Combine LayoutObject::previousPaintOffset and paintOffset in paint properties

third_party/WebKit/Source/core/layout/LayoutObject.h

 /*
  * Copyright (C) 2000 Lars Knoll (knoll@kde.org)
  *           (C) 2000 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  *           (C) 2004 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2012 Apple Inc.
  *               All rights reserved.
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 1557 matching lines @@
   // container (*not* the graphics layer that paints this object).
   LayoutRect previousVisualRectIncludingCompositedScrolling(
       const LayoutBoxModelObject& paintInvalidationContainer) const;
 
   // The returned rect does *not* account for composited scrolling.
   const LayoutRect& previousVisualRect() const { return m_previousVisualRect; }
 
   // Called when the previous visual rect(s) is no longer valid.
   virtual void clearPreviousVisualRects();
 
-  const LayoutPoint& previousPaintOffset() const {
-    return m_previousPaintOffset;
-  }
+  const LayoutPoint& paintOffset() const { return m_paintOffset; }
 
   PaintInvalidationReason fullPaintInvalidationReason() const {
     return m_bitfields.fullPaintInvalidationReason();
   }
   bool shouldDoFullPaintInvalidation() const {
     return m_bitfields.fullPaintInvalidationReason() != PaintInvalidationNone;
   }
   void setShouldDoFullPaintInvalidation(
       PaintInvalidationReason = PaintInvalidationFull);
   void clearShouldDoFullPaintInvalidation() {
@@ skipping 78 matching lines @@
     void setShouldDoFullPaintInvalidation(PaintInvalidationReason reason) {
       m_layoutObject.setShouldDoFullPaintInvalidation(reason);
     }
     void setBackgroundChangedSinceLastPaintInvalidation() {
       m_layoutObject.setBackgroundChangedSinceLastPaintInvalidation();
     }
     void ensureIsReadyForPaintInvalidation() {
       m_layoutObject.ensureIsReadyForPaintInvalidation();
     }
 
+    // The following setters store the current values as calculated during the
+    // pre-paint tree walk. TODO(wangxianzhu): Add check of lifecycle states.

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

The TODO means I'm not sure for now if we can check the lifecycle state in all
methods, especially when we still support non-spinvalidation. I feel that we
could change MutableForPainting to MutableForPrePaint and check lifecycle state
in the constructor, but not sure either for now.

[pdr., 2017/01/06 19:40:01]

SGTM

What about the paintOffset accessor (line 1578)? Can we DCHECK in there too?

[Xianzhu, 2017/01/06 22:12:18]

I would like to defer the decision to the TODO. For now there is no harm to
access paintOffset().

     void setPreviousVisualRect(const LayoutRect& r) {
       m_layoutObject.setPreviousVisualRect(r);
     }
-    void setPreviousPaintOffset(const LayoutPoint& p) {
+    void setPaintOffset(const LayoutPoint& p) {
       DCHECK(RuntimeEnabledFeatures::slimmingPaintInvalidationEnabled());
-      m_layoutObject.m_previousPaintOffset = p;
+      DCHECK_EQ(m_layoutObject.document().lifecycle().state(),
+                DocumentLifecycle::InPrePaint);
+      m_layoutObject.m_paintOffset = p;
     }
     void setHasPreviousLocationInBacking(bool b) {
       m_layoutObject.m_bitfields.setHasPreviousLocationInBacking(b);
     }
     void setHasPreviousSelectionVisualRect(bool b) {
       m_layoutObject.m_bitfields.setHasPreviousSelectionVisualRect(b);
     }
     void setHasPreviousBoxGeometries(bool b) {
       m_layoutObject.m_bitfields.setHasPreviousBoxGeometries(b);
     }
     void setPreviousBackgroundObscured(bool b) {
       m_layoutObject.setPreviousBackgroundObscured(b);
     }
+
     void clearPreviousVisualRects() {
       m_layoutObject.clearPreviousVisualRects();
     }
     void setNeedsPaintPropertyUpdate() {
       m_layoutObject.setNeedsPaintPropertyUpdate();
     }
 #if DCHECK_IS_ON()
     // Same as setNeedsPaintPropertyUpdate() but does not mark ancestors as
     // having a descendant needing a paint property update.
     void setOnlyThisNeedsPaintPropertyUpdateForTesting() {
@@ skipping 730 matching lines @@
   // This stores the visual rect computed by the latest paint invalidation.
   // This rect does *not* account for composited scrolling. See
   // adjustVisualRectForCompositedScrolling().
   LayoutRect m_previousVisualRect;
 
   // This stores the paint offset computed by the latest paint property tree
   // building. It is relative to the containing transform space. It is the same
   // offset that will be used to paint the object on SPv2. It's used to detect
   // paint offset change for paint invalidation on SPv2, and partial paint
   // property tree update for SlimmingPaintInvalidation on SPv1 and SPv2.
-  LayoutPoint m_previousPaintOffset;
+  LayoutPoint m_paintOffset;
 
   // For SPv2 only. The ObjectPaintProperties structure holds references to the
   // property tree nodes that are created by the layout object for painting.
   std::unique_ptr<ObjectPaintProperties> m_paintProperties;
 };
 
 // FIXME: remove this once the layout object lifecycle ASSERTS are no longer
 // hit.
 class DeprecatedDisableModifyLayoutTreeStructureAsserts {
   STACK_ALLOCATED();
@@ skipping 211 matching lines @@
 CORE_EXPORT void showLineTree(const blink::LayoutObject*);
 CORE_EXPORT void showLayoutTree(const blink::LayoutObject* object1);
 // We don't make object2 an optional parameter so that showLayoutTree
 // can be called from gdb easily.
 CORE_EXPORT void showLayoutTree(const blink::LayoutObject* object1,
                                 const blink::LayoutObject* object2);
 
 #endif
 
 #endif  // LayoutObject_h