allow conic chop to fail

src/pathops/SkOpEdgeBuilder.cpp

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 #include "SkGeometry.h"
 #include "SkOpEdgeBuilder.h"
 #include "SkReduceOrder.h"
 
@@ skipping 213 matching lines @@
             case SkPath::kConic_Verb: {
                 SkVector v1 = pointsPtr[1] - pointsPtr[0];
                 SkVector v2 = pointsPtr[2] - pointsPtr[1];
                 SkScalar weight = *weightPtr++;
                 if (v1.dot(v2) < 0) {
                     // FIXME: max curvature for conics hasn't been implemented; use placeholder
                     SkScalar maxCurvature = SkFindQuadMaxCurvature(pointsPtr);
                     if (maxCurvature > 0) {
                         SkConic conic(pointsPtr, weight);
                         SkConic pair[2];
-                        conic.chopAt(maxCurvature, pair);
+                        if (!conic.chopAt(maxCurvature, pair)) {
+                            // if result can't be computed, use original
+                            fCurrentContour->addConic(pointsPtr, weight);
+                            break;
+                        }
                         SkPoint cStorage[2][3];
                         SkPath::Verb v1 = SkReduceOrder::Conic(pair[0], cStorage[0]);
                         SkPath::Verb v2 = SkReduceOrder::Conic(pair[1], cStorage[1]);
                         SkPoint* curve1 = v1 != SkPath::kLine_Verb ? pair[0].fPts : cStorage[0];
                         SkPoint* curve2 = v2 != SkPath::kLine_Verb ? pair[1].fPts : cStorage[1];
                         if (can_add_curve(v1, curve1) && can_add_curve(v2, curve2)) {
                             fCurrentContour->addCurve(v1, curve1, pair[0].fW);
                             fCurrentContour->addCurve(v2, curve2, pair[1].fW);
                             break;
                         }
@@ skipping 39 matching lines @@
         }
         SkASSERT(fCurrentContour);
         fCurrentContour->debugValidate();
         pointsPtr += SkPathOpsVerbToPoints(verb);
     }
    if (fCurrentContour && fCurrentContour->count() &&!fAllowOpenContours && !close()) {
        return false;
    }
    return true;
 }