void SVGUseElement::buildInstanceTree(SVGElement* target, SVGElementInstance* targetInstance, bool& foundProblem, bool foundUse)
{
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(toSVGUseElement(target), targetInstance, newTarget);
if (foundProblem)
return;
// We only need to track first degree <use> dependencies. Indirect references are handled
// as the invalidation bubbles up the dependency chain.
if (!foundUse) {
document().accessSVGExtensions()->addElementReferencingTarget(this, target);
foundUse = true;
}
} else if (isDisallowedElement(*target)) {
foundProblem = true;
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 (auto& element : childrenOfType<SVGElement>(*target)) {
// Skip any non-svg nodes or any disallowed element.
if (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, foundUse);
if (foundProblem)
return;
}
if (!targetHasUseTag || !newTarget)
return;
RefPtr<SVGElementInstance> newInstance = SVGElementInstance::create(this, toSVGUseElement(target), newTarget);
SVGElementInstance* newInstancePtr = newInstance.get();
targetInstance->appendChild(newInstance.release());
buildInstanceTree(newTarget, newInstancePtr, foundProblem, foundUse);
}
void SVGUseElement::expandUseElementsInShadowTree(SVGShadowTreeRootElement* shadowRoot, 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);
String id = SVGURIReference::getTarget(use->href());
Element* targetElement = document()->getElementById(id);
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 = new SVGShadowTreeContainerElement(document());
// 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();
// 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(newChildPtr);
cloneParent->appendChild(newChild.release(), ec);
ASSERT(!ec);
}
// Replace <use> with referenced content.
ASSERT(use->parentNode());
use->parentNode()->replaceChild(cloneParent.release(), use, ec);
ASSERT(!ec);
// Immediately stop here, and restart expanding.
expandUseElementsInShadowTree(shadowRoot, shadowRoot);
return;
}
for (RefPtr<Node> child = element->firstChild(); child; child = child->nextSibling())
expandUseElementsInShadowTree(shadowRoot, child.get());
}
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(newChildPtr);
ExceptionCode ec = 0;
shadowRoot->appendChild(newChild.release(), ec);
ASSERT(!ec);
}
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.
RefPtr<SVGElementInstance> instance = SVGElementInstance::create(this, element);
SVGElementInstance* instancePtr = instance.get();
targetInstance->appendChild(instance.release());
// Enter recursion, appending new instance tree nodes to the "instance" object.
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 (target->hasTagName(SVGNames::useTag))
handleDeepUseReferencing(static_cast<SVGUseElement*>(target), targetInstance, foundProblem);
}
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);
}
void SVGUseElement::buildShadowAndInstanceTree(SVGElement* target)
{
ASSERT(!m_targetElementInstance);
ASSERT(!m_needsShadowTreeRecreation);
// <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 (inUseShadowTree())
return;
// Do not allow self-referencing.
// 'target' may be null, if it's a non SVG namespaced element.
if (!target || target == this || isDisallowedElement(target))
return;
// Set up root SVG element in shadow tree.
RefPtrWillBeRawPtr<Element> newChild = target->cloneElementWithoutChildren();
m_targetElementInstance = toSVGElement(newChild.get());
ShadowRoot* shadowTreeRootElement = userAgentShadowRoot();
shadowTreeRootElement->appendChild(newChild.release());
// Clone the target subtree into the shadow tree, not handling <use> and <symbol> yet.
// 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 (!buildShadowTree(target, m_targetElementInstance.get(), false)) {
clearShadowTree();
return;
}
if (instanceTreeIsLoading(m_targetElementInstance.get()))
return;
// Assure shadow tree building was successfull
ASSERT(m_targetElementInstance);
ASSERT(m_targetElementInstance->correspondingUseElement() == this);
ASSERT(m_targetElementInstance->correspondingElement() == target);
// Expand all <use> elements in the shadow tree.
// Expand means: replace the actual <use> element by what it references.
if (!expandUseElementsInShadowTree(m_targetElementInstance.get())) {
clearShadowTree();
return;
}
// Expand all <symbol> elements in the shadow tree.
