Bug 1235686 part.1 MouseScrollHandler should refresh the cache of system settings at handling wheel messages if the pref doesn't allow to cache system settings r=jimm

modules/libpref/init/all.js

@@ -3261,6 +3261,16 @@ pref("ui.panel.default_level_parent", false);
 
 pref("mousewheel.system_scroll_override_on_root_content.enabled", true);
 
+// Enable system settings cache for mouse wheel message handling.
+// Note that even if this pref is set to true, Gecko may not cache the system
+// settings if Gecko detects that the cache won't be refreshed properly when
+// the settings are changed.
+pref("mousewheel.system_settings_cache.enabled", true);
+
+// This is a pref to test system settings cache for mouse wheel message
+// handling.  If this is set to true, Gecko forcibly use the cache.
+pref("mousewheel.system_settings_cache.force_enabled", false);
+
 // High resolution scrolling with supported mouse drivers on Vista or later.
 pref("mousewheel.enable_pixel_scrolling", true);
 

widget/windows/WinMouseScrollHandler.cpp

@@ -603,6 +603,10 @@ MouseScrollHandler::HandleMouseWheelMessage(nsWindowBase* aWidget,
 
   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(aMessage == MOZ_WM_MOUSEVWHEEL);
+
   EventInfo eventInfo(aWidget, WinUtils::GetNativeMessage(aMessage),
                       aWParam, aLParam);
   if (!eventInfo.CanDispatchWheelEvent()) {
@@ -881,30 +885,41 @@ MouseScrollHandler::SystemSettings::Init()
     return;
   }
 
+  InitScrollLines();
+  InitScrollChars();
+
   mInitialized = true;
 
-  MouseScrollHandler::UserPrefs& userPrefs =
+  MOZ_LOG(gMouseScrollLog, LogLevel::Info,
-    MouseScrollHandler::sInstance->mUserPrefs;
+    ("MouseScroll::SystemSettings::Init(): initialized, "
+       "mScrollLines=%d, mScrollChars=%d",
+     mScrollLines, mScrollChars));
+}
 
-  mScrollLines = userPrefs.GetOverriddenVerticalScrollAmout();
+bool
+MouseScrollHandler::SystemSettings::InitScrollLines()
+{
+  int32_t oldValue = mInitialized ? mScrollLines : 0;
+  mScrollLines = MouseScrollHandler::sInstance->
+                   mUserPrefs.GetOverriddenVerticalScrollAmout();
   if (mScrollLines >= 0) {
     // overridden by the pref.
     MOZ_LOG(gMouseScrollLog, LogLevel::Info,
-      ("MouseScroll::SystemSettings::Init(): mScrollLines is overridden by "
+      ("MouseScroll::SystemSettings::InitScrollLines(): mScrollLines is "
-       "the pref: %d",
+       "overridden by the pref: %d",
        mScrollLines));
   } else if (!::SystemParametersInfo(SPI_GETWHEELSCROLLLINES, 0,
                                      &mScrollLines, 0)) {
     MOZ_LOG(gMouseScrollLog, LogLevel::Info,
-      ("MouseScroll::SystemSettings::Init(): ::SystemParametersInfo("
+      ("MouseScroll::SystemSettings::InitScrollLines(): ::SystemParametersInfo("
-         "SPI_GETWHEELSCROLLLINES) failed"));
+       "SPI_GETWHEELSCROLLLINES) failed"));
     mScrollLines = 3;
   }
 
   if (mScrollLines > WHEEL_DELTA) {
     MOZ_LOG(gMouseScrollLog, LogLevel::Info,
-      ("MouseScroll::SystemSettings::Init(): the result of "
+      ("MouseScroll::SystemSettings::InitScrollLines(): the result of "
-         "::SystemParametersInfo(SPI_GETWHEELSCROLLLINES) is too large: %d",
+       "::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
@@ -915,18 +930,26 @@ MouseScrollHandler::SystemSettings::Init()
     mScrollLines = WHEEL_PAGESCROLL;
   }
 
-  mScrollChars = userPrefs.GetOverriddenHorizontalScrollAmout();
+  return oldValue != mScrollLines;
+}
+
+bool
+MouseScrollHandler::SystemSettings::InitScrollChars()
+{
+  int32_t oldValue = mInitialized ? mScrollChars : 0;
+  mScrollChars = MouseScrollHandler::sInstance->
+                   mUserPrefs.GetOverriddenHorizontalScrollAmout();
   if (mScrollChars >= 0) {
     // overridden by the pref.
     MOZ_LOG(gMouseScrollLog, LogLevel::Info,
-      ("MouseScroll::SystemSettings::Init(): mScrollChars is overridden by "
+      ("MouseScroll::SystemSettings::InitScrollChars(): mScrollChars is "
-       "the pref: %d",
+       "overridden by the pref: %d",
        mScrollChars));
   } else if (!::SystemParametersInfo(SPI_GETWHEELSCROLLCHARS, 0,
                                      &mScrollChars, 0)) {
     MOZ_LOG(gMouseScrollLog, LogLevel::Info,
-      ("MouseScroll::SystemSettings::Init(): ::SystemParametersInfo("
+      ("MouseScroll::SystemSettings::InitScrollChars(): ::SystemParametersInfo("
-         "SPI_GETWHEELSCROLLCHARS) failed, %s",
+       "SPI_GETWHEELSCROLLCHARS) failed, %s",
        IsVistaOrLater() ?
          "this is unexpected on Vista or later" :
          "but on XP or earlier, this is not a problem"));
@@ -935,17 +958,14 @@ MouseScrollHandler::SystemSettings::Init()
 
