Fix clip caching bug in GeometryMapper.

third_party/WebKit/Source/platform/graphics/paint/GeometryMapper.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef GeometryMapper_h
 #define GeometryMapper_h
 
 #include "platform/geometry/FloatRect.h"
 #include "platform/graphics/paint/PropertyTreeState.h"
 #include "platform/transforms/TransformationMatrix.h"
 #include "wtf/HashMap.h"
 
 namespace blink {
 
+// Maps from a descendant clip node to its equivalent "clip visual rect" in
+// the space of the ancestor. The clip visual rect is defined as the
+// intersection of all clips between the descendant and the ancestor (*not*
+// including the ancestor) in the clip tree, individually transformed from
+// their localTransformSpace into the ancestor's localTransformSpace.
+typedef HashMap<const ClipPaintPropertyNode*, FloatRect> ClipCache;
+
+// Maps from a transform node that is a descendant of the ancestor to the
+// combined transform between the descendant's and the ancestor's coordinate
+typedef HashMap<const TransformPaintPropertyNode*, TransformationMatrix>
+    TransformCache;
+
 struct PrecomputedDataForAncestor {
-  // Maps from a transform node that is a descendant of the ancestor to the
-  // combined transform between the descendant's and the ancestor's coordinate
-  // space.
-  HashMap<const TransformPaintPropertyNode*, TransformationMatrix>
-      toAncestorTransforms;
+  TransformCache toAncestorTransforms;
 
-  // Maps from a descendant clip node to its equivalent "clip visual rect" in
-  // the space of the ancestor. The clip visual rect is defined as the
-  // intersection of all clips between the descendant and the ancestor (*not*
-  // including the ancestor) in the clip tree, individually transformed from
-  // their localTransformSpace into the ancestor's localTransformSpace.
-  HashMap<const ClipPaintPropertyNode*, FloatRect> toAncestorClipRects;
+  // There can be multiple clips within the same transform space. This
+  // maps from the desired destination clip within the same transform
+  // space to its corresponding ClipCache.
+  HashMap<const ClipPaintPropertyNode*, std::unique_ptr<ClipCache>>
+      precomputedClips;
 
   static std::unique_ptr<PrecomputedDataForAncestor> create() {
     return WTF::makeUnique<PrecomputedDataForAncestor>();
   }
 };

[Xianzhu, 2017/02/05 02:03:45]

Nit: Move the above types into private section of Geometry?

 
 // GeometryMapper is a helper class for fast computations of transformed and
 // visual rects in different PropertyTreeStates. The design document has a
 // number of details on use cases, algorithmic definitions, and running times.
 //
 // NOTE: A GeometryMapper object is only valid for property trees that do not
 // change. If any mutation occurs, a new GeometryMapper object must be allocated
 // corresponding to the new state.
 //
 // Design document: http://bit.ly/28P4FDA
@@ skipping 123 matching lines @@
   FloatRect localToAncestorClipRectInternal(
       const PropertyTreeState& localTransformState,
       const PropertyTreeState& ancestorState,
       bool& success);
 
   // Returns the precomputed data if already set, or adds and memoizes a new
   // PrecomputedDataForAncestor otherwise.
   PrecomputedDataForAncestor& getPrecomputedDataForAncestor(
       const TransformPaintPropertyNode*);
 
+  // Returns the transform cache for the given ancestor transform node.
+  TransformCache& getTransformCache(const TransformPaintPropertyNode*);
+
+  // Returns the clip cache for the given ancestor clip node.
+  ClipCache& getClipCache(const TransformPaintPropertyNode*,
+                          const ClipPaintPropertyNode*);
+
   friend class GeometryMapperTest;
   friend class PaintLayerClipperTest;
 
   HashMap<const TransformPaintPropertyNode*,
           std::unique_ptr<PrecomputedDataForAncestor>>
       m_data;
 
   const TransformationMatrix m_identity;
 
   DISALLOW_COPY_AND_ASSIGN(GeometryMapper);
 };
 
 }  // namespace blink
 
 #endif  // GeometryMapper_h