Reland main thread position sticky implementation.

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 253 matching lines @@
     LayoutRect rect() const { return LayoutRect(location(), LayoutSize(size())); }
 
     bool isRootLayer() const { return m_isRootLayer; }
 
     PaintLayerCompositor* compositor() const;
 
     // Notification from the layoutObject that its content changed (e.g. current frame of image changed).
     // Allows updates of layer content without invalidating paint.
     void contentChanged(ContentChangeType);
 
+    void updateLayerPosition();
+
     void updateLayerPositionsAfterLayout();
     void updateLayerPositionsAfterOverflowScroll(const DoubleSize& scrollDelta);
 
     PaintLayer* enclosingPaginationLayer() const { return m_rareData ? m_rareData->enclosingPaginationLayer : nullptr; }
 
     void updateTransformationMatrix();
     PaintLayer* renderingContextRoot();
     const PaintLayer* renderingContextRoot() const;
 
     LayoutSize offsetForInFlowPosition() const { return m_rareData ? m_rareData->offsetForInFlowPosition : LayoutSize(); }
@@ skipping 243 matching lines @@
             , nearestFixedPositionLayer(nullptr)
             , scrollParent(nullptr)
             , clipParent(nullptr)
         { }
 
         bool isDefault() const { return !opacityAncestor && !transformAncestor && !filterAncestor && !ancestorScrollingLayer && !nearestFixedPositionLayer && !scrollParent && !clipParent; }
 
         const PaintLayer* opacityAncestor;
         const PaintLayer* transformAncestor;
         const PaintLayer* filterAncestor;
+
+        // The fist ancestor which can scroll. This is a subset of the
+        // ancestorOverflowLayer chain where the scrolling layer is visible and
+        // has a larger scroll content than its bounds.
         const PaintLayer* ancestorScrollingLayer;
         const PaintLayer* nearestFixedPositionLayer;
 
         // A scroll parent is a compositor concept. It's only needed in blink
         // because we need to use it as a promotion trigger. A layer has a
         // scroll parent if neither its compositor scrolling ancestor, nor any
         // other layer scrolled by this ancestor, is a stacking ancestor of this
         // layer. Layers with scroll parents must be scrolled with the main
         // scrolling layer by the compositor.
         const PaintLayer* scrollParent;
 
         // A clip parent is another compositor concept that has leaked into
         // blink so that it may be used as a promotion trigger. Layers with clip
         // parents escape the clip of a stacking tree ancestor. The compositor
         // needs to know about clip parents in order to circumvent its normal
         // clipping logic.
         const PaintLayer* clipParent;
     };
 
     void setNeedsCompositingInputsUpdate();
     bool childNeedsCompositingInputsUpdate() const { return m_childNeedsCompositingInputsUpdate; }
     bool needsCompositingInputsUpdate() const
     {
         // While we're updating the compositing inputs, these values may differ.
         // We should never be asking for this value when that is the case.
         ASSERT(m_needsDescendantDependentCompositingInputsUpdate == m_needsAncestorDependentCompositingInputsUpdate);
         return m_needsDescendantDependentCompositingInputsUpdate;
     }
 
+    void updateAncestorOverflowLayer(const PaintLayer* ancestorOverflowLayer) { m_ancestorOverflowLayer = ancestorOverflowLayer; }
     void updateAncestorDependentCompositingInputs(const AncestorDependentCompositingInputs&, const RareAncestorDependentCompositingInputs&, bool hasAncestorWithClipPath);
     void updateDescendantDependentCompositingInputs(bool hasDescendantWithClipPath, bool hasNonIsolatedDescendantWithBlendMode);
     void didUpdateCompositingInputs();
 
