    hr = mTaskbar->SetProgressValue(mWnd, mCurrentValue, mMaxValue);
+
+  return SUCCEEDED(hr) ? NS_OK : NS_ERROR_FAILURE;
+}
+
+nsresult TaskbarWindowPreview::UpdateOverlayIcon() {
+  HRESULT hr =
+      mTaskbar->SetOverlayIcon(mWnd, mOverlayIcon, mIconDescription.get());
+  return SUCCEEDED(hr) ? NS_OK : NS_ERROR_FAILURE;
+}
+
+LRESULT
+TaskbarWindowPreview::WndProc(UINT nMsg, WPARAM wParam, LPARAM lParam) {
+  RefPtr<TaskbarWindowPreview> kungFuDeathGrip(this);
+  switch (nMsg) {
+    case WM_COMMAND: {
+      uint32_t id = LOWORD(wParam);
+      uint32_t index = id;
+      nsCOMPtr<nsITaskbarPreviewButton> button;
+      nsresult rv = GetButton(index, getter_AddRefs(button));
+      if (NS_SUCCEEDED(rv)) mController->OnClick(button);
+    }
+      return 0;
+  }
+  return TaskbarPreview::WndProc(nMsg, wParam, lParam);
+}
+
+/* static */
+bool TaskbarWindowPreview::TaskbarWindowHook(void* aContext, HWND hWnd,
+                                             UINT nMsg, WPARAM wParam,
+                                             LPARAM lParam, LRESULT* aResult) {
+  NS_ASSERTION(nMsg == nsAppShell::GetTaskbarButtonCreatedMessage(),
+               "Window hook proc called with wrong message");
+  TaskbarWindowPreview* preview =
+      reinterpret_cast<TaskbarWindowPreview*>(aContext);
+  // Now we can make all the calls to mTaskbar
+  preview->UpdateTaskbarProperties();
+  return false;
+}
+
+nsresult TaskbarWindowPreview::Enable() {
+  nsresult rv = TaskbarPreview::Enable();
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  return FAILED(mTaskbar->AddTab(mWnd)) ? NS_ERROR_FAILURE : NS_OK;
+}
+
+nsresult TaskbarWindowPreview::Disable() {
+  nsresult rv = TaskbarPreview::Disable();
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  return FAILED(mTaskbar->DeleteTab(mWnd)) ? NS_ERROR_FAILURE : NS_OK;
+}
+
+void TaskbarWindowPreview::DetachFromNSWindow() {
+  // Remove the hooks we have for drawing
+  SetEnableCustomDrawing(false);
+
+  if (WindowHook* hook = GetWindowHook()) {
+    (void)hook->RemoveHook(WM_COMMAND, WindowHookProc, this);
+    (void)hook->RemoveMonitor(nsAppShell::GetTaskbarButtonCreatedMessage(),
+                              TaskbarWindowHook, this);
+  }
+  TaskbarPreview::DetachFromNSWindow();
+}
+
+nsresult TaskbarWindowPreview::UpdateButtons() {
+  NS_ASSERTION(mVisible, "UpdateButtons called on invisible preview");
+
+  if (FAILED(mTaskbar->ThumbBarUpdateButtons(
+          mWnd, nsITaskbarWindowPreview::NUM_TOOLBAR_BUTTONS, mThumbButtons)))
+    return NS_ERROR_FAILURE;
+  return NS_OK;
+}
+
+nsresult TaskbarWindowPreview::UpdateButton(uint32_t index) {
+  if (index >= nsITaskbarWindowPreview::NUM_TOOLBAR_BUTTONS)
+    return NS_ERROR_INVALID_ARG;
+  if (mVisible) {
+    if (FAILED(mTaskbar->ThumbBarUpdateButtons(mWnd, 1, &mThumbButtons[index])))
+      return NS_ERROR_FAILURE;
+  }
+  return NS_OK;
+}
+
+}  // namespace widget
+}  // namespace mozilla
diff --git a/widget/windows/TaskbarWindowPreview.h b/widget/windows/TaskbarWindowPreview.h
new file mode 100644
index 0000000000..97c074197c
--- /dev/null
+++ b/widget/windows/TaskbarWindowPreview.h
@@ -0,0 +1,85 @@
+/* vim: se cin sw=2 ts=2 et : */
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef __mozilla_widget_TaskbarWindowPreview_h__
+#define __mozilla_widget_TaskbarWindowPreview_h__
+
+#include "nsITaskbarWindowPreview.h"
+#include "nsITaskbarProgress.h"
+#include "nsITaskbarOverlayIconController.h"
+#include "TaskbarPreview.h"
+#include "nsWeakReference.h"
+
+namespace mozilla {
+namespace widget {
+
+class TaskbarPreviewButton;
+class TaskbarWindowPreview : public TaskbarPreview,
+                             public nsITaskbarWindowPreview,
+                             public nsITaskbarProgress,
+                             public nsITaskbarOverlayIconController,
+                             public nsSupportsWeakReference {
+  virtual ~TaskbarWindowPreview();
+
+ public:
+  TaskbarWindowPreview(ITaskbarList4* aTaskbar,
+                       nsITaskbarPreviewController* aController, HWND aHWND,
+                       nsIDocShell* aShell);
+  virtual nsresult Init() override;
+
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSITASKBARWINDOWPREVIEW
+  NS_DECL_NSITASKBARPROGRESS
+  NS_DECL_NSITASKBAROVERLAYICONCONTROLLER
+  NS_FORWARD_NSITASKBARPREVIEW(TaskbarPreview::)
+
+  virtual LRESULT WndProc(UINT nMsg, WPARAM wParam, LPARAM lParam) override;
+
+ private:
+  virtual nsresult ShowActive(bool active) override;
+  virtual HWND& PreviewWindow() override;
+
+  virtual nsresult UpdateTaskbarProperties() override;
+  virtual nsresult Enable() override;
+  virtual nsresult Disable() override;
+  virtual void DetachFromNSWindow() override;
+  nsresult UpdateButton(uint32_t index);
+  nsresult UpdateButtons();
+
+  // Is custom drawing enabled?
+  bool mCustomDrawing;
+  // Have we made any buttons?
+  bool mHaveButtons;
+  // Windows button format
+  THUMBBUTTON mThumbButtons[nsITaskbarWindowPreview::NUM_TOOLBAR_BUTTONS];
+  // Pointers to our button class (cached instances)
+  nsWeakPtr mWeakButtons[nsITaskbarWindowPreview::NUM_TOOLBAR_BUTTONS];
+
+  // Called to update ITaskbarList4 dependent properties
+  nsresult UpdateTaskbarProgress();
+  nsresult UpdateOverlayIcon();
+
+  // The taskbar progress
+  TBPFLAG mState;
+  ULONGLONG mCurrentValue;
+  ULONGLONG mMaxValue;
+
+  // Taskbar overlay icon
+  HICON mOverlayIcon;
+  nsString mIconDescription;
+
+  // WindowHook procedure for hooking mWnd for taskbar progress and icon stuff
+  static bool TaskbarWindowHook(void* aContext, HWND hWnd, UINT nMsg,
+                                WPARAM wParam, LPARAM lParam, LRESULT* aResult);
+
+  friend class TaskbarPreviewButton;
+};
+
+}  // namespace widget
+}  // namespace mozilla
+
+#endif /* __mozilla_widget_TaskbarWindowPreview_h__ */
diff --git a/widget/windows/ToastNotification.cpp b/widget/windows/ToastNotification.cpp
new file mode 100644
index 0000000000..afdffc19ac
--- /dev/null
+++ b/widget/windows/ToastNotification.cpp
@@ -0,0 +1,915 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:set ts=2 sts=2 sw=2 et cin: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "ToastNotification.h"
+
+#include <windows.h>
+#include <appmodel.h>
+#include <ktmw32.h>
+#include <windows.foundation.h>
+#include <wrl/client.h>
+
+#include "ErrorList.h"
+#include "mozilla/BasePrincipal.h"
+#include "mozilla/Buffer.h"
+#include "mozilla/dom/Promise.h"
+#include "mozilla/DynamicallyLinkedFunctionPtr.h"
+#include "mozilla/ErrorResult.h"
+#include "mozilla/mscom/COMWrappers.h"
+#include "mozilla/mscom/Utils.h"
+#include "mozilla/widget/WinRegistry.h"
+#include "mozilla/Logging.h"
+#include "mozilla/Services.h"
+#include "mozilla/WidgetUtils.h"
+#include "nsAppRunner.h"
+#include "nsComponentManagerUtils.h"
+#include "nsCOMPtr.h"
+#include "nsIObserverService.h"
+#include "nsIWindowMediator.h"
+#include "nsPIDOMWindow.h"
+#include "nsString.h"
+#include "nsThreadUtils.h"
+#include "nsWindowsHelpers.h"
+#include "nsXREDirProvider.h"
+#include "prenv.h"
+#include "ToastNotificationHandler.h"
+#include "ToastNotificationHeaderOnlyUtils.h"
+
+namespace mozilla {
+namespace widget {
+
+using namespace toastnotification;
+
+using namespace ABI::Windows::Foundation;
+using namespace Microsoft::WRL;
+using namespace Microsoft::WRL::Wrappers;
+// Needed to disambiguate internal and Windows `ToastNotification` classes.
+using namespace ABI::Windows::UI::Notifications;
+using WinToastNotification = ABI::Windows::UI::Notifications::ToastNotification;
+using IVectorView_ToastNotification =
+    ABI::Windows::Foundation::Collections::IVectorView<WinToastNotification*>;
+using IVectorView_ScheduledToastNotification =
+    ABI::Windows::Foundation::Collections::IVectorView<
+        ScheduledToastNotification*>;
+
+LazyLogModule sWASLog("WindowsAlertsService");
+
+NS_IMPL_ISUPPORTS(ToastNotification, nsIAlertsService, nsIWindowsAlertsService,
+                  nsIAlertsDoNotDisturb, nsIObserver)
+
+ToastNotification::ToastNotification() = default;
+
+ToastNotification::~ToastNotification() = default;
+
+nsresult ToastNotification::Init() {
+  if (!PR_GetEnv("XPCSHELL_TEST_PROFILE_DIR")) {
+    // Windows Toast Notification requires AppId.  But allow `xpcshell` to
+    // create the service to test other functionality.
+    if (!EnsureAumidRegistered()) {
+      MOZ_LOG(sWASLog, LogLevel::Warning, ("Failed to register AUMID!"));
+      return NS_ERROR_NOT_IMPLEMENTED;
+    }
+  } else {
+    MOZ_LOG(sWASLog, LogLevel::Info, ("Using dummy AUMID in xpcshell test"));
+    mAumid.emplace(u"XpcshellTestToastAumid"_ns);
+  }
+
+  MOZ_LOG(sWASLog, LogLevel::Info,
+          ("Using AUMID: '%s'", NS_ConvertUTF16toUTF8(mAumid.ref()).get()));
+
+  nsCOMPtr<nsIObserverService> obsServ =
+      mozilla::services::GetObserverService();
+  if (obsServ) {
+    Unused << NS_WARN_IF(
+        NS_FAILED(obsServ->AddObserver(this, "last-pb-context-exited", false)));
+    Unused << NS_WARN_IF(
+        NS_FAILED(obsServ->AddObserver(this, "quit-application", false)));
+  }
+
+  return NS_OK;
+}
+
+bool ToastNotification::EnsureAumidRegistered() {
+  // Check if this is an MSIX install, app identity is provided by the package
+  // so no registration is necessary.
+  if (AssignIfMsixAumid(mAumid)) {
+    MOZ_LOG(
+        sWASLog, LogLevel::Info,
+        ("Found MSIX AUMID: '%s'", NS_ConvertUTF16toUTF8(mAumid.ref()).get()));
+    return true;
+  }
+
+  nsAutoString installHash;
+  nsresult rv = gDirServiceProvider->GetInstallHash(installHash);
+  NS_ENSURE_SUCCESS(rv, false);
+
+  // Check if toasts were registered during NSIS/MSI installation.
+  if (AssignIfNsisAumid(installHash, mAumid)) {
+    MOZ_LOG(sWASLog, LogLevel::Info,
+            ("Found AUMID from installer (with install hash '%s'): '%s'",
+             NS_ConvertUTF16toUTF8(installHash).get(),
+             NS_ConvertUTF16toUTF8(mAumid.ref()).get()));
+    return true;
+  }
+
+  // No AUMID registered, fall through to runtime registration for development
+  // and portable builds.
+  if (RegisterRuntimeAumid(installHash, mAumid)) {
+    MOZ_LOG(
+        sWASLog, LogLevel::Info,
+        ("Updated AUMID registration at runtime (for install hash '%s'): '%s'",
+         NS_ConvertUTF16toUTF8(installHash).get(),
+         NS_ConvertUTF16toUTF8(mAumid.ref()).get()));
+    return true;
+  }
+
+  MOZ_LOG(sWASLog, LogLevel::Warning,
+          ("Failed to register AUMID at runtime! (for install hash '%s')",
+           NS_ConvertUTF16toUTF8(installHash).get()));
+  return false;
+}
+
+bool ToastNotification::AssignIfMsixAumid(Maybe<nsAutoString>& aAumid) {
+  UINT32 len = 0;
+  // ERROR_INSUFFICIENT_BUFFER signals that we're in an MSIX package, and
+  // therefore should use the package's AUMID.
+  if (GetCurrentApplicationUserModelId(&len, nullptr) !=
+      ERROR_INSUFFICIENT_BUFFER) {
+    MOZ_LOG(sWASLog, LogLevel::Debug, ("Not an MSIX package"));
+    return false;
+  }
+  mozilla::Buffer<wchar_t> buffer(len);
+  LONG success = GetCurrentApplicationUserModelId(&len, buffer.Elements());
+  NS_ENSURE_TRUE(success == ERROR_SUCCESS, false);
+
+  aAumid.emplace(buffer.Elements());
+  return true;
+}
+
+bool ToastNotification::AssignIfNsisAumid(nsAutoString& aInstallHash,
+                                          Maybe<nsAutoString>& aAumid) {
+  nsAutoString nsisAumidName =
+      u""_ns MOZ_TOAST_APP_NAME u"Toast-"_ns + aInstallHash;
+  nsAutoString nsisAumidPath = u"AppUserModelId\\"_ns + nsisAumidName;
+  if (!WinRegistry::HasKey(HKEY_CLASSES_ROOT, nsisAumidPath)) {
+    MOZ_LOG(sWASLog, LogLevel::Debug,
+            ("No CustomActivator value from installer in key 'HKCR\\%s'",
+             NS_ConvertUTF16toUTF8(nsisAumidPath).get()));
+    return false;
+  }
+
+  aAumid.emplace(nsisAumidName);
+  return true;
+}
+
+bool ToastNotification::RegisterRuntimeAumid(nsAutoString& aInstallHash,
+                                             Maybe<nsAutoString>& aAumid) {
+  // Portable AUMID slightly differs from installed AUMID so we can
+  // differentiate installed to HKCU vs portable installs if necessary.
+  nsAutoString portableAumid =
+      u""_ns MOZ_TOAST_APP_NAME u"PortableToast-"_ns + aInstallHash;
+
+  nsCOMPtr<nsIFile> appdir;
+  nsresult rv = gDirServiceProvider->GetGREDir()->Clone(getter_AddRefs(appdir));
+  NS_ENSURE_SUCCESS(rv, false);
+
+  nsCOMPtr<nsIFile> icon;
+  rv = appdir->Clone(getter_AddRefs(icon));
+  NS_ENSURE_SUCCESS(rv, false);
+
+  rv = icon->Append(u"browser"_ns);
+  NS_ENSURE_SUCCESS(rv, false);
+
+  rv = icon->Append(u"VisualElements"_ns);
+  NS_ENSURE_SUCCESS(rv, false);
+
+  rv = icon->Append(u"VisualElements_70.png"_ns);
+  NS_ENSURE_SUCCESS(rv, false);
+
+  nsAutoString iconPath;
+  rv = icon->GetPath(iconPath);
+  NS_ENSURE_SUCCESS(rv, false);
+
+  nsCOMPtr<nsIFile> comDll;
+  rv = appdir->Clone(getter_AddRefs(comDll));
+  NS_ENSURE_SUCCESS(rv, false);
+
+  rv = comDll->Append(u"notificationserver.dll"_ns);
+  NS_ENSURE_SUCCESS(rv, false);
+
+  nsAutoString dllPath;
+  rv = comDll->GetPath(dllPath);
+  NS_ENSURE_SUCCESS(rv, false);
+
+  nsAutoHandle txn;
+  // Manipulate the registry using a transaction so that any failures are
+  // rolled back.
+  wchar_t transactionName[] = L"" MOZ_TOAST_APP_NAME L" toast registration";
+  txn.own(::CreateTransaction(nullptr, nullptr, TRANSACTION_DO_NOT_PROMOTE, 0,
+                              0, 0, transactionName));
+  NS_ENSURE_TRUE(txn.get() != INVALID_HANDLE_VALUE, false);
+
+  LSTATUS status;
+
+  auto RegisterKey = [&](const nsAString& path, nsAutoRegKey& key) {
+    HKEY rawKey;
+    status = ::RegCreateKeyTransactedW(
+        HKEY_CURRENT_USER, PromiseFlatString(path).get(), 0, nullptr,
+        REG_OPTION_NON_VOLATILE, KEY_ALL_ACCESS, nullptr, &rawKey, nullptr, txn,
+        nullptr);
+    NS_ENSURE_TRUE(status == ERROR_SUCCESS, false);
+
+    key.own(rawKey);
+    return true;
+  };
+  auto RegisterValue = [&](nsAutoRegKey& key, const nsAString& name,
+                           unsigned long type, const nsAString& data) {
+    status = ::RegSetValueExW(
+        key, PromiseFlatString(name).get(), 0, type,
+        static_cast<const BYTE*>(PromiseFlatString(data).get()),
+        (data.Length() + 1) * sizeof(wchar_t));
+
+    return status == ERROR_SUCCESS;
+  };
+
+  // clang-format off
+  /* Writes the following keys and values to the registry.
+   * HKEY_CURRENT_USER\Software\Classes\AppID\{GUID}                                                      DllSurrogate    : REG_SZ        = ""
+   *                                   \AppUserModelId\{MOZ_TOAST_APP_NAME}PortableToast-{install hash}   CustomActivator : REG_SZ        = {GUID}
+   *                                                                                                      DisplayName     : REG_EXPAND_SZ = {display name}
+   *                                                                                                      IconUri         : REG_EXPAND_SZ = {icon path}
+   *                                   \CLSID\{GUID}                                                      AppID           : REG_SZ        = {GUID}
+   *                                                \InprocServer32                                       (Default)       : REG_SZ        = {notificationserver.dll path}
+   */
+  // clang-format on
+
+  constexpr nsLiteralString classes = u"Software\\Classes\\"_ns;
+
+  nsAutoString aumid = classes + u"AppUserModelId\\"_ns + portableAumid;
+  nsAutoRegKey aumidKey;
+  NS_ENSURE_TRUE(RegisterKey(aumid, aumidKey), false);
+
+  nsAutoString guidStr;
+  {
+    DWORD bufferSizeBytes = NSID_LENGTH * sizeof(wchar_t);
+    Buffer<wchar_t> guidBuffer(bufferSizeBytes);
+    status = ::RegGetValueW(HKEY_CURRENT_USER, aumid.get(), L"CustomActivator",
+                            RRF_RT_REG_SZ, 0, guidBuffer.Elements(),
+                            &bufferSizeBytes);
+
+    CLSID unused;
+    if (status == ERROR_SUCCESS &&
+        SUCCEEDED(CLSIDFromString(guidBuffer.Elements(), &unused))) {
+      guidStr = guidBuffer.Elements();
+    } else {
+      nsIDToCString uuidString(nsID::GenerateUUID());
+      size_t len = strlen(uuidString.get());
+      MOZ_ASSERT(len == NSID_LENGTH - 1);
+      CopyASCIItoUTF16(nsDependentCSubstring(uuidString.get(), len), guidStr);
+    }
+
+    if (status == ERROR_SUCCESS) {
+      MOZ_LOG(sWASLog, LogLevel::Debug,
+              ("Existing CustomActivator guid found: '%s'",
+               NS_ConvertUTF16toUTF8(guidStr).get()));
+    } else {
+      MOZ_LOG(sWASLog, LogLevel::Debug,
+              ("New CustomActivator guid generated: '%s'",
+               NS_ConvertUTF16toUTF8(guidStr).get()));
+    }
+  }
+  NS_ENSURE_TRUE(
+      RegisterValue(aumidKey, u"CustomActivator"_ns, REG_SZ, guidStr), false);
+  nsAutoString brandName;
+  WidgetUtils::GetBrandShortName(brandName);
+  NS_ENSURE_TRUE(
+      RegisterValue(aumidKey, u"DisplayName"_ns, REG_EXPAND_SZ, brandName),
+      false);
+  NS_ENSURE_TRUE(
+      RegisterValue(aumidKey, u"IconUri"_ns, REG_EXPAND_SZ, iconPath), false);
+
+  nsAutoString appid = classes + u"AppID\\"_ns + guidStr;
+  nsAutoRegKey appidKey;
+  NS_ENSURE_TRUE(RegisterKey(appid, appidKey), false);
+  NS_ENSURE_TRUE(RegisterValue(appidKey, u"DllSurrogate"_ns, REG_SZ, u""_ns),
+                 false);
+
+  nsAutoString clsid = classes + u"CLSID\\"_ns + guidStr;
+  nsAutoRegKey clsidKey;
+  NS_ENSURE_TRUE(RegisterKey(clsid, clsidKey), false);
+  NS_ENSURE_TRUE(RegisterValue(clsidKey, u"AppID"_ns, REG_SZ, guidStr), false);
+
+  nsAutoString inproc = clsid + u"\\InprocServer32"_ns;
+  nsAutoRegKey inprocKey;
+  NS_ENSURE_TRUE(RegisterKey(inproc, inprocKey), false);
+  // Set the component's path to this DLL
+  NS_ENSURE_TRUE(RegisterValue(inprocKey, u""_ns, REG_SZ, dllPath), false);
+
+  NS_ENSURE_TRUE(::CommitTransaction(txn), false);
+
+  MOZ_LOG(
+      sWASLog, LogLevel::Debug,
+      ("Updated registration for CustomActivator value in key 'HKCU\\%s': '%s'",
+       NS_ConvertUTF16toUTF8(aumid).get(),
+       NS_ConvertUTF16toUTF8(guidStr).get()));
+  aAumid.emplace(portableAumid);
+  return true;
+}
+
+nsresult ToastNotification::BackgroundDispatch(nsIRunnable* runnable) {
+  return NS_DispatchBackgroundTask(runnable);
+}
+
+NS_IMETHODIMP
+ToastNotification::GetSuppressForScreenSharing(bool* aRetVal) {
+  *aRetVal = mSuppressForScreenSharing;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+ToastNotification::SetSuppressForScreenSharing(bool aSuppress) {
+  mSuppressForScreenSharing = aSuppress;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+ToastNotification::Observe(nsISupports* aSubject, const char* aTopic,
+                           const char16_t* aData) {
+  nsDependentCString topic(aTopic);
+
+  for (auto iter = mActiveHandlers.Iter(); !iter.Done(); iter.Next()) {
+    RefPtr<ToastNotificationHandler> handler = iter.UserData();
+
+    auto removeNotification = [&]() {
+      // The handlers' destructors will do the right thing (de-register with
+      // Windows).
+      iter.Remove();
+
+      // Break the cycle between the handler and the MSCOM notification so the
+      // handler's destructor will be called.
+      handler->UnregisterHandler();
+    };
+
+    if (topic == "last-pb-context-exited"_ns) {
+      if (handler->IsPrivate()) {
+        handler->HideAlert();
+        removeNotification();
+      }
+    } else if (topic == "quit-application"_ns) {
+      removeNotification();
+    }
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+ToastNotification::ShowAlertNotification(
+    const nsAString& aImageUrl, const nsAString& aAlertTitle,
+    const nsAString& aAlertText, bool aAlertTextClickable,
+    const nsAString& aAlertCookie, nsIObserver* aAlertListener,
+    const nsAString& aAlertName, const nsAString& aBidi, const nsAString& aLang,
+    const nsAString& aData, nsIPrincipal* aPrincipal, bool aInPrivateBrowsing,
+    bool aRequireInteraction) {
+  nsCOMPtr<nsIAlertNotification> alert =
+      do_CreateInstance(ALERT_NOTIFICATION_CONTRACTID);
+  if (NS_WARN_IF(!alert)) {
+    return NS_ERROR_FAILURE;
+  }
+  // vibrate is unused for now
+  nsTArray<uint32_t> vibrate;
+  nsresult rv = alert->Init(aAlertName, aImageUrl, aAlertTitle, aAlertText,
+                            aAlertTextClickable, aAlertCookie, aBidi, aLang,
+                            aData, aPrincipal, aInPrivateBrowsing,
+                            aRequireInteraction, false, vibrate);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+  return ShowAlert(alert, aAlertListener);
+}
+
+NS_IMETHODIMP
+ToastNotification::ShowPersistentNotification(const nsAString& aPersistentData,
+                                              nsIAlertNotification* aAlert,
+                                              nsIObserver* aAlertListener) {
+  return ShowAlert(aAlert, aAlertListener);
+}
+
+NS_IMETHODIMP
+ToastNotification::SetManualDoNotDisturb(bool aDoNotDisturb) {
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP
+ToastNotification::GetManualDoNotDisturb(bool* aRet) {
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP
+ToastNotification::ShowAlert(nsIAlertNotification* aAlert,
+                             nsIObserver* aAlertListener) {
+  NS_ENSURE_ARG(aAlert);
+
+  if (mSuppressForScreenSharing) {
+    return NS_OK;
+  }
+
+  nsAutoString cookie;
+  MOZ_TRY(aAlert->GetCookie(cookie));
+
+  nsAutoString name;
+  MOZ_TRY(aAlert->GetName(name));
+
+  nsAutoString title;
+  MOZ_TRY(aAlert->GetTitle(title));
+  if (!EnsureUTF16Validity(title)) {
+    MOZ_LOG(sWASLog, LogLevel::Warning,
+            ("Notification title was invalid UTF16, unpaired surrogates have "
+             "been replaced."));
+  }
+
+  nsAutoString text;
+  MOZ_TRY(aAlert->GetText(text));
+  if (!EnsureUTF16Validity(text)) {
+    MOZ_LOG(sWASLog, LogLevel::Warning,
+            ("Notification text was invalid UTF16, unpaired surrogates have "
+             "been replaced."));
+  }
+
+  bool textClickable;
+  MOZ_TRY(aAlert->GetTextClickable(&textClickable));
+
+  bool isSilent;
+  MOZ_TRY(aAlert->GetSilent(&isSilent));
+
+  nsAutoString hostPort;
+  MOZ_TRY(aAlert->GetSource(hostPort));
+
+  nsAutoString opaqueRelaunchData;
+  MOZ_TRY(aAlert->GetOpaqueRelaunchData(opaqueRelaunchData));
+
+  bool requireInteraction;
+  MOZ_TRY(aAlert->GetRequireInteraction(&requireInteraction));
+
+  bool inPrivateBrowsing;
+  MOZ_TRY(aAlert->GetInPrivateBrowsing(&inPrivateBrowsing));
+
+  nsTArray<RefPtr<nsIAlertAction>> actions;
+  MOZ_TRY(aAlert->GetActions(actions));
+
+  nsCOMPtr<nsIPrincipal> principal;
+  MOZ_TRY(aAlert->GetPrincipal(getter_AddRefs(principal)));
+  bool isSystemPrincipal = principal && principal->IsSystemPrincipal();
+
+  bool handleActions = false;
+  auto imagePlacement = ImagePlacement::eInline;
+  if (isSystemPrincipal) {
+    nsCOMPtr<nsIWindowsAlertNotification> winAlert(do_QueryInterface(aAlert));
+    if (winAlert) {
+      MOZ_TRY(winAlert->GetHandleActions(&handleActions));
+
+      nsIWindowsAlertNotification::ImagePlacement placement;
+      MOZ_TRY(winAlert->GetImagePlacement(&placement));
+      switch (placement) {
+        case nsIWindowsAlertNotification::eHero:
+          imagePlacement = ImagePlacement::eHero;
+          break;
+        case nsIWindowsAlertNotification::eIcon:
+          imagePlacement = ImagePlacement::eIcon;
+          break;
+        case nsIWindowsAlertNotification::eInline:
+          imagePlacement = ImagePlacement::eInline;
+          break;
+        default:
+          MOZ_LOG(sWASLog, LogLevel::Error,
+                  ("Invalid image placement enum value: %hhu", placement));
+          return NS_ERROR_UNEXPECTED;
+      }
+    }
+  }
+
+  RefPtr<ToastNotificationHandler> oldHandler = mActiveHandlers.Get(name);
+
+  NS_ENSURE_TRUE(mAumid.isSome(), NS_ERROR_UNEXPECTED);
+  RefPtr<ToastNotificationHandler> handler = new ToastNotificationHandler(
+      this, mAumid.ref(), aAlertListener, name, cookie, title, text, hostPort,
+      textClickable, requireInteraction, actions, isSystemPrincipal,
+      opaqueRelaunchData, inPrivateBrowsing, isSilent, handleActions,
+      imagePlacement);
+  mActiveHandlers.InsertOrUpdate(name, RefPtr{handler});
+
+  MOZ_LOG(sWASLog, LogLevel::Debug,
+          ("Adding handler '%s': [%p] (now %d handlers)",
+           NS_ConvertUTF16toUTF8(name).get(), handler.get(),
+           mActiveHandlers.Count()));
+
+  nsresult rv = handler->InitAlertAsync(aAlert);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    MOZ_LOG(sWASLog, LogLevel::Debug,
+            ("Failed to init alert, removing '%s'",
+             NS_ConvertUTF16toUTF8(name).get()));
+    mActiveHandlers.Remove(name);
+    handler->UnregisterHandler();
+    return rv;
+  }
+
+  // If there was a previous handler with the same name then unregister it.
+  if (oldHandler) {
+    oldHandler->UnregisterHandler();
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+ToastNotification::GetXmlStringForWindowsAlert(nsIAlertNotification* aAlert,
+                                               const nsAString& aWindowsTag,
+                                               nsAString& aString) {
+  NS_ENSURE_ARG(aAlert);
+
+  nsAutoString cookie;
+  MOZ_TRY(aAlert->GetCookie(cookie));
+
+  nsAutoString name;
+  MOZ_TRY(aAlert->GetName(name));
+
+  nsAutoString title;
+  MOZ_TRY(aAlert->GetTitle(title));
+
+  nsAutoString text;
+  MOZ_TRY(aAlert->GetText(text));
+
+  bool textClickable;
+  MOZ_TRY(aAlert->GetTextClickable(&textClickable));
+
+  bool isSilent;
+  MOZ_TRY(aAlert->GetSilent(&isSilent));
+
+  nsAutoString hostPort;
+  MOZ_TRY(aAlert->GetSource(hostPort));
+
+  nsAutoString opaqueRelaunchData;
+  MOZ_TRY(aAlert->GetOpaqueRelaunchData(opaqueRelaunchData));
+
+  bool requireInteraction;
+  MOZ_TRY(aAlert->GetRequireInteraction(&requireInteraction));
+
+  bool inPrivateBrowsing;
+  MOZ_TRY(aAlert->GetInPrivateBrowsing(&inPrivateBrowsing));
+
+  nsTArray<RefPtr<nsIAlertAction>> actions;
+  MOZ_TRY(aAlert->GetActions(actions));
+
+  nsCOMPtr<nsIPrincipal> principal;
+  MOZ_TRY(aAlert->GetPrincipal(getter_AddRefs(principal)));
+  bool isSystemPrincipal = principal && principal->IsSystemPrincipal();
+
+  NS_ENSURE_TRUE(mAumid.isSome(), NS_ERROR_UNEXPECTED);
+  RefPtr<ToastNotificationHandler> handler = new ToastNotificationHandler(
+      this, mAumid.ref(), nullptr /* aAlertListener */, name, cookie, title,
+      text, hostPort, textClickable, requireInteraction, actions,
+      isSystemPrincipal, opaqueRelaunchData, inPrivateBrowsing, isSilent);
+
+  // Usually, this will be empty during testing, making test output
+  // deterministic.
+  MOZ_TRY(handler->SetWindowsTag(aWindowsTag));
+
+  nsAutoString imageURL;
+  MOZ_TRY(aAlert->GetImageURL(imageURL));
+
+  return handler->CreateToastXmlString(imageURL, aString);
+}
+
+// Verifies that the tag recieved associates to a notification created during
+// this application's session, or handles fallback behavior.
+RefPtr<ToastHandledPromise> ToastNotification::VerifyTagPresentOrFallback(
+    const nsAString& aWindowsTag) {
+  MOZ_LOG(sWASLog, LogLevel::Debug,
+          ("Iterating %d handlers", mActiveHandlers.Count()));
+
+  for (auto iter = mActiveHandlers.Iter(); !iter.Done(); iter.Next()) {
+    RefPtr<ToastNotificationHandler> handler = iter.UserData();
+    nsAutoString tag;
+    nsresult rv = handler->GetWindowsTag(tag);
+
+    if (NS_SUCCEEDED(rv)) {
+      MOZ_LOG(sWASLog, LogLevel::Debug,
+              ("Comparing external windowsTag '%s' to handled windowsTag '%s'",
+               NS_ConvertUTF16toUTF8(aWindowsTag).get(),
+               NS_ConvertUTF16toUTF8(tag).get()));
+      if (aWindowsTag.Equals(tag)) {
+        MOZ_LOG(sWASLog, LogLevel::Debug,
+                ("External windowsTag '%s' is handled by handler [%p]",
+                 NS_ConvertUTF16toUTF8(aWindowsTag).get(), handler.get()));
+        return ToastHandledPromise::CreateAndResolve(true, __func__);
+      }
+    } else {
+      MOZ_LOG(sWASLog, LogLevel::Debug,
+              ("Failed to get windowsTag for handler [%p]", handler.get()));
+    }
+  }
+
+  // Fallback handling is required.
+
+  MOZ_LOG(sWASLog, LogLevel::Debug,
+          ("External windowsTag '%s' is not handled",
+           NS_ConvertUTF16toUTF8(aWindowsTag).get()));
+
+  RefPtr<ToastHandledPromise::Private> fallbackPromise =
+      new ToastHandledPromise::Private(__func__);
+
+  // TODO: Bug 1806005 - At time of writing this function is called in a call
+  // stack containing `WndProc` callback on an STA thread. As a result attempts
+  // to create a `ToastNotificationManager` instance results an an
+  // `RPC_E_CANTCALLOUT_ININPUTSYNCCALL` error. We can simplify the the XPCOM
+  // interface and synchronize the COM interactions if notification fallback
+  // handling were no longer handled in a `WndProc` context.
+  NS_DispatchBackgroundTask(NS_NewRunnableFunction(
+      "VerifyTagPresentOrFallback fallback background task",
+      [fallbackPromise]() { fallbackPromise->Resolve(false, __func__); }));
+
+  return fallbackPromise;
+}
+
+// Send our window's PID to the notification server so that it can grant us
+// `SetForegroundWindow` permissions. PID 0 is sent to signal no window PID.
+// Absense of PID which may occur when we are yet unable to retrieve the
+// window during startup, which is not a problem in practice as new windows
+// receive focus by default.
+void ToastNotification::SignalComNotificationHandled(
+    const nsAString& aWindowsTag) {
+  DWORD pid = 0;
+
+  nsCOMPtr<nsIWindowMediator> winMediator(
+      do_GetService(NS_WINDOWMEDIATOR_CONTRACTID));
+  if (winMediator) {
+    nsCOMPtr<mozIDOMWindowProxy> navWin;
+    winMediator->GetMostRecentWindow(u"navigator:browser",
+                                     getter_AddRefs(navWin));
+    if (navWin) {
+      nsCOMPtr<nsIWidget> widget =
+          WidgetUtils::DOMWindowToWidget(nsPIDOMWindowOuter::From(navWin));
+      if (widget) {
+        HWND hwnd = (HWND)widget->GetNativeData(NS_NATIVE_WINDOW);
+        GetWindowThreadProcessId(hwnd, &pid);
+      } else {
+        MOZ_LOG(sWASLog, LogLevel::Debug, ("Failed to get widget"));
+      }
+    } else {
+      MOZ_LOG(sWASLog, LogLevel::Debug, ("Failed to get navWin"));
+    }
+  } else {
+    MOZ_LOG(sWASLog, LogLevel::Debug, ("Failed to get WinMediator"));
+  }
+
+  // Run pipe communication off the main thread to prevent UI jank from
+  // blocking. Nothing relies on the COM server's response or that it has
+  // responded at time of commit.
+  NS_DispatchBackgroundTask(
+      NS_NewRunnableFunction(
+          "SignalComNotificationHandled background task",
+          [pid, aWindowsTag = nsString{aWindowsTag}]() mutable {
+            std::wstring pipeName = GetNotificationPipeName(aWindowsTag.get());
+
+            nsAutoHandle pipe;
+            pipe.own(CreateFileW(pipeName.c_str(), GENERIC_READ | GENERIC_WRITE,
+                                 0, nullptr, OPEN_EXISTING,
+                                 FILE_FLAG_OVERLAPPED, nullptr));
+            if (pipe.get() == INVALID_HANDLE_VALUE) {
+              MOZ_LOG(sWASLog, LogLevel::Error,
+                      ("Unable to open notification server pipe."));
+              return;
+            }
+
+            DWORD pipeFlags = PIPE_READMODE_MESSAGE;
+            if (!SetNamedPipeHandleState(pipe.get(), &pipeFlags, nullptr,
+                                         nullptr)) {
+              MOZ_LOG(sWASLog, LogLevel::Error,
+                      ("Error setting pipe handle state, error %lu",
+                       GetLastError()));
+              return;
+            }
+
+            // Pass our window's PID to the COM server receive
+            // `SetForegroundWindow` permissions, and wait for a message
+            // acknowledging the permission has been granted.
+            ToastNotificationPidMessage in{};
+            in.pid = pid;
+            ToastNotificationPermissionMessage out{};
+            auto transact = [&](OVERLAPPED& overlapped) {
+              return TransactNamedPipe(pipe.get(), &in, sizeof(in), &out,
+                                       sizeof(out), nullptr, &overlapped);
+            };
+            bool result =
+                SyncDoOverlappedIOWithTimeout(pipe, sizeof(out), transact);
+
+            if (result && out.setForegroundPermissionGranted && pid != 0) {
+              MOZ_LOG(
+                  sWASLog, LogLevel::Info,
+                  ("SetForegroundWindow permission granted to our window."));
+            } else {
+              MOZ_LOG(sWASLog, LogLevel::Error,
+                      ("SetForegroundWindow permission not granted to our "
+                       "window."));
+            }
+          }),
+      NS_DISPATCH_EVENT_MAY_BLOCK);
+}
+
+NS_IMETHODIMP
+ToastNotification::HandleWindowsTag(const nsAString& aWindowsTag,
+                                    JSContext* aCx, dom::Promise** aPromise) {
+  NS_ENSURE_TRUE(mAumid.isSome(), NS_ERROR_UNEXPECTED);
+  NS_ENSURE_TRUE(NS_IsMainThread(), NS_ERROR_NOT_SAME_THREAD);
+
+  ErrorResult rv;
+  RefPtr<dom::Promise> promise =
+      dom::Promise::Create(xpc::CurrentNativeGlobal(aCx), rv);
+  ENSURE_SUCCESS(rv, rv.StealNSResult());
+
+  this->VerifyTagPresentOrFallback(aWindowsTag)
+      ->Then(
+          GetMainThreadSerialEventTarget(), __func__,
+          [aWindowsTag = nsString(aWindowsTag),
+           promise](const bool aTagWasHandled) {
+            // We no longer need to query toast information from OS and can
+            // allow the COM server to proceed (toast information is lost once
+            // the COM server's `Activate` callback returns).
+            SignalComNotificationHandled(aWindowsTag);
+
+            dom::AutoJSAPI js;
+            if (NS_WARN_IF(!js.Init(promise->GetGlobalObject()))) {
+              promise->MaybeReject(NS_ERROR_FAILURE);
+              return;
+            }
+
+            // Resolve the DOM Promise with a JS object. Set properties if
+            // fallback handling is necessary.
+
+            JSContext* cx = js.cx();
+            JS::Rooted<JSObject*> obj(cx, JS_NewPlainObject(cx));
+
+            JS::Rooted<JS::Value> attVal(cx, JS::BooleanValue(aTagWasHandled));
+            Unused << NS_WARN_IF(
+                !JS_SetProperty(cx, obj, "tagWasHandled", attVal));
+
+            promise->MaybeResolve(obj);
+          },
+          [aWindowsTag = nsString(aWindowsTag), promise]() {
+            // We no longer need to query toast information from OS and can
+            // allow the COM server to proceed (toast information is lost once
+            // the COM server's `Activate` callback returns).
+            SignalComNotificationHandled(aWindowsTag);
+
+            promise->MaybeReject(NS_ERROR_FAILURE);
+          });
+
+  promise.forget(aPromise);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+ToastNotification::CloseAlert(const nsAString& aAlertName,
+                              bool aContextClosed) {
+  RefPtr<ToastNotificationHandler> handler;
+  if (NS_WARN_IF(!mActiveHandlers.Get(aAlertName, getter_AddRefs(handler)))) {
+    return NS_OK;
+  }
+
+  if (!aContextClosed || handler->IsPrivate()) {
+    // Hide the alert when not implicitly closed by tab/window closing or when
+    // notification originated from a private tab.
+    handler->HideAlert();
+  }
+
+  mActiveHandlers.Remove(aAlertName);
+  handler->UnregisterHandler();
+
+  return NS_OK;
+}
+
+bool ToastNotification::IsActiveHandler(const nsAString& aAlertName,
+                                        ToastNotificationHandler* aHandler) {
+  RefPtr<ToastNotificationHandler> handler;
+  if (NS_WARN_IF(!mActiveHandlers.Get(aAlertName, getter_AddRefs(handler)))) {
+    return false;
+  }
+  return handler == aHandler;
+}
+
+void ToastNotification::RemoveHandler(const nsAString& aAlertName,
+                                      ToastNotificationHandler* aHandler) {
+  // The alert may have been replaced; only remove it from the active
+  // handler's map if it's the same.
+  if (IsActiveHandler(aAlertName, aHandler)) {
+    // Terrible things happen if the destructor of a handler is called inside
+    // the hashtable .Remove() method. Wait until we have returned from there.
+    RefPtr<ToastNotificationHandler> kungFuDeathGrip(aHandler);
+    mActiveHandlers.Remove(aAlertName);
+    aHandler->UnregisterHandler();
+  }
+}
+
+NS_IMETHODIMP
+ToastNotification::RemoveAllNotificationsForInstall() {
+  HRESULT hr = S_OK;
+
+  ComPtr<IToastNotificationManagerStatics> manager;
+  hr = GetActivationFactory(
+      HStringReference(
+          RuntimeClass_Windows_UI_Notifications_ToastNotificationManager)
+          .Get(),
+      &manager);
+  NS_ENSURE_TRUE(SUCCEEDED(hr), NS_ERROR_FAILURE);
+
+  HString aumid;
+  MOZ_ASSERT(mAumid.isSome());
+  hr = aumid.Set(mAumid.ref().get());
+  NS_ENSURE_TRUE(SUCCEEDED(hr), NS_ERROR_FAILURE);
+
+  // Hide toasts in action center.
+  [&]() {
+    ComPtr<IToastNotificationManagerStatics2> manager2;
+    hr = manager.As(&manager2);
+    NS_ENSURE_TRUE_VOID(SUCCEEDED(hr));
+
+    ComPtr<IToastNotificationHistory> history;
+    hr = manager2->get_History(&history);
+    NS_ENSURE_TRUE_VOID(SUCCEEDED(hr));
+
+    hr = history->ClearWithId(aumid.Get());
+    NS_ENSURE_TRUE_VOID(SUCCEEDED(hr));
+  }();
+
+  // Hide scheduled toasts.
+  [&]() {
+    ComPtr<IToastNotifier> notifier;
+    hr = manager->CreateToastNotifierWithId(aumid.Get(), &notifier);
+    NS_ENSURE_TRUE_VOID(SUCCEEDED(hr));
+
+    ComPtr<IVectorView_ScheduledToastNotification> scheduledToasts;
+    hr = notifier->GetScheduledToastNotifications(&scheduledToasts);
+    NS_ENSURE_TRUE_VOID(SUCCEEDED(hr));
+
+    unsigned int schedSize;
+    hr = scheduledToasts->get_Size(&schedSize);
+    NS_ENSURE_TRUE_VOID(SUCCEEDED(hr));
+
+    for (unsigned int i = 0; i < schedSize; i++) {
+      ComPtr<IScheduledToastNotification> schedToast;
+      hr = scheduledToasts->GetAt(i, &schedToast);
+      if (NS_WARN_IF(FAILED(hr))) {
+        continue;
+      }
+
+      hr = notifier->RemoveFromSchedule(schedToast.Get());
+      Unused << NS_WARN_IF(FAILED(hr));
+    }
+  }();
+
+  return NS_OK;
+}
+
+NS_IMPL_ISUPPORTS_INHERITED(WindowsAlertNotification, AlertNotification,
+                            nsIWindowsAlertNotification)
+
+NS_IMETHODIMP
+WindowsAlertNotification::GetHandleActions(bool* aHandleActions) {
+  *aHandleActions = mHandleActions;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+WindowsAlertNotification::SetHandleActions(bool aHandleActions) {
+  mHandleActions = aHandleActions;
+  return NS_OK;
+}
+
+NS_IMETHODIMP WindowsAlertNotification::GetImagePlacement(
+    nsIWindowsAlertNotification::ImagePlacement* aImagePlacement) {
+  *aImagePlacement = mImagePlacement;
+  return NS_OK;
+}
+
+NS_IMETHODIMP WindowsAlertNotification::SetImagePlacement(
+    nsIWindowsAlertNotification::ImagePlacement aImagePlacement) {
+  switch (aImagePlacement) {
+    case eHero:
+    case eIcon:
+    case eInline:
+      mImagePlacement = aImagePlacement;
+      break;
+    default:
+      MOZ_LOG(sWASLog, LogLevel::Error,
+              ("Invalid image placement enum value: %hhu", aImagePlacement));
+      return NS_ERROR_INVALID_ARG;
+  }
+
+  return NS_OK;
+}
+
+}  // namespace widget
+}  // namespace mozilla
diff --git a/widget/windows/ToastNotification.h b/widget/windows/ToastNotification.h
new file mode 100644
index 0000000000..9beb08cc27
--- /dev/null
+++ b/widget/windows/ToastNotification.h
@@ -0,0 +1,83 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef ToastNotification_h__
+#define ToastNotification_h__
+
+#include "mozilla/Maybe.h"
+#include "mozilla/MozPromise.h"
+#include "nsIAlertsService.h"
+#include "nsIObserver.h"
+#include "nsIThread.h"
+#include "nsIWindowsAlertsService.h"
+#include "nsRefPtrHashtable.h"
+#include "mozilla/AlertNotification.h"
+
+namespace mozilla {
+namespace widget {
+
+using ToastHandledPromise = MozPromise<bool, bool, true>;
+
+class ToastNotificationHandler;
+
+class WindowsAlertNotification final : public AlertNotification,
+                                       public nsIWindowsAlertNotification {
+ public:
+  NS_DECL_NSIWINDOWSALERTNOTIFICATION
+  NS_FORWARD_NSIALERTNOTIFICATION(AlertNotification::)
+  NS_DECL_ISUPPORTS_INHERITED
+
+  WindowsAlertNotification() = default;
+
+ protected:
+  virtual ~WindowsAlertNotification() = default;
+  bool mHandleActions = false;
+  nsIWindowsAlertNotification::ImagePlacement mImagePlacement = eInline;
+};
+
+class ToastNotification final : public nsIWindowsAlertsService,
+                                public nsIAlertsDoNotDisturb,
+                                public nsIObserver {
+ public:
+  NS_DECL_NSIALERTSSERVICE
+  NS_DECL_NSIWINDOWSALERTSSERVICE
+  NS_DECL_NSIALERTSDONOTDISTURB
+  NS_DECL_NSIOBSERVER
+  NS_DECL_ISUPPORTS
+
+  ToastNotification();
+
+  nsresult Init();
+
+  bool IsActiveHandler(const nsAString& aAlertName,
+                       ToastNotificationHandler* aHandler);
+  void RemoveHandler(const nsAString& aAlertName,
+                     ToastNotificationHandler* aHandler);
+
+  nsresult BackgroundDispatch(nsIRunnable* runnable);
+
+ protected:
+  virtual ~ToastNotification();
+  bool EnsureAumidRegistered();
+
+  static bool AssignIfMsixAumid(Maybe<nsAutoString>& aAumid);
+  static bool AssignIfNsisAumid(nsAutoString& aInstallHash,
+                                Maybe<nsAutoString>& aAumid);
+  static bool RegisterRuntimeAumid(nsAutoString& aInstallHash,
+                                   Maybe<nsAutoString>& aAumid);
+
+  RefPtr<ToastHandledPromise> VerifyTagPresentOrFallback(
+      const nsAString& aWindowsTag);
+  static void SignalComNotificationHandled(const nsAString& aWindowsTag);
+
+  nsRefPtrHashtable<nsStringHashKey, ToastNotificationHandler> mActiveHandlers;
+  Maybe<nsAutoString> mAumid;
+  bool mSuppressForScreenSharing = false;
+};
+
+}  // namespace widget
+}  // namespace mozilla
+
+#endif
diff --git a/widget/windows/ToastNotificationHandler.cpp b/widget/windows/ToastNotificationHandler.cpp
new file mode 100644
index 0000000000..a493342719
--- /dev/null
+++ b/widget/windows/ToastNotificationHandler.cpp
@@ -0,0 +1,1167 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:set ts=2 sts=2 sw=2 et cin: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "ToastNotificationHandler.h"
+
+#include <windows.foundation.h>
+
+#include "gfxUtils.h"
+#include "gfxPlatform.h"
+#include "imgIContainer.h"
+#include "imgIRequest.h"
+#include "json/json.h"
+#include "mozilla/gfx/2D.h"
+#ifdef MOZ_BACKGROUNDTASKS
+#  include "mozilla/BackgroundTasks.h"
+#endif
+#include "mozilla/HashFunctions.h"
+#include "mozilla/JSONStringWriteFuncs.h"
+#include "mozilla/Result.h"
+#include "mozilla/Logging.h"
+#include "mozilla/Tokenizer.h"
+#include "mozilla/Unused.h"
+#include "mozilla/WindowsVersion.h"
+#include "mozilla/intl/Localization.h"
+#include "nsAppDirectoryServiceDefs.h"
+#include "nsAppRunner.h"
+#include "nsDirectoryServiceDefs.h"
+#include "nsDirectoryServiceUtils.h"
+#include "nsIDUtils.h"
+#include "nsIStringBundle.h"
+#include "nsIToolkitProfile.h"
+#include "nsIToolkitProfileService.h"
+#include "nsIURI.h"
+#include "nsIWidget.h"
+#include "nsIWindowMediator.h"
+#include "nsNetUtil.h"
+#include "nsPIDOMWindow.h"
+#include "nsProxyRelease.h"
+#include "nsXREDirProvider.h"
+#include "ToastNotificationHeaderOnlyUtils.h"
+#include "WidgetUtils.h"
+#include "WinUtils.h"
+
+#include "ToastNotification.h"
+
+namespace mozilla {
+namespace widget {
+
+extern LazyLogModule sWASLog;
+
+using namespace ABI::Windows::Data::Xml::Dom;
+using namespace ABI::Windows::Foundation;
+using namespace ABI::Windows::UI::Notifications;
+using namespace Microsoft::WRL;
+using namespace Microsoft::WRL::Wrappers;
+using namespace toastnotification;
+
+// Needed to disambiguate internal and Windows `ToastNotification` classes.
+using WinToastNotification = ABI::Windows::UI::Notifications::ToastNotification;
+using ToastActivationHandler =
+    ITypedEventHandler<WinToastNotification*, IInspectable*>;
+using ToastDismissedHandler =
+    ITypedEventHandler<WinToastNotification*, ToastDismissedEventArgs*>;
+using ToastFailedHandler =
+    ITypedEventHandler<WinToastNotification*, ToastFailedEventArgs*>;
+using IVectorView_ToastNotification =
+    Collections::IVectorView<WinToastNotification*>;
+
+NS_IMPL_ISUPPORTS(ToastNotificationHandler, nsIAlertNotificationImageListener)
+
+static bool SetNodeValueString(const nsString& aString, IXmlNode* node,
+                               IXmlDocument* xml) {
+  ComPtr<IXmlText> inputText;
+  HRESULT hr;
+  hr = xml->CreateTextNode(HStringReference(aString.get()).Get(), &inputText);
+  NS_ENSURE_TRUE(SUCCEEDED(hr), false);
+
+  ComPtr<IXmlNode> inputTextNode;
+  hr = inputText.As(&inputTextNode);
+  NS_ENSURE_TRUE(SUCCEEDED(hr), false);
+
+  ComPtr<IXmlNode> appendedChild;
+  hr = node->AppendChild(inputTextNode.Get(), &appendedChild);
+  NS_ENSURE_TRUE(SUCCEEDED(hr), false);
+
+  return true;
+}
+
+static bool SetAttribute(ComPtr<IXmlElement>& element,
+                         const HStringReference& name, const nsAString& value) {
+  HString valueStr;
+  valueStr.Set(PromiseFlatString(value).get());
+
+  HRESULT hr = element->SetAttribute(name.Get(), valueStr.Get());
+  NS_ENSURE_TRUE(SUCCEEDED(hr), false);
+
+  return true;
+}
+
+static bool AddActionNode(ComPtr<IXmlDocument>& toastXml,
+                          ComPtr<IXmlNode>& actionsNode,
+                          const nsAString& actionTitle,
+                          const nsAString& launchArg,
+                          const nsAString& actionArgs,
+                          const nsAString& actionPlacement = u""_ns,
+                          const nsAString& activationType = u""_ns) {
+  ComPtr<IXmlElement> action;
+  HRESULT hr =
+      toastXml->CreateElement(HStringReference(L"action").Get(), &action);
+  NS_ENSURE_TRUE(SUCCEEDED(hr), false);
+
+  bool success =
+      SetAttribute(action, HStringReference(L"content"), actionTitle);
+  NS_ENSURE_TRUE(success, false);
+
+  // Action arguments overwrite the toast's launch arguments, so we need to
+  // prepend the launch arguments necessary for the Notification Server to
+  // reconstruct the toast's origin.
+  //
+  // Web Notification actions are arbitrary strings; to prevent breaking launch
+  // argument parsing the action argument must be last. All delimiters after
+  // `action` are part of the action arugment.
+  nsAutoString args = launchArg + u"\n"_ns +
+                      nsDependentString(kLaunchArgAction) + u"\n"_ns +
+                      actionArgs;
+  success = SetAttribute(action, HStringReference(L"arguments"), args);
+  NS_ENSURE_TRUE(success, false);
+
+  if (!actionPlacement.IsEmpty()) {
+    success =
+        SetAttribute(action, HStringReference(L"placement"), actionPlacement);
+    NS_ENSURE_TRUE(success, false);
+  }
+
+  if (!activationType.IsEmpty()) {
+    success = SetAttribute(action, HStringReference(L"activationType"),
+                           activationType);
+    NS_ENSURE_TRUE(success, false);
+
+    // No special argument handling: when `activationType="system"`, `arguments`
+    // should be a Windows-specific keyword, namely "dismiss" or "snooze", which
+    // are supposed to make a system handled dismiss/snooze buttons.
+    // https://learn.microsoft.com/en-us/windows/apps/design/shell/tiles-and-notifications/adaptive-interactive-toasts?tabs=xml#snoozedismiss
+    //
+    // Note that while using it prevents calling our notification COM server,
+    // it somehow still calls OnActivate instead of OnDismiss. Thus, we still
+    // need to handle such callbacks manually by checking `arguments`.
+    success = SetAttribute(action, HStringReference(L"arguments"), actionArgs);
+    NS_ENSURE_TRUE(success, false);
+  }
+
+  // Add <action> to <actions>
+  ComPtr<IXmlNode> actionNode;
+  hr = action.As(&actionNode);
+  NS_ENSURE_TRUE(SUCCEEDED(hr), false);
+
+  ComPtr<IXmlNode> appendedChild;
+  hr = actionsNode->AppendChild(actionNode.Get(), &appendedChild);
+  NS_ENSURE_TRUE(SUCCEEDED(hr), false);
+
+  return true;
+}
+
+nsresult ToastNotificationHandler::GetWindowsTag(nsAString& aWindowsTag) {
+  aWindowsTag.Assign(mWindowsTag);
+  return NS_OK;
+}
+
+nsresult ToastNotificationHandler::SetWindowsTag(const nsAString& aWindowsTag) {
+  mWindowsTag.Assign(aWindowsTag);
+  return NS_OK;
+}
+
+// clang - format off
+/* Populate the launch argument so the COM server can reconstruct the toast
+ * origin.
+ *
+ *   program
+ *   {MOZ_APP_NAME}
+ *   profile
+ *   {path to profile}
+ */
+// clang-format on
+Result<nsString, nsresult> ToastNotificationHandler::GetLaunchArgument() {
+  nsString launchArg;
+
+  // When the preference is false, the COM notification server will be invoked,
+  // discover that there is no `program`, and exit (successfully), after which
+  // Windows will invoke the in-product Windows 8-style callbacks.  When true,
+  // the COM notification server will launch Firefox with sufficient arguments
+  // for Firefox to handle the notification.
+  if (!Preferences::GetBool(
+          "alerts.useSystemBackend.windows.notificationserver.enabled",
+          false)) {
+    // Include dummy key/value so that newline appended arguments aren't off by
+    // one line.
+    launchArg += u"invalid key\ninvalid value"_ns;
+    return launchArg;
+  }
+
+  // `program` argument.
+  launchArg += nsDependentString(kLaunchArgProgram) + u"\n"_ns MOZ_APP_NAME;
+
+  // `profile` argument.
+  nsCOMPtr<nsIFile> profDir;
+  bool wantCurrentProfile = true;
+#ifdef MOZ_BACKGROUNDTASKS
+  if (BackgroundTasks::IsBackgroundTaskMode()) {
+    // Notifications popped from a background task want to invoke Firefox with a
+    // different profile -- the default browsing profile.  We'd prefer to not
+    // specify a profile, so that the Firefox invoked by the notification server
+    // chooses its default profile, but this might pop the profile chooser in
+    // some configurations.
+    wantCurrentProfile = false;
+
+    nsCOMPtr<nsIToolkitProfileService> profileSvc =
+        do_GetService(NS_PROFILESERVICE_CONTRACTID);
+    if (profileSvc) {
+      nsCOMPtr<nsIToolkitProfile> defaultProfile;
+      nsresult rv =
+          profileSvc->GetDefaultProfile(getter_AddRefs(defaultProfile));
+      if (NS_SUCCEEDED(rv) && defaultProfile) {
+        // Not all installations have a default profile.  But if one is set,
+        // then it should have a profile directory.
+        MOZ_TRY(defaultProfile->GetRootDir(getter_AddRefs(profDir)));
+      }
+    }
+  }
+#endif
+  if (wantCurrentProfile) {
+    MOZ_TRY(NS_GetSpecialDirectory(NS_APP_USER_PROFILE_50_DIR,
+                                   getter_AddRefs(profDir)));
+  }
+
+  if (profDir) {
+    nsAutoString profilePath;
+    MOZ_TRY(profDir->GetPath(profilePath));
+    launchArg += u"\n"_ns + nsDependentString(kLaunchArgProfile) + u"\n"_ns +
+                 profilePath;
+  }
+
+  // `windowsTag` argument.
+  launchArg +=
+      u"\n"_ns + nsDependentString(kLaunchArgTag) + u"\n"_ns + mWindowsTag;
+
+  // `logging` argument.
+  if (Preferences::GetBool(
+          "alerts.useSystemBackend.windows.notificationserver.verbose",
+          false)) {
+    // Signal notification to log verbose messages.
+    launchArg +=
+        u"\n"_ns + nsDependentString(kLaunchArgLogging) + u"\nverbose"_ns;
+  }
+
+  return launchArg;
+}
+
+static ComPtr<IToastNotificationManagerStatics>
+GetToastNotificationManagerStatics() {
+  ComPtr<IToastNotificationManagerStatics> toastNotificationManagerStatics;
+  HRESULT hr = GetActivationFactory(
+      HStringReference(
+          RuntimeClass_Windows_UI_Notifications_ToastNotificationManager)
+          .Get(),
+      &toastNotificationManagerStatics);
+  NS_ENSURE_TRUE(SUCCEEDED(hr), nullptr);
+
+  return toastNotificationManagerStatics;
+}
+
+ToastNotificationHandler::~ToastNotificationHandler() {
+  if (mImageRequest) {
+    mImageRequest->Cancel(NS_BINDING_ABORTED);
+    mImageRequest = nullptr;
+  }
+
+  if (mHasImage && mImageFile) {
+    DebugOnly<nsresult> rv = mImageFile->Remove(false);
+    NS_ASSERTION(NS_SUCCEEDED(rv), "Cannot remove temporary image file");
+  }
+
+  UnregisterHandler();
+}
+
+void ToastNotificationHandler::UnregisterHandler() {
+  if (mNotification) {
+    mNotification->remove_Dismissed(mDismissedToken);
+    mNotification->remove_Activated(mActivatedToken);
+    mNotification->remove_Failed(mFailedToken);
+  }
+
+  mNotification = nullptr;
+  mNotifier = nullptr;
+
+  SendFinished();
+}
+
+nsresult ToastNotificationHandler::InitAlertAsync(
+    nsIAlertNotification* aAlert) {
+  MOZ_TRY(InitWindowsTag());
+
+#ifdef MOZ_BACKGROUNDTASKS
+  nsAutoString imageUrl;
+  if (BackgroundTasks::IsBackgroundTaskMode() &&
+      NS_SUCCEEDED(aAlert->GetImageURL(imageUrl)) && !imageUrl.IsEmpty()) {
+    // Bug 1870750: Image decoding relies on gfx and runs on a thread pool,
+    // which expects to have been initialized early and on the main thread.
+    // Since background tasks run headless this never occurs. In this case we
+    // force gfx initialization.
+    Unused << NS_WARN_IF(!gfxPlatform::GetPlatform());
+  }
+#endif
+
+  return aAlert->LoadImage(/* aTimeout = */ 0, this, /* aUserData = */ nullptr,
+                           getter_AddRefs(mImageRequest));
+}
+
+// Uniquely identify this toast to Windows.  Existing names and cookies are not
+// suitable: we want something generated and unique.  This is needed to check if
+// toast is still present in the Windows Action Center when we receive a dismiss
+// timeout.
+//
+// Local testing reveals that the space of tags is not global but instead is per
+// AUMID.  Since an installation uses a unique AUMID incorporating the install
+// directory hash, it should not witness another installation's tag.
+nsresult ToastNotificationHandler::InitWindowsTag() {
+  mWindowsTag.Truncate();
+
+  nsAutoString tag;
+
+  // Multiple profiles might overwrite each other's toast messages when a
+  // common name is used for a given host port. We prevent this by including
+  // the profile directory as part of the toast hash.
+  nsCOMPtr<nsIFile> profDir;
+  MOZ_TRY(NS_GetSpecialDirectory(NS_APP_USER_PROFILE_50_DIR,
+                                 getter_AddRefs(profDir)));
+  MOZ_TRY(profDir->GetPath(tag));
+
+  if (!mHostPort.IsEmpty()) {
+    // Notification originated from a web notification.
+    // `mName` will be in the form `{mHostPort}#tag:{tag}` if the notification
+    // was created with a tag and `{mHostPort}#notag:{uuid}` otherwise.
+    tag += mName;
+  } else {
+    // Notification originated from the browser chrome.
+    if (!mName.IsEmpty()) {
+      tag += u"chrome#tag:"_ns;
+      // Browser chrome notifications don't follow any convention for naming.
+      tag += mName;
+    } else {
+      // No associated name, append a UUID to prevent reuse of the same tag.
+      nsIDToCString uuidString(nsID::GenerateUUID());
+      size_t len = strlen(uuidString.get());
+      MOZ_ASSERT(len == NSID_LENGTH - 1);
+      nsAutoString uuid;
+      CopyASCIItoUTF16(nsDependentCSubstring(uuidString.get(), len), uuid);
+
+      tag += u"chrome#notag:"_ns;
+      tag += uuid;
+    }
+  }
+
+  // Windows notification tags are limited to 16 characters, or 64 characters
+  // after the Creators Update; therefore we hash the tag to fit the minimum
+  // range.
+  HashNumber hash = HashString(tag);
+  mWindowsTag.AppendPrintf("%010u", hash);
+
+  return NS_OK;
+}
+
+nsString ToastNotificationHandler::ActionArgsJSONString(
+    const nsString& aAction, const nsString& aOpaqueRelaunchData = u""_ns) {
+  nsAutoCString actionArgsData;
+
+  JSONStringRefWriteFunc js(actionArgsData);
+  JSONWriter w(js, JSONWriter::SingleLineStyle);
+  w.Start();
+
+  w.StringProperty("action", NS_ConvertUTF16toUTF8(aAction));
+
+  if (mIsSystemPrincipal) {
+    // Privileged/chrome alerts (not activated by Windows) can have custom
+    // relaunch data.
+    if (!aOpaqueRelaunchData.IsEmpty()) {
+      w.StringProperty("opaqueRelaunchData",
+                       NS_ConvertUTF16toUTF8(aOpaqueRelaunchData));
+    }
+
+    // Privileged alerts include any provided name for metrics.
+    if (!mName.IsEmpty()) {
+      w.StringProperty("privilegedName", NS_ConvertUTF16toUTF8(mName));
+    }
+  } else {
+    if (!mHostPort.IsEmpty()) {
+      w.StringProperty("launchUrl", NS_ConvertUTF16toUTF8(mHostPort));
+    }
+  }
+
+  w.End();
+
+  return NS_ConvertUTF8toUTF16(actionArgsData);
+}
+
+ComPtr<IXmlDocument> ToastNotificationHandler::CreateToastXmlDocument() {
+  ComPtr<IToastNotificationManagerStatics> toastNotificationManagerStatics =
+      GetToastNotificationManagerStatics();
+  NS_ENSURE_TRUE(toastNotificationManagerStatics, nullptr);
+
+  ToastTemplateType toastTemplate;
+  if (mHostPort.IsEmpty()) {
+    toastTemplate =
+        mHasImage ? ToastTemplateType::ToastTemplateType_ToastImageAndText03
+                  : ToastTemplateType::ToastTemplateType_ToastText03;
+  } else {
+    toastTemplate =
+        mHasImage ? ToastTemplateType::ToastTemplateType_ToastImageAndText04
+                  : ToastTemplateType::ToastTemplateType_ToastText04;
+  }
+
+  ComPtr<IXmlDocument> toastXml;
+  toastNotificationManagerStatics->GetTemplateContent(toastTemplate, &toastXml);
+
+  if (!toastXml) {
+    return nullptr;
+  }
+
+  nsresult ns;
+  HRESULT hr;
+  bool success;
+
+  if (mHasImage) {
+    ComPtr<IXmlNodeList> toastImageElements;
+    hr = toastXml->GetElementsByTagName(HStringReference(L"image").Get(),
+                                        &toastImageElements);
+    NS_ENSURE_TRUE(SUCCEEDED(hr), nullptr);
+
+    ComPtr<IXmlNode> imageNode;
+    hr = toastImageElements->Item(0, &imageNode);
+    NS_ENSURE_TRUE(SUCCEEDED(hr), nullptr);
+
+    ComPtr<IXmlElement> image;
+    hr = imageNode.As(&image);
+    NS_ENSURE_TRUE(SUCCEEDED(hr), nullptr);
+
+    success = SetAttribute(image, HStringReference(L"src"), mImageUri);
+    NS_ENSURE_TRUE(success, nullptr);
+
+    switch (mImagePlacement) {
+      case ImagePlacement::eHero:
+        success =
+            SetAttribute(image, HStringReference(L"placement"), u"hero"_ns);
+        NS_ENSURE_TRUE(success, nullptr);
+        break;
+      case ImagePlacement::eIcon:
+        success = SetAttribute(image, HStringReference(L"placement"),
+                               u"appLogoOverride"_ns);
+        NS_ENSURE_TRUE(success, nullptr);
+        break;
+      case ImagePlacement::eInline:
+        // No attribute placement attribute for inline images.
+        break;
+    }
+  }
+
+  ComPtr<IXmlNodeList> toastTextElements;
+  hr = toastXml->GetElementsByTagName(HStringReference(L"text").Get(),
+                                      &toastTextElements);
+  NS_ENSURE_TRUE(SUCCEEDED(hr), nullptr);
+
+  ComPtr<IXmlNode> titleTextNodeRoot;
+  hr = toastTextElements->Item(0, &titleTextNodeRoot);
+  NS_ENSURE_TRUE(SUCCEEDED(hr), nullptr);
+
+  ComPtr<IXmlNode> msgTextNodeRoot;
+  hr = toastTextElements->Item(1, &msgTextNodeRoot);
+  NS_ENSURE_TRUE(SUCCEEDED(hr), nullptr);
+
+  success = SetNodeValueString(mTitle, titleTextNodeRoot.Get(), toastXml.Get());
+  NS_ENSURE_TRUE(success, nullptr);
+
+  success = SetNodeValueString(mMsg, msgTextNodeRoot.Get(), toastXml.Get());
+  NS_ENSURE_TRUE(success, nullptr);
+
+  ComPtr<IXmlNodeList> toastElements;
+  hr = toastXml->GetElementsByTagName(HStringReference(L"toast").Get(),
+                                      &toastElements);
+  NS_ENSURE_TRUE(SUCCEEDED(hr), nullptr);
+
+  ComPtr<IXmlNode> toastNodeRoot;
+  hr = toastElements->Item(0, &toastNodeRoot);
+  NS_ENSURE_TRUE(SUCCEEDED(hr), nullptr);
+
+  ComPtr<IXmlElement> toastElement;
+  hr = toastNodeRoot.As(&toastElement);
+  NS_ENSURE_TRUE(SUCCEEDED(hr), nullptr);
+
+  if (mRequireInteraction) {
+    success = SetAttribute(toastElement, HStringReference(L"scenario"),
+                           u"reminder"_ns);
+    NS_ENSURE_TRUE(success, nullptr);
+  }
+
+  auto maybeLaunchArg = GetLaunchArgument();
+  NS_ENSURE_TRUE(maybeLaunchArg.isOk(), nullptr);
+  nsString launchArg = maybeLaunchArg.unwrap();
+
+  nsString launchArgWithoutAction = launchArg;
+
+  if (!mIsSystemPrincipal) {
+    // Unprivileged/content alerts can't have custom relaunch data.
+    NS_WARNING_ASSERTION(mOpaqueRelaunchData.IsEmpty(),
+                         "unprivileged/content alert "
+                         "should have trivial `mOpaqueRelaunchData`");
+  }
+
+  launchArg += u"\n"_ns + nsDependentString(kLaunchArgAction) + u"\n"_ns +
+               ActionArgsJSONString(u""_ns, mOpaqueRelaunchData);
+
+  success = SetAttribute(toastElement, HStringReference(L"launch"), launchArg);
+  NS_ENSURE_TRUE(success, nullptr);
+
+  MOZ_LOG(sWASLog, LogLevel::Debug,
+          ("launchArg: '%s'", NS_ConvertUTF16toUTF8(launchArg).get()));
+
+  // Use newer toast layout for system (chrome-privileged) toasts. This gains us
+  // UI elements such as new image placement options (default image placement is
+  // larger and inline) and buttons.
+  if (mIsSystemPrincipal) {
+    ComPtr<IXmlNodeList> bindingElements;
+    hr = toastXml->GetElementsByTagName(HStringReference(L"binding").Get(),
+                                        &bindingElements);
+    NS_ENSURE_TRUE(SUCCEEDED(hr), nullptr);
+
+    ComPtr<IXmlNode> bindingNodeRoot;
+    hr = bindingElements->Item(0, &bindingNodeRoot);
+    NS_ENSURE_TRUE(SUCCEEDED(hr), nullptr);
+
+    ComPtr<IXmlElement> bindingElement;
+    hr = bindingNodeRoot.As(&bindingElement);
+    NS_ENSURE_TRUE(SUCCEEDED(hr), nullptr);
+
+    success = SetAttribute(bindingElement, HStringReference(L"template"),
+                           u"ToastGeneric"_ns);
+    NS_ENSURE_TRUE(success, nullptr);
+  }
+
+  ComPtr<IXmlElement> actions;
+  hr = toastXml->CreateElement(HStringReference(L"actions").Get(), &actions);
+  NS_ENSURE_TRUE(SUCCEEDED(hr), nullptr);
+
+  ComPtr<IXmlNode> actionsNode;
+  hr = actions.As(&actionsNode);
+  NS_ENSURE_TRUE(SUCCEEDED(hr), nullptr);
+
+  nsCOMPtr<nsIStringBundleService> sbs =
+      do_GetService(NS_STRINGBUNDLE_CONTRACTID);
+  NS_ENSURE_TRUE(sbs, nullptr);
+
+  nsCOMPtr<nsIStringBundle> bundle;
+  sbs->CreateBundle("chrome://alerts/locale/alert.properties",
+                    getter_AddRefs(bundle));
+  NS_ENSURE_TRUE(bundle, nullptr);
+
+  if (!mHostPort.IsEmpty()) {
+    AutoTArray<nsString, 1> formatStrings = {mHostPort};
+
+    ComPtr<IXmlNode> urlTextNodeRoot;
+    hr = toastTextElements->Item(2, &urlTextNodeRoot);
+    NS_ENSURE_TRUE(SUCCEEDED(hr), nullptr);
+
+    nsAutoString urlReference;
+    bundle->FormatStringFromName("source.label", formatStrings, urlReference);
+
+    success =
+        SetNodeValueString(urlReference, urlTextNodeRoot.Get(), toastXml.Get());
+    NS_ENSURE_TRUE(success, nullptr);
+
+    if (IsWin10AnniversaryUpdateOrLater()) {
+      ComPtr<IXmlElement> placementText;
+      hr = urlTextNodeRoot.As(&placementText);
+      if (SUCCEEDED(hr)) {
+        // placement is supported on Windows 10 Anniversary Update or later
+        SetAttribute(placementText, HStringReference(L"placement"),
+                     u"attribution"_ns);
+      }
+    }
+
+    nsAutoString disableButtonTitle;
+    ns = bundle->FormatStringFromName("webActions.disableForOrigin.label",
+                                      formatStrings, disableButtonTitle);
+    NS_ENSURE_SUCCESS(ns, nullptr);
+
+    AddActionNode(toastXml, actionsNode, disableButtonTitle,
+                  // TODO: launch into `about:preferences`?
+                  launchArgWithoutAction, ActionArgsJSONString(u"snooze"_ns),
+                  u"contextmenu"_ns);
+  }
+
+  bool wantSettings = true;
+#ifdef MOZ_BACKGROUNDTASKS
+  if (BackgroundTasks::IsBackgroundTaskMode()) {
+    // Notifications popped from a background task want to invoke Firefox with a
+    // different profile -- the default browsing profile.  Don't link to Firefox
+    // settings in some different profile: the relevant Firefox settings won't
+    // take effect.
+    wantSettings = false;
+  }
+#endif
+  if (MOZ_LIKELY(wantSettings)) {
+    nsAutoString settingsButtonTitle;
+    bundle->GetStringFromName("webActions.settings.label", settingsButtonTitle);
+    success = AddActionNode(
+        toastXml, actionsNode, settingsButtonTitle, launchArgWithoutAction,
+        // TODO: launch into `about:preferences`?
+        ActionArgsJSONString(u"settings"_ns), u"contextmenu"_ns);
+    NS_ENSURE_TRUE(success, nullptr);
+  }
+
+  for (const auto& action : mActions) {
+    // Bug 1778596: include per-action icon from image URL.
+    nsString title;
+    ns = action->GetTitle(title);
+    NS_ENSURE_SUCCESS(ns, nullptr);
+
+    nsString actionString;
+    ns = action->GetAction(actionString);
+    NS_ENSURE_SUCCESS(ns, nullptr);
+
+    nsString opaqueRelaunchData;
+    ns = action->GetOpaqueRelaunchData(opaqueRelaunchData);
+    NS_ENSURE_SUCCESS(ns, nullptr);
+
+    MOZ_LOG(sWASLog, LogLevel::Debug,
+            ("launchArgWithoutAction for '%s': '%s'",
+             NS_ConvertUTF16toUTF8(actionString).get(),
+             NS_ConvertUTF16toUTF8(launchArgWithoutAction).get()));
+
+    // Privileged/chrome alerts can have actions that are activated by Windows.
+    // Recognize these actions and enable these activations.
+    bool activationType(false);
+    ns = action->GetWindowsSystemActivationType(&activationType);
+    NS_ENSURE_SUCCESS(ns, nullptr);
+
+    nsString activationTypeString(
+        (mIsSystemPrincipal && activationType) ? u"system"_ns : u""_ns);
+
+    nsString actionArgs;
+    if (mIsSystemPrincipal && activationType) {
+      // Privileged/chrome alerts that are activated by Windows can't have
+      // custom relaunch data.
+      actionArgs = actionString;
+
+      NS_WARNING_ASSERTION(opaqueRelaunchData.IsEmpty(),
+                           "action with `windowsSystemActivationType=true` "
+                           "should have trivial `opaqueRelaunchData`");
+    } else {
+      actionArgs = ActionArgsJSONString(actionString, opaqueRelaunchData);
+    }
+
+    success = AddActionNode(toastXml, actionsNode, title,
+                            /* launchArg */ launchArgWithoutAction,
+                            /* actionArgs */ actionArgs,
+                            /* actionPlacement */ u""_ns,
+                            /* activationType */ activationTypeString);
+    NS_ENSURE_TRUE(success, nullptr);
+  }
+
+  // Windows ignores scenario=reminder added by mRequiredInteraction if
+  // there's no non-contextmenu action.
+  if (mRequireInteraction && !mActions.Length()) {
+    // `activationType="system" arguments="dismiss" content=""` provides
+    // localized text from Windows, but we support more locales than Windows
+    // does, so let's have our own.
+    nsTArray<nsCString> resIds = {
+        "toolkit/global/alert.ftl"_ns,
+    };
+    RefPtr<intl::Localization> l10n = intl::Localization::Create(resIds, true);
+    IgnoredErrorResult rv;
+    nsAutoCString closeTitle;
+    l10n->FormatValueSync("notification-default-dismiss"_ns, {}, closeTitle,
+                          rv);
+    NS_ENSURE_TRUE(!rv.Failed(), nullptr);
+
+    NS_ENSURE_TRUE(
+        AddActionNode(toastXml, actionsNode, NS_ConvertUTF8toUTF16(closeTitle),
+                      u""_ns, u"dismiss"_ns, u""_ns, u"system"_ns),
+        nullptr);
+  }
+
+  ComPtr<IXmlNode> appendedChild;
+  hr = toastNodeRoot->AppendChild(actionsNode.Get(), &appendedChild);
+  NS_ENSURE_TRUE(SUCCEEDED(hr), nullptr);
+
+  if (mIsSilent) {
+    ComPtr<IXmlNode> audioNode;
+    // Create <audio silent="true"/> for silent notifications.
+    ComPtr<IXmlElement> audio;
+    hr = toastXml->CreateElement(HStringReference(L"audio").Get(), &audio);
+    NS_ENSURE_TRUE(SUCCEEDED(hr), nullptr);
+
+    SetAttribute(audio, HStringReference(L"silent"), u"true"_ns);
+
+    hr = audio.As(&audioNode);
+    NS_ENSURE_TRUE(SUCCEEDED(hr), nullptr);
+    hr = toastNodeRoot->AppendChild(audioNode.Get(), &appendedChild);
+    NS_ENSURE_TRUE(SUCCEEDED(hr), nullptr);
+  }
+
+  return toastXml;
+}
+
+nsresult ToastNotificationHandler::CreateToastXmlString(
+    const nsAString& aImageURL, nsAString& aString) {
+  HRESULT hr;
+
+  if (!aImageURL.IsEmpty()) {
+    // For testing: don't fetch and write image to disk, just include the URL.
+    mHasImage = true;
+    mImageUri.Assign(aImageURL);
+  }
+
+  ComPtr<IXmlDocument> toastXml = CreateToastXmlDocument();
+  if (!toastXml) {
+    return NS_ERROR_FAILURE;
+  }
+
+  ComPtr<IXmlNodeSerializer> ser;
+  hr = toastXml.As(&ser);
+  NS_ENSURE_TRUE(SUCCEEDED(hr), NS_ERROR_FAILURE);
+
+  HString data;
+  hr = ser->GetXml(data.GetAddressOf());
+  NS_ENSURE_TRUE(SUCCEEDED(hr), NS_ERROR_FAILURE);
+
+  uint32_t len = 0;
+  const wchar_t* rawData = data.GetRawBuffer(&len);
+  NS_ENSURE_TRUE(rawData, NS_ERROR_FAILURE);
+  aString.Assign(rawData, len);
+
+  return NS_OK;
+}
+
+bool ToastNotificationHandler::ShowAlert() {
+  if (!mBackend->IsActiveHandler(mName, this)) {
+    return false;
+  }
+
+  ComPtr<IXmlDocument> toastXml = CreateToastXmlDocument();
+
+  if (!toastXml) {
+    return false;
+  }
+
+  return CreateWindowsNotificationFromXml(toastXml);
+}
+
+bool ToastNotificationHandler::IsPrivate() { return mInPrivateBrowsing; }
+
+void ToastNotificationHandler::HideAlert() {
+  if (mNotifier && mNotification) {
+    mNotifier->Hide(mNotification.Get());
+  }
+}
+
+bool ToastNotificationHandler::CreateWindowsNotificationFromXml(
+    ComPtr<IXmlDocument>& aXml) {
+  ComPtr<IToastNotificationFactory> factory;
+  HRESULT hr;
+
+  hr = GetActivationFactory(
+      HStringReference(RuntimeClass_Windows_UI_Notifications_ToastNotification)
+          .Get(),
+      &factory);
+  NS_ENSURE_TRUE(SUCCEEDED(hr), false);
+
+  hr = factory->CreateToastNotification(aXml.Get(), &mNotification);
+  NS_ENSURE_TRUE(SUCCEEDED(hr), false);
+
+  RefPtr<ToastNotificationHandler> self = this;
+
+  hr = mNotification->add_Activated(
+      Callback<ToastActivationHandler>([self](IToastNotification* aNotification,
+                                              IInspectable* aInspectable) {
+        return self->OnActivate(ComPtr<IToastNotification>(aNotification),
+                                ComPtr<IInspectable>(aInspectable));
+      }).Get(),
+      &mActivatedToken);
+  NS_ENSURE_TRUE(SUCCEEDED(hr), false);
+
+  hr = mNotification->add_Dismissed(
+      Callback<ToastDismissedHandler>([self](IToastNotification* aNotification,
+                                             IToastDismissedEventArgs* aArgs) {
+        return self->OnDismiss(ComPtr<IToastNotification>(aNotification),
+                               ComPtr<IToastDismissedEventArgs>(aArgs));
+      }).Get(),
+      &mDismissedToken);
+  NS_ENSURE_TRUE(SUCCEEDED(hr), false);
+
+  hr = mNotification->add_Failed(
+      Callback<ToastFailedHandler>([self](IToastNotification* aNotification,
+                                          IToastFailedEventArgs* aArgs) {
+        return self->OnFail(ComPtr<IToastNotification>(aNotification),
+                            ComPtr<IToastFailedEventArgs>(aArgs));
+      }).Get(),
+      &mFailedToken);
+  NS_ENSURE_TRUE(SUCCEEDED(hr), false);
+
+  ComPtr<IToastNotification2> notification2;
+  hr = mNotification.As(&notification2);
+  NS_ENSURE_TRUE(SUCCEEDED(hr), false);
+
+  HString hTag;
+  hr = hTag.Set(mWindowsTag.get());
+  NS_ENSURE_TRUE(SUCCEEDED(hr), false);
+
+  hr = notification2->put_Tag(hTag.Get());
+  NS_ENSURE_TRUE(SUCCEEDED(hr), false);
+
+  ComPtr<IToastNotificationManagerStatics> toastNotificationManagerStatics =
+      GetToastNotificationManagerStatics();
+  NS_ENSURE_TRUE(toastNotificationManagerStatics, false);
+
+  HString aumid;
+  hr = aumid.Set(mAumid.get());
+  NS_ENSURE_TRUE(SUCCEEDED(hr), false);
+  hr = toastNotificationManagerStatics->CreateToastNotifierWithId(aumid.Get(),
+                                                                  &mNotifier);
+  NS_ENSURE_TRUE(SUCCEEDED(hr), false);
+
+  hr = mNotifier->Show(mNotification.Get());
+  NS_ENSURE_TRUE(SUCCEEDED(hr), false);
+
+  if (mAlertListener) {
+    mAlertListener->Observe(nullptr, "alertshow", mCookie.get());
+  }
+
+  return true;
+}
+
+void ToastNotificationHandler::SendFinished() {
+  if (!mSentFinished && mAlertListener) {
+    mAlertListener->Observe(nullptr, "alertfinished", mCookie.get());
+  }
+
+  mSentFinished = true;
+}
+
+HRESULT
+ToastNotificationHandler::OnActivate(
+    const ComPtr<IToastNotification>& notification,
+    const ComPtr<IInspectable>& inspectable) {
+  MOZ_LOG(sWASLog, LogLevel::Info, ("OnActivate"));
+
+  if (mAlertListener) {
+    // Extract the `action` value from the argument string.
+    nsAutoString argumentsString;
+    nsAutoString actionString;
+    if (inspectable) {
+      ComPtr<IToastActivatedEventArgs> eventArgs;
+      HRESULT hr = inspectable.As(&eventArgs);
+      if (SUCCEEDED(hr)) {
+        HString arguments;
+        hr = eventArgs->get_Arguments(arguments.GetAddressOf());
+        if (SUCCEEDED(hr)) {
+          uint32_t len = 0;
+          const char16_t* buffer = (char16_t*)arguments.GetRawBuffer(&len);
+          if (buffer) {
+            MOZ_LOG(sWASLog, LogLevel::Info,
+                    ("OnActivate: arguments: %s",
+                     NS_ConvertUTF16toUTF8(buffer).get()));
+            argumentsString.Assign(buffer);
+
+            // Toast arguments are a newline separated key/value combination of
+            // launch arguments and an optional action argument provided as an
+            // argument to the toast's constructor. After the `action` key is
+            // found, the remainder of toast argument (including newlines) is
+            // the `action` value.
+            Tokenizer16 parse(buffer);
+            nsDependentSubstring token;
+
+            while (parse.ReadUntil(Tokenizer16::Token::NewLine(), token)) {
+              if (token == nsDependentString(kLaunchArgAction)) {
+                Unused << parse.ReadUntil(Tokenizer16::Token::EndOfFile(),
+                                          actionString);
+              } else {
+                // Next line is a value in a key/value pair, skip.
+                parse.SkipUntil(Tokenizer16::Token::NewLine());
+              }
+              // Skip newline.
+              Tokenizer16::Token unused;
+              Unused << parse.Next(unused);
+            }
+          }
+        }
+      }
+    }
+
+    if (argumentsString.EqualsLiteral("dismiss")) {
+      // XXX: Somehow Windows still fires OnActivate instead of OnDismiss for
+      // supposedly system managed dismiss button (with activationType=system
+      // and arguments=dismiss). We have to manually treat such callback as a
+      // dismiss action. For this case `arguments` only includes a keyword so we
+      // don't need to compare with a parsed result.
+      SendFinished();
+    } else if (actionString.EqualsLiteral("settings")) {
+      mAlertListener->Observe(nullptr, "alertsettingscallback", mCookie.get());
+    } else if (actionString.EqualsLiteral("snooze")) {
+      mAlertListener->Observe(nullptr, "alertdisablecallback", mCookie.get());
+    } else if (mClickable) {
+      // When clicking toast, focus moves to another process, but we want to set
+      // focus on Firefox process.
+      nsCOMPtr<nsIWindowMediator> winMediator(
+          do_GetService(NS_WINDOWMEDIATOR_CONTRACTID));
+      if (winMediator) {
+        nsCOMPtr<mozIDOMWindowProxy> navWin;
+        winMediator->GetMostRecentWindow(u"navigator:browser",
+                                         getter_AddRefs(navWin));
+        if (navWin) {
+          nsCOMPtr<nsIWidget> widget =
+              WidgetUtils::DOMWindowToWidget(nsPIDOMWindowOuter::From(navWin));
+          if (widget) {
+            SetForegroundWindow(
+                static_cast<HWND>(widget->GetNativeData(NS_NATIVE_WINDOW)));
+          }
+        }
+      }
+
+      if (mHandleActions) {
+        Json::Value jsonData;
+        Json::Reader jsonReader;
+
+        if (jsonReader.parse(NS_ConvertUTF16toUTF8(actionString).get(),
+                             jsonData, false)) {
+          char actionKey[] = "action";
+          if (jsonData.isMember(actionKey) && jsonData[actionKey].isString()) {
+            mAlertListener->Observe(
+                nullptr, "alertactioncallback",
+                NS_ConvertUTF8toUTF16(jsonData[actionKey].asCString()).get());
+          }
+        }
+      }
+
+      mAlertListener->Observe(nullptr, "alertclickcallback", mCookie.get());
+    }
+  }
+  mBackend->RemoveHandler(mName, this);
+  return S_OK;
+}
+
+// Returns `nullptr` if no such toast exists.
+/* static */ ComPtr<IToastNotification>
+ToastNotificationHandler::FindNotificationByTag(const nsAString& aWindowsTag,
+                                                const nsAString& aAumid) {
+  HRESULT hr = S_OK;
+
+  HString current_id;
+  current_id.Set(PromiseFlatString(aWindowsTag).get());
+
+  ComPtr<IToastNotificationManagerStatics> manager =
+      GetToastNotificationManagerStatics();
+  NS_ENSURE_TRUE(manager, nullptr);
+
+  ComPtr<IToastNotificationManagerStatics2> manager2;
+  hr = manager.As(&manager2);
+  NS_ENSURE_TRUE(SUCCEEDED(hr), nullptr);
+
+  ComPtr<IToastNotificationHistory> history;
+  hr = manager2->get_History(&history);
+  NS_ENSURE_TRUE(SUCCEEDED(hr), nullptr);
+  ComPtr<IToastNotificationHistory2> history2;
+  hr = history.As(&history2);
+  NS_ENSURE_TRUE(SUCCEEDED(hr), nullptr);
+
+  ComPtr<IVectorView_ToastNotification> toasts;
+  hr = history2->GetHistoryWithId(
+      HStringReference(PromiseFlatString(aAumid).get()).Get(), &toasts);
+  NS_ENSURE_TRUE(SUCCEEDED(hr), nullptr);
+
+  unsigned int hist_size;
+  hr = toasts->get_Size(&hist_size);
+  NS_ENSURE_TRUE(SUCCEEDED(hr), nullptr);
+  for (unsigned int i = 0; i < hist_size; i++) {
+    ComPtr<IToastNotification> hist_toast;
+    hr = toasts->GetAt(i, &hist_toast);
+    if (NS_WARN_IF(FAILED(hr))) {
+      continue;
+    }
+
+    ComPtr<IToastNotification2> hist_toast2;
+    hr = hist_toast.As(&hist_toast2);
+    NS_ENSURE_TRUE(SUCCEEDED(hr), nullptr);
+
+    HString history_id;
+    hr = hist_toast2->get_Tag(history_id.GetAddressOf());
+    NS_ENSURE_TRUE(SUCCEEDED(hr), nullptr);
+
+    // We can not directly compare IToastNotification objects; their IUnknown
+    // pointers should be equivalent but under inspection were not. Therefore we
+    // use the notification's tag instead.
+    if (current_id == history_id) {
+      return hist_toast;
+    }
+  }
+
+  return nullptr;
+}
+
+// A single toast message can receive multiple dismiss events, at most one for
+// the popup and at most one for the action center. We can't simply count
+// dismiss events as the user may have disabled either popups or action center
+// notifications, therefore we have to check if the toast remains in the history
+// (action center) to determine if the toast is fully dismissed.
+HRESULT
+ToastNotificationHandler::OnDismiss(
+    const ComPtr<IToastNotification>& notification,
+    const ComPtr<IToastDismissedEventArgs>& aArgs) {
+  ComPtr<IToastNotification2> notification2;
+  HRESULT hr = notification.As(&notification2);
+  NS_ENSURE_TRUE(SUCCEEDED(hr), E_FAIL);
+
+  HString tagHString;
+  hr = notification2->get_Tag(tagHString.GetAddressOf());
+  NS_ENSURE_TRUE(SUCCEEDED(hr), E_FAIL);
+
+  unsigned int len;
+  const wchar_t* tagPtr = tagHString.GetRawBuffer(&len);
+  nsAutoString tag(tagPtr, len);
+
+  if (FindNotificationByTag(tag, mAumid)) {
+    return S_OK;
+  }
+
+  SendFinished();
+  mBackend->RemoveHandler(mName, this);
+  return S_OK;
+}
+
+HRESULT
+ToastNotificationHandler::OnFail(const ComPtr<IToastNotification>& notification,
+                                 const ComPtr<IToastFailedEventArgs>& aArgs) {
+  HRESULT err;
+  aArgs->get_ErrorCode(&err);
+  MOZ_LOG(sWASLog, LogLevel::Error,
+          ("Error creating notification, error: %ld", err));
+
+  if (mHandleActions) {
+    mAlertListener->Observe(nullptr, "alerterror", mCookie.get());
+  }
+
+  SendFinished();
+  mBackend->RemoveHandler(mName, this);
+  return S_OK;
+}
+
+nsresult ToastNotificationHandler::TryShowAlert() {
+  if (NS_WARN_IF(!ShowAlert())) {
+    mBackend->RemoveHandler(mName, this);
+    return NS_ERROR_FAILURE;
+  }
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+ToastNotificationHandler::OnImageMissing(nsISupports*) {
+  return TryShowAlert();
+}
+
+NS_IMETHODIMP
+ToastNotificationHandler::OnImageReady(nsISupports*, imgIRequest* aRequest) {
+  nsresult rv = AsyncSaveImage(aRequest);
+  if (NS_FAILED(rv)) {
+    return TryShowAlert();
+  }
+  return rv;
+}
+
+nsresult ToastNotificationHandler::AsyncSaveImage(imgIRequest* aRequest) {
+  nsresult rv =
+      NS_GetSpecialDirectory(NS_OS_TEMP_DIR, getter_AddRefs(mImageFile));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  rv = mImageFile->Append(u"notificationimages"_ns);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  rv = mImageFile->Create(nsIFile::DIRECTORY_TYPE, 0500);
+  if (NS_FAILED(rv) && rv != NS_ERROR_FILE_ALREADY_EXISTS) {
+    return rv;
+  }
+
+  nsID uuid;
+  rv = nsID::GenerateUUIDInPlace(uuid);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  NSID_TrimBracketsASCII uuidStr(uuid);
+  uuidStr.AppendLiteral(".png");
+  mImageFile->AppendNative(uuidStr);
+
+  nsCOMPtr<imgIContainer> imgContainer;
+  rv = aRequest->GetImage(getter_AddRefs(imgContainer));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsMainThreadPtrHandle<ToastNotificationHandler> self(
+      new nsMainThreadPtrHolder<ToastNotificationHandler>(
+          "ToastNotificationHandler", this));
+
+  nsCOMPtr<nsIFile> imageFile(mImageFile);
+  RefPtr<mozilla::gfx::SourceSurface> surface = imgContainer->GetFrame(
+      imgIContainer::FRAME_FIRST,
+      imgIContainer::FLAG_SYNC_DECODE | imgIContainer::FLAG_ASYNC_NOTIFY);
+  nsCOMPtr<nsIRunnable> r = NS_NewRunnableFunction(
+      "ToastNotificationHandler::AsyncWriteImage",
+      [self, imageFile, surface]() -> void {
+        nsresult rv = NS_ERROR_FAILURE;
+        if (surface) {
+          FILE* file = nullptr;
+          rv = imageFile->OpenANSIFileDesc("wb", &file);
+          if (NS_SUCCEEDED(rv)) {
+            rv = gfxUtils::EncodeSourceSurface(surface, ImageType::PNG, u""_ns,
+                                               gfxUtils::eBinaryEncode, file);
+            fclose(file);
+          }
+        }
+
+        nsCOMPtr<nsIRunnable> cbRunnable = NS_NewRunnableFunction(
+            "ToastNotificationHandler::AsyncWriteImageCb",
+            [self, rv]() -> void {
+              auto handler = const_cast<ToastNotificationHandler*>(self.get());
+              handler->OnWriteImageFinished(rv);
+            });
+
+        NS_DispatchToMainThread(cbRunnable);
+      });
+
+  return mBackend->BackgroundDispatch(r);
+}
+
+void ToastNotificationHandler::OnWriteImageFinished(nsresult rv) {
+  if (NS_SUCCEEDED(rv)) {
+    OnWriteImageSuccess();
+  }
+  TryShowAlert();
+}
+
+nsresult ToastNotificationHandler::OnWriteImageSuccess() {
+  nsresult rv;
+
+  nsCOMPtr<nsIURI> fileURI;
+  rv = NS_NewFileURI(getter_AddRefs(fileURI), mImageFile);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsAutoCString uriStr;
+  rv = fileURI->GetSpec(uriStr);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  AppendUTF8toUTF16(uriStr, mImageUri);
+
+  mHasImage = true;
+
+  return NS_OK;
+}
+
+}  // namespace widget
+}  // namespace mozilla
diff --git a/widget/windows/ToastNotificationHandler.h b/widget/windows/ToastNotificationHandler.h
new file mode 100644
index 0000000000..b3be34709c
--- /dev/null
+++ b/widget/windows/ToastNotificationHandler.h
@@ -0,0 +1,162 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef ToastNotificationHandler_h__
+#define ToastNotificationHandler_h__
+
+#include <windows.ui.notifications.h>
+#include <windows.data.xml.dom.h>
+#include <wrl.h>
+#include "nsCOMPtr.h"
+#include "nsICancelable.h"
+#include "nsIFile.h"
+#include "nsIWindowsAlertsService.h"
+#include "nsString.h"
+#include "mozilla/Result.h"
+
+namespace mozilla {
+namespace widget {
+
+enum class ImagePlacement {
+  eInline,
+  eHero,
+  eIcon,
+};
+
+class ToastNotification;
+
+class ToastNotificationHandler final
+    : public nsIAlertNotificationImageListener {
+ public:
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIALERTNOTIFICATIONIMAGELISTENER
+
+  ToastNotificationHandler(
+      ToastNotification* backend, const nsAString& aumid,
+      nsIObserver* aAlertListener, const nsAString& aName,
+      const nsAString& aCookie, const nsAString& aTitle, const nsAString& aMsg,
+      const nsAString& aHostPort, bool aClickable, bool aRequireInteraction,
+      const nsTArray<RefPtr<nsIAlertAction>>& aActions, bool aIsSystemPrincipal,
+      const nsAString& aOpaqueRelaunchData, bool aInPrivateBrowsing,
+      bool aIsSilent, bool aHandlesActions = false,
+      ImagePlacement aImagePlacement = ImagePlacement::eInline)
+      : mBackend(backend),
+        mAumid(aumid),
+        mHasImage(false),
+        mAlertListener(aAlertListener),
+        mName(aName),
+        mCookie(aCookie),
+        mTitle(aTitle),
+        mMsg(aMsg),
+        mHostPort(aHostPort),
+        mClickable(aClickable),
+        mRequireInteraction(aRequireInteraction),
+        mInPrivateBrowsing(aInPrivateBrowsing),
+        mActions(aActions.Clone()),
+        mIsSystemPrincipal(aIsSystemPrincipal),
+        mOpaqueRelaunchData(aOpaqueRelaunchData),
+        mIsSilent(aIsSilent),
+        mSentFinished(!aAlertListener),
+        mHandleActions(aHandlesActions),
+        mImagePlacement(aImagePlacement) {}
+
+  nsresult InitAlertAsync(nsIAlertNotification* aAlert);
+
+  void OnWriteImageFinished(nsresult rv);
+
+  void HideAlert();
+  bool IsPrivate();
+
+  void UnregisterHandler();
+
+  nsString ActionArgsJSONString(
+      const nsString& aAction,
+      const nsString& aOpaqueRelaunchData /* = u""_ns */);
+  nsresult CreateToastXmlString(const nsAString& aImageURL, nsAString& aString);
+
+  nsresult GetWindowsTag(nsAString& aWindowsTag);
+  nsresult SetWindowsTag(const nsAString& aWindowsTag);
+
+  // Exposed for consumption by `ToastNotification.cpp`.
+  static nsresult FindNotificationDataForWindowsTag(
+      const nsAString& aWindowsTag, const nsAString& aAumid, bool& aFoundTag,
+      nsAString& aNotificationData);
+
+ protected:
+  virtual ~ToastNotificationHandler();
+
+  using IXmlDocument = ABI::Windows::Data::Xml::Dom::IXmlDocument;
+  using IToastNotifier = ABI::Windows::UI::Notifications::IToastNotifier;
+  using IToastNotification =
+      ABI::Windows::UI::Notifications::IToastNotification;
+  using IToastDismissedEventArgs =
+      ABI::Windows::UI::Notifications::IToastDismissedEventArgs;
+  using IToastFailedEventArgs =
+      ABI::Windows::UI::Notifications::IToastFailedEventArgs;
+  using ToastTemplateType = ABI::Windows::UI::Notifications::ToastTemplateType;
+  template <typename T>
+  using ComPtr = Microsoft::WRL::ComPtr<T>;
+
+  Result<nsString, nsresult> GetLaunchArgument();
+
+  ComPtr<IToastNotification> mNotification;
+  ComPtr<IToastNotifier> mNotifier;
+
+  RefPtr<ToastNotification> mBackend;
+
+  nsString mAumid;
+  nsString mWindowsTag;
+
+  nsCOMPtr<nsICancelable> mImageRequest;
+  nsCOMPtr<nsIFile> mImageFile;
+  nsString mImageUri;
+  bool mHasImage;
+
+  EventRegistrationToken mActivatedToken;
+  EventRegistrationToken mDismissedToken;
+  EventRegistrationToken mFailedToken;
+
+  nsCOMPtr<nsIObserver> mAlertListener;
+  nsString mName;
+  nsString mCookie;
+  nsString mTitle;
+  nsString mMsg;
+  nsString mHostPort;
+  bool mClickable;
+  bool mRequireInteraction;
+  bool mInPrivateBrowsing;
+  nsTArray<RefPtr<nsIAlertAction>> mActions;
+  bool mIsSystemPrincipal;
+  nsString mOpaqueRelaunchData;
+  bool mIsSilent;
+  bool mSentFinished;
+  bool mHandleActions;
+  ImagePlacement mImagePlacement;
+
+  nsresult TryShowAlert();
+  bool ShowAlert();
+  nsresult AsyncSaveImage(imgIRequest* aRequest);
+  nsresult OnWriteImageSuccess();
+  void SendFinished();
+
+  nsresult InitWindowsTag();
+  bool CreateWindowsNotificationFromXml(ComPtr<IXmlDocument>& aToastXml);
+  ComPtr<IXmlDocument> CreateToastXmlDocument();
+
+  HRESULT OnActivate(const ComPtr<IToastNotification>& notification,
+                     const ComPtr<IInspectable>& inspectable);
+  HRESULT OnDismiss(const ComPtr<IToastNotification>& notification,
+                    const ComPtr<IToastDismissedEventArgs>& aArgs);
+  HRESULT OnFail(const ComPtr<IToastNotification>& notification,
+                 const ComPtr<IToastFailedEventArgs>& aArgs);
+
+  static ComPtr<IToastNotification> FindNotificationByTag(
+      const nsAString& aWindowsTag, const nsAString& aAumid);
+};
+
+}  // namespace widget
+}  // namespace mozilla
+
+#endif
diff --git a/widget/windows/ToastNotificationHeaderOnlyUtils.h b/widget/windows/ToastNotificationHeaderOnlyUtils.h
new file mode 100644
index 0000000000..dd777c0c32
--- /dev/null
+++ b/widget/windows/ToastNotificationHeaderOnlyUtils.h
@@ -0,0 +1,155 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_ToastNotificationHeaderOnlyUtils_h
+#define mozilla_ToastNotificationHeaderOnlyUtils_h
+
+/**
+ * This header is intended for self-contained, header-only, utility code to
+ * share between Windows toast notification code in firefox.exe and
+ * notificationserver.dll.
+ */
+
+// Use XPCOM logging if we're in a XUL context, otherwise use Windows Event
+// logging.
+// NOTE: The `printf` `format` equivalent argument to `NOTIFY_LOG` is converted
+// to a wide string when outside of a XUL context. String format specifiers need
+// to specify they're a wide string with `%ls` or narrow string with `%hs`.
+#include "mozilla/Logging.h"
+#ifdef IMPL_LIBXUL
+namespace mozilla::widget {
+extern LazyLogModule sWASLog;
+}  // namespace mozilla::widget
+#  define NOTIFY_LOG(_level, _args) \
+    MOZ_LOG(mozilla::widget::sWASLog, _level, _args)
+#else
+#  include "mozilla/WindowsEventLog.h"
+
+bool gVerbose = false;
+
+#  define NOTIFY_LOG(_level, _args)                       \
+    if (gVerbose || _level == mozilla::LogLevel::Error) { \
+      POST_EXPAND_NOTIFY_LOG(MOZ_LOG_EXPAND_ARGS _args);  \
+    }
+#  define POST_EXPAND_NOTIFY_LOG(...) \
+    MOZ_WIN_EVENT_LOG_ERROR_MESSAGE(  \
+        L"" MOZ_APP_DISPLAYNAME " Notification Server", L"" __VA_ARGS__)
+#endif
+
+#include <functional>
+#include <string>
+
+#include "nsWindowsHelpers.h"
+
+namespace mozilla::widget::toastnotification {
+
+const wchar_t kLaunchArgProgram[] = L"program";
+const wchar_t kLaunchArgProfile[] = L"profile";
+const wchar_t kLaunchArgTag[] = L"windowsTag";
+const wchar_t kLaunchArgLogging[] = L"logging";
+const wchar_t kLaunchArgAction[] = L"action";
+
+const DWORD kNotificationServerTimeoutMs = (10 * 1000);
+
+struct ToastNotificationPidMessage {
+  DWORD pid = 0;
+};
+
+struct ToastNotificationPermissionMessage {
+  DWORD setForegroundPermissionGranted = 0;
+};
+
+inline std::wstring GetNotificationPipeName(const wchar_t* aTag) {
+  // Prefix required by pipe API.
+  std::wstring pipeName(LR"(\\.\pipe\)");
+
+  pipeName += L"" MOZ_APP_NAME;
+  pipeName += aTag;
+
+  return pipeName;
+}
+
+inline bool WaitEventWithTimeout(const HANDLE& event) {
+  DWORD result = WaitForSingleObject(event, kNotificationServerTimeoutMs);
+
+  switch (result) {
+    case WAIT_OBJECT_0:
+      NOTIFY_LOG(LogLevel::Info, ("Pipe wait signaled"));
+      return true;
+    case WAIT_TIMEOUT:
+      NOTIFY_LOG(LogLevel::Warning, ("Pipe wait timed out"));
+      return false;
+    case WAIT_FAILED:
+      NOTIFY_LOG(LogLevel::Error,
+                 ("Pipe wait failed, error %lu", GetLastError()));
+      return false;
+    case WAIT_ABANDONED:
+      NOTIFY_LOG(LogLevel::Error, ("Pipe wait abandoned"));
+      return false;
+    default:
+      NOTIFY_LOG(LogLevel::Error, ("Pipe wait unknown error"));
+      return false;
+  }
+}
+
+/* Handles running overlapped transactions for a Windows pipe. This function
+ * manages lifetimes of Event and OVERLAPPED objects to ensure they are not used
+ * while an overlapped operation is pending. */
+inline bool SyncDoOverlappedIOWithTimeout(
+    const nsAutoHandle& pipe, const size_t bytesExpected,
+    const std::function<BOOL(OVERLAPPED&)>& transactPipe) {
+  nsAutoHandle event(CreateEventW(nullptr, TRUE, FALSE, nullptr));
+  if (!event) {
+    NOTIFY_LOG(
+        LogLevel::Error,
+        ("Error creating pipe transaction event, error %lu", GetLastError()));
+    return false;
+  }
+
+  OVERLAPPED overlapped{};
+  overlapped.hEvent = event.get();
+  BOOL result = transactPipe(overlapped);
+
+  if (!result && GetLastError() != ERROR_IO_PENDING) {
+    NOTIFY_LOG(LogLevel::Error,
+               ("Error reading from pipe, error %lu", GetLastError()));
+    return false;
+  }
+
+  if (!WaitEventWithTimeout(overlapped.hEvent)) {
+    NOTIFY_LOG(LogLevel::Warning, ("Pipe transaction timed out, canceling "
+                                   "(transaction may still succeed)."));
+
+    CancelIo(pipe.get());
+
+    // Transaction may still succeed before cancellation is handled; fall
+    // through to normal handling.
+  }
+
+  DWORD bytesTransferred = 0;
+  // Pipe transfer has either been signaled or cancelled by this point, so it
+  // should be safe to wait on.
+  BOOL overlappedResult =
+      GetOverlappedResult(pipe.get(), &overlapped, &bytesTransferred, TRUE);
+
+  if (!overlappedResult) {
+    NOTIFY_LOG(
+        LogLevel::Error,
+        ("Error retrieving pipe overlapped result, error %lu", GetLastError()));
+    return false;
+  } else if (bytesTransferred != bytesExpected) {
+    NOTIFY_LOG(LogLevel::Error,
+               ("%lu bytes read from pipe, but %zu bytes expected",
+                bytesTransferred, bytesExpected));
+    return false;
+  }
+
+  return true;
+}
+
+}  // namespace mozilla::widget::toastnotification
+
+#endif  // mozilla_ToastNotificationHeaderOnlyUtils_h
diff --git a/widget/windows/UrlmonHeaderOnlyUtils.h b/widget/windows/UrlmonHeaderOnlyUtils.h
new file mode 100644
index 0000000000..dd9209f78f
--- /dev/null
+++ b/widget/windows/UrlmonHeaderOnlyUtils.h
@@ -0,0 +1,76 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_UrlmonHeaderOnlyUtils_h
+#define mozilla_UrlmonHeaderOnlyUtils_h
+
+#include "mozilla/ShellHeaderOnlyUtils.h"
+
+namespace mozilla {
+
+/**
+ * We used to validate a uri with SHParseDisplayName to mitigate the Windows
+ * bug (Bug 394974).  However, Bug 1573051 revealed an issue that a fragment,
+ * a string following a hash mark (#), is dropped when we extract a string
+ * from PIDL.  This is the intended behavior of Windows.
+ *
+ * To deal with the fragment issue as well as keeping our mitigation, we
+ * decided to use CreateUri to validate a uri string, but we also keep using
+ * SHParseDisplayName as a pre-check.  This is because there are several
+ * cases where CreateUri succeeds while SHParseDisplayName fails such as
+ * a non-existent file: uri.
+ *
+ * To minimize the impact of introducing CreateUri into the validation logic,
+ * we try to mimic the logic of windows_storage!IUriToPidl (ieframe!IUriToPidl
+ * in Win7) which is executed behind SHParseDisplayName.
+ * What IUriToPidl does is:
+ *   1) If a given uri has a fragment, removes a fragment.
+ *   2) Takes an absolute uri if it's available in the given uri, otherwise
+ *      takes a raw uri.
+ *
+ * As we need to get a full uri including a fragment, this function does 2).
+ */
+inline LauncherResult<_bstr_t> UrlmonValidateUri(const wchar_t* aUri) {
+  LauncherResult<UniqueAbsolutePidl> pidlResult = ShellParseDisplayName(aUri);
+  if (pidlResult.isErr()) {
+    return pidlResult.propagateErr();
+  }
+
+  // The value of |flags| is the same value as used in ieframe!_EnsureIUri in
+  // Win7, which is called behind SHParseDisplayName.  In Win10, on the other
+  // hand, an flag 0x03000000 is also passed to CreateUri, but we don't
+  // specify it because it's undocumented and unknown.
+  constexpr DWORD flags =
+      Uri_CREATE_NO_DECODE_EXTRA_INFO | Uri_CREATE_CANONICALIZE |
+      Uri_CREATE_CRACK_UNKNOWN_SCHEMES | Uri_CREATE_PRE_PROCESS_HTML_URI |
+      Uri_CREATE_IE_SETTINGS;
+  RefPtr<IUri> uri;
+  HRESULT hr;
+  SAFECALL_URLMON_FUNC(CreateUri, aUri, flags, 0, getter_AddRefs(uri));
+  if (FAILED(hr)) {
+    return LAUNCHER_ERROR_FROM_HRESULT(hr);
+  }
+
+  _bstr_t bstrUri;
+
+  hr = uri->GetAbsoluteUri(bstrUri.GetAddress());
+  if (FAILED(hr)) {
+    return LAUNCHER_ERROR_FROM_HRESULT(hr);
+  }
+
+  if (hr == S_FALSE) {
+    hr = uri->GetRawUri(bstrUri.GetAddress());
+    if (FAILED(hr)) {
+      return LAUNCHER_ERROR_FROM_HRESULT(hr);
+    }
+  }
+
+  return bstrUri;
+}
+
+}  // namespace mozilla
+
+#endif  // mozilla_UrlmonHeaderOnlyUtils_h
diff --git a/widget/windows/WidgetTraceEvent.cpp b/widget/windows/WidgetTraceEvent.cpp
new file mode 100644
index 0000000000..15bb4d720c
--- /dev/null
+++ b/widget/windows/WidgetTraceEvent.cpp
@@ -0,0 +1,121 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/*
+ * Windows widget support for event loop instrumentation.
+ * See toolkit/xre/EventTracer.cpp for more details.
+ */
+
+#include <stdio.h>
+#include <windows.h>
+
+#include "mozilla/RefPtr.h"
+#include "mozilla/WidgetTraceEvent.h"
+#include "nsAppShellCID.h"
+#include "nsComponentManagerUtils.h"
+#include "nsCOMPtr.h"
+#include "nsIAppShellService.h"
+#include "nsIBaseWindow.h"
+#include "nsIDocShell.h"
+#include "nsISupportsImpl.h"
+#include "nsIWidget.h"
+#include "nsIAppWindow.h"
+#include "nsServiceManagerUtils.h"
+#include "nsThreadUtils.h"
+#include "nsWindowDefs.h"
+
+namespace {
+
+// Used for signaling the background thread from the main thread.
+HANDLE sEventHandle = nullptr;
+
+// We need a runnable in order to find the hidden window on the main
+// thread.
+class HWNDGetter : public mozilla::Runnable {
+ public:
+  HWNDGetter() : Runnable("HWNDGetter"), hidden_window_hwnd(nullptr) {}
+
+  HWND hidden_window_hwnd;
+
+  NS_IMETHOD Run() override {
+    // Jump through some hoops to locate the hidden window.
+    nsCOMPtr<nsIAppShellService> appShell(
+        do_GetService(NS_APPSHELLSERVICE_CONTRACTID));
+    nsCOMPtr<nsIAppWindow> hiddenWindow;
+
+    nsresult rv = appShell->GetHiddenWindow(getter_AddRefs(hiddenWindow));
+    if (NS_FAILED(rv)) {
+      return rv;
+    }
+
+    nsCOMPtr<nsIDocShell> docShell;
+    rv = hiddenWindow->GetDocShell(getter_AddRefs(docShell));
+    if (NS_FAILED(rv) || !docShell) {
+      return rv;
+    }
+
+    nsCOMPtr<nsIBaseWindow> baseWindow(do_QueryInterface(docShell));
+
+    if (!baseWindow) return NS_ERROR_FAILURE;
+
+    nsCOMPtr<nsIWidget> widget;
+    baseWindow->GetMainWidget(getter_AddRefs(widget));
+
+    if (!widget) return NS_ERROR_FAILURE;
+
+    hidden_window_hwnd = (HWND)widget->GetNativeData(NS_NATIVE_WINDOW);
+
+    return NS_OK;
+  }
+};
+
+HWND GetHiddenWindowHWND() {
+  // Need to dispatch this to the main thread because plenty of
+  // the things it wants to access are main-thread-only.
+  RefPtr<HWNDGetter> getter = new HWNDGetter();
+  NS_DispatchAndSpinEventLoopUntilComplete(
+      "GetHiddenWindowHWND"_ns, mozilla::GetMainThreadSerialEventTarget(),
+      do_AddRef(getter));
+  return getter->hidden_window_hwnd;
+}
+
+}  // namespace
+
+namespace mozilla {
+
+bool InitWidgetTracing() {
+  sEventHandle = CreateEventW(nullptr, FALSE, FALSE, nullptr);
+  return sEventHandle != nullptr;
+}
+
+void CleanUpWidgetTracing() {
+  CloseHandle(sEventHandle);
+  sEventHandle = nullptr;
+}
+
+// This function is called from the main (UI) thread.
+void SignalTracerThread() {
+  if (sEventHandle != nullptr) SetEvent(sEventHandle);
+}
+
+// This function is called from the background tracer thread.
+bool FireAndWaitForTracerEvent() {
+  MOZ_ASSERT(sEventHandle, "Tracing not initialized!");
+
+  // First, try to find the hidden window.
+  static HWND hidden_window = nullptr;
+  if (hidden_window == nullptr) {
+    hidden_window = GetHiddenWindowHWND();
+  }
+
+  if (hidden_window == nullptr) return false;
+
+  // Post the tracer message into the hidden window's message queue,
+  // and then block until it's processed.
+  PostMessage(hidden_window, MOZ_WM_TRACE, 0, 0);
+  WaitForSingleObject(sEventHandle, INFINITE);
+  return true;
+}
+
+}  // namespace mozilla
diff --git a/widget/windows/WinCompositorWidget.cpp b/widget/windows/WinCompositorWidget.cpp
new file mode 100644
index 0000000000..15957a1c3f
--- /dev/null
+++ b/widget/windows/WinCompositorWidget.cpp
@@ -0,0 +1,105 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "WinCompositorWidget.h"
+
+#include "mozilla/StaticPrefs_layers.h"
+#include "mozilla/gfx/DeviceManagerDx.h"
+#include "mozilla/gfx/Point.h"
+#include "mozilla/layers/Compositor.h"
+#include "mozilla/layers/CompositorThread.h"
+#include "mozilla/webrender/RenderThread.h"
+#include "mozilla/widget/PlatformWidgetTypes.h"
+#include "nsWindow.h"
+#include "VsyncDispatcher.h"
+#include "WinCompositorWindowThread.h"
+#include "VRShMem.h"
+
+#include <ddraw.h>
+
+namespace mozilla {
+namespace widget {
+
+using namespace mozilla::gfx;
+using namespace mozilla;
+
+WinCompositorWidget::WinCompositorWidget(
+    const WinCompositorWidgetInitData& aInitData,
+    const layers::CompositorOptions& aOptions)
+    : CompositorWidget(aOptions),
+      mSetParentCompleted(false),
+      mWidgetKey(aInitData.widgetKey()),
+      mWnd(reinterpret_cast<HWND>(aInitData.hWnd())),
+      mCompositorWnds(nullptr, nullptr) {
+  MOZ_ASSERT(mWnd && ::IsWindow(mWnd));
+}
+
+WinCompositorWidget::~WinCompositorWidget() { DestroyCompositorWindow(); }
+
+uintptr_t WinCompositorWidget::GetWidgetKey() { return mWidgetKey; }
+
+void WinCompositorWidget::EnsureCompositorWindow() {
+  if (mCompositorWnds.mCompositorWnd || mCompositorWnds.mInitialParentWnd) {
+    return;
+  }
+
+  mCompositorWnds = WinCompositorWindowThread::CreateCompositorWindow();
+  UpdateCompositorWnd(mCompositorWnds.mCompositorWnd, mWnd);
+
+  MOZ_ASSERT(mCompositorWnds.mCompositorWnd);
+  MOZ_ASSERT(mCompositorWnds.mInitialParentWnd);
+}
+
+void WinCompositorWidget::DestroyCompositorWindow() {
+  if (!mCompositorWnds.mCompositorWnd && !mCompositorWnds.mInitialParentWnd) {
+    return;
+  }
+  WinCompositorWindowThread::DestroyCompositorWindow(mCompositorWnds);
+  mCompositorWnds = WinCompositorWnds(nullptr, nullptr);
+}
+
+void WinCompositorWidget::UpdateCompositorWndSizeIfNecessary() {
+  if (!mCompositorWnds.mCompositorWnd) {
+    return;
+  }
+
+  LayoutDeviceIntSize size = GetClientSize();
+  if (mLastCompositorWndSize == size) {
+    return;
+  }
+
+  // This code is racing with the compositor, which needs to reparent the
+  // compositor surface to the actual window (mWnd). To avoid racing mutations,
+  // we refuse to proceed until ::SetParent() is called in the parent process.
+  // After the ::SetParent() call, composition is scheduled in
+  // CompositorWidgetParent::UpdateCompositorWnd().
+  if (!mSetParentCompleted) {
+    // ::SetParent() is not completed yet.
+    return;
+  }
+
+  MOZ_ASSERT(mWnd == ::GetParent(mCompositorWnds.mCompositorWnd));
+
+  // Force a resize and redraw (but not a move, activate, etc.).
+  if (!::SetWindowPos(
+          mCompositorWnds.mCompositorWnd, nullptr, 0, 0, size.width,
+          size.height,
+          SWP_NOACTIVATE | SWP_NOCOPYBITS | SWP_NOOWNERZORDER | SWP_NOZORDER)) {
+    return;
+  }
+
+  mLastCompositorWndSize = size;
+}
+
+// Creates a new instance of FxROutputHandler so that this compositor widget
+// can send its output to Firefox Reality for Desktop.
+void WinCompositorWidget::RequestFxrOutput() {
+  MOZ_ASSERT(mFxrHandler == nullptr);
+
+  mFxrHandler.reset(new FxROutputHandler());
+}
+
+}  // namespace widget
+}  // namespace mozilla
diff --git a/widget/windows/WinCompositorWidget.h b/widget/windows/WinCompositorWidget.h
new file mode 100644
index 0000000000..fef967380c
--- /dev/null
+++ b/widget/windows/WinCompositorWidget.h
@@ -0,0 +1,103 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef widget_windows_WinCompositorWidget_h
+#define widget_windows_WinCompositorWidget_h
+
+#include "CompositorWidget.h"
+#include "mozilla/Atomics.h"
+#include "mozilla/gfx/CriticalSection.h"
+#include "mozilla/gfx/Point.h"
+#include "mozilla/layers/LayersTypes.h"
+#include "mozilla/Mutex.h"
+#include "mozilla/widget/WinCompositorWindowThread.h"
+#include "FxROutputHandler.h"
+#include "nsIWidget.h"
+
+class nsWindow;
+
+namespace mozilla {
+namespace widget {
+
+class PlatformCompositorWidgetDelegate : public CompositorWidgetDelegate {
+ public:
+  // Callbacks for nsWindow.
+  virtual void EnterPresentLock() = 0;
+  virtual void LeavePresentLock() = 0;
+  virtual void OnDestroyWindow() = 0;
+  virtual bool OnWindowResize(const LayoutDeviceIntSize& aSize) = 0;
+  virtual void OnWindowModeChange(nsSizeMode aSizeMode) = 0;
+
+  // Transparency handling.
+  virtual void UpdateTransparency(TransparencyMode aMode) = 0;
+  virtual void ClearTransparentWindow() = 0;
+
+  // Deliver visibility info
+  virtual void NotifyVisibilityUpdated(nsSizeMode aSizeMode,
+                                       bool aIsFullyOccluded) = 0;
+
+  // CompositorWidgetDelegate Overrides
+
+  PlatformCompositorWidgetDelegate* AsPlatformSpecificDelegate() override {
+    return this;
+  }
+};
+
+class WinCompositorWidgetInitData;
+
+// This is the Windows-specific implementation of CompositorWidget. For
+// the most part it only requires an HWND, however it maintains extra state
+// for transparent windows, as well as for synchronizing WM_SETTEXT messages
+// with the compositor.
+class WinCompositorWidget : public CompositorWidget {
+ public:
+  WinCompositorWidget(const WinCompositorWidgetInitData& aInitData,
+                      const layers::CompositorOptions& aOptions);
+  ~WinCompositorWidget() override;
+
+  // CompositorWidget Overrides
+
+  uintptr_t GetWidgetKey() override;
+  WinCompositorWidget* AsWindows() override { return this; }
+
+  HWND GetHwnd() const {
+    return mCompositorWnds.mCompositorWnd ? mCompositorWnds.mCompositorWnd
+                                          : mWnd;
+  }
+
+  HWND GetCompositorHwnd() const { return mCompositorWnds.mCompositorWnd; }
+
+  void EnsureCompositorWindow();
+  void DestroyCompositorWindow();
+  void UpdateCompositorWndSizeIfNecessary();
+
+  void RequestFxrOutput();
+  bool HasFxrOutputHandler() const { return mFxrHandler != nullptr; }
+  FxROutputHandler* GetFxrOutputHandler() const { return mFxrHandler.get(); }
+
+  virtual nsSizeMode GetWindowSizeMode() const = 0;
+  virtual bool GetWindowIsFullyOccluded() const = 0;
+
+  virtual void UpdateCompositorWnd(const HWND aCompositorWnd,
+                                   const HWND aParentWnd) = 0;
+  virtual void SetRootLayerTreeID(const layers::LayersId& aRootLayerTreeId) = 0;
+
+ protected:
+  bool mSetParentCompleted;
+
+ private:
+  uintptr_t mWidgetKey;
+  HWND mWnd;
+
+  WinCompositorWnds mCompositorWnds;
+  LayoutDeviceIntSize mLastCompositorWndSize;
+
+  UniquePtr<FxROutputHandler> mFxrHandler;
+};
+
+}  // namespace widget
+}  // namespace mozilla
+
+#endif  // widget_windows_WinCompositorWidget_h
diff --git a/widget/windows/WinCompositorWindowThread.cpp b/widget/windows/WinCompositorWindowThread.cpp
new file mode 100644
index 0000000000..3b06c098e6
--- /dev/null
+++ b/widget/windows/WinCompositorWindowThread.cpp
@@ -0,0 +1,294 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "base/platform_thread.h"
+#include "WinCompositorWindowThread.h"
+#include "mozilla/gfx/Logging.h"
+#include "mozilla/layers/SynchronousTask.h"
+#include "mozilla/StaticPtr.h"
+#include "transport/runnable_utils.h"
+#include "mozilla/StaticPrefs_apz.h"
+
+namespace mozilla {
+namespace widget {
+
+static StaticRefPtr<WinCompositorWindowThread> sWinCompositorWindowThread;
+
+/// A window procedure that logs when an input event is received to the gfx
+/// error log
+///
+/// This is done because this window is supposed to be WM_DISABLED, but
+/// malfunctioning software may still end up targetting this window. If that
+/// happens, it's almost-certainly a bug and should be brought to the attention
+/// of the developers that are debugging the issue.
+static LRESULT CALLBACK InputEventRejectingWindowProc(HWND window, UINT msg,
+                                                      WPARAM wparam,
+                                                      LPARAM lparam) {
+  switch (msg) {
+    case WM_LBUTTONDOWN:
+    case WM_LBUTTONUP:
+    case WM_RBUTTONDOWN:
+    case WM_RBUTTONUP:
+    case WM_MBUTTONDOWN:
+    case WM_MBUTTONUP:
+    case WM_MOUSEWHEEL:
+    case WM_MOUSEHWHEEL:
+    case WM_MOUSEMOVE:
+    case WM_KEYDOWN:
+    case WM_KEYUP:
+    case WM_SYSKEYDOWN:
+    case WM_SYSKEYUP:
+      gfxCriticalNoteOnce
+          << "The compositor window received an input event even though it's "
+             "disabled. There is likely malfunctioning "
+             "software on the user's machine.";
+
+      break;
+    default:
+      break;
+  }
+  return ::DefWindowProcW(window, msg, wparam, lparam);
+}
+
+WinCompositorWindowThread::WinCompositorWindowThread(base::Thread* aThread)
+    : mThread(aThread), mMonitor("WinCompositorWindowThread") {}
+
+/* static */
+WinCompositorWindowThread* WinCompositorWindowThread::Get() {
+  if (!sWinCompositorWindowThread ||
+      sWinCompositorWindowThread->mHasAttemptedShutdown) {
+    return nullptr;
+  }
+  return sWinCompositorWindowThread;
+}
+
+/* static */
+void WinCompositorWindowThread::Start() {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  base::Thread::Options options;
+  // HWND requests ui thread.
+  options.message_loop_type = MessageLoop::TYPE_UI;
+
+  if (sWinCompositorWindowThread) {
+    // Try to reuse the thread, which involves stopping and restarting it.
+    sWinCompositorWindowThread->mThread->Stop();
+    if (sWinCompositorWindowThread->mThread->StartWithOptions(options)) {
+      // Success!
+      sWinCompositorWindowThread->mHasAttemptedShutdown = false;
+      return;
+    }
+    // Restart failed, so null out our sWinCompositorWindowThread and
+    // try again with a new thread. This will cause the old singleton
+    // instance to be deallocated, which will destroy its mThread as well.
+    sWinCompositorWindowThread = nullptr;
+  }
+
+  base::Thread* thread = new base::Thread("WinCompositor");
+  if (!thread->StartWithOptions(options)) {
+    delete thread;
+    return;
+  }
+
+  sWinCompositorWindowThread = new WinCompositorWindowThread(thread);
+}
+
+/* static */
+void WinCompositorWindowThread::ShutDown() {
+  MOZ_ASSERT(NS_IsMainThread());
+  MOZ_ASSERT(sWinCompositorWindowThread);
+
+  sWinCompositorWindowThread->mHasAttemptedShutdown = true;
+
+  // Our thread could hang while we're waiting for it to stop.
+  // Since we're shutting down, that's not a critical problem.
+  // We set a reasonable amount of time to wait for shutdown,
+  // and if it succeeds within that time, we correctly stop
+  // our thread by nulling out the refptr, which will cause it
+  // to be deallocated and join the thread. If it times out,
+  // we do nothing, which means that the thread will not be
+  // joined and sWinCompositorWindowThread memory will leak.
+  CVStatus status;
+  {
+    // It's important to hold the lock before posting the
+    // runnable. This ensures that the runnable can't begin
+    // until we've started our Wait, which prevents us from
+    // Waiting on a monitor that has already been notified.
+    MonitorAutoLock lock(sWinCompositorWindowThread->mMonitor);
+
+    static const TimeDuration TIMEOUT = TimeDuration::FromSeconds(2.0);
+    RefPtr<Runnable> runnable =
+        NewRunnableMethod("WinCompositorWindowThread::ShutDownTask",
+                          sWinCompositorWindowThread.get(),
+                          &WinCompositorWindowThread::ShutDownTask);
+    Loop()->PostTask(runnable.forget());
+
+    // Monitor uses SleepConditionVariableSRW, which can have
+    // spurious wakeups which are reported as timeouts, so we
+    // check timestamps to ensure that we've waited as long we
+    // intended to. If we wake early, we don't bother calculating
+    // a precise amount for the next wait; we just wait the same
+    // amount of time. This means timeout might happen after as
+    // much as 2x the TIMEOUT time.
+    TimeStamp timeStart = TimeStamp::NowLoRes();
+    do {
+      status = sWinCompositorWindowThread->mMonitor.Wait(TIMEOUT);
+    } while ((status == CVStatus::Timeout) &&
+             ((TimeStamp::NowLoRes() - timeStart) < TIMEOUT));
+  }
+
+  if (status == CVStatus::NoTimeout) {
+    sWinCompositorWindowThread = nullptr;
+  }
+}
+
+void WinCompositorWindowThread::ShutDownTask() {
+  MonitorAutoLock lock(mMonitor);
+
+  MOZ_ASSERT(IsInCompositorWindowThread());
+  mMonitor.NotifyAll();
+}
+
+/* static */
+MessageLoop* WinCompositorWindowThread::Loop() {
+  return sWinCompositorWindowThread
+             ? sWinCompositorWindowThread->mThread->message_loop()
+             : nullptr;
+}
+
+/* static */
+bool WinCompositorWindowThread::IsInCompositorWindowThread() {
+  return sWinCompositorWindowThread &&
+         sWinCompositorWindowThread->mThread->thread_id() ==
+             PlatformThread::CurrentId();
+}
+
+const wchar_t kClassNameCompositorInitalParent[] =
+    L"MozillaCompositorInitialParentClass";
+const wchar_t kClassNameCompositor[] = L"MozillaCompositorWindowClass";
+
+ATOM g_compositor_inital_parent_window_class;
+ATOM g_compositor_window_class;
+
+// This runs on the window owner thread.
+void InitializeInitialParentWindowClass() {
+  if (g_compositor_inital_parent_window_class) {
+    return;
+  }
+
+  WNDCLASSW wc;
+  wc.style = 0;
+  wc.lpfnWndProc = ::DefWindowProcW;
+  wc.cbClsExtra = 0;
+  wc.cbWndExtra = 0;
+  wc.hInstance = GetModuleHandle(nullptr);
+  wc.hIcon = nullptr;
+  wc.hCursor = nullptr;
+  wc.hbrBackground = nullptr;
+  wc.lpszMenuName = nullptr;
+  wc.lpszClassName = kClassNameCompositorInitalParent;
+  g_compositor_inital_parent_window_class = ::RegisterClassW(&wc);
+}
+
+// This runs on the window owner thread.
+void InitializeWindowClass() {
+  if (g_compositor_window_class) {
+    return;
+  }
+
+  WNDCLASSW wc;
+  wc.style = CS_OWNDC;
+  wc.lpfnWndProc = InputEventRejectingWindowProc;
+  wc.cbClsExtra = 0;
+  wc.cbWndExtra = 0;
+  wc.hInstance = GetModuleHandle(nullptr);
+  wc.hIcon = nullptr;
+  wc.hCursor = nullptr;
+  wc.hbrBackground = nullptr;
+  wc.lpszMenuName = nullptr;
+  wc.lpszClassName = kClassNameCompositor;
+  g_compositor_window_class = ::RegisterClassW(&wc);
+}
+
+/* static */
+WinCompositorWnds WinCompositorWindowThread::CreateCompositorWindow() {
+  MOZ_ASSERT(Loop());
+
+  if (!Loop()) {
+    return WinCompositorWnds(nullptr, nullptr);
+  }
+
+  layers::SynchronousTask task("Create compositor window");
+
+  HWND initialParentWnd = nullptr;
+  HWND compositorWnd = nullptr;
+
+  RefPtr<Runnable> runnable = NS_NewRunnableFunction(
+      "WinCompositorWindowThread::CreateCompositorWindow::Runnable", [&]() {
+        layers::AutoCompleteTask complete(&task);
+
+        InitializeInitialParentWindowClass();
+        InitializeWindowClass();
+
+        // Create initial parent window.
+        // We could not directly create a compositor window with a main window
+        // as parent window, so instead create it with a temporary placeholder
+        // parent. Its parent is set as main window in UI process.
+        initialParentWnd =
+            ::CreateWindowEx(WS_EX_TOOLWINDOW, kClassNameCompositorInitalParent,
+                             nullptr, WS_POPUP | WS_DISABLED, 0, 0, 1, 1,
+                             nullptr, 0, GetModuleHandle(nullptr), 0);
+        if (!initialParentWnd) {
+          gfxCriticalNoteOnce << "Inital parent window failed "
+                              << ::GetLastError();
+          return;
+        }
+
+        DWORD extendedStyle = WS_EX_NOPARENTNOTIFY | WS_EX_NOREDIRECTIONBITMAP;
+
+        if (!StaticPrefs::apz_windows_force_disable_direct_manipulation()) {
+          extendedStyle |= WS_EX_LAYERED | WS_EX_TRANSPARENT;
+        }
+
+        compositorWnd = ::CreateWindowEx(
+            extendedStyle, kClassNameCompositor, nullptr,
+            WS_CHILDWINDOW | WS_DISABLED | WS_VISIBLE, 0, 0, 1, 1,
+            initialParentWnd, 0, GetModuleHandle(nullptr), 0);
+        if (!compositorWnd) {
+          gfxCriticalNoteOnce << "Compositor window failed "
+                              << ::GetLastError();
+        }
+      });
+
+  Loop()->PostTask(runnable.forget());
+
+  task.Wait();
+
+  return WinCompositorWnds(compositorWnd, initialParentWnd);
+}
+
+/* static */
+void WinCompositorWindowThread::DestroyCompositorWindow(
+    WinCompositorWnds aWnds) {
+  MOZ_ASSERT(aWnds.mCompositorWnd);
+  MOZ_ASSERT(aWnds.mInitialParentWnd);
+  MOZ_ASSERT(Loop());
+
+  if (!Loop()) {
+    return;
+  }
+
+  RefPtr<Runnable> runnable = NS_NewRunnableFunction(
+      "WinCompositorWidget::CreateNativeWindow::Runnable", [aWnds]() {
+        ::DestroyWindow(aWnds.mCompositorWnd);
+        ::DestroyWindow(aWnds.mInitialParentWnd);
+      });
+
+  Loop()->PostTask(runnable.forget());
+}
+
+}  // namespace widget
+}  // namespace mozilla
diff --git a/widget/windows/WinCompositorWindowThread.h b/widget/windows/WinCompositorWindowThread.h
new file mode 100644
index 0000000000..372e3d91c2
--- /dev/null
+++ b/widget/windows/WinCompositorWindowThread.h
@@ -0,0 +1,67 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef widget_windows_WinCompositorWindowThread_h
+#define widget_windows_WinCompositorWindowThread_h
+
+#include "base/thread.h"
+#include "base/message_loop.h"
+#include "mozilla/Monitor.h"
+
+namespace mozilla {
+namespace widget {
+
+struct WinCompositorWnds {
+  HWND mCompositorWnd;
+  HWND mInitialParentWnd;
+  WinCompositorWnds(HWND aCompositorWnd, HWND aInitialParentWnd)
+      : mCompositorWnd(aCompositorWnd), mInitialParentWnd(aInitialParentWnd) {}
+};
+
+class WinCompositorWindowThread final {
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING_WITH_DELETE_ON_MAIN_THREAD(
+      WinCompositorWindowThread)
+
+ public:
+  /// Can be called from any thread.
+  static WinCompositorWindowThread* Get();
+
+  /// Can only be called from the main thread.
+  static void Start();
+
+  /// Can only be called from the main thread.
+  static void ShutDown();
+
+  /// Can be called from any thread.
+  static MessageLoop* Loop();
+
+  /// Can be called from any thread.
+  static bool IsInCompositorWindowThread();
+
+  /// Can be called from any thread.
+  static WinCompositorWnds CreateCompositorWindow();
+
+  /// Can be called from any thread.
+  static void DestroyCompositorWindow(WinCompositorWnds aWnds);
+
+ private:
+  explicit WinCompositorWindowThread(base::Thread* aThread);
+  ~WinCompositorWindowThread() {}
+
+  void ShutDownTask();
+
+  UniquePtr<base::Thread> const mThread;
+  Monitor mMonitor;
+
+  // Has ShutDown been called on us? We might have survived if our thread join
+  // timed out.
+  bool mHasAttemptedShutdown = false;
+};
+
+}  // namespace widget
+}  // namespace mozilla
+
+#endif  // widget_windows_WinCompositorWindowThread_h
diff --git a/widget/windows/WinEventObserver.cpp b/widget/windows/WinEventObserver.cpp
new file mode 100644
index 0000000000..7abac8a59a
--- /dev/null
+++ b/widget/windows/WinEventObserver.cpp
@@ -0,0 +1,223 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <windows.h>
+#include <winuser.h>
+#include <wtsapi32.h>
+
+#include "WinEventObserver.h"
+
+#include "mozilla/ClearOnShutdown.h"
+#include "mozilla/Logging.h"
+#include "mozilla/StaticPtr.h"
+#include "nsHashtablesFwd.h"
+#include "nsdefs.h"
+
+namespace mozilla::widget {
+
+LazyLogModule gWinEventObserverLog("WinEventObserver");
+#define LOG(...) MOZ_LOG(gWinEventObserverLog, LogLevel::Info, (__VA_ARGS__))
+
+// static
+StaticRefPtr<WinEventHub> WinEventHub::sInstance;
+
+// static
+bool WinEventHub::Ensure() {
+  if (sInstance) {
+    return true;
+  }
+
+  LOG("WinEventHub::Ensure()");
+
+  RefPtr<WinEventHub> instance = new WinEventHub();
+  if (!instance->Initialize()) {
+    MOZ_ASSERT_UNREACHABLE("unexpected to be called");
+    return false;
+  }
+  sInstance = instance;
+  ClearOnShutdown(&sInstance);
+  return true;
+}
+
+WinEventHub::WinEventHub() {
+  MOZ_ASSERT(NS_IsMainThread());
+  LOG("WinEventHub::WinEventHub()");
+}
+
+WinEventHub::~WinEventHub() {
+  MOZ_ASSERT(NS_IsMainThread());
+  MOZ_ASSERT(mObservers.IsEmpty());
+  LOG("WinEventHub::~WinEventHub()");
+
+  if (mHWnd) {
+    ::DestroyWindow(mHWnd);
+    mHWnd = nullptr;
+  }
+}
+
+bool WinEventHub::Initialize() {
+  WNDCLASSW wc;
+  HMODULE hSelf = ::GetModuleHandle(nullptr);
+
+  if (!GetClassInfoW(hSelf, L"MozillaWinEventHubClass", &wc)) {
+    ZeroMemory(&wc, sizeof(WNDCLASSW));
+    wc.hInstance = hSelf;
+    wc.lpfnWndProc = WinEventProc;
+    wc.lpszClassName = L"MozillaWinEventHubClass";
+    RegisterClassW(&wc);
+  }
+
+  mHWnd = ::CreateWindowW(L"MozillaWinEventHubClass", L"WinEventHub", 0, 0, 0,
+                          0, 0, nullptr, nullptr, hSelf, nullptr);
+  if (!mHWnd) {
+    return false;
+  }
+
+  return true;
+}
+
+// static
+LRESULT CALLBACK WinEventHub::WinEventProc(HWND aHwnd, UINT aMsg,
+                                           WPARAM aWParam, LPARAM aLParam) {
+  if (sInstance) {
+    sInstance->ProcessWinEventProc(aHwnd, aMsg, aWParam, aLParam);
+  }
+  return ::DefWindowProc(aHwnd, aMsg, aWParam, aLParam);
+}
+
+void WinEventHub::ProcessWinEventProc(HWND aHwnd, UINT aMsg, WPARAM aWParam,
+                                      LPARAM aLParam) {
+  for (const auto& observer : mObservers) {
+    observer->OnWinEventProc(aHwnd, aMsg, aWParam, aLParam);
+  }
+}
+
+void WinEventHub::AddObserver(WinEventObserver* aObserver) {
+  LOG("WinEventHub::AddObserver() aObserver %p", aObserver);
+
+  mObservers.Insert(aObserver);
+}
+
+void WinEventHub::RemoveObserver(WinEventObserver* aObserver) {
+  LOG("WinEventHub::RemoveObserver() aObserver %p", aObserver);
+
+  mObservers.Remove(aObserver);
+}
+
+WinEventObserver::~WinEventObserver() {
+  MOZ_ASSERT(NS_IsMainThread());
+  MOZ_ASSERT(mDestroyed);
+}
+
+void WinEventObserver::Destroy() {
+  LOG("WinEventObserver::Destroy() this %p", this);
+
+  WinEventHub::Get()->RemoveObserver(this);
+  mDestroyed = true;
+}
+
+// static
+already_AddRefed<DisplayStatusObserver> DisplayStatusObserver::Create(
+    DisplayStatusListener* aListener) {
+  if (!WinEventHub::Ensure()) {
+    return nullptr;
+  }
+  RefPtr<DisplayStatusObserver> observer = new DisplayStatusObserver(aListener);
+  WinEventHub::Get()->AddObserver(observer);
+  return observer.forget();
+}
+
+DisplayStatusObserver::DisplayStatusObserver(DisplayStatusListener* aListener)
+    : mListener(aListener) {
+  MOZ_ASSERT(NS_IsMainThread());
+  LOG("DisplayStatusObserver::DisplayStatusObserver() this %p", this);
+
+  mDisplayStatusHandle = ::RegisterPowerSettingNotification(
+      WinEventHub::Get()->GetWnd(), &GUID_SESSION_DISPLAY_STATUS,
+      DEVICE_NOTIFY_WINDOW_HANDLE);
+}
+
+DisplayStatusObserver::~DisplayStatusObserver() {
+  MOZ_ASSERT(NS_IsMainThread());
+  LOG("DisplayStatusObserver::~DisplayStatusObserver() this %p", this);
+
+  if (mDisplayStatusHandle) {
+    ::UnregisterPowerSettingNotification(mDisplayStatusHandle);
+    mDisplayStatusHandle = nullptr;
+  }
+}
+
+void DisplayStatusObserver::OnWinEventProc(HWND aHwnd, UINT aMsg,
+                                           WPARAM aWParam, LPARAM aLParam) {
+  if (aMsg == WM_POWERBROADCAST && aWParam == PBT_POWERSETTINGCHANGE) {
+    POWERBROADCAST_SETTING* setting = (POWERBROADCAST_SETTING*)aLParam;
+    if (setting &&
+        ::IsEqualGUID(setting->PowerSetting, GUID_SESSION_DISPLAY_STATUS) &&
+        setting->DataLength == sizeof(DWORD)) {
+      bool displayOn = PowerMonitorOff !=
+                       static_cast<MONITOR_DISPLAY_STATE>(setting->Data[0]);
+
+      LOG("DisplayStatusObserver::OnWinEventProc() displayOn %d this %p",
+          displayOn, this);
+      mListener->OnDisplayStateChanged(displayOn);
+    }
+  }
+}
+
+// static
+already_AddRefed<SessionChangeObserver> SessionChangeObserver::Create(
+    SessionChangeListener* aListener) {
+  if (!WinEventHub::Ensure()) {
+    return nullptr;
+  }
+  RefPtr<SessionChangeObserver> observer = new SessionChangeObserver(aListener);
+  WinEventHub::Get()->AddObserver(observer);
+  return observer.forget();
+}
+
+SessionChangeObserver::SessionChangeObserver(SessionChangeListener* aListener)
+    : mListener(aListener) {
+  MOZ_ASSERT(NS_IsMainThread());
+  LOG("SessionChangeObserver::SessionChangeObserver() this %p", this);
+
+  auto hwnd = WinEventHub::Get()->GetWnd();
+  DebugOnly<BOOL> wtsRegistered =
+      ::WTSRegisterSessionNotification(hwnd, NOTIFY_FOR_THIS_SESSION);
+  NS_ASSERTION(wtsRegistered, "WTSRegisterSessionNotification failed!\n");
+}
+SessionChangeObserver::~SessionChangeObserver() {
+  MOZ_ASSERT(NS_IsMainThread());
+  LOG("SessionChangeObserver::~SessionChangeObserver() this %p", this);
+
+  auto hwnd = WinEventHub::Get()->GetWnd();
+  // Unregister notifications from terminal services
+  ::WTSUnRegisterSessionNotification(hwnd);
+}
+
+void SessionChangeObserver::OnWinEventProc(HWND aHwnd, UINT aMsg,
+                                           WPARAM aWParam, LPARAM aLParam) {
+  if (aMsg == WM_WTSSESSION_CHANGE &&
+      (aWParam == WTS_SESSION_LOCK || aWParam == WTS_SESSION_UNLOCK)) {
+    Maybe<bool> isCurrentSession;
+    DWORD currentSessionId = 0;
+    if (!::ProcessIdToSessionId(::GetCurrentProcessId(), &currentSessionId)) {
+      isCurrentSession = Nothing();
+    } else {
+      LOG("SessionChangeObserver::OnWinEventProc() aWParam %zu aLParam "
+          "%" PRIdLPTR
+          " "
+          "currentSessionId %lu this %p",
+          aWParam, aLParam, currentSessionId, this);
+
+      isCurrentSession = Some(static_cast<DWORD>(aLParam) == currentSessionId);
+    }
+    mListener->OnSessionChange(aWParam, isCurrentSession);
+  }
+}
+
+#undef LOG
+
+}  // namespace mozilla::widget
diff --git a/widget/windows/WinEventObserver.h b/widget/windows/WinEventObserver.h
new file mode 100644
index 0000000000..6a267871dd
--- /dev/null
+++ b/widget/windows/WinEventObserver.h
@@ -0,0 +1,115 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef widget_windows_WinEventObserver_h
+#define widget_windows_WinEventObserver_h
+
+#include <windows.h>
+
+#include "mozilla/Maybe.h"
+#include "nsISupportsImpl.h"
+#include "nsTHashSet.h"
+
+namespace mozilla {
+
+namespace widget {
+
+class WinEventObserver {
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(WinEventObserver)
+ public:
+  virtual void OnWinEventProc(HWND aHwnd, UINT aMsg, WPARAM aWParam,
+                              LPARAM aLParam) {}
+  virtual void Destroy();
+
+ protected:
+  virtual ~WinEventObserver();
+
+  bool mDestroyed = false;
+};
+
+// Uses singleton window to observe events like display status and session
+// change.
+class WinEventHub final {
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(WinEventHub)
+
+ public:
+  // Returns true if the singleton exists (or was created). Will return
+  // false if the singleton couldn't be created, in which case a call
+  // to Get() will return a nullptr. It is safe to call this function
+  // repeatedly.
+  static bool Ensure();
+  static RefPtr<WinEventHub> Get() { return sInstance; }
+
+  void AddObserver(WinEventObserver* aObserver);
+  void RemoveObserver(WinEventObserver* aObserver);
+
+  HWND GetWnd() { return mHWnd; }
+
+ private:
+  WinEventHub();
+  ~WinEventHub();
+
+  static LRESULT CALLBACK WinEventProc(HWND aHwnd, UINT aMsg, WPARAM aWParam,
+                                       LPARAM aLParam);
+
+  bool Initialize();
+  void ProcessWinEventProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam);
+
+  HWND mHWnd = nullptr;
+  nsTHashSet<nsRefPtrHashKey<WinEventObserver>> mObservers;
+
+  static StaticRefPtr<WinEventHub> sInstance;
+};
+
+class DisplayStatusListener {
+ public:
+  virtual void OnDisplayStateChanged(bool aDisplayOn) = 0;
+};
+
+// Observe Display on/off event
+class DisplayStatusObserver final : public WinEventObserver {
+ public:
+  static already_AddRefed<DisplayStatusObserver> Create(
+      DisplayStatusListener* aListener);
+
+ private:
+  explicit DisplayStatusObserver(DisplayStatusListener* aListener);
+  virtual ~DisplayStatusObserver();
+  void OnWinEventProc(HWND aHwnd, UINT aMsg, WPARAM aWParam,
+                      LPARAM aLParam) override;
+
+  DisplayStatusListener* mListener;
+
+  HPOWERNOTIFY mDisplayStatusHandle = nullptr;
+};
+
+class SessionChangeListener {
+ public:
+  virtual void OnSessionChange(WPARAM aStatusCode,
+                               Maybe<bool> aIsCurrentSession) = 0;
+};
+
+// Observe session lock/unlock event
+class SessionChangeObserver : public WinEventObserver {
+ public:
+  static already_AddRefed<SessionChangeObserver> Create(
+      SessionChangeListener* aListener);
+
+ private:
+  explicit SessionChangeObserver(SessionChangeListener* aListener);
+  virtual ~SessionChangeObserver();
+
+  void Initialize();
+  void OnWinEventProc(HWND aHwnd, UINT aMsg, WPARAM aWParam,
+                      LPARAM aLParam) override;
+
+  SessionChangeListener* mListener;
+};
+
+}  // namespace widget
+}  // namespace mozilla
+
+#endif  // widget_windows_WinEventObserver_h
diff --git a/widget/windows/WinHeaderOnlyUtils.h b/widget/windows/WinHeaderOnlyUtils.h
new file mode 100644
index 0000000000..15861cc73b
--- /dev/null
+++ b/widget/windows/WinHeaderOnlyUtils.h
@@ -0,0 +1,820 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_WinHeaderOnlyUtils_h
+#define mozilla_WinHeaderOnlyUtils_h
+
+#include <windows.h>
+#include <winerror.h>
+#include <winnt.h>
+#include <winternl.h>
+#include <objbase.h>
+#include <shlwapi.h>
+#undef ParseURL
+#include <stdlib.h>
+#include <tuple>
+
+#include "mozilla/Assertions.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/DynamicallyLinkedFunctionPtr.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/ResultVariant.h"
+#include "mozilla/UniquePtr.h"
+#include "nsWindowsHelpers.h"
+
+#if defined(MOZILLA_INTERNAL_API)
+#  include "nsIFile.h"
+#  include "nsString.h"
+#endif  // defined(MOZILLA_INTERNAL_API)
+
+/**
+ * This header is intended for self-contained, header-only, utility code for
+ * Win32. It may be used outside of xul.dll, in places such as firefox.exe or
+ * mozglue.dll. If your code creates dependencies on Mozilla libraries, you
+ * should put it elsewhere.
+ */
+
+#if !defined(STATUS_SUCCESS)
+#  define STATUS_SUCCESS ((NTSTATUS)0x00000000L)
+#endif  // !defined(STATUS_SUCCESS)
+
+// Our data indicates a few users of Win7 x86 hit failure to load urlmon.dll
+// for unknown reasons.  Since we don't always require urlmon.dll on Win7,
+// we delay-load it, which causes a crash if loading urlmon.dll fails.  This
+// macro is to safely load and call urlmon's API graciously without crash.
+#if defined(_X86_)
+#  define SAFECALL_URLMON_FUNC(FuncName, ...)                                  \
+    do {                                                                       \
+      static const mozilla::StaticDynamicallyLinkedFunctionPtr<                \
+          decltype(&::FuncName)>                                               \
+          func(L"urlmon.dll", #FuncName);                                      \
+      hr =                                                                     \
+          func ? func(__VA_ARGS__) : HRESULT_FROM_WIN32(ERROR_PROC_NOT_FOUND); \
+    } while (0)
+#else
+#  define SAFECALL_URLMON_FUNC(FuncName, ...) hr = ::FuncName(__VA_ARGS__)
+#endif
+
+namespace mozilla {
+
+class WindowsError final {
+ private:
+  // HRESULT and NTSTATUS are both typedefs of LONG, so we cannot use
+  // overloading to properly differentiate between the two. Instead we'll use
+  // static functions to convert the various error types to HRESULTs before
+  // instantiating.
+  explicit constexpr WindowsError(HRESULT aHResult) : mHResult(aHResult) {}
+
+ public:
+  using UniqueString = UniquePtr<WCHAR[], LocalFreeDeleter>;
+
+  static constexpr WindowsError FromNtStatus(NTSTATUS aNtStatus) {
+    if (aNtStatus == STATUS_SUCCESS) {
+      // Special case: we don't want to set FACILITY_NT_BIT
+      // (HRESULT_FROM_NT does not handle this case, unlike HRESULT_FROM_WIN32)
+      return WindowsError(S_OK);
+    }
+
+    return WindowsError(HRESULT_FROM_NT(aNtStatus));
+  }
+
+  static constexpr WindowsError FromHResult(HRESULT aHResult) {
+    return WindowsError(aHResult);
+  }
+
+  static constexpr WindowsError FromWin32Error(DWORD aWin32Err) {
+    return WindowsError(HRESULT_FROM_WIN32(aWin32Err));
+  }
+
+  static WindowsError FromLastError() {
+    return FromWin32Error(::GetLastError());
+  }
+
+  static WindowsError CreateSuccess() { return WindowsError(S_OK); }
+
+  static WindowsError CreateGeneric() {
+    return FromWin32Error(ERROR_UNIDENTIFIED_ERROR);
+  }
+
+  bool IsSuccess() const { return SUCCEEDED(mHResult); }
+
+  bool IsFailure() const { return FAILED(mHResult); }
+
+  bool IsAvailableAsWin32Error() const {
+    return IsAvailableAsNtStatus() ||
+           HRESULT_FACILITY(mHResult) == FACILITY_WIN32;
+  }
+
+  bool IsAvailableAsNtStatus() const {
+    return mHResult == S_OK || (mHResult & FACILITY_NT_BIT);
+  }
+
+  bool IsAvailableAsHResult() const { return true; }
+
+  UniqueString AsString() const {
+    LPWSTR rawMsgBuf = nullptr;
+    constexpr DWORD flags = FORMAT_MESSAGE_ALLOCATE_BUFFER |
+                            FORMAT_MESSAGE_FROM_SYSTEM |
+                            FORMAT_MESSAGE_IGNORE_INSERTS;
+    DWORD result =
+        ::FormatMessageW(flags, nullptr, mHResult, 0,
+                         reinterpret_cast<LPWSTR>(&rawMsgBuf), 0, nullptr);
+    if (!result) {
+      return nullptr;
+    }
+
+    return UniqueString(rawMsgBuf);
+  }
+
+  HRESULT AsHResult() const { return mHResult; }
+
+  // Not all HRESULTs are convertible to Win32 Errors, so we use Maybe
+  Maybe<DWORD> AsWin32Error() const {
+    if (mHResult == S_OK) {
+      return Some(static_cast<DWORD>(ERROR_SUCCESS));
+    }
+
+    if (HRESULT_FACILITY(mHResult) == FACILITY_WIN32) {
+      // This is the inverse of HRESULT_FROM_WIN32
+      return Some(static_cast<DWORD>(HRESULT_CODE(mHResult)));
+    }
+
+    // The NTSTATUS facility is a special case and thus does not utilize the
+    // HRESULT_FACILITY and HRESULT_CODE macros.
+    if (mHResult & FACILITY_NT_BIT) {
+      return Some(NtStatusToWin32Error(
+          static_cast<NTSTATUS>(mHResult & ~FACILITY_NT_BIT)));
+    }
+
+    return Nothing();
+  }
+
+  // Not all HRESULTs are convertible to NTSTATUS, so we use Maybe
+  Maybe<NTSTATUS> AsNtStatus() const {
+    if (mHResult == S_OK) {
+      return Some(STATUS_SUCCESS);
+    }
+
+    // The NTSTATUS facility is a special case and thus does not utilize the
+    // HRESULT_FACILITY and HRESULT_CODE macros.
+    if (mHResult & FACILITY_NT_BIT) {
+      return Some(static_cast<NTSTATUS>(mHResult & ~FACILITY_NT_BIT));
+    }
+
+    return Nothing();
+  }
+
+  constexpr bool operator==(const WindowsError& aOther) const {
+    return mHResult == aOther.mHResult;
+  }
+
+  constexpr bool operator!=(const WindowsError& aOther) const {
+    return mHResult != aOther.mHResult;
+  }
+
+  static DWORD NtStatusToWin32Error(NTSTATUS aNtStatus) {
+    static const StaticDynamicallyLinkedFunctionPtr<
+        decltype(&RtlNtStatusToDosError)>
+        pRtlNtStatusToDosError(L"ntdll.dll", "RtlNtStatusToDosError");
+
+    MOZ_ASSERT(!!pRtlNtStatusToDosError);
+    if (!pRtlNtStatusToDosError) {
+      return ERROR_UNIDENTIFIED_ERROR;
+    }
+
+    return pRtlNtStatusToDosError(aNtStatus);
+  }
+
+ private:
+  // We store the error code as an HRESULT because they can encode both Win32
+  // error codes and NTSTATUS codes.
+  HRESULT mHResult;
+};
+
+namespace detail {
+template <>
+struct UnusedZero<WindowsError> {
+  using StorageType = WindowsError;
+
+  static constexpr bool value = true;
+  static constexpr StorageType nullValue = WindowsError::FromHResult(S_OK);
+
+  static constexpr void AssertValid(StorageType aValue) {}
+  static constexpr const WindowsError& Inspect(const StorageType& aValue) {
+    return aValue;
+  }
+  static constexpr WindowsError Unwrap(StorageType aValue) { return aValue; }
+  static constexpr StorageType Store(WindowsError aValue) { return aValue; }
+};
+}  // namespace detail
+
+enum DetourResultCode : uint32_t {
+  RESULT_OK = 0,
+  INTERCEPTOR_MOD_NULL,
+  INTERCEPTOR_MOD_INACCESSIBLE,
+  INTERCEPTOR_PROC_NULL,
+  INTERCEPTOR_PROC_INACCESSIBLE,
+  DETOUR_PATCHER_RESERVE_FOR_MODULE_PE_ERROR,
+  DETOUR_PATCHER_RESERVE_FOR_MODULE_TEXT_ERROR,
+  DETOUR_PATCHER_RESERVE_FOR_MODULE_RESERVE_ERROR,
+  DETOUR_PATCHER_DO_RESERVE_ERROR,
+  DETOUR_PATCHER_NEXT_TRAMPOLINE_ERROR,
+  DETOUR_PATCHER_INVALID_TRAMPOLINE,
+  DETOUR_PATCHER_WRITE_POINTER_ERROR,
+  DETOUR_PATCHER_CREATE_TRAMPOLINE_ERROR,
+  FUNCHOOKCROSSPROCESS_COPYSTUB_ERROR,
+  MMPOLICY_RESERVE_INVALIDARG,
+  MMPOLICY_RESERVE_ZERO_RESERVATIONSIZE,
+  MMPOLICY_RESERVE_CREATEFILEMAPPING,
+  MMPOLICY_RESERVE_MAPVIEWOFFILE,
+  MMPOLICY_RESERVE_NOBOUND_RESERVE_ERROR,
+  MMPOLICY_RESERVE_FINDREGION_INVALIDLEN,
+  MMPOLICY_RESERVE_FINDREGION_INVALIDRANGE,
+  MMPOLICY_RESERVE_FINDREGION_VIRTUALQUERY_ERROR,
+  MMPOLICY_RESERVE_FINDREGION_NO_FREE_REGION,
+  MMPOLICY_RESERVE_FINAL_RESERVE_ERROR,
+};
+
+#if defined(NIGHTLY_BUILD)
+struct DetourError {
+  // We have a 16-bytes buffer, but only minimum bytes to detour per
+  // architecture are copied.  See CreateTrampoline in PatcherDetour.h.
+  DetourResultCode mErrorCode;
+  uint8_t mOrigBytes[16];
+  explicit DetourError(DetourResultCode aError)
+      : mErrorCode(aError), mOrigBytes{} {}
+  DetourError(DetourResultCode aError, DWORD aWin32Error)
+      : mErrorCode(aError), mOrigBytes{} {
+    static_assert(sizeof(mOrigBytes) >= sizeof(aWin32Error),
+                  "Can't fit a DWORD in mOrigBytes");
+    *reinterpret_cast<DWORD*>(mOrigBytes) = aWin32Error;
+  }
+  operator WindowsError() const {
+    return WindowsError::FromHResult(mErrorCode);
+  }
+};
+#endif  // defined(NIGHTLY_BUILD)
+
+template <typename T>
+using WindowsErrorResult = Result<T, WindowsError>;
+
+struct LauncherError {
+  LauncherError(const char* aFile, int aLine, WindowsError aWin32Error)
+      : mFile(aFile), mLine(aLine), mError(aWin32Error) {}
+
+#if defined(NIGHTLY_BUILD)
+  LauncherError(const char* aFile, int aLine,
+                const Maybe<DetourError>& aDetourError)
+      : mFile(aFile),
+        mLine(aLine),
+        mError(aDetourError.isSome() ? aDetourError.value()
+                                     : WindowsError::CreateGeneric()),
+        mDetourError(aDetourError) {}
+#endif  // defined(NIGHTLY_BUILD)
+
+  const char* mFile;
+  int mLine;
+  WindowsError mError;
+#if defined(NIGHTLY_BUILD)
+  Maybe<DetourError> mDetourError;
+#endif  // defined(NIGHTLY_BUILD)
+
+  bool operator==(const LauncherError& aOther) const {
+    return mError == aOther.mError;
+  }
+
+  bool operator!=(const LauncherError& aOther) const {
+    return mError != aOther.mError;
+  }
+
+  bool operator==(const WindowsError& aOther) const { return mError == aOther; }
+
+  bool operator!=(const WindowsError& aOther) const { return mError != aOther; }
+};
+
+#if defined(MOZ_USE_LAUNCHER_ERROR)
+
+template <typename T>
+using LauncherResult = Result<T, LauncherError>;
+
+template <typename T>
+using LauncherResultWithLineInfo = LauncherResult<T>;
+
+using WindowsErrorType = LauncherError;
+
+#else
+
+template <typename T>
+using LauncherResult = WindowsErrorResult<T>;
+
+template <typename T>
+using LauncherResultWithLineInfo = Result<T, LauncherError>;
+
+using WindowsErrorType = WindowsError;
+
+#endif  // defined(MOZ_USE_LAUNCHER_ERROR)
+
+using LauncherVoidResult = LauncherResult<Ok>;
+
+using LauncherVoidResultWithLineInfo = LauncherResultWithLineInfo<Ok>;
+
+#if defined(MOZ_USE_LAUNCHER_ERROR)
+
+#  define LAUNCHER_ERROR_GENERIC()           \
+    ::mozilla::Err(::mozilla::LauncherError( \
+        __FILE__, __LINE__, ::mozilla::WindowsError::CreateGeneric()))
+
+#  if defined(NIGHTLY_BUILD)
+#    define LAUNCHER_ERROR_FROM_DETOUR_ERROR(err) \
+      ::mozilla::Err(::mozilla::LauncherError(__FILE__, __LINE__, err))
+#  else
+#    define LAUNCHER_ERROR_FROM_DETOUR_ERROR(err) LAUNCHER_ERROR_GENERIC()
+#  endif  // defined(NIGHTLY_BUILD)
+
+#  define LAUNCHER_ERROR_FROM_WIN32(err)     \
+    ::mozilla::Err(::mozilla::LauncherError( \
+        __FILE__, __LINE__, ::mozilla::WindowsError::FromWin32Error(err)))
+
+#  define LAUNCHER_ERROR_FROM_LAST()         \
+    ::mozilla::Err(::mozilla::LauncherError( \
+        __FILE__, __LINE__, ::mozilla::WindowsError::FromLastError()))
+
+#  define LAUNCHER_ERROR_FROM_NTSTATUS(ntstatus) \
+    ::mozilla::Err(::mozilla::LauncherError(     \
+        __FILE__, __LINE__, ::mozilla::WindowsError::FromNtStatus(ntstatus)))
+
+#  define LAUNCHER_ERROR_FROM_HRESULT(hresult) \
+    ::mozilla::Err(::mozilla::LauncherError(   \
+        __FILE__, __LINE__, ::mozilla::WindowsError::FromHResult(hresult)))
+
+// This macro wraps the supplied WindowsError with a LauncherError
+#  define LAUNCHER_ERROR_FROM_MOZ_WINDOWS_ERROR(err) \
+    ::mozilla::Err(::mozilla::LauncherError(__FILE__, __LINE__, err))
+
+#else
+
+#  define LAUNCHER_ERROR_GENERIC() \
+    ::mozilla::Err(::mozilla::WindowsError::CreateGeneric())
+
+#  define LAUNCHER_ERROR_FROM_DETOUR_ERROR(err) LAUNCHER_ERROR_GENERIC()
+
+#  define LAUNCHER_ERROR_FROM_WIN32(err) \
+    ::mozilla::Err(::mozilla::WindowsError::FromWin32Error(err))
+
+#  define LAUNCHER_ERROR_FROM_LAST() \
+    ::mozilla::Err(::mozilla::WindowsError::FromLastError())
+
+#  define LAUNCHER_ERROR_FROM_NTSTATUS(ntstatus) \
+    ::mozilla::Err(::mozilla::WindowsError::FromNtStatus(ntstatus))
+
+#  define LAUNCHER_ERROR_FROM_HRESULT(hresult) \
+    ::mozilla::Err(::mozilla::WindowsError::FromHResult(hresult))
+
+#  define LAUNCHER_ERROR_FROM_MOZ_WINDOWS_ERROR(err) ::mozilla::Err(err)
+
+#endif  // defined(MOZ_USE_LAUNCHER_ERROR)
+
+// How long to wait for a created process to become available for input,
+// to prevent that process's windows being forced to the background.
+// This is used across update, restart, and the launcher.
+const DWORD kWaitForInputIdleTimeoutMS = 10 * 1000;
+
+/**
+ * Wait for a child GUI process to become "idle." Idle means that the process
+ * has created its message queue and has begun waiting for user input.
+ *
+ * Note that this must only be used when the child process is going to display
+ * GUI! Otherwise you're going to be waiting for a very long time ;-)
+ *
+ * @return true if we successfully waited for input idle;
+ *         false if we timed out or failed to wait.
+ */
+inline bool WaitForInputIdle(HANDLE aProcess,
+                             DWORD aTimeoutMs = kWaitForInputIdleTimeoutMS) {
+  const DWORD kSleepTimeMs = 10;
+  const DWORD waitStart = aTimeoutMs == INFINITE ? 0 : ::GetTickCount();
+  DWORD elapsed = 0;
+
+  while (true) {
+    if (aTimeoutMs != INFINITE) {
+      elapsed = ::GetTickCount() - waitStart;
+    }
+
+    if (elapsed >= aTimeoutMs) {
+      return false;
+    }
+
+    // ::WaitForInputIdle() doesn't always set the last-error code on failure
+    ::SetLastError(ERROR_SUCCESS);
+
+    DWORD waitResult = ::WaitForInputIdle(aProcess, aTimeoutMs - elapsed);
+    if (!waitResult) {
+      return true;
+    }
+
+    if (waitResult == WAIT_FAILED &&
+        ::GetLastError() == ERROR_NOT_GUI_PROCESS) {
+      ::Sleep(kSleepTimeMs);
+      continue;
+    }
+
+    return false;
+  }
+}
+
+enum class PathType {
+  eNtPath,
+  eDosPath,
+};
+
+class FileUniqueId final {
+ public:
+  explicit FileUniqueId(const wchar_t* aPath, PathType aPathType)
+      : mId(FILE_ID_INFO()) {
+    if (!aPath) {
+      mId = LAUNCHER_ERROR_FROM_HRESULT(E_INVALIDARG);
+      return;
+    }
+
+    nsAutoHandle file;
+
+    switch (aPathType) {
+      default:
+        mId = LAUNCHER_ERROR_FROM_HRESULT(E_INVALIDARG);
+        MOZ_ASSERT_UNREACHABLE("Unhandled PathType");
+        return;
+
+      case PathType::eNtPath: {
+        UNICODE_STRING unicodeString;
+        ::RtlInitUnicodeString(&unicodeString, aPath);
+        OBJECT_ATTRIBUTES objectAttributes;
+        InitializeObjectAttributes(&objectAttributes, &unicodeString,
+                                   OBJ_CASE_INSENSITIVE, nullptr, nullptr);
+        IO_STATUS_BLOCK ioStatus = {};
+        HANDLE ntHandle;
+        NTSTATUS status = ::NtOpenFile(
+            &ntHandle, SYNCHRONIZE | FILE_READ_ATTRIBUTES, &objectAttributes,
+            &ioStatus, FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE,
+            FILE_SYNCHRONOUS_IO_NONALERT | FILE_OPEN_FOR_BACKUP_INTENT);
+        // We don't need to check |ntHandle| for INVALID_HANDLE_VALUE here,
+        // as that value is set by the Win32 layer.
+        if (!NT_SUCCESS(status)) {
+          mId = LAUNCHER_ERROR_FROM_NTSTATUS(status);
+          return;
+        }
+
+        file.own(ntHandle);
+        break;
+      }
+
+      case PathType::eDosPath: {
+        file.own(::CreateFileW(
+            aPath, 0, FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE,
+            nullptr, OPEN_EXISTING, FILE_FLAG_BACKUP_SEMANTICS, nullptr));
+        if (file == INVALID_HANDLE_VALUE) {
+          mId = LAUNCHER_ERROR_FROM_LAST();
+          return;
+        }
+
+        break;
+      }
+    }
+
+    GetId(file);
+  }
+
+  explicit FileUniqueId(const nsAutoHandle& aFile) : mId(FILE_ID_INFO()) {
+    GetId(aFile);
+  }
+
+  ~FileUniqueId() = default;
+
+  bool IsError() const { return mId.isErr(); }
+
+  const WindowsErrorType& GetError() const { return mId.inspectErr(); }
+
+  FileUniqueId(FileUniqueId&& aOther) = default;
+  FileUniqueId& operator=(FileUniqueId&& aOther) = delete;
+
+  bool operator==(const FileUniqueId& aOther) const {
+    return mId.isOk() && aOther.mId.isOk() &&
+           !memcmp(&mId.inspect(), &aOther.mId.inspect(), sizeof(FILE_ID_INFO));
+  }
+
+  bool operator!=(const FileUniqueId& aOther) const {
+    return !((*this) == aOther);
+  }
+
+ private:
+  void GetId(const nsAutoHandle& aFile) {
+    FILE_ID_INFO fileIdInfo = {};
+    if (::GetFileInformationByHandleEx(aFile.get(), FileIdInfo, &fileIdInfo,
+                                       sizeof(fileIdInfo))) {
+      mId = fileIdInfo;
+      return;
+    }
+    // Only NTFS and ReFS support FileIdInfo. So we have to fallback if
+    // GetFileInformationByHandleEx failed.
+
+    BY_HANDLE_FILE_INFORMATION info = {};
+    if (!::GetFileInformationByHandle(aFile.get(), &info)) {
+      mId = LAUNCHER_ERROR_FROM_LAST();
+      return;
+    }
+
+    fileIdInfo.VolumeSerialNumber = info.dwVolumeSerialNumber;
+    memcpy(&fileIdInfo.FileId.Identifier[0], &info.nFileIndexLow,
+           sizeof(DWORD));
+    memcpy(&fileIdInfo.FileId.Identifier[sizeof(DWORD)], &info.nFileIndexHigh,
+           sizeof(DWORD));
+    mId = fileIdInfo;
+  }
+
+ private:
+  LauncherResult<FILE_ID_INFO> mId;
+};
+
+class MOZ_RAII AutoVirtualProtect final {
+ public:
+  AutoVirtualProtect(void* aAddress, size_t aLength, DWORD aProtFlags,
+                     HANDLE aTargetProcess = ::GetCurrentProcess())
+      : mAddress(aAddress),
+        mLength(aLength),
+        mTargetProcess(aTargetProcess),
+        mPrevProt(0),
+        mError(WindowsError::CreateSuccess()) {
+    if (!::VirtualProtectEx(aTargetProcess, aAddress, aLength, aProtFlags,
+                            &mPrevProt)) {
+      mError = WindowsError::FromLastError();
+    }
+  }
+
+  ~AutoVirtualProtect() {
+    if (mError.IsFailure()) {
+      return;
+    }
+
+    ::VirtualProtectEx(mTargetProcess, mAddress, mLength, mPrevProt,
+                       &mPrevProt);
+  }
+
+  explicit operator bool() const { return mError.IsSuccess(); }
+
+  WindowsError GetError() const { return mError; }
+
+  DWORD PrevProt() const { return mPrevProt; }
+
+  AutoVirtualProtect(const AutoVirtualProtect&) = delete;
+  AutoVirtualProtect(AutoVirtualProtect&&) = delete;
+  AutoVirtualProtect& operator=(const AutoVirtualProtect&) = delete;
+  AutoVirtualProtect& operator=(AutoVirtualProtect&&) = delete;
+
+ private:
+  void* mAddress;
+  size_t mLength;
+  HANDLE mTargetProcess;
+  DWORD mPrevProt;
+  WindowsError mError;
+};
+
+inline UniquePtr<wchar_t[]> GetFullModulePath(HMODULE aModule) {
+  DWORD bufLen = MAX_PATH;
+  mozilla::UniquePtr<wchar_t[]> buf;
+  DWORD retLen;
+
+  while (true) {
+    buf = mozilla::MakeUnique<wchar_t[]>(bufLen);
+    retLen = ::GetModuleFileNameW(aModule, buf.get(), bufLen);
+    if (!retLen) {
+      return nullptr;
+    }
+
+    if (retLen == bufLen && ::GetLastError() == ERROR_INSUFFICIENT_BUFFER) {
+      bufLen *= 2;
+      continue;
+    }
+
+    break;
+  }
+
+  // Upon success, retLen *excludes* the null character
+  ++retLen;
+
+  // Since we're likely to have a bunch of unused space in buf, let's
+  // reallocate a string to the actual size of the file name.
+  auto result = mozilla::MakeUnique<wchar_t[]>(retLen);
+  if (wcscpy_s(result.get(), retLen, buf.get())) {
+    return nullptr;
+  }
+
+  return result;
+}
+
+inline UniquePtr<wchar_t[]> GetFullBinaryPath() {
+  return GetFullModulePath(nullptr);
+}
+
+// Generates the install directory without a trailing path separator.
+inline bool GetInstallDirectory(UniquePtr<wchar_t[]>& installPath) {
+  installPath = GetFullBinaryPath();
+  // It's not safe to use PathRemoveFileSpecW with strings longer than MAX_PATH
+  // (including null terminator).
+  if (wcslen(installPath.get()) >= MAX_PATH) {
+    return false;
+  }
+  ::PathRemoveFileSpecW(installPath.get());
+  return true;
+}
+
+class ModuleVersion final {
+ public:
+  constexpr ModuleVersion() : mVersion(0ULL) {}
+
+  explicit ModuleVersion(const VS_FIXEDFILEINFO& aFixedInfo)
+      : mVersion((static_cast<uint64_t>(aFixedInfo.dwFileVersionMS) << 32) |
+                 static_cast<uint64_t>(aFixedInfo.dwFileVersionLS)) {}
+
+  explicit ModuleVersion(const uint64_t aVersion) : mVersion(aVersion) {}
+
+  ModuleVersion(const ModuleVersion& aOther) : mVersion(aOther.mVersion) {}
+
+  uint64_t AsInteger() const { return mVersion; }
+
+  operator uint64_t() const { return AsInteger(); }
+
+  std::tuple<uint16_t, uint16_t, uint16_t, uint16_t> AsTuple() const {
+    uint16_t major = static_cast<uint16_t>((mVersion >> 48) & 0xFFFFU);
+    uint16_t minor = static_cast<uint16_t>((mVersion >> 32) & 0xFFFFU);
+    uint16_t patch = static_cast<uint16_t>((mVersion >> 16) & 0xFFFFU);
+    uint16_t build = static_cast<uint16_t>(mVersion & 0xFFFFU);
+
+    return {major, minor, patch, build};
+  }
+
+  explicit operator bool() const { return !!mVersion; }
+
+  bool operator<(const ModuleVersion& aOther) const {
+    return mVersion < aOther.mVersion;
+  }
+
+  bool operator<(const uint64_t& aOther) const { return mVersion < aOther; }
+
+  ModuleVersion& operator=(const uint64_t aIntVersion) {
+    mVersion = aIntVersion;
+    return *this;
+  }
+
+ private:
+  uint64_t mVersion;
+};
+
+inline LauncherResult<ModuleVersion> GetModuleVersion(
+    const wchar_t* aModuleFullPath) {
+  DWORD verInfoLen = ::GetFileVersionInfoSizeW(aModuleFullPath, nullptr);
+  if (!verInfoLen) {
+    return LAUNCHER_ERROR_FROM_LAST();
+  }
+
+  auto verInfoBuf = MakeUnique<BYTE[]>(verInfoLen);
+  if (!::GetFileVersionInfoW(aModuleFullPath, 0, verInfoLen,
+                             verInfoBuf.get())) {
+    return LAUNCHER_ERROR_FROM_LAST();
+  }
+
+  UINT fixedInfoLen;
+  VS_FIXEDFILEINFO* fixedInfo = nullptr;
+  if (!::VerQueryValueW(verInfoBuf.get(), L"\\",
+                        reinterpret_cast<LPVOID*>(&fixedInfo), &fixedInfoLen)) {
+    // VerQueryValue may fail if the resource does not exist. This is not an
+    // error; we'll return 0 in this case.
+    return ModuleVersion(0ULL);
+  }
+
+  return ModuleVersion(*fixedInfo);
+}
+
+inline LauncherResult<ModuleVersion> GetModuleVersion(HMODULE aModule) {
+  UniquePtr<wchar_t[]> fullPath(GetFullModulePath(aModule));
+  if (!fullPath) {
+    return LAUNCHER_ERROR_GENERIC();
+  }
+
+  return GetModuleVersion(fullPath.get());
+}
+
+#if defined(MOZILLA_INTERNAL_API)
+inline LauncherResult<ModuleVersion> GetModuleVersion(nsIFile* aFile) {
+  if (!aFile) {
+    return LAUNCHER_ERROR_FROM_HRESULT(E_INVALIDARG);
+  }
+
+  nsAutoString fullPath;
+  nsresult rv = aFile->GetPath(fullPath);
+  if (NS_FAILED(rv)) {
+    return LAUNCHER_ERROR_GENERIC();
+  }
+
+  return GetModuleVersion(fullPath.get());
+}
+#endif  // defined(MOZILLA_INTERNAL_API)
+
+struct CoTaskMemFreeDeleter {
+  void operator()(void* aPtr) { ::CoTaskMemFree(aPtr); }
+};
+
+inline LauncherResult<TOKEN_ELEVATION_TYPE> GetElevationType(
+    const nsAutoHandle& aToken) {
+  DWORD retLen;
+  TOKEN_ELEVATION_TYPE elevationType;
+  if (!::GetTokenInformation(aToken.get(), TokenElevationType, &elevationType,
+                             sizeof(elevationType), &retLen)) {
+    return LAUNCHER_ERROR_FROM_LAST();
+  }
+
+  return elevationType;
+}
+
+inline bool HasPackageIdentity() {
+  HMODULE kernel32Dll = ::GetModuleHandleW(L"kernel32");
+  if (!kernel32Dll) {
+    return false;
+  }
+
+  typedef LONG(WINAPI * GetCurrentPackageIdProc)(UINT32*, BYTE*);
+  GetCurrentPackageIdProc pGetCurrentPackageId =
+      (GetCurrentPackageIdProc)::GetProcAddress(kernel32Dll,
+                                                "GetCurrentPackageId");
+
+  // If there was any package identity to retrieve, we get
+  // ERROR_INSUFFICIENT_BUFFER. If there had been no package identity it
+  // would instead return APPMODEL_ERROR_NO_PACKAGE.
+  UINT32 packageNameSize = 0;
+  return pGetCurrentPackageId &&
+         (pGetCurrentPackageId(&packageNameSize, nullptr) ==
+          ERROR_INSUFFICIENT_BUFFER);
+}
+
+inline UniquePtr<wchar_t[]> GetPackageFamilyName() {
+  HMODULE kernel32Dll = ::GetModuleHandleW(L"kernel32");
+  if (!kernel32Dll) {
+    return nullptr;
+  }
+
+  typedef LONG(WINAPI * GetCurrentPackageFamilyNameProc)(UINT32*, PWSTR);
+  GetCurrentPackageFamilyNameProc pGetCurrentPackageFamilyName =
+      (GetCurrentPackageFamilyNameProc)::GetProcAddress(
+          kernel32Dll, "GetCurrentPackageFamilyName");
+  if (!pGetCurrentPackageFamilyName) {
+    return nullptr;
+  }
+
+  UINT32 packageNameSize = 0;
+  if (pGetCurrentPackageFamilyName(&packageNameSize, nullptr) !=
+      ERROR_INSUFFICIENT_BUFFER) {
+    return nullptr;
+  }
+
+  UniquePtr<wchar_t[]> packageIdentity = MakeUnique<wchar_t[]>(packageNameSize);
+  if (pGetCurrentPackageFamilyName(&packageNameSize, packageIdentity.get()) !=
+      ERROR_SUCCESS) {
+    return nullptr;
+  }
+
+  return packageIdentity;
+}
+
+// This implementation is equivalent to PathGetDriveNumber[AW].
+// We define our own version because using PathGetDriveNumber
+// delay-loads shlwapi.dll, which may fail when the process is
+// sandboxed.
+template <typename T>
+int MozPathGetDriveNumber(const T* aPath) {
+  const auto ToDriveNumber = [](const T* aPath) -> int {
+    if (*aPath == '\0' || *(aPath + 1) != ':') {
+      return -1;
+    }
+
+    T c = *aPath;
+    return (c >= 'A' && c <= 'Z')   ? c - 'A'
+           : (c >= 'a' && c <= 'z') ? c - 'a'
+                                    : -1;
+  };
+
+  if (!aPath) {
+    return -1;
+  }
+
+  if (*aPath == '\\' && *(aPath + 1) == '\\' && *(aPath + 2) == '?' &&
+      *(aPath + 3) == '\\') {
+    return ToDriveNumber(aPath + 4);
+  }
+
+  return ToDriveNumber(aPath);
+}
+
+}  // namespace mozilla
+
+#endif  // mozilla_WinHeaderOnlyUtils_h
diff --git a/widget/windows/WinIMEHandler.cpp b/widget/windows/WinIMEHandler.cpp
new file mode 100644
index 0000000000..961c61fae0
--- /dev/null
+++ b/widget/windows/WinIMEHandler.cpp
@@ -0,0 +1,1081 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "WinIMEHandler.h"
+
+#include "IMMHandler.h"
+#include "KeyboardLayout.h"
+#include "mozilla/Preferences.h"
+#include "mozilla/StaticPrefs_intl.h"
+#include "mozilla/StaticPrefs_ui.h"
+#include "mozilla/TextEvents.h"
+#include "mozilla/Unused.h"
+#include "mozilla/WindowsVersion.h"
+#include "nsWindowDefs.h"
+#include "WinTextEventDispatcherListener.h"
+
+#include "TSFTextStore.h"
+
+#include "OSKInputPaneManager.h"
+#include "OSKTabTipManager.h"
+#include "OSKVRManager.h"
+#include "nsLookAndFeel.h"
+#include "nsWindow.h"
+#include "WinUtils.h"
+#include "nsIWindowsRegKey.h"
+#include "WindowsUIUtils.h"
+
+#ifdef ACCESSIBILITY
+#  include "nsAccessibilityService.h"
+#endif  // #ifdef ACCESSIBILITY
+
+#include "shellapi.h"
+#include "shlobj.h"
+#include "powrprof.h"
+#include "setupapi.h"
+#include "cfgmgr32.h"
+
+#include "FxRWindowManager.h"
+#include "moz_external_vr.h"
+
+const char* kOskEnabled = "ui.osk.enabled";
+const char* kOskDetectPhysicalKeyboard = "ui.osk.detect_physical_keyboard";
+const char* kOskDebugReason = "ui.osk.debug.keyboardDisplayReason";
+
+namespace mozilla {
+namespace widget {
+
+/******************************************************************************
+ * IMEHandler
+ ******************************************************************************/
+
+nsWindow* IMEHandler::sFocusedWindow = nullptr;
+InputContextAction::Cause IMEHandler::sLastContextActionCause =
+    InputContextAction::CAUSE_UNKNOWN;
+bool IMEHandler::sMaybeEditable = false;
+bool IMEHandler::sForceDisableCurrentIMM_IME = false;
+bool IMEHandler::sNativeCaretIsCreated = false;
+bool IMEHandler::sHasNativeCaretBeenRequested = false;
+
+bool IMEHandler::sIsInTSFMode = false;
+bool IMEHandler::sIsIMMEnabled = true;
+decltype(SetInputScopes)* IMEHandler::sSetInputScopes = nullptr;
+
+static POWER_PLATFORM_ROLE sPowerPlatformRole = PlatformRoleUnspecified;
+static bool sDeterminedPowerPlatformRole = false;
+
+// static
+void IMEHandler::Initialize() {
+  TSFTextStore::Initialize();
+  sIsInTSFMode = TSFTextStore::IsInTSFMode();
+  sIsIMMEnabled =
+      !sIsInTSFMode || StaticPrefs::intl_tsf_support_imm_AtStartup();
+  if (!sIsInTSFMode) {
+    // When full TSFTextStore is not available, try to use SetInputScopes API
+    // to enable at least InputScope. Use GET_MODULE_HANDLE_EX_FLAG_PIN to
+    // ensure that msctf.dll will not be unloaded.
+    HMODULE module = nullptr;
+    if (GetModuleHandleExW(GET_MODULE_HANDLE_EX_FLAG_PIN, L"msctf.dll",
+                           &module)) {
+      sSetInputScopes = reinterpret_cast<decltype(SetInputScopes)*>(
+          GetProcAddress(module, "SetInputScopes"));
+    }
+  }
+
+  IMMHandler::Initialize();
+
+  sForceDisableCurrentIMM_IME = IMMHandler::IsActiveIMEInBlockList();
+}
+
+// static
+void IMEHandler::Terminate() {
+  if (sIsInTSFMode) {
+    TSFTextStore::Terminate();
+    sIsInTSFMode = false;
+  }
+
+  IMMHandler::Terminate();
+  WinTextEventDispatcherListener::Shutdown();
+}
+
+// static
+void* IMEHandler::GetNativeData(nsWindow* aWindow, uint32_t aDataType) {
+  if (aDataType == NS_RAW_NATIVE_IME_CONTEXT) {
+    if (IsTSFAvailable()) {
+      return TSFTextStore::GetThreadManager();
+    }
+    IMEContext context(aWindow);
+    if (context.IsValid()) {
+      return context.get();
+    }
+    // If IMC isn't associated with the window, IME is disabled on the window
+    // now.  In such case, we should return default IMC instead.
+    const IMEContext& defaultIMC = aWindow->DefaultIMC();
+    if (defaultIMC.IsValid()) {
+      return defaultIMC.get();
+    }
+    // If there is no default IMC, we should return the pointer to the window
+    // since if we return nullptr, IMEStateManager cannot manage composition
+    // with TextComposition instance.  This is possible if no IME is installed,
+    // but composition may occur with dead key sequence.
+    return aWindow;
+  }
+
+  void* result = TSFTextStore::GetNativeData(aDataType);
+  if (!result || !(*(static_cast<void**>(result)))) {
+    return nullptr;
+  }
+  // XXX During the TSF module test, sIsInTSFMode must be true.  After that,
+  //     the value should be restored but currently, there is no way for that.
+  //     When the TSF test is enabled again, we need to fix this.  Perhaps,
+  //     sending a message can fix this.
+  sIsInTSFMode = true;
+  return result;
+}
+
+// static
+bool IMEHandler::ProcessRawKeyMessage(const MSG& aMsg) {
+  if (StaticPrefs::ui_key_layout_load_when_first_needed()) {
+    // Getting instance creates the singleton instance and that will
+    // automatically load active keyboard layout data.  We should do that
+    // before TSF or TranslateMessage handles a key message.
+    Unused << KeyboardLayout::GetInstance();
+  }
+  if (IsTSFAvailable()) {
+    return TSFTextStore::ProcessRawKeyMessage(aMsg);
+  }
+  return false;  // noting to do in IMM mode.
+}
+
+// static
+bool IMEHandler::ProcessMessage(nsWindow* aWindow, UINT aMessage,
+                                WPARAM& aWParam, LPARAM& aLParam,
+                                MSGResult& aResult) {
+  // If we're putting native caret over our caret, Windows dispatches
+  // EVENT_OBJECT_LOCATIONCHANGE event on other applications which hook
+  // the event with ::SetWinEventHook() and handles WM_GETOBJECT for
+  // OBJID_CARET (this is request of caret from such applications) instead
+  // of us.  If a11y module is active, it observes every our caret change
+  // and put native caret over it automatically.  However, if other
+  // applications require only caret information, activating a11y module is
+  // overwork and such applications may requires carets only in editors.
+  // Therefore, if it'd be possible, IMEHandler should put native caret over
+  // our caret, but there is a problem.  Some versions of ATOK (Japanese TIP)
+  // refer native caret and if there is, the behavior is worse than the
+  // behavior without native caret.  Therefore, we shouldn't put native caret
+  // as far as possible.
+  if (!sHasNativeCaretBeenRequested && aMessage == WM_GETOBJECT &&
+      static_cast<LONG>(aLParam) == OBJID_CARET) {
+    // So, when we receive first WM_GETOBJECT for OBJID_CARET, let's start to
+    // create native caret for such applications.
+    sHasNativeCaretBeenRequested = true;
+    // If an editable element has focus, we can put native caret now.
+    // XXX Should we avoid doing this if there is composition?
+    MaybeCreateNativeCaret(aWindow);
+  }
+
+  if (IsTSFAvailable()) {
+    TSFTextStore::ProcessMessage(aWindow, aMessage, aWParam, aLParam, aResult);
+    if (aResult.mConsumed) {
+      return true;
+    }
+    // If we don't support IMM in TSF mode, we don't use IMMHandler.
+    if (!sIsIMMEnabled) {
+      return false;
+    }
+    // IME isn't implemented with IMM, IMMHandler shouldn't handle any
+    // messages.
+    if (!IsIMMActive()) {
+      return false;
+    }
+  }
+
+  bool keepGoing =
+      IMMHandler::ProcessMessage(aWindow, aMessage, aWParam, aLParam, aResult);
+
+  // If user changes active IME to an IME which is listed in our block list,
+  // we should disassociate IMC from the window for preventing the IME to work
+  // and crash.
+  if (aMessage == WM_INPUTLANGCHANGE) {
+    bool disableIME = IMMHandler::IsActiveIMEInBlockList();
+    if (disableIME != sForceDisableCurrentIMM_IME) {
+      bool enable =
+          !disableIME && WinUtils::IsIMEEnabled(aWindow->InputContextRef());
+      AssociateIMEContext(aWindow, enable);
+      sForceDisableCurrentIMM_IME = disableIME;
+    }
+  }
+
+  return keepGoing;
+}
+
+// static
+bool IMEHandler::IsA11yHandlingNativeCaret() {
+#ifndef ACCESSIBILITY
+  return false;
+#else   // #ifndef ACCESSIBILITY
+  // Let's assume that when there is the service, it handles native caret.
+  return GetAccService() != nullptr;
+#endif  // #ifndef ACCESSIBILITY #else
+}
+
+// static
+bool IMEHandler::IsIMMActive() { return TSFTextStore::IsIMM_IMEActive(); }
+
+// static
+bool IMEHandler::IsComposing() {
+  if (IsTSFAvailable()) {
+    return TSFTextStore::IsComposing() || IMMHandler::IsComposing();
+  }
+
+  return IMMHandler::IsComposing();
+}
+
+// static
+bool IMEHandler::IsComposingOn(nsWindow* aWindow) {
+  if (IsTSFAvailable()) {
+    return TSFTextStore::IsComposingOn(aWindow) ||
+           IMMHandler::IsComposingOn(aWindow);
+  }
+
+  return IMMHandler::IsComposingOn(aWindow);
+}
+
+// static
+nsresult IMEHandler::NotifyIME(nsWindow* aWindow,
+                               const IMENotification& aIMENotification) {
+  if (IsTSFAvailable()) {
+    switch (aIMENotification.mMessage) {
+      case NOTIFY_IME_OF_SELECTION_CHANGE: {
+        nsresult rv = TSFTextStore::OnSelectionChange(aIMENotification);
+        // If IMM IME is active, we need to notify IMMHandler of updating
+        // composition change.  It will adjust candidate window position or
+        // composition window position.
+        bool isIMMActive = IsIMMActive();
+        if (isIMMActive) {
+          IMMHandler::OnUpdateComposition(aWindow);
+        }
+        IMMHandler::OnSelectionChange(aWindow, aIMENotification, isIMMActive);
+        return rv;
+      }
+      case NOTIFY_IME_OF_COMPOSITION_EVENT_HANDLED:
+        // If IMM IME is active, we need to notify IMMHandler of updating
+        // composition change.  It will adjust candidate window position or
+        // composition window position.
+        if (IsIMMActive()) {
+          IMMHandler::OnUpdateComposition(aWindow);
+        } else {
+          TSFTextStore::OnUpdateComposition();
+        }
+        return NS_OK;
+      case NOTIFY_IME_OF_TEXT_CHANGE:
+        return TSFTextStore::OnTextChange(aIMENotification);
+      case NOTIFY_IME_OF_FOCUS: {
+        sFocusedWindow = aWindow;
+        IMMHandler::OnFocusChange(true, aWindow);
+        nsresult rv = TSFTextStore::OnFocusChange(true, aWindow,
+                                                  aWindow->GetInputContext());
+        MaybeCreateNativeCaret(aWindow);
+        IMEHandler::MaybeShowOnScreenKeyboard(aWindow,
+                                              aWindow->GetInputContext());
+        return rv;
+      }
+      case NOTIFY_IME_OF_BLUR:
+        sFocusedWindow = nullptr;
+        IMEHandler::MaybeDismissOnScreenKeyboard(aWindow);
+        IMMHandler::OnFocusChange(false, aWindow);
+        return TSFTextStore::OnFocusChange(false, aWindow,
+                                           aWindow->GetInputContext());
+      case NOTIFY_IME_OF_MOUSE_BUTTON_EVENT:
+        // If IMM IME is active, we should send a mouse button event via IMM.
+        if (IsIMMActive()) {
+          return IMMHandler::OnMouseButtonEvent(aWindow, aIMENotification);
+        }
+        return TSFTextStore::OnMouseButtonEvent(aIMENotification);
+      case REQUEST_TO_COMMIT_COMPOSITION:
+        if (TSFTextStore::IsComposingOn(aWindow)) {
+          TSFTextStore::CommitComposition(false);
+        } else if (IsIMMActive()) {
+          IMMHandler::CommitComposition(aWindow);
+        }
+        return NS_OK;
+      case REQUEST_TO_CANCEL_COMPOSITION:
+        if (TSFTextStore::IsComposingOn(aWindow)) {
+          TSFTextStore::CommitComposition(true);
+        } else if (IsIMMActive()) {
+          IMMHandler::CancelComposition(aWindow);
+        }
+        return NS_OK;
+      case NOTIFY_IME_OF_POSITION_CHANGE:
+        return TSFTextStore::OnLayoutChange();
+      default:
+        return NS_ERROR_NOT_IMPLEMENTED;
+    }
+  }
+
+  switch (aIMENotification.mMessage) {
+    case REQUEST_TO_COMMIT_COMPOSITION:
+      IMMHandler::CommitComposition(aWindow);
+      return NS_OK;
+    case REQUEST_TO_CANCEL_COMPOSITION:
+      IMMHandler::CancelComposition(aWindow);
+      return NS_OK;
+    case NOTIFY_IME_OF_POSITION_CHANGE:
+    case NOTIFY_IME_OF_COMPOSITION_EVENT_HANDLED:
+      IMMHandler::OnUpdateComposition(aWindow);
+      return NS_OK;
+    case NOTIFY_IME_OF_SELECTION_CHANGE:
+      IMMHandler::OnSelectionChange(aWindow, aIMENotification, true);
+      // IMMHandler::OnSelectionChange() cannot work without its singleton
+      // instance.  Therefore, IMEHandler needs to create native caret instead
+      // if it's necessary.
+      MaybeCreateNativeCaret(aWindow);
+      return NS_OK;
+    case NOTIFY_IME_OF_MOUSE_BUTTON_EVENT:
+      return IMMHandler::OnMouseButtonEvent(aWindow, aIMENotification);
+    case NOTIFY_IME_OF_FOCUS:
+      sFocusedWindow = aWindow;
+      IMMHandler::OnFocusChange(true, aWindow);
+      IMEHandler::MaybeShowOnScreenKeyboard(aWindow,
+                                            aWindow->GetInputContext());
+      MaybeCreateNativeCaret(aWindow);
+      return NS_OK;
+    case NOTIFY_IME_OF_BLUR:
+      sFocusedWindow = nullptr;
+      IMEHandler::MaybeDismissOnScreenKeyboard(aWindow);
+      IMMHandler::OnFocusChange(false, aWindow);
+      // If a plugin gets focus while TSF has focus, we need to notify TSF of
+      // the blur.
+      if (TSFTextStore::ThinksHavingFocus()) {
+        return TSFTextStore::OnFocusChange(false, aWindow,
+                                           aWindow->GetInputContext());
+      }
+      return NS_OK;
+    default:
+      return NS_ERROR_NOT_IMPLEMENTED;
+  }
+}
+
+// static
+IMENotificationRequests IMEHandler::GetIMENotificationRequests() {
+  if (IsTSFAvailable()) {
+    if (!sIsIMMEnabled) {
+      return TSFTextStore::GetIMENotificationRequests();
+    }
+    // Even if TSF is available, the active IME may be an IMM-IME.
+    // Unfortunately, changing the result of GetIMENotificationRequests() while
+    // an editor has focus isn't supported by IMEContentObserver nor
+    // ContentCacheInParent.  Therefore, we need to request whole notifications
+    // which are necessary either IMMHandler or TSFTextStore.
+    return IMMHandler::GetIMENotificationRequests() |
+           TSFTextStore::GetIMENotificationRequests();
+  }
+
+  return IMMHandler::GetIMENotificationRequests();
+}
+
+// static
+TextEventDispatcherListener*
+IMEHandler::GetNativeTextEventDispatcherListener() {
+  return WinTextEventDispatcherListener::GetInstance();
+}
+
+// static
+bool IMEHandler::GetOpenState(nsWindow* aWindow) {
+  if (IsTSFAvailable() && !IsIMMActive()) {
+    return TSFTextStore::GetIMEOpenState();
+  }
+
+  IMEContext context(aWindow);
+  return context.GetOpenState();
+}
+
+// static
+void IMEHandler::OnDestroyWindow(nsWindow* aWindow) {
+  // When focus is in remote process, but the window is being destroyed, we
+  // need to clean up TSFTextStore here since NOTIFY_IME_OF_BLUR won't reach
+  // here because BrowserParent already lost the reference to the nsWindow when
+  // it receives from the remote process.
+  if (sFocusedWindow == aWindow) {
+    MOZ_ASSERT(aWindow->GetInputContext().IsOriginContentProcess(),
+               "input context of focused widget should've been set by a remote "
+               "process "
+               "if IME focus isn't cleared before destroying the widget");
+    NotifyIME(aWindow, IMENotification(NOTIFY_IME_OF_BLUR));
+  }
+
+  // We need to do nothing here for TSF. Just restore the default context
+  // if it's been disassociated.
+  if (!sIsInTSFMode) {
+    // MSDN says we need to set IS_DEFAULT to avoid memory leak when we use
+    // SetInputScopes API. Use an empty string to do this.
+    SetInputScopeForIMM32(aWindow, u""_ns, u""_ns, false);
+  }
+  AssociateIMEContext(aWindow, true);
+}
+
+// static
+bool IMEHandler::NeedsToAssociateIMC() { return !sForceDisableCurrentIMM_IME; }
+
+// static
+void IMEHandler::SetInputContext(nsWindow* aWindow, InputContext& aInputContext,
+                                 const InputContextAction& aAction) {
+  sLastContextActionCause = aAction.mCause;
+  // FYI: If there is no composition, this call will do nothing.
+  NotifyIME(aWindow, IMENotification(REQUEST_TO_COMMIT_COMPOSITION));
+
+  if (aInputContext.mHTMLInputMode.EqualsLiteral("none")) {
+    IMEHandler::MaybeDismissOnScreenKeyboard(aWindow, Sync::Yes);
+  } else if (aAction.UserMightRequestOpenVKB()) {
+    IMEHandler::MaybeShowOnScreenKeyboard(aWindow, aInputContext);
+  }
+
+  bool enable = WinUtils::IsIMEEnabled(aInputContext);
+  bool adjustOpenState = (enable && aInputContext.mIMEState.mOpen !=
+                                        IMEState::DONT_CHANGE_OPEN_STATE);
+  bool open =
+      (adjustOpenState && aInputContext.mIMEState.mOpen == IMEState::OPEN);
+
+  // Note that even while a plugin has focus, we need to notify TSF of that.
+  if (sIsInTSFMode) {
+    TSFTextStore::SetInputContext(aWindow, aInputContext, aAction);
+    if (IsTSFAvailable()) {
+      if (sIsIMMEnabled) {
+        // Associate IMC with aWindow only when it's necessary.
+        AssociateIMEContext(aWindow, enable && NeedsToAssociateIMC());
+      }
+      if (adjustOpenState) {
+        TSFTextStore::SetIMEOpenState(open);
+      }
+      return;
+    }
+  } else {
+    // Set at least InputScope even when TextStore is not available.
+    SetInputScopeForIMM32(aWindow, aInputContext.mHTMLInputType,
+                          aInputContext.mHTMLInputMode,
+                          aInputContext.mInPrivateBrowsing);
+  }
+
+  AssociateIMEContext(aWindow, enable);
+
+  IMEContext context(aWindow);
+  if (adjustOpenState) {
+    context.SetOpenState(open);
+  }
+}
+
+// static
+void IMEHandler::AssociateIMEContext(nsWindow* aWindowBase, bool aEnable) {
+  IMEContext context(aWindowBase);
+  if (aEnable) {
+    context.AssociateDefaultContext();
+    return;
+  }
+  // Don't disassociate the context after the window is destroyed.
+  if (aWindowBase->Destroyed()) {
+    return;
+  }
+  context.Disassociate();
+}
+
+// static
+void IMEHandler::InitInputContext(nsWindow* aWindow,
+                                  InputContext& aInputContext) {
+  MOZ_ASSERT(aWindow);
+  MOZ_ASSERT(aWindow->GetWindowHandle(),
+             "IMEHandler::SetInputContext() requires non-nullptr HWND");
+
+  static bool sInitialized = false;
+  if (!sInitialized) {
+    sInitialized = true;
+    // Some TIPs like QQ Input (Simplified Chinese) may need normal window
+    // (i.e., windows except message window) when initializing themselves.
+    // Therefore, we need to initialize TSF/IMM modules after first normal
+    // window is created.  InitInputContext() should be called immediately
+    // after creating each normal window, so, here is a good place to
+    // initialize these modules.
+    Initialize();
+  }
+
+  // For a11y, the default enabled state should be 'enabled'.
+  aInputContext.mIMEState.mEnabled = IMEEnabled::Enabled;
+
+  if (sIsInTSFMode) {
+    TSFTextStore::SetInputContext(
+        aWindow, aInputContext,
+        InputContextAction(InputContextAction::CAUSE_UNKNOWN,
+                           InputContextAction::WIDGET_CREATED));
+    // IME context isn't necessary in pure TSF mode.
+    if (!sIsIMMEnabled) {
+      AssociateIMEContext(aWindow, false);
+    }
+    return;
+  }
+
+#ifdef DEBUG
+  // NOTE: IMC may be null if IMM module isn't installed.
+  IMEContext context(aWindow);
+  MOZ_ASSERT(context.IsValid() || !CurrentKeyboardLayoutHasIME());
+#endif  // #ifdef DEBUG
+}
+
+#ifdef DEBUG
+// static
+bool IMEHandler::CurrentKeyboardLayoutHasIME() {
+  if (sIsInTSFMode) {
+    return TSFTextStore::CurrentKeyboardLayoutHasIME();
+  }
+
+  return IMMHandler::IsIMEAvailable();
+}
+#endif  // #ifdef DEBUG
+
+// static
+void IMEHandler::OnKeyboardLayoutChanged() {
+  // Be aware, this method won't be called until TSFStaticSink starts to
+  // observe active TIP change.  If you need to be notified of this, you
+  // need to create TSFStaticSink::Observe() or something and call it
+  // TSFStaticSink::EnsureInitActiveTIPKeyboard() forcibly.
+
+  if (!sIsIMMEnabled || !IsTSFAvailable()) {
+    return;
+  }
+}
+
+// static
+void IMEHandler::SetInputScopeForIMM32(nsWindow* aWindow,
+                                       const nsAString& aHTMLInputType,
+                                       const nsAString& aHTMLInputMode,
+                                       bool aInPrivateBrowsing) {
+  if (sIsInTSFMode || !sSetInputScopes || aWindow->Destroyed()) {
+    return;
+  }
+  AutoTArray<InputScope, 3> scopes;
+
+  // IME may refer only first input scope, but we will append inputmode's
+  // input scopes since IME may refer it like Chrome.
+  AppendInputScopeFromType(aHTMLInputType, scopes);
+  AppendInputScopeFromInputMode(aHTMLInputMode, scopes);
+
+  if (aInPrivateBrowsing) {
+    scopes.AppendElement(IS_PRIVATE);
+  }
+
+  if (scopes.IsEmpty()) {
+    // At least, 1 item is necessary.
+    scopes.AppendElement(IS_DEFAULT);
+  }
+
+  sSetInputScopes(aWindow->GetWindowHandle(), scopes.Elements(),
+                  scopes.Length(), nullptr, 0, nullptr, nullptr);
+}
+
+// static
+void IMEHandler::AppendInputScopeFromInputMode(const nsAString& aHTMLInputMode,
+                                               nsTArray<InputScope>& aScopes) {
+  if (aHTMLInputMode.EqualsLiteral("mozAwesomebar")) {
+    // Even if Awesomebar has focus, user may not input URL directly.
+    // However, on-screen keyboard for URL should be shown because it has
+    // some useful additional keys like ".com" and they are not hindrances
+    // even when inputting non-URL text, e.g., words to search something in
+    // the web.  On the other hand, a lot of Microsoft's IMEs and Google
+    // Japanese Input make their open state "closed" automatically if we
+    // notify them of URL as the input scope.  However, this is very annoying
+    // for the users when they try to input some words to search the web or
+    // bookmark/history items.  Therefore, if they are active, we need to
+    // notify them of the default input scope for avoiding this issue.
+    // FYI: We cannot check active TIP without TSF.  Therefore, if it's
+    //      not in TSF mode, this will check only if active IMM-IME is Google
+    //      Japanese Input.  Google Japanese Input is a TIP of TSF basically.
+    //      However, if the OS is Win7 or it's installed on Win7 but has not
+    //      been updated yet even after the OS is upgraded to Win8 or later,
+    //      it's installed as IMM-IME.
+    if (TSFTextStore::ShouldSetInputScopeOfURLBarToDefault()) {
+      return;
+    }
+    // Don't append IS_SEARCH here for showing on-screen keyboard for URL.
+    if (!aScopes.Contains(IS_URL)) {
+      aScopes.AppendElement(IS_URL);
+    }
+    return;
+  }
+
+  // https://html.spec.whatwg.org/dev/interaction.html#attr-inputmode
+  if (aHTMLInputMode.EqualsLiteral("url")) {
+    if (!aScopes.Contains(IS_SEARCH)) {
+      aScopes.AppendElement(IS_URL);
+    }
+    return;
+  }
+  if (aHTMLInputMode.EqualsLiteral("email")) {
+    if (!aScopes.Contains(IS_EMAIL_SMTPEMAILADDRESS)) {
+      aScopes.AppendElement(IS_EMAIL_SMTPEMAILADDRESS);
+    }
+    return;
+  }
+  if (aHTMLInputMode.EqualsLiteral("tel")) {
+    if (!aScopes.Contains(IS_TELEPHONE_FULLTELEPHONENUMBER)) {
+      aScopes.AppendElement(IS_TELEPHONE_FULLTELEPHONENUMBER);
+    }
+    if (!aScopes.Contains(IS_TELEPHONE_LOCALNUMBER)) {
+      aScopes.AppendElement(IS_TELEPHONE_LOCALNUMBER);
+    }
+    return;
+  }
+  if (aHTMLInputMode.EqualsLiteral("numeric")) {
+    if (!aScopes.Contains(IS_DIGITS)) {
+      aScopes.AppendElement(IS_DIGITS);
+    }
+    return;
+  }
+  if (aHTMLInputMode.EqualsLiteral("decimal")) {
+    if (!aScopes.Contains(IS_NUMBER)) {
+      aScopes.AppendElement(IS_NUMBER);
+    }
+    return;
+  }
+  if (aHTMLInputMode.EqualsLiteral("search")) {
+    if (NeedsSearchInputScope() && !aScopes.Contains(IS_SEARCH)) {
+      aScopes.AppendElement(IS_SEARCH);
+    }
+    return;
+  }
+}
+
+// static
+void IMEHandler::AppendInputScopeFromType(const nsAString& aHTMLInputType,
+                                          nsTArray<InputScope>& aScopes) {
+  // http://www.whatwg.org/specs/web-apps/current-work/multipage/the-input-element.html
+  if (aHTMLInputType.EqualsLiteral("url")) {
+    aScopes.AppendElement(IS_URL);
+    return;
+  }
+  if (aHTMLInputType.EqualsLiteral("search")) {
+    if (NeedsSearchInputScope()) {
+      aScopes.AppendElement(IS_SEARCH);
+    }
+    return;
+  }
+  if (aHTMLInputType.EqualsLiteral("email")) {
+    aScopes.AppendElement(IS_EMAIL_SMTPEMAILADDRESS);
+    return;
+  }
+  if (aHTMLInputType.EqualsLiteral("password")) {
+    aScopes.AppendElement(IS_PASSWORD);
+    return;
+  }
+  if (aHTMLInputType.EqualsLiteral("datetime") ||
+      aHTMLInputType.EqualsLiteral("datetime-local")) {
+    aScopes.AppendElement(IS_DATE_FULLDATE);
+    aScopes.AppendElement(IS_TIME_FULLTIME);
+    return;
+  }
+  if (aHTMLInputType.EqualsLiteral("date") ||
+      aHTMLInputType.EqualsLiteral("month") ||
+      aHTMLInputType.EqualsLiteral("week")) {
+    aScopes.AppendElement(IS_DATE_FULLDATE);
+    return;
+  }
+  if (aHTMLInputType.EqualsLiteral("time")) {
+    aScopes.AppendElement(IS_TIME_FULLTIME);
+    return;
+  }
+  if (aHTMLInputType.EqualsLiteral("tel")) {
+    aScopes.AppendElement(IS_TELEPHONE_FULLTELEPHONENUMBER);
+    aScopes.AppendElement(IS_TELEPHONE_LOCALNUMBER);
+    return;
+  }
+  if (aHTMLInputType.EqualsLiteral("number")) {
+    aScopes.AppendElement(IS_NUMBER);
+    return;
+  }
+}
+
+// static
+bool IMEHandler::NeedsSearchInputScope() {
+  return !StaticPrefs::intl_tsf_hack_atok_search_input_scope_disabled() ||
+         !TSFTextStore::IsATOKActive();
+}
+
+// static
+bool IMEHandler::IsOnScreenKeyboardSupported() {
+#ifdef NIGHTLY_BUILD
+  if (FxRWindowManager::GetInstance()->IsFxRWindow(sFocusedWindow)) {
+    return true;
+  }
+#endif  // NIGHTLY_BUILD
+  if (!Preferences::GetBool(kOskEnabled, true) ||
+      !IMEHandler::NeedOnScreenKeyboard()) {
+    return false;
+  }
+
+  // On Windows 11, we ignore tablet mode (see bug 1722208)
+  if (!IsWin11OrLater()) {
+    // On Windows 10 we require tablet mode, unless the user has set the
+    // relevant setting to enable the on-screen keyboard in desktop mode.
+    if (!IsInTabletMode() && !AutoInvokeOnScreenKeyboardInDesktopMode()) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+// static
+void IMEHandler::MaybeShowOnScreenKeyboard(nsWindow* aWindow,
+                                           const InputContext& aInputContext) {
+  if (aInputContext.mHTMLInputMode.EqualsLiteral("none")) {
+    return;
+  }
+
+  if (!IsOnScreenKeyboardSupported()) {
+    return;
+  }
+
+  IMEHandler::ShowOnScreenKeyboard(aWindow);
+}
+
+// static
+void IMEHandler::MaybeDismissOnScreenKeyboard(nsWindow* aWindow, Sync aSync) {
+#ifdef NIGHTLY_BUILD
+  if (FxRWindowManager::GetInstance()->IsFxRWindow(aWindow)) {
+    OSKVRManager::DismissOnScreenKeyboard();
+  }
+#endif  // NIGHTLY_BUILD
+  if (aSync == Sync::Yes) {
+    DismissOnScreenKeyboard(aWindow);
+    return;
+  }
+
+  RefPtr<nsWindow> window(aWindow);
+  NS_DispatchToCurrentThreadQueue(
+      NS_NewRunnableFunction("IMEHandler::MaybeDismissOnScreenKeyboard",
+                             [window]() {
+                               if (window->Destroyed()) {
+                                 return;
+                               }
+                               if (!sFocusedWindow) {
+                                 DismissOnScreenKeyboard(window);
+                               }
+                             }),
+      EventQueuePriority::Idle);
+}
+
+// static
+bool IMEHandler::WStringStartsWithCaseInsensitive(const std::wstring& aHaystack,
+                                                  const std::wstring& aNeedle) {
+  std::wstring lowerCaseHaystack(aHaystack);
+  std::wstring lowerCaseNeedle(aNeedle);
+  std::transform(lowerCaseHaystack.begin(), lowerCaseHaystack.end(),
+                 lowerCaseHaystack.begin(), ::tolower);
+  std::transform(lowerCaseNeedle.begin(), lowerCaseNeedle.end(),
+                 lowerCaseNeedle.begin(), ::tolower);
+  return wcsstr(lowerCaseHaystack.c_str(), lowerCaseNeedle.c_str()) ==
+         lowerCaseHaystack.c_str();
+}
+
+// Returns false if a physical keyboard is detected on Windows 8 and up,
+// or there is some other reason why an onscreen keyboard is not necessary.
+// Returns true if no keyboard is found and this device looks like it needs
+// an on-screen keyboard for text input.
+// static
+bool IMEHandler::NeedOnScreenKeyboard() {
+  if (!Preferences::GetBool(kOskDetectPhysicalKeyboard, true)) {
+    Preferences::SetString(kOskDebugReason, L"IKPOS: Detection disabled.");
+    return true;
+  }
+
+  // If the last focus cause was not user-initiated (ie a result of code
+  // setting focus to an element) then don't auto-show a keyboard. This
+  // avoids cases where the keyboard would pop up "just" because e.g. a
+  // web page chooses to focus a search field on the page, even when that
+  // really isn't what the user is trying to do at that moment.
+  if (!InputContextAction::IsHandlingUserInput(sLastContextActionCause)) {
+    return false;
+  }
+
+  // This function should be only invoked for machines with touch screens.
+  if ((::GetSystemMetrics(SM_DIGITIZER) & NID_INTEGRATED_TOUCH) !=
+      NID_INTEGRATED_TOUCH) {
+    Preferences::SetString(kOskDebugReason, L"IKPOS: Touch screen not found.");
+    return false;
+  }
+
+  // If the device is docked, the user is treating the device as a PC.
+  if (::GetSystemMetrics(SM_SYSTEMDOCKED) != 0) {
+    Preferences::SetString(kOskDebugReason, L"IKPOS: System docked.");
+    return false;
+  }
+
+  // To determine whether a keyboard is present on the device, we do the
+  // following:-
+  // 1. If the platform role is that of a mobile or slate device, check the
+  //    system metric SM_CONVERTIBLESLATEMODE to see if it is being used
+  //    in slate mode. If it is, also check that the last input was a touch.
+  //    If all of this is true, then we should show the on-screen keyboard.
+
+  // 2. If step 1 didn't determine we should show the keyboard, we check if
+  //    this device has keyboards attached to it.
+
+  // Check if the device is being used as a laptop or a tablet. This can be
+  // checked by first checking the role of the device and then the
+  // corresponding system metric (SM_CONVERTIBLESLATEMODE). If it is being
+  // used as a tablet then we want the OSK to show up.
+  if (!sDeterminedPowerPlatformRole) {
+    sDeterminedPowerPlatformRole = true;
+    sPowerPlatformRole = WinUtils::GetPowerPlatformRole();
+  }
+
+  // If this a mobile or slate (tablet) device, check if it is in slate mode.
+  // If the last input was touch, ignore whether or not a keyboard is present.
+  if ((sPowerPlatformRole == PlatformRoleMobile ||
+       sPowerPlatformRole == PlatformRoleSlate) &&
+      ::GetSystemMetrics(SM_CONVERTIBLESLATEMODE) == 0 &&
+      sLastContextActionCause == InputContextAction::CAUSE_TOUCH) {
+    Preferences::SetString(
+        kOskDebugReason,
+        L"IKPOS: Mobile/Slate Platform role, in slate mode with touch event.");
+    return true;
+  }
+
+  return !IMEHandler::IsKeyboardPresentOnSlate();
+}
+
+// Uses the Setup APIs to enumerate the attached keyboards and returns true
+// if the keyboard count is 1 or more. While this will work in most cases
+// it won't work if there are devices which expose keyboard interfaces which
+// are attached to the machine.
+// Based on IsKeyboardPresentOnSlate() in Chromium's base/win/win_util.cc.
+// static
+bool IMEHandler::IsKeyboardPresentOnSlate() {
+  const GUID KEYBOARD_CLASS_GUID = {
+      0x4D36E96B,
+      0xE325,
+      0x11CE,
+      {0xBF, 0xC1, 0x08, 0x00, 0x2B, 0xE1, 0x03, 0x18}};
+
+  // Query for all the keyboard devices.
+  HDEVINFO device_info = ::SetupDiGetClassDevs(&KEYBOARD_CLASS_GUID, nullptr,
+                                               nullptr, DIGCF_PRESENT);
+  if (device_info == INVALID_HANDLE_VALUE) {
+    Preferences::SetString(kOskDebugReason, L"IKPOS: No keyboard info.");
+    return false;
+  }
+
+  // Enumerate all keyboards and look for ACPI\PNP and HID\VID devices. If
+  // the count is more than 1 we assume that a keyboard is present. This is
+  // under the assumption that there will always be one keyboard device.
+  for (DWORD i = 0;; ++i) {
+    SP_DEVINFO_DATA device_info_data = {0};
+    device_info_data.cbSize = sizeof(device_info_data);
+    if (!::SetupDiEnumDeviceInfo(device_info, i, &device_info_data)) {
+      break;
+    }
+
+    // Get the device ID.
+    wchar_t device_id[MAX_DEVICE_ID_LEN];
+    CONFIGRET status = ::CM_Get_Device_ID(device_info_data.DevInst, device_id,
+                                          MAX_DEVICE_ID_LEN, 0);
+    if (status == CR_SUCCESS) {
+      static const std::wstring BT_HID_DEVICE = L"HID\\{00001124";
+      static const std::wstring BT_HOGP_DEVICE = L"HID\\{00001812";
+      // To reduce the scope of the hack we only look for ACPI and HID\\VID
+      // prefixes in the keyboard device ids.
+      if (IMEHandler::WStringStartsWithCaseInsensitive(device_id, L"ACPI") ||
+          IMEHandler::WStringStartsWithCaseInsensitive(device_id,
+                                                       L"HID\\VID") ||
+          IMEHandler::WStringStartsWithCaseInsensitive(device_id,
+                                                       BT_HID_DEVICE) ||
+          IMEHandler::WStringStartsWithCaseInsensitive(device_id,
+                                                       BT_HOGP_DEVICE)) {
+        // The heuristic we are using is to check the count of keyboards and
+        // return true if the API's report one or more keyboards. Please note
+        // that this will break for non keyboard devices which expose a
+        // keyboard PDO.
+        Preferences::SetString(kOskDebugReason,
+                               L"IKPOS: Keyboard presence confirmed.");
+        return true;
+      }
+    }
+  }
+  Preferences::SetString(kOskDebugReason,
+                         L"IKPOS: Lack of keyboard confirmed.");
+  return false;
+}
+
+// static
+bool IMEHandler::IsInTabletMode() {
+  bool isInTabletMode = WindowsUIUtils::GetInTabletMode();
+  if (isInTabletMode) {
+    Preferences::SetString(kOskDebugReason, L"IITM: GetInTabletMode=true.");
+  } else {
+    Preferences::SetString(kOskDebugReason, L"IITM: GetInTabletMode=false.");
+  }
+  return isInTabletMode;
+}
+
+static bool ReadEnableDesktopModeAutoInvoke(uint32_t aRoot,
+                                            nsIWindowsRegKey* aRegKey,
+                                            uint32_t& aValue) {
+  nsresult rv;
+  rv = aRegKey->Open(aRoot, u"SOFTWARE\\Microsoft\\TabletTip\\1.7"_ns,
+                     nsIWindowsRegKey::ACCESS_QUERY_VALUE);
+  if (NS_FAILED(rv)) {
+    Preferences::SetString(kOskDebugReason,
+                           L"AIOSKIDM: failed opening regkey.");
+    return false;
+  }
+  // EnableDesktopModeAutoInvoke is an opt-in option from the Windows
+  // Settings to "Automatically show the touch keyboard in windowed apps
+  // when there's no keyboard attached to your device." If the user has
+  // opted-in to this behavior, the tablet-mode requirement is skipped.
+  rv = aRegKey->ReadIntValue(u"EnableDesktopModeAutoInvoke"_ns, &aValue);
+  if (NS_FAILED(rv)) {
+    Preferences::SetString(kOskDebugReason,
+                           L"AIOSKIDM: failed reading value of regkey.");
+    return false;
+  }
+  return true;
+}
+
+// static
+bool IMEHandler::AutoInvokeOnScreenKeyboardInDesktopMode() {
+  nsresult rv;
+  nsCOMPtr<nsIWindowsRegKey> regKey(
+      do_CreateInstance("@mozilla.org/windows-registry-key;1", &rv));
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    Preferences::SetString(kOskDebugReason,
+                           L"AIOSKIDM: "
+                           L"nsIWindowsRegKey not available");
+    return false;
+  }
+
+  uint32_t value;
+  if (!ReadEnableDesktopModeAutoInvoke(nsIWindowsRegKey::ROOT_KEY_CURRENT_USER,
+                                       regKey, value) &&
+      !ReadEnableDesktopModeAutoInvoke(nsIWindowsRegKey::ROOT_KEY_LOCAL_MACHINE,
+                                       regKey, value)) {
+    return false;
+  }
+  if (!!value) {
+    Preferences::SetString(kOskDebugReason, L"AIOSKIDM: regkey value=true.");
+  } else {
+    Preferences::SetString(kOskDebugReason, L"AIOSKIDM: regkey value=false.");
+  }
+  return !!value;
+}
+
+// Based on DisplayVirtualKeyboard() in Chromium's base/win/win_util.cc.
+// static
+void IMEHandler::ShowOnScreenKeyboard(nsWindow* aWindow) {
+#ifdef NIGHTLY_BUILD
+  if (FxRWindowManager::GetInstance()->IsFxRWindow(sFocusedWindow)) {
+    OSKVRManager::ShowOnScreenKeyboard();
+    return;
+  }
+#endif  // NIGHTLY_BUILD
+
+  if (IsWin10AnniversaryUpdateOrLater()) {
+    OSKInputPaneManager::ShowOnScreenKeyboard(aWindow->GetWindowHandle());
+    return;
+  }
+
+  OSKTabTipManager::ShowOnScreenKeyboard();
+}
+
+// Based on DismissVirtualKeyboard() in Chromium's base/win/win_util.cc.
+// static
+void IMEHandler::DismissOnScreenKeyboard(nsWindow* aWindow) {
+  // Dismiss the virtual keyboard if it's open
+  if (IsWin10AnniversaryUpdateOrLater()) {
+    OSKInputPaneManager::DismissOnScreenKeyboard(aWindow->GetWindowHandle());
+    return;
+  }
+
+  OSKTabTipManager::DismissOnScreenKeyboard();
+}
+
+bool IMEHandler::MaybeCreateNativeCaret(nsWindow* aWindow) {
+  MOZ_ASSERT(aWindow);
+
+  if (IsA11yHandlingNativeCaret()) {
+    return false;
+  }
+
+  if (!sHasNativeCaretBeenRequested) {
+    // If we have not received WM_GETOBJECT for OBJID_CARET, there may be new
+    // application which requires our caret information.  For kicking its
+    // window event proc, we should fire a window event here.
+    // (If there is such application, sHasNativeCaretBeenRequested will be set
+    // to true later.)
+    // FYI: If we create native caret and move its position, native caret
+    //      causes EVENT_OBJECT_LOCATIONCHANGE event with OBJID_CARET and
+    //      OBJID_CLIENT.
+    ::NotifyWinEvent(EVENT_OBJECT_LOCATIONCHANGE, aWindow->GetWindowHandle(),
+                     OBJID_CARET, OBJID_CLIENT);
+    return false;
+  }
+
+  MaybeDestroyNativeCaret();
+
+  // If focused content is not text editable, we don't support caret
+  // caret information without a11y module.
+  if (!aWindow->GetInputContext().mIMEState.IsEditable()) {
+    return false;
+  }
+
+  WidgetQueryContentEvent queryCaretRectEvent(true, eQueryCaretRect, aWindow);
+  aWindow->InitEvent(queryCaretRectEvent);
+
+  WidgetQueryContentEvent::Options options;
+  options.mRelativeToInsertionPoint = true;
+  queryCaretRectEvent.InitForQueryCaretRect(0, options);
+
+  aWindow->DispatchWindowEvent(queryCaretRectEvent);
+  if (NS_WARN_IF(queryCaretRectEvent.Failed())) {
+    return false;
+  }
+
+  return CreateNativeCaret(aWindow, queryCaretRectEvent.mReply->mRect);
+}
+
+bool IMEHandler::CreateNativeCaret(nsWindow* aWindow,
+                                   const LayoutDeviceIntRect& aCaretRect) {
+  MOZ_ASSERT(aWindow);
+
+  MOZ_ASSERT(!IsA11yHandlingNativeCaret());
+
+  sNativeCaretIsCreated =
+      ::CreateCaret(aWindow->GetWindowHandle(), nullptr, aCaretRect.Width(),
+                    aCaretRect.Height());
+  if (!sNativeCaretIsCreated) {
+    return false;
+  }
+  nsWindow* toplevelWindow = aWindow->GetTopLevelWindow(false);
+  if (NS_WARN_IF(!toplevelWindow)) {
+    MaybeDestroyNativeCaret();
+    return false;
+  }
+
+  LayoutDeviceIntPoint caretPosition(aCaretRect.TopLeft());
+  if (toplevelWindow != aWindow) {
+    caretPosition += toplevelWindow->WidgetToScreenOffset();
+    caretPosition -= aWindow->WidgetToScreenOffset();
+  }
+
+  ::SetCaretPos(caretPosition.x, caretPosition.y);
+  return true;
+}
+
+void IMEHandler::MaybeDestroyNativeCaret() {
+  if (!sNativeCaretIsCreated) {
+    return;
+  }
+  ::DestroyCaret();
+  sNativeCaretIsCreated = false;
+}
+
+}  // namespace widget
+}  // namespace mozilla
diff --git a/widget/windows/WinIMEHandler.h b/widget/windows/WinIMEHandler.h
new file mode 100644
index 0000000000..410e1ebd22
--- /dev/null
+++ b/widget/windows/WinIMEHandler.h
@@ -0,0 +1,247 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef WinIMEHandler_h_
+#define WinIMEHandler_h_
+
+#include "nscore.h"
+#include "nsWindow.h"
+#include "npapi.h"
+#include <windows.h>
+#include <inputscope.h>
+
+#define NS_WM_IMEFIRST WM_IME_SETCONTEXT
+#define NS_WM_IMELAST WM_IME_KEYUP
+
+class nsWindow;
+
+namespace mozilla {
+namespace widget {
+
+struct MSGResult;
+
+/**
+ * IMEHandler class is a mediator class.  On Windows, there are two IME API
+ * sets: One is IMM which is legacy API set. The other is TSF which is modern
+ * API set. By using this class, non-IME handler classes don't need to worry
+ * that we're in which mode.
+ */
+class IMEHandler final {
+ private:
+  /**
+   * Initialize() initializes both TSF modules and IMM modules.  Some TIPs
+   * may require a normal window (i.e., not message window) belonging to
+   * this process.  Therefore, this is called immediately after first normal
+   * window is created.
+   */
+  static void Initialize();
+
+ public:
+  static void Terminate();
+
+  /**
+   * Returns TSF related native data or native IME context.
+   */
+  static void* GetNativeData(nsWindow* aWindow, uint32_t aDataType);
+
+  /**
+   * ProcessRawKeyMessage() message is called before calling TranslateMessage()
+   * and DispatchMessage().  If this returns true, the message is consumed.
+   * Then, caller must not perform TranslateMessage() nor DispatchMessage().
+   */
+  static bool ProcessRawKeyMessage(const MSG& aMsg);
+
+  /**
+   * When the message is not needed to handle anymore by the caller, this
+   * returns true.  Otherwise, false.
+   */
+  static bool ProcessMessage(nsWindow* aWindow, UINT aMessage, WPARAM& aWParam,
+                             LPARAM& aLParam, MSGResult& aResult);
+
+  /**
+   * IsA11yHandlingNativeCaret() returns true if a11y is handling
+   * native caret.  In such case, IME modules shouldn't touch native caret.
+   **/
+  static bool IsA11yHandlingNativeCaret();
+
+  /**
+   * NeedsToCreateNativeCaret() returns true if IME handler needs to create
+   * native caret for other applications which requests OBJID_CARET with
+   * WM_GETOBJECT and a11y module isn't active (if a11y module is active,
+   * it always creates native caret, i.e., even if no editor has focus).
+   */
+  static bool NeedsToCreateNativeCaret() {
+    return sHasNativeCaretBeenRequested && !IsA11yHandlingNativeCaret();
+  }
+
+  /**
+   * CreateNativeCaret() create native caret if this has been created it.
+   *
+   * @param aWindow     The window which owns the caret.
+   * @param aCaretRect  The caret rect relative to aWindow.
+   */
+  static bool CreateNativeCaret(nsWindow* aWindow,
+                                const LayoutDeviceIntRect& aCaretRect);
+
+  /**
+   * MaybeDestroyNativeCaret() destroies native caret if it has been created
+   * by IMEHandler.
+   */
+  static void MaybeDestroyNativeCaret();
+
+  /**
+   * HasNativeCaret() returns true if there is native caret and it was created
+   * by IMEHandler.
+   */
+  static bool HasNativeCaret() { return sNativeCaretIsCreated; }
+
+  /**
+   * When there is a composition, returns true.  Otherwise, false.
+   */
+  static bool IsComposing();
+
+  /**
+   * When there is a composition and it's in the window, returns true.
+   * Otherwise, false.
+   */
+  static bool IsComposingOn(nsWindow* aWindow);
+
+  /**
+   * Notifies IME of the notification (a request or an event).
+   */
+  static nsresult NotifyIME(nsWindow* aWindow,
+                            const IMENotification& aIMENotification);
+
+  /**
+   * Returns notification requests of IME.
+   */
+  static IMENotificationRequests GetIMENotificationRequests();
+
+  /**
+   * Returns native text event dispatcher listener.
+   */
+  static TextEventDispatcherListener* GetNativeTextEventDispatcherListener();
+
+  /**
+   * Returns IME open state on the window.
+   */
+  static bool GetOpenState(nsWindow* aWindow);
+
+  /**
+   * Called when the window is destroying.
+   */
+  static void OnDestroyWindow(nsWindow* aWindow);
+
+  /**
+   * Called when nsIWidget::SetInputContext() is called before the window's
+   * InputContext is modified actually.
+   */
+  static void SetInputContext(nsWindow* aWindow, InputContext& aInputContext,
+                              const InputContextAction& aAction);
+
+  /**
+   * Associate or disassociate IME context to/from the aWindowBase.
+   */
+  static void AssociateIMEContext(nsWindow* aWindowBase, bool aEnable);
+
+  /**
+   * Called when the window is created.
+   */
+  static void InitInputContext(nsWindow* aWindow, InputContext& aInputContext);
+
+  /**
+   * This is called by TSFStaticSink when active IME is changed.
+   */
+  static void OnKeyboardLayoutChanged();
+
+#ifdef DEBUG
+  /**
+   * Returns true when current keyboard layout has IME.  Otherwise, false.
+   */
+  static bool CurrentKeyboardLayoutHasIME();
+#endif  // #ifdef DEBUG
+
+  /**
+   * Append InputScope values from inputmode string.
+   */
+  static void AppendInputScopeFromInputMode(const nsAString& aHTMLInputMode,
+                                            nsTArray<InputScope>& aScopes);
+
+  /**
+   * Append InputScope values from type attreibute string of input element
+   */
+  static void AppendInputScopeFromType(const nsAString& aInputType,
+                                       nsTArray<InputScope>& aScopes);
+
+  /**
+   * Return focused window if this receives focus notification and has not
+   * received blur notification yet.
+   */
+  static nsWindow* GetFocusedWindow() { return sFocusedWindow; }
+
+ private:
+  static nsWindow* sFocusedWindow;
+  static InputContextAction::Cause sLastContextActionCause;
+
+  static bool sMaybeEditable;
+  static bool sForceDisableCurrentIMM_IME;
+  static bool sNativeCaretIsCreated;
+  static bool sHasNativeCaretBeenRequested;
+
+  /**
+   * MaybeCreateNativeCaret() may create native caret over our caret if
+   * focused content is text editable and we need to create native caret
+   * for other applications.
+   *
+   * @param aWindow     The window which owns the native caret.
+   */
+  static bool MaybeCreateNativeCaret(nsWindow* aWindow);
+
+  static decltype(SetInputScopes)* sSetInputScopes;
+  static void SetInputScopeForIMM32(nsWindow* aWindow,
+                                    const nsAString& aHTMLInputType,
+                                    const nsAString& aHTMLInputMode,
+                                    bool aInPrivateBrowsing);
+  static bool sIsInTSFMode;
+  // If sIMMEnabled is false, any IME messages are not handled in TSF mode.
+  // Additionally, IME context is always disassociated from focused window.
+  static bool sIsIMMEnabled;
+
+  static bool IsTSFAvailable() { return sIsInTSFMode; }
+  static bool IsIMMActive();
+
+  static bool IsOnScreenKeyboardSupported();
+
+  static void MaybeShowOnScreenKeyboard(nsWindow* aWindow,
+                                        const InputContext& aInputContext);
+  enum class Sync { Yes, No };
+  static void MaybeDismissOnScreenKeyboard(nsWindow* aWindow,
+                                           Sync aSync = Sync::No);
+  static bool WStringStartsWithCaseInsensitive(const std::wstring& aHaystack,
+                                               const std::wstring& aNeedle);
+  static bool NeedOnScreenKeyboard();
+  static bool IsKeyboardPresentOnSlate();
+  static bool IsInTabletMode();
+  static bool AutoInvokeOnScreenKeyboardInDesktopMode();
+  static bool NeedsToAssociateIMC();
+  static bool NeedsSearchInputScope();
+
+  /**
+   * Show the Windows on-screen keyboard. Only allowed for
+   * chrome documents and Windows 8 and higher.
+   */
+  static void ShowOnScreenKeyboard(nsWindow* aWindow);
+
+  /**
+   * Dismiss the Windows on-screen keyboard. Only allowed for
+   * Windows 8 and higher.
+   */
+  static void DismissOnScreenKeyboard(nsWindow* aWindow);
+};
+
+}  // namespace widget
+}  // namespace mozilla
+
+#endif  // #ifndef WinIMEHandler_h_
diff --git a/widget/windows/WinMessages.h b/widget/windows/WinMessages.h
new file mode 100644
index 0000000000..8c90460e8e
--- /dev/null
+++ b/widget/windows/WinMessages.h
@@ -0,0 +1,93 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_widget_WinMessages_h_
+#define mozilla_widget_WinMessages_h_
+
+/*****************************************************************************
+ * MOZ_WM_* messages
+ ****************************************************************************/
+
+// A magic APP message that can be sent to quit, sort of like a
+// QUERYENDSESSION/ENDSESSION, but without the query.
+#define MOZ_WM_APP_QUIT (WM_APP + 0x0300)
+// Used as a "tracer" event to probe event loop latency.
+#define MOZ_WM_TRACE (WM_APP + 0x0301)
+// accessibility priming
+#define MOZ_WM_STARTA11Y (WM_APP + 0x0302)
+// Our internal message for WM_MOUSEWHEEL, WM_MOUSEHWHEEL, WM_VSCROLL and
+// WM_HSCROLL
+#define MOZ_WM_MOUSEVWHEEL (WM_APP + 0x0310)
+#define MOZ_WM_MOUSEHWHEEL (WM_APP + 0x0311)
+#define MOZ_WM_VSCROLL (WM_APP + 0x0312)
+#define MOZ_WM_HSCROLL (WM_APP + 0x0313)
+#define MOZ_WM_MOUSEWHEEL_FIRST MOZ_WM_MOUSEVWHEEL
+#define MOZ_WM_MOUSEWHEEL_LAST MOZ_WM_HSCROLL
+// If a popup window is being activated, we try to reactivate the previous
+// window with this message.
+#define MOZ_WM_REACTIVATE (WM_APP + 0x0314)
+// If TSFTextStore needs to notify TSF/TIP of layout change later, this
+// message is posted.
+#define MOZ_WM_NOTIY_TSF_OF_LAYOUT_CHANGE (WM_APP + 0x0315)
+// Internal message used in correcting backwards clock skew
+#define MOZ_WM_SKEWFIX (WM_APP + 0x0316)
+// Internal message used for rolling up popups for dmanip events
+#define MOZ_WM_DMANIP (WM_APP + 0x0317)
+
+// Internal message used to work around race condition in explorer.exe's
+// fullscreen window-state update handler in Windows 10+. (See bug 1835851.)
+#define MOZ_WM_FULLSCREEN_STATE_UPDATE (WM_APP + 0x0318)
+
+// XXX Should rename them to MOZ_WM_* and use safer values!
+// Messages for fullscreen transition window
+#define WM_FULLSCREEN_TRANSITION_BEFORE (WM_USER + 0)
+#define WM_FULLSCREEN_TRANSITION_AFTER (WM_USER + 1)
+
+#ifndef APPCOMMAND_BROWSER_BACKWARD
+#  define APPCOMMAND_BROWSER_BACKWARD 1
+#  define APPCOMMAND_BROWSER_FORWARD 2
+#  define APPCOMMAND_BROWSER_REFRESH 3
+#  define APPCOMMAND_BROWSER_STOP 4
+#  define APPCOMMAND_BROWSER_SEARCH 5
+#  define APPCOMMAND_BROWSER_FAVORITES 6
+#  define APPCOMMAND_BROWSER_HOME 7
+
+#  define APPCOMMAND_MEDIA_NEXTTRACK 11
+#  define APPCOMMAND_MEDIA_PREVIOUSTRACK 12
+#  define APPCOMMAND_MEDIA_STOP 13
+#  define APPCOMMAND_MEDIA_PLAY_PAUSE 14
+
+/*
+ * Additional commands currently not in use.
+ *
+ *#define APPCOMMAND_VOLUME_MUTE            8
+ *#define APPCOMMAND_VOLUME_DOWN            9
+ *#define APPCOMMAND_VOLUME_UP              10
+ *#define APPCOMMAND_LAUNCH_MAIL            15
+ *#define APPCOMMAND_LAUNCH_MEDIA_SELECT    16
+ *#define APPCOMMAND_LAUNCH_APP1            17
+ *#define APPCOMMAND_LAUNCH_APP2            18
+ *#define APPCOMMAND_BASS_DOWN              19
+ *#define APPCOMMAND_BASS_BOOST             20
+ *#define APPCOMMAND_BASS_UP                21
+ *#define APPCOMMAND_TREBLE_DOWN            22
+ *#define APPCOMMAND_TREBLE_UP              23
+ *#define FAPPCOMMAND_MOUSE                 0x8000
+ *#define FAPPCOMMAND_KEY                   0
+ *#define FAPPCOMMAND_OEM                   0x1000
+ */
+
+#  define GET_APPCOMMAND_LPARAM(lParam) \
+    ((short)(HIWORD(lParam) & ~FAPPCOMMAND_MASK))
+
+/*
+ *#define GET_DEVICE_LPARAM(lParam)         ((WORD)(HIWORD(lParam) &
+ *FAPPCOMMAND_MASK)) #define GET_MOUSEORKEY_LPARAM             GET_DEVICE_LPARAM
+ *#define GET_FLAGS_LPARAM(lParam)          (LOWORD(lParam))
+ *#define GET_KEYSTATE_LPARAM(lParam)       GET_FLAGS_LPARAM(lParam)
+ */
+#endif  // #ifndef APPCOMMAND_BROWSER_BACKWARD
+
+#endif  // #ifndef mozilla_widget_WinMessages_h_
diff --git a/widget/windows/WinModifierKeyState.h b/widget/windows/WinModifierKeyState.h
new file mode 100644
index 0000000000..0788c25939
--- /dev/null
+++ b/widget/windows/WinModifierKeyState.h
@@ -0,0 +1,59 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_widget_WinModifierKeyState_h_
+#define mozilla_widget_WinModifierKeyState_h_
+
+#include "mozilla/RefPtr.h"
+#include "mozilla/EventForwards.h"
+#include "nsStringFwd.h"
+#include <windows.h>
+
+namespace mozilla {
+namespace widget {
+
+class MOZ_STACK_CLASS ModifierKeyState final {
+ public:
+  ModifierKeyState();
+  explicit ModifierKeyState(Modifiers aModifiers);
+
+  void Update();
+
+  void Unset(Modifiers aRemovingModifiers);
+  void Set(Modifiers aAddingModifiers);
+
+  void InitInputEvent(WidgetInputEvent& aInputEvent) const;
+
+  // Do not create IsAltGr() because it's unclear whether:
+  // - AltGr key is actually pressed.
+  // - Both Ctrl and Alt keys are pressed when a keyboard layout which
+  //   has AltGr key.
+  // - Both Ctrl and Alt keys are pressed when a keyboard layout which
+  //   does not have AltGr key.
+  bool IsShift() const;
+  bool IsControl() const;
+  bool IsAlt() const;
+  bool IsWin() const;
+
+  bool MaybeMatchShortcutKey() const;
+
+  bool IsCapsLocked() const;
+  bool IsNumLocked() const;
+  bool IsScrollLocked() const;
+
+  MOZ_ALWAYS_INLINE Modifiers GetModifiers() const { return mModifiers; }
+
+ private:
+  Modifiers mModifiers;
+
+  void InitMouseEvent(WidgetInputEvent& aMouseEvent) const;
+};
+
+const nsCString ToString(const ModifierKeyState& aModifierKeyState);
+
+}  // namespace widget
+}  // namespace mozilla
+
+#endif  // #ifndef mozilla_widget_WinModifierKeyState_h_
diff --git a/widget/windows/WinMouseScrollHandler.cpp b/widget/windows/WinMouseScrollHandler.cpp
new file mode 100644
index 0000000000..e10f7b29dc
--- /dev/null
+++ b/widget/windows/WinMouseScrollHandler.cpp
@@ -0,0 +1,1634 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/DebugOnly.h"
+
+#include "mozilla/Logging.h"
+
+#include "WinMouseScrollHandler.h"
+#include "nsWindow.h"
+#include "nsWindowDefs.h"
+#include "KeyboardLayout.h"
+#include "WinUtils.h"
+#include "nsGkAtoms.h"
+#include "nsIDOMWindowUtils.h"
+
+#include "mozilla/MiscEvents.h"
+#include "mozilla/MouseEvents.h"
+#include "mozilla/Preferences.h"
+#include "mozilla/dom/WheelEventBinding.h"
+#include "mozilla/StaticPrefs_mousewheel.h"
+#include "mozilla/widget/WinRegistry.h"
+
+#include <psapi.h>
+
+namespace mozilla {
+namespace widget {
+
+LazyLogModule gMouseScrollLog("MouseScrollHandlerWidgets");
+
+static const char* GetBoolName(bool aBool) { return aBool ? "TRUE" : "FALSE"; }
+
+MouseScrollHandler* MouseScrollHandler::sInstance = nullptr;
+
+bool MouseScrollHandler::Device::sFakeScrollableWindowNeeded = false;
+
+bool MouseScrollHandler::Device::SynTP::sInitialized = false;
+int32_t MouseScrollHandler::Device::SynTP::sMajorVersion = 0;
+int32_t MouseScrollHandler::Device::SynTP::sMinorVersion = -1;
+
+bool MouseScrollHandler::Device::Elantech::sUseSwipeHack = false;
+bool MouseScrollHandler::Device::Elantech::sUsePinchHack = false;
+DWORD MouseScrollHandler::Device::Elantech::sZoomUntil = 0;
+
+bool MouseScrollHandler::Device::Apoint::sInitialized = false;
+int32_t MouseScrollHandler::Device::Apoint::sMajorVersion = 0;
+int32_t MouseScrollHandler::Device::Apoint::sMinorVersion = -1;
+
+bool MouseScrollHandler::Device::SetPoint::sMightBeUsing = false;
+
+// The duration until timeout of events transaction.  The value is 1.5 sec,
+// it's just a magic number, it was suggested by Logitech's engineer, see
+// bug 605648 comment 90.
+#define DEFAULT_TIMEOUT_DURATION 1500
+
+/******************************************************************************
+ *
+ * MouseScrollHandler
+ *
+ ******************************************************************************/
+
+/* static */
+POINTS
+MouseScrollHandler::GetCurrentMessagePos() {
+  if (SynthesizingEvent::IsSynthesizing()) {
+    return sInstance->mSynthesizingEvent->GetCursorPoint();
+  }
+  DWORD pos = ::GetMessagePos();
+  return MAKEPOINTS(pos);
+}
+
+// Get rid of the GetMessagePos() API.
+#define GetMessagePos()
+
+/* static */
+void MouseScrollHandler::Initialize() { Device::Init(); }
+
+/* static */
+void MouseScrollHandler::Shutdown() {
+  delete sInstance;
+  sInstance = nullptr;
+}
+
+/* static */
+MouseScrollHandler* MouseScrollHandler::GetInstance() {
+  if (!sInstance) {
+    sInstance = new MouseScrollHandler();
+  }
+  return sInstance;
+}
+
+MouseScrollHandler::MouseScrollHandler()
+    : mIsWaitingInternalMessage(false), mSynthesizingEvent(nullptr) {
+  MOZ_LOG(gMouseScrollLog, LogLevel::Info,
+          ("MouseScroll: Creating an instance, this=%p, sInstance=%p", this,
+           sInstance));
+}
+
+MouseScrollHandler::~MouseScrollHandler() {
+  MOZ_LOG(gMouseScrollLog, LogLevel::Info,
+          ("MouseScroll: Destroying an instance, this=%p, sInstance=%p", this,
+           sInstance));
+
+  delete mSynthesizingEvent;
+}
+
+/* static */
+void MouseScrollHandler::MaybeLogKeyState() {
+  if (!MOZ_LOG_TEST(gMouseScrollLog, LogLevel::Debug)) {
+    return;
+  }
+  BYTE keyboardState[256];
+  if (::GetKeyboardState(keyboardState)) {
+    for (size_t i = 0; i < ArrayLength(keyboardState); i++) {
+      if (keyboardState[i]) {
+        MOZ_LOG(gMouseScrollLog, LogLevel::Debug,
+                ("    Current key state: keyboardState[0x%02zX]=0x%02X (%s)", i,
+                 keyboardState[i],
+                 ((keyboardState[i] & 0x81) == 0x81) ? "Pressed and Toggled"
+                 : (keyboardState[i] & 0x80)         ? "Pressed"
+                 : (keyboardState[i] & 0x01)         ? "Toggled"
+                                                     : "Unknown"));
+      }
+    }
+  } else {
+    MOZ_LOG(
+        gMouseScrollLog, LogLevel::Debug,
+        ("MouseScroll::MaybeLogKeyState(): Failed to print current keyboard "
+         "state"));
+  }
+}
+
+/* static */
+bool MouseScrollHandler::NeedsMessage(UINT aMsg) {
+  switch (aMsg) {
+    case WM_SETTINGCHANGE:
+    case WM_MOUSEWHEEL:
+    case WM_MOUSEHWHEEL:
+    case WM_HSCROLL:
+    case WM_VSCROLL:
+    case MOZ_WM_MOUSEVWHEEL:
+    case MOZ_WM_MOUSEHWHEEL:
+    case MOZ_WM_HSCROLL:
+    case MOZ_WM_VSCROLL:
+    case WM_KEYDOWN:
+    case WM_KEYUP:
+      return true;
+  }
+  return false;
+}
+
+/* static */
+bool MouseScrollHandler::ProcessMessage(nsWindow* aWidget, UINT msg,
+                                        WPARAM wParam, LPARAM lParam,
+                                        MSGResult& aResult) {
+  Device::Elantech::UpdateZoomUntil();
+
+  switch (msg) {
+    case WM_SETTINGCHANGE:
+      if (!sInstance) {
+        return false;
+      }
+      if (wParam == SPI_SETWHEELSCROLLLINES ||
+          wParam == SPI_SETWHEELSCROLLCHARS) {
+        sInstance->mSystemSettings.MarkDirty();
+      }
+      return false;
+
+    case WM_MOUSEWHEEL:
+    case WM_MOUSEHWHEEL:
+      GetInstance()->ProcessNativeMouseWheelMessage(aWidget, msg, wParam,
+                                                    lParam);
+      sInstance->mSynthesizingEvent->NotifyNativeMessageHandlingFinished();
+      // We don't need to call next wndproc for WM_MOUSEWHEEL and
+      // WM_MOUSEHWHEEL.  We should consume them always.  If the messages
+      // would be handled by our window again, it caused making infinite
+      // message loop.
+      aResult.mConsumed = true;
+      aResult.mResult = (msg != WM_MOUSEHWHEEL);
+      return true;
+
+    case WM_HSCROLL:
+    case WM_VSCROLL:
+      aResult.mConsumed = GetInstance()->ProcessNativeScrollMessage(
+          aWidget, msg, wParam, lParam);
+      sInstance->mSynthesizingEvent->NotifyNativeMessageHandlingFinished();
+      aResult.mResult = 0;
+      return true;
+
+    case MOZ_WM_MOUSEVWHEEL:
+    case MOZ_WM_MOUSEHWHEEL:
+      GetInstance()->HandleMouseWheelMessage(aWidget, msg, wParam, lParam);
+      sInstance->mSynthesizingEvent->NotifyInternalMessageHandlingFinished();
+      // Doesn't need to call next wndproc for internal wheel message.
+      aResult.mConsumed = true;
+      return true;
+
+    case MOZ_WM_HSCROLL:
+    case MOZ_WM_VSCROLL:
+      GetInstance()->HandleScrollMessageAsMouseWheelMessage(aWidget, msg,
+                                                            wParam, lParam);
+      sInstance->mSynthesizingEvent->NotifyInternalMessageHandlingFinished();
+      // Doesn't need to call next wndproc for internal scroll message.
+      aResult.mConsumed = true;
+      return true;
+
+    case WM_KEYDOWN:
+    case WM_KEYUP:
+      MOZ_LOG(gMouseScrollLog, LogLevel::Info,
+              ("MouseScroll::ProcessMessage(): aWidget=%p, "
+               "msg=%s(0x%04X), wParam=0x%02zX, ::GetMessageTime()=%ld",
+               aWidget,
+               msg == WM_KEYDOWN ? "WM_KEYDOWN"
+               : msg == WM_KEYUP ? "WM_KEYUP"
+                                 : "Unknown",
+               msg, wParam, ::GetMessageTime()));
+      MaybeLogKeyState();
+      if (Device::Elantech::HandleKeyMessage(aWidget, msg, wParam, lParam)) {
+        aResult.mResult = 0;
+        aResult.mConsumed = true;
+        return true;
+      }
+      return false;
+
+    default:
+      return false;
+  }
+}
+
+/* static */
+nsresult MouseScrollHandler::SynthesizeNativeMouseScrollEvent(
+    nsWindow* aWidget, const LayoutDeviceIntPoint& aPoint,
+    uint32_t aNativeMessage, int32_t aDelta, uint32_t aModifierFlags,
+    uint32_t aAdditionalFlags) {
+  bool useFocusedWindow = !(
+      aAdditionalFlags & nsIDOMWindowUtils::MOUSESCROLL_PREFER_WIDGET_AT_POINT);
+
+  POINT pt;
+  pt.x = aPoint.x;
+  pt.y = aPoint.y;
+
+  HWND target = useFocusedWindow ? ::WindowFromPoint(pt) : ::GetFocus();
+  NS_ENSURE_TRUE(target, NS_ERROR_FAILURE);
+
+  WPARAM wParam = 0;
+  LPARAM lParam = 0;
+  switch (aNativeMessage) {
+    case WM_MOUSEWHEEL:
+    case WM_MOUSEHWHEEL: {
+      lParam = MAKELPARAM(pt.x, pt.y);
+      WORD mod = 0;
+      if (aModifierFlags & (nsIWidget::CTRL_L | nsIWidget::CTRL_R)) {
+        mod |= MK_CONTROL;
+      }
+      if (aModifierFlags & (nsIWidget::SHIFT_L | nsIWidget::SHIFT_R)) {
+        mod |= MK_SHIFT;
+      }
+      wParam = MAKEWPARAM(mod, aDelta);
+      break;
+    }
+    case WM_VSCROLL:
+    case WM_HSCROLL:
+      lParam = (aAdditionalFlags &
+                nsIDOMWindowUtils::MOUSESCROLL_WIN_SCROLL_LPARAM_NOT_NULL)
+                   ? reinterpret_cast<LPARAM>(target)
+                   : 0;
+      wParam = aDelta;
+      break;
+    default:
+      return NS_ERROR_INVALID_ARG;
+  }
+
+  // Ensure to make the instance.
+  GetInstance();
+
+  BYTE kbdState[256];
+  memset(kbdState, 0, sizeof(kbdState));
+
+  AutoTArray<KeyPair, 10> keySequence;
+  WinUtils::SetupKeyModifiersSequence(&keySequence, aModifierFlags,
+                                      aNativeMessage);
+
+  for (uint32_t i = 0; i < keySequence.Length(); ++i) {
+    uint8_t key = keySequence[i].mGeneral;
+    uint8_t keySpecific = keySequence[i].mSpecific;
+    kbdState[key] = 0x81;  // key is down and toggled on if appropriate
+    if (keySpecific) {
+      kbdState[keySpecific] = 0x81;
+    }
+  }
+
+  if (!sInstance->mSynthesizingEvent) {
+    sInstance->mSynthesizingEvent = new SynthesizingEvent();
+  }
+
+  POINTS pts;
+  pts.x = static_cast<SHORT>(pt.x);
+  pts.y = static_cast<SHORT>(pt.y);
+  return sInstance->mSynthesizingEvent->Synthesize(pts, target, aNativeMessage,
+                                                   wParam, lParam, kbdState);
+}
+
+/* static */
+void MouseScrollHandler::InitEvent(nsWindow* aWidget, WidgetGUIEvent& aEvent,
+                                   LPARAM* aPoint) {
+  NS_ENSURE_TRUE_VOID(aWidget);
+
+  // If a point is provided, use it; otherwise, get current message point or
+  // synthetic point
+  POINTS pointOnScreen;
+  if (aPoint != nullptr) {
+    pointOnScreen = MAKEPOINTS(*aPoint);
+  } else {
+    pointOnScreen = GetCurrentMessagePos();
+  }
+
+  // InitEvent expects the point to be in window coordinates, so translate the
+  // point from screen coordinates.
+  POINT pointOnWindow;
+  POINTSTOPOINT(pointOnWindow, pointOnScreen);
+  ::ScreenToClient(aWidget->GetWindowHandle(), &pointOnWindow);
+
+  LayoutDeviceIntPoint point;
+  point.x = pointOnWindow.x;
+  point.y = pointOnWindow.y;
+
+  aWidget->InitEvent(aEvent, &point);
+}
+
+/* static */
+ModifierKeyState MouseScrollHandler::GetModifierKeyState(UINT aMessage) {
+  ModifierKeyState result;
+  // Assume the Control key is down if the Elantech touchpad has sent the
+  // mis-ordered WM_KEYDOWN/WM_MOUSEWHEEL messages.  (See the comment in
+  // MouseScrollHandler::Device::Elantech::HandleKeyMessage().)
+  if ((aMessage == MOZ_WM_MOUSEVWHEEL || aMessage == WM_MOUSEWHEEL) &&
+      !result.IsControl() && Device::Elantech::IsZooming()) {
+    // XXX Do we need to unset MODIFIER_SHIFT, MODIFIER_ALT, MODIFIER_META too?
+    //     If one of them are true, the default action becomes not zooming.
+    result.Unset(MODIFIER_ALTGRAPH);
+    result.Set(MODIFIER_CONTROL);
+  }
+  return result;
+}
+
+POINT
+MouseScrollHandler::ComputeMessagePos(UINT aMessage, WPARAM aWParam,
+                                      LPARAM aLParam) {
+  POINT point;
+  if (Device::SetPoint::IsGetMessagePosResponseValid(aMessage, aWParam,
+                                                     aLParam)) {
+    MOZ_LOG(gMouseScrollLog, LogLevel::Info,
+            ("MouseScroll::ComputeMessagePos: Using ::GetCursorPos()"));
+    ::GetCursorPos(&point);
+  } else {
+    POINTS pts = GetCurrentMessagePos();
+    point.x = pts.x;
+    point.y = pts.y;
+  }
+  return point;
+}
+
+void MouseScrollHandler::ProcessNativeMouseWheelMessage(nsWindow* aWidget,
+                                                        UINT aMessage,
+                                                        WPARAM aWParam,
+                                                        LPARAM aLParam) {
+  if (SynthesizingEvent::IsSynthesizing()) {
+    mSynthesizingEvent->NativeMessageReceived(aWidget, aMessage, aWParam,
+                                              aLParam);
+  }
+
+  POINT point = ComputeMessagePos(aMessage, aWParam, aLParam);
+
+  MOZ_LOG(gMouseScrollLog, LogLevel::Info,
+          ("MouseScroll::ProcessNativeMouseWheelMessage: aWidget=%p, "
+           "aMessage=%s, wParam=0x%08zX, lParam=0x%08" PRIXLPTR
+           ", point: { x=%ld, y=%ld }",
+           aWidget,
+           aMessage == WM_MOUSEWHEEL    ? "WM_MOUSEWHEEL"
+           : aMessage == WM_MOUSEHWHEEL ? "WM_MOUSEHWHEEL"
+           : aMessage == WM_VSCROLL     ? "WM_VSCROLL"
+                                        : "WM_HSCROLL",
+           aWParam, aLParam, point.x, point.y));
+  MaybeLogKeyState();
+
+  HWND underCursorWnd = ::WindowFromPoint(point);
+  if (!underCursorWnd) {
+    MOZ_LOG(gMouseScrollLog, LogLevel::Info,
+            ("MouseScroll::ProcessNativeMouseWheelMessage: "
+             "No window is not found under the cursor"));
+    return;
+  }
+
+  if (Device::Elantech::IsPinchHackNeeded() &&
+      Device::Elantech::IsHelperWindow(underCursorWnd)) {
+    // The Elantech driver places a window right underneath the cursor
+    // when sending a WM_MOUSEWHEEL event to us as part of a pinch-to-zoom
+    // gesture.  We detect that here, and search for our window that would
+    // be beneath the cursor if that window wasn't there.
+    underCursorWnd = WinUtils::FindOurWindowAtPoint(point);
+    if (!underCursorWnd) {
+      MOZ_LOG(gMouseScrollLog, LogLevel::Info,
+              ("MouseScroll::ProcessNativeMouseWheelMessage: "
+               "Our window is not found under the Elantech helper window"));
+      return;
+    }
+  }
+
+  // Handle most cases first.  If the window under mouse cursor is our window
+  // except plugin window (MozillaWindowClass), we should handle the message
+  // on the window.
+  if (WinUtils::IsOurProcessWindow(underCursorWnd)) {
+    nsWindow* destWindow = WinUtils::GetNSWindowPtr(underCursorWnd);
+    if (!destWindow) {
+      MOZ_LOG(gMouseScrollLog, LogLevel::Info,
+              ("MouseScroll::ProcessNativeMouseWheelMessage: "
+               "Found window under the cursor isn't managed by nsWindow..."));
+      HWND wnd = ::GetParent(underCursorWnd);
+      for (; wnd; wnd = ::GetParent(wnd)) {
+        destWindow = WinUtils::GetNSWindowPtr(wnd);
+        if (destWindow) {
+          break;
+        }
+      }
+      if (!wnd) {
+        MOZ_LOG(
+            gMouseScrollLog, LogLevel::Info,
+            ("MouseScroll::ProcessNativeMouseWheelMessage: Our window which is "
+             "managed by nsWindow is not found under the cursor"));
+        return;
+      }
+    }
+
+    MOZ_ASSERT(destWindow, "destWindow must not be NULL");
+
+    // Some odd touchpad utils sets focus to window under the mouse cursor.
+    // this emulates the odd behavior for debug.
+    if (mUserPrefs.ShouldEmulateToMakeWindowUnderCursorForeground() &&
+        (aMessage == WM_MOUSEWHEEL || aMessage == WM_MOUSEHWHEEL) &&
+        ::GetForegroundWindow() != destWindow->GetWindowHandle()) {
+      ::SetForegroundWindow(destWindow->GetWindowHandle());
+    }
+
+    MOZ_LOG(gMouseScrollLog, LogLevel::Info,
+            ("MouseScroll::ProcessNativeMouseWheelMessage: Succeeded, "
+             "Posting internal message to an nsWindow (%p)...",
+             destWindow));
+    mIsWaitingInternalMessage = true;
+    UINT internalMessage = WinUtils::GetInternalMessage(aMessage);
+    ::PostMessage(destWindow->GetWindowHandle(), internalMessage, aWParam,
+                  aLParam);
+    return;
+  }
+
+  // If the window under cursor is not in our process, it means:
+  // 1. The window may be a plugin window (GeckoPluginWindow or its descendant).
+  // 2. The window may be another application's window.
+  HWND pluginWnd = WinUtils::FindOurProcessWindow(underCursorWnd);
+  if (!pluginWnd) {
+    // If there is no plugin window in ancestors of the window under cursor,
+    // the window is for another applications (case 2).
+    // We don't need to handle this message.
+    MOZ_LOG(gMouseScrollLog, LogLevel::Info,
+            ("MouseScroll::ProcessNativeMouseWheelMessage: "
+             "Our window is not found under the cursor"));
+    return;
+  }
+
+  // If the window is a part of plugin, we should post the message to it.
+  MOZ_LOG(
+      gMouseScrollLog, LogLevel::Info,
+      ("MouseScroll::ProcessNativeMouseWheelMessage: Succeeded, "
+       "Redirecting the message to a window which is a plugin child window"));
+  ::PostMessage(underCursorWnd, aMessage, aWParam, aLParam);
+}
+
+bool MouseScrollHandler::ProcessNativeScrollMessage(nsWindow* aWidget,
+                                                    UINT aMessage,
+                                                    WPARAM aWParam,
+                                                    LPARAM aLParam) {
+  if (aLParam || mUserPrefs.IsScrollMessageHandledAsWheelMessage()) {
+    // Scroll message generated by Thinkpad Trackpoint Driver or similar
+    // Treat as a mousewheel message and scroll appropriately
+    ProcessNativeMouseWheelMessage(aWidget, aMessage, aWParam, aLParam);
+    // Always consume the scroll message if we try to emulate mouse wheel
+    // action.
+    return true;
+  }
+
+  if (SynthesizingEvent::IsSynthesizing()) {
+    mSynthesizingEvent->NativeMessageReceived(aWidget, aMessage, aWParam,
+                                              aLParam);
+  }
+
+  MOZ_LOG(gMouseScrollLog, LogLevel::Info,
+          ("MouseScroll::ProcessNativeScrollMessage: aWidget=%p, "
+           "aMessage=%s, wParam=0x%08zX, lParam=0x%08" PRIXLPTR,
+           aWidget, aMessage == WM_VSCROLL ? "WM_VSCROLL" : "WM_HSCROLL",
+           aWParam, aLParam));
+
+  // Scroll message generated by external application
+  WidgetContentCommandEvent commandEvent(true, eContentCommandScroll, aWidget);
+  commandEvent.mScroll.mIsHorizontal = (aMessage == WM_HSCROLL);
+
+  switch (LOWORD(aWParam)) {
+    case SB_LINEUP:  // SB_LINELEFT
+      commandEvent.mScroll.mUnit =
+          WidgetContentCommandEvent::eCmdScrollUnit_Line;
+      commandEvent.mScroll.mAmount = -1;
+      break;
+    case SB_LINEDOWN:  // SB_LINERIGHT
+      commandEvent.mScroll.mUnit =
+          WidgetContentCommandEvent::eCmdScrollUnit_Line;
+      commandEvent.mScroll.mAmount = 1;
+      break;
+    case SB_PAGEUP:  // SB_PAGELEFT
+      commandEvent.mScroll.mUnit =
+          WidgetContentCommandEvent::eCmdScrollUnit_Page;
+      commandEvent.mScroll.mAmount = -1;
+      break;
+    case SB_PAGEDOWN:  // SB_PAGERIGHT
+      commandEvent.mScroll.mUnit =
+          WidgetContentCommandEvent::eCmdScrollUnit_Page;
+      commandEvent.mScroll.mAmount = 1;
+      break;
+    case SB_TOP:  // SB_LEFT
+      commandEvent.mScroll.mUnit =
+          WidgetContentCommandEvent::eCmdScrollUnit_Whole;
+      commandEvent.mScroll.mAmount = -1;
+      break;
+    case SB_BOTTOM:  // SB_RIGHT
+      commandEvent.mScroll.mUnit =
+          WidgetContentCommandEvent::eCmdScrollUnit_Whole;
+      commandEvent.mScroll.mAmount = 1;
+      break;
+    default:
+      return false;
+  }
+  // XXX If this is a plugin window, we should dispatch the event from
+  //     parent window.
+  aWidget->DispatchContentCommandEvent(&commandEvent);
+  return true;
+}
+
+void MouseScrollHandler::HandleMouseWheelMessage(nsWindow* aWidget,
+                                                 UINT aMessage, WPARAM aWParam,
+                                                 LPARAM aLParam) {
+  MOZ_ASSERT((aMessage == MOZ_WM_MOUSEVWHEEL || aMessage == MOZ_WM_MOUSEHWHEEL),
+             "HandleMouseWheelMessage must be called with "
+             "MOZ_WM_MOUSEVWHEEL or MOZ_WM_MOUSEHWHEEL");
+
+  MOZ_LOG(
+      gMouseScrollLog, LogLevel::Info,
+      ("MouseScroll::HandleMouseWheelMessage: aWidget=%p, "
+       "aMessage=MOZ_WM_MOUSE%sWHEEL, aWParam=0x%08zX, aLParam=0x%08" PRIXLPTR,
+       aWidget, aMessage == MOZ_WM_MOUSEVWHEEL ? "V" : "H", aWParam, aLParam));
+
+  mIsWaitingInternalMessage = false;
+
+  // If it's not allowed to cache system settings, we need to reset the cache
+  // before handling the mouse wheel message.
+  mSystemSettings.TrustedScrollSettingsDriver();
+
+  EventInfo eventInfo(aWidget, WinUtils::GetNativeMessage(aMessage), aWParam,
+                      aLParam);
+  if (!eventInfo.CanDispatchWheelEvent()) {
+    MOZ_LOG(
+        gMouseScrollLog, LogLevel::Info,
+        ("MouseScroll::HandleMouseWheelMessage: Cannot dispatch the events"));
+    mLastEventInfo.ResetTransaction();
+    return;
+  }
+
+  // Discard the remaining delta if current wheel message and last one are
+  // received by different window or to scroll different direction or
+  // different unit scroll.  Furthermore, if the last event was too old.
+  if (!mLastEventInfo.CanContinueTransaction(eventInfo)) {
+    mLastEventInfo.ResetTransaction();
+  }
+
+  mLastEventInfo.RecordEvent(eventInfo);
+
+  ModifierKeyState modKeyState = GetModifierKeyState(aMessage);
+
+  // Grab the widget, it might be destroyed by a DOM event handler.
+  RefPtr<nsWindow> kungFuDethGrip(aWidget);
+
+  WidgetWheelEvent wheelEvent(true, eWheel, aWidget);
+  if (mLastEventInfo.InitWheelEvent(aWidget, wheelEvent, modKeyState,
+                                    aLParam)) {
+    MOZ_LOG(gMouseScrollLog, LogLevel::Info,
+            ("MouseScroll::HandleMouseWheelMessage: dispatching "
+             "eWheel event"));
+    aWidget->DispatchWheelEvent(&wheelEvent);
+    if (aWidget->Destroyed()) {
+      MOZ_LOG(gMouseScrollLog, LogLevel::Info,
+              ("MouseScroll::HandleMouseWheelMessage: The window was destroyed "
+               "by eWheel event"));
+      mLastEventInfo.ResetTransaction();
+      return;
+    }
+  } else {
+    MOZ_LOG(gMouseScrollLog, LogLevel::Info,
+            ("MouseScroll::HandleMouseWheelMessage: eWheel event is not "
+             "dispatched"));
+  }
+}
+
+void MouseScrollHandler::HandleScrollMessageAsMouseWheelMessage(
+    nsWindow* aWidget, UINT aMessage, WPARAM aWParam, LPARAM aLParam) {
+  MOZ_ASSERT((aMessage == MOZ_WM_VSCROLL || aMessage == MOZ_WM_HSCROLL),
+             "HandleScrollMessageAsMouseWheelMessage must be called with "
+             "MOZ_WM_VSCROLL or MOZ_WM_HSCROLL");
+
+  mIsWaitingInternalMessage = false;
+
+  ModifierKeyState modKeyState = GetModifierKeyState(aMessage);
+
+  WidgetWheelEvent wheelEvent(true, eWheel, aWidget);
+  double& delta =
+      (aMessage == MOZ_WM_VSCROLL) ? wheelEvent.mDeltaY : wheelEvent.mDeltaX;
+  int32_t& lineOrPageDelta = (aMessage == MOZ_WM_VSCROLL)
+                                 ? wheelEvent.mLineOrPageDeltaY
+                                 : wheelEvent.mLineOrPageDeltaX;
+
+  delta = 1.0;
+  lineOrPageDelta = 1;
+
+  switch (LOWORD(aWParam)) {
+    case SB_PAGEUP:
+      delta = -1.0;
+      lineOrPageDelta = -1;
+      [[fallthrough]];
+    case SB_PAGEDOWN:
+      wheelEvent.mDeltaMode = dom::WheelEvent_Binding::DOM_DELTA_PAGE;
+      break;
+
+    case SB_LINEUP:
+      delta = -1.0;
+      lineOrPageDelta = -1;
+      [[fallthrough]];
+    case SB_LINEDOWN:
+      wheelEvent.mDeltaMode = dom::WheelEvent_Binding::DOM_DELTA_LINE;
+      break;
+
+    default:
+      return;
+  }
+  modKeyState.InitInputEvent(wheelEvent);
+
+  // Current mouse position may not be same as when the original message
+  // is received. However, this data is not available with the original
+  // message, which is why nullptr is passed in. We need to know the actual
+  // mouse cursor position when the original message was received.
+  InitEvent(aWidget, wheelEvent, nullptr);
+
+  MOZ_LOG(
+      gMouseScrollLog, LogLevel::Info,
+      ("MouseScroll::HandleScrollMessageAsMouseWheelMessage: aWidget=%p, "
+       "aMessage=MOZ_WM_%sSCROLL, aWParam=0x%08zX, aLParam=0x%08" PRIXLPTR ", "
+       "wheelEvent { mRefPoint: { x: %d, y: %d }, mDeltaX: %f, mDeltaY: %f, "
+       "mLineOrPageDeltaX: %d, mLineOrPageDeltaY: %d, "
+       "isShift: %s, isControl: %s, isAlt: %s, isMeta: %s }",
+       aWidget, (aMessage == MOZ_WM_VSCROLL) ? "V" : "H", aWParam, aLParam,
+       wheelEvent.mRefPoint.x.value, wheelEvent.mRefPoint.y.value,
+       wheelEvent.mDeltaX, wheelEvent.mDeltaY, wheelEvent.mLineOrPageDeltaX,
+       wheelEvent.mLineOrPageDeltaY, GetBoolName(wheelEvent.IsShift()),
+       GetBoolName(wheelEvent.IsControl()), GetBoolName(wheelEvent.IsAlt()),
+       GetBoolName(wheelEvent.IsMeta())));
+
+  aWidget->DispatchWheelEvent(&wheelEvent);
+}
+
+/******************************************************************************
+ *
+ * EventInfo
+ *
+ ******************************************************************************/
+
+MouseScrollHandler::EventInfo::EventInfo(nsWindow* aWidget, UINT aMessage,
+                                         WPARAM aWParam, LPARAM aLParam) {
+  MOZ_ASSERT(
+      aMessage == WM_MOUSEWHEEL || aMessage == WM_MOUSEHWHEEL,
+      "EventInfo must be initialized with WM_MOUSEWHEEL or WM_MOUSEHWHEEL");
+
+  MouseScrollHandler::GetInstance()->mSystemSettings.Init();
+
+  mIsVertical = (aMessage == WM_MOUSEWHEEL);
+  mIsPage =
+      MouseScrollHandler::sInstance->mSystemSettings.IsPageScroll(mIsVertical);
+  mDelta = (short)HIWORD(aWParam);
+  mWnd = aWidget->GetWindowHandle();
+  mTimeStamp = TimeStamp::Now();
+}
+
+bool MouseScrollHandler::EventInfo::CanDispatchWheelEvent() const {
+  if (!GetScrollAmount()) {
+    // XXX I think that we should dispatch mouse wheel events even if the
+    // operation will not scroll because the wheel operation really happened
+    // and web application may want to handle the event for non-scroll action.
+    return false;
+  }
+
+  return (mDelta != 0);
+}
+
+int32_t MouseScrollHandler::EventInfo::GetScrollAmount() const {
+  if (mIsPage) {
+    return 1;
+  }
+  return MouseScrollHandler::sInstance->mSystemSettings.GetScrollAmount(
+      mIsVertical);
+}
+
+/******************************************************************************
+ *
+ * LastEventInfo
+ *
+ ******************************************************************************/
+
+bool MouseScrollHandler::LastEventInfo::CanContinueTransaction(
+    const EventInfo& aNewEvent) {
+  int32_t timeout = MouseScrollHandler::sInstance->mUserPrefs
+                        .GetMouseScrollTransactionTimeout();
+  return !mWnd ||
+         (mWnd == aNewEvent.GetWindowHandle() &&
+          IsPositive() == aNewEvent.IsPositive() &&
+          mIsVertical == aNewEvent.IsVertical() &&
+          mIsPage == aNewEvent.IsPage() &&
+          (timeout < 0 || TimeStamp::Now() - mTimeStamp <=
+                              TimeDuration::FromMilliseconds(timeout)));
+}
+
+void MouseScrollHandler::LastEventInfo::ResetTransaction() {
+  if (!mWnd) {
+    return;
+  }
+
+  MOZ_LOG(gMouseScrollLog, LogLevel::Info,
+          ("MouseScroll::LastEventInfo::ResetTransaction()"));
+
+  mWnd = nullptr;
+  mAccumulatedDelta = 0;
+}
+
+void MouseScrollHandler::LastEventInfo::RecordEvent(const EventInfo& aEvent) {
+  mWnd = aEvent.GetWindowHandle();
+  mDelta = aEvent.GetNativeDelta();
+  mIsVertical = aEvent.IsVertical();
+  mIsPage = aEvent.IsPage();
+  mTimeStamp = TimeStamp::Now();
+}
+
+/* static */
+int32_t MouseScrollHandler::LastEventInfo::RoundDelta(double aDelta) {
+  return (aDelta >= 0) ? (int32_t)floor(aDelta) : (int32_t)ceil(aDelta);
+}
+
+bool MouseScrollHandler::LastEventInfo::InitWheelEvent(
+    nsWindow* aWidget, WidgetWheelEvent& aWheelEvent,
+    const ModifierKeyState& aModKeyState, LPARAM aLParam) {
+  MOZ_ASSERT(aWheelEvent.mMessage == eWheel);
+
+  if (StaticPrefs::mousewheel_ignore_cursor_position_in_lparam()) {
+    InitEvent(aWidget, aWheelEvent, nullptr);
+  } else {
+    InitEvent(aWidget, aWheelEvent, &aLParam);
+  }
+
+  aModKeyState.InitInputEvent(aWheelEvent);
+
+  // Our positive delta value means to bottom or right.
+  // But positive native delta value means to top or right.
+  // Use orienter for computing our delta value with native delta value.
+  int32_t orienter = mIsVertical ? -1 : 1;
+
+  aWheelEvent.mDeltaMode = mIsPage ? dom::WheelEvent_Binding::DOM_DELTA_PAGE
+                                   : dom::WheelEvent_Binding::DOM_DELTA_LINE;
+
+  double ticks = double(mDelta) * orienter / double(WHEEL_DELTA);
+  if (mIsVertical) {
+    aWheelEvent.mWheelTicksY = ticks;
+  } else {
+    aWheelEvent.mWheelTicksX = ticks;
+  }
+
+  double& delta = mIsVertical ? aWheelEvent.mDeltaY : aWheelEvent.mDeltaX;
+  int32_t& lineOrPageDelta = mIsVertical ? aWheelEvent.mLineOrPageDeltaY
+                                         : aWheelEvent.mLineOrPageDeltaX;
+
+  double nativeDeltaPerUnit =
+      mIsPage ? double(WHEEL_DELTA) : double(WHEEL_DELTA) / GetScrollAmount();
+
+  delta = double(mDelta) * orienter / nativeDeltaPerUnit;
+  mAccumulatedDelta += mDelta;
+  lineOrPageDelta =
+      mAccumulatedDelta * orienter / RoundDelta(nativeDeltaPerUnit);
+  mAccumulatedDelta -=
+      lineOrPageDelta * orienter * RoundDelta(nativeDeltaPerUnit);
+
+  if (aWheelEvent.mDeltaMode != dom::WheelEvent_Binding::DOM_DELTA_LINE) {
+    // If the scroll delta mode isn't per line scroll, we shouldn't allow to
+    // override the system scroll speed setting.
+    aWheelEvent.mAllowToOverrideSystemScrollSpeed = false;
+  }
+
+  MOZ_LOG(
+      gMouseScrollLog, LogLevel::Info,
+      ("MouseScroll::LastEventInfo::InitWheelEvent: aWidget=%p, "
+       "aWheelEvent { mRefPoint: { x: %d, y: %d }, mDeltaX: %f, mDeltaY: %f, "
+       "mLineOrPageDeltaX: %d, mLineOrPageDeltaY: %d, "
+       "isShift: %s, isControl: %s, isAlt: %s, isMeta: %s, "
+       "mAllowToOverrideSystemScrollSpeed: %s }, "
+       "mAccumulatedDelta: %d",
+       aWidget, aWheelEvent.mRefPoint.x.value, aWheelEvent.mRefPoint.y.value,
+       aWheelEvent.mDeltaX, aWheelEvent.mDeltaY, aWheelEvent.mLineOrPageDeltaX,
+       aWheelEvent.mLineOrPageDeltaY, GetBoolName(aWheelEvent.IsShift()),
+       GetBoolName(aWheelEvent.IsControl()), GetBoolName(aWheelEvent.IsAlt()),
+       GetBoolName(aWheelEvent.IsMeta()),
+       GetBoolName(aWheelEvent.mAllowToOverrideSystemScrollSpeed),
+       mAccumulatedDelta));
+
+  return (delta != 0);
+}
+
+/******************************************************************************
+ *
+ * SystemSettings
+ *
+ ******************************************************************************/
+
+void MouseScrollHandler::SystemSettings::Init() {
+  if (mInitialized) {
+    return;
+  }
+
+  InitScrollLines();
+  InitScrollChars();
+
+  mInitialized = true;
+
+  MOZ_LOG(gMouseScrollLog, LogLevel::Info,
+          ("MouseScroll::SystemSettings::Init(): initialized, "
+           "mScrollLines=%d, mScrollChars=%d",
+           mScrollLines, mScrollChars));
+}
+
+bool MouseScrollHandler::SystemSettings::InitScrollLines() {
+  int32_t oldValue = mInitialized ? mScrollLines : 0;
+  mIsReliableScrollLines = false;
+  mScrollLines = MouseScrollHandler::sInstance->mUserPrefs
+                     .GetOverriddenVerticalScrollAmout();
+  if (mScrollLines >= 0) {
+    // overridden by the pref.
+    mIsReliableScrollLines = true;
+    MOZ_LOG(gMouseScrollLog, LogLevel::Info,
+            ("MouseScroll::SystemSettings::InitScrollLines(): mScrollLines is "
+             "overridden by the pref: %d",
+             mScrollLines));
+  } else if (!::SystemParametersInfo(SPI_GETWHEELSCROLLLINES, 0, &mScrollLines,
+                                     0)) {
+    MOZ_LOG(gMouseScrollLog, LogLevel::Info,
+            ("MouseScroll::SystemSettings::InitScrollLines(): "
+             "::SystemParametersInfo("
+             "SPI_GETWHEELSCROLLLINES) failed"));
+    mScrollLines = DefaultScrollLines();
+  }
+
+  if (mScrollLines > WHEEL_DELTA) {
+    MOZ_LOG(gMouseScrollLog, LogLevel::Info,
+            ("MouseScroll::SystemSettings::InitScrollLines(): the result of "
+             "::SystemParametersInfo(SPI_GETWHEELSCROLLLINES) is too large: %d",
+             mScrollLines));
+    // sScrollLines usually equals 3 or 0 (for no scrolling)
+    // However, if sScrollLines > WHEEL_DELTA, we assume that
+    // the mouse driver wants a page scroll.  The docs state that
+    // sScrollLines should explicitly equal WHEEL_PAGESCROLL, but
+    // since some mouse drivers use an arbitrary large number instead,
+    // we have to handle that as well.
+    mScrollLines = WHEEL_PAGESCROLL;
+  }
+
+  return oldValue != mScrollLines;
+}
+
+bool MouseScrollHandler::SystemSettings::InitScrollChars() {
+  int32_t oldValue = mInitialized ? mScrollChars : 0;
+  mIsReliableScrollChars = false;
+  mScrollChars = MouseScrollHandler::sInstance->mUserPrefs
+                     .GetOverriddenHorizontalScrollAmout();
+  if (mScrollChars >= 0) {
+    // overridden by the pref.
+    mIsReliableScrollChars = true;
+    MOZ_LOG(gMouseScrollLog, LogLevel::Info,
+            ("MouseScroll::SystemSettings::InitScrollChars(): mScrollChars is "
+             "overridden by the pref: %d",
+             mScrollChars));
+  } else if (!::SystemParametersInfo(SPI_GETWHEELSCROLLCHARS, 0, &mScrollChars,
+                                     0)) {
+    MOZ_LOG(gMouseScrollLog, LogLevel::Info,
+            ("MouseScroll::SystemSettings::InitScrollChars(): "
+             "::SystemParametersInfo("
+             "SPI_GETWHEELSCROLLCHARS) failed, this is unexpected on Vista or "
+             "later"));
+    // XXX Should we use DefaultScrollChars()?
+    mScrollChars = 1;
+  }
+
+  if (mScrollChars > WHEEL_DELTA) {
+    MOZ_LOG(gMouseScrollLog, LogLevel::Info,
+            ("MouseScroll::SystemSettings::InitScrollChars(): the result of "
+             "::SystemParametersInfo(SPI_GETWHEELSCROLLCHARS) is too large: %d",
+             mScrollChars));
+    // See the comments for the case mScrollLines > WHEEL_DELTA.
+    mScrollChars = WHEEL_PAGESCROLL;
+  }
+
+  return oldValue != mScrollChars;
+}
+
+void MouseScrollHandler::SystemSettings::MarkDirty() {
+  MOZ_LOG(gMouseScrollLog, LogLevel::Info,
+          ("MouseScrollHandler::SystemSettings::MarkDirty(): "
+           "Marking SystemSettings dirty"));
+  mInitialized = false;
+  // When system settings are changed, we should reset current transaction.
+  MOZ_ASSERT(sInstance,
+             "Must not be called at initializing MouseScrollHandler");
+  MouseScrollHandler::sInstance->mLastEventInfo.ResetTransaction();
+}
+
+void MouseScrollHandler::SystemSettings::RefreshCache() {
+  bool isChanged = InitScrollLines();
+  isChanged = InitScrollChars() || isChanged;
+  if (!isChanged) {
+    return;
+  }
+  // If the scroll amount is changed, we should reset current transaction.
+  MOZ_ASSERT(sInstance,
+             "Must not be called at initializing MouseScrollHandler");
+  MouseScrollHandler::sInstance->mLastEventInfo.ResetTransaction();
+}
+
+void MouseScrollHandler::SystemSettings::TrustedScrollSettingsDriver() {
+  if (!mInitialized) {
+    return;
+  }
+
+  // if the cache is initialized with prefs, we don't need to refresh it.
+  if (mIsReliableScrollLines && mIsReliableScrollChars) {
+    return;
+  }
+
+  MouseScrollHandler::UserPrefs& userPrefs =
+      MouseScrollHandler::sInstance->mUserPrefs;
+
+  // If system settings cache is disabled, we should always refresh them.
+  if (!userPrefs.IsSystemSettingCacheEnabled()) {
+    RefreshCache();
+    return;
+  }
+
+  // If pref is set to as "always trust the cache", we shouldn't refresh them
+  // in any environments.
+  if (userPrefs.IsSystemSettingCacheForciblyEnabled()) {
+    return;
+  }
+
+  // If SynTP of Synaptics or Apoint of Alps is installed, it may hook
+  // ::SystemParametersInfo() and returns different value from system settings.
+  if (Device::SynTP::IsDriverInstalled() ||
+      Device::Apoint::IsDriverInstalled()) {
+    RefreshCache();
+    return;
+  }
+
+  // XXX We're not sure about other touchpad drivers...
+}
+
+/******************************************************************************
+ *
+ * UserPrefs
+ *
+ ******************************************************************************/
+
+MouseScrollHandler::UserPrefs::UserPrefs() : mInitialized(false) {
+  // We need to reset mouse wheel transaction when all of mousewheel related
+  // prefs are changed.
+  DebugOnly<nsresult> rv =
+      Preferences::RegisterPrefixCallback(OnChange, "mousewheel.", this);
+  MOZ_ASSERT(NS_SUCCEEDED(rv), "Failed to register callback for mousewheel.");
+}
+
+MouseScrollHandler::UserPrefs::~UserPrefs() {
+  DebugOnly<nsresult> rv =
+      Preferences::UnregisterPrefixCallback(OnChange, "mousewheel.", this);
+  MOZ_ASSERT(NS_SUCCEEDED(rv), "Failed to unregister callback for mousewheel.");
+}
+
+void MouseScrollHandler::UserPrefs::Init() {
+  if (mInitialized) {
+    return;
+  }
+
+  mInitialized = true;
+
+  mScrollMessageHandledAsWheelMessage =
+      Preferences::GetBool("mousewheel.emulate_at_wm_scroll", false);
+  mEnableSystemSettingCache =
+      Preferences::GetBool("mousewheel.system_settings_cache.enabled", true);
+  mForceEnableSystemSettingCache = Preferences::GetBool(
+      "mousewheel.system_settings_cache.force_enabled", false);
+  mEmulateToMakeWindowUnderCursorForeground = Preferences::GetBool(
+      "mousewheel.debug.make_window_under_cursor_foreground", false);
+  mOverriddenVerticalScrollAmount =
+      Preferences::GetInt("mousewheel.windows.vertical_amount_override", -1);
+  mOverriddenHorizontalScrollAmount =
+      Preferences::GetInt("mousewheel.windows.horizontal_amount_override", -1);
+  mMouseScrollTransactionTimeout = Preferences::GetInt(
+      "mousewheel.windows.transaction.timeout", DEFAULT_TIMEOUT_DURATION);
+
+  MOZ_LOG(gMouseScrollLog, LogLevel::Info,
+          ("MouseScroll::UserPrefs::Init(): initialized, "
+           "mScrollMessageHandledAsWheelMessage=%s, "
+           "mEnableSystemSettingCache=%s, "
+           "mForceEnableSystemSettingCache=%s, "
+           "mEmulateToMakeWindowUnderCursorForeground=%s, "
+           "mOverriddenVerticalScrollAmount=%d, "
+           "mOverriddenHorizontalScrollAmount=%d, "
+           "mMouseScrollTransactionTimeout=%d",
+           GetBoolName(mScrollMessageHandledAsWheelMessage),
+           GetBoolName(mEnableSystemSettingCache),
+           GetBoolName(mForceEnableSystemSettingCache),
+           GetBoolName(mEmulateToMakeWindowUnderCursorForeground),
+           mOverriddenVerticalScrollAmount, mOverriddenHorizontalScrollAmount,
+           mMouseScrollTransactionTimeout));
+}
+
+void MouseScrollHandler::UserPrefs::MarkDirty() {
+  MOZ_LOG(
+      gMouseScrollLog, LogLevel::Info,
+      ("MouseScrollHandler::UserPrefs::MarkDirty(): Marking UserPrefs dirty"));
+  mInitialized = false;
+  // Some prefs might override system settings, so, we should mark them dirty.
+  MouseScrollHandler::sInstance->mSystemSettings.MarkDirty();
+  // When user prefs for mousewheel are changed, we should reset current
+  // transaction.
+  MOZ_ASSERT(sInstance,
+             "Must not be called at initializing MouseScrollHandler");
+  MouseScrollHandler::sInstance->mLastEventInfo.ResetTransaction();
+}
+
+/******************************************************************************
+ *
+ * Device
+ *
+ ******************************************************************************/
+
+/* static */
+bool MouseScrollHandler::Device::GetWorkaroundPref(const char* aPrefName,
+                                                   bool aValueIfAutomatic) {
+  if (!aPrefName) {
+    MOZ_LOG(gMouseScrollLog, LogLevel::Info,
+            ("MouseScroll::Device::GetWorkaroundPref(): Failed, aPrefName is "
+             "NULL"));
+    return aValueIfAutomatic;
+  }
+
+  int32_t lHackValue = 0;
+  if (NS_FAILED(Preferences::GetInt(aPrefName, &lHackValue))) {
+    MOZ_LOG(gMouseScrollLog, LogLevel::Info,
+            ("MouseScroll::Device::GetWorkaroundPref(): Preferences::GetInt() "
+             "failed,"
+             " aPrefName=\"%s\", aValueIfAutomatic=%s",
+             aPrefName, GetBoolName(aValueIfAutomatic)));
+    return aValueIfAutomatic;
+  }
+
+  MOZ_LOG(gMouseScrollLog, LogLevel::Info,
+          ("MouseScroll::Device::GetWorkaroundPref(): Succeeded, "
+           "aPrefName=\"%s\", aValueIfAutomatic=%s, lHackValue=%d",
+           aPrefName, GetBoolName(aValueIfAutomatic), lHackValue));
+
+  switch (lHackValue) {
+    case 0:  // disabled
+      return false;
+    case 1:  // enabled
+      return true;
+    default:  // -1: autodetect
+      return aValueIfAutomatic;
+  }
+}
+
+/* static */
+void MouseScrollHandler::Device::Init() {
+  // FYI: Thinkpad's TrackPoint is Apoint of Alps and UltraNav is SynTP of
+  //      Synaptics.  So, those drivers' information should be initialized
+  //      before calling methods of TrackPoint and UltraNav.
+  SynTP::Init();
+  Elantech::Init();
+  Apoint::Init();
+
+  sFakeScrollableWindowNeeded = GetWorkaroundPref(
+      "ui.trackpoint_hack.enabled", (TrackPoint::IsDriverInstalled() ||
+                                     UltraNav::IsObsoleteDriverInstalled()));
+
+  MOZ_LOG(gMouseScrollLog, LogLevel::Info,
+          ("MouseScroll::Device::Init(): sFakeScrollableWindowNeeded=%s",
+           GetBoolName(sFakeScrollableWindowNeeded)));
+}
+
+/******************************************************************************
+ *
+ * Device::SynTP
+ *
+ ******************************************************************************/
+
+/* static */
+void MouseScrollHandler::Device::SynTP::Init() {
+  if (sInitialized) {
+    return;
+  }
+
+  sInitialized = true;
+  sMajorVersion = 0;
+  sMinorVersion = -1;
+
+  wchar_t buf[40];
+  if (!WinRegistry::GetString(
+          HKEY_LOCAL_MACHINE, u"Software\\Synaptics\\SynTP\\Install"_ns,
+          u"DriverVersion"_ns, buf, WinRegistry::kLegacyWinUtilsStringFlags)) {
+    MOZ_LOG(gMouseScrollLog, LogLevel::Info,
+            ("MouseScroll::Device::SynTP::Init(): "
+             "SynTP driver is not found"));
+    return;
+  }
+
+  sMajorVersion = wcstol(buf, nullptr, 10);
+  sMinorVersion = 0;
+  wchar_t* p = wcschr(buf, L'.');
+  if (p) {
+    sMinorVersion = wcstol(p + 1, nullptr, 10);
+  }
+  MOZ_LOG(gMouseScrollLog, LogLevel::Info,
+          ("MouseScroll::Device::SynTP::Init(): "
+           "found driver version = %d.%d",
+           sMajorVersion, sMinorVersion));
+}
+
+/******************************************************************************
+ *
+ * Device::Elantech
+ *
+ ******************************************************************************/
+
+/* static */
+void MouseScrollHandler::Device::Elantech::Init() {
+  int32_t version = GetDriverMajorVersion();
+  bool needsHack = Device::GetWorkaroundPref(
+      "ui.elantech_gesture_hacks.enabled", version != 0);
+  sUseSwipeHack = needsHack && version <= 7;
+  sUsePinchHack = needsHack && version <= 8;
+
+  MOZ_LOG(
+      gMouseScrollLog, LogLevel::Info,
+      ("MouseScroll::Device::Elantech::Init(): version=%d, sUseSwipeHack=%s, "
+       "sUsePinchHack=%s",
+       version, GetBoolName(sUseSwipeHack), GetBoolName(sUsePinchHack)));
+}
+
+/* static */
+int32_t MouseScrollHandler::Device::Elantech::GetDriverMajorVersion() {
+  wchar_t buf[40];
+  // The driver version is found in one of these two registry keys.
+  if (!WinRegistry::GetString(
+          HKEY_CURRENT_USER, u"Software\\Elantech\\MainOption"_ns,
+          u"DriverVersion"_ns, buf, WinRegistry::kLegacyWinUtilsStringFlags) &&
+      !WinRegistry::GetString(HKEY_CURRENT_USER, u"Software\\Elantech"_ns,
+                              u"DriverVersion"_ns, buf,
+                              WinRegistry::kLegacyWinUtilsStringFlags)) {
