Reland main thread position sticky implementation.

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

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. 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>
  *   Randall Jesup <rjesup@wgate.com>
@@ skipping 81 matching lines @@
 
 namespace blink {
 
 namespace {
 
 static CompositingQueryMode gCompositingQueryMode =
     CompositingQueriesAreOnlyAllowedInCertainDocumentLifecyclePhases;
 
 struct SameSizeAsPaintLayer : DisplayItemClient {
     int bitFields;
-    void* pointers[9];
+    void* pointers[10];
     LayoutUnit layoutUnits[4];
     IntSize size;
     OwnPtrWillBePersistent<PaintLayerScrollableArea> scrollableArea;
     struct {
         IntRect rect;
         void* pointers[2];
     } ancestorCompositingInputs;
     struct {
         IntSize size;
         void* pointer;
@@ skipping 52 matching lines @@
     , m_hasNonIsolatedDescendantWithBlendMode(false)
     , m_hasAncestorWithClipPath(false)
     , m_layoutObject(layoutObject)
     , m_parent(0)
     , m_previous(0)
     , m_next(0)
     , m_first(0)
     , m_last(0)
     , m_staticInlinePosition(0)
     , m_staticBlockPosition(0)
+    , m_ancestorOverflowLayer(nullptr)
 {
     updateStackingNode();
 
     m_isSelfPaintingLayer = shouldBeSelfPaintingLayer();
 
     if (!layoutObject->slowFirstChild() && layoutObject->style()) {
         m_visibleContentStatusDirty = false;
         m_hasVisibleContent = layoutObject->style()->visibility() == VISIBLE;
     }
 
@@ skipping 157 matching lines @@
         // in this case, there is no need to dirty our ancestors further.
         if (layer->isSelfPaintingLayer()) {
             ASSERT(!parent() || parent()->m_hasSelfPaintingLayerDescendantDirty || parent()->m_hasSelfPaintingLayerDescendant);
             break;
         }
     }
 }
 
 bool PaintLayer::scrollsWithViewport() const
 {
-    return layoutObject()->style()->position() == FixedPosition && layoutObject()->containerForFixedPosition() == layoutObject()->view();
+    return (layoutObject()->style()->position() == FixedPosition && layoutObject()->containerForFixedPosition() == layoutObject()->view())
+        || (layoutObject()->style()->position() == StickyPosition && !ancestorScrollingLayer());
 }
 
 bool PaintLayer::scrollsWithRespectTo(const PaintLayer* other) const
 {
     if (scrollsWithViewport() != other->scrollsWithViewport())
         return true;
     return ancestorScrollingLayer() != other->ancestorScrollingLayer();
 }
 
 void PaintLayer::updateLayerPositionsAfterOverflowScroll(const DoubleSize& scrollDelta)
@@ skipping 377 matching lines @@
     }
 
     // If we live in a 3d hierarchy, then the layer at the root of that hierarchy needs
     // the m_has3DTransformedDescendant set.
     if (preserves3D())
         return has3DTransform() || m_has3DTransformedDescendant;
 
     return has3DTransform();
 }
 
-bool PaintLayer::updateLayerPosition()
+void PaintLayer::updateLayerPosition()
 {
     LayoutPoint localPoint;
     LayoutPoint inlineBoundingBoxOffset; // We don't put this into the Layer x/y for inlines, so we need to subtract it out when done.
 
     if (layoutObject()->isInline() && layoutObject()->isLayoutInline()) {
         LayoutInline* inlineFlow = toLayoutInline(layoutObject());
         IntRect lineBox = inlineFlow->linesBoundingBox();
         m_size = lineBox.size();
         inlineBoundingBoxOffset = lineBox.location();
         localPoint.moveBy(inlineBoundingBoxOffset);
@@ skipping 30 matching lines @@
 
         if (containingLayer->layoutObject()->isInFlowPositioned() && containingLayer->layoutObject()->isLayoutInline()) {
             LayoutSize offset = toLayoutInline(containingLayer->layoutObject())->offsetForInFlowPositionedInline(*toLayoutBox(layoutObject()));
             localPoint += offset;
         }
     } else if (parent() && parent()->layoutObject()->hasOverflowClip()) {
         IntSize scrollOffset = parent()->layoutBox()->scrolledContentOffset();
         localPoint -= scrollOffset;
     }
 
-    bool positionOrOffsetChanged = false;
     if (layoutObject()->isInFlowPositioned()) {
         LayoutSize newOffset = layoutObject()->offsetForInFlowPosition();
-        positionOrOffsetChanged = newOffset != offsetForInFlowPosition();
         if (m_rareData || !newOffset.isZero())
             ensureRareData().offsetForInFlowPosition = newOffset;
         localPoint.move(newOffset);
     } else if (m_rareData) {
         m_rareData->offsetForInFlowPosition = LayoutSize();
     }
 
     // FIXME: We'd really like to just get rid of the concept of a layer rectangle and rely on the layoutObjects.
     localPoint.moveBy(-inlineBoundingBoxOffset);
 
     if (m_location != localPoint) {
-        positionOrOffsetChanged = true;
         setNeedsRepaint();
     }
     m_location = localPoint;
 
 #if ENABLE(ASSERT)
     m_needsPositionUpdate = false;
 #endif
-    return positionOrOffsetChanged;
 }
 
