pathops coincidence and security rewrite

src/pathops/SkPathOpsDebug.cpp

Index: src/pathops/SkPathOpsDebug.cpp
diff --git a/src/pathops/SkPathOpsDebug.cpp b/src/pathops/SkPathOpsDebug.cpp
index 546771e84c6be240e75837dd83f1707bd799e6ec..93743f3d6cfc3f8a18ab75ac0f5332e10d9bc206 100644
--- a/src/pathops/SkPathOpsDebug.cpp
+++ b/src/pathops/SkPathOpsDebug.cpp
@@ -12,7 +12,7 @@
 #include "SkPathOpsDebug.h"
 #include "SkString.h"
 
-struct SkCoincidentSpans;
+class SkCoincidentSpans;
 
 #if DEBUG_VALIDATE
 extern bool FLAGS_runFail;
@@ -46,11 +46,15 @@ bool SkPathOpsDebug::ChaseContains(const SkTDArray<SkOpSpanBase* >& chaseArray,
 }
 #endif
 
-#if DEBUG_COINCIDENCE
+#if DEBUG_COINCIDENCE_VERBOSE
 enum GlitchType {
     kAddCorruptCoin_Glitch,
     kAddExpandedCoin_Glitch,
+    kAddExpandedFail_Glitch,
+    kAddIfMissingCoin_Glitch,
     kAddMissingCoin_Glitch,
+    kAddMissingExtend_Glitch,
+    kAddOrOverlap_Glitch,
     kCollapsedCoin_Glitch,
     kCollapsedDone_Glitch,
     kCollapsedOppValue_Glitch,
@@ -60,30 +64,41 @@ enum GlitchType {
     kExpandCoin_Glitch,
     kMarkCoinEnd_Glitch,
     kMarkCoinInsert_Glitch,
+    kMarkCoinMissing_Glitch,
+    kMarkCoinStart_Glitch,
+    kMergeContained_Glitch,
     kMissingCoin_Glitch,
     kMissingDone_Glitch,
     kMissingIntersection_Glitch,
     kMoveMultiple_Glitch,
+    kMoveNearbyClearAll_Glitch,
+    kMoveNearbyClearAll2_Glitch,
+    kMoveNearbyMerge_Glitch,
+    kMoveNearbyMergeFinal_Glitch,
+    kMoveNearbyRelease_Glitch,
+    kMoveNearbyReleaseFinal_Glitch,
+    kReleasedSpan_Glitch,
     kUnaligned_Glitch,
     kUnalignedHead_Glitch,
     kUnalignedTail_Glitch,
-    kUndetachedSpan_Glitch,
-    kUnmergedSpan_Glitch,
 };
 
-static const int kGlitchType_Count = kUnmergedSpan_Glitch + 1;
+static const int kGlitchType_Count = kUnalignedTail_Glitch + 1;
 
 struct SpanGlitch {
     const char* fStage;
     const SkOpSpanBase* fBase;
     const SkOpSpanBase* fSuspect;
-    const SkCoincidentSpans* fCoin;
     const SkOpSegment* fSegment;
+    const SkOpSegment* fOppSegment;
     const SkOpPtT* fCoinSpan;
     const SkOpPtT* fEndSpan;
     const SkOpPtT* fOppSpan;
     const SkOpPtT* fOppEndSpan;
-    double fT;
+    double fStartT;
+    double fEndT;
+    double fOppStartT;
+    double fOppEndT;
     SkPoint fPt;
     GlitchType fType;
 };
@@ -94,13 +109,16 @@ struct SkPathOpsDebug::GlitchLog {
         glitch->fStage = stage;
         glitch->fBase = nullptr;
         glitch->fSuspect = nullptr;
-        glitch->fCoin = nullptr;
         glitch->fSegment = nullptr;
+        glitch->fOppSegment = nullptr;
         glitch->fCoinSpan = nullptr;
         glitch->fEndSpan = nullptr;
         glitch->fOppSpan = nullptr;
         glitch->fOppEndSpan = nullptr;
-        glitch->fT = SK_ScalarNaN;
+        glitch->fStartT = SK_ScalarNaN;
+        glitch->fEndT = SK_ScalarNaN;
+        glitch->fOppStartT = SK_ScalarNaN;
+        glitch->fOppEndT = SK_ScalarNaN;
         glitch->fPt = { SK_ScalarNaN, SK_ScalarNaN };
         glitch->fType = type;
         return glitch;
@@ -113,11 +131,22 @@ struct SkPathOpsDebug::GlitchLog {
         glitch->fSuspect = suspect;
     }
 
+    void record(GlitchType type, const char* stage, const SkOpSpanBase* base,
+            const SkOpPtT* ptT) {
+        SpanGlitch* glitch = recordCommon(type, stage);
+        glitch->fBase = base;
+        glitch->fCoinSpan = ptT;
+    }
+
     void record(GlitchType type, const char* stage, const SkCoincidentSpans* coin,
-            const SkOpPtT* coinSpan) {
+            const SkCoincidentSpans* opp = NULL) {
         SpanGlitch* glitch = recordCommon(type, stage);
-        glitch->fCoin = coin;
-        glitch->fCoinSpan = coinSpan;
+        glitch->fCoinSpan = coin->coinPtTStart();
+        glitch->fEndSpan = coin->coinPtTEnd();
+        if (opp) {
+            glitch->fOppSpan = opp->coinPtTStart();
+            glitch->fOppEndSpan = opp->coinPtTEnd();
+        }
     }
 
     void record(GlitchType type, const char* stage, const SkOpSpanBase* base,
@@ -125,7 +154,7 @@ struct SkPathOpsDebug::GlitchLog {
         SpanGlitch* glitch = recordCommon(type, stage);
         glitch->fBase = base;
         glitch->fSegment = seg;
-        glitch->fT = t;
+        glitch->fStartT = t;
         glitch->fPt = pt;
     }
 
