Implement Paint Containment

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 248 matching lines @@
     bool hasVisibleNonLayerContent() const { return m_hasVisibleNonLayerContent; }
     bool hasNonCompositedChild() const { ASSERT(isAllowedToQueryCompositingState()); return m_hasNonCompositedChild; }
 
     // Gets the ancestor layer that serves as the containing block of this layer. It is assumed
     // that this layer is established by an out-of-flow positioned layout object (i.e. either
     // absolutely or fixed positioned).
     // If |ancestor| is specified, |*skippedAncestor| will be set to true if |ancestor| is found in
     // the ancestry chain between this layer and the containing block layer; if not found, it will
     // be set to false. Either both |ancestor| and |skippedAncestor| should be nullptr, or none of
     // them should.
-    PaintLayer* enclosingPositionedAncestor(const PaintLayer* ancestor = nullptr, bool* skippedAncestor = nullptr) const;
+    PaintLayer* enclosingPositionedOrContainedAncestor(const PaintLayer* ancestor = nullptr, bool* skippedAncestor = nullptr) const;
 
     bool isPaintInvalidationContainer() const;
 
     // Do *not* call this method unless you know what you are dooing. You probably want to call enclosingCompositingLayerForPaintInvalidation() instead.
     // If includeSelf is true, may return this.
     PaintLayer* enclosingLayerWithCompositedLayerMapping(IncludeSelfOrNot) const;
 
     // Returns the enclosing layer root into which this layer paints, inclusive of this one. Note that the enclosing layer may or may not have its own
     // GraphicsLayer backing, but is nevertheless the root for a call to the Layer::paint*() methods.
     PaintLayer* enclosingLayerForPaintInvalidation() const;
@@ skipping 176 matching lines @@
     PaintLayerScrollableArea* scrollableArea() const { return m_scrollableArea.get(); }
     PaintLayerClipper& clipper() { return m_clipper; }
     const PaintLayerClipper& clipper() const { return m_clipper; }
 
     inline bool isPositionedContainer() const
     {
         // FIXME: This is not in sync with containingBlock.
         // LayoutObject::canContainFixedPositionObjects() should probably be used
         // instead.
         LayoutBoxModelObject* layerlayoutObject = layoutObject();
-        return isRootLayer() || layerlayoutObject->isPositioned() || hasTransformRelatedProperty();
+        return isRootLayer() || layerlayoutObject->isPositioned() || hasTransformRelatedProperty() || layerlayoutObject->style()->containsPaint();

[chrishtr, 2015/12/09 01:41:46]

It's not really positioned..

[leviw_travelin_and_unemployed, 2015/12/09 21:09:24]

That's because this method and its one caller, despite the name, aren't really
looking for a positioned container, they're looking for the container for a
positioned items. I'm not a fan of this code being here to begin with, honestly.

     }
 
     bool scrollsOverflow() const;
 
     CompositingReasons potentialCompositingReasonsFromStyle() const { return m_potentialCompositingReasonsFromStyle; }
     void setPotentialCompositingReasonsFromStyle(CompositingReasons reasons) { ASSERT(reasons == (reasons & CompositingReasonComboAllStyleDeterminedReasons)); m_potentialCompositingReasonsFromStyle = reasons; }
 
     bool hasStyleDeterminedDirectCompositingReasons() const { return m_potentialCompositingReasonsFromStyle & CompositingReasonComboAllDirectStyleDeterminedReasons; }
 
     class AncestorDependentCompositingInputs {
@@ skipping 339 matching lines @@
 
 } // namespace blink
 
 #ifndef NDEBUG
 // Outside the WebCore namespace for ease of invocation from gdb.
 void showLayerTree(const blink::PaintLayer*);
 void showLayerTree(const blink::LayoutObject*);
 #endif
 
 #endif // Layer_h