When three or more edges are coincident, the logic needs

to compute the overlapping ranges and combine the winding
into a single destination.

This computes coincidence more rigorously, fixing the
edge cases exposed by this bug.

Also, add the ability to debug and dump pathop structures
from the coincident context.

TBR=reed@google.com
BUG=skia:3651

Review URL: https://codereview.chromium.org/1182493015

14 files changed, 620 insertions, 89 deletions

diff --git a/src/pathops/SkOpCoincidence.cpp b/src/pathops/SkOpCoincidence.cpp
index eb0ccc1737..58ff7f3ab9 100755
--- a/src/pathops/SkOpCoincidence.cpp
+++ b/src/pathops/SkOpCoincidence.cpp
@@ -65,6 +65,90 @@ static void t_range(const SkOpPtT* overS, const SkOpPtT* overE, double tStart, d
     *coinTe = coinPtTStart->fT + (coinPtTEnd->fT - coinPtTStart->fT) * eRatio;
 }
 
+void SkOpCoincidence::addExpanded(SkChunkAlloc* allocator
+        PATH_OPS_DEBUG_VALIDATE_PARAMS(SkOpGlobalState* globalState)) {
+#if DEBUG_VALIDATE
+    globalState->setPhase(SkOpGlobalState::kIntersecting);
+#endif
+    // for each coincident pair, match the spans
+    // if the spans don't match, add the mssing pt to the segment and loop it in the opposite span
+    SkCoincidentSpans* coin = this->fHead;
+    SkASSERT(coin);
+    do {
+        SkOpPtT* startPtT = coin->fCoinPtTStart;
+        SkOpPtT* oStartPtT = coin->fOppPtTStart;
+        SkASSERT(startPtT->contains(oStartPtT));
+        SkASSERT(coin->fCoinPtTEnd->contains(coin->fOppPtTEnd));
+        SkOpSpanBase* start = startPtT->span();
+        SkOpSpanBase* oStart = oStartPtT->span();
+        const SkOpSpanBase* end = coin->fCoinPtTEnd->span();
+        const SkOpSpanBase* oEnd = coin->fOppPtTEnd->span();
+        SkOpSpanBase* test = start->upCast()->next();
+        SkOpSpanBase* oTest = coin->fFlipped ? oStart->prev() : oStart->upCast()->next();
+        while (test != end || oTest != oEnd) {
+            if (!test->ptT()->contains(oTest->ptT())) {
+                // use t ranges to guess which one is missing
+                double startRange = coin->fCoinPtTEnd->fT - startPtT->fT;
+                double startPart = (test->t() - startPtT->fT) / startRange;
+                double oStartRange = coin->fOppPtTEnd->fT - oStartPtT->fT;
+                double oStartPart = (oTest->t() - oStartPtT->fT) / oStartRange;
+                SkASSERT(startPart != oStartPart);
+                SkOpPtT* newPt;
+                if (startPart < oStartPart) {
+                    double newT = oStartPtT->fT + oStartRange * startPart;
+                    newPt = oStart->segment()->addT(newT, SkOpSegment::kAllowAlias, allocator);
+                    newPt->fPt = test->pt();
+                    test->ptT()->addOpp(newPt);
+                } else {
+                    double newT = startPtT->fT + startRange * oStartPart;
+                    newPt = start->segment()->addT(newT, SkOpSegment::kAllowAlias, allocator);
+                    newPt->fPt = oTest->pt();
+                    oTest->ptT()->addOpp(newPt);
+                }
+                // start over
+                test = start;
+                oTest = oStart;
+            }
+            if (test != end) {
+                test = test->upCast()->next();
+            }
+            if (oStart != oEnd) {
+                oTest = coin->fFlipped ? oTest->prev() : oTest->upCast()->next();
+            }
+        }
+    } while ((coin = coin->fNext));
+#if DEBUG_VALIDATE
+    globalState->setPhase(SkOpGlobalState::kWalking);
+#endif
+}
+
+void SkOpCoincidence::addIfMissing(const SkCoincidentSpans* outer, SkOpPtT* over1s,
+            SkOpPtT* over1e, SkChunkAlloc* allocator) {
+    SkCoincidentSpans* check = this->fTop;
+    do {
+        if (check->fCoinPtTStart->span() == over1s->span()
+                && check->fOppPtTStart->span() == outer->fOppPtTStart->span()) {
+            SkASSERT(check->fCoinPtTEnd->span() == over1e->span()
+                    || !fDebugState->debugRunFail());
+            SkASSERT(check->fOppPtTEnd->span() == outer->fOppPtTEnd->span()
+                    || !fDebugState->debugRunFail());
+            return;
+        }
+        if (check->fCoinPtTStart->span() == outer->fCoinPtTStart->span()
+                && check->fOppPtTStart->span() == over1s->span()) {
+            SkASSERT(check->fCoinPtTEnd->span() == outer->fCoinPtTEnd->span()
+                    || !fDebugState->debugRunFail());
+            SkASSERT(check->fOppPtTEnd->span() == over1e->span()
+                    || !fDebugState->debugRunFail());
+            return;
+        }
+    } while ((check = check->fNext));
+    this->add(outer->fCoinPtTStart, outer->fCoinPtTEnd, over1s, over1e, allocator);
+#if 0
+    // FIXME: up to four flavors could be added -- do we need only one?
+#endif
+}
+
 bool SkOpCoincidence::addIfMissing(const SkOpPtT* over1s, const SkOpPtT* over1e,
                       const SkOpPtT* over2s, const SkOpPtT* over2e, double tStart, double tEnd,
         SkOpPtT* coinPtTStart, const SkOpPtT* coinPtTEnd,
@@ -75,7 +159,7 @@ bool SkOpCoincidence::addIfMissing(const SkOpPtT* over1s, const SkOpPtT* over1e,
     SkOpSegment* coinSeg = coinPtTStart->segment();
     SkOpSegment* oppSeg = oppPtTStart->segment();
     SkASSERT(coinSeg != oppSeg);
-    SkCoincidentSpans* check = this->fHead;
+    SkCoincidentSpans* check = this->fTop;
     do {
         const SkOpSegment* checkCoinSeg = check->fCoinPtTStart->segment();
         if (checkCoinSeg != coinSeg && checkCoinSeg != oppSeg) {
@@ -124,52 +208,136 @@ bool SkOpCoincidence::addIfMissing(const SkOpPtT* over1s, const SkOpPtT* over1e,
     return true;
 }
 
