Imported WebKit commit 2ea9d364d0f6efa8fa64acf19f451504c59be0e4 (http://svn.webkit.org/repository/webkit/trunk@104285)

1 files changed, 1065 insertions, 0 deletions

diff --git a/Source/WebCore/svg/SVGUseElement.cpp b/Source/WebCore/svg/SVGUseElement.cpp
new file mode 100644
index 000000000..55f70f453
--- /dev/null
+++ b/Source/WebCore/svg/SVGUseElement.cpp
@@ -0,0 +1,1065 @@
+/*
+ * 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.
+ *
+ * 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"
+
+#if ENABLE(SVG)
+#include "SVGUseElement.h"
+
+#include "Attribute.h"
+#include "CSSStyleSelector.h"
+#include "Document.h"
+#include "Event.h"
+#include "EventListener.h"
+#include "HTMLNames.h"
+#include "NodeRenderStyle.h"
+#include "RegisteredEventListener.h"
+#include "RenderSVGResource.h"
+#include "RenderSVGShadowTreeRootContainer.h"
+#include "SVGElementInstance.h"
+#include "SVGElementRareData.h"
+#include "SVGElementInstanceList.h"
+#include "SVGGElement.h"
+#include "SVGLengthContext.h"
+#include "SVGNames.h"
+#include "SVGSMILElement.h"
+#include "SVGSVGElement.h"
+#include "SVGShadowTreeElements.h"
+#include "SVGSymbolElement.h"
+#include "XLinkNames.h"
+#include "XMLDocumentParser.h"
+#include "XMLSerializer.h"
+
+// Dump SVGElementInstance object tree - useful to debug instanceRoot problems
+// #define DUMP_INSTANCE_TREE
+
+// Dump the deep-expanded shadow tree (where the renderers are built from)
+// #define DUMP_SHADOW_TREE
+
+namespace WebCore {
+
+// Animated property definitions
+DEFINE_ANIMATED_LENGTH(SVGUseElement, SVGNames::xAttr, X, x)
+DEFINE_ANIMATED_LENGTH(SVGUseElement, SVGNames::yAttr, Y, y)
+DEFINE_ANIMATED_LENGTH(SVGUseElement, SVGNames::widthAttr, Width, width)
+DEFINE_ANIMATED_LENGTH(SVGUseElement, SVGNames::heightAttr, Height, height)
+DEFINE_ANIMATED_STRING(SVGUseElement, XLinkNames::hrefAttr, Href, href)
+DEFINE_ANIMATED_BOOLEAN(SVGUseElement, SVGNames::externalResourcesRequiredAttr, ExternalResourcesRequired, externalResourcesRequired)
+
+BEGIN_REGISTER_ANIMATED_PROPERTIES(SVGUseElement)
+    REGISTER_LOCAL_ANIMATED_PROPERTY(x)
+    REGISTER_LOCAL_ANIMATED_PROPERTY(y)
+    REGISTER_LOCAL_ANIMATED_PROPERTY(width)
+    REGISTER_LOCAL_ANIMATED_PROPERTY(height)
+    REGISTER_LOCAL_ANIMATED_PROPERTY(href)
+    REGISTER_LOCAL_ANIMATED_PROPERTY(externalResourcesRequired)
+    REGISTER_PARENT_ANIMATED_PROPERTIES(SVGStyledTransformableElement)
+    REGISTER_PARENT_ANIMATED_PROPERTIES(SVGTests)
+END_REGISTER_ANIMATED_PROPERTIES
+
+inline SVGUseElement::SVGUseElement(const QualifiedName& tagName, Document* document)
+    : SVGStyledTransformableElement(tagName, document)
+    , m_x(LengthModeWidth)
+    , m_y(LengthModeHeight)
+    , m_width(LengthModeWidth)
+    , m_height(LengthModeHeight)
+    , m_updatesBlocked(false)
+    , m_needsShadowTreeRecreation(false)
+{
+    ASSERT(hasTagName(SVGNames::useTag));
+    registerAnimatedPropertiesForSVGUseElement();
+    
+    setHasCustomWillOrDidRecalcStyle();
+}
+
+PassRefPtr<SVGUseElement> SVGUseElement::create(const QualifiedName& tagName, Document* document)
+{
+    return adoptRef(new SVGUseElement(tagName, document));
+}
+
+SVGElementInstance* SVGUseElement::instanceRoot()
+{
+    // If there is no element instance tree, force immediate SVGElementInstance tree
+    // creation by asking the document to invoke our recalcStyle function - as we can't
+    // wait for the lazy creation to happen if e.g. JS wants to access the instanceRoot
+    // object right after creating the element on-the-fly
+    if (!m_targetElementInstance)
+        document()->updateLayoutIgnorePendingStylesheets();
+
+    return m_targetElementInstance.get();
+}
+
+SVGElementInstance* SVGUseElement::animatedInstanceRoot() const
+{
+    // FIXME: Implement me.
