Add a new mechanism for watching SVGElement 'href' targets

third_party/WebKit/Source/core/svg/SVGURIReference.cpp

 /*
  * Copyright (C) 2004, 2005, 2008 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2004, 2005, 2006 Rob Buis <buis@kde.org>
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Library General Public License for more details.
  *
  * You should have received a copy of the GNU Library General Public License
  * along with this library; see the file COPYING.LIB.  If not, write to
  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  * Boston, MA 02110-1301, USA.
  */
 
 #include "core/svg/SVGURIReference.h"
 
 #include "core/XLinkNames.h"
+#include "core/dom/IdTargetObserver.h"
 #include "core/html/parser/HTMLParserIdioms.h"
 #include "core/svg/SVGElement.h"
 #include "platform/weborigin/KURL.h"
 
 namespace blink {
 
+namespace {
+
+class SVGElementReferenceObserver : public IdTargetObserver {
+ public:
+  SVGElementReferenceObserver(TreeScope& treeScope,
+                              const AtomicString& id,
+                              std::unique_ptr<WTF::Closure> closure)
+      : IdTargetObserver(treeScope.idTargetObserverRegistry(), id),
+        m_closure(std::move(closure)) {}
+
+ private:
+  void idTargetChanged() override { (*m_closure)(); }
+  std::unique_ptr<WTF::Closure> m_closure;
+};
+}
+
 SVGURIReference::SVGURIReference(SVGElement* element)
     : m_href(SVGAnimatedHref::create(element)) {
   ASSERT(element);
   m_href->addToPropertyMap(element);
 }
 
 DEFINE_TRACE(SVGURIReference) {
   visitor->trace(m_href);
 }
 
@@ skipping 51 matching lines @@
     const TreeScope& treeScope,
     AtomicString* fragmentIdentifier) {
   AtomicString id = fragmentIdentifierFromIRIString(urlString, treeScope);
   if (id.isEmpty())
     return nullptr;
   if (fragmentIdentifier)
     *fragmentIdentifier = id;
   return treeScope.getElementById(id);
 }
 
+Element* SVGURIReference::observeTarget(Member<IdTargetObserver>& observer,
+                                        SVGElement& contextElement) {
+  DCHECK(!observer);
+  TreeScope& treeScope = contextElement.treeScope();
+  AtomicString id = fragmentIdentifierFromIRIString(hrefString(), treeScope);
+  if (id.isEmpty())
+    return nullptr;
+  observer = new SVGElementReferenceObserver(
+      treeScope, id,
+      WTF::bind(&SVGElement::buildPendingResource,
+                wrapWeakPersistent(&contextElement)));
+  return treeScope.getElementById(id);
+}
+
+void SVGURIReference::unobserveTarget(Member<IdTargetObserver>& observer) {
+  if (!observer)
+    return;
+  observer->unregister();
+  observer = nullptr;
+}
+
 }  // namespace blink