Avoid using SVGElementInstance in calcViewport

Source/core/svg/SVGUseElement.cpp

 /*
  * 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.
  * Copyright (C) 2012 University of Szeged
  * Copyright (C) 2012 Renata Hodovan <reni@webkit.org>
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ skipping 382 matching lines @@
     }
 
     if (target->isSVGElement()) {
         buildShadowAndInstanceTree(toSVGElement(target));
         invalidateDependentShadowTrees();
     }
 
     ASSERT(!m_needsShadowTreeRecreation);
 }
 
+inline void transferUseWidthAndHeightIfNeeded(const SVGUseElement& use, Element& element)

[pdr., 2014/04/29 04:30:59]

It may be better to put the relevant code from this function into
expandSymbolElementsInShadowTree and expandUseElementsInShadowTree instead of
breaking it into a function.

+{
+    if (isSVGSymbolElement(element)) {
+        // 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.
+        element.setAttribute(SVGNames::widthAttr, use.hasAttribute(SVGNames::widthAttr) ? use.getAttribute(SVGNames::widthAttr) : "100%");
+        element.setAttribute(SVGNames::heightAttr, use.hasAttribute(SVGNames::heightAttr) ? use.getAttribute(SVGNames::heightAttr) : "100%");
+    } else if (isSVGSVGElement(element)) {
+        // 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 (use.hasAttribute(SVGNames::widthAttr))

[Erik Dahlström (inactive), 2014/04/29 13:01:02]

Will this work if the width/height attributes are animated with SMIL? In those
cases the transferred values should really be the animated (current) value.

Will this patch mean worse performance for svgs that modify (either in script or
by other means) the width/height on <use> a lot?

+            element.setAttribute(SVGNames::widthAttr, use.getAttribute(SVGNames::widthAttr));
+        if (use.hasAttribute(SVGNames::heightAttr))
+            element.setAttribute(SVGNames::heightAttr, use.getAttribute(SVGNames::heightAttr));
+    }
+}
+
 void SVGUseElement::buildShadowAndInstanceTree(SVGElement* target)
 {
     ASSERT(!m_targetElementInstance);
 
     // <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;
 
@@ skipping 32 matching lines @@
     ASSERT(m_targetElementInstance);
     ASSERT(!m_targetElementInstance->shadowTreeElement());
     ASSERT(m_targetElementInstance->correspondingUseElement() == this);
     ASSERT(m_targetElementInstance->directUseElement() == this);
     ASSERT(m_targetElementInstance->correspondingElement() == target);
 
     ShadowRoot* shadowTreeRootElement = userAgentShadowRoot();
     ASSERT(shadowTreeRootElement);
 
     // Build shadow tree from instance tree
-    // This also handles the special cases: <use> on <symbol>, <use> on <svg>.
+    // This clones the element corresponding to the target element instance
     buildShadowTree(target, m_targetElementInstance.get());
 
     // Expand all <use> elements in the shadow tree.
     // Expand means: replace the actual <use> element by what it references.
     expandUseElementsInShadowTree(shadowTreeRootElement);
 
+    transferUseWidthAndHeightIfNeeded(*this, *toSVGElement(shadowTreeRootElement->firstChild()));
     // Expand all <symbol> elements in the shadow tree.
     // Expand means: replace the actual <symbol> element by the <svg> element.
     expandSymbolElementsInShadowTree(shadowTreeRootElement);
 
     // Now that the shadow tree is completly expanded, we can associate
     // shadow tree elements <-> instances in the instance tree.
     associateInstancesWithShadowTreeElements(shadowTreeRootElement->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>)
@@ skipping 223 matching lines @@
         RefPtr<SVGGElement> cloneParent = SVGGElement::create(referencedScope()->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());
 
         if (target && !isDisallowedElement(target)) {
             RefPtr<Element> newChild = target->cloneElementWithChildren();
             ASSERT(newChild->isSVGElement());
+            transferUseWidthAndHeightIfNeeded(*use, *newChild);

[pdr., 2014/04/29 04:30:59]

I think the use width/height code would go here.

+
             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);
@@ skipping 22 matching lines @@
         // 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.
         ASSERT(referencedScope());
         RefPtr<SVGSVGElement> svgElement = SVGSVGElement::create(referencedScope()->document());
 
         // Transfer all data (attributes, etc.) from <symbol> to the new <svg> element.
         svgElement->cloneDataFromElement(*toElement(element));

[pdr., 2014/04/29 04:30:59]

I think the symbol-specific width/height code would go here.

 
         // Only clone symbol children, and add them to the new <svg> element
         for (Node* child = element->firstChild(); child; child = child->nextSibling()) {
             RefPtr<Node> newChild = child->cloneNode(true);
             svgElement->appendChild(newChild.release());
         }
 
         // 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>).
@@ skipping 207 matching lines @@
 
     if (m_resource)
         m_resource->removeClient(this);
 
     m_resource = resource;
     if (m_resource)
         m_resource->addClient(this);
 }
 
 }