handle NaN in curve choppers and edgeclipper

git-svn-id: http://skia.googlecode.com/svn/trunk@522 2bbb7eff-a529-9590-31e7-b0007b416f81

src/core/SkEdgeClipper.cpp

@@ -280,7 +280,11 @@ static void chop_cubic_in_Y(SkPoint pts[4], const SkRect& clip) {
     if (pts[0].fY < clip.fTop) {
         if (chopMonoCubicAtY(pts, clip.fTop, &t)) {
             SkChopCubicAt(pts, tmp, t);
-            clamp_ge(tmp[3].fY, clip.fTop);
+            // given the imprecision of computing t, we just slam our Y coord
+            // to the top of the clip. This also saves us in the bad case where
+            // the t was soooo bad that the entire segment could have been
+            // below fBottom
+            tmp[3].fY = clip.fTop;
             clamp_ge(tmp[4].fY, clip.fTop);
             clamp_ge(tmp[5].fY, clip.fTop);
             pts[0] = tmp[3];

src/core/SkGeometry.cpp

@@ -100,6 +100,9 @@ static int valid_unit_divide(SkScalar numer, SkScalar denom, SkScalar* ratio)
         return 0;
 
     SkScalar r = SkScalarDiv(numer, denom);
+    if (SkScalarIsNaN(r)) {
+        return 0;
+    }
     SkASSERT(r >= 0 && r < SK_Scalar1);
     if (r == 0) // catch underflow if numer <<<< denom
         return 0;
@@ -124,8 +127,9 @@ int SkFindUnitQuadRoots(SkScalar A, SkScalar B, SkScalar C, SkScalar roots[2])
 
 #ifdef SK_SCALAR_IS_FLOAT
     float R = B*B - 4*A*C;
-    if (R < 0)  // complex roots
+    if (R < 0 || SkScalarIsNaN(R)) {  // complex roots
         return 0;
+    }
     R = sk_float_sqrt(R);
 #else
     Sk64    RR, tmp;