Source/core/svg/SVGDocumentExtensions.cpp - chromium/blink - Git at Google

 /*
  * Copyright (C) 2006 Apple Inc. All rights reserved.
  * Copyright (C) 2006 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2007 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 "config.h"
 #include "core/svg/SVGDocumentExtensions.h"

 #include "XLinkNames.h"
 #include "core/dom/Document.h"
 #include "core/rendering/svg/SVGResourcesCache.h"
 #include "core/svg/SVGElement.h"
 #include "core/svg/SVGSVGElement.h"
 #include "core/svg/animation/SMILTimeContainer.h"
 #include "wtf/text/AtomicString.h"

 namespace WebCore {

 SVGDocumentExtensions::SVGDocumentExtensions(Document* document)
     : m_document(document)
     , m_resourcesCache(adoptPtr(new SVGResourcesCache))
 {
 }

 SVGDocumentExtensions::~SVGDocumentExtensions()
 {
 }

 void SVGDocumentExtensions::addTimeContainer(SVGSVGElement* element)
 {
     m_timeContainers.add(element);
 }

 void SVGDocumentExtensions::removeTimeContainer(SVGSVGElement* element)
 {
     m_timeContainers.remove(element);
 }

 void SVGDocumentExtensions::addResource(const AtomicString& id, RenderSVGResourceContainer* resource)
 {
     ASSERT(resource);

     if (id.isEmpty())
         return;

     // Replaces resource if already present, to handle potential id changes
     m_resources.set(id, resource);
 }

 void SVGDocumentExtensions::removeResource(const AtomicString& id)
 {
     if (id.isEmpty() || !m_resources.contains(id))
         return;

     m_resources.remove(id);
 }

 RenderSVGResourceContainer* SVGDocumentExtensions::resourceById(const AtomicString& id) const
 {
     if (id.isEmpty())
         return 0;

     return m_resources.get(id);
 }

 void SVGDocumentExtensions::startAnimations()
 {
     // FIXME: Eventually every "Time Container" will need a way to latch on to some global timer
     // starting animations for a document will do this "latching"
     // FIXME: We hold a ref pointers to prevent a shadow tree from getting removed out from underneath us.
     // In the future we should refactor the use-element to avoid this. See https://webkit.org/b/53704
     Vector<RefPtr<SVGSVGElement> > timeContainers;
     timeContainers.appendRange(m_timeContainers.begin(), m_timeContainers.end());
     Vector<RefPtr<SVGSVGElement> >::iterator end = timeContainers.end();
     for (Vector<RefPtr<SVGSVGElement> >::iterator itr = timeContainers.begin(); itr != end; ++itr)
         (*itr)->timeContainer()->begin();
 }

 void SVGDocumentExtensions::pauseAnimations()
 {
     HashSet<SVGSVGElement*>::iterator end = m_timeContainers.end();
     for (HashSet<SVGSVGElement*>::iterator itr = m_timeContainers.begin(); itr != end; ++itr)
         (*itr)->pauseAnimations();
 }

 void SVGDocumentExtensions::unpauseAnimations()
 {
     HashSet<SVGSVGElement*>::iterator end = m_timeContainers.end();
     for (HashSet<SVGSVGElement*>::iterator itr = m_timeContainers.begin(); itr != end; ++itr)
         (*itr)->unpauseAnimations();
 }

 void SVGDocumentExtensions::dispatchSVGLoadEventToOutermostSVGElements()
 {
     Vector<RefPtr<SVGSVGElement> > timeContainers;
     timeContainers.appendRange(m_timeContainers.begin(), m_timeContainers.end());

