optimizing layout performance when only transform3d matrix changed by

Source/core/rendering/RenderObject.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  *           (C) 2004 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2009 Google Inc. All rights reserved.
  * Copyright (C) 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 1808 matching lines @@
         // FIXME: when transforms are taken into account for overflow, we will need to do a layout.
         if (!isText() && (!hasLayer() || !toRenderLayerModelObject(this)->layer()->hasDirectReasonsForCompositing())) {
             // We need to set at least SimplifiedLayout, but if PositionedMovementOnly is already set
             // then we actually need SimplifiedLayoutAndPositionedMovement.
             if (!hasLayer())
                 diff = StyleDifferenceLayout; // FIXME: Do this for now since SimplifiedLayout cannot handle updating floating objects lists.
             else if (diff < StyleDifferenceLayoutPositionedMovementOnly)
                 diff = StyleDifferenceSimplifiedLayout;
             else if (diff < StyleDifferenceSimplifiedLayout)
                 diff = StyleDifferenceSimplifiedLayoutAndPositionedMovement;
-        } else if (diff < StyleDifferenceRecompositeLayer)
-            diff = StyleDifferenceRecompositeLayer;
+        } else if (diff < StyleDifferenceRecompositeLayer) {
+            if (diff <= StyleDifferenceRecompositeLayer && (contextSensitiveProperties & ContextSensitivePropertyTransform3D))
+                diff = StyleDifferenceMinRecompositeLayer;
+        }
+
     }
 
     // If opacity or filters changed, and the layer does not paint into its own separate backing, then we need to repaint (also
     // ignoring text nodes)
     if (contextSensitiveProperties & ContextSensitivePropertyOpacity && diff <= StyleDifferenceRepaintLayer) {
         if (!isText() && (!hasLayer() || !toRenderLayerModelObject(this)->layer()->hasDirectReasonsForCompositing()))
             diff = StyleDifferenceRepaintLayer;
         else if (diff < StyleDifferenceRecompositeLayer)
-            diff = StyleDifferenceRecompositeLayer;
+            diff = StyleDifferenceMinRecompositeLayer;
     }
 
     if ((contextSensitiveProperties & ContextSensitivePropertyFilter) && hasLayer() && diff <= StyleDifferenceRepaintLayer) {
         RenderLayer* layer = toRenderLayerModelObject(this)->layer();
         if (!layer->hasDirectReasonsForCompositing() || layer->paintsWithFilters())
             diff = StyleDifferenceRepaintLayer;
         else if (diff < StyleDifferenceRecompositeLayer)
             diff = StyleDifferenceRecompositeLayer;
     }
 
@@ skipping 109 matching lines @@
         if (updatedDiff == StyleDifferenceLayout)
             setNeedsLayoutAndPrefWidthsRecalc();
         else if (updatedDiff == StyleDifferenceLayoutPositionedMovementOnly)
             setNeedsPositionedMovementLayout();
         else if (updatedDiff == StyleDifferenceSimplifiedLayoutAndPositionedMovement) {
             setNeedsPositionedMovementLayout();
             setNeedsSimplifiedNormalFlowLayout();
         } else if (updatedDiff == StyleDifferenceSimplifiedLayout)
             setNeedsSimplifiedNormalFlowLayout();
     }
+    if (updatedDiff > StyleDifferenceMinRecompositeLayer) {
+        TRACE_EVENT0("webkit", "setCompleteCompositing");
+        // trigger complete compositing
+        document().setFastCompositing(false);
+    }
 
     if (updatedDiff == StyleDifferenceRepaintLayer || shouldRepaintForStyleDifference(updatedDiff)) {
         // Do a repaint with the new style now, e.g., for example if we go from
         // not having an outline to having an outline.
         repaint();
     }
 }
 
 static inline bool rendererHasBackground(const RenderObject* renderer)
 {
@@ skipping 1373 matching lines @@
 {
     if (object1) {
         const WebCore::RenderObject* root = object1;
         while (root->parent())
             root = root->parent();
         root->showRenderTreeAndMark(object1, "*", object2, "-", 0);
     }
 }
 
 #endif