Add flag for tracking descendant paint property updates

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 1689 matching lines @@
     }
     void clearPreviousVisualRects() {
       m_layoutObject.clearPreviousVisualRects();
     }
     void setNeedsPaintPropertyUpdate() {
       m_layoutObject.setNeedsPaintPropertyUpdate();
     }
     void clearNeedsPaintPropertyUpdate() {
       m_layoutObject.clearNeedsPaintPropertyUpdate();
     }
+    void clearDescendantNeedsPaintPropertyUpdate() {
+      m_layoutObject.clearDescendantNeedsPaintPropertyUpdate();
+    }
 
    protected:
     friend class PaintPropertyTreeBuilder;
     // The following two functions can be called from PaintPropertyTreeBuilder
     // only.
     ObjectPaintProperties& ensurePaintProperties() {
       return m_layoutObject.ensurePaintProperties();
     }
     ObjectPaintProperties* paintProperties() {
       return const_cast<ObjectPaintProperties*>(
           m_layoutObject.paintProperties());
     }
 
     friend class LayoutObject;
     MutableForPainting(const LayoutObject& layoutObject)
         : m_layoutObject(const_cast<LayoutObject&>(layoutObject)) {}
 
     LayoutObject& m_layoutObject;
   };
   MutableForPainting getMutableForPainting() const {
     return MutableForPainting(*this);
   }
 
   // Paint properties (see: |ObjectPaintProperties|) are built from an object's
   // state (location, transform, etc) as well as properties from ancestors.
   // When these inputs change, setNeedsPaintPropertyUpdate will cause a property
   // tree update during the next document lifecycle update.
-  // TODO(pdr): Add additional granularity such as the ability to signal that
-  // only a local paint property update is needed.
-  void setNeedsPaintPropertyUpdate() {
-    m_bitfields.setNeedsPaintPropertyUpdate(true);
-  }
-  // TODO(pdr): This can be removed once we have more granular update flags.
-  void setAllAncestorsNeedPaintPropertyUpdate() {
-    if (m_parent) {
-      m_parent->setNeedsPaintPropertyUpdate();
-      m_parent->setAllAncestorsNeedPaintPropertyUpdate();
-    }
+  //
+  // In addition to tracking if an object needs its own paint properties
+  // updated, |descendantNeedsPaintPropertyUpdate| is used to track if any
+  // descendant needs an update too. This bit is up the tree, crossing frames,
+  // when calling |setNeedsPaintPropertyUpdate|.
+  void setNeedsPaintPropertyUpdate();
+  bool needsPaintPropertyUpdate() const {
+    return m_bitfields.needsPaintPropertyUpdate();
   }
   void clearNeedsPaintPropertyUpdate() {
     DCHECK_EQ(document().lifecycle().state(), DocumentLifecycle::InPrePaint);
     m_bitfields.setNeedsPaintPropertyUpdate(false);
   }
-  bool needsPaintPropertyUpdate() const {
-    return m_bitfields.needsPaintPropertyUpdate();
+  bool descendantNeedsPaintPropertyUpdate() const {
+    return m_bitfields.descendantNeedsPaintPropertyUpdate();
   }
+  void clearDescendantNeedsPaintPropertyUpdate() {
+    DCHECK_EQ(document().lifecycle().state(), DocumentLifecycle::InPrePaint);
+    m_bitfields.setDescendantNeedsPaintPropertyUpdate(false);
+  }
+  // Main thread scrolling reasons require fully updating paint propeties of all
+  // ancestors (see: ScrollPaintPropertyNode.h).
+  void setAncestorsNeedPaintPropertyUpdateForMainThreadScrolling();
 
   void setIsScrollAnchorObject() { m_bitfields.setIsScrollAnchorObject(true); }
   // Clears the IsScrollAnchorObject bit if and only if no ScrollAnchors still
   // reference this LayoutObject.
   void maybeClearIsScrollAnchorObject();
 
   bool scrollAnchorDisablingStyleChanged() {
     return m_bitfields.scrollAnchorDisablingStyleChanged();
   }
   void setScrollAnchorDisablingStyleChanged(bool changed) {
@@ skipping 281 matching lines @@
     return isText() || (isSVG() && !isSVGRoot());
   }
 
   static bool isAllowedToModifyLayoutTreeStructure(Document&);
 
