Implement incremental paint property tree rebuilding

third_party/WebKit/Source/core/frame/FrameView.h

 /*
    Copyright (C) 1997 Martin Jones (mjones@kde.org)
              (C) 1998 Waldo Bastian (bastian@kde.org)
              (C) 1998, 1999 Torben Weis (weis@kde.org)
              (C) 1999 Lars Knoll (knoll@kde.org)
              (C) 1999 Antti Koivisto (koivisto@kde.org)
    Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights
    reserved.
 
    This library is free software; you can redistribute it and/or
@@ skipping 701 matching lines @@
   // properties are either created by this FrameView or are inherited from
   // an ancestor.
   void setTotalPropertyTreeStateForContents(
       std::unique_ptr<PropertyTreeState> state) {
     m_totalPropertyTreeStateForContents = std::move(state);
   }
   const PropertyTreeState* totalPropertyTreeStateForContents() const {
     return m_totalPropertyTreeStateForContents.get();
   }
 
+  // Paint properties (e.g., m_preTranslation, etc.) are built from the
+  // FrameView's state (e.g., x(), y(), etc.) as well as inherited context.
+  // 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_needsPaintPropertyUpdate = true; }
+  void clearNeedsPaintPropertyUpdate() {
+    DCHECK_EQ(lifecycle().state(), DocumentLifecycle::InPrePaint);
+    m_needsPaintPropertyUpdate = false;
+  }
+  bool needsPaintPropertyUpdate() const { return m_needsPaintPropertyUpdate; }
   // TODO(ojan): Merge this with IntersectionObserver once it lands.
   IntRect computeVisibleArea();
 
   // Viewport size that should be used for viewport units (i.e. 'vh'/'vw').
   FloatSize viewportSizeForViewportUnits() const;
 
   ScrollAnchor* scrollAnchor() override { return &m_scrollAnchor; }
   void clearScrollAnchor();
   bool shouldPerformScrollAnchoring() const override;
 
@@ skipping 332 matching lines @@
   RefPtr<TransformPaintPropertyNode> m_scrollTranslation;
   RefPtr<ScrollPaintPropertyNode> m_scroll;
   // The content clip clips the document (= LayoutView) but not the scrollbars.
   // TODO(trchen): This will not be needed once settings->rootLayerScrolls() is
   // enabled.
   RefPtr<ClipPaintPropertyNode> m_contentClip;
   // The property tree state that should be used for painting contents. These
   // properties are either created by this FrameView or are inherited from
   // an ancestor.
   std::unique_ptr<PropertyTreeState> m_totalPropertyTreeStateForContents;
+  // Whether the paint properties need to be updated. For more details, see
+  // FrameView::needsPaintPropertyUpdate().
+  bool m_needsPaintPropertyUpdate;
 
   // This is set on the local root frame view only.
   DocumentLifecycle::LifecycleState m_currentUpdateLifecyclePhasesTargetState;
 
   ScrollAnchor m_scrollAnchor;
 
   // ScrollbarManager holds the Scrollbar instances.
   ScrollbarManager m_scrollbarManager;
 
   bool m_needsScrollbarsUpdate;
@@ skipping 44 matching lines @@
                   widget.isFrameView());
 DEFINE_TYPE_CASTS(FrameView,
                   ScrollableArea,
                   scrollableArea,
                   scrollableArea->isFrameView(),
                   scrollableArea.isFrameView());
 
 }  // namespace blink
 
 #endif  // FrameView_h