 TransformationMatrix PaintLayer::perspectiveTransform() const
 {
     if (!layoutObject()->hasTransformRelatedProperty())
         return TransformationMatrix();
 
     const ComputedStyle& style = layoutObject()->styleRef();
     if (!style.hasPerspective())
         return TransformationMatrix();
@@ skipping 341 matching lines @@
     if (beforeChild) {
         beforeChild->setPreviousSibling(child);
         child->setNextSibling(beforeChild);
         ASSERT(beforeChild != child);
     } else {
         setLastChild(child);
     }
 
     child->m_parent = this;
 
+    // The ancestor overflow layer is calculated during compositing inputs update and should not be set yet.
+    ASSERT(!child->ancestorOverflowLayer());
+
     setNeedsCompositingInputsUpdate();
 
     if (!child->stackingNode()->isStacked() && !layoutObject()->documentBeingDestroyed())
         compositor()->setNeedsCompositingUpdate(CompositingUpdateRebuildTree);
 
     if (child->stackingNode()->isStacked() || child->firstChild()) {
         // Dirty the z-order list in which we are contained. The ancestorStackingContextNode() can be null in the
         // case where we're building up generated content layers. This is ok, since the lists will start
         // off dirty in that case anyway.
         child->stackingNode()->dirtyStackingContextZOrderLists();
@@ skipping 33 matching lines @@
         // |stackingContext| value.
         oldChild->stackingNode()->dirtyStackingContextZOrderLists();
     }
 
     if (layoutObject()->style()->visibility() != VISIBLE)
         dirtyVisibleContentStatus();
 
     oldChild->setPreviousSibling(0);
     oldChild->setNextSibling(0);
     oldChild->m_parent = 0;
+    if (oldChild->ancestorOverflowLayer())
+        oldChild->ancestorOverflowLayer()->getScrollableArea()->invalidateStickyConstraintsFor(oldChild);
+    oldChild->updateAncestorOverflowLayer(nullptr);

[flackr, 2016/04/12 14:26:25]

In order to ensure we don't have any stale ancestor pointers, the correct thing
to do would be to call removeAncestorOverflowLayer here, rather than in
removeOnlyThisLayer, but it may be wasteful to do this if the only time we
reattach the children layers is in removeOnlyThisLayer. Do you think we should
try the patch as is? Do you know of other cases where we reattach the child
branches that may also cause the crash?

 
     dirtyAncestorChainHasSelfPaintingLayerDescendantStatus();
 
     oldChild->updateDescendantDependentFlags();
 
     if (oldChild->m_hasVisibleContent || oldChild->m_hasVisibleDescendant)
         dirtyAncestorChainVisibleDescendantStatus();
 
     if (oldChild->enclosingPaginationLayer())
         oldChild->clearPaginationRecursive();
@@ skipping 29 matching lines @@
     if (PaintLayerReflectionInfo* reflectionInfo = this->reflectionInfo())
         removeChild(reflectionInfo->reflectionLayer());
 
     // Now walk our kids and reattach them to our parent.
     PaintLayer* current = m_first;
     while (current) {
         PaintLayer* next = current->nextSibling();
         removeChild(current);
         m_parent->addChild(current, nextSib);
 
+        // Remove ourselves from descendant overflow layers.
+        current->removeAncestorOverflowLayer(this);
+
         // FIXME: We should call a specialized version of this function.
         current->updateLayerPositionsAfterLayout();
         current = next;
     }
 
     // Remove us from the parent.
     m_parent->removeChild(this);
     m_layoutObject->destroyLayer();
 }
 
@@ skipping 1359 matching lines @@
 }
 
 PaintLayerFilterInfo& PaintLayer::ensureFilterInfo()
 {
     PaintLayerRareData& rareData = ensureRareData();
     if (!rareData.filterInfo)
         rareData.filterInfo = adoptPtr(new PaintLayerFilterInfo(this));
     return *rareData.filterInfo;
 }
 
+void PaintLayer::removeAncestorOverflowLayer(const PaintLayer* removedLayer)
+{
+    // If the current ancestor overflow layer does not match the removed layer
+    // the ancestor overflow layer has changed so we can stop searching.
+    if (ancestorOverflowLayer() && ancestorOverflowLayer() != removedLayer)
+        return;
+
+    updateAncestorOverflowLayer(nullptr);
+    PaintLayer* current = m_first;
+    while (current) {
+        current->removeAncestorOverflowLayer(removedLayer);
+        current = current->nextSibling();
+    }
+}
+
 void PaintLayer::updateOrRemoveFilterClients()
 {
     const auto& filter = layoutObject()->style()->filter();
     if (filter.isEmpty() && m_rareData) {
         m_rareData->filterInfo = nullptr;
     } else if (filter.hasReferenceFilter()) {
         ensureFilterInfo().updateReferenceFilterClients(filter);
     } else if (filterInfo()) {
         filterInfo()->clearFilterReferences();
     }
@@ skipping 199 matching lines @@
 
 void showLayerTree(const blink::LayoutObject* layoutObject)
 {
     if (!layoutObject) {
         fprintf(stderr, "Cannot showLayerTree. Root is (nil)\n");
         return;
     }
     showLayerTree(layoutObject->enclosingLayer());
 }
 #endif