     Vector<RefPtr<SVGSVGElement> >::iterator end = timeContainers.end();
     for (Vector<RefPtr<SVGSVGElement> >::iterator it = timeContainers.begin(); it != end; ++it) {
         SVGSVGElement* outerSVG = (*it).get();
         if (!outerSVG->isOutermostSVGSVGElement())
             continue;
         outerSVG->sendSVGLoadEventIfPossible();
     }
 }

 static void reportMessage(Document* document, MessageLevel level, const String& message)
 {
     if (document->frame())
         document->addConsoleMessage(RenderingMessageSource, level, message);
 }

 void SVGDocumentExtensions::reportWarning(const String& message)
 {
     reportMessage(m_document, WarningMessageLevel, "Warning: " + message);
 }

 void SVGDocumentExtensions::reportError(const String& message)
 {
     reportMessage(m_document, ErrorMessageLevel, "Error: " + message);
 }

 void SVGDocumentExtensions::addPendingResource(const AtomicString& id, Element* element)
 {
     ASSERT(element);

     if (id.isEmpty())
         return;

     HashMap<AtomicString, OwnPtr<SVGPendingElements> >::AddResult result = m_pendingResources.add(id, nullptr);
     if (result.isNewEntry)
         result.iterator->value = adoptPtr(new SVGPendingElements);
     result.iterator->value->add(element);

     element->setHasPendingResources();
 }

 bool SVGDocumentExtensions::hasPendingResource(const AtomicString& id) const
 {
     if (id.isEmpty())
         return false;

     return m_pendingResources.contains(id);
 }

 bool SVGDocumentExtensions::isElementPendingResources(Element* element) const
 {
     // This algorithm takes time proportional to the number of pending resources and need not.
     // If performance becomes an issue we can keep a counted set of elements and answer the question efficiently.

     ASSERT(element);

     HashMap<AtomicString, OwnPtr<SVGPendingElements> >::const_iterator end = m_pendingResources.end();
     for (HashMap<AtomicString, OwnPtr<SVGPendingElements> >::const_iterator it = m_pendingResources.begin(); it != end; ++it) {
         SVGPendingElements* elements = it->value.get();
         ASSERT(elements);

         if (elements->contains(element))
             return true;
     }
     return false;
 }

 bool SVGDocumentExtensions::isElementPendingResource(Element* element, const AtomicString& id) const
 {
     ASSERT(element);

     if (!hasPendingResource(id))
         return false;

     return m_pendingResources.get(id)->contains(element);
 }

 void SVGDocumentExtensions::clearHasPendingResourcesIfPossible(Element* element)
 {
     if (!isElementPendingResources(element))
         element->clearHasPendingResources();
 }

 void SVGDocumentExtensions::removeElementFromPendingResources(Element* element)
 {
     ASSERT(element);

     // Remove the element from pending resources.
     if (!m_pendingResources.isEmpty() && element->hasPendingResources()) {
         Vector<AtomicString> toBeRemoved;
         HashMap<AtomicString, OwnPtr<SVGPendingElements> >::iterator end = m_pendingResources.end();
         for (HashMap<AtomicString, OwnPtr<SVGPendingElements> >::iterator it = m_pendingResources.begin(); it != end; ++it) {
             SVGPendingElements* elements = it->value.get();
             ASSERT(elements);
             ASSERT(!elements->isEmpty());

             elements->remove(element);
             if (elements->isEmpty())
                 toBeRemoved.append(it->key);
         }

         clearHasPendingResourcesIfPossible(element);

         // We use the removePendingResource function here because it deals with set lifetime correctly.
         Vector<AtomicString>::iterator vectorEnd = toBeRemoved.end();
         for (Vector<AtomicString>::iterator it = toBeRemoved.begin(); it != vectorEnd; ++it)
             removePendingResource(*it);
     }

     // Remove the element from pending resources that were scheduled for removal.
     if (!m_pendingResourcesForRemoval.isEmpty()) {
         Vector<AtomicString> toBeRemoved;
         HashMap<AtomicString, OwnPtr<SVGPendingElements> >::iterator end = m_pendingResourcesForRemoval.end();
         for (HashMap<AtomicString, OwnPtr<SVGPendingElements> >::iterator it = m_pendingResourcesForRemoval.begin(); it != end; ++it) {
             SVGPendingElements* elements = it->value.get();
             ASSERT(elements);
             ASSERT(!elements->isEmpty());

             elements->remove(element);
             if (elements->isEmpty())
                 toBeRemoved.append(it->key);
         }

