fail when coincidence is too far apart

src/pathops/SkOpContour.cpp

 /*
 * Copyright 2013 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 "SkOpContour.h"
 #include "SkPathWriter.h"
 #include "SkTSort.h"
@@ skipping 39 matching lines @@
         *start = *end = 0;
         while (testSegment->nextCandidate(start, end)) {
             if (!testSegment->isVertical(*start, *end)) {
                 return testSegment;
             }
         }
     }
     return NULL;
 }
 
+// if one is very large the smaller may have collapsed to nothing
+static void bump_out_close_span(double* startTPtr, double* endTPtr) {
+    double startT = *startTPtr;
+    double endT = *endTPtr;
+    if (approximately_negative(endT - startT)) {
+        if (endT <= 1 - FLT_EPSILON) {
+            *endTPtr += FLT_EPSILON;
+            SkASSERT(*endTPtr <= 1);
+        } else {
+            *startTPtr -= FLT_EPSILON;
+            SkASSERT(*startTPtr >= 0);
+        }
+    }
+}
+
 // first pass, add missing T values
 // second pass, determine winding values of overlaps
 void SkOpContour::addCoincidentPoints() {
     int count = fCoincidences.count();
     for (int index = 0; index < count; ++index) {
         SkCoincidence& coincidence = fCoincidences[index];
         int thisIndex = coincidence.fSegments[0];
         SkOpSegment& thisOne = fSegments[thisIndex];
         SkOpContour* otherContour = coincidence.fOther;
         int otherIndex = coincidence.fSegments[1];
         SkOpSegment& other = otherContour->fSegments[otherIndex];
         if ((thisOne.done() || other.done()) && thisOne.complete() && other.complete()) {
             // OPTIMIZATION: remove from array
             continue;
         }
     #if DEBUG_CONCIDENT
         thisOne.debugShowTs("-");
         other.debugShowTs("o");
     #endif
         double startT = coincidence.fTs[0][0];
         double endT = coincidence.fTs[0][1];
         bool startSwapped, oStartSwapped, cancelers;
         if ((cancelers = startSwapped = startT > endT)) {
             SkTSwap(startT, endT);
         }
-        if (startT == endT) { // if one is very large the smaller may have collapsed to nothing
-            if (endT <= 1 - FLT_EPSILON) {
-                endT += FLT_EPSILON;
-                SkASSERT(endT <= 1);
-            } else {
-                startT -= FLT_EPSILON;
-                SkASSERT(startT >= 0);
-            }
-        }
+        bump_out_close_span(&startT, &endT);
         SkASSERT(!approximately_negative(endT - startT));
         double oStartT = coincidence.fTs[1][0];
         double oEndT = coincidence.fTs[1][1];
         if ((oStartSwapped = oStartT > oEndT)) {
             SkTSwap(oStartT, oEndT);
             cancelers ^= true;
         }
+        bump_out_close_span(&oStartT, &oEndT);
         SkASSERT(!approximately_negative(oEndT - oStartT));
         const SkPoint& startPt = coincidence.fPts[0][startSwapped];
         if (cancelers) {
             // make sure startT and endT have t entries
             if (startT > 0 || oEndT < 1
                     || thisOne.isMissing(startT, startPt) || other.isMissing(oEndT, startPt)) {
                 thisOne.addTPair(startT, &other, oEndT, true, startPt,
                         coincidence.fPts[1][startSwapped]);
             }
             const SkPoint& oStartPt = coincidence.fPts[1][oStartSwapped];
@@ skipping 441 matching lines @@
     }
     double startT = coincidence.fTs[0][0];
     double endT = coincidence.fTs[0][1];
     const SkPoint* startPt = &coincidence.fPts[0][0];
     const SkPoint* endPt = &coincidence.fPts[0][1];
     bool cancelers;
     if ((cancelers = startT > endT)) {
         SkTSwap<double>(startT, endT);
         SkTSwap<const SkPoint*>(startPt, endPt);
     }
-    if (startT == endT) { // if span is very large, the smaller may have collapsed to nothing
-        if (endT <= 1 - FLT_EPSILON) {
-            endT += FLT_EPSILON;
-            SkASSERT(endT <= 1);
-        } else {
-            startT -= FLT_EPSILON;
-            SkASSERT(startT >= 0);
-        }
-    }
+    bump_out_close_span(&startT, &endT);
     SkASSERT(!approximately_negative(endT - startT));
     double oStartT = coincidence.fTs[1][0];
     double oEndT = coincidence.fTs[1][1];
     if (oStartT > oEndT) {
         SkTSwap<double>(oStartT, oEndT);
         cancelers ^= true;
     }
+    bump_out_close_span(&oStartT, &oEndT);
     SkASSERT(!approximately_negative(oEndT - oStartT));
     if (cancelers) {
         thisOne.addTCancel(*startPt, *endPt, &other);
     } else {
         thisOne.addTCoincident(*startPt, *endPt, endT, &other);
     }
 #if DEBUG_CONCIDENT
     thisOne.debugShowTs("p");
     other.debugShowTs("o");
 #endif
@@ skipping 159 matching lines @@
         SkDebugf("%s empty contour\n", __FUNCTION__);
         SkASSERT(0);
         // FIXME: delete empty contour?
         return;
     }
     fBounds = fSegments.front().bounds();
     for (int index = 1; index < count; ++index) {
         fBounds.add(fSegments[index].bounds());
     }
 }