+/* detects overlaps of different coincident runs on same segment */
+/* does not detect overlaps for pairs without any segments in common */
 bool SkOpCoincidence::addMissing(SkChunkAlloc* allocator) {
-    SkCoincidentSpans* outer = this->fHead;
+    SkCoincidentSpans* outer = fHead;
     if (!outer) {
         return true;
     }
+    bool result;
+    fTop = outer;
+    fHead = NULL;
     do {
+    // addifmissing can modify the list that this is walking
+    // maybe save head so that walker can iterate over old data unperturbed
+    // and addifmissing can add to head freely then add saved head in the end
+        const SkOpSegment* outerCoin = outer->fCoinPtTStart->segment();
+        SkASSERT(outerCoin == outer->fCoinPtTEnd->segment());
+        const SkOpSegment* outerOpp = outer->fOppPtTStart->segment();
+        SkASSERT(outerOpp == outer->fOppPtTEnd->segment());
         SkCoincidentSpans* inner = outer;
         while ((inner = inner->fNext)) {
             double overS, overE;
-            if (this->overlap(outer->fCoinPtTStart, outer->fCoinPtTEnd,
+            const SkOpSegment* innerCoin = inner->fCoinPtTStart->segment();
+            SkASSERT(innerCoin == inner->fCoinPtTEnd->segment());
+            const SkOpSegment* innerOpp = inner->fOppPtTStart->segment();
+            SkASSERT(innerOpp == inner->fOppPtTEnd->segment());
+            if (outerCoin == innerCoin
+                    && this->overlap(outer->fCoinPtTStart, outer->fCoinPtTEnd,
                     inner->fCoinPtTStart, inner->fCoinPtTEnd, &overS, &overE)) {
                 if (!this->addIfMissing(outer->fCoinPtTStart, outer->fCoinPtTEnd,
                         inner->fCoinPtTStart, inner->fCoinPtTEnd, overS, overE,
                         outer->fOppPtTStart, outer->fOppPtTEnd,
                         inner->fOppPtTStart, inner->fOppPtTEnd, allocator)) {
-                    return false;
+                    result = false;
+                    goto returnResult;
                 }
-            } else if (this->overlap(outer->fCoinPtTStart, outer->fCoinPtTEnd,
+            } else if (outerCoin == innerOpp
+                    && this->overlap(outer->fCoinPtTStart, outer->fCoinPtTEnd,
                     inner->fOppPtTStart, inner->fOppPtTEnd, &overS, &overE)) {
                 if (!this->addIfMissing(outer->fCoinPtTStart, outer->fCoinPtTEnd,
                         inner->fOppPtTStart, inner->fOppPtTEnd, overS, overE,
                         outer->fOppPtTStart, outer->fOppPtTEnd,
                         inner->fCoinPtTStart, inner->fCoinPtTEnd, allocator)) {
-                    return false;
+                    result = false;
+                    goto returnResult;
                 }
-            } else if (this->overlap(outer->fOppPtTStart, outer->fOppPtTEnd,
+            } else if (outerOpp == innerCoin
+                    && this->overlap(outer->fOppPtTStart, outer->fOppPtTEnd,
                     inner->fCoinPtTStart, inner->fCoinPtTEnd, &overS, &overE)) {
                 if (!this->addIfMissing(outer->fOppPtTStart, outer->fOppPtTEnd,
                         inner->fCoinPtTStart, inner->fCoinPtTEnd, overS, overE,
                         outer->fCoinPtTStart, outer->fCoinPtTEnd,
                         inner->fOppPtTStart, inner->fOppPtTEnd, allocator)) {
-                    return false;
+                    result = false;
+                    goto returnResult;
                 }
-            } else if (this->overlap(outer->fOppPtTStart, outer->fOppPtTEnd,
+            } else if (outerOpp == innerOpp
+                    && this->overlap(outer->fOppPtTStart, outer->fOppPtTEnd,
                     inner->fOppPtTStart, inner->fOppPtTEnd, &overS, &overE)) {
                 if (!this->addIfMissing(outer->fOppPtTStart, outer->fOppPtTEnd,
                         inner->fOppPtTStart, inner->fOppPtTEnd, overS, overE,
                         outer->fCoinPtTStart, outer->fCoinPtTEnd,
                         inner->fCoinPtTStart, inner->fCoinPtTEnd, allocator)) {
-                    return false;
+                    result = false;
+                    goto returnResult;
+                }
+            } else if (outerCoin != innerCoin) {
+                // check to see if outer span overlaps the inner span
+                    // look for inner segment in pt-t list
+                    // if present, and if t values are in coincident range
+                    // add two pairs of new coincidence
+                SkOpPtT* testS = outer->fCoinPtTStart->contains(innerCoin);
+                SkOpPtT* testE = outer->fCoinPtTEnd->contains(innerCoin);
+                if (testS && testS->fT >= inner->fCoinPtTStart->fT
+                        && testE && testE->fT <= inner->fCoinPtTEnd->fT
+                        && this->testForCoincidence(outer, testS, testE)) {
+                    this->addIfMissing(outer, testS, testE, allocator);
+                } else {
+                    testS = inner->fCoinPtTStart->contains(outerCoin);
+                    testE = inner->fCoinPtTEnd->contains(outerCoin);
+                    if (testS && testS->fT >= outer->fCoinPtTStart->fT
+                            && testE && testE->fT <= outer->fCoinPtTEnd->fT
+                            && this->testForCoincidence(inner, testS, testE)) {
+                        this->addIfMissing(inner, testS, testE, allocator);
+                    }
                 }
             }
         }
-
     } while ((outer = outer->fNext));
-    return true;
+    result = true;
+returnResult:
+    SkCoincidentSpans** headPtr = &fHead;
+    while (*headPtr) {
+        SkCoincidentSpans** headNext = &(*headPtr)->fNext;
+        if (*headNext) {
+            break;
+        }
+        headPtr = headNext;
+    }
+    *headPtr = fTop;
+    return result;
+}
+
+void SkOpCoincidence::addOverlap(SkOpSegment* seg1, SkOpSegment* seg1o, SkOpSegment* seg2,
+        SkOpSegment* seg2o, SkOpPtT* overS, SkOpPtT* overE, SkChunkAlloc* allocator) {
+    SkOpPtT* s1 = overS->find(seg1);
+    SkOpPtT* e1 = overE->find(seg1);
+    if (!s1->starter(e1)->span()->upCast()->windValue()) {
+        s1 = overS->find(seg1o);
+        e1 = overE->find(seg1o);
+        if (!s1->starter(e1)->span()->upCast()->windValue()) {
+            return;
+        }
+    }
+    SkOpPtT* s2 = overS->find(seg2);
+    SkOpPtT* e2 = overE->find(seg2);
+    if (!s2->starter(e2)->span()->upCast()->windValue()) {
+        s2 = overS->find(seg2o);
+        e2 = overE->find(seg2o);
+        if (!s2->starter(e2)->span()->upCast()->windValue()) {
+            return;
+        }
+    }
+    if (s1->segment() == s2->segment()) {
+        return;
+    }
+    if (s1->fT > e1->fT) {
+        SkTSwap(s1, e1);
+        SkTSwap(s2, e2);
+    }
+    this->add(s1, e1, s2, e2, allocator);
 }
 
 bool SkOpCoincidence::contains(SkOpPtT* coinPtTStart, SkOpPtT* coinPtTEnd, SkOpPtT* oppPtTStart,
@@ -316,11 +484,12 @@ void SkOpCoincidence::detach(SkCoincidentSpans* remove) {
     SkASSERT(coin);
 }
 