@@ -133,23 +162,26 @@ struct SkPathOpsDebug::GlitchLog {
             SkPoint pt) {
         SpanGlitch* glitch = recordCommon(type, stage);
         glitch->fBase = base;
-        glitch->fT = t;
+        glitch->fStartT = t;
         glitch->fPt = pt;
     }
 
     void record(GlitchType type, const char* stage, const SkCoincidentSpans* coin,
             const SkOpPtT* coinSpan, const SkOpPtT* endSpan) {
         SpanGlitch* glitch = recordCommon(type, stage);
-        glitch->fCoin = coin;
-        glitch->fCoinSpan = coinSpan;
+        glitch->fCoinSpan = coin->coinPtTStart();
+        glitch->fEndSpan = coin->coinPtTEnd();
         glitch->fEndSpan = endSpan;
+        glitch->fOppSpan = coinSpan;
+        glitch->fOppEndSpan = endSpan;
     }
 
     void record(GlitchType type, const char* stage, const SkCoincidentSpans* coin,
-            const SkOpSpanBase* suspect) {
+            const SkOpSpanBase* base) {
         SpanGlitch* glitch = recordCommon(type, stage);
-        glitch->fSuspect = suspect;
-        glitch->fCoin = coin;
+        glitch->fBase = base;
+        glitch->fCoinSpan = coin->coinPtTStart();
+        glitch->fEndSpan = coin->coinPtTEnd();
     }
 
     void record(GlitchType type, const char* stage, const SkOpPtT* ptTS, const SkOpPtT* ptTE,
@@ -161,22 +193,73 @@ struct SkPathOpsDebug::GlitchLog {
         glitch->fOppEndSpan = oPtTE;
     }
 
+    void record(GlitchType type, const char* stage, const SkOpSegment* seg, double startT,
+            double endT, const SkOpSegment* oppSeg, double oppStartT, double oppEndT) {
+        SpanGlitch* glitch = recordCommon(type, stage);
+        glitch->fSegment = seg;
+        glitch->fStartT = startT;
+        glitch->fEndT = endT;
+        glitch->fOppSegment = oppSeg;
+        glitch->fOppStartT = oppStartT;
+        glitch->fOppEndT = oppEndT;
+    }
+
+    void record(GlitchType type, const char* stage, const SkOpSegment* seg,
+            const SkOpSpan* span) {
+        SpanGlitch* glitch = recordCommon(type, stage);
+        glitch->fSegment = seg;
+        glitch->fBase = span;
+    }
+
+    void record(GlitchType type, const char* stage, double t, const SkOpSpanBase* span) {
+        SpanGlitch* glitch = recordCommon(type, stage);
+        glitch->fStartT = t;
+        glitch->fBase = span;
+    }
+
+    void record(GlitchType type, const char* stage, const SkOpSegment* seg) {
+        SpanGlitch* glitch = recordCommon(type, stage);
+        glitch->fSegment = seg;
+    }
+
+    void record(GlitchType type, const char* stage, const SkCoincidentSpans* coin,
+            const SkOpPtT* ptT) {
+        SpanGlitch* glitch = recordCommon(type, stage);
+        glitch->fCoinSpan = coin->coinPtTStart();
+        glitch->fEndSpan = ptT;
+    }
+
     SkTDArray<SpanGlitch> fGlitches;
 };
+#endif
 
