WIP: Prune the prepaint tree walk

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 setDescendantNeedsPaintPropertyUpdate() {
+      m_layoutObject.setDescendantNeedsPaintPropertyUpdate();
+    }
+    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.
+  //
+  // 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.
+  //
+  // TODO(pdr): We may want to add more granular paint property update types
+  // such as the ability to only update one property type.
   void setNeedsPaintPropertyUpdate() {
     m_bitfields.setNeedsPaintPropertyUpdate(true);
+    // TODO(pdr): paintInvalidationParent is not inlined. May want to optimize
+    // this to check m_parent first.
+    if (auto* parent = paintInvalidationParent())
+      parent->setDescendantNeedsPaintPropertyUpdate();
   }
-  // TODO(pdr): This can be removed once we have more granular update flags.
+  void setDescendantNeedsPaintPropertyUpdate() {
+    if (!m_bitfields.descendantNeedsPaintPropertyUpdate()) {
+      m_bitfields.setDescendantNeedsPaintPropertyUpdate(true);
+      // TODO(pdr): paintInvalidationParent is not inlined. May want to optimize
+      // this to check m_parent first.
+      if (auto* parent = paintInvalidationParent())
+        parent->setDescendantNeedsPaintPropertyUpdate();
+    } else {
+      auto* parent = paintInvalidationParent();
+      DCHECK(!parent || parent->descendantNeedsPaintPropertyUpdate());
+    }
+  }
   void setAllAncestorsNeedPaintPropertyUpdate() {
-    if (m_parent) {
-      m_parent->setNeedsPaintPropertyUpdate();
-      m_parent->setAllAncestorsNeedPaintPropertyUpdate();
+    if (auto* parent = paintInvalidationParent()) {
+      parent->setNeedsPaintPropertyUpdate();
+      parent->setAllAncestorsNeedPaintPropertyUpdate();
     }
   }
   void clearNeedsPaintPropertyUpdate() {
     DCHECK_EQ(document().lifecycle().state(), DocumentLifecycle::InPrePaint);
     m_bitfields.setNeedsPaintPropertyUpdate(false);
   }
   bool needsPaintPropertyUpdate() const {
     return m_bitfields.needsPaintPropertyUpdate();
   }
+  void clearDescendantNeedsPaintPropertyUpdate() {
+    DCHECK_EQ(document().lifecycle().state(), DocumentLifecycle::InPrePaint);
+    m_bitfields.setDescendantNeedsPaintPropertyUpdate(false);
+  }
+  bool descendantNeedsPaintPropertyUpdate() const {
+    return m_bitfields.descendantNeedsPaintPropertyUpdate();
+  }
 
   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 376 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