Simply SVGSVGElement::getElementById method

Source/core/svg/SVGSVGElement.cpp

 /*
  * Copyright (C) 2004, 2005, 2006 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2010 Rob Buis <buis@kde.org>
  * Copyright (C) 2007 Apple Inc. 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.
  *
@@ skipping 749 matching lines @@
     if (viewElement->hasAttribute(SVGNames::zoomAndPanAttr))
         view->setZoomAndPan(viewElement->zoomAndPan());
     else
         view->setZoomAndPan(zoomAndPan());
 }
 
 // getElementById on SVGSVGElement is restricted to only the child subtree defined by the <svg> element.
 // See http://www.w3.org/TR/SVG11/struct.html#InterfaceSVGSVGElement
 Element* SVGSVGElement::getElementById(const AtomicString& id) const
 {
-    Element* element = treeScope().getElementById(id);
-    if (element && element->isDescendantOf(this))
+    if (!treeScope().containsMultipleElementsWithId(id)) {
+        Element* element = treeScope().getElementById(id);

[f(malita), 2014/02/24 23:47:24]

Isn't this introducing an extra lookup for the common case?

(one for containsMultipleElementsWithId() and another one for getElementById())

Whereas before, the fast path only took one lookup: getElementById().

+        if (!element || !element->isDescendantOf(this))
+            return 0;
+
         return element;
+    }
 
-    // Fall back to traversing our subtree. Duplicate ids are allowed, the first found will
-    // be returned.
-    for (Node* node = firstChild(); node; node = NodeTraversal::next(*node, this)) {
-        if (!node->isElementNode())
-            continue;
+    // If duplicate IDs are there, return the first descendant of the svg element.
+    const Vector<Element*>& elements = treeScope().getAllElementsById(id);
+    Vector<Element*>::const_iterator end = elements.end();
+    for (Vector<Element*>::const_iterator it = elements.begin(); it != end; ++it) {
+        if ((*it)->isDescendantOf(this))
+            return *it;
+    }
 
-        Element* element = toElement(node);
-        if (element->getIdAttribute() == id)
-            return element;
-    }
     return 0;
 }
 
 }