+    return 0;
+  }
+
+  // Assume that the major version number can be found just after a space
+  // or at the start of the string.
+  for (wchar_t* p = buf; *p; p++) {
+    if (*p >= L'0' && *p <= L'9' && (p == buf || *(p - 1) == L' ')) {
+      return wcstol(p, nullptr, 10);
+    }
+  }
+
+  return 0;
+}
+
+/* static */
+bool MouseScrollHandler::Device::Elantech::IsHelperWindow(HWND aWnd) {
+  // The helper window cannot be distinguished based on its window class, so we
+  // need to check if it is owned by the helper process, ETDCtrl.exe.
+
+  const wchar_t* filenameSuffix = L"\\etdctrl.exe";
+  const int filenameSuffixLength = 12;
+
+  DWORD pid;
+  ::GetWindowThreadProcessId(aWnd, &pid);
+
+  HANDLE hProcess = ::OpenProcess(PROCESS_QUERY_INFORMATION, FALSE, pid);
+  if (!hProcess) {
+    return false;
+  }
+
+  bool result = false;
+  wchar_t path[256] = {L'\0'};
+  if (::GetProcessImageFileNameW(hProcess, path, ArrayLength(path))) {
+    int pathLength = lstrlenW(path);
+    if (pathLength >= filenameSuffixLength) {
+      if (lstrcmpiW(path + pathLength - filenameSuffixLength, filenameSuffix) ==
+          0) {
+        result = true;
+      }
+    }
+  }
+  ::CloseHandle(hProcess);
+
+  return result;
+}
+
+/* static */
+bool MouseScrollHandler::Device::Elantech::HandleKeyMessage(nsWindow* aWidget,
+                                                            UINT aMsg,
+                                                            WPARAM aWParam,
+                                                            LPARAM aLParam) {
+  // The Elantech touchpad driver understands three-finger swipe left and
+  // right gestures, and translates them into Page Up and Page Down key
+  // events for most applications.  For Firefox 3.6, it instead sends
+  // Alt+Left and Alt+Right to trigger browser back/forward actions.  As
+  // with the Thinkpad Driver hack in nsWindow::Create, the change in
+  // HWND structure makes Firefox not trigger the driver's heuristics
+  // any longer.
+  //
+  // The Elantech driver actually sends these messages for a three-finger
+  // swipe right:
+  //
+  //   WM_KEYDOWN virtual_key = 0xCC or 0xFF ScanCode = 00
+  //   WM_KEYDOWN virtual_key = VK_NEXT      ScanCode = 00
+  //   WM_KEYUP   virtual_key = VK_NEXT      ScanCode = 00
+  //   WM_KEYUP   virtual_key = 0xCC or 0xFF ScanCode = 00
+  //
+  // Whether 0xCC or 0xFF is sent is suspected to depend on the driver
+  // version.  7.0.4.12_14Jul09_WHQL, 7.0.5.10, and 7.0.6.0 generate 0xCC.
+  // 7.0.4.3 from Asus on EeePC generates 0xFF.
+  //
+  // On some hardware, IS_VK_DOWN(0xFF) returns true even when Elantech
+  // messages are not involved, meaning that alone is not enough to
+  // distinguish the gesture from a regular Page Up or Page Down key press.
+  // The ScanCode is therefore also tested to detect the gesture.
+  // We then pretend that we should dispatch "Go Forward" command.  Similarly
+  // for VK_PRIOR and "Go Back" command.
+  if (sUseSwipeHack && (aWParam == VK_NEXT || aWParam == VK_PRIOR) &&
+      WinUtils::GetScanCode(aLParam) == 0 &&
+      (IS_VK_DOWN(0xFF) || IS_VK_DOWN(0xCC))) {
+    if (aMsg == WM_KEYDOWN) {
+      MOZ_LOG(gMouseScrollLog, LogLevel::Info,
+              ("MouseScroll::Device::Elantech::HandleKeyMessage(): Dispatching "
+               "%s command event",
+               aWParam == VK_NEXT ? "Forward" : "Back"));
+
+      WidgetCommandEvent appCommandEvent(
+          true, (aWParam == VK_NEXT) ? nsGkAtoms::Forward : nsGkAtoms::Back,
+          aWidget);
+
+      // In this scenario, the coordinate of the event isn't supplied, so pass
+      // nullptr as an argument to indicate using the coordinate from the last
+      // available window message.
+      InitEvent(aWidget, appCommandEvent, nullptr);
+      aWidget->DispatchWindowEvent(appCommandEvent);
+    } else {
+      MOZ_LOG(gMouseScrollLog, LogLevel::Info,
+              ("MouseScroll::Device::Elantech::HandleKeyMessage(): Consumed"));
+    }
+    return true;  // consume the message (doesn't need to dispatch key events)
+  }
+
+  // Version 8 of the Elantech touchpad driver sends these messages for
+  // zoom gestures:
+  //
+  //   WM_KEYDOWN    virtual_key = 0xCC        time = 10
+  //   WM_KEYDOWN    virtual_key = VK_CONTROL  time = 10
+  //   WM_MOUSEWHEEL                           time = ::GetTickCount()
+  //   WM_KEYUP      virtual_key = VK_CONTROL  time = 10
+  //   WM_KEYUP      virtual_key = 0xCC        time = 10
+  //
+  // The result of this is that we process all of the WM_KEYDOWN/WM_KEYUP
+  // messages first because their timestamps make them appear to have
+  // been sent before the WM_MOUSEWHEEL message.  To work around this,
+  // we store the current time when we process the WM_KEYUP message and
+  // assume that any WM_MOUSEWHEEL message with a timestamp before that
+  // time is one that should be processed as if the Control key was down.
+  if (sUsePinchHack && aMsg == WM_KEYUP && aWParam == VK_CONTROL &&
+      ::GetMessageTime() == 10) {
+    // We look only at the bottom 31 bits of the system tick count since
+    // GetMessageTime returns a LONG, which is signed, so we want values
+    // that are more easily comparable.
+    sZoomUntil = ::GetTickCount() & 0x7FFFFFFF;
+
+    MOZ_LOG(
+        gMouseScrollLog, LogLevel::Info,
+        ("MouseScroll::Device::Elantech::HandleKeyMessage(): sZoomUntil=%lu",
+         sZoomUntil));
+  }
+
+  return false;
+}
+
+/* static */
+void MouseScrollHandler::Device::Elantech::UpdateZoomUntil() {
+  if (!sZoomUntil) {
+    return;
+  }
+
+  // For the Elantech Touchpad Zoom Gesture Hack, we should check that the
+  // system time (32-bit milliseconds) hasn't wrapped around.  Otherwise we
+  // might get into the situation where wheel events for the next 50 days of
+  // system uptime are assumed to be Ctrl+Wheel events.  (It is unlikely that
+  // we would get into that state, because the system would already need to be
+  // up for 50 days and the Control key message would need to be processed just
+  // before the system time overflow and the wheel message just after.)
+  //
+  // We also take the chance to reset sZoomUntil if we simply have passed that
+  // time.
+  LONG msgTime = ::GetMessageTime();
+  if ((sZoomUntil >= 0x3fffffffu && DWORD(msgTime) < 0x40000000u) ||
+      (sZoomUntil < DWORD(msgTime))) {
+    sZoomUntil = 0;
+
+    MOZ_LOG(gMouseScrollLog, LogLevel::Info,
+            ("MouseScroll::Device::Elantech::UpdateZoomUntil(): "
+             "sZoomUntil was reset"));
+  }
+}
+
+/* static */
+bool MouseScrollHandler::Device::Elantech::IsZooming() {
+  // Assume the Control key is down if the Elantech touchpad has sent the
+  // mis-ordered WM_KEYDOWN/WM_MOUSEWHEEL messages.  (See the comment in
+  // OnKeyUp.)
+  return (sZoomUntil && static_cast<DWORD>(::GetMessageTime()) < sZoomUntil);
+}
+
+/******************************************************************************
+ *
+ * Device::Apoint
+ *
+ ******************************************************************************/
+
+/* static */
+void MouseScrollHandler::Device::Apoint::Init() {
+  if (sInitialized) {
+    return;
+  }
+
+  sInitialized = true;
+  sMajorVersion = 0;
+  sMinorVersion = -1;
+
+  wchar_t buf[40];
+  if (!WinRegistry::GetString(HKEY_LOCAL_MACHINE, u"Software\\Alps\\Apoint"_ns,
+                              u"ProductVer"_ns, buf,
+                              WinRegistry::kLegacyWinUtilsStringFlags)) {
+    MOZ_LOG(gMouseScrollLog, LogLevel::Info,
+            ("MouseScroll::Device::Apoint::Init(): "
+             "Apoint driver is not found"));
+    return;
+  }
+
+  sMajorVersion = wcstol(buf, nullptr, 10);
+  sMinorVersion = 0;
+  wchar_t* p = wcschr(buf, L'.');
+  if (p) {
+    sMinorVersion = wcstol(p + 1, nullptr, 10);
+  }
+  MOZ_LOG(gMouseScrollLog, LogLevel::Info,
+          ("MouseScroll::Device::Apoint::Init(): "
+           "found driver version = %d.%d",
+           sMajorVersion, sMinorVersion));
+}
+
+/******************************************************************************
+ *
+ * Device::TrackPoint
+ *
+ ******************************************************************************/
+
+/* static */
+bool MouseScrollHandler::Device::TrackPoint::IsDriverInstalled() {
+  if (WinRegistry::HasKey(HKEY_CURRENT_USER,
+                          u"Software\\Lenovo\\TrackPoint"_ns)) {
+    MOZ_LOG(gMouseScrollLog, LogLevel::Info,
+            ("MouseScroll::Device::TrackPoint::IsDriverInstalled(): "
+             "Lenovo's TrackPoint driver is found"));
+    return true;
+  }
+
+  if (WinRegistry::HasKey(HKEY_CURRENT_USER,
+                          u"Software\\Alps\\Apoint\\TrackPoint"_ns)) {
+    MOZ_LOG(gMouseScrollLog, LogLevel::Info,
+            ("MouseScroll::Device::TrackPoint::IsDriverInstalled(): "
+             "Alps's TrackPoint driver is found"));
+    return true;
+  }
+
+  return false;
+}
+
+/******************************************************************************
+ *
+ * Device::UltraNav
+ *
+ ******************************************************************************/
+
+/* static */
+bool MouseScrollHandler::Device::UltraNav::IsObsoleteDriverInstalled() {
+  if (WinRegistry::HasKey(HKEY_CURRENT_USER,
+                          u"Software\\Lenovo\\UltraNav"_ns)) {
+    MOZ_LOG(gMouseScrollLog, LogLevel::Info,
+            ("MouseScroll::Device::UltraNav::IsObsoleteDriverInstalled(): "
+             "Lenovo's UltraNav driver is found"));
+    return true;
+  }
+
+  bool installed = false;
+  if (WinRegistry::HasKey(HKEY_CURRENT_USER,
+                          u"Software\\Synaptics\\SynTPEnh\\UltraNavUSB"_ns)) {
+    MOZ_LOG(gMouseScrollLog, LogLevel::Info,
+            ("MouseScroll::Device::UltraNav::IsObsoleteDriverInstalled(): "
+             "Synaptics's UltraNav (USB) driver is found"));
+    installed = true;
+  } else if (WinRegistry::HasKey(
+                 HKEY_CURRENT_USER,
+                 u"Software\\Synaptics\\SynTPEnh\\UltraNavPS2"_ns)) {
+    MOZ_LOG(gMouseScrollLog, LogLevel::Info,
+            ("MouseScroll::Device::UltraNav::IsObsoleteDriverInstalled(): "
+             "Synaptics's UltraNav (PS/2) driver is found"));
+    installed = true;
+  }
+
+  if (!installed) {
+    return false;
+  }
+
+  int32_t majorVersion = Device::SynTP::GetDriverMajorVersion();
+  if (!majorVersion) {
+    MOZ_LOG(gMouseScrollLog, LogLevel::Info,
+            ("MouseScroll::Device::UltraNav::IsObsoleteDriverInstalled(): "
+             "Failed to get UltraNav driver version"));
+    return false;
+  }
+  int32_t minorVersion = Device::SynTP::GetDriverMinorVersion();
+  return majorVersion < 15 || (majorVersion == 15 && minorVersion == 0);
+}
+
+/******************************************************************************
+ *
+ * Device::SetPoint
+ *
+ ******************************************************************************/
+
+/* static */
+bool MouseScrollHandler::Device::SetPoint::IsGetMessagePosResponseValid(
+    UINT aMessage, WPARAM aWParam, LPARAM aLParam) {
+  if (aMessage != WM_MOUSEHWHEEL) {
+    return false;
+  }
+
+  POINTS pts = MouseScrollHandler::GetCurrentMessagePos();
+  LPARAM messagePos = MAKELPARAM(pts.x, pts.y);
+
+  // XXX We should check whether SetPoint is installed or not by registry.
+
+  // SetPoint, Logitech (Logicool) mouse driver, (confirmed with 4.82.11 and
+  // MX-1100) always sets 0 to the lParam of WM_MOUSEHWHEEL.  The driver SENDs
+  // one message at first time, this time, ::GetMessagePos() works fine.
+  // Then, we will return 0 (0 means we process it) to the message. Then, the
+  // driver will POST the same messages continuously during the wheel tilted.
+  // But ::GetMessagePos() API always returns (0, 0) for them, even if the
+  // actual mouse cursor isn't 0,0.  Therefore, we cannot trust the result of
+  // ::GetMessagePos API if the sender is SetPoint.
+  if (!sMightBeUsing && !aLParam && aLParam != messagePos &&
+      ::InSendMessage()) {
+    sMightBeUsing = true;
+    MOZ_LOG(gMouseScrollLog, LogLevel::Info,
+            ("MouseScroll::Device::SetPoint::IsGetMessagePosResponseValid(): "
+             "Might using SetPoint"));
+  } else if (sMightBeUsing && aLParam != 0 && ::InSendMessage()) {
+    // The user has changed the mouse from Logitech's to another one (e.g.,
+    // the user has changed to the touchpad of the notebook.
+    sMightBeUsing = false;
+    MOZ_LOG(gMouseScrollLog, LogLevel::Info,
+            ("MouseScroll::Device::SetPoint::IsGetMessagePosResponseValid(): "
+             "Might stop using SetPoint"));
+  }
+  return (sMightBeUsing && !aLParam && !messagePos);
+}
+
+/******************************************************************************
+ *
+ * SynthesizingEvent
+ *
+ ******************************************************************************/
+
+/* static */
+bool MouseScrollHandler::SynthesizingEvent::IsSynthesizing() {
+  return MouseScrollHandler::sInstance &&
+         MouseScrollHandler::sInstance->mSynthesizingEvent &&
+         MouseScrollHandler::sInstance->mSynthesizingEvent->mStatus !=
+             NOT_SYNTHESIZING;
+}
+
+nsresult MouseScrollHandler::SynthesizingEvent::Synthesize(
+    const POINTS& aCursorPoint, HWND aWnd, UINT aMessage, WPARAM aWParam,
+    LPARAM aLParam, const BYTE (&aKeyStates)[256]) {
+  MOZ_LOG(
+      gMouseScrollLog, LogLevel::Info,
+      ("MouseScrollHandler::SynthesizingEvent::Synthesize(): aCursorPoint: { "
+       "x: %d, y: %d }, aWnd=0x%p, aMessage=0x%04X, aWParam=0x%08zX, "
+       "aLParam=0x%08" PRIXLPTR ", IsSynthesized()=%s, mStatus=%s",
+       aCursorPoint.x, aCursorPoint.y, aWnd, aMessage, aWParam, aLParam,
+       GetBoolName(IsSynthesizing()), GetStatusName()));
+
+  if (IsSynthesizing()) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  ::GetKeyboardState(mOriginalKeyState);
+
+  // Note that we cannot use ::SetCursorPos() because it works asynchronously.
+  // We should SEND the message for reducing the possibility of receiving
+  // unexpected message which were not sent from here.
+  mCursorPoint = aCursorPoint;
+
+  mWnd = aWnd;
+  mMessage = aMessage;
+  mWParam = aWParam;
+  mLParam = aLParam;
+
+  memcpy(mKeyState, aKeyStates, sizeof(mKeyState));
+  ::SetKeyboardState(mKeyState);
+
+  mStatus = SENDING_MESSAGE;
+
+  // Don't assume that aWnd is always managed by nsWindow.  It might be
+  // a plugin window.
+  ::SendMessage(aWnd, aMessage, aWParam, aLParam);
+
+  return NS_OK;
+}
+
+void MouseScrollHandler::SynthesizingEvent::NativeMessageReceived(
+    nsWindow* aWidget, UINT aMessage, WPARAM aWParam, LPARAM aLParam) {
+  if (mStatus == SENDING_MESSAGE && mMessage == aMessage &&
+      mWParam == aWParam && mLParam == aLParam) {
+    mStatus = NATIVE_MESSAGE_RECEIVED;
+    if (aWidget && aWidget->GetWindowHandle() == mWnd) {
+      return;
+    }
+    // Otherwise, the message may not be sent by us.
+  }
+
+  MOZ_LOG(gMouseScrollLog, LogLevel::Info,
+          ("MouseScrollHandler::SynthesizingEvent::NativeMessageReceived(): "
+           "aWidget=%p, aWidget->GetWindowHandle()=0x%p, mWnd=0x%p, "
+           "aMessage=0x%04X, aWParam=0x%08zX, aLParam=0x%08" PRIXLPTR
+           ", mStatus=%s",
+           aWidget, aWidget ? aWidget->GetWindowHandle() : nullptr, mWnd,
+           aMessage, aWParam, aLParam, GetStatusName()));
+
+  // We failed to receive our sent message, we failed to do the job.
+  Finish();
+
+  return;
+}
+
+void MouseScrollHandler::SynthesizingEvent::
+    NotifyNativeMessageHandlingFinished() {
+  if (!IsSynthesizing()) {
+    return;
+  }
+
+  MOZ_LOG(gMouseScrollLog, LogLevel::Info,
+          ("MouseScrollHandler::SynthesizingEvent::"
+           "NotifyNativeMessageHandlingFinished(): IsWaitingInternalMessage=%s",
+           GetBoolName(MouseScrollHandler::IsWaitingInternalMessage())));
+
+  if (MouseScrollHandler::IsWaitingInternalMessage()) {
+    mStatus = INTERNAL_MESSAGE_POSTED;
+    return;
+  }
+
+  // If the native message handler didn't post our internal message,
+  // we our job is finished.
+  // TODO: When we post the message to plugin window, there is remaning job.
+  Finish();
+}
+
+void MouseScrollHandler::SynthesizingEvent::
+    NotifyInternalMessageHandlingFinished() {
+  if (!IsSynthesizing()) {
+    return;
+  }
+
+  MOZ_LOG(gMouseScrollLog, LogLevel::Info,
+          ("MouseScrollHandler::SynthesizingEvent::"
+           "NotifyInternalMessageHandlingFinished()"));
+
+  Finish();
+}
+
+void MouseScrollHandler::SynthesizingEvent::Finish() {
+  if (!IsSynthesizing()) {
+    return;
+  }
+
+  MOZ_LOG(gMouseScrollLog, LogLevel::Info,
+          ("MouseScrollHandler::SynthesizingEvent::Finish()"));
+
+  // Restore the original key state.
+  ::SetKeyboardState(mOriginalKeyState);
+
+  mStatus = NOT_SYNTHESIZING;
+}
+
+}  // namespace widget
+}  // namespace mozilla
diff --git a/widget/windows/WinMouseScrollHandler.h b/widget/windows/WinMouseScrollHandler.h
new file mode 100644
index 0000000000..ecf6c3df44
--- /dev/null
+++ b/widget/windows/WinMouseScrollHandler.h
@@ -0,0 +1,567 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_widget_WinMouseScrollHandler_h__
+#define mozilla_widget_WinMouseScrollHandler_h__
+
+#include "nscore.h"
+#include "nsDebug.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/EventForwards.h"
+#include "mozilla/TimeStamp.h"
+#include "Units.h"
+#include <windows.h>
+#include "nsPoint.h"
+
+class nsWindow;
+
+namespace mozilla {
+namespace widget {
+
+class ModifierKeyState;
+
+struct MSGResult;
+
+class MouseScrollHandler {
+ public:
+  static MouseScrollHandler* GetInstance();
+
+  static void Initialize();
+  static void Shutdown();
+
+  static bool NeedsMessage(UINT aMsg);
+  static bool ProcessMessage(nsWindow* aWidget, UINT msg, WPARAM wParam,
+                             LPARAM lParam, MSGResult& aResult);
+
+  /**
+   * See nsIWidget::SynthesizeNativeMouseScrollEvent() for the detail about
+   * this method.
+   */
+  static nsresult SynthesizeNativeMouseScrollEvent(
+      nsWindow* aWidget, const LayoutDeviceIntPoint& aPoint,
+      uint32_t aNativeMessage, int32_t aDelta, uint32_t aModifierFlags,
+      uint32_t aAdditionalFlags);
+
+  /**
+   * IsWaitingInternalMessage() returns true if MouseScrollHandler posted
+   * an internal message for a native mouse wheel message and has not
+   * received it. Otherwise, false.
+   */
+  static bool IsWaitingInternalMessage() {
+    return sInstance && sInstance->mIsWaitingInternalMessage;
+  }
+
+ private:
+  MouseScrollHandler();
+  ~MouseScrollHandler();
+
+  bool mIsWaitingInternalMessage;
+
+  static void MaybeLogKeyState();
+
+  static MouseScrollHandler* sInstance;
+
+  /**
+   * InitEvent() initializes the aEvent.  If aPoint is null, the result of
+   * GetCurrentMessagePos() will be used.
+   */
+  static void InitEvent(nsWindow* aWidget, WidgetGUIEvent& aEvent,
+                        LPARAM* aPoint);
+
+  /**
+   * GetModifierKeyState() returns current modifier key state.
+   * Note that some devices need some hack for the modifier key state.
+   * This method does it automatically.
+   *
+   * @param aMessage    Handling message.
+   */
+  static ModifierKeyState GetModifierKeyState(UINT aMessage);
+
+  /**
+   * MozGetMessagePos() returns the mouse cursor position when GetMessage()
+   * was called last time.  However, if we're sending a native message,
+   * this returns the specified cursor position by
+   * SynthesizeNativeMouseScrollEvent().
+   */
+  static POINTS GetCurrentMessagePos();
+
+  /**
+   * ProcessNativeMouseWheelMessage() processes WM_MOUSEWHEEL and
+   * WM_MOUSEHWHEEL.  Additionally, processes WM_VSCROLL and WM_HSCROLL if they
+   * should be processed as mouse wheel message.
+   * This method posts MOZ_WM_MOUSEVWHEEL, MOZ_WM_MOUSEHWHEEL,
+   * MOZ_WM_VSCROLL or MOZ_WM_HSCROLL if we need to dispatch mouse scroll
+   * events.  That avoids deadlock with plugin process.
+   *
+   * @param aWidget     A window which receives the message.
+   * @param aMessage    WM_MOUSEWHEEL, WM_MOUSEHWHEEL, WM_VSCROLL or
+   *                    WM_HSCROLL.
+   * @param aWParam     The wParam value of the message.
+   * @param aLParam     The lParam value of the message.
+   */
+  void ProcessNativeMouseWheelMessage(nsWindow* aWidget, UINT aMessage,
+                                      WPARAM aWParam, LPARAM aLParam);
+
+  /**
+   * ProcessNativeScrollMessage() processes WM_VSCROLL and WM_HSCROLL.
+   * This method just call ProcessMouseWheelMessage() if the message should be
+   * processed as mouse wheel message.  Otherwise, dispatches a content
+   * command event.
+   *
+   * @param aWidget     A window which receives the message.
+   * @param aMessage    WM_VSCROLL or WM_HSCROLL.
+   * @param aWParam     The wParam value of the message.
+   * @param aLParam     The lParam value of the message.
+   * @return            TRUE if the message is processed.  Otherwise, FALSE.
+   */
+  bool ProcessNativeScrollMessage(nsWindow* aWidget, UINT aMessage,
+                                  WPARAM aWParam, LPARAM aLParam);
+
+  /**
+   * HandleMouseWheelMessage() processes MOZ_WM_MOUSEVWHEEL and
+   * MOZ_WM_MOUSEHWHEEL which are posted when one of our windows received
+   * WM_MOUSEWHEEL or WM_MOUSEHWHEEL for avoiding deadlock with OOPP.
+   *
+   * @param aWidget     A window which receives the wheel message.
+   * @param aMessage    MOZ_WM_MOUSEWHEEL or MOZ_WM_MOUSEHWHEEL.
+   * @param aWParam     The wParam value of the original message.
+   * @param aLParam     The lParam value of the original message.
+   */
+  void HandleMouseWheelMessage(nsWindow* aWidget, UINT aMessage, WPARAM aWParam,
+                               LPARAM aLParam);
+
+  /**
+   * HandleScrollMessageAsMouseWheelMessage() processes the MOZ_WM_VSCROLL and
+   * MOZ_WM_HSCROLL which are posted when one of mouse windows received
+   * WM_VSCROLL or WM_HSCROLL and user wants them to emulate mouse wheel
+   * message's behavior.
+   *
+   * @param aWidget     A window which receives the scroll message.
+   * @param aMessage    MOZ_WM_VSCROLL or MOZ_WM_HSCROLL.
+   * @param aWParam     The wParam value of the original message.
+   * @param aLParam     The lParam value of the original message.
+   */
+  void HandleScrollMessageAsMouseWheelMessage(nsWindow* aWidget, UINT aMessage,
+                                              WPARAM aWParam, LPARAM aLParam);
+
+  /**
+   * ComputeMessagePos() computes the cursor position when the message was
+   * added to the queue.
+   *
+   * @param aMessage    Handling message.
+   * @param aWParam     Handling message's wParam.
+   * @param aLParam     Handling message's lParam.
+   * @return            Mouse cursor position when the message is added to
+   *                    the queue or current cursor position if the result of
+   *                    ::GetMessagePos() is broken.
+   */
+  POINT ComputeMessagePos(UINT aMessage, WPARAM aWParam, LPARAM aLParam);
+
+  class EventInfo {
+   public:
+    /**
+     * @param aWidget   An nsWindow which is handling the event.
+     * @param aMessage  Must be WM_MOUSEWHEEL or WM_MOUSEHWHEEL.
+     */
+    EventInfo(nsWindow* aWidget, UINT aMessage, WPARAM aWParam, LPARAM aLParam);
+
+    bool CanDispatchWheelEvent() const;
+
+    int32_t GetNativeDelta() const { return mDelta; }
+    HWND GetWindowHandle() const { return mWnd; }
+    const TimeStamp& GetTimeStamp() const { return mTimeStamp; }
+    bool IsVertical() const { return mIsVertical; }
+    bool IsPositive() const { return (mDelta > 0); }
+    bool IsPage() const { return mIsPage; }
+
+    /**
+     * @return          Number of lines or pages scrolled per WHEEL_DELTA.
+     */
+    int32_t GetScrollAmount() const;
+
+   protected:
+    EventInfo()
+        : mIsVertical(false), mIsPage(false), mDelta(0), mWnd(nullptr) {}
+
+    // TRUE if event is for vertical scroll.  Otherwise, FALSE.
+    bool mIsVertical;
+    // TRUE if event scrolls per page, otherwise, FALSE.
+    bool mIsPage;
+    // The native delta value.
+    int32_t mDelta;
+    // The window handle which is handling the event.
+    HWND mWnd;
+    // Timestamp of the event.
+    TimeStamp mTimeStamp;
+  };
+
+  class LastEventInfo : public EventInfo {
+   public:
+    LastEventInfo() : EventInfo(), mAccumulatedDelta(0) {}
+
+    /**
+     * CanContinueTransaction() checks whether the new event can continue the
+     * last transaction or not.  Note that if there is no transaction, this
+     * returns true.
+     */
+    bool CanContinueTransaction(const EventInfo& aNewEvent);
+
+    /**
+     * ResetTransaction() resets the transaction, i.e., the instance forgets
+     * the last event information.
+     */
+    void ResetTransaction();
+
+    /**
+     * RecordEvent() saves the information of new event.
+     */
+    void RecordEvent(const EventInfo& aEvent);
+
+    /**
+     * InitWheelEvent() initializes NS_WHEEL_WHEEL event and
+     * recomputes the remaning detla for the event.
+     * This must be called only once during handling a message and after
+     * RecordEvent() is called.
+     *
+     * @param aWidget           A window which will dispatch the event.
+     * @param aWheelEvent       An NS_WHEEL_WHEEL event, this will be
+     *                          initialized.
+     * @param aModKeyState      Current modifier key state.
+     * @return                  TRUE if the event is ready to dispatch.
+     *                          Otherwise, FALSE.
+     */
+    bool InitWheelEvent(nsWindow* aWidget, WidgetWheelEvent& aWheelEvent,
+                        const ModifierKeyState& aModKeyState, LPARAM aLParam);
+
+   private:
+    static int32_t RoundDelta(double aDelta);
+
+    int32_t mAccumulatedDelta;
+  };
+
+  LastEventInfo mLastEventInfo;
+
+  class SystemSettings {
+   public:
+    SystemSettings() : mInitialized(false) {}
+
+    void Init();
+    void MarkDirty();
+    void NotifyUserPrefsMayOverrideSystemSettings();
+
+    // On some environments, SystemParametersInfo() may be hooked by touchpad
+    // utility or something.  In such case, when user changes active pointing
+    // device to another one, the result of SystemParametersInfo() may be
+    // changed without WM_SETTINGCHANGE message.  For avoiding this trouble,
+    // we need to modify cache of system settings at every wheel message
+    // handling if we meet known device whose utility may hook the API.
+    void TrustedScrollSettingsDriver();
+
+    int32_t GetScrollAmount(bool aForVertical) const {
+      MOZ_ASSERT(mInitialized, "SystemSettings must be initialized");
+      return aForVertical ? mScrollLines : mScrollChars;
+    }
+
+    bool IsPageScroll(bool aForVertical) const {
+      MOZ_ASSERT(mInitialized, "SystemSettings must be initialized");
+      return aForVertical ? (uint32_t(mScrollLines) == WHEEL_PAGESCROLL)
+                          : (uint32_t(mScrollChars) == WHEEL_PAGESCROLL);
+    }
+
+    // The default vertical and horizontal scrolling speed is 3, this is defined
+    // on the document of SystemParametersInfo in MSDN.
+    static int32_t DefaultScrollLines() { return 3; }
+
+   private:
+    bool mInitialized;
+    // The result of SystemParametersInfo() may not be reliable since it may
+    // be hooked.  So, if the values are initialized with prefs, we can trust
+    // the value.  Following mIsReliableScroll* are set true when mScroll* are
+    // initialized with prefs.
+    bool mIsReliableScrollLines;
+    bool mIsReliableScrollChars;
+
+    int32_t mScrollLines;
+    int32_t mScrollChars;
+
+    // Returns true if cached value is changed.
+    bool InitScrollLines();
+    bool InitScrollChars();
+
+    void RefreshCache();
+  };
+
+  SystemSettings mSystemSettings;
+
+  class UserPrefs {
+   public:
+    UserPrefs();
+    ~UserPrefs();
+
+    void MarkDirty();
+
+    bool IsScrollMessageHandledAsWheelMessage() {
+      Init();
+      return mScrollMessageHandledAsWheelMessage;
+    }
+
+    bool IsSystemSettingCacheEnabled() {
+      Init();
+      return mEnableSystemSettingCache;
+    }
+
+    bool IsSystemSettingCacheForciblyEnabled() {
+      Init();
+      return mForceEnableSystemSettingCache;
+    }
+
+    bool ShouldEmulateToMakeWindowUnderCursorForeground() {
+      Init();
+      return mEmulateToMakeWindowUnderCursorForeground;
+    }
+
+    int32_t GetOverriddenVerticalScrollAmout() {
+      Init();
+      return mOverriddenVerticalScrollAmount;
+    }
+
+    int32_t GetOverriddenHorizontalScrollAmout() {
+      Init();
+      return mOverriddenHorizontalScrollAmount;
+    }
+
+    int32_t GetMouseScrollTransactionTimeout() {
+      Init();
+      return mMouseScrollTransactionTimeout;
+    }
+
+   private:
+    void Init();
+
+    static void OnChange(const char* aPrefName, void* aSelf) {
+      static_cast<UserPrefs*>(aSelf)->MarkDirty();
+    }
+
+    bool mInitialized;
+    bool mScrollMessageHandledAsWheelMessage;
+    bool mEnableSystemSettingCache;
+    bool mForceEnableSystemSettingCache;
+    bool mEmulateToMakeWindowUnderCursorForeground;
+    int32_t mOverriddenVerticalScrollAmount;
+    int32_t mOverriddenHorizontalScrollAmount;
+    int32_t mMouseScrollTransactionTimeout;
+  };
+
+  UserPrefs mUserPrefs;
+
+  class SynthesizingEvent {
+   public:
+    SynthesizingEvent()
+        : mWnd(nullptr),
+          mMessage(0),
+          mWParam(0),
+          mLParam(0),
+          mStatus(NOT_SYNTHESIZING) {}
+
+    ~SynthesizingEvent() {}
+
+    static bool IsSynthesizing();
+
+    nsresult Synthesize(const POINTS& aCursorPoint, HWND aWnd, UINT aMessage,
+                        WPARAM aWParam, LPARAM aLParam,
+                        const BYTE (&aKeyStates)[256]);
+
+    void NativeMessageReceived(nsWindow* aWidget, UINT aMessage, WPARAM aWParam,
+                               LPARAM aLParam);
+
+    void NotifyNativeMessageHandlingFinished();
+    void NotifyInternalMessageHandlingFinished();
+
+    const POINTS& GetCursorPoint() const { return mCursorPoint; }
+
+   private:
+    POINTS mCursorPoint;
+    HWND mWnd;
+    UINT mMessage;
+    WPARAM mWParam;
+    LPARAM mLParam;
+    BYTE mKeyState[256];
+    BYTE mOriginalKeyState[256];
+
+    enum Status {
+      NOT_SYNTHESIZING,
+      SENDING_MESSAGE,
+      NATIVE_MESSAGE_RECEIVED,
+      INTERNAL_MESSAGE_POSTED,
+    };
+    Status mStatus;
+
+    const char* GetStatusName() {
+      switch (mStatus) {
+        case NOT_SYNTHESIZING:
+          return "NOT_SYNTHESIZING";
+        case SENDING_MESSAGE:
+          return "SENDING_MESSAGE";
+        case NATIVE_MESSAGE_RECEIVED:
+          return "NATIVE_MESSAGE_RECEIVED";
+        case INTERNAL_MESSAGE_POSTED:
+          return "INTERNAL_MESSAGE_POSTED";
+        default:
+          return "Unknown";
+      }
+    }
+
+    void Finish();
+  };  // SynthesizingEvent
+
+  SynthesizingEvent* mSynthesizingEvent;
+
+ public:
+  class Device {
+   public:
+    // SynTP is a touchpad driver of Synaptics.
+    class SynTP {
+     public:
+      static bool IsDriverInstalled() { return sMajorVersion != 0; }
+      /**
+       * GetDriverMajorVersion() returns the installed driver's major version.
+       * If SynTP driver isn't installed, this returns 0.
+       */
+      static int32_t GetDriverMajorVersion() { return sMajorVersion; }
+      /**
+       * GetDriverMinorVersion() returns the installed driver's minor version.
+       * If SynTP driver isn't installed, this returns -1.
+       */
+      static int32_t GetDriverMinorVersion() { return sMinorVersion; }
+
+      static void Init();
+
+     private:
+      static bool sInitialized;
+      static int32_t sMajorVersion;
+      static int32_t sMinorVersion;
+    };
+
+    class Elantech {
+     public:
+      /**
+       * GetDriverMajorVersion() returns the installed driver's major version.
+       * If Elantech's driver was installed, returns 0.
+       */
+      static int32_t GetDriverMajorVersion();
+
+      /**
+       * IsHelperWindow() checks whether aWnd is a helper window of Elantech's
+       * touchpad.  Returns TRUE if so.  Otherwise, FALSE.
+       */
+      static bool IsHelperWindow(HWND aWnd);
+
+      /**
+       * Key message handler for Elantech's hack.  Returns TRUE if the message
+       * is consumed by this handler.  Otherwise, FALSE.
+       */
+      static bool HandleKeyMessage(nsWindow* aWidget, UINT aMsg, WPARAM aWParam,
+                                   LPARAM aLParam);
+
+      static void UpdateZoomUntil();
+      static bool IsZooming();
+
+      static void Init();
+
+      static bool IsPinchHackNeeded() { return sUsePinchHack; }
+
+     private:
+      // Whether to enable the Elantech swipe gesture hack.
+      static bool sUseSwipeHack;
+      // Whether to enable the Elantech pinch-to-zoom gesture hack.
+      static bool sUsePinchHack;
+      static DWORD sZoomUntil;
+    };  // class Elantech
+
+    // Apoint is a touchpad driver of Alps.
+    class Apoint {
+     public:
+      static bool IsDriverInstalled() { return sMajorVersion != 0; }
+      /**
+       * GetDriverMajorVersion() returns the installed driver's major version.
+       * If Apoint driver isn't installed, this returns 0.
+       */
+      static int32_t GetDriverMajorVersion() { return sMajorVersion; }
+      /**
+       * GetDriverMinorVersion() returns the installed driver's minor version.
+       * If Apoint driver isn't installed, this returns -1.
+       */
+      static int32_t GetDriverMinorVersion() { return sMinorVersion; }
+
+      static void Init();
+
+     private:
+      static bool sInitialized;
+      static int32_t sMajorVersion;
+      static int32_t sMinorVersion;
+    };
+
+    class TrackPoint {
+     public:
+      /**
+       * IsDriverInstalled() returns TRUE if TrackPoint's driver is installed.
+       * Otherwise, returns FALSE.
+       */
+      static bool IsDriverInstalled();
+    };  // class TrackPoint
+
+    class UltraNav {
+     public:
+      /**
+       * IsObsoleteDriverInstalled() checks whether obsoleted UltraNav
+       * is installed on the environment.
+       * Returns TRUE if it was installed.  Otherwise, FALSE.
+       */
+      static bool IsObsoleteDriverInstalled();
+    };  // class UltraNav
+
+    class SetPoint {
+     public:
+      /**
+       * SetPoint, Logitech's mouse driver, may report wrong cursor position
+       * for WM_MOUSEHWHEEL message.  See comment in the implementation for
+       * the detail.
+       */
+      static bool IsGetMessagePosResponseValid(UINT aMessage, WPARAM aWParam,
+                                               LPARAM aLParam);
+
+     private:
+      static bool sMightBeUsing;
+    };
+
+    static void Init();
+
+    static bool IsFakeScrollableWindowNeeded() {
+      return sFakeScrollableWindowNeeded;
+    }
+
+   private:
+    /**
+     * Gets the bool value of aPrefName used to enable or disable an input
+     * workaround (like the Trackpoint hack).  The pref can take values 0 (for
+     * disabled), 1 (for enabled) or -1 (to automatically detect whether to
+     * enable the workaround).
+     *
+     * @param aPrefName The name of the pref.
+     * @param aValueIfAutomatic Whether the given input workaround should be
+     *                          enabled by default.
+     */
+    static bool GetWorkaroundPref(const char* aPrefName,
+                                  bool aValueIfAutomatic);
+
+    static bool sFakeScrollableWindowNeeded;
+  };  // class Device
+};
+
+}  // namespace widget
+}  // namespace mozilla
+
+#endif  // mozilla_widget_WinMouseScrollHandler_h__
diff --git a/widget/windows/WinPointerEvents.cpp b/widget/windows/WinPointerEvents.cpp
new file mode 100644
index 0000000000..57e19a0c4b
--- /dev/null
+++ b/widget/windows/WinPointerEvents.cpp
@@ -0,0 +1,181 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/*
+ * WinPointerEvents - Helper functions to retrieve PointerEvent's attributes
+ */
+
+#include "nscore.h"
+#include "nsWindowDefs.h"
+#include "WinPointerEvents.h"
+#include "WinUtils.h"
+#include "mozilla/MouseEvents.h"
+#include "mozilla/StaticPrefs_dom.h"
+#include "mozilla/dom/MouseEventBinding.h"
+
+using namespace mozilla;
+using namespace mozilla::widget;
+
+const wchar_t WinPointerEvents::kPointerLibraryName[] = L"user32.dll";
+HMODULE WinPointerEvents::sLibraryHandle = nullptr;
+WinPointerEvents::GetPointerTypePtr WinPointerEvents::getPointerType = nullptr;
+WinPointerEvents::GetPointerInfoPtr WinPointerEvents::getPointerInfo = nullptr;
+WinPointerEvents::GetPointerPenInfoPtr WinPointerEvents::getPointerPenInfo =
+    nullptr;
+
+WinPointerEvents::WinPointerEvents() { InitLibrary(); }
+
+/* Load and shutdown */
+void WinPointerEvents::InitLibrary() {
+  MOZ_ASSERT(XRE_IsParentProcess());
+  if (getPointerType) {
+    // Return if we already initialized the PointerEvent related interfaces
+    return;
+  }
+  sLibraryHandle = ::LoadLibraryW(kPointerLibraryName);
+  MOZ_ASSERT(sLibraryHandle, "cannot load pointer library");
+  if (sLibraryHandle) {
+    getPointerType =
+        (GetPointerTypePtr)GetProcAddress(sLibraryHandle, "GetPointerType");
+    getPointerInfo =
+        (GetPointerInfoPtr)GetProcAddress(sLibraryHandle, "GetPointerInfo");
+    getPointerPenInfo = (GetPointerPenInfoPtr)GetProcAddress(
+        sLibraryHandle, "GetPointerPenInfo");
+  }
+
+  if (!getPointerType || !getPointerInfo || !getPointerPenInfo) {
+    MOZ_ASSERT(false, "get PointerEvent interfaces failed");
+    getPointerType = nullptr;
+    getPointerInfo = nullptr;
+    getPointerPenInfo = nullptr;
+    return;
+  }
+}
+
+bool WinPointerEvents::ShouldHandleWinPointerMessages(UINT aMsg,
+                                                      WPARAM aWParam) {
+  MOZ_ASSERT(aMsg == WM_POINTERDOWN || aMsg == WM_POINTERUP ||
+             aMsg == WM_POINTERUPDATE || aMsg == WM_POINTERLEAVE);
+  if (!sLibraryHandle) {
+    return false;
+  }
+
+  // We only handle WM_POINTER* when the input source is pen. This is because
+  // we need some information (e.g. tiltX, tiltY) which can't be retrieved by
+  // WM_*BUTTONDOWN.
+  uint32_t pointerId = GetPointerId(aWParam);
+  POINTER_INPUT_TYPE pointerType = PT_POINTER;
+  if (!GetPointerType(pointerId, &pointerType)) {
+    MOZ_ASSERT(false, "cannot find PointerType");
+    return false;
+  }
+  return (pointerType == PT_PEN);
+}
+
+bool WinPointerEvents::GetPointerType(uint32_t aPointerId,
+                                      POINTER_INPUT_TYPE* aPointerType) {
+  if (!getPointerType) {
+    return false;
+  }
+  return getPointerType(aPointerId, aPointerType);
+}
+
+POINTER_INPUT_TYPE
+WinPointerEvents::GetPointerType(uint32_t aPointerId) {
+  POINTER_INPUT_TYPE pointerType = PT_POINTER;
+  Unused << GetPointerType(aPointerId, &pointerType);
+  return pointerType;
+}
+
+bool WinPointerEvents::GetPointerInfo(uint32_t aPointerId,
+                                      POINTER_INFO* aPointerInfo) {
+  if (!getPointerInfo) {
+    return false;
+  }
+  return getPointerInfo(aPointerId, aPointerInfo);
+}
+
+bool WinPointerEvents::GetPointerPenInfo(uint32_t aPointerId,
+                                         POINTER_PEN_INFO* aPenInfo) {
+  if (!getPointerPenInfo) {
+    return false;
+  }
+  return getPointerPenInfo(aPointerId, aPenInfo);
+}
+
+bool WinPointerEvents::ShouldRollupOnPointerEvent(UINT aMsg, WPARAM aWParam) {
+  MOZ_ASSERT(aMsg == WM_POINTERDOWN);
+  // Only roll up popups when we handling WM_POINTER* to fire Gecko
+  // WidgetMouseEvent and suppress Windows WM_*BUTTONDOWN.
+  return ShouldHandleWinPointerMessages(aMsg, aWParam) &&
+         ShouldFirePointerEventByWinPointerMessages();
+}
+
+bool WinPointerEvents::ShouldFirePointerEventByWinPointerMessages() {
+  MOZ_ASSERT(sLibraryHandle);
+  return StaticPrefs::dom_w3c_pointer_events_dispatch_by_pointer_messages();
+}
+
+WinPointerInfo* WinPointerEvents::GetCachedPointerInfo(UINT aMsg,
+                                                       WPARAM aWParam) {
+  if (!sLibraryHandle ||
+      MOUSE_INPUT_SOURCE() != dom::MouseEvent_Binding::MOZ_SOURCE_PEN ||
+      ShouldFirePointerEventByWinPointerMessages()) {
+    return nullptr;
+  }
+  switch (aMsg) {
+    case WM_LBUTTONDOWN:
+    case WM_MBUTTONDOWN:
+    case WM_RBUTTONDOWN:
+      return &mPenPointerDownInfo;
+    case WM_LBUTTONUP:
+    case WM_MBUTTONUP:
+    case WM_RBUTTONUP:
+      return &mPenPointerDownInfo;
+    case WM_MOUSEMOVE:
+      return &mPenPointerUpdateInfo;
+    default:
+      MOZ_ASSERT(false);
+  }
+  return nullptr;
+}
+
+void WinPointerEvents::ConvertAndCachePointerInfo(UINT aMsg, WPARAM aWParam) {
+  MOZ_ASSERT(
+      !StaticPrefs::dom_w3c_pointer_events_dispatch_by_pointer_messages());
+  // Windows doesn't support chorded buttons for pen, so we can simply keep the
+  // latest information from pen generated pointer messages and use them when
+  // handling mouse messages. Used different pointer info for pointerdown,
+  // pointerupdate, and pointerup because Windows doesn't always interleave
+  // pointer messages and mouse messages.
+  switch (aMsg) {
+    case WM_POINTERDOWN:
+      ConvertAndCachePointerInfo(aWParam, &mPenPointerDownInfo);
+      break;
+    case WM_POINTERUP:
+      ConvertAndCachePointerInfo(aWParam, &mPenPointerUpInfo);
+      break;
+    case WM_POINTERUPDATE:
+      ConvertAndCachePointerInfo(aWParam, &mPenPointerUpdateInfo);
+      break;
+    default:
+      break;
+  }
+}
+
+void WinPointerEvents::ConvertAndCachePointerInfo(WPARAM aWParam,
+                                                  WinPointerInfo* aInfo) {
+  MOZ_ASSERT(
+      !StaticPrefs::dom_w3c_pointer_events_dispatch_by_pointer_messages());
+  aInfo->pointerId = GetPointerId(aWParam);
+  MOZ_ASSERT(GetPointerType(aInfo->pointerId) == PT_PEN);
+  POINTER_PEN_INFO penInfo;
+  GetPointerPenInfo(aInfo->pointerId, &penInfo);
+  aInfo->tiltX = penInfo.tiltX;
+  aInfo->tiltY = penInfo.tiltY;
+  // Windows defines the pen pressure is normalized to a range between 0 and
+  // 1024. Convert it to float.
+  aInfo->mPressure = penInfo.pressure ? (float)penInfo.pressure / 1024 : 0;
+}
diff --git a/widget/windows/WinPointerEvents.h b/widget/windows/WinPointerEvents.h
new file mode 100644
index 0000000000..94179e7b4e
--- /dev/null
+++ b/widget/windows/WinPointerEvents.h
@@ -0,0 +1,75 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef WinPointerEvents_h__
+#define WinPointerEvents_h__
+
+#include "mozilla/MouseEvents.h"
+#include "touchinjection_sdk80.h"
+#include <windef.h>
+
+/******************************************************************************
+ * WinPointerInfo
+ *
+ * This is a helper class to handle WM_POINTER*. It only supports Win8 or later.
+ *
+ ******************************************************************************/
+class WinPointerInfo final : public mozilla::WidgetPointerHelper {
+ public:
+  WinPointerInfo() : WidgetPointerHelper(), mPressure(0), mButtons(0) {}
+
+  WinPointerInfo(uint32_t aPointerId, uint32_t aTiltX, uint32_t aTiltY,
+                 float aPressure, int16_t aButtons)
+      : WidgetPointerHelper(aPointerId, aTiltX, aTiltY),
+        mPressure(aPressure),
+        mButtons(aButtons) {}
+
+  float mPressure;
+  int16_t mButtons;
+};
+
+class WinPointerEvents final {
+ public:
+  explicit WinPointerEvents();
+
+ public:
+  bool ShouldHandleWinPointerMessages(UINT aMsg, WPARAM aWParam);
+
+  uint32_t GetPointerId(WPARAM aWParam) {
+    return GET_POINTERID_WPARAM(aWParam);
+  }
+  bool GetPointerType(uint32_t aPointerId, POINTER_INPUT_TYPE* aPointerType);
+  POINTER_INPUT_TYPE GetPointerType(uint32_t aPointerId);
+  bool GetPointerInfo(uint32_t aPointerId, POINTER_INFO* aPointerInfo);
+  bool GetPointerPenInfo(uint32_t aPointerId, POINTER_PEN_INFO* aPenInfo);
+  bool ShouldRollupOnPointerEvent(UINT aMsg, WPARAM aWParam);
+  bool ShouldFirePointerEventByWinPointerMessages();
+  WinPointerInfo* GetCachedPointerInfo(UINT aMsg, WPARAM aWParam);
+  void ConvertAndCachePointerInfo(UINT aMsg, WPARAM aWParam);
+  void ConvertAndCachePointerInfo(WPARAM aWParam, WinPointerInfo* aInfo);
+
+ private:
+  // Function prototypes
+  typedef BOOL(WINAPI* GetPointerTypePtr)(uint32_t aPointerId,
+                                          POINTER_INPUT_TYPE* aPointerType);
+  typedef BOOL(WINAPI* GetPointerInfoPtr)(uint32_t aPointerId,
+                                          POINTER_INFO* aPointerInfo);
+  typedef BOOL(WINAPI* GetPointerPenInfoPtr)(uint32_t aPointerId,
+                                             POINTER_PEN_INFO* aPenInfo);
+
+  void InitLibrary();
+
+  static HMODULE sLibraryHandle;
+  static const wchar_t kPointerLibraryName[];
+  // Static function pointers
+  static GetPointerTypePtr getPointerType;
+  static GetPointerInfoPtr getPointerInfo;
+  static GetPointerPenInfoPtr getPointerPenInfo;
+  WinPointerInfo mPenPointerDownInfo;
+  WinPointerInfo mPenPointerUpInfo;
+  WinPointerInfo mPenPointerUpdateInfo;
+};
+
+#endif  // #ifndef WinPointerEvents_h__
diff --git a/widget/windows/WinRegistry.cpp b/widget/windows/WinRegistry.cpp
new file mode 100644
index 0000000000..b04ae1df45
--- /dev/null
+++ b/widget/windows/WinRegistry.cpp
@@ -0,0 +1,325 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:set ts=2 sts=2 sw=2 et cin: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "WinRegistry.h"
+#include "nsThreadUtils.h"
+
+namespace mozilla::widget::WinRegistry {
+
+Key::Key(HKEY aParent, const nsString& aPath, KeyMode aMode, CreateFlag) {
+  MOZ_ASSERT(aParent);
+  DWORD disposition;
+  ::RegCreateKeyExW(aParent, aPath.get(), 0, nullptr, REG_OPTION_NON_VOLATILE,
+                    (REGSAM)aMode, nullptr, &mKey, &disposition);
+}
+
+Key::Key(HKEY aParent, const nsString& aPath, KeyMode aMode) {
+  MOZ_ASSERT(aParent);
+  ::RegOpenKeyExW(aParent, aPath.get(), 0, (REGSAM)aMode, &mKey);
+}
+
+uint32_t Key::GetChildCount() const {
+  MOZ_ASSERT(mKey);
+  DWORD result = 0;
+  ::RegQueryInfoKeyW(mKey, nullptr, nullptr, nullptr, &result, nullptr, nullptr,
+                     nullptr, nullptr, nullptr, nullptr, nullptr);
+  return result;
+}
+
+bool Key::GetChildName(uint32_t aIndex, nsAString& aResult) const {
+  MOZ_ASSERT(mKey);
+  FILETIME lastWritten;
+
+  wchar_t nameBuf[kMaxKeyNameLen + 1];
+  DWORD nameLen = std::size(nameBuf);
+
+  LONG rv = RegEnumKeyExW(mKey, aIndex, nameBuf, &nameLen, nullptr, nullptr,
+                          nullptr, &lastWritten);
+  if (rv != ERROR_SUCCESS) {
+    return false;
+  }
+  aResult.Assign(nameBuf, nameLen);
+  return true;
+}
+
+bool Key::RemoveChildKey(const nsString& aName) const {
+  MOZ_ASSERT(mKey);
+  return SUCCEEDED(RegDeleteKeyW(mKey, aName.get()));
+}
+
+uint32_t Key::GetValueCount() const {
+  MOZ_ASSERT(mKey);
+  DWORD result = 0;
+  ::RegQueryInfoKeyW(mKey, nullptr, nullptr, nullptr, nullptr, nullptr, nullptr,
+                     &result, nullptr, nullptr, nullptr, nullptr);
+  return result;
+}
+
+bool Key::GetValueName(uint32_t aIndex, nsAString& aResult) const {
+  MOZ_ASSERT(mKey);
+  wchar_t nameBuf[kMaxValueNameLen + 1];
+  DWORD nameLen = std::size(nameBuf);
+
+  LONG rv = RegEnumValueW(mKey, aIndex, nameBuf, &nameLen, nullptr, nullptr,
+                          nullptr, nullptr);
+  if (rv != ERROR_SUCCESS) {
+    return false;
+  }
+  aResult.Assign(nameBuf, nameLen);
+  return true;
+}
+
+ValueType Key::GetValueType(const nsString& aName) const {
+  MOZ_ASSERT(mKey);
+  DWORD result;
+  LONG rv =
+      RegQueryValueExW(mKey, aName.get(), nullptr, &result, nullptr, nullptr);
+  return SUCCEEDED(rv) ? ValueType(result) : ValueType::None;
+}
+
+bool Key::RemoveValue(const nsString& aName) const {
+  MOZ_ASSERT(mKey);
+  return SUCCEEDED(RegDeleteValueW(mKey, aName.get()));
+}
+
+Maybe<uint32_t> Key::GetValueAsDword(const nsString& aName) const {
+  MOZ_ASSERT(mKey);
+  DWORD type;
+  DWORD value = 0;
+  DWORD size = sizeof(DWORD);
+  HRESULT rv = RegQueryValueExW(mKey, aName.get(), nullptr, &type,
+                                (LPBYTE)&value, &size);
+  if (FAILED(rv) || type != REG_DWORD) {
+    return Nothing();
+  }
+  return Some(value);
+}
+
+bool Key::WriteValueAsDword(const nsString& aName, uint32_t aValue) {
+  MOZ_ASSERT(mKey);
+  return SUCCEEDED(RegSetValueExW(mKey, aName.get(), 0, REG_DWORD,
+                                  (const BYTE*)&aValue, sizeof(aValue)));
+}
+
+Maybe<uint64_t> Key::GetValueAsQword(const nsString& aName) const {
+  MOZ_ASSERT(mKey);
+  DWORD type;
+  uint64_t value = 0;
+  DWORD size = sizeof(uint64_t);
+  HRESULT rv = RegQueryValueExW(mKey, aName.get(), nullptr, &type,
+                                (LPBYTE)&value, &size);
+  if (FAILED(rv) || type != REG_QWORD) {
+    return Nothing();
+  }
+  return Some(value);
+}
+
+bool Key::WriteValueAsQword(const nsString& aName, uint64_t aValue) {
+  MOZ_ASSERT(mKey);
+  return SUCCEEDED(RegSetValueExW(mKey, aName.get(), 0, REG_QWORD,
+                                  (const BYTE*)&aValue, sizeof(aValue)));
+}
+
+bool Key::GetValueAsBinary(const nsString& aName,
+                           nsTArray<uint8_t>& aResult) const {
+  MOZ_ASSERT(mKey);
+  DWORD type;
+  DWORD size;
+  LONG rv = RegQueryValueExW(mKey, aName.get(), nullptr, &type, nullptr, &size);
+  if (FAILED(rv) || type != REG_BINARY) {
+    return false;
+  }
+  if (!aResult.SetLength(size, fallible)) {
+    return false;
+  }
+  rv = RegQueryValueExW(mKey, aName.get(), nullptr, nullptr, aResult.Elements(),
+                        &size);
+  return SUCCEEDED(rv);
+}
+
+Maybe<nsTArray<uint8_t>> Key::GetValueAsBinary(const nsString& aName) const {
+  nsTArray<uint8_t> value;
+  Maybe<nsTArray<uint8_t>> result;
+  if (GetValueAsBinary(aName, value)) {
+    result.emplace(std::move(value));
+  }
+  return result;
+}
+
+bool Key::WriteValueAsBinary(const nsString& aName,
+                             Span<const uint8_t> aValue) {
+  MOZ_ASSERT(mKey);
+  return SUCCEEDED(RegSetValueExW(mKey, aName.get(), 0, REG_BINARY,
+                                  (const BYTE*)aValue.data(), aValue.size()));
+}
+
+static bool IsStringType(DWORD aType, StringFlags aFlags) {
+  switch (aType) {
+    case REG_SZ:
+      return bool(aFlags & StringFlags::Sz);
+    case REG_EXPAND_SZ:
+      return bool(aFlags & StringFlags::ExpandSz);
+    case REG_MULTI_SZ:
+      return bool(aFlags & StringFlags::LegacyMultiSz);
+    default:
+      return false;
+  }
+}
+
+bool Key::GetValueAsString(const nsString& aName, nsString& aResult,
+                           StringFlags aFlags) const {
+  MOZ_ASSERT(mKey);
+  DWORD type;
+  DWORD size;
+  LONG rv = RegQueryValueExW(mKey, aName.get(), nullptr, &type, nullptr, &size);
+  if (FAILED(rv) || !IsStringType(type, aFlags)) {
+    return false;
+  }
+  if (!size) {
+    aResult.Truncate();
+    return true;
+  }
+  // The buffer size must be a multiple of 2.
+  if (NS_WARN_IF(size % 2 != 0)) {
+    return false;
+  }
+  size_t resultLen = size / 2;
+  {
+    auto handleOrError =
+        aResult.BulkWrite(resultLen, 0, /* aAllowShrinking = */ false);
+    if (NS_WARN_IF(handleOrError.isErr())) {
+      return false;
+    }
+    auto handle = handleOrError.unwrap();
+    auto len = GetValueAsString(aName, {handle.Elements(), handle.Length() + 1},
+                                aFlags & ~StringFlags::ExpandEnvironment);
+    if (NS_WARN_IF(!len)) {
+      return false;
+    }
+    handle.Finish(*len, /* aAllowShrinking = */ false);
+    if (*len && !aResult.CharAt(*len - 1)) {
+      // The string passed to us had a null terminator in the final
+      // position.
+      aResult.Truncate(*len - 1);
+    }
+  }
+  if (type == REG_EXPAND_SZ && (aFlags & StringFlags::ExpandEnvironment)) {
+    resultLen = ExpandEnvironmentStringsW(aResult.get(), nullptr, 0);
+    if (resultLen > 1) {
+      nsString expandedResult;
+      // |resultLen| includes the terminating null character
+      resultLen--;
+      if (!expandedResult.SetLength(resultLen, fallible)) {
+        return false;
+      }
+      resultLen = ExpandEnvironmentStringsW(aResult.get(), expandedResult.get(),
+                                            resultLen + 1);
+      if (resultLen <= 0) {
+        return false;
+      }
+      aResult = std::move(expandedResult);
+    } else if (resultLen == 1) {
+      // It apparently expands to nothing (just a null terminator).
+      resultLen = 0;
+      aResult.Truncate();
+    }
+  }
+  return true;
+}
+
+Maybe<nsString> Key::GetValueAsString(const nsString& aName,
+                                      StringFlags aFlags) const {
+  nsString value;
+  Maybe<nsString> result;
+  if (GetValueAsString(aName, value, aFlags)) {
+    result.emplace(std::move(value));
+  }
+  return result;
+}
+
+Maybe<uint32_t> Key::GetValueAsString(const nsString& aName,
+                                      Span<char16_t> aBuffer,
+                                      StringFlags aFlags) const {
+  MOZ_ASSERT(mKey);
+  MOZ_ASSERT(aBuffer.Length(), "Empty buffer?");
+  MOZ_ASSERT(!(aFlags & StringFlags::ExpandEnvironment),
+             "Environment expansion not performed on a single buffer");
+
+  DWORD size = aBuffer.LengthBytes();
+  DWORD type;
+  HRESULT rv = RegQueryValueExW(mKey, aName.get(), nullptr, &type,
+                                (LPBYTE)aBuffer.data(), &size);
+  if (FAILED(rv)) {
+    return Nothing();
+  }
+  if (!IsStringType(type, aFlags)) {
+    return Nothing();
+  }
+  uint32_t len = size ? size / sizeof(char16_t) - 1 : 0;
+  aBuffer[len] = 0;
+  return Some(len);
+}
+
+KeyWatcher::KeyWatcher(Key&& aKey,
+                       nsISerialEventTarget* aTargetSerialEventTarget,
+                       Callback&& aCallback)
+    : mKey(std::move(aKey)),
+      mEventTarget(aTargetSerialEventTarget),
+      mCallback(std::move(aCallback)) {
+  MOZ_ASSERT(mKey);
+  MOZ_ASSERT(mEventTarget);
+  MOZ_ASSERT(mCallback);
+  mEvent = CreateEvent(nullptr, /* bManualReset = */ FALSE,
+                       /* bInitialState = */ FALSE, nullptr);
+  if (NS_WARN_IF(!mEvent)) {
+    return;
+  }
+
+  if (NS_WARN_IF(!Register())) {
+    return;
+  }
+
+  // The callback only dispatches to the relevant event target, so we can use
+  // WT_EXECUTEINWAITTHREAD.
+  RegisterWaitForSingleObject(&mWaitObject, mEvent, WatchCallback, this,
+                              INFINITE, WT_EXECUTEINWAITTHREAD);
+}
+
+void KeyWatcher::WatchCallback(void* aContext, BOOLEAN) {
+  auto* watcher = static_cast<KeyWatcher*>(aContext);
+  watcher->Register();
+  watcher->mEventTarget->Dispatch(
+      NS_NewRunnableFunction("KeyWatcher callback", watcher->mCallback));
+}
+
+// As per the documentation in:
+// https://learn.microsoft.com/en-us/windows/win32/api/winreg/nf-winreg-regnotifychangekeyvalue
+//
+// This function detects a single change. After the caller receives a
+// notification event, it should call the function again to receive the next
+// notification.
+bool KeyWatcher::Register() {
+  MOZ_ASSERT(mEvent);
+  DWORD flags = REG_NOTIFY_CHANGE_NAME | REG_NOTIFY_CHANGE_ATTRIBUTES |
+                REG_NOTIFY_CHANGE_LAST_SET | REG_NOTIFY_CHANGE_SECURITY |
+                REG_NOTIFY_THREAD_AGNOSTIC;
+  HRESULT rv =
+      RegNotifyChangeKeyValue(mKey.RawKey(), /* bWatchSubtree = */ TRUE, flags,
+                              mEvent, /* fAsynchronous = */ TRUE);
+  return !NS_WARN_IF(FAILED(rv));
+}
+
+KeyWatcher::~KeyWatcher() {
+  if (mWaitObject) {
+    UnregisterWait(mWaitObject);
+    CloseHandle(mWaitObject);
+  }
+  if (mEvent) {
+    CloseHandle(mEvent);
+  }
+}
+
+}  // namespace mozilla::widget::WinRegistry
diff --git a/widget/windows/WinRegistry.h b/widget/windows/WinRegistry.h
new file mode 100644
index 0000000000..8ab221928e
--- /dev/null
+++ b/widget/windows/WinRegistry.h
@@ -0,0 +1,235 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_widget_WinRegistry_h__
+#define mozilla_widget_WinRegistry_h__
+
+#include <windows.h>
+#include <functional>
+#include "nsCOMPtr.h"
+#include "nsString.h"
+#include "nsTArray.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/Span.h"
+
+class nsISerialEventTarget;
+
+namespace mozilla::widget::WinRegistry {
+
+// According to MSDN, the following limits apply (in characters excluding room
+// for terminating null character):
+static constexpr size_t kMaxKeyNameLen = 255;
+static constexpr size_t kMaxValueNameLen = 16383;
+
+/// https://learn.microsoft.com/en-us/windows/win32/shell/regsam
+enum class KeyMode : uint32_t {
+  AllAccess = KEY_ALL_ACCESS,
+  QueryValue = KEY_QUERY_VALUE,
+  CreateLink = KEY_CREATE_LINK,
+  CreateSubKey = KEY_CREATE_SUB_KEY,
+  EnumerateSubkeys = KEY_ENUMERATE_SUB_KEYS,
+  Execute = KEY_EXECUTE,
+  Notify = KEY_NOTIFY,
+  Read = KEY_READ,
+  SetValue = KEY_SET_VALUE,
+  Write = KEY_WRITE,
+};
+
+MOZ_MAKE_ENUM_CLASS_BITWISE_OPERATORS(KeyMode);
+
+enum class StringFlags : uint32_t {
+  // Whether to allow REG_SZ strings.
+  Sz = 1 << 0,
+  // Whether to read EXPAND_SZ strings.
+  ExpandSz = 1 << 1,
+  // Whether to treat MULTI_SZ values as strings. This is a historical
+  // idiosyncrasy of the nsIWindowsRegKey, but most likely not what you want.
+  LegacyMultiSz = 1 << 2,
+  // Whether to expand environment variables in EXPAND_SZ values.
+  // Only makes sense along with the ExpandSz variable.
+  ExpandEnvironment = 1 << 3,
+  // By default, only allow regular Sz, and don't perform environment expansion.
+  Default = Sz,
+};
+
+MOZ_MAKE_ENUM_CLASS_BITWISE_OPERATORS(StringFlags);
+
+// Convenience alias for legacy WinUtils callers, to preserve behavior.
+// Chances are users of these flags could just look at Sz strings, tho.
+static constexpr auto kLegacyWinUtilsStringFlags =
+    StringFlags::Sz | StringFlags::ExpandSz;
+
+// https://learn.microsoft.com/en-us/windows/win32/sysinfo/registry-value-types
+enum class ValueType : uint32_t {
+  Binary = REG_BINARY,
+  Dword = REG_DWORD,
+  ExpandSz = REG_EXPAND_SZ,
+  Link = REG_LINK,
+  MultiSz = REG_MULTI_SZ,
+  None = REG_NONE,
+  Qword = REG_QWORD,
+  Sz = REG_SZ,
+};
+
+class Key {
+ public:
+  enum CreateFlag {
+    Create,
+  };
+
+  Key() = default;
+  Key(const Key&) = delete;
+  Key(Key&& aOther) { std::swap(mKey, aOther.mKey); }
+
+  Key& operator=(const Key&) = delete;
+  Key& operator=(Key&& aOther) {
+    std::swap(mKey, aOther.mKey);
+    return *this;
+  }
+
+  Key(HKEY aParent, const nsString& aPath, KeyMode aMode, CreateFlag);
+  Key(HKEY aParent, const nsString& aPath, KeyMode aMode);
+
+  Key(const Key& aParent, const nsString& aPath, KeyMode aMode, CreateFlag)
+      : Key(aParent.mKey, aPath, aMode, Create) {}
+  Key(const Key& aParent, const nsString& aPath, KeyMode aMode)
+      : Key(aParent.mKey, aPath, aMode) {}
+
+  ~Key() {
+    if (mKey) {
+      ::RegCloseKey(mKey);
+    }
+  }
+
+  explicit operator bool() const { return !!mKey; }
+
+  uint32_t GetChildCount() const;
+  [[nodiscard]] bool GetChildName(uint32_t aIndex, nsAString& aResult) const;
+  [[nodiscard]] bool RemoveChildKey(const nsString& aName) const;
+
+  uint32_t GetValueCount() const;
+  [[nodiscard]] bool GetValueName(uint32_t aIndex, nsAString& aResult) const;
+  ValueType GetValueType(const nsString& aName) const;
+  bool RemoveValue(const nsString& aName) const;
+
+  Maybe<uint32_t> GetValueAsDword(const nsString& aName) const;
+  bool WriteValueAsDword(const nsString& aName, uint32_t aValue);
+
+  Maybe<uint64_t> GetValueAsQword(const nsString& aName) const;
+  [[nodiscard]] bool WriteValueAsQword(const nsString& aName, uint64_t aValue);
+
+  [[nodiscard]] bool GetValueAsBinary(const nsString& aName,
+                                      nsTArray<uint8_t>&) const;
+  Maybe<nsTArray<uint8_t>> GetValueAsBinary(const nsString& aName) const;
+  [[nodiscard]] bool WriteValueAsBinary(const nsString& aName,
+                                        Span<const uint8_t> aValue);
+
+  [[nodiscard]] bool GetValueAsString(const nsString& aName, nsString& aResult,
+                                      StringFlags = StringFlags::Default) const;
+  Maybe<nsString> GetValueAsString(const nsString& aName,
+                                   StringFlags = StringFlags::Default) const;
+  // Reads a string value into a buffer. Returns Some(length) if the string is
+  // read fully, in which case the passed memory region contains a
+  // null-terminated string.
+  // Doesn't perform environment expansion (and asserts if you pass the
+  // ExpandEnvironment flag).
+  [[nodiscard]] Maybe<uint32_t> GetValueAsString(
+      const nsString& aName, Span<char16_t>,
+      StringFlags = StringFlags::Default) const;
+  [[nodiscard]] Maybe<uint32_t> GetValueAsString(
+      const nsString& aName, Span<wchar_t> aBuffer,
+      StringFlags aFlags = StringFlags::Default) const {
+    return GetValueAsString(
+        aName, Span<char16_t>((char16_t*)aBuffer.data(), aBuffer.Length()),
+        aFlags);
+  }
+
+  [[nodiscard]] bool WriteValueAsString(const nsString& aName,
+                                        const nsString& aValue) {
+    MOZ_ASSERT(mKey);
+    return SUCCEEDED(RegSetValueExW(mKey, aName.get(), 0, REG_SZ,
+                                    (const BYTE*)aValue.get(),
+                                    (aValue.Length() + 1) * sizeof(char16_t)));
+  }
+
+  HKEY RawKey() const { return mKey; }
+
+ private:
+  HKEY mKey = nullptr;
+};
+
+inline bool HasKey(HKEY aRootKey, const nsString& aKeyName) {
+  return !!Key(aRootKey, aKeyName, KeyMode::Read);
+}
+
+// Returns a single string value from the registry into a buffer.
+[[nodiscard]] inline bool GetString(HKEY aRootKey, const nsString& aKeyName,
+                                    const nsString& aValueName,
+                                    Span<char16_t> aBuffer,
+                                    StringFlags aFlags = StringFlags::Default) {
+  Key k(aRootKey, aKeyName, KeyMode::QueryValue);
+  return k && k.GetValueAsString(aValueName, aBuffer, aFlags);
+}
+[[nodiscard]] inline bool GetString(HKEY aRootKey, const nsString& aKeyName,
+                                    const nsString& aValueName,
+                                    Span<wchar_t> aBuffer,
+                                    StringFlags aFlags = StringFlags::Default) {
+  return GetString(aRootKey, aKeyName, aValueName,
+                   Span<char16_t>((char16_t*)aBuffer.data(), aBuffer.Length()),
+                   aFlags);
+}
+[[nodiscard]] inline bool GetString(HKEY aRootKey, const nsString& aKeyName,
+                                    const nsString& aValueName,
+                                    nsString& aBuffer,
+                                    StringFlags aFlags = StringFlags::Default) {
+  Key k(aRootKey, aKeyName, KeyMode::QueryValue);
+  return k && k.GetValueAsString(aValueName, aBuffer, aFlags);
+}
+inline Maybe<nsString> GetString(HKEY aRootKey, const nsString& aKeyName,
+                                 const nsString& aValueName,
+                                 StringFlags aFlags = StringFlags::Default) {
+  Key k(aRootKey, aKeyName, KeyMode::QueryValue);
+  if (!k) {
+    return Nothing();
+  }
+  return k.GetValueAsString(aValueName, aFlags);
+}
+
+class KeyWatcher final {
+ public:
+  using Callback = std::function<void()>;
+
+  KeyWatcher(const KeyWatcher&) = delete;
+
+  const Key& GetKey() const { return mKey; }
+
+  // Start watching a key. The watching is recursive (the whole key subtree is
+  // watched), and the callback is executed every time the key or any of its
+  // descendants change until the watcher is destroyed.
+  //
+  // @param aKey the key to watch. Must have been opened with the
+  //             KeyMode::Notify flag.
+  // @param aTargetSerialEventTarget the target event target to dispatch the
+  //        callback to.
+  // @param aCallback the closure to run every time that registry key changes.
+  KeyWatcher(Key&& aKey, nsISerialEventTarget* aTargetSerialEventTarget,
+             Callback&& aCallback);
+
+  ~KeyWatcher();
+
+ private:
+  static void CALLBACK WatchCallback(void* aContext, BOOLEAN);
+  bool Register();
+
+  Key mKey;
+  nsCOMPtr<nsISerialEventTarget> mEventTarget;
+  Callback mCallback;
+  HANDLE mEvent = nullptr;
+  HANDLE mWaitObject = nullptr;
+};
+
+}  // namespace mozilla::widget::WinRegistry
+
+#endif
diff --git a/widget/windows/WinTaskbar.cpp b/widget/windows/WinTaskbar.cpp
new file mode 100644
index 0000000000..56608503da
--- /dev/null
+++ b/widget/windows/WinTaskbar.cpp
@@ -0,0 +1,493 @@
+/* vim: se cin sw=2 ts=2 et : */
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsIWinTaskbar.h"
+#include "WinTaskbar.h"
+#include "TaskbarPreview.h"
+#include "nsITaskbarPreviewController.h"
+
+#include "mozilla/RefPtr.h"
+#include "mozilla/widget/JumpListBuilder.h"
+#include <nsError.h>
+#include <nsCOMPtr.h>
+#include <nsIWidget.h>
+#include <nsIBaseWindow.h>
+#include <nsServiceManagerUtils.h>
+#include "nsIXULAppInfo.h"
+#include "nsILegacyJumpListBuilder.h"
+#include "nsUXThemeData.h"
+#include "nsWindow.h"
+#include "WinUtils.h"
+#include "TaskbarTabPreview.h"
+#include "TaskbarWindowPreview.h"
+#include "LegacyJumpListBuilder.h"
+#include "nsWidgetsCID.h"
+#include "nsPIDOMWindow.h"
+#include "nsAppDirectoryServiceDefs.h"
+#include "mozilla/Preferences.h"
+#include "nsAppRunner.h"
+#include "nsXREDirProvider.h"
+#include "mozilla/widget/WinRegistry.h"
+#include <io.h>
+#include <propvarutil.h>
+#include <propkey.h>
+#include <shellapi.h>
+
+static NS_DEFINE_CID(kLegacyJumpListBuilderCID,
+                     NS_WIN_LEGACYJUMPLISTBUILDER_CID);
+
+namespace {
+
+HWND GetHWNDFromDocShell(nsIDocShell* aShell) {
+  nsCOMPtr<nsIBaseWindow> baseWindow(
+      do_QueryInterface(reinterpret_cast<nsISupports*>(aShell)));
+
+  if (!baseWindow) return nullptr;
+
+  nsCOMPtr<nsIWidget> widget;
+  baseWindow->GetMainWidget(getter_AddRefs(widget));
+
+  return widget ? (HWND)widget->GetNativeData(NS_NATIVE_WINDOW) : nullptr;
+}
+
+HWND GetHWNDFromDOMWindow(mozIDOMWindow* dw) {
+  nsCOMPtr<nsIWidget> widget;
+
+  if (!dw) return nullptr;
+
+  nsCOMPtr<nsPIDOMWindowInner> window = nsPIDOMWindowInner::From(dw);
+  return GetHWNDFromDocShell(window->GetDocShell());
+}
+
+nsresult SetWindowAppUserModelProp(mozIDOMWindow* aParent,
+                                   const nsString& aIdentifier) {
+  NS_ENSURE_ARG_POINTER(aParent);
+
+  if (aIdentifier.IsEmpty()) return NS_ERROR_INVALID_ARG;
+
+  HWND toplevelHWND = ::GetAncestor(GetHWNDFromDOMWindow(aParent), GA_ROOT);
+
+  if (!toplevelHWND) return NS_ERROR_INVALID_ARG;
+
+  RefPtr<IPropertyStore> pPropStore;
+  if (FAILED(SHGetPropertyStoreForWindow(toplevelHWND, IID_IPropertyStore,
+                                         getter_AddRefs(pPropStore)))) {
+    return NS_ERROR_INVALID_ARG;
+  }
+
+  PROPVARIANT pv;
+  if (FAILED(InitPropVariantFromString(aIdentifier.get(), &pv))) {
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  nsresult rv = NS_OK;
+  if (FAILED(pPropStore->SetValue(PKEY_AppUserModel_ID, pv)) ||
+      FAILED(pPropStore->Commit())) {
+    rv = NS_ERROR_FAILURE;
+  }
+
+  PropVariantClear(&pv);
+
+  return rv;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+// default nsITaskbarPreviewController
+
+class DefaultController final : public nsITaskbarPreviewController {
+  ~DefaultController() {}
+  HWND mWnd;
+
+ public:
+  explicit DefaultController(HWND hWnd) : mWnd(hWnd) {}
+
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSITASKBARPREVIEWCONTROLLER
+};
+
+NS_IMETHODIMP
+DefaultController::GetWidth(uint32_t* aWidth) {
+  RECT r;
+  ::GetClientRect(mWnd, &r);
+  *aWidth = r.right;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+DefaultController::GetHeight(uint32_t* aHeight) {
+  RECT r;
+  ::GetClientRect(mWnd, &r);
+  *aHeight = r.bottom;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+DefaultController::GetThumbnailAspectRatio(float* aThumbnailAspectRatio) {
+  uint32_t width, height;
+  GetWidth(&width);
+  GetHeight(&height);
+  if (!height) height = 1;
+
+  *aThumbnailAspectRatio = width / float(height);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+DefaultController::RequestThumbnail(nsITaskbarPreviewCallback* aCallback,
+                                    uint32_t width, uint32_t height) {
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+DefaultController::RequestPreview(nsITaskbarPreviewCallback* aCallback) {
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+DefaultController::OnClose(void) {
+  MOZ_ASSERT_UNREACHABLE(
+      "OnClose should not be called for "
+      "TaskbarWindowPreviews");
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+DefaultController::OnActivate(bool* rAcceptActivation) {
+  *rAcceptActivation = true;
+  MOZ_ASSERT_UNREACHABLE(
+      "OnActivate should not be called for "
+      "TaskbarWindowPreviews");
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+DefaultController::OnClick(nsITaskbarPreviewButton* button) { return NS_OK; }
+
+NS_IMPL_ISUPPORTS(DefaultController, nsITaskbarPreviewController)
+}  // namespace
+
+namespace mozilla {
+namespace widget {
+
+///////////////////////////////////////////////////////////////////////////////
+// nsIWinTaskbar
+
+NS_IMPL_ISUPPORTS(WinTaskbar, nsIWinTaskbar)
+
+bool WinTaskbar::Initialize() {
+  if (mTaskbar) return true;
+
+  ::CoInitialize(nullptr);
+  HRESULT hr =
+      ::CoCreateInstance(CLSID_TaskbarList, nullptr, CLSCTX_INPROC_SERVER,
+                         IID_ITaskbarList4, (void**)&mTaskbar);
+  if (FAILED(hr)) return false;
+
+  hr = mTaskbar->HrInit();
+  if (FAILED(hr)) {
+    // This may fail with shell extensions like blackbox installed.
+    NS_WARNING("Unable to initialize taskbar");
+    NS_RELEASE(mTaskbar);
+    return false;
+  }
+  return true;
+}
+
+WinTaskbar::WinTaskbar() : mTaskbar(nullptr) {}
+
+WinTaskbar::~WinTaskbar() {
+  if (mTaskbar) {  // match successful Initialize() call
+    NS_RELEASE(mTaskbar);
+    ::CoUninitialize();
+  }
+}
+
+// static
+bool WinTaskbar::GenerateAppUserModelID(nsAString& aAppUserModelId,
+                                        bool aPrivateBrowsing) {
+  // If marked as such in prefs, use a hash of the profile path for the id
+  // instead of the install path hash setup by the installer.
+  if (Preferences::GetBool("taskbar.grouping.useprofile", false)) {
+    nsCOMPtr<nsIFile> profileDir;
+    NS_GetSpecialDirectory(NS_APP_USER_PROFILE_50_DIR,
+                           getter_AddRefs(profileDir));
+    bool exists = false;
+    if (profileDir && NS_SUCCEEDED(profileDir->Exists(&exists)) && exists) {
+      nsAutoCString path;
+      if (NS_SUCCEEDED(profileDir->GetPersistentDescriptor(path))) {
+        nsAutoString id;
+        id.AppendInt(HashString(path));
+        if (!id.IsEmpty()) {
+          aAppUserModelId.Assign(id);
+          return true;
+        }
+      }
+    }
+  }
+
+  // The default value is set by the installer and is stored in the registry
+  // under (HKLM||HKCU)/Software/Mozilla/Firefox/TaskBarIDs. If for any reason
+  // hash generation operation fails, the installer will not store a value in
+  // the registry or set ids on shortcuts. A lack of an id can also occur for
+  // zipped builds.
+  nsCOMPtr<nsIXULAppInfo> appInfo =
+      do_GetService("@mozilla.org/xre/app-info;1");
+  nsCString appName;
+  if (appInfo && NS_SUCCEEDED(appInfo->GetName(appName))) {
+    nsAutoString regKey;
+    regKey.AssignLiteral("Software\\Mozilla\\");
+    AppendASCIItoUTF16(appName, regKey);
+    regKey.AppendLiteral("\\TaskBarIDs");
+
+    WCHAR path[MAX_PATH];
+    if (GetModuleFileNameW(nullptr, path, MAX_PATH)) {
+      wchar_t* slash = wcsrchr(path, '\\');
+      if (!slash) return false;
+      *slash = '\0';  // no trailing slash
+
+      nsDependentString pathStr(path);
+      for (auto* rootKey : {HKEY_LOCAL_MACHINE, HKEY_CURRENT_USER}) {
+        if (auto aumid = WinRegistry::GetString(rootKey, regKey, pathStr)) {
+          aAppUserModelId = std::move(*aumid);
+          break;
+        }
+      }
+    }
+  }
+
+  // If we haven't found an ID yet then use the install hash. In xpcshell tests
+  // the directory provider may not have been initialized so bypass in this
+  // case.
+  if (aAppUserModelId.IsEmpty() && gDirServiceProvider) {
+    gDirServiceProvider->GetInstallHash(aAppUserModelId);
+  }
+
+  if (aPrivateBrowsing) {
+    aAppUserModelId.AppendLiteral(";PrivateBrowsingAUMID");
+  }
+
+  return !aAppUserModelId.IsEmpty();
+}
+
+// static
+bool WinTaskbar::GetAppUserModelID(nsAString& aAppUserModelId,
+                                   bool aPrivateBrowsing) {
+  // If an ID has already been set then use that.
+  PWSTR id;
+  if (SUCCEEDED(GetCurrentProcessExplicitAppUserModelID(&id))) {
+    aAppUserModelId.Assign(id);
+    CoTaskMemFree(id);
+  }
+
+  return GenerateAppUserModelID(aAppUserModelId, aPrivateBrowsing);
+}
+
+NS_IMETHODIMP
+WinTaskbar::GetDefaultGroupId(nsAString& aDefaultGroupId) {
+  if (!GetAppUserModelID(aDefaultGroupId)) return NS_ERROR_UNEXPECTED;
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+WinTaskbar::GetDefaultPrivateGroupId(nsAString& aDefaultPrivateGroupId) {
+  if (!GetAppUserModelID(aDefaultPrivateGroupId, true))
+    return NS_ERROR_UNEXPECTED;
+
+  return NS_OK;
+}
+
+// (static) Called from AppShell
+bool WinTaskbar::RegisterAppUserModelID() {
+  nsAutoString uid;
+  if (!GetAppUserModelID(uid)) return false;
+
+  return SUCCEEDED(SetCurrentProcessExplicitAppUserModelID(uid.get()));
+}
+
+NS_IMETHODIMP
+WinTaskbar::GetAvailable(bool* aAvailable) {
+  // ITaskbarList4::HrInit() may fail with shell extensions like blackbox
+  // installed. Initialize early to return available=false in those cases.
+  *aAvailable = Initialize();
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+WinTaskbar::CreateTaskbarTabPreview(nsIDocShell* shell,
+                                    nsITaskbarPreviewController* controller,
+                                    nsITaskbarTabPreview** _retval) {
+  if (!Initialize()) return NS_ERROR_NOT_AVAILABLE;
+
+  NS_ENSURE_ARG_POINTER(shell);
+  NS_ENSURE_ARG_POINTER(controller);
+
+  HWND toplevelHWND = ::GetAncestor(GetHWNDFromDocShell(shell), GA_ROOT);
+
+  if (!toplevelHWND) return NS_ERROR_INVALID_ARG;
+
+  RefPtr<TaskbarTabPreview> preview(
+      new TaskbarTabPreview(mTaskbar, controller, toplevelHWND, shell));
+  if (!preview) return NS_ERROR_OUT_OF_MEMORY;
+
+  nsresult rv = preview->Init();
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+
+  preview.forget(_retval);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+WinTaskbar::GetTaskbarWindowPreview(nsIDocShell* shell,
+                                    nsITaskbarWindowPreview** _retval) {
+  if (!Initialize()) return NS_ERROR_NOT_AVAILABLE;
+
+  NS_ENSURE_ARG_POINTER(shell);
+
+  HWND toplevelHWND = ::GetAncestor(GetHWNDFromDocShell(shell), GA_ROOT);
+
+  if (!toplevelHWND) return NS_ERROR_INVALID_ARG;
+
+  nsWindow* window = WinUtils::GetNSWindowPtr(toplevelHWND);
+
+  if (!window) return NS_ERROR_FAILURE;
+
+  nsCOMPtr<nsITaskbarWindowPreview> preview = window->GetTaskbarPreview();
+  if (!preview) {
+    RefPtr<DefaultController> defaultController =
+        new DefaultController(toplevelHWND);
+
+    TaskbarWindowPreview* previewRaw = new TaskbarWindowPreview(
+        mTaskbar, defaultController, toplevelHWND, shell);
+    if (!previewRaw) {
+      return NS_ERROR_OUT_OF_MEMORY;
+    }
+
+    preview = previewRaw;
+
+    nsresult rv = previewRaw->Init();
+    if (NS_FAILED(rv)) {
+      return rv;
+    }
+    window->SetTaskbarPreview(preview);
+  }
+
+  preview.forget(_retval);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+WinTaskbar::GetTaskbarProgress(nsIDocShell* shell,
+                               nsITaskbarProgress** _retval) {
+  nsCOMPtr<nsITaskbarWindowPreview> preview;
+  nsresult rv = GetTaskbarWindowPreview(shell, getter_AddRefs(preview));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  return CallQueryInterface(preview, _retval);
+}
+
+NS_IMETHODIMP
+WinTaskbar::GetOverlayIconController(
+    nsIDocShell* shell, nsITaskbarOverlayIconController** _retval) {
+  nsCOMPtr<nsITaskbarWindowPreview> preview;
+  nsresult rv = GetTaskbarWindowPreview(shell, getter_AddRefs(preview));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  return CallQueryInterface(preview, _retval);
+}
+
+NS_IMETHODIMP
+WinTaskbar::CreateLegacyJumpListBuilder(
+    bool aPrivateBrowsing, nsILegacyJumpListBuilder** aJumpListBuilder) {
+  nsresult rv;
+
+  if (LegacyJumpListBuilder::sBuildingList) return NS_ERROR_ALREADY_INITIALIZED;
+
+  nsCOMPtr<nsILegacyJumpListBuilder> builder =
+      do_CreateInstance(kLegacyJumpListBuilderCID, &rv);
+  if (NS_FAILED(rv)) return NS_ERROR_UNEXPECTED;
+
+  NS_IF_ADDREF(*aJumpListBuilder = builder);
+
+  nsAutoString aumid;
+  GenerateAppUserModelID(aumid, aPrivateBrowsing);
+  builder->SetAppUserModelID(aumid);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+WinTaskbar::CreateJumpListBuilder(bool aPrivateBrowsing,
+                                  nsIJumpListBuilder** aJumpListBuilder) {
+  nsAutoString aumid;
+  GenerateAppUserModelID(aumid, aPrivateBrowsing);
+
+  nsCOMPtr<nsIJumpListBuilder> builder = new JumpListBuilder(aumid);
+  if (!builder) {
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  NS_IF_ADDREF(*aJumpListBuilder = builder);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+WinTaskbar::GetGroupIdForWindow(mozIDOMWindow* aParent,
+                                nsAString& aIdentifier) {
+  NS_ENSURE_ARG_POINTER(aParent);
+  HWND toplevelHWND = ::GetAncestor(GetHWNDFromDOMWindow(aParent), GA_ROOT);
+  if (!toplevelHWND) return NS_ERROR_INVALID_ARG;
+  RefPtr<IPropertyStore> pPropStore;
+  if (FAILED(SHGetPropertyStoreForWindow(toplevelHWND, IID_IPropertyStore,
+                                         getter_AddRefs(pPropStore)))) {
+    return NS_ERROR_INVALID_ARG;
+  }
+  PROPVARIANT pv;
+  PropVariantInit(&pv);
+  auto cleanupPropVariant = MakeScopeExit([&] { PropVariantClear(&pv); });
+  if (FAILED(pPropStore->GetValue(PKEY_AppUserModel_ID, &pv))) {
+    return NS_ERROR_FAILURE;
+  }
+  if (pv.vt != VT_LPWSTR) {
+    // This can happen when there is no window specific group ID set
+    // It's not an error case so we have to check for empty strings
+    // returned from the function.
+    return NS_OK;
+  }
+  aIdentifier.Assign(char16ptr_t(pv.pwszVal));
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+WinTaskbar::SetGroupIdForWindow(mozIDOMWindow* aParent,
+                                const nsAString& aIdentifier) {
+  return SetWindowAppUserModelProp(aParent, nsString(aIdentifier));
+}
+
+NS_IMETHODIMP
+WinTaskbar::PrepareFullScreen(void* aHWND, bool aFullScreen) {
+  if (!Initialize()) return NS_ERROR_NOT_AVAILABLE;
+
+  NS_ENSURE_ARG_POINTER(aHWND);
+
+  if (!::IsWindow((HWND)aHWND)) return NS_ERROR_INVALID_ARG;
+
+  HRESULT hr = mTaskbar->MarkFullscreenWindow((HWND)aHWND, aFullScreen);
+  if (FAILED(hr)) {
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  return NS_OK;
+}
+
+}  // namespace widget
+}  // namespace mozilla
diff --git a/widget/windows/WinTaskbar.h b/widget/windows/WinTaskbar.h
new file mode 100644
index 0000000000..a6c483a561
--- /dev/null
+++ b/widget/windows/WinTaskbar.h
@@ -0,0 +1,46 @@
+/* vim: se cin sw=2 ts=2 et : */
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef __WinTaskbar_h__
+#define __WinTaskbar_h__
+
+#include <windows.h>
+#include <shobjidl.h>
+#undef LogSeverity  // SetupAPI.h #defines this as DWORD
+#include "nsIWinTaskbar.h"
+#include "mozilla/Attributes.h"
+
+namespace mozilla {
+namespace widget {
+
+class WinTaskbar final : public nsIWinTaskbar {
+  ~WinTaskbar();
+
+ public:
+  WinTaskbar();
+
+  NS_DECL_THREADSAFE_ISUPPORTS
+  NS_DECL_NSIWINTASKBAR
+
+  static bool GenerateAppUserModelID(nsAString& aAppUserModelId,
+                                     bool aPrivateBrowsing = false);
+  // Registers the global app user model id for the instance.
+  // See comments in WinTaskbar.cpp for more information.
+  static bool RegisterAppUserModelID();
+  static bool GetAppUserModelID(nsAString& aDefaultGroupId,
+                                bool aPrivateBrowsing = false);
+
+ private:
+  bool Initialize();
+
+  ITaskbarList4* mTaskbar;
+};
+
+}  // namespace widget
+}  // namespace mozilla
+
+#endif /* __WinTaskbar_h__ */
diff --git a/widget/windows/WinTextEventDispatcherListener.cpp b/widget/windows/WinTextEventDispatcherListener.cpp
new file mode 100644
index 0000000000..aeed8be01b
--- /dev/null
+++ b/widget/windows/WinTextEventDispatcherListener.cpp
@@ -0,0 +1,68 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "KeyboardLayout.h"
+#include "mozilla/TextEventDispatcher.h"
+#include "mozilla/widget/IMEData.h"
+#include "nsWindow.h"
+#include "WinIMEHandler.h"
+#include "WinTextEventDispatcherListener.h"
+
+namespace mozilla {
+namespace widget {
+
+StaticRefPtr<WinTextEventDispatcherListener>
+    WinTextEventDispatcherListener::sInstance;
+
+// static
+WinTextEventDispatcherListener* WinTextEventDispatcherListener::GetInstance() {
+  if (!sInstance) {
+    sInstance = new WinTextEventDispatcherListener();
+  }
+  return sInstance.get();
+}
+
+void WinTextEventDispatcherListener::Shutdown() { sInstance = nullptr; }
+
+NS_IMPL_ISUPPORTS(WinTextEventDispatcherListener, TextEventDispatcherListener,
+                  nsISupportsWeakReference)
+
+WinTextEventDispatcherListener::WinTextEventDispatcherListener() {}
+
+WinTextEventDispatcherListener::~WinTextEventDispatcherListener() {}
+
+NS_IMETHODIMP
+WinTextEventDispatcherListener::NotifyIME(
+    TextEventDispatcher* aTextEventDispatcher,
+    const IMENotification& aNotification) {
+  nsWindow* window = static_cast<nsWindow*>(aTextEventDispatcher->GetWidget());
+  if (NS_WARN_IF(!window)) {
+    return NS_ERROR_FAILURE;
+  }
+  return IMEHandler::NotifyIME(window, aNotification);
+}
+
+NS_IMETHODIMP_(IMENotificationRequests)
+WinTextEventDispatcherListener::GetIMENotificationRequests() {
+  return IMEHandler::GetIMENotificationRequests();
+}
+
+NS_IMETHODIMP_(void)
+WinTextEventDispatcherListener::OnRemovedFrom(
+    TextEventDispatcher* aTextEventDispatcher) {
+  // XXX When input transaction is being stolen by add-on, what should we do?
+}
+
+NS_IMETHODIMP_(void)
+WinTextEventDispatcherListener::WillDispatchKeyboardEvent(
+    TextEventDispatcher* aTextEventDispatcher,
+    WidgetKeyboardEvent& aKeyboardEvent, uint32_t aIndexOfKeypress,
+    void* aData) {
+  static_cast<NativeKey*>(aData)->WillDispatchKeyboardEvent(aKeyboardEvent,
+                                                            aIndexOfKeypress);
+}
+
+}  // namespace widget
+}  // namespace mozilla
diff --git a/widget/windows/WinTextEventDispatcherListener.h b/widget/windows/WinTextEventDispatcherListener.h
new file mode 100644
index 0000000000..d799d0b280
--- /dev/null
+++ b/widget/windows/WinTextEventDispatcherListener.h
@@ -0,0 +1,50 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef WinTextEventDispatcherListener_h_
+#define WinTextEventDispatcherListener_h_
+
+#include "mozilla/Attributes.h"
+#include "mozilla/StaticPtr.h"
+#include "mozilla/TextEventDispatcherListener.h"
+
+namespace mozilla {
+namespace widget {
+
+/**
+ * On Windows, it's enough TextEventDispatcherListener to be a singleton
+ * because we have only one input context per process (IMM can create
+ * multiple IM context but we don't support such behavior).
+ */
+
+class WinTextEventDispatcherListener final
+    : public TextEventDispatcherListener {
+ public:
+  static WinTextEventDispatcherListener* GetInstance();
+  static void Shutdown();
+
+  NS_DECL_ISUPPORTS
+
+  NS_IMETHOD NotifyIME(TextEventDispatcher* aTextEventDispatcher,
+                       const IMENotification& aNotification) override;
+  NS_IMETHOD_(IMENotificationRequests) GetIMENotificationRequests() override;
+  NS_IMETHOD_(void)
+  OnRemovedFrom(TextEventDispatcher* aTextEventDispatcher) override;
+  NS_IMETHOD_(void)
+  WillDispatchKeyboardEvent(TextEventDispatcher* aTextEventDispatcher,
+                            WidgetKeyboardEvent& aKeyboardEvent,
+                            uint32_t aIndexOfKeypress, void* aData) override;
+
+ private:
+  WinTextEventDispatcherListener();
+  virtual ~WinTextEventDispatcherListener();
+
+  static StaticRefPtr<WinTextEventDispatcherListener> sInstance;
+};
+
+}  // namespace widget
+}  // namespace mozilla
+
+#endif  // #ifndef WinTextEventDispatcherListener_h_
diff --git a/widget/windows/WinUtils.cpp b/widget/windows/WinUtils.cpp
new file mode 100644
index 0000000000..1d8fad16f7
--- /dev/null
+++ b/widget/windows/WinUtils.cpp
@@ -0,0 +1,2107 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:set ts=2 sts=2 sw=2 et cin: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "WinUtils.h"
+
+#include <knownfolders.h>
+#include <winioctl.h>
+
+#include "gfxPlatform.h"
+#include "gfxUtils.h"
+#include "nsWindow.h"
+#include "nsWindowDefs.h"
+#include "InputDeviceUtils.h"
+#include "KeyboardLayout.h"
+#include "mozilla/ArrayUtils.h"
+#include "mozilla/BackgroundHangMonitor.h"
+#include "mozilla/ClearOnShutdown.h"
+#include "mozilla/dom/MouseEventBinding.h"
+#include "mozilla/gfx/2D.h"
+#include "mozilla/gfx/DataSurfaceHelpers.h"
+#include "mozilla/gfx/DisplayConfigWindows.h"
+#include "mozilla/gfx/Logging.h"
+#include "mozilla/Preferences.h"
+#include "mozilla/ProfilerThreadSleep.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/SchedulerGroup.h"
+#include "mozilla/WinHeaderOnlyUtils.h"
+#include "mozilla/Unused.h"
+#include "nsIContentPolicy.h"
+#include "WindowsUIUtils.h"
+#include "nsContentUtils.h"
+
+#include "mozilla/Logging.h"
+
+#include "nsString.h"
+#include "nsDirectoryServiceUtils.h"
+#include "imgIContainer.h"
+#include "imgITools.h"
+#include "nsNetUtil.h"
+#include "nsIOutputStream.h"
+#include "nsNetCID.h"
+#include "prtime.h"
+#ifdef MOZ_PLACES
+#  include "nsIFaviconService.h"
+#endif
+#include "nsIDownloader.h"
+#include "nsIChannel.h"
+#include "nsIThread.h"
+#include "MainThreadUtils.h"
+#include "nsLookAndFeel.h"
+#include "nsUnicharUtils.h"
+#include "nsWindowsHelpers.h"
+#include "WinWindowOcclusionTracker.h"
+
+#include <textstor.h>
+#include "TSFTextStore.h"
+
+#include <shellscalingapi.h>
+#include <shlobj.h>
+#include <shlwapi.h>
+
+mozilla::LazyLogModule gWindowsLog("Widget");
+
+#define LOG_E(...) MOZ_LOG(gWindowsLog, LogLevel::Error, (__VA_ARGS__))
+#define LOG_D(...) MOZ_LOG(gWindowsLog, LogLevel::Debug, (__VA_ARGS__))
+
+using namespace mozilla::gfx;
+
+namespace mozilla {
+namespace widget {
+
+#ifdef MOZ_PLACES
+NS_IMPL_ISUPPORTS(myDownloadObserver, nsIDownloadObserver)
+NS_IMPL_ISUPPORTS(AsyncFaviconDataReady, nsIFaviconDataCallback)
+#endif
+NS_IMPL_ISUPPORTS(AsyncEncodeAndWriteIcon, nsIRunnable)
+NS_IMPL_ISUPPORTS(AsyncDeleteAllFaviconsFromDisk, nsIRunnable)
+
+const char FaviconHelper::kJumpListCacheDir[] = "jumpListCache";
+const char FaviconHelper::kShortcutCacheDir[] = "shortcutCache";
+
+struct CoTaskMemFreePolicy {
+  void operator()(void* aPtr) { ::CoTaskMemFree(aPtr); }
+};
+
+SetThreadDpiAwarenessContextProc WinUtils::sSetThreadDpiAwarenessContext = NULL;
+EnableNonClientDpiScalingProc WinUtils::sEnableNonClientDpiScaling = NULL;
+GetSystemMetricsForDpiProc WinUtils::sGetSystemMetricsForDpi = NULL;
+bool WinUtils::sHasPackageIdentity = false;
+
+using GetDpiForWindowProc = UINT(WINAPI*)(HWND);
+static GetDpiForWindowProc sGetDpiForWindow = NULL;
+
+/* static */
+void WinUtils::Initialize() {
+  // Dpi-Awareness is not supported with Win32k Lockdown enabled, so we don't
+  // initialize DPI-related members and assert later that nothing accidently
+  // uses these static members
+  if (!IsWin32kLockedDown()) {
+    HMODULE user32Dll = ::GetModuleHandleW(L"user32");
+    if (user32Dll) {
+      auto getThreadDpiAwarenessContext =
+          (decltype(GetThreadDpiAwarenessContext)*)::GetProcAddress(
+              user32Dll, "GetThreadDpiAwarenessContext");
+      auto areDpiAwarenessContextsEqual =
+          (decltype(AreDpiAwarenessContextsEqual)*)::GetProcAddress(
+              user32Dll, "AreDpiAwarenessContextsEqual");
+      if (getThreadDpiAwarenessContext && areDpiAwarenessContextsEqual &&
+          areDpiAwarenessContextsEqual(
+              getThreadDpiAwarenessContext(),
+              DPI_AWARENESS_CONTEXT_PER_MONITOR_AWARE)) {
+        // Only per-monitor v1 requires these workarounds.
+        sEnableNonClientDpiScaling =
+            (EnableNonClientDpiScalingProc)::GetProcAddress(
+                user32Dll, "EnableNonClientDpiScaling");
+        sSetThreadDpiAwarenessContext =
+            (SetThreadDpiAwarenessContextProc)::GetProcAddress(
+                user32Dll, "SetThreadDpiAwarenessContext");
+      }
+
+      sGetSystemMetricsForDpi = (GetSystemMetricsForDpiProc)::GetProcAddress(
+          user32Dll, "GetSystemMetricsForDpi");
+      sGetDpiForWindow =
+          (GetDpiForWindowProc)::GetProcAddress(user32Dll, "GetDpiForWindow");
+    }
+  }
+
+  sHasPackageIdentity = mozilla::HasPackageIdentity();
+}
+
+// static
+LRESULT WINAPI WinUtils::NonClientDpiScalingDefWindowProcW(HWND hWnd, UINT msg,
+                                                           WPARAM wParam,
+                                                           LPARAM lParam) {
+  MOZ_DIAGNOSTIC_ASSERT(!IsWin32kLockedDown());
+
+  // NOTE: this function was copied out into the body of the pre-XUL skeleton
+  // UI window proc (PreXULSkeletonUI.cpp). If this function changes at any
+  // point, we should probably factor this out and use it from both locations.
+  if (msg == WM_NCCREATE && sEnableNonClientDpiScaling) {
+    sEnableNonClientDpiScaling(hWnd);
+  }
+  return ::DefWindowProcW(hWnd, msg, wParam, lParam);
+}
+
+// static
+void WinUtils::LogW(const wchar_t* fmt, ...) {
+  va_list args = nullptr;
+  if (!lstrlenW(fmt)) {
+    return;
+  }
+  va_start(args, fmt);
+  int buflen = _vscwprintf(fmt, args);
+  wchar_t* buffer = new wchar_t[buflen + 1];
+  if (!buffer) {
+    va_end(args);
+    return;
+  }
+  vswprintf(buffer, buflen, fmt, args);
+  va_end(args);
+
+  // MSVC, including remote debug sessions
+  OutputDebugStringW(buffer);
+  OutputDebugStringW(L"\n");
+
+  int len =
+      WideCharToMultiByte(CP_ACP, 0, buffer, -1, nullptr, 0, nullptr, nullptr);
+  if (len) {
+    char* utf8 = new char[len];
+    if (WideCharToMultiByte(CP_ACP, 0, buffer, -1, utf8, len, nullptr,
+                            nullptr) > 0) {
+      // desktop console
+      printf("%s\n", utf8);
+      NS_ASSERTION(gWindowsLog,
+                   "Called WinUtils Log() but Widget "
+                   "log module doesn't exist!");
+      MOZ_LOG(gWindowsLog, LogLevel::Error, ("%s", utf8));
+    }
+    delete[] utf8;
+  }
+  delete[] buffer;
+}
+
+// static
+void WinUtils::Log(const char* fmt, ...) {
+  va_list args = nullptr;
+  if (!strlen(fmt)) {
+    return;
+  }
+  va_start(args, fmt);
+  int buflen = _vscprintf(fmt, args);
+  char* buffer = new char[buflen + 1];
+  if (!buffer) {
+    va_end(args);
+    return;
+  }
+  vsprintf(buffer, fmt, args);
+  va_end(args);
+
+  // MSVC, including remote debug sessions
+  OutputDebugStringA(buffer);
+  OutputDebugStringW(L"\n");
+
+  // desktop console
+  printf("%s\n", buffer);
+
+  NS_ASSERTION(gWindowsLog,
+               "Called WinUtils Log() but Widget "
+               "log module doesn't exist!");
+  MOZ_LOG(gWindowsLog, LogLevel::Error, ("%s", buffer));
+  delete[] buffer;
+}
+
+// static
+float WinUtils::SystemDPI() {
+  // The result of GetDeviceCaps won't change dynamically, as it predates
+  // per-monitor DPI and support for on-the-fly resolution changes.
+  // Therefore, we only need to look it up once.
+  static float dpi = 0;
+  if (dpi <= 0) {
+    HDC screenDC = GetDC(nullptr);
+    dpi = GetDeviceCaps(screenDC, LOGPIXELSY);
+    ReleaseDC(nullptr, screenDC);
+  }
+
+  // Bug 1012487 - dpi can be 0 when the Screen DC is used off the
+  // main thread on windows. For now just assume a 100% DPI for this
+  // drawing call.
+  // XXX - fixme!
+  return dpi > 0 ? dpi : 96;
+}
+
+// static
+double WinUtils::SystemScaleFactor() { return SystemDPI() / 96.0; }
+
+typedef HRESULT(WINAPI* GETDPIFORMONITORPROC)(HMONITOR, MONITOR_DPI_TYPE, UINT*,
+                                              UINT*);
+
+typedef HRESULT(WINAPI* GETPROCESSDPIAWARENESSPROC)(HANDLE,
+                                                    PROCESS_DPI_AWARENESS*);
+
+GETDPIFORMONITORPROC sGetDpiForMonitor;
+GETPROCESSDPIAWARENESSPROC sGetProcessDpiAwareness;
+
+static bool SlowIsPerMonitorDPIAware() {
+  // Intentionally leak the handle.
+  HMODULE shcore = LoadLibraryEx(L"shcore", NULL, LOAD_LIBRARY_SEARCH_SYSTEM32);
+  if (shcore) {
+    sGetDpiForMonitor =
+        (GETDPIFORMONITORPROC)GetProcAddress(shcore, "GetDpiForMonitor");
+    sGetProcessDpiAwareness = (GETPROCESSDPIAWARENESSPROC)GetProcAddress(
+        shcore, "GetProcessDpiAwareness");
+  }
+  PROCESS_DPI_AWARENESS dpiAwareness;
+  return sGetDpiForMonitor && sGetProcessDpiAwareness &&
+         SUCCEEDED(
+             sGetProcessDpiAwareness(GetCurrentProcess(), &dpiAwareness)) &&
+         dpiAwareness == PROCESS_PER_MONITOR_DPI_AWARE;
+}
+
+/* static */
+bool WinUtils::IsPerMonitorDPIAware() {
+  static bool perMonitorDPIAware = SlowIsPerMonitorDPIAware();
+  return perMonitorDPIAware;
+}
+
+/* static */
+float WinUtils::MonitorDPI(HMONITOR aMonitor) {
+  if (IsPerMonitorDPIAware()) {
+    UINT dpiX, dpiY = 96;
+    sGetDpiForMonitor(aMonitor ? aMonitor : GetPrimaryMonitor(),
+                      MDT_EFFECTIVE_DPI, &dpiX, &dpiY);
+    return dpiY;
+  }
+
+  // We're not per-monitor aware, use system DPI instead.
+  return SystemDPI();
+}
+
+/* static */
+double WinUtils::LogToPhysFactor(HMONITOR aMonitor) {
+  return MonitorDPI(aMonitor) / 96.0;
+}
+
+/* static */
+int32_t WinUtils::LogToPhys(HMONITOR aMonitor, double aValue) {
+  return int32_t(NS_round(aValue * LogToPhysFactor(aMonitor)));
+}
+
+/* static */
+double WinUtils::LogToPhysFactor(HWND aWnd) {
+  // if there's an ancestor window, we want to share its DPI setting
+  HWND ancestor = ::GetAncestor(aWnd, GA_ROOTOWNER);
+
+  // The GetDpiForWindow api is not available everywhere where we run as
+  // per-monitor, but if it is available rely on it to tell us the scale
+  // factor of the window.  See bug 1722085.
+  if (sGetDpiForWindow) {
+    UINT dpi = sGetDpiForWindow(ancestor ? ancestor : aWnd);
+    if (dpi > 0) {
+      return static_cast<double>(dpi) / 96.0;
+    }
+  }
+  return LogToPhysFactor(::MonitorFromWindow(ancestor ? ancestor : aWnd,
+                                             MONITOR_DEFAULTTOPRIMARY));
+}
+
+/* static */
+HMONITOR
+WinUtils::GetPrimaryMonitor() {
+  const POINT pt = {0, 0};
+  return ::MonitorFromPoint(pt, MONITOR_DEFAULTTOPRIMARY);
+}
+
+/* static */
+HMONITOR
+WinUtils::MonitorFromRect(const gfx::Rect& rect) {
+  // convert coordinates from desktop to device pixels for MonitorFromRect
+  double dpiScale =
+      IsPerMonitorDPIAware() ? 1.0 : LogToPhysFactor(GetPrimaryMonitor());
+
+  RECT globalWindowBounds = {NSToIntRound(dpiScale * rect.X()),
+                             NSToIntRound(dpiScale * rect.Y()),
+                             NSToIntRound(dpiScale * (rect.XMost())),
+                             NSToIntRound(dpiScale * (rect.YMost()))};
+
+  return ::MonitorFromRect(&globalWindowBounds, MONITOR_DEFAULTTONEAREST);
+}
+
+/* static */
+bool WinUtils::HasSystemMetricsForDpi() {
+  MOZ_DIAGNOSTIC_ASSERT(!IsWin32kLockedDown());
+  return (sGetSystemMetricsForDpi != NULL);
+}
+
+/* static */
+int WinUtils::GetSystemMetricsForDpi(int nIndex, UINT dpi) {
+  MOZ_DIAGNOSTIC_ASSERT(!IsWin32kLockedDown());
+  if (HasSystemMetricsForDpi()) {
+    return sGetSystemMetricsForDpi(nIndex, dpi);
+  } else {
+    double scale = IsPerMonitorDPIAware() ? dpi / SystemDPI() : 1.0;
+    return NSToIntRound(::GetSystemMetrics(nIndex) * scale);
+  }
+}
+
+/* static */
+gfx::MarginDouble WinUtils::GetUnwriteableMarginsForDeviceInInches(HDC aHdc) {
+  if (!aHdc) {
+    return gfx::MarginDouble();
+  }
+
+  int pixelsPerInchY = ::GetDeviceCaps(aHdc, LOGPIXELSY);
+  int marginTop = ::GetDeviceCaps(aHdc, PHYSICALOFFSETY);
+  int printableAreaHeight = ::GetDeviceCaps(aHdc, VERTRES);
+  int physicalHeight = ::GetDeviceCaps(aHdc, PHYSICALHEIGHT);
+
+  double marginTopInch = double(marginTop) / pixelsPerInchY;
+
+  double printableAreaHeightInch = double(printableAreaHeight) / pixelsPerInchY;
+  double physicalHeightInch = double(physicalHeight) / pixelsPerInchY;
+  double marginBottomInch =
+      physicalHeightInch - printableAreaHeightInch - marginTopInch;
+
+  int pixelsPerInchX = ::GetDeviceCaps(aHdc, LOGPIXELSX);
+  int marginLeft = ::GetDeviceCaps(aHdc, PHYSICALOFFSETX);
+  int printableAreaWidth = ::GetDeviceCaps(aHdc, HORZRES);
+  int physicalWidth = ::GetDeviceCaps(aHdc, PHYSICALWIDTH);
+
+  double marginLeftInch = double(marginLeft) / pixelsPerInchX;
+
+  double printableAreaWidthInch = double(printableAreaWidth) / pixelsPerInchX;
+  double physicalWidthInch = double(physicalWidth) / pixelsPerInchX;
+  double marginRightInch =
+      physicalWidthInch - printableAreaWidthInch - marginLeftInch;
+
+  return gfx::MarginDouble(marginTopInch, marginRightInch, marginBottomInch,
+                           marginLeftInch);
+}
+
+#ifdef ACCESSIBILITY
+/* static */
+a11y::LocalAccessible* WinUtils::GetRootAccessibleForHWND(HWND aHwnd) {
+  nsWindow* window = GetNSWindowPtr(aHwnd);
+  if (!window) {
+    return nullptr;
+  }
+
+  return window->GetAccessible();
+}
+#endif  // ACCESSIBILITY
+
+/* static */
+bool WinUtils::PeekMessage(LPMSG aMsg, HWND aWnd, UINT aFirstMessage,
+                           UINT aLastMessage, UINT aOption) {
+  RefPtr<ITfMessagePump> msgPump = TSFTextStore::GetMessagePump();
+  if (msgPump) {
+    BOOL ret = FALSE;
+    HRESULT hr = msgPump->PeekMessageW(aMsg, aWnd, aFirstMessage, aLastMessage,
+                                       aOption, &ret);
+    NS_ENSURE_TRUE(SUCCEEDED(hr), false);
+    return ret;
+  }
+  return ::PeekMessageW(aMsg, aWnd, aFirstMessage, aLastMessage, aOption);
+}
+
+/* static */
+bool WinUtils::GetMessage(LPMSG aMsg, HWND aWnd, UINT aFirstMessage,
+                          UINT aLastMessage) {
+  RefPtr<ITfMessagePump> msgPump = TSFTextStore::GetMessagePump();
+  if (msgPump) {
+    BOOL ret = FALSE;
+    HRESULT hr =
+        msgPump->GetMessageW(aMsg, aWnd, aFirstMessage, aLastMessage, &ret);
+    NS_ENSURE_TRUE(SUCCEEDED(hr), false);
+    return ret;
+  }
+  return ::GetMessageW(aMsg, aWnd, aFirstMessage, aLastMessage);
+}
+
+#if defined(ACCESSIBILITY)
+static DWORD GetWaitFlags() {
+  DWORD result = MWMO_INPUTAVAILABLE;
+  if (XRE_IsContentProcess()) {
+    result |= MWMO_ALERTABLE;
+  }
+  return result;
+}
+#endif
+
+/* static */
+void WinUtils::WaitForMessage(DWORD aTimeoutMs) {
+#if defined(ACCESSIBILITY)
+  static const DWORD waitFlags = GetWaitFlags();
+#else
+  const DWORD waitFlags = MWMO_INPUTAVAILABLE;
+#endif
+
+  const DWORD waitStart = ::GetTickCount();
+  DWORD elapsed = 0;
+  while (true) {
+    if (aTimeoutMs != INFINITE) {
+      elapsed = ::GetTickCount() - waitStart;
+    }
+    if (elapsed >= aTimeoutMs) {
+      break;
+    }
+    DWORD result;
+    {
+      AUTO_PROFILER_THREAD_SLEEP;
+      result = ::MsgWaitForMultipleObjectsEx(0, NULL, aTimeoutMs - elapsed,
+                                             MOZ_QS_ALLEVENT, waitFlags);
+    }
+    NS_WARNING_ASSERTION(result != WAIT_FAILED, "Wait failed");
+    if (result == WAIT_TIMEOUT) {
+      break;
+    }
+#if defined(ACCESSIBILITY)
+    if (result == WAIT_IO_COMPLETION) {
+      if (NS_IsMainThread()) {
+        // We executed an APC that would have woken up the hang monitor. Since
+        // there are no more APCs pending and we are now going to sleep again,
+        // we should notify the hang monitor.
+        mozilla::BackgroundHangMonitor().NotifyWait();
+      }
+      continue;
+    }
+#endif  // defined(ACCESSIBILITY)
+
+    // Sent messages (via SendMessage and friends) are processed differently
+    // than queued messages (via PostMessage); the destination window procedure
+    // of the sent message is called during (Get|Peek)Message. Since PeekMessage
+    // does not tell us whether it processed any sent messages, we need to query
+    // this ahead of time.
+    bool haveSentMessagesPending =
+        (HIWORD(::GetQueueStatus(QS_SENDMESSAGE)) & QS_SENDMESSAGE) != 0;
+
+    MSG msg = {0};
+    if (haveSentMessagesPending ||
+        ::PeekMessageW(&msg, nullptr, 0, 0, PM_NOREMOVE)) {
+      break;
+    }
+    // The message is intended for another thread that has been synchronized
+    // with our input queue; yield to give other threads an opportunity to
+    // process the message. This should prevent busy waiting if resumed due
+    // to another thread's message.
+    ::SwitchToThread();
+  }
+}
+
+/* static */
+HWND WinUtils::GetTopLevelHWND(HWND aWnd, bool aStopIfNotChild,
+                               bool aStopIfNotPopup) {
+  HWND curWnd = aWnd;
+  HWND topWnd = nullptr;
+
+  while (curWnd) {
+    topWnd = curWnd;
+
+    if (aStopIfNotChild) {
+      DWORD_PTR style = ::GetWindowLongPtrW(curWnd, GWL_STYLE);
+
+      VERIFY_WINDOW_STYLE(style);
+
+      if (!(style & WS_CHILD))  // first top-level window
+        break;
+    }
+
+    HWND upWnd = ::GetParent(curWnd);  // Parent or owner (if has no parent)
+
+    // GetParent will only return the owner if the passed in window
+    // has the WS_POPUP style.
+    if (!upWnd && !aStopIfNotPopup) {
+      upWnd = ::GetWindow(curWnd, GW_OWNER);
+    }
+    curWnd = upWnd;
+  }
+
+  return topWnd;
+}
+
+// Map from native window handles to nsWindow structures. Does not AddRef.
+// Inherently unsafe to access outside the main thread.
+static nsTHashMap<HWND, nsWindow*> sExtantNSWindows;
+
+/* static */
+void WinUtils::SetNSWindowPtr(HWND aWnd, nsWindow* aWindow) {
+  MOZ_ASSERT(NS_IsMainThread());
+  if (!aWindow) {
+    sExtantNSWindows.Remove(aWnd);
+  } else {
+    sExtantNSWindows.InsertOrUpdate(aWnd, aWindow);
+  }
+}
+
+/* static */
+nsWindow* WinUtils::GetNSWindowPtr(HWND aWnd) {
+  MOZ_ASSERT(NS_IsMainThread());
+  return sExtantNSWindows.Get(aWnd);  // or nullptr
+}
+
+/* static */
+bool WinUtils::IsOurProcessWindow(HWND aWnd) {
+  if (!aWnd) {
+    return false;
+  }
+  DWORD processId = 0;
+  ::GetWindowThreadProcessId(aWnd, &processId);
+  return (processId == ::GetCurrentProcessId());
+}
+
+/* static */
+HWND WinUtils::FindOurProcessWindow(HWND aWnd) {
+  for (HWND wnd = ::GetParent(aWnd); wnd; wnd = ::GetParent(wnd)) {
+    if (IsOurProcessWindow(wnd)) {
+      return wnd;
+    }
+  }
+  return nullptr;
+}
+
+static bool IsPointInWindow(HWND aWnd, const POINT& aPointInScreen) {
+  RECT bounds;
+  if (!::GetWindowRect(aWnd, &bounds)) {
+    return false;
+  }
+
+  return (aPointInScreen.x >= bounds.left && aPointInScreen.x < bounds.right &&
+          aPointInScreen.y >= bounds.top && aPointInScreen.y < bounds.bottom);
+}
+
+/**
+ * FindTopmostWindowAtPoint() returns the topmost child window (topmost means
+ * forground in this context) of aWnd.
+ */
+
+static HWND FindTopmostWindowAtPoint(HWND aWnd, const POINT& aPointInScreen) {
+  if (!::IsWindowVisible(aWnd) || !IsPointInWindow(aWnd, aPointInScreen)) {
+    return nullptr;
+  }
+
+  HWND childWnd = ::GetTopWindow(aWnd);
+  while (childWnd) {
+    HWND topmostWnd = FindTopmostWindowAtPoint(childWnd, aPointInScreen);
+    if (topmostWnd) {
+      return topmostWnd;
+    }
+    childWnd = ::GetNextWindow(childWnd, GW_HWNDNEXT);
+  }
+
+  return aWnd;
+}
+
+struct FindOurWindowAtPointInfo {
+  POINT mInPointInScreen;
+  HWND mOutWnd;
+};
+
+static BOOL CALLBACK FindOurWindowAtPointCallback(HWND aWnd, LPARAM aLPARAM) {
+  if (!WinUtils::IsOurProcessWindow(aWnd)) {
+    // This isn't one of our top-level windows; continue enumerating.
+    return TRUE;
+  }
+
+  // Get the top-most child window under the point.  If there's no child
+  // window, and the point is within the top-level window, then the top-level
+  // window will be returned.  (This is the usual case.  A child window
+  // would be returned for plugins.)
+  FindOurWindowAtPointInfo* info =
+      reinterpret_cast<FindOurWindowAtPointInfo*>(aLPARAM);
+  HWND childWnd = FindTopmostWindowAtPoint(aWnd, info->mInPointInScreen);
+  if (!childWnd) {
+    // This window doesn't contain the point; continue enumerating.
+    return TRUE;
+  }
+
+  // Return the HWND and stop enumerating.
+  info->mOutWnd = childWnd;
+  return FALSE;
+}
+
+/* static */
+HWND WinUtils::FindOurWindowAtPoint(const POINT& aPointInScreen) {
+  FindOurWindowAtPointInfo info;
+  info.mInPointInScreen = aPointInScreen;
+  info.mOutWnd = nullptr;
+
+  // This will enumerate all top-level windows in order from top to bottom.
+  EnumWindows(FindOurWindowAtPointCallback, reinterpret_cast<LPARAM>(&info));
+  return info.mOutWnd;
+}
+
+/* static */
+UINT WinUtils::GetInternalMessage(UINT aNativeMessage) {
+  switch (aNativeMessage) {
+    case WM_MOUSEWHEEL:
+      return MOZ_WM_MOUSEVWHEEL;
+    case WM_MOUSEHWHEEL:
+      return MOZ_WM_MOUSEHWHEEL;
+    case WM_VSCROLL:
+      return MOZ_WM_VSCROLL;
+    case WM_HSCROLL:
+      return MOZ_WM_HSCROLL;
+    default:
+      return aNativeMessage;
+  }
+}
+
+/* static */
+UINT WinUtils::GetNativeMessage(UINT aInternalMessage) {
+  switch (aInternalMessage) {
+    case MOZ_WM_MOUSEVWHEEL:
+      return WM_MOUSEWHEEL;
+    case MOZ_WM_MOUSEHWHEEL:
+      return WM_MOUSEHWHEEL;
+    case MOZ_WM_VSCROLL:
+      return WM_VSCROLL;
+    case MOZ_WM_HSCROLL:
+      return WM_HSCROLL;
+    default:
+      return aInternalMessage;
+  }
+}
+
+/* static */
+uint16_t WinUtils::GetMouseInputSource() {
+  int32_t inputSource = dom::MouseEvent_Binding::MOZ_SOURCE_MOUSE;
+  LPARAM lParamExtraInfo = ::GetMessageExtraInfo();
+  if ((lParamExtraInfo & TABLET_INK_SIGNATURE) == TABLET_INK_CHECK) {
+    inputSource = (lParamExtraInfo & TABLET_INK_TOUCH)
+                      ? dom::MouseEvent_Binding::MOZ_SOURCE_TOUCH
+                      : dom::MouseEvent_Binding::MOZ_SOURCE_PEN;
+  }
+  return static_cast<uint16_t>(inputSource);
+}
+
+/* static */
+uint16_t WinUtils::GetMousePointerID() {
+  LPARAM lParamExtraInfo = ::GetMessageExtraInfo();
+  return lParamExtraInfo & TABLET_INK_ID_MASK;
+}
+
+/* static */
+bool WinUtils::GetIsMouseFromTouch(EventMessage aEventMessage) {
+  const uint32_t MOZ_T_I_SIGNATURE = TABLET_INK_TOUCH | TABLET_INK_SIGNATURE;
+  const uint32_t MOZ_T_I_CHECK_TCH = TABLET_INK_TOUCH | TABLET_INK_CHECK;
+  return ((aEventMessage == eMouseMove || aEventMessage == eMouseDown ||
+           aEventMessage == eMouseUp || aEventMessage == eMouseAuxClick ||
+           aEventMessage == eMouseDoubleClick) &&
+          (GetMessageExtraInfo() & MOZ_T_I_SIGNATURE) == MOZ_T_I_CHECK_TCH);
+}
+
+/* static */
+MSG WinUtils::InitMSG(UINT aMessage, WPARAM wParam, LPARAM lParam, HWND aWnd) {
+  MSG msg;
+  msg.message = aMessage;
+  msg.wParam = wParam;
+  msg.lParam = lParam;
+  msg.hwnd = aWnd;
+  return msg;
+}
+
+#ifdef MOZ_PLACES
+/************************************************************************
+ * Constructs as AsyncFaviconDataReady Object
+ * @param aIOThread : the thread which performs the action
+ * @param aURLShortcut : Differentiates between (false)Jumplistcache and
+ *                       (true)Shortcutcache
+ * @param aRunnable : Executed in the aIOThread when the favicon cache is
+ *                    avaiable
+ ************************************************************************/
+
+AsyncFaviconDataReady::AsyncFaviconDataReady(
+    nsIURI* aNewURI, RefPtr<LazyIdleThread>& aIOThread, const bool aURLShortcut,
+    already_AddRefed<nsIRunnable> aRunnable)
+    : mNewURI(aNewURI),
+      mIOThread(aIOThread),
+      mRunnable(aRunnable),
+      mURLShortcut(aURLShortcut) {}
+
+NS_IMETHODIMP
+myDownloadObserver::OnDownloadComplete(nsIDownloader* downloader,
+                                       nsIRequest* request, nsresult status,
+                                       nsIFile* result) {
+  return NS_OK;
+}
+
+nsresult AsyncFaviconDataReady::OnFaviconDataNotAvailable(void) {
+  if (!mURLShortcut) {
+    return NS_OK;
+  }
+
+  nsCOMPtr<nsIFile> icoFile;
+  nsresult rv =
+      FaviconHelper::GetOutputIconPath(mNewURI, icoFile, mURLShortcut);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsCOMPtr<nsIURI> mozIconURI;
+  rv = NS_NewURI(getter_AddRefs(mozIconURI), "moz-icon://.html?size=32");
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+
+  nsCOMPtr<nsIChannel> channel;
+  rv = NS_NewChannel(getter_AddRefs(channel), mozIconURI,
+                     nsContentUtils::GetSystemPrincipal(),
+                     nsILoadInfo::SEC_ALLOW_CROSS_ORIGIN_SEC_CONTEXT_IS_NULL,
+                     nsIContentPolicy::TYPE_INTERNAL_IMAGE);
+
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsCOMPtr<nsIDownloadObserver> downloadObserver = new myDownloadObserver;
+  nsCOMPtr<nsIStreamListener> listener;
+  rv = NS_NewDownloader(getter_AddRefs(listener), downloadObserver, icoFile);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  return channel->AsyncOpen(listener);
+}
+
+NS_IMETHODIMP
+AsyncFaviconDataReady::OnComplete(nsIURI* aFaviconURI, uint32_t aDataLen,
+                                  const uint8_t* aData,
+                                  const nsACString& aMimeType,
+                                  uint16_t aWidth) {
+  if (!aDataLen || !aData) {
+    if (mURLShortcut) {
+      OnFaviconDataNotAvailable();
+    }
+
+    return NS_OK;
+  }
+
+  nsCOMPtr<nsIFile> icoFile;
+  nsresult rv =
+      FaviconHelper::GetOutputIconPath(mNewURI, icoFile, mURLShortcut);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsAutoString path;
+  rv = icoFile->GetPath(path);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // Decode the image from the format it was returned to us in (probably PNG)
+  nsCOMPtr<imgIContainer> container;
+  nsCOMPtr<imgITools> imgtool = do_CreateInstance("@mozilla.org/image/tools;1");
+  rv = imgtool->DecodeImageFromBuffer(reinterpret_cast<const char*>(aData),
+                                      aDataLen, aMimeType,
+                                      getter_AddRefs(container));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  RefPtr<SourceSurface> surface = container->GetFrame(
+      imgIContainer::FRAME_FIRST,
+      imgIContainer::FLAG_SYNC_DECODE | imgIContainer::FLAG_ASYNC_NOTIFY);
+  NS_ENSURE_TRUE(surface, NS_ERROR_FAILURE);
+
+  RefPtr<DataSourceSurface> dataSurface;
+  IntSize size;
+
+  if (mURLShortcut &&
+      (surface->GetSize().width < 48 || surface->GetSize().height < 48)) {
+    // Create a 48x48 surface and paint the icon into the central rect.
+    size.width = std::max(surface->GetSize().width, 48);
+    size.height = std::max(surface->GetSize().height, 48);
+    dataSurface =
+        Factory::CreateDataSourceSurface(size, SurfaceFormat::B8G8R8A8);
+    NS_ENSURE_TRUE(dataSurface, NS_ERROR_FAILURE);
+
+    DataSourceSurface::MappedSurface map;
+    if (!dataSurface->Map(DataSourceSurface::MapType::WRITE, &map)) {
+      return NS_ERROR_FAILURE;
+    }
+
+    RefPtr<DrawTarget> dt = Factory::CreateDrawTargetForData(
+        BackendType::CAIRO, map.mData, dataSurface->GetSize(), map.mStride,
+        dataSurface->GetFormat());
+    if (!dt) {
+      gfxWarning() << "AsyncFaviconDataReady::OnComplete failed in "
+                      "CreateDrawTargetForData";
+      return NS_ERROR_OUT_OF_MEMORY;
+    }
+    dt->FillRect(Rect(0, 0, size.width, size.height),
+                 ColorPattern(ToDeviceColor(sRGBColor::OpaqueWhite())));
+    IntPoint point;
+    point.x = (size.width - surface->GetSize().width) / 2;
+    point.y = (size.height - surface->GetSize().height) / 2;
+    dt->DrawSurface(surface,
+                    Rect(point.x, point.y, surface->GetSize().width,
+                         surface->GetSize().height),
+                    Rect(Point(0, 0), Size(surface->GetSize().width,
+                                           surface->GetSize().height)));
+
+    dataSurface->Unmap();
+  } else {
+    // By using the input image surface's size, we may end up encoding
+    // to a different size than a 16x16 (or bigger for higher DPI) ICO, but
+    // Windows will resize appropriately for us. If we want to encode ourselves
+    // one day because we like our resizing better, we'd have to manually
+    // resize the image here and use GetSystemMetrics w/ SM_CXSMICON and
+    // SM_CYSMICON. We don't support resizing images asynchronously at the
+    // moment anyway so getting the DPI aware icon size won't help.
+    size.width = surface->GetSize().width;
+    size.height = surface->GetSize().height;
+    dataSurface = surface->GetDataSurface();
+    NS_ENSURE_TRUE(dataSurface, NS_ERROR_FAILURE);
+  }
+
+  // Allocate a new buffer that we own and can use out of line in
+  // another thread.
+  UniquePtr<uint8_t[]> data = SurfaceToPackedBGRA(dataSurface);
+  if (!data) {
+    return NS_ERROR_OUT_OF_MEMORY;
+  }
+  int32_t stride = 4 * size.width;
+
+  // AsyncEncodeAndWriteIcon takes ownership of the heap allocated buffer
+  nsCOMPtr<nsIRunnable> event =
+      new AsyncEncodeAndWriteIcon(path, std::move(data), stride, size.width,
+                                  size.height, mRunnable.forget());
+  mIOThread->Dispatch(event, NS_DISPATCH_NORMAL);
+
+  return NS_OK;
+}
+#endif
+
+// Warning: AsyncEncodeAndWriteIcon assumes ownership of the aData buffer passed
+// in
+AsyncEncodeAndWriteIcon::AsyncEncodeAndWriteIcon(
+    const nsAString& aIconPath, UniquePtr<uint8_t[]> aBuffer, uint32_t aStride,
+    uint32_t aWidth, uint32_t aHeight, already_AddRefed<nsIRunnable> aRunnable)
+    : mIconPath(aIconPath),
+      mBuffer(std::move(aBuffer)),
+      mRunnable(aRunnable),
+      mStride(aStride),
+      mWidth(aWidth),
+      mHeight(aHeight) {}
+
+NS_IMETHODIMP AsyncEncodeAndWriteIcon::Run() {
+  MOZ_ASSERT(!NS_IsMainThread(), "Should not be called on the main thread.");
+
+  // Note that since we're off the main thread we can't use
+  // gfxPlatform::GetPlatform()->ScreenReferenceDrawTarget()
+  RefPtr<DataSourceSurface> surface = Factory::CreateWrappingDataSourceSurface(
+      mBuffer.get(), mStride, IntSize(mWidth, mHeight),
+      SurfaceFormat::B8G8R8A8);
+
+  FILE* file = _wfopen(mIconPath.get(), L"wb");
+  if (!file) {
+    // Maybe the directory doesn't exist; try creating it, then fopen again.
+    nsresult rv = NS_ERROR_FAILURE;
+    nsCOMPtr<nsIFile> comFile = do_CreateInstance("@mozilla.org/file/local;1");
+    if (comFile) {
+      rv = comFile->InitWithPath(mIconPath);
+      if (NS_SUCCEEDED(rv)) {
+        nsCOMPtr<nsIFile> dirPath;
+        comFile->GetParent(getter_AddRefs(dirPath));
+        if (dirPath) {
+          rv = dirPath->Create(nsIFile::DIRECTORY_TYPE, 0777);
+          if (NS_SUCCEEDED(rv) || rv == NS_ERROR_FILE_ALREADY_EXISTS) {
+            file = _wfopen(mIconPath.get(), L"wb");
+            if (!file) {
+              rv = NS_ERROR_FAILURE;
+            }
+          }
+        }
+      }
+    }
+    if (!file) {
+      return rv;
+    }
+  }
+  nsresult rv = gfxUtils::EncodeSourceSurface(surface, ImageType::ICO, u""_ns,
+                                              gfxUtils::eBinaryEncode, file);
+  fclose(file);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  if (mRunnable) {
+    mRunnable->Run();
+  }
+  return rv;
+}
+
+AsyncEncodeAndWriteIcon::~AsyncEncodeAndWriteIcon() {}
+
+AsyncDeleteAllFaviconsFromDisk::AsyncDeleteAllFaviconsFromDisk(
+    bool aIgnoreRecent)
+    : mIgnoreRecent(aIgnoreRecent) {
+  // We can't call FaviconHelper::GetICOCacheSecondsTimeout() on non-main
+  // threads, as it reads a pref, so cache its value here.
+  mIcoNoDeleteSeconds = FaviconHelper::GetICOCacheSecondsTimeout() + 600;
+
+  // Prepare the profile directory cache on the main thread, to ensure we wont
+  // do this on non-main threads.
+  Unused << NS_GetSpecialDirectory("ProfLDS",
+                                   getter_AddRefs(mJumpListCacheDir));
+}
+
+NS_IMETHODIMP AsyncDeleteAllFaviconsFromDisk::Run() {
+  if (!mJumpListCacheDir) {
+    return NS_ERROR_FAILURE;
+  }
+  // Construct the path of our jump list cache
+  nsresult rv = mJumpListCacheDir->AppendNative(
+      nsDependentCString(FaviconHelper::kJumpListCacheDir));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsCOMPtr<nsIDirectoryEnumerator> entries;
+  rv = mJumpListCacheDir->GetDirectoryEntries(getter_AddRefs(entries));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // Loop through each directory entry and remove all ICO files found
+  do {
+    nsCOMPtr<nsIFile> currFile;
+    if (NS_FAILED(entries->GetNextFile(getter_AddRefs(currFile))) || !currFile)
+      break;
+
+    nsAutoString path;
+    if (NS_FAILED(currFile->GetPath(path))) continue;
+
+    if (StringTail(path, 4).LowerCaseEqualsASCII(".ico")) {
+      // Check if the cached ICO file exists
+      bool exists;
+      if (NS_FAILED(currFile->Exists(&exists)) || !exists) continue;
+
+      if (mIgnoreRecent) {
+        // Check to make sure the icon wasn't just recently created.
+        // If it was created recently, don't delete it yet.
+        int64_t fileModTime = 0;
+        rv = currFile->GetLastModifiedTime(&fileModTime);
+        fileModTime /= PR_MSEC_PER_SEC;
+        // If the icon is older than the regeneration time (+ 10 min to be
+        // safe), then it's old and we can get rid of it.
+        // This code is only hit directly after a regeneration.
+        int64_t nowTime = PR_Now() / int64_t(PR_USEC_PER_SEC);
+        if (NS_FAILED(rv) || (nowTime - fileModTime) < mIcoNoDeleteSeconds) {
+          continue;
+        }
+      }
+
+      // We found an ICO file that exists, so we should remove it
+      currFile->Remove(false);
+    }
+  } while (true);
+
+  return NS_OK;
+}
+
+AsyncDeleteAllFaviconsFromDisk::~AsyncDeleteAllFaviconsFromDisk() {}
+
+/*
+ * (static) If the data is available, will return the path on disk where
+ * the favicon for page aFaviconPageURI is stored.  If the favicon does not
+ * exist, or its cache is expired, this method will kick off an async request
+ * for the icon so that next time the method is called it will be available.
+ * @param aFaviconPageURI The URI of the page to obtain
+ * @param aICOFilePath The path of the icon file
+ * @param aIOThread The thread to perform the Fetch on
+ * @param aURLShortcut to distinguish between jumplistcache(false) and
+ *                     shortcutcache(true)
+ * @param aRunnable Executed in the aIOThread when the favicon cache is
+ *                  avaiable
+ */
+nsresult FaviconHelper::ObtainCachedIconFile(
+    nsCOMPtr<nsIURI> aFaviconPageURI, nsString& aICOFilePath,
+    RefPtr<LazyIdleThread>& aIOThread, bool aURLShortcut,
+    already_AddRefed<nsIRunnable> aRunnable) {
+  nsCOMPtr<nsIRunnable> runnable = aRunnable;
+  // Obtain the ICO file path
+  nsCOMPtr<nsIFile> icoFile;
+  nsresult rv = GetOutputIconPath(aFaviconPageURI, icoFile, aURLShortcut);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // Check if the cached ICO file already exists
+  bool exists;
+  rv = icoFile->Exists(&exists);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  if (exists) {
+    // Obtain the file's last modification date in seconds
+    int64_t fileModTime = 0;
+    rv = icoFile->GetLastModifiedTime(&fileModTime);
+    fileModTime /= PR_MSEC_PER_SEC;
+    int32_t icoReCacheSecondsTimeout = GetICOCacheSecondsTimeout();
+    int64_t nowTime = PR_Now() / int64_t(PR_USEC_PER_SEC);
+
+    // If the last mod call failed or the icon is old then re-cache it
+    // This check is in case the favicon of a page changes
+    // the next time we try to build the jump list, the data will be available.
+    if (NS_FAILED(rv) || (nowTime - fileModTime) > icoReCacheSecondsTimeout) {
+      CacheIconFileFromFaviconURIAsync(aFaviconPageURI, icoFile, aIOThread,
+                                       aURLShortcut, runnable.forget());
+      return NS_ERROR_NOT_AVAILABLE;
+    }
+  } else {
+    // The file does not exist yet, obtain it async from the favicon service so
+    // that the next time we try to build the jump list it'll be available.
+    CacheIconFileFromFaviconURIAsync(aFaviconPageURI, icoFile, aIOThread,
+                                     aURLShortcut, runnable.forget());
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  // The icoFile is filled with a path that exists, get its path
+  rv = icoFile->GetPath(aICOFilePath);
+  return rv;
+}
+
+// Hash a URI using a cryptographic hash function (currently SHA-256)
+// Output will be a base64-encoded string of the hash.
+static nsresult HashURI(nsIURI* aUri, nsACString& aUriHash) {
+  nsAutoCString spec;
+  nsresult rv = aUri->GetSpec(spec);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsCOMPtr<nsICryptoHash> cryptoHash =
+      do_CreateInstance(NS_CRYPTO_HASH_CONTRACTID, &rv);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  rv = cryptoHash->Init(nsICryptoHash::SHA256);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // Add some context to the hash to even further reduce the chances of
+  // collision. Note that we are hashing this string with its null-terminator.
+  const char kHashUriContext[] = "firefox-uri";
+  rv = cryptoHash->Update(reinterpret_cast<const uint8_t*>(kHashUriContext),
+                          sizeof(kHashUriContext));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  rv = cryptoHash->Update(reinterpret_cast<const uint8_t*>(spec.BeginReading()),
+                          spec.Length());
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  rv = cryptoHash->Finish(true, aUriHash);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  return NS_OK;
+}
+
+// (static) Obtains the ICO file for the favicon at page aFaviconPageURI
+// If successful, the file path on disk is in the format:
+// <ProfLDS>\jumpListCache\<hash(aFaviconPageURI)>.ico
+//
+// We generate the name with a cryptographically secure hash function in order
+// to ensure that malicious websites can't intentionally craft URLs to collide
+// with legitimate websites.
+nsresult FaviconHelper::GetOutputIconPath(nsCOMPtr<nsIURI> aFaviconPageURI,
+                                          nsCOMPtr<nsIFile>& aICOFile,
+                                          bool aURLShortcut) {
+  nsAutoCString inputURIHash;
+  nsresult rv = HashURI(aFaviconPageURI, inputURIHash);
+  NS_ENSURE_SUCCESS(rv, rv);
+  char* cur = inputURIHash.BeginWriting();
+  char* end = inputURIHash.EndWriting();
+  for (; cur < end; ++cur) {
+    if ('/' == *cur) {
+      *cur = '_';
+    }
+  }
+
+  // Obtain the local profile directory and construct the output icon file path
+  rv = NS_GetSpecialDirectory("ProfLDS", getter_AddRefs(aICOFile));
+  NS_ENSURE_SUCCESS(rv, rv);
+  if (!aURLShortcut)
+    rv = aICOFile->AppendNative(nsDependentCString(kJumpListCacheDir));
+  else
+    rv = aICOFile->AppendNative(nsDependentCString(kShortcutCacheDir));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // Append the icon extension
+  inputURIHash.AppendLiteral(".ico");
+  rv = aICOFile->AppendNative(inputURIHash);
+
+  return rv;
+}
+
+// (static) Asynchronously creates a cached ICO file on disk for the favicon of
+// page aFaviconPageURI and stores it to disk at the path of aICOFile.
+nsresult FaviconHelper::CacheIconFileFromFaviconURIAsync(
+    nsCOMPtr<nsIURI> aFaviconPageURI, nsCOMPtr<nsIFile> aICOFile,
+    RefPtr<LazyIdleThread>& aIOThread, bool aURLShortcut,
+    already_AddRefed<nsIRunnable> aRunnable) {
+  nsCOMPtr<nsIRunnable> runnable = aRunnable;
+#ifdef MOZ_PLACES
+  // Obtain the favicon service and get the favicon for the specified page
+  nsCOMPtr<nsIFaviconService> favIconSvc(
+      do_GetService("@mozilla.org/browser/favicon-service;1"));
+  NS_ENSURE_TRUE(favIconSvc, NS_ERROR_FAILURE);
+
+  nsCOMPtr<nsIFaviconDataCallback> callback =
+      new mozilla::widget::AsyncFaviconDataReady(
+          aFaviconPageURI, aIOThread, aURLShortcut, runnable.forget());
+
+  favIconSvc->GetFaviconDataForPage(aFaviconPageURI, callback, 0);
+#endif
+  return NS_OK;
+}
+
+// Obtains the jump list 'ICO cache timeout in seconds' pref
+int32_t FaviconHelper::GetICOCacheSecondsTimeout() {
+  // Only obtain the setting at most once from the pref service.
+  // In the rare case that 2 threads call this at the same
+  // time it is no harm and we will simply obtain the pref twice.
+  // None of the taskbar list prefs are currently updated via a
+  // pref observer so I think this should suffice.
+  const int32_t kSecondsPerDay = 86400;
+  static bool alreadyObtained = false;
+  static int32_t icoReCacheSecondsTimeout = kSecondsPerDay;
+  if (alreadyObtained) {
+    return icoReCacheSecondsTimeout;
+  }
+
+  // Obtain the pref
+  const char PREF_ICOTIMEOUT[] = "browser.taskbar.lists.icoTimeoutInSeconds";
+  icoReCacheSecondsTimeout =
+      Preferences::GetInt(PREF_ICOTIMEOUT, kSecondsPerDay);
+  alreadyObtained = true;
+  return icoReCacheSecondsTimeout;
+}
+
+/* static */
+LayoutDeviceIntRegion WinUtils::ConvertHRGNToRegion(HRGN aRgn) {
+  NS_ASSERTION(aRgn, "Don't pass NULL region here");
+
+  LayoutDeviceIntRegion rgn;
+
+  DWORD size = ::GetRegionData(aRgn, 0, nullptr);
+  AutoTArray<uint8_t, 100> buffer;
+  buffer.SetLength(size);
+
+  RGNDATA* data = reinterpret_cast<RGNDATA*>(buffer.Elements());
+  if (!::GetRegionData(aRgn, size, data)) return rgn;
+
+  if (data->rdh.nCount > MAX_RECTS_IN_REGION) {
+    rgn = ToIntRect(data->rdh.rcBound);
+    return rgn;
+  }
+
+  RECT* rects = reinterpret_cast<RECT*>(data->Buffer);
+  for (uint32_t i = 0; i < data->rdh.nCount; ++i) {
+    RECT* r = rects + i;
+    rgn.Or(rgn, ToIntRect(*r));
+  }
+
+  return rgn;
+}
+
+LayoutDeviceIntRect WinUtils::ToIntRect(const RECT& aRect) {
+  return LayoutDeviceIntRect(aRect.left, aRect.top, aRect.right - aRect.left,
+                             aRect.bottom - aRect.top);
+}
+
+/* static */
+bool WinUtils::IsIMEEnabled(const InputContext& aInputContext) {
+  return IsIMEEnabled(aInputContext.mIMEState.mEnabled);
+}
+
+/* static */
+bool WinUtils::IsIMEEnabled(IMEEnabled aIMEState) {
+  return aIMEState == IMEEnabled::Enabled;
+}
+
+/* static */
+void WinUtils::SetupKeyModifiersSequence(nsTArray<KeyPair>* aArray,
+                                         uint32_t aModifiers, UINT aMessage) {
+  MOZ_ASSERT(!(aModifiers & nsIWidget::ALTGRAPH) ||
+             !(aModifiers & (nsIWidget::CTRL_L | nsIWidget::ALT_R)));
+  if (aMessage == WM_KEYUP) {
+    // If AltGr is released, ControlLeft key is released first, then,
+    // AltRight key is released.
+    if (aModifiers & nsIWidget::ALTGRAPH) {
+      aArray->AppendElement(
+          KeyPair(VK_CONTROL, VK_LCONTROL, ScanCode::eControlLeft));
+      aArray->AppendElement(KeyPair(VK_MENU, VK_RMENU, ScanCode::eAltRight));
+    }
+    for (uint32_t i = ArrayLength(sModifierKeyMap); i; --i) {
+      const uint32_t* map = sModifierKeyMap[i - 1];
+      if (aModifiers & map[0]) {
+        aArray->AppendElement(KeyPair(map[1], map[2], map[3]));
+      }
+    }
+  } else {
+    for (uint32_t i = 0; i < ArrayLength(sModifierKeyMap); ++i) {
+      const uint32_t* map = sModifierKeyMap[i];
+      if (aModifiers & map[0]) {
+        aArray->AppendElement(KeyPair(map[1], map[2], map[3]));
+      }
+    }
+    // If AltGr is pressed, ControlLeft key is pressed first, then,
+    // AltRight key is pressed.
+    if (aModifiers & nsIWidget::ALTGRAPH) {
+      aArray->AppendElement(
+          KeyPair(VK_CONTROL, VK_LCONTROL, ScanCode::eControlLeft));
+      aArray->AppendElement(KeyPair(VK_MENU, VK_RMENU, ScanCode::eAltRight));
+    }
+  }
+}
+
+/* static */
+nsresult WinUtils::WriteBitmap(nsIFile* aFile, imgIContainer* aImage) {
+  RefPtr<SourceSurface> surface = aImage->GetFrame(
+      imgIContainer::FRAME_FIRST,
+      imgIContainer::FLAG_SYNC_DECODE | imgIContainer::FLAG_ASYNC_NOTIFY);
+  NS_ENSURE_TRUE(surface, NS_ERROR_FAILURE);
+
+  return WriteBitmap(aFile, surface);
+}
+
+/* static */
+nsresult WinUtils::WriteBitmap(nsIFile* aFile, SourceSurface* surface) {
+  nsresult rv;
+
+  // For either of the following formats we want to set the biBitCount member
+  // of the BITMAPINFOHEADER struct to 32, below. For that value the bitmap
+  // format defines that the A8/X8 WORDs in the bitmap byte stream be ignored
+  // for the BI_RGB value we use for the biCompression member.
+  MOZ_ASSERT(surface->GetFormat() == SurfaceFormat::B8G8R8A8 ||
+             surface->GetFormat() == SurfaceFormat::B8G8R8X8);
+
+  RefPtr<DataSourceSurface> dataSurface = surface->GetDataSurface();
+  NS_ENSURE_TRUE(dataSurface, NS_ERROR_FAILURE);
+
+  int32_t width = dataSurface->GetSize().width;
+  int32_t height = dataSurface->GetSize().height;
+  int32_t bytesPerPixel = 4 * sizeof(uint8_t);
+  uint32_t bytesPerRow = bytesPerPixel * width;
+  bool hasAlpha = surface->GetFormat() == SurfaceFormat::B8G8R8A8;
+
+  // initialize these bitmap structs which we will later
+  // serialize directly to the head of the bitmap file
+  BITMAPV4HEADER bmi;
+  memset(&bmi, 0, sizeof(BITMAPV4HEADER));
+  bmi.bV4Size = sizeof(BITMAPV4HEADER);
+  bmi.bV4Width = width;
+  bmi.bV4Height = height;
+  bmi.bV4Planes = 1;
+  bmi.bV4BitCount = (WORD)bytesPerPixel * 8;
+  bmi.bV4V4Compression = hasAlpha ? BI_BITFIELDS : BI_RGB;
+  bmi.bV4SizeImage = bytesPerRow * height;
+  bmi.bV4CSType = LCS_sRGB;
+  if (hasAlpha) {
+    bmi.bV4RedMask = 0x00FF0000;
+    bmi.bV4GreenMask = 0x0000FF00;
+    bmi.bV4BlueMask = 0x000000FF;
+    bmi.bV4AlphaMask = 0xFF000000;
+  }
+
+  BITMAPFILEHEADER bf;
+  DWORD colormask[3];
+  bf.bfType = 0x4D42;  // 'BM'
+  bf.bfReserved1 = 0;
+  bf.bfReserved2 = 0;
+  bf.bfOffBits = sizeof(BITMAPFILEHEADER) + sizeof(BITMAPV4HEADER) +
+                 (hasAlpha ? sizeof(colormask) : 0);
+  bf.bfSize = bf.bfOffBits + bmi.bV4SizeImage;
+
+  // get a file output stream
+  nsCOMPtr<nsIOutputStream> stream;
+  rv = NS_NewLocalFileOutputStream(getter_AddRefs(stream), aFile);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  DataSourceSurface::MappedSurface map;
+  if (!dataSurface->Map(DataSourceSurface::MapType::READ, &map)) {
+    return NS_ERROR_FAILURE;
+  }
+
+  // write the bitmap headers and rgb pixel data to the file
+  rv = NS_ERROR_FAILURE;
+  if (stream) {
+    uint32_t written;
+    stream->Write((const char*)&bf, sizeof(BITMAPFILEHEADER), &written);
+    if (written == sizeof(BITMAPFILEHEADER)) {
+      stream->Write((const char*)&bmi, sizeof(BITMAPV4HEADER), &written);
+      if (written == sizeof(BITMAPV4HEADER)) {
+        if (hasAlpha) {
+          // color mask
+          colormask[0] = 0x00FF0000;
+          colormask[1] = 0x0000FF00;
+          colormask[2] = 0x000000FF;
+
+          stream->Write((const char*)colormask, sizeof(colormask), &written);
+        }
+        if (!hasAlpha || written == sizeof(colormask)) {
+          // write out the image data backwards because the desktop won't
+          // show bitmaps with negative heights for top-to-bottom
+          uint32_t i = map.mStride * height;
+          do {
+            i -= map.mStride;
+            stream->Write(((const char*)map.mData) + i, bytesPerRow, &written);
+            if (written == bytesPerRow) {
+              rv = NS_OK;
+            } else {
+              rv = NS_ERROR_FAILURE;
+              break;
+            }
+          } while (i != 0);
+        }
+      }
+    }
+
+    stream->Close();
+  }
+
+  dataSurface->Unmap();
+
+  return rv;
+}
+
+// This is in use here and in dom/events/TouchEvent.cpp
+/* static */
+uint32_t WinUtils::IsTouchDeviceSupportPresent() {
+  int32_t touchCapabilities = ::GetSystemMetrics(SM_DIGITIZER);
+  int32_t touchFlags = NID_EXTERNAL_TOUCH | NID_INTEGRATED_TOUCH;
+  if (StaticPrefs::dom_w3c_pointer_events_scroll_by_pen_enabled()) {
+    touchFlags |= NID_EXTERNAL_PEN | NID_INTEGRATED_PEN;
+  }
+  return (touchCapabilities & NID_READY) && (touchCapabilities & touchFlags);
+}
+
+/* static */
+uint32_t WinUtils::GetMaxTouchPoints() {
+  if (IsTouchDeviceSupportPresent()) {
+    return GetSystemMetrics(SM_MAXIMUMTOUCHES);
+  }
+  return 0;
+}
+
+/* static */
+POWER_PLATFORM_ROLE
+WinUtils::GetPowerPlatformRole() {
+  typedef POWER_PLATFORM_ROLE(WINAPI *
+                              PowerDeterminePlatformRoleEx)(ULONG Version);
+  static PowerDeterminePlatformRoleEx power_determine_platform_role =
+      reinterpret_cast<PowerDeterminePlatformRoleEx>(::GetProcAddress(
+          ::LoadLibraryW(L"PowrProf.dll"), "PowerDeterminePlatformRoleEx"));
+
+  POWER_PLATFORM_ROLE powerPlatformRole = PlatformRoleUnspecified;
+  if (!power_determine_platform_role) {
+    return powerPlatformRole;
+  }
+
+  return power_determine_platform_role(POWER_PLATFORM_ROLE_V2);
+}
+
+// static
+bool WinUtils::GetAutoRotationState(AR_STATE* aRotationState) {
+  typedef BOOL(WINAPI * GetAutoRotationStateFunc)(PAR_STATE pState);
+  static GetAutoRotationStateFunc get_auto_rotation_state_func =
+      reinterpret_cast<GetAutoRotationStateFunc>(::GetProcAddress(
+          GetModuleHandleW(L"user32.dll"), "GetAutoRotationState"));
+  if (get_auto_rotation_state_func) {
+    ZeroMemory(aRotationState, sizeof(AR_STATE));
+    return get_auto_rotation_state_func(aRotationState);
+  }
+  return false;
+}
+
+// static
+void WinUtils::GetClipboardFormatAsString(UINT aFormat, nsAString& aOutput) {
+  wchar_t buf[256] = {};
+  // Get registered format name and ensure the existence of a terminating '\0'
+  // if the registered name is more than 256 characters.
+  if (::GetClipboardFormatNameW(aFormat, buf, ARRAYSIZE(buf) - 1)) {
+    aOutput.Append(buf);
+    return;
+  }
+  // Standard clipboard formats
+  // https://learn.microsoft.com/en-us/windows/win32/dataxchg/standard-clipboard-formats
+  switch (aFormat) {
+    case CF_TEXT:  // 1
+      aOutput.Append(u"CF_TEXT"_ns);
+      break;
+    case CF_BITMAP:  // 2
+      aOutput.Append(u"CF_BITMAP"_ns);
+      break;
+    case CF_DIB:  // 8
+      aOutput.Append(u"CF_DIB"_ns);
+      break;
+    case CF_UNICODETEXT:  // 13
+      aOutput.Append(u"CF_UNICODETEXT"_ns);
+      break;
+    case CF_HDROP:  // 15
+      aOutput.Append(u"CF_HDROP"_ns);
+      break;
+    case CF_DIBV5:  // 17
+      aOutput.Append(u"CF_DIBV5"_ns);
+      break;
+    default:
+      aOutput.AppendPrintf("%u", aFormat);
+      break;
+  }
+}
+
+static bool IsTabletDevice() {
+  // Guarantees that:
+  // - The device has a touch screen.
+  // - It is used as a tablet which means that it has no keyboard connected.
+  // On Windows 10 it means that it is verifying with ConvertibleSlateMode.
+
+  if (WindowsUIUtils::GetInTabletMode()) {
+    return true;
+  }
+
+  if (!GetSystemMetrics(SM_MAXIMUMTOUCHES)) {
+    return false;
+  }
+
+  // If the device is docked, the user is treating the device as a PC.
+  if (GetSystemMetrics(SM_SYSTEMDOCKED)) {
+    return false;
+  }
+
+  // If the device is not supporting rotation, it's unlikely to be a tablet,
+  // a convertible or a detachable. See:
+  // https://msdn.microsoft.com/en-us/library/windows/desktop/dn629263(v=vs.85).aspx
+  AR_STATE rotation_state;
+  if (WinUtils::GetAutoRotationState(&rotation_state) &&
+      (rotation_state & (AR_NOT_SUPPORTED | AR_LAPTOP | AR_NOSENSOR))) {
+    return false;
+  }
+
+  // PlatformRoleSlate was added in Windows 8+.
+  POWER_PLATFORM_ROLE role = WinUtils::GetPowerPlatformRole();
+  if (role == PlatformRoleMobile || role == PlatformRoleSlate) {
+    return !GetSystemMetrics(SM_CONVERTIBLESLATEMODE);
+  }
+  return false;
+}
+
+static bool SystemHasMouse() {
+  // As per MSDN, this value is rarely false because of virtual mice, and
+  // some machines report the existance of a mouse port as a mouse.
+  //
+  // We probably could try to distinguish if we wanted, but a virtual mouse
+  // might be there for a reason, and maybe we shouldn't assume we know
+  // better.
+  return !!::GetSystemMetrics(SM_MOUSEPRESENT);
+}
+
+/* static */
+PointerCapabilities WinUtils::GetPrimaryPointerCapabilities() {
+  if (IsTabletDevice()) {
+    return PointerCapabilities::Coarse;
+  }
+
+  if (SystemHasMouse()) {
+    return PointerCapabilities::Fine | PointerCapabilities::Hover;
+  }
+
+  if (IsTouchDeviceSupportPresent()) {
+    return PointerCapabilities::Coarse;
+  }
+
+  return PointerCapabilities::None;
+}
+
+static bool SystemHasTouchscreen() {
+  int digitizerMetrics = ::GetSystemMetrics(SM_DIGITIZER);
+  return (digitizerMetrics & NID_INTEGRATED_TOUCH) ||
+         (digitizerMetrics & NID_EXTERNAL_TOUCH);
+}
+
+static bool SystemHasPenDigitizer() {
+  int digitizerMetrics = ::GetSystemMetrics(SM_DIGITIZER);
+  return (digitizerMetrics & NID_INTEGRATED_PEN) ||
+         (digitizerMetrics & NID_EXTERNAL_PEN);
+}
+
+/* static */
+PointerCapabilities WinUtils::GetAllPointerCapabilities() {
+  PointerCapabilities pointerCapabilities = PointerCapabilities::None;
+
+  if (SystemHasTouchscreen()) {
+    pointerCapabilities |= PointerCapabilities::Coarse;
+  }
+
+  if (SystemHasPenDigitizer() || SystemHasMouse()) {
+    pointerCapabilities |=
+        PointerCapabilities::Fine | PointerCapabilities::Hover;
+  }
+
+  return pointerCapabilities;
+}
+
+void WinUtils::GetPointerExplanation(nsAString* aExplanation) {
+  // To support localization, we will return a comma-separated list of
+  // Fluent IDs
+  *aExplanation = u"pointing-device-none";
+
+  bool first = true;
+  auto append = [&](const char16_t* str) {
+    if (first) {
+      aExplanation->Truncate();
+      first = false;
+    } else {
+      aExplanation->Append(u",");
+    }
+    aExplanation->Append(str);
+  };
+
+  if (SystemHasTouchscreen()) {
+    append(u"pointing-device-touchscreen");
+  }
+
+  if (SystemHasPenDigitizer()) {
+    append(u"pointing-device-pen-digitizer");
+  }
+
+  if (SystemHasMouse()) {
+    append(u"pointing-device-mouse");
+  }
+}
+
+/* static */
+bool WinUtils::ResolveJunctionPointsAndSymLinks(std::wstring& aPath) {
+  LOG_D("ResolveJunctionPointsAndSymLinks: Resolving path: %S", aPath.c_str());
+
+  wchar_t path[MAX_PATH] = {0};
+
+  nsAutoHandle handle(::CreateFileW(
+      aPath.c_str(), 0, FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE,
+      nullptr, OPEN_EXISTING, FILE_FLAG_BACKUP_SEMANTICS, nullptr));
+
+  if (handle == INVALID_HANDLE_VALUE) {
+    LOG_E("Failed to open file handle to resolve path. GetLastError=%lu",
+          GetLastError());
+    return false;
+  }
+
+  DWORD pathLen = GetFinalPathNameByHandleW(
+      handle, path, MAX_PATH, FILE_NAME_NORMALIZED | VOLUME_NAME_DOS);
+  if (pathLen == 0 || pathLen >= MAX_PATH) {
+    LOG_E("GetFinalPathNameByHandleW failed. GetLastError=%lu", GetLastError());
+    return false;
+  }
+  aPath = path;
+
+  // GetFinalPathNameByHandle sticks a '\\?\' in front of the path,
+  // but that confuses some APIs so strip it off. It will also put
+  // '\\?\UNC\' in front of network paths, we convert that to '\\'.
+  if (aPath.compare(0, 7, L"\\\\?\\UNC") == 0) {
+    aPath.erase(2, 6);
+  } else if (aPath.compare(0, 4, L"\\\\?\\") == 0) {
+    aPath.erase(0, 4);
+  }
+
+  LOG_D("ResolveJunctionPointsAndSymLinks: Resolved path to: %S",
+        aPath.c_str());
+  return true;
+}
+
+/* static */
+bool WinUtils::ResolveJunctionPointsAndSymLinks(nsIFile* aPath) {
+  MOZ_ASSERT(aPath);
+
+  nsAutoString filePath;
+  nsresult rv = aPath->GetPath(filePath);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return false;
+  }
+
+  std::wstring resolvedPath(filePath.get());
+  if (!ResolveJunctionPointsAndSymLinks(resolvedPath)) {
+    return false;
+  }
+
+  rv = aPath->InitWithPath(nsDependentString(resolvedPath.c_str()));
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return false;
+  }
+
+  return true;
+}
+
+/* static */
+bool WinUtils::RunningFromANetworkDrive() {
+  wchar_t exePath[MAX_PATH];
+  if (!::GetModuleFileNameW(nullptr, exePath, MAX_PATH)) {
+    return false;
+  }
+
+  std::wstring exeString(exePath);
+  if (!widget::WinUtils::ResolveJunctionPointsAndSymLinks(exeString)) {
+    return false;
+  }
+
+  wchar_t volPath[MAX_PATH];
+  if (!::GetVolumePathNameW(exeString.c_str(), volPath, MAX_PATH)) {
+    return false;
+  }
+
+  return (::GetDriveTypeW(volPath) == DRIVE_REMOTE);
+}
+
+/* static */
+bool WinUtils::CanonicalizePath(nsAString& aPath) {
+  wchar_t tempPath[MAX_PATH + 1];
+  if (!PathCanonicalizeW(tempPath,
+                         (char16ptr_t)PromiseFlatString(aPath).get())) {
+    return false;
+  }
+  aPath = tempPath;
+  MOZ_ASSERT(aPath.Length() <= MAX_PATH);
+  return true;
+}
+
+/* static */
+bool WinUtils::MakeLongPath(nsAString& aPath) {
+  wchar_t tempPath[MAX_PATH + 1];
+  DWORD longResult =
+      GetLongPathNameW((char16ptr_t)PromiseFlatString(aPath).get(), tempPath,
+                       ArrayLength(tempPath));
+  if (longResult > ArrayLength(tempPath)) {
+    // Our buffer is too short, and we're guaranteeing <= MAX_PATH results.
+    return false;
+  } else if (longResult) {
+    // Success.
+    aPath = tempPath;
+    MOZ_ASSERT(aPath.Length() <= MAX_PATH);
+  }
+  // GetLongPathNameW returns 0 if the path is not found or is not rooted,
+  // but we shouldn't consider that a failure condition.
+  return true;
+}
+
+/* static */
+bool WinUtils::UnexpandEnvVars(nsAString& aPath) {
+  wchar_t tempPath[MAX_PATH + 1];
+  // PathUnExpandEnvStringsW returns false if it doesn't make any
+  // substitutions. Silently continue using the unaltered path.
+  if (PathUnExpandEnvStringsW((char16ptr_t)PromiseFlatString(aPath).get(),
+                              tempPath, ArrayLength(tempPath))) {
+    aPath = tempPath;
+    MOZ_ASSERT(aPath.Length() <= MAX_PATH);
+  }
+  return true;
+}
+
+/* static */
+WinUtils::WhitelistVec WinUtils::BuildWhitelist() {
+  WhitelistVec result;
+
+  Unused << result.emplaceBack(
+      std::make_pair(nsString(u"%ProgramFiles%"_ns), nsDependentString()));
+
+  // When no substitution is required, set the void flag
+  result.back().second.SetIsVoid(true);
+
+  Unused << result.emplaceBack(
+      std::make_pair(nsString(u"%SystemRoot%"_ns), nsDependentString()));
+  result.back().second.SetIsVoid(true);
+
+  wchar_t tmpPath[MAX_PATH + 1] = {};
+  if (GetTempPath(MAX_PATH, tmpPath)) {
+    // GetTempPath's result always ends with a backslash, which we don't want
+    uint32_t tmpPathLen = wcslen(tmpPath);
+    if (tmpPathLen) {
+      tmpPath[tmpPathLen - 1] = 0;
+    }
+
+    nsAutoString cleanTmpPath(tmpPath);
+    if (UnexpandEnvVars(cleanTmpPath)) {
+      constexpr auto tempVar = u"%TEMP%"_ns;
+      Unused << result.emplaceBack(std::make_pair(
+          nsString(cleanTmpPath), nsDependentString(tempVar, 0)));
+    }
+  }
+
+  // If we add more items to the whitelist, ensure we still don't invoke an
+  // unnecessary heap allocation.
+  MOZ_ASSERT(result.length() <= kMaxWhitelistedItems);
+
+  return result;
+}
+
+/**
+ * This function provides an array of (system path, substitution) pairs that are
+ * considered to be acceptable with respect to privacy, for the purposes of
+ * submitting within telemetry or crash reports.
+ *
+ * The substitution string's void flag may be set. If it is, no subsitution is
+ * necessary. Otherwise, the consumer should replace the system path with the
+ * substitution.
+ *
+ * @see PreparePathForTelemetry for an example of its usage.
+ */
+/* static */
+const WinUtils::WhitelistVec& WinUtils::GetWhitelistedPaths() {
+  static WhitelistVec sWhitelist([]() -> WhitelistVec {
+    auto setClearFn = [ptr = &sWhitelist]() -> void {
+      RunOnShutdown([ptr]() -> void { ptr->clear(); },
+                    ShutdownPhase::XPCOMShutdownFinal);
+    };
+
+    if (NS_IsMainThread()) {
+      setClearFn();
+    } else {
+      SchedulerGroup::Dispatch(NS_NewRunnableFunction(
+          "WinUtils::GetWhitelistedPaths", std::move(setClearFn)));
+    }
+
+    return BuildWhitelist();
+  }());
+  return sWhitelist;
+}
+
+/**
+ * This function is located here (as opposed to nsSystemInfo or elsewhere)
+ * because we need to gather this information as early as possible during
+ * startup.
+ */
+/* static */
+bool WinUtils::GetAppInitDLLs(nsAString& aOutput) {
+  aOutput.Truncate();
+  HKEY hkey = NULL;
+  if (RegOpenKeyExW(HKEY_LOCAL_MACHINE,
+                    L"SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion\\Windows",
+                    0, KEY_QUERY_VALUE, &hkey)) {
+    return false;
+  }
+  nsAutoRegKey key(hkey);
+  LONG status;
+  const wchar_t kLoadAppInitDLLs[] = L"LoadAppInit_DLLs";
+  DWORD loadAppInitDLLs = 0;
+  DWORD loadAppInitDLLsLen = sizeof(loadAppInitDLLs);
+  status = RegQueryValueExW(hkey, kLoadAppInitDLLs, nullptr, nullptr,
+                            (LPBYTE)&loadAppInitDLLs, &loadAppInitDLLsLen);
+  if (status != ERROR_SUCCESS) {
+    return false;
+  }
+  if (!loadAppInitDLLs) {
+    // If loadAppInitDLLs is zero then AppInit_DLLs is disabled.
+    // In this case we'll return true along with an empty output string.
+    return true;
+  }
+  DWORD numBytes = 0;
+  const wchar_t kAppInitDLLs[] = L"AppInit_DLLs";
+  // Query for required buffer size
+  status = RegQueryValueExW(hkey, kAppInitDLLs, nullptr, nullptr, nullptr,
+                            &numBytes);
+  if (status != ERROR_SUCCESS) {
+    return false;
+  }
+  // Allocate the buffer and query for the actual data
+  mozilla::UniquePtr<wchar_t[]> data =
+      mozilla::MakeUnique<wchar_t[]>(numBytes / sizeof(wchar_t));
+  status = RegQueryValueExW(hkey, kAppInitDLLs, nullptr, nullptr,
+                            (LPBYTE)data.get(), &numBytes);
+  if (status != ERROR_SUCCESS) {
+    return false;
+  }
+  // For each token, split up the filename components and then check the
+  // name of the file.
+  const wchar_t kDelimiters[] = L", ";
+  wchar_t* tokenContext = nullptr;
+  wchar_t* token = wcstok_s(data.get(), kDelimiters, &tokenContext);
+  while (token) {
+    nsAutoString cleanPath(token);
+    // Since these paths are short paths originating from the registry, we need
+    // to canonicalize them, lengthen them, and sanitize them before we can
+    // check them against the whitelist
+    if (PreparePathForTelemetry(cleanPath)) {
+      if (!aOutput.IsEmpty()) {
+        aOutput += L";";
+      }
+      aOutput += cleanPath;
+    }
+    token = wcstok_s(nullptr, kDelimiters, &tokenContext);
+  }
+  return true;
+}
+
+/* static */
+bool WinUtils::PreparePathForTelemetry(nsAString& aPath,
+                                       PathTransformFlags aFlags) {
+  if (aFlags & PathTransformFlags::Canonicalize) {
+    if (!CanonicalizePath(aPath)) {
+      return false;
+    }
+  }
+  if (aFlags & PathTransformFlags::Lengthen) {
+    if (!MakeLongPath(aPath)) {
+      return false;
+    }
+  }
+  if (aFlags & PathTransformFlags::UnexpandEnvVars) {
+    if (!UnexpandEnvVars(aPath)) {
+      return false;
+    }
+  }
+
+  const WhitelistVec& whitelistedPaths = GetWhitelistedPaths();
+
+  for (uint32_t i = 0; i < whitelistedPaths.length(); ++i) {
+    const nsString& testPath = whitelistedPaths[i].first;
+    const nsDependentString& substitution = whitelistedPaths[i].second;
+    if (StringBeginsWith(aPath, testPath, nsCaseInsensitiveStringComparator)) {
+      if (!substitution.IsVoid()) {
+        aPath.Replace(0, testPath.Length(), substitution);
+      }
+      return true;
+    }
+  }
+
+  // For non-whitelisted paths, we strip the path component and just leave
+  // the filename. We can't use nsLocalFile to do this because these paths may
+  // begin with environment variables, and nsLocalFile doesn't like
+  // non-absolute paths.
+  const nsString& flatPath = PromiseFlatString(aPath);
+  LPCWSTR leafStart = ::PathFindFileNameW(flatPath.get());
+  ptrdiff_t cutLen = leafStart - flatPath.get();
+  if (cutLen) {
+    aPath.Cut(0, cutLen);
+  } else if (aFlags & PathTransformFlags::RequireFilePath) {
+    return false;
+  }
+
+  return true;
+}
+
+nsString WinUtils::GetPackageFamilyName() {
+  nsString rv;
+
+  UniquePtr<wchar_t[]> packageIdentity = mozilla::GetPackageFamilyName();
+  if (packageIdentity) {
+    rv = packageIdentity.get();
+  }
+
+  return rv;
+}
+
+bool WinUtils::GetClassName(HWND aHwnd, nsAString& aClassName) {
+  const int bufferLength = 256;
+  aClassName.SetLength(bufferLength);
+
+  int length = ::GetClassNameW(aHwnd, (char16ptr_t)aClassName.BeginWriting(),
+                               bufferLength);
+  if (length == 0) {
+    return false;
+  }
+  MOZ_RELEASE_ASSERT(length <= (bufferLength - 1));
+  aClassName.Truncate(length);
+  return true;
+}
+
+static BOOL CALLBACK EnumUpdateWindowOcclusionProc(HWND aHwnd, LPARAM aLParam) {
+  const bool* const enable = reinterpret_cast<bool*>(aLParam);
+  nsWindow* window = WinUtils::GetNSWindowPtr(aHwnd);
+  if (window) {
+    window->MaybeEnableWindowOcclusion(*enable);
+  }
+  return TRUE;
+}
+
+void WinUtils::EnableWindowOcclusion(const bool aEnable) {
+  if (aEnable) {
+    WinWindowOcclusionTracker::Ensure();
+  }
+  ::EnumWindows(EnumUpdateWindowOcclusionProc,
+                reinterpret_cast<LPARAM>(&aEnable));
+}
+
+bool WinUtils::GetTimezoneName(wchar_t* aBuffer) {
+  DYNAMIC_TIME_ZONE_INFORMATION tzInfo;
+  DWORD tzid = GetDynamicTimeZoneInformation(&tzInfo);
+
+  if (tzid == TIME_ZONE_ID_INVALID) {
+    return false;
+  }
+
+  wcscpy_s(aBuffer, 128, tzInfo.TimeZoneKeyName);
+
+  return true;
+}
+
+// There are undocumented APIs to query/change the system DPI settings found by
+// https://github.com/lihas/ . We use those APIs only for testing purpose, i.e.
+// in mochitests or some such. To avoid exposing them in our official release
+// builds unexpectedly we restrict them only in debug builds.
+#ifdef DEBUG
+
+#  define DISPLAYCONFIG_DEVICE_INFO_SET_SOURCE_DPI_SCALE (int)-4
+#  define DISPLAYCONFIG_DEVICE_INFO_GET_SOURCE_DPI_SCALE (int)-3
+
+// Following two struts are copied from
+// https://github.com/lihas/windows-DPI-scaling-sample/blob/master/DPIHelper/DpiHelper.h
+
+/*
+ * struct DISPLAYCONFIG_SOURCE_DPI_SCALE_GET
+ * @brief used to fetch min, max, suggested, and currently applied DPI scaling
+ * values. All values are relative to the recommended DPI scaling value Note
+ * that DPI scaling is a property of the source, and not of target.
+ */
+struct DISPLAYCONFIG_SOURCE_DPI_SCALE_GET {
+  DISPLAYCONFIG_DEVICE_INFO_HEADER header;
+  /*
+   * @brief min value of DPI scaling is always 100, minScaleRel gives no. of
+   * steps down from recommended scaling eg. if minScaleRel is -3 => 100 is 3
+   * steps down from recommended scaling => recommended scaling is 175%
+   */
+  int32_t minScaleRel;
+
+  /*
+   * @brief currently applied DPI scaling value wrt the recommended value. eg.
+   * if recommended value is 175%,
+   * => if curScaleRel == 0 the current scaling is 175%, if curScaleRel == -1,
+   * then current scale is 150%
+   */
+  int32_t curScaleRel;
+
+  /*
+   * @brief maximum supported DPI scaling wrt recommended value
+   */
+  int32_t maxScaleRel;
+};
+
+/*
+ * struct DISPLAYCONFIG_SOURCE_DPI_SCALE_SET
+ * @brief set DPI scaling value of a source
+ * Note that DPI scaling is a property of the source, and not of target.
+ */
+struct DISPLAYCONFIG_SOURCE_DPI_SCALE_SET {
+  DISPLAYCONFIG_DEVICE_INFO_HEADER header;
+  /*
+   * @brief The value we want to set. The value should be relative to the
+   * recommended DPI scaling value of source. eg. if scaleRel == 1, and
+   * recommended value is 175% => we are trying to set 200% scaling for the
+   * source
+   */
+  int32_t scaleRel;
+};
+
+static int32_t sCurRelativeScaleStep = std::numeric_limits<int32_t>::max();
+
+static LONG SetRelativeScaleStep(LUID aAdapterId, int32_t aRelativeScaleStep) {
+  DISPLAYCONFIG_SOURCE_DPI_SCALE_SET setDPIScale = {};
+  setDPIScale.header.adapterId = aAdapterId;
+  setDPIScale.header.type = (DISPLAYCONFIG_DEVICE_INFO_TYPE)
+      DISPLAYCONFIG_DEVICE_INFO_SET_SOURCE_DPI_SCALE;
+  setDPIScale.header.size = sizeof(setDPIScale);
+  setDPIScale.scaleRel = aRelativeScaleStep;
+
+  return DisplayConfigSetDeviceInfo(&setDPIScale.header);
+}
+
+nsresult WinUtils::SetHiDPIMode(bool aHiDPI) {
+  auto config = GetDisplayConfig();
+  if (!config) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  if (config->mPaths.empty()) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  DISPLAYCONFIG_SOURCE_DPI_SCALE_GET dpiScale = {};
+  dpiScale.header.adapterId = config->mPaths[0].targetInfo.adapterId;
+  dpiScale.header.type = (DISPLAYCONFIG_DEVICE_INFO_TYPE)
+      DISPLAYCONFIG_DEVICE_INFO_GET_SOURCE_DPI_SCALE;
+  dpiScale.header.size = sizeof(dpiScale);
+  LONG result = ::DisplayConfigGetDeviceInfo(&dpiScale.header);
+  if (result != ERROR_SUCCESS) {
+    return NS_ERROR_FAILURE;
+  }
+
+  if (dpiScale.minScaleRel == dpiScale.maxScaleRel) {
+    // We can't change the setting at all.
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  if (aHiDPI && dpiScale.curScaleRel == dpiScale.maxScaleRel) {
+    // We've already at the maximum level.
+    if (sCurRelativeScaleStep == std::numeric_limits<int32_t>::max()) {
+      sCurRelativeScaleStep = dpiScale.curScaleRel;
+    }
+    return NS_OK;
+  }
+
+  if (!aHiDPI && dpiScale.curScaleRel == dpiScale.minScaleRel) {
+    // We've already at the minimum level.
+    if (sCurRelativeScaleStep == std::numeric_limits<int32_t>::max()) {
+      sCurRelativeScaleStep = dpiScale.curScaleRel;
+    }
+    return NS_OK;
+  }
+
+  result = SetRelativeScaleStep(
+      config->mPaths[0].targetInfo.adapterId,
+      aHiDPI ? dpiScale.maxScaleRel : dpiScale.minScaleRel);
+  if (result != ERROR_SUCCESS) {
+    return NS_ERROR_FAILURE;
+  }
+
+  if (sCurRelativeScaleStep == std::numeric_limits<int>::max()) {
+    sCurRelativeScaleStep = dpiScale.curScaleRel;
+  }
+
+  return NS_OK;
+}
+
+nsresult WinUtils::RestoreHiDPIMode() {
+  if (sCurRelativeScaleStep == std::numeric_limits<int>::max()) {
+    // The DPI setting hasn't been changed.
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  auto config = GetDisplayConfig();
+  if (!config) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  if (config->mPaths.empty()) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  LONG result = SetRelativeScaleStep(config->mPaths[0].targetInfo.adapterId,
+                                     sCurRelativeScaleStep);
+  sCurRelativeScaleStep = std::numeric_limits<int32_t>::max();
+  if (result != ERROR_SUCCESS) {
+    return NS_ERROR_FAILURE;
+  }
+  return NS_OK;
+}
+#endif
+
+/* static */
+const char* WinUtils::WinEventToEventName(UINT msg) {
+  const auto eventMsgInfo = mozilla::widget::gAllEvents.find(msg);
+  return eventMsgInfo != mozilla::widget::gAllEvents.end()
+             ? eventMsgInfo->second.mStr
+             : nullptr;
+}
+
+// Note to testers and/or test-authors: on Windows 10, and possibly on other
+// versions as well, supplying the `WS_EX_LAYOUTRTL` flag here has no effect
+// whatsoever on child common-dialogs **unless the system UI locale is also set
+// to an RTL language**.
+//
+// If it is, the flag is still required; otherwise, the picker dialog will be
+// presented in English (or possibly some other LTR language) as a fallback.
+ScopedRtlShimWindow::ScopedRtlShimWindow(nsIWidget* aParent) : mWnd(nullptr) {
+  NS_ENSURE_TRUE_VOID(aParent);
+
+  // Headless windows don't have HWNDs, but also probably shouldn't be launching
+  // print dialogs.
+  HWND const hwnd = (HWND)aParent->GetNativeData(NS_NATIVE_WINDOW);
+  NS_ENSURE_TRUE_VOID(hwnd);
+
+  nsWindow* const win = WinUtils::GetNSWindowPtr(hwnd);
+  NS_ENSURE_TRUE_VOID(win);
+
+  ATOM const wclass = ::GetClassWord(hwnd, GCW_ATOM);
+  mWnd = ::CreateWindowExW(
+      win->IsRTL() ? WS_EX_LAYOUTRTL : 0, (LPCWSTR)(uintptr_t)wclass, L"",
+      WS_CHILD, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT,
+      hwnd, nullptr, nsToolkit::mDllInstance, nullptr);
+
+  MOZ_ASSERT(mWnd);
+}
+
+ScopedRtlShimWindow::~ScopedRtlShimWindow() {
+  if (mWnd) {
+    ::DestroyWindow(mWnd);
+  }
+}
+
+}  // namespace widget
+}  // namespace mozilla
diff --git a/widget/windows/WinUtils.h b/widget/windows/WinUtils.h
new file mode 100644
index 0000000000..daef5ff4bc
--- /dev/null
+++ b/widget/windows/WinUtils.h
@@ -0,0 +1,684 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_widget_WinUtils_h__
+#define mozilla_widget_WinUtils_h__
+
+#include "nscore.h"
+#include <windows.h>
+#include <shobjidl.h>
+#include <uxtheme.h>
+#include <dwmapi.h>
+#include <unordered_map>
+#include <utility>
+
+// Undo the windows.h damage
+#undef GetMessage
+#undef CreateEvent
+#undef GetClassName
+#undef GetBinaryType
+#undef RemoveDirectory
+
+#include "nsString.h"
+#include "nsRegion.h"
+#include "nsRect.h"
+
+#include "nsIRunnable.h"
+#include "nsICryptoHash.h"
+#ifdef MOZ_PLACES
+#  include "nsIFaviconService.h"
+#endif
+#include "nsIDownloader.h"
+#include "nsIURI.h"
+#include "nsIWidget.h"
+#include "nsIThread.h"
+
+#include "mozilla/Attributes.h"
+#include "mozilla/EventForwards.h"
+#include "mozilla/HalScreenConfiguration.h"
+#include "mozilla/HashTable.h"
+#include "mozilla/LazyIdleThread.h"
+#include "mozilla/UniquePtr.h"
+#include "mozilla/Vector.h"
+#include "mozilla/WindowsDpiAwareness.h"
+#include "mozilla/WindowsProcessMitigations.h"
+#include "mozilla/gfx/2D.h"
+
+/**
+ * NS_INLINE_DECL_IUNKNOWN_REFCOUNTING should be used for defining and
+ * implementing AddRef() and Release() of IUnknown interface.
+ * This depends on xpcom/base/nsISupportsImpl.h.
+ */
+
+#define NS_INLINE_DECL_IUNKNOWN_REFCOUNTING(_class)                         \
+ public:                                                                    \
+  STDMETHODIMP_(ULONG) AddRef() {                                           \
+    MOZ_ASSERT_TYPE_OK_FOR_REFCOUNTING(_class)                              \
+    MOZ_ASSERT(int32_t(mRefCnt) >= 0, "illegal refcnt");                    \
+    NS_ASSERT_OWNINGTHREAD(_class);                                         \
+    ++mRefCnt;                                                              \
+    NS_LOG_ADDREF(this, mRefCnt, #_class, sizeof(*this));                   \
+    return static_cast<ULONG>(mRefCnt.get());                               \
+  }                                                                         \
+  STDMETHODIMP_(ULONG) Release() {                                          \
+    MOZ_ASSERT(int32_t(mRefCnt) > 0,                                        \
+               "Release called on object that has already been released!"); \
+    NS_ASSERT_OWNINGTHREAD(_class);                                         \
+    --mRefCnt;                                                              \
+    NS_LOG_RELEASE(this, mRefCnt, #_class);                                 \
+    if (mRefCnt == 0) {                                                     \
+      NS_ASSERT_OWNINGTHREAD(_class);                                       \
+      mRefCnt = 1; /* stabilize */                                          \
+      delete this;                                                          \
+      return 0;                                                             \
+    }                                                                       \
+    return static_cast<ULONG>(mRefCnt.get());                               \
+  }                                                                         \
+                                                                            \
+ protected:                                                                 \
+  nsAutoRefCnt mRefCnt;                                                     \
+  NS_DECL_OWNINGTHREAD                                                      \
+ public:
+
+class nsWindow;
+struct KeyPair;
+
+namespace mozilla {
+enum class PointerCapabilities : uint8_t;
+#if defined(ACCESSIBILITY)
+namespace a11y {
+class LocalAccessible;
+}  // namespace a11y
+#endif  // defined(ACCESSIBILITY)
+
+// Helper function: enumerate all the toplevel HWNDs attached to the current
+// thread via ::EnumThreadWindows().
+//
+// Note that this use of ::EnumThreadWindows() is, unfortunately, not an
+// abstract implementation detail.
+template <typename F>
+void EnumerateThreadWindows(F&& f)
+// requires requires(F f, HWND h) { f(h); }
+{
+  class Impl {
+   public:
+    F f;
+    explicit Impl(F&& f) : f(std::forward<F>(f)) {}
+
+    void invoke() {
+      WNDENUMPROC proc = &Impl::Callback;
+      ::EnumThreadWindows(::GetCurrentThreadId(), proc,
+                          reinterpret_cast<LPARAM>(&f));
+    }
+
+   private:
+    static BOOL CALLBACK Callback(HWND hwnd, LPARAM lp) {
+      (*reinterpret_cast<F*>(lp))(hwnd);
+      return TRUE;
+    }
+  };
+
+  Impl(std::forward<F>(f)).invoke();
+}
+
+namespace widget {
+
+// More complete QS definitions for MsgWaitForMultipleObjects() and
+// GetQueueStatus() that include newer win8 specific defines.
+
+#ifndef QS_RAWINPUT
+#  define QS_RAWINPUT 0x0400
+#endif
+
+#ifndef QS_TOUCH
+#  define QS_TOUCH 0x0800
+#  define QS_POINTER 0x1000
+#endif
+
+#define MOZ_QS_ALLEVENT                                                      \
+  (QS_KEY | QS_MOUSEMOVE | QS_MOUSEBUTTON | QS_POSTMESSAGE | QS_TIMER |      \
+   QS_PAINT | QS_SENDMESSAGE | QS_HOTKEY | QS_ALLPOSTMESSAGE | QS_RAWINPUT | \
+   QS_TOUCH | QS_POINTER)
+
+// Logging macros
+#define LogFunction() mozilla::widget::WinUtils::Log(__FUNCTION__)
+#define LogThread()                                                 \
+  mozilla::widget::WinUtils::Log("%s: IsMainThread:%d ThreadId:%X", \
+                                 __FUNCTION__, NS_IsMainThread(),   \
+                                 GetCurrentThreadId())
+#define LogThis() mozilla::widget::WinUtils::Log("[%X] %s", this, __FUNCTION__)
+#define LogException(e)                                           \
+  mozilla::widget::WinUtils::Log("%s Exception:%s", __FUNCTION__, \
+                                 e->ToString()->Data())
+#define LogHRESULT(hr) \
+  mozilla::widget::WinUtils::Log("%s hr=%X", __FUNCTION__, hr)
+
+#ifdef MOZ_PLACES
+class myDownloadObserver final : public nsIDownloadObserver {
+  ~myDownloadObserver() {}
+
+ public:
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIDOWNLOADOBSERVER
+};
+#endif
+
+class WinUtils {
+  // Function pointers for APIs that may not be available depending on
+  // the Win10 update version -- will be set up in Initialize().
+  static SetThreadDpiAwarenessContextProc sSetThreadDpiAwarenessContext;
+  static EnableNonClientDpiScalingProc sEnableNonClientDpiScaling;
+  static GetSystemMetricsForDpiProc sGetSystemMetricsForDpi;
+
+  // Set on Initialize().
+  static bool sHasPackageIdentity;
+
+ public:
+  class AutoSystemDpiAware {
+   public:
+    AutoSystemDpiAware() {
+      MOZ_DIAGNOSTIC_ASSERT(!IsWin32kLockedDown());
+
+      if (sSetThreadDpiAwarenessContext) {
+        mPrevContext =
+            sSetThreadDpiAwarenessContext(DPI_AWARENESS_CONTEXT_SYSTEM_AWARE);
+      }
+    }
+
+    ~AutoSystemDpiAware() {
+      if (sSetThreadDpiAwarenessContext) {
+        sSetThreadDpiAwarenessContext(mPrevContext);
+      }
+    }
+
+   private:
+    DPI_AWARENESS_CONTEXT mPrevContext;
+  };
+
+  // Wrapper for DefWindowProc that will enable non-client dpi scaling on the
+  // window during creation.
+  static LRESULT WINAPI NonClientDpiScalingDefWindowProcW(HWND hWnd, UINT msg,
+                                                          WPARAM wParam,
+                                                          LPARAM lParam);
+
+  /**
+   * Get the system's default logical-to-physical DPI scaling factor,
+   * which is based on the primary display. Note however that unlike
+   * LogToPhysFactor(GetPrimaryMonitor()), this will not change during
+   * a session even if the displays are reconfigured. This scale factor
+   * is used by Windows theme metrics etc, which do not fully support
+   * dynamic resolution changes but are only updated on logout.
+   */
+  static double SystemScaleFactor();
+
+  static bool IsPerMonitorDPIAware();
+  /**
+   * Get the DPI of the given monitor if it's per-monitor DPI aware, otherwise
+   * return the system DPI.
+   */
+  static float MonitorDPI(HMONITOR aMonitor);
+  static float SystemDPI();
+  /**
+   * Functions to convert between logical pixels as used by most Windows APIs
+   * and physical (device) pixels.
+   */
+  static double LogToPhysFactor(HMONITOR aMonitor);
+  static double LogToPhysFactor(HWND aWnd);
+  static double LogToPhysFactor(HDC aDC) {
+    return LogToPhysFactor(::WindowFromDC(aDC));
+  }
+  static int32_t LogToPhys(HMONITOR aMonitor, double aValue);
+  static HMONITOR GetPrimaryMonitor();
+  static HMONITOR MonitorFromRect(const gfx::Rect& rect);
+
+  static bool HasSystemMetricsForDpi();
+  static int GetSystemMetricsForDpi(int nIndex, UINT dpi);
+
+  /**
+   * @param msg Windows event message
+   * @return User-friendly event name, or nullptr if no
+   *         match is found.
+   */
+  static const char* WinEventToEventName(UINT msg);
+
+  /**
+   * @param aHdc HDC for printer
+   * @return unwritable margins for currently set page on aHdc or empty margins
+   *         if aHdc is null
+   */
+  static gfx::MarginDouble GetUnwriteableMarginsForDeviceInInches(HDC aHdc);
+
+  static bool HasPackageIdentity() { return sHasPackageIdentity; }
+
+  /*
+   * The "family name" of a Windows app package is the full name without any of
+   * the components that might change during the life cycle of the app (such as
+   * the version number, or the architecture). This leaves only those properties
+   * which together serve to uniquely identify the app within one Windows
+   * installation, namely the base name and the publisher name. Meaning, this
+   * string is safe to use anywhere that a string uniquely identifying an app
+   * installation is called for (because multiple copies of the same app on the
+   * same system is not a supported feature in the app framework).
+   */
+  static nsString GetPackageFamilyName();
+
+  /**
+   * Logging helpers that dump output to prlog module 'Widget', console, and
+   * OutputDebugString. Note these output in both debug and release builds.
+   */
+  static void Log(const char* fmt, ...);
+  static void LogW(const wchar_t* fmt, ...);
+
+  /**
+   * PeekMessage() and GetMessage() are wrapper methods for PeekMessageW(),
+   * GetMessageW(), ITfMessageMgr::PeekMessageW() and
+   * ITfMessageMgr::GetMessageW().
+   * Don't call the native APIs directly.  You MUST use these methods instead.
+   */
+  static bool PeekMessage(LPMSG aMsg, HWND aWnd, UINT aFirstMessage,
+                          UINT aLastMessage, UINT aOption);
+  static bool GetMessage(LPMSG aMsg, HWND aWnd, UINT aFirstMessage,
+                         UINT aLastMessage);
+
+  /**
+   * Wait until a message is ready to be processed.
+   * Prefer using this method to directly calling ::WaitMessage since
+   * ::WaitMessage will wait if there is an unread message in the queue.
+   * That can cause freezes until another message enters the queue if the
+   * message is marked read by a call to PeekMessage which the caller is
+   * not aware of (e.g., from a different thread).
+   * Note that this method may cause sync dispatch of sent (as opposed to
+   * posted) messages.
+   * @param aTimeoutMs Timeout for waiting in ms, defaults to INFINITE
+   */
+  static void WaitForMessage(DWORD aTimeoutMs = INFINITE);
+
+  /**
+   * GetTopLevelHWND() returns a window handle of the top level window which
+   * aWnd belongs to.  Note that the result may not be our window, i.e., it
+   * may not be managed by nsWindow.
+   *
+   * See follwing table for the detail of the result window type.
+   *
+   * +-------------------------+-----------------------------------------------+
+   * |                         |                aStopIfNotPopup                |
+   * +-------------------------+-----------------------+-----------------------+
+   * |                         |         TRUE          |         FALSE         |
+   + +-----------------+-------+-----------------------+-----------------------+
+   * |                 |       |  * an independent top level window            |
+   * |                 | TRUE  |  * a pupup window (WS_POPUP)                  |
+   * |                 |       |  * an owned top level window (like dialog)    |
+   * | aStopIfNotChild +-------+-----------------------+-----------------------+
+   * |                 |       |  * independent window | * only an independent |
+   * |                 | FALSE |  * non-popup-owned-   |   top level window    |
+   * |                 |       |    window like dialog |                       |
+   * +-----------------+-------+-----------------------+-----------------------+
+   */
+  static HWND GetTopLevelHWND(HWND aWnd, bool aStopIfNotChild = false,
+                              bool aStopIfNotPopup = true);
+
+  /**
+   * SetNSWindowPtr() associates aWindow with aWnd. If aWidget is nullptr, it
+   * instead dissociates any nsWindow from aWnd.
+   *
+   * No AddRef is performed. May not be used off of the main thread.
+   */
+  static void SetNSWindowPtr(HWND aWnd, nsWindow* aWindow);
+  /**
+   * GetNSWindowPtr() returns a pointer to the associated nsWindow pointer, if
+   * one exists, or nullptr, if not.
+   *
+   * No AddRef is performed. May not be used off of the main thread.
+   */
+  static nsWindow* GetNSWindowPtr(HWND aWnd);
+
+  /**
+   * IsOurProcessWindow() returns TRUE if aWnd belongs our process.
+   * Otherwise, FALSE.
+   */
+  static bool IsOurProcessWindow(HWND aWnd);
+
+  /**
+   * FindOurProcessWindow() returns the nearest ancestor window which
+   * belongs to our process.  If it fails to find our process's window by the
+   * top level window, returns nullptr.  And note that this is using
+   * ::GetParent() for climbing the window hierarchy, therefore, it gives
+   * up at an owned top level window except popup window (e.g., dialog).
+   */
+  static HWND FindOurProcessWindow(HWND aWnd);
+
+  /**
+   * FindOurWindowAtPoint() returns the topmost child window which belongs to
+   * our process's top level window.
+   *
+   * NOTE: the topmost child window may NOT be our process's window like a
+   *       plugin's window.
+   */
+  static HWND FindOurWindowAtPoint(const POINT& aPointInScreen);
+
+  /**
+   * InitMSG() returns an MSG struct which was initialized by the params.
+   * Don't trust the other members in the result.
+   */
+  static MSG InitMSG(UINT aMessage, WPARAM wParam, LPARAM lParam, HWND aWnd);
+
+  /**
+   * GetScanCode() returns a scan code for the LPARAM of WM_KEYDOWN, WM_KEYUP,
+   * WM_CHAR and WM_UNICHAR.
+   *
+   */
+  static WORD GetScanCode(LPARAM aLParam) { return (aLParam >> 16) & 0xFF; }
+
+  /**
+   * IsExtendedScanCode() returns TRUE if the LPARAM indicates the key message
+   * is an extended key event.
+   */
+  static bool IsExtendedScanCode(LPARAM aLParam) {
+    return (aLParam & 0x1000000) != 0;
+  }
+
+  /**
+   * GetInternalMessage() converts a native message to an internal message.
+   * If there is no internal message for the given native message, returns
+   * the native message itself.
+   */
+  static UINT GetInternalMessage(UINT aNativeMessage);
+
+  /**
+   * GetNativeMessage() converts an internal message to a native message.
+   * If aInternalMessage is a native message, returns the native message itself.
+   */
+  static UINT GetNativeMessage(UINT aInternalMessage);
+
+  /**
+   * GetMouseInputSource() returns a pointing device information.  The value is
+   * one of MouseEvent_Binding::MOZ_SOURCE_*.  This method MUST be called during
+   * mouse message handling.
+   */
+  static uint16_t GetMouseInputSource();
+
+  /**
+   * Windows also fires mouse window messages for pens and touches, so we should
+   * retrieve their pointer ID on receiving mouse events as well. Please refer
+   * to
+   * https://msdn.microsoft.com/en-us/library/windows/desktop/ms703320(v=vs.85).aspx
+   */
+  static uint16_t GetMousePointerID();
+
+  static bool GetIsMouseFromTouch(EventMessage aEventType);
+
+  /**
+   * ConvertHRGNToRegion converts a Windows HRGN to an LayoutDeviceIntRegion.
+   *
+   * aRgn the HRGN to convert.
+   * returns the LayoutDeviceIntRegion.
+   */
+  static LayoutDeviceIntRegion ConvertHRGNToRegion(HRGN aRgn);
+
+  /**
+   * ToIntRect converts a Windows RECT to a LayoutDeviceIntRect.
+   *
+   * aRect the RECT to convert.
+   * returns the LayoutDeviceIntRect.
+   */
+  static LayoutDeviceIntRect ToIntRect(const RECT& aRect);
+
+  /**
+   * Returns true if the context or IME state is enabled.  Otherwise, false.
+   */
+  static bool IsIMEEnabled(const InputContext& aInputContext);
+  static bool IsIMEEnabled(IMEEnabled aIMEState);
+
+  /**
+   * Returns modifier key array for aModifiers.  This is for
+   * nsIWidget::SynthethizeNative*Event().
+   */
+  static void SetupKeyModifiersSequence(nsTArray<KeyPair>* aArray,
+                                        uint32_t aModifiers, UINT aMessage);
+
+  /**
+   * Does device have touch support
+   */
+  static uint32_t IsTouchDeviceSupportPresent();
+
+  /**
+   * The maximum number of simultaneous touch contacts supported by the device.
+   * In the case of devices with multiple digitizers (e.g. multiple touch
+   * screens), the value will be the maximum of the set of maximum supported
+   * contacts by each individual digitizer.
+   */
+  static uint32_t GetMaxTouchPoints();
+
+  /**
+   * Returns the windows power platform role, which is useful for detecting
+   * tablets.
+   */
+  static POWER_PLATFORM_ROLE GetPowerPlatformRole();
+
+  // For pointer and hover media queries features.
+  static PointerCapabilities GetPrimaryPointerCapabilities();
+  // For any-pointer and any-hover media queries features.
+  static PointerCapabilities GetAllPointerCapabilities();
+  // Returns a string containing a comma-separated list of Fluent IDs
+  // representing the currently active pointing devices
+  static void GetPointerExplanation(nsAString* aExplanation);
+
+  /**
+   * Fully resolves a path to its final path name. So if path contains
+   * junction points or symlinks to other folders, we'll resolve the path
+   * fully to the actual path that the links target.
+   *
+   * @param aPath path to be resolved.
+   * @return true if successful, including if nothing needs to be changed.
+   *         false if something failed or aPath does not exist, aPath will
+   *               remain unchanged.
+   */
+  static bool ResolveJunctionPointsAndSymLinks(std::wstring& aPath);
+  static bool ResolveJunctionPointsAndSymLinks(nsIFile* aPath);
+
+  /**
+   * Returns true if executable's path is on a network drive.
+   */
+  static bool RunningFromANetworkDrive();
+
+  static void Initialize();
+
+  static nsresult WriteBitmap(nsIFile* aFile,
+                              mozilla::gfx::SourceSurface* surface);
+  // This function is a helper, but it cannot be called from the main thread.
+  // Use the one above!
+  static nsresult WriteBitmap(nsIFile* aFile, imgIContainer* aImage);
+
+  /**
+   * Wrapper for PathCanonicalize().
+   * Upon success, the resulting output string length is <= MAX_PATH.
+   * @param  aPath [in,out] The path to transform.
+   * @return true on success, false on failure.
+   */
+  static bool CanonicalizePath(nsAString& aPath);
+
+  /**
+   * Converts short paths (e.g. "C:\\PROGRA~1\\XYZ") to full paths.
+   * Upon success, the resulting output string length is <= MAX_PATH.
+   * @param  aPath [in,out] The path to transform.
+   * @return true on success, false on failure.
+   */
+  static bool MakeLongPath(nsAString& aPath);
+
+  /**
+   * Wrapper for PathUnExpandEnvStringsW().
+   * Upon success, the resulting output string length is <= MAX_PATH.
+   * @param  aPath [in,out] The path to transform.
+   * @return true on success, false on failure.
+   */
+  static bool UnexpandEnvVars(nsAString& aPath);
+
+  /**
+   * Retrieve a semicolon-delimited list of DLL files derived from AppInit_DLLs
+   */
+  static bool GetAppInitDLLs(nsAString& aOutput);
+
+  enum class PathTransformFlags : uint32_t {
+    Canonicalize = 1,
+    Lengthen = 2,
+    UnexpandEnvVars = 4,
+    RequireFilePath = 8,
+
+    Default = 7,  // Default omits RequireFilePath
+  };
+
+  /**
+   * Given a path, transforms it in preparation to be reported via telemetry.
+   * That can include canonicalization, converting short to long paths,
+   * unexpanding environment strings, and removing potentially sensitive data
+   * from the path.
+   *
+   * @param  aPath  [in,out] The path to transform.
+   * @param  aFlags [in] Specifies which transformations to perform, allowing
+   *                the caller to skip operations they know have already been
+   *                performed.
+   * @return true on success, false on failure.
+   */
+  static bool PreparePathForTelemetry(
+      nsAString& aPath,
+      PathTransformFlags aFlags = PathTransformFlags::Default);
+
+  static const size_t kMaxWhitelistedItems = 3;
+  using WhitelistVec =
+      Vector<std::pair<nsString, nsDependentString>, kMaxWhitelistedItems>;
+
+  static const WhitelistVec& GetWhitelistedPaths();
+
+  static bool GetClassName(HWND aHwnd, nsAString& aName);
+
+  static void EnableWindowOcclusion(const bool aEnable);
+
+  static bool GetTimezoneName(wchar_t* aBuffer);
+
+#ifdef DEBUG
+  static nsresult SetHiDPIMode(bool aHiDPI);
+  static nsresult RestoreHiDPIMode();
+#endif
+
+  static bool GetAutoRotationState(AR_STATE* aRotationState);
+
+  static void GetClipboardFormatAsString(UINT aFormat, nsAString& aOutput);
+
+ private:
+  static WhitelistVec BuildWhitelist();
+
+ public:
+#ifdef ACCESSIBILITY
+  static a11y::LocalAccessible* GetRootAccessibleForHWND(HWND aHwnd);
+#endif
+};
+
+#ifdef MOZ_PLACES
+class AsyncFaviconDataReady final : public nsIFaviconDataCallback {
+ public:
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIFAVICONDATACALLBACK
+
+  AsyncFaviconDataReady(nsIURI* aNewURI, RefPtr<LazyIdleThread>& aIOThread,
+                        const bool aURLShortcut,
+                        already_AddRefed<nsIRunnable> aRunnable);
+  nsresult OnFaviconDataNotAvailable(void);
+
+ private:
+  ~AsyncFaviconDataReady() {}
+
+  nsCOMPtr<nsIURI> mNewURI;
+  RefPtr<LazyIdleThread> mIOThread;
+  nsCOMPtr<nsIRunnable> mRunnable;
+  const bool mURLShortcut;
+};
+#endif
+
+/**
+ * Asynchronously tries add the list to the build
+ */
+class AsyncEncodeAndWriteIcon : public nsIRunnable {
+ public:
+  NS_DECL_THREADSAFE_ISUPPORTS
+  NS_DECL_NSIRUNNABLE
+
+  // Warning: AsyncEncodeAndWriteIcon assumes ownership of the aData buffer
+  // passed in
+  AsyncEncodeAndWriteIcon(const nsAString& aIconPath,
+                          UniquePtr<uint8_t[]> aData, uint32_t aStride,
+                          uint32_t aWidth, uint32_t aHeight,
+                          already_AddRefed<nsIRunnable> aRunnable);
+
+ private:
+  virtual ~AsyncEncodeAndWriteIcon();
+
+  nsAutoString mIconPath;
+  UniquePtr<uint8_t[]> mBuffer;
+  nsCOMPtr<nsIRunnable> mRunnable;
+  uint32_t mStride;
+  uint32_t mWidth;
+  uint32_t mHeight;
+};
+
+class AsyncDeleteAllFaviconsFromDisk : public nsIRunnable {
+ public:
+  NS_DECL_THREADSAFE_ISUPPORTS
+  NS_DECL_NSIRUNNABLE
+
+  explicit AsyncDeleteAllFaviconsFromDisk(bool aIgnoreRecent = false);
+
+ private:
+  virtual ~AsyncDeleteAllFaviconsFromDisk();
+
+  int32_t mIcoNoDeleteSeconds;
+  bool mIgnoreRecent;
+  nsCOMPtr<nsIFile> mJumpListCacheDir;
+};
+
+class FaviconHelper {
+ public:
+  static const char kJumpListCacheDir[];
+  static const char kShortcutCacheDir[];
+  static nsresult ObtainCachedIconFile(
+      nsCOMPtr<nsIURI> aFaviconPageURI, nsString& aICOFilePath,
+      RefPtr<LazyIdleThread>& aIOThread, bool aURLShortcut,
+      already_AddRefed<nsIRunnable> aRunnable = nullptr);
+
+  static nsresult GetOutputIconPath(nsCOMPtr<nsIURI> aFaviconPageURI,
+                                    nsCOMPtr<nsIFile>& aICOFile,
+                                    bool aURLShortcut);
+
+  static nsresult CacheIconFileFromFaviconURIAsync(
+      nsCOMPtr<nsIURI> aFaviconPageURI, nsCOMPtr<nsIFile> aICOFile,
+      RefPtr<LazyIdleThread>& aIOThread, bool aURLShortcut,
+      already_AddRefed<nsIRunnable> aRunnable);
+
+  static int32_t GetICOCacheSecondsTimeout();
+};
+
+MOZ_MAKE_ENUM_CLASS_BITWISE_OPERATORS(WinUtils::PathTransformFlags);
+
+// RTL shim windows are temporary child windows of our nsWindows created to
+// address RTL issues in picker dialogs. (See bug 588735.)
+class ScopedRtlShimWindow {
+ public:
+  explicit ScopedRtlShimWindow(nsIWidget* aParent);
+  ~ScopedRtlShimWindow();
+
+  ScopedRtlShimWindow(const ScopedRtlShimWindow&) = delete;
+  ScopedRtlShimWindow(ScopedRtlShimWindow&& that) noexcept : mWnd(that.mWnd) {
+    that.mWnd = nullptr;
+  };
+
+  HWND get() const { return mWnd; }
+
+ private:
+  HWND mWnd;
+};
+
+}  // namespace widget
+}  // namespace mozilla
+
+#endif  // mozilla_widget_WinUtils_h__
diff --git a/widget/windows/WinWindowOcclusionTracker.cpp b/widget/windows/WinWindowOcclusionTracker.cpp
new file mode 100644
index 0000000000..a38f950585
--- /dev/null
+++ b/widget/windows/WinWindowOcclusionTracker.cpp
@@ -0,0 +1,1471 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <queue>
+#include <windows.h>
+#include <winuser.h>
+#include <wtsapi32.h>
+
+#include "WinWindowOcclusionTracker.h"
+
+#include "base/thread.h"
+#include "base/message_loop.h"
+#include "base/platform_thread.h"
+#include "gfxConfig.h"
+#include "nsThreadUtils.h"
+#include "mozilla/DataMutex.h"
+#include "mozilla/gfx/Logging.h"
+#include "mozilla/TimeStamp.h"
+#include "mozilla/Logging.h"
+#include "mozilla/StaticPrefs_widget.h"
+#include "mozilla/StaticPtr.h"
+#include "nsBaseWidget.h"
+#include "nsWindow.h"
+#include "transport/runnable_utils.h"
+#include "WinUtils.h"
+
+namespace mozilla::widget {
+
+// Can be called on Main thread
+LazyLogModule gWinOcclusionTrackerLog("WinOcclusionTracker");
+#define LOG(type, ...) MOZ_LOG(gWinOcclusionTrackerLog, type, (__VA_ARGS__))
+
+// Can be called on OcclusionCalculator thread
+LazyLogModule gWinOcclusionCalculatorLog("WinOcclusionCalculator");
+#define CALC_LOG(type, ...) \
+  MOZ_LOG(gWinOcclusionCalculatorLog, type, (__VA_ARGS__))
+
+// ~16 ms = time between frames when frame rate is 60 FPS.
+const int kOcclusionUpdateRunnableDelayMs = 16;
+
+class OcclusionUpdateRunnable : public CancelableRunnable {
+ public:
+  explicit OcclusionUpdateRunnable(
+      WinWindowOcclusionTracker::WindowOcclusionCalculator*
+          aOcclusionCalculator)
+      : CancelableRunnable("OcclusionUpdateRunnable"),
+        mOcclusionCalculator(aOcclusionCalculator) {
+    mTimeStamp = TimeStamp::Now();
+  }
+
+  NS_IMETHOD Run() override {
+    if (mIsCanceled) {
+      return NS_OK;
+    }
+    MOZ_ASSERT(WinWindowOcclusionTracker::IsInWinWindowOcclusionThread());
+
+    uint32_t latencyMs =
+        round((TimeStamp::Now() - mTimeStamp).ToMilliseconds());
+    CALC_LOG(LogLevel::Debug,
+             "ComputeNativeWindowOcclusionStatus() latencyMs %u", latencyMs);
+
+    mOcclusionCalculator->ComputeNativeWindowOcclusionStatus();
+    return NS_OK;
+  }
+
+  nsresult Cancel() override {
+    mIsCanceled = true;
+    mOcclusionCalculator = nullptr;
+    return NS_OK;
+  }
+
+ private:
+  bool mIsCanceled = false;
+  RefPtr<WinWindowOcclusionTracker::WindowOcclusionCalculator>
+      mOcclusionCalculator;
+  TimeStamp mTimeStamp;
+};
+
+// Used to serialize tasks related to mRootWindowHwndsOcclusionState.
+class SerializedTaskDispatcher {
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(SerializedTaskDispatcher)
+
+ public:
+  SerializedTaskDispatcher();
+
+  void Destroy();
+  void PostTaskToMain(already_AddRefed<nsIRunnable> aTask);
+  void PostTaskToCalculator(already_AddRefed<nsIRunnable> aTask);
+  void PostDelayedTaskToCalculator(already_AddRefed<Runnable> aTask,
+                                   int aDelayMs);
+  bool IsOnCurrentThread();
+
+ private:
+  friend class DelayedTaskRunnable;
+
+  ~SerializedTaskDispatcher();
+
+  struct Data {
+    std::queue<std::pair<RefPtr<nsIRunnable>, RefPtr<nsISerialEventTarget>>>
+        mTasks;
+    bool mDestroyed = false;
+    RefPtr<Runnable> mCurrentRunnable;
+  };
+
+  void PostTasksIfNecessary(nsISerialEventTarget* aEventTarget,
+                            const DataMutex<Data>::AutoLock& aProofOfLock);
+  void HandleDelayedTask(already_AddRefed<nsIRunnable> aTask);
+  void HandleTasks();
+
+  // Hold current EventTarget during calling nsIRunnable::Run().
+  RefPtr<nsISerialEventTarget> mCurrentEventTarget = nullptr;
+
+  DataMutex<Data> mData;
+};
+
+class DelayedTaskRunnable : public Runnable {
+ public:
+  DelayedTaskRunnable(SerializedTaskDispatcher* aSerializedTaskDispatcher,
+                      already_AddRefed<Runnable> aTask)
+      : Runnable("DelayedTaskRunnable"),
+        mSerializedTaskDispatcher(aSerializedTaskDispatcher),
+        mTask(aTask) {}
+
+  NS_IMETHOD Run() override {
+    mSerializedTaskDispatcher->HandleDelayedTask(mTask.forget());
+    return NS_OK;
+  }
+
+ private:
+  RefPtr<SerializedTaskDispatcher> mSerializedTaskDispatcher;
+  RefPtr<Runnable> mTask;
+};
+
+SerializedTaskDispatcher::SerializedTaskDispatcher()
+    : mData("SerializedTaskDispatcher::mData") {
+  MOZ_RELEASE_ASSERT(NS_IsMainThread());
+  LOG(LogLevel::Info,
+      "SerializedTaskDispatcher::SerializedTaskDispatcher() this %p", this);
+}
+
+SerializedTaskDispatcher::~SerializedTaskDispatcher() {
+#ifdef DEBUG
+  auto data = mData.Lock();
+  MOZ_ASSERT(data->mDestroyed);
+  MOZ_ASSERT(data->mTasks.empty());
+#endif
+}
+
+void SerializedTaskDispatcher::Destroy() {
+  MOZ_RELEASE_ASSERT(NS_IsMainThread());
+  LOG(LogLevel::Info, "SerializedTaskDispatcher::Destroy() this %p", this);
+
+  auto data = mData.Lock();
+  if (data->mDestroyed) {
+    return;
+  }
+
+  data->mDestroyed = true;
+  std::queue<std::pair<RefPtr<nsIRunnable>, RefPtr<nsISerialEventTarget>>>
+      empty;
+  std::swap(data->mTasks, empty);
+}
+
+void SerializedTaskDispatcher::PostTaskToMain(
+    already_AddRefed<nsIRunnable> aTask) {
+  RefPtr<nsIRunnable> task = aTask;
+
+  auto data = mData.Lock();
+  if (data->mDestroyed) {
+    return;
+  }
+
+  nsISerialEventTarget* eventTarget = GetMainThreadSerialEventTarget();
+  data->mTasks.push({std::move(task), eventTarget});
+
+  MOZ_ASSERT_IF(!data->mCurrentRunnable, data->mTasks.size() == 1);
+  PostTasksIfNecessary(eventTarget, data);
+}
+
+void SerializedTaskDispatcher::PostTaskToCalculator(
+    already_AddRefed<nsIRunnable> aTask) {
+  RefPtr<nsIRunnable> task = aTask;
+
+  auto data = mData.Lock();
+  if (data->mDestroyed) {
+    return;
+  }
+
+  nsISerialEventTarget* eventTarget =
+      WinWindowOcclusionTracker::OcclusionCalculatorLoop()->SerialEventTarget();
+  data->mTasks.push({std::move(task), eventTarget});
+
+  MOZ_ASSERT_IF(!data->mCurrentRunnable, data->mTasks.size() == 1);
+  PostTasksIfNecessary(eventTarget, data);
+}
+
+void SerializedTaskDispatcher::PostDelayedTaskToCalculator(
+    already_AddRefed<Runnable> aTask, int aDelayMs) {
+  CALC_LOG(LogLevel::Debug,
+           "SerializedTaskDispatcher::PostDelayedTaskToCalculator()");
+
+  RefPtr<DelayedTaskRunnable> runnable =
+      new DelayedTaskRunnable(this, std::move(aTask));
+  MessageLoop* targetLoop =
+      WinWindowOcclusionTracker::OcclusionCalculatorLoop();
+  targetLoop->PostDelayedTask(runnable.forget(), aDelayMs);
+}
+
+bool SerializedTaskDispatcher::IsOnCurrentThread() {
+  return !!mCurrentEventTarget;
+}
+
+void SerializedTaskDispatcher::PostTasksIfNecessary(
+    nsISerialEventTarget* aEventTarget,
+    const DataMutex<Data>::AutoLock& aProofOfLock) {
+  MOZ_ASSERT(!aProofOfLock->mTasks.empty());
+
+  if (aProofOfLock->mCurrentRunnable) {
+    return;
+  }
+
+  RefPtr<Runnable> runnable =
+      WrapRunnable(RefPtr<SerializedTaskDispatcher>(this),
+                   &SerializedTaskDispatcher::HandleTasks);
+  aProofOfLock->mCurrentRunnable = runnable;
+  aEventTarget->Dispatch(runnable.forget());
+}
+
+void SerializedTaskDispatcher::HandleDelayedTask(
+    already_AddRefed<nsIRunnable> aTask) {
+  MOZ_ASSERT(WinWindowOcclusionTracker::IsInWinWindowOcclusionThread());
+  CALC_LOG(LogLevel::Debug, "SerializedTaskDispatcher::HandleDelayedTask()");
+
+  RefPtr<nsIRunnable> task = aTask;
+
+  auto data = mData.Lock();
+  if (data->mDestroyed) {
+    return;
+  }
+
+  nsISerialEventTarget* eventTarget =
+      WinWindowOcclusionTracker::OcclusionCalculatorLoop()->SerialEventTarget();
+  data->mTasks.push({std::move(task), eventTarget});
+
+  MOZ_ASSERT_IF(!data->mCurrentRunnable, data->mTasks.size() == 1);
+  PostTasksIfNecessary(eventTarget, data);
+}
+
+void SerializedTaskDispatcher::HandleTasks() {
+  RefPtr<nsIRunnable> frontTask;
+
+  // Get front task
+  {
+    auto data = mData.Lock();
+    if (data->mDestroyed) {
+      return;
+    }
+    MOZ_RELEASE_ASSERT(data->mCurrentRunnable);
+    MOZ_RELEASE_ASSERT(!data->mTasks.empty());
+
+    frontTask = data->mTasks.front().first;
+
+    MOZ_RELEASE_ASSERT(!mCurrentEventTarget);
+    mCurrentEventTarget = data->mTasks.front().second;
+  }
+
+  while (frontTask) {
+    if (NS_IsMainThread()) {
+      LOG(LogLevel::Debug, "SerializedTaskDispatcher::HandleTasks()");
+    } else {
+      CALC_LOG(LogLevel::Debug, "SerializedTaskDispatcher::HandleTasks()");
+    }
+
+    MOZ_ASSERT_IF(NS_IsMainThread(),
+                  mCurrentEventTarget == GetMainThreadSerialEventTarget());
+    MOZ_ASSERT_IF(
+        !NS_IsMainThread(),
+        mCurrentEventTarget == MessageLoop::current()->SerialEventTarget());
+
+    frontTask->Run();
+
+    // Get next task
+    {
+      auto data = mData.Lock();
+      if (data->mDestroyed) {
+        return;
+      }
+
+      frontTask = nullptr;
+      data->mTasks.pop();
+      // Check if next task could be handled on current thread
+      if (!data->mTasks.empty() &&
+          data->mTasks.front().second == mCurrentEventTarget) {
+        frontTask = data->mTasks.front().first;
+      }
+    }
+  }
+
+  MOZ_ASSERT(!frontTask);
+
+  // Post tasks to different thread if pending tasks exist.
+  {
+    auto data = mData.Lock();
+    data->mCurrentRunnable = nullptr;
+    mCurrentEventTarget = nullptr;
+
+    if (data->mDestroyed || data->mTasks.empty()) {
+      return;
+    }
+
+    PostTasksIfNecessary(data->mTasks.front().second, data);
+  }
+}
+
+// static
+StaticRefPtr<WinWindowOcclusionTracker> WinWindowOcclusionTracker::sTracker;
+
+/* static */
+WinWindowOcclusionTracker* WinWindowOcclusionTracker::Get() {
+  MOZ_ASSERT(NS_IsMainThread());
+  if (!sTracker || sTracker->mHasAttemptedShutdown) {
+    return nullptr;
+  }
+  return sTracker;
+}
+
+/* static */
+void WinWindowOcclusionTracker::Ensure() {
+  MOZ_ASSERT(NS_IsMainThread());
+  LOG(LogLevel::Info, "WinWindowOcclusionTracker::Ensure()");
+
+  base::Thread::Options options;
+  options.message_loop_type = MessageLoop::TYPE_UI;
+
+  if (sTracker) {
+    // Try to reuse the thread, which involves stopping and restarting it.
+    sTracker->mThread->Stop();
+    if (sTracker->mThread->StartWithOptions(options)) {
+      // Success!
+      sTracker->mHasAttemptedShutdown = false;
+
+      // Take this opportunity to ensure that mDisplayStatusObserver and
+      // mSessionChangeObserver exist. They might have failed to be
+      // created when sTracker was created.
+      sTracker->EnsureDisplayStatusObserver();
+      sTracker->EnsureSessionChangeObserver();
+      return;
+    }
+    // Restart failed, so null out our sTracker and try again with a new
+    // thread. This will cause the old singleton instance to be deallocated,
+    // which will destroy its mThread as well.
+    sTracker = nullptr;
+  }
+
+  UniquePtr<base::Thread> thread =
+      MakeUnique<base::Thread>("WinWindowOcclusionCalc");
+
+  if (!thread->StartWithOptions(options)) {
+    return;
+  }
+
+  sTracker = new WinWindowOcclusionTracker(std::move(thread));
+  WindowOcclusionCalculator::CreateInstance();
+
+  RefPtr<Runnable> runnable =
+      WrapRunnable(RefPtr<WindowOcclusionCalculator>(
+                       WindowOcclusionCalculator::GetInstance()),
+                   &WindowOcclusionCalculator::Initialize);
+  sTracker->mSerializedTaskDispatcher->PostTaskToCalculator(runnable.forget());
+}
+
+/* static */
+void WinWindowOcclusionTracker::ShutDown() {
+  if (!sTracker) {
+    return;
+  }
+
+  MOZ_ASSERT(NS_IsMainThread());
+  LOG(LogLevel::Info, "WinWindowOcclusionTracker::ShutDown()");
+
+  sTracker->mHasAttemptedShutdown = true;
+  sTracker->Destroy();
+
+  // Our thread could hang while we're waiting for it to stop.
+  // Since we're shutting down, that's not a critical problem.
+  // We set a reasonable amount of time to wait for shutdown,
+  // and if it succeeds within that time, we correctly stop
+  // our thread by nulling out the refptr, which will cause it
+  // to be deallocated and join the thread. If it times out,
+  // we do nothing, which means that the thread will not be
+  // joined and sTracker memory will leak.
+  CVStatus status;
+  {
+    // It's important to hold the lock before posting the
+    // runnable. This ensures that the runnable can't begin
+    // until we've started our Wait, which prevents us from
+    // Waiting on a monitor that has already been notified.
+    MonitorAutoLock lock(sTracker->mMonitor);
+
+    static const TimeDuration TIMEOUT = TimeDuration::FromSeconds(2.0);
+    RefPtr<Runnable> runnable =
+        WrapRunnable(RefPtr<WindowOcclusionCalculator>(
+                         WindowOcclusionCalculator::GetInstance()),
+                     &WindowOcclusionCalculator::Shutdown);
+    OcclusionCalculatorLoop()->PostTask(runnable.forget());
+
+    // Monitor uses SleepConditionVariableSRW, which can have
+    // spurious wakeups which are reported as timeouts, so we
+    // check timestamps to ensure that we've waited as long we
+    // intended to. If we wake early, we don't bother calculating
+    // a precise amount for the next wait; we just wait the same
+    // amount of time. This means timeout might happen after as
+    // much as 2x the TIMEOUT time.
+    TimeStamp timeStart = TimeStamp::NowLoRes();
+    do {
+      status = sTracker->mMonitor.Wait(TIMEOUT);
+    } while ((status == CVStatus::Timeout) &&
+             ((TimeStamp::NowLoRes() - timeStart) < TIMEOUT));
+  }
+
+  if (status == CVStatus::NoTimeout) {
+    WindowOcclusionCalculator::ClearInstance();
+    sTracker = nullptr;
+  }
+}
+
+void WinWindowOcclusionTracker::Destroy() {
+  if (mDisplayStatusObserver) {
+    mDisplayStatusObserver->Destroy();
+    mDisplayStatusObserver = nullptr;
+  }
+  if (mSessionChangeObserver) {
+    mSessionChangeObserver->Destroy();
+    mSessionChangeObserver = nullptr;
+  }
+  if (mSerializedTaskDispatcher) {
+    mSerializedTaskDispatcher->Destroy();
+  }
+}
+
+/* static */
+MessageLoop* WinWindowOcclusionTracker::OcclusionCalculatorLoop() {
+  return sTracker ? sTracker->mThread->message_loop() : nullptr;
+}
+
+/* static */
+bool WinWindowOcclusionTracker::IsInWinWindowOcclusionThread() {
+  return sTracker &&
+         sTracker->mThread->thread_id() == PlatformThread::CurrentId();
+}
+
+void WinWindowOcclusionTracker::EnsureDisplayStatusObserver() {
+  if (mDisplayStatusObserver) {
+    return;
+  }
+  if (StaticPrefs::
+          widget_windows_window_occlusion_tracking_display_state_enabled()) {
+    mDisplayStatusObserver = DisplayStatusObserver::Create(this);
+  }
+}
+
+void WinWindowOcclusionTracker::EnsureSessionChangeObserver() {
+  if (mSessionChangeObserver) {
+    return;
+  }
+  if (StaticPrefs::
+          widget_windows_window_occlusion_tracking_session_lock_enabled()) {
+    mSessionChangeObserver = SessionChangeObserver::Create(this);
+  }
+}
+
+void WinWindowOcclusionTracker::Enable(nsBaseWidget* aWindow, HWND aHwnd) {
+  MOZ_ASSERT(NS_IsMainThread());
+  LOG(LogLevel::Info, "WinWindowOcclusionTracker::Enable() aWindow %p aHwnd %p",
+      aWindow, aHwnd);
+
+  auto it = mHwndRootWindowMap.find(aHwnd);
+  if (it != mHwndRootWindowMap.end()) {
+    return;
+  }
+
+  nsWeakPtr weak = do_GetWeakReference(aWindow);
+  mHwndRootWindowMap.emplace(aHwnd, weak);
+
+  RefPtr<Runnable> runnable = WrapRunnable(
+      RefPtr<WindowOcclusionCalculator>(
+          WindowOcclusionCalculator::GetInstance()),
+      &WindowOcclusionCalculator::EnableOcclusionTrackingForWindow, aHwnd);
+  mSerializedTaskDispatcher->PostTaskToCalculator(runnable.forget());
+}
+
+void WinWindowOcclusionTracker::Disable(nsBaseWidget* aWindow, HWND aHwnd) {
+  MOZ_ASSERT(NS_IsMainThread());
+  LOG(LogLevel::Info,
+      "WinWindowOcclusionTracker::Disable() aWindow %p aHwnd %p", aWindow,
+      aHwnd);
+
+  auto it = mHwndRootWindowMap.find(aHwnd);
+  if (it == mHwndRootWindowMap.end()) {
+    return;
+  }
+
+  mHwndRootWindowMap.erase(it);
+
+  RefPtr<Runnable> runnable = WrapRunnable(
+      RefPtr<WindowOcclusionCalculator>(
+          WindowOcclusionCalculator::GetInstance()),
+      &WindowOcclusionCalculator::DisableOcclusionTrackingForWindow, aHwnd);
+  mSerializedTaskDispatcher->PostTaskToCalculator(runnable.forget());
+}
+
+void WinWindowOcclusionTracker::OnWindowVisibilityChanged(nsBaseWidget* aWindow,
+                                                          bool aVisible) {
+  MOZ_ASSERT(NS_IsMainThread());
+  LOG(LogLevel::Info,
+      "WinWindowOcclusionTracker::OnWindowVisibilityChanged() aWindow %p "
+      "aVisible %d",
+      aWindow, aVisible);
+
+  RefPtr<Runnable> runnable = WrapRunnable(
+      RefPtr<WindowOcclusionCalculator>(
+          WindowOcclusionCalculator::GetInstance()),
+      &WindowOcclusionCalculator::HandleVisibilityChanged, aVisible);
+  mSerializedTaskDispatcher->PostTaskToCalculator(runnable.forget());
+}
+
+WinWindowOcclusionTracker::WinWindowOcclusionTracker(
+    UniquePtr<base::Thread> aThread)
+    : mThread(std::move(aThread)), mMonitor("WinWindowOcclusionTracker") {
+  MOZ_ASSERT(NS_IsMainThread());
+  LOG(LogLevel::Info, "WinWindowOcclusionTracker::WinWindowOcclusionTracker()");
+
+  EnsureDisplayStatusObserver();
+  EnsureSessionChangeObserver();
+
+  mSerializedTaskDispatcher = new SerializedTaskDispatcher();
+}
+
+WinWindowOcclusionTracker::~WinWindowOcclusionTracker() {
+  MOZ_ASSERT(NS_IsMainThread());
+  LOG(LogLevel::Info,
+      "WinWindowOcclusionTracker::~WinWindowOcclusionTracker()");
+}
+
+// static
+bool WinWindowOcclusionTracker::IsWindowVisibleAndFullyOpaque(
+    HWND aHwnd, LayoutDeviceIntRect* aWindowRect) {
+  // Filter out windows that are not "visible", IsWindowVisible().
+  if (!::IsWindow(aHwnd) || !::IsWindowVisible(aHwnd)) {
+    return false;
+  }
+
+  // Filter out minimized windows.
+  if (::IsIconic(aHwnd)) {
+    return false;
+  }
+
+  LONG exStyles = ::GetWindowLong(aHwnd, GWL_EXSTYLE);
+  // Filter out "transparent" windows, windows where the mouse clicks fall
+  // through them.
+  if (exStyles & WS_EX_TRANSPARENT) {
+    return false;
+  }
+
+  // Filter out "tool windows", which are floating windows that do not appear on
+  // the taskbar or ALT-TAB. Floating windows can have larger window rectangles
+  // than what is visible to the user, so by filtering them out we will avoid
+  // incorrectly marking native windows as occluded. We do not filter out the
+  // Windows Taskbar.
+  if (exStyles & WS_EX_TOOLWINDOW) {
+    nsAutoString className;
+    if (WinUtils::GetClassName(aHwnd, className)) {
+      if (!className.Equals(L"Shell_TrayWnd")) {
+        return false;
+      }
+    }
+  }
+
+  // Filter out layered windows that are not opaque or that set a transparency
+  // colorkey.
+  if (exStyles & WS_EX_LAYERED) {
+    BYTE alpha;
+    DWORD flags;
+
+    // GetLayeredWindowAttributes only works if the application has
+    // previously called SetLayeredWindowAttributes on the window.
+    // The function will fail if the layered window was setup with
+    // UpdateLayeredWindow. Treat this failure as the window being transparent.
+    // See Remarks section of
+    // https://docs.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-getlayeredwindowattributes
+    if (!::GetLayeredWindowAttributes(aHwnd, nullptr, &alpha, &flags)) {
+      return false;
+    }
+
+    if (flags & LWA_ALPHA && alpha < 255) {
+      return false;
+    }
+    if (flags & LWA_COLORKEY) {
+      return false;
+    }
+  }
+
+  // Filter out windows that do not have a simple rectangular region.
+  HRGN region = ::CreateRectRgn(0, 0, 0, 0);
+  int result = GetWindowRgn(aHwnd, region);
+  ::DeleteObject(region);
+  if (result == COMPLEXREGION) {
+    return false;
+  }
+
+  // Windows 10 has cloaked windows, windows with WS_VISIBLE attribute but
+  // not displayed. explorer.exe, in particular has one that's the
+  // size of the desktop. It's usually behind Chrome windows in the z-order,
+  // but using a remote desktop can move it up in the z-order. So, ignore them.
+  DWORD reason;
+  if (SUCCEEDED(::DwmGetWindowAttribute(aHwnd, DWMWA_CLOAKED, &reason,
+                                        sizeof(reason))) &&
+      reason != 0) {
+    return false;
+  }
+
+  RECT winRect;
+  // Filter out windows that take up zero area. The call to GetWindowRect is one
+  // of the most expensive parts of this function, so it is last.
+  if (!::GetWindowRect(aHwnd, &winRect)) {
+    return false;
+  }
+  if (::IsRectEmpty(&winRect)) {
+    return false;
+  }
+
+  // Ignore popup windows since they're transient unless it is the Windows
+  // Taskbar
+  // XXX Chrome Widget popup handling is removed for now.
+  if (::GetWindowLong(aHwnd, GWL_STYLE) & WS_POPUP) {
+    nsAutoString className;
+    if (WinUtils::GetClassName(aHwnd, className)) {
+      if (!className.Equals(L"Shell_TrayWnd")) {
+        return false;
+      }
+    }
+  }
+
+  *aWindowRect = LayoutDeviceIntRect(winRect.left, winRect.top,
+                                     winRect.right - winRect.left,
+                                     winRect.bottom - winRect.top);
+
+  WINDOWPLACEMENT windowPlacement = {0};
+  windowPlacement.length = sizeof(WINDOWPLACEMENT);
+  ::GetWindowPlacement(aHwnd, &windowPlacement);
+  if (windowPlacement.showCmd == SW_MAXIMIZE) {
+    // If the window is maximized the window border extends beyond the visible
+    // region of the screen.  Adjust the maximized window rect to fit the
+    // screen dimensions to ensure that fullscreen windows, which do not extend
+    // beyond the screen boundaries since they typically have no borders, will
+    // occlude maximized windows underneath them.
+    HMONITOR hmon = ::MonitorFromWindow(aHwnd, MONITOR_DEFAULTTONEAREST);
+    if (hmon) {
+      MONITORINFO mi;
+      mi.cbSize = sizeof(mi);
+      if (GetMonitorInfo(hmon, &mi)) {
+        LayoutDeviceIntRect workArea(mi.rcWork.left, mi.rcWork.top,
+                                     mi.rcWork.right - mi.rcWork.left,
+                                     mi.rcWork.bottom - mi.rcWork.top);
+        // Adjust aWindowRect to fit to monitor.
+        aWindowRect->width = std::min(workArea.width, aWindowRect->width);
+        if (aWindowRect->x < workArea.x) {
+          aWindowRect->x = workArea.x;
+        } else {
+          aWindowRect->x = std::min(workArea.x + workArea.width,
+                                    aWindowRect->x + aWindowRect->width) -
+                           aWindowRect->width;
+        }
+        aWindowRect->height = std::min(workArea.height, aWindowRect->height);
+        if (aWindowRect->y < workArea.y) {
+          aWindowRect->y = workArea.y;
+        } else {
+          aWindowRect->y = std::min(workArea.y + workArea.height,
+                                    aWindowRect->y + aWindowRect->height) -
+                           aWindowRect->height;
+        }
+      }
+    }
+  }
+
+  return true;
+}
+
+// static
+void WinWindowOcclusionTracker::CallUpdateOcclusionState(
+    std::unordered_map<HWND, OcclusionState>* aMap, bool aShowAllWindows) {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  auto* tracker = WinWindowOcclusionTracker::Get();
+  if (!tracker) {
+    return;
+  }
+  tracker->UpdateOcclusionState(aMap, aShowAllWindows);
+}
+
+void WinWindowOcclusionTracker::UpdateOcclusionState(
+    std::unordered_map<HWND, OcclusionState>* aMap, bool aShowAllWindows) {
+  MOZ_ASSERT(NS_IsMainThread());
+  MOZ_ASSERT(mSerializedTaskDispatcher->IsOnCurrentThread());
+  LOG(LogLevel::Debug,
+      "WinWindowOcclusionTracker::UpdateOcclusionState() aShowAllWindows %d",
+      aShowAllWindows);
+
+  mNumVisibleRootWindows = 0;
+  for (auto& [hwnd, state] : *aMap) {
+    auto it = mHwndRootWindowMap.find(hwnd);
+    // The window was destroyed while processing occlusion.
+    if (it == mHwndRootWindowMap.end()) {
+      continue;
+    }
+    auto occlState = state;
+
+    // If the screen is locked or off, ignore occlusion state results and
+    // mark the window as occluded.
+    if (mScreenLocked || !mDisplayOn) {
+      occlState = OcclusionState::OCCLUDED;
+    } else if (aShowAllWindows) {
+      occlState = OcclusionState::VISIBLE;
+    }
+    nsCOMPtr<nsIWidget> widget = do_QueryReferent(it->second);
+    if (!widget) {
+      continue;
+    }
+    auto* baseWidget = static_cast<nsBaseWidget*>(widget.get());
+    baseWidget->NotifyOcclusionState(occlState);
+    if (baseWidget->SizeMode() != nsSizeMode_Minimized) {
+      mNumVisibleRootWindows++;
+    }
+  }
+}
+
+void WinWindowOcclusionTracker::OnSessionChange(WPARAM aStatusCode,
+                                                Maybe<bool> aIsCurrentSession) {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  if (aIsCurrentSession.isNothing() || !*aIsCurrentSession) {
+    return;
+  }
+
+  if (aStatusCode == WTS_SESSION_UNLOCK) {
+    LOG(LogLevel::Info,
+        "WinWindowOcclusionTracker::OnSessionChange() WTS_SESSION_UNLOCK");
+
+    // UNLOCK will cause a foreground window change, which will
+    // trigger an occlusion calculation on its own.
+    mScreenLocked = false;
+  } else if (aStatusCode == WTS_SESSION_LOCK) {
+    LOG(LogLevel::Info,
+        "WinWindowOcclusionTracker::OnSessionChange() WTS_SESSION_LOCK");
+
+    mScreenLocked = true;
+    MarkNonIconicWindowsOccluded();
+  }
+}
+
+void WinWindowOcclusionTracker::OnDisplayStateChanged(bool aDisplayOn) {
+  MOZ_ASSERT(NS_IsMainThread());
+  LOG(LogLevel::Info,
+      "WinWindowOcclusionTracker::OnDisplayStateChanged() aDisplayOn %d",
+      aDisplayOn);
+
+  if (mDisplayOn == aDisplayOn) {
+    return;
+  }
+
+  mDisplayOn = aDisplayOn;
+  if (aDisplayOn) {
+    // Notify the window occlusion calculator of the display turning on
+    // which will schedule an occlusion calculation. This must be run
+    // on the WindowOcclusionCalculator thread.
+    RefPtr<Runnable> runnable =
+        WrapRunnable(RefPtr<WindowOcclusionCalculator>(
+                         WindowOcclusionCalculator::GetInstance()),
+                     &WindowOcclusionCalculator::HandleVisibilityChanged,
+                     /* aVisible */ true);
+    mSerializedTaskDispatcher->PostTaskToCalculator(runnable.forget());
+  } else {
+    MarkNonIconicWindowsOccluded();
+  }
+}
+
+void WinWindowOcclusionTracker::MarkNonIconicWindowsOccluded() {
+  MOZ_ASSERT(NS_IsMainThread());
+  LOG(LogLevel::Info,
+      "WinWindowOcclusionTracker::MarkNonIconicWindowsOccluded()");
+
+  // Set all visible root windows as occluded. If not visible,
+  // set them as hidden.
+  for (auto& [hwnd, weak] : mHwndRootWindowMap) {
+    nsCOMPtr<nsIWidget> widget = do_QueryReferent(weak);
+    if (!widget) {
+      continue;
+    }
+    auto* baseWidget = static_cast<nsBaseWidget*>(widget.get());
+    auto state = (baseWidget->SizeMode() == nsSizeMode_Minimized)
+                     ? OcclusionState::HIDDEN
+                     : OcclusionState::OCCLUDED;
+    baseWidget->NotifyOcclusionState(state);
+  }
+}
+
+void WinWindowOcclusionTracker::TriggerCalculation() {
+  RefPtr<Runnable> runnable =
+      WrapRunnable(RefPtr<WindowOcclusionCalculator>(
+                       WindowOcclusionCalculator::GetInstance()),
+                   &WindowOcclusionCalculator::HandleTriggerCalculation);
+  mSerializedTaskDispatcher->PostTaskToCalculator(runnable.forget());
+}
+
+// static
+BOOL WinWindowOcclusionTracker::DumpOccludingWindowsCallback(HWND aHWnd,
+                                                             LPARAM aLParam) {
+  HWND hwnd = reinterpret_cast<HWND>(aLParam);
+
+  LayoutDeviceIntRect windowRect;
+  bool windowIsOccluding = IsWindowVisibleAndFullyOpaque(aHWnd, &windowRect);
+  if (windowIsOccluding) {
+    nsAutoString className;
+    if (WinUtils::GetClassName(aHWnd, className)) {
+      const auto name = NS_ConvertUTF16toUTF8(className);
+      printf_stderr(
+          "DumpOccludingWindowsCallback() aHWnd %p className %s windowRect(%d, "
+          "%d, %d, %d)\n",
+          aHWnd, name.get(), windowRect.x, windowRect.y, windowRect.width,
+          windowRect.height);
+    }
+  }
+
+  if (aHWnd == hwnd) {
+    return false;
+  }
+  return true;
+}
+
+void WinWindowOcclusionTracker::DumpOccludingWindows(HWND aHWnd) {
+  printf_stderr("DumpOccludingWindows() until aHWnd %p visible %d iconic %d\n",
+                aHWnd, ::IsWindowVisible(aHWnd), ::IsIconic(aHWnd));
+  ::EnumWindows(&DumpOccludingWindowsCallback, reinterpret_cast<LPARAM>(aHWnd));
+}
+
+// static
+StaticRefPtr<WinWindowOcclusionTracker::WindowOcclusionCalculator>
+    WinWindowOcclusionTracker::WindowOcclusionCalculator::sCalculator;
+
+WinWindowOcclusionTracker::WindowOcclusionCalculator::
+    WindowOcclusionCalculator()
+    : mMonitor(WinWindowOcclusionTracker::Get()->mMonitor) {
+  MOZ_ASSERT(NS_IsMainThread());
+  LOG(LogLevel::Info, "WindowOcclusionCalculator()");
+
+  mSerializedTaskDispatcher =
+      WinWindowOcclusionTracker::Get()->GetSerializedTaskDispatcher();
+}
+
+WinWindowOcclusionTracker::WindowOcclusionCalculator::
+    ~WindowOcclusionCalculator() {}
+
+// static
+void WinWindowOcclusionTracker::WindowOcclusionCalculator::CreateInstance() {
+  MOZ_ASSERT(NS_IsMainThread());
+  sCalculator = new WindowOcclusionCalculator();
+}
+
+// static
+void WinWindowOcclusionTracker::WindowOcclusionCalculator::ClearInstance() {
+  MOZ_ASSERT(NS_IsMainThread());
+  sCalculator = nullptr;
+}
+
+void WinWindowOcclusionTracker::WindowOcclusionCalculator::Initialize() {
+  MOZ_ASSERT(IsInWinWindowOcclusionThread());
+  MOZ_ASSERT(!mVirtualDesktopManager);
+  CALC_LOG(LogLevel::Info, "Initialize()");
+
+#ifndef __MINGW32__
+  RefPtr<IVirtualDesktopManager> desktopManager;
+  HRESULT hr = ::CoCreateInstance(
+      CLSID_VirtualDesktopManager, NULL, CLSCTX_INPROC_SERVER,
+      __uuidof(IVirtualDesktopManager), getter_AddRefs(desktopManager));
+  if (FAILED(hr)) {
+    return;
+  }
+  mVirtualDesktopManager = desktopManager;
+#endif
+}
+
+void WinWindowOcclusionTracker::WindowOcclusionCalculator::Shutdown() {
+  MonitorAutoLock lock(mMonitor);
+
+  MOZ_ASSERT(IsInWinWindowOcclusionThread());
+  CALC_LOG(LogLevel::Info, "Shutdown()");
+
+  UnregisterEventHooks();
+  if (mOcclusionUpdateRunnable) {
+    mOcclusionUpdateRunnable->Cancel();
+    mOcclusionUpdateRunnable = nullptr;
+  }
+  mVirtualDesktopManager = nullptr;
+
+  mMonitor.NotifyAll();
+}
+
+void WinWindowOcclusionTracker::WindowOcclusionCalculator::
+    EnableOcclusionTrackingForWindow(HWND aHwnd) {
+  MOZ_ASSERT(IsInWinWindowOcclusionThread());
+  MOZ_ASSERT(mSerializedTaskDispatcher->IsOnCurrentThread());
+  CALC_LOG(LogLevel::Info, "EnableOcclusionTrackingForWindow() aHwnd %p",
+           aHwnd);
+
+  MOZ_RELEASE_ASSERT(mRootWindowHwndsOcclusionState.find(aHwnd) ==
+                     mRootWindowHwndsOcclusionState.end());
+  mRootWindowHwndsOcclusionState[aHwnd] = OcclusionState::UNKNOWN;
+
+  if (mGlobalEventHooks.empty()) {
+    RegisterEventHooks();
+  }
+
+  // Schedule an occlusion calculation so that the newly tracked window does
+  // not have a stale occlusion status.
+  ScheduleOcclusionCalculationIfNeeded();
+}
+
+void WinWindowOcclusionTracker::WindowOcclusionCalculator::
+    DisableOcclusionTrackingForWindow(HWND aHwnd) {
+  MOZ_ASSERT(IsInWinWindowOcclusionThread());
+  MOZ_ASSERT(mSerializedTaskDispatcher->IsOnCurrentThread());
+  CALC_LOG(LogLevel::Info, "DisableOcclusionTrackingForWindow() aHwnd %p",
+           aHwnd);
+
+  MOZ_RELEASE_ASSERT(mRootWindowHwndsOcclusionState.find(aHwnd) !=
+                     mRootWindowHwndsOcclusionState.end());
+  mRootWindowHwndsOcclusionState.erase(aHwnd);
+
+  if (mMovingWindow == aHwnd) {
+    mMovingWindow = 0;
+  }
+
+  if (mRootWindowHwndsOcclusionState.empty()) {
+    UnregisterEventHooks();
+    if (mOcclusionUpdateRunnable) {
+      mOcclusionUpdateRunnable->Cancel();
+      mOcclusionUpdateRunnable = nullptr;
+    }
+  }
+}
+
+void WinWindowOcclusionTracker::WindowOcclusionCalculator::
+    HandleVisibilityChanged(bool aVisible) {
+  MOZ_ASSERT(IsInWinWindowOcclusionThread());
+  CALC_LOG(LogLevel::Info, "HandleVisibilityChange() aVisible %d", aVisible);
+
+  // May have gone from having no visible windows to having one, in
+  // which case we need to register event hooks, and make sure that an
+  // occlusion calculation is scheduled.
+  if (aVisible) {
+    MaybeRegisterEventHooks();
+    ScheduleOcclusionCalculationIfNeeded();
+  }
+}
+
+void WinWindowOcclusionTracker::WindowOcclusionCalculator::
+    HandleTriggerCalculation() {
+  MOZ_ASSERT(IsInWinWindowOcclusionThread());
+  CALC_LOG(LogLevel::Info, "HandleTriggerCalculation()");
+
+  MaybeRegisterEventHooks();
+  ScheduleOcclusionCalculationIfNeeded();
+}
+
+void WinWindowOcclusionTracker::WindowOcclusionCalculator::
+    MaybeRegisterEventHooks() {
+  if (mGlobalEventHooks.empty()) {
+    RegisterEventHooks();
+  }
+}
+
+// static
+void CALLBACK
+WinWindowOcclusionTracker::WindowOcclusionCalculator::EventHookCallback(
+    HWINEVENTHOOK aWinEventHook, DWORD aEvent, HWND aHwnd, LONG aIdObject,
+    LONG aIdChild, DWORD aEventThread, DWORD aMsEventTime) {
+  if (sCalculator) {
+    sCalculator->ProcessEventHookCallback(aWinEventHook, aEvent, aHwnd,
+                                          aIdObject, aIdChild);
+  }
+}
+
+// static
+BOOL CALLBACK WinWindowOcclusionTracker::WindowOcclusionCalculator::
+    ComputeNativeWindowOcclusionStatusCallback(HWND aHwnd, LPARAM aLParam) {
+  if (sCalculator) {
+    return sCalculator->ProcessComputeNativeWindowOcclusionStatusCallback(
+        aHwnd, reinterpret_cast<std::unordered_set<DWORD>*>(aLParam));
+  }
+  return FALSE;
+}
+
+// static
+BOOL CALLBACK WinWindowOcclusionTracker::WindowOcclusionCalculator::
+    UpdateVisibleWindowProcessIdsCallback(HWND aHwnd, LPARAM aLParam) {
+  if (sCalculator) {
+    sCalculator->ProcessUpdateVisibleWindowProcessIdsCallback(aHwnd);
+    return TRUE;
+  }
+  return FALSE;
+}
+
+void WinWindowOcclusionTracker::WindowOcclusionCalculator::
+    UpdateVisibleWindowProcessIds() {
+  mPidsForLocationChangeHook.clear();
+  ::EnumWindows(&UpdateVisibleWindowProcessIdsCallback, 0);
+}
+
+void WinWindowOcclusionTracker::WindowOcclusionCalculator::
+    ComputeNativeWindowOcclusionStatus() {
+  MOZ_ASSERT(IsInWinWindowOcclusionThread());
+  MOZ_ASSERT(mSerializedTaskDispatcher->IsOnCurrentThread());
+
+  if (mOcclusionUpdateRunnable) {
+    mOcclusionUpdateRunnable = nullptr;
+  }
+
+  if (mRootWindowHwndsOcclusionState.empty()) {
+    return;
+  }
+
+  // Set up initial conditions for occlusion calculation.
+  bool shouldUnregisterEventHooks = true;
+
+  // Compute the LayoutDeviceIntRegion for the screen.
+  int screenLeft = ::GetSystemMetrics(SM_XVIRTUALSCREEN);
+  int screenTop = ::GetSystemMetrics(SM_YVIRTUALSCREEN);
+  int screenWidth = ::GetSystemMetrics(SM_CXVIRTUALSCREEN);
+  int screenHeight = ::GetSystemMetrics(SM_CYVIRTUALSCREEN);
+  LayoutDeviceIntRegion screenRegion =
+      LayoutDeviceIntRect(screenLeft, screenTop, screenWidth, screenHeight);
+  mNumRootWindowsWithUnknownOcclusionState = 0;
+
+  CALC_LOG(LogLevel::Debug,
+           "ComputeNativeWindowOcclusionStatus() screen(%d, %d, %d, %d)",
+           screenLeft, screenTop, screenWidth, screenHeight);
+
+  for (auto& [hwnd, state] : mRootWindowHwndsOcclusionState) {
+    // IsIconic() checks for a minimized window. Immediately set the state of
+    // minimized windows to HIDDEN.
+    if (::IsIconic(hwnd)) {
+      state = OcclusionState::HIDDEN;
+    } else if (IsWindowOnCurrentVirtualDesktop(hwnd) == Some(false)) {
+      // If window is not on the current virtual desktop, immediately
+      // set the state of the window to OCCLUDED.
+      state = OcclusionState::OCCLUDED;
+      // Don't unregister event hooks when not on current desktop. There's no
+      // notification when that changes, so we can't reregister event hooks.
+      shouldUnregisterEventHooks = false;
+    } else {
+      state = OcclusionState::UNKNOWN;
+      shouldUnregisterEventHooks = false;
+      mNumRootWindowsWithUnknownOcclusionState++;
+    }
+  }
+
+  // Unregister event hooks if all native windows are minimized.
+  if (shouldUnregisterEventHooks) {
+    UnregisterEventHooks();
+  } else {
+    std::unordered_set<DWORD> currentPidsWithVisibleWindows;
+    mUnoccludedDesktopRegion = screenRegion;
+    // Calculate unoccluded region if there is a non-minimized native window.
+    // Also compute |current_pids_with_visible_windows| as we enumerate
+    // the windows.
+    EnumWindows(&ComputeNativeWindowOcclusionStatusCallback,
+                reinterpret_cast<LPARAM>(&currentPidsWithVisibleWindows));
+    // Check if mPidsForLocationChangeHook has any pids of processes
+    // currently without visible windows. If so, unhook the win event,
+    // remove the pid from mPidsForLocationChangeHook and remove
+    // the corresponding event hook from mProcessEventHooks.
+    std::unordered_set<DWORD> pidsToRemove;
+    for (auto locChangePid : mPidsForLocationChangeHook) {
+      if (currentPidsWithVisibleWindows.find(locChangePid) ==
+          currentPidsWithVisibleWindows.end()) {
+        // Remove the event hook from our map, and unregister the event hook.
+        // It's possible the eventhook will no longer be valid, but if we don't
+        // unregister the event hook, a process that toggles between having
+        // visible windows and not having visible windows could cause duplicate
+        // event hooks to get registered for the process.
+        UnhookWinEvent(mProcessEventHooks[locChangePid]);
+        mProcessEventHooks.erase(locChangePid);
+        pidsToRemove.insert(locChangePid);
+      }
+    }
+    if (!pidsToRemove.empty()) {
+      // XXX simplify
+      for (auto it = mPidsForLocationChangeHook.begin();
+           it != mPidsForLocationChangeHook.end();) {
+        if (pidsToRemove.find(*it) != pidsToRemove.end()) {
+          it = mPidsForLocationChangeHook.erase(it);
+        } else {
+          ++it;
+        }
+      }
+    }
+  }
+
+  std::unordered_map<HWND, OcclusionState>* map =
+      &mRootWindowHwndsOcclusionState;
+  bool showAllWindows = mShowingThumbnails;
+  RefPtr<Runnable> runnable = NS_NewRunnableFunction(
+      "CallUpdateOcclusionState", [map, showAllWindows]() {
+        WinWindowOcclusionTracker::CallUpdateOcclusionState(map,
+                                                            showAllWindows);
+      });
+  mSerializedTaskDispatcher->PostTaskToMain(runnable.forget());
+}
+
+void WinWindowOcclusionTracker::WindowOcclusionCalculator::
+    ScheduleOcclusionCalculationIfNeeded() {
+  MOZ_ASSERT(IsInWinWindowOcclusionThread());
+
+  // OcclusionUpdateRunnable is already queued.
+  if (mOcclusionUpdateRunnable) {
+    return;
+  }
+
+  CALC_LOG(LogLevel::Debug, "ScheduleOcclusionCalculationIfNeeded()");
+
+  RefPtr<CancelableRunnable> task = new OcclusionUpdateRunnable(this);
+  mOcclusionUpdateRunnable = task;
+  mSerializedTaskDispatcher->PostDelayedTaskToCalculator(
+      task.forget(), kOcclusionUpdateRunnableDelayMs);
+}
+
+void WinWindowOcclusionTracker::WindowOcclusionCalculator::
+    RegisterGlobalEventHook(DWORD aEventMin, DWORD aEventMax) {
+  HWINEVENTHOOK eventHook =
+      ::SetWinEventHook(aEventMin, aEventMax, nullptr, &EventHookCallback, 0, 0,
+                        WINEVENT_OUTOFCONTEXT);
+  mGlobalEventHooks.push_back(eventHook);
+}
+
+void WinWindowOcclusionTracker::WindowOcclusionCalculator::
+    RegisterEventHookForProcess(DWORD aPid) {
+  mPidsForLocationChangeHook.insert(aPid);
+  mProcessEventHooks[aPid] = SetWinEventHook(
+      EVENT_OBJECT_LOCATIONCHANGE, EVENT_OBJECT_LOCATIONCHANGE, nullptr,
+      &EventHookCallback, aPid, 0, WINEVENT_OUTOFCONTEXT);
+}
+
+void WinWindowOcclusionTracker::WindowOcclusionCalculator::
+    RegisterEventHooks() {
+  MOZ_ASSERT(IsInWinWindowOcclusionThread());
+  MOZ_RELEASE_ASSERT(mGlobalEventHooks.empty());
+  CALC_LOG(LogLevel::Info, "RegisterEventHooks()");
+
+  // Detects native window lost mouse capture
+  RegisterGlobalEventHook(EVENT_SYSTEM_CAPTUREEND, EVENT_SYSTEM_CAPTUREEND);
+
+  // Detects native window move (drag) and resizing events.
+  RegisterGlobalEventHook(EVENT_SYSTEM_MOVESIZESTART, EVENT_SYSTEM_MOVESIZEEND);
+
+  // Detects native window minimize and restore from taskbar events.
+  RegisterGlobalEventHook(EVENT_SYSTEM_MINIMIZESTART, EVENT_SYSTEM_MINIMIZEEND);
+
+  // Detects foreground window changing.
+  RegisterGlobalEventHook(EVENT_SYSTEM_FOREGROUND, EVENT_SYSTEM_FOREGROUND);
+
+  // Detects objects getting shown and hidden. Used to know when the task bar
+  // and alt tab are showing preview windows so we can unocclude windows.
+  RegisterGlobalEventHook(EVENT_OBJECT_SHOW, EVENT_OBJECT_HIDE);
+
+  // Detects object state changes, e.g., enable/disable state, native window
+  // maximize and native window restore events.
+  RegisterGlobalEventHook(EVENT_OBJECT_STATECHANGE, EVENT_OBJECT_STATECHANGE);
+
+  // Cloaking and uncloaking of windows should trigger an occlusion calculation.
+  // In particular, switching virtual desktops seems to generate these events.
+  RegisterGlobalEventHook(EVENT_OBJECT_CLOAKED, EVENT_OBJECT_UNCLOAKED);
+
+  // Determine which subset of processes to set EVENT_OBJECT_LOCATIONCHANGE on
+  // because otherwise event throughput is very high, as it generates events
+  // for location changes of all objects, including the mouse moving on top of a
+  // window.
+  UpdateVisibleWindowProcessIds();
+  for (DWORD pid : mPidsForLocationChangeHook) {
+    RegisterEventHookForProcess(pid);
+  }
+}
+
+void WinWindowOcclusionTracker::WindowOcclusionCalculator::
+    UnregisterEventHooks() {
+  MOZ_ASSERT(IsInWinWindowOcclusionThread());
+  CALC_LOG(LogLevel::Info, "UnregisterEventHooks()");
+
+  for (const auto eventHook : mGlobalEventHooks) {
+    ::UnhookWinEvent(eventHook);
+  }
+  mGlobalEventHooks.clear();
+
+  for (const auto& [pid, eventHook] : mProcessEventHooks) {
+    ::UnhookWinEvent(eventHook);
+  }
+  mProcessEventHooks.clear();
+
+  mPidsForLocationChangeHook.clear();
+}
+
+bool WinWindowOcclusionTracker::WindowOcclusionCalculator::
+    ProcessComputeNativeWindowOcclusionStatusCallback(
+        HWND aHwnd, std::unordered_set<DWORD>* aCurrentPidsWithVisibleWindows) {
+  LayoutDeviceIntRegion currUnoccludedDestkop = mUnoccludedDesktopRegion;
+  LayoutDeviceIntRect windowRect;
+  bool windowIsOccluding =
+      WindowCanOccludeOtherWindowsOnCurrentVirtualDesktop(aHwnd, &windowRect);
+  if (windowIsOccluding) {
+    // Hook this window's process with EVENT_OBJECT_LOCATION_CHANGE, if we are
+    // not already doing so.
+    DWORD pid;
+    ::GetWindowThreadProcessId(aHwnd, &pid);
+    aCurrentPidsWithVisibleWindows->insert(pid);
+    auto it = mProcessEventHooks.find(pid);
+    if (it == mProcessEventHooks.end()) {
+      RegisterEventHookForProcess(pid);
+    }
+
+    // If no more root windows to consider, return true so we can continue
+    // looking for windows we haven't hooked.
+    if (mNumRootWindowsWithUnknownOcclusionState == 0) {
+      return true;
+    }
+
+    mUnoccludedDesktopRegion.SubOut(windowRect);
+  } else if (mNumRootWindowsWithUnknownOcclusionState == 0) {
+    // This window can't occlude other windows, but we've determined the
+    // occlusion state of all root windows, so we can return.
+    return true;
+  }
+
+  // Ignore moving windows when deciding if windows under it are occluded.
+  if (aHwnd == mMovingWindow) {
+    return true;
+  }
+
+  // Check if |hwnd| is a root window; if so, we're done figuring out
+  // if it's occluded because we've seen all the windows "over" it.
+  auto it = mRootWindowHwndsOcclusionState.find(aHwnd);
+  if (it == mRootWindowHwndsOcclusionState.end() ||
+      it->second != OcclusionState::UNKNOWN) {
+    return true;
+  }
+
+  CALC_LOG(LogLevel::Debug,
+           "ProcessComputeNativeWindowOcclusionStatusCallback() windowRect(%d, "
+           "%d, %d, %d) IsOccluding %d",
+           windowRect.x, windowRect.y, windowRect.width, windowRect.height,
+           windowIsOccluding);
+
+  // On Win7, default theme makes root windows have complex regions by
+  // default. But we can still check if their bounding rect is occluded.
+  if (!windowIsOccluding) {
+    RECT rect;
+    if (::GetWindowRect(aHwnd, &rect) != 0) {
+      LayoutDeviceIntRect windowRect(
+          rect.left, rect.top, rect.right - rect.left, rect.bottom - rect.top);
+      currUnoccludedDestkop.SubOut(windowRect);
+    }
+  }
+
+  it->second = (mUnoccludedDesktopRegion == currUnoccludedDestkop)
+                   ? OcclusionState::OCCLUDED
+                   : OcclusionState::VISIBLE;
+  mNumRootWindowsWithUnknownOcclusionState--;
+
+  return true;
+}
+
+void WinWindowOcclusionTracker::WindowOcclusionCalculator::
+    ProcessEventHookCallback(HWINEVENTHOOK aWinEventHook, DWORD aEvent,
+                             HWND aHwnd, LONG aIdObject, LONG aIdChild) {
+  MOZ_ASSERT(IsInWinWindowOcclusionThread());
+
+  // No need to calculate occlusion if a zero HWND generated the event. This
+  // happens if there is no window associated with the event, e.g., mouse move
+  // events.
+  if (!aHwnd) {
+    return;
+  }
+
+  // We only care about events for window objects. In particular, we don't care
+  // about OBJID_CARET, which is spammy.
+  if (aIdObject != OBJID_WINDOW) {
+    return;
+  }
+
+  CALC_LOG(LogLevel::Debug,
+           "WindowOcclusionCalculator::ProcessEventHookCallback() aEvent 0x%lx",
+           aEvent);
+
+  // We generally ignore events for popup windows, except for when the taskbar
+  // is hidden or Windows Taskbar, in which case we recalculate occlusion.
+  // XXX Chrome Widget popup handling is removed for now.
+  bool calculateOcclusion = true;
+  if (::GetWindowLong(aHwnd, GWL_STYLE) & WS_POPUP) {
+    nsAutoString className;
+    if (WinUtils::GetClassName(aHwnd, className)) {
+      calculateOcclusion = className.Equals(L"Shell_TrayWnd");
+    }
+  }
+
+  // Detect if either the alt tab view or the task list thumbnail is being
+  // shown. If so, mark all non-hidden windows as occluded, and remember that
+  // we're in the showing_thumbnails state. This lasts until we get told that
+  // either the alt tab view or task list thumbnail are hidden.
+  if (aEvent == EVENT_OBJECT_SHOW) {
+    // Avoid getting the aHwnd's class name, and recomputing occlusion, if not
+    // needed.
+    if (mShowingThumbnails) {
+      return;
+    }
+    nsAutoString className;
+    if (WinUtils::GetClassName(aHwnd, className)) {
+      const auto name = NS_ConvertUTF16toUTF8(className);
+      CALC_LOG(LogLevel::Debug,
+               "ProcessEventHookCallback() EVENT_OBJECT_SHOW %s", name.get());
+
+      if (name.Equals("MultitaskingViewFrame") ||
+          name.Equals("TaskListThumbnailWnd")) {
+        CALC_LOG(LogLevel::Info,
+                 "ProcessEventHookCallback() mShowingThumbnails = true");
+        mShowingThumbnails = true;
+
+        std::unordered_map<HWND, OcclusionState>* map =
+            &mRootWindowHwndsOcclusionState;
+        bool showAllWindows = mShowingThumbnails;
+        RefPtr<Runnable> runnable = NS_NewRunnableFunction(
+            "CallUpdateOcclusionState", [map, showAllWindows]() {
+              WinWindowOcclusionTracker::CallUpdateOcclusionState(
+                  map, showAllWindows);
+            });
+        mSerializedTaskDispatcher->PostTaskToMain(runnable.forget());
+      }
+    }
+    return;
+  } else if (aEvent == EVENT_OBJECT_HIDE) {
+    // Avoid getting the aHwnd's class name, and recomputing occlusion, if not
+    // needed.
+    if (!mShowingThumbnails) {
+      return;
+    }
+    nsAutoString className;
+    WinUtils::GetClassName(aHwnd, className);
+    const auto name = NS_ConvertUTF16toUTF8(className);
+    CALC_LOG(LogLevel::Debug, "ProcessEventHookCallback() EVENT_OBJECT_HIDE %s",
+             name.get());
+    if (name.Equals("MultitaskingViewFrame") ||
+        name.Equals("TaskListThumbnailWnd")) {
+      CALC_LOG(LogLevel::Info,
+               "ProcessEventHookCallback() mShowingThumbnails = false");
+      mShowingThumbnails = false;
+      // Let occlusion calculation fix occlusion state, even though hwnd might
+      // be a popup window.
+      calculateOcclusion = true;
+    } else {
+      return;
+    }
+  }
+  // Don't continually calculate occlusion while a window is moving (unless it's
+  // a root window), but instead once at the beginning and once at the end.
+  // Remember the window being moved so if it's a root window, we can ignore
+  // it when deciding if windows under it are occluded.
+  else if (aEvent == EVENT_SYSTEM_MOVESIZESTART) {
+    mMovingWindow = aHwnd;
+  } else if (aEvent == EVENT_SYSTEM_MOVESIZEEND) {
+    mMovingWindow = 0;
+  } else if (mMovingWindow != 0) {
+    if (aEvent == EVENT_OBJECT_LOCATIONCHANGE ||
+        aEvent == EVENT_OBJECT_STATECHANGE) {
+      // Ignore move events if it's not a root window that's being moved. If it
+      // is a root window, we want to calculate occlusion to support tab
+      // dragging to windows that were occluded when the drag was started but
+      // are no longer occluded.
+      if (mRootWindowHwndsOcclusionState.find(aHwnd) ==
+          mRootWindowHwndsOcclusionState.end()) {
+        return;
+      }
+    } else {
+      // If we get an event that isn't a location/state change, then we probably
+      // missed the movesizeend notification, or got events out of order. In
+      // that case, we want to go back to normal occlusion calculation.
+      mMovingWindow = 0;
+    }
+  }
+
+  if (!calculateOcclusion) {
+    return;
+  }
+
+  ScheduleOcclusionCalculationIfNeeded();
+}
+
+void WinWindowOcclusionTracker::WindowOcclusionCalculator::
+    ProcessUpdateVisibleWindowProcessIdsCallback(HWND aHwnd) {
+  MOZ_ASSERT(IsInWinWindowOcclusionThread());
+
+  LayoutDeviceIntRect windowRect;
+  if (WindowCanOccludeOtherWindowsOnCurrentVirtualDesktop(aHwnd, &windowRect)) {
+    DWORD pid;
+    ::GetWindowThreadProcessId(aHwnd, &pid);
+    mPidsForLocationChangeHook.insert(pid);
+  }
+}
+
+bool WinWindowOcclusionTracker::WindowOcclusionCalculator::
+    WindowCanOccludeOtherWindowsOnCurrentVirtualDesktop(
+        HWND aHwnd, LayoutDeviceIntRect* aWindowRect) {
+  return IsWindowVisibleAndFullyOpaque(aHwnd, aWindowRect) &&
+         (IsWindowOnCurrentVirtualDesktop(aHwnd) == Some(true));
+}
+
+Maybe<bool> WinWindowOcclusionTracker::WindowOcclusionCalculator::
+    IsWindowOnCurrentVirtualDesktop(HWND aHwnd) {
+  if (!mVirtualDesktopManager) {
+    return Some(true);
+  }
+
+  BOOL onCurrentDesktop;
+  HRESULT hr = mVirtualDesktopManager->IsWindowOnCurrentVirtualDesktop(
+      aHwnd, &onCurrentDesktop);
+  if (FAILED(hr)) {
+    // In this case, we do not know the window is in which virtual desktop.
+    return Nothing();
+  }
+
+  if (onCurrentDesktop) {
+    return Some(true);
+  }
+
+  GUID workspaceGuid;
+  hr = mVirtualDesktopManager->GetWindowDesktopId(aHwnd, &workspaceGuid);
+  if (FAILED(hr)) {
+    // In this case, we do not know the window is in which virtual desktop.
+    return Nothing();
+  }
+
+  // IsWindowOnCurrentVirtualDesktop() is flaky for newly opened windows,
+  // which causes test flakiness. Occasionally, it incorrectly says a window
+  // is not on the current virtual desktop when it is. In this situation,
+  // it also returns GUID_NULL for the desktop id.
+  if (workspaceGuid == GUID_NULL) {
+    // In this case, we do not know if the window is in which virtual desktop.
+    // But we hanle it as on current virtual desktop.
+    // It does not cause a problem to window occlusion.
+    // Since if window is not on current virtual desktop, window size becomes
+    // (0, 0, 0, 0). It makes window occlusion handling explicit. It is
+    // necessary for gtest.
+    return Some(true);
+  }
+
+  return Some(false);
+}
+
+#undef LOG
+#undef CALC_LOG
+
+}  // namespace mozilla::widget
diff --git a/widget/windows/WinWindowOcclusionTracker.h b/widget/windows/WinWindowOcclusionTracker.h
new file mode 100644
index 0000000000..b82a41b984
--- /dev/null
+++ b/widget/windows/WinWindowOcclusionTracker.h
@@ -0,0 +1,333 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef widget_windows_WinWindowOcclusionTracker_h
+#define widget_windows_WinWindowOcclusionTracker_h
+
+#include <string>
+#include <unordered_map>
+#include <unordered_set>
+#include <vector>
+
+#include "nsIWeakReferenceUtils.h"
+#include "mozilla/Monitor.h"
+#include "mozilla/StaticPtr.h"
+#include "mozilla/WindowsVersion.h"
+#include "mozilla/ThreadSafeWeakPtr.h"
+#include "mozilla/widget/WindowOcclusionState.h"
+#include "mozilla/widget/WinEventObserver.h"
+#include "Units.h"
+#include "nsThreadUtils.h"
+
+class nsBaseWidget;
+struct IVirtualDesktopManager;
+class WinWindowOcclusionTrackerTest;
+class WinWindowOcclusionTrackerInteractiveTest;
+
+namespace base {
+class Thread;
+}  // namespace base
+
+namespace mozilla {
+
+namespace widget {
+
+class OcclusionUpdateRunnable;
+class SerializedTaskDispatcher;
+class UpdateOcclusionStateRunnable;
+
+// This class handles window occlusion tracking by using HWND.
+// Implementation is borrowed from chromium's NativeWindowOcclusionTrackerWin.
+class WinWindowOcclusionTracker final : public DisplayStatusListener,
+                                        public SessionChangeListener {
+ public:
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(WinWindowOcclusionTracker)
+
+  /// Can only be called from the main thread.
+  static WinWindowOcclusionTracker* Get();
+
+  /// Can only be called from the main thread.
+  static void Ensure();
+
+  /// Can only be called from the main thread.
+  static void ShutDown();
+
+  /// Can be called from any thread.
+  static MessageLoop* OcclusionCalculatorLoop();
+
+  /// Can be called from any thread.
+  static bool IsInWinWindowOcclusionThread();
+
+  /// Can only be called from the main thread.
+  void EnsureDisplayStatusObserver();
+
+  /// Can only be called from the main thread.
+  void EnsureSessionChangeObserver();
+
+  // Enables notifying to widget via NotifyOcclusionState() when the occlusion
+  // state has been computed.
+  void Enable(nsBaseWidget* aWindow, HWND aHwnd);
+
+  // Disables notifying to widget via NotifyOcclusionState() when the occlusion
+  // state has been computed.
+  void Disable(nsBaseWidget* aWindow, HWND aHwnd);
+
+  // Called when widget's visibility is changed
+  void OnWindowVisibilityChanged(nsBaseWidget* aWindow, bool aVisible);
+
+  SerializedTaskDispatcher* GetSerializedTaskDispatcher() {
+    return mSerializedTaskDispatcher;
+  }
+
+  void TriggerCalculation();
+
+  void DumpOccludingWindows(HWND aHWnd);
+
+ private:
+  friend class ::WinWindowOcclusionTrackerTest;
+  friend class ::WinWindowOcclusionTrackerInteractiveTest;
+
+  explicit WinWindowOcclusionTracker(UniquePtr<base::Thread> aThread);
+  virtual ~WinWindowOcclusionTracker();
+
+  // This class computes the occlusion state of the tracked windows.
+  // It runs on a separate thread, and notifies the main thread of
+  // the occlusion state of the tracked windows.
+  class WindowOcclusionCalculator {
+    NS_INLINE_DECL_THREADSAFE_REFCOUNTING(WindowOcclusionCalculator)
+   public:
+    // Creates WindowOcclusionCalculator instance.
+    static void CreateInstance();
+
+    // Clear WindowOcclusionCalculator instance.
+    static void ClearInstance();
+
+    // Returns existing WindowOcclusionCalculator instance.
+    static WindowOcclusionCalculator* GetInstance() { return sCalculator; }
+
+    void Initialize();
+    void Shutdown();
+
+    void EnableOcclusionTrackingForWindow(HWND hwnd);
+    void DisableOcclusionTrackingForWindow(HWND hwnd);
+
+    // If a window becomes visible, makes sure event hooks are registered.
+    void HandleVisibilityChanged(bool aVisible);
+
+    void HandleTriggerCalculation();
+
+   private:
+    WindowOcclusionCalculator();
+    ~WindowOcclusionCalculator();
+
+    // Registers event hooks, if not registered.
+    void MaybeRegisterEventHooks();
+
+    // This is the callback registered to get notified of various Windows
+    // events, like window moving/resizing.
+    static void CALLBACK EventHookCallback(HWINEVENTHOOK aWinEventHook,
+                                           DWORD aEvent, HWND aHwnd,
+                                           LONG aIdObject, LONG aIdChild,
+                                           DWORD aEventThread,
+                                           DWORD aMsEventTime);
+
+    // EnumWindows callback used to iterate over all hwnds to determine
+    // occlusion status of all tracked root windows.  Also builds up
+    // |current_pids_with_visible_windows_| and registers event hooks for newly
+    // discovered processes with visible hwnds.
+    static BOOL CALLBACK
+    ComputeNativeWindowOcclusionStatusCallback(HWND hwnd, LPARAM lParam);
+
+    // EnumWindows callback used to update the list of process ids with
+    // visible hwnds, |pids_for_location_change_hook_|.
+    static BOOL CALLBACK UpdateVisibleWindowProcessIdsCallback(HWND aHwnd,
+                                                               LPARAM aLParam);
+
+    // Determines which processes owning visible application windows to set the
+    // EVENT_OBJECT_LOCATIONCHANGE event hook for and stores the pids in
+    // |pids_for_location_change_hook_|.
+    void UpdateVisibleWindowProcessIds();
+
+    // Computes the native window occlusion status for all tracked root gecko
+    // windows in |root_window_hwnds_occlusion_state_| and notifies them if
+    // their occlusion status has changed.
+    void ComputeNativeWindowOcclusionStatus();
+
+    // Schedules an occlusion calculation , if one isn't already scheduled.
+    void ScheduleOcclusionCalculationIfNeeded();
+
+    // Registers a global event hook (not per process) for the events in the
+    // range from |event_min| to |event_max|, inclusive.
+    void RegisterGlobalEventHook(DWORD aEventMin, DWORD aEventMax);
+
+    // Registers the EVENT_OBJECT_LOCATIONCHANGE event hook for the process with
+    // passed id. The process has one or more visible, opaque windows.
+    void RegisterEventHookForProcess(DWORD aPid);
+
+    // Registers/Unregisters the event hooks necessary for occlusion tracking
+    // via calls to RegisterEventHook. These event hooks are disabled when all
+    // tracked windows are minimized.
+    void RegisterEventHooks();
+    void UnregisterEventHooks();
+
+    // EnumWindows callback for occlusion calculation. Returns true to
+    // continue enumeration, false otherwise. Currently, always returns
+    // true because this function also updates currentPidsWithVisibleWindows,
+    // and needs to see all HWNDs.
+    bool ProcessComputeNativeWindowOcclusionStatusCallback(
+        HWND aHwnd, std::unordered_set<DWORD>* aCurrentPidsWithVisibleWindows);
+
+    // Processes events sent to OcclusionEventHookCallback.
+    // It generally triggers scheduling of the occlusion calculation, but
+    // ignores certain events in order to not calculate occlusion more than
+    // necessary.
+    void ProcessEventHookCallback(HWINEVENTHOOK aWinEventHook, DWORD aEvent,
+                                  HWND aHwnd, LONG aIdObject, LONG aIdChild);
+
+    // EnumWindows callback for determining which processes to set the
+    // EVENT_OBJECT_LOCATIONCHANGE event hook for. We set that event hook for
+    // processes hosting fully visible, opaque windows.
+    void ProcessUpdateVisibleWindowProcessIdsCallback(HWND aHwnd);
+
+    // Returns true if the window is visible, fully opaque, and on the current
+    // virtual desktop, false otherwise.
+    bool WindowCanOccludeOtherWindowsOnCurrentVirtualDesktop(
+        HWND aHwnd, LayoutDeviceIntRect* aWindowRect);
+
+    // Returns true if aHwnd is definitely on the current virtual desktop,
+    // false if it's definitely not on the current virtual desktop, and Nothing
+    // if we we can't tell for sure.
+    Maybe<bool> IsWindowOnCurrentVirtualDesktop(HWND aHwnd);
+
+    static StaticRefPtr<WindowOcclusionCalculator> sCalculator;
+
+    // Map of root app window hwnds and their occlusion state. This contains
+    // both visible and hidden windows.
+    // It is accessed from WinWindowOcclusionTracker::UpdateOcclusionState()
+    // without using mutex. The access is safe by using
+    // SerializedTaskDispatcher.
+    std::unordered_map<HWND, OcclusionState> mRootWindowHwndsOcclusionState;
+
+    // Values returned by SetWinEventHook are stored so that hooks can be
+    // unregistered when necessary.
+    std::vector<HWINEVENTHOOK> mGlobalEventHooks;
+
+    // Map from process id to EVENT_OBJECT_LOCATIONCHANGE event hook.
+    std::unordered_map<DWORD, HWINEVENTHOOK> mProcessEventHooks;
+
+    // Pids of processes for which the EVENT_OBJECT_LOCATIONCHANGE event hook is
+    // set.
+    std::unordered_set<DWORD> mPidsForLocationChangeHook;
+
+    // Used as a timer to delay occlusion update.
+    RefPtr<CancelableRunnable> mOcclusionUpdateRunnable;
+
+    // Used to determine if a window is occluded. As we iterate through the
+    // hwnds in z-order, we subtract each opaque window's rect from
+    // mUnoccludedDesktopRegion. When we get to a root window, we subtract
+    // it from mUnoccludedDesktopRegion, and if mUnoccludedDesktopRegion
+    // doesn't change, the root window was already occluded.
+    LayoutDeviceIntRegion mUnoccludedDesktopRegion;
+
+    // Keeps track of how many root windows we need to compute the occlusion
+    // state of in a call to ComputeNativeWindowOcclusionStatus. Once we've
+    // determined the state of all root windows, we can stop subtracting
+    // windows from mUnoccludedDesktopRegion;.
+    int mNumRootWindowsWithUnknownOcclusionState;
+
+    // This is true if the task bar thumbnails or the alt tab thumbnails are
+    // showing.
+    bool mShowingThumbnails = false;
+
+    // Used to keep track of the window that's currently moving. That window
+    // is ignored for calculation occlusion so that tab dragging won't
+    // ignore windows occluded by the dragged window.
+    HWND mMovingWindow = 0;
+
+    // Only used on Win10+.
+    RefPtr<IVirtualDesktopManager> mVirtualDesktopManager;
+
+    // Used to serialize tasks related to mRootWindowHwndsOcclusionState.
+    RefPtr<SerializedTaskDispatcher> mSerializedTaskDispatcher;
+
+    // This is an alias to the singleton WinWindowOcclusionTracker mMonitor,
+    // and is used in ShutDown().
+    Monitor& mMonitor;
+
+    friend class OcclusionUpdateRunnable;
+  };
+
+  static BOOL CALLBACK DumpOccludingWindowsCallback(HWND aHWnd, LPARAM aLParam);
+
+  // Returns true if we are interested in |hwnd| for purposes of occlusion
+  // calculation. We are interested in |hwnd| if it is a window that is
+  // visible, opaque, bounded, and not a popup or floating window. If we are
+  // interested in |hwnd|, stores the window rectangle in |window_rect|.
+  static bool IsWindowVisibleAndFullyOpaque(HWND aHwnd,
+                                            LayoutDeviceIntRect* aWindowRect);
+
+  void Destroy();
+
+  static void CallUpdateOcclusionState(
+      std::unordered_map<HWND, OcclusionState>* aMap, bool aShowAllWindows);
+
+  // Updates root windows occclusion state. If aShowAllWindows is true,
+  // all non-hidden windows will be marked visible.  This is used to force
+  // rendering of thumbnails.
+  void UpdateOcclusionState(std::unordered_map<HWND, OcclusionState>* aMap,
+                            bool aShowAllWindows);
+
+  // This is called with session changed notifications. If the screen is locked
+  // by the current session, it marks app windows as occluded.
+  void OnSessionChange(WPARAM aStatusCode,
+                       Maybe<bool> aIsCurrentSession) override;
+
+  // This is called when the display is put to sleep. If the display is sleeping
+  // it marks app windows as occluded.
+  void OnDisplayStateChanged(bool aDisplayOn) override;
+
+  // Marks all root windows as either occluded, or if hwnd IsIconic, hidden.
+  void MarkNonIconicWindowsOccluded();
+
+  static StaticRefPtr<WinWindowOcclusionTracker> sTracker;
+
+  // "WinWindowOcclusionCalc" thread.
+  UniquePtr<base::Thread> mThread;
+  Monitor mMonitor;
+
+  // Has ShutDown been called on us? We might have survived if our thread join
+  // timed out.
+  bool mHasAttemptedShutdown = false;
+
+  // Map of HWND to widget. Maintained on main thread, and used to send
+  // occlusion state notifications to Windows from
+  // mRootWindowHwndsOcclusionState.
+  std::unordered_map<HWND, nsWeakPtr> mHwndRootWindowMap;
+
+  // This is set by UpdateOcclusionState(). It is currently only used by tests.
+  int mNumVisibleRootWindows = 0;
+
+  // If the screen is locked, windows are considered occluded.
+  bool mScreenLocked = false;
+
+  // If the display is off, windows are considered occluded.
+  bool mDisplayOn = true;
+
+  RefPtr<DisplayStatusObserver> mDisplayStatusObserver;
+
+  RefPtr<SessionChangeObserver> mSessionChangeObserver;
+
+  // Used to serialize tasks related to mRootWindowHwndsOcclusionState.
+  RefPtr<SerializedTaskDispatcher> mSerializedTaskDispatcher;
+
+  friend class OcclusionUpdateRunnable;
+  friend class UpdateOcclusionStateRunnable;
+};
+
+}  // namespace widget
+}  // namespace mozilla
+
+#endif  // widget_windows_WinWindowOcclusionTracker_h
diff --git a/widget/windows/WindowHook.cpp b/widget/windows/WindowHook.cpp
new file mode 100644
index 0000000000..06773f21b7
--- /dev/null
+++ b/widget/windows/WindowHook.cpp
@@ -0,0 +1,113 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "WindowHook.h"
+#include "nsWindow.h"
+#include "nsWindowDefs.h"
+
+namespace mozilla {
+namespace widget {
+
+nsresult WindowHook::AddHook(UINT nMsg, Callback callback, void* context) {
+  MessageData* data = LookupOrCreate(nMsg);
+
+  if (!data) return NS_ERROR_OUT_OF_MEMORY;
+
+  // Ensure we don't overwrite another hook
+  NS_ENSURE_TRUE(nullptr == data->hook.cb, NS_ERROR_UNEXPECTED);
+
+  data->hook = CallbackData(callback, context);
+
+  return NS_OK;
+}
+
+nsresult WindowHook::RemoveHook(UINT nMsg, Callback callback, void* context) {
+  CallbackData cbdata(callback, context);
+  MessageData* data = Lookup(nMsg);
+  if (!data) return NS_ERROR_UNEXPECTED;
+  if (data->hook != cbdata) return NS_ERROR_UNEXPECTED;
+  data->hook = CallbackData();
+
+  DeleteIfEmpty(data);
+  return NS_OK;
+}
+
+nsresult WindowHook::AddMonitor(UINT nMsg, Callback callback, void* context) {
+  MessageData* data = LookupOrCreate(nMsg);
+  return (data && data->monitors.AppendElement(CallbackData(callback, context),
+                                               fallible))
+             ? NS_OK
+             : NS_ERROR_OUT_OF_MEMORY;
+}
+
+nsresult WindowHook::RemoveMonitor(UINT nMsg, Callback callback,
+                                   void* context) {
+  CallbackData cbdata(callback, context);
+  MessageData* data = Lookup(nMsg);
+  if (!data) return NS_ERROR_UNEXPECTED;
+  CallbackDataArray::index_type idx = data->monitors.IndexOf(cbdata);
+  if (idx == CallbackDataArray::NoIndex) return NS_ERROR_UNEXPECTED;
+  data->monitors.RemoveElementAt(idx);
+  DeleteIfEmpty(data);
+  return NS_OK;
+}
+
+WindowHook::MessageData* WindowHook::Lookup(UINT nMsg) {
+  MessageDataArray::index_type idx;
+  for (idx = 0; idx < mMessageData.Length(); idx++) {
+    MessageData& data = mMessageData[idx];
+    if (data.nMsg == nMsg) return &data;
+  }
+  return nullptr;
+}
+
+WindowHook::MessageData* WindowHook::LookupOrCreate(UINT nMsg) {
+  MessageData* data = Lookup(nMsg);
+  if (!data) {
+    data = mMessageData.AppendElement();
+
+    if (!data) return nullptr;
+
+    data->nMsg = nMsg;
+  }
+  return data;
+}
+
+void WindowHook::DeleteIfEmpty(MessageData* data) {
+  // Never remove a MessageData that has still a hook or monitor entries.
+  if (data->hook || !data->monitors.IsEmpty()) return;
+
+  MessageDataArray::index_type idx;
+  idx = data - mMessageData.Elements();
+  NS_ASSERTION(
+      idx < mMessageData.Length(),
+      "Attempted to delete MessageData that doesn't belong to this array!");
+  mMessageData.RemoveElementAt(idx);
+}
+
+bool WindowHook::Notify(HWND hWnd, UINT nMsg, WPARAM wParam, LPARAM lParam,
+                        MSGResult& aResult) {
+  MessageData* data = Lookup(nMsg);
+  if (!data) return false;
+
+  uint32_t length = data->monitors.Length();
+  for (uint32_t midx = 0; midx < length; midx++) {
+    data->monitors[midx].Invoke(hWnd, nMsg, wParam, lParam, &aResult.mResult);
+  }
+
+  aResult.mConsumed =
+      data->hook.Invoke(hWnd, nMsg, wParam, lParam, &aResult.mResult);
+  return aResult.mConsumed;
+}
+
+bool WindowHook::CallbackData::Invoke(HWND hWnd, UINT msg, WPARAM wParam,
+                                      LPARAM lParam, LRESULT* aResult) {
+  if (!cb) return false;
+  return cb(context, hWnd, msg, wParam, lParam, aResult);
+}
+
+}  // namespace widget
+}  // namespace mozilla
diff --git a/widget/windows/WindowHook.h b/widget/windows/WindowHook.h
new file mode 100644
index 0000000000..1d1f4b02da
--- /dev/null
+++ b/widget/windows/WindowHook.h
@@ -0,0 +1,76 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef __mozilla_WindowHook_h__
+#define __mozilla_WindowHook_h__
+
+#include <windows.h>
+
+#include <nsHashKeys.h>
+#include <nsClassHashtable.h>
+#include <nsTArray.h>
+
+#include "nsAppShell.h"
+
+class nsWindow;
+
+namespace mozilla {
+namespace widget {
+
+struct MSGResult;
+
+class WindowHook {
+ public:
+  // It is expected that most callbacks will return false
+  typedef bool (*Callback)(void* aContext, HWND hWnd, UINT nMsg, WPARAM wParam,
+                           LPARAM lParam, LRESULT* aResult);
+
+  nsresult AddHook(UINT nMsg, Callback callback, void* context);
+  nsresult RemoveHook(UINT nMsg, Callback callback, void* context);
+  nsresult AddMonitor(UINT nMsg, Callback callback, void* context);
+  nsresult RemoveMonitor(UINT nMsg, Callback callback, void* context);
+
+ private:
+  struct CallbackData {
+    Callback cb;
+    void* context;
+
+    CallbackData() : cb(nullptr), context(nullptr) {}
+    CallbackData(Callback cb, void* ctx) : cb(cb), context(ctx) {}
+    bool Invoke(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam,
+                LRESULT* aResult);
+    bool operator==(const CallbackData& rhs) const {
+      return cb == rhs.cb && context == rhs.context;
+    }
+    bool operator!=(const CallbackData& rhs) const { return !(*this == rhs); }
+    explicit operator bool() const { return !!cb; }
+  };
+
+  typedef nsTArray<CallbackData> CallbackDataArray;
+  struct MessageData {
+    UINT nMsg;
+    CallbackData hook;
+    CallbackDataArray monitors;
+  };
+
+  bool Notify(HWND hWnd, UINT nMsg, WPARAM wParam, LPARAM lParam,
+              MSGResult& aResult);
+
+  MessageData* Lookup(UINT nMsg);
+  MessageData* LookupOrCreate(UINT nMsg);
+  void DeleteIfEmpty(MessageData* data);
+
+  typedef nsTArray<MessageData> MessageDataArray;
+  MessageDataArray mMessageData;
+
+  // For Notify
+  friend class ::nsWindow;
+};
+
+}  // namespace widget
+}  // namespace mozilla
+
+#endif  // __mozilla_WindowHook_h__
diff --git a/widget/windows/WindowsConsole.cpp b/widget/windows/WindowsConsole.cpp
new file mode 100644
index 0000000000..c8e7eb1a11
--- /dev/null
+++ b/widget/windows/WindowsConsole.cpp
@@ -0,0 +1,53 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "WindowsConsole.h"
+
+#include <windows.h>
+#include <fcntl.h>
+#include <cstdio>
+#include <io.h>
+
+namespace mozilla {
+
+static void AssignStdHandle(const char* aPath, const char* aMode, FILE* aStream,
+                            DWORD aStdHandle) {
+  // Visual Studio's _fileno() returns -2 for the standard
+  // streams if they aren't associated with an output stream.
+  const int fd = _fileno(aStream);
+  if (fd == -2) {
+    freopen(aPath, aMode, aStream);
+    return;
+  }
+  if (fd < 0) {
+    return;
+  }
+
+  const HANDLE handle = reinterpret_cast<HANDLE>(_get_osfhandle(fd));
+  if (handle == INVALID_HANDLE_VALUE) {
+    return;
+  }
+
+  const HANDLE oldHandle = GetStdHandle(aStdHandle);
+  if (handle == oldHandle) {
+    return;
+  }
+
+  SetStdHandle(aStdHandle, handle);
+}
+
+// This code attaches the process to the appropriate console.
+void UseParentConsole() {
+  if (AttachConsole(ATTACH_PARENT_PROCESS)) {
+    // Redirect the standard streams to the existing console, but
