Fix invalid selection produced when dragging mouse outside the SVG text element

third_party/WebKit/Source/core/layout/svg/SVGLayoutSupport.cpp

 /*
  * Copyright (C) 2007, 2008 Rob Buis <buis@kde.org>
  * Copyright (C) 2007 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2007 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2009 Google, Inc.  All rights reserved.
  * Copyright (C) 2009 Dirk Schulze <krit@webkit.org>
  * Copyright (C) Research In Motion Limited 2009-2010. 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
@@ skipping 458 matching lines @@
     ASSERT(layoutObject);
 
     // FIXME: trying to compute a device space transform at record time is wrong. All clients
     // should be updated to avoid relying on this information, and the method should be removed.
     AffineTransform ctm = deprecatedCalculateTransformToLayer(layoutObject) * SubtreeContentTransformScope::currentContentTransformation();
     ctm.scale(layoutObject->document().frameHost()->deviceScaleFactor());
 
     return narrowPrecisionToFloat(sqrt((pow(ctm.xScale(), 2) + pow(ctm.yScale(), 2)) / 2));
 }
 
+LayoutObject* SVGLayoutSupport::findClosestLayoutSVGText(LayoutObject* layoutObject, const FloatPoint& point)
+{
+    LayoutObject* closestLayoutObject = nullptr;
+    float closestDistance = std::numeric_limits<float>::max();
+    Vector<LayoutObject*> overlappedObjects;
+    for (LayoutObject* child = layoutObject->slowLastChild(); child; child = child->previousSibling()) {
+        if (!child->isSVGContainer() && !child->isSVGText())
+            continue;
+        if (child->isSVGHiddenContainer())
+            continue;
+
+        FloatRect boundingBox = child->objectBoundingBox();

[fs, 2016/01/19 13:30:04]

Move down.

+
+        if (!child->localToParentTransform().isInvertible())
+            continue;
+
+        FloatPoint childLocalPoint = child->localToParentTransform().inverse().mapPoint(point);
+        float distance = boundingBox.squaredDistanceTo(childLocalPoint);
+
+        if (distance <= closestDistance) {
+            // The reason is that if the closest LayoutObject is not found LayoutSVGText, try to find
+            // LayoutSVGText object on other LayoutObjects overlapped by closest LayoutObject
+            if (closestLayoutObject && boundingBox.contains(closestLayoutObject->objectBoundingBox())) {
+                overlappedObjects.append(child);
+                continue;
+            }
+
+            overlappedObjects.clear();
+
+            closestLayoutObject = child;
+            closestDistance = distance;
+        }
+    }
+
+    if (!closestLayoutObject || closestLayoutObject->isSVGText())
+        return closestLayoutObject;
+
+    FloatPoint absolutePoint = closestLayoutObject->localToParentTransform().inverse().mapPoint(point);

[fs, 2016/01/19 13:30:04]

Calling this "pointInChild" or "childLocalPoint" like above seems to better
describe what it is.

+    if (LayoutObject* result = findClosestLayoutSVGText(closestLayoutObject, absolutePoint))
+        return result;
+
+    // No found LayoutSVGText on closest LayoutObject, after all try to search on other LayoutObjects which store
+    // on vector called `overlappedObjects`.
+    LayoutObject* result;
+    for (LayoutObject* overlappedObject : overlappedObjects) {
+        absolutePoint = overlappedObject->localToParentTransform().inverse().mapPoint(point);
+        result = findClosestLayoutSVGText(overlappedObject, absolutePoint);
+        if (result)

[fs, 2016/01/19 13:30:04]

You could write this like the previous version before the for-loop, and then
just return nullptr at the end instead.

+            break;
+    }
+
+    return result;
 }
+
+}