-void SkOpCoincidence::expand() {
+bool SkOpCoincidence::expand() {
     SkCoincidentSpans* coin = fHead;
     if (!coin) {
-        return;
+        return false;
     }
+    bool expanded = false;
     do {
         SkOpSpan* start = coin->fCoinPtTStart->span()->upCast();
         SkOpSpanBase* end = coin->fCoinPtTEnd->span();
@@ -333,6 +502,7 @@ void SkOpCoincidence::expand() {
             if (segment->isClose(midT, oppSegment)) {
                 coin->fCoinPtTStart = prev->ptT();
                 coin->fOppPtTStart = oppPtT;
+                expanded = true;
             }
         }
         SkOpSpanBase* next = end->final() ? NULL : end->upCast()->next();
@@ -341,7 +511,61 @@ void SkOpCoincidence::expand() {
             if (segment->isClose(midT, oppSegment)) {
                 coin->fCoinPtTEnd = next->ptT();
                 coin->fOppPtTEnd = oppPtT;
+                expanded = true;
+            }
+        }
+    } while ((coin = coin->fNext));
+    return expanded;
+}
+
+void SkOpCoincidence::findOverlaps(SkOpCoincidence* overlaps, SkChunkAlloc* allocator) const {
+    overlaps->fHead = overlaps->fTop = NULL;
+    SkDEBUGCODE_(overlaps->debugSetGlobalState(fDebugState));
+    SkCoincidentSpans* outer = fHead;
+    while (outer) {
+        SkOpSegment* outerCoin = outer->fCoinPtTStart->segment();
+        SkOpSegment* outerOpp = outer->fOppPtTStart->segment();
+        SkCoincidentSpans* inner = outer;
+        while ((inner = inner->fNext)) {
+            SkOpSegment* innerCoin = inner->fCoinPtTStart->segment();
+            if (outerCoin == innerCoin) {
+                continue;  // both winners are the same segment, so there's no additional overlap
             }
+            SkOpSegment* innerOpp = inner->fOppPtTStart->segment();
+            SkOpPtT* overlapS, * overlapE;
+            if ((outerOpp == innerCoin && SkOpPtT::Overlaps(outer->fOppPtTStart, outer->fOppPtTEnd,
+                    inner->fCoinPtTStart, inner->fCoinPtTEnd, &overlapS, &overlapE))
+                    || (outerCoin == innerOpp && SkOpPtT::Overlaps(outer->fCoinPtTStart,
+                    outer->fCoinPtTEnd, inner->fOppPtTStart, inner->fOppPtTEnd,
+                    &overlapS, &overlapE))
+                    || (outerOpp == innerOpp && SkOpPtT::Overlaps(outer->fOppPtTStart,
+                    outer->fOppPtTEnd, inner->fOppPtTStart, inner->fOppPtTEnd,
+                    &overlapS, &overlapE))) {
+                overlaps->addOverlap(outerCoin, outerOpp, innerCoin, innerOpp,
+                        overlapS, overlapE, allocator);
+            }
+        }
+        outer = outer->fNext;
+    }
+}
+
+void SkOpCoincidence::fixAligned() {
+    SkCoincidentSpans* coin = fHead;
+    if (!coin) {
+        return;
+    }
+    do {
+        if (coin->fCoinPtTStart->deleted()) {
+            coin->fCoinPtTStart = coin->fCoinPtTStart->doppelganger();
+        }
+        if (coin->fCoinPtTEnd->deleted()) {
+            coin->fCoinPtTEnd = coin->fCoinPtTEnd->doppelganger();
+        }
+        if (coin->fOppPtTStart->deleted()) {
+            coin->fOppPtTStart = coin->fOppPtTStart->doppelganger();
+        }
+        if (coin->fOppPtTEnd->deleted()) {
+            coin->fOppPtTEnd = coin->fOppPtTEnd->doppelganger();
         }
     } while ((coin = coin->fNext));
 }
@@ -354,31 +578,36 @@ void SkOpCoincidence::fixUp(SkOpPtT* deleted, SkOpPtT* kept) {
     do {
         if (coin->fCoinPtTStart == deleted) {
             if (coin->fCoinPtTEnd->span() == kept->span()) {
-                return this->detach(coin);
+                this->detach(coin);
+                continue;
             }
             coin->fCoinPtTStart = kept;
         }
         if (coin->fCoinPtTEnd == deleted) {
             if (coin->fCoinPtTStart->span() == kept->span()) {
-                return this->detach(coin);
+                this->detach(coin);
+                continue;
             }
             coin->fCoinPtTEnd = kept;
         }
         if (coin->fOppPtTStart == deleted) {
             if (coin->fOppPtTEnd->span() == kept->span()) {
-                return this->detach(coin);
+                this->detach(coin);
+                continue;
             }
             coin->fOppPtTStart = kept;
         }
         if (coin->fOppPtTEnd == deleted) {
             if (coin->fOppPtTStart->span() == kept->span()) {
-                return this->detach(coin);
+                this->detach(coin);
+                continue;
             }
             coin->fOppPtTEnd = kept;
         }
     } while ((coin = coin->fNext));
 }
 
+/* this sets up the coincidence links in the segments when the coincidence crosses multiple spans */
 void SkOpCoincidence::mark() {
     SkCoincidentSpans* coin = fHead;
     if (!coin) {
@@ -397,8 +626,6 @@ void SkOpCoincidence::mark() {
         }
         SkOpSpanBase* next = start;
         SkOpSpanBase* oNext = oStart;
-        // check to see if coincident span could be bigger
-
         do {
             next = next->upCast()->next();
             oNext = flipped ? oNext->prev() : oNext->upCast()->next();
@@ -419,10 +646,14 @@ void SkOpCoincidence::mark() {
 
 bool SkOpCoincidence::overlap(const SkOpPtT* coin1s, const SkOpPtT* coin1e, 
         const SkOpPtT* coin2s, const SkOpPtT* coin2e, double* overS, double* overE) const {
-    if (coin1s->segment() != coin2s->segment()) {
-        return false;
-    }
+    SkASSERT(coin1s->segment() == coin2s->segment());
     *overS = SkTMax(SkTMin(coin1s->fT, coin1e->fT), SkTMin(coin2s->fT, coin2e->fT));
     *overE = SkTMin(SkTMax(coin1s->fT, coin1e->fT), SkTMax(coin2s->fT, coin2e->fT));
     return *overS < *overE;
 }
+
+bool SkOpCoincidence::testForCoincidence(const SkCoincidentSpans* outer, SkOpPtT* testS,
+        SkOpPtT* testE) const {
+    return testS->segment()->testForCoincidence(testS, testE, testS->span(),
+            testE->span(), outer->fCoinPtTStart->segment(), 120000);  // FIXME: replace with tuned
+}
diff --git a/src/pathops/SkOpCoincidence.h b/src/pathops/SkOpCoincidence.h
index ce57999b1d..83ba70a0f9 100644
--- a/src/pathops/SkOpCoincidence.h
+++ b/src/pathops/SkOpCoincidence.h
@@ -9,6 +9,7 @@
 
 #include "SkOpTAllocator.h"
 #include "SkOpSpan.h"
+#include "SkPathOpsTypes.h"
 
 class SkOpPtT;
 
