Bug 1284586 - Disable paint-skipping for scrollframes that we detect as having a CSS-clipped descendant. r=mstange

MozReview-Commit-ID: AvjokFZMwdd

layout/base/DisplayListClipState.cpp

@@ -35,6 +35,24 @@ DisplayListClipState::GetCurrentCombinedClip(nsDisplayListBuilder* aBuilder)
   return mCurrentCombinedClip;
 }
 
+void
+DisplayListClipState::SetScrollClipForContainingBlockDescendants(
+    nsDisplayListBuilder* aBuilder,
+    const DisplayItemScrollClip* aScrollClip)
+{
+  if (aBuilder->IsPaintingToWindow() &&
+      mClipContentDescendants &&
+      aScrollClip != mScrollClipContainingBlockDescendants &&
+      !DisplayItemScrollClip::IsAncestor(mClipContentDescendantsScrollClip, aScrollClip)) {
+    if (mClipContentDescendantsScrollClip && mClipContentDescendantsScrollClip->mScrollableFrame) {
+      mClipContentDescendantsScrollClip->mScrollableFrame->SetScrollsClipOnUnscrolledOutOfFlow();
+    }
+    mClipContentDescendantsScrollClip = nullptr;
+  }
+  mScrollClipContainingBlockDescendants = aScrollClip;
+  mStackingContextAncestorSC = DisplayItemScrollClip::PickAncestor(mStackingContextAncestorSC, aScrollClip);
+}
+
 void
 DisplayListClipState::ClipContainingBlockDescendants(const nsRect& aRect,
                                                      const nscoord* aRadii,
@@ -49,6 +67,7 @@ DisplayListClipState::ClipContainingBlockDescendants(const nsRect& aRect,
     aClipOnStack.IntersectWith(*mClipContainingBlockDescendants);
   }
   mClipContainingBlockDescendants = &aClipOnStack;
+  mClipContentDescendantsScrollClip = GetCurrentInnermostScrollClip();
   mCurrentCombinedClip = nullptr;
 }
 

layout/base/DisplayListClipState.h

@@ -29,6 +29,7 @@ public:
     , mCurrentCombinedClip(nullptr)
     , mScrollClipContentDescendants(nullptr)
     , mScrollClipContainingBlockDescendants(nullptr)
+    , mClipContentDescendantsScrollClip(nullptr)
     , mStackingContextAncestorSC(nullptr)
   {}
 
@@ -74,11 +75,8 @@ private:
     mCurrentCombinedClip = nullptr;
   }
 
-  void SetScrollClipForContainingBlockDescendants(const DisplayItemScrollClip* aScrollClip)
-  {
-    mScrollClipContainingBlockDescendants = aScrollClip;
-    mStackingContextAncestorSC = DisplayItemScrollClip::PickAncestor(mStackingContextAncestorSC, aScrollClip);
-  }
+  void SetScrollClipForContainingBlockDescendants(nsDisplayListBuilder* aBuilder,
+                                                  const DisplayItemScrollClip* aScrollClip);
 
   void Clear()
   {
@@ -183,6 +181,11 @@ private:
   const DisplayItemScrollClip* mScrollClipContentDescendants;
   const DisplayItemScrollClip* mScrollClipContainingBlockDescendants;
 
+  /**
+   * The scroll clip that was in effect when mClipContentDescendants was set.
+   */
+  const DisplayItemScrollClip* mClipContentDescendantsScrollClip;
+
   /**
    * A scroll clip that is an ancestor of all the scroll clips that were
    * "current" on this clip state since EnterStackingContextContents was
@@ -431,9 +434,10 @@ public:
     mState.SetClipForContainingBlockDescendants(aClip);
   }
 
-  void SetScrollClipForContainingBlockDescendants(const DisplayItemScrollClip* aScrollClip)
+  void SetScrollClipForContainingBlockDescendants(nsDisplayListBuilder* aBuilder,
+                                                  const DisplayItemScrollClip* aScrollClip)
   {
-    mState.SetScrollClipForContainingBlockDescendants(aScrollClip);
+    mState.SetScrollClipForContainingBlockDescendants(aBuilder, aScrollClip);
   }
 
   /**

layout/generic/nsFrame.cpp

@@ -2803,7 +2803,7 @@ nsIFrame::BuildDisplayListForChild(nsDisplayListBuilder*   aBuilder,
 
     clipState.SetClipForContainingBlockDescendants(
       &savedOutOfFlowData->mContainingBlockClip);
-    clipState.SetScrollClipForContainingBlockDescendants(
+    clipState.SetScrollClipForContainingBlockDescendants(aBuilder,
       savedOutOfFlowData->mContainingBlockScrollClip);
   } else if (GetStateBits() & NS_FRAME_FORCE_DISPLAY_LIST_DESCEND_INTO &&
              isPlaceholder) {
@@ -2818,7 +2818,7 @@ nsIFrame::BuildDisplayListForChild(nsDisplayListBuilder*   aBuilder,
     // instead since we know we won't render anything, and the inner out-of-flow
     // frame will setup the correct clip for itself.
     clipState.SetClipForContainingBlockDescendants(nullptr);
-    clipState.SetScrollClipForContainingBlockDescendants(nullptr);
+    clipState.SetScrollClipForContainingBlockDescendants(aBuilder, nullptr);
   }
 
