Allow <use> inside author shadow roots

Source/core/svg/SVGUseElement.cpp

 /*
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007 Rob Buis <buis@kde.org>
  * Copyright (C) Research In Motion Limited 2009-2010. All rights reserved.
  * Copyright (C) 2011 Torch Mobile (Beijing) Co. Ltd. All rights reserved.
  * Copyright (C) 2012 University of Szeged
  * Copyright (C) 2012 Renata Hodovan <reni@webkit.org>
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ skipping 56 matching lines @@
     ScriptWrappable::init(this);
 
     addToPropertyMap(m_x);
     addToPropertyMap(m_y);
     addToPropertyMap(m_width);
     addToPropertyMap(m_height);
 }
 
 PassRefPtr<SVGUseElement> SVGUseElement::create(Document& document, bool wasInsertedByParser)
 {
-    // Always build a #shadow-root for SVGUseElement.
+    // Always build a user agent #shadow-root for SVGUseElement.
     RefPtr<SVGUseElement> use = adoptRef(new SVGUseElement(document, wasInsertedByParser));
     use->ensureUserAgentShadowRoot();
     return use.release();
 }
 
 SVGUseElement::~SVGUseElement()
 {
     setDocumentResource(0);
 
     clearResourceReferences();
@@ skipping 250 matching lines @@
     for (Node* cur = start->firstChild(); cur; cur = cur->nextSibling()) {
         if (subtreeContainsDisallowedElement(cur))
             return true;
     }
 
     return false;
 }
 
 void SVGUseElement::scheduleShadowTreeRecreation()
 {
-    if (!referencedDocument() || isInShadowTree())
+    if (!referencedDocument() || isInUserAgentShadowTree())
         return;
     m_needsShadowTreeRecreation = true;
     document().scheduleUseShadowTreeUpdate(*this);
 }
 
 void SVGUseElement::clearResourceReferences()
 {
     // FIXME: We should try to optimize this, to at least allow partial reclones.
     if (ShadowRoot* shadowTreeRootElement = userAgentShadowRoot())
         shadowTreeRootElement->removeChildren();
 
     if (m_targetElementInstance) {
         m_targetElementInstance->detach();
         m_targetElementInstance = nullptr;
     }
 
     m_needsShadowTreeRecreation = false;
     document().unscheduleUseShadowTreeUpdate(*this);
 
     document().accessSVGExtensions().removeAllTargetReferencesForElement(this);
 }
 
 void SVGUseElement::buildPendingResource()
 {
-    if (!referencedDocument() || isInShadowTree())
+    if (!referencedDocument() || isInUserAgentShadowTree())
         return;
     clearResourceReferences();
     if (!inDocument())
         return;
 
     AtomicString id;
     Element* target = SVGURIReference::targetElementFromIRIString(hrefString(), document(), &id, externalDocument());
     if (!target || !target->inDocument()) {
         // If we can't find the target of an external element, just give up.
         // We can't observe if the target somewhen enters the external document, nor should we do it.
@@ skipping 12 matching lines @@
         invalidateDependentShadowTrees();
     }
 
     ASSERT(!m_needsShadowTreeRecreation);
 }
 
 void SVGUseElement::buildShadowAndInstanceTree(SVGElement* target)
 {
     ASSERT(!m_targetElementInstance);
 
-    // Do not build the shadow/instance tree for <use> elements living in a shadow tree.
-    // The will be expanded soon anyway - see expandUseElementsInShadowTree().
-    if (isInShadowTree())
+    // <use> creates a "user agent" shadow root. Do not build the shadow/instance tree for <use>
+    // elements living in a user agent shadow tree because they will get expanded in a second
+    // pass -- see expandUseElementsInShadowTree().
+    if (isInUserAgentShadowTree())
         return;
 
     // Do not allow self-referencing.
     // 'target' may be null, if it's a non SVG namespaced element.
     if (!target || target == this)
         return;
 
     // Why a seperated instance/shadow tree? SVG demands it:
     // The instance tree is accesable from JavaScript, and has to
     // expose a 1:1 copy of the referenced tree, whereas internally we need
@@ skipping 248 matching lines @@
 
     userAgentShadowRoot()->appendChild(newChild.release());
 }
 
 void SVGUseElement::expandUseElementsInShadowTree(Node* element)
 {
     ASSERT(element);
     // Why expand the <use> elements in the shadow tree here, and not just
     // do this directly in buildShadowTree, if we encounter a <use> element?
     //
-    // Short answer: Because we may miss to expand some elements. Ie. if a <symbol>
-    // contains <use> tags, we'd miss them. So once we're done with settin' up the
+    // Short answer: Because we may miss to expand some elements. For example, if a <symbol>
+    // contains <use> tags, we'd miss them. So once we're done with setting up the
     // actual shadow tree (after the special case modification for svg/symbol) we have
     // to walk it completely and expand all <use> elements.
     if (isSVGUseElement(*element)) {
         SVGUseElement* use = toSVGUseElement(element);
         ASSERT(!use->resourceIsStillLoading());
 
         ASSERT(referencedDocument());
         Element* targetElement = SVGURIReference::targetElementFromIRIString(use->hrefString(), *referencedDocument());
         SVGElement* target = 0;
         if (targetElement && targetElement->isSVGElement())
@@ skipping 193 matching lines @@
 
     to->cloneDataFromElement(*from);
 
     to->removeAttribute(SVGNames::xAttr);
     to->removeAttribute(SVGNames::yAttr);
     to->removeAttribute(SVGNames::widthAttr);
     to->removeAttribute(SVGNames::heightAttr);
     to->removeAttribute(XLinkNames::hrefAttr);
 }
 
+bool SVGUseElement::isInUserAgentShadowTree() const
+{
+    if (ShadowRoot* shadowRoot = containingShadowRoot())
+        return shadowRoot->type() == ShadowRoot::UserAgentShadowRoot;
+    return false;
+}
+
 bool SVGUseElement::selfHasRelativeLengths() const
 {
     if (m_x->currentValue()->isRelative()
         || m_y->currentValue()->isRelative()
         || m_width->currentValue()->isRelative()
         || m_height->currentValue()->isRelative())
         return true;
 
     if (!m_targetElementInstance)
         return false;
@@ skipping 61 matching lines @@
 
     if (m_resource)
         m_resource->removeClient(this);
 
     m_resource = resource;
     if (m_resource)
         m_resource->addClient(this);
 }
 
 }