@@ -26,36 +27,81 @@ struct SkCoincidentSpans {
 class SkOpCoincidence {
 public:
     SkOpCoincidence()
-        : fHead(NULL) {
+        : fHead(NULL)
+        , fTop(NULL)
+        SkDEBUGPARAMS(fDebugState(NULL))
+        {
     }
 
     void add(SkOpPtT* coinPtTStart, SkOpPtT* coinPtTEnd, SkOpPtT* oppPtTStart,
              SkOpPtT* oppPtTEnd, SkChunkAlloc* allocator);
+    void addExpanded(SkChunkAlloc* allocator  PATH_OPS_DEBUG_VALIDATE_PARAMS(SkOpGlobalState* ));
     bool addMissing(SkChunkAlloc* allocator);
     void addMissing(SkCoincidentSpans* check, SkChunkAlloc* allocator);
     bool apply();
     bool contains(SkOpPtT* coinPtTStart, SkOpPtT* coinPtTEnd, SkOpPtT* oppPtTStart,
                   SkOpPtT* oppPtTEnd, bool flipped);
+
+    const SkOpAngle* debugAngle(int id) const {
+        return SkDEBUGRELEASE(fDebugState->debugAngle(id), NULL);
+    }
+
+    SkOpContour* debugContour(int id) {
+        return SkDEBUGRELEASE(fDebugState->debugContour(id), NULL);
+    }
+
+    const SkOpPtT* debugPtT(int id) const {
+        return SkDEBUGRELEASE(fDebugState->debugPtT(id), NULL);
+    }
+
+    const SkOpSegment* debugSegment(int id) const {
+        return SkDEBUGRELEASE(fDebugState->debugSegment(id), NULL);
+    }
+
+    void debugSetGlobalState(SkOpGlobalState* debugState) {
+        SkDEBUGCODE(fDebugState = debugState);
+    }
+
     void debugShowCoincidence() const;
+
+    const SkOpSpanBase* debugSpan(int id) const {
+        return SkDEBUGRELEASE(fDebugState->debugSpan(id), NULL);
+    }
+
     void detach(SkCoincidentSpans* );
     void dump() const;
-    void expand();
+    bool expand();
     bool extend(SkOpPtT* coinPtTStart, SkOpPtT* coinPtTEnd, SkOpPtT* oppPtTStart,
         SkOpPtT* oppPtTEnd);
+    void findOverlaps(SkOpCoincidence* , SkChunkAlloc* allocator) const;
+    void fixAligned();
     void fixUp(SkOpPtT* deleted, SkOpPtT* kept);
+
+    bool isEmpty() const {
+        return !fHead;
+    }
+
     void mark();
 
 private:
+    void addIfMissing(const SkCoincidentSpans* outer, SkOpPtT* over1s, SkOpPtT* over1e,
+                      SkChunkAlloc* );
     bool addIfMissing(const SkOpPtT* over1s, const SkOpPtT* over1e,
-                      const SkOpPtT* over2s, const SkOpPtT* over2e, double tStart, double tEnd,
+                      const SkOpPtT* over2s, const SkOpPtT* over2e,
+                      double tStart, double tEnd,
                       SkOpPtT* coinPtTStart, const SkOpPtT* coinPtTEnd,
                       SkOpPtT* oppPtTStart, const SkOpPtT* oppPtTEnd,
-                      SkChunkAlloc* allocator);
+                      SkChunkAlloc* );
+    void addOverlap(SkOpSegment* seg1, SkOpSegment* seg1o, SkOpSegment* seg2, SkOpSegment* seg2o,
+                    SkOpPtT* overS, SkOpPtT* overE, SkChunkAlloc* );
     bool overlap(const SkOpPtT* coinStart1, const SkOpPtT* coinEnd1,
                  const SkOpPtT* coinStart2, const SkOpPtT* coinEnd2,
                  double* overS, double* overE) const;
 
+    bool testForCoincidence(const SkCoincidentSpans* outer, SkOpPtT* testS, SkOpPtT* testE) const;
     SkCoincidentSpans* fHead;
+    SkCoincidentSpans* fTop;
+    SkDEBUGCODE_(SkOpGlobalState* fDebugState);
 };
 
 #endif
diff --git a/src/pathops/SkOpContour.h b/src/pathops/SkOpContour.h
index f8143cf555..1225416eaa 100644
--- a/src/pathops/SkOpContour.h
+++ b/src/pathops/SkOpContour.h
@@ -34,6 +34,14 @@ public:
                 : fBounds.fTop < rh.fBounds.fTop;
     }
 
+    void addAlignIntersections(SkOpContourHead* contourList, SkChunkAlloc* allocator) {
+        SkASSERT(fCount > 0);
+        SkOpSegment* segment = &fHead;
+        do {
+            segment->addAlignIntersections(contourList, allocator);
+        } while ((segment = segment->next()));
+    }
+
     void addConic(SkPoint pts[3], SkScalar weight, SkChunkAlloc* allocator) {
         appendSegment(allocator).addConic(pts, weight, this);
     }
@@ -222,16 +230,23 @@ public:
         } while ((segment = segment->next()));
     }
 
-    void missingCoincidence(SkOpCoincidence* coincidences, SkChunkAlloc* allocator) {
+    bool missingCoincidence(SkOpCoincidence* coincidences, SkChunkAlloc* allocator) {
         SkASSERT(fCount > 0);
         SkOpSegment* segment = &fHead;
+        bool result = false;
         do {
             if (fState->angleCoincidence()) {
                 segment->checkAngleCoin(coincidences, allocator);
-            } else {
-                segment->missingCoincidence(coincidences, allocator);
+            } else if (segment->missingCoincidence(coincidences, allocator)) {
+                result = true;
+    // FIXME: trying again loops forever in issue3651_6
+    // The continue below is speculative -- once there's an actual case that requires it,
+    // add the plumbing necessary to look for another missing coincidence in the same segment
+         //       continue; // try again in case another missing coincidence is further along
             }
-        } while ((segment = segment->next()));
+            segment = segment->next();
+        } while (segment);
+        return result;
     }
 
     bool moveMultiples() {
diff --git a/src/pathops/SkOpSegment.cpp b/src/pathops/SkOpSegment.cpp
index 462cff60cf..fd8ab65acd 100644
--- a/src/pathops/SkOpSegment.cpp
+++ b/src/pathops/SkOpSegment.cpp
@@ -159,6 +159,87 @@ bool SkOpSegment::activeWinding(SkOpSpanBase* start, SkOpSpanBase* end, int* sum
     return result;
 }
 