   if (mScrollChars > WHEEL_DELTA) {
     MOZ_LOG(gMouseScrollLog, LogLevel::Info,
-      ("MouseScroll::SystemSettings::Init(): the result of "
+      ("MouseScroll::SystemSettings::InitScrollChars(): the result of "
-         "::SystemParametersInfo(SPI_GETWHEELSCROLLCHARS) is too large: %d",
+       "::SystemParametersInfo(SPI_GETWHEELSCROLLCHARS) is too large: %d",
        mScrollChars));
     // See the comments for the case mScrollLines > WHEEL_DELTA.
     mScrollChars = WHEEL_PAGESCROLL;
   }
 
-  MOZ_LOG(gMouseScrollLog, LogLevel::Info,
+  return oldValue != mScrollChars;
-    ("MouseScroll::SystemSettings::Init(): initialized, "
-       "mScrollLines=%d, mScrollChars=%d",
-     mScrollLines, mScrollChars));
 }
 
 void
@@ -961,6 +981,45 @@ MouseScrollHandler::SystemSettings::MarkDirty()
   MouseScrollHandler::sInstance->mLastEventInfo.ResetTransaction();
 }
 
+void
+MouseScrollHandler::SystemSettings::RefreshCache(bool aForVertical)
+{
+  bool isChanged = aForVertical ? InitScrollLines() : InitScrollChars();
+  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(
+                                      bool aIsVertical)
+{
+  if (!mInitialized) {
+    return;
+  }
+
+  MouseScrollHandler::UserPrefs& userPrefs =
+    MouseScrollHandler::sInstance->mUserPrefs;
+
+  // If system settings cache is disabled, we should always refresh them.
+  if (!userPrefs.IsSystemSettingCacheEnabled()) {
+    RefreshCache(aIsVertical);
+    return;
+  }
+
+  // If pref is set to as "always trust the cache", we shouldn't refresh them
+  // in any environments.
+  if (userPrefs.IsSystemSettingCacheForciblyEnabled()) {
+    return;
+  }
+
+  // TODO: Implement to check if we can trust the cache in the environment.
+}
+
 /******************************************************************************
  *
  * UserPrefs
@@ -997,6 +1056,11 @@ MouseScrollHandler::UserPrefs::Init()
 
   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);
   mOverriddenVerticalScrollAmount =
     Preferences::GetInt("mousewheel.windows.vertical_amount_override", -1);
   mOverriddenHorizontalScrollAmount =
@@ -1008,10 +1072,14 @@ MouseScrollHandler::UserPrefs::Init()
   MOZ_LOG(gMouseScrollLog, LogLevel::Info,
     ("MouseScroll::UserPrefs::Init(): initialized, "
        "mScrollMessageHandledAsWheelMessage=%s, "
+       "mEnableSystemSettingCache=%s, "
+       "mForceEnableSystemSettingCache=%s, "
        "mOverriddenVerticalScrollAmount=%d, "
        "mOverriddenHorizontalScrollAmount=%d, "
        "mMouseScrollTransactionTimeout=%d",
      GetBoolName(mScrollMessageHandledAsWheelMessage),
+     GetBoolName(mEnableSystemSettingCache),
+     GetBoolName(mForceEnableSystemSettingCache),
      mOverriddenVerticalScrollAmount, mOverriddenHorizontalScrollAmount,
      mMouseScrollTransactionTimeout));
 }

widget/windows/WinMouseScrollHandler.h

@@ -273,6 +273,14 @@ private:
     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(bool aIsVertical);
+
     int32_t GetScrollAmount(bool aForVertical) const
     {
       MOZ_ASSERT(mInitialized, "SystemSettings must be initialized");
@@ -290,6 +298,12 @@ private:
     bool mInitialized;
     int32_t mScrollLines;
     int32_t mScrollChars;
+
+    // Returns true if cached value is changed.
+    bool InitScrollLines();
+    bool InitScrollChars();
+
+    void RefreshCache(bool aForVertical);
   };
 
   SystemSettings mSystemSettings;
@@ -307,6 +321,18 @@ private:
       return mScrollMessageHandledAsWheelMessage;
     }
 
+    bool IsSystemSettingCacheEnabled()
+    {
+      Init();
+      return mEnableSystemSettingCache;
+    }
+
+    bool IsSystemSettingCacheForciblyEnabled()
+    {
+      Init();
+      return mForceEnableSystemSettingCache;
+    }
+
     int32_t GetOverriddenVerticalScrollAmout()
     {
       Init();
@@ -335,6 +361,8 @@ private:
 
     bool mInitialized;
     bool mScrollMessageHandledAsWheelMessage;
+    bool mEnableSystemSettingCache;
+    bool mForceEnableSystemSettingCache;
     int32_t mOverriddenVerticalScrollAmount;
     int32_t mOverriddenHorizontalScrollAmount;
     int32_t mMouseScrollTransactionTimeout;