svguseelement.cpp

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            return;

        parent = parent->parentNode();
    }
 
    SVGElement* target = 0;
    if (targetElement && targetElement->isSVGElement())
        target = static_cast<SVGElement*>(targetElement);

    if (m_targetElementInstance) {
        m_targetElementInstance->forgetWrapper();
        m_targetElementInstance = 0;
    }

    // Do not allow self-referencing.
    // 'target' may be null, if it's a non SVG namespaced element.
    if (!target || target == this) {
        m_shadowTreeRootElement = 0;
        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 = new SVGElementInstance(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) {
        m_targetElementInstance = 0;
        m_shadowTreeRootElement = 0;
        return;
    }

    // Assure instance tree building was successfull
    ASSERT(m_targetElementInstance);
    ASSERT(m_targetElementInstance->correspondingUseElement() == this);

    // Setup shadow tree root node
    m_shadowTreeRootElement = new SVGGElement(SVGNames::gTag, document());
    m_shadowTreeRootElement->setInDocument();
    m_shadowTreeRootElement->setShadowParentNode(this);

    // 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. 
    if (x().value(this) != 0.0 || y().value(this) != 0.0) {
        String transformString = String::format("translate(%f, %f)", x().value(this), y().value(this));
        m_shadowTreeRootElement->setAttribute(SVGNames::transformAttr, transformString);
    }

    // Build shadow tree from instance tree
    // This also handles the special cases: <use> on <symbol>, <use> on <svg>.
    buildShadowTree(target, m_targetElementInstance.get());

#if ENABLE(SVG) && ENABLE(SVG_USE)
    // Expand all <use> elements in the shadow tree.
    // Expand means: replace the actual <use> element by what it references.
    expandUseElementsInShadowTree(m_shadowTreeRootElement.get());

    // Expand all <symbol> elements in the shadow tree.
    // Expand means: replace the actual <symbol> element by the <svg> element.
    expandSymbolElementsInShadowTree(m_shadowTreeRootElement.get());

#endif

    // Now that the shadow tree is completly expanded, we can associate
    // shadow tree elements <-> instances in the instance tree.
    associateInstancesWithShadowTreeElements(m_shadowTreeRootElement->firstChild(), m_targetElementInstance.get());

    // 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;

    PassRefPtr<XMLSerializer> serializer = XMLSerializer::create();

    String markup = serializer->serializeToString(m_shadowTreeRootElement.get(), ec);
    ASSERT(ec == 0);

    fprintf(stderr, "Dumping <use> shadow tree markup:\n%s\n", markup.latin1().data());
#endif

    // Transfer event listeners assigned to the referenced element to our shadow tree elements.
    transferEventListenersToShadowTree(m_targetElementInstance.get());

    // The DOM side is setup properly. Now we have to attach the root shadow
    // tree element manually - using attach() won't work for "shadow nodes".
    attachShadowTree();
}

RenderObject* SVGUseElement::createRenderer(RenderArena* arena, RenderStyle*)
{
    return new (arena) RenderSVGTransformableContainer(this);
}

void SVGUseElement::attach()
{
    SVGStyledTransformableElement::attach();

    // If we're a pending resource, this doesn't have any effect.
    attachShadowTree();
}

void SVGUseElement::detach()
{
    SVGStyledTransformableElement::detach();

    if (m_shadowTreeRootElement)
        m_shadowTreeRootElement->detach();
}

static bool isDirectReference(Node* n)
{
    return n->hasTagName(SVGNames::pathTag) ||
           n->hasTagName(SVGNames::rectTag) ||
           n->hasTagName(SVGNames::circleTag) ||
           n->hasTagName(SVGNames::ellipseTag) ||
           n->hasTagName(SVGNames::polygonTag) ||
           n->hasTagName(SVGNames::polylineTag) ||
           n->hasTagName(SVGNames::textTag);
}

Path SVGUseElement::toClipPath() const
{
    if (!m_shadowTreeRootElement)
        const_cast<SVGUseElement*>(this)->buildPendingResource();

    Node* n = m_shadowTreeRootElement->firstChild();
    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
            return static_cast<SVGStyledTransformableElement*>(n)->toClipPath();
    }

    return Path();
}

void SVGUseElement::buildInstanceTree(SVGElement* target, SVGElementInstance* targetInstance, bool& foundProblem)
{
    ASSERT(target);
    ASSERT(targetInstance);

    // 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.
        SVGElementInstance* instancePtr = new SVGElementInstance(this, element);
        targetInstance->appendChild(instancePtr);

        // Enter recursion, appending new instance tree nodes to the "instance" object.
        if (element->hasChildNodes())
            buildInstanceTree(element, instancePtr, foundProblem);

        // 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.
        if (element->hasTagName(SVGNames::useTag))
            handleDeepUseReferencing(static_cast<SVGUseElement*>(element), instancePtr, foundProblem);
    }

    // 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.
    if (target->hasTagName(SVGNames::useTag))
        handleDeepUseReferencing(static_cast<SVGUseElement*>(target), targetInstance, foundProblem);
}

void SVGUseElement::handleDeepUseReferencing(SVGUseElement* use, SVGElementInstance* targetInstance, bool& foundProblem)
{
    String id = SVGURIReference::getTarget(use->href());
    Element* targetElement = document()->getElementById(id); 
    SVGElement* target = 0;
    if (targetElement && targetElement->isSVGElement())
        target = static_cast<SVGElement*>(targetElement);

    if (!target)
        return;

    // Cycle detection first!
    foundProblem = (target == this);

    // Shortcut for self-references
    if (foundProblem)
        return;

    SVGElementInstance* instance = targetInstance->parentNode();
    while (instance) {
        SVGElement* element = instance->correspondingElement();

        if (element->getIDAttribute() == id) {
            foundProblem = true;
            return;
        }
    
        instance = instance->parentNode();
    }

    // Create an instance object, even if we're dealing with a cycle
    SVGElementInstance* newInstance = new SVGElementInstance(this, target);
    targetInstance->appendChild(newInstance);

    // Eventually enter recursion to build SVGElementInstance objects for the sub-tree children
    buildInstanceTree(target, newInstance, foundProblem);
}

void SVGUseElement::alterShadowTreeForSVGTag(SVGElement* target)
{
    String widthString = String::number(width().value(this));
    String heightString = String::number(height().value(this));

    if (hasAttribute(SVGNames::widthAttr))
        target->setAttribute(SVGNames::widthAttr, widthString);

    if (hasAttribute(SVGNames::heightAttr))
        target->setAttribute(SVGNames::heightAttr, heightString);
}

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->parent()->removeChild(node, ec);
            node = next;
        } else
            node = node->traverseNextNode(subtree);
    }
}

void SVGUseElement::buildShadowTree(SVGElement* target, SVGElementInstance* targetInstance)
{
    // For instance <use> on <foreignObject> (direct case).
    if (isDisallowedElement(target))
        return;

    RefPtr<Node> newChild = targetInstance->correspondingElement()->cloneNode(true);

    // 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(newChild.get()))
        removeDisallowedElementsFromSubtree(newChild.get());

    SVGElement* newChildPtr = 0;
    if (newChild->isSVGElement())
        newChildPtr = static_cast<SVGElement*>(newChild.get());
    ASSERT(newChildPtr);

    ExceptionCode ec = 0;
    m_shadowTreeRootElement->appendChild(newChild.release(), ec);
    ASSERT(ec == 0);

    // Handle use referencing <svg> special case
    if (target->hasTagName(SVGNames::svgTag))
        alterShadowTreeForSVGTag(newChildPtr);