Use the outermost SVG as base when computing offsetX/Y for SVG elements

third_party/WebKit/Source/core/events/MouseRelatedEvent.cpp

 /*
  * Copyright (C) 2001 Peter Kelly (pmk@post.com)
  * Copyright (C) 2001 Tobias Anton (anton@stud.fbi.fh-darmstadt.de)
  * Copyright (C) 2006 Samuel Weinig (sam.weinig@gmail.com)
  * Copyright (C) 2003, 2005, 2006, 2008 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 114 matching lines @@
 {
     float scaleFactor = pageZoomFactor(this);
     setAbsoluteLocation(roundedLayoutPoint(FloatPoint(pageX() * scaleFactor, pageY() * scaleFactor)));
 }
 
 void MouseRelatedEvent::receivedTarget()
 {
     m_hasCachedRelativePosition = false;
 }
 
+static const LayoutObject* findTargetLayoutObject(Node*& targetNode)
+{
+    LayoutObject* layoutObject = targetNode->layoutObject();
+    if (!layoutObject || !layoutObject->isSVG())
+        return layoutObject;
+    // If this is an SVG node, compute the offset to the padding box of the
+    // outermost SVG root (== the closest ancestor that has a CSS layout box.)
+    while (!layoutObject->isSVGRoot())
+        layoutObject = layoutObject->parent();
+    // Update the target node to point to the SVG root.
+    targetNode = layoutObject->node();
+    DCHECK(!targetNode
+        || (targetNode->isSVGElement() && toSVGElement(*targetNode).isOutermostSVGSVGElement()));
+    return layoutObject;
+}
+
 void MouseRelatedEvent::computeRelativePosition()
 {
     Node* targetNode = target() ? target()->toNode() : nullptr;
     if (!targetNode)
         return;
 
     // Compute coordinates that are based on the target.
     m_layerLocation = m_pageLocation;
     m_offsetLocation = m_pageLocation;
 
     // Must have an updated layout tree for this math to work correctly.
     targetNode->document().updateStyleAndLayoutIgnorePendingStylesheets();
 
     // Adjust offsetLocation to be relative to the target's padding box.
-    if (LayoutObject* r = targetNode->layoutObject()) {
-        FloatPoint localPos = r->absoluteToLocal(FloatPoint(absoluteLocation()), UseTransforms);
+    if (const LayoutObject* layoutObject = findTargetLayoutObject(targetNode)) {
+        FloatPoint localPos = layoutObject->absoluteToLocal(FloatPoint(absoluteLocation()), UseTransforms);
 
         // Adding this here to address crbug.com/570666. Basically we'd like to
         // find the local coordinates relative to the padding box not the border box.
-        if (r->isBoxModelObject()) {
-            LayoutBoxModelObject* layoutBox = toLayoutBoxModelObject(r);
+        if (layoutObject->isBoxModelObject()) {
+            const LayoutBoxModelObject* layoutBox = toLayoutBoxModelObject(layoutObject);
             localPos.move(-layoutBox->borderLeft(), -layoutBox->borderTop());
         }
 
         m_offsetLocation = roundedLayoutPoint(localPos);
         float scaleFactor = 1 / pageZoomFactor(this);
         if (scaleFactor != 1.0f)
             m_offsetLocation.scale(scaleFactor, scaleFactor);
     }
 
     // Adjust layerLocation to be relative to the layer.
@@ skipping 68 matching lines @@
     // See Microsoft documentation and <http://www.quirksmode.org/dom/w3c_events.html>.
     return m_clientLocation.y();
 }
 
 DEFINE_TRACE(MouseRelatedEvent)
 {
     UIEventWithKeyState::trace(visitor);
 }
 
 } // namespace blink