Fix an issue where hit detection could fail on rect and ellipse shapes

Source/core/rendering/svg/RenderSVGRect.cpp

Index: Source/core/rendering/svg/RenderSVGRect.cpp
diff --git a/Source/core/rendering/svg/RenderSVGRect.cpp b/Source/core/rendering/svg/RenderSVGRect.cpp
index a8d37354f857f1a685ad47d61c941fcc3601492a..e9fe5fad7b06592d5acd490a90f9a12a9f355b9b 100644
--- a/Source/core/rendering/svg/RenderSVGRect.cpp
+++ b/Source/core/rendering/svg/RenderSVGRect.cpp
@@ -62,8 +62,12 @@ void RenderSVGRect::updateShapeFromElement()
 
     // Spec: "A value of zero disables rendering of the element."
     if (!boundingBoxSize.isEmpty()) {
-        // Fallback to RenderSVGShape if rect has rounded corners or a non-scaling stroke.
-        if (rect->rx()->currentValue()->value(lengthContext) > 0 || rect->ry()->currentValue()->value(lengthContext) > 0 || hasNonScalingStroke()) {
+        // Fallback to RenderSVGShape and path-based hit detection if the rect
+        // has rounded corners or a non-scaling or non-simple stroke.
+        if (rect->rx()->currentValue()->value(lengthContext) > 0
+            || rect->ry()->currentValue()->value(lengthContext) > 0
+            || hasNonScalingStroke()
+            || !hasSimpleStroke()) {
             RenderSVGShape::updateShapeFromElement();
             m_usePathFallback = true;
             return;
@@ -90,7 +94,7 @@ bool RenderSVGRect::shapeDependentStrokeContains(const FloatPoint& point)
 {
     // The optimized contains code below does not support non-smooth strokes so we need
     // to fall back to RenderSVGShape::shapeDependentStrokeContains in these cases.
-    if (m_usePathFallback || !hasSmoothStroke()) {
+    if (m_usePathFallback || !hasSimpleStroke()) {
         if (!hasPath())
             RenderSVGShape::updateShapeFromElement();
         return RenderSVGShape::shapeDependentStrokeContains(point);
@@ -106,4 +110,12 @@ bool RenderSVGRect::shapeDependentFillContains(const FloatPoint& point, const Wi
     return m_fillBoundingBox.contains(point.x(), point.y());
 }
 
+bool RenderSVGRect::hasSimpleStroke() const
+{
+    const SVGRenderStyle& svgStyle = style()->svgStyle();
+    return svgStyle.strokeDashArray()->isEmpty()
+        && svgStyle.strokeMiterLimit() == SVGRenderStyle::initialStrokeMiterLimit()
+        && svgStyle.joinStyle() == SVGRenderStyle::initialJoinStyle();

[Erik Dahlström (inactive), 2014/12/04 14:25:48]

Here's an example where this might fail: http://jsfiddle.net/upqffmwa/

Since we have a rect (only 90 degree angles), I think it should return true if
stroke-linejoin==miter && stroke-miterlimit > 1.414 (approx.), as indicated in
the spec: http://www.w3.org/TR/SVG11/painting.html#StrokeMiterlimitProperty. You
may wish to compute a more exact value for this.

+}
+
 }