+    // only if they haven't been redirected to a valid file.
+    AssignStdHandle("CONOUT$", "w", stdout, STD_OUTPUT_HANDLE);
+    // There is no CONERR$, so use CONOUT$ for stderr as well.
+    AssignStdHandle("CONOUT$", "w", stderr, STD_ERROR_HANDLE);
+    AssignStdHandle("CONIN$", "r", stdin, STD_INPUT_HANDLE);
+  }
+}
+
+}  // namespace mozilla
diff --git a/widget/windows/WindowsConsole.h b/widget/windows/WindowsConsole.h
new file mode 100644
index 0000000000..4b8ecf1823
--- /dev/null
+++ b/widget/windows/WindowsConsole.h
@@ -0,0 +1,16 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_WindowsConsole_h
+#define mozilla_WindowsConsole_h
+
+namespace mozilla {
+
+// This code attaches the process to the appropriate console.
+void UseParentConsole();
+
+}  // namespace mozilla
+
+#endif  // mozilla_WindowsConsole_h
diff --git a/widget/windows/WindowsEMF.cpp b/widget/windows/WindowsEMF.cpp
new file mode 100644
index 0000000000..71e3631bea
--- /dev/null
+++ b/widget/windows/WindowsEMF.cpp
@@ -0,0 +1,94 @@
+/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "WindowsEMF.h"
+
+namespace mozilla {
+namespace widget {
+
+WindowsEMF::WindowsEMF() : mEmf(nullptr), mDC(nullptr) {}
+
+WindowsEMF::~WindowsEMF() { ReleaseAllResource(); }
+
+bool WindowsEMF::InitForDrawing(const wchar_t* aMetafilePath /* = nullptr */) {
+  ReleaseAllResource();
+
+  mDC = ::CreateEnhMetaFile(nullptr, aMetafilePath, nullptr, nullptr);
+  return !!mDC;
+}
+
+bool WindowsEMF::InitFromFileContents(const wchar_t* aMetafilePath) {
+  MOZ_ASSERT(aMetafilePath);
+  ReleaseAllResource();
+
+  mEmf = ::GetEnhMetaFileW(aMetafilePath);
+  return !!mEmf;
+}
+
+bool WindowsEMF::InitFromFileContents(LPBYTE aBytes, UINT aSize) {
+  MOZ_ASSERT(aBytes && aSize != 0);
+  ReleaseAllResource();
+
+  mEmf = SetEnhMetaFileBits(aSize, aBytes);
+
+  return !!mEmf;
+}
+
+bool WindowsEMF::FinishDocument() {
+  if (mDC) {
+    mEmf = ::CloseEnhMetaFile(mDC);
+    mDC = nullptr;
+  }
+  return !!mEmf;
+}
+
+void WindowsEMF::ReleaseEMFHandle() {
+  if (mEmf) {
+    ::DeleteEnhMetaFile(mEmf);
+    mEmf = nullptr;
+  }
+}
+
+void WindowsEMF::ReleaseAllResource() {
+  FinishDocument();
+  ReleaseEMFHandle();
+}
+
+bool WindowsEMF::Playback(HDC aDeviceContext, const RECT& aRect) {
+  DebugOnly<bool> result = FinishDocument();
+  MOZ_ASSERT(result, "This function should be used after InitXXX.");
+
+  return ::PlayEnhMetaFile(aDeviceContext, mEmf, &aRect) != 0;
+}
+
+bool WindowsEMF::SaveToFile() {
+  DebugOnly<bool> result = FinishDocument();
+  MOZ_ASSERT(result, "This function should be used after InitXXX.");
+
+  ReleaseEMFHandle();
+  return true;
+}
+
+UINT WindowsEMF::GetEMFContentSize() {
+  DebugOnly<bool> result = FinishDocument();
+  MOZ_ASSERT(result, "This function should be used after InitXXX.");
+
+  return GetEnhMetaFileBits(mEmf, 0, NULL);
+}
+
+bool WindowsEMF::GetEMFContentBits(LPBYTE aBytes) {
+  DebugOnly<bool> result = FinishDocument();
+  MOZ_ASSERT(result, "This function should be used after InitXXX.");
+
+  UINT emfSize = GetEMFContentSize();
+  if (GetEnhMetaFileBits(mEmf, emfSize, aBytes) != emfSize) {
+    return false;
+  }
+
+  return true;
+}
+
+}  // namespace widget
+}  // namespace mozilla
diff --git a/widget/windows/WindowsEMF.h b/widget/windows/WindowsEMF.h
new file mode 100644
index 0000000000..3a7a20173c
--- /dev/null
+++ b/widget/windows/WindowsEMF.h
@@ -0,0 +1,106 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef MOZILLA_WIDGET_WINDOWSEMF_H
+#define MOZILLA_WIDGET_WINDOWSEMF_H
+
+/* include windows.h for the HDC definitions that we need. */
+#include <windows.h>
+
+namespace mozilla {
+namespace widget {
+
+/**
+ * Windows Enhance Metafile: https://en.wikipedia.org/wiki/Windows_Metafile
+ * A metafile, also called a vector image, is an image that is stored as a
+ * sequence of drawing commands and settings. The commands and settings
+ * recorded in a Metafile object can be stored in memory or saved to a file.
+ *
+ * The metafile device context is used for all drawing operations required to
+ * create the picture. When the system processes a GDI function associated with
+ * a metafile DC, it converts the function into the appropriate data and stores
+ * this data in a record appended to the metafile.
+ */
+class WindowsEMF {
+ public:
+  WindowsEMF();
+  ~WindowsEMF();
+
+  /**
+   * Initializes the object with the path of a file where the EMF data stream
+   * should be stored. Callers are then expected to call GetDC() to draw output
+   * before going on to call Playback() or SaveToFile() to generate the EMF
+   * output.
+   */
+  bool InitForDrawing(const wchar_t* aMetafilePath = nullptr);
+
+  /**
+   * Initializes the object with an existing EMF file. Consumers cannot use
+   * GetDC() to obtain an HDC to modify the file. They can only use Playback().
+   */
+  bool InitFromFileContents(const wchar_t* aMetafilePath);
+
+  /**
+   * Creates the EMF from the specified data
+   *
+   * @param aByte Pointer to a buffer that contains EMF data.
+   * @param aSize Specifies the size, in bytes, of aByte.
+   */
+  bool InitFromFileContents(PBYTE aBytes, UINT aSize);
+
+  /**
+   * If this object was initiaziled using InitForDrawing() then this function
+   * returns an HDC that can be drawn to generate the EMF output. Otherwise it
+   * returns null. After finishing with the HDC, consumers could call Playback()
+   * to draw EMF onto the given DC or call SaveToFile() to finish writing the
+   * EMF file.
+   */
+  HDC GetDC() const {
+    MOZ_ASSERT(mDC,
+               "GetDC can be used only after "
+               "InitForDrawing/ InitFromFileContents and before"
+               "Playback/ SaveToFile");
+    return mDC;
+  }
+
+  /**
+   * Play the EMF's drawing commands onto the given DC.
+   */
+  bool Playback(HDC aDeviceContext, const RECT& aRect);
+
+  /**
+   * Called to generate the EMF file once a consumer has finished drawing to
+   * the HDC returned by GetDC(), if initializes the object with the path of a
+   * file.
+   */
+  bool SaveToFile();
+
+  /**
+   * Return the size of the enhanced metafile, in bytes.
+   */
+  UINT GetEMFContentSize();
+
+  /**
+   * Retrieves the contents of the EMF and copies them into a buffer.
+   *
+   * @param aByte the buffer to receive the data.
+   */
+  bool GetEMFContentBits(PBYTE aBytes);
+
+ private:
+  WindowsEMF(const WindowsEMF& aEMF) = delete;
+  bool FinishDocument();
+  void ReleaseEMFHandle();
+  void ReleaseAllResource();
+
+  /* Compiled EMF data handle. */
+  HENHMETAFILE mEmf;
+  HDC mDC;
+};
+
+}  // namespace widget
+}  // namespace mozilla
+
+#endif /* MOZILLA_WIDGET_WINDOWSEMF_H */
diff --git a/widget/windows/WindowsEventLog.h b/widget/windows/WindowsEventLog.h
new file mode 100644
index 0000000000..e98d5077a0
--- /dev/null
+++ b/widget/windows/WindowsEventLog.h
@@ -0,0 +1,99 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:set ts=2 sw=2 sts=2 et cindent: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_WindowsEventLog_h
+#define mozilla_WindowsEventLog_h
+
+/**
+ * Report messages to the Windows Event Log.
+ */
+
+#include <stdio.h>
+#include <windows.h>
+
+#include "mozilla/Attributes.h"
+#include "mozilla/UniquePtr.h"
+
+/**
+ * This header is intended for self-contained, header-only, utility code for
+ * Win32. It may be used outside of xul.dll, in places such as
+ * default-browser-agent.exe or notificationrouter.dll. If your code creates
+ * dependencies on Mozilla libraries, you should put it elsewhere.
+ */
+
+#define MOZ_WIN_EVENT_LOG_ERROR(source, hr) \
+  mozilla::WriteWindowsEventLogHresult(source, hr, __FUNCTION__, __LINE__)
+#define MOZ_WIN_EVENT_LOG_ERROR_MESSAGE(source, format, ...)              \
+  mozilla::WriteWindowsEventLogErrorMessage(source, format, __FUNCTION__, \
+                                            __LINE__, ##__VA_ARGS__)
+
+namespace mozilla {
+
+static void WriteWindowsEventLogErrorBuffer(const wchar_t* eventSourceName,
+                                            const wchar_t* buffer,
+                                            DWORD eventId) {
+  HANDLE source = RegisterEventSourceW(nullptr, eventSourceName);
+  if (!source) {
+    // Not much we can do about this.
+    return;
+  }
+
+  const wchar_t* stringsArray[] = {buffer};
+  ReportEventW(source, EVENTLOG_ERROR_TYPE, 0, eventId, nullptr, 1, 0,
+               stringsArray, nullptr);
+
+  DeregisterEventSource(source);
+}
+
+inline void WriteWindowsEventLogHresult(const wchar_t* eventSourceName,
+                                        HRESULT hr, const char* sourceFile,
+                                        int sourceLine) {
+  const wchar_t* format = L"0x%X in %S:%d";
+  int bufferSize = _scwprintf(format, hr, sourceFile, sourceLine);
+  ++bufferSize;  // Extra character for terminating null
+  mozilla::UniquePtr<wchar_t[]> errorStr =
+      mozilla::MakeUnique<wchar_t[]>(bufferSize);
+
+  _snwprintf_s(errorStr.get(), bufferSize, _TRUNCATE, format, hr, sourceFile,
+               sourceLine);
+
+  WriteWindowsEventLogErrorBuffer(eventSourceName, errorStr.get(), hr);
+}
+
+MOZ_FORMAT_WPRINTF(1, 4)
+inline void WriteWindowsEventLogErrorMessage(const wchar_t* eventSourceName,
+                                             const wchar_t* messageFormat,
+                                             const char* sourceFile,
+                                             int sourceLine, ...) {
+  // First assemble the passed message
+  va_list ap;
+  va_start(ap, sourceLine);
+  int bufferSize = _vscwprintf(messageFormat, ap);
+  ++bufferSize;  // Extra character for terminating null
+  va_end(ap);
+  mozilla::UniquePtr<wchar_t[]> message =
+      mozilla::MakeUnique<wchar_t[]>(bufferSize);
+
+  va_start(ap, sourceLine);
+  vswprintf(message.get(), bufferSize, messageFormat, ap);
+  va_end(ap);
+
+  // Next, assemble the complete error message to print
+  const wchar_t* errorFormat = L"Error: %s (%S:%d)";
+  bufferSize = _scwprintf(errorFormat, message.get(), sourceFile, sourceLine);
+  ++bufferSize;  // Extra character for terminating null
+  mozilla::UniquePtr<wchar_t[]> errorStr =
+      mozilla::MakeUnique<wchar_t[]>(bufferSize);
+
+  _snwprintf_s(errorStr.get(), bufferSize, _TRUNCATE, errorFormat,
+               message.get(), sourceFile, sourceLine);
+
+  WriteWindowsEventLogErrorBuffer(eventSourceName, errorStr.get(), 0);
+}
+
+}  // namespace mozilla
+
+#endif  // mozilla_WindowsEventLog_h
diff --git a/widget/windows/WindowsSMTCProvider.cpp b/widget/windows/WindowsSMTCProvider.cpp
new file mode 100644
index 0000000000..04d833a8e7
--- /dev/null
+++ b/widget/windows/WindowsSMTCProvider.cpp
@@ -0,0 +1,716 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* mingw currently doesn't support windows.media.h, so we disable
+ * the whole related class until this is fixed.
+ * @TODO: Maybe contact MinGW Team for inclusion?*/
+#ifndef __MINGW32__
+
+#  include "WindowsSMTCProvider.h"
+
+#  include <windows.h>
+#  include <windows.media.h>
+#  include <wrl.h>
+
+#  include "nsMimeTypes.h"
+#  include "mozilla/Assertions.h"
+#  include "mozilla/Logging.h"
+#  include "mozilla/Maybe.h"
+#  include "mozilla/WidgetUtils.h"
+#  include "mozilla/ScopeExit.h"
+#  include "mozilla/dom/MediaControlUtils.h"
+#  include "mozilla/media/MediaUtils.h"
+#  include "nsThreadUtils.h"
+
+#  pragma comment(lib, "runtimeobject.lib")
+
+using namespace ABI::Windows::Foundation;
+using namespace ABI::Windows::Media;
+using namespace ABI::Windows::Storage::Streams;
+using namespace Microsoft::WRL;
+using namespace Microsoft::WRL::Wrappers;
+using namespace mozilla;
+
+#  ifndef RuntimeClass_Windows_Media_SystemMediaTransportControls
+#    define RuntimeClass_Windows_Media_SystemMediaTransportControls \
+      L"Windows.Media.SystemMediaTransportControls"
+#  endif
+
+#  ifndef RuntimeClass_Windows_Storage_Streams_RandomAccessStreamReference
+#    define RuntimeClass_Windows_Storage_Streams_RandomAccessStreamReference \
+      L"Windows.Storage.Streams.RandomAccessStreamReference"
+#  endif
+
+#  ifndef ISystemMediaTransportControlsInterop
+EXTERN_C const IID IID_ISystemMediaTransportControlsInterop;
+MIDL_INTERFACE("ddb0472d-c911-4a1f-86d9-dc3d71a95f5a")
+ISystemMediaTransportControlsInterop : public IInspectable {
+ public:
+  virtual HRESULT STDMETHODCALLTYPE GetForWindow(
+      /* [in] */ __RPC__in HWND appWindow,
+      /* [in] */ __RPC__in REFIID riid,
+      /* [iid_is][retval][out] */
+      __RPC__deref_out_opt void** mediaTransportControl) = 0;
+};
+#  endif /* __ISystemMediaTransportControlsInterop_INTERFACE_DEFINED__ */
+
+extern mozilla::LazyLogModule gMediaControlLog;
+
+#  undef LOG
+#  define LOG(msg, ...)                        \
+    MOZ_LOG(gMediaControlLog, LogLevel::Debug, \
+            ("WindowSMTCProvider=%p, " msg, this, ##__VA_ARGS__))
+
+static inline Maybe<mozilla::dom::MediaControlKey> TranslateKeycode(
+    SystemMediaTransportControlsButton keycode) {
+  switch (keycode) {
+    case SystemMediaTransportControlsButton_Play:
+      return Some(mozilla::dom::MediaControlKey::Play);
+    case SystemMediaTransportControlsButton_Pause:
+      return Some(mozilla::dom::MediaControlKey::Pause);
+    case SystemMediaTransportControlsButton_Next:
+      return Some(mozilla::dom::MediaControlKey::Nexttrack);
+    case SystemMediaTransportControlsButton_Previous:
+      return Some(mozilla::dom::MediaControlKey::Previoustrack);
+    case SystemMediaTransportControlsButton_Stop:
+      return Some(mozilla::dom::MediaControlKey::Stop);
+    case SystemMediaTransportControlsButton_FastForward:
+      return Some(mozilla::dom::MediaControlKey::Seekforward);
+    case SystemMediaTransportControlsButton_Rewind:
+      return Some(mozilla::dom::MediaControlKey::Seekbackward);
+    default:
+      return Nothing();  // Not supported Button
+  }
+}
+
+static IAsyncInfo* GetIAsyncInfo(IAsyncOperation<unsigned int>* aAsyncOp) {
+  MOZ_ASSERT(aAsyncOp);
+  IAsyncInfo* asyncInfo;
+  HRESULT hr = aAsyncOp->QueryInterface(IID_IAsyncInfo,
+                                        reinterpret_cast<void**>(&asyncInfo));
+  // The assertion always works since IAsyncOperation implements IAsyncInfo
+  MOZ_ASSERT(SUCCEEDED(hr));
+  Unused << hr;
+  MOZ_ASSERT(asyncInfo);
+  return asyncInfo;
+}
+
+WindowsSMTCProvider::WindowsSMTCProvider() {
+  LOG("Creating an empty and invisible window");
+
+  // In order to create a SMTC-Provider, we need a hWnd, which shall be created
+  // dynamically from an invisible window. This leads to the following
+  // boilerplate code.
+  WNDCLASS wnd{};
+  wnd.lpszClassName = L"Firefox-MediaKeys";
+  wnd.hInstance = nullptr;
+  wnd.lpfnWndProc = DefWindowProc;
+  GetLastError();  // Clear the error
+  RegisterClass(&wnd);
+  MOZ_ASSERT(!GetLastError());
+
+  mWindow = CreateWindowExW(0, L"Firefox-MediaKeys", L"Firefox Media Keys", 0,
+                            CW_USEDEFAULT, CW_USEDEFAULT, 0, 0, nullptr,
+                            nullptr, nullptr, nullptr);
+  MOZ_ASSERT(mWindow);
+  MOZ_ASSERT(!GetLastError());
+}
+
+WindowsSMTCProvider::~WindowsSMTCProvider() {
+  // Dispose the window
+  MOZ_ASSERT(mWindow);
+  if (!DestroyWindow(mWindow)) {
+    LOG("Failed to destroy the hidden window. Error Code: %lu", GetLastError());
+  }
+  if (!UnregisterClass(L"Firefox-MediaKeys", nullptr)) {
+    // Note that this is logged when the class wasn't even registered.
+    LOG("Failed to unregister the class. Error Code: %lu", GetLastError());
+  }
+}
+
+bool WindowsSMTCProvider::IsOpened() const { return mInitialized; }
+
+bool WindowsSMTCProvider::Open() {
+  LOG("Opening Source");
+  MOZ_ASSERT(!mInitialized);
+
+  if (!InitDisplayAndControls()) {
+    LOG("Failed to initialize the SMTC and its display");
+    return false;
+  }
+
+  if (!UpdateButtons()) {
+    LOG("Failed to initialize the buttons");
+    return false;
+  }
+
+  if (!RegisterEvents()) {
+    LOG("Failed to register SMTC key-event listener");
+    return false;
+  }
+
+  if (!EnableControl(true)) {
+    LOG("Failed to enable SMTC control");
+    return false;
+  }
+
+  mInitialized = true;
+  SetPlaybackState(mozilla::dom::MediaSessionPlaybackState::None);
+  return mInitialized;
+}
+
+void WindowsSMTCProvider::Close() {
+  MediaControlKeySource::Close();
+  // Prevent calling Set methods when init failed
+  if (mInitialized) {
+    SetPlaybackState(mozilla::dom::MediaSessionPlaybackState::None);
+    UnregisterEvents();
+    ClearMetadata();
+    // We have observed an Windows issue, if we modify `mControls` , (such as
+    // setting metadata, disable buttons) before disabling control, and those
+    // operations are not done sequentially within a same main thread task,
+    // then it would cause a problem where the SMTC wasn't clean up completely
+    // and show the executable name.
+    EnableControl(false);
+    mInitialized = false;
+  }
+}
+
+void WindowsSMTCProvider::SetPlaybackState(
+    mozilla::dom::MediaSessionPlaybackState aState) {
+  MOZ_ASSERT(mInitialized);
+  MediaControlKeySource::SetPlaybackState(aState);
+
+  HRESULT hr;
+
+  // Note: we can't return the status of put_PlaybackStatus, but we can at least
+  // assert it.
+  switch (aState) {
+    case mozilla::dom::MediaSessionPlaybackState::Paused:
+      hr = mControls->put_PlaybackStatus(
+          ABI::Windows::Media::MediaPlaybackStatus_Paused);
+      break;
+    case mozilla::dom::MediaSessionPlaybackState::Playing:
+      hr = mControls->put_PlaybackStatus(
+          ABI::Windows::Media::MediaPlaybackStatus_Playing);
+      break;
+    case mozilla::dom::MediaSessionPlaybackState::None:
+      hr = mControls->put_PlaybackStatus(
+          ABI::Windows::Media::MediaPlaybackStatus_Stopped);
+      break;
+      // MediaPlaybackStatus still supports Closed and Changing, which we don't
+      // use (yet)
+    default:
+      MOZ_ASSERT_UNREACHABLE(
+          "Enum Inconsitency between PlaybackState and WindowsSMTCProvider");
+      break;
+  }
+
+  MOZ_ASSERT(SUCCEEDED(hr));
+  Unused << hr;
+}
+
+void WindowsSMTCProvider::SetMediaMetadata(
+    const mozilla::dom::MediaMetadataBase& aMetadata) {
+  MOZ_ASSERT(mInitialized);
+  SetMusicMetadata(aMetadata.mArtist, aMetadata.mTitle);
+  LoadThumbnail(aMetadata.mArtwork);
+}
+
+void WindowsSMTCProvider::ClearMetadata() {
+  MOZ_ASSERT(mDisplay);
+  if (FAILED(mDisplay->ClearAll())) {
+    LOG("Failed to clear SMTC display");
+  }
+  mImageFetchRequest.DisconnectIfExists();
+  CancelPendingStoreAsyncOperation();
+  mThumbnailUrl.Truncate();
+  mProcessingUrl.Truncate();
+  mNextImageIndex = 0;
+  mSupportedKeys = 0;
+}
+
+void WindowsSMTCProvider::SetSupportedMediaKeys(
+    const MediaKeysArray& aSupportedKeys) {
+  MOZ_ASSERT(mInitialized);
+
+  uint32_t supportedKeys = 0;
+  for (const mozilla::dom::MediaControlKey& key : aSupportedKeys) {
+    supportedKeys |= GetMediaKeyMask(key);
+  }
+
+  if (supportedKeys == mSupportedKeys) {
+    LOG("Supported keys stay the same");
+    return;
+  }
+
+  LOG("Update supported keys");
+  mSupportedKeys = supportedKeys;
+  UpdateButtons();
+}
+
+void WindowsSMTCProvider::UnregisterEvents() {
+  if (mControls && mButtonPressedToken.value != 0) {
+    mControls->remove_ButtonPressed(mButtonPressedToken);
+  }
+}
+
+bool WindowsSMTCProvider::RegisterEvents() {
+  MOZ_ASSERT(mControls);
+  auto self = RefPtr<WindowsSMTCProvider>(this);
+  auto callbackbtnPressed = Callback<
+      ITypedEventHandler<SystemMediaTransportControls*,
+                         SystemMediaTransportControlsButtonPressedEventArgs*>>(
+      [this, self](ISystemMediaTransportControls*,
+                   ISystemMediaTransportControlsButtonPressedEventArgs* pArgs)
+          -> HRESULT {
+        MOZ_ASSERT(pArgs);
+        SystemMediaTransportControlsButton btn;
+
+        if (FAILED(pArgs->get_Button(&btn))) {
+          LOG("SystemMediaTransportControls: ButtonPressedEvent - Could "
+              "not get Button.");
+          return S_OK;  // Propagating the error probably wouldn't help.
+        }
+
+        Maybe<mozilla::dom::MediaControlKey> keyCode = TranslateKeycode(btn);
+        if (keyCode.isSome() && IsOpened()) {
+          OnButtonPressed(keyCode.value());
+        }
+        return S_OK;
+      });
+
+  if (FAILED(mControls->add_ButtonPressed(callbackbtnPressed.Get(),
+                                          &mButtonPressedToken))) {
+    LOG("SystemMediaTransportControls: Failed at "
+        "registerEvents().add_ButtonPressed()");
+    return false;
+  }
+
+  return true;
+}
+
+void WindowsSMTCProvider::OnButtonPressed(
+    mozilla::dom::MediaControlKey aKey) const {
+  if (!IsKeySupported(aKey)) {
+    LOG("key: %s is not supported", ToMediaControlKeyStr(aKey));
+    return;
+  }
+
+  for (auto& listener : mListeners) {
+    listener->OnActionPerformed(mozilla::dom::MediaControlAction(aKey));
+  }
+}
+
+bool WindowsSMTCProvider::EnableControl(bool aEnabled) const {
+  MOZ_ASSERT(mControls);
+  return SUCCEEDED(mControls->put_IsEnabled(aEnabled));
+}
+
+bool WindowsSMTCProvider::UpdateButtons() const {
+  static const mozilla::dom::MediaControlKey kKeys[] = {
+      mozilla::dom::MediaControlKey::Play, mozilla::dom::MediaControlKey::Pause,
+      mozilla::dom::MediaControlKey::Previoustrack,
+      mozilla::dom::MediaControlKey::Nexttrack,
+      mozilla::dom::MediaControlKey::Stop};
+
+  bool success = true;
+  for (const mozilla::dom::MediaControlKey& key : kKeys) {
+    if (!EnableKey(key, IsKeySupported(key))) {
+      success = false;
+      LOG("Failed to set %s=%s", ToMediaControlKeyStr(key),
+          IsKeySupported(key) ? "true" : "false");
+    }
+  }
+
+  return success;
+}
+
+bool WindowsSMTCProvider::IsKeySupported(
+    mozilla::dom::MediaControlKey aKey) const {
+  return mSupportedKeys & GetMediaKeyMask(aKey);
+}
+
+bool WindowsSMTCProvider::EnableKey(mozilla::dom::MediaControlKey aKey,
+                                    bool aEnable) const {
+  MOZ_ASSERT(mControls);
+  switch (aKey) {
+    case mozilla::dom::MediaControlKey::Play:
+      return SUCCEEDED(mControls->put_IsPlayEnabled(aEnable));
+    case mozilla::dom::MediaControlKey::Pause:
+      return SUCCEEDED(mControls->put_IsPauseEnabled(aEnable));
+    case mozilla::dom::MediaControlKey::Previoustrack:
+      return SUCCEEDED(mControls->put_IsPreviousEnabled(aEnable));
+    case mozilla::dom::MediaControlKey::Nexttrack:
+      return SUCCEEDED(mControls->put_IsNextEnabled(aEnable));
+    case mozilla::dom::MediaControlKey::Stop:
+      return SUCCEEDED(mControls->put_IsStopEnabled(aEnable));
+    default:
+      LOG("No button for %s", ToMediaControlKeyStr(aKey));
+      return false;
+  }
+}
+
+bool WindowsSMTCProvider::InitDisplayAndControls() {
+  // As Open() might be called multiple times, "cache" the results of the COM
+  // API
+  if (mControls && mDisplay) {
+    return true;
+  }
+  ComPtr<ISystemMediaTransportControlsInterop> interop;
+  HRESULT hr = GetActivationFactory(
+      HStringReference(RuntimeClass_Windows_Media_SystemMediaTransportControls)
+          .Get(),
+      interop.GetAddressOf());
+  if (FAILED(hr)) {
+    LOG("SystemMediaTransportControls: Failed at instantiating the "
+        "Interop object");
+    return false;
+  }
+  MOZ_ASSERT(interop);
+
+  if (!mControls && FAILED(interop->GetForWindow(
+                        mWindow, IID_PPV_ARGS(mControls.GetAddressOf())))) {
+    LOG("SystemMediaTransportControls: Failed at GetForWindow()");
+    return false;
+  }
+  MOZ_ASSERT(mControls);
+
+  if (!mDisplay &&
+      FAILED(mControls->get_DisplayUpdater(mDisplay.GetAddressOf()))) {
+    LOG("SystemMediaTransportControls: Failed at get_DisplayUpdater()");
+  }
+
+  MOZ_ASSERT(mDisplay);
+  return true;
+}
+
+bool WindowsSMTCProvider::SetMusicMetadata(const nsString& aArtist,
+                                           const nsString& aTitle) {
+  MOZ_ASSERT(mDisplay);
+  ComPtr<IMusicDisplayProperties> musicProps;
+
+  HRESULT hr = mDisplay->put_Type(MediaPlaybackType::MediaPlaybackType_Music);
+  MOZ_ASSERT(SUCCEEDED(hr));
+  Unused << hr;
+  hr = mDisplay->get_MusicProperties(musicProps.GetAddressOf());
+  if (FAILED(hr)) {
+    LOG("Failed to get music properties");
+    return false;
+  }
+
+  hr = musicProps->put_Artist(HStringReference(aArtist.get()).Get());
+  if (FAILED(hr)) {
+    LOG("Failed to set the music's artist");
+    return false;
+  }
+
+  hr = musicProps->put_Title(HStringReference(aTitle.get()).Get());
+  if (FAILED(hr)) {
+    LOG("Failed to set the music's title");
+    return false;
+  }
+
+  hr = mDisplay->Update();
+  if (FAILED(hr)) {
+    LOG("Failed to refresh the display");
+    return false;
+  }
+
+  return true;
+}
+
+void WindowsSMTCProvider::LoadThumbnail(
+    const nsTArray<mozilla::dom::MediaImage>& aArtwork) {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  // TODO: Sort the images by the preferred size or format.
+  mArtwork = aArtwork;
+  mNextImageIndex = 0;
+
+  // Abort the loading if
+  // 1) thumbnail is being updated, and one in processing is in the artwork
+  // 2) thumbnail is not being updated, and one in use is in the artwork
+  if (!mProcessingUrl.IsEmpty()) {
+    LOG("Load thumbnail while image: %s is being processed",
+        NS_ConvertUTF16toUTF8(mProcessingUrl).get());
+    if (mozilla::dom::IsImageIn(mArtwork, mProcessingUrl)) {
+      LOG("No need to load thumbnail. The one being processed is in the "
+          "artwork");
+      return;
+    }
+  } else if (!mThumbnailUrl.IsEmpty()) {
+    if (mozilla::dom::IsImageIn(mArtwork, mThumbnailUrl)) {
+      LOG("No need to load thumbnail. The one in use is in the artwork");
+      return;
+    }
+  }
+
+  // If there is a pending image store operation, that image must be different
+  // from the new image will be loaded below, so the pending one should be
+  // cancelled.
+  CancelPendingStoreAsyncOperation();
+  // Remove the current thumbnail on the interface
+  ClearThumbnail();
+  // Then load the new thumbnail asynchronously
+  LoadImageAtIndex(mNextImageIndex++);
+}
+
+void WindowsSMTCProvider::LoadImageAtIndex(const size_t aIndex) {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  if (aIndex >= mArtwork.Length()) {
+    LOG("Stop loading thumbnail. No more available images");
+    mImageFetchRequest.DisconnectIfExists();
+    mProcessingUrl.Truncate();
+    return;
+  }
+
+  const mozilla::dom::MediaImage& image = mArtwork[aIndex];
+
+  // TODO: No need to fetch the default image and do image processing since the
+  // the default image is local file and it's trustworthy. For the default
+  // image, we can use `CreateFromFile` to create the IRandomAccessStream. We
+  // should probably cache it since it could be used very often (Bug 1643102)
+
+  if (!mozilla::dom::IsValidImageUrl(image.mSrc)) {
+    LOG("Skip the image with invalid URL. Try next image");
+    mImageFetchRequest.DisconnectIfExists();
+    LoadImageAtIndex(mNextImageIndex++);
+    return;
+  }
+
+  mImageFetchRequest.DisconnectIfExists();
+  mProcessingUrl = image.mSrc;
+
+  mImageFetcher = mozilla::MakeUnique<mozilla::dom::FetchImageHelper>(image);
+  RefPtr<WindowsSMTCProvider> self = this;
+  mImageFetcher->FetchImage()
+      ->Then(
+          AbstractThread::MainThread(), __func__,
+          [this, self](const nsCOMPtr<imgIContainer>& aImage) {
+            LOG("The image is fetched successfully");
+            mImageFetchRequest.Complete();
+
+            // Although IMAGE_JPEG or IMAGE_BMP are valid types as well, but a
+            // png image with transparent background will be converted into a
+            // jpeg/bmp file with a colored background. IMAGE_PNG format seems
+            // to be the best choice for now.
+            uint32_t size = 0;
+            char* src = nullptr;
+            // Only used to hold the image data
+            nsCOMPtr<nsIInputStream> inputStream;
+            nsresult rv = mozilla::dom::GetEncodedImageBuffer(
+                aImage, nsLiteralCString(IMAGE_PNG),
+                getter_AddRefs(inputStream), &size, &src);
+            if (NS_FAILED(rv) || !inputStream || size == 0 || !src) {
+              LOG("Failed to get the image buffer info. Try next image");
+              LoadImageAtIndex(mNextImageIndex++);
+              return;
+            }
+
+            LoadImage(src, size);
+          },
+          [this, self](bool) {
+            LOG("Failed to fetch image. Try next image");
+            mImageFetchRequest.Complete();
+            LoadImageAtIndex(mNextImageIndex++);
+          })
+      ->Track(mImageFetchRequest);
+}
+
+void WindowsSMTCProvider::LoadImage(const char* aImageData,
+                                    uint32_t aDataSize) {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  // 1. Use mImageDataWriter to write the binary data of image into mImageStream
+  // 2. Refer the image by mImageStreamReference and then set it to the SMTC
+  // In case of the race condition between they are being destroyed and the
+  // async operation for image loading, mImageDataWriter, mImageStream, and
+  // mImageStreamReference are member variables
+
+  HRESULT hr = ActivateInstance(
+      HStringReference(
+          RuntimeClass_Windows_Storage_Streams_InMemoryRandomAccessStream)
+          .Get(),
+      mImageStream.GetAddressOf());
+  if (FAILED(hr)) {
+    LOG("Failed to make mImageStream refer to an instance of "
+        "InMemoryRandomAccessStream");
+    return;
+  }
+
+  ComPtr<IOutputStream> outputStream;
+  hr = mImageStream.As(&outputStream);
+  if (FAILED(hr)) {
+    LOG("Failed when query IOutputStream interface from mImageStream");
+    return;
+  }
+
+  ComPtr<IDataWriterFactory> dataWriterFactory;
+  hr = GetActivationFactory(
+      HStringReference(RuntimeClass_Windows_Storage_Streams_DataWriter).Get(),
+      dataWriterFactory.GetAddressOf());
+  if (FAILED(hr)) {
+    LOG("Failed to get an activation factory for IDataWriterFactory");
+    return;
+  }
+
+  hr = dataWriterFactory->CreateDataWriter(outputStream.Get(),
+                                           mImageDataWriter.GetAddressOf());
+  if (FAILED(hr)) {
+    LOG("Failed to create mImageDataWriter that writes data to mImageStream");
+    return;
+  }
+
+  hr = mImageDataWriter->WriteBytes(
+      aDataSize, reinterpret_cast<BYTE*>(const_cast<char*>(aImageData)));
+  if (FAILED(hr)) {
+    LOG("Failed to write data to mImageStream");
+    return;
+  }
+
+  hr = mImageDataWriter->StoreAsync(&mStoreAsyncOperation);
+  if (FAILED(hr)) {
+    LOG("Failed to create a DataWriterStoreOperation for mStoreAsyncOperation");
+    return;
+  }
+
+  // Upon the image is stored in mImageStream, set the image to the SMTC
+  // interface
+  auto onStoreCompleted = Callback<
+      IAsyncOperationCompletedHandler<unsigned int>>(
+      [this, self = RefPtr<WindowsSMTCProvider>(this),
+       aImageUrl = nsString(mProcessingUrl)](
+          IAsyncOperation<unsigned int>* aAsyncOp, AsyncStatus aStatus) {
+        MOZ_ASSERT(NS_IsMainThread());
+
+        if (aStatus != AsyncStatus::Completed) {
+          LOG("Asynchronous operation is not completed");
+          return E_ABORT;
+        }
+
+        HRESULT hr = S_OK;
+        IAsyncInfo* asyncInfo = GetIAsyncInfo(aAsyncOp);
+        asyncInfo->get_ErrorCode(&hr);
+        if (FAILED(hr)) {
+          LOG("Failed to get termination status of the asynchronous operation");
+          return hr;
+        }
+
+        if (!UpdateThumbnail(aImageUrl)) {
+          LOG("Failed to update thumbnail");
+        }
+
+        // If an error occurs above:
+        // - If aImageUrl is not mProcessingUrl. It's fine.
+        // - If aImageUrl is mProcessingUrl, then mProcessingUrl won't be reset.
+        //   Therefore the thumbnail will remain empty until a new image whose
+        //   url is different from mProcessingUrl is loaded.
+
+        return S_OK;
+      });
+
+  hr = mStoreAsyncOperation->put_Completed(onStoreCompleted.Get());
+  if (FAILED(hr)) {
+    LOG("Failed to set callback on completeing the asynchronous operation");
+  }
+}
+
+bool WindowsSMTCProvider::SetThumbnail(const nsAString& aUrl) {
+  MOZ_ASSERT(mDisplay);
+  MOZ_ASSERT(mImageStream);
+  MOZ_ASSERT(!aUrl.IsEmpty());
+
+  ComPtr<IRandomAccessStreamReferenceStatics> streamRefFactory;
+
+  HRESULT hr = GetActivationFactory(
+      HStringReference(
+          RuntimeClass_Windows_Storage_Streams_RandomAccessStreamReference)
+          .Get(),
+      streamRefFactory.GetAddressOf());
+  auto cleanup =
+      MakeScopeExit([this, self = RefPtr<WindowsSMTCProvider>(this)] {
+        LOG("Clean mThumbnailUrl");
+        mThumbnailUrl.Truncate();
+      });
+
+  if (FAILED(hr)) {
+    LOG("Failed to get an activation factory for "
+        "IRandomAccessStreamReferenceStatics type");
+    return false;
+  }
+
+  hr = streamRefFactory->CreateFromStream(mImageStream.Get(),
+                                          mImageStreamReference.GetAddressOf());
+  if (FAILED(hr)) {
+    LOG("Failed to create mImageStreamReference from mImageStream");
+    return false;
+  }
+
+  hr = mDisplay->put_Thumbnail(mImageStreamReference.Get());
+  if (FAILED(hr)) {
+    LOG("Failed to update thumbnail");
+    return false;
+  }
+
+  hr = mDisplay->Update();
+  if (FAILED(hr)) {
+    LOG("Failed to refresh display");
+    return false;
+  }
+
+  // No need to clean mThumbnailUrl since thumbnail is set successfully
+  cleanup.release();
+  mThumbnailUrl = aUrl;
+
+  return true;
+}
+
+void WindowsSMTCProvider::ClearThumbnail() {
+  MOZ_ASSERT(mDisplay);
+  HRESULT hr = mDisplay->put_Thumbnail(nullptr);
+  MOZ_ASSERT(SUCCEEDED(hr));
+  hr = mDisplay->Update();
+  MOZ_ASSERT(SUCCEEDED(hr));
+  Unused << hr;
+  mThumbnailUrl.Truncate();
+}
+
+bool WindowsSMTCProvider::UpdateThumbnail(const nsAString& aUrl) {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  if (!IsOpened()) {
+    LOG("Abort the thumbnail update: SMTC is closed");
+    return false;
+  }
+
+  if (aUrl != mProcessingUrl) {
+    LOG("Abort the thumbnail update: The image from %s is out of date",
+        NS_ConvertUTF16toUTF8(aUrl).get());
+    return false;
+  }
+
+  mProcessingUrl.Truncate();
+
+  if (!SetThumbnail(aUrl)) {
+    LOG("Failed to update thumbnail");
+    return false;
+  }
+
+  MOZ_ASSERT(mThumbnailUrl == aUrl);
+  LOG("The thumbnail is updated to the image from: %s",
+      NS_ConvertUTF16toUTF8(mThumbnailUrl).get());
+  return true;
+}
+
+void WindowsSMTCProvider::CancelPendingStoreAsyncOperation() const {
+  if (mStoreAsyncOperation) {
+    IAsyncInfo* asyncInfo = GetIAsyncInfo(mStoreAsyncOperation.Get());
+    asyncInfo->Cancel();
+  }
+}
+
+#endif  // __MINGW32__
diff --git a/widget/windows/WindowsSMTCProvider.h b/widget/windows/WindowsSMTCProvider.h
new file mode 100644
index 0000000000..3926618d1f
--- /dev/null
+++ b/widget/windows/WindowsSMTCProvider.h
@@ -0,0 +1,128 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef WIDGET_WINDOWS_WINDOWSSTMCPROVIDER_H_
+#define WIDGET_WINDOWS_WINDOWSSTMCPROVIDER_H_
+
+#ifndef __MINGW32__
+
+#  include <functional>
+#  include <Windows.Media.h>
+#  include <wrl.h>
+
+#  include "mozilla/dom/FetchImageHelper.h"
+#  include "mozilla/dom/MediaController.h"
+#  include "mozilla/dom/MediaControlKeySource.h"
+#  include "mozilla/UniquePtr.h"
+
+using ISMTC = ABI::Windows::Media::ISystemMediaTransportControls;
+using SMTCProperty = ABI::Windows::Media::SystemMediaTransportControlsProperty;
+using ISMTCDisplayUpdater =
+    ABI::Windows::Media::ISystemMediaTransportControlsDisplayUpdater;
+
+using ABI::Windows::Foundation::IAsyncOperation;
+using ABI::Windows::Storage::Streams::IDataWriter;
+using ABI::Windows::Storage::Streams::IRandomAccessStream;
+using ABI::Windows::Storage::Streams::IRandomAccessStreamReference;
+using Microsoft::WRL::ComPtr;
+
+class WindowsSMTCProvider final : public mozilla::dom::MediaControlKeySource {
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(WindowsSMTCProvider, override)
+
+ public:
+  WindowsSMTCProvider();
+
+  bool IsOpened() const override;
+  bool Open() override;
+  void Close() override;
+
+  void SetPlaybackState(
+      mozilla::dom::MediaSessionPlaybackState aState) override;
+
+  void SetMediaMetadata(
+      const mozilla::dom::MediaMetadataBase& aMetadata) override;
+
+  void SetSupportedMediaKeys(const MediaKeysArray& aSupportedKeys) override;
+
+ private:
+  ~WindowsSMTCProvider();
+  void UnregisterEvents();
+  bool RegisterEvents();
+
+  void OnButtonPressed(mozilla::dom::MediaControlKey aKey) const;
+  // Enable the SMTC interface
+  bool EnableControl(bool aEnabled) const;
+  // Sets the play, pause, next, previous buttons on the SMTC interface by
+  // mSupportedKeys
+  bool UpdateButtons() const;
+  bool IsKeySupported(mozilla::dom::MediaControlKey aKey) const;
+  bool EnableKey(mozilla::dom::MediaControlKey aKey, bool aEnable) const;
+
+  bool InitDisplayAndControls();
+
+  // Sets the Metadata for the currently playing media and sets the playback
+  // type to "MUSIC"
+  bool SetMusicMetadata(const nsString& aArtist, const nsString& aTitle);
+
+  // Sets one of the artwork to the SMTC interface asynchronously
+  void LoadThumbnail(const nsTArray<mozilla::dom::MediaImage>& aArtwork);
+  // Stores the image at index aIndex of the mArtwork to the Thumbnail
+  // asynchronously
+  void LoadImageAtIndex(const size_t aIndex);
+  // Stores the raw binary data of an image to mImageStream and set it to the
+  // Thumbnail asynchronously
+  void LoadImage(const char* aImageData, uint32_t aDataSize);
+  // Sets the Thumbnail to the image stored in mImageStream
+  bool SetThumbnail(const nsAString& aUrl);
+  void ClearThumbnail();
+
+  bool UpdateThumbnail(const nsAString& aUrl);
+  void CancelPendingStoreAsyncOperation() const;
+
+  void ClearMetadata();
+
+  bool mInitialized = false;
+
+  // A bit table indicating what keys are enabled
+  uint32_t mSupportedKeys = 0;
+
+  ComPtr<ISMTC> mControls;
+  ComPtr<ISMTCDisplayUpdater> mDisplay;
+
+  // Use mImageDataWriter to write the binary data of image into mImageStream
+  // and refer the image by mImageStreamReference and then set it to the SMTC
+  // interface
+  ComPtr<IDataWriter> mImageDataWriter;
+  ComPtr<IRandomAccessStream> mImageStream;
+  ComPtr<IRandomAccessStreamReference> mImageStreamReference;
+  ComPtr<IAsyncOperation<unsigned int>> mStoreAsyncOperation;
+
+  // mThumbnailUrl is the url of the current Thumbnail
+  // mProcessingUrl is the url that is being processed. The process starts from
+  // fetching an image from the url and then storing the fetched image to the
+  // mImageStream. If mProcessingUrl is not empty, it means there is an image is
+  // in processing
+  // mThumbnailUrl and mProcessingUrl won't be set at the same time and they can
+  // only be touched on main thread
+  nsString mThumbnailUrl;
+  nsString mProcessingUrl;
+
+  // mArtwork can only be used in main thread in case of data racing
+  CopyableTArray<mozilla::dom::MediaImage> mArtwork;
+  size_t mNextImageIndex;
+
+  mozilla::UniquePtr<mozilla::dom::FetchImageHelper> mImageFetcher;
+  mozilla::MozPromiseRequestHolder<mozilla::dom::ImagePromise>
+      mImageFetchRequest;
+
+  HWND mWindow;  // handle to the invisible window
+
+  // EventRegistrationTokens are used to have a handle on a callback (to remove
+  // it again)
+  EventRegistrationToken mButtonPressedToken;
+};
+
+#endif  // __MINGW32__
+#endif  // WIDGET_WINDOWS_WINDOWSSTMCPROVIDER_H_
diff --git a/widget/windows/WindowsUIUtils.cpp b/widget/windows/WindowsUIUtils.cpp
new file mode 100644
index 0000000000..3d5cff7e23
--- /dev/null
+++ b/widget/windows/WindowsUIUtils.cpp
@@ -0,0 +1,809 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <windows.h>
+#include <wrl.h>
+
+#include "nsServiceManagerUtils.h"
+
+#include "WindowsUIUtils.h"
+
+#include "nsIObserverService.h"
+#include "nsIAppShellService.h"
+#include "nsAppShellCID.h"
+#include "mozilla/ClearOnShutdown.h"
+#include "mozilla/ResultVariant.h"
+#include "mozilla/Services.h"
+#include "mozilla/StaticPrefs_widget.h"
+#include "mozilla/WidgetUtils.h"
+#include "mozilla/WindowsVersion.h"
+#include "mozilla/LookAndFeel.h"
+#include "mozilla/ScopeExit.h"
+#include "mozilla/media/MediaUtils.h"
+#include "nsString.h"
+#include "nsGlobalWindowOuter.h"
+#include "nsIWidget.h"
+#include "nsIWindowMediator.h"
+#include "nsPIDOMWindow.h"
+#include "nsWindowGfx.h"
+#include "Units.h"
+
+/* mingw currently doesn't support windows.ui.viewmanagement.h, so we disable it
+ * until it's fixed. */
+
+// See
+// https://github.com/tpn/winsdk-10/blob/master/Include/10.0.14393.0/winrt/windows.ui.viewmanagement.h
+// for the source of some of these definitions for older SDKs.
+#ifndef __MINGW32__
+
+#  include <inspectable.h>
+#  include <roapi.h>
+#  include <windows.ui.viewmanagement.h>
+
+#  pragma comment(lib, "runtimeobject.lib")
+
+using namespace ABI::Windows::UI;
+using namespace ABI::Windows::UI::ViewManagement;
+using namespace Microsoft::WRL;
+using namespace Microsoft::WRL::Wrappers;
+using namespace ABI::Windows::Foundation;
+using namespace ABI::Windows::ApplicationModel::DataTransfer;
+
+#  ifndef RuntimeClass_Windows_UI_ViewManagement_UIViewSettings
+#    define RuntimeClass_Windows_UI_ViewManagement_UIViewSettings \
+      L"Windows.UI.ViewManagement.UIViewSettings"
+#  endif
+
+#  ifndef IUIViewSettingsInterop
+
+using IUIViewSettingsInterop = interface IUIViewSettingsInterop;
+
+MIDL_INTERFACE("3694dbf9-8f68-44be-8ff5-195c98ede8a6")
+IUIViewSettingsInterop : public IInspectable {
+ public:
+  virtual HRESULT STDMETHODCALLTYPE GetForWindow(HWND hwnd, REFIID riid,
+                                                 void** ppv) = 0;
+};
+#  endif
+
+#  ifndef __IDataTransferManagerInterop_INTERFACE_DEFINED__
+#    define __IDataTransferManagerInterop_INTERFACE_DEFINED__
+
+using IDataTransferManagerInterop = interface IDataTransferManagerInterop;
+
+MIDL_INTERFACE("3A3DCD6C-3EAB-43DC-BCDE-45671CE800C8")
+IDataTransferManagerInterop : public IUnknown {
+ public:
+  virtual HRESULT STDMETHODCALLTYPE GetForWindow(
+      HWND appWindow, REFIID riid, void** dataTransferManager) = 0;
+  virtual HRESULT STDMETHODCALLTYPE ShowShareUIForWindow(HWND appWindow) = 0;
+};
+
+#  endif
+
+#  if !defined( \
+      ____x_ABI_CWindows_CApplicationModel_CDataTransfer_CIDataPackage4_INTERFACE_DEFINED__)
+#    define ____x_ABI_CWindows_CApplicationModel_CDataTransfer_CIDataPackage4_INTERFACE_DEFINED__
+
+MIDL_INTERFACE("13a24ec8-9382-536f-852a-3045e1b29a3b")
+IDataPackage4 : public IInspectable {
+ public:
+  virtual HRESULT STDMETHODCALLTYPE add_ShareCanceled(
+      __FITypedEventHandler_2_Windows__CApplicationModel__CDataTransfer__CDataPackage_IInspectable *
+          handler,
+      EventRegistrationToken * token) = 0;
+  virtual HRESULT STDMETHODCALLTYPE remove_ShareCanceled(
+      EventRegistrationToken token) = 0;
+};
+
+#  endif
+
+#  ifndef RuntimeClass_Windows_UI_ViewManagement_UISettings
+#    define RuntimeClass_Windows_UI_ViewManagement_UISettings \
+      L"Windows.UI.ViewManagement.UISettings"
+#  endif
+#  if WINDOWS_FOUNDATION_UNIVERSALAPICONTRACT_VERSION < 0x80000
+namespace ABI {
+namespace Windows {
+namespace UI {
+namespace ViewManagement {
+
+class UISettings;
+class UISettingsAutoHideScrollBarsChangedEventArgs;
+interface IUISettingsAutoHideScrollBarsChangedEventArgs;
+MIDL_INTERFACE("87afd4b2-9146-5f02-8f6b-06d454174c0f")
+IUISettingsAutoHideScrollBarsChangedEventArgs : public IInspectable{};
+
+}  // namespace ViewManagement
+}  // namespace UI
+}  // namespace Windows
+}  // namespace ABI
+
+namespace ABI {
+namespace Windows {
+namespace Foundation {
+
+template <>
+struct __declspec(uuid("808aef30-2660-51b0-9c11-f75dd42006b4"))
+    ITypedEventHandler<ABI::Windows::UI::ViewManagement::UISettings*,
+                       ABI::Windows::UI::ViewManagement::
+                           UISettingsAutoHideScrollBarsChangedEventArgs*>
+    : ITypedEventHandler_impl<
+          ABI::Windows::Foundation::Internal::AggregateType<
+              ABI::Windows::UI::ViewManagement::UISettings*,
+              ABI::Windows::UI::ViewManagement::IUISettings*>,
+          ABI::Windows::Foundation::Internal::AggregateType<
+              ABI::Windows::UI::ViewManagement::
+                  UISettingsAutoHideScrollBarsChangedEventArgs*,
+              ABI::Windows::UI::ViewManagement::
+                  IUISettingsAutoHideScrollBarsChangedEventArgs*>> {
+  static const wchar_t* z_get_rc_name_impl() {
+    return L"Windows.Foundation.TypedEventHandler`2<Windows.UI.ViewManagement."
+           L"UISettings, "
+           L"Windows.UI.ViewManagement."
+           L"UISettingsAutoHideScrollBarsChangedEventArgs>";
+  }
+};
+// Define a typedef for the parameterized interface specialization's mangled
+// name. This allows code which uses the mangled name for the parameterized
+// interface to access the correct parameterized interface specialization.
+typedef ITypedEventHandler<ABI::Windows::UI::ViewManagement::UISettings*,
+                           ABI::Windows::UI::ViewManagement::
+                               UISettingsAutoHideScrollBarsChangedEventArgs*>
+    __FITypedEventHandler_2_Windows__CUI__CViewManagement__CUISettings_Windows__CUI__CViewManagement__CUISettingsAutoHideScrollBarsChangedEventArgs_t;
+#    define __FITypedEventHandler_2_Windows__CUI__CViewManagement__CUISettings_Windows__CUI__CViewManagement__CUISettingsAutoHideScrollBarsChangedEventArgs \
+      ABI::Windows::Foundation::                                                                                                                            \
+          __FITypedEventHandler_2_Windows__CUI__CViewManagement__CUISettings_Windows__CUI__CViewManagement__CUISettingsAutoHideScrollBarsChangedEventArgs_t
+
+}  // namespace Foundation
+}  // namespace Windows
+}  // namespace ABI
+
+namespace ABI {
+namespace Windows {
+namespace UI {
+namespace ViewManagement {
+class UISettings;
+class UISettingsAutoHideScrollBarsChangedEventArgs;
+interface IUISettings5;
+MIDL_INTERFACE("5349d588-0cb5-5f05-bd34-706b3231f0bd")
+IUISettings5 : public IInspectable {
+ public:
+  virtual HRESULT STDMETHODCALLTYPE get_AutoHideScrollBars(boolean * value) = 0;
+  virtual HRESULT STDMETHODCALLTYPE add_AutoHideScrollBarsChanged(
+      __FITypedEventHandler_2_Windows__CUI__CViewManagement__CUISettings_Windows__CUI__CViewManagement__CUISettingsAutoHideScrollBarsChangedEventArgs *
+          handler,
+      EventRegistrationToken * token) = 0;
+  virtual HRESULT STDMETHODCALLTYPE remove_AutoHideScrollBarsChanged(
+      EventRegistrationToken token) = 0;
+};
+}  // namespace ViewManagement
+}  // namespace UI
+}  // namespace Windows
+}  // namespace ABI
+#  endif
+#endif
+
+using namespace mozilla;
+
+enum class TabletModeState : uint8_t { Unknown, Off, On };
+static TabletModeState sInTabletModeState;
+
+WindowsUIUtils::WindowsUIUtils() = default;
+WindowsUIUtils::~WindowsUIUtils() = default;
+
+NS_IMPL_ISUPPORTS(WindowsUIUtils, nsIWindowsUIUtils)
+
+NS_IMETHODIMP
+WindowsUIUtils::GetSystemSmallIconSize(int32_t* aSize) {
+  NS_ENSURE_ARG(aSize);
+
+  mozilla::LayoutDeviceIntSize size =
+      nsWindowGfx::GetIconMetrics(nsWindowGfx::kSmallIcon);
+  *aSize = std::max(size.width, size.height);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+WindowsUIUtils::GetSystemLargeIconSize(int32_t* aSize) {
+  NS_ENSURE_ARG(aSize);
+
+  mozilla::LayoutDeviceIntSize size =
+      nsWindowGfx::GetIconMetrics(nsWindowGfx::kRegularIcon);
+  *aSize = std::max(size.width, size.height);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+WindowsUIUtils::SetWindowIcon(mozIDOMWindowProxy* aWindow,
+                              imgIContainer* aSmallIcon,
+                              imgIContainer* aBigIcon) {
+  NS_ENSURE_ARG(aWindow);
+
+  nsCOMPtr<nsIWidget> widget =
+      nsGlobalWindowOuter::Cast(aWindow)->GetMainWidget();
+  nsWindow* window = static_cast<nsWindow*>(widget.get());
+
+  nsresult rv;
+
+  if (aSmallIcon) {
+    HICON hIcon = nullptr;
+    rv = nsWindowGfx::CreateIcon(
+        aSmallIcon, false, mozilla::LayoutDeviceIntPoint(),
+        nsWindowGfx::GetIconMetrics(nsWindowGfx::kSmallIcon), &hIcon);
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    window->SetSmallIcon(hIcon);
+  }
+
+  if (aBigIcon) {
+    HICON hIcon = nullptr;
+    rv = nsWindowGfx::CreateIcon(
+        aBigIcon, false, mozilla::LayoutDeviceIntPoint(),
+        nsWindowGfx::GetIconMetrics(nsWindowGfx::kRegularIcon), &hIcon);
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    window->SetBigIcon(hIcon);
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+WindowsUIUtils::SetWindowIconFromExe(mozIDOMWindowProxy* aWindow,
+                                     const nsAString& aExe, uint16_t aIndex) {
+  NS_ENSURE_ARG(aWindow);
+
+  nsCOMPtr<nsIWidget> widget =
+      nsGlobalWindowOuter::Cast(aWindow)->GetMainWidget();
+  nsWindow* window = static_cast<nsWindow*>(widget.get());
+
+  HICON icon = ::LoadIconW(::GetModuleHandleW(PromiseFlatString(aExe).get()),
+                           MAKEINTRESOURCEW(aIndex));
+  window->SetBigIcon(icon);
+  window->SetSmallIcon(icon);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+WindowsUIUtils::SetWindowIconNoData(mozIDOMWindowProxy* aWindow) {
+  NS_ENSURE_ARG(aWindow);
+
+  nsCOMPtr<nsIWidget> widget =
+      nsGlobalWindowOuter::Cast(aWindow)->GetMainWidget();
+  nsWindow* window = static_cast<nsWindow*>(widget.get());
+
+  window->SetSmallIconNoData();
+  window->SetBigIconNoData();
+
+  return NS_OK;
+}
+
+bool WindowsUIUtils::GetInTabletMode() {
+  MOZ_DIAGNOSTIC_ASSERT(NS_IsMainThread());
+  if (sInTabletModeState == TabletModeState::Unknown) {
+    UpdateInTabletMode();
+  }
+  return sInTabletModeState == TabletModeState::On;
+}
+
+NS_IMETHODIMP
+WindowsUIUtils::GetInTabletMode(bool* aResult) {
+  *aResult = GetInTabletMode();
+  return NS_OK;
+}
+
+static IInspectable* GetUISettings() {
+  MOZ_DIAGNOSTIC_ASSERT(NS_IsMainThread());
+#ifndef __MINGW32__
+  // We need to keep this alive for ~ever so that change callbacks work as
+  // expected, sigh.
+  static StaticRefPtr<IInspectable> sUiSettingsAsInspectable;
+
+  if (!sUiSettingsAsInspectable) {
+    ComPtr<IInspectable> uiSettingsAsInspectable;
+    ::RoActivateInstance(
+        HStringReference(RuntimeClass_Windows_UI_ViewManagement_UISettings)
+            .Get(),
+        &uiSettingsAsInspectable);
+    if (NS_WARN_IF(!uiSettingsAsInspectable)) {
+      return nullptr;
+    }
+
+    ComPtr<IUISettings5> uiSettings5;
+    if (SUCCEEDED(uiSettingsAsInspectable.As(&uiSettings5))) {
+      EventRegistrationToken unusedToken;
+      auto callback = Callback<ITypedEventHandler<
+          UISettings*, UISettingsAutoHideScrollBarsChangedEventArgs*>>(
+          [](auto...) {
+            // Scrollbar sizes change layout.
+            LookAndFeel::NotifyChangedAllWindows(
+                widget::ThemeChangeKind::StyleAndLayout);
+            return S_OK;
+          });
+      (void)NS_WARN_IF(FAILED(uiSettings5->add_AutoHideScrollBarsChanged(
+          callback.Get(), &unusedToken)));
+    }
+
+    ComPtr<IUISettings2> uiSettings2;
+    if (SUCCEEDED(uiSettingsAsInspectable.As(&uiSettings2))) {
+      EventRegistrationToken unusedToken;
+      auto callback =
+          Callback<ITypedEventHandler<UISettings*, IInspectable*>>([](auto...) {
+            // Text scale factor changes style and layout.
+            LookAndFeel::NotifyChangedAllWindows(
+                widget::ThemeChangeKind::StyleAndLayout);
+            return S_OK;
+          });
+      (void)NS_WARN_IF(FAILED(uiSettings2->add_TextScaleFactorChanged(
+          callback.Get(), &unusedToken)));
+    }
+
+    ComPtr<IUISettings3> uiSettings3;
+    if (SUCCEEDED(uiSettingsAsInspectable.As(&uiSettings3))) {
+      EventRegistrationToken unusedToken;
+      auto callback =
+          Callback<ITypedEventHandler<UISettings*, IInspectable*>>([](auto...) {
+            // System color changes change style only.
+            LookAndFeel::NotifyChangedAllWindows(
+                widget::ThemeChangeKind::Style);
+            return S_OK;
+          });
+      (void)NS_WARN_IF(FAILED(
+          uiSettings3->add_ColorValuesChanged(callback.Get(), &unusedToken)));
+    }
+
+    ComPtr<IUISettings4> uiSettings4;
+    if (SUCCEEDED(uiSettingsAsInspectable.As(&uiSettings4))) {
+      EventRegistrationToken unusedToken;
+      auto callback =
+          Callback<ITypedEventHandler<UISettings*, IInspectable*>>([](auto...) {
+            // Transparent effects changes change media queries only.
+            LookAndFeel::NotifyChangedAllWindows(
+                widget::ThemeChangeKind::MediaQueriesOnly);
+            return S_OK;
+          });
+      (void)NS_WARN_IF(FAILED(uiSettings4->add_AdvancedEffectsEnabledChanged(
+          callback.Get(), &unusedToken)));
+    }
+
+    sUiSettingsAsInspectable = dont_AddRef(uiSettingsAsInspectable.Detach());
+    ClearOnShutdown(&sUiSettingsAsInspectable);
+  }
+
+  return sUiSettingsAsInspectable.get();
+#else
+  return nullptr;
+#endif
+}
+
+Maybe<nscolor> WindowsUIUtils::GetAccentColor(int aTone) {
+  MOZ_ASSERT(aTone >= -3);
+  MOZ_ASSERT(aTone <= 3);
+#ifndef __MINGW32__
+  ComPtr<IInspectable> settings = GetUISettings();
+  if (NS_WARN_IF(!settings)) {
+    return Nothing();
+  }
+  ComPtr<IUISettings3> uiSettings3;
+  if (NS_WARN_IF(FAILED(settings.As(&uiSettings3)))) {
+    return Nothing();
+  }
+  Color color;
+  auto colorType = UIColorType(int(UIColorType_Accent) + aTone);
+  if (NS_WARN_IF(FAILED(uiSettings3->GetColorValue(colorType, &color)))) {
+    return Nothing();
+  }
+  return Some(NS_RGBA(color.R, color.G, color.B, color.A));
+#else
+  return Nothing();
+#endif
+}
+
+Maybe<nscolor> WindowsUIUtils::GetSystemColor(ColorScheme aScheme,
+                                              int aSysColor) {
+#ifndef __MINGW32__
+  if (!StaticPrefs::widget_windows_uwp_system_colors_enabled()) {
+    return Nothing();
+  }
+
+  // https://docs.microsoft.com/en-us/windows/apps/design/style/color
+  // Is a useful resource to see which values have decent contrast.
+  if (StaticPrefs::widget_windows_uwp_system_colors_highlight_accent()) {
+    if (aSysColor == COLOR_HIGHLIGHT) {
+      int tone = aScheme == ColorScheme::Light ? 0 : -1;
+      if (auto c = GetAccentColor(tone)) {
+        return c;
+      }
+    }
+    if (aSysColor == COLOR_HIGHLIGHTTEXT && GetAccentColor()) {
+      return Some(NS_RGBA(255, 255, 255, 255));
+    }
+  }
+
+  if (aScheme == ColorScheme::Dark) {
+    // There are no explicitly dark colors in UWP, other than the highlight
+    // colors above.
+    return Nothing();
+  }
+
+  auto knownType = [&]() -> Maybe<UIElementType> {
+#  define MAP(_win32, _uwp) \
+    case COLOR_##_win32:    \
+      return Some(UIElementType_##_uwp)
+    switch (aSysColor) {
+      MAP(HIGHLIGHT, Highlight);
+      MAP(HIGHLIGHTTEXT, HighlightText);
+      MAP(ACTIVECAPTION, ActiveCaption);
+      MAP(BTNFACE, ButtonFace);
+      MAP(BTNTEXT, ButtonText);
+      MAP(CAPTIONTEXT, CaptionText);
+      MAP(GRAYTEXT, GrayText);
+      MAP(HOTLIGHT, Hotlight);
+      MAP(INACTIVECAPTION, InactiveCaption);
+      MAP(INACTIVECAPTIONTEXT, InactiveCaptionText);
+      MAP(WINDOW, Window);
+      MAP(WINDOWTEXT, WindowText);
+      default:
+        return Nothing();
+    }
+#  undef MAP
+  }();
+  if (!knownType) {
+    return Nothing();
+  }
+  ComPtr<IInspectable> settings = GetUISettings();
+  if (NS_WARN_IF(!settings)) {
+    return Nothing();
+  }
+  ComPtr<IUISettings> uiSettings;
+  if (NS_WARN_IF(FAILED(settings.As(&uiSettings)))) {
+    return Nothing();
+  }
+  Color color;
+  if (NS_WARN_IF(FAILED(uiSettings->UIElementColor(*knownType, &color)))) {
+    return Nothing();
+  }
+  return Some(NS_RGBA(color.R, color.G, color.B, color.A));
+#else
+  return Nothing();
+#endif
+}
+bool WindowsUIUtils::ComputeOverlayScrollbars() {
+#ifndef __MINGW32__
+  if (!IsWin11OrLater()) {
+    // While in theory Windows 10 supports overlay scrollbar settings, it's off
+    // by default and it's untested whether our Win10 scrollbar drawing code
+    // deals with it properly.
+    return false;
+  }
+  if (!StaticPrefs::widget_windows_overlay_scrollbars_enabled()) {
+    return false;
+  }
+  ComPtr<IInspectable> settings = GetUISettings();
+  if (NS_WARN_IF(!settings)) {
+    return false;
+  }
+  ComPtr<IUISettings5> uiSettings5;
+  if (NS_WARN_IF(FAILED(settings.As(&uiSettings5)))) {
+    return false;
+  }
+  boolean autoHide = false;
+  if (NS_WARN_IF(FAILED(uiSettings5->get_AutoHideScrollBars(&autoHide)))) {
+    return false;
+  }
+  return autoHide;
+#else
+  return false;
+#endif
+}
+
+double WindowsUIUtils::ComputeTextScaleFactor() {
+#ifndef __MINGW32__
+  ComPtr<IInspectable> settings = GetUISettings();
+  if (NS_WARN_IF(!settings)) {
+    return 1.0;
+  }
+  ComPtr<IUISettings2> uiSettings2;
+  if (NS_WARN_IF(FAILED(settings.As(&uiSettings2)))) {
+    return false;
+  }
+  double scaleFactor = 1.0;
+  if (NS_WARN_IF(FAILED(uiSettings2->get_TextScaleFactor(&scaleFactor)))) {
+    return 1.0;
+  }
+  return scaleFactor;
+#else
+  return 1.0;
+#endif
+}
+
+bool WindowsUIUtils::ComputeTransparencyEffects() {
+  constexpr bool kDefault = true;
+#ifndef __MINGW32__
+  ComPtr<IInspectable> settings = GetUISettings();
+  if (NS_WARN_IF(!settings)) {
+    return kDefault;
+  }
+  ComPtr<IUISettings4> uiSettings4;
+  if (NS_WARN_IF(FAILED(settings.As(&uiSettings4)))) {
+    return kDefault;
+  }
+  boolean transparencyEffects = kDefault;
+  if (NS_WARN_IF(FAILED(
+          uiSettings4->get_AdvancedEffectsEnabled(&transparencyEffects)))) {
+    return kDefault;
+  }
+  return transparencyEffects;
+#else
+  return kDefault;
+#endif
+}
+
+void WindowsUIUtils::UpdateInTabletMode() {
+#ifndef __MINGW32__
+  nsresult rv;
+  nsCOMPtr<nsIWindowMediator> winMediator(
+      do_GetService(NS_WINDOWMEDIATOR_CONTRACTID, &rv));
+  if (NS_FAILED(rv)) {
+    return;
+  }
+
+  nsCOMPtr<nsIWidget> widget;
+  nsCOMPtr<mozIDOMWindowProxy> navWin;
+
+  rv = winMediator->GetMostRecentWindow(u"navigator:browser",
+                                        getter_AddRefs(navWin));
+  if (NS_FAILED(rv) || !navWin) {
+    // Fall back to the hidden window
+    nsCOMPtr<nsIAppShellService> appShell(
+        do_GetService(NS_APPSHELLSERVICE_CONTRACTID));
+
+    rv = appShell->GetHiddenDOMWindow(getter_AddRefs(navWin));
+    if (NS_FAILED(rv) || !navWin) {
+      return;
+    }
+  }
+
+  nsPIDOMWindowOuter* win = nsPIDOMWindowOuter::From(navWin);
+  widget = widget::WidgetUtils::DOMWindowToWidget(win);
+
+  if (!widget) {
+    return;
+  }
+
+  HWND winPtr = (HWND)widget->GetNativeData(NS_NATIVE_WINDOW);
+  ComPtr<IUIViewSettingsInterop> uiViewSettingsInterop;
+
+  HRESULT hr = GetActivationFactory(
+      HStringReference(RuntimeClass_Windows_UI_ViewManagement_UIViewSettings)
+          .Get(),
+      &uiViewSettingsInterop);
+  if (FAILED(hr)) {
+    return;
+  }
+  ComPtr<IUIViewSettings> uiViewSettings;
+  hr = uiViewSettingsInterop->GetForWindow(winPtr,
+                                           IID_PPV_ARGS(&uiViewSettings));
+  if (FAILED(hr)) {
+    return;
+  }
+  UserInteractionMode mode;
+  hr = uiViewSettings->get_UserInteractionMode(&mode);
+  if (FAILED(hr)) {
+    return;
+  }
+
+  TabletModeState oldTabletModeState = sInTabletModeState;
+  sInTabletModeState = mode == UserInteractionMode_Touch ? TabletModeState::On
+                                                         : TabletModeState::Off;
+  if (sInTabletModeState != oldTabletModeState) {
+    nsCOMPtr<nsIObserverService> observerService =
+        mozilla::services::GetObserverService();
+    observerService->NotifyObservers(nullptr, "tablet-mode-change",
+                                     sInTabletModeState == TabletModeState::On
+                                         ? u"tablet-mode"
+                                         : u"normal-mode");
+  }
+#endif
+}
+
+#ifndef __MINGW32__
+struct HStringDeleter {
+  using pointer = HSTRING;
+  void operator()(pointer aString) { WindowsDeleteString(aString); }
+};
+
+using HStringUniquePtr = UniquePtr<HSTRING, HStringDeleter>;
+
+Result<HStringUniquePtr, HRESULT> ConvertToWindowsString(
+    const nsAString& aStr) {
+  HSTRING rawStr;
+  HRESULT hr = WindowsCreateString(PromiseFlatString(aStr).get(), aStr.Length(),
+                                   &rawStr);
+  if (FAILED(hr)) {
+    return Err(hr);
+  }
+  return HStringUniquePtr(rawStr);
+}
+
+static Result<Ok, nsresult> RequestShare(
+    const std::function<HRESULT(IDataRequestedEventArgs* pArgs)>& aCallback) {
+  HWND hwnd = GetForegroundWindow();
+  if (!hwnd) {
+    return Err(NS_ERROR_FAILURE);
+  }
+
+  ComPtr<IDataTransferManagerInterop> dtmInterop;
+  ComPtr<IDataTransferManager> dtm;
+
+  HRESULT hr = RoGetActivationFactory(
+      HStringReference(
+          RuntimeClass_Windows_ApplicationModel_DataTransfer_DataTransferManager)
+          .Get(),
+      IID_PPV_ARGS(&dtmInterop));
+  if (FAILED(hr) ||
+      FAILED(dtmInterop->GetForWindow(hwnd, IID_PPV_ARGS(&dtm)))) {
+    return Err(NS_ERROR_FAILURE);
+  }
+
+  auto callback = Callback<
+      ITypedEventHandler<DataTransferManager*, DataRequestedEventArgs*>>(
+      [aCallback](IDataTransferManager*,
+                  IDataRequestedEventArgs* pArgs) -> HRESULT {
+        return aCallback(pArgs);
+      });
+
+  EventRegistrationToken dataRequestedToken;
+  if (FAILED(dtm->add_DataRequested(callback.Get(), &dataRequestedToken)) ||
+      FAILED(dtmInterop->ShowShareUIForWindow(hwnd))) {
+    return Err(NS_ERROR_FAILURE);
+  }
+
+  return Ok();
+}
+
+static Result<Ok, nsresult> AddShareEventListeners(
+    const RefPtr<mozilla::media::Refcountable<MozPromiseHolder<SharePromise>>>&
+        aPromiseHolder,
+    const ComPtr<IDataPackage>& aDataPackage) {
+  ComPtr<IDataPackage3> spDataPackage3;
+
+  if (FAILED(aDataPackage.As(&spDataPackage3))) {
+    return Err(NS_ERROR_FAILURE);
+  }
+
+  auto completedCallback =
+      Callback<ITypedEventHandler<DataPackage*, ShareCompletedEventArgs*>>(
+          [aPromiseHolder](IDataPackage*,
+                           IShareCompletedEventArgs*) -> HRESULT {
+            aPromiseHolder->Resolve(true, __func__);
+            return S_OK;
+          });
+
+  EventRegistrationToken dataRequestedToken;
+  if (FAILED(spDataPackage3->add_ShareCompleted(completedCallback.Get(),
+                                                &dataRequestedToken))) {
+    return Err(NS_ERROR_FAILURE);
+  }
+
+  ComPtr<IDataPackage4> spDataPackage4;
+  if (SUCCEEDED(aDataPackage.As(&spDataPackage4))) {
+    // Use SharedCanceled API only on supported versions of Windows
+    // So that the older ones can still use ShareUrl()
+
+    auto canceledCallback =
+        Callback<ITypedEventHandler<DataPackage*, IInspectable*>>(
+            [aPromiseHolder](IDataPackage*, IInspectable*) -> HRESULT {
+              aPromiseHolder->Reject(NS_ERROR_FAILURE, __func__);
+              return S_OK;
+            });
+
+    if (FAILED(spDataPackage4->add_ShareCanceled(canceledCallback.Get(),
+                                                 &dataRequestedToken))) {
+      return Err(NS_ERROR_FAILURE);
+    }
+  }
+
+  return Ok();
+}
+#endif
+
+RefPtr<SharePromise> WindowsUIUtils::Share(nsAutoString aTitle,
+                                           nsAutoString aText,
+                                           nsAutoString aUrl) {
+  auto promiseHolder = MakeRefPtr<
+      mozilla::media::Refcountable<MozPromiseHolder<SharePromise>>>();
+  RefPtr<SharePromise> promise = promiseHolder->Ensure(__func__);
+
+#ifndef __MINGW32__
+  auto result = RequestShare([promiseHolder, title = std::move(aTitle),
+                              text = std::move(aText), url = std::move(aUrl)](
+                                 IDataRequestedEventArgs* pArgs) {
+    ComPtr<IDataRequest> spDataRequest;
+    ComPtr<IDataPackage> spDataPackage;
+    ComPtr<IDataPackage2> spDataPackage2;
+    ComPtr<IDataPackagePropertySet> spDataPackageProperties;
+
+    if (FAILED(pArgs->get_Request(&spDataRequest)) ||
+        FAILED(spDataRequest->get_Data(&spDataPackage)) ||
+        FAILED(spDataPackage.As(&spDataPackage2)) ||
+        FAILED(spDataPackage->get_Properties(&spDataPackageProperties))) {
+      promiseHolder->Reject(NS_ERROR_FAILURE, __func__);
+      return E_FAIL;
+    }
+
+    /*
+     * Windows always requires a title, and an empty string does not work.
+     * Thus we trick the API by passing a whitespace when we have no title.
+     * https://docs.microsoft.com/en-us/windows/uwp/app-to-app/share-data
+     */
+    auto wTitle = ConvertToWindowsString((title.IsVoid() || title.Length() == 0)
+                                             ? nsAutoString(u" "_ns)
+                                             : title);
+    if (wTitle.isErr() ||
+        FAILED(spDataPackageProperties->put_Title(wTitle.unwrap().get()))) {
+      promiseHolder->Reject(NS_ERROR_FAILURE, __func__);
+      return E_FAIL;
+    }
+
+    // Assign even if empty, as Windows requires some data to share
+    auto wText = ConvertToWindowsString(text);
+    if (wText.isErr() || FAILED(spDataPackage->SetText(wText.unwrap().get()))) {
+      promiseHolder->Reject(NS_ERROR_FAILURE, __func__);
+      return E_FAIL;
+    }
+
+    if (!url.IsVoid()) {
+      auto wUrl = ConvertToWindowsString(url);
+      if (wUrl.isErr()) {
+        promiseHolder->Reject(NS_ERROR_FAILURE, __func__);
+        return wUrl.unwrapErr();
+      }
+
+      ComPtr<IUriRuntimeClassFactory> uriFactory;
+      ComPtr<IUriRuntimeClass> uri;
+
+      auto hr = GetActivationFactory(
+          HStringReference(RuntimeClass_Windows_Foundation_Uri).Get(),
+          &uriFactory);
+
+      if (FAILED(hr) ||
+          FAILED(uriFactory->CreateUri(wUrl.unwrap().get(), &uri)) ||
+          FAILED(spDataPackage2->SetWebLink(uri.Get()))) {
+        promiseHolder->Reject(NS_ERROR_FAILURE, __func__);
+        return E_FAIL;
+      }
+    }
+
+    if (!StaticPrefs::widget_windows_share_wait_action_enabled()) {
+      promiseHolder->Resolve(true, __func__);
+    } else if (AddShareEventListeners(promiseHolder, spDataPackage).isErr()) {
+      promiseHolder->Reject(NS_ERROR_FAILURE, __func__);
+      return E_FAIL;
+    }
+
+    return S_OK;
+  });
+  if (result.isErr()) {
+    promiseHolder->Reject(result.unwrapErr(), __func__);
+  }
+#else
+  promiseHolder->Reject(NS_ERROR_FAILURE, __func__);
+#endif
+
+  return promise;
+}
+
+NS_IMETHODIMP
+WindowsUIUtils::ShareUrl(const nsAString& aUrlToShare,
+                         const nsAString& aShareTitle) {
+  nsAutoString text;
+  text.SetIsVoid(true);
+  WindowsUIUtils::Share(nsAutoString(aShareTitle), text,
+                        nsAutoString(aUrlToShare));
+  return NS_OK;
+}
diff --git a/widget/windows/WindowsUIUtils.h b/widget/windows/WindowsUIUtils.h
new file mode 100644
index 0000000000..a55f92c8da
--- /dev/null
+++ b/widget/windows/WindowsUIUtils.h
@@ -0,0 +1,50 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_widget_WindowsUIUtils_h__
+#define mozilla_widget_WindowsUIUtils_h__
+
+#include "nsIWindowsUIUtils.h"
+#include "nsString.h"
+#include "nsColor.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/MozPromise.h"
+
+using SharePromise =
+    mozilla::MozPromise<bool, nsresult, /* IsExclusive */ true>;
+
+namespace mozilla {
+enum class ColorScheme : uint8_t;
+}
+
+class WindowsUIUtils final : public nsIWindowsUIUtils {
+ public:
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIWINDOWSUIUTILS
+
+  WindowsUIUtils();
+
+  static RefPtr<SharePromise> Share(nsAutoString aTitle, nsAutoString aText,
+                                    nsAutoString aUrl);
+
+  static void UpdateInTabletMode();
+  static bool GetInTabletMode();
+
+  // Gets the system accent color, or one of the darker / lighter variants
+  // (darker = -1/2/3, lighter=+1/2/3, values outside of that range are
+  // disallowed).
+  static mozilla::Maybe<nscolor> GetAccentColor(int aTone = 0);
+  static mozilla::Maybe<nscolor> GetSystemColor(mozilla::ColorScheme, int);
+
+  // Use LookAndFeel for a cached getter.
+  static bool ComputeOverlayScrollbars();
+  static double ComputeTextScaleFactor();
+  static bool ComputeTransparencyEffects();
+
+ protected:
+  ~WindowsUIUtils();
+};
+
+#endif  // mozilla_widget_WindowsUIUtils_h__
diff --git a/widget/windows/components.conf b/widget/windows/components.conf
new file mode 100644
index 0000000000..e5089ed9e1
--- /dev/null
+++ b/widget/windows/components.conf
@@ -0,0 +1,220 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+Headers = [
+    '/widget/windows/nsWidgetFactory.h',
+]
+
+InitFunc = 'nsWidgetWindowsModuleCtor'
+UnloadFunc = 'nsWidgetWindowsModuleDtor'
+
+Classes = [
+    {
+        'cid': '{4c9dee4a-b083-4261-8bbe-c6883d2a6bc9}',
+        'contract_ids': ['@mozilla.org/gfx/parent/screenmanager;1'],
+        'singleton': True,
+        'type': 'mozilla::widget::ScreenManager',
+        'constructor': 'mozilla::widget::ScreenManager::GetAddRefedSingleton',
+        'headers': ['/widget/ScreenManager.h'],
+        'processes': ProcessSelector.ALLOW_IN_GPU_AND_MAIN_PROCESS,
+    },
+    {
+        'cid': '{2d96b3df-c051-11d1-a827-0040959a28c9}',
+        'contract_ids': ['@mozilla.org/widget/appshell/win;1'],
+        'headers': ['/widget/windows/nsWidgetFactory.h'],
+        'legacy_constructor': 'nsAppShellConstructor',
+        'processes': ProcessSelector.ALLOW_IN_GPU_RDD_VR_SOCKET_UTILITY_AND_GMPLUGIN_PROCESS,
+    },
+    {
+        'cid': '{6987230e-0098-4e78-bc5f-1493ee7519fa}',
+        'contract_ids': ['@mozilla.org/widget/useridleservice;1'],
+        'singleton': True,
+        'type': 'nsUserIdleServiceWin',
+        'constructor': 'nsUserIdleServiceWin::GetInstance',
+        'headers': ['/widget/windows/nsUserIdleServiceWin.h', 'nsUserIdleService.h'],
+    },
+    {
+        'cid': '{b148eed2-236d-11d3-b35c-00a0cc3c1cde}',
+        'contract_ids': ['@mozilla.org/sound;1'],
+        'singleton': True,
+        'type': 'nsISound',
+        'constructor': 'nsSound::GetInstance',
+        'headers': ['/widget/windows/nsSound.h'],
+        'processes': ProcessSelector.MAIN_PROCESS_ONLY,
+    },
+    {
+        'cid': '{77221d5a-1dd2-11b2-8c69-c710f15d2ed5}',
+        'contract_ids': ['@mozilla.org/widget/clipboardhelper;1'],
+        'type': 'nsClipboardHelper',
+        'headers': ['/widget/nsClipboardHelper.h'],
+    },
+    {
+        'cid': '{b8e5bc54-a22f-4eb2-b061-24cb6d19c15f}',
+        'contract_ids': ['@mozilla.org/windows-taskbar;1'],
+        'type': 'mozilla::widget::WinTaskbar',
+        'headers': ['/widget/windows/WinTaskbar.h'],
+    },
+    {
+        'cid': '{73a5946f-608d-454f-9d33-0b8f8c7294b6}',
+        'contract_ids': ['@mozilla.org/windows-legacyjumplistbuilder;1'],
+        'type': 'mozilla::widget::LegacyJumpListBuilder',
+        'headers': ['/widget/windows/LegacyJumpListBuilder.h'],
+    },
+    {
+        'cid': '{2b9a1f2c-27ce-45b6-8d4e-755d0e34f8db}',
+        'contract_ids': ['@mozilla.org/windows-legacyjumplistitem;1'],
+        'type': 'mozilla::widget::LegacyJumpListItem',
+        'headers': ['/widget/windows/LegacyJumpListItem.h'],
+    },
+    {
+        'cid': '{21f1f13b-f75a-42ad-867a-d91ad694447e}',
+        'contract_ids': ['@mozilla.org/windows-legacyjumplistseparator;1'],
+        'type': 'mozilla::widget::LegacyJumpListSeparator',
+        'headers': ['/widget/windows/LegacyJumpListItem.h'],
+    },
+    {
+        'cid': '{f72c5dc4-5a12-47be-be28-ab105f33b08f}',
+        'contract_ids': ['@mozilla.org/windows-legacyjumplistlink;1'],
+        'type': 'mozilla::widget::LegacyJumpListLink',
+        'headers': ['/widget/windows/LegacyJumpListItem.h'],
+    },
+    {
+        'cid': '{b16656b2-5187-498f-abf4-56346126bfdb}',
+        'contract_ids': ['@mozilla.org/windows-legacyjumplistshortcut;1'],
+        'type': 'mozilla::widget::LegacyJumpListShortcut',
+        'headers': ['/widget/windows/LegacyJumpListItem.h'],
+    },
+    {
+        'cid': '{e04a55e8-fee3-4ea2-a98b-41d2621adc3c}',
+        'contract_ids': ['@mozilla.org/windows-ui-utils;1'],
+        'type': 'WindowsUIUtils',
+        'headers': ['/widget/windows/WindowsUIUtils.h'],
+    },
+    {
+        'cid': '{8b5314bc-db01-11d2-96ce-0060b0fb9956}',
+        'contract_ids': ['@mozilla.org/widget/transferable;1'],
+        'type': 'nsTransferable',
+        'headers': ['/widget/nsTransferable.h'],
+    },
+    {
+        'cid': '{948a0023-e3a7-11d2-96cf-0060b0fb9956}',
+        'contract_ids': ['@mozilla.org/widget/htmlformatconverter;1'],
+        'type': 'nsHTMLFormatConverter',
+        'headers': ['/widget/nsHTMLFormatConverter.h'],
+    },
+    {
+        'cid': '{f92e733e-33a3-4752-90e5-25801ddeaf7b}',
+        'contract_ids': ['@mozilla.org/widget/parent/dragservice;1'],
+        'type': 'nsDragService',
+        'headers': ['/widget/windows/nsDragService.h'],
+        'processes': ProcessSelector.MAIN_PROCESS_ONLY,
+    },
+    {
+        'cid': '{9a0cb62b-d638-4faf-9588-ae96f5e29093}',
+        'contract_ids': ['@mozilla.org/widget/taskbar-preview-callback;1'],
+        'type': 'mozilla::widget::TaskbarPreviewCallback',
+        'headers': ['/widget/windows/TaskbarPreview.h'],
+    },
+    {
+        'name': 'GfxInfo',
+        'cid': '{d755a760-9f27-11df-0800-200c9a664242}',
+        'contract_ids': ['@mozilla.org/gfx/info;1'],
+        'type': 'mozilla::widget::GfxInfo',
+        'headers': ['/widget/windows/GfxInfo.h'],
+        'init_method': 'Init',
+        'processes': ProcessSelector.ALLOW_IN_GPU_RDD_SOCKET_AND_UTILITY_PROCESS,
+    },
+    {
+        'cid': '{e2fc3e45-c893-4b34-8f6d-b87faf65a897}',
+        'contract_ids': ['@mozilla.org/parent/filepicker;1'],
+        'type': 'nsFilePicker',
+        'headers': ['/widget/windows/nsFilePicker.h'],
+        'processes': ProcessSelector.MAIN_PROCESS_ONLY,
+    },
+    {
+        'cid': '{035d92f3-3802-4cf5-87cb-1758bfc5d4da}',
+        'contract_ids': ['@mozilla.org/parent/colorpicker;1'],
+        'type': 'nsColorPicker',
+        'headers': ['/widget/windows/nsColorPicker.h'],
+        'processes': ProcessSelector.MAIN_PROCESS_ONLY,
+    },
+    {
+        'cid': '{1201d357-8417-4926-a694-e6408fbedcf8}',
+        'contract_ids': ['@mozilla.org/sharepicker;1'],
+        'type': 'nsSharePicker',
+        'headers': ['/widget/windows/nsSharePicker.h'],
+        'processes': ProcessSelector.MAIN_PROCESS_ONLY,
+    },
+    {
+        'cid': '{25b4efa0-7054-4787-9cd6-630efb3fe6fa}',
+        'contract_ids': ['@mozilla.org/widget/parent/clipboard;1'],
+        'interfaces': ['nsIClipboard'],
+        'type': 'nsIClipboard',
+        'processes': ProcessSelector.MAIN_PROCESS_ONLY,
+    },
+    {
+        'cid': '{b6e1a890-b2b8-4883-a65f-9476f6185313}',
+        'contract_ids': ['@mozilla.org/widget/systemstatusbar;1'],
+        'singleton': True,
+        'init_method': 'Init',
+        'type': 'mozilla::widget::SystemStatusBar',
+        'constructor': 'mozilla::widget::SystemStatusBar::GetAddRefedSingleton',
+        'headers': ['/widget/windows/SystemStatusBar.h'],
+        'processes': ProcessSelector.MAIN_PROCESS_ONLY,
+    },
+]
+
+if buildconfig.substs['CC_TYPE'] == 'clang-cl':
+    Classes += [
+        {
+            'cid': '{84e11f80-ca55-11dd-ad8b-0800200c9a66}',
+            'contract_ids': ['@mozilla.org/system-alerts-service;1'],
+            'type': 'mozilla::widget::ToastNotification',
+            'headers': ['/widget/windows/ToastNotification.h'],
+            'init_method': 'Init',
+            'processes': ProcessSelector.MAIN_PROCESS_ONLY,
+        },
+        {
+            'cid': '{a46c385b-a45c-4b48-ab7c-aaed1252bb83}',
+            'contract_ids': ['@mozilla.org/windows-alert-notification;1'],
+            'type': 'mozilla::widget::WindowsAlertNotification',
+            'headers': ['/widget/windows/ToastNotification.h'],
+            'processes': ProcessSelector.MAIN_PROCESS_ONLY,
+        }
+    ]
+
+if defined('NS_PRINTING'):
+    Classes += [
+        {
+            'cid': '{d3f69889-e13a-4321-980c-a39332e21f34}',
+            'contract_ids': ['@mozilla.org/gfx/devicecontextspec;1'],
+            'type': 'nsDeviceContextSpecWin',
+            'headers': ['/widget/windows/nsDeviceContextSpecWin.h'],
+            'processes': ProcessSelector.MAIN_PROCESS_ONLY,
+        },
+        {
+            'cid': '{06beec76-a183-4d9f-85dd-085f26da565a}',
+            'contract_ids': ['@mozilla.org/widget/printdialog-service;1'],
+            'type': 'nsPrintDialogServiceWin',
+            'headers': ['/widget/windows/nsPrintDialogWin.h'],
+            'init_method': 'Init',
+            'processes': ProcessSelector.MAIN_PROCESS_ONLY,
+        },
+        {
+            'cid': '{841387c8-72e6-484b-9296-bf6eea80d58a}',
+            'contract_ids': ['@mozilla.org/gfx/printsettings-service;1'],
+            'type': 'nsPrintSettingsServiceWin',
+            'headers': ['/widget/windows/nsPrintSettingsServiceWin.h'],
+            'init_method': 'Init',
+        },
+        {
+            'cid': '{a6cf9129-15b3-11d2-932e-00805f8add32}',
+            'contract_ids': ['@mozilla.org/gfx/printerlist;1'],
+            'type': 'nsPrinterListWin',
+            'headers': ['/widget/windows/nsDeviceContextSpecWin.h'],
+            'processes': ProcessSelector.MAIN_PROCESS_ONLY,
+        },
+    ]
diff --git a/widget/windows/docs/blocklist.rst b/widget/windows/docs/blocklist.rst
new file mode 100644
index 0000000000..5450faaa1b
--- /dev/null
+++ b/widget/windows/docs/blocklist.rst
@@ -0,0 +1,347 @@
+========================
+Windows DLL Blocklisting
+========================
+
+--------
+Overview
+--------
+
+There are many applications which interact with another application, which means
+they run their code as a DLL in a different process. This technique is used, for
+example, when an antivirus software tries to monitor/block navigation to a
+malicious website, or a screen reader tries to access UI parts. If such an
+application injects their code into Firefox, and if there is a bug in their code
+running in our firefox.exe, it will emerge as Firefox’s bug even though it’s
+not.
+
+Firefox for Windows has a feature to prevent DLLs from being loaded into our
+processes. If we are aware that a particular DLL causes a problem in our
+processes such as a crash or performance degradation, we can stop the problem by
+blocking the DLL from being loaded.
+
+This blocklist is about a third-party application which runs outside Firefox but
+interacts with Firefox. For add-ons, there is `a different process
+<https://extensionworkshop.com/documentation/publish/add-ons-blocking-process/>`_.
+
+This page explains how to request to block a DLL which you think we should block
+it as well as technical details about the feature.
+
+-----------------------
+Two types of blocklists
+-----------------------
+
+There are two types of blocklists in Firefox:
+
+1. A static blocklist that is compiled in to Firefox. This consists of DLLs
+   known to cause problems with Firefox, and this blocklist cannot be disabled
+   by the user. For more information and instructions on how to add a new DLL
+   to this list, see :ref:`Process for blocking a DLL in the static blocklist
+   <how-to-block-dll-in-static-blocklist>` below.
+2. A dynamic blocklist that users can use to block DLLs that are giving them
+   problems. This was added in
+   `bug 1744362 <https://bugzilla.mozilla.org/show_bug.cgi?id=1744362>`_.
+
+The static blocklist has ways to specify if only certain versions of a DLL
+should be blocked, or only for certain Firefox processes, etc. The dynamic
+blocklist does not have this capability; if a DLL is on the list it will always
+be blocked.
+
+Regardless of which blocklist the DLL is on, if it meets the criteria for being
+blocked Firefox uses the same mechanism to block it. There are more details
+below in :ref:`How the blocklist blocks a DLL <how-the-blocklist-blocks-a-dll>`.
+
+.. _how-to-block-dll-in-static-blocklist:
+
+--------------------------------------------------
+Process for blocking a DLL in the static blocklist
+--------------------------------------------------
+
+But wait, should we really block it?
+------------------------------------
+
+Blocking a DLL with the static blocklist should be our last resort to fix a
+problem because doing it normally breaks functionality of an application which
+installed the DLL. If there is another option, we should always go for it.
+Sometimes we can safely bypass a third-party’s problem by changing our code even
+though its root cause is not on our side.
+
+When we decide to block it, we must be certain that the issue at hand is so
+great that it outweighs the user's choice to install the software, the utility
+it provides, and the vendor's freedom to distribute and control their software.
+
+How to request to block a DLL
+-----------------------------
+
+Our codebase has the file named
+`WindowsDllBlocklistDefs.in <https://searchfox.org/mozilla-central/source/toolkit/xre/dllservices/mozglue/WindowsDllBlocklistDefs.in>`_ from which our build process generates DLL blocklists as C++ header files and compiles them. To block a new DLL, you create a patch to update WindowsDllBlocklistDefs.in and land it on our codebase, following our standard development process. Moreover, you need to fill out a form specific to the DLL blockling request so that reviewers can review the impact and risk as well as the patch itself.
+
+Here are the steps:
+
+1. File `a bug
+   <https://bugzilla.mozilla.org/enter_bug.cgi?format=__default__&bug_type=defect&product=Toolkit&component=Blocklist%20Policy%20Requests&op_sys=Windows&short_desc=DLL%20block%20request%3A%20%3CDLL%20name%3E&comment=Please%20go%20through%20https%3A%2F%2Fwiki.mozilla.org%2FBlocklisting%2FDLL%20before%20filing%20a%20new%20bug.>`_
+   if it does not exist.
+2. Answer all the questions in `this questionnaire
+   <https://msmania.github.io/assets/mozilla/third-party-modules/questionnaire.txt>`_,
+   and attach it to the bug as a plaintext.
+3. Make a patch and start a code review via Phabricator as usual.
+
+How to edit WindowsDllBlocklistDefs.in
+--------------------------------------
+
+WindowsDllBlocklistDefs.in defines several variables as a Python Array. When you
+add a new entry in the blocklists, you pick one of the variables and add an
+entry in the following syntax:
+
+Syntax
+******
+
+::
+
+ Variable += [
+ ...
+     # One-liner comment including a bug number
+     EntryType(Name, Version, Flags),
+ ...
+ ]
+
+Parameters
+**********
+
++-----------+--------------------------------------------------------------------------------+
+| Parameter | Value                                                                          |
++===========+================================================================================+
+| Variable  | ALL_PROCESSES \| BROWSER_PROCESS \| CHILD_PROCESSES \| GMPLUGIN_PROCESSES \|   |
+|           | GPU_PROCESSES \| SOCKET_PROCESSES \| UTILITY_PROCESSES                         |
++-----------+--------------------------------------------------------------------------------+
+| EntryType | DllBlocklistEntry \| A11yBlocklistEntry \| RedirectToNoOpEntryPoint            |
++-----------+--------------------------------------------------------------------------------+
+| Name      | A case-insensitive string representing a DLL's filename to block               |
++-----------+--------------------------------------------------------------------------------+
+| Version   | One of the following formats:                                                  |
+|           |                                                                                |
+|           |   - ALL_VERSIONS \| UNVERSIONED                                                |
+|           |   - A tuple consisting of four digits                                          |
+|           |   - A 32-bit integer representing a Unix timestamp with PETimeStamp            |
++-----------+--------------------------------------------------------------------------------+
+
+Variable
+********
+
+Choose one of the following predefined variables.
+
+- **ALL_PROCESSES**: DLLs defined here are blocked in BROWSER_PROCESS +
+  CHILD_PROCESSES
+- **BROWSER_PROCESS**: DLLs defined here are blocked in the browser process
+- **CHILD_PROCESSES**: DLLs defined here are blocked in non-browser processes
+- **GMPLUGIN_PROCESSES**: DLLs defined here are blocked in GMPlugin processes
+- **GPU_PROCESSES**: DLLs defined here are blocked in GPU processes
+- **SOCKET_PROCESSES**: DLLs defined here are blocked in socket processes
+- **UTILITY_PROCESSES**: DLLs defined here are blocked in utility processes
+
+EntryType
+*********
+Choose one of the following predefined EntryTypes.
+
+- **DllBlocklistEntry**: Use this EntryType unless your case matches the other
+  EntryTypes.
+- **A11yBlocklistEntry**: If you want to block a module only when it’s loaded by
+  an accessibility application such as a screen reader, you can use this
+  EntryType.
+- **RedirectToNoOpEntryPoint**: If a modules is injected via Import Directory
+  Table, adding the module as DllBlocklistEntry breaks process launch, meaning
+  DllBlocklistEntry is not an option. You can use RedirectToNoOpEntryPoint
+  instead.
+
+Name
+****
+A case-insensitive string representing a DLL's filename to block. Don’t include a directory name.
+
+Version
+*******
+
+A maximum version to be blocked. If you specify a value, a module with the
+specified version, older versions, and a module with no version are blocked.
+
+| If you want to block a module regardless of its version, use ALL_VERSIONS.
+| If you want to block a module with no version, use UNVERSIONED.
+
+
+To specify a version, you can use either of the following formats:
+
+- | A tuple consisting of four digits. This is compared to the version that is embedded in a DLL as a version resource.
+  | Example: (1, 2, 3, 4)
+- | A 32-bit integer representing a Unix timestamp with PETimeStamp. This is compared to an integer of IMAGE_FILE_HEADER::TimeDateStamp.
+  | Example: PETimeStamp(0x12345678)
+
+
+-----------------
+Technical details
+-----------------
+
+.. _how-the-blocklist-blocks-a-dll:
+
+How the blocklist blocks a DLL
+------------------------------
+
+Briefly speaking, we make ntdll!NtMapViewOfSection return
+``STATUS_ACCESS_DENIED`` if a given module is on the blocklist, thereby a
+third-party’s code, or even Firefox’s legitimate code, which tries to load a DLL
+in our processes in any way such as LoadLibrary API fails and receives an
+access-denied error.
+
+Cases where we should not block a module
+----------------------------------------
+
+As our blocklist works as explained above, there are the cases where we should not block a module.
+
+- | A module is loaded via `Import Directory Table <https://docs.microsoft.com/en-us/windows/win32/debug/pe-format#import-directory-table>`_
+  | Blocking this type of module blocks even a process from launching. You may be able to block this type of module with RedirectToNoOpEntryPoint.
+- | A module is loaded as a `Layered Service Provider <https://docs.microsoft.com/en-us/windows/win32/winsock/categorizing-layered-service-providers-and-applications>`_
+  | Blocking this type of module on Windows 8 or newer breaks networking. Blocking a LSP on Windows 7 is ok.
+
+(we used to have to avoid blocking modules loaded via a
+`Window hook <https://docs.microsoft.com/en-us/windows/win32/winmsg/hooks>`_ because blocking this type of
+module would cause repetitive attempts to load a module, resulting in slow performance
+like `Bug 1633718 <https://bugzilla.mozilla.org/show_bug.cgi?id=1633718>`_, but this should be fixed
+as of `Bug 1823412 <https://bugzilla.mozilla.org/show_bug.cgi?id=1823412>`_.)
+
+Third-party-module ping
+-----------------------
+
+We’re collecting the :ref:`third-party-module ping <third-party-modules-ping>`
+which captures a moment when a third-party module is loaded into the
+Browser/Tab/RDD process. As it’s asked in the request form, it’s important to
+check the third-party-module ping and see whether a module we want to block
+appears in the ping or not. If it appears, you may be able to know how a module
+is loaded by looking at a callstack in the ping.
+
+How to view callstacks in the ping
+**********************************
+
+1. You can run a query on BigQuery console or STMO.  (BigQuery console is much
+   faster and can handle larger data.)
+
+   - BigQuery console (visit
+     `here <https://docs.telemetry.mozilla.org/cookbooks/bigquery.html#gcp-bigquery-console>`_
+     to request access): https://console.cloud.google.com/bigquery
+   - STMO: https://sql.telemetry.mozilla.org/
+
+2. Make your own query based on `this template
+   <https://msmania.github.io/assets/mozilla/third-party-modules/query-template.txt>`_.
+3. Run the query.
+4. Save the result as a JSON file.
+
+   - In BigQuery console, click [SAVE RESULTS] and choose [JSON (local file)].
+   - In STMO, click [...] at the right-top corner and select [Show API Key],
+     then you can download a JSON from a URL shown in the [Results in JSON format].
+
+5. | Go to https://msmania.github.io/assets/mozilla/third-party-modules/
+   |   (A temporal link. Need to find a permanent place.)
+6. Click [Upload JSON] and select the file you saved at the step 4.
+7. Click a row in the table to view a callstack
+
+
+How to see the versions of a specific module in the ping
+********************************************************
+
+You can use `this template query
+<https://msmania.github.io/assets/mozilla/third-party-modules/query-groupby-template.txt>`_
+to query which versions of a specific module are captured in the ping. This
+tells the product versions which are actively used including the crashing
+versions and the working versions.
+
+You can also get the crashing versions by querying the crash reports or the
+Socorro table. Having two version lists, you can decide whether you can specify
+the Version parameter in a blocklist entry.
+
+Initialization
+--------------
+
+In order to have the most effective blocking of DLLs, the blocklist is
+initialized very early during browser startup. If the :ref:`launcher process
+<launcher-process>` is available, the steps are:
+
+- Launcher process loads dynamic blocklist from disk (see
+  `DynamicBlocklist::LoadFile()
+  <https://searchfox.org/mozilla-central/search?q=DynamicBlocklist%3A%3ALoadFile&path=&case=false&regexp=false>`_)
+- Launcher process puts dynamic blocklist data in shared section (see
+  `SharedSection::AddBlocklist()
+  <https://searchfox.org/mozilla-central/search?q=SharedSection%3A%3AAddBlocklist&path=&case=false&regexp=false>`_)
+- Launcher process creates the browser process in a suspended mode, sets up its
+  dynamic blocklist, then starts it. (see `LauncherMain()
+  <https://searchfox.org/mozilla-central/search?q=LauncherMain&path=&case=false&regexp=false>`_)
+
+  - This is so (ideally) no DLLs can be injected before the blocklist is set up.
+
+If the launcher process is not available, a different blocklist is used, defined
+in `mozglue/WindowsDllBlocklist.cpp
+<https://searchfox.org/mozilla-central/source/toolkit/xre/dllservices/mozglue/WindowsDllBlocklist.cpp>`_.
+This code does not currently support the dynamic blocklist. This is intended to
+only be used in testing and other non-deployed scenarios, so this shouldn't be
+a problem for users.
+
+Note that the mozglue blocklist also has a feature to block threads that start
+in ``LoadLibrary`` and variants. This code is currently only turned on in
+Nightly builds because it breaks some third-party DLP products.
+
+Dynamic blocklist file location
+-------------------------------
+
+Because the blocklist is loaded so early during startup, we don't have access to
+what profile is going to be loaded, so the blocklist file can't be stored there.
+Instead, by default the blocklist file is stored in the Windows user's roaming
+app data directory, specifically
+
+``<Roaming AppData directory>\Mozilla\Firefox\blocklist-<install hash>``
+
+Note that the install hash here is what is returned by `GetInstallHash()
+<https://searchfox.org/mozilla-central/source/toolkit/mozapps/update/common/commonupdatedir.cpp#404>`_,
+and is suitable for uniquely identifying the particular Firefox installation
+that is running.
+
+On first launch, this location will be written to the registry, and can be
+overriden by setting that key to a different file location. The registry key is
+``HKEY_CURRENT_USER\Software\Mozilla\Firefox\Launcher``, and the name is the
+full path to firefox.exe with "\|Blocklist" appended. This code is in
+`LauncherRegistryInfo
+<https://searchfox.org/mozilla-central/source/toolkit/xre/LauncherRegistryInfo.cpp>`_.
+
+Adding to and removing from the dynamic blocklist
+-------------------------------------------------
+
+Users can add or remove DLLs from the dynamic blocklist by navigating to
+``about:third-party``, finding the entry for the DLL they are interested in, and
+clicking on the dash icon. They will then be prompted to restart the browser, as
+the change will only take effect after the browser restarts.
+
+Disabling the dynamic blocklist
+-------------------------------
+
+It is possible that users can get Firefox into a bad state by putting a DLL on
+the dynamic blocklist. One possibility is that the user blocks only one of a set
+of DLLs that interact, which could make Firefox behave in unpredictable ways or
+crash.
+
+By launching Firefox with ``--disableDynamicBlocklist``\, the dynamic blocklist
+will be loaded but not used to block DLLs. This lets the user go to
+``about:third-party`` and attempt to fix the problem by unblocking or blocking
+DLLs.
+
+Similarly, in safe mode the dynamic blocklist is also disabled.
+
+Enterprise policy
+-----------------
+
+The dynamic blocklist can be disabled by setting a registry key at
+``HKEY_CURRENT_USER\Software\Policies\Mozilla\Firefox`` with a name of
+DisableThirdPartyModuleBlocking and a DWORD value of 1. This will have the
+effect of not loading the dynamic blocklist, and no icons will show up in
+``about:third-party`` to allow blocking DLLs.
+
+-------
+Contact
+-------
+
+Any questions or feedback are welcome!
+
+**Matrix**: `#hardening <https://app.element.io/#/room/#hardening:mozilla.org>`_
diff --git a/widget/windows/docs/index.rst b/widget/windows/docs/index.rst
new file mode 100644
index 0000000000..9a24cb9cdb
--- /dev/null
+++ b/widget/windows/docs/index.rst
@@ -0,0 +1,9 @@
+==================
+Firefox on Windows
+==================
+
+.. toctree::
+   :maxdepth: 2
+
+   blocklist
+   windows-pointing-device/index
diff --git a/widget/windows/docs/windows-pointing-device/apple_vision.jpg b/widget/windows/docs/windows-pointing-device/apple_vision.jpg
new file mode 100644
index 0000000000..9515f4d4fb
--- /dev/null
+++ b/widget/windows/docs/windows-pointing-device/apple_vision.jpg
diff --git a/widget/windows/docs/windows-pointing-device/apple_vision_user.webp b/widget/windows/docs/windows-pointing-device/apple_vision_user.webp
new file mode 100644
index 0000000000..64f8afc0e5
--- /dev/null
+++ b/widget/windows/docs/windows-pointing-device/apple_vision_user.webp
diff --git a/widget/windows/docs/windows-pointing-device/index.rst b/widget/windows/docs/windows-pointing-device/index.rst
new file mode 100644
index 0000000000..eda552b3dd
--- /dev/null
+++ b/widget/windows/docs/windows-pointing-device/index.rst
@@ -0,0 +1,1384 @@
+################################################################################
+Windows Pointing Device Support in Firefox
+################################################################################
+
+.. contents:: Table of Contents
+    :depth: 4
+
+================================================================================
+Introduction
+================================================================================
+
+This document is intended to provide the reader with a quick primer and/or
+refresher on pointing devices and the various operating system APIs, user
+experience guidelines, and Web standards that contribute to the way Firefox
+handles input devices on Microsoft Windows.
+
+The documentation for these things is scattered across the web and has varying
+levels of detail and completeness; some of it is missing or ambiguous and was
+only determined experimentally or by reading about other people's experiences
+through forum posts. An explicit goal of this document is to gather this
+information into a cohesive picture.
+
+We will then discuss the ways in which Firefox currently (as of early 2023)
+produces incorrect or suboptimal behavior when implementing those standards
+and guidelines.
+
+Finally, we will raise some thoughts and questions to spark discussion on how
+we might improve the situation and handle corner cases. Some of
+these issues are intrinsically "opinion based" or "policy based", so clear
+direction on these is desirable before engineering effort is invested into
+reimplementation.
+
+
+================================================================================
+Motivation
+================================================================================
+
+A quick look at the `pile of defects  <https://bugzilla.mozilla.orgbuglist.cgi?query_format=advanced&status_whiteboard=%5Bwin%3Atouch%5D&list_id=16586149&status_whiteboard_type=allwordssubstr>`__
+on *bugzilla.mozilla.org* marked with *[win:touch]* will show anyone that
+Firefox's input stack for pointer devices has issues, but the bugs recorded
+there don't begin to capture the full range of unreported glitches and
+difficult-to-reproduce hiccups that users run into while using touchscreen
+hardware and pen digitizers on Firefox, nor does it capture the ways that
+Firefox misbehaves according to various W3C standards that are (luckily) either
+rarely used or worked around in web apps (and thus go undetected or
+unreported).
+
+These bugs primarily manifest in a few ways that will each be discussed in
+their own section:
+
+1.  Firefox failing to return the proper values for the ``pointer``,
+    ``any-pointer``, ``hover``, and ``any-hover`` CSS Media Queries
+
+2.  Firefox failing to fire the correct pointer-related DOM events at the
+    correct time (or at all)
+
+3.  Firefox's inconsistent handling of touch-related gestures like scrolling,
+    where certain machines (like the Surface Pro) fail to meet the expected
+    behavior of scrolling inertia and overscroll. This leads to a weird touch
+    experience where the page comes to a choppy, dead-stop when using
+    single-finger scrolling
+
+
+It's worth noting that Firefox is not alone in having these types of issues,
+and that handling input devices is a notoriously difficult task for many
+applications; even a substantial amount of Microsoft's own software has trouble
+navigating this minefield on their own Microsoft Surface devices. Defects are
+instigated by a combination of the *intrinsic complexity* of the problem domain
+and the *accidential complexity* introduced by device vendors and Windows
+itself.
+
+The *intrinsic complexity* comes from the simple fact that human-machine
+interaction is difficult. A person must attempt to convey complex
+and abstract goals through a series of simple movements involving a few pieces
+of physical hardware. The devices can send signals that are unclear
+or even contradictory, and the software must decide how to handle
+this.
+
+As a trivial example, every software engineer that's ever written
+page scrolling logic has to answer the question, "What should my
+program do if the user hits 'Page Up' and 'Page Down' at the same time?".
+While it may seem obvious that the answer is "Do nothing.", naively-written
+keyboard input logic might assume the two are mutually-exclusive and only
+process whichever key is handled first in program order.
+
+Occasionally, a new device will be invented that doesn't obviously map to
+existing abstractions and input pipelines. There will be a period of time where
+applications will want to support the new device, but it won't be well
+understood by either the application developers nor the device vendor
+themselves what ideal integration would look like. The new Apple Vision VR
+headset is such a device; traditional VR headsets have used controllers to
+point at things, but Apple insists that the entire thing should be done using
+only hand tracking and eye tracking. Developers of VR video games and other
+apps (like Firefox) will inevitably make many mistakes on the road to
+supporting this new headset.
+
+A major source of defect-causing *accidental complexity* is the lack of clear
+expectations and documentation from Microsoft for apps (like Firefox) that are
+not using their Universal Windows Platform (UWP). The Microsoft Developer
+Network (MSDN) mentions concepts like inertia, overscroll, elastic bounce,
+single-finger panning, etc., but the solution is presented in the context
+of UWP, and the solution for non-UWP apps is either unclear or undocumented.
+
+Adding to this complexity is the fact that Windows itself has gone through
+several iterations of input APIs for different classes of devices, and
+these APIs interact with each other in ways that are surprising or
+unintuitive. Again, the advice given on MSDN pertains to UWP apps, and the
+documentation about the newer "pointer" based window messages is
+a mix of incomplete and inaccurate.
+
+Finally, individual input devices have bugs in their driver software that
+would disrupt even applications that are using the Windows input APIs perfectly.
+Handling all of these deviations is impossible and would result in fragile,
+unmaintainable code, but Firefox inevitably has to work around common ones to
+avoid alienating large portions of the userbase.
+
+
+================================================================================
+Technical Background
+================================================================================
+
+
+A Quick Primer on Pointing Devices
+======================================
+
+
+Traditionally, web browsers were designed to accommodate computer mice and
+devices that behave in a similar way, like trackballs and touchpads on
+laptops. Generally, it was assumed that there would be one such device attached
+to the computer, and it would be used to control a hovering "cursor" whose
+movements would be changed by relative movement of the physical input device.
+
+However, modern computers can be controlled using a variety of different
+pointing devices, all with different characteristics. Many allow
+multiple concurrent targets to be pointed at and have multiple sensors,
+buttons, and other actuators.
+
+For example, the screen of the Microsoft Surface Pro has dual capabilities
+of being a touch sensor and a digitizer for a tablet pen. When being used as a
+workstation, it's not uncommon for a user to also connect the "keyboard +
+touchpad" cover and a mouse (via USB or Bluetooth) to provide the more
+productivity-oriented "keyboard and mouse" setup. In that configuration, there
+are 4 pointer devices connected to the machine simultaneously: a touch screen,
+a pen digitizer, a touchpad, and a mouse.
+
+The next section will give a quick overview of common pointing devices.
+Many will be familiar to the reader, but they are still mentioned to establish
+common terminology and to avoid making assumptions about familiarity with every
+input device.
+
+
+Common Pointing Devices
+---------------------------
+
+Here are some descriptions of a few pointing device types that demonstrate
+the diversity of hardware:
+
+**Touchscreen**
+
+    A touchscreen is a computer display that is able to sense the
+    location of (possibly-multiple) fingers (or stylus) making contact with its
+    surface. Software can then respond to the touches by changing the displayed
+    objects quickly, giving the user a sense of actually physically manipulating
+    them on screen with their hands.
+
+    .. image:: touchscreen.jpg
+        :width: 25%
+
+
+**Digitizing Tablet + Pen Stylus**
+
+    These advanced pointing devices tend to
+    exist in two forms: as an external sensing "pad" that can be plugged into a
+    computer and sits on a desk or in someone's lap, or as a sensor built right
+    into a computer display. Both use a "stylus", which is a pen-shaped
+    electronic device that is detectable by the surface. Common features
+    include the ability to distinguish proximity to the surface ("hovering")
+    versus actual contact, pressure sensitivity, angle/tilt detection, multiple
+    "ends" such as a tip and an eraser, and one-or-more buttons/switch
+    actuators.
+
+    .. image:: wacom_tablet.png
+        :width: 25%
+
+
+**Joystick/Pointer Stick**
+
+    Pointer sticks are most often seen in laptop
+    computers made by IBM/Lenovo, where they exist as a little red nub located
+    between the G, H, and B keys on a standard QWERTY keyboard. They function
+    similarly to the analog sticks on a game controller -- The user displaces
+    the stick from its center position, and that is interpreted as a relative
+    direction to move the on-screen cursor. A greater displacement from center
+    is interpreted as increased velocity of movement.
+
+    .. image:: trackpoint.jpg
+        :width: 25%
+
+
+**Touchpad**
+
+    A touchpad is a rectangular surface (often found on laptop
+    computers) that detects touch and motion of a finger and moves an on-screen
+    cursor relative to the motion. Modern touchpads often support multiple
+    touches simultaneously, and therefore offer functionality that is quite
+    similar to a touchscreen, albeit with different movement semantics because
+    of their physical separation from the screen (discussed below).
+
+    .. image:: touchpad.jpg
+        :width: 25%
+
+
+**VR Controllers**
+
+    VR controllers (and other similar devices like the
+    Wiimote from the Nintendo Wii) allow users to point at objects in a
+    three-dimensional virtual world by moving a real-world controller and
+    "projecting" the controller's position into the virtual space. They often
+    also include sensors to detect the yaw, pitch, and roll of the sensors.
+    There are often other inputs in the controller device, like analog sticks
+    and buttons.
+
+    .. image:: vrcontroller.jpg
+        :width: 25%
+
+
+**Hand Tracking**
+
+    Devices like the Apple Vision (introduced during the
+    time this document was being written) and (to a lesser extent) the Meta
+    Quest have the ability to track the wearer's hand and directly interpret
+    gestures and movements as input. As the human hand can assume a staggering
+    number of orientations and configurations, a finite list of specific shapes
+    and movements must be identified and labelled to allow for clear
+    software-user interaction.
+
+    .. image:: apple_vision_user.webp
+        :width: 25%
+
+    .. image:: apple_vision.jpg
+        :width: 25%
+
+
+**Mouse**
+
+    A pointing device that needs no introduction. Moving a physical
+    clam-shaped device across a surface translates to relative movement of a
+    cursor on screen.
+
+    .. image:: mouse.jpg
+        :width: 25%
+
+
+The Buxton Three-State Model
+-------------------------------
+
+
+Bill Buxton, an early pioneer in the field of human-computer interaction,
+came up with a three-state model for pointing devices; a device can be
+"Out of Range", "Tracking", or "Dragging". Not all devices support all three
+states, and some devices have multiple actuators that can have the three-state
+model individually applied.
+
+.. mermaid::
+
+    stateDiagram-v2
+        direction LR
+        state "State 0" as s0
+        state "State 1" as s1
+        state "State 2" as s2
+        s0 --> s0 : Out Of Range
+        s1 --> s1 : Tracking
+        s2 --> s2 : Dragging
+        s0 --> s1 : Stylus On
+        s1 --> s0 : Stylus Lift
+        s1 --> s2 : Tip Switch Close
+        s2 --> s1 : Tip Switch Open
+
+
+For demonstration, here is the model applied to a few devices:
+
+**Computer Mouse**
+
+    A mouse is never in the "Out of Range" state. Even though it can technically
+    be lifted off its surface, the mouse does not report this as a separate
+    condition; instead, it behaves as-if it is stationary until it can once
+    again sense the surface moving underneath.
+
+    The remaining two states apply to each button individually; when a button is
+    not being pressed, the mouse is considered in the "tracking" state with
+    respect to that button. When a button is held down, the mouse is "dragging"
+    with respect to that button. A "click" is simply considered a zero-length
+    drag under this model.
+
+    In the case of a two-button mouse, this means that the mouse can be in a
+    total of 4 different states: tracking, left button dragging, right button
+    dragging, and two-button dragging. In practice, very little software
+    actually does anything meaningful with two-button dragging.
+
+**Touch Screen**
+
+    Applying the model to a touch screen, one can observe that current hardware
+    has no way to sense that a finger that is "hovering, but not quite making
+    contact with the screen". This means that the "Tracking" state can be ruled
+    out, leaving only the "Out of Range" and "Dragging" states. Since many touch
+    screens can support multiple fingers touching the screen concurrently, and
+    each finger can be in one of two states, there are potentially 2^N different
+    "states" that a touchscreen can be in. Windows assigns meaning to many two,
+    three, and four-finger gestures.
+
+**Tablet Digitizer**
+
+    A tablet digitizer supports all three states: when the stylus is far away
+    from the surface, it is considered "out of range"; when it is located
+    slightly above the surface, it is "tracking"; and when it is making contact
+    with the surface, it is "dragging".
+
+The W3C standards for pointing devices are based on this three-state model, but
+applied to each individual web element instead of the entire system. This
+makes things like "Out-of-Range" possible for the mouse, since it can be
+out of range of a web element.
+
+The W3C uses the terms "over" and "out" to convey the transition between
+"out-of-range" and "tracking" (which the W3C calls "hover"), and the terms
+"down" and "up" convey the transition between "tracking" and "dragging".
+
+The standard also address some of the known shortcomings of the model to
+improve portability and consistency; these improvements will be discussed more
+below.
+
+The Windows Pointer API is *supposedly* based around this model,
+but unfortunately real-world testing shows that the model is not followed
+very consistently with respect to the actual signals sent to the application.
+
+
+Gestures
+=====================================
+
+
+In contrast to the sort-of "anything goes" UI designs of the past,
+modern operating systems like Windows, Mac OS X, iOS, Android, and even
+modern Linux DEs have an "opinionated" idea of how user interaction
+should behave across all apps on the platform (the so-called "look and feel"
+of the operating system).
+
+Users expect gestures like swipes, pinches, and taps to act the same way
+across all apps for a given operating system, and they expect things like
+on-screen keyboards or handwriting recognition to pop up in certain contexts.
+Failing to meet those expectations makes an app look less polished, and
+(especially as far as accessibility is concerned) it frustrates the user
+and makes it more difficult for them to interact with the app.
+
+Microsoft defines guidelines for various behaviours that Windows applications
+should ideally adhere to in the `Input and Interactions <https://learn.microsoft.com/en-us/windows/apps/design/input/>`__
+section on MSDN. Some of these are summarized quickly below:
+
+**Drag and Drop**
+
+    Drag and drop allows a user to transfer data from one application to
+    another. The gesture begins when a pointer device moves into the "Dragging"
+    state over top of a UI element, usually as a result of holding down a mouse
+    button or pressing a finger on a touchscreen. The user moves the pointer
+    over top of the receiver of the data, and then ends the gesture by releasing
+    the mouse button or lifting their finger off the touchscreen. Window
+    interprets this transition out of the "Dragging" state as permission to
+    initiate the data transfer.
+
+    Firefox has supported Drag and Drop for a very long time, so it will not be
+    discussed further.
+
+
+**Pan and Zoom**
+
+    When using touchscreens (and multi-touch touchpads), users expect to be able
+    to cause the viewport to "pan" left/right/up/down by pressing two fingers on
+    the screen (creating two pointers in "Dragging" state) and moving their
+    fingers in the direction of movement. When they are done, they can release
+    both fingers (changing both pointers to "Out of Bounds").
+
+    A zoom can be signalled by moving the two fingers apart or together
+    in a "pinch" or "reverse pinch" gesture.
+
+
+**Single Pointer Panning**
+
+    Applications that are based on a UI model of the user interacting with a
+    "page" often allow a single pointer "Dragging" over the viewport to cause
+    the viewport to pan, similarly to the two-finger panning discussed in the
+    previous section.
+
+    Note that this gesture is not as universal as two-finger panning is -- as a
+    counterexample, graphics programs tend to treat one-finger dragging as
+    object manipulation and two-finger dragging as viewport panning.
+
+
+**Inertia**
+
+    When a user is done panning, they may lift their finger/pen off the screen
+    while the viewport is still in motion. Users expect that the page will
+    continue to move for a little while, as-if the user had "tossed" the page
+    when they let go. Effectively, the page behaves as though it has "momentum"
+    that needs to be gradually lost before the page comes to a full stop.
+
+    Modern operating systems provide this behavior via their various native
+    widget toolkits, and the curve that objects follow as they slow to a stop
+    are different across OSes. In that way, they can be considered part of the
+    unique "look and feel" of the OS. Users expect the scrolling of pages in
+    their web browser to behave this way, and so when Firefox fails to provide
+    this behavior it can be jarring.
+
+
+**Overscroll and Elastic Bounce**
+
+    When a user is panning the page and reaches the outer edges, Microsoft
+    recommends that the app should begin an "elastic bounce" animation, where
+    the page will allow the user to scroll past the end ("overscroll"),
+    show empty space underneath the page, and then sort of "snap back" like a
+    rubber band that's been stretched and then released.  You can see a
+    demonstration in `this article <https://www.windowslatest.com/2020/05/21/microsoft-is-adding-elastic-scrolling-to-chrome-on-windows-10/>`__,
+    which discusses Microsoft adding it to Chromium.
+
+
+History of Web Standards and Windows APIs
+===========================================
+
+The World-Wide Web Consortium (W3C) and the Web Hypertext Application
+Technology Working Group (WHATWG) manage the standards that detail the
+interface between a user agent (like Firefox) and applications designed to run
+on the Web Platform. The user agent, in turn, must rely on the operating system
+(Windows, in this case) to provide the necessary APIs to implement the
+standards required by the Web Platform.
+
+As a result of that relationship, a Web Standard is unlikely to be created
+until all widely-used operating systems provide the required APIs. That allows
+us to build a linear timeline with a predictable pattern: a new type of device
+becomes popular, the APIs to support it are introduced into operating systems,
+and eventually a cross-platform standard is introduced into the Web Platform.
+
+The following sections detail the history of input devices supported by
+Windows and the Web Platform:
+
+
+**1985 - Computer Mouse Support (Windows 1.0)**
+
+    The first version of Windows (1985) supported a computer mouse. Support
+    for other input devices is not well-documented, but probably non-existant.
+
+
+**1991 - Third-Party De-facto Pen Support (Wintab)**
+
+    In the late 80s and early 90s, any tablet pen hardware vendor that wanted
+    to support Windows would need to write a device driver and design a
+    proprietary user-mode API to expose the device to user applications. In
+    turn, application developers would have to write and maintain code to
+    support the APIs of every relevant device vendor.
+
+    In 1991, a company named LCS/Telegraphics released an API for Windows
+    called "Wintab", which was designed in collaboration with hardware and
+    software vendors to define a general API that could be targetted by
+    device drivers and applications.
+
+    It would take Microsoft more than a decade to include first-party support
+    for tablet pens in Windows, which allowed Wintab to become the de-facto
+    standard for pen support on Windows. The Wintab API continues to be
+    supported by virtually all artist tablets to this day. Notable companies
+    include Wacom, Huion, XP-Pen, etc.
+
+
+**1992 - Early Windows Pen Support (Windows for Pen Computing)**
+
+    The earliest Windows operating system to support non-mouse pointing devices
+    was Windows 3.1 with the "Windows for Pen Computing" add-on (1992).
+    (`For the curious <https://socket3.wordpress.com/2019/07/31/windows-for-pen-computing-1-0/>`__,
+    and I'm certain `this book <https://www.amazon.com/Microsoft-Windows-Pen-Computing-Programmers/dp/1556154690>`__
+    is a must-read!). Pen support was mostly implemented by translating actions
+    into the existing ``WM_MOUSExxx`` messages, but also "upgraded" any
+    application's ``EDIT`` controls into ``HEDIT`` controls, which looked the
+    same but were capable of being handwritten into using a pen. This was not
+    very user-friendly, as the controls stayed the same size and the UI was not
+    adapted to the input method. This add-on never achieved much popularity.
+
+    It is not documented whether Netscape Navigator (the ancestor of Mozilla
+    Firefox) supported this add-on or not, but there is no trace of it in modern
+    Firefox code.
+
+
+**1995 - Introduction of JavaScript and Mouse Events (De-facto Web Standard)**
+
+    The introduction of JavaScript in 1995 by Netscape Communications added a
+    programmable, event-driven scripting environment to the Web Platform.
+    Browser vendors quickly added the ability for scripts to listen for and
+    react to mouse events. These are the well-known events like ``mouseover``,
+    ``mouseenter``, ``mousedown``, etc. that are ubiquitous on the web, and are
+    known by basically anyone who has ever written front-end JavaScript.
+
+    This ubiquity created a de-facto standard for mouse input, which would
+    eventually be formally standardized by the W3C in the HTML Living Standard
+    in 2001.
+
+    The Mouse Event APIs assume that the computer has one single pointing device
+    which is always present, has a single cursor capable of "hovering" over an
+    element, and has between one and three buttons.
+
+    When support for other pointing devices like touchscreen and pen first
+    became available in operating systems, it was exposed to the web by
+    interpreting user actions into equivalent mouse events. Unfortunately, this
+    is unable to handle multiple concurrent pointers (like one would get from
+    multitouch screens) or report the kind of rich information a pen digitizer
+    can provide, like tilt angle, pressure, etc. This eventually lead the W3C
+    to develop the new "Touch Events" standard to expose touch functionality,
+    and eventually the "Pointer Events" to expose more of the rich information
+    provided by pens.
+
+
+**2005 - Mainstream Pen Support (Windows XP Tablet PC Edition)**
+
+    It was the release of Windows XP Tablet PC Edition (2005) that allowed
+    Windows applications to directly support tablet pens by using the new COM
+    "`Windows Tablet PC <https://learn.microsoft.com/en-us/windows/win32/tablet/tablet-pc-development-guide>`__"
+    APIs, most of which are provided through the main `InkCollector <https://learn.microsoft.com/en-us/windows/win32/tablet/inkcollector-class>`__
+    class. The ``InkCollector`` functionality would eventually be "mainlined"
+    into Windows XP Professional Service Pack 2, and continues to exist in
+    modern Windows releases.
+
+    The Tablet PC APIs consist of a large group of COM objects that work
+    together to facilitate enumerating attached pens, detecting pen movement and
+    pen strokes, and analyzing them to provide:
+
+    1.  **Cursor Movement**: translates the movements of the pen into the
+        standard mouse events that applications expect from mouse cursor
+        movement, namely ``WM_NCHITTEST``, ``WM_SETCURSOR`` and
+        ``WM_MOUSEMOVE``.
+
+    2.  **Gesture Recognition**: detects common user actions, like "tap",
+        "double-tap", "press-and-hold", and "drag". The `InkCollector` delivers
+        these events via COM `SystemGesture <https://learn.microsoft.com/en-us/windows/win32/tablet/inkcollector-systemgesture>`__
+        events using the `InkSystemGesture <https://learn.microsoft.com/en-us/windows/win32/api/msinkaut/ne-msinkaut-inksystemgesture>`__
+        enumeration. It will also translate them into common Win32 messages; for
+        example, a "drag" gesture would be translated into a ``WM_LBUTTONDOWN``
+        message, several ``WM_MOUSEMOVE`` messages, and finally a
+        ``WM_LBUTTONUP`` message.
+
+        An application that is using ``InkCollector`` will receive both types of
+        messages: traditional mouse input through the Win32 message queue, and
+        "Tablet PC API" events through COM callbacks. It is up to the
+        application to determine which events matter to it in a given context,
+        as the two types of events are not guaranteed by Microsoft to correspond
+        in any predictable way.
+
+    3.  **Shape and Text Recognition**: allows the app to
+        recognize letters, numbers, punctuation, and other `common shapes <https://learn.microsoft.com/en-us/windows/win32/api/msinkaut/ne-msinkaut-inkapplicationgesture>`__
+        the user might make using their pen. Supported shapes include circles,
+        squares, arrows, and motions like "scratch out" to correct a misspelled
+        word. Custom recognizers exist that allow recognition of other symbols,
+        like music notes or mathematical notation.
+
+    4.  **Flick Recognition**: allows the user to invoke actions via quick,
+        linear motions that are recognized by Windows and sent to the app as
+        ``WM_TABLET_FLICK`` messages. The app can choose to handle the window
+        message or pass it on to the default window procedure, which will
+        translate it to scrolling messages or mouse messages.
+
+        For example, a quick upward 'flick' corresponds to "Page up", and
+        a quick sideways flick in a web browser would be "back". Flicks were
+        never widely used by Windows apps, and they may have been removed in
+        more recent versions of Windows, as the existing Control Panel menus
+        for configuring them seem to no longer exist as of Windows 10 22H2.
+
+
+    Firefox does not appear to have ever used these APIs to allow tablet pen
+    input, with the exception of `one piece of code <https://searchfox.org/mozilla-central/rev/e6cb503ac22402421186e7488d4250cc1c5fecab/widget/windows/InkCollector.cpp>`__
+    to detect when the pen leaves the Firefox window to solve
+    `Bug 1016232 <https://bugzilla.mozilla.org/show_bug.cgi?id=1016232>`__.
+
+
+**2009 - Touch Support: WM_GESTURE (Windows 7)**
+
+    While attempts were made with the release of Windows Vista (2007) to support
+    touchscreens through the existing tablet APIs, it was ultimately the release
+    of Windows 7 (2009) that brought first-class support for Touchscreen devices
+    to Windows with new Win32 APIs and two main window messages: ``WM_TOUCH``
+    and ``WM_GESTURE``.
+
+    These two messages are mutually-exclusive, and all applications are
+    initially set to receive only ``WM_GESTURE`` messages. Under this
+    configuration, Windows will attempt to recognize specific movements on a
+    touch digitizer and post "gesture" messages to the application's message
+    queue. These gestures are similar to (but, somewhat-confusingly, not
+    identical to) the gestures provided by the "Windows Tablet PC" APIs
+    mentioned above. The main gesture messages are: zoom, pan, rotate,
+    two-finger-tap, and press-and-tap (one finger presses, another finger
+    quickly taps the screen).
+
+    In contrast to the behavior of the ``InkCollector`` APIs, which will send
+    both gesture events and translated mouse messages, the ``WM_GESTURE``
+    message is truly "upstream" of the translated mouse messages; the translated
+    mouse messages will only be generated if the application forwards the
+    ``WM_GESTURE`` message to the default window procedure. This makes
+    programming against this API simpler than the ``InkCollector`` API, as
+    there is no need to state-fully "remember" that an action has already been
+    serviced by one codepath and needs to be ignored by the other.
+
+    Firefox current supports the ``WM_GESTURE`` message when Asynchronous Pan
+    and Zoom (APZ) is not enabled (although we do not handle inertia in this
+    case, so the page comes to a dead-stop immediately when the user stops
+    scrolling).
+
+
+**2009 - Touch Support: WM_TOUCH (Windows 7)**
+
+    Also introduced in Windows 7, an application that needs full control over
+    touchscreen events can use `RegisterTouchWindow <https://learn.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-registertouchwindow>`__
+    to change any of its windows to receive ``WM_TOUCH`` messages instead of the
+    more high-level ``WM_GESTURE`` messages. These messages explicitly notify
+    the application about every finger that contacts or breaks contact with the
+    digitizer (as well as each finger's movement over time). This provides
+    absolute control over touch interpretation, but also means that the burden
+    of handling touch behavior falls completely on the application.
+
+    To help ease this burden, Microsoft provides two COM APIs to interpret
+    touch messages, ``IManipulationProcessor`` and ``IInertiaProcessor``.
+
+    ``IManipulationProcessor`` can be considered a superset of the functionality
+    available through normal gestures. The application feeds ``WM_TOUCH`` data
+    into it (along with other state, such as pivot points and timestamps), and
+    it allows for manipulations like: two-finger rotation around a pivot,
+    single-finger rotation around a pivot, simultaneous rotation and translation
+    (for example, 'dragging' a single corner of a square).
+    `These MSDN diagrams <https://learn.microsoft.com/en-us/windows/win32/wintouch/advanced-manipulations-overview>`__
+    give a good overview of the kinds of advanced manipulations an app might
+    support.
+
+    ``IInertiaProcessor`` works with ``IManipulationProcessor`` to add inertia
+    to objects in a standard way across the operating system. It is likely that
+    later APIs that provide this (like DirectManipulation) are using these COM
+    objects under the hood to accomplish their inertia handling.
+
+    Firefox currently handles the ``WM_TOUCH`` event when Asynchronous Pan and
+    Zoom (APZ) is enabled, but we do not use either the ``IInertiaProcessor``
+    nor the ``IManipulationProcessor``.
+
+
+**2012 - Unified Pointer API (Windows 8)**
+
+    Windows 8 (2012) was Microsoft's initial attempt to make a touch-first,
+    mobile-first operating system that (ideally) would make it easy for app
+    developers to treat touch, pen, and mouse as first-class input devices.
+
+    By this point, the Windows Tablet APIs would allow tablet pens to draw
+    text and shapes like squares, triangles, and music notes, and those shapes
+    would be recognizable by the Windows Ink subsystem.
+
+    At the same time, Windows Touch allowed touchscreens to have advanced
+    manipulation, like rotate + translate, or simultaneous pan and zoom, and it
+    allowed objects manipulated by touch to have momentum and angular velocity.
+
+    The shortcomings of having separate input stacks for these various devices
+    starts to be become apparent after a while: Why shouldn't a touchscreen be
+    able to recognize a circle or a triangle? Why shouldn't a pen be able to
+    have complex rotation and zoom functionality? How do we handle these newer
+    laptop touchpads that are starting to handle multi-touch gestures like a
+    touchscreen, but still cause relative cursor movement like a mouse? Why does
+    my program have to have 3 separate codepaths for different pointing devices
+    that are all very similar?
+
+    The Windows Pointer Device Input Stack introduces new APIs and window
+    messages that generalize the various types of pointing devices under a
+    single API while still falling back to the legacy touch and tablet input
+    stacks in the event that the API is unused. (Note that the touch and tablet
+    stacks themselves fall back to the traditional mouse input stack when they
+    are unused.)
+
+    Microsoft based their pointer APIs off the Buxton Three-State Model
+    (discussed earlier), where changes between "Out-of-Range" and "Tracking" are
+    signalled by ``WM_POINTERENTER`` AND ``WM_POINTERLEAVE`` messages, and
+    changes between "Tracking" and "Dragging" are signalled by
+    ``WM_POINTERDOWN`` and ``WM_POINTERUP``. Movement is indicated via
+    ``WM_POINTERUPDATE`` messages.
+
+    If these messages are unhandled (the message is forwarded to
+    ``DefWindowProc``), the Win32 subsystem will translate them
+    into touch or gesture messages. If unhandled, those will be further
+    translated into mouse and system messages.
+
+    While the Pointer API is not without some unfortunate pitfalls (which will
+    be discussed later), it still provides several advantages over the
+    previously available APIs: it can allow a mostly-unified codepath for
+    handling pointing devices, it circumvents many of the often-complex
+    interactions between the previous APIs, and it provides the ability to
+    simulate pointing devices to help facilitate end-to-end automated testing.
+
+    Firefox currently uses the Pointer APIs to handle tablet stylus input only,
+    while other input methods still use the historical mouse and touch input
+    APIs above.
+
+
+**2013 - DirectManipulation (Windows 8.1)**
+
+    DirectManipulation is a DirectX based API that was added during the release
+    of Windows 8.1 (2013). This API allows an app to create a series of
+    "viewports" inside a window and have scrollable content within each of these
+    viewports. The manipulation engine will then take care of automatically
+    reading Pointer API messages from the window's event queue and generating
+    pan and zoom events to be consumed by the app.
+
+    In the case that the app is also using DirectComposition to draw its window,
+    DirectManipulation can pipe the events directly into it, causing the app
+    to essentially get asynchronous pan and zoom with proper handling of inertia
+    and overscroll with very little coding.
+
+    DirectManipulation is only used in Firefox to handle data coming from
+    Precision Touchpads, as Microsoft provides no other convenient API for
+    obtaining data from such devices. Firefox creates fake content inside of
+    a fake viewport to capture the incoming events from the touchpad and
+    translates them into the standard Asynchronous Pan and Zoom (APZ) events
+    that the rest of the input pipeline uses.
+
+
+**2013 - Touch Events (Web Standard)**
+
+    "`Touch Events <https://www.w3.org/TR/touch-events/>`__" became a W3C
+    recommendation in October, 2013.
+
+    At this point, Microsoft's first operating system to include touch support
+    (Windows 7) was the most popular desktop operating system, and the ubiquity
+    of smart phones brought a huge uptick in users with touchscreen inputs. All
+    major browsers included some API that allowed reading touch input,
+    prompting the W3C to formalize a new standard to ensure interoperability.
+
+    With the Touch Events API, multiple touch interactions may be reported
+    simultaneously, each with their own separate identifier for tracking and
+    their own coordinates within the screen, viewport, and client area. A
+    touch is reported by: a ``touchstart`` event with a unique ID for each
+    contact, zero-or-more ``touchmove`` events with that ID, and finally a
+    ``touchend`` event to signal the end of that specific contact.
+
+    The API also has some amount of support for pen styluses, but it lacks
+    important features necessary to truly support them: hovering, pressure,
+    tilt, or multiple cursors like an erasure. Ultimately, its functionality
+    has been superceded by the newer "Pointer Events" API, discussed below.
+
+
+**2016 - Precision Touchpads (Windows 10)**
+
+    Early touchpads emulated a computer mouse by directly using the same IBM
+    PS/2 interface that most computer mice used and translating relative
+    movement of the user's finger into equivalent movements of a mouse on a
+    surface.
+
+    As touchpad technology advanced and more powerful interface standards like
+    USB begun to take over the consumer market, touchpad vendors started adding
+    extra features to their hardware, like tap-to-click, tap-and-drag, and
+    tap-and-hold (to simulate a right click). These behaviors were implemented
+    by touchpad vendors either in hardware drivers and/or user mode "hooks" that
+    injected equivalent Win32 messages into the appropriate target.
+
+    As expected, each touchpad vendor's driver had its own subtly-different
+    behavior from others, its own bugs, and its own negative interactions with
+    other software.
+
+    During the later years of Windows 8, Microsoft and touchpad company
+    Synaptics co-developed the "Precision Touchpad" standard, which defines an
+    interface for touchpad hardware to report its physical measurements,
+    precision, and sensor configuration to Windows and allows it to deliver raw
+    touch data. Windows then interprets the data and generates gestures and
+    window messages in a standard way, removing the burden of implementing these
+    behaviors from the touchpad vendor and providing the OS with rich
+    information about the user's movements.
+
+    It wasn't until the 2016 release of Windows 10 14946 that Microsoft would
+    support all the standard gestures through the new standard. Although
+    adoption by vendors has been a bit slow, the fact that
+    `it is a requirement for Windows 11 <https://pocketnow.com/all-windows-11-pcs-will-be-required-to-have-a-precision-touchpad-and-webcam/>`__
+    means that vendor support for this standard is imminent.
+
+    Unfortunately, there's a piece of bad news: Microsoft did not
+    implement the above "Unified Pointer API" for use with touchpads, as the
+    developers of Blender discovered when `they moved to the Pointer API <https://archive.blender.org/developer/D7660>`__.
+    Instead, Microsoft expects developers to either use DirectManipulation to
+    automatically get pan/zoom enabled for their app, or the RawInput API to
+    directly read touchpad data.
+
+
+**2019 - Pointer Events (Web Standard)**
+
+    "`Pointer Events <https://www.w3.org/TR/pointerevents/>`__" became a level 2
+    W3C recommendation in April, 2019. They considered `the work done by Microsoft <https://www.w3.org/Submission/2012/SUBM-pointer-events-20120907/>`__
+    as part of the design of their own Pointer API, and in many ways the W3C
+    standard resembles an improved, better specified, more consistent, and
+    easier-to-use version of the APIs provided by the Win32 subsystem.
+
+    The Pointer Events API generalizes devices like touchscreens, mice, tablet
+    pens, VR controllers, etc. into a "thing that points". A pointer has
+    (optional) properties: a width and height (big for a finger, 1px for a
+    mouse), an amount of pressure, a tilt angle relative to the surface, some
+    buttons, etc. This helps applications maximize code reuse for handling
+    pointer input by having a common codebase written against these generalized
+    traits. If needed, the application may also have smaller, specialized
+    sections of code for each concrete pointer type.
+
+    Certain types of pointers (like pens and touchscreens) have a behavior where
+    they are always "captured" by the first object that they interact with. For
+    example, if a user puts their finger on an empty part of a web page and
+    starts to scroll, their finger is now "captured" by the web page itself.
+    "Captured" means that even if their finger moves over an element in
+    the web page, that element will not receive events from the finger -- the
+    page itself will until the entire interaction stops.
+
+    The events themselves very closely follow the Buxton Three-State Model
+    (discussed earlier), where  ``pointerover/pointerout`` messages indicate
+    transitions from "Out of Range" to "Tracking" and visa-versa, and
+    ``pointerdown/pointerup`` messages transition between "Tracking" and
+    "Dragging". ``pointermove`` updates the position of the pointer, and a
+    special ``pointercancel`` message is sent to inform the page that the
+    browser is "cancelling" a ``pointerdown`` event because it has decided to
+    consume it for a gesture or because the operating system cancelled the
+    pointer for its own reasons.
+
+
+CSS "interaction" Media Queries
+==========================================
+
+(Note that this section is **not** about the `pointer-events <https://developer.mozilla.org/en-US/docs/Web/CSS/pointer-events>`__
+CSS property, which defines the circumstances where an element can be the target
+of pointer events.)
+
+The W3C defines the interaction-related media queries in the
+`Media Queries Level 4 - Interaction Media Features <https://www.w3.org/TR/mediaqueries-4/#mf-interaction>`__
+document.
+
+To summarize, the main interaction-related CSS Media Queries that Firefox must
+support are ``pointer``,  ``any-pointer``, ``hover`` and ``any-hover``.
+
+
+``pointer``
+
+    Allows the webpage to query the existence of a pointing device on
+    the machine, and (if available) the assumed "pointing accuracy" of the
+    "primary" pointing device. The device considered "primary" on a machine with
+    multiple input devices is a policy decision that must be made by the web
+    browser; Windows simply provides the APIs to query information about
+    attached devices.
+
+    The browser is expected to return one of three strings to this media query:
+
+    ``none``
+
+        There is no pointing device attached to the computer.
+
+    ``coarse``
+
+        The primary pointing device is capable of approximately
+        pointing at a relatively large target (like a finger on a
+        touchscreen).
+
+    ``fine``
+
+        The primary pointing device is capable of near-pixel-level
+        accuracy (like a computer mouse or a tablet pen).
+
+
+``any-pointer``
+
+    Similar to ``pointer``, but represents the union of
+    capabilities of all pointers attached to the system, such that the meanings
+    become:
+
+    ``none``
+
+        There is no pointing device attached to the computer.
+
+    ``coarse``
+
+        There is at-least one "coarse" pointer attached.
+
+    ``fine``
+
+        There is at-least one "fine" pointer attached.
+
+
+``hover``
+
+    Allows the webpage to query whether the primary pointer is
+    capable of "hovering" over top of elements on the page. Computer mice,
+    touchpad cursors, and higher-end pen tablets all support this, whereas
+    current touchscreens are "touch" or "no touch", and they cannot detect a
+    finger hovering over the screen.
+
+    ``hover``
+
+        The primary pointer is capable of reporting hovering.
+
+    ``none``
+
+        The primary pointer is not capable of reporting hovering.
+
+``any-hover``
+
+    Indicates whether any pointer attached to the system has the
+    ``hover`` capability.
+
+
+Selection of the Primary Pointing Device
+--------------------------------------------
+
+To illustrate the complexity of this topic, consider the Microsoft Surface Pro.
+
+The Surface Pro has an advanced screen that is capable of receiving touch
+input, but it can also behave like a pen digitizer and receive input from a
+stylus with advanced pen capabilities, like hover sensing, pressure
+sensitivity, multiple buttons, and even multiple "tips" (a pen and eraser end).
+
+In this case, what should Firefox consider the primary pointing device?
+
+Perhaps the user intends to use their Surface Pro like a touchscreen tablet,
+at which point Firefox should report ``pointer: coarse`` and ``hover: none``
+capabilities.
+
+But what if, instead, the user wants to sketch art or take notes using a pen on
+their Surface Pro? In this case, Firefox should be reporting ``pointer: fine``
+and ``hover: hover``.
+
+Imagine that the user then attaches the "keyboard + touchpad" cover attachment
+to their Surface Pro; naturally, we will consider that the user's intent is for
+the touchpad to become the primary pointing device, and so it is fairly clear
+that we should return ``pointer: fine`` and ``hover: hover`` in this state.
+
+However, what if the user tucks the keyboard/touchpad attachment behind the
+tablet and begins exclusively operating the device with their finger?
+
+This example shows that complex, multi-input machines can resist classification
+and blur the lines between labels like "touch device", "laptop", "drawing
+tablet", etc. It also illustrates that identifying the "primary" pointing
+device using only machine configuration may yield unintuitive and suboptimal
+results.
+
+While we can almost-certainly improve our hardware detection heuristics to
+better answer this question (and we should, at the very least), perhaps it
+makes more sense for Firefox to incorporate user intentions into the decision.
+Intentions could be communicated directly by the user through some sort of
+setting or indirectly through the user's actions.
+
+For example, if the user intends to draw on the screen with a pen, perhaps
+Firefox provides something like a "drawing mode" that the user can toggle to
+change the primary pointing device to the pen. Or perhaps it's better for
+Firefox to interpret the mere fact of receiving pen input as evidence of the
+user's intent and switch the reported primary pointing device automatically.
+
+If we wanted to switch automatically, there are predictable traps and pitfalls
+we need to think about: we need to ensure that we don't create frustrating user
+experiences where web pages may "pop" beneath the user suddenly, and
+we should likely incorporate some kind of "settling time" so we don't
+oscillate between devices.
+
+It's worth noting that Chromium doesn't seem to incorporate anything like
+what's being suggested here, so if this is well-designed it may be an
+opportunity for Firefox to try something novel.
+
+
+
+
+================================================================================
+State of the Browser
+================================================================================
+
+Pan and Zoom, Inertia, Overscroll, and Elastic Bounce
+=========================================================
+
+As can be seen in the videos below, Firefox's support for inertia, overscroll,
+and elastic bounce works well on all platforms when a stylus pen is used
+as the input device, and it also works just fine with the touchscreen on the
+Dell XPS 15. However, it completely fails when the touchscreen is used on
+the Microsoft Surface Pro. While more investigation is needed to completely
+understand these issues, the fact that the correctly-behaving digitizing pens
+use the Pointer API and the misbehaving input devices do not may be related.
+
+-   `Video 1 <https://drive.google.com/file/d/1Z1QRSf2RluNhJwkKCzPb6-14vRtkqK8s/view?usp=sharing>`__
+    showcasing overscroll and bounce not working on Surface Pro with touch, but
+    other devices/inputs are working
+
+-   `Video 2 <https://drive.google.com/file/d/1bOgpVGBeZtwelvPJzYdA6uFRpubGtu4W/view?usp=sharing>`__
+    showing that everything works just fine with an external Wacom digitizer
+
+
+Pointer Media Queries
+=========================================================
+
+**"any-pointer" Queries**
+
+Unlike the ``pointer`` media queries, which rely on the browser to make a policy
+decision about what should be considered the "primary" pointer in a given
+system configuration, the ``any-pointer`` queries are much more objective and
+binary: the computer either has a type of device attached to it, or it
+doesn't.
+
+**any-pointer: coarse**
+
+Firefox reports that there are "coarse" pointing devices present if either of
+these two points is true:
+
+1.  ``GetSystemMetrics(SM_DIGITIZER)`` reports that a device that supports
+    touch or pen is present.
+
+2.  Based on heuristics, Firefox concludes that it is running on a computer it
+    considers a "tablet".
+
+Point #1 is incorrect, as a pen is not a "coarse" pointing device. Note that
+this is a recent regression in `Bug 1811303 <https://bugzilla.mozilla.org/show_bug.cgi?id=1811303>`__
+that was uplifted to Firefox 112, so this actually regressed as this document
+was being written! This is responsible for the incorrect "Windows 10 Desktop +
+Wacom USB Tablet" issue in the table.
+
+Point #2 is a clear case of the `XY Problem <https://en.wikipedia.org/wiki/XY_problem>`__,
+where Firefox is trying to determine if a coarse pointing device is present
+by determining whether it is running on a tablet, when instead it should be
+directly testing for coarse pointing devices (since, of course, those can exist
+on machines that wouldn't normally be considered a "tablet"). This is
+responsible for the incorrect "Windows 10 Dell XPS 15 (Touch Disabled) + Wacom
+USB Tablet" issue in the table below.
+
+**any-pointer: fine**
+
+Firefox reports that there are "fine" pointing devices present if and only if
+it detects a mouse. This is clearly already wrong. Firefox determines that the
+computer has a mouse using the following algorithm:
+
+1.  If ``GetSystemMetrics(SM_MOUSEPRESENT)`` returns false, report no mouse.
+
+2.  If Firefox does not consider the current computer to be a tablet, report a
+    mouse if there is at-least one "mouse" device driver running on the
+    computer.
+
+3.  If Firefox considers the current computer to be a tablet or a touch system,
+    only report a mouse if there are at-least two "mouse" device drivers
+    running. This exists because some tablet pens and touch digitizers report
+    themselves as computer mice.
+
+This algorithm also suffers from the XY problem -- Firefox is trying to
+determine whether a fine pointing device exists by determining if there is
+a computer mouse present, when instead it should be directly testing for
+fine pointing devices, since mice are not the only fine pointing
+devices.
+
+Because of this proxy question, this algorithm is completely dependent on any
+attached fine pointing device (like a pen tablet) to report itself as a mouse.
+Point #3 makes the problem even worse, because if a computer that resembles a
+tablet fails to report its digitizers as mice, the algorithm will completely
+ignore an actual computer mouse attached to the system because it expects two
+of them to be reported!
+
+Unfortunately, the Surface Pro has both a pen digitizer and a touch digitizer,
+and it reports neither as a mouse. As a result, this algorithm completely falls
+apart on the Surface Pro, failing to report any "fine" pointing device even
+when a computer mouse is plugged in, a pen is plugged in, or even when
+the tablet is docked because its touchpad is only one mouse and it expects
+at least two.
+
+This is also responsible for failing to report the trackpad on the Dell XPS 15
+as "fine", because the Dell XPS 15 has a touchscreen and therefore looks like
+a "tablet", but doesn't report 2 mouse drivers.
+
+**any-pointer: hover**
+
+
+Firefox reports that any device that is a "fine" pointer also supports "hover",
+which does generally hold true, but isn't necessarily true for lower-end pens
+that only support tapping. It would be better for Firefox to directly
+query the operating system instead of just assuming.
+
+**"pointer" media query**
+
+As discussed previously at length, this media query relies on a "primary"
+designation made by the browser. Below is the current algorithm used to
+determine this:
+
+1.  If the computer is considered a "tablet" (see below), report primary
+    pointer as "coarse" (this is clearly already the wrong behavior).
+
+2.  Otherwise, if the computer has a mouse plugged in, report "fine".
+
+3.  Otherwise, if the computer has a touchscreen or pen digitizer, report
+    "coarse" (this is wrong in the case of the digitizer).
+
+4.  Otherwise, report "fine" (this is wrong; should report "None").
+
+Firefox uses the following algorithm to determine if the computer is a
+"tablet" for point #1 above:
+
+1.  It is not a tablet if it's not at-least running Windows 8.
+
+2.  If Windows "Tablet Mode" is enabled, it is a tablet no matter what.
+
+3.  If no touch-capable digitizers are attached, it is not a tablet.
+
+4.  If the system doesn't support auto-rotation, perhaps because it has
+    no rotation sensor, or perhaps because it's docked and operating in
+    "laptop mode" where rotation won't happen, it's not a tablet.
+
+5.  If the vendor that made the computer reports to Windows that it supports
+    "convertible slate mode" and it is currently operating in "slate mode",
+    it's a tablet.
+
+6.  Otherwise, it's not a tablet.
+
+
+**Table with comparison to Chromium**
+
+The following table shows how Firefox and Chromium respond to various pointer
+queries. The "any-pointer" and "any-hover" columns are not subjective and
+therefore are always either green or red to indicate "pass" or "fail", but the
+"pointer" and "hover" may also be yellow to indicate that it's "open to
+interpretation" because of the aforementioned difficulty in determining the
+"primary pointer".
+
+.. image:: touch_media_queries.png
+    :width: 100%
+
+
+**Related Bugs**
+
+-   Bug 1813979 - For Surface Pro media query "any-pointer: fine" is true only
+    when both the Type Cover and mouse are connected
+
+-   Bug 1747942 - Incorrect CSS media query matches for pointer, any-pointer,
+    hover and any-hover on Surface Laptop
+
+-   Bug 1528441 - @media (hover) and (any-hover) does not work on Firefox 64/65
+    where certain dual inputs are present
+
+-   Bug 1697294 - Content processes unable to detect Windows 10 Tablet Mode
+
+-   Bug 1806259 - CSS media queries wrongly detect a Win10 desktop computer
+    with a mouse and a touchscreen, as a device with no mouse (hover: none)
+    and a touchscreen (pointer: coarse)
+
+
+Web Events
+=====================
+
+The pen stylus worked well on all tested systems -- The correct pointer events
+were fired in the correct order, and mouse events were properly simulated in
+case the default behavior was allowed.
+
+The touchscreen input was less reliable. On the Dell XPS 15, the
+"Pointer Events" were flawless, but the "Touch Events" were missing
+an important step: the ``touchstart`` and ``touchmove`` messages were sent just
+fine, but Firefox never sends the ``touchend`` message! (Hopefully that isn't
+too difficult to fix!)
+
+Unfortunately, everything really falls apart on the Surface Pro using the
+touchscreen -- neither the "Pointer Events" nor the "Touch Events" fire at all!
+Instead, the touch is completely absorbed by pan and zoom gestures, and nothing
+is sent to the web page. The website's request for ``touch-action: none`` is
+ignored, and the web page is never given any opportunity to call
+``Event.preventDefault()`` to cancel the pan/zoom behavior.
+
+
+Operating System Interfaces
+================================
+
+As was discussed above, Windows has multiple input APIs that were each
+introduced in newer version of Windows to handle devices that were not
+well-served by existing APIs.
+
+Backward compatibility with applications designed against older APIs is
+realized when applications call the default event handler (``DefWindowProc``)
+upon receiving an event type that they don't recognize (which is what apps have
+always been instructed to do if they receive events they don't recognize).
+The unrecognized newer events will be translated by the default event handler
+into older events and sent back to the application. A very old application may
+have this process repeat through several generations of APIs until it finally
+sees events that it recognizes.
+
+Firefox currently uses a mix of the older and newer APIs, which complicates
+the input handling logic and may be responsible for some of the
+difficult-to-explain bugs that we see reported by users.
+
+Here is an explanation of the codepaths Firefox uses to handle pointer input:
+
+1.  Firefox handles the ``WM_POINTER[LEAVE|DOWN|UP|UPDATE]`` messages if the
+    input device is a tablet pen and an Asynchronous Pan and Zoom (APZ)
+    compositor is available. Note that this already may not be ideal, as
+    Microsoft warns (`here <https://learn.microsoft.com/en-us/windows/win32/inputmsg/wm-pointercapturechanged>`__)
+    that handling some pointer messages and passing other pointer messages to
+    ``DefWindowProc`` has unspecified behavior (meaning that Win32 may do
+    something unexpected or nonsensical).
+
+    If the above criteria aren't met, Firefox will call ``DefWindowProc``, which
+    will re-post the pointer messages as either touch messages or mouse
+    messages.
+
+2.  If DirectManipulation is being used for APZ, it will output the
+    ``WM_POINTERCAPTURECHANGED`` if it detects a pan or zoom gesture it can
+    handle. It will then handle the rest of the gesture itself.
+
+    DirectManipulation is used for all top-level and popup windows as long as
+    it isn't disabled via the ``apz.allow_zooming``,
+    ``apz.windows.use_direct_manipulation``, or
+    ``apz.windows.force_disable_direct_manipulation`` prefs.
+
+3.  If the pointing device is touch, the next action depends on
+    whether an Asynchronous Pan and Zoom (APZ) compositor is available. If it
+    is, the window will have been registered using ``RegisterTouchWindow``, and
+    Firefox will receive ``WM_TOUCH`` messages, which will be sent to the
+    "Touch Event" API and handled directly by the APZ compositor.
+
+    If there is no APZ compositor, it will instead be received as a
+    ``WM_GESTURE`` message or a mouse message, depending on the movement. Note
+    that these will be more basic gestures, like tap-and-hold.
+
+4.  If none of the above apply, the message will be converted into standard
+    ``WM_MOUSExxx`` messages via a call to ``DefWindowProc``.
+
+
+================================================================================
+Discussion
+================================================================================
+
+Here is where some of the outstanding thoughts or questions can be listed.
+This can be updated as more questions come about and (hopefully) as answers to
+questions become apparent.
+
+CSS "pointer" Media Queries
+===============================
+
+-   The logic for the ``any-pointer`` and ``any-hover`` queries are objectively
+    incorrect and should be rewritten altogether. That is not as
+    big of a job as it sounds, as the code is fairly straightforward and
+    self-contained. (Note: Improvements have already been made in
+    `Bug 1813979 <https://bugzilla.mozilla.org/show_bug.cgi?id=1813979>`__)
+
+-   There are a few behaviors for ``pointer`` and ``hover`` that are
+    objectively wrong (such as reporting a ``coarse`` pointer when the
+    Surface Pro is docked with a touchpad). Those should be fixable with a
+    code change similar to the previous bullet.
+
+-   Do we want to continue to use only machine configuration to decide what
+    the "primary" pointer is, or do we also want to incorporate user intent
+    into the algorithm? Or, alternatively:
+
+    1.  Do we create a way for the user to override? For example, a "Drawing
+        Mode" button if a tablet digitizer is sensed.
+
+    2.  Do we attempt to change automatically in response to user action?
+
+        -   An example was used above of a docked Surface Pro computer, where
+            the user may use the keyboard and touchpad for a while, then perhaps
+            tuck that behind and use the device as a touchscreen, and then
+            perhaps draw on it with a tablet stylus.
+
+        -   We would need to be careful to avoid careless "popping" or
+            "oscillating" if we react too quickly to changing input types.
+
+-   On a separate-but-related note, the `W3C suggested <https://www.w3.org/TR/mediaqueries-5/#descdef-media-pointer>`__
+    that it might be beneficial to allow users to at-least disable all
+    reporting of ``fine`` pointing devices for users who may have a disability
+    that prevents them from being able to click small objects, even with a fine
+    pointing device.
+
+
+Pan-and-Zoom, Inertia, Overscroll, and Elastic Bounce
+=========================================================
+
+-   Inertia, overscroll, and elastic bounce are just plain broken on the
+    Surface Pro. That should definitely be investigated.
+
+-   We can see from the video below that Microsoft Edge has quite a bit more
+    overscroll and a more elastic bounce than Firefox does, and it also
+    allows elastic bounce in directions that the page itself doesn't scroll.
+
+    Edge's way seems more similar to the user experience I'd expect from using
+    Firefox on an iPhone or Android device. Perhaps we should consider
+    following suit?
+
+    (`Link to video <https://drive.google.com/file/d/14XVLT6CNn2RaXcHHCRIrQmRwoMYjj6fu/view?usp=sharing>`__)
+
+
+Web Events
+==============
+
+-   It's worth investigating why the ``touchend`` message never seems
+    to be sent by Firefox on any tested devices.
+
+-   It's very disappointing that neither the Pointer Events API nor the
+    Touch Events API works at all on Firefox on the Surface Pro. That should
+    be investigated very soon!
+
+
+Operating System Interfaces
+================================
+
+-   With the upcoming sun-setting of Windows 7 support, Firefox has an
+    opportunity to revisit the implementation of our input handling and try to
+    simplify our codepaths and eliminate some of the workarounds that exist to
+    handle some of these complex interactions, as well as fix entire classes of
+    bugs - both reported and unreported - that currently exist as a result.
+
+-   Does it make sense to combine the touchscreen and pen handling together
+    and use the ``WM_POINTERXXX`` messages for both?
+
+    -   This would eliminate the need to handle the ``WM_TOUCH`` and
+        ``WM_GESTURE`` messages at all.
+
+    -   Note that there is precedent for this, as  `GTK <https://gitlab.gnome.org/GNOME/gtk/-/merge_requests/1563>`__
+        has already done so. It appears that `Blender <https://archive.blender.org/developer/D7660>`__
+        has plans to move toward this as well.
+
+    -   Tablet pens seemed to do very well in most of the testing,
+        and they are also the part of the code that mainly exercises the
+        ``WM_POINTERXXX`` codepaths. That may imply increased reliability in
+        that codepath?
+
+    -   The Pointer APIs also have good device simulation for integration
+        testing.
+
+    -   Would we also want to roll mouse handling into it using the
+        `EnableMouseInPointer <https://learn.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-enablemouseinpointer>` __
+        call? That would allow us to also get rid of handling
+        ``WM_MOUSE[MOVE/WHEEL/HWHEEL]`` and ``WM_[LRM]BUTTON[UP|DOWN]``
+        messages. Truly one codepath (with a few minor branches) to rule them
+        all!
+
+    -   Nick Rishel sent `this link <http://the-witness.net/news/2012/10/wm_touch-is-totally-bananas/>`__
+        that details the troubles that the developers of The Witness (a video
+        game) ran into when using the ``WM_TOUCH`` API. It argues that the API
+        is poorly-designed, and advises that if Windows 7 support is not
+        needed, the API should be avoided.
+
+-   Should we exclusively use DirectManipulation for Pan/Zoom?
+
+    -   Multitouch touchpads bypass all of the ``WM_POINTER`` machinery
+        for anything gesture-related and directly send their messages to
+        DirectManipulation. We then "capture" all the DirectManipulation events
+        and pump them into our events pipeline, as explained above.
+
+    -   DirectManipulation also handles "overscroll + elastic bounce" in a way
+        that aligns with Windows look-and-feel.
+
+    -   Perhaps it makes sense to just use DirectManipulation for all APZ
+        handling and eliminate any attempt at handling this through other
+        codepaths.
+
+High-Frequency Input
+================================
+
+"High-Frequency Input" refers to the ability for an app to be able to still
+perceive input events despite them happening at a rate faster than the app
+itself actually handles them.
+
+Consider a mouse that moves through several points: "A->B->C->D->E". If the
+application processes input when the mouse is at "A" and doesn't poll again
+until the mouse is at point "E", the default behavior of all modern operating
+systems is to "coalesce" these events and simply report "A->E". This is fine
+for the majority of use cases, but certain workloads (such as digital
+handwriting and video games) can benefit from knowing the complete path that
+was taken to get from the start point to the end point.
+
+Generally, solutions to this involve the operating system keeping a history of
+pointer movements that can be retrieved through an API. For example,
+Android provides the `MotionEvent <https://developer.android.com/reference/android/view/MotionEvent.html>`__
+API that batches historal movements.
+
+Unfortunately, the APIs to do this in Windows are terribly broken. As
+`this blog <https://blog.getpaint.net/2019/11/14/paint-net-4-2-6-alpha-build-7258/>`__
+makes clear, `GetMouseMovePointsEx <https://docs.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-getmousemovepointsex>`__
+has so many issues that they had to remove its usage from their program because
+of the burden. That same blog entry also details that the newer Pointer API has
+the `GetPointerInfoHistory <https://docs.microsoft.com/en-us/windows/win32/api/winuser/nf-winuser-getpointerinfohistory>`__
+that is *supposed* to support tracking pointer history, but it only ever tracks
+a single entry!
+
+Perhaps luckily, there is currently no web standard for high-frequency input,
+although it `has been asked about in the past <https://lists.w3.org/Archives/Public/public-pointer-events/2014AprJun/0057.html>`__.
+
+If such a standard was ever created, it would likely be very difficult for
+Firefox on Windows to support it.
+
+
+DirectManipulation and Pens
+=============================
+
+-   This is a todo item, but it needs to be investigated whether or not
+    DirectManipulation can directly scoop up pen input, or whether it has
+    to be handled by the application (and forwarded to DM if desired).
diff --git a/widget/windows/docs/windows-pointing-device/mouse.jpg b/widget/windows/docs/windows-pointing-device/mouse.jpg
new file mode 100644
index 0000000000..c4fca9ba31
--- /dev/null
+++ b/widget/windows/docs/windows-pointing-device/mouse.jpg
diff --git a/widget/windows/docs/windows-pointing-device/touch_media_queries.png b/widget/windows/docs/windows-pointing-device/touch_media_queries.png
new file mode 100644
index 0000000000..f0de661d7f
--- /dev/null
+++ b/widget/windows/docs/windows-pointing-device/touch_media_queries.png
diff --git a/widget/windows/docs/windows-pointing-device/touchpad.jpg b/widget/windows/docs/windows-pointing-device/touchpad.jpg
new file mode 100644
index 0000000000..1327ec5b1c
--- /dev/null
+++ b/widget/windows/docs/windows-pointing-device/touchpad.jpg
diff --git a/widget/windows/docs/windows-pointing-device/touchscreen.jpg b/widget/windows/docs/windows-pointing-device/touchscreen.jpg
new file mode 100644
index 0000000000..90246ca02e
--- /dev/null
+++ b/widget/windows/docs/windows-pointing-device/touchscreen.jpg
diff --git a/widget/windows/docs/windows-pointing-device/trackpoint.jpg b/widget/windows/docs/windows-pointing-device/trackpoint.jpg
new file mode 100644
index 0000000000..9eae5b5c21
--- /dev/null
+++ b/widget/windows/docs/windows-pointing-device/trackpoint.jpg
diff --git a/widget/windows/docs/windows-pointing-device/vrcontroller.jpg b/widget/windows/docs/windows-pointing-device/vrcontroller.jpg
new file mode 100644
index 0000000000..20f2e90bfe
--- /dev/null
+++ b/widget/windows/docs/windows-pointing-device/vrcontroller.jpg
diff --git a/widget/windows/docs/windows-pointing-device/wacom_tablet.png b/widget/windows/docs/windows-pointing-device/wacom_tablet.png
new file mode 100644
index 0000000000..2bc30a3b4f
--- /dev/null
+++ b/widget/windows/docs/windows-pointing-device/wacom_tablet.png
diff --git a/widget/windows/filedialog/PWinFileDialog.ipdl b/widget/windows/filedialog/PWinFileDialog.ipdl
new file mode 100644
index 0000000000..812db7e103
--- /dev/null
+++ b/widget/windows/filedialog/PWinFileDialog.ipdl
@@ -0,0 +1,32 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set sw=2 ts=8 et ft=ipdl : */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+include WinFileDialogCommandsDefn;
+using mozilla::WindowsHandle from "mozilla/ipc/IPCTypes.h";
+using mozilla::widget::filedialog::FileDialogType from "mozilla/widget/filedialog/WinFileDialogCommands.h";
+
+namespace mozilla {
+namespace widget {
+namespace filedialog {
+
+[ChildProc=Utility]
+protocol PWinFileDialog {
+
+child:
+  // Exactly one Show function should be called per instance. Further calls will
+  // result in IPC failure.
+  //
+  // Each will return `Nothing` iff the operation was canceled by the user.
+
+  async ShowFileDialog(WindowsHandle parentHwnd, FileDialogType type, Command[] commands)
+    returns (Results? results);
+  async ShowFolderDialog(WindowsHandle parentHwnd, Command[] commands)
+    returns (nsString? path);
+};
+
+}  // namespace filedialog
+}  // namespace widget
+}  // namespace mozilla
diff --git a/widget/windows/filedialog/WinFileDialogChild.cpp b/widget/windows/filedialog/WinFileDialogChild.cpp
new file mode 100644
index 0000000000..1a2903f8ec
--- /dev/null
+++ b/widget/windows/filedialog/WinFileDialogChild.cpp
@@ -0,0 +1,110 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/widget/filedialog/WinFileDialogChild.h"
+
+#include <combaseapi.h>
+#include <objbase.h>
+#include <shobjidl.h>
+
+#include "mozilla/Assertions.h"
+#include "mozilla/ipc/ProtocolUtils.h"
+#include "mozilla/widget/filedialog/WinFileDialogCommands.h"
+#include "nsPrintfCString.h"
+
+namespace mozilla::widget::filedialog {
+
+/* extern */ mozilla::LazyLogModule sLogFileDialog("FileDialog");
+
+WinFileDialogChild::WinFileDialogChild() {
+  MOZ_LOG(sLogFileDialog, LogLevel::Info, ("%s %p", __PRETTY_FUNCTION__, this));
+};
+
+WinFileDialogChild::~WinFileDialogChild() {
+  MOZ_LOG(sLogFileDialog, LogLevel::Info, ("%s %p", __PRETTY_FUNCTION__, this));
+};
+
+#define MOZ_ABORT_IF_ALREADY_USED()                                            \
+  do {                                                                         \
+    MOZ_RELEASE_ASSERT(                                                        \
+        !mUsed, "called Show* twice on a single WinFileDialog instance");      \
+    MOZ_LOG(                                                                   \
+        sLogFileDialog, LogLevel::Info,                                        \
+        ("%s %p: first call to a Show* function", __PRETTY_FUNCTION__, this)); \
+    mUsed = true;                                                              \
+  } while (0)
+
+template <size_t N>
+WinFileDialogChild::IPCResult WinFileDialogChild::MakeIpcFailure(
+    HRESULT hr, const char (&what)[N]) {
+  // The crash-report annotator stringifies integer values anyway. We do so
+  // eagerly here to avoid questions about C int/long conversion semantics.
+  nsPrintfCString data("%lu", hr);
+  CrashReporter::AnnotateCrashReport(
+      CrashReporter::Annotation::WindowsFileDialogErrorCode, data);
+
+  return IPC_FAIL(this, what);
+}
+
+#define MOZ_IPC_ENSURE_HRESULT_OK(hr, what)             \
+  do {                                                  \
+    MOZ_LOG(sLogFileDialog, LogLevel::Verbose,          \
+            ("checking HRESULT for %s", what));         \
+    HRESULT const _hr_ = (hr);                          \
+    if (FAILED(_hr_)) {                                 \
+      MOZ_LOG(sLogFileDialog, LogLevel::Error,          \
+              ("HRESULT %8lX while %s", (hr), (what))); \
+      return MakeIpcFailure(_hr_, (what));              \
+    }                                                   \
+  } while (0)
+
+WinFileDialogChild::IPCResult WinFileDialogChild::RecvShowFileDialog(
+    uintptr_t parentHwnd, FileDialogType type, nsTArray<Command> commands,
+    FileResolver&& resolver) {
+  MOZ_ABORT_IF_ALREADY_USED();
+
+  SpawnFilePicker(HWND(parentHwnd), type, std::move(commands))
+      ->Then(
+          GetMainThreadSerialEventTarget(), __PRETTY_FUNCTION__,
+          [resolver = std::move(resolver)](Maybe<Results> const& res) {
+            resolver(res);
+          },
+          [self = RefPtr(this)](HRESULT hr) {
+            // this doesn't need to be returned anywhere; it'll crash the
+            // process as a side effect of construction
+            self->MakeIpcFailure(hr, "SpawnFilePicker");
+          });
+
+  return IPC_OK();
+}
+
+WinFileDialogChild::IPCResult WinFileDialogChild::RecvShowFolderDialog(
+    uintptr_t parentHwnd, nsTArray<Command> commands,
+    FolderResolver&& resolver) {
+  MOZ_ABORT_IF_ALREADY_USED();
+
+  SpawnFolderPicker(HWND(parentHwnd), std::move(commands))
+      ->Then(
+          GetMainThreadSerialEventTarget(), __PRETTY_FUNCTION__,
+          [resolver = std::move(resolver)](Maybe<nsString> const& res) {
+            resolver(res);
+          },
+          [self = RefPtr(this), resolver](HRESULT hr) {
+            // this doesn't need to be returned anywhere; it'll crash the
+            // process as a side effect of construction
+            self->MakeIpcFailure(hr, "SpawnFolderPicker");
+          });
+
+  return IPC_OK();
+}
+
+#undef MOZ_IPC_ENSURE_HRESULT_OK
+
+void WinFileDialogChild::ProcessingError(Result aCode, const char* aReason) {
+  detail::LogProcessingError(sLogFileDialog, this, aCode, aReason);
+}
+
+}  // namespace mozilla::widget::filedialog
diff --git a/widget/windows/filedialog/WinFileDialogChild.h b/widget/windows/filedialog/WinFileDialogChild.h
new file mode 100644
index 0000000000..b0939ce2ed
--- /dev/null
+++ b/widget/windows/filedialog/WinFileDialogChild.h
@@ -0,0 +1,52 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef widget_windows_filedialog_WinFileDialogChild_h__
+#define widget_windows_filedialog_WinFileDialogChild_h__
+
+#include "mozilla/widget/filedialog/PWinFileDialogChild.h"
+
+// forward declaration of native Windows interface-struct
+struct IFileDialog;
+
+namespace mozilla::widget::filedialog {
+
+class WinFileDialogChild : public PWinFileDialogChild {
+ public:
+  using Command = mozilla::widget::filedialog::Command;
+  using IPCResult = mozilla::ipc::IPCResult;
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(WinFileDialogChild, override);
+
+  WinFileDialogChild();
+
+ public:
+  using FileResolver = PWinFileDialogChild::ShowFileDialogResolver;
+  IPCResult RecvShowFileDialog(uintptr_t parentHwnd, FileDialogType,
+                               nsTArray<Command>, FileResolver&&);
+
+  using FolderResolver = PWinFileDialogChild::ShowFolderDialogResolver;
+  IPCResult RecvShowFolderDialog(uintptr_t parentHwnd, nsTArray<Command>,
+                                 FolderResolver&&);
+
+ private:
+  ~WinFileDialogChild();
+
+  void ProcessingError(Result aCode, const char* aReason) override;
+
+  // Defined and used only in WinFileDialogChild.cpp.
+  template <size_t N>
+  IPCResult MakeIpcFailure(HRESULT hr, const char (&what)[N]);
+
+  // This flag properly _should_ be static (_i.e._, per-process) rather than
+  // per-instance; but we can't presently instantiate two separate utility
+  // processes with the same sandbox type, so we have to reuse the existing
+  // utility process if there is one.
+  bool mUsed = false;
+};
+
+}  // namespace mozilla::widget::filedialog
+
+#endif  // widget_windows_filedialog_WinFileDialogChild_h__
diff --git a/widget/windows/filedialog/WinFileDialogCommands.cpp b/widget/windows/filedialog/WinFileDialogCommands.cpp
new file mode 100644
index 0000000000..f0503ab8f0
--- /dev/null
+++ b/widget/windows/filedialog/WinFileDialogCommands.cpp
@@ -0,0 +1,460 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/widget/filedialog/WinFileDialogCommands.h"
+
+#include <type_traits>
+#include <shobjidl.h>
+#include <shtypes.h>
+#include <winerror.h>
+#include "WinUtils.h"
+#include "mozilla/Logging.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/UniquePtrExtensions.h"
+#include "mozilla/WinHeaderOnlyUtils.h"
+#include "mozilla/ipc/ProtocolUtils.h"
+#include "mozilla/ipc/UtilityProcessManager.h"
+#include "mozilla/mscom/ApartmentRegion.h"
+#include "nsThreadUtils.h"
+
+namespace mozilla::widget::filedialog {
+
+// Visitor to apply commands to the dialog.
+struct Applicator {
+  IFileDialog* dialog = nullptr;
+
+  HRESULT Visit(Command const& c) {
+    switch (c.type()) {
+      default:
+      case Command::T__None:
+        return E_INVALIDARG;
+
+      case Command::TSetOptions:
+        return Apply(c.get_SetOptions());
+      case Command::TSetTitle:
+        return Apply(c.get_SetTitle());
+      case Command::TSetOkButtonLabel:
+        return Apply(c.get_SetOkButtonLabel());
+      case Command::TSetFolder:
+        return Apply(c.get_SetFolder());
+      case Command::TSetFileName:
+        return Apply(c.get_SetFileName());
+      case Command::TSetDefaultExtension:
+        return Apply(c.get_SetDefaultExtension());
+      case Command::TSetFileTypes:
+        return Apply(c.get_SetFileTypes());
+      case Command::TSetFileTypeIndex:
+        return Apply(c.get_SetFileTypeIndex());
+    }
+  }
+
+  HRESULT Apply(SetOptions const& c) { return dialog->SetOptions(c.options()); }
+  HRESULT Apply(SetTitle const& c) { return dialog->SetTitle(c.title().get()); }
+  HRESULT Apply(SetOkButtonLabel const& c) {
+    return dialog->SetOkButtonLabel(c.label().get());
+  }
+  HRESULT Apply(SetFolder const& c) {
+    RefPtr<IShellItem> folder;
+    if (SUCCEEDED(SHCreateItemFromParsingName(
+            c.path().get(), nullptr, IID_IShellItem, getter_AddRefs(folder)))) {
+      return dialog->SetFolder(folder);
+    }
+    // graciously accept that the provided path may have been nonsense
+    return S_OK;
+  }
+  HRESULT Apply(SetFileName const& c) {
+    return dialog->SetFileName(c.filename().get());
+  }
+  HRESULT Apply(SetDefaultExtension const& c) {
+    return dialog->SetDefaultExtension(c.extension().get());
+  }
+  HRESULT Apply(SetFileTypes const& c) {
+    std::vector<COMDLG_FILTERSPEC> vec;
+    for (auto const& filter : c.filterList()) {
+      vec.push_back(
+          {.pszName = filter.name().get(), .pszSpec = filter.spec().get()});
+    }
+    return dialog->SetFileTypes(vec.size(), vec.data());
+  }
+  HRESULT Apply(SetFileTypeIndex const& c) {
+    return dialog->SetFileTypeIndex(c.index());
+  }
+};
+
+namespace {
+static HRESULT GetShellItemPath(IShellItem* aItem, nsString& aResultString) {
+  NS_ENSURE_TRUE(aItem, E_INVALIDARG);
+
+  mozilla::UniquePtr<wchar_t, CoTaskMemFreeDeleter> str;
+  HRESULT const hr =
+      aItem->GetDisplayName(SIGDN_FILESYSPATH, getter_Transfers(str));
+  if (SUCCEEDED(hr)) {
+    aResultString.Assign(str.get());
+  }
+  return hr;
+}
+}  // namespace
+
+#define MOZ_ENSURE_HRESULT_OK(call_)            \
+  do {                                          \
+    HRESULT const _tmp_hr_ = (call_);           \
+    if (FAILED(_tmp_hr_)) return Err(_tmp_hr_); \
+  } while (0)
+
+mozilla::Result<RefPtr<IFileDialog>, HRESULT> MakeFileDialog(
+    FileDialogType type) {
+  RefPtr<IFileDialog> dialog;
+
+  CLSID const clsid = type == FileDialogType::Open ? CLSID_FileOpenDialog
+                                                   : CLSID_FileSaveDialog;
+  HRESULT const hr = CoCreateInstance(clsid, nullptr, CLSCTX_INPROC_SERVER,
+                                      IID_IFileDialog, getter_AddRefs(dialog));
+  MOZ_ENSURE_HRESULT_OK(hr);
+
+  return std::move(dialog);
+}
+
+HRESULT ApplyCommands(::IFileDialog* dialog,
+                      nsTArray<Command> const& commands) {
+  Applicator applicator{.dialog = dialog};
+  for (auto const& cmd : commands) {
+    HRESULT const hr = applicator.Visit(cmd);
+    if (FAILED(hr)) {
+      return hr;
+    }
+  }
+  return S_OK;
+}
+
+mozilla::Result<Results, HRESULT> GetFileResults(::IFileDialog* dialog) {
+  FILEOPENDIALOGOPTIONS fos;
+  MOZ_ENSURE_HRESULT_OK(dialog->GetOptions(&fos));
+
+  using widget::WinUtils;
+
+  // Extract which filter type the user selected
+  UINT index;
+  MOZ_ENSURE_HRESULT_OK(dialog->GetFileTypeIndex(&index));
+
+  // single selection
+  if ((fos & FOS_ALLOWMULTISELECT) == 0) {
+    RefPtr<IShellItem> item;
+    MOZ_ENSURE_HRESULT_OK(dialog->GetResult(getter_AddRefs(item)));
+    if (!item) {
+      return Err(E_FAIL);
+    }
+
+    nsAutoString path;
+    MOZ_ENSURE_HRESULT_OK(GetShellItemPath(item, path));
+
+    return Results({path}, index);
+  }
+
+  // multiple selection
+  RefPtr<IFileOpenDialog> openDlg;
+  dialog->QueryInterface(IID_IFileOpenDialog, getter_AddRefs(openDlg));
+  if (!openDlg) {
+    MOZ_ASSERT(false, "a file-save dialog was given FOS_ALLOWMULTISELECT?");
+    return Err(E_UNEXPECTED);
+  }
+
+  RefPtr<IShellItemArray> items;
+  MOZ_ENSURE_HRESULT_OK(openDlg->GetResults(getter_AddRefs(items)));
+  if (!items) {
+    return Err(E_FAIL);
+  }
+
+  nsTArray<nsString> paths;
+
+  DWORD count = 0;
+  MOZ_ENSURE_HRESULT_OK(items->GetCount(&count));
+  for (DWORD idx = 0; idx < count; idx++) {
+    RefPtr<IShellItem> item;
+    MOZ_ENSURE_HRESULT_OK(items->GetItemAt(idx, getter_AddRefs(item)));
+
+    nsAutoString str;
+    MOZ_ENSURE_HRESULT_OK(GetShellItemPath(item, str));
+
+    paths.EmplaceBack(str);
+  }
+
+  return Results(std::move(paths), std::move(index));
+}
+
+mozilla::Result<nsString, HRESULT> GetFolderResults(::IFileDialog* dialog) {
+  RefPtr<IShellItem> item;
+  MOZ_ENSURE_HRESULT_OK(dialog->GetResult(getter_AddRefs(item)));
+  if (!item) {
+    // shouldn't happen -- probably a precondition failure on our part, but
+    // might be due to misbehaving shell extensions?
+    MOZ_ASSERT(false,
+               "unexpected lack of item: was `Show`'s return value checked?");
+    return Err(E_FAIL);
+  }
+
+  // If the user chose a Win7 Library, resolve to the library's
+  // default save folder.
+  RefPtr<IShellLibrary> shellLib;
+  RefPtr<IShellItem> folderPath;
+  MOZ_ENSURE_HRESULT_OK(
+      CoCreateInstance(CLSID_ShellLibrary, nullptr, CLSCTX_INPROC_SERVER,
+                       IID_IShellLibrary, getter_AddRefs(shellLib)));
+
+  if (shellLib && SUCCEEDED(shellLib->LoadLibraryFromItem(item, STGM_READ)) &&
+      SUCCEEDED(shellLib->GetDefaultSaveFolder(DSFT_DETECT, IID_IShellItem,
+                                               getter_AddRefs(folderPath)))) {
+    item.swap(folderPath);
+  }
+
+  // get the folder's file system path
+  nsAutoString str;
+  MOZ_ENSURE_HRESULT_OK(GetShellItemPath(item, str));
+  return str;
+}
+
+#undef MOZ_ENSURE_HRESULT_OK
+
+namespace detail {
+void LogProcessingError(LogModule* aModule, ipc::IProtocol* aCaller,
+                        ipc::HasResultCodes::Result aCode,
+                        const char* aReason) {
+  LogLevel const level = [&]() {
+    switch (aCode) {
+      case ipc::HasResultCodes::MsgProcessed:
+        // Normal operation. (We probably never actually get this code.)
+        return LogLevel::Verbose;
+
+      case ipc::HasResultCodes::MsgDropped:
+        return LogLevel::Verbose;
+
+      default:
+        return LogLevel::Error;
+    }
+  }();
+
+  // Processing errors are sometimes unhelpfully formatted. We can't fix that
+  // directly because the unhelpful formatting has made its way to telemetry
+  // (table `telemetry.socorro_crash`, column `ipc_channel_error`) and is being
+  // aggregated on. :(
+  nsCString reason(aReason);
+  if (reason.Last() == '\n') {
+    reason.Truncate(reason.Length() - 1);
+  }
+
+  if (MOZ_LOG_TEST(aModule, level)) {
+    const char* const side = [&]() {
+      switch (aCaller->GetSide()) {
+        case ipc::ParentSide:
+          return "parent";
+        case ipc::ChildSide:
+          return "child";
+        case ipc::UnknownSide:
+          return "unknown side";
+        default:
+          return "<illegal value>";
+      }
+    }();
+
+    const char* const errorStr = [&]() {
+      switch (aCode) {
+        case ipc::HasResultCodes::MsgProcessed:
+          return "Processed";
+        case ipc::HasResultCodes::MsgDropped:
+          return "Dropped";
+        case ipc::HasResultCodes::MsgNotKnown:
+          return "NotKnown";
+        case ipc::HasResultCodes::MsgNotAllowed:
+          return "NotAllowed";
+        case ipc::HasResultCodes::MsgPayloadError:
+          return "PayloadError";
+        case ipc::HasResultCodes::MsgProcessingError:
+          return "ProcessingError";
+        case ipc::HasResultCodes::MsgRouteError:
+          return "RouteError";
+        case ipc::HasResultCodes::MsgValueError:
+          return "ValueError";
+        default:
+          return "<illegal error type>";
+      }
+    }();
+
+    MOZ_LOG(aModule, level,
+            ("%s [%s]: IPC error (%s): %s", aCaller->GetProtocolName(), side,
+             errorStr, reason.get()));
+  }
+
+  if (level == LogLevel::Error) {
+    // kill the child process...
+    if (aCaller->GetSide() == ipc::ParentSide) {
+      // ... which isn't us
+      ipc::UtilityProcessManager::GetSingleton()->CleanShutdown(
+          ipc::SandboxingKind::WINDOWS_FILE_DIALOG);
+    } else {
+      // ... which (presumably) is us
+      CrashReporter::AnnotateCrashReport(
+          CrashReporter::Annotation::ipc_channel_error, reason);
+
+      MOZ_CRASH("IPC error");
+    }
+  }
+}
+
+// Given a (synchronous) Action returning a Result<T, HRESULT>, perform that
+// action on a new single-purpose "File Dialog" thread, with COM initialized as
+// STA. (The thread will be destroyed afterwards.)
+//
+// Returns a Promise which will resolve to T (if the action returns Ok) or
+// reject with an HRESULT (if the action either returns Err or couldn't be
+// performed).
+template <typename Res, typename Action, size_t N>
+RefPtr<Promise<Res>> SpawnFileDialogThread(const char (&where)[N],
+                                           Action action) {
+  RefPtr<nsIThread> thread;
+  {
+    nsresult rv = NS_NewNamedThread("File Dialog", getter_AddRefs(thread),
+                                    nullptr, {.isUiThread = true});
+    if (NS_FAILED(rv)) {
+      return Promise<Res>::CreateAndReject((HRESULT)rv, where);
+    }
+  }
+  // `thread` is single-purpose, and should not perform any additional work
+  // after `action`. Shut it down after we've dispatched that.
+  auto close_thread_ = MakeScopeExit([&]() {
+    auto const res = thread->AsyncShutdown();
+    static_assert(
+        std::is_same_v<uint32_t, std::underlying_type_t<decltype(res)>>);
+    if (NS_FAILED(res)) {
+      MOZ_LOG(sLogFileDialog, LogLevel::Warning,
+              ("thread->AsyncShutdown() failed: res=0x%08" PRIX32,
+               static_cast<uint32_t>(res)));
+    }
+  });
+
+  // our eventual return value
+  RefPtr promise = MakeRefPtr<typename Promise<Res>::Private>(where);
+
+  // alias to reduce indentation depth
+  auto const dispatch = [&](auto closure) {
+    return thread->DispatchToQueue(
+        NS_NewRunnableFunction(where, std::move(closure)),
+        mozilla::EventQueuePriority::Normal);
+  };
+
+  dispatch([thread, promise, where, action = std::move(action)]() {
+    // Like essentially all COM UI components, the file dialog is STA: it must
+    // be associated with a specific thread to create its HWNDs and receive
+    // messages for them. If it's launched from a thread in the multithreaded
+    // apartment (including via implicit MTA), COM will proxy out to the
+    // process's main STA thread, and the file-dialog's modal loop will run
+    // there.
+    //
+    // This of course would completely negate any point in using a separate
+    // thread, since behind the scenes the dialog would still be running on the
+    // process's main thread. In particular, under that arrangement, file
+    // dialogs (and other nested modal loops, like those performed by
+    // `SpinEventLoopUntil`) will resolve in strictly LIFO order, effectively
+    // remaining suspended until all later modal loops resolve.
+    //
+    // To avoid this, we initialize COM as STA, so that it (rather than the main
+    // STA thread) is the file dialog's "home" thread and the IFileDialog's home
+    // apartment.
+
+    mozilla::mscom::STARegion staRegion;
+    if (!staRegion) {
+      MOZ_LOG(sLogFileDialog, LogLevel::Error,
+              ("COM init failed on file dialog thread: hr = %08lx",
+               staRegion.GetHResult()));
+
+      APTTYPE at;
+      APTTYPEQUALIFIER atq;
+      HRESULT const hr = ::CoGetApartmentType(&at, &atq);
+      MOZ_LOG(sLogFileDialog, LogLevel::Error,
+              ("  current COM apartment state: hr = %08lX, APTTYPE = "
+               "%08X, APTTYPEQUALIFIER = %08X",
+               hr, at, atq));
+
+      // If this happens in the utility process, crash so we learn about it.
+      // (TODO: replace this with a telemetry ping.)
+      if (!XRE_IsParentProcess()) {
+        // Preserve relevant data on the stack for later analysis.
+        std::tuple volatile info{staRegion.GetHResult(), hr, at, atq};
+        MOZ_CRASH("Could not initialize COM STA in utility process");
+      }
+
+      // If this happens in the parent process, don't crash; just fall back to a
+      // nested modal loop. This isn't ideal, but it will probably still work
+      // well enough for the common case, wherein no other modal loops are
+      // active.
+      //
+      // (TODO: replace this with a telemetry ping, too.)
+    }
+
+    // Actually invoke the action and report the result.
+    Result<Res, HRESULT> val = action();
+    if (val.isErr()) {
+      promise->Reject(val.unwrapErr(), where);
+    } else {
+      promise->Resolve(val.unwrap(), where);
+    }
+  });
+
+  return promise;
+}
+
+// For F returning `Result<T, E>`, yields the type `T`.
+template <typename F, typename... Args>
+using inner_result_of =
+    typename std::remove_reference_t<decltype(std::declval<F>()(
+        std::declval<Args>()...))>::ok_type;
+
+template <typename ExtractorF,
+          typename RetT = inner_result_of<ExtractorF, IFileDialog*>>
+auto SpawnPickerT(HWND parent, FileDialogType type, ExtractorF&& extractor,
+                  nsTArray<Command> commands) -> RefPtr<Promise<Maybe<RetT>>> {
+  return detail::SpawnFileDialogThread<Maybe<RetT>>(
+      __PRETTY_FUNCTION__,
+      [=, commands = std::move(commands)]() -> Result<Maybe<RetT>, HRESULT> {
+        // On Win10, the picker doesn't support per-monitor DPI, so we create it
+        // with our context set temporarily to system-dpi-aware.
+        WinUtils::AutoSystemDpiAware dpiAwareness;
+
+        RefPtr<IFileDialog> dialog;
+        MOZ_TRY_VAR(dialog, MakeFileDialog(type));
+
+        if (HRESULT const rv = ApplyCommands(dialog, commands); FAILED(rv)) {
+          return mozilla::Err(rv);
+        }
+
+        if (HRESULT const rv = dialog->Show(parent); FAILED(rv)) {
+          if (rv == HRESULT_FROM_WIN32(ERROR_CANCELLED)) {
+            return Result<Maybe<RetT>, HRESULT>(Nothing());
+          }
+          return mozilla::Err(rv);
+        }
+
+        RetT res;
+        MOZ_TRY_VAR(res, extractor(dialog.get()));
+
+        return Some(res);
+      });
+}
+
+}  // namespace detail
+
+RefPtr<Promise<Maybe<Results>>> SpawnFilePicker(HWND parent,
+                                                FileDialogType type,
+                                                nsTArray<Command> commands) {
+  return detail::SpawnPickerT(parent, type, GetFileResults,
+                              std::move(commands));
+}
+
+RefPtr<Promise<Maybe<nsString>>> SpawnFolderPicker(HWND parent,
+                                                   nsTArray<Command> commands) {
+  return detail::SpawnPickerT(parent, FileDialogType::Open, GetFolderResults,
+                              std::move(commands));
+}
+
+}  // namespace mozilla::widget::filedialog
diff --git a/widget/windows/filedialog/WinFileDialogCommands.h b/widget/windows/filedialog/WinFileDialogCommands.h
new file mode 100644
index 0000000000..ca4561a8f2
--- /dev/null
+++ b/widget/windows/filedialog/WinFileDialogCommands.h
@@ -0,0 +1,74 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef widget_windows_filedialog_WinFileDialogCommands_h__
+#define widget_windows_filedialog_WinFileDialogCommands_h__
+
+#include "ipc/EnumSerializer.h"
+#include "mozilla/Logging.h"
+#include "mozilla/MozPromise.h"
+#include "mozilla/ipc/MessageLink.h"
+#include "mozilla/widget/filedialog/WinFileDialogCommandsDefn.h"
+
+// Windows interface types, defined in <shobjidl.h>
+struct IFileDialog;
+struct IFileOpenDialog;
+
+namespace mozilla::widget::filedialog {
+
+extern LazyLogModule sLogFileDialog;
+
+enum class FileDialogType : uint8_t { Open, Save };
+
+// Create a file-dialog of the relevant type. Requires MSCOM to be initialized.
+mozilla::Result<RefPtr<IFileDialog>, HRESULT> MakeFileDialog(FileDialogType);
+
+// Apply the selected commands to the IFileDialog, in preparation for showing
+// it. (The actual showing step is left to the caller.)
+[[nodiscard]] HRESULT ApplyCommands(::IFileDialog*,
+                                    nsTArray<Command> const& commands);
+
+// Extract one or more results from the file-picker dialog.
+//
+// Requires that Show() has been called and has returned S_OK.
+mozilla::Result<Results, HRESULT> GetFileResults(::IFileDialog*);
+
+// Extract the chosen folder from the folder-picker dialog.
+//
+// Requires that Show() has been called and has returned S_OK.
+mozilla::Result<nsString, HRESULT> GetFolderResults(::IFileDialog*);
+
+namespace detail {
+// Log the error. If it's a notable error, kill the child process.
+void LogProcessingError(LogModule* aModule, ipc::IProtocol* aCaller,
+                        ipc::HasResultCodes::Result aCode, const char* aReason);
+
+}  // namespace detail
+
+template <typename R>
+using Promise = MozPromise<R, HRESULT, true>;
+
+// Show a file-picker on another thread in the current process.
+RefPtr<Promise<Maybe<Results>>> SpawnFilePicker(HWND parent,
+                                                FileDialogType type,
+                                                nsTArray<Command> commands);
+
+// Show a folder-picker on another thread in the current process.
+RefPtr<Promise<Maybe<nsString>>> SpawnFolderPicker(HWND parent,
+                                                   nsTArray<Command> commands);
+
+}  // namespace mozilla::widget::filedialog
+
+namespace IPC {
+template <>
+struct ParamTraits<mozilla::widget::filedialog::FileDialogType>
+    : public ContiguousEnumSerializerInclusive<
+          mozilla::widget::filedialog::FileDialogType,
+          mozilla::widget::filedialog::FileDialogType::Open,
+          mozilla::widget::filedialog::FileDialogType::Save> {};
+}  // namespace IPC
+
+#endif  // widget_windows_filedialog_WinFileDialogCommands_h__
diff --git a/widget/windows/filedialog/WinFileDialogCommandsDefn.ipdlh b/widget/windows/filedialog/WinFileDialogCommandsDefn.ipdlh
new file mode 100644
index 0000000000..dd85942f24
--- /dev/null
+++ b/widget/windows/filedialog/WinFileDialogCommandsDefn.ipdlh
@@ -0,0 +1,49 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set sw=2 ts=8 et ft=ipdl : */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+namespace mozilla {
+namespace widget {
+namespace filedialog {
+
+// Commands corresponding to the various functions in IFileDialog (or at least
+// the ones we actually make use of).
+//
+// All commands' semantics are direct parallels of their equivalently-named
+// functions on IFileDialog, with the only changes being those necessary to use
+// IPDLable representation-datatypes. (Thus, e.g., `SetOptions` effectively
+// takes a `FILEOPENDIALOGOPTIONS`, and `SetFileTypeIndex` is 1-based.)
+struct SetOptions          { uint32_t options; };
+struct SetTitle            { nsString title; };
+struct SetOkButtonLabel    { nsString label; };
+struct SetFolder           { nsString path; };
+struct SetFileName         { nsString filename; };
+struct SetDefaultExtension { nsString extension; };
+struct ComDlgFilterSpec    { nsString name; nsString spec; };
+struct SetFileTypes        { ComDlgFilterSpec[] filterList; };
+struct SetFileTypeIndex    { uint32_t index; };
+
+// Union of the above.
+union Command {
+  SetOptions;
+  SetTitle;
+  SetOkButtonLabel;
+  SetFolder;
+  SetFileName;
+  SetDefaultExtension;
+  SetFileTypes;
+  SetFileTypeIndex;
+};
+
+// The results from opening a file dialog. (Note that folder selection only
+// returns an nsString.)
+struct Results {
+  nsString[] paths;
+  uint32_t selectedFileTypeIndex;
+};
+
+} // namespace filedialog
+} // namespace widget
+} // namespace mozilla
diff --git a/widget/windows/filedialog/WinFileDialogParent.cpp b/widget/windows/filedialog/WinFileDialogParent.cpp
new file mode 100644
index 0000000000..2c256a1506
--- /dev/null
+++ b/widget/windows/filedialog/WinFileDialogParent.cpp
@@ -0,0 +1,94 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/widget/filedialog/WinFileDialogParent.h"
+
+#include "mozilla/Logging.h"
+#include "mozilla/Result.h"
+#include "mozilla/SpinEventLoopUntil.h"
+#include "mozilla/ipc/UtilityProcessManager.h"
+#include "nsISupports.h"
+
+namespace mozilla::widget::filedialog {
+
+// Count of currently-open file dialogs (not just open-file dialogs).
+static size_t sOpenDialogActors = 0;
+
+WinFileDialogParent::WinFileDialogParent() {
+  MOZ_LOG(sLogFileDialog, LogLevel::Debug,
+          ("%s %p", __PRETTY_FUNCTION__, this));
+}
+
+WinFileDialogParent::~WinFileDialogParent() {
+  MOZ_LOG(sLogFileDialog, LogLevel::Debug,
+          ("%s %p", __PRETTY_FUNCTION__, this));
+}
+
+PWinFileDialogParent::nsresult WinFileDialogParent::BindToUtilityProcess(
+    mozilla::ipc::UtilityProcessParent* aUtilityParent) {
+  Endpoint<PWinFileDialogParent> parentEnd;
+  Endpoint<PWinFileDialogChild> childEnd;
+  nsresult rv = PWinFileDialog::CreateEndpoints(base::GetCurrentProcId(),
+                                                aUtilityParent->OtherPid(),
+                                                &parentEnd, &childEnd);
+
+  if (NS_FAILED(rv)) {
+    MOZ_ASSERT(false, "Protocol endpoints failure");
+    return NS_ERROR_FAILURE;
+  }
+
+  if (!aUtilityParent->SendStartWinFileDialogService(std::move(childEnd))) {
+    MOZ_ASSERT(false, "SendStartWinFileDialogService failed");
+    return NS_ERROR_FAILURE;
+  }
+
+  if (!parentEnd.Bind(this)) {
+    MOZ_ASSERT(false, "parentEnd.Bind failed");
+    return NS_ERROR_FAILURE;
+  }
+
+  sOpenDialogActors++;
+  return NS_OK;
+}
+
+void WinFileDialogParent::ProcessingError(Result aCode, const char* aReason) {
+  detail::LogProcessingError(sLogFileDialog, this, aCode, aReason);
+}
+
+ProcessProxy::ProcessProxy(RefPtr<WFDP>&& obj)
+    : data(MakeRefPtr<Contents>(std::move(obj))) {}
+
+ProcessProxy::Contents::Contents(RefPtr<WFDP>&& obj) : ptr(std::move(obj)) {}
+
+ProcessProxy::Contents::~Contents() {
+  AssertIsOnMainThread();
+
+  // destroy the actor...
+  ptr->Close();
+
+  // ... and possibly the process
+  if (!--sOpenDialogActors) {
+    StopProcess();
+  }
+}
+
+void ProcessProxy::Contents::StopProcess() {
+  auto const upm = ipc::UtilityProcessManager::GetSingleton();
+  if (!upm) {
+    // This is only possible when the UtilityProcessManager has shut down -- in
+    // which case the file-dialog process has also already been directed to shut
+    // down, and there's nothing we need to do here.
+    return;
+  }
+
+  MOZ_LOG(sLogFileDialog, LogLevel::Debug,
+          ("%s: killing the WINDOWS_FILE_DIALOG process (no more live "
+           "actors)",
+           __PRETTY_FUNCTION__));
+  upm->CleanShutdown(ipc::SandboxingKind::WINDOWS_FILE_DIALOG);
+}
+
+}  // namespace mozilla::widget::filedialog
diff --git a/widget/windows/filedialog/WinFileDialogParent.h b/widget/windows/filedialog/WinFileDialogParent.h
new file mode 100644
index 0000000000..a2c1197c55
--- /dev/null
+++ b/widget/windows/filedialog/WinFileDialogParent.h
@@ -0,0 +1,90 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef widget_windows_filedialog_WinFileDialogParent_h__
+#define widget_windows_filedialog_WinFileDialogParent_h__
+
+#include "mozilla/Assertions.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/MozPromise.h"
+#include "mozilla/ProcInfo.h"
+#include "mozilla/Result.h"
+#include "mozilla/SpinEventLoopUntil.h"
+#include "mozilla/dom/ChromeUtilsBinding.h"
+#include "mozilla/ipc/UtilityProcessParent.h"
+#include "mozilla/widget/filedialog/PWinFileDialogParent.h"
+#include "nsISupports.h"
+#include "nsStringFwd.h"
+
+namespace mozilla::widget::filedialog {
+
+class WinFileDialogParent : public PWinFileDialogParent {
+ public:
+  using UtilityActorName = ::mozilla::UtilityActorName;
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(WinFileDialogParent, override);
+
+ public:
+  WinFileDialogParent();
+  nsresult BindToUtilityProcess(
+      mozilla::ipc::UtilityProcessParent* aUtilityParent);
+
+  UtilityActorName GetActorName() {
+    return UtilityActorName::WindowsFileDialog;
+  }
+
+ private:
+  ~WinFileDialogParent();
+
+  void ProcessingError(Result aCode, const char* aReason) override;
+};
+
+// Proxy for the WinFileDialog process and actor.
+//
+// The IPC subsystem holds a strong reference to all IPC actors, so releasing
+// the last RefPtr for such an actor does not actually cause the actor to be
+// destroyed. Similarly, the UtilityProcessManager owns the host process for an
+// actor, and merely destroying all actors within that host process will not
+// cause it to be reaped.
+//
+// This object, then, acts as a proxy for those objects' lifetimes: when the
+// last reference to `Contents` is released, the necessary explicit cleanup of
+// the actor (and, if possible, the host process) will be performed.
+class ProcessProxy {
+ public:
+  using WFDP = WinFileDialogParent;
+
+  explicit ProcessProxy(RefPtr<WFDP>&& obj);
+  ~ProcessProxy() = default;
+
+  explicit operator bool() const { return data->ptr && data->ptr->CanSend(); }
+  bool operator!() const { return !bool(*this); }
+
+  WFDP& operator*() const { return *data->ptr; }
+  WFDP* operator->() const { return data->ptr; }
+  WFDP* get() const { return data->ptr; }
+
+  ProcessProxy(ProcessProxy const& that) = default;
+  ProcessProxy(ProcessProxy&&) = default;
+
+ private:
+  struct Contents {
+    NS_INLINE_DECL_REFCOUNTING(Contents);
+
+   public:
+    explicit Contents(RefPtr<WFDP>&& obj);
+    RefPtr<WFDP> const ptr;
+
+   private:
+    ~Contents();
+    void StopProcess();
+  };
+  // guaranteed nonnull
+  RefPtr<Contents> data;
+};
+
+}  // namespace mozilla::widget::filedialog
+
+#endif  // widget_windows_filedialog_WinFileDialogParent_h__
diff --git a/widget/windows/filedialog/moz.build b/widget/windows/filedialog/moz.build
new file mode 100644
index 0000000000..d2732faf78
--- /dev/null
+++ b/widget/windows/filedialog/moz.build
@@ -0,0 +1,27 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+IPDL_SOURCES += [
+    "PWinFileDialog.ipdl",
+    "WinFileDialogCommandsDefn.ipdlh",
+]
+
+UNIFIED_SOURCES += [
+    "WinFileDialogChild.cpp",
+    "WinFileDialogCommands.cpp",
+    "WinFileDialogParent.cpp",
+]
+
+EXPORTS.mozilla.widget.filedialog += [
+    "WinFileDialogChild.h",
+    "WinFileDialogCommands.h",
+    "WinFileDialogParent.h",
+]
+
+# needed for IPC header files
+include("/ipc/chromium/chromium-config.mozbuild")
+
+FINAL_LIBRARY = "xul"
diff --git a/widget/windows/metrics.yaml b/widget/windows/metrics.yaml
new file mode 100644
index 0000000000..e9d3b4f5cf
--- /dev/null
+++ b/widget/windows/metrics.yaml
@@ -0,0 +1,58 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# Adding a new metric? We have docs for that!
+# https://firefox-source-docs.mozilla.org/toolkit/components/glean/user/new_definitions_file.html
+
+---
+$schema: moz://mozilla.org/schemas/glean/metrics/2-0-0
+$tags:
+  - 'Core :: Widget: Win32'
+
+file_dialog:
+  fallback:
+    type: event
+    description: >
+      Records the result of an attempt to open and use the out-of-process file
+      dialog when the in-process file-dialog is available as a fallback.
+    metadata:
+      # mostly technical, but includes timing data that may derive from user
+      # interactions
+      data-sensitivity: [technical, interaction]
+    notification_emails:
+      - rkraesig@mozilla.com
+    bugs:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1872397
+    # this event may alternatively be manually expired once bug 1677170 is
+    # closed
+    expires: 135
+    data_reviews:
+      - https://bugzilla.mozilla.org/show_bug.cgi?id=1872397#c7
+    extra_keys:
+      succeeded:
+        type: boolean
+        description: >
+          Whether the out-of-process dialog succeeded or failed. (Note that
+          user-induced cancellation is considered a form of success.)
+      time_remote:
+        type: quantity
+        description: >
+          The time between the out-of-process file dialog's instantiation
+          attempt and its failure, in milliseconds.
+      hresult_remote:
+        type: string
+        description: >
+          The failure code produced by the out-of-process file dialog, formatted
+          as eight hexdigits. Only present when `!succeeded`.
+      time_local:
+        type: quantity
+        description: >
+          The time between the in-process file dialog's instantiation attempt
+          and its conclusion (successfully or otherwise), in milliseconds. Only
+          present when `!succeeded`.
+      hresult_local:
+        type: string
+        description: >
+          The return code produced by the in-process file dialog, formatted as
+          eight hexdigits. Only present when `!succeeded`.
diff --git a/widget/windows/moz.build b/widget/windows/moz.build
new file mode 100644
index 0000000000..f19a46caf1
--- /dev/null
+++ b/widget/windows/moz.build
@@ -0,0 +1,213 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+with Files("**"):
+    BUG_COMPONENT = ("Core", "Widget: Win32")
+    SCHEDULES.exclusive = ["windows"]
+
+with Files("*CompositorWidget*"):
+    BUG_COMPONENT = ("Core", "Graphics")
+
+with Files("*IMEHandler*"):
+    BUG_COMPONENT = ("Core", "DOM: UI Events & Focus Handling")
+
+with Files("*IMMHandler*"):
+    BUG_COMPONENT = ("Core", "DOM: UI Events & Focus Handling")
+
+with Files("*KeyboardLayout*"):
+    BUG_COMPONENT = ("Core", "DOM: UI Events & Focus Handling")
+
+with Files("OSK*"):
+    BUG_COMPONENT = ("Core", "DOM: UI Events & Focus Handling")
+
+with Files("*TSFTextStore*"):
+    BUG_COMPONENT = ("Core", "DOM: UI Events & Focus Handling")
+
+DIRS += [
+    "filedialog",
+]
+
+TEST_DIRS += ["tests"]
+
+EXPORTS += [
+    "nsdefs.h",
+    "WindowHook.h",
+    "WinUtils.h",
+]
+
+EXPORTS.mozilla += [
+    "ShellHeaderOnlyUtils.h",
+    "ToastNotificationHeaderOnlyUtils.h",
+    "UrlmonHeaderOnlyUtils.h",
+    "WindowsConsole.h",
+    "WindowsEventLog.h",
+    "WinHeaderOnlyUtils.h",
+]
+
+EXPORTS.mozilla.widget += [
+    "AudioSession.h",
+    "CompositorWidgetChild.h",
+    "CompositorWidgetParent.h",
+    "InProcessWinCompositorWidget.h",
+    "JumpListBuilder.h",
+    "nsWindowLoggedMessages.h",
+    "WinCompositorWidget.h",
+    "WinCompositorWindowThread.h",
+    "WindowsEMF.h",
+    "WindowsSMTCProvider.h",
+    "WinEventObserver.h",
+    "WinMessages.h",
+    "WinModifierKeyState.h",
+    "WinRegistry.h",
+    "WinTaskbar.h",
+    "WinWindowOcclusionTracker.h",
+]
+
+UNIFIED_SOURCES += [
+    "AudioSession.cpp",
+    "CompositorWidgetChild.cpp",
+    "DirectManipulationOwner.cpp",
+    "GfxInfo.cpp",
+    "IEnumFE.cpp",
+    "IMMHandler.cpp",
+    "JumpListBuilder.cpp",
+    "KeyboardLayout.cpp",
+    "LegacyJumpListItem.cpp",
+    "LSPAnnotator.cpp",
+    "nsAppShell.cpp",
+    "nsClipboard.cpp",
+    "nsColorPicker.cpp",
+    "nsDataObj.cpp",
+    "nsDataObjCollection.cpp",
+    "nsDragService.cpp",
+    "nsLookAndFeel.cpp",
+    "nsNativeDragSource.cpp",
+    "nsNativeDragTarget.cpp",
+    "nsNativeThemeWin.cpp",
+    "nsSound.cpp",
+    "nsToolkit.cpp",
+    "nsUserIdleServiceWin.cpp",
+    "nsUXThemeData.cpp",
+    "nsWindow.cpp",
+    "nsWindowDbg.cpp",
+    "nsWindowGfx.cpp",
+    "nsWindowLoggedMessages.cpp",
+    "nsWindowTaskbarConcealer.cpp",
+    "nsWinGesture.cpp",
+    "OSKTabTipManager.cpp",
+    "OSKVRManager.cpp",
+    "RemoteBackbuffer.cpp",
+    "ScreenHelperWin.cpp",
+    "SystemStatusBar.cpp",
+    "TaskbarPreview.cpp",
+    "TaskbarPreviewButton.cpp",
+    "TaskbarTabPreview.cpp",
+    "TaskbarWindowPreview.cpp",
+    "WidgetTraceEvent.cpp",
+    "WinCompositorWindowThread.cpp",
+    "WindowHook.cpp",
+    "WindowsConsole.cpp",
+    "WinEventObserver.cpp",
+    "WinIMEHandler.cpp",
+    "WinPointerEvents.cpp",
+    "WinRegistry.cpp",
+    "WinTaskbar.cpp",
+    "WinTextEventDispatcherListener.cpp",
+    "WinUtils.cpp",
+    "WinWindowOcclusionTracker.cpp",
+]
+
+# The following files cannot be built in unified mode because of name clashes.
+SOURCES += [
+    "CompositorWidgetParent.cpp",
+    "InProcessWinCompositorWidget.cpp",
+    "LegacyJumpListBuilder.cpp",
+    "MediaKeysEventSourceFactory.cpp",
+    "nsBidiKeyboard.cpp",
+    "nsFilePicker.cpp",
+    "nsSharePicker.cpp",
+    "nsWidgetFactory.cpp",
+    "OSKInputPaneManager.cpp",
+    "WinCompositorWidget.cpp",
+    "WindowsSMTCProvider.cpp",
+    "WindowsUIUtils.cpp",
+    "WinMouseScrollHandler.cpp",
+]
+
+# Needs INITGUID and we don't allow INITGUID in unified sources since bug 970429.
+SOURCES += [
+    "InputDeviceUtils.cpp",
+    "TSFTextStore.cpp",
+]
+
+if CONFIG["NS_PRINTING"]:
+    UNIFIED_SOURCES += [
+        "nsDeviceContextSpecWin.cpp",
+        "nsPrintDialogWin.cpp",
+        "nsPrinterWin.cpp",
+        "nsPrintSettingsServiceWin.cpp",
+        "nsPrintSettingsWin.cpp",
+    ]
+    SOURCES += [
+        "nsPrintDialogUtil.cpp",
+    ]
+
+if CONFIG["MOZ_ENABLE_SKIA_PDF"]:
+    UNIFIED_SOURCES += [
+        "WindowsEMF.cpp",
+    ]
+
+XPCOM_MANIFESTS += [
+    "components.conf",
+]
+
+include("/ipc/chromium/chromium-config.mozbuild")
+
+FINAL_LIBRARY = "xul"
+
+if CONFIG["MOZ_ENABLE_SKIA_PDF"]:
+    LOCAL_INCLUDES += CONFIG["SKIA_INCLUDES"]
+
+LOCAL_INCLUDES += [
+    "/gfx/cairo/cairo/src",
+    "/layout/forms",
+    "/layout/generic",
+    "/layout/style",
+    "/layout/xul",
+    "/toolkit/components/jsoncpp/include",
+    "/toolkit/xre",
+    "/widget",
+    "/widget/headless",
+    "/xpcom/base",
+]
+
+DEFINES["MOZ_UNICODE"] = True
+DEFINES["MOZ_APP_NAME"] = '"%s"' % CONFIG["MOZ_APP_NAME"]
+# Turn `firefox` into `Firefox`.
+DEFINES["MOZ_TOAST_APP_NAME"] = '"%s"' % CONFIG["MOZ_APP_NAME"].title()
+
+for var in ("MOZ_ENABLE_D3D10_LAYER",):
+    if CONFIG[var]:
+        DEFINES[var] = True
+
+USE_LIBS += [
+    "jsoncpp",
+]
+
+OS_LIBS += [
+    "ktmw32",
+    "rpcrt4",
+    "urlmon",
+]
+
+# mingw is missing Windows toast notification definitions.
+if CONFIG["CC_TYPE"] == "clang-cl":
+    SOURCES += [
+        "ToastNotification.cpp",
+        "ToastNotificationHandler.cpp",
+    ]
+
+SPHINX_TREES["/widget/windows"] = "docs"
diff --git a/widget/windows/nsAppShell.cpp b/widget/windows/nsAppShell.cpp
new file mode 100644
index 0000000000..314176766d
--- /dev/null
+++ b/widget/windows/nsAppShell.cpp
@@ -0,0 +1,1000 @@
+/* -*- Mode: c++; tab-width: 2; indent-tabs-mode: nil; -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/Attributes.h"
+#include "mozilla/ScopeExit.h"
+#include "mozilla/ipc/MessageChannel.h"
+#include "mozilla/ipc/WindowsMessageLoop.h"
+#include "nsAppShell.h"
+#include "nsToolkit.h"
+#include "nsThreadUtils.h"
+#include "WinUtils.h"
+#include "WinTaskbar.h"
+#include "WinMouseScrollHandler.h"
+#include "nsWindowDefs.h"
+#include "nsWindow.h"
+#include "nsString.h"
+#include "WinIMEHandler.h"
+#include "mozilla/widget/AudioSession.h"
+#include "mozilla/BackgroundHangMonitor.h"
+#include "mozilla/Hal.h"
+#include "nsIDOMWakeLockListener.h"
+#include "nsIPowerManagerService.h"
+#include "mozilla/ProfilerLabels.h"
+#include "mozilla/StaticPtr.h"
+#include "nsTHashtable.h"
+#include "nsHashKeys.h"
+#include "nsComponentManagerUtils.h"
+#include "ScreenHelperWin.h"
+#include "HeadlessScreenHelper.h"
+#include "mozilla/widget/ScreenManager.h"
+#include "mozilla/Atomics.h"
+#include "mozilla/NativeNt.h"
+#include "mozilla/WindowsProcessMitigations.h"
+
+#include <winternl.h>
+
+#ifdef MOZ_BACKGROUNDTASKS
+#  include "mozilla/BackgroundTasks.h"
+#endif
+
+#if defined(ACCESSIBILITY)
+#  include "mozilla/a11y/Compatibility.h"
+#  include "mozilla/a11y/Platform.h"
+#endif  // defined(ACCESSIBILITY)
+
+using namespace mozilla;
+using namespace mozilla::widget;
+
+#define WAKE_LOCK_LOG(...) \
+  MOZ_LOG(gWinWakeLockLog, mozilla::LogLevel::Debug, (__VA_ARGS__))
+static mozilla::LazyLogModule gWinWakeLockLog("WinWakeLock");
+
+// This wakelock listener is used for Window7 and above.
+class WinWakeLockListener final : public nsIDOMMozWakeLockListener {
+ public:
+  NS_DECL_ISUPPORTS
+  WinWakeLockListener() { MOZ_ASSERT(XRE_IsParentProcess()); }
+
+ private:
+  ~WinWakeLockListener() {
+    ReleaseWakelockIfNeeded(PowerRequestDisplayRequired);
+    ReleaseWakelockIfNeeded(PowerRequestExecutionRequired);
+  }
+
+  void SetHandle(HANDLE aHandle, POWER_REQUEST_TYPE aType) {
+    switch (aType) {
+      case PowerRequestDisplayRequired: {
+        if (!aHandle && mDisplayHandle) {
+          CloseHandle(mDisplayHandle);
+        }
+        mDisplayHandle = aHandle;
+        return;
+      }
+      case PowerRequestExecutionRequired: {
+        if (!aHandle && mNonDisplayHandle) {
+          CloseHandle(mNonDisplayHandle);
+        }
+        mNonDisplayHandle = aHandle;
+        return;
+      }
+      default:
+        MOZ_ASSERT_UNREACHABLE("Invalid request type");
+        return;
+    }
+  }
+
+  HANDLE GetHandle(POWER_REQUEST_TYPE aType) const {
+    switch (aType) {
+      case PowerRequestDisplayRequired:
+        return mDisplayHandle;
+      case PowerRequestExecutionRequired:
+        return mNonDisplayHandle;
+      default:
+        MOZ_ASSERT_UNREACHABLE("Invalid request type");
+        return nullptr;
+    }
+  }
+
+  HANDLE CreateHandle(POWER_REQUEST_TYPE aType) {
+    MOZ_ASSERT(!GetHandle(aType));
+    REASON_CONTEXT context = {0};
+    context.Version = POWER_REQUEST_CONTEXT_VERSION;
+    context.Flags = POWER_REQUEST_CONTEXT_SIMPLE_STRING;
+    context.Reason.SimpleReasonString = RequestTypeLPWSTR(aType);
+    HANDLE handle = PowerCreateRequest(&context);
+    if (!handle) {
+      WAKE_LOCK_LOG("Failed to create handle for %s, error=%lu",
+                    RequestTypeStr(aType), GetLastError());
+      return nullptr;
+    }
+    SetHandle(handle, aType);
+    return handle;
+  }
+
+  LPWSTR RequestTypeLPWSTR(POWER_REQUEST_TYPE aType) const {
+    switch (aType) {
+      case PowerRequestDisplayRequired:
+        return const_cast<LPWSTR>(L"display request");  // -Wwritable-strings
+      case PowerRequestExecutionRequired:
+        return const_cast<LPWSTR>(
+            L"non-display request");  // -Wwritable-strings
+      default:
+        MOZ_ASSERT_UNREACHABLE("Invalid request type");
+        return const_cast<LPWSTR>(L"unknown");  // -Wwritable-strings
+    }
+  }
+
+  const char* RequestTypeStr(POWER_REQUEST_TYPE aType) const {
+    switch (aType) {
+      case PowerRequestDisplayRequired:
+        return "display request";
+      case PowerRequestExecutionRequired:
+        return "non-display request";
+      default:
+        MOZ_ASSERT_UNREACHABLE("Invalid request type");
+        return "unknown";
+    }
+  }
+
+  void RequestWakelockIfNeeded(POWER_REQUEST_TYPE aType) {
+    if (GetHandle(aType)) {
+      WAKE_LOCK_LOG("Already requested lock for %s", RequestTypeStr(aType));
+      return;
+    }
+
+    WAKE_LOCK_LOG("Prepare a wakelock for %s", RequestTypeStr(aType));
+    HANDLE handle = CreateHandle(aType);
+    if (!handle) {
+      WAKE_LOCK_LOG("Failed due to no handle for %s", RequestTypeStr(aType));
+      return;
+    }
+
+    if (PowerSetRequest(handle, aType)) {
+      WAKE_LOCK_LOG("Requested %s lock", RequestTypeStr(aType));
+    } else {
+      WAKE_LOCK_LOG("Failed to request %s lock, error=%lu",
+                    RequestTypeStr(aType), GetLastError());
+      SetHandle(nullptr, aType);
+    }
+  }
+
+  void ReleaseWakelockIfNeeded(POWER_REQUEST_TYPE aType) {
+    if (!GetHandle(aType)) {
+      WAKE_LOCK_LOG("Already released lock for %s", RequestTypeStr(aType));
+      return;
+    }
+
+    WAKE_LOCK_LOG("Prepare to release wakelock for %s", RequestTypeStr(aType));
+    if (!PowerClearRequest(GetHandle(aType), aType)) {
+      WAKE_LOCK_LOG("Failed to release %s lock, error=%lu",
+                    RequestTypeStr(aType), GetLastError());
+      return;
+    }
+    SetHandle(nullptr, aType);
+    WAKE_LOCK_LOG("Released wakelock for %s", RequestTypeStr(aType));
+  }
+
+  NS_IMETHOD Callback(const nsAString& aTopic,
+                      const nsAString& aState) override {
+    WAKE_LOCK_LOG("topic=%s, state=%s", NS_ConvertUTF16toUTF8(aTopic).get(),
+                  NS_ConvertUTF16toUTF8(aState).get());
+    if (!aTopic.EqualsASCII("screen") && !aTopic.EqualsASCII("audio-playing") &&
+        !aTopic.EqualsASCII("video-playing")) {
+      return NS_OK;
+    }
+
+    const bool isNonDisplayLock = aTopic.EqualsASCII("audio-playing");
+    bool requestLock = false;
+    if (isNonDisplayLock) {
+      requestLock = aState.EqualsASCII("locked-foreground") ||
+                    aState.EqualsASCII("locked-background");
+    } else {
+      requestLock = aState.EqualsASCII("locked-foreground");
+    }
+
+    if (isNonDisplayLock) {
+      if (requestLock) {
+        RequestWakelockIfNeeded(PowerRequestExecutionRequired);
+      } else {
+        ReleaseWakelockIfNeeded(PowerRequestExecutionRequired);
+      }
+    } else {
+      if (requestLock) {
+        RequestWakelockIfNeeded(PowerRequestDisplayRequired);
+      } else {
+        ReleaseWakelockIfNeeded(PowerRequestDisplayRequired);
+      }
+    }
+    return NS_OK;
+  }
+
+  // Handle would only exist when we request wakelock successfully.
+  HANDLE mDisplayHandle = nullptr;
+  HANDLE mNonDisplayHandle = nullptr;
+};
+NS_IMPL_ISUPPORTS(WinWakeLockListener, nsIDOMMozWakeLockListener)
+StaticRefPtr<nsIDOMMozWakeLockListener> sWakeLockListener;
+
+static void AddScreenWakeLockListener() {
+  nsCOMPtr<nsIPowerManagerService> sPowerManagerService =
+      do_GetService(POWERMANAGERSERVICE_CONTRACTID);
+  if (sPowerManagerService) {
+    sWakeLockListener = new WinWakeLockListener();
+    sPowerManagerService->AddWakeLockListener(sWakeLockListener);
+  } else {
+    NS_WARNING(
+        "Failed to retrieve PowerManagerService, wakelocks will be broken!");
+  }
+}
+
+static void RemoveScreenWakeLockListener() {
+  nsCOMPtr<nsIPowerManagerService> sPowerManagerService =
+      do_GetService(POWERMANAGERSERVICE_CONTRACTID);
+  if (sPowerManagerService) {
+    sPowerManagerService->RemoveWakeLockListener(sWakeLockListener);
+    sPowerManagerService = nullptr;
+    sWakeLockListener = nullptr;
+  }
+}
+
+class SingleNativeEventPump final : public nsIThreadObserver {
+ public:
+  NS_DECL_THREADSAFE_ISUPPORTS
+  NS_DECL_NSITHREADOBSERVER
+
+  SingleNativeEventPump() {
+    MOZ_ASSERT(!XRE_UseNativeEventProcessing(),
+               "Should only be used when not properly processing events.");
+  }
+
+ private:
+  ~SingleNativeEventPump() {}
+};
+
+NS_IMPL_ISUPPORTS(SingleNativeEventPump, nsIThreadObserver)
+
+NS_IMETHODIMP
+SingleNativeEventPump::OnDispatchedEvent() { return NS_OK; }
+
+NS_IMETHODIMP
+SingleNativeEventPump::OnProcessNextEvent(nsIThreadInternal* aThread,
+                                          bool aMayWait) {
+  MSG msg;
+  bool gotMessage = WinUtils::PeekMessage(&msg, nullptr, 0, 0, PM_REMOVE);
+  if (gotMessage) {
+    ::TranslateMessage(&msg);
+    ::DispatchMessageW(&msg);
+  }
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+SingleNativeEventPump::AfterProcessNextEvent(nsIThreadInternal* aThread,
+                                             bool aMayWait) {
+  return NS_OK;
+}
+
+// RegisterWindowMessage values
+// Native event callback message
+const wchar_t* kAppShellGeckoEventId = L"nsAppShell:EventID";
+UINT sAppShellGeckoMsgId = 0x10001;  // initialize to invalid message ID
+// Taskbar button creation message
+const wchar_t* kTaskbarButtonEventId = L"TaskbarButtonCreated";
+UINT sTaskbarButtonCreatedMsg = 0x10002;  // initialize to invalid message ID
+
+/* static */
+UINT nsAppShell::GetTaskbarButtonCreatedMessage() {
+  return sTaskbarButtonCreatedMsg;
+}
+
+namespace mozilla {
+namespace crashreporter {
+void LSPAnnotate();
+}  // namespace crashreporter
+}  // namespace mozilla
+
+using mozilla::crashreporter::LSPAnnotate;
+
+//-------------------------------------------------------------------------
+
+// Note that since we're on x86-ish processors here, ReleaseAcquire is the
+// semantics that normal loads and stores would use anyway.
+static Atomic<size_t, ReleaseAcquire> sOutstandingNativeEventCallbacks;
+
+/*static*/ LRESULT CALLBACK nsAppShell::EventWindowProc(HWND hwnd, UINT uMsg,
+                                                        WPARAM wParam,
+                                                        LPARAM lParam) {
+  NativeEventLogger eventLogger("AppShell", hwnd, uMsg, wParam, lParam);
+
+  if (uMsg == sAppShellGeckoMsgId) {
+    // The app shell might have been destroyed between this message being
+    // posted and being executed, so be extra careful.
+    if (!sOutstandingNativeEventCallbacks) {
+      return TRUE;
+    }
+
+    nsAppShell* as = reinterpret_cast<nsAppShell*>(lParam);
+    as->NativeEventCallback();
+    --sOutstandingNativeEventCallbacks;
+    return TRUE;
+  }
+
+  LRESULT ret = DefWindowProc(hwnd, uMsg, wParam, lParam);
+  eventLogger.SetResult(ret, false);
+  return ret;
+}
+
+nsAppShell::~nsAppShell() {
+  hal::Shutdown();
+
+  if (mEventWnd) {
+    // DestroyWindow doesn't do anything when called from a non UI thread.
+    // Since mEventWnd was created on the UI thread, it must be destroyed on
+    // the UI thread.
+    SendMessage(mEventWnd, WM_CLOSE, 0, 0);
+  }
+
+  // Cancel any outstanding native event callbacks.
+  sOutstandingNativeEventCallbacks = 0;
+}
+
+NS_IMETHODIMP
+nsAppShell::Observe(nsISupports* aSubject, const char* aTopic,
+                    const char16_t* aData) {
+  if (XRE_IsParentProcess()) {
+    nsCOMPtr<nsIObserverService> obsServ(
+        mozilla::services::GetObserverService());
+
+    if (!strcmp(aTopic, "sessionstore-restoring-on-startup")) {
+      nsWindow::SetIsRestoringSession(true);
+      // Now that we've handled the observer notification, we can remove it
+      obsServ->RemoveObserver(this, "sessionstore-restoring-on-startup");
+      return NS_OK;
+    }
+
+    if (!strcmp(aTopic, "sessionstore-windows-restored")) {
+      nsWindow::SetIsRestoringSession(false);
+      // Now that we've handled the observer notification, we can remove it
+      obsServ->RemoveObserver(this, "sessionstore-windows-restored");
+      return NS_OK;
+    }
+  }
+
+  return nsBaseAppShell::Observe(aSubject, aTopic, aData);
+}
+
+namespace {
+
+// Struct storing the visible, loggable error-state of a Windows thread.
+// Approximately `std:pair(::GetLastError(), ::RtlGetLastNtStatus())`.
+//
+// Uses sentinel values rather than a proper `Maybe` type to simplify
+// minidump-analysis.
+struct WinErrorState {
+  // Last error, as provided by ::GetLastError().
+  DWORD error = ~0;
+  // Last NTSTATUS, as provided by the TIB.
+  NTSTATUS ntStatus = ~0;
+
+ private:
+  // per WINE et al.; stable since NT 3.51
+  constexpr static size_t kLastNtStatusOffset =
+      sizeof(size_t) == 8 ? 0x1250 : 0xbf4;
+
+  static void SetLastNtStatus(NTSTATUS status) {
+    auto* teb = ::NtCurrentTeb();
+    *reinterpret_cast<NTSTATUS*>(reinterpret_cast<char*>(teb) +
+                                 kLastNtStatusOffset) = status;
+  }
+
+  static NTSTATUS GetLastNtStatus() {
+    auto const* teb = ::NtCurrentTeb();
+    return *reinterpret_cast<NTSTATUS const*>(
+        reinterpret_cast<char const*>(teb) + kLastNtStatusOffset);
+  }
+
+ public:
+  // Restore (or just set) the error state of the current thread.
+  static void Apply(WinErrorState const& state) {
+    SetLastNtStatus(state.ntStatus);
+    ::SetLastError(state.error);
+  }
+
+  // Clear the error-state of the current thread.
+  static void Clear() { Apply({.error = 0, .ntStatus = 0}); }
+
+  // Get the error-state of the current thread.
+  static WinErrorState Get() {
+    return WinErrorState{
+        .error = ::GetLastError(),
+        .ntStatus = GetLastNtStatus(),
+    };
+  }
+
+  bool operator==(WinErrorState const& that) const {
+    return this->error == that.error && this->ntStatus == that.ntStatus;
+  }
+
+  bool operator!=(WinErrorState const& that) const { return !operator==(that); }
+};
+
+// Struct containing information about the user atom table. (See
+// DiagnoseUserAtomTable(), below.)
+struct AtomTableInformation {
+  // Number of atoms in use. (Exactly 0x4000 == 16384, if all are.)
+  UINT in_use = 0;
+  // Number of atoms confirmed not in use.
+  UINT free = 0;
+  // Number of atoms which gave errors when checked.
+  UINT errors = 0;
+
+  // Last atom which gave an unexpected error...
+  UINT lastErrorAtom = ~0u;
+  // ... and the error it gave.
+  WinErrorState lastErrorState;
+};
+
+// Return a summary of the state of the atom table.
+MOZ_NEVER_INLINE static AtomTableInformation DiagnoseUserAtomTable() {
+  // Restore error state on exit, for the sake of automated minidump analyses.
+  auto const _restoreErrState =
+      mozilla::MakeScopeExit([oldErrState = WinErrorState::Get()]() {
+        WinErrorState::Apply(oldErrState);
+      });
+
+  AtomTableInformation retval;
+
+  // Expected error-state on failure-return when the atom is assigned, but not
+  // enough space was provided for the full string.
+  constexpr WinErrorState kBufferTooSmall = {
+      .error = ERROR_INSUFFICIENT_BUFFER,
+      .ntStatus = ((NTSTATUS)0xC0000023),  // == STATUS_BUFFER_TOO_SMALL
+  };
+  // Expected error-state on failure-return when the atom is not assigned.
+  constexpr WinErrorState kInvalidAtom = {
+      .error = ERROR_INVALID_HANDLE,
+      .ntStatus = ((NTSTATUS)STATUS_INVALID_HANDLE),
+  };
+
+  // Iterate over only the dynamic portion of the atom table.
+  for (UINT atom = 0xC000; atom <= 0xFFFF; ++atom) {
+    // The actual atom values are PII. Don't acquire them in their entirety, and
+    // don't keep more information about them than is needed.
+    WCHAR buf[2] = {};
+    // USE OF UNDOCUMENTED BEHAVIOR: The user atom table is shared by message
+    // names, window-class names, and clipboard-format names. Only the last has
+    // a documented getter-mechanism.
+    BOOL const ok = ::GetClipboardFormatNameW(atom, buf, 1);
+    WinErrorState const errState = WinErrorState::Get();
+    if (ok || errState == kBufferTooSmall) {
+      ++retval.in_use;
+    } else if (errState == kInvalidAtom) {
+      ++retval.free;
+    } else {
+      // Unexpected error-state.
+      ++retval.errors;
+      retval.lastErrorAtom = atom;
+      retval.lastErrorState = errState;
+    }
+  }
+
+  return retval;
+}
+
+}  // namespace
+
+#if defined(MOZ_DIAGNOSTIC_ASSERT_ENABLED) && defined(_M_X64)
+MOZ_NEVER_INLINE MOZ_NAKED void EnableTrapFlag() {
+  asm volatile(
+      "pushfq;"
+      "orw $0x100,(%rsp);"
+      "popfq;"
+      "retq;");
+}
+
+MOZ_NEVER_INLINE MOZ_NAKED void DisableTrapFlag() { asm volatile("retq;"); }
+
+#  define SSD_MAX_USER32_STEPS 0x1800
+#  define SSD_MAX_ERROR_STATES 0x200
+struct SingleStepData {
+  uint32_t mUser32StepsLog[SSD_MAX_USER32_STEPS]{};
+  WinErrorState mErrorStatesLog[SSD_MAX_ERROR_STATES];
+  uint16_t mUser32StepsAtErrorState[SSD_MAX_ERROR_STATES]{};
+};
+
+struct SingleStepStaticState {
+  SingleStepData* mData{};
+  uintptr_t mUser32Start{};
+  uintptr_t mUser32End{};
+  uint32_t mUser32Steps{};
+  uint32_t mErrorStates{};
+  WinErrorState mLastRecordedErrorState;
+
+  constexpr void Reset() { *this = SingleStepStaticState{}; }
+};
+
+static SingleStepStaticState sSingleStepStaticState{};
+
+LONG SingleStepExceptionHandler(_EXCEPTION_POINTERS* aExceptionInfo) {
+  auto& state = sSingleStepStaticState;
+  if (state.mData &&
+      aExceptionInfo->ExceptionRecord->ExceptionCode == EXCEPTION_SINGLE_STEP) {
+    auto instructionPointer = aExceptionInfo->ContextRecord->Rip;
+    if (instructionPointer == reinterpret_cast<uintptr_t>(&DisableTrapFlag)) {
+      // Stop handling any exception in this handler
+      state.mData = nullptr;
+    } else {
+      // Record data for the current step, if in user32
+      if (state.mUser32Start <= instructionPointer &&
+          instructionPointer < state.mUser32End) {
+        // We record the instruction pointer
+        if (state.mUser32Steps < SSD_MAX_USER32_STEPS) {
+          state.mData->mUser32StepsLog[state.mUser32Steps] =
+              static_cast<uint32_t>(instructionPointer - state.mUser32Start);
+        }
+
+        // We record changes in the error state
+        auto currentErrorState{WinErrorState::Get()};
+        if (currentErrorState != state.mLastRecordedErrorState) {
+          state.mLastRecordedErrorState = currentErrorState;
+
+          if (state.mErrorStates < SSD_MAX_ERROR_STATES) {
+            state.mData->mErrorStatesLog[state.mErrorStates] =
+                currentErrorState;
+            state.mData->mUser32StepsAtErrorState[state.mErrorStates] =
+                state.mUser32Steps;
+          }
+
+          ++state.mErrorStates;
+        }
+
+        ++state.mUser32Steps;
+      }
+
+      // Continue single-stepping
+      aExceptionInfo->ContextRecord->EFlags |= 0x100;
+    }
+    return EXCEPTION_CONTINUE_EXECUTION;
+  }
+  return EXCEPTION_CONTINUE_SEARCH;
+}
+
+enum CSSD_RESULT {
+  CSSD_SUCCESS = 0,
+  CSSD_ERROR_DEBUGGER_PRESENT = 1,
+  CSSD_ERROR_GET_MODULE_HANDLE = 2,
+  CSSD_ERROR_PARSING_USER32 = 3,
+  CSSD_ERROR_ADD_VECTORED_EXCEPTION_HANDLER = 4,
+};
+
+template <typename CallbackToRun, typename PostCollectionCallback>
+[[clang::optnone]] MOZ_NEVER_INLINE CSSD_RESULT
+CollectSingleStepData(CallbackToRun aCallbackToRun,
+                      PostCollectionCallback aPostCollectionCallback) {
+  if (::IsDebuggerPresent()) {
+    return CSSD_ERROR_DEBUGGER_PRESENT;
+  }
+
+  MOZ_DIAGNOSTIC_ASSERT(!sSingleStepStaticState.mData,
+                        "Single-stepping is already active");
+  HANDLE user32 = ::GetModuleHandleW(L"user32.dll");
+  if (!user32) {
+    return CSSD_ERROR_GET_MODULE_HANDLE;
+  }
+
+  nt::PEHeaders user32Headers{user32};
+  auto bounds = user32Headers.GetBounds();
+  if (bounds.isNothing()) {
+    return CSSD_ERROR_PARSING_USER32;
+  }
+
+  SingleStepData singleStepData{};
+
+  sSingleStepStaticState.Reset();
+  sSingleStepStaticState.mUser32Start =
+      reinterpret_cast<uintptr_t>(bounds.ref().begin().get());
+  sSingleStepStaticState.mUser32End =
+      reinterpret_cast<uintptr_t>(bounds.ref().end().get());
+  sSingleStepStaticState.mData = &singleStepData;
+  auto veh = ::AddVectoredExceptionHandler(TRUE, SingleStepExceptionHandler);
+  if (!veh) {
+    sSingleStepStaticState.mData = nullptr;
+    return CSSD_ERROR_ADD_VECTORED_EXCEPTION_HANDLER;
+  }
+
+  EnableTrapFlag();
+  aCallbackToRun();
+  DisableTrapFlag();
+  ::RemoveVectoredExceptionHandler(veh);
+  sSingleStepStaticState.mData = nullptr;
+
+  aPostCollectionCallback();
+
+  return CSSD_SUCCESS;
+}
+#endif  // MOZ_DIAGNOSTIC_ASSERT_ENABLED && _M_X64
+
+// Collect data for bug 1571516. We don't automatically send up `GetLastError`
+// or `GetLastNtStatus` data for beta/release builds, so extract the relevant
+// error values and store them on the stack, where they can be viewed in
+// minidumps -- in fact, do so after each individual API call. This takes the
+// form of various local variables whose initial character is an underscore,
+// most of which are also marked [[maybe_unused]].
+//
+// We tag this function `[[clang::optnone]]` to prevent the compiler from
+// eliding those values as _actually_ unused, as well as to generally simplify
+// the haruspex's task once the minidumps are in. (As this function should be
+// called at most once per process, the minor performance hit is not a concern.)
+//
+[[clang::optnone]] MOZ_NEVER_INLINE nsresult nsAppShell::InitHiddenWindow() {
+  // note the incoming error-state; this may be relevant to errors we get later
+  auto _initialErr [[maybe_unused]] = WinErrorState::Get();
+  // reset the error-state, to avoid ambiguity below
+  WinErrorState::Clear();
+
+  // Diagnostic variable. Only collected in the event of a failure in one of the
+  // functions that attempts to register an atom.
+  AtomTableInformation _atomTableInfo [[maybe_unused]];
+
+  // Attempt to register the window message. On failure, retain the initial
+  // value of `sAppShellGeckoMsgId`.
+  auto const _msgId = ::RegisterWindowMessageW(kAppShellGeckoEventId);
+  if (_msgId) {
+    sAppShellGeckoMsgId = _msgId;
+  }
+  auto const _sAppShellGeckoMsgId [[maybe_unused]] = sAppShellGeckoMsgId;
+  auto const _rwmErr [[maybe_unused]] = WinErrorState::Get();
+  if (!_msgId) _atomTableInfo = DiagnoseUserAtomTable();
+  NS_ASSERTION(sAppShellGeckoMsgId,
+               "Could not register hidden window event message!");
+
+  mLastNativeEventScheduled = TimeStamp::NowLoRes();
+
+  WNDCLASSW wc;
+  HINSTANCE const module = GetModuleHandle(nullptr);
+
+  constexpr const wchar_t* kWindowClass = L"nsAppShell:EventWindowClass";
+  // (Undocumented behavior note: on success, this will specifically be the
+  // window-class atom. We don't rely on this.)
+  BOOL const _gciwRet = ::GetClassInfoW(module, kWindowClass, &wc);
+  auto const _gciwErr [[maybe_unused]] = WinErrorState::Get();
+  WinErrorState::Clear();
+
+  WinErrorState _rcErr [[maybe_unused]];
+  if (!_gciwRet) {
+    wc.style = 0;
+    wc.lpfnWndProc = EventWindowProc;
+    wc.cbClsExtra = 0;
+    wc.cbWndExtra = 0;
+    wc.hInstance = module;
+    wc.hIcon = nullptr;
+    wc.hCursor = nullptr;
+    wc.hbrBackground = (HBRUSH) nullptr;
+    wc.lpszMenuName = (LPCWSTR) nullptr;
+    wc.lpszClassName = kWindowClass;
+
+    ATOM _windowClassAtom = ::RegisterClassW(&wc);
+    _rcErr = WinErrorState::Get();
+
+    if (!_windowClassAtom) _atomTableInfo = DiagnoseUserAtomTable();
+
+#if defined(MOZ_DIAGNOSTIC_ASSERT_ENABLED) && defined(_M_X64)
+    if (!_windowClassAtom) {
+      // Retry with single-step data collection
+      auto cssdResult = CollectSingleStepData(
+          [&wc, &_windowClassAtom]() {
+            _windowClassAtom = ::RegisterClassW(&wc);
+          },
+          [&_windowClassAtom]() {
+            // Crashing here gives access to the single step data on stack
+            MOZ_DIAGNOSTIC_ASSERT(
+                _windowClassAtom,
+                "RegisterClassW for EventWindowClass failed twice");
+          });
+      auto const _cssdErr [[maybe_unused]] = WinErrorState::Get();
+      MOZ_DIAGNOSTIC_ASSERT(
+          cssdResult == CSSD_SUCCESS,
+          "Failed to collect single step data for RegisterClassW");
+      // If we reach this point then somehow the single-stepped call succeeded
+      // and we can proceed
+    }
+#endif  // MOZ_DIAGNOSTIC_ASSERT_ENABLED && _M_X64
+
+    MOZ_DIAGNOSTIC_ASSERT(_windowClassAtom,
+                          "RegisterClassW for EventWindowClass failed");
+    WinErrorState::Clear();
+  }
+
+  mEventWnd = CreateWindowW(kWindowClass, L"nsAppShell:EventWindow", 0, 0, 0,
+                            10, 10, HWND_MESSAGE, nullptr, module, nullptr);
+  auto const _cwErr [[maybe_unused]] = WinErrorState::Get();
+
+#if defined(MOZ_DIAGNOSTIC_ASSERT_ENABLED) && defined(_M_X64)
+  if (!mEventWnd) {
+    // Retry with single-step data collection
+    HWND eventWnd{};
+    auto cssdResult = CollectSingleStepData(
+        [module, &eventWnd]() {
+          eventWnd =
+              CreateWindowW(kWindowClass, L"nsAppShell:EventWindow", 0, 0, 0,
+                            10, 10, HWND_MESSAGE, nullptr, module, nullptr);
+        },
+        [&eventWnd]() {
+          // Crashing here gives access to the single step data on stack
+          MOZ_DIAGNOSTIC_ASSERT(eventWnd,
+                                "CreateWindowW for EventWindow failed twice");
+        });
+    auto const _cssdErr [[maybe_unused]] = WinErrorState::Get();
+    MOZ_DIAGNOSTIC_ASSERT(
+        cssdResult == CSSD_SUCCESS,
+        "Failed to collect single step data for CreateWindowW");
+    // If we reach this point then somehow the single-stepped call succeeded and
+    // we can proceed
+    mEventWnd = eventWnd;
+  }
+#endif  // MOZ_DIAGNOSTIC_ASSERT_ENABLED && _M_X64
+
+  MOZ_DIAGNOSTIC_ASSERT(mEventWnd, "CreateWindowW for EventWindow failed");
+  NS_ENSURE_STATE(mEventWnd);
+
+  return NS_OK;
+}
+
+nsresult nsAppShell::Init() {
+  LSPAnnotate();
+
+  hal::Init();
+
+  if (XRE_IsParentProcess()) {
+    sTaskbarButtonCreatedMsg = ::RegisterWindowMessageW(kTaskbarButtonEventId);
+    NS_ASSERTION(sTaskbarButtonCreatedMsg,
+                 "Could not register taskbar button creation message");
+  }
+
+  // The hidden message window is used for interrupting the processing of native
+  // events, so that we can process gecko events. Therefore, we only need it if
+  // we are processing native events. Disabling this is required for win32k
+  // syscall lockdown.
+  if (XRE_UseNativeEventProcessing()) {
+    if (nsresult rv = this->InitHiddenWindow(); NS_FAILED(rv)) {
+      return rv;
+    }
+  } else if (XRE_IsContentProcess() && !IsWin32kLockedDown()) {
+    // We're not generally processing native events, but still using GDI and we
+    // still have some internal windows, e.g. from calling CoInitializeEx.
+    // So we use a class that will do a single event pump where previously we
+    // might have processed multiple events to make sure any occasional messages
+    // to these windows are processed. This also allows any internal Windows
+    // messages to be processed to ensure the GDI data remains fresh.
+    nsCOMPtr<nsIThreadInternal> threadInt =
+        do_QueryInterface(NS_GetCurrentThread());
+    if (threadInt) {
+      threadInt->SetObserver(new SingleNativeEventPump());
+    }
+  }
+
+  if (XRE_IsParentProcess()) {
+    ScreenManager& screenManager = ScreenManager::GetSingleton();
+    if (gfxPlatform::IsHeadless()) {
+      screenManager.SetHelper(mozilla::MakeUnique<HeadlessScreenHelper>());
+    } else {
+      screenManager.SetHelper(mozilla::MakeUnique<ScreenHelperWin>());
+      ScreenHelperWin::RefreshScreens();
+    }
+
+    nsCOMPtr<nsIObserverService> obsServ(
+        mozilla::services::GetObserverService());
+
+    obsServ->AddObserver(this, "sessionstore-restoring-on-startup", false);
+    obsServ->AddObserver(this, "sessionstore-windows-restored", false);
+  }
+
+  if (!WinUtils::GetTimezoneName(mTimezoneName)) {
+    NS_WARNING("Unable to get system timezone name, timezone may be invalid\n");
+  }
+
+  return nsBaseAppShell::Init();
+}
+
+NS_IMETHODIMP
+nsAppShell::Run(void) {
+  bool wantAudio = true;
+  if (XRE_IsParentProcess()) {
+#ifdef MOZ_BACKGROUNDTASKS
+    if (BackgroundTasks::IsBackgroundTaskMode()) {
+      wantAudio = false;
+    }
+#endif
+    if (MOZ_LIKELY(wantAudio)) {
+      mozilla::widget::StartAudioSession();
+    }
+
+    // Add an observer that disables the screen saver when requested by Gecko.
+    // For example when we're playing video in the foreground tab. Whole firefox
+    // only needs one wakelock instance, so we would only create one listener in
+    // chrome process to prevent requesting unnecessary wakelock.
+    AddScreenWakeLockListener();
+  }
+
+  nsresult rv = nsBaseAppShell::Run();
+
+  if (XRE_IsParentProcess()) {
+    RemoveScreenWakeLockListener();
+
+    if (MOZ_LIKELY(wantAudio)) {
+      mozilla::widget::StopAudioSession();
+    }
+  }
+
+  return rv;
+}
+
+void nsAppShell::DoProcessMoreGeckoEvents() {
+  // Called by nsBaseAppShell's NativeEventCallback() after it has finished
+  // processing pending gecko events and there are still gecko events pending
+  // for the thread. (This can happen if NS_ProcessPendingEvents reached it's
+  // starvation timeout limit.) The default behavior in nsBaseAppShell is to
+  // call ScheduleNativeEventCallback to post a follow up native event callback
+  // message. This triggers an additional call to NativeEventCallback for more
+  // gecko event processing.
+
+  // There's a deadlock risk here with certain internal Windows modal loops. In
+  // our dispatch code, we prioritize messages so that input is handled first.
+  // However Windows modal dispatch loops often prioritize posted messages. If
+  // we find ourselves in a tight gecko timer loop where NS_ProcessPendingEvents
+  // takes longer than the timer duration, NS_HasPendingEvents(thread) will
+  // always be true. ScheduleNativeEventCallback will be called on every
+  // NativeEventCallback callback, and in a Windows modal dispatch loop, the
+  // callback message will be processed first -> input gets starved, dead lock.
+
+  // To avoid, don't post native callback messages from NativeEventCallback
+  // when we're in a modal loop. This gets us back into the Windows modal
+  // dispatch loop dispatching input messages. Once we drop out of the modal
+  // loop, we use mNativeCallbackPending to fire off a final NativeEventCallback
+  // if we need it, which insures NS_ProcessPendingEvents gets called and all
+  // gecko events get processed.
+  if (mEventloopNestingLevel < 2) {
+    OnDispatchedEvent();
+    mNativeCallbackPending = false;
+  } else {
+    mNativeCallbackPending = true;
+  }
+}
+
+void nsAppShell::ScheduleNativeEventCallback() {
+  MOZ_ASSERT(mEventWnd,
+             "We should have created mEventWnd in Init, if this is called.");
+
+  // Post a message to the hidden message window
+  ++sOutstandingNativeEventCallbacks;
+  {
+    MutexAutoLock lock(mLastNativeEventScheduledMutex);
+    // Time stamp this event so we can detect cases where the event gets
+    // dropping in sub classes / modal loops we do not control.
+    mLastNativeEventScheduled = TimeStamp::NowLoRes();
+  }
+  ::PostMessage(mEventWnd, sAppShellGeckoMsgId, 0,
+                reinterpret_cast<LPARAM>(this));
+}
+
+bool nsAppShell::ProcessNextNativeEvent(bool mayWait) {
+  // Notify ipc we are spinning a (possibly nested) gecko event loop.
+  mozilla::ipc::MessageChannel::NotifyGeckoEventDispatch();
+
+  bool gotMessage = false;
+
+  do {
+    MSG msg;
+
+    // For avoiding deadlock between our process and plugin process by
+    // mouse wheel messages, we're handling actually when we receive one of
+    // following internal messages which is posted by native mouse wheel
+    // message handler. Any other events, especially native modifier key
+    // events, should not be handled between native message and posted
+    // internal message because it may make different modifier key state or
+    // mouse cursor position between them.
+    if (mozilla::widget::MouseScrollHandler::IsWaitingInternalMessage()) {
+      gotMessage = WinUtils::PeekMessage(&msg, nullptr, MOZ_WM_MOUSEWHEEL_FIRST,
+                                         MOZ_WM_MOUSEWHEEL_LAST, PM_REMOVE);
+      NS_ASSERTION(gotMessage,
+                   "waiting internal wheel message, but it has not come");
+    }
+
+    if (!gotMessage) {
+      gotMessage = WinUtils::PeekMessage(&msg, nullptr, 0, 0, PM_REMOVE);
+    }
+
+    if (gotMessage) {
+      if (msg.message == WM_QUIT) {
+        ::PostQuitMessage(msg.wParam);
+        Exit();
+      } else {
+        // If we had UI activity we would be processing it now so we know we
+        // have either kUIActivity or kActivityNoUIAVail.
+        mozilla::BackgroundHangMonitor().NotifyActivity();
+
+        if (msg.message >= WM_KEYFIRST && msg.message <= WM_KEYLAST &&
+            IMEHandler::ProcessRawKeyMessage(msg)) {
+          continue;  // the message is consumed.
+        }
+
+#if defined(_X86_)
+        // Store Printer dialog messages for reposting on x86, because on x86
+        // Windows 7 they are not processed by a window procedure, but are
+        // explicitly waited for in the winspool.drv code that will be further
+        // up the stack (winspool!WaitForCompletionMessage). These are
+        // undocumented Windows Message identifiers found in winspool.drv.
+        if (msg.message == 0x5b7a || msg.message == 0x5b7f ||
+            msg.message == 0x5b80 || msg.message == 0x5b81) {
+          mMsgsToRepost.push_back(msg);
+          continue;
+        }
+#endif
+
+        // Windows documentation suggets that WM_SETTINGSCHANGE is the message
+        // to watch for timezone changes, but experimentation showed that it
+        // doesn't fire on changing the timezone, but that WM_TIMECHANGE does,
+        // even if there's no immediate effect on the clock (e.g., changing
+        // from Pacific Daylight at UTC-7 to Arizona at UTC-7).
+        if (msg.message == WM_TIMECHANGE) {
+          // The message may not give us sufficient information to determine
+          // if the timezone changed, so keep track of it ourselves.
+          wchar_t systemTimezone[128];
+          bool getSystemTimeSucceeded =
+              WinUtils::GetTimezoneName(systemTimezone);
+          if (getSystemTimeSucceeded && wcscmp(systemTimezone, mTimezoneName)) {
+            nsBaseAppShell::OnSystemTimezoneChange();
+
+            wcscpy_s(mTimezoneName, 128, systemTimezone);
+          }
+        }
+
+        ::TranslateMessage(&msg);
+        ::DispatchMessageW(&msg);
+      }
+    } else if (mayWait) {
+      // Block and wait for any posted application message
+      mozilla::BackgroundHangMonitor().NotifyWait();
+      {
+        AUTO_PROFILER_LABEL("nsAppShell::ProcessNextNativeEvent::Wait", IDLE);
+        WinUtils::WaitForMessage();
+      }
+    }
+  } while (!gotMessage && mayWait);
+
+  // See DoProcessNextNativeEvent, mEventloopNestingLevel will be
+  // one when a modal loop unwinds.
+  if (mNativeCallbackPending && mEventloopNestingLevel == 1)
+    DoProcessMoreGeckoEvents();
+
+  // Check for starved native callbacks. If we haven't processed one
+  // of these events in NATIVE_EVENT_STARVATION_LIMIT, fire one off.
+  static const mozilla::TimeDuration nativeEventStarvationLimit =
+      mozilla::TimeDuration::FromSeconds(NATIVE_EVENT_STARVATION_LIMIT);
+
+  TimeDuration timeSinceLastNativeEventScheduled;
+  {
+    MutexAutoLock lock(mLastNativeEventScheduledMutex);
+    timeSinceLastNativeEventScheduled =
+        TimeStamp::NowLoRes() - mLastNativeEventScheduled;
+  }
+  if (timeSinceLastNativeEventScheduled > nativeEventStarvationLimit) {
+    ScheduleNativeEventCallback();
+  }
+
+  return gotMessage;
+}
+
+nsresult nsAppShell::AfterProcessNextEvent(nsIThreadInternal* /* unused */,
+                                           bool /* unused */) {
+  if (!mMsgsToRepost.empty()) {
+    for (MSG msg : mMsgsToRepost) {
+      ::PostMessageW(msg.hwnd, msg.message, msg.wParam, msg.lParam);
+    }
+    mMsgsToRepost.clear();
+  }
+  return NS_OK;
+}
diff --git a/widget/windows/nsAppShell.h b/widget/windows/nsAppShell.h
new file mode 100644
index 0000000000..20ea65e834
--- /dev/null
+++ b/widget/windows/nsAppShell.h
@@ -0,0 +1,64 @@
+/* -*- Mode: c++; tab-width: 2; indent-tabs-mode: nil; -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef nsAppShell_h__
+#define nsAppShell_h__
+
+#include "nsBaseAppShell.h"
+#include <windows.h>
+#include <vector>
+#include "mozilla/TimeStamp.h"
+#include "mozilla/Mutex.h"
+
+// The maximum time we allow before forcing a native event callback.
+// In seconds.
+#define NATIVE_EVENT_STARVATION_LIMIT 1
+
+/**
+ * Native Win32 Application shell wrapper
+ */
+class nsAppShell final : public nsBaseAppShell {
+ public:
+  nsAppShell()
+      : mEventWnd(nullptr),
+        mNativeCallbackPending(false),
+        mLastNativeEventScheduledMutex(
+            "nsAppShell::mLastNativeEventScheduledMutex") {}
+  typedef mozilla::TimeStamp TimeStamp;
+  typedef mozilla::Mutex Mutex;
+
+  nsresult Init();
+  void DoProcessMoreGeckoEvents();
+
+  static UINT GetTaskbarButtonCreatedMessage();
+
+  NS_IMETHOD AfterProcessNextEvent(nsIThreadInternal* thread,
+                                   bool eventWasProcessed) final;
+
+ protected:
+  NS_IMETHOD Run() override;
+  NS_IMETHOD Observe(nsISupports* aSubject, const char* aTopic,
+                     const char16_t* aData) override;
+
+  virtual void ScheduleNativeEventCallback();
+  virtual bool ProcessNextNativeEvent(bool mayWait);
+  virtual ~nsAppShell();
+
+  static LRESULT CALLBACK EventWindowProc(HWND, UINT, WPARAM, LPARAM);
+
+ protected:
+  nsresult InitHiddenWindow();
+  HWND mEventWnd;
+  bool mNativeCallbackPending;
+
+  Mutex mLastNativeEventScheduledMutex MOZ_UNANNOTATED;
+  TimeStamp mLastNativeEventScheduled;
+  std::vector<MSG> mMsgsToRepost;
+
+ private:
+  wchar_t mTimezoneName[128];
+};
+
+#endif  // nsAppShell_h__
diff --git a/widget/windows/nsBidiKeyboard.cpp b/widget/windows/nsBidiKeyboard.cpp
new file mode 100644
index 0000000000..87d81d458e
--- /dev/null
+++ b/widget/windows/nsBidiKeyboard.cpp
@@ -0,0 +1,169 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <stdio.h>
+#include "nsBidiKeyboard.h"
+#include "WidgetUtils.h"
+#include "nsIWidget.h"
+#include <tchar.h>
+
+NS_IMPL_ISUPPORTS(nsBidiKeyboard, nsIBidiKeyboard)
+
+nsBidiKeyboard::nsBidiKeyboard() : nsIBidiKeyboard() { Reset(); }
+
+nsBidiKeyboard::~nsBidiKeyboard() {}
+
+NS_IMETHODIMP nsBidiKeyboard::Reset() {
+  mInitialized = false;
+  mHaveBidiKeyboards = false;
+  mLTRKeyboard[0] = '\0';
+  mRTLKeyboard[0] = '\0';
+  mCurrentLocaleName[0] = '\0';
+  return NS_OK;
+}
+
+NS_IMETHODIMP nsBidiKeyboard::IsLangRTL(bool* aIsRTL) {
+  *aIsRTL = false;
+
+  nsresult result = SetupBidiKeyboards();
+  if (NS_FAILED(result)) return result;
+
+  HKL currentLocale;
+
+  currentLocale = ::GetKeyboardLayout(0);
+  *aIsRTL = IsRTLLanguage(currentLocale);
+
+  if (!::GetKeyboardLayoutNameW(mCurrentLocaleName)) return NS_ERROR_FAILURE;
+
+  NS_ASSERTION(*mCurrentLocaleName,
+               "GetKeyboardLayoutName return string length == 0");
+  NS_ASSERTION((wcslen(mCurrentLocaleName) < KL_NAMELENGTH),
+               "GetKeyboardLayoutName return string length >= KL_NAMELENGTH");
+
+  // The language set by the user overrides the default language for that
+  // direction
+  if (*aIsRTL) {
+    wcsncpy(mRTLKeyboard, mCurrentLocaleName, KL_NAMELENGTH);
+    mRTLKeyboard[KL_NAMELENGTH - 1] = '\0';  // null terminate
+  } else {
+    wcsncpy(mLTRKeyboard, mCurrentLocaleName, KL_NAMELENGTH);
+    mLTRKeyboard[KL_NAMELENGTH - 1] = '\0';  // null terminate
+  }
+
+  NS_ASSERTION((wcslen(mRTLKeyboard) < KL_NAMELENGTH),
+               "mLTRKeyboard has string length >= KL_NAMELENGTH");
+  NS_ASSERTION((wcslen(mLTRKeyboard) < KL_NAMELENGTH),
+               "mRTLKeyboard has string length >= KL_NAMELENGTH");
+  return NS_OK;
+}
+
+NS_IMETHODIMP nsBidiKeyboard::GetHaveBidiKeyboards(bool* aResult) {
+  NS_ENSURE_ARG_POINTER(aResult);
+
+  nsresult result = SetupBidiKeyboards();
+  if (NS_FAILED(result)) return result;
+
+  *aResult = mHaveBidiKeyboards;
+  return NS_OK;
+}
+
+// Get the list of keyboard layouts available in the system
+// Set mLTRKeyboard to the first LTR keyboard in the list and mRTLKeyboard to
+// the first RTL keyboard in the list These defaults will be used unless the
+// user explicitly sets something else.
+nsresult nsBidiKeyboard::SetupBidiKeyboards() {
+  if (mInitialized) return mHaveBidiKeyboards ? NS_OK : NS_ERROR_FAILURE;
+
+  int keyboards;
+  HKL far* buf;
+  HKL locale;
+  wchar_t localeName[KL_NAMELENGTH];
+  bool isLTRKeyboardSet = false;
+  bool isRTLKeyboardSet = false;
+
+  // GetKeyboardLayoutList with 0 as first parameter returns the number of
+  // keyboard layouts available
+  keyboards = ::GetKeyboardLayoutList(0, nullptr);
+  if (!keyboards) return NS_ERROR_FAILURE;
+
+  // allocate a buffer to hold the list
+  buf = (HKL far*)malloc(keyboards * sizeof(HKL));
+  if (!buf) return NS_ERROR_OUT_OF_MEMORY;
+
+  // Call again to fill the buffer
+  if (::GetKeyboardLayoutList(keyboards, buf) != keyboards) {
+    free(buf);
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  // Go through the list and pick a default LTR and RTL keyboard layout
+  while (keyboards--) {
+    locale = buf[keyboards];
+    if (IsRTLLanguage(locale)) {
+      _snwprintf(mRTLKeyboard, KL_NAMELENGTH, L"%.*x", KL_NAMELENGTH - 1,
+                 LANGIDFROMLCID((DWORD_PTR)locale));
+      isRTLKeyboardSet = true;
+    } else {
+      _snwprintf(mLTRKeyboard, KL_NAMELENGTH, L"%.*x", KL_NAMELENGTH - 1,
+                 LANGIDFROMLCID((DWORD_PTR)locale));
+      isLTRKeyboardSet = true;
+    }
+  }
+  free(buf);
+  mInitialized = true;
+
+  // If there is not at least one keyboard of each directionality, Bidi
+  // keyboard functionality will be disabled.
+  mHaveBidiKeyboards = (isRTLKeyboardSet && isLTRKeyboardSet);
+  if (!mHaveBidiKeyboards) return NS_ERROR_FAILURE;
+
+  // Get the current keyboard layout and use it for either mRTLKeyboard or
+  // mLTRKeyboard as appropriate. If the user has many keyboard layouts
+  // installed this prevents us from arbitrarily resetting the current
+  // layout (bug 80274)
+  locale = ::GetKeyboardLayout(0);
+  if (!::GetKeyboardLayoutNameW(localeName)) return NS_ERROR_FAILURE;
+
+  NS_ASSERTION(*localeName, "GetKeyboardLayoutName return string length == 0");
+  NS_ASSERTION((wcslen(localeName) < KL_NAMELENGTH),
+               "GetKeyboardLayout return string length >= KL_NAMELENGTH");
+
+  if (IsRTLLanguage(locale)) {
+    wcsncpy(mRTLKeyboard, localeName, KL_NAMELENGTH);
+    mRTLKeyboard[KL_NAMELENGTH - 1] = '\0';  // null terminate
+  } else {
+    wcsncpy(mLTRKeyboard, localeName, KL_NAMELENGTH);
+    mLTRKeyboard[KL_NAMELENGTH - 1] = '\0';  // null terminate
+  }
+
+  NS_ASSERTION(*mRTLKeyboard, "mLTRKeyboard has string length == 0");
+  NS_ASSERTION(*mLTRKeyboard, "mLTRKeyboard has string length == 0");
+
+  return NS_OK;
+}
+
+// Test whether the language represented by this locale identifier is a
+//  right-to-left language, using bit 123 of the Unicode subset bitfield in
+//  the LOCALESIGNATURE
+// See
+// http://msdn.microsoft.com/library/default.asp?url=/library/en-us/intl/unicode_63ub.asp
+bool nsBidiKeyboard::IsRTLLanguage(HKL aLocale) {
+  LOCALESIGNATURE localesig;
+  return (::GetLocaleInfoW(PRIMARYLANGID((DWORD_PTR)aLocale),
+                           LOCALE_FONTSIGNATURE, (LPWSTR)&localesig,
+                           (sizeof(localesig) / sizeof(WCHAR))) &&
+          (localesig.lsUsb[3] & 0x08000000));
+}
+
+// static
+void nsBidiKeyboard::OnLayoutChange() {
+  mozilla::widget::WidgetUtils::SendBidiKeyboardInfoToContent();
+}
+
+// static
+already_AddRefed<nsIBidiKeyboard> nsIWidget::CreateBidiKeyboardInner() {
