Bug 793612 - Make nsSVGArcConverter robust against zero-sized arc segments. r=longsonr

content/svg/content/src/nsSVGPathDataParser.cpp

@@ -855,6 +855,12 @@ nsSVGArcConverter::nsSVGArcConverter(const gfxPoint &from,
                                      bool sweepFlag)
 {
   const double radPerDeg = M_PI/180.0;
+  mSegIndex = 0;
+
+  if (from == to) {
+    mNumSegs = 0;
+    return;
+  }
 
   // Convert to center parameterization as shown in
   // http://www.w3.org/TR/SVG/implnote.html
@@ -910,7 +916,6 @@ nsSVGArcConverter::nsSVGArcConverter(const gfxPoint &from,
   mT = 8.0/3.0 * sin(mDelta/4.0) * sin(mDelta/4.0) / sin(mDelta/2.0);
 
   mFrom = from;
-  mSegIndex = 0;
 }
 
 bool

layout/reftests/svg/path-06-ref.svg

@@ -0,0 +1,13 @@
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<svg xmlns="http://www.w3.org/2000/svg">
+
+  <title>Reference for zero-sized path arc handling</title>
+
+  <!-- From https://bugzilla.mozilla.org/show_bug.cgi?id=793612 -->
+
+  <!-- Check that a zero-sized arc segment is ignored. -->
+  <path d="M 100,100 H 200 H 300" stroke="red" stroke-width="3px"/>
+</svg>

layout/reftests/svg/path-06.svg

@@ -0,0 +1,13 @@
+<!--
+     Any copyright is dedicated to the Public Domain.
+     http://creativecommons.org/publicdomain/zero/1.0/
+-->
+<svg xmlns="http://www.w3.org/2000/svg">
+
+  <title>Testcase for zero-sized path arc handling</title>
+
+  <!-- From https://bugzilla.mozilla.org/show_bug.cgi?id=793612 -->
+
+  <!-- Check that a zero-sized arc segment is ignored. -->
+  <path d="M 100,100 H 200 A 200,100 0 0 0 200,100 H 300" stroke="red" stroke-width="3px"/>
+</svg>

layout/reftests/svg/reftest.list

@@ -200,6 +200,7 @@ random-if(gtk2Widget) == objectBoundingBox-and-fePointLight-02.svg objectBoundin
 == path-03.svg pass.svg
 == path-04.svg pass.svg
 == path-05.svg pass.svg
+== path-06.svg path-06-ref.svg
 == pathLength-01.svg pass.svg
 == pathLength-02.svg pass.svg
 == pattern-invalid-01.svg pattern-invalid-01-ref.svg