         // We use the removePendingResourceForRemoval function here because it deals with set lifetime correctly.
         Vector<AtomicString>::iterator vectorEnd = toBeRemoved.end();
         for (Vector<AtomicString>::iterator it = toBeRemoved.begin(); it != vectorEnd; ++it)
             removePendingResourceForRemoval(*it);
     }
 }

 PassOwnPtr<SVGDocumentExtensions::SVGPendingElements> SVGDocumentExtensions::removePendingResource(const AtomicString& id)
 {
     ASSERT(m_pendingResources.contains(id));
     return m_pendingResources.take(id);
 }

 PassOwnPtr<SVGDocumentExtensions::SVGPendingElements> SVGDocumentExtensions::removePendingResourceForRemoval(const AtomicString& id)
 {
     ASSERT(m_pendingResourcesForRemoval.contains(id));
     return m_pendingResourcesForRemoval.take(id);
 }

 void SVGDocumentExtensions::markPendingResourcesForRemoval(const AtomicString& id)
 {
     if (id.isEmpty())
         return;

     ASSERT(!m_pendingResourcesForRemoval.contains(id));

     OwnPtr<SVGPendingElements> existing = m_pendingResources.take(id);
     if (existing && !existing->isEmpty())
         m_pendingResourcesForRemoval.add(id, existing.release());
 }

 Element* SVGDocumentExtensions::removeElementFromPendingResourcesForRemoval(const AtomicString& id)
 {
     if (id.isEmpty())
         return 0;

     SVGPendingElements* resourceSet = m_pendingResourcesForRemoval.get(id);
     if (!resourceSet || resourceSet->isEmpty())
         return 0;

     SVGPendingElements::iterator firstElement = resourceSet->begin();
     Element* element = *firstElement;

     resourceSet->remove(firstElement);

     if (resourceSet->isEmpty())
         removePendingResourceForRemoval(id);

     return element;
 }

 HashSet<SVGElement*>* SVGDocumentExtensions::setOfElementsReferencingTarget(SVGElement* referencedElement) const
 {
     ASSERT(referencedElement);
     const HashMap<SVGElement*, OwnPtr<HashSet<SVGElement*> > >::const_iterator it = m_elementDependencies.find(referencedElement);
     if (it == m_elementDependencies.end())
         return 0;
     return it->value.get();
 }

 void SVGDocumentExtensions::addElementReferencingTarget(SVGElement* referencingElement, SVGElement* referencedElement)
 {
     ASSERT(referencingElement);
     ASSERT(referencedElement);

     if (HashSet<SVGElement*>* elements = m_elementDependencies.get(referencedElement)) {
         elements->add(referencingElement);
         return;
     }

     OwnPtr<HashSet<SVGElement*> > elements = adoptPtr(new HashSet<SVGElement*>);
     elements->add(referencingElement);
     m_elementDependencies.set(referencedElement, elements.release());
 }

 void SVGDocumentExtensions::removeAllTargetReferencesForElement(SVGElement* referencingElement)
 {
     Vector<SVGElement*> toBeRemoved;

     HashMap<SVGElement*, OwnPtr<HashSet<SVGElement*> > >::iterator end = m_elementDependencies.end();
     for (HashMap<SVGElement*, OwnPtr<HashSet<SVGElement*> > >::iterator it = m_elementDependencies.begin(); it != end; ++it) {
         SVGElement* referencedElement = it->key;
         HashSet<SVGElement*>* referencingElements = it->value.get();
         HashSet<SVGElement*>::iterator setIt = referencingElements->find(referencingElement);
         if (setIt == referencingElements->end())
             continue;

         referencingElements->remove(setIt);
         if (referencingElements->isEmpty())
             toBeRemoved.append(referencedElement);
     }

     Vector<SVGElement*>::iterator vectorEnd = toBeRemoved.end();
     for (Vector<SVGElement*>::iterator it = toBeRemoved.begin(); it != vectorEnd; ++it)
         m_elementDependencies.remove(*it);
 }

 void SVGDocumentExtensions::rebuildAllElementReferencesForTarget(SVGElement* referencedElement)
 {
     ASSERT(referencedElement);
     HashMap<SVGElement*, OwnPtr<HashSet<SVGElement*> > >::iterator it = m_elementDependencies.find(referencedElement);
     if (it == m_elementDependencies.end())
         return;
     ASSERT(it->key == referencedElement);
     Vector<SVGElement*> toBeNotified;