+  return do_AddRef(new nsBidiKeyboard());
+}
diff --git a/widget/windows/nsBidiKeyboard.h b/widget/windows/nsBidiKeyboard.h
new file mode 100644
index 0000000000..584d4d2dee
--- /dev/null
+++ b/widget/windows/nsBidiKeyboard.h
@@ -0,0 +1,34 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef __nsBidiKeyboard
+#define __nsBidiKeyboard
+#include "nsIBidiKeyboard.h"
+#include <windows.h>
+
+class nsBidiKeyboard : public nsIBidiKeyboard {
+  virtual ~nsBidiKeyboard();
+
+ public:
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIBIDIKEYBOARD
+
+  nsBidiKeyboard();
+
+  static void OnLayoutChange();
+
+ protected:
+  nsresult SetupBidiKeyboards();
+  bool IsRTLLanguage(HKL aLocale);
+
+  bool mInitialized;
+  bool mHaveBidiKeyboards;
+  wchar_t mLTRKeyboard[KL_NAMELENGTH];
+  wchar_t mRTLKeyboard[KL_NAMELENGTH];
+  wchar_t mCurrentLocaleName[KL_NAMELENGTH];
+};
+
+#endif  // __nsBidiKeyboard
diff --git a/widget/windows/nsClipboard.cpp b/widget/windows/nsClipboard.cpp
new file mode 100644
index 0000000000..8783affd1e
--- /dev/null
+++ b/widget/windows/nsClipboard.cpp
@@ -0,0 +1,1472 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsClipboard.h"
+
+#include <shlobj.h>
+#include <intshcut.h>
+
+// shellapi.h is needed to build with WIN32_LEAN_AND_MEAN
+#include <shellapi.h>
+
+#include <functional>
+#include <thread>
+#include <chrono>
+
+#ifdef ACCESSIBILITY
+#  include "mozilla/a11y/Compatibility.h"
+#endif
+#include "mozilla/Logging.h"
+#include "mozilla/ScopeExit.h"
+#include "mozilla/StaticPrefs_clipboard.h"
+#include "mozilla/StaticPrefs_widget.h"
+#include "mozilla/WindowsVersion.h"
+#include "SpecialSystemDirectory.h"
+
+#include "nsArrayUtils.h"
+#include "nsCOMPtr.h"
+#include "nsComponentManagerUtils.h"
+#include "nsDataObj.h"
+#include "nsString.h"
+#include "nsNativeCharsetUtils.h"
+#include "nsIInputStream.h"
+#include "nsITransferable.h"
+#include "nsXPCOM.h"
+#include "nsReadableUtils.h"
+#include "nsUnicharUtils.h"
+#include "nsPrimitiveHelpers.h"
+#include "nsIWidget.h"
+#include "nsWidgetsCID.h"
+#include "nsCRT.h"
+#include "nsNetUtil.h"
+#include "nsIFileProtocolHandler.h"
+#include "nsEscape.h"
+#include "nsIObserverService.h"
+#include "nsMimeTypes.h"
+#include "imgITools.h"
+#include "imgIContainer.h"
+#include "WinUtils.h"
+
+/* static */
+UINT nsClipboard::GetClipboardFileDescriptorFormatA() {
+  static UINT format = ::RegisterClipboardFormatW(CFSTR_FILEDESCRIPTORA);
+  MOZ_ASSERT(format);
+  return format;
+}
+
+/* static */
+UINT nsClipboard::GetClipboardFileDescriptorFormatW() {
+  static UINT format = ::RegisterClipboardFormatW(CFSTR_FILEDESCRIPTORW);
+  MOZ_ASSERT(format);
+  return format;
+}
+
+/* static */
+UINT nsClipboard::GetHtmlClipboardFormat() {
+  static UINT format = ::RegisterClipboardFormatW(L"HTML Format");
+  return format;
+}
+
+/* static */
+UINT nsClipboard::GetCustomClipboardFormat() {
+  static UINT format =
+      ::RegisterClipboardFormatW(L"application/x-moz-custom-clipdata");
+  return format;
+}
+
+//-------------------------------------------------------------------------
+//
+// nsClipboard constructor
+//
+//-------------------------------------------------------------------------
+nsClipboard::nsClipboard()
+    : nsBaseClipboard(mozilla::dom::ClipboardCapabilities(
+          false /* supportsSelectionClipboard */,
+          false /* supportsFindClipboard */,
+          false /* supportsSelectionCache */)) {
+  mWindow = nullptr;
+
+  // Register for a shutdown notification so that we can flush data
+  // to the OS clipboard.
+  nsCOMPtr<nsIObserverService> observerService =
+      do_GetService("@mozilla.org/observer-service;1");
+  if (observerService) {
+    observerService->AddObserver(this, NS_XPCOM_WILL_SHUTDOWN_OBSERVER_ID,
+                                 false);
+  }
+}
+
+//-------------------------------------------------------------------------
+// nsClipboard destructor
+//-------------------------------------------------------------------------
+nsClipboard::~nsClipboard() {}
+
+NS_IMPL_ISUPPORTS_INHERITED(nsClipboard, nsBaseClipboard, nsIObserver)
+
+NS_IMETHODIMP
+nsClipboard::Observe(nsISupports* aSubject, const char* aTopic,
+                     const char16_t* aData) {
+  // This will be called on shutdown.
+  ::OleFlushClipboard();
+  ::CloseClipboard();
+
+  return NS_OK;
+}
+
+//-------------------------------------------------------------------------
+UINT nsClipboard::GetFormat(const char* aMimeStr, bool aMapHTMLMime) {
+  UINT format;
+
+  if (strcmp(aMimeStr, kTextMime) == 0) {
+    format = CF_UNICODETEXT;
+  } else if (strcmp(aMimeStr, kRTFMime) == 0) {
+    format = ::RegisterClipboardFormat(L"Rich Text Format");
+  } else if (strcmp(aMimeStr, kJPEGImageMime) == 0 ||
+             strcmp(aMimeStr, kJPGImageMime) == 0 ||
+             strcmp(aMimeStr, kPNGImageMime) == 0) {
+    format = CF_DIBV5;
+  } else if (strcmp(aMimeStr, kFileMime) == 0 ||
+             strcmp(aMimeStr, kFilePromiseMime) == 0) {
+    format = CF_HDROP;
+  } else if ((strcmp(aMimeStr, kNativeHTMLMime) == 0) ||
+             (aMapHTMLMime && strcmp(aMimeStr, kHTMLMime) == 0)) {
+    format = GetHtmlClipboardFormat();
+  } else if (strcmp(aMimeStr, kCustomTypesMime) == 0) {
+    format = GetCustomClipboardFormat();
+  } else {
+    format = ::RegisterClipboardFormatW(NS_ConvertASCIItoUTF16(aMimeStr).get());
+  }
+
+  return format;
+}
+
+//-------------------------------------------------------------------------
+// static
+nsresult nsClipboard::CreateNativeDataObject(
+    nsITransferable* aTransferable, IDataObject** aDataObj, nsIURI* aUri,
+    MightNeedToFlush* aMightNeedToFlush) {
+  MOZ_ASSERT(aTransferable);
+  if (!aTransferable) {
+    return NS_ERROR_FAILURE;
+  }
+
+  // Create our native DataObject that implements the OLE IDataObject interface
+  RefPtr<nsDataObj> dataObj = new nsDataObj(aUri);
+
+  // Now set it up with all the right data flavors & enums
+  nsresult res =
+      SetupNativeDataObject(aTransferable, dataObj, aMightNeedToFlush);
+  if (NS_SUCCEEDED(res)) {
+    dataObj.forget(aDataObj);
+  }
+  return res;
+}
+
+static nsresult StoreValueInDataObject(nsDataObj* aObj,
+                                       LPCWSTR aClipboardFormat, DWORD value) {
+  HGLOBAL hGlobalMemory = ::GlobalAlloc(GMEM_MOVEABLE, sizeof(DWORD));
+  if (!hGlobalMemory) {
+    return NS_ERROR_OUT_OF_MEMORY;
+  }
+  DWORD* pdw = (DWORD*)::GlobalLock(hGlobalMemory);
+  *pdw = value;
+  ::GlobalUnlock(hGlobalMemory);
+
+  STGMEDIUM stg;
+  stg.tymed = TYMED_HGLOBAL;
+  stg.pUnkForRelease = nullptr;
+  stg.hGlobal = hGlobalMemory;
+
+  FORMATETC fe;
+  SET_FORMATETC(fe, ::RegisterClipboardFormat(aClipboardFormat), 0,
+                DVASPECT_CONTENT, -1, TYMED_HGLOBAL)
+  aObj->SetData(&fe, &stg, TRUE);
+
+  return NS_OK;
+}
+
+//-------------------------------------------------------------------------
+nsresult nsClipboard::SetupNativeDataObject(
+    nsITransferable* aTransferable, IDataObject* aDataObj,
+    MightNeedToFlush* aMightNeedToFlush) {
+  MOZ_ASSERT(aTransferable);
+  MOZ_ASSERT(aDataObj);
+  if (!aTransferable || !aDataObj) {
+    return NS_ERROR_FAILURE;
+  }
+
+  auto* dObj = static_cast<nsDataObj*>(aDataObj);
+  if (aMightNeedToFlush) {
+    *aMightNeedToFlush = MightNeedToFlush::No;
+  }
+
+  // Now give the Transferable to the DataObject
+  // for getting the data out of it
+  dObj->SetTransferable(aTransferable);
+
+  // Get the transferable list of data flavors
+  nsTArray<nsCString> flavors;
+  aTransferable->FlavorsTransferableCanExport(flavors);
+
+  // Walk through flavors that contain data and register them
+  // into the DataObj as supported flavors
+  for (uint32_t i = 0; i < flavors.Length(); i++) {
+    nsCString& flavorStr = flavors[i];
+
+    // When putting data onto the clipboard, we want to maintain kHTMLMime
+    // ("text/html") and not map it to CF_HTML here since this will be done
+    // below.
+    UINT format = GetFormat(flavorStr.get(), false);
+
+    // Now tell the native IDataObject about both our mime type and
+    // the native data format
+    FORMATETC fe;
+    SET_FORMATETC(fe, format, 0, DVASPECT_CONTENT, -1, TYMED_HGLOBAL);
+    dObj->AddDataFlavor(flavorStr.get(), &fe);
+
+    // Do various things internal to the implementation, like map one
+    // flavor to another or add additional flavors based on what's required
+    // for the win32 impl.
+    if (flavorStr.EqualsLiteral(kTextMime)) {
+      // if we find text/plain, also add CF_TEXT, but we can add it for
+      // text/plain as well.
+      FORMATETC textFE;
+      SET_FORMATETC(textFE, CF_TEXT, 0, DVASPECT_CONTENT, -1, TYMED_HGLOBAL);
+      dObj->AddDataFlavor(kTextMime, &textFE);
+      if (aMightNeedToFlush) {
+        *aMightNeedToFlush = MightNeedToFlush::Yes;
+      }
+    } else if (flavorStr.EqualsLiteral(kHTMLMime)) {
+      // if we find text/html, also advertise win32's html flavor (which we will
+      // convert on our own in nsDataObj::GetText().
+      FORMATETC htmlFE;
+      SET_FORMATETC(htmlFE, GetHtmlClipboardFormat(), 0, DVASPECT_CONTENT, -1,
+                    TYMED_HGLOBAL);
+      dObj->AddDataFlavor(kHTMLMime, &htmlFE);
+    } else if (flavorStr.EqualsLiteral(kURLMime)) {
+      // if we're a url, in addition to also being text, we need to register
+      // the "file" flavors so that the win32 shell knows to create an internet
+      // shortcut when it sees one of these beasts.
+      FORMATETC shortcutFE;
+      SET_FORMATETC(shortcutFE,
+                    ::RegisterClipboardFormat(CFSTR_FILEDESCRIPTORA), 0,
+                    DVASPECT_CONTENT, -1, TYMED_HGLOBAL)
+      dObj->AddDataFlavor(kURLMime, &shortcutFE);
+      SET_FORMATETC(shortcutFE,
+                    ::RegisterClipboardFormat(CFSTR_FILEDESCRIPTORW), 0,
+                    DVASPECT_CONTENT, -1, TYMED_HGLOBAL)
+      dObj->AddDataFlavor(kURLMime, &shortcutFE);
+      SET_FORMATETC(shortcutFE, ::RegisterClipboardFormat(CFSTR_FILECONTENTS),
+                    0, DVASPECT_CONTENT, -1, TYMED_HGLOBAL)
+      dObj->AddDataFlavor(kURLMime, &shortcutFE);
+      SET_FORMATETC(shortcutFE, ::RegisterClipboardFormat(CFSTR_INETURLA), 0,
+                    DVASPECT_CONTENT, -1, TYMED_HGLOBAL)
+      dObj->AddDataFlavor(kURLMime, &shortcutFE);
+      SET_FORMATETC(shortcutFE, ::RegisterClipboardFormat(CFSTR_INETURLW), 0,
+                    DVASPECT_CONTENT, -1, TYMED_HGLOBAL)
+      dObj->AddDataFlavor(kURLMime, &shortcutFE);
+    } else if (flavorStr.EqualsLiteral(kPNGImageMime) ||
+               flavorStr.EqualsLiteral(kJPEGImageMime) ||
+               flavorStr.EqualsLiteral(kJPGImageMime) ||
+               flavorStr.EqualsLiteral(kGIFImageMime) ||
+               flavorStr.EqualsLiteral(kNativeImageMime)) {
+      // if we're an image, register the native bitmap flavor
+      FORMATETC imageFE;
+      // Add DIBv5
+      SET_FORMATETC(imageFE, CF_DIBV5, 0, DVASPECT_CONTENT, -1, TYMED_HGLOBAL)
+      dObj->AddDataFlavor(flavorStr.get(), &imageFE);
+      // Add DIBv3
+      SET_FORMATETC(imageFE, CF_DIB, 0, DVASPECT_CONTENT, -1, TYMED_HGLOBAL)
+      dObj->AddDataFlavor(flavorStr.get(), &imageFE);
+    } else if (flavorStr.EqualsLiteral(kFilePromiseMime)) {
+      // if we're a file promise flavor, also register the
+      // CFSTR_PREFERREDDROPEFFECT format.  The data object
+      // returns a value of DROPEFFECTS_MOVE to the drop target
+      // when it asks for the value of this format.  This causes
+      // the file to be moved from the temporary location instead
+      // of being copied.  The right thing to do here is to call
+      // SetData() on the data object and set the value of this format
+      // to DROPEFFECTS_MOVE on this particular data object.  But,
+      // since all the other clipboard formats follow the model of setting
+      // data on the data object only when the drop object calls GetData(),
+      // I am leaving this format's value hard coded in the data object.
+      // We can change this if other consumers of this format get added to this
+      // codebase and they need different values.
+      FORMATETC shortcutFE;
+      SET_FORMATETC(shortcutFE,
+                    ::RegisterClipboardFormat(CFSTR_PREFERREDDROPEFFECT), 0,
+                    DVASPECT_CONTENT, -1, TYMED_HGLOBAL)
+      dObj->AddDataFlavor(kFilePromiseMime, &shortcutFE);
+    }
+  }
+
+  if (!mozilla::StaticPrefs::
+          clipboard_copyPrivateDataToClipboardCloudOrHistory()) {
+    // Let Clipboard know that data is sensitive and must not be copied to
+    // the Cloud Clipboard, Clipboard History and similar.
+    // https://docs.microsoft.com/en-us/windows/win32/dataxchg/clipboard-formats#cloud-clipboard-and-clipboard-history-formats
+    if (aTransferable->GetIsPrivateData()) {
+      nsresult rv =
+          StoreValueInDataObject(dObj, TEXT("CanUploadToCloudClipboard"), 0);
+      NS_ENSURE_SUCCESS(rv, rv);
+      rv =
+          StoreValueInDataObject(dObj, TEXT("CanIncludeInClipboardHistory"), 0);
+      NS_ENSURE_SUCCESS(rv, rv);
+      rv = StoreValueInDataObject(
+          dObj, TEXT("ExcludeClipboardContentFromMonitorProcessing"), 0);
+      NS_ENSURE_SUCCESS(rv, rv);
+    }
+  }
+
+  return NS_OK;
+}
+
+// See methods listed at
+// <https://docs.microsoft.com/en-us/windows/win32/api/objidl/nn-objidl-idataobject#methods>.
+static void IDataObjectMethodResultToString(const HRESULT aHres,
+                                            nsACString& aResult) {
+  switch (aHres) {
+    case E_INVALIDARG:
+      aResult = "E_INVALIDARG";
+      break;
+    case E_UNEXPECTED:
+      aResult = "E_UNEXPECTED";
+      break;
+    case E_OUTOFMEMORY:
+      aResult = "E_OUTOFMEMORY";
+      break;
+    case DV_E_LINDEX:
+      aResult = "DV_E_LINDEX";
+      break;
+    case DV_E_FORMATETC:
+      aResult = "DV_E_FORMATETC";
+      break;
+    case DV_E_TYMED:
+      aResult = "DV_E_TYMED";
+      break;
+    case DV_E_DVASPECT:
+      aResult = "DV_E_DVASPECT";
+      break;
+    case OLE_E_NOTRUNNING:
+      aResult = "OLE_E_NOTRUNNING";
+      break;
+    case STG_E_MEDIUMFULL:
+      aResult = "STG_E_MEDIUMFULL";
+      break;
+    case DV_E_CLIPFORMAT:
+      aResult = "DV_E_CLIPFORMAT";
+      break;
+    case S_OK:
+      aResult = "S_OK";
+      break;
+    default:
+      // Explicit template instantiaton, because otherwise the call is
+      // ambiguous.
+      constexpr int kRadix = 16;
+      aResult = IntToCString<int32_t>(aHres, kRadix);
+      break;
+  }
+}
+
+// See
+// <https://docs.microsoft.com/en-us/windows/win32/api/ole2/nf-ole2-olegetclipboard>.
+static void OleGetClipboardResultToString(const HRESULT aHres,
+                                          nsACString& aResult) {
+  switch (aHres) {
+    case S_OK:
+      aResult = "S_OK";
+      break;
+    case CLIPBRD_E_CANT_OPEN:
+      aResult = "CLIPBRD_E_CANT_OPEN";
+      break;
+    case CLIPBRD_E_CANT_CLOSE:
+      aResult = "CLIPBRD_E_CANT_CLOSE";
+      break;
+    default:
+      // Explicit template instantiaton, because otherwise the call is
+      // ambiguous.
+      constexpr int kRadix = 16;
+      aResult = IntToCString<int32_t>(aHres, kRadix);
+      break;
+  }
+}
+
+// See
+// <https://docs.microsoft.com/en-us/windows/win32/api/ole2/nf-ole2-olegetclipboard>.
+static void LogOleGetClipboardResult(const HRESULT aHres) {
+  if (MOZ_CLIPBOARD_LOG_ENABLED()) {
+    nsAutoCString hresString;
+    OleGetClipboardResultToString(aHres, hresString);
+    MOZ_CLIPBOARD_LOG("OleGetClipboard result: %s", hresString.get());
+  }
+}
+
+// See
+// <https://docs.microsoft.com/en-us/windows/win32/api/ole2/nf-ole2-olesetclipboard>.
+static void OleSetClipboardResultToString(HRESULT aHres, nsACString& aResult) {
+  switch (aHres) {
+    case S_OK:
+      aResult = "S_OK";
+      break;
+    case CLIPBRD_E_CANT_OPEN:
+      aResult = "CLIPBRD_E_CANT_OPEN";
+      break;
+    case CLIPBRD_E_CANT_EMPTY:
+      aResult = "CLIPBRD_E_CANT_EMPTY";
+      break;
+    case CLIPBRD_E_CANT_CLOSE:
+      aResult = "CLIPBRD_E_CANT_CLOSE";
+      break;
+    case CLIPBRD_E_CANT_SET:
+      aResult = "CLIPBRD_E_CANT_SET";
+      break;
+    default:
+      // Explicit template instantiaton, because otherwise the call is
+      // ambiguous.
+      constexpr int kRadix = 16;
+      aResult = IntToCString<int32_t>(aHres, kRadix);
+      break;
+  }
+}
+
+// See
+// <https://docs.microsoft.com/en-us/windows/win32/api/ole2/nf-ole2-olesetclipboard>.
+static void LogOleSetClipboardResult(const HRESULT aHres) {
+  if (MOZ_CLIPBOARD_LOG_ENABLED()) {
+    nsAutoCString hresString;
+    OleSetClipboardResultToString(aHres, hresString);
+    MOZ_CLIPBOARD_LOG("OleSetClipboard result: %s", hresString.get());
+  }
+}
+
+template <typename Function, typename LogFunction, typename... Args>
+static HRESULT RepeatedlyTry(Function aFunction, LogFunction aLogFunction,
+                             Args... aArgs) {
+  // These are magic values based on local testing. They are chosen not higher
+  // to avoid jank (<https://developer.mozilla.org/en-US/docs/Glossary/Jank>).
+  // When changing them, be careful.
+  static constexpr int kNumberOfTries = 3;
+  static constexpr int kDelayInMs = 3;
+
+  HRESULT hres;
+  for (int i = 0; i < kNumberOfTries; ++i) {
+    hres = aFunction(aArgs...);
+    aLogFunction(hres);
+
+    if (hres == S_OK) {
+      break;
+    }
+
+    std::this_thread::sleep_for(std::chrono::milliseconds(kDelayInMs));
+  }
+
+  return hres;
+}
+
+// Other apps can block access to the clipboard. This repeatedly
+// calls `::OleSetClipboard` for a fixed number of times and should be called
+// instead of `::OleSetClipboard`.
+static void RepeatedlyTryOleSetClipboard(IDataObject* aDataObj) {
+  RepeatedlyTry(::OleSetClipboard, LogOleSetClipboardResult, aDataObj);
+}
+
+//-------------------------------------------------------------------------
+NS_IMETHODIMP nsClipboard::SetNativeClipboardData(
+    nsITransferable* aTransferable, int32_t aWhichClipboard) {
+  MOZ_CLIPBOARD_LOG("%s", __FUNCTION__);
+
+  if (aWhichClipboard != kGlobalClipboard) {
+    return NS_ERROR_FAILURE;
+  }
+
+  // make sure we have a good transferable
+  if (!aTransferable) {
+    return NS_ERROR_FAILURE;
+  }
+
+#ifdef ACCESSIBILITY
+  mozilla::a11y::Compatibility::SuppressA11yForClipboardCopy();
+#endif
+
+  RefPtr<IDataObject> dataObj;
+  auto mightNeedToFlush = MightNeedToFlush::No;
+  if (NS_SUCCEEDED(CreateNativeDataObject(aTransferable,
+                                          getter_AddRefs(dataObj), nullptr,
+                                          &mightNeedToFlush))) {
+    RepeatedlyTryOleSetClipboard(dataObj);
+
+    const bool doFlush = [&] {
+      switch (mozilla::StaticPrefs::widget_windows_sync_clipboard_flush()) {
+        case 0:
+          return false;
+        case 1:
+          return true;
+        default:
+          // Bug 1774285: Windows Suggested Actions (introduced in Windows 11
+          // 22H2) walks the entire a11y tree using UIA if something is placed
+          // on the clipboard using delayed rendering. (The OLE clipboard always
+          // uses delayed rendering.) This a11y tree walk causes an unacceptable
+          // hang, particularly when the a11y cache is disabled. We choose the
+          // lesser of the two performance/memory evils here and force immediate
+          // rendering as part of our workaround.
+          return mightNeedToFlush == MightNeedToFlush::Yes &&
+                 mozilla::IsWin1122H2OrLater();
+      }
+    }();
+    if (doFlush) {
+      RepeatedlyTry(::OleFlushClipboard, [](HRESULT) {});
+    }
+  } else {
+    // Clear the native clipboard
+    RepeatedlyTryOleSetClipboard(nullptr);
+  }
+
+  return NS_OK;
+}
+
+//-------------------------------------------------------------------------
+nsresult nsClipboard::GetGlobalData(HGLOBAL aHGBL, void** aData,
+                                    uint32_t* aLen) {
+  MOZ_CLIPBOARD_LOG("%s", __FUNCTION__);
+
+  // Allocate a new memory buffer and copy the data from global memory.
+  // Recall that win98 allocates to nearest DWORD boundary. As a safety
+  // precaution, allocate an extra 3 bytes (but don't report them in |aLen|!)
+  // and null them out to ensure that all of our NS_strlen calls will succeed.
+  // NS_strlen operates on char16_t, so we need 3 NUL bytes to ensure it finds
+  // a full NUL char16_t when |*aLen| is odd.
+  nsresult result = NS_ERROR_FAILURE;
+  if (aHGBL != nullptr) {
+    LPSTR lpStr = (LPSTR)GlobalLock(aHGBL);
+    mozilla::CheckedInt<uint32_t> allocSize =
+        mozilla::CheckedInt<uint32_t>(GlobalSize(aHGBL)) + 3;
+    if (!allocSize.isValid()) {
+      return NS_ERROR_INVALID_ARG;
+    }
+    char* data = static_cast<char*>(malloc(allocSize.value()));
+    if (data) {
+      uint32_t size = allocSize.value() - 3;
+      memcpy(data, lpStr, size);
+      // null terminate for safety
+      data[size] = data[size + 1] = data[size + 2] = '\0';
+
+      GlobalUnlock(aHGBL);
+      *aData = data;
+      *aLen = size;
+
+      result = NS_OK;
+    }
+  } else {
+    // We really shouldn't ever get here
+    // but just in case
+    *aData = nullptr;
+    *aLen = 0;
+    LPVOID lpMsgBuf;
+
+    FormatMessageW(
+        FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM, nullptr,
+        GetLastError(),
+        MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),  // Default language
+        (LPWSTR)&lpMsgBuf, 0, nullptr);
+
+    // Display the string.
+    MessageBoxW(nullptr, (LPCWSTR)lpMsgBuf, L"GetLastError",
+                MB_OK | MB_ICONINFORMATION);
+
+    // Free the buffer.
+    LocalFree(lpMsgBuf);
+  }
+
+  return result;
+}
+
+//-------------------------------------------------------------------------
+nsresult nsClipboard::GetNativeDataOffClipboard(nsIWidget* aWidget,
+                                                UINT /*aIndex*/, UINT aFormat,
+                                                void** aData, uint32_t* aLen) {
+  MOZ_CLIPBOARD_LOG("%s: overload taking nsIWidget*.", __FUNCTION__);
+
+  HGLOBAL hglb;
+  nsresult result = NS_ERROR_FAILURE;
+
+  HWND nativeWin = nullptr;
+  if (::OpenClipboard(nativeWin)) {
+    hglb = ::GetClipboardData(aFormat);
+    result = GetGlobalData(hglb, aData, aLen);
+    ::CloseClipboard();
+  }
+  return result;
+}
+
+// See methods listed at
+// <https://docs.microsoft.com/en-us/windows/win32/api/objidl/nn-objidl-idataobject#methods>.
+static void LogIDataObjectMethodResult(const HRESULT aHres,
+                                       const nsCString& aMethodName) {
+  if (MOZ_CLIPBOARD_LOG_ENABLED()) {
+    nsAutoCString hresString;
+    IDataObjectMethodResultToString(aHres, hresString);
+    MOZ_CLIPBOARD_LOG("IDataObject::%s result : %s", aMethodName.get(),
+                      hresString.get());
+  }
+}
+
+// Other apps can block access to the clipboard. This repeatedly calls
+// `GetData` for a fixed number of times and should be called instead of
+// `GetData`. See
+// <https://docs.microsoft.com/en-us/windows/win32/api/objidl/nf-objidl-idataobject-getdata>.
+// While Microsoft's documentation doesn't include `CLIPBRD_E_CANT_OPEN`
+// explicitly, it allows it implicitly and in local experiments it was indeed
+// returned.
+static HRESULT RepeatedlyTryGetData(IDataObject& aDataObject, LPFORMATETC pFE,
+                                    LPSTGMEDIUM pSTM) {
+  return RepeatedlyTry(
+      [&aDataObject, &pFE, &pSTM]() { return aDataObject.GetData(pFE, pSTM); },
+      std::bind(LogIDataObjectMethodResult, std::placeholders::_1,
+                "GetData"_ns));
+}
+
+//-------------------------------------------------------------------------
+// static
+HRESULT nsClipboard::FillSTGMedium(IDataObject* aDataObject, UINT aFormat,
+                                   LPFORMATETC pFE, LPSTGMEDIUM pSTM,
+                                   DWORD aTymed) {
+  SET_FORMATETC(*pFE, aFormat, 0, DVASPECT_CONTENT, -1, aTymed);
+
+  // Starting by querying for the data to see if we can get it as from global
+  // memory
+  HRESULT hres = S_FALSE;
+  hres = aDataObject->QueryGetData(pFE);
+  LogIDataObjectMethodResult(hres, "QueryGetData"_ns);
+  if (S_OK == hres) {
+    hres = RepeatedlyTryGetData(*aDataObject, pFE, pSTM);
+  }
+  return hres;
+}
+
+//-------------------------------------------------------------------------
+// If aFormat is CF_DIBV5, aMIMEImageFormat must be a type for which we have
+// an image encoder (e.g. image/png).
+// For other values of aFormat, it is OK to pass null for aMIMEImageFormat.
+nsresult nsClipboard::GetNativeDataOffClipboard(IDataObject* aDataObject,
+                                                UINT aIndex, UINT aFormat,
+                                                const char* aMIMEImageFormat,
+                                                void** aData, uint32_t* aLen) {
+  MOZ_CLIPBOARD_LOG("%s: overload taking IDataObject*.", __FUNCTION__);
+
+  nsresult result = NS_ERROR_FAILURE;
+  *aData = nullptr;
+  *aLen = 0;
+
+  if (!aDataObject) {
+    return result;
+  }
+
+  UINT format = aFormat;
+  HRESULT hres = S_FALSE;
+
+  // XXX at the moment we only support global memory transfers
+  // It is here where we will add support for native images
+  // and IStream
+  FORMATETC fe;
+  STGMEDIUM stm;
+  hres = FillSTGMedium(aDataObject, format, &fe, &stm, TYMED_HGLOBAL);
+
+  // If the format is CF_HDROP and we haven't found any files we can try looking
+  // for virtual files with FILEDESCRIPTOR.
+  if (FAILED(hres) && format == CF_HDROP) {
+    hres = FillSTGMedium(aDataObject,
+                         nsClipboard::GetClipboardFileDescriptorFormatW(), &fe,
+                         &stm, TYMED_HGLOBAL);
+    if (FAILED(hres)) {
+      hres = FillSTGMedium(aDataObject,
+                           nsClipboard::GetClipboardFileDescriptorFormatA(),
+                           &fe, &stm, TYMED_HGLOBAL);
+    }
+  }
+
+  // Currently this is only handling TYMED_HGLOBAL data
+  // For Text, Dibs, Files, and generic data (like HTML)
+  if (S_OK == hres) {
+    static CLIPFORMAT fileDescriptorFlavorA =
+        ::RegisterClipboardFormat(CFSTR_FILEDESCRIPTORA);
+    static CLIPFORMAT fileDescriptorFlavorW =
+        ::RegisterClipboardFormat(CFSTR_FILEDESCRIPTORW);
+    static CLIPFORMAT fileFlavor =
+        ::RegisterClipboardFormat(CFSTR_FILECONTENTS);
+    static CLIPFORMAT preferredDropEffect =
+        ::RegisterClipboardFormat(CFSTR_PREFERREDDROPEFFECT);
+
+    switch (stm.tymed) {
+      case TYMED_HGLOBAL: {
+        switch (fe.cfFormat) {
+          case CF_TEXT: {
+            // Get the data out of the global data handle. The size we
+            // return should not include the null because the other
+            // platforms don't use nulls, so just return the length we get
+            // back from strlen(), since we know CF_TEXT is null
+            // terminated. Recall that GetGlobalData() returns the size of
+            // the allocated buffer, not the size of the data (on 98, these
+            // are not the same) so we can't use that.
+            uint32_t allocLen = 0;
+            if (NS_SUCCEEDED(GetGlobalData(stm.hGlobal, aData, &allocLen))) {
+              *aLen = strlen(reinterpret_cast<char*>(*aData));
+              result = NS_OK;
+            }
+          } break;
+
+          case CF_UNICODETEXT: {
+            // Get the data out of the global data handle. The size we
+            // return should not include the null because the other
+            // platforms don't use nulls, so just return the length we get
+            // back from strlen(), since we know CF_UNICODETEXT is null
+            // terminated. Recall that GetGlobalData() returns the size of
+            // the allocated buffer, not the size of the data (on 98, these
+            // are not the same) so we can't use that.
+            uint32_t allocLen = 0;
+            if (NS_SUCCEEDED(GetGlobalData(stm.hGlobal, aData, &allocLen))) {
+              *aLen = NS_strlen(reinterpret_cast<char16_t*>(*aData)) * 2;
+              result = NS_OK;
+            }
+          } break;
+
+          case CF_DIBV5:
+            if (aMIMEImageFormat) {
+              uint32_t allocLen = 0;
+              const char* clipboardData;
+              if (NS_SUCCEEDED(GetGlobalData(
+                      stm.hGlobal, (void**)&clipboardData, &allocLen))) {
+                nsCOMPtr<imgIContainer> container;
+                nsCOMPtr<imgITools> imgTools =
+                    do_CreateInstance("@mozilla.org/image/tools;1");
+                result = imgTools->DecodeImageFromBuffer(
+                    clipboardData, allocLen,
+                    nsLiteralCString(IMAGE_BMP_MS_CLIPBOARD),
+                    getter_AddRefs(container));
+                if (NS_FAILED(result)) {
+                  break;
+                }
+
+                nsAutoCString mimeType;
+                if (strcmp(aMIMEImageFormat, kJPGImageMime) == 0) {
+                  mimeType.Assign(IMAGE_JPEG);
+                } else {
+                  mimeType.Assign(aMIMEImageFormat);
+                }
+
+                nsCOMPtr<nsIInputStream> inputStream;
+                result = imgTools->EncodeImage(container, mimeType, u""_ns,
+                                               getter_AddRefs(inputStream));
+                if (NS_FAILED(result)) {
+                  break;
+                }
+
+                if (!inputStream) {
+                  result = NS_ERROR_FAILURE;
+                  break;
+                }
+
+                *aData = inputStream.forget().take();
+                *aLen = sizeof(nsIInputStream*);
+              }
+            }
+            break;
+
+          case CF_HDROP: {
+            // in the case of a file drop, multiple files are stashed within a
+            // single data object. In order to match mozilla's D&D apis, we
+            // just pull out the file at the requested index, pretending as
+            // if there really are multiple drag items.
+            HDROP dropFiles = (HDROP)GlobalLock(stm.hGlobal);
+
+            UINT numFiles = ::DragQueryFileW(dropFiles, 0xFFFFFFFF, nullptr, 0);
+            NS_ASSERTION(numFiles > 0,
+                         "File drop flavor, but no files...hmmmm");
+            NS_ASSERTION(aIndex < numFiles,
+                         "Asked for a file index out of range of list");
+            if (numFiles > 0) {
+              UINT fileNameLen =
+                  ::DragQueryFileW(dropFiles, aIndex, nullptr, 0);
+              wchar_t* buffer = reinterpret_cast<wchar_t*>(
+                  moz_xmalloc((fileNameLen + 1) * sizeof(wchar_t)));
+              ::DragQueryFileW(dropFiles, aIndex, buffer, fileNameLen + 1);
+              *aData = buffer;
+              *aLen = fileNameLen * sizeof(char16_t);
+              result = NS_OK;
+            }
+            GlobalUnlock(stm.hGlobal);
+
+          } break;
+
+          default: {
+            if (fe.cfFormat == fileDescriptorFlavorA ||
+                fe.cfFormat == fileDescriptorFlavorW) {
+              nsAutoString tempPath;
+
+              LPFILEGROUPDESCRIPTOR fgdesc =
+                  static_cast<LPFILEGROUPDESCRIPTOR>(GlobalLock(stm.hGlobal));
+              if (fgdesc) {
+                result = GetTempFilePath(
+                    nsDependentString((fgdesc->fgd)[aIndex].cFileName),
+                    tempPath);
+                GlobalUnlock(stm.hGlobal);
+              }
+              if (NS_FAILED(result)) {
+                break;
+              }
+              result = SaveStorageOrStream(aDataObject, aIndex, tempPath);
+              if (NS_FAILED(result)) {
+                break;
+              }
+              wchar_t* buffer = reinterpret_cast<wchar_t*>(
+                  moz_xmalloc((tempPath.Length() + 1) * sizeof(wchar_t)));
+              wcscpy(buffer, tempPath.get());
+              *aData = buffer;
+              *aLen = tempPath.Length() * sizeof(wchar_t);
+              result = NS_OK;
+            } else if (fe.cfFormat == fileFlavor) {
+              NS_WARNING(
+                  "Mozilla doesn't yet understand how to read this type of "
+                  "file flavor");
+            } else {
+              // Get the data out of the global data handle. The size we
+              // return should not include the null because the other
+              // platforms don't use nulls, so just return the length we get
+              // back from strlen(), since we know CF_UNICODETEXT is null
+              // terminated. Recall that GetGlobalData() returns the size of
+              // the allocated buffer, not the size of the data (on 98, these
+              // are not the same) so we can't use that.
+              //
+              // NOTE: we are assuming that anything that falls into this
+              //        default case is unicode. As we start to get more
+              //        kinds of binary data, this may become an incorrect
+              //        assumption. Stay tuned.
+              uint32_t allocLen = 0;
+              if (NS_SUCCEEDED(GetGlobalData(stm.hGlobal, aData, &allocLen))) {
+                if (fe.cfFormat == GetHtmlClipboardFormat()) {
+                  // CF_HTML is actually UTF8, not unicode, so disregard the
+                  // assumption above. We have to check the header for the
+                  // actual length, and we'll do that in FindPlatformHTML().
+                  // For now, return the allocLen. This case is mostly to
+                  // ensure we don't try to call strlen on the buffer.
+                  *aLen = allocLen;
+                } else if (fe.cfFormat == GetCustomClipboardFormat()) {
+                  // Binary data
+                  *aLen = allocLen;
+                } else if (fe.cfFormat == preferredDropEffect) {
+                  // As per the MSDN doc entitled: "Shell Clipboard Formats"
+                  // CFSTR_PREFERREDDROPEFFECT should return a DWORD
+                  // Reference:
+                  // http://msdn.microsoft.com/en-us/library/bb776902(v=vs.85).aspx
+                  NS_ASSERTION(
+                      allocLen == sizeof(DWORD),
+                      "CFSTR_PREFERREDDROPEFFECT should return a DWORD");
+                  *aLen = allocLen;
+                } else {
+                  *aLen = NS_strlen(reinterpret_cast<char16_t*>(*aData)) *
+                          sizeof(char16_t);
+                }
+                result = NS_OK;
+              }
+            }
+          } break;
+        }  // switch
+      } break;
+
+      case TYMED_GDI: {
+#ifdef DEBUG
+        MOZ_CLIPBOARD_LOG("*********************** TYMED_GDI");
+#endif
+      } break;
+
+      default:
+        break;
+    }  // switch
+
+    ReleaseStgMedium(&stm);
+  }
+
+  return result;
+}
+
+//-------------------------------------------------------------------------
+nsresult nsClipboard::GetDataFromDataObject(IDataObject* aDataObject,
+                                            UINT anIndex, nsIWidget* aWindow,
+                                            nsITransferable* aTransferable) {
+  MOZ_CLIPBOARD_LOG("%s", __FUNCTION__);
+
+  // make sure we have a good transferable
+  if (!aTransferable) {
+    return NS_ERROR_INVALID_ARG;
+  }
+
+  nsresult res = NS_ERROR_FAILURE;
+
+  // get flavor list that includes all flavors that can be written (including
+  // ones obtained through conversion)
+  nsTArray<nsCString> flavors;
+  res = aTransferable->FlavorsTransferableCanImport(flavors);
+  if (NS_FAILED(res)) {
+    return NS_ERROR_FAILURE;
+  }
+
+  // Walk through flavors and see which flavor is on the clipboard them on the
+  // native clipboard,
+  for (uint32_t i = 0; i < flavors.Length(); i++) {
+    nsCString& flavorStr = flavors[i];
+    UINT format = GetFormat(flavorStr.get());
+
+    // Try to get the data using the desired flavor. This might fail, but all is
+    // not lost.
+    void* data = nullptr;
+    uint32_t dataLen = 0;
+    bool dataFound = false;
+    if (nullptr != aDataObject) {
+      if (NS_SUCCEEDED(GetNativeDataOffClipboard(aDataObject, anIndex, format,
+                                                 flavorStr.get(), &data,
+                                                 &dataLen))) {
+        dataFound = true;
+      }
+    } else if (nullptr != aWindow) {
+      if (NS_SUCCEEDED(GetNativeDataOffClipboard(aWindow, anIndex, format,
+                                                 &data, &dataLen))) {
+        dataFound = true;
+      }
+    }
+
+    // This is our second chance to try to find some data, having not found it
+    // when directly asking for the flavor. Let's try digging around in other
+    // flavors to help satisfy our craving for data.
+    if (!dataFound) {
+      if (flavorStr.EqualsLiteral(kTextMime)) {
+        dataFound =
+            FindUnicodeFromPlainText(aDataObject, anIndex, &data, &dataLen);
+      } else if (flavorStr.EqualsLiteral(kURLMime)) {
+        // drags from other windows apps expose the native
+        // CFSTR_INETURL{A,W} flavor
+        dataFound = FindURLFromNativeURL(aDataObject, anIndex, &data, &dataLen);
+        if (!dataFound) {
+          dataFound =
+              FindURLFromLocalFile(aDataObject, anIndex, &data, &dataLen);
+        }
+      }
+    }  // if we try one last ditch effort to find our data
+
+    // Hopefully by this point we've found it and can go about our business
+    if (dataFound) {
+      nsCOMPtr<nsISupports> genericDataWrapper;
+      if (flavorStr.EqualsLiteral(kFileMime)) {
+        // we have a file path in |data|. Create an nsLocalFile object.
+        nsDependentString filepath(reinterpret_cast<char16_t*>(data));
+        nsCOMPtr<nsIFile> file;
+        if (NS_SUCCEEDED(
+                NS_NewLocalFile(filepath, false, getter_AddRefs(file)))) {
+          genericDataWrapper = do_QueryInterface(file);
+        }
+        free(data);
+      } else if (flavorStr.EqualsLiteral(kNativeHTMLMime)) {
+        uint32_t dummy;
+        // the editor folks want CF_HTML exactly as it's on the clipboard, no
+        // conversions, no fancy stuff. Pull it off the clipboard, stuff it into
+        // a wrapper and hand it back to them.
+        if (FindPlatformHTML(aDataObject, anIndex, &data, &dummy, &dataLen)) {
+          nsPrimitiveHelpers::CreatePrimitiveForData(
+              flavorStr, data, dataLen, getter_AddRefs(genericDataWrapper));
+        } else {
+          free(data);
+          continue;  // something wrong with this flavor, keep looking for other
+                     // data
+        }
+        free(data);
+      } else if (flavorStr.EqualsLiteral(kHTMLMime)) {
+        uint32_t startOfData = 0;
+        // The JS folks want CF_HTML exactly as it is on the clipboard, but
+        // minus the CF_HTML header index information.
+        // It also needs to be converted to UTF16 and have linebreaks changed.
+        if (FindPlatformHTML(aDataObject, anIndex, &data, &startOfData,
+                             &dataLen)) {
+          dataLen -= startOfData;
+          nsPrimitiveHelpers::CreatePrimitiveForCFHTML(
+              static_cast<char*>(data) + startOfData, &dataLen,
+              getter_AddRefs(genericDataWrapper));
+        } else {
+          free(data);
+          continue;  // something wrong with this flavor, keep looking for other
+                     // data
+        }
+        free(data);
+      } else if (flavorStr.EqualsLiteral(kJPEGImageMime) ||
+                 flavorStr.EqualsLiteral(kJPGImageMime) ||
+                 flavorStr.EqualsLiteral(kPNGImageMime)) {
+        nsIInputStream* imageStream = reinterpret_cast<nsIInputStream*>(data);
+        genericDataWrapper = do_QueryInterface(imageStream);
+        NS_IF_RELEASE(imageStream);
+      } else {
+        // Treat custom types as a string of bytes.
+        if (!flavorStr.EqualsLiteral(kCustomTypesMime)) {
+          bool isRTF = flavorStr.EqualsLiteral(kRTFMime);
+          // we probably have some form of text. The DOM only wants LF, so
+          // convert from Win32 line endings to DOM line endings.
+          int32_t signedLen = static_cast<int32_t>(dataLen);
+          nsLinebreakHelpers::ConvertPlatformToDOMLinebreaks(isRTF, &data,
+                                                             &signedLen);
+          dataLen = signedLen;
+
+          if (isRTF) {
+            // RTF on Windows is known to sometimes deliver an extra null byte.
+            if (dataLen > 0 && static_cast<char*>(data)[dataLen - 1] == '\0') {
+              dataLen--;
+            }
+          }
+        }
+
+        nsPrimitiveHelpers::CreatePrimitiveForData(
+            flavorStr, data, dataLen, getter_AddRefs(genericDataWrapper));
+        free(data);
+      }
+
+      NS_ASSERTION(genericDataWrapper,
+                   "About to put null data into the transferable");
+      aTransferable->SetTransferData(flavorStr.get(), genericDataWrapper);
+      res = NS_OK;
+
+      // we found one, get out of the loop
+      break;
+    }
+  }  // foreach flavor
+
+  return res;
+}
+
+//
+// FindPlatformHTML
+//
+// Someone asked for the OS CF_HTML flavor. We give it back to them exactly
+// as-is.
+//
+bool nsClipboard ::FindPlatformHTML(IDataObject* inDataObject, UINT inIndex,
+                                    void** outData, uint32_t* outStartOfData,
+                                    uint32_t* outDataLen) {
+  // Reference: MSDN doc entitled "HTML Clipboard Format"
+  // http://msdn.microsoft.com/en-us/library/aa767917(VS.85).aspx#unknown_854
+  // CF_HTML is UTF8, not unicode. We also can't rely on it being
+  // null-terminated so we have to check the CF_HTML header for the correct
+  // length. The length we return is the bytecount from the beginning of the
+  // selected data to the end of the selected data, without the null
+  // termination. Because it's UTF8, we're guaranteed the header is ASCII.
+
+  if (!outData || !*outData) {
+    return false;
+  }
+
+  char version[8] = {0};
+  int32_t startOfData = 0;
+  int32_t endOfData = 0;
+  int numFound =
+      sscanf((char*)*outData, "Version:%7s\nStartHTML:%d\nEndHTML:%d", version,
+             &startOfData, &endOfData);
+
+  if (numFound != 3 || startOfData < -1 || endOfData < -1) {
+    return false;
+  }
+
+  // Fixup the start and end markers if they have no context (set to -1)
+  if (startOfData == -1) {
+    startOfData = 0;
+  }
+  if (endOfData == -1) {
+    endOfData = *outDataLen;
+  }
+
+  // Make sure we were passed sane values within our buffer size.
+  // (Note that we've handled all cases of negative endOfData above, so we can
+  // safely cast it to be unsigned here.)
+  if (!endOfData || startOfData >= endOfData ||
+      static_cast<uint32_t>(endOfData) > *outDataLen) {
+    return false;
+  }
+
+  // We want to return the buffer not offset by startOfData because it will be
+  // parsed out later (probably by HTMLEditor::ParseCFHTML) when it is still
+  // in CF_HTML format.
+
+  // We return the byte offset from the start of the data buffer to where the
+  // HTML data starts. The caller might want to extract the HTML only.
+  *outStartOfData = startOfData;
+  *outDataLen = endOfData;
+  return true;
+}
+
+//
+// FindUnicodeFromPlainText
+//
+// Looks for CF_TEXT on the clipboard and converts it into an UTF-16 string
+// if present. Returns this string in outData, and its length in outDataLen.
+// XXXndeakin Windows converts between CF_UNICODE and CF_TEXT automatically
+// so it doesn't seem like this is actually needed.
+//
+bool nsClipboard ::FindUnicodeFromPlainText(IDataObject* inDataObject,
+                                            UINT inIndex, void** outData,
+                                            uint32_t* outDataLen) {
+  MOZ_CLIPBOARD_LOG("%s", __FUNCTION__);
+
+  // We are looking for text/plain and we failed to find it on the clipboard
+  // first, so try again with CF_TEXT. If that is present, convert it to
+  // unicode.
+  nsresult rv = GetNativeDataOffClipboard(inDataObject, inIndex, CF_TEXT,
+                                          nullptr, outData, outDataLen);
+  if (NS_FAILED(rv) || !*outData) {
+    return false;
+  }
+
+  const char* castedText = static_cast<char*>(*outData);
+  nsAutoString tmp;
+  rv = NS_CopyNativeToUnicode(nsDependentCSubstring(castedText, *outDataLen),
+                              tmp);
+  if (NS_FAILED(rv)) {
+    return false;
+  }
+
+  // out with the old, in with the new
+  free(*outData);
+  *outData = ToNewUnicode(tmp);
+  *outDataLen = tmp.Length() * sizeof(char16_t);
+
+  return true;
+
+}  // FindUnicodeFromPlainText
+
+//
+// FindURLFromLocalFile
+//
+// we are looking for a URL and couldn't find it, try again with looking for
+// a local file. If we have one, it may either be a normal file or an internet
+// shortcut. In both cases, however, we can get a URL (it will be a file:// url
+// in the local file case).
+//
+bool nsClipboard ::FindURLFromLocalFile(IDataObject* inDataObject, UINT inIndex,
+                                        void** outData, uint32_t* outDataLen) {
+  MOZ_CLIPBOARD_LOG("%s", __FUNCTION__);
+
+  bool dataFound = false;
+
+  nsresult loadResult =
+      GetNativeDataOffClipboard(inDataObject, inIndex, GetFormat(kFileMime),
+                                nullptr, outData, outDataLen);
+  if (NS_SUCCEEDED(loadResult) && *outData) {
+    // we have a file path in |data|. Is it an internet shortcut or a normal
+    // file?
+    const nsDependentString filepath(static_cast<char16_t*>(*outData));
+    nsCOMPtr<nsIFile> file;
+    nsresult rv = NS_NewLocalFile(filepath, true, getter_AddRefs(file));
+    if (NS_FAILED(rv)) {
+      free(*outData);
+      return dataFound;
+    }
+
+    if (IsInternetShortcut(filepath)) {
+      free(*outData);
+      nsAutoCString url;
+      ResolveShortcut(file, url);
+      if (!url.IsEmpty()) {
+        // convert it to unicode and pass it out
+        NS_ConvertUTF8toUTF16 urlString(url);
+        // the internal mozilla URL format, text/x-moz-url, contains
+        // URL\ntitle.  We can guess the title from the file's name.
+        nsAutoString title;
+        file->GetLeafName(title);
+        // We rely on IsInternetShortcut check that file has a .url extension.
+        title.SetLength(title.Length() - 4);
+        if (title.IsEmpty()) {
+          title = urlString;
+        }
+        *outData = ToNewUnicode(urlString + u"\n"_ns + title);
+        *outDataLen =
+            NS_strlen(static_cast<char16_t*>(*outData)) * sizeof(char16_t);
+
+        dataFound = true;
+      }
+    } else {
+      // we have a normal file, use some Necko objects to get our file path
+      nsAutoCString urlSpec;
+      NS_GetURLSpecFromFile(file, urlSpec);
+
+      // convert it to unicode and pass it out
+      free(*outData);
+      *outData = UTF8ToNewUnicode(urlSpec);
+      *outDataLen =
+          NS_strlen(static_cast<char16_t*>(*outData)) * sizeof(char16_t);
+      dataFound = true;
+    }  // else regular file
+  }
+
+  return dataFound;
+}  // FindURLFromLocalFile
+
+//
+// FindURLFromNativeURL
+//
+// we are looking for a URL and couldn't find it using our internal
+// URL flavor, so look for it using the native URL flavor,
+// CF_INETURLSTRW (We don't handle CF_INETURLSTRA currently)
+//
+bool nsClipboard ::FindURLFromNativeURL(IDataObject* inDataObject, UINT inIndex,
+                                        void** outData, uint32_t* outDataLen) {
+  MOZ_CLIPBOARD_LOG("%s", __FUNCTION__);
+
+  bool dataFound = false;
+
+  void* tempOutData = nullptr;
+  uint32_t tempDataLen = 0;
+
+  nsresult loadResult = GetNativeDataOffClipboard(
+      inDataObject, inIndex, ::RegisterClipboardFormat(CFSTR_INETURLW), nullptr,
+      &tempOutData, &tempDataLen);
+  if (NS_SUCCEEDED(loadResult) && tempOutData) {
+    nsDependentString urlString(static_cast<char16_t*>(tempOutData));
+    // the internal mozilla URL format, text/x-moz-url, contains
+    // URL\ntitle.  Since we don't actually have a title here,
+    // just repeat the URL to fake it.
+    *outData = ToNewUnicode(urlString + u"\n"_ns + urlString);
+    *outDataLen =
+        NS_strlen(static_cast<char16_t*>(*outData)) * sizeof(char16_t);
+    free(tempOutData);
+    dataFound = true;
+  } else {
+    loadResult = GetNativeDataOffClipboard(
+        inDataObject, inIndex, ::RegisterClipboardFormat(CFSTR_INETURLA),
+        nullptr, &tempOutData, &tempDataLen);
+    if (NS_SUCCEEDED(loadResult) && tempOutData) {
+      // CFSTR_INETURLA is (currently) equal to CFSTR_SHELLURL which is equal to
+      // CF_TEXT which is by definition ANSI encoded.
+      nsCString urlUnescapedA;
+      bool unescaped =
+          NS_UnescapeURL(static_cast<char*>(tempOutData), tempDataLen,
+                         esc_OnlyNonASCII | esc_SkipControl, urlUnescapedA);
+
+      nsString urlString;
+      if (unescaped) {
+        NS_CopyNativeToUnicode(urlUnescapedA, urlString);
+      } else {
+        NS_CopyNativeToUnicode(
+            nsDependentCString(static_cast<char*>(tempOutData), tempDataLen),
+            urlString);
+      }
+
+      // the internal mozilla URL format, text/x-moz-url, contains
+      // URL\ntitle.  Since we don't actually have a title here,
+      // just repeat the URL to fake it.
+      *outData = ToNewUnicode(urlString + u"\n"_ns + urlString);
+      *outDataLen =
+          NS_strlen(static_cast<char16_t*>(*outData)) * sizeof(char16_t);
+      free(tempOutData);
+      dataFound = true;
+    }
+  }
+
+  return dataFound;
+}  // FindURLFromNativeURL
+
+// Other apps can block access to the clipboard. This repeatedly
+// calls `::OleGetClipboard` for a fixed number of times and should be called
+// instead of `::OleGetClipboard`.
+static HRESULT RepeatedlyTryOleGetClipboard(IDataObject** aDataObj) {
+  return RepeatedlyTry(::OleGetClipboard, LogOleGetClipboardResult, aDataObj);
+}
+
+//
+// ResolveShortcut
+//
+void nsClipboard ::ResolveShortcut(nsIFile* aFile, nsACString& outURL) {
+  nsCOMPtr<nsIFileProtocolHandler> fph;
+  nsresult rv = NS_GetFileProtocolHandler(getter_AddRefs(fph));
+  if (NS_FAILED(rv)) {
+    return;
+  }
+
+  nsCOMPtr<nsIURI> uri;
+  rv = fph->ReadURLFile(aFile, getter_AddRefs(uri));
+  if (NS_FAILED(rv)) {
+    return;
+  }
+
+  uri->GetSpec(outURL);
+}  // ResolveShortcut
+
+//
+// IsInternetShortcut
+//
+// A file is an Internet Shortcut if it ends with .URL
+//
+bool nsClipboard ::IsInternetShortcut(const nsAString& inFileName) {
+  return StringEndsWith(inFileName, u".url"_ns,
+                        nsCaseInsensitiveStringComparator);
+}  // IsInternetShortcut
+
+//-------------------------------------------------------------------------
+NS_IMETHODIMP
+nsClipboard::GetNativeClipboardData(nsITransferable* aTransferable,
+                                    int32_t aWhichClipboard) {
+  MOZ_DIAGNOSTIC_ASSERT(aTransferable);
+  MOZ_DIAGNOSTIC_ASSERT(
+      nsIClipboard::IsClipboardTypeSupported(aWhichClipboard));
+
+  MOZ_CLIPBOARD_LOG("%s aWhichClipboard=%i", __FUNCTION__, aWhichClipboard);
+
+  nsresult res;
+  // This makes sure we can use the OLE functionality for the clipboard
+  IDataObject* dataObj;
+  if (S_OK == RepeatedlyTryOleGetClipboard(&dataObj)) {
+    // Use OLE IDataObject for clipboard operations
+    MOZ_CLIPBOARD_LOG("    use OLE IDataObject:");
+    if (MOZ_CLIPBOARD_LOG_ENABLED()) {
+      IEnumFORMATETC* pEnum = nullptr;
+      if (S_OK == dataObj->EnumFormatEtc(DATADIR_GET, &pEnum)) {
+        FORMATETC fEtc;
+        while (S_OK == pEnum->Next(1, &fEtc, nullptr)) {
+          nsAutoString format;
+          mozilla::widget::WinUtils::GetClipboardFormatAsString(fEtc.cfFormat,
+                                                                format);
+          MOZ_CLIPBOARD_LOG("        FORMAT %s",
+                            NS_ConvertUTF16toUTF8(format).get());
+        }
+      }
+      pEnum->Release();
+    }
+
+    res = GetDataFromDataObject(dataObj, 0, nullptr, aTransferable);
+    dataObj->Release();
+  } else {
+    // do it the old manual way
+    res = GetDataFromDataObject(nullptr, 0, mWindow, aTransferable);
+  }
+  return res;
+}
+
+nsresult nsClipboard::EmptyNativeClipboardData(int32_t aWhichClipboard) {
+  MOZ_DIAGNOSTIC_ASSERT(
+      nsIClipboard::IsClipboardTypeSupported(aWhichClipboard));
+  // Some programs such as ZoneAlarm monitor clipboard usage and then open the
+  // clipboard to scan it.  If we i) empty and then ii) set data, then the
+  // 'set data' can sometimes fail with access denied becacuse another program
+  // has the clipboard open.  So to avoid this race condition for OpenClipboard
+  // we do not empty the clipboard when we're setting it.
+  RepeatedlyTryOleSetClipboard(nullptr);
+  return NS_OK;
+}
+
+mozilla::Result<int32_t, nsresult>
+nsClipboard::GetNativeClipboardSequenceNumber(int32_t aWhichClipboard) {
+  MOZ_DIAGNOSTIC_ASSERT(kGlobalClipboard == aWhichClipboard);
+  return (int32_t)::GetClipboardSequenceNumber();
+}
+
+//-------------------------------------------------------------------------
+mozilla::Result<bool, nsresult>
+nsClipboard::HasNativeClipboardDataMatchingFlavors(
+    const nsTArray<nsCString>& aFlavorList, int32_t aWhichClipboard) {
+  MOZ_DIAGNOSTIC_ASSERT(
+      nsIClipboard::IsClipboardTypeSupported(aWhichClipboard));
+  for (const auto& flavor : aFlavorList) {
+    UINT format = GetFormat(flavor.get());
+    if (IsClipboardFormatAvailable(format)) {
+      return true;
+    }
+  }
+  return false;
+}
+
+//-------------------------------------------------------------------------
+nsresult nsClipboard::GetTempFilePath(const nsAString& aFileName,
+                                      nsAString& aFilePath) {
+  nsresult result = NS_OK;
+
+  nsCOMPtr<nsIFile> tmpFile;
+  result =
+      GetSpecialSystemDirectory(OS_TemporaryDirectory, getter_AddRefs(tmpFile));
+  NS_ENSURE_SUCCESS(result, result);
+
+  result = tmpFile->Append(aFileName);
+  NS_ENSURE_SUCCESS(result, result);
+
+  result = tmpFile->CreateUnique(nsIFile::NORMAL_FILE_TYPE, 0660);
+  NS_ENSURE_SUCCESS(result, result);
+  result = tmpFile->GetPath(aFilePath);
+
+  return result;
+}
+
+//-------------------------------------------------------------------------
+nsresult nsClipboard::SaveStorageOrStream(IDataObject* aDataObject, UINT aIndex,
+                                          const nsAString& aFileName) {
+  NS_ENSURE_ARG_POINTER(aDataObject);
+
+  FORMATETC fe = {0};
+  SET_FORMATETC(fe, RegisterClipboardFormat(CFSTR_FILECONTENTS), 0,
+                DVASPECT_CONTENT, aIndex, TYMED_ISTORAGE | TYMED_ISTREAM);
+
+  STGMEDIUM stm = {0};
+  HRESULT hres = aDataObject->GetData(&fe, &stm);
+  if (FAILED(hres)) {
+    return NS_ERROR_FAILURE;
+  }
+
+  auto releaseMediumGuard =
+      mozilla::MakeScopeExit([&] { ReleaseStgMedium(&stm); });
+
+  // We do this check because, even though we *asked* for IStorage or IStream,
+  // it seems that IDataObject providers can just hand us back whatever they
+  // feel like. See Bug 1824644 for a fun example of that!
+  if (stm.tymed != TYMED_ISTORAGE && stm.tymed != TYMED_ISTREAM) {
+    return NS_ERROR_FAILURE;
+  }
+
+  if (stm.tymed == TYMED_ISTORAGE) {
+    RefPtr<IStorage> file;
+    hres = StgCreateStorageEx(
+        aFileName.Data(), STGM_CREATE | STGM_READWRITE | STGM_SHARE_EXCLUSIVE,
+        STGFMT_STORAGE, 0, NULL, NULL, IID_IStorage, getter_AddRefs(file));
+    if (FAILED(hres)) {
+      return NS_ERROR_FAILURE;
+    }
+
+    hres = stm.pstg->CopyTo(0, NULL, NULL, file);
+    if (FAILED(hres)) {
+      return NS_ERROR_FAILURE;
+    }
+
+    file->Commit(STGC_DEFAULT);
+
+    return NS_OK;
+  }
+
+  MOZ_ASSERT(stm.tymed == TYMED_ISTREAM);
+
+  HANDLE handle = CreateFile(aFileName.Data(), GENERIC_WRITE, FILE_SHARE_READ,
+                             NULL, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL);
+  if (handle == INVALID_HANDLE_VALUE) {
+    return NS_ERROR_FAILURE;
+  }
+
+  auto fileCloseGuard = mozilla::MakeScopeExit([&] { CloseHandle(handle); });
+
+  const ULONG bufferSize = 4096;
+  char buffer[bufferSize] = {0};
+  ULONG bytesRead = 0;
+  DWORD bytesWritten = 0;
+  while (true) {
+    HRESULT result = stm.pstm->Read(buffer, bufferSize, &bytesRead);
+    if (FAILED(result)) {
+      return NS_ERROR_FAILURE;
+    }
+    if (bytesRead == 0) {
+      break;
+    }
+    if (!WriteFile(handle, buffer, static_cast<DWORD>(bytesRead), &bytesWritten,
+                   NULL)) {
+      return NS_ERROR_FAILURE;
+    }
+  }
+  return NS_OK;
+}
diff --git a/widget/windows/nsClipboard.h b/widget/windows/nsClipboard.h
new file mode 100644
index 0000000000..b0afb9ee40
--- /dev/null
+++ b/widget/windows/nsClipboard.h
@@ -0,0 +1,113 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef nsClipboard_h__
+#define nsClipboard_h__
+
+#include "nsBaseClipboard.h"
+#include "nsIObserver.h"
+#include "nsIURI.h"
+
+#include <ole2.h>
+#include <windows.h>
+
+class nsITransferable;
+class nsIWidget;
+class nsIFile;
+struct IDataObject;
+
+/**
+ * Native Win32 Clipboard wrapper
+ */
+
+class nsClipboard : public nsBaseClipboard, public nsIObserver {
+  virtual ~nsClipboard();
+
+ public:
+  nsClipboard();
+
+  NS_DECL_ISUPPORTS_INHERITED
+
+  // nsIObserver
+  NS_DECL_NSIOBSERVER
+
+  // Internal Native Routines
+  enum class MightNeedToFlush : bool { No, Yes };
+  static nsresult CreateNativeDataObject(nsITransferable* aTransferable,
+                                         IDataObject** aDataObj, nsIURI* aUri,
+                                         MightNeedToFlush* = nullptr);
+  static nsresult SetupNativeDataObject(nsITransferable* aTransferable,
+                                        IDataObject* aDataObj,
+                                        MightNeedToFlush* = nullptr);
+  static nsresult GetDataFromDataObject(IDataObject* aDataObject, UINT anIndex,
+                                        nsIWidget* aWindow,
+                                        nsITransferable* aTransferable);
+  static nsresult GetNativeDataOffClipboard(nsIWidget* aWindow, UINT aIndex,
+                                            UINT aFormat, void** aData,
+                                            uint32_t* aLen);
+  static nsresult GetNativeDataOffClipboard(IDataObject* aDataObject,
+                                            UINT aIndex, UINT aFormat,
+                                            const char* aMIMEImageFormat,
+                                            void** aData, uint32_t* aLen);
+  static nsresult GetGlobalData(HGLOBAL aHGBL, void** aData, uint32_t* aLen);
+
+  // This function returns the internal Windows clipboard format identifier
+  // for a given Mime string. The default is to map kHTMLMime ("text/html")
+  // to the clipboard format CF_HTML ("HTLM Format"), but it can also be
+  // registered as clipboard format "text/html" to support previous versions
+  // of Gecko.
+  static UINT GetFormat(const char* aMimeStr, bool aMapHTMLMime = true);
+
+  static UINT GetClipboardFileDescriptorFormatA();
+  static UINT GetClipboardFileDescriptorFormatW();
+  static UINT GetHtmlClipboardFormat();
+  static UINT GetCustomClipboardFormat();
+
+ protected:
+  // @param aDataObject must be non-nullptr.
+  static HRESULT FillSTGMedium(IDataObject* aDataObject, UINT aFormat,
+                               LPFORMATETC pFE, LPSTGMEDIUM pSTM, DWORD aTymed);
+
+  // Implement the native clipboard behavior.
+  NS_IMETHOD SetNativeClipboardData(nsITransferable* aTransferable,
+                                    int32_t aWhichClipboard) override;
+  NS_IMETHOD GetNativeClipboardData(nsITransferable* aTransferable,
+                                    int32_t aWhichClipboard) override;
+  nsresult EmptyNativeClipboardData(int32_t aWhichClipboard) override;
+  mozilla::Result<int32_t, nsresult> GetNativeClipboardSequenceNumber(
+      int32_t aWhichClipboard) override;
+  mozilla::Result<bool, nsresult> HasNativeClipboardDataMatchingFlavors(
+      const nsTArray<nsCString>& aFlavorList, int32_t aWhichClipboard) override;
+
+  static bool IsInternetShortcut(const nsAString& inFileName);
+  static bool FindURLFromLocalFile(IDataObject* inDataObject, UINT inIndex,
+                                   void** outData, uint32_t* outDataLen);
+  static bool FindURLFromNativeURL(IDataObject* inDataObject, UINT inIndex,
+                                   void** outData, uint32_t* outDataLen);
+  static bool FindUnicodeFromPlainText(IDataObject* inDataObject, UINT inIndex,
+                                       void** outData, uint32_t* outDataLen);
+  static bool FindPlatformHTML(IDataObject* inDataObject, UINT inIndex,
+                               void** outData, uint32_t* outStartOfData,
+                               uint32_t* outDataLen);
+
+  static void ResolveShortcut(nsIFile* inFileName, nsACString& outURL);
+  static nsresult GetTempFilePath(const nsAString& aFileName,
+                                  nsAString& aFilePath);
+  static nsresult SaveStorageOrStream(IDataObject* aDataObject, UINT aIndex,
+                                      const nsAString& aFileName);
+
+  nsIWidget* mWindow;
+};
+
+#define SET_FORMATETC(fe, cf, td, asp, li, med) \
+  {                                             \
+    (fe).cfFormat = cf;                         \
+    (fe).ptd = td;                              \
+    (fe).dwAspect = asp;                        \
+    (fe).lindex = li;                           \
+    (fe).tymed = med;                           \
+  }
+
+#endif  // nsClipboard_h__
diff --git a/widget/windows/nsColorPicker.cpp b/widget/windows/nsColorPicker.cpp
new file mode 100644
index 0000000000..5074b620f5
--- /dev/null
+++ b/widget/windows/nsColorPicker.cpp
@@ -0,0 +1,202 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsColorPicker.h"
+
+#include <shlwapi.h>
+
+#include "mozilla/ArrayUtils.h"
+#include "mozilla/AutoRestore.h"
+#include "nsIWidget.h"
+#include "nsString.h"
+#include "WidgetUtils.h"
+#include "WinUtils.h"
+#include "nsPIDOMWindow.h"
+
+using namespace mozilla::widget;
+
+namespace {
+static DWORD ColorStringToRGB(const nsAString& aColor) {
+  DWORD result = 0;
+
+  for (uint32_t i = 1; i < aColor.Length(); ++i) {
+    result *= 16;
+
+    char16_t c = aColor[i];
+    if (c >= '0' && c <= '9') {
+      result += c - '0';
+    } else if (c >= 'a' && c <= 'f') {
+      result += 10 + (c - 'a');
+    } else {
+      result += 10 + (c - 'A');
+    }
+  }
+
+  DWORD r = result & 0x00FF0000;
+  DWORD g = result & 0x0000FF00;
+  DWORD b = result & 0x000000FF;
+
+  r = r >> 16;
+  b = b << 16;
+
+  result = r | g | b;
+
+  return result;
+}
+
+static nsString ToHexString(BYTE n) {
+  nsString result;
+  if (n <= 0x0F) {
+    result.Append('0');
+  }
+  result.AppendInt(n, 16);
+  return result;
+}
+
+static void BGRIntToRGBString(DWORD color, nsAString& aResult) {
+  BYTE r = GetRValue(color);
+  BYTE g = GetGValue(color);
+  BYTE b = GetBValue(color);
+
+  aResult.Assign('#');
+  aResult.Append(ToHexString(r));
+  aResult.Append(ToHexString(g));
+  aResult.Append(ToHexString(b));
+}
+}  // namespace
+
+static AsyncColorChooser* gColorChooser;
+
+AsyncColorChooser::AsyncColorChooser(COLORREF aInitialColor,
+                                     const nsTArray<nsString>& aDefaultColors,
+                                     nsIWidget* aParentWidget,
+                                     nsIColorPickerShownCallback* aCallback)
+    : mozilla::Runnable("AsyncColorChooser"),
+      mInitialColor(aInitialColor),
+      mDefaultColors(aDefaultColors.Clone()),
+      mColor(aInitialColor),
+      mParentWidget(aParentWidget),
+      mCallback(aCallback) {}
+
+NS_IMETHODIMP
+AsyncColorChooser::Run() {
+  MOZ_ASSERT(NS_IsMainThread(),
+             "Color pickers can only be opened from main thread currently");
+
+  // Allow only one color picker to be opened at a time, to workaround bug
+  // 944737
+  if (!gColorChooser) {
+    mozilla::AutoRestore<AsyncColorChooser*> restoreColorChooser(gColorChooser);
+    gColorChooser = this;
+
+    ScopedRtlShimWindow shim(mParentWidget.get());
+
+    COLORREF customColors[16];
+    for (size_t i = 0; i < mozilla::ArrayLength(customColors); i++) {
+      if (i < mDefaultColors.Length()) {
+        customColors[i] = ColorStringToRGB(mDefaultColors[i]);
+      } else {
+        customColors[i] = 0x00FFFFFF;
+      }
+    }
+
+    CHOOSECOLOR options;
+    options.lStructSize = sizeof(options);
+    options.hwndOwner = shim.get();
+    options.Flags = CC_RGBINIT | CC_FULLOPEN | CC_ENABLEHOOK;
+    options.rgbResult = mInitialColor;
+    options.lpCustColors = customColors;
+    options.lpfnHook = HookProc;
+
+    mColor = ChooseColor(&options) ? options.rgbResult : mInitialColor;
+  } else {
+    NS_WARNING(
+        "Currently, it's not possible to open more than one color "
+        "picker at a time");
+    mColor = mInitialColor;
+  }
+
+  if (mCallback) {
+    nsAutoString colorStr;
+    BGRIntToRGBString(mColor, colorStr);
+    mCallback->Done(colorStr);
+  }
+
+  return NS_OK;
+}
+
+void AsyncColorChooser::Update(COLORREF aColor) {
+  if (mColor != aColor) {
+    mColor = aColor;
+
+    nsAutoString colorStr;
+    BGRIntToRGBString(mColor, colorStr);
+    mCallback->Update(colorStr);
+  }
+}
+
+/* static */ UINT_PTR CALLBACK AsyncColorChooser::HookProc(HWND aDialog,
+                                                           UINT aMsg,
+                                                           WPARAM aWParam,
+                                                           LPARAM aLParam) {
+  if (!gColorChooser) {
+    return 0;
+  }
+
+  if (aMsg == WM_INITDIALOG) {
+    // "The default dialog box procedure processes the WM_INITDIALOG message
+    // before passing it to the hook procedure.
+    // For all other messages, the hook procedure receives the message first."
+    // https://docs.microsoft.com/en-us/windows/win32/api/commdlg/nc-commdlg-lpcchookproc
+    // "The dialog box procedure should return TRUE to direct the system to
+    // set the keyboard focus to the control specified by wParam."
+    // https://docs.microsoft.com/en-us/windows/win32/dlgbox/wm-initdialog
+    return 1;
+  }
+
+  if (aMsg == WM_CTLCOLORSTATIC) {
+    // The color picker does not expose a proper way to retrieve the current
+    // color, so we need to obtain it from the static control displaying the
+    // current color instead.
+    const int kCurrentColorBoxID = 709;
+    if ((HWND)aLParam == GetDlgItem(aDialog, kCurrentColorBoxID)) {
+      gColorChooser->Update(GetPixel((HDC)aWParam, 0, 0));
+    }
+  }
+
+  // Let the default dialog box procedure processes the message.
+  return 0;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+// nsIColorPicker
+
+nsColorPicker::nsColorPicker() {}
+
+nsColorPicker::~nsColorPicker() {}
+
+NS_IMPL_ISUPPORTS(nsColorPicker, nsIColorPicker)
+
+NS_IMETHODIMP
+nsColorPicker::Init(mozIDOMWindowProxy* parent, const nsAString& title,
+                    const nsAString& aInitialColor,
+                    const nsTArray<nsString>& aDefaultColors) {
+  MOZ_ASSERT(parent,
+             "Null parent passed to colorpicker, no color picker for you!");
+  mParentWidget =
+      WidgetUtils::DOMWindowToWidget(nsPIDOMWindowOuter::From(parent));
+  mInitialColor = ColorStringToRGB(aInitialColor);
+  mDefaultColors.Assign(aDefaultColors);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsColorPicker::Open(nsIColorPickerShownCallback* aCallback) {
+  NS_ENSURE_ARG(aCallback);
+  nsCOMPtr<nsIRunnable> event = new AsyncColorChooser(
+      mInitialColor, mDefaultColors, mParentWidget, aCallback);
+  return NS_DispatchToMainThread(event);
+}
diff --git a/widget/windows/nsColorPicker.h b/widget/windows/nsColorPicker.h
new file mode 100644
index 0000000000..ff34b9bd48
--- /dev/null
+++ b/widget/windows/nsColorPicker.h
@@ -0,0 +1,55 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef nsColorPicker_h__
+#define nsColorPicker_h__
+
+#include <windows.h>
+#include <commdlg.h>
+
+#include "nsCOMPtr.h"
+#include "nsIColorPicker.h"
+#include "nsThreadUtils.h"
+
+class nsIWidget;
+
+class AsyncColorChooser : public mozilla::Runnable {
+ public:
+  AsyncColorChooser(COLORREF aInitialColor,
+                    const nsTArray<nsString>& aDefaultColors,
+                    nsIWidget* aParentWidget,
+                    nsIColorPickerShownCallback* aCallback);
+  NS_IMETHOD Run() override;
+
+ private:
+  void Update(COLORREF aColor);
+
+  static UINT_PTR CALLBACK HookProc(HWND aDialog, UINT aMsg, WPARAM aWParam,
+                                    LPARAM aLParam);
+
+  COLORREF mInitialColor;
+  nsTArray<nsString> mDefaultColors;
+  COLORREF mColor;
+  nsCOMPtr<nsIWidget> mParentWidget;
+  nsCOMPtr<nsIColorPickerShownCallback> mCallback;
+};
+
+class nsColorPicker : public nsIColorPicker {
+  virtual ~nsColorPicker();
+
+ public:
+  nsColorPicker();
+
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSICOLORPICKER
+
+ private:
+  COLORREF mInitialColor;
+  nsTArray<nsString> mDefaultColors;
+  nsCOMPtr<nsIWidget> mParentWidget;
+};
+
+#endif  // nsColorPicker_h__
diff --git a/widget/windows/nsDataObj.cpp b/widget/windows/nsDataObj.cpp
new file mode 100644
index 0000000000..88a2a2ad09
--- /dev/null
+++ b/widget/windows/nsDataObj.cpp
@@ -0,0 +1,2276 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/ArrayUtils.h"
+#include "mozilla/TextUtils.h"
+
+#include <ole2.h>
+#include <shlobj.h>
+
+#include "nsComponentManagerUtils.h"
+#include "nsDataObj.h"
+#include "nsArrayUtils.h"
+#include "nsClipboard.h"
+#include "nsReadableUtils.h"
+#include "nsICookieJarSettings.h"
+#include "nsIHttpChannel.h"
+#include "nsISupportsPrimitives.h"
+#include "nsITransferable.h"
+#include "IEnumFE.h"
+#include "nsPrimitiveHelpers.h"
+#include "nsString.h"
+#include "nsCRT.h"
+#include "nsPrintfCString.h"
+#include "nsIStringBundle.h"
+#include "nsEscape.h"
+#include "nsIURL.h"
+#include "nsNetUtil.h"
+#include "mozilla/Components.h"
+#include "mozilla/SpinEventLoopUntil.h"
+#include "mozilla/Unused.h"
+#include "nsProxyRelease.h"
+#include "nsIObserverService.h"
+#include "nsIOutputStream.h"
+#include "nscore.h"
+#include "nsDirectoryServiceDefs.h"
+#include "nsITimer.h"
+#include "nsThreadUtils.h"
+#include "mozilla/Preferences.h"
+#include "nsContentUtils.h"
+#include "nsIPrincipal.h"
+#include "nsNativeCharsetUtils.h"
+#include "nsMimeTypes.h"
+#include "nsIMIMEService.h"
+#include "imgIEncoder.h"
+#include "imgITools.h"
+#include "WinUtils.h"
+#include "nsLocalFile.h"
+
+#include "mozilla/LazyIdleThread.h"
+#include <algorithm>
+
+using namespace mozilla;
+using namespace mozilla::glue;
+using namespace mozilla::widget;
+
+#define BFH_LENGTH 14
+#define DEFAULT_THREAD_TIMEOUT_MS 30000
+
+//-----------------------------------------------------------------------------
+// CStreamBase implementation
+nsDataObj::CStreamBase::CStreamBase() : mStreamRead(0) {}
+
+//-----------------------------------------------------------------------------
+nsDataObj::CStreamBase::~CStreamBase() {}
+
+NS_IMPL_ISUPPORTS(nsDataObj::CStream, nsIStreamListener)
+
+//-----------------------------------------------------------------------------
+// CStream implementation
+nsDataObj::CStream::CStream() : mChannelRead(false) {}
+
+//-----------------------------------------------------------------------------
+nsDataObj::CStream::~CStream() {}
+
+//-----------------------------------------------------------------------------
+// helper - initializes the stream
+nsresult nsDataObj::CStream::Init(nsIURI* pSourceURI,
+                                  nsContentPolicyType aContentPolicyType,
+                                  nsIPrincipal* aRequestingPrincipal,
+                                  nsICookieJarSettings* aCookieJarSettings,
+                                  nsIReferrerInfo* aReferrerInfo) {
+  // we can not create a channel without a requestingPrincipal
+  if (!aRequestingPrincipal) {
+    return NS_ERROR_FAILURE;
+  }
+  nsresult rv;
+  rv = NS_NewChannel(getter_AddRefs(mChannel), pSourceURI, aRequestingPrincipal,
+                     nsILoadInfo::SEC_ALLOW_CROSS_ORIGIN_INHERITS_SEC_CONTEXT,
+                     aContentPolicyType, aCookieJarSettings,
+                     nullptr,  // PerformanceStorage
+                     nullptr,  // loadGroup
+                     nullptr,  // aCallbacks
+                     nsIRequest::LOAD_FROM_CACHE);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  if (nsCOMPtr<nsIHttpChannel> httpChannel = do_QueryInterface(mChannel)) {
+    rv = httpChannel->SetReferrerInfo(aReferrerInfo);
+    Unused << NS_WARN_IF(NS_FAILED(rv));
+  }
+
+  rv = mChannel->AsyncOpen(this);
+  NS_ENSURE_SUCCESS(rv, rv);
+  return NS_OK;
+}
+
+//-----------------------------------------------------------------------------
+// IUnknown's QueryInterface, nsISupport's AddRef and Release are shared by
+// IUnknown and nsIStreamListener.
+STDMETHODIMP nsDataObj::CStream::QueryInterface(REFIID refiid,
+                                                void** ppvResult) {
+  *ppvResult = nullptr;
+  if (IID_IUnknown == refiid || refiid == IID_IStream)
+
+  {
+    *ppvResult = this;
+  }
+
+  if (nullptr != *ppvResult) {
+    ((LPUNKNOWN)*ppvResult)->AddRef();
+    return S_OK;
+  }
+
+  return E_NOINTERFACE;
+}
+
+// nsIStreamListener implementation
+NS_IMETHODIMP
+nsDataObj::CStream::OnDataAvailable(
+    nsIRequest* aRequest, nsIInputStream* aInputStream,
+    uint64_t aOffset,  // offset within the stream
+    uint32_t aCount)   // bytes available on this call
+{
+  // If we've been asked to read zero bytes, call `Read` once, just to ensure
+  // any side-effects take place, and return immediately.
+  if (aCount == 0) {
+    char buffer[1] = {0};
+    uint32_t bytesReadByCall = 0;
+    nsresult rv = aInputStream->Read(buffer, 0, &bytesReadByCall);
+    MOZ_ASSERT(bytesReadByCall == 0);
+    return rv;
+  }
+
+  // Extend the write buffer for the incoming data.
+  size_t oldLength = mChannelData.Length();
+  char* buffer =
+      reinterpret_cast<char*>(mChannelData.AppendElements(aCount, fallible));
+  if (!buffer) {
+    return NS_ERROR_OUT_OF_MEMORY;
+  }
+  MOZ_ASSERT(mChannelData.Length() == (aOffset + aCount),
+             "stream length mismatch w/write buffer");
+
+  // Read() may not return aCount on a single call, so loop until we've
+  // accumulated all the data OnDataAvailable has promised.
+  uint32_t bytesRead = 0;
+  while (bytesRead < aCount) {
+    uint32_t bytesReadByCall = 0;
+    nsresult rv = aInputStream->Read(buffer + bytesRead, aCount - bytesRead,
+                                     &bytesReadByCall);
+    bytesRead += bytesReadByCall;
+
+    if (bytesReadByCall == 0) {
+      // A `bytesReadByCall` of zero indicates EOF without failure... but we
+      // were promised `aCount` elements and haven't gotten them. Return a
+      // generic failure.
+      rv = NS_ERROR_FAILURE;
+    }
+
+    if (NS_FAILED(rv)) {
+      // Drop any trailing uninitialized elements before erroring out.
+      mChannelData.RemoveElementsAt(oldLength + bytesRead, aCount - bytesRead);
+      return rv;
+    }
+  }
+  return NS_OK;
+}
+
+NS_IMETHODIMP nsDataObj::CStream::OnStartRequest(nsIRequest* aRequest) {
+  mChannelResult = NS_OK;
+  return NS_OK;
+}
+
+NS_IMETHODIMP nsDataObj::CStream::OnStopRequest(nsIRequest* aRequest,
+                                                nsresult aStatusCode) {
+  mChannelRead = true;
+  mChannelResult = aStatusCode;
+  return NS_OK;
+}
+
+// Pumps thread messages while waiting for the async listener operation to
+// complete. Failing this call will fail the stream incall from Windows
+// and cancel the operation.
+nsresult nsDataObj::CStream::WaitForCompletion() {
+  // We are guaranteed OnStopRequest will get called, so this should be ok.
+  SpinEventLoopUntil("widget:nsDataObj::CStream::WaitForCompletion"_ns,
+                     [&]() { return mChannelRead; });
+
+  if (!mChannelData.Length()) mChannelResult = NS_ERROR_FAILURE;
+
+  return mChannelResult;
+}
+
+//-----------------------------------------------------------------------------
+// IStream
+STDMETHODIMP nsDataObj::CStreamBase::Clone(IStream** ppStream) {
+  return E_NOTIMPL;
+}
+
+//-----------------------------------------------------------------------------
+STDMETHODIMP nsDataObj::CStreamBase::Commit(DWORD dwFrags) { return E_NOTIMPL; }
+
+//-----------------------------------------------------------------------------
+STDMETHODIMP nsDataObj::CStreamBase::CopyTo(IStream* pDestStream,
+                                            ULARGE_INTEGER nBytesToCopy,
+                                            ULARGE_INTEGER* nBytesRead,
+                                            ULARGE_INTEGER* nBytesWritten) {
+  return E_NOTIMPL;
+}
+
+//-----------------------------------------------------------------------------
+STDMETHODIMP nsDataObj::CStreamBase::LockRegion(ULARGE_INTEGER nStart,
+                                                ULARGE_INTEGER nBytes,
+                                                DWORD dwFlags) {
+  return E_NOTIMPL;
+}
+
+//-----------------------------------------------------------------------------
+STDMETHODIMP nsDataObj::CStream::Read(void* pvBuffer, ULONG nBytesToRead,
+                                      ULONG* nBytesRead) {
+  // Wait for the write into our buffer to complete via the stream listener.
+  // We can't respond to this by saying "call us back later".
+  if (NS_FAILED(WaitForCompletion())) return E_FAIL;
+
+  // Bytes left for Windows to read out of our buffer
+  ULONG bytesLeft = mChannelData.Length() - mStreamRead;
+  // Let Windows know what we will hand back, usually this is the entire buffer
+  *nBytesRead = std::min(bytesLeft, nBytesToRead);
+  // Copy the buffer data over
+  memcpy(pvBuffer, ((char*)mChannelData.Elements() + mStreamRead), *nBytesRead);
+  // Update our bytes read tracking
+  mStreamRead += *nBytesRead;
+  return S_OK;
+}
+
+//-----------------------------------------------------------------------------
+STDMETHODIMP nsDataObj::CStreamBase::Revert(void) { return E_NOTIMPL; }
+
+//-----------------------------------------------------------------------------
+STDMETHODIMP nsDataObj::CStreamBase::Seek(LARGE_INTEGER nMove, DWORD dwOrigin,
+                                          ULARGE_INTEGER* nNewPos) {
+  if (nNewPos == nullptr) return STG_E_INVALIDPOINTER;
+
+  if (nMove.LowPart == 0 && nMove.HighPart == 0 &&
+      (dwOrigin == STREAM_SEEK_SET || dwOrigin == STREAM_SEEK_CUR)) {
+    nNewPos->LowPart = 0;
+    nNewPos->HighPart = 0;
+    return S_OK;
+  }
+
+  return E_NOTIMPL;
+}
+
+//-----------------------------------------------------------------------------
+STDMETHODIMP nsDataObj::CStreamBase::SetSize(ULARGE_INTEGER nNewSize) {
+  return E_NOTIMPL;
+}
+
+//-----------------------------------------------------------------------------
+STDMETHODIMP nsDataObj::CStream::Stat(STATSTG* statstg, DWORD dwFlags) {
+  if (statstg == nullptr) return STG_E_INVALIDPOINTER;
+
+  if (!mChannel || NS_FAILED(WaitForCompletion())) return E_FAIL;
+
+  memset((void*)statstg, 0, sizeof(STATSTG));
+
+  if (dwFlags != STATFLAG_NONAME) {
+    nsCOMPtr<nsIURI> sourceURI;
+    if (NS_FAILED(mChannel->GetURI(getter_AddRefs(sourceURI)))) {
+      return E_FAIL;
+    }
+
+    nsAutoCString strFileName;
+    nsCOMPtr<nsIURL> sourceURL = do_QueryInterface(sourceURI);
+    sourceURL->GetFileName(strFileName);
+
+    if (strFileName.IsEmpty()) return E_FAIL;
+
+    NS_UnescapeURL(strFileName);
+    NS_ConvertUTF8toUTF16 wideFileName(strFileName);
+
+    uint32_t nMaxNameLength = (wideFileName.Length() * 2) + 2;
+    void* retBuf = CoTaskMemAlloc(nMaxNameLength);  // freed by caller
+    if (!retBuf) return STG_E_INSUFFICIENTMEMORY;
+
+    ZeroMemory(retBuf, nMaxNameLength);
+    memcpy(retBuf, wideFileName.get(), wideFileName.Length() * 2);
+    statstg->pwcsName = (LPOLESTR)retBuf;
+  }
+
+  SYSTEMTIME st;
+
+  statstg->type = STGTY_STREAM;
+
+  GetSystemTime(&st);
+  SystemTimeToFileTime((const SYSTEMTIME*)&st, (LPFILETIME)&statstg->mtime);
+  statstg->ctime = statstg->atime = statstg->mtime;
+
+  statstg->cbSize.QuadPart = mChannelData.Length();
+  statstg->grfMode = STGM_READ;
+  statstg->grfLocksSupported = LOCK_ONLYONCE;
+  statstg->clsid = CLSID_NULL;
+
+  return S_OK;
+}
+
+//-----------------------------------------------------------------------------
+STDMETHODIMP nsDataObj::CStreamBase::UnlockRegion(ULARGE_INTEGER nStart,
+                                                  ULARGE_INTEGER nBytes,
+                                                  DWORD dwFlags) {
+  return E_NOTIMPL;
+}
+
+//-----------------------------------------------------------------------------
+STDMETHODIMP nsDataObj::CStreamBase::Write(const void* pvBuffer,
+                                           ULONG nBytesToRead,
+                                           ULONG* nBytesRead) {
+  return E_NOTIMPL;
+}
+
+//-----------------------------------------------------------------------------
+HRESULT nsDataObj::CreateStream(IStream** outStream) {
+  NS_ENSURE_TRUE(outStream, E_INVALIDARG);
+
+  nsresult rv = NS_ERROR_FAILURE;
+  nsAutoString wideFileName;
+  nsCOMPtr<nsIURI> sourceURI;
+  HRESULT res;
+
+  res = GetDownloadDetails(getter_AddRefs(sourceURI), wideFileName);
+  if (FAILED(res)) return res;
+
+  nsDataObj::CStream* pStream = new nsDataObj::CStream();
+  NS_ENSURE_TRUE(pStream, E_OUTOFMEMORY);
+
+  pStream->AddRef();
+
+  // query the requestingPrincipal from the transferable and add it to the new
+  // channel
+  nsCOMPtr<nsIPrincipal> requestingPrincipal =
+      mTransferable->GetRequestingPrincipal();
+  MOZ_ASSERT(requestingPrincipal, "can not create channel without a principal");
+
+  // Note that the cookieJarSettings could be null if the data object is for the
+  // image copy. We will fix this in Bug 1690532.
+  nsCOMPtr<nsICookieJarSettings> cookieJarSettings =
+      mTransferable->GetCookieJarSettings();
+
+  // The referrer is optional.
+  nsCOMPtr<nsIReferrerInfo> referrerInfo = mTransferable->GetReferrerInfo();
+
+  nsContentPolicyType contentPolicyType = mTransferable->GetContentPolicyType();
+  rv = pStream->Init(sourceURI, contentPolicyType, requestingPrincipal,
+                     cookieJarSettings, referrerInfo);
+  if (NS_FAILED(rv)) {
+    pStream->Release();
+    return E_FAIL;
+  }
+  *outStream = pStream;
+
+  return S_OK;
+}
+
+//-----------------------------------------------------------------------------
+// AutoCloseEvent implementation
+nsDataObj::AutoCloseEvent::AutoCloseEvent()
+    : mEvent(::CreateEventW(nullptr, TRUE, FALSE, nullptr)) {}
+
+bool nsDataObj::AutoCloseEvent::IsInited() const { return !!mEvent; }
+
+void nsDataObj::AutoCloseEvent::Signal() const { ::SetEvent(mEvent); }
+
+DWORD nsDataObj::AutoCloseEvent::Wait(DWORD aMillisec) const {
+  return ::WaitForSingleObject(mEvent, aMillisec);
+}
+
+//-----------------------------------------------------------------------------
+// AutoSetEvent implementation
+nsDataObj::AutoSetEvent::AutoSetEvent(NotNull<AutoCloseEvent*> aEvent)
+    : mEvent(aEvent) {}
+
+nsDataObj::AutoSetEvent::~AutoSetEvent() { Signal(); }
+
+void nsDataObj::AutoSetEvent::Signal() const { mEvent->Signal(); }
+
+bool nsDataObj::AutoSetEvent::IsWaiting() const {
+  return mEvent->Wait(0) == WAIT_TIMEOUT;
+}
+
+//-----------------------------------------------------------------------------
+// CMemStream implementation
+Win32SRWLock nsDataObj::CMemStream::mLock;
+
+//-----------------------------------------------------------------------------
+nsDataObj::CMemStream::CMemStream(nsHGLOBAL aGlobalMem, uint32_t aTotalLength,
+                                  already_AddRefed<AutoCloseEvent> aEvent)
+    : mGlobalMem(aGlobalMem), mEvent(aEvent), mTotalLength(aTotalLength) {
+  ::CoCreateFreeThreadedMarshaler(this, getter_AddRefs(mMarshaler));
+}
+
+//-----------------------------------------------------------------------------
+nsDataObj::CMemStream::~CMemStream() {}
+
+//-----------------------------------------------------------------------------
+// IUnknown
+STDMETHODIMP nsDataObj::CMemStream::QueryInterface(REFIID refiid,
+                                                   void** ppvResult) {
+  *ppvResult = nullptr;
+  if (refiid == IID_IUnknown || refiid == IID_IStream ||
+      refiid == IID_IAgileObject) {
+    *ppvResult = this;
+  } else if (refiid == IID_IMarshal && mMarshaler) {
+    return mMarshaler->QueryInterface(refiid, ppvResult);
+  }
+
+  if (nullptr != *ppvResult) {
+    ((LPUNKNOWN)*ppvResult)->AddRef();
+    return S_OK;
+  }
+
+  return E_NOINTERFACE;
+}
+
+void nsDataObj::CMemStream::WaitForCompletion() {
+  if (!mEvent) {
+    // We are not waiting for obtaining the icon cache.
+    return;
+  }
+  if (!NS_IsMainThread()) {
+    mEvent->Wait(INFINITE);
+  } else {
+    // We should not block the main thread.
+    mEvent->Signal();
+  }
+  // mEvent will always be in the signaled state here.
+}
+
+//-----------------------------------------------------------------------------
+// IStream
+STDMETHODIMP nsDataObj::CMemStream::Read(void* pvBuffer, ULONG nBytesToRead,
+                                         ULONG* nBytesRead) {
+  // Wait until the event is signaled.
+  WaitForCompletion();
+
+  AutoExclusiveLock lock(mLock);
+  char* contents = reinterpret_cast<char*>(GlobalLock(mGlobalMem.get()));
+  if (!contents) {
+    return E_OUTOFMEMORY;
+  }
+
+  // Bytes left for Windows to read out of our buffer
+  ULONG bytesLeft = mTotalLength - mStreamRead;
+  // Let Windows know what we will hand back, usually this is the entire buffer
+  *nBytesRead = std::min(bytesLeft, nBytesToRead);
+  // Copy the buffer data over
+  memcpy(pvBuffer, contents + mStreamRead, *nBytesRead);
+  // Update our bytes read tracking
+  mStreamRead += *nBytesRead;
+
+  GlobalUnlock(mGlobalMem.get());
+  return S_OK;
+}
+
+//-----------------------------------------------------------------------------
+STDMETHODIMP nsDataObj::CMemStream::Stat(STATSTG* statstg, DWORD dwFlags) {
+  if (statstg == nullptr) return STG_E_INVALIDPOINTER;
+
+  memset((void*)statstg, 0, sizeof(STATSTG));
+
+  if (dwFlags != STATFLAG_NONAME) {
+    constexpr size_t kMaxNameLength = sizeof(wchar_t);
+    void* retBuf = CoTaskMemAlloc(kMaxNameLength);  // freed by caller
+    if (!retBuf) return STG_E_INSUFFICIENTMEMORY;
+
+    ZeroMemory(retBuf, kMaxNameLength);
+    statstg->pwcsName = (LPOLESTR)retBuf;
+  }
+
+  SYSTEMTIME st;
+
+  statstg->type = STGTY_STREAM;
+
+  GetSystemTime(&st);
+  SystemTimeToFileTime((const SYSTEMTIME*)&st, (LPFILETIME)&statstg->mtime);
+  statstg->ctime = statstg->atime = statstg->mtime;
+
+  statstg->cbSize.QuadPart = mTotalLength;
+  statstg->grfMode = STGM_READ;
+  statstg->grfLocksSupported = LOCK_ONLYONCE;
+  statstg->clsid = CLSID_NULL;
+
+  return S_OK;
+}
+
+/*
+ * Class nsDataObj
+ */
+
+//-----------------------------------------------------
+// construction
+//-----------------------------------------------------
+nsDataObj::nsDataObj(nsIURI* uri)
+    : m_cRef(0),
+      mTransferable(nullptr),
+      mIsAsyncMode(FALSE),
+      mIsInOperation(FALSE) {
+  mIOThread = new LazyIdleThread(DEFAULT_THREAD_TIMEOUT_MS, "nsDataObj",
+                                 LazyIdleThread::ManualShutdown);
+  m_enumFE = new CEnumFormatEtc();
+  m_enumFE->AddRef();
+
+  if (uri) {
+    // A URI was obtained, so pass this through to the DataObject
+    // so it can create a SourceURL for CF_HTML flavour
+    uri->GetSpec(mSourceURL);
+  }
+}
+//-----------------------------------------------------
+// destruction
+//-----------------------------------------------------
+nsDataObj::~nsDataObj() {
+  NS_IF_RELEASE(mTransferable);
+
+  mDataFlavors.Clear();
+
+  m_enumFE->Release();
+
+  // Free arbitrary system formats
+  for (uint32_t idx = 0; idx < mDataEntryList.Length(); idx++) {
+    CoTaskMemFree(mDataEntryList[idx]->fe.ptd);
+    ReleaseStgMedium(&mDataEntryList[idx]->stgm);
+    CoTaskMemFree(mDataEntryList[idx]);
+  }
+}
+
+//-----------------------------------------------------
+// IUnknown interface methods - see inknown.h for documentation
+//-----------------------------------------------------
+STDMETHODIMP nsDataObj::QueryInterface(REFIID riid, void** ppv) {
+  *ppv = nullptr;
+
+  if ((IID_IUnknown == riid) || (IID_IDataObject == riid)) {
+    *ppv = this;
+    AddRef();
+    return S_OK;
+  } else if (IID_IDataObjectAsyncCapability == riid) {
+    *ppv = static_cast<IDataObjectAsyncCapability*>(this);
+    AddRef();
+    return S_OK;
+  }
+
+  return E_NOINTERFACE;
+}
+
+//-----------------------------------------------------
+STDMETHODIMP_(ULONG) nsDataObj::AddRef() {
+  ++m_cRef;
+  NS_LOG_ADDREF(this, m_cRef, "nsDataObj", sizeof(*this));
+
+  // When the first reference is taken, hold our own internal reference.
+  if (m_cRef == 1) {
+    mKeepAlive = this;
+  }
+
+  return m_cRef;
+}
+
+namespace {
+class RemoveTempFileHelper final : public nsIObserver, public nsINamed {
+ public:
+  explicit RemoveTempFileHelper(nsIFile* aTempFile) : mTempFile(aTempFile) {
+    MOZ_ASSERT(mTempFile);
+  }
+
+  // The attach method is seperate from the constructor as we may be addref-ing
+  // ourself, and we want to be sure someone has a strong reference to us.
+  void Attach() {
+    // We need to listen to both the xpcom shutdown message and our timer, and
+    // fire when the first of either of these two messages is received.
+    nsresult rv;
+    rv = NS_NewTimerWithObserver(getter_AddRefs(mTimer), this, 500,
+                                 nsITimer::TYPE_ONE_SHOT);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      return;
+    }
+
+    nsCOMPtr<nsIObserverService> observerService =
+        do_GetService("@mozilla.org/observer-service;1");
+    if (NS_WARN_IF(!observerService)) {
+      mTimer->Cancel();
+      mTimer = nullptr;
+      return;
+    }
+    observerService->AddObserver(this, NS_XPCOM_SHUTDOWN_OBSERVER_ID, false);
+  }
+
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIOBSERVER
+  NS_DECL_NSINAMED
+
+ private:
+  ~RemoveTempFileHelper() {
+    if (mTempFile) {
+      mTempFile->Remove(false);
+    }
+  }
+
+  nsCOMPtr<nsIFile> mTempFile;
+  nsCOMPtr<nsITimer> mTimer;
+};
+
+NS_IMPL_ISUPPORTS(RemoveTempFileHelper, nsIObserver, nsINamed);
+
+NS_IMETHODIMP
+RemoveTempFileHelper::Observe(nsISupports* aSubject, const char* aTopic,
+                              const char16_t* aData) {
+  // Let's be careful and make sure that we don't die immediately
+  RefPtr<RemoveTempFileHelper> grip = this;
+
+  // Make sure that we aren't called again by destroying references to ourself.
+  nsCOMPtr<nsIObserverService> observerService =
+      do_GetService("@mozilla.org/observer-service;1");
+  if (observerService) {
+    observerService->RemoveObserver(this, NS_XPCOM_SHUTDOWN_OBSERVER_ID);
+  }
+
+  if (mTimer) {
+    mTimer->Cancel();
+    mTimer = nullptr;
+  }
+
+  // Remove the tempfile
+  if (mTempFile) {
+    mTempFile->Remove(false);
+    mTempFile = nullptr;
+  }
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+RemoveTempFileHelper::GetName(nsACString& aName) {
+  aName.AssignLiteral("RemoveTempFileHelper");
+  return NS_OK;
+}
+}  // namespace
+
+//-----------------------------------------------------
+STDMETHODIMP_(ULONG) nsDataObj::Release() {
+  --m_cRef;
+
+  NS_LOG_RELEASE(this, m_cRef, "nsDataObj");
+
+  // If we hold the last reference, submit release of it to the main thread.
+  if (m_cRef == 1 && mKeepAlive) {
+    NS_ReleaseOnMainThread("nsDataObj release", mKeepAlive.forget(), true);
+  }
+
+  if (0 != m_cRef) return m_cRef;
+
+  // We have released our last ref on this object and need to delete the
+  // temp file. External app acting as drop target may still need to open the
+  // temp file. Addref a timer so it can delay deleting file and destroying
+  // this object.
+  if (mCachedTempFile) {
+    RefPtr<RemoveTempFileHelper> helper =
+        new RemoveTempFileHelper(mCachedTempFile);
+    mCachedTempFile = nullptr;
+    helper->Attach();
+  }
+
+  // In case the destructor ever AddRef/Releases, ensure we don't delete twice
+  // or take mKeepAlive as another reference.
+  m_cRef = 1;
+
+  delete this;
+
+  return 0;
+}
+
+//-----------------------------------------------------
+BOOL nsDataObj::FormatsMatch(const FORMATETC& source,
+                             const FORMATETC& target) const {
+  if ((source.cfFormat == target.cfFormat) &&
+      (source.dwAspect & target.dwAspect) && (source.tymed & target.tymed)) {
+    return TRUE;
+  } else {
+    return FALSE;
+  }
+}
+
+//-----------------------------------------------------
+// IDataObject methods
+//-----------------------------------------------------
+STDMETHODIMP nsDataObj::GetData(LPFORMATETC aFormat, LPSTGMEDIUM pSTM) {
+  if (!mTransferable) return DV_E_FORMATETC;
+
+  // Hold an extra reference in case we end up spinning the event loop.
+  RefPtr<nsDataObj> keepAliveDuringGetData(this);
+
+  uint32_t dfInx = 0;
+
+  static CLIPFORMAT fileDescriptorFlavorA =
+      ::RegisterClipboardFormat(CFSTR_FILEDESCRIPTORA);
+  static CLIPFORMAT fileDescriptorFlavorW =
+      ::RegisterClipboardFormat(CFSTR_FILEDESCRIPTORW);
+  static CLIPFORMAT uniformResourceLocatorA =
+      ::RegisterClipboardFormat(CFSTR_INETURLA);
+  static CLIPFORMAT uniformResourceLocatorW =
+      ::RegisterClipboardFormat(CFSTR_INETURLW);
+  static CLIPFORMAT fileFlavor = ::RegisterClipboardFormat(CFSTR_FILECONTENTS);
+  static CLIPFORMAT PreferredDropEffect =
+      ::RegisterClipboardFormat(CFSTR_PREFERREDDROPEFFECT);
+
+  // Arbitrary system formats are used for image feedback during drag
+  // and drop. We are responsible for storing these internally during
+  // drag operations.
+  LPDATAENTRY pde;
+  if (LookupArbitraryFormat(aFormat, &pde, FALSE)) {
+    return CopyMediumData(pSTM, &pde->stgm, aFormat, FALSE) ? S_OK
+                                                            : E_UNEXPECTED;
+  }
+
+  // Firefox internal formats
+  ULONG count;
+  FORMATETC fe;
+  m_enumFE->Reset();
+  while (NOERROR == m_enumFE->Next(1, &fe, &count) &&
+         dfInx < mDataFlavors.Length()) {
+    nsCString& df = mDataFlavors.ElementAt(dfInx);
+    if (FormatsMatch(fe, *aFormat)) {
+      pSTM->pUnkForRelease =
+          nullptr;  // caller is responsible for deleting this data
+      CLIPFORMAT format = aFormat->cfFormat;
+      switch (format) {
+        // Someone is asking for plain or unicode text
+        case CF_TEXT:
+        case CF_UNICODETEXT:
+          return GetText(df, *aFormat, *pSTM);
+
+        // Some 3rd party apps that receive drag and drop files from the browser
+        // window require support for this.
+        case CF_HDROP:
+          return GetFile(*aFormat, *pSTM);
+
+        // Someone is asking for an image
+        case CF_DIBV5:
+        case CF_DIB:
+          return GetDib(df, *aFormat, *pSTM);
+
+        default:
+          if (format == fileDescriptorFlavorA)
+            return GetFileDescriptor(*aFormat, *pSTM, false);
+          if (format == fileDescriptorFlavorW)
+            return GetFileDescriptor(*aFormat, *pSTM, true);
+          if (format == uniformResourceLocatorA)
+            return GetUniformResourceLocator(*aFormat, *pSTM, false);
+          if (format == uniformResourceLocatorW)
+            return GetUniformResourceLocator(*aFormat, *pSTM, true);
+          if (format == fileFlavor) return GetFileContents(*aFormat, *pSTM);
+          if (format == PreferredDropEffect)
+            return GetPreferredDropEffect(*aFormat, *pSTM);
+          // MOZ_LOG(gWindowsLog, LogLevel::Info,
+          //       ("***** nsDataObj::GetData - Unknown format %u\n", format));
+          return GetText(df, *aFormat, *pSTM);
+      }  // switch
+    }    // if
+    dfInx++;
+  }  // while
+
+  return DATA_E_FORMATETC;
+}
+
+//-----------------------------------------------------
+STDMETHODIMP nsDataObj::GetDataHere(LPFORMATETC pFE, LPSTGMEDIUM pSTM) {
+  return E_FAIL;
+}
+
+//-----------------------------------------------------
+// Other objects querying to see if we support a
+// particular format
+//-----------------------------------------------------
+STDMETHODIMP nsDataObj::QueryGetData(LPFORMATETC pFE) {
+  // Arbitrary system formats are used for image feedback during drag
+  // and drop. We are responsible for storing these internally during
+  // drag operations.
+  LPDATAENTRY pde;
+  if (LookupArbitraryFormat(pFE, &pde, FALSE)) return S_OK;
+
+  // Firefox internal formats
+  ULONG count;
+  FORMATETC fe;
+  m_enumFE->Reset();
+  while (NOERROR == m_enumFE->Next(1, &fe, &count)) {
+    if (fe.cfFormat == pFE->cfFormat) {
+      return S_OK;
+    }
+  }
+  return E_FAIL;
+}
+
+//-----------------------------------------------------
+STDMETHODIMP nsDataObj::GetCanonicalFormatEtc(LPFORMATETC pFEIn,
+                                              LPFORMATETC pFEOut) {
+  return E_NOTIMPL;
+}
+
+//-----------------------------------------------------
+STDMETHODIMP nsDataObj::SetData(LPFORMATETC aFormat, LPSTGMEDIUM aMedium,
+                                BOOL shouldRel) {
+  // Arbitrary system formats are used for image feedback during drag
+  // and drop. We are responsible for storing these internally during
+  // drag operations.
+  LPDATAENTRY pde;
+  if (LookupArbitraryFormat(aFormat, &pde, TRUE)) {
+    // Release the old data the lookup handed us for this format. This
+    // may have been set in CopyMediumData when we originally stored the
+    // data.
+    if (pde->stgm.tymed) {
+      ReleaseStgMedium(&pde->stgm);
+      memset(&pde->stgm, 0, sizeof(STGMEDIUM));
+    }
+
+    bool result = true;
+    if (shouldRel) {
+      // If shouldRel is TRUE, the data object called owns the storage medium
+      // after the call returns. Store the incoming data in our data array for
+      // release when we are destroyed. This is the common case with arbitrary
+      // data from explorer.
+      pde->stgm = *aMedium;
+    } else {
+      // Copy the incoming data into our data array. (AFAICT, this never gets
+      // called with arbitrary formats for drag images.)
+      result = CopyMediumData(&pde->stgm, aMedium, aFormat, TRUE);
+    }
+    pde->fe.tymed = pde->stgm.tymed;
+
+    return result ? S_OK : DV_E_TYMED;
+  }
+
+  if (shouldRel) ReleaseStgMedium(aMedium);
+
+  return S_OK;
+}
+
+bool nsDataObj::LookupArbitraryFormat(FORMATETC* aFormat,
+                                      LPDATAENTRY* aDataEntry,
+                                      BOOL aAddorUpdate) {
+  *aDataEntry = nullptr;
+
+  if (aFormat->ptd != nullptr) return false;
+
+  // See if it's already in our list. If so return the data entry.
+  for (uint32_t idx = 0; idx < mDataEntryList.Length(); idx++) {
+    if (mDataEntryList[idx]->fe.cfFormat == aFormat->cfFormat &&
+        mDataEntryList[idx]->fe.dwAspect == aFormat->dwAspect &&
+        mDataEntryList[idx]->fe.lindex == aFormat->lindex) {
+      if (aAddorUpdate || (mDataEntryList[idx]->fe.tymed & aFormat->tymed)) {
+        // If the caller requests we update, or if the
+        // medium type matches, return the entry.
+        *aDataEntry = mDataEntryList[idx];
+        return true;
+      } else {
+        // Medium does not match, not found.
+        return false;
+      }
+    }
+  }
+
+  if (!aAddorUpdate) return false;
+
+  // Add another entry to mDataEntryList
+  LPDATAENTRY dataEntry = (LPDATAENTRY)CoTaskMemAlloc(sizeof(DATAENTRY));
+  if (!dataEntry) return false;
+
+  dataEntry->fe = *aFormat;
+  *aDataEntry = dataEntry;
+  memset(&dataEntry->stgm, 0, sizeof(STGMEDIUM));
+
+  // Add this to our IEnumFORMATETC impl. so we can return it when
+  // it's requested.
+  m_enumFE->AddFormatEtc(aFormat);
+
+  // Store a copy internally in the arbitrary formats array.
+  mDataEntryList.AppendElement(dataEntry);
+
+  return true;
+}
+
+bool nsDataObj::CopyMediumData(STGMEDIUM* aMediumDst, STGMEDIUM* aMediumSrc,
+                               LPFORMATETC aFormat, BOOL aSetData) {
+  STGMEDIUM stgmOut = *aMediumSrc;
+
+  switch (stgmOut.tymed) {
+    case TYMED_ISTREAM:
+      stgmOut.pstm->AddRef();
+      break;
+    case TYMED_ISTORAGE:
+      stgmOut.pstg->AddRef();
+      break;
+    case TYMED_HGLOBAL:
+      if (!aMediumSrc->pUnkForRelease) {
+        if (aSetData) {
+          if (aMediumSrc->tymed != TYMED_HGLOBAL) return false;
+          stgmOut.hGlobal =
+              OleDuplicateData(aMediumSrc->hGlobal, aFormat->cfFormat, 0);
+          if (!stgmOut.hGlobal) return false;
+        } else {
+          // We are returning this data from LookupArbitraryFormat, indicate to
+          // the shell we hold it and will free it.
+          stgmOut.pUnkForRelease = static_cast<IDataObject*>(this);
+        }
+      }
+      break;
+    default:
+      return false;
+  }
+
+  if (stgmOut.pUnkForRelease) stgmOut.pUnkForRelease->AddRef();
+
+  *aMediumDst = stgmOut;
+
+  return true;
+}
+
+//-----------------------------------------------------
+STDMETHODIMP nsDataObj::EnumFormatEtc(DWORD dwDir, LPENUMFORMATETC* ppEnum) {
+  switch (dwDir) {
+    case DATADIR_GET:
+      m_enumFE->Clone(ppEnum);
+      break;
+    case DATADIR_SET:
+      // fall through
+    default:
+      *ppEnum = nullptr;
+  }  // switch
+
+  if (nullptr == *ppEnum) return E_FAIL;
+
+  (*ppEnum)->Reset();
+  // Clone already AddRefed the result so don't addref it again.
+  return NOERROR;
+}
+
+//-----------------------------------------------------
+STDMETHODIMP nsDataObj::DAdvise(LPFORMATETC pFE, DWORD dwFlags,
+                                LPADVISESINK pIAdviseSink, DWORD* pdwConn) {
+  return OLE_E_ADVISENOTSUPPORTED;
+}
+
+//-----------------------------------------------------
+STDMETHODIMP nsDataObj::DUnadvise(DWORD dwConn) {
+  return OLE_E_ADVISENOTSUPPORTED;
+}
+
+//-----------------------------------------------------
+STDMETHODIMP nsDataObj::EnumDAdvise(LPENUMSTATDATA* ppEnum) {
+  return OLE_E_ADVISENOTSUPPORTED;
+}
+
+// IDataObjectAsyncCapability methods
+STDMETHODIMP nsDataObj::EndOperation(HRESULT hResult, IBindCtx* pbcReserved,
+                                     DWORD dwEffects) {
+  mIsInOperation = FALSE;
+  return S_OK;
+}
+
+STDMETHODIMP nsDataObj::GetAsyncMode(BOOL* pfIsOpAsync) {
+  *pfIsOpAsync = mIsAsyncMode;
+
+  return S_OK;
+}
+
+STDMETHODIMP nsDataObj::InOperation(BOOL* pfInAsyncOp) {
+  *pfInAsyncOp = mIsInOperation;
+
+  return S_OK;
+}
+
+STDMETHODIMP nsDataObj::SetAsyncMode(BOOL fDoOpAsync) {
+  mIsAsyncMode = fDoOpAsync;
+  return S_OK;
+}
+
+STDMETHODIMP nsDataObj::StartOperation(IBindCtx* pbcReserved) {
+  mIsInOperation = TRUE;
+  return S_OK;
+}
+
+//
+// GetDIB
+//
+// Someone is asking for a bitmap. The data in the transferable will be a
+// straight imgIContainer, so just QI it.
+//
+HRESULT
+nsDataObj::GetDib(const nsACString& inFlavor, FORMATETC& aFormat,
+                  STGMEDIUM& aSTG) {
+  nsCOMPtr<nsISupports> genericDataWrapper;
+  if (NS_FAILED(
+          mTransferable->GetTransferData(PromiseFlatCString(inFlavor).get(),
+                                         getter_AddRefs(genericDataWrapper)))) {
+    return E_FAIL;
+  }
+
+  nsCOMPtr<imgIContainer> image = do_QueryInterface(genericDataWrapper);
+  if (!image) {
+    return E_FAIL;
+  }
+
+  nsCOMPtr<imgITools> imgTools =
+      do_CreateInstance("@mozilla.org/image/tools;1");
+
+  nsAutoString options(u"bpp=32;"_ns);
+  if (aFormat.cfFormat == CF_DIBV5) {
+    options.AppendLiteral("version=5");
+  } else {
+    options.AppendLiteral("version=3");
+  }
+
+  nsCOMPtr<nsIInputStream> inputStream;
+  nsresult rv = imgTools->EncodeImage(image, nsLiteralCString(IMAGE_BMP),
+                                      options, getter_AddRefs(inputStream));
+  if (NS_FAILED(rv) || !inputStream) {
+    return E_FAIL;
+  }
+
+  nsCOMPtr<imgIEncoder> encoder = do_QueryInterface(inputStream);
+  if (!encoder) {
+    return E_FAIL;
+  }
+
+  uint32_t size = 0;
+  rv = encoder->GetImageBufferUsed(&size);
+  if (NS_FAILED(rv) || size <= BFH_LENGTH) {
+    return E_FAIL;
+  }
+
+  char* src = nullptr;
+  rv = encoder->GetImageBuffer(&src);
+  if (NS_FAILED(rv) || !src) {
+    return E_FAIL;
+  }
+
+  // We don't want the file header.
+  src += BFH_LENGTH;
+  size -= BFH_LENGTH;
+
+  HGLOBAL glob = ::GlobalAlloc(GMEM_MOVEABLE | GMEM_ZEROINIT, size);
+  if (!glob) {
+    return E_FAIL;
+  }
+
+  char* dst = (char*)::GlobalLock(glob);
+  ::CopyMemory(dst, src, size);
+  ::GlobalUnlock(glob);
+
+  aSTG.hGlobal = glob;
+  aSTG.tymed = TYMED_HGLOBAL;
+  return S_OK;
+}
+
+//
+// GetFileDescriptor
+//
+
+HRESULT
+nsDataObj ::GetFileDescriptor(FORMATETC& aFE, STGMEDIUM& aSTG,
+                              bool aIsUnicode) {
+  HRESULT res = S_OK;
+
+  // How we handle this depends on if we're dealing with an internet
+  // shortcut, since those are done under the covers.
+  if (IsFlavourPresent(kFilePromiseMime) || IsFlavourPresent(kFileMime)) {
+    if (aIsUnicode)
+      return GetFileDescriptor_IStreamW(aFE, aSTG);
+    else
+      return GetFileDescriptor_IStreamA(aFE, aSTG);
+  } else if (IsFlavourPresent(kURLMime)) {
+    if (aIsUnicode)
+      res = GetFileDescriptorInternetShortcutW(aFE, aSTG);
+    else
+      res = GetFileDescriptorInternetShortcutA(aFE, aSTG);
+  } else
+    NS_WARNING("Not yet implemented\n");
+
+  return res;
+}  // GetFileDescriptor
+
+//
+HRESULT
+nsDataObj ::GetFileContents(FORMATETC& aFE, STGMEDIUM& aSTG) {
+  HRESULT res = S_OK;
+
+  // How we handle this depends on if we're dealing with an internet
+  // shortcut, since those are done under the covers.
+  if (IsFlavourPresent(kFilePromiseMime) || IsFlavourPresent(kFileMime))
+    return GetFileContents_IStream(aFE, aSTG);
+  else if (IsFlavourPresent(kURLMime))
+    return GetFileContentsInternetShortcut(aFE, aSTG);
+  else
+    NS_WARNING("Not yet implemented\n");
+
+  return res;
+
+}  // GetFileContents
+
+// Ensure that the supplied name doesn't have invalid characters.
+static void ValidateFilename(nsString& aFilename, bool isShortcut) {
+  nsCOMPtr<nsIMIMEService> mimeService = do_GetService("@mozilla.org/mime;1");
+  if (NS_WARN_IF(!mimeService)) {
+    aFilename.Truncate();
+    return;
+  }
+
+  uint32_t flags = nsIMIMEService::VALIDATE_SANITIZE_ONLY;
+  if (isShortcut) {
+    flags |= nsIMIMEService::VALIDATE_ALLOW_INVALID_FILENAMES;
+  }
+
+  nsAutoString outFilename;
+  mimeService->ValidateFileNameForSaving(aFilename, EmptyCString(), flags,
+                                         outFilename);
+  aFilename = outFilename;
+}
+
+//
+// Given a unicode string, convert it to a valid local charset filename
+// and append the .url extension to be used for a shortcut file.
+// This ensures that we do not cut MBCS characters in the middle.
+//
+// It would seem that this is more functionality suited to being in nsIFile.
+//
+static bool CreateURLFilenameFromTextA(nsAutoString& aText, char* aFilename) {
+  if (aText.IsEmpty()) {
+    return false;
+  }
+  aText.AppendLiteral(".url");
+  ValidateFilename(aText, true);
+  if (aText.IsEmpty()) {
+    return false;
+  }
+
+  // ValidateFilename should already be checking the filename length, but do
+  // an extra check to verify for the local code page that the converted text
+  // doesn't go over MAX_PATH and just return false if it does.
+  char defaultChar = '_';
+  int currLen = WideCharToMultiByte(CP_ACP, WC_COMPOSITECHECK | WC_DEFAULTCHAR,
+                                    aText.get(), -1, aFilename, MAX_PATH,
+                                    &defaultChar, nullptr);
+  return currLen != 0;
+}
+
+// Wide character version of CreateURLFilenameFromTextA
+static bool CreateURLFilenameFromTextW(nsAutoString& aText,
+                                       wchar_t* aFilename) {
+  if (aText.IsEmpty()) {
+    return false;
+  }
+  aText.AppendLiteral(".url");
+  ValidateFilename(aText, true);
+  if (aText.IsEmpty() || aText.Length() >= MAX_PATH) {
+    return false;
+  }
+
+  wcscpy(&aFilename[0], aText.get());
+  return true;
+}
+
+#define PAGEINFO_PROPERTIES "chrome://navigator/locale/pageInfo.properties"
+
+static bool GetLocalizedString(const char* aName, nsAString& aString) {
+  nsCOMPtr<nsIStringBundleService> stringService =
+      mozilla::components::StringBundle::Service();
+  if (!stringService) return false;
+
+  nsCOMPtr<nsIStringBundle> stringBundle;
+  nsresult rv = stringService->CreateBundle(PAGEINFO_PROPERTIES,
+                                            getter_AddRefs(stringBundle));
+  if (NS_FAILED(rv)) return false;
+
+  rv = stringBundle->GetStringFromName(aName, aString);
+  return NS_SUCCEEDED(rv);
+}
+
+//
+// GetFileDescriptorInternetShortcut
+//
+// Create the special format for an internet shortcut and build up the data
+// structures the shell is expecting.
+//
+HRESULT
+nsDataObj ::GetFileDescriptorInternetShortcutA(FORMATETC& aFE,
+                                               STGMEDIUM& aSTG) {
+  // get the title of the shortcut
+  nsAutoString title;
+  if (NS_FAILED(ExtractShortcutTitle(title))) return E_OUTOFMEMORY;
+
+  HGLOBAL fileGroupDescHandle =
+      ::GlobalAlloc(GMEM_ZEROINIT | GMEM_SHARE, sizeof(FILEGROUPDESCRIPTORA));
+  if (!fileGroupDescHandle) return E_OUTOFMEMORY;
+
+  LPFILEGROUPDESCRIPTORA fileGroupDescA =
+      reinterpret_cast<LPFILEGROUPDESCRIPTORA>(
+          ::GlobalLock(fileGroupDescHandle));
+  if (!fileGroupDescA) {
+    ::GlobalFree(fileGroupDescHandle);
+    return E_OUTOFMEMORY;
+  }
+
+  // get a valid filename in the following order: 1) from the page title,
+  // 2) localized string for an untitled page, 3) just use "Untitled.url"
+  if (!CreateURLFilenameFromTextA(title, fileGroupDescA->fgd[0].cFileName)) {
+    nsAutoString untitled;
+    if (!GetLocalizedString("noPageTitle", untitled) ||
+        !CreateURLFilenameFromTextA(untitled,
+                                    fileGroupDescA->fgd[0].cFileName)) {
+      strcpy(fileGroupDescA->fgd[0].cFileName, "Untitled.url");
+    }
+  }
+
+  // one file in the file block
+  fileGroupDescA->cItems = 1;
+  fileGroupDescA->fgd[0].dwFlags = FD_LINKUI;
+
+  ::GlobalUnlock(fileGroupDescHandle);
+  aSTG.hGlobal = fileGroupDescHandle;
+  aSTG.tymed = TYMED_HGLOBAL;
+
+  return S_OK;
+}  // GetFileDescriptorInternetShortcutA
+
+HRESULT
+nsDataObj ::GetFileDescriptorInternetShortcutW(FORMATETC& aFE,
+                                               STGMEDIUM& aSTG) {
+  // get the title of the shortcut
+  nsAutoString title;
+  if (NS_FAILED(ExtractShortcutTitle(title))) return E_OUTOFMEMORY;
+
+  HGLOBAL fileGroupDescHandle =
+      ::GlobalAlloc(GMEM_ZEROINIT | GMEM_SHARE, sizeof(FILEGROUPDESCRIPTORW));
+  if (!fileGroupDescHandle) return E_OUTOFMEMORY;
+
+  LPFILEGROUPDESCRIPTORW fileGroupDescW =
+      reinterpret_cast<LPFILEGROUPDESCRIPTORW>(
+          ::GlobalLock(fileGroupDescHandle));
+  if (!fileGroupDescW) {
+    ::GlobalFree(fileGroupDescHandle);
+    return E_OUTOFMEMORY;
+  }
+
+  // get a valid filename in the following order: 1) from the page title,
+  // 2) localized string for an untitled page, 3) just use "Untitled.url"
+  if (!CreateURLFilenameFromTextW(title, fileGroupDescW->fgd[0].cFileName)) {
+    nsAutoString untitled;
+    if (!GetLocalizedString("noPageTitle", untitled) ||
+        !CreateURLFilenameFromTextW(untitled,
+                                    fileGroupDescW->fgd[0].cFileName)) {
+      wcscpy(fileGroupDescW->fgd[0].cFileName, L"Untitled.url");
+    }
+  }
+
+  // one file in the file block
+  fileGroupDescW->cItems = 1;
+  fileGroupDescW->fgd[0].dwFlags = FD_LINKUI;
+
+  ::GlobalUnlock(fileGroupDescHandle);
+  aSTG.hGlobal = fileGroupDescHandle;
+  aSTG.tymed = TYMED_HGLOBAL;
+
+  return S_OK;
+}  // GetFileDescriptorInternetShortcutW
+
+//
+// GetFileContentsInternetShortcut
+//
+// Create the special format for an internet shortcut and build up the data
+// structures the shell is expecting.
+//
+HRESULT
+nsDataObj ::GetFileContentsInternetShortcut(FORMATETC& aFE, STGMEDIUM& aSTG) {
+  static const char* kShellIconPref = "browser.shell.shortcutFavicons";
+  nsAutoString url;
+  if (NS_FAILED(ExtractShortcutURL(url))) return E_OUTOFMEMORY;
+
+  nsCOMPtr<nsIURI> aUri;
+  nsresult rv = NS_NewURI(getter_AddRefs(aUri), url);
+  if (NS_FAILED(rv)) {
+    return E_FAIL;
+  }
+
+  nsAutoCString asciiUrl;
+  rv = aUri->GetAsciiSpec(asciiUrl);
+  if (NS_FAILED(rv)) {
+    return E_FAIL;
+  }
+
+  RefPtr<AutoCloseEvent> event;
+
+  const char* shortcutFormatStr;
+  int totalLen;
+  nsCString asciiPath;
+  if (!Preferences::GetBool(kShellIconPref, true)) {
+    shortcutFormatStr = "[InternetShortcut]\r\nURL=%s\r\n";
+    const int formatLen = strlen(shortcutFormatStr) - 2;  // don't include %s
+    totalLen = formatLen + asciiUrl.Length();  // don't include null character
+  } else {
+    nsCOMPtr<nsIFile> icoFile;
+
+    nsAutoString aUriHash;
+
+    event = new AutoCloseEvent();
+    if (!event->IsInited()) {
+      return E_FAIL;
+    }
+
+    RefPtr<AutoSetEvent> e = new AutoSetEvent(WrapNotNull(event));
+    mozilla::widget::FaviconHelper::ObtainCachedIconFile(
+        aUri, aUriHash, mIOThread, true,
+        NS_NewRunnableFunction(
+            "FaviconHelper::RefreshDesktop", [e = std::move(e)] {
+              if (e->IsWaiting()) {
+                // Unblock IStream:::Read.
+                e->Signal();
+              } else {
+                // We could not wait until the favicon was available. We have
+                // to refresh to refect the favicon.
+                SendNotifyMessage(HWND_BROADCAST, WM_SETTINGCHANGE,
+                                  SPI_SETNONCLIENTMETRICS, 0);
+              }
+            }));
+
+    rv = mozilla::widget::FaviconHelper::GetOutputIconPath(aUri, icoFile, true);
+    NS_ENSURE_SUCCESS(rv, E_FAIL);
+    nsString path;
+    rv = icoFile->GetPath(path);
+    NS_ENSURE_SUCCESS(rv, E_FAIL);
+
+    if (IsAsciiNullTerminated(static_cast<const char16_t*>(path.get()))) {
+      LossyCopyUTF16toASCII(path, asciiPath);
+      shortcutFormatStr =
+          "[InternetShortcut]\r\nURL=%s\r\n"
+          "IDList=\r\nHotKey=0\r\nIconFile=%s\r\n"
+          "IconIndex=0\r\n";
+    } else {
+      int len =
+          WideCharToMultiByte(CP_UTF7, 0, char16ptr_t(path.BeginReading()),
+                              path.Length(), nullptr, 0, nullptr, nullptr);
+      NS_ENSURE_TRUE(len > 0, E_FAIL);
+      asciiPath.SetLength(len);
+      WideCharToMultiByte(CP_UTF7, 0, char16ptr_t(path.BeginReading()),
+                          path.Length(), asciiPath.BeginWriting(), len, nullptr,
+                          nullptr);
+      shortcutFormatStr =
+          "[InternetShortcut]\r\nURL=%s\r\n"
+          "IDList=\r\nHotKey=0\r\nIconIndex=0\r\n"
+          "[InternetShortcut.W]\r\nIconFile=%s\r\n";
+    }
+    const int formatLen = strlen(shortcutFormatStr) - 2 * 2;  // no %s twice
+    totalLen = formatLen + asciiUrl.Length() +
+               asciiPath.Length();  // we don't want a null character on the end
+  }
+
+  // create a global memory area and build up the file contents w/in it
+  nsAutoGlobalMem globalMem(nsHGLOBAL(::GlobalAlloc(GMEM_SHARE, totalLen)));
+  if (!globalMem) return E_OUTOFMEMORY;
+
+  char* contents = reinterpret_cast<char*>(::GlobalLock(globalMem.get()));
+  if (!contents) {
+    return E_OUTOFMEMORY;
+  }
+
+  // NOTE: we intentionally use the Microsoft version of snprintf here because
+  // it does NOT null
+  // terminate strings which reach the maximum size of the buffer. Since we know
+  // that the formatted length here is totalLen, this call to _snprintf will
+  // format the string into the buffer without appending the null character.
+
+  if (!Preferences::GetBool(kShellIconPref, true)) {
+    _snprintf(contents, totalLen, shortcutFormatStr, asciiUrl.get());
+  } else {
+    _snprintf(contents, totalLen, shortcutFormatStr, asciiUrl.get(),
+              asciiPath.get());
+  }
+
+  ::GlobalUnlock(globalMem.get());
+
+  if (aFE.tymed & TYMED_ISTREAM) {
+    if (!mIsInOperation) {
+      // The drop target didn't initiate an async operation.
+      // We can't block CMemStream::Read.
+      event = nullptr;
+    }
+    RefPtr<IStream> stream =
+        new CMemStream(globalMem.disown(), totalLen, event.forget());
+    stream.forget(&aSTG.pstm);
+    aSTG.tymed = TYMED_ISTREAM;
+  } else {
+    if (event && event->IsInited()) {
+      event->Signal();  // We can't block reading the global memory
+    }
+    aSTG.hGlobal = globalMem.disown();
+    aSTG.tymed = TYMED_HGLOBAL;
+  }
+
+  return S_OK;
+}  // GetFileContentsInternetShortcut
+
+// check if specified flavour is present in the transferable
+bool nsDataObj ::IsFlavourPresent(const char* inFlavour) {
+  bool retval = false;
+  NS_ENSURE_TRUE(mTransferable, false);
+
+  // get the list of flavors available in the transferable
+  nsTArray<nsCString> flavors;
+  nsresult rv = mTransferable->FlavorsTransferableCanExport(flavors);
+  NS_ENSURE_SUCCESS(rv, false);
+
+  // try to find requested flavour
+  for (uint32_t i = 0; i < flavors.Length(); ++i) {
+    if (flavors[i].Equals(inFlavour)) {
+      retval = true;  // found it!
+      break;
+    }
+  }  // for each flavor
+
+  return retval;
+}
+
+HRESULT nsDataObj::GetPreferredDropEffect(FORMATETC& aFE, STGMEDIUM& aSTG) {
+  HRESULT res = S_OK;
+  aSTG.tymed = TYMED_HGLOBAL;
+  aSTG.pUnkForRelease = nullptr;
+  HGLOBAL hGlobalMemory = nullptr;
+  hGlobalMemory = ::GlobalAlloc(GMEM_MOVEABLE, sizeof(DWORD));
+  if (hGlobalMemory) {
+    DWORD* pdw = (DWORD*)GlobalLock(hGlobalMemory);
+    // The PreferredDropEffect clipboard format is only registered if a
+    // drag/drop of an image happens from Mozilla to the desktop.  We want its
+    // value to be DROPEFFECT_MOVE in that case so that the file is moved from
+    // the temporary location, not copied. This value should, ideally, be set on
+    // the data object via SetData() but our IDataObject implementation doesn't
+    // implement SetData.  It adds data to the data object lazily only when the
+    // drop target asks for it.
+    *pdw = (DWORD)DROPEFFECT_MOVE;
+    GlobalUnlock(hGlobalMemory);
+  } else {
+    res = E_OUTOFMEMORY;
+  }
+  aSTG.hGlobal = hGlobalMemory;
+  return res;
+}
+
+//-----------------------------------------------------
+HRESULT nsDataObj::GetText(const nsACString& aDataFlavor, FORMATETC& aFE,
+                           STGMEDIUM& aSTG) {
+  void* data = nullptr;
+
+  const nsPromiseFlatCString& flavorStr = PromiseFlatCString(aDataFlavor);
+
+  // NOTE: CreateDataFromPrimitive creates new memory, that needs to be deleted
+  nsCOMPtr<nsISupports> genericDataWrapper;
+  nsresult rv = mTransferable->GetTransferData(
+      flavorStr.get(), getter_AddRefs(genericDataWrapper));
+  if (NS_FAILED(rv) || !genericDataWrapper) {
+    return E_FAIL;
+  }
+
+  uint32_t len;
+  nsPrimitiveHelpers::CreateDataFromPrimitive(
+      nsDependentCString(flavorStr.get()), genericDataWrapper, &data, &len);
+  if (!data) return E_FAIL;
+
+  HGLOBAL hGlobalMemory = nullptr;
+
+  aSTG.tymed = TYMED_HGLOBAL;
+  aSTG.pUnkForRelease = nullptr;
+
+  // We play games under the hood and advertise flavors that we know we
+  // can support, only they require a bit of conversion or munging of the data.
+  // Do that here.
+  //
+  // The transferable gives us data that is null-terminated, but this isn't
+  // reflected in the |len| parameter. Windoze apps expect this null to be there
+  // so bump our data buffer by the appropriate size to account for the null
+  // (one char for CF_TEXT, one char16_t for CF_UNICODETEXT).
+  DWORD allocLen = (DWORD)len;
+  if (aFE.cfFormat == CF_TEXT) {
+    // Someone is asking for text/plain; convert the unicode (assuming it's
+    // present) to text with the correct platform encoding.
+    size_t bufferSize = sizeof(char) * (len + 2);
+    char* plainTextData = static_cast<char*>(moz_xmalloc(bufferSize));
+    char16_t* castedUnicode = reinterpret_cast<char16_t*>(data);
+    int32_t plainTextLen =
+        WideCharToMultiByte(CP_ACP, 0, (LPCWSTR)castedUnicode, len / 2 + 1,
+                            plainTextData, bufferSize, NULL, NULL);
+    // replace the unicode data with our plaintext data. Recall that
+    // |plainTextLen| doesn't include the null in the length.
+    free(data);
+    if (plainTextLen) {
+      data = plainTextData;
+      allocLen = plainTextLen;
+    } else {
+      free(plainTextData);
+      NS_WARNING("Oh no, couldn't convert unicode to plain text");
+      return S_OK;
+    }
+  } else if (aFE.cfFormat == nsClipboard::GetHtmlClipboardFormat()) {
+    // Someone is asking for win32's HTML flavor. Convert our html fragment
+    // from unicode to UTF-8 then put it into a format specified by msft.
+    NS_ConvertUTF16toUTF8 converter(reinterpret_cast<char16_t*>(data));
+    char* utf8HTML = nullptr;
+    nsresult rv =
+        BuildPlatformHTML(converter.get(), &utf8HTML);  // null terminates
+
+    free(data);
+    if (NS_SUCCEEDED(rv) && utf8HTML) {
+      // replace the unicode data with our HTML data. Don't forget the null.
+      data = utf8HTML;
+      allocLen = strlen(utf8HTML) + sizeof(char);
+    } else {
+      NS_WARNING("Oh no, couldn't convert to HTML");
+      return S_OK;
+    }
+  } else if (aFE.cfFormat != nsClipboard::GetCustomClipboardFormat()) {
+    // we assume that any data that isn't caught above is unicode. This may
+    // be an erroneous assumption, but is true so far.
+    allocLen += sizeof(char16_t);
+  }
+
+  hGlobalMemory = (HGLOBAL)GlobalAlloc(GMEM_MOVEABLE, allocLen);
+
+  // Copy text to Global Memory Area
+  if (hGlobalMemory) {
+    char* dest = reinterpret_cast<char*>(GlobalLock(hGlobalMemory));
+    char* source = reinterpret_cast<char*>(data);
+    memcpy(dest, source, allocLen);  // copies the null as well
+    GlobalUnlock(hGlobalMemory);
+  }
+  aSTG.hGlobal = hGlobalMemory;
+
+  // Now, delete the memory that was created by CreateDataFromPrimitive (or our
+  // text/plain data)
+  free(data);
+
+  return S_OK;
+}
+
+//-----------------------------------------------------
+HRESULT nsDataObj::GetFile(FORMATETC& aFE, STGMEDIUM& aSTG) {
+  uint32_t dfInx = 0;
+  ULONG count;
+  FORMATETC fe;
+  m_enumFE->Reset();
+  while (NOERROR == m_enumFE->Next(1, &fe, &count) &&
+         dfInx < mDataFlavors.Length()) {
+    if (mDataFlavors[dfInx].EqualsLiteral(kNativeImageMime))
+      return DropImage(aFE, aSTG);
+    if (mDataFlavors[dfInx].EqualsLiteral(kFileMime))
+      return DropFile(aFE, aSTG);
+    if (mDataFlavors[dfInx].EqualsLiteral(kFilePromiseMime))
+      return DropTempFile(aFE, aSTG);
+    dfInx++;
+  }
+  return E_FAIL;
+}
+
+HRESULT nsDataObj::DropFile(FORMATETC& aFE, STGMEDIUM& aSTG) {
+  nsresult rv;
+  nsCOMPtr<nsISupports> genericDataWrapper;
+
+  if (NS_FAILED(mTransferable->GetTransferData(
+          kFileMime, getter_AddRefs(genericDataWrapper)))) {
+    return E_FAIL;
+  }
+  nsCOMPtr<nsIFile> file(do_QueryInterface(genericDataWrapper));
+  if (!file) return E_FAIL;
+
+  aSTG.tymed = TYMED_HGLOBAL;
+  aSTG.pUnkForRelease = nullptr;
+
+  nsAutoString path;
+  rv = file->GetPath(path);
+  if (NS_FAILED(rv)) return E_FAIL;
+
+  uint32_t allocLen = path.Length() + 2;
+  HGLOBAL hGlobalMemory = nullptr;
+  char16_t* dest;
+
+  hGlobalMemory = GlobalAlloc(GMEM_MOVEABLE,
+                              sizeof(DROPFILES) + allocLen * sizeof(char16_t));
+  if (!hGlobalMemory) return E_FAIL;
+
+  DROPFILES* pDropFile = (DROPFILES*)GlobalLock(hGlobalMemory);
+
+  // First, populate the drop file structure
+  pDropFile->pFiles = sizeof(DROPFILES);  // Offset to start of file name string
+  pDropFile->fNC = 0;
+  pDropFile->pt.x = 0;
+  pDropFile->pt.y = 0;
+  pDropFile->fWide = TRUE;
+
+  // Copy the filename right after the DROPFILES structure
+  dest = (char16_t*)(((char*)pDropFile) + pDropFile->pFiles);
+  memcpy(dest, path.get(), (allocLen - 1) * sizeof(char16_t));
+
+  // Two null characters are needed at the end of the file name.
+  // Lookup the CF_HDROP shell clipboard format for more info.
+  // Add the second null character right after the first one.
+  dest[allocLen - 1] = L'\0';
+
+  GlobalUnlock(hGlobalMemory);
+
+  aSTG.hGlobal = hGlobalMemory;
+
+  return S_OK;
+}
+
+HRESULT nsDataObj::DropImage(FORMATETC& aFE, STGMEDIUM& aSTG) {
+  nsresult rv;
+  if (!mCachedTempFile) {
+    nsCOMPtr<nsISupports> genericDataWrapper;
+
+    if (NS_FAILED(mTransferable->GetTransferData(
+            kNativeImageMime, getter_AddRefs(genericDataWrapper)))) {
+      return E_FAIL;
+    }
+    nsCOMPtr<imgIContainer> image(do_QueryInterface(genericDataWrapper));
+    if (!image) return E_FAIL;
+
+    nsCOMPtr<imgITools> imgTools =
+        do_CreateInstance("@mozilla.org/image/tools;1");
+    nsCOMPtr<nsIInputStream> inputStream;
+    rv = imgTools->EncodeImage(image, nsLiteralCString(IMAGE_BMP),
+                               u"bpp=32;version=3"_ns,
+                               getter_AddRefs(inputStream));
+    if (NS_FAILED(rv) || !inputStream) {
+      return E_FAIL;
+    }
+
+    nsCOMPtr<imgIEncoder> encoder = do_QueryInterface(inputStream);
+    if (!encoder) {
+      return E_FAIL;
+    }
+
+    uint32_t size = 0;
+    rv = encoder->GetImageBufferUsed(&size);
+    if (NS_FAILED(rv)) {
+      return E_FAIL;
+    }
+
+    char* src = nullptr;
+    rv = encoder->GetImageBuffer(&src);
+    if (NS_FAILED(rv) || !src) {
+      return E_FAIL;
+    }
+
+    // Save the bitmap to a temporary location.
+    nsCOMPtr<nsIFile> dropFile;
+    rv = NS_GetSpecialDirectory(NS_OS_TEMP_DIR, getter_AddRefs(dropFile));
+    if (!dropFile) {
+      return E_FAIL;
+    }
+
+    // Filename must be random so as not to confuse apps like
+    // Photoshop which handle multiple drags into a single window.
+    char buf[13];
+    nsCString filename;
+    NS_MakeRandomString(buf, 8);
+    memcpy(buf + 8, ".bmp", 5);
+    filename.Append(nsDependentCString(buf, 12));
+    dropFile->AppendNative(filename);
+    rv = dropFile->CreateUnique(nsIFile::NORMAL_FILE_TYPE, 0660);
+    if (NS_FAILED(rv)) {
+      return E_FAIL;
+    }
+
+    // Cache the temp file so we can delete it later and so
+    // it doesn't get recreated over and over on multiple calls
+    // which does occur from windows shell.
+    dropFile->Clone(getter_AddRefs(mCachedTempFile));
+
+    // Write the data to disk.
+    nsCOMPtr<nsIOutputStream> outStream;
+    rv = NS_NewLocalFileOutputStream(getter_AddRefs(outStream), dropFile);
+    if (NS_FAILED(rv)) {
+      return E_FAIL;
+    }
+
+    uint32_t written = 0;
+    rv = outStream->Write(src, size, &written);
+    if (NS_FAILED(rv) || written != size) {
+      return E_FAIL;
+    }
+
+    outStream->Close();
+  }
+
+  // Pass the file name back to the drop target so that it can access the file.
+  nsAutoString path;
+  rv = mCachedTempFile->GetPath(path);
+  if (NS_FAILED(rv)) return E_FAIL;
+
+  // Two null characters are needed to terminate the file name list.
+  HGLOBAL hGlobalMemory = nullptr;
+
+  uint32_t allocLen = path.Length() + 2;
+
+  aSTG.tymed = TYMED_HGLOBAL;
+  aSTG.pUnkForRelease = nullptr;
+
+  hGlobalMemory = GlobalAlloc(GMEM_MOVEABLE,
+                              sizeof(DROPFILES) + allocLen * sizeof(char16_t));
+  if (!hGlobalMemory) return E_FAIL;
+
+  DROPFILES* pDropFile = (DROPFILES*)GlobalLock(hGlobalMemory);
+
+  // First, populate the drop file structure.
+  pDropFile->pFiles =
+      sizeof(DROPFILES);  // Offset to start of file name char array.
+  pDropFile->fNC = 0;
+  pDropFile->pt.x = 0;
+  pDropFile->pt.y = 0;
+  pDropFile->fWide = TRUE;
+
+  // Copy the filename right after the DROPFILES structure.
+  char16_t* dest = (char16_t*)(((char*)pDropFile) + pDropFile->pFiles);
+  memcpy(dest, path.get(),
+         (allocLen - 1) *
+             sizeof(char16_t));  // Copies the null character in path as well.
+
+  // Two null characters are needed at the end of the file name.
+  // Lookup the CF_HDROP shell clipboard format for more info.
+  // Add the second null character right after the first one.
+  dest[allocLen - 1] = L'\0';
+
+  GlobalUnlock(hGlobalMemory);
+
+  aSTG.hGlobal = hGlobalMemory;
+
+  return S_OK;
+}
+
+HRESULT nsDataObj::DropTempFile(FORMATETC& aFE, STGMEDIUM& aSTG) {
+  nsresult rv;
+  if (!mCachedTempFile) {
+    // Tempfile will need a temporary location.
+    nsCOMPtr<nsIFile> dropFile;
+    rv = NS_GetSpecialDirectory(NS_OS_TEMP_DIR, getter_AddRefs(dropFile));
+    if (!dropFile) return E_FAIL;
+
+    // Filename must be random
+    nsCString filename;
+    nsAutoString wideFileName;
+    nsCOMPtr<nsIURI> sourceURI;
+    HRESULT res;
+    res = GetDownloadDetails(getter_AddRefs(sourceURI), wideFileName);
+    if (FAILED(res)) return res;
+    NS_CopyUnicodeToNative(wideFileName, filename);
+
+    dropFile->AppendNative(filename);
+    rv = dropFile->CreateUnique(nsIFile::NORMAL_FILE_TYPE, 0660);
+    if (NS_FAILED(rv)) return E_FAIL;
+
+    // Cache the temp file so we can delete it later and so
+    // it doesn't get recreated over and over on multiple calls
+    // which does occur from windows shell.
+    dropFile->Clone(getter_AddRefs(mCachedTempFile));
+
+    // Write the data to disk.
+    nsCOMPtr<nsIOutputStream> outStream;
+    rv = NS_NewLocalFileOutputStream(getter_AddRefs(outStream), dropFile);
+    if (NS_FAILED(rv)) return E_FAIL;
+
+    IStream* pStream = nullptr;
+    nsDataObj::CreateStream(&pStream);
+    NS_ENSURE_TRUE(pStream, E_FAIL);
+
+    char buffer[512];
+    ULONG readCount = 0;
+    uint32_t writeCount = 0;
+    while (1) {
+      HRESULT hres = pStream->Read(buffer, sizeof(buffer), &readCount);
+      if (FAILED(hres)) return E_FAIL;
+      if (readCount == 0) break;
+      rv = outStream->Write(buffer, readCount, &writeCount);
+      if (NS_FAILED(rv)) return E_FAIL;
+    }
+    outStream->Close();
+    pStream->Release();
+  }
+
+  // Pass the file name back to the drop target so that it can access the file.
+  nsAutoString path;
+  rv = mCachedTempFile->GetPath(path);
+  if (NS_FAILED(rv)) return E_FAIL;
+
+  uint32_t allocLen = path.Length() + 2;
+
+  // Two null characters are needed to terminate the file name list.
+  HGLOBAL hGlobalMemory = nullptr;
+
+  aSTG.tymed = TYMED_HGLOBAL;
+  aSTG.pUnkForRelease = nullptr;
+
+  hGlobalMemory = GlobalAlloc(GMEM_MOVEABLE,
+                              sizeof(DROPFILES) + allocLen * sizeof(char16_t));
+  if (!hGlobalMemory) return E_FAIL;
+
+  DROPFILES* pDropFile = (DROPFILES*)GlobalLock(hGlobalMemory);
+
+  // First, populate the drop file structure.
+  pDropFile->pFiles =
+      sizeof(DROPFILES);  // Offset to start of file name char array.
+  pDropFile->fNC = 0;
+  pDropFile->pt.x = 0;
+  pDropFile->pt.y = 0;
+  pDropFile->fWide = TRUE;
+
+  // Copy the filename right after the DROPFILES structure.
+  char16_t* dest = (char16_t*)(((char*)pDropFile) + pDropFile->pFiles);
+  memcpy(dest, path.get(),
+         (allocLen - 1) *
+             sizeof(char16_t));  // Copies the null character in path as well.
+
+  // Two null characters are needed at the end of the file name.
+  // Lookup the CF_HDROP shell clipboard format for more info.
+  // Add the second null character right after the first one.
+  dest[allocLen - 1] = L'\0';
+
+  GlobalUnlock(hGlobalMemory);
+
+  aSTG.hGlobal = hGlobalMemory;
+
+  return S_OK;
+}
+
+//-----------------------------------------------------
+// Registers the DataFlavor/FE pair.
+//-----------------------------------------------------
+void nsDataObj::AddDataFlavor(const char* aDataFlavor, LPFORMATETC aFE) {
+  // These two lists are the mapping to and from data flavors and FEs.
+  // Later, OLE will tell us it needs a certain type of FORMATETC (text,
+  // unicode, etc) unicode, etc), so we will look up the data flavor that
+  // corresponds to the FE and then ask the transferable for that type of data.
+  mDataFlavors.AppendElement(aDataFlavor);
+  m_enumFE->AddFormatEtc(aFE);
+}
+
+//-----------------------------------------------------
+// Sets the transferable object
+//-----------------------------------------------------
+void nsDataObj::SetTransferable(nsITransferable* aTransferable) {
+  NS_IF_RELEASE(mTransferable);
+
+  mTransferable = aTransferable;
+  if (nullptr == mTransferable) {
+    return;
+  }
+
+  NS_ADDREF(mTransferable);
+
+  return;
+}
+
+//
+// ExtractURL
+//
+// Roots around in the transferable for the appropriate flavor that indicates
+// a url and pulls out the url portion of the data. Used mostly for creating
+// internet shortcuts on the desktop. The url flavor is of the format:
+//
+//   <url> <linefeed> <page title>
+//
+nsresult nsDataObj ::ExtractShortcutURL(nsString& outURL) {
+  NS_ASSERTION(mTransferable, "We don't have a good transferable");
+  nsresult rv = NS_ERROR_FAILURE;
+
+  nsCOMPtr<nsISupports> genericURL;
+  if (NS_SUCCEEDED(mTransferable->GetTransferData(
+          kURLMime, getter_AddRefs(genericURL)))) {
+    nsCOMPtr<nsISupportsString> urlObject(do_QueryInterface(genericURL));
+    if (urlObject) {
+      nsAutoString url;
+      urlObject->GetData(url);
+      outURL = url;
+
+      // find the first linefeed in the data, that's where the url ends. trunc
+      // the result string at that point.
+      int32_t lineIndex = outURL.FindChar('\n');
+      NS_ASSERTION(lineIndex > 0,
+                   "Format for url flavor is <url> <linefeed> <page title>");
+      if (lineIndex > 0) {
+        outURL.Truncate(lineIndex);
+        rv = NS_OK;
+      }
+    }
+  } else if (NS_SUCCEEDED(mTransferable->GetTransferData(
+                 kURLDataMime, getter_AddRefs(genericURL))) ||
+             NS_SUCCEEDED(mTransferable->GetTransferData(
+                 kURLPrivateMime, getter_AddRefs(genericURL)))) {
+    nsCOMPtr<nsISupportsString> urlObject(do_QueryInterface(genericURL));
+    if (urlObject) {
+      nsAutoString url;
+      urlObject->GetData(url);
+      outURL = url;
+
+      rv = NS_OK;
+    }
+
+  }  // if found flavor
+
+  return rv;
+
+}  // ExtractShortcutURL
+
+//
+// ExtractShortcutTitle
+//
+// Roots around in the transferable for the appropriate flavor that indicates
+// a url and pulls out the title portion of the data. Used mostly for creating
+// internet shortcuts on the desktop. The url flavor is of the format:
+//
+//   <url> <linefeed> <page title>
+//
+nsresult nsDataObj ::ExtractShortcutTitle(nsString& outTitle) {
+  NS_ASSERTION(mTransferable, "We'd don't have a good transferable");
+  nsresult rv = NS_ERROR_FAILURE;
+
+  nsCOMPtr<nsISupports> genericURL;
+  if (NS_SUCCEEDED(mTransferable->GetTransferData(
+          kURLMime, getter_AddRefs(genericURL)))) {
+    nsCOMPtr<nsISupportsString> urlObject(do_QueryInterface(genericURL));
+    if (urlObject) {
+      nsAutoString url;
+      urlObject->GetData(url);
+
+      // find the first linefeed in the data, that's where the url ends. we want
+      // everything after that linefeed. FindChar() returns -1 if we can't find
+      int32_t lineIndex = url.FindChar('\n');
+      NS_ASSERTION(lineIndex != -1,
+                   "Format for url flavor is <url> <linefeed> <page title>");
+      if (lineIndex != -1) {
+        url.Mid(outTitle, lineIndex + 1, url.Length() - (lineIndex + 1));
+        rv = NS_OK;
+      }
+    }
+  }  // if found flavor
+
+  return rv;
+
+}  // ExtractShortcutTitle
+
+//
+// BuildPlatformHTML
+//
+// Munge our HTML data to win32's CF_HTML spec. Basically, put the requisite
+// header information on it. This will null-terminate |outPlatformHTML|. See
+//  https://docs.microsoft.com/en-us/windows/win32/dataxchg/html-clipboard-format
+// for details.
+//
+// We assume that |inOurHTML| is already a fragment (ie, doesn't have <HTML>
+// or <BODY> tags). We'll wrap the fragment with them to make other apps
+// happy.
+//
+nsresult nsDataObj ::BuildPlatformHTML(const char* inOurHTML,
+                                       char** outPlatformHTML) {
+  *outPlatformHTML = nullptr;
+  nsDependentCString inHTMLString(inOurHTML);
+
+  // Do we already have mSourceURL from a drag?
+  if (mSourceURL.IsEmpty()) {
+    nsAutoString url;
+    ExtractShortcutURL(url);
+
+    AppendUTF16toUTF8(url, mSourceURL);
+  }
+
+  constexpr auto kStartHTMLPrefix = "Version:0.9\r\nStartHTML:"_ns;
+  constexpr auto kEndHTMLPrefix = "\r\nEndHTML:"_ns;
+  constexpr auto kStartFragPrefix = "\r\nStartFragment:"_ns;
+  constexpr auto kEndFragPrefix = "\r\nEndFragment:"_ns;
+  constexpr auto kStartSourceURLPrefix = "\r\nSourceURL:"_ns;
+  constexpr auto kEndFragTrailer = "\r\n"_ns;
+
+  // The CF_HTML's size is embedded in the fragment, in such a way that the
+  // number of digits in the size is part of the size itself. While it _is_
+  // technically possible to compute the necessary size of the size-field
+  // precisely -- by trial and error, if nothing else -- it's simpler just to
+  // pick a rough but generous estimate and zero-pad it. (Zero-padding is
+  // explicitly permitted by the format definition.)
+  //
+  // Originally, in 2001, the "rough but generous estimate" was 8 digits. While
+  // a maximum size of (10**9 - 1) bytes probably would have covered all
+  // possible use-cases at the time, it's somewhat more likely to overflow
+  // nowadays. Nonetheless, for the sake of backwards compatibility with any
+  // misbehaving consumers of our existing CF_HTML output, we retain exactly
+  // that padding for (most) fragments where it suffices. (No such misbehaving
+  // consumers are actually known, so this is arguably paranoia.)
+  //
+  // It is now 2022. A padding size of 16 will cover up to about 8.8 petabytes,
+  // which should be enough for at least the next few years or so.
+  const size_t numberLength = inHTMLString.Length() < 9999'0000 ? 8 : 16;
+
+  const size_t sourceURLLength = mSourceURL.Length();
+
+  const size_t fixedHeaderLen =
+      kStartHTMLPrefix.Length() + kEndHTMLPrefix.Length() +
+      kStartFragPrefix.Length() + kEndFragPrefix.Length() +
+      kEndFragTrailer.Length() + (4 * numberLength);
+
+  const size_t totalHeaderLen =
+      fixedHeaderLen + (sourceURLLength > 0
+                            ? kStartSourceURLPrefix.Length() + sourceURLLength
+                            : 0);
+
+  constexpr auto kHeaderString = "<html><body>\r\n<!--StartFragment-->"_ns;
+  constexpr auto kTrailingString =
+      "<!--EndFragment-->\r\n"
+      "</body>\r\n"
+      "</html>"_ns;
+
+  // calculate the offsets
+  size_t startHTMLOffset = totalHeaderLen;
+  size_t startFragOffset = startHTMLOffset + kHeaderString.Length();
+
+  size_t endFragOffset = startFragOffset + inHTMLString.Length();
+  size_t endHTMLOffset = endFragOffset + kTrailingString.Length();
+
+  // now build the final version
+  nsCString clipboardString;
+  clipboardString.SetCapacity(endHTMLOffset);
+
+  const int numberLengthInt = static_cast<int>(numberLength);
+  clipboardString.Append(kStartHTMLPrefix);
+  clipboardString.AppendPrintf("%0*zu", numberLengthInt, startHTMLOffset);
+
+  clipboardString.Append(kEndHTMLPrefix);
+  clipboardString.AppendPrintf("%0*zu", numberLengthInt, endHTMLOffset);
+
+  clipboardString.Append(kStartFragPrefix);
+  clipboardString.AppendPrintf("%0*zu", numberLengthInt, startFragOffset);
+
+  clipboardString.Append(kEndFragPrefix);
+  clipboardString.AppendPrintf("%0*zu", numberLengthInt, endFragOffset);
+
+  if (sourceURLLength > 0) {
+    clipboardString.Append(kStartSourceURLPrefix);
+    clipboardString.Append(mSourceURL);
+  }
+
+  clipboardString.Append(kEndFragTrailer);
+
+  // Assert that the positional values were correct as we pass by their
+  // corresponding positions.
+  MOZ_ASSERT(clipboardString.Length() == startHTMLOffset);
+  clipboardString.Append(kHeaderString);
+  MOZ_ASSERT(clipboardString.Length() == startFragOffset);
+  clipboardString.Append(inHTMLString);
+  MOZ_ASSERT(clipboardString.Length() == endFragOffset);
+  clipboardString.Append(kTrailingString);
+  MOZ_ASSERT(clipboardString.Length() == endHTMLOffset);
+
+  *outPlatformHTML = ToNewCString(clipboardString, mozilla::fallible);
+  if (!*outPlatformHTML) return NS_ERROR_OUT_OF_MEMORY;
+
+  return NS_OK;
+}
+
+HRESULT
+nsDataObj ::GetUniformResourceLocator(FORMATETC& aFE, STGMEDIUM& aSTG,
+                                      bool aIsUnicode) {
+  HRESULT res = S_OK;
+  if (IsFlavourPresent(kURLMime)) {
+    if (aIsUnicode)
+      res = ExtractUniformResourceLocatorW(aFE, aSTG);
+    else
+      res = ExtractUniformResourceLocatorA(aFE, aSTG);
+  } else
+    NS_WARNING("Not yet implemented\n");
+  return res;
+}
+
+HRESULT
+nsDataObj::ExtractUniformResourceLocatorA(FORMATETC& aFE, STGMEDIUM& aSTG) {
+  HRESULT result = S_OK;
+
+  nsAutoString url;
+  if (NS_FAILED(ExtractShortcutURL(url))) return E_OUTOFMEMORY;
+
+  NS_LossyConvertUTF16toASCII asciiUrl(url);
+  const int totalLen = asciiUrl.Length() + 1;
+  HGLOBAL hGlobalMemory = GlobalAlloc(GMEM_ZEROINIT | GMEM_SHARE, totalLen);
+  if (!hGlobalMemory) return E_OUTOFMEMORY;
+
+  char* contents = reinterpret_cast<char*>(GlobalLock(hGlobalMemory));
+  if (!contents) {
+    GlobalFree(hGlobalMemory);
+    return E_OUTOFMEMORY;
+  }
+
+  strcpy(contents, asciiUrl.get());
+  GlobalUnlock(hGlobalMemory);
+  aSTG.hGlobal = hGlobalMemory;
+  aSTG.tymed = TYMED_HGLOBAL;
+
+  return result;
+}
+
+HRESULT
+nsDataObj::ExtractUniformResourceLocatorW(FORMATETC& aFE, STGMEDIUM& aSTG) {
+  HRESULT result = S_OK;
+
+  nsAutoString url;
+  if (NS_FAILED(ExtractShortcutURL(url))) return E_OUTOFMEMORY;
+
+  const int totalLen = (url.Length() + 1) * sizeof(char16_t);
+  HGLOBAL hGlobalMemory = GlobalAlloc(GMEM_ZEROINIT | GMEM_SHARE, totalLen);
+  if (!hGlobalMemory) return E_OUTOFMEMORY;
+
+  wchar_t* contents = reinterpret_cast<wchar_t*>(GlobalLock(hGlobalMemory));
+  if (!contents) {
+    GlobalFree(hGlobalMemory);
+    return E_OUTOFMEMORY;
+  }
+
+  wcscpy(contents, url.get());
+  GlobalUnlock(hGlobalMemory);
+  aSTG.hGlobal = hGlobalMemory;
+  aSTG.tymed = TYMED_HGLOBAL;
+
+  return result;
+}
+
+// Gets the filename from the kFilePromiseURLMime flavour
+HRESULT nsDataObj::GetDownloadDetails(nsIURI** aSourceURI,
+                                      nsAString& aFilename) {
+  *aSourceURI = nullptr;
+
+  NS_ENSURE_TRUE(mTransferable, E_FAIL);
+
+  // get the URI from the kFilePromiseURLMime flavor
+  nsCOMPtr<nsISupports> urlPrimitive;
+  nsresult rv = mTransferable->GetTransferData(kFilePromiseURLMime,
+                                               getter_AddRefs(urlPrimitive));
+  NS_ENSURE_SUCCESS(rv, E_FAIL);
+  nsCOMPtr<nsISupportsString> srcUrlPrimitive = do_QueryInterface(urlPrimitive);
+  NS_ENSURE_TRUE(srcUrlPrimitive, E_FAIL);
+
+  nsAutoString srcUri;
+  srcUrlPrimitive->GetData(srcUri);
+  if (srcUri.IsEmpty()) return E_FAIL;
+  nsCOMPtr<nsIURI> sourceURI;
+  NS_NewURI(getter_AddRefs(sourceURI), srcUri);
+
+  nsAutoString srcFileName;
+  nsCOMPtr<nsISupports> fileNamePrimitive;
+  Unused << mTransferable->GetTransferData(kFilePromiseDestFilename,
+                                           getter_AddRefs(fileNamePrimitive));
+  nsCOMPtr<nsISupportsString> srcFileNamePrimitive =
+      do_QueryInterface(fileNamePrimitive);
+  if (srcFileNamePrimitive) {
+    srcFileNamePrimitive->GetData(srcFileName);
+  } else {
+    nsCOMPtr<nsIURL> sourceURL = do_QueryInterface(sourceURI);
+    if (!sourceURL) return E_FAIL;
+
+    nsAutoCString urlFileName;
+    sourceURL->GetFileName(urlFileName);
+    NS_UnescapeURL(urlFileName);
+    CopyUTF8toUTF16(urlFileName, srcFileName);
+  }
+
+  // make the name safe for the filesystem
+  ValidateFilename(srcFileName, false);
+  if (srcFileName.IsEmpty()) return E_FAIL;
+
+  sourceURI.swap(*aSourceURI);
+  aFilename = srcFileName;
+  return S_OK;
+}
+
+HRESULT nsDataObj::GetFileDescriptor_IStreamA(FORMATETC& aFE, STGMEDIUM& aSTG) {
+  HGLOBAL fileGroupDescHandle =
+      ::GlobalAlloc(GMEM_ZEROINIT | GMEM_SHARE, sizeof(FILEGROUPDESCRIPTORW));
+  NS_ENSURE_TRUE(fileGroupDescHandle, E_OUTOFMEMORY);
+
+  LPFILEGROUPDESCRIPTORA fileGroupDescA =
+      reinterpret_cast<LPFILEGROUPDESCRIPTORA>(GlobalLock(fileGroupDescHandle));
+  if (!fileGroupDescA) {
+    ::GlobalFree(fileGroupDescHandle);
+    return E_OUTOFMEMORY;
+  }
+
+  nsAutoString wideFileName;
+  HRESULT res;
+  nsCOMPtr<nsIURI> sourceURI;
+  res = GetDownloadDetails(getter_AddRefs(sourceURI), wideFileName);
+  if (FAILED(res)) {
+    ::GlobalFree(fileGroupDescHandle);
+    return res;
+  }
+
+  nsAutoCString nativeFileName;
+  NS_CopyUnicodeToNative(wideFileName, nativeFileName);
+
+  strncpy(fileGroupDescA->fgd[0].cFileName, nativeFileName.get(), MAX_PATH - 1);
+  fileGroupDescA->fgd[0].cFileName[MAX_PATH - 1] = '\0';
+
+  // one file in the file block
+  fileGroupDescA->cItems = 1;
+  fileGroupDescA->fgd[0].dwFlags = FD_PROGRESSUI;
+
+  GlobalUnlock(fileGroupDescHandle);
+  aSTG.hGlobal = fileGroupDescHandle;
+  aSTG.tymed = TYMED_HGLOBAL;
+
+  return S_OK;
+}
+
+HRESULT nsDataObj::GetFileDescriptor_IStreamW(FORMATETC& aFE, STGMEDIUM& aSTG) {
+  HGLOBAL fileGroupDescHandle =
+      ::GlobalAlloc(GMEM_ZEROINIT | GMEM_SHARE, sizeof(FILEGROUPDESCRIPTORW));
+  NS_ENSURE_TRUE(fileGroupDescHandle, E_OUTOFMEMORY);
+
+  LPFILEGROUPDESCRIPTORW fileGroupDescW =
+      reinterpret_cast<LPFILEGROUPDESCRIPTORW>(GlobalLock(fileGroupDescHandle));
+  if (!fileGroupDescW) {
+    ::GlobalFree(fileGroupDescHandle);
+    return E_OUTOFMEMORY;
+  }
+
+  nsAutoString wideFileName;
+  HRESULT res;
+  nsCOMPtr<nsIURI> sourceURI;
+  res = GetDownloadDetails(getter_AddRefs(sourceURI), wideFileName);
+  if (FAILED(res)) {
+    ::GlobalFree(fileGroupDescHandle);
+    return res;
+  }
+
+  wcsncpy(fileGroupDescW->fgd[0].cFileName, wideFileName.get(), MAX_PATH - 1);
+  fileGroupDescW->fgd[0].cFileName[MAX_PATH - 1] = '\0';
+  // one file in the file block
+  fileGroupDescW->cItems = 1;
+  fileGroupDescW->fgd[0].dwFlags = FD_PROGRESSUI;
+
+  GlobalUnlock(fileGroupDescHandle);
+  aSTG.hGlobal = fileGroupDescHandle;
+  aSTG.tymed = TYMED_HGLOBAL;
+
+  return S_OK;
+}
+
+HRESULT nsDataObj::GetFileContents_IStream(FORMATETC& aFE, STGMEDIUM& aSTG) {
+  IStream* pStream = nullptr;
+
+  nsDataObj::CreateStream(&pStream);
+  NS_ENSURE_TRUE(pStream, E_FAIL);
+
+  aSTG.tymed = TYMED_ISTREAM;
+  aSTG.pstm = pStream;
+  aSTG.pUnkForRelease = nullptr;
+
+  return S_OK;
+}
diff --git a/widget/windows/nsDataObj.h b/widget/windows/nsDataObj.h
new file mode 100644
index 0000000000..17683e371a
--- /dev/null
+++ b/widget/windows/nsDataObj.h
@@ -0,0 +1,315 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef _NSDATAOBJ_H_
+#define _NSDATAOBJ_H_
+
+#include <oleidl.h>
+#include <shldisp.h>
+
+#include "mozilla/glue/WinUtils.h"
+#include "mozilla/LazyIdleThread.h"
+#include "nsCOMPtr.h"
+#include "nsString.h"
+#include "nsIFile.h"
+#include "nsIURI.h"
+#include "nsIStreamListener.h"
+#include "nsIChannel.h"
+#include "nsCOMArray.h"
+#include "nsITimer.h"
+#include "nsIURI.h"
+#include "nsString.h"
+#include "nsWindowsHelpers.h"
+
+class nsICookieJarSettings;
+class nsIPrincipal;
+class nsIReferrerInfo;
+class nsIThread;
+class nsITransferable;
+class CEnumFormatEtc;
+
+/*
+ * This ole registered class is used to facilitate drag-drop of objects which
+ * can be adapted by an object derived from CfDragDrop. The CfDragDrop is
+ * associated with instances via SetDragDrop().
+ */
+class nsDataObj : public IDataObject, public IDataObjectAsyncCapability {
+  RefPtr<mozilla::LazyIdleThread> mIOThread;
+
+ public:  // construction, destruction
+  explicit nsDataObj(nsIURI* uri = nullptr);
+
+ protected:
+  virtual ~nsDataObj();
+
+ public:  // IUnknown methods - see iunknown.h for documentation
+  STDMETHODIMP_(ULONG) AddRef() override;
+  STDMETHODIMP QueryInterface(REFIID, void**) override;
+  STDMETHODIMP_(ULONG) Release() override;
+
+  // support for clipboard
+  virtual void AddDataFlavor(const char* aDataFlavor, LPFORMATETC aFE);
+  void SetTransferable(nsITransferable* aTransferable);
+
+ public:  // IDataObject methods - these are general comments. see CfDragDrop
+          // for overriding behavior
+  // Store data in pSTM according to the format specified by pFE, if the
+  // format is supported (supported formats are specified in CfDragDrop::
+  // GetFormats) and return NOERROR; otherwise return DATA_E_FORMATETC. It
+  // is the callers responsibility to free pSTM if NOERROR is returned.
+  STDMETHODIMP GetData(LPFORMATETC pFE, LPSTGMEDIUM pSTM) override;
+
+  // Similar to GetData except that the caller allocates the structure
+  // referenced by pSTM.
+  STDMETHODIMP GetDataHere(LPFORMATETC pFE, LPSTGMEDIUM pSTM) override;
+
+  // Returns S_TRUE if this object supports the format specified by pSTM,
+  // S_FALSE otherwise.
+  STDMETHODIMP QueryGetData(LPFORMATETC pFE) override;
+
+  // Set pCanonFE to the canonical format of pFE if one exists and return
+  // NOERROR, otherwise return DATA_S_SAMEFORMATETC. A canonical format
+  // implies an identical rendering.
+  STDMETHODIMP GetCanonicalFormatEtc(LPFORMATETC pFE,
+                                     LPFORMATETC pCanonFE) final;
+
+  // Set this objects data according to the format specified by pFE and
+  // the storage medium specified by pSTM and return NOERROR, if the format
+  // is supported. If release is TRUE this object must release the storage
+  // associated with pSTM.
+  STDMETHODIMP SetData(LPFORMATETC pFE, LPSTGMEDIUM pSTM,
+                       BOOL release) override;
+
+  // Set ppEnum to an IEnumFORMATETC object which will iterate all of the
+  // data formats that this object supports. direction is either DATADIR_GET
+  // or DATADIR_SET.
+  STDMETHODIMP EnumFormatEtc(DWORD direction, LPENUMFORMATETC* ppEnum) final;
+
+  // Set up an advisory connection to this object based on the format specified
+  // by pFE, flags, and the pAdvise. Set pConn to the established advise
+  // connection.
+  STDMETHODIMP DAdvise(LPFORMATETC pFE, DWORD flags, LPADVISESINK pAdvise,
+                       DWORD* pConn) final;
+
+  // Turn off advising of a previous call to DAdvise which set pConn.
+  STDMETHODIMP DUnadvise(DWORD pConn) final;
+
+  // Set ppEnum to an IEnumSTATDATA object which will iterate over the
+  // existing objects which have established advisory connections to this
+  // object.
+  STDMETHODIMP EnumDAdvise(LPENUMSTATDATA* ppEnum) final;
+
+  // IDataObjectAsyncCapability methods
+  STDMETHODIMP EndOperation(HRESULT hResult, IBindCtx* pbcReserved,
+                            DWORD dwEffects) final;
+  STDMETHODIMP GetAsyncMode(BOOL* pfIsOpAsync) final;
+  STDMETHODIMP InOperation(BOOL* pfInAsyncOp) final;
+  STDMETHODIMP SetAsyncMode(BOOL fDoOpAsync) final;
+  STDMETHODIMP StartOperation(IBindCtx* pbcReserved) final;
+
+ private:  // other methods
+  // Gets the filename from the kFilePromiseURLMime flavour
+  HRESULT GetDownloadDetails(nsIURI** aSourceURI, nsAString& aFilename);
+
+  // help determine the kind of drag
+  bool IsFlavourPresent(const char* inFlavour);
+
+ protected:
+  HRESULT GetFile(FORMATETC& aFE, STGMEDIUM& aSTG);
+  HRESULT GetText(const nsACString& aDF, FORMATETC& aFE, STGMEDIUM& aSTG);
+
+ private:
+  HRESULT GetDib(const nsACString& inFlavor, FORMATETC&, STGMEDIUM& aSTG);
+
+  HRESULT DropImage(FORMATETC& aFE, STGMEDIUM& aSTG);
+  HRESULT DropFile(FORMATETC& aFE, STGMEDIUM& aSTG);
+  HRESULT DropTempFile(FORMATETC& aFE, STGMEDIUM& aSTG);
+
+  HRESULT GetUniformResourceLocator(FORMATETC& aFE, STGMEDIUM& aSTG,
+                                    bool aIsUnicode);
+  HRESULT ExtractUniformResourceLocatorA(FORMATETC& aFE, STGMEDIUM& aSTG);
+  HRESULT ExtractUniformResourceLocatorW(FORMATETC& aFE, STGMEDIUM& aSTG);
+  HRESULT GetFileDescriptor(FORMATETC& aFE, STGMEDIUM& aSTG, bool aIsUnicode);
+
+ protected:
+  HRESULT GetFileContents(FORMATETC& aFE, STGMEDIUM& aSTG);
+
+ private:
+  HRESULT GetPreferredDropEffect(FORMATETC& aFE, STGMEDIUM& aSTG);
+
+  // Provide the structures needed for an internet shortcut by the shell
+  HRESULT GetFileDescriptorInternetShortcutA(FORMATETC& aFE, STGMEDIUM& aSTG);
+  HRESULT GetFileDescriptorInternetShortcutW(FORMATETC& aFE, STGMEDIUM& aSTG);
+  HRESULT GetFileContentsInternetShortcut(FORMATETC& aFE, STGMEDIUM& aSTG);
+
+  // IStream implementation
+  HRESULT GetFileDescriptor_IStreamA(FORMATETC& aFE, STGMEDIUM& aSTG);
+  HRESULT GetFileDescriptor_IStreamW(FORMATETC& aFE, STGMEDIUM& aSTG);
+  HRESULT GetFileContents_IStream(FORMATETC& aFE, STGMEDIUM& aSTG);
+
+  nsresult ExtractShortcutURL(nsString& outURL);
+  nsresult ExtractShortcutTitle(nsString& outTitle);
+
+  // munge our HTML data to win32's CF_HTML spec. Will null terminate
+  nsresult BuildPlatformHTML(const char* inOurHTML, char** outPlatformHTML);
+
+  // Used for the SourceURL part of CF_HTML
+  nsCString mSourceURL;
+
+ protected:
+  BOOL FormatsMatch(const FORMATETC& source, const FORMATETC& target) const;
+
+  ULONG m_cRef;  // the reference count
+
+ private:
+  nsTArray<nsCString> mDataFlavors;
+
+  nsITransferable* mTransferable;  // nsDataObj owns and ref counts
+                                   // nsITransferable, the nsITransferable does
+                                   // know anything about the nsDataObj
+
+ protected:
+  CEnumFormatEtc* m_enumFE;  // Ownership Rules:
+                             // nsDataObj owns and ref counts CEnumFormatEtc,
+
+ private:
+  nsCOMPtr<nsIFile> mCachedTempFile;
+  RefPtr<nsDataObj> mKeepAlive;
+
+  BOOL mIsAsyncMode;
+  BOOL mIsInOperation;
+  ///////////////////////////////////////////////////////////////////////////////
+  // CStream class implementation
+  // this class is used in Drag and drop with download sample
+  // called from IDataObject::GetData
+  class CStreamBase : public IStream {
+    // IStream
+    STDMETHODIMP Clone(IStream** ppStream) final;
+    STDMETHODIMP Commit(DWORD dwFrags) final;
+    STDMETHODIMP CopyTo(IStream* pDestStream, ULARGE_INTEGER nBytesToCopy,
+                        ULARGE_INTEGER* nBytesRead,
+                        ULARGE_INTEGER* nBytesWritten) final;
+    STDMETHODIMP LockRegion(ULARGE_INTEGER nStart, ULARGE_INTEGER nBytes,
+                            DWORD dwFlags) final;
+    STDMETHODIMP Revert(void) final;
+    STDMETHODIMP Seek(LARGE_INTEGER nMove, DWORD dwOrigin,
+                      ULARGE_INTEGER* nNewPos) final;
+    STDMETHODIMP SetSize(ULARGE_INTEGER nNewSize) final;
+    STDMETHODIMP UnlockRegion(ULARGE_INTEGER nStart, ULARGE_INTEGER nBytes,
+                              DWORD dwFlags) final;
+    STDMETHODIMP Write(const void* pvBuffer, ULONG nBytesToRead,
+                       ULONG* nBytesRead) final;
+
+   protected:
+    uint32_t mStreamRead;
+
+    CStreamBase();
+    virtual ~CStreamBase();
+  };
+
+  class CStream final : public CStreamBase, public nsIStreamListener {
+    nsCOMPtr<nsIChannel> mChannel;
+    FallibleTArray<uint8_t> mChannelData;
+    nsresult mChannelResult;
+    bool mChannelRead;
+
+    virtual ~CStream();
+    nsresult WaitForCompletion();
+
+    // IUnknown
+    STDMETHOD(QueryInterface)(REFIID refiid, void** ppvResult) final;
+
+    // IStream
+    STDMETHODIMP Read(void* pvBuffer, ULONG nBytesToRead,
+                      ULONG* nBytesRead) final;
+    STDMETHODIMP Stat(STATSTG* statstg, DWORD dwFlags) final;
+
+   public:
+    CStream();
+    nsresult Init(nsIURI* pSourceURI, nsContentPolicyType aContentPolicyType,
+                  nsIPrincipal* aRequestingPrincipal,
+                  nsICookieJarSettings* aCookieJarSettings,
+                  nsIReferrerInfo* aReferrerInfo);
+
+    NS_DECL_ISUPPORTS
+    NS_DECL_NSIREQUESTOBSERVER
+    NS_DECL_NSISTREAMLISTENER
+  };
+
+  HRESULT CreateStream(IStream** outStream);
+
+  // This class must be thread-safe.
+  class AutoCloseEvent final {
+    const nsAutoHandle mEvent;
+
+    AutoCloseEvent(const AutoCloseEvent&) = delete;
+    void operator=(const AutoCloseEvent&) = delete;
+    ~AutoCloseEvent() = default;
+
+   public:
+    AutoCloseEvent();
+    bool IsInited() const;
+    void Signal() const;
+    DWORD Wait(DWORD aMillisec) const;
+    NS_INLINE_DECL_THREADSAFE_REFCOUNTING(AutoCloseEvent)
+  };
+
+  // This class must be thread-safe.
+  class AutoSetEvent final {
+    const RefPtr<AutoCloseEvent> mEvent;
+
+    AutoSetEvent(const AutoSetEvent&) = delete;
+    void operator=(const AutoSetEvent&) = delete;
+    ~AutoSetEvent();
+
+   public:
+    explicit AutoSetEvent(mozilla::NotNull<AutoCloseEvent*> aEvent);
+    void Signal() const;
+    bool IsWaiting() const;
+    NS_INLINE_DECL_THREADSAFE_REFCOUNTING(AutoSetEvent)
+  };
+
+  // This class must be thread-safe.
+  class CMemStream final : public CStreamBase {
+    static mozilla::glue::Win32SRWLock mLock;
+    const nsAutoGlobalMem mGlobalMem;
+    const RefPtr<AutoCloseEvent> mEvent;
+    const uint32_t mTotalLength;
+    RefPtr<IUnknown> mMarshaler;
+
+    virtual ~CMemStream();
+    void WaitForCompletion();
+
+    // IStream
+    STDMETHODIMP Read(void* pvBuffer, ULONG nBytesToRead,
+                      ULONG* nBytesRead) final;
+    STDMETHODIMP Stat(STATSTG* statstg, DWORD dwFlags) final;
+
+   public:
+    CMemStream(nsHGLOBAL aGlobalMem, uint32_t mTotalLength,
+               already_AddRefed<AutoCloseEvent> aEvent);
+
+    // IUnknown
+    STDMETHOD(QueryInterface)(REFIID refiid, void** ppvResult) final;
+    NS_INLINE_DECL_THREADSAFE_VIRTUAL_REFCOUNTING(CMemStream, final)
+  };
+
+ private:
+  // Drag and drop helper data for implementing drag and drop image support
+  typedef struct {
+    FORMATETC fe;
+    STGMEDIUM stgm;
+  } DATAENTRY, *LPDATAENTRY;
+
+  nsTArray<LPDATAENTRY> mDataEntryList;
+  nsCOMPtr<nsITimer> mTimer;
+
+  bool LookupArbitraryFormat(FORMATETC* aFormat, LPDATAENTRY* aDataEntry,
+                             BOOL aAddorUpdate);
+  bool CopyMediumData(STGMEDIUM* aMediumDst, STGMEDIUM* aMediumSrc,
+                      LPFORMATETC aFormat, BOOL aSetData);
+};
+
+#endif  // _NSDATAOBJ_H_
diff --git a/widget/windows/nsDataObjCollection.cpp b/widget/windows/nsDataObjCollection.cpp
new file mode 100644
index 0000000000..8750563602
--- /dev/null
+++ b/widget/windows/nsDataObjCollection.cpp
@@ -0,0 +1,370 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <shlobj.h>
+
+#include "nsDataObjCollection.h"
+#include "nsClipboard.h"
+#include "IEnumFE.h"
+
+#include <ole2.h>
+
+// {25589C3E-1FAC-47b9-BF43-CAEA89B79533}
+const IID IID_IDataObjCollection = {
+    0x25589c3e,
+    0x1fac,
+    0x47b9,
+    {0xbf, 0x43, 0xca, 0xea, 0x89, 0xb7, 0x95, 0x33}};
+
+/*
+ * Class nsDataObjCollection
+ */
+
+nsDataObjCollection::nsDataObjCollection() {}
+
+nsDataObjCollection::~nsDataObjCollection() { mDataObjects.Clear(); }
+
+// IUnknown interface methods - see iunknown.h for documentation
+STDMETHODIMP nsDataObjCollection::QueryInterface(REFIID riid, void** ppv) {
+  *ppv = nullptr;
+
+  if ((IID_IUnknown == riid) || (IID_IDataObject == riid)) {
+    *ppv = static_cast<IDataObject*>(this);
+    AddRef();
+    return NOERROR;
+  }
+
+  if (IID_IDataObjCollection == riid) {
+    *ppv = static_cast<nsIDataObjCollection*>(this);
+    AddRef();
+    return NOERROR;
+  }
+  // offer to operate asynchronously (required by nsDragService)
+  if (IID_IDataObjectAsyncCapability == riid) {
+    *ppv = static_cast<IDataObjectAsyncCapability*>(this);
+    AddRef();
+    return NOERROR;
+  }
+
+  return E_NOINTERFACE;
+}
+
+STDMETHODIMP_(ULONG) nsDataObjCollection::AddRef() { return ++m_cRef; }
+
+STDMETHODIMP_(ULONG) nsDataObjCollection::Release() {
+  if (0 != --m_cRef) return m_cRef;
+
+  delete this;
+
+  return 0;
+}
+
+// IDataObject methods
+STDMETHODIMP nsDataObjCollection::GetData(LPFORMATETC pFE, LPSTGMEDIUM pSTM) {
+  static CLIPFORMAT fileDescriptorFlavorA =
+      ::RegisterClipboardFormat(CFSTR_FILEDESCRIPTORA);
+  static CLIPFORMAT fileDescriptorFlavorW =
+      ::RegisterClipboardFormat(CFSTR_FILEDESCRIPTORW);
+  static CLIPFORMAT fileFlavor = ::RegisterClipboardFormat(CFSTR_FILECONTENTS);
+
+  switch (pFE->cfFormat) {
+    case CF_TEXT:
+    case CF_UNICODETEXT:
+      return GetText(pFE, pSTM);
+    case CF_HDROP:
+      return GetFile(pFE, pSTM);
+    default:
+      if (pFE->cfFormat == fileDescriptorFlavorA ||
+          pFE->cfFormat == fileDescriptorFlavorW) {
+        return GetFileDescriptors(pFE, pSTM);
+      }
+      if (pFE->cfFormat == fileFlavor) {
+        return GetFileContents(pFE, pSTM);
+      }
+  }
+  return GetFirstSupporting(pFE, pSTM);
+}
+
+STDMETHODIMP nsDataObjCollection::GetDataHere(LPFORMATETC pFE,
+                                              LPSTGMEDIUM pSTM) {
+  return E_FAIL;
+}
+
+// Other objects querying to see if we support a particular format
+STDMETHODIMP nsDataObjCollection::QueryGetData(LPFORMATETC pFE) {
+  UINT format = nsClipboard::GetFormat(MULTI_MIME);
+
+  if (format == pFE->cfFormat) {
+    return S_OK;
+  }
+
+  for (uint32_t i = 0; i < mDataObjects.Length(); ++i) {
+    IDataObject* dataObj = mDataObjects.ElementAt(i);
+    if (S_OK == dataObj->QueryGetData(pFE)) {
+      return S_OK;
+    }
+  }
+
+  return DV_E_FORMATETC;
+}
+
+STDMETHODIMP nsDataObjCollection::SetData(LPFORMATETC pFE, LPSTGMEDIUM pSTM,
+                                          BOOL fRelease) {
+  // Set arbitrary data formats on the first object in the collection and let
+  // it handle the heavy lifting
+  if (mDataObjects.Length() == 0) return E_FAIL;
+  return mDataObjects.ElementAt(0)->SetData(pFE, pSTM, fRelease);
+}
+
+// Registers a DataFlavor/FE pair
+void nsDataObjCollection::AddDataFlavor(const char* aDataFlavor,
+                                        LPFORMATETC aFE) {
+  // Add the FormatEtc to our list if it's not already there.  We don't care
+  // about the internal aDataFlavor because nsDataObj handles that.
+  IEnumFORMATETC* ifEtc;
+  FORMATETC fEtc;
+  ULONG num;
+  if (S_OK != this->EnumFormatEtc(DATADIR_GET, &ifEtc)) return;
+  while (S_OK == ifEtc->Next(1, &fEtc, &num)) {
+    NS_ASSERTION(
+        1 == num,
+        "Bit off more than we can chew in nsDataObjCollection::AddDataFlavor");
+    if (FormatsMatch(fEtc, *aFE)) {
+      ifEtc->Release();
+      return;
+    }
+  }  // If we didn't find a matching format, add this one
+  ifEtc->Release();
+  m_enumFE->AddFormatEtc(aFE);
+}
+
+// We accept ownership of the nsDataObj which we free on destruction
+void nsDataObjCollection::AddDataObject(IDataObject* aDataObj) {
+  nsDataObj* dataObj = reinterpret_cast<nsDataObj*>(aDataObj);
+  mDataObjects.AppendElement(dataObj);
+}
+
+// Methods for getting data
+HRESULT nsDataObjCollection::GetFile(LPFORMATETC pFE, LPSTGMEDIUM pSTM) {
+  STGMEDIUM workingmedium;
+  FORMATETC fe = *pFE;
+  HGLOBAL hGlobalMemory;
+  HRESULT hr;
+  // Make enough space for the header and the trailing null
+  uint32_t buffersize = sizeof(DROPFILES) + sizeof(char16_t);
+  uint32_t alloclen = 0;
+  char16_t* realbuffer;
+  nsAutoString filename;
+
+  hGlobalMemory = GlobalAlloc(GHND, buffersize);
+
+  for (uint32_t i = 0; i < mDataObjects.Length(); ++i) {
+    nsDataObj* dataObj = mDataObjects.ElementAt(i);
+    hr = dataObj->GetData(&fe, &workingmedium);
+    if (hr != S_OK) {
+      switch (hr) {
+        case DV_E_FORMATETC:
+          continue;
+        default:
+          return hr;
+      }
+    }
+    // Now we need to pull out the filename
+    char16_t* buffer = (char16_t*)GlobalLock(workingmedium.hGlobal);
+    if (buffer == nullptr) return E_FAIL;
+    buffer += sizeof(DROPFILES) / sizeof(char16_t);
+    filename = buffer;
+    GlobalUnlock(workingmedium.hGlobal);
+    ReleaseStgMedium(&workingmedium);
+    // Now put the filename into our buffer
+    alloclen = (filename.Length() + 1) * sizeof(char16_t);
+    hGlobalMemory = ::GlobalReAlloc(hGlobalMemory, buffersize + alloclen, GHND);
+    if (hGlobalMemory == nullptr) return E_FAIL;
+    realbuffer = (char16_t*)((char*)GlobalLock(hGlobalMemory) + buffersize);
+    if (!realbuffer) return E_FAIL;
+    realbuffer--;  // Overwrite the preceding null
+    memcpy(realbuffer, filename.get(), alloclen);
+    GlobalUnlock(hGlobalMemory);
+    buffersize += alloclen;
+  }
+  // We get the last null (on the double null terminator) for free since we used
+  // the zero memory flag when we allocated.  All we need to do is fill the
+  // DROPFILES structure
+  DROPFILES* df = (DROPFILES*)GlobalLock(hGlobalMemory);
+  if (!df) return E_FAIL;
+  df->pFiles = sizeof(DROPFILES);  // Offset to start of file name string
+  df->fNC = 0;
+  df->pt.x = 0;
+  df->pt.y = 0;
+  df->fWide = TRUE;  // utf-16 chars
+  GlobalUnlock(hGlobalMemory);
+  // Finally fill out the STGMEDIUM struct
+  pSTM->tymed = TYMED_HGLOBAL;
+  pSTM->pUnkForRelease = nullptr;  // Caller gets to free the data
+  pSTM->hGlobal = hGlobalMemory;
+  return S_OK;
+}
+
+HRESULT nsDataObjCollection::GetText(LPFORMATETC pFE, LPSTGMEDIUM pSTM) {
+  STGMEDIUM workingmedium;
+  FORMATETC fe = *pFE;
+  HGLOBAL hGlobalMemory;
+  HRESULT hr;
+  uint32_t buffersize = 1;
+  uint32_t alloclen = 0;
+
+  hGlobalMemory = GlobalAlloc(GHND, buffersize);
+
+  if (pFE->cfFormat == CF_TEXT) {
+    nsAutoCString text;
+    for (uint32_t i = 0; i < mDataObjects.Length(); ++i) {
+      nsDataObj* dataObj = mDataObjects.ElementAt(i);
+      hr = dataObj->GetData(&fe, &workingmedium);
+      if (hr != S_OK) {
+        switch (hr) {
+          case DV_E_FORMATETC:
+            continue;
+          default:
+            return hr;
+        }
+      }
+      // Now we need to pull out the text
+      char* buffer = (char*)GlobalLock(workingmedium.hGlobal);
+      if (buffer == nullptr) return E_FAIL;
+      text = buffer;
+      GlobalUnlock(workingmedium.hGlobal);
+      ReleaseStgMedium(&workingmedium);
+      // Now put the text into our buffer
+      alloclen = text.Length();
+      hGlobalMemory =
+          ::GlobalReAlloc(hGlobalMemory, buffersize + alloclen, GHND);
+      if (hGlobalMemory == nullptr) return E_FAIL;
+      buffer = ((char*)GlobalLock(hGlobalMemory) + buffersize);
+      if (!buffer) return E_FAIL;
+      buffer--;  // Overwrite the preceding null
+      memcpy(buffer, text.get(), alloclen);
+      GlobalUnlock(hGlobalMemory);
+      buffersize += alloclen;
+    }
+    pSTM->tymed = TYMED_HGLOBAL;
+    pSTM->pUnkForRelease = nullptr;  // Caller gets to free the data
+    pSTM->hGlobal = hGlobalMemory;
+    return S_OK;
+  }
+  if (pFE->cfFormat == CF_UNICODETEXT) {
+    buffersize = sizeof(char16_t);
+    nsAutoString text;
+    for (uint32_t i = 0; i < mDataObjects.Length(); ++i) {
+      nsDataObj* dataObj = mDataObjects.ElementAt(i);
+      hr = dataObj->GetData(&fe, &workingmedium);
+      if (hr != S_OK) {
+        switch (hr) {
+          case DV_E_FORMATETC:
+            continue;
+          default:
+            return hr;
+        }
+      }
+      // Now we need to pull out the text
+      char16_t* buffer = (char16_t*)GlobalLock(workingmedium.hGlobal);
+      if (buffer == nullptr) return E_FAIL;
+      text = buffer;
+      GlobalUnlock(workingmedium.hGlobal);
+      ReleaseStgMedium(&workingmedium);
+      // Now put the text into our buffer
+      alloclen = text.Length() * sizeof(char16_t);
+      hGlobalMemory =
+          ::GlobalReAlloc(hGlobalMemory, buffersize + alloclen, GHND);
+      if (hGlobalMemory == nullptr) return E_FAIL;
+      buffer = (char16_t*)((char*)GlobalLock(hGlobalMemory) + buffersize);
+      if (!buffer) return E_FAIL;
+      buffer--;  // Overwrite the preceding null
+      memcpy(buffer, text.get(), alloclen);
+      GlobalUnlock(hGlobalMemory);
+      buffersize += alloclen;
+    }
+    pSTM->tymed = TYMED_HGLOBAL;
+    pSTM->pUnkForRelease = nullptr;  // Caller gets to free the data
+    pSTM->hGlobal = hGlobalMemory;
+    return S_OK;
+  }
+
+  return E_FAIL;
+}
+
+HRESULT nsDataObjCollection::GetFileDescriptors(LPFORMATETC pFE,
+                                                LPSTGMEDIUM pSTM) {
+  STGMEDIUM workingmedium;
+  FORMATETC fe = *pFE;
+  HGLOBAL hGlobalMemory;
+  HRESULT hr;
+  uint32_t buffersize = sizeof(UINT);
+  uint32_t alloclen = sizeof(FILEDESCRIPTOR);
+
+  hGlobalMemory = GlobalAlloc(GHND, buffersize);
+
+  for (uint32_t i = 0; i < mDataObjects.Length(); ++i) {
+    nsDataObj* dataObj = mDataObjects.ElementAt(i);
+    hr = dataObj->GetData(&fe, &workingmedium);
+    if (hr != S_OK) {
+      switch (hr) {
+        case DV_E_FORMATETC:
+          continue;
+        default:
+          return hr;
+      }
+    }
+    // Now we need to pull out the filedescriptor
+    FILEDESCRIPTOR* buffer =
+        (FILEDESCRIPTOR*)((char*)GlobalLock(workingmedium.hGlobal) +
+                          sizeof(UINT));
+    if (buffer == nullptr) return E_FAIL;
+    hGlobalMemory = ::GlobalReAlloc(hGlobalMemory, buffersize + alloclen, GHND);
+    if (hGlobalMemory == nullptr) return E_FAIL;
+    FILEGROUPDESCRIPTOR* realbuffer =
+        (FILEGROUPDESCRIPTOR*)GlobalLock(hGlobalMemory);
+    if (!realbuffer) return E_FAIL;
+    FILEDESCRIPTOR* copyloc = (FILEDESCRIPTOR*)((char*)realbuffer + buffersize);
+    memcpy(copyloc, buffer, alloclen);
+    realbuffer->cItems++;
+    GlobalUnlock(hGlobalMemory);
+    GlobalUnlock(workingmedium.hGlobal);
+    ReleaseStgMedium(&workingmedium);
+    buffersize += alloclen;
+  }
+  pSTM->tymed = TYMED_HGLOBAL;
+  pSTM->pUnkForRelease = nullptr;  // Caller gets to free the data
+  pSTM->hGlobal = hGlobalMemory;
+  return S_OK;
+}
+
+HRESULT nsDataObjCollection::GetFileContents(LPFORMATETC pFE,
+                                             LPSTGMEDIUM pSTM) {
+  ULONG num = 0;
+  ULONG numwanted = (pFE->lindex == -1) ? 0 : pFE->lindex;
+  FORMATETC fEtc = *pFE;
+  fEtc.lindex = -1;  // We're lying to the data object so it thinks it's alone
+
+  // The key for this data type is to figure out which data object the index
+  // corresponds to and then just pass it along
+  for (uint32_t i = 0; i < mDataObjects.Length(); ++i) {
+    nsDataObj* dataObj = mDataObjects.ElementAt(i);
+    if (dataObj->QueryGetData(&fEtc) != S_OK) continue;
+    if (num == numwanted) return dataObj->GetData(pFE, pSTM);
+    num++;
+  }
+  return DV_E_LINDEX;
+}
+
+HRESULT nsDataObjCollection::GetFirstSupporting(LPFORMATETC pFE,
+                                                LPSTGMEDIUM pSTM) {
+  // There is no way to pass more than one of this, so just find the first data
+  // object that supports it and pass it along
+  for (uint32_t i = 0; i < mDataObjects.Length(); ++i) {
+    if (mDataObjects.ElementAt(i)->QueryGetData(pFE) == S_OK)
+      return mDataObjects.ElementAt(i)->GetData(pFE, pSTM);
+  }
+  return DV_E_FORMATETC;
+}
diff --git a/widget/windows/nsDataObjCollection.h b/widget/windows/nsDataObjCollection.h
new file mode 100644
index 0000000000..02ec7e8916
--- /dev/null
+++ b/widget/windows/nsDataObjCollection.h
@@ -0,0 +1,92 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef _NSDATAOBJCOLLECTION_H_
+#define _NSDATAOBJCOLLECTION_H_
+
+#include <oleidl.h>
+
+#include "mozilla/RefPtr.h"
+#include "nsString.h"
+#include "nsTArray.h"
+#include "nsDataObj.h"
+#include "mozilla/Attributes.h"
+
+#define MULTI_MIME "Mozilla/IDataObjectCollectionFormat"
+
+EXTERN_C const IID IID_IDataObjCollection;
+
+// An interface to make sure we have the right kind of object for D&D
+// this way we can filter out collection objects that aren't ours
+class nsIDataObjCollection : public IUnknown {
+ public:
+};
+
+/*
+ * This ole registered class is used to facilitate drag-drop of objects which
+ * can be adapted by an object derived from CfDragDrop. The CfDragDrop is
+ * associated with instances via SetDragDrop().
+ */
+
+class nsDataObjCollection final : public nsIDataObjCollection,
+                                  public nsDataObj {
+ public:
+  nsDataObjCollection();
+
+ private:
+  ~nsDataObjCollection() final;
+
+ public:  // IUnknown methods - see iunknown.h for documentation
+  STDMETHODIMP_(ULONG) AddRef() final;
+  STDMETHODIMP QueryInterface(REFIID, void**) final;
+  STDMETHODIMP_(ULONG) Release() final;
+
+ private:  // DataGet and DataSet helper methods
+  HRESULT GetFile(LPFORMATETC pFE, LPSTGMEDIUM pSTM);
+  HRESULT GetText(LPFORMATETC pFE, LPSTGMEDIUM pSTM);
+  HRESULT GetFileDescriptors(LPFORMATETC pFE, LPSTGMEDIUM pSTM);
+  HRESULT GetFileContents(LPFORMATETC pFE, LPSTGMEDIUM pSTM);
+  HRESULT GetFirstSupporting(LPFORMATETC pFE, LPSTGMEDIUM pSTM);
+
+  using nsDataObj::GetFile;
+  using nsDataObj::GetFileContents;
+  using nsDataObj::GetText;
+
+  // support for clipboard
+  void AddDataFlavor(const char* aDataFlavor, LPFORMATETC aFE) final;
+
+ public:  // from nsPIDataObjCollection
+  void AddDataObject(IDataObject* aDataObj);
+  int32_t GetNumDataObjects() { return mDataObjects.Length(); }
+  nsDataObj* GetDataObjectAt(uint32_t aItem) {
+    return mDataObjects.SafeElementAt(aItem, RefPtr<nsDataObj>());
+  }
+
+ public:
+  // Store data in pSTM according to the format specified by pFE, if the
+  // format is supported (supported formats are specified in CfDragDrop::
+  // GetFormats) and return NOERROR; otherwise return DATA_E_FORMATETC. It
+  // is the callers responsibility to free pSTM if NOERROR is returned.
+  STDMETHODIMP GetData(LPFORMATETC pFE, LPSTGMEDIUM pSTM) final;
+
+  // Similar to GetData except that the caller allocates the structure
+  // referenced by pSTM.
+  STDMETHODIMP GetDataHere(LPFORMATETC pFE, LPSTGMEDIUM pSTM) final;
+
+  // Returns S_TRUE if this object supports the format specified by pSTM,
+  // S_FALSE otherwise.
+  STDMETHODIMP QueryGetData(LPFORMATETC pFE) final;
+
+  // Set this objects data according to the format specified by pFE and
+  // the storage medium specified by pSTM and return NOERROR, if the format
+  // is supported. If release is TRUE this object must release the storage
+  // associated with pSTM.
+  STDMETHODIMP SetData(LPFORMATETC pFE, LPSTGMEDIUM pSTM, BOOL release) final;
+
+ private:
+  nsTArray<RefPtr<nsDataObj> > mDataObjects;
+};
+
+#endif  //
diff --git a/widget/windows/nsDeviceContextSpecWin.cpp b/widget/windows/nsDeviceContextSpecWin.cpp
new file mode 100644
index 0000000000..ac3bf6f6ed
--- /dev/null
+++ b/widget/windows/nsDeviceContextSpecWin.cpp
@@ -0,0 +1,680 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsDeviceContextSpecWin.h"
+
+#include "mozilla/ArrayUtils.h"
+#include "mozilla/gfx/PrintPromise.h"
+#include "mozilla/gfx/PrintTargetPDF.h"
+#include "mozilla/gfx/PrintTargetWindows.h"
+#include "mozilla/Logging.h"
+#include "mozilla/Preferences.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/Telemetry.h"
+#include "nsAnonymousTemporaryFile.h"
+
+#include <wchar.h>
+#include <windef.h>
+#include <winspool.h>
+
+#include "nsIWidget.h"
+
+#include "nsTArray.h"
+#include "nsIPrintSettingsWin.h"
+
+#include "nsComponentManagerUtils.h"
+#include "nsPrinterWin.h"
+#include "nsReadableUtils.h"
+#include "nsString.h"
+
+#include "gfxWindowsSurface.h"
+
+#include "nsIFileStreams.h"
+#include "nsWindowsHelpers.h"
+
+#include "mozilla/gfx/Logging.h"
+
+#ifdef MOZ_ENABLE_SKIA_PDF
+#  include "mozilla/gfx/PrintTargetSkPDF.h"
+#  include "mozilla/gfx/PrintTargetEMF.h"
+#  include "nsIUUIDGenerator.h"
+#  include "nsDirectoryServiceDefs.h"
+#  include "nsPrintfCString.h"
+#  include "nsThreadUtils.h"
+#endif
+
+extern mozilla::LazyLogModule gPrintingLog;
+#define PR_PL(_p1) MOZ_LOG(gPrintingLog, mozilla::LogLevel::Debug, _p1)
+
+using namespace mozilla;
+using namespace mozilla::gfx;
+
+#ifdef MOZ_ENABLE_SKIA_PDF
+using namespace mozilla::widget;
+#endif
+
+static const wchar_t kDriverName[] = L"WINSPOOL";
+
+//----------------------------------------------------------------------------------
+//---------------
+// static members
+//----------------------------------------------------------------------------------
+nsDeviceContextSpecWin::nsDeviceContextSpecWin() = default;
+
+//----------------------------------------------------------------------------------
+
+NS_IMPL_ISUPPORTS(nsDeviceContextSpecWin, nsIDeviceContextSpec)
+
+nsDeviceContextSpecWin::~nsDeviceContextSpecWin() {
+  SetDevMode(nullptr);
+
+  if (mTempFile) {
+    mTempFile->Remove(/* recursive = */ false);
+  }
+
+  if (nsCOMPtr<nsIPrintSettingsWin> ps = do_QueryInterface(mPrintSettings)) {
+    ps->SetDeviceName(u""_ns);
+    ps->SetDriverName(u""_ns);
+    ps->SetDevMode(nullptr);
+  }
+}
+
+static bool GetDefaultPrinterName(nsAString& aDefaultPrinterName) {
+  DWORD length = 0;
+  GetDefaultPrinterW(nullptr, &length);
+
+  if (length) {
+    aDefaultPrinterName.SetLength(length);
+    if (GetDefaultPrinterW((LPWSTR)aDefaultPrinterName.BeginWriting(),
+                           &length)) {
+      // `length` includes the terminating null, so we subtract that from our
+      // string length.
+      aDefaultPrinterName.SetLength(length - 1);
+      PR_PL(("DEFAULT PRINTER [%s]\n",
+             NS_ConvertUTF16toUTF8(aDefaultPrinterName).get()));
+      return true;
+    }
+  }
+
+  aDefaultPrinterName.Truncate();
+  PR_PL(("NO DEFAULT PRINTER\n"));
+  return false;
+}
+
+//----------------------------------------------------------------------------------
+NS_IMETHODIMP nsDeviceContextSpecWin::Init(nsIPrintSettings* aPrintSettings,
+                                           bool aIsPrintPreview) {
+  mPrintSettings = aPrintSettings;
+
+  // Get the Printer Name to be used and output format.
+  nsAutoString printerName;
+  if (mPrintSettings) {
+    mOutputFormat = mPrintSettings->GetOutputFormat();
+    mPrintSettings->GetPrinterName(printerName);
+  }
+
+  // If there is no name then use the default printer
+  if (printerName.IsEmpty()) {
+    GetDefaultPrinterName(printerName);
+  }
+
+  // Gather telemetry on the print target type.
+  //
+  // Unfortunately, if we're not using our own internal save-to-pdf codepaths,
+  // there isn't a good way to determine whether a print is going to be to a
+  // physical printer or to a file or some other non-physical output. We do our
+  // best by checking for what seems to be the most common save-to-PDF virtual
+  // printers.
+  //
+  // We use StringBeginsWith below, since printer names are often followed by a
+  // version number or other product differentiating string.  (True for doPDF,
+  // novaPDF, PDF-XChange and Soda PDF, for example.)
+  if (mOutputFormat == nsIPrintSettings::kOutputFormatPDF) {
+    Telemetry::ScalarAdd(Telemetry::ScalarID::PRINTING_TARGET_TYPE,
+                         u"pdf_file"_ns, 1);
+  } else if (StringBeginsWith(printerName, u"Microsoft Print to PDF"_ns) ||
+             StringBeginsWith(printerName, u"Adobe PDF"_ns) ||
+             StringBeginsWith(printerName, u"Bullzip PDF Printer"_ns) ||
+             StringBeginsWith(printerName, u"CutePDF Writer"_ns) ||
+             StringBeginsWith(printerName, u"doPDF"_ns) ||
+             StringBeginsWith(printerName, u"Foxit Reader PDF Printer"_ns) ||
+             StringBeginsWith(printerName, u"Nitro PDF Creator"_ns) ||
+             StringBeginsWith(printerName, u"novaPDF"_ns) ||
+             StringBeginsWith(printerName, u"PDF-XChange"_ns) ||
+             StringBeginsWith(printerName, u"PDF24 PDF"_ns) ||
+             StringBeginsWith(printerName, u"PDFCreator"_ns) ||
+             StringBeginsWith(printerName, u"PrimoPDF"_ns) ||
+             StringBeginsWith(printerName, u"Soda PDF"_ns) ||
+             StringBeginsWith(printerName, u"Solid PDF Creator"_ns) ||
+             StringBeginsWith(printerName,
+                              u"Universal Document Converter"_ns)) {
+    Telemetry::ScalarAdd(Telemetry::ScalarID::PRINTING_TARGET_TYPE,
+                         u"pdf_file"_ns, 1);
+  } else if (printerName.EqualsLiteral("Microsoft XPS Document Writer")) {
+    Telemetry::ScalarAdd(Telemetry::ScalarID::PRINTING_TARGET_TYPE,
+                         u"xps_file"_ns, 1);
+  } else {
+    nsAString::const_iterator start, end;
+    printerName.BeginReading(start);
+    printerName.EndReading(end);
+    if (CaseInsensitiveFindInReadable(u"pdf"_ns, start, end)) {
+      Telemetry::ScalarAdd(Telemetry::ScalarID::PRINTING_TARGET_TYPE,
+                           u"pdf_unknown"_ns, 1);
+    } else {
+      Telemetry::ScalarAdd(Telemetry::ScalarID::PRINTING_TARGET_TYPE,
+                           u"unknown"_ns, 1);
+    }
+  }
+
+  nsresult rv = NS_ERROR_GFX_PRINTER_NO_PRINTER_AVAILABLE;
+  if (aPrintSettings) {
+#ifdef MOZ_ENABLE_SKIA_PDF
+    nsAutoString printViaPdf;
+    Preferences::GetString("print.print_via_pdf_encoder", printViaPdf);
+    if (printViaPdf.EqualsLiteral("skia-pdf")) {
+      mPrintViaSkPDF = true;
+    }
+#endif
+
+    // If we're in the child or we're printing to PDF we only need information
+    // from the print settings.
+    if (XRE_IsContentProcess() ||
+        mOutputFormat == nsIPrintSettings::kOutputFormatPDF) {
+      return NS_OK;
+    }
+
+    nsCOMPtr<nsIPrintSettingsWin> psWin(do_QueryInterface(aPrintSettings));
+    if (psWin) {
+      nsAutoString deviceName;
+      nsAutoString driverName;
+      psWin->GetDeviceName(deviceName);
+      psWin->GetDriverName(driverName);
+
+      LPDEVMODEW devMode;
+      psWin->GetDevMode(&devMode);  // creates new memory (makes a copy)
+
+      if (!deviceName.IsEmpty() && !driverName.IsEmpty() && devMode) {
+        // Scaling is special, it is one of the few
+        // devMode items that we control in layout
+        if (devMode->dmFields & DM_SCALE) {
+          double scale = double(devMode->dmScale) / 100.0f;
+          if (scale != 1.0) {
+            aPrintSettings->SetScaling(scale);
+            devMode->dmScale = 100;
+          }
+        }
+
+        SetDeviceName(deviceName);
+        SetDriverName(driverName);
+        SetDevMode(devMode);
+
+        return NS_OK;
+      } else {
+        PR_PL(
+            ("***** nsDeviceContextSpecWin::Init - "
+             "deviceName/driverName/devMode was NULL!\n"));
+        if (devMode) ::HeapFree(::GetProcessHeap(), 0, devMode);
+      }
+    }
+  } else {
+    PR_PL(("***** nsDeviceContextSpecWin::Init - aPrintSettingswas NULL!\n"));
+  }
+
+  if (printerName.IsEmpty()) {
+    return rv;
+  }
+
+  return GetDataFromPrinter(printerName, mPrintSettings);
+}
+
+//----------------------------------------------------------
+
+already_AddRefed<PrintTarget> nsDeviceContextSpecWin::MakePrintTarget() {
+  NS_ASSERTION(mDevMode || mOutputFormat == nsIPrintSettings::kOutputFormatPDF,
+               "DevMode can't be NULL here unless we're printing to PDF.");
+
+#ifdef MOZ_ENABLE_SKIA_PDF
+  if (mPrintViaSkPDF) {
+    double width, height;
+    mPrintSettings->GetEffectivePageSize(&width, &height);
+    if (width <= 0 || height <= 0) {
+      return nullptr;
+    }
+
+    // convert twips to points
+    width /= TWIPS_PER_POINT_FLOAT;
+    height /= TWIPS_PER_POINT_FLOAT;
+    IntSize size = IntSize::Ceil(width, height);
+
+    if (mOutputFormat == nsIPrintSettings::kOutputFormatPDF) {
+      nsString filename;
+      // TODO(dshin):
+      // - Does this handle bug 1659470?
+      // - Should this code path be enabled, we should use temporary files and
+      // then move the file in `EndDocument()`.
+      mPrintSettings->GetToFileName(filename);
+
+      nsAutoCString printFile(NS_ConvertUTF16toUTF8(filename).get());
+      auto skStream = MakeUnique<SkFILEWStream>(printFile.get());
+      return PrintTargetSkPDF::CreateOrNull(std::move(skStream), size);
+    }
+
+    if (mDevMode) {
+      NS_WARNING_ASSERTION(!mDriverName.IsEmpty(), "No driver!");
+      HDC dc =
+          ::CreateDCW(mDriverName.get(), mDeviceName.get(), nullptr, mDevMode);
+      if (!dc) {
+        gfxCriticalError(gfxCriticalError::DefaultOptions(false))
+            << "Failed to create device context in GetSurfaceForPrinter";
+        return nullptr;
+      }
+      return PrintTargetEMF::CreateOrNull(dc, size);
+    }
+  }
+#endif
+
+  if (mOutputFormat == nsIPrintSettings::kOutputFormatPDF) {
+    double width, height;
+    mPrintSettings->GetEffectiveSheetSize(&width, &height);
+    if (width <= 0 || height <= 0) {
+      return nullptr;
+    }
+
+    // convert twips to points
+    width /= TWIPS_PER_POINT_FLOAT;
+    height /= TWIPS_PER_POINT_FLOAT;
+
+    auto stream = [&]() -> nsCOMPtr<nsIOutputStream> {
+      if (mPrintSettings->GetOutputDestination() ==
+          nsIPrintSettings::kOutputDestinationStream) {
+        nsCOMPtr<nsIOutputStream> out;
+        mPrintSettings->GetOutputStream(getter_AddRefs(out));
+        return out;
+      }
+
+      // Even if the destination may be a named path, write to a temp file -
+      // this is consistent with behaviour of `PrintTarget` on other platforms.
+      nsCOMPtr<nsIFile> file;
+      nsresult rv = NS_OpenAnonymousTemporaryNsIFile(getter_AddRefs(mTempFile));
+      file = mTempFile;
+
+      if (NS_WARN_IF(NS_FAILED(rv))) {
+        return nullptr;
+      }
+
+      nsCOMPtr<nsIFileOutputStream> stream =
+          do_CreateInstance("@mozilla.org/network/file-output-stream;1");
+      if (NS_FAILED(stream->Init(file, -1, -1, 0))) {
+        return nullptr;
+      }
+      return stream;
+    }();
+
+    return PrintTargetPDF::CreateOrNull(stream, IntSize::Ceil(width, height));
+  }
+
+  if (mDevMode) {
+    NS_WARNING_ASSERTION(!mDriverName.IsEmpty(), "No driver!");
+    HDC dc =
+        ::CreateDCW(mDriverName.get(), mDeviceName.get(), nullptr, mDevMode);
+    if (!dc) {
+      gfxCriticalError(gfxCriticalError::DefaultOptions(false))
+          << "Failed to create device context in GetSurfaceForPrinter";
+      return nullptr;
+    }
+
+    // The PrintTargetWindows takes over ownership of this DC
+    return PrintTargetWindows::CreateOrNull(dc);
+  }
+
+  return nullptr;
+}
+
+RefPtr<PrintEndDocumentPromise> nsDeviceContextSpecWin::EndDocument() {
+  if (mPrintSettings->GetOutputDestination() !=
+          nsIPrintSettings::kOutputDestinationFile ||
+      mOutputFormat != nsIPrintSettings::kOutputFormatPDF) {
+    return PrintEndDocumentPromise::CreateAndResolve(true, __func__);
+  }
+
+#ifdef MOZ_ENABLE_SKIA_PDF
+  if (mPrintViaSkPDF) {
+    return PrintEndDocumentPromise::CreateAndResolve(true, __func__);
+  }
+#endif
+
+  MOZ_ASSERT(mTempFile, "No handle to temporary PDF file.");
+
+  nsAutoString targetPath;
+  mPrintSettings->GetToFileName(targetPath);
+
+  if (targetPath.IsEmpty()) {
+    return PrintEndDocumentPromise::CreateAndResolve(true, __func__);
+  }
+
+  // We still need to move the file to its actual destination.
+  nsCOMPtr<nsIFile> destFile;
+  auto rv = NS_NewLocalFile(targetPath, false, getter_AddRefs(destFile));
+  if (NS_FAILED(rv)) {
+    return PrintEndDocumentPromise::CreateAndReject(rv, __func__);
+  }
+
+  return nsIDeviceContextSpec::EndDocumentAsync(
+      __func__,
+      [destFile = std::move(destFile),
+       tempFile = std::move(mTempFile)]() -> nsresult {
+        nsAutoString destLeafName;
+        MOZ_TRY(destFile->GetLeafName(destLeafName));
+
+        nsCOMPtr<nsIFile> destDir;
+        MOZ_TRY(destFile->GetParent(getter_AddRefs(destDir)));
+
+        // This should be fine - Windows API calls usually prevent moving
+        // between different volumes (See Win32 API's `MOVEFILE_COPY_ALLOWED`
+        // flag), but we handle that down this call.
+        MOZ_TRY(tempFile->MoveTo(destDir, destLeafName));
+        return NS_OK;
+      });
+}
+
+//----------------------------------------------------------------------------------
+void nsDeviceContextSpecWin::SetDeviceName(const nsAString& aDeviceName) {
+  mDeviceName = aDeviceName;
+}
+
+//----------------------------------------------------------------------------------
+void nsDeviceContextSpecWin::SetDriverName(const nsAString& aDriverName) {
+  mDriverName = aDriverName;
+}
+
+//----------------------------------------------------------------------------------
+void nsDeviceContextSpecWin::SetDevMode(LPDEVMODEW aDevMode) {
+  if (mDevMode) {
+    ::HeapFree(::GetProcessHeap(), 0, mDevMode);
+  }
+
+  mDevMode = aDevMode;
+}
+
+//------------------------------------------------------------------
+void nsDeviceContextSpecWin::GetDevMode(LPDEVMODEW& aDevMode) {
+  aDevMode = mDevMode;
+}
+
+#define DISPLAY_LAST_ERROR
+
+//----------------------------------------------------------------------------------
+// Setup the object's data member with the selected printer's data
+nsresult nsDeviceContextSpecWin::GetDataFromPrinter(const nsAString& aName,
+                                                    nsIPrintSettings* aPS) {
+  nsresult rv = NS_ERROR_FAILURE;
+
+  nsHPRINTER hPrinter = nullptr;
+  const nsString& flat = PromiseFlatString(aName);
+  wchar_t* name =
+      (wchar_t*)flat.get();  // Windows APIs use non-const name argument
+
+  BOOL status = ::OpenPrinterW(name, &hPrinter, nullptr);
+  if (status) {
+    nsAutoPrinter autoPrinter(hPrinter);
+
+    LPDEVMODEW pDevMode;
+
+    // Allocate a buffer of the correct size.
+    LONG needed =
+        ::DocumentPropertiesW(nullptr, hPrinter, name, nullptr, nullptr, 0);
+    if (needed < 0) {
+      PR_PL(
+          ("**** nsDeviceContextSpecWin::GetDataFromPrinter - Couldn't get "
+           "size of DEVMODE using DocumentPropertiesW(pDeviceName = \"%s\"). "
+           "GetLastEror() = %08lx\n",
+           NS_ConvertUTF16toUTF8(aName).get(), GetLastError()));
+      return NS_ERROR_FAILURE;
+    }
+
+    // Some drivers do not return the correct size for their DEVMODE, so we
+    // over-allocate to try and compensate.
+    // (See https://bugzilla.mozilla.org/show_bug.cgi?id=1664530#c5)
+    needed *= 2;
+    pDevMode =
+        (LPDEVMODEW)::HeapAlloc(::GetProcessHeap(), HEAP_ZERO_MEMORY, needed);
+    if (!pDevMode) return NS_ERROR_FAILURE;
+
+    // Get the default DevMode for the printer and modify it for our needs.
+    LONG ret = ::DocumentPropertiesW(nullptr, hPrinter, name, pDevMode, nullptr,
+                                     DM_OUT_BUFFER);
+
+    if (ret == IDOK && aPS) {
+      nsCOMPtr<nsIPrintSettingsWin> psWin = do_QueryInterface(aPS);
+      MOZ_ASSERT(psWin);
+      psWin->CopyToNative(pDevMode);
+      // Sets back the changes we made to the DevMode into the Printer Driver
+      ret = ::DocumentPropertiesW(nullptr, hPrinter, name, pDevMode, pDevMode,
+                                  DM_IN_BUFFER | DM_OUT_BUFFER);
+
+      // We need to copy the final DEVMODE settings back to our print settings,
+      // because they may have been set from invalid prefs.
+      if (ret == IDOK) {
+        // We need to get information from the device as well.
+        nsAutoHDC printerDC(::CreateICW(kDriverName, name, nullptr, pDevMode));
+        if (NS_WARN_IF(!printerDC)) {
+          ::HeapFree(::GetProcessHeap(), 0, pDevMode);
+          return NS_ERROR_FAILURE;
+        }
+
+        psWin->CopyFromNative(printerDC, pDevMode);
+      }
+    }
+
+    if (ret != IDOK) {
+      ::HeapFree(::GetProcessHeap(), 0, pDevMode);
+      PR_PL(
+          ("***** nsDeviceContextSpecWin::GetDataFromPrinter - "
+           "DocumentProperties call failed code: %ld/0x%lx\n",
+           ret, ret));
+      DISPLAY_LAST_ERROR
+      return NS_ERROR_FAILURE;
+    }
+
+    SetDevMode(
+        pDevMode);  // cache the pointer and takes responsibility for the memory
+
+    SetDeviceName(aName);
+
+    SetDriverName(nsDependentString(kDriverName));
+
+    rv = NS_OK;
+  } else {
+    rv = NS_ERROR_GFX_PRINTER_NAME_NOT_FOUND;
+    PR_PL(
+        ("***** nsDeviceContextSpecWin::GetDataFromPrinter - Couldn't open "
+         "printer: [%s]\n",
+         NS_ConvertUTF16toUTF8(aName).get()));
+    DISPLAY_LAST_ERROR
+  }
+  return rv;
+}
+
+//***********************************************************
+//  Printer List
+//***********************************************************
+
+nsPrinterListWin::~nsPrinterListWin() = default;
+
+// Helper to get the array of PRINTER_INFO_4 records from the OS into a
+// caller-supplied byte array; returns the number of records present.
+static unsigned GetPrinterInfo4(nsTArray<BYTE>& aBuffer) {
+  const DWORD kLevel = 4;
+  DWORD needed = 0;
+  DWORD count = 0;
+  const DWORD kFlags = PRINTER_ENUM_LOCAL | PRINTER_ENUM_CONNECTIONS;
+  BOOL ok = ::EnumPrintersW(kFlags,
+                            nullptr,  // Name
+                            kLevel,   // Level
+                            nullptr,  // pPrinterEnum
+                            0,        // cbBuf (buffer size)
+                            &needed,  // Bytes needed in buffer
+                            &count);
+  if (needed > 0) {
+    if (!aBuffer.SetLength(needed, fallible)) {
+      return 0;
+    }
+    ok = ::EnumPrintersW(kFlags, nullptr, kLevel, aBuffer.Elements(),
+                         aBuffer.Length(), &needed, &count);
+  }
+  if (!ok) {
+    return 0;
+  }
+  return count;
+}
+
+nsTArray<nsPrinterListBase::PrinterInfo> nsPrinterListWin::Printers() const {
+  PR_PL(("nsPrinterListWin::Printers\n"));
+
+  AutoTArray<BYTE, 1024> buffer;
+  unsigned count = GetPrinterInfo4(buffer);
+
+  if (!count) {
+    PR_PL(("[No printers found]\n"));
+    return {};
+  }
+
+  const auto* printers =
+      reinterpret_cast<const _PRINTER_INFO_4W*>(buffer.Elements());
+  nsTArray<PrinterInfo> list;
+  for (unsigned i = 0; i < count; i++) {
+    // For LOCAL printers, we check whether OpenPrinter succeeds, and omit
+    // them from the list if not. This avoids presenting printers that the
+    // user cannot actually use (e.g. due to Windows permissions).
+    // For NETWORK printers, this check may block for a long time (waiting for
+    // network timeout), so we skip it; if the user tries to access a printer
+    // that isn't available, we'll have to show an error later.
+    // (We always need to be able to handle an error, anyhow, as the printer
+    // could get disconnected after we've created the list, for example.)
+    bool isAvailable = false;
+    if (printers[i].Attributes & PRINTER_ATTRIBUTE_NETWORK) {
+      isAvailable = true;
+    } else if (printers[i].Attributes & PRINTER_ATTRIBUTE_LOCAL) {
+      HANDLE handle;
+      if (::OpenPrinterW(printers[i].pPrinterName, &handle, nullptr)) {
+        ::ClosePrinter(handle);
+        isAvailable = true;
+      }
+    }
+    if (isAvailable) {
+      list.AppendElement(PrinterInfo{nsString(printers[i].pPrinterName)});
+      PR_PL(("Printer Name: %s\n",
+             NS_ConvertUTF16toUTF8(printers[i].pPrinterName).get()));
+    }
+  }
+
+  if (list.IsEmpty()) {
+    PR_PL(("[No usable printers found]\n"));
+    return {};
+  }
+
+  list.Sort([](const PrinterInfo& a, const PrinterInfo& b) {
+    size_t len = std::min(a.mName.Length(), b.mName.Length());
+    int result = CaseInsensitiveCompare(a.mName.BeginReading(),
+                                        b.mName.BeginReading(), len);
+    return result ? result : int(a.mName.Length()) - int(b.mName.Length());
+  });
+
+  return list;
+}
+
+Maybe<nsPrinterListBase::PrinterInfo> nsPrinterListWin::PrinterByName(
+    nsString aName) const {
+  Maybe<PrinterInfo> rv;
+
+  AutoTArray<BYTE, 1024> buffer;
+  unsigned count = GetPrinterInfo4(buffer);
+
+  const auto* printers =
+      reinterpret_cast<const _PRINTER_INFO_4W*>(buffer.Elements());
+  for (unsigned i = 0; i < count; ++i) {
+    if (aName.Equals(nsString(printers[i].pPrinterName))) {
+      rv.emplace(PrinterInfo{aName});
+      break;
+    }
+  }
+
+  return rv;
+}
+
+Maybe<nsPrinterListBase::PrinterInfo> nsPrinterListWin::PrinterBySystemName(
+    nsString aName) const {
+  return PrinterByName(std::move(aName));
+}
+
+RefPtr<nsIPrinter> nsPrinterListWin::CreatePrinter(PrinterInfo aInfo) const {
+  return nsPrinterWin::Create(mCommonPaperInfo, std::move(aInfo.mName));
+}
+
+nsresult nsPrinterListWin::SystemDefaultPrinterName(nsAString& aName) const {
+  if (!GetDefaultPrinterName(aName)) {
+    NS_WARNING("Uh oh, GetDefaultPrinterName failed");
+    // Indicate failure by leaving aName untouched, i.e. the empty string.
+  }
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsPrinterListWin::InitPrintSettingsFromPrinter(
+    const nsAString& aPrinterName, nsIPrintSettings* aPrintSettings) {
+  NS_ENSURE_ARG_POINTER(aPrintSettings);
+
+  if (aPrinterName.IsEmpty()) {
+    return NS_OK;
+  }
+
+  // When printing to PDF on Windows there is no associated printer driver.
+  int16_t outputFormat = aPrintSettings->GetOutputFormat();
+  if (outputFormat == nsIPrintSettings::kOutputFormatPDF) {
+    return NS_OK;
+  }
+
+  RefPtr<nsDeviceContextSpecWin> devSpecWin = new nsDeviceContextSpecWin();
+  if (!devSpecWin) return NS_ERROR_OUT_OF_MEMORY;
+
+  // If the settings have already been initialized from prefs then pass these to
+  // GetDataFromPrinter, so that they are saved to the printer.
+  bool initializedFromPrefs;
+  nsresult rv =
+      aPrintSettings->GetIsInitializedFromPrefs(&initializedFromPrefs);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+  if (initializedFromPrefs) {
+    // If we pass in print settings to GetDataFromPrinter it already copies
+    // things back to the settings, so we can return here.
+    return devSpecWin->GetDataFromPrinter(aPrinterName, aPrintSettings);
+  }
+
+  devSpecWin->GetDataFromPrinter(aPrinterName);
+
+  LPDEVMODEW devmode;
+  devSpecWin->GetDevMode(devmode);
+  if (NS_WARN_IF(!devmode)) {
+    return NS_ERROR_FAILURE;
+  }
+
+  aPrintSettings->SetPrinterName(aPrinterName);
+
+  // We need to get information from the device as well.
+  const nsString& flat = PromiseFlatString(aPrinterName);
+  char16ptr_t printerName = flat.get();
+  HDC dc = ::CreateICW(kDriverName, printerName, nullptr, devmode);
+  if (NS_WARN_IF(!dc)) {
+    return NS_ERROR_FAILURE;
+  }
+
+  nsCOMPtr<nsIPrintSettingsWin> psWin = do_QueryInterface(aPrintSettings);
+  MOZ_ASSERT(psWin);
+  psWin->CopyFromNative(dc, devmode);
+  ::DeleteDC(dc);
+
+  return NS_OK;
+}
diff --git a/widget/windows/nsDeviceContextSpecWin.h b/widget/windows/nsDeviceContextSpecWin.h
new file mode 100644
index 0000000000..fff6472d62
--- /dev/null
+++ b/widget/windows/nsDeviceContextSpecWin.h
@@ -0,0 +1,98 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef nsDeviceContextSpecWin_h___
+#define nsDeviceContextSpecWin_h___
+
+#include "nsCOMPtr.h"
+#include "nsIDeviceContextSpec.h"
+#include "nsPrinterListBase.h"
+#include "nsIPrintSettings.h"
+#include <windows.h>
+#include "mozilla/Attributes.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/gfx/PrintPromise.h"
+
+class nsIFile;
+class nsIWidget;
+
+class nsDeviceContextSpecWin : public nsIDeviceContextSpec {
+ public:
+  nsDeviceContextSpecWin();
+
+  NS_DECL_ISUPPORTS
+
+  already_AddRefed<PrintTarget> MakePrintTarget() final;
+  NS_IMETHOD BeginDocument(const nsAString& aTitle,
+                           const nsAString& aPrintToFileName,
+                           int32_t aStartPage, int32_t aEndPage) override {
+    return NS_OK;
+  }
+  RefPtr<mozilla::gfx::PrintEndDocumentPromise> EndDocument() override;
+  NS_IMETHOD BeginPage(const IntSize& aSizeInPoints) override { return NS_OK; }
+  NS_IMETHOD EndPage() override { return NS_OK; }
+
+  NS_IMETHOD Init(nsIPrintSettings* aPS, bool aIsPrintPreview) override;
+
+  void GetDriverName(nsAString& aDriverName) const {
+    aDriverName = mDriverName;
+  }
+  void GetDeviceName(nsAString& aDeviceName) const {
+    aDeviceName = mDeviceName;
+  }
+
+  // The GetDevMode will return a pointer to a DevMode
+  // whether it is from the Global memory handle or just the DevMode
+  // To get the DevMode from the Global memory Handle it must lock it
+  // So this call must be paired with a call to UnlockGlobalHandle
+  void GetDevMode(LPDEVMODEW& aDevMode);
+
+  // helper functions
+  nsresult GetDataFromPrinter(const nsAString& aName,
+                              nsIPrintSettings* aPS = nullptr);
+
+ protected:
+  void SetDeviceName(const nsAString& aDeviceName);
+  void SetDriverName(const nsAString& aDriverName);
+  void SetDevMode(LPDEVMODEW aDevMode);
+
+  virtual ~nsDeviceContextSpecWin();
+
+  nsString mDriverName;
+  nsString mDeviceName;
+  LPDEVMODEW mDevMode = nullptr;
+
+  int16_t mOutputFormat = nsIPrintSettings::kOutputFormatNative;
+
+  // A temporary file to create an "anonymous" print target. See bug 1664253,
+  // this should ideally not be needed.
+  nsCOMPtr<nsIFile> mTempFile;
+};
+
+//-------------------------------------------------------------------------
+// Printer List
+//-------------------------------------------------------------------------
+class nsPrinterListWin final : public nsPrinterListBase {
+ public:
+  NS_IMETHOD InitPrintSettingsFromPrinter(const nsAString&,
+                                          nsIPrintSettings*) final;
+
+  nsTArray<PrinterInfo> Printers() const final;
+  RefPtr<nsIPrinter> CreatePrinter(PrinterInfo) const final;
+
+  nsPrinterListWin() = default;
+
+ protected:
+  nsresult SystemDefaultPrinterName(nsAString&) const final;
+
+  mozilla::Maybe<PrinterInfo> PrinterByName(nsString) const final;
+  mozilla::Maybe<PrinterInfo> PrinterBySystemName(
+      nsString aPrinterName) const final;
+
+ private:
+  ~nsPrinterListWin();
+};
+
+#endif
diff --git a/widget/windows/nsDragService.cpp b/widget/windows/nsDragService.cpp
new file mode 100644
index 0000000000..80f545d9a7
--- /dev/null
+++ b/widget/windows/nsDragService.cpp
@@ -0,0 +1,664 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <ole2.h>
+#include <oleidl.h>
+#include <shlobj.h>
+#include <shlwapi.h>
+
+// shellapi.h is needed to build with WIN32_LEAN_AND_MEAN
+#include <shellapi.h>
+
+#include "mozilla/RefPtr.h"
+#include "nsDragService.h"
+#include "nsITransferable.h"
+#include "nsDataObj.h"
+
+#include "nsWidgetsCID.h"
+#include "nsNativeDragTarget.h"
+#include "nsNativeDragSource.h"
+#include "nsClipboard.h"
+#include "mozilla/dom/Document.h"
+#include "mozilla/dom/DocumentInlines.h"
+#include "nsDataObjCollection.h"
+
+#include "nsArrayUtils.h"
+#include "nsString.h"
+#include "nsEscape.h"
+#include "nsIScreenManager.h"
+#include "nsToolkit.h"
+#include "nsCRT.h"
+#include "nsDirectoryServiceDefs.h"
+#include "nsUnicharUtils.h"
+#include "nsRect.h"
+#include "nsMathUtils.h"
+#include "WinUtils.h"
+#include "KeyboardLayout.h"
+#include "gfxContext.h"
+#include "mozilla/gfx/2D.h"
+#include "mozilla/gfx/DataSurfaceHelpers.h"
+#include "mozilla/gfx/Tools.h"
+#include "mozilla/ScopeExit.h"
+
+using namespace mozilla;
+using namespace mozilla::gfx;
+using namespace mozilla::widget;
+
+//-------------------------------------------------------------------------
+//
+// DragService constructor
+//
+//-------------------------------------------------------------------------
+nsDragService::nsDragService()
+    : mDataObject(nullptr), mSentLocalDropEvent(false) {}
+
+//-------------------------------------------------------------------------
+//
+// DragService destructor
+//
+//-------------------------------------------------------------------------
+nsDragService::~nsDragService() { NS_IF_RELEASE(mDataObject); }
+
+bool nsDragService::CreateDragImage(nsINode* aDOMNode,
+                                    const Maybe<CSSIntRegion>& aRegion,
+                                    SHDRAGIMAGE* psdi) {
+  if (!psdi) return false;
+
+  memset(psdi, 0, sizeof(SHDRAGIMAGE));
+  if (!aDOMNode) return false;
+
+  // Prepare the drag image
+  LayoutDeviceIntRect dragRect;
+  RefPtr<SourceSurface> surface;
+  nsPresContext* pc;
+  DrawDrag(aDOMNode, aRegion, mScreenPosition, &dragRect, &surface, &pc);
+  if (!surface) return false;
+
+  uint32_t bmWidth = dragRect.Width(), bmHeight = dragRect.Height();
+
+  if (bmWidth == 0 || bmHeight == 0) return false;
+
+  psdi->crColorKey = CLR_NONE;
+
+  RefPtr<DataSourceSurface> dataSurface = Factory::CreateDataSourceSurface(
+      IntSize(bmWidth, bmHeight), SurfaceFormat::B8G8R8A8);
+  NS_ENSURE_TRUE(dataSurface, false);
+
+  DataSourceSurface::MappedSurface map;
+  if (!dataSurface->Map(DataSourceSurface::MapType::READ_WRITE, &map)) {
+    return false;
+  }
+
+  RefPtr<DrawTarget> dt = Factory::CreateDrawTargetForData(
+      BackendType::CAIRO, map.mData, dataSurface->GetSize(), map.mStride,
+      dataSurface->GetFormat());
+  if (!dt) {
+    dataSurface->Unmap();
+    return false;
+  }
+
+  dt->DrawSurface(
+      surface,
+      Rect(0, 0, dataSurface->GetSize().width, dataSurface->GetSize().height),
+      Rect(0, 0, surface->GetSize().width, surface->GetSize().height),
+      DrawSurfaceOptions(), DrawOptions(1.0f, CompositionOp::OP_SOURCE));
+  dt->Flush();
+
+  BITMAPV5HEADER bmih;
+  memset((void*)&bmih, 0, sizeof(BITMAPV5HEADER));
+  bmih.bV5Size = sizeof(BITMAPV5HEADER);
+  bmih.bV5Width = bmWidth;
+  bmih.bV5Height = -(int32_t)bmHeight;  // flip vertical
+  bmih.bV5Planes = 1;
+  bmih.bV5BitCount = 32;
+  bmih.bV5Compression = BI_BITFIELDS;
+  bmih.bV5RedMask = 0x00FF0000;
+  bmih.bV5GreenMask = 0x0000FF00;
+  bmih.bV5BlueMask = 0x000000FF;
+  bmih.bV5AlphaMask = 0xFF000000;
+
+  HDC hdcSrc = CreateCompatibleDC(nullptr);
+  void* lpBits = nullptr;
+  if (hdcSrc) {
+    psdi->hbmpDragImage =
+        ::CreateDIBSection(hdcSrc, (BITMAPINFO*)&bmih, DIB_RGB_COLORS,
+                           (void**)&lpBits, nullptr, 0);
+    if (psdi->hbmpDragImage && lpBits) {
+      CopySurfaceDataToPackedArray(map.mData, static_cast<uint8_t*>(lpBits),
+                                   dataSurface->GetSize(), map.mStride,
+                                   BytesPerPixel(dataSurface->GetFormat()));
+    }
+
+    psdi->sizeDragImage.cx = bmWidth;
+    psdi->sizeDragImage.cy = bmHeight;
+
+    const auto screenPoint =
+        LayoutDeviceIntPoint::Round(mScreenPosition * pc->CSSToDevPixelScale());
+    psdi->ptOffset.x = screenPoint.x - dragRect.X();
+    psdi->ptOffset.y = screenPoint.y - dragRect.Y();
+
+    DeleteDC(hdcSrc);
+  }
+
+  dataSurface->Unmap();
+
+  return psdi->hbmpDragImage != nullptr;
+}
+
+//-------------------------------------------------------------------------
+nsresult nsDragService::InvokeDragSessionImpl(
+    nsIArray* anArrayTransferables, const Maybe<CSSIntRegion>& aRegion,
+    uint32_t aActionType) {
+  // Try and get source URI of the items that are being dragged
+  nsIURI* uri = nullptr;
+
+  RefPtr<dom::Document> doc(mSourceDocument);
+  if (doc) {
+    uri = doc->GetDocumentURI();
+  }
+
+  uint32_t numItemsToDrag = 0;
+  nsresult rv = anArrayTransferables->GetLength(&numItemsToDrag);
+  if (!numItemsToDrag) return NS_ERROR_FAILURE;
+
+  // The clipboard class contains some static utility methods that we
+  // can use to create an IDataObject from the transferable
+
+  // if we're dragging more than one item, we need to create a
+  // "collection" object to fake out the OS. This collection contains
+  // one |IDataObject| for each transferable. If there is just the one
+  // (most cases), only pass around the native |IDataObject|.
+  RefPtr<IDataObject> itemToDrag;
+  if (numItemsToDrag > 1) {
+    nsDataObjCollection* dataObjCollection = new nsDataObjCollection();
+    if (!dataObjCollection) return NS_ERROR_OUT_OF_MEMORY;
+    itemToDrag = dataObjCollection;
+    for (uint32_t i = 0; i < numItemsToDrag; ++i) {
+      nsCOMPtr<nsITransferable> trans =
+          do_QueryElementAt(anArrayTransferables, i);
+      if (trans) {
+        RefPtr<IDataObject> dataObj;
+        rv = nsClipboard::CreateNativeDataObject(trans, getter_AddRefs(dataObj),
+                                                 uri);
+        NS_ENSURE_SUCCESS(rv, rv);
+        // Add the flavors to the collection object too
+        rv = nsClipboard::SetupNativeDataObject(trans, dataObjCollection);
+        NS_ENSURE_SUCCESS(rv, rv);
+
+        dataObjCollection->AddDataObject(dataObj);
+      }
+    }
+  }  // if dragging multiple items
+  else {
+    nsCOMPtr<nsITransferable> trans =
+        do_QueryElementAt(anArrayTransferables, 0);
+    if (trans) {
+      rv = nsClipboard::CreateNativeDataObject(trans,
+                                               getter_AddRefs(itemToDrag), uri);
+      NS_ENSURE_SUCCESS(rv, rv);
+    }
+  }  // else dragging a single object
+
+  // Create a drag image if support is available
+  IDragSourceHelper* pdsh;
+  if (SUCCEEDED(CoCreateInstance(CLSID_DragDropHelper, nullptr,
+                                 CLSCTX_INPROC_SERVER, IID_IDragSourceHelper,
+                                 (void**)&pdsh))) {
+    SHDRAGIMAGE sdi;
+    if (CreateDragImage(mSourceNode, aRegion, &sdi)) {
+      if (FAILED(pdsh->InitializeFromBitmap(&sdi, itemToDrag)))
+        DeleteObject(sdi.hbmpDragImage);
+    }
+    pdsh->Release();
+  }
+
+  // Kick off the native drag session
+  return StartInvokingDragSession(itemToDrag, aActionType);
+}
+
+static HWND GetSourceWindow(dom::Document* aSourceDocument) {
+  if (!aSourceDocument) {
+    return nullptr;
+  }
+
+  auto* pc = aSourceDocument->GetPresContext();
+  if (!pc) {
+    return nullptr;
+  }
+
+  nsCOMPtr<nsIWidget> widget = pc->GetRootWidget();
+  if (!widget) {
+    return nullptr;
+  }
+
+  return (HWND)widget->GetNativeData(NS_NATIVE_WINDOW);
+}
+
+//-------------------------------------------------------------------------
+nsresult nsDragService::StartInvokingDragSession(IDataObject* aDataObj,
+                                                 uint32_t aActionType) {
+  // To do the drag we need to create an object that
+  // implements the IDataObject interface (for OLE)
+  RefPtr<nsNativeDragSource> nativeDragSrc =
+      new nsNativeDragSource(mDataTransfer);
+
+  // Now figure out what the native drag effect should be
+  DWORD winDropRes;
+  DWORD effects = DROPEFFECT_SCROLL;
+  if (aActionType & DRAGDROP_ACTION_COPY) {
+    effects |= DROPEFFECT_COPY;
+  }
+  if (aActionType & DRAGDROP_ACTION_MOVE) {
+    effects |= DROPEFFECT_MOVE;
+  }
+  if (aActionType & DRAGDROP_ACTION_LINK) {
+    effects |= DROPEFFECT_LINK;
+  }
+
+  // XXX not sure why we bother to cache this, it can change during
+  // the drag
+  mDragAction = aActionType;
+  mSentLocalDropEvent = false;
+
+  // Start dragging
+  StartDragSession();
+  OpenDragPopup();
+
+  RefPtr<IDataObjectAsyncCapability> pAsyncOp;
+  // Offer to do an async drag
+  if (SUCCEEDED(aDataObj->QueryInterface(IID_IDataObjectAsyncCapability,
+                                         getter_AddRefs(pAsyncOp)))) {
+    pAsyncOp->SetAsyncMode(VARIANT_TRUE);
+  } else {
+    MOZ_ASSERT_UNREACHABLE("When did our data object stop being async");
+  }
+
+  // Call the native D&D method
+  HRESULT res = ::DoDragDrop(aDataObj, nativeDragSrc, effects, &winDropRes);
+
+  // In  cases where the drop operation completed outside the application,
+  // update the source node's DataTransfer dropEffect value so it is up to date.
+  if (!mSentLocalDropEvent) {
+    uint32_t dropResult;
+    // Order is important, since multiple flags can be returned.
+    if (winDropRes & DROPEFFECT_COPY)
+      dropResult = DRAGDROP_ACTION_COPY;
+    else if (winDropRes & DROPEFFECT_LINK)
+      dropResult = DRAGDROP_ACTION_LINK;
+    else if (winDropRes & DROPEFFECT_MOVE)
+      dropResult = DRAGDROP_ACTION_MOVE;
+    else
+      dropResult = DRAGDROP_ACTION_NONE;
+
+    if (mDataTransfer) {
+      if (res == DRAGDROP_S_DROP)  // Success
+        mDataTransfer->SetDropEffectInt(dropResult);
+      else
+        mDataTransfer->SetDropEffectInt(DRAGDROP_ACTION_NONE);
+    }
+  }
+
+  mUserCancelled = nativeDragSrc->UserCancelled();
+
+  // We're done dragging, get the cursor position and end the drag
+  // Use GetMessagePos to get the position of the mouse at the last message
+  // seen by the event loop. (Bug 489729)
+  // Note that we must convert this from device pixels back to Windows logical
+  // pixels (bug 818927).
+  DWORD pos = ::GetMessagePos();
+  POINT cpos;
+  cpos.x = GET_X_LPARAM(pos);
+  cpos.y = GET_Y_LPARAM(pos);
+  if (auto wnd = GetSourceWindow(mSourceDocument)) {
+    // Convert from screen to client coordinates like nsWindow::InitEvent does.
+    ::ScreenToClient(wnd, &cpos);
+  }
+  SetDragEndPoint(LayoutDeviceIntPoint(cpos.x, cpos.y));
+
+  ModifierKeyState modifierKeyState;
+  EndDragSession(true, modifierKeyState.GetModifiers());
+
+  mDoingDrag = false;
+
+  return DRAGDROP_S_DROP == res ? NS_OK : NS_ERROR_FAILURE;
+}
+
+//-------------------------------------------------------------------------
+// Make Sure we have the right kind of object
+nsDataObjCollection* nsDragService::GetDataObjCollection(
+    IDataObject* aDataObj) {
+  nsDataObjCollection* dataObjCol = nullptr;
+  if (aDataObj) {
+    nsIDataObjCollection* dataObj;
+    if (aDataObj->QueryInterface(IID_IDataObjCollection, (void**)&dataObj) ==
+        S_OK) {
+      dataObjCol = static_cast<nsDataObjCollection*>(aDataObj);
+      dataObj->Release();
+    }
+  }
+
+  return dataObjCol;
+}
+
+//-------------------------------------------------------------------------
+NS_IMETHODIMP
+nsDragService::GetNumDropItems(uint32_t* aNumItems) {
+  if (!mDataObject) {
+    *aNumItems = 0;
+    return NS_OK;
+  }
+
+  if (IsCollectionObject(mDataObject)) {
+    nsDataObjCollection* dataObjCol = GetDataObjCollection(mDataObject);
+    // If the count cannot be determined just return 0.
+    // This can happen if we have collection data of type
+    // MULTI_MIME ("Mozilla/IDataObjectCollectionFormat") on the clipboard
+    // from another process but we can't obtain an IID_IDataObjCollection
+    // from this process.
+    *aNumItems = dataObjCol ? dataObjCol->GetNumDataObjects() : 0;
+    return NS_OK;
+  }
+  // Next check if we have a file drop. Return the number of files in
+  // the file drop as the number of items we have, pretending like we
+  // actually have > 1 drag item.
+  FORMATETC fe2;
+  SET_FORMATETC(fe2, CF_HDROP, 0, DVASPECT_CONTENT, -1, TYMED_HGLOBAL);
+  if (SUCCEEDED(mDataObject->QueryGetData(&fe2))) {
+    STGMEDIUM stm;
+    if (FAILED(mDataObject->GetData(&fe2, &stm))) {
+      *aNumItems = 1;
+      return NS_OK;
+    }
+    HDROP hdrop = static_cast<HDROP>(GlobalLock(stm.hGlobal));
+    MOZ_ASSERT(hdrop != NULL);
+    *aNumItems = ::DragQueryFileW(hdrop, 0xFFFFFFFF, nullptr, 0);
+    ::GlobalUnlock(stm.hGlobal);
+    ::ReleaseStgMedium(&stm);
+    // Data may be provided later, so assume we have 1 item
+    if (*aNumItems == 0) {
+      *aNumItems = 1;
+    }
+    return NS_OK;
+  }
+  // Next check if we have a virtual file drop.
+  SET_FORMATETC(fe2, nsClipboard::GetClipboardFileDescriptorFormatW(), 0,
+                DVASPECT_CONTENT, -1, TYMED_HGLOBAL);
+  STGMEDIUM stm;
+
+  if (SUCCEEDED(mDataObject->GetData(&fe2, &stm))) {
+    LPFILEGROUPDESCRIPTOR pDesc =
+        static_cast<LPFILEGROUPDESCRIPTOR>(GlobalLock(stm.hGlobal));
+    if (pDesc) {
+      *aNumItems = pDesc->cItems;
+    }
+    GlobalUnlock(stm.hGlobal);
+    ReleaseStgMedium(&stm);
+    return NS_OK;
+  }
+  *aNumItems = 1;
+  return NS_OK;
+}
+
+//-------------------------------------------------------------------------
+NS_IMETHODIMP
+nsDragService::GetData(nsITransferable* aTransferable, uint32_t anItem) {
+  // This typcially happens on a drop, the target would be asking
+  // for it's transferable to be filled in
+  // Use a static clipboard utility method for this
+  if (!mDataObject) return NS_ERROR_FAILURE;
+
+  nsresult dataFound = NS_ERROR_FAILURE;
+
+  if (IsCollectionObject(mDataObject)) {
+    // multiple items, use |anItem| as an index into our collection
+    nsDataObjCollection* dataObjCol = GetDataObjCollection(mDataObject);
+    uint32_t cnt = dataObjCol->GetNumDataObjects();
+    if (anItem < cnt) {
+      IDataObject* dataObj = dataObjCol->GetDataObjectAt(anItem);
+      dataFound = nsClipboard::GetDataFromDataObject(dataObj, 0, nullptr,
+                                                     aTransferable);
+    } else
+      NS_WARNING("Index out of range!");
+  } else {
+    // If they are asking for item "0", we can just get it...
+    if (anItem == 0) {
+      dataFound = nsClipboard::GetDataFromDataObject(mDataObject, anItem,
+                                                     nullptr, aTransferable);
+    } else {
+      // It better be a file drop, or else non-zero indexes are invalid!
+      FORMATETC fe2;
+      FORMATETC fe3;
+      SET_FORMATETC(fe2, CF_HDROP, 0, DVASPECT_CONTENT, -1, TYMED_HGLOBAL);
+      SET_FORMATETC(fe3, nsClipboard::GetClipboardFileDescriptorFormatW(), 0,
+                    DVASPECT_CONTENT, -1, TYMED_HGLOBAL);
+      if (SUCCEEDED(mDataObject->QueryGetData(&fe2)) ||
+          SUCCEEDED(mDataObject->QueryGetData(&fe3)))
+        dataFound = nsClipboard::GetDataFromDataObject(mDataObject, anItem,
+                                                       nullptr, aTransferable);
+      else
+        NS_WARNING(
+            "Reqesting non-zero index, but clipboard data is not a "
+            "collection!");
+    }
+  }
+  return dataFound;
+}
+
+//---------------------------------------------------------
+NS_IMETHODIMP
+nsDragService::SetIDataObject(IDataObject* aDataObj) {
+  // When the native drag starts the DragService gets
+  // the IDataObject that is being dragged
+  NS_IF_RELEASE(mDataObject);
+  mDataObject = aDataObj;
+  NS_IF_ADDREF(mDataObject);
+
+  if (MOZ_DRAGSERVICE_LOG_ENABLED()) {
+    MOZ_DRAGSERVICE_LOG("nsDragService::SetIDataObject (%p)", mDataObject);
+    IEnumFORMATETC* pEnum = nullptr;
+    if (mDataObject &&
+        S_OK == mDataObject->EnumFormatEtc(DATADIR_GET, &pEnum)) {
+      MOZ_DRAGSERVICE_LOG("    formats in DataObject:");
+
+      FORMATETC fEtc;
+      while (S_OK == pEnum->Next(1, &fEtc, nullptr)) {
+        nsAutoString format;
+        WinUtils::GetClipboardFormatAsString(fEtc.cfFormat, format);
+        MOZ_DRAGSERVICE_LOG("        FORMAT %s",
+                            NS_ConvertUTF16toUTF8(format).get());
+      }
+      pEnum->Release();
+    }
+  }
+
+  return NS_OK;
+}
+
+//---------------------------------------------------------
+void nsDragService::SetDroppedLocal() {
+  // Sent from the native drag handler, letting us know
+  // a drop occurred within the application vs. outside of it.
+  mSentLocalDropEvent = true;
+  return;
+}
+
+//-------------------------------------------------------------------------
+NS_IMETHODIMP
+nsDragService::IsDataFlavorSupported(const char* aDataFlavor, bool* _retval) {
+  if (!aDataFlavor || !mDataObject || !_retval) {
+    MOZ_DRAGSERVICE_LOG("%s: error", __PRETTY_FUNCTION__);
+    return NS_ERROR_FAILURE;
+  }
+
+  *_retval = false;
+  auto logging = MakeScopeExit([&] {
+    MOZ_DRAGSERVICE_LOG("IsDataFlavorSupported: %s is%s found", aDataFlavor,
+                        *_retval ? "" : " not");
+  });
+
+  FORMATETC fe;
+  UINT format = 0;
+
+  if (IsCollectionObject(mDataObject)) {
+    // We know we have one of our special collection objects.
+    format = nsClipboard::GetFormat(aDataFlavor);
+    SET_FORMATETC(fe, format, 0, DVASPECT_CONTENT, -1,
+                  TYMED_HGLOBAL | TYMED_FILE | TYMED_GDI);
+
+    // See if any one of the IDataObjects in the collection supports
+    // this data type
+    nsDataObjCollection* dataObjCol = GetDataObjCollection(mDataObject);
+    if (dataObjCol) {
+      uint32_t cnt = dataObjCol->GetNumDataObjects();
+      for (uint32_t i = 0; i < cnt; ++i) {
+        IDataObject* dataObj = dataObjCol->GetDataObjectAt(i);
+        if (S_OK == dataObj->QueryGetData(&fe)) {
+          *_retval = true;  // found it!
+        }
+      }
+    }
+    return NS_OK;
+  }
+
+  // Ok, so we have a single object. Check to see if has the correct
+  // data type. Since this can come from an outside app, we also
+  // need to see if we need to perform text->unicode conversion if
+  // the client asked for unicode and it wasn't available.
+  format = nsClipboard::GetFormat(aDataFlavor);
+  SET_FORMATETC(fe, format, 0, DVASPECT_CONTENT, -1,
+                TYMED_HGLOBAL | TYMED_FILE | TYMED_GDI);
+  if (mDataObject->QueryGetData(&fe) == S_OK) {
+    *_retval = true;  // found it!
+    return NS_OK;
+  }
+
+  // We haven't found the exact flavor the client asked for, but
+  // maybe we can still find it from something else that's in the
+  // data object.
+  if (strcmp(aDataFlavor, kTextMime) == 0) {
+    // If unicode wasn't there, it might exist as CF_TEXT, client asked
+    // for unicode and it wasn't present, check if we
+    // have CF_TEXT.  We'll handle the actual data substitution in
+    // the data object.
+    SET_FORMATETC(fe, CF_TEXT, 0, DVASPECT_CONTENT, -1,
+                  TYMED_HGLOBAL | TYMED_FILE | TYMED_GDI);
+    if (mDataObject->QueryGetData(&fe) == S_OK) {
+      *_retval = true;  // found it!
+    }
+    return NS_OK;
+  }
+
+  if (strcmp(aDataFlavor, kURLMime) == 0) {
+    // client asked for a url and it wasn't present, but if we
+    // have a file, then we have a URL to give them (the path, or
+    // the internal URL if an InternetShortcut).
+    format = nsClipboard::GetFormat(kFileMime);
+    SET_FORMATETC(fe, format, 0, DVASPECT_CONTENT, -1,
+                  TYMED_HGLOBAL | TYMED_FILE | TYMED_GDI);
+    if (mDataObject->QueryGetData(&fe) == S_OK) {
+      *_retval = true;  // found it!
+    }
+    return NS_OK;
+  }
+
+  if (format == CF_HDROP) {
+    // Dragging a link from browsers creates both a URL and a FILE which is a
+    // *.url shortcut in the data object. The file is useful when dropping in
+    // Windows Explorer to create a internet shortcut. But when dropping in the
+    // browser, users do not expect to have this file. So do not try to look up
+    // virtal file if there is a URL in the data object.
+    format = nsClipboard::GetFormat(kURLMime);
+    SET_FORMATETC(fe, format, 0, DVASPECT_CONTENT, -1, TYMED_HGLOBAL);
+    if (mDataObject->QueryGetData(&fe) == S_OK) {
+      return NS_OK;
+    }
+
+    // If the client wants a file, maybe we find a virtual file.
+    format = nsClipboard::GetClipboardFileDescriptorFormatW();
+    SET_FORMATETC(fe, format, 0, DVASPECT_CONTENT, -1, TYMED_HGLOBAL);
+    if (mDataObject->QueryGetData(&fe) == S_OK) {
+      *_retval = true;  // found it!
+    }
+
+    // XXX should we fall back to CFSTR_FILEDESCRIPTORA?
+    return NS_OK;
+  }
+
+  return NS_OK;
+}
+
+//
+// IsCollectionObject
+//
+// Determine if this is a single |IDataObject| or one of our private
+// collection objects. We know the difference because our collection
+// object will respond to supporting the private |MULTI_MIME| format.
+//
+bool nsDragService::IsCollectionObject(IDataObject* inDataObj) {
+  bool isCollection = false;
+
+  // setup the format object to ask for the MULTI_MIME format. We only
+  // need to do this once
+  static UINT sFormat = 0;
+  static FORMATETC sFE;
+  if (!sFormat) {
+    sFormat = nsClipboard::GetFormat(MULTI_MIME);
+    SET_FORMATETC(sFE, sFormat, 0, DVASPECT_CONTENT, -1, TYMED_HGLOBAL);
+  }
+
+  // ask the object if it supports it. If yes, we have a collection
+  // object
+  if (inDataObj->QueryGetData(&sFE) == S_OK) isCollection = true;
+
+  return isCollection;
+
+}  // IsCollectionObject
+
+//
+// EndDragSession
+//
+// Override the default to make sure that we release the data object
+// when the drag ends. It seems that OLE doesn't like to let apps quit
+// w/out crashing when we're still holding onto their data
+//
+NS_IMETHODIMP
+nsDragService::EndDragSession(bool aDoneDrag, uint32_t aKeyModifiers) {
+  // Bug 100180: If we've got mouse events captured, make sure we release it -
+  // that way, if we happen to call EndDragSession before diving into a nested
+  // event loop, we can still respond to mouse events.
+  if (::GetCapture()) {
+    ::ReleaseCapture();
+  }
+
+  nsBaseDragService::EndDragSession(aDoneDrag, aKeyModifiers);
+  NS_IF_RELEASE(mDataObject);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsDragService::UpdateDragImage(nsINode* aImage, int32_t aImageX,
+                               int32_t aImageY) {
+  if (!mDataObject) {
+    return NS_OK;
+  }
+
+  nsBaseDragService::UpdateDragImage(aImage, aImageX, aImageY);
+
+  IDragSourceHelper* pdsh;
+  if (SUCCEEDED(CoCreateInstance(CLSID_DragDropHelper, nullptr,
+                                 CLSCTX_INPROC_SERVER, IID_IDragSourceHelper,
+                                 (void**)&pdsh))) {
+    SHDRAGIMAGE sdi;
+    if (CreateDragImage(mSourceNode, Nothing(), &sdi)) {
+      nsNativeDragTarget::DragImageChanged();
+      if (FAILED(pdsh->InitializeFromBitmap(&sdi, mDataObject)))
+        DeleteObject(sdi.hbmpDragImage);
+    }
+    pdsh->Release();
+  }
+
+  return NS_OK;
+}
diff --git a/widget/windows/nsDragService.h b/widget/windows/nsDragService.h
new file mode 100644
index 0000000000..5a86a74f76
--- /dev/null
+++ b/widget/windows/nsDragService.h
@@ -0,0 +1,67 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef nsDragService_h__
+#define nsDragService_h__
+
+#include "nsBaseDragService.h"
+#include <windows.h>
+#include <shlobj.h>
+
+struct IDataObject;
+class nsDataObjCollection;
+
+/**
+ * Native Win32 DragService wrapper
+ */
+
+class nsDragService : public nsBaseDragService {
+ public:
+  nsDragService();
+  virtual ~nsDragService();
+
+  // nsBaseDragService
+  MOZ_CAN_RUN_SCRIPT virtual nsresult InvokeDragSessionImpl(
+      nsIArray* anArrayTransferables,
+      const mozilla::Maybe<mozilla::CSSIntRegion>& aRegion,
+      uint32_t aActionType);
+
+  // nsIDragSession
+  NS_IMETHOD GetData(nsITransferable* aTransferable, uint32_t anItem) override;
+  NS_IMETHOD GetNumDropItems(uint32_t* aNumItems) override;
+  NS_IMETHOD IsDataFlavorSupported(const char* aDataFlavor,
+                                   bool* _retval) override;
+  MOZ_CAN_RUN_SCRIPT NS_IMETHOD EndDragSession(bool aDoneDrag,
+                                               uint32_t aKeyModifiers) override;
+  NS_IMETHOD UpdateDragImage(nsINode* aImage, int32_t aImageX,
+                             int32_t aImageY) override;
+
+  // native impl.
+  NS_IMETHOD SetIDataObject(IDataObject* aDataObj);
+  MOZ_CAN_RUN_SCRIPT nsresult StartInvokingDragSession(IDataObject* aDataObj,
+                                                       uint32_t aActionType);
+
+  // A drop occurred within the application vs. outside of it.
+  void SetDroppedLocal();
+
+  IDataObject* GetDataObject() { return mDataObject; }
+
+ protected:
+  nsDataObjCollection* GetDataObjCollection(IDataObject* aDataObj);
+
+  // determine if we have a single data object or one of our private
+  // collections
+  bool IsCollectionObject(IDataObject* inDataObj);
+
+  // Create a bitmap for drag operations
+  bool CreateDragImage(nsINode* aDOMNode,
+                       const mozilla::Maybe<mozilla::CSSIntRegion>& aRegion,
+                       SHDRAGIMAGE* psdi);
+
+  IDataObject* mDataObject;
+  bool mSentLocalDropEvent;
+};
+
+#endif  // nsDragService_h__
diff --git a/widget/windows/nsFilePicker.cpp b/widget/windows/nsFilePicker.cpp
new file mode 100644
index 0000000000..310c54bb40
--- /dev/null
+++ b/widget/windows/nsFilePicker.cpp
@@ -0,0 +1,1078 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsFilePicker.h"
+
+#include <cderr.h>
+#include <shlobj.h>
+#include <shlwapi.h>
+#include <sysinfoapi.h>
+#include <winerror.h>
+#include <winuser.h>
+#include <utility>
+
+#include "ContentAnalysis.h"
+#include "mozilla/Assertions.h"
+#include "mozilla/BackgroundHangMonitor.h"
+#include "mozilla/Components.h"
+#include "mozilla/dom/BrowsingContext.h"
+#include "mozilla/dom/Directory.h"
+#include "mozilla/Logging.h"
+#include "mozilla/ipc/UtilityProcessManager.h"
+#include "mozilla/ProfilerLabels.h"
+#include "mozilla/StaticPrefs_widget.h"
+#include "mozilla/UniquePtr.h"
+#include "mozilla/WindowsVersion.h"
+#include "nsCRT.h"
+#include "nsEnumeratorUtils.h"
+#include "nsIContentAnalysis.h"
+#include "nsNetUtil.h"
+#include "nsPIDOMWindow.h"
+#include "nsPrintfCString.h"
+#include "nsReadableUtils.h"
+#include "nsString.h"
+#include "nsToolkit.h"
+#include "nsWindow.h"
+#include "WinUtils.h"
+
+#include "mozilla/glean/GleanMetrics.h"
+
+#include "mozilla/widget/filedialog/WinFileDialogCommands.h"
+#include "mozilla/widget/filedialog/WinFileDialogParent.h"
+
+using mozilla::UniquePtr;
+
+using namespace mozilla::widget;
+
+UniquePtr<char16_t[], nsFilePicker::FreeDeleter>
+    nsFilePicker::sLastUsedUnicodeDirectory;
+
+using mozilla::LogLevel;
+
+#define MAX_EXTENSION_LENGTH 10
+
+///////////////////////////////////////////////////////////////////////////////
+// Helper classes
+
+// Manages matching PickerOpen/PickerClosed calls on the parent widget.
+class AutoWidgetPickerState {
+  static RefPtr<nsWindow> GetWindowForWidget(nsIWidget* aWidget) {
+    MOZ_ASSERT(NS_IsMainThread());
+    if (!aWidget) {
+      return nullptr;
+    }
+    HWND hwnd = (HWND)aWidget->GetNativeData(NS_NATIVE_WINDOW);
+    return RefPtr(WinUtils::GetNSWindowPtr(hwnd));
+  }
+
+ public:
+  explicit AutoWidgetPickerState(nsIWidget* aWidget)
+      : mWindow(GetWindowForWidget(aWidget)) {
+    MOZ_ASSERT(mWindow);
+    if (mWindow) mWindow->PickerOpen();
+  }
+  ~AutoWidgetPickerState() {
+    // may be null if moved-from
+    if (mWindow) mWindow->PickerClosed();
+  }
+
+  AutoWidgetPickerState(AutoWidgetPickerState const&) = delete;
+  AutoWidgetPickerState(AutoWidgetPickerState&& that) noexcept = default;
+
+ private:
+  RefPtr<nsWindow> mWindow;
+};
+
+///////////////////////////////////////////////////////////////////////////////
+// nsIFilePicker
+
+nsFilePicker::nsFilePicker() : mSelectedType(1) {}
+
+NS_IMPL_ISUPPORTS(nsFilePicker, nsIFilePicker)
+
+NS_IMETHODIMP nsFilePicker::Init(
+    mozIDOMWindowProxy* aParent, const nsAString& aTitle,
+    nsIFilePicker::Mode aMode,
+    mozilla::dom::BrowsingContext* aBrowsingContext) {
+  // Don't attempt to open a real file-picker in headless mode.
+  if (gfxPlatform::IsHeadless()) {
+    return nsresult::NS_ERROR_NOT_AVAILABLE;
+  }
+
+  nsCOMPtr<nsPIDOMWindowOuter> window = do_QueryInterface(aParent);
+  nsIDocShell* docShell = window ? window->GetDocShell() : nullptr;
+  mLoadContext = do_QueryInterface(docShell);
+
+  return nsBaseFilePicker::Init(aParent, aTitle, aMode, aBrowsingContext);
+}
+
+namespace mozilla::detail {
+// Boilerplate for remotely showing a file dialog.
+template <typename ActionType,
+          typename ReturnType = typename decltype(std::declval<ActionType>()(
+              nullptr))::element_type::ResolveValueType>
+static auto ShowRemote(ActionType&& action)
+    -> RefPtr<MozPromise<ReturnType, HRESULT, true>> {
+  using RetPromise = MozPromise<ReturnType, HRESULT, true>;
+
+  constexpr static const auto fail = []() {
+    return RetPromise::CreateAndReject(E_FAIL, __PRETTY_FUNCTION__);
+  };
+
+  auto mgr = mozilla::ipc::UtilityProcessManager::GetSingleton();
+  if (!mgr) {
+    MOZ_ASSERT(false);
+    return fail();
+  }
+
+  auto wfda = mgr->CreateWinFileDialogActor();
+  if (!wfda) {
+    return fail();
+  }
+
+  using mozilla::widget::filedialog::sLogFileDialog;
+
+  return wfda->Then(
+      mozilla::GetMainThreadSerialEventTarget(),
+      "nsFilePicker ShowRemote acquire",
+      [action = std::forward<ActionType>(action)](
+          filedialog::ProcessProxy const& p) -> RefPtr<RetPromise> {
+        MOZ_LOG(sLogFileDialog, LogLevel::Info,
+                ("nsFilePicker ShowRemote first callback: p = [%p]", p.get()));
+
+        // false positive: not actually redundant
+        // NOLINTNEXTLINE(readability-redundant-smartptr-get)
+        return action(p.get())->Then(
+            mozilla::GetMainThreadSerialEventTarget(),
+            "nsFilePicker ShowRemote call",
+            [p](ReturnType ret) {
+              return RetPromise::CreateAndResolve(std::move(ret),
+                                                  __PRETTY_FUNCTION__);
+            },
+            [](mozilla::ipc::ResponseRejectReason error) {
+              MOZ_LOG(sLogFileDialog, LogLevel::Error,
+                      ("IPC call rejected: %zu", size_t(error)));
+              return fail();
+            });
+      },
+      [](nsresult error) -> RefPtr<RetPromise> {
+        MOZ_LOG(sLogFileDialog, LogLevel::Error,
+                ("could not acquire WinFileDialog: %zu", size_t(error)));
+        return fail();
+      });
+}
+
+// fd_async
+//
+// Wrapper-namespace for the AsyncExecute() and AsyncAll() functions.
+namespace fd_async {
+
+// Implementation details of, specifically, the AsyncExecute() and AsyncAll()
+// functions.
+namespace details {
+// Helper for generically copying ordinary types and nsTArray (which lacks a
+// copy constructor) in the same breath.
+template <typename T>
+static T Copy(T const& val) {
+  return val;
+}
+template <typename T>
+static nsTArray<T> Copy(nsTArray<T> const& arr) {
+  return arr.Clone();
+}
+
+// The possible execution strategies of AsyncExecute.
+enum Strategy { Local, Remote, RemoteWithFallback };
+
+// Decode the relevant preference to determine the desired execution-
+// strategy.
+static Strategy GetStrategy() {
+  int32_t const pref =
+      mozilla::StaticPrefs::widget_windows_utility_process_file_picker();
+  switch (pref) {
+    case -1:
+      return Local;
+    case 2:
+      return Remote;
+    case 1:
+      return RemoteWithFallback;
+
+    default:
+#ifdef NIGHTLY_BUILD
+      // on Nightly builds, fall back to local on failure
+      return RemoteWithFallback;
+#else
+      // on release and beta, remain local-only for now
+      return Local;
+#endif
+  }
+};
+
+template <typename T>
+class AsyncAllIterator final {
+ public:
+  NS_INLINE_DECL_REFCOUNTING(AsyncAllIterator)
+  AsyncAllIterator(
+      nsTArray<T> aItems,
+      std::function<
+          RefPtr<mozilla::MozPromise<bool, nsresult, true>>(const T& item)>
+          aPredicate,
+      RefPtr<mozilla::MozPromise<bool, nsresult, true>::Private> aPromise)
+      : mItems(std::move(aItems)),
+        mNextIndex(0),
+        mPredicate(std::move(aPredicate)),
+        mPromise(std::move(aPromise)) {}
+
+  void StartIterating() { ContinueIterating(); }
+
+ private:
+  ~AsyncAllIterator() = default;
+  void ContinueIterating() {
+    if (mNextIndex >= mItems.Length()) {
+      mPromise->Resolve(true, __func__);
+      return;
+    }
+    mPredicate(mItems.ElementAt(mNextIndex))
+        ->Then(
+            mozilla::GetMainThreadSerialEventTarget(), __func__,
+            [self = RefPtr{this}](bool aResult) {
+              if (!aResult) {
+                self->mPromise->Resolve(false, __func__);
+                return;
+              }
+              ++self->mNextIndex;
+              self->ContinueIterating();
+            },
+            [self = RefPtr{this}](nsresult aError) {
+              self->mPromise->Reject(aError, __func__);
+            });
+  }
+  nsTArray<T> mItems;
+  uint32_t mNextIndex;
+  std::function<RefPtr<mozilla::MozPromise<bool, nsresult, true>>(
+      const T& item)>
+      mPredicate;
+  RefPtr<mozilla::MozPromise<bool, nsresult, true>::Private> mPromise;
+};
+
+namespace telemetry {
+static uint32_t Delta(uint64_t tb, uint64_t ta) {
+  // FILETIMEs are 100ns intervals; we reduce that to 1ms.
+  // (`u32::max()` milliseconds is roughly 47.91 days.)
+  return uint32_t((tb - ta) / 10'000);
+};
+static nsCString HexString(HRESULT val) {
+  return nsPrintfCString("%08lX", val);
+};
+
+static void RecordSuccess(uint64_t (&&time)[2]) {
+  auto [t0, t1] = time;
+
+  namespace glean_fd = mozilla::glean::file_dialog;
+  glean_fd::FallbackExtra extra{
+      .hresultLocal = Nothing(),
+      .hresultRemote = Nothing(),
+      .succeeded = Some(true),
+      .timeLocal = Nothing(),
+      .timeRemote = Some(Delta(t1, t0)),
+  };
+  glean_fd::fallback.Record(Some(extra));
+}
+
+static void RecordFailure(uint64_t (&&time)[3], HRESULT hrRemote,
+                          HRESULT hrLocal) {
+  auto [t0, t1, t2] = time;
+
+  {
+    namespace glean_fd = mozilla::glean::file_dialog;
+    glean_fd::FallbackExtra extra{
+        .hresultLocal = Some(HexString(hrLocal)),
+        .hresultRemote = Some(HexString(hrRemote)),
+        .succeeded = Some(false),
+        .timeLocal = Some(Delta(t2, t1)),
+        .timeRemote = Some(Delta(t1, t0)),
+    };
+    glean_fd::fallback.Record(Some(extra));
+  }
+}
+
+}  // namespace telemetry
+}  // namespace details
+
+// Invoke either or both of a "do locally" and "do remotely" function with the
+// provided arguments, depending on the relevant preference-value and whether
+// or not the remote version fails.
+//
+// Both functions must be asynchronous, returning a `RefPtr<MozPromise<...>>`.
+// "Failure" is defined as the promise being rejected.
+template <typename Fn1, typename Fn2, typename... Args>
+static auto AsyncExecute(Fn1 local, Fn2 remote, Args const&... args)
+    -> std::invoke_result_t<Fn1, Args...> {
+  using namespace details;
+
+  static_assert(std::is_same_v<std::invoke_result_t<Fn1, Args...>,
+                               std::invoke_result_t<Fn2, Args...>>);
+  using PromiseT = typename std::invoke_result_t<Fn1, Args...>::element_type;
+
+  constexpr static char kFunctionName[] = "LocalAndOrRemote::AsyncExecute";
+
+  switch (GetStrategy()) {
+    case Local:
+      return local(args...);
+
+    case Remote:
+      return remote(args...);
+
+    case RemoteWithFallback:
+      // more complicated; continue below
+      break;
+  }
+
+  // capture time for telemetry
+  constexpr static const auto GetTime = []() -> uint64_t {
+    FILETIME t;
+    ::GetSystemTimeAsFileTime(&t);
+    return (uint64_t(t.dwHighDateTime) << 32) | t.dwLowDateTime;
+  };
+  uint64_t const t0 = GetTime();
+
+  return remote(args...)->Then(
+      NS_GetCurrentThread(), kFunctionName,
+      [t0](typename PromiseT::ResolveValueType result) -> RefPtr<PromiseT> {
+        // success; stop here
+        auto const t1 = GetTime();
+        // record success
+        telemetry::RecordSuccess({t0, t1});
+        return PromiseT::CreateAndResolve(result, kFunctionName);
+      },
+      // initialized lambda pack captures are C++20 (clang 9, gcc 9);
+      // `make_tuple` is just a C++17 workaround
+      [=, tuple = std::make_tuple(Copy(args)...)](
+          typename PromiseT::RejectValueType err) mutable -> RefPtr<PromiseT> {
+        // failure; record time
+        auto const t1 = GetTime();
+        HRESULT const hrRemote = err;
+
+        // retry locally...
+        auto p0 = std::apply(local, std::move(tuple));
+        // ...then record the telemetry event
+        return p0->Then(
+            NS_GetCurrentThread(), kFunctionName,
+            [t0, t1,
+             hrRemote](typename PromiseT::ResolveOrRejectValue const& val)
+                -> RefPtr<PromiseT> {
+              auto const t2 = GetTime();
+              HRESULT const hrLocal = val.IsReject() ? val.RejectValue() : S_OK;
+              telemetry::RecordFailure({t0, t1, t2}, hrRemote, hrLocal);
+
+              return PromiseT::CreateAndResolveOrReject(val, kFunctionName);
+            });
+      });
+}
+
+// Asynchronously invokes `aPredicate` on each member of `aItems`.
+// Yields `false` (and stops immediately) if any invocation of
+// `predicate` yielded `false`; otherwise yields `true`.
+template <typename T>
+static RefPtr<mozilla::MozPromise<bool, nsresult, true>> AsyncAll(
+    nsTArray<T> aItems,
+    std::function<
+        RefPtr<mozilla::MozPromise<bool, nsresult, true>>(const T& item)>
+        aPredicate) {
+  auto promise =
+      mozilla::MakeRefPtr<mozilla::MozPromise<bool, nsresult, true>::Private>(
+          __func__);
+  auto iterator = mozilla::MakeRefPtr<details::AsyncAllIterator<T>>(
+      std::move(aItems), aPredicate, promise);
+  iterator->StartIterating();
+  return promise;
+}
+}  // namespace fd_async
+
+using fd_async::AsyncAll;
+using fd_async::AsyncExecute;
+
+}  // namespace mozilla::detail
+
+/* static */
+nsFilePicker::FPPromise<filedialog::Results> nsFilePicker::ShowFilePickerRemote(
+    HWND parent, filedialog::FileDialogType type,
+    nsTArray<filedialog::Command> const& commands) {
+  using mozilla::widget::filedialog::sLogFileDialog;
+  return mozilla::detail::ShowRemote(
+      [parent, type,
+       commands = commands.Clone()](filedialog::WinFileDialogParent* p) {
+        MOZ_LOG(sLogFileDialog, LogLevel::Info,
+                ("%s: p = [%p]", __PRETTY_FUNCTION__, p));
+        return p->SendShowFileDialog((uintptr_t)parent, type, commands);
+      });
+}
+
+/* static */
+nsFilePicker::FPPromise<nsString> nsFilePicker::ShowFolderPickerRemote(
+    HWND parent, nsTArray<filedialog::Command> const& commands) {
+  using mozilla::widget::filedialog::sLogFileDialog;
+  return mozilla::detail::ShowRemote([parent, commands = commands.Clone()](
+                                         filedialog::WinFileDialogParent* p) {
+    MOZ_LOG(sLogFileDialog, LogLevel::Info,
+            ("%s: p = [%p]", __PRETTY_FUNCTION__, p));
+    return p->SendShowFolderDialog((uintptr_t)parent, commands);
+  });
+}
+
+/* static */
+nsFilePicker::FPPromise<filedialog::Results> nsFilePicker::ShowFilePickerLocal(
+    HWND parent, filedialog::FileDialogType type,
+    nsTArray<filedialog::Command> const& commands) {
+  return filedialog::SpawnFilePicker(parent, type, commands.Clone());
+}
+
+/* static */
+nsFilePicker::FPPromise<nsString> nsFilePicker::ShowFolderPickerLocal(
+    HWND parent, nsTArray<filedialog::Command> const& commands) {
+  return filedialog::SpawnFolderPicker(parent, commands.Clone());
+}
+
+/*
+ * Folder picker invocation
+ */
+
+/*
+ * Show a folder picker.
+ *
+ * @param aInitialDir   The initial directory. The last-used directory will be
+ *                      used if left blank.
+ * @return  A promise which:
+ *          - resolves to true if a file was selected successfully (in which
+ *            case mUnicodeFile will be updated);
+ *          - resolves to false if the dialog was cancelled by the user;
+ *          - is rejected with the associated HRESULT if some error occurred.
+ */
+RefPtr<mozilla::MozPromise<bool, HRESULT, true>> nsFilePicker::ShowFolderPicker(
+    const nsString& aInitialDir) {
+  using Promise = mozilla::MozPromise<bool, HRESULT, true>;
+  constexpr static auto Ok = [](bool val) {
+    return Promise::CreateAndResolve(val, "nsFilePicker::ShowFolderPicker");
+  };
+  constexpr static auto NotOk = [](HRESULT val = E_FAIL) {
+    return Promise::CreateAndReject(val, "nsFilePicker::ShowFolderPicker");
+  };
+
+  namespace fd = ::mozilla::widget::filedialog;
+  nsTArray<fd::Command> commands = {
+      fd::SetOptions(FOS_PICKFOLDERS),
+      fd::SetTitle(mTitle),
+  };
+
+  if (!mOkButtonLabel.IsEmpty()) {
+    commands.AppendElement(fd::SetOkButtonLabel(mOkButtonLabel));
+  }
+
+  if (!aInitialDir.IsEmpty()) {
+    commands.AppendElement(fd::SetFolder(aInitialDir));
+  }
+
+  ScopedRtlShimWindow shim(mParentWidget.get());
+  AutoWidgetPickerState awps(mParentWidget);
+
+  return mozilla::detail::AsyncExecute(&ShowFolderPickerLocal,
+                                       &ShowFolderPickerRemote, shim.get(),
+                                       commands)
+      ->Then(
+          NS_GetCurrentThread(), __PRETTY_FUNCTION__,
+          [self = RefPtr(this), shim = std::move(shim),
+           awps = std::move(awps)](Maybe<nsString> val) {
+            if (val) {
+              self->mUnicodeFile = val.extract();
+              return Ok(true);
+            }
+            return Ok(false);
+          },
+          [](HRESULT err) {
+            NS_WARNING("ShowFolderPicker failed");
+            return NotOk(err);
+          });
+}
+
+/*
+ * File open and save picker invocation
+ */
+
+/*
+ * Show a file picker.
+ *
+ * @param aInitialDir   The initial directory. The last-used directory will be
+ *                      used if left blank.
+ * @return  A promise which:
+ *          - resolves to true if one or more files were selected successfully
+ *            (in which case mUnicodeFile and/or mFiles will be updated);
+ *          - resolves to false if the dialog was cancelled by the user;
+ *          - is rejected with the associated HRESULT if some error occurred.
+ */
+RefPtr<mozilla::MozPromise<bool, HRESULT, true>> nsFilePicker::ShowFilePicker(
+    const nsString& aInitialDir) {
+  AUTO_PROFILER_LABEL("nsFilePicker::ShowFilePicker", OTHER);
+
+  using Promise = mozilla::MozPromise<bool, HRESULT, true>;
+  constexpr static auto Ok = [](bool val) {
+    return Promise::CreateAndResolve(val, "nsFilePicker::ShowFilePicker");
+  };
+  constexpr static auto NotOk = [](HRESULT val = E_FAIL) {
+    return Promise::CreateAndReject(val, "nsFilePicker::ShowFilePicker");
+  };
+
+  namespace fd = ::mozilla::widget::filedialog;
+  nsTArray<fd::Command> commands;
+  // options
+  {
+    FILEOPENDIALOGOPTIONS fos = 0;
+    fos |= FOS_SHAREAWARE | FOS_OVERWRITEPROMPT | FOS_FORCEFILESYSTEM;
+
+    // Handle add to recent docs settings
+    if (IsPrivacyModeEnabled() || !mAddToRecentDocs) {
+      fos |= FOS_DONTADDTORECENT;
+    }
+
+    // mode specific
+    switch (mMode) {
+      case modeOpen:
+        fos |= FOS_FILEMUSTEXIST;
+        break;
+
+      case modeOpenMultiple:
+        fos |= FOS_FILEMUSTEXIST | FOS_ALLOWMULTISELECT;
+        break;
+
+      case modeSave:
+        fos |= FOS_NOREADONLYRETURN;
+        // Don't follow shortcuts when saving a shortcut, this can be used
+        // to trick users (bug 271732)
+        if (IsDefaultPathLink()) fos |= FOS_NODEREFERENCELINKS;
+        break;
+
+      case modeGetFolder:
+        MOZ_ASSERT(false, "file-picker opened in directory-picker mode");
+        return NotOk(E_FAIL);
+    }
+
+    commands.AppendElement(fd::SetOptions(fos));
+  }
+
+  // initial strings
+
+  // title
+  commands.AppendElement(fd::SetTitle(mTitle));
+
+  // default filename
+  if (!mDefaultFilename.IsEmpty()) {
+    // Prevent the shell from expanding environment variables by removing
+    // the % characters that are used to delimit them.
+    nsAutoString sanitizedFilename(mDefaultFilename);
+    sanitizedFilename.ReplaceChar('%', '_');
+
+    commands.AppendElement(fd::SetFileName(sanitizedFilename));
+  }
+
+  // default extension to append to new files
+  if (!mDefaultExtension.IsEmpty()) {
+    // We don't want environment variables expanded in the extension either.
+    nsAutoString sanitizedExtension(mDefaultExtension);
+    sanitizedExtension.ReplaceChar('%', '_');
+
+    commands.AppendElement(fd::SetDefaultExtension(sanitizedExtension));
+  } else if (IsDefaultPathHtml()) {
+    commands.AppendElement(fd::SetDefaultExtension(u"html"_ns));
+  }
+
+  // initial location
+  if (!aInitialDir.IsEmpty()) {
+    commands.AppendElement(fd::SetFolder(aInitialDir));
+  }
+
+  // filter types and the default index
+  if (!mFilterList.IsEmpty()) {
+    nsTArray<fd::ComDlgFilterSpec> fileTypes;
+    for (auto const& filter : mFilterList) {
+      fileTypes.EmplaceBack(filter.title, filter.filter);
+    }
+    commands.AppendElement(fd::SetFileTypes(std::move(fileTypes)));
+    commands.AppendElement(fd::SetFileTypeIndex(mSelectedType));
+  }
+
+  ScopedRtlShimWindow shim(mParentWidget.get());
+  AutoWidgetPickerState awps(mParentWidget);
+
+  mozilla::BackgroundHangMonitor().NotifyWait();
+  auto type = mMode == modeSave ? FileDialogType::Save : FileDialogType::Open;
+
+  auto promise = mozilla::detail::AsyncExecute(
+      &ShowFilePickerLocal, &ShowFilePickerRemote, shim.get(), type, commands);
+
+  return promise->Then(
+      mozilla::GetMainThreadSerialEventTarget(), __PRETTY_FUNCTION__,
+      [self = RefPtr(this), mode = mMode, shim = std::move(shim),
+       awps = std::move(awps)](Maybe<Results> res_opt) {
+        if (!res_opt) {
+          return Ok(false);
+        }
+        auto result = res_opt.extract();
+
+        // Remember what filter type the user selected
+        self->mSelectedType = int32_t(result.selectedFileTypeIndex());
+
+        auto const& paths = result.paths();
+
+        // single selection
+        if (mode != modeOpenMultiple) {
+          if (!paths.IsEmpty()) {
+            MOZ_ASSERT(paths.Length() == 1);
+            self->mUnicodeFile = paths[0];
+            return Ok(true);
+          }
+          return Ok(false);
+        }
+
+        // multiple selection
+        for (auto const& str : paths) {
+          nsCOMPtr<nsIFile> file;
+          if (NS_SUCCEEDED(NS_NewLocalFile(str, false, getter_AddRefs(file)))) {
+            self->mFiles.AppendObject(file);
+          }
+        }
+
+        return Ok(true);
+      },
+      [](HRESULT err) {
+        NS_WARNING("ShowFilePicker failed");
+        return NotOk(err);
+      });
+}
+
+void nsFilePicker::ClearFiles() {
+  mUnicodeFile.Truncate();
+  mFiles.Clear();
+}
+
+namespace {
+class GetFilesInDirectoryCallback final
+    : public mozilla::dom::GetFilesCallback {
+ public:
+  explicit GetFilesInDirectoryCallback(
+      RefPtr<mozilla::MozPromise<nsTArray<mozilla::PathString>, nsresult,
+                                 true>::Private>
+          aPromise)
+      : mPromise(std::move(aPromise)) {}
+  void Callback(
+      nsresult aStatus,
+      const FallibleTArray<RefPtr<mozilla::dom::BlobImpl>>& aBlobImpls) {
+    if (NS_FAILED(aStatus)) {
+      mPromise->Reject(aStatus, __func__);
+      return;
+    }
+    nsTArray<mozilla::PathString> filePaths;
+    filePaths.SetCapacity(aBlobImpls.Length());
+    for (const auto& blob : aBlobImpls) {
+      if (blob->IsFile()) {
+        mozilla::PathString pathString;
+        mozilla::ErrorResult error;
+        blob->GetMozFullPathInternal(pathString, error);
+        nsresult rv = error.StealNSResult();
+        if (NS_WARN_IF(NS_FAILED(rv))) {
+          mPromise->Reject(rv, __func__);
+          return;
+        }
+        filePaths.AppendElement(pathString);
+      } else {
+        NS_WARNING("Got a non-file blob, can't do content analysis on it");
+      }
+    }
+    mPromise->Resolve(std::move(filePaths), __func__);
+  }
+
+ private:
+  RefPtr<mozilla::MozPromise<nsTArray<mozilla::PathString>, nsresult,
+                             true>::Private>
+      mPromise;
+};
+}  // anonymous namespace
+
+RefPtr<nsFilePicker::ContentAnalysisResponse>
+nsFilePicker::CheckContentAnalysisService() {
+  nsresult rv;
+  nsCOMPtr<nsIContentAnalysis> contentAnalysis =
+      mozilla::components::nsIContentAnalysis::Service(&rv);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return nsFilePicker::ContentAnalysisResponse::CreateAndReject(rv, __func__);
+  }
+  bool contentAnalysisIsActive = false;
+  rv = contentAnalysis->GetIsActive(&contentAnalysisIsActive);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return nsFilePicker::ContentAnalysisResponse::CreateAndReject(rv, __func__);
+  }
+  if (!contentAnalysisIsActive) {
+    return nsFilePicker::ContentAnalysisResponse::CreateAndResolve(true,
+                                                                   __func__);
+  }
+
+  nsCOMPtr<nsIURI> uri = mBrowsingContext->Canonical()->GetCurrentURI();
+
+  auto processOneItem = [self = RefPtr{this},
+                         contentAnalysis = std::move(contentAnalysis),
+                         uri =
+                             std::move(uri)](const mozilla::PathString& aItem) {
+    nsCString emptyDigestString;
+    auto* windowGlobal =
+        self->mBrowsingContext->Canonical()->GetCurrentWindowGlobal();
+    nsCOMPtr<nsIContentAnalysisRequest> contentAnalysisRequest(
+        new mozilla::contentanalysis::ContentAnalysisRequest(
+            nsIContentAnalysisRequest::AnalysisType::eFileAttached, aItem, true,
+            std::move(emptyDigestString), uri,
+            nsIContentAnalysisRequest::OperationType::eCustomDisplayString,
+            windowGlobal));
+
+    auto promise =
+        mozilla::MakeRefPtr<nsFilePicker::ContentAnalysisResponse::Private>(
+            __func__);
+    auto contentAnalysisCallback =
+        mozilla::MakeRefPtr<mozilla::contentanalysis::ContentAnalysisCallback>(
+            [promise](nsIContentAnalysisResponse* aResponse) {
+              promise->Resolve(aResponse->GetShouldAllowContent(), __func__);
+            },
+            [promise](nsresult aError) { promise->Reject(aError, __func__); });
+
+    nsresult rv = contentAnalysis->AnalyzeContentRequestCallback(
+        contentAnalysisRequest, /* aAutoAcknowledge */ true,
+        contentAnalysisCallback);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      promise->Reject(rv, __func__);
+    }
+    return promise;
+  };
+
+  // Since getting the files to analyze might be asynchronous, use a MozPromise
+  // to unify the logic below.
+  auto getFilesToAnalyzePromise = mozilla::MakeRefPtr<mozilla::MozPromise<
+      nsTArray<mozilla::PathString>, nsresult, true>::Private>(__func__);
+  if (mMode == modeGetFolder) {
+    nsCOMPtr<nsISupports> tmp;
+    nsresult rv = GetDomFileOrDirectory(getter_AddRefs(tmp));
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      getFilesToAnalyzePromise->Reject(rv, __func__);
+      return nsFilePicker::ContentAnalysisResponse::CreateAndReject(rv,
+                                                                    __func__);
+    }
+    auto* directory = static_cast<mozilla::dom::Directory*>(tmp.get());
+    mozilla::dom::OwningFileOrDirectory owningDirectory;
+    owningDirectory.SetAsDirectory() = directory;
+    nsTArray<mozilla::dom::OwningFileOrDirectory> directoryArray{
+        std::move(owningDirectory)};
+
+    mozilla::ErrorResult error;
+    RefPtr<mozilla::dom::GetFilesHelper> helper =
+        mozilla::dom::GetFilesHelper::Create(directoryArray, true, error);
