pathops work in progress

src/pathops/SkPathOpsTriangle.cpp

Index: src/pathops/SkPathOpsTriangle.cpp
diff --git a/src/pathops/SkPathOpsTriangle.cpp b/src/pathops/SkPathOpsTriangle.cpp
index 49391667ac6b3abd2b3404c2b6c5a62ea7cf0ca3..003968ddba67ec55cd7b14d0504c243b80363f97 100644
--- a/src/pathops/SkPathOpsTriangle.cpp
+++ b/src/pathops/SkPathOpsTriangle.cpp
@@ -8,6 +8,7 @@
 #include "SkPathOpsTriangle.h"
 
 // http://www.blackpawn.com/texts/pointinpoly/default.html
+// return true if pt is inside triangle; false if outside or on the line
 bool SkDTriangle::contains(const SkDPoint& pt) const {
 // Compute vectors
     SkDVector v0 = fPts[2] - fPts[0];
@@ -21,11 +22,30 @@ bool SkDTriangle::contains(const SkDPoint& pt) const {
     double dot11 = v1.dot(v1);
     double dot12 = v1.dot(v2);
 
+// original code doesn't handle degenerate input; isn't symmetric with inclusion of corner pts;
+// introduces necessary error with divide; doesn't short circuit on early answer
+#if 0
 // Compute barycentric coordinates
     double invDenom = 1 / (dot00 * dot11 - dot01 * dot01);
     double u = (dot11 * dot02 - dot01 * dot12) * invDenom;
     double v = (dot00 * dot12 - dot01 * dot02) * invDenom;
 
 // Check if point is in triangle
-    return (u >= 0) && (v >= 0) && (u + v < 1);
+    return (u >= 0) && (v >= 0) && (u + v <= 1);
+#else
+    double w = dot00 * dot11 - dot01 * dot01;
+    if (w == 0) {
+        return false;
+    }
+    double wSign = w < 0 ? -1 : 1;
+    double u = (dot11 * dot02 - dot01 * dot12) * wSign;
+    if (u <= 0) {
+        return false;
+    }
+    double v = (dot00 * dot12 - dot01 * dot02) * wSign;
+    if (v <= 0) {
+        return false;
+    }
+    return u + v < w * wSign; 
+#endif
 }