+    return 0;
+}
+ 
+bool SVGUseElement::isSupportedAttribute(const QualifiedName& attrName)
+{
+    DEFINE_STATIC_LOCAL(HashSet<QualifiedName>, supportedAttributes, ());
+    if (supportedAttributes.isEmpty()) {
+        SVGTests::addSupportedAttributes(supportedAttributes);
+        SVGLangSpace::addSupportedAttributes(supportedAttributes);
+        SVGExternalResourcesRequired::addSupportedAttributes(supportedAttributes);
+        SVGURIReference::addSupportedAttributes(supportedAttributes);
+        supportedAttributes.add(SVGNames::xAttr);
+        supportedAttributes.add(SVGNames::yAttr);
+        supportedAttributes.add(SVGNames::widthAttr);
+        supportedAttributes.add(SVGNames::heightAttr);
+    }
+    return supportedAttributes.contains<QualifiedName, SVGAttributeHashTranslator>(attrName);
+}
+
+void SVGUseElement::parseMappedAttribute(Attribute* attr)
+{
+    SVGParsingError parseError = NoError;
+
+    if (!isSupportedAttribute(attr->name()))
+        SVGStyledTransformableElement::parseMappedAttribute(attr);
+    else if (attr->name() == SVGNames::xAttr)
+        setXBaseValue(SVGLength::construct(LengthModeWidth, attr->value(), parseError));
+    else if (attr->name() == SVGNames::yAttr)
+        setYBaseValue(SVGLength::construct(LengthModeHeight, attr->value(), parseError));
+    else if (attr->name() == SVGNames::widthAttr)
+        setWidthBaseValue(SVGLength::construct(LengthModeWidth, attr->value(), parseError, ForbidNegativeLengths));
+    else if (attr->name() == SVGNames::heightAttr)
+        setHeightBaseValue(SVGLength::construct(LengthModeHeight, attr->value(), parseError, ForbidNegativeLengths));
+    else if (SVGTests::parseMappedAttribute(attr)
+             || SVGLangSpace::parseMappedAttribute(attr)
+             || SVGExternalResourcesRequired::parseMappedAttribute(attr)
+             || SVGURIReference::parseMappedAttribute(attr)) {
+    } else
+        ASSERT_NOT_REACHED();
+
+    reportAttributeParsingError(parseError, attr);
+}
+
+static inline bool isWellFormedDocument(Document* document)
+{
+    if (document->isSVGDocument() || document->isXHTMLDocument())
+        return static_cast<XMLDocumentParser*>(document->parser())->wellFormed();
+    return true;
+}
+
+void SVGUseElement::insertedIntoDocument()
+{
+    // This functions exists to assure assumptions made in the code regarding SVGElementInstance creation/destruction are satisfied.
+    SVGStyledTransformableElement::insertedIntoDocument();
+    ASSERT(!m_targetElementInstance || !isWellFormedDocument(document()));
+    ASSERT(!hasPendingResources() || !isWellFormedDocument(document()));
+}
+
+void SVGUseElement::removedFromDocument()
+{
+    SVGStyledTransformableElement::removedFromDocument();
+    detachInstance();
+}
+
+void SVGUseElement::svgAttributeChanged(const QualifiedName& attrName)
+{
+    if (!isSupportedAttribute(attrName)) {
+        SVGStyledTransformableElement::svgAttributeChanged(attrName);
+        return;
+    }
+
+    SVGElementInstance::InvalidationGuard invalidationGuard(this);
+
+    bool isXYAttribute = attrName == SVGNames::xAttr || attrName == SVGNames::yAttr;
+    bool isWidthHeightAttribute = attrName == SVGNames::widthAttr || attrName == SVGNames::heightAttr;
+
+    if (isXYAttribute || isWidthHeightAttribute)
+        updateRelativeLengthsInformation();
+
+    if (SVGTests::handleAttributeChange(this, attrName))
+        return;
+
+    RenderObject* object = renderer();
+    if (!object)
+        return;
+
+    if (SVGURIReference::isKnownAttribute(attrName)) {
+        if (hasPendingResources()) {
+            OwnPtr<SVGDocumentExtensions::SVGPendingElements> clients(document()->accessSVGExtensions()->removePendingResource(m_resourceId));
+            ASSERT(!clients->isEmpty());
+
+            const SVGDocumentExtensions::SVGPendingElements::const_iterator end = clients->end();
+            for (SVGDocumentExtensions::SVGPendingElements::const_iterator it = clients->begin(); it != end; ++it) {
+                ASSERT((*it)->hasPendingResources());
+                (*it)->clearHasPendingResourcesIfPossible();
+            }
+
+            m_resourceId = String();
+            clearHasPendingResourcesIfPossible();
+        }
+
+        m_targetElementInstance = 0;
+        invalidateShadowTree();
+        return;
+    }
+
+    if (isXYAttribute) {
+        updateContainerOffsets();
+        return;
+    }
+
+    if (isWidthHeightAttribute) {
+        updateContainerSizes();
+        return;
+    }
+
+    // Be very careful here, if svgAttributeChanged() has been called because a SVG CSS property changed, we do NOT want to reclone the tree!
+    if (SVGStyledElement::isKnownAttribute(attrName)) {
+        setNeedsStyleRecalc();
+        return;
+    }
+
+    if (SVGLangSpace::isKnownAttribute(attrName) || SVGExternalResourcesRequired::isKnownAttribute(attrName)) {
+        invalidateShadowTree();
+        return;
+    }
+
+    ASSERT_NOT_REACHED();
+}
+
+static void updateContainerSize(SVGElementInstance* targetInstance)
+{
+    // Depth-first used to write the method in early exit style, no particular other reason.
+    for (SVGElementInstance* instance = targetInstance->firstChild(); instance; instance = instance->nextSibling())
+        updateContainerSize(instance);
+
+    SVGUseElement* useElement = targetInstance->directUseElement();
+    if (!useElement)
+        return;
+
+    SVGElement* correspondingElement = targetInstance->correspondingElement();
+    ASSERT(correspondingElement);
+
+    bool isSymbolTag = correspondingElement->hasTagName(SVGNames::symbolTag);
+    if (!correspondingElement->hasTagName(SVGNames::svgTag) && !isSymbolTag)
+        return;
+
+    SVGElement* shadowTreeElement = targetInstance->shadowTreeElement();
+    ASSERT(shadowTreeElement);
+    ASSERT(shadowTreeElement->hasTagName(SVGNames::svgTag));
+
+    // Spec (<use> on <symbol>): This generated 'svg' will always have explicit values for attributes width and height.
