Reuse existing paint property node is possible

third_party/WebKit/Source/core/paint/PaintPropertyTreeBuilder.h

 // Copyright 2015 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 PaintPropertyTreeBuilder_h
 #define PaintPropertyTreeBuilder_h
 
 #include "platform/geometry/LayoutPoint.h"
 #include "platform/graphics/paint/ClipPaintPropertyNode.h"
 #include "platform/graphics/paint/EffectPaintPropertyNode.h"
 #include "platform/graphics/paint/TransformPaintPropertyNode.h"
 #include "wtf/RefPtr.h"
 
 namespace blink {
 
 class FrameView;
 class LayoutObject;
+class ObjectPaintProperties;
 
 // The context for PaintPropertyTreeBuilder.
 // It's responsible for bookkeeping tree state in other order, for example, the most recent
 // position container seen.
 struct PaintPropertyTreeBuilderContext {
     // State that propagates on the containing block chain (and so is adjusted
     // when an absolute or fixed position object is encountered).
     struct ContainingBlockContext {
         // The combination of a transform and paint offset describes a linear space.
         // When a layout object recur to its children, the main context is expected to refer
@@ skipping 32 matching lines @@
 // Special things include but not limit to: overflow clip, transform, fixed-pos, animation,
 // mask, filter, ... etc.
 // It expects to be invoked for each layout tree node in DOM order during InPrePaint phase.
 class PaintPropertyTreeBuilder {
 public:
     void buildTreeRootNodes(FrameView&, PaintPropertyTreeBuilderContext&);
     void buildTreeNodes(FrameView&, PaintPropertyTreeBuilderContext&);
     void buildTreeNodes(const LayoutObject&, PaintPropertyTreeBuilderContext&);
 
 private:
+    // Common logic to update a paint property. It tries to reuse the existing paint property node of
+    // the object if the value is not changed. Returns the existing or newly created paint property node,
+    // or nullptr if no paint property node is needed.
+    // It requires a ComputeProperty function which computes the paint property node value if needed and
+    // returns true, or returns false if no paint property node value is needed.
+    template <
+        typename PropertyNode,
+        PropertyNode* (ObjectPaintProperties::*Getter)() const,
+        void (ObjectPaintProperties::*Setter)(PassRefPtr<PropertyNode>),
+        bool (*ComputeProperty)(const LayoutObject&, PaintPropertyTreeBuilderContext&, typename PropertyNode::Value&)>
+    static PropertyNode* updateObjectPaintProperty(const LayoutObject&, PaintPropertyTreeBuilderContext&, PropertyNode*& contextProperty);
+
+    static bool computePaintOffsetTranslation(const LayoutObject&, PaintPropertyTreeBuilderContext&, TransformPaintPropertyNode::Value&);
     static void updatePaintOffsetTranslation(const LayoutObject&, PaintPropertyTreeBuilderContext&);
+
+    static bool computeTransform(const LayoutObject&, PaintPropertyTreeBuilderContext&, TransformPaintPropertyNode::Value&);
     static void updateTransform(const LayoutObject&, PaintPropertyTreeBuilderContext&);
+
+    static bool computeEffect(const LayoutObject&, PaintPropertyTreeBuilderContext&, EffectPaintPropertyNode::Value&);
     static void updateEffect(const LayoutObject&, PaintPropertyTreeBuilderContext&);
+
+    static bool computeCssClip(const LayoutObject&, PaintPropertyTreeBuilderContext&, ClipPaintPropertyNode::Value&);
     static void updateCssClip(const LayoutObject&, PaintPropertyTreeBuilderContext&);
+
     static void updateLocalBorderBoxContext(const LayoutObject&, const PaintPropertyTreeBuilderContext&);
+
+    static bool computeScrollbarPaintOffset(const LayoutObject&, const PaintPropertyTreeBuilderContext&, TransformPaintPropertyNode::Value&);
     static void updateScrollbarPaintOffset(const LayoutObject&, const PaintPropertyTreeBuilderContext&);
+
+    static bool computeOverflowClip(const LayoutObject&, PaintPropertyTreeBuilderContext&, ClipPaintPropertyNode::Value&);
     static void updateOverflowClip(const LayoutObject&, PaintPropertyTreeBuilderContext&);
+
+    static bool computePerspective(const LayoutObject&, PaintPropertyTreeBuilderContext&, TransformPaintPropertyNode::Value&);
     static void updatePerspective(const LayoutObject&, PaintPropertyTreeBuilderContext&);
+
+    static bool computeSvgLocalToBorderBoxTransform(const LayoutObject&, PaintPropertyTreeBuilderContext&, TransformPaintPropertyNode::Value&);
     static void updateSvgLocalToBorderBoxTransform(const LayoutObject&, PaintPropertyTreeBuilderContext&);
+
+    static bool computeScrollTranslation(const LayoutObject&, PaintPropertyTreeBuilderContext&, TransformPaintPropertyNode::Value&);
     static void updateScrollTranslation(const LayoutObject&, PaintPropertyTreeBuilderContext&);
+
+    static bool computeOutOfFlowContext(const LayoutObject&, PaintPropertyTreeBuilderContext&, ClipPaintPropertyNode::Value&);
     static void updateOutOfFlowContext(const LayoutObject&, PaintPropertyTreeBuilderContext&);
 };
 
 } // namespace blink
 
 #endif // PaintPropertyTreeBuilder_h