fix bugs found by computing flat clips in 800K skps

src/pathops/SkIntersections.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"
 
 void SkIntersections::append(const SkIntersections& i) {
@@ skipping 85 matching lines @@
     }
     if (fUsed >= fMax) {
         SkASSERT(0);  // FIXME : this error, if it is to be handled at runtime in release, must
                       // be propagated all the way back down to the caller, and return failure.
         fUsed = 0;
         return 0;
     }
     int remaining = fUsed - index;
     if (remaining > 0) {
         memmove(&fPt[index + 1], &fPt[index], sizeof(fPt[0]) * remaining);
+        memmove(&fPt2[index + 1], &fPt2[index], sizeof(fPt2[0]) * remaining);
         memmove(&fT[0][index + 1], &fT[0][index], sizeof(fT[0][0]) * remaining);
         memmove(&fT[1][index + 1], &fT[1][index], sizeof(fT[1][0]) * remaining);
         int clearMask = ~((1 << index) - 1);
         fIsCoincident[0] += fIsCoincident[0] & clearMask;
         fIsCoincident[1] += fIsCoincident[1] & clearMask;
     }
     fPt[index] = pt;
     fT[0][index] = one;
     fT[1][index] = two;
     ++fUsed;
     return index;
 }
 
+void SkIntersections::insertNear(double one, double two, const SkDPoint& pt1, const SkDPoint& pt2) {
+    SkASSERT(one == 0 || one == 1);
+    SkASSERT(two == 0 || two == 1);
+    SkASSERT(pt1 != pt2);
+    SkASSERT(fNearlySame[(int) one]);
+    (void) insert(one, two, pt1);
+    fPt2[one ? fUsed - 1 : 0] = pt2;
+}
+
 void SkIntersections::insertCoincident(double one, double two, const SkDPoint& pt) {
     int index = insertSwap(one, two, pt);
     int bit = 1 << index;
     fIsCoincident[0] |= bit;
     fIsCoincident[1] |= bit;
 }
 
 int SkIntersections::lineRay(const SkPoint pts[2], const SkDLine& line) {
     SkDLine l;
     l.set(pts);
@@ skipping 22 matching lines @@
         fT[0][index] = fT[0][replace];
     }
 }
 
 void SkIntersections::removeOne(int index) {
     int remaining = --fUsed - index;
     if (remaining <= 0) {
         return;
     }
     memmove(&fPt[index], &fPt[index + 1], sizeof(fPt[0]) * remaining);
+    memmove(&fPt2[index], &fPt2[index + 1], sizeof(fPt2[0]) * remaining);
     memmove(&fT[0][index], &fT[0][index + 1], sizeof(fT[0][0]) * remaining);
     memmove(&fT[1][index], &fT[1][index + 1], sizeof(fT[1][0]) * remaining);
     SkASSERT(fIsCoincident[0] == 0);
     int coBit = fIsCoincident[0] & (1 << index);
     fIsCoincident[0] -= ((fIsCoincident[0] >> 1) & ~((1 << index) - 1)) + coBit;
     SkASSERT(!(coBit ^ (fIsCoincident[1] & (1 << index))));
     fIsCoincident[1] -= ((fIsCoincident[1] >> 1) & ~((1 << index) - 1)) + coBit;
 }
 
 void SkIntersections::swapPts() {
@@ skipping 16 matching lines @@
     quad.set(a);
     return vertical(quad, top, bottom, x, flipped);
 }
 
 int SkIntersections::verticalCubic(const SkPoint a[4], SkScalar top, SkScalar bottom,
         SkScalar x, bool flipped) {
     SkDCubic cubic;
     cubic.set(a);
     return vertical(cubic, top, bottom, x, flipped);
 }