Clear scrollbar damages in time

Source/core/rendering/RenderBox.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2005 Allan Sandfeld Jensen (kde@carewolf.com)
  *           (C) 2005, 2006 Samuel Weinig (sam.weinig@gmail.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2013 Adobe Systems Incorporated. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ skipping 1585 matching lines @@
     if (!RenderObject::invalidatePaintIfNeeded(newPaintInvalidationContainer, oldPaintInvalidationRect, oldPositionFromPaintInvalidationContainer, paintInvalidationState))
         invalidatePaintForOverflowIfNeeded();
 
     // Issue paint invalidations for any scrollbars if there is a scrollable area for this renderer.
     if (enclosingLayer()) {
         if (RenderLayerScrollableArea* area = enclosingLayer()->scrollableArea()) {
             if (area->hasVerticalBarDamage())
                 invalidatePaintRectangle(area->verticalBarDamage());
             if (area->hasHorizontalBarDamage())
                 invalidatePaintRectangle(area->horizontalBarDamage());
-            area->resetScrollbarDamage();
         }
     }
 }
 
+void RenderBox::clearPaintInvalidationState()
+{
+    RenderBoxModelObject::clearPaintInvalidationState();
+
+    if (enclosingLayer()) {

[Julien - ping for review, 2014/08/01 18:13:45]

I missed this in our current code: we will end up invalidating / clearing the
same scrollbars several times as enclosingLayer can return the same RenderLayer
in a subtree.

It also potentially makes this algorithm supra-linear as we walk up the tree :-(

[Xianzhu, 2014/08/01 18:20:01]

Thanks for catching this. I think we should use hasLayer() here. Will try.

+        if (RenderLayerScrollableArea* area = enclosingLayer()->scrollableArea())
+            area->resetScrollbarDamage();
+    }
+}
+
+#if ENABLE(ASSERT)
+bool RenderBox::paintInvalidationStateIsDirty() const
+{
+    if (enclosingLayer()) {
+        if (RenderLayerScrollableArea* area = enclosingLayer()->scrollableArea()) {
+            if (area->hasVerticalBarDamage() || area->hasHorizontalBarDamage())
+                return true;
+        }
+    }
+    return RenderBoxModelObject::paintInvalidationStateIsDirty();
+}
+#endif
+
 bool RenderBox::pushContentsClip(PaintInfo& paintInfo, const LayoutPoint& accumulatedOffset, ContentsClipBehavior contentsClipBehavior)
 {
     if (paintInfo.phase == PaintPhaseBlockBackground || paintInfo.phase == PaintPhaseSelfOutline || paintInfo.phase == PaintPhaseMask)
         return false;
 
     bool isControlClip = hasControlClip();
     bool isOverflowClip = hasOverflowClip() && !layer()->isSelfPaintingLayer();
 
     if (!isControlClip && !isOverflowClip)
         return false;
@@ skipping 3058 matching lines @@
 RenderBox::BoxDecorationData::BoxDecorationData(const RenderStyle& style)
 {
     backgroundColor = style.visitedDependentColor(CSSPropertyBackgroundColor);
     hasBackground = backgroundColor.alpha() || style.hasBackgroundImage();
     ASSERT(hasBackground == style.hasBackground());
     hasBorder = style.hasBorder();
     hasAppearance = style.hasAppearance();
 }
 
 } // namespace blink