+void SkPathOpsDebug::ShowActiveSpans(SkOpContourHead* contourList) {
+#if DEBUG_ACTIVE_SPANS
+    SkOpContour* contour = contourList;
+    do {
+        contour->debugShowActiveSpans();
+    } while ((contour = contour->next()));
+#endif
+}
+
+#if DEBUG_COINCIDENCE
 void SkPathOpsDebug::CheckHealth(SkOpContourHead* contourList, const char* id) {
+    contourList->globalState()->debugSetCheckHealth(true);
+#if DEBUG_COINCIDENCE_VERBOSE
     GlitchLog glitches;
     const SkOpContour* contour = contourList;
     const SkOpCoincidence* coincidence = contour->globalState()->coincidence();
+    coincidence->debugCheckValid(id, &glitches); // don't call validate; spans may be inconsistent
     do {
         contour->debugCheckHealth(id, &glitches);
-        contour->debugMissingCoincidence(id, &glitches, coincidence);
+        contour->debugMissingCoincidence(id, &glitches);
     } while ((contour = contour->next()));
-    coincidence->debugFixAligned(id, &glitches);
+    coincidence->debugRemoveCollapsed(id, &glitches);
     coincidence->debugAddMissing(id, &glitches);
     coincidence->debugExpand(id, &glitches);
     coincidence->debugAddExpanded(id, &glitches);
     coincidence->debugMark(id, &glitches);
+    coincidence->debugReorder(id, &glitches);
     unsigned mask = 0;
     for (int index = 0; index < glitches.fGlitches.count(); ++index) {
         const SpanGlitch& glitch = glitches.fGlitches[index];
@@ -186,6 +269,92 @@ void SkPathOpsDebug::CheckHealth(SkOpContourHead* contourList, const char* id) {
         SkDebugf(mask & (1 << index) ? "x" : "-");
     }
     SkDebugf("  %s\n", id);
+    for (int index = 0; index < glitches.fGlitches.count(); ++index) {
+        const SpanGlitch& glitch = glitches.fGlitches[index];
+        SkDebugf("%02d: ", index);
+        if (glitch.fBase) {
+            SkDebugf(" base=%d", glitch.fBase->debugID());
+        }
+        if (glitch.fSuspect) {
+            SkDebugf(" base=%d", glitch.fSuspect->debugID());
+        }
+        if (glitch.fSegment) {
+            SkDebugf(" segment=%d", glitch.fSegment->debugID());
+        }
+        if (glitch.fCoinSpan) {
+            SkDebugf(" coinSpan=%d", glitch.fCoinSpan->debugID());
+        }
+        if (glitch.fEndSpan) {
+            SkDebugf(" endSpan=%d", glitch.fEndSpan->debugID());
+        }
+        if (glitch.fOppSpan) {
+            SkDebugf(" oppSpan=%d", glitch.fOppSpan->debugID());
+        }
+        if (glitch.fOppEndSpan) {
+            SkDebugf(" oppEndSpan=%d", glitch.fOppEndSpan->debugID());
+        }
+        if (!SkScalarIsNaN(glitch.fStartT)) {
+            SkDebugf(" startT=%g", glitch.fStartT);
+        }
+        if (!SkScalarIsNaN(glitch.fEndT)) {
+            SkDebugf(" endT=%g", glitch.fEndT);
+        }
+        if (glitch.fOppSegment) {
+            SkDebugf(" segment=%d", glitch.fOppSegment->debugID());
+        }
+        if (!SkScalarIsNaN(glitch.fOppStartT)) {
+            SkDebugf(" oppStartT=%g", glitch.fOppStartT);
+        }
+        if (!SkScalarIsNaN(glitch.fOppEndT)) {
+            SkDebugf(" oppEndT=%g", glitch.fOppEndT);
+        }
+        if (!SkScalarIsNaN(glitch.fPt.fX) || !SkScalarIsNaN(glitch.fPt.fY)) {
+            SkDebugf(" pt=%g,%g", glitch.fPt.fX, glitch.fPt.fY);
+        }
+        switch (glitch.fType) {
+            case kAddCorruptCoin_Glitch: SkDebugf(" AddCorruptCoin"); break;
+            case kAddExpandedCoin_Glitch: SkDebugf(" AddExpandedCoin"); break;
+            case kAddExpandedFail_Glitch: SkDebugf(" AddExpandedFail"); break;
+            case kAddIfMissingCoin_Glitch: SkDebugf(" AddIfMissingCoin"); break;
+            case kAddMissingCoin_Glitch: SkDebugf(" AddMissingCoin"); break;
+            case kAddMissingExtend_Glitch: SkDebugf(" AddMissingExtend"); break;
+            case kAddOrOverlap_Glitch: SkDebugf(" AAddOrOverlap"); break;
+            case kCollapsedCoin_Glitch: SkDebugf(" CollapsedCoin"); break;
+            case kCollapsedDone_Glitch: SkDebugf(" CollapsedDone"); break;
+            case kCollapsedOppValue_Glitch: SkDebugf(" CollapsedOppValue"); break;
+            case kCollapsedSpan_Glitch: SkDebugf(" CollapsedSpan"); break;
+            case kCollapsedWindValue_Glitch: SkDebugf(" CollapsedWindValue"); break;
+            case kDeletedCoin_Glitch: SkDebugf(" DeletedCoin"); break;
+            case kExpandCoin_Glitch: SkDebugf(" ExpandCoin"); break;
+            case kMarkCoinEnd_Glitch: SkDebugf(" MarkCoinEnd"); break;
+            case kMarkCoinInsert_Glitch: SkDebugf(" MarkCoinInsert"); break;
+            case kMarkCoinMissing_Glitch: SkDebugf(" MarkCoinMissing"); break;
+            case kMarkCoinStart_Glitch: SkDebugf(" MarkCoinStart"); break;
+            case kMergeContained_Glitch: SkDebugf(" MergeContained"); break;
+            case kMissingCoin_Glitch: SkDebugf(" MissingCoin"); break;
+            case kMissingDone_Glitch: SkDebugf(" MissingDone"); break;
+            case kMissingIntersection_Glitch: SkDebugf(" MissingIntersection"); break;
+            case kMoveMultiple_Glitch: SkDebugf(" MoveMultiple"); break;
+            case kMoveNearbyClearAll_Glitch: SkDebugf(" MoveNearbyClearAll"); break;
+            case kMoveNearbyClearAll2_Glitch: SkDebugf(" MoveNearbyClearAll2"); break;
+            case kMoveNearbyMerge_Glitch: SkDebugf(" MoveNearbyMerge"); break;
+            case kMoveNearbyMergeFinal_Glitch: SkDebugf(" MoveNearbyMergeFinal"); break;
+            case kMoveNearbyRelease_Glitch: SkDebugf(" MoveNearbyRelease"); break;
+            case kMoveNearbyReleaseFinal_Glitch: SkDebugf(" MoveNearbyReleaseFinal"); break;
+            case kReleasedSpan_Glitch: SkDebugf(" ReleasedSpan"); break;
+            case kUnaligned_Glitch: SkDebugf(" Unaligned"); break;
+            case kUnalignedHead_Glitch: SkDebugf(" UnalignedHead"); break;
+            case kUnalignedTail_Glitch: SkDebugf(" UnalignedTail"); break;
+            default: SkASSERT(0);
+        }
+        SkDebugf("\n");
+    }
+    contourList->globalState()->debugSetCheckHealth(false);
+#if DEBUG_ACTIVE_SPANS
+    SkDebugf("active after %s:\n", id);
+    ShowActiveSpans(contourList);
+#endif
+#endif
 }
 #endif
 