     HashSet<SVGElement*>* referencingElements = it->value.get();
     HashSet<SVGElement*>::iterator setEnd = referencingElements->end();
     for (HashSet<SVGElement*>::iterator setIt = referencingElements->begin(); setIt != setEnd; ++setIt)
         toBeNotified.append(*setIt);

     // Force rebuilding the referencingElement so it knows about this change.
     Vector<SVGElement*>::iterator vectorEnd = toBeNotified.end();
     for (Vector<SVGElement*>::iterator vectorIt = toBeNotified.begin(); vectorIt != vectorEnd; ++vectorIt) {
         // Before rebuilding referencingElement ensure it was not removed from under us.
         if (HashSet<SVGElement*>* referencingElements = setOfElementsReferencingTarget(referencedElement)) {
             if (referencingElements->contains(*vectorIt))
                 (*vectorIt)->svgAttributeChanged(XLinkNames::hrefAttr);
         }
     }
 }

 void SVGDocumentExtensions::removeAllElementReferencesForTarget(SVGElement* referencedElement)
 {
     ASSERT(referencedElement);
     HashMap<SVGElement*, OwnPtr<HashSet<SVGElement*> > >::iterator it = m_elementDependencies.find(referencedElement);
     if (it == m_elementDependencies.end())
         return;
     ASSERT(it->key == referencedElement);

     m_elementDependencies.remove(it);
 }

 #if ENABLE(SVG_FONTS)
 void SVGDocumentExtensions::registerSVGFontFaceElement(SVGFontFaceElement* element)
 {
     m_svgFontFaceElements.add(element);
 }

 void SVGDocumentExtensions::unregisterSVGFontFaceElement(SVGFontFaceElement* element)
 {
     ASSERT(m_svgFontFaceElements.contains(element));
     m_svgFontFaceElements.remove(element);
 }
 #endif

 }
	/*
	* Copyright (C) 2006 Apple Inc. All rights reserved.
	* Copyright (C) 2006 Nikolas Zimmermann <zimmermann@kde.org>
	* Copyright (C) 2007 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 "config.h"
	#include "core/svg/SVGDocumentExtensions.h"

	#include "XLinkNames.h"
	#include "core/dom/Document.h"
	#include "core/rendering/svg/SVGResourcesCache.h"
	#include "core/svg/SVGElement.h"
	#include "core/svg/SVGSVGElement.h"
	#include "core/svg/animation/SMILTimeContainer.h"
	#include "wtf/text/AtomicString.h"

	namespace WebCore {

	SVGDocumentExtensions::SVGDocumentExtensions(Document* document)
	: m_document(document)
	, m_resourcesCache(adoptPtr(new SVGResourcesCache))
	{
	}

	SVGDocumentExtensions::~SVGDocumentExtensions()
	{
	}

	void SVGDocumentExtensions::addTimeContainer(SVGSVGElement* element)
	{
	m_timeContainers.add(element);
	}

	void SVGDocumentExtensions::removeTimeContainer(SVGSVGElement* element)
	{
	m_timeContainers.remove(element);
	}

	void SVGDocumentExtensions::addResource(const AtomicString& id, RenderSVGResourceContainer* resource)
	{
	ASSERT(resource);

	if (id.isEmpty())
	return;

	// Replaces resource if already present, to handle potential id changes
	m_resources.set(id, resource);
	}

	void SVGDocumentExtensions::removeResource(const AtomicString& id)
	{
	if (id.isEmpty() \|\| !m_resources.contains(id))
	return;

	m_resources.remove(id);
	}

	RenderSVGResourceContainer* SVGDocumentExtensions::resourceById(const AtomicString& id) const
	{
	if (id.isEmpty())
	return 0;