// Expand means: replace the actual <symbol> element by the <svg> element.
expandSymbolElementsInShadowTree(toSVGElement(shadowTreeRootElement->firstChild()));
m_targetElementInstance = toSVGElement(shadowTreeRootElement->firstChild());
transferUseWidthAndHeightIfNeeded(*this, m_targetElementInstance.get(), *m_targetElementInstance->correspondingElement());
ASSERT(m_targetElementInstance->parentNode() == shadowTreeRootElement);
// Update relative length information.
updateRelativeLengthsInformation();
}
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 = toSVGUseElement(element);
ASSERT(!use->cachedDocumentIsStillLoading());
ASSERT(referencedDocument());
Element* targetElement = SVGURIReference::targetElementFromIRIString(use->href(), *referencedDocument());
SVGElement* target = 0;
if (targetElement && targetElement->isSVGElement())
target = toSVGElement(targetElement);
// Don't ASSERT(target) here, it may be "pending", too.
// Setup sub-shadow tree root node
RefPtr<SVGGElement> cloneParent = SVGGElement::create(SVGNames::gTag, *referencedDocument());
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());
if (target && !isDisallowedElement(*target)) {
RefPtr<Element> newChild = target->cloneElementWithChildren();
ASSERT(newChild->isSVGElement());
cloneParent->appendChild(newChild.release());
}
// 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))
removeDisallowedElementsFromSubtree(*cloneParent);
RefPtr<Node> replacingElement(cloneParent.get());
// Replace <use> with referenced content.
ASSERT(use->parentNode());
use->parentNode()->replaceChild(cloneParent.release(), use);
// 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());
}
static bool subtreeContainsDisallowedElement(SVGElement& start)
{
for (auto& element : descendantsOfType<Element>(start)) {
if (isDisallowedElement(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;
}
bool SVGUseElement::buildShadowTree(SVGElement* target, SVGElement* targetInstance, bool foundUse)
{
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.
if (isSVGUseElement(*target)) {
// We only need to track first degree <use> dependencies. Indirect references are handled
// as the invalidation bubbles up the dependency chain.
if (!foundUse && !isStructurallyExternal()) {
addReferenceTo(target);
foundUse = true;
}
} else if (isDisallowedElement(target)) {
return false;
}
targetInstance->setCorrespondingElement(target);
if (EventTargetData* data = target->eventTargetData())
data->eventListenerMap.copyEventListenersNotCreatedFromMarkupToTarget(targetInstance);
for (RefPtrWillBeRawPtr<Node> child = target->firstChild(); child; child = child->nextSibling()) {
// Skip any disallowed element.
if (isDisallowedElement(child.get()))
continue;
RefPtrWillBeRawPtr<Node> newChild = child->cloneNode(false);
targetInstance->appendChild(newChild.get());
if (newChild->isSVGElement()) {
// Enter recursion, appending new instance tree nodes to the "instance" object.
if (!buildShadowTree(toSVGElement(child), toSVGElement(newChild), foundUse))
return false;
}
}
return true;
}
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);
}
}
static inline void removeDisallowedElementsFromSubtree(Element& subtree)
{
ASSERT(!subtree.inDocument());
Element* element = ElementTraversal::firstWithin(subtree);
while (element) {
if (isDisallowedElement(element)) {
Element* next = ElementTraversal::nextSkippingChildren(*element, &subtree);
// The subtree is not in document so this won't generate events that could mutate the tree.
element->parentNode()->removeChild(element);
element = next;
} else {
element = ElementTraversal::next(*element, &subtree);
}
}
}
static inline void removeDisallowedElementsFromSubtree(SVGElement& subtree)
{
ASSERT(!subtree.inDocument());
Vector<Element*> toRemove;
auto it = descendantsOfType<Element>(subtree).begin();
auto end = descendantsOfType<Element>(subtree).end();
while (it != end) {
if (isDisallowedElement(*it)) {
toRemove.append(&*it);
it.traverseNextSkippingChildren();
continue;
}
++it;
}
// The subtree is not in document so this won't generate events that could mutate the tree.
for (unsigned i = 0; i < toRemove.size(); ++i)
toRemove[i]->parentNode()->removeChild(toRemove[i]);
}
void SVGUseElement::buildShadowTree(SVGElement* target, SVGElementInstance* targetInstance)
{
ASSERT(target); // FIXME: Don't be a pointer!