+    // If attributes width and/or height are provided on the 'use' element, then these attributes
+    // will be transferred to the generated 'svg'. If attributes width and/or height are not specified,
+    // the generated 'svg' element will use values of 100% for these attributes.
+    
+    // Spec (<use> on <svg>): If attributes width and/or height are provided on the 'use' element, then these
+    // values will override the corresponding attributes on the 'svg' in the generated tree.
+
+    if (useElement->hasAttribute(SVGNames::widthAttr))
+        shadowTreeElement->setAttribute(SVGNames::widthAttr, useElement->getAttribute(SVGNames::widthAttr));
+    else if (isSymbolTag && shadowTreeElement->hasAttribute(SVGNames::widthAttr))
+        shadowTreeElement->setAttribute(SVGNames::widthAttr, "100%");
+
+    if (useElement->hasAttribute(SVGNames::heightAttr))
+        shadowTreeElement->setAttribute(SVGNames::heightAttr, useElement->getAttribute(SVGNames::heightAttr));
+    else if (isSymbolTag && shadowTreeElement->hasAttribute(SVGNames::heightAttr))
+        shadowTreeElement->setAttribute(SVGNames::heightAttr, "100%");
+}   
+
+void SVGUseElement::updateContainerSizes()
+{
+    if (!m_targetElementInstance)
+        return;
+
+    // Update whole subtree, scanning for shadow container elements, that correspond to <svg>/<symbol> tags
+    ASSERT(m_targetElementInstance->directUseElement() == this);
+    updateContainerSize(m_targetElementInstance.get());
+
+    if (RenderObject* object = renderer())
+        RenderSVGResource::markForLayoutAndParentResourceInvalidation(object);
+}
+
+static void updateContainerOffset(SVGElementInstance* targetInstance)
+{
+    // Depth-first used to write the method in early exit style, no particular other reason.
+    for (SVGElementInstance* instance = targetInstance->firstChild(); instance; instance = instance->nextSibling())
+        updateContainerOffset(instance);
+
+    SVGElement* correspondingElement = targetInstance->correspondingElement();
+    ASSERT(correspondingElement);
+
+    if (!correspondingElement->hasTagName(SVGNames::useTag))
+        return;
+
+    SVGElement* shadowTreeElement = targetInstance->shadowTreeElement();
+    ASSERT(shadowTreeElement);
+    ASSERT(shadowTreeElement->hasTagName(SVGNames::gTag));
+
+    if (!static_cast<SVGGElement*>(shadowTreeElement)->isShadowTreeContainerElement())
+        return;
+
+    // Spec: An additional transformation translate(x,y) is appended to the end
+    // (i.e., right-side) of the transform attribute on the generated 'g', where x
+    // and y represent the values of the x and y attributes on the 'use' element. 
+    SVGUseElement* useElement = static_cast<SVGUseElement*>(correspondingElement);
+    SVGShadowTreeContainerElement* containerElement = static_cast<SVGShadowTreeContainerElement*>(shadowTreeElement);
+    containerElement->setContainerOffset(useElement->x(), useElement->y());
+}
+
+void SVGUseElement::updateContainerOffsets()
+{
+    if (!m_targetElementInstance)
+        return;
+
+    // Update root container offset (not reachable through instance tree)
+    SVGElement* shadowRoot = m_targetElementInstance->shadowTreeElement();
+    ASSERT(shadowRoot);
+
+    ContainerNode* parentNode = shadowRoot->parentNode();
+    ASSERT(parentNode);
+    ASSERT(parentNode->isSVGElement());
+    ASSERT(parentNode->hasTagName(SVGNames::gTag));
+    ASSERT(static_cast<SVGGElement*>(parentNode)->isShadowTreeContainerElement());
+
+    SVGShadowTreeContainerElement* containerElement = static_cast<SVGShadowTreeContainerElement*>(parentNode);
+    containerElement->setContainerOffset(x(), y());
+
+    // Update whole subtree, scanning for shadow container elements, marking a cloned use subtree
+    updateContainerOffset(m_targetElementInstance.get());
+
+    if (RenderObject* object = renderer())
+        RenderSVGResource::markForLayoutAndParentResourceInvalidation(object);
+}
+
+bool SVGUseElement::willRecalcStyle(StyleChange change)
+{
+    // Eventually mark shadow root element needing style recalc
+    if ((change >= Inherit || needsStyleRecalc() || childNeedsStyleRecalc()) && m_targetElementInstance && !m_updatesBlocked) {
+        if (SVGElement* shadowRoot = m_targetElementInstance->shadowTreeElement())
+            shadowRoot->setNeedsStyleRecalc();
+    }
+    return true;
+}
+
+void SVGUseElement::didRecalcStyle(StyleChange change)
+{
+    // Assure that the shadow tree has not been marked for recreation, while we're building it.
