Force subtree paint property updates on local border box changes

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 106 matching lines @@
   // because some properties inherit from the containing block chain instead of
   // the painting parent and cannot be derived in O(1) during the paint walk.
   // For example, <div style='opacity: 0.3; position: relative; margin: 11px;'/>
   // would have a paint offset of (11px, 11px) and propertyTreeState.effect()
   // would be an effect node with opacity of 0.3 which was created by the div
   // itself. Note that propertyTreeState.transform() would not be null but would
   // instead point to the transform space setup by div's ancestors.
   const PropertyTreeStateWithOffset* localBorderBoxProperties() const {
     return m_localBorderBoxProperties.get();
   }
-  void updateLocalBorderBoxProperties(
-      LayoutPoint& paintOffset,
-      const TransformPaintPropertyNode* transform,
-      const ClipPaintPropertyNode* clip,
-      const EffectPaintPropertyNode* effect,
-      const ScrollPaintPropertyNode* scroll) {
-    if (m_localBorderBoxProperties) {
-      m_localBorderBoxProperties->paintOffset = paintOffset;
-      m_localBorderBoxProperties->propertyTreeState.setTransform(transform);
-      m_localBorderBoxProperties->propertyTreeState.setClip(clip);
-      m_localBorderBoxProperties->propertyTreeState.setEffect(effect);
-      m_localBorderBoxProperties->propertyTreeState.setScroll(scroll);
-    } else {
+  // True if local border box changes, false otherwise.
+  bool updateLocalBorderBoxProperties(LayoutPoint& paintOffset,
+                                      const TransformPaintPropertyNode* xform,
+                                      const ClipPaintPropertyNode* clip,
+                                      const EffectPaintPropertyNode* effect,
+                                      const ScrollPaintPropertyNode* scroll) {
+    if (!m_localBorderBoxProperties) {
       m_localBorderBoxProperties = WTF::wrapUnique(
           new ObjectPaintProperties::PropertyTreeStateWithOffset(
-              paintOffset, PropertyTreeState(transform, clip, effect, scroll)));
+              paintOffset, PropertyTreeState(xform, clip, effect, scroll)));
+      return true;
     }
+    bool changed = false;
+    if (m_localBorderBoxProperties->paintOffset != paintOffset) {
+      m_localBorderBoxProperties->paintOffset = paintOffset;

[Xianzhu, 2016/12/15 19:46:28]

What's the relationship between this check of paint offset change and the check
in PrePaintTreeWalk of paint offset change? Why doesn't the latter need paint
property update of subtree?

+      changed = true;
+    }
+    if (m_localBorderBoxProperties->propertyTreeState.transform() != xform) {
+      m_localBorderBoxProperties->propertyTreeState.setTransform(xform);
+      changed = true;
+    }
+    if (m_localBorderBoxProperties->propertyTreeState.clip() != clip) {
+      m_localBorderBoxProperties->propertyTreeState.setClip(clip);
+      changed = true;
+    }
+    if (m_localBorderBoxProperties->propertyTreeState.effect() != effect) {
+      m_localBorderBoxProperties->propertyTreeState.setEffect(effect);
+      changed = true;
+    }
+    if (m_localBorderBoxProperties->propertyTreeState.scroll() != scroll) {
+      m_localBorderBoxProperties->propertyTreeState.setScroll(scroll);
+      changed = true;
+    }
+    return changed;
   }
-  void clearLocalBorderBoxProperties() { m_localBorderBoxProperties = nullptr; }
+  // True if an existing property was deleted, false otherwise.
+  bool clearLocalBorderBoxProperties() {
+    if (m_localBorderBoxProperties) {
+      m_localBorderBoxProperties = nullptr;
+      return true;
+    }
+    return false;
+  }
 
   // This is the complete set of property nodes and paint offset that can be
   // used to paint the contents of this object. It is similar to
   // localBorderBoxProperties but includes properties (e.g., overflow clip,
   // scroll translation) that apply to contents. This is suitable for paint
   // invalidation.
   ObjectPaintProperties::PropertyTreeStateWithOffset contentsProperties() const;
 
   // True if an existing property was deleted, false otherwise.
   bool clearPaintOffsetTranslation() { return clear(m_paintOffsetTranslation); }
@@ skipping 168 matching lines @@
   RefPtr<TransformPaintPropertyNode> m_scrollTranslation;
   RefPtr<TransformPaintPropertyNode> m_scrollbarPaintOffset;
   RefPtr<ScrollPaintPropertyNode> m_scroll;
 
   std::unique_ptr<PropertyTreeStateWithOffset> m_localBorderBoxProperties;
 };
 
 }  // namespace blink
 
 #endif  // ObjectPaintProperties_h