+    rv = error.StealNSResult();
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      getFilesToAnalyzePromise->Reject(rv, __func__);
+      return nsFilePicker::ContentAnalysisResponse::CreateAndReject(rv,
+                                                                    __func__);
+    }
+    auto getFilesCallback = mozilla::MakeRefPtr<GetFilesInDirectoryCallback>(
+        getFilesToAnalyzePromise);
+    helper->AddCallback(getFilesCallback);
+  } else {
+    nsCOMArray<nsIFile> files;
+    if (!mUnicodeFile.IsEmpty()) {
+      nsCOMPtr<nsIFile> file;
+      rv = GetFile(getter_AddRefs(file));
+      if (NS_WARN_IF(NS_FAILED(rv))) {
+        getFilesToAnalyzePromise->Reject(rv, __func__);
+        return nsFilePicker::ContentAnalysisResponse::CreateAndReject(rv,
+                                                                      __func__);
+      }
+      files.AppendElement(file);
+    } else {
+      files.AppendElements(mFiles);
+    }
+    nsTArray<mozilla::PathString> paths(files.Length());
+    std::transform(files.begin(), files.end(), MakeBackInserter(paths),
+                   [](auto* entry) { return entry->NativePath(); });
+    getFilesToAnalyzePromise->Resolve(std::move(paths), __func__);
+  }
+
+  return getFilesToAnalyzePromise->Then(
+      mozilla::GetMainThreadSerialEventTarget(), __func__,
+      [processOneItem](nsTArray<mozilla::PathString> aPaths) mutable {
+        return mozilla::detail::AsyncAll<mozilla::PathString>(std::move(aPaths),
+                                                              processOneItem);
+      },
+      [](nsresult aError) {
+        return nsFilePicker::ContentAnalysisResponse::CreateAndReject(aError,
+                                                                      __func__);
+      });
+};
+
+///////////////////////////////////////////////////////////////////////////////
+// nsIFilePicker impl.
+
+nsresult nsFilePicker::Open(nsIFilePickerShownCallback* aCallback) {
+  NS_ENSURE_ARG_POINTER(aCallback);
+
+  if (MaybeBlockFilePicker(aCallback)) {
+    return NS_OK;
+  }
+
+  // Don't attempt to open a real file-picker in headless mode.
+  if (gfxPlatform::IsHeadless()) {
+    return nsresult::NS_ERROR_NOT_AVAILABLE;
+  }
+
+  nsAutoString initialDir;
+  if (mDisplayDirectory) mDisplayDirectory->GetPath(initialDir);
+
+  // If no display directory, re-use the last one.
+  if (initialDir.IsEmpty()) {
+    // Allocate copy of last used dir.
+    initialDir = sLastUsedUnicodeDirectory.get();
+  }
+
+  // Clear previous file selections
+  ClearFiles();
+
+  auto promise = mMode == modeGetFolder ? ShowFolderPicker(initialDir)
+                                        : ShowFilePicker(initialDir);
+
+  auto p2 = promise->Then(
+      mozilla::GetMainThreadSerialEventTarget(), __PRETTY_FUNCTION__,
+      [self = RefPtr(this),
+       callback = RefPtr(aCallback)](bool selectionMade) -> void {
+        if (!selectionMade) {
+          callback->Done(ResultCode::returnCancel);
+          return;
+        }
+
+        self->RememberLastUsedDirectory();
+
+        nsIFilePicker::ResultCode retValue = ResultCode::returnOK;
+
+        if (self->mMode == modeSave) {
+          // Windows does not return resultReplace; we must check whether the
+          // file already exists.
+          nsCOMPtr<nsIFile> file;
+          nsresult rv =
+              NS_NewLocalFile(self->mUnicodeFile, false, getter_AddRefs(file));
+
+          bool flag = false;
+          if (NS_SUCCEEDED(rv) && NS_SUCCEEDED(file->Exists(&flag)) && flag) {
+            retValue = ResultCode::returnReplace;
+          }
+        }
+
+        if (self->mBrowsingContext && !self->mBrowsingContext->IsChrome() &&
+            self->mMode != modeSave && retValue != ResultCode::returnCancel) {
+          self->CheckContentAnalysisService()->Then(
+              mozilla::GetMainThreadSerialEventTarget(), __func__,
+              [retValue, callback, self = RefPtr{self}](bool aAllowContent) {
+                if (aAllowContent) {
+                  callback->Done(retValue);
+                } else {
+                  self->ClearFiles();
+                  callback->Done(ResultCode::returnCancel);
+                }
+              },
+              [callback, self = RefPtr{self}](nsresult aError) {
+                self->ClearFiles();
+                callback->Done(ResultCode::returnCancel);
+              });
+          return;
+        }
+
+        callback->Done(retValue);
+      },
+      [callback = RefPtr(aCallback)](HRESULT err) {
+        using mozilla::widget::filedialog::sLogFileDialog;
+        MOZ_LOG(sLogFileDialog, LogLevel::Error,
+                ("nsFilePicker: Show failed with hr=0x%08lX", err));
+        callback->Done(ResultCode::returnCancel);
+      });
+
+  return NS_OK;
+}
+
+nsresult nsFilePicker::Show(nsIFilePicker::ResultCode* aReturnVal) {
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP
+nsFilePicker::GetFile(nsIFile** aFile) {
+  NS_ENSURE_ARG_POINTER(aFile);
+  *aFile = nullptr;
+
+  if (mUnicodeFile.IsEmpty()) return NS_OK;
+
+  nsCOMPtr<nsIFile> file;
+  nsresult rv = NS_NewLocalFile(mUnicodeFile, false, getter_AddRefs(file));
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+
+  file.forget(aFile);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsFilePicker::GetFileURL(nsIURI** aFileURL) {
+  *aFileURL = nullptr;
+  nsCOMPtr<nsIFile> file;
+  nsresult rv = GetFile(getter_AddRefs(file));
+  if (!file) return rv;
+
+  return NS_NewFileURI(aFileURL, file);
+}
+
+NS_IMETHODIMP
+nsFilePicker::GetFiles(nsISimpleEnumerator** aFiles) {
+  NS_ENSURE_ARG_POINTER(aFiles);
+  return NS_NewArrayEnumerator(aFiles, mFiles, NS_GET_IID(nsIFile));
+}
+
+// Get the file + path
+NS_IMETHODIMP
+nsBaseWinFilePicker::SetDefaultString(const nsAString& aString) {
+  mDefaultFilePath = aString;
+
+  // First, make sure the file name is not too long.
+  int32_t nameLength;
+  int32_t nameIndex = mDefaultFilePath.RFind(u"\\");
+  if (nameIndex == kNotFound)
+    nameIndex = 0;
+  else
+    nameIndex++;
+  nameLength = mDefaultFilePath.Length() - nameIndex;
+  mDefaultFilename.Assign(Substring(mDefaultFilePath, nameIndex));
+
+  if (nameLength > MAX_PATH) {
+    int32_t extIndex = mDefaultFilePath.RFind(u".");
+    if (extIndex == kNotFound) extIndex = mDefaultFilePath.Length();
+
+    // Let's try to shave the needed characters from the name part.
+    int32_t charsToRemove = nameLength - MAX_PATH;
+    if (extIndex - nameIndex >= charsToRemove) {
+      mDefaultFilePath.Cut(extIndex - charsToRemove, charsToRemove);
+    }
+  }
+
+  // Then, we need to replace illegal characters. At this stage, we cannot
+  // replace the backslash as the string might represent a file path.
+  mDefaultFilePath.ReplaceChar(u"" FILE_ILLEGAL_CHARACTERS, u'-');
+  mDefaultFilename.ReplaceChar(u"" FILE_ILLEGAL_CHARACTERS, u'-');
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsBaseWinFilePicker::GetDefaultString(nsAString& aString) {
+  return NS_ERROR_FAILURE;
+}
+
+// The default extension to use for files
+NS_IMETHODIMP
+nsBaseWinFilePicker::GetDefaultExtension(nsAString& aExtension) {
+  aExtension = mDefaultExtension;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsBaseWinFilePicker::SetDefaultExtension(const nsAString& aExtension) {
+  mDefaultExtension = aExtension;
+  return NS_OK;
+}
+
+// Set the filter index
+NS_IMETHODIMP
+nsFilePicker::GetFilterIndex(int32_t* aFilterIndex) {
+  // Windows' filter index is 1-based, we use a 0-based system.
+  *aFilterIndex = mSelectedType - 1;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsFilePicker::SetFilterIndex(int32_t aFilterIndex) {
+  // Windows' filter index is 1-based, we use a 0-based system.
+  mSelectedType = aFilterIndex + 1;
+  return NS_OK;
+}
+
+void nsFilePicker::InitNative(nsIWidget* aParent, const nsAString& aTitle) {
+  mParentWidget = aParent;
+  mTitle.Assign(aTitle);
+}
+
+NS_IMETHODIMP
+nsFilePicker::AppendFilter(const nsAString& aTitle, const nsAString& aFilter) {
+  nsString sanitizedFilter(aFilter);
+  sanitizedFilter.ReplaceChar('%', '_');
+
+  if (sanitizedFilter == u"..apps"_ns) {
+    sanitizedFilter = u"*.exe;*.com"_ns;
+  } else {
+    sanitizedFilter.StripWhitespace();
+    if (sanitizedFilter == u"*"_ns) {
+      sanitizedFilter = u"*.*"_ns;
+    }
+  }
+  mFilterList.AppendElement(
+      Filter{.title = nsString(aTitle), .filter = std::move(sanitizedFilter)});
+  return NS_OK;
+}
+
+void nsFilePicker::RememberLastUsedDirectory() {
+  if (IsPrivacyModeEnabled()) {
+    // Don't remember the directory if private browsing was in effect
+    return;
+  }
+
+  nsCOMPtr<nsIFile> file;
+  if (NS_FAILED(NS_NewLocalFile(mUnicodeFile, false, getter_AddRefs(file)))) {
+    NS_WARNING("RememberLastUsedDirectory failed to init file path.");
+    return;
+  }
+
+  nsCOMPtr<nsIFile> dir;
+  nsAutoString newDir;
+  if (NS_FAILED(file->GetParent(getter_AddRefs(dir))) ||
+      !(mDisplayDirectory = dir) ||
+      NS_FAILED(mDisplayDirectory->GetPath(newDir)) || newDir.IsEmpty()) {
+    NS_WARNING("RememberLastUsedDirectory failed to get parent directory.");
+    return;
+  }
+
+  sLastUsedUnicodeDirectory.reset(ToNewUnicode(newDir));
+}
+
+bool nsFilePicker::IsPrivacyModeEnabled() {
+  return mLoadContext && mLoadContext->UsePrivateBrowsing();
+}
+
+bool nsFilePicker::IsDefaultPathLink() {
+  NS_ConvertUTF16toUTF8 ext(mDefaultFilePath);
+  ext.Trim(" .", false, true);  // watch out for trailing space and dots
+  ToLowerCase(ext);
+  return StringEndsWith(ext, ".lnk"_ns) || StringEndsWith(ext, ".pif"_ns) ||
+         StringEndsWith(ext, ".url"_ns);
+}
+
+bool nsFilePicker::IsDefaultPathHtml() {
+  int32_t extIndex = mDefaultFilePath.RFind(u".");
+  if (extIndex >= 0) {
+    nsAutoString ext;
+    mDefaultFilePath.Right(ext, mDefaultFilePath.Length() - extIndex);
+    if (ext.LowerCaseEqualsLiteral(".htm") ||
+        ext.LowerCaseEqualsLiteral(".html") ||
+        ext.LowerCaseEqualsLiteral(".shtml"))
+      return true;
+  }
+  return false;
+}
diff --git a/widget/windows/nsFilePicker.h b/widget/windows/nsFilePicker.h
new file mode 100644
index 0000000000..1938b8bcb6
--- /dev/null
+++ b/widget/windows/nsFilePicker.h
@@ -0,0 +1,140 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef nsFilePicker_h__
+#define nsFilePicker_h__
+
+#include <windows.h>
+
+#include "mozilla/MozPromise.h"
+#include "mozilla/dom/BlobImpl.h"
+#include "mozilla/dom/BrowsingContext.h"
+#include "mozilla/dom/GetFilesHelper.h"
+#include "nsIContentAnalysis.h"
+#include "nsIFile.h"
+#include "nsISimpleEnumerator.h"
+#include "nsCOMArray.h"
+#include "nsBaseFilePicker.h"
+#include "nsString.h"
+#include "nsdefs.h"
+#include <commdlg.h>
+#include <shobjidl.h>
+#undef LogSeverity  // SetupAPI.h #defines this as DWORD
+
+class nsILoadContext;
+
+namespace mozilla::widget::filedialog {
+class Command;
+class Results;
+enum class FileDialogType : uint8_t;
+}  // namespace mozilla::widget::filedialog
+
+class nsBaseWinFilePicker : public nsBaseFilePicker {
+ public:
+  NS_IMETHOD GetDefaultString(nsAString& aDefaultString) override;
+  NS_IMETHOD SetDefaultString(const nsAString& aDefaultString) override;
+  NS_IMETHOD GetDefaultExtension(nsAString& aDefaultExtension) override;
+  NS_IMETHOD SetDefaultExtension(const nsAString& aDefaultExtension) override;
+
+ protected:
+  nsString mDefaultFilePath;
+  nsString mDefaultFilename;
+  nsString mDefaultExtension;
+};
+
+/**
+ * Native Windows FileSelector wrapper
+ */
+
+class nsFilePicker final : public nsBaseWinFilePicker {
+  virtual ~nsFilePicker() = default;
+
+  template <typename T>
+  using Maybe = mozilla::Maybe<T>;
+  template <typename T>
+  using Result = mozilla::Result<T, HRESULT>;
+  template <typename Res>
+  using FPPromise = RefPtr<mozilla::MozPromise<Maybe<Res>, HRESULT, true>>;
+
+  using Command = mozilla::widget::filedialog::Command;
+  using Results = mozilla::widget::filedialog::Results;
+  using FileDialogType = mozilla::widget::filedialog::FileDialogType;
+
+ public:
+  nsFilePicker();
+
+  NS_IMETHOD Init(mozIDOMWindowProxy* aParent, const nsAString& aTitle,
+                  nsIFilePicker::Mode aMode,
+                  mozilla::dom::BrowsingContext* aBrowsingContext) override;
+
+  NS_DECL_ISUPPORTS
+
+  // nsIFilePicker (less what's in nsBaseFilePicker and nsBaseWinFilePicker)
+  NS_IMETHOD GetFilterIndex(int32_t* aFilterIndex) override;
+  NS_IMETHOD SetFilterIndex(int32_t aFilterIndex) override;
+  NS_IMETHOD GetFile(nsIFile** aFile) override;
+  NS_IMETHOD GetFileURL(nsIURI** aFileURL) override;
+  NS_IMETHOD GetFiles(nsISimpleEnumerator** aFiles) override;
+  NS_IMETHOD AppendFilter(const nsAString& aTitle,
+                          const nsAString& aFilter) override;
+
+ protected:
+  /* method from nsBaseFilePicker */
+  virtual void InitNative(nsIWidget* aParent, const nsAString& aTitle) override;
+  nsresult Show(nsIFilePicker::ResultCode* aReturnVal) override;
+  void GetFilterListArray(nsString& aFilterList);
+
+  NS_IMETHOD Open(nsIFilePickerShownCallback* aCallback) override;
+
+ private:
+  RefPtr<mozilla::MozPromise<bool, HRESULT, true>> ShowFolderPicker(
+      const nsString& aInitialDir);
+  RefPtr<mozilla::MozPromise<bool, HRESULT, true>> ShowFilePicker(
+      const nsString& aInitialDir);
+
+  // Show the dialog out-of-process.
+  static FPPromise<Results> ShowFilePickerRemote(
+      HWND aParent, FileDialogType type, nsTArray<Command> const& commands);
+  static FPPromise<nsString> ShowFolderPickerRemote(
+      HWND aParent, nsTArray<Command> const& commands);
+
+  // Show the dialog in-process.
+  static FPPromise<Results> ShowFilePickerLocal(
+      HWND aParent, FileDialogType type, nsTArray<Command> const& commands);
+  static FPPromise<nsString> ShowFolderPickerLocal(
+      HWND aParent, nsTArray<Command> const& commands);
+
+  void ClearFiles();
+  using ContentAnalysisResponse = mozilla::MozPromise<bool, nsresult, true>;
+  RefPtr<ContentAnalysisResponse> CheckContentAnalysisService();
+
+ protected:
+  void RememberLastUsedDirectory();
+  bool IsPrivacyModeEnabled();
+  bool IsDefaultPathLink();
+  bool IsDefaultPathHtml();
+
+  nsCOMPtr<nsILoadContext> mLoadContext;
+  nsCOMPtr<nsIWidget> mParentWidget;
+  nsString mTitle;
+  nsCString mFile;
+  int32_t mSelectedType;
+  nsCOMArray<nsIFile> mFiles;
+  nsString mUnicodeFile;
+
+  struct FreeDeleter {
+    void operator()(void* aPtr) { ::free(aPtr); }
+  };
+  static mozilla::UniquePtr<char16_t[], FreeDeleter> sLastUsedUnicodeDirectory;
+
+  struct Filter {
+    nsString title;
+    nsString filter;
+  };
+  AutoTArray<Filter, 1> mFilterList;
+};
+
+#endif  // nsFilePicker_h__
diff --git a/widget/windows/nsLookAndFeel.cpp b/widget/windows/nsLookAndFeel.cpp
new file mode 100644
index 0000000000..01b126cd42
--- /dev/null
+++ b/widget/windows/nsLookAndFeel.cpp
@@ -0,0 +1,916 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsLookAndFeel.h"
+#include <stdint.h>
+#include <windows.h>
+#include <shellapi.h>
+#include "nsStyleConsts.h"
+#include "nsUXThemeData.h"
+#include "nsUXThemeConstants.h"
+#include "nsWindowsHelpers.h"
+#include "WinUtils.h"
+#include "WindowsUIUtils.h"
+#include "mozilla/FontPropertyTypes.h"
+#include "mozilla/Telemetry.h"
+#include "mozilla/widget/WinRegistry.h"
+
+using namespace mozilla;
+using namespace mozilla::widget;
+
+static Maybe<nscolor> GetColorFromTheme(nsUXThemeClass cls, int32_t aPart,
+                                        int32_t aState, int32_t aPropId) {
+  COLORREF color;
+  HRESULT hr = GetThemeColor(nsUXThemeData::GetTheme(cls), aPart, aState,
+                             aPropId, &color);
+  if (hr == S_OK) {
+    return Some(COLOREF_2_NSRGB(color));
+  }
+  return Nothing();
+}
+
+static int32_t GetSystemParam(long flag, int32_t def) {
+  DWORD value;
+  return ::SystemParametersInfo(flag, 0, &value, 0) ? value : def;
+}
+
+static bool SystemWantsDarkTheme() {
+  if (nsUXThemeData::IsHighContrastOn()) {
+    return LookAndFeel::IsDarkColor(
+        LookAndFeel::Color(StyleSystemColor::Window, ColorScheme::Light,
+                           LookAndFeel::UseStandins::No));
+  }
+
+  WinRegistry::Key key(
+      HKEY_CURRENT_USER,
+      u"SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Themes\\Personalize"_ns,
+      WinRegistry::KeyMode::QueryValue);
+  if (NS_WARN_IF(!key)) {
+    return false;
+  }
+  uint32_t light = key.GetValueAsDword(u"AppsUseLightTheme"_ns).valueOr(1);
+  return !light;
+}
+
+uint32_t nsLookAndFeel::SystemColorFilter() {
+  if (NS_WARN_IF(!mColorFilterWatcher)) {
+    return 0;
+  }
+
+  const auto& key = mColorFilterWatcher->GetKey();
+  if (!key.GetValueAsDword(u"Active"_ns).valueOr(0)) {
+    return 0;
+  }
+  return key.GetValueAsDword(u"FilterType"_ns).valueOr(0);
+}
+
+nsLookAndFeel::nsLookAndFeel() {
+  mozilla::Telemetry::Accumulate(mozilla::Telemetry::TOUCH_ENABLED_DEVICE,
+                                 WinUtils::IsTouchDeviceSupportPresent());
+}
+
+nsLookAndFeel::~nsLookAndFeel() = default;
+
+void nsLookAndFeel::NativeInit() { EnsureInit(); }
+
+/* virtual */
+void nsLookAndFeel::RefreshImpl() {
+  mInitialized = false;  // Fetch system colors next time they're used.
+  nsXPLookAndFeel::RefreshImpl();
+}
+
+static bool UseNonNativeMenuColors(ColorScheme aScheme) {
+  return !LookAndFeel::GetInt(LookAndFeel::IntID::UseAccessibilityTheme) ||
+         aScheme == ColorScheme::Dark;
+}
+
+nsresult nsLookAndFeel::NativeGetColor(ColorID aID, ColorScheme aScheme,
+                                       nscolor& aColor) {
+  EnsureInit();
+
+  auto IsHighlightColor = [&] {
+    switch (aID) {
+      case ColorID::MozMenuhover:
+        return !UseNonNativeMenuColors(aScheme);
+      case ColorID::Highlight:
+      case ColorID::Selecteditem:
+        // We prefer the generic dark selection color if we don't have an
+        // explicit one.
+        return aScheme != ColorScheme::Dark || mDarkHighlight;
+      case ColorID::IMESelectedRawTextBackground:
+      case ColorID::IMESelectedConvertedTextBackground:
+        return true;
+      default:
+        return false;
+    }
+  };
+
+  auto IsHighlightTextColor = [&] {
+    switch (aID) {
+      case ColorID::MozMenubarhovertext:
+        if (UseNonNativeMenuColors(aScheme)) {
+          return false;
+        }
+        [[fallthrough]];
+      case ColorID::MozMenuhovertext:
+        if (UseNonNativeMenuColors(aScheme)) {
+          return false;
+        }
+        return !mColorMenuHoverText;
+      case ColorID::Highlighttext:
+      case ColorID::Selecteditemtext:
+        // We prefer the generic dark selection color if we don't have an
+        // explicit one.
+        return aScheme != ColorScheme::Dark || mDarkHighlightText;
+      case ColorID::IMESelectedRawTextForeground:
+      case ColorID::IMESelectedConvertedTextForeground:
+        return true;
+      default:
+        return false;
+    }
+  };
+
+  if (IsHighlightColor()) {
+    if (aScheme == ColorScheme::Dark && mDarkHighlight) {
+      aColor = *mDarkHighlight;
+    } else {
+      aColor = GetColorForSysColorIndex(COLOR_HIGHLIGHT);
+    }
+    return NS_OK;
+  }
+
+  if (IsHighlightTextColor()) {
+    if (aScheme == ColorScheme::Dark && mDarkHighlightText) {
+      aColor = *mDarkHighlightText;
+    } else {
+      aColor = GetColorForSysColorIndex(COLOR_HIGHLIGHTTEXT);
+    }
+    return NS_OK;
+  }
+
+  // Titlebar colors are color-scheme aware.
+  switch (aID) {
+    case ColorID::Activecaption:
+      aColor = mTitlebarColors.Get(aScheme, true).mBg;
+      return NS_OK;
+    case ColorID::Captiontext:
+      aColor = mTitlebarColors.Get(aScheme, true).mFg;
+      return NS_OK;
+    case ColorID::Activeborder:
+      aColor = mTitlebarColors.Get(aScheme, true).mBorder;
+      return NS_OK;
+    case ColorID::Inactivecaption:
+      aColor = mTitlebarColors.Get(aScheme, false).mBg;
+      return NS_OK;
+    case ColorID::Inactivecaptiontext:
+      aColor = mTitlebarColors.Get(aScheme, false).mFg;
+      return NS_OK;
+    case ColorID::Inactiveborder:
+      aColor = mTitlebarColors.Get(aScheme, false).mBorder;
+      return NS_OK;
+    default:
+      break;
+  }
+
+  if (aScheme == ColorScheme::Dark) {
+    if (auto color = GenericDarkColor(aID)) {
+      aColor = *color;
+      return NS_OK;
+    }
+  }
+
+  static constexpr auto kNonNativeMenuText = NS_RGB(0x15, 0x14, 0x1a);
+  nsresult res = NS_OK;
+  int idx;
+  switch (aID) {
+    case ColorID::IMERawInputBackground:
+    case ColorID::IMEConvertedTextBackground:
+      aColor = NS_TRANSPARENT;
+      return NS_OK;
+    case ColorID::IMERawInputForeground:
+    case ColorID::IMEConvertedTextForeground:
+      aColor = NS_SAME_AS_FOREGROUND_COLOR;
+      return NS_OK;
+    case ColorID::IMERawInputUnderline:
+    case ColorID::IMEConvertedTextUnderline:
+      aColor = NS_SAME_AS_FOREGROUND_COLOR;
+      return NS_OK;
+    case ColorID::IMESelectedRawTextUnderline:
+    case ColorID::IMESelectedConvertedTextUnderline:
+      aColor = NS_TRANSPARENT;
+      return NS_OK;
+
+    // New CSS 2 Color definitions
+    case ColorID::Appworkspace:
+      idx = COLOR_APPWORKSPACE;
+      break;
+    case ColorID::Background:
+      idx = COLOR_BACKGROUND;
+      break;
+    case ColorID::Buttonface:
+    case ColorID::MozButtonhoverface:
+    case ColorID::MozButtonactiveface:
+    case ColorID::MozButtondisabledface:
+    case ColorID::MozColheader:
+    case ColorID::MozColheaderhover:
+    case ColorID::MozColheaderactive:
+      idx = COLOR_BTNFACE;
+      break;
+    case ColorID::Buttonhighlight:
+      idx = COLOR_BTNHIGHLIGHT;
+      break;
+    case ColorID::Buttonshadow:
+      idx = COLOR_BTNSHADOW;
+      break;
+    case ColorID::Buttontext:
+    case ColorID::MozButtonhovertext:
+    case ColorID::MozButtonactivetext:
+      idx = COLOR_BTNTEXT;
+      break;
+    case ColorID::MozCellhighlighttext:
+      aColor = NS_RGB(0, 0, 0);
+      return NS_OK;
+    case ColorID::MozCellhighlight:
+      aColor = NS_RGB(206, 206, 206);
+      return NS_OK;
+    case ColorID::Graytext:
+      idx = COLOR_GRAYTEXT;
+      break;
+    case ColorID::MozMenubarhovertext:
+      if (UseNonNativeMenuColors(aScheme)) {
+        aColor = kNonNativeMenuText;
+        return NS_OK;
+      }
+      [[fallthrough]];
+    case ColorID::MozMenuhovertext:
+      if (UseNonNativeMenuColors(aScheme)) {
+        aColor = kNonNativeMenuText;
+        return NS_OK;
+      }
+      if (mColorMenuHoverText) {
+        aColor = *mColorMenuHoverText;
+        return NS_OK;
+      }
+      idx = COLOR_HIGHLIGHTTEXT;
+      break;
+    case ColorID::MozMenuhover:
+      MOZ_ASSERT(UseNonNativeMenuColors(aScheme));
+      aColor = NS_RGB(0xe0, 0xe0, 0xe6);
+      return NS_OK;
+    case ColorID::MozMenuhoverdisabled:
+      if (UseNonNativeMenuColors(aScheme)) {
+        aColor = NS_RGB(0xf0, 0xf0, 0xf3);
+        return NS_OK;
+      }
+      aColor = NS_TRANSPARENT;
+      return NS_OK;
+    case ColorID::Infobackground:
+      idx = COLOR_INFOBK;
+      break;
+    case ColorID::Infotext:
+      idx = COLOR_INFOTEXT;
+      break;
+    case ColorID::Menu:
+      if (UseNonNativeMenuColors(aScheme)) {
+        aColor = NS_RGB(0xf9, 0xf9, 0xfb);
+        return NS_OK;
+      }
+      idx = COLOR_MENU;
+      break;
+    case ColorID::Menutext:
+      if (UseNonNativeMenuColors(aScheme)) {
+        aColor = kNonNativeMenuText;
+        return NS_OK;
+      }
+      idx = COLOR_MENUTEXT;
+      break;
+    case ColorID::Scrollbar:
+      idx = COLOR_SCROLLBAR;
+      break;
+    case ColorID::Threeddarkshadow:
+      idx = COLOR_3DDKSHADOW;
+      break;
+    case ColorID::Threedface:
+      idx = COLOR_3DFACE;
+      break;
+    case ColorID::Threedhighlight:
+      idx = COLOR_3DHIGHLIGHT;
+      break;
+    case ColorID::Threedlightshadow:
+    case ColorID::Buttonborder:
+    case ColorID::MozDisabledfield:
+    case ColorID::MozSidebarborder:
+      idx = COLOR_3DLIGHT;
+      break;
+    case ColorID::Threedshadow:
+      idx = COLOR_3DSHADOW;
+      break;
+    case ColorID::Window:
+      idx = COLOR_WINDOW;
+      break;
+    case ColorID::Windowframe:
+      idx = COLOR_WINDOWFRAME;
+      break;
+    case ColorID::Windowtext:
+      idx = COLOR_WINDOWTEXT;
+      break;
+    case ColorID::MozEventreerow:
+    case ColorID::MozOddtreerow:
+    case ColorID::Field:
+    case ColorID::MozSidebar:
+    case ColorID::MozCombobox:
+      idx = COLOR_WINDOW;
+      break;
+    case ColorID::Fieldtext:
+    case ColorID::MozSidebartext:
+    case ColorID::MozComboboxtext:
+      idx = COLOR_WINDOWTEXT;
+      break;
+    case ColorID::MozHeaderbar:
+    case ColorID::MozHeaderbarinactive:
+    case ColorID::MozDialog:
+      idx = COLOR_3DFACE;
+      break;
+    case ColorID::Accentcolor:
+      aColor = mColorAccent;
+      return NS_OK;
+    case ColorID::Accentcolortext:
+      aColor = mColorAccentText;
+      return NS_OK;
+    case ColorID::MozHeaderbartext:
+    case ColorID::MozHeaderbarinactivetext:
+    case ColorID::MozDialogtext:
+    case ColorID::MozColheadertext:
+    case ColorID::MozColheaderhovertext:
+    case ColorID::MozColheaderactivetext:
+      idx = COLOR_WINDOWTEXT;
+      break;
+    case ColorID::MozNativehyperlinktext:
+      idx = COLOR_HOTLIGHT;
+      break;
+    case ColorID::Marktext:
+    case ColorID::Mark:
+    case ColorID::SpellCheckerUnderline:
+      aColor = GetStandinForNativeColor(aID, aScheme);
+      return NS_OK;
+    default:
+      idx = COLOR_WINDOW;
+      res = NS_ERROR_FAILURE;
+      break;
+  }
+
+  aColor = GetColorForSysColorIndex(idx);
+
+  return res;
+}
+
+nsresult nsLookAndFeel::NativeGetInt(IntID aID, int32_t& aResult) {
+  EnsureInit();
+  nsresult res = NS_OK;
+
+  switch (aID) {
+    case IntID::ScrollButtonLeftMouseButtonAction:
+      aResult = 0;
+      break;
+    case IntID::ScrollButtonMiddleMouseButtonAction:
+    case IntID::ScrollButtonRightMouseButtonAction:
+      aResult = 3;
+      break;
+    case IntID::CaretBlinkTime:
+      aResult = static_cast<int32_t>(::GetCaretBlinkTime());
+      break;
+    case IntID::CaretBlinkCount: {
+      int32_t timeout = GetSystemParam(SPI_GETCARETTIMEOUT, 5000);
+      auto blinkTime = ::GetCaretBlinkTime();
+      if (timeout <= 0 || blinkTime <= 0) {
+        aResult = -1;
+        break;
+      }
+      // 2 * blinkTime because this integer is a full blink cycle.
+      aResult = std::ceil(float(timeout) / (2.0f * float(blinkTime)));
+      break;
+    }
+
+    case IntID::CaretWidth:
+      aResult = 1;
+      break;
+    case IntID::ShowCaretDuringSelection:
+      aResult = 0;
+      break;
+    case IntID::SelectTextfieldsOnKeyFocus:
+      // Select textfield content when focused by kbd
+      // used by EventStateManager::sTextfieldSelectModel
+      aResult = 1;
+      break;
+    case IntID::SubmenuDelay:
+      // This will default to the Windows' default
+      // (400ms) on error.
+      aResult = GetSystemParam(SPI_GETMENUSHOWDELAY, 400);
+      break;
+    case IntID::TooltipDelay:
+      aResult = 500;
+      break;
+    case IntID::MenusCanOverlapOSBar:
+      // we want XUL popups to be able to overlap the task bar.
+      aResult = 1;
+      break;
+    case IntID::DragThresholdX:
+      // The system metric is the number of pixels at which a drag should
+      // start.  Our look and feel metric is the number of pixels you can
+      // move before starting a drag, so subtract 1.
+      aResult = ::GetSystemMetrics(SM_CXDRAG) - 1;
+      break;
+    case IntID::DragThresholdY:
+      aResult = ::GetSystemMetrics(SM_CYDRAG) - 1;
+      break;
+    case IntID::UseAccessibilityTheme:
+      // High contrast is a misnomer under Win32 -- any theme can be used with
+      // it, e.g. normal contrast with large fonts, low contrast, etc. The high
+      // contrast flag really means -- use this theme and don't override it.
+      aResult = nsUXThemeData::IsHighContrastOn();
+      break;
+    case IntID::ScrollArrowStyle:
+      aResult = eScrollArrowStyle_Single;
+      break;
+    case IntID::TreeOpenDelay:
+      aResult = 1000;
+      break;
+    case IntID::TreeCloseDelay:
+      aResult = 0;
+      break;
+    case IntID::TreeLazyScrollDelay:
+      aResult = 150;
+      break;
+    case IntID::TreeScrollDelay:
+      aResult = 100;
+      break;
+    case IntID::TreeScrollLinesMax:
+      aResult = 3;
+      break;
+    case IntID::WindowsAccentColorInTitlebar: {
+      aResult = mTitlebarColors.mUseAccent;
+    } break;
+    case IntID::AlertNotificationOrigin:
+      aResult = 0;
+      {
+        // Get task bar window handle
+        HWND shellWindow = FindWindowW(L"Shell_TrayWnd", nullptr);
+
+        if (shellWindow != nullptr) {
+          // Determine position
+          APPBARDATA appBarData;
+          appBarData.hWnd = shellWindow;
+          appBarData.cbSize = sizeof(appBarData);
+          if (SHAppBarMessage(ABM_GETTASKBARPOS, &appBarData)) {
+            // Set alert origin as a bit field - see LookAndFeel.h
+            // 0 represents bottom right, sliding vertically.
+            switch (appBarData.uEdge) {
+              case ABE_LEFT:
+                aResult = NS_ALERT_HORIZONTAL | NS_ALERT_LEFT;
+                break;
+              case ABE_RIGHT:
+                aResult = NS_ALERT_HORIZONTAL;
+                break;
+              case ABE_TOP:
+                aResult = NS_ALERT_TOP;
+                [[fallthrough]];
+              case ABE_BOTTOM:
+                // If the task bar is right-to-left,
+                // move the origin to the left
+                if (::GetWindowLong(shellWindow, GWL_EXSTYLE) & WS_EX_LAYOUTRTL)
+                  aResult |= NS_ALERT_LEFT;
+                break;
+            }
+          }
+        }
+      }
+      break;
+    case IntID::IMERawInputUnderlineStyle:
+    case IntID::IMEConvertedTextUnderlineStyle:
+      aResult = static_cast<int32_t>(StyleTextDecorationStyle::Dashed);
+      break;
+    case IntID::IMESelectedRawTextUnderlineStyle:
+    case IntID::IMESelectedConvertedTextUnderline:
+      aResult = static_cast<int32_t>(StyleTextDecorationStyle::None);
+      break;
+    case IntID::SpellCheckerUnderlineStyle:
+      aResult = static_cast<int32_t>(StyleTextDecorationStyle::Wavy);
+      break;
+    case IntID::ScrollbarButtonAutoRepeatBehavior:
+      aResult = 0;
+      break;
+    case IntID::SwipeAnimationEnabled:
+      // Forcibly enable the swipe animation on Windows. It doesn't matter on
+      // platforms where "Drag two fingers to scroll" isn't supported since on
+      // the platforms we will never generate any swipe gesture events.
+      aResult = 1;
+      break;
+    case IntID::UseOverlayScrollbars:
+      aResult = WindowsUIUtils::ComputeOverlayScrollbars();
+      break;
+    case IntID::AllowOverlayScrollbarsOverlap:
+      aResult = 0;
+      break;
+    case IntID::ScrollbarDisplayOnMouseMove:
+      aResult = 1;
+      break;
+    case IntID::ScrollbarFadeBeginDelay:
+      aResult = 2500;
+      break;
+    case IntID::ScrollbarFadeDuration:
+      aResult = 350;
+      break;
+    case IntID::ContextMenuOffsetVertical:
+    case IntID::ContextMenuOffsetHorizontal:
+      aResult = 2;
+      break;
+    case IntID::SystemUsesDarkTheme:
+      aResult = SystemWantsDarkTheme();
+      break;
+    case IntID::SystemScrollbarSize:
+      aResult = std::max(WinUtils::GetSystemMetricsForDpi(SM_CXVSCROLL, 96),
+                         WinUtils::GetSystemMetricsForDpi(SM_CXHSCROLL, 96));
+      break;
+    case IntID::PrefersReducedMotion: {
+      BOOL enable = TRUE;
+      ::SystemParametersInfoW(SPI_GETCLIENTAREAANIMATION, 0, &enable, 0);
+      aResult = !enable;
+      break;
+    }
+    case IntID::PrefersReducedTransparency: {
+      // Prefers reduced transparency if the option for "Transparency Effects"
+      // is disabled
+      aResult = !WindowsUIUtils::ComputeTransparencyEffects();
+      break;
+    }
+    case IntID::InvertedColors: {
+      // Color filter values
+      // 1: Inverted
+      // 2: Grayscale inverted
+      aResult = mCurrentColorFilter == 1 || mCurrentColorFilter == 2;
+      break;
+    }
+    case IntID::PrimaryPointerCapabilities: {
+      aResult = static_cast<int32_t>(
+          widget::WinUtils::GetPrimaryPointerCapabilities());
+      break;
+    }
+    case IntID::AllPointerCapabilities: {
+      aResult =
+          static_cast<int32_t>(widget::WinUtils::GetAllPointerCapabilities());
+      break;
+    }
+    case IntID::TouchDeviceSupportPresent:
+      aResult = !!WinUtils::IsTouchDeviceSupportPresent();
+      break;
+    case IntID::PanelAnimations:
+      aResult = 1;
+      break;
+    case IntID::HideCursorWhileTyping: {
+      BOOL enable = TRUE;
+      ::SystemParametersInfoW(SPI_GETMOUSEVANISH, 0, &enable, 0);
+      aResult = enable;
+      break;
+    }
+    default:
+      aResult = 0;
+      res = NS_ERROR_FAILURE;
+  }
+  return res;
+}
+
+nsresult nsLookAndFeel::NativeGetFloat(FloatID aID, float& aResult) {
+  nsresult res = NS_OK;
+
+  switch (aID) {
+    case FloatID::IMEUnderlineRelativeSize:
+      aResult = 1.0f;
+      break;
+    case FloatID::SpellCheckerUnderlineRelativeSize:
+      aResult = 1.0f;
+      break;
+    case FloatID::TextScaleFactor:
+      aResult = WindowsUIUtils::ComputeTextScaleFactor();
+      break;
+    default:
+      aResult = -1.0;
+      res = NS_ERROR_FAILURE;
+  }
+  return res;
+}
+
+LookAndFeelFont nsLookAndFeel::GetLookAndFeelFontInternal(
+    const LOGFONTW& aLogFont, bool aUseShellDlg) {
+  LookAndFeelFont result{};
+
+  result.haveFont() = false;
+
+  // Get scaling factor from physical to logical pixels
+  double pixelScale =
+      1.0 / WinUtils::SystemScaleFactor() / LookAndFeel::GetTextScaleFactor();
+
+  // The lfHeight is in pixels, and it needs to be adjusted for the
+  // device it will be displayed on.
+  // Screens and Printers will differ in DPI
+  //
+  // So this accounts for the difference in the DeviceContexts
+  // The pixelScale will typically be 1.0 for the screen
+  // (though larger for hi-dpi screens where the Windows resolution
+  // scale factor is 125% or 150% or even more), and could be
+  // any value when going to a printer, for example pixelScale is
+  // 6.25 when going to a 600dpi printer.
+  float pixelHeight = -aLogFont.lfHeight;
+  if (pixelHeight < 0) {
+    nsAutoFont hFont(::CreateFontIndirectW(&aLogFont));
+    if (!hFont) {
+      return result;
+    }
+
+    nsAutoHDC dc(::GetDC(nullptr));
+    HGDIOBJ hObject = ::SelectObject(dc, hFont);
+    TEXTMETRIC tm;
+    ::GetTextMetrics(dc, &tm);
+    ::SelectObject(dc, hObject);
+
+    pixelHeight = tm.tmAscent;
+  }
+
+  pixelHeight *= pixelScale;
+
+  // we have problem on Simplified Chinese system because the system
+  // report the default font size is 8 points. but if we use 8, the text
+  // display very ugly. force it to be at 9 points (12 pixels) on that
+  // system (cp936), but leave other sizes alone.
+  if (pixelHeight < 12 && ::GetACP() == 936) {
+    pixelHeight = 12;
+  }
+
+  result.haveFont() = true;
+
+  if (aUseShellDlg) {
+    result.name() = u"MS Shell Dlg 2"_ns;
+  } else {
+    result.name() = aLogFont.lfFaceName;
+  }
+
+  result.size() = pixelHeight;
+  result.italic() = !!aLogFont.lfItalic;
+  // FIXME: Other weights?
+  result.weight() =
+      ((aLogFont.lfWeight == FW_BOLD) ? FontWeight::BOLD : FontWeight::NORMAL)
+          .ToFloat();
+
+  return result;
+}
+
+LookAndFeelFont nsLookAndFeel::GetLookAndFeelFont(LookAndFeel::FontID anID) {
+  LookAndFeelFont result{};
+
+  result.haveFont() = false;
+
+  // FontID::Icon is handled differently than the others
+  if (anID == LookAndFeel::FontID::Icon) {
+    LOGFONTW logFont;
+    if (::SystemParametersInfoW(SPI_GETICONTITLELOGFONT, sizeof(logFont),
+                                (PVOID)&logFont, 0)) {
+      result = GetLookAndFeelFontInternal(logFont, false);
+    }
+    return result;
+  }
+
+  NONCLIENTMETRICSW ncm;
+  ncm.cbSize = sizeof(NONCLIENTMETRICSW);
+  if (!::SystemParametersInfoW(SPI_GETNONCLIENTMETRICS, sizeof(ncm),
+                               (PVOID)&ncm, 0)) {
+    return result;
+  }
+
+  switch (anID) {
+    case LookAndFeel::FontID::Menu:
+    case LookAndFeel::FontID::MozPullDownMenu:
+      result = GetLookAndFeelFontInternal(ncm.lfMenuFont, false);
+      break;
+    case LookAndFeel::FontID::Caption:
+      result = GetLookAndFeelFontInternal(ncm.lfCaptionFont, false);
+      break;
+    case LookAndFeel::FontID::SmallCaption:
+      result = GetLookAndFeelFontInternal(ncm.lfSmCaptionFont, false);
+      break;
+    case LookAndFeel::FontID::StatusBar:
+      result = GetLookAndFeelFontInternal(ncm.lfStatusFont, false);
+      break;
+    case LookAndFeel::FontID::MozButton:
+    case LookAndFeel::FontID::MozField:
+    case LookAndFeel::FontID::MozList:
+      // XXX It's not clear to me whether this is exactly the right
+      // set of LookAndFeel values to map to the dialog font; we may
+      // want to add or remove cases here after reviewing the visual
+      // results under various Windows versions.
+      result = GetLookAndFeelFontInternal(ncm.lfMessageFont, true);
+      break;
+    default:
+      result = GetLookAndFeelFontInternal(ncm.lfMessageFont, false);
+      break;
+  }
+
+  return result;
+}
+
+bool nsLookAndFeel::NativeGetFont(LookAndFeel::FontID anID, nsString& aFontName,
+                                  gfxFontStyle& aFontStyle) {
+  LookAndFeelFont font = GetLookAndFeelFont(anID);
+  return LookAndFeelFontToStyle(font, aFontName, aFontStyle);
+}
+
+/* virtual */
+char16_t nsLookAndFeel::GetPasswordCharacterImpl() {
+#define UNICODE_BLACK_CIRCLE_CHAR 0x25cf
+  return UNICODE_BLACK_CIRCLE_CHAR;
+}
+
+static nscolor GetAccentColorText(const nscolor aAccentColor) {
+  // We want the color that we return for text that will be drawn over
+  // a background that has the accent color to have good contrast with
+  // the accent color.  Windows itself uses either white or black text
+  // depending on how light or dark the accent color is.  We do the same
+  // here based on the luminance of the accent color with a threshhold
+  // value.  This algorithm should match what Windows does.  It comes from:
+  //
+  // https://docs.microsoft.com/en-us/windows/uwp/style/color
+  float luminance = (NS_GET_R(aAccentColor) * 2 + NS_GET_G(aAccentColor) * 5 +
+                     NS_GET_B(aAccentColor)) /
+                    8;
+  return luminance <= 128 ? NS_RGB(255, 255, 255) : NS_RGB(0, 0, 0);
+}
+
+static Maybe<nscolor> GetAccentColorText(const Maybe<nscolor>& aAccentColor) {
+  if (!aAccentColor) {
+    return Nothing();
+  }
+  return Some(GetAccentColorText(*aAccentColor));
+}
+
+nscolor nsLookAndFeel::GetColorForSysColorIndex(int index) {
+  MOZ_ASSERT(index >= SYS_COLOR_MIN && index <= SYS_COLOR_MAX);
+  return mSysColorTable[index - SYS_COLOR_MIN];
+}
+
+auto nsLookAndFeel::ComputeTitlebarColors() -> TitlebarColors {
+  TitlebarColors result;
+
+  // Start with the native / non-accent-in-titlebar colors.
+  result.mActiveLight = {GetColorForSysColorIndex(COLOR_ACTIVECAPTION),
+                         GetColorForSysColorIndex(COLOR_CAPTIONTEXT),
+                         GetColorForSysColorIndex(COLOR_ACTIVEBORDER)};
+
+  result.mInactiveLight = {GetColorForSysColorIndex(COLOR_INACTIVECAPTION),
+                           GetColorForSysColorIndex(COLOR_INACTIVECAPTIONTEXT),
+                           GetColorForSysColorIndex(COLOR_INACTIVEBORDER)};
+
+  if (!nsUXThemeData::IsHighContrastOn()) {
+    // Use our non-native colors.
+    result.mActiveLight = {
+        GetStandinForNativeColor(ColorID::Activecaption, ColorScheme::Light),
+        GetStandinForNativeColor(ColorID::Captiontext, ColorScheme::Light),
+        GetStandinForNativeColor(ColorID::Activeborder, ColorScheme::Light)};
+    result.mInactiveLight = {
+        GetStandinForNativeColor(ColorID::Inactivecaption, ColorScheme::Light),
+        GetStandinForNativeColor(ColorID::Inactivecaptiontext,
+                                 ColorScheme::Light),
+        GetStandinForNativeColor(ColorID::Inactiveborder, ColorScheme::Light)};
+  }
+
+  // Our dark colors are always non-native.
+  result.mActiveDark = {*GenericDarkColor(ColorID::Activecaption),
+                        *GenericDarkColor(ColorID::Captiontext),
+                        *GenericDarkColor(ColorID::Activeborder)};
+  result.mInactiveDark = {*GenericDarkColor(ColorID::Inactivecaption),
+                          *GenericDarkColor(ColorID::Inactivecaptiontext),
+                          *GenericDarkColor(ColorID::Inactiveborder)};
+
+  // TODO(bug 1825241): Somehow get notified when this changes? Hopefully the
+  // sys color notification is enough.
+  WinRegistry::Key dwmKey(HKEY_CURRENT_USER,
+                          u"SOFTWARE\\Microsoft\\Windows\\DWM"_ns,
+                          WinRegistry::KeyMode::QueryValue);
+  if (NS_WARN_IF(!dwmKey)) {
+    return result;
+  }
+
+  // The order of the color components in the DWORD stored in the registry
+  // happens to be the same order as we store the components in nscolor
+  // so we can just assign directly here.
+  result.mAccent = dwmKey.GetValueAsDword(u"AccentColor"_ns);
+  result.mAccentText = GetAccentColorText(result.mAccent);
+
+  if (!result.mAccent) {
+    return result;
+  }
+
+  result.mAccentInactive = dwmKey.GetValueAsDword(u"AccentColorInactive"_ns);
+  result.mAccentInactiveText = GetAccentColorText(result.mAccentInactive);
+
+  // The ColorPrevalence value is set to 1 when the "Show color on title bar"
+  // setting in the Color section of Window's Personalization settings is
+  // turned on.
+  result.mUseAccent =
+      dwmKey.GetValueAsDword(u"ColorPrevalence"_ns).valueOr(0) == 1;
+  if (!result.mUseAccent) {
+    return result;
+  }
+
+  // TODO(emilio): Consider reading ColorizationColorBalance to compute a
+  // more correct border color, see [1]. Though for opaque accent colors this
+  // isn't needed.
+  //
+  // [1]:
+  // https://source.chromium.org/chromium/chromium/src/+/refs/heads/main:ui/color/win/accent_color_observer.cc;l=42;drc=9d4eb7ed25296abba8fd525a6bdd0fdbf4bcdd9f
+  result.mActiveDark.mBorder = result.mActiveLight.mBorder = *result.mAccent;
+  result.mInactiveDark.mBorder = result.mInactiveLight.mBorder =
+      result.mAccentInactive.valueOr(NS_RGB(57, 57, 57));
+  result.mActiveLight.mBg = result.mActiveDark.mBg = *result.mAccent;
+  result.mActiveLight.mFg = result.mActiveDark.mFg = *result.mAccentText;
+  if (result.mAccentInactive) {
+    result.mInactiveLight.mBg = result.mInactiveDark.mBg =
+        *result.mAccentInactive;
+    result.mInactiveLight.mFg = result.mInactiveDark.mFg =
+        *result.mAccentInactiveText;
+  } else {
+    // This is hand-picked to .8 to change the accent color a bit but not too
+    // much.
+    constexpr uint8_t kBgAlpha = 208;
+    const auto BlendWithAlpha = [](nscolor aBg, nscolor aFg,
+                                   uint8_t aAlpha) -> nscolor {
+      return NS_ComposeColors(
+          aBg, NS_RGBA(NS_GET_R(aFg), NS_GET_G(aFg), NS_GET_B(aFg), aAlpha));
+    };
+    result.mInactiveLight.mBg =
+        BlendWithAlpha(NS_RGB(255, 255, 255), *result.mAccent, kBgAlpha);
+    result.mInactiveDark.mBg =
+        BlendWithAlpha(NS_RGB(0, 0, 0), *result.mAccent, kBgAlpha);
+    result.mInactiveLight.mFg = result.mInactiveDark.mFg = *result.mAccentText;
+  }
+  return result;
+}
+
+void nsLookAndFeel::EnsureInit() {
+  if (mInitialized) {
+    return;
+  }
+  mInitialized = true;
+
+  mColorMenuHoverText =
+      ::GetColorFromTheme(eUXMenu, MENU_POPUPITEM, MPI_HOT, TMT_TEXTCOLOR);
+
+  // Fill out the sys color table.
+  for (int i = SYS_COLOR_MIN; i <= SYS_COLOR_MAX; ++i) {
+    mSysColorTable[i - SYS_COLOR_MIN] = [&] {
+      if (auto c = WindowsUIUtils::GetSystemColor(ColorScheme::Light, i)) {
+        return *c;
+      }
+      DWORD color = ::GetSysColor(i);
+      return COLOREF_2_NSRGB(color);
+    }();
+  }
+
+  mDarkHighlight =
+      WindowsUIUtils::GetSystemColor(ColorScheme::Dark, COLOR_HIGHLIGHT);
+  mDarkHighlightText =
+      WindowsUIUtils::GetSystemColor(ColorScheme::Dark, COLOR_HIGHLIGHTTEXT);
+
+  mTitlebarColors = ComputeTitlebarColors();
+
+  mColorAccent = [&] {
+    if (auto accent = WindowsUIUtils::GetAccentColor()) {
+      return *accent;
+    }
+    // Try the titlebar accent as a fallback.
+    if (mTitlebarColors.mAccent) {
+      return *mTitlebarColors.mAccent;
+    }
+    // Seems to be the default color (hardcoded because of bug 1065998)
+    return NS_RGB(0, 120, 215);
+  }();
+  mColorAccentText = GetAccentColorText(mColorAccent);
+
+  if (!mColorFilterWatcher) {
+    WinRegistry::Key key(
+        HKEY_CURRENT_USER, u"Software\\Microsoft\\ColorFiltering"_ns,
+        WinRegistry::KeyMode::QueryValue | WinRegistry::KeyMode::Notify);
+    if (key) {
+      mColorFilterWatcher = MakeUnique<WinRegistry::KeyWatcher>(
+          std::move(key), GetCurrentSerialEventTarget(), [this] {
+            MOZ_DIAGNOSTIC_ASSERT(NS_IsMainThread());
+            if (mCurrentColorFilter != SystemColorFilter()) {
+              LookAndFeel::NotifyChangedAllWindows(
+                  widget::ThemeChangeKind::MediaQueriesOnly);
+            }
+          });
+    }
+  }
+  mCurrentColorFilter = SystemColorFilter();
+
+  RecordTelemetry();
+}
diff --git a/widget/windows/nsLookAndFeel.h b/widget/windows/nsLookAndFeel.h
new file mode 100644
index 0000000000..d19aa91329
--- /dev/null
+++ b/widget/windows/nsLookAndFeel.h
@@ -0,0 +1,124 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef __nsLookAndFeel
+#define __nsLookAndFeel
+
+#include <windows.h>
+
+#include "nsXPLookAndFeel.h"
+#include "gfxFont.h"
+
+/*
+ * Gesture System Metrics
+ */
+#ifndef SM_DIGITIZER
+#  define SM_DIGITIZER 94
+#  define TABLET_CONFIG_NONE 0x00000000
+#  define NID_INTEGRATED_TOUCH 0x00000001
+#  define NID_EXTERNAL_TOUCH 0x00000002
+#  define NID_INTEGRATED_PEN 0x00000004
+#  define NID_EXTERNAL_PEN 0x00000008
+#  define NID_MULTI_INPUT 0x00000040
+#  define NID_READY 0x00000080
+#endif
+
+/*
+ * Tablet mode detection
+ */
+#ifndef SM_SYSTEMDOCKED
+#  define SM_CONVERTIBLESLATEMODE 0x00002003
+#  define SM_SYSTEMDOCKED 0x00002004
+#endif
+
+/*
+ * Color constant inclusive bounds for GetSysColor
+ */
+#define SYS_COLOR_MIN 0
+#define SYS_COLOR_MAX 30
+#define SYS_COLOR_COUNT (SYS_COLOR_MAX - SYS_COLOR_MIN + 1)
+
+namespace mozilla::widget::WinRegistry {
+class KeyWatcher;
+}
+
+class nsLookAndFeel final : public nsXPLookAndFeel {
+ public:
+  nsLookAndFeel();
+  virtual ~nsLookAndFeel();
+
+  void NativeInit() final;
+  void RefreshImpl() override;
+  nsresult NativeGetInt(IntID, int32_t& aResult) override;
+  nsresult NativeGetFloat(FloatID, float& aResult) override;
+  nsresult NativeGetColor(ColorID, ColorScheme, nscolor& aResult) override;
+  bool NativeGetFont(FontID aID, nsString& aFontName,
+                     gfxFontStyle& aFontStyle) override;
+  char16_t GetPasswordCharacterImpl() override;
+
+ private:
+  struct TitlebarColors {
+    // NOTE: These are the DWM accent colors, which might not match the
+    // UISettings/UWP accent color in some cases, see bug 1796730.
+    mozilla::Maybe<nscolor> mAccent;
+    mozilla::Maybe<nscolor> mAccentText;
+    mozilla::Maybe<nscolor> mAccentInactive;
+    mozilla::Maybe<nscolor> mAccentInactiveText;
+
+    bool mUseAccent = false;
+
+    struct Set {
+      nscolor mBg = 0;
+      nscolor mFg = 0;
+      nscolor mBorder = 0;
+    };
+
+    Set mActiveLight;
+    Set mActiveDark;
+
+    Set mInactiveLight;
+    Set mInactiveDark;
+
+    const Set& Get(mozilla::ColorScheme aScheme, bool aActive) const {
+      if (aScheme == mozilla::ColorScheme::Dark) {
+        return aActive ? mActiveDark : mInactiveDark;
+      }
+      return aActive ? mActiveLight : mInactiveLight;
+    }
+  };
+
+  TitlebarColors ComputeTitlebarColors();
+
+  nscolor GetColorForSysColorIndex(int index);
+
+  LookAndFeelFont GetLookAndFeelFontInternal(const LOGFONTW& aLogFont,
+                                             bool aUseShellDlg);
+
+  uint32_t SystemColorFilter();
+
+  LookAndFeelFont GetLookAndFeelFont(LookAndFeel::FontID anID);
+
+  // Cached colors and flags indicating success in their retrieval.
+  mozilla::Maybe<nscolor> mColorMenuHoverText;
+
+  mozilla::Maybe<nscolor> mDarkHighlight;
+  mozilla::Maybe<nscolor> mDarkHighlightText;
+
+  TitlebarColors mTitlebarColors;
+
+  nscolor mColorAccent = 0;
+  nscolor mColorAccentText = 0;
+
+  nscolor mSysColorTable[SYS_COLOR_COUNT];
+
+  mozilla::UniquePtr<mozilla::widget::WinRegistry::KeyWatcher>
+      mColorFilterWatcher;
+  uint32_t mCurrentColorFilter = 0;
+
+  bool mInitialized = false;
+  void EnsureInit();
+};
+
+#endif
diff --git a/widget/windows/nsNativeDragSource.cpp b/widget/windows/nsNativeDragSource.cpp
new file mode 100644
index 0000000000..ca5459e9df
--- /dev/null
+++ b/widget/windows/nsNativeDragSource.cpp
@@ -0,0 +1,98 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsNativeDragSource.h"
+#include <stdio.h>
+#include "nsISupportsImpl.h"
+#include "nsString.h"
+#include "nsToolkit.h"
+#include "nsWidgetsCID.h"
+#include "nsIDragService.h"
+#include "nsServiceManagerUtils.h"
+#include "mozilla/dom/DataTransfer.h"
+
+/*
+ * class nsNativeDragSource
+ */
+nsNativeDragSource::nsNativeDragSource(
+    mozilla::dom::DataTransfer* aDataTransfer)
+    : m_cRef(0), m_hCursor(nullptr), mUserCancelled(false) {
+  mDataTransfer = aDataTransfer;
+}
+
+nsNativeDragSource::~nsNativeDragSource() {}
+
+STDMETHODIMP
+nsNativeDragSource::QueryInterface(REFIID riid, void** ppv) {
+  *ppv = nullptr;
+
+  if (IID_IUnknown == riid || IID_IDropSource == riid) *ppv = this;
+
+  if (nullptr != *ppv) {
+    ((LPUNKNOWN)*ppv)->AddRef();
+    return S_OK;
+  }
+
+  return E_NOINTERFACE;
+}
+
+STDMETHODIMP_(ULONG)
+nsNativeDragSource::AddRef(void) {
+  ++m_cRef;
+  NS_LOG_ADDREF(this, m_cRef, "nsNativeDragSource", sizeof(*this));
+  return m_cRef;
+}
+
+STDMETHODIMP_(ULONG)
+nsNativeDragSource::Release(void) {
+  --m_cRef;
+  NS_LOG_RELEASE(this, m_cRef, "nsNativeDragSource");
+  if (0 != m_cRef) return m_cRef;
+
+  delete this;
+  return 0;
+}
+
+STDMETHODIMP
+nsNativeDragSource::QueryContinueDrag(BOOL fEsc, DWORD grfKeyState) {
+  nsCOMPtr<nsIDragService> dragService =
+      do_GetService("@mozilla.org/widget/dragservice;1");
+  if (dragService) {
+    DWORD pos = ::GetMessagePos();
+    dragService->DragMoved(GET_X_LPARAM(pos), GET_Y_LPARAM(pos));
+  }
+
+  if (fEsc) {
+    mUserCancelled = true;
+    return DRAGDROP_S_CANCEL;
+  }
+
+  if (!(grfKeyState & MK_LBUTTON) || (grfKeyState & MK_RBUTTON))
+    return DRAGDROP_S_DROP;
+
+  return S_OK;
+}
+
+STDMETHODIMP
+nsNativeDragSource::GiveFeedback(DWORD dwEffect) {
+  // For drags involving tabs, we do some custom work with cursors.
+  if (mDataTransfer) {
+    nsAutoString cursor;
+    mDataTransfer->GetMozCursor(cursor);
+    if (cursor.EqualsLiteral("default")) {
+      m_hCursor = ::LoadCursor(0, IDC_ARROW);
+    } else {
+      m_hCursor = nullptr;
+    }
+  }
+
+  if (m_hCursor) {
+    ::SetCursor(m_hCursor);
+    return S_OK;
+  }
+
+  // Let the system choose which cursor to apply.
+  return DRAGDROP_S_USEDEFAULTCURSORS;
+}
diff --git a/widget/windows/nsNativeDragSource.h b/widget/windows/nsNativeDragSource.h
new file mode 100644
index 0000000000..a8e37b90a8
--- /dev/null
+++ b/widget/windows/nsNativeDragSource.h
@@ -0,0 +1,68 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+#ifndef _nsNativeDragSource_h_
+#define _nsNativeDragSource_h_
+
+#include "nscore.h"
+#include <ole2.h>
+#include <oleidl.h>
+#include "mozilla/Attributes.h"
+#include "mozilla/RefPtr.h"
+
+namespace mozilla {
+namespace dom {
+class DataTransfer;
+}  // namespace dom
+}  // namespace mozilla
+
+// class nsIDragSource;
+
+/*
+ * nsNativeDragSource implements the IDropSource interface and gets
+ * most of its behavior from the associated adapter (m_dragDrop).
+ */
+class nsNativeDragSource final : public IDropSource {
+ public:
+  // construct an nsNativeDragSource referencing adapter
+  // nsNativeDragSource(nsIDragSource * adapter);
+  explicit nsNativeDragSource(mozilla::dom::DataTransfer* aDataTransfer);
+  ~nsNativeDragSource();
+
+  // IUnknown methods - see iunknown.h for documentation
+
+  STDMETHODIMP QueryInterface(REFIID, void**);
+  STDMETHODIMP_(ULONG) AddRef();
+  STDMETHODIMP_(ULONG) Release();
+
+  // IDropSource methods - see idropsrc.h for documentation
+
+  // Return DRAGDROP_S_USEDEFAULTCURSORS if this object lets OLE provide
+  // default cursors, otherwise return NOERROR. This method gets called in
+  // response to changes that the target makes to dEffect (DragEnter,
+  // DragOver).
+  STDMETHODIMP GiveFeedback(DWORD dEffect);
+
+  // This method gets called if there is any change in the mouse or key
+  // state.  Return DRAGDROP_S_CANCEL to stop the drag, DRAGDROP_S_DROP
+  // to execute the drop, otherwise NOERROR.
+  STDMETHODIMP QueryContinueDrag(BOOL fESC, DWORD grfKeyState);
+
+  bool UserCancelled() { return mUserCancelled; }
+
+ protected:
+  // Reference count
+  ULONG m_cRef;
+
+  // Data object, hold information about cursor state
+  RefPtr<mozilla::dom::DataTransfer> mDataTransfer;
+
+  // Custom drag cursor
+  HCURSOR m_hCursor;
+
+  // true if the user cancelled the drag by pressing escape
+  bool mUserCancelled;
+};
+
+#endif  // _nsNativeDragSource_h_
diff --git a/widget/windows/nsNativeDragTarget.cpp b/widget/windows/nsNativeDragTarget.cpp
new file mode 100644
index 0000000000..b615a3e4bc
--- /dev/null
+++ b/widget/windows/nsNativeDragTarget.cpp
@@ -0,0 +1,472 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <stdio.h>
+#include "nsIDragService.h"
+#include "nsWidgetsCID.h"
+#include "nsNativeDragTarget.h"
+#include "nsDragService.h"
+#include "nsINode.h"
+#include "nsCOMPtr.h"
+
+#include "nsIWidget.h"
+#include "nsWindow.h"
+#include "nsClipboard.h"
+#include "KeyboardLayout.h"
+
+#include "mozilla/MouseEvents.h"
+
+using namespace mozilla;
+using namespace mozilla::widget;
+
+// This is cached for Leave notification
+static POINTL gDragLastPoint;
+
+bool nsNativeDragTarget::gDragImageChanged = false;
+
+/*
+ * class nsNativeDragTarget
+ */
+nsNativeDragTarget::nsNativeDragTarget(nsIWidget* aWidget)
+    : m_cRef(0),
+      mEffectsAllowed(DROPEFFECT_MOVE | DROPEFFECT_COPY | DROPEFFECT_LINK),
+      mEffectsPreferred(DROPEFFECT_NONE),
+      mTookOwnRef(false),
+      mWidget(aWidget),
+      mDropTargetHelper(nullptr) {
+  mHWnd = (HWND)mWidget->GetNativeData(NS_NATIVE_WINDOW);
+
+  mDragService = do_GetService("@mozilla.org/widget/dragservice;1");
+}
+
+nsNativeDragTarget::~nsNativeDragTarget() {
+  if (mDropTargetHelper) {
+    mDropTargetHelper->Release();
+    mDropTargetHelper = nullptr;
+  }
+}
+
+// IUnknown methods - see iunknown.h for documentation
+STDMETHODIMP
+nsNativeDragTarget::QueryInterface(REFIID riid, void** ppv) {
+  *ppv = nullptr;
+
+  if (IID_IUnknown == riid || IID_IDropTarget == riid) *ppv = this;
+
+  if (nullptr != *ppv) {
+    ((LPUNKNOWN)*ppv)->AddRef();
+    return S_OK;
+  }
+
+  return E_NOINTERFACE;
+}
+
+STDMETHODIMP_(ULONG)
+nsNativeDragTarget::AddRef(void) {
+  ++m_cRef;
+  NS_LOG_ADDREF(this, m_cRef, "nsNativeDragTarget", sizeof(*this));
+  return m_cRef;
+}
+
+STDMETHODIMP_(ULONG) nsNativeDragTarget::Release(void) {
+  --m_cRef;
+  NS_LOG_RELEASE(this, m_cRef, "nsNativeDragTarget");
+  if (0 != m_cRef) return m_cRef;
+
+  delete this;
+  return 0;
+}
+
+void nsNativeDragTarget::GetGeckoDragAction(DWORD grfKeyState,
+                                            LPDWORD pdwEffect,
+                                            uint32_t* aGeckoAction) {
+  // If a window is disabled or a modal window is on top of it
+  // (which implies it is disabled), then we should not allow dropping.
+  if (!mWidget->IsEnabled()) {
+    *pdwEffect = DROPEFFECT_NONE;
+    *aGeckoAction = nsIDragService::DRAGDROP_ACTION_NONE;
+    return;
+  }
+
+  // If the user explicitly uses a modifier key, they want the associated action
+  // Shift + Control -> LINK, Shift -> MOVE, Ctrl -> COPY
+  DWORD desiredEffect = DROPEFFECT_NONE;
+  if ((grfKeyState & MK_CONTROL) && (grfKeyState & MK_SHIFT)) {
+    desiredEffect = DROPEFFECT_LINK;
+  } else if (grfKeyState & MK_SHIFT) {
+    desiredEffect = DROPEFFECT_MOVE;
+  } else if (grfKeyState & MK_CONTROL) {
+    desiredEffect = DROPEFFECT_COPY;
+  }
+
+  // Determine the desired effect from what is allowed and preferred.
+  if (!(desiredEffect &= mEffectsAllowed)) {
+    // No modifier key effect is set which is also allowed, check
+    // the preference of the data.
+    desiredEffect = mEffectsPreferred & mEffectsAllowed;
+    if (!desiredEffect) {
+      // No preference is set, so just fall back to the allowed effect itself
+      desiredEffect = mEffectsAllowed;
+    }
+  }
+
+  // Otherwise we should specify the first available effect
+  // from MOVE, COPY, or LINK.
+  if (desiredEffect & DROPEFFECT_MOVE) {
+    *pdwEffect = DROPEFFECT_MOVE;
+    *aGeckoAction = nsIDragService::DRAGDROP_ACTION_MOVE;
+  } else if (desiredEffect & DROPEFFECT_COPY) {
+    *pdwEffect = DROPEFFECT_COPY;
+    *aGeckoAction = nsIDragService::DRAGDROP_ACTION_COPY;
+  } else if (desiredEffect & DROPEFFECT_LINK) {
+    *pdwEffect = DROPEFFECT_LINK;
+    *aGeckoAction = nsIDragService::DRAGDROP_ACTION_LINK;
+  } else {
+    *pdwEffect = DROPEFFECT_NONE;
+    *aGeckoAction = nsIDragService::DRAGDROP_ACTION_NONE;
+  }
+}
+
+inline bool IsKeyDown(char key) { return GetKeyState(key) < 0; }
+
+void nsNativeDragTarget::DispatchDragDropEvent(EventMessage aEventMessage,
+                                               const POINTL& aPT) {
+  WidgetDragEvent event(true, aEventMessage, mWidget);
+
+  nsWindow* win = static_cast<nsWindow*>(mWidget);
+  win->InitEvent(event);
+  POINT cpos;
+
+  cpos.x = aPT.x;
+  cpos.y = aPT.y;
+
+  if (mHWnd != nullptr) {
+    ::ScreenToClient(mHWnd, &cpos);
+    event.mRefPoint = LayoutDeviceIntPoint(cpos.x, cpos.y);
+  } else {
+    event.mRefPoint = LayoutDeviceIntPoint(0, 0);
+  }
+
+  ModifierKeyState modifierKeyState;
+  modifierKeyState.InitInputEvent(event);
+
+  event.mInputSource =
+      static_cast<nsBaseDragService*>(mDragService.get())->GetInputSource();
+
+  mWidget->DispatchInputEvent(&event);
+}
+
+void nsNativeDragTarget::ProcessDrag(EventMessage aEventMessage,
+                                     DWORD grfKeyState, POINTL ptl,
+                                     DWORD* pdwEffect) {
+  // Before dispatching the event make sure we have the correct drop action set
+  uint32_t geckoAction;
+  GetGeckoDragAction(grfKeyState, pdwEffect, &geckoAction);
+
+  // Set the current action into the Gecko specific type
+  nsCOMPtr<nsIDragSession> currSession;
+  mDragService->GetCurrentSession(getter_AddRefs(currSession));
+  if (!currSession) {
+    return;
+  }
+
+  currSession->SetDragAction(geckoAction);
+
+  // Dispatch the event into Gecko
+  DispatchDragDropEvent(aEventMessage, ptl);
+
+  // If TakeChildProcessDragAction returns something other than
+  // DRAGDROP_ACTION_UNINITIALIZED, it means that the last event was sent
+  // to the child process and this event is also being sent to the child
+  // process. In this case, use the last event's action instead.
+  nsDragService* dragService = static_cast<nsDragService*>(mDragService.get());
+  currSession->GetDragAction(&geckoAction);
+
+  int32_t childDragAction = dragService->TakeChildProcessDragAction();
+  if (childDragAction != nsIDragService::DRAGDROP_ACTION_UNINITIALIZED) {
+    geckoAction = childDragAction;
+  }
+
+  if (nsIDragService::DRAGDROP_ACTION_LINK & geckoAction) {
+    *pdwEffect = DROPEFFECT_LINK;
+  } else if (nsIDragService::DRAGDROP_ACTION_COPY & geckoAction) {
+    *pdwEffect = DROPEFFECT_COPY;
+  } else if (nsIDragService::DRAGDROP_ACTION_MOVE & geckoAction) {
+    *pdwEffect = DROPEFFECT_MOVE;
+  } else {
+    *pdwEffect = DROPEFFECT_NONE;
+  }
+
+  if (aEventMessage != eDrop) {
+    // Get the cached drag effect from the drag service, the data member should
+    // have been set by whoever handled the WidgetGUIEvent or nsIDOMEvent on
+    // drags.
+    bool canDrop;
+    currSession->GetCanDrop(&canDrop);
+    if (!canDrop) {
+      *pdwEffect = DROPEFFECT_NONE;
+    }
+  }
+
+  // Clear the cached value
+  currSession->SetCanDrop(false);
+}
+
+// IDropTarget methods
+STDMETHODIMP
+nsNativeDragTarget::DragEnter(LPDATAOBJECT pIDataSource, DWORD grfKeyState,
+                              POINTL ptl, DWORD* pdwEffect) {
+  if (!mDragService) {
+    return E_FAIL;
+  }
+
+  mEffectsAllowed = *pdwEffect;
+  AddLinkSupportIfCanBeGenerated(pIDataSource);
+
+  // Drag and drop image helper
+  if (GetDropTargetHelper()) {
+    // We get a lot of crashes (often uncaught by our handler) later on during
+    // DragOver calls, see bug 1465513. It looks like this might be because
+    // we're not cleaning up previous drags fully and now released resources get
+    // used. Calling IDropTargetHelper::DragLeave before DragEnter seems to fix
+    // this for at least one reproduction of this crash.
+    GetDropTargetHelper()->DragLeave();
+    POINT pt = {ptl.x, ptl.y};
+    GetDropTargetHelper()->DragEnter(mHWnd, pIDataSource, &pt, *pdwEffect);
+  }
+
+  // save a ref to this, in case the window is destroyed underneath us
+  NS_ASSERTION(!mTookOwnRef, "own ref already taken!");
+  this->AddRef();
+  mTookOwnRef = true;
+
+  // tell the drag service about this drag (it may have come from an
+  // outside app).
+  mDragService->StartDragSession();
+
+  void* tempOutData = nullptr;
+  uint32_t tempDataLen = 0;
+  nsresult loadResult = nsClipboard::GetNativeDataOffClipboard(
+      pIDataSource, 0, ::RegisterClipboardFormat(CFSTR_PREFERREDDROPEFFECT),
+      nullptr, &tempOutData, &tempDataLen);
+  if (NS_SUCCEEDED(loadResult) && tempOutData) {
+    mEffectsPreferred = *((DWORD*)tempOutData);
+    free(tempOutData);
+  } else {
+    // We have no preference if we can't obtain it
+    mEffectsPreferred = DROPEFFECT_NONE;
+  }
+
+  // Set the native data object into drag service
+  //
+  // This cast is ok because in the constructor we created a
+  // the actual implementation we wanted, so we know this is
+  // a nsDragService. It should be a private interface, though.
+  nsDragService* winDragService =
+      static_cast<nsDragService*>(mDragService.get());
+  winDragService->SetIDataObject(pIDataSource);
+
+  // Now process the native drag state and then dispatch the event
+  ProcessDrag(eDragEnter, grfKeyState, ptl, pdwEffect);
+
+  return S_OK;
+}
+
+void nsNativeDragTarget::AddLinkSupportIfCanBeGenerated(
+    LPDATAOBJECT aIDataSource) {
+  // If we don't have a link effect, but we can generate one, fix the
+  // drop effect to include it.
+  if (!(mEffectsAllowed & DROPEFFECT_LINK) && aIDataSource) {
+    if (S_OK == ::OleQueryLinkFromData(aIDataSource)) {
+      mEffectsAllowed |= DROPEFFECT_LINK;
+    }
+  }
+}
+
+STDMETHODIMP
+nsNativeDragTarget::DragOver(DWORD grfKeyState, POINTL ptl, LPDWORD pdwEffect) {
+  if (!mDragService) {
+    return E_FAIL;
+  }
+
+  bool dragImageChanged = gDragImageChanged;
+  gDragImageChanged = false;
+
+  // If a LINK effect could be generated previously from a DragEnter(),
+  // then we should include it as an allowed effect.
+  mEffectsAllowed = (*pdwEffect) | (mEffectsAllowed & DROPEFFECT_LINK);
+
+  nsCOMPtr<nsIDragSession> currentDragSession;
+  mDragService->GetCurrentSession(getter_AddRefs(currentDragSession));
+  if (!currentDragSession) {
+    return S_OK;  // Drag was canceled.
+  }
+
+  // without the AddRef() |this| can get destroyed in an event handler
+  this->AddRef();
+
+  // Drag and drop image helper
+  if (GetDropTargetHelper()) {
+    if (dragImageChanged) {
+      // See comment in nsNativeDragTarget::DragEnter.
+      GetDropTargetHelper()->DragLeave();
+      // The drop helper only updates the image during DragEnter, so emulate
+      // a DragEnter if the image was changed.
+      POINT pt = {ptl.x, ptl.y};
+      nsDragService* dragService =
+          static_cast<nsDragService*>(mDragService.get());
+      GetDropTargetHelper()->DragEnter(mHWnd, dragService->GetDataObject(), &pt,
+                                       *pdwEffect);
+    }
+    POINT pt = {ptl.x, ptl.y};
+    GetDropTargetHelper()->DragOver(&pt, *pdwEffect);
+  }
+
+  ModifierKeyState modifierKeyState;
+  nsCOMPtr<nsIDragService> dragService = mDragService;
+  dragService->FireDragEventAtSource(eDrag, modifierKeyState.GetModifiers());
+  // Now process the native drag state and then dispatch the event
+  ProcessDrag(eDragOver, grfKeyState, ptl, pdwEffect);
+
+  this->Release();
+
+  return S_OK;
+}
+
+STDMETHODIMP
+nsNativeDragTarget::DragLeave() {
+  if (!mDragService) {
+    return E_FAIL;
+  }
+
+  // Drag and drop image helper
+  if (GetDropTargetHelper()) {
+    GetDropTargetHelper()->DragLeave();
+  }
+
+  // dispatch the event into Gecko
+  DispatchDragDropEvent(eDragExit, gDragLastPoint);
+
+  nsCOMPtr<nsIDragSession> currentDragSession;
+  mDragService->GetCurrentSession(getter_AddRefs(currentDragSession));
+
+  if (currentDragSession) {
+    nsCOMPtr<nsINode> sourceNode;
+    currentDragSession->GetSourceNode(getter_AddRefs(sourceNode));
+
+    if (!sourceNode) {
+      // We're leaving a window while doing a drag that was
+      // initiated in a different app. End the drag session, since
+      // we're done with it for now (until the user drags back into
+      // mozilla).
+      ModifierKeyState modifierKeyState;
+      nsCOMPtr<nsIDragService> dragService = mDragService;
+      dragService->EndDragSession(false, modifierKeyState.GetModifiers());
+    }
+  }
+
+  // release the ref that was taken in DragEnter
+  NS_ASSERTION(mTookOwnRef, "want to release own ref, but not taken!");
+  if (mTookOwnRef) {
+    this->Release();
+    mTookOwnRef = false;
+  }
+
+  return S_OK;
+}
+
+void nsNativeDragTarget::DragCancel() {
+  // Cancel the drag session if we did DragEnter.
+  if (mTookOwnRef) {
+    if (GetDropTargetHelper()) {
+      GetDropTargetHelper()->DragLeave();
+    }
+    if (mDragService) {
+      ModifierKeyState modifierKeyState;
+      nsCOMPtr<nsIDragService> dragService = mDragService;
+      dragService->EndDragSession(false, modifierKeyState.GetModifiers());
+    }
+    this->Release();  // matching the AddRef in DragEnter
+    mTookOwnRef = false;
+  }
+}
+
+STDMETHODIMP
+nsNativeDragTarget::Drop(LPDATAOBJECT pData, DWORD grfKeyState, POINTL aPT,
+                         LPDWORD pdwEffect) {
+  if (!mDragService) {
+    return E_FAIL;
+  }
+
+  mEffectsAllowed = *pdwEffect;
+  AddLinkSupportIfCanBeGenerated(pData);
+
+  // Drag and drop image helper
+  if (GetDropTargetHelper()) {
+    POINT pt = {aPT.x, aPT.y};
+    GetDropTargetHelper()->Drop(pData, &pt, *pdwEffect);
+  }
+
+  // Set the native data object into the drag service
+  //
+  // This cast is ok because in the constructor we created a
+  // the actual implementation we wanted, so we know this is
+  // a nsDragService (but it should still be a private interface)
+  nsDragService* winDragService =
+      static_cast<nsDragService*>(mDragService.get());
+  winDragService->SetIDataObject(pData);
+
+  // NOTE: ProcessDrag spins the event loop which may destroy arbitrary objects.
+  // We use strong refs to prevent it from destroying these:
+  RefPtr<nsNativeDragTarget> kungFuDeathGrip = this;
+  nsCOMPtr<nsIDragService> serv = mDragService;
+
+  // Now process the native drag state and then dispatch the event
+  ProcessDrag(eDrop, grfKeyState, aPT, pdwEffect);
+
+  nsCOMPtr<nsIDragSession> currentDragSession;
+  serv->GetCurrentSession(getter_AddRefs(currentDragSession));
+  if (!currentDragSession) {
+    return S_OK;  // DragCancel() was called.
+  }
+
+  // Let the win drag service know whether this session experienced
+  // a drop event within the application. Drop will not oocur if the
+  // drop landed outside the app. (used in tab tear off, bug 455884)
+  winDragService->SetDroppedLocal();
+
+  // tell the drag service we're done with the session
+  // Use GetMessagePos to get the position of the mouse at the last message
+  // seen by the event loop. (Bug 489729)
+  DWORD pos = ::GetMessagePos();
+  POINT cpos;
+  cpos.x = GET_X_LPARAM(pos);
+  cpos.y = GET_Y_LPARAM(pos);
+  winDragService->SetDragEndPoint(nsIntPoint(cpos.x, cpos.y));
+  ModifierKeyState modifierKeyState;
+  serv->EndDragSession(true, modifierKeyState.GetModifiers());
+
+  // release the ref that was taken in DragEnter
+  NS_ASSERTION(mTookOwnRef, "want to release own ref, but not taken!");
+  if (mTookOwnRef) {
+    this->Release();
+    mTookOwnRef = false;
+  }
+
+  return S_OK;
+}
+
+/**
+ * By lazy loading mDropTargetHelper we save 50-70ms of startup time
+ * which is ~5% of startup time.
+ */
+IDropTargetHelper* nsNativeDragTarget::GetDropTargetHelper() {
+  if (!mDropTargetHelper) {
+    CoCreateInstance(CLSID_DragDropHelper, nullptr, CLSCTX_INPROC_SERVER,
+                     IID_IDropTargetHelper, (LPVOID*)&mDropTargetHelper);
+  }
+
+  return mDropTargetHelper;
+}
diff --git a/widget/windows/nsNativeDragTarget.h b/widget/windows/nsNativeDragTarget.h
new file mode 100644
index 0000000000..82edc7aae7
--- /dev/null
+++ b/widget/windows/nsNativeDragTarget.h
@@ -0,0 +1,103 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+#ifndef _nsNativeDragTarget_h_
+#define _nsNativeDragTarget_h_
+
+#include "nsCOMPtr.h"
+#include <ole2.h>
+#include <shlobj.h>
+
+#ifndef IDropTargetHelper
+#  include <shobjidl.h>  // Vista drag image interfaces
+#  undef LogSeverity     // SetupAPI.h #defines this as DWORD
+#endif
+
+#include "mozilla/Attributes.h"
+#include "mozilla/EventForwards.h"
+
+class nsIDragService;
+class nsIWidget;
+
+/*
+ * nsNativeDragTarget implements the IDropTarget interface and gets most of its
+ * behavior from the associated adapter (m_dragDrop).
+ */
+
+class nsNativeDragTarget final : public IDropTarget {
+ public:
+  explicit nsNativeDragTarget(nsIWidget* aWidget);
+  ~nsNativeDragTarget();
+
+  // IUnknown members - see iunknown.h for documentation
+  STDMETHODIMP QueryInterface(REFIID, void**);
+  STDMETHODIMP_(ULONG) AddRef();
+  STDMETHODIMP_(ULONG) Release();
+
+  // IDataTarget members
+
+  // Set pEffect based on whether this object can support a drop based on
+  // the data available from pSource, the key and mouse states specified
+  // in grfKeyState, and the coordinates specified by point. This is
+  // called by OLE when a drag enters this object's window (as registered
+  // by Initialize).
+  STDMETHODIMP DragEnter(LPDATAOBJECT pSource, DWORD grfKeyState, POINTL point,
+                         DWORD* pEffect);
+
+  // Similar to DragEnter except it is called frequently while the drag
+  // is over this object's window.
+  MOZ_CAN_RUN_SCRIPT_BOUNDARY STDMETHODIMP DragOver(DWORD grfKeyState,
+                                                    POINTL point,
+                                                    DWORD* pEffect);
+
+  // Release the drag-drop source and put internal state back to the point
+  // before the call to DragEnter. This is called when the drag leaves
+  // without a drop occurring.
+  MOZ_CAN_RUN_SCRIPT_BOUNDARY STDMETHODIMP DragLeave();
+
+  // If point is within our region of interest and pSource's data supports
+  // one of our formats, get the data and set pEffect according to
+  // grfKeyState (DROPEFFECT_MOVE if the control key was not pressed,
+  // DROPEFFECT_COPY if the control key was pressed). Otherwise return
+  // E_FAIL.
+  MOZ_CAN_RUN_SCRIPT_BOUNDARY STDMETHODIMP Drop(LPDATAOBJECT pSource,
+                                                DWORD grfKeyState, POINTL point,
+                                                DWORD* pEffect);
+  /**
+   * Cancel the current drag session, if any.
+   */
+  MOZ_CAN_RUN_SCRIPT_BOUNDARY void DragCancel();
+
+  static void DragImageChanged() { gDragImageChanged = true; }
+
+ protected:
+  void GetGeckoDragAction(DWORD grfKeyState, LPDWORD pdwEffect,
+                          uint32_t* aGeckoAction);
+  void ProcessDrag(mozilla::EventMessage aEventMessage, DWORD grfKeyState,
+                   POINTL pt, DWORD* pdwEffect);
+  void DispatchDragDropEvent(mozilla::EventMessage aEventMessage,
+                             const POINTL& aPT);
+  void AddLinkSupportIfCanBeGenerated(LPDATAOBJECT aIDataSource);
+
+  // Native Stuff
+  ULONG m_cRef;  // reference count
+  HWND mHWnd;
+  DWORD mEffectsAllowed;
+  DWORD mEffectsPreferred;
+  bool mTookOwnRef;
+
+  // Gecko Stuff
+  nsIWidget* mWidget;
+  nsCOMPtr<nsIDragService> mDragService;
+  // Drag target helper
+  IDropTargetHelper* GetDropTargetHelper();
+
+ private:
+  // Drag target helper
+  IDropTargetHelper* mDropTargetHelper;
+
+  static bool gDragImageChanged;
+};
+
+#endif  // _nsNativeDragTarget_h_
diff --git a/widget/windows/nsNativeThemeWin.cpp b/widget/windows/nsNativeThemeWin.cpp
new file mode 100644
index 0000000000..04883a833f
--- /dev/null
+++ b/widget/windows/nsNativeThemeWin.cpp
@@ -0,0 +1,1975 @@
+/* -*- Mode: C++; tab-width: 40; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsNativeThemeWin.h"
+
+#include <algorithm>
+#include <malloc.h>
+
+#include "gfxContext.h"
+#include "gfxPlatform.h"
+#include "gfxWindowsNativeDrawing.h"
+#include "gfxWindowsPlatform.h"
+#include "gfxWindowsSurface.h"
+#include "mozilla/ClearOnShutdown.h"
+#include "mozilla/gfx/Types.h"  // for Color::FromABGR
+#include "mozilla/Logging.h"
+#include "mozilla/RelativeLuminanceUtils.h"
+#include "mozilla/StaticPrefs_layout.h"
+#include "mozilla/StaticPrefs_widget.h"
+#include "mozilla/dom/XULButtonElement.h"
+#include "nsColor.h"
+#include "nsComboboxControlFrame.h"
+#include "nsDeviceContext.h"
+#include "nsGkAtoms.h"
+#include "nsIContent.h"
+#include "nsIContentInlines.h"
+#include "nsIFrame.h"
+#include "nsLayoutUtils.h"
+#include "nsLookAndFeel.h"
+#include "nsNameSpaceManager.h"
+#include "Theme.h"
+#include "nsPresContext.h"
+#include "nsRect.h"
+#include "nsSize.h"
+#include "nsStyleConsts.h"
+#include "nsTransform2D.h"
+#include "nsWindow.h"
+#include "prinrval.h"
+#include "WinUtils.h"
+
+using namespace mozilla;
+using namespace mozilla::gfx;
+using namespace mozilla::widget;
+
+using ElementState = dom::ElementState;
+
+extern mozilla::LazyLogModule gWindowsLog;
+
+namespace mozilla::widget {
+
+nsNativeThemeWin::nsNativeThemeWin()
+    : Theme(ScrollbarStyle()),
+      mProgressDeterminateTimeStamp(TimeStamp::Now()),
+      mProgressIndeterminateTimeStamp(TimeStamp::Now()),
+      mBorderCacheValid(),
+      mMinimumWidgetSizeCacheValid(),
+      mGutterSizeCacheValid(false) {}
+
+nsNativeThemeWin::~nsNativeThemeWin() { nsUXThemeData::Invalidate(); }
+
+bool nsNativeThemeWin::IsWidgetAlwaysNonNative(nsIFrame* aFrame,
+                                               StyleAppearance aAppearance) {
+  return Theme::IsWidgetAlwaysNonNative(aFrame, aAppearance) ||
+         aAppearance == StyleAppearance::Checkbox ||
+         aAppearance == StyleAppearance::Radio ||
+         aAppearance == StyleAppearance::MozMenulistArrowButton ||
+         aAppearance == StyleAppearance::SpinnerUpbutton ||
+         aAppearance == StyleAppearance::SpinnerDownbutton;
+}
+
+auto nsNativeThemeWin::IsWidgetNonNative(nsIFrame* aFrame,
+                                         StyleAppearance aAppearance)
+    -> NonNative {
+  if (IsWidgetAlwaysNonNative(aFrame, aAppearance)) {
+    return NonNative::Always;
+  }
+
+  // We only know how to draw light widgets, so we defer to the non-native
+  // theme when appropriate.
+  if (Theme::ThemeSupportsWidget(aFrame->PresContext(), aFrame, aAppearance) &&
+      LookAndFeel::ColorSchemeForFrame(aFrame) ==
+          LookAndFeel::ColorScheme::Dark) {
+    return NonNative::BecauseColorMismatch;
+  }
+  return NonNative::No;
+}
+
+static MARGINS GetCheckboxMargins(HANDLE theme, HDC hdc) {
+  MARGINS checkboxContent = {0};
+  GetThemeMargins(theme, hdc, MENU_POPUPCHECK, MCB_NORMAL, TMT_CONTENTMARGINS,
+                  nullptr, &checkboxContent);
+  return checkboxContent;
+}
+
+static SIZE GetCheckboxBGSize(HANDLE theme, HDC hdc) {
+  SIZE checkboxSize;
+  GetThemePartSize(theme, hdc, MENU_POPUPCHECK, MC_CHECKMARKNORMAL, nullptr,
+                   TS_TRUE, &checkboxSize);
+
+  MARGINS checkboxMargins = GetCheckboxMargins(theme, hdc);
+
+  int leftMargin = checkboxMargins.cxLeftWidth;
+  int rightMargin = checkboxMargins.cxRightWidth;
+  int topMargin = checkboxMargins.cyTopHeight;
+  int bottomMargin = checkboxMargins.cyBottomHeight;
+
+  int width = leftMargin + checkboxSize.cx + rightMargin;
+  int height = topMargin + checkboxSize.cy + bottomMargin;
+  SIZE ret;
+  ret.cx = width;
+  ret.cy = height;
+  return ret;
+}
+
+static SIZE GetCheckboxBGBounds(HANDLE theme, HDC hdc) {
+  MARGINS checkboxBGSizing = {0};
+  MARGINS checkboxBGContent = {0};
+  GetThemeMargins(theme, hdc, MENU_POPUPCHECKBACKGROUND, MCB_NORMAL,
+                  TMT_SIZINGMARGINS, nullptr, &checkboxBGSizing);
+  GetThemeMargins(theme, hdc, MENU_POPUPCHECKBACKGROUND, MCB_NORMAL,
+                  TMT_CONTENTMARGINS, nullptr, &checkboxBGContent);
+
+#define posdx(d) ((d) > 0 ? d : 0)
+
+  int dx =
+      posdx(checkboxBGContent.cxRightWidth - checkboxBGSizing.cxRightWidth) +
+      posdx(checkboxBGContent.cxLeftWidth - checkboxBGSizing.cxLeftWidth);
+  int dy =
+      posdx(checkboxBGContent.cyTopHeight - checkboxBGSizing.cyTopHeight) +
+      posdx(checkboxBGContent.cyBottomHeight - checkboxBGSizing.cyBottomHeight);
+
+#undef posdx
+
+  SIZE ret(GetCheckboxBGSize(theme, hdc));
+  ret.cx += dx;
+  ret.cy += dy;
+  return ret;
+}
+
+static SIZE GetGutterSize(HANDLE theme, HDC hdc) {
+  SIZE gutterSize;
+  GetThemePartSize(theme, hdc, MENU_POPUPGUTTER, 0, nullptr, TS_TRUE,
+                   &gutterSize);
+
+  SIZE checkboxBGSize(GetCheckboxBGBounds(theme, hdc));
+
+  SIZE itemSize;
+  GetThemePartSize(theme, hdc, MENU_POPUPITEM, MPI_NORMAL, nullptr, TS_TRUE,
+                   &itemSize);
+
+  // Figure out how big the menuitem's icon will be (if present) at current DPI
+  // Needs the system scale for consistency with Windows Theme API.
+  double scaleFactor = WinUtils::SystemScaleFactor();
+  int iconDevicePixels = NSToIntRound(16 * scaleFactor);
+  SIZE iconSize = {iconDevicePixels, iconDevicePixels};
+  // Not really sure what margins should be used here, but this seems to work in
+  // practice...
+  MARGINS margins = {0};
+  GetThemeMargins(theme, hdc, MENU_POPUPCHECKBACKGROUND, MCB_NORMAL,
+                  TMT_CONTENTMARGINS, nullptr, &margins);
+  iconSize.cx += margins.cxLeftWidth + margins.cxRightWidth;
+  iconSize.cy += margins.cyTopHeight + margins.cyBottomHeight;
+
+  int width = std::max(
+      itemSize.cx, std::max(iconSize.cx, checkboxBGSize.cx) + gutterSize.cx);
+  int height = std::max(itemSize.cy, std::max(iconSize.cy, checkboxBGSize.cy));
+
+  SIZE ret;
+  ret.cx = width;
+  ret.cy = height;
+  return ret;
+}
+
+SIZE nsNativeThemeWin::GetCachedGutterSize(HANDLE theme) {
+  if (mGutterSizeCacheValid) {
+    return mGutterSizeCache;
+  }
+
+  mGutterSizeCache = GetGutterSize(theme, nullptr);
+  mGutterSizeCacheValid = true;
+
+  return mGutterSizeCache;
+}
+
+/*
+ * Notes on progress track and meter part constants:
+ * xp and up:
+ * PP_BAR(_VERT)            - base progress track
+ * PP_TRANSPARENTBAR(_VERT) - transparent progress track. this only works if
+ *                            the underlying surface supports alpha. otherwise
+ *                            theme lib's DrawThemeBackground falls back on
+ *                            opaque PP_BAR. we currently don't use this.
+ * PP_CHUNK(_VERT)          - xp progress meter. this does not draw an xp style
+ *                            progress w/chunks, it draws fill using the chunk
+ *                            graphic.
+ * vista and up:
+ * PP_FILL(_VERT)           - progress meter. these have four states/colors.
+ * PP_PULSEOVERLAY(_VERT)   - white reflection - an overlay, not sure what this
+ *                            is used for.
+ * PP_MOVEOVERLAY(_VERT)    - green pulse - the pulse effect overlay on
+ *                            determined progress bars. we also use this for
+ *                            indeterminate chunk.
+ *
+ * Notes on state constants:
+ * PBBS_NORMAL               - green progress
+ * PBBVS_PARTIAL/PBFVS_ERROR - red error progress
+ * PBFS_PAUSED               - yellow paused progress
+ *
+ * There is no common controls style indeterminate part on vista and up.
+ */
+
+/*
+ * Progress bar related constants. These values are found by experimenting and
+ * comparing against native widgets used by the system. They are very unlikely
+ * exact but try to not be too wrong.
+ */
+// The amount of time we animate progress meters parts across the frame.
+static const double kProgressDeterminateTimeSpan = 3.0;
+static const double kProgressIndeterminateTimeSpan = 5.0;
+// The width of the overlay used to animate the horizontal progress bar (Vista
+// and later).
+static const int32_t kProgressHorizontalOverlaySize = 120;
+// The height of the overlay used to animate the vertical progress bar (Vista
+// and later).
+static const int32_t kProgressVerticalOverlaySize = 45;
+// The height of the overlay used for the vertical indeterminate progress bar
+// (Vista and later).
+static const int32_t kProgressVerticalIndeterminateOverlaySize = 60;
+// The width of the overlay used to animate the indeterminate progress bar
+// (Windows Classic).
+static const int32_t kProgressClassicOverlaySize = 40;
+
+/*
+ * GetProgressOverlayStyle - returns the proper overlay part for themed
+ * progress bars based on os and orientation.
+ */
+static int32_t GetProgressOverlayStyle(bool aIsVertical) {
+  return aIsVertical ? PP_MOVEOVERLAYVERT : PP_MOVEOVERLAY;
+}
+
+/*
+ * GetProgressOverlaySize - returns the minimum width or height for themed
+ * progress bar overlays. This includes the width of indeterminate chunks
+ * and vista pulse overlays.
+ */
+static int32_t GetProgressOverlaySize(bool aIsVertical, bool aIsIndeterminate) {
+  if (aIsVertical) {
+    return aIsIndeterminate ? kProgressVerticalIndeterminateOverlaySize
+                            : kProgressVerticalOverlaySize;
+  }
+  return kProgressHorizontalOverlaySize;
+}
+
+/*
+ * IsProgressMeterFilled - Determines if a progress meter is at 100% fill based
+ * on a comparison of the current value and maximum.
+ */
+static bool IsProgressMeterFilled(nsIFrame* aFrame) {
+  NS_ENSURE_TRUE(aFrame, false);
+  nsIFrame* parentFrame = aFrame->GetParent();
+  NS_ENSURE_TRUE(parentFrame, false);
+  return nsNativeTheme::GetProgressValue(parentFrame) ==
+         nsNativeTheme::GetProgressMaxValue(parentFrame);
+}
+
+/*
+ * CalculateProgressOverlayRect - returns the padded overlay animation rect
+ * used in rendering progress bars. Resulting rects are used in rendering
+ * vista+ pulse overlays and indeterminate progress meters. Graphics should
+ * be rendered at the origin.
+ */
+RECT nsNativeThemeWin::CalculateProgressOverlayRect(nsIFrame* aFrame,
+                                                    RECT* aWidgetRect,
+                                                    bool aIsVertical,
+                                                    bool aIsIndeterminate,
+                                                    bool aIsClassic) {
+  NS_ASSERTION(aFrame, "bad frame pointer");
+  NS_ASSERTION(aWidgetRect, "bad rect pointer");
+
+  int32_t frameSize = aIsVertical ? aWidgetRect->bottom - aWidgetRect->top
+                                  : aWidgetRect->right - aWidgetRect->left;
+
+  // Recycle a set of progress pulse timers - these timers control the position
+  // of all progress overlays and indeterminate chunks that get rendered.
+  double span = aIsIndeterminate ? kProgressIndeterminateTimeSpan
+                                 : kProgressDeterminateTimeSpan;
+  TimeDuration period;
+  if (!aIsIndeterminate) {
+    if (TimeStamp::Now() >
+        (mProgressDeterminateTimeStamp + TimeDuration::FromSeconds(span))) {
+      mProgressDeterminateTimeStamp = TimeStamp::Now();
+    }
+    period = TimeStamp::Now() - mProgressDeterminateTimeStamp;
+  } else {
+    if (TimeStamp::Now() >
+        (mProgressIndeterminateTimeStamp + TimeDuration::FromSeconds(span))) {
+      mProgressIndeterminateTimeStamp = TimeStamp::Now();
+    }
+    period = TimeStamp::Now() - mProgressIndeterminateTimeStamp;
+  }
+
+  double percent = period / TimeDuration::FromSeconds(span);
+
+  if (!aIsVertical && IsFrameRTL(aFrame)) percent = 1 - percent;
+
+  RECT overlayRect = *aWidgetRect;
+  int32_t overlaySize;
+  if (!aIsClassic) {
+    overlaySize = GetProgressOverlaySize(aIsVertical, aIsIndeterminate);
+  } else {
+    overlaySize = kProgressClassicOverlaySize;
+  }
+
+  // Calculate a bounds that is larger than the meters frame such that the
+  // overlay starts and ends completely off the edge of the frame:
+  // [overlay][frame][overlay]
+  // This also yields a nice delay on rotation. Use overlaySize as the minimum
+  // size for [overlay] based on the graphics dims. If [frame] is larger, use
+  // the frame size instead.
+  int trackWidth = frameSize > overlaySize ? frameSize : overlaySize;
+  if (!aIsVertical) {
+    int xPos = aWidgetRect->left - trackWidth;
+    xPos += (int)ceil(((double)(trackWidth * 2) * percent));
+    overlayRect.left = xPos;
+    overlayRect.right = xPos + overlaySize;
+  } else {
+    int yPos = aWidgetRect->bottom + trackWidth;
+    yPos -= (int)ceil(((double)(trackWidth * 2) * percent));
+    overlayRect.bottom = yPos;
+    overlayRect.top = yPos - overlaySize;
+  }
+  return overlayRect;
+}
+
+/*
+ * DrawProgressMeter - render an appropriate progress meter based on progress
+ * meter style, orientation, and os. Note, this does not render the underlying
+ * progress track.
+ *
+ * @param aFrame       the widget frame
+ * @param aAppearance  type of widget
+ * @param aTheme       progress theme handle
+ * @param aHdc         hdc returned by gfxWindowsNativeDrawing
+ * @param aPart        the PP_X progress part
+ * @param aState       the theme state
+ * @param aWidgetRect  bounding rect for the widget
+ * @param aClipRect    dirty rect that needs drawing.
+ * @param aAppUnits    app units per device pixel
+ */
+void nsNativeThemeWin::DrawThemedProgressMeter(
+    nsIFrame* aFrame, StyleAppearance aAppearance, HANDLE aTheme, HDC aHdc,
+    int aPart, int aState, RECT* aWidgetRect, RECT* aClipRect) {
+  if (!aFrame || !aTheme || !aHdc) return;
+
+  NS_ASSERTION(aWidgetRect, "bad rect pointer");
+  NS_ASSERTION(aClipRect, "bad clip rect pointer");
+
+  RECT adjWidgetRect, adjClipRect;
+  adjWidgetRect = *aWidgetRect;
+  adjClipRect = *aClipRect;
+
+  nsIFrame* parentFrame = aFrame->GetParent();
+  if (!parentFrame) {
+    // We have no parent to work with, just bail.
+    NS_WARNING("No parent frame for progress rendering. Can't paint.");
+    return;
+  }
+
+  ElementState elementState = GetContentState(parentFrame, aAppearance);
+  bool vertical = IsVerticalProgress(parentFrame);
+  bool indeterminate = elementState.HasState(ElementState::INDETERMINATE);
+  bool animate = indeterminate;
+
+  // Vista and up progress meter is fill style, rendered here. We render
+  // the pulse overlay in the follow up section below.
+  DrawThemeBackground(aTheme, aHdc, aPart, aState, &adjWidgetRect,
+                      &adjClipRect);
+  if (!IsProgressMeterFilled(aFrame)) {
+    animate = true;
+  }
+
+  if (animate) {
+    // Indeterminate rendering
+    int32_t overlayPart = GetProgressOverlayStyle(vertical);
+    RECT overlayRect = CalculateProgressOverlayRect(
+        aFrame, &adjWidgetRect, vertical, indeterminate, false);
+    DrawThemeBackground(aTheme, aHdc, overlayPart, aState, &overlayRect,
+                        &adjClipRect);
+
+    if (!QueueAnimatedContentForRefresh(aFrame->GetContent(), 60)) {
+      NS_WARNING("unable to animate progress widget!");
+    }
+  }
+}
+
+LayoutDeviceIntMargin nsNativeThemeWin::GetCachedWidgetBorder(
+    HTHEME aTheme, nsUXThemeClass aThemeClass, StyleAppearance aAppearance,
+    int32_t aPart, int32_t aState) {
+  int32_t cacheIndex = aThemeClass * THEME_PART_DISTINCT_VALUE_COUNT + aPart;
+  int32_t cacheBitIndex = cacheIndex / 8;
+  uint8_t cacheBit = 1u << (cacheIndex % 8);
+
+  if (mBorderCacheValid[cacheBitIndex] & cacheBit) {
+    return mBorderCache[cacheIndex];
+  }
+
+  // Get our info.
+  RECT outerRect;  // Create a fake outer rect.
+  outerRect.top = outerRect.left = 100;
+  outerRect.right = outerRect.bottom = 200;
+  RECT contentRect(outerRect);
+  HRESULT res = GetThemeBackgroundContentRect(aTheme, nullptr, aPart, aState,
+                                              &outerRect, &contentRect);
+
+  if (FAILED(res)) {
+    return LayoutDeviceIntMargin();
+  }
+
+  // Now compute the delta in each direction and place it in our
+  // nsIntMargin struct.
+  LayoutDeviceIntMargin result;
+  result.top = contentRect.top - outerRect.top;
+  result.bottom = outerRect.bottom - contentRect.bottom;
+  result.left = contentRect.left - outerRect.left;
+  result.right = outerRect.right - contentRect.right;
+
+  mBorderCacheValid[cacheBitIndex] |= cacheBit;
+  mBorderCache[cacheIndex] = result;
+
+  return result;
+}
+
+nsresult nsNativeThemeWin::GetCachedMinimumWidgetSize(
+    nsIFrame* aFrame, HANDLE aTheme, nsUXThemeClass aThemeClass,
+    StyleAppearance aAppearance, int32_t aPart, int32_t aState,
+    THEMESIZE aSizeReq, mozilla::LayoutDeviceIntSize* aResult) {
+  int32_t cachePart = aPart;
+
+  if (aAppearance == StyleAppearance::Button && aSizeReq == TS_MIN) {
+    // In practice, StyleAppearance::Button is the only widget type which has an
+    // aSizeReq that varies for us, and it can only be TS_MIN or TS_TRUE. Just
+    // stuff that extra bit into the aPart part of the cache, since BP_Count is
+    // well below THEME_PART_DISTINCT_VALUE_COUNT anyway.
+    cachePart = BP_Count;
+  }
+
+  MOZ_ASSERT(aPart < THEME_PART_DISTINCT_VALUE_COUNT);
+  int32_t cacheIndex =
+      aThemeClass * THEME_PART_DISTINCT_VALUE_COUNT + cachePart;
+  int32_t cacheBitIndex = cacheIndex / 8;
+  uint8_t cacheBit = 1u << (cacheIndex % 8);
+
+  if (mMinimumWidgetSizeCacheValid[cacheBitIndex] & cacheBit) {
+    *aResult = mMinimumWidgetSizeCache[cacheIndex];
+    return NS_OK;
+  }
+
+  HDC hdc = ::GetDC(NULL);
+  if (!hdc) {
+    return NS_ERROR_FAILURE;
+  }
+
+  SIZE sz;
+  GetThemePartSize(aTheme, hdc, aPart, aState, nullptr, aSizeReq, &sz);
+  aResult->width = sz.cx;
+  aResult->height = sz.cy;
+
+  ::ReleaseDC(nullptr, hdc);
+
+  mMinimumWidgetSizeCacheValid[cacheBitIndex] |= cacheBit;
+  mMinimumWidgetSizeCache[cacheIndex] = *aResult;
+
+  return NS_OK;
+}
+
+mozilla::Maybe<nsUXThemeClass> nsNativeThemeWin::GetThemeClass(
+    StyleAppearance aAppearance) {
+  switch (aAppearance) {
+    case StyleAppearance::Button:
+      return Some(eUXButton);
+    case StyleAppearance::NumberInput:
+    case StyleAppearance::Textfield:
+    case StyleAppearance::Textarea:
+      return Some(eUXEdit);
+    case StyleAppearance::Toolbox:
+      return Some(eUXRebar);
+    case StyleAppearance::Toolbar:
+    case StyleAppearance::Toolbarbutton:
+    case StyleAppearance::Separator:
+      return Some(eUXToolbar);
+    case StyleAppearance::ProgressBar:
+    case StyleAppearance::Progresschunk:
+      return Some(eUXProgress);
+    case StyleAppearance::Tab:
+    case StyleAppearance::Tabpanel:
+    case StyleAppearance::Tabpanels:
+      return Some(eUXTab);
+    case StyleAppearance::Range:
+    case StyleAppearance::RangeThumb:
+      return Some(eUXTrackbar);
+    case StyleAppearance::Menulist:
+    case StyleAppearance::MenulistButton:
+      return Some(eUXCombobox);
+    case StyleAppearance::Treeheadercell:
+      return Some(eUXHeader);
+    case StyleAppearance::Listbox:
+    case StyleAppearance::Treeview:
+    case StyleAppearance::Treetwistyopen:
+    case StyleAppearance::Treeitem:
+      return Some(eUXListview);
+    default:
+      return Nothing();
+  }
+}
+
+HANDLE
+nsNativeThemeWin::GetTheme(StyleAppearance aAppearance) {
+  mozilla::Maybe<nsUXThemeClass> themeClass = GetThemeClass(aAppearance);
+  if (themeClass.isNothing()) {
+    return nullptr;
+  }
+  return nsUXThemeData::GetTheme(themeClass.value());
+}
+
+int32_t nsNativeThemeWin::StandardGetState(nsIFrame* aFrame,
+                                           StyleAppearance aAppearance,
+                                           bool wantFocused) {
+  ElementState elementState = GetContentState(aFrame, aAppearance);
+  if (elementState.HasAllStates(ElementState::HOVER | ElementState::ACTIVE)) {
+    return TS_ACTIVE;
+  }
+  if (elementState.HasState(ElementState::HOVER)) {
+    return TS_HOVER;
+  }
+  if (wantFocused) {
+    if (elementState.HasState(ElementState::FOCUSRING)) {
+      return TS_FOCUSED;
+    }
+    // On Windows, focused buttons are always drawn as such by the native
+    // theme, that's why we check ElementState::FOCUS instead of
+    // ElementState::FOCUSRING.
+    if (aAppearance == StyleAppearance::Button &&
+        elementState.HasState(ElementState::FOCUS)) {
+      return TS_FOCUSED;
+    }
+  }
+
+  return TS_NORMAL;
+}
+
+bool nsNativeThemeWin::IsMenuActive(nsIFrame* aFrame,
+                                    StyleAppearance aAppearance) {
+  nsIContent* content = aFrame->GetContent();
+  if (content->IsXULElement() &&
+      content->NodeInfo()->Equals(nsGkAtoms::richlistitem))
+    return CheckBooleanAttr(aFrame, nsGkAtoms::selected);
+
+  return CheckBooleanAttr(aFrame, nsGkAtoms::menuactive);
+}
+
+/**
+ * aPart is filled in with the UXTheme part code. On return, values > 0
+ * are the actual UXTheme part code; -1 means the widget will be drawn by
+ * us; 0 means that we should use part code 0, which isn't a real part code
+ * but elicits some kind of default behaviour from UXTheme when drawing
+ * (but isThemeBackgroundPartiallyTransparent may not work).
+ */
+nsresult nsNativeThemeWin::GetThemePartAndState(nsIFrame* aFrame,
+                                                StyleAppearance aAppearance,
+                                                int32_t& aPart,
+                                                int32_t& aState) {
+  switch (aAppearance) {
+    case StyleAppearance::Button: {
+      aPart = BP_BUTTON;
+      if (!aFrame) {
+        aState = TS_NORMAL;
+        return NS_OK;
+      }
+
+      ElementState elementState = GetContentState(aFrame, aAppearance);
+      if (elementState.HasState(ElementState::DISABLED)) {
+        aState = TS_DISABLED;
+        return NS_OK;
+      }
+      if (IsOpenButton(aFrame) || IsCheckedButton(aFrame)) {
+        aState = TS_ACTIVE;
+        return NS_OK;
+      }
+
+      aState = StandardGetState(aFrame, aAppearance, true);
+
+      // Check for default dialog buttons.  These buttons should always look
+      // focused.
+      if (aState == TS_NORMAL && IsDefaultButton(aFrame)) aState = TS_FOCUSED;
+      return NS_OK;
+    }
+    case StyleAppearance::NumberInput:
+    case StyleAppearance::Textfield:
+    case StyleAppearance::Textarea: {
+      ElementState elementState = GetContentState(aFrame, aAppearance);
+
+      /* Note: the NOSCROLL type has a rounded corner in each corner.  The more
+       * specific HSCROLL, VSCROLL, HVSCROLL types have side and/or top/bottom
+       * edges rendered as straight horizontal lines with sharp corners to
+       * accommodate a scrollbar.  However, the scrollbar gets rendered on top
+       * of this for us, so we don't care, and can just use NOSCROLL here.
+       */
+      aPart = TFP_EDITBORDER_NOSCROLL;
+
+      if (!aFrame) {
+        aState = TFS_EDITBORDER_NORMAL;
+      } else if (elementState.HasState(ElementState::DISABLED)) {
+        aState = TFS_EDITBORDER_DISABLED;
+      } else if (IsReadOnly(aFrame)) {
+        /* no special read-only state */
+        aState = TFS_EDITBORDER_NORMAL;
+      } else if (elementState.HasAtLeastOneOfStates(ElementState::ACTIVE |
+                                                    ElementState::FOCUSRING)) {
+        aState = TFS_EDITBORDER_FOCUSED;
+      } else if (elementState.HasState(ElementState::HOVER)) {
+        aState = TFS_EDITBORDER_HOVER;
+      } else {
+        aState = TFS_EDITBORDER_NORMAL;
+      }
+
+      return NS_OK;
+    }
+    case StyleAppearance::ProgressBar: {
+      bool vertical = IsVerticalProgress(aFrame);
+      aPart = vertical ? PP_BARVERT : PP_BAR;
+      aState = PBBS_NORMAL;
+      return NS_OK;
+    }
+    case StyleAppearance::Progresschunk: {
+      nsIFrame* parentFrame = aFrame->GetParent();
+      if (IsVerticalProgress(parentFrame)) {
+        aPart = PP_FILLVERT;
+      } else {
+        aPart = PP_FILL;
+      }
+
+      aState = PBBVS_NORMAL;
+      return NS_OK;
+    }
+    case StyleAppearance::Toolbarbutton: {
+      aPart = BP_BUTTON;
+      if (!aFrame) {
+        aState = TS_NORMAL;
+        return NS_OK;
+      }
+
+      ElementState elementState = GetContentState(aFrame, aAppearance);
+      if (elementState.HasState(ElementState::DISABLED)) {
+        aState = TS_DISABLED;
+        return NS_OK;
+      }
+      if (IsOpenButton(aFrame)) {
+        aState = TS_ACTIVE;
+        return NS_OK;
+      }
+
+      if (elementState.HasAllStates(ElementState::HOVER | ElementState::ACTIVE))
+        aState = TS_ACTIVE;
+      else if (elementState.HasState(ElementState::HOVER)) {
+        if (IsCheckedButton(aFrame))
+          aState = TB_HOVER_CHECKED;
+        else
+          aState = TS_HOVER;
+      } else {
+        if (IsCheckedButton(aFrame))
+          aState = TB_CHECKED;
+        else
+          aState = TS_NORMAL;
+      }
+
+      return NS_OK;
+    }
+    case StyleAppearance::Separator: {
+      aPart = TP_SEPARATOR;
+      aState = TS_NORMAL;
+      return NS_OK;
+    }
+    case StyleAppearance::Range: {
+      if (IsRangeHorizontal(aFrame)) {
+        aPart = TKP_TRACK;
+        aState = TRS_NORMAL;
+      } else {
+        aPart = TKP_TRACKVERT;
+        aState = TRVS_NORMAL;
+      }
+      return NS_OK;
+    }
+    case StyleAppearance::RangeThumb: {
+      if (IsRangeHorizontal(aFrame)) {
+        aPart = TKP_THUMBBOTTOM;
+      } else {
+        aPart = IsFrameRTL(aFrame) ? TKP_THUMBLEFT : TKP_THUMBRIGHT;
+      }
+      ElementState elementState = GetContentState(aFrame, aAppearance);
+      if (!aFrame) {
+        aState = TS_NORMAL;
+      } else if (elementState.HasState(ElementState::DISABLED)) {
+        aState = TKP_DISABLED;
+      } else {
+        if (elementState.HasState(
+                ElementState::ACTIVE))  // Hover is not also a requirement for
+                                        // the thumb, since the drag is not
+                                        // canceled when you move outside the
+                                        // thumb.
+          aState = TS_ACTIVE;
+        else if (elementState.HasState(ElementState::FOCUSRING))
+          aState = TKP_FOCUSED;
+        else if (elementState.HasState(ElementState::HOVER))
+          aState = TS_HOVER;
+        else
+          aState = TS_NORMAL;
+      }
+      return NS_OK;
+    }
+    case StyleAppearance::Toolbox: {
+      aState = 0;
+      aPart = RP_BACKGROUND;
+      return NS_OK;
+    }
+    case StyleAppearance::Toolbar: {
+      // Use -1 to indicate we don't wish to have the theme background drawn
+      // for this item. We will pass any nessessary information via aState,
+      // and will render the item using separate code.
+      aPart = -1;
+      aState = 0;
+      if (aFrame) {
+        nsIContent* content = aFrame->GetContent();
+        nsIContent* parent = content->GetParent();
+        // XXXzeniko hiding the first toolbar will result in an unwanted margin
+        if (parent && parent->GetFirstChild() == content) {
+          aState = 1;
+        }
+      }
+      return NS_OK;
+    }
+    case StyleAppearance::Treeview:
+    case StyleAppearance::Listbox: {
+      aPart = TREEVIEW_BODY;
+      aState = TS_NORMAL;
+      return NS_OK;
+    }
+    case StyleAppearance::Tabpanels: {
+      aPart = TABP_PANELS;
+      aState = TS_NORMAL;
+      return NS_OK;
+    }
+    case StyleAppearance::Tabpanel: {
+      aPart = TABP_PANEL;
+      aState = TS_NORMAL;
+      return NS_OK;
+    }
+    case StyleAppearance::Tab: {
+      aPart = TABP_TAB;
+      if (!aFrame) {
+        aState = TS_NORMAL;
+        return NS_OK;
+      }
+
+      ElementState elementState = GetContentState(aFrame, aAppearance);
+      if (elementState.HasState(ElementState::DISABLED)) {
+        aState = TS_DISABLED;
+        return NS_OK;
+      }
+
+      if (IsSelectedTab(aFrame)) {
+        aPart = TABP_TAB_SELECTED;
+        aState = TS_ACTIVE;  // The selected tab is always "pressed".
+      } else
+        aState = StandardGetState(aFrame, aAppearance, true);
+
+      return NS_OK;
+    }
+    case StyleAppearance::Treeheadercell: {
+      aPart = 1;
+      if (!aFrame) {
+        aState = TS_NORMAL;
+        return NS_OK;
+      }
+
+      aState = StandardGetState(aFrame, aAppearance, true);
+
+      return NS_OK;
+    }
+    case StyleAppearance::MenulistButton:
+    case StyleAppearance::Menulist: {
+      nsIContent* content = aFrame->GetContent();
+      bool useDropBorder = content && content->IsHTMLElement();
+      ElementState elementState = GetContentState(aFrame, aAppearance);
+
+      /* On Vista/Win7, we use CBP_DROPBORDER instead of DROPFRAME for HTML
+       * content or for editable menulists; this gives us the thin outline,
+       * instead of the gradient-filled background */
+      if (useDropBorder)
+        aPart = CBP_DROPBORDER;
+      else
+        aPart = CBP_DROPFRAME;
+
+      if (elementState.HasState(ElementState::DISABLED)) {
+        aState = TS_DISABLED;
+      } else if (IsReadOnly(aFrame)) {
+        aState = TS_NORMAL;
+      } else if (IsOpenButton(aFrame)) {
+        aState = TS_ACTIVE;
+      } else if (useDropBorder &&
+                 elementState.HasState(ElementState::FOCUSRING)) {
+        aState = TS_ACTIVE;
+      } else if (elementState.HasAllStates(ElementState::HOVER |
+                                           ElementState::ACTIVE)) {
+        aState = TS_ACTIVE;
+      } else if (elementState.HasState(ElementState::HOVER)) {
+        aState = TS_HOVER;
+      } else {
+        aState = TS_NORMAL;
+      }
+
+      return NS_OK;
+    }
+    default:
+      aPart = 0;
+      aState = 0;
+      return NS_ERROR_FAILURE;
+  }
+}
+
+static bool AssumeThemePartAndStateAreTransparent(int32_t aPart,
+                                                  int32_t aState) {
+  if (!nsUXThemeData::IsHighContrastOn() && aPart == MENU_POPUPITEM &&
+      aState == MBI_NORMAL) {
+    return true;
+  }
+  return false;
+}
+
+// When running with per-monitor DPI (on Win8.1+), and rendering on a display
+// with a different DPI setting from the system's default scaling, we need to
+// apply scaling to native-themed elements as the Windows theme APIs assume
+// the system default resolution.
+static inline double GetThemeDpiScaleFactor(nsPresContext* aPresContext) {
+  if (WinUtils::IsPerMonitorDPIAware() ||
+      StaticPrefs::layout_css_devPixelsPerPx() > 0.0) {
+    nsCOMPtr<nsIWidget> rootWidget = aPresContext->GetRootWidget();
+    if (rootWidget) {
+      double systemScale = WinUtils::SystemScaleFactor();
+      return rootWidget->GetDefaultScale().scale / systemScale;
+    }
+  }
+  return 1.0;
+}
+
+static inline double GetThemeDpiScaleFactor(nsIFrame* aFrame) {
+  return GetThemeDpiScaleFactor(aFrame->PresContext());
+}
+
+NS_IMETHODIMP
+nsNativeThemeWin::DrawWidgetBackground(gfxContext* aContext, nsIFrame* aFrame,
+                                       StyleAppearance aAppearance,
+                                       const nsRect& aRect,
+                                       const nsRect& aDirtyRect,
+                                       DrawOverflow aDrawOverflow) {
+  if (IsWidgetNonNative(aFrame, aAppearance) != NonNative::No) {
+    return Theme::DrawWidgetBackground(aContext, aFrame, aAppearance, aRect,
+                                       aDirtyRect, aDrawOverflow);
+  }
+
+  HANDLE theme = GetTheme(aAppearance);
+  if (!theme)
+    return ClassicDrawWidgetBackground(aContext, aFrame, aAppearance, aRect,
+                                       aDirtyRect);
+
+  // ^^ without the right sdk, assume xp theming and fall through.
+  int32_t part, state;
+  nsresult rv = GetThemePartAndState(aFrame, aAppearance, part, state);
+  if (NS_FAILED(rv)) return rv;
+
+  if (AssumeThemePartAndStateAreTransparent(part, state)) {
+    return NS_OK;
+  }
+
+  gfxContextMatrixAutoSaveRestore save(aContext);
+
+  double themeScale = GetThemeDpiScaleFactor(aFrame);
+  if (themeScale != 1.0) {
+    aContext->SetMatrix(
+        aContext->CurrentMatrix().PreScale(themeScale, themeScale));
+  }
+
+  gfxFloat p2a = gfxFloat(aFrame->PresContext()->AppUnitsPerDevPixel());
+  RECT widgetRect;
+  RECT clipRect;
+  gfxRect tr(aRect.X(), aRect.Y(), aRect.Width(), aRect.Height()),
+      dr(aDirtyRect.X(), aDirtyRect.Y(), aDirtyRect.Width(),
+         aDirtyRect.Height());
+
+  tr.Scale(1.0 / (p2a * themeScale));
+  dr.Scale(1.0 / (p2a * themeScale));
+
+  gfxWindowsNativeDrawing nativeDrawing(
+      aContext, dr, GetWidgetNativeDrawingFlags(aAppearance));
+
+RENDER_AGAIN:
+
+  HDC hdc = nativeDrawing.BeginNativeDrawing();
+  if (!hdc) return NS_ERROR_FAILURE;
+
+  nativeDrawing.TransformToNativeRect(tr, widgetRect);
+  nativeDrawing.TransformToNativeRect(dr, clipRect);
+
+#if 0
+  {
+    MOZ_LOG(gWindowsLog, LogLevel::Error,
+           (stderr, "xform: %f %f %f %f [%f %f]\n", m._11, m._21, m._12, m._22,
+            m._31, m._32));
+    MOZ_LOG(gWindowsLog, LogLevel::Error,
+           (stderr, "tr: [%d %d %d %d]\ndr: [%d %d %d %d]\noff: [%f %f]\n",
+            tr.x, tr.y, tr.width, tr.height, dr.x, dr.y, dr.width, dr.height,
+            offset.x, offset.y));
+  }
+#endif
+
+  if (aAppearance == StyleAppearance::Tab) {
+    // For left edge and right edge tabs, we need to adjust the widget
+    // rects and clip rects so that the edges don't get drawn.
+    bool isLeft = IsLeftToSelectedTab(aFrame);
+    bool isRight = !isLeft && IsRightToSelectedTab(aFrame);
+
+    if (isLeft || isRight) {
+      // HACK ALERT: There appears to be no way to really obtain this value, so
+      // we're forced to just use the default value for Luna (which also happens
+      // to be correct for all the other skins I've tried).
+      int32_t edgeSize = 2;
+
+      // Armed with the size of the edge, we now need to either shift to the
+      // left or to the right.  The clip rect won't include this extra area, so
+      // we know that we're effectively shifting the edge out of view (such that
+      // it won't be painted).
+      if (isLeft)
+        // The right edge should not be drawn.  Extend our rect by the edge
+        // size.
+        widgetRect.right += edgeSize;
+      else
+        // The left edge should not be drawn.  Move the widget rect's left coord
+        // back.
+        widgetRect.left -= edgeSize;
+    }
+  }
+
+  // widgetRect is the bounding box for a widget, yet the scale track is only
+  // a small portion of this size, so the edges of the scale need to be
+  // adjusted to the real size of the track.
+  if (aAppearance == StyleAppearance::Range) {
+    RECT contentRect;
+    GetThemeBackgroundContentRect(theme, hdc, part, state, &widgetRect,
+                                  &contentRect);
+
+    SIZE siz;
+    GetThemePartSize(theme, hdc, part, state, &widgetRect, TS_TRUE, &siz);
+
+    // When rounding is necessary, we round the position of the track
+    // away from the chevron of the thumb to make it look better.
+    if (IsRangeHorizontal(aFrame)) {
+      contentRect.top += (contentRect.bottom - contentRect.top - siz.cy) / 2;
+      contentRect.bottom = contentRect.top + siz.cy;
+    } else {
+      if (!IsFrameRTL(aFrame)) {
+        contentRect.left += (contentRect.right - contentRect.left - siz.cx) / 2;
+        contentRect.right = contentRect.left + siz.cx;
+      } else {
+        contentRect.right -=
+            (contentRect.right - contentRect.left - siz.cx) / 2;
+        contentRect.left = contentRect.right - siz.cx;
+      }
+    }
+
+    DrawThemeBackground(theme, hdc, part, state, &contentRect, &clipRect);
+  } else if (aAppearance == StyleAppearance::NumberInput ||
+             aAppearance == StyleAppearance::Textfield ||
+             aAppearance == StyleAppearance::Textarea) {
+    DrawThemeBackground(theme, hdc, part, state, &widgetRect, &clipRect);
+
+    if (state == TFS_EDITBORDER_DISABLED) {
+      InflateRect(&widgetRect, -1, -1);
+      ::FillRect(hdc, &widgetRect, reinterpret_cast<HBRUSH>(COLOR_BTNFACE + 1));
+    }
+  } else if (aAppearance == StyleAppearance::ProgressBar) {
+    // DrawThemeBackground renders each corner with a solid white pixel.
+    // Restore these pixels to the underlying color. Tracks are rendered
+    // using alpha recovery, so this makes the corners transparent.
+    COLORREF color;
+    color = GetPixel(hdc, widgetRect.left, widgetRect.top);
+    DrawThemeBackground(theme, hdc, part, state, &widgetRect, &clipRect);
+    SetPixel(hdc, widgetRect.left, widgetRect.top, color);
+    SetPixel(hdc, widgetRect.right - 1, widgetRect.top, color);
+    SetPixel(hdc, widgetRect.right - 1, widgetRect.bottom - 1, color);
+    SetPixel(hdc, widgetRect.left, widgetRect.bottom - 1, color);
+  } else if (aAppearance == StyleAppearance::Progresschunk) {
+    DrawThemedProgressMeter(aFrame, aAppearance, theme, hdc, part, state,
+                            &widgetRect, &clipRect);
+  }
+  // If part is negative, the element wishes us to not render a themed
+  // background, instead opting to be drawn specially below.
+  else if (part >= 0) {
+    DrawThemeBackground(theme, hdc, part, state, &widgetRect, &clipRect);
+  }
+
+  // Draw focus rectangles for range elements
+  // XXX it'd be nice to draw these outside of the frame
+  if (aAppearance == StyleAppearance::Range) {
+    ElementState contentState = GetContentState(aFrame, aAppearance);
+
+    if (contentState.HasState(ElementState::FOCUSRING)) {
+      POINT vpOrg;
+      HPEN hPen = nullptr;
+
+      uint8_t id = SaveDC(hdc);
+
+      ::SelectClipRgn(hdc, nullptr);
+      ::GetViewportOrgEx(hdc, &vpOrg);
+      ::SetBrushOrgEx(hdc, vpOrg.x + widgetRect.left, vpOrg.y + widgetRect.top,
+                      nullptr);
+      ::SetTextColor(hdc, 0);
+      ::DrawFocusRect(hdc, &widgetRect);
+      ::RestoreDC(hdc, id);
+      if (hPen) {
+        ::DeleteObject(hPen);
+      }
+    }
+  } else if (aAppearance == StyleAppearance::Toolbar && state == 0) {
+    // Draw toolbar separator lines above all toolbars except the first one.
+    // The lines are part of the Rebar theme, which is loaded for
+    // StyleAppearance::Toolbox.
+    theme = GetTheme(StyleAppearance::Toolbox);
+    if (!theme) return NS_ERROR_FAILURE;
+
+    widgetRect.bottom = widgetRect.top + TB_SEPARATOR_HEIGHT;
+    DrawThemeEdge(theme, hdc, RP_BAND, 0, &widgetRect, EDGE_ETCHED, BF_TOP,
+                  nullptr);
+  }
+
+  nativeDrawing.EndNativeDrawing();
+
+  if (nativeDrawing.ShouldRenderAgain()) goto RENDER_AGAIN;
+
+  nativeDrawing.PaintToContext();
+
+  return NS_OK;
+}
+
+bool nsNativeThemeWin::CreateWebRenderCommandsForWidget(
+    wr::DisplayListBuilder& aBuilder, wr::IpcResourceUpdateQueue& aResources,
+    const layers::StackingContextHelper& aSc,
+    layers::RenderRootStateManager* aManager, nsIFrame* aFrame,
+    StyleAppearance aAppearance, const nsRect& aRect) {
+  if (IsWidgetNonNative(aFrame, aAppearance) != NonNative::No) {
+    return Theme::CreateWebRenderCommandsForWidget(
+        aBuilder, aResources, aSc, aManager, aFrame, aAppearance, aRect);
+  }
+  return false;
+}
+
+static void ScaleForFrameDPI(LayoutDeviceIntMargin* aMargin, nsIFrame* aFrame) {
+  double themeScale = GetThemeDpiScaleFactor(aFrame);
+  if (themeScale != 1.0) {
+    aMargin->top = NSToIntRound(aMargin->top * themeScale);
+    aMargin->left = NSToIntRound(aMargin->left * themeScale);
+    aMargin->bottom = NSToIntRound(aMargin->bottom * themeScale);
+    aMargin->right = NSToIntRound(aMargin->right * themeScale);
+  }
+}
+
+static void ScaleForFrameDPI(LayoutDeviceIntSize* aSize, nsIFrame* aFrame) {
+  double themeScale = GetThemeDpiScaleFactor(aFrame);
+  if (themeScale != 1.0) {
+    aSize->width = NSToIntRound(aSize->width * themeScale);
+    aSize->height = NSToIntRound(aSize->height * themeScale);
+  }
+}
+
+LayoutDeviceIntMargin nsNativeThemeWin::GetWidgetBorder(
+    nsDeviceContext* aContext, nsIFrame* aFrame, StyleAppearance aAppearance) {
+  if (IsWidgetAlwaysNonNative(aFrame, aAppearance)) {
+    return Theme::GetWidgetBorder(aContext, aFrame, aAppearance);
+  }
+
+  LayoutDeviceIntMargin result;
+  mozilla::Maybe<nsUXThemeClass> themeClass = GetThemeClass(aAppearance);
+  HTHEME theme = NULL;
+  if (!themeClass.isNothing()) {
+    theme = nsUXThemeData::GetTheme(themeClass.value());
+  }
+  if (!theme) {
+    result = ClassicGetWidgetBorder(aContext, aFrame, aAppearance);
+    ScaleForFrameDPI(&result, aFrame);
+    return result;
+  }
+
+  if (!WidgetIsContainer(aAppearance) ||
+      aAppearance == StyleAppearance::Toolbox ||
+      aAppearance == StyleAppearance::Tabpanel)
+    return result;  // Don't worry about it.
+
+  int32_t part, state;
+  nsresult rv = GetThemePartAndState(aFrame, aAppearance, part, state);
+  if (NS_FAILED(rv)) return result;
+
+  if (aAppearance == StyleAppearance::Toolbar) {
+    // make space for the separator line above all toolbars but the first
+    if (state == 0) result.top = TB_SEPARATOR_HEIGHT;
+    return result;
+  }
+
+  result = GetCachedWidgetBorder(theme, themeClass.value(), aAppearance, part,
+                                 state);
+
+  // Remove the edges for tabs that are before or after the selected tab,
+  if (aAppearance == StyleAppearance::Tab) {
+    if (IsLeftToSelectedTab(aFrame))
+      // Remove the right edge, since we won't be drawing it.
+      result.right = 0;
+    else if (IsRightToSelectedTab(aFrame))
+      // Remove the left edge, since we won't be drawing it.
+      result.left = 0;
+  }
+
+  if (aFrame && (aAppearance == StyleAppearance::NumberInput ||
+                 aAppearance == StyleAppearance::Textfield ||
+                 aAppearance == StyleAppearance::Textarea)) {
+    nsIContent* content = aFrame->GetContent();
+    if (content && content->IsHTMLElement()) {
+      // We need to pad textfields by 1 pixel, since the caret will draw
+      // flush against the edge by default if we don't.
+      result.top.value++;
+      result.left.value++;
+      result.bottom.value++;
+      result.right.value++;
+    }
+  }
+
+  ScaleForFrameDPI(&result, aFrame);
+  return result;
+}
+
+bool nsNativeThemeWin::GetWidgetPadding(nsDeviceContext* aContext,
+                                        nsIFrame* aFrame,
+                                        StyleAppearance aAppearance,
+                                        LayoutDeviceIntMargin* aResult) {
+  if (IsWidgetAlwaysNonNative(aFrame, aAppearance)) {
+    return Theme::GetWidgetPadding(aContext, aFrame, aAppearance, aResult);
+  }
+
+  bool ok = true;
+  HANDLE theme = GetTheme(aAppearance);
+  if (!theme) {
+    ok = ClassicGetWidgetPadding(aContext, aFrame, aAppearance, aResult);
+    ScaleForFrameDPI(aResult, aFrame);
+    return ok;
+  }
+
+  /* textfields need extra pixels on all sides, otherwise they wrap their
+   * content too tightly.  The actual border is drawn 1px inside the specified
+   * rectangle, so Gecko will end up making the contents look too small.
+   * Instead, we add 2px padding for the contents and fix this. (Used to be 1px
+   * added, see bug 430212)
+   */
+  if (aAppearance == StyleAppearance::NumberInput ||
+      aAppearance == StyleAppearance::Textfield ||
+      aAppearance == StyleAppearance::Textarea) {
+    aResult->top = aResult->bottom = 2;
+    aResult->left = aResult->right = 2;
+    ScaleForFrameDPI(aResult, aFrame);
+    return ok;
+  } else if (IsHTMLContent(aFrame) &&
+             (aAppearance == StyleAppearance::Menulist ||
+              aAppearance == StyleAppearance::MenulistButton)) {
+    /* For content menulist controls, we need an extra pixel so that we have
+     * room to draw our focus rectangle stuff. Otherwise, the focus rect might
+     * overlap the control's border.
+     */
+    aResult->top = aResult->bottom = 1;
+    aResult->left = aResult->right = 1;
+    ScaleForFrameDPI(aResult, aFrame);
+    return ok;
+  }
+
+  int32_t right, left, top, bottom;
+  right = left = top = bottom = 0;
+  switch (aAppearance) {
+    case StyleAppearance::Button:
+      if (aFrame->GetContent()->IsXULElement()) {
+        top = 2;
+        bottom = 3;
+      }
+      left = right = 5;
+      break;
+    default:
+      return false;
+  }
+
+  if (IsFrameRTL(aFrame)) {
+    aResult->right = left;
+    aResult->left = right;
+  } else {
+    aResult->right = right;
+    aResult->left = left;
+  }
+  aResult->top = top;
+  aResult->bottom = bottom;
+
+  ScaleForFrameDPI(aResult, aFrame);
+  return ok;
+}
+
+bool nsNativeThemeWin::GetWidgetOverflow(nsDeviceContext* aContext,
+                                         nsIFrame* aFrame,
+                                         StyleAppearance aAppearance,
+                                         nsRect* aOverflowRect) {
+  if (IsWidgetNonNative(aFrame, aAppearance) != NonNative::No) {
+    return Theme::GetWidgetOverflow(aContext, aFrame, aAppearance,
+                                    aOverflowRect);
+  }
+
+  /* This is disabled for now, because it causes invalidation problems --
+   * see bug 420381.  The effect of not updating the overflow area is that
+   * for dropdown buttons in content areas, there is a 1px border on 3 sides
+   * where, if invalidated, the dropdown control probably won't be repainted.
+   * This is fairly minor, as by default there is nothing in that area, and
+   * a border only shows up if the widget is being hovered.
+   *
+   * TODO(jwatt): Figure out what do to about
+   * StyleAppearance::MozMenulistArrowButton too.
+   */
+#if 0
+  /* We explicitly draw dropdown buttons in HTML content 1px bigger up, right,
+   * and bottom so that they overlap the dropdown's border like they're
+   * supposed to.
+   */
+  if (aAppearance == StyleAppearance::MenulistButton &&
+      IsHTMLContent(aFrame) &&
+      !IsWidgetStyled(aFrame->GetParent()->PresContext(),
+                      aFrame->GetParent(),
+                      StyleAppearance::Menulist))
+  {
+    int32_t p2a = aContext->AppUnitsPerDevPixel();
+    /* Note: no overflow on the left */
+    nsMargin m(p2a, p2a, p2a, 0);
+    aOverflowRect->Inflate (m);
+    return true;
+  }
+#endif
+
+  return false;
+}
+
+LayoutDeviceIntSize nsNativeThemeWin::GetMinimumWidgetSize(
+    nsPresContext* aPresContext, nsIFrame* aFrame,
+    StyleAppearance aAppearance) {
+  if (IsWidgetAlwaysNonNative(aFrame, aAppearance)) {
+    return Theme::GetMinimumWidgetSize(aPresContext, aFrame, aAppearance);
+  }
+
+  mozilla::Maybe<nsUXThemeClass> themeClass = GetThemeClass(aAppearance);
+  HTHEME theme = NULL;
+  if (!themeClass.isNothing()) {
+    theme = nsUXThemeData::GetTheme(themeClass.value());
+  }
+  if (!theme) {
+    auto result = ClassicGetMinimumWidgetSize(aFrame, aAppearance);
+    ScaleForFrameDPI(&result, aFrame);
+    return result;
+  }
+
+  switch (aAppearance) {
+    case StyleAppearance::NumberInput:
+    case StyleAppearance::Textfield:
+    case StyleAppearance::Toolbox:
+    case StyleAppearance::Toolbar:
+    case StyleAppearance::Progresschunk:
+    case StyleAppearance::Tabpanels:
+    case StyleAppearance::Tabpanel:
+    case StyleAppearance::Listbox:
+    case StyleAppearance::Treeview:
+      return {};  // Don't worry about it.
+    default:
+      break;
+  }
+
+  // Call GetSystemMetrics to determine size for WinXP scrollbars
+  // (GetThemeSysSize API returns the optimal size for the theme, but
+  //  Windows appears to always use metrics when drawing standard scrollbars)
+  THEMESIZE sizeReq = TS_TRUE;  // Best-fit size
+  switch (aAppearance) {
+    case StyleAppearance::ProgressBar:
+      // Best-fit size for progress meters is too large for most
+      // themes. We want these widgets to be able to really shrink
+      // down, so use the min-size request value (of 0).
+      sizeReq = TS_MIN;
+      break;
+
+    case StyleAppearance::RangeThumb: {
+      LayoutDeviceIntSize result(12, 20);
+      if (!IsRangeHorizontal(aFrame)) {
+        std::swap(result.width, result.height);
+      }
+      ScaleForFrameDPI(&result, aFrame);
+      return result;
+    }
+
+    case StyleAppearance::Separator: {
+      // that's 2px left margin, 2px right margin and 2px separator
+      // (the margin is drawn as part of the separator, though)
+      LayoutDeviceIntSize result(6, 0);
+      ScaleForFrameDPI(&result, aFrame);
+      return result;
+    }
+
+    case StyleAppearance::Button:
+      // We should let HTML buttons shrink to their min size.
+      // FIXME bug 403934: We should probably really separate
+      // GetPreferredWidgetSize from GetMinimumWidgetSize, so callers can
+      // use the one they want.
+      if (aFrame->GetContent()->IsHTMLElement()) {
+        sizeReq = TS_MIN;
+      }
+      break;
+
+    default:
+      break;
+  }
+
+  int32_t part, state;
+  nsresult rv = GetThemePartAndState(aFrame, aAppearance, part, state);
+  if (NS_FAILED(rv)) {
+    return {};
+  }
+
+  LayoutDeviceIntSize result;
+  rv = GetCachedMinimumWidgetSize(aFrame, theme, themeClass.value(),
+                                  aAppearance, part, state, sizeReq, &result);
+  ScaleForFrameDPI(&result, aFrame);
+  return result;
+}
+
+NS_IMETHODIMP
+nsNativeThemeWin::WidgetStateChanged(nsIFrame* aFrame,
+                                     StyleAppearance aAppearance,
+                                     nsAtom* aAttribute, bool* aShouldRepaint,
+                                     const nsAttrValue* aOldValue) {
+  // Some widget types just never change state.
+  if (aAppearance == StyleAppearance::Toolbox ||
+      aAppearance == StyleAppearance::Toolbar ||
+      aAppearance == StyleAppearance::Progresschunk ||
+      aAppearance == StyleAppearance::ProgressBar ||
+      aAppearance == StyleAppearance::Tabpanels ||
+      aAppearance == StyleAppearance::Tabpanel ||
+      aAppearance == StyleAppearance::Separator) {
+    *aShouldRepaint = false;
+    return NS_OK;
+  }
+
+  // We need to repaint the dropdown arrow in vista HTML combobox controls when
+  // the control is closed to get rid of the hover effect.
+  if ((aAppearance == StyleAppearance::Menulist ||
+       aAppearance == StyleAppearance::MenulistButton) &&
+      nsNativeTheme::IsHTMLContent(aFrame)) {
+    *aShouldRepaint = true;
+    return NS_OK;
+  }
+
+  // XXXdwh Not sure what can really be done here.  Can at least guess for
+  // specific widgets that they're highly unlikely to have certain states.
+  // For example, a toolbar doesn't care about any states.
+  if (!aAttribute) {
+    // Hover/focus/active changed.  Always repaint.
+    *aShouldRepaint = true;
+  } else {
+    // Check the attribute to see if it's relevant.
+    // disabled, checked, dlgtype, default, etc.
+    *aShouldRepaint = false;
+    if (aAttribute == nsGkAtoms::disabled || aAttribute == nsGkAtoms::checked ||
+        aAttribute == nsGkAtoms::selected ||
+        aAttribute == nsGkAtoms::visuallyselected ||
+        aAttribute == nsGkAtoms::readonly || aAttribute == nsGkAtoms::open ||
+        aAttribute == nsGkAtoms::menuactive || aAttribute == nsGkAtoms::focused)
+      *aShouldRepaint = true;
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsNativeThemeWin::ThemeChanged() {
+  nsUXThemeData::Invalidate();
+  memset(mBorderCacheValid, 0, sizeof(mBorderCacheValid));
+  memset(mMinimumWidgetSizeCacheValid, 0, sizeof(mMinimumWidgetSizeCacheValid));
+  mGutterSizeCacheValid = false;
+  return NS_OK;
+}
+
+bool nsNativeThemeWin::ThemeSupportsWidget(nsPresContext* aPresContext,
+                                           nsIFrame* aFrame,
+                                           StyleAppearance aAppearance) {
+  // XXXdwh We can go even further and call the API to ask if support exists for
+  // specific widgets.
+
+  if (IsWidgetAlwaysNonNative(aFrame, aAppearance)) {
+    return Theme::ThemeSupportsWidget(aPresContext, aFrame, aAppearance);
+  }
+
+  HANDLE theme = GetTheme(aAppearance);
+  if (theme || ClassicThemeSupportsWidget(aFrame, aAppearance))
+    // turn off theming for some HTML widgets styled by the page
+    return !IsWidgetStyled(aPresContext, aFrame, aAppearance);
+
+  return false;
+}
+
+bool nsNativeThemeWin::ThemeDrawsFocusForWidget(nsIFrame* aFrame,
+                                                StyleAppearance aAppearance) {
+  if (IsWidgetNonNative(aFrame, aAppearance) != NonNative::No) {
+    return Theme::ThemeDrawsFocusForWidget(aFrame, aAppearance);
+  }
+  switch (aAppearance) {
+    case StyleAppearance::Menulist:
+    case StyleAppearance::MenulistButton:
+    case StyleAppearance::Textarea:
+    case StyleAppearance::Textfield:
+    case StyleAppearance::NumberInput:
+      return true;
+    default:
+      return false;
+  }
+}
+
+bool nsNativeThemeWin::ThemeNeedsComboboxDropmarker() { return true; }
+
+nsITheme::Transparency nsNativeThemeWin::GetWidgetTransparency(
+    nsIFrame* aFrame, StyleAppearance aAppearance) {
+  if (IsWidgetNonNative(aFrame, aAppearance) != NonNative::No) {
+    return Theme::GetWidgetTransparency(aFrame, aAppearance);
+  }
+
+  switch (aAppearance) {
+    case StyleAppearance::ProgressBar:
+    case StyleAppearance::Progresschunk:
+    case StyleAppearance::Range:
+      return eTransparent;
+    default:
+      break;
+  }
+
+  HANDLE theme = GetTheme(aAppearance);
+  // For the classic theme we don't really have a way of knowing
+  if (!theme) {
+    return eUnknownTransparency;
+  }
+
+  int32_t part, state;
+  nsresult rv = GetThemePartAndState(aFrame, aAppearance, part, state);
+  // Fail conservatively
+  NS_ENSURE_SUCCESS(rv, eUnknownTransparency);
+
+  if (part <= 0) {
+    // Not a real part code, so IsThemeBackgroundPartiallyTransparent may
+    // not work, so don't call it.
+    return eUnknownTransparency;
+  }
+
+  if (IsThemeBackgroundPartiallyTransparent(theme, part, state))
+    return eTransparent;
+  return eOpaque;
+}
+
+/* Windows 9x/NT/2000/Classic XP Theme Support */
+
+bool nsNativeThemeWin::ClassicThemeSupportsWidget(nsIFrame* aFrame,
+                                                  StyleAppearance aAppearance) {
+  switch (aAppearance) {
+    case StyleAppearance::Button:
+    case StyleAppearance::NumberInput:
+    case StyleAppearance::Textfield:
+    case StyleAppearance::Textarea:
+    case StyleAppearance::Range:
+    case StyleAppearance::RangeThumb:
+    case StyleAppearance::Menulist:
+    case StyleAppearance::MenulistButton:
+    case StyleAppearance::Listbox:
+    case StyleAppearance::Treeview:
+    case StyleAppearance::ProgressBar:
+    case StyleAppearance::Progresschunk:
+    case StyleAppearance::Tab:
+    case StyleAppearance::Tabpanel:
+    case StyleAppearance::Tabpanels:
+      return true;
+    default:
+      return false;
+  }
+}
+
+LayoutDeviceIntMargin nsNativeThemeWin::ClassicGetWidgetBorder(
+    nsDeviceContext* aContext, nsIFrame* aFrame, StyleAppearance aAppearance) {
+  LayoutDeviceIntMargin result;
+  switch (aAppearance) {
+    case StyleAppearance::Button:
+      result.top = result.left = result.bottom = result.right = 2;
+      break;
+    case StyleAppearance::Listbox:
+    case StyleAppearance::Treeview:
+    case StyleAppearance::Menulist:
+    case StyleAppearance::MenulistButton:
+    case StyleAppearance::Tab:
+    case StyleAppearance::NumberInput:
+    case StyleAppearance::Textfield:
+    case StyleAppearance::Textarea:
+      result.top = result.left = result.bottom = result.right = 2;
+      break;
+    case StyleAppearance::ProgressBar:
+      result.top = result.left = result.bottom = result.right = 1;
+      break;
+    default:
+      result.top = result.bottom = result.left = result.right = 0;
+      break;
+  }
+  return result;
+}
+
+bool nsNativeThemeWin::ClassicGetWidgetPadding(nsDeviceContext* aContext,
+                                               nsIFrame* aFrame,
+                                               StyleAppearance aAppearance,
+                                               LayoutDeviceIntMargin* aResult) {
+  switch (aAppearance) {
+    case StyleAppearance::ProgressBar:
+      (*aResult).top = (*aResult).left = (*aResult).bottom = (*aResult).right =
+          1;
+      return true;
+    default:
+      return false;
+  }
+}
+
+LayoutDeviceIntSize nsNativeThemeWin::ClassicGetMinimumWidgetSize(
+    nsIFrame* aFrame, StyleAppearance aAppearance) {
+  LayoutDeviceIntSize result;
+  switch (aAppearance) {
+    case StyleAppearance::RangeThumb: {
+      if (IsRangeHorizontal(aFrame)) {
+        result.width = 12;
+        result.height = 20;
+      } else {
+        result.width = 20;
+        result.height = 12;
+      }
+      break;
+    }
+    case StyleAppearance::Menulist:
+    case StyleAppearance::MenulistButton:
+    case StyleAppearance::Button:
+    case StyleAppearance::Listbox:
+    case StyleAppearance::Treeview:
+    case StyleAppearance::NumberInput:
+    case StyleAppearance::Textfield:
+    case StyleAppearance::Textarea:
+    case StyleAppearance::Progresschunk:
+    case StyleAppearance::ProgressBar:
+    case StyleAppearance::Tab:
+    case StyleAppearance::Tabpanel:
+    case StyleAppearance::Tabpanels:
+      // no minimum widget size
+      break;
+
+    default:
+      break;
+  }
+  return result;
+}
+
+nsresult nsNativeThemeWin::ClassicGetThemePartAndState(
+    nsIFrame* aFrame, StyleAppearance aAppearance, int32_t& aPart,
+    int32_t& aState, bool& aFocused) {
+  aFocused = false;
+  switch (aAppearance) {
+    case StyleAppearance::Button: {
+      aPart = DFC_BUTTON;
+      aState = DFCS_BUTTONPUSH;
+      aFocused = false;
+
+      ElementState contentState = GetContentState(aFrame, aAppearance);
+      if (contentState.HasState(ElementState::DISABLED)) {
+        aState |= DFCS_INACTIVE;
+      } else if (IsOpenButton(aFrame)) {
+        aState |= DFCS_PUSHED;
+      } else if (IsCheckedButton(aFrame)) {
+        aState |= DFCS_CHECKED;
+      } else {
+        if (contentState.HasAllStates(ElementState::ACTIVE |
+                                      ElementState::HOVER)) {
+          aState |= DFCS_PUSHED;
+          // The down state is flat if the button is focusable
+          if (aFrame->StyleUI()->UserFocus() == StyleUserFocus::Normal) {
+            if (!aFrame->GetContent()->IsHTMLElement()) aState |= DFCS_FLAT;
+
+            aFocused = true;
+          }
+        }
+        // On Windows, focused buttons are always drawn as such by the native
+        // theme, that's why we check ElementState::FOCUS instead of
+        // ElementState::FOCUSRING.
+        if (contentState.HasState(ElementState::FOCUS) ||
+            (aState == DFCS_BUTTONPUSH && IsDefaultButton(aFrame))) {
+          aFocused = true;
+        }
+      }
+
+      return NS_OK;
+    }
+    case StyleAppearance::Listbox:
+    case StyleAppearance::Treeview:
+    case StyleAppearance::NumberInput:
+    case StyleAppearance::Textfield:
+    case StyleAppearance::Textarea:
+    case StyleAppearance::Menulist:
+    case StyleAppearance::MenulistButton:
+    case StyleAppearance::Range:
+    case StyleAppearance::RangeThumb:
+    case StyleAppearance::Progresschunk:
+    case StyleAppearance::ProgressBar:
+    case StyleAppearance::Tab:
+    case StyleAppearance::Tabpanel:
+    case StyleAppearance::Tabpanels:
+      // these don't use DrawFrameControl
+      return NS_OK;
+    default:
+      return NS_ERROR_FAILURE;
+  }
+}
+
+// Draw classic Windows tab
+// (no system API for this, but DrawEdge can draw all the parts of a tab)
+static void DrawTab(HDC hdc, const RECT& R, int32_t aPosition, bool aSelected,
+                    bool aDrawLeft, bool aDrawRight) {
+  int32_t leftFlag, topFlag, rightFlag, lightFlag, shadeFlag;
+  RECT topRect, sideRect, bottomRect, lightRect, shadeRect;
+  int32_t selectedOffset, lOffset, rOffset;
+
+  selectedOffset = aSelected ? 1 : 0;
+  lOffset = aDrawLeft ? 2 : 0;
+  rOffset = aDrawRight ? 2 : 0;
+
+  // Get info for tab orientation/position (Left, Top, Right, Bottom)
+  switch (aPosition) {
+    case BF_LEFT:
+      leftFlag = BF_TOP;
+      topFlag = BF_LEFT;
+      rightFlag = BF_BOTTOM;
+      lightFlag = BF_DIAGONAL_ENDTOPRIGHT;
+      shadeFlag = BF_DIAGONAL_ENDBOTTOMRIGHT;
+
+      ::SetRect(&topRect, R.left, R.top + lOffset, R.right, R.bottom - rOffset);
+      ::SetRect(&sideRect, R.left + 2, R.top, R.right - 2 + selectedOffset,
+                R.bottom);
+      ::SetRect(&bottomRect, R.right - 2, R.top, R.right, R.bottom);
+      ::SetRect(&lightRect, R.left, R.top, R.left + 3, R.top + 3);
+      ::SetRect(&shadeRect, R.left + 1, R.bottom - 2, R.left + 2, R.bottom - 1);
+      break;
+    case BF_TOP:
+      leftFlag = BF_LEFT;
+      topFlag = BF_TOP;
+      rightFlag = BF_RIGHT;
+      lightFlag = BF_DIAGONAL_ENDTOPRIGHT;
+      shadeFlag = BF_DIAGONAL_ENDBOTTOMRIGHT;
+
+      ::SetRect(&topRect, R.left + lOffset, R.top, R.right - rOffset, R.bottom);
+      ::SetRect(&sideRect, R.left, R.top + 2, R.right,
+                R.bottom - 1 + selectedOffset);
+      ::SetRect(&bottomRect, R.left, R.bottom - 1, R.right, R.bottom);
+      ::SetRect(&lightRect, R.left, R.top, R.left + 3, R.top + 3);
+      ::SetRect(&shadeRect, R.right - 2, R.top + 1, R.right - 1, R.top + 2);
+      break;
+    case BF_RIGHT:
+      leftFlag = BF_TOP;
+      topFlag = BF_RIGHT;
+      rightFlag = BF_BOTTOM;
+      lightFlag = BF_DIAGONAL_ENDTOPLEFT;
+      shadeFlag = BF_DIAGONAL_ENDBOTTOMLEFT;
+
+      ::SetRect(&topRect, R.left, R.top + lOffset, R.right, R.bottom - rOffset);
+      ::SetRect(&sideRect, R.left + 2 - selectedOffset, R.top, R.right - 2,
+                R.bottom);
+      ::SetRect(&bottomRect, R.left, R.top, R.left + 2, R.bottom);
+      ::SetRect(&lightRect, R.right - 3, R.top, R.right - 1, R.top + 2);
+      ::SetRect(&shadeRect, R.right - 2, R.bottom - 3, R.right, R.bottom - 1);
+      break;
+    case BF_BOTTOM:
+      leftFlag = BF_LEFT;
+      topFlag = BF_BOTTOM;
+      rightFlag = BF_RIGHT;
+      lightFlag = BF_DIAGONAL_ENDTOPLEFT;
+      shadeFlag = BF_DIAGONAL_ENDBOTTOMLEFT;
+
+      ::SetRect(&topRect, R.left + lOffset, R.top, R.right - rOffset, R.bottom);
+      ::SetRect(&sideRect, R.left, R.top + 2 - selectedOffset, R.right,
+                R.bottom - 2);
+      ::SetRect(&bottomRect, R.left, R.top, R.right, R.top + 2);
+      ::SetRect(&lightRect, R.left, R.bottom - 3, R.left + 2, R.bottom - 1);
+      ::SetRect(&shadeRect, R.right - 2, R.bottom - 3, R.right, R.bottom - 1);
+      break;
+    default:
+      MOZ_CRASH();
+  }
+
+  // Background
+  ::FillRect(hdc, &R, (HBRUSH)(COLOR_3DFACE + 1));
+
+  // Tab "Top"
+  ::DrawEdge(hdc, &topRect, EDGE_RAISED, BF_SOFT | topFlag);
+
+  // Tab "Bottom"
+  if (!aSelected) ::DrawEdge(hdc, &bottomRect, EDGE_RAISED, BF_SOFT | topFlag);
+
+  // Tab "Sides"
+  if (!aDrawLeft) leftFlag = 0;
+  if (!aDrawRight) rightFlag = 0;
+  ::DrawEdge(hdc, &sideRect, EDGE_RAISED, BF_SOFT | leftFlag | rightFlag);
+
+  // Tab Diagonal Corners
+  if (aDrawLeft) ::DrawEdge(hdc, &lightRect, EDGE_RAISED, BF_SOFT | lightFlag);
+
+  if (aDrawRight) ::DrawEdge(hdc, &shadeRect, EDGE_RAISED, BF_SOFT | shadeFlag);
+}
+
+void nsNativeThemeWin::DrawCheckedRect(HDC hdc, const RECT& rc, int32_t fore,
+                                       int32_t back, HBRUSH defaultBack) {
+  static WORD patBits[8] = {0xaa, 0x55, 0xaa, 0x55, 0xaa, 0x55, 0xaa, 0x55};
+
+  HBITMAP patBmp = ::CreateBitmap(8, 8, 1, 1, patBits);
+  if (patBmp) {
+    HBRUSH brush = (HBRUSH)::CreatePatternBrush(patBmp);
+    if (brush) {
+      COLORREF oldForeColor = ::SetTextColor(hdc, ::GetSysColor(fore));
+      COLORREF oldBackColor = ::SetBkColor(hdc, ::GetSysColor(back));
+      POINT vpOrg;
+
+      ::UnrealizeObject(brush);
+      ::GetViewportOrgEx(hdc, &vpOrg);
+      ::SetBrushOrgEx(hdc, vpOrg.x + rc.left, vpOrg.y + rc.top, nullptr);
+      HBRUSH oldBrush = (HBRUSH)::SelectObject(hdc, brush);
+      ::FillRect(hdc, &rc, brush);
+      ::SetTextColor(hdc, oldForeColor);
+      ::SetBkColor(hdc, oldBackColor);
+      ::SelectObject(hdc, oldBrush);
+      ::DeleteObject(brush);
+    } else
+      ::FillRect(hdc, &rc, defaultBack);
+
+    ::DeleteObject(patBmp);
+  }
+}
+
+nsresult nsNativeThemeWin::ClassicDrawWidgetBackground(
+    gfxContext* aContext, nsIFrame* aFrame, StyleAppearance aAppearance,
+    const nsRect& aRect, const nsRect& aDirtyRect) {
+  int32_t part, state;
+  bool focused;
+  nsresult rv;
+  rv = ClassicGetThemePartAndState(aFrame, aAppearance, part, state, focused);
+  if (NS_FAILED(rv)) return rv;
+
+  if (AssumeThemePartAndStateAreTransparent(part, state)) {
+    return NS_OK;
+  }
+
+  gfxFloat p2a = gfxFloat(aFrame->PresContext()->AppUnitsPerDevPixel());
+  RECT widgetRect;
+  gfxRect tr(aRect.X(), aRect.Y(), aRect.Width(), aRect.Height()),
+      dr(aDirtyRect.X(), aDirtyRect.Y(), aDirtyRect.Width(),
+         aDirtyRect.Height());
+
+  tr.Scale(1.0 / p2a);
+  dr.Scale(1.0 / p2a);
+
+  gfxWindowsNativeDrawing nativeDrawing(
+      aContext, dr, GetWidgetNativeDrawingFlags(aAppearance));
+
+RENDER_AGAIN:
+
+  HDC hdc = nativeDrawing.BeginNativeDrawing();
+  if (!hdc) return NS_ERROR_FAILURE;
+
+  nativeDrawing.TransformToNativeRect(tr, widgetRect);
+
+  rv = NS_OK;
+  switch (aAppearance) {
+    // Draw button
+    case StyleAppearance::Button: {
+      if (focused) {
+        // draw dark button focus border first
+        if (HBRUSH brush = ::GetSysColorBrush(COLOR_3DDKSHADOW)) {
+          ::FrameRect(hdc, &widgetRect, brush);
+        }
+        InflateRect(&widgetRect, -1, -1);
+      }
+      // setup DC to make DrawFrameControl draw correctly
+      int32_t oldTA = ::SetTextAlign(hdc, TA_TOP | TA_LEFT | TA_NOUPDATECP);
+      ::DrawFrameControl(hdc, &widgetRect, part, state);
+      ::SetTextAlign(hdc, oldTA);
+      break;
+    }
+    // Draw controls with 2px 3D inset border
+    case StyleAppearance::NumberInput:
+    case StyleAppearance::Textfield:
+    case StyleAppearance::Textarea:
+    case StyleAppearance::Listbox:
+    case StyleAppearance::Menulist:
+    case StyleAppearance::MenulistButton: {
+      // Draw inset edge
+      ::DrawEdge(hdc, &widgetRect, EDGE_SUNKEN, BF_RECT | BF_ADJUST);
+
+      ElementState elementState = GetContentState(aFrame, aAppearance);
+
+      // Fill in background
+
+      if (elementState.HasState(ElementState::DISABLED) ||
+          (aFrame->GetContent()->IsXULElement() && IsReadOnly(aFrame)))
+        ::FillRect(hdc, &widgetRect, (HBRUSH)(COLOR_BTNFACE + 1));
+      else
+        ::FillRect(hdc, &widgetRect, (HBRUSH)(COLOR_WINDOW + 1));
+
+      break;
+    }
+    case StyleAppearance::Treeview: {
+      // Draw inset edge
+      ::DrawEdge(hdc, &widgetRect, EDGE_SUNKEN, BF_RECT | BF_ADJUST);
+
+      // Fill in window color background
+      ::FillRect(hdc, &widgetRect, (HBRUSH)(COLOR_WINDOW + 1));
+
+      break;
+    }
+    // Draw 3D face background controls
+    case StyleAppearance::ProgressBar:
+      // Draw 3D border
+      ::DrawEdge(hdc, &widgetRect, BDR_SUNKENOUTER, BF_RECT | BF_MIDDLE);
+      InflateRect(&widgetRect, -1, -1);
+      [[fallthrough]];
+    case StyleAppearance::Tabpanel: {
+      ::FillRect(hdc, &widgetRect, (HBRUSH)(COLOR_BTNFACE + 1));
+      break;
+    }
+    case StyleAppearance::RangeThumb: {
+      ElementState elementState = GetContentState(aFrame, aAppearance);
+
+      ::DrawEdge(hdc, &widgetRect, EDGE_RAISED,
+                 BF_RECT | BF_SOFT | BF_MIDDLE | BF_ADJUST);
+      if (elementState.HasState(ElementState::DISABLED)) {
+        DrawCheckedRect(hdc, widgetRect, COLOR_3DFACE, COLOR_3DHILIGHT,
+                        (HBRUSH)COLOR_3DHILIGHT);
+      }
+
+      break;
+    }
+    // Draw scale track background
+    case StyleAppearance::Range: {
+      const int32_t trackWidth = 4;
+      // When rounding is necessary, we round the position of the track
+      // away from the chevron of the thumb to make it look better.
+      if (IsRangeHorizontal(aFrame)) {
+        widgetRect.top += (widgetRect.bottom - widgetRect.top - trackWidth) / 2;
+        widgetRect.bottom = widgetRect.top + trackWidth;
+      } else {
+        if (!IsFrameRTL(aFrame)) {
+          widgetRect.left +=
+              (widgetRect.right - widgetRect.left - trackWidth) / 2;
+          widgetRect.right = widgetRect.left + trackWidth;
+        } else {
+          widgetRect.right -=
+              (widgetRect.right - widgetRect.left - trackWidth) / 2;
+          widgetRect.left = widgetRect.right - trackWidth;
+        }
+      }
+
+      ::DrawEdge(hdc, &widgetRect, EDGE_SUNKEN, BF_RECT | BF_ADJUST);
+      ::FillRect(hdc, &widgetRect, (HBRUSH)GetStockObject(GRAY_BRUSH));
+
+      break;
+    }
+    case StyleAppearance::Progresschunk: {
+      nsIFrame* stateFrame = aFrame->GetParent();
+      ElementState elementState = GetContentState(stateFrame, aAppearance);
+
+      const bool indeterminate =
+          elementState.HasState(ElementState::INDETERMINATE);
+      bool vertical = IsVerticalProgress(stateFrame);
+
+      nsIContent* content = aFrame->GetContent();
+      if (!indeterminate || !content) {
+        ::FillRect(hdc, &widgetRect, (HBRUSH)(COLOR_HIGHLIGHT + 1));
+        break;
+      }
+
+      RECT overlayRect = CalculateProgressOverlayRect(
+          aFrame, &widgetRect, vertical, indeterminate, true);
+
+      ::FillRect(hdc, &overlayRect, (HBRUSH)(COLOR_HIGHLIGHT + 1));
+
+      if (!QueueAnimatedContentForRefresh(aFrame->GetContent(), 30)) {
+        NS_WARNING("unable to animate progress widget!");
+      }
+      break;
+    }
+
+    // Draw Tab
+    case StyleAppearance::Tab: {
+      DrawTab(hdc, widgetRect, IsBottomTab(aFrame) ? BF_BOTTOM : BF_TOP,
+              IsSelectedTab(aFrame), !IsRightToSelectedTab(aFrame),
+              !IsLeftToSelectedTab(aFrame));
+
+      break;
+    }
+    case StyleAppearance::Tabpanels:
+      ::DrawEdge(hdc, &widgetRect, EDGE_RAISED,
+                 BF_SOFT | BF_MIDDLE | BF_LEFT | BF_RIGHT | BF_BOTTOM);
+
+      break;
+
+    default:
+      rv = NS_ERROR_FAILURE;
+      break;
+  }
+
+  nativeDrawing.EndNativeDrawing();
+
+  if (NS_FAILED(rv)) return rv;
+
+  if (nativeDrawing.ShouldRenderAgain()) goto RENDER_AGAIN;
+
+  nativeDrawing.PaintToContext();
+
+  return rv;
+}
+
+uint32_t nsNativeThemeWin::GetWidgetNativeDrawingFlags(
+    StyleAppearance aAppearance) {
+  switch (aAppearance) {
+    case StyleAppearance::Button:
+    case StyleAppearance::NumberInput:
+    case StyleAppearance::Textfield:
+    case StyleAppearance::Textarea:
+    case StyleAppearance::Menulist:
+    case StyleAppearance::MenulistButton:
+      return gfxWindowsNativeDrawing::CANNOT_DRAW_TO_COLOR_ALPHA |
+             gfxWindowsNativeDrawing::CAN_AXIS_ALIGNED_SCALE |
+             gfxWindowsNativeDrawing::CANNOT_COMPLEX_TRANSFORM;
+
+    // need to check these others
+    default:
+      return gfxWindowsNativeDrawing::CANNOT_DRAW_TO_COLOR_ALPHA |
+             gfxWindowsNativeDrawing::CANNOT_AXIS_ALIGNED_SCALE |
+             gfxWindowsNativeDrawing::CANNOT_COMPLEX_TRANSFORM;
+  }
+}
+
+}  // namespace mozilla::widget
+
+///////////////////////////////////////////
+// Creation Routine
+///////////////////////////////////////////
+
+already_AddRefed<Theme> do_CreateNativeThemeDoNotUseDirectly() {
+  return do_AddRef(new nsNativeThemeWin());
+}
diff --git a/widget/windows/nsNativeThemeWin.h b/widget/windows/nsNativeThemeWin.h
new file mode 100644
index 0000000000..9937018197
--- /dev/null
+++ b/widget/windows/nsNativeThemeWin.h
@@ -0,0 +1,166 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef nsNativeThemeWin_h
+#define nsNativeThemeWin_h
+
+#include <windows.h>
+
+#include "mozilla/Maybe.h"
+#include "mozilla/TimeStamp.h"
+#include "Theme.h"
+#include "nsUXThemeConstants.h"
+#include "nsUXThemeData.h"
+
+namespace mozilla::widget {
+
+class nsNativeThemeWin : public Theme {
+ protected:
+  virtual ~nsNativeThemeWin();
+
+ public:
+  // Whether we draw a non-native widget.
+  //
+  // We always draw scrollbars as non-native so that all of Firefox has
+  // consistent scrollbar styles both in chrome and content (plus, the
+  // non-native scrollbars support scrollbar-width, auto-darkening...).
+  //
+  // We draw other widgets as non-native when their color-scheme is dark.  In
+  // that case (`BecauseColorMismatch`) we don't call into the non-native theme
+  // for sizing information (GetWidgetPadding/Border and GetMinimumWidgetSize),
+  // to avoid subtle sizing changes. The non-native theme can basically draw at
+  // any size, so we prefer to have consistent sizing information.
+  enum class NonNative { No, Always, BecauseColorMismatch };
+  static bool IsWidgetAlwaysNonNative(nsIFrame*, StyleAppearance);
+  NonNative IsWidgetNonNative(nsIFrame*, StyleAppearance);
+
+  // The nsITheme interface.
+  NS_IMETHOD DrawWidgetBackground(gfxContext* aContext, nsIFrame* aFrame,
+                                  StyleAppearance aAppearance,
+                                  const nsRect& aRect, const nsRect& aDirtyRect,
+                                  DrawOverflow) override;
+
+  bool CreateWebRenderCommandsForWidget(wr::DisplayListBuilder&,
+                                        wr::IpcResourceUpdateQueue&,
+                                        const layers::StackingContextHelper&,
+                                        layers::RenderRootStateManager*,
+                                        nsIFrame*, StyleAppearance,
+                                        const nsRect&) override;
+
+  [[nodiscard]] LayoutDeviceIntMargin GetWidgetBorder(
+      nsDeviceContext* aContext, nsIFrame* aFrame,
+      StyleAppearance aAppearance) override;
+
+  bool GetWidgetPadding(nsDeviceContext* aContext, nsIFrame* aFrame,
+                        StyleAppearance aAppearance,
+                        LayoutDeviceIntMargin* aResult) override;
+
+  virtual bool GetWidgetOverflow(nsDeviceContext* aContext, nsIFrame* aFrame,
+                                 StyleAppearance aAppearance,
+                                 nsRect* aOverflowRect) override;
+
+  LayoutDeviceIntSize GetMinimumWidgetSize(
+      nsPresContext* aPresContext, nsIFrame* aFrame,
+      StyleAppearance aAppearance) override;
+
+  virtual Transparency GetWidgetTransparency(
+      nsIFrame* aFrame, StyleAppearance aAppearance) override;
+
+  NS_IMETHOD WidgetStateChanged(nsIFrame* aFrame, StyleAppearance aAppearance,
+                                nsAtom* aAttribute, bool* aShouldRepaint,
+                                const nsAttrValue* aOldValue) override;
+
+  NS_IMETHOD ThemeChanged() override;
+
+  bool ThemeSupportsWidget(nsPresContext* aPresContext, nsIFrame* aFrame,
+                           StyleAppearance aAppearance) override;
+
+  bool ThemeDrawsFocusForWidget(nsIFrame*, StyleAppearance) override;
+
+  bool ThemeWantsButtonInnerFocusRing() override { return true; }
+
+  bool ThemeNeedsComboboxDropmarker() override;
+
+  nsNativeThemeWin();
+
+ protected:
+  Maybe<nsUXThemeClass> GetThemeClass(StyleAppearance aAppearance);
+  HANDLE GetTheme(StyleAppearance aAppearance);
+  nsresult GetThemePartAndState(nsIFrame* aFrame, StyleAppearance aAppearance,
+                                int32_t& aPart, int32_t& aState);
+  nsresult ClassicGetThemePartAndState(nsIFrame* aFrame,
+                                       StyleAppearance aAppearance,
+                                       int32_t& aPart, int32_t& aState,
+                                       bool& aFocused);
+  nsresult ClassicDrawWidgetBackground(gfxContext* aContext, nsIFrame* aFrame,
+                                       StyleAppearance aAppearance,
+                                       const nsRect& aRect,
+                                       const nsRect& aClipRect);
+  [[nodiscard]] LayoutDeviceIntMargin ClassicGetWidgetBorder(
+      nsDeviceContext* aContext, nsIFrame* aFrame, StyleAppearance aAppearance);
+  bool ClassicGetWidgetPadding(nsDeviceContext* aContext, nsIFrame* aFrame,
+                               StyleAppearance aAppearance,
+                               LayoutDeviceIntMargin* aResult);
+  LayoutDeviceIntSize ClassicGetMinimumWidgetSize(nsIFrame* aFrame,
+                                                  StyleAppearance aAppearance);
+  bool ClassicThemeSupportsWidget(nsIFrame* aFrame,
+                                  StyleAppearance aAppearance);
+  void DrawCheckedRect(HDC hdc, const RECT& rc, int32_t fore, int32_t back,
+                       HBRUSH defaultBack);
+  uint32_t GetWidgetNativeDrawingFlags(StyleAppearance aAppearance);
+  int32_t StandardGetState(nsIFrame* aFrame, StyleAppearance aAppearance,
+                           bool wantFocused);
+  bool IsMenuActive(nsIFrame* aFrame, StyleAppearance aAppearance);
+  RECT CalculateProgressOverlayRect(nsIFrame* aFrame, RECT* aWidgetRect,
+                                    bool aIsVertical, bool aIsIndeterminate,
+                                    bool aIsClassic);
+  void DrawThemedProgressMeter(nsIFrame* aFrame, StyleAppearance aAppearance,
+                               HANDLE aTheme, HDC aHdc, int aPart, int aState,
+                               RECT* aWidgetRect, RECT* aClipRect);
+
+  [[nodiscard]] LayoutDeviceIntMargin GetCachedWidgetBorder(
+      HANDLE aTheme, nsUXThemeClass aThemeClass, StyleAppearance aAppearance,
+      int32_t aPart, int32_t aState);
+
+  nsresult GetCachedMinimumWidgetSize(nsIFrame* aFrame, HANDLE aTheme,
+                                      nsUXThemeClass aThemeClass,
+                                      StyleAppearance aAppearance,
+                                      int32_t aPart, int32_t aState,
+                                      THEMESIZE aSizeReq,
+                                      LayoutDeviceIntSize* aResult);
+
+  SIZE GetCachedGutterSize(HANDLE theme);
+
+ private:
+  TimeStamp mProgressDeterminateTimeStamp;
+  TimeStamp mProgressIndeterminateTimeStamp;
+
+  // eUXNumClasses * THEME_PART_DISTINCT_VALUE_COUNT is about 800 at the time of
+  // writing this, and nsIntMargin is 16 bytes wide, which makes this cache (1/8
+  // + 16) * 800 bytes, or about ~12KB. We could probably reduce this cache to
+  // 3KB by caching on the aAppearance value instead, but there would be some
+  // uncacheable values, since we derive some theme parts from other arguments.
+  uint8_t
+      mBorderCacheValid[(eUXNumClasses * THEME_PART_DISTINCT_VALUE_COUNT + 7) /
+                        8];
+  LayoutDeviceIntMargin
+      mBorderCache[eUXNumClasses * THEME_PART_DISTINCT_VALUE_COUNT];
+
+  // See the above not for mBorderCache and friends. However
+  // LayoutDeviceIntSize is half the size of nsIntMargin, making the
+  // cache roughly half as large. In total the caches should come to about 18KB.
+  uint8_t mMinimumWidgetSizeCacheValid
+      [(eUXNumClasses * THEME_PART_DISTINCT_VALUE_COUNT + 7) / 8];
+  LayoutDeviceIntSize
+      mMinimumWidgetSizeCache[eUXNumClasses * THEME_PART_DISTINCT_VALUE_COUNT];
+
+  bool mGutterSizeCacheValid;
+  SIZE mGutterSizeCache;
+};
+
+}  // namespace mozilla::widget
+
+#endif
diff --git a/widget/windows/nsPrintDialogUtil.cpp b/widget/windows/nsPrintDialogUtil.cpp
new file mode 100644
index 0000000000..43f56e9706
--- /dev/null
+++ b/widget/windows/nsPrintDialogUtil.cpp
@@ -0,0 +1,360 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* -------------------------------------------------------------------
+To Build This:
+
+  You need to add this to the the makefile.win in mozilla/dom/base:
+
+        .\$(OBJDIR)\nsFlyOwnPrintDialog.obj	\
+
+
+  And this to the makefile.win in mozilla/content/build:
+
+WIN_LIBS=                                       \
+        winspool.lib                           \
+        comctl32.lib                           \
+        comdlg32.lib
+
+---------------------------------------------------------------------- */
+
+#include <windows.h>
+#include <tchar.h>
+
+#include <unknwn.h>
+#include <commdlg.h>
+
+#include "mozilla/BackgroundHangMonitor.h"
+#include "mozilla/ScopeExit.h"
+#include "mozilla/Span.h"
+#include "nsString.h"
+#include "nsReadableUtils.h"
+#include "nsIPrintSettings.h"
+#include "nsIPrintSettingsWin.h"
+#include "nsIPrinterList.h"
+#include "nsServiceManagerUtils.h"
+
+#include "nsRect.h"
+
+#include "nsCRT.h"
+#include "prenv.h" /* for PR_GetEnv */
+
+#include <windows.h>
+#include <winspool.h>
+
+// For Localization
+
+// For NS_CopyUnicodeToNative
+#include "nsNativeCharsetUtils.h"
+
+// This is for extending the dialog
+#include <dlgs.h>
+
+#include "nsWindowsHelpers.h"
+#include "WinUtils.h"
+
+//-----------------------------------------------
+// Global Data
+//-----------------------------------------------
+
+static HWND gParentWnd = nullptr;
+
+//----------------------------------------------------------------------------------
+// Returns a Global Moveable Memory Handle to a DevMode
+// from the Printer by the name of aPrintName
+//
+// NOTE:
+//   This function assumes that aPrintName has already been converted from
+//   unicode
+//
+static nsReturnRef<nsHGLOBAL> CreateGlobalDevModeAndInit(
+    const nsString& aPrintName, nsIPrintSettings* aPS) {
+  nsHPRINTER hPrinter = nullptr;
+  // const cast kludge for silly Win32 api's
+  LPWSTR printName =
+      const_cast<wchar_t*>(static_cast<const wchar_t*>(aPrintName.get()));
+  BOOL status = ::OpenPrinterW(printName, &hPrinter, nullptr);
+  if (!status) {
+    return nsReturnRef<nsHGLOBAL>();
+  }
+
+  // Make sure hPrinter is closed on all paths
+  nsAutoPrinter autoPrinter(hPrinter);
+
+  // Get the buffer size
+  LONG needed = ::DocumentPropertiesW(gParentWnd, hPrinter, printName, nullptr,
+                                      nullptr, 0);
+  if (needed < 0) {
+    return nsReturnRef<nsHGLOBAL>();
+  }
+
+  // Some drivers do not return the correct size for their DEVMODE, so we
+  // over-allocate to try and compensate.
+  // (See https://bugzilla.mozilla.org/show_bug.cgi?id=1664530#c5)
+  needed *= 2;
+  nsAutoDevMode newDevMode(
+      (LPDEVMODEW)::HeapAlloc(::GetProcessHeap(), HEAP_ZERO_MEMORY, needed));
+  if (!newDevMode) {
+    return nsReturnRef<nsHGLOBAL>();
+  }
+
+  nsHGLOBAL hDevMode = ::GlobalAlloc(GHND, needed);
+  nsAutoGlobalMem globalDevMode(hDevMode);
+  if (!hDevMode) {
+    return nsReturnRef<nsHGLOBAL>();
+  }
+
+  LONG ret = ::DocumentPropertiesW(gParentWnd, hPrinter, printName, newDevMode,
+                                   nullptr, DM_OUT_BUFFER);
+  if (ret != IDOK) {
+    return nsReturnRef<nsHGLOBAL>();
+  }
+
+  // Lock memory and copy contents from DEVMODE (current printer)
+  // to Global Memory DEVMODE
+  LPDEVMODEW devMode = (DEVMODEW*)::GlobalLock(hDevMode);
+  if (!devMode) {
+    return nsReturnRef<nsHGLOBAL>();
+  }
+
+  memcpy(devMode, newDevMode.get(), needed);
+  // Initialize values from the PrintSettings
+  nsCOMPtr<nsIPrintSettingsWin> psWin = do_QueryInterface(aPS);
+  MOZ_ASSERT(psWin);
+  psWin->CopyToNative(devMode);
+
+  // Sets back the changes we made to the DevMode into the Printer Driver
+  ret = ::DocumentPropertiesW(gParentWnd, hPrinter, printName, devMode, devMode,
+                              DM_IN_BUFFER | DM_OUT_BUFFER);
+  if (ret != IDOK) {
+    ::GlobalUnlock(hDevMode);
+    return nsReturnRef<nsHGLOBAL>();
+  }
+
+  ::GlobalUnlock(hDevMode);
+
+  return globalDevMode.out();
+}
+
+//------------------------------------------------------------------
+// helper
+static void GetDefaultPrinterNameFromGlobalPrinters(nsAString& aPrinterName) {
+  aPrinterName.Truncate();
+  nsCOMPtr<nsIPrinterList> printerList =
+      do_GetService("@mozilla.org/gfx/printerlist;1");
+  if (printerList) {
+    printerList->GetSystemDefaultPrinterName(aPrinterName);
+  }
+}
+
+//------------------------------------------------------------------
+// Displays the native Print Dialog
+nsresult NativeShowPrintDialog(HWND aHWnd, bool aHaveSelection,
+                               nsIPrintSettings* aPrintSettings) {
+  // NS_ENSURE_ARG_POINTER(aHWnd);
+  NS_ENSURE_ARG_POINTER(aPrintSettings);
+
+  // Get the Print Name to be used
+  nsString printerName;
+  aPrintSettings->GetPrinterName(printerName);
+
+  // If there is no name then use the default printer
+  if (printerName.IsEmpty()) {
+    GetDefaultPrinterNameFromGlobalPrinters(printerName);
+  } else {
+    HANDLE hPrinter = nullptr;
+    if (!::OpenPrinterW(const_cast<wchar_t*>(
+                            static_cast<const wchar_t*>(printerName.get())),
+                        &hPrinter, nullptr)) {
+      // If the last used printer is not found, we should use default printer.
+      GetDefaultPrinterNameFromGlobalPrinters(printerName);
+    } else {
+      ::ClosePrinter(hPrinter);
+    }
+  }
+
+  // Now create a DEVNAMES struct so the the dialog is initialized correctly.
+
+  uint32_t len = printerName.Length();
+  nsHGLOBAL hDevNames =
+      ::GlobalAlloc(GHND, sizeof(wchar_t) * (len + 1) + sizeof(DEVNAMES));
+  nsAutoGlobalMem autoDevNames(hDevNames);
+  if (!hDevNames) {
+    return NS_ERROR_OUT_OF_MEMORY;
+  }
+
+  DEVNAMES* pDevNames = (DEVNAMES*)::GlobalLock(hDevNames);
+  if (!pDevNames) {
+    return NS_ERROR_FAILURE;
+  }
+  pDevNames->wDriverOffset = sizeof(DEVNAMES) / sizeof(wchar_t);
+  pDevNames->wDeviceOffset = sizeof(DEVNAMES) / sizeof(wchar_t);
+  pDevNames->wOutputOffset = sizeof(DEVNAMES) / sizeof(wchar_t) + len;
+  pDevNames->wDefault = 0;
+
+  memcpy(pDevNames + 1, printerName.get(), (len + 1) * sizeof(wchar_t));
+  ::GlobalUnlock(hDevNames);
+
+  // Create a Moveable Memory Object that holds a new DevMode
+  // from the Printer Name
+  // The PRINTDLG.hDevMode requires that it be a moveable memory object
+  // NOTE: autoDevMode is automatically freed when any error occurred
+  nsAutoGlobalMem autoDevMode(
+      CreateGlobalDevModeAndInit(printerName, aPrintSettings));
+
+  // Prepare to Display the Print Dialog
+  // https://docs.microsoft.com/en-us/previous-versions/windows/desktop/legacy/ms646942(v=vs.85)
+  // https://docs.microsoft.com/en-us/windows/win32/api/commdlg/ns-commdlg-printdlgexw
+  PRINTDLGEXW prntdlg;
+  memset(&prntdlg, 0, sizeof(prntdlg));
+
+  prntdlg.lStructSize = sizeof(prntdlg);
+  prntdlg.hwndOwner = aHWnd;
+  prntdlg.hDevMode = autoDevMode.get();
+  prntdlg.hDevNames = hDevNames;
+  prntdlg.hDC = nullptr;
+  prntdlg.Flags = PD_ALLPAGES | PD_RETURNIC | PD_USEDEVMODECOPIESANDCOLLATE |
+                  PD_COLLATE | PD_NOCURRENTPAGE;
+
+  // If there is a current selection then enable the "Selection" radio button
+  if (!aHaveSelection) {
+    prntdlg.Flags |= PD_NOSELECTION;
+  }
+
+  // 10 seems like a reasonable max number of ranges to support by default if
+  // the user doesn't choose a greater thing in the UI.
+  constexpr size_t kMinSupportedRanges = 10;
+
+  AutoTArray<PRINTPAGERANGE, kMinSupportedRanges> winPageRanges;
+  // Set up the page ranges.
+  {
+    AutoTArray<int32_t, kMinSupportedRanges * 2> pageRanges;
+    aPrintSettings->GetPageRanges(pageRanges);
+    // If there is a specified page range then enable the "Custom" radio button
+    if (!pageRanges.IsEmpty()) {
+      prntdlg.Flags |= PD_PAGENUMS;
+    }
+
+    const size_t specifiedRanges = pageRanges.Length() / 2;
+    const size_t maxRanges = std::max(kMinSupportedRanges, specifiedRanges);
+
+    prntdlg.nMaxPageRanges = maxRanges;
+    prntdlg.nPageRanges = specifiedRanges;
+
+    winPageRanges.SetCapacity(maxRanges);
+    for (size_t i = 0; i < pageRanges.Length(); i += 2) {
+      PRINTPAGERANGE* range = winPageRanges.AppendElement();
+      range->nFromPage = pageRanges[i];
+      range->nToPage = pageRanges[i + 1];
+    }
+    prntdlg.lpPageRanges = winPageRanges.Elements();
+
+    prntdlg.nMinPage = 1;
+    // TODO(emilio): Could probably get the right page number here from the
+    // new print UI.
+    prntdlg.nMaxPage = 0xFFFF;
+  }
+
+  // NOTE(emilio): This can always be 1 because we use the DEVMODE copies
+  // feature (see PD_USEDEVMODECOPIESANDCOLLATE).
+  prntdlg.nCopies = 1;
+
+  prntdlg.hInstance = nullptr;
+  prntdlg.lpPrintTemplateName = nullptr;
+
+  prntdlg.lpCallback = nullptr;
+  prntdlg.nPropertyPages = 0;
+  prntdlg.lphPropertyPages = nullptr;
+
+  prntdlg.nStartPage = START_PAGE_GENERAL;
+  prntdlg.dwResultAction = 0;
+
+  HRESULT result;
+  {
+    mozilla::widget::WinUtils::AutoSystemDpiAware dpiAwareness;
+    mozilla::BackgroundHangMonitor().NotifyWait();
+    result = ::PrintDlgExW(&prntdlg);
+  }
+
+  auto cancelOnExit = mozilla::MakeScopeExit([&] { ::SetFocus(aHWnd); });
+
+  if (NS_WARN_IF(!SUCCEEDED(result))) {
+#ifdef DEBUG
+    printf_stderr("PrintDlgExW failed with %lx\n", result);
+#endif
+    return NS_ERROR_FAILURE;
+  }
+  if (NS_WARN_IF(prntdlg.dwResultAction != PD_RESULT_PRINT)) {
+    return NS_ERROR_ABORT;
+  }
+  // check to make sure we don't have any nullptr pointers
+  NS_ENSURE_TRUE(prntdlg.hDevMode, NS_ERROR_ABORT);
+  NS_ENSURE_TRUE(prntdlg.hDevNames, NS_ERROR_ABORT);
+  // Lock the deviceNames and check for nullptr
+  DEVNAMES* devnames = (DEVNAMES*)::GlobalLock(prntdlg.hDevNames);
+  NS_ENSURE_TRUE(devnames, NS_ERROR_ABORT);
+
+  char16_t* device = &(((char16_t*)devnames)[devnames->wDeviceOffset]);
+  char16_t* driver = &(((char16_t*)devnames)[devnames->wDriverOffset]);
+
+  // Check to see if the "Print To File" control is checked
+  // then take the name from devNames and set it in the PrintSettings
+  //
+  // NOTE:
+  // As per Microsoft SDK documentation the returned value offset from
+  // devnames->wOutputOffset is either "FILE:" or nullptr
+  // if the "Print To File" checkbox is checked it MUST be "FILE:"
+  // We assert as an extra safety check.
+  if (prntdlg.Flags & PD_PRINTTOFILE) {
+    char16ptr_t fileName = &(((wchar_t*)devnames)[devnames->wOutputOffset]);
+    NS_ASSERTION(wcscmp(fileName, L"FILE:") == 0, "FileName must be `FILE:`");
+    aPrintSettings->SetOutputDestination(
+        nsIPrintSettings::kOutputDestinationFile);
+    aPrintSettings->SetToFileName(nsDependentString(fileName));
+  } else {
+    // clear "print to file" info
+    aPrintSettings->SetOutputDestination(
+        nsIPrintSettings::kOutputDestinationPrinter);
+    aPrintSettings->SetToFileName(u""_ns);
+  }
+
+  nsCOMPtr<nsIPrintSettingsWin> psWin(do_QueryInterface(aPrintSettings));
+  MOZ_RELEASE_ASSERT(psWin);
+
+  // Setup local Data members
+  psWin->SetDeviceName(nsDependentString(device));
+  psWin->SetDriverName(nsDependentString(driver));
+
+  // Fill the print options with the info from the dialog
+  aPrintSettings->SetPrinterName(nsDependentString(device));
+  aPrintSettings->SetPrintSelectionOnly(prntdlg.Flags & PD_SELECTION);
+
+  AutoTArray<int32_t, kMinSupportedRanges * 2> pageRanges;
+  if (prntdlg.Flags & PD_PAGENUMS) {
+    pageRanges.SetCapacity(prntdlg.nPageRanges * 2);
+    for (const auto& range :
+         mozilla::Span(prntdlg.lpPageRanges, prntdlg.nPageRanges)) {
+      pageRanges.AppendElement(range.nFromPage);
+      pageRanges.AppendElement(range.nToPage);
+    }
+  }
+  aPrintSettings->SetPageRanges(pageRanges);
+
+  // Unlock DeviceNames
+  ::GlobalUnlock(prntdlg.hDevNames);
+
+  // Transfer the settings from the native data to the PrintSettings
+  LPDEVMODEW devMode = (LPDEVMODEW)::GlobalLock(prntdlg.hDevMode);
+  if (!devMode || !prntdlg.hDC) {
+    return NS_ERROR_FAILURE;
+  }
+  psWin->SetDevMode(devMode);  // copies DevMode
+  psWin->CopyFromNative(prntdlg.hDC, devMode);
+  ::GlobalUnlock(prntdlg.hDevMode);
+  ::DeleteDC(prntdlg.hDC);
+
+  cancelOnExit.release();
+  return NS_OK;
+}
diff --git a/widget/windows/nsPrintDialogUtil.h b/widget/windows/nsPrintDialogUtil.h
new file mode 100644
index 0000000000..3ec16e1b1d
--- /dev/null
+++ b/widget/windows/nsPrintDialogUtil.h
@@ -0,0 +1,11 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+#ifndef nsFlyOwnDialog_h___
+#define nsFlyOwnDialog_h___
+
+nsresult NativeShowPrintDialog(HWND aHWnd, bool aHaveSelection,
+                               nsIPrintSettings* aPrintSettings);
+
+#endif /* nsFlyOwnDialog_h___ */
diff --git a/widget/windows/nsPrintDialogWin.cpp b/widget/windows/nsPrintDialogWin.cpp
new file mode 100644
index 0000000000..35ea52b17b
--- /dev/null
+++ b/widget/windows/nsPrintDialogWin.cpp
@@ -0,0 +1,147 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsPrintDialogWin.h"
+
+#include "nsArray.h"
+#include "nsComponentManagerUtils.h"
+#include "nsCOMPtr.h"
+#include "nsIBaseWindow.h"
+#include "nsIBrowserChild.h"
+#include "nsIDialogParamBlock.h"
+#include "nsIDocShell.h"
+#include "nsIInterfaceRequestorUtils.h"
+#include "nsIPrintSettings.h"
+#include "nsIWebBrowserChrome.h"
+#include "nsIWidget.h"
+#include "nsPrintDialogUtil.h"
+#include "nsIPrintSettings.h"
+#include "nsIWebBrowserChrome.h"
+#include "nsServiceManagerUtils.h"
+#include "nsPIDOMWindow.h"
+#include "nsQueryObject.h"
+#include "WidgetUtils.h"
+#include "WinUtils.h"
+
+static const char* kPageSetupDialogURL =
+    "chrome://global/content/printPageSetup.xhtml";
+
+using namespace mozilla;
+using namespace mozilla::widget;
+
+/**
+ * ParamBlock
+ */
+
+class ParamBlock {
+ public:
+  ParamBlock() { mBlock = 0; }
+  ~ParamBlock() { NS_IF_RELEASE(mBlock); }
+  nsresult Init() {
+    return CallCreateInstance(NS_DIALOGPARAMBLOCK_CONTRACTID, &mBlock);
+  }
+  nsIDialogParamBlock* operator->() const MOZ_NO_ADDREF_RELEASE_ON_RETURN {
+    return mBlock;
+  }
+  operator nsIDialogParamBlock* const() { return mBlock; }
+
+ private:
+  nsIDialogParamBlock* mBlock;
+};
+
+NS_IMPL_ISUPPORTS(nsPrintDialogServiceWin, nsIPrintDialogService)
+
+nsPrintDialogServiceWin::nsPrintDialogServiceWin() {}
+
+nsPrintDialogServiceWin::~nsPrintDialogServiceWin() {}
+
+NS_IMETHODIMP
+nsPrintDialogServiceWin::Init() {
+  nsresult rv;
+  mWatcher = do_GetService(NS_WINDOWWATCHER_CONTRACTID, &rv);
+  return rv;
+}
+
+NS_IMETHODIMP
+nsPrintDialogServiceWin::ShowPrintDialog(mozIDOMWindowProxy* aParent,
+                                         bool aHaveSelection,
+                                         nsIPrintSettings* aSettings) {
+  NS_ENSURE_ARG(aParent);
+  RefPtr<nsIWidget> parentWidget =
+      WidgetUtils::DOMWindowToWidget(nsPIDOMWindowOuter::From(aParent));
+
+  ScopedRtlShimWindow shim(parentWidget.get());
+  NS_ASSERTION(shim.get(), "Couldn't get native window for PRint Dialog!");
+
+  return NativeShowPrintDialog(shim.get(), aHaveSelection, aSettings);
+}
+
+NS_IMETHODIMP
+nsPrintDialogServiceWin::ShowPageSetupDialog(mozIDOMWindowProxy* aParent,
+                                             nsIPrintSettings* aNSSettings) {
+  NS_ENSURE_ARG(aParent);
+  NS_ENSURE_ARG(aNSSettings);
+
+  ParamBlock block;
+  nsresult rv = block.Init();
+  if (NS_FAILED(rv)) return rv;
+
+  block->SetInt(0, 0);
+  rv = DoDialog(aParent, block, aNSSettings, kPageSetupDialogURL);
+
+  // if aWebBrowserPrint is not null then we are printing
+  // so we want to pass back NS_ERROR_ABORT on cancel
+  if (NS_SUCCEEDED(rv)) {
+    int32_t status;
+    block->GetInt(0, &status);
+    return status == 0 ? NS_ERROR_ABORT : NS_OK;
+  }
+
+  // We don't call nsPrintSettingsService::MaybeSavePrintSettingsToPrefs here
+  // since it's called for us in printPageSetup.js.  Maybe we should move that
+  // call here for consistency with the other platforms though?
+
+  return rv;
+}
+
+nsresult nsPrintDialogServiceWin::DoDialog(mozIDOMWindowProxy* aParent,
+                                           nsIDialogParamBlock* aParamBlock,
+                                           nsIPrintSettings* aPS,
+                                           const char* aChromeURL) {
+  NS_ENSURE_ARG(aParamBlock);
+  NS_ENSURE_ARG(aPS);
+  NS_ENSURE_ARG(aChromeURL);
+
+  if (!mWatcher) return NS_ERROR_FAILURE;
+
+  // get a parent, if at all possible
+  // (though we'd rather this didn't fail, it's OK if it does. so there's
+  // no failure or null check.)
+  // retain ownership for method lifetime
+  nsCOMPtr<mozIDOMWindowProxy> activeParent;
+  if (!aParent) {
+    mWatcher->GetActiveWindow(getter_AddRefs(activeParent));
+    aParent = activeParent;
+  }
+
+  // create a nsIMutableArray of the parameters
+  // being passed to the window
+  nsCOMPtr<nsIMutableArray> array = nsArray::Create();
+
+  nsCOMPtr<nsISupports> psSupports(do_QueryInterface(aPS));
+  NS_ASSERTION(psSupports, "PrintSettings must be a supports");
+  array->AppendElement(psSupports);
+
+  nsCOMPtr<nsISupports> blkSupps(do_QueryInterface(aParamBlock));
+  NS_ASSERTION(blkSupps, "IOBlk must be a supports");
+  array->AppendElement(blkSupps);
+
+  nsCOMPtr<mozIDOMWindowProxy> dialog;
+  nsresult rv = mWatcher->OpenWindow(
+      aParent, nsDependentCString(aChromeURL), "_blank"_ns,
+      "centerscreen,chrome,modal,titlebar"_ns, array, getter_AddRefs(dialog));
+
+  return rv;
+}
diff --git a/widget/windows/nsPrintDialogWin.h b/widget/windows/nsPrintDialogWin.h
new file mode 100644
index 0000000000..bb8f212eb5
--- /dev/null
+++ b/widget/windows/nsPrintDialogWin.h
@@ -0,0 +1,39 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef nsPrintDialog_h__
+#define nsPrintDialog_h__
+
+#include "nsIPrintDialogService.h"
+
+#include "nsCOMPtr.h"
+#include "nsIWindowWatcher.h"
+
+#include <windef.h>
+
+class nsIPrintSettings;
+class nsIDialogParamBlock;
+
+class nsPrintDialogServiceWin final : public nsIPrintDialogService {
+ public:
+  nsPrintDialogServiceWin();
+
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIPRINTDIALOGSERVICE
+
+ private:
+  virtual ~nsPrintDialogServiceWin();
+
+  nsresult DoDialog(mozIDOMWindowProxy* aParent,
+                    nsIDialogParamBlock* aParamBlock, nsIPrintSettings* aPS,
+                    const char* aChromeURL);
+
+  nsCOMPtr<nsIWindowWatcher> mWatcher;
+};
+
+NS_DEFINE_STATIC_IID_ACCESSOR(nsPrintDialogServiceWin,
+                              NS_IPRINTDIALOGSERVICE_IID)
+
+#endif
diff --git a/widget/windows/nsPrintSettingsServiceWin.cpp b/widget/windows/nsPrintSettingsServiceWin.cpp
new file mode 100644
index 0000000000..cbc99441ab
--- /dev/null
+++ b/widget/windows/nsPrintSettingsServiceWin.cpp
@@ -0,0 +1,127 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsPrintSettingsServiceWin.h"
+
+#include "nsCOMPtr.h"
+#include "nsPrintSettingsWin.h"
+#include "nsPrintDialogUtil.h"
+
+#include "nsGfxCIID.h"
+#include "nsIServiceManager.h"
+#include "nsWindowsHelpers.h"
+#include "ipc/IPCMessageUtils.h"
+#include "chrome/common/ipc_channel.h"
+#include "mozilla/embedding/PPrintingTypes.h"
+
+using namespace mozilla::embedding;
+
+NS_IMETHODIMP
+nsPrintSettingsServiceWin::SerializeToPrintData(nsIPrintSettings* aSettings,
+                                                PrintData* data) {
+  nsresult rv = nsPrintSettingsService::SerializeToPrintData(aSettings, data);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsCOMPtr<nsIPrintSettingsWin> psWin = do_QueryInterface(aSettings);
+  if (!psWin) {
+    return NS_ERROR_FAILURE;
+  }
+
+  nsAutoString deviceName;
+  nsAutoString driverName;
+
+  psWin->GetDeviceName(deviceName);
+  psWin->GetDriverName(driverName);
+
+  data->deviceName().Assign(deviceName);
+  data->driverName().Assign(driverName);
+
+  // When creating the print dialog on Windows, we only need to send certain
+  // print settings information from the parent to the child not vice versa.
+  if (XRE_IsParentProcess()) {
+    // A DEVMODE can actually be of arbitrary size. If it turns out that it'll
+    // make our IPC message larger than the limit, then we'll error out.
+    LPDEVMODEW devModeRaw;
+    psWin->GetDevMode(&devModeRaw);  // This actually allocates a copy of the
+                                     // the nsIPrintSettingsWin DEVMODE, so
+                                     // we're now responsible for deallocating
+                                     // it. We'll use an nsAutoDevMode helper
+                                     // to do this.
+    if (devModeRaw) {
+      nsAutoDevMode devMode(devModeRaw);
+      devModeRaw = nullptr;
+
+      size_t devModeTotalSize = devMode->dmSize + devMode->dmDriverExtra;
+      size_t msgTotalSize = sizeof(PrintData) + devModeTotalSize;
+
+      if (msgTotalSize > IPC::Channel::kMaximumMessageSize / 2) {
+        return NS_ERROR_FAILURE;
+      }
+
+      // Instead of reaching in and manually reading each member, we'll just
+      // copy the bits over.
+      const char* devModeData = reinterpret_cast<const char*>(devMode.get());
+      nsTArray<uint8_t> arrayBuf;
+      arrayBuf.AppendElements(devModeData, devModeTotalSize);
+      data->devModeData() = std::move(arrayBuf);
+    }
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsPrintSettingsServiceWin::DeserializeToPrintSettings(
+    const PrintData& data, nsIPrintSettings* settings) {
+  nsresult rv =
+      nsPrintSettingsService::DeserializeToPrintSettings(data, settings);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsCOMPtr<nsIPrintSettingsWin> psWin = do_QueryInterface(settings);
+  if (!settings) {
+    return NS_ERROR_FAILURE;
+  }
+
+  if (XRE_IsContentProcess()) {
+    psWin->SetDeviceName(data.deviceName());
+    psWin->SetDriverName(data.driverName());
+
+    if (data.devModeData().IsEmpty()) {
+      psWin->SetDevMode(nullptr);
+    } else {
+      // Check minimum length of DEVMODE data.
+      auto devModeDataLength = data.devModeData().Length();
+      if (devModeDataLength < sizeof(DEVMODEW)) {
+        NS_WARNING("DEVMODE data is too short.");
+        return NS_ERROR_FAILURE;
+      }
+
+      DEVMODEW* devMode = reinterpret_cast<DEVMODEW*>(
+          const_cast<uint8_t*>(data.devModeData().Elements()));
+
+      // Check actual length of DEVMODE data.
+      if ((devMode->dmSize + devMode->dmDriverExtra) != devModeDataLength) {
+        NS_WARNING("DEVMODE length is incorrect.");
+        return NS_ERROR_FAILURE;
+      }
+
+      psWin->SetDevMode(devMode);  // Copies
+    }
+  }
+
+  return NS_OK;
+}
+
+nsresult nsPrintSettingsServiceWin::_CreatePrintSettings(
+    nsIPrintSettings** _retval) {
+  *_retval = nullptr;
+  nsPrintSettingsWin* printSettings =
+      new nsPrintSettingsWin();  // does not initially ref count
+  NS_ENSURE_TRUE(printSettings, NS_ERROR_OUT_OF_MEMORY);
+
+  NS_ADDREF(*_retval = printSettings);  // ref count
+
+  return NS_OK;
+}
diff --git a/widget/windows/nsPrintSettingsServiceWin.h b/widget/windows/nsPrintSettingsServiceWin.h
new file mode 100644
index 0000000000..e11d307a8b
--- /dev/null
+++ b/widget/windows/nsPrintSettingsServiceWin.h
@@ -0,0 +1,29 @@
+/* -*- Mode: IDL; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef nsPrintSettingsServiceWin_h
+#define nsPrintSettingsServiceWin_h
+
+#include "nsPrintSettingsService.h"
+
+class nsIPrintSettings;
+
+class nsPrintSettingsServiceWin final : public nsPrintSettingsService {
+ public:
+  nsPrintSettingsServiceWin() {}
+
+  NS_IMETHODIMP SerializeToPrintData(
+      nsIPrintSettings* aSettings,
+      mozilla::embedding::PrintData* data) override;
+
+  NS_IMETHODIMP DeserializeToPrintSettings(
+      const mozilla::embedding::PrintData& data,
+      nsIPrintSettings* settings) override;
+
+  nsresult _CreatePrintSettings(nsIPrintSettings** _retval) override;
+};
+
+#endif  // nsPrintSettingsServiceWin_h
diff --git a/widget/windows/nsPrintSettingsWin.cpp b/widget/windows/nsPrintSettingsWin.cpp
new file mode 100644
index 0000000000..788c4ab6da
--- /dev/null
+++ b/widget/windows/nsPrintSettingsWin.cpp
@@ -0,0 +1,477 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+#include "nsPrintSettingsWin.h"
+
+#include "mozilla/ArrayUtils.h"
+#include "nsCRT.h"
+#include "nsDeviceContextSpecWin.h"
+#include "nsPrintSettingsImpl.h"
+#include "WinUtils.h"
+
+using namespace mozilla;
+
+// Using paper sizes from wingdi.h and the units given there, plus a little
+// extra research for the ones it doesn't give. Looks like the list hasn't
+// changed since Windows 2000, so should be fairly stable now.
+const short kPaperSizeUnits[] = {
+    nsIPrintSettings::kPaperSizeMillimeters,  // Not Used default to mm as
+                                              // DEVMODE uses tenths of mm, just
+                                              // in case
+    nsIPrintSettings::kPaperSizeInches,       // DMPAPER_LETTER
+    nsIPrintSettings::kPaperSizeInches,       // DMPAPER_LETTERSMALL
+    nsIPrintSettings::kPaperSizeInches,       // DMPAPER_TABLOID
+    nsIPrintSettings::kPaperSizeInches,       // DMPAPER_LEDGER
+    nsIPrintSettings::kPaperSizeInches,       // DMPAPER_LEGAL
+    nsIPrintSettings::kPaperSizeInches,       // DMPAPER_STATEMENT
+    nsIPrintSettings::kPaperSizeInches,       // DMPAPER_EXECUTIVE
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_A3
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_A4
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_A4SMALL
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_A5
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_B4
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_B5
+    nsIPrintSettings::kPaperSizeInches,       // DMPAPER_FOLIO
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_QUARTO
+    nsIPrintSettings::kPaperSizeInches,       // DMPAPER_10X14
+    nsIPrintSettings::kPaperSizeInches,       // DMPAPER_11X17
+    nsIPrintSettings::kPaperSizeInches,       // DMPAPER_NOTE
+    nsIPrintSettings::kPaperSizeInches,       // DMPAPER_ENV_9
+    nsIPrintSettings::kPaperSizeInches,       // DMPAPER_ENV_10
+    nsIPrintSettings::kPaperSizeInches,       // DMPAPER_ENV_11
+    nsIPrintSettings::kPaperSizeInches,       // DMPAPER_ENV_12
+    nsIPrintSettings::kPaperSizeInches,       // DMPAPER_ENV_14
+    nsIPrintSettings::kPaperSizeInches,       // DMPAPER_CSHEET
+    nsIPrintSettings::kPaperSizeInches,       // DMPAPER_DSHEET
+    nsIPrintSettings::kPaperSizeInches,       // DMPAPER_ESHEET
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_ENV_DL
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_ENV_C5
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_ENV_C3
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_ENV_C4
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_ENV_C6
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_ENV_C65
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_ENV_B4
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_ENV_B5
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_ENV_B6
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_ENV_ITALY
+    nsIPrintSettings::kPaperSizeInches,       // DMPAPER_ENV_MONARCH
+    nsIPrintSettings::kPaperSizeInches,       // DMPAPER_ENV_PERSONAL
+    nsIPrintSettings::kPaperSizeInches,       // DMPAPER_FANFOLD_US
+    nsIPrintSettings::kPaperSizeInches,       // DMPAPER_FANFOLD_STD_GERMAN
+    nsIPrintSettings::kPaperSizeInches,       // DMPAPER_FANFOLD_LGL_GERMAN
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_ISO_B4
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_JAPANESE_POSTCARD
+    nsIPrintSettings::kPaperSizeInches,       // DMPAPER_9X11
+    nsIPrintSettings::kPaperSizeInches,       // DMPAPER_10X11
+    nsIPrintSettings::kPaperSizeInches,       // DMPAPER_15X11
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_ENV_INVITE
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_RESERVED_48
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_RESERVED_49
+    nsIPrintSettings::kPaperSizeInches,       // DMPAPER_LETTER_EXTRA
+    nsIPrintSettings::kPaperSizeInches,       // DMPAPER_LEGAL_EXTRA
+    nsIPrintSettings::kPaperSizeInches,       // DMPAPER_TABLOID_EXTRA
+    nsIPrintSettings::kPaperSizeInches,       // DMPAPER_A4_EXTRA
+    nsIPrintSettings::kPaperSizeInches,       // DMPAPER_LETTER_TRANSVERSE
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_A4_TRANSVERSE
+    nsIPrintSettings::kPaperSizeInches,       // DMPAPER_LETTER_EXTRA_TRANSVERSE
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_A_PLUS
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_B_PLUS
+    nsIPrintSettings::kPaperSizeInches,       // DMPAPER_LETTER_PLUS
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_A4_PLUS
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_A5_TRANSVERSE
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_B5_TRANSVERSE
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_A3_EXTRA
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_A5_EXTRA
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_B5_EXTRA
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_A2
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_A3_TRANSVERSE
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_A3_EXTRA_TRANSVERSE
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_DBL_JAPANESE_POSTCARD
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_A6
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_JENV_KAKU2
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_JENV_KAKU3
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_JENV_CHOU3
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_JENV_CHOU4
+    nsIPrintSettings::kPaperSizeInches,       // DMPAPER_LETTER_ROTATED
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_A3_ROTATED
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_A4_ROTATED
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_A5_ROTATED
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_B4_JIS_ROTATED
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_B5_JIS_ROTATED
+    nsIPrintSettings::
+        kPaperSizeMillimeters,  // DMPAPER_JAPANESE_POSTCARD_ROTATED
+    nsIPrintSettings::
+        kPaperSizeMillimeters,  // DMPAPER_DBL_JAPANESE_POSTCARD_ROTATED
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_A6_ROTATED
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_JENV_KAKU2_ROTATED
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_JENV_KAKU3_ROTATED
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_JENV_CHOU3_ROTATED
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_JENV_CHOU4_ROTATED
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_B6_JIS
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_B6_JIS_ROTATED
+    nsIPrintSettings::kPaperSizeInches,       // DMPAPER_12X11
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_JENV_YOU4
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_JENV_YOU4_ROTATED
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_P16K
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_P32K
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_P32KBIG
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_PENV_1
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_PENV_2
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_PENV_3
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_PENV_4
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_PENV_5
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_PENV_6
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_PENV_7
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_PENV_8
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_PENV_9
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_PENV_10
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_P16K_ROTATED
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_P32K_ROTATED
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_P32KBIG_ROTATED
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_PENV_1_ROTATED
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_PENV_2_ROTATED
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_PENV_3_ROTATED
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_PENV_4_ROTATED
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_PENV_5_ROTATED
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_PENV_6_ROTATED
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_PENV_7_ROTATED
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_PENV_8_ROTATED
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_PENV_9_ROTATED
+    nsIPrintSettings::kPaperSizeMillimeters,  // DMPAPER_PENV_10_ROTATED
+};
+
+NS_IMPL_ISUPPORTS_INHERITED(nsPrintSettingsWin, nsPrintSettings,
+                            nsIPrintSettingsWin)
+
+/** ---------------------------------------------------
+ *  See documentation in nsPrintSettingsWin.h
+ *	@update
+ */
+nsPrintSettingsWin::nsPrintSettingsWin()
+    : nsPrintSettings(),
+      mDeviceName(nullptr),
+      mDriverName(nullptr),
+      mDevMode(nullptr) {}
+
+/** ---------------------------------------------------
+ *  See documentation in nsPrintSettingsWin.h
+ *	@update
+ */
+nsPrintSettingsWin::nsPrintSettingsWin(const nsPrintSettingsWin& aPS)
+    : mDevMode(nullptr) {
+  *this = aPS;
+}
+
+/* static */
+void nsPrintSettingsWin::PaperSizeUnitFromDmPaperSize(short aPaperSize,
+                                                      int16_t& aPaperSizeUnit) {
+  if (aPaperSize > 0 && aPaperSize < int32_t(ArrayLength(kPaperSizeUnits))) {
+    aPaperSizeUnit = kPaperSizeUnits[aPaperSize];
+  }
+}
+
+void nsPrintSettingsWin::InitWithInitializer(
+    const PrintSettingsInitializer& aSettings) {
+  nsPrintSettings::InitWithInitializer(aSettings);
+
+  if (aSettings.mDevmodeWStorage.Length() < sizeof(DEVMODEW)) {
+    return;
+  }
+
+  auto* devmode =
+      reinterpret_cast<const DEVMODEW*>(aSettings.mDevmodeWStorage.Elements());
+  if (devmode->dmSize != sizeof(DEVMODEW) ||
+      devmode->dmSize + devmode->dmDriverExtra >
+          aSettings.mDevmodeWStorage.Length()) {
+    return;
+  }
+
+  // SetDevMode copies the DEVMODE.
+  SetDevMode(const_cast<DEVMODEW*>(devmode));
+
+  if (mDevMode->dmFields & DM_SCALE) {
+    // Since we do the scaling, grab the DEVMODE value and reset it back to 100.
+    double scale = double(mDevMode->dmScale) / 100.0f;
+    if (mScaling == 1.0 || scale != 1.0) {
+      SetScaling(scale);
+    }
+    mDevMode->dmScale = 100;
+  }
+}
+
+already_AddRefed<nsIPrintSettings> CreatePlatformPrintSettings(
+    const PrintSettingsInitializer& aSettings) {
+  RefPtr<nsPrintSettings> settings = aSettings.mPrintSettings.get();
+  if (!settings) {
+    settings = MakeRefPtr<nsPrintSettingsWin>();
+  }
+  settings->InitWithInitializer(aSettings);
+  return settings.forget();
+}
+
+/** ---------------------------------------------------
+ *  See documentation in nsPrintSettingsWin.h
+ *	@update
+ */
+nsPrintSettingsWin::~nsPrintSettingsWin() {
+  if (mDevMode) ::HeapFree(::GetProcessHeap(), 0, mDevMode);
+}
+
+NS_IMETHODIMP nsPrintSettingsWin::SetDeviceName(const nsAString& aDeviceName) {
+  mDeviceName = aDeviceName;
+  return NS_OK;
+}
+NS_IMETHODIMP nsPrintSettingsWin::GetDeviceName(nsAString& aDeviceName) {
+  aDeviceName = mDeviceName;
+  return NS_OK;
+}
+
+NS_IMETHODIMP nsPrintSettingsWin::SetDriverName(const nsAString& aDriverName) {
+  mDriverName = aDriverName;
+  return NS_OK;
+}
+NS_IMETHODIMP nsPrintSettingsWin::GetDriverName(nsAString& aDriverName) {
+  aDriverName = mDriverName;
+  return NS_OK;
+}
+
+void nsPrintSettingsWin::CopyDevMode(DEVMODEW* aInDevMode,
+                                     DEVMODEW*& aOutDevMode) {
+  aOutDevMode = nullptr;
+  size_t size = aInDevMode->dmSize + aInDevMode->dmDriverExtra;
+  aOutDevMode =
+      (LPDEVMODEW)::HeapAlloc(::GetProcessHeap(), HEAP_ZERO_MEMORY, size);
+  if (aOutDevMode) {
+    memcpy(aOutDevMode, aInDevMode, size);
+  }
+}
+
+NS_IMETHODIMP nsPrintSettingsWin::GetDevMode(DEVMODEW** aDevMode) {
+  NS_ENSURE_ARG_POINTER(aDevMode);
+
+  if (mDevMode) {
+    CopyDevMode(mDevMode, *aDevMode);
+  } else {
+    *aDevMode = nullptr;
+  }
+  return NS_OK;
+}
+
+NS_IMETHODIMP nsPrintSettingsWin::SetDevMode(DEVMODEW* aDevMode) {
+  if (mDevMode) {
+    ::HeapFree(::GetProcessHeap(), 0, mDevMode);
+    mDevMode = nullptr;
+  }
+
+  if (aDevMode) {
+    CopyDevMode(aDevMode, mDevMode);
+  }
+  return NS_OK;
+}
+
+void nsPrintSettingsWin::InitUnwriteableMargin(HDC aHdc) {
+  mozilla::gfx::MarginDouble margin =
+      mozilla::widget::WinUtils::GetUnwriteableMarginsForDeviceInInches(aHdc);
+
+  mUnwriteableMargin.SizeTo(NS_INCHES_TO_INT_TWIPS(margin.top),
+                            NS_INCHES_TO_INT_TWIPS(margin.right),
+                            NS_INCHES_TO_INT_TWIPS(margin.bottom),
+                            NS_INCHES_TO_INT_TWIPS(margin.left));
+}
+
+void nsPrintSettingsWin::CopyFromNative(HDC aHdc, DEVMODEW* aDevMode) {
+  MOZ_ASSERT(aHdc);
+  MOZ_ASSERT(aDevMode);
+
+  mIsInitedFromPrinter = true;
+  if (aDevMode->dmFields & DM_ORIENTATION) {
+    const bool areSheetsOfPaperPortraitMode =
+        (aDevMode->dmOrientation == DMORIENT_PORTRAIT);
+
+    // If our Windows print settings say that we're producing portrait-mode
+    // sheets of paper, then our page format must also be portrait-mode; unless
+    // we've got a pages-per-sheet value with orthogonal pages/sheets, in which
+    // case it's reversed.
+    const bool arePagesPortraitMode =
+        (areSheetsOfPaperPortraitMode != HasOrthogonalPagesPerSheet());
+
+    // Record the orientation of the pages (determined above) in mOrientation:
+    mOrientation = int32_t(arePagesPortraitMode ? kPortraitOrientation
+                                                : kLandscapeOrientation);
+  }
+
+  if (aDevMode->dmFields & DM_COPIES) {
+    mNumCopies = aDevMode->dmCopies;
+  }
+
+  if (aDevMode->dmFields & DM_DUPLEX) {
+    switch (aDevMode->dmDuplex) {
+      default:
+        MOZ_FALLTHROUGH_ASSERT("bad value for dmDuplex field");
+      case DMDUP_SIMPLEX:
+        mDuplex = kDuplexNone;
+        break;
+      case DMDUP_VERTICAL:
+        mDuplex = kDuplexFlipOnLongEdge;
+        break;
+      case DMDUP_HORIZONTAL:
+        mDuplex = kDuplexFlipOnShortEdge;
+        break;
+    }
+  }
+
+  // Since we do the scaling, grab their value and reset back to 100.
+  if (aDevMode->dmFields & DM_SCALE) {
+    double scale = double(aDevMode->dmScale) / 100.0f;
+    if (mScaling == 1.0 || scale != 1.0) {
+      mScaling = scale;
+    }
+    aDevMode->dmScale = 100;
+  }
+
+  if (aDevMode->dmFields & DM_PAPERSIZE) {
+    mPaperId.Truncate(0);
+    mPaperId.AppendInt(aDevMode->dmPaperSize);
+    // If it is not a paper size we know about, the unit will remain unchanged.
+    PaperSizeUnitFromDmPaperSize(aDevMode->dmPaperSize, mPaperSizeUnit);
+  }
+
+  if (aDevMode->dmFields & DM_COLOR) {
+    mPrintInColor = aDevMode->dmColor == DMCOLOR_COLOR;
+  }
+
+  InitUnwriteableMargin(aHdc);
+
+  int pixelsPerInchY = ::GetDeviceCaps(aHdc, LOGPIXELSY);
+  int physicalHeight = ::GetDeviceCaps(aHdc, PHYSICALHEIGHT);
+  double physicalHeightInch = double(physicalHeight) / pixelsPerInchY;
+  int pixelsPerInchX = ::GetDeviceCaps(aHdc, LOGPIXELSX);
+  int physicalWidth = ::GetDeviceCaps(aHdc, PHYSICALWIDTH);
+  double physicalWidthInch = double(physicalWidth) / pixelsPerInchX;
+
+  // Get the paper size from the device context rather than the DEVMODE, because
+  // it is always available.
+  double paperHeightInch = mOrientation == kPortraitOrientation
+                               ? physicalHeightInch
+                               : physicalWidthInch;
+  mPaperHeight = mPaperSizeUnit == kPaperSizeInches
+                     ? paperHeightInch
+                     : paperHeightInch * MM_PER_INCH_FLOAT;
+
+  double paperWidthInch = mOrientation == kPortraitOrientation
+                              ? physicalWidthInch
+                              : physicalHeightInch;
+  mPaperWidth = mPaperSizeUnit == kPaperSizeInches
+                    ? paperWidthInch
+                    : paperWidthInch * MM_PER_INCH_FLOAT;
+
+  // Using LOGPIXELSY to match existing code for print scaling calculations.
+  mResolution = pixelsPerInchY;
+}
+
+void nsPrintSettingsWin::CopyToNative(DEVMODEW* aDevMode) {
+  MOZ_ASSERT(aDevMode);
+
+  if (!mPaperId.IsEmpty()) {
+    aDevMode->dmPaperSize = _wtoi((const wchar_t*)mPaperId.BeginReading());
+    aDevMode->dmFields |= DM_PAPERSIZE;
+  } else {
+    aDevMode->dmPaperSize = 0;
+    aDevMode->dmFields &= ~DM_PAPERSIZE;
+  }
+
+  aDevMode->dmFields |= DM_COLOR;
+  aDevMode->dmColor = mPrintInColor ? DMCOLOR_COLOR : DMCOLOR_MONOCHROME;
+
+  // The length and width in DEVMODE are always in tenths of a millimeter.
+  double tenthsOfAmmPerSizeUnit =
+      mPaperSizeUnit == kPaperSizeInches ? MM_PER_INCH_FLOAT * 10.0 : 10.0;
+
+  // Note: small page sizes can be required here for sticker, label and slide
+  // printers etc. see bug 1271900.
+  if (mPaperHeight > 0) {
+    aDevMode->dmPaperLength = std::round(mPaperHeight * tenthsOfAmmPerSizeUnit);
+    aDevMode->dmFields |= DM_PAPERLENGTH;
+  } else {
+    aDevMode->dmPaperLength = 0;
+    aDevMode->dmFields &= ~DM_PAPERLENGTH;
+  }
+
+  if (mPaperWidth > 0) {
+    aDevMode->dmPaperWidth = std::round(mPaperWidth * tenthsOfAmmPerSizeUnit);
+    aDevMode->dmFields |= DM_PAPERWIDTH;
+  } else {
+    aDevMode->dmPaperWidth = 0;
+    aDevMode->dmFields &= ~DM_PAPERWIDTH;
+  }
+
+  // Setup Orientation
+  aDevMode->dmOrientation = GetSheetOrientation() == kPortraitOrientation
+                                ? DMORIENT_PORTRAIT
+                                : DMORIENT_LANDSCAPE;
+  aDevMode->dmFields |= DM_ORIENTATION;
+
+  // Setup Number of Copies
+  aDevMode->dmCopies = mNumCopies;
+  aDevMode->dmFields |= DM_COPIES;
+
+  // Setup Simplex/Duplex mode
+  switch (mDuplex) {
+    case kDuplexNone:
+      aDevMode->dmDuplex = DMDUP_SIMPLEX;
+      aDevMode->dmFields |= DM_DUPLEX;
+      break;
+    case kDuplexFlipOnLongEdge:
+      aDevMode->dmDuplex = DMDUP_VERTICAL;
+      aDevMode->dmFields |= DM_DUPLEX;
+      break;
+    case kDuplexFlipOnShortEdge:
+      aDevMode->dmDuplex = DMDUP_HORIZONTAL;
+      aDevMode->dmFields |= DM_DUPLEX;
+      break;
+    default:
+      MOZ_ASSERT_UNREACHABLE("bad value for duplex option");
+      break;
+  }
+}
+
+//-------------------------------------------
+nsresult nsPrintSettingsWin::_Clone(nsIPrintSettings** _retval) {
+  RefPtr<nsPrintSettingsWin> printSettings = new nsPrintSettingsWin(*this);
+  printSettings.forget(_retval);
+  return NS_OK;
+}
+
+//-------------------------------------------
+nsPrintSettingsWin& nsPrintSettingsWin::operator=(
+    const nsPrintSettingsWin& rhs) {
+  if (this == &rhs) {
+    return *this;
+  }
+
+  ((nsPrintSettings&)*this) = rhs;
+
+  // Use free because we used the native malloc to create the memory
+  if (mDevMode) {
+    ::HeapFree(::GetProcessHeap(), 0, mDevMode);
+  }
+
+  mDeviceName = rhs.mDeviceName;
+  mDriverName = rhs.mDriverName;
+
+  if (rhs.mDevMode) {
+    CopyDevMode(rhs.mDevMode, mDevMode);
+  } else {
+    mDevMode = nullptr;
+  }
+
+  return *this;
+}
+
+//-------------------------------------------
+nsresult nsPrintSettingsWin::_Assign(nsIPrintSettings* aPS) {
+  nsPrintSettingsWin* psWin = static_cast<nsPrintSettingsWin*>(aPS);
+  *this = *psWin;
+  return NS_OK;
+}
diff --git a/widget/windows/nsPrintSettingsWin.h b/widget/windows/nsPrintSettingsWin.h
new file mode 100644
index 0000000000..c127efbeb6
--- /dev/null
+++ b/widget/windows/nsPrintSettingsWin.h
@@ -0,0 +1,62 @@
+/* -*- Mode: IDL; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef nsPrintSettingsWin_h__
+#define nsPrintSettingsWin_h__
+
+#include "nsPrintSettingsImpl.h"
+#include "nsIPrintSettingsWin.h"
+#include <windows.h>
+
+//*****************************************************************************
+//***    nsPrintSettingsWin
+//*****************************************************************************
+class nsPrintSettingsWin : public nsPrintSettings, public nsIPrintSettingsWin {
+  virtual ~nsPrintSettingsWin();
+
+ public:
+  NS_DECL_ISUPPORTS_INHERITED
+  NS_DECL_NSIPRINTSETTINGSWIN
+
+  nsPrintSettingsWin();
+  nsPrintSettingsWin(const nsPrintSettingsWin& aPS);
+
+  /**
+   * @param aPaperSize the Windows dmPaperSize
+   * @param aPaperSizeUnit will be set to the nsIPrintSettings paper size unit
+   *                       associated with aPaperSize or left unchanged if
+   *                       aPaperSize is not recognized
+   */
+  static void PaperSizeUnitFromDmPaperSize(short aPaperSize,
+                                           int16_t& aPaperSizeUnit);
+
+  void InitWithInitializer(const PrintSettingsInitializer& aSettings) final;
+
+  /**
+   * Makes a new copy
+   */
+  virtual nsresult _Clone(nsIPrintSettings** _retval);
+
+  /**
+   * Assigns values
+   */
+  virtual nsresult _Assign(nsIPrintSettings* aPS);
+
+  /**
+   * Assignment
+   */
+  nsPrintSettingsWin& operator=(const nsPrintSettingsWin& rhs);
+
+ protected:
+  void CopyDevMode(DEVMODEW* aInDevMode, DEVMODEW*& aOutDevMode);
+  void InitUnwriteableMargin(HDC aHdc);
+
+  nsString mDeviceName;
+  nsString mDriverName;
+  LPDEVMODEW mDevMode;
+};
+
+#endif /* nsPrintSettingsWin_h__ */
diff --git a/widget/windows/nsPrinterWin.cpp b/widget/windows/nsPrinterWin.cpp
new file mode 100644
index 0000000000..75676cd613
--- /dev/null
+++ b/widget/windows/nsPrinterWin.cpp
@@ -0,0 +1,521 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsPrinterWin.h"
+
+#include <algorithm>
+#include <windows.h>
+#include <winspool.h>
+
+#include "mozilla/Array.h"
+#include "mozilla/dom/Promise.h"
+#include "nsPaper.h"
+#include "nsPrintSettingsImpl.h"
+#include "nsPrintSettingsWin.h"
+#include "nsWindowsHelpers.h"
+#include "PrintBackgroundTask.h"
+#include "WinUtils.h"
+
+using namespace mozilla;
+using namespace mozilla::gfx;
+using namespace mozilla::widget;
+using mozilla::PrintSettingsInitializer;
+using mozilla::dom::Promise;
+
+static const double kPointsPerTenthMM = 72.0 / 254.0;
+static const double kPointsPerInch = 72.0;
+
+nsPrinterWin::nsPrinterWin(const CommonPaperInfoArray* aArray,
+                           const nsAString& aName)
+    : nsPrinterBase(aArray),
+      mName(aName),
+      mDefaultDevmodeWStorage("nsPrinterWin::mDefaultDevmodeWStorage") {}
+
+// static
+already_AddRefed<nsPrinterWin> nsPrinterWin::Create(
+    const CommonPaperInfoArray* aArray, const nsAString& aName) {
+  return do_AddRef(new nsPrinterWin(aArray, aName));
+}
+
+template <class T>
+static nsTArray<T> GetDeviceCapabilityArray(const LPWSTR aPrinterName,
+                                            WORD aCapabilityID,
+                                            mozilla::Mutex& aDriverMutex,
+                                            int& aCount) {
+  MOZ_ASSERT(aCount >= 0, "Possibly passed aCount from previous error case.");
+
+  nsTArray<T> caps;
+
+  // We only want to access printer drivers in the parent process.
+  if (!XRE_IsParentProcess()) {
+    return caps;
+  }
+
+  // Both the call to get the size and the call to actually populate the array
+  // are relatively expensive, so as sometimes the lengths of the arrays that we
+  // retrieve depend on each other we allow a count to be passed in to save the
+  // first call. As we allocate double the count anyway this should allay any
+  // safety worries.
+  if (!aCount) {
+    // Passing nullptr as the port here seems to work. Given that we would have
+    // to OpenPrinter with just the name anyway to get the port that makes
+    // sense. Also, the printer set-up seems to stop you from having two
+    // printers with the same name. Note: this (and the call below) are blocking
+    // calls, which could be slow.
+    MutexAutoLock autoLock(aDriverMutex);
+    aCount = ::DeviceCapabilitiesW(aPrinterName, nullptr, aCapabilityID,
+                                   nullptr, nullptr);
+    if (aCount <= 0) {
+      return caps;
+    }
+  }
+
+  // As DeviceCapabilitiesW doesn't take a size, there is a greater risk of the
+  // buffer being overflowed, so we over-allocate for safety.
+  caps.SetLength(aCount * 2);
+  MutexAutoLock autoLock(aDriverMutex);
+  int count =
+      ::DeviceCapabilitiesW(aPrinterName, nullptr, aCapabilityID,
+                            reinterpret_cast<LPWSTR>(caps.Elements()), nullptr);
+  if (count <= 0) {
+    caps.Clear();
+    return caps;
+  }
+
+  // We know from bug 1673708 that sometimes the final array returned is smaller
+  // than the required array count. Assert here to see if this is reproduced on
+  // test servers.
+  MOZ_ASSERT(count == aCount, "Different array count returned than expected.");
+
+  // Note that TruncateLength will crash if count > caps.Length().
+  caps.TruncateLength(count);
+  return caps;
+}
+
+static void DevmodeToSettingsInitializer(
+    const nsString& aPrinterName, const DEVMODEW* aDevmode,
+    mozilla::Mutex& aDriverMutex,
+    PrintSettingsInitializer& aSettingsInitializer) {
+  aSettingsInitializer.mPrinter.Assign(aPrinterName);
+
+  HDC dc;
+  {
+    MutexAutoLock autoLock(aDriverMutex);
+    dc = ::CreateICW(nullptr, aPrinterName.get(), nullptr, aDevmode);
+  }
+  nsAutoHDC printerDc(dc);
+  MOZ_ASSERT(printerDc, "CreateICW failed");
+  if (!printerDc) {
+    return;
+  }
+
+  if (aDevmode->dmFields & DM_PAPERSIZE) {
+    aSettingsInitializer.mPaperInfo.mId.Truncate();
+    aSettingsInitializer.mPaperInfo.mId.AppendInt(aDevmode->dmPaperSize);
+    // If it is not a paper size we know about, the unit will remain unchanged.
+    nsPrintSettingsWin::PaperSizeUnitFromDmPaperSize(
+        aDevmode->dmPaperSize, aSettingsInitializer.mPaperSizeUnit);
+  }
+
+  int pixelsPerInchY = ::GetDeviceCaps(printerDc, LOGPIXELSY);
+  int physicalHeight = ::GetDeviceCaps(printerDc, PHYSICALHEIGHT);
+  double heightInInches = double(physicalHeight) / pixelsPerInchY;
+  int pixelsPerInchX = ::GetDeviceCaps(printerDc, LOGPIXELSX);
+  int physicalWidth = ::GetDeviceCaps(printerDc, PHYSICALWIDTH);
+  double widthInches = double(physicalWidth) / pixelsPerInchX;
+  if (aDevmode->dmFields & DM_ORIENTATION &&
+      aDevmode->dmOrientation == DMORIENT_LANDSCAPE) {
+    std::swap(widthInches, heightInInches);
+  }
+  aSettingsInitializer.mPaperInfo.mSize.SizeTo(widthInches * kPointsPerInch,
+                                               heightInInches * kPointsPerInch);
+
+  gfx::MarginDouble margin =
+      WinUtils::GetUnwriteableMarginsForDeviceInInches(printerDc);
+  aSettingsInitializer.mPaperInfo.mUnwriteableMargin = Some(MarginDouble{
+      margin.top * kPointsPerInch, margin.right * kPointsPerInch,
+      margin.bottom * kPointsPerInch, margin.left * kPointsPerInch});
+
+  // Using Y to match existing code for print scaling calculations.
+  aSettingsInitializer.mResolution = pixelsPerInchY;
+
+  if (aDevmode->dmFields & DM_COLOR) {
+    // See comment for PrintSettingsInitializer.mPrintInColor
+    aSettingsInitializer.mPrintInColor =
+        aDevmode->dmColor != DMCOLOR_MONOCHROME;
+  }
+
+  if (aDevmode->dmFields & DM_ORIENTATION) {
+    aSettingsInitializer.mSheetOrientation =
+        int32_t(aDevmode->dmOrientation == DMORIENT_PORTRAIT
+                    ? nsPrintSettings::kPortraitOrientation
+                    : nsPrintSettings::kLandscapeOrientation);
+  }
+
+  if (aDevmode->dmFields & DM_COPIES) {
+    aSettingsInitializer.mNumCopies = aDevmode->dmCopies;
+  }
+
+  if (aDevmode->dmFields & DM_DUPLEX) {
+    switch (aDevmode->dmDuplex) {
+      default:
+        MOZ_FALLTHROUGH_ASSERT("bad value for dmDuplex field");
+      case DMDUP_SIMPLEX:
+        aSettingsInitializer.mDuplex = nsPrintSettings::kDuplexNone;
+        break;
+      case DMDUP_VERTICAL:
+        aSettingsInitializer.mDuplex = nsPrintSettings::kDuplexFlipOnLongEdge;
+        break;
+      case DMDUP_HORIZONTAL:
+        aSettingsInitializer.mDuplex = nsPrintSettings::kDuplexFlipOnShortEdge;
+        break;
+    }
+  }
+}
+
+NS_IMETHODIMP
+nsPrinterWin::GetName(nsAString& aName) {
+  aName.Assign(mName);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsPrinterWin::GetSystemName(nsAString& aName) {
+  aName.Assign(mName);
+  return NS_OK;
+}
+
+namespace mozilla {
+template <>
+void ResolveOrReject(Promise& aPromise, nsPrinterWin& aPrinter,
+                     const PrintSettingsInitializer& aResult) {
+  aPromise.MaybeResolve(
+      RefPtr<nsIPrintSettings>(CreatePlatformPrintSettings(aResult)));
+}
+}  // namespace mozilla
+
+NS_IMETHODIMP nsPrinterWin::CopyFromWithValidation(
+    nsIPrintSettings* aSettingsToCopyFrom, JSContext* aCx,
+    Promise** aResultPromise) {
+  MOZ_ASSERT(NS_IsMainThread());
+  MOZ_ASSERT(aResultPromise);
+
+  PrintSettingsInitializer settingsInitializer =
+      aSettingsToCopyFrom->GetSettingsInitializer();
+  return PrintBackgroundTaskPromise(
+      *this, aCx, aResultPromise, "CopyFromWithValidation"_ns,
+      &nsPrinterWin::GetValidatedSettings, settingsInitializer);
+}
+
+bool nsPrinterWin::SupportsDuplex() const {
+  MutexAutoLock autoLock(mDriverMutex);
+  return ::DeviceCapabilitiesW(mName.get(), nullptr, DC_DUPLEX, nullptr,
+                               nullptr) == 1;
+}
+
+bool nsPrinterWin::SupportsColor() const {
+  MutexAutoLock autoLock(mDriverMutex);
+  return ::DeviceCapabilitiesW(mName.get(), nullptr, DC_COLORDEVICE, nullptr,
+                               nullptr) == 1;
+}
+
+bool nsPrinterWin::SupportsMonochrome() const {
+  if (!SupportsColor()) {
+    return true;
+  }
+
+  nsHPRINTER hPrinter = nullptr;
+  if (NS_WARN_IF(!::OpenPrinterW(mName.get(), &hPrinter, nullptr))) {
+    return false;
+  }
+  nsAutoPrinter autoPrinter(hPrinter);
+
+  nsTArray<uint8_t> devmodeWStorage = CopyDefaultDevmodeW();
+  if (devmodeWStorage.IsEmpty()) {
+    return false;
+  }
+
+  auto* devmode = reinterpret_cast<DEVMODEW*>(devmodeWStorage.Elements());
+
+  devmode->dmFields |= DM_COLOR;
+  devmode->dmColor = DMCOLOR_MONOCHROME;
+  // Try to modify the devmode settings and see if the setting sticks.
+  //
+  // This has been the only reliable way to detect it that we've found.
+  MutexAutoLock autoLock(mDriverMutex);
+  LONG ret =
+      ::DocumentPropertiesW(nullptr, autoPrinter.get(), mName.get(), devmode,
+                            devmode, DM_IN_BUFFER | DM_OUT_BUFFER);
+  if (ret != IDOK) {
+    return false;
+  }
+  return !(devmode->dmFields & DM_COLOR) ||
+         devmode->dmColor == DMCOLOR_MONOCHROME;
+}
+
+bool nsPrinterWin::SupportsCollation() const {
+  MutexAutoLock autoLock(mDriverMutex);
+  return ::DeviceCapabilitiesW(mName.get(), nullptr, DC_COLLATE, nullptr,
+                               nullptr) == 1;
+}
+
+nsPrinterBase::PrinterInfo nsPrinterWin::CreatePrinterInfo() const {
+  return PrinterInfo{PaperList(), DefaultSettings()};
+}
+
+mozilla::gfx::MarginDouble nsPrinterWin::GetMarginsForPaper(
+    nsString aPaperId) const {
+  gfx::MarginDouble margin;
+
+  nsTArray<uint8_t> devmodeWStorage = CopyDefaultDevmodeW();
+  if (devmodeWStorage.IsEmpty()) {
+    return margin;
+  }
+
+  auto* devmode = reinterpret_cast<DEVMODEW*>(devmodeWStorage.Elements());
+
+  devmode->dmFields = DM_PAPERSIZE;
+  devmode->dmPaperSize = _wtoi((const wchar_t*)aPaperId.BeginReading());
+  HDC dc;
+  {
+    MutexAutoLock autoLock(mDriverMutex);
+    dc = ::CreateICW(nullptr, mName.get(), nullptr, devmode);
+  }
+  nsAutoHDC printerDc(dc);
+  MOZ_ASSERT(printerDc, "CreateICW failed");
+  if (!printerDc) {
+    return margin;
+  }
+  margin = WinUtils::GetUnwriteableMarginsForDeviceInInches(printerDc);
+  margin.top *= kPointsPerInch;
+  margin.right *= kPointsPerInch;
+  margin.bottom *= kPointsPerInch;
+  margin.left *= kPointsPerInch;
+
+  return margin;
+}
+
+nsTArray<uint8_t> nsPrinterWin::CopyDefaultDevmodeW() const {
+  nsTArray<uint8_t> devmodeStorageW;
+
+  auto devmodeStorageWLock = mDefaultDevmodeWStorage.Lock();
+  if (devmodeStorageWLock->IsEmpty()) {
+    nsHPRINTER hPrinter = nullptr;
+    // OpenPrinter could fail if, for example, the printer has been removed
+    // or otherwise become inaccessible since it was selected.
+    if (NS_WARN_IF(!::OpenPrinterW(mName.get(), &hPrinter, nullptr))) {
+      return devmodeStorageW;
+    }
+    nsAutoPrinter autoPrinter(hPrinter);
+    // Allocate devmode storage of the correct size.
+    MutexAutoLock autoLock(mDriverMutex);
+    LONG bytesNeeded = ::DocumentPropertiesW(nullptr, autoPrinter.get(),
+                                             mName.get(), nullptr, nullptr, 0);
+    // Note that we must cast the sizeof() to a signed type so that comparison
+    // with the signed, potentially-negative bytesNeeded will work!
+    MOZ_ASSERT(bytesNeeded >= LONG(sizeof(DEVMODEW)),
+               "DocumentPropertiesW failed to get valid size");
+    if (bytesNeeded < LONG(sizeof(DEVMODEW))) {
+      return devmodeStorageW;
+    }
+
+    // Allocate extra space in case of bad drivers that return a too-small
+    // result from DocumentProperties.
+    // (See https://bugzilla.mozilla.org/show_bug.cgi?id=1664530#c5)
+    if (!devmodeStorageWLock->SetLength(bytesNeeded * 2, fallible)) {
+      return devmodeStorageW;
+    }
+
+    memset(devmodeStorageWLock->Elements(), 0, devmodeStorageWLock->Length());
+    auto* devmode =
+        reinterpret_cast<DEVMODEW*>(devmodeStorageWLock->Elements());
+    LONG ret = ::DocumentPropertiesW(nullptr, autoPrinter.get(), mName.get(),
+                                     devmode, nullptr, DM_OUT_BUFFER);
+    MOZ_ASSERT(ret == IDOK, "DocumentPropertiesW failed");
+    // Make sure that the lengths in the DEVMODEW make sense.
+    if (ret != IDOK || devmode->dmSize != sizeof(DEVMODEW) ||
+        devmode->dmSize + devmode->dmDriverExtra >
+            devmodeStorageWLock->Length()) {
+      // Clear mDefaultDevmodeWStorage to make sure we try again next time.
+      devmodeStorageWLock->Clear();
+      return devmodeStorageW;
+    }
+  }
+
+  devmodeStorageW.Assign(devmodeStorageWLock.ref());
+  return devmodeStorageW;
+}
+
+nsTArray<mozilla::PaperInfo> nsPrinterWin::PaperList() const {
+  // Paper IDs are returned as WORDs.
+  int requiredArrayCount = 0;
+  auto paperIds = GetDeviceCapabilityArray<WORD>(
+      mName.get(), DC_PAPERS, mDriverMutex, requiredArrayCount);
+  if (!paperIds.Length()) {
+    return {};
+  }
+
+  // Paper names are returned in 64 long character buffers.
+  auto paperNames = GetDeviceCapabilityArray<Array<wchar_t, 64>>(
+      mName.get(), DC_PAPERNAMES, mDriverMutex, requiredArrayCount);
+  // Check that we have the same number of names as IDs.
+  if (paperNames.Length() != paperIds.Length()) {
+    return {};
+  }
+
+  // Paper sizes are returned as POINT structs with a tenth of a millimeter as
+  // the unit.
+  auto paperSizes = GetDeviceCapabilityArray<POINT>(
+      mName.get(), DC_PAPERSIZE, mDriverMutex, requiredArrayCount);
+  // Check that we have the same number of sizes as IDs.
+  if (paperSizes.Length() != paperIds.Length()) {
+    return {};
+  }
+
+  nsTArray<mozilla::PaperInfo> paperList;
+  paperList.SetCapacity(paperNames.Length());
+  for (size_t i = 0; i < paperNames.Length(); ++i) {
+    // Paper names are null terminated unless they are 64 characters long.
+    auto firstNull =
+        std::find(paperNames[i].cbegin(), paperNames[i].cend(), L'\0');
+    auto nameLength = firstNull - paperNames[i].cbegin();
+    double width = paperSizes[i].x * kPointsPerTenthMM;
+    double height = paperSizes[i].y * kPointsPerTenthMM;
+
+    // Skip if no name or invalid size.
+    if (!nameLength || width <= 0 || height <= 0) {
+      continue;
+    }
+
+    // Windows paper IDs are 16-bit integers; we stringify them to store in the
+    // PaperInfo.mId field.
+    nsString paperIdString;
+    paperIdString.AppendInt(paperIds[i]);
+
+    // We don't resolve the margins eagerly because they're really expensive (on
+    // the order of seconds for some drivers).
+    nsDependentSubstring name(paperNames[i].cbegin(), nameLength);
+    paperList.AppendElement(mozilla::PaperInfo(paperIdString, nsString(name),
+                                               {width, height}, Nothing()));
+  }
+
+  return paperList;
+}
+
+PrintSettingsInitializer nsPrinterWin::DefaultSettings() const {
+  nsTArray<uint8_t> devmodeWStorage = CopyDefaultDevmodeW();
+  if (devmodeWStorage.IsEmpty()) {
+    return {};
+  }
+
+  const auto* devmode =
+      reinterpret_cast<const DEVMODEW*>(devmodeWStorage.Elements());
+
+  PrintSettingsInitializer settingsInitializer;
+  DevmodeToSettingsInitializer(mName, devmode, mDriverMutex,
+                               settingsInitializer);
+  settingsInitializer.mDevmodeWStorage = std::move(devmodeWStorage);
+  return settingsInitializer;
+}
+
+PrintSettingsInitializer nsPrinterWin::GetValidatedSettings(
+    PrintSettingsInitializer aSettingsToValidate) const {
+  // This function validates the settings by relying on the printer driver
+  // rejecting any invalid settings and resetting them to valid values.
+
+  // Create a copy of the default DEVMODE for this printer.
+  nsTArray<uint8_t> devmodeWStorage = CopyDefaultDevmodeW();
+  if (devmodeWStorage.IsEmpty()) {
+    return aSettingsToValidate;
+  }
+
+  nsHPRINTER hPrinter = nullptr;
+  if (NS_WARN_IF(!::OpenPrinterW(mName.get(), &hPrinter, nullptr))) {
+    return aSettingsToValidate;
+  }
+  nsAutoPrinter autoPrinter(hPrinter);
+
+  // Copy the settings from aSettingsToValidate into our DEVMODE.
+  DEVMODEW* devmode = reinterpret_cast<DEVMODEW*>(devmodeWStorage.Elements());
+  if (!aSettingsToValidate.mPaperInfo.mId.IsEmpty()) {
+    devmode->dmPaperSize = _wtoi(
+        (const wchar_t*)aSettingsToValidate.mPaperInfo.mId.BeginReading());
+    devmode->dmFields |= DM_PAPERSIZE;
+  } else {
+    devmode->dmPaperSize = 0;
+    devmode->dmFields &= ~DM_PAPERSIZE;
+  }
+
+  devmode->dmFields |= DM_COLOR;
+  devmode->dmColor =
+      aSettingsToValidate.mPrintInColor ? DMCOLOR_COLOR : DMCOLOR_MONOCHROME;
+
+  // Note: small page sizes can be required here for sticker, label and slide
+  // printers etc. see bug 1271900.
+  if (aSettingsToValidate.mPaperInfo.mSize.height > 0) {
+    devmode->dmPaperLength = std::round(
+        aSettingsToValidate.mPaperInfo.mSize.height / kPointsPerTenthMM);
+    devmode->dmFields |= DM_PAPERLENGTH;
+  } else {
+    devmode->dmPaperLength = 0;
+    devmode->dmFields &= ~DM_PAPERLENGTH;
+  }
+
+  if (aSettingsToValidate.mPaperInfo.mSize.width > 0) {
+    devmode->dmPaperWidth = std::round(
+        aSettingsToValidate.mPaperInfo.mSize.width / kPointsPerTenthMM);
+    devmode->dmFields |= DM_PAPERWIDTH;
+  } else {
+    devmode->dmPaperWidth = 0;
+    devmode->dmFields &= ~DM_PAPERWIDTH;
+  }
+
+  // Setup Orientation
+  devmode->dmOrientation = aSettingsToValidate.mSheetOrientation ==
+                                   nsPrintSettings::kPortraitOrientation
+                               ? DMORIENT_PORTRAIT
+                               : DMORIENT_LANDSCAPE;
+  devmode->dmFields |= DM_ORIENTATION;
+
+  // Setup Number of Copies
+  devmode->dmCopies = aSettingsToValidate.mNumCopies;
+  devmode->dmFields |= DM_COPIES;
+
+  // Setup Simplex/Duplex mode
+  devmode->dmFields |= DM_DUPLEX;
+  switch (aSettingsToValidate.mDuplex) {
+    case nsPrintSettings::kDuplexNone:
+      devmode->dmDuplex = DMDUP_SIMPLEX;
+      break;
+    case nsPrintSettings::kDuplexFlipOnLongEdge:
+      devmode->dmDuplex = DMDUP_VERTICAL;
+      break;
+    case nsPrintSettings::kDuplexFlipOnShortEdge:
+      devmode->dmDuplex = DMDUP_HORIZONTAL;
+      break;
+    default:
+      MOZ_ASSERT_UNREACHABLE("bad value for duplex option");
+      break;
+  }
+
+  // Apply the settings in the DEVMODE to the printer and retrieve the updated
+  // DEVMODE back into the same structure.
+  LONG ret;
+  {
+    MutexAutoLock autoLock(mDriverMutex);
+    ret = ::DocumentPropertiesW(nullptr, autoPrinter.get(), mName.get(),
+                                devmode, devmode, DM_IN_BUFFER | DM_OUT_BUFFER);
+  }
+  if (ret != IDOK) {
+    return aSettingsToValidate;
+  }
+
+  // Copy the settings back from the DEVMODE into aSettingsToValidate and
+  // return.
+  DevmodeToSettingsInitializer(mName, devmode, mDriverMutex,
+                               aSettingsToValidate);
+  aSettingsToValidate.mDevmodeWStorage = std::move(devmodeWStorage);
+  return aSettingsToValidate;
+}
diff --git a/widget/windows/nsPrinterWin.h b/widget/windows/nsPrinterWin.h
new file mode 100644
index 0000000000..8afcf14d0e
--- /dev/null
+++ b/widget/windows/nsPrinterWin.h
@@ -0,0 +1,53 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef nsPrinterWin_h_
+#define nsPrinterWin_h_
+
+#include "nsPrinterBase.h"
+#include "mozilla/DataMutex.h"
+#include "nsTArrayForwardDeclare.h"
+
+class nsPrinterWin final : public nsPrinterBase {
+ public:
+  NS_IMETHOD GetName(nsAString& aName) override;
+  NS_IMETHOD GetSystemName(nsAString& aName) override;
+  NS_IMETHOD CopyFromWithValidation(nsIPrintSettings*, JSContext*,
+                                    Promise**) final;
+  bool SupportsDuplex() const final;
+  bool SupportsColor() const final;
+  bool SupportsMonochrome() const final;
+  bool SupportsCollation() const final;
+  PrinterInfo CreatePrinterInfo() const final;
+  MarginDouble GetMarginsForPaper(nsString aPaperId) const final;
+
+  nsPrinterWin() = delete;
+  static already_AddRefed<nsPrinterWin> Create(
+      const mozilla::CommonPaperInfoArray* aPaperInfoArray,
+      const nsAString& aName);
+
+ private:
+  nsPrinterWin(const mozilla::CommonPaperInfoArray* aPaperInfoArray,
+               const nsAString& aName);
+  ~nsPrinterWin() = default;
+
+  PrintSettingsInitializer GetValidatedSettings(
+      PrintSettingsInitializer aSettingsToValidate) const;
+
+  nsTArray<uint8_t> CopyDefaultDevmodeW() const;
+  nsTArray<mozilla::PaperInfo> PaperList() const;
+  PrintSettingsInitializer DefaultSettings() const;
+
+  const nsString mName;
+  mutable mozilla::DataMutex<nsTArray<uint8_t>> mDefaultDevmodeWStorage;
+  // Even though some documentation seems to suggest that you should be able to
+  // use printer drivers on separate threads if you have separate handles, we
+  // see threading issues with multiple drivers. This Mutex is used to lock
+  // around all calls to DeviceCapabilitiesW, DocumentPropertiesW and
+  // CreateICW/DCW, to hopefully prevent these issues.
+  mutable mozilla::Mutex mDriverMutex MOZ_UNANNOTATED{"nsPrinterWin::Driver"};
+};
+
+#endif  // nsPrinterWin_h_
diff --git a/widget/windows/nsSharePicker.cpp b/widget/windows/nsSharePicker.cpp
new file mode 100644
index 0000000000..9cdc792718
--- /dev/null
+++ b/widget/windows/nsSharePicker.cpp
@@ -0,0 +1,81 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsSharePicker.h"
+
+#include "nsString.h"
+#include "nsThreadUtils.h"
+#include "WindowsUIUtils.h"
+#include "nsPIDOMWindow.h"
+#include "mozilla/dom/Promise.h"
+#include "mozilla/ErrorResult.h"
+#include "mozilla/Unused.h"
+
+using mozilla::dom::Promise;
+
+///////////////////////////////////////////////////////////////////////////////
+// nsISharePicker
+
+NS_IMPL_ISUPPORTS(nsSharePicker, nsISharePicker)
+
+namespace {
+inline NS_ConvertUTF8toUTF16 NS_ConvertUTF8toUTF16_MaybeVoid(
+    const nsACString& aStr) {
+  auto str = NS_ConvertUTF8toUTF16(aStr);
+  str.SetIsVoid(aStr.IsVoid());
+  return str;
+}
+inline nsIGlobalObject* GetGlobalObject() {
+  return xpc::NativeGlobal(xpc::PrivilegedJunkScope());
+}
+}  // namespace
+
+NS_IMETHODIMP
+nsSharePicker::Init(mozIDOMWindowProxy* aOpenerWindow) {
+  if (mInited) {
+    return NS_ERROR_FAILURE;
+  }
+  mOpenerWindow = aOpenerWindow;
+  mInited = true;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsSharePicker::GetOpenerWindow(mozIDOMWindowProxy** aOpenerWindow) {
+  *aOpenerWindow = mOpenerWindow;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsSharePicker::Share(const nsACString& aTitle, const nsACString& aText,
+                     nsIURI* aUrl, Promise** aPromise) {
+  mozilla::ErrorResult result;
+  RefPtr<Promise> promise = Promise::Create(GetGlobalObject(), result);
+  if (NS_WARN_IF(result.Failed())) {
+    return result.StealNSResult();
+  }
+  nsAutoCString urlString;
+  if (aUrl) {
+    nsresult rv = aUrl->GetSpec(urlString);
+    MOZ_ASSERT(NS_SUCCEEDED(rv));
+    mozilla::Unused << rv;
+  } else {
+    urlString.SetIsVoid(true);
+  }
+
+  auto mozPromise =
+      WindowsUIUtils::Share(NS_ConvertUTF8toUTF16_MaybeVoid(aTitle),
+                            NS_ConvertUTF8toUTF16_MaybeVoid(aText),
+                            NS_ConvertUTF8toUTF16_MaybeVoid(urlString));
+  mozPromise->Then(
+      mozilla::GetCurrentSerialEventTarget(), __func__,
+      [promise]() { promise->MaybeResolveWithUndefined(); },
+      [promise]() { promise->MaybeReject(NS_ERROR_DOM_ABORT_ERR); });
+
+  promise.forget(aPromise);
+
+  return NS_OK;
+}
diff --git a/widget/windows/nsSharePicker.h b/widget/windows/nsSharePicker.h
new file mode 100644
index 0000000000..d9ba9d2a6d
--- /dev/null
+++ b/widget/windows/nsSharePicker.h
@@ -0,0 +1,29 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef nsSharePicker_h__
+#define nsSharePicker_h__
+
+#include "nsCOMPtr.h"
+#include "nsISharePicker.h"
+#include "nsPIDOMWindow.h"
+#include "nsThreadUtils.h"
+
+class nsSharePicker : public nsISharePicker {
+  virtual ~nsSharePicker() = default;
+
+ public:
+  nsSharePicker() = default;
+
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSISHAREPICKER
+
+ private:
+  bool mInited = false;
+  mozIDOMWindowProxy* mOpenerWindow;
+};
+
+#endif  // nsSharePicker_h__
diff --git a/widget/windows/nsSound.cpp b/widget/windows/nsSound.cpp
new file mode 100644
index 0000000000..1fecf09c3a
--- /dev/null
+++ b/widget/windows/nsSound.cpp
@@ -0,0 +1,331 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nscore.h"
+#include <stdio.h>
+#include "nsString.h"
+#include <windows.h>
+
+// mmsystem.h is needed to build with WIN32_LEAN_AND_MEAN
+#include <mmsystem.h>
+
+#include "HeadlessSound.h"
+#include "nsSound.h"
+#include "nsIURL.h"
+#include "nsNetUtil.h"
+#include "nsIChannel.h"
+#include "nsContentUtils.h"
+#include "nsCRT.h"
+#include "nsIObserverService.h"
+
+#include "mozilla/Logging.h"
+#include "prtime.h"
+
+#include "nsNativeCharsetUtils.h"
+#include "nsThreadUtils.h"
+#include "mozilla/ClearOnShutdown.h"
+#include "gfxPlatform.h"
+
+using mozilla::LogLevel;
+
+#ifdef DEBUG
+static mozilla::LazyLogModule gWin32SoundLog("nsSound");
+#endif
+
+// Hackaround for bug 1644240
+// When we call PlaySound for the first time in the process, winmm.dll creates
+// a new thread and starts a message loop in winmm!mciwindow.  After that,
+// every call of PlaySound communicates with that thread via Window messages.
+// It seems that Warsaw application hooks USER32!GetMessageA, and there is
+// a timing window where they free their trampoline region without reverting
+// the hook on USER32!GetMessageA, resulting in crash when winmm!mciwindow
+// receives a message because it tries to jump to a freed buffer.
+// Based on the crash reports, it happened on all versions of Windows x64, and
+// the possible condition was wslbdhm64.dll was loaded but wslbscrwh64.dll was
+// unloaded.  Therefore we suppress playing a sound under such a condition.
+static bool ShouldSuppressPlaySound() {
+#if defined(_M_AMD64)
+  if (::GetModuleHandle(L"wslbdhm64.dll") &&
+      !::GetModuleHandle(L"wslbscrwh64.dll")) {
+    return true;
+  }
+#endif  // defined(_M_AMD64)
+  return false;
+}
+
+class nsSoundPlayer : public mozilla::Runnable {
+ public:
+  explicit nsSoundPlayer(const nsAString& aSoundName)
+      : mozilla::Runnable("nsSoundPlayer"),
+        mSoundName(aSoundName),
+        mSoundData(nullptr) {}
+
+  nsSoundPlayer(const uint8_t* aData, size_t aSize)
+      : mozilla::Runnable("nsSoundPlayer"), mSoundName(u""_ns) {
+    MOZ_ASSERT(aSize > 0, "Size should not be zero");
+    MOZ_ASSERT(aData, "Data shoud not be null");
+
+    // We will disptach nsSoundPlayer to playerthread, so keep a data copy
+    mSoundData = new uint8_t[aSize];
+    memcpy(mSoundData, aData, aSize);
+  }
+
+  NS_DECL_NSIRUNNABLE
+
+ protected:
+  ~nsSoundPlayer();
+
+  nsString mSoundName;
+  uint8_t* mSoundData;
+};
+
+NS_IMETHODIMP
+nsSoundPlayer::Run() {
+  if (ShouldSuppressPlaySound()) {
+    return NS_OK;
+  }
+
+  MOZ_ASSERT(!mSoundName.IsEmpty() || mSoundData,
+             "Sound name or sound data should be specified");
+  DWORD flags = SND_NODEFAULT | SND_ASYNC;
+
+  if (mSoundData) {
+    flags |= SND_MEMORY;
+    ::PlaySoundW(reinterpret_cast<LPCWSTR>(mSoundData), nullptr, flags);
+  } else {
+    flags |= SND_ALIAS;
+    ::PlaySoundW(mSoundName.get(), nullptr, flags);
+  }
+  return NS_OK;
+}
+
+nsSoundPlayer::~nsSoundPlayer() { delete[] mSoundData; }
+
+mozilla::StaticRefPtr<nsISound> nsSound::sInstance;
+
+/* static */
+already_AddRefed<nsISound> nsSound::GetInstance() {
+  if (!sInstance) {
+    if (gfxPlatform::IsHeadless()) {
+      sInstance = new mozilla::widget::HeadlessSound();
+    } else {
+      RefPtr<nsSound> sound = new nsSound();
+      nsresult rv = sound->CreatePlayerThread();
+      if (NS_WARN_IF(NS_FAILED(rv))) {
+        return nullptr;
+      }
+      sInstance = sound.forget();
+    }
+    ClearOnShutdown(&sInstance);
+  }
+
+  RefPtr<nsISound> service = sInstance;
+  return service.forget();
+}
+
+#ifndef SND_PURGE
+// Not available on Windows CE, and according to MSDN
+// doesn't do anything on recent windows either.
+#  define SND_PURGE 0
+#endif
+
+NS_IMPL_ISUPPORTS(nsSound, nsISound, nsIStreamLoaderObserver, nsIObserver)
+
+nsSound::nsSound() : mInited(false) {}
+
+nsSound::~nsSound() {}
+
+void nsSound::PurgeLastSound() {
+  // Halt any currently playing sound.
+  if (mSoundPlayer) {
+    if (mPlayerThread) {
+      mPlayerThread->Dispatch(
+          NS_NewRunnableFunction("nsSound::PurgeLastSound",
+                                 [player = std::move(mSoundPlayer)]() {
+                                   // Capture move mSoundPlayer to lambda then
+                                   // PlaySoundW(nullptr, nullptr, SND_PURGE)
+                                   // will be called before freeing the
+                                   // nsSoundPlayer.
+                                   if (ShouldSuppressPlaySound()) {
+                                     return;
+                                   }
+                                   ::PlaySoundW(nullptr, nullptr, SND_PURGE);
+                                 }),
+          NS_DISPATCH_NORMAL);
+    }
+  }
+}
+
+NS_IMETHODIMP nsSound::Beep() {
+  ::MessageBeep(0);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP nsSound::OnStreamComplete(nsIStreamLoader* aLoader,
+                                        nsISupports* context, nsresult aStatus,
+                                        uint32_t dataLen, const uint8_t* data) {
+  MOZ_ASSERT(mPlayerThread, "player thread should not be null ");
+  // print a load error on bad status
+  if (NS_FAILED(aStatus)) {
+#ifdef DEBUG
+    if (aLoader) {
+      nsCOMPtr<nsIRequest> request;
+      nsCOMPtr<nsIChannel> channel;
+      aLoader->GetRequest(getter_AddRefs(request));
+      if (request) channel = do_QueryInterface(request);
+      if (channel) {
+        nsCOMPtr<nsIURI> uri;
+        channel->GetURI(getter_AddRefs(uri));
+        if (uri) {
+          nsAutoCString uriSpec;
+          uri->GetSpec(uriSpec);
+          MOZ_LOG(gWin32SoundLog, LogLevel::Info,
+                  ("Failed to load %s\n", uriSpec.get()));
+        }
+      }
+    }
+#endif
+    return aStatus;
+  }
+
+  PurgeLastSound();
+
+  if (data && dataLen > 0) {
+    MOZ_ASSERT(!mSoundPlayer, "mSoundPlayer should be null");
+    mSoundPlayer = new nsSoundPlayer(data, dataLen);
+    MOZ_ASSERT(mSoundPlayer, "Could not create player");
+
+    nsresult rv = mPlayerThread->Dispatch(mSoundPlayer, NS_DISPATCH_NORMAL);
+    if (NS_WARN_IF(FAILED(rv))) {
+      return rv;
+    }
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP nsSound::Play(nsIURL* aURL) {
+  nsresult rv;
+
+#ifdef DEBUG_SOUND
+  char* url;
+  aURL->GetSpec(&url);
+  MOZ_LOG(gWin32SoundLog, LogLevel::Info, ("%s\n", url));
+#endif
+
+  nsCOMPtr<nsIStreamLoader> loader;
+  rv = NS_NewStreamLoader(
+      getter_AddRefs(loader), aURL,
+      this,  // aObserver
+      nsContentUtils::GetSystemPrincipal(),
+      nsILoadInfo::SEC_ALLOW_CROSS_ORIGIN_SEC_CONTEXT_IS_NULL,
+      nsIContentPolicy::TYPE_OTHER);
+  return rv;
+}
+
+nsresult nsSound::CreatePlayerThread() {
+  if (mPlayerThread) {
+    return NS_OK;
+  }
+  if (NS_WARN_IF(NS_FAILED(NS_NewNamedThread("PlayEventSound",
+                                             getter_AddRefs(mPlayerThread))))) {
+    return NS_ERROR_FAILURE;
+  }
+
+  // Add an observer for shutdown event to release the thread at that time
+  nsCOMPtr<nsIObserverService> observerService =
+      mozilla::services::GetObserverService();
+  if (!observerService) {
+    return NS_ERROR_FAILURE;
+  }
+
+  observerService->AddObserver(this, "xpcom-shutdown-threads", false);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+nsSound::Observe(nsISupports* aSubject, const char* aTopic,
+                 const char16_t* aData) {
+  if (!strcmp(aTopic, "xpcom-shutdown-threads")) {
+    PurgeLastSound();
+
+    if (mPlayerThread) {
+      mPlayerThread->Shutdown();
+      mPlayerThread = nullptr;
+    }
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP nsSound::Init() {
+  if (mInited) {
+    return NS_OK;
+  }
+
+  MOZ_ASSERT(mPlayerThread, "player thread should not be null ");
+  // This call halts a sound if it was still playing.
+  // We have to use the sound library for something to make sure
+  // it is initialized.
+  // If we wait until the first sound is played, there will
+  // be a time lag as the library gets loaded.
+  // This should be done in player thread otherwise it will block main thread
+  // at the first time loading sound library.
+  mPlayerThread->Dispatch(
+      NS_NewRunnableFunction("nsSound::Init",
+                             []() {
+                               if (ShouldSuppressPlaySound()) {
+                                 return;
+                               }
+                               ::PlaySoundW(nullptr, nullptr, SND_PURGE);
+                             }),
+      NS_DISPATCH_NORMAL);
+
+  mInited = true;
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP nsSound::PlayEventSound(uint32_t aEventId) {
+  MOZ_ASSERT(mPlayerThread, "player thread should not be null ");
+  PurgeLastSound();
+
+  const wchar_t* sound = nullptr;
+  switch (aEventId) {
+    case EVENT_NEW_MAIL_RECEIVED:
+      sound = L"MailBeep";
+      break;
+    case EVENT_ALERT_DIALOG_OPEN:
+      sound = L"SystemExclamation";
+      break;
+    case EVENT_CONFIRM_DIALOG_OPEN:
+      sound = L"SystemQuestion";
+      break;
+    case EVENT_MENU_EXECUTE:
+      sound = L"MenuCommand";
+      break;
+    case EVENT_MENU_POPUP:
+      sound = L"MenuPopup";
+      break;
+    case EVENT_EDITOR_MAX_LEN:
+      sound = L".Default";
+      break;
+    default:
+      // Win32 plays no sounds at NS_SYSSOUND_PROMPT_DIALOG and
+      // NS_SYSSOUND_SELECT_DIALOG.
+      return NS_OK;
+  }
+  NS_ASSERTION(sound, "sound is null");
+  MOZ_ASSERT(!mSoundPlayer, "mSoundPlayer should be null");
+  mSoundPlayer = new nsSoundPlayer(nsDependentString(sound));
+  MOZ_ASSERT(mSoundPlayer, "Could not create player");
+  nsresult rv = mPlayerThread->Dispatch(mSoundPlayer, NS_DISPATCH_NORMAL);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return rv;
+  }
+  return NS_OK;
+}
diff --git a/widget/windows/nsSound.h b/widget/windows/nsSound.h
new file mode 100644
index 0000000000..d600b0873a
--- /dev/null
+++ b/widget/windows/nsSound.h
@@ -0,0 +1,47 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef __nsSound_h__
+#define __nsSound_h__
+
+#include "nsISound.h"
+#include "nsIObserver.h"
+#include "nsIStreamLoader.h"
+#include "nsCOMPtr.h"
+#include "mozilla/StaticPtr.h"
+
+class nsIThread;
+class nsIRunnable;
+
+class nsSound : public nsISound,
+                public nsIStreamLoaderObserver,
+                public nsIObserver
+
+{
+ public:
+  nsSound();
+  static already_AddRefed<nsISound> GetInstance();
+
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSISOUND
+  NS_DECL_NSISTREAMLOADEROBSERVER
+  NS_DECL_NSIOBSERVER
+
+ private:
+  virtual ~nsSound();
+  void PurgeLastSound();
+
+ private:
+  nsresult CreatePlayerThread();
+
+  nsCOMPtr<nsIThread> mPlayerThread;
+  nsCOMPtr<nsIRunnable> mSoundPlayer;
+  bool mInited;
+
+  static mozilla::StaticRefPtr<nsISound> sInstance;
+};
+
+#endif /* __nsSound_h__ */
diff --git a/widget/windows/nsToolkit.cpp b/widget/windows/nsToolkit.cpp
new file mode 100644
index 0000000000..6eea9c958f
--- /dev/null
+++ b/widget/windows/nsToolkit.cpp
@@ -0,0 +1,69 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsToolkit.h"
+#include "nsAppShell.h"
+#include "nsWindow.h"
+#include "nsWidgetsCID.h"
+#include "prmon.h"
+#include "prtime.h"
+#include "nsComponentManagerUtils.h"
+#include <objbase.h>
+#include "WinUtils.h"
+
+#include "nsUXThemeData.h"
+
+// unknwn.h is needed to build with WIN32_LEAN_AND_MEAN
+#include <unknwn.h>
+
+using namespace mozilla::widget;
+
+nsToolkit* nsToolkit::gToolkit = nullptr;
+HINSTANCE nsToolkit::mDllInstance = 0;
+
+//-------------------------------------------------------------------------
+//
+// constructor
+//
+//-------------------------------------------------------------------------
+nsToolkit::nsToolkit() {
+  MOZ_COUNT_CTOR(nsToolkit);
+
+#if defined(MOZ_STATIC_COMPONENT_LIBS)
+  nsToolkit::Startup(GetModuleHandle(nullptr));
+#endif
+}
+
+//-------------------------------------------------------------------------
+//
+// destructor
+//
+//-------------------------------------------------------------------------
+nsToolkit::~nsToolkit() { MOZ_COUNT_DTOR(nsToolkit); }
+
+void nsToolkit::Startup(HMODULE hModule) {
+  nsToolkit::mDllInstance = hModule;
+  WinUtils::Initialize();
+}
+
+void nsToolkit::Shutdown() {
+  delete gToolkit;
+  gToolkit = nullptr;
+}
+
+//-------------------------------------------------------------------------
+//
+// Return the nsToolkit for the current thread.  If a toolkit does not
+// yet exist, then one will be created...
+//
+//-------------------------------------------------------------------------
+// static
+nsToolkit* nsToolkit::GetToolkit() {
+  if (!gToolkit) {
+    gToolkit = new nsToolkit();
+  }
+
+  return gToolkit;
+}
diff --git a/widget/windows/nsToolkit.h b/widget/windows/nsToolkit.h
new file mode 100644
index 0000000000..4be7bdb80a
--- /dev/null
+++ b/widget/windows/nsToolkit.h
@@ -0,0 +1,47 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef nsToolkit_h__
+#define nsToolkit_h__
+
+#include "nsdefs.h"
+
+#include "nsCOMPtr.h"
+#include <windows.h>
+
+// Avoid including windowsx.h to prevent macro pollution
+#ifndef GET_X_LPARAM
+#  define GET_X_LPARAM(pt) (short(LOWORD(pt)))
+#endif
+#ifndef GET_Y_LPARAM
+#  define GET_Y_LPARAM(pt) (short(HIWORD(pt)))
+#endif
+
+/**
+ * Wrapper around the thread running the message pump.
+ * The toolkit abstraction is necessary because the message pump must
+ * execute within the same thread that created the widget under Win32.
+ */
+
+class nsToolkit {
+ public:
+  nsToolkit();
+
+ private:
+  ~nsToolkit();
+
+ public:
+  static nsToolkit* GetToolkit();
+
+  static HINSTANCE mDllInstance;
+
+  static void Startup(HMODULE hModule);
+  static void Shutdown();
+
+ protected:
+  static nsToolkit* gToolkit;
+};
+
+#endif  // TOOLKIT_H
diff --git a/widget/windows/nsUXThemeConstants.h b/widget/windows/nsUXThemeConstants.h
new file mode 100644
index 0000000000..44ce9ab34e
--- /dev/null
+++ b/widget/windows/nsUXThemeConstants.h
@@ -0,0 +1,256 @@
+/* vim: se cin sw=2 ts=2 et : */
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef nsUXThemeConstants_h
+#define nsUXThemeConstants_h
+
+/*
+ * The following constants are used to determine how a widget is drawn using
+ * Windows' Theme API. For more information on theme parts and states see
+ * http://msdn.microsoft.com/en-us/library/bb773210(VS.85).aspx
+ */
+
+#include <vssym32.h>
+#include <vsstyle.h>
+
+#define THEME_COLOR 204
+#define THEME_FONT 210
+
+// Generic state constants
+#define TS_NORMAL 1
+#define TS_HOVER 2
+#define TS_ACTIVE 3
+#define TS_DISABLED 4
+#define TS_FOCUSED 5
+
+// These constants are reversed for the trackbar (scale) thumb
+#define TKP_FOCUSED 4
+#define TKP_DISABLED 5
+
+// Toolbarbutton constants
+#define TB_CHECKED 5
+#define TB_HOVER_CHECKED 6
+
+// Button constants
+#define BP_BUTTON 1
+#define BP_RADIO 2
+#define BP_CHECKBOX 3
+#define BP_GROUPBOX 4
+#define BP_Count 5
+
+// Textfield constants
+/* This is the EP_EDITTEXT part */
+#define TFP_TEXTFIELD 1
+#define TFP_EDITBORDER_NOSCROLL 6
+#define TFS_READONLY 6
+
+/* These are the state constants for the EDITBORDER parts */
+#define TFS_EDITBORDER_NORMAL 1
+#define TFS_EDITBORDER_HOVER 2
+#define TFS_EDITBORDER_FOCUSED 3
+#define TFS_EDITBORDER_DISABLED 4
+
+// Treeview/listbox constants
+#define TREEVIEW_BODY 1
+
+// Scrollbar constants
+#define SP_BUTTON 1
+#define SP_THUMBHOR 2
+#define SP_THUMBVERT 3
+#define SP_TRACKSTARTHOR 4
+#define SP_TRACKENDHOR 5
+#define SP_TRACKSTARTVERT 6
+#define SP_TRACKENDVERT 7
+#define SP_GRIPPERHOR 8
+#define SP_GRIPPERVERT 9
+
+// Implicit hover state.
+// BASE + 0 = UP, + 1 = DOWN, etc.
+#define SP_BUTTON_IMPLICIT_HOVER_BASE 17
+
+// Scale constants
+#define TKP_TRACK 1
+#define TKP_TRACKVERT 2
+#define TKP_THUMB 3
+#define TKP_THUMBBOTTOM 4
+#define TKP_THUMBTOP 5
+#define TKP_THUMBVERT 6
+#define TKP_THUMBLEFT 7
+#define TKP_THUMBRIGHT 8
+
+// Track state contstants
+#define TRS_NORMAL 1
+
+// Track vertical state constants
+#define TRVS_NORMAL 1
+
+// Spin constants
+#define SPNP_UP 1
+#define SPNP_DOWN 2
+
+// Tab constants
+#define TABP_TAB 4
+#define TABP_TAB_SELECTED 5
+#define TABP_PANELS 9
+#define TABP_PANEL 10
+
+// Tooltip constants
+#define TTP_STANDARD 1
+
+// Dropdown constants
+#define CBP_DROPMARKER 1
+#define CBP_DROPBORDER 4
+/* This is actually the 'READONLY' style */
+#define CBP_DROPFRAME 5
+#define CBP_DROPMARKER_VISTA 6
+
+// Menu Constants
+#define MENU_BARBACKGROUND 7
+#define MENU_BARITEM 8
+#define MENU_POPUPBACKGROUND 9
+#define MENU_POPUPBORDERS 10
+#define MENU_POPUPCHECK 11
+#define MENU_POPUPCHECKBACKGROUND 12
+#define MENU_POPUPGUTTER 13
+#define MENU_POPUPITEM 14
+#define MENU_POPUPSEPARATOR 15
+#define MENU_POPUPSUBMENU 16
+#define MENU_SYSTEMCLOSE 17
+#define MENU_SYSTEMMAXIMIZE 18
+#define MENU_SYSTEMMINIMIZE 19
+#define MENU_SYSTEMRESTORE 20
+
+#define MB_ACTIVE 1
+#define MB_INACTIVE 2
+
+#define MS_NORMAL 1
+#define MS_SELECTED 2
+#define MS_DEMOTED 3
+
+#define MBI_NORMAL 1
+#define MBI_HOT 2
+#define MBI_PUSHED 3
+#define MBI_DISABLED 4
+#define MBI_DISABLEDHOT 5
+#define MBI_DISABLEDPUSHED 6
+
+#define MC_CHECKMARKNORMAL 1
+#define MC_CHECKMARKDISABLED 2
+#define MC_BULLETNORMAL 3
+#define MC_BULLETDISABLED 4
+
+#define MCB_DISABLED 1
+#define MCB_NORMAL 2
+#define MCB_BITMAP 3
+
+#define MPI_NORMAL 1
+#define MPI_HOT 2
+#define MPI_DISABLED 3
+#define MPI_DISABLEDHOT 4
+
+#define MSM_NORMAL 1
+#define MSM_DISABLED 2
+
+// Rebar constants
+#define RP_BAND 3
+#define RP_BACKGROUND 6
+
+// Constants only found in new (98+, 2K+, XP+, etc.) Windows.
+#ifdef DFCS_HOT
+#  undef DFCS_HOT
+#endif
+#define DFCS_HOT 0x00001000
+
+#ifdef COLOR_MENUHILIGHT
+#  undef COLOR_MENUHILIGHT
+#endif
+#define COLOR_MENUHILIGHT 29
+
+#ifdef SPI_GETFLATMENU
+#  undef SPI_GETFLATMENU
+#endif
+#define SPI_GETFLATMENU 0x1022
+#ifndef SPI_GETMENUSHOWDELAY
+#  define SPI_GETMENUSHOWDELAY 106
+#endif  // SPI_GETMENUSHOWDELAY
+#ifndef SPI_GETCARETTIMEOUT
+#  define SPI_GETCARETTIMEOUT 0x2022
+#endif  // SPI_GETCARETTIMEOUT
+#ifndef WS_EX_LAYOUTRTL
+#  define WS_EX_LAYOUTRTL 0x00400000L  // Right to left mirroring
+#endif
+
+// Our extra constants for passing a little bit more info to the renderer.
+#define DFCS_RTL 0x00010000
+
+// Toolbar separator dimension which can't be gotten from Windows
+#define TB_SEPARATOR_HEIGHT 2
+
+namespace mozilla {
+namespace widget {
+namespace themeconst {
+
+// Pulled from sdk/include/vsstyle.h
+enum {
+  WP_CAPTION = 1,
+  WP_SMALLCAPTION = 2,
+  WP_MINCAPTION = 3,
+  WP_SMALLMINCAPTION = 4,
+  WP_MAXCAPTION = 5,
+  WP_SMALLMAXCAPTION = 6,
+  WP_FRAMELEFT = 7,
+  WP_FRAMERIGHT = 8,
+  WP_FRAMEBOTTOM = 9,
+  WP_SMALLFRAMELEFT = 10,
+  WP_SMALLFRAMERIGHT = 11,
+  WP_SMALLFRAMEBOTTOM = 12,
+  WP_SYSBUTTON = 13,
+  WP_MDISYSBUTTON = 14,
+  WP_MINBUTTON = 15,
+  WP_MDIMINBUTTON = 16,
+  WP_MAXBUTTON = 17,
+  WP_CLOSEBUTTON = 18,
+  WP_SMALLCLOSEBUTTON = 19,
+  WP_MDICLOSEBUTTON = 20,
+  WP_RESTOREBUTTON = 21,
+  WP_MDIRESTOREBUTTON = 22,
+  WP_HELPBUTTON = 23,
+  WP_MDIHELPBUTTON = 24,
+  WP_HORZSCROLL = 25,
+  WP_HORZTHUMB = 26,
+  WP_VERTSCROLL = 27,
+  WP_VERTTHUMB = 28,
+  WP_DIALOG = 29,
+  WP_CAPTIONSIZINGTEMPLATE = 30,
+  WP_SMALLCAPTIONSIZINGTEMPLATE = 31,
+  WP_FRAMELEFTSIZINGTEMPLATE = 32,
+  WP_SMALLFRAMELEFTSIZINGTEMPLATE = 33,
+  WP_FRAMERIGHTSIZINGTEMPLATE = 34,
+  WP_SMALLFRAMERIGHTSIZINGTEMPLATE = 35,
+  WP_FRAMEBOTTOMSIZINGTEMPLATE = 36,
+  WP_SMALLFRAMEBOTTOMSIZINGTEMPLATE = 37,
+  WP_FRAME = 38,
+  WP_Count
+};
+
+enum {
+  BS_NORMAL = 1,
+  BS_HOT = 2,
+  BS_PUSHED = 3,
+  BS_DISABLED = 4,
+  BS_INACTIVE = 5 /* undocumented, inactive caption button */
+};
+
+}  // namespace themeconst
+}  // namespace widget
+}  // namespace mozilla
+
+// If any theme part ends up having a value higher than WP_Count, this will
+// need to change.
+#define THEME_PART_DISTINCT_VALUE_COUNT mozilla::widget::themeconst::WP_Count
+
+#endif
diff --git a/widget/windows/nsUXThemeData.cpp b/widget/windows/nsUXThemeData.cpp
new file mode 100644
index 0000000000..b3f9e6fce9
--- /dev/null
+++ b/widget/windows/nsUXThemeData.cpp
@@ -0,0 +1,98 @@
+/* vim: se cin sw=2 ts=2 et : */
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/ArrayUtils.h"
+#include "mozilla/WindowsVersion.h"
+
+#include "nsUXThemeData.h"
+#include "nsDebug.h"
+#include "nsToolkit.h"
+#include "nsUXThemeConstants.h"
+#include "gfxWindowsPlatform.h"
+
+using namespace mozilla;
+using namespace mozilla::widget;
+
+nsUXThemeData::ThemeHandle nsUXThemeData::sThemes[eUXNumClasses];
+
+nsUXThemeData::ThemeHandle::~ThemeHandle() { Close(); }
+
+void nsUXThemeData::ThemeHandle::OpenOnce(HWND aWindow, LPCWSTR aClassList) {
+  if (mHandle.isSome()) {
+    return;
+  }
+
+  mHandle = Some(OpenThemeData(aWindow, aClassList));
+}
+
+void nsUXThemeData::ThemeHandle::Close() {
+  if (mHandle.isNothing()) {
+    return;
+  }
+
+  if (HANDLE rawHandle = mHandle.extract()) {
+    CloseThemeData(rawHandle);
+  }
+}
+
+nsUXThemeData::ThemeHandle::operator HANDLE() {
+  return mHandle.valueOr(nullptr);
+}
+
+void nsUXThemeData::Invalidate() {
+  for (auto& theme : sThemes) {
+    theme.Close();
+  }
+}
+
+HANDLE
+nsUXThemeData::GetTheme(nsUXThemeClass cls) {
+  NS_ASSERTION(cls < eUXNumClasses, "Invalid theme class!");
+  sThemes[cls].OpenOnce(nullptr, GetClassName(cls));
+  return sThemes[cls];
+}
+
+const wchar_t* nsUXThemeData::GetClassName(nsUXThemeClass cls) {
+  switch (cls) {
+    case eUXButton:
+      return L"Button";
+    case eUXEdit:
+      return L"Edit";
+    case eUXRebar:
+      return L"Rebar";
+    case eUXToolbar:
+      return L"Toolbar";
+    case eUXProgress:
+      return L"Progress";
+    case eUXTab:
+      return L"Tab";
+    case eUXTrackbar:
+      return L"Trackbar";
+    case eUXCombobox:
+      return L"Combobox";
+    case eUXHeader:
+      return L"Header";
+    case eUXListview:
+      return L"Listview";
+    case eUXMenu:
+      return L"Menu";
+    default:
+      MOZ_ASSERT_UNREACHABLE("unknown uxtheme class");
+      return L"";
+  }
+}
+
+bool nsUXThemeData::sIsHighContrastOn = false;
+
+// static
+void nsUXThemeData::UpdateNativeThemeInfo() {
+  HIGHCONTRAST highContrastInfo;
+  highContrastInfo.cbSize = sizeof(HIGHCONTRAST);
+  sIsHighContrastOn =
+      SystemParametersInfo(SPI_GETHIGHCONTRAST, 0, &highContrastInfo, 0) &&
+      highContrastInfo.dwFlags & HCF_HIGHCONTRASTON;
+}
diff --git a/widget/windows/nsUXThemeData.h b/widget/windows/nsUXThemeData.h
new file mode 100644
index 0000000000..38be8b4484
--- /dev/null
+++ b/widget/windows/nsUXThemeData.h
@@ -0,0 +1,69 @@
+/* vim: se cin sw=2 ts=2 et : */
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+#ifndef __UXThemeData_h__
+#define __UXThemeData_h__
+#include <windows.h>
+#include <uxtheme.h>
+
+#include "nscore.h"
+#include "mozilla/LookAndFeel.h"
+#include "mozilla/Maybe.h"
+#include "WinUtils.h"
+
+#include "nsWindowDefs.h"
+
+enum nsUXThemeClass {
+  eUXButton = 0,
+  eUXEdit,
+  eUXRebar,
+  eUXToolbar,
+  eUXProgress,
+  eUXTab,
+  eUXTrackbar,
+  eUXCombobox,
+  eUXHeader,
+  eUXListview,
+  eUXMenu,
+  eUXNumClasses
+};
+
+class nsUXThemeData {
+  // This class makes sure we don't attempt to open a theme if the previous
+  // loading attempt has failed because OpenThemeData is a heavy task and
+  // it's less likely that the API returns a different result.
+  class ThemeHandle final {
+    mozilla::Maybe<HANDLE> mHandle;
+
+   public:
+    ThemeHandle() = default;
+    ~ThemeHandle();
+
+    // Disallow copy and move
+    ThemeHandle(const ThemeHandle&) = delete;
+    ThemeHandle(ThemeHandle&&) = delete;
+    ThemeHandle& operator=(const ThemeHandle&) = delete;
+    ThemeHandle& operator=(ThemeHandle&&) = delete;
+
+    operator HANDLE();
+    void OpenOnce(HWND aWindow, LPCWSTR aClassList);
+    void Close();
+  };
+
+  static ThemeHandle sThemes[eUXNumClasses];
+  static const wchar_t* GetClassName(nsUXThemeClass);
+
+ public:
+  static bool sIsHighContrastOn;
+
+  static void Invalidate();
+  static HANDLE GetTheme(nsUXThemeClass cls);
+  static HMODULE GetThemeDLL();
+
+  static void UpdateNativeThemeInfo();
+  static bool IsHighContrastOn() { return sIsHighContrastOn; }
+};
+#endif  // __UXThemeData_h__
diff --git a/widget/windows/nsUserIdleServiceWin.cpp b/widget/windows/nsUserIdleServiceWin.cpp
new file mode 100644
index 0000000000..7cf957dffd
--- /dev/null
+++ b/widget/windows/nsUserIdleServiceWin.cpp
@@ -0,0 +1,20 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:expandtab:shiftwidth=4:tabstop=4:
+ */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsUserIdleServiceWin.h"
+#include <windows.h>
+
+bool nsUserIdleServiceWin::PollIdleTime(uint32_t* aIdleTime) {
+  LASTINPUTINFO inputInfo;
+  inputInfo.cbSize = sizeof(inputInfo);
+  if (!::GetLastInputInfo(&inputInfo)) return false;
+
+  *aIdleTime =
+      SAFE_COMPARE_EVEN_WITH_WRAPPING(GetTickCount(), inputInfo.dwTime);
+
+  return true;
+}
diff --git a/widget/windows/nsUserIdleServiceWin.h b/widget/windows/nsUserIdleServiceWin.h
new file mode 100644
index 0000000000..f9a47c8df5
--- /dev/null
+++ b/widget/windows/nsUserIdleServiceWin.h
@@ -0,0 +1,48 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:expandtab:shiftwidth=4:tabstop=4:
+ */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef nsUserIdleServiceWin_h__
+#define nsUserIdleServiceWin_h__
+
+#include "nsUserIdleService.h"
+#include "mozilla/AppShutdown.h"
+
+/* NOTE: Compare of GetTickCount() could overflow.  This corrects for
+ * overflow situations.
+ ***/
+#ifndef SAFE_COMPARE_EVEN_WITH_WRAPPING
+#  define SAFE_COMPARE_EVEN_WITH_WRAPPING(A, B) \
+    (((int)((long)A - (long)B) & 0xFFFFFFFF))
+#endif
+
+class nsUserIdleServiceWin : public nsUserIdleService {
+ public:
+  NS_INLINE_DECL_REFCOUNTING_INHERITED(nsUserIdleServiceWin, nsUserIdleService)
+
+  bool PollIdleTime(uint32_t* aIdleTime) override;
+
+  static already_AddRefed<nsUserIdleServiceWin> GetInstance() {
+    RefPtr<nsUserIdleServiceWin> idleService =
+        nsUserIdleService::GetInstance().downcast<nsUserIdleServiceWin>();
+    if (!idleService) {
+      // Avoid late instantiation or resurrection during shutdown.
+      if (mozilla::AppShutdown::IsInOrBeyond(
+              mozilla::ShutdownPhase::AppShutdownConfirmed)) {
+        return nullptr;
+      }
+      idleService = new nsUserIdleServiceWin();
+    }
+
+    return idleService.forget();
+  }
+
+ protected:
+  nsUserIdleServiceWin() {}
+  virtual ~nsUserIdleServiceWin() {}
+};
+
+#endif  // nsUserIdleServiceWin_h__
diff --git a/widget/windows/nsWidgetFactory.cpp b/widget/windows/nsWidgetFactory.cpp
new file mode 100644
index 0000000000..47c7d021ed
--- /dev/null
+++ b/widget/windows/nsWidgetFactory.cpp
@@ -0,0 +1,60 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsWidgetFactory.h"
+
+#include "mozilla/Components.h"
+#include "nsISupports.h"
+#include "nsdefs.h"
+#include "nsWidgetsCID.h"
+#include "nsAppShell.h"
+#include "nsAppShellSingleton.h"
+#include "mozilla/WidgetUtils.h"
+#include "mozilla/widget/ScreenManager.h"
+#include "nsLookAndFeel.h"
+#include "WinMouseScrollHandler.h"
+#include "KeyboardLayout.h"
+#include "nsToolkit.h"
+
+// Modules that switch out based on the environment
+#include "nsXULAppAPI.h"
+// Desktop
+#include "nsFilePicker.h"  // needs to be included before other shobjidl.h includes
+#include "nsColorPicker.h"
+// Content processes
+#include "nsFilePickerProxy.h"
+
+// Clipboard
+#include "nsClipboardHelper.h"
+#include "nsClipboard.h"
+#include "HeadlessClipboard.h"
+
+#include "WindowsUIUtils.h"
+
+using namespace mozilla;
+using namespace mozilla::widget;
+
+NS_IMPL_COMPONENT_FACTORY(nsIClipboard) {
+  nsCOMPtr<nsIClipboard> inst;
+  if (gfxPlatform::IsHeadless()) {
+    inst = new HeadlessClipboard();
+  } else {
+    inst = new nsClipboard();
+  }
+  return inst.forget().downcast<nsISupports>();
+}
+
+nsresult nsWidgetWindowsModuleCtor() { return nsAppShellInit(); }
+
+void nsWidgetWindowsModuleDtor() {
+  // Shutdown all XP level widget classes.
+  WidgetUtils::Shutdown();
+
+  KeyboardLayout::Shutdown();
+  MouseScrollHandler::Shutdown();
+  nsLookAndFeel::Shutdown();
+  nsToolkit::Shutdown();
+  nsAppShellShutdown();
+}
diff --git a/widget/windows/nsWidgetFactory.h b/widget/windows/nsWidgetFactory.h
new file mode 100644
index 0000000000..41a39220e3
--- /dev/null
+++ b/widget/windows/nsWidgetFactory.h
@@ -0,0 +1,21 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:expandtab:shiftwidth=4:tabstop=4:
+ */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef widget_windows_nsWidgetFactory_h
+#define widget_windows_nsWidgetFactory_h
+
+#include "nscore.h"
+#include "nsID.h"
+
+class nsISupports;
+
+nsresult nsAppShellConstructor(const nsIID& iid, void** result);
+
+nsresult nsWidgetWindowsModuleCtor();
+void nsWidgetWindowsModuleDtor();
+
+#endif  // defined widget_windows_nsWidgetFactory_h
diff --git a/widget/windows/nsWinGesture.cpp b/widget/windows/nsWinGesture.cpp
new file mode 100644
index 0000000000..8fd00b3ff0
--- /dev/null
+++ b/widget/windows/nsWinGesture.cpp
@@ -0,0 +1,388 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/*
+ * nsWinGesture - Touch input handling for tablet displays.
+ */
+
+#include "nscore.h"
+#include "nsWinGesture.h"
+#include "nsUXThemeData.h"
+#include "mozilla/Logging.h"
+#include "mozilla/MouseEvents.h"
+#include "mozilla/Preferences.h"
+#include "mozilla/TouchEvents.h"
+#include "mozilla/dom/SimpleGestureEventBinding.h"
+#include "mozilla/dom/WheelEventBinding.h"
+
+#include <cmath>
+
+using namespace mozilla;
+using namespace mozilla::widget;
+
+extern mozilla::LazyLogModule gWindowsLog;
+
+static bool gEnableSingleFingerPanEvents = false;
+
+nsWinGesture::nsWinGesture()
+    : mPanActive(false),
+      mFeedbackActive(false),
+      mXAxisFeedback(false),
+      mYAxisFeedback(false),
+      mPanInertiaActive(false) {
+  (void)InitLibrary();
+  mPixelScrollOverflow = 0;
+}
+
+/* Load and shutdown */
+
+bool nsWinGesture::InitLibrary() {
+  // Check to see if we want single finger gesture input. Only do this once
+  // for the app so we don't have to look it up on every window create.
+  gEnableSingleFingerPanEvents =
+      Preferences::GetBool("gestures.enable_single_finger_input", false);
+
+  return true;
+}
+
+#define GCOUNT 5
+
+bool nsWinGesture::SetWinGestureSupport(
+    HWND hWnd, WidgetGestureNotifyEvent::PanDirection aDirection) {
+  GESTURECONFIG config[GCOUNT];
+
+  memset(&config, 0, sizeof(config));
+
+  config[0].dwID = GID_ZOOM;
+  config[0].dwWant = GC_ZOOM;
+  config[0].dwBlock = 0;
+
+  config[1].dwID = GID_ROTATE;
+  config[1].dwWant = GC_ROTATE;
+  config[1].dwBlock = 0;
+
+  config[2].dwID = GID_PAN;
+  config[2].dwWant = GC_PAN | GC_PAN_WITH_INERTIA | GC_PAN_WITH_GUTTER;
+  config[2].dwBlock = GC_PAN_WITH_SINGLE_FINGER_VERTICALLY |
+                      GC_PAN_WITH_SINGLE_FINGER_HORIZONTALLY;
+
+  if (gEnableSingleFingerPanEvents) {
+    if (aDirection == WidgetGestureNotifyEvent::ePanVertical ||
+        aDirection == WidgetGestureNotifyEvent::ePanBoth) {
+      config[2].dwWant |= GC_PAN_WITH_SINGLE_FINGER_VERTICALLY;
+      config[2].dwBlock -= GC_PAN_WITH_SINGLE_FINGER_VERTICALLY;
+    }
+
+    if (aDirection == WidgetGestureNotifyEvent::ePanHorizontal ||
+        aDirection == WidgetGestureNotifyEvent::ePanBoth) {
