path ops -- rewrite angle sort

src/pathops/SkDCubicIntersection.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 "SkPathOpsCubic.h"
 #include "SkPathOpsLine.h"
@@ skipping 408 matching lines @@
     }
     SkDPoint pt[2];
     if (closeStart(c1, 0, *this, pt[0]) && closeStart(c2, 1, *this, pt[1])
             && pt[0].approximatelyEqual(pt[1])) {
         removeOne(1);
     }
     if (closeEnd(c1, 0, *this, pt[0]) && closeEnd(c2, 1, *this, pt[1])
             && pt[0].approximatelyEqual(pt[1])) {
         removeOne(used() - 2);
     }
+    // vet the pairs of t values to see if the mid value is also on the curve. If so, mark
+    // the span as coincident
+    if (fUsed >= 2 && !coincidentUsed()) {
+        int last = fUsed - 1;
+        int match = 0;
+        for (int index = 0; index < last; ++index) {
+            double mid1 = (fT[0][index] + fT[0][index + 1]) / 2;
+            double mid2 = (fT[1][index] + fT[1][index + 1]) / 2;
+            pt[0] = c1.xyAtT(mid1);
+            pt[1] = c2.xyAtT(mid2);
+            if (pt[0].approximatelyEqual(pt[1])) {
+                match |= 1 << index;
+            }
+        }
+        if (match) {
+            if (((match + 1) & match) != 0) {
+                SkDebugf("%s coincident hole\n", __FUNCTION__);
+            }
+            // for now, assume that everything from start to finish is coincident
+            if (fUsed > 2) {
+                  fPt[1] = fPt[last];
+                  fT[0][1] = fT[0][last];
+                  fT[1][1] = fT[1][last];
+                  fIsCoincident[0] = 0x03;
+                  fIsCoincident[1] = 0x03;
+                  fUsed = 2;
+            }
+        }
+    }
     return fUsed;
 }
 
 // Up promote the quad to a cubic.
 // OPTIMIZATION If this is a common use case, optimize by duplicating
 // the intersect 3 loop to avoid the promotion  / demotion code
 int SkIntersections::intersect(const SkDCubic& cubic, const SkDQuad& quad) {
     SkDCubic up = quad.toCubic();
     (void) intersect(cubic, up);
     return used();
@@ skipping 13 matching lines @@
     }
     (void) intersect(c, c);
     if (used() > 0) {
         SkASSERT(used() == 1);
         if (fT[0][0] > fT[1][0]) {
             swapPts();
         }
     }
     return used();
 }