@@ -254,7 +423,7 @@ static const char* gOpStrs[] = {
     "kDifference_SkPathOp",
     "kIntersect_SkPathOp",
     "kUnion_SkPathOp",
-    "kXor_PathOp",
+    "kXOR_PathOp",
     "kReverseDifference_SkPathOp",
 };
 
@@ -412,132 +581,72 @@ void SkDRect::debugInit() {
 #include "SkOpSegment.h"
 
 #if DEBUG_COINCIDENCE
-void SkOpSegment::debugAddAlignIntersection(const char* id, SkPathOpsDebug::GlitchLog* log,
-        const SkOpPtT& endPtT, const SkPoint& oldPt,  const SkOpContourHead* contourList) const {
-    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);
-    const SkOpContour* current = contourList;
+// commented-out lines keep this in sync with addT()
+ const SkOpPtT* SkOpSegment::debugAddT(double t, AliasMatch allowAlias, bool* allocated) const {
+    debugValidate();
+    SkPoint pt = this->ptAtT(t);
+    const SkOpSpanBase* span = &fHead;
     do {
-        if (!SkPathOpsBounds::Intersects(current->bounds(), lineBounds)) {
-            continue;
-        }
-        const 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.debugContains(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();
+        const SkOpPtT* result = span->ptT();
+        const SkOpPtT* loop;
+        bool duplicatePt;
+        if (t == result->fT) {
+            goto bumpSpan;
+        }
+        if (this->match(result, this, t, pt, allowAlias)) {
+            // see if any existing alias matches segment, pt, and t
+            loop = result->next();
+            duplicatePt = false;
+            while (loop != result) {
+                bool ptMatch = loop->fPt == pt;
+                if (loop->segment() == this && loop->fT == t && ptMatch) {
+                    goto bumpSpan;
                 }
-                log->record(kMissingIntersection_Glitch, id, checkSpan, segment, i[0][0], newPt);
+                duplicatePt |= ptMatch;
+                loop = loop->next();
             }
-    nextSegment:
-            ;
-        } while ((segment = segment->next()));
-    } while ((current = current->next()));
-}
-
-bool SkOpSegment::debugAddMissing(double t, const SkOpSegment* opp) const {
-    const SkOpSpanBase* existing = nullptr;
-    const SkOpSpanBase* test = &fHead;
-    double testT;
-    do {
-        if ((testT = test->ptT()->fT) >= t) {
-            if (testT == t) {
-                existing = test;
+            if (kNoAliasMatch == allowAlias) {
+    bumpSpan:
+//                 span->bumpSpanAdds();
+                return result;
             }
-            break;
-        }
-    } while ((test = test->upCast()->next()));
-    return !existing || !existing->debugContains(opp);
-}
-
-void SkOpSegment::debugAlign(const char* id, SkPathOpsDebug::GlitchLog* glitches) const {
-    const SkOpSpanBase* span = &fHead;
-    if (!span->aligned()) {
-        if (!span->debugAlignedEnd(0, fPts[0])) {
-            glitches->record(kUnalignedHead_Glitch, id, span);
-        }
-    }
-    while ((span = span->upCast()->next())) {
-        if (span == &fTail) {
-            break;
-        }
-        if (!span->aligned()) {
-            glitches->record(kUnaligned_Glitch, id, span);
-        }
-    }
-    if (!span->aligned()) {
-        span->debugAlignedEnd(1, fPts[SkPathOpsVerbToPoints(fVerb)]);
-    }
-    if (this->collapsed()) {
-        const SkOpSpan* span = &fHead;
-        do {
-            if (span->windValue()) {
-                glitches->record(kCollapsedWindValue_Glitch, id, span);
+//             SkOpPtT* alias = SkOpTAllocator<SkOpPtT>::Allocate(allocator);
+//             alias->init(result->span(), t, pt, duplicatePt);
+//             result->insert(alias);
+//             result->span()->unaligned();
+            this->debugValidate();
+// #if DEBUG_ADD_T
+//             SkDebugf("%s alias t=%1.9g segID=%d spanID=%d\n",  __FUNCTION__, t,
+//                     alias->segment()->debugID(), alias->span()->debugID());
+// #endif
+//             span->bumpSpanAdds();
+            if (allocated) {
+                *allocated = true;
             }
-            if (span->oppValue()) {
-                glitches->record(kCollapsedOppValue_Glitch, id, span);
+            return nullptr;
+        }
+        if (t < result->fT) {
+            const SkOpSpan* prev = result->span()->prev();
+            if (!prev) {
+                return nullptr;  // FIXME: this is a fail case; nullptr return elsewhere means result was allocated in non-const version
             }
-            if (!span->done()) {
-                glitches->record(kCollapsedDone_Glitch, id, span);
+//             SkOpSpan* span = insert(prev, allocator);
+//             span->init(this, prev, t, pt);
+            this->debugValidate();
+// #if DEBUG_ADD_T
+//             SkDebugf("%s insert t=%1.9g segID=%d spanID=%d\n", __FUNCTION__, t,
+//                     span->segment()->debugID(), span->debugID());
+// #endif
+//             span->bumpSpanAdds();
+            if (allocated) {
+                *allocated = true;
             }
-        } while ((span = span->next()->upCastable()));
-    }
+            return nullptr;
+        }
+        SkASSERT(span != &fTail);
+    } while ((span = span->upCast()->next()));
+    SkASSERT(0);
+    return nullptr;
 }
 #endif
 