   // Setup clipping for the parent's overflow:-moz-hidden-unscrollable,

layout/generic/nsGfxScrollFrame.cpp

@@ -1891,6 +1891,7 @@ ScrollFrameHelper::ScrollFrameHelper(nsContainerFrame* aOuter,
   , mTransformingByAPZ(false)
   , mScrollableByAPZ(false)
   , mZoomableByAPZ(false)
+  , mScrollsClipOnUnscrolledOutOfFlow(false)
   , mVelocityQueue(aOuter->PresContext())
   , mAsyncScrollEvent(END_DOM)
 {
@@ -2118,6 +2119,12 @@ ScrollFrameHelper::HasPerspective() const
   return disp->mChildPerspective.GetUnit() != eStyleUnit_None;
 }
 
+void
+ScrollFrameHelper::SetScrollsClipOnUnscrolledOutOfFlow()
+{
+  mScrollsClipOnUnscrolledOutOfFlow = true;
+}
+
 void
 ScrollFrameHelper::ScrollToCSSPixels(const CSSIntPoint& aScrollPosition,
                                      nsIScrollableFrame::ScrollMode aMode)
@@ -2755,11 +2762,11 @@ ScrollFrameHelper::ScrollToImpl(nsPoint aPt, const nsRect& aRange, nsIAtom* aOri
       nsLayoutUtils::GetHighResolutionDisplayPort(content, &displayPort);
     displayPort.MoveBy(-mScrolledFrame->GetPosition());
 
-    PAINT_SKIP_LOG("New scrollpos %s usingDP %d dpEqual %d scrollableByApz %d plugins %d perspective %d\n",
+    PAINT_SKIP_LOG("New scrollpos %s usingDP %d dpEqual %d scrollableByApz %d plugins %d perspective %d clip %d\n",
         Stringify(CSSPoint::FromAppUnits(GetScrollPosition())).c_str(),
         usingDisplayPort, displayPort.IsEqualEdges(oldDisplayPort),
-        mScrollableByAPZ, HasPluginFrames(), HasPerspective());
-    if (usingDisplayPort && displayPort.IsEqualEdges(oldDisplayPort) && !HasPerspective()) {
+        mScrollableByAPZ, HasPluginFrames(), HasPerspective(), mScrollsClipOnUnscrolledOutOfFlow);
+    if (usingDisplayPort && displayPort.IsEqualEdges(oldDisplayPort) && !HasPerspective() && !mScrollsClipOnUnscrolledOutOfFlow) {
       bool haveScrollLinkedEffects = content->GetComposedDoc()->HasScrollLinkedEffect();
       bool apzDisabled = haveScrollLinkedEffects && gfxPrefs::APZDisableForScrollLinkedEffects();
       if (!apzDisabled) {

layout/generic/nsGfxScrollFrame.h

@@ -386,6 +386,7 @@ public:
   }
   void SetScrollableByAPZ(bool aScrollable);
   void SetZoomableByAPZ(bool aZoomable);
+  void SetScrollsClipOnUnscrolledOutOfFlow();
 
   bool UsesContainerScrolling() const;
 
@@ -581,6 +582,8 @@ public:
   // True if we don't want the scrollbar to repaint itself right now.
   bool mSuppressScrollbarRepaints:1;
 
+  bool mScrollsClipOnUnscrolledOutOfFlow:1;
+
   mozilla::layout::ScrollVelocityQueue mVelocityQueue;
 
 protected:
@@ -1006,6 +1009,9 @@ public:
   void SetZoomableByAPZ(bool aZoomable) override {
     mHelper.SetZoomableByAPZ(aZoomable);
   }
+  void SetScrollsClipOnUnscrolledOutOfFlow() override {
+    mHelper.SetScrollsClipOnUnscrolledOutOfFlow();
+  }
   
   ScrollSnapInfo GetScrollSnapInfo() const override {
     return mHelper.GetScrollSnapInfo();
@@ -1409,6 +1415,9 @@ public:
   void SetZoomableByAPZ(bool aZoomable) override {
     mHelper.SetZoomableByAPZ(aZoomable);
   }
+  void SetScrollsClipOnUnscrolledOutOfFlow() override {
+    mHelper.SetScrollsClipOnUnscrolledOutOfFlow();
+  }
   virtual bool DecideScrollableLayer(nsDisplayListBuilder* aBuilder,
                                      nsRect* aDirtyRect,
                                      bool aAllowCreateDisplayPort) override {

layout/generic/nsIScrollableFrame.h

@@ -464,6 +464,8 @@ public:
    * Returns information required to determine where to snap to after a scroll.
    */
   virtual ScrollSnapInfo GetScrollSnapInfo() const = 0;
+
+  virtual void SetScrollsClipOnUnscrolledOutOfFlow() = 0;
 };
 
 #endif

layout/generic/nsViewportFrame.cpp

@@ -107,7 +107,7 @@ BuildDisplayListForTopLayerFrame(nsDisplayListBuilder* aBuilder,
     clipState.SetClipForContainingBlockDescendants(
       &savedOutOfFlowData->mContainingBlockClip);
     clipState.SetScrollClipForContainingBlockDescendants(
-      savedOutOfFlowData->mContainingBlockScrollClip);
+      aBuilder, savedOutOfFlowData->mContainingBlockScrollClip);
   }
   nsDisplayList list;
   aFrame->BuildDisplayListForStackingContext(aBuilder, dirty, &list);