Clear scroll anchor on all parent scrollers from ScrollAnchor::clear

third_party/WebKit/Source/core/layout/LayoutObject.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  *           (C) 2004 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2009 Google Inc. All rights reserved.
  * Copyright (C) 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 24 matching lines @@
 #include "core/dom/shadow/ShadowRoot.h"
 #include "core/editing/EditingUtilities.h"
 #include "core/editing/FrameSelection.h"
 #include "core/editing/TextAffinity.h"
 #include "core/frame/DeprecatedScheduleStyleRecalcDuringLayout.h"
 #include "core/frame/EventHandlerRegistry.h"
 #include "core/frame/FrameView.h"
 #include "core/frame/LocalFrame.h"
 #include "core/frame/Settings.h"
 #include "core/html/HTMLElement.h"
+#include "core/html/HTMLFrameOwnerElement.h"
 #include "core/html/HTMLHtmlElement.h"
 #include "core/html/HTMLTableCellElement.h"
 #include "core/html/HTMLTableElement.h"
 #include "core/input/EventHandler.h"
 #include "core/inspector/InstanceCounters.h"
 #include "core/layout/HitTestResult.h"
 #include "core/layout/LayoutCounter.h"
 #include "core/layout/LayoutDeprecatedFlexibleBox.h"
 #include "core/layout/LayoutFlexibleBox.h"
 #include "core/layout/LayoutFlowThread.h"
@@ skipping 2515 matching lines @@
       layer->dirtyVisibleContentStatus();
   }
 
   if (parent()->childrenInline())
     parent()->dirtyLinesFromChangedChild(this);
 
   if (LayoutFlowThread* flowThread = flowThreadContainingBlock())
     flowThread->flowThreadDescendantWasInserted(this);
 }
 
-enum FindReferencingScrollAnchorsBehavior { DontClear, Clear };
+enum FindScrollAnchorsBehavior { FindReferencing, ClearReferencing, ClearAll };
 
-static bool findReferencingScrollAnchors(
-    LayoutObject* layoutObject,
-    FindReferencingScrollAnchorsBehavior behavior) {
+// Returns true if scroller has layoutObject as its anchor.
+static bool clearScrollAnchorForScroller(ScrollableArea* scroller,

[ymalik, 2016/10/06 19:51:13]

@skobes, a note to make reviewing easier.

This function can be called in 3 different ways.
FindReferencing: This will walk up the parent chain and return true of
layoutObject is referenced by any other scroller. This is used when we want to
set the isScrollAnchorObject when a scroll anchor is cleared for only a single
scroller (for cases like these:
https://cs.chromium.org/chromium/src/third_party/WebKit/Source/core/layout/Sc...)

ClearReferencing: This will walk up the parent chain and clear the anchors for
scrollers that reference layoutObject. This is needed when an element is removed
from the tree. In this case, we don't want to clear anchors for all scroller in
the parent chain.

ClearAll: This will clear scroll anchors for all parent scrollers of
layoutObject. This is when a non-anchoring scroll happens on a child scroller.

+                                         LayoutObject* layoutObject,
+                                         FindScrollAnchorsBehavior behavior) {
+  DCHECK(scroller);
+  ScrollAnchor* anchor = scroller->scrollAnchor();
+  DCHECK(anchor);
+  bool refersTo = false;
+  if (anchor->refersTo(layoutObject)) {
+    refersTo = true;
+    if (behavior == FindReferencing)
+      return refersTo;
+    layoutObject->setIsScrollAnchorObject(false);
+    anchor->releaseAnchor();
+  } else if (behavior == ClearAll && anchor->anchorObject()) {
+    anchor->anchorObject()->setIsScrollAnchorObject(false);
+    anchor->releaseAnchor();
+  }
+  return refersTo;
+}
+
+// Returns true if any of scroller in the parent chain of layoutObject has
+// layoutObject as its anchor. If FindScrollAnchorsBehavior is ClearAll, all
+// the scrollers in the parent chain of layoutObject will have their scroll
+// anchor cleared. If FindScrollAnchorsBehavior is ClearReferencing, all the
+// scrollers in the parent chain of layoutObject that have layoutObject as their
+// anchor will have their scroll anchor cleared.
+static bool findScrollAnchors(LayoutObject* layoutObject,
+                              FindScrollAnchorsBehavior behavior) {
   PaintLayer* layer = nullptr;
   if (LayoutObject* parent = layoutObject->parent())
     layer = parent->enclosingLayer();
   bool found = false;
 