@@ -547,7 +656,7 @@ void SkOpSegment::debugCheckAngleCoin() const {
     const SkOpSpan* span;
     do {
         const SkOpAngle* angle = base->fromAngle();
-        if (angle && angle->fCheckCoincidence) {
+        if (angle && angle->debugCheckCoincidence()) {
             angle->debugCheckNearCoincidence();
         }
         if (base->final()) {
@@ -555,41 +664,35 @@ void SkOpSegment::debugCheckAngleCoin() const {
         }
         span = base->upCast();
         angle = span->toAngle();
-        if (angle && angle->fCheckCoincidence) {
+        if (angle && angle->debugCheckCoincidence()) {
             angle->debugCheckNearCoincidence();
         }
     } while ((base = span->next()));
 }
 #endif
 
-#if DEBUG_COINCIDENCE
+#if DEBUG_COINCIDENCE_VERBOSE
 // this mimics the order of the checks in handle coincidence
 void SkOpSegment::debugCheckHealth(const char* id, SkPathOpsDebug::GlitchLog* glitches) const {
     debugMoveMultiples(id, glitches);
-    debugFindCollapsed(id, glitches);
     debugMoveNearby(id, glitches);
-    debugAlign(id, glitches);
-    debugAddAlignIntersections(id, glitches, this->globalState()->contourHead());
+    debugMissingCoincidence(id, glitches);
+}
 
+// commented-out lines keep this in sync with clearAll()
+void SkOpSegment::debugClearAll(const char* id, SkPathOpsDebug::GlitchLog* glitches) const {
+    const SkOpSpan* span = &fHead;
+    do {
+        this->debugClearOne(span, id, glitches);
+    } while ((span = span->next()->upCastable()));
+    this->globalState()->coincidence()->debugRelease(id, glitches, this);
 }
 
-void SkOpSegment::debugFindCollapsed(const char* id, SkPathOpsDebug::GlitchLog* glitches) const {
-    if (fHead.contains(&fTail)) {
-        const SkOpSpan* span = this->head();
-        bool missingDone = false;
-        do {
-            missingDone |= !span->done();
-        } while ((span = span->next()->upCastable()));
-        if (missingDone) {
-            glitches->record(kMissingDone_Glitch, id, &fHead);
-        }
-        if (!fHead.debugAlignedEnd(0, fHead.pt())) {
-            glitches->record(kUnalignedHead_Glitch, id, &fHead);
-        }
-        if (!fTail.aligned()) {
-            glitches->record(kUnalignedTail_Glitch, id, &fTail);
-        }
-    }
+// commented-out lines keep this in sync with clearOne()
+void SkOpSegment::debugClearOne(const SkOpSpan* span, const char* id, SkPathOpsDebug::GlitchLog* glitches) const {
+    if (span->windValue()) glitches->record(kCollapsedWindValue_Glitch, id, span);
+    if (span->oppValue()) glitches->record(kCollapsedOppValue_Glitch, id, span);
+    if (!span->done()) glitches->record(kCollapsedDone_Glitch, id, span);
 }
 #endif
 
@@ -607,16 +710,37 @@ SkOpAngle* SkOpSegment::debugLastAngle() {
 }
 
 #if DEBUG_COINCIDENCE
-void SkOpSegment::debugMissingCoincidence(const char* id, SkPathOpsDebug::GlitchLog* log,
-        const SkOpCoincidence* coincidences) const {
-    if (this->verb() != SkPath::kLine_Verb) {
-        return;
-    }
+// commented-out lines keep this in sync with ClearVisited
+void SkOpSegment::DebugClearVisited(const SkOpSpanBase* span) {
+    // reset visited flag back to false
+    do {
+        const SkOpPtT* ptT = span->ptT(), * stopPtT = ptT;
+        while ((ptT = ptT->next()) != stopPtT) {
+            const SkOpSegment* opp = ptT->segment();
+            opp->resetDebugVisited();
+        }
+    } while (!span->final() && (span = span->upCast()->next()));
+}
+#endif
+
+#if DEBUG_COINCIDENCE_VERBOSE
+// commented-out lines keep this in sync with missingCoincidence()
+// look for pairs of undetected coincident curves
+// assumes that segments going in have visited flag clear
+// Even though pairs of curves correct detect coincident runs, a run may be missed
+// if the coincidence is a product of multiple intersections. For instance, given
+// curves A, B, and C:
+// A-B intersect at a point 1; A-C and B-C intersect at point 2, so near
+// the end of C that the intersection is replaced with the end of C.
+// Even though A-B correctly do not detect an intersection at point 2,
+// the resulting run from point 1 to point 2 is coincident on A and B.
+void SkOpSegment::debugMissingCoincidence(const char* id, SkPathOpsDebug::GlitchLog* log) const {
     if (this->done()) {
         return;
     }
     const SkOpSpan* prior = nullptr;
     const SkOpSpanBase* spanBase = &fHead;
+//    bool result = false;
     do {
         const SkOpPtT* ptT = spanBase->ptT(), * spanStopPtT = ptT;
         SkASSERT(ptT->span() == spanBase);
@@ -624,29 +748,29 @@ void SkOpSegment::debugMissingCoincidence(const char* id, SkPathOpsDebug::Glitch
             if (ptT->deleted()) {
                 continue;
             }
-            SkOpSegment* opp = ptT->span()->segment();
-//            if (opp->verb() == SkPath::kLine_Verb) {
-//                continue;
-//            }
+            const SkOpSegment* opp = ptT->span()->segment();
             if (opp->done()) {
                 continue;
             }
             // when opp is encounted the 1st time, continue; on 2nd encounter, look for coincidence
-            if (!opp->visited()) {
+            if (!opp->debugVisited()) {
                 continue;
             }
             if (spanBase == &fHead) {
                 continue;
             }
+            if (ptT->segment() == this) {
+                continue;
+            }
             const SkOpSpan* span = spanBase->upCastable();
             // FIXME?: this assumes that if the opposite segment is coincident then no more
             // coincidence needs to be detected. This may not be true.
-            if (span && span->segment() != opp && span->containsCoincidence(opp)) {
+            if (span && span->segment() != opp && span->containsCoincidence(opp)) {  // debug has additional condition since it may be called before inner duplicate points have been deleted

[herb_g, 2016/07/18 15:13:39]

Comments on next line?