	return m_resources.get(id);
	}

	void SVGDocumentExtensions::startAnimations()
	{
	// FIXME: Eventually every "Time Container" will need a way to latch on to some global timer
	// starting animations for a document will do this "latching"
	// FIXME: We hold a ref pointers to prevent a shadow tree from getting removed out from underneath us.
	// In the future we should refactor the use-element to avoid this. See https://webkit.org/b/53704
	Vector<RefPtr<SVGSVGElement> > timeContainers;
	timeContainers.appendRange(m_timeContainers.begin(), m_timeContainers.end());
	Vector<RefPtr<SVGSVGElement> >::iterator end = timeContainers.end();
	for (Vector<RefPtr<SVGSVGElement> >::iterator itr = timeContainers.begin(); itr != end; ++itr)
	(*itr)->timeContainer()->begin();
	}

	void SVGDocumentExtensions::pauseAnimations()
	{
	HashSet<SVGSVGElement*>::iterator end = m_timeContainers.end();
	for (HashSet<SVGSVGElement*>::iterator itr = m_timeContainers.begin(); itr != end; ++itr)
	(*itr)->pauseAnimations();
	}

	void SVGDocumentExtensions::unpauseAnimations()
	{
	HashSet<SVGSVGElement*>::iterator end = m_timeContainers.end();
	for (HashSet<SVGSVGElement*>::iterator itr = m_timeContainers.begin(); itr != end; ++itr)
	(*itr)->unpauseAnimations();
	}

	void SVGDocumentExtensions::dispatchSVGLoadEventToOutermostSVGElements()
	{
	Vector<RefPtr<SVGSVGElement> > timeContainers;
	timeContainers.appendRange(m_timeContainers.begin(), m_timeContainers.end());

	Vector<RefPtr<SVGSVGElement> >::iterator end = timeContainers.end();
	for (Vector<RefPtr<SVGSVGElement> >::iterator it = timeContainers.begin(); it != end; ++it) {
	SVGSVGElement* outerSVG = (*it).get();
	if (!outerSVG->isOutermostSVGSVGElement())
	continue;
	outerSVG->sendSVGLoadEventIfPossible();
	}
	}

	static void reportMessage(Document* document, MessageLevel level, const String& message)
	{
	if (document->frame())
	document->addConsoleMessage(RenderingMessageSource, level, message);
	}

	void SVGDocumentExtensions::reportWarning(const String& message)
	{
	reportMessage(m_document, WarningMessageLevel, "Warning: " + message);
	}

	void SVGDocumentExtensions::reportError(const String& message)
	{
	reportMessage(m_document, ErrorMessageLevel, "Error: " + message);
	}

	void SVGDocumentExtensions::addPendingResource(const AtomicString& id, Element* element)
	{
	ASSERT(element);

	if (id.isEmpty())
	return;

	HashMap<AtomicString, OwnPtr<SVGPendingElements> >::AddResult result = m_pendingResources.add(id, nullptr);
	if (result.isNewEntry)
	result.iterator->value = adoptPtr(new SVGPendingElements);
	result.iterator->value->add(element);

	element->setHasPendingResources();
	}

	bool SVGDocumentExtensions::hasPendingResource(const AtomicString& id) const
	{
	if (id.isEmpty())
	return false;

	return m_pendingResources.contains(id);
	}

	bool SVGDocumentExtensions::isElementPendingResources(Element* element) const
	{
	// This algorithm takes time proportional to the number of pending resources and need not.
	// If performance becomes an issue we can keep a counted set of elements and answer the question efficiently.

	ASSERT(element);

	HashMap<AtomicString, OwnPtr<SVGPendingElements> >::const_iterator end = m_pendingResources.end();
	for (HashMap<AtomicString, OwnPtr<SVGPendingElements> >::const_iterator it = m_pendingResources.begin(); it != end; ++it) {
	SVGPendingElements* elements = it->value.get();
	ASSERT(elements);

	if (elements->contains(element))
	return true;
	}
	return false;
	}

	bool SVGDocumentExtensions::isElementPendingResource(Element* element, const AtomicString& id) const
	{
	ASSERT(element);

	if (!hasPendingResource(id))
	return false;

	return m_pendingResources.get(id)->contains(element);
	}

	void SVGDocumentExtensions::clearHasPendingResourcesIfPossible(Element* element)
	{
	if (!isElementPendingResources(element))
	element->clearHasPendingResources();
	}

	void SVGDocumentExtensions::removeElementFromPendingResources(Element* element)
	{
	ASSERT(element);