     IntRect clippedAbsoluteBoundingBox() const { ASSERT(!m_needsAncestorDependentCompositingInputsUpdate); return m_ancestorDependentCompositingInputs.clippedAbsoluteBoundingBox; }
     const PaintLayer* opacityAncestor() const { ASSERT(!m_needsAncestorDependentCompositingInputsUpdate); return m_rareAncestorDependentCompositingInputs ? m_rareAncestorDependentCompositingInputs->opacityAncestor : nullptr; }
     const PaintLayer* transformAncestor() const { ASSERT(!m_needsAncestorDependentCompositingInputsUpdate); return m_rareAncestorDependentCompositingInputs ? m_rareAncestorDependentCompositingInputs->transformAncestor : nullptr; }
     const PaintLayer* filterAncestor() const { ASSERT(!m_needsAncestorDependentCompositingInputsUpdate); return m_rareAncestorDependentCompositingInputs ? m_rareAncestorDependentCompositingInputs->filterAncestor : nullptr; }
     const LayoutObject* clippingContainer() const { ASSERT(!m_needsAncestorDependentCompositingInputsUpdate); return m_ancestorDependentCompositingInputs.clippingContainer; }
+    const PaintLayer* ancestorOverflowLayer() const { return m_ancestorOverflowLayer; }
     const PaintLayer* ancestorScrollingLayer() const { ASSERT(!m_needsAncestorDependentCompositingInputsUpdate); return m_rareAncestorDependentCompositingInputs ? m_rareAncestorDependentCompositingInputs->ancestorScrollingLayer : nullptr; }
     const PaintLayer* nearestFixedPositionLayer() const { ASSERT(!m_needsAncestorDependentCompositingInputsUpdate); return m_rareAncestorDependentCompositingInputs ? m_rareAncestorDependentCompositingInputs->nearestFixedPositionLayer : nullptr; }
     const PaintLayer* scrollParent() const { ASSERT(!m_needsAncestorDependentCompositingInputsUpdate); return m_rareAncestorDependentCompositingInputs ? m_rareAncestorDependentCompositingInputs->scrollParent : nullptr; }
     const PaintLayer* clipParent() const { ASSERT(!m_needsAncestorDependentCompositingInputsUpdate); return m_rareAncestorDependentCompositingInputs ? m_rareAncestorDependentCompositingInputs->clipParent : nullptr; }
     bool hasAncestorWithClipPath() const { ASSERT(!m_needsAncestorDependentCompositingInputsUpdate); return m_hasAncestorWithClipPath; }
     bool hasDescendantWithClipPath() const { ASSERT(!m_needsDescendantDependentCompositingInputsUpdate); return m_hasDescendantWithClipPath; }
     bool hasNonIsolatedDescendantWithBlendMode() const;
 
     bool lostGroupedMapping() const { ASSERT(isAllowedToQueryCompositingState()); return m_lostGroupedMapping; }
     void setLostGroupedMapping(bool b) { m_lostGroupedMapping = b; }
@@ skipping 97 matching lines @@
     void clearClipRectsCache() const { m_clipRectsCache.clear(); }
 
 private:
     // Bounding box in the coordinates of this layer.
     LayoutRect logicalBoundingBox() const;
 
     bool hasOverflowControls() const;
 
     void dirtyAncestorChainHasSelfPaintingLayerDescendantStatus();
 
-    // Returns true if the position changed.
-    bool updateLayerPosition();
-
     void updateLayerPositionRecursive();
     void updateLayerPositionsAfterScrollRecursive(const DoubleSize& scrollDelta, bool paintInvalidationContainerWasScrolled);
 
     void setNextSibling(PaintLayer* next) { m_next = next; }
     void setPreviousSibling(PaintLayer* prev) { m_previous = prev; }
     void setFirstChild(PaintLayer* first) { m_first = first; }
     void setLastChild(PaintLayer* last) { m_last = last; }
 
     void updateHasSelfPaintingLayerDescendant() const;
     PaintLayer* hitTestLayer(PaintLayer* rootLayer, PaintLayer* containerLayer, HitTestResult&,
@@ skipping 36 matching lines @@
 
     void dirtyAncestorChainVisibleDescendantStatus();
 
     bool attemptDirectCompositingUpdate(StyleDifference, const ComputedStyle* oldStyle);
     void updateTransform(const ComputedStyle* oldStyle, const ComputedStyle& newStyle);
 
     void dirty3DTransformedDescendantStatus();
     // Both updates the status, and returns true if descendants of this have 3d.
     bool update3DTransformedDescendantStatus();
 
+    void removeAncestorOverflowLayer(const PaintLayer* removedLayer);
+
     void updateOrRemoveFilterClients();
 
     void updatePaginationRecursive(bool needsPaginationUpdate = false);
     void clearPaginationRecursive();
 
     void markCompositingContainerChainForNeedsRepaint();
 
     PaintLayerRareData& ensureRareData()
     {
         if (!m_rareData)
@@ skipping 77 matching lines @@
     // The layer's size.
     //
     // If the associated LayoutBoxModelObject is a LayoutBox, it's its border
     // box. Otherwise, this is the LayoutInline's lines' bounding box.
     IntSize m_size;
 
     // Cached normal flow values for absolute positioned elements with static left/top values.
     LayoutUnit m_staticInlinePosition;
     LayoutUnit m_staticBlockPosition;
 
+    // The first ancestor having a non visible overflow.
+    const PaintLayer* m_ancestorOverflowLayer;
+
     AncestorDependentCompositingInputs m_ancestorDependentCompositingInputs;
     OwnPtr<RareAncestorDependentCompositingInputs> m_rareAncestorDependentCompositingInputs;
 
     OwnPtrWillBePersistent<PaintLayerScrollableArea> m_scrollableArea;
 
     mutable OwnPtr<ClipRectsCache> m_clipRectsCache;
 
     OwnPtr<PaintLayerStackingNode> m_stackingNode;
 
     IntSize m_previousScrollOffsetAccumulationForPainting;
     RefPtr<ClipRects> m_previousPaintingClipRects;
     LayoutRect m_previousPaintDirtyRect;
 
     OwnPtr<PaintLayerRareData> m_rareData;
 };
 
 } // 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