+void SkOpSegment::addAlignIntersection(SkOpPtT& endPtT, SkPoint& oldPt,
+        SkOpContourHead* contourList, SkChunkAlloc* allocator) {
+    const SkPoint& newPt = endPtT.fPt;
+    if (newPt == oldPt) {
+        return;
+    }
+    SkPoint line[2] = { newPt, oldPt };
+    SkPathOpsBounds lineBounds;
+    lineBounds.setBounds(line, 2);
+    SkDLine aLine;
+    aLine.set(line);
+    SkOpContour* current = contourList;
+    do {
+        if (!SkPathOpsBounds::Intersects(current->bounds(), lineBounds)) {
+            continue;
+        }
+        SkOpSegment* segment = current->first();
+        do {
+            if (!SkPathOpsBounds::Intersects(segment->bounds(), lineBounds)) {
+                continue;
+            }
+            if (newPt == segment->fPts[0]) {
+                continue;
+            }
+            if (newPt == segment->fPts[SkPathOpsVerbToPoints(segment->fVerb)]) {
+                continue;
+            }
+            if (oldPt == segment->fPts[0]) {
+                continue;
+            }
+            if (oldPt == segment->fPts[SkPathOpsVerbToPoints(segment->fVerb)]) {
+                continue;
+            }
+            if (endPtT.contains(segment)) {
+                continue;
+            }
+            SkIntersections i;
+            switch (segment->fVerb) {
+                case SkPath::kLine_Verb: {
+                    SkDLine bLine;
+                    bLine.set(segment->fPts);
+                    i.intersect(bLine, aLine);
+                    } break;
+                case SkPath::kQuad_Verb: {
+                    SkDQuad bQuad;
+                    bQuad.set(segment->fPts);
+                    i.intersect(bQuad, aLine);
+                    } break;
+                case SkPath::kConic_Verb: {
+                    SkDConic bConic;
+                    bConic.set(segment->fPts, segment->fWeight);
+                    i.intersect(bConic, aLine);
+                    } break;
+                case SkPath::kCubic_Verb: {
+                    SkDCubic bCubic;
+                    bCubic.set(segment->fPts);
+                    i.intersect(bCubic, aLine);
+                    } break;
+                default:
+                    SkASSERT(0);
+            }
+            if (i.used()) {
+                SkASSERT(i.used() == 1);
+                SkASSERT(!zero_or_one(i[0][0]));
+                SkOpSpanBase* checkSpan = fHead.next();
+                while (!checkSpan->final()) {
+                    if (checkSpan->contains(segment)) {
+                        goto nextSegment;
+                    }
+                    checkSpan = checkSpan->upCast()->next();
+                }
+                SkOpPtT* ptT = segment->addT(i[0][0], SkOpSegment::kAllowAlias, allocator);
+                ptT->fPt = newPt;
+                endPtT.addOpp(ptT);
+            }
+    nextSegment:
+            ;
+        } while ((segment = segment->next()));
+    } while ((current = current->next()));
+}
+
 void SkOpSegment::addCurveTo(const SkOpSpanBase* start, const SkOpSpanBase* end,
         SkPathWriter* path, bool active) const {
     SkOpCurve edge;
@@ -770,7 +851,7 @@ SkOpSegment* SkOpSegment::findNextXor(SkOpSpanBase** nextStart, SkOpSpanBase** n
     SkASSERT(start != endNear);
     SkASSERT((start->t() < endNear->t()) ^ (step < 0));
     SkOpAngle* angle = this->spanToAngle(end, start);
-    if (angle->unorderable()) {
+    if (!angle || angle->unorderable()) {
         *unsortable = true;
         markDone(start->starter(end));
         return NULL;
@@ -817,6 +898,8 @@ SkOpGlobalState* SkOpSegment::globalState() const {
 void SkOpSegment::init(SkPoint pts[], SkScalar weight, SkOpContour* contour, SkPath::Verb verb) {
     fContour = contour;
     fNext = NULL;
+    fOriginal[0] = pts[0];
+    fOriginal[1] = pts[SkPathOpsVerbToPoints(verb)];
     fPts = pts;
     fWeight = weight;
     fVerb = verb;
@@ -1113,12 +1196,12 @@ static void clear_visited(SkOpSpanBase* span) {
 // curve/curve intersection should now do a pretty good job of finding coincident runs so 
 // this may be only be necessary for line/curve pairs -- so skip unless this is a line and the
 // the opp is not a line
-void SkOpSegment::missingCoincidence(SkOpCoincidence* coincidences, SkChunkAlloc* allocator) {
+bool SkOpSegment::missingCoincidence(SkOpCoincidence* coincidences, SkChunkAlloc* allocator) {
     if (this->verb() != SkPath::kLine_Verb) {
-        return;
+        return false;
     }
     if (this->done()) {
-        return;
+        return false;
     }
     SkOpSpan* prior = NULL;
     SkOpSpanBase* spanBase = &fHead;
@@ -1186,34 +1269,7 @@ void SkOpSegment::missingCoincidence(SkOpCoincidence* coincidences, SkChunkAlloc
             if (coincidences->contains(priorPtT, ptT, oppStart, oppEnd, flipped)) {
                 goto swapBack;
             }
-            {
-                // average t, find mid pt
-                double midT = (prior->t() + spanBase->t()) / 2;
-                SkPoint midPt = this->ptAtT(midT);
-                coincident = true;
-                // if the mid pt is not near either end pt, project perpendicular through opp seg
-                if (!SkDPoint::ApproximatelyEqual(priorPtT->fPt, midPt)
-                        && !SkDPoint::ApproximatelyEqual(ptT->fPt, midPt)) {
-                    coincident = false;
-                    SkIntersections i;
-                    SkVector dxdy = (*CurveSlopeAtT[fVerb])(this->pts(), this->weight(), midT);
-                    SkDLine ray = {{{midPt.fX, midPt.fY},
-                            {midPt.fX + dxdy.fY, midPt.fY - dxdy.fX}}};
-                    (*CurveIntersectRay[opp->verb()])(opp->pts(), opp->weight(), ray, &i);
-                    // measure distance and see if it's small enough to denote coincidence
-                    for (int index = 0; index < i.used(); ++index) {
-                        SkDPoint oppPt = i.pt(index);
-                        if (oppPt.approximatelyEqual(midPt)) {
-                            SkVector oppDxdy = (*CurveSlopeAtT[opp->verb()])(opp->pts(),
-                                    opp->weight(), i[index][0]);
-                            oppDxdy.normalize();
-                            dxdy.normalize();
-                            SkScalar flatness = SkScalarAbs(dxdy.cross(oppDxdy) / FLT_EPSILON);
-                            coincident |= flatness < 5000;  // FIXME: replace with tuned value
-                        }
-                    }
-                }
-            }
+            coincident = testForCoincidence(priorPtT, ptT, prior, spanBase, opp, 5000);
             if (coincident) {
             // mark coincidence
                 if (!coincidences->extend(priorPtT, ptT, oppStart, oppEnd)
@@ -1221,7 +1277,7 @@ void SkOpSegment::missingCoincidence(SkOpCoincidence* coincidences, SkChunkAlloc
                     coincidences->add(priorPtT, ptT, oppStart, oppEnd, allocator);
                 }
                 clear_visited(&fHead);
-                return;
+                return true;
             }
     swapBack:
             if (swapped) {
@@ -1230,6 +1286,7 @@ void SkOpSegment::missingCoincidence(SkOpCoincidence* coincidences, SkChunkAlloc
         }
     } while ((spanBase = spanBase->final() ? NULL : spanBase->upCast()->next()));
     clear_visited(&fHead);
+    return false;
 }
 
