Define contentsProperties on ObjectPaintProperties, for use in paint invalidation.

third_party/WebKit/Source/core/paint/ObjectPaintProperties.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 ObjectPaintProperties_h
 #define ObjectPaintProperties_h
 
 #include "core/CoreExport.h"
 #include "platform/geometry/LayoutPoint.h"
 #include "platform/graphics/paint/ClipPaintPropertyNode.h"
@@ skipping 59 matching lines @@
     // not painting parent, thus can't be derived in O(1) during paint walk.
     // Note: If this layout object has transform or stacking-context effects, those are already
     // baked into in the context here. However for properties that affects only children,
     // for example, perspective and overflow clip, those should be applied by the painter
     // at the right painting step.
     struct LocalBorderBoxProperties {
         LayoutPoint paintOffset;
         PropertyTreeState propertyTreeState;
     };
     const LocalBorderBoxProperties* localBorderBoxProperties() const { return m_localBorderBoxProperties.get(); }
+    // ContentsProperties is the PropertyTreeState state that is the same as in localBorderBoxProperties, except that it is inside
+    // any clips and scrolls caused by this object. This PropertyTreeState is suitable as the destination for paint invalidation.
+    const PropertyTreeState* contentsProperties() const { return m_contentsProperties.get(); }
 
     void clearPaintOffsetTranslation() { m_paintOffsetTranslation = nullptr; }
     void clearTransform() { m_transform = nullptr; }
     void clearEffect() { m_effect = nullptr; }
     void clearCssClip() { m_cssClip = nullptr; }
     void clearCssClipFixedPosition() { m_cssClipFixedPosition = nullptr; }
     void clearOverflowClip() { m_overflowClip = nullptr; }
     void clearPerspective() { m_perspective = nullptr; }
     void clearSvgLocalToBorderBoxTransform() { m_svgLocalToBorderBoxTransform = nullptr; }
     void clearScrollTranslation() { m_scrollTranslation = nullptr; }
@@ skipping 12 matching lines @@
         DCHECK(!svgLocalToBorderBoxTransform()) << "SVG elements cannot scroll so there should never be both a scroll translation and an SVG local to border box transform.";
         return createOrUpdateProperty(m_scrollTranslation, std::forward<Args>(args)...);
     }
     template <typename... Args> TransformPaintPropertyNode* createOrUpdateScrollbarPaintOffset(Args&&... args) { return createOrUpdateProperty(m_scrollbarPaintOffset, std::forward<Args>(args)...); }
     template <typename... Args> EffectPaintPropertyNode* createOrUpdateEffect(Args&&... args) { return createOrUpdateProperty(m_effect, std::forward<Args>(args)...); }
     template <typename... Args> ClipPaintPropertyNode* createOrUpdateCssClip(Args&&... args) { return createOrUpdateProperty(m_cssClip, std::forward<Args>(args)...); }
     template <typename... Args> ClipPaintPropertyNode* createOrUpdateCssClipFixedPosition(Args&&... args) { return createOrUpdateProperty(m_cssClipFixedPosition, std::forward<Args>(args)...); }
     template <typename... Args> ClipPaintPropertyNode* createOrUpdateOverflowClip(Args&&... args) { return createOrUpdateProperty(m_overflowClip, std::forward<Args>(args)...); }
 
     void setLocalBorderBoxProperties(std::unique_ptr<LocalBorderBoxProperties> properties) { m_localBorderBoxProperties = std::move(properties); }
+    void setContentsProperties(std::unique_ptr<PropertyTreeState> properties) { m_contentsProperties = std::move(properties); }
 
 private:
     ObjectPaintProperties() { }
 
     template <typename PaintPropertyNode, typename... Args>
     PaintPropertyNode* createOrUpdateProperty(RefPtr<PaintPropertyNode>& field, Args&&... args)
     {
         if (field)
             field->update(std::forward<Args>(args)...);
         else
             field = PaintPropertyNode::create(std::forward<Args>(args)...);
         return field.get();
     }
 
     RefPtr<TransformPaintPropertyNode> m_paintOffsetTranslation;
     RefPtr<TransformPaintPropertyNode> m_transform;
     RefPtr<EffectPaintPropertyNode> m_effect;
     RefPtr<ClipPaintPropertyNode> m_cssClip;
     RefPtr<ClipPaintPropertyNode> m_cssClipFixedPosition;
     RefPtr<ClipPaintPropertyNode> m_overflowClip;
     RefPtr<TransformPaintPropertyNode> m_perspective;
     // TODO(pdr): Only LayoutSVGRoot needs this and it should be moved there.
     RefPtr<TransformPaintPropertyNode> m_svgLocalToBorderBoxTransform;
     RefPtr<TransformPaintPropertyNode> m_scrollTranslation;
     RefPtr<TransformPaintPropertyNode> m_scrollbarPaintOffset;
 
     std::unique_ptr<LocalBorderBoxProperties> m_localBorderBoxProperties;
+    std::unique_ptr<PropertyTreeState> m_contentsProperties;

[pdr., 2016/08/31 04:48:52]

Instead of caching such a large object, could we compute this dynamically in
O(1) using LocalBorderBoxProperties and the nodes on ObjectPaintProperties?

[szager1, 2016/08/31 16:31:22]

+1, I don't think it should be stored; it should be generated dynamically on
each call to contentsProperties().

[chrishtr, 2016/08/31 17:43:30]

Yes. I think you could say the same for localBorderBoxProperties. I can change
one or both. Why was it cached for the other one? Is it anticipated to be used
often?

 };
 
 } // namespace blink
 
 #endif // ObjectPaintProperties_h