fix path op conic bugs

src/pathops/SkPathOpsTSect.h

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkChunkAlloc.h"
 #include "SkPathOpsBounds.h"
 #include "SkPathOpsRect.h"
@@ skipping 969 matching lines @@
     bool deleteEmptySpans = this->updateBounded(first, last, oppFirst);
     deleteEmptySpans |= sect2->updateBounded(oppFirst, oppLast, first);
     this->removeSpanRange(first, last);
     sect2->removeSpanRange(oppFirst, oppLast);
     first->fStartT = start1s;
     first->fEndT = start1e;
     first->resetBounds(fCurve);
     first->fCoinStart.setPerp(fCurve, start1s, fCurve[0], sect2->fCurve);
     first->fCoinEnd.setPerp(fCurve, start1e, fCurve[TCurve::kPointLast], sect2->fCurve);
     bool oppMatched = first->fCoinStart.perpT() < first->fCoinEnd.perpT();
-    double oppStartT = SkTMax(0., first->fCoinStart.perpT());
-    double oppEndT = SkTMin(1., first->fCoinEnd.perpT());
+    double oppStartT = first->fCoinStart.perpT() == -1 ? 0 : SkTMax(0., first->fCoinStart.perpT());
+    double oppEndT = first->fCoinEnd.perpT() == -1 ? 1 : SkTMin(1., first->fCoinEnd.perpT());
     if (!oppMatched) {
         SkTSwap(oppStartT, oppEndT);
     }
     oppFirst->fStartT = oppStartT;
     oppFirst->fEndT = oppEndT;
     oppFirst->resetBounds(sect2->fCurve);
     this->removeCoincident(first, false);
     sect2->removeCoincident(oppFirst, true);
     if (deleteEmptySpans) {
         this->deleteEmptySpans();
@@ skipping 1077 matching lines @@
             if (coinLoopCount == kMaxCoinLoopCount) {
                 start1s = sect1->fHead->fStartT;
                 start1e = sect1->tail()->fEndT;
             }
             sect1->coincidentCheck(sect2);
             sect1->validate();
             sect2->validate();
 #if DEBUG_T_SECT_LOOP_COUNT
             intersections->debugBumpLoopCount(SkIntersections::kCoinCheck_DebugLoop);
 #endif
-            if (!--coinLoopCount) {
+            if (!--coinLoopCount && sect1->fHead && sect2->fHead) {
                 /* All known working cases resolve in two tries. Sadly, cubicConicTests[0]
                    gets stuck in a loop. It adds an extension to allow a coincident end
                    perpendicular to track its intersection in the opposite curve. However,
                    the bounding box of the extension does not intersect the original curve,
                    so the extension is discarded, only to be added again the next time around. */ 
                 sect1->coincidentForce(sect2, start1s, start1e);
                 sect1->validate();
                 sect2->validate();
             }
         }
@@ skipping 20 matching lines @@
     } while (true);
     SkTSpan<TCurve, OppCurve>* coincident = sect1->fCoincident;
     if (coincident) {
         // if there is more than one coincident span, check loosely to see if they should be joined
         if (coincident->fNext) {
             sect1->mergeCoincidence(sect2);
             coincident = sect1->fCoincident;
         }
         SkASSERT(sect2->fCoincident);  // courtesy check : coincidence only looks at sect 1
         do {
-            SkASSERT(coincident->fCoinStart.isCoincident());
-            SkASSERT(coincident->fCoinEnd.isCoincident());
+            if (!coincident->fCoinStart.isCoincident()) {
+                continue;
+            }
+            if (!coincident->fCoinEnd.isCoincident()) {
+                continue;
+            }
             int index = intersections->insertCoincident(coincident->fStartT,
                     coincident->fCoinStart.perpT(), coincident->fPart[0]);
             if ((intersections->insertCoincident(coincident->fEndT,
                     coincident->fCoinEnd.perpT(),
                     coincident->fPart[TCurve::kPointLast]) < 0) && index >= 0) {
                 intersections->clearCoincidence(index);
             }
         } while ((coincident = coincident->fNext));
     }
     int zeroOneSet = EndsEqual(sect1, sect2, intersections);
@@ skipping 82 matching lines @@
         } else if (intersections->isCoincident(index + 1)) {
             intersections->removeOne(index + 1);
             --last;
         } else {
             intersections->setCoincident(index++);
         }
         intersections->setCoincident(index);
     }
     SkASSERT(intersections->used() <= TCurve::kMaxIntersections);
 }