[caryclark, 2016/07/18 15:55:49]

The crazy formatting here is so that SkOpSegment::debugMissingCoincidence() will
line up exactly with SkOpSegment::missingCoincidence(). There are many functions
here of the form  SkOpXXX::debugXXX() that follow this convention. These
functions are read-only versions of the actual code to permit preflighting
coincident logic. All possible code paths are executed so I can visualize the
various side effects that each code path may cause. This is all bracketed by #if
DEBUG_COINCIDENCE_VERBOSE

                 continue;
             }
-            if (spanBase->segment() != opp && spanBase->containsCoinEnd(opp)) {
+            if (spanBase->segment() != opp && spanBase->containsCoinEnd(opp)) {  // debug has additional condition since it may be called before inner duplicate points have been deleted
                 continue;
-            } 
+            }
             const SkOpPtT* priorPtT = nullptr, * priorStopPtT;
             // find prior span containing opp segment
             const SkOpSegment* priorOpp = nullptr;
@@ -669,6 +793,9 @@ void SkOpSegment::debugMissingCoincidence(const char* id, SkPathOpsDebug::Glitch
             if (!priorOpp) {
                 continue;
             }
+            if (priorPtT == ptT) {
+                continue;
+            }
             const SkOpPtT* oppStart = prior->ptT();
             const SkOpPtT* oppEnd = spanBase->ptT();
             bool swapped = priorPtT->fT > ptT->fT;
@@ -676,22 +803,28 @@ void SkOpSegment::debugMissingCoincidence(const char* id, SkPathOpsDebug::Glitch
                 SkTSwap(priorPtT, ptT);
                 SkTSwap(oppStart, oppEnd);
             }
-            bool flipped = oppStart->fT > oppEnd->fT;
-            bool coincident = false;
-            if (coincidences->contains(priorPtT, ptT, oppStart, oppEnd, flipped)) {
+            const SkOpCoincidence* coincidence = this->globalState()->coincidence();
+            const SkOpPtT* rootPriorPtT = priorPtT->span()->ptT();
+            const SkOpPtT* rootPtT = ptT->span()->ptT();
+            const SkOpPtT* rootOppStart = oppStart->span()->ptT();
+            const SkOpPtT* rootOppEnd = oppEnd->span()->ptT();
+            if (coincidence->contains(rootPriorPtT, rootPtT, rootOppStart, rootOppEnd)) {
                 goto swapBack;
             }
-            if (opp->verb() == SkPath::kLine_Verb) {
-                coincident = (SkDPoint::ApproximatelyEqual(priorPtT->fPt, oppStart->fPt) ||
-                        SkDPoint::ApproximatelyEqual(priorPtT->fPt, oppEnd->fPt)) &&
-                        (SkDPoint::ApproximatelyEqual(ptT->fPt, oppStart->fPt) ||
-                        SkDPoint::ApproximatelyEqual(ptT->fPt, oppEnd->fPt));
-            }
-            if (!coincident) {
-                coincident = testForCoincidence(priorPtT, ptT, prior, spanBase, opp, 5000);
-            }
-            if (coincident) {
+            if (testForCoincidence(rootPriorPtT, rootPtT, prior, spanBase, opp)) {
+            // mark coincidence
+#if DEBUG_COINCIDENCE
+//                 SkDebugf("%s coinSpan=%d endSpan=%d oppSpan=%d oppEndSpan=%d\n", __FUNCTION__,

[herb_g, 2016/07/18 15:13:39]

Remove commented out code.

[caryclark, 2016/07/18 15:55:49]

See above

+//                         rootPriorPtT->debugID(), rootPtT->debugID(), rootOppStart->debugID(),
+//                         rootOppEnd->debugID());
+#endif
                 log->record(kMissingCoin_Glitch, id, priorPtT, ptT, oppStart, oppEnd);
+                //   coincidences->add(rootPriorPtT, rootPtT, rootOppStart, rootOppEnd);
+                // }
+#if DEBUG_COINCIDENCE
+//                SkASSERT(coincidences->contains(rootPriorPtT, rootPtT, rootOppStart, rootOppEnd)
+#endif
+                // result = true;
             }
     swapBack:
             if (swapped) {
@@ -699,9 +832,14 @@ void SkOpSegment::debugMissingCoincidence(const char* id, SkPathOpsDebug::Glitch
             }
         }
     } while ((spanBase = spanBase->final() ? nullptr : spanBase->upCast()->next()));
+    DebugClearVisited(&fHead);
+    return;
 }
 