+      config[2].dwWant |= GC_PAN_WITH_SINGLE_FINGER_HORIZONTALLY;
+      config[2].dwBlock -= GC_PAN_WITH_SINGLE_FINGER_HORIZONTALLY;
+    }
+  }
+
+  config[3].dwWant = GC_TWOFINGERTAP;
+  config[3].dwID = GID_TWOFINGERTAP;
+  config[3].dwBlock = 0;
+
+  config[4].dwWant = GC_PRESSANDTAP;
+  config[4].dwID = GID_PRESSANDTAP;
+  config[4].dwBlock = 0;
+
+  return SetGestureConfig(hWnd, 0, GCOUNT, (PGESTURECONFIG)&config,
+                          sizeof(GESTURECONFIG));
+}
+
+/* Helpers */
+
+bool nsWinGesture::IsPanEvent(LPARAM lParam) {
+  GESTUREINFO gi;
+
+  ZeroMemory(&gi, sizeof(GESTUREINFO));
+  gi.cbSize = sizeof(GESTUREINFO);
+
+  BOOL result = GetGestureInfo((HGESTUREINFO)lParam, &gi);
+  if (!result) return false;
+
+  if (gi.dwID == GID_PAN) return true;
+
+  return false;
+}
+
+/* Gesture event processing */
+
+bool nsWinGesture::ProcessGestureMessage(HWND hWnd, WPARAM wParam,
+                                         LPARAM lParam,
+                                         WidgetSimpleGestureEvent& evt) {
+  GESTUREINFO gi;
+
+  ZeroMemory(&gi, sizeof(GESTUREINFO));
+  gi.cbSize = sizeof(GESTUREINFO);
+
+  BOOL result = GetGestureInfo((HGESTUREINFO)lParam, &gi);
+  if (!result) return false;
+
+  // The coordinates of this event
+  nsPointWin coord;
+  coord = gi.ptsLocation;
+  coord.ScreenToClient(hWnd);
+
+  evt.mRefPoint = LayoutDeviceIntPoint(coord.x, coord.y);
+
+  // Multiple gesture can occur at the same time so gesture state
+  // info can't be shared.
+  switch (gi.dwID) {
+    case GID_BEGIN:
+    case GID_END:
+      // These should always fall through to DefWndProc
+      return false;
+      break;
+
+    case GID_ZOOM: {
+      if (gi.dwFlags & GF_BEGIN) {
+        // Send a zoom start event
+
+        // The low 32 bits are the distance in pixels.
+        mZoomIntermediate = (float)gi.ullArguments;
+
+        evt.mMessage = eMagnifyGestureStart;
+        evt.mDelta = 0.0;
+      } else if (gi.dwFlags & GF_END) {
+        // Send a zoom end event, the delta is the change
+        // in touch points.
+        evt.mMessage = eMagnifyGesture;
+        // (positive for a "zoom in")
+        evt.mDelta = -1.0 * (mZoomIntermediate - (float)gi.ullArguments);
+        mZoomIntermediate = (float)gi.ullArguments;
+      } else {
+        // Send a zoom intermediate event, the delta is the change
+        // in touch points.
+        evt.mMessage = eMagnifyGestureUpdate;
+        // (positive for a "zoom in")
+        evt.mDelta = -1.0 * (mZoomIntermediate - (float)gi.ullArguments);
+        mZoomIntermediate = (float)gi.ullArguments;
+      }
+    } break;
+
+    case GID_ROTATE: {
+      // Send a rotate start event
+      double radians = 0.0;
+
+      // On GF_BEGIN, ullArguments contains the absolute rotation at the
+      // start of the gesture. In later events it contains the offset from
+      // the start angle.
+      if (gi.ullArguments != 0)
+        radians = GID_ROTATE_ANGLE_FROM_ARGUMENT(gi.ullArguments);
+
+      double degrees = -1 * radians * (180 / M_PI);
+
+      if (gi.dwFlags & GF_BEGIN) {
+        // At some point we should pass the initial angle in
+        // along with delta. It's useful.
+        degrees = mRotateIntermediate = 0.0;
+      }
+
+      evt.mDirection = 0;
+      evt.mDelta = degrees - mRotateIntermediate;
+      mRotateIntermediate = degrees;
+
+      if (evt.mDelta > 0) {
+        evt.mDirection =
+            dom::SimpleGestureEvent_Binding::ROTATION_COUNTERCLOCKWISE;
+      } else if (evt.mDelta < 0) {
+        evt.mDirection = dom::SimpleGestureEvent_Binding::ROTATION_CLOCKWISE;
+      }
+
+      if (gi.dwFlags & GF_BEGIN) {
+        evt.mMessage = eRotateGestureStart;
+      } else if (gi.dwFlags & GF_END) {
+        evt.mMessage = eRotateGesture;
+      } else {
+        evt.mMessage = eRotateGestureUpdate;
+      }
+    } break;
+
+    case GID_TWOFINGERTAP:
+      // Normally maps to "restore" from whatever you may have recently changed.
+      // A simple double click.
+      evt.mMessage = eTapGesture;
+      evt.mClickCount = 1;
+      break;
+
+    case GID_PRESSANDTAP:
+      // Two finger right click. Defaults to right click if it falls through.
+      evt.mMessage = ePressTapGesture;
+      evt.mClickCount = 1;
+      break;
+  }
+
+  return true;
+}
+
+bool nsWinGesture::ProcessPanMessage(HWND hWnd, WPARAM wParam, LPARAM lParam) {
+  GESTUREINFO gi;
+
+  ZeroMemory(&gi, sizeof(GESTUREINFO));
+  gi.cbSize = sizeof(GESTUREINFO);
+
+  BOOL result = GetGestureInfo((HGESTUREINFO)lParam, &gi);
+  if (!result) return false;
+
+  // The coordinates of this event
+  nsPointWin coord;
+  coord = mPanRefPoint = gi.ptsLocation;
+  // We want screen coordinates in our local offsets as client coordinates will
+  // change when feedback is taking place. Gui events though require client
+  // coordinates.
+  mPanRefPoint.ScreenToClient(hWnd);
+
+  switch (gi.dwID) {
+    case GID_BEGIN:
+    case GID_END:
+      // These should always fall through to DefWndProc
+      return false;
+      break;
+
+    // Setup pixel scroll events for both axis
+    case GID_PAN: {
+      if (gi.dwFlags & GF_BEGIN) {
+        mPanIntermediate = coord;
+        mPixelScrollDelta = 0;
+        mPanActive = true;
+        mPanInertiaActive = false;
+      } else {
+#ifdef DBG_jimm
+        int32_t deltaX = mPanIntermediate.x - coord.x;
+        int32_t deltaY = mPanIntermediate.y - coord.y;
+        MOZ_LOG(gWindowsLog, LogLevel::Info,
+                ("coordX=%d coordY=%d deltaX=%d deltaY=%d x:%d y:%d\n", coord.x,
+                 coord.y, deltaX, deltaY, mXAxisFeedback, mYAxisFeedback));
+#endif
+
+        mPixelScrollDelta.x = mPanIntermediate.x - coord.x;
+        mPixelScrollDelta.y = mPanIntermediate.y - coord.y;
+        mPanIntermediate = coord;
+
+        if (gi.dwFlags & GF_INERTIA) mPanInertiaActive = true;
+
+        if (gi.dwFlags & GF_END) {
+          mPanActive = false;
+          mPanInertiaActive = false;
+          PanFeedbackFinalize(hWnd, true);
+        }
+      }
+    } break;
+  }
+  return true;
+}
+
+inline bool TestTransition(int32_t a, int32_t b) {
+  // If a is zero, overflow is zero, implying the cursor has moved back to the
+  // start position. If b is zero, cached overscroll is zero, implying feedback
+  // just begun.
+  if (a == 0 || b == 0) return true;
+  // Test for different signs.
+  return (a < 0) == (b < 0);
+}
+
+void nsWinGesture::UpdatePanFeedbackX(HWND hWnd, int32_t scrollOverflow,
+                                      bool& endFeedback) {
+  // If scroll overflow was returned indicating we panned past the bounds of
+  // the scrollable view port, start feeback.
+  if (scrollOverflow != 0) {
+    if (!mFeedbackActive) {
+      BeginPanningFeedback(hWnd);
+      mFeedbackActive = true;
+    }
+    endFeedback = false;
+    mXAxisFeedback = true;
+    return;
+  }
+
+  if (mXAxisFeedback) {
+    int32_t newOverflow = mPixelScrollOverflow.x - mPixelScrollDelta.x;
+
+    // Detect a reverse transition past the starting drag point. This tells us
+    // the user has panned all the way back so we can stop providing feedback
+    // for this axis.
+    if (!TestTransition(newOverflow, mPixelScrollOverflow.x) ||
+        newOverflow == 0)
+      return;
+
+    // Cache the total over scroll in pixels.
+    mPixelScrollOverflow.x = newOverflow;
+    endFeedback = false;
+  }
+}
+
+void nsWinGesture::UpdatePanFeedbackY(HWND hWnd, int32_t scrollOverflow,
+                                      bool& endFeedback) {
+  // If scroll overflow was returned indicating we panned past the bounds of
+  // the scrollable view port, start feeback.
+  if (scrollOverflow != 0) {
+    if (!mFeedbackActive) {
+      BeginPanningFeedback(hWnd);
+      mFeedbackActive = true;
+    }
+    endFeedback = false;
+    mYAxisFeedback = true;
+    return;
+  }
+
+  if (mYAxisFeedback) {
+    int32_t newOverflow = mPixelScrollOverflow.y - mPixelScrollDelta.y;
+
+    // Detect a reverse transition past the starting drag point. This tells us
+    // the user has panned all the way back so we can stop providing feedback
+    // for this axis.
+    if (!TestTransition(newOverflow, mPixelScrollOverflow.y) ||
+        newOverflow == 0)
+      return;
+
+    // Cache the total over scroll in pixels.
+    mPixelScrollOverflow.y = newOverflow;
+    endFeedback = false;
+  }
+}
+
+void nsWinGesture::PanFeedbackFinalize(HWND hWnd, bool endFeedback) {
+  if (!mFeedbackActive) return;
+
+  if (endFeedback) {
+    mFeedbackActive = false;
+    mXAxisFeedback = false;
+    mYAxisFeedback = false;
+    mPixelScrollOverflow = 0;
+    EndPanningFeedback(hWnd, TRUE);
+    return;
+  }
+
+  UpdatePanningFeedback(hWnd, mPixelScrollOverflow.x, mPixelScrollOverflow.y,
+                        mPanInertiaActive);
+}
+
+bool nsWinGesture::PanDeltaToPixelScroll(WidgetWheelEvent& aWheelEvent) {
+  aWheelEvent.mDeltaX = aWheelEvent.mDeltaY = aWheelEvent.mDeltaZ = 0.0;
+  aWheelEvent.mLineOrPageDeltaX = aWheelEvent.mLineOrPageDeltaY = 0;
+
+  aWheelEvent.mRefPoint = LayoutDeviceIntPoint(mPanRefPoint.x, mPanRefPoint.y);
+  aWheelEvent.mDeltaMode = dom::WheelEvent_Binding::DOM_DELTA_PIXEL;
+  aWheelEvent.mScrollType = WidgetWheelEvent::SCROLL_SYNCHRONOUSLY;
+  aWheelEvent.mIsNoLineOrPageDelta = true;
+
+  aWheelEvent.mOverflowDeltaX = 0.0;
+  aWheelEvent.mOverflowDeltaY = 0.0;
+
+  // Don't scroll the view if we are currently at a bounds, or, if we are
+  // panning back from a max feedback position. This keeps the original drag
+  // point constant.
+  if (!mXAxisFeedback) {
+    aWheelEvent.mDeltaX = mPixelScrollDelta.x;
+  }
+  if (!mYAxisFeedback) {
+    aWheelEvent.mDeltaY = mPixelScrollDelta.y;
+  }
+
+  return (aWheelEvent.mDeltaX != 0 || aWheelEvent.mDeltaY != 0);
+}
diff --git a/widget/windows/nsWinGesture.h b/widget/windows/nsWinGesture.h
new file mode 100644
index 0000000000..040b460da9
--- /dev/null
+++ b/widget/windows/nsWinGesture.h
@@ -0,0 +1,91 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef WinGesture_h__
+#define WinGesture_h__
+
+/*
+ * nsWinGesture - Touch input handling for tablet displays.
+ */
+
+#include "nsdefs.h"
+#include <winuser.h>
+#include <tpcshrd.h>
+#include "nsPoint.h"
+#include "mozilla/EventForwards.h"
+#include "mozilla/TouchEvents.h"
+
+// WM_TABLET_QUERYSYSTEMGESTURESTATUS return values
+#define TABLET_ROTATE_GESTURE_ENABLE 0x02000000
+
+class nsPointWin : public nsIntPoint {
+ public:
+  nsPointWin& operator=(const POINTS& aPoint) {
+    x = aPoint.x;
+    y = aPoint.y;
+    return *this;
+  }
+  nsPointWin& operator=(const POINT& aPoint) {
+    x = aPoint.x;
+    y = aPoint.y;
+    return *this;
+  }
+  nsPointWin& operator=(int val) {
+    x = y = val;
+    return *this;
+  }
+  void ScreenToClient(HWND hWnd) {
+    POINT tmp;
+    tmp.x = x;
+    tmp.y = y;
+    ::ScreenToClient(hWnd, &tmp);
+    *this = tmp;
+  }
+};
+
+class nsWinGesture {
+ public:
+  nsWinGesture();
+
+ public:
+  bool SetWinGestureSupport(
+      HWND hWnd, mozilla::WidgetGestureNotifyEvent::PanDirection aDirection);
+  bool ShutdownWinGestureSupport();
+
+  // Simple gesture process
+  bool ProcessGestureMessage(HWND hWnd, WPARAM wParam, LPARAM lParam,
+                             mozilla::WidgetSimpleGestureEvent& evt);
+
+  // Pan processing
+  bool IsPanEvent(LPARAM lParam);
+  bool ProcessPanMessage(HWND hWnd, WPARAM wParam, LPARAM lParam);
+  bool PanDeltaToPixelScroll(mozilla::WidgetWheelEvent& aWheelEvent);
+  void UpdatePanFeedbackX(HWND hWnd, int32_t scrollOverflow, bool& endFeedback);
+  void UpdatePanFeedbackY(HWND hWnd, int32_t scrollOverflow, bool& endFeedback);
+  void PanFeedbackFinalize(HWND hWnd, bool endFeedback);
+
+ private:
+  // Delay load info
+  bool InitLibrary();
+
+  // Pan and feedback state
+  nsPointWin mPanIntermediate;
+  nsPointWin mPanRefPoint;
+  nsPointWin mPixelScrollDelta;
+  bool mPanActive;
+  bool mFeedbackActive;
+  bool mXAxisFeedback;
+  bool mYAxisFeedback;
+  bool mPanInertiaActive;
+  nsPointWin mPixelScrollOverflow;
+
+  // Zoom state
+  double mZoomIntermediate;
+
+  // Rotate state
+  double mRotateIntermediate;
+};
+
+#endif /* WinGesture_h__ */
diff --git a/widget/windows/nsWindow.cpp b/widget/windows/nsWindow.cpp
new file mode 100644
index 0000000000..1a8646d620
--- /dev/null
+++ b/widget/windows/nsWindow.cpp
@@ -0,0 +1,9000 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:set ts=2 sts=2 sw=2 et cin: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/*
+ * nsWindow - Native window management and event handling.
+ *
+ * nsWindow is organized into a set of major blocks and
+ * block subsections. The layout is as follows:
+ *
+ *  Includes
+ *  Variables
+ *  nsIWidget impl.
+ *     nsIWidget methods and utilities
+ *  nsSwitchToUIThread impl.
+ *     nsSwitchToUIThread methods and utilities
+ *  Moz events
+ *     Event initialization
+ *     Event dispatching
+ *  Native events
+ *     Wndproc(s)
+ *     Event processing
+ *     OnEvent event handlers
+ *  IME management and accessibility
+ *  Transparency
+ *  Popup hook handling
+ *  Misc. utilities
+ *  Child window impl.
+ *
+ * Search for "BLOCK:" to find major blocks.
+ * Search for "SECTION:" to find specific sections.
+ *
+ * Blocks should be split out into separate files if they
+ * become unmanageable.
+ *
+ * Notable related sources:
+ *
+ *  nsWindowDefs.h     - Definitions, macros, structs, enums
+ *                       and general setup.
+ *  nsWindowDbg.h/.cpp - Debug related code and directives.
+ *  nsWindowGfx.h/.cpp - Graphics and painting.
+ *
+ */
+
+/**************************************************************
+ **************************************************************
+ **
+ ** BLOCK: Includes
+ **
+ ** Include headers.
+ **
+ **************************************************************
+ **************************************************************/
+
+#include "gfx2DGlue.h"
+#include "gfxEnv.h"
+#include "gfxPlatform.h"
+
+#include "mozilla/AppShutdown.h"
+#include "mozilla/AutoRestore.h"
+#include "mozilla/Likely.h"
+#include "mozilla/PreXULSkeletonUI.h"
+#include "mozilla/Logging.h"
+#include "mozilla/MathAlgorithms.h"
+#include "mozilla/MiscEvents.h"
+#include "mozilla/MouseEvents.h"
+#include "mozilla/PresShell.h"
+#include "mozilla/ScopeExit.h"
+#include "mozilla/StaticPrefs_browser.h"
+#include "mozilla/SwipeTracker.h"
+#include "mozilla/TouchEvents.h"
+#include "mozilla/TimeStamp.h"
+
+#include "mozilla/ipc/MessageChannel.h"
+#include <algorithm>
+#include <limits>
+
+#include "mozilla/widget/WinMessages.h"
+#include "nsWindow.h"
+#include "nsWindowTaskbarConcealer.h"
+#include "nsAppRunner.h"
+
+#include <shellapi.h>
+#include <windows.h>
+#include <wtsapi32.h>
+#include <process.h>
+#include <commctrl.h>
+#include <dbt.h>
+#include <unknwn.h>
+#include <psapi.h>
+#include <rpc.h>
+#include <propvarutil.h>
+#include <propkey.h>
+
+#include "mozilla/Logging.h"
+#include "prtime.h"
+#include "prenv.h"
+
+#include "mozilla/WidgetTraceEvent.h"
+#include "nsContentUtils.h"
+#include "nsISupportsPrimitives.h"
+#include "nsITheme.h"
+#include "nsIObserverService.h"
+#include "nsIScreenManager.h"
+#include "imgIContainer.h"
+#include "nsIFile.h"
+#include "nsIRollupListener.h"
+#include "nsIClipboard.h"
+#include "WinMouseScrollHandler.h"
+#include "nsFontMetrics.h"
+#include "nsIFontEnumerator.h"
+#include "nsFont.h"
+#include "nsRect.h"
+#include "nsThreadUtils.h"
+#include "nsNativeCharsetUtils.h"
+#include "nsGkAtoms.h"
+#include "nsCRT.h"
+#include "nsAppDirectoryServiceDefs.h"
+#include "nsWidgetsCID.h"
+#include "nsTHashtable.h"
+#include "nsHashKeys.h"
+#include "nsString.h"
+#include "mozilla/Components.h"
+#include "nsNativeThemeWin.h"
+#include "nsXULPopupManager.h"
+#include "nsWindowsDllInterceptor.h"
+#include "nsLayoutUtils.h"
+#include "nsView.h"
+#include "nsWindowGfx.h"
+#include "gfxWindowsPlatform.h"
+#include "gfxDWriteFonts.h"
+#include "nsPrintfCString.h"
+#include "mozilla/Preferences.h"
+#include "SystemTimeConverter.h"
+#include "WinTaskbar.h"
+#include "WidgetUtils.h"
+#include "WinWindowOcclusionTracker.h"
+#include "nsIWidgetListener.h"
+#include "mozilla/dom/Document.h"
+#include "mozilla/dom/MouseEventBinding.h"
+#include "mozilla/dom/Touch.h"
+#include "mozilla/gfx/2D.h"
+#include "mozilla/gfx/GPUProcessManager.h"
+#include "mozilla/intl/LocaleService.h"
+#include "mozilla/layers/WebRenderLayerManager.h"
+#include "mozilla/WindowsVersion.h"
+#include "mozilla/TextEvents.h"  // For WidgetKeyboardEvent
+#include "mozilla/TextEventDispatcherListener.h"
+#include "mozilla/widget/nsAutoRollup.h"
+#include "mozilla/widget/PlatformWidgetTypes.h"
+#include "mozilla/widget/Screen.h"
+#include "nsStyleConsts.h"
+#include "nsBidiKeyboard.h"
+#include "nsStyleConsts.h"
+#include "gfxConfig.h"
+#include "InProcessWinCompositorWidget.h"
+#include "InputDeviceUtils.h"
+#include "ScreenHelperWin.h"
+#include "mozilla/StaticPrefs_apz.h"
+#include "mozilla/StaticPrefs_dom.h"
+#include "mozilla/StaticPrefs_gfx.h"
+#include "mozilla/StaticPrefs_layout.h"
+#include "mozilla/StaticPrefs_ui.h"
+#include "mozilla/StaticPrefs_widget.h"
+#include "nsNativeAppSupportWin.h"
+#include "mozilla/browser/NimbusFeatures.h"
+
+#include "nsIGfxInfo.h"
+#include "nsUXThemeConstants.h"
+#include "KeyboardLayout.h"
+#include "nsNativeDragTarget.h"
+#include <mmsystem.h>  // needed for WIN32_LEAN_AND_MEAN
+#include <zmouse.h>
+#include <richedit.h>
+
+#if defined(ACCESSIBILITY)
+
+#  ifdef DEBUG
+#    include "mozilla/a11y/Logging.h"
+#  endif
+
+#  include "oleidl.h"
+#  include <winuser.h>
+#  include "nsAccessibilityService.h"
+#  include "mozilla/a11y/DocAccessible.h"
+#  include "mozilla/a11y/LazyInstantiator.h"
+#  include "mozilla/a11y/Platform.h"
+#  if !defined(WINABLEAPI)
+#    include <winable.h>
+#  endif  // !defined(WINABLEAPI)
+#endif    // defined(ACCESSIBILITY)
+
+#include "WindowsUIUtils.h"
+
+#include "nsWindowDefs.h"
+
+#include "nsCrashOnException.h"
+
+#include "nsIContent.h"
+
+#include "mozilla/BackgroundHangMonitor.h"
+#include "WinIMEHandler.h"
+
+#include "npapi.h"
+
+#include <d3d11.h>
+
+// ERROR from wingdi.h (below) gets undefined by some code.
+// #define ERROR               0
+// #define RGN_ERROR ERROR
+#define ERROR 0
+
+#if !defined(SM_CONVERTIBLESLATEMODE)
+#  define SM_CONVERTIBLESLATEMODE 0x2003
+#endif
+
+#include "mozilla/gfx/DeviceManagerDx.h"
+#include "mozilla/layers/APZInputBridge.h"
+#include "mozilla/layers/InputAPZContext.h"
+#include "mozilla/layers/KnowsCompositor.h"
+#include "InputData.h"
+
+#include "mozilla/TaskController.h"
+#include "mozilla/Telemetry.h"
+#include "mozilla/webrender/WebRenderAPI.h"
+#include "mozilla/layers/IAPZCTreeManager.h"
+
+#include "DirectManipulationOwner.h"
+
+using namespace mozilla;
+using namespace mozilla::dom;
+using namespace mozilla::gfx;
+using namespace mozilla::layers;
+using namespace mozilla::widget;
+using namespace mozilla::plugins;
+
+/**************************************************************
+ **************************************************************
+ **
+ ** BLOCK: Variables
+ **
+ ** nsWindow Class static initializations and global variables.
+ **
+ **************************************************************
+ **************************************************************/
+
+/**************************************************************
+ *
+ * SECTION: nsWindow statics
+ *
+ **************************************************************/
+static const wchar_t kUser32LibName[] = L"user32.dll";
+
+uint32_t nsWindow::sInstanceCount = 0;
+bool nsWindow::sIsOleInitialized = false;
+nsIWidget::Cursor nsWindow::sCurrentCursor = {};
+nsWindow* nsWindow::sCurrentWindow = nullptr;
+bool nsWindow::sJustGotDeactivate = false;
+bool nsWindow::sJustGotActivate = false;
+bool nsWindow::sIsInMouseCapture = false;
+
+// Urgent-message reentrancy depth for the static `WindowProc` callback.
+//
+// Three unfortunate facts collide:
+//
+// 𝛼) Some messages must be processed promptly. If not, Windows will leave the
+//    receiving window in an intermediate, and potentially unusable, state until
+//    the WindowProc invocation that is handling it returns.
+//
+// 𝛽) Some messages have indefinitely long processing time. These are mostly
+//    messages which may cause us to enter a nested modal loop (via
+//    `SpinEventLoopUntil` or similar).
+//
+// 𝛾) Sometimes, messages skip the queue entirely. Our `WindowProc` may be
+//    reentrantly reinvoked from the kernel while we're blocking _on_ the
+//    kernel, even briefly, during processing of other messages. (Relevant
+//    search term: `KeUserModeCallback`.)
+//
+// The nightmare scenario, then, is that during processing of an 𝛼-message, we
+// briefly become blocked (e.g., by calling `::SendMessageW()`), and the kernel
+// takes that opportunity to use 𝛾 to hand us a 𝛽-message. (Concretely, see
+// bug 1842170.)
+//
+// There is little we can do to prevent the first half of this scenario. 𝛼) and
+// 𝛾) are effectively immutable facts of Windows, and we sometimes legitimately
+// need to make blocking calls to process 𝛼-messages. (We may not even be aware
+// that we're making such calls, if they're undocumented implementation details
+// of another API.)
+//
+// In an ideal world, WindowProc would always return promptly (or at least in
+// bounded time), and 𝛽-messages would not _per se_ exist; long-running modal
+// states would instead be implemented in async fashion. In practice, that's far
+// easier said than done -- replacing existing uses of `SpinEventLoopUntil` _et
+// al._ with asynchronous mechanisms is a collection of mostly-unrelated cross-
+// cutting architectural tasks, each of potentially unbounded scope. For now,
+// and for the foreseeable future, we're stuck with them.
+//
+// We therefore simply punt. More specifically: if a known 𝛽-message jumps the
+// queue to come in while we're in the middle of processing a known 𝛼-message,
+// we:
+//  * properly queue the message for processing later;
+//  * respond to the 𝛽-message as though we actually had processed it; and
+//  * just hope that it can wait until we get around to it.
+//
+// The word "known" requires a bit of justification. There is no canonical set
+// of 𝛼-messages, nor is the set of 𝛽-messages fixed (or even demarcable). We
+// can't safely assume that all messages are 𝛼-messages, as that could cause
+// 𝛽-messages to be arbitrarily and surprisingly delayed whenever any nested
+// event loop is active. We also can't assume all messages are 𝛽-messages,
+// since one 𝛼-message jumping the queue while processing another 𝛼-message is
+// part of normal and required operation for windowed Windows applications.
+//
+// So we simply add messages to those sets as we identify them. (Or, preferably,
+// rework the 𝛽-message's handling to make it no longer 𝛽. But see above.)
+//
+// ---
+//
+// The actual value of `sDepth` is the number of active invocations of
+// `WindowProc` that are processing known 𝛼-messages.
+size_t nsWindow::WndProcUrgentInvocation::sDepth = 0;
+
+// Hook Data Members for Dropdowns. sProcessHook Tells the
+// hook methods whether they should be processing the hook
+// messages.
+HHOOK nsWindow::sMsgFilterHook = nullptr;
+HHOOK nsWindow::sCallProcHook = nullptr;
+HHOOK nsWindow::sCallMouseHook = nullptr;
+bool nsWindow::sProcessHook = false;
+UINT nsWindow::sRollupMsgId = 0;
+HWND nsWindow::sRollupMsgWnd = nullptr;
+UINT nsWindow::sHookTimerId = 0;
+
+// Used to prevent dispatching mouse events that do not originate from user
+// input.
+POINT nsWindow::sLastMouseMovePoint = {0};
+
+bool nsWindow::sIsRestoringSession = false;
+
+bool nsWindow::sTouchInjectInitialized = false;
+InjectTouchInputPtr nsWindow::sInjectTouchFuncPtr;
+
+static SystemTimeConverter<DWORD>& TimeConverter() {
+  static SystemTimeConverter<DWORD> timeConverterSingleton;
+  return timeConverterSingleton;
+}
+
+// Global event hook for window cloaking. Never deregistered.
+//  - `Nothing` if not yet set.
+//  - `Some(nullptr)` if no attempt should be made to set it.
+static mozilla::Maybe<HWINEVENTHOOK> sWinCloakEventHook = Nothing();
+static mozilla::LazyLogModule sCloakingLog("DWMCloaking");
+
+namespace mozilla {
+
+class CurrentWindowsTimeGetter {
+ public:
+  explicit CurrentWindowsTimeGetter(HWND aWnd) : mWnd(aWnd) {}
+
+  DWORD GetCurrentTime() const { return ::GetTickCount(); }
+
+  void GetTimeAsyncForPossibleBackwardsSkew(const TimeStamp& aNow) {
+    DWORD currentTime = GetCurrentTime();
+    if (sBackwardsSkewStamp && currentTime == sLastPostTime) {
+      // There's already one inflight with this timestamp. Don't
+      // send a duplicate.
+      return;
+    }
+    sBackwardsSkewStamp = Some(aNow);
+    sLastPostTime = currentTime;
+    static_assert(sizeof(WPARAM) >= sizeof(DWORD),
+                  "Can't fit a DWORD in a WPARAM");
+    ::PostMessage(mWnd, MOZ_WM_SKEWFIX, sLastPostTime, 0);
+  }
+
+  static bool GetAndClearBackwardsSkewStamp(DWORD aPostTime,
+                                            TimeStamp* aOutSkewStamp) {
+    if (aPostTime != sLastPostTime) {
+      // The SKEWFIX message is stale; we've sent a new one since then.
+      // Ignore this one.
+      return false;
+    }
+    MOZ_ASSERT(sBackwardsSkewStamp);
+    *aOutSkewStamp = sBackwardsSkewStamp.value();
+    sBackwardsSkewStamp = Nothing();
+    return true;
+  }
+
+ private:
+  static Maybe<TimeStamp> sBackwardsSkewStamp;
+  static DWORD sLastPostTime;
+  HWND mWnd;
+};
+
+Maybe<TimeStamp> CurrentWindowsTimeGetter::sBackwardsSkewStamp;
+DWORD CurrentWindowsTimeGetter::sLastPostTime = 0;
+
+}  // namespace mozilla
+
+/**************************************************************
+ *
+ * SECTION: globals variables
+ *
+ **************************************************************/
+
+static const char* sScreenManagerContractID =
+    "@mozilla.org/gfx/screenmanager;1";
+
+extern mozilla::LazyLogModule gWindowsLog;
+
+static NS_DEFINE_CID(kCClipboardCID, NS_CLIPBOARD_CID);
+
+// General purpose user32.dll hook object
+static WindowsDllInterceptor sUser32Intercept;
+
+// When the client area is extended out into the default window frame area,
+// this is the minimum amount of space along the edge of resizable windows
+// we will always display a resize cursor in, regardless of the underlying
+// content.
+static const int32_t kResizableBorderMinSize = 3;
+
+// Getting this object from the window server can be expensive. Keep it
+// around, also get it off the main thread. (See bug 1640852)
+StaticRefPtr<IVirtualDesktopManager> gVirtualDesktopManager;
+static bool gInitializedVirtualDesktopManager = false;
+
+// We should never really try to accelerate windows bigger than this. In some
+// cases this might lead to no D3D9 acceleration where we could have had it
+// but D3D9 does not reliably report when it supports bigger windows. 8192
+// is as safe as we can get, we know at least D3D10 hardware always supports
+// this, other hardware we expect to report correctly in D3D9.
+#define MAX_ACCELERATED_DIMENSION 8192
+
+// On window open (as well as after), Windows has an unfortunate habit of
+// sending rather a lot of WM_NCHITTEST messages. Because we have to do point
+// to DOM target conversions for these, we cache responses for a given
+// coordinate this many milliseconds:
+#define HITTEST_CACHE_LIFETIME_MS 50
+
+#if defined(ACCESSIBILITY)
+
+namespace mozilla {
+
+/**
+ * Windows touchscreen code works by setting a global WH_GETMESSAGE hook and
+ * injecting tiptsf.dll. The touchscreen process then posts registered messages
+ * to our main thread. The tiptsf hook picks up those registered messages and
+ * uses them as commands, some of which call into UIA, which then calls into
+ * MSAA, which then sends WM_GETOBJECT to us.
+ *
+ * We can get ahead of this by installing our own thread-local WH_GETMESSAGE
+ * hook. Since thread-local hooks are called ahead of global hooks, we will
+ * see these registered messages before tiptsf does. At this point we can then
+ * raise a flag that blocks a11y before invoking CallNextHookEx which will then
+ * invoke the global tiptsf hook. Then when we see WM_GETOBJECT, we check the
+ * flag by calling TIPMessageHandler::IsA11yBlocked().
+ *
+ * For Windows 8, we also hook tiptsf!ProcessCaretEvents, which is an a11y hook
+ * function that also calls into UIA.
+ */
+class TIPMessageHandler {
+ public:
+  ~TIPMessageHandler() {
+    if (mHook) {
+      ::UnhookWindowsHookEx(mHook);
+    }
+  }
+
+  static void Initialize() {
+    if (sInstance) {
+      return;
+    }
+
+    sInstance = new TIPMessageHandler();
+    ClearOnShutdown(&sInstance);
+  }
+
+  static bool IsA11yBlocked() {
+    if (!sInstance) {
+      return false;
+    }
+
+    return sInstance->mA11yBlockCount > 0;
+  }
+
+ private:
+  TIPMessageHandler() : mHook(nullptr), mA11yBlockCount(0) {
+    MOZ_ASSERT(NS_IsMainThread());
+
+    // Registered messages used by tiptsf
+    mMessages[0] = ::RegisterWindowMessage(L"ImmersiveFocusNotification");
+    mMessages[1] = ::RegisterWindowMessage(L"TipCloseMenus");
+    mMessages[2] = ::RegisterWindowMessage(L"TabletInputPanelOpening");
+    mMessages[3] = ::RegisterWindowMessage(L"IHM Pen or Touch Event noticed");
+    mMessages[4] = ::RegisterWindowMessage(L"ProgrammabilityCaretVisibility");
+    mMessages[5] = ::RegisterWindowMessage(L"CaretTrackingUpdateIPHidden");
+    mMessages[6] = ::RegisterWindowMessage(L"CaretTrackingUpdateIPInfo");
+
+    mHook = ::SetWindowsHookEx(WH_GETMESSAGE, &TIPHook, nullptr,
+                               ::GetCurrentThreadId());
+    MOZ_ASSERT(mHook);
+
+    if (!sSendMessageTimeoutWStub) {
+      sUser32Intercept.Init("user32.dll");
+      DebugOnly<bool> hooked = sSendMessageTimeoutWStub.Set(
+          sUser32Intercept, "SendMessageTimeoutW", &SendMessageTimeoutWHook);
+      MOZ_ASSERT(hooked);
+    }
+  }
+
+  class MOZ_RAII A11yInstantiationBlocker {
+   public:
+    A11yInstantiationBlocker() {
+      if (!TIPMessageHandler::sInstance) {
+        return;
+      }
+      ++TIPMessageHandler::sInstance->mA11yBlockCount;
+    }
+
+    ~A11yInstantiationBlocker() {
+      if (!TIPMessageHandler::sInstance) {
+        return;
+      }
+      MOZ_ASSERT(TIPMessageHandler::sInstance->mA11yBlockCount > 0);
+      --TIPMessageHandler::sInstance->mA11yBlockCount;
+    }
+  };
+
+  friend class A11yInstantiationBlocker;
+
+  static LRESULT CALLBACK TIPHook(int aCode, WPARAM aWParam, LPARAM aLParam) {
+    if (aCode < 0 || !sInstance) {
+      return ::CallNextHookEx(nullptr, aCode, aWParam, aLParam);
+    }
+
+    MSG* msg = reinterpret_cast<MSG*>(aLParam);
+    UINT& msgCode = msg->message;
+
+    for (uint32_t i = 0; i < ArrayLength(sInstance->mMessages); ++i) {
+      if (msgCode == sInstance->mMessages[i]) {
+        A11yInstantiationBlocker block;
+        return ::CallNextHookEx(nullptr, aCode, aWParam, aLParam);
+      }
+    }
+
+    return ::CallNextHookEx(nullptr, aCode, aWParam, aLParam);
+  }
+
+  static LRESULT WINAPI SendMessageTimeoutWHook(HWND aHwnd, UINT aMsgCode,
+                                                WPARAM aWParam, LPARAM aLParam,
+                                                UINT aFlags, UINT aTimeout,
+                                                PDWORD_PTR aMsgResult) {
+    // We don't want to handle this unless the message is a WM_GETOBJECT that we
+    // want to block, and the aHwnd is a nsWindow that belongs to the current
+    // (i.e., main) thread.
+    if (!aMsgResult || aMsgCode != WM_GETOBJECT ||
+        static_cast<LONG>(aLParam) != OBJID_CLIENT || !::NS_IsMainThread() ||
+        !WinUtils::GetNSWindowPtr(aHwnd) || !IsA11yBlocked()) {
+      return sSendMessageTimeoutWStub(aHwnd, aMsgCode, aWParam, aLParam, aFlags,
+                                      aTimeout, aMsgResult);
+    }
+
+    // In this case we want to fake the result that would happen if we had
+    // decided not to handle WM_GETOBJECT in our WndProc. We hand the message
+    // off to DefWindowProc to accomplish this.
+    *aMsgResult = static_cast<DWORD_PTR>(
+        ::DefWindowProcW(aHwnd, aMsgCode, aWParam, aLParam));
+
+    return static_cast<LRESULT>(TRUE);
+  }
+
+  static WindowsDllInterceptor::FuncHookType<decltype(&SendMessageTimeoutW)>
+      sSendMessageTimeoutWStub;
+  static StaticAutoPtr<TIPMessageHandler> sInstance;
+
+  HHOOK mHook;
+  UINT mMessages[7];
+  uint32_t mA11yBlockCount;
+};
+
+WindowsDllInterceptor::FuncHookType<decltype(&SendMessageTimeoutW)>
+    TIPMessageHandler::sSendMessageTimeoutWStub;
+StaticAutoPtr<TIPMessageHandler> TIPMessageHandler::sInstance;
+
+}  // namespace mozilla
+
+#endif  // defined(ACCESSIBILITY)
+
+namespace mozilla {
+
+// This task will get the VirtualDesktopManager from the generic thread pool
+// since doing this on the main thread on startup causes performance issues.
+//
+// See bug 1640852.
+//
+// This should be fine and should not require any locking, as when the main
+// thread will access it, if it races with this function it will either find
+// it to be null or to have a valid value.
+class InitializeVirtualDesktopManagerTask : public Task {
+ public:
+  InitializeVirtualDesktopManagerTask()
+      : Task(Kind::OffMainThreadOnly, kDefaultPriorityValue) {}
+
+#ifdef MOZ_COLLECTING_RUNNABLE_TELEMETRY
+  bool GetName(nsACString& aName) override {
+    aName.AssignLiteral("InitializeVirtualDesktopManagerTask");
+    return true;
+  }
+#endif
+
+  virtual TaskResult Run() override {
+    RefPtr<IVirtualDesktopManager> desktopManager;
+    HRESULT hr = ::CoCreateInstance(
+        CLSID_VirtualDesktopManager, NULL, CLSCTX_INPROC_SERVER,
+        __uuidof(IVirtualDesktopManager), getter_AddRefs(desktopManager));
+    if (FAILED(hr)) {
+      return TaskResult::Complete;
+    }
+
+    gVirtualDesktopManager = desktopManager;
+    return TaskResult::Complete;
+  }
+};
+
+// Ground-truth query: does Windows claim the window is cloaked right now?
+static bool IsCloaked(HWND hwnd) {
+  DWORD cloakedState;
+  HRESULT hr = ::DwmGetWindowAttribute(hwnd, DWMWA_CLOAKED, &cloakedState,
+                                       sizeof(cloakedState));
+
+  if (FAILED(hr)) {
+    MOZ_LOG(sCloakingLog, LogLevel::Warning,
+            ("failed (%08lX) to query cloaking state for HWND %p", hr, hwnd));
+    return false;
+  }
+
+  return cloakedState != 0;
+}
+
+}  // namespace mozilla
+
+/**************************************************************
+ **************************************************************
+ **
+ ** BLOCK: nsIWidget impl.
+ **
+ ** nsIWidget interface implementation, broken down into
+ ** sections.
+ **
+ **************************************************************
+ **************************************************************/
+
+/**************************************************************
+ *
+ * SECTION: nsWindow construction and destruction
+ *
+ **************************************************************/
+
+nsWindow::nsWindow(bool aIsChildWindow)
+    : nsBaseWidget(BorderStyle::Default),
+      mBrush(::CreateSolidBrush(NSRGB_2_COLOREF(::GetSysColor(COLOR_BTNFACE)))),
+      mFrameState(std::in_place, this),
+      mIsChildWindow(aIsChildWindow),
+      mLastPaintEndTime(TimeStamp::Now()),
+      mCachedHitTestTime(TimeStamp::Now()),
+      mSizeConstraintsScale(GetDefaultScale().scale),
+      mDesktopId("DesktopIdMutex") {
+  MOZ_ASSERT(mWindowType == WindowType::Child);
+
+  if (!gInitializedVirtualDesktopManager) {
+    TaskController::Get()->AddTask(
+        MakeAndAddRef<InitializeVirtualDesktopManagerTask>());
+    gInitializedVirtualDesktopManager = true;
+  }
+
+  // Global initialization
+  if (!sInstanceCount) {
+    // Global app registration id for Win7 and up. See
+    // WinTaskbar.cpp for details.
+    // MSIX packages explicitly do not support setting the appid from within
+    // the app, as it is set in the package manifest instead.
+    if (!WinUtils::HasPackageIdentity()) {
+      mozilla::widget::WinTaskbar::RegisterAppUserModelID();
+    }
+    if (!StaticPrefs::ui_key_layout_load_when_first_needed()) {
+      KeyboardLayout::GetInstance()->OnLayoutChange(::GetKeyboardLayout(0));
+    }
+#if defined(ACCESSIBILITY)
+    mozilla::TIPMessageHandler::Initialize();
+#endif  // defined(ACCESSIBILITY)
+    if (SUCCEEDED(::OleInitialize(nullptr))) {
+      sIsOleInitialized = true;
+    }
+    NS_ASSERTION(sIsOleInitialized, "***** OLE is not initialized!\n");
+    MouseScrollHandler::Initialize();
+    // Init theme data
+    nsUXThemeData::UpdateNativeThemeInfo();
+    RedirectedKeyDownMessageManager::Forget();
+  }  // !sInstanceCount
+
+  sInstanceCount++;
+}
+
+nsWindow::~nsWindow() {
+  mInDtor = true;
+
+  // If the widget was released without calling Destroy() then the native window
+  // still exists, and we need to destroy it. Destroy() will early-return if it
+  // was already called. In any case it is important to call it before
+  // destroying mPresentLock (cf. 1156182).
+  Destroy();
+
+  // Free app icon resources.  This must happen after `OnDestroy` (see bug
+  // 708033).
+  if (mIconSmall) ::DestroyIcon(mIconSmall);
+
+  if (mIconBig) ::DestroyIcon(mIconBig);
+
+  sInstanceCount--;
+
+  // Global shutdown
+  if (sInstanceCount == 0) {
+    IMEHandler::Terminate();
+    sCurrentCursor = {};
+    if (sIsOleInitialized) {
+      ::OleFlushClipboard();
+      ::OleUninitialize();
+      sIsOleInitialized = false;
+    }
+  }
+
+  NS_IF_RELEASE(mNativeDragTarget);
+}
+
+/**************************************************************
+ *
+ * SECTION: nsIWidget::Create, nsIWidget::Destroy
+ *
+ * Creating and destroying windows for this widget.
+ *
+ **************************************************************/
+
+// Allow Derived classes to modify the height that is passed
+// when the window is created or resized.
+int32_t nsWindow::GetHeight(int32_t aProposedHeight) { return aProposedHeight; }
+
+void nsWindow::SendAnAPZEvent(InputData& aEvent) {
+  LRESULT popupHandlingResult;
+  if (DealWithPopups(mWnd, MOZ_WM_DMANIP, 0, 0, &popupHandlingResult)) {
+    // We need to consume the event after using it to roll up the popup(s).
+    return;
+  }
+
+  if (mSwipeTracker && aEvent.mInputType == PANGESTURE_INPUT) {
+    // Give the swipe tracker a first pass at the event. If a new pan gesture
+    // has been started since the beginning of the swipe, the swipe tracker
+    // will know to ignore the event.
+    nsEventStatus status =
+        mSwipeTracker->ProcessEvent(aEvent.AsPanGestureInput());
+    if (status == nsEventStatus_eConsumeNoDefault) {
+      return;
+    }
+  }
+
+  APZEventResult result;
+  if (mAPZC) {
+    result = mAPZC->InputBridge()->ReceiveInputEvent(aEvent);
+  }
+  if (result.GetStatus() == nsEventStatus_eConsumeNoDefault) {
+    return;
+  }
+
+  MOZ_ASSERT(aEvent.mInputType == PANGESTURE_INPUT ||
+             aEvent.mInputType == PINCHGESTURE_INPUT);
+
+  if (aEvent.mInputType == PANGESTURE_INPUT) {
+    PanGestureInput& panInput = aEvent.AsPanGestureInput();
+    WidgetWheelEvent event = panInput.ToWidgetEvent(this);
+    if (!mAPZC) {
+      if (MayStartSwipeForNonAPZ(panInput)) {
+        return;
+      }
+    } else {
+      event = MayStartSwipeForAPZ(panInput, result);
+    }
+
+    ProcessUntransformedAPZEvent(&event, result);
+
+    return;
+  }
+
+  PinchGestureInput& pinchInput = aEvent.AsPinchGestureInput();
+  WidgetWheelEvent event = pinchInput.ToWidgetEvent(this);
+  ProcessUntransformedAPZEvent(&event, result);
+}
+
+void nsWindow::RecreateDirectManipulationIfNeeded() {
+  DestroyDirectManipulation();
+
+  if (mWindowType != WindowType::TopLevel && mWindowType != WindowType::Popup) {
+    return;
+  }
+
+  if (!(StaticPrefs::apz_allow_zooming() ||
+        StaticPrefs::apz_windows_use_direct_manipulation()) ||
+      StaticPrefs::apz_windows_force_disable_direct_manipulation()) {
+    return;
+  }
+
+  mDmOwner = MakeUnique<DirectManipulationOwner>(this);
+
+  LayoutDeviceIntRect bounds(mBounds.X(), mBounds.Y(), mBounds.Width(),
+                             GetHeight(mBounds.Height()));
+  mDmOwner->Init(bounds);
+}
+
+void nsWindow::ResizeDirectManipulationViewport() {
+  if (mDmOwner) {
+    LayoutDeviceIntRect bounds(mBounds.X(), mBounds.Y(), mBounds.Width(),
+                               GetHeight(mBounds.Height()));
+    mDmOwner->ResizeViewport(bounds);
+  }
+}
+
+void nsWindow::DestroyDirectManipulation() {
+  if (mDmOwner) {
+    mDmOwner->Destroy();
+    mDmOwner.reset();
+  }
+}
+
+// Create the proper widget
+nsresult nsWindow::Create(nsIWidget* aParent, nsNativeWidget aNativeParent,
+                          const LayoutDeviceIntRect& aRect,
+                          widget::InitData* aInitData) {
+  // Historical note: there was once some belief and/or intent that nsWindows
+  // could be created on arbitrary threads, and this may still be reflected in
+  // some comments.
+  MOZ_ASSERT(NS_IsMainThread());
+
+  widget::InitData defaultInitData;
+  if (!aInitData) aInitData = &defaultInitData;
+
+  nsIWidget* baseParent =
+      aInitData->mWindowType == WindowType::Dialog ||
+              aInitData->mWindowType == WindowType::TopLevel ||
+              aInitData->mWindowType == WindowType::Invisible
+          ? nullptr
+          : aParent;
+
+  mIsTopWidgetWindow = (nullptr == baseParent);
+  mBounds = aRect;
+
+  // Ensure that the toolkit is created.
+  nsToolkit::GetToolkit();
+
+  BaseCreate(baseParent, aInitData);
+
+  HWND parent;
+  if (aParent) {  // has a nsIWidget parent
+    parent = aParent ? (HWND)aParent->GetNativeData(NS_NATIVE_WINDOW) : nullptr;
+    mParent = aParent;
+  } else {  // has a nsNative parent
+    parent = (HWND)aNativeParent;
+    mParent =
+        aNativeParent ? WinUtils::GetNSWindowPtr((HWND)aNativeParent) : nullptr;
+  }
+
+  mIsRTL = aInitData->mRTL;
+  mOpeningAnimationSuppressed = aInitData->mIsAnimationSuppressed;
+  mAlwaysOnTop = aInitData->mAlwaysOnTop;
+  mIsAlert = aInitData->mIsAlert;
+  mResizable = aInitData->mResizable;
+
+  DWORD style = WindowStyle();
+  DWORD extendedStyle = WindowExStyle();
+
+  if (mWindowType == WindowType::Popup) {
+    if (!aParent) {
+      parent = nullptr;
+    }
+  } else if (mWindowType == WindowType::Invisible) {
+    // Make sure CreateWindowEx succeeds at creating a toplevel window
+    style &= ~0x40000000;  // WS_CHILDWINDOW
+  } else {
+    // See if the caller wants to explictly set clip children and clip siblings
+    if (aInitData->mClipChildren) {
+      style |= WS_CLIPCHILDREN;
+    } else {
+      style &= ~WS_CLIPCHILDREN;
+    }
+    if (aInitData->mClipSiblings) {
+      style |= WS_CLIPSIBLINGS;
+    }
+  }
+
+  const wchar_t* className = ChooseWindowClass(mWindowType);
+
+  // Take specific actions when creating the first top-level window
+  static bool sFirstTopLevelWindowCreated = false;
+  if (aInitData->mWindowType == WindowType::TopLevel && !aParent &&
+      !sFirstTopLevelWindowCreated) {
+    sFirstTopLevelWindowCreated = true;
+    mWnd = ConsumePreXULSkeletonUIHandle();
+    auto skeletonUIError = GetPreXULSkeletonUIErrorReason();
+    if (skeletonUIError) {
+      nsAutoString errorString(
+          GetPreXULSkeletonUIErrorString(skeletonUIError.value()));
+      Telemetry::ScalarSet(
+          Telemetry::ScalarID::STARTUP_SKELETON_UI_DISABLED_REASON,
+          errorString);
+    }
+    if (mWnd) {
+      MOZ_ASSERT(style == kPreXULSkeletonUIWindowStyle,
+                 "The skeleton UI window style should match the expected "
+                 "style for the first window created");
+      MOZ_ASSERT(extendedStyle == kPreXULSkeletonUIWindowStyleEx,
+                 "The skeleton UI window extended style should match the "
+                 "expected extended style for the first window created");
+      MOZ_ASSERT(
+          ::GetWindowThreadProcessId(mWnd, nullptr) == ::GetCurrentThreadId(),
+          "The skeleton UI window should be created on the same thread as "
+          "other windows");
+      mIsShowingPreXULSkeletonUI = true;
+
+      // If we successfully consumed the pre-XUL skeleton UI, just update
+      // our internal state to match what is currently being displayed.
+      mIsVisible = true;
+      mIsCloaked = mozilla::IsCloaked(mWnd);
+      mFrameState->ConsumePreXULSkeletonState(WasPreXULSkeletonUIMaximized());
+
+      // These match the margins set in browser-tabsintitlebar.js with
+      // default prefs on Windows. Bug 1673092 tracks lining this up with
+      // that more correctly instead of hard-coding it.
+      SetNonClientMargins(LayoutDeviceIntMargin(0, 2, 2, 2));
+
+      // Reset the WNDPROC for this window and its whole class, as we had
+      // to use our own WNDPROC when creating the the skeleton UI window.
+      ::SetWindowLongPtrW(mWnd, GWLP_WNDPROC,
+                          reinterpret_cast<LONG_PTR>(
+                              WinUtils::NonClientDpiScalingDefWindowProcW));
+      ::SetClassLongPtrW(mWnd, GCLP_WNDPROC,
+                         reinterpret_cast<LONG_PTR>(
+                             WinUtils::NonClientDpiScalingDefWindowProcW));
+    }
+  }
+
+  if (!mWnd) {
+    mWnd =
+        ::CreateWindowExW(extendedStyle, className, L"", style, aRect.X(),
+                          aRect.Y(), aRect.Width(), GetHeight(aRect.Height()),
+                          parent, nullptr, nsToolkit::mDllInstance, nullptr);
+  }
+
+  if (!mWnd) {
+    NS_WARNING("nsWindow CreateWindowEx failed.");
+    return NS_ERROR_FAILURE;
+  }
+
+  if (!sWinCloakEventHook) {
+    MOZ_LOG(sCloakingLog, LogLevel::Info, ("Registering cloaking event hook"));
+
+    // C++03 lambda approximation until P2173R1 is available (-std=c++2b)
+    struct StdcallLambda {
+      static void CALLBACK OnCloakUncloakHook(HWINEVENTHOOK hWinEventHook,
+                                              DWORD event, HWND hwnd,
+                                              LONG idObject, LONG idChild,
+                                              DWORD idEventThread,
+                                              DWORD dwmsEventTime) {
+        const bool isCloaked = event == EVENT_OBJECT_CLOAKED ? true : false;
+        nsWindow::OnCloakEvent(hwnd, isCloaked);
+      }
+    };
+
+    const HWINEVENTHOOK hook = ::SetWinEventHook(
+        EVENT_OBJECT_CLOAKED, EVENT_OBJECT_UNCLOAKED, HMODULE(nullptr),
+        &StdcallLambda::OnCloakUncloakHook, ::GetCurrentProcessId(),
+        ::GetCurrentThreadId(), WINEVENT_OUTOFCONTEXT);
+    sWinCloakEventHook = Some(hook);
+
+    if (!hook) {
+      const DWORD err = ::GetLastError();
+      MOZ_LOG(sCloakingLog, LogLevel::Error,
+              ("Failed to register cloaking event hook! GLE = %lu (0x%lX)", err,
+               err));
+    }
+  }
+
+  if (aInitData->mIsPrivate) {
+    if (NimbusFeatures::GetBool("majorRelease2022"_ns,
+                                "feltPrivacyWindowSeparation"_ns, true) &&
+        // Although permanent Private Browsing mode is indeed Private Browsing,
+        // we choose to make it look like regular Firefox in terms of the icon
+        // it uses (which also means we shouldn't use the Private Browsing
+        // AUMID).
+        !StaticPrefs::browser_privatebrowsing_autostart()) {
+      RefPtr<IPropertyStore> pPropStore;
+      if (!FAILED(SHGetPropertyStoreForWindow(mWnd, IID_IPropertyStore,
+                                              getter_AddRefs(pPropStore)))) {
+        PROPVARIANT pv;
+        nsAutoString aumid;
+        // make sure we're using the private browsing AUMID so that taskbar
+        // grouping works properly
+        Unused << NS_WARN_IF(
+            !mozilla::widget::WinTaskbar::GenerateAppUserModelID(aumid, true));
+        if (!FAILED(InitPropVariantFromString(aumid.get(), &pv))) {
+          if (!FAILED(pPropStore->SetValue(PKEY_AppUserModel_ID, pv))) {
+            pPropStore->Commit();
+          }
+
+          PropVariantClear(&pv);
+        }
+      }
+      HICON icon = ::LoadIconW(::GetModuleHandleW(nullptr),
+                               MAKEINTRESOURCEW(IDI_PBMODE));
+      SetBigIcon(icon);
+      SetSmallIcon(icon);
+    }
+  }
+
+  mDeviceNotifyHandle = InputDeviceUtils::RegisterNotification(mWnd);
+
+  // If mDefaultScale is set before mWnd has been set, it will have the scale of
+  // the primary monitor, rather than the monitor that the window is actually
+  // on. For non-popup windows this gets corrected by the WM_DPICHANGED message
+  // which resets mDefaultScale, but for popup windows we don't reset
+  // mDefaultScale on that message. In order to ensure that popup windows
+  // spawned on a non-primary monitor end up with the correct scale, we reset
+  // mDefaultScale here so that it gets recomputed using the correct monitor now
+  // that we have a mWnd.
+  mDefaultScale = -1.0;
+
+  if (mIsRTL) {
+    DWORD dwAttribute = TRUE;
+    DwmSetWindowAttribute(mWnd, DWMWA_NONCLIENT_RTL_LAYOUT, &dwAttribute,
+                          sizeof dwAttribute);
+  }
+
+  UpdateDarkModeToolbar();
+
+  if (mOpeningAnimationSuppressed) {
+    SuppressAnimation(true);
+  }
+
+  if (mAlwaysOnTop) {
+    ::SetWindowPos(mWnd, HWND_TOPMOST, 0, 0, 0, 0,
+                   SWP_NOMOVE | SWP_NOSIZE | SWP_NOACTIVATE);
+  }
+
+  if (mWindowType != WindowType::Invisible &&
+      MouseScrollHandler::Device::IsFakeScrollableWindowNeeded()) {
+    // Ugly Thinkpad Driver Hack (Bugs 507222 and 594977)
+    //
+    // We create two zero-sized windows as descendants of the top-level window,
+    // like so:
+    //
+    //   Top-level window (MozillaWindowClass)
+    //     FAKETRACKPOINTSCROLLCONTAINER (MozillaWindowClass)
+    //       FAKETRACKPOINTSCROLLABLE (MozillaWindowClass)
+    //
+    // We need to have the middle window, otherwise the Trackpoint driver
+    // will fail to deliver scroll messages.  WM_MOUSEWHEEL messages are
+    // sent to the FAKETRACKPOINTSCROLLABLE, which then propagate up the
+    // window hierarchy until they are handled by nsWindow::WindowProc.
+    // WM_HSCROLL messages are also sent to the FAKETRACKPOINTSCROLLABLE,
+    // but these do not propagate automatically, so we have the window
+    // procedure pretend that they were dispatched to the top-level window
+    // instead.
+    //
+    // The FAKETRACKPOINTSCROLLABLE needs to have the specific window styles it
+    // is given below so that it catches the Trackpoint driver's heuristics.
+    HWND scrollContainerWnd = ::CreateWindowW(
+        className, L"FAKETRACKPOINTSCROLLCONTAINER", WS_CHILD | WS_VISIBLE, 0,
+        0, 0, 0, mWnd, nullptr, nsToolkit::mDllInstance, nullptr);
+    HWND scrollableWnd = ::CreateWindowW(
+        className, L"FAKETRACKPOINTSCROLLABLE",
+        WS_CHILD | WS_VISIBLE | WS_VSCROLL | WS_TABSTOP | 0x30, 0, 0, 0, 0,
+        scrollContainerWnd, nullptr, nsToolkit::mDllInstance, nullptr);
+
+    // Give the FAKETRACKPOINTSCROLLABLE window a specific ID so that
+    // WindowProcInternal can distinguish it from the top-level window
+    // easily.
+    ::SetWindowLongPtrW(scrollableWnd, GWLP_ID, eFakeTrackPointScrollableID);
+
+    // Make FAKETRACKPOINTSCROLLABLE use nsWindow::WindowProc, and store the
+    // old window procedure in its "user data".
+    WNDPROC oldWndProc = (WNDPROC)::SetWindowLongPtrW(
+        scrollableWnd, GWLP_WNDPROC, (LONG_PTR)nsWindow::WindowProc);
+    ::SetWindowLongPtrW(scrollableWnd, GWLP_USERDATA, (LONG_PTR)oldWndProc);
+  }
+
+  // We will start receiving native events after associating with our native
+  // window. We will also become the output of WinUtils::GetNSWindowPtr for that
+  // window.
+  if (!AssociateWithNativeWindow()) {
+    return NS_ERROR_FAILURE;
+  }
+
+  // Starting with Windows XP, a process always runs within a terminal services
+  // session. In order to play nicely with RDP, fast user switching, and the
+  // lock screen, we should be handling WM_WTSSESSION_CHANGE. We must register
+  // our HWND in order to receive this message.
+  DebugOnly<BOOL> wtsRegistered =
+      ::WTSRegisterSessionNotification(mWnd, NOTIFY_FOR_THIS_SESSION);
+  NS_ASSERTION(wtsRegistered, "WTSRegisterSessionNotification failed!\n");
+
+  mDefaultIMC.Init(this);
+  IMEHandler::InitInputContext(this, mInputContext);
+
+  static bool a11yPrimed = false;
+  if (!a11yPrimed && mWindowType == WindowType::TopLevel) {
+    a11yPrimed = true;
+    if (Preferences::GetInt("accessibility.force_disabled", 0) == -1) {
+      ::PostMessage(mWnd, MOZ_WM_STARTA11Y, 0, 0);
+    }
+  }
+
+  RecreateDirectManipulationIfNeeded();
+
+  return NS_OK;
+}
+
+void nsWindow::LocalesChanged() {
+  bool isRTL = intl::LocaleService::GetInstance()->IsAppLocaleRTL();
+  if (mIsRTL != isRTL) {
+    DWORD dwAttribute = isRTL;
+    DwmSetWindowAttribute(mWnd, DWMWA_NONCLIENT_RTL_LAYOUT, &dwAttribute,
+                          sizeof dwAttribute);
+    mIsRTL = isRTL;
+  }
+}
+
+// Close this nsWindow
+void nsWindow::Destroy() {
+  // WM_DESTROY has already fired, avoid calling it twice
+  if (mOnDestroyCalled) return;
+
+  // Don't destroy windows that have file pickers open, we'll tear these down
+  // later once the picker is closed.
+  mDestroyCalled = true;
+  if (mPickerDisplayCount) return;
+
+  // During the destruction of all of our children, make sure we don't get
+  // deleted.
+  nsCOMPtr<nsIWidget> kungFuDeathGrip(this);
+
+  DestroyDirectManipulation();
+
+  /**
+   * On windows the LayerManagerOGL destructor wants the widget to be around for
+   * cleanup. It also would like to have the HWND intact, so we nullptr it here.
+   */
+  DestroyLayerManager();
+
+  InputDeviceUtils::UnregisterNotification(mDeviceNotifyHandle);
+  mDeviceNotifyHandle = nullptr;
+
+  // The DestroyWindow function destroys the specified window. The function
+  // sends WM_DESTROY and WM_NCDESTROY messages to the window to deactivate it
+  // and remove the keyboard focus from it. The function also destroys the
+  // window's menu, flushes the thread message queue, destroys timers, removes
+  // clipboard ownership, and breaks the clipboard viewer chain (if the window
+  // is at the top of the viewer chain).
+  //
+  // If the specified window is a parent or owner window, DestroyWindow
+  // automatically destroys the associated child or owned windows when it
+  // destroys the parent or owner window. The function first destroys child or
+  // owned windows, and then it destroys the parent or owner window.
+  VERIFY(::DestroyWindow(mWnd));
+
+  // Our windows can be subclassed which may prevent us receiving WM_DESTROY. If
+  // OnDestroy() didn't get called, call it now.
+  if (false == mOnDestroyCalled) {
+    MSGResult msgResult;
+    mWindowHook.Notify(mWnd, WM_DESTROY, 0, 0, msgResult);
+    OnDestroy();
+  }
+}
+
+/**************************************************************
+ *
+ * SECTION: Window class utilities
+ *
+ * Utilities for calculating the proper window class name for
+ * Create window.
+ *
+ **************************************************************/
+
+/* static */
+const wchar_t* nsWindow::RegisterWindowClass(const wchar_t* aClassName,
+                                             UINT aExtraStyle, LPWSTR aIconID) {
+  WNDCLASSW wc;
+  if (::GetClassInfoW(nsToolkit::mDllInstance, aClassName, &wc)) {
+    // already registered
+    return aClassName;
+  }
+
+  wc.style = CS_DBLCLKS | aExtraStyle;
+  wc.lpfnWndProc = WinUtils::NonClientDpiScalingDefWindowProcW;
+  wc.cbClsExtra = 0;
+  wc.cbWndExtra = 0;
+  wc.hInstance = nsToolkit::mDllInstance;
+  wc.hIcon =
+      aIconID ? ::LoadIconW(::GetModuleHandleW(nullptr), aIconID) : nullptr;
+  wc.hCursor = nullptr;
+  wc.hbrBackground = nullptr;
+  wc.lpszMenuName = nullptr;
+  wc.lpszClassName = aClassName;
+
+  if (!::RegisterClassW(&wc)) {
+    // For older versions of Win32 (i.e., not XP), the registration may
+    // fail with aExtraStyle, so we have to re-register without it.
+    wc.style = CS_DBLCLKS;
+    ::RegisterClassW(&wc);
+  }
+  return aClassName;
+}
+
+static LPWSTR const gStockApplicationIcon = MAKEINTRESOURCEW(32512);
+
+/* static */
+const wchar_t* nsWindow::ChooseWindowClass(WindowType aWindowType) {
+  switch (aWindowType) {
+    case WindowType::Invisible:
+      return RegisterWindowClass(kClassNameHidden, 0, gStockApplicationIcon);
+    case WindowType::Dialog:
+      return RegisterWindowClass(kClassNameDialog, 0, nullptr);
+    case WindowType::Popup:
+      return RegisterWindowClass(kClassNameDropShadow, 0,
+                                 gStockApplicationIcon);
+    default:
+      return RegisterWindowClass(GetMainWindowClass(), 0,
+                                 gStockApplicationIcon);
+  }
+}
+
+/**************************************************************
+ *
+ * SECTION: Window styles utilities
+ *
+ * Return the proper windows styles and extended styles.
+ *
+ **************************************************************/
+
+// Return nsWindow styles
+DWORD nsWindow::WindowStyle() {
+  DWORD style;
+
+  switch (mWindowType) {
+    case WindowType::Child:
+      style = WS_OVERLAPPED;
+      break;
+
+    case WindowType::Dialog:
+      style = WS_OVERLAPPED | WS_BORDER | WS_DLGFRAME | WS_SYSMENU | DS_3DLOOK |
+              DS_MODALFRAME | WS_CLIPCHILDREN;
+      if (mBorderStyle != BorderStyle::Default)
+        style |= WS_THICKFRAME | WS_MINIMIZEBOX | WS_MAXIMIZEBOX;
+      break;
+
+    case WindowType::Popup:
+      style = WS_POPUP | WS_OVERLAPPED;
+      break;
+
+    default:
+      NS_ERROR("unknown border style");
+      [[fallthrough]];
+
+    case WindowType::TopLevel:
+    case WindowType::Invisible:
+      style = WS_OVERLAPPED | WS_BORDER | WS_DLGFRAME | WS_SYSMENU |
+              WS_THICKFRAME | WS_MINIMIZEBOX | WS_MAXIMIZEBOX | WS_CLIPCHILDREN;
+      break;
+  }
+
+  if (mBorderStyle != BorderStyle::Default &&
+      mBorderStyle != BorderStyle::All) {
+    if (mBorderStyle == BorderStyle::None ||
+        !(mBorderStyle & BorderStyle::Border))
+      style &= ~WS_BORDER;
+
+    if (mBorderStyle == BorderStyle::None ||
+        !(mBorderStyle & BorderStyle::Title)) {
+      style &= ~WS_DLGFRAME;
+    }
+
+    if (mBorderStyle == BorderStyle::None ||
+        !(mBorderStyle & BorderStyle::Close))
+      style &= ~0;
+    // XXX The close box can only be removed by changing the window class,
+    // as far as I know   --- roc+moz@cs.cmu.edu
+
+    if (mBorderStyle == BorderStyle::None ||
+        !(mBorderStyle & (BorderStyle::Menu | BorderStyle::Close)))
+      style &= ~WS_SYSMENU;
+    // Looks like getting rid of the system menu also does away with the
+    // close box. So, we only get rid of the system menu if you want neither it
+    // nor the close box. How does the Windows "Dialog" window class get just
+    // closebox and no sysmenu? Who knows.
+
+    if (mBorderStyle == BorderStyle::None ||
+        !(mBorderStyle & BorderStyle::ResizeH))
+      style &= ~WS_THICKFRAME;
+
+    if (mBorderStyle == BorderStyle::None ||
+        !(mBorderStyle & BorderStyle::Minimize))
+      style &= ~WS_MINIMIZEBOX;
+
+    if (mBorderStyle == BorderStyle::None ||
+        !(mBorderStyle & BorderStyle::Maximize))
+      style &= ~WS_MAXIMIZEBOX;
+
+    if (IsPopupWithTitleBar()) {
+      style |= WS_CAPTION;
+      if (mBorderStyle & BorderStyle::Close) {
+        style |= WS_SYSMENU;
+      }
+    }
+  }
+
+  if (mIsChildWindow) {
+    style |= WS_CLIPCHILDREN;
+    if (!(style & WS_POPUP)) {
+      style |= WS_CHILD;  // WS_POPUP and WS_CHILD are mutually exclusive.
+    }
+  }
+
+  VERIFY_WINDOW_STYLE(style);
+  return style;
+}
+
+// Return nsWindow extended styles
+DWORD nsWindow::WindowExStyle() {
+  MOZ_ASSERT_IF(mIsAlert, mWindowType == WindowType::Dialog);
+  switch (mWindowType) {
+    case WindowType::Child:
+      return 0;
+    case WindowType::Popup: {
+      DWORD extendedStyle = WS_EX_TOOLWINDOW;
+      if (mPopupLevel == PopupLevel::Top) {
+        extendedStyle |= WS_EX_TOPMOST;
+      }
+      return extendedStyle;
+    }
+    case WindowType::Dialog: {
+      if (mIsAlert) {
+        return WS_EX_TOOLWINDOW | WS_EX_TOPMOST;
+      }
+      return WS_EX_WINDOWEDGE | WS_EX_DLGMODALFRAME;
+    }
+    case WindowType::Sheet:
+      MOZ_FALLTHROUGH_ASSERT("Sheets are macOS specific");
+    case WindowType::TopLevel:
+    case WindowType::Invisible:
+      break;
+  }
+  return WS_EX_WINDOWEDGE;
+}
+
+/**************************************************************
+ *
+ * SECTION: Native window association utilities
+ *
+ * Used in Create and Destroy. A nsWindow can associate with its
+ * underlying native window mWnd. Once a native window is
+ * associated with a nsWindow, its native events will be handled
+ * by the static member function nsWindow::WindowProc. Moreover,
+ * the association will be registered in the WinUtils association
+ * list, that is, calling WinUtils::GetNSWindowPtr on the native
+ * window will return the associated nsWindow. This is used in
+ * nsWindow::WindowProc to correctly dispatch native events to
+ * the handler methods defined in nsWindow, even though it is a
+ * static member function.
+ *
+ * After dissociation, the native events of the native window will
+ * no longer be handled by nsWindow::WindowProc, and will thus not
+ * be dispatched to the nsWindow native event handler methods.
+ * Moreover, the association will no longer be registered in the
+ * WinUtils association list, so calling WinUtils::GetNSWindowPtr
+ * on the native window will return nullptr.
+ *
+ **************************************************************/
+
+bool nsWindow::AssociateWithNativeWindow() {
+  if (!mWnd || !IsWindow(mWnd)) {
+    NS_ERROR("Invalid window handle");
+    return false;
+  }
+
+  // Connect the this pointer to the native window handle.
+  // This should be done before SetWindowLongPtrW, because nsWindow::WindowProc
+  // uses WinUtils::GetNSWindowPtr internally.
+  WinUtils::SetNSWindowPtr(mWnd, this);
+
+  ::SetLastError(ERROR_SUCCESS);
+  const auto prevWndProc = reinterpret_cast<WNDPROC>(::SetWindowLongPtrW(
+      mWnd, GWLP_WNDPROC, reinterpret_cast<LONG_PTR>(nsWindow::WindowProc)));
+  if (!prevWndProc && GetLastError() != ERROR_SUCCESS) {
+    NS_ERROR("Failure in SetWindowLongPtrW");
+    WinUtils::SetNSWindowPtr(mWnd, nullptr);
+    return false;
+  }
+
+  mPrevWndProc.emplace(prevWndProc);
+  return true;
+}
+
+void nsWindow::DissociateFromNativeWindow() {
+  if (!mWnd || !IsWindow(mWnd) || mPrevWndProc.isNothing()) {
+    return;
+  }
+
+  DebugOnly<WNDPROC> wndProcBeforeDissociate =
+      reinterpret_cast<WNDPROC>(::SetWindowLongPtrW(
+          mWnd, GWLP_WNDPROC, reinterpret_cast<LONG_PTR>(*mPrevWndProc)));
+  NS_ASSERTION(wndProcBeforeDissociate == nsWindow::WindowProc,
+               "Unstacked an unexpected native window procedure");
+
+  WinUtils::SetNSWindowPtr(mWnd, nullptr);
+  mPrevWndProc.reset();
+}
+
+/**************************************************************
+ *
+ * SECTION: nsIWidget::SetParent, nsIWidget::GetParent
+ *
+ * Set or clear the parent widgets using window properties, and
+ * handles calculating native parent handles.
+ *
+ **************************************************************/
+
+// Get and set parent widgets
+void nsWindow::SetParent(nsIWidget* aNewParent) {
+  nsCOMPtr<nsIWidget> kungFuDeathGrip(this);
+  nsIWidget* parent = GetParent();
+  if (parent) {
+    parent->RemoveChild(this);
+  }
+
+  mParent = aNewParent;
+
+  if (aNewParent) {
+    ReparentNativeWidget(aNewParent);
+    aNewParent->AddChild(this);
+    return;
+  }
+  if (mWnd) {
+    // If we have no parent, SetParent should return the desktop.
+    VERIFY(::SetParent(mWnd, nullptr));
+    RecreateDirectManipulationIfNeeded();
+  }
+}
+
+void nsWindow::ReparentNativeWidget(nsIWidget* aNewParent) {
+  MOZ_ASSERT(aNewParent, "null widget");
+
+  mParent = aNewParent;
+  if (mWindowType == WindowType::Popup) {
+    return;
+  }
+  HWND newParent = (HWND)aNewParent->GetNativeData(NS_NATIVE_WINDOW);
+  NS_ASSERTION(newParent, "Parent widget has a null native window handle");
+  if (newParent && mWnd) {
+    ::SetParent(mWnd, newParent);
+    RecreateDirectManipulationIfNeeded();
+  }
+}
+
+nsIWidget* nsWindow::GetParent(void) {
+  if (mIsTopWidgetWindow) {
+    return nullptr;
+  }
+  if (mInDtor || mOnDestroyCalled) {
+    return nullptr;
+  }
+  return mParent;
+}
+
+static int32_t RoundDown(double aDouble) {
+  return aDouble > 0 ? static_cast<int32_t>(floor(aDouble))
+                     : static_cast<int32_t>(ceil(aDouble));
+}
+
+float nsWindow::GetDPI() {
+  float dpi = 96.0f;
+  nsCOMPtr<nsIScreen> screen = GetWidgetScreen();
+  if (screen) {
+    screen->GetDpi(&dpi);
+  }
+  return dpi;
+}
+
+double nsWindow::GetDefaultScaleInternal() {
+  if (mDefaultScale <= 0.0) {
+    mDefaultScale = WinUtils::LogToPhysFactor(mWnd);
+  }
+  return mDefaultScale;
+}
+
+int32_t nsWindow::LogToPhys(double aValue) {
+  return WinUtils::LogToPhys(
+      ::MonitorFromWindow(mWnd, MONITOR_DEFAULTTOPRIMARY), aValue);
+}
+
+nsWindow* nsWindow::GetParentWindow(bool aIncludeOwner) {
+  return static_cast<nsWindow*>(GetParentWindowBase(aIncludeOwner));
+}
+
+nsWindow* nsWindow::GetParentWindowBase(bool aIncludeOwner) {
+  if (mIsTopWidgetWindow) {
+    // Must use a flag instead of mWindowType to tell if the window is the
+    // owned by the topmost widget, because a child window can be embedded
+    // inside a HWND which is not associated with a nsIWidget.
+    return nullptr;
+  }
+
+  // If this widget has already been destroyed, pretend we have no parent.
+  // This corresponds to code in Destroy which removes the destroyed
+  // widget from its parent's child list.
+  if (mInDtor || mOnDestroyCalled) return nullptr;
+
+  // aIncludeOwner set to true implies walking the parent chain to retrieve the
+  // root owner. aIncludeOwner set to false implies the search will stop at the
+  // true parent (default).
+  nsWindow* widget = nullptr;
+  if (mWnd) {
+    HWND parent = nullptr;
+    if (aIncludeOwner)
+      parent = ::GetParent(mWnd);
+    else
+      parent = ::GetAncestor(mWnd, GA_PARENT);
+
+    if (parent) {
+      widget = WinUtils::GetNSWindowPtr(parent);
+      if (widget) {
+        // If the widget is in the process of being destroyed then
+        // do NOT return it
+        if (widget->mInDtor) {
+          widget = nullptr;
+        }
+      }
+    }
+  }
+
+  return widget;
+}
+
+/**************************************************************
+ *
+ * SECTION: nsIWidget::Show
+ *
+ * Hide or show this component.
+ *
+ **************************************************************/
+
+void nsWindow::Show(bool bState) {
+  if (bState && mIsShowingPreXULSkeletonUI) {
+    // The first time we decide to actually show the window is when we decide
+    // that we've taken over the window from the skeleton UI, and we should
+    // no longer treat resizes / moves specially.
+    mIsShowingPreXULSkeletonUI = false;
+#if defined(ACCESSIBILITY)
+    // If our HWND has focus and the a11y engine hasn't started yet, fire a
+    // focus win event. Windows already did this when the skeleton UI appeared,
+    // but a11y wouldn't have been able to start at that point even if a client
+    // responded. Firing this now gives clients the chance to respond with
+    // WM_GETOBJECT, which will trigger the a11y engine. We don't want to do
+    // this if the a11y engine has already started because it has probably
+    // already fired focus on a descendant.
+    if (::GetFocus() == mWnd && !GetAccService()) {
+      ::NotifyWinEvent(EVENT_OBJECT_FOCUS, mWnd, OBJID_CLIENT, CHILDID_SELF);
+    }
+#endif  // defined(ACCESSIBILITY)
+  }
+
+  if (mWindowType == WindowType::Popup) {
+    MOZ_ASSERT(ChooseWindowClass(mWindowType) == kClassNameDropShadow);
+    // WS_EX_COMPOSITED conflicts with the WS_EX_LAYERED style and causes
+    // some popup menus to become invisible.
+    LONG_PTR exStyle = ::GetWindowLongPtrW(mWnd, GWL_EXSTYLE);
+    if (exStyle & WS_EX_LAYERED) {
+      ::SetWindowLongPtrW(mWnd, GWL_EXSTYLE, exStyle & ~WS_EX_COMPOSITED);
+    }
+  }
+
+  bool syncInvalidate = false;
+
+  bool wasVisible = mIsVisible;
+  // Set the status now so that anyone asking during ShowWindow or
+  // SetWindowPos would get the correct answer.
+  mIsVisible = bState;
+
+  // We may have cached an out of date visible state. This can happen
+  // when session restore sets the full screen mode.
+  if (mIsVisible)
+    mOldStyle |= WS_VISIBLE;
+  else
+    mOldStyle &= ~WS_VISIBLE;
+
+  if (mWnd) {
+    if (bState) {
+      if (!wasVisible && mWindowType == WindowType::TopLevel) {
+        // speed up the initial paint after show for
+        // top level windows:
+        syncInvalidate = true;
+
+        // Set the cursor before showing the window to avoid the default wait
+        // cursor.
+        SetCursor(Cursor{eCursor_standard});
+
+        switch (mFrameState->GetSizeMode()) {
+          case nsSizeMode_Fullscreen:
+            ::ShowWindow(mWnd, SW_SHOW);
+            break;
+          case nsSizeMode_Maximized:
+            ::ShowWindow(mWnd, SW_SHOWMAXIMIZED);
+            break;
+          case nsSizeMode_Minimized:
+            ::ShowWindow(mWnd, SW_SHOWMINIMIZED);
+            break;
+          default:
+            if (CanTakeFocus() && !mAlwaysOnTop) {
+              ::ShowWindow(mWnd, SW_SHOWNORMAL);
+            } else {
+              ::ShowWindow(mWnd, SW_SHOWNOACTIVATE);
+              // Don't flicker the window if we're restoring session
+              if (!sIsRestoringSession) {
+                Unused << GetAttention(2);
+              }
+            }
+            break;
+        }
+      } else {
+        DWORD flags = SWP_NOSIZE | SWP_NOMOVE | SWP_SHOWWINDOW;
+        if (wasVisible) {
+          flags |= SWP_NOZORDER;
+        }
+        if (mAlwaysOnTop || mIsAlert) {
+          flags |= SWP_NOACTIVATE;
+        }
+
+        if (mWindowType == WindowType::Popup) {
+          // ensure popups are the topmost of the TOPMOST
+          // layer. Remember not to set the SWP_NOZORDER
+          // flag as that might allow the taskbar to overlap
+          // the popup.
+          flags |= SWP_NOACTIVATE;
+          HWND owner = ::GetWindow(mWnd, GW_OWNER);
+          if (owner) {
+            // PopupLevel::Top popups should be above all else.  All other
+            // types should be placed in front of their owner, without
+            // changing the owner's z-level relative to other windows.
+            if (mPopupLevel != PopupLevel::Top) {
+              ::SetWindowPos(mWnd, owner, 0, 0, 0, 0, flags);
+              ::SetWindowPos(owner, mWnd, 0, 0, 0, 0,
+                             SWP_NOMOVE | SWP_NOSIZE | SWP_NOACTIVATE);
+            } else {
+              ::SetWindowPos(mWnd, HWND_TOP, 0, 0, 0, 0, flags);
+            }
+          } else {
+            ::SetWindowPos(mWnd, HWND_TOPMOST, 0, 0, 0, 0, flags);
+          }
+        } else {
+          if (mWindowType == WindowType::Dialog && !CanTakeFocus())
+            flags |= SWP_NOACTIVATE;
+
+          ::SetWindowPos(mWnd, HWND_TOP, 0, 0, 0, 0, flags);
+        }
+      }
+    } else {
+      // Clear contents to avoid ghosting of old content if we display
+      // this window again.
+      if (wasVisible && mTransparencyMode == TransparencyMode::Transparent) {
+        if (mCompositorWidgetDelegate) {
+          mCompositorWidgetDelegate->ClearTransparentWindow();
+        }
+      }
+      if (mWindowType != WindowType::Dialog) {
+        ::ShowWindow(mWnd, SW_HIDE);
+      } else {
+        ::SetWindowPos(mWnd, 0, 0, 0, 0, 0,
+                       SWP_HIDEWINDOW | SWP_NOSIZE | SWP_NOMOVE | SWP_NOZORDER |
+                           SWP_NOACTIVATE);
+      }
+    }
+  }
+
+  if (!wasVisible && bState) {
+    Invalidate();
+    if (syncInvalidate && !mInDtor && !mOnDestroyCalled) {
+      ::UpdateWindow(mWnd);
+    }
+  }
+
+  if (mOpeningAnimationSuppressed) {
+    SuppressAnimation(false);
+  }
+}
+
+/**************************************************************
+ *
+ * SECTION: nsIWidget::IsVisible
+ *
+ * Returns the visibility state.
+ *
+ **************************************************************/
+
+// Return true if the component is visible, false otherwise.
+//
+// This does not take cloaking into account.
+bool nsWindow::IsVisible() const { return mIsVisible; }
+
+/**************************************************************
+ *
+ * SECTION: Touch and APZ-related functions
+ *
+ **************************************************************/
+
+void nsWindow::RegisterTouchWindow() {
+  mTouchWindow = true;
+  ::RegisterTouchWindow(mWnd, TWF_WANTPALM);
+  ::EnumChildWindows(mWnd, nsWindow::RegisterTouchForDescendants, 0);
+}
+
+BOOL CALLBACK nsWindow::RegisterTouchForDescendants(HWND aWnd, LPARAM aMsg) {
+  nsWindow* win = WinUtils::GetNSWindowPtr(aWnd);
+  if (win) {
+    ::RegisterTouchWindow(aWnd, TWF_WANTPALM);
+  }
+  return TRUE;
+}
+
+void nsWindow::LockAspectRatio(bool aShouldLock) {
+  if (aShouldLock) {
+    mAspectRatio = (float)mBounds.Width() / (float)mBounds.Height();
+  } else {
+    mAspectRatio = 0.0;
+  }
+}
+
+/**************************************************************
+ *
+ * SECTION: nsIWidget::SetInputRegion
+ *
+ * Sets whether the window should ignore mouse events.
+ *
+ **************************************************************/
+void nsWindow::SetInputRegion(const InputRegion& aInputRegion) {
+  mInputRegion = aInputRegion;
+}
+
+/**************************************************************
+ *
+ * SECTION: nsIWidget::Move, nsIWidget::Resize, nsIWidget::Size
+ *
+ * Repositioning and sizing a window.
+ *
+ **************************************************************/
+
+void nsWindow::SetSizeConstraints(const SizeConstraints& aConstraints) {
+  SizeConstraints c = aConstraints;
+
+  if (mWindowType != WindowType::Popup && mResizable) {
+    c.mMinSize.width =
+        std::max(int32_t(::GetSystemMetrics(SM_CXMINTRACK)), c.mMinSize.width);
+    c.mMinSize.height =
+        std::max(int32_t(::GetSystemMetrics(SM_CYMINTRACK)), c.mMinSize.height);
+  }
+
+  if (mMaxTextureSize > 0) {
+    // We can't make ThebesLayers bigger than this anyway.. no point it letting
+    // a window grow bigger as we won't be able to draw content there in
+    // general.
+    c.mMaxSize.width = std::min(c.mMaxSize.width, mMaxTextureSize);
+    c.mMaxSize.height = std::min(c.mMaxSize.height, mMaxTextureSize);
+  }
+
+  mSizeConstraintsScale = GetDefaultScale().scale;
+
+  nsBaseWidget::SetSizeConstraints(c);
+}
+
+const SizeConstraints nsWindow::GetSizeConstraints() {
+  double scale = GetDefaultScale().scale;
+  if (mSizeConstraintsScale == scale || mSizeConstraintsScale == 0.0) {
+    return mSizeConstraints;
+  }
+  scale /= mSizeConstraintsScale;
+  SizeConstraints c = mSizeConstraints;
+  if (c.mMinSize.width != NS_MAXSIZE) {
+    c.mMinSize.width = NSToIntRound(c.mMinSize.width * scale);
+  }
+  if (c.mMinSize.height != NS_MAXSIZE) {
+    c.mMinSize.height = NSToIntRound(c.mMinSize.height * scale);
+  }
+  if (c.mMaxSize.width != NS_MAXSIZE) {
+    c.mMaxSize.width = NSToIntRound(c.mMaxSize.width * scale);
+  }
+  if (c.mMaxSize.height != NS_MAXSIZE) {
+    c.mMaxSize.height = NSToIntRound(c.mMaxSize.height * scale);
+  }
+  return c;
+}
+
+// Move this component
+void nsWindow::Move(double aX, double aY) {
+  if (mWindowType == WindowType::TopLevel ||
+      mWindowType == WindowType::Dialog) {
+    SetSizeMode(nsSizeMode_Normal);
+  }
+
+  // for top-level windows only, convert coordinates from desktop pixels
+  // (the "parent" coordinate space) to the window's device pixel space
+  double scale =
+      BoundsUseDesktopPixels() ? GetDesktopToDeviceScale().scale : 1.0;
+  int32_t x = NSToIntRound(aX * scale);
+  int32_t y = NSToIntRound(aY * scale);
+
+  // Check to see if window needs to be moved first
+  // to avoid a costly call to SetWindowPos. This check
+  // can not be moved to the calling code in nsView, because
+  // some platforms do not position child windows correctly
+
+  // Only perform this check for non-popup windows, since the positioning can
+  // in fact change even when the x/y do not.  We always need to perform the
+  // check. See bug #97805 for details.
+  if (mWindowType != WindowType::Popup && mBounds.IsEqualXY(x, y)) {
+    // Nothing to do, since it is already positioned correctly.
+    return;
+  }
+
+  mBounds.MoveTo(x, y);
+
+  if (mWnd) {
+#ifdef DEBUG
+    // complain if a window is moved offscreen (legal, but potentially
+    // worrisome)
+    if (mIsTopWidgetWindow) {  // only a problem for top-level windows
+      // Make sure this window is actually on the screen before we move it
+      // XXX: Needs multiple monitor support
+      HDC dc = ::GetDC(mWnd);
+      if (dc) {
+        if (::GetDeviceCaps(dc, TECHNOLOGY) == DT_RASDISPLAY) {
+          RECT workArea;
+          ::SystemParametersInfo(SPI_GETWORKAREA, 0, &workArea, 0);
+          // no annoying assertions. just mention the issue.
+          if (x < 0 || x >= workArea.right || y < 0 || y >= workArea.bottom) {
+            MOZ_LOG(gWindowsLog, LogLevel::Info,
+                    ("window moved to offscreen position\n"));
+          }
+        }
+        ::ReleaseDC(mWnd, dc);
+      }
+    }
+#endif
+
+    // Normally, when the skeleton UI is disabled, we resize+move the window
+    // before showing it in order to ensure that it restores to the correct
+    // position when the user un-maximizes it. However, when we are using the
+    // skeleton UI, this results in the skeleton UI window being moved around
+    // undesirably before being locked back into the maximized position. To
+    // avoid this, we simply set the placement to restore to via
+    // SetWindowPlacement. It's a little bit more of a dance, though, since we
+    // need to convert the workspace coords that SetWindowPlacement uses to the
+    // screen space coordinates we normally use with SetWindowPos.
+    if (mIsShowingPreXULSkeletonUI && WasPreXULSkeletonUIMaximized()) {
+      WINDOWPLACEMENT pl = {sizeof(WINDOWPLACEMENT)};
+      VERIFY(::GetWindowPlacement(mWnd, &pl));
+
+      HMONITOR monitor = ::MonitorFromWindow(mWnd, MONITOR_DEFAULTTONULL);
+      if (NS_WARN_IF(!monitor)) {
+        return;
+      }
+      MONITORINFO mi = {sizeof(MONITORINFO)};
+      VERIFY(::GetMonitorInfo(monitor, &mi));
+
+      int32_t deltaX =
+          x + mi.rcWork.left - mi.rcMonitor.left - pl.rcNormalPosition.left;
+      int32_t deltaY =
+          y + mi.rcWork.top - mi.rcMonitor.top - pl.rcNormalPosition.top;
+      pl.rcNormalPosition.left += deltaX;
+      pl.rcNormalPosition.right += deltaX;
+      pl.rcNormalPosition.top += deltaY;
+      pl.rcNormalPosition.bottom += deltaY;
+      VERIFY(::SetWindowPlacement(mWnd, &pl));
+    } else {
+      UINT flags = SWP_NOZORDER | SWP_NOACTIVATE | SWP_NOSIZE;
+      double oldScale = mDefaultScale;
+      mResizeState = IN_SIZEMOVE;
+      VERIFY(::SetWindowPos(mWnd, nullptr, x, y, 0, 0, flags));
+      mResizeState = NOT_RESIZING;
+      if (WinUtils::LogToPhysFactor(mWnd) != oldScale) {
+        ChangedDPI();
+      }
+    }
+
+    ResizeDirectManipulationViewport();
+  }
+}
+
+// Resize this component
+void nsWindow::Resize(double aWidth, double aHeight, bool aRepaint) {
+  // for top-level windows only, convert coordinates from desktop pixels
+  // (the "parent" coordinate space) to the window's device pixel space
+  double scale =
+      BoundsUseDesktopPixels() ? GetDesktopToDeviceScale().scale : 1.0;
+  int32_t width = NSToIntRound(aWidth * scale);
+  int32_t height = NSToIntRound(aHeight * scale);
+
+  NS_ASSERTION((width >= 0), "Negative width passed to nsWindow::Resize");
+  NS_ASSERTION((height >= 0), "Negative height passed to nsWindow::Resize");
+  if (width < 0 || height < 0) {
+    gfxCriticalNoteOnce << "Negative passed to Resize(" << width << ", "
+                        << height << ") repaint: " << aRepaint;
+  }
+
+  ConstrainSize(&width, &height);
+
+  // Avoid unnecessary resizing calls
+  if (mBounds.IsEqualSize(width, height)) {
+    if (aRepaint) {
+      Invalidate();
+    }
+    return;
+  }
+
+  // Set cached value for lightweight and printing
+  bool wasLocking = mAspectRatio != 0.0;
+  mBounds.SizeTo(width, height);
+  if (wasLocking) {
+    LockAspectRatio(true);  // This causes us to refresh the mAspectRatio value
+  }
+
+  if (mWnd) {
+    // Refer to the comment above a similar check in nsWindow::Move
+    if (mIsShowingPreXULSkeletonUI && WasPreXULSkeletonUIMaximized()) {
+      WINDOWPLACEMENT pl = {sizeof(WINDOWPLACEMENT)};
+      VERIFY(::GetWindowPlacement(mWnd, &pl));
+      pl.rcNormalPosition.right = pl.rcNormalPosition.left + width;
+      pl.rcNormalPosition.bottom = pl.rcNormalPosition.top + GetHeight(height);
+      mResizeState = RESIZING;
+      VERIFY(::SetWindowPlacement(mWnd, &pl));
+      mResizeState = NOT_RESIZING;
+    } else {
+      UINT flags = SWP_NOZORDER | SWP_NOACTIVATE | SWP_NOMOVE;
+
+      if (!aRepaint) {
+        flags |= SWP_NOREDRAW;
+      }
+
+      double oldScale = mDefaultScale;
+      mResizeState = RESIZING;
+      VERIFY(
+          ::SetWindowPos(mWnd, nullptr, 0, 0, width, GetHeight(height), flags));
+
+      mResizeState = NOT_RESIZING;
+      if (WinUtils::LogToPhysFactor(mWnd) != oldScale) {
+        ChangedDPI();
+      }
+    }
+
+    ResizeDirectManipulationViewport();
+  }
+
+  if (aRepaint) Invalidate();
+}
+
+// Resize this component
+void nsWindow::Resize(double aX, double aY, double aWidth, double aHeight,
+                      bool aRepaint) {
+  // for top-level windows only, convert coordinates from desktop pixels
+  // (the "parent" coordinate space) to the window's device pixel space
+  double scale =
+      BoundsUseDesktopPixels() ? GetDesktopToDeviceScale().scale : 1.0;
+  int32_t x = NSToIntRound(aX * scale);
+  int32_t y = NSToIntRound(aY * scale);
+  int32_t width = NSToIntRound(aWidth * scale);
+  int32_t height = NSToIntRound(aHeight * scale);
+
+  NS_ASSERTION((width >= 0), "Negative width passed to nsWindow::Resize");
+  NS_ASSERTION((height >= 0), "Negative height passed to nsWindow::Resize");
+  if (width < 0 || height < 0) {
+    gfxCriticalNoteOnce << "Negative passed to Resize(" << x << " ," << y
+                        << ", " << width << ", " << height
+                        << ") repaint: " << aRepaint;
+  }
+
+  ConstrainSize(&width, &height);
+
+  // Avoid unnecessary resizing calls
+  if (mBounds.IsEqualRect(x, y, width, height)) {
+    if (aRepaint) {
+      Invalidate();
+    }
+    return;
+  }
+
+  // Set cached value for lightweight and printing
+  mBounds.SetRect(x, y, width, height);
+
+  if (mWnd) {
+    // Refer to the comment above a similar check in nsWindow::Move
+    if (mIsShowingPreXULSkeletonUI && WasPreXULSkeletonUIMaximized()) {
+      WINDOWPLACEMENT pl = {sizeof(WINDOWPLACEMENT)};
+      VERIFY(::GetWindowPlacement(mWnd, &pl));
+
+      HMONITOR monitor = ::MonitorFromWindow(mWnd, MONITOR_DEFAULTTONULL);
+      if (NS_WARN_IF(!monitor)) {
+        return;
+      }
+      MONITORINFO mi = {sizeof(MONITORINFO)};
+      VERIFY(::GetMonitorInfo(monitor, &mi));
+
+      int32_t deltaX =
+          x + mi.rcWork.left - mi.rcMonitor.left - pl.rcNormalPosition.left;
+      int32_t deltaY =
+          y + mi.rcWork.top - mi.rcMonitor.top - pl.rcNormalPosition.top;
+      pl.rcNormalPosition.left += deltaX;
+      pl.rcNormalPosition.right = pl.rcNormalPosition.left + width;
+      pl.rcNormalPosition.top += deltaY;
+      pl.rcNormalPosition.bottom = pl.rcNormalPosition.top + GetHeight(height);
+      VERIFY(::SetWindowPlacement(mWnd, &pl));
+    } else {
+      UINT flags = SWP_NOZORDER | SWP_NOACTIVATE;
+      if (!aRepaint) {
+        flags |= SWP_NOREDRAW;
+      }
+
+      double oldScale = mDefaultScale;
+      mResizeState = RESIZING;
+      VERIFY(
+          ::SetWindowPos(mWnd, nullptr, x, y, width, GetHeight(height), flags));
+      mResizeState = NOT_RESIZING;
+      if (WinUtils::LogToPhysFactor(mWnd) != oldScale) {
+        ChangedDPI();
+      }
+
+      if (mTransitionWnd) {
+        // If we have a fullscreen transition window, we need to make
+        // it topmost again, otherwise the taskbar may be raised by
+        // the system unexpectedly when we leave fullscreen state.
+        ::SetWindowPos(mTransitionWnd, HWND_TOPMOST, 0, 0, 0, 0,
+                       SWP_NOMOVE | SWP_NOSIZE | SWP_NOACTIVATE);
+      }
+    }
+
+    ResizeDirectManipulationViewport();
+  }
+
+  if (aRepaint) Invalidate();
+}
+
+mozilla::Maybe<bool> nsWindow::IsResizingNativeWidget() {
+  if (mResizeState == RESIZING) {
+    return Some(true);
+  }
+  return Some(false);
+}
+
+/**************************************************************
+ *
+ * SECTION: Window Z-order and state.
+ *
+ * nsIWidget::PlaceBehind, nsIWidget::SetSizeMode,
+ * nsIWidget::ConstrainPosition
+ *
+ * Z-order, positioning, restore, minimize, and maximize.
+ *
+ **************************************************************/
+
+// Position the window behind the given window
+void nsWindow::PlaceBehind(nsTopLevelWidgetZPlacement aPlacement,
+                           nsIWidget* aWidget, bool aActivate) {
+  HWND behind = HWND_TOP;
+  if (aPlacement == eZPlacementBottom)
+    behind = HWND_BOTTOM;
+  else if (aPlacement == eZPlacementBelow && aWidget)
+    behind = (HWND)aWidget->GetNativeData(NS_NATIVE_WINDOW);
+  UINT flags = SWP_NOMOVE | SWP_NOREPOSITION | SWP_NOSIZE;
+  if (!aActivate) flags |= SWP_NOACTIVATE;
+
+  if (!CanTakeFocus() && behind == HWND_TOP) {
+    // Can't place the window to top so place it behind the foreground window
+    // (as long as it is not topmost)
+    HWND wndAfter = ::GetForegroundWindow();
+    if (!wndAfter)
+      behind = HWND_BOTTOM;
+    else if (!(GetWindowLongPtrW(wndAfter, GWL_EXSTYLE) & WS_EX_TOPMOST))
+      behind = wndAfter;
+    flags |= SWP_NOACTIVATE;
+  }
+
+  ::SetWindowPos(mWnd, behind, 0, 0, 0, 0, flags);
+}
+
+static UINT GetCurrentShowCmd(HWND aWnd) {
+  WINDOWPLACEMENT pl;
+  pl.length = sizeof(pl);
+  ::GetWindowPlacement(aWnd, &pl);
+  return pl.showCmd;
+}
+
+// Maximize, minimize or restore the window.
+void nsWindow::SetSizeMode(nsSizeMode aMode) {
+  // If we are still displaying a maximized pre-XUL skeleton UI, ignore the
+  // noise of sizemode changes. Once we have "shown" the window for the first
+  // time (called nsWindow::Show(true), even though the window is already
+  // technically displayed), we will again accept sizemode changes.
+  if (mIsShowingPreXULSkeletonUI && WasPreXULSkeletonUIMaximized()) {
+    return;
+  }
+
+  mFrameState->EnsureSizeMode(aMode);
+}
+
+nsSizeMode nsWindow::SizeMode() { return mFrameState->GetSizeMode(); }
+
+void DoGetWorkspaceID(HWND aWnd, nsAString* aWorkspaceID) {
+  RefPtr<IVirtualDesktopManager> desktopManager = gVirtualDesktopManager;
+  if (!desktopManager || !aWnd) {
+    return;
+  }
+
+  GUID desktop;
+  HRESULT hr = desktopManager->GetWindowDesktopId(aWnd, &desktop);
+  if (FAILED(hr)) {
+    return;
+  }
+
+  RPC_WSTR workspaceIDStr = nullptr;
+  if (UuidToStringW(&desktop, &workspaceIDStr) == RPC_S_OK) {
+    aWorkspaceID->Assign((wchar_t*)workspaceIDStr);
+    RpcStringFreeW(&workspaceIDStr);
+  }
+}
+
+void nsWindow::GetWorkspaceID(nsAString& workspaceID) {
+  // If we have a value cached, use that, but also make sure it is
+  // scheduled to be updated.  If we don't yet have a value, get
+  // one synchronously.
+  auto desktop = mDesktopId.Lock();
+  if (desktop->mID.IsEmpty()) {
+    DoGetWorkspaceID(mWnd, &desktop->mID);
+    desktop->mUpdateIsQueued = false;
+  } else {
+    AsyncUpdateWorkspaceID(*desktop);
+  }
+
+  workspaceID = desktop->mID;
+}
+
+void nsWindow::AsyncUpdateWorkspaceID(Desktop& aDesktop) {
+  struct UpdateWorkspaceIdTask : public Task {
+    explicit UpdateWorkspaceIdTask(nsWindow* aSelf)
+        : Task(Kind::OffMainThreadOnly, EventQueuePriority::Normal),
+          mSelf(aSelf) {}
+
+    TaskResult Run() override {
+      auto desktop = mSelf->mDesktopId.Lock();
+      if (desktop->mUpdateIsQueued) {
+        DoGetWorkspaceID(mSelf->mWnd, &desktop->mID);
+        desktop->mUpdateIsQueued = false;
+      }
+      return TaskResult::Complete;
+    }
+
+#ifdef MOZ_COLLECTING_RUNNABLE_TELEMETRY
+    bool GetName(nsACString& aName) override {
+      aName.AssignLiteral("UpdateWorkspaceIdTask");
+      return true;
+    }
+#endif
+
+    RefPtr<nsWindow> mSelf;
+  };
+
+  if (aDesktop.mUpdateIsQueued) {
+    return;
+  }
+
+  aDesktop.mUpdateIsQueued = true;
+  TaskController::Get()->AddTask(MakeAndAddRef<UpdateWorkspaceIdTask>(this));
+}
+
+void nsWindow::MoveToWorkspace(const nsAString& workspaceID) {
+  RefPtr<IVirtualDesktopManager> desktopManager = gVirtualDesktopManager;
+  if (!desktopManager) {
+    return;
+  }
+
+  GUID desktop;
+  const nsString flat = PromiseFlatString(workspaceID);
+  RPC_WSTR workspaceIDStr = reinterpret_cast<RPC_WSTR>((wchar_t*)flat.get());
+  if (UuidFromStringW(workspaceIDStr, &desktop) == RPC_S_OK) {
+    if (SUCCEEDED(desktopManager->MoveWindowToDesktop(mWnd, desktop))) {
+      auto desktop = mDesktopId.Lock();
+      desktop->mID = workspaceID;
+    }
+  }
+}
+
+void nsWindow::SuppressAnimation(bool aSuppress) {
+  DWORD dwAttribute = aSuppress ? TRUE : FALSE;
+  DwmSetWindowAttribute(mWnd, DWMWA_TRANSITIONS_FORCEDISABLED, &dwAttribute,
+                        sizeof dwAttribute);
+}
+
+// Constrain a potential move to fit onscreen
+// Position (aX, aY) is specified in Windows screen (logical) pixels,
+// except when using per-monitor DPI, in which case it's device pixels.
+void nsWindow::ConstrainPosition(DesktopIntPoint& aPoint) {
+  if (!mIsTopWidgetWindow)  // only a problem for top-level windows
+    return;
+
+  double dpiScale = GetDesktopToDeviceScale().scale;
+
+  // We need to use the window size in the kind of pixels used for window-
+  // manipulation APIs.
+  int32_t logWidth =
+      std::max<int32_t>(NSToIntRound(mBounds.Width() / dpiScale), 1);
+  int32_t logHeight =
+      std::max<int32_t>(NSToIntRound(mBounds.Height() / dpiScale), 1);
+
+  /* get our playing field. use the current screen, or failing that
+  for any reason, use device caps for the default screen. */
+  RECT screenRect;
+
+  nsCOMPtr<nsIScreenManager> screenmgr =
+      do_GetService(sScreenManagerContractID);
+  if (!screenmgr) {
+    return;
+  }
+  nsCOMPtr<nsIScreen> screen;
+  int32_t left, top, width, height;
+
+  screenmgr->ScreenForRect(aPoint.x, aPoint.y, logWidth, logHeight,
+                           getter_AddRefs(screen));
+  if (mFrameState->GetSizeMode() != nsSizeMode_Fullscreen) {
+    // For normalized windows, use the desktop work area.
+    nsresult rv = screen->GetAvailRectDisplayPix(&left, &top, &width, &height);
+    if (NS_FAILED(rv)) {
+      return;
+    }
+  } else {
+    // For full screen windows, use the desktop.
+    nsresult rv = screen->GetRectDisplayPix(&left, &top, &width, &height);
+    if (NS_FAILED(rv)) {
+      return;
+    }
+  }
+  screenRect.left = left;
+  screenRect.right = left + width;
+  screenRect.top = top;
+  screenRect.bottom = top + height;
+
+  if (aPoint.x < screenRect.left)
+    aPoint.x = screenRect.left;
+  else if (aPoint.x >= screenRect.right - logWidth)
+    aPoint.x = screenRect.right - logWidth;
+
+  if (aPoint.y < screenRect.top)
+    aPoint.y = screenRect.top;
+  else if (aPoint.y >= screenRect.bottom - logHeight)
+    aPoint.y = screenRect.bottom - logHeight;
+}
+
+/**************************************************************
+ *
+ * SECTION: nsIWidget::Enable, nsIWidget::IsEnabled
+ *
+ * Enabling and disabling the widget.
+ *
+ **************************************************************/
+
+// Enable/disable this component
+void nsWindow::Enable(bool bState) {
+  if (mWnd) {
+    ::EnableWindow(mWnd, bState);
+  }
+}
+
+// Return the current enable state
+bool nsWindow::IsEnabled() const {
+  return !mWnd || (::IsWindowEnabled(mWnd) &&
+                   ::IsWindowEnabled(::GetAncestor(mWnd, GA_ROOT)));
+}
+
+/**************************************************************
+ *
+ * SECTION: nsIWidget::SetFocus
+ *
+ * Give the focus to this widget.
+ *
+ **************************************************************/
+
+void nsWindow::SetFocus(Raise aRaise, mozilla::dom::CallerType aCallerType) {
+  if (mWnd) {
+#ifdef WINSTATE_DEBUG_OUTPUT
+    if (mWnd == WinUtils::GetTopLevelHWND(mWnd)) {
+      MOZ_LOG(gWindowsLog, LogLevel::Info,
+              ("*** SetFocus: [  top] raise=%d\n", aRaise == Raise::Yes));
+    } else {
+      MOZ_LOG(gWindowsLog, LogLevel::Info,
+              ("*** SetFocus: [child] raise=%d\n", aRaise == Raise::Yes));
+    }
+#endif
+    // Uniconify, if necessary
+    HWND toplevelWnd = WinUtils::GetTopLevelHWND(mWnd);
+    if (aRaise == Raise::Yes && ::IsIconic(toplevelWnd)) {
+      ::ShowWindow(toplevelWnd, SW_RESTORE);
+    }
+    ::SetFocus(mWnd);
+  }
+}
+
+/**************************************************************
+ *
+ * SECTION: Bounds
+ *
+ * GetBounds, GetClientBounds, GetScreenBounds,
+ * GetRestoredBounds, GetClientOffset, SetNonClientMargins
+ *
+ * Bound calculations.
+ *
+ **************************************************************/
+
+// Return the window's full dimensions in screen coordinates.
+// If the window has a parent, converts the origin to an offset
+// of the parent's screen origin.
+LayoutDeviceIntRect nsWindow::GetBounds() {
+  if (!mWnd) {
+    return mBounds;
+  }
+
+  RECT r;
+  VERIFY(::GetWindowRect(mWnd, &r));
+
+  LayoutDeviceIntRect rect;
+
+  // assign size
+  rect.SizeTo(r.right - r.left, r.bottom - r.top);
+
+  // popup window bounds' are in screen coordinates, not relative to parent
+  // window
+  if (mWindowType == WindowType::Popup) {
+    rect.MoveTo(r.left, r.top);
+    return rect;
+  }
+
+  // chrome on parent:
+  //  ___      5,5   (chrome start)
+  // |  ____   10,10 (client start)
+  // | |  ____ 20,20 (child start)
+  // | | |
+  // 20,20 - 5,5 = 15,15 (??)
+  // minus GetClientOffset:
+  // 15,15 - 5,5 = 10,10
+  //
+  // no chrome on parent:
+  //  ______   10,10 (win start)
+  // |  ____   20,20 (child start)
+  // | |
+  // 20,20 - 10,10 = 10,10
+  //
+  // walking the chain:
+  //  ___      5,5   (chrome start)
+  // |  ___    10,10 (client start)
+  // | |  ___  20,20 (child start)
+  // | | |  __ 30,30 (child start)
+  // | | | |
+  // 30,30 - 20,20 = 10,10 (offset from second child to first)
+  // 20,20 - 5,5 = 15,15 + 10,10 = 25,25 (??)
+  // minus GetClientOffset:
+  // 25,25 - 5,5 = 20,20 (offset from second child to parent client)
+
+  // convert coordinates if parent exists
+  HWND parent = ::GetParent(mWnd);
+  if (parent) {
+    RECT pr;
+    VERIFY(::GetWindowRect(parent, &pr));
+    r.left -= pr.left;
+    r.top -= pr.top;
+    // adjust for chrome
+    nsWindow* pWidget = static_cast<nsWindow*>(GetParent());
+    if (pWidget && pWidget->IsTopLevelWidget()) {
+      LayoutDeviceIntPoint clientOffset = pWidget->GetClientOffset();
+      r.left -= clientOffset.x;
+      r.top -= clientOffset.y;
+    }
+  }
+  rect.MoveTo(r.left, r.top);
+  if (mCompositorSession &&
+      !wr::WindowSizeSanityCheck(rect.width, rect.height)) {
+    gfxCriticalNoteOnce << "Invalid size" << rect << " size mode "
+                        << mFrameState->GetSizeMode();
+  }
+
+  return rect;
+}
+
+// Get this component dimension
+LayoutDeviceIntRect nsWindow::GetClientBounds() {
+  if (!mWnd) {
+    return LayoutDeviceIntRect(0, 0, 0, 0);
+  }
+
+  RECT r;
+  if (!::GetClientRect(mWnd, &r)) {
+    MOZ_ASSERT_UNREACHABLE("unexpected to be called");
+    gfxCriticalNoteOnce << "GetClientRect failed " << ::GetLastError();
+    return mBounds;
+  }
+
+  LayoutDeviceIntRect bounds = GetBounds();
+  LayoutDeviceIntRect rect;
+  rect.MoveTo(bounds.TopLeft() + GetClientOffset());
+  rect.SizeTo(r.right - r.left, r.bottom - r.top);
+  return rect;
+}
+
+// Like GetBounds, but don't offset by the parent
+LayoutDeviceIntRect nsWindow::GetScreenBounds() {
+  if (!mWnd) {
+    return mBounds;
+  }
+
+  RECT r;
+  VERIFY(::GetWindowRect(mWnd, &r));
+
+  return LayoutDeviceIntRect(r.left, r.top, r.right - r.left, r.bottom - r.top);
+}
+
+nsresult nsWindow::GetRestoredBounds(LayoutDeviceIntRect& aRect) {
+  if (SizeMode() == nsSizeMode_Normal) {
+    aRect = GetScreenBounds();
+    return NS_OK;
+  }
+  if (!mWnd) {
+    return NS_ERROR_FAILURE;
+  }
+
+  WINDOWPLACEMENT pl = {sizeof(WINDOWPLACEMENT)};
+  VERIFY(::GetWindowPlacement(mWnd, &pl));
+  const RECT& r = pl.rcNormalPosition;
+
+  HMONITOR monitor = ::MonitorFromWindow(mWnd, MONITOR_DEFAULTTONULL);
+  if (!monitor) {
+    return NS_ERROR_FAILURE;
+  }
+  MONITORINFO mi = {sizeof(MONITORINFO)};
+  VERIFY(::GetMonitorInfo(monitor, &mi));
+
+  aRect.SetRect(r.left, r.top, r.right - r.left, r.bottom - r.top);
+  aRect.MoveBy(mi.rcWork.left - mi.rcMonitor.left,
+               mi.rcWork.top - mi.rcMonitor.top);
+  return NS_OK;
+}
+
+// Return the x,y offset of the client area from the origin of the window. If
+// the window is borderless returns (0,0).
+LayoutDeviceIntPoint nsWindow::GetClientOffset() {
+  if (!mWnd) {
+    return LayoutDeviceIntPoint(0, 0);
+  }
+
+  RECT r1;
+  GetWindowRect(mWnd, &r1);
+  LayoutDeviceIntPoint pt = WidgetToScreenOffset();
+  return LayoutDeviceIntPoint(pt.x - LayoutDeviceIntCoord(r1.left),
+                              pt.y - LayoutDeviceIntCoord(r1.top));
+}
+
+void nsWindow::ResetLayout() {
+  // This will trigger a frame changed event, triggering
+  // nc calc size and a sizemode gecko event.
+  SetWindowPos(mWnd, 0, 0, 0, 0, 0,
+               SWP_FRAMECHANGED | SWP_NOACTIVATE | SWP_NOMOVE |
+                   SWP_NOOWNERZORDER | SWP_NOSIZE | SWP_NOZORDER);
+
+  // If hidden, just send the frame changed event for now.
+  if (!mIsVisible) {
+    return;
+  }
+
+  // Send a gecko size event to trigger reflow.
+  RECT clientRc = {0};
+  GetClientRect(mWnd, &clientRc);
+  OnResize(WinUtils::ToIntRect(clientRc).Size());
+
+  // Invalidate and update
+  Invalidate();
+}
+
+// Internally track the caption status via a window property. Required
+// due to our internal handling of WM_NCACTIVATE when custom client
+// margins are set.
+static const wchar_t kManageWindowInfoProperty[] = L"ManageWindowInfoProperty";
+typedef BOOL(WINAPI* GetWindowInfoPtr)(HWND hwnd, PWINDOWINFO pwi);
+static WindowsDllInterceptor::FuncHookType<GetWindowInfoPtr>
+    sGetWindowInfoPtrStub;
+
+BOOL WINAPI GetWindowInfoHook(HWND hWnd, PWINDOWINFO pwi) {
+  if (!sGetWindowInfoPtrStub) {
+    NS_ASSERTION(FALSE, "Something is horribly wrong in GetWindowInfoHook!");
+    return FALSE;
+  }
+  int windowStatus =
+      reinterpret_cast<LONG_PTR>(GetPropW(hWnd, kManageWindowInfoProperty));
+  // No property set, return the default data.
+  if (!windowStatus) return sGetWindowInfoPtrStub(hWnd, pwi);
+  // Call GetWindowInfo and update dwWindowStatus with our
+  // internally tracked value.
+  BOOL result = sGetWindowInfoPtrStub(hWnd, pwi);
+  if (result && pwi)
+    pwi->dwWindowStatus = (windowStatus == 1 ? 0 : WS_ACTIVECAPTION);
+  return result;
+}
+
+void nsWindow::UpdateGetWindowInfoCaptionStatus(bool aActiveCaption) {
+  if (!mWnd) return;
+
+  sUser32Intercept.Init("user32.dll");
+  sGetWindowInfoPtrStub.Set(sUser32Intercept, "GetWindowInfo",
+                            &GetWindowInfoHook);
+  if (!sGetWindowInfoPtrStub) {
+    return;
+  }
+
+  // Update our internally tracked caption status
+  SetPropW(mWnd, kManageWindowInfoProperty,
+           reinterpret_cast<HANDLE>(static_cast<INT_PTR>(aActiveCaption) + 1));
+}
+
+#define DWMWA_USE_IMMERSIVE_DARK_MODE_BEFORE_20H1 19
+#define DWMWA_USE_IMMERSIVE_DARK_MODE 20
+
+void nsWindow::UpdateDarkModeToolbar() {
+  PreferenceSheet::EnsureInitialized();
+  BOOL dark = PreferenceSheet::ColorSchemeForChrome() == ColorScheme::Dark;
+  DwmSetWindowAttribute(mWnd, DWMWA_USE_IMMERSIVE_DARK_MODE_BEFORE_20H1, &dark,
+                        sizeof dark);
+  DwmSetWindowAttribute(mWnd, DWMWA_USE_IMMERSIVE_DARK_MODE, &dark,
+                        sizeof dark);
+}
+
+LayoutDeviceIntMargin nsWindow::NormalWindowNonClientOffset() const {
+  LayoutDeviceIntMargin nonClientOffset;
+
+  // We're dealing with a "normal" window (not maximized, minimized, or
+  // fullscreen), so process `mNonClientMargins` and set `mNonClientOffset`
+  // accordingly.
+  //
+  // Setting `mNonClientOffset` to 0 has the effect of leaving the default
+  // frame intact.  Setting it to a value greater than 0 reduces the frame
+  // size by that amount.
+
+  if (mNonClientMargins.top > 0) {
+    nonClientOffset.top = std::min(mCaptionHeight, mNonClientMargins.top);
+  } else if (mNonClientMargins.top == 0) {
+    nonClientOffset.top = mCaptionHeight;
+  } else {
+    nonClientOffset.top = 0;
+  }
+
+  if (mNonClientMargins.bottom > 0) {
+    nonClientOffset.bottom =
+        std::min(mVertResizeMargin, mNonClientMargins.bottom);
+  } else if (mNonClientMargins.bottom == 0) {
+    nonClientOffset.bottom = mVertResizeMargin;
+  } else {
+    nonClientOffset.bottom = 0;
+  }
+
+  if (mNonClientMargins.left > 0) {
+    nonClientOffset.left = std::min(mHorResizeMargin, mNonClientMargins.left);
+  } else if (mNonClientMargins.left == 0) {
+    nonClientOffset.left = mHorResizeMargin;
+  } else {
+    nonClientOffset.left = 0;
+  }
+
+  if (mNonClientMargins.right > 0) {
+    nonClientOffset.right = std::min(mHorResizeMargin, mNonClientMargins.right);
+  } else if (mNonClientMargins.right == 0) {
+    nonClientOffset.right = mHorResizeMargin;
+  } else {
+    nonClientOffset.right = 0;
+  }
+  return nonClientOffset;
+}
+
+/**
+ * Called when the window layout changes: full screen mode transitions,
+ * theme changes, and composition changes. Calculates the new non-client
+ * margins and fires off a frame changed event, which triggers an nc calc
+ * size windows event, kicking the changes in.
+ *
+ * The offsets calculated here are based on the value of `mNonClientMargins`
+ * which is specified in the "chromemargins" attribute of the window.  For
+ * each margin, the value specified has the following meaning:
+ *    -1 - leave the default frame in place
+ *     0 - remove the frame
+ *    >0 - frame size equals min(0, (default frame size - margin value))
+ *
+ * This function calculates and populates `mNonClientOffset`.
+ * In our processing of `WM_NCCALCSIZE`, the frame size will be calculated
+ * as (default frame size - offset).  For example, if the left frame should
+ * be 1 pixel narrower than the default frame size, `mNonClientOffset.left`
+ * will equal 1.
+ *
+ * For maximized, fullscreen, and minimized windows, the values stored in
+ * `mNonClientMargins` are ignored, and special processing takes place.
+ *
+ * For non-glass windows, we only allow frames to be their default size
+ * or removed entirely.
+ */
+bool nsWindow::UpdateNonClientMargins(bool aReflowWindow) {
+  if (!mCustomNonClient) {
+    return false;
+  }
+
+  const nsSizeMode sizeMode = mFrameState->GetSizeMode();
+
+  bool hasCaption =
+      bool(mBorderStyle & (BorderStyle::All | BorderStyle::Title |
+                           BorderStyle::Menu | BorderStyle::Default));
+
+  float dpi = GetDPI();
+
+  // mCaptionHeight is the default size of the NC area at
+  // the top of the window. If the window has a caption,
+  // the size is calculated as the sum of:
+  //      SM_CYFRAME        - The thickness of the sizing border
+  //                          around a resizable window
+  //      SM_CXPADDEDBORDER - The amount of border padding
+  //                          for captioned windows
+  //      SM_CYCAPTION      - The height of the caption area
+  //
+  // If the window does not have a caption, mCaptionHeight will be equal to
+  // `WinUtils::GetSystemMetricsForDpi(SM_CYFRAME, dpi)`
+  mCaptionHeight =
+      WinUtils::GetSystemMetricsForDpi(SM_CYFRAME, dpi) +
+      (hasCaption ? WinUtils::GetSystemMetricsForDpi(SM_CYCAPTION, dpi) +
+                        WinUtils::GetSystemMetricsForDpi(SM_CXPADDEDBORDER, dpi)
+                  : 0);
+  if (!mUseResizeMarginOverrides) {
+    // mHorResizeMargin is the size of the default NC areas on the
+    // left and right sides of our window.  It is calculated as
+    // the sum of:
+    //      SM_CXFRAME        - The thickness of the sizing border
+    //      SM_CXPADDEDBORDER - The amount of border padding
+    //                          for captioned windows
+    //
+    // If the window does not have a caption, mHorResizeMargin will be equal to
+    // `WinUtils::GetSystemMetricsForDpi(SM_CXFRAME, dpi)`
+    mHorResizeMargin =
+        WinUtils::GetSystemMetricsForDpi(SM_CXFRAME, dpi) +
+        (hasCaption ? WinUtils::GetSystemMetricsForDpi(SM_CXPADDEDBORDER, dpi)
+                    : 0);
+
+    // mVertResizeMargin is the size of the default NC area at the
+    // bottom of the window. It is calculated as the sum of:
+    //      SM_CYFRAME        - The thickness of the sizing border
+    //      SM_CXPADDEDBORDER - The amount of border padding
+    //                          for captioned windows.
+    //
+    // If the window does not have a caption, mVertResizeMargin will be equal to
+    // `WinUtils::GetSystemMetricsForDpi(SM_CYFRAME, dpi)`
+    mVertResizeMargin =
+        WinUtils::GetSystemMetricsForDpi(SM_CYFRAME, dpi) +
+        (hasCaption ? WinUtils::GetSystemMetricsForDpi(SM_CXPADDEDBORDER, dpi)
+                    : 0);
+  }
+
+  if (sizeMode == nsSizeMode_Minimized) {
+    // Use default frame size for minimized windows
+    mNonClientOffset.top = 0;
+    mNonClientOffset.left = 0;
+    mNonClientOffset.right = 0;
+    mNonClientOffset.bottom = 0;
+  } else if (sizeMode == nsSizeMode_Fullscreen) {
+    // Remove the default frame from the top of our fullscreen window.  This
+    // makes the whole caption part of our client area, allowing us to draw
+    // in the whole caption area.  Additionally remove the default frame from
+    // the left, right, and bottom.
+    mNonClientOffset.top = mCaptionHeight;
+    mNonClientOffset.bottom = mVertResizeMargin;
+    mNonClientOffset.left = mHorResizeMargin;
+    mNonClientOffset.right = mHorResizeMargin;
+  } else if (sizeMode == nsSizeMode_Maximized) {
+    // We make the entire frame part of the client area. We leave the default
+    // frame sizes for left, right and bottom since Windows will automagically
+    // position the edges "offscreen" for maximized windows.
+    int verticalResize =
+        WinUtils::GetSystemMetricsForDpi(SM_CYFRAME, dpi) +
+        (hasCaption ? WinUtils::GetSystemMetricsForDpi(SM_CXPADDEDBORDER, dpi)
+                    : 0);
+
+    mNonClientOffset.top = mCaptionHeight - verticalResize;
+    mNonClientOffset.bottom = 0;
+    mNonClientOffset.left = 0;
+    mNonClientOffset.right = 0;
+
+    mozilla::Maybe<UINT> maybeEdge = GetHiddenTaskbarEdge();
+    if (maybeEdge) {
+      auto edge = maybeEdge.value();
+      if (ABE_LEFT == edge) {
+        mNonClientOffset.left -= kHiddenTaskbarSize;
+      } else if (ABE_RIGHT == edge) {
+        mNonClientOffset.right -= kHiddenTaskbarSize;
+      } else if (ABE_BOTTOM == edge || ABE_TOP == edge) {
+        mNonClientOffset.bottom -= kHiddenTaskbarSize;
+      }
+
+      // When we are drawing the non-client region, we need
+      // to clear the portion of the NC region that is exposed by the
+      // hidden taskbar.  As above, we clear the bottom of the NC region
+      // when the taskbar is at the top of the screen.
+      UINT clearEdge = (edge == ABE_TOP) ? ABE_BOTTOM : edge;
+      mClearNCEdge = Some(clearEdge);
+    }
+  } else {
+    mNonClientOffset = NormalWindowNonClientOffset();
+  }
+
+  if (aReflowWindow) {
+    // Force a reflow of content based on the new client
+    // dimensions.
+    ResetLayout();
+  }
+
+  return true;
+}
+
+nsresult nsWindow::SetNonClientMargins(const LayoutDeviceIntMargin& margins) {
+  if (!mIsTopWidgetWindow || mBorderStyle == BorderStyle::None)
+    return NS_ERROR_INVALID_ARG;
+
+  if (mHideChrome) {
+    mFutureMarginsOnceChromeShows = margins;
+    mFutureMarginsToUse = true;
+    return NS_OK;
+  }
+  mFutureMarginsToUse = false;
+
+  // Request for a reset
+  if (margins.top == -1 && margins.left == -1 && margins.right == -1 &&
+      margins.bottom == -1) {
+    mCustomNonClient = false;
+    mNonClientMargins = margins;
+    // Force a reflow of content based on the new client
+    // dimensions.
+    ResetLayout();
+
+    int windowStatus =
+        reinterpret_cast<LONG_PTR>(GetPropW(mWnd, kManageWindowInfoProperty));
+    if (windowStatus) {
+      ::SendMessageW(mWnd, WM_NCACTIVATE, 1 != windowStatus, 0);
+    }
+
+    return NS_OK;
+  }
+
+  if (margins.top < -1 || margins.bottom < -1 || margins.left < -1 ||
+      margins.right < -1)
+    return NS_ERROR_INVALID_ARG;
+
+  mNonClientMargins = margins;
+  mCustomNonClient = true;
+  if (!UpdateNonClientMargins()) {
+    NS_WARNING("UpdateNonClientMargins failed!");
+    return NS_OK;
+  }
+
+  return NS_OK;
+}
+
+void nsWindow::SetResizeMargin(mozilla::LayoutDeviceIntCoord aResizeMargin) {
+  mUseResizeMarginOverrides = true;
+  mHorResizeMargin = aResizeMargin;
+  mVertResizeMargin = aResizeMargin;
+  UpdateNonClientMargins();
+}
+
+void nsWindow::InvalidateNonClientRegion() {
+  // +-+-----------------------+-+
+  // | | app non-client chrome | |
+  // | +-----------------------+ |
+  // | |   app client chrome   | | }
+  // | +-----------------------+ | }
+  // | |      app content      | | } area we don't want to invalidate
+  // | +-----------------------+ | }
+  // | |   app client chrome   | | }
+  // | +-----------------------+ |
+  // +---------------------------+ <
+  //  ^                         ^    windows non-client chrome
+  // client area = app *
+  RECT rect;
+  GetWindowRect(mWnd, &rect);
+  MapWindowPoints(nullptr, mWnd, (LPPOINT)&rect, 2);
+  HRGN winRgn = CreateRectRgnIndirect(&rect);
+
+  // Subtract app client chrome and app content leaving
+  // windows non-client chrome and app non-client chrome
+  // in winRgn.
+  GetWindowRect(mWnd, &rect);
+  rect.top += mCaptionHeight;
+  rect.right -= mHorResizeMargin;
+  rect.bottom -= mVertResizeMargin;
+  rect.left += mHorResizeMargin;
+  MapWindowPoints(nullptr, mWnd, (LPPOINT)&rect, 2);
+  HRGN clientRgn = CreateRectRgnIndirect(&rect);
+  CombineRgn(winRgn, winRgn, clientRgn, RGN_DIFF);
+  DeleteObject(clientRgn);
+
+  // triggers ncpaint and paint events for the two areas
+  RedrawWindow(mWnd, nullptr, winRgn, RDW_FRAME | RDW_INVALIDATE);
+  DeleteObject(winRgn);
+}
+
+/**************************************************************
+ *
+ * SECTION: nsIWidget::SetBackgroundColor
+ *
+ * Sets the window background paint color.
+ *
+ **************************************************************/
+
+void nsWindow::SetBackgroundColor(const nscolor& aColor) {
+  if (mBrush) ::DeleteObject(mBrush);
+
+  mBrush = ::CreateSolidBrush(NSRGB_2_COLOREF(aColor));
+  if (mWnd != nullptr) {
+    ::SetClassLongPtrW(mWnd, GCLP_HBRBACKGROUND, (LONG_PTR)mBrush);
+  }
+}
+
+/**************************************************************
+ *
+ * SECTION: nsIWidget::SetCursor
+ *
+ * SetCursor and related utilities for manging cursor state.
+ *
+ **************************************************************/
+
+// Set this component cursor
+static HCURSOR CursorFor(nsCursor aCursor) {
+  switch (aCursor) {
+    case eCursor_select:
+      return ::LoadCursor(nullptr, IDC_IBEAM);
+    case eCursor_wait:
+      return ::LoadCursor(nullptr, IDC_WAIT);
+    case eCursor_hyperlink:
+      return ::LoadCursor(nullptr, IDC_HAND);
+    case eCursor_standard:
+    case eCursor_context_menu:  // XXX See bug 258960.
+      return ::LoadCursor(nullptr, IDC_ARROW);
+
+    case eCursor_n_resize:
+    case eCursor_s_resize:
+      return ::LoadCursor(nullptr, IDC_SIZENS);
+
+    case eCursor_w_resize:
+    case eCursor_e_resize:
+      return ::LoadCursor(nullptr, IDC_SIZEWE);
+
+    case eCursor_nw_resize:
+    case eCursor_se_resize:
+      return ::LoadCursor(nullptr, IDC_SIZENWSE);
+
+    case eCursor_ne_resize:
+    case eCursor_sw_resize:
+      return ::LoadCursor(nullptr, IDC_SIZENESW);
+
+    case eCursor_crosshair:
+      return ::LoadCursor(nullptr, IDC_CROSS);
+
+    case eCursor_move:
+      return ::LoadCursor(nullptr, IDC_SIZEALL);
+
+    case eCursor_help:
+      return ::LoadCursor(nullptr, IDC_HELP);
+
+    case eCursor_copy:  // CSS3
+      return ::LoadCursor(nsToolkit::mDllInstance, MAKEINTRESOURCE(IDC_COPY));
+
+    case eCursor_alias:
+      return ::LoadCursor(nsToolkit::mDllInstance, MAKEINTRESOURCE(IDC_ALIAS));
+
+    case eCursor_cell:
+      return ::LoadCursor(nsToolkit::mDllInstance, MAKEINTRESOURCE(IDC_CELL));
+    case eCursor_grab:
+      return ::LoadCursor(nsToolkit::mDllInstance, MAKEINTRESOURCE(IDC_GRAB));
+
+    case eCursor_grabbing:
+      return ::LoadCursor(nsToolkit::mDllInstance,
+                          MAKEINTRESOURCE(IDC_GRABBING));
+
+    case eCursor_spinning:
+      return ::LoadCursor(nullptr, IDC_APPSTARTING);
+
+    case eCursor_zoom_in:
+      return ::LoadCursor(nsToolkit::mDllInstance, MAKEINTRESOURCE(IDC_ZOOMIN));
+
+    case eCursor_zoom_out:
+      return ::LoadCursor(nsToolkit::mDllInstance,
+                          MAKEINTRESOURCE(IDC_ZOOMOUT));
+
+    case eCursor_not_allowed:
+    case eCursor_no_drop:
+      return ::LoadCursor(nullptr, IDC_NO);
+
+    case eCursor_col_resize:
+      return ::LoadCursor(nsToolkit::mDllInstance,
+                          MAKEINTRESOURCE(IDC_COLRESIZE));
+
+    case eCursor_row_resize:
+      return ::LoadCursor(nsToolkit::mDllInstance,
+                          MAKEINTRESOURCE(IDC_ROWRESIZE));
+
+    case eCursor_vertical_text:
+      return ::LoadCursor(nsToolkit::mDllInstance,
+                          MAKEINTRESOURCE(IDC_VERTICALTEXT));
+
+    case eCursor_all_scroll:
+      // XXX not 100% appropriate perhaps
+      return ::LoadCursor(nullptr, IDC_SIZEALL);
+
+    case eCursor_nesw_resize:
+      return ::LoadCursor(nullptr, IDC_SIZENESW);
+
+    case eCursor_nwse_resize:
+      return ::LoadCursor(nullptr, IDC_SIZENWSE);
+
+    case eCursor_ns_resize:
+      return ::LoadCursor(nullptr, IDC_SIZENS);
+
+    case eCursor_ew_resize:
+      return ::LoadCursor(nullptr, IDC_SIZEWE);
+
+    case eCursor_none:
+      return ::LoadCursor(nsToolkit::mDllInstance, MAKEINTRESOURCE(IDC_NONE));
+
+    default:
+      NS_ERROR("Invalid cursor type");
+      return nullptr;
+  }
+}
+
+static HCURSOR CursorForImage(const nsIWidget::Cursor& aCursor,
+                              CSSToLayoutDeviceScale aScale) {
+  if (!aCursor.IsCustom()) {
+    return nullptr;
+  }
+
+  nsIntSize size = nsIWidget::CustomCursorSize(aCursor);
+
+  // Reject cursors greater than 128 pixels in either direction, to prevent
+  // spoofing.
+  // XXX ideally we should rescale. Also, we could modify the API to
+  // allow trusted content to set larger cursors.
+  if (size.width > 128 || size.height > 128) {
+    return nullptr;
+  }
+
+  LayoutDeviceIntSize layoutSize =
+      RoundedToInt(CSSIntSize(size.width, size.height) * aScale);
+  LayoutDeviceIntPoint hotspot =
+      RoundedToInt(CSSIntPoint(aCursor.mHotspotX, aCursor.mHotspotY) * aScale);
+  HCURSOR cursor;
+  nsresult rv = nsWindowGfx::CreateIcon(aCursor.mContainer, true, hotspot,
+                                        layoutSize, &cursor);
+  if (NS_FAILED(rv)) {
+    return nullptr;
+  }
+
+  return cursor;
+}
+
+void nsWindow::SetCursor(const Cursor& aCursor) {
+  static HCURSOR sCurrentHCursor = nullptr;
+  static bool sCurrentHCursorIsCustom = false;
+
+  mCursor = aCursor;
+
+  if (sCurrentCursor == aCursor && sCurrentHCursor && !mUpdateCursor) {
+    // Cursors in windows are global, so even if our mUpdateCursor flag is
+    // false we always need to make sure the Windows cursor is up-to-date,
+    // since stuff like native drag and drop / resizers code can mutate it
+    // outside of this method.
+    ::SetCursor(sCurrentHCursor);
+    return;
+  }
+
+  mUpdateCursor = false;
+
+  if (sCurrentHCursorIsCustom) {
+    ::DestroyIcon(sCurrentHCursor);
+  }
+  sCurrentHCursor = nullptr;
+  sCurrentHCursorIsCustom = false;
+  sCurrentCursor = aCursor;
+
+  HCURSOR cursor = nullptr;
+  if (mCustomCursorAllowed) {
+    cursor = CursorForImage(aCursor, GetDefaultScale());
+  }
+  bool custom = false;
+  if (cursor) {
+    custom = true;
+  } else {
+    cursor = CursorFor(aCursor.mDefaultCursor);
+  }
+
+  if (!cursor) {
+    return;
+  }
+
+  sCurrentHCursor = cursor;
+  sCurrentHCursorIsCustom = custom;
+  ::SetCursor(cursor);
+}
+
+/**************************************************************
+ *
+ * SECTION: nsIWidget::Get/SetTransparencyMode
+ *
+ * Manage the transparency mode of the window containing this
+ * widget. Only works for popup and dialog windows when the
+ * Desktop Window Manager compositor is not enabled.
+ *
+ **************************************************************/
+
+TransparencyMode nsWindow::GetTransparencyMode() {
+  return GetTopLevelWindow(true)->GetWindowTranslucencyInner();
+}
+
+void nsWindow::SetTransparencyMode(TransparencyMode aMode) {
+  nsWindow* window = GetTopLevelWindow(true);
+  MOZ_ASSERT(window);
+
+  if (!window || window->DestroyCalled()) {
+    return;
+  }
+
+  window->SetWindowTranslucencyInner(aMode);
+}
+
+/**************************************************************
+ *
+ * SECTION: nsIWidget::UpdateWindowDraggingRegion
+ *
+ * For setting the draggable titlebar region from CSS
+ * with -moz-window-dragging: drag.
+ *
+ **************************************************************/
+
+void nsWindow::UpdateWindowDraggingRegion(
+    const LayoutDeviceIntRegion& aRegion) {
+  if (mDraggableRegion != aRegion) {
+    mDraggableRegion = aRegion;
+  }
+}
+
+/**************************************************************
+ *
+ * SECTION: nsIWidget::HideWindowChrome
+ *
+ * Show or hide window chrome.
+ *
+ **************************************************************/
+
+void nsWindow::HideWindowChrome(bool aShouldHide) {
+  HWND hwnd = WinUtils::GetTopLevelHWND(mWnd, true);
+  if (!WinUtils::GetNSWindowPtr(hwnd)) {
+    NS_WARNING("Trying to hide window decorations in an embedded context");
+    return;
+  }
+
+  if (mHideChrome == aShouldHide) return;
+
+  DWORD_PTR style, exStyle;
+  mHideChrome = aShouldHide;
+  if (aShouldHide) {
+    DWORD_PTR tempStyle = ::GetWindowLongPtrW(hwnd, GWL_STYLE);
+    DWORD_PTR tempExStyle = ::GetWindowLongPtrW(hwnd, GWL_EXSTYLE);
+
+    style = tempStyle & ~(WS_CAPTION | WS_THICKFRAME);
+    exStyle = tempExStyle & ~(WS_EX_DLGMODALFRAME | WS_EX_WINDOWEDGE |
+                              WS_EX_CLIENTEDGE | WS_EX_STATICEDGE);
+
+    mOldStyle = tempStyle;
+    mOldExStyle = tempExStyle;
+  } else {
+    if (!mOldStyle || !mOldExStyle) {
+      mOldStyle = ::GetWindowLongPtrW(hwnd, GWL_STYLE);
+      mOldExStyle = ::GetWindowLongPtrW(hwnd, GWL_EXSTYLE);
+    }
+
+    style = mOldStyle;
+    exStyle = mOldExStyle;
+    if (mFutureMarginsToUse) {
+      SetNonClientMargins(mFutureMarginsOnceChromeShows);
+    }
+  }
+
+  VERIFY_WINDOW_STYLE(style);
+  ::SetWindowLongPtrW(hwnd, GWL_STYLE, style);
+  ::SetWindowLongPtrW(hwnd, GWL_EXSTYLE, exStyle);
+}
+
+/**************************************************************
+ *
+ * SECTION: nsWindow::Invalidate
+ *
+ * Invalidate an area of the client for painting.
+ *
+ **************************************************************/
+
+// Invalidate this component visible area
+void nsWindow::Invalidate(bool aEraseBackground, bool aUpdateNCArea,
+                          bool aIncludeChildren) {
+  if (!mWnd) {
+    return;
+  }
+
+#ifdef WIDGET_DEBUG_OUTPUT
+  debug_DumpInvalidate(stdout, this, nullptr, "noname", (int32_t)mWnd);
+#endif  // WIDGET_DEBUG_OUTPUT
+
+  DWORD flags = RDW_INVALIDATE;
+  if (aEraseBackground) {
+    flags |= RDW_ERASE;
+  }
+  if (aUpdateNCArea) {
+    flags |= RDW_FRAME;
+  }
+  if (aIncludeChildren) {
+    flags |= RDW_ALLCHILDREN;
+  }
+
+  VERIFY(::RedrawWindow(mWnd, nullptr, nullptr, flags));
+}
+
+// Invalidate this component visible area
+void nsWindow::Invalidate(const LayoutDeviceIntRect& aRect) {
+  if (mWnd) {
+#ifdef WIDGET_DEBUG_OUTPUT
+    debug_DumpInvalidate(stdout, this, &aRect, "noname", (int32_t)mWnd);
+#endif  // WIDGET_DEBUG_OUTPUT
+
+    RECT rect;
+
+    rect.left = aRect.X();
+    rect.top = aRect.Y();
+    rect.right = aRect.XMost();
+    rect.bottom = aRect.YMost();
+
+    VERIFY(::InvalidateRect(mWnd, &rect, FALSE));
+  }
+}
+
+static LRESULT CALLBACK FullscreenTransitionWindowProc(HWND hWnd, UINT uMsg,
+                                                       WPARAM wParam,
+                                                       LPARAM lParam) {
+  switch (uMsg) {
+    case WM_FULLSCREEN_TRANSITION_BEFORE:
+    case WM_FULLSCREEN_TRANSITION_AFTER: {
+      DWORD duration = (DWORD)lParam;
+      DWORD flags = AW_BLEND;
+      if (uMsg == WM_FULLSCREEN_TRANSITION_AFTER) {
+        flags |= AW_HIDE;
+      }
+      ::AnimateWindow(hWnd, duration, flags);
+      // The message sender should have added ref for us.
+      NS_DispatchToMainThread(
+          already_AddRefed<nsIRunnable>((nsIRunnable*)wParam));
+      break;
+    }
+    case WM_DESTROY:
+      ::PostQuitMessage(0);
+      break;
+    default:
+      return ::DefWindowProcW(hWnd, uMsg, wParam, lParam);
+  }
+  return 0;
+}
+
+struct FullscreenTransitionInitData {
+  LayoutDeviceIntRect mBounds;
+  HANDLE mSemaphore;
+  HANDLE mThread;
+  HWND mWnd;
+
+  FullscreenTransitionInitData()
+      : mSemaphore(nullptr), mThread(nullptr), mWnd(nullptr) {}
+
+  ~FullscreenTransitionInitData() {
+    if (mSemaphore) {
+      ::CloseHandle(mSemaphore);
+    }
+    if (mThread) {
+      ::CloseHandle(mThread);
+    }
+  }
+};
+
+static DWORD WINAPI FullscreenTransitionThreadProc(LPVOID lpParam) {
+  // Initialize window class
+  static bool sInitialized = false;
+  if (!sInitialized) {
+    WNDCLASSW wc = {};
+    wc.lpfnWndProc = ::FullscreenTransitionWindowProc;
+    wc.hInstance = nsToolkit::mDllInstance;
+    wc.hbrBackground = ::CreateSolidBrush(RGB(0, 0, 0));
+    wc.lpszClassName = kClassNameTransition;
+    ::RegisterClassW(&wc);
+    sInitialized = true;
+  }
+
+  auto data = static_cast<FullscreenTransitionInitData*>(lpParam);
+  HWND wnd = ::CreateWindowW(kClassNameTransition, L"", 0, 0, 0, 0, 0, nullptr,
+                             nullptr, nsToolkit::mDllInstance, nullptr);
+  if (!wnd) {
+    ::ReleaseSemaphore(data->mSemaphore, 1, nullptr);
+    return 0;
+  }
+
+  // Since AnimateWindow blocks the thread of the transition window,
+  // we need to hide the cursor for that window, otherwise the system
+  // would show the busy pointer to the user.
+  ::ShowCursor(false);
+  ::SetWindowLongW(wnd, GWL_STYLE, 0);
+  ::SetWindowLongW(
+      wnd, GWL_EXSTYLE,
+      WS_EX_LAYERED | WS_EX_TRANSPARENT | WS_EX_TOOLWINDOW | WS_EX_NOACTIVATE);
+  ::SetWindowPos(wnd, HWND_TOPMOST, data->mBounds.X(), data->mBounds.Y(),
+                 data->mBounds.Width(), data->mBounds.Height(), 0);
+  data->mWnd = wnd;
+  ::ReleaseSemaphore(data->mSemaphore, 1, nullptr);
+  // The initialization data may no longer be valid
+  // after we release the semaphore.
+  data = nullptr;
+
+  MSG msg;
+  while (::GetMessageW(&msg, nullptr, 0, 0)) {
+    ::TranslateMessage(&msg);
+    ::DispatchMessage(&msg);
+  }
+  ::ShowCursor(true);
+  ::DestroyWindow(wnd);
+  return 0;
+}
+
+class FullscreenTransitionData final : public nsISupports {
+ public:
+  NS_DECL_ISUPPORTS
+
+  explicit FullscreenTransitionData(HWND aWnd) : mWnd(aWnd) {
+    MOZ_ASSERT(NS_IsMainThread(),
+               "FullscreenTransitionData "
+               "should be constructed in the main thread");
+  }
+
+  const HWND mWnd;
+
+ private:
+  ~FullscreenTransitionData() {
+    MOZ_ASSERT(NS_IsMainThread(),
+               "FullscreenTransitionData "
+               "should be deconstructed in the main thread");
+    ::PostMessageW(mWnd, WM_DESTROY, 0, 0);
+  }
+};
+
+NS_IMPL_ISUPPORTS0(FullscreenTransitionData)
+
+/* virtual */
+bool nsWindow::PrepareForFullscreenTransition(nsISupports** aData) {
+  FullscreenTransitionInitData initData;
+  nsCOMPtr<nsIScreen> screen = GetWidgetScreen();
+  const DesktopIntRect rect = screen->GetRectDisplayPix();
+  MOZ_ASSERT(BoundsUseDesktopPixels(),
+             "Should only be called on top-level window");
+  initData.mBounds =
+      LayoutDeviceIntRect::Round(rect * GetDesktopToDeviceScale());
+
+  // Create a semaphore for synchronizing the window handle which will
+  // be created by the transition thread and used by the main thread for
+  // posting the transition messages.
+  initData.mSemaphore = ::CreateSemaphore(nullptr, 0, 1, nullptr);
+  if (initData.mSemaphore) {
+    initData.mThread = ::CreateThread(
+        nullptr, 0, FullscreenTransitionThreadProc, &initData, 0, nullptr);
+    if (initData.mThread) {
+      ::WaitForSingleObject(initData.mSemaphore, INFINITE);
+    }
+  }
+  if (!initData.mWnd) {
+    return false;
+  }
+
+  mTransitionWnd = initData.mWnd;
+
+  auto data = new FullscreenTransitionData(initData.mWnd);
+  *aData = data;
+  NS_ADDREF(data);
+  return true;
+}
+
+/* virtual */
+void nsWindow::PerformFullscreenTransition(FullscreenTransitionStage aStage,
+                                           uint16_t aDuration,
+                                           nsISupports* aData,
+                                           nsIRunnable* aCallback) {
+  auto data = static_cast<FullscreenTransitionData*>(aData);
+  nsCOMPtr<nsIRunnable> callback = aCallback;
+  UINT msg = aStage == eBeforeFullscreenToggle ? WM_FULLSCREEN_TRANSITION_BEFORE
+                                               : WM_FULLSCREEN_TRANSITION_AFTER;
+  WPARAM wparam = (WPARAM)callback.forget().take();
+  ::PostMessage(data->mWnd, msg, wparam, (LPARAM)aDuration);
+}
+
+/* virtual */
+void nsWindow::CleanupFullscreenTransition() {
+  MOZ_ASSERT(NS_IsMainThread(),
+             "CleanupFullscreenTransition "
+             "should only run on the main thread");
+
+  mTransitionWnd = nullptr;
+}
+
+void nsWindow::TryDwmResizeHack() {
+  // The "DWM resize hack", aka the "fullscreen resize hack", is a workaround
+  // for DWM's occasional and not-entirely-predictable failure to update its
+  // internal state when the client area of a window changes without changing
+  // the window size. The effect of this is that DWM will clip the content of
+  // the window to its former client area.
+  //
+  // It is not known under what circumstances the bug will trigger. Windows 11
+  // is known to be required, but many Windows 11 machines do not exhibit the
+  // issue. Even machines that _do_ exhibit it will sometimes not do so when
+  // apparently-irrelevant changes are made to the configuration. (See bug
+  // 1763981.)
+  //
+  // The bug is triggered by Firefox when a maximized window (which has window
+  // decorations) becomes fullscreen (which doesn't). To work around this, if we
+  // think it may occur, we "flicker-resize" the relevant window -- that is, we
+  // reduce its height by 1px, then restore it. This causes DWM to acquire the
+  // new client-area metrics.
+  //
+  // Note that, in particular, this bug will not occur when using a separate
+  // compositor window, as our compositor windows never have any nonclient area.
+  //
+  // This is admittedly a sledgehammer where a screwdriver should suffice.
+
+  // ---------------------------------------------------------------------------
+
+  // Regardless of preferences or heuristics, only apply the hack if this is the
+  // first time we've entered fullscreen across the entire Firefox session.
+  // (Subsequent transitions to fullscreen, even with different windows, don't
+  // appear to induce the bug.)
+  {
+    // (main thread only; `atomic` not needed)
+    static bool sIsFirstFullscreenEntry = true;
+    bool isFirstFullscreenEntry = sIsFirstFullscreenEntry;
+    sIsFirstFullscreenEntry = false;
+    if (MOZ_LIKELY(!isFirstFullscreenEntry)) {
+      return;
+    }
+    MOZ_LOG(gWindowsLog, LogLevel::Verbose,
+            ("%s: first fullscreen entry", __PRETTY_FUNCTION__));
+  }
+
+  // Check whether to try to apply the DWM resize hack, based on the override
+  // pref and/or some internal heuristics.
+  {
+    const auto hackApplicationHeuristics = [&]() -> bool {
+      // The bug has only been seen under Windows 11. (At time of writing, this
+      // is the latest version of Windows.)
+      if (!IsWin11OrLater()) {
+        return false;
+      }
+
+      KnowsCompositor const* const kc = mWindowRenderer->AsKnowsCompositor();
+      // This should never happen...
+      MOZ_ASSERT(kc);
+      // ... so if it does, we are in uncharted territory: don't apply the hack.
+      if (!kc) {
+        return false;
+      }
+
+      // The bug doesn't occur when we're using a separate compositor window
+      // (since the compositor window always comprises exactly its client area,
+      // with no non-client border).
+      if (kc->GetUseCompositorWnd()) {
+        return false;
+      }
+
+      // Otherwise, apply the hack.
+      return true;
+    };
+
+    // Figure out whether or not we should perform the hack, and -- arguably
+    // more importantly -- log that decision.
+    bool const shouldApplyHack = [&]() {
+      enum Reason : bool { Pref, Heuristics };
+      auto const msg = [&](bool decision, Reason reason) -> bool {
+        MOZ_LOG(gWindowsLog, LogLevel::Verbose,
+                ("%s %s per %s", decision ? "applying" : "skipping",
+                 "DWM resize hack", reason == Pref ? "pref" : "heuristics"));
+        return decision;
+      };
+      switch (StaticPrefs::widget_windows_apply_dwm_resize_hack()) {
+        case 0:
+          return msg(false, Pref);
+        case 1:
+          return msg(true, Pref);
+        default:  // treat all other values as `auto`
+          return msg(hackApplicationHeuristics(), Heuristics);
+      }
+    }();
+
+    if (!shouldApplyHack) {
+      return;
+    }
+  }
+
+  // The DWM bug is believed to involve a race condition: some users have
+  // reported that setting a custom theme or adding unused command-line
+  // parameters sometimes causes the bug to vanish.
+  //
+  // Out of an abundance of caution, we therefore apply the hack in a later
+  // event, rather than inline.
+  NS_DispatchToMainThread(NS_NewRunnableFunction(
+      "nsWindow::TryFullscreenResizeHack", [self = RefPtr(this)]() {
+        HWND const hwnd = self->GetWindowHandle();
+
+        if (self->mFrameState->GetSizeMode() != nsSizeMode_Fullscreen) {
+          MOZ_LOG(gWindowsLog, mozilla::LogLevel::Info,
+                  ("DWM resize hack: window no longer fullscreen; aborting"));
+          return;
+        }
+
+        RECT origRect;
+        if (!::GetWindowRect(hwnd, &origRect)) {
+          MOZ_LOG(gWindowsLog, mozilla::LogLevel::Error,
+                  ("DWM resize hack: could not get window size?!"));
+          return;
+        }
+        LONG const x = origRect.left;
+        LONG const y = origRect.top;
+        LONG const width = origRect.right - origRect.left;
+        LONG const height = origRect.bottom - origRect.top;
+
+        MOZ_DIAGNOSTIC_ASSERT(!self->mIsPerformingDwmFlushHack);
+        auto const onExit =
+            MakeScopeExit([&, oldVal = self->mIsPerformingDwmFlushHack]() {
+              self->mIsPerformingDwmFlushHack = oldVal;
+            });
+        self->mIsPerformingDwmFlushHack = true;
+
+        MOZ_LOG(gWindowsLog, LogLevel::Debug,
+                ("beginning DWM resize hack for HWND %08" PRIXPTR,
+                 uintptr_t(hwnd)));
+        ::MoveWindow(hwnd, x, y, width, height - 1, FALSE);
+        ::MoveWindow(hwnd, x, y, width, height, TRUE);
+        MOZ_LOG(gWindowsLog, LogLevel::Debug,
+                ("concluded DWM resize hack for HWND %08" PRIXPTR,
+                 uintptr_t(hwnd)));
+      }));
+}
+
+void nsWindow::OnFullscreenChanged(nsSizeMode aOldSizeMode, bool aFullScreen) {
+  MOZ_ASSERT((aOldSizeMode != nsSizeMode_Fullscreen) == aFullScreen);
+
+  // HACK: Potentially flicker-resize the window, to force DWM to get the right
+  // client-area information.
+  if (aFullScreen) {
+    TryDwmResizeHack();
+  }
+
+  // Hide chrome and reposition window. Note this will also cache dimensions for
+  // restoration, so it should only be called once per fullscreen request.
+  //
+  // Don't do this when minimized, since our bounds make no sense then, nor when
+  // coming back from that state.
+  const bool toOrFromMinimized =
+      mFrameState->GetSizeMode() == nsSizeMode_Minimized ||
+      aOldSizeMode == nsSizeMode_Minimized;
+  if (!toOrFromMinimized) {
+    InfallibleMakeFullScreen(aFullScreen);
+  }
+
+  // Possibly notify the taskbar that we have changed our fullscreen mode.
+  TaskbarConcealer::OnFullscreenChanged(this, aFullScreen);
+}
+
+nsresult nsWindow::MakeFullScreen(bool aFullScreen) {
+  mFrameState->EnsureFullscreenMode(aFullScreen);
+  return NS_OK;
+}
+
+/**************************************************************
+ *
+ * SECTION: Native data storage
+ *
+ * nsIWidget::GetNativeData
+ * nsIWidget::FreeNativeData
+ *
+ * Set or clear native data based on a constant.
+ *
+ **************************************************************/
+
+// Return some native data according to aDataType
+void* nsWindow::GetNativeData(uint32_t aDataType) {
+  switch (aDataType) {
+    case NS_NATIVE_WIDGET:
+    case NS_NATIVE_WINDOW:
+    case NS_NATIVE_WINDOW_WEBRTC_DEVICE_ID:
+      return (void*)mWnd;
+    case NS_NATIVE_GRAPHIC:
+      MOZ_ASSERT_UNREACHABLE("Not supported on Windows:");
+      return nullptr;
+    case NS_RAW_NATIVE_IME_CONTEXT: {
+      void* pseudoIMEContext = GetPseudoIMEContext();
+      if (pseudoIMEContext) {
+        return pseudoIMEContext;
+      }
+      [[fallthrough]];
+    }
+    case NS_NATIVE_TSF_THREAD_MGR:
+    case NS_NATIVE_TSF_CATEGORY_MGR:
+    case NS_NATIVE_TSF_DISPLAY_ATTR_MGR:
+      return IMEHandler::GetNativeData(this, aDataType);
+
+    default:
+      break;
+  }
+
+  return nullptr;
+}
+
+// Free some native data according to aDataType
+void nsWindow::FreeNativeData(void* data, uint32_t aDataType) {
+  switch (aDataType) {
+    case NS_NATIVE_GRAPHIC:
+    case NS_NATIVE_WIDGET:
+    case NS_NATIVE_WINDOW:
+      break;
+    default:
+      break;
+  }
+}
+
+/**************************************************************
+ *
+ * SECTION: nsIWidget::SetTitle
+ *
+ * Set the main windows title text.
+ *
+ **************************************************************/
+
+nsresult nsWindow::SetTitle(const nsAString& aTitle) {
+  const nsString& strTitle = PromiseFlatString(aTitle);
+  AutoRestore<bool> sendingText(mSendingSetText);
+  mSendingSetText = true;
+  ::SendMessageW(mWnd, WM_SETTEXT, (WPARAM)0, (LPARAM)(LPCWSTR)strTitle.get());
+  return NS_OK;
+}
+
+/**************************************************************
+ *
+ * SECTION: nsIWidget::SetIcon
+ *
+ * Set the main windows icon.
+ *
+ **************************************************************/
+
+void nsWindow::SetBigIcon(HICON aIcon) {
+  HICON icon =
+      (HICON)::SendMessageW(mWnd, WM_SETICON, (WPARAM)ICON_BIG, (LPARAM)aIcon);
+  if (icon) {
+    ::DestroyIcon(icon);
+  }
+
+  mIconBig = aIcon;
+}
+
+void nsWindow::SetSmallIcon(HICON aIcon) {
+  HICON icon = (HICON)::SendMessageW(mWnd, WM_SETICON, (WPARAM)ICON_SMALL,
+                                     (LPARAM)aIcon);
+  if (icon) {
+    ::DestroyIcon(icon);
+  }
+
+  mIconSmall = aIcon;
+}
+
+void nsWindow::SetIcon(const nsAString& aIconSpec) {
+  // Assume the given string is a local identifier for an icon file.
+
+  nsCOMPtr<nsIFile> iconFile;
+  ResolveIconName(aIconSpec, u".ico"_ns, getter_AddRefs(iconFile));
+  if (!iconFile) return;
+
+  nsAutoString iconPath;
+  iconFile->GetPath(iconPath);
+
+  // XXX this should use MZLU (see bug 239279)
+
+  ::SetLastError(0);
+
+  HICON bigIcon =
+      (HICON)::LoadImageW(nullptr, (LPCWSTR)iconPath.get(), IMAGE_ICON,
+                          ::GetSystemMetrics(SM_CXICON),
+                          ::GetSystemMetrics(SM_CYICON), LR_LOADFROMFILE);
+  HICON smallIcon =
+      (HICON)::LoadImageW(nullptr, (LPCWSTR)iconPath.get(), IMAGE_ICON,
+                          ::GetSystemMetrics(SM_CXSMICON),
+                          ::GetSystemMetrics(SM_CYSMICON), LR_LOADFROMFILE);
+
+  if (bigIcon) {
+    SetBigIcon(bigIcon);
+  }
+#ifdef DEBUG_SetIcon
+  else {
+    NS_LossyConvertUTF16toASCII cPath(iconPath);
+    MOZ_LOG(gWindowsLog, LogLevel::Info,
+            ("\nIcon load error; icon=%s, rc=0x%08X\n\n", cPath.get(),
+             ::GetLastError()));
+  }
+#endif
+  if (smallIcon) {
+    SetSmallIcon(smallIcon);
+  }
+#ifdef DEBUG_SetIcon
+  else {
+    NS_LossyConvertUTF16toASCII cPath(iconPath);
+    MOZ_LOG(gWindowsLog, LogLevel::Info,
+            ("\nSmall icon load error; icon=%s, rc=0x%08X\n\n", cPath.get(),
+             ::GetLastError()));
+  }
+#endif
+}
+
+void nsWindow::SetBigIconNoData() {
+  HICON bigIcon =
+      ::LoadIconW(::GetModuleHandleW(nullptr), gStockApplicationIcon);
+  SetBigIcon(bigIcon);
+}
+
+void nsWindow::SetSmallIconNoData() {
+  HICON smallIcon =
+      ::LoadIconW(::GetModuleHandleW(nullptr), gStockApplicationIcon);
+  SetSmallIcon(smallIcon);
+}
+
+/**************************************************************
+ *
+ * SECTION: nsIWidget::WidgetToScreenOffset
+ *
+ * Return this widget's origin in screen coordinates.
+ *
+ **************************************************************/
+
+LayoutDeviceIntPoint nsWindow::WidgetToScreenOffset() {
+  POINT point;
+  point.x = 0;
+  point.y = 0;
+  ::ClientToScreen(mWnd, &point);
+  return LayoutDeviceIntPoint(point.x, point.y);
+}
+
+LayoutDeviceIntMargin nsWindow::ClientToWindowMargin() {
+  if (mWindowType == WindowType::Popup && !IsPopupWithTitleBar()) {
+    return {};
+  }
+
+  if (mCustomNonClient) {
+    return NonClientSizeMargin(NormalWindowNonClientOffset());
+  }
+
+  // Just use a dummy 200x200 at (200, 200) client rect as the rect.
+  RECT clientRect;
+  clientRect.left = 200;
+  clientRect.top = 200;
+  clientRect.right = 400;
+  clientRect.bottom = 400;
+
+  auto ToRect = [](const RECT& aRect) -> LayoutDeviceIntRect {
+    return {aRect.left, aRect.top, aRect.right - aRect.left,
+            aRect.bottom - aRect.top};
+  };
+
+  RECT windowRect = clientRect;
+  ::AdjustWindowRectEx(&windowRect, WindowStyle(), false, WindowExStyle());
+
+  return ToRect(windowRect) - ToRect(clientRect);
+}
+
+/**************************************************************
+ *
+ * SECTION: nsIWidget::EnableDragDrop
+ *
+ * Enables/Disables drag and drop of files on this widget.
+ *
+ **************************************************************/
+
+void nsWindow::EnableDragDrop(bool aEnable) {
+  if (!mWnd) {
+    // Return early if the window already closed
+    return;
+  }
+
+  if (aEnable) {
+    if (!mNativeDragTarget) {
+      mNativeDragTarget = new nsNativeDragTarget(this);
+      mNativeDragTarget->AddRef();
+      ::RegisterDragDrop(mWnd, (LPDROPTARGET)mNativeDragTarget);
+    }
+  } else {
+    if (mWnd && mNativeDragTarget) {
+      ::RevokeDragDrop(mWnd);
+      mNativeDragTarget->DragCancel();
+      NS_RELEASE(mNativeDragTarget);
+    }
+  }
+}
+
+/**************************************************************
+ *
+ * SECTION: nsIWidget::CaptureMouse
+ *
+ * Enables/Disables system mouse capture.
+ *
+ **************************************************************/
+
+void nsWindow::CaptureMouse(bool aCapture) {
+  TRACKMOUSEEVENT mTrack;
+  mTrack.cbSize = sizeof(TRACKMOUSEEVENT);
+  mTrack.dwHoverTime = 0;
+  mTrack.hwndTrack = mWnd;
+  if (aCapture) {
+    mTrack.dwFlags = TME_CANCEL | TME_LEAVE;
+    ::SetCapture(mWnd);
+  } else {
+    mTrack.dwFlags = TME_LEAVE;
+    ::ReleaseCapture();
+  }
+  sIsInMouseCapture = aCapture;
+  TrackMouseEvent(&mTrack);
+}
+
+/**************************************************************
+ *
+ * SECTION: nsIWidget::CaptureRollupEvents
+ *
+ * Dealing with event rollup on destroy for popups. Enables &
+ * Disables system capture of any and all events that would
+ * cause a dropdown to be rolled up.
+ *
+ **************************************************************/
+
+void nsWindow::CaptureRollupEvents(bool aDoCapture) {
+  if (aDoCapture) {
+    if (!sMsgFilterHook && !sCallProcHook && !sCallMouseHook) {
+      RegisterSpecialDropdownHooks();
+    }
+    sProcessHook = true;
+  } else {
+    sProcessHook = false;
+    UnregisterSpecialDropdownHooks();
+  }
+}
+
+/**************************************************************
+ *
+ * SECTION: nsIWidget::GetAttention
+ *
+ * Bring this window to the user's attention.
+ *
+ **************************************************************/
+
+// Draw user's attention to this window until it comes to foreground.
+nsresult nsWindow::GetAttention(int32_t aCycleCount) {
+  // Got window?
+  if (!mWnd) return NS_ERROR_NOT_INITIALIZED;
+
+  HWND flashWnd = WinUtils::GetTopLevelHWND(mWnd, false, false);
+  HWND fgWnd = ::GetForegroundWindow();
+  // Don't flash if the flash count is 0 or if the foreground window is our
+  // window handle or that of our owned-most window.
+  if (aCycleCount == 0 || flashWnd == fgWnd ||
+      flashWnd == WinUtils::GetTopLevelHWND(fgWnd, false, false)) {
+    return NS_OK;
+  }
+
+  DWORD defaultCycleCount = 0;
+  ::SystemParametersInfo(SPI_GETFOREGROUNDFLASHCOUNT, 0, &defaultCycleCount, 0);
+
+  FLASHWINFO flashInfo = {sizeof(FLASHWINFO), flashWnd, FLASHW_ALL,
+                          aCycleCount > 0 ? aCycleCount : defaultCycleCount, 0};
+  ::FlashWindowEx(&flashInfo);
+
+  return NS_OK;
+}
+
+void nsWindow::StopFlashing() {
+  HWND flashWnd = mWnd;
+  while (HWND ownerWnd = ::GetWindow(flashWnd, GW_OWNER)) {
+    flashWnd = ownerWnd;
+  }
+
+  FLASHWINFO flashInfo = {sizeof(FLASHWINFO), flashWnd, FLASHW_STOP, 0, 0};
+  ::FlashWindowEx(&flashInfo);
+}
+
+/**************************************************************
+ *
+ * SECTION: nsIWidget::HasPendingInputEvent
+ *
+ * Ask whether there user input events pending.  All input events are
+ * included, including those not targeted at this nsIwidget instance.
+ *
+ **************************************************************/
+
+bool nsWindow::HasPendingInputEvent() {
+  // If there is pending input or the user is currently
+  // moving the window then return true.
+  // Note: When the user is moving the window WIN32 spins
+  // a separate event loop and input events are not
+  // reported to the application.
+  if (HIWORD(GetQueueStatus(QS_INPUT))) return true;
+  GUITHREADINFO guiInfo;
+  guiInfo.cbSize = sizeof(GUITHREADINFO);
+  if (!GetGUIThreadInfo(GetCurrentThreadId(), &guiInfo)) return false;
+  return GUI_INMOVESIZE == (guiInfo.flags & GUI_INMOVESIZE);
+}
+
+/**************************************************************
+ *
+ * SECTION: nsIWidget::GetWindowRenderer
+ *
+ * Get the window renderer associated with this widget.
+ *
+ **************************************************************/
+
+WindowRenderer* nsWindow::GetWindowRenderer() {
+  if (mWindowRenderer) {
+    return mWindowRenderer;
+  }
+
+  if (!mLocalesChangedObserver) {
+    mLocalesChangedObserver = new LocalesChangedObserver(this);
+  }
+
+  // Try OMTC first.
+  if (!mWindowRenderer && ShouldUseOffMainThreadCompositing()) {
+    gfxWindowsPlatform::GetPlatform()->UpdateRenderMode();
+    CreateCompositor();
+  }
+
+  if (!mWindowRenderer) {
+    MOZ_ASSERT(!mCompositorSession && !mCompositorBridgeChild);
+    MOZ_ASSERT(!mCompositorWidgetDelegate);
+
+    // Ensure we have a widget proxy even if we're not using the compositor,
+    // since all our transparent window handling lives there.
+    WinCompositorWidgetInitData initData(
+        reinterpret_cast<uintptr_t>(mWnd),
+        reinterpret_cast<uintptr_t>(static_cast<nsIWidget*>(this)),
+        mTransparencyMode, mFrameState->GetSizeMode());
+    // If we're not using the compositor, the options don't actually matter.
+    CompositorOptions options(false, false);
+    mBasicLayersSurface =
+        new InProcessWinCompositorWidget(initData, options, this);
+    mCompositorWidgetDelegate = mBasicLayersSurface;
+    mWindowRenderer = CreateFallbackRenderer();
+  }
+
+  NS_ASSERTION(mWindowRenderer, "Couldn't provide a valid window renderer.");
+
+  if (mWindowRenderer) {
+    // Update the size constraints now that the layer manager has been
+    // created.
+    KnowsCompositor* knowsCompositor = mWindowRenderer->AsKnowsCompositor();
+    if (knowsCompositor) {
+      SizeConstraints c = mSizeConstraints;
+      mMaxTextureSize = knowsCompositor->GetMaxTextureSize();
+      c.mMaxSize.width = std::min(c.mMaxSize.width, mMaxTextureSize);
+      c.mMaxSize.height = std::min(c.mMaxSize.height, mMaxTextureSize);
+      nsBaseWidget::SetSizeConstraints(c);
+    }
+  }
+
+  return mWindowRenderer;
+}
+
+/**************************************************************
+ *
+ * SECTION: nsBaseWidget::SetCompositorWidgetDelegate
+ *
+ * Called to connect the nsWindow to the delegate providing
+ * platform compositing API access.
+ *
+ **************************************************************/
+
+void nsWindow::SetCompositorWidgetDelegate(CompositorWidgetDelegate* delegate) {
+  if (delegate) {
+    mCompositorWidgetDelegate = delegate->AsPlatformSpecificDelegate();
+    MOZ_ASSERT(mCompositorWidgetDelegate,
+               "nsWindow::SetCompositorWidgetDelegate called with a "
+               "non-PlatformCompositorWidgetDelegate");
+  } else {
+    mCompositorWidgetDelegate = nullptr;
+  }
+}
+
+/**************************************************************
+ *
+ * SECTION: nsIWidget::OnDefaultButtonLoaded
+ *
+ * Called after the dialog is loaded and it has a default button.
+ *
+ **************************************************************/
+
+nsresult nsWindow::OnDefaultButtonLoaded(
+    const LayoutDeviceIntRect& aButtonRect) {
+  if (aButtonRect.IsEmpty()) return NS_OK;
+
+  // Don't snap when we are not active.
+  HWND activeWnd = ::GetActiveWindow();
+  if (activeWnd != ::GetForegroundWindow() ||
+      WinUtils::GetTopLevelHWND(mWnd, true) !=
+          WinUtils::GetTopLevelHWND(activeWnd, true)) {
+    return NS_OK;
+  }
+
+  bool isAlwaysSnapCursor =
+      Preferences::GetBool("ui.cursor_snapping.always_enabled", false);
+
+  if (!isAlwaysSnapCursor) {
+    BOOL snapDefaultButton;
+    if (!::SystemParametersInfo(SPI_GETSNAPTODEFBUTTON, 0, &snapDefaultButton,
+                                0) ||
+        !snapDefaultButton)
+      return NS_OK;
+  }
+
+  LayoutDeviceIntRect widgetRect = GetScreenBounds();
+  LayoutDeviceIntRect buttonRect(aButtonRect + widgetRect.TopLeft());
+
+  LayoutDeviceIntPoint centerOfButton(buttonRect.X() + buttonRect.Width() / 2,
+                                      buttonRect.Y() + buttonRect.Height() / 2);
+  // The center of the button can be outside of the widget.
+  // E.g., it could be hidden by scrolling.
+  if (!widgetRect.Contains(centerOfButton)) {
+    return NS_OK;
+  }
+
+  if (!::SetCursorPos(centerOfButton.x, centerOfButton.y)) {
+    NS_ERROR("SetCursorPos failed");
+    return NS_ERROR_FAILURE;
+  }
+  return NS_OK;
+}
+
+uint32_t nsWindow::GetMaxTouchPoints() const {
+  return WinUtils::GetMaxTouchPoints();
+}
+
+void nsWindow::SetWindowClass(const nsAString& xulWinType,
+                              const nsAString& xulWinClass,
+                              const nsAString& xulWinName) {
+  mIsEarlyBlankWindow = xulWinType.EqualsLiteral("navigator:blank");
+}
+
+/**************************************************************
+ **************************************************************
+ **
+ ** BLOCK: Moz Events
+ **
+ ** Moz GUI event management.
+ **
+ **************************************************************
+ **************************************************************/
+
+/**************************************************************
+ *
+ * SECTION: Mozilla event initialization
+ *
+ * Helpers for initializing moz events.
+ *
+ **************************************************************/
+
+// Event initialization
+void nsWindow::InitEvent(WidgetGUIEvent& event, LayoutDeviceIntPoint* aPoint) {
+  if (nullptr == aPoint) {  // use the point from the event
+    // get the message position in client coordinates
+    if (mWnd != nullptr) {
+      DWORD pos = ::GetMessagePos();
+      POINT cpos;
+
+      cpos.x = GET_X_LPARAM(pos);
+      cpos.y = GET_Y_LPARAM(pos);
+
+      ::ScreenToClient(mWnd, &cpos);
+      event.mRefPoint = LayoutDeviceIntPoint(cpos.x, cpos.y);
+    } else {
+      event.mRefPoint = LayoutDeviceIntPoint(0, 0);
+    }
+  } else {
+    // use the point override if provided
+    event.mRefPoint = *aPoint;
+  }
+
+  event.AssignEventTime(CurrentMessageWidgetEventTime());
+}
+
+WidgetEventTime nsWindow::CurrentMessageWidgetEventTime() const {
+  LONG messageTime = ::GetMessageTime();
+  return WidgetEventTime(GetMessageTimeStamp(messageTime));
+}
+
+/**************************************************************
+ *
+ * SECTION: Moz event dispatch helpers
+ *
+ * Helpers for dispatching different types of moz events.
+ *
+ **************************************************************/
+
+// Main event dispatch. Invokes callback and ProcessEvent method on
+// Event Listener object. Part of nsIWidget.
+nsresult nsWindow::DispatchEvent(WidgetGUIEvent* event,
+                                 nsEventStatus& aStatus) {
+#ifdef WIDGET_DEBUG_OUTPUT
+  debug_DumpEvent(stdout, event->mWidget, event, "something", (int32_t)mWnd);
+#endif  // WIDGET_DEBUG_OUTPUT
+
+  aStatus = nsEventStatus_eIgnore;
+
+  // Top level windows can have a view attached which requires events be sent
+  // to the underlying base window and the view. Added when we combined the
+  // base chrome window with the main content child for nc client area (title
+  // bar) rendering.
+  if (mAttachedWidgetListener) {
+    aStatus = mAttachedWidgetListener->HandleEvent(event, mUseAttachedEvents);
+  } else if (mWidgetListener) {
+    aStatus = mWidgetListener->HandleEvent(event, mUseAttachedEvents);
+  }
+
+  // the window can be destroyed during processing of seemingly innocuous events
+  // like, say, mousedowns due to the magic of scripting. mousedowns will return
+  // nsEventStatus_eIgnore, which causes problems with the deleted window.
+  // therefore:
+  if (mOnDestroyCalled) aStatus = nsEventStatus_eConsumeNoDefault;
+  return NS_OK;
+}
+
+bool nsWindow::DispatchStandardEvent(EventMessage aMsg) {
+  WidgetGUIEvent event(true, aMsg, this);
+  InitEvent(event);
+
+  bool result = DispatchWindowEvent(event);
+  return result;
+}
+
+bool nsWindow::DispatchKeyboardEvent(WidgetKeyboardEvent* event) {
+  nsEventStatus status = DispatchInputEvent(event).mContentStatus;
+  return ConvertStatus(status);
+}
+
+bool nsWindow::DispatchContentCommandEvent(WidgetContentCommandEvent* aEvent) {
+  nsEventStatus status;
+  DispatchEvent(aEvent, status);
+  return ConvertStatus(status);
+}
+
+bool nsWindow::DispatchWheelEvent(WidgetWheelEvent* aEvent) {
+  nsEventStatus status =
+      DispatchInputEvent(aEvent->AsInputEvent()).mContentStatus;
+  return ConvertStatus(status);
+}
+
+// Recursively dispatch synchronous paints for nsIWidget
+// descendants with invalidated rectangles.
+BOOL CALLBACK nsWindow::DispatchStarvedPaints(HWND aWnd, LPARAM aMsg) {
+  LONG_PTR proc = ::GetWindowLongPtrW(aWnd, GWLP_WNDPROC);
+  if (proc == (LONG_PTR)&nsWindow::WindowProc) {
+    // its one of our windows so check to see if it has a
+    // invalidated rect. If it does. Dispatch a synchronous
+    // paint.
+    if (GetUpdateRect(aWnd, nullptr, FALSE)) VERIFY(::UpdateWindow(aWnd));
+  }
+  return TRUE;
+}
+
+// Check for pending paints and dispatch any pending paint
+// messages for any nsIWidget which is a descendant of the
+// top-level window that *this* window is embedded within.
+//
+// Note: We do not dispatch pending paint messages for non
+// nsIWidget managed windows.
+void nsWindow::DispatchPendingEvents() {
+  // We need to ensure that reflow events do not get starved.
+  // At the same time, we don't want to recurse through here
+  // as that would prevent us from dispatching starved paints.
+  static int recursionBlocker = 0;
+  if (recursionBlocker++ == 0) {
+    NS_ProcessPendingEvents(nullptr, PR_MillisecondsToInterval(100));
+    --recursionBlocker;
+  }
+
+  // Quickly check to see if there are any paint events pending,
+  // but only dispatch them if it has been long enough since the
+  // last paint completed.
+  if (::GetQueueStatus(QS_PAINT) &&
+      ((TimeStamp::Now() - mLastPaintEndTime).ToMilliseconds() >= 50)) {
+    // Find the top level window.
+    HWND topWnd = WinUtils::GetTopLevelHWND(mWnd);
+
+    // Dispatch pending paints for topWnd and all its descendant windows.
+    // Note: EnumChildWindows enumerates all descendant windows not just
+    // the children (but not the window itself).
+    nsWindow::DispatchStarvedPaints(topWnd, 0);
+    ::EnumChildWindows(topWnd, nsWindow::DispatchStarvedPaints, 0);
+  }
+}
+
+void nsWindow::DispatchCustomEvent(const nsString& eventName) {
+  if (Document* doc = GetDocument()) {
+    if (nsPIDOMWindowOuter* win = doc->GetWindow()) {
+      win->DispatchCustomEvent(eventName, ChromeOnlyDispatch::eYes);
+    }
+  }
+}
+
+bool nsWindow::TouchEventShouldStartDrag(EventMessage aEventMessage,
+                                         LayoutDeviceIntPoint aEventPoint) {
+  // Allow users to start dragging by double-tapping.
+  if (aEventMessage == eMouseDoubleClick) {
+    return true;
+  }
+
+  // In chrome UI, allow touchdownstartsdrag attributes
+  // to cause any touchdown event to trigger a drag.
+  if (aEventMessage == eMouseDown) {
+    WidgetMouseEvent hittest(true, eMouseHitTest, this,
+                             WidgetMouseEvent::eReal);
+    hittest.mRefPoint = aEventPoint;
+    hittest.mIgnoreRootScrollFrame = true;
+    hittest.mInputSource = MouseEvent_Binding::MOZ_SOURCE_TOUCH;
+    DispatchInputEvent(&hittest);
+
+    if (EventTarget* target = hittest.GetDOMEventTarget()) {
+      if (nsIContent* content = nsIContent::FromEventTarget(target)) {
+        // Check if the element or any parent element has the
+        // attribute we're looking for.
+        for (Element* element = content->GetAsElementOrParentElement(); element;
+             element = element->GetParentElement()) {
+          nsAutoString startDrag;
+          element->GetAttribute(u"touchdownstartsdrag"_ns, startDrag);
+          if (!startDrag.IsEmpty()) {
+            return true;
+          }
+        }
+      }
+    }
+  }
+
+  return false;
+}
+
+// Deal with all sort of mouse event
+bool nsWindow::DispatchMouseEvent(EventMessage aEventMessage, WPARAM wParam,
+                                  LPARAM lParam, bool aIsContextMenuKey,
+                                  int16_t aButton, uint16_t aInputSource,
+                                  WinPointerInfo* aPointerInfo,
+                                  bool aIgnoreAPZ) {
+  ContextMenuPreventer contextMenuPreventer(this);
+  bool result = false;
+
+  UserActivity();
+
+  if (!mWidgetListener) {
+    return result;
+  }
+
+  LayoutDeviceIntPoint eventPoint(GET_X_LPARAM(lParam), GET_Y_LPARAM(lParam));
+  LayoutDeviceIntPoint mpScreen = eventPoint + WidgetToScreenOffset();
+
+  // Suppress mouse moves caused by widget creation. Make sure to do this early
+  // so that we update sLastMouseMovePoint even for touch-induced mousemove
+  // events.
+  if (aEventMessage == eMouseMove) {
+    if ((sLastMouseMovePoint.x == mpScreen.x.value) &&
+        (sLastMouseMovePoint.y == mpScreen.y.value)) {
+      return result;
+    }
+    sLastMouseMovePoint.x = mpScreen.x;
+    sLastMouseMovePoint.y = mpScreen.y;
+  }
+
+  if (!aIgnoreAPZ && WinUtils::GetIsMouseFromTouch(aEventMessage)) {
+    if (mTouchWindow) {
+      // If mTouchWindow is true, then we must have APZ enabled and be
+      // feeding it raw touch events. In that case we only want to
+      // send touch-generated mouse events to content if they should
+      // start a touch-based drag-and-drop gesture, such as on
+      // double-tapping or when tapping elements marked with the
+      // touchdownstartsdrag attribute in chrome UI.
+      MOZ_ASSERT(mAPZC);
+      if (TouchEventShouldStartDrag(aEventMessage, eventPoint)) {
+        aEventMessage = eMouseTouchDrag;
+      } else {
+        return result;
+      }
+    }
+  }
+
+  uint32_t pointerId =
+      aPointerInfo ? aPointerInfo->pointerId : MOUSE_POINTERID();
+
+  switch (aEventMessage) {
+    case eMouseDown:
+      CaptureMouse(true);
+      break;
+
+    // eMouseMove and eMouseExitFromWidget are here because we need to make
+    // sure capture flag isn't left on after a drag where we wouldn't see a
+    // button up message (see bug 324131).
+    case eMouseUp:
+    case eMouseMove:
+    case eMouseExitFromWidget:
+      if (!(wParam & (MK_LBUTTON | MK_MBUTTON | MK_RBUTTON)) &&
+          sIsInMouseCapture)
+        CaptureMouse(false);
+      break;
+
+    default:
+      break;
+
+  }  // switch
+
+  WidgetMouseEvent event(true, aEventMessage, this, WidgetMouseEvent::eReal,
+                         aIsContextMenuKey ? WidgetMouseEvent::eContextMenuKey
+                                           : WidgetMouseEvent::eNormal);
+  if (aEventMessage == eContextMenu && aIsContextMenuKey) {
+    LayoutDeviceIntPoint zero(0, 0);
+    InitEvent(event, &zero);
+  } else {
+    InitEvent(event, &eventPoint);
+  }
+
+  ModifierKeyState modifierKeyState;
+  modifierKeyState.InitInputEvent(event);
+
+  // eContextMenu with Shift state is special.  It won't fire "contextmenu"
+  // event in the web content for blocking web content to prevent its default.
+  // However, Shift+F10 is a standard shortcut key on Windows.  Therefore,
+  // this should not block web page to prevent its default.  I.e., it should
+  // behave same as ContextMenu key without Shift key.
+  // XXX Should we allow to block web page to prevent its default with
+  //     Ctrl+Shift+F10 or Alt+Shift+F10 instead?
+  if (aEventMessage == eContextMenu && aIsContextMenuKey && event.IsShift() &&
+      NativeKey::LastKeyOrCharMSG().message == WM_SYSKEYDOWN &&
+      NativeKey::LastKeyOrCharMSG().wParam == VK_F10) {
+    event.mModifiers &= ~MODIFIER_SHIFT;
+  }
+
+  event.mButton = aButton;
+  event.mInputSource = aInputSource;
+  if (aPointerInfo) {
+    // Mouse events from Windows WM_POINTER*. Fill more information in
+    // WidgetMouseEvent.
+    event.AssignPointerHelperData(*aPointerInfo);
+    event.mPressure = aPointerInfo->mPressure;
+    event.mButtons = aPointerInfo->mButtons;
+  } else {
+    // If we get here the mouse events must be from non-touch sources, so
+    // convert it to pointer events as well
+    event.convertToPointer = true;
+    event.pointerId = pointerId;
+  }
+
+  // Static variables used to distinguish simple-, double- and triple-clicks.
+  static POINT sLastMousePoint = {0};
+  static LONG sLastMouseDownTime = 0L;
+  static LONG sLastClickCount = 0L;
+  static BYTE sLastMouseButton = 0;
+
+  bool insideMovementThreshold =
+      (DeprecatedAbs(sLastMousePoint.x - eventPoint.x.value) <
+       (short)::GetSystemMetrics(SM_CXDOUBLECLK)) &&
+      (DeprecatedAbs(sLastMousePoint.y - eventPoint.y.value) <
+       (short)::GetSystemMetrics(SM_CYDOUBLECLK));
+
+  BYTE eventButton;
+  switch (aButton) {
+    case MouseButton::ePrimary:
+      eventButton = VK_LBUTTON;
+      break;
+    case MouseButton::eMiddle:
+      eventButton = VK_MBUTTON;
+      break;
+    case MouseButton::eSecondary:
+      eventButton = VK_RBUTTON;
+      break;
+    default:
+      eventButton = 0;
+      break;
+  }
+
+  // Doubleclicks are used to set the click count, then changed to mousedowns
+  // We're going to time double-clicks from mouse *up* to next mouse *down*
+  LONG curMsgTime = ::GetMessageTime();
+
+  switch (aEventMessage) {
+    case eMouseDoubleClick:
+      event.mMessage = eMouseDown;
+      event.mButton = aButton;
+      sLastClickCount = 2;
+      sLastMouseDownTime = curMsgTime;
+      break;
+    case eMouseUp:
+      // remember when this happened for the next mouse down
+      sLastMousePoint.x = eventPoint.x;
+      sLastMousePoint.y = eventPoint.y;
+      sLastMouseButton = eventButton;
+      break;
+    case eMouseDown:
+      // now look to see if we want to convert this to a double- or triple-click
+      if (((curMsgTime - sLastMouseDownTime) < (LONG)::GetDoubleClickTime()) &&
+          insideMovementThreshold && eventButton == sLastMouseButton) {
+        sLastClickCount++;
+      } else {
+        // reset the click count, to count *this* click
+        sLastClickCount = 1;
+      }
+      // Set last Click time on MouseDown only
+      sLastMouseDownTime = curMsgTime;
+      break;
+    case eMouseMove:
+      if (!insideMovementThreshold) {
+        sLastClickCount = 0;
+      }
+      break;
+    case eMouseExitFromWidget:
+      event.mExitFrom =
+          Some(IsTopLevelMouseExit(mWnd) ? WidgetMouseEvent::ePlatformTopLevel
+                                         : WidgetMouseEvent::ePlatformChild);
+      break;
+    default:
+      break;
+  }
+  event.mClickCount = sLastClickCount;
+
+#ifdef NS_DEBUG_XX
+  MOZ_LOG(gWindowsLog, LogLevel::Info,
+          ("Msg Time: %d Click Count: %d\n", curMsgTime, event.mClickCount));
+#endif
+
+  // call the event callback
+  if (mWidgetListener) {
+    if (aEventMessage == eMouseMove) {
+      LayoutDeviceIntRect rect = GetBounds();
+      rect.MoveTo(0, 0);
+
+      if (rect.Contains(event.mRefPoint)) {
+        if (sCurrentWindow == nullptr || sCurrentWindow != this) {
+          if ((nullptr != sCurrentWindow) && (!sCurrentWindow->mInDtor)) {
+            LPARAM pos = sCurrentWindow->lParamToClient(lParamToScreen(lParam));
+            sCurrentWindow->DispatchMouseEvent(
+                eMouseExitFromWidget, wParam, pos, false, MouseButton::ePrimary,
+                aInputSource, aPointerInfo);
+          }
+          sCurrentWindow = this;
+          if (!mInDtor) {
+            LPARAM pos = sCurrentWindow->lParamToClient(lParamToScreen(lParam));
+            sCurrentWindow->DispatchMouseEvent(
+                eMouseEnterIntoWidget, wParam, pos, false,
+                MouseButton::ePrimary, aInputSource, aPointerInfo);
+          }
+        }
+      }
+    } else if (aEventMessage == eMouseExitFromWidget) {
+      if (sCurrentWindow == this) {
+        sCurrentWindow = nullptr;
+      }
+    }
+
+    nsIWidget::ContentAndAPZEventStatus eventStatus =
+        DispatchInputEvent(&event);
+    contextMenuPreventer.Update(event, eventStatus);
+    return ConvertStatus(eventStatus.mContentStatus);
+  }
+
+  return result;
+}
+
+HWND nsWindow::GetTopLevelForFocus(HWND aCurWnd) {
+  // retrieve the toplevel window or dialogue
+  HWND toplevelWnd = nullptr;
+  while (aCurWnd) {
+    toplevelWnd = aCurWnd;
+    nsWindow* win = WinUtils::GetNSWindowPtr(aCurWnd);
+    if (win) {
+      if (win->mWindowType == WindowType::TopLevel ||
+          win->mWindowType == WindowType::Dialog) {
+        break;
+      }
+    }
+
+    aCurWnd = ::GetParent(aCurWnd);  // Parent or owner (if has no parent)
+  }
+  return toplevelWnd;
+}
+
+void nsWindow::DispatchFocusToTopLevelWindow(bool aIsActivate) {
+  if (aIsActivate) {
+    sJustGotActivate = false;
+  }
+  sJustGotDeactivate = false;
+  mLastKillFocusWindow = nullptr;
+
+  HWND toplevelWnd = GetTopLevelForFocus(mWnd);
+
+  if (toplevelWnd) {
+    nsWindow* win = WinUtils::GetNSWindowPtr(toplevelWnd);
+    if (win && win->mWidgetListener) {
+      if (aIsActivate) {
+        win->mWidgetListener->WindowActivated();
+      } else {
+        win->mWidgetListener->WindowDeactivated();
+      }
+    }
+  }
+}
+
+HWND nsWindow::WindowAtMouse() {
+  DWORD pos = ::GetMessagePos();
+  POINT mp;
+  mp.x = GET_X_LPARAM(pos);
+  mp.y = GET_Y_LPARAM(pos);
+  return ::WindowFromPoint(mp);
+}
+
+bool nsWindow::IsTopLevelMouseExit(HWND aWnd) {
+  HWND mouseWnd = WindowAtMouse();
+
+  // WinUtils::GetTopLevelHWND() will return a HWND for the window frame
+  // (which includes the non-client area).  If the mouse has moved into
+  // the non-client area, we should treat it as a top-level exit.
+  HWND mouseTopLevel = WinUtils::GetTopLevelHWND(mouseWnd);
+  if (mouseWnd == mouseTopLevel) return true;
+
+  return WinUtils::GetTopLevelHWND(aWnd) != mouseTopLevel;
+}
+
+/**************************************************************
+ *
+ * SECTION: IPC
+ *
+ * IPC related helpers.
+ *
+ **************************************************************/
+
+// static
+bool nsWindow::IsAsyncResponseEvent(UINT aMsg, LRESULT& aResult) {
+  switch (aMsg) {
+    case WM_SETFOCUS:
+    case WM_KILLFOCUS:
+    case WM_ENABLE:
+    case WM_WINDOWPOSCHANGING:
+    case WM_WINDOWPOSCHANGED:
+    case WM_PARENTNOTIFY:
+    case WM_ACTIVATEAPP:
+    case WM_NCACTIVATE:
+    case WM_ACTIVATE:
+    case WM_CHILDACTIVATE:
+    case WM_IME_SETCONTEXT:
+    case WM_IME_NOTIFY:
+    case WM_SHOWWINDOW:
+    case WM_CANCELMODE:
+    case WM_MOUSEACTIVATE:
+    case WM_CONTEXTMENU:
+      aResult = 0;
+      return true;
+
+    case WM_SETTINGCHANGE:
+    case WM_SETCURSOR:
+      return false;
+  }
+
+#ifdef DEBUG
+  char szBuf[200];
+  sprintf(szBuf,
+          "An unhandled ISMEX_SEND message was received during spin loop! (%X)",
+          aMsg);
+  NS_WARNING(szBuf);
+#endif
+
+  return false;
+}
+
+void nsWindow::IPCWindowProcHandler(UINT& msg, WPARAM& wParam, LPARAM& lParam) {
+  MOZ_ASSERT_IF(
+      msg != WM_GETOBJECT,
+      !mozilla::ipc::MessageChannel::IsPumpingMessages() ||
+          mozilla::ipc::SuppressedNeuteringRegion::IsNeuteringSuppressed());
+
+  // Modal UI being displayed in windowless plugins.
+  if (mozilla::ipc::MessageChannel::IsSpinLoopActive() &&
+      (InSendMessageEx(nullptr) & (ISMEX_REPLIED | ISMEX_SEND)) == ISMEX_SEND) {
+    LRESULT res;
+    if (IsAsyncResponseEvent(msg, res)) {
+      ReplyMessage(res);
+    }
+    return;
+  }
+
+  // Handle certain sync plugin events sent to the parent which
+  // trigger ipc calls that result in deadlocks.
+
+  DWORD dwResult = 0;
+  bool handled = false;
+
+  switch (msg) {
+    // Windowless flash sending WM_ACTIVATE events to the main window
+    // via calls to ShowWindow.
+    case WM_ACTIVATE:
+      if (lParam != 0 && LOWORD(wParam) == WA_ACTIVE &&
+          IsWindow((HWND)lParam)) {
+        // Check for Adobe Reader X sync activate message from their
+        // helper window and ignore. Fixes an annoying focus problem.
+        if ((InSendMessageEx(nullptr) & (ISMEX_REPLIED | ISMEX_SEND)) ==
+            ISMEX_SEND) {
+          wchar_t szClass[10];
+          HWND focusWnd = (HWND)lParam;
+          if (IsWindowVisible(focusWnd) &&
+              GetClassNameW(focusWnd, szClass,
+                            sizeof(szClass) / sizeof(char16_t)) &&
+              !wcscmp(szClass, L"Edit") &&
+              !WinUtils::IsOurProcessWindow(focusWnd)) {
+            break;
+          }
+        }
+        handled = true;
+      }
+      break;
+    // Plugins taking or losing focus triggering focus app messages.
+    case WM_SETFOCUS:
+    case WM_KILLFOCUS:
+    // Windowed plugins that pass sys key events to defwndproc generate
+    // WM_SYSCOMMAND events to the main window.
+    case WM_SYSCOMMAND:
+    // Windowed plugins that fire context menu selection events to parent
+    // windows.
+    case WM_CONTEXTMENU:
+    // IME events fired as a result of synchronous focus changes
+    case WM_IME_SETCONTEXT:
+      handled = true;
+      break;
+  }
+
+  if (handled &&
+      (InSendMessageEx(nullptr) & (ISMEX_REPLIED | ISMEX_SEND)) == ISMEX_SEND) {
+    ReplyMessage(dwResult);
+  }
+}
+
+/**************************************************************
+ **************************************************************
+ **
+ ** BLOCK: Native events
+ **
+ ** Main Windows message handlers and OnXXX handlers for
+ ** Windows event handling.
+ **
+ **************************************************************
+ **************************************************************/
+
+/**************************************************************
+ *
+ * SECTION: Wind proc.
+ *
+ * The main Windows event procedures and associated
+ * message processing methods.
+ *
+ **************************************************************/
+
+static bool DisplaySystemMenu(HWND hWnd, nsSizeMode sizeMode, bool isRtl,
+                              int32_t x, int32_t y) {
+  HMENU hMenu = GetSystemMenu(hWnd, FALSE);
+  if (hMenu) {
+    MENUITEMINFO mii;
+    mii.cbSize = sizeof(MENUITEMINFO);
+    mii.fMask = MIIM_STATE;
+    mii.fType = 0;
+
+    // update the options
+    mii.fState = MF_ENABLED;
+    SetMenuItemInfo(hMenu, SC_RESTORE, FALSE, &mii);
+    SetMenuItemInfo(hMenu, SC_SIZE, FALSE, &mii);
+    SetMenuItemInfo(hMenu, SC_MOVE, FALSE, &mii);
+    SetMenuItemInfo(hMenu, SC_MAXIMIZE, FALSE, &mii);
+    SetMenuItemInfo(hMenu, SC_MINIMIZE, FALSE, &mii);
+
+    mii.fState = MF_GRAYED;
+    switch (sizeMode) {
+      case nsSizeMode_Fullscreen:
+        // intentional fall through
+      case nsSizeMode_Maximized:
+        SetMenuItemInfo(hMenu, SC_SIZE, FALSE, &mii);
+        SetMenuItemInfo(hMenu, SC_MOVE, FALSE, &mii);
+        SetMenuItemInfo(hMenu, SC_MAXIMIZE, FALSE, &mii);
+        break;
+      case nsSizeMode_Minimized:
+        SetMenuItemInfo(hMenu, SC_MINIMIZE, FALSE, &mii);
+        break;
+      case nsSizeMode_Normal:
+        SetMenuItemInfo(hMenu, SC_RESTORE, FALSE, &mii);
+        break;
+      case nsSizeMode_Invalid:
+        NS_ASSERTION(false, "Did the argument come from invalid IPC?");
+        break;
+      default:
+        MOZ_ASSERT_UNREACHABLE("Unhnalded nsSizeMode value detected");
+        break;
+    }
+    LPARAM cmd = TrackPopupMenu(
+        hMenu,
+        (TPM_LEFTBUTTON | TPM_RIGHTBUTTON | TPM_RETURNCMD | TPM_TOPALIGN |
+         (isRtl ? TPM_RIGHTALIGN : TPM_LEFTALIGN)),
+        x, y, 0, hWnd, nullptr);
+    if (cmd) {
+      PostMessage(hWnd, WM_SYSCOMMAND, cmd, 0);
+      return true;
+    }
+  }
+  return false;
+}
+
+// The WndProc procedure for all nsWindows in this toolkit. This merely catches
+// SEH exceptions and passes the real work to WindowProcInternal. See bug 587406
+// and http://msdn.microsoft.com/en-us/library/ms633573%28VS.85%29.aspx
+LRESULT CALLBACK nsWindow::WindowProc(HWND hWnd, UINT msg, WPARAM wParam,
+                                      LPARAM lParam) {
+  mozilla::ipc::CancelCPOWs();
+
+  BackgroundHangMonitor().NotifyActivity();
+
+  return mozilla::CallWindowProcCrashProtected(WindowProcInternal, hWnd, msg,
+                                               wParam, lParam);
+}
+
+LRESULT CALLBACK nsWindow::WindowProcInternal(HWND hWnd, UINT msg,
+                                              WPARAM wParam, LPARAM lParam) {
+  if (::GetWindowLongPtrW(hWnd, GWLP_ID) == eFakeTrackPointScrollableID) {
+    // This message was sent to the FAKETRACKPOINTSCROLLABLE.
+    if (msg == WM_HSCROLL) {
+      // Route WM_HSCROLL messages to the main window.
+      hWnd = ::GetParent(::GetParent(hWnd));
+    } else {
+      // Handle all other messages with its original window procedure.
+      WNDPROC prevWindowProc = (WNDPROC)::GetWindowLongPtr(hWnd, GWLP_USERDATA);
+      return ::CallWindowProcW(prevWindowProc, hWnd, msg, wParam, lParam);
+    }
+  }
+
+  if (msg == MOZ_WM_TRACE) {
+    // This is a tracer event for measuring event loop latency.
+    // See WidgetTraceEvent.cpp for more details.
+    mozilla::SignalTracerThread();
+    return 0;
+  }
+
+  // Get the window which caused the event and ask it to process the message
+  nsWindow* targetWindow = WinUtils::GetNSWindowPtr(hWnd);
+  NS_ASSERTION(targetWindow, "nsWindow* is null!");
+  if (!targetWindow) return ::DefWindowProcW(hWnd, msg, wParam, lParam);
+
+  // Hold the window for the life of this method, in case it gets
+  // destroyed during processing, unless we're in the dtor already.
+  nsCOMPtr<nsIWidget> kungFuDeathGrip;
+  if (!targetWindow->mInDtor) kungFuDeathGrip = targetWindow;
+
+  targetWindow->IPCWindowProcHandler(msg, wParam, lParam);
+
+  // Create this here so that we store the last rolled up popup until after
+  // the event has been processed.
+  nsAutoRollup autoRollup;
+
+  LRESULT popupHandlingResult;
+  if (DealWithPopups(hWnd, msg, wParam, lParam, &popupHandlingResult))
+    return popupHandlingResult;
+
+  // Call ProcessMessage
+  LRESULT retValue;
+  if (targetWindow->ProcessMessage(msg, wParam, lParam, &retValue)) {
+    return retValue;
+  }
+
+  LRESULT res = ::CallWindowProcW(targetWindow->GetPrevWindowProc(), hWnd, msg,
+                                  wParam, lParam);
+
+  return res;
+}
+
+const char16_t* GetQuitType() {
+  if (Preferences::GetBool(PREF_WIN_REGISTER_APPLICATION_RESTART, false)) {
+    DWORD cchCmdLine = 0;
+    HRESULT rc = ::GetApplicationRestartSettings(::GetCurrentProcess(), nullptr,
+                                                 &cchCmdLine, nullptr);
+    if (rc == S_OK) {
+      return u"os-restart";
+    }
+  }
+  return nullptr;
+}
+
+bool nsWindow::ExternalHandlerProcessMessage(UINT aMessage, WPARAM& aWParam,
+                                             LPARAM& aLParam,
+                                             MSGResult& aResult) {
+  if (mWindowHook.Notify(mWnd, aMessage, aWParam, aLParam, aResult)) {
+    return true;
+  }
+
+  if (IMEHandler::ProcessMessage(this, aMessage, aWParam, aLParam, aResult)) {
+    return true;
+  }
+
+  if (MouseScrollHandler::ProcessMessage(this, aMessage, aWParam, aLParam,
+                                         aResult)) {
+    return true;
+  }
+
+  return false;
+}
+
+// The main windows message processing method. Wraps ProcessMessageInternal so
+// we can log aRetValue.
+bool nsWindow::ProcessMessage(UINT msg, WPARAM& wParam, LPARAM& lParam,
+                              LRESULT* aRetValue) {
+  // For some events we might change the parameter values, so log
+  // before and after we process them.
+  NativeEventLogger eventLogger("nsWindow", mWnd, msg, wParam, lParam);
+  bool result = ProcessMessageInternal(msg, wParam, lParam, aRetValue);
+  eventLogger.SetResult(*aRetValue, result);
+
+  return result;
+}
+
+// The main windows message processing method. Called by ProcessMessage.
+bool nsWindow::ProcessMessageInternal(UINT msg, WPARAM& wParam, LPARAM& lParam,
+                                      LRESULT* aRetValue) {
+  MSGResult msgResult(aRetValue);
+  if (ExternalHandlerProcessMessage(msg, wParam, lParam, msgResult)) {
+    return (msgResult.mConsumed || !mWnd);
+  }
+
+  bool result = false;  // call the default nsWindow proc
+  *aRetValue = 0;
+
+  // The DWM resize hack (see bug 1763981) causes us to process a number of
+  // messages, notably including some WM_WINDOWPOSCHANG{ING,ED} messages which
+  // would ordinarily result in a whole lot of internal state being updated.
+  //
+  // Since we're supposed to end in the same state we started in (and since the
+  // content shouldn't know about any of this nonsense), just discard any
+  // messages synchronously dispatched from within the hack.
+  if (MOZ_UNLIKELY(mIsPerformingDwmFlushHack)) {
+    return true;
+  }
+
+  // Glass hit testing w/custom transparent margins.
+  //
+  // FIXME(emilio): is this needed? We deal with titlebar buttons non-natively
+  // now.
+  LRESULT dwmHitResult;
+  if (mCustomNonClient &&
+      DwmDefWindowProc(mWnd, msg, wParam, lParam, &dwmHitResult)) {
+    *aRetValue = dwmHitResult;
+    return true;
+  }
+
+  // The preference whether to use a different keyboard layout for each
+  // window is cached, and updating it will not take effect until the
+  // next restart. We read the preference here and not upon WM_ACTIVATE to make
+  // sure that this behavior is consistent. Otherwise, if the user changed the
+  // preference before having ever lowered the window, the preference would take
+  // effect immediately.
+  static const bool sSwitchKeyboardLayout =
+      Preferences::GetBool("intl.keyboard.per_window_layout", false);
+  AppShutdownReason shutdownReason = AppShutdownReason::Unknown;
+
+  // (Large blocks of code should be broken out into OnEvent handlers.)
+  switch (msg) {
+    // WM_QUERYENDSESSION must be handled by all windows.
+    // Otherwise Windows thinks the window can just be killed at will.
+    case WM_QUERYENDSESSION: {
+      // Ask around if it's ok to quit.
+      nsCOMPtr<nsIObserverService> obsServ =
+          mozilla::services::GetObserverService();
+      nsCOMPtr<nsISupportsPRBool> cancelQuitWrapper =
+          do_CreateInstance(NS_SUPPORTS_PRBOOL_CONTRACTID);
+      cancelQuitWrapper->SetData(false);
+
+      const char16_t* quitType = GetQuitType();
+      obsServ->NotifyObservers(cancelQuitWrapper, "quit-application-requested",
+                               quitType);
+
+      bool shouldCancelQuit;
+      cancelQuitWrapper->GetData(&shouldCancelQuit);
+      *aRetValue = !shouldCancelQuit;
+      result = true;
+    } break;
+
+    case MOZ_WM_STARTA11Y:
+#if defined(ACCESSIBILITY)
+      Unused << GetAccessible();
+      result = true;
+#else
+      result = false;
+#endif
+      break;
+
+    case WM_ENDSESSION: {
+      // For WM_ENDSESSION, wParam indicates whether we need to shutdown
+      // (TRUE) or not (FALSE).
+      if (!wParam) {
+        result = true;
+        break;
+      }
+      // According to WM_ENDSESSION lParam documentation:
+      //   0 -> OS shutdown or restart (no way to distinguish)
+      //   ENDSESSION_LOGOFF -> User is logging off
+      //   ENDSESSION_CLOSEAPP -> Application must shutdown
+      //   ENDSESSION_CRITICAL -> Application is forced to shutdown
+      // The difference of the last two is not very clear.
+      if (lParam == 0) {
+        shutdownReason = AppShutdownReason::OSShutdown;
+      } else if (lParam & ENDSESSION_LOGOFF) {
+        shutdownReason = AppShutdownReason::OSSessionEnd;
+      } else if (lParam & (ENDSESSION_CLOSEAPP | ENDSESSION_CRITICAL)) {
+        shutdownReason = AppShutdownReason::OSForceClose;
+      } else {
+        MOZ_DIAGNOSTIC_ASSERT(false,
+                              "Received WM_ENDSESSION with unknown flags.");
+        shutdownReason = AppShutdownReason::OSForceClose;
+      }
+    }
+      [[fallthrough]];
+    case MOZ_WM_APP_QUIT: {
+      if (shutdownReason == AppShutdownReason::Unknown) {
+        // TODO: We do not expect that these days anybody sends us
+        // MOZ_WM_APP_QUIT, see bug 1827807.
+        shutdownReason = AppShutdownReason::WinUnexpectedMozQuit;
+      }
+      // Let's fake a shutdown sequence without actually closing windows etc.
+      // to avoid Windows killing us in the middle. A proper shutdown would
+      // require having a chance to pump some messages. Unfortunately
+      // Windows won't let us do that. Bug 212316.
+      nsCOMPtr<nsIObserverService> obsServ =
+          mozilla::services::GetObserverService();
+      const char16_t* syncShutdown = u"syncShutdown";
+      const char16_t* quitType = GetQuitType();
+
+      AppShutdown::Init(AppShutdownMode::Normal, 0, shutdownReason);
+
+      obsServ->NotifyObservers(nullptr, "quit-application-granted",
+                               syncShutdown);
+      obsServ->NotifyObservers(nullptr, "quit-application-forced", nullptr);
+
+      AppShutdown::OnShutdownConfirmed();
+
+      AppShutdown::AdvanceShutdownPhase(ShutdownPhase::AppShutdownConfirmed,
+                                        quitType);
+      AppShutdown::AdvanceShutdownPhase(ShutdownPhase::AppShutdownNetTeardown,
+                                        nullptr);
+      AppShutdown::AdvanceShutdownPhase(ShutdownPhase::AppShutdownTeardown,
+                                        nullptr);
+      AppShutdown::AdvanceShutdownPhase(ShutdownPhase::AppShutdown, nullptr);
+      AppShutdown::AdvanceShutdownPhase(ShutdownPhase::AppShutdownQM, nullptr);
+      AppShutdown::AdvanceShutdownPhase(ShutdownPhase::AppShutdownTelemetry,
+                                        nullptr);
+
+      AppShutdown::DoImmediateExit();
+      MOZ_ASSERT_UNREACHABLE("Our process was supposed to exit.");
+    } break;
+
+    case WM_SYSCOLORCHANGE:
+      // No need to invalidate layout for system color changes, but we need to
+      // invalidate style.
+      NotifyThemeChanged(widget::ThemeChangeKind::Style);
+      break;
+
+    case WM_THEMECHANGED: {
+      // Update non-client margin offsets
+      UpdateNonClientMargins();
+      nsUXThemeData::UpdateNativeThemeInfo();
+
+      // We assume pretty much everything could've changed here.
+      NotifyThemeChanged(widget::ThemeChangeKind::StyleAndLayout);
+
+      UpdateDarkModeToolbar();
+
+      // Invalidate the window so that the repaint will
+      // pick up the new theme.
+      Invalidate(true, true, true);
+    } break;
+
+    case WM_WTSSESSION_CHANGE: {
+      switch (wParam) {
+        case WTS_CONSOLE_CONNECT:
+        case WTS_REMOTE_CONNECT:
+        case WTS_SESSION_UNLOCK:
+          // When a session becomes visible, we should invalidate.
+          Invalidate(true, true, true);
+          break;
+        default:
+          break;
+      }
+    } break;
+
+    case WM_FONTCHANGE: {
+      // We only handle this message for the hidden window,
+      // as we only need to update the (global) font list once
+      // for any given change, not once per window!
+      if (mWindowType != WindowType::Invisible) {
+        break;
+      }
+
+      // update the global font list
+      gfxPlatform::GetPlatform()->UpdateFontList();
+    } break;
+
+    case WM_SETTINGCHANGE: {
+      if (wParam == SPI_SETCLIENTAREAANIMATION ||
+          wParam == SPI_SETKEYBOARDDELAY || wParam == SPI_SETMOUSEVANISH) {
+        // These need to update LookAndFeel cached values.
+        // They affect reduced motion settings / caret blink count / show
+        // pointer while typing, so no need to invalidate style / layout.
+        NotifyThemeChanged(widget::ThemeChangeKind::MediaQueriesOnly);
+        break;
+      }
+      if (wParam == SPI_SETFONTSMOOTHING ||
+          wParam == SPI_SETFONTSMOOTHINGTYPE) {
+        gfxDWriteFont::UpdateSystemTextVars();
+        break;
+      }
+      if (wParam == SPI_SETWORKAREA) {
+        // NB: We also refresh screens on WM_DISPLAYCHANGE but the rcWork
+        // values are sometimes wrong at that point.  This message then
+        // arrives soon afterward, when we can get the right rcWork values.
+        ScreenHelperWin::RefreshScreens();
+        break;
+      }
+      if (auto lParamString = reinterpret_cast<const wchar_t*>(lParam)) {
+        if (!wcscmp(lParamString, L"ImmersiveColorSet")) {
+          // This affects system colors (-moz-win-accentcolor), so gotta pass
+          // the style flag.
+          NotifyThemeChanged(widget::ThemeChangeKind::Style);
+          break;
+        }
+
+        // UserInteractionMode, ConvertibleSlateMode, SystemDockMode may cause
+        // @media(pointer) queries to change, which layout needs to know about
+        //
+        // (WM_SETTINGCHANGE will be sent to all top-level windows, so we
+        //  only respond to the hidden top-level window to avoid hammering
+        //  layout with a bunch of NotifyThemeChanged() calls)
+        //
+        if (mWindowType == WindowType::Invisible) {
+          if (!wcscmp(lParamString, L"UserInteractionMode") ||
+              !wcscmp(lParamString, L"ConvertibleSlateMode") ||
+              !wcscmp(lParamString, L"SystemDockMode")) {
+            NotifyThemeChanged(widget::ThemeChangeKind::MediaQueriesOnly);
+            WindowsUIUtils::UpdateInTabletMode();
+          }
+        }
+      }
+    } break;
+
+    case WM_DEVICECHANGE: {
+      if (wParam == DBT_DEVICEARRIVAL || wParam == DBT_DEVICEREMOVECOMPLETE) {
+        DEV_BROADCAST_HDR* hdr = reinterpret_cast<DEV_BROADCAST_HDR*>(lParam);
+        // Check dbch_devicetype explicitly since we will get other device types
+        // (e.g. DBT_DEVTYP_VOLUME) for some reasons even if we specify
+        // DBT_DEVTYP_DEVICEINTERFACE in the filter for
+        // RegisterDeviceNotification.
+        if (hdr->dbch_devicetype == DBT_DEVTYP_DEVICEINTERFACE) {
+          // This can only change media queries (any-hover/any-pointer).
+          NotifyThemeChanged(widget::ThemeChangeKind::MediaQueriesOnly);
+        }
+      }
+    } break;
+
+    case WM_NCCALCSIZE: {
+      // NOTE: the following block is mirrored in PreXULSkeletonUI.cpp, and
+      // will need to be kept in sync.
+      if (mCustomNonClient) {
+        // If `wParam` is `FALSE`, `lParam` points to a `RECT` that contains
+        // the proposed window rectangle for our window.  During our
+        // processing of the `WM_NCCALCSIZE` message, we are expected to
+        // modify the `RECT` that `lParam` points to, so that its value upon
+        // our return is the new client area.  We must return 0 if `wParam`
+        // is `FALSE`.
+        //
+        // If `wParam` is `TRUE`, `lParam` points to a `NCCALCSIZE_PARAMS`
+        // struct.  This struct contains an array of 3 `RECT`s, the first of
+        // which has the exact same meaning as the `RECT` that is pointed to
+        // by `lParam` when `wParam` is `FALSE`.  The remaining `RECT`s, in
+        // conjunction with our return value, can
+        // be used to specify portions of the source and destination window
+        // rectangles that are valid and should be preserved.  We opt not to
+        // implement an elaborate client-area preservation technique, and
+        // simply return 0, which means "preserve the entire old client area
+        // and align it with the upper-left corner of our new client area".
+        RECT* clientRect =
+            wParam ? &(reinterpret_cast<NCCALCSIZE_PARAMS*>(lParam))->rgrc[0]
+                   : (reinterpret_cast<RECT*>(lParam));
+        auto margin = NonClientSizeMargin();
+        clientRect->top += margin.top;
+        clientRect->left += margin.left;
+        clientRect->right -= margin.right;
+        clientRect->bottom -= margin.bottom;
+        // Make client rect's width and height more than 0 to
+        // avoid problems of webrender and angle.
+        clientRect->right = std::max(clientRect->right, clientRect->left + 1);
+        clientRect->bottom = std::max(clientRect->bottom, clientRect->top + 1);
+
+        result = true;
+        *aRetValue = 0;
+      }
+      break;
+    }
+
+    case WM_NCHITTEST: {
+      if (mInputRegion.mFullyTransparent) {
+        // Treat this window as transparent.
+        *aRetValue = HTTRANSPARENT;
+        result = true;
+        break;
+      }
+
+      if (mInputRegion.mMargin) {
+        const LayoutDeviceIntPoint screenPoint(GET_X_LPARAM(lParam),
+                                               GET_Y_LPARAM(lParam));
+        LayoutDeviceIntRect screenRect = GetScreenBounds();
+        screenRect.Deflate(mInputRegion.mMargin);
+        if (!screenRect.Contains(screenPoint)) {
+          *aRetValue = HTTRANSPARENT;
+          result = true;
+          break;
+        }
+      }
+
+      /*
+       * If an nc client area margin has been moved, we are responsible
+       * for calculating where the resize margins are and returning the
+       * appropriate set of hit test constants. DwmDefWindowProc (above)
+       * will handle hit testing on it's command buttons if we are on a
+       * composited desktop.
+       */
+
+      if (!mCustomNonClient) {
+        break;
+      }
+
+      *aRetValue =
+          ClientMarginHitTestPoint(GET_X_LPARAM(lParam), GET_Y_LPARAM(lParam));
+      result = true;
+      break;
+    }
+
+    case WM_SETTEXT:
+      /*
+       * WM_SETTEXT paints the titlebar area. Avoid this if we have a
+       * custom titlebar we paint ourselves, or if we're the ones
+       * sending the message with an updated title
+       */
+
+      if (mSendingSetText || !mCustomNonClient || mNonClientMargins.top == -1)
+        break;
+
+      {
+        // From msdn, the way around this is to disable the visible state
+        // temporarily. We need the text to be set but we don't want the
+        // redraw to occur. However, we need to make sure that we don't
+        // do this at the same time that a Present is happening.
+        //
+        // To do this we take mPresentLock in nsWindow::PreRender and
+        // if that lock is taken we wait before doing WM_SETTEXT
+        if (mCompositorWidgetDelegate) {
+          mCompositorWidgetDelegate->EnterPresentLock();
+        }
+        DWORD style = GetWindowLong(mWnd, GWL_STYLE);
+        SetWindowLong(mWnd, GWL_STYLE, style & ~WS_VISIBLE);
+        *aRetValue =
+            CallWindowProcW(GetPrevWindowProc(), mWnd, msg, wParam, lParam);
+        SetWindowLong(mWnd, GWL_STYLE, style);
+        if (mCompositorWidgetDelegate) {
+          mCompositorWidgetDelegate->LeavePresentLock();
+        }
+
+        return true;
+      }
+
+    case WM_NCACTIVATE: {
+      /*
+       * WM_NCACTIVATE paints nc areas. Avoid this and re-route painting
+       * through WM_NCPAINT via InvalidateNonClientRegion.
+       */
+      UpdateGetWindowInfoCaptionStatus(FALSE != wParam);
+
+      if (!mCustomNonClient) {
+        break;
+      }
+
+      // There is a case that rendered result is not kept. Bug 1237617
+      if (wParam == TRUE && !gfxEnv::MOZ_DISABLE_FORCE_PRESENT()) {
+        NS_DispatchToMainThread(NewRunnableMethod(
+            "nsWindow::ForcePresent", this, &nsWindow::ForcePresent));
+      }
+
+      // let the dwm handle nc painting on glass
+      // Never allow native painting if we are on fullscreen
+      if (mFrameState->GetSizeMode() != nsSizeMode_Fullscreen) break;
+
+      if (wParam == TRUE) {
+        // going active
+        *aRetValue = FALSE;  // ignored
+        result = true;
+        // invalidate to trigger a paint
+        InvalidateNonClientRegion();
+        break;
+      } else {
+        // going inactive
+        *aRetValue = TRUE;  // go ahead and deactive
+        result = true;
+        // invalidate to trigger a paint
+        InvalidateNonClientRegion();
+        break;
+      }
+    }
+
+    case WM_NCPAINT: {
+      /*
+       * ClearType changes often don't send a WM_SETTINGCHANGE message. But they
+       * do seem to always send a WM_NCPAINT message, so let's update on that.
+       */
+      gfxDWriteFont::UpdateSystemTextVars();
+    } break;
+
+    case WM_POWERBROADCAST:
+      switch (wParam) {
+        case PBT_APMSUSPEND:
+          PostSleepWakeNotification(true);
+          break;
+        case PBT_APMRESUMEAUTOMATIC:
+        case PBT_APMRESUMECRITICAL:
+        case PBT_APMRESUMESUSPEND:
+          PostSleepWakeNotification(false);
+          break;
+      }
+      break;
+
+    case WM_CLOSE:  // close request
+      if (mWidgetListener) mWidgetListener->RequestWindowClose(this);
+      result = true;  // abort window closure
+      break;
+
+    case WM_DESTROY:
+      // clean up.
+      DestroyLayerManager();
+      OnDestroy();
+      result = true;
+      break;
+
+    case WM_PAINT:
+      *aRetValue = (int)OnPaint(0);
+      result = true;
+      break;
+
+    case WM_HOTKEY:
+      result = OnHotKey(wParam, lParam);
+      break;
+
+    case WM_SYSCHAR:
+    case WM_CHAR: {
+      MSG nativeMsg = WinUtils::InitMSG(msg, wParam, lParam, mWnd);
+      result = ProcessCharMessage(nativeMsg, nullptr);
+      DispatchPendingEvents();
+    } break;
+
+    case WM_SYSKEYUP:
+    case WM_KEYUP: {
+      MSG nativeMsg = WinUtils::InitMSG(msg, wParam, lParam, mWnd);
+      nativeMsg.time = ::GetMessageTime();
+      result = ProcessKeyUpMessage(nativeMsg, nullptr);
+      DispatchPendingEvents();
+    } break;
+
+    case WM_SYSKEYDOWN:
+    case WM_KEYDOWN: {
+      MSG nativeMsg = WinUtils::InitMSG(msg, wParam, lParam, mWnd);
+      result = ProcessKeyDownMessage(nativeMsg, nullptr);
+      DispatchPendingEvents();
+    } break;
+
+    // Say we've dealt with erasing the background. (This is actually handled in
+    // WM_PAINT, where necessary.)
+    case WM_ERASEBKGND: {
+      *aRetValue = 1;
+      result = true;
+    } break;
+
+    case WM_MOUSEMOVE: {
+      LPARAM lParamScreen = lParamToScreen(lParam);
+      mSimulatedClientArea = IsSimulatedClientArea(GET_X_LPARAM(lParamScreen),
+                                                   GET_Y_LPARAM(lParamScreen));
+
+      if (!mMousePresent && !sIsInMouseCapture) {
+        // First MOUSEMOVE over the client area. Ask for MOUSELEAVE
+        TRACKMOUSEEVENT mTrack;
+        mTrack.cbSize = sizeof(TRACKMOUSEEVENT);
+        mTrack.dwFlags = TME_LEAVE;
+        mTrack.dwHoverTime = 0;
+        mTrack.hwndTrack = mWnd;
+        TrackMouseEvent(&mTrack);
+      }
+      mMousePresent = true;
+
+      // Suppress dispatch of pending events
+      // when mouse moves are generated by widget
+      // creation instead of user input.
+      POINT mp;
+      mp.x = GET_X_LPARAM(lParamScreen);
+      mp.y = GET_Y_LPARAM(lParamScreen);
+      bool userMovedMouse = false;
+      if ((sLastMouseMovePoint.x != mp.x) || (sLastMouseMovePoint.y != mp.y)) {
+        userMovedMouse = true;
+      }
+
+      if (userMovedMouse) {
+        result = DispatchMouseEvent(
+            eMouseMove, wParam, lParam, false, MouseButton::ePrimary,
+            MOUSE_INPUT_SOURCE(),
+            mPointerEvents.GetCachedPointerInfo(msg, wParam));
+        DispatchPendingEvents();
+      }
+    } break;
+
+    case WM_NCMOUSEMOVE: {
+      LPARAM lParamClient = lParamToClient(lParam);
+      if (IsSimulatedClientArea(GET_X_LPARAM(lParam), GET_Y_LPARAM(lParam))) {
+        if (!sIsInMouseCapture) {
+          TRACKMOUSEEVENT mTrack;
+          mTrack.cbSize = sizeof(TRACKMOUSEEVENT);
+          mTrack.dwFlags = TME_LEAVE | TME_NONCLIENT;
+          mTrack.dwHoverTime = 0;
+          mTrack.hwndTrack = mWnd;
+          TrackMouseEvent(&mTrack);
+        }
+        // If we noticed the mouse moving in our draggable region, forward the
+        // message as a normal WM_MOUSEMOVE.
+        SendMessage(mWnd, WM_MOUSEMOVE, 0, lParamClient);
+      } else {
+        // We've transitioned from a draggable area to somewhere else within
+        // the non-client area - perhaps one of the edges of the window for
+        // resizing.
+        mSimulatedClientArea = false;
+      }
+
+      if (mMousePresent && !sIsInMouseCapture && !mSimulatedClientArea) {
+        SendMessage(mWnd, WM_MOUSELEAVE, 0, 0);
+      }
+    } break;
+
+    case WM_LBUTTONDOWN: {
+      result =
+          DispatchMouseEvent(eMouseDown, wParam, lParam, false,
+                             MouseButton::ePrimary, MOUSE_INPUT_SOURCE(),
+                             mPointerEvents.GetCachedPointerInfo(msg, wParam));
+      DispatchPendingEvents();
+    } break;
+
+    case WM_LBUTTONUP: {
+      result =
+          DispatchMouseEvent(eMouseUp, wParam, lParam, false,
+                             MouseButton::ePrimary, MOUSE_INPUT_SOURCE(),
+                             mPointerEvents.GetCachedPointerInfo(msg, wParam));
+      DispatchPendingEvents();
+    } break;
+
+    case WM_NCMOUSELEAVE: {
+      mSimulatedClientArea = false;
+
+      if (EventIsInsideWindow(this)) {
+        // If we're handling WM_NCMOUSELEAVE and the mouse is still over the
+        // window, then by process of elimination, the mouse has moved from the
+        // non-client to client area, so no need to fall-through to the
+        // WM_MOUSELEAVE handler. We also need to re-register for the
+        // WM_MOUSELEAVE message, since according to the documentation at [1],
+        // all tracking requested via TrackMouseEvent is cleared once
+        // WM_NCMOUSELEAVE or WM_MOUSELEAVE fires.
+        // [1]:
+        // https://docs.microsoft.com/en-us/windows/desktop/api/winuser/nf-winuser-trackmouseevent
+        TRACKMOUSEEVENT mTrack;
+        mTrack.cbSize = sizeof(TRACKMOUSEEVENT);
+        mTrack.dwFlags = TME_LEAVE;
+        mTrack.dwHoverTime = 0;
+        mTrack.hwndTrack = mWnd;
+        TrackMouseEvent(&mTrack);
+        break;
+      }
+      // We've transitioned from non-client to outside of the window, so
+      // fall-through to the WM_MOUSELEAVE handler.
+      [[fallthrough]];
+    }
+    case WM_MOUSELEAVE: {
+      if (!mMousePresent) break;
+      if (mSimulatedClientArea) break;
+      mMousePresent = false;
+
+      // Check if the mouse is over the fullscreen transition window, if so
+      // clear sLastMouseMovePoint. This way the WM_MOUSEMOVE we get after the
+      // transition window disappears will not be ignored, even if the mouse
+      // hasn't moved.
+      if (mTransitionWnd && WindowAtMouse() == mTransitionWnd) {
+        sLastMouseMovePoint = {0};
+      }
+
+      // We need to check mouse button states and put them in for
+      // wParam.
+      WPARAM mouseState = (GetKeyState(VK_LBUTTON) ? MK_LBUTTON : 0) |
+                          (GetKeyState(VK_MBUTTON) ? MK_MBUTTON : 0) |
+                          (GetKeyState(VK_RBUTTON) ? MK_RBUTTON : 0);
+      // Synthesize an event position because we don't get one from
+      // WM_MOUSELEAVE.
+      LPARAM pos = lParamToClient(::GetMessagePos());
+      DispatchMouseEvent(eMouseExitFromWidget, mouseState, pos, false,
+                         MouseButton::ePrimary, MOUSE_INPUT_SOURCE());
+    } break;
+
+    case WM_CONTEXTMENU: {
+      // If the context menu is brought up by a touch long-press, then
+      // the APZ code is responsible for dealing with this, so we don't
+      // need to do anything.
+      if (mTouchWindow &&
+          MOUSE_INPUT_SOURCE() == MouseEvent_Binding::MOZ_SOURCE_TOUCH) {
+        MOZ_ASSERT(mAPZC);  // since mTouchWindow is true, APZ must be enabled
+        result = true;
+        break;
+      }
+
+      // If this WM_CONTEXTMENU is triggered by a mouse's secondary button up
+      // event in overscroll gutter, we shouldn't open context menu.
+      if (MOUSE_INPUT_SOURCE() == MouseEvent_Binding::MOZ_SOURCE_MOUSE &&
+          mNeedsToPreventContextMenu) {
+        result = true;
+        break;
+      }
+
+      // if the context menu is brought up from the keyboard, |lParam|
+      // will be -1.
+      LPARAM pos;
+      bool contextMenukey = false;
+      if (lParam == -1) {
+        contextMenukey = true;
+        pos = lParamToClient(GetMessagePos());
+      } else {
+        pos = lParamToClient(lParam);
+      }
+
+      result = DispatchMouseEvent(
+          eContextMenu, wParam, pos, contextMenukey,
+          contextMenukey ? MouseButton::ePrimary : MouseButton::eSecondary,
+          MOUSE_INPUT_SOURCE());
+      if (lParam != -1 && !result && mCustomNonClient &&
+          mDraggableRegion.Contains(GET_X_LPARAM(pos), GET_Y_LPARAM(pos))) {
+        // Blank area hit, throw up the system menu.
+        DisplaySystemMenu(mWnd, mFrameState->GetSizeMode(), mIsRTL,
+                          GET_X_LPARAM(lParam), GET_Y_LPARAM(lParam));
+        result = true;
+      }
+    } break;
+
+    case WM_POINTERLEAVE:
+    case WM_POINTERDOWN:
+    case WM_POINTERUP:
+    case WM_POINTERUPDATE:
+      result = OnPointerEvents(msg, wParam, lParam);
+      if (result) {
+        DispatchPendingEvents();
+      }
+      break;
+
+    case DM_POINTERHITTEST:
+      if (mDmOwner) {
+        UINT contactId = GET_POINTERID_WPARAM(wParam);
+        POINTER_INPUT_TYPE pointerType;
+        if (mPointerEvents.GetPointerType(contactId, &pointerType) &&
+            pointerType == PT_TOUCHPAD) {
+          mDmOwner->SetContact(contactId);
+        }
+      }
+      break;
+
+    case WM_LBUTTONDBLCLK:
+      result = DispatchMouseEvent(eMouseDoubleClick, wParam, lParam, false,
+                                  MouseButton::ePrimary, MOUSE_INPUT_SOURCE());
+      DispatchPendingEvents();
+      break;
+
+    case WM_MBUTTONDOWN:
+      result = DispatchMouseEvent(eMouseDown, wParam, lParam, false,
+                                  MouseButton::eMiddle, MOUSE_INPUT_SOURCE());
+      DispatchPendingEvents();
+      break;
+
+    case WM_MBUTTONUP:
+      result = DispatchMouseEvent(eMouseUp, wParam, lParam, false,
+                                  MouseButton::eMiddle, MOUSE_INPUT_SOURCE());
+      DispatchPendingEvents();
+      break;
+
+    case WM_MBUTTONDBLCLK:
+      result = DispatchMouseEvent(eMouseDoubleClick, wParam, lParam, false,
+                                  MouseButton::eMiddle, MOUSE_INPUT_SOURCE());
+      DispatchPendingEvents();
+      break;
+
+    case WM_NCMBUTTONDOWN:
+      result = DispatchMouseEvent(eMouseDown, 0, lParamToClient(lParam), false,
+                                  MouseButton::eMiddle, MOUSE_INPUT_SOURCE());
+      DispatchPendingEvents();
+      break;
+
+    case WM_NCMBUTTONUP:
+      result = DispatchMouseEvent(eMouseUp, 0, lParamToClient(lParam), false,
+                                  MouseButton::eMiddle, MOUSE_INPUT_SOURCE());
+      DispatchPendingEvents();
+      break;
+
+    case WM_NCMBUTTONDBLCLK:
+      result =
+          DispatchMouseEvent(eMouseDoubleClick, 0, lParamToClient(lParam),
+                             false, MouseButton::eMiddle, MOUSE_INPUT_SOURCE());
+      DispatchPendingEvents();
+      break;
+
+    case WM_RBUTTONDOWN:
+      result =
+          DispatchMouseEvent(eMouseDown, wParam, lParam, false,
+                             MouseButton::eSecondary, MOUSE_INPUT_SOURCE(),
+                             mPointerEvents.GetCachedPointerInfo(msg, wParam));
+      DispatchPendingEvents();
+      break;
+
+    case WM_RBUTTONUP:
+      result =
+          DispatchMouseEvent(eMouseUp, wParam, lParam, false,
+                             MouseButton::eSecondary, MOUSE_INPUT_SOURCE(),
+                             mPointerEvents.GetCachedPointerInfo(msg, wParam));
+      DispatchPendingEvents();
+      break;
+
+    case WM_RBUTTONDBLCLK:
+      result =
+          DispatchMouseEvent(eMouseDoubleClick, wParam, lParam, false,
+                             MouseButton::eSecondary, MOUSE_INPUT_SOURCE());
+      DispatchPendingEvents();
+      break;
+
+    case WM_NCRBUTTONDOWN:
+      result =
+          DispatchMouseEvent(eMouseDown, 0, lParamToClient(lParam), false,
+                             MouseButton::eSecondary, MOUSE_INPUT_SOURCE());
+      DispatchPendingEvents();
+      break;
+
+    case WM_NCRBUTTONUP:
+      result =
+          DispatchMouseEvent(eMouseUp, 0, lParamToClient(lParam), false,
+                             MouseButton::eSecondary, MOUSE_INPUT_SOURCE());
+      DispatchPendingEvents();
+      break;
+
+    case WM_NCRBUTTONDBLCLK:
+      result = DispatchMouseEvent(eMouseDoubleClick, 0, lParamToClient(lParam),
+                                  false, MouseButton::eSecondary,
+                                  MOUSE_INPUT_SOURCE());
+      DispatchPendingEvents();
+      break;
+
+    // Windows doesn't provide to customize the behavior of 4th nor 5th button
+    // of mouse.  If 5-button mouse works with standard mouse deriver of
+    // Windows, users cannot disable 4th button (browser back) nor 5th button
+    // (browser forward).  We should allow to do it with our prefs since we can
+    // prevent Windows to generate WM_APPCOMMAND message if WM_XBUTTONUP
+    // messages are not sent to DefWindowProc.
+    case WM_XBUTTONDOWN:
+    case WM_XBUTTONUP:
+    case WM_NCXBUTTONDOWN:
+    case WM_NCXBUTTONUP:
+      *aRetValue = TRUE;
+      switch (GET_XBUTTON_WPARAM(wParam)) {
+        case XBUTTON1:
+          result = !Preferences::GetBool("mousebutton.4th.enabled", true);
+          break;
+        case XBUTTON2:
+          result = !Preferences::GetBool("mousebutton.5th.enabled", true);
+          break;
+        default:
+          break;
+      }
+      break;
+
+    case WM_SIZING: {
+      if (mAspectRatio > 0) {
+        LPRECT rect = (LPRECT)lParam;
+        int32_t newWidth, newHeight;
+
+        // The following conditions and switch statement borrow heavily from the
+        // Chromium source code from
+        // https://chromium.googlesource.com/chromium/src/+/456d6e533cfb4531995e0ef52c279d4b5aa8a352/ui/views/window/window_resize_utils.cc#45
+        if (wParam == WMSZ_LEFT || wParam == WMSZ_RIGHT ||
+            wParam == WMSZ_TOPLEFT || wParam == WMSZ_BOTTOMLEFT) {
+          newWidth = rect->right - rect->left;
+          newHeight = newWidth / mAspectRatio;
+          if (newHeight < mSizeConstraints.mMinSize.height) {
+            newHeight = mSizeConstraints.mMinSize.height;
+            newWidth = newHeight * mAspectRatio;
+          } else if (newHeight > mSizeConstraints.mMaxSize.height) {
+            newHeight = mSizeConstraints.mMaxSize.height;
+            newWidth = newHeight * mAspectRatio;
+          }
+        } else {
+          newHeight = rect->bottom - rect->top;
+          newWidth = newHeight * mAspectRatio;
+          if (newWidth < mSizeConstraints.mMinSize.width) {
+            newWidth = mSizeConstraints.mMinSize.width;
+            newHeight = newWidth / mAspectRatio;
+          } else if (newWidth > mSizeConstraints.mMaxSize.width) {
+            newWidth = mSizeConstraints.mMaxSize.width;
+            newHeight = newWidth / mAspectRatio;
+          }
+        }
+
+        switch (wParam) {
+          case WMSZ_RIGHT:
+          case WMSZ_BOTTOM:
+            rect->right = newWidth + rect->left;
+            rect->bottom = rect->top + newHeight;
+            break;
+          case WMSZ_TOP:
+            rect->right = newWidth + rect->left;
+            rect->top = rect->bottom - newHeight;
+            break;
+          case WMSZ_LEFT:
+          case WMSZ_TOPLEFT:
+            rect->left = rect->right - newWidth;
+            rect->top = rect->bottom - newHeight;
+            break;
+          case WMSZ_TOPRIGHT:
+            rect->right = rect->left + newWidth;
+            rect->top = rect->bottom - newHeight;
+            break;
+          case WMSZ_BOTTOMLEFT:
+            rect->left = rect->right - newWidth;
+            rect->bottom = rect->top + newHeight;
+            break;
+          case WMSZ_BOTTOMRIGHT:
+            rect->right = rect->left + newWidth;
+            rect->bottom = rect->top + newHeight;
+            break;
+        }
+      }
+
+      // When we get WM_ENTERSIZEMOVE we don't know yet if we're in a live
+      // resize or move event. Instead we wait for first VM_SIZING message
+      // within a ENTERSIZEMOVE to consider this a live resize event.
+      if (mResizeState == IN_SIZEMOVE) {
+        mResizeState = RESIZING;
+        NotifyLiveResizeStarted();
+      }
+      break;
+    }
+
+    case WM_MOVING:
+      FinishLiveResizing(MOVING);
+      if (WinUtils::IsPerMonitorDPIAware()) {
+        // Sometimes, we appear to miss a WM_DPICHANGED message while moving
+        // a window around. Therefore, call ChangedDPI and ResetLayout here
+        // if it appears that the window's scaling is not what we expect.
+        // This causes the prescontext and appshell window management code to
+        // check the appUnitsPerDevPixel value and current widget size, and
+        // refresh them if necessary. If nothing has changed, these calls will
+        // return without actually triggering any extra reflow or painting.
+        if (WinUtils::LogToPhysFactor(mWnd) != mDefaultScale) {
+          ChangedDPI();
+          ResetLayout();
+          if (mWidgetListener) {
+            mWidgetListener->UIResolutionChanged();
+          }
+        }
+      }
+      break;
+
+    case WM_ENTERSIZEMOVE: {
+      if (mResizeState == NOT_RESIZING) {
+        mResizeState = IN_SIZEMOVE;
+      }
+      break;
+    }
+
+    case WM_EXITSIZEMOVE: {
+      FinishLiveResizing(NOT_RESIZING);
+
+      if (!sIsInMouseCapture) {
+        NotifySizeMoveDone();
+      }
+
+      // Windows spins a separate hidden event loop when moving a window so we
+      // don't hear mouse events during this time and WM_EXITSIZEMOVE is fired
+      // when the hidden event loop exits. We set mDraggingWindowWithMouse to
+      // true in WM_NCLBUTTONDOWN when we started moving the window with the
+      // mouse so we know that if mDraggingWindowWithMouse is true, we can send
+      // a mouse up event.
+      if (mDraggingWindowWithMouse) {
+        mDraggingWindowWithMouse = false;
+        result = DispatchMouseEvent(
+            eMouseUp, wParam, lParam, false, MouseButton::ePrimary,
+            MOUSE_INPUT_SOURCE(),
+            mPointerEvents.GetCachedPointerInfo(msg, wParam));
+      }
+
+      break;
+    }
+
+    case WM_DISPLAYCHANGE: {
+      ScreenHelperWin::RefreshScreens();
+      if (mWidgetListener) {
+        mWidgetListener->UIResolutionChanged();
+      }
+      break;
+    }
+
+    case WM_NCLBUTTONDBLCLK:
+      DispatchMouseEvent(eMouseDoubleClick, 0, lParamToClient(lParam), false,
+                         MouseButton::ePrimary, MOUSE_INPUT_SOURCE());
+      result = DispatchMouseEvent(eMouseUp, 0, lParamToClient(lParam), false,
+                                  MouseButton::ePrimary, MOUSE_INPUT_SOURCE());
+      DispatchPendingEvents();
+      break;
+
+    case WM_NCLBUTTONDOWN: {
+      // Dispatch a custom event when this happens in the draggable region, so
+      // that non-popup-based panels can react to it. This doesn't send an
+      // actual mousedown event because that would break dragging or interfere
+      // with other mousedown handling in the caption area.
+      if (ClientMarginHitTestPoint(GET_X_LPARAM(lParam),
+                                   GET_Y_LPARAM(lParam)) == HTCAPTION) {
+        DispatchCustomEvent(u"draggableregionleftmousedown"_ns);
+        mDraggingWindowWithMouse = true;
+      }
+
+      if (IsWindowButton(wParam) && mCustomNonClient) {
+        DispatchMouseEvent(eMouseDown, wParamFromGlobalMouseState(),
+                           lParamToClient(lParam), false, MouseButton::ePrimary,
+                           MOUSE_INPUT_SOURCE(), nullptr, true);
+        DispatchPendingEvents();
+        result = true;
+      }
+      break;
+    }
+
+    case WM_APPCOMMAND: {
+      MSG nativeMsg = WinUtils::InitMSG(msg, wParam, lParam, mWnd);
+      result = HandleAppCommandMsg(nativeMsg, aRetValue);
+      break;
+    }
+
+    // The WM_ACTIVATE event is fired when a window is raised or lowered,
+    // and the loword of wParam specifies which. But we don't want to tell
+    // the focus system about this until the WM_SETFOCUS or WM_KILLFOCUS
+    // events are fired. Instead, set either the sJustGotActivate or
+    // gJustGotDeactivate flags and activate/deactivate once the focus
+    // events arrive.
+    case WM_ACTIVATE: {
+      int32_t fActive = LOWORD(wParam);
+      if (mWidgetListener) {
+        if (WA_INACTIVE == fActive) {
+          // when minimizing a window, the deactivation and focus events will
+          // be fired in the reverse order. Instead, just deactivate right away.
+          // This can also happen when a modal system dialog is opened, so check
+          // if the last window to receive the WM_KILLFOCUS message was this one
+          // or a child of this one.
+          if (HIWORD(wParam) ||
+              (mLastKillFocusWindow &&
+               (GetTopLevelForFocus(mLastKillFocusWindow) == mWnd))) {
+            DispatchFocusToTopLevelWindow(false);
+          } else {
+            sJustGotDeactivate = true;
+          }
+          if (mIsTopWidgetWindow) {
+            mLastKeyboardLayout = KeyboardLayout::GetLayout();
+          }
+        } else {
+          StopFlashing();
+
+          sJustGotActivate = true;
+          WidgetMouseEvent event(true, eMouseActivate, this,
+                                 WidgetMouseEvent::eReal);
+          InitEvent(event);
+          ModifierKeyState modifierKeyState;
+          modifierKeyState.InitInputEvent(event);
+          DispatchInputEvent(&event);
+          if (sSwitchKeyboardLayout && mLastKeyboardLayout)
+            ActivateKeyboardLayout(mLastKeyboardLayout, 0);
+
+#ifdef ACCESSIBILITY
+          a11y::LazyInstantiator::ResetUiaDetectionCache();
+#endif
+        }
+      }
+    } break;
+
+    case WM_ACTIVATEAPP: {
+      // Bug 1851991: Sometimes this can be called before gfxPlatform::Init
+      // when a window is created very early. In that case we just forego
+      // setting this and accept the GPU process might briefly run at a lower
+      // priority.
+      if (GPUProcessManager::Get()) {
+        GPUProcessManager::Get()->SetAppInForeground(wParam);
+      }
+    } break;
+
+    case WM_MOUSEACTIVATE:
+      // A popup with a parent owner should not be activated when clicked but
+      // should still allow the mouse event to be fired, so the return value
+      // is set to MA_NOACTIVATE. But if the owner isn't the frontmost window,
+      // just use default processing so that the window is activated.
+      if (IsPopup() && IsOwnerForegroundWindow()) {
+        *aRetValue = MA_NOACTIVATE;
+        result = true;
+      }
+      break;
+
+    case WM_WINDOWPOSCHANGING: {
+      LPWINDOWPOS info = (LPWINDOWPOS)lParam;
+      OnWindowPosChanging(info);
+      result = true;
+    } break;
+
+    // Workaround for race condition in explorer.exe.
+    case MOZ_WM_FULLSCREEN_STATE_UPDATE: {
+      TaskbarConcealer::OnAsyncStateUpdateRequest(mWnd);
+      result = true;
+    } break;
+
+    case WM_GETMINMAXINFO: {
+      MINMAXINFO* mmi = (MINMAXINFO*)lParam;
+      // Set the constraints. The minimum size should also be constrained to the
+      // default window maximum size so that it fits on screen.
+      mmi->ptMinTrackSize.x =
+          std::min((int32_t)mmi->ptMaxTrackSize.x,
+                   std::max((int32_t)mmi->ptMinTrackSize.x,
+                            mSizeConstraints.mMinSize.width));
+      mmi->ptMinTrackSize.y =
+          std::min((int32_t)mmi->ptMaxTrackSize.y,
+                   std::max((int32_t)mmi->ptMinTrackSize.y,
+                            mSizeConstraints.mMinSize.height));
+      mmi->ptMaxTrackSize.x = std::min((int32_t)mmi->ptMaxTrackSize.x,
+                                       mSizeConstraints.mMaxSize.width);
+      mmi->ptMaxTrackSize.y = std::min((int32_t)mmi->ptMaxTrackSize.y,
+                                       mSizeConstraints.mMaxSize.height);
+    } break;
+
+    case WM_SETFOCUS: {
+      WndProcUrgentInvocation::Marker _marker;
+
+      // If previous focused window isn't ours, it must have received the
+      // redirected message.  So, we should forget it.
+      if (!WinUtils::IsOurProcessWindow(HWND(wParam))) {
+        RedirectedKeyDownMessageManager::Forget();
+      }
+      if (sJustGotActivate) {
+        DispatchFocusToTopLevelWindow(true);
+      }
+      TaskbarConcealer::OnFocusAcquired(this);
+    } break;
+
+    case WM_KILLFOCUS:
+      if (sJustGotDeactivate) {
+        DispatchFocusToTopLevelWindow(false);
+      } else {
+        mLastKillFocusWindow = mWnd;
+      }
+      break;
+
+    case WM_WINDOWPOSCHANGED: {
+      WINDOWPOS* wp = (LPWINDOWPOS)lParam;
+      OnWindowPosChanged(wp);
+      TaskbarConcealer::OnWindowPosChanged(this);
+      result = true;
+    } break;
+
+    case WM_INPUTLANGCHANGEREQUEST:
+      *aRetValue = TRUE;
+      result = false;
+      break;
+
+    case WM_INPUTLANGCHANGE:
+      KeyboardLayout::GetInstance()->OnLayoutChange(
+          reinterpret_cast<HKL>(lParam));
+      nsBidiKeyboard::OnLayoutChange();
+      result = false;  // always pass to child window
+      break;
+
+    case WM_DESTROYCLIPBOARD: {
+      nsIClipboard* clipboard;
+      nsresult rv = CallGetService(kCClipboardCID, &clipboard);
+      if (NS_SUCCEEDED(rv)) {
+        clipboard->EmptyClipboard(nsIClipboard::kGlobalClipboard);
+        NS_RELEASE(clipboard);
+      }
+    } break;
+
+#ifdef ACCESSIBILITY
+    case WM_GETOBJECT: {
+      *aRetValue = 0;
+      // Do explicit casting to make it working on 64bit systems (see bug 649236
+      // for details).
+      int32_t objId = static_cast<DWORD>(lParam);
+      if (objId == OBJID_CLIENT) {  // oleacc.dll will be loaded dynamically
+        RefPtr<IAccessible> root(
+            a11y::LazyInstantiator::GetRootAccessible(mWnd));
+        if (root) {
+          *aRetValue = LresultFromObject(IID_IAccessible, wParam, root);
+          a11y::LazyInstantiator::EnableBlindAggregation(mWnd);
+          result = true;
+        }
+      }
+    } break;
+#endif
+
+    case WM_SYSCOMMAND: {
+      WPARAM const filteredWParam = (wParam & 0xFFF0);
+
+      // SC_CLOSE may trigger a synchronous confirmation prompt. If we're in the
+      // middle of something important, put off responding to it.
+      if (filteredWParam == SC_CLOSE && WndProcUrgentInvocation::IsActive()) {
+        ::PostMessageW(mWnd, msg, wParam, lParam);
+        result = true;
+        break;
+      }
+
+      if (mFrameState->GetSizeMode() == nsSizeMode_Fullscreen &&
+          filteredWParam == SC_RESTORE &&
+          GetCurrentShowCmd(mWnd) != SW_SHOWMINIMIZED) {
+        mFrameState->EnsureFullscreenMode(false);
+        result = true;
+      }
+
+      // Handle the system menu manually when we're in full screen mode
+      // so we can set the appropriate options.
+      if (filteredWParam == SC_KEYMENU && lParam == VK_SPACE &&
+          mFrameState->GetSizeMode() == nsSizeMode_Fullscreen) {
+        DisplaySystemMenu(mWnd, mFrameState->GetSizeMode(), mIsRTL,
+                          MOZ_SYSCONTEXT_X_POS, MOZ_SYSCONTEXT_Y_POS);
+        result = true;
+      }
+    } break;
+
+    case WM_DPICHANGED: {
+      LPRECT rect = (LPRECT)lParam;
+      OnDPIChanged(rect->left, rect->top, rect->right - rect->left,
+                   rect->bottom - rect->top);
+      break;
+    }
+
+    /* Gesture support events */
+    case WM_TABLET_QUERYSYSTEMGESTURESTATUS:
+      // According to MS samples, this must be handled to enable
+      // rotational support in multi-touch drivers.
+      result = true;
+      *aRetValue = TABLET_ROTATE_GESTURE_ENABLE;
+      break;
+
+    case WM_TOUCH:
+      result = OnTouch(wParam, lParam);
+      if (result) {
+        *aRetValue = 0;
+      }
+      break;
+
+    case WM_GESTURE:
+      result = OnGesture(wParam, lParam);
+      break;
+
+    case WM_GESTURENOTIFY: {
+      if (mWindowType != WindowType::Invisible) {
+        // A GestureNotify event is dispatched to decide which single-finger
+        // panning direction should be active (including none) and if pan
+        // feedback should be displayed. Java and plugin windows can make their
+        // own calls.
+
+        GESTURENOTIFYSTRUCT* gestureinfo = (GESTURENOTIFYSTRUCT*)lParam;
+        nsPointWin touchPoint;
+        touchPoint = gestureinfo->ptsLocation;
+        touchPoint.ScreenToClient(mWnd);
+        WidgetGestureNotifyEvent gestureNotifyEvent(true, eGestureNotify, this);
+        gestureNotifyEvent.mRefPoint =
+            LayoutDeviceIntPoint::FromUnknownPoint(touchPoint);
+        nsEventStatus status;
+        DispatchEvent(&gestureNotifyEvent, status);
+        mDisplayPanFeedback = gestureNotifyEvent.mDisplayPanFeedback;
+        if (!mTouchWindow)
+          mGesture.SetWinGestureSupport(mWnd, gestureNotifyEvent.mPanDirection);
+      }
+      result = false;  // should always bubble to DefWindowProc
+    } break;
+
+    case WM_CLEAR: {
+      WidgetContentCommandEvent command(true, eContentCommandDelete, this);
+      DispatchWindowEvent(command);
+      result = true;
+    } break;
+
+    case WM_CUT: {
+      WidgetContentCommandEvent command(true, eContentCommandCut, this);
+      DispatchWindowEvent(command);
+      result = true;
+    } break;
+
+    case WM_COPY: {
+      WidgetContentCommandEvent command(true, eContentCommandCopy, this);
+      DispatchWindowEvent(command);
+      result = true;
+    } break;
+
+    case WM_PASTE: {
+      WidgetContentCommandEvent command(true, eContentCommandPaste, this);
+      DispatchWindowEvent(command);
+      result = true;
+    } break;
+
+    case EM_UNDO: {
+      WidgetContentCommandEvent command(true, eContentCommandUndo, this);
+      DispatchWindowEvent(command);
+      *aRetValue = (LRESULT)(command.mSucceeded && command.mIsEnabled);
+      result = true;
+    } break;
+
+    case EM_REDO: {
+      WidgetContentCommandEvent command(true, eContentCommandRedo, this);
+      DispatchWindowEvent(command);
+      *aRetValue = (LRESULT)(command.mSucceeded && command.mIsEnabled);
+      result = true;
+    } break;
+
+    case EM_CANPASTE: {
+      // Support EM_CANPASTE message only when wParam isn't specified or
+      // is plain text format.
+      if (wParam == 0 || wParam == CF_TEXT || wParam == CF_UNICODETEXT) {
+        WidgetContentCommandEvent command(true, eContentCommandPaste, this,
+                                          true);
+        DispatchWindowEvent(command);
+        *aRetValue = (LRESULT)(command.mSucceeded && command.mIsEnabled);
+        result = true;
+      }
+    } break;
+
+    case EM_CANUNDO: {
+      WidgetContentCommandEvent command(true, eContentCommandUndo, this, true);
+      DispatchWindowEvent(command);
+      *aRetValue = (LRESULT)(command.mSucceeded && command.mIsEnabled);
+      result = true;
+    } break;
+
+    case EM_CANREDO: {
+      WidgetContentCommandEvent command(true, eContentCommandRedo, this, true);
+      DispatchWindowEvent(command);
+      *aRetValue = (LRESULT)(command.mSucceeded && command.mIsEnabled);
+      result = true;
+    } break;
+
+    case MOZ_WM_SKEWFIX: {
+      TimeStamp skewStamp;
+      if (CurrentWindowsTimeGetter::GetAndClearBackwardsSkewStamp(wParam,
+                                                                  &skewStamp)) {
+        TimeConverter().CompensateForBackwardsSkew(::GetMessageTime(),
+                                                   skewStamp);
+      }
+    } break;
+
+    default: {
+      if (msg == nsAppShell::GetTaskbarButtonCreatedMessage()) {
+        SetHasTaskbarIconBeenCreated();
+      }
+    } break;
+  }
+
+  //*aRetValue = result;
+  if (mWnd) {
+    return result;
+  } else {
+    // Events which caused mWnd destruction and aren't consumed
+    // will crash during the Windows default processing.
+    return true;
+  }
+}
+
+void nsWindow::FinishLiveResizing(ResizeState aNewState) {
+  if (mResizeState == RESIZING) {
+    NotifyLiveResizeStopped();
+  }
+  mResizeState = aNewState;
+  ForcePresent();
+}
+
+/**************************************************************
+ *
+ * SECTION: Event processing helpers
+ *
+ * Special processing for certain event types and
+ * synthesized events.
+ *
+ **************************************************************/
+
+LayoutDeviceIntMargin nsWindow::NonClientSizeMargin(
+    const LayoutDeviceIntMargin& aNonClientOffset) const {
+  return LayoutDeviceIntMargin(mCaptionHeight - aNonClientOffset.top,
+                               mHorResizeMargin - aNonClientOffset.right,
+                               mVertResizeMargin - aNonClientOffset.bottom,
+                               mHorResizeMargin - aNonClientOffset.left);
+}
+
+int32_t nsWindow::ClientMarginHitTestPoint(int32_t aX, int32_t aY) {
+  const nsSizeMode sizeMode = mFrameState->GetSizeMode();
+  if (sizeMode == nsSizeMode_Minimized || sizeMode == nsSizeMode_Fullscreen) {
+    return HTCLIENT;
+  }
+
+  // Calculations are done in screen coords
+  const LayoutDeviceIntRect winRect = GetScreenBounds();
+  const LayoutDeviceIntPoint point(aX, aY);
+
+  // hit return constants:
+  // HTBORDER                     - non-resizable border
+  // HTBOTTOM, HTLEFT, HTRIGHT, HTTOP - resizable border
+  // HTBOTTOMLEFT, HTBOTTOMRIGHT  - resizable corner
+  // HTTOPLEFT, HTTOPRIGHT        - resizable corner
+  // HTCAPTION                    - general title bar area
+  // HTCLIENT                     - area considered the client
+  // HTCLOSE                      - hovering over the close button
+  // HTMAXBUTTON                  - maximize button
+  // HTMINBUTTON                  - minimize button
+
+  int32_t testResult = HTCLIENT;
+  const bool isResizable =
+      sizeMode != nsSizeMode_Maximized &&
+      (mBorderStyle &
+       (BorderStyle::All | BorderStyle::ResizeH | BorderStyle::Default));
+
+  LayoutDeviceIntMargin nonClientSizeMargin = NonClientSizeMargin();
+
+  // Ensure being accessible to borders of window.  Even if contents are in
+  // this area, the area must behave as border.
+  nonClientSizeMargin.EnsureAtLeast(
+      LayoutDeviceIntMargin(kResizableBorderMinSize, kResizableBorderMinSize,
+                            kResizableBorderMinSize, kResizableBorderMinSize));
+
+  LayoutDeviceIntRect clientRect = winRect;
+  clientRect.Deflate(nonClientSizeMargin);
+
+  const bool allowContentOverride =
+      sizeMode == nsSizeMode_Maximized || clientRect.Contains(point);
+
+  // The border size.  If there is no content under mouse cursor, the border
+  // size should be larger than the values in system settings.  Otherwise,
+  // contents under the mouse cursor should be able to override the behavior.
+  // E.g., user must expect that Firefox button always opens the popup menu
+  // even when the user clicks on the above edge of it.
+  LayoutDeviceIntMargin borderSize = nonClientSizeMargin;
+  borderSize.EnsureAtLeast(
+      LayoutDeviceIntMargin(mVertResizeMargin, mHorResizeMargin,
+                            mVertResizeMargin, mHorResizeMargin));
+
+  bool top = false;
+  bool bottom = false;
+  bool left = false;
+  bool right = false;
+
+  if (point.y >= winRect.y && point.y < winRect.y + borderSize.top) {
+    top = true;
+  } else if (point.y <= winRect.YMost() &&
+             point.y > winRect.YMost() - borderSize.bottom) {
+    bottom = true;
+  }
+
+  // (the 2x case here doubles the resize area for corners)
+  int multiplier = (top || bottom) ? 2 : 1;
+  if (point.x >= winRect.x &&
+      point.x < winRect.x + (multiplier * borderSize.left)) {
+    left = true;
+  } else if (point.x <= winRect.XMost() &&
+             point.x > winRect.XMost() - (multiplier * borderSize.right)) {
+    right = true;
+  }
+
+  bool inResizeRegion = false;
+  if (isResizable) {
+    if (top) {
+      testResult = HTTOP;
+      if (left) {
+        testResult = HTTOPLEFT;
+      } else if (right) {
+        testResult = HTTOPRIGHT;
+      }
+    } else if (bottom) {
+      testResult = HTBOTTOM;
+      if (left) {
+        testResult = HTBOTTOMLEFT;
+      } else if (right) {
+        testResult = HTBOTTOMRIGHT;
+      }
+    } else {
+      if (left) {
+        testResult = HTLEFT;
+      }
+      if (right) {
+        testResult = HTRIGHT;
+      }
+    }
+    inResizeRegion = (testResult != HTCLIENT);
+  } else {
+    if (top) {
+      testResult = HTCAPTION;
+    } else if (bottom || left || right) {
+      testResult = HTBORDER;
+    }
+  }
+
+  if (!sIsInMouseCapture && allowContentOverride) {
+    {
+      POINT pt = {aX, aY};
+      ::ScreenToClient(mWnd, &pt);
+
+      if (pt.x == mCachedHitTestPoint.x.value &&
+          pt.y == mCachedHitTestPoint.y.value &&
+          TimeStamp::Now() - mCachedHitTestTime <
+              TimeDuration::FromMilliseconds(HITTEST_CACHE_LIFETIME_MS)) {
+        return mCachedHitTestResult;
+      }
+
+      mCachedHitTestPoint = {pt.x, pt.y};
+      mCachedHitTestTime = TimeStamp::Now();
+    }
+
+    auto pt = mCachedHitTestPoint;
+
+    if (mWindowBtnRect[WindowButtonType::Minimize].Contains(pt)) {
+      testResult = HTMINBUTTON;
+    } else if (mWindowBtnRect[WindowButtonType::Maximize].Contains(pt)) {
+      testResult = HTMAXBUTTON;
+    } else if (mWindowBtnRect[WindowButtonType::Close].Contains(pt)) {
+      testResult = HTCLOSE;
+    } else if (!inResizeRegion) {
+      // If we're in the resize region, avoid overriding that with either a
+      // drag or a client result; resize takes priority over either (but not
+      // over the window controls, which is why we check this after those).
+      if (mDraggableRegion.Contains(pt)) {
+        testResult = HTCAPTION;
+      } else {
+        testResult = HTCLIENT;
+      }
+    }
+
+    mCachedHitTestResult = testResult;
+  }
+
+  return testResult;
+}
+
+bool nsWindow::IsSimulatedClientArea(int32_t screenX, int32_t screenY) {
+  int32_t testResult = ClientMarginHitTestPoint(screenX, screenY);
+  return testResult == HTCAPTION || IsWindowButton(testResult);
+}
+
+bool nsWindow::IsWindowButton(int32_t hitTestResult) {
+  return hitTestResult == HTMINBUTTON || hitTestResult == HTMAXBUTTON ||
+         hitTestResult == HTCLOSE;
+}
+
+TimeStamp nsWindow::GetMessageTimeStamp(LONG aEventTime) const {
+  CurrentWindowsTimeGetter getCurrentTime(mWnd);
+  return TimeConverter().GetTimeStampFromSystemTime(aEventTime, getCurrentTime);
+}
+
+void nsWindow::PostSleepWakeNotification(const bool aIsSleepMode) {
+  // Retain the previous mode that was notified to observers
+  static bool sWasSleepMode = false;
+
+  // Only notify observers if mode changed
+  if (aIsSleepMode == sWasSleepMode) return;
+
+  sWasSleepMode = aIsSleepMode;
+
+  nsCOMPtr<nsIObserverService> observerService =
+      mozilla::services::GetObserverService();
+  if (observerService)
+    observerService->NotifyObservers(nullptr,
+                                     aIsSleepMode
+                                         ? NS_WIDGET_SLEEP_OBSERVER_TOPIC
+                                         : NS_WIDGET_WAKE_OBSERVER_TOPIC,
+                                     nullptr);
+}
+
+LRESULT nsWindow::ProcessCharMessage(const MSG& aMsg, bool* aEventDispatched) {
+  if (IMEHandler::IsComposingOn(this)) {
+    IMEHandler::NotifyIME(this, REQUEST_TO_COMMIT_COMPOSITION);
+  }
+  // These must be checked here too as a lone WM_CHAR could be received
+  // if a child window didn't handle it (for example Alt+Space in a content
+  // window)
+  ModifierKeyState modKeyState;
+  NativeKey nativeKey(this, aMsg, modKeyState);
+  return static_cast<LRESULT>(nativeKey.HandleCharMessage(aEventDispatched));
+}
+
+LRESULT nsWindow::ProcessKeyUpMessage(const MSG& aMsg, bool* aEventDispatched) {
+  ModifierKeyState modKeyState;
+  NativeKey nativeKey(this, aMsg, modKeyState);
+  bool result = nativeKey.HandleKeyUpMessage(aEventDispatched);
+  if (aMsg.wParam == VK_F10) {
+    // Bug 1382199: Windows default behavior will trigger the System menu bar
+    // when F10 is released. Among other things, this causes the System menu bar
+    // to appear when a web page overrides the contextmenu event. We *never*
+    // want this default behavior, so eat this key (never pass it to Windows).
+    return true;
+  }
+  return result;
+}
+
+LRESULT nsWindow::ProcessKeyDownMessage(const MSG& aMsg,
+                                        bool* aEventDispatched) {
+  // If this method doesn't call NativeKey::HandleKeyDownMessage(), this method
+  // must clean up the redirected message information itself.  For more
+  // information, see above comment of
+  // RedirectedKeyDownMessageManager::AutoFlusher class definition in
+  // KeyboardLayout.h.
+  RedirectedKeyDownMessageManager::AutoFlusher redirectedMsgFlusher(this, aMsg);
+
+  ModifierKeyState modKeyState;
+
+  NativeKey nativeKey(this, aMsg, modKeyState);
+  LRESULT result =
+      static_cast<LRESULT>(nativeKey.HandleKeyDownMessage(aEventDispatched));
+  // HandleKeyDownMessage cleaned up the redirected message information
+  // itself, so, we should do nothing.
+  redirectedMsgFlusher.Cancel();
+
+  if (aMsg.wParam == VK_MENU ||
+      (aMsg.wParam == VK_F10 && !modKeyState.IsShift())) {
+    // We need to let Windows handle this keypress,
+    // by returning false, if there's a native menu
+    // bar somewhere in our containing window hierarchy.
+    // Otherwise we handle the keypress and don't pass
+    // it on to Windows, by returning true.
+    bool hasNativeMenu = false;
+    HWND hWnd = mWnd;
+    while (hWnd) {
+      if (::GetMenu(hWnd)) {
+        hasNativeMenu = true;
+        break;
+      }
+      hWnd = ::GetParent(hWnd);
+    }
+    result = !hasNativeMenu;
+  }
+
+  return result;
+}
+
+nsresult nsWindow::SynthesizeNativeKeyEvent(
+    int32_t aNativeKeyboardLayout, int32_t aNativeKeyCode,
+    uint32_t aModifierFlags, const nsAString& aCharacters,
+    const nsAString& aUnmodifiedCharacters, nsIObserver* aObserver) {
+  AutoObserverNotifier notifier(aObserver, "keyevent");
+
+  KeyboardLayout* keyboardLayout = KeyboardLayout::GetInstance();
+  return keyboardLayout->SynthesizeNativeKeyEvent(
+      this, aNativeKeyboardLayout, aNativeKeyCode, aModifierFlags, aCharacters,
+      aUnmodifiedCharacters);
+}
+
+nsresult nsWindow::SynthesizeNativeMouseEvent(
+    LayoutDeviceIntPoint aPoint, NativeMouseMessage aNativeMessage,
+    MouseButton aButton, nsIWidget::Modifiers aModifierFlags,
+    nsIObserver* aObserver) {
+  AutoObserverNotifier notifier(aObserver, "mouseevent");
+
+  INPUT input;
+  memset(&input, 0, sizeof(input));
+
+  // TODO (bug 1693240):
+  // Now, we synthesize native mouse events asynchronously since we want to
+  // synthesize the event on the front window at the point. However, Windows
+  // does not provide a way to set modifier only while a mouse message is
+  // being handled, and MOUSEEVENTF_MOVE may be coalesced by Windows.  So, we
+  // need a trick for handling it.
+
+  switch (aNativeMessage) {
+    case NativeMouseMessage::Move:
+      input.mi.dwFlags = MOUSEEVENTF_MOVE;
+      // Reset sLastMouseMovePoint so that even if we're moving the mouse
+      // to the position it's already at, we still dispatch a mousemove
+      // event, because the callers of this function expect that.
+      sLastMouseMovePoint = {0};
+      break;
+    case NativeMouseMessage::ButtonDown:
+    case NativeMouseMessage::ButtonUp: {
+      const bool isDown = aNativeMessage == NativeMouseMessage::ButtonDown;
+      switch (aButton) {
+        case MouseButton::ePrimary:
+          input.mi.dwFlags = isDown ? MOUSEEVENTF_LEFTDOWN : MOUSEEVENTF_LEFTUP;
+          break;
+        case MouseButton::eMiddle:
+          input.mi.dwFlags =
+              isDown ? MOUSEEVENTF_MIDDLEDOWN : MOUSEEVENTF_MIDDLEUP;
+          break;
+        case MouseButton::eSecondary:
+          input.mi.dwFlags =
+              isDown ? MOUSEEVENTF_RIGHTDOWN : MOUSEEVENTF_RIGHTUP;
+          break;
+        case MouseButton::eX1:
+          input.mi.dwFlags = isDown ? MOUSEEVENTF_XDOWN : MOUSEEVENTF_XUP;
+          input.mi.mouseData = XBUTTON1;
+          break;
+        case MouseButton::eX2:
+          input.mi.dwFlags = isDown ? MOUSEEVENTF_XDOWN : MOUSEEVENTF_XUP;
+          input.mi.mouseData = XBUTTON2;
+          break;
+        default:
+          return NS_ERROR_INVALID_ARG;
+      }
+      break;
+    }
+    case NativeMouseMessage::EnterWindow:
+    case NativeMouseMessage::LeaveWindow:
+      MOZ_ASSERT_UNREACHABLE("Non supported mouse event on Windows");
+      return NS_ERROR_INVALID_ARG;
+  }
+
+  input.type = INPUT_MOUSE;
+  ::SetCursorPos(aPoint.x, aPoint.y);
+  ::SendInput(1, &input, sizeof(INPUT));
+
+  return NS_OK;
+}
+
+nsresult nsWindow::SynthesizeNativeMouseScrollEvent(
+    LayoutDeviceIntPoint aPoint, uint32_t aNativeMessage, double aDeltaX,
+    double aDeltaY, double aDeltaZ, uint32_t aModifierFlags,
+    uint32_t aAdditionalFlags, nsIObserver* aObserver) {
+  AutoObserverNotifier notifier(aObserver, "mousescrollevent");
+  return MouseScrollHandler::SynthesizeNativeMouseScrollEvent(
+      this, aPoint, aNativeMessage,
+      (aNativeMessage == WM_MOUSEWHEEL || aNativeMessage == WM_VSCROLL)
+          ? static_cast<int32_t>(aDeltaY)
+          : static_cast<int32_t>(aDeltaX),
+      aModifierFlags, aAdditionalFlags);
+}
+
+nsresult nsWindow::SynthesizeNativeTouchpadPan(TouchpadGesturePhase aEventPhase,
+                                               LayoutDeviceIntPoint aPoint,
+                                               double aDeltaX, double aDeltaY,
+                                               int32_t aModifierFlags,
+                                               nsIObserver* aObserver) {
+  AutoObserverNotifier notifier(aObserver, "touchpadpanevent");
+  DirectManipulationOwner::SynthesizeNativeTouchpadPan(
+      this, aEventPhase, aPoint, aDeltaX, aDeltaY, aModifierFlags);
+  return NS_OK;
+}
+
+static void MaybeLogPosChanged(HWND aWnd, WINDOWPOS* wp) {
+#ifdef WINSTATE_DEBUG_OUTPUT
+  if (aWnd == WinUtils::GetTopLevelHWND(aWnd)) {
+    MOZ_LOG(gWindowsLog, LogLevel::Info, ("*** OnWindowPosChanged: [  top] "));
+  } else {
+    MOZ_LOG(gWindowsLog, LogLevel::Info, ("*** OnWindowPosChanged: [child] "));
+  }
+  MOZ_LOG(gWindowsLog, LogLevel::Info, ("WINDOWPOS flags:"));
+  if (wp->flags & SWP_FRAMECHANGED) {
+    MOZ_LOG(gWindowsLog, LogLevel::Info, ("SWP_FRAMECHANGED "));
+  }
+  if (wp->flags & SWP_SHOWWINDOW) {
+    MOZ_LOG(gWindowsLog, LogLevel::Info, ("SWP_SHOWWINDOW "));
+  }
+  if (wp->flags & SWP_NOSIZE) {
+    MOZ_LOG(gWindowsLog, LogLevel::Info, ("SWP_NOSIZE "));
+  }
+  if (wp->flags & SWP_HIDEWINDOW) {
+    MOZ_LOG(gWindowsLog, LogLevel::Info, ("SWP_HIDEWINDOW "));
+  }
+  if (wp->flags & SWP_NOZORDER) {
+    MOZ_LOG(gWindowsLog, LogLevel::Info, ("SWP_NOZORDER "));
+  }
+  if (wp->flags & SWP_NOACTIVATE) {
+    MOZ_LOG(gWindowsLog, LogLevel::Info, ("SWP_NOACTIVATE "));
+  }
+  MOZ_LOG(gWindowsLog, LogLevel::Info, ("\n"));
+#endif
+}
+
+/**************************************************************
+ *
+ * SECTION: OnXXX message handlers
+ *
+ * For message handlers that need to be broken out or
+ * implemented in specific platform code.
+ *
+ **************************************************************/
+
+void nsWindow::OnWindowPosChanged(WINDOWPOS* wp) {
+  if (!wp) {
+    return;
+  }
+
+  MaybeLogPosChanged(mWnd, wp);
+
+  // Handle window size mode changes
+  if (wp->flags & SWP_FRAMECHANGED) {
+    // Bug 566135 - Windows theme code calls show window on SW_SHOWMINIMIZED
+    // windows when fullscreen games disable desktop composition. If we're
+    // minimized and not being activated, ignore the event and let windows
+    // handle it.
+    if (mFrameState->GetSizeMode() == nsSizeMode_Minimized &&
+        (wp->flags & SWP_NOACTIVATE)) {
+      return;
+    }
+
+    mFrameState->OnFrameChanged();
+
+    if (mFrameState->GetSizeMode() == nsSizeMode_Minimized) {
+      // Skip window size change events below on minimization.
+      return;
+    }
+  }
+
+  // Notify visibility change when window is activated.
+  if (!(wp->flags & SWP_NOACTIVATE) && NeedsToTrackWindowOcclusionState()) {
+    WinWindowOcclusionTracker::Get()->OnWindowVisibilityChanged(
+        this, mFrameState->GetSizeMode() != nsSizeMode_Minimized);
+  }
+
+  // Handle window position changes
+  if (!(wp->flags & SWP_NOMOVE)) {
+    mBounds.MoveTo(wp->x, wp->y);
+    NotifyWindowMoved(wp->x, wp->y);
+  }
+
+  // Handle window size changes
+  if (!(wp->flags & SWP_NOSIZE)) {
+    RECT r;
+    int32_t newWidth, newHeight;
+
+    ::GetWindowRect(mWnd, &r);
+
+    newWidth = r.right - r.left;
+    newHeight = r.bottom - r.top;
+
+    if (newWidth > mLastSize.width) {
+      RECT drect;
+
+      // getting wider
+      drect.left = wp->x + mLastSize.width;
+      drect.top = wp->y;
+      drect.right = drect.left + (newWidth - mLastSize.width);
+      drect.bottom = drect.top + newHeight;
+
+      ::RedrawWindow(mWnd, &drect, nullptr,
+                     RDW_INVALIDATE | RDW_NOERASE | RDW_NOINTERNALPAINT |
+                         RDW_ERASENOW | RDW_ALLCHILDREN);
+    }
+    if (newHeight > mLastSize.height) {
+      RECT drect;
+
+      // getting taller
+      drect.left = wp->x;
+      drect.top = wp->y + mLastSize.height;
+      drect.right = drect.left + newWidth;
+      drect.bottom = drect.top + (newHeight - mLastSize.height);
+
+      ::RedrawWindow(mWnd, &drect, nullptr,
+                     RDW_INVALIDATE | RDW_NOERASE | RDW_NOINTERNALPAINT |
+                         RDW_ERASENOW | RDW_ALLCHILDREN);
+    }
+
+    mBounds.SizeTo(newWidth, newHeight);
+    mLastSize.width = newWidth;
+    mLastSize.height = newHeight;
+
+#ifdef WINSTATE_DEBUG_OUTPUT
+    MOZ_LOG(gWindowsLog, LogLevel::Info,
+            ("*** Resize window: %d x %d x %d x %d\n", wp->x, wp->y, newWidth,
+             newHeight));
+#endif
+
+    if (mAspectRatio > 0) {
+      // It's possible (via Windows Aero Snap) that the size of the window
+      // has changed such that it violates the aspect ratio constraint. If so,
+      // queue up an event to enforce the aspect ratio constraint and repaint.
+      // When resized with Windows Aero Snap, we are in the NOT_RESIZING state.
+      float newAspectRatio = (float)newWidth / newHeight;
+      if (mResizeState == NOT_RESIZING && mAspectRatio != newAspectRatio) {
+        // Hold a reference to self alive and pass it into the lambda to make
+        // sure this nsIWidget stays alive long enough to run this function.
+        nsCOMPtr<nsIWidget> self(this);
+        NS_DispatchToMainThread(NS_NewRunnableFunction(
+            "EnforceAspectRatio", [self, this, newWidth]() -> void {
+              if (mWnd) {
+                Resize(newWidth, newWidth / mAspectRatio, true);
+              }
+            }));
+      }
+    }
+
+    // If a maximized window is resized, recalculate the non-client margins.
+    if (mFrameState->GetSizeMode() == nsSizeMode_Maximized) {
+      if (UpdateNonClientMargins(true)) {
+        // gecko resize event already sent by UpdateNonClientMargins.
+        return;
+      }
+    }
+  }
+
+  // Notify the widget listener for size change of client area for gecko
+  // events. This needs to be done when either window size is changed,
+  // or window frame is changed. They may not happen together.
+  // However, we don't invoke that for popup when window frame changes,
+  // because popups may trigger frame change before size change via
+  // {Set,Clear}ThemeRegion they invoke in Resize. That would make the
+  // code below call OnResize with a wrong client size first, which can
+  // lead to flickerling for some popups.
+  if (!(wp->flags & SWP_NOSIZE) ||
+      ((wp->flags & SWP_FRAMECHANGED) && !IsPopup())) {
+    RECT r;
+    LayoutDeviceIntSize clientSize;
+    if (::GetClientRect(mWnd, &r)) {
+      clientSize = WinUtils::ToIntRect(r).Size();
+    } else {
+      clientSize = mBounds.Size();
+    }
+    // Send a gecko resize event
+    OnResize(clientSize);
+  }
+}
+
+void nsWindow::OnWindowPosChanging(WINDOWPOS* info) {
+  // Update non-client margins if the frame size is changing, and let the
+  // browser know we are changing size modes, so alternative css can kick in.
+  // If we're going into fullscreen mode, ignore this, since it'll reset
+  // margins to normal mode.
+  if (info->flags & SWP_FRAMECHANGED && !(info->flags & SWP_NOSIZE)) {
+    mFrameState->OnFrameChanging();
+  }
+
+  // Force fullscreen. This works around a bug in Windows 10 1809 where
+  // using fullscreen when a window is "snapped" causes a spurious resize
+  // smaller than the full screen, see bug 1482920.
+  if (mFrameState->GetSizeMode() == nsSizeMode_Fullscreen &&
+      !(info->flags & SWP_NOMOVE) && !(info->flags & SWP_NOSIZE)) {
+    nsCOMPtr<nsIScreenManager> screenmgr =
+        do_GetService(sScreenManagerContractID);
+    if (screenmgr) {
+      LayoutDeviceIntRect bounds(info->x, info->y, info->cx, info->cy);
+      DesktopIntRect deskBounds =
+          RoundedToInt(bounds / GetDesktopToDeviceScale());
+      nsCOMPtr<nsIScreen> screen;
+      screenmgr->ScreenForRect(deskBounds.X(), deskBounds.Y(),
+                               deskBounds.Width(), deskBounds.Height(),
+                               getter_AddRefs(screen));
+
+      if (screen) {
+        auto rect = screen->GetRect();
+        info->x = rect.x;
+        info->y = rect.y;
+        info->cx = rect.width;
+        info->cy = rect.height;
+      }
+    }
+  }
+
+  // enforce local z-order rules
+  if (!(info->flags & SWP_NOZORDER)) {
+    HWND hwndAfter = info->hwndInsertAfter;
+
+    nsWindow* aboveWindow = 0;
+    nsWindowZ placement;
+
+    if (hwndAfter == HWND_BOTTOM)
+      placement = nsWindowZBottom;
+    else if (hwndAfter == HWND_TOP || hwndAfter == HWND_TOPMOST ||
+             hwndAfter == HWND_NOTOPMOST)
+      placement = nsWindowZTop;
+    else {
+      placement = nsWindowZRelative;
+      aboveWindow = WinUtils::GetNSWindowPtr(hwndAfter);
+    }
+
+    if (mWidgetListener) {
+      nsCOMPtr<nsIWidget> actualBelow = nullptr;
+      if (mWidgetListener->ZLevelChanged(false, &placement, aboveWindow,
+                                         getter_AddRefs(actualBelow))) {
+        if (placement == nsWindowZBottom)
+          info->hwndInsertAfter = HWND_BOTTOM;
+        else if (placement == nsWindowZTop)
+          info->hwndInsertAfter = HWND_TOP;
+        else {
+          info->hwndInsertAfter =
+              (HWND)actualBelow->GetNativeData(NS_NATIVE_WINDOW);
+        }
+      }
+    }
+  }
+  // prevent rude external programs from making hidden window visible
+  if (mWindowType == WindowType::Invisible) info->flags &= ~SWP_SHOWWINDOW;
+
+  // When waking from sleep or switching out of tablet mode, Windows 10
+  // Version 1809 will reopen popup windows that should be hidden. Detect
+  // this case and refuse to show the window.
+  static bool sDWMUnhidesPopups = IsWin10Sep2018UpdateOrLater();
+  if (sDWMUnhidesPopups && (info->flags & SWP_SHOWWINDOW) &&
+      mWindowType == WindowType::Popup && mWidgetListener &&
+      mWidgetListener->ShouldNotBeVisible()) {
+    info->flags &= ~SWP_SHOWWINDOW;
+  }
+}
+
+void nsWindow::UserActivity() {
+  // Check if we have the idle service, if not we try to get it.
+  if (!mIdleService) {
+    mIdleService = do_GetService("@mozilla.org/widget/useridleservice;1");
+  }
+
+  // Check that we now have the idle service.
+  if (mIdleService) {
+    mIdleService->ResetIdleTimeOut(0);
+  }
+}
+
+// Helper function for TouchDeviceNeedsPanGestureConversion(PTOUCHINPUT,
+// uint32_t).
+static bool TouchDeviceNeedsPanGestureConversion(HANDLE aSource) {
+  std::string deviceName;
+  UINT dataSize = 0;
+  // The first call just queries how long the name string will be.
+  GetRawInputDeviceInfoA(aSource, RIDI_DEVICENAME, nullptr, &dataSize);
+  if (!dataSize || dataSize > 0x10000) {
+    return false;
+  }
+  deviceName.resize(dataSize);
+  // The second call actually populates the string.
+  UINT result = GetRawInputDeviceInfoA(aSource, RIDI_DEVICENAME, &deviceName[0],
+                                       &dataSize);
+  if (result == UINT_MAX) {
+    return false;
+  }
+  // The affected device name is "\\?\VIRTUAL_DIGITIZER", but each backslash
+  // needs to be escaped with another one.
+  std::string expectedDeviceName = "\\\\?\\VIRTUAL_DIGITIZER";
+  // For some reason, the dataSize returned by the first call is double the
+  // actual length of the device name (as if it were returning the size of a
+  // wide-character string in bytes) even though we are using the narrow
+  // version of the API. For the comparison against the expected device name
+  // to pass, we truncate the buffer to be no longer tha the expected device
+  // name.
+  if (deviceName.substr(0, expectedDeviceName.length()) != expectedDeviceName) {
+    return false;
+  }
+
+  RID_DEVICE_INFO deviceInfo;
+  deviceInfo.cbSize = sizeof(deviceInfo);
+  dataSize = sizeof(deviceInfo);
+  result =
+      GetRawInputDeviceInfoA(aSource, RIDI_DEVICEINFO, &deviceInfo, &dataSize);
+  if (result == UINT_MAX) {
+    return false;
+  }
+  // The device identifiers that we check for here come from bug 1355162
+  // comment 1 (see also bug 1511901 comment 35).
+  return deviceInfo.dwType == RIM_TYPEHID && deviceInfo.hid.dwVendorId == 0 &&
+         deviceInfo.hid.dwProductId == 0 &&
+         deviceInfo.hid.dwVersionNumber == 1 &&
+         deviceInfo.hid.usUsagePage == 13 && deviceInfo.hid.usUsage == 4;
+}
+
+// Determine if the touch device that originated |aOSEvent| needs to have
+// touch events representing a two-finger gesture converted to pan
+// gesture events.
+// We only do this for touch devices with a specific name and identifiers.
+static bool TouchDeviceNeedsPanGestureConversion(PTOUCHINPUT aOSEvent,
+                                                 uint32_t aTouchCount) {
+  if (!StaticPrefs::apz_windows_check_for_pan_gesture_conversion()) {
+    return false;
+  }
+  if (aTouchCount == 0) {
+    return false;
+  }
+  HANDLE source = aOSEvent[0].hSource;
+
+  // Cache the result of this computation for each touch device.
+  // Touch devices are identified by the HANDLE stored in the hSource
+  // field of TOUCHINPUT.
+  static std::map<HANDLE, bool> sResultCache;
+  auto [iter, inserted] = sResultCache.emplace(source, false);
+  if (inserted) {
+    iter->second = TouchDeviceNeedsPanGestureConversion(source);
+  }
+  return iter->second;
+}
+
+Maybe<PanGestureInput> nsWindow::ConvertTouchToPanGesture(
+    const MultiTouchInput& aTouchInput, PTOUCHINPUT aOSEvent) {
+  // Checks if the touch device that originated the touch event is one
+  // for which we want to convert the touch events to pang gesture events.
+  bool shouldConvert = TouchDeviceNeedsPanGestureConversion(
+      aOSEvent, aTouchInput.mTouches.Length());
+  if (!shouldConvert) {
+    return Nothing();
+  }
+
+  // Only two-finger gestures need conversion.
+  if (aTouchInput.mTouches.Length() != 2) {
+    return Nothing();
+  }
+
+  PanGestureInput::PanGestureType eventType = PanGestureInput::PANGESTURE_PAN;
+  if (aTouchInput.mType == MultiTouchInput::MULTITOUCH_START) {
+    eventType = PanGestureInput::PANGESTURE_START;
+  } else if (aTouchInput.mType == MultiTouchInput::MULTITOUCH_END) {
+    eventType = PanGestureInput::PANGESTURE_END;
+  } else if (aTouchInput.mType == MultiTouchInput::MULTITOUCH_CANCEL) {
+    eventType = PanGestureInput::PANGESTURE_CANCELLED;
+  }
+
+  // Use the midpoint of the two touches as the start point of the pan gesture.
+  ScreenPoint focusPoint = (aTouchInput.mTouches[0].mScreenPoint +
+                            aTouchInput.mTouches[1].mScreenPoint) /
+                           2;
+  // To compute the displacement of the pan gesture, we keep track of the
+  // location of the previous event.
+  ScreenPoint displacement = (eventType == PanGestureInput::PANGESTURE_START)
+                                 ? ScreenPoint(0, 0)
+                                 : (focusPoint - mLastPanGestureFocus);
+  mLastPanGestureFocus = focusPoint;
+
+  // We need to negate the displacement because for a touch event, moving the
+  // fingers down results in scrolling up, but for a touchpad gesture, we want
+  // moving the fingers down to result in scrolling down.
+  PanGestureInput result(eventType, aTouchInput.mTimeStamp, focusPoint,
+                         -displacement, aTouchInput.modifiers);
+  result.mSimulateMomentum = true;
+
+  return Some(result);
+}
+
+// Dispatch an event that originated as an OS touch event.
+// Usually, we want to dispatch it as a touch event, but some touchpads
+// produce touch events for two-finger scrolling, which need to be converted
+// to pan gesture events for correct behaviour.
+void nsWindow::DispatchTouchOrPanGestureInput(MultiTouchInput& aTouchInput,
+                                              PTOUCHINPUT aOSEvent) {
+  if (Maybe<PanGestureInput> panInput =
+          ConvertTouchToPanGesture(aTouchInput, aOSEvent)) {
+    DispatchPanGestureInput(*panInput);
+    return;
+  }
+
+  DispatchTouchInput(aTouchInput);
+}
+
+bool nsWindow::OnTouch(WPARAM wParam, LPARAM lParam) {
+  uint32_t cInputs = LOWORD(wParam);
+  PTOUCHINPUT pInputs = new TOUCHINPUT[cInputs];
+
+  if (GetTouchInputInfo((HTOUCHINPUT)lParam, cInputs, pInputs,
+                        sizeof(TOUCHINPUT))) {
+    MultiTouchInput touchInput, touchEndInput;
+
+    // Walk across the touch point array processing each contact point.
+    for (uint32_t i = 0; i < cInputs; i++) {
+      bool addToEvent = false, addToEndEvent = false;
+
+      // N.B.: According with MS documentation
+      // https://msdn.microsoft.com/en-us/library/windows/desktop/dd317334(v=vs.85).aspx
+      // TOUCHEVENTF_DOWN cannot be combined with TOUCHEVENTF_MOVE or
+      // TOUCHEVENTF_UP.  Possibly, it means that TOUCHEVENTF_MOVE and
+      // TOUCHEVENTF_UP can be combined together.
+
+      if (pInputs[i].dwFlags & (TOUCHEVENTF_DOWN | TOUCHEVENTF_MOVE)) {
+        if (touchInput.mTimeStamp.IsNull()) {
+          // Initialize a touch event to send.
+          touchInput.mType = MultiTouchInput::MULTITOUCH_MOVE;
+          touchInput.mTimeStamp = GetMessageTimeStamp(::GetMessageTime());
+          ModifierKeyState modifierKeyState;
+          touchInput.modifiers = modifierKeyState.GetModifiers();
+        }
+        // Pres shell expects this event to be a eTouchStart