+    if (m_updatesBlocked)
+        ASSERT(!m_needsShadowTreeRecreation);
+
+    RenderSVGShadowTreeRootContainer* shadowRoot = static_cast<RenderSVGShadowTreeRootContainer*>(renderer());
+    if (!shadowRoot)
+        return;
+    
+    bool needsStyleUpdate = !m_needsShadowTreeRecreation;
+    if (m_needsShadowTreeRecreation) {
+        shadowRoot->markShadowTreeForRecreation();
+        m_needsShadowTreeRecreation = false;
+    }
+
+    shadowRoot->updateFromElement();
+
+    if (!needsStyleUpdate)
+        return;
+
+    shadowRoot->updateStyle(change);
+}
+
+#ifdef DUMP_INSTANCE_TREE
+void dumpInstanceTree(unsigned int& depth, String& text, SVGElementInstance* targetInstance)
+{
+    SVGElement* element = targetInstance->correspondingElement();
+    ASSERT(element);
+
+    SVGElement* shadowTreeElement = targetInstance->shadowTreeElement();
+    ASSERT(shadowTreeElement);
+
+    SVGUseElement* directUseElement = targetInstance->directUseElement();
+    String directUseElementName = directUseElement ? directUseElement->nodeName() : "null";
+
+    String elementId = element->getIdAttribute();
+    String elementNodeName = element->nodeName();
+    String shadowTreeElementNodeName = shadowTreeElement->nodeName();
+    String parentNodeName = element->parentNode() ? element->parentNode()->nodeName() : "null";
+    String firstChildNodeName = element->firstChild() ? element->firstChild()->nodeName() : "null";
+
+    for (unsigned int i = 0; i < depth; ++i)
+        text += "  ";
+
+    text += String::format("SVGElementInstance this=%p, (parentNode=%s (%p), firstChild=%s (%p), correspondingElement=%s (%p), directUseElement=%s (%p), shadowTreeElement=%s (%p), id=%s)\n",
+                           targetInstance, parentNodeName.latin1().data(), element->parentNode(), firstChildNodeName.latin1().data(), element->firstChild(),
+                           elementNodeName.latin1().data(), element, directUseElementName.latin1().data(), directUseElement, shadowTreeElementNodeName.latin1().data(), shadowTreeElement, elementId.latin1().data());
+
+    for (unsigned int i = 0; i < depth; ++i)
+        text += "  ";
+
+    const HashSet<SVGElementInstance*>& elementInstances = element->instancesForElement();
+    text += "Corresponding element is associated with " + String::number(elementInstances.size()) + " instance(s):\n";
+
+    const HashSet<SVGElementInstance*>::const_iterator end = elementInstances.end();
+    for (HashSet<SVGElementInstance*>::const_iterator it = elementInstances.begin(); it != end; ++it) {
+        for (unsigned int i = 0; i < depth; ++i)
+            text += "  ";
+
+        text += String::format(" -> SVGElementInstance this=%p, (refCount: %i, shadowTreeElement in document? %i)\n",
+                               *it, (*it)->refCount(), (*it)->shadowTreeElement()->inDocument());
+    }
+
+    ++depth;
+
+    for (SVGElementInstance* instance = targetInstance->firstChild(); instance; instance = instance->nextSibling())
+        dumpInstanceTree(depth, text, instance);
+
+    --depth;
+}
+#endif
+
+static bool isDisallowedElement(Node* element)
+{
+    // <foreignObject> should never be contained in a <use> tree. Too dangerous side effects possible.
+    if (element->hasTagName(SVGNames::foreignObjectTag))
+        return true;
+    if (SVGSMILElement::isSMILElement(element))
+        return true;
+    return false;
+}
+
+static bool subtreeContainsDisallowedElement(Node* start)
+{
+    if (isDisallowedElement(start))
+        return true;
+
+    for (Node* cur = start->firstChild(); cur; cur = cur->nextSibling()) {
+        if (subtreeContainsDisallowedElement(cur))
+            return true;
+    }
+
+    return false;
+}
+
+void SVGUseElement::buildPendingResource()
+{
+    // If we're called the first time (during shadow tree root creation from RenderSVGShadowTreeRootContainer)
+    // we either determine that our target is available or not - then we add ourselves to the pending resource list
+    // Once the pending resource appears, it will call buildPendingResource(), so we're called a second time.
+    String id;
+    Element* targetElement = SVGURIReference::targetElementFromIRIString(href(), document(), &id);
+    ASSERT(!m_targetElementInstance);
+
+    if (!targetElement) {
+        if (hasPendingResources() || id.isEmpty())
+            return;
+
+        m_resourceId = id;
+        ASSERT(!hasPendingResources());
+        document()->accessSVGExtensions()->addPendingResource(id, this);
+        ASSERT(hasPendingResources());
+        return;
+    }
+
+
+    if (hasPendingResources()) {
+        ASSERT(!m_targetElementInstance);
+        m_resourceId = String();
+        invalidateShadowTree();
+    }
+}
+
+void SVGUseElement::buildShadowAndInstanceTree(SVGShadowTreeRootElement* shadowRoot)
+{
+    struct ShadowTreeUpdateBlocker {
+        ShadowTreeUpdateBlocker(SVGUseElement* currentUseElement)
+            : useElement(currentUseElement)
+        {
+            useElement->setUpdatesBlocked(true);
+        }
+
+        ~ShadowTreeUpdateBlocker()
+        {
+            useElement->setUpdatesBlocked(false);
+        }
+
+        SVGUseElement* useElement;
+    };
+
+    // When cloning the target nodes, they may decide to synchronize style and/or animated SVG attributes.
+    // That causes calls to SVGElementInstance::updateAllInstancesOfElement(), which mark the shadow tree for recreation.
+    // Solution: block any updates to the shadow tree while we're building it.
+    ShadowTreeUpdateBlocker blocker(this);
+
+    Element* targetElement = SVGURIReference::targetElementFromIRIString(href(), document());
+    if (!targetElement) {
+        // The only time we should get here is when the use element has not been
+        // given a resource to target.
