1 files changed, 346 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