	// Remove the element from pending resources.
	if (!m_pendingResources.isEmpty() && element->hasPendingResources()) {
	Vector<AtomicString> toBeRemoved;
	HashMap<AtomicString, OwnPtr<SVGPendingElements> >::iterator end = m_pendingResources.end();
	for (HashMap<AtomicString, OwnPtr<SVGPendingElements> >::iterator it = m_pendingResources.begin(); it != end; ++it) {
	SVGPendingElements* elements = it->value.get();
	ASSERT(elements);
	ASSERT(!elements->isEmpty());

	elements->remove(element);
	if (elements->isEmpty())
	toBeRemoved.append(it->key);
	}

	clearHasPendingResourcesIfPossible(element);

	// We use the removePendingResource function here because it deals with set lifetime correctly.
	Vector<AtomicString>::iterator vectorEnd = toBeRemoved.end();
	for (Vector<AtomicString>::iterator it = toBeRemoved.begin(); it != vectorEnd; ++it)
	removePendingResource(*it);
	}

	// Remove the element from pending resources that were scheduled for removal.
	if (!m_pendingResourcesForRemoval.isEmpty()) {
	Vector<AtomicString> toBeRemoved;
	HashMap<AtomicString, OwnPtr<SVGPendingElements> >::iterator end = m_pendingResourcesForRemoval.end();
	for (HashMap<AtomicString, OwnPtr<SVGPendingElements> >::iterator it = m_pendingResourcesForRemoval.begin(); it != end; ++it) {
	SVGPendingElements* elements = it->value.get();
	ASSERT(elements);
	ASSERT(!elements->isEmpty());

	elements->remove(element);
	if (elements->isEmpty())
	toBeRemoved.append(it->key);
	}

	// We use the removePendingResourceForRemoval function here because it deals with set lifetime correctly.
	Vector<AtomicString>::iterator vectorEnd = toBeRemoved.end();
	for (Vector<AtomicString>::iterator it = toBeRemoved.begin(); it != vectorEnd; ++it)
	removePendingResourceForRemoval(*it);
	}
	}

	PassOwnPtr<SVGDocumentExtensions::SVGPendingElements> SVGDocumentExtensions::removePendingResource(const AtomicString& id)
	{
	ASSERT(m_pendingResources.contains(id));
	return m_pendingResources.take(id);
	}

	PassOwnPtr<SVGDocumentExtensions::SVGPendingElements> SVGDocumentExtensions::removePendingResourceForRemoval(const AtomicString& id)
	{
	ASSERT(m_pendingResourcesForRemoval.contains(id));
	return m_pendingResourcesForRemoval.take(id);
	}

	void SVGDocumentExtensions::markPendingResourcesForRemoval(const AtomicString& id)
	{
	if (id.isEmpty())
	return;

	ASSERT(!m_pendingResourcesForRemoval.contains(id));

	OwnPtr<SVGPendingElements> existing = m_pendingResources.take(id);
	if (existing && !existing->isEmpty())
	m_pendingResourcesForRemoval.add(id, existing.release());
	}

	Element* SVGDocumentExtensions::removeElementFromPendingResourcesForRemoval(const AtomicString& id)
	{
	if (id.isEmpty())
	return 0;

	SVGPendingElements* resourceSet = m_pendingResourcesForRemoval.get(id);
	if (!resourceSet \|\| resourceSet->isEmpty())
	return 0;