+        ASSERT(m_resourceId.isEmpty());
+        return;
+    }
+
+    // Do not build the shadow/instance tree for <use> elements living in a shadow tree.
+    // The will be expanded soon anyway - see expandUseElementsInShadowTree().
+    ContainerNode* parent = parentNode();
+    while (parent) {
+        if (parent->isSVGShadowRoot())
+            return;
+
+        parent = parent->parentNodeGuaranteedHostFree();
+    }
+
+    SVGElement* target = 0;
+    if (targetElement && targetElement->isSVGElement())
+        target = static_cast<SVGElement*>(targetElement);
+
+    detachInstance();
+
+    // 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
+    // to alter the tree for correct "use-on-symbol", "use-on-svg" support.  
+ 
+    // Build instance tree. Create root SVGElementInstance object for the first sub-tree node.
+    //
+    // Spec: If the 'use' element references a simple graphics element such as a 'rect', then there is only a
+    // single SVGElementInstance object, and the correspondingElement attribute on this SVGElementInstance object
+    // is the SVGRectElement that corresponds to the referenced 'rect' element.
+    m_targetElementInstance = SVGElementInstance::create(this, this, target);
+
+    // Eventually enter recursion to build SVGElementInstance objects for the sub-tree children
+    bool foundProblem = false;
+    buildInstanceTree(target, m_targetElementInstance.get(), foundProblem);
+
+    // SVG specification does not say a word about <use> & cycles. My view on this is: just ignore it!
+    // Non-appearing <use> content is easier to debug, then half-appearing content.
+    if (foundProblem) {
+        detachInstance();
+        return;
+    }
+
+    // Assure instance tree building was successfull
+    ASSERT(m_targetElementInstance);
+    ASSERT(!m_targetElementInstance->shadowTreeElement());
+    ASSERT(m_targetElementInstance->correspondingUseElement() == this);
+    ASSERT(m_targetElementInstance->directUseElement() == this);
+    ASSERT(m_targetElementInstance->correspondingElement() == target);
+
+    // Build shadow tree from instance tree
+    // This also handles the special cases: <use> on <symbol>, <use> on <svg>.
+    buildShadowTree(shadowRoot, target, m_targetElementInstance.get());
+
+    // Expand all <use> elements in the shadow tree.
+    // Expand means: replace the actual <use> element by what it references.
+    expandUseElementsInShadowTree(shadowRoot);
+
+    // Expand all <symbol> elements in the shadow tree.
+    // Expand means: replace the actual <symbol> element by the <svg> element.
+    expandSymbolElementsInShadowTree(shadowRoot);
+
+    // Now that the shadow tree is completly expanded, we can associate
+    // shadow tree elements <-> instances in the instance tree.
+    associateInstancesWithShadowTreeElements(shadowRoot->firstChild(), m_targetElementInstance.get());
+
+    // If no shadow tree element is present, this means that the reference root
+    // element was removed, as it is disallowed (ie. <use> on <foreignObject>)
+    // Do NOT leave an inconsistent instance tree around, instead destruct it.
+    if (!m_targetElementInstance->shadowTreeElement()) {
+        shadowRoot->removeAllChildren();
+        detachInstance();
+        return;
+    }
+
+    // Consistency checks - this is assumed in updateContainerOffset().
+    ASSERT(m_targetElementInstance->shadowTreeElement()->parentNode() == shadowRoot);
+
+    // Transfer event listeners assigned to the referenced element to our shadow tree elements.
+    transferEventListenersToShadowTree(m_targetElementInstance.get());
+
+    // Update container offset/size
+    updateContainerOffsets();
+    updateContainerSizes();
+
+    // Update relative length information
+    updateRelativeLengthsInformation();
+
+    // Eventually dump instance tree
+#ifdef DUMP_INSTANCE_TREE
+    String text;
+    unsigned int depth = 0;
+
+    dumpInstanceTree(depth, text, m_targetElementInstance.get());
+    fprintf(stderr, "\nDumping <use> instance tree:\n%s\n", text.latin1().data());
+#endif
+
+    // Eventually dump shadow tree
+#ifdef DUMP_SHADOW_TREE
+    ExceptionCode ec = 0;
+
+    RefPtr<XMLSerializer> serializer = XMLSerializer::create();
+
+    String markup = serializer->serializeToString(shadowRoot, ec);
+    ASSERT(!ec);
+
+    fprintf(stderr, "Dumping <use> shadow tree markup:\n%s\n", markup.latin1().data());
+#endif
+}
+
+void SVGUseElement::detachInstance()
+{
+    if (!m_targetElementInstance)
+        return;
+    m_targetElementInstance->detach();
+    m_targetElementInstance = 0;
+}
+
+RenderObject* SVGUseElement::createRenderer(RenderArena* arena, RenderStyle*)
+{
+    return new (arena) RenderSVGShadowTreeRootContainer(this);
+}
+
+static void updateFromElementCallback(Node* node, unsigned)
+{
+    if (RenderObject* renderer = node->renderer())
+        renderer->updateFromElement();
+}
+
+void SVGUseElement::attach()
+{
+    SVGStyledTransformableElement::attach();
+
+    if (renderer())
+        queuePostAttachCallback(updateFromElementCallback, this);
+}
+
+void SVGUseElement::detach()
+{
+    SVGStyledTransformableElement::detach();
+    detachInstance();
+}
+
+static bool isDirectReference(const Node* node)
+{
+    return node->hasTagName(SVGNames::pathTag)
+           || node->hasTagName(SVGNames::rectTag)
+           || node->hasTagName(SVGNames::circleTag)
+           || node->hasTagName(SVGNames::ellipseTag)
+           || node->hasTagName(SVGNames::polygonTag)
+           || node->hasTagName(SVGNames::polylineTag)
+           || node->hasTagName(SVGNames::textTag);
+}
+
+void SVGUseElement::toClipPath(Path& path)
+{
+    ASSERT(path.isEmpty());
+
+    Node* n = m_targetElementInstance ? m_targetElementInstance->shadowTreeElement() : 0;
+    if (!n)
+        return;
+
+    if (n->isSVGElement() && static_cast<SVGElement*>(n)->isStyledTransformable()) {
+        if (!isDirectReference(n))
+            // Spec: Indirect references are an error (14.3.5)
+            document()->accessSVGExtensions()->reportError("Not allowed to use indirect reference in <clip-path>");
+        else {
+            static_cast<SVGStyledTransformableElement*>(n)->toClipPath(path);
+            // FIXME: Avoid manual resolution of x/y here. Its potentially harmful.
