Bug 990907 - Add a flag on nsIScrollableFrame to indicate if it is actively being scrolled by APZ. r=tn

gfx/layers/apz/util/APZEventState.cpp

@@ -249,6 +249,9 @@ APZEventState::ProcessAPZStateChange(const nsCOMPtr<nsIDocument>& aDocument,
   case APZStateChange::TransformBegin:
   {
     nsIScrollableFrame* sf = nsLayoutUtils::FindScrollableFrameFor(aViewId);
+    if (sf) {
+      sf->SetTransformingByAPZ(true);
+    }
     nsIScrollbarMediator* scrollbarMediator = do_QueryFrame(sf);
     if (scrollbarMediator) {
       scrollbarMediator->ScrollbarActivityStarted();
@@ -266,6 +269,9 @@ APZEventState::ProcessAPZStateChange(const nsCOMPtr<nsIDocument>& aDocument,
   case APZStateChange::TransformEnd:
   {
     nsIScrollableFrame* sf = nsLayoutUtils::FindScrollableFrameFor(aViewId);
+    if (sf) {
+      sf->SetTransformingByAPZ(false);
+    }
     nsIScrollbarMediator* scrollbarMediator = do_QueryFrame(sf);
     if (scrollbarMediator) {
       scrollbarMediator->ScrollbarActivityStopped();

layout/generic/nsGfxScrollFrame.cpp

@@ -1896,6 +1896,7 @@ ScrollFrameHelper::ScrollFrameHelper(nsContainerFrame* aOuter,
   , mHasBeenScrolled(false)
   , mIsResolutionSet(false)
   , mScaleToResolution(false)
+  , mTransformingByAPZ(false)
 {
   if (LookAndFeel::GetInt(LookAndFeel::eIntID_UseOverlayScrollbars) != 0) {
     mScrollbarActivity = new ScrollbarActivity(do_QueryFrame(aOuter));

layout/generic/nsGfxScrollFrame.h

@@ -324,6 +324,13 @@ public:
   void MarkNotRecentlyScrolled();
   nsExpirationState* GetExpirationState() { return &mActivityExpirationState; }
 
+  void SetTransformingByAPZ(bool aTransforming) {
+    mTransformingByAPZ = aTransforming;
+  }
+  bool IsTransformingByAPZ() const {
+    return mTransformingByAPZ;
+  }
+
   void ScheduleSyntheticMouseMove();
   static void ScrollActivityCallback(nsITimer *aTimer, void* anInstance);
 
@@ -466,6 +473,10 @@ public:
   // Only meaningful for root scroll frames.
   bool mScaleToResolution:1;
 
+  // True if the APZ is in the process of async-transforming this scrollframe,
+  // (as best as we can tell on the main thread, anyway).
+  bool mTransformingByAPZ:1;
+
 protected:
   /**
    * @note This method might destroy the frame, pres shell and other objects.
@@ -812,6 +823,13 @@ public:
   virtual void ScrollbarActivityStarted() const MOZ_OVERRIDE;
   virtual void ScrollbarActivityStopped() const MOZ_OVERRIDE;
 
+  virtual void SetTransformingByAPZ(bool aTransforming) MOZ_OVERRIDE {
+    mHelper.SetTransformingByAPZ(aTransforming);
+  }
+  bool IsTransformingByAPZ() const MOZ_OVERRIDE {
+    return mHelper.IsTransformingByAPZ();
+  }
+  
 #ifdef DEBUG_FRAME_DUMP
   virtual nsresult GetFrameName(nsAString& aResult) const MOZ_OVERRIDE;
 #endif
@@ -1181,6 +1199,13 @@ public:
   virtual void ScrollbarActivityStarted() const MOZ_OVERRIDE;
   virtual void ScrollbarActivityStopped() const MOZ_OVERRIDE;
 
+  virtual void SetTransformingByAPZ(bool aTransforming) MOZ_OVERRIDE {
+    mHelper.SetTransformingByAPZ(aTransforming);
+  }
+  bool IsTransformingByAPZ() const MOZ_OVERRIDE {
+    return mHelper.IsTransformingByAPZ();
+  }
+
 #ifdef DEBUG_FRAME_DUMP
   virtual nsresult GetFrameName(nsAString& aResult) const MOZ_OVERRIDE;
 #endif

layout/generic/nsIScrollableFrame.h

@@ -397,6 +397,9 @@ public:
    * Mark the scrollbar frames for reflow.
    */
   virtual void MarkScrollbarsDirtyForReflow() const = 0;
+
+  virtual void SetTransformingByAPZ(bool aTransforming) = 0;
+  virtual bool IsTransformingByAPZ() const = 0;
 };
 
 #endif