Implement closed shadow adjustment for Element.offsetParent

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 3226 matching lines @@
     ASSERT(m_node);
 
     // Image change notifications should not be received during paint because
     // the resulting invalidations will be cleared following paint. This can also
     // lead to modifying the tree out from under paint(), see: crbug.com/616700.
     DCHECK(document().lifecycle().state() != DocumentLifecycle::LifecycleState::InPaint);
 
     imageChanged(static_cast<WrappedImagePtr>(image), rect);
 }
 
-Element* LayoutObject::offsetParent() const
+Element* LayoutObject::offsetParentInternal() const
 {
     if (isDocumentElement() || isBody())
         return nullptr;
 
     if (isOutOfFlowPositioned() && style()->position() == FixedPosition)
         return nullptr;
 
     float effectiveZoom = style()->effectiveZoom();
     Node* node = nullptr;
     for (LayoutObject* ancestor = parent(); ancestor; ancestor = ancestor->parent()) {
@@ skipping 14 matching lines @@
             break;
 
         // Webkit specific extension where offsetParent stops at zoom level changes.
         if (effectiveZoom != ancestor->style()->effectiveZoom())
             break;
     }
 
     return node && node->isElementNode() ? toElement(node) : nullptr;
 }
 
+Element* LayoutObject::offsetParent() const

[hayato, 2016/06/09 08:22:03]

A binding layer is the only client for this method?
Unless that, do not change the behavior of LayoutObject::offsetParent().
That would break something if there are other callers than bindings.

Rather, we should have Element::offsetParentForBinding(), and remove *unclosed
check* from Element::offsetParent and LayoutObject::offsetParent().

[kochi, 2016/06/09 13:09:28]

Good catch!

Currently Element::offsetParent() is only used for HTMLElement.offsetParent
binding
so it should be fine, but LayoutObject::offsetParent() is used for other
purposes,
thus this may break something.

So I separated LayoutObject::offsetParent() into offsetParent() and
offsetParentForBinding(), because LayoutBoxModelObject::offsetTop() et al.
depend on the returned element of offsetParentForBinding() - otherwise
Element.offsetTop et al. would return wrong offset.

The logic in the original offsetParent() looks quite tied with the CSSOM spec,
so I'm not sure how other users (e.g. spatial navigation and hit-test region
visualizer) depend on the Shadow DOM unclosed node behavior.
But I guess spatial navigation should work regardless of Shadow DOM, so keeping
the original offsetParent() should make sense here.

I'll ask for another look from layout team reviewer.

+{
+    Element* element = offsetParentInternal();
+
+    while (element && !element->isUnclosedNodeOf(*node()))
+        element = element->layoutObject()->offsetParent();
+
+    return element;
+}
+
 PositionWithAffinity LayoutObject::createPositionWithAffinity(int offset, TextAffinity affinity)
 {
     // If this is a non-anonymous layoutObject in an editable area, then it's simple.
     if (Node* node = nonPseudoNode()) {
         if (!node->hasEditableStyle()) {
             // If it can be found, we prefer a visually equivalent position that is editable.
             const Position position = Position(node, offset);
             Position candidate = mostForwardCaretPosition(position, CanCrossEditingBoundary);
             if (candidate.anchorNode()->hasEditableStyle())
                 return PositionWithAffinity(candidate, affinity);
@@ skipping 416 matching lines @@
         const blink::LayoutObject* root = object1;
         while (root->parent())
             root = root->parent();
         root->showLayoutTreeAndMark(object1, "*", object2, "-", 0);
     } else {
         fprintf(stderr, "Cannot showLayoutTree. Root is (nil)\n");
     }
 }
 
 #endif