+        // if any new contact points have been added since the last event sent.
+        if (pInputs[i].dwFlags & TOUCHEVENTF_DOWN) {
+          touchInput.mType = MultiTouchInput::MULTITOUCH_START;
+        }
+        addToEvent = true;
+      }
+      if (pInputs[i].dwFlags & TOUCHEVENTF_UP) {
+        // Pres shell expects removed contacts points to be delivered in a
+        // separate eTouchEnd event containing only the contact points that were
+        // removed.
+        if (touchEndInput.mTimeStamp.IsNull()) {
+          // Initialize a touch event to send.
+          touchEndInput.mType = MultiTouchInput::MULTITOUCH_END;
+          touchEndInput.mTimeStamp = GetMessageTimeStamp(::GetMessageTime());
+          ModifierKeyState modifierKeyState;
+          touchEndInput.modifiers = modifierKeyState.GetModifiers();
+        }
+        addToEndEvent = true;
+      }
+      if (!addToEvent && !addToEndEvent) {
+        // Filter out spurious Windows events we don't understand, like palm
+        // contact.
+        continue;
+      }
+
+      // Setup the touch point we'll append to the touch event array.
+      nsPointWin touchPoint;
+      touchPoint.x = TOUCH_COORD_TO_PIXEL(pInputs[i].x);
+      touchPoint.y = TOUCH_COORD_TO_PIXEL(pInputs[i].y);
+      touchPoint.ScreenToClient(mWnd);
+
+      // Initialize the touch data.
+      SingleTouchData touchData(
+          pInputs[i].dwID,                               // aIdentifier
+          ScreenIntPoint::FromUnknownPoint(touchPoint),  // aScreenPoint
+          // The contact area info cannot be trusted even when
+          // TOUCHINPUTMASKF_CONTACTAREA is set when the input source is pen,
+          // which somehow violates the API docs. (bug 1710509) Ultimately the
+          // dwFlags check will become redundant since we want to migrate to
+          // WM_POINTER for pens. (bug 1707075)
+          (pInputs[i].dwMask & TOUCHINPUTMASKF_CONTACTAREA) &&
+                  !(pInputs[i].dwFlags & TOUCHEVENTF_PEN)
+              ? ScreenSize(TOUCH_COORD_TO_PIXEL(pInputs[i].cxContact) / 2,
+                           TOUCH_COORD_TO_PIXEL(pInputs[i].cyContact) / 2)
+              : ScreenSize(1, 1),  // aRadius
+          0.0f,                    // aRotationAngle
+          0.0f);                   // aForce
+
+      // Append touch data to the appropriate event.
+      if (addToEvent) {
+        touchInput.mTouches.AppendElement(touchData);
+      }
+      if (addToEndEvent) {
+        touchEndInput.mTouches.AppendElement(touchData);
+      }
+    }
+
+    // Dispatch touch start and touch move event if we have one.
+    if (!touchInput.mTimeStamp.IsNull()) {
+      DispatchTouchOrPanGestureInput(touchInput, pInputs);
+    }
+    // Dispatch touch end event if we have one.
+    if (!touchEndInput.mTimeStamp.IsNull()) {
+      DispatchTouchOrPanGestureInput(touchEndInput, pInputs);
+    }
+  }
+
+  delete[] pInputs;
+  CloseTouchInputHandle((HTOUCHINPUT)lParam);
+  return true;
+}
+
+// Gesture event processing. Handles WM_GESTURE events.
+bool nsWindow::OnGesture(WPARAM wParam, LPARAM lParam) {
+  // Treatment for pan events which translate into scroll events:
+  if (mGesture.IsPanEvent(lParam)) {
+    if (!mGesture.ProcessPanMessage(mWnd, wParam, lParam))
+      return false;  // ignore
+
+    nsEventStatus status;
+
+    WidgetWheelEvent wheelEvent(true, eWheel, this);
+
+    ModifierKeyState modifierKeyState;
+    modifierKeyState.InitInputEvent(wheelEvent);
+
+    wheelEvent.mButton = 0;
+    wheelEvent.mTimeStamp = GetMessageTimeStamp(::GetMessageTime());
+    wheelEvent.mInputSource = MouseEvent_Binding::MOZ_SOURCE_TOUCH;
+
+    bool endFeedback = true;
+
+    if (mGesture.PanDeltaToPixelScroll(wheelEvent)) {
+      DispatchEvent(&wheelEvent, status);
+    }
+
+    if (mDisplayPanFeedback) {
+      mGesture.UpdatePanFeedbackX(
+          mWnd, DeprecatedAbs(RoundDown(wheelEvent.mOverflowDeltaX)),
+          endFeedback);
+      mGesture.UpdatePanFeedbackY(
+          mWnd, DeprecatedAbs(RoundDown(wheelEvent.mOverflowDeltaY)),
+          endFeedback);
+      mGesture.PanFeedbackFinalize(mWnd, endFeedback);
+    }
+
+    CloseGestureInfoHandle((HGESTUREINFO)lParam);
+
+    return true;
+  }
+
+  // Other gestures translate into simple gesture events:
+  WidgetSimpleGestureEvent event(true, eVoidEvent, this);
+  if (!mGesture.ProcessGestureMessage(mWnd, wParam, lParam, event)) {
+    return false;  // fall through to DefWndProc
+  }
+
+  // Polish up and send off the new event
+  ModifierKeyState modifierKeyState;
+  modifierKeyState.InitInputEvent(event);
+  event.mButton = 0;
+  event.mTimeStamp = GetMessageTimeStamp(::GetMessageTime());
+  event.mInputSource = MouseEvent_Binding::MOZ_SOURCE_TOUCH;
+
+  nsEventStatus status;
+  DispatchEvent(&event, status);
+  if (status == nsEventStatus_eIgnore) {
+    return false;  // Ignored, fall through
+  }
+
+  // Only close this if we process and return true.
+  CloseGestureInfoHandle((HGESTUREINFO)lParam);
+
+  return true;  // Handled
+}
+
+// WM_DESTROY event handler
+void nsWindow::OnDestroy() {
+  mOnDestroyCalled = true;
+
+  // If this is a toplevel window, notify the taskbar concealer to clean up any
+  // relevant state.
+  if (!mParent) {
+    TaskbarConcealer::OnWindowDestroyed(mWnd);
+  }
+
+  // Make sure we don't get destroyed in the process of tearing down.
+  nsCOMPtr<nsIWidget> kungFuDeathGrip(this);
+
+  // Dispatch the destroy notification.
+  if (!mInDtor) NotifyWindowDestroyed();
+
+  // Prevent the widget from sending additional events.
+  mWidgetListener = nullptr;
+  mAttachedWidgetListener = nullptr;
+
+  DestroyDirectManipulation();
+
+  if (mWnd == mLastKillFocusWindow) {
+    mLastKillFocusWindow = nullptr;
+  }
+  // Unregister notifications from terminal services
+  ::WTSUnRegisterSessionNotification(mWnd);
+
+  // We will stop receiving native events after dissociating from our native
+  // window. We will also disappear from the output of WinUtils::GetNSWindowPtr
+  // for that window.
+  DissociateFromNativeWindow();
+
+  // Once mWidgetListener is cleared and the subclass is reset, sCurrentWindow
+  // can be cleared. (It's used in tracking windows for mouse events.)
+  if (sCurrentWindow == this) sCurrentWindow = nullptr;
+
+  // Disconnects us from our parent, will call our GetParent().
+  nsBaseWidget::Destroy();
+
+  // Release references to children, device context, toolkit, and app shell.
+  nsBaseWidget::OnDestroy();
+
+  // Clear our native parent handle.
+  // XXX Windows will take care of this in the proper order, and
+  // SetParent(nullptr)'s remove child on the parent already took place in
+  // nsBaseWidget's Destroy call above.
+  // SetParent(nullptr);
+  mParent = nullptr;
+
+  // We have to destroy the native drag target before we null out our window
+  // pointer.
+  EnableDragDrop(false);
+
+  // If we're going away and for some reason we're still the rollup widget,
+  // rollup and turn off capture.
+  nsIRollupListener* rollupListener = nsBaseWidget::GetActiveRollupListener();
+  nsCOMPtr<nsIWidget> rollupWidget;
+  if (rollupListener) {
+    rollupWidget = rollupListener->GetRollupWidget();
+  }
+  if (this == rollupWidget) {
+    rollupListener->Rollup({});
+    CaptureRollupEvents(false);
+  }
+
+  IMEHandler::OnDestroyWindow(this);
+
+  // Free GDI window class objects
+  if (mBrush) {
+    VERIFY(::DeleteObject(mBrush));
+    mBrush = nullptr;
+  }
+
+  // Destroy any custom cursor resources.
+  if (mCursor.IsCustom()) {
+    SetCursor(Cursor{eCursor_standard});
+  }
+
+  if (mCompositorWidgetDelegate) {
+    mCompositorWidgetDelegate->OnDestroyWindow();
+  }
+  mBasicLayersSurface = nullptr;
+
+  // Finalize panning feedback to possibly restore window displacement
+  mGesture.PanFeedbackFinalize(mWnd, true);
+
+  // Clear the main HWND.
+  mWnd = nullptr;
+}
+
+// Send a resize message to the listener
+bool nsWindow::OnResize(const LayoutDeviceIntSize& aSize) {
+  if (mCompositorWidgetDelegate &&
+      !mCompositorWidgetDelegate->OnWindowResize(aSize)) {
+    return false;
+  }
+
+  bool result = false;
+  if (mWidgetListener) {
+    result = mWidgetListener->WindowResized(this, aSize.width, aSize.height);
+  }
+
+  // If there is an attached view, inform it as well as the normal widget
+  // listener.
+  if (mAttachedWidgetListener) {
+    return mAttachedWidgetListener->WindowResized(this, aSize.width,
+                                                  aSize.height);
+  }
+
+  return result;
+}
+
+void nsWindow::OnSizeModeChange() {
+  const nsSizeMode mode = mFrameState->GetSizeMode();
+
+  MOZ_LOG(gWindowsLog, LogLevel::Info,
+          ("nsWindow::OnSizeModeChange() sizeMode %d", mode));
+
+  if (NeedsToTrackWindowOcclusionState()) {
+    WinWindowOcclusionTracker::Get()->OnWindowVisibilityChanged(
+        this, mode != nsSizeMode_Minimized);
+
+    wr::DebugFlags flags{0};
+    flags._0 = gfx::gfxVars::WebRenderDebugFlags();
+    bool debugEnabled = bool(flags & wr::DebugFlags::WINDOW_VISIBILITY_DBG);
+    if (debugEnabled && mCompositorWidgetDelegate) {
+      mCompositorWidgetDelegate->NotifyVisibilityUpdated(mode,
+                                                         mIsFullyOccluded);
+    }
+  }
+
+  if (mCompositorWidgetDelegate) {
+    mCompositorWidgetDelegate->OnWindowModeChange(mode);
+  }
+
+  if (mWidgetListener) {
+    mWidgetListener->SizeModeChanged(mode);
+  }
+}
+
+bool nsWindow::OnHotKey(WPARAM wParam, LPARAM lParam) { return true; }
+
+bool nsWindow::IsPopup() { return mWindowType == WindowType::Popup; }
+
+bool nsWindow::ShouldUseOffMainThreadCompositing() {
+  if (mWindowType == WindowType::Popup && mPopupType == PopupType::Tooltip) {
+    return false;
+  }
+
+  // Content rendering of popup is always done by child window.
+  // See nsDocumentViewer::ShouldAttachToTopLevel().
+  if (mWindowType == WindowType::Popup && !mIsChildWindow) {
+    MOZ_ASSERT(!mParent);
+    return false;
+  }
+
+  return nsBaseWidget::ShouldUseOffMainThreadCompositing();
+}
+
+void nsWindow::WindowUsesOMTC() {
+  ULONG_PTR style = ::GetClassLongPtr(mWnd, GCL_STYLE);
+  if (!style) {
+    NS_WARNING("Could not get window class style");
+    return;
+  }
+  style |= CS_HREDRAW | CS_VREDRAW;
+  DebugOnly<ULONG_PTR> result = ::SetClassLongPtr(mWnd, GCL_STYLE, style);
+  NS_WARNING_ASSERTION(result, "Could not reset window class style");
+}
+
+void nsWindow::OnDPIChanged(int32_t x, int32_t y, int32_t width,
+                            int32_t height) {
+  // Don't try to handle WM_DPICHANGED for popup windows (see bug 1239353);
+  // they remain tied to their original parent's resolution.
+  if (mWindowType == WindowType::Popup) {
+    return;
+  }
+  if (StaticPrefs::layout_css_devPixelsPerPx() > 0.0) {
+    return;
+  }
+  mDefaultScale = -1.0;  // force recomputation of scale factor
+
+  if (mResizeState != RESIZING &&
+      mFrameState->GetSizeMode() == nsSizeMode_Normal) {
+    // Limit the position (if not in the middle of a drag-move) & size,
+    // if it would overflow the destination screen
+    nsCOMPtr<nsIScreenManager> sm = do_GetService(sScreenManagerContractID);
+    if (sm) {
+      nsCOMPtr<nsIScreen> screen;
+      sm->ScreenForRect(x, y, width, height, getter_AddRefs(screen));
+      if (screen) {
+        int32_t availLeft, availTop, availWidth, availHeight;
+        screen->GetAvailRect(&availLeft, &availTop, &availWidth, &availHeight);
+        if (mResizeState != MOVING) {
+          x = std::max(x, availLeft);
+          y = std::max(y, availTop);
+        }
+        width = std::min(width, availWidth);
+        height = std::min(height, availHeight);
+      }
+    }
+
+    Resize(x, y, width, height, true);
+  }
+  UpdateNonClientMargins();
+  ChangedDPI();
+  ResetLayout();
+}
+
+// Callback to generate OnCloakChanged pseudo-events.
+/* static */
+void nsWindow::OnCloakEvent(HWND aWnd, bool aCloaked) {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  const char* const kEventName = aCloaked ? "CLOAKED" : "UNCLOAKED";
+  nsWindow* pWin = WinUtils::GetNSWindowPtr(aWnd);
+  if (!pWin) {
+    MOZ_LOG(
+        sCloakingLog, LogLevel::Debug,
+        ("Received %s event for HWND %p (not an nsWindow)", kEventName, aWnd));
+    return;
+  }
+
+  const char* const kWasCloakedStr = pWin->mIsCloaked ? "cloaked" : "uncloaked";
+  if (mozilla::IsCloaked(aWnd) == pWin->mIsCloaked) {
+    MOZ_LOG(sCloakingLog, LogLevel::Debug,
+            ("Received redundant %s event for %s HWND %p; discarding",
+             kEventName, kWasCloakedStr, aWnd));
+    return;
+  }
+
+  MOZ_LOG(
+      sCloakingLog, LogLevel::Info,
+      ("Received %s event for %s HWND %p", kEventName, kWasCloakedStr, aWnd));
+
+  // Cloaking events like the one we've just received are sent asynchronously.
+  // Rather than process them one-by-one, we jump the gun a bit and perform
+  // updates on all newly cloaked/uncloaked nsWindows at once. This also lets us
+  // batch operations that consider more than one window's state.
+  struct Item {
+    nsWindow* win;
+    bool nowCloaked;
+  };
+  nsTArray<Item> changedWindows;
+
+  mozilla::EnumerateThreadWindows([&](HWND hwnd) {
+    nsWindow* pWin = WinUtils::GetNSWindowPtr(hwnd);
+    if (!pWin) {
+      return;
+    }
+
+    const bool isCloaked = mozilla::IsCloaked(hwnd);
+    if (isCloaked != pWin->mIsCloaked) {
+      changedWindows.AppendElement(Item{pWin, isCloaked});
+    }
+  });
+
+  if (changedWindows.IsEmpty()) {
+    return;
+  }
+
+  for (const Item& item : changedWindows) {
+    item.win->OnCloakChanged(item.nowCloaked);
+  }
+
+  nsWindow::TaskbarConcealer::OnCloakChanged();
+}
+
+void nsWindow::OnCloakChanged(bool aCloaked) {
+  MOZ_LOG(sCloakingLog, LogLevel::Info,
+          ("Calling OnCloakChanged(): HWND %p, aCloaked %s", mWnd,
+           aCloaked ? "true" : "false"));
+  mIsCloaked = aCloaked;
+}
+
+/**************************************************************
+ **************************************************************
+ **
+ ** BLOCK: IME management and accessibility
+ **
+ ** Handles managing IME input and accessibility.
+ **
+ **************************************************************
+ **************************************************************/
+
+void nsWindow::SetInputContext(const InputContext& aContext,
+                               const InputContextAction& aAction) {
+  InputContext newInputContext = aContext;
+  IMEHandler::SetInputContext(this, newInputContext, aAction);
+  mInputContext = newInputContext;
+}
+
+InputContext nsWindow::GetInputContext() {
+  mInputContext.mIMEState.mOpen = IMEState::CLOSED;
+  if (WinUtils::IsIMEEnabled(mInputContext) && IMEHandler::GetOpenState(this)) {
+    mInputContext.mIMEState.mOpen = IMEState::OPEN;
+  } else {
+    mInputContext.mIMEState.mOpen = IMEState::CLOSED;
+  }
+  return mInputContext;
+}
+
+TextEventDispatcherListener* nsWindow::GetNativeTextEventDispatcherListener() {
+  return IMEHandler::GetNativeTextEventDispatcherListener();
+}
+
+#ifdef ACCESSIBILITY
+#  ifdef DEBUG
+#    define NS_LOG_WMGETOBJECT(aWnd, aHwnd, aAcc)                            \
+      if (a11y::logging::IsEnabled(a11y::logging::ePlatforms)) {             \
+        printf(                                                              \
+            "Get the window:\n  {\n     HWND: %p, parent HWND: %p, wndobj: " \
+            "%p,\n",                                                         \
+            aHwnd, ::GetParent(aHwnd), aWnd);                                \
+        printf("     acc: %p", aAcc);                                        \
+        if (aAcc) {                                                          \
+          nsAutoString name;                                                 \
+          aAcc->Name(name);                                                  \
+          printf(", accname: %s", NS_ConvertUTF16toUTF8(name).get());        \
+        }                                                                    \
+        printf("\n }\n");                                                    \
+      }
+
+#  else
+#    define NS_LOG_WMGETOBJECT(aWnd, aHwnd, aAcc)
+#  endif
+
+a11y::LocalAccessible* nsWindow::GetAccessible() {
+  // If the pref was ePlatformIsDisabled, return null here, disabling a11y.
+  if (a11y::PlatformDisabledState() == a11y::ePlatformIsDisabled)
+    return nullptr;
+
+  if (mInDtor || mOnDestroyCalled || mWindowType == WindowType::Invisible) {
+    return nullptr;
+  }
+
+  // In case of popup window return a popup accessible.
+  nsView* view = nsView::GetViewFor(this);
+  if (view) {
+    nsIFrame* frame = view->GetFrame();
+    if (frame && nsLayoutUtils::IsPopup(frame)) {
+      nsAccessibilityService* accService = GetOrCreateAccService();
+      if (accService) {
+        a11y::DocAccessible* docAcc =
+            GetAccService()->GetDocAccessible(frame->PresShell());
+        if (docAcc) {
+          NS_LOG_WMGETOBJECT(
+              this, mWnd,
+              docAcc->GetAccessibleOrDescendant(frame->GetContent()));
+          return docAcc->GetAccessibleOrDescendant(frame->GetContent());
+        }
+      }
+    }
+  }
+
+  // otherwise root document accessible.
+  NS_LOG_WMGETOBJECT(this, mWnd, GetRootAccessible());
+  return GetRootAccessible();
+}
+#endif
+
+/**************************************************************
+ **************************************************************
+ **
+ ** BLOCK: Transparency
+ **
+ ** Window transparency helpers.
+ **
+ **************************************************************
+ **************************************************************/
+
+void nsWindow::SetWindowTranslucencyInner(TransparencyMode aMode) {
+  if (aMode == mTransparencyMode) return;
+
+  // stop on dialogs and popups!
+  HWND hWnd = WinUtils::GetTopLevelHWND(mWnd, true);
+  nsWindow* parent = WinUtils::GetNSWindowPtr(hWnd);
+
+  if (!parent) {
+    NS_WARNING("Trying to use transparent chrome in an embedded context");
+    return;
+  }
+
+  if (parent != this) {
+    NS_WARNING(
+        "Setting SetWindowTranslucencyInner on a parent this is not us!");
+  }
+
+  if (aMode == TransparencyMode::Transparent) {
+    // If we're switching to the use of a transparent window, hide the chrome
+    // on our parent.
+    HideWindowChrome(true);
+  } else if (mHideChrome &&
+             mTransparencyMode == TransparencyMode::Transparent) {
+    // if we're switching out of transparent, re-enable our parent's chrome.
+    HideWindowChrome(false);
+  }
+
+  LONG_PTR style = ::GetWindowLongPtrW(hWnd, GWL_STYLE),
+           exStyle = ::GetWindowLongPtr(hWnd, GWL_EXSTYLE);
+
+  if (parent->mIsVisible) {
+    style |= WS_VISIBLE;
+    if (parent->mFrameState->GetSizeMode() == nsSizeMode_Maximized) {
+      style |= WS_MAXIMIZE;
+    } else if (parent->mFrameState->GetSizeMode() == nsSizeMode_Minimized) {
+      style |= WS_MINIMIZE;
+    }
+  }
+
+  if (aMode == TransparencyMode::Transparent)
+    exStyle |= WS_EX_LAYERED;
+  else
+    exStyle &= ~WS_EX_LAYERED;
+
+  VERIFY_WINDOW_STYLE(style);
+  ::SetWindowLongPtrW(hWnd, GWL_STYLE, style);
+  ::SetWindowLongPtrW(hWnd, GWL_EXSTYLE, exStyle);
+
+  mTransparencyMode = aMode;
+
+  if (mCompositorWidgetDelegate) {
+    mCompositorWidgetDelegate->UpdateTransparency(aMode);
+  }
+}
+
+/**************************************************************
+ **************************************************************
+ **
+ ** BLOCK: Popup rollup hooks
+ **
+ ** Deals with CaptureRollup on popup windows.
+ **
+ **************************************************************
+ **************************************************************/
+
+// Schedules a timer for a window, so we can rollup after processing the hook
+// event
+void nsWindow::ScheduleHookTimer(HWND aWnd, UINT aMsgId) {
+  // In some cases multiple hooks may be scheduled
+  // so ignore any other requests once one timer is scheduled
+  if (sHookTimerId == 0) {
+    // Remember the window handle and the message ID to be used later
+    sRollupMsgId = aMsgId;
+    sRollupMsgWnd = aWnd;
+    // Schedule native timer for doing the rollup after
+    // this event is done being processed
+    sHookTimerId = ::SetTimer(nullptr, 0, 0, (TIMERPROC)HookTimerForPopups);
+    NS_ASSERTION(sHookTimerId, "Timer couldn't be created.");
+  }
+}
+
+#ifdef POPUP_ROLLUP_DEBUG_OUTPUT
+int gLastMsgCode = 0;
+extern MSGFEventMsgInfo gMSGFEvents[];
+#endif
+
+// Process Menu messages, rollup when popup is clicked.
+LRESULT CALLBACK nsWindow::MozSpecialMsgFilter(int code, WPARAM wParam,
+                                               LPARAM lParam) {
+#ifdef POPUP_ROLLUP_DEBUG_OUTPUT
+  if (sProcessHook) {
+    MSG* pMsg = (MSG*)lParam;
+
+    int inx = 0;
+    while (gMSGFEvents[inx].mId != code && gMSGFEvents[inx].mStr != nullptr) {
+      inx++;
+    }
+    if (code != gLastMsgCode) {
+      if (gMSGFEvents[inx].mId == code) {
+#  ifdef DEBUG
+        MOZ_LOG(gWindowsLog, LogLevel::Info,
+                ("MozSpecialMessageProc - code: 0x%X  - %s  hw: %p\n", code,
+                 gMSGFEvents[inx].mStr, pMsg->hwnd));
+#  endif
+      } else {
+#  ifdef DEBUG
+        MOZ_LOG(gWindowsLog, LogLevel::Info,
+                ("MozSpecialMessageProc - code: 0x%X  - %d  hw: %p\n", code,
+                 gMSGFEvents[inx].mId, pMsg->hwnd));
+#  endif
+      }
+      gLastMsgCode = code;
+    }
+    PrintEvent(pMsg->message, FALSE, FALSE);
+  }
+#endif  // #ifdef POPUP_ROLLUP_DEBUG_OUTPUT
+
+  if (sProcessHook && code == MSGF_MENU) {
+    MSG* pMsg = (MSG*)lParam;
+    ScheduleHookTimer(pMsg->hwnd, pMsg->message);
+  }
+
+  return ::CallNextHookEx(sMsgFilterHook, code, wParam, lParam);
+}
+
+// Process all mouse messages. Roll up when a click is in a native window
+// that doesn't have an nsIWidget.
+LRESULT CALLBACK nsWindow::MozSpecialMouseProc(int code, WPARAM wParam,
+                                               LPARAM lParam) {
+  if (sProcessHook) {
+    switch (WinUtils::GetNativeMessage(wParam)) {
+      case WM_LBUTTONDOWN:
+      case WM_RBUTTONDOWN:
+      case WM_MBUTTONDOWN:
+      case WM_MOUSEWHEEL:
+      case WM_MOUSEHWHEEL: {
+        MOUSEHOOKSTRUCT* ms = (MOUSEHOOKSTRUCT*)lParam;
+        nsIWidget* mozWin = WinUtils::GetNSWindowPtr(ms->hwnd);
+        if (!mozWin) {
+          ScheduleHookTimer(ms->hwnd, (UINT)wParam);
+        }
+        break;
+      }
+    }
+  }
+  return ::CallNextHookEx(sCallMouseHook, code, wParam, lParam);
+}
+
+// Process all messages. Roll up when the window is moving, or
+// is resizing or when maximized or mininized.
+LRESULT CALLBACK nsWindow::MozSpecialWndProc(int code, WPARAM wParam,
+                                             LPARAM lParam) {
+#ifdef POPUP_ROLLUP_DEBUG_OUTPUT
+  if (sProcessHook) {
+    CWPSTRUCT* cwpt = (CWPSTRUCT*)lParam;
+    PrintEvent(cwpt->message, FALSE, FALSE);
+  }
+#endif
+
+  if (sProcessHook) {
+    CWPSTRUCT* cwpt = (CWPSTRUCT*)lParam;
+    if (cwpt->message == WM_MOVING || cwpt->message == WM_SIZING ||
+        cwpt->message == WM_GETMINMAXINFO) {
+      ScheduleHookTimer(cwpt->hwnd, (UINT)cwpt->message);
+    }
+  }
+
+  return ::CallNextHookEx(sCallProcHook, code, wParam, lParam);
+}
+
+// Register the special "hooks" for dropdown processing.
+void nsWindow::RegisterSpecialDropdownHooks() {
+  NS_ASSERTION(!sMsgFilterHook, "sMsgFilterHook must be NULL!");
+  NS_ASSERTION(!sCallProcHook, "sCallProcHook must be NULL!");
+
+  DISPLAY_NMM_PRT("***************** Installing Msg Hooks ***************\n");
+
+  // Install msg hook for moving the window and resizing
+  if (!sMsgFilterHook) {
+    DISPLAY_NMM_PRT("***** Hooking sMsgFilterHook!\n");
+    sMsgFilterHook = SetWindowsHookEx(WH_MSGFILTER, MozSpecialMsgFilter,
+                                      nullptr, GetCurrentThreadId());
+#ifdef POPUP_ROLLUP_DEBUG_OUTPUT
+    if (!sMsgFilterHook) {
+      MOZ_LOG(gWindowsLog, LogLevel::Info,
+              ("***** SetWindowsHookEx is NOT installed for WH_MSGFILTER!\n"));
+    }
+#endif
+  }
+
+  // Install msg hook for menus
+  if (!sCallProcHook) {
+    DISPLAY_NMM_PRT("***** Hooking sCallProcHook!\n");
+    sCallProcHook = SetWindowsHookEx(WH_CALLWNDPROC, MozSpecialWndProc, nullptr,
+                                     GetCurrentThreadId());
+#ifdef POPUP_ROLLUP_DEBUG_OUTPUT
+    if (!sCallProcHook) {
+      MOZ_LOG(
+          gWindowsLog, LogLevel::Info,
+          ("***** SetWindowsHookEx is NOT installed for WH_CALLWNDPROC!\n"));
+    }
+#endif
+  }
+
+  // Install msg hook for the mouse
+  if (!sCallMouseHook) {
+    DISPLAY_NMM_PRT("***** Hooking sCallMouseHook!\n");
+    sCallMouseHook = SetWindowsHookEx(WH_MOUSE, MozSpecialMouseProc, nullptr,
+                                      GetCurrentThreadId());
+#ifdef POPUP_ROLLUP_DEBUG_OUTPUT
+    if (!sCallMouseHook) {
+      MOZ_LOG(gWindowsLog, LogLevel::Info,
+              ("***** SetWindowsHookEx is NOT installed for WH_MOUSE!\n"));
+    }
+#endif
+  }
+}
+
+// Unhook special message hooks for dropdowns.
+void nsWindow::UnregisterSpecialDropdownHooks() {
+  DISPLAY_NMM_PRT(
+      "***************** De-installing Msg Hooks ***************\n");
+
+  if (sCallProcHook) {
+    DISPLAY_NMM_PRT("***** Unhooking sCallProcHook!\n");
+    if (!::UnhookWindowsHookEx(sCallProcHook)) {
+      DISPLAY_NMM_PRT("***** UnhookWindowsHookEx failed for sCallProcHook!\n");
+    }
+    sCallProcHook = nullptr;
+  }
+
+  if (sMsgFilterHook) {
+    DISPLAY_NMM_PRT("***** Unhooking sMsgFilterHook!\n");
+    if (!::UnhookWindowsHookEx(sMsgFilterHook)) {
+      DISPLAY_NMM_PRT("***** UnhookWindowsHookEx failed for sMsgFilterHook!\n");
+    }
+    sMsgFilterHook = nullptr;
+  }
+
+  if (sCallMouseHook) {
+    DISPLAY_NMM_PRT("***** Unhooking sCallMouseHook!\n");
+    if (!::UnhookWindowsHookEx(sCallMouseHook)) {
+      DISPLAY_NMM_PRT("***** UnhookWindowsHookEx failed for sCallMouseHook!\n");
+    }
+    sCallMouseHook = nullptr;
+  }
+}
+
+// This timer is designed to only fire one time at most each time a "hook"
+// function is used to rollup the dropdown. In some cases, the timer may be
+// scheduled from the hook, but that hook event or a subsequent event may roll
+// up the dropdown before this timer function is executed.
+//
+// For example, if an MFC control takes focus, the combobox will lose focus and
+// rollup before this function fires.
+VOID CALLBACK nsWindow::HookTimerForPopups(HWND hwnd, UINT uMsg, UINT idEvent,
+                                           DWORD dwTime) {
+  if (sHookTimerId != 0) {
+    // if the window is nullptr then we need to use the ID to kill the timer
+    DebugOnly<BOOL> status = ::KillTimer(nullptr, sHookTimerId);
+    NS_ASSERTION(status, "Hook Timer was not killed.");
+    sHookTimerId = 0;
+  }
+
+  if (sRollupMsgId != 0) {
+    // Note: DealWithPopups does the check to make sure that the rollup widget
+    // is set.
+    LRESULT popupHandlingResult;
+    nsAutoRollup autoRollup;
+    DealWithPopups(sRollupMsgWnd, sRollupMsgId, 0, 0, &popupHandlingResult);
+    sRollupMsgId = 0;
+    sRollupMsgWnd = nullptr;
+  }
+}
+
+static bool IsDifferentThreadWindow(HWND aWnd) {
+  return ::GetCurrentThreadId() != ::GetWindowThreadProcessId(aWnd, nullptr);
+}
+
+// static
+bool nsWindow::EventIsInsideWindow(nsWindow* aWindow,
+                                   Maybe<POINT> aEventPoint) {
+  RECT r;
+  ::GetWindowRect(aWindow->mWnd, &r);
+  POINT mp;
+  if (aEventPoint) {
+    mp = *aEventPoint;
+  } else {
+    DWORD pos = ::GetMessagePos();
+    mp.x = GET_X_LPARAM(pos);
+    mp.y = GET_Y_LPARAM(pos);
+  }
+
+  auto margin = aWindow->mInputRegion.mMargin;
+  if (margin > 0) {
+    r.top += margin;
+    r.bottom -= margin;
+    r.left += margin;
+    r.right -= margin;
+  }
+
+  // was the event inside this window?
+  return static_cast<bool>(::PtInRect(&r, mp));
+}
+
+// static
+bool nsWindow::GetPopupsToRollup(nsIRollupListener* aRollupListener,
+                                 uint32_t* aPopupsToRollup,
+                                 Maybe<POINT> aEventPoint) {
+  // If we're dealing with menus, we probably have submenus and we don't want
+  // to rollup some of them if the click is in a parent menu of the current
+  // submenu.
+  *aPopupsToRollup = UINT32_MAX;
+  AutoTArray<nsIWidget*, 5> widgetChain;
+  uint32_t sameTypeCount = aRollupListener->GetSubmenuWidgetChain(&widgetChain);
+  for (uint32_t i = 0; i < widgetChain.Length(); ++i) {
+    nsIWidget* widget = widgetChain[i];
+    if (EventIsInsideWindow(static_cast<nsWindow*>(widget), aEventPoint)) {
+      // Don't roll up if the mouse event occurred within a menu of the
+      // same type. If the mouse event occurred in a menu higher than that,
+      // roll up, but pass the number of popups to Rollup so that only those
+      // of the same type close up.
+      if (i < sameTypeCount) {
+        return false;
+      }
+
+      *aPopupsToRollup = sameTypeCount;
+      break;
+    }
+  }
+  return true;
+}
+
+// static
+bool nsWindow::NeedsToHandleNCActivateDelayed(HWND aWnd) {
+  // While popup is open, popup window might be activated by other application.
+  // At this time, we need to take back focus to the previous window but it
+  // causes flickering its nonclient area because WM_NCACTIVATE comes before
+  // WM_ACTIVATE and we cannot know which window will take focus at receiving
+  // WM_NCACTIVATE. Therefore, we need a hack for preventing the flickerling.
+  //
+  // If non-popup window receives WM_NCACTIVATE at deactivating, default
+  // wndproc shouldn't handle it as deactivating. Instead, at receiving
+  // WM_ACTIVIATE after that, WM_NCACTIVATE should be sent again manually.
+  // This returns true if the window needs to handle WM_NCACTIVATE later.
+
+  nsWindow* window = WinUtils::GetNSWindowPtr(aWnd);
+  return window && !window->IsPopup();
+}
+
+static bool IsTouchSupportEnabled(HWND aWnd) {
+  nsWindow* topWindow =
+      WinUtils::GetNSWindowPtr(WinUtils::GetTopLevelHWND(aWnd, true));
+  return topWindow ? topWindow->IsTouchWindow() : false;
+}
+
+static Maybe<POINT> GetSingleTouch(WPARAM wParam, LPARAM lParam) {
+  Maybe<POINT> ret;
+  uint32_t cInputs = LOWORD(wParam);
+  if (cInputs != 1) {
+    return ret;
+  }
+  TOUCHINPUT input;
+  if (GetTouchInputInfo((HTOUCHINPUT)lParam, cInputs, &input,
+                        sizeof(TOUCHINPUT))) {
+    ret.emplace();
+    ret->x = TOUCH_COORD_TO_PIXEL(input.x);
+    ret->y = TOUCH_COORD_TO_PIXEL(input.y);
+  }
+  // Note that we don't call CloseTouchInputHandle here because we need
+  // to read the touch input info again in OnTouch later.
+  return ret;
+}
+
+// static
+bool nsWindow::DealWithPopups(HWND aWnd, UINT aMessage, WPARAM aWParam,
+                              LPARAM aLParam, LRESULT* aResult) {
+  NS_ASSERTION(aResult, "Bad outResult");
+
+  // XXX Why do we use the return value of WM_MOUSEACTIVATE for all messages?
+  *aResult = MA_NOACTIVATE;
+
+  if (!::IsWindowVisible(aWnd)) {
+    return false;
+  }
+
+  if (MOZ_UNLIKELY(aMessage == WM_KILLFOCUS)) {
+    // NOTE: We deal with this here rather than on the switch below because we
+    // want to do this even if there are no menus to rollup (tooltips don't set
+    // the rollup listener etc).
+    if (RefPtr pm = nsXULPopupManager::GetInstance()) {
+      pm->RollupTooltips();
+    }
+  }
+
+  nsIRollupListener* rollupListener = nsBaseWidget::GetActiveRollupListener();
+  NS_ENSURE_TRUE(rollupListener, false);
+
+  nsCOMPtr<nsIWidget> popup = rollupListener->GetRollupWidget();
+  if (!popup) {
+    return false;
+  }
+
+  static bool sSendingNCACTIVATE = false;
+  static bool sPendingNCACTIVATE = false;
+  uint32_t popupsToRollup = UINT32_MAX;
+
+  bool consumeRollupEvent = false;
+  Maybe<POINT> touchPoint;  // In screen coords.
+
+  // If we rollup with animations but get occluded right away, we might not
+  // advance the refresh driver enough for the animation to finish.
+  auto allowAnimations = nsIRollupListener::AllowAnimations::Yes;
+  nsWindow* popupWindow = static_cast<nsWindow*>(popup.get());
+  UINT nativeMessage = WinUtils::GetNativeMessage(aMessage);
+  switch (nativeMessage) {
+    case WM_TOUCH:
+      if (!IsTouchSupportEnabled(aWnd)) {
+        // If APZ is disabled, don't allow touch inputs to dismiss popups. The
+        // compatibility mouse events will do it instead.
+        return false;
+      }
+      touchPoint = GetSingleTouch(aWParam, aLParam);
+      if (!touchPoint) {
+        return false;
+      }
+      [[fallthrough]];
+    case WM_LBUTTONDOWN:
+    case WM_RBUTTONDOWN:
+    case WM_MBUTTONDOWN:
+    case WM_NCLBUTTONDOWN:
+    case WM_NCRBUTTONDOWN:
+    case WM_NCMBUTTONDOWN:
+      if (nativeMessage != WM_TOUCH && IsTouchSupportEnabled(aWnd) &&
+          MOUSE_INPUT_SOURCE() == MouseEvent_Binding::MOZ_SOURCE_TOUCH) {
+        // If any of these mouse events are really compatibility events that
+        // Windows is sending for touch inputs, then don't allow them to dismiss
+        // popups when APZ is enabled (instead we do the dismissing as part of
+        // WM_TOUCH handling which is more correct).
+        // If we don't do this, then when the user lifts their finger after a
+        // long-press, the WM_RBUTTONDOWN compatibility event that Windows sends
+        // us will dismiss the contextmenu popup that we displayed as part of
+        // handling the long-tap-up.
+        return false;
+      }
+      if (!EventIsInsideWindow(popupWindow, touchPoint) &&
+          GetPopupsToRollup(rollupListener, &popupsToRollup, touchPoint)) {
+        break;
+      }
+      return false;
+    case WM_POINTERDOWN: {
+      WinPointerEvents pointerEvents;
+      if (!pointerEvents.ShouldRollupOnPointerEvent(nativeMessage, aWParam)) {
+        return false;
+      }
+      POINT pt;
+      pt.x = GET_X_LPARAM(aLParam);
+      pt.y = GET_Y_LPARAM(aLParam);
+      if (!GetPopupsToRollup(rollupListener, &popupsToRollup, Some(pt))) {
+        return false;
+      }
+      if (EventIsInsideWindow(popupWindow, Some(pt))) {
+        // Don't roll up if the event is inside the popup window.
+        return false;
+      }
+    } break;
+    case MOZ_WM_DMANIP: {
+      POINT pt;
+      ::GetCursorPos(&pt);
+      if (!GetPopupsToRollup(rollupListener, &popupsToRollup, Some(pt))) {
+        return false;
+      }
+      if (EventIsInsideWindow(popupWindow, Some(pt))) {
+        // Don't roll up if the event is inside the popup window
+        return false;
+      }
+    } break;
+    case WM_MOUSEWHEEL:
+    case WM_MOUSEHWHEEL:
+      // We need to check if the popup thinks that it should cause closing
+      // itself when mouse wheel events are fired outside the rollup widget.
+      if (!EventIsInsideWindow(popupWindow)) {
+        // Check if we should consume this event even if we don't roll-up:
+        consumeRollupEvent = rollupListener->ShouldConsumeOnMouseWheelEvent();
+        *aResult = MA_ACTIVATE;
+        if (rollupListener->ShouldRollupOnMouseWheelEvent() &&
+            GetPopupsToRollup(rollupListener, &popupsToRollup)) {
+          break;
+        }
+      }
+      return consumeRollupEvent;
+
+    case WM_ACTIVATEAPP:
+      allowAnimations = nsIRollupListener::AllowAnimations::No;
+      break;
+
+    case WM_ACTIVATE: {
+      WndProcUrgentInvocation::Marker _marker;
+
+      // NOTE: Don't handle WA_INACTIVE for preventing popup taking focus
+      // because we cannot distinguish it's caused by mouse or not.
+      if (LOWORD(aWParam) == WA_ACTIVE && aLParam) {
+        nsWindow* window = WinUtils::GetNSWindowPtr(aWnd);
+        if (window && (window->IsPopup() || window->mIsAlert)) {
+          // Cancel notifying widget listeners of deactivating the previous
+          // active window (see WM_KILLFOCUS case in ProcessMessage()).
+          sJustGotDeactivate = false;
+          // Reactivate the window later.
+          ::PostMessageW(aWnd, MOZ_WM_REACTIVATE, aWParam, aLParam);
+          return true;
+        }
+        // Don't rollup the popup when focus moves back to the parent window
+        // from a popup because such case is caused by strange mouse drivers.
+        nsWindow* prevWindow =
+            WinUtils::GetNSWindowPtr(reinterpret_cast<HWND>(aLParam));
+        if (prevWindow && prevWindow->IsPopup()) {
+          // Consume this message here since previous window must not have
+          // been inactivated since we've already stopped accepting the
+          // inactivation below.
+          return true;
+        }
+      } else if (LOWORD(aWParam) == WA_INACTIVE) {
+        nsWindow* activeWindow =
+            WinUtils::GetNSWindowPtr(reinterpret_cast<HWND>(aLParam));
+        if (sPendingNCACTIVATE && NeedsToHandleNCActivateDelayed(aWnd)) {
+          // If focus moves to non-popup widget or focusable popup, the window
+          // needs to update its nonclient area.
+          if (!activeWindow || !activeWindow->IsPopup()) {
+            sSendingNCACTIVATE = true;
+            ::SendMessageW(aWnd, WM_NCACTIVATE, false, 0);
+            sSendingNCACTIVATE = false;
+          }
+          sPendingNCACTIVATE = false;
+        }
+        // If focus moves from/to popup, we don't need to rollup the popup
+        // because such case is caused by strange mouse drivers.  And in
+        // such case, we should consume the message here since we need to
+        // hide this odd focus move from our content.  (If we didn't consume
+        // the message here, ProcessMessage() will notify widget listener of
+        // inactivation and that causes unnecessary reflow for supporting
+        // -moz-window-inactive pseudo class.
+        if (activeWindow) {
+          if (activeWindow->IsPopup()) {
+            return true;
+          }
+          nsWindow* deactiveWindow = WinUtils::GetNSWindowPtr(aWnd);
+          if (deactiveWindow && deactiveWindow->IsPopup()) {
+            return true;
+          }
+        }
+      } else if (LOWORD(aWParam) == WA_CLICKACTIVE) {
+        // If the WM_ACTIVATE message is caused by a click in a popup,
+        // we should not rollup any popups.
+        nsWindow* window = WinUtils::GetNSWindowPtr(aWnd);
+        if ((window && window->IsPopup()) ||
+            !GetPopupsToRollup(rollupListener, &popupsToRollup)) {
+          return false;
+        }
+      }
+      allowAnimations = nsIRollupListener::AllowAnimations::No;
+    } break;
+
+    case MOZ_WM_REACTIVATE:
+      // The previous active window should take back focus.
+      if (::IsWindow(reinterpret_cast<HWND>(aLParam))) {
+        // FYI: Even without this API call, you see expected result (e.g., the
+        //      owner window of the popup keeps active without flickering
+        //      the non-client area).  And also this causes initializing
+        //      TSF and it causes using CPU time a lot.  However, even if we
+        //      consume WM_ACTIVE messages, native focus change has already
+        //      been occurred.  I.e., a popup window is active now.  Therefore,
+        //      you'll see some odd behavior if we don't reactivate the owner
+        //      window here.  For example, if you do:
+        //        1. Turn wheel on a bookmark panel.
+        //        2. Turn wheel on another window.
+        //      then, you'll see that the another window becomes active but the
+        //      owner window of the bookmark panel looks still active and the
+        //      bookmark panel keeps open.  The reason is that the first wheel
+        //      operation gives focus to the bookmark panel.  Therefore, when
+        //      the next operation gives focus to the another window, previous
+        //      focus window is the bookmark panel (i.e., a popup window).
+        //      So, in this case, our hack around here prevents to inactivate
+        //      the owner window and roll up the bookmark panel.
+        ::SetForegroundWindow(reinterpret_cast<HWND>(aLParam));
+      }
+      return true;
+
+    case WM_NCACTIVATE:
+      if (!aWParam && !sSendingNCACTIVATE &&
+          NeedsToHandleNCActivateDelayed(aWnd)) {
+        // Don't just consume WM_NCACTIVATE. It doesn't handle only the
+        // nonclient area state change.
+        ::DefWindowProcW(aWnd, aMessage, TRUE, aLParam);
+        // Accept the deactivating because it's necessary to receive following
+        // WM_ACTIVATE.
+        *aResult = TRUE;
+        sPendingNCACTIVATE = true;
+        return true;
+      }
+      return false;
+
+    case WM_MOUSEACTIVATE:
+      if (!EventIsInsideWindow(popupWindow) &&
+          GetPopupsToRollup(rollupListener, &popupsToRollup)) {
+        // WM_MOUSEACTIVATE may be caused by moving the mouse (e.g., X-mouse
+        // of TweakUI is enabled. Then, check if the popup should be rolled up
+        // with rollup listener. If not, just consume the message.
+        if (HIWORD(aLParam) == WM_MOUSEMOVE &&
+            !rollupListener->ShouldRollupOnMouseActivate()) {
+          return true;
+        }
+        // Otherwise, it should be handled by wndproc.
+        return false;
+      }
+
+      // Prevent the click inside the popup from causing a change in window
+      // activation. Since the popup is shown non-activated, we need to eat any
+      // requests to activate the window while it is displayed. Windows will
+      // automatically activate the popup on the mousedown otherwise.
+      return true;
+
+    case WM_SHOWWINDOW:
+      // If the window is being minimized, close popups.
+      if (aLParam == SW_PARENTCLOSING) {
+        allowAnimations = nsIRollupListener::AllowAnimations::No;
+        break;
+      }
+      return false;
+
+    case WM_KILLFOCUS:
+      // If focus moves to other window created in different process/thread,
+      // e.g., a plugin window, popups should be rolled up.
+      if (IsDifferentThreadWindow(reinterpret_cast<HWND>(aWParam))) {
+        allowAnimations = nsIRollupListener::AllowAnimations::No;
+        break;
+      }
+      return false;
+
+    case WM_MOVING:
+    case WM_MENUSELECT:
+      break;
+
+    default:
+      return false;
+  }
+
+  // Only need to deal with the last rollup for left mouse down events.
+  NS_ASSERTION(!nsAutoRollup::GetLastRollup(), "last rollup is null");
+
+  nsIRollupListener::RollupOptions rollupOptions{
+      popupsToRollup,
+      nsIRollupListener::FlushViews::Yes,
+      /* mPoint = */ nullptr,
+      allowAnimations,
+  };
+
+  if (nativeMessage == WM_TOUCH || nativeMessage == WM_LBUTTONDOWN ||
+      nativeMessage == WM_POINTERDOWN) {
+    LayoutDeviceIntPoint pos;
+    if (nativeMessage == WM_TOUCH) {
+      pos.x = touchPoint->x;
+      pos.y = touchPoint->y;
+    } else {
+      POINT pt;
+      pt.x = GET_X_LPARAM(aLParam);
+      pt.y = GET_Y_LPARAM(aLParam);
+      // POINTERDOWN is already in screen coords.
+      if (nativeMessage == WM_LBUTTONDOWN) {
+        ::ClientToScreen(aWnd, &pt);
+      }
+      pos = LayoutDeviceIntPoint(pt.x, pt.y);
+    }
+
+    rollupOptions.mPoint = &pos;
+    nsIContent* lastRollup = nullptr;
+    consumeRollupEvent = rollupListener->Rollup(rollupOptions, &lastRollup);
+    nsAutoRollup::SetLastRollup(lastRollup);
+  } else {
+    consumeRollupEvent = rollupListener->Rollup(rollupOptions);
+  }
+
+  // Tell hook to stop processing messages
+  sProcessHook = false;
+  sRollupMsgId = 0;
+  sRollupMsgWnd = nullptr;
+
+  // If we are NOT supposed to be consuming events, let it go through
+  if (consumeRollupEvent && nativeMessage != WM_RBUTTONDOWN) {
+    *aResult = MA_ACTIVATE;
+    return true;
+  }
+
+  return false;
+}
+
+/**************************************************************
+ **************************************************************
+ **
+ ** BLOCK: Misc. utility methods and functions.
+ **
+ ** General use.
+ **
+ **************************************************************
+ **************************************************************/
+
+// Note that the result of GetTopLevelWindow method can be different from the
+// result of WinUtils::GetTopLevelHWND().  The result can be non-floating
+// window.  Because our top level window may be contained in another window
+// which is not managed by us.
+nsWindow* nsWindow::GetTopLevelWindow(bool aStopOnDialogOrPopup) {
+  nsWindow* curWindow = this;
+
+  while (true) {
+    if (aStopOnDialogOrPopup) {
+      switch (curWindow->mWindowType) {
+        case WindowType::Dialog:
+        case WindowType::Popup:
+          return curWindow;
+        default:
+          break;
+      }
+    }
+
+    // Retrieve the top level parent or owner window
+    nsWindow* parentWindow = curWindow->GetParentWindow(true);
+
+    if (!parentWindow) return curWindow;
+
+    curWindow = parentWindow;
+  }
+}
+
+// Set a flag if hwnd is a (non-popup) visible window from this process,
+// and bail out of the enumeration. Otherwise leave the flag unmodified
+// and continue the enumeration.
+// lParam must be a bool* pointing at the flag to be set.
+static BOOL CALLBACK EnumVisibleWindowsProc(HWND hwnd, LPARAM lParam) {
+  DWORD pid;
+  ::GetWindowThreadProcessId(hwnd, &pid);
+  if (pid == ::GetCurrentProcessId() && ::IsWindowVisible(hwnd)) {
+    // Don't count popups as visible windows, since they don't take focus,
+    // in case we only have a popup visible (see bug 1554490 where the gfx
+    // test window is an offscreen popup).
+    nsWindow* window = WinUtils::GetNSWindowPtr(hwnd);
+    if (!window || !window->IsPopup()) {
+      bool* windowsVisible = reinterpret_cast<bool*>(lParam);
+      *windowsVisible = true;
+      return FALSE;
+    }
+  }
+  return TRUE;
+}
+
+// Determine if it would be ok to activate a window, taking focus.
+// We want to avoid stealing focus from another app (bug 225305).
+bool nsWindow::CanTakeFocus() {
+  HWND fgWnd = ::GetForegroundWindow();
+  if (!fgWnd) {
+    // There is no foreground window, so don't worry about stealing focus.
+    return true;
+  }
+  // We can take focus if the current foreground window is already from
+  // this process.
+  DWORD pid;
+  ::GetWindowThreadProcessId(fgWnd, &pid);
+  if (pid == ::GetCurrentProcessId()) {
+    return true;
+  }
+
+  bool windowsVisible = false;
+  ::EnumWindows(EnumVisibleWindowsProc,
+                reinterpret_cast<LPARAM>(&windowsVisible));
+
+  if (!windowsVisible) {
+    // We're probably creating our first visible window, allow that to
+    // take focus.
+    return true;
+  }
+  return false;
+}
+
+/* static */ const wchar_t* nsWindow::GetMainWindowClass() {
+  static const wchar_t* sMainWindowClass = nullptr;
+  if (!sMainWindowClass) {
+    nsAutoString className;
+    Preferences::GetString("ui.window_class_override", className);
+    if (!className.IsEmpty()) {
+      sMainWindowClass = wcsdup(className.get());
+    } else {
+      sMainWindowClass = kClassNameGeneral;
+    }
+  }
+  return sMainWindowClass;
+}
+
+LPARAM nsWindow::lParamToScreen(LPARAM lParam) {
+  POINT pt;
+  pt.x = GET_X_LPARAM(lParam);
+  pt.y = GET_Y_LPARAM(lParam);
+  ::ClientToScreen(mWnd, &pt);
+  return MAKELPARAM(pt.x, pt.y);
+}
+
+LPARAM nsWindow::lParamToClient(LPARAM lParam) {
+  POINT pt;
+  pt.x = GET_X_LPARAM(lParam);
+  pt.y = GET_Y_LPARAM(lParam);
+  ::ScreenToClient(mWnd, &pt);
+  return MAKELPARAM(pt.x, pt.y);
+}
+
+WPARAM nsWindow::wParamFromGlobalMouseState() {
+  WPARAM result = 0;
+
+  if (!!::GetKeyState(VK_CONTROL)) {
+    result |= MK_CONTROL;
+  }
+
+  if (!!::GetKeyState(VK_SHIFT)) {
+    result |= MK_SHIFT;
+  }
+
+  if (!!::GetKeyState(VK_LBUTTON)) {
+    result |= MK_LBUTTON;
+  }
+
+  if (!!::GetKeyState(VK_MBUTTON)) {
+    result |= MK_MBUTTON;
+  }
+
+  if (!!::GetKeyState(VK_RBUTTON)) {
+    result |= MK_RBUTTON;
+  }
+
+  if (!!::GetKeyState(VK_XBUTTON1)) {
+    result |= MK_XBUTTON1;
+  }
+
+  if (!!::GetKeyState(VK_XBUTTON2)) {
+    result |= MK_XBUTTON2;
+  }
+
+  return result;
+}
+
+void nsWindow::PickerOpen() {
+  AssertIsOnMainThread();
+  mPickerDisplayCount++;
+}
+
+void nsWindow::PickerClosed() {
+  AssertIsOnMainThread();
+  NS_ASSERTION(mPickerDisplayCount > 0, "mPickerDisplayCount out of sync!");
+  if (!mPickerDisplayCount) return;
+  mPickerDisplayCount--;
+
+  // WORKAROUND FOR UNDOCUMENTED BEHAVIOR: `IFileDialog::Show` disables the
+  // top-level ancestor of its provided owner-window. If the modal window's
+  // container process crashes, it will never get a chance to undo that, so we
+  // do it manually here.
+  //
+  // Note that this may cause problems in the embedded case if you reparent a
+  // subtree of the native window hierarchy containing a Gecko window while that
+  // Gecko window has a file-dialog open.
+  if (!mPickerDisplayCount) {
+    ::EnableWindow(::GetAncestor(GetWindowHandle(), GA_ROOT), TRUE);
+  }
+
+  if (!mPickerDisplayCount && mDestroyCalled) {
+    Destroy();
+  }
+}
+
+bool nsWindow::WidgetTypeSupportsAcceleration() {
+  // We don't currently support using an accelerated layer manager with
+  // transparent windows so don't even try. I'm also not sure if we even
+  // want to support this case. See bug 593471.
+  //
+  // Windows' support for transparent accelerated surfaces isn't great.
+  // Some possible approaches:
+  //  - Readback the data and update it using
+  //  UpdateLayeredWindow/UpdateLayeredWindowIndirect
+  //    This is what WPF does. See
+  //    CD3DDeviceLevel1::PresentWithGDI/CD3DSwapChainWithSwDC in WpfGfx. The
+  //    rationale for not using IDirect3DSurface9::GetDC is explained here:
+  //    https://web.archive.org/web/20160521191104/https://blogs.msdn.microsoft.com/dwayneneed/2008/09/08/transparent-windows-in-wpf/
+  //  - Use D3D11_RESOURCE_MISC_GDI_COMPATIBLE, IDXGISurface1::GetDC(),
+  //    and UpdateLayeredWindowIndirect.
+  //    This is suggested here:
+  //    https://docs.microsoft.com/en-us/archive/msdn-magazine/2009/december/windows-with-c-layered-windows-with-direct2d
+  //    but might have the same problem that IDirect3DSurface9::GetDC has.
+  //  - Creating the window with the WS_EX_NOREDIRECTIONBITMAP flag and use
+  //  DirectComposition.
+  //    Not supported on Win7.
+  //  - Using DwmExtendFrameIntoClientArea with negative margins and something
+  //  to turn off the glass effect.
+  //    This doesn't work when the DWM is not running (Win7)
+  //
+  // Also see bug 1150376, D3D11 composition can cause issues on some devices
+  // on Windows 7 where presentation fails randomly for windows with drop
+  // shadows.
+  return mTransparencyMode != TransparencyMode::Transparent &&
+         !(IsPopup() && DeviceManagerDx::Get()->IsWARP());
+}
+
+bool nsWindow::DispatchTouchEventFromWMPointer(
+    UINT msg, LPARAM aLParam, const WinPointerInfo& aPointerInfo,
+    mozilla::MouseButton aButton) {
+  MultiTouchInput::MultiTouchType touchType;
+  switch (msg) {
+    case WM_POINTERDOWN:
+      touchType = MultiTouchInput::MULTITOUCH_START;
+      break;
+    case WM_POINTERUPDATE:
+      if (aPointerInfo.mPressure == 0) {
+        return false;  // hover
+      }
+      touchType = MultiTouchInput::MULTITOUCH_MOVE;
+      break;
+    case WM_POINTERUP:
+      touchType = MultiTouchInput::MULTITOUCH_END;
+      break;
+    default:
+      return false;
+  }
+
+  nsPointWin touchPoint;
+  touchPoint.x = GET_X_LPARAM(aLParam);
+  touchPoint.y = GET_Y_LPARAM(aLParam);
+  touchPoint.ScreenToClient(mWnd);
+
+  SingleTouchData touchData(static_cast<int32_t>(aPointerInfo.pointerId),
+                            ScreenIntPoint::FromUnknownPoint(touchPoint),
+                            ScreenSize(1, 1),  // pixel size radius for pen
+                            0.0f,              // no radius rotation
+                            aPointerInfo.mPressure);
+  touchData.mTiltX = aPointerInfo.tiltX;
+  touchData.mTiltY = aPointerInfo.tiltY;
+  touchData.mTwist = aPointerInfo.twist;
+
+  MultiTouchInput touchInput;
+  touchInput.mType = touchType;
+  touchInput.mTimeStamp = GetMessageTimeStamp(::GetMessageTime());
+  touchInput.mTouches.AppendElement(touchData);
+  touchInput.mButton = aButton;
+  touchInput.mButtons = aPointerInfo.mButtons;
+
+  // POINTER_INFO.dwKeyStates can't be used as it only supports Shift and Ctrl
+  ModifierKeyState modifierKeyState;
+  touchInput.modifiers = modifierKeyState.GetModifiers();
+
+  DispatchTouchInput(touchInput, MouseEvent_Binding::MOZ_SOURCE_PEN);
+  return true;
+}
+
+static MouseButton PenFlagsToMouseButton(PEN_FLAGS aPenFlags) {
+  // Theoretically flags can be set together but they do not
+  if (aPenFlags & PEN_FLAG_BARREL) {
+    return MouseButton::eSecondary;
+  }
+  if (aPenFlags & PEN_FLAG_ERASER) {
+    return MouseButton::eEraser;
+  }
+  return MouseButton::ePrimary;
+}
+
+bool nsWindow::OnPointerEvents(UINT msg, WPARAM aWParam, LPARAM aLParam) {
+  if (!mAPZC) {
+    // APZ is not available on context menu. Follow the behavior of touch input
+    // which fallbacks to WM_LBUTTON* and WM_GESTURE, to keep consistency.
+    return false;
+  }
+  if (!mPointerEvents.ShouldHandleWinPointerMessages(msg, aWParam)) {
+    return false;
+  }
+  if (!mPointerEvents.ShouldFirePointerEventByWinPointerMessages()) {
+    // We have to handle WM_POINTER* to fetch and cache pen related information
+    // and fire WidgetMouseEvent with the cached information the WM_*BUTTONDOWN
+    // handler. This is because Windows doesn't support ::DoDragDrop in the
+    // touch or pen message handlers.
+    mPointerEvents.ConvertAndCachePointerInfo(msg, aWParam);
+    // Don't consume the Windows WM_POINTER* messages
+    return false;
+  }
+
+  uint32_t pointerId = mPointerEvents.GetPointerId(aWParam);
+  POINTER_PEN_INFO penInfo{};
+  if (!mPointerEvents.GetPointerPenInfo(pointerId, &penInfo)) {
+    return false;
+  }
+
+  // When dispatching mouse events with pen, there may be some
+  // WM_POINTERUPDATE messages between WM_POINTERDOWN and WM_POINTERUP with
+  // small movements. Those events will reset sLastMousePoint and reset
+  // sLastClickCount. To prevent that, we keep the last pen down position
+  // and compare it with the subsequent WM_POINTERUPDATE. If the movement is
+  // smaller than GetSystemMetrics(SM_CXDRAG), then we suppress firing
+  // eMouseMove for WM_POINTERUPDATE.
+  static POINT sLastPointerDownPoint = {0};
+
+  // We don't support chorded buttons for pen. Keep the button at
+  // WM_POINTERDOWN.
+  static mozilla::MouseButton sLastPenDownButton = MouseButton::ePrimary;
+  static bool sPointerDown = false;
+
+  EventMessage message;
+  mozilla::MouseButton button = MouseButton::ePrimary;
+  switch (msg) {
+    case WM_POINTERDOWN: {
+      LayoutDeviceIntPoint eventPoint(GET_X_LPARAM(aLParam),
+                                      GET_Y_LPARAM(aLParam));
+      sLastPointerDownPoint.x = eventPoint.x;
+      sLastPointerDownPoint.y = eventPoint.y;
+      message = eMouseDown;
+      button = PenFlagsToMouseButton(penInfo.penFlags);
+      sLastPenDownButton = button;
+      sPointerDown = true;
+    } break;
+    case WM_POINTERUP:
+      message = eMouseUp;
+      MOZ_ASSERT(sPointerDown, "receive WM_POINTERUP w/o WM_POINTERDOWN");
+      button = sPointerDown ? sLastPenDownButton : MouseButton::ePrimary;
+      sPointerDown = false;
+      break;
+    case WM_POINTERUPDATE:
+      message = eMouseMove;
+      if (sPointerDown) {
+        LayoutDeviceIntPoint eventPoint(GET_X_LPARAM(aLParam),
+                                        GET_Y_LPARAM(aLParam));
+        int32_t movementX = sLastPointerDownPoint.x > eventPoint.x
+                                ? sLastPointerDownPoint.x - eventPoint.x.value
+                                : eventPoint.x.value - sLastPointerDownPoint.x;
+        int32_t movementY = sLastPointerDownPoint.y > eventPoint.y
+                                ? sLastPointerDownPoint.y - eventPoint.y.value
+                                : eventPoint.y.value - sLastPointerDownPoint.y;
+        bool insideMovementThreshold =
+            movementX < (int32_t)::GetSystemMetrics(SM_CXDRAG) &&
+            movementY < (int32_t)::GetSystemMetrics(SM_CYDRAG);
+
+        if (insideMovementThreshold) {
+          // Suppress firing eMouseMove for WM_POINTERUPDATE if the movement
+          // from last WM_POINTERDOWN is smaller than SM_CXDRAG / SM_CYDRAG
+          return false;
+        }
+        button = sLastPenDownButton;
+      }
+      break;
+    case WM_POINTERLEAVE:
+      message = eMouseExitFromWidget;
+      break;
+    default:
+      return false;
+  }
+
+  // Windows defines the pen pressure is normalized to a range between 0 and
+  // 1024. Convert it to float.
+  float pressure = penInfo.pressure ? (float)penInfo.pressure / 1024 : 0;
+  int16_t buttons = sPointerDown
+                        ? nsContentUtils::GetButtonsFlagForButton(button)
+                        : MouseButtonsFlag::eNoButtons;
+  WinPointerInfo pointerInfo(pointerId, penInfo.tiltX, penInfo.tiltY, pressure,
+                             buttons);
+  // Per
+  // https://learn.microsoft.com/en-us/windows/win32/api/winuser/ns-winuser-pointer_pen_info,
+  // the rotation is normalized in a range of 0 to 359.
+  MOZ_ASSERT(penInfo.rotation <= 359);
+  pointerInfo.twist = (int32_t)penInfo.rotation;
+
+  // Fire touch events but not when the barrel button is pressed.
+  if (button != MouseButton::eSecondary &&
+      StaticPrefs::dom_w3c_pointer_events_scroll_by_pen_enabled() &&
+      DispatchTouchEventFromWMPointer(msg, aLParam, pointerInfo, button)) {
+    return true;
+  }
+
+  // The aLParam of WM_POINTER* is the screen location. Convert it to client
+  // location
+  LPARAM newLParam = lParamToClient(aLParam);
+  DispatchMouseEvent(message, aWParam, newLParam, false, button,
+                     MouseEvent_Binding::MOZ_SOURCE_PEN, &pointerInfo);
+
+  if (button == MouseButton::eSecondary && message == eMouseUp) {
+    // Fire eContextMenu manually since consuming WM_POINTER* blocks
+    // WM_CONTEXTMENU
+    DispatchMouseEvent(eContextMenu, aWParam, newLParam, false, button,
+                       MouseEvent_Binding::MOZ_SOURCE_PEN, &pointerInfo);
+  }
+  // Consume WM_POINTER* to stop Windows fires WM_*BUTTONDOWN / WM_*BUTTONUP
+  // WM_MOUSEMOVE.
+  return true;
+}
+
+void nsWindow::GetCompositorWidgetInitData(
+    mozilla::widget::CompositorWidgetInitData* aInitData) {
+  *aInitData = WinCompositorWidgetInitData(
+      reinterpret_cast<uintptr_t>(mWnd),
+      reinterpret_cast<uintptr_t>(static_cast<nsIWidget*>(this)),
+      mTransparencyMode, mFrameState->GetSizeMode());
+}
+
+bool nsWindow::SynchronouslyRepaintOnResize() { return false; }
+
+void nsWindow::MaybeDispatchInitialFocusEvent() {
+  if (mIsShowingPreXULSkeletonUI && ::GetActiveWindow() == mWnd) {
+    DispatchFocusToTopLevelWindow(true);
+  }
+}
+
+already_AddRefed<nsIWidget> nsIWidget::CreateTopLevelWindow() {
+  nsCOMPtr<nsIWidget> window = new nsWindow();
+  return window.forget();
+}
+
+already_AddRefed<nsIWidget> nsIWidget::CreateChildWindow() {
+  nsCOMPtr<nsIWidget> window = new nsWindow(true);
+  return window.forget();
+}
+
+// static
+bool nsWindow::InitTouchInjection() {
+  if (!sTouchInjectInitialized) {
+    // Initialize touch injection on the first call
+    HMODULE hMod = LoadLibraryW(kUser32LibName);
+    if (!hMod) {
+      return false;
+    }
+
+    InitializeTouchInjectionPtr func =
+        (InitializeTouchInjectionPtr)GetProcAddress(hMod,
+                                                    "InitializeTouchInjection");
+    if (!func) {
+      WinUtils::Log("InitializeTouchInjection not available.");
+      return false;
+    }
+
+    if (!func(TOUCH_INJECT_MAX_POINTS, TOUCH_FEEDBACK_DEFAULT)) {
+      WinUtils::Log("InitializeTouchInjection failure. GetLastError=%d",
+                    GetLastError());
+      return false;
+    }
+
+    sInjectTouchFuncPtr =
+        (InjectTouchInputPtr)GetProcAddress(hMod, "InjectTouchInput");
+    if (!sInjectTouchFuncPtr) {
+      WinUtils::Log("InjectTouchInput not available.");
+      return false;
+    }
+    sTouchInjectInitialized = true;
+  }
+  return true;
+}
+
+bool nsWindow::InjectTouchPoint(uint32_t aId, LayoutDeviceIntPoint& aPoint,
+                                POINTER_FLAGS aFlags, uint32_t aPressure,
+                                uint32_t aOrientation) {
+  if (aId > TOUCH_INJECT_MAX_POINTS) {
+    WinUtils::Log("Pointer ID exceeds maximum. See TOUCH_INJECT_MAX_POINTS.");
+    return false;
+  }
+
+  POINTER_TOUCH_INFO info{};
+
+  info.touchFlags = TOUCH_FLAG_NONE;
+  info.touchMask =
+      TOUCH_MASK_CONTACTAREA | TOUCH_MASK_ORIENTATION | TOUCH_MASK_PRESSURE;
+  info.pressure = aPressure;
+  info.orientation = aOrientation;
+
+  info.pointerInfo.pointerFlags = aFlags;
+  info.pointerInfo.pointerType = PT_TOUCH;
+  info.pointerInfo.pointerId = aId;
+  info.pointerInfo.ptPixelLocation.x = aPoint.x;
+  info.pointerInfo.ptPixelLocation.y = aPoint.y;
+
+  info.rcContact.top = info.pointerInfo.ptPixelLocation.y - 2;
+  info.rcContact.bottom = info.pointerInfo.ptPixelLocation.y + 2;
+  info.rcContact.left = info.pointerInfo.ptPixelLocation.x - 2;
+  info.rcContact.right = info.pointerInfo.ptPixelLocation.x + 2;
+
+  for (int i = 0; i < 3; i++) {
+    if (sInjectTouchFuncPtr(1, &info)) {
+      break;
+    }
+    DWORD error = GetLastError();
+    if (error == ERROR_NOT_READY && i < 2) {
+      // We sent it too quickly after the previous injection (see bug 1535140
+      // comment 10). On the first loop iteration we just yield (via Sleep(0))
+      // and try again. If it happens again on the second loop iteration we
+      // explicitly Sleep(1) and try again. If that doesn't work either we just
+      // error out.
+      ::Sleep(i);
+      continue;
+    }
+    WinUtils::Log("InjectTouchInput failure. GetLastError=%d", error);
+    return false;
+  }
+  return true;
+}
+
+void nsWindow::ChangedDPI() {
+  if (mWidgetListener) {
+    if (PresShell* presShell = mWidgetListener->GetPresShell()) {
+      presShell->BackingScaleFactorChanged();
+    }
+  }
+}
+
+static Result<POINTER_FLAGS, nsresult> PointerStateToFlag(
+    nsWindow::TouchPointerState aPointerState, bool isUpdate) {
+  bool hover = aPointerState & nsWindow::TOUCH_HOVER;
+  bool contact = aPointerState & nsWindow::TOUCH_CONTACT;
+  bool remove = aPointerState & nsWindow::TOUCH_REMOVE;
+  bool cancel = aPointerState & nsWindow::TOUCH_CANCEL;
+
+  POINTER_FLAGS flags;
+  if (isUpdate) {
+    // We know about this pointer, send an update
+    flags = POINTER_FLAG_UPDATE;
+    if (hover) {
+      flags |= POINTER_FLAG_INRANGE;
+    } else if (contact) {
+      flags |= POINTER_FLAG_INCONTACT | POINTER_FLAG_INRANGE;
+    } else if (remove) {
+      flags = POINTER_FLAG_UP;
+    }
+
+    if (cancel) {
+      flags |= POINTER_FLAG_CANCELED;
+    }
+  } else {
+    // Missing init state, error out
+    if (remove || cancel) {
+      return Err(NS_ERROR_INVALID_ARG);
+    }
+
+    // Create a new pointer
+    flags = POINTER_FLAG_INRANGE;
+    if (contact) {
+      flags |= POINTER_FLAG_INCONTACT | POINTER_FLAG_DOWN;
+    }
+  }
+  return flags;
+}
+
+nsresult nsWindow::SynthesizeNativeTouchPoint(
+    uint32_t aPointerId, nsIWidget::TouchPointerState aPointerState,
+    LayoutDeviceIntPoint aPoint, double aPointerPressure,
+    uint32_t aPointerOrientation, nsIObserver* aObserver) {
+  AutoObserverNotifier notifier(aObserver, "touchpoint");
+
+  if (StaticPrefs::apz_test_fails_with_native_injection() ||
+      !InitTouchInjection()) {
+    // If we don't have touch injection from the OS, or if we are running a test
+    // that cannot properly inject events to satisfy the OS requirements (see
+    // bug 1313170)  we can just fake it and synthesize the events from here.
+    MOZ_ASSERT(NS_IsMainThread());
+    if (aPointerState == TOUCH_HOVER) {
+      return NS_ERROR_UNEXPECTED;
+    }
+
+    if (!mSynthesizedTouchInput) {
+      mSynthesizedTouchInput = MakeUnique<MultiTouchInput>();
+    }
+
+    WidgetEventTime time = CurrentMessageWidgetEventTime();
+    LayoutDeviceIntPoint pointInWindow = aPoint - WidgetToScreenOffset();
+    MultiTouchInput inputToDispatch = UpdateSynthesizedTouchState(
+        mSynthesizedTouchInput.get(), time.mTimeStamp, aPointerId,
+        aPointerState, pointInWindow, aPointerPressure, aPointerOrientation);
+    DispatchTouchInput(inputToDispatch);
+    return NS_OK;
+  }
+
+  // win api expects a value from 0 to 1024. aPointerPressure is a value
+  // from 0.0 to 1.0.
+  uint32_t pressure = (uint32_t)ceil(aPointerPressure * 1024);
+
+  // If we already know about this pointer id get it's record
+  return mActivePointers.WithEntryHandle(aPointerId, [&](auto&& entry) {
+    POINTER_FLAGS flags;
+    // Can't use MOZ_TRY_VAR because it confuses WithEntryHandle
+    auto result = PointerStateToFlag(aPointerState, !!entry);
+    if (result.isOk()) {
+      flags = result.unwrap();
+    } else {
+      return result.unwrapErr();
+    }
+
+    if (!entry) {
+      entry.Insert(MakeUnique<PointerInfo>(aPointerId, aPoint,
+                                           PointerInfo::PointerType::TOUCH));
+    } else {
+      if (entry.Data()->mType != PointerInfo::PointerType::TOUCH) {
+        return NS_ERROR_UNEXPECTED;
+      }
+      if (aPointerState & TOUCH_REMOVE) {
+        // Remove the pointer from our tracking list. This is UniquePtr wrapped,
+        // so shouldn't leak.
+        entry.Remove();
+      }
+    }
+
+    return !InjectTouchPoint(aPointerId, aPoint, flags, pressure,
+                             aPointerOrientation)
+               ? NS_ERROR_UNEXPECTED
+               : NS_OK;
+  });
+}
+
+nsresult nsWindow::ClearNativeTouchSequence(nsIObserver* aObserver) {
+  AutoObserverNotifier notifier(aObserver, "cleartouch");
+  if (!sTouchInjectInitialized) {
+    return NS_OK;
+  }
+
+  // cancel all input points
+  for (auto iter = mActivePointers.Iter(); !iter.Done(); iter.Next()) {
+    auto* info = iter.UserData();
+    if (info->mType != PointerInfo::PointerType::TOUCH) {
+      continue;
+    }
+    InjectTouchPoint(info->mPointerId, info->mPosition, POINTER_FLAG_CANCELED);
+    iter.Remove();
+  }
+
+  nsBaseWidget::ClearNativeTouchSequence(nullptr);
+
+  return NS_OK;
+}
+
+#if !defined(NTDDI_WIN10_RS5) || (NTDDI_VERSION < NTDDI_WIN10_RS5)
+static CreateSyntheticPointerDevicePtr CreateSyntheticPointerDevice;
+static DestroySyntheticPointerDevicePtr DestroySyntheticPointerDevice;
+static InjectSyntheticPointerInputPtr InjectSyntheticPointerInput;
+#endif
+static HSYNTHETICPOINTERDEVICE sSyntheticPenDevice;
+
+static bool InitPenInjection() {
+  if (sSyntheticPenDevice) {
+    return true;
+  }
+#if !defined(NTDDI_WIN10_RS5) || (NTDDI_VERSION < NTDDI_WIN10_RS5)
+  HMODULE hMod = LoadLibraryW(kUser32LibName);
+  if (!hMod) {
+    return false;
+  }
+  CreateSyntheticPointerDevice =
+      (CreateSyntheticPointerDevicePtr)GetProcAddress(
+          hMod, "CreateSyntheticPointerDevice");
+  if (!CreateSyntheticPointerDevice) {
+    WinUtils::Log("CreateSyntheticPointerDevice not available.");
+    return false;
+  }
+  DestroySyntheticPointerDevice =
+      (DestroySyntheticPointerDevicePtr)GetProcAddress(
+          hMod, "DestroySyntheticPointerDevice");
+  if (!DestroySyntheticPointerDevice) {
+    WinUtils::Log("DestroySyntheticPointerDevice not available.");
+    return false;
+  }
+  InjectSyntheticPointerInput = (InjectSyntheticPointerInputPtr)GetProcAddress(
+      hMod, "InjectSyntheticPointerInput");
+  if (!InjectSyntheticPointerInput) {
+    WinUtils::Log("InjectSyntheticPointerInput not available.");
+    return false;
+  }
+#endif
+  sSyntheticPenDevice =
+      CreateSyntheticPointerDevice(PT_PEN, 1, POINTER_FEEDBACK_DEFAULT);
+  return !!sSyntheticPenDevice;
+}
+
+nsresult nsWindow::SynthesizeNativePenInput(
+    uint32_t aPointerId, nsIWidget::TouchPointerState aPointerState,
+    LayoutDeviceIntPoint aPoint, double aPressure, uint32_t aRotation,
+    int32_t aTiltX, int32_t aTiltY, int32_t aButton, nsIObserver* aObserver) {
+  AutoObserverNotifier notifier(aObserver, "peninput");
+  if (!InitPenInjection()) {
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  // win api expects a value from 0 to 1024. aPointerPressure is a value
+  // from 0.0 to 1.0.
+  uint32_t pressure = (uint32_t)ceil(aPressure * 1024);
+
+  // If we already know about this pointer id get it's record
+  return mActivePointers.WithEntryHandle(aPointerId, [&](auto&& entry) {
+    POINTER_FLAGS flags;
+    // Can't use MOZ_TRY_VAR because it confuses WithEntryHandle
+    auto result = PointerStateToFlag(aPointerState, !!entry);
+    if (result.isOk()) {
+      flags = result.unwrap();
+    } else {
+      return result.unwrapErr();
+    }
+
+    if (!entry) {
+      entry.Insert(MakeUnique<PointerInfo>(aPointerId, aPoint,
+                                           PointerInfo::PointerType::PEN));
+    } else {
+      if (entry.Data()->mType != PointerInfo::PointerType::PEN) {
+        return NS_ERROR_UNEXPECTED;
+      }
+      if (aPointerState & TOUCH_REMOVE) {
+        // Remove the pointer from our tracking list. This is UniquePtr wrapped,
+        // so shouldn't leak.
+        entry.Remove();
+      }
+    }
+
+    POINTER_TYPE_INFO info{};
+
+    info.type = PT_PEN;
+    info.penInfo.pointerInfo.pointerType = PT_PEN;
+    info.penInfo.pointerInfo.pointerFlags = flags;
+    info.penInfo.pointerInfo.pointerId = aPointerId;
+    info.penInfo.pointerInfo.ptPixelLocation.x = aPoint.x;
+    info.penInfo.pointerInfo.ptPixelLocation.y = aPoint.y;
+
+    info.penInfo.penFlags = PEN_FLAG_NONE;
+    // PEN_FLAG_ERASER is not supported this way, unfortunately.
+    if (aButton == 2) {
+      info.penInfo.penFlags |= PEN_FLAG_BARREL;
+    }
+    info.penInfo.penMask = PEN_MASK_PRESSURE | PEN_MASK_ROTATION |
+                           PEN_MASK_TILT_X | PEN_MASK_TILT_Y;
+    info.penInfo.pressure = pressure;
+    info.penInfo.rotation = aRotation;
+    info.penInfo.tiltX = aTiltX;
+    info.penInfo.tiltY = aTiltY;
+
+    return InjectSyntheticPointerInput(sSyntheticPenDevice, &info, 1)
+               ? NS_OK
+               : NS_ERROR_UNEXPECTED;
+  });
+};
+
+bool nsWindow::HandleAppCommandMsg(const MSG& aAppCommandMsg,
+                                   LRESULT* aRetValue) {
+  ModifierKeyState modKeyState;
+  NativeKey nativeKey(this, aAppCommandMsg, modKeyState);
+  bool consumed = nativeKey.HandleAppCommandMessage();
+  *aRetValue = consumed ? 1 : 0;
+  return consumed;
+}
+
+#ifdef DEBUG
+nsresult nsWindow::SetHiDPIMode(bool aHiDPI) {
+  return WinUtils::SetHiDPIMode(aHiDPI);
+}
+
+nsresult nsWindow::RestoreHiDPIMode() { return WinUtils::RestoreHiDPIMode(); }
+#endif
+
+mozilla::Maybe<UINT> nsWindow::GetHiddenTaskbarEdge() {
+  HMONITOR windowMonitor = ::MonitorFromWindow(mWnd, MONITOR_DEFAULTTONEAREST);
+
+  // Check all four sides of our monitor for an appbar.  Skip any that aren't
+  // the system taskbar.
+  MONITORINFO mi;
+  mi.cbSize = sizeof(MONITORINFO);
+  ::GetMonitorInfo(windowMonitor, &mi);
+
+  APPBARDATA appBarData;
+  appBarData.cbSize = sizeof(appBarData);
+  appBarData.rc = mi.rcMonitor;
+  const auto kEdges = {ABE_BOTTOM, ABE_TOP, ABE_LEFT, ABE_RIGHT};
+  for (auto edge : kEdges) {
+    appBarData.uEdge = edge;
+    HWND appBarHwnd = (HWND)SHAppBarMessage(ABM_GETAUTOHIDEBAREX, &appBarData);
+    if (appBarHwnd) {
+      nsAutoString className;
+      if (WinUtils::GetClassName(appBarHwnd, className)) {
+        if (className.Equals(L"Shell_TrayWnd") ||
+            className.Equals(L"Shell_SecondaryTrayWnd")) {
+          return Some(edge);
+        }
+      }
+    }
+  }
+
+  return Nothing();
+}
+
+static nsSizeMode GetSizeModeForWindowFrame(HWND aWnd, bool aFullscreenMode) {
+  WINDOWPLACEMENT pl;
+  pl.length = sizeof(pl);
+  ::GetWindowPlacement(aWnd, &pl);
+
+  if (pl.showCmd == SW_SHOWMINIMIZED) {
+    return nsSizeMode_Minimized;
+  } else if (aFullscreenMode) {
+    return nsSizeMode_Fullscreen;
+  } else if (pl.showCmd == SW_SHOWMAXIMIZED) {
+    return nsSizeMode_Maximized;
+  } else {
+    return nsSizeMode_Normal;
+  }
+}
+
+static void ShowWindowWithMode(HWND aWnd, nsSizeMode aMode) {
+  // This will likely cause a callback to
+  // nsWindow::FrameState::{OnFrameChanging() and OnFrameChanged()}
+  switch (aMode) {
+    case nsSizeMode_Fullscreen:
+      ::ShowWindow(aWnd, SW_SHOW);
+      break;
+
+    case nsSizeMode_Maximized:
+      ::ShowWindow(aWnd, SW_MAXIMIZE);
+      break;
+
+    case nsSizeMode_Minimized:
+      ::ShowWindow(aWnd, SW_MINIMIZE);
+      break;
+
+    default:
+      // Don't call ::ShowWindow if we're trying to "restore" a window that is
+      // already in a normal state.  Prevents a bug where snapping to one side
+      // of the screen and then minimizing would cause Windows to forget our
+      // window's correct restored position/size.
+      if (GetCurrentShowCmd(aWnd) != SW_SHOWNORMAL) {
+        ::ShowWindow(aWnd, SW_RESTORE);
+      }
+  }
+}
+
+nsWindow::FrameState::FrameState(nsWindow* aWindow) : mWindow(aWindow) {}
+
+nsSizeMode nsWindow::FrameState::GetSizeMode() const { return mSizeMode; }
+
+void nsWindow::FrameState::CheckInvariant() const {
+  MOZ_ASSERT(mSizeMode >= 0 && mSizeMode < nsSizeMode_Invalid);
+  MOZ_ASSERT(mLastSizeMode >= 0 && mLastSizeMode < nsSizeMode_Invalid);
+  MOZ_ASSERT(mPreFullscreenSizeMode >= 0 &&
+             mPreFullscreenSizeMode < nsSizeMode_Invalid);
+  MOZ_ASSERT(mWindow);
+
+  // We should never observe fullscreen sizemode unless fullscreen is enabled
+  MOZ_ASSERT_IF(mSizeMode == nsSizeMode_Fullscreen, mFullscreenMode);
+  MOZ_ASSERT_IF(!mFullscreenMode, mSizeMode != nsSizeMode_Fullscreen);
+
+  // Something went wrong if we somehow saved fullscreen mode when we are
+  // changing into fullscreen mode
+  MOZ_ASSERT(mPreFullscreenSizeMode != nsSizeMode_Fullscreen);
+}
+
+void nsWindow::FrameState::ConsumePreXULSkeletonState(bool aWasMaximized) {
+  mSizeMode = aWasMaximized ? nsSizeMode_Maximized : nsSizeMode_Normal;
+}
+
+void nsWindow::FrameState::EnsureSizeMode(nsSizeMode aMode,
+                                          DoShowWindow aDoShowWindow) {
+  if (mSizeMode == aMode) {
+    return;
+  }
+
+  if (StaticPrefs::widget_windows_fullscreen_remind_taskbar()) {
+    // If we're unminimizing a window, asynchronously notify the taskbar after
+    // the message has been processed. This redundant notification works around
+    // a race condition in explorer.exe. (See bug 1835851, or comments in
+    // TaskbarConcealer.)
+    //
+    // Note that we notify regardless of `aMode`: unminimizing a non-fullscreen
+    // window can also affect the correct taskbar state, yet fail to affect the
+    // current taskbar state.
+    if (mSizeMode == nsSizeMode_Minimized) {
+      ::PostMessage(mWindow->mWnd, MOZ_WM_FULLSCREEN_STATE_UPDATE, 0, 0);
+    }
+  }
+
+  if (aMode == nsSizeMode_Fullscreen) {
+    EnsureFullscreenMode(true, aDoShowWindow);
+    MOZ_ASSERT(mSizeMode == nsSizeMode_Fullscreen);
+  } else if (mSizeMode == nsSizeMode_Fullscreen && aMode == nsSizeMode_Normal) {
+    // If we are in fullscreen mode, minimize should work like normal and
+    // return us to fullscreen mode when unminimized. Maximize isn't really
+    // available and won't do anything. "Restore" should do the same thing as
+    // requesting to end fullscreen.
+    EnsureFullscreenMode(false, aDoShowWindow);
+  } else {
+    SetSizeModeInternal(aMode, aDoShowWindow);
+  }
+}
+
+void nsWindow::FrameState::EnsureFullscreenMode(bool aFullScreen,
+                                                DoShowWindow aDoShowWindow) {
+  const bool changed = aFullScreen != mFullscreenMode;
+  if (changed && aFullScreen) {
+    // Save the size mode from before fullscreen.
+    mPreFullscreenSizeMode = mSizeMode;
+  }
+  mFullscreenMode = aFullScreen;
+  if (changed || aFullScreen) {
+    // NOTE(emilio): When minimizing a fullscreen window we remain with
+    // mFullscreenMode = true, but mSizeMode = nsSizeMode_Minimized. We need to
+    // make sure to call SetSizeModeInternal even if mFullscreenMode didn't
+    // change, to ensure we actually end up with a fullscreen sizemode when
+    // restoring a window from that state.
+    SetSizeModeInternal(
+        aFullScreen ? nsSizeMode_Fullscreen : mPreFullscreenSizeMode,
+        aDoShowWindow);
+  }
+}
+
+void nsWindow::FrameState::OnFrameChanging() {
+  const nsSizeMode newSizeMode =
+      GetSizeModeForWindowFrame(mWindow->mWnd, mFullscreenMode);
+  EnsureSizeMode(newSizeMode);
+  mWindow->UpdateNonClientMargins(false);
+}
+
+void nsWindow::FrameState::OnFrameChanged() {
+  // We don't want to perform the ShowWindow ourselves if we're on the frame
+  // changed message. Windows has done the frame change for us, and we take care
+  // of activating as needed. We also don't want to potentially trigger
+  // more focus / restore. Among other things, this addresses a bug on Win7
+  // related to window docking. (bug 489258)
+  const auto newSizeMode =
+      GetSizeModeForWindowFrame(mWindow->mWnd, mFullscreenMode);
+  EnsureSizeMode(newSizeMode, DoShowWindow::No);
+
+  // If window was restored, activate the window now to get correct attributes.
+  if (mWindow->mIsVisible && mWindow->IsForegroundWindow() &&
+      mLastSizeMode == nsSizeMode_Minimized &&
+      mSizeMode != nsSizeMode_Minimized) {
+    mWindow->DispatchFocusToTopLevelWindow(true);
+  }
+  mLastSizeMode = mSizeMode;
+}
+
+static void MaybeLogSizeMode(nsSizeMode aMode) {
+#ifdef WINSTATE_DEBUG_OUTPUT
+  MOZ_LOG(gWindowsLog, LogLevel::Info, ("*** SizeMode: %d\n", int(aMode)));
+#endif
+}
+
+void nsWindow::FrameState::SetSizeModeInternal(nsSizeMode aMode,
+                                               DoShowWindow aDoShowWindow) {
+  if (mSizeMode == aMode) {
+    return;
+  }
+
+  const auto oldSizeMode = mSizeMode;
+  const bool fullscreenChange =
+      mSizeMode == nsSizeMode_Fullscreen || aMode == nsSizeMode_Fullscreen;
+  const bool fullscreen = aMode == nsSizeMode_Fullscreen;
+
+  mLastSizeMode = mSizeMode;
+  mSizeMode = aMode;
+
+  MaybeLogSizeMode(mSizeMode);
+
+  if (bool(aDoShowWindow) && mWindow->mIsVisible) {
+    ShowWindowWithMode(mWindow->mWnd, aMode);
+  }
+
+  mWindow->UpdateNonClientMargins(false);
+
+  if (fullscreenChange) {
+    mWindow->OnFullscreenChanged(oldSizeMode, fullscreen);
+  }
+
+  mWindow->OnSizeModeChange();
+}
+
+void nsWindow::ContextMenuPreventer::Update(
+    const WidgetMouseEvent& aEvent,
+    const nsIWidget::ContentAndAPZEventStatus& aEventStatus) {
+  mNeedsToPreventContextMenu =
+      aEvent.mMessage == eMouseUp &&
+      aEvent.mButton == MouseButton::eSecondary &&
+      aEvent.mInputSource == MouseEvent_Binding::MOZ_SOURCE_MOUSE &&
+      aEventStatus.mApzStatus == nsEventStatus_eConsumeNoDefault;
+}
diff --git a/widget/windows/nsWindow.h b/widget/windows/nsWindow.h
new file mode 100644
index 0000000000..c75c9d174d
--- /dev/null
+++ b/widget/windows/nsWindow.h
@@ -0,0 +1,905 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef WIDGET_WINDOWS_NSWINDOW_H_
+#define WIDGET_WINDOWS_NSWINDOW_H_
+
+/*
+ * nsWindow - Native window management and event handling.
+ */
+
+#include "mozilla/RefPtr.h"
+#include "nsBaseWidget.h"
+#include "CompositorWidget.h"
+#include "mozilla/EventForwards.h"
+#include "nsClassHashtable.h"
+#include <windows.h>
+#include "touchinjection_sdk80.h"
+#include "nsdefs.h"
+#include "nsUserIdleService.h"
+#include "nsToolkit.h"
+#include "nsString.h"
+#include "nsTArray.h"
+#include "gfxWindowsPlatform.h"
+#include "gfxWindowsSurface.h"
+#include "nsWindowDbg.h"
+#include "cairo.h"
+#include "nsRegion.h"
+#include "mozilla/EnumeratedArray.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/MouseEvents.h"
+#include "mozilla/TimeStamp.h"
+#include "mozilla/webrender/WebRenderTypes.h"
+#include "mozilla/dom/MouseEventBinding.h"
+#include "mozilla/DataMutex.h"
+#include "mozilla/UniquePtr.h"
+#include "nsMargin.h"
+#include "nsRegionFwd.h"
+
+#include "nsWinGesture.h"
+#include "WinPointerEvents.h"
+#include "WinUtils.h"
+#include "WindowHook.h"
+#include "TaskbarWindowPreview.h"
+
+#ifdef ACCESSIBILITY
+#  include "oleacc.h"
+#  include "mozilla/a11y/LocalAccessible.h"
+#endif
+
+#include "nsUXThemeData.h"
+#include "nsIUserIdleServiceInternal.h"
+
+#include "IMMHandler.h"
+#include "CheckInvariantWrapper.h"
+
+/**
+ * Forward class definitions
+ */
+
+class nsNativeDragTarget;
+class nsIRollupListener;
+class imgIContainer;
+
+namespace mozilla {
+class WidgetMouseEvent;
+namespace widget {
+class NativeKey;
+class InProcessWinCompositorWidget;
+struct MSGResult;
+class DirectManipulationOwner;
+}  // namespace widget
+}  // namespace mozilla
+
+/**
+ * Forward Windows-internal definitions of otherwise incomplete ones provided by
+ * the SDK.
+ */
+const CLSID CLSID_ImmersiveShell = {
+    0xC2F03A33,
+    0x21F5,
+    0x47FA,
+    {0xB4, 0xBB, 0x15, 0x63, 0x62, 0xA2, 0xF2, 0x39}};
+
+/**
+ * Native WIN32 window wrapper.
+ */
+
+class nsWindow final : public nsBaseWidget {
+ public:
+  using WindowHook = mozilla::widget::WindowHook;
+  using IMEContext = mozilla::widget::IMEContext;
+  using WidgetEventTime = mozilla::WidgetEventTime;
+
+  NS_INLINE_DECL_REFCOUNTING_INHERITED(nsWindow, nsBaseWidget)
+
+  explicit nsWindow(bool aIsChildWindow = false);
+
+  void SendAnAPZEvent(mozilla::InputData& aEvent);
+
+  /*
+   * Init a standard gecko event for this widget.
+   * @param aEvent the event to initialize.
+   * @param aPoint message position in physical coordinates.
+   */
+  void InitEvent(mozilla::WidgetGUIEvent& aEvent,
+                 LayoutDeviceIntPoint* aPoint = nullptr);
+
+  /*
+   * Returns WidgetEventTime instance which is initialized with current message
+   * time.
+   */
+  WidgetEventTime CurrentMessageWidgetEventTime() const;
+
+  /*
+   * Dispatch a gecko keyboard event for this widget. This
+   * is called by KeyboardLayout to dispatch gecko events.
+   * Returns true if it's consumed.  Otherwise, false.
+   */
+  bool DispatchKeyboardEvent(mozilla::WidgetKeyboardEvent* aEvent);
+
+  /*
+   * Dispatch a gecko wheel event for this widget. This
+   * is called by ScrollHandler to dispatch gecko events.
+   * Returns true if it's consumed.  Otherwise, false.
+   */
+  bool DispatchWheelEvent(mozilla::WidgetWheelEvent* aEvent);
+
+  /*
+   * Dispatch a gecko content command event for this widget. This
+   * is called by ScrollHandler to dispatch gecko events.
+   * Returns true if it's consumed.  Otherwise, false.
+   */
+  bool DispatchContentCommandEvent(mozilla::WidgetContentCommandEvent* aEvent);
+
+  /*
+   * Return the parent window, if it exists.
+   */
+  nsWindow* GetParentWindowBase(bool aIncludeOwner);
+
+  /*
+   * Return true if this is a top level widget.
+   */
+  bool IsTopLevelWidget() { return mIsTopWidgetWindow; }
+
+  // nsIWidget interface
+  using nsBaseWidget::Create;  // for Create signature not overridden here
+  [[nodiscard]] nsresult Create(nsIWidget* aParent,
+                                nsNativeWidget aNativeParent,
+                                const LayoutDeviceIntRect& aRect,
+                                InitData* aInitData = nullptr) override;
+  void Destroy() override;
+  void SetParent(nsIWidget* aNewParent) override;
+  nsIWidget* GetParent(void) override;
+  float GetDPI() override;
+  double GetDefaultScaleInternal() override;
+  int32_t LogToPhys(double aValue);
+  mozilla::DesktopToLayoutDeviceScale GetDesktopToDeviceScale() override {
+    if (mozilla::widget::WinUtils::IsPerMonitorDPIAware()) {
+      return mozilla::DesktopToLayoutDeviceScale(1.0);
+    } else {
+      return mozilla::DesktopToLayoutDeviceScale(GetDefaultScaleInternal());
+    }
+  }
+
+  void Show(bool aState) override;
+  bool IsVisible() const override;
+  void ConstrainPosition(DesktopIntPoint&) override;
+  void SetSizeConstraints(const SizeConstraints& aConstraints) override;
+  void LockAspectRatio(bool aShouldLock) override;
+  const SizeConstraints GetSizeConstraints() override;
+  void SetInputRegion(const InputRegion&) override;
+  void Move(double aX, double aY) override;
+  void Resize(double aWidth, double aHeight, bool aRepaint) override;
+  void Resize(double aX, double aY, double aWidth, double aHeight,
+              bool aRepaint) override;
+  mozilla::Maybe<bool> IsResizingNativeWidget() override;
+  void PlaceBehind(nsTopLevelWidgetZPlacement aPlacement, nsIWidget* aWidget,
+                   bool aActivate) override;
+  void SetSizeMode(nsSizeMode aMode) override;
+  nsSizeMode SizeMode() override;
+  void GetWorkspaceID(nsAString& workspaceID) override;
+  void MoveToWorkspace(const nsAString& workspaceID) override;
+  void SuppressAnimation(bool aSuppress) override;
+  void Enable(bool aState) override;
+  bool IsEnabled() const override;
+  void SetFocus(Raise, mozilla::dom::CallerType aCallerType) override;
+  LayoutDeviceIntRect GetBounds() override;
+  LayoutDeviceIntRect GetScreenBounds() override;
+  [[nodiscard]] nsresult GetRestoredBounds(LayoutDeviceIntRect& aRect) override;
+  LayoutDeviceIntRect GetClientBounds() override;
+  LayoutDeviceIntPoint GetClientOffset() override;
+  void SetBackgroundColor(const nscolor& aColor) override;
+  void SetCursor(const Cursor&) override;
+  bool PrepareForFullscreenTransition(nsISupports** aData) override;
+  void PerformFullscreenTransition(FullscreenTransitionStage aStage,
+                                   uint16_t aDuration, nsISupports* aData,
+                                   nsIRunnable* aCallback) override;
+  void CleanupFullscreenTransition() override;
+  nsresult MakeFullScreen(bool aFullScreen) override;
+  void HideWindowChrome(bool aShouldHide) override;
+  void Invalidate(bool aEraseBackground = false, bool aUpdateNCArea = false,
+                  bool aIncludeChildren = false);
+  void Invalidate(const LayoutDeviceIntRect& aRect) override;
+  void* GetNativeData(uint32_t aDataType) override;
+  void FreeNativeData(void* data, uint32_t aDataType) override;
+  nsresult SetTitle(const nsAString& aTitle) override;
+  void SetIcon(const nsAString& aIconSpec) override;
+  LayoutDeviceIntPoint WidgetToScreenOffset() override;
+  LayoutDeviceIntMargin ClientToWindowMargin() override;
+  nsresult DispatchEvent(mozilla::WidgetGUIEvent* aEvent,
+                         nsEventStatus& aStatus) override;
+  void EnableDragDrop(bool aEnable) override;
+  void CaptureMouse(bool aCapture);
+  void CaptureRollupEvents(bool aDoCapture) override;
+  [[nodiscard]] nsresult GetAttention(int32_t aCycleCount) override;
+  bool HasPendingInputEvent() override;
+  WindowRenderer* GetWindowRenderer() override;
+  void SetCompositorWidgetDelegate(CompositorWidgetDelegate* delegate) override;
+  [[nodiscard]] nsresult OnDefaultButtonLoaded(
+      const LayoutDeviceIntRect& aButtonRect) override;
+  nsresult SynthesizeNativeKeyEvent(int32_t aNativeKeyboardLayout,
+                                    int32_t aNativeKeyCode,
+                                    uint32_t aModifierFlags,
+                                    const nsAString& aCharacters,
+                                    const nsAString& aUnmodifiedCharacters,
+                                    nsIObserver* aObserver) override;
+  nsresult SynthesizeNativeMouseEvent(LayoutDeviceIntPoint aPoint,
+                                      NativeMouseMessage aNativeMessage,
+                                      mozilla::MouseButton aButton,
+                                      nsIWidget::Modifiers aModifierFlags,
+                                      nsIObserver* aObserver) override;
+
+  nsresult SynthesizeNativeMouseMove(LayoutDeviceIntPoint aPoint,
+                                     nsIObserver* aObserver) override {
+    return SynthesizeNativeMouseEvent(
+        aPoint, NativeMouseMessage::Move, mozilla::MouseButton::eNotPressed,
+        nsIWidget::Modifiers::NO_MODIFIERS, aObserver);
+  }
+
+  nsresult SynthesizeNativeMouseScrollEvent(
+      LayoutDeviceIntPoint aPoint, uint32_t aNativeMessage, double aDeltaX,
+      double aDeltaY, double aDeltaZ, uint32_t aModifierFlags,
+      uint32_t aAdditionalFlags, nsIObserver* aObserver) override;
+
+  nsresult SynthesizeNativeTouchpadPan(TouchpadGesturePhase aEventPhase,
+                                       LayoutDeviceIntPoint aPoint,
+                                       double aDeltaX, double aDeltaY,
+                                       int32_t aModifierFlagsn,
+                                       nsIObserver* aObserver) override;
+
+  void SetInputContext(const InputContext& aContext,
+                       const InputContextAction& aAction) override;
+  InputContext GetInputContext() override;
+  TextEventDispatcherListener* GetNativeTextEventDispatcherListener() override;
+  void SetTransparencyMode(TransparencyMode aMode) override;
+  TransparencyMode GetTransparencyMode() override;
+  nsresult SetNonClientMargins(const LayoutDeviceIntMargin&) override;
+  void SetResizeMargin(mozilla::LayoutDeviceIntCoord aResizeMargin) override;
+  void UpdateWindowDraggingRegion(
+      const LayoutDeviceIntRegion& aRegion) override;
+
+  uint32_t GetMaxTouchPoints() const override;
+  void SetWindowClass(const nsAString& xulWinType, const nsAString& xulWinClass,
+                      const nsAString& xulWinName) override;
+
+  /**
+   * Event helpers
+   */
+  bool DispatchMouseEvent(mozilla::EventMessage aEventMessage, WPARAM wParam,
+                          LPARAM lParam, bool aIsContextMenuKey,
+                          int16_t aButton, uint16_t aInputSource,
+                          WinPointerInfo* aPointerInfo = nullptr,
+                          bool aIgnoreAPZ = false);
+  void DispatchPendingEvents();
+  void DispatchCustomEvent(const nsString& eventName);
+
+#ifdef ACCESSIBILITY
+  /**
+   * Return an accessible associated with the window.
+   */
+  mozilla::a11y::LocalAccessible* GetAccessible();
+#endif  // ACCESSIBILITY
+
+  /**
+   * Window utilities
+   */
+  nsWindow* GetTopLevelWindow(bool aStopOnDialogOrPopup);
+  WNDPROC GetPrevWindowProc() { return mPrevWndProc.valueOr(nullptr); }
+  WindowHook& GetWindowHook() { return mWindowHook; }
+  nsWindow* GetParentWindow(bool aIncludeOwner);
+
+  /**
+   * Misc.
+   */
+  bool WidgetTypeSupportsAcceleration() override;
+
+  void ForcePresent();
+  bool TouchEventShouldStartDrag(mozilla::EventMessage aEventMessage,
+                                 LayoutDeviceIntPoint aEventPoint);
+
+  void SetSmallIcon(HICON aIcon);
+  void SetBigIcon(HICON aIcon);
+  void SetSmallIconNoData();
+  void SetBigIconNoData();
+
+  static void SetIsRestoringSession(const bool aIsRestoringSession) {
+    sIsRestoringSession = aIsRestoringSession;
+  }
+
+  bool IsRTL() const { return mIsRTL; }
+
+  /**
+   * AssociateDefaultIMC() associates or disassociates the default IMC for
+   * the window.
+   *
+   * @param aAssociate    TRUE, associates the default IMC with the window.
+   *                      Otherwise, disassociates the default IMC from the
+   *                      window.
+   * @return              TRUE if this method associated the default IMC with
+   *                      disassociated window or disassociated the default IMC
+   *                      from associated window.
+   *                      Otherwise, i.e., if this method did nothing actually,
+   *                      FALSE.
+   */
+  bool AssociateDefaultIMC(bool aAssociate);
+
+  bool HasTaskbarIconBeenCreated() { return mHasTaskbarIconBeenCreated; }
+  // Called when either the nsWindow or an nsITaskbarTabPreview receives the
+  // noticiation that this window has its icon placed on the taskbar.
+  void SetHasTaskbarIconBeenCreated(bool created = true) {
+    mHasTaskbarIconBeenCreated = created;
+  }
+
+  // Getter/setter for the nsITaskbarWindowPreview for this nsWindow
+  already_AddRefed<nsITaskbarWindowPreview> GetTaskbarPreview() {
+    nsCOMPtr<nsITaskbarWindowPreview> preview(
+        do_QueryReferent(mTaskbarPreview));
+    return preview.forget();
+  }
+  void SetTaskbarPreview(nsITaskbarWindowPreview* preview) {
+    mTaskbarPreview = do_GetWeakReference(preview);
+  }
+
+  void ReparentNativeWidget(nsIWidget* aNewParent) override;
+
+  // Open file picker tracking
+  void PickerOpen();
+  void PickerClosed();
+
+  bool DestroyCalled() { return mDestroyCalled; }
+
+  bool IsPopup();
+  bool ShouldUseOffMainThreadCompositing() override;
+
+  const IMEContext& DefaultIMC() const { return mDefaultIMC; }
+
+  void GetCompositorWidgetInitData(
+      mozilla::widget::CompositorWidgetInitData* aInitData) override;
+  bool IsTouchWindow() const { return mTouchWindow; }
+  bool SynchronouslyRepaintOnResize() override;
+  void MaybeDispatchInitialFocusEvent() override;
+
+  void LocalesChanged() override;
+
+  void NotifyOcclusionState(mozilla::widget::OcclusionState aState) override;
+  void MaybeEnableWindowOcclusion(bool aEnable);
+
+  /*
+   * Return the HWND or null for this widget.
+   */
+  HWND GetWindowHandle() {
+    return static_cast<HWND>(GetNativeData(NS_NATIVE_WINDOW));
+  }
+
+  /*
+   * Touch input injection apis
+   */
+  nsresult SynthesizeNativeTouchPoint(uint32_t aPointerId,
+                                      TouchPointerState aPointerState,
+                                      LayoutDeviceIntPoint aPoint,
+                                      double aPointerPressure,
+                                      uint32_t aPointerOrientation,
+                                      nsIObserver* aObserver) override;
+  nsresult ClearNativeTouchSequence(nsIObserver* aObserver) override;
+
+  nsresult SynthesizeNativePenInput(uint32_t aPointerId,
+                                    TouchPointerState aPointerState,
+                                    LayoutDeviceIntPoint aPoint,
+                                    double aPressure, uint32_t aRotation,
+                                    int32_t aTiltX, int32_t aTiltY,
+                                    int32_t aButton,
+                                    nsIObserver* aObserver) override;
+
+  /*
+   * WM_APPCOMMAND common handler.
+   * Sends events via NativeKey::HandleAppCommandMessage().
+   */
+  bool HandleAppCommandMsg(const MSG& aAppCommandMsg, LRESULT* aRetValue);
+
+  const InputContext& InputContextRef() const { return mInputContext; }
+
+ private:
+  using TimeStamp = mozilla::TimeStamp;
+  using TimeDuration = mozilla::TimeDuration;
+  using TaskbarWindowPreview = mozilla::widget::TaskbarWindowPreview;
+  using NativeKey = mozilla::widget::NativeKey;
+  using MSGResult = mozilla::widget::MSGResult;
+  using PlatformCompositorWidgetDelegate =
+      mozilla::widget::PlatformCompositorWidgetDelegate;
+
+  struct Desktop {
+    // Cached GUID of the virtual desktop this window should be on.
+    // This value may be stale.
+    nsString mID;
+    bool mUpdateIsQueued = false;
+  };
+
+  class PointerInfo {
+   public:
+    enum class PointerType : uint8_t {
+      TOUCH,
+      PEN,
+    };
+
+    PointerInfo(int32_t aPointerId, LayoutDeviceIntPoint& aPoint,
+                PointerType aType)
+        : mPointerId(aPointerId), mPosition(aPoint), mType(aType) {}
+
+    int32_t mPointerId;
+    LayoutDeviceIntPoint mPosition;
+    PointerType mType;
+  };
+
+  class FrameState {
+   public:
+    explicit FrameState(nsWindow* aWindow);
+
+    void ConsumePreXULSkeletonState(bool aWasMaximized);
+
+    // Whether we should call ShowWindow with the relevant size mode if needed.
+    // We want to avoid that when Windows is already performing the change for
+    // us (via the SWP_FRAMECHANGED messages).
+    enum class DoShowWindow : bool { No, Yes };
+
+    void EnsureSizeMode(nsSizeMode, DoShowWindow = DoShowWindow::Yes);
+    void EnsureFullscreenMode(bool, DoShowWindow = DoShowWindow::Yes);
+    void OnFrameChanging();
+    void OnFrameChanged();
+
+    nsSizeMode GetSizeMode() const;
+
+    void CheckInvariant() const;
+
+   private:
+    void SetSizeModeInternal(nsSizeMode, DoShowWindow);
+
+    nsSizeMode mSizeMode = nsSizeMode_Normal;
+    // XXX mLastSizeMode is rather bizarre and needs some documentation.
+    nsSizeMode mLastSizeMode = nsSizeMode_Normal;
+    // The old size mode before going into fullscreen mode. This should never
+    // be nsSizeMode_Fullscreen.
+    nsSizeMode mPreFullscreenSizeMode = nsSizeMode_Normal;
+    // Whether we're in fullscreen. We need to keep this state out of band,
+    // rather than just using mSizeMode, because a window can be minimized
+    // while fullscreen, and we don't store the fullscreen state anywhere else.
+    bool mFullscreenMode = false;
+    nsWindow* mWindow;
+  };
+
+  // Manager for taskbar-hiding. No persistent state.
+  class TaskbarConcealer;
+
+  // A magic number to identify the FAKETRACKPOINTSCROLLABLE window created
+  // when the trackpoint hack is enabled.
+  enum { eFakeTrackPointScrollableID = 0x46545053 };
+
+  // Used for displayport suppression during window resize
+  enum ResizeState { NOT_RESIZING, IN_SIZEMOVE, RESIZING, MOVING };
+
+  ~nsWindow() override;
+
+  void WindowUsesOMTC() override;
+  void RegisterTouchWindow() override;
+
+  /**
+   * Callbacks
+   */
+  static LRESULT CALLBACK WindowProc(HWND hWnd, UINT msg, WPARAM wParam,
+                                     LPARAM lParam);
+  static LRESULT CALLBACK WindowProcInternal(HWND hWnd, UINT msg, WPARAM wParam,
+                                             LPARAM lParam);
+
+  static BOOL CALLBACK DispatchStarvedPaints(HWND aTopWindow, LPARAM aMsg);
+  static BOOL CALLBACK RegisterTouchForDescendants(HWND aTopWindow,
+                                                   LPARAM aMsg);
+  static BOOL CALLBACK UnregisterTouchForDescendants(HWND aTopWindow,
+                                                     LPARAM aMsg);
+  static LRESULT CALLBACK MozSpecialMsgFilter(int code, WPARAM wParam,
+                                              LPARAM lParam);
+  static LRESULT CALLBACK MozSpecialWndProc(int code, WPARAM wParam,
+                                            LPARAM lParam);
+  static LRESULT CALLBACK MozSpecialMouseProc(int code, WPARAM wParam,
+                                              LPARAM lParam);
+  static VOID CALLBACK HookTimerForPopups(HWND hwnd, UINT uMsg, UINT idEvent,
+                                          DWORD dwTime);
+
+  /**
+   * Window utilities
+   */
+  LPARAM lParamToScreen(LPARAM lParam);
+  LPARAM lParamToClient(LPARAM lParam);
+
+  WPARAM wParamFromGlobalMouseState();
+
+  bool AssociateWithNativeWindow();
+  void DissociateFromNativeWindow();
+  bool CanTakeFocus();
+  bool UpdateNonClientMargins(bool aReflowWindow = true);
+  void UpdateDarkModeToolbar();
+  void UpdateGetWindowInfoCaptionStatus(bool aActiveCaption);
+  void ResetLayout();
+  void InvalidateNonClientRegion();
+  static const wchar_t* GetMainWindowClass();
+  HWND GetOwnerWnd() const { return ::GetWindow(mWnd, GW_OWNER); }
+  bool IsOwnerForegroundWindow() const {
+    HWND owner = GetOwnerWnd();
+    return owner && owner == ::GetForegroundWindow();
+  }
+  bool IsForegroundWindow() const { return mWnd == ::GetForegroundWindow(); }
+  bool IsPopup() const { return mWindowType == WindowType::Popup; }
+  bool IsCloaked() const { return mIsCloaked; }
+
+  /**
+   * Event processing helpers
+   */
+  HWND GetTopLevelForFocus(HWND aCurWnd);
+  void DispatchFocusToTopLevelWindow(bool aIsActivate);
+  bool DispatchStandardEvent(mozilla::EventMessage aMsg);
+  void RelayMouseEvent(UINT aMsg, WPARAM wParam, LPARAM lParam);
+  bool ProcessMessage(UINT msg, WPARAM& wParam, LPARAM& lParam,
+                      LRESULT* aRetValue);
+  // We wrap this in ProcessMessage so we can log the return value
+  bool ProcessMessageInternal(UINT msg, WPARAM& wParam, LPARAM& lParam,
+                              LRESULT* aRetValue);
+  bool ExternalHandlerProcessMessage(UINT aMessage, WPARAM& aWParam,
+                                     LPARAM& aLParam, MSGResult& aResult);
+  LRESULT ProcessCharMessage(const MSG& aMsg, bool* aEventDispatched);
+  LRESULT ProcessKeyUpMessage(const MSG& aMsg, bool* aEventDispatched);
+  LRESULT ProcessKeyDownMessage(const MSG& aMsg, bool* aEventDispatched);
+  static bool EventIsInsideWindow(
+      nsWindow* aWindow,
+      mozilla::Maybe<POINT> aEventPoint = mozilla::Nothing());
+  static void PostSleepWakeNotification(const bool aIsSleepMode);
+  int32_t ClientMarginHitTestPoint(int32_t mx, int32_t my);
+  void SetWindowButtonRect(WindowButtonType aButtonType,
+                           const LayoutDeviceIntRect& aClientRect) override {
+    mWindowBtnRect[aButtonType] = aClientRect;
+  }
+  TimeStamp GetMessageTimeStamp(LONG aEventTime) const;
+  static void UpdateFirstEventTime(DWORD aEventTime);
+  void FinishLiveResizing(ResizeState aNewState);
+  mozilla::Maybe<mozilla::PanGestureInput> ConvertTouchToPanGesture(
+      const mozilla::MultiTouchInput& aTouchInput, PTOUCHINPUT aOriginalEvent);
+  void DispatchTouchOrPanGestureInput(mozilla::MultiTouchInput& aTouchInput,
+                                      PTOUCHINPUT aOSEvent);
+
+  /**
+   * Event handlers
+   */
+  void OnDestroy() override;
+  bool OnResize(const LayoutDeviceIntSize& aSize);
+  void OnSizeModeChange();
+  bool OnGesture(WPARAM wParam, LPARAM lParam);
+  bool OnTouch(WPARAM wParam, LPARAM lParam);
+  bool OnHotKey(WPARAM wParam, LPARAM lParam);
+  bool OnPaint(uint32_t aNestingLevel);
+  void OnWindowPosChanging(WINDOWPOS* info);
+  void OnWindowPosChanged(WINDOWPOS* wp);
+  void OnSysColorChanged();
+  void OnDPIChanged(int32_t x, int32_t y, int32_t width, int32_t height);
+  bool OnPointerEvents(UINT msg, WPARAM wParam, LPARAM lParam);
+
+  /**
+   * Function that registers when the user has been active (used for detecting
+   * when the user is idle).
+   */
+  void UserActivity();
+
+  int32_t GetHeight(int32_t aProposedHeight);
+
+  DWORD WindowStyle();
+  DWORD WindowExStyle();
+
+  static const wchar_t* ChooseWindowClass(WindowType);
+  // This method registers the given window class, and returns the class name.
+  static const wchar_t* RegisterWindowClass(const wchar_t* aClassName,
+                                            UINT aExtraStyle, LPWSTR aIconID);
+
+  /**
+   * Popup hooks
+   */
+  static void ScheduleHookTimer(HWND aWnd, UINT aMsgId);
+  static void RegisterSpecialDropdownHooks();
+  static void UnregisterSpecialDropdownHooks();
+  static bool GetPopupsToRollup(
+      nsIRollupListener* aRollupListener, uint32_t* aPopupsToRollup,
+      mozilla::Maybe<POINT> aEventPoint = mozilla::Nothing());
+  static bool NeedsToHandleNCActivateDelayed(HWND aWnd);
+  static bool DealWithPopups(HWND inWnd, UINT inMsg, WPARAM inWParam,
+                             LPARAM inLParam, LRESULT* outResult);
+
+  /**
+   * Window transparency helpers
+   */
+  void SetWindowTranslucencyInner(TransparencyMode aMode);
+  TransparencyMode GetWindowTranslucencyInner() const {
+    return mTransparencyMode;
+  }
+  bool IsSimulatedClientArea(int32_t clientX, int32_t clientY);
+  bool IsWindowButton(int32_t hitTestResult);
+
+  bool DispatchTouchEventFromWMPointer(UINT msg, LPARAM aLParam,
+                                       const WinPointerInfo& aPointerInfo,
+                                       mozilla::MouseButton aButton);
+
+  static bool IsAsyncResponseEvent(UINT aMsg, LRESULT& aResult);
+  void IPCWindowProcHandler(UINT& msg, WPARAM& wParam, LPARAM& lParam);
+
+  /**
+   * Misc.
+   */
+  void StopFlashing();
+  static HWND WindowAtMouse();
+  static bool IsTopLevelMouseExit(HWND aWnd);
+  LayoutDeviceIntRegion GetRegionToPaint(bool aForceFullRepaint, PAINTSTRUCT ps,
+                                         HDC aDC);
+  nsIWidgetListener* GetPaintListener();
+
+  void CreateCompositor() override;
+  void DestroyCompositor() override;
+  void RequestFxrOutput() override;
+
+  void RecreateDirectManipulationIfNeeded();
+  void ResizeDirectManipulationViewport();
+  void DestroyDirectManipulation();
+
+  bool NeedsToTrackWindowOcclusionState();
+
+  void AsyncUpdateWorkspaceID(Desktop& aDesktop);
+
+  // See bug 603793
+  static bool HasBogusPopupsDropShadowOnMultiMonitor();
+
+  static void InitMouseWheelScrollData();
+
+  void ChangedDPI();
+
+  static bool InitTouchInjection();
+
+  bool InjectTouchPoint(uint32_t aId, LayoutDeviceIntPoint& aPoint,
+                        POINTER_FLAGS aFlags, uint32_t aPressure = 1024,
+                        uint32_t aOrientation = 90);
+
+  void OnFullscreenChanged(nsSizeMode aOldSizeMode, bool aFullScreen);
+  void TryDwmResizeHack();
+
+  static void OnCloakEvent(HWND aWnd, bool aCloaked);
+  void OnCloakChanged(bool aCloaked);
+
+#ifdef DEBUG
+  virtual nsresult SetHiDPIMode(bool aHiDPI) override;
+  virtual nsresult RestoreHiDPIMode() override;
+#endif
+
+  // Get the orientation of the hidden taskbar, on the screen that this window
+  // is on, or Nothing if taskbar isn't hidden.
+  mozilla::Maybe<UINT> GetHiddenTaskbarEdge();
+
+  static bool sTouchInjectInitialized;
+  static InjectTouchInputPtr sInjectTouchFuncPtr;
+  static uint32_t sInstanceCount;
+  static nsWindow* sCurrentWindow;
+  static bool sIsOleInitialized;
+  static Cursor sCurrentCursor;
+  static bool sJustGotDeactivate;
+  static bool sJustGotActivate;
+  static bool sIsInMouseCapture;
+  static bool sIsRestoringSession;
+
+  // Message postponement hack. See the definition-site of
+  // WndProcUrgentInvocation::sDepth for details.
+  struct MOZ_STACK_CLASS WndProcUrgentInvocation {
+    struct Marker {
+      Marker() { ++sDepth; }
+      ~Marker() { --sDepth; }
+    };
+    inline static bool IsActive() { return sDepth > 0; }
+    static size_t sDepth;
+  };
+
+  // Hook Data Members for Dropdowns. sProcessHook Tells the
+  // hook methods whether they should be processing the hook
+  // messages.
+  static HHOOK sMsgFilterHook;
+  static HHOOK sCallProcHook;
+  static HHOOK sCallMouseHook;
+  static bool sProcessHook;
+  static UINT sRollupMsgId;
+  static HWND sRollupMsgWnd;
+  static UINT sHookTimerId;
+
+  // Used to prevent dispatching mouse events that do not originate from user
+  // input.
+  static POINT sLastMouseMovePoint;
+
+  nsClassHashtable<nsUint32HashKey, PointerInfo> mActivePointers;
+
+  // This is used by SynthesizeNativeTouchPoint to maintain state between
+  // multiple synthesized points, in the case where we can't call InjectTouch
+  // directly.
+  mozilla::UniquePtr<mozilla::MultiTouchInput> mSynthesizedTouchInput;
+
+  InputContext mInputContext;
+
+  nsCOMPtr<nsIWidget> mParent;
+  nsIntSize mLastSize = nsIntSize(0, 0);
+  nsIntPoint mLastPoint;
+  HWND mWnd = nullptr;
+  HWND mTransitionWnd = nullptr;
+  mozilla::Maybe<WNDPROC> mPrevWndProc;
+  HBRUSH mBrush;
+  IMEContext mDefaultIMC;
+  HDEVNOTIFY mDeviceNotifyHandle = nullptr;
+  bool mIsTopWidgetWindow = false;
+  bool mInDtor = false;
+  bool mIsVisible = false;
+  bool mIsCloaked = false;
+  bool mTouchWindow = false;
+  bool mDisplayPanFeedback = false;
+  bool mHideChrome = false;
+  bool mIsRTL;
+  bool mMousePresent = false;
+  bool mSimulatedClientArea = false;
+  bool mDestroyCalled = false;
+  bool mOpeningAnimationSuppressed;
+  bool mAlwaysOnTop;
+  bool mIsEarlyBlankWindow = false;
+  bool mIsShowingPreXULSkeletonUI = false;
+  bool mResizable = false;
+  // Whether we're an alert window. Alert windows don't have taskbar icons and
+  // don't steal focus from other windows when opened. They're also expected to
+  // be of type WindowType::Dialog.
+  bool mIsAlert = false;
+  bool mIsPerformingDwmFlushHack = false;
+  bool mDraggingWindowWithMouse = false;
+  DWORD_PTR mOldStyle = 0;
+  DWORD_PTR mOldExStyle = 0;
+  nsNativeDragTarget* mNativeDragTarget = nullptr;
+  HKL mLastKeyboardLayout = 0;
+  mozilla::CheckInvariantWrapper<FrameState> mFrameState;
+  WindowHook mWindowHook;
+  uint32_t mPickerDisplayCount = 0;
+  HICON mIconSmall = nullptr;
+  HICON mIconBig = nullptr;
+  HWND mLastKillFocusWindow = nullptr;
+  PlatformCompositorWidgetDelegate* mCompositorWidgetDelegate = nullptr;
+
+  LayoutDeviceIntMargin NonClientSizeMargin() const {
+    return NonClientSizeMargin(mNonClientOffset);
+  }
+  LayoutDeviceIntMargin NonClientSizeMargin(
+      const LayoutDeviceIntMargin& aNonClientOffset) const;
+  LayoutDeviceIntMargin NormalWindowNonClientOffset() const;
+
+  // Non-client margin settings
+  // Pre-calculated outward offset applied to default frames
+  LayoutDeviceIntMargin mNonClientOffset;
+  // Margins set by the owner
+  LayoutDeviceIntMargin mNonClientMargins;
+  // Margins we'd like to set once chrome is reshown:
+  LayoutDeviceIntMargin mFutureMarginsOnceChromeShows;
+  // Indicates we need to apply margins once toggling chrome into showing:
+  bool mFutureMarginsToUse = false;
+
+  // Indicates custom frames are enabled
+  bool mCustomNonClient = false;
+  // Indicates custom resize margins are in effect
+  bool mUseResizeMarginOverrides = false;
+  // Width of the left and right portions of the resize region
+  mozilla::LayoutDeviceIntCoord mHorResizeMargin;
+  // Height of the top and bottom portions of the resize region
+  mozilla::LayoutDeviceIntCoord mVertResizeMargin;
+  // Height of the caption plus border
+  mozilla::LayoutDeviceIntCoord mCaptionHeight;
+
+  // not yet set, will be calculated on first use
+  double mDefaultScale = -1.0;
+
+  // not yet set, will be calculated on first use
+  float mAspectRatio = 0.0;
+
+  nsCOMPtr<nsIUserIdleServiceInternal> mIdleService;
+
+  // Draggable titlebar region maintained by UpdateWindowDraggingRegion
+  LayoutDeviceIntRegion mDraggableRegion;
+
+  // Graphics
+  LayoutDeviceIntRect mLastPaintBounds;
+
+  ResizeState mResizeState = NOT_RESIZING;
+
+  // Transparency
+  TransparencyMode mTransparencyMode = TransparencyMode::Opaque;
+  nsIntRegion mPossiblyTransparentRegion;
+
+  // Win7 Gesture processing and management
+  nsWinGesture mGesture;
+
+  // Weak ref to the nsITaskbarWindowPreview associated with this window
+  nsWeakPtr mTaskbarPreview = nullptr;
+
+  // The input region that determines whether mouse events should be ignored
+  // and pass through to the window below. This is currently only used for
+  // popups.
+  InputRegion mInputRegion;
+
+  // True if the taskbar (possibly through the tab preview) tells us that the
+  // icon has been created on the taskbar.
+  bool mHasTaskbarIconBeenCreated = false;
+
+  // Whether we're in the process of sending a WM_SETTEXT ourselves
+  bool mSendingSetText = false;
+
+  // Whether we were created as a child window (aka ChildWindow) or not.
+  bool mIsChildWindow : 1;
+
+  int32_t mCachedHitTestResult = 0;
+
+  // The point in time at which the last paint completed. We use this to avoid
+  //  painting too rapidly in response to frequent input events.
+  TimeStamp mLastPaintEndTime;
+
+  // Caching for hit test results (in client coordinates)
+  LayoutDeviceIntPoint mCachedHitTestPoint;
+  TimeStamp mCachedHitTestTime;
+
+  RefPtr<mozilla::widget::InProcessWinCompositorWidget> mBasicLayersSurface;
+
+  double mSizeConstraintsScale;  // scale in effect when setting constraints
+
+  // Will be calculated when layer manager is created.
+  int32_t mMaxTextureSize = -1;
+
+  // Pointer events processing and management
+  WinPointerEvents mPointerEvents;
+
+  ScreenPoint mLastPanGestureFocus;
+
+  // When true, used to indicate an async call to RequestFxrOutput to the GPU
+  // process after the Compositor is created
+  bool mRequestFxrOutputPending = false;
+
+  // A stack based class used in DispatchMouseEvent() to tell whether we should
+  // NOT open context menu when we receives WM_CONTEXTMENU after the
+  // DispatchMouseEvent calls.
+  // This class now works only in the case where a mouse up event happened in
+  // the overscroll gutter.
+  class MOZ_STACK_CLASS ContextMenuPreventer final {
+   public:
+    explicit ContextMenuPreventer(nsWindow* aWindow)
+        : mWindow(aWindow), mNeedsToPreventContextMenu(false){};
+    ~ContextMenuPreventer() {
+      mWindow->mNeedsToPreventContextMenu = mNeedsToPreventContextMenu;
+    }
+    void Update(const mozilla::WidgetMouseEvent& aEvent,
+                const nsIWidget::ContentAndAPZEventStatus& aEventStatus);
+
+   private:
+    nsWindow* mWindow;
+    bool mNeedsToPreventContextMenu = false;
+  };
+  friend class ContextMenuPreventer;
+  bool mNeedsToPreventContextMenu = false;
+
+  mozilla::UniquePtr<mozilla::widget::DirectManipulationOwner> mDmOwner;
+
+  // Client rect for minimize, maximize and close buttons.
+  mozilla::EnumeratedArray<WindowButtonType, WindowButtonType::Count,
+                           LayoutDeviceIntRect>
+      mWindowBtnRect;
+
+  mozilla::DataMutex<Desktop> mDesktopId;
+
+  // If set, indicates the edge of the NC region we should clear to black
+  // on next paint.  One of: ABE_TOP, ABE_BOTTOM, ABE_LEFT or ABE_RIGHT.
+  mozilla::Maybe<UINT> mClearNCEdge;
+
+  friend class nsWindowGfx;
+
+  static constexpr int kHiddenTaskbarSize = 2;
+};
+
+#endif  // WIDGET_WINDOWS_NSWINDOW_H_
diff --git a/widget/windows/nsWindowDbg.cpp b/widget/windows/nsWindowDbg.cpp
new file mode 100644
index 0000000000..8125a8532b
--- /dev/null
+++ b/widget/windows/nsWindowDbg.cpp
@@ -0,0 +1,1612 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/*
+ * nsWindowDbg - Debug related utilities for nsWindow.
+ */
+
+#include "nsWindowDbg.h"
+#include "nsToolkit.h"
+#include "WinPointerEvents.h"
+#include "nsWindowLoggedMessages.h"
+#include "mozilla/Logging.h"
+#include "mozilla/Maybe.h"
+#include "nsWindow.h"
+#include "GeckoProfiler.h"
+#include "mozilla/PresShell.h"
+#include "mozilla/dom/Document.h"
+
+#include <winuser.h>
+#include <dbt.h>
+#include <imm.h>
+#include <tpcshrd.h>
+
+#include <unordered_set>
+
+using namespace mozilla;
+using namespace mozilla::widget;
+extern mozilla::LazyLogModule gWindowsLog;
+static mozilla::LazyLogModule gWindowsEventLog("WindowsEvent");
+
+// currently defined in widget/windows/nsAppShell.cpp
+extern UINT sAppShellGeckoMsgId;
+
+#if defined(POPUP_ROLLUP_DEBUG_OUTPUT)
+MSGFEventMsgInfo gMSGFEvents[] = {
+    "MSGF_DIALOGBOX", 0,    "MSGF_MESSAGEBOX", 1, "MSGF_MENU", 2,
+    "MSGF_SCROLLBAR", 5,    "MSGF_NEXTWINDOW", 6, "MSGF_MAX",  8,
+    "MSGF_USER",      4096, nullptr,           0};
+#endif
+
+static long gEventCounter = 0;
+static UINT gLastEventMsg = 0;
+
+namespace geckoprofiler::markers {
+
+struct WindowProcMarker {
+  static constexpr Span<const char> MarkerTypeName() {
+    return MakeStringSpan("WindowProc");
+  }
+  static void StreamJSONMarkerData(baseprofiler::SpliceableJSONWriter& aWriter,
+                                   const ProfilerString8View& aMsgLoopName,
+                                   UINT aMsg, WPARAM aWParam, LPARAM aLParam) {
+    aWriter.StringProperty("messageLoop", aMsgLoopName);
+    aWriter.IntProperty("uMsg", aMsg);
+    const char* name;
+    if (aMsg < WM_USER) {
+      const auto eventMsgInfo = mozilla::widget::gAllEvents.find(aMsg);
+      if (eventMsgInfo != mozilla::widget::gAllEvents.end()) {
+        name = eventMsgInfo->second.mStr;
+      } else {
+        name = "ui message";
+      }
+    } else if (aMsg >= WM_USER && aMsg < WM_APP) {
+      name = "WM_USER message";
+    } else if (aMsg >= WM_APP && aMsg < 0xC000) {
+      name = "WM_APP message";
+    } else if (aMsg >= 0xC000 && aMsg < 0x10000) {
+      if (aMsg == sAppShellGeckoMsgId) {
+        name = "nsAppShell:EventID";
+      } else {
+        name = "registered Windows message";
+      }
+    } else {
+      name = "system message";
+    }
+    aWriter.StringProperty("name", MakeStringSpan(name));
+
+    if (aWParam) {
+      aWriter.IntProperty("wParam", aWParam);
+    }
+    if (aLParam) {
+      aWriter.IntProperty("lParam", aLParam);
+    }
+  }
+
+  static MarkerSchema MarkerTypeDisplay() {
+    using MS = MarkerSchema;
+    MS schema{MS::Location::MarkerChart, MS::Location::MarkerTable};
+    schema.AddKeyFormat("uMsg", MS::Format::Integer);
+    schema.SetChartLabel(
+        "{marker.data.messageLoop} | {marker.data.name} ({marker.data.uMsg})");
+    schema.SetTableLabel(
+        "{marker.name} - {marker.data.messageLoop} - {marker.data.name} "
+        "({marker.data.uMsg})");
+    schema.SetTooltipLabel(
+        "{marker.data.messageLoop} - {marker.name} - {marker.data.name}");
+    schema.AddKeyFormat("wParam", MS::Format::Integer);
+    schema.AddKeyFormat("lParam", MS::Format::Integer);
+    return schema;
+  }
+};
+
+}  // namespace geckoprofiler::markers
+
+namespace mozilla::widget {
+
+AutoProfilerMessageMarker::AutoProfilerMessageMarker(
+    Span<const char> aMsgLoopName, HWND hWnd, UINT msg, WPARAM wParam,
+    LPARAM lParam)
+    : mMsgLoopName(aMsgLoopName), mMsg(msg), mWParam(wParam), mLParam(lParam) {
+  if (profiler_thread_is_being_profiled_for_markers()) {
+    mOptions.emplace(MarkerOptions(MarkerTiming::IntervalStart()));
+    nsWindow* win = WinUtils::GetNSWindowPtr(hWnd);
+    if (win) {
+      nsIWidgetListener* wl = win->GetWidgetListener();
+      if (wl) {
+        PresShell* presShell = wl->GetPresShell();
+        if (presShell) {
+          dom::Document* doc = presShell->GetDocument();
+          if (doc) {
+            mOptions->Set(MarkerInnerWindowId(doc->InnerWindowID()));
+          }
+        }
+      }
+    }
+  }
+}
+
+AutoProfilerMessageMarker::~AutoProfilerMessageMarker() {
+  if (!profiler_thread_is_being_profiled_for_markers()) {
+    return;
+  }
+
+  if (mOptions) {
+    mOptions->TimingRef().SetIntervalEnd();
+  } else {
+    mOptions.emplace(MarkerOptions(MarkerTiming::IntervalEnd()));
+  }
+  profiler_add_marker(
+      "WindowProc", ::mozilla::baseprofiler::category::OTHER,
+      std::move(*mOptions), geckoprofiler::markers::WindowProcMarker{},
+      ProfilerString8View::WrapNullTerminatedString(mMsgLoopName.data()), mMsg,
+      mWParam, mLParam);
+}
+
+// Using an unordered_set so we can initialize this with nice syntax instead of
+// having to add them one at a time to a mozilla::HashSet.
+std::unordered_set<UINT> gEventsToLogOriginalParams = {
+    WM_WINDOWPOSCHANGING,  // (dummy comments for clang-format)
+    WM_SIZING,             //
+    WM_STYLECHANGING,
+    WM_GETTEXT,
+    WM_GETMINMAXINFO,
+    WM_MEASUREITEM,
+    WM_NCCALCSIZE,
+};
+
+// If you add an event here, you must add cases for these to
+// MakeMessageSpecificData() and AppendFriendlyMessageSpecificData()
+// in nsWindowLoggedMessages.cpp.
+std::unordered_set<UINT> gEventsToRecordInAboutPage = {
+    WM_WINDOWPOSCHANGING,  // (dummy comments for clang-format)
+    WM_WINDOWPOSCHANGED,   //
+    WM_SIZING,
+    WM_SIZE,
+    WM_DPICHANGED,
+    WM_SETTINGCHANGE,
+    WM_NCCALCSIZE,
+    WM_MOVE,
+    WM_MOVING,
+    WM_GETMINMAXINFO,
+};
+
+NativeEventLogger::NativeEventLogger(Span<const char> aMsgLoopName, HWND hwnd,
+                                     UINT msg, WPARAM wParam, LPARAM lParam)
+    : mProfilerMarker(aMsgLoopName, hwnd, msg, wParam, lParam),
+      mMsgLoopName(aMsgLoopName.data()),
+      mHwnd(hwnd),
+      mMsg(msg),
+      mWParam(wParam),
+      mLParam(lParam),
+      mResult(mozilla::Nothing()),
+      mShouldLogPostCall(false) {
+  if (NativeEventLoggerInternal()) {
+    // this event was logged, so reserve this counter number for the post-call
+    mEventCounter = mozilla::Some(gEventCounter);
+    ++gEventCounter;
+  }
+}
+
+NativeEventLogger::~NativeEventLogger() {
+  // If mResult is Nothing, perhaps an exception was thrown or something
+  // before SetResult() was supposed to be called.
+  if (mResult.isSome()) {
+    if (NativeEventLoggerInternal() && mEventCounter.isNothing()) {
+      // We didn't reserve a counter in the pre-call, so reserve it here.
+      ++gEventCounter;
+    }
+  }
+  if (mMsg == WM_DESTROY) {
+    // Remove any logged messages for this window.
+    WindowClosed(mHwnd);
+  }
+}
+
+void EventMsgInfo::LogParameters(nsCString& str, WPARAM wParam, LPARAM lParam,
+                                 bool isPreCall) {
+  if (mParamInfoFn) {
+    str = mParamInfoFn(wParam, lParam, isPreCall);
+  } else {
+    if (mWParamInfoFn) {
+      mWParamInfoFn(str, wParam, mWParamName, isPreCall);
+    }
+    if (mLParamInfoFn) {
+      if (mWParamInfoFn) {
+        str.AppendASCII(" ");
+      }
+      mLParamInfoFn(str, lParam, mLParamName, isPreCall);
+    }
+  }
+}
+
+nsAutoCString DefaultParamInfo(uint64_t wParam, uint64_t lParam,
+                               bool /* isPreCall */) {
+  nsAutoCString result;
+  result.AppendPrintf("wParam=0x%08llX lParam=0x%08llX", wParam, lParam);
+  return result;
+}
+
+void AppendEnumValueInfo(
+    nsCString& str, uint64_t value,
+    const std::unordered_map<uint64_t, const char*>& valuesAndNames,
+    const char* name) {
+  if (name != nullptr) {
+    str.AppendPrintf("%s=", name);
+  }
+  auto entry = valuesAndNames.find(value);
+  if (entry == valuesAndNames.end()) {
+    str.AppendPrintf("Unknown (0x%08llX)", value);
+  } else {
+    str.AppendASCII(entry->second);
+  }
+}
+
+bool AppendFlagsInfo(nsCString& str, uint64_t flags,
+                     const nsTArray<EnumValueAndName>& flagsAndNames,
+                     const char* name) {
+  if (name != nullptr) {
+    str.AppendPrintf("%s=", name);
+  }
+  bool firstAppend = true;
+  for (const EnumValueAndName& flagAndName : flagsAndNames) {
+    if (MOZ_UNLIKELY(flagAndName.mFlag == 0)) {
+      // Special case - only want to write this if nothing else was set.
+      // For this to make sense, 0 values should come at the end of
+      // flagsAndNames.
+      if (flags == 0 && firstAppend) {
+        firstAppend = false;
+        str.AppendASCII(flagAndName.mName);
+      }
+    } else if ((flags & flagAndName.mFlag) == flagAndName.mFlag) {
+      if (MOZ_LIKELY(!firstAppend)) {
+        str.Append('|');
+      }
+      firstAppend = false;
+      str.AppendASCII(flagAndName.mName);
+      flags = flags & ~flagAndName.mFlag;
+    }
+  }
+  if (flags != 0) {
+    if (MOZ_LIKELY(!firstAppend)) {
+      str.Append('|');
+    }
+    firstAppend = false;
+    str.AppendPrintf("Unknown (0x%08llX)", flags);
+  }
+  return !firstAppend;
+}
+
+// if mResult is not set, this is used to log the parameters passed in the
+// message, otherwise we are logging the parameters after we have handled the
+// message. This is useful for events where we might change the parameters while
+// handling the message (for example WM_GETTEXT and WM_NCCALCSIZE)
+// Returns whether this message was logged, so we need to reserve a
+// counter number for it.
+bool NativeEventLogger::NativeEventLoggerInternal() {
+  mozilla::LogLevel const targetLogLevel = [&] {
+    // These messages often take up more than 90% of logs if not filtered out.
+    if (mMsg == WM_SETCURSOR || mMsg == WM_MOUSEMOVE || mMsg == WM_NCHITTEST) {
+      return LogLevel::Verbose;
+    }
+    if (gLastEventMsg == mMsg) {
+      return LogLevel::Debug;
+    }
+    return LogLevel::Info;
+  }();
+
+  bool isPreCall = mResult.isNothing();
+  if (isPreCall || mShouldLogPostCall) {
+    bool recordInAboutPage = gEventsToRecordInAboutPage.find(mMsg) !=
+                             gEventsToRecordInAboutPage.end();
+    bool writeToWindowsLog;
+    if (isPreCall) {
+      writeToWindowsLog = MOZ_LOG_TEST(gWindowsEventLog, targetLogLevel);
+      bool shouldLogAtAll = recordInAboutPage || writeToWindowsLog;
+      // Since calling mParamInfoFn() allocates a string, only go down this code
+      // path if we're going to log this message to reduce allocations.
+      if (!shouldLogAtAll) {
+        return false;
+      }
+      mShouldLogPostCall = true;
+      bool shouldLogPreCall = gEventsToLogOriginalParams.find(mMsg) !=
+                              gEventsToLogOriginalParams.end();
+      if (!shouldLogPreCall) {
+        // Pre-call and we don't want to log both, so skip this one.
+        return false;
+      }
+    } else {
+      writeToWindowsLog = true;
+    }
+    if (recordInAboutPage) {
+      LogWindowMessage(mHwnd, mMsg, isPreCall,
+                       mEventCounter.valueOr(gEventCounter), mWParam, mLParam,
+                       mResult, mRetValue);
+    }
+    gLastEventMsg = mMsg;
+    if (writeToWindowsLog) {
+      const auto& eventMsgInfo = gAllEvents.find(mMsg);
+      const char* msgText = eventMsgInfo != gAllEvents.end()
+                                ? eventMsgInfo->second.mStr
+                                : nullptr;
+      nsAutoCString paramInfo;
+      if (eventMsgInfo != gAllEvents.end()) {
+        eventMsgInfo->second.LogParameters(paramInfo, mWParam, mLParam,
+                                           isPreCall);
+      } else {
+        paramInfo = DefaultParamInfo(mWParam, mLParam, isPreCall);
+      }
+      const char* resultMsg = mResult.isSome()
+                                  ? (mResult.value() ? "true" : "false")
+                                  : "initial call";
+      nsAutoCString logMessage;
+      logMessage.AppendPrintf(
+          "%s | %6ld %08" PRIX64 " - 0x%04X %s%s%s: 0x%08" PRIX64 " (%s)\n",
+          mMsgLoopName, mEventCounter.valueOr(gEventCounter),
+          reinterpret_cast<uint64_t>(mHwnd), mMsg,
+          msgText ? msgText : "Unknown", paramInfo.IsEmpty() ? "" : " ",
+          paramInfo.get(),
+          mResult.isSome() ? static_cast<uint64_t>(mRetValue) : 0, resultMsg);
+      const char* logMessageData = logMessage.Data();
+      MOZ_LOG(gWindowsEventLog, targetLogLevel, ("%s", logMessageData));
+    }
+    return true;
+  }
+  return false;
+}
+
+void TrueFalseParamInfo(nsCString& result, uint64_t value, const char* name,
+                        bool /* isPreCall */) {
+  result.AppendPrintf("%s=%s", name, value == TRUE ? "TRUE" : "FALSE");
+}
+
+void TrueFalseLowOrderWordParamInfo(nsCString& result, uint64_t value,
+                                    const char* name, bool /* isPreCall */) {
+  result.AppendPrintf("%s=%s", name, LOWORD(value) == TRUE ? "TRUE" : "FALSE");
+}
+
+void HexParamInfo(nsCString& result, uint64_t value, const char* name,
+                  bool /* isPreCall */) {
+  result.AppendPrintf("%s=0x%08llX", name, value);
+}
+
+void IntParamInfo(nsCString& result, uint64_t value, const char* name,
+                  bool /* isPreCall */) {
+  result.AppendPrintf("%s=%lld", name, value);
+}
+
+void RectParamInfo(nsCString& str, uint64_t value, const char* name,
+                   bool /* isPreCall */) {
+  LPRECT rect = reinterpret_cast<LPRECT>(value);
+  if (rect == nullptr) {
+    str.AppendPrintf("NULL rect?");
+    return;
+  }
+  if (name != nullptr) {
+    str.AppendPrintf("%s ", name);
+  }
+  str.AppendPrintf("left=%ld top=%ld right=%ld bottom=%ld", rect->left,
+                   rect->top, rect->right, rect->bottom);
+}
+
+#define VALANDNAME_ENTRY(_msg) \
+  { _msg, #_msg }
+
+void CreateStructParamInfo(nsCString& str, uint64_t value, const char* name,
+                           bool /* isPreCall */) {
+  CREATESTRUCT* createStruct = reinterpret_cast<CREATESTRUCT*>(value);
+  if (createStruct == nullptr) {
+    str.AppendASCII("NULL createStruct?");
+    return;
+  }
+  str.AppendPrintf(
+      "%s: hInstance=%p hMenu=%p hwndParent=%p lpszName=%S lpszClass=%S x=%d "
+      "y=%d cx=%d cy=%d",
+      name, createStruct->hInstance, createStruct->hMenu,
+      createStruct->hwndParent, createStruct->lpszName, createStruct->lpszClass,
+      createStruct->x, createStruct->y, createStruct->cx, createStruct->cy);
+  str.AppendASCII(" ");
+  const static nsTArray<EnumValueAndName> windowStyles = {
+      // these combinations of other flags need to come first
+      VALANDNAME_ENTRY(WS_OVERLAPPEDWINDOW), VALANDNAME_ENTRY(WS_POPUPWINDOW),
+      VALANDNAME_ENTRY(WS_CAPTION),
+      // regular flags
+      VALANDNAME_ENTRY(WS_POPUP), VALANDNAME_ENTRY(WS_CHILD),
+      VALANDNAME_ENTRY(WS_MINIMIZE), VALANDNAME_ENTRY(WS_VISIBLE),
+      VALANDNAME_ENTRY(WS_DISABLED), VALANDNAME_ENTRY(WS_CLIPSIBLINGS),
+      VALANDNAME_ENTRY(WS_CLIPCHILDREN), VALANDNAME_ENTRY(WS_MAXIMIZE),
+      VALANDNAME_ENTRY(WS_BORDER), VALANDNAME_ENTRY(WS_DLGFRAME),
+      VALANDNAME_ENTRY(WS_VSCROLL), VALANDNAME_ENTRY(WS_HSCROLL),
+      VALANDNAME_ENTRY(WS_SYSMENU), VALANDNAME_ENTRY(WS_THICKFRAME),
+      VALANDNAME_ENTRY(WS_GROUP), VALANDNAME_ENTRY(WS_TABSTOP),
+      // zero value needs to come last
+      VALANDNAME_ENTRY(WS_OVERLAPPED)};
+  AppendFlagsInfo(str, createStruct->style, windowStyles, "style");
+  str.AppendASCII(" ");
+  const nsTArray<EnumValueAndName> extendedWindowStyles = {
+      // these combinations of other flags need to come first
+      VALANDNAME_ENTRY(WS_EX_OVERLAPPEDWINDOW),
+      VALANDNAME_ENTRY(WS_EX_PALETTEWINDOW),
+      // regular flags
+      VALANDNAME_ENTRY(WS_EX_DLGMODALFRAME),
+      VALANDNAME_ENTRY(WS_EX_NOPARENTNOTIFY),
+      VALANDNAME_ENTRY(WS_EX_TOPMOST),
+      VALANDNAME_ENTRY(WS_EX_ACCEPTFILES),
+      VALANDNAME_ENTRY(WS_EX_TRANSPARENT),
+      VALANDNAME_ENTRY(WS_EX_MDICHILD),
+      VALANDNAME_ENTRY(WS_EX_TOOLWINDOW),
+      VALANDNAME_ENTRY(WS_EX_WINDOWEDGE),
+      VALANDNAME_ENTRY(WS_EX_CLIENTEDGE),
+      VALANDNAME_ENTRY(WS_EX_CONTEXTHELP),
+      VALANDNAME_ENTRY(WS_EX_RIGHT),
+      VALANDNAME_ENTRY(WS_EX_LEFT),
+      VALANDNAME_ENTRY(WS_EX_RTLREADING),
+      VALANDNAME_ENTRY(WS_EX_LTRREADING),
+      VALANDNAME_ENTRY(WS_EX_LEFTSCROLLBAR),
+      VALANDNAME_ENTRY(WS_EX_RIGHTSCROLLBAR),
+      VALANDNAME_ENTRY(WS_EX_CONTROLPARENT),
+      VALANDNAME_ENTRY(WS_EX_STATICEDGE),
+      VALANDNAME_ENTRY(WS_EX_APPWINDOW),
+      VALANDNAME_ENTRY(WS_EX_LAYERED),
+      VALANDNAME_ENTRY(WS_EX_NOINHERITLAYOUT),
+      VALANDNAME_ENTRY(WS_EX_LAYOUTRTL),
+      VALANDNAME_ENTRY(WS_EX_NOACTIVATE),
+      VALANDNAME_ENTRY(WS_EX_COMPOSITED),
+      VALANDNAME_ENTRY(WS_EX_NOREDIRECTIONBITMAP),
+  };
+  AppendFlagsInfo(str, createStruct->dwExStyle, extendedWindowStyles,
+                  "dwExStyle");
+}
+
+void XLowWordYHighWordParamInfo(nsCString& str, uint64_t value,
+                                const char* name, bool /* isPreCall */) {
+  str.AppendPrintf("%s: x=%d y=%d", name, static_cast<int>(LOWORD(value)),
+                   static_cast<int>(HIWORD(value)));
+}
+
+void PointParamInfo(nsCString& str, uint64_t value, const char* name,
+                    bool /* isPreCall */) {
+  str.AppendPrintf("%s: x=%d y=%d", name, static_cast<int>(GET_X_LPARAM(value)),
+                   static_cast<int>(GET_Y_LPARAM(value)));
+}
+
+void PointExplicitParamInfo(nsCString& str, POINT point, const char* name) {
+  str.AppendPrintf("%s: x=%ld y=%ld", name, point.x, point.y);
+}
+
+void PointsParamInfo(nsCString& str, uint64_t value, const char* name,
+                     bool /* isPreCall */) {
+  PPOINTS points = reinterpret_cast<PPOINTS>(&value);
+  str.AppendPrintf("%s: x=%d y=%d", name, points->x, points->y);
+}
+
+void VirtualKeyParamInfo(nsCString& result, uint64_t param, const char* name,
+                         bool /* isPreCall */) {
+  const static std::unordered_map<uint64_t, const char*> virtualKeys{
+      VALANDNAME_ENTRY(VK_LBUTTON),
+      VALANDNAME_ENTRY(VK_RBUTTON),
+      VALANDNAME_ENTRY(VK_CANCEL),
+      VALANDNAME_ENTRY(VK_MBUTTON),
+      VALANDNAME_ENTRY(VK_XBUTTON1),
+      VALANDNAME_ENTRY(VK_XBUTTON2),
+      VALANDNAME_ENTRY(VK_BACK),
+      VALANDNAME_ENTRY(VK_TAB),
+      VALANDNAME_ENTRY(VK_CLEAR),
+      VALANDNAME_ENTRY(VK_RETURN),
+      VALANDNAME_ENTRY(VK_SHIFT),
+      VALANDNAME_ENTRY(VK_CONTROL),
+      VALANDNAME_ENTRY(VK_MENU),
+      VALANDNAME_ENTRY(VK_PAUSE),
+      VALANDNAME_ENTRY(VK_CAPITAL),
+      VALANDNAME_ENTRY(VK_KANA),
+      VALANDNAME_ENTRY(VK_HANGUL),
+#ifdef VK_IME_ON
+      VALANDNAME_ENTRY(VK_IME_ON),
+#endif
+      VALANDNAME_ENTRY(VK_JUNJA),
+      VALANDNAME_ENTRY(VK_FINAL),
+      VALANDNAME_ENTRY(VK_HANJA),
+      VALANDNAME_ENTRY(VK_KANJI),
+#ifdef VK_IME_OFF
+      VALANDNAME_ENTRY(VK_IME_OFF),
+#endif
+      VALANDNAME_ENTRY(VK_ESCAPE),
+      VALANDNAME_ENTRY(VK_CONVERT),
+      VALANDNAME_ENTRY(VK_NONCONVERT),
+      VALANDNAME_ENTRY(VK_ACCEPT),
+      VALANDNAME_ENTRY(VK_MODECHANGE),
+      VALANDNAME_ENTRY(VK_SPACE),
+      VALANDNAME_ENTRY(VK_PRIOR),
+      VALANDNAME_ENTRY(VK_NEXT),
+      VALANDNAME_ENTRY(VK_END),
+      VALANDNAME_ENTRY(VK_HOME),
+      VALANDNAME_ENTRY(VK_LEFT),
+      VALANDNAME_ENTRY(VK_UP),
+      VALANDNAME_ENTRY(VK_RIGHT),
+      VALANDNAME_ENTRY(VK_DOWN),
+      VALANDNAME_ENTRY(VK_SELECT),
+      VALANDNAME_ENTRY(VK_PRINT),
+      VALANDNAME_ENTRY(VK_EXECUTE),
+      VALANDNAME_ENTRY(VK_SNAPSHOT),
+      VALANDNAME_ENTRY(VK_INSERT),
+      VALANDNAME_ENTRY(VK_DELETE),
+      VALANDNAME_ENTRY(VK_HELP),
+      VALANDNAME_ENTRY(VK_LWIN),
+      VALANDNAME_ENTRY(VK_RWIN),
+      VALANDNAME_ENTRY(VK_APPS),
+      VALANDNAME_ENTRY(VK_SLEEP),
+      VALANDNAME_ENTRY(VK_NUMPAD0),
+      VALANDNAME_ENTRY(VK_NUMPAD1),
+      VALANDNAME_ENTRY(VK_NUMPAD2),
+      VALANDNAME_ENTRY(VK_NUMPAD3),
+      VALANDNAME_ENTRY(VK_NUMPAD4),
+      VALANDNAME_ENTRY(VK_NUMPAD5),
+      VALANDNAME_ENTRY(VK_NUMPAD6),
+      VALANDNAME_ENTRY(VK_NUMPAD7),
+      VALANDNAME_ENTRY(VK_NUMPAD8),
+      VALANDNAME_ENTRY(VK_NUMPAD9),
+      VALANDNAME_ENTRY(VK_MULTIPLY),
+      VALANDNAME_ENTRY(VK_ADD),
+      VALANDNAME_ENTRY(VK_SEPARATOR),
+      VALANDNAME_ENTRY(VK_SUBTRACT),
+      VALANDNAME_ENTRY(VK_DECIMAL),
+      VALANDNAME_ENTRY(VK_DIVIDE),
+      VALANDNAME_ENTRY(VK_F1),
+      VALANDNAME_ENTRY(VK_F2),
+      VALANDNAME_ENTRY(VK_F3),
+      VALANDNAME_ENTRY(VK_F4),
+      VALANDNAME_ENTRY(VK_F5),
+      VALANDNAME_ENTRY(VK_F6),
+      VALANDNAME_ENTRY(VK_F7),
+      VALANDNAME_ENTRY(VK_F8),
+      VALANDNAME_ENTRY(VK_F9),
+      VALANDNAME_ENTRY(VK_F10),
+      VALANDNAME_ENTRY(VK_F11),
+      VALANDNAME_ENTRY(VK_F12),
+      VALANDNAME_ENTRY(VK_F13),
+      VALANDNAME_ENTRY(VK_F14),
+      VALANDNAME_ENTRY(VK_F15),
+      VALANDNAME_ENTRY(VK_F16),
+      VALANDNAME_ENTRY(VK_F17),
+      VALANDNAME_ENTRY(VK_F18),
+      VALANDNAME_ENTRY(VK_F19),
+      VALANDNAME_ENTRY(VK_F20),
+      VALANDNAME_ENTRY(VK_F21),
+      VALANDNAME_ENTRY(VK_F22),
+      VALANDNAME_ENTRY(VK_F23),
+      VALANDNAME_ENTRY(VK_F24),
+      VALANDNAME_ENTRY(VK_NUMLOCK),
+      VALANDNAME_ENTRY(VK_SCROLL),
+      VALANDNAME_ENTRY(VK_LSHIFT),
+      VALANDNAME_ENTRY(VK_RSHIFT),
+      VALANDNAME_ENTRY(VK_LCONTROL),
+      VALANDNAME_ENTRY(VK_RCONTROL),
+      VALANDNAME_ENTRY(VK_LMENU),
+      VALANDNAME_ENTRY(VK_RMENU),
+      VALANDNAME_ENTRY(VK_BROWSER_BACK),
+      VALANDNAME_ENTRY(VK_BROWSER_FORWARD),
+      VALANDNAME_ENTRY(VK_BROWSER_REFRESH),
+      VALANDNAME_ENTRY(VK_BROWSER_STOP),
+      VALANDNAME_ENTRY(VK_BROWSER_SEARCH),
+      VALANDNAME_ENTRY(VK_BROWSER_FAVORITES),
+      VALANDNAME_ENTRY(VK_BROWSER_HOME),
+      VALANDNAME_ENTRY(VK_VOLUME_MUTE),
+      VALANDNAME_ENTRY(VK_VOLUME_DOWN),
+      VALANDNAME_ENTRY(VK_VOLUME_UP),
+      VALANDNAME_ENTRY(VK_MEDIA_NEXT_TRACK),
+      VALANDNAME_ENTRY(VK_MEDIA_PREV_TRACK),
+      VALANDNAME_ENTRY(VK_MEDIA_STOP),
+      VALANDNAME_ENTRY(VK_MEDIA_PLAY_PAUSE),
+      VALANDNAME_ENTRY(VK_LAUNCH_MAIL),
+      VALANDNAME_ENTRY(VK_LAUNCH_MEDIA_SELECT),
+      VALANDNAME_ENTRY(VK_LAUNCH_APP1),
+      VALANDNAME_ENTRY(VK_LAUNCH_APP2),
+      VALANDNAME_ENTRY(VK_OEM_1),
+      VALANDNAME_ENTRY(VK_OEM_PLUS),
+      VALANDNAME_ENTRY(VK_OEM_COMMA),
+      VALANDNAME_ENTRY(VK_OEM_MINUS),
+      VALANDNAME_ENTRY(VK_OEM_PERIOD),
+      VALANDNAME_ENTRY(VK_OEM_2),
+      VALANDNAME_ENTRY(VK_OEM_3),
+      VALANDNAME_ENTRY(VK_OEM_4),
+      VALANDNAME_ENTRY(VK_OEM_5),
+      VALANDNAME_ENTRY(VK_OEM_6),
+      VALANDNAME_ENTRY(VK_OEM_7),
+      VALANDNAME_ENTRY(VK_OEM_8),
+      VALANDNAME_ENTRY(VK_OEM_102),
+      VALANDNAME_ENTRY(VK_PROCESSKEY),
+      VALANDNAME_ENTRY(VK_PACKET),
+      VALANDNAME_ENTRY(VK_ATTN),
+      VALANDNAME_ENTRY(VK_CRSEL),
+      VALANDNAME_ENTRY(VK_EXSEL),
+      VALANDNAME_ENTRY(VK_EREOF),
+      VALANDNAME_ENTRY(VK_PLAY),
+      VALANDNAME_ENTRY(VK_ZOOM),
+      VALANDNAME_ENTRY(VK_NONAME),
+      VALANDNAME_ENTRY(VK_PA1),
+      VALANDNAME_ENTRY(VK_OEM_CLEAR),
+      {0x30, "0"},
+      {0x31, "1"},
+      {0x32, "2"},
+      {0x33, "3"},
+      {0x34, "4"},
+      {0x35, "5"},
+      {0x36, "6"},
+      {0x37, "7"},
+      {0x38, "8"},
+      {0x39, "9"},
+      {0x41, "A"},
+      {0x42, "B"},
+      {0x43, "C"},
+      {0x44, "D"},
+      {0x45, "E"},
+      {0x46, "F"},
+      {0x47, "G"},
+      {0x48, "H"},
+      {0x49, "I"},
+      {0x4A, "J"},
+      {0x4B, "K"},
+      {0x4C, "L"},
+      {0x4D, "M"},
+      {0x4E, "N"},
+      {0x4F, "O"},
+      {0x50, "P"},
+      {0x51, "Q"},
+      {0x52, "S"},
+      {0x53, "T"},
+      {0x54, "U"},
+      {0x55, "V"},
+      {0x56, "W"},
+      {0x57, "X"},
+      {0x58, "Y"},
+      {0x59, "Z"},
+  };
+  AppendEnumValueInfo(result, param, virtualKeys, name);
+}
+
+void VirtualModifierKeysParamInfo(nsCString& result, uint64_t param,
+                                  const char* name, bool /* isPreCall */) {
+  const static nsTArray<EnumValueAndName> virtualKeys{
+      VALANDNAME_ENTRY(MK_CONTROL),  VALANDNAME_ENTRY(MK_LBUTTON),
+      VALANDNAME_ENTRY(MK_MBUTTON),  VALANDNAME_ENTRY(MK_RBUTTON),
+      VALANDNAME_ENTRY(MK_SHIFT),    VALANDNAME_ENTRY(MK_XBUTTON1),
+      VALANDNAME_ENTRY(MK_XBUTTON2), {0, "(none)"}};
+  AppendFlagsInfo(result, param, virtualKeys, name);
+}
+
+void ParentNotifyEventParamInfo(nsCString& str, uint64_t param,
+                                const char* /* name */, bool /* isPreCall */) {
+  const static std::unordered_map<uint64_t, const char*> eventValues{
+      VALANDNAME_ENTRY(WM_CREATE),      VALANDNAME_ENTRY(WM_DESTROY),
+      VALANDNAME_ENTRY(WM_LBUTTONDOWN), VALANDNAME_ENTRY(WM_MBUTTONDOWN),
+      VALANDNAME_ENTRY(WM_RBUTTONDOWN), VALANDNAME_ENTRY(WM_XBUTTONDOWN),
+      VALANDNAME_ENTRY(WM_POINTERDOWN)};
+  AppendEnumValueInfo(str, LOWORD(param), eventValues, "event");
+  str.AppendASCII(" ");
+  HexParamInfo(str, HIWORD(param), "hiWord", false);
+}
+
+void KeystrokeFlagsParamInfo(nsCString& str, uint64_t param,
+                             const char* /* name */, bool /* isPreCall */) {
+  WORD repeatCount = LOWORD(param);
+  WORD keyFlags = HIWORD(param);
+  WORD scanCode = LOBYTE(keyFlags);
+  bool isExtendedKey = (keyFlags & KF_EXTENDED) == KF_EXTENDED;
+  if (isExtendedKey) {
+    scanCode = MAKEWORD(scanCode, 0xE0);
+  }
+  bool contextCode = (keyFlags & KF_ALTDOWN) == KF_ALTDOWN;
+  bool wasKeyDown = (keyFlags & KF_REPEAT) == KF_REPEAT;
+  bool transitionState = (keyFlags & KF_UP) == KF_UP;
+
+  str.AppendPrintf(
+      "repeatCount: %d scanCode: %d isExtended: %d, contextCode: %d "
+      "previousKeyState: %d transitionState: %d",
+      repeatCount, scanCode, isExtendedKey ? 1 : 0, contextCode ? 1 : 0,
+      wasKeyDown ? 1 : 0, transitionState ? 1 : 0);
+};
+
+void VirtualKeysLowWordDistanceHighWordParamInfo(nsCString& str, uint64_t value,
+                                                 const char* /* name */,
+                                                 bool isPreCall) {
+  VirtualModifierKeysParamInfo(str, LOWORD(value), "virtualKeys", isPreCall);
+  str.AppendASCII(" ");
+  IntParamInfo(str, HIWORD(value), "distance", isPreCall);
+}
+
+void ShowWindowReasonParamInfo(nsCString& str, uint64_t value, const char* name,
+                               bool /* isPreCall */) {
+  const static std::unordered_map<uint64_t, const char*> showWindowReasonValues{
+      VALANDNAME_ENTRY(SW_OTHERUNZOOM),
+      VALANDNAME_ENTRY(SW_OTHERZOOM),
+      VALANDNAME_ENTRY(SW_PARENTCLOSING),
+      VALANDNAME_ENTRY(SW_PARENTOPENING),
+      {0, "Call to ShowWindow()"}};
+  AppendEnumValueInfo(str, value, showWindowReasonValues, name);
+}
+
+void WindowEdgeParamInfo(nsCString& str, uint64_t value, const char* name,
+                         bool /* isPreCall */) {
+  const static std::unordered_map<uint64_t, const char*> windowEdgeValues{
+      VALANDNAME_ENTRY(WMSZ_BOTTOM),      VALANDNAME_ENTRY(WMSZ_BOTTOMLEFT),
+      VALANDNAME_ENTRY(WMSZ_BOTTOMRIGHT), VALANDNAME_ENTRY(WMSZ_LEFT),
+      VALANDNAME_ENTRY(WMSZ_RIGHT),       VALANDNAME_ENTRY(WMSZ_TOP),
+      VALANDNAME_ENTRY(WMSZ_TOPLEFT),     VALANDNAME_ENTRY(WMSZ_TOPRIGHT)};
+  AppendEnumValueInfo(str, value, windowEdgeValues, name);
+}
+
+void UiActionParamInfo(nsCString& str, uint64_t value, const char* name,
+                       bool /* isPreCall */) {
+  const static std::unordered_map<uint64_t, const char*> uiActionValues{
+      VALANDNAME_ENTRY(SPI_GETACCESSTIMEOUT),
+      VALANDNAME_ENTRY(SPI_GETAUDIODESCRIPTION),
+      VALANDNAME_ENTRY(SPI_GETCLIENTAREAANIMATION),
+      VALANDNAME_ENTRY(SPI_GETDISABLEOVERLAPPEDCONTENT),
+      VALANDNAME_ENTRY(SPI_GETFILTERKEYS),
+      VALANDNAME_ENTRY(SPI_GETFOCUSBORDERHEIGHT),
+      VALANDNAME_ENTRY(SPI_GETFOCUSBORDERWIDTH),
+      VALANDNAME_ENTRY(SPI_GETHIGHCONTRAST),
+      VALANDNAME_ENTRY(SPI_GETLOGICALDPIOVERRIDE),
+      VALANDNAME_ENTRY(SPI_SETLOGICALDPIOVERRIDE),
+      VALANDNAME_ENTRY(SPI_GETMESSAGEDURATION),
+      VALANDNAME_ENTRY(SPI_GETMOUSECLICKLOCK),
+      VALANDNAME_ENTRY(SPI_GETMOUSECLICKLOCKTIME),
+      VALANDNAME_ENTRY(SPI_GETMOUSEKEYS),
+      VALANDNAME_ENTRY(SPI_GETMOUSESONAR),
+      VALANDNAME_ENTRY(SPI_GETMOUSEVANISH),
+      VALANDNAME_ENTRY(SPI_GETSCREENREADER),
+      VALANDNAME_ENTRY(SPI_GETSERIALKEYS),
+      VALANDNAME_ENTRY(SPI_GETSHOWSOUNDS),
+      VALANDNAME_ENTRY(SPI_GETSOUNDSENTRY),
+      VALANDNAME_ENTRY(SPI_GETSTICKYKEYS),
+      VALANDNAME_ENTRY(SPI_GETTOGGLEKEYS),
+      VALANDNAME_ENTRY(SPI_SETACCESSTIMEOUT),
+      VALANDNAME_ENTRY(SPI_SETAUDIODESCRIPTION),
+      VALANDNAME_ENTRY(SPI_SETCLIENTAREAANIMATION),
+      VALANDNAME_ENTRY(SPI_SETDISABLEOVERLAPPEDCONTENT),
+      VALANDNAME_ENTRY(SPI_SETFILTERKEYS),
+      VALANDNAME_ENTRY(SPI_SETFOCUSBORDERHEIGHT),
+      VALANDNAME_ENTRY(SPI_SETFOCUSBORDERWIDTH),
+      VALANDNAME_ENTRY(SPI_SETHIGHCONTRAST),
+      VALANDNAME_ENTRY(SPI_SETMESSAGEDURATION),
+      VALANDNAME_ENTRY(SPI_SETMOUSECLICKLOCK),
+      VALANDNAME_ENTRY(SPI_SETMOUSECLICKLOCKTIME),
+      VALANDNAME_ENTRY(SPI_SETMOUSEKEYS),
+      VALANDNAME_ENTRY(SPI_SETMOUSESONAR),
+      VALANDNAME_ENTRY(SPI_SETMOUSEVANISH),
+      VALANDNAME_ENTRY(SPI_SETSCREENREADER),
+      VALANDNAME_ENTRY(SPI_SETSERIALKEYS),
+      VALANDNAME_ENTRY(SPI_SETSHOWSOUNDS),
+      VALANDNAME_ENTRY(SPI_SETSOUNDSENTRY),
+      VALANDNAME_ENTRY(SPI_SETSTICKYKEYS),
+      VALANDNAME_ENTRY(SPI_SETTOGGLEKEYS),
+      VALANDNAME_ENTRY(SPI_GETCLEARTYPE),
+      VALANDNAME_ENTRY(SPI_GETDESKWALLPAPER),
+      VALANDNAME_ENTRY(SPI_GETDROPSHADOW),
+      VALANDNAME_ENTRY(SPI_GETFLATMENU),
+      VALANDNAME_ENTRY(SPI_GETFONTSMOOTHING),
+      VALANDNAME_ENTRY(SPI_GETFONTSMOOTHINGCONTRAST),
+      VALANDNAME_ENTRY(SPI_GETFONTSMOOTHINGORIENTATION),
+      VALANDNAME_ENTRY(SPI_GETFONTSMOOTHINGTYPE),
+      VALANDNAME_ENTRY(SPI_GETWORKAREA),
+      VALANDNAME_ENTRY(SPI_SETCLEARTYPE),
+      VALANDNAME_ENTRY(SPI_SETCURSORS),
+      VALANDNAME_ENTRY(SPI_SETDESKPATTERN),
+      VALANDNAME_ENTRY(SPI_SETDESKWALLPAPER),
+      VALANDNAME_ENTRY(SPI_SETDROPSHADOW),
+      VALANDNAME_ENTRY(SPI_SETFLATMENU),
+      VALANDNAME_ENTRY(SPI_SETFONTSMOOTHING),
+      VALANDNAME_ENTRY(SPI_SETFONTSMOOTHINGCONTRAST),
+      VALANDNAME_ENTRY(SPI_SETFONTSMOOTHINGORIENTATION),
+      VALANDNAME_ENTRY(SPI_SETFONTSMOOTHINGTYPE),
+      VALANDNAME_ENTRY(SPI_SETWORKAREA),
+      VALANDNAME_ENTRY(SPI_GETICONMETRICS),
+      VALANDNAME_ENTRY(SPI_GETICONTITLELOGFONT),
+      VALANDNAME_ENTRY(SPI_GETICONTITLEWRAP),
+      VALANDNAME_ENTRY(SPI_ICONHORIZONTALSPACING),
+      VALANDNAME_ENTRY(SPI_ICONVERTICALSPACING),
+      VALANDNAME_ENTRY(SPI_SETICONMETRICS),
+      VALANDNAME_ENTRY(SPI_SETICONS),
+      VALANDNAME_ENTRY(SPI_SETICONTITLELOGFONT),
+      VALANDNAME_ENTRY(SPI_SETICONTITLEWRAP),
+      VALANDNAME_ENTRY(SPI_GETBEEP),
+      VALANDNAME_ENTRY(SPI_GETBLOCKSENDINPUTRESETS),
+      VALANDNAME_ENTRY(SPI_GETCONTACTVISUALIZATION),
+      VALANDNAME_ENTRY(SPI_SETCONTACTVISUALIZATION),
+      VALANDNAME_ENTRY(SPI_GETDEFAULTINPUTLANG),
+      VALANDNAME_ENTRY(SPI_GETGESTUREVISUALIZATION),
+      VALANDNAME_ENTRY(SPI_SETGESTUREVISUALIZATION),
+      VALANDNAME_ENTRY(SPI_GETKEYBOARDCUES),
+      VALANDNAME_ENTRY(SPI_GETKEYBOARDDELAY),
+      VALANDNAME_ENTRY(SPI_GETKEYBOARDPREF),
+      VALANDNAME_ENTRY(SPI_GETKEYBOARDSPEED),
+      VALANDNAME_ENTRY(SPI_GETMOUSE),
+      VALANDNAME_ENTRY(SPI_GETMOUSEHOVERHEIGHT),
+      VALANDNAME_ENTRY(SPI_GETMOUSEHOVERTIME),
+      VALANDNAME_ENTRY(SPI_GETMOUSEHOVERWIDTH),
+      VALANDNAME_ENTRY(SPI_GETMOUSESPEED),
+      VALANDNAME_ENTRY(SPI_GETMOUSETRAILS),
+      VALANDNAME_ENTRY(SPI_GETMOUSEWHEELROUTING),
+      VALANDNAME_ENTRY(SPI_SETMOUSEWHEELROUTING),
+      VALANDNAME_ENTRY(SPI_GETPENVISUALIZATION),
+      VALANDNAME_ENTRY(SPI_SETPENVISUALIZATION),
+      VALANDNAME_ENTRY(SPI_GETSNAPTODEFBUTTON),
+      VALANDNAME_ENTRY(SPI_GETSYSTEMLANGUAGEBAR),
+      VALANDNAME_ENTRY(SPI_SETSYSTEMLANGUAGEBAR),
+      VALANDNAME_ENTRY(SPI_GETTHREADLOCALINPUTSETTINGS),
+      VALANDNAME_ENTRY(SPI_SETTHREADLOCALINPUTSETTINGS),
+      VALANDNAME_ENTRY(SPI_GETWHEELSCROLLCHARS),
+      VALANDNAME_ENTRY(SPI_GETWHEELSCROLLLINES),
+      VALANDNAME_ENTRY(SPI_SETBEEP),
+      VALANDNAME_ENTRY(SPI_SETBLOCKSENDINPUTRESETS),
+      VALANDNAME_ENTRY(SPI_SETDEFAULTINPUTLANG),
+      VALANDNAME_ENTRY(SPI_SETDOUBLECLICKTIME),
+      VALANDNAME_ENTRY(SPI_SETDOUBLECLKHEIGHT),
+      VALANDNAME_ENTRY(SPI_SETDOUBLECLKWIDTH),
+      VALANDNAME_ENTRY(SPI_SETKEYBOARDCUES),
+      VALANDNAME_ENTRY(SPI_SETKEYBOARDDELAY),
+      VALANDNAME_ENTRY(SPI_SETKEYBOARDPREF),
+      VALANDNAME_ENTRY(SPI_SETKEYBOARDSPEED),
+      VALANDNAME_ENTRY(SPI_SETLANGTOGGLE),
+      VALANDNAME_ENTRY(SPI_SETMOUSE),
+      VALANDNAME_ENTRY(SPI_SETMOUSEBUTTONSWAP),
+      VALANDNAME_ENTRY(SPI_SETMOUSEHOVERHEIGHT),
+      VALANDNAME_ENTRY(SPI_SETMOUSEHOVERTIME),
+      VALANDNAME_ENTRY(SPI_SETMOUSEHOVERWIDTH),
+      VALANDNAME_ENTRY(SPI_SETMOUSESPEED),
+      VALANDNAME_ENTRY(SPI_SETMOUSETRAILS),
+      VALANDNAME_ENTRY(SPI_SETSNAPTODEFBUTTON),
+      VALANDNAME_ENTRY(SPI_SETWHEELSCROLLCHARS),
+      VALANDNAME_ENTRY(SPI_SETWHEELSCROLLLINES),
+      VALANDNAME_ENTRY(SPI_GETMENUDROPALIGNMENT),
+      VALANDNAME_ENTRY(SPI_GETMENUFADE),
+      VALANDNAME_ENTRY(SPI_GETMENUSHOWDELAY),
+      VALANDNAME_ENTRY(SPI_SETMENUDROPALIGNMENT),
+      VALANDNAME_ENTRY(SPI_SETMENUFADE),
+      VALANDNAME_ENTRY(SPI_SETMENUSHOWDELAY),
+      VALANDNAME_ENTRY(SPI_GETLOWPOWERACTIVE),
+      VALANDNAME_ENTRY(SPI_GETLOWPOWERTIMEOUT),
+      VALANDNAME_ENTRY(SPI_GETPOWEROFFACTIVE),
+      VALANDNAME_ENTRY(SPI_GETPOWEROFFTIMEOUT),
+      VALANDNAME_ENTRY(SPI_SETLOWPOWERACTIVE),
+      VALANDNAME_ENTRY(SPI_SETLOWPOWERTIMEOUT),
+      VALANDNAME_ENTRY(SPI_SETPOWEROFFACTIVE),
+      VALANDNAME_ENTRY(SPI_SETPOWEROFFTIMEOUT),
+      VALANDNAME_ENTRY(SPI_GETSCREENSAVEACTIVE),
+      VALANDNAME_ENTRY(SPI_GETSCREENSAVERRUNNING),
+      VALANDNAME_ENTRY(SPI_GETSCREENSAVESECURE),
+      VALANDNAME_ENTRY(SPI_GETSCREENSAVETIMEOUT),
+      VALANDNAME_ENTRY(SPI_SETSCREENSAVEACTIVE),
+      VALANDNAME_ENTRY(SPI_SETSCREENSAVERRUNNING),
+      VALANDNAME_ENTRY(SPI_SETSCREENSAVESECURE),
+      VALANDNAME_ENTRY(SPI_SETSCREENSAVETIMEOUT),
+      VALANDNAME_ENTRY(SPI_GETHUNGAPPTIMEOUT),
+      VALANDNAME_ENTRY(SPI_GETWAITTOKILLTIMEOUT),
+      VALANDNAME_ENTRY(SPI_GETWAITTOKILLSERVICETIMEOUT),
+      VALANDNAME_ENTRY(SPI_SETHUNGAPPTIMEOUT),
+      VALANDNAME_ENTRY(SPI_SETWAITTOKILLTIMEOUT),
+      VALANDNAME_ENTRY(SPI_SETWAITTOKILLSERVICETIMEOUT),
+      VALANDNAME_ENTRY(SPI_GETCOMBOBOXANIMATION),
+      VALANDNAME_ENTRY(SPI_GETCURSORSHADOW),
+      VALANDNAME_ENTRY(SPI_GETGRADIENTCAPTIONS),
+      VALANDNAME_ENTRY(SPI_GETHOTTRACKING),
+      VALANDNAME_ENTRY(SPI_GETLISTBOXSMOOTHSCROLLING),
+      VALANDNAME_ENTRY(SPI_GETMENUANIMATION),
+      VALANDNAME_ENTRY(SPI_GETMENUUNDERLINES),
+      VALANDNAME_ENTRY(SPI_GETSELECTIONFADE),
+      VALANDNAME_ENTRY(SPI_GETTOOLTIPANIMATION),
+      VALANDNAME_ENTRY(SPI_GETTOOLTIPFADE),
+      VALANDNAME_ENTRY(SPI_GETUIEFFECTS),
+      VALANDNAME_ENTRY(SPI_SETCOMBOBOXANIMATION),
+      VALANDNAME_ENTRY(SPI_SETCURSORSHADOW),
+      VALANDNAME_ENTRY(SPI_SETGRADIENTCAPTIONS),
+      VALANDNAME_ENTRY(SPI_SETHOTTRACKING),
+      VALANDNAME_ENTRY(SPI_SETLISTBOXSMOOTHSCROLLING),
+      VALANDNAME_ENTRY(SPI_SETMENUANIMATION),
+      VALANDNAME_ENTRY(SPI_SETMENUUNDERLINES),
+      VALANDNAME_ENTRY(SPI_SETSELECTIONFADE),
+      VALANDNAME_ENTRY(SPI_SETTOOLTIPANIMATION),
+      VALANDNAME_ENTRY(SPI_SETTOOLTIPFADE),
+      VALANDNAME_ENTRY(SPI_SETUIEFFECTS),
+      VALANDNAME_ENTRY(SPI_GETACTIVEWINDOWTRACKING),
+      VALANDNAME_ENTRY(SPI_GETACTIVEWNDTRKZORDER),
+      VALANDNAME_ENTRY(SPI_GETACTIVEWNDTRKTIMEOUT),
+      VALANDNAME_ENTRY(SPI_GETANIMATION),
+      VALANDNAME_ENTRY(SPI_GETBORDER),
+      VALANDNAME_ENTRY(SPI_GETCARETWIDTH),
+      VALANDNAME_ENTRY(SPI_GETDOCKMOVING),
+      VALANDNAME_ENTRY(SPI_GETDRAGFROMMAXIMIZE),
+      VALANDNAME_ENTRY(SPI_GETDRAGFULLWINDOWS),
+      VALANDNAME_ENTRY(SPI_GETFOREGROUNDFLASHCOUNT),
+      VALANDNAME_ENTRY(SPI_GETFOREGROUNDLOCKTIMEOUT),
+      VALANDNAME_ENTRY(SPI_GETMINIMIZEDMETRICS),
+      VALANDNAME_ENTRY(SPI_GETMOUSEDOCKTHRESHOLD),
+      VALANDNAME_ENTRY(SPI_GETMOUSEDRAGOUTTHRESHOLD),
+      VALANDNAME_ENTRY(SPI_GETMOUSESIDEMOVETHRESHOLD),
+      VALANDNAME_ENTRY(SPI_GETNONCLIENTMETRICS),
+      VALANDNAME_ENTRY(SPI_GETPENDOCKTHRESHOLD),
+      VALANDNAME_ENTRY(SPI_GETPENDRAGOUTTHRESHOLD),
+      VALANDNAME_ENTRY(SPI_GETPENSIDEMOVETHRESHOLD),
+      VALANDNAME_ENTRY(SPI_GETSHOWIMEUI),
+      VALANDNAME_ENTRY(SPI_GETSNAPSIZING),
+      VALANDNAME_ENTRY(SPI_GETWINARRANGING),
+      VALANDNAME_ENTRY(SPI_SETACTIVEWINDOWTRACKING),
+      VALANDNAME_ENTRY(SPI_SETACTIVEWNDTRKZORDER),
+      VALANDNAME_ENTRY(SPI_SETACTIVEWNDTRKTIMEOUT),
+      VALANDNAME_ENTRY(SPI_SETANIMATION),
+      VALANDNAME_ENTRY(SPI_SETBORDER),
+      VALANDNAME_ENTRY(SPI_SETCARETWIDTH),
+      VALANDNAME_ENTRY(SPI_SETDOCKMOVING),
+      VALANDNAME_ENTRY(SPI_SETDRAGFROMMAXIMIZE),
+      VALANDNAME_ENTRY(SPI_SETDRAGFULLWINDOWS),
+      VALANDNAME_ENTRY(SPI_SETFOREGROUNDFLASHCOUNT),
+      VALANDNAME_ENTRY(SPI_SETFOREGROUNDLOCKTIMEOUT),
+      VALANDNAME_ENTRY(SPI_SETMINIMIZEDMETRICS),
+      VALANDNAME_ENTRY(SPI_SETMOUSEDOCKTHRESHOLD),
+      VALANDNAME_ENTRY(SPI_SETMOUSEDRAGOUTTHRESHOLD),
+      VALANDNAME_ENTRY(SPI_SETMOUSESIDEMOVETHRESHOLD),
+      VALANDNAME_ENTRY(SPI_SETNONCLIENTMETRICS),
+      VALANDNAME_ENTRY(SPI_SETPENDOCKTHRESHOLD),
+      VALANDNAME_ENTRY(SPI_SETPENDRAGOUTTHRESHOLD),
+      VALANDNAME_ENTRY(SPI_SETPENSIDEMOVETHRESHOLD),
+      VALANDNAME_ENTRY(SPI_SETSHOWIMEUI),
+      VALANDNAME_ENTRY(SPI_SETSNAPSIZING),
+      VALANDNAME_ENTRY(SPI_SETWINARRANGING),
+  };
+  AppendEnumValueInfo(str, value, uiActionValues, name);
+}
+
+nsAutoCString WmSizeParamInfo(uint64_t wParam, uint64_t lParam,
+                              bool /* isPreCall */) {
+  nsAutoCString result;
+  const static std::unordered_map<uint64_t, const char*> sizeValues{
+      VALANDNAME_ENTRY(SIZE_RESTORED), VALANDNAME_ENTRY(SIZE_MINIMIZED),
+      VALANDNAME_ENTRY(SIZE_MAXIMIZED), VALANDNAME_ENTRY(SIZE_MAXSHOW),
+      VALANDNAME_ENTRY(SIZE_MAXHIDE)};
+  AppendEnumValueInfo(result, wParam, sizeValues, "size");
+  result.AppendPrintf(" width=%d height=%d", static_cast<int>(LOWORD(lParam)),
+                      static_cast<int>(HIWORD(lParam)));
+  return result;
+}
+
+const nsTArray<EnumValueAndName> windowPositionFlags = {
+    VALANDNAME_ENTRY(SWP_DRAWFRAME),  VALANDNAME_ENTRY(SWP_HIDEWINDOW),
+    VALANDNAME_ENTRY(SWP_NOACTIVATE), VALANDNAME_ENTRY(SWP_NOCOPYBITS),
+    VALANDNAME_ENTRY(SWP_NOMOVE),     VALANDNAME_ENTRY(SWP_NOOWNERZORDER),
+    VALANDNAME_ENTRY(SWP_NOREDRAW),   VALANDNAME_ENTRY(SWP_NOSENDCHANGING),
+    VALANDNAME_ENTRY(SWP_NOSIZE),     VALANDNAME_ENTRY(SWP_NOZORDER),
+    VALANDNAME_ENTRY(SWP_SHOWWINDOW),
+};
+
+void WindowPosParamInfo(nsCString& str, uint64_t value, const char* name,
+                        bool /* isPreCall */) {
+  LPWINDOWPOS windowPos = reinterpret_cast<LPWINDOWPOS>(value);
+  if (windowPos == nullptr) {
+    str.AppendASCII("null windowPos?");
+    return;
+  }
+  HexParamInfo(str, reinterpret_cast<uint64_t>(windowPos->hwnd), "hwnd", false);
+  str.AppendASCII(" ");
+  HexParamInfo(str, reinterpret_cast<uint64_t>(windowPos->hwndInsertAfter),
+               "hwndInsertAfter", false);
+  str.AppendASCII(" ");
+  IntParamInfo(str, windowPos->x, "x", false);
+  str.AppendASCII(" ");
+  IntParamInfo(str, windowPos->y, "y", false);
+  str.AppendASCII(" ");
+  IntParamInfo(str, windowPos->cx, "cx", false);
+  str.AppendASCII(" ");
+  IntParamInfo(str, windowPos->cy, "cy", false);
+  str.AppendASCII(" ");
+  AppendFlagsInfo(str, windowPos->flags, windowPositionFlags, "flags");
+}
+
+void StyleOrExtendedParamInfo(nsCString& str, uint64_t value, const char* name,
+                              bool /* isPreCall */) {
+  const static std::unordered_map<uint64_t, const char*> styleOrExtended{
+      VALANDNAME_ENTRY(GWL_EXSTYLE), VALANDNAME_ENTRY(GWL_STYLE)};
+  AppendEnumValueInfo(str, value, styleOrExtended, name);
+}
+
+void StyleStructParamInfo(nsCString& str, uint64_t value, const char* name,
+                          bool /* isPreCall */) {
+  LPSTYLESTRUCT styleStruct = reinterpret_cast<LPSTYLESTRUCT>(value);
+  if (styleStruct == nullptr) {
+    str.AppendASCII("null STYLESTRUCT?");
+    return;
+  }
+  HexParamInfo(str, styleStruct->styleOld, "styleOld", false);
+  str.AppendASCII(" ");
+  HexParamInfo(str, styleStruct->styleNew, "styleNew", false);
+}
+
+void NcCalcSizeParamsParamInfo(nsCString& str, uint64_t value, const char* name,
+                               bool /* isPreCall */) {
+  LPNCCALCSIZE_PARAMS params = reinterpret_cast<LPNCCALCSIZE_PARAMS>(value);
+  if (params == nullptr) {
+    str.AppendASCII("null NCCALCSIZE_PARAMS?");
+    return;
+  }
+  str.AppendPrintf("%s[0]: ", name);
+  RectParamInfo(str, reinterpret_cast<uintptr_t>(&params->rgrc[0]), nullptr,
+                false);
+  str.AppendPrintf(" %s[1]: ", name);
+  RectParamInfo(str, reinterpret_cast<uintptr_t>(&params->rgrc[1]), nullptr,
+                false);
+  str.AppendPrintf(" %s[2]: ", name);
+  RectParamInfo(str, reinterpret_cast<uintptr_t>(&params->rgrc[2]), nullptr,
+                false);
+  str.AppendASCII(" ");
+  WindowPosParamInfo(str, reinterpret_cast<uintptr_t>(params->lppos), nullptr,
+                     false);
+}
+
+nsAutoCString WmNcCalcSizeParamInfo(uint64_t wParam, uint64_t lParam,
+                                    bool /* isPreCall */) {
+  nsAutoCString result;
+  TrueFalseParamInfo(result, wParam, "shouldIndicateValidArea", false);
+  result.AppendASCII(" ");
+  if (wParam == TRUE) {
+    NcCalcSizeParamsParamInfo(result, lParam, "ncCalcSizeParams", false);
+  } else {
+    RectParamInfo(result, lParam, "rect", false);
+  }
+  return result;
+}
+
+void ActivateWParamInfo(nsCString& result, uint64_t wParam, const char* name,
+                        bool /* isPreCall */) {
+  const static std::unordered_map<uint64_t, const char*> activateValues{
+      VALANDNAME_ENTRY(WA_ACTIVE), VALANDNAME_ENTRY(WA_CLICKACTIVE),
+      VALANDNAME_ENTRY(WA_INACTIVE)};
+  AppendEnumValueInfo(result, wParam, activateValues, name);
+}
+
+void HitTestParamInfo(nsCString& result, uint64_t param, const char* name,
+                      bool /* isPreCall */) {
+  const static std::unordered_map<uint64_t, const char*> hitTestResults{
+      VALANDNAME_ENTRY(HTBORDER),     VALANDNAME_ENTRY(HTBOTTOM),
+      VALANDNAME_ENTRY(HTBOTTOMLEFT), VALANDNAME_ENTRY(HTBOTTOMRIGHT),
+      VALANDNAME_ENTRY(HTCAPTION),    VALANDNAME_ENTRY(HTCLIENT),
+      VALANDNAME_ENTRY(HTCLOSE),      VALANDNAME_ENTRY(HTERROR),
+      VALANDNAME_ENTRY(HTGROWBOX),    VALANDNAME_ENTRY(HTHELP),
+      VALANDNAME_ENTRY(HTHSCROLL),    VALANDNAME_ENTRY(HTLEFT),
+      VALANDNAME_ENTRY(HTMENU),       VALANDNAME_ENTRY(HTMAXBUTTON),
+      VALANDNAME_ENTRY(HTMINBUTTON),  VALANDNAME_ENTRY(HTNOWHERE),
+      VALANDNAME_ENTRY(HTREDUCE),     VALANDNAME_ENTRY(HTRIGHT),
+      VALANDNAME_ENTRY(HTSIZE),       VALANDNAME_ENTRY(HTSYSMENU),
+      VALANDNAME_ENTRY(HTTOP),        VALANDNAME_ENTRY(HTTOPLEFT),
+      VALANDNAME_ENTRY(HTTOPRIGHT),   VALANDNAME_ENTRY(HTTRANSPARENT),
+      VALANDNAME_ENTRY(HTVSCROLL),    VALANDNAME_ENTRY(HTZOOM),
+  };
+  AppendEnumValueInfo(result, param, hitTestResults, name);
+}
+
+void SetCursorLParamInfo(nsCString& result, uint64_t lParam,
+                         const char* /* name */, bool /* isPreCall */) {
+  HitTestParamInfo(result, LOWORD(lParam), "hitTestResult", false);
+  result.AppendASCII(" ");
+  HexParamInfo(result, HIWORD(lParam), "message", false);
+}
+
+void MinMaxInfoParamInfo(nsCString& result, uint64_t value,
+                         const char* /* name */, bool /* isPreCall */) {
+  PMINMAXINFO minMaxInfo = reinterpret_cast<PMINMAXINFO>(value);
+  if (minMaxInfo == nullptr) {
+    result.AppendPrintf("NULL minMaxInfo?");
+    return;
+  }
+  PointExplicitParamInfo(result, minMaxInfo->ptMaxSize, "maxSize");
+  result.AppendASCII(" ");
+  PointExplicitParamInfo(result, minMaxInfo->ptMaxPosition, "maxPosition");
+  result.AppendASCII(" ");
+  PointExplicitParamInfo(result, minMaxInfo->ptMinTrackSize, "minTrackSize");
+  result.AppendASCII(" ");
+  PointExplicitParamInfo(result, minMaxInfo->ptMaxTrackSize, "maxTrackSize");
+}
+
+void WideStringParamInfo(nsCString& result, uint64_t value, const char* name,
+                         bool /* isPreCall */) {
+  result.AppendPrintf("%s=%S", name, reinterpret_cast<LPCWSTR>(value));
+}
+
+void DeviceEventParamInfo(nsCString& result, uint64_t value, const char* name,
+                          bool /* isPreCall */) {
+  const static std::unordered_map<uint64_t, const char*> deviceEventValues{
+      VALANDNAME_ENTRY(DBT_DEVNODES_CHANGED),
+      VALANDNAME_ENTRY(DBT_QUERYCHANGECONFIG),
+      VALANDNAME_ENTRY(DBT_CONFIGCHANGED),
+      VALANDNAME_ENTRY(DBT_CONFIGCHANGECANCELED),
+      VALANDNAME_ENTRY(DBT_DEVICEARRIVAL),
+      VALANDNAME_ENTRY(DBT_DEVICEQUERYREMOVE),
+      VALANDNAME_ENTRY(DBT_DEVICEQUERYREMOVEFAILED),
+      VALANDNAME_ENTRY(DBT_DEVICEREMOVEPENDING),
+      VALANDNAME_ENTRY(DBT_DEVICEREMOVECOMPLETE),
+      VALANDNAME_ENTRY(DBT_DEVICETYPESPECIFIC),
+      VALANDNAME_ENTRY(DBT_CUSTOMEVENT),
+      VALANDNAME_ENTRY(DBT_USERDEFINED)};
+  AppendEnumValueInfo(result, value, deviceEventValues, name);
+}
+
+void ResolutionParamInfo(nsCString& result, uint64_t value, const char* name,
+                         bool /* isPreCall */) {
+  result.AppendPrintf("horizontalRes=%d verticalRes=%d", LOWORD(value),
+                      HIWORD(value));
+}
+
+// Window message with default wParam/lParam logging
+#define ENTRY(_msg)                         \
+  {                                         \
+    _msg, { #_msg, _msg, DefaultParamInfo } \
+  }
+// Window message with no parameters
+#define ENTRY_WITH_NO_PARAM_INFO(_msg) \
+  {                                    \
+    _msg, { #_msg, _msg, nullptr }     \
+  }
+// Window message with custom parameter logging functions
+#define ENTRY_WITH_CUSTOM_PARAM_INFO(_msg, paramInfoFn) \
+  {                                                     \
+    _msg, { #_msg, _msg, paramInfoFn }                  \
+  }
+// Window message with separate custom wParam and lParam logging functions
+#define ENTRY_WITH_SPLIT_PARAM_INFOS(_msg, wParamInfoFn, wParamName,           \
+                                     lParamInfoFn, lParamName)                 \
+  {                                                                            \
+    _msg, {                                                                    \
+      #_msg, _msg, nullptr, wParamInfoFn, wParamName, lParamInfoFn, lParamName \
+    }                                                                          \
+  }
+std::unordered_map<UINT, EventMsgInfo> gAllEvents = {
+    ENTRY_WITH_NO_PARAM_INFO(WM_NULL),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_CREATE, nullptr, nullptr,
+                                 CreateStructParamInfo, "createStruct"),
+    ENTRY_WITH_NO_PARAM_INFO(WM_DESTROY),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_MOVE, nullptr, nullptr,
+                                 XLowWordYHighWordParamInfo, "upperLeft"),
+    ENTRY_WITH_CUSTOM_PARAM_INFO(WM_SIZE, WmSizeParamInfo),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_ACTIVATE, ActivateWParamInfo, "wParam",
+                                 HexParamInfo, "handle"),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_SETFOCUS, HexParamInfo, "handle", nullptr,
+                                 nullptr),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_KILLFOCUS, HexParamInfo, "handle", nullptr,
+                                 nullptr),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_ENABLE, TrueFalseParamInfo, "enabled",
+                                 nullptr, nullptr),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_SETREDRAW, TrueFalseParamInfo,
+                                 "redrawState", nullptr, nullptr),
+    ENTRY(WM_SETTEXT),
+    ENTRY(WM_GETTEXT),
+    ENTRY(WM_GETTEXTLENGTH),
+    ENTRY_WITH_NO_PARAM_INFO(WM_PAINT),
+    ENTRY_WITH_NO_PARAM_INFO(WM_CLOSE),
+    ENTRY(WM_QUERYENDSESSION),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_QUIT, HexParamInfo, "exitCode", nullptr,
+                                 nullptr),
+    ENTRY(WM_QUERYOPEN),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_ERASEBKGND, HexParamInfo, "deviceContext",
+                                 nullptr, nullptr),
+    ENTRY(WM_SYSCOLORCHANGE),
+    ENTRY(WM_ENDSESSION),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_SHOWWINDOW, TrueFalseParamInfo,
+                                 "windowBeingShown", ShowWindowReasonParamInfo,
+                                 "status"),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_SETTINGCHANGE, UiActionParamInfo,
+                                 "uiAction", WideStringParamInfo,
+                                 "paramChanged"),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_DEVMODECHANGE, nullptr, nullptr,
+                                 WideStringParamInfo, "deviceName"),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_ACTIVATEAPP, TrueFalseParamInfo,
+                                 "activated", HexParamInfo, "threadId"),
+    ENTRY(WM_FONTCHANGE),
+    ENTRY(WM_TIMECHANGE),
+    ENTRY(WM_CANCELMODE),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_SETCURSOR, HexParamInfo, "windowHandle",
+                                 SetCursorLParamInfo, ""),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_MOUSEACTIVATE, HexParamInfo, "windowHandle",
+                                 SetCursorLParamInfo, ""),
+    ENTRY(WM_CHILDACTIVATE),
+    ENTRY(WM_QUEUESYNC),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_GETMINMAXINFO, nullptr, nullptr,
+                                 MinMaxInfoParamInfo, ""),
+    ENTRY(WM_PAINTICON),
+    ENTRY(WM_ICONERASEBKGND),
+    ENTRY(WM_NEXTDLGCTL),
+    ENTRY(WM_SPOOLERSTATUS),
+    ENTRY(WM_DRAWITEM),
+    ENTRY(WM_MEASUREITEM),
+    ENTRY(WM_DELETEITEM),
+    ENTRY(WM_VKEYTOITEM),
+    ENTRY(WM_CHARTOITEM),
+    ENTRY(WM_SETFONT),
+    ENTRY(WM_GETFONT),
+    ENTRY(WM_SETHOTKEY),
+    ENTRY(WM_GETHOTKEY),
+    ENTRY(WM_QUERYDRAGICON),
+    ENTRY(WM_COMPAREITEM),
+    ENTRY(WM_GETOBJECT),
+    ENTRY(WM_COMPACTING),
+    ENTRY(WM_COMMNOTIFY),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_WINDOWPOSCHANGING, nullptr, nullptr,
+                                 WindowPosParamInfo, "newSizeAndPos"),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_WINDOWPOSCHANGED, nullptr, nullptr,
+                                 WindowPosParamInfo, "newSizeAndPos"),
+    ENTRY(WM_POWER),
+    ENTRY(WM_COPYDATA),
+    ENTRY(WM_CANCELJOURNAL),
+    ENTRY(WM_NOTIFY),
+    ENTRY(WM_INPUTLANGCHANGEREQUEST),
+    ENTRY(WM_INPUTLANGCHANGE),
+    ENTRY(WM_TCARD),
+    ENTRY(WM_HELP),
+    ENTRY(WM_USERCHANGED),
+    ENTRY(WM_NOTIFYFORMAT),
+    ENTRY(WM_CONTEXTMENU),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_STYLECHANGING, StyleOrExtendedParamInfo,
+                                 "styleOrExtended", StyleStructParamInfo,
+                                 "newStyles"),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_STYLECHANGED, StyleOrExtendedParamInfo,
+                                 "styleOrExtended", StyleStructParamInfo,
+                                 "newStyles"),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_DISPLAYCHANGE, IntParamInfo, "bitsPerPixel",
+                                 ResolutionParamInfo, ""),
+    ENTRY(WM_GETICON),
+    ENTRY(WM_SETICON),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_NCCREATE, nullptr, nullptr,
+                                 CreateStructParamInfo, "createStruct"),
+    ENTRY_WITH_NO_PARAM_INFO(WM_NCDESTROY),
+    ENTRY_WITH_CUSTOM_PARAM_INFO(WM_NCCALCSIZE, WmNcCalcSizeParamInfo),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_NCHITTEST, nullptr, nullptr,
+                                 XLowWordYHighWordParamInfo, "mousePos"),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_NCPAINT, HexParamInfo, "updateRegionHandle",
+                                 nullptr, nullptr),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_NCACTIVATE, TrueFalseParamInfo,
+                                 "isTitleBarOrIconActive", HexParamInfo,
+                                 "updateRegion"),
+    ENTRY(WM_GETDLGCODE),
+    ENTRY(WM_SYNCPAINT),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_NCMOUSEMOVE, VirtualModifierKeysParamInfo,
+                                 "virtualKeys", XLowWordYHighWordParamInfo,
+                                 "mousePos"),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_NCLBUTTONDOWN, HitTestParamInfo,
+                                 "hitTestValue", PointsParamInfo, "mousePos"),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_NCLBUTTONUP, HitTestParamInfo,
+                                 "hitTestValue", PointsParamInfo, "mousePos"),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_NCLBUTTONDBLCLK, HitTestParamInfo,
+                                 "hitTestValue", PointsParamInfo, "mousePos"),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_NCRBUTTONDOWN, HitTestParamInfo,
+                                 "hitTestValue", PointsParamInfo, "mousePos"),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_NCRBUTTONUP, HitTestParamInfo,
+                                 "hitTestValue", PointsParamInfo, "mousePos"),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_NCRBUTTONDBLCLK, HitTestParamInfo,
+                                 "hitTestValue", PointsParamInfo, "mousePos"),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_NCMBUTTONDOWN, HitTestParamInfo,
+                                 "hitTestValue", PointsParamInfo, "mousePos"),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_NCMBUTTONUP, HitTestParamInfo,
+                                 "hitTestValue", PointsParamInfo, "mousePos"),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_NCMBUTTONDBLCLK, HitTestParamInfo,
+                                 "hitTestValue", PointsParamInfo, "mousePos"),
+    ENTRY(EM_GETSEL),
+    ENTRY(EM_SETSEL),
+    ENTRY(EM_GETRECT),
+    ENTRY(EM_SETRECT),
+    ENTRY(EM_SETRECTNP),
+    ENTRY(EM_SCROLL),
+    ENTRY(EM_LINESCROLL),
+    ENTRY(EM_SCROLLCARET),
+    ENTRY(EM_GETMODIFY),
+    ENTRY(EM_SETMODIFY),
+    ENTRY(EM_GETLINECOUNT),
+    ENTRY(EM_LINEINDEX),
+    ENTRY(EM_SETHANDLE),
+    ENTRY(EM_GETHANDLE),
+    ENTRY(EM_GETTHUMB),
+    ENTRY(EM_LINELENGTH),
+    ENTRY(EM_REPLACESEL),
+    ENTRY(EM_GETLINE),
+    ENTRY(EM_LIMITTEXT),
+    ENTRY(EM_CANUNDO),
+    ENTRY(EM_UNDO),
+    ENTRY(EM_FMTLINES),
+    ENTRY(EM_LINEFROMCHAR),
+    ENTRY(EM_SETTABSTOPS),
+    ENTRY(EM_SETPASSWORDCHAR),
+    ENTRY(EM_EMPTYUNDOBUFFER),
+    ENTRY(EM_GETFIRSTVISIBLELINE),
+    ENTRY(EM_SETREADONLY),
+    ENTRY(EM_SETWORDBREAKPROC),
+    ENTRY(EM_GETWORDBREAKPROC),
+    ENTRY(EM_GETPASSWORDCHAR),
+    ENTRY(EM_SETMARGINS),
+    ENTRY(EM_GETMARGINS),
+    ENTRY(EM_GETLIMITTEXT),
+    ENTRY(EM_POSFROMCHAR),
+    ENTRY(EM_CHARFROMPOS),
+    ENTRY(EM_SETIMESTATUS),
+    ENTRY(EM_GETIMESTATUS),
+    ENTRY(SBM_SETPOS),
+    ENTRY(SBM_GETPOS),
+    ENTRY(SBM_SETRANGE),
+    ENTRY(SBM_SETRANGEREDRAW),
+    ENTRY(SBM_GETRANGE),
+    ENTRY(SBM_ENABLE_ARROWS),
+    ENTRY(SBM_SETSCROLLINFO),
+    ENTRY(SBM_GETSCROLLINFO),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_KEYDOWN, VirtualKeyParamInfo, "vKey",
+                                 KeystrokeFlagsParamInfo, ""),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_KEYUP, VirtualKeyParamInfo, "vKey",
+                                 KeystrokeFlagsParamInfo, ""),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_CHAR, IntParamInfo, "charCode",
+                                 KeystrokeFlagsParamInfo, ""),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_DEADCHAR, IntParamInfo, "charCode",
+                                 KeystrokeFlagsParamInfo, ""),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_SYSKEYDOWN, VirtualKeyParamInfo, "vKey",
+                                 KeystrokeFlagsParamInfo, ""),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_SYSKEYUP, VirtualKeyParamInfo, "vKey",
+                                 KeystrokeFlagsParamInfo, ""),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_SYSCHAR, IntParamInfo, "charCode",
+                                 KeystrokeFlagsParamInfo, ""),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_SYSDEADCHAR, IntParamInfo, "charCode",
+                                 KeystrokeFlagsParamInfo, ""),
+    ENTRY(WM_KEYLAST),
+    ENTRY(WM_IME_STARTCOMPOSITION),
+    ENTRY(WM_IME_ENDCOMPOSITION),
+    ENTRY(WM_IME_COMPOSITION),
+    ENTRY(WM_INITDIALOG),
+    ENTRY(WM_COMMAND),
+    ENTRY(WM_SYSCOMMAND),
+    ENTRY(WM_TIMER),
+    ENTRY(WM_HSCROLL),
+    ENTRY(WM_VSCROLL),
+    ENTRY(WM_INITMENU),
+    ENTRY(WM_INITMENUPOPUP),
+    ENTRY(WM_MENUSELECT),
+    ENTRY(WM_MENUCHAR),
+    ENTRY(WM_ENTERIDLE),
+    ENTRY(WM_MENURBUTTONUP),
+    ENTRY(WM_MENUDRAG),
+    ENTRY(WM_MENUGETOBJECT),
+    ENTRY(WM_UNINITMENUPOPUP),
+    ENTRY(WM_MENUCOMMAND),
+    ENTRY(WM_CHANGEUISTATE),
+    ENTRY(WM_QUERYUISTATE),
+    ENTRY(WM_UPDATEUISTATE),
+    ENTRY(WM_CTLCOLORMSGBOX),
+    ENTRY(WM_CTLCOLOREDIT),
+    ENTRY(WM_CTLCOLORLISTBOX),
+    ENTRY(WM_CTLCOLORBTN),
+    ENTRY(WM_CTLCOLORDLG),
+    ENTRY(WM_CTLCOLORSCROLLBAR),
+    ENTRY(WM_CTLCOLORSTATIC),
+    ENTRY(CB_GETEDITSEL),
+    ENTRY(CB_LIMITTEXT),
+    ENTRY(CB_SETEDITSEL),
+    ENTRY(CB_ADDSTRING),
+    ENTRY(CB_DELETESTRING),
+    ENTRY(CB_DIR),
+    ENTRY(CB_GETCOUNT),
+    ENTRY(CB_GETCURSEL),
+    ENTRY(CB_GETLBTEXT),
+    ENTRY(CB_GETLBTEXTLEN),
+    ENTRY(CB_INSERTSTRING),
+    ENTRY(CB_RESETCONTENT),
+    ENTRY(CB_FINDSTRING),
+    ENTRY(CB_SELECTSTRING),
+    ENTRY(CB_SETCURSEL),
+    ENTRY(CB_SHOWDROPDOWN),
+    ENTRY(CB_GETITEMDATA),
+    ENTRY(CB_SETITEMDATA),
+    ENTRY(CB_GETDROPPEDCONTROLRECT),
+    ENTRY(CB_SETITEMHEIGHT),
+    ENTRY(CB_GETITEMHEIGHT),
+    ENTRY(CB_SETEXTENDEDUI),
+    ENTRY(CB_GETEXTENDEDUI),
+    ENTRY(CB_GETDROPPEDSTATE),
+    ENTRY(CB_FINDSTRINGEXACT),
+    ENTRY(CB_SETLOCALE),
+    ENTRY(CB_GETLOCALE),
+    ENTRY(CB_GETTOPINDEX),
+    ENTRY(CB_SETTOPINDEX),
+    ENTRY(CB_GETHORIZONTALEXTENT),
+    ENTRY(CB_SETHORIZONTALEXTENT),
+    ENTRY(CB_GETDROPPEDWIDTH),
+    ENTRY(CB_SETDROPPEDWIDTH),
+    ENTRY(CB_INITSTORAGE),
+    ENTRY(CB_MSGMAX),
+    ENTRY(LB_ADDSTRING),
+    ENTRY(LB_INSERTSTRING),
+    ENTRY(LB_DELETESTRING),
+    ENTRY(LB_SELITEMRANGEEX),
+    ENTRY(LB_RESETCONTENT),
+    ENTRY(LB_SETSEL),
+    ENTRY(LB_SETCURSEL),
+    ENTRY(LB_GETSEL),
+    ENTRY(LB_GETCURSEL),
+    ENTRY(LB_GETTEXT),
+    ENTRY(LB_GETTEXTLEN),
+    ENTRY(LB_GETCOUNT),
+    ENTRY(LB_SELECTSTRING),
+    ENTRY(LB_DIR),
+    ENTRY(LB_GETTOPINDEX),
+    ENTRY(LB_FINDSTRING),
+    ENTRY(LB_GETSELCOUNT),
+    ENTRY(LB_GETSELITEMS),
+    ENTRY(LB_SETTABSTOPS),
+    ENTRY(LB_GETHORIZONTALEXTENT),
+    ENTRY(LB_SETHORIZONTALEXTENT),
+    ENTRY(LB_SETCOLUMNWIDTH),
+    ENTRY(LB_ADDFILE),
+    ENTRY(LB_SETTOPINDEX),
+    ENTRY(LB_GETITEMRECT),
+    ENTRY(LB_GETITEMDATA),
+    ENTRY(LB_SETITEMDATA),
+    ENTRY(LB_SELITEMRANGE),
+    ENTRY(LB_SETANCHORINDEX),
+    ENTRY(LB_GETANCHORINDEX),
+    ENTRY(LB_SETCARETINDEX),
+    ENTRY(LB_GETCARETINDEX),
+    ENTRY(LB_SETITEMHEIGHT),
+    ENTRY(LB_GETITEMHEIGHT),
+    ENTRY(LB_FINDSTRINGEXACT),
+    ENTRY(LB_SETLOCALE),
+    ENTRY(LB_GETLOCALE),
+    ENTRY(LB_SETCOUNT),
+    ENTRY(LB_INITSTORAGE),
+    ENTRY(LB_ITEMFROMPOINT),
+    ENTRY(LB_MSGMAX),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_MOUSEMOVE, VirtualModifierKeysParamInfo,
+                                 "virtualKeys", XLowWordYHighWordParamInfo,
+                                 "mousePos"),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_LBUTTONDOWN, VirtualModifierKeysParamInfo,
+                                 "virtualKeys", XLowWordYHighWordParamInfo,
+                                 "mousePos"),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_LBUTTONUP, VirtualModifierKeysParamInfo,
+                                 "virtualKeys", XLowWordYHighWordParamInfo,
+                                 "mousePos"),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_LBUTTONDBLCLK, VirtualModifierKeysParamInfo,
+                                 "virtualKeys", XLowWordYHighWordParamInfo,
+                                 "mousePos"),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_RBUTTONDOWN, VirtualModifierKeysParamInfo,
+                                 "virtualKeys", XLowWordYHighWordParamInfo,
+                                 "mousePos"),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_RBUTTONUP, VirtualModifierKeysParamInfo,
+                                 "virtualKeys", XLowWordYHighWordParamInfo,
+                                 "mousePos"),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_RBUTTONDBLCLK, VirtualModifierKeysParamInfo,
+                                 "virtualKeys", XLowWordYHighWordParamInfo,
+                                 "mousePos"),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_MBUTTONDOWN, VirtualModifierKeysParamInfo,
+                                 "virtualKeys", XLowWordYHighWordParamInfo,
+                                 "mousePos"),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_MBUTTONUP, VirtualModifierKeysParamInfo,
+                                 "virtualKeys", XLowWordYHighWordParamInfo,
+                                 "mousePos"),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_MBUTTONDBLCLK, VirtualModifierKeysParamInfo,
+                                 "virtualKeys", XLowWordYHighWordParamInfo,
+                                 "mousePos"),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_MOUSEWHEEL,
+                                 VirtualKeysLowWordDistanceHighWordParamInfo,
+                                 "", XLowWordYHighWordParamInfo, "mousePos"),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_MOUSEHWHEEL,
+                                 VirtualKeysLowWordDistanceHighWordParamInfo,
+                                 "", XLowWordYHighWordParamInfo, "mousePos"),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_PARENTNOTIFY, ParentNotifyEventParamInfo,
+                                 "", PointParamInfo, "pointerLocation"),
+    ENTRY(WM_ENTERMENULOOP),
+    ENTRY(WM_EXITMENULOOP),
+    ENTRY(WM_NEXTMENU),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_SIZING, WindowEdgeParamInfo, "edge",
+                                 RectParamInfo, "rect"),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_CAPTURECHANGED, nullptr, nullptr,
+                                 HexParamInfo, "windowHandle"),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_MOVING, nullptr, nullptr, RectParamInfo,
+                                 "rect"),
+    ENTRY(WM_POWERBROADCAST),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_DEVICECHANGE, DeviceEventParamInfo, "event",
+                                 HexParamInfo, "data"),
+    ENTRY(WM_MDICREATE),
+    ENTRY(WM_MDIDESTROY),
+    ENTRY(WM_MDIACTIVATE),
+    ENTRY(WM_MDIRESTORE),
+    ENTRY(WM_MDINEXT),
+    ENTRY(WM_MDIMAXIMIZE),
+    ENTRY(WM_MDITILE),
+    ENTRY(WM_MDICASCADE),
+    ENTRY(WM_MDIICONARRANGE),
+    ENTRY(WM_MDIGETACTIVE),
+    ENTRY(WM_MDISETMENU),
+    ENTRY(WM_ENTERSIZEMOVE),
+    ENTRY(WM_EXITSIZEMOVE),
+    ENTRY(WM_DROPFILES),
+    ENTRY(WM_MDIREFRESHMENU),
+    ENTRY(WM_IME_SETCONTEXT),
+    ENTRY(WM_IME_NOTIFY),
+    ENTRY(WM_IME_CONTROL),
+    ENTRY(WM_IME_COMPOSITIONFULL),
+    ENTRY(WM_IME_SELECT),
+    ENTRY(WM_IME_CHAR),
+    ENTRY(WM_IME_REQUEST),
+    ENTRY(WM_IME_KEYDOWN),
+    ENTRY(WM_IME_KEYUP),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_NCMOUSEHOVER, VirtualModifierKeysParamInfo,
+                                 "virtualKeys", XLowWordYHighWordParamInfo,
+                                 "mousePos"),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_MOUSEHOVER, VirtualModifierKeysParamInfo,
+                                 "virtualKeys", XLowWordYHighWordParamInfo,
+                                 "mousePos"),
+    ENTRY_WITH_NO_PARAM_INFO(WM_NCMOUSELEAVE),
+    ENTRY_WITH_NO_PARAM_INFO(WM_MOUSELEAVE),
+    ENTRY(WM_CUT),
+    ENTRY(WM_COPY),
+    ENTRY(WM_PASTE),
+    ENTRY(WM_CLEAR),
+    ENTRY(WM_UNDO),
+    ENTRY(WM_RENDERFORMAT),
+    ENTRY(WM_RENDERALLFORMATS),
+    ENTRY(WM_DESTROYCLIPBOARD),
+    ENTRY(WM_DRAWCLIPBOARD),
+    ENTRY(WM_PAINTCLIPBOARD),
+    ENTRY(WM_VSCROLLCLIPBOARD),
+    ENTRY(WM_SIZECLIPBOARD),
+    ENTRY(WM_ASKCBFORMATNAME),
+    ENTRY(WM_CHANGECBCHAIN),
+    ENTRY(WM_HSCROLLCLIPBOARD),
+    ENTRY(WM_QUERYNEWPALETTE),
+    ENTRY(WM_PALETTEISCHANGING),
+    ENTRY(WM_PALETTECHANGED),
+    ENTRY(WM_HOTKEY),
+    ENTRY(WM_PRINT),
+    ENTRY(WM_PRINTCLIENT),
+    ENTRY(WM_THEMECHANGED),
+    ENTRY(WM_HANDHELDFIRST),
+    ENTRY(WM_HANDHELDLAST),
+    ENTRY(WM_AFXFIRST),
+    ENTRY(WM_AFXLAST),
+    ENTRY(WM_PENWINFIRST),
+    ENTRY(WM_PENWINLAST),
+    ENTRY(WM_APP),
+    ENTRY_WITH_NO_PARAM_INFO(WM_DWMCOMPOSITIONCHANGED),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_DWMNCRENDERINGCHANGED, TrueFalseParamInfo,
+                                 "DwmNcRendering", nullptr, nullptr),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_DWMCOLORIZATIONCOLORCHANGED, HexParamInfo,
+                                 "color:AARRGGBB", TrueFalseParamInfo,
+                                 "isOpaque"),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_DWMWINDOWMAXIMIZEDCHANGE,
+                                 TrueFalseParamInfo, "maximized", nullptr,
+                                 nullptr),
+    ENTRY(WM_DWMSENDICONICTHUMBNAIL),  // lParam: HIWORD is x, LOWORD is y
+    ENTRY_WITH_NO_PARAM_INFO(WM_DWMSENDICONICLIVEPREVIEWBITMAP),
+    ENTRY(WM_TABLET_QUERYSYSTEMGESTURESTATUS),
+    ENTRY(WM_GESTURE),
+    ENTRY(WM_GESTURENOTIFY),
+    ENTRY(WM_GETTITLEBARINFOEX),
+    ENTRY_WITH_SPLIT_PARAM_INFOS(WM_DPICHANGED, XLowWordYHighWordParamInfo,
+                                 "newDPI", RectParamInfo,
+                                 "suggestedSizeAndPos"),
+};
+#undef ENTRY
+#undef ENTRY_WITH_NO_PARAM_INFO
+#undef ENTRY_WITH_CUSTOM_PARAM_INFO
+#undef ENTRY_WITH_SPLIT_PARAM_INFO
+
+}  // namespace mozilla::widget
+
+#ifdef DEBUG
+void DDError(const char* msg, HRESULT hr) {
+  /*XXX make nicer */
+  MOZ_LOG(gWindowsLog, LogLevel::Error,
+          ("DirectDraw error %s: 0x%08lx\n", msg, hr));
+}
+#endif
+
+#ifdef DEBUG_VK
+bool is_vk_down(int vk) {
+  SHORT st = GetKeyState(vk);
+#  ifdef DEBUG
+  MOZ_LOG(gWindowsLog, LogLevel::Info, ("is_vk_down vk=%x st=%x\n", vk, st));
+#  endif
+  return (st < 0);
+}
+#endif
diff --git a/widget/windows/nsWindowDbg.h b/widget/windows/nsWindowDbg.h
new file mode 100644
index 0000000000..c739966fd5
--- /dev/null
+++ b/widget/windows/nsWindowDbg.h
@@ -0,0 +1,153 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef WindowDbg_h__
+#define WindowDbg_h__
+
+/*
+ * nsWindowDbg - Debug related utilities for nsWindow.
+ */
+
+#include "nsWindowDefs.h"
+#include "mozilla/BaseProfilerMarkersPrerequisites.h"
+
+// Enables debug output for popup rollup hooks
+// #define POPUP_ROLLUP_DEBUG_OUTPUT
+
+// Enable window size and state debug output
+// #define WINSTATE_DEBUG_OUTPUT
+
+// nsIWidget defines a set of debug output statements
+// that are called in various places within the code.
+// #define WIDGET_DEBUG_OUTPUT
+
+// Enable IS_VK_DOWN debug output
+// #define DEBUG_VK
+
+namespace mozilla::widget {
+
+class MOZ_RAII AutoProfilerMessageMarker {
+ public:
+  explicit AutoProfilerMessageMarker(Span<const char> aMsgLoopName, HWND hWnd,
+                                     UINT msg, WPARAM wParam, LPARAM lParam);
+
+  ~AutoProfilerMessageMarker();
+
+ protected:
+  Maybe<MarkerOptions> mOptions;
+  Span<const char> mMsgLoopName;
+  UINT mMsg;
+  WPARAM mWParam;
+  LPARAM mLParam;
+};
+
+// Windows message debugging data
+struct EventMsgInfo {
+  const char* mStr;
+  UINT mId;
+  std::function<nsAutoCString(WPARAM, LPARAM, bool)> mParamInfoFn;
+  std::function<void(nsCString&, WPARAM, const char*, bool)> mWParamInfoFn;
+  const char* mWParamName;
+  std::function<void(nsCString&, LPARAM, const char*, bool)> mLParamInfoFn;
+  const char* mLParamName;
+  void LogParameters(nsCString& str, WPARAM wParam, LPARAM lParam,
+                     bool isPreCall);
+};
+extern std::unordered_map<UINT, EventMsgInfo> gAllEvents;
+
+// RAII-style class to log before and after an event is handled.
+class NativeEventLogger final {
+ public:
+  template <size_t N>
+  NativeEventLogger(const char (&aMsgLoopName)[N], HWND hwnd, UINT msg,
+                    WPARAM wParam, LPARAM lParam)
+      : NativeEventLogger(Span(aMsgLoopName), hwnd, msg, wParam, lParam) {}
+
+  void SetResult(LRESULT lresult, bool result) {
+    mRetValue = lresult;
+    mResult = mozilla::Some(result);
+  }
+  ~NativeEventLogger();
+
+ private:
+  NativeEventLogger(Span<const char> aMsgLoopName, HWND hwnd, UINT msg,
+                    WPARAM wParam, LPARAM lParam);
+  bool NativeEventLoggerInternal();
+
+  AutoProfilerMessageMarker mProfilerMarker;
+  const char* mMsgLoopName;
+  const HWND mHwnd;
+  const UINT mMsg;
+  const WPARAM mWParam;
+  const LPARAM mLParam;
+  mozilla::Maybe<long> mEventCounter;
+  // not const because these will be set after the event is handled
+  mozilla::Maybe<bool> mResult;
+  LRESULT mRetValue = 0;
+
+  bool mShouldLogPostCall;
+};
+
+struct EnumValueAndName {
+  uint64_t mFlag;
+  const char* mName;
+};
+
+// Appends to str a description of the flags passed in.
+// flagsAndNames is a list of flag values with a string description
+// for each one. These are processed in order, so if there are
+// flag values that are combination of individual values (for example
+// something like WS_OVERLAPPEDWINDOW) they need to come first
+// in the flagsAndNames array.
+// A 0 flag value will only be written if the flags input is exactly
+// 0, and it must come last in the flagsAndNames array.
+// Returns whether any info was appended to str.
+bool AppendFlagsInfo(nsCString& str, uint64_t flags,
+                     const nsTArray<EnumValueAndName>& flagsAndNames,
+                     const char* name);
+
+nsAutoCString WmSizeParamInfo(uint64_t wParam, uint64_t lParam, bool isPreCall);
+void XLowWordYHighWordParamInfo(nsCString& str, uint64_t value,
+                                const char* name, bool isPreCall);
+void WindowPosParamInfo(nsCString& str, uint64_t value, const char* name,
+                        bool isPreCall);
+void WindowEdgeParamInfo(nsCString& str, uint64_t value, const char* name,
+                         bool isPreCall);
+void RectParamInfo(nsCString& str, uint64_t value, const char* name,
+                   bool isPreCall);
+void UiActionParamInfo(nsCString& str, uint64_t value, const char* name,
+                       bool isPreCall);
+void WideStringParamInfo(nsCString& result, uint64_t value, const char* name,
+                         bool isPreCall);
+void MinMaxInfoParamInfo(nsCString& result, uint64_t value, const char* name,
+                         bool isPreCall);
+nsAutoCString WmNcCalcSizeParamInfo(uint64_t wParam, uint64_t lParam,
+                                    bool isPreCall);
+}  // namespace mozilla::widget
+
+#if defined(POPUP_ROLLUP_DEBUG_OUTPUT)
+typedef struct {
+  char* mStr;
+  int mId;
+} MSGFEventMsgInfo;
+
+#  define DISPLAY_NMM_PRT(_arg) \
+    MOZ_LOG(gWindowsLog, mozilla::LogLevel::Info, ((_arg)));
+#else
+#  define DISPLAY_NMM_PRT(_arg)
+#endif  // defined(POPUP_ROLLUP_DEBUG_OUTPUT)
+
+#if defined(DEBUG)
+void DDError(const char* msg, HRESULT hr);
+#endif  // defined(DEBUG)
+
+#if defined(DEBUG_VK)
+bool is_vk_down(int vk);
+#  define IS_VK_DOWN is_vk_down
+#else
+#  define IS_VK_DOWN(a) (GetKeyState(a) < 0)
+#endif  // defined(DEBUG_VK)
+
+#endif /* WindowDbg_h__ */
diff --git a/widget/windows/nsWindowDefs.h b/widget/windows/nsWindowDefs.h
new file mode 100644
index 0000000000..320d6ef07b
--- /dev/null
+++ b/widget/windows/nsWindowDefs.h
@@ -0,0 +1,119 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef WindowDefs_h__
+#define WindowDefs_h__
+
+/*
+ * nsWindowDefs - nsWindow related definitions, consts, and macros.
+ */
+
+#include "mozilla/widget/WinMessages.h"
+#include "nsBaseWidget.h"
+#include "nsdefs.h"
+#include "resource.h"
+
+/**************************************************************
+ *
+ * SECTION: defines
+ *
+ **************************************************************/
+
+// ConstrainPosition window positioning slop value
+#define kWindowPositionSlop 20
+
+// Origin of the system context menu when displayed in full screen mode
+#define MOZ_SYSCONTEXT_X_POS 20
+#define MOZ_SYSCONTEXT_Y_POS 20
+
+// Don't put more than this many rects in the dirty region, just fluff
+// out to the bounding-box if there are more
+#define MAX_RECTS_IN_REGION 100
+
+// Tablet PC Mouse Input Source
+#define TABLET_INK_SIGNATURE 0xFFFFFF00
+#define TABLET_INK_CHECK 0xFF515700
+#define TABLET_INK_TOUCH 0x00000080
+#define TABLET_INK_ID_MASK 0x0000007F
+#define MOUSE_INPUT_SOURCE() WinUtils::GetMouseInputSource()
+#define MOUSE_POINTERID() WinUtils::GetMousePointerID()
+
+/**************************************************************
+ *
+ * SECTION: constants
+ *
+ **************************************************************/
+
+/*
+ * Native windows class names
+ *
+ * ::: IMPORTANT :::
+ *
+ * External apps and drivers depend on window class names.
+ * For example, changing the window classes could break
+ * touchpad scrolling or screen readers.
+ *
+ * See bug 1776498.
+ */
+const wchar_t kClassNameHidden[] = L"MozillaHiddenWindowClass";
+const wchar_t kClassNameGeneral[] = L"MozillaWindowClass";
+const wchar_t kClassNameDialog[] = L"MozillaDialogClass";
+const wchar_t kClassNameDropShadow[] = L"MozillaDropShadowWindowClass";
+const wchar_t kClassNameTransition[] = L"MozillaTransitionWindowClass";
+
+/**************************************************************
+ *
+ * SECTION: structs
+ *
+ **************************************************************/
+
+// Used for synthesizing events
+struct KeyPair {
+  uint8_t mGeneral;
+  uint8_t mSpecific;
+  uint16_t mScanCode;
+  KeyPair(uint32_t aGeneral, uint32_t aSpecific)
+      : mGeneral(aGeneral & 0xFF),
+        mSpecific(aSpecific & 0xFF),
+        mScanCode((aGeneral & 0xFFFF0000) >> 16) {}
+  KeyPair(uint8_t aGeneral, uint8_t aSpecific, uint16_t aScanCode)
+      : mGeneral(aGeneral), mSpecific(aSpecific), mScanCode(aScanCode) {}
+};
+
+namespace mozilla {
+namespace widget {
+
+struct MSGResult {
+  // Result for the message.
+  LRESULT& mResult;
+  // If mConsumed is true, the caller shouldn't call next wndproc.
+  bool mConsumed;
+
+  explicit MSGResult(LRESULT* aResult = nullptr)
+      : mResult(aResult ? *aResult : mDefaultResult), mConsumed(false) {}
+
+ private:
+  LRESULT mDefaultResult;
+};
+
+}  // namespace widget
+}  // namespace mozilla
+
+/**************************************************************
+ *
+ * SECTION: macros
+ *
+ **************************************************************/
+
+#define NSRGB_2_COLOREF(color) \
+  RGB(NS_GET_R(color), NS_GET_G(color), NS_GET_B(color))
+#define COLOREF_2_NSRGB(color) \
+  NS_RGB(GetRValue(color), GetGValue(color), GetBValue(color))
+
+#define VERIFY_WINDOW_STYLE(s)                                         \
+  NS_ASSERTION(((s) & (WS_CHILD | WS_POPUP)) != (WS_CHILD | WS_POPUP), \
+               "WS_POPUP and WS_CHILD are mutually exclusive")
+
+#endif /* WindowDefs_h__ */
diff --git a/widget/windows/nsWindowGfx.cpp b/widget/windows/nsWindowGfx.cpp
new file mode 100644
index 0000000000..c2a91dcf6b
--- /dev/null
+++ b/widget/windows/nsWindowGfx.cpp
@@ -0,0 +1,718 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/*
+ * nsWindowGfx - Painting and aceleration.
+ */
+
+/**************************************************************
+ **************************************************************
+ **
+ ** BLOCK: Includes
+ **
+ ** Include headers.
+ **
+ **************************************************************
+ **************************************************************/
+
+#include "mozilla/dom/ContentParent.h"
+
+#include "nsWindowGfx.h"
+#include "nsAppRunner.h"
+#include <windows.h>
+#include <shellapi.h>
+#include "gfxEnv.h"
+#include "gfxImageSurface.h"
+#include "gfxUtils.h"
+#include "gfxConfig.h"
+#include "gfxWindowsSurface.h"
+#include "gfxWindowsPlatform.h"
+#include "gfxDWriteFonts.h"
+#include "mozilla/gfx/2D.h"
+#include "mozilla/gfx/DataSurfaceHelpers.h"
+#include "mozilla/gfx/Tools.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/UniquePtrExtensions.h"
+#include "nsGfxCIID.h"
+#include "gfxContext.h"
+#include "WinUtils.h"
+#include "WinWindowOcclusionTracker.h"
+#include "nsIWidgetListener.h"
+#include "mozilla/Unused.h"
+#include "nsDebug.h"
+#include "WindowRenderer.h"
+#include "mozilla/layers/WebRenderLayerManager.h"
+
+#include "mozilla/gfx/GPUProcessManager.h"
+#include "mozilla/layers/CompositorBridgeParent.h"
+#include "mozilla/layers/CompositorBridgeChild.h"
+#include "InProcessWinCompositorWidget.h"
+
+#include "nsUXThemeData.h"
+#include "nsUXThemeConstants.h"
+
+using namespace mozilla;
+using namespace mozilla::gfx;
+using namespace mozilla::layers;
+using namespace mozilla::widget;
+using namespace mozilla::plugins;
+extern mozilla::LazyLogModule gWindowsLog;
+
+/**************************************************************
+ **************************************************************
+ **
+ ** BLOCK: Variables
+ **
+ ** nsWindow Class static initializations and global variables.
+ **
+ **************************************************************
+ **************************************************************/
+
+/**************************************************************
+ *
+ * SECTION: nsWindow statics
+ *
+ **************************************************************/
+
+struct IconMetrics {
+  int32_t xMetric;
+  int32_t yMetric;
+  int32_t defaultSize;
+};
+
+// Corresponds 1:1 to the IconSizeType enum
+static IconMetrics sIconMetrics[] = {
+    {SM_CXSMICON, SM_CYSMICON, 16},  // small icon
+    {SM_CXICON, SM_CYICON, 32}       // regular icon
+};
+
+/**************************************************************
+ **************************************************************
+ **
+ ** BLOCK: nsWindow impl.
+ **
+ ** Paint related nsWindow methods.
+ **
+ **************************************************************
+ **************************************************************/
+
+// GetRegionToPaint returns the invalidated region that needs to be painted
+LayoutDeviceIntRegion nsWindow::GetRegionToPaint(bool aForceFullRepaint,
+                                                 PAINTSTRUCT ps, HDC aDC) {
+  if (aForceFullRepaint) {
+    RECT paintRect;
+    ::GetClientRect(mWnd, &paintRect);
+    return LayoutDeviceIntRegion(WinUtils::ToIntRect(paintRect));
+  }
+
+  HRGN paintRgn = ::CreateRectRgn(0, 0, 0, 0);
+  if (paintRgn != nullptr) {
+    int result = GetRandomRgn(aDC, paintRgn, SYSRGN);
+    if (result == 1) {
+      POINT pt = {0, 0};
+      ::MapWindowPoints(nullptr, mWnd, &pt, 1);
+      ::OffsetRgn(paintRgn, pt.x, pt.y);
+    }
+    LayoutDeviceIntRegion rgn(WinUtils::ConvertHRGNToRegion(paintRgn));
+    ::DeleteObject(paintRgn);
+    return rgn;
+  }
+  return LayoutDeviceIntRegion(WinUtils::ToIntRect(ps.rcPaint));
+}
+
+nsIWidgetListener* nsWindow::GetPaintListener() {
+  if (mDestroyCalled) return nullptr;
+  return mAttachedWidgetListener ? mAttachedWidgetListener : mWidgetListener;
+}
+
+void nsWindow::ForcePresent() {
+  if (mResizeState != RESIZING) {
+    if (CompositorBridgeChild* remoteRenderer = GetRemoteRenderer()) {
+      remoteRenderer->SendForcePresent(wr::RenderReasons::WIDGET);
+    }
+  }
+}
+
+bool nsWindow::OnPaint(uint32_t aNestingLevel) {
+  DeviceResetReason resetReason = DeviceResetReason::OK;
+  if (gfxWindowsPlatform::GetPlatform()->DidRenderingDeviceReset(
+          &resetReason)) {
+    gfxCriticalNote << "(nsWindow) Detected device reset: " << (int)resetReason;
+
+    gfxWindowsPlatform::GetPlatform()->UpdateRenderMode();
+
+    bool guilty;
+    switch (resetReason) {
+      case DeviceResetReason::HUNG:
+      case DeviceResetReason::RESET:
+      case DeviceResetReason::INVALID_CALL:
+        guilty = true;
+        break;
+      default:
+        guilty = false;
+        break;
+    }
+
+    GPUProcessManager::Get()->OnInProcessDeviceReset(guilty);
+
+    gfxCriticalNote << "(nsWindow) Finished device reset.";
+    return false;
+  }
+
+  PAINTSTRUCT ps;
+
+  // Avoid starting the GPU process for the initial navigator:blank window.
+  if (mIsEarlyBlankWindow) {
+    // Call BeginPaint/EndPaint or Windows will keep sending us messages.
+    ::BeginPaint(mWnd, &ps);
+    ::EndPaint(mWnd, &ps);
+    return true;
+  }
+
+  WindowRenderer* renderer = GetWindowRenderer();
+  KnowsCompositor* knowsCompositor = renderer->AsKnowsCompositor();
+  WebRenderLayerManager* layerManager = renderer->AsWebRender();
+
+  if (mClearNCEdge) {
+    // We need to clear this edge of the non-client region to black (once).
+    HDC hdc;
+    RECT rect;
+    hdc = ::GetWindowDC(mWnd);
+    ::GetWindowRect(mWnd, &rect);
+    ::MapWindowPoints(nullptr, mWnd, (LPPOINT)&rect, 2);
+    switch (mClearNCEdge.value()) {
+      case ABE_TOP:
+        rect.bottom = rect.top + kHiddenTaskbarSize;
+        break;
+      case ABE_LEFT:
+        rect.right = rect.left + kHiddenTaskbarSize;
+        break;
+      case ABE_BOTTOM:
+        rect.top = rect.bottom - kHiddenTaskbarSize;
+        break;
+      case ABE_RIGHT:
+        rect.left = rect.right - kHiddenTaskbarSize;
+        break;
+      default:
+        MOZ_ASSERT_UNREACHABLE("Invalid edge value");
+        break;
+    }
+    ::FillRect(hdc, &rect,
+               reinterpret_cast<HBRUSH>(::GetStockObject(BLACK_BRUSH)));
+    ::ReleaseDC(mWnd, hdc);
+
+    mClearNCEdge.reset();
+  }
+
+  if (knowsCompositor && layerManager &&
+      !mBounds.IsEqualEdges(mLastPaintBounds)) {
+    // Do an early async composite so that we at least have something on the
+    // screen in the right place, even if the content is out of date.
+    layerManager->ScheduleComposite(wr::RenderReasons::WIDGET);
+  }
+  mLastPaintBounds = mBounds;
+
+  // For layered translucent windows all drawing should go to memory DC and no
+  // WM_PAINT messages are normally generated. To support asynchronous painting
+  // we force generation of WM_PAINT messages by invalidating window areas with
+  // RedrawWindow, InvalidateRect or InvalidateRgn function calls.
+  const bool usingMemoryDC =
+      renderer->GetBackendType() == LayersBackend::LAYERS_NONE &&
+      mTransparencyMode == TransparencyMode::Transparent;
+
+  HDC hDC = nullptr;
+  if (usingMemoryDC) {
+    // BeginPaint/EndPaint must be called to make Windows think that invalid
+    // area is painted. Otherwise it will continue sending the same message
+    // endlessly.
+    ::BeginPaint(mWnd, &ps);
+    ::EndPaint(mWnd, &ps);
+
+    // We're guaranteed to have a widget proxy since we called
+    // GetLayerManager().
+    hDC = mBasicLayersSurface->GetTransparentDC();
+  } else {
+    hDC = ::BeginPaint(mWnd, &ps);
+  }
+
+  const bool forceRepaint = mTransparencyMode == TransparencyMode::Transparent;
+  const LayoutDeviceIntRegion region = GetRegionToPaint(forceRepaint, ps, hDC);
+
+  if (knowsCompositor && layerManager) {
+    // We need to paint to the screen even if nothing changed, since if we
+    // don't have a compositing window manager, our pixels could be stale.
+    layerManager->SetNeedsComposite(true);
+    layerManager->SendInvalidRegion(region.ToUnknownRegion());
+  }
+
+  RefPtr<nsWindow> strongThis(this);
+
+  nsIWidgetListener* listener = GetPaintListener();
+  if (listener) {
+    listener->WillPaintWindow(this);
+  }
+  // Re-get the listener since the will paint notification may have killed it.
+  listener = GetPaintListener();
+  if (!listener) {
+    return false;
+  }
+
+  if (knowsCompositor && layerManager && layerManager->NeedsComposite()) {
+    layerManager->ScheduleComposite(wr::RenderReasons::WIDGET);
+    layerManager->SetNeedsComposite(false);
+  }
+
+  bool result = true;
+  if (!region.IsEmpty() && listener) {
+    // Should probably pass in a real region here, using GetRandomRgn
+    // http://msdn.microsoft.com/library/default.asp?url=/library/en-us/gdi/clipping_4q0e.asp
+
+#ifdef WIDGET_DEBUG_OUTPUT
+    debug_DumpPaintEvent(stdout, this, region.ToUnknownRegion(), "noname",
+                         (int32_t)mWnd);
+#endif  // WIDGET_DEBUG_OUTPUT
+
+    switch (renderer->GetBackendType()) {
+      case LayersBackend::LAYERS_NONE: {
+        RefPtr<gfxASurface> targetSurface;
+
+        // don't support transparency for non-GDI rendering, for now
+        if (TransparencyMode::Transparent == mTransparencyMode) {
+          // This mutex needs to be held when EnsureTransparentSurface is
+          // called.
+          MutexAutoLock lock(mBasicLayersSurface->GetTransparentSurfaceLock());
+          targetSurface = mBasicLayersSurface->EnsureTransparentSurface();
+        }
+
+        RefPtr<gfxWindowsSurface> targetSurfaceWin;
+        if (!targetSurface) {
+          uint32_t flags = (mTransparencyMode == TransparencyMode::Opaque)
+                               ? 0
+                               : gfxWindowsSurface::FLAG_IS_TRANSPARENT;
+          targetSurfaceWin = new gfxWindowsSurface(hDC, flags);
+          targetSurface = targetSurfaceWin;
+        }
+
+        if (!targetSurface) {
+          NS_ERROR("Invalid RenderMode!");
+          return false;
+        }
+
+        RECT paintRect;
+        ::GetClientRect(mWnd, &paintRect);
+        RefPtr<DrawTarget> dt = gfxPlatform::CreateDrawTargetForSurface(
+            targetSurface, IntSize(paintRect.right - paintRect.left,
+                                   paintRect.bottom - paintRect.top));
+        if (!dt || !dt->IsValid()) {
+          gfxWarning()
+              << "nsWindow::OnPaint failed in CreateDrawTargetForSurface";
+          return false;
+        }
+
+        // don't need to double buffer with anything but GDI
+        BufferMode doubleBuffering = mozilla::layers::BufferMode::BUFFER_NONE;
+        switch (mTransparencyMode) {
+          case TransparencyMode::Transparent:
+            // If we're rendering with translucency, we're going to be
+            // rendering the whole window; make sure we clear it first
+            dt->ClearRect(
+                Rect(0.f, 0.f, dt->GetSize().width, dt->GetSize().height));
+            break;
+          default:
+            // If we're not doing translucency, then double buffer
+            doubleBuffering = mozilla::layers::BufferMode::BUFFERED;
+            break;
+        }
+
+        gfxContext thebesContext(dt);
+
+        {
+          AutoLayerManagerSetup setupLayerManager(this, &thebesContext,
+                                                  doubleBuffering);
+          result = listener->PaintWindow(this, region);
+        }
+
+        if (TransparencyMode::Transparent == mTransparencyMode) {
+          // Data from offscreen drawing surface was copied to memory bitmap of
+          // transparent bitmap. Now it can be read from memory bitmap to apply
+          // alpha channel and after that displayed on the screen.
+          mBasicLayersSurface->RedrawTransparentWindow();
+        }
+      } break;
+      case LayersBackend::LAYERS_WR: {
+        result = listener->PaintWindow(this, region);
+        if (!gfxEnv::MOZ_DISABLE_FORCE_PRESENT()) {
+          nsCOMPtr<nsIRunnable> event = NewRunnableMethod(
+              "nsWindow::ForcePresent", this, &nsWindow::ForcePresent);
+          NS_DispatchToMainThread(event);
+        }
+      } break;
+      default:
+        NS_ERROR("Unknown layers backend used!");
+        break;
+    }
+  }
+
+  if (!usingMemoryDC) {
+    ::EndPaint(mWnd, &ps);
+  }
+
+  mLastPaintEndTime = TimeStamp::Now();
+
+  // Re-get the listener since painting may have killed it.
+  listener = GetPaintListener();
+  if (listener) listener->DidPaintWindow();
+
+  if (aNestingLevel == 0 && ::GetUpdateRect(mWnd, nullptr, false)) {
+    OnPaint(1);
+  }
+
+  return result;
+}
+
+bool nsWindow::NeedsToTrackWindowOcclusionState() {
+  if (!WinWindowOcclusionTracker::Get()) {
+    return false;
+  }
+
+  if (mCompositorSession && mWindowType == WindowType::TopLevel) {
+    return true;
+  }
+
+  return false;
+}
+
+void nsWindow::NotifyOcclusionState(mozilla::widget::OcclusionState aState) {
+  MOZ_ASSERT(NeedsToTrackWindowOcclusionState());
+
+  bool isFullyOccluded = aState == mozilla::widget::OcclusionState::OCCLUDED;
+  // When window is minimized, it is not set as fully occluded.
+  if (mFrameState->GetSizeMode() == nsSizeMode_Minimized) {
+    isFullyOccluded = false;
+  }
+
+  // Don't dispatch if the new occlustion state is the same as the current
+  // state.
+  if (mIsFullyOccluded == isFullyOccluded) {
+    return;
+  }
+
+  mIsFullyOccluded = isFullyOccluded;
+
+  MOZ_LOG(gWindowsLog, LogLevel::Info,
+          ("nsWindow::NotifyOcclusionState() mIsFullyOccluded %d "
+           "mFrameState->GetSizeMode() %d",
+           mIsFullyOccluded, mFrameState->GetSizeMode()));
+
+  wr::DebugFlags flags{0};
+  flags._0 = gfx::gfxVars::WebRenderDebugFlags();
+  bool debugEnabled = bool(flags & wr::DebugFlags::WINDOW_VISIBILITY_DBG);
+  if (debugEnabled && mCompositorWidgetDelegate) {
+    mCompositorWidgetDelegate->NotifyVisibilityUpdated(
+        mFrameState->GetSizeMode(), mIsFullyOccluded);
+  }
+
+  if (mWidgetListener) {
+    mWidgetListener->OcclusionStateChanged(mIsFullyOccluded);
+  }
+}
+
+void nsWindow::MaybeEnableWindowOcclusion(bool aEnable) {
+  // WindowOcclusion is enabled/disabled only when compositor session exists.
+  // See nsWindow::NeedsToTrackWindowOcclusionState().
+  if (!mCompositorSession) {
+    return;
+  }
+
+  bool enabled = gfxConfig::IsEnabled(gfx::Feature::WINDOW_OCCLUSION);
+
+  if (aEnable) {
+    // Enable window occlusion.
+    if (enabled && NeedsToTrackWindowOcclusionState()) {
+      WinWindowOcclusionTracker::Get()->Enable(this, mWnd);
+
+      wr::DebugFlags flags{0};
+      flags._0 = gfx::gfxVars::WebRenderDebugFlags();
+      bool debugEnabled = bool(flags & wr::DebugFlags::WINDOW_VISIBILITY_DBG);
+      if (debugEnabled && mCompositorWidgetDelegate) {
+        mCompositorWidgetDelegate->NotifyVisibilityUpdated(
+            mFrameState->GetSizeMode(), mIsFullyOccluded);
+      }
+    }
+    return;
+  }
+
+  // Disable window occlusion.
+  MOZ_ASSERT(!aEnable);
+
+  if (!NeedsToTrackWindowOcclusionState()) {
+    return;
+  }
+
+  WinWindowOcclusionTracker::Get()->Disable(this, mWnd);
+  NotifyOcclusionState(OcclusionState::VISIBLE);
+
+  wr::DebugFlags flags{0};
+  flags._0 = gfx::gfxVars::WebRenderDebugFlags();
+  bool debugEnabled = bool(flags & wr::DebugFlags::WINDOW_VISIBILITY_DBG);
+  if (debugEnabled && mCompositorWidgetDelegate) {
+    mCompositorWidgetDelegate->NotifyVisibilityUpdated(
+        mFrameState->GetSizeMode(), mIsFullyOccluded);
+  }
+}
+
+// This override of CreateCompositor is to add support for sending the IPC
+// call for RequesetFxrOutput as soon as the compositor for this widget is
+// available.
+void nsWindow::CreateCompositor() {
+  nsBaseWidget::CreateCompositor();
+
+  MaybeEnableWindowOcclusion(/* aEnable */ true);
+
+  if (mRequestFxrOutputPending) {
+    GetRemoteRenderer()->SendRequestFxrOutput();
+  }
+}
+
+void nsWindow::DestroyCompositor() {
+  MaybeEnableWindowOcclusion(/* aEnable */ false);
+
+  nsBaseWidget::DestroyCompositor();
+}
+
+void nsWindow::RequestFxrOutput() {
+  if (GetRemoteRenderer() != nullptr) {
+    MOZ_CRASH("RequestFxrOutput should happen before Compositor is created.");
+  } else {
+    // The compositor isn't ready, so indicate to make the IPC call when
+    // it is available.
+    mRequestFxrOutputPending = true;
+  }
+}
+
+LayoutDeviceIntSize nsWindowGfx::GetIconMetrics(IconSizeType aSizeType) {
+  int32_t width = ::GetSystemMetrics(sIconMetrics[aSizeType].xMetric);
+  int32_t height = ::GetSystemMetrics(sIconMetrics[aSizeType].yMetric);
+
+  if (width == 0 || height == 0) {
+    width = height = sIconMetrics[aSizeType].defaultSize;
+  }
+
+  return LayoutDeviceIntSize(width, height);
+}
+
+nsresult nsWindowGfx::CreateIcon(imgIContainer* aContainer, bool aIsCursor,
+                                 LayoutDeviceIntPoint aHotspot,
+                                 LayoutDeviceIntSize aScaledSize,
+                                 HICON* aIcon) {
+  MOZ_ASSERT(aHotspot.x >= 0 && aHotspot.y >= 0);
+  MOZ_ASSERT((aScaledSize.width > 0 && aScaledSize.height > 0) ||
+             (aScaledSize.width == 0 && aScaledSize.height == 0));
+
+  // Get the image data
+  RefPtr<SourceSurface> surface = aContainer->GetFrame(
+      imgIContainer::FRAME_CURRENT,
+      imgIContainer::FLAG_SYNC_DECODE | imgIContainer::FLAG_ASYNC_NOTIFY);
+  NS_ENSURE_TRUE(surface, NS_ERROR_NOT_AVAILABLE);
+
+  IntSize frameSize = surface->GetSize();
+  if (frameSize.IsEmpty()) {
+    return NS_ERROR_FAILURE;
+  }
+
+  IntSize iconSize(aScaledSize.width, aScaledSize.height);
+  if (iconSize == IntSize(0, 0)) {  // use frame's intrinsic size
+    iconSize = frameSize;
+  }
+
+  RefPtr<DataSourceSurface> dataSurface;
+  bool mappedOK;
+  DataSourceSurface::MappedSurface map;
+
+  if (iconSize != frameSize) {
+    // Scale the surface
+    dataSurface =
+        Factory::CreateDataSourceSurface(iconSize, SurfaceFormat::B8G8R8A8);
+    NS_ENSURE_TRUE(dataSurface, NS_ERROR_FAILURE);
+    mappedOK = dataSurface->Map(DataSourceSurface::MapType::READ_WRITE, &map);
+    NS_ENSURE_TRUE(mappedOK, NS_ERROR_FAILURE);
+
+    RefPtr<DrawTarget> dt = Factory::CreateDrawTargetForData(
+        BackendType::CAIRO, map.mData, dataSurface->GetSize(), map.mStride,
+        SurfaceFormat::B8G8R8A8);
+    if (!dt) {
+      gfxWarning()
+          << "nsWindowGfx::CreatesIcon failed in CreateDrawTargetForData";
+      return NS_ERROR_OUT_OF_MEMORY;
+    }
+    dt->DrawSurface(surface, Rect(0, 0, iconSize.width, iconSize.height),
+                    Rect(0, 0, frameSize.width, frameSize.height),
+                    DrawSurfaceOptions(),
+                    DrawOptions(1.0f, CompositionOp::OP_SOURCE));
+  } else if (surface->GetFormat() != SurfaceFormat::B8G8R8A8) {
+    // Convert format to SurfaceFormat::B8G8R8A8
+    dataSurface = gfxUtils::CopySurfaceToDataSourceSurfaceWithFormat(
+        surface, SurfaceFormat::B8G8R8A8);
+    NS_ENSURE_TRUE(dataSurface, NS_ERROR_FAILURE);
+    mappedOK = dataSurface->Map(DataSourceSurface::MapType::READ, &map);
+  } else {
+    dataSurface = surface->GetDataSurface();
+    NS_ENSURE_TRUE(dataSurface, NS_ERROR_FAILURE);
+    mappedOK = dataSurface->Map(DataSourceSurface::MapType::READ, &map);
+  }
+  NS_ENSURE_TRUE(dataSurface && mappedOK, NS_ERROR_FAILURE);
+  MOZ_ASSERT(dataSurface->GetFormat() == SurfaceFormat::B8G8R8A8);
+
+  uint8_t* data = nullptr;
+  UniquePtr<uint8_t[]> autoDeleteArray;
+  if (map.mStride == BytesPerPixel(dataSurface->GetFormat()) * iconSize.width) {
+    // Mapped data is already packed
+    data = map.mData;
+  } else {
+    // We can't use map.mData since the pixels are not packed (as required by
+    // CreateDIBitmap, which is called under the DataToBitmap call below).
+    //
+    // We must unmap before calling SurfaceToPackedBGRA because it needs access
+    // to the pixel data.
+    dataSurface->Unmap();
+    map.mData = nullptr;
+
+    autoDeleteArray = SurfaceToPackedBGRA(dataSurface);
+    data = autoDeleteArray.get();
+    NS_ENSURE_TRUE(data, NS_ERROR_FAILURE);
+  }
+
+  HBITMAP bmp = DataToBitmap(data, iconSize.width, -iconSize.height, 32);
+  uint8_t* a1data = Data32BitTo1Bit(data, iconSize.width, iconSize.height);
+  if (map.mData) {
+    dataSurface->Unmap();
+  }
+  if (!a1data) {
+    return NS_ERROR_FAILURE;
+  }
+
+  HBITMAP mbmp = DataToBitmap(a1data, iconSize.width, -iconSize.height, 1);
+  free(a1data);
+
+  ICONINFO info = {0};
+  info.fIcon = !aIsCursor;
+  info.xHotspot = aHotspot.x;
+  info.yHotspot = aHotspot.y;
+  info.hbmMask = mbmp;
+  info.hbmColor = bmp;
+
+  HCURSOR icon = ::CreateIconIndirect(&info);
+  ::DeleteObject(mbmp);
+  ::DeleteObject(bmp);
+  if (!icon) return NS_ERROR_FAILURE;
+  *aIcon = icon;
+  return NS_OK;
+}
+
+// Adjust cursor image data
+uint8_t* nsWindowGfx::Data32BitTo1Bit(uint8_t* aImageData, uint32_t aWidth,
+                                      uint32_t aHeight) {
+  // We need (aWidth + 7) / 8 bytes plus zero-padding up to a multiple of
+  // 4 bytes for each row (HBITMAP requirement). Bug 353553.
+  uint32_t outBpr = ((aWidth + 31) / 8) & ~3;
+
+  // Allocate and clear mask buffer
+  uint8_t* outData = (uint8_t*)calloc(outBpr, aHeight);
+  if (!outData) return nullptr;
+
+  int32_t* imageRow = (int32_t*)aImageData;
+  for (uint32_t curRow = 0; curRow < aHeight; curRow++) {
+    uint8_t* outRow = outData + curRow * outBpr;
+    uint8_t mask = 0x80;
+    for (uint32_t curCol = 0; curCol < aWidth; curCol++) {
+      // Use sign bit to test for transparency, as alpha byte is highest byte
+      if (*imageRow++ < 0) *outRow |= mask;
+
+      mask >>= 1;
+      if (!mask) {
+        outRow++;
+        mask = 0x80;
+      }
+    }
+  }
+
+  return outData;
+}
+
+/**
+ * Convert the given image data to a HBITMAP. If the requested depth is
+ * 32 bit, a bitmap with an alpha channel will be returned.
+ *
+ * @param aImageData The image data to convert. Must use the format accepted
+ *                   by CreateDIBitmap.
+ * @param aWidth     With of the bitmap, in pixels.
+ * @param aHeight    Height of the image, in pixels.
+ * @param aDepth     Image depth, in bits. Should be one of 1, 24 and 32.
+ *
+ * @return The HBITMAP representing the image. Caller should call
+ *         DeleteObject when done with the bitmap.
+ *         On failure, nullptr will be returned.
+ */
+HBITMAP nsWindowGfx::DataToBitmap(uint8_t* aImageData, uint32_t aWidth,
+                                  uint32_t aHeight, uint32_t aDepth) {
+  HDC dc = ::GetDC(nullptr);
+
+  if (aDepth == 32) {
+    // Alpha channel. We need the new header.
+    BITMAPV4HEADER head = {0};
+    head.bV4Size = sizeof(head);
+    head.bV4Width = aWidth;
+    head.bV4Height = aHeight;
+    head.bV4Planes = 1;
+    head.bV4BitCount = aDepth;
+    head.bV4V4Compression = BI_BITFIELDS;
+    head.bV4SizeImage = 0;  // Uncompressed
+    head.bV4XPelsPerMeter = 0;
+    head.bV4YPelsPerMeter = 0;
+    head.bV4ClrUsed = 0;
+    head.bV4ClrImportant = 0;
+
+    head.bV4RedMask = 0x00FF0000;
+    head.bV4GreenMask = 0x0000FF00;
+    head.bV4BlueMask = 0x000000FF;
+    head.bV4AlphaMask = 0xFF000000;
+
+    HBITMAP bmp = ::CreateDIBitmap(
+        dc, reinterpret_cast<CONST BITMAPINFOHEADER*>(&head), CBM_INIT,
+        aImageData, reinterpret_cast<CONST BITMAPINFO*>(&head), DIB_RGB_COLORS);
+    ::ReleaseDC(nullptr, dc);
+    return bmp;
+  }
+
+  char reserved_space[sizeof(BITMAPINFOHEADER) + sizeof(RGBQUAD) * 2];
+  BITMAPINFOHEADER& head = *(BITMAPINFOHEADER*)reserved_space;
+
+  head.biSize = sizeof(BITMAPINFOHEADER);
+  head.biWidth = aWidth;
+  head.biHeight = aHeight;
+  head.biPlanes = 1;
+  head.biBitCount = (WORD)aDepth;
+  head.biCompression = BI_RGB;
+  head.biSizeImage = 0;  // Uncompressed
+  head.biXPelsPerMeter = 0;
+  head.biYPelsPerMeter = 0;
+  head.biClrUsed = 0;
+  head.biClrImportant = 0;
+
+  BITMAPINFO& bi = *(BITMAPINFO*)reserved_space;
+
+  if (aDepth == 1) {
+    RGBQUAD black = {0, 0, 0, 0};
+    RGBQUAD white = {255, 255, 255, 0};
+
+    bi.bmiColors[0] = white;
+    bi.bmiColors[1] = black;
+  }
+
+  HBITMAP bmp =
+      ::CreateDIBitmap(dc, &head, CBM_INIT, aImageData, &bi, DIB_RGB_COLORS);
+  ::ReleaseDC(nullptr, dc);
+  return bmp;
+}
diff --git a/widget/windows/nsWindowGfx.h b/widget/windows/nsWindowGfx.h
new file mode 100644
index 0000000000..0d5fd9e01a
--- /dev/null
+++ b/widget/windows/nsWindowGfx.h
@@ -0,0 +1,35 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef WindowGfx_h__
+#define WindowGfx_h__
+
+/*
+ * nsWindowGfx - Painting and aceleration.
+ */
+
+#include "nsWindow.h"
+#include <imgIContainer.h>
+
+class nsWindowGfx {
+ public:
+  enum IconSizeType { kSmallIcon, kRegularIcon };
+  static mozilla::LayoutDeviceIntSize GetIconMetrics(IconSizeType aSizeType);
+  static nsresult CreateIcon(imgIContainer* aContainer, bool aIsCursor,
+                             mozilla::LayoutDeviceIntPoint aHotspot,
+                             mozilla::LayoutDeviceIntSize aScaledSize,
+                             HICON* aIcon);
+
+ private:
+  /**
+   * Cursor helpers
+   */
+  static uint8_t* Data32BitTo1Bit(uint8_t* aImageData, uint32_t aWidth,
+                                  uint32_t aHeight);
+  static HBITMAP DataToBitmap(uint8_t* aImageData, uint32_t aWidth,
+                              uint32_t aHeight, uint32_t aDepth);
+};
+
+#endif  // WindowGfx_h__
diff --git a/widget/windows/nsWindowLoggedMessages.cpp b/widget/windows/nsWindowLoggedMessages.cpp
new file mode 100644
index 0000000000..ac0f05a875
--- /dev/null
+++ b/widget/windows/nsWindowLoggedMessages.cpp
@@ -0,0 +1,307 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <windef.h>
+#include <winuser.h>
+#include "mozilla/StaticPrefs_storage.h"
+#include "mozilla/StaticPrefs_widget.h"
+#include "nsWindowLoggedMessages.h"
+#include "nsWindow.h"
+#include "WinUtils.h"
+#include <map>
+#include <algorithm>
+
+namespace mozilla::widget {
+
+// NCCALCSIZE_PARAMS and WINDOWPOS are relatively large structures, so store
+// them as a pointer to save memory
+using NcCalcSizeVariantData =
+    Variant<UniquePtr<std::pair<NCCALCSIZE_PARAMS, WINDOWPOS>>, RECT>;
+// to save memory, hold the raw data and only convert to string
+// when requested
+using MessageSpecificData =
+    Variant<std::pair<WPARAM, LPARAM>,  // WM_SIZE, WM_MOVE
+            WINDOWPOS,  // WM_WINDOWPOSCHANGING, WM_WINDOWPOSCHANGED
+            std::pair<WPARAM, RECT>,      // WM_SIZING, WM_DPICHANGED, WM_MOVING
+            std::pair<WPARAM, nsString>,  // WM_SETTINGCHANGE
+            std::pair<bool, NcCalcSizeVariantData>,  // WM_NCCALCSIZE
+            MINMAXINFO                               // WM_GETMINMAXINFO
+            >;
+
+struct WindowMessageData {
+  long mEventCounter;
+  bool mIsPreEvent;
+  MessageSpecificData mSpecificData;
+  mozilla::Maybe<bool> mResult;
+  LRESULT mRetValue;
+  WindowMessageData(long eventCounter, bool isPreEvent,
+                    MessageSpecificData&& specificData,
+                    mozilla::Maybe<bool> result, LRESULT retValue)
+      : mEventCounter(eventCounter),
+        mIsPreEvent(isPreEvent),
+        mSpecificData(std::move(specificData)),
+        mResult(result),
+        mRetValue(retValue) {}
+  // Disallow copy constructor/operator since MessageSpecificData has a
+  // UniquePtr
+  WindowMessageData(const WindowMessageData&) = delete;
+  WindowMessageData& operator=(const WindowMessageData&) = delete;
+  WindowMessageData(WindowMessageData&&) = default;
+  WindowMessageData& operator=(WindowMessageData&&) = default;
+};
+
+struct WindowMessageDataSortKey {
+  long mEventCounter;
+  bool mIsPreEvent;
+  explicit WindowMessageDataSortKey(const WindowMessageData& data)
+      : mEventCounter(data.mEventCounter), mIsPreEvent(data.mIsPreEvent) {}
+  bool operator<(const WindowMessageDataSortKey& other) const {
+    if (mEventCounter < other.mEventCounter) {
+      return true;
+    }
+    if (other.mEventCounter < mEventCounter) {
+      return false;
+    }
+    if (mIsPreEvent && !other.mIsPreEvent) {
+      return true;
+    }
+    if (other.mIsPreEvent && !mIsPreEvent) {
+      return false;
+    }
+    // they're equal
+    return false;
+  }
+};
+
+struct CircularMessageBuffer {
+  // Only used when the vector is at its maximum size
+  size_t mNextFreeIndex = 0;
+  std::vector<WindowMessageData> mMessages;
+};
+static std::map<HWND, std::map<UINT, CircularMessageBuffer>> gWindowMessages;
+
+static HWND GetHwndFromWidget(nsIWidget* windowWidget) {
+  nsWindow* window = static_cast<nsWindow*>(windowWidget);
+  return window->GetWindowHandle();
+}
+
+MessageSpecificData MakeMessageSpecificData(UINT event, WPARAM wParam,
+                                            LPARAM lParam) {
+  // Since we store this data for every message we log, make sure it's of a
+  // reasonable size. Keep in mind we're storing up to 10 (number of message
+  // types)
+  // * 6 (default number of messages per type to keep) of these messages per
+  // window.
+  static_assert(sizeof(MessageSpecificData) <= 48);
+  switch (event) {
+    case WM_SIZE:
+    case WM_MOVE:
+      return MessageSpecificData(std::make_pair(wParam, lParam));
+    case WM_WINDOWPOSCHANGING:
+    case WM_WINDOWPOSCHANGED: {
+      LPWINDOWPOS windowPosPtr = reinterpret_cast<LPWINDOWPOS>(lParam);
+      WINDOWPOS windowPos = *windowPosPtr;
+      return MessageSpecificData(std::move(windowPos));
+    }
+    case WM_SIZING:
+    case WM_DPICHANGED:
+    case WM_MOVING: {
+      LPRECT rectPtr = reinterpret_cast<LPRECT>(lParam);
+      RECT rect = *rectPtr;
+      return MessageSpecificData(std::make_pair(wParam, std::move(rect)));
+    }
+    case WM_SETTINGCHANGE: {
+      LPCWSTR wideStrPtr = reinterpret_cast<LPCWSTR>(lParam);
+      nsString str(wideStrPtr);
+      return MessageSpecificData(std::make_pair(wParam, std::move(str)));
+    }
+    case WM_NCCALCSIZE: {
+      bool shouldIndicateValidArea = wParam == TRUE;
+      if (shouldIndicateValidArea) {
+        LPNCCALCSIZE_PARAMS ncCalcSizeParamsPtr =
+            reinterpret_cast<LPNCCALCSIZE_PARAMS>(lParam);
+        NCCALCSIZE_PARAMS ncCalcSizeParams = *ncCalcSizeParamsPtr;
+        WINDOWPOS windowPos = *ncCalcSizeParams.lppos;
+        UniquePtr<std::pair<NCCALCSIZE_PARAMS, WINDOWPOS>> ncCalcSizeData =
+            MakeUnique<std::pair<NCCALCSIZE_PARAMS, WINDOWPOS>>(
+                std::pair(std::move(ncCalcSizeParams), std::move(windowPos)));
+        return MessageSpecificData(
+            std::make_pair(shouldIndicateValidArea,
+                           NcCalcSizeVariantData(std::move(ncCalcSizeData))));
+      } else {
+        LPRECT rectPtr = reinterpret_cast<LPRECT>(lParam);
+        RECT rect = *rectPtr;
+        return MessageSpecificData(std::make_pair(
+            shouldIndicateValidArea, NcCalcSizeVariantData(std::move(rect))));
+      }
+    }
+    case WM_GETMINMAXINFO: {
+      PMINMAXINFO minMaxInfoPtr = reinterpret_cast<PMINMAXINFO>(lParam);
+      MINMAXINFO minMaxInfo = *minMaxInfoPtr;
+      return MessageSpecificData(std::move(minMaxInfo));
+    }
+    default:
+      MOZ_ASSERT_UNREACHABLE(
+          "Unhandled message type in MakeMessageSpecificData");
+      return MessageSpecificData(std::make_pair(wParam, lParam));
+  }
+}
+
+void AppendFriendlyMessageSpecificData(nsCString& str, UINT event,
+                                       bool isPreEvent,
+                                       const MessageSpecificData& data) {
+  switch (event) {
+    case WM_SIZE: {
+      const auto& params = data.as<std::pair<WPARAM, LPARAM>>();
+      nsAutoCString tempStr =
+          WmSizeParamInfo(params.first, params.second, isPreEvent);
+      str.AppendASCII(tempStr);
+      break;
+    }
+    case WM_MOVE: {
+      const auto& params = data.as<std::pair<WPARAM, LPARAM>>();
+      XLowWordYHighWordParamInfo(str, params.second, "upperLeft", isPreEvent);
+      break;
+    }
+    case WM_WINDOWPOSCHANGING:
+    case WM_WINDOWPOSCHANGED: {
+      const auto& params = data.as<WINDOWPOS>();
+      WindowPosParamInfo(str, reinterpret_cast<uint64_t>(&params),
+                         "newSizeAndPos", isPreEvent);
+      break;
+    }
+    case WM_SIZING: {
+      const auto& params = data.as<std::pair<WPARAM, RECT>>();
+      WindowEdgeParamInfo(str, params.first, "edge", isPreEvent);
+      str.AppendASCII(" ");
+      RectParamInfo(str, reinterpret_cast<uint64_t>(&params.second), "rect",
+                    isPreEvent);
+      break;
+    }
+    case WM_DPICHANGED: {
+      const auto& params = data.as<std::pair<WPARAM, RECT>>();
+      XLowWordYHighWordParamInfo(str, params.first, "newDPI", isPreEvent);
+      str.AppendASCII(" ");
+      RectParamInfo(str, reinterpret_cast<uint64_t>(&params.second),
+                    "suggestedSizeAndPos", isPreEvent);
+      break;
+    }
+    case WM_MOVING: {
+      const auto& params = data.as<std::pair<WPARAM, RECT>>();
+      RectParamInfo(str, reinterpret_cast<uint64_t>(&params.second), "rect",
+                    isPreEvent);
+      break;
+    }
+    case WM_SETTINGCHANGE: {
+      const auto& params = data.as<std::pair<WPARAM, nsString>>();
+      UiActionParamInfo(str, params.first, "uiAction", isPreEvent);
+      str.AppendASCII(" ");
+      WideStringParamInfo(
+          str,
+          reinterpret_cast<uint64_t>((const wchar_t*)(params.second.Data())),
+          "paramChanged", isPreEvent);
+      break;
+    }
+    case WM_NCCALCSIZE: {
+      const auto& params = data.as<std::pair<bool, NcCalcSizeVariantData>>();
+      bool shouldIndicateValidArea = params.first;
+      if (shouldIndicateValidArea) {
+        const auto& validAreaParams =
+            params.second
+                .as<UniquePtr<std::pair<NCCALCSIZE_PARAMS, WINDOWPOS>>>();
+        // Make pointer point to the cached data
+        validAreaParams->first.lppos = &validAreaParams->second;
+        nsAutoCString tempStr = WmNcCalcSizeParamInfo(
+            TRUE, reinterpret_cast<uint64_t>(&validAreaParams->first),
+            isPreEvent);
+        str.AppendASCII(tempStr);
+      } else {
+        RECT rect = params.second.as<RECT>();
+        nsAutoCString tempStr = WmNcCalcSizeParamInfo(
+            FALSE, reinterpret_cast<uint64_t>(&rect), isPreEvent);
+        str.AppendASCII(tempStr);
+      }
+      break;
+    }
+    case WM_GETMINMAXINFO: {
+      const auto& params = data.as<MINMAXINFO>();
+      MinMaxInfoParamInfo(str, reinterpret_cast<uint64_t>(&params), "",
+                          isPreEvent);
+      break;
+    }
+    default:
+      MOZ_ASSERT(false,
+                 "Unhandled message type in AppendFriendlyMessageSpecificData");
+      str.AppendASCII("???");
+  }
+}
+
+nsCString MakeFriendlyMessage(UINT event, bool isPreEvent, long eventCounter,
+                              const MessageSpecificData& data,
+                              mozilla::Maybe<bool> result, LRESULT retValue) {
+  nsCString str;
+  const char* eventName = mozilla::widget::WinUtils::WinEventToEventName(event);
+  MOZ_ASSERT(eventName, "Unknown event name in MakeFriendlyMessage");
+  eventName = eventName ? eventName : "(unknown)";
+  str.AppendPrintf("%6ld %04x (%s) - ", eventCounter, event, eventName);
+  AppendFriendlyMessageSpecificData(str, event, isPreEvent, data);
+  const char* resultMsg =
+      result.isSome() ? (result.value() ? "true" : "false") : "initial call";
+  str.AppendPrintf(" 0x%08llX (%s)",
+                   result.isSome() ? static_cast<uint64_t>(retValue) : 0,
+                   resultMsg);
+  return str;
+}
+
+void WindowClosed(HWND hwnd) { gWindowMessages.erase(hwnd); }
+
+void LogWindowMessage(HWND hwnd, UINT event, bool isPreEvent, long eventCounter,
+                      WPARAM wParam, LPARAM lParam, mozilla::Maybe<bool> result,
+                      LRESULT retValue) {
+  auto& hwndMessages = gWindowMessages[hwnd];
+  auto& hwndWindowMessages = hwndMessages[event];
+  WindowMessageData messageData = {
+      eventCounter, isPreEvent, MakeMessageSpecificData(event, wParam, lParam),
+      result, retValue};
+  uint32_t numberOfMessagesToKeep =
+      StaticPrefs::widget_windows_messages_to_log();
+  if (hwndWindowMessages.mMessages.size() < numberOfMessagesToKeep) {
+    // haven't reached limit yet
+    hwndWindowMessages.mMessages.push_back(std::move(messageData));
+  } else {
+    hwndWindowMessages.mMessages[hwndWindowMessages.mNextFreeIndex] =
+        std::move(messageData);
+  }
+  hwndWindowMessages.mNextFreeIndex =
+      (hwndWindowMessages.mNextFreeIndex + 1) % numberOfMessagesToKeep;
+}
+
+void GetLatestWindowMessages(RefPtr<nsIWidget> windowWidget,
+                             nsTArray<nsCString>& messages) {
+  HWND hwnd = GetHwndFromWidget(windowWidget);
+  const auto& rawMessages = gWindowMessages[hwnd];
+  nsTArray<std::pair<WindowMessageDataSortKey, nsCString>>
+      sortKeyAndMessageArray;
+  sortKeyAndMessageArray.SetCapacity(
+      rawMessages.size() * StaticPrefs::widget_windows_messages_to_log());
+  for (const auto& eventAndMessage : rawMessages) {
+    for (const auto& messageData : eventAndMessage.second.mMessages) {
+      nsCString message = MakeFriendlyMessage(
+          eventAndMessage.first, messageData.mIsPreEvent,
+          messageData.mEventCounter, messageData.mSpecificData,
+          messageData.mResult, messageData.mRetValue);
+      WindowMessageDataSortKey sortKey(messageData);
+      sortKeyAndMessageArray.AppendElement(
+          std::make_pair(sortKey, std::move(message)));
+    }
+  }
+  std::sort(sortKeyAndMessageArray.begin(), sortKeyAndMessageArray.end());
+  messages.SetCapacity(sortKeyAndMessageArray.Length());
+  for (const std::pair<WindowMessageDataSortKey, nsCString>& entry :
+       sortKeyAndMessageArray) {
+    messages.AppendElement(std::move(entry.second));
+  }
+}
+}  // namespace mozilla::widget
diff --git a/widget/windows/nsWindowLoggedMessages.h b/widget/windows/nsWindowLoggedMessages.h
new file mode 100644
index 0000000000..c0ea632bb0
--- /dev/null
+++ b/widget/windows/nsWindowLoggedMessages.h
@@ -0,0 +1,26 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef WindowLoggedMessages_h__
+#define WindowLoggedMessages_h__
+
+#include "minwindef.h"
+#include "wtypes.h"
+
+#include "nsIWidget.h"
+#include "nsStringFwd.h"
+
+namespace mozilla::widget {
+
+void LogWindowMessage(HWND hwnd, UINT event, bool isPreEvent, long eventCounter,
+                      WPARAM wParam, LPARAM lParam, mozilla::Maybe<bool> result,
+                      LRESULT retValue);
+void WindowClosed(HWND hwnd);
+void GetLatestWindowMessages(RefPtr<nsIWidget> windowWidget,
+                             nsTArray<nsCString>& messages);
+
+}  // namespace mozilla::widget
+
+#endif /* WindowLoggedMessages */
diff --git a/widget/windows/nsWindowTaskbarConcealer.cpp b/widget/windows/nsWindowTaskbarConcealer.cpp
new file mode 100644
index 0000000000..b2b6b13a1d
--- /dev/null
+++ b/widget/windows/nsWindowTaskbarConcealer.cpp
@@ -0,0 +1,384 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "nsWindowTaskbarConcealer.h"
+
+#include "nsIWinTaskbar.h"
+#define NS_TASKBAR_CONTRACTID "@mozilla.org/windows-taskbar;1"
+
+#include "mozilla/Logging.h"
+#include "mozilla/StaticPrefs_widget.h"
+#include "WinUtils.h"
+
+using namespace mozilla;
+
+/**
+ * TaskbarConcealerImpl
+ *
+ * Implement Windows-fullscreen marking.
+ *
+ * nsWindow::TaskbarConcealer implements logic determining _whether_ to tell
+ * Windows that a given window is fullscreen. TaskbarConcealerImpl performs the
+ * platform-specific work of actually communicating that fact to Windows.
+ *
+ * (This object is not persistent; it's constructed on the stack when needed.)
+ */
+struct TaskbarConcealerImpl {
+  void MarkAsHidingTaskbar(HWND aWnd, bool aMark);
+
+ private:
+  nsCOMPtr<nsIWinTaskbar> mTaskbarInfo;
+};
+
+/**
+ * nsWindow::TaskbarConcealer
+ *
+ * Issue taskbar-hide requests to the OS as needed.
+ */
+
+/*
+  Per MSDN [0], one should mark and unmark fullscreen windows via the
+  ITaskbarList2::MarkFullscreenWindow method. Unfortunately, Windows pays less
+  attention to this than one might prefer -- in particular, it typically fails
+  to show the taskbar when switching focus from a window marked as fullscreen to
+  one not thus marked. [1]
+
+  Experimentation has (so far) suggested that its behavior is reasonable when
+  switching between multiple monitors, or between a set of windows which are all
+  from different processes [2]. This leaves us to handle the same-monitor, same-
+  process case.
+
+  Rather than do anything subtle here, we take the blanket approach of simply
+  listening for every potentially-relevant state change, and then explicitly
+  marking or unmarking every potentially-visible toplevel window.
+
+  ----
+
+  [0] Relevant link:
+      https://docs.microsoft.com/en-us/windows/win32/api/shobjidl_core/nf-shobjidl_core-itaskbarlist2-markfullscreenwindow
+
+      The "NonRudeHWND" property described therein doesn't help with anything
+      in this comment, unfortunately. (See its use in MarkAsHidingTaskbar for
+      more details.)
+
+  [1] This is an oversimplification; Windows' actual behavior here is...
+      complicated. See bug 1732517 comment 6 for some examples.
+
+  [2] A comment in Chromium asserts that this is actually different threads. For
+      us, of course, that makes no difference.
+      https://github.com/chromium/chromium/blob/2b822268bd3/ui/views/win/hwnd_message_handler.cc#L1342
+*/
+
+/**************************************************************
+ *
+ * SECTION: TaskbarConcealer utilities
+ *
+ **************************************************************/
+
+static mozilla::LazyLogModule sTaskbarConcealerLog("TaskbarConcealer");
+
+// Map of all relevant Gecko windows, along with the monitor on which each
+// window was last known to be located.
+/* static */
+nsTHashMap<HWND, HMONITOR> nsWindow::TaskbarConcealer::sKnownWindows;
+
+// Returns Nothing if the window in question is irrelevant (for any reason),
+// or Some(the window's current state) otherwise.
+/* static */
+Maybe<nsWindow::TaskbarConcealer::WindowState>
+nsWindow::TaskbarConcealer::GetWindowState(HWND aWnd) {
+  // Classical Win32 visibility conditions.
+  if (!::IsWindowVisible(aWnd)) {
+    return Nothing();
+  }
+  if (::IsIconic(aWnd)) {
+    return Nothing();
+  }
+
+  // Non-nsWindow windows associated with this thread may include file dialogs
+  // and IME input popups.
+  nsWindow* pWin = widget::WinUtils::GetNSWindowPtr(aWnd);
+  if (!pWin) {
+    return Nothing();
+  }
+
+  // nsWindows of other window-classes include tooltips and drop-shadow-bearing
+  // menus.
+  if (pWin->mWindowType != WindowType::TopLevel) {
+    return Nothing();
+  }
+
+  // Cloaked windows are (presumably) on a different virtual desktop.
+  // https://devblogs.microsoft.com/oldnewthing/20200302-00/?p=103507
+  if (pWin->mIsCloaked) {
+    return Nothing();
+  }
+
+  return Some(
+      WindowState{::MonitorFromWindow(aWnd, MONITOR_DEFAULTTONULL),
+                  pWin->mFrameState->GetSizeMode() == nsSizeMode_Fullscreen});
+}
+
+/**************************************************************
+ *
+ * SECTION: TaskbarConcealer::UpdateAllState
+ *
+ **************************************************************/
+
+// Update all Windows-fullscreen-marking state and internal caches to represent
+// the current state of the system.
+/* static */
+void nsWindow::TaskbarConcealer::UpdateAllState(
+    HWND destroyedHwnd /* = nullptr */
+) {
+  // sKnownWindows is otherwise-unprotected shared state
+  MOZ_ASSERT(NS_IsMainThread(),
+             "TaskbarConcealer can only be used from the main thread!");
+
+  if (MOZ_LOG_TEST(sTaskbarConcealerLog, LogLevel::Info)) {
+    static size_t sLogCounter = 0;
+    MOZ_LOG(sTaskbarConcealerLog, LogLevel::Info,
+            ("Calling UpdateAllState() for the %zuth time", sLogCounter++));
+
+    MOZ_LOG(sTaskbarConcealerLog, LogLevel::Info, ("Last known state:"));
+    if (sKnownWindows.IsEmpty()) {
+      MOZ_LOG(sTaskbarConcealerLog, LogLevel::Info,
+              ("  none (no windows known)"));
+    } else {
+      for (const auto& entry : sKnownWindows) {
+        MOZ_LOG(
+            sTaskbarConcealerLog, LogLevel::Info,
+            ("  window %p was on monitor %p", entry.GetKey(), entry.GetData()));
+      }
+    }
+  }
+
+  // Array of all our potentially-relevant HWNDs, in Z-order (topmost first),
+  // along with their associated relevant state.
+  struct Item {
+    HWND hwnd;
+    HMONITOR monitor;
+    bool isGkFullscreen;
+  };
+  const nsTArray<Item> windows = [&] {
+    nsTArray<Item> windows;
+
+    // USE OF UNDOCUMENTED BEHAVIOR: The EnumWindows family of functions
+    // enumerates windows in Z-order, topmost first. (This has been true since
+    // at least Windows 2000, and possibly since Windows 3.0.)
+    //
+    // It's necessarily unreliable if windows are reordered while being
+    // enumerated; but in that case we'll get a message informing us of that
+    // fact, and can redo our state-calculations then.
+    //
+    // There exists no documented interface to acquire this information (other
+    // than ::GetWindow(), which is racy).
+    mozilla::EnumerateThreadWindows([&](HWND hwnd) {
+      // Depending on details of window-destruction that probably shouldn't be
+      // relied on, this HWND may or may not still be in the window list.
+      // Pretend it's not.
+      if (hwnd == destroyedHwnd) {
+        return;
+      }
+
+      const auto maybeState = GetWindowState(hwnd);
+      if (!maybeState) {
+        return;
+      }
+      const WindowState& state = *maybeState;
+
+      windows.AppendElement(Item{.hwnd = hwnd,
+                                 .monitor = state.monitor,
+                                 .isGkFullscreen = state.isGkFullscreen});
+    });
+
+    return windows;
+  }();
+
+  // Relevant monitors are exactly those with relevant windows.
+  const nsTHashSet<HMONITOR> relevantMonitors = [&]() {
+    nsTHashSet<HMONITOR> relevantMonitors;
+    for (const Item& item : windows) {
+      relevantMonitors.Insert(item.monitor);
+    }
+    return relevantMonitors;
+  }();
+
+  // Update the cached mapping from windows to monitors. (This is only used as
+  // an optimization in TaskbarConcealer::OnWindowPosChanged().)
+  sKnownWindows.Clear();
+  for (const Item& item : windows) {
+    MOZ_LOG(
+        sTaskbarConcealerLog, LogLevel::Debug,
+        ("Found relevant window %p on monitor %p", item.hwnd, item.monitor));
+    sKnownWindows.InsertOrUpdate(item.hwnd, item.monitor);
+  }
+
+  // Auxiliary function. Does what it says on the tin.
+  const auto FindUppermostWindowOn = [&windows](HMONITOR aMonitor) -> HWND {
+    for (const Item& item : windows) {
+      if (item.monitor == aMonitor) {
+        MOZ_LOG(sTaskbarConcealerLog, LogLevel::Info,
+                ("on monitor %p, uppermost relevant HWND is %p", aMonitor,
+                 item.hwnd));
+        return item.hwnd;
+      }
+    }
+
+    // This should never happen, since we're drawing our monitor-set from the
+    // set of relevant windows.
+    MOZ_LOG(sTaskbarConcealerLog, LogLevel::Warning,
+            ("on monitor %p, no relevant windows were found", aMonitor));
+    return nullptr;
+  };
+
+  TaskbarConcealerImpl impl;
+
+  // Mark all relevant windows as not hiding the taskbar, unless they're both
+  // Gecko-fullscreen and the uppermost relevant window on their monitor.
+  for (HMONITOR monitor : relevantMonitors) {
+    const HWND topmost = FindUppermostWindowOn(monitor);
+
+    for (const Item& item : windows) {
+      if (item.monitor != monitor) continue;
+      impl.MarkAsHidingTaskbar(item.hwnd,
+                               item.isGkFullscreen && item.hwnd == topmost);
+    }
+  }
+}  // nsWindow::TaskbarConcealer::UpdateAllState()
+
+// Mark this window as requesting to occlude the taskbar. (The caller is
+// responsible for keeping any local state up-to-date.)
+void TaskbarConcealerImpl::MarkAsHidingTaskbar(HWND aWnd, bool aMark) {
+  const char* const sMark = aMark ? "true" : "false";
+
+  if (!mTaskbarInfo) {
+    mTaskbarInfo = do_GetService(NS_TASKBAR_CONTRACTID);
+
+    if (!mTaskbarInfo) {
+      MOZ_LOG(
+          sTaskbarConcealerLog, LogLevel::Warning,
+          ("could not acquire IWinTaskbar (aWnd %p, aMark %s)", aWnd, sMark));
+      return;
+    }
+  }
+
+  MOZ_LOG(sTaskbarConcealerLog, LogLevel::Info,
+          ("Calling PrepareFullScreen(%p, %s)", aWnd, sMark));
+
+  const nsresult hr = mTaskbarInfo->PrepareFullScreen(aWnd, aMark);
+
+  if (FAILED(hr)) {
+    MOZ_LOG(sTaskbarConcealerLog, LogLevel::Error,
+            ("Call to PrepareFullScreen(%p, %s) failed with nsresult %x", aWnd,
+             sMark, uint32_t(hr)));
+  }
+};
+
+/**************************************************************
+ *
+ * SECTION: TaskbarConcealer event callbacks
+ *
+ **************************************************************/
+
+void nsWindow::TaskbarConcealer::OnWindowDestroyed(HWND aWnd) {
+  MOZ_LOG(sTaskbarConcealerLog, LogLevel::Info,
+          ("==> OnWindowDestroyed() for HWND %p", aWnd));
+
+  UpdateAllState(aWnd);
+}
+
+void nsWindow::TaskbarConcealer::OnFocusAcquired(nsWindow* aWin) {
+  // Update state unconditionally.
+  //
+  // This is partially because focus-acquisition only updates the z-order, which
+  // we don't cache and therefore can't notice changes to -- but also because
+  // it's probably a good idea to give the user a natural way to refresh the
+  // current fullscreen-marking state if it's somehow gone bad.
+
+  MOZ_LOG(sTaskbarConcealerLog, LogLevel::Info,
+          ("==> OnFocusAcquired() for HWND %p on HMONITOR %p", aWin->mWnd,
+           ::MonitorFromWindow(aWin->mWnd, MONITOR_DEFAULTTONULL)));
+
+  UpdateAllState();
+}
+
+void nsWindow::TaskbarConcealer::OnFullscreenChanged(nsWindow* aWin,
+                                                     bool enteredFullscreen) {
+  MOZ_LOG(sTaskbarConcealerLog, LogLevel::Info,
+          ("==> OnFullscreenChanged() for HWND %p on HMONITOR %p", aWin->mWnd,
+           ::MonitorFromWindow(aWin->mWnd, MONITOR_DEFAULTTONULL)));
+
+  UpdateAllState();
+}
+
+void nsWindow::TaskbarConcealer::OnWindowPosChanged(nsWindow* aWin) {
+  // Optimization: don't bother updating the state if the window hasn't moved
+  // (including appearances and disappearances).
+  const HWND myHwnd = aWin->mWnd;
+  const HMONITOR oldMonitor = sKnownWindows.Get(myHwnd);  // or nullptr
+  const HMONITOR newMonitor = GetWindowState(myHwnd)
+                                  .map([](auto state) { return state.monitor; })
+                                  .valueOr(nullptr);
+
+  if (oldMonitor == newMonitor) {
+    return;
+  }
+
+  MOZ_LOG(sTaskbarConcealerLog, LogLevel::Info,
+          ("==> OnWindowPosChanged() for HWND %p (HMONITOR %p -> %p)", myHwnd,
+           oldMonitor, newMonitor));
+
+  UpdateAllState();
+}
+
+void nsWindow::TaskbarConcealer::OnAsyncStateUpdateRequest(HWND hwnd) {
+  MOZ_LOG(sTaskbarConcealerLog, LogLevel::Info,
+          ("==> OnAsyncStateUpdateRequest()"));
+
+  // Work around a race condition in explorer.exe.
+  //
+  // When a window is unminimized (and on several other events), the taskbar
+  // receives a notification that it needs to recalculate the current
+  // is-a-fullscreen-window-active-here-state ("rudeness") of each monitor.
+  // Unfortunately, this notification is sent concurrently with the
+  // WM_WINDOWPOSCHANGING message that performs the unminimization.
+  //
+  // Until that message is resolved, the window's position is still "minimized".
+  // If the taskbar processes its notification faster than the window handles
+  // its WM_WINDOWPOSCHANGING message, then the window will appear to the
+  // taskbar to still be minimized, and won't be taken into account for
+  // computing rudeness. This usually presents as a just-unminimized Firefox
+  // fullscreen-window occasionally having the taskbar stuck above it.
+  //
+  // Unfortunately, it's a bit difficult to improve Firefox's speed-of-response
+  // to WM_WINDOWPOSCHANGING messages (we can, and do, execute JavaScript during
+  // these), and even if we could that wouldn't always fix it. We instead adopt
+  // a variant of a strategy by Etienne Duchamps, who has investigated and
+  // documented this issue extensively[0]: we simply send another signal to the
+  // shell to notify it to recalculate the current rudeness state of all
+  // monitors.
+  //
+  // [0]
+  // https://github.com/dechamps/RudeWindowFixer#a-race-condition-activating-a-minimized-window
+  //
+  static UINT const shellHookMsg = ::RegisterWindowMessageW(L"SHELLHOOK");
+  if (shellHookMsg != 0) {
+    // Identifying the particular thread of the particular instance of the
+    // shell associated with our current desktop is probably possible, but
+    // also probably not worth the effort. Just broadcast the message
+    // globally.
+    DWORD info = BSM_APPLICATIONS;
+    ::BroadcastSystemMessage(BSF_POSTMESSAGE | BSF_IGNORECURRENTTASK, &info,
+                             shellHookMsg, HSHELL_WINDOWACTIVATED,
+                             (LPARAM)hwnd);
+  }
+}
+
+void nsWindow::TaskbarConcealer::OnCloakChanged() {
+  MOZ_LOG(sTaskbarConcealerLog, LogLevel::Info, ("==> OnCloakChanged()"));
+
+  UpdateAllState();
+}
diff --git a/widget/windows/nsWindowTaskbarConcealer.h b/widget/windows/nsWindowTaskbarConcealer.h
new file mode 100644
index 0000000000..84567fc857
--- /dev/null
+++ b/widget/windows/nsWindowTaskbarConcealer.h
@@ -0,0 +1,53 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef WIDGET_WINDOWS_NSWINDOWTASKBARCONCEALER_H_
+#define WIDGET_WINDOWS_NSWINDOWTASKBARCONCEALER_H_
+
+#include "nsWindow.h"
+#include "mozilla/Maybe.h"
+
+/**
+ * nsWindow::TaskbarConcealer
+ *
+ * Fullscreen-state (and, thus, taskbar-occlusion) manager.
+ */
+class nsWindow::TaskbarConcealer {
+ public:
+  // To be called when a window acquires focus. (Note that no action need be
+  // taken when focus is lost.)
+  static void OnFocusAcquired(nsWindow* aWin);
+
+  // To be called during or after a window's destruction. The corresponding
+  // nsWindow pointer is not needed, and will not be acquired or accessed.
+  static void OnWindowDestroyed(HWND aWnd);
+
+  // To be called when the Gecko-fullscreen state of a window changes.
+  static void OnFullscreenChanged(nsWindow* aWin, bool enteredFullscreen);
+
+  // To be called when the position of a window changes. (Performs its own
+  // batching; irrelevant movements will be cheap.)
+  static void OnWindowPosChanged(nsWindow* aWin);
+
+  // To be called when the cloaking state of any window changes. (Expects that
+  // all windows' internal cloaking-state mirror variables are up-to-date.)
+  static void OnCloakChanged();
+
+  // To be called upon receipt of MOZ_WM_FULLSCREEN_STATE_UPDATE.
+  static void OnAsyncStateUpdateRequest(HWND);
+
+ private:
+  static void UpdateAllState(HWND destroyedHwnd = nullptr);
+
+  struct WindowState {
+    HMONITOR monitor;
+    bool isGkFullscreen;
+  };
+  static mozilla::Maybe<WindowState> GetWindowState(HWND);
+
+  static nsTHashMap<HWND, HMONITOR> sKnownWindows;
+};
+
+#endif  // WIDGET_WINDOWS_NSWINDOWTASKBARCONCEALER_H_
diff --git a/widget/windows/nsdefs.h b/widget/windows/nsdefs.h
new file mode 100644
index 0000000000..ebf7892fda
--- /dev/null
+++ b/widget/windows/nsdefs.h
@@ -0,0 +1,58 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef NSDEFS_H
+#define NSDEFS_H
+
+#include <windows.h>
+
+#ifdef _DEBUG
+#  define BREAK_TO_DEBUGGER DebugBreak()
+#else
+#  define BREAK_TO_DEBUGGER
+#endif
+
+#ifdef _DEBUG
+#  define VERIFY(exp)    \
+    if (!(exp)) {        \
+      GetLastError();    \
+      BREAK_TO_DEBUGGER; \
+    }
+#else  // !_DEBUG
+#  define VERIFY(exp) (exp)
+#endif  // !_DEBUG
+
+// inttypes.h-like macro for LONG_PTR/LPARAM formatting.
+#ifdef HAVE_64BIT_BUILD
+#  define PRIdLPTR "lld"
+#  define PRIxLPTR "llx"
+#  define PRIXLPTR "llX"
+#else
+#  define PRIdLPTR "ld"
+#  define PRIxLPTR "lx"
+#  define PRIXLPTR "lX"
+#endif
+
+// Win32 logging modules:
+// nsWindow, nsSound, and nsClipboard
+//
+// Logging can be changed at runtime without recompiling in the General
+// property page of Visual Studio under the "Environment" property.
+//
+// Two variables are of importance to be set:
+// MOZ_LOG and MOZ_LOG_FILE
+//
+// MOZ_LOG:
+// MOZ_LOG=all:5                 (To log everything completely)
+// MOZ_LOG=nsWindow:5,nsSound:5,nsClipboard:5
+//                               (To log windows widget stuff)
+// MOZ_LOG=                      (To turn off logging)
+//
+// MOZ_LOG_FILE:
+// MOZ_LOG_FILE=C:\log.txt       (To a file on disk)
+// MOZ_LOG_FILE=WinDebug         (To the debug window)
+// MOZ_LOG_FILE=                 (To stdout/stderr)
+
+#endif  // NSDEFS_H
diff --git a/widget/windows/res/aliasb.cur b/widget/windows/res/aliasb.cur
new file mode 100644
index 0000000000..8d9ac9478c
--- /dev/null
+++ b/widget/windows/res/aliasb.cur
diff --git a/widget/windows/res/cell.cur b/widget/windows/res/cell.cur
new file mode 100644
index 0000000000..decfbdcac5
--- /dev/null
+++ b/widget/windows/res/cell.cur
diff --git a/widget/windows/res/col_resize.cur b/widget/windows/res/col_resize.cur
new file mode 100644
index 0000000000..8f7f675122
--- /dev/null
+++ b/widget/windows/res/col_resize.cur
diff --git a/widget/windows/res/copy.cur b/widget/windows/res/copy.cur
new file mode 100644
index 0000000000..87f1519cd1
--- /dev/null
+++ b/widget/windows/res/copy.cur
diff --git a/widget/windows/res/grab.cur b/widget/windows/res/grab.cur
new file mode 100644
index 0000000000..db7ad5aed3
--- /dev/null
+++ b/widget/windows/res/grab.cur
diff --git a/widget/windows/res/grabbing.cur b/widget/windows/res/grabbing.cur
new file mode 100644
index 0000000000..e0dfd04e4d
--- /dev/null
+++ b/widget/windows/res/grabbing.cur
diff --git a/widget/windows/res/none.cur b/widget/windows/res/none.cur
new file mode 100644
index 0000000000..2114dfaee3
--- /dev/null
+++ b/widget/windows/res/none.cur
diff --git a/widget/windows/res/row_resize.cur b/widget/windows/res/row_resize.cur
new file mode 100644
index 0000000000..a7369d32d1
--- /dev/null
+++ b/widget/windows/res/row_resize.cur
diff --git a/widget/windows/res/select.cur b/widget/windows/res/select.cur
new file mode 100644
index 0000000000..5a88b3707e
--- /dev/null
+++ b/widget/windows/res/select.cur
diff --git a/widget/windows/res/vertical_text.cur b/widget/windows/res/vertical_text.cur
new file mode 100644
index 0000000000..3de04ebec3
--- /dev/null
+++ b/widget/windows/res/vertical_text.cur
diff --git a/widget/windows/res/zoom_in.cur b/widget/windows/res/zoom_in.cur
new file mode 100644
index 0000000000..b594d79271
--- /dev/null
+++ b/widget/windows/res/zoom_in.cur
diff --git a/widget/windows/res/zoom_out.cur b/widget/windows/res/zoom_out.cur
new file mode 100644
index 0000000000..7e495fbaa4
--- /dev/null
+++ b/widget/windows/res/zoom_out.cur
diff --git a/widget/windows/resource.h b/widget/windows/resource.h
new file mode 100644
index 0000000000..a367e9f3e9
--- /dev/null
+++ b/widget/windows/resource.h
@@ -0,0 +1,16 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+#define IDC_GRAB 4101
+#define IDC_GRABBING 4102
+#define IDC_CELL 4103
+#define IDC_COPY 4104
+#define IDC_ALIAS 4105
+#define IDC_ZOOMIN 4106
+#define IDC_ZOOMOUT 4107
+#define IDC_COLRESIZE 4108
+#define IDC_ROWRESIZE 4109
+#define IDC_VERTICALTEXT 4110
+#define IDC_DUMMY_CE_MENUBAR 4111
+#define IDC_NONE 4112
diff --git a/widget/windows/tests/TestUriValidation.cpp b/widget/windows/tests/TestUriValidation.cpp
new file mode 100644
index 0000000000..d8a0ca09ce
--- /dev/null
+++ b/widget/windows/tests/TestUriValidation.cpp
@@ -0,0 +1,135 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+#define MOZ_USE_LAUNCHER_ERROR
+
+#define UNICODE
+#include "mozilla/UrlmonHeaderOnlyUtils.h"
+#include "TestUrisToValidate.h"
+
+#include <urlmon.h>
+
+using namespace mozilla;
+
+static LauncherResult<_bstr_t> ShellValidateUri(const wchar_t* aUri) {
+  LauncherResult<UniqueAbsolutePidl> pidlResult = ShellParseDisplayName(aUri);
+  if (pidlResult.isErr()) {
+    return pidlResult.propagateErr();
+  }
+  UniqueAbsolutePidl pidl = pidlResult.unwrap();
+
+  // |pidl| is an absolute path. IShellFolder::GetDisplayNameOf requires a
+  // valid child ID, so the first thing we need to resolve is the IShellFolder
+  // for |pidl|'s parent, as well as the childId that represents |pidl|.
+  // Fortunately SHBindToParent does exactly that!
+  PCUITEMID_CHILD childId = nullptr;
+  RefPtr<IShellFolder> parentFolder;
+  HRESULT hr = SHBindToParent(pidl.get(), IID_IShellFolder,
+                              getter_AddRefs(parentFolder), &childId);
+  if (FAILED(hr)) {
+    return LAUNCHER_ERROR_FROM_HRESULT(hr);
+  }
+
+  // Now we retrieve the display name of |childId|, telling the shell that we
+  // plan to have the string parsed.
+  STRRET strret;
+  hr = parentFolder->GetDisplayNameOf(childId, SHGDN_FORPARSING, &strret);
+  if (FAILED(hr)) {
+    return LAUNCHER_ERROR_FROM_HRESULT(hr);
+  }
+
+  // StrRetToBSTR automatically takes care of freeing any dynamically
+  // allocated memory in |strret|.
+  _bstr_t bstrUri;
+  hr = StrRetToBSTR(&strret, nullptr, bstrUri.GetAddress());
+  if (FAILED(hr)) {
+    return LAUNCHER_ERROR_FROM_HRESULT(hr);
+  }
+
+  return bstrUri;
+}
+
+static LauncherResult<_bstr_t> GetFragment(const wchar_t* aUri) {
+  constexpr DWORD flags =
+      Uri_CREATE_NO_DECODE_EXTRA_INFO | Uri_CREATE_CANONICALIZE |
+      Uri_CREATE_CRACK_UNKNOWN_SCHEMES | Uri_CREATE_PRE_PROCESS_HTML_URI |
+      Uri_CREATE_IE_SETTINGS;
+  RefPtr<IUri> uri;
+  HRESULT hr = CreateUri(aUri, flags, 0, getter_AddRefs(uri));
+  if (FAILED(hr)) {
+    return LAUNCHER_ERROR_FROM_HRESULT(hr);
+  }
+
+  _bstr_t bstrFragment;
+  hr = uri->GetFragment(bstrFragment.GetAddress());
+  if (FAILED(hr)) {
+    return LAUNCHER_ERROR_FROM_HRESULT(hr);
+  }
+  return bstrFragment;
+}
+
+static bool RunSingleTest(const wchar_t* aUri) {
+  LauncherResult<_bstr_t> uriOld = ShellValidateUri(aUri),
+                          uriNew = UrlmonValidateUri(aUri);
+  if (uriOld.isErr() != uriNew.isErr()) {
+    printf("TEST-FAILED | UriValidation | Validation result mismatch on %S\n",
+           aUri);
+    return false;
+  }
+
+  if (uriOld.isErr()) {
+    if (uriOld.unwrapErr().mError != uriNew.unwrapErr().mError) {
+      printf("TEST-FAILED | UriValidation | Error code mismatch on %S\n", aUri);
+      return false;
+    }
+    return true;
+  }
+
+  LauncherResult<_bstr_t> bstrFragment = GetFragment(aUri);
+  if (bstrFragment.isErr()) {
+    printf("TEST-FAILED | UriValidation | Failed to get a fragment from %S\n",
+           aUri);
+    return false;
+  }
+
+  // We validate a uri with two logics: the current one UrlmonValidateUri and
+  // the older one ShellValidateUri, to make sure the same validation result.
+  // We introduced UrlmonValidateUri because ShellValidateUri drops a fragment
+  // in a uri due to the design of Windows.  To bypass the fragment issue, we
+  // extract a fragment and appends it into the validated string, and compare.
+  _bstr_t bstrUriOldCorrected = uriOld.unwrap() + bstrFragment.unwrap();
+  const _bstr_t& bstrUriNew = uriNew.unwrap();
+  if (bstrUriOldCorrected != bstrUriNew) {
+    printf("TEST-FAILED | UriValidation | %S %S %S\n", aUri,
+           static_cast<const wchar_t*>(bstrUriOldCorrected),
+           static_cast<const wchar_t*>(bstrUriNew));
+    return false;
+  }
+
+  return true;
+}
+
+int wmain(int argc, wchar_t* argv[]) {
+  HRESULT hr = CoInitialize(nullptr);
+  if (FAILED(hr)) {
+    return 1;
+  }
+
+  bool isOk = true;
+
+  if (argc == 2) {
+    isOk = RunSingleTest(argv[1]);
+  } else {
+    for (const wchar_t*& testUri : kTestUris) {
+      if (!RunSingleTest(testUri)) {
+        isOk = false;
+      }
+    }
+  }
+
+  CoUninitialize();
+  return isOk ? 0 : 1;
+}
diff --git a/widget/windows/tests/TestUrisToValidate.h b/widget/windows/tests/TestUrisToValidate.h
new file mode 100644
index 0000000000..cb00366d1e
--- /dev/null
+++ b/widget/windows/tests/TestUrisToValidate.h
@@ -0,0 +1,471 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */

