Fix ellipse hit testing in the non-circle case

Source/core/rendering/svg/RenderSVGEllipse.cpp

Index: Source/core/rendering/svg/RenderSVGEllipse.cpp
diff --git a/Source/core/rendering/svg/RenderSVGEllipse.cpp b/Source/core/rendering/svg/RenderSVGEllipse.cpp
index 3d8f8c0cc1a3d359c2b5d29dfafd7c1d8e1779b1..4053648c194455dc90928bf9daffe4b096a8dc22 100644
--- a/Source/core/rendering/svg/RenderSVGEllipse.cpp
+++ b/Source/core/rendering/svg/RenderSVGEllipse.cpp
@@ -31,6 +31,8 @@
 #include "core/svg/SVGCircleElement.h"
 #include "core/svg/SVGEllipseElement.h"
 
+#include <cmath>
+
 namespace blink {
 
 RenderSVGEllipse::RenderSVGEllipse(SVGGraphicsElement* node)
@@ -61,19 +63,14 @@ void RenderSVGEllipse::updateShapeFromElement()
         return;
 
     if (!m_radii.isEmpty()) {
-        // Fallback to RenderSVGShape and path-based hit detection if the ellipse
+        // Fall back to RenderSVGShape and path-based hit detection if the ellipse
         // has a non-scaling or discontinuous stroke.
         if (hasNonScalingStroke() || !hasContinuousStroke()) {
-            RenderSVGShape::updateShapeFromElement();
             m_usePathFallback = true;
-            return;
         }
     }
 
-    m_fillBoundingBox = FloatRect(m_center.x() - m_radii.width(), m_center.y() - m_radii.height(), 2 * m_radii.width(), 2 * m_radii.height());

[fs, 2015/01/26 12:25:21]

This code is still valid, no?

-    m_hitTestStrokeBoundingBox = m_fillBoundingBox;
-    m_hitTestStrokeBoundingBox.inflate(strokeWidth() / 2);
-    m_strokeBoundingBox = style()->svgStyle().hasStroke() ? m_hitTestStrokeBoundingBox : m_fillBoundingBox;
+    RenderSVGShape::updateShapeFromElement();
 }
 
 void RenderSVGEllipse::calculateRadiiAndCenter()
@@ -98,40 +95,29 @@ void RenderSVGEllipse::calculateRadiiAndCenter()
 
 bool RenderSVGEllipse::shapeDependentStrokeContains(const FloatPoint& point)
 {
-    // The optimized code below does not support discontinuous strokes so we need
-    // to fall back to RenderSVGShape::shapeDependentStrokeContains in these cases.
-    if (m_usePathFallback || !hasContinuousStroke()) {
-        if (!hasPath())
-            RenderSVGShape::updateShapeFromElement();
+    // The optimized check below for circles does not support non-scaling or
+    // discontinuous strokes.
+    if (m_usePathFallback
+        || !hasContinuousStroke()
+        || m_radii.width() != m_radii.height()) {
+        ASSERT(hasPath());
         return RenderSVGShape::shapeDependentStrokeContains(point);
     }
 
-    float halfStrokeWidth = strokeWidth() / 2;
-    FloatPoint center = FloatPoint(m_center.x() - point.x(), m_center.y() - point.y());
-
-    // This works by checking if the point satisfies the ellipse equation,
-    // (x/rX)^2 + (y/rY)^2 <= 1, for the outer but not the inner stroke.
-    float xrXOuter = center.x() / (m_radii.width() + halfStrokeWidth);
-    float yrYOuter = center.y() / (m_radii.height() + halfStrokeWidth);
-    if (xrXOuter * xrXOuter + yrYOuter * yrYOuter > 1.0)
-        return false;
-
-    float xrXInner = center.x() / (m_radii.width() - halfStrokeWidth);
-    float yrYInner = center.y() / (m_radii.height() - halfStrokeWidth);
-    return xrXInner * xrXInner + yrYInner * yrYInner >= 1.0;
+    const FloatPoint center = FloatPoint(m_center.x() - point.x(), m_center.y() - point.y());
+    const float halfStrokeWidth = strokeWidth() / 2;
+    const float r = m_radii.width();
+    return std::abs(center.length() - r) <= halfStrokeWidth;
 }
 
 bool RenderSVGEllipse::shapeDependentFillContains(const FloatPoint& point, const WindRule fillRule) const
 {
-    if (m_usePathFallback)
-        return RenderSVGShape::shapeDependentFillContains(point, fillRule);
-
-    FloatPoint center = FloatPoint(m_center.x() - point.x(), m_center.y() - point.y());
+    const FloatPoint center = FloatPoint(m_center.x() - point.x(), m_center.y() - point.y());
 
     // This works by checking if the point satisfies the ellipse equation.
     // (x/rX)^2 + (y/rY)^2 <= 1
-    float xrX = center.x() / m_radii.width();
-    float yrY = center.y() / m_radii.height();
+    const float xrX = center.x() / m_radii.width();
+    const float yrY = center.y() / m_radii.height();
     return xrX * xrX + yrY * yrY <= 1.0;
 }