Combine LayoutObject::previousPaintOffset and paintOffset in paint properties

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

 // 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.
 
 #include "core/paint/PaintPropertyTreeBuilder.h"
 
 #include "core/dom/DOMNodeIds.h"
 #include "core/frame/FrameView.h"
 #include "core/frame/LocalFrame.h"
 #include "core/frame/Settings.h"
@@ skipping 551 matching lines @@
   if (properties && properties->cssClip())
     context.current.clip = properties->cssClip();
 }
 
 void PaintPropertyTreeBuilder::updateLocalBorderBoxContext(
     const LayoutObject& object,
     PaintPropertyTreeBuilderContext& context) {
   if (!object.needsPaintPropertyUpdate() && !context.forceSubtreeUpdate)
     return;
 
+  object.getMutableForPainting().setPaintOffset(context.current.paintOffset);
+
   // Avoid adding an ObjectPaintProperties for non-boxes to save memory, since
   // we don't need them at the moment.
   if (!object.isBox() && !object.hasLayer()) {
     if (auto* properties = object.getMutableForPainting().paintProperties())
       properties->clearLocalBorderBoxProperties();
   } else {
     auto& properties = object.getMutableForPainting().ensurePaintProperties();
     properties.updateLocalBorderBoxProperties(
-        context.current.paintOffset, context.current.transform,
-        context.current.clip, context.currentEffect, context.current.scroll);
+        context.current.transform, context.current.clip, context.currentEffect,
+        context.current.scroll);
   }
 }
 
 // TODO(trchen): Remove this once we bake the paint offset into frameRect.
 void PaintPropertyTreeBuilder::updateScrollbarPaintOffset(
     const LayoutObject& object,
     PaintPropertyTreeBuilderContext& context) {
   if (!object.needsPaintPropertyUpdate() && !context.forceSubtreeUpdate)
     return;
 
@@ skipping 281 matching lines @@
 // tree-walk order of "columns" -> spanner placeholder -> spanner -> absolute.
 // Here we rebuild a ContainingBlockContext based on the properties of
 // "relative" for "absolute".
 static void overrideContainingBlockContextFromRealContainingBlock(
     const LayoutBlock& containingBlock,
     PaintPropertyTreeBuilderContext::ContainingBlockContext& context) {
   const auto* properties =
       containingBlock.paintProperties()->localBorderBoxProperties();
   DCHECK(properties);
 
-  context.transform = properties->propertyTreeState.transform();
-  context.paintOffset = properties->paintOffset;
+  context.transform = properties->transform();
+  context.paintOffset = containingBlock.paintOffset();
   context.shouldFlattenInheritedTransform =
       context.transform && context.transform->flattensInheritedTransform();
   context.renderingContextId =
       context.transform ? context.transform->renderingContextId() : 0;
-  context.clip = properties->propertyTreeState.clip();
-  context.scroll = properties->propertyTreeState.scroll();
+  context.clip = properties->clip();
+  context.scroll = properties->scroll();
 }
 
 void PaintPropertyTreeBuilder::updateContextForBoxPosition(
     const LayoutObject& object,
     PaintPropertyTreeBuilderContext& context) {
   if (!object.isBoxModelObject())
     return;
 
   const LayoutBoxModelObject& boxModelObject = toLayoutBoxModelObject(object);
   switch (object.styleRef().position()) {
@@ skipping 65 matching lines @@
     if (boxModelObject.isTableCell()) {
       LayoutObject* parentRow = boxModelObject.parent();
       DCHECK(parentRow && parentRow->isTableRow());
       context.current.paintOffset.moveBy(
           -toLayoutBox(parentRow)->physicalLocation());
     }
   }
 
   // Many paint properties depend on paint offset so we force an update of
   // the entire subtree on paint offset changes.
-  if (object.previousPaintOffset() != context.current.paintOffset)
+  if (object.paintOffset() != context.current.paintOffset)
     context.forceSubtreeUpdate = true;
 }
 
 void PaintPropertyTreeBuilder::updatePropertiesForSelf(
     const LayoutObject& object,
     PaintPropertyTreeBuilderContext& context) {
-  if (!object.isBoxModelObject() && !object.isSVG())
+  if (!object.isBoxModelObject() && !object.isSVG()) {
+    object.getMutableForPainting().setPaintOffset(context.current.paintOffset);

[pdr., 2017/01/06 18:27:42]

Do we need to check that an update is needed too? For example:
if (!object.isBoxModelObject() && !object.isSVG()) {
  if (object.needsPaintPropertyUpdate() || context.forceSubtreeUpdate)
    object.getMutableForPainting().setPaintOffset(context.current.paintOffset);
}

Also, I think the checkNeedsUpdateScope should be moved above this
setPaintOffset call.

WDYT about unifying both setPaintOffset calls in this function? Something like:
void PaintPropertyTreeBuilder::updatePropertiesForSelf(...) {
    checkNeedsUpdateScope...
    if (object.isBoxModelObject() || object.isSVG()) {
      do updates here...
    }
    object.getMutableForPainting().setPaintOffset(context.current.paintOffset);
}

[Xianzhu, 2017/01/06 19:24:18]

Done.
Done.
Done.

     return;
+  }
 
 #if DCHECK_IS_ON()
   FindObjectPropertiesNeedingUpdateScope checkNeedsUpdateScope(object, context);
 #endif
 
   updatePaintOffsetTranslation(object, context);
   updateTransform(object, context);
   updateEffect(object, context);
   updateCssClip(object, context);
   updateLocalBorderBoxContext(object, context);
@@ skipping 13 matching lines @@
   updateOverflowClip(object, context);
   updatePerspective(object, context);
   updateSvgLocalToBorderBoxTransform(object, context);
   updateScrollAndScrollTranslation(object, context);
   updateOutOfFlowContext(object, context);
 
   context.forceSubtreeUpdate |= object.subtreeNeedsPaintPropertyUpdate();
 }
 
 }  // namespace blink