allow conic chop to fail

src/core/SkGeometry.cpp

Index: src/core/SkGeometry.cpp
diff --git a/src/core/SkGeometry.cpp b/src/core/SkGeometry.cpp
index 027b65f0f1962e82e0bbfc38afb77184a23fdc12..cb515e1d14b1eb06de3c415e32cee7c5e62c6713 100644
--- a/src/core/SkGeometry.cpp
+++ b/src/core/SkGeometry.cpp
@@ -975,7 +975,8 @@ static void ratquad_mapTo3D(const SkPoint src[3], SkScalar w, SkP3D dst[]) {
     dst[2].set(src[2].fX * 1, src[2].fY * 1, 1);
 }
 
-void SkConic::chopAt(SkScalar t, SkConic dst[2]) const {
+// return false if infinity or NaN is generated; caller must check
+bool SkConic::chopAt(SkScalar t, SkConic dst[2]) const {
     SkP3D tmp[3], tmp2[3];
 
     ratquad_mapTo3D(fPts, fW, tmp);
@@ -1001,18 +1002,23 @@ void SkConic::chopAt(SkScalar t, SkConic dst[2]) const {
     SkScalar root = SkScalarSqrt(tmp2[1].fZ);
     dst[0].fW = tmp2[0].fZ / root;
     dst[1].fW = tmp2[2].fZ / root;
+    SkASSERT(sizeof(dst[0]) == sizeof(SkScalar) * 7);
+    SkASSERT(0 == offsetof(SkConic, fPts[0].fX));
+    return SkScalarsAreFinite(&dst[0].fPts[0].fX, 7 * 2);
 }
 
 void SkConic::chopAt(SkScalar t1, SkScalar t2, SkConic* dst) const {
     if (0 == t1 || 1 == t2) {
         if (0 == t1 && 1 == t2) {
             *dst = *this;
+            return;
         } else {
             SkConic pair[2];
-            this->chopAt(t1 ? t1 : t2, pair);
-            *dst = pair[SkToBool(t1)];
+            if (this->chopAt(t1 ? t1 : t2, pair)) {
+                *dst = pair[SkToBool(t1)];
+                return;
+            }
         }
-        return;
     }
     SkConicCoeff coeff(*this);
     Sk2s tt1(t1);
@@ -1243,7 +1249,10 @@ bool SkConic::findYExtrema(SkScalar* t) const {
 bool SkConic::chopAtXExtrema(SkConic dst[2]) const {
     SkScalar t;
     if (this->findXExtrema(&t)) {
-        this->chopAt(t, dst);
+        if (!this->chopAt(t, dst)) {
+            // if chop can't return finite values, don't chop
+            return false;
+        }
         // now clean-up the middle, since we know t was meant to be at
         // an X-extrema
         SkScalar value = dst[0].fPts[2].fX;
@@ -1258,7 +1267,10 @@ bool SkConic::chopAtXExtrema(SkConic dst[2]) const {
 bool SkConic::chopAtYExtrema(SkConic dst[2]) const {
     SkScalar t;
     if (this->findYExtrema(&t)) {
-        this->chopAt(t, dst);
+        if (!this->chopAt(t, dst)) {
+            // if chop can't return finite values, don't chop
+            return false;
+        }
         // now clean-up the middle, since we know t was meant to be at
         // an Y-extrema
         SkScalar value = dst[0].fPts[2].fY;