+/* vim: set ts=8 sts=2 et sw=2 tw=80: */

+/* This Source Code Form is subject to the terms of the Mozilla Public

+ * License, v. 2.0. If a copy of the MPL was not distributed with this

+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */

+

+#ifndef mozilla_TestUrisToValidate_h

+#define mozilla_TestUrisToValidate_h

+

+const wchar_t* kTestUris[] = {

+    L"callto:%.txt",

+    L"callto:%00.txt",

+    L"callto:%41%2D%31%5Ftest&quot;ing?%41%31%00.txt",

+    L"fdaction:%.txt",

+    L"fdaction:%00.txt",

+    L"fdaction:%41%2D%31%5Ftest&quot;ing?%41%31%00.txt",

+    L"feed:%.txt",

+    L"feed:%00.txt",

+    L"feed:%41%2D%31%5Ftest&quot;ing?%41%31%00.txt",

+    L"feeds:%.txt",

+    L"feeds:%00.txt",

+    L"feeds:%41%2D%31%5Ftest&quot;ing?%41%31%00.txt",

+    L"file:///%.txt",

+    L"file:///%00.txt",

+    L"file:///%41%2D%31%5Ftest%22ing?%41%31%00.txt",

+    L"firefox.url:%.txt",

+    L"firefox.url:%00.txt",

+    L"firefox.url:%41%2D%31%5Ftest&quot;ing?%41%31%00.txt",

+    L"firefoxurl:%.txt",

+    L"firefoxurl:%00.txt",

+    L"firefoxurl:%41%2D%31%5Ftest&quot;ing?%41%31%00.txt",

+    L"ftp:%.txt",

+    L"ftp:%00.txt",

+    L"ftp:%41%2D%31%5Ftest&quot;ing?%41%31%00.txt",

+    L"gopher:%.txt",

+    L"gopher:%00.txt",

+    L"gopher:%41%2D%31%5Ftest&quot;ing?%41%31%00.txt",

+    L"gtalk:%.txt",

+    L"gtalk:%00.txt",

+    L"gtalk:%41%2D%31%5Ftest&quot;ing?%41%31%00.txt",

+    L"HTTP:%.txt",

+    L"HTTP:%00.txt",

+    L"HTTP:%41%2D%31%5Ftest&quot;ing?%41%31%00.txt",

+    L"http:%.txt",

+    L"http:%00.txt",

+    L"http:%41%2D%31%5Ftest&quot;ing?%41%31%00.txt",

+    L"https://bug389580.bmoattachments.org/%.txt",

+    L"https://bug389580.bmoattachments.org/%00.txt",

+    L"https://bug389580.bmoattachments.org/"

+    L"%41%2D%31%5Ftest%22ing?%41%31%00.txt",

+    L"ie.ftp:%.txt",

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+    L"unsv:%.txt",

+    L"unsv:%00.txt",

+    L"unsv:%41%2D%31%5Ftest&quot;ing?%41%31%00.txt",

+    L"uvox:%.txt",

+    L"uvox:%00.txt",

+    L"uvox:%41%2D%31%5Ftest&quot;ing?%41%31%00.txt",

+    L"ventrilo:%.txt",

+    L"ventrilo:%00.txt",

+    L"ventrilo:%41%2D%31%5Ftest&quot;ing?%41%31%00.txt",

+    L"vs:%.txt",

+    L"vs:%00.txt",

+    L"vs:%41%2D%31%5Ftest&quot;ing?%41%31%00.txt",

+    L"zune:%.txt",

+    L"zune:%00.txt",

+    L"zune:%41%2D%31%5Ftest&quot;ing?%41%31%00.txt",

+    L"https://example.com/?a=123&b=456",

+    L"https://example.com/#123?a=123&b=456",

+    L"https://example.com/?#123a=123&b=456",

+    L"https://example.com/?a=123&b=456#123",

+    L"mailto:%41%42%23%31",

+    L"mailto:%41%42%23%31#fragment",

+    L"news:%41%42%23%31",

+    L"news:%41%42%23%31#fragment",

+    L"microsoft-edge:%41%42%23%31",

+    L"microsoft-edge:%41%42%23%31#fragment",

+    L"microsoft-edge:%41%42%23%31#fragment#",

+    L"microsoft-edge:%41%42%23%31####",

+    L"something-unknown:",

+    L"something-unknown:x=123",

+    L"something-unknown:?=123",

+    L"something-unknown:#code=0123456789%200123456789&x=01234567890123456789",

+};

+

+#endif  // mozilla_TestUrisToValidate_h

diff --git a/widget/windows/tests/gtest/TestJumpListBuilder.cpp b/widget/windows/tests/gtest/TestJumpListBuilder.cpp
new file mode 100644
index 0000000000..5494c42d37
--- /dev/null
+++ b/widget/windows/tests/gtest/TestJumpListBuilder.cpp
@@ -0,0 +1,823 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <objectarray.h>
+#include <shobjidl.h>
+#include <windows.h>
+#include <string.h>
+#include <propvarutil.h>
+#include <propkey.h>
+
+#ifdef __MINGW32__
+// MinGW-w64 headers are missing PropVariantToString.
+#  include <propsys.h>
+PSSTDAPI PropVariantToString(REFPROPVARIANT propvar, PWSTR psz, UINT cch);
+#endif
+
+#include "gtest/gtest.h"
+#include "gmock/gmock.h"
+
+#include "mozilla/dom/BindingDeclarations.h"
+#include "mozilla/dom/Promise.h"
+#include "mozilla/dom/PromiseNativeHandler.h"
+#include "mozilla/dom/ScriptSettings.h"
+#include "mozilla/dom/ToJSValue.h"
+#include "mozilla/dom/WindowsJumpListShortcutDescriptionBinding.h"
+#include "mozilla/SpinEventLoopUntil.h"
+#include "JumpListBuilder.h"
+
+using namespace mozilla;
+using namespace testing;
+using mozilla::dom::AutoJSAPI;
+using mozilla::dom::Promise;
+using mozilla::dom::PromiseNativeHandler;
+using mozilla::dom::ToJSValue;
+using mozilla::dom::WindowsJumpListShortcutDescription;
+using mozilla::widget::JumpListBackend;
+using mozilla::widget::JumpListBuilder;
+
+/**
+ * GMock matcher that ensures that two LPCWSTRs match.
+ */
+MATCHER_P(LPCWSTREq, value, "The equivalent of StrEq for LPCWSTRs") {
+  return (wcscmp(arg, value)) == 0;
+}
+
+/**
+ * GMock matcher that ensures that a IObjectArray* contains nsIShellLinkW's
+ * that match an equivalent set of nsTArray<WindowsJumpListShortcutDescriptions>
+ */
+MATCHER_P(ShellLinksEq, descs,
+          "Comparing generated IShellLinkW with "
+          "WindowsJumpListShortcutDescription definitions") {
+  uint32_t count = 0;
+  HRESULT hr = arg->GetCount(&count);
+  if (FAILED(hr) || count != descs->Length()) {
+    return false;
+  }
+
+  for (uint32_t i = 0; i < descs->Length(); ++i) {
+    RefPtr<IShellLinkW> link;
+    if (FAILED(arg->GetAt(i, IID_IShellLinkW,
+                          static_cast<void**>(getter_AddRefs(link))))) {
+      return false;
+    }
+
+    if (!link) {
+      return false;
+    }
+
+    const WindowsJumpListShortcutDescription& desc = descs->ElementAt(i);
+
+    // We'll now compare each member of the WindowsJumpListShortcutDescription
+    // with what is stored in the IShellLink.
+
+    // WindowsJumpListShortcutDescription.title
+    IPropertyStore* propStore = nullptr;
+    hr = link->QueryInterface(IID_IPropertyStore, (LPVOID*)&propStore);
+    if (FAILED(hr)) {
+      return false;
+    }
+
+    PROPVARIANT pv;
+    hr = propStore->GetValue(PKEY_Title, &pv);
+    if (FAILED(hr)) {
+      return false;
+    }
+
+    wchar_t title[PKEYSTR_MAX];
+    hr = PropVariantToString(pv, title, PKEYSTR_MAX);
+    if (FAILED(hr)) {
+      return false;
+    }
+
+    if (!desc.mTitle.Equals(title)) {
+      return false;
+    }
+
+    // WindowsJumpListShortcutDescription.path
+    wchar_t pathBuf[MAX_PATH];
+    hr = link->GetPath(pathBuf, MAX_PATH, nullptr, SLGP_SHORTPATH);
+    if (FAILED(hr)) {
+      return false;
+    }
+
+    if (!desc.mPath.Equals(pathBuf)) {
+      return false;
+    }
+
+    // WindowsJumpListShortcutDescription.arguments (optional)
+    wchar_t argsBuf[MAX_PATH];
+    hr = link->GetArguments(argsBuf, MAX_PATH);
+    if (FAILED(hr)) {
+      return false;
+    }
+
+    if (desc.mArguments.WasPassed()) {
+      if (!desc.mArguments.Value().Equals(argsBuf)) {
+        return false;
+      }
+    } else {
+      // Otherwise, the arguments should be empty.
+      if (wcsnlen(argsBuf, MAX_PATH) != 0) {
+        return false;
+      }
+    }
+
+    // WindowsJumpListShortcutDescription.description
+    wchar_t descBuf[MAX_PATH];
+    hr = link->GetDescription(descBuf, MAX_PATH);
+    if (FAILED(hr)) {
+      return false;
+    }
+
+    if (!desc.mDescription.Equals(descBuf)) {
+      return false;
+    }
+
+    // WindowsJumpListShortcutDescription.iconPath and
+    // WindowsJumpListShortcutDescription.fallbackIconIndex
+    int iconIdx = 0;
+    wchar_t iconPathBuf[MAX_PATH];
+    hr = link->GetIconLocation(iconPathBuf, MAX_PATH, &iconIdx);
+    if (FAILED(hr)) {
+      return false;
+    }
+
+    if (desc.mIconPath.WasPassed() && !desc.mIconPath.Value().IsEmpty()) {
+      // If the WindowsJumpListShortcutDescription supplied an iconPath,
+      // then it should match iconPathBuf and have an icon index of 0.
+      if (!desc.mIconPath.Value().Equals(iconPathBuf) || iconIdx != 0) {
+        return false;
+      }
+    } else {
+      // Otherwise, the iconPathBuf should equal the
+      // WindowsJumpListShortcutDescription path, and the iconIdx should match
+      // the fallbackIconIndex.
+      if (!desc.mPath.Equals(iconPathBuf) ||
+          desc.mFallbackIconIndex != iconIdx) {
+        return false;
+      }
+    }
+  }
+
+  return true;
+}
+
+/**
+ * This is a helper class that allows our tests to wait for a native DOM Promise
+ * to resolve, and get the JS::Value that the Promise resolves with. This is
+ * expected to run on the main thread.
+ */
+class WaitForResolver : public PromiseNativeHandler {
+ public:
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(WaitForResolver, override)
+
+  NS_IMETHODIMP QueryInterface(REFNSIID aIID, void** aInstancePtr) override {
+    nsresult rv = NS_ERROR_UNEXPECTED;
+    NS_INTERFACE_TABLE0(WaitForResolver)
+
+    return rv;
+  }
+
+  WaitForResolver() : mIsDone(false) {}
+
+  void ResolvedCallback(JSContext* aCx, JS::Handle<JS::Value> aValue,
+                        ErrorResult& aError) override {
+    mResult = aValue;
+    mIsDone = true;
+  }
+
+  void RejectedCallback(JSContext* aCx, JS::Handle<JS::Value> aValue,
+                        ErrorResult& aError) override {
+    ASSERT_TRUE(false);  // Should never reach here.
+  }
+
+  /**
+   * Spins a nested event loop and blocks until the Promise has resolved.
+   */
+  void SpinUntilResolved() {
+    SpinEventLoopUntil("WaitForResolver::SpinUntilResolved"_ns,
+                       [&]() { return mIsDone; });
+  }
+
+  /**
+   * Spins a nested event loop and blocks until the Promise has resolved,
+   * after which the JS::Value that the Promise resolves with is returned via
+   * the aRetval outparam.
+   *
+   * @param {JS::MutableHandle<JS::Value>} aRetval
+   *   The outparam for the JS::Value that the Promise resolves with.
+   */
+  void SpinUntilResolvedWithResult(JS::MutableHandle<JS::Value> aRetval) {
+    SpinEventLoopUntil("WaitForResolver::SpinUntilResolved"_ns,
+                       [&]() { return mIsDone; });
+    aRetval.set(mResult);
+  }
+
+ private:
+  virtual ~WaitForResolver() = default;
+
+  JS::Heap<JS::Value> mResult;
+  bool mIsDone;
+};
+
+/**
+ * An implementation of JumpListBackend that is instrumented using the GMock
+ * framework to record calls. Unlike the NativeJumpListBackend, this backend
+ * is expected to be instantiated on the main thread and passed as an argument
+ * to the JumpListBuilder's worker thread. Testers should wait for the methods
+ * that call these functions to resolve their Promises before checking the
+ * recorded values.
+ */
+class TestingJumpListBackend : public JumpListBackend {
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(JumpListBackend, override)
+
+  TestingJumpListBackend() : mMonitor("TestingJumpListBackend::mMonitor") {}
+
+  virtual bool IsAvailable() override { return true; }
+
+  MOCK_METHOD(HRESULT, SetAppID, (LPCWSTR));
+  MOCK_METHOD(HRESULT, BeginList, (UINT*, REFIID, void**));
+  MOCK_METHOD(HRESULT, AddUserTasks, (IObjectArray*));
+  MOCK_METHOD(HRESULT, AppendCategory, (LPCWSTR, IObjectArray*));
+  MOCK_METHOD(HRESULT, CommitList, ());
+  MOCK_METHOD(HRESULT, AbortList, ());
+  MOCK_METHOD(HRESULT, DeleteList, (LPCWSTR));
+
+  virtual HRESULT AppendKnownCategory(KNOWNDESTCATEGORY category) override {
+    return 0;
+  }
+
+  // In one case (construction), an operation occurs off of the main thread that
+  // we must wait for without an associated Promise.
+  Monitor& GetMonitor() { return mMonitor; }
+
+ protected:
+  virtual ~TestingJumpListBackend() override{};
+
+ private:
+  Monitor mMonitor;
+};
+
+/**
+ * A helper function that creates some fake WindowsJumpListShortcutDescription
+ * objects as well as JS::Value representations of those objects. These are
+ * returned to the caller through outparams.
+ *
+ * @param {JSContext*} aCx
+ *   The current JSContext in the execution environment.
+ * @param {uint32_t} howMany
+ *   The number of WindowsJumpListShortcutDescriptions to generate.
+ * @param {boolean} longDescription
+ *   True if the description should be greater than MAX_PATH (260 characters).
+ * @param {nsTArray<WindowsJumpListShortcutDescription>&} aArray
+ *   The outparam for the array of generated
+ * WindowsJumpListShortcutDescriptions.
+ * @param {nsTArray<JS::Value>&} aJSValArray
+ *   The outparam for the array of JS::Value's representing the generated
+ *   WindowsJumpListShortcutDescriptions.
+ */
+void GenerateWindowsJumpListShortcutDescriptions(
+    JSContext* aCx, uint32_t howMany, bool longDescription,
+    nsTArray<WindowsJumpListShortcutDescription>& aArray,
+    nsTArray<JS::Value>& aJSValArray) {
+  for (uint32_t i = 0; i < howMany; ++i) {
+    WindowsJumpListShortcutDescription desc;
+    nsAutoString title(u"Test Task #");
+    title.AppendInt(i);
+    desc.mTitle = title;
+
+    nsAutoString path(u"C:\\Some\\Test\\Path.exe");
+    desc.mPath = path;
+    nsAutoString description;
+
+    if (longDescription) {
+      description.AppendPrintf(
+          "For item #%i, this is a very very very very VERY VERY very very "
+          "very very very very very very very very very very VERY VERY very "
+          "very very very very very very very very very very very VERY VERY "
+          "very very very very very very very very very very very very VERY "
+          "VERY very very very very very very very very very very very very "
+          "VERY VERY very very very very very very very very very very very "
+          "very VERY VERY very very very very very very very very long test "
+          "description for an item",
+          i);
+    } else {
+      description.AppendPrintf("This is a test description for an item #%i", i);
+    }
+
+    desc.mDescription = description;
+    desc.mFallbackIconIndex = 0;
+
+    if (!(i % 2)) {
+      nsAutoString arguments(u"-arg1 -arg2 -arg3");
+      desc.mArguments.Construct(arguments);
+      nsAutoString iconPath(u"C:\\Some\\icon.png");
+      desc.mIconPath.Construct(iconPath);
+    }
+
+    aArray.AppendElement(desc);
+    JS::Rooted<JS::Value> descJSValue(aCx);
+    ASSERT_TRUE(ToJSValue(aCx, desc, &descJSValue));
+    aJSValArray.AppendElement(std::move(descJSValue));
+  }
+}
+
+/**
+ * Tests construction and that the application ID is properly passed to the
+ * backend.
+ */
+TEST(JumpListBuilder, Construction)
+{
+  RefPtr<StrictMock<TestingJumpListBackend>> testBackend =
+      new StrictMock<TestingJumpListBackend>();
+  ASSERT_TRUE(testBackend);
+
+  nsAutoString aumid(u"TestApplicationID");
+  LPCWSTR passedID = aumid.get();
+  // Construction of our class (or any class of that matter) does not return a
+  // Promise that we can wait on to ensure that the background thread got the
+  // right information. We therefore use a monitor on the testing backend as
+  // well as an EXPECT_CALL to block execution of the test until the background
+  // work has completed.
+  Monitor& mon = testBackend->GetMonitor();
+  MonitorAutoLock lock(mon);
+  EXPECT_CALL(*testBackend, SetAppID(LPCWSTREq(passedID))).WillOnce([&mon] {
+    MonitorAutoLock lock(mon);
+    mon.Notify();
+    return S_OK;
+  });
+
+  nsCOMPtr<nsIJumpListBuilder> builder =
+      new JumpListBuilder(aumid, testBackend);
+  ASSERT_TRUE(builder);
+
+  // This is the amount of time that we will wait for the background thread to
+  // respond before considering it a timeout failure.
+  const int kWaitTimeoutMs = 5000;
+
+  ASSERT_TRUE(mon.Wait(TimeDuration::FromMilliseconds(kWaitTimeoutMs)) !=
+              CVStatus::Timeout);
+}
+
+/**
+ * Tests calling CheckForRemovals and receiving a series of removed jump list
+ * entries. Calling CheckForRemovals should call the following methods on the
+ * backend, in order:
+ *
+ * - SetAppID
+ * - AbortList
+ * - BeginList
+ * - AbortList
+ */
+TEST(JumpListBuilder, CheckForRemovals)
+{
+  RefPtr<StrictMock<TestingJumpListBackend>> testBackend =
+      new StrictMock<TestingJumpListBackend>();
+  nsAutoString aumid(u"TestApplicationID");
+  // We set up this expectation here because SetAppID will be called soon
+  // after construction of the JumpListBuilder via the background thread.
+  EXPECT_CALL(*testBackend, SetAppID(_)).Times(1);
+
+  nsCOMPtr<nsIJumpListBuilder> builder =
+      new JumpListBuilder(aumid, testBackend);
+  ASSERT_TRUE(builder);
+
+  EXPECT_CALL(*testBackend, AbortList()).Times(2);
+
+  // Let's prepare BeginList to return a two entry collection of IShellLinks.
+  // The first IShellLink will have the URL be https://example.com, the second
+  // will have the URL be https://mozilla.org.
+  EXPECT_CALL(*testBackend, BeginList)
+      .WillOnce([](UINT* pcMinSlots, REFIID riid, void** ppv) {
+        RefPtr<IObjectCollection> collection;
+        DebugOnly<HRESULT> hr = CoCreateInstance(
+            CLSID_EnumerableObjectCollection, nullptr, CLSCTX_INPROC_SERVER,
+            IID_IObjectCollection, getter_AddRefs(collection));
+        MOZ_ASSERT(SUCCEEDED(hr));
+
+        RefPtr<IShellLinkW> link;
+        hr = CoCreateInstance(CLSID_ShellLink, nullptr, CLSCTX_INPROC_SERVER,
+                              IID_IShellLinkW, getter_AddRefs(link));
+        MOZ_ASSERT(SUCCEEDED(hr));
+
+        nsAutoString firstLinkHref(u"https://example.com"_ns);
+        link->SetArguments(firstLinkHref.get());
+
+        nsAutoString appPath(u"C:\\Tmp\\firefox.exe"_ns);
+        link->SetIconLocation(appPath.get(), 0);
+
+        collection->AddObject(link);
+
+        // Let's re-use the same IShellLink, but change the URL to add our
+        // second entry. The values of the IShellLink are ultimately copied
+        // over to the items being added to the collection.
+        nsAutoString secondLinkHref(u"https://mozilla.org"_ns);
+        link->SetArguments(secondLinkHref.get());
+        collection->AddObject(link);
+
+        RefPtr<IObjectArray> pArray;
+        hr = collection->QueryInterface(IID_IObjectArray,
+                                        getter_AddRefs(pArray));
+        MOZ_ASSERT(SUCCEEDED(hr));
+
+        *ppv = static_cast<IObjectArray*>(pArray);
+        (static_cast<IUnknown*>(*ppv))->AddRef();
+
+        // This is the default value to return, according to
+        // https://learn.microsoft.com/en-us/windows/win32/api/shobjidl_core/nf-shobjidl_core-icustomdestinationlist-beginlist
+        *pcMinSlots = 10;
+
+        return S_OK;
+      });
+
+  AutoJSAPI jsapi;
+  MOZ_ALWAYS_TRUE(jsapi.Init(xpc::PrivilegedJunkScope()));
+  JSContext* cx = jsapi.cx();
+  RefPtr<Promise> promise;
+  nsresult rv = builder->CheckForRemovals(cx, getter_AddRefs(promise));
+  ASSERT_TRUE(NS_SUCCEEDED(rv));
+  ASSERT_TRUE(promise);
+
+  RefPtr<WaitForResolver> resolver = new WaitForResolver();
+  promise->AppendNativeHandler(resolver);
+  JS::Rooted<JS::Value> result(cx);
+  resolver->SpinUntilResolvedWithResult(&result);
+
+  ASSERT_TRUE(result.isObject());
+  JS::Rooted<JSObject*> obj(cx, result.toObjectOrNull());
+
+  bool isArray;
+  ASSERT_TRUE(JS::IsArrayObject(cx, obj, &isArray));
+  ASSERT_TRUE(isArray);
+
+  // We should expect to see 2 URL strings returned in the array.
+  uint32_t length = 0;
+  ASSERT_TRUE(JS::GetArrayLength(cx, obj, &length));
+  ASSERT_EQ(length, 2U);
+
+  // The first one should be https://example.com
+  JS::Rooted<JS::Value> firstURLValue(cx);
+  ASSERT_TRUE(JS_GetElement(cx, obj, 0, &firstURLValue));
+  JS::Rooted<JSString*> firstURLJSString(cx, firstURLValue.toString());
+  nsAutoJSString firstURLAutoString;
+  ASSERT_TRUE(firstURLAutoString.init(cx, firstURLJSString));
+
+  ASSERT_TRUE(firstURLAutoString.EqualsLiteral("https://example.com"));
+
+  // The second one should be https://mozilla.org
+  JS::Rooted<JS::Value> secondURLValue(cx);
+  ASSERT_TRUE(JS_GetElement(cx, obj, 1, &secondURLValue));
+  JS::Rooted<JSString*> secondURLJSString(cx, secondURLValue.toString());
+  nsAutoJSString secondURLAutoString;
+  ASSERT_TRUE(secondURLAutoString.init(cx, secondURLJSString));
+
+  ASSERT_TRUE(secondURLAutoString.EqualsLiteral("https://mozilla.org"));
+}
+
+/**
+ * Tests calling PopulateJumpList with empty arguments, which should call the
+ * following methods on the backend, in order:
+ *
+ * - SetAppID
+ * - AbortList
+ * - BeginList
+ * - CommitList
+ *
+ * This should result in an empty jump list for the user.
+ */
+TEST(JumpListBuilder, PopulateJumpListEmpty)
+{
+  RefPtr<StrictMock<TestingJumpListBackend>> testBackend =
+      new StrictMock<TestingJumpListBackend>();
+  nsAutoString aumid(u"TestApplicationID");
+  // We set up this expectation here because SetAppID will be called soon
+  // after construction of the JumpListBuilder via the background thread.
+  EXPECT_CALL(*testBackend, SetAppID(_)).Times(1);
+
+  nsCOMPtr<nsIJumpListBuilder> builder =
+      new JumpListBuilder(aumid, testBackend);
+  ASSERT_TRUE(builder);
+
+  AutoJSAPI jsapi;
+  MOZ_ALWAYS_TRUE(jsapi.Init(xpc::PrivilegedJunkScope()));
+  JSContext* cx = jsapi.cx();
+  RefPtr<Promise> promise;
+
+  nsTArray<JS::Value> taskDescJSVals;
+  nsAutoString customTitle(u"");
+  nsTArray<JS::Value> customDescJSVals;
+
+  EXPECT_CALL(*testBackend, AbortList()).Times(1);
+  EXPECT_CALL(*testBackend, BeginList(_, _, _)).Times(1);
+  EXPECT_CALL(*testBackend, CommitList()).Times(1);
+  EXPECT_CALL(*testBackend, DeleteList(_)).Times(0);
+
+  nsresult rv =
+      builder->PopulateJumpList(taskDescJSVals, customTitle, customDescJSVals,
+                                cx, getter_AddRefs(promise));
+  ASSERT_TRUE(NS_SUCCEEDED(rv));
+  ASSERT_TRUE(promise);
+
+  RefPtr<WaitForResolver> resolver = new WaitForResolver();
+  promise->AppendNativeHandler(resolver);
+  JS::Rooted<JS::Value> result(cx);
+  resolver->SpinUntilResolved();
+}
+
+/**
+ * Tests calling PopulateJumpList with only tasks, and no custom items.
+ * This should call the following methods on the backend, in order:
+ *
+ * - SetAppID
+ * - AbortList
+ * - BeginList
+ * - AddUserTasks
+ * - CommitList
+ *
+ * This should result in a jump list with just tasks shown to the user, and
+ * no custom section.
+ */
+TEST(JumpListBuilder, PopulateJumpListOnlyTasks)
+{
+  RefPtr<StrictMock<TestingJumpListBackend>> testBackend =
+      new StrictMock<TestingJumpListBackend>();
+  nsAutoString aumid(u"TestApplicationID");
+  // We set up this expectation here because SetAppID will be called soon
+  // after construction of the JumpListBuilder via the background thread.
+  EXPECT_CALL(*testBackend, SetAppID(_)).Times(1);
+
+  nsCOMPtr<nsIJumpListBuilder> builder =
+      new JumpListBuilder(aumid, testBackend);
+  ASSERT_TRUE(builder);
+
+  AutoJSAPI jsapi;
+  MOZ_ALWAYS_TRUE(jsapi.Init(xpc::PrivilegedJunkScope()));
+  JSContext* cx = jsapi.cx();
+  RefPtr<Promise> promise;
+
+  nsTArray<JS::Value> taskDescJSVals;
+  nsTArray<WindowsJumpListShortcutDescription> taskDescs;
+  GenerateWindowsJumpListShortcutDescriptions(cx, 2, false, taskDescs,
+                                              taskDescJSVals);
+
+  nsAutoString customTitle(u"");
+  nsTArray<JS::Value> customDescJSVals;
+
+  EXPECT_CALL(*testBackend, AbortList()).Times(1);
+  EXPECT_CALL(*testBackend, BeginList(_, _, _)).Times(1);
+  EXPECT_CALL(*testBackend, AddUserTasks(ShellLinksEq(&taskDescs))).Times(1);
+
+  EXPECT_CALL(*testBackend, AppendCategory(_, _)).Times(0);
+  EXPECT_CALL(*testBackend, CommitList()).Times(1);
+  EXPECT_CALL(*testBackend, DeleteList(_)).Times(0);
+
+  nsresult rv =
+      builder->PopulateJumpList(taskDescJSVals, customTitle, customDescJSVals,
+                                cx, getter_AddRefs(promise));
+  ASSERT_TRUE(NS_SUCCEEDED(rv));
+  ASSERT_TRUE(promise);
+
+  RefPtr<WaitForResolver> resolver = new WaitForResolver();
+  promise->AppendNativeHandler(resolver);
+  JS::Rooted<JS::Value> result(cx);
+  resolver->SpinUntilResolved();
+}
+
+/**
+ * Tests calling PopulateJumpList with only custom items, and no tasks.
+ * This should call the following methods on the backend, in order:
+ *
+ * - SetAppID
+ * - AbortList
+ * - BeginList
+ * - AppendCategory
+ * - CommitList
+ *
+ * This should result in a jump list with just custom items shown to the user,
+ * and no tasks.
+ */
+TEST(JumpListBuilder, PopulateJumpListOnlyCustomItems)
+{
+  RefPtr<StrictMock<TestingJumpListBackend>> testBackend =
+      new StrictMock<TestingJumpListBackend>();
+  nsAutoString aumid(u"TestApplicationID");
+  // We set up this expectation here because SetAppID will be called soon
+  // after construction of the JumpListBuilder via the background thread.
+  EXPECT_CALL(*testBackend, SetAppID(_)).Times(1);
+
+  nsCOMPtr<nsIJumpListBuilder> builder =
+      new JumpListBuilder(aumid, testBackend);
+  ASSERT_TRUE(builder);
+
+  AutoJSAPI jsapi;
+  MOZ_ALWAYS_TRUE(jsapi.Init(xpc::PrivilegedJunkScope()));
+  JSContext* cx = jsapi.cx();
+  RefPtr<Promise> promise;
+
+  nsTArray<WindowsJumpListShortcutDescription> descs;
+  nsTArray<JS::Value> customDescJSVals;
+  GenerateWindowsJumpListShortcutDescriptions(cx, 2, false, descs,
+                                              customDescJSVals);
+
+  nsAutoString customTitle(u"My custom title");
+  nsTArray<JS::Value> taskDescJSVals;
+
+  EXPECT_CALL(*testBackend, AbortList()).Times(1);
+  EXPECT_CALL(*testBackend, BeginList(_, _, _)).Times(1);
+  EXPECT_CALL(*testBackend, AddUserTasks(_)).Times(0);
+
+  EXPECT_CALL(*testBackend, AppendCategory(LPCWSTREq(customTitle.get()),
+                                           ShellLinksEq(&descs)))
+      .Times(1);
+  EXPECT_CALL(*testBackend, CommitList()).Times(1);
+  EXPECT_CALL(*testBackend, DeleteList(_)).Times(0);
+
+  nsresult rv =
+      builder->PopulateJumpList(taskDescJSVals, customTitle, customDescJSVals,
+                                cx, getter_AddRefs(promise));
+  ASSERT_TRUE(NS_SUCCEEDED(rv));
+  ASSERT_TRUE(promise);
+
+  RefPtr<WaitForResolver> resolver = new WaitForResolver();
+  promise->AppendNativeHandler(resolver);
+  JS::Rooted<JS::Value> result(cx);
+  resolver->SpinUntilResolved();
+}
+
+/**
+ * Tests calling PopulateJumpList with tasks and custom items.
+ * This should call the following methods on the backend, in order:
+ *
+ * - SetAppID
+ * - AbortList
+ * - BeginList
+ * - AddUserTasks
+ * - AppendCategory
+ * - CommitList
+ *
+ * This should result in a jump list with both built-in tasks as well as
+ * custom tasks with a custom label.
+ */
+TEST(JumpListBuilder, PopulateJumpList)
+{
+  RefPtr<StrictMock<TestingJumpListBackend>> testBackend =
+      new StrictMock<TestingJumpListBackend>();
+  nsAutoString aumid(u"TestApplicationID");
+  // We set up this expectation here because SetAppID will be called soon
+  // after construction of the JumpListBuilder via the background thread.
+  EXPECT_CALL(*testBackend, SetAppID(_)).Times(1);
+
+  nsCOMPtr<nsIJumpListBuilder> builder =
+      new JumpListBuilder(aumid, testBackend);
+  ASSERT_TRUE(builder);
+
+  AutoJSAPI jsapi;
+  MOZ_ALWAYS_TRUE(jsapi.Init(xpc::PrivilegedJunkScope()));
+  JSContext* cx = jsapi.cx();
+  RefPtr<Promise> promise;
+
+  nsTArray<WindowsJumpListShortcutDescription> taskDescs;
+  nsTArray<JS::Value> taskDescJSVals;
+  GenerateWindowsJumpListShortcutDescriptions(cx, 2, false, taskDescs,
+                                              taskDescJSVals);
+
+  nsTArray<WindowsJumpListShortcutDescription> customDescs;
+  nsTArray<JS::Value> customDescJSVals;
+  GenerateWindowsJumpListShortcutDescriptions(cx, 2, false, customDescs,
+                                              customDescJSVals);
+
+  nsAutoString customTitle(u"My custom title");
+
+  EXPECT_CALL(*testBackend, AbortList()).Times(1);
+  EXPECT_CALL(*testBackend, BeginList(_, _, _)).Times(1);
+  EXPECT_CALL(*testBackend, AddUserTasks(ShellLinksEq(&taskDescs))).Times(1);
+
+  EXPECT_CALL(*testBackend, AppendCategory(LPCWSTREq(customTitle.get()),
+                                           ShellLinksEq(&customDescs)))
+      .Times(1);
+  EXPECT_CALL(*testBackend, CommitList()).Times(1);
+  EXPECT_CALL(*testBackend, DeleteList(_)).Times(0);
+
+  nsresult rv =
+      builder->PopulateJumpList(taskDescJSVals, customTitle, customDescJSVals,
+                                cx, getter_AddRefs(promise));
+  ASSERT_TRUE(NS_SUCCEEDED(rv));
+  ASSERT_TRUE(promise);
+
+  RefPtr<WaitForResolver> resolver = new WaitForResolver();
+  promise->AppendNativeHandler(resolver);
+  JS::Rooted<JS::Value> result(cx);
+  resolver->SpinUntilResolved();
+}
+
+/**
+ * Tests calling ClearJumpList calls the following:
+ *
+ * - SetAppID
+ * - DeleteList (passing the aumid)
+ *
+ * This results in an empty jump list for the user.
+ */
+TEST(JumpListBuilder, ClearJumpList)
+{
+  RefPtr<StrictMock<TestingJumpListBackend>> testBackend =
+      new StrictMock<TestingJumpListBackend>();
+  nsAutoString aumid(u"TestApplicationID");
+  // We set up this expectation here because SetAppID will be called soon
+  // after construction of the JumpListBuilder via the background thread.
+  EXPECT_CALL(*testBackend, SetAppID(_)).Times(1);
+
+  nsCOMPtr<nsIJumpListBuilder> builder =
+      new JumpListBuilder(aumid, testBackend);
+  ASSERT_TRUE(builder);
+
+  AutoJSAPI jsapi;
+  MOZ_ALWAYS_TRUE(jsapi.Init(xpc::PrivilegedJunkScope()));
+  JSContext* cx = jsapi.cx();
+  RefPtr<Promise> promise;
+
+  EXPECT_CALL(*testBackend, AbortList()).Times(0);
+  EXPECT_CALL(*testBackend, BeginList(_, _, _)).Times(0);
+  EXPECT_CALL(*testBackend, AddUserTasks(_)).Times(0);
+
+  EXPECT_CALL(*testBackend, AppendCategory(_, _)).Times(0);
+  EXPECT_CALL(*testBackend, CommitList()).Times(0);
+  EXPECT_CALL(*testBackend, DeleteList(LPCWSTREq(aumid.get()))).Times(1);
+
+  nsresult rv = builder->ClearJumpList(cx, getter_AddRefs(promise));
+  ASSERT_TRUE(NS_SUCCEEDED(rv));
+  ASSERT_TRUE(promise);
+
+  RefPtr<WaitForResolver> resolver = new WaitForResolver();
+  promise->AppendNativeHandler(resolver);
+  JS::Rooted<JS::Value> result(cx);
+  resolver->SpinUntilResolved();
+}
+
+/**
+ * Test that a WindowsJumpListShortcutDescription with a description
+ * longer than MAX_PATH gets truncated to MAX_PATH. This is because a
+ * description longer than MAX_PATH will cause CommitList to fail.
+ */
+TEST(JumpListBuilder, TruncateDescription)
+{
+  RefPtr<StrictMock<TestingJumpListBackend>> testBackend =
+      new StrictMock<TestingJumpListBackend>();
+  nsAutoString aumid(u"TestApplicationID");
+  // We set up this expectation here because SetAppID will be called soon
+  // after construction of the JumpListBuilder via the background thread.
+  EXPECT_CALL(*testBackend, SetAppID(_)).Times(1);
+
+  nsCOMPtr<nsIJumpListBuilder> builder =
+      new JumpListBuilder(aumid, testBackend);
+  ASSERT_TRUE(builder);
+
+  AutoJSAPI jsapi;
+  MOZ_ALWAYS_TRUE(jsapi.Init(xpc::PrivilegedJunkScope()));
+  JSContext* cx = jsapi.cx();
+  RefPtr<Promise> promise;
+
+  nsTArray<WindowsJumpListShortcutDescription> taskDescs;
+  nsTArray<JS::Value> taskDescJSVals;
+  GenerateWindowsJumpListShortcutDescriptions(cx, 2, true, taskDescs,
+                                              taskDescJSVals);
+
+  nsTArray<WindowsJumpListShortcutDescription> customDescs;
+  nsTArray<JS::Value> customDescJSVals;
+  GenerateWindowsJumpListShortcutDescriptions(cx, 2, true, customDescs,
+                                              customDescJSVals);
+  // We expect the long descriptions to be truncated to 260 characters, so
+  // we'll truncate the descriptions here ourselves.
+  for (auto& taskDesc : taskDescs) {
+    taskDesc.mDescription.SetLength(MAX_PATH - 1);
+  }
+  for (auto& customDesc : customDescs) {
+    customDesc.mDescription.SetLength(MAX_PATH - 1);
+  }
+
+  nsAutoString customTitle(u"My custom title");
+
+  EXPECT_CALL(*testBackend, AbortList()).Times(1);
+  EXPECT_CALL(*testBackend, BeginList(_, _, _)).Times(1);
+  EXPECT_CALL(*testBackend, AddUserTasks(ShellLinksEq(&taskDescs))).Times(1);
+
+  EXPECT_CALL(*testBackend, AppendCategory(LPCWSTREq(customTitle.get()),
+                                           ShellLinksEq(&customDescs)))
+      .Times(1);
+  EXPECT_CALL(*testBackend, CommitList()).Times(1);
+  EXPECT_CALL(*testBackend, DeleteList(_)).Times(0);
+
+  nsresult rv =
+      builder->PopulateJumpList(taskDescJSVals, customTitle, customDescJSVals,
+                                cx, getter_AddRefs(promise));
+  ASSERT_TRUE(NS_SUCCEEDED(rv));
+  ASSERT_TRUE(promise);
+
+  RefPtr<WaitForResolver> resolver = new WaitForResolver();
+  promise->AppendNativeHandler(resolver);
+  JS::Rooted<JS::Value> result(cx);
+  resolver->SpinUntilResolved();
+}
diff --git a/widget/windows/tests/gtest/TestWinDND.cpp b/widget/windows/tests/gtest/TestWinDND.cpp
new file mode 100644
index 0000000000..fb7849fd79
--- /dev/null
+++ b/widget/windows/tests/gtest/TestWinDND.cpp
@@ -0,0 +1,728 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// #include <windows.h>
+#include <ole2.h>
+#include <shlobj.h>
+
+#include "nsArray.h"
+#include "nsArrayUtils.h"
+#include "nsComponentManagerUtils.h"
+#include "nsDirectoryServiceDefs.h"
+#include "nsDirectoryServiceUtils.h"
+#include "nsIFile.h"
+#include "nsNetUtil.h"
+#include "nsISupportsPrimitives.h"
+#include "nsITransferable.h"
+
+#include "nsClipboard.h"
+#include "nsDataObjCollection.h"
+
+#include "gtest/gtest.h"
+
+// shims for conversion from cppunittest to gtest
+template <size_t N>
+void fail(const char (&msg)[N]) {
+  ADD_FAILURE() << "TEST-UNEXPECTED-FAIL | " << msg;
+}
+template <size_t N>
+void passed(const char (&msg)[N]) {
+  GTEST_SUCCEED() << "TEST-PASS | " << msg;
+}
+
+nsIFile* xferFile;
+
+nsresult CheckValidHDROP(STGMEDIUM* pSTG) {
+  if (pSTG->tymed != TYMED_HGLOBAL) {
+    fail("Received data is not in an HGLOBAL");
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  HGLOBAL hGlobal = pSTG->hGlobal;
+  DROPFILES* pDropFiles;
+  pDropFiles = (DROPFILES*)GlobalLock(hGlobal);
+  if (!pDropFiles) {
+    fail("There is no data at the given HGLOBAL");
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  if (pDropFiles->pFiles != sizeof(DROPFILES)) {
+    fail("DROPFILES struct has wrong size");
+  }
+
+  if (!pDropFiles->fWide) {
+    fail("Received data is not Unicode");
+    return NS_ERROR_UNEXPECTED;
+  }
+  nsString s;
+  unsigned long offset = 0;
+  while (true) {
+    s = (char16_t*)((char*)pDropFiles + pDropFiles->pFiles + offset);
+    if (s.IsEmpty()) break;
+    nsresult rv;
+    nsCOMPtr<nsIFile> localFile(
+        do_CreateInstance(NS_LOCAL_FILE_CONTRACTID, &rv));
+    rv = localFile->InitWithPath(s);
+    if (NS_FAILED(rv)) {
+      fail("File could not be opened");
+      return NS_ERROR_UNEXPECTED;
+    }
+    offset += sizeof(char16_t) * (s.Length() + 1);
+  }
+  return NS_OK;
+}
+
+nsresult CheckValidTEXT(STGMEDIUM* pSTG) {
+  if (pSTG->tymed != TYMED_HGLOBAL) {
+    fail("Received data is not in an HGLOBAL");
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  HGLOBAL hGlobal = pSTG->hGlobal;
+  char* pText;
+  pText = (char*)GlobalLock(hGlobal);
+  if (!pText) {
+    fail("There is no data at the given HGLOBAL");
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  nsCString string;
+  string = pText;
+
+  if (!string.EqualsLiteral("Mozilla can drag and drop")) {
+    fail("Text passed through drop object wrong");
+    return NS_ERROR_UNEXPECTED;
+  }
+  return NS_OK;
+}
+
+nsresult CheckValidTEXTTwo(STGMEDIUM* pSTG) {
+  if (pSTG->tymed != TYMED_HGLOBAL) {
+    fail("Received data is not in an HGLOBAL");
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  HGLOBAL hGlobal = pSTG->hGlobal;
+  char* pText;
+  pText = (char*)GlobalLock(hGlobal);
+  if (!pText) {
+    fail("There is no data at the given HGLOBAL");
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  nsCString string;
+  string = pText;
+
+  if (!string.EqualsLiteral("Mozilla can drag and drop twice over")) {
+    fail("Text passed through drop object wrong");
+    return NS_ERROR_UNEXPECTED;
+  }
+  return NS_OK;
+}
+
+nsresult CheckValidUNICODE(STGMEDIUM* pSTG) {
+  if (pSTG->tymed != TYMED_HGLOBAL) {
+    fail("Received data is not in an HGLOBAL");
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  HGLOBAL hGlobal = pSTG->hGlobal;
+  char16_t* pText;
+  pText = (char16_t*)GlobalLock(hGlobal);
+  if (!pText) {
+    fail("There is no data at the given HGLOBAL");
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  nsString string;
+  string = pText;
+
+  if (!string.EqualsLiteral("Mozilla can drag and drop")) {
+    fail("Text passed through drop object wrong");
+    return NS_ERROR_UNEXPECTED;
+  }
+  return NS_OK;
+}
+
+nsresult CheckValidUNICODETwo(STGMEDIUM* pSTG) {
+  if (pSTG->tymed != TYMED_HGLOBAL) {
+    fail("Received data is not in an HGLOBAL");
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  HGLOBAL hGlobal = pSTG->hGlobal;
+  char16_t* pText;
+  pText = (char16_t*)GlobalLock(hGlobal);
+  if (!pText) {
+    fail("There is no data at the given HGLOBAL");
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  nsString string;
+  string = pText;
+
+  if (!string.EqualsLiteral("Mozilla can drag and drop twice over")) {
+    fail("Text passed through drop object wrong");
+    return NS_ERROR_UNEXPECTED;
+  }
+  return NS_OK;
+}
+
+nsresult GetTransferableFile(nsCOMPtr<nsITransferable>& pTransferable) {
+  nsresult rv;
+
+  nsCOMPtr<nsISupports> genericWrapper = do_QueryInterface(xferFile);
+
+  pTransferable = do_CreateInstance("@mozilla.org/widget/transferable;1");
+  pTransferable->Init(nullptr);
+  rv = pTransferable->SetTransferData("application/x-moz-file", genericWrapper);
+  return rv;
+}
+
+nsresult GetTransferableText(nsCOMPtr<nsITransferable>& pTransferable) {
+  nsresult rv;
+  constexpr auto mozString = u"Mozilla can drag and drop"_ns;
+  nsCOMPtr<nsISupportsString> xferString =
+      do_CreateInstance(NS_SUPPORTS_STRING_CONTRACTID);
+  rv = xferString->SetData(mozString);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsCOMPtr<nsISupports> genericWrapper = do_QueryInterface(xferString);
+
+  pTransferable = do_CreateInstance("@mozilla.org/widget/transferable;1");
+  pTransferable->Init(nullptr);
+  rv = pTransferable->SetTransferData("text/plain", genericWrapper);
+  return rv;
+}
+
+nsresult GetTransferableTextTwo(nsCOMPtr<nsITransferable>& pTransferable) {
+  nsresult rv;
+  constexpr auto mozString = u" twice over"_ns;
+  nsCOMPtr<nsISupportsString> xferString =
+      do_CreateInstance(NS_SUPPORTS_STRING_CONTRACTID);
+  rv = xferString->SetData(mozString);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsCOMPtr<nsISupports> genericWrapper = do_QueryInterface(xferString);
+
+  pTransferable = do_CreateInstance("@mozilla.org/widget/transferable;1");
+  pTransferable->Init(nullptr);
+  rv = pTransferable->SetTransferData("text/plain", genericWrapper);
+  return rv;
+}
+
+nsresult GetTransferableURI(nsCOMPtr<nsITransferable>& pTransferable) {
+  nsresult rv;
+
+  nsCOMPtr<nsIURI> xferURI;
+
+  rv = NS_NewURI(getter_AddRefs(xferURI), "http://www.mozilla.org");
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsCOMPtr<nsISupports> genericWrapper = do_QueryInterface(xferURI);
+
+  pTransferable = do_CreateInstance("@mozilla.org/widget/transferable;1");
+  pTransferable->Init(nullptr);
+  rv = pTransferable->SetTransferData("text/x-moz-url", genericWrapper);
+  return rv;
+}
+
+nsresult MakeDataObject(nsIArray* transferableArray,
+                        RefPtr<IDataObject>& itemToDrag) {
+  nsresult rv;
+  uint32_t itemCount = 0;
+
+  nsCOMPtr<nsIURI> uri;
+  rv = NS_NewURI(getter_AddRefs(uri), "http://www.mozilla.org");
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  rv = transferableArray->GetLength(&itemCount);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // Copied more or less exactly from nsDragService::InvokeDragSession
+  // This is what lets us play fake Drag Service for the test
+  if (itemCount > 1) {
+    nsDataObjCollection* dataObjCollection = new nsDataObjCollection();
+    if (!dataObjCollection) return NS_ERROR_OUT_OF_MEMORY;
+    itemToDrag = dataObjCollection;
+    for (uint32_t i = 0; i < itemCount; ++i) {
+      nsCOMPtr<nsITransferable> trans = do_QueryElementAt(transferableArray, i);
+      if (trans) {
+        RefPtr<IDataObject> dataObj;
+        rv = nsClipboard::CreateNativeDataObject(trans, getter_AddRefs(dataObj),
+                                                 uri);
+        NS_ENSURE_SUCCESS(rv, rv);
+        // Add the flavors to the collection object too
+        rv = nsClipboard::SetupNativeDataObject(trans, dataObjCollection);
+        NS_ENSURE_SUCCESS(rv, rv);
+
+        dataObjCollection->AddDataObject(dataObj);
+      }
+    }
+  }  // if dragging multiple items
+  else {
+    nsCOMPtr<nsITransferable> trans = do_QueryElementAt(transferableArray, 0);
+    if (trans) {
+      rv = nsClipboard::CreateNativeDataObject(trans,
+                                               getter_AddRefs(itemToDrag), uri);
+      NS_ENSURE_SUCCESS(rv, rv);
+    }
+  }  // else dragging a single object
+  return rv;
+}
+
+nsresult Do_CheckOneFile() {
+  nsresult rv;
+  nsCOMPtr<nsITransferable> transferable;
+  nsCOMPtr<nsIMutableArray> transferableArray = nsArray::Create();
+  nsCOMPtr<nsISupports> genericWrapper;
+  RefPtr<IDataObject> dataObj;
+
+  rv = GetTransferableFile(transferable);
+  if (NS_FAILED(rv)) {
+    fail("Could not create the proper nsITransferable!");
+    return rv;
+  }
+  genericWrapper = do_QueryInterface(transferable);
+  rv = transferableArray->AppendElement(genericWrapper);
+  if (NS_FAILED(rv)) {
+    fail("Could not append element to transferable array");
+    return rv;
+  }
+
+  rv = MakeDataObject(transferableArray, dataObj);
+  if (NS_FAILED(rv)) {
+    fail("Could not create data object");
+    return rv;
+  }
+
+  FORMATETC fe;
+  SET_FORMATETC(fe, CF_HDROP, 0, DVASPECT_CONTENT, -1, TYMED_HGLOBAL);
+  if (dataObj->QueryGetData(&fe) != S_OK) {
+    fail("File data object does not support the file data type!");
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  STGMEDIUM* stg;
+  stg = (STGMEDIUM*)CoTaskMemAlloc(sizeof(STGMEDIUM));
+  if (dataObj->GetData(&fe, stg) != S_OK) {
+    fail("File data object did not provide data on request");
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  rv = CheckValidHDROP(stg);
+  if (NS_FAILED(rv)) {
+    fail("HDROP was invalid");
+    return rv;
+  }
+
+  ReleaseStgMedium(stg);
+
+  return NS_OK;
+}
+
+nsresult Do_CheckTwoFiles() {
+  nsresult rv;
+  nsCOMPtr<nsITransferable> transferable;
+  nsCOMPtr<nsIMutableArray> transferableArray = nsArray::Create();
+  nsCOMPtr<nsISupports> genericWrapper;
+  RefPtr<IDataObject> dataObj;
+
+  rv = GetTransferableFile(transferable);
+  if (NS_FAILED(rv)) {
+    fail("Could not create the proper nsITransferable!");
+    return rv;
+  }
+  genericWrapper = do_QueryInterface(transferable);
+  rv = transferableArray->AppendElement(genericWrapper);
+  if (NS_FAILED(rv)) {
+    fail("Could not append element to transferable array");
+    return rv;
+  }
+
+  rv = GetTransferableFile(transferable);
+  if (NS_FAILED(rv)) {
+    fail("Could not create the proper nsITransferable!");
+    return rv;
+  }
+  genericWrapper = do_QueryInterface(transferable);
+  rv = transferableArray->AppendElement(genericWrapper);
+  if (NS_FAILED(rv)) {
+    fail("Could not append element to transferable array");
+    return rv;
+  }
+
+  rv = MakeDataObject(transferableArray, dataObj);
+  if (NS_FAILED(rv)) {
+    fail("Could not create data object");
+    return rv;
+  }
+
+  FORMATETC fe;
+  SET_FORMATETC(fe, CF_HDROP, 0, DVASPECT_CONTENT, -1, TYMED_HGLOBAL);
+  if (dataObj->QueryGetData(&fe) != S_OK) {
+    fail("File data object does not support the file data type!");
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  STGMEDIUM* stg;
+  stg = (STGMEDIUM*)CoTaskMemAlloc(sizeof(STGMEDIUM));
+  if (dataObj->GetData(&fe, stg) != S_OK) {
+    fail("File data object did not provide data on request");
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  rv = CheckValidHDROP(stg);
+  if (NS_FAILED(rv)) {
+    fail("HDROP was invalid");
+    return rv;
+  }
+
+  ReleaseStgMedium(stg);
+
+  return NS_OK;
+}
+
+nsresult Do_CheckOneString() {
+  nsresult rv;
+  nsCOMPtr<nsITransferable> transferable;
+  nsCOMPtr<nsIMutableArray> transferableArray = nsArray::Create();
+  nsCOMPtr<nsISupports> genericWrapper;
+  RefPtr<IDataObject> dataObj;
+
+  rv = GetTransferableText(transferable);
+  if (NS_FAILED(rv)) {
+    fail("Could not create the proper nsITransferable!");
+    return rv;
+  }
+  genericWrapper = do_QueryInterface(transferable);
+  rv = transferableArray->AppendElement(genericWrapper);
+  if (NS_FAILED(rv)) {
+    fail("Could not append element to transferable array");
+    return rv;
+  }
+
+  rv = MakeDataObject(transferableArray, dataObj);
+  if (NS_FAILED(rv)) {
+    fail("Could not create data object");
+    return rv;
+  }
+
+  FORMATETC fe;
+  SET_FORMATETC(fe, CF_TEXT, 0, DVASPECT_CONTENT, -1, TYMED_HGLOBAL);
+  if (dataObj->QueryGetData(&fe) != S_OK) {
+    fail("String data object does not support the ASCII text data type!");
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  STGMEDIUM* stg;
+  stg = (STGMEDIUM*)CoTaskMemAlloc(sizeof(STGMEDIUM));
+  if (dataObj->GetData(&fe, stg) != S_OK) {
+    fail("String data object did not provide ASCII data on request");
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  rv = CheckValidTEXT(stg);
+  if (NS_FAILED(rv)) {
+    fail("TEXT was invalid");
+    return rv;
+  }
+
+  ReleaseStgMedium(stg);
+
+  SET_FORMATETC(fe, CF_UNICODETEXT, 0, DVASPECT_CONTENT, -1, TYMED_HGLOBAL);
+  if (dataObj->QueryGetData(&fe) != S_OK) {
+    fail("String data object does not support the wide text data type!");
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  if (dataObj->GetData(&fe, stg) != S_OK) {
+    fail("String data object did not provide wide data on request");
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  rv = CheckValidUNICODE(stg);
+  if (NS_FAILED(rv)) {
+    fail("UNICODE was invalid");
+    return rv;
+  }
+
+  return NS_OK;
+}
+
+nsresult Do_CheckTwoStrings() {
+  nsresult rv;
+  nsCOMPtr<nsITransferable> transferable;
+  nsCOMPtr<nsIMutableArray> transferableArray = nsArray::Create();
+  nsCOMPtr<nsISupports> genericWrapper;
+  RefPtr<IDataObject> dataObj;
+
+  rv = GetTransferableText(transferable);
+  if (NS_FAILED(rv)) {
+    fail("Could not create the proper nsITransferable!");
+    return rv;
+  }
+  genericWrapper = do_QueryInterface(transferable);
+  rv = transferableArray->AppendElement(genericWrapper);
+  if (NS_FAILED(rv)) {
+    fail("Could not append element to transferable array");
+    return rv;
+  }
+
+  rv = GetTransferableTextTwo(transferable);
+  if (NS_FAILED(rv)) {
+    fail("Could not create the proper nsITransferable!");
+    return rv;
+  }
+  genericWrapper = do_QueryInterface(transferable);
+  rv = transferableArray->AppendElement(genericWrapper);
+  if (NS_FAILED(rv)) {
+    fail("Could not append element to transferable array");
+    return rv;
+  }
+
+  rv = MakeDataObject(transferableArray, dataObj);
+  if (NS_FAILED(rv)) {
+    fail("Could not create data object");
+    return rv;
+  }
+
+  FORMATETC fe;
+  SET_FORMATETC(fe, CF_TEXT, 0, DVASPECT_CONTENT, -1, TYMED_HGLOBAL);
+  if (dataObj->QueryGetData(&fe) != S_OK) {
+    fail("String data object does not support the ASCII text data type!");
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  STGMEDIUM* stg;
+  stg = (STGMEDIUM*)CoTaskMemAlloc(sizeof(STGMEDIUM));
+  if (dataObj->GetData(&fe, stg) != S_OK) {
+    fail("String data object did not provide ASCII data on request");
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  rv = CheckValidTEXTTwo(stg);
+  if (NS_FAILED(rv)) {
+    fail("TEXT was invalid");
+    return rv;
+  }
+
+  ReleaseStgMedium(stg);
+
+  SET_FORMATETC(fe, CF_UNICODETEXT, 0, DVASPECT_CONTENT, -1, TYMED_HGLOBAL);
+  if (dataObj->QueryGetData(&fe) != S_OK) {
+    fail("String data object does not support the wide text data type!");
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  if (dataObj->GetData(&fe, stg) != S_OK) {
+    fail("String data object did not provide wide data on request");
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  rv = CheckValidUNICODETwo(stg);
+  if (NS_FAILED(rv)) {
+    fail("UNICODE was invalid");
+    return rv;
+  }
+
+  return NS_OK;
+}
+
+nsresult Do_CheckSetArbitraryData(bool aMultiple) {
+  nsresult rv;
+  nsCOMPtr<nsITransferable> transferable;
+  nsCOMPtr<nsIMutableArray> transferableArray = nsArray::Create();
+  nsCOMPtr<nsISupports> genericWrapper;
+  RefPtr<IDataObject> dataObj;
+
+  rv = GetTransferableText(transferable);
+  if (NS_FAILED(rv)) {
+    fail("Could not create the proper nsITransferable!");
+    return rv;
+  }
+  genericWrapper = do_QueryInterface(transferable);
+  rv = transferableArray->AppendElement(genericWrapper);
+  if (NS_FAILED(rv)) {
+    fail("Could not append element to transferable array");
+    return rv;
+  }
+
+  if (aMultiple) {
+    rv = GetTransferableText(transferable);
+    if (NS_FAILED(rv)) {
+      fail("Could not create the proper nsITransferable!");
+      return rv;
+    }
+    genericWrapper = do_QueryInterface(transferable);
+    rv = transferableArray->AppendElement(genericWrapper);
+    if (NS_FAILED(rv)) {
+      fail("Could not append element to transferable array");
+      return rv;
+    }
+  }
+
+  rv = MakeDataObject(transferableArray, dataObj);
+  if (NS_FAILED(rv)) {
+    fail("Could not create data object");
+    return rv;
+  }
+
+  static CLIPFORMAT mozArbitraryFormat =
+      ::RegisterClipboardFormatW(L"MozillaTestFormat");
+  FORMATETC fe;
+  STGMEDIUM stg;
+  SET_FORMATETC(fe, mozArbitraryFormat, 0, DVASPECT_CONTENT, -1, TYMED_HGLOBAL);
+
+  HGLOBAL hg = GlobalAlloc(GPTR, 1024);
+  stg.tymed = TYMED_HGLOBAL;
+  stg.hGlobal = hg;
+  stg.pUnkForRelease = nullptr;
+
+  if (dataObj->SetData(&fe, &stg, true) != S_OK) {
+    if (aMultiple) {
+      fail("Unable to set arbitrary data type on data object collection!");
+    } else {
+      fail("Unable to set arbitrary data type on data object!");
+    }
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  if (dataObj->QueryGetData(&fe) != S_OK) {
+    fail("Arbitrary data set on data object is not advertised!");
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  STGMEDIUM* stg2;
+  stg2 = (STGMEDIUM*)CoTaskMemAlloc(sizeof(STGMEDIUM));
+  if (dataObj->GetData(&fe, stg2) != S_OK) {
+    fail("Data object did not provide arbitrary data upon request!");
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  if (stg2->hGlobal != hg) {
+    fail("Arbitrary data was not returned properly!");
+    return rv;
+  }
+  ReleaseStgMedium(stg2);
+
+  return NS_OK;
+}
+
+// This function performs basic drop tests, testing a data object consisting
+// of one transferable
+nsresult Do_Test1() {
+  nsresult rv = NS_OK;
+  nsresult workingrv;
+
+  workingrv = Do_CheckOneFile();
+  if (NS_FAILED(workingrv)) {
+    fail("Drag object tests failed on a single file");
+    rv = NS_ERROR_UNEXPECTED;
+  } else {
+    passed("Successfully created a working file drag object!");
+  }
+
+  workingrv = Do_CheckOneString();
+  if (NS_FAILED(workingrv)) {
+    fail("Drag object tests failed on a single string");
+    rv = NS_ERROR_UNEXPECTED;
+  } else {
+    passed("Successfully created a working string drag object!");
+  }
+
+  workingrv = Do_CheckSetArbitraryData(false);
+  if (NS_FAILED(workingrv)) {
+    fail("Drag object tests failed on setting arbitrary data");
+    rv = NS_ERROR_UNEXPECTED;
+  } else {
+    passed("Successfully set arbitrary data on a drag object");
+  }
+
+  return rv;
+}
+
+// This function performs basic drop tests, testing a data object consisting of
+// two transferables.
+nsresult Do_Test2() {
+  nsresult rv = NS_OK;
+  nsresult workingrv;
+
+  workingrv = Do_CheckTwoFiles();
+  if (NS_FAILED(workingrv)) {
+    fail("Drag object tests failed on multiple files");
+    rv = NS_ERROR_UNEXPECTED;
+  } else {
+    passed("Successfully created a working multiple file drag object!");
+  }
+
+  workingrv = Do_CheckTwoStrings();
+  if (NS_FAILED(workingrv)) {
+    fail("Drag object tests failed on multiple strings");
+    rv = NS_ERROR_UNEXPECTED;
+  } else {
+    passed("Successfully created a working multiple string drag object!");
+  }
+
+  workingrv = Do_CheckSetArbitraryData(true);
+  if (NS_FAILED(workingrv)) {
+    fail("Drag object tests failed on setting arbitrary data");
+    rv = NS_ERROR_UNEXPECTED;
+  } else {
+    passed("Successfully set arbitrary data on a drag object");
+  }
+
+  return rv;
+}
+
+// This function performs advanced drag and drop tests, testing a data object
+// consisting of multiple transferables that have different data types
+nsresult Do_Test3() {
+  nsresult rv = NS_OK;
+  // nsresult workingrv;
+
+  // XXX TODO Write more advanced tests in Bug 535860
+  return rv;
+}
+
+nsCOMPtr<nsIFile> GetTemporaryDirectory() {
+  nsCOMPtr<nsIFile> tmpdir;
+
+#define ENSURE(expr) NS_ENSURE_SUCCESS(expr, nullptr);
+
+  ENSURE(NS_GetSpecialDirectory(NS_OS_TEMP_DIR, getter_AddRefs(tmpdir)));
+  MOZ_ASSERT(tmpdir);
+
+  ENSURE(tmpdir->AppendNative("TestWinDND"_ns));
+  ENSURE(tmpdir->CreateUnique(nsIFile::DIRECTORY_TYPE, 0777));
+
+#undef ENSURE
+
+  return tmpdir;
+}
+
+TEST(TestWinDND, All)
+{
+  nsCOMPtr<nsIFile> file = GetTemporaryDirectory();
+  if (!file) {
+    fail("could not create temporary directory!");
+    return;
+  }
+  xferFile = file;
+
+  if (NS_SUCCEEDED(Do_Test1())) {
+    passed(
+        "Basic Drag and Drop data type tests (single transferable) succeeded!");
+  }
+
+  if (NS_SUCCEEDED(Do_Test2())) {
+    passed(
+        "Basic Drag and Drop data type tests (multiple transferables) "
+        "succeeded!");
+  }
+
+  // if (NS_SUCCEEDED(Do_Test3()))
+  //  passed("Advanced Drag and Drop data type tests succeeded!");
+}
diff --git a/widget/windows/tests/gtest/moz.build b/widget/windows/tests/gtest/moz.build
new file mode 100644
index 0000000000..4057b7ae57
--- /dev/null
+++ b/widget/windows/tests/gtest/moz.build
@@ -0,0 +1,19 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+UNIFIED_SOURCES += [
+    "TestJumpListBuilder.cpp",
+    "TestWinDND.cpp",
+]
+
+LOCAL_INCLUDES += [
+    "/widget",
+    "/widget/windows",
+]
+
+include("/ipc/chromium/chromium-config.mozbuild")
+
+FINAL_LIBRARY = "xul-gtest"
diff --git a/widget/windows/tests/moz.build b/widget/windows/tests/moz.build
new file mode 100644
index 0000000000..2c7d200571
--- /dev/null
+++ b/widget/windows/tests/moz.build
@@ -0,0 +1,33 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+GeckoCppUnitTests(
+    [
+        "TestUriValidation",
+    ],
+    linkage=None,
+)
+
+DIRS = ["gtest"]
+
+LOCAL_INCLUDES += []
+
+OS_LIBS += [
+    "oleaut32",
+    "ole32",
+    "shell32",
+    "shlwapi",
+    "urlmon",
+    "uuid",
+]
+
+if CONFIG["OS_TARGET"] == "WINNT" and CONFIG["CC_TYPE"] in ("gcc", "clang"):
+    # This allows us to use wmain as the entry point on mingw
+    LDFLAGS += [
+        "-municode",
+    ]
+
+XPCSHELL_TESTS_MANIFESTS += ["unit/xpcshell.toml"]
diff --git a/widget/windows/tests/unit/test_windows_alert_service.js b/widget/windows/tests/unit/test_windows_alert_service.js
new file mode 100644
index 0000000000..0ba0d2a4d4
--- /dev/null
+++ b/widget/windows/tests/unit/test_windows_alert_service.js
@@ -0,0 +1,667 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+/*
+ * Test that Windows alert notifications generate expected XML.
+ */
+
+var { AppConstants } = ChromeUtils.importESModule(
+  "resource://gre/modules/AppConstants.sys.mjs"
+);
+
+let gProfD = do_get_profile();
+
+// Setup that allows to use the profile service in xpcshell tests,
+// lifted from `toolkit/profile/xpcshell/head.js`.
+function setupProfileService() {
+  let gDataHome = gProfD.clone();
+  gDataHome.append("data");
+  gDataHome.createUnique(Ci.nsIFile.DIRECTORY_TYPE, 0o755);
+  let gDataHomeLocal = gProfD.clone();
+  gDataHomeLocal.append("local");
+  gDataHomeLocal.createUnique(Ci.nsIFile.DIRECTORY_TYPE, 0o755);
+
+  let xreDirProvider = Cc["@mozilla.org/xre/directory-provider;1"].getService(
+    Ci.nsIXREDirProvider
+  );
+  xreDirProvider.setUserDataDirectory(gDataHome, false);
+  xreDirProvider.setUserDataDirectory(gDataHomeLocal, true);
+}
+
+add_setup(setupProfileService);
+
+function makeAlert(options) {
+  var alert = Cc["@mozilla.org/alert-notification;1"].createInstance(
+    Ci.nsIAlertNotification
+  );
+  alert.init(
+    options.name,
+    options.imageURL,
+    options.title,
+    options.text,
+    options.textClickable,
+    options.cookie,
+    options.dir,
+    options.lang,
+    options.data,
+    options.principal,
+    options.inPrivateBrowsing,
+    options.requireInteraction,
+    options.silent,
+    options.vibrate || []
+  );
+  if (options.actions) {
+    alert.actions = options.actions;
+  }
+  if (options.opaqueRelaunchData) {
+    alert.opaqueRelaunchData = options.opaqueRelaunchData;
+  }
+  return alert;
+}
+
+/**
+ * Take a `key1\nvalue1\n...` string encoding as used by the Windows native
+ * notification server DLL, and split it into an object, keeping `action\n...`
+ * intact.
+ *
+ * @param {string} t string encoding.
+ * @returns {object} an object with keys and values.
+ */
+function parseOneEncoded(t) {
+  var launch = {};
+
+  var lines = t.split("\n");
+  while (lines.length) {
+    var key = lines.shift();
+    var value;
+    if (key === "action") {
+      value = lines.join("\n");
+      lines = [];
+    } else {
+      value = lines.shift();
+    }
+    launch[key] = value;
+  }
+
+  return launch;
+}
+
+/**
+ * This complicated-looking function takes a (XML) string representation of a
+ * Windows alert (toast notification), parses it into XML, extracts and further
+ * parses internal data, and returns a simplified XML representation together
+ * with the parsed internals.
+ *
+ * Doing this lets us compare JSON objects rather than stringified-JSON further
+ * encoded as XML strings, which have lots of slashes and `&quot;` characters to
+ * contend with.
+ *
+ * @param {string} s XML string for Windows alert.
+
+ * @returns {Array} a pair of a simplified XML string and an object with
+ *                  `launch` and `actions` keys.
+ */
+function parseLaunchAndActions(s) {
+  var document = new DOMParser().parseFromString(s, "text/xml");
+  var root = document.documentElement;
+
+  var launchString = root.getAttribute("launch");
+  root.setAttribute("launch", "launch");
+  var launch = parseOneEncoded(launchString);
+
+  // `actions` is keyed by "content" attribute.
+  let actions = {};
+  for (var actionElement of root.querySelectorAll("action")) {
+    // `activationType="system"` is special.  Leave them alone.
+    let systemActivationType =
+      actionElement.getAttribute("activationType") === "system";
+
+    let action = {};
+    let names = [...actionElement.attributes].map(attribute => attribute.name);
+
+    for (var name of names) {
+      let value = actionElement.getAttribute(name);
+
+      // Here is where we parse stringified-JSON to simplify comparisons.
+      if (value.startsWith("{")) {
+        value = JSON.parse(value);
+        if ("opaqueRelaunchData" in value) {
+          value.opaqueRelaunchData = JSON.parse(value.opaqueRelaunchData);
+        }
+      }
+
+      if (name == "arguments" && !systemActivationType) {
+        action[name] = parseOneEncoded(value);
+      } else {
+        action[name] = value;
+      }
+
+      if (name != "content" && !systemActivationType) {
+        actionElement.removeAttribute(name);
+      }
+    }
+
+    let actionName = actionElement.getAttribute("content");
+    actions[actionName] = action;
+  }
+
+  return [new XMLSerializer().serializeToString(document), { launch, actions }];
+}
+
+function escape(s) {
+  return s
+    .replace(/&/g, "&amp;")
+    .replace(/"/g, "&quot;")
+    .replace(/</g, "&lt;")
+    .replace(/>/g, "&gt;")
+    .replace(/\n/g, "&#xA;");
+}
+
+function unescape(s) {
+  return s
+    .replace(/&amp;/g, "&")
+    .replace(/&quot;/g, '"')
+    .replace(/&lt;/g, "<")
+    .replace(/&gt;/g, ">")
+    .replace(/&#xA;/g, "\n");
+}
+
+function testAlert(when, { serverEnabled, profD, isBackgroundTaskMode } = {}) {
+  let argumentString = action => {
+    // &#xA; is "\n".
+    let s = ``;
+    if (serverEnabled) {
+      s += `program&#xA;${AppConstants.MOZ_APP_NAME}`;
+    } else {
+      s += `invalid key&#xA;invalid value`;
+    }
+    if (serverEnabled && profD) {
+      s += `&#xA;profile&#xA;${profD.path}`;
+    }
+    if (serverEnabled) {
+      s += "&#xA;windowsTag&#xA;";
+    }
+    if (action) {
+      s += `&#xA;action&#xA;${escape(JSON.stringify(action))}`;
+    }
+
+    return s;
+  };
+
+  let parsedArgumentString = action =>
+    parseOneEncoded(unescape(argumentString(action)));
+
+  let settingsAction = isBackgroundTaskMode
+    ? ""
+    : `<action content="Notification settings"/>`;
+
+  let parsedSettingsAction = hostport => {
+    if (isBackgroundTaskMode) {
+      return [];
+    }
+    let content = "Notification settings";
+    return [
+      content,
+      {
+        content,
+        arguments: parsedArgumentString(
+          Object.assign(
+            {
+              action: "settings",
+            },
+            hostport && {
+              launchUrl: hostport,
+            }
+          )
+        ),
+        placement: "contextmenu",
+      },
+    ];
+  };
+
+  let parsedSnoozeAction = hostport => {
+    let content = `Disable notifications from ${hostport}`;
+    return [
+      content,
+      {
+        content,
+        arguments: parsedArgumentString(
+          Object.assign(
+            {
+              action: "snooze",
+            },
+            hostport && {
+              launchUrl: hostport,
+            }
+          )
+        ),
+        placement: "contextmenu",
+      },
+    ];
+  };
+
+  let alertsService = Cc["@mozilla.org/system-alerts-service;1"]
+    .getService(Ci.nsIAlertsService)
+    .QueryInterface(Ci.nsIWindowsAlertsService);
+
+  let name = "name";
+  let title = "title";
+  let text = "text";
+  let imageURL = "file:///image.png";
+  let actions = [
+    { action: "action1", title: "title1", iconURL: "file:///iconURL1.png" },
+    { action: "action2", title: "title2", iconURL: "file:///iconURL2.png" },
+  ];
+  let opaqueRelaunchData = { foo: 1, bar: "two" };
+
+  let alert = makeAlert({ name, title, text });
+  let expected = `<toast launch="launch"><visual><binding template="ToastText03"><text id="1">title</text><text id="2">text</text></binding></visual><actions>${settingsAction}</actions></toast>`;
+  Assert.deepEqual(
+    [
+      expected.replace("<actions></actions>", "<actions/>"),
+      {
+        launch: parsedArgumentString({ action: "" }),
+        actions: Object.fromEntries(
+          [parsedSettingsAction()].filter(x => x.length)
+        ),
+      },
+    ],
+    parseLaunchAndActions(alertsService.getXmlStringForWindowsAlert(alert)),
+    when
+  );
+
+  alert = makeAlert({ name, title, text, imageURL });
+  expected = `<toast launch="launch"><visual><binding template="ToastImageAndText03"><image id="1" src="file:///image.png"/><text id="1">title</text><text id="2">text</text></binding></visual><actions>${settingsAction}</actions></toast>`;
+  Assert.deepEqual(
+    [
+      expected.replace("<actions></actions>", "<actions/>"),
+      {
+        launch: parsedArgumentString({ action: "" }),
+        actions: Object.fromEntries(
+          [parsedSettingsAction()].filter(x => x.length)
+        ),
+      },
+    ],
+    parseLaunchAndActions(alertsService.getXmlStringForWindowsAlert(alert)),
+    when
+  );
+
+  alert = makeAlert({ name, title, text, imageURL, requireInteraction: true });
+  expected = `<toast scenario="reminder" launch="launch"><visual><binding template="ToastImageAndText03"><image id="1" src="file:///image.png"/><text id="1">title</text><text id="2">text</text></binding></visual><actions>${settingsAction}<action content="Dismiss" arguments="dismiss" activationType="system"/></actions></toast>`;
+  Assert.deepEqual(
+    [
+      expected.replace("<actions></actions>", "<actions/>"),
+      {
+        launch: parsedArgumentString({ action: "" }),
+        actions: Object.fromEntries(
+          [
+            parsedSettingsAction(),
+            [
+              "Dismiss",
+              {
+                content: "Dismiss",
+                arguments: "dismiss",
+                activationType: "system",
+              },
+            ],
+          ].filter(x => x.length)
+        ),
+      },
+    ],
+    parseLaunchAndActions(alertsService.getXmlStringForWindowsAlert(alert)),
+    when
+  );
+
+  alert = makeAlert({ name, title, text, imageURL, actions });
+  expected = `<toast launch="launch"><visual><binding template="ToastImageAndText03"><image id="1" src="file:///image.png"/><text id="1">title</text><text id="2">text</text></binding></visual><actions>${settingsAction}<action content="title1"/><action content="title2"/></actions></toast>`;
+  Assert.deepEqual(
+    [
+      expected.replace("<actions></actions>", "<actions/>"),
+      {
+        launch: parsedArgumentString({ action: "" }),
+        actions: Object.fromEntries(
+          [
+            parsedSettingsAction(),
+            [
+              "title1",
+              {
+                content: "title1",
+                arguments: parsedArgumentString({ action: "action1" }),
+              },
+            ],
+            [
+              "title2",
+              {
+                content: "title2",
+                arguments: parsedArgumentString({ action: "action2" }),
+              },
+            ],
+          ].filter(x => x.length)
+        ),
+      },
+    ],
+    parseLaunchAndActions(alertsService.getXmlStringForWindowsAlert(alert)),
+    when
+  );
+
+  // Chrome privileged alerts can use `windowsSystemActivationType`.
+  let systemActions = [
+    {
+      action: "dismiss",
+      title: "dismissTitle",
+      windowsSystemActivationType: true,
+    },
+    {
+      action: "snooze",
+      title: "snoozeTitle",
+      windowsSystemActivationType: true,
+    },
+  ];
+  let systemPrincipal = Services.scriptSecurityManager.getSystemPrincipal();
+  alert = makeAlert({
+    name,
+    title,
+    text,
+    imageURL,
+    principal: systemPrincipal,
+    actions: systemActions,
+  });
+  let parsedSettingsActionWithPrivilegedName = isBackgroundTaskMode
+    ? []
+    : [
+        "Notification settings",
+        {
+          content: "Notification settings",
+          arguments: parsedArgumentString({
+            action: "settings",
+            privilegedName: name,
+          }),
+          placement: "contextmenu",
+        },
+      ];
+
+  expected = `<toast launch="launch"><visual><binding template="ToastGeneric"><image id="1" src="file:///image.png"/><text id="1">title</text><text id="2">text</text></binding></visual><actions>${settingsAction}<action content="dismissTitle" arguments="dismiss" activationType="system"/><action content="snoozeTitle" arguments="snooze" activationType="system"/></actions></toast>`;
+  Assert.deepEqual(
+    [
+      expected.replace("<actions></actions>", "<actions/>"),
+      {
+        launch: parsedArgumentString({ action: "", privilegedName: name }),
+        actions: Object.fromEntries(
+          [
+            parsedSettingsActionWithPrivilegedName,
+            [
+              "dismissTitle",
+              {
+                content: "dismissTitle",
+                arguments: "dismiss",
+                activationType: "system",
+              },
+            ],
+            [
+              "snoozeTitle",
+              {
+                content: "snoozeTitle",
+                arguments: "snooze",
+                activationType: "system",
+              },
+            ],
+          ].filter(x => x.length)
+        ),
+      },
+    ],
+    parseLaunchAndActions(alertsService.getXmlStringForWindowsAlert(alert)),
+    when
+  );
+
+  // But content unprivileged alerts can't use `windowsSystemActivationType`.
+  let launchUrl = "https://example.com/foo/bar.html";
+  const principaluri = Services.io.newURI(launchUrl);
+  const principal = Services.scriptSecurityManager.createContentPrincipal(
+    principaluri,
+    {}
+  );
+
+  alert = makeAlert({
+    name,
+    title,
+    text,
+    imageURL,
+    actions: systemActions,
+    principal,
+  });
+  expected = `<toast launch="launch"><visual><binding template="ToastImageAndText04"><image id="1" src="file:///image.png"/><text id="1">title</text><text id="2">text</text><text id="3" placement="attribution">via example.com</text></binding></visual><actions><action content="Disable notifications from example.com"/>${settingsAction}<action content="dismissTitle"/><action content="snoozeTitle"/></actions></toast>`;
+  Assert.deepEqual(
+    [
+      expected.replace("<actions></actions>", "<actions/>"),
+      {
+        launch: parsedArgumentString({
+          action: "",
+          launchUrl: principaluri.hostPort,
+        }),
+        actions: Object.fromEntries(
+          [
+            parsedSnoozeAction(principaluri.hostPort),
+            parsedSettingsAction(principaluri.hostPort),
+            [
+              "dismissTitle",
+              {
+                content: "dismissTitle",
+                arguments: parsedArgumentString({
+                  action: "dismiss",
+                  launchUrl: principaluri.hostPort,
+                }),
+              },
+            ],
+            [
+              "snoozeTitle",
+              {
+                content: "snoozeTitle",
+                arguments: parsedArgumentString({
+                  action: "snooze",
+                  launchUrl: principaluri.hostPort,
+                }),
+              },
+            ],
+          ].filter(x => x.length)
+        ),
+      },
+    ],
+    parseLaunchAndActions(alertsService.getXmlStringForWindowsAlert(alert)),
+    when
+  );
+
+  // Chrome privileged alerts can set `opaqueRelaunchData`.
+  alert = makeAlert({
+    name,
+    title,
+    text,
+    imageURL,
+    principal: systemPrincipal,
+    opaqueRelaunchData: JSON.stringify(opaqueRelaunchData),
+  });
+  expected = `<toast launch="launch"><visual><binding template="ToastGeneric"><image id="1" src="file:///image.png"/><text id="1">title</text><text id="2">text</text></binding></visual><actions>${settingsAction}</actions></toast>`;
+  Assert.deepEqual(
+    [
+      expected.replace("<actions></actions>", "<actions/>"),
+      {
+        launch: parsedArgumentString({
+          action: "",
+          opaqueRelaunchData: JSON.stringify(opaqueRelaunchData),
+          privilegedName: name,
+        }),
+        actions: Object.fromEntries(
+          [parsedSettingsActionWithPrivilegedName].filter(x => x.length)
+        ),
+      },
+    ],
+    parseLaunchAndActions(alertsService.getXmlStringForWindowsAlert(alert)),
+    when
+  );
+
+  // But content unprivileged alerts can't set `opaqueRelaunchData`.
+  alert = makeAlert({
+    name,
+    title,
+    text,
+    imageURL,
+    principal,
+    opaqueRelaunchData: JSON.stringify(opaqueRelaunchData),
+  });
+  expected = `<toast launch="launch"><visual><binding template="ToastImageAndText04"><image id="1" src="file:///image.png"/><text id="1">title</text><text id="2">text</text><text id="3" placement="attribution">via example.com</text></binding></visual><actions><action content="Disable notifications from example.com"/>${settingsAction}</actions></toast>`;
+  Assert.deepEqual(
+    [
+      expected.replace("<actions></actions>", "<actions/>"),
+      {
+        launch: parsedArgumentString({
+          action: "",
+          launchUrl: principaluri.hostPort,
+        }),
+        actions: Object.fromEntries(
+          [
+            parsedSnoozeAction(principaluri.hostPort),
+            parsedSettingsAction(principaluri.hostPort),
+          ].filter(x => x.length)
+        ),
+      },
+    ],
+    parseLaunchAndActions(alertsService.getXmlStringForWindowsAlert(alert)),
+    when
+  );
+
+  // Chrome privileged alerts can set action-specific relaunch parameters.
+  let systemRelaunchActions = [
+    {
+      action: "action1",
+      title: "title1",
+      opaqueRelaunchData: JSON.stringify({ json: "data1" }),
+    },
+    {
+      action: "action2",
+      title: "title2",
+      opaqueRelaunchData: JSON.stringify({ json: "data2" }),
+    },
+  ];
+  systemPrincipal = Services.scriptSecurityManager.getSystemPrincipal();
+  alert = makeAlert({
+    name,
+    title,
+    text,
+    imageURL,
+    principal: systemPrincipal,
+    actions: systemRelaunchActions,
+  });
+  expected = `<toast launch="launch"><visual><binding template="ToastGeneric"><image id="1" src="file:///image.png"/><text id="1">title</text><text id="2">text</text></binding></visual><actions>${settingsAction}<action content="title1"/><action content="title2"/></actions></toast>`;
+  Assert.deepEqual(
+    [
+      expected.replace("<actions></actions>", "<actions/>"),
+      {
+        launch: parsedArgumentString({ action: "", privilegedName: name }),
+        actions: Object.fromEntries(
+          [
+            parsedSettingsActionWithPrivilegedName,
+            [
+              "title1",
+              {
+                content: "title1",
+                arguments: parsedArgumentString(
+                  {
+                    action: "action1",
+                    opaqueRelaunchData: JSON.stringify({ json: "data1" }),
+                    privilegedName: name,
+                  },
+                  null,
+                  name
+                ),
+              },
+            ],
+
+            [
+              "title2",
+              {
+                content: "title2",
+                arguments: parsedArgumentString(
+                  {
+                    action: "action2",
+                    opaqueRelaunchData: JSON.stringify({ json: "data2" }),
+                    privilegedName: name,
+                  },
+                  null,
+                  name
+                ),
+              },
+            ],
+          ].filter(x => x.length)
+        ),
+      },
+    ],
+    parseLaunchAndActions(alertsService.getXmlStringForWindowsAlert(alert)),
+    when
+  );
+}
+
+add_task(async () => {
+  Services.prefs.deleteBranch(
+    "alerts.useSystemBackend.windows.notificationserver.enabled"
+  );
+  testAlert("when notification server pref is unset", {
+    profD: gProfD,
+  });
+
+  Services.prefs.setBoolPref(
+    "alerts.useSystemBackend.windows.notificationserver.enabled",
+    false
+  );
+  testAlert("when notification server pref is false", { profD: gProfD });
+
+  Services.prefs.setBoolPref(
+    "alerts.useSystemBackend.windows.notificationserver.enabled",
+    true
+  );
+  testAlert("when notification server pref is true", {
+    serverEnabled: true,
+    profD: gProfD,
+  });
+});
+
+let condition = {
+  skip_if: () => !AppConstants.MOZ_BACKGROUNDTASKS,
+};
+
+add_task(condition, async () => {
+  const bts = Cc["@mozilla.org/backgroundtasks;1"]?.getService(
+    Ci.nsIBackgroundTasks
+  );
+
+  // Pretend that this is a background task.
+  bts.overrideBackgroundTaskNameForTesting("taskname");
+
+  Services.prefs.setBoolPref(
+    "alerts.useSystemBackend.windows.notificationserver.enabled",
+    true
+  );
+  testAlert(
+    "when notification server pref is true in background task, no default profile",
+    { serverEnabled: true, isBackgroundTaskMode: true }
+  );
+
+  let profileService = Cc["@mozilla.org/toolkit/profile-service;1"].getService(
+    Ci.nsIToolkitProfileService
+  );
+
+  let profilePath = do_get_profile();
+  profilePath.append(`test_windows_alert_service`);
+  let profile = profileService.createUniqueProfile(
+    profilePath,
+    "test_windows_alert_service"
+  );
+
+  profileService.defaultProfile = profile;
+
+  testAlert(
+    "when notification server pref is true in background task, default profile",
+    { serverEnabled: true, isBackgroundTaskMode: true, profD: profilePath }
+  );
+
+  // No longer a background task,
+  bts.overrideBackgroundTaskNameForTesting("");
+});
diff --git a/widget/windows/tests/unit/xpcshell.toml b/widget/windows/tests/unit/xpcshell.toml
new file mode 100644
index 0000000000..9943d5510e
--- /dev/null
+++ b/widget/windows/tests/unit/xpcshell.toml
@@ -0,0 +1,3 @@
+[DEFAULT]
+
+["test_windows_alert_service.js"]
diff --git a/widget/windows/touchinjection_sdk80.h b/widget/windows/touchinjection_sdk80.h
new file mode 100644
index 0000000000..7e9f5410d2
--- /dev/null
+++ b/widget/windows/touchinjection_sdk80.h
@@ -0,0 +1,171 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef touchinjection_sdk80_h
+#define touchinjection_sdk80_h
+
+#include <windows.h>
+
+// Note, this isn't inclusive of all touch injection header info.
+// You may need to add more to expand on current apis.
+
+#ifndef TOUCH_FEEDBACK_DEFAULT
+
+#  define TOUCH_FEEDBACK_DEFAULT 0x1
+#  define TOUCH_FEEDBACK_INDIRECT 0x2
+#  define TOUCH_FEEDBACK_NONE 0x3
+
+enum POINTER_FEEDBACK_MODE {
+  POINTER_FEEDBACK_DEFAULT =
+      1,  // The injected pointer input feedback may get suppressed by the
+          // end-user settings in the Pen and Touch control panel.
+  POINTER_FEEDBACK_INDIRECT =
+      2,  // The injected pointer input feedback overrides the end-user settings
+          // in the Pen and Touch control panel.
+  POINTER_FEEDBACK_NONE = 3,  // No touch visualizations.
+};
+
+enum {
+  PT_POINTER = 0x00000001,   // Generic pointer
+  PT_TOUCH = 0x00000002,     // Touch
+  PT_PEN = 0x00000003,       // Pen
+  PT_MOUSE = 0x00000004,     // Mouse
+  PT_TOUCHPAD = 0x00000005,  // Touch pad
+};
+
+using POINTER_INPUT_TYPE = DWORD;
+using POINTER_FLAGS = UINT32;
+
+enum POINTER_BUTTON_CHANGE_TYPE {
+  POINTER_CHANGE_NONE,
+  POINTER_CHANGE_FIRSTBUTTON_DOWN,
+  POINTER_CHANGE_FIRSTBUTTON_UP,
+  POINTER_CHANGE_SECONDBUTTON_DOWN,
+  POINTER_CHANGE_SECONDBUTTON_UP,
+  POINTER_CHANGE_THIRDBUTTON_DOWN,
+  POINTER_CHANGE_THIRDBUTTON_UP,
+  POINTER_CHANGE_FOURTHBUTTON_DOWN,
+  POINTER_CHANGE_FOURTHBUTTON_UP,
+  POINTER_CHANGE_FIFTHBUTTON_DOWN,
+  POINTER_CHANGE_FIFTHBUTTON_UP,
+};
+
+struct POINTER_INFO {
+  POINTER_INPUT_TYPE pointerType;
+  UINT32 pointerId;
+  UINT32 frameId;
+  POINTER_FLAGS pointerFlags;
+  HANDLE sourceDevice;
+  HWND hwndTarget;
+  POINT ptPixelLocation;
+  POINT ptHimetricLocation;
+  POINT ptPixelLocationRaw;
+  POINT ptHimetricLocationRaw;
+  DWORD dwTime;
+  UINT32 historyCount;
+  INT32 InputData;
+  DWORD dwKeyStates;
+  UINT64 PerformanceCount;
+  POINTER_BUTTON_CHANGE_TYPE ButtonChangeType;
+};
+
+using TOUCH_FLAGS = UINT32;
+using TOUCH_MASK = UINT32;
+
+struct POINTER_TOUCH_INFO {
+  POINTER_INFO pointerInfo;
+  TOUCH_FLAGS touchFlags;
+  TOUCH_MASK touchMask;
+  RECT rcContact;
+  RECT rcContactRaw;
+  UINT32 orientation;
+  UINT32 pressure;
+};
+
+#  define PEN_FLAG_NONE 0x00000000      // Default
+#  define PEN_FLAG_BARREL 0x00000001    // The barrel button is pressed
+#  define PEN_FLAG_INVERTED 0x00000002  // The pen is inverted
+#  define PEN_FLAG_ERASER 0x00000004    // The eraser button is pressed
+
+#  define PEN_MASK_NONE \
+    0x00000000  // Default - none of the optional fields are valid
+#  define PEN_MASK_PRESSURE 0x00000001  // The pressure field is valid
+#  define PEN_MASK_ROTATION 0x00000002  // The rotation field is valid
+#  define PEN_MASK_TILT_X 0x00000004    // The tiltX field is valid
+#  define PEN_MASK_TILT_Y 0x00000008    // The tiltY field is valid
+
+using PEN_FLAGS = UINT32;
+using PEN_MASK = UINT32;
+
+struct POINTER_PEN_INFO {
+  POINTER_INFO pointerInfo;
+  PEN_FLAGS penFlags;
+  PEN_MASK penMask;
+  UINT32 pressure;
+  UINT32 rotation;
+  INT32 tiltX;
+  INT32 tiltY;
+};
+
+struct POINTER_TYPE_INFO {
+  POINTER_INPUT_TYPE type;
+  union {
+    POINTER_TOUCH_INFO touchInfo;
+    POINTER_PEN_INFO penInfo;
+  };
+};
+
+#  define TOUCH_FLAG_NONE 0x00000000  // Default
+
+#  define TOUCH_MASK_NONE \
+    0x00000000  // Default - none of the optional fields are valid
+#  define TOUCH_MASK_CONTACTAREA 0x00000001  // The rcContact field is valid
+#  define TOUCH_MASK_ORIENTATION 0x00000002  // The orientation field is valid
+#  define TOUCH_MASK_PRESSURE 0x00000004     // The pressure field is valid
+
+#  define POINTER_FLAG_NONE 0x00000000          // Default
+#  define POINTER_FLAG_NEW 0x00000001           // New pointer
+#  define POINTER_FLAG_INRANGE 0x00000002       // Pointer has not departed
+#  define POINTER_FLAG_INCONTACT 0x00000004     // Pointer is in contact
+#  define POINTER_FLAG_FIRSTBUTTON 0x00000010   // Primary action
+#  define POINTER_FLAG_SECONDBUTTON 0x00000020  // Secondary action
+#  define POINTER_FLAG_THIRDBUTTON 0x00000040   // Third button
+#  define POINTER_FLAG_FOURTHBUTTON 0x00000080  // Fourth button
+#  define POINTER_FLAG_FIFTHBUTTON 0x00000100   // Fifth button
+#  define POINTER_FLAG_PRIMARY 0x00002000       // Pointer is primary
+#  define POINTER_FLAG_CONFIDENCE \
+    0x00004000  // Pointer is considered unlikely to be accidental
+#  define POINTER_FLAG_CANCELED \
+    0x00008000  // Pointer is departing in an abnormal manner
+#  define POINTER_FLAG_DOWN \
+    0x00010000  // Pointer transitioned to down state (made contact)
+#  define POINTER_FLAG_UPDATE 0x00020000  // Pointer update
+#  define POINTER_FLAG_UP \
+    0x00040000  // Pointer transitioned from down state (broke contact)
+#  define POINTER_FLAG_WHEEL 0x00080000           // Vertical wheel
+#  define POINTER_FLAG_HWHEEL 0x00100000          // Horizontal wheel
+#  define POINTER_FLAG_CAPTURECHANGED 0x00200000  // Lost capture
+
+#endif  // TOUCH_FEEDBACK_DEFAULT
+
+#define TOUCH_FLAGS_CONTACTUPDATE \
+  (POINTER_FLAG_UPDATE | POINTER_FLAG_INRANGE | POINTER_FLAG_INCONTACT)
+#define TOUCH_FLAGS_CONTACTDOWN \
+  (POINTER_FLAG_DOWN | POINTER_FLAG_INRANGE | POINTER_FLAG_INCONTACT)
+
+using InitializeTouchInjectionPtr = BOOL(WINAPI*)(UINT32, DWORD);
+using InjectTouchInputPtr = BOOL(WINAPI*)(UINT32, const POINTER_TOUCH_INFO*);
+
+#if !defined(NTDDI_WIN10_RS5) || (NTDDI_VERSION < NTDDI_WIN10_RS5)
+#  define HSYNTHETICPOINTERDEVICE intptr_t
+#endif  // NTDDI_VERSION < NTDDI_WIN10_RS5
+
+using CreateSyntheticPointerDevicePtr = HSYNTHETICPOINTERDEVICE(WINAPI*)(
+    POINTER_INPUT_TYPE, ULONG, POINTER_FEEDBACK_MODE);
+using DestroySyntheticPointerDevicePtr = void(WINAPI*)(HSYNTHETICPOINTERDEVICE);
+using InjectSyntheticPointerInputPtr = BOOL(WINAPI*)(HSYNTHETICPOINTERDEVICE,
+                                                     const POINTER_TYPE_INFO*,
+                                                     UINT32);
+
+#endif  // touchinjection_sdk80_h
diff --git a/widget/windows/widget.rc b/widget/windows/widget.rc
new file mode 100644
index 0000000000..9361f9e48c
--- /dev/null
+++ b/widget/windows/widget.rc
@@ -0,0 +1,30 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "resource.h"
+#include <winresrc.h>
+#include <dlgs.h>
+
+IDC_GRAB                CURSOR  DISCARDABLE     "res/grab.cur"
+IDC_GRABBING            CURSOR  DISCARDABLE     "res/grabbing.cur"
+IDC_CELL                CURSOR  DISCARDABLE     "res/cell.cur"
+IDC_COPY                CURSOR  DISCARDABLE     "res/copy.cur"
+IDC_ALIAS               CURSOR  DISCARDABLE     "res/aliasb.cur"
+IDC_ZOOMIN              CURSOR  DISCARDABLE     "res/zoom_in.cur"
+IDC_ZOOMOUT             CURSOR  DISCARDABLE     "res/zoom_out.cur"
+IDC_COLRESIZE           CURSOR  DISCARDABLE     "res/col_resize.cur"
+IDC_ROWRESIZE           CURSOR  DISCARDABLE     "res/row_resize.cur"
+IDC_VERTICALTEXT        CURSOR  DISCARDABLE     "res/vertical_text.cur"
+IDC_NONE                CURSOR  DISCARDABLE     "res/none.cur"
+
+OPTPROPSHEET DIALOG DISCARDABLE  32, 32, 288, 226
+STYLE DS_MODALFRAME | DS_3DLOOK | DS_CONTEXTHELP | WS_POPUP | WS_VISIBLE | 
+    WS_CAPTION | WS_SYSMENU
+CAPTION "Options"
+FONT 8, "MS Sans Serif"
+BEGIN
+
+END