+// commented-out lines keep this in sync with moveMultiples()
+// if a span has more than one intersection, merge the other segments' span as needed
 void SkOpSegment::debugMoveMultiples(const char* id, SkPathOpsDebug::GlitchLog* glitches) const {
+    debugValidate();
     const SkOpSpanBase* test = &fHead;
     do {
         int addCount = test->spanAddsCount();
@@ -777,6 +915,7 @@ void SkOpSegment::debugMoveMultiples(const char* id, SkPathOpsDebug::GlitchLog*
                     } while ((matchPtT = matchPtT->next()) != startPtT);
                     goto tryNextSpan;
             foundMatch:  // merge oppTest and oppSpan
+                    oppSegment->debugValidate();
                     if (oppTest == &oppSegment->fTail || oppTest == &oppSegment->fHead) {
                         SkASSERT(oppSpan != &oppSegment->fHead); // don't expect collapse
                         SkASSERT(oppSpan != &oppSegment->fTail);
@@ -784,60 +923,67 @@ void SkOpSegment::debugMoveMultiples(const char* id, SkPathOpsDebug::GlitchLog*
                     } else {
                         glitches->record(kMoveMultiple_Glitch, id, oppSpan, oppTest);
                     }
+                    oppSegment->debugValidate();
                     goto checkNextSpan;
                 }
-        tryNextSpan: 
+        tryNextSpan:
                 ;
             } while (oppTest != oppLast && (oppTest = oppTest->upCast()->next()));
         } while ((testPtT = testPtT->next()) != startPtT);
-checkNextSpan: 
+checkNextSpan:
         ;
     } while ((test = test->final() ? nullptr : test->upCast()->next()));
+   debugValidate();
+   return;
 }
 
+// commented-out lines keep this in sync with moveNearby()
+// Move nearby t values and pts so they all hang off the same span. Alignment happens later.
 void SkOpSegment::debugMoveNearby(const char* id, SkPathOpsDebug::GlitchLog* glitches) const {
-        const SkOpSpanBase* spanS = &fHead;
+    debugValidate();
+    // release undeleted spans pointing to this seg that are linked to the primary span
+    const SkOpSpanBase* spanBase = &fHead;
     do {
-        const SkOpSpanBase* test = spanS->upCast()->next();
-        const SkOpSpanBase* next;
-        if (spanS->contains(test)) {
-            if (!test->final()) {
-                glitches->record(kUndetachedSpan_Glitch, id, test, spanS);
-            } else if (spanS != &fHead) {
-                glitches->record(kUndetachedSpan_Glitch, id, spanS, test);
+        const SkOpPtT* ptT = spanBase->ptT();
+        const SkOpPtT* headPtT = ptT;
+        while ((ptT = ptT->next()) != headPtT) {
+              const SkOpSpanBase* test = ptT->span();
+            if (ptT->segment() == this && !ptT->deleted() && test != spanBase
+                    && test->ptT() == ptT) {
+                if (test->final()) {
+                    if (spanBase == &fHead) {
+                        glitches->record(kMoveNearbyClearAll_Glitch, id, this);
+//                        return;

[herb_g, 2016/07/18 15:13:39]

Remove commented out code.

[caryclark, 2016/07/18 15:55:49]

See comment above.

+                    }
+                    glitches->record(kMoveNearbyReleaseFinal_Glitch, id, spanBase, ptT);
+                } else if (test->prev()) {
+                    glitches->record(kMoveNearbyRelease_Glitch, id, test, headPtT);
+                }
+//                break;
             }
         }
-        do {  // iterate through all spans associated with start
-            const SkOpPtT* startBase = spanS->ptT();
-            next = test->final() ? nullptr : test->upCast()->next();
-            do {
-                const SkOpPtT* testBase = test->ptT();
-                do {
-                    if (startBase == testBase) {
-                        goto checkNextSpan;
-                    }
-                    if (testBase->duplicate()) {
-                        continue;
-                    }
-                    if (this->match(startBase, testBase->segment(), testBase->fT, testBase->fPt)) {
-                        if (test == &this->fTail) {
-                            if (spanS == &fHead) {
-                                glitches->record(kCollapsedSpan_Glitch, id, spanS);
-                            } else {
-                                glitches->record(kUnmergedSpan_Glitch, id, &this->fTail, spanS);
-                            }
-                        } else {
-                            glitches->record(kUnmergedSpan_Glitch, id, spanS, test);
-                            goto checkNextSpan;
-                        }
-                    }
-                } while ((testBase = testBase->next()) != test->ptT());
-            } while ((startBase = startBase->next()) != spanS->ptT());
-    checkNextSpan:
-            ;
-        } while ((test = next));
-        spanS = spanS->upCast()->next();
-    } while (!spanS->final());
+        spanBase = spanBase->upCast()->next();
+    } while (!spanBase->final());
+
+    // This loop looks for adjacent spans which are near by
+    spanBase = &fHead;
+    do {  // iterate through all spans associated with start
+        const SkOpSpanBase* test = spanBase->upCast()->next();
+        if (this->spansNearby(spanBase, test)) {
+            if (test->final()) {
+                if (spanBase->prev()) {
+                    glitches->record(kMoveNearbyMergeFinal_Glitch, id, test);
+                } else {
+                    glitches->record(kMoveNearbyClearAll2_Glitch, id, this);
+                    // return
+                }
+            } else {
+                glitches->record(kMoveNearbyMerge_Glitch, id, spanBase);
+            }
+        }
+        spanBase = test;
+    } while (!spanBase->final());
+    debugValidate();
 }
 #endif
 
