Adding upstream version 115.8.0esr.upstream/115.8.0esr

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

1 files changed, 1668 insertions, 0 deletions

diff --git a/widget/windows/WinMouseScrollHandler.cpp b/widget/windows/WinMouseScrollHandler.cpp
new file mode 100644
index 0000000000..74cb112569
--- /dev/null
+++ b/widget/windows/WinMouseScrollHandler.cpp
@@ -0,0 +1,1668 @@
+/* -*- 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 <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_OS 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;
+  } else if (!MouseScrollHandler::sInstance->mSystemSettings
+                  .IsOverridingSystemScrollSpeedAllowed()) {
+    // If the system settings are customized by either the user or
+    // the mouse utility, we shouldn't allow to override the system scroll
+    // speed setting.
+    aWheelEvent.mAllowToOverrideSystemScrollSpeed = false;
+  } else {
+    // For suppressing too fast scroll, we should ensure that the maximum
+    // overridden delta value should be less than overridden scroll speed
+    // with default scroll amount.
+    double defaultScrollAmount = mIsVertical
+                                     ? SystemSettings::DefaultScrollLines()
+                                     : SystemSettings::DefaultScrollChars();
+    double maxDelta = WidgetWheelEvent::ComputeOverriddenDelta(
+        defaultScrollAmount, mIsVertical);
+    if (maxDelta != defaultScrollAmount) {
+      double overriddenDelta =
+          WidgetWheelEvent::ComputeOverriddenDelta(Abs(delta), mIsVertical);
+      if (overriddenDelta > maxDelta) {
+        // Suppress to fast scroll since overriding system scroll speed with
+        // current delta value causes too big delta value.
+        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...
+}
+
+bool MouseScrollHandler::SystemSettings::
+    IsOverridingSystemScrollSpeedAllowed() {
+  return mScrollLines == DefaultScrollLines() &&
+         mScrollChars == DefaultScrollChars();
+}
+
+/******************************************************************************
+ *
+ * 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];
+  bool foundKey = WinUtils::GetRegistryKey(
+      HKEY_LOCAL_MACHINE, L"Software\\Synaptics\\SynTP\\Install",
+      L"DriverVersion", buf, sizeof buf);
+  if (!foundKey) {
+    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.
+  bool foundKey = WinUtils::GetRegistryKey(HKEY_CURRENT_USER,
+                                           L"Software\\Elantech\\MainOption",
+                                           L"DriverVersion", buf, sizeof buf);
+  if (!foundKey) {
+    foundKey =
+        WinUtils::GetRegistryKey(HKEY_CURRENT_USER, L"Software\\Elantech",
+                                 L"DriverVersion", buf, sizeof buf);
+  }
+
+  if (!foundKey) {
+    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];
+  bool foundKey =
+      WinUtils::GetRegistryKey(HKEY_LOCAL_MACHINE, L"Software\\Alps\\Apoint",
+                               L"ProductVer", buf, sizeof buf);
+  if (!foundKey) {
+    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 (WinUtils::HasRegistryKey(HKEY_CURRENT_USER,
+                               L"Software\\Lenovo\\TrackPoint")) {
+    MOZ_LOG(gMouseScrollLog, LogLevel::Info,
+            ("MouseScroll::Device::TrackPoint::IsDriverInstalled(): "
+             "Lenovo's TrackPoint driver is found"));
+    return true;
+  }
+
+  if (WinUtils::HasRegistryKey(HKEY_CURRENT_USER,
+                               L"Software\\Alps\\Apoint\\TrackPoint")) {
+    MOZ_LOG(gMouseScrollLog, LogLevel::Info,
+            ("MouseScroll::Device::TrackPoint::IsDriverInstalled(): "
+             "Alps's TrackPoint driver is found"));
+  }
+
+  return false;
+}
+
+/******************************************************************************
+ *
+ * Device::UltraNav
+ *
+ ******************************************************************************/
+
+/* static */
+bool MouseScrollHandler::Device::UltraNav::IsObsoleteDriverInstalled() {
+  if (WinUtils::HasRegistryKey(HKEY_CURRENT_USER,
+                               L"Software\\Lenovo\\UltraNav")) {
+    MOZ_LOG(gMouseScrollLog, LogLevel::Info,
+            ("MouseScroll::Device::UltraNav::IsObsoleteDriverInstalled(): "
+             "Lenovo's UltraNav driver is found"));
+    return true;
+  }
+
+  bool installed = false;
+  if (WinUtils::HasRegistryKey(HKEY_CURRENT_USER,
+                               L"Software\\Synaptics\\SynTPEnh\\UltraNavUSB")) {
+    MOZ_LOG(gMouseScrollLog, LogLevel::Info,
+            ("MouseScroll::Device::UltraNav::IsObsoleteDriverInstalled(): "
+             "Synaptics's UltraNav (USB) driver is found"));
+    installed = true;
+  } else if (WinUtils::HasRegistryKey(
+                 HKEY_CURRENT_USER,
+                 L"Software\\Synaptics\\SynTPEnh\\UltraNavPS2")) {
+    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