-  // Walk up the layer tree to clear any scroll anchors that reference us.
+  // Walk up the layer tree to clear scroll anchors if required.
   while (layer) {
-    if (PaintLayerScrollableArea* scrollableArea = layer->getScrollableArea()) {
-      ScrollAnchor* anchor = scrollableArea->scrollAnchor();
-      DCHECK(anchor);
-      if (anchor->refersTo(layoutObject)) {
-        found = true;
-        if (behavior == Clear)
-          anchor->notifyRemoved(layoutObject);
-        else
-          return true;
-      }
+    if (PaintLayerScrollableArea* scroller = layer->getScrollableArea()) {
+      found = clearScrollAnchorForScroller(scroller, layoutObject, behavior) ||
+              found;
+      if (found && behavior == FindReferencing)
+        return found;
     }
     layer = layer->parent();
   }
+
   if (FrameView* view = layoutObject->frameView()) {
-    ScrollAnchor* anchor = view->scrollAnchor();
-    DCHECK(anchor);
-    if (anchor->refersTo(layoutObject)) {
-      found = true;
-      if (behavior == Clear)
-        anchor->notifyRemoved(layoutObject);
-    }
+    found = clearScrollAnchorForScroller(view, layoutObject, behavior) || found;
+    if (found && behavior == FindReferencing)
+      return found;
+  }
+
+  // Continue walk past frame boundary.
+  if (layoutObject->document().localOwner()) {
+    found =
+        findScrollAnchors(layoutObject->document().localOwner()->layoutObject(),
+                          behavior) ||
+        found;
   }
   return found;
 }
 
 void LayoutObject::willBeRemovedFromTree() {
   // FIXME: We should ASSERT(isRooted()) but we have some out-of-order removals which would need to be fixed first.
 
   // If we remove a visible child from an invisible parent, we don't know the layer visibility any more.
   PaintLayer* layer = nullptr;
   if (parent()->style()->visibility() != EVisibility::Visible &&
@@ skipping 13 matching lines @@
   if (isOutOfFlowPositioned() && parent()->childrenInline())
     parent()->dirtyLinesFromChangedChild(this);
 
   removeFromLayoutFlowThread();
 
   // Update cached boundaries in SVG layoutObjects if a child is removed.
   if (parent()->isSVG())
     parent()->setNeedsBoundariesUpdate();
 
   if (RuntimeEnabledFeatures::scrollAnchoringEnabled() &&
-      m_bitfields.isScrollAnchorObject()) {
-    // Clear the bit first so that anchor.clear() doesn't recurse into findReferencingScrollAnchors.
-    m_bitfields.setIsScrollAnchorObject(false);
-    findReferencingScrollAnchors(this, Clear);
+      m_bitfields.isScrollAnchorObject())
+    findScrollAnchors(this, ClearReferencing);
+}
+
+void LayoutObject::maybeClearIsScrollAnchorObject() {
+  if (m_bitfields.isScrollAnchorObject()) {
+    m_bitfields.setIsScrollAnchorObject(
+        findScrollAnchors(this, FindReferencing));
   }
 }
 
-void LayoutObject::maybeClearIsScrollAnchorObject() {
-  if (m_bitfields.isScrollAnchorObject())
-    m_bitfields.setIsScrollAnchorObject(
-        findReferencingScrollAnchors(this, DontClear));
+void LayoutObject::clearScrollAnchors() {
+  findScrollAnchors(this, ClearAll);
 }
 
 void LayoutObject::removeFromLayoutFlowThread() {
   if (!isInsideFlowThread())
     return;
 
   // Sometimes we remove the element from the flow, but it's not destroyed at that time.
   // It's only until later when we actually destroy it and remove all the children from it.
   // Currently, that happens for firstLetter elements and list markers.
   // Pass in the flow thread so that we don't have to look it up for all the children.
@@ skipping 789 matching lines @@
     const blink::LayoutObject* root = object1;
     while (root->parent())
       root = root->parent();
     root->showLayoutTreeAndMark(object1, "*", object2, "-", 0);
   } else {
     WTFLogAlways("%s", "Cannot showLayoutTree. Root is (nil)");
   }
 }
 
 #endif