	SVGPendingElements::iterator firstElement = resourceSet->begin();
	Element* element = *firstElement;

	resourceSet->remove(firstElement);

	if (resourceSet->isEmpty())
	removePendingResourceForRemoval(id);

	return element;
	}

	HashSet<SVGElement> SVGDocumentExtensions::setOfElementsReferencingTarget(SVGElement* referencedElement) const
	{
	ASSERT(referencedElement);
	const HashMap<SVGElement, OwnPtr<HashSet<SVGElement> > >::const_iterator it = m_elementDependencies.find(referencedElement);
	if (it == m_elementDependencies.end())
	return 0;
	return it->value.get();
	}

	void SVGDocumentExtensions::addElementReferencingTarget(SVGElement* referencingElement, SVGElement* referencedElement)
	{
	ASSERT(referencingElement);
	ASSERT(referencedElement);

	if (HashSet<SVGElement> elements = m_elementDependencies.get(referencedElement)) {
	elements->add(referencingElement);
	return;
	}

	OwnPtr<HashSet<SVGElement> > elements = adoptPtr(new HashSet<SVGElement>);
	elements->add(referencingElement);
	m_elementDependencies.set(referencedElement, elements.release());
	}

	void SVGDocumentExtensions::removeAllTargetReferencesForElement(SVGElement* referencingElement)
	{
	Vector<SVGElement*> toBeRemoved;

	HashMap<SVGElement, OwnPtr<HashSet<SVGElement> > >::iterator end = m_elementDependencies.end();
	for (HashMap<SVGElement, OwnPtr<HashSet<SVGElement> > >::iterator it = m_elementDependencies.begin(); it != end; ++it) {
	SVGElement* referencedElement = it->key;
	HashSet<SVGElement> referencingElements = it->value.get();
	HashSet<SVGElement*>::iterator setIt = referencingElements->find(referencingElement);
	if (setIt == referencingElements->end())
	continue;

	referencingElements->remove(setIt);
	if (referencingElements->isEmpty())
	toBeRemoved.append(referencedElement);
	}

	Vector<SVGElement*>::iterator vectorEnd = toBeRemoved.end();
	for (Vector<SVGElement*>::iterator it = toBeRemoved.begin(); it != vectorEnd; ++it)
	m_elementDependencies.remove(*it);
	}

	void SVGDocumentExtensions::rebuildAllElementReferencesForTarget(SVGElement* referencedElement)
	{
	ASSERT(referencedElement);
	HashMap<SVGElement, OwnPtr<HashSet<SVGElement> > >::iterator it = m_elementDependencies.find(referencedElement);
	if (it == m_elementDependencies.end())
	return;
	ASSERT(it->key == referencedElement);
	Vector<SVGElement*> toBeNotified;

	HashSet<SVGElement> referencingElements = it->value.get();
	HashSet<SVGElement*>::iterator setEnd = referencingElements->end();
	for (HashSet<SVGElement*>::iterator setIt = referencingElements->begin(); setIt != setEnd; ++setIt)
	toBeNotified.append(*setIt);

	// Force rebuilding the referencingElement so it knows about this change.
	Vector<SVGElement*>::iterator vectorEnd = toBeNotified.end();
	for (Vector<SVGElement*>::iterator vectorIt = toBeNotified.begin(); vectorIt != vectorEnd; ++vectorIt) {
	// Before rebuilding referencingElement ensure it was not removed from under us.
	if (HashSet<SVGElement> referencingElements = setOfElementsReferencingTarget(referencedElement)) {
	if (referencingElements->contains(*vectorIt))
	(*vectorIt)->svgAttributeChanged(XLinkNames::hrefAttr);
	}
	}
	}

	void SVGDocumentExtensions::removeAllElementReferencesForTarget(SVGElement* referencedElement)
	{
	ASSERT(referencedElement);
	HashMap<SVGElement, OwnPtr<HashSet<SVGElement> > >::iterator it = m_elementDependencies.find(referencedElement);
	if (it == m_elementDependencies.end())
	return;
	ASSERT(it->key == referencedElement);

	m_elementDependencies.remove(it);
	}

	#if ENABLE(SVG_FONTS)
	void SVGDocumentExtensions::registerSVGFontFaceElement(SVGFontFaceElement* element)
	{
	m_svgFontFaceElements.add(element);
	}

	void SVGDocumentExtensions::unregisterSVGFontFaceElement(SVGFontFaceElement* element)
	{
	ASSERT(m_svgFontFaceElements.contains(element));
	m_svgFontFaceElements.remove(element);
	}
	#endif

	}