+            SVGLengthContext lengthContext(this);
+            path.translate(FloatSize(x().value(lengthContext), y().value(lengthContext)));
+            path.transform(animatedLocalTransform());
+        }
+    }
+}
+
+RenderObject* SVGUseElement::rendererClipChild() const
+{
+    Node* n = m_targetElementInstance ? m_targetElementInstance->shadowTreeElement() : 0;
+    if (!n)
+        return 0;
+
+    if (n->isSVGElement() && isDirectReference(n))
+        return static_cast<SVGElement*>(n)->renderer();
+
+    return 0;
+}
+
+void SVGUseElement::buildInstanceTree(SVGElement* target, SVGElementInstance* targetInstance, bool& foundProblem)
+{
+    ASSERT(target);
+    ASSERT(targetInstance);
+
+    // Spec: If the referenced object is itself a 'use', or if there are 'use' subelements within the referenced
+    // object, the instance tree will contain recursive expansion of the indirect references to form a complete tree.
+    bool targetHasUseTag = target->hasTagName(SVGNames::useTag);
+    SVGElement* newTarget = 0;
+    if (targetHasUseTag) {
+        foundProblem = hasCycleUseReferencing(static_cast<SVGUseElement*>(target), targetInstance, newTarget);
+        if (foundProblem)
+            return;
+    }
+
+    // A general description from the SVG spec, describing what buildInstanceTree() actually does.
+    //
+    // Spec: If the 'use' element references a 'g' which contains two 'rect' elements, then the instance tree
+    // contains three SVGElementInstance objects, a root SVGElementInstance object whose correspondingElement
+    // is the SVGGElement object for the 'g', and then two child SVGElementInstance objects, each of which has
+    // its correspondingElement that is an SVGRectElement object.
+
+    for (Node* node = target->firstChild(); node; node = node->nextSibling()) {
+        SVGElement* element = 0;
+        if (node->isSVGElement())
+            element = static_cast<SVGElement*>(node);
+
+        // Skip any non-svg nodes or any disallowed element.
+        if (!element || isDisallowedElement(element))
+            continue;
+
+        // Create SVGElementInstance object, for both container/non-container nodes.
+        RefPtr<SVGElementInstance> instance = SVGElementInstance::create(this, 0, element);
+        SVGElementInstance* instancePtr = instance.get();
+        targetInstance->appendChild(instance.release());
+
+        // Enter recursion, appending new instance tree nodes to the "instance" object.
+        buildInstanceTree(element, instancePtr, foundProblem);
+        if (foundProblem)
+            return;
+    }
+
+    if (!targetHasUseTag || !newTarget)
+        return;
+
+    RefPtr<SVGElementInstance> newInstance = SVGElementInstance::create(this, static_cast<SVGUseElement*>(target), newTarget);
+    SVGElementInstance* newInstancePtr = newInstance.get();
+    targetInstance->appendChild(newInstance.release());
+    buildInstanceTree(newTarget, newInstancePtr, foundProblem);
+}
+
+bool SVGUseElement::hasCycleUseReferencing(SVGUseElement* use, SVGElementInstance* targetInstance, SVGElement*& newTarget)
+{
+    Element* targetElement = SVGURIReference::targetElementFromIRIString(use->href(), document());
+    newTarget = 0;
+    if (targetElement && targetElement->isSVGElement())
+        newTarget = static_cast<SVGElement*>(targetElement);
+
+    if (!newTarget)
+        return false;
+
+    // Shortcut for self-references
+    if (newTarget == this)
+        return true;
+
+    SVGElementInstance* instance = targetInstance->parentNode();
+    while (instance) {
+        SVGElement* element = instance->correspondingElement();
+
+        // FIXME: This should probably be using getIdAttribute instead of idForStyleResolution.
+        if (element->hasID() && element->idForStyleResolution() == newTarget->getIdAttribute())
+            return true;
+    
+        instance = instance->parentNode();
+    }
+    return false;
+}
+
+void SVGUseElement::removeDisallowedElementsFromSubtree(Node* subtree)
+{
+    ASSERT(!subtree->inDocument());
+    ExceptionCode ec;
+    Node* node = subtree->firstChild();
+    while (node) {
+        if (isDisallowedElement(node)) {
+            Node* next = node->traverseNextSibling(subtree);
+            // The subtree is not in document so this won't generate events that could mutate the tree.