   // Returns the parent for paint invalidation.
   // - For LayoutView, returns the owner layout object in the containing frame
   //   if any or nullptr;
   // - For multi-column spanner, returns the spanner placeholder;
   // - Otherwise returns parent().
-  LayoutObject* paintInvalidationParent() const;
+  inline LayoutObject* paintInvalidationParent() const;
+  LayoutObject* slowPaintInvalidationParentForTesting() const;

[Xianzhu, 2016/11/23 00:12:48]

I wonder if it works to omit 'inline' in header but use 'inline' on impl in .cc.
I saw several examples like that, e.g. clearLayoutRootIfNeeded(), but not sure
what the result is.

 
   RefPtr<ComputedStyle> m_style;
 
   // Oilpan: This untraced pointer to the owning Node is considered safe.
   UntracedMember<Node> m_node;
 
   LayoutObject* m_parent;
   LayoutObject* m_previous;
   LayoutObject* m_next;
 
@@ skipping 74 matching lines @@
           m_alwaysCreateLineBoxesForLayoutInline(false),
           m_previousBackgroundObscured(false),
           m_isBackgroundAttachmentFixedObject(false),
           m_isScrollAnchorObject(false),
           m_scrollAnchorDisablingStyleChanged(false),
           m_hasBoxDecorationBackground(false),
           m_hasPreviousLocationInBacking(false),
           m_hasPreviousSelectionVisualRect(false),
           m_hasPreviousBoxGeometries(false),
           m_needsPaintPropertyUpdate(true),
+          m_descendantNeedsPaintPropertyUpdate(true),
           m_backgroundChangedSinceLastPaintInvalidation(false),
           m_positionedState(IsStaticallyPositioned),
           m_selectionState(SelectionNone),
           m_backgroundObscurationState(BackgroundObscurationStatusInvalid),
           m_fullPaintInvalidationReason(PaintInvalidationNone) {}
 
     // Self needs layout means that this layout object is marked for a full
     // layout. This is the default layout but it is expensive as it recomputes
     // everything. For CSS boxes, this includes the width (laying out the line
     // boxes again), the margins (due to block collapsing margins), the
@@ skipping 152 matching lines @@
 
     ADD_BOOLEAN_BITFIELD(hasPreviousLocationInBacking,
                          HasPreviousLocationInBacking);
     ADD_BOOLEAN_BITFIELD(hasPreviousSelectionVisualRect,
                          HasPreviousSelectionVisualRect);
     ADD_BOOLEAN_BITFIELD(hasPreviousBoxGeometries, HasPreviousBoxGeometries);
 
     // Whether the paint properties need to be updated. For more details, see
     // LayoutObject::needsPaintPropertyUpdate().
     ADD_BOOLEAN_BITFIELD(needsPaintPropertyUpdate, NeedsPaintPropertyUpdate);
+    // Whether the paint properties of a descendant need to be updated. For more
+    // details, see LayoutObject::descendantNeedsPaintPropertyUpdate().
+    ADD_BOOLEAN_BITFIELD(descendantNeedsPaintPropertyUpdate,
+                         DescendantNeedsPaintPropertyUpdate);
 
     ADD_BOOLEAN_BITFIELD(backgroundChangedSinceLastPaintInvalidation,
                          BackgroundChangedSinceLastPaintInvalidation);
 
    protected:
     // Use protected to avoid warning about unused variable.
-    unsigned m_unusedBits : 8;
+    unsigned m_unusedBits : 7;
 
    private:
     // This is the cached 'position' value of this object
     // (see ComputedStyle::position).
     unsigned m_positionedState : 2;  // PositionedState
     unsigned m_selectionState : 3;   // SelectionState
     // Mutable for getter which lazily update this field.
     mutable unsigned
         m_backgroundObscurationState : 2;        // BackgroundObscurationState
     unsigned m_fullPaintInvalidationReason : 5;  // PaintInvalidationReason
@@ skipping 304 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