Generalize visible descendant dirty bits to prepare for more properties.

third_party/WebKit/Source/core/paint/PaintLayer.h

 /*
  * Copyright (C) 2003, 2009, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2013 Intel Corporation. All rights reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@web.de>
@@ skipping 297 matching lines @@
 
   PaintLayerStackingNode* stackingNode() { return m_stackingNode.get(); }
   const PaintLayerStackingNode* stackingNode() const {
     return m_stackingNode.get();
   }
 
   bool subtreeIsInvisible() const {
     return !hasVisibleContent() && !hasVisibleDescendant();
   }
 
-  // FIXME: hasVisibleContent() should call updateDescendantDependentFlags() if
-  // m_isVisibleContentDirty.
   bool hasVisibleContent() const {
     DCHECK(!m_isVisibleContentDirty);
     return m_hasVisibleContent;
   }
 
-  // FIXME: hasVisibleDescendant() should call updateDescendantDependentFlags()
-  // if m_isVisibleDescendantDirty.
   bool hasVisibleDescendant() const {
-    DCHECK(!m_isVisibleDescendantDirty);
+    DCHECK(!m_needsDescendantDependentFlagsUpdate);
     return m_hasVisibleDescendant;
   }
 
   void dirtyVisibleContentStatus();
-  void potentiallyDirtyVisibleContentStatus(EVisibility);
 
   bool hasBoxDecorationsOrBackground() const;
   bool hasVisibleBoxDecorations() const;
   // True if this layer container layoutObjects that paint.
   bool hasNonEmptyChildLayoutObjects() const;
 
   // Will ensure that isAllScrollingContentComposited() is up to date.
   void updateScrollingStateAfterCompositingChange();
   bool isAllScrollingContentComposited() const {
     return m_isAllScrollingContentComposited;
@@ skipping 722 matching lines @@
   void updateStackingNode();
 
   FilterOperations addReflectionToFilterOperations(const ComputedStyle&) const;
 
   // FIXME: We could lazily allocate our ScrollableArea based on style
   // properties ('overflow', ...) but for now, we are always allocating it for
   // LayoutBox as it's safer.  crbug.com/467721.
   bool requiresScrollableArea() const { return layoutBox(); }
   void updateScrollableArea();
 
-  void dirtyAncestorChainVisibleDescendantStatus();
+  void markAncestorChainForDescendantDependentFlagsUpdate();
 
   bool attemptDirectCompositingUpdate(StyleDifference,
                                       const ComputedStyle* oldStyle);
   void updateTransform(const ComputedStyle* oldStyle,
                        const ComputedStyle& newStyle);
 
   void removeAncestorOverflowLayer(const PaintLayer* removedLayer);
 
   void updatePaginationRecursive(bool needsPaginationUpdate = false);
   void clearPaginationRecursive();
@@ skipping 41 matching lines @@
   // during painting. This can lead to significant savings, especially if the
   // tree has lots of non-self-painting layers grouped together (e.g. table
   // cells).
   mutable unsigned m_hasSelfPaintingLayerDescendant : 1;
   mutable unsigned m_hasSelfPaintingLayerDescendantDirty : 1;
 
   const unsigned m_isRootLayer : 1;
 
   unsigned m_isVisibleContentDirty : 1;
   unsigned m_hasVisibleContent : 1;
-  unsigned m_isVisibleDescendantDirty : 1;
+  unsigned m_needsDescendantDependentFlagsUpdate : 1;

[Xianzhu, 2016/12/01 17:59:32]

I'm not sure if the renaming is a good idea.

updateDescendantDependentFlags() updated both m_isVisibleContentDirty and
m_isVisibleDescendantDirty, so both of them seemed descendant (object and layer)
dependent flags.

If we want m_needsDescendantDependentFlagsUpdate cover both conditions (like in
this patch dirtyVisibleContentStatus unconditionally calling
markAncestorChainForDescendantDependentFlagsUpdate), we will do an extra level
of traverse into child layers in updateDescendantDependentFlags().

[chrishtr, 2016/12/01 18:05:22]

I could update the patch to try removing m_isVisibleContentDirty..
The new code for dirtyVisibleContentStatus will indeed cause recursion from the
root PaintLayer down to the one
whose visible contents status may have changed. I don't think that is a
significant problem, do you?

[Xianzhu, 2016/12/01 18:05:25]

Can this be m_childNeedsDecendantDependengFlagsUpdate?

[chrishtr, 2016/12/01 18:06:01]

Seem my comment in response to your one in PaintLayer.cpp about why it's not
just child any more.

[Xianzhu, 2016/12/01 18:07:03]

Removing m_isVisibleContentDirty SGTM.

[chrishtr, 2016/12/01 23:54:20]

Done.

   unsigned m_hasVisibleDescendant : 1;
 
 #if DCHECK_IS_ON()
   unsigned m_needsPositionUpdate : 1;
 #endif
 
   unsigned m_is3DTransformedDescendantDirty : 1;
   // Set on a stacking context layer that has 3D descendants anywhere
   // in a preserves3D hierarchy. Hint to do 3D-aware hit testing.
   unsigned m_has3DTransformedDescendant : 1;
@@ skipping 83 matching lines @@
 
 }  // namespace blink
 
 #ifndef NDEBUG
 // Outside the WebCore namespace for ease of invocation from gdb.
 CORE_EXPORT void showLayerTree(const blink::PaintLayer*);
 CORE_EXPORT void showLayerTree(const blink::LayoutObject*);
 #endif
 
 #endif  // Layer_h