+            node->parentNode()->removeChild(node, ec);
+            node = next;
+        } else
+            node = node->traverseNextNode(subtree);
+    }
+}
+
+void SVGUseElement::buildShadowTree(SVGShadowTreeRootElement* shadowRoot, SVGElement* target, SVGElementInstance* targetInstance)
+{
+    // For instance <use> on <foreignObject> (direct case).
+    if (isDisallowedElement(target))
+        return;
+
+    RefPtr<Element> newChild = targetInstance->correspondingElement()->cloneElementWithChildren();
+
+    // We don't walk the target tree element-by-element, and clone each element,
+    // but instead use cloneElementWithChildren(). This is an optimization for the common
+    // case where <use> doesn't contain disallowed elements (ie. <foreignObject>).
+    // Though if there are disallowed elements in the subtree, we have to remove them.
+    // For instance: <use> on <g> containing <foreignObject> (indirect case).
+    if (subtreeContainsDisallowedElement(newChild.get()))
+        removeDisallowedElementsFromSubtree(newChild.get());
+
+    SVGElement* newChildPtr = 0;
+    if (newChild->isSVGElement())
+        newChildPtr = static_cast<SVGElement*>(newChild.get());
+    ASSERT_UNUSED(newChildPtr, newChildPtr);
+
+    ExceptionCode ec = 0;
+    shadowRoot->appendChild(newChild.release(), ec);
+    ASSERT(!ec);
+}
+
+void SVGUseElement::expandUseElementsInShadowTree(Node* 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
+    // actual shadow tree (after the special case modification for svg/symbol) we have
+    // to walk it completely and expand all <use> elements.
+    if (element->hasTagName(SVGNames::useTag)) {
+        SVGUseElement* use = static_cast<SVGUseElement*>(element);
+
+        Element* targetElement = SVGURIReference::targetElementFromIRIString(use->href(), document());
+        SVGElement* target = 0;
+        if (targetElement && targetElement->isSVGElement())
+            target = static_cast<SVGElement*>(targetElement);
+
+        // Don't ASSERT(target) here, it may be "pending", too.
+        // Setup sub-shadow tree root node
+        RefPtr<SVGShadowTreeContainerElement> cloneParent = SVGShadowTreeContainerElement::create(document());
+        use->cloneChildNodes(cloneParent.get());
+
+        // Spec: In the generated content, the 'use' will be replaced by 'g', where all attributes from the
+        // 'use' element except for x, y, width, height and xlink:href are transferred to the generated 'g' element.
+        transferUseAttributesToReplacedElement(use, cloneParent.get());
+
+        ExceptionCode ec = 0;
+        if (target && !isDisallowedElement(target)) {
+            RefPtr<Element> newChild = target->cloneElementWithChildren();
+
+            SVGElement* newChildPtr = 0;
+            if (newChild->isSVGElement())
+                newChildPtr = static_cast<SVGElement*>(newChild.get());
+            ASSERT_UNUSED(newChildPtr, newChildPtr);
+
+            cloneParent->appendChild(newChild.release(), ec);
+            ASSERT(!ec);
+        }
+
+        // We don't walk the target tree element-by-element, and clone each element,
+        // but instead use cloneElementWithChildren(). This is an optimization for the common
+        // case where <use> doesn't contain disallowed elements (ie. <foreignObject>).
+        // Though if there are disallowed elements in the subtree, we have to remove them.
+        // For instance: <use> on <g> containing <foreignObject> (indirect case).
+        if (subtreeContainsDisallowedElement(cloneParent.get()))
+            removeDisallowedElementsFromSubtree(cloneParent.get());
+
+        RefPtr<Node> replacingElement(cloneParent.get());
+
+        // Replace <use> with referenced content.
+        ASSERT(use->parentNode()); 
+        use->parentNode()->replaceChild(cloneParent.release(), use, ec);
+        ASSERT(!ec);
+
+        // Expand the siblings because the *element* is replaced and we will
+        // lose the sibling chain when we are back from recursion.
+        element = replacingElement.get();
+        for (RefPtr<Node> sibling = element->nextSibling(); sibling; sibling = sibling->nextSibling())
+            expandUseElementsInShadowTree(sibling.get());
+    }
+
+    for (RefPtr<Node> child = element->firstChild(); child; child = child->nextSibling())
+        expandUseElementsInShadowTree(child.get());
+}
+
+void SVGUseElement::expandSymbolElementsInShadowTree(Node* element)
+{
+    if (element->hasTagName(SVGNames::symbolTag)) {
+        // Spec: The referenced 'symbol' and its contents are deep-cloned into the generated tree,
+        // with the exception that the 'symbol' is replaced by an 'svg'. This generated 'svg' will
+        // always have explicit values for attributes width and height. If attributes width and/or
+        // height are provided on the 'use' element, then these attributes will be transferred to
+        // the generated 'svg'. If attributes width and/or height are not specified, the generated
+        // 'svg' element will use values of 100% for these attributes.
+        RefPtr<SVGSVGElement> svgElement = SVGSVGElement::create(SVGNames::svgTag, document());
+
+        // Transfer all attributes from <symbol> to the new <svg> element
+        svgElement->setAttributesFromElement(*toElement(element));
+
+        // Only clone symbol children, and add them to the new <svg> element    
+        ExceptionCode ec = 0;
+        for (Node* child = element->firstChild(); child; child = child->nextSibling()) {
+            RefPtr<Node> newChild = child->cloneNode(true);
+            svgElement->appendChild(newChild.release(), ec);
+            ASSERT(!ec);
+        }
+    
+        // We don't walk the target tree element-by-element, and clone each element,
+        // but instead use cloneNode(deep=true). This is an optimization for the common
+        // case where <use> doesn't contain disallowed elements (ie. <foreignObject>).