 // if a span has more than one intersection, merge the other segments' span as needed
@@ -1607,6 +1664,37 @@ bool SkOpSegment::subDivide(const SkOpSpanBase* start, const SkOpSpanBase* end,
     return true;
 }
 
+bool SkOpSegment::testForCoincidence(const SkOpPtT* priorPtT, const SkOpPtT* ptT,
+        const SkOpSpanBase* prior, const SkOpSpanBase* spanBase, const SkOpSegment* opp,
+        SkScalar flatnessLimit) const {
+    // average t, find mid pt
+    double midT = (prior->t() + spanBase->t()) / 2;
+    SkPoint midPt = this->ptAtT(midT);
+    bool coincident = true;
+    // if the mid pt is not near either end pt, project perpendicular through opp seg
+    if (!SkDPoint::ApproximatelyEqual(priorPtT->fPt, midPt)
+            && !SkDPoint::ApproximatelyEqual(ptT->fPt, midPt)) {
+        coincident = false;
+        SkIntersections i;
+        SkVector dxdy = (*CurveSlopeAtT[fVerb])(this->pts(), this->weight(), midT);
+        SkDLine ray = {{{midPt.fX, midPt.fY}, {midPt.fX + dxdy.fY, midPt.fY - dxdy.fX}}};
+        (*CurveIntersectRay[opp->verb()])(opp->pts(), opp->weight(), ray, &i);
+        // measure distance and see if it's small enough to denote coincidence
+        for (int index = 0; index < i.used(); ++index) {
+            SkDPoint oppPt = i.pt(index);
+            if (oppPt.approximatelyEqual(midPt)) {
+                SkVector oppDxdy = (*CurveSlopeAtT[opp->verb()])(opp->pts(),
+                        opp->weight(), i[index][0]);
+                oppDxdy.normalize();
+                dxdy.normalize();
+                SkScalar flatness = SkScalarAbs(dxdy.cross(oppDxdy) / FLT_EPSILON);
+                coincident |= flatness < flatnessLimit;
+            }
+        }
+    }
+    return coincident;
+}
+
 void SkOpSegment::undoneSpan(SkOpSpanBase** start, SkOpSpanBase** end) {
     SkOpSpan* span = this->head();
     do {
diff --git a/src/pathops/SkOpSegment.h b/src/pathops/SkOpSegment.h
index 38de40617a..6873203b25 100644
--- a/src/pathops/SkOpSegment.h
+++ b/src/pathops/SkOpSegment.h
@@ -45,6 +45,13 @@ public:
 
     bool activeWinding(SkOpSpanBase* start, SkOpSpanBase* end);
     bool activeWinding(SkOpSpanBase* start, SkOpSpanBase* end, int* sumWinding);
+    void addAlignIntersection(SkOpPtT& endPtT, SkPoint& oldPt,
+        SkOpContourHead* contourList, SkChunkAlloc* allocator);
+
+    void addAlignIntersections(SkOpContourHead* contourList, SkChunkAlloc* allocator) {
+        this->addAlignIntersection(*fHead.ptT(), fOriginal[0], contourList, allocator);
+        this->addAlignIntersection(*fTail.ptT(), fOriginal[1], contourList, allocator);
+    }
 
     SkOpSegment* addConic(SkPoint pts[3], SkScalar weight, SkOpContour* parent) {
         init(pts, weight, parent, SkPath::kConic_Verb);
@@ -244,7 +251,7 @@ public:
     bool markWinding(SkOpSpan* , int winding);
     bool markWinding(SkOpSpan* , int winding, int oppWinding);
     bool match(const SkOpPtT* span, const SkOpSegment* parent, double t, const SkPoint& pt) const;
-    void missingCoincidence(SkOpCoincidence* coincidences, SkChunkAlloc* allocator);
+    bool missingCoincidence(SkOpCoincidence* coincidences, SkChunkAlloc* allocator);
     void moveMultiples();
     void moveNearby();
 
@@ -346,6 +353,9 @@ public:
         return &fTail;
     }
 
+    bool testForCoincidence(const SkOpPtT* priorPtT, const SkOpPtT* ptT, const SkOpSpanBase* prior,
+            const SkOpSpanBase* spanBase, const SkOpSegment* opp, SkScalar flatnessLimit) const;
+
     void undoneSpan(SkOpSpanBase** start, SkOpSpanBase** end);
     int updateOppWinding(const SkOpSpanBase* start, const SkOpSpanBase* end) const;
     int updateOppWinding(const SkOpAngle* angle) const;
@@ -386,6 +396,7 @@ private:
     SkOpContour* fContour;
     SkOpSegment* fNext;  // forward-only linked list used by contour to walk the segments
     const SkOpSegment* fPrev;
+    SkPoint fOriginal[2];  // if aligned, the original unaligned points are here
     SkPoint* fPts;  // pointer into array of points owned by edge builder that may be tweaked
     SkPathOpsBounds fBounds;  // tight bounds
     SkScalar fWeight;
diff --git a/src/pathops/SkOpSpan.cpp b/src/pathops/SkOpSpan.cpp
index ae4771cffc..f5a52099da 100755
--- a/src/pathops/SkOpSpan.cpp
+++ b/src/pathops/SkOpSpan.cpp
@@ -13,10 +13,64 @@ bool SkOpPtT::alias() const {
     return this->span()->ptT() != this;
 }
 
+bool SkOpPtT::contains(const SkOpPtT* check) const {
+    SkASSERT(this != check);
+    const SkOpPtT* ptT = this;
+    const SkOpPtT* stopPtT = ptT;
+    while ((ptT = ptT->next()) != stopPtT) {
+        if (ptT == check) {
+            return true;
+        }
+    }
+    return false;
+}
+
+SkOpPtT* SkOpPtT::contains(const SkOpSegment* check) {
+    SkASSERT(this->segment() != check);
+    SkOpPtT* ptT = this;
+    const SkOpPtT* stopPtT = ptT;
+    while ((ptT = ptT->next()) != stopPtT) {
+        if (ptT->segment() == check) {
+            return ptT;
+        }
+    }
+    return NULL;
+}
+
 SkOpContour* SkOpPtT::contour() const {
     return segment()->contour();
 }
 
+SkOpPtT* SkOpPtT::doppelganger() {
+    SkASSERT(fDeleted);
+    SkOpPtT* ptT = fNext;
+    while (ptT->fDeleted) {
+        ptT = ptT->fNext;
+    }
+    const SkOpPtT* stopPtT = ptT;
+    do {
+        if (ptT->fSpan == fSpan) {
+            return ptT;
+        }
+        ptT = ptT->fNext;
+    } while (stopPtT != ptT);
+    SkASSERT(0);
+    return NULL;
+}
+
+SkOpPtT* SkOpPtT::find(SkOpSegment* segment) {
+    SkOpPtT* ptT = this;
+    const SkOpPtT* stopPtT = ptT;
+    do {
+        if (ptT->segment() == segment) {
+            return ptT;
+        }
+        ptT = ptT->fNext;
+    } while (stopPtT != ptT);
+    SkASSERT(0);
+    return NULL;
+}
+
 SkOpGlobalState* SkOpPtT::globalState() const {
     return contour()->globalState(); 
 }
diff --git a/src/pathops/SkOpSpan.h b/src/pathops/SkOpSpan.h
index 9b44247341..ec62246c31 100644
--- a/src/pathops/SkOpSpan.h
+++ b/src/pathops/SkOpSpan.h
@@ -8,6 +8,7 @@
 #define SkOpSpan_DEFINED
 
