Improve performance of GeometryMapper cache.

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/graphics/paint/FloatClipRect.h"
 #include "platform/graphics/paint/PropertyTreeState.h"
 #include "platform/transforms/TransformationMatrix.h"
@@ skipping 138 matching lines @@
       const FloatRect&,
       const TransformPaintPropertyNode* localTransformNode,
       const TransformPaintPropertyNode* ancestorTransformNode,
       bool& success);
 
   const TransformationMatrix& localToAncestorMatrixInternal(
       const TransformPaintPropertyNode* localTransformNode,
       const TransformPaintPropertyNode* ancestorTransformNode,
       bool& success);
 
-  FloatClipRect localToAncestorClipRectInternal(
+  const FloatClipRect& localToAncestorClipRectInternal(
       const ClipPaintPropertyNode* descendant,
       const ClipPaintPropertyNode* ancestorClip,
       const TransformPaintPropertyNode* ancestorTransform,
       bool& success);
 
   FloatClipRect sourceToDestinationClipRectInternal(
       const PropertyTreeState& sourceState,
       const PropertyTreeState& destinationState,
       bool& success);
 
   FloatClipRect slowLocalToAncestorVisualRectWithEffects(
       const FloatRect&,
       const PropertyTreeState& localState,
       const PropertyTreeState& ancestorState,
       bool& success);
 
-  // Maps from a transform node that is a descendant of the implied ancestor
-  // transform node to the combined transform between the descendant's and the
-  // ancestor's coordinate space.
-  // The "implied ancestor" is the key of the m_transformCache object for which
-  // this TransformCache is a value.
-  using TransformCache =
-      HashMap<const TransformPaintPropertyNode*, TransformationMatrix>;
-
-  // Returns the transform cache for the given ancestor transform node.
-  TransformCache& getTransformCache(const TransformPaintPropertyNode* ancestor);
-
-  // Maps from a descendant clip node to its equivalent "clip visual rect" in
-  // the local transform space of the implied ancestor clip node. 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. If one of the clips that contributes to it
-  // has a border radius, the hasRadius() field is set to true.
-  // The "implied ancestor" is the key of the TransformToClip cachefor which
-  // this ClipCache is a value.
-  using ClipCache = HashMap<const ClipPaintPropertyNode*, FloatClipRect>;
-
-  using TransformToClip =
-      HashMap<const TransformPaintPropertyNode*, std::unique_ptr<ClipCache>>;
-
-  // Returns the clip cache for the given transform space relative to the
-  // given ancestor clip node.
-  ClipCache& getClipCache(const ClipPaintPropertyNode* ancestorClip,
-                          const TransformPaintPropertyNode* ancestorTransform);
-
   friend class GeometryMapperTest;
   friend class PaintLayerClipperTest;
 
-  HashMap<const TransformPaintPropertyNode*, std::unique_ptr<TransformCache>>
-      m_transformCache;
-  HashMap<const ClipPaintPropertyNode*, std::unique_ptr<TransformToClip>>
-      m_clipCache;
-
   const TransformationMatrix m_identity;
+  const FloatClipRect m_infiniteClip;

[pdr., 2017/03/08 02:34:55]

I still don't understand this. Is it needed?

[chrishtr, 2017/03/08 02:59:28]

Yes. Since localToAncestorClipRectInternal now returns a reference instead of
a value, there needs to always be a non-local object to take the reference of.
This variable is the return value when there is no cached clip to return
(e.g. for mapping a clip to itself, or if it fails to find an ancestor).

 
   DISALLOW_COPY_AND_ASSIGN(GeometryMapper);
 };
 
 }  // namespace blink
 
 #endif  // GeometryMapper_h