harden pathops for pathological test

src/pathops/SkDLineIntersection.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 "SkIntersections.h"
 #include "SkPathOpsLine.h"
 
 /* Determine the intersection point of two lines. This assumes the lines are not parallel,
    and that that the lines are infinite.
    From http://en.wikipedia.org/wiki/Line-line_intersection
  */
 SkDPoint SkIntersections::Line(const SkDLine& a, const SkDLine& b) {
     double axLen = a[1].fX - a[0].fX;
     double ayLen = a[1].fY - a[0].fY;
     double bxLen = b[1].fX - b[0].fX;
     double byLen = b[1].fY - b[0].fY;
     double denom = byLen * axLen - ayLen * bxLen;
     SkASSERT(denom);
     double term1 = a[1].fX * a[0].fY - a[1].fY * a[0].fX;
     double term2 = b[1].fX * b[0].fY - b[1].fY * b[0].fX;
     SkDPoint p;
     p.fX = (term1 * bxLen - axLen * term2) / denom;
     p.fY = (term1 * byLen - ayLen * term2) / denom;
     return p;
 }
 
-void SkIntersections::cleanUpCoincidence() {
-    SkASSERT(fUsed == 2);
-    // both t values are good
-    bool startMatch = fT[0][0] == 0 && (fT[1][0] == 0 || fT[1][0] == 1);
-    bool endMatch = fT[0][1] == 1 && (fT[1][1] == 0 || fT[1][1] == 1);
-    if (startMatch || endMatch) {
-        removeOne(startMatch);
-        return;
-    }
-    // either t value is good
-    bool pStartMatch = fT[0][0] == 0 || fT[1][0] == 0 || fT[1][0] == 1;
-    bool pEndMatch = fT[0][1] == 1 || fT[1][1] == 0 || fT[1][1] == 1;
-    removeOne(pStartMatch || !pEndMatch);
+int SkIntersections::cleanUpCoincidence() {
+    do {
+        int last = fUsed - 1;
+        for (int index = 0; index < last; ++index) {
+            if (fT[0][index] == fT[0][index + 1]) {
+                removeOne(index + (int) (fT[1][index] == 0 || fT[1][index] == 1));
+                goto tryAgain;
+            }
+        }
+        for (int index = 0; index < last; ++index) {
+            if (fT[1][index] == fT[1][index + 1]) {
+                removeOne(index + (int) (fT[0][index] == 0 || fT[0][index] == 1));
+                goto tryAgain;
+            }
+        }
+        return fUsed;
+tryAgain: ;
+    } while (true);
 }
 
 void SkIntersections::cleanUpParallelLines(bool parallel) {
     while (fUsed > 2) {
         removeOne(1);
     }
     if (fUsed == 2 && !parallel) {
         bool startMatch = fT[0][0] == 0 || fT[1][0] == 0 || fT[1][0] == 1;
         bool endMatch = fT[0][1] == 1 || fT[1][1] == 0 || fT[1][1] == 1;
         if ((!startMatch && !endMatch) || approximately_equal(fT[0][0], fT[0][1])) {
@@ skipping 340 matching lines @@
 // 4 subs, 2 muls, 1 cmp
 static bool ccw(const SkDPoint& A, const SkDPoint& B, const SkDPoint& C) {
     return (C.fY - A.fY) * (B.fX - A.fX) > (B.fY - A.fY) * (C.fX - A.fX);
 }
 
 // 16 subs, 8 muls, 6 cmps
 bool SkIntersections::Test(const SkDLine& a, const SkDLine& b) {
     return ccw(a[0], b[0], b[1]) != ccw(a[1], b[0], b[1])
             && ccw(a[0], a[1], b[0]) != ccw(a[0], a[1], b[1]);
 }