 #include "SkPathOpsDebug.h"
+#include "SkPathOpsTypes.h"
 #include "SkPoint.h"
 
 class SkChunkAlloc;
@@ -47,6 +48,8 @@ public:
     }
 
     bool alias() const;
+    bool contains(const SkOpPtT* ) const;
+    SkOpPtT* contains(const SkOpSegment* );
     SkOpContour* contour() const;
 
     int debugID() const {
@@ -67,6 +70,8 @@ public:
         return fDeleted;
     }
 
+    SkOpPtT* doppelganger();
+
     bool duplicate() const {
         return fDuplicatePt;
     }
@@ -75,6 +80,7 @@ public:
     void dumpAll() const;
     void dumpBase() const;
 
+    SkOpPtT* find(SkOpSegment* );
     void init(SkOpSpanBase* , double t, const SkPoint& , bool dup);
 
     void insert(SkOpPtT* span) {
@@ -92,6 +98,25 @@ public:
     }
 
     bool onEnd() const;
+
+    static bool Overlaps(SkOpPtT* s1, SkOpPtT* e1, SkOpPtT* s2, SkOpPtT* e2,
+            SkOpPtT** sOut, SkOpPtT** eOut) {
+        SkOpPtT* start1 = s1->fT < e1->fT ? s1 : e1;
+        SkOpPtT* start2 = s2->fT < e2->fT ? s2 : e2;
+        *sOut = between(s1->fT, start2->fT, e1->fT) ? start2
+                : between(s2->fT, start1->fT, e2->fT) ? start1 : NULL;
+        SkOpPtT* end1 = s1->fT < e1->fT ? e1 : s1;
+        SkOpPtT* end2 = s2->fT < e2->fT ? e2 : s2;
+        *eOut = between(s1->fT, end2->fT, e1->fT) ? end2
+                : between(s2->fT, end1->fT, e2->fT) ? end1 : NULL;
+        if (*sOut == *eOut) {
+            SkASSERT(start1->fT >= end2->fT || start2->fT >= end1->fT);
+            return false;
+        }
+        SkASSERT(!*sOut || *sOut != *eOut);
+        return *sOut && *eOut;
+    }
+
     SkOpPtT* prev();
     SkOpPtT* remove();
     void removeNext(SkOpPtT* kept);
@@ -112,6 +137,10 @@ public:
         return fSpan;
     }
 
+    const SkOpPtT* starter(const SkOpPtT* end) const {
+        return fT < end->fT ? this : end;
+    }
+
     double fT; 
     SkPoint fPt;   // cache of point value at this t
 protected:
diff --git a/src/pathops/SkPathOpsCommon.cpp b/src/pathops/SkPathOpsCommon.cpp
index 98cce15fb2..4ead297f7d 100644
--- a/src/pathops/SkPathOpsCommon.cpp
+++ b/src/pathops/SkPathOpsCommon.cpp
@@ -394,6 +394,13 @@ static void align(SkOpContourHead* contourList) {
     } while ((contour = contour->next()));
 }
 
+static void addAlignIntersections(SkOpContourHead* contourList, SkChunkAlloc* allocator) {
+    SkOpContour* contour = contourList;
+    do {
+        contour->addAlignIntersections(contourList, allocator);
+    } while ((contour = contour->next()));
+}
+
 static void calcAngles(SkOpContourHead* contourList, SkChunkAlloc* allocator) {
     SkOpContour* contour = contourList;
     do {
@@ -401,12 +408,14 @@ static void calcAngles(SkOpContourHead* contourList, SkChunkAlloc* allocator) {
     } while ((contour = contour->next()));
 }
 
-static void missingCoincidence(SkOpContourHead* contourList,
+static bool missingCoincidence(SkOpContourHead* contourList,
         SkOpCoincidence* coincidence, SkChunkAlloc* allocator) {
     SkOpContour* contour = contourList;
+    bool result = false;
     do {
-        contour->missingCoincidence(coincidence, allocator);
+        result |= contour->missingCoincidence(coincidence, allocator);
     } while ((contour = contour->next()));
+    return result;
 }
 
 static void moveMultiples(SkOpContourHead* contourList) {
@@ -438,23 +447,42 @@ bool HandleCoincidence(SkOpContourHead* contourList, SkOpCoincidence* coincidenc
     // move t values and points together to eliminate small/tiny gaps
     moveNearby(contourList);
     align(contourList);  // give all span members common values
+    coincidence->fixAligned();  // aligning may have marked a coincidence pt-t deleted
 #if DEBUG_VALIDATE
     globalState->setPhase(SkOpGlobalState::kIntersecting);
 #endif
+    // look for intersections on line segments formed by moving end points
+    addAlignIntersections(contourList, allocator);
     coincidence->addMissing(allocator);
 #if DEBUG_VALIDATE
     globalState->setPhase(SkOpGlobalState::kWalking);
 #endif
-    coincidence->expand();  // check to see if, loosely, coincident ranges may be expanded
+    // check to see if, loosely, coincident ranges may be expanded
+    if (coincidence->expand()) {
+        coincidence->addExpanded(allocator  PATH_OPS_DEBUG_VALIDATE_PARAMS(globalState));
+    }
+    // the expanded ranges may not align -- add the missing spans
     coincidence->mark();  // mark spans of coincident segments as coincident
-    missingCoincidence(contourList, coincidence, allocator);  // look for coincidence missed earlier
-    if (!coincidence->apply()) {  // adjust the winding value to account for coincident edges
-        return false;
+    // look for coincidence missed earlier
+    if (missingCoincidence(contourList, coincidence, allocator)) {
+        (void) coincidence->expand();
+        coincidence->addExpanded(allocator  PATH_OPS_DEBUG_VALIDATE_PARAMS(globalState));
+        coincidence->mark();
     }
+    SkOpCoincidence overlaps;
+    do {
+        SkOpCoincidence* pairs = overlaps.isEmpty() ? coincidence : &overlaps;
+        if (!pairs->apply()) {  // adjust the winding value to account for coincident edges
+            return false;
+        }
+        // For each coincident pair that overlaps another, when the receivers (the 1st of the pair)
+        // are different, construct a new pair to resolve their mutual span
+        pairs->findOverlaps(&overlaps, allocator);
+    } while (!overlaps.isEmpty());
     calcAngles(contourList, allocator);
     sortAngles(contourList);
     if (globalState->angleCoincidence()) {
-        missingCoincidence(contourList, coincidence, allocator);
+        (void) missingCoincidence(contourList, coincidence, allocator);
         if (!coincidence->apply()) {
             return false;
         }
diff --git a/src/pathops/SkPathOpsDebug.cpp b/src/pathops/SkPathOpsDebug.cpp
index 627a7c9f40..49422305a7 100644
--- a/src/pathops/SkPathOpsDebug.cpp
+++ b/src/pathops/SkPathOpsDebug.cpp
@@ -135,6 +135,18 @@ void SkPathOpsDebug::ShowPath(const SkPath& a, const SkPath& b, SkPathOp shapeOp
     show_op(shapeOp, "path", "pathB");
 }
 