+        // Though if there are disallowed elements in the subtree, we have to remove them.
+        // For instance: <use> on <g> containing <foreignObject> (indirect case).
+        if (subtreeContainsDisallowedElement(svgElement.get()))
+            removeDisallowedElementsFromSubtree(svgElement.get());
+
+        RefPtr<Node> replacingElement(svgElement.get());
+
+        // Replace <symbol> with <svg>.
+        ASSERT(element->parentNode()); 
+        element->parentNode()->replaceChild(svgElement.release(), element, ec);
+        ASSERT(!ec);
+
+        // Expand the siblings because the *element* is replaced and we will
+        // lose the sibling chain when we are back from recursion.
+        element = replacingElement.get();
+        for (RefPtr<Node> sibling = element->nextSibling(); sibling; sibling = sibling->nextSibling())
+            expandSymbolElementsInShadowTree(sibling.get());
+    }
+
+    for (RefPtr<Node> child = element->firstChild(); child; child = child->nextSibling())
+        expandSymbolElementsInShadowTree(child.get());
+}
+
+void SVGUseElement::transferEventListenersToShadowTree(SVGElementInstance* target)
+{
+    if (!target)
+        return;
+
+    SVGElement* originalElement = target->correspondingElement();
+    ASSERT(originalElement);
+
+    if (SVGElement* shadowTreeElement = target->shadowTreeElement()) {
+        if (EventTargetData* data = originalElement->eventTargetData())
+            data->eventListenerMap.copyEventListenersNotCreatedFromMarkupToTarget(shadowTreeElement);
+    }
+
+    for (SVGElementInstance* instance = target->firstChild(); instance; instance = instance->nextSibling())
+        transferEventListenersToShadowTree(instance);
+}
+
+void SVGUseElement::associateInstancesWithShadowTreeElements(Node* target, SVGElementInstance* targetInstance)
+{
+    if (!target || !targetInstance)
+        return;
+
+    SVGElement* originalElement = targetInstance->correspondingElement();
+
+    if (originalElement->hasTagName(SVGNames::useTag)) {
+        // <use> gets replaced by <g>
+        ASSERT(target->nodeName() == SVGNames::gTag);
+    } else if (originalElement->hasTagName(SVGNames::symbolTag)) {
+        // <symbol> gets replaced by <svg>
+        ASSERT(target->nodeName() == SVGNames::svgTag);
+    } else
+        ASSERT(target->nodeName() == originalElement->nodeName());
+
+    SVGElement* element = 0;
+    if (target->isSVGElement())
+        element = static_cast<SVGElement*>(target);
+
+    ASSERT(!targetInstance->shadowTreeElement());
+    targetInstance->setShadowTreeElement(element);
+    element->setCorrespondingElement(originalElement);
+
+    Node* node = target->firstChild();
+    for (SVGElementInstance* instance = targetInstance->firstChild(); node && instance; instance = instance->nextSibling()) {
+        // Skip any non-svg elements in shadow tree
+        while (node && !node->isSVGElement())
+           node = node->nextSibling();
+
+        if (!node)
+            break;
+
+        associateInstancesWithShadowTreeElements(node, instance);
+        node = node->nextSibling();
+    }
+}
+
+SVGElementInstance* SVGUseElement::instanceForShadowTreeElement(Node* element) const
+{
+    if (!m_targetElementInstance) {
+        ASSERT(!inDocument());
+        return 0;
+    }
+
+    return instanceForShadowTreeElement(element, m_targetElementInstance.get());
+}
+
+SVGElementInstance* SVGUseElement::instanceForShadowTreeElement(Node* element, SVGElementInstance* instance) const
+{
+    ASSERT(element);
+    ASSERT(instance);
+
+    // We're dispatching a mutation event during shadow tree construction
+    // this instance hasn't yet been associated to a shadowTree element.
+    if (!instance->shadowTreeElement())
+        return 0;
+
+    if (element == instance->shadowTreeElement())
+        return instance;
+
+    for (SVGElementInstance* current = instance->firstChild(); current; current = current->nextSibling()) {
+        if (SVGElementInstance* search = instanceForShadowTreeElement(element, current))
+            return search;
+    }
+
+    return 0;
+}
+
+void SVGUseElement::invalidateShadowTree()
+{
+    // Don't mutate the shadow tree while we're building it.
+    if (m_updatesBlocked)
+        return;
+
+    m_needsShadowTreeRecreation = true;
+    setNeedsStyleRecalc();
+}
+
+void SVGUseElement::transferUseAttributesToReplacedElement(SVGElement* from, SVGElement* to) const
+{
+    ASSERT(from);
+    ASSERT(to);
+
+    to->setAttributesFromElement(*from);
+
+    to->removeAttribute(SVGNames::xAttr);
+    to->removeAttribute(SVGNames::yAttr);
+    to->removeAttribute(SVGNames::widthAttr);
+    to->removeAttribute(SVGNames::heightAttr);
+    to->removeAttribute(XLinkNames::hrefAttr);
+}
+
+bool SVGUseElement::selfHasRelativeLengths() const
+{
+    if (x().isRelative()
+     || y().isRelative()
+     || width().isRelative()
+     || height().isRelative())
+        return true;
+
+    if (!m_targetElementInstance)
+        return false;
+
+    SVGElement* element = m_targetElementInstance->correspondingElement();
+    if (!element || !element->isStyled())
+        return false;
+
+    return static_cast<SVGStyledElement*>(element)->hasRelativeLengths();
+}
+
+}
+
+#endif // ENABLE(SVG)