@@ -864,16 +1010,18 @@ void SkOpSegment::debugShowActiveSpans() const {
         lastId = this->debugID();
         lastT = span->t();
         SkDebugf("%s id=%d", __FUNCTION__, this->debugID());
-        SkDebugf(" (%1.9g,%1.9g", fPts[0].fX, fPts[0].fY);
+        // since endpoints may have be adjusted, show actual computed curves
+        SkDCurve curvePart;
+        this->subDivide(span, span->next(), &curvePart);
+        const SkDPoint* pts = curvePart.fCubic.fPts;
+        SkDebugf(" (%1.9g,%1.9g", pts[0].fX, pts[0].fY);
         for (int vIndex = 1; vIndex <= SkPathOpsVerbToPoints(fVerb); ++vIndex) {
-            SkDebugf(" %1.9g,%1.9g", fPts[vIndex].fX, fPts[vIndex].fY);
+            SkDebugf(" %1.9g,%1.9g", pts[vIndex].fX, pts[vIndex].fY);
         }
         if (SkPath::kConic_Verb == fVerb) {
-            SkDebugf(" %1.9gf", fWeight);
+            SkDebugf(" %1.9gf", curvePart.fConic.fWeight);
         }
-        const SkOpPtT* ptT = span->ptT();
-        SkDebugf(") t=%1.9g (%1.9g,%1.9g)", ptT->fT, ptT->fPt.fX, ptT->fPt.fY);
-        SkDebugf(" tEnd=%1.9g", span->next()->t());
+        SkDebugf(") t=%1.9g tEnd=%1.9g", span->t(), span->next()->t());
         if (span->windSum() == SK_MinS32) {
             SkDebugf(" windSum=?");
         } else {
@@ -958,7 +1106,7 @@ void SkOpSegment::debugShowNewWinding(const char* fun, const SkOpSpan* span, int
 // loop looking for a pair of angle parts that are too close to be sorted
 /* This is called after other more simple intersection and angle sorting tests have been exhausted.
    This should be rarely called -- the test below is thorough and time consuming.
-   This checks the distance between start points; the distance between 
+   This checks the distance between start points; the distance between
 */
 #if DEBUG_ANGLE
 void SkOpAngle::debugCheckNearCoincidence() const {
@@ -996,7 +1144,7 @@ void SkOpAngle::debugCheckNearCoincidence() const {
             SkDebugf("\n");
         }
         test = test->fNext;
-    } while (test->fNext != this); 
+    } while (test->fNext != this);
 }
 #endif
 
@@ -1046,6 +1194,11 @@ void SkOpAngle::debugLoop() const {
 #endif
 
 void SkOpAngle::debugValidate() const {
+#if DEBUG_COINCIDENCE
+    if (this->globalState()->debugCheckHealth()) {
+        return;
+    }
+#endif
 #if DEBUG_VALIDATE
     const SkOpAngle* first = this;
     const SkOpAngle* next = this;
@@ -1108,243 +1261,409 @@ void SkOpAngle::debugValidateNext() const {
 #endif
 }
 
+#ifdef SK_DEBUG
+void SkCoincidentSpans::debugStartCheck(const SkOpSpanBase* outer, const SkOpSpanBase* over,
+        const SkOpGlobalState* debugState) const {
+    SkASSERT(coinPtTEnd()->span() == over || !debugState->debugRunFail());
+    SkASSERT(oppPtTEnd()->span() == outer || !debugState->debugRunFail());
+}
+#endif
 
-#if DEBUG_COINCIDENCE
+#if DEBUG_COINCIDENCE_VERBOSE
+/* Commented-out lines keep this in sync with expand */
+bool SkCoincidentSpans::debugExpand(const char* id, SkPathOpsDebug::GlitchLog* log) const {
+    bool expanded = false;
+    const SkOpSegment* segment = coinPtTStart()->segment();
+    const SkOpSegment* oppSegment = oppPtTStart()->segment();
+    do {
+        const SkOpSpan* start = coinPtTStart()->span()->upCast();
+        const SkOpSpan* prev = start->prev();
+        const SkOpPtT* oppPtT;
+        if (!prev || !(oppPtT = prev->contains(oppSegment))) {
+            break;
+        }
+        double midT = (prev->t() + start->t()) / 2;
+        if (!segment->isClose(midT, oppSegment)) {
+            break;
+        }
+        if (log) log->record(kExpandCoin_Glitch, id, this, prev->ptT(), oppPtT);
+        expanded = true;
+    } while (false);  // actual continues while expansion is possible
+    do {
+        const SkOpSpanBase* end = coinPtTEnd()->span();
+        SkOpSpanBase* next = end->final() ? nullptr : end->upCast()->next();
+        const SkOpPtT* oppPtT;
+        if (!next || !(oppPtT = next->contains(oppSegment))) {
+            break;
+        }
+        double midT = (end->t() + next->t()) / 2;
+        if (!segment->isClose(midT, oppSegment)) {
+            break;
+        }
+        if (log) log->record(kExpandCoin_Glitch, id, this, next->ptT(), oppPtT);
+        expanded = true;
+    } while (false);  // actual continues while expansion is possible
+    return expanded;
+}
+
+#define FAIL_IF(cond)  do { if (cond) log->record(kAddExpandedFail_Glitch, id, coin); } while (false)
+
+/* Commented-out lines keep this in sync with addExpanded */
+// 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
 void SkOpCoincidence::debugAddExpanded(const char* id, SkPathOpsDebug::GlitchLog* log) const {
-    // 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
     const SkCoincidentSpans* coin = this->fHead;
     if (!coin) {
-        coin = this->fTop;
-    }
-    if (!coin) {
         return;
     }
     do {
-        const SkOpPtT* startPtT = coin->fCoinPtTStart;
-        const SkOpPtT* oStartPtT = coin->fOppPtTStart;
+        const SkOpPtT* startPtT = coin->coinPtTStart();
+        const SkOpPtT* oStartPtT = coin