// For instance <use> on <foreignObject> (direct case).
if (isDisallowedElement(*target))
return;
RefPtr<SVGElement> newChild = static_pointer_cast<SVGElement>(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))
removeDisallowedElementsFromSubtree(*newChild);
shadowRoot()->appendChild(newChild.release());
}
bool SVGUseElement::expandUseElementsInShadowTree(SVGElement* 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. 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());
SVGElement* target = 0;
if (hasCycleUseReferencing(toSVGUseElement(use->correspondingElement()), use, target))
return false;
if (target && isDisallowedElement(target))
return false;
// Don't ASSERT(target) here, it may be "pending", too.
// Setup sub-shadow tree root node
RefPtrWillBeRawPtr<SVGGElement> cloneParent = SVGGElement::create(referencedScope()->document());
cloneParent->setCorrespondingElement(use->correspondingElement());
// Move already cloned elements to the new <g> element
for (RefPtrWillBeRawPtr<Node> child = use->firstChild(); child; ) {
RefPtrWillBeRawPtr<Node> nextChild = child->nextSibling();
cloneParent->appendChild(child);
child = nextChild.release();
}
// 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());
if (target) {
RefPtrWillBeRawPtr<Node> newChild = cloneNodeAndAssociate(*target);
ASSERT(newChild->isSVGElement());
transferUseWidthAndHeightIfNeeded(*use, toSVGElement(newChild.get()), *target);
cloneParent->appendChild(newChild.release());
}
// 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);
RefPtrWillBeRawPtr<SVGElement> replacingElement(cloneParent.get());
// Replace <use> with referenced content.
ASSERT(use->parentNode());
use->parentNode()->replaceChild(cloneParent.release(), use);
// 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 (RefPtrWillBeRawPtr<SVGElement> sibling = Traversal<SVGElement>::nextSibling(*element); sibling; sibling = Traversal<SVGElement>::nextSibling(*sibling)) {
if (!expandUseElementsInShadowTree(sibling.get()))
return false;
}
}
for (RefPtrWillBeRawPtr<SVGElement> child = Traversal<SVGElement>::firstChild(*element); child; child = Traversal<SVGElement>::nextSibling(*child)) {
if (!expandUseElementsInShadowTree(child.get()))
return false;
}
return true;
}
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);
String id = SVGURIReference::getTarget(use->href());
Element* targetElement = document()->getElementById(id);
SVGElement* target = 0;
if (targetElement && targetElement->isSVGElement())
target = static_cast<SVGElement*>(targetElement);
// Don't ASSERT(target) here, it may be "pending", too.
if (target) {
// Setup sub-shadow tree root node
RefPtr<SVGElement> cloneParent = new SVGGElement(SVGNames::gTag, document());
// 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());
// 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 (use->x().value() != 0.0 || use->y().value() != 0.0) {
if (!cloneParent->hasAttribute(SVGNames::transformAttr)) {
String transformString = String::format("translate(%f, %f)", use->x().value(), use->y().value());
cloneParent->setAttribute(SVGNames::transformAttr, transformString);
} else {
String transformString = String::format(" translate(%f, %f)", use->x().value(), use->y().value());
const AtomicString& transformAttribute = cloneParent->getAttribute(SVGNames::transformAttr);
cloneParent->setAttribute(SVGNames::transformAttr, transformAttribute + transformString);
}
}
ExceptionCode ec = 0;
// For instance <use> on <foreignObject> (direct case).
if (isDisallowedElement(target)) {
// We still have to setup the <use> replacment (<g>). Otherwhise
// associateInstancesWithShadowTreeElements() makes wrong assumptions.
// Replace <use> with referenced content.
ASSERT(use->parentNode());
use->parentNode()->replaceChild(cloneParent.release(), use, ec);
ASSERT(ec == 0);
return;
}
RefPtr<Node> newChild = target->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);
cloneParent->appendChild(newChild.release(), ec);
ASSERT(ec == 0);
// Replace <use> with referenced content.
ASSERT(use->parentNode());
use->parentNode()->replaceChild(cloneParent.release(), use, ec);
ASSERT(ec == 0);
// Handle use referencing <svg> special case
if (target->hasTagName(SVGNames::svgTag))
alterShadowTreeForSVGTag(newChildPtr);
// Immediately stop here, and restart expanding.
expandUseElementsInShadowTree(m_shadowTreeRootElement.get());
return;
}
}
for (RefPtr<Node> child = element->firstChild(); child; child = child->nextSibling())
expandUseElementsInShadowTree(child.get());
}