+#include "SkPathOpsTypes.h"
+
+#ifdef SK_DEBUG
+bool SkOpGlobalState::debugRunFail() const {
+#if DEBUG_VALIDATE
+    return FLAGS_runFail;
+#else
+    return false;
+#endif
+}
+#endif
+
 #include "SkPathOpsCubic.h"
 #include "SkPathOpsQuad.h"
 
diff --git a/src/pathops/SkPathOpsDebug.h b/src/pathops/SkPathOpsDebug.h
index 61c2ecab53..ee2c291869 100644
--- a/src/pathops/SkPathOpsDebug.h
+++ b/src/pathops/SkPathOpsDebug.h
@@ -95,6 +95,12 @@
     #define SkDEBUGCODE_(...) __VA_ARGS__  // temporary until SkDEBUGCODE is fixed
 #endif
 
+#if DEBUG_VALIDATE == 0
+    #define PATH_OPS_DEBUG_VALIDATE_PARAMS(...)
+#else
+    #define PATH_OPS_DEBUG_VALIDATE_PARAMS(...) , __VA_ARGS__
+#endif
+
 #if DEBUG_T_SECT == 0
     #define PATH_OPS_DEBUG_T_SECT_RELEASE(a, b) b
     #define PATH_OPS_DEBUG_T_SECT_PARAMS(...)
@@ -179,6 +185,12 @@ public:
     static const class SkOpSegment* DebugContourSegment(class SkOpContour*, int id);
     static const class SkOpSpanBase* DebugContourSpan(class SkOpContour*, int id);
 
+    static const struct SkOpAngle* DebugCoincidenceAngle(class SkOpCoincidence*, int id);
+    static class SkOpContour* DebugCoincidenceContour(class SkOpCoincidence*, int id);
+    static const class SkOpPtT* DebugCoincidencePtT(class SkOpCoincidence*, int id);
+    static const class SkOpSegment* DebugCoincidenceSegment(class SkOpCoincidence*, int id);
+    static const class SkOpSpanBase* DebugCoincidenceSpan(class SkOpCoincidence*, int id);
+
     static const struct SkOpAngle* DebugPtTAngle(const class SkOpPtT*, int id);
     static class SkOpContour* DebugPtTContour(class SkOpPtT*, int id);
     static const class SkOpPtT* DebugPtTPtT(const class SkOpPtT*, int id);
diff --git a/src/pathops/SkPathOpsRect.h b/src/pathops/SkPathOpsRect.h
index 7fec70a32a..2b1e6393f4 100644
--- a/src/pathops/SkPathOpsRect.h
+++ b/src/pathops/SkPathOpsRect.h
@@ -25,9 +25,6 @@ struct SkDRect {
     }
 
     bool intersects(const SkDRect& r) const {
-        if (fLeft > fRight) {
-            SkDebugf("!");
-        }
         SkASSERT(fLeft <= fRight);
         SkASSERT(fTop <= fBottom);
         SkASSERT(r.fLeft <= r.fRight);
diff --git a/src/pathops/SkPathOpsTypes.cpp b/src/pathops/SkPathOpsTypes.cpp
index 2c8d778c69..dcd33c9d73 100644
--- a/src/pathops/SkPathOpsTypes.cpp
+++ b/src/pathops/SkPathOpsTypes.cpp
@@ -5,6 +5,7 @@
  * found in the LICENSE file.
  */
 #include "SkFloatBits.h"
+#include "SkOpCoincidence.h"
 #include "SkPathOpsTypes.h"
 
 static bool arguments_denormalized(float a, float b, int epsilon) {
@@ -198,3 +199,21 @@ double SkDCubeRoot(double x) {
     }
     return result;
 }
+
+SkOpGlobalState::SkOpGlobalState(SkOpCoincidence* coincidence, SkOpContourHead* head)
+    : fCoincidence(coincidence)
+    , fContourHead(head)
+    , fNested(0)
+    , fWindingFailed(false)
+    , fAngleCoincidence(false)
+    , fPhase(kIntersecting)
+    SkDEBUGPARAMS(fAngleID(0))
+    SkDEBUGPARAMS(fContourID(0))
+    SkDEBUGPARAMS(fPtTID(0))
+    SkDEBUGPARAMS(fSegmentID(0))
+    SkDEBUGPARAMS(fSpanID(0)) {
+    if (coincidence) {
+        coincidence->debugSetGlobalState(this);
+    }
+}
+
diff --git a/src/pathops/SkPathOpsTypes.h b/src/pathops/SkPathOpsTypes.h
index 13ebfee84d..9550aa1ead 100644
--- a/src/pathops/SkPathOpsTypes.h
+++ b/src/pathops/SkPathOpsTypes.h
@@ -28,19 +28,7 @@ class SkOpContourHead;
 
 class SkOpGlobalState {
 public:
-    SkOpGlobalState(SkOpCoincidence* coincidence, SkOpContourHead* head)
-        : fCoincidence(coincidence)
-        , fContourHead(head)
-        , fNested(0)
-        , fWindingFailed(false)
-        , fAngleCoincidence(false)
-        , fPhase(kIntersecting)
-        SkDEBUGPARAMS(fAngleID(0))
-        SkDEBUGPARAMS(fContourID(0))
-        SkDEBUGPARAMS(fPtTID(0))
-        SkDEBUGPARAMS(fSegmentID(0))
-        SkDEBUGPARAMS(fSpanID(0)) {
-    }
+    SkOpGlobalState(SkOpCoincidence* coincidence, SkOpContourHead* head);
 
     enum Phase {
         kIntersecting,
@@ -76,6 +64,7 @@ public:
     const struct SkOpAngle* debugAngle(int id) const;
     SkOpContour* debugContour(int id);
     const class SkOpPtT* debugPtT(int id) const;
+    bool debugRunFail() const;
     const class SkOpSegment* debugSegment(int id) const;
     const class SkOpSpanBase* debugSpan(int id) const;
 #endif
diff --git a/src/ports/SkDebug_win.cpp b/src/ports/SkDebug_win.cpp
index fe28ee27b1..8bbbef58e0 100644
--- a/src/ports/SkDebug_win.cpp
+++ b/src/ports/SkDebug_win.cpp
@@ -25,7 +25,7 @@ void SkDebugf(const char format[], ...) {
     va_end(args);
     // When we crash on Windows we often are missing a lot of prints. Since we don't really care
     // about SkDebugf performance we flush after every print.
-    fflush(stdout);
+//    fflush(stdout);
 
     va_start(args, format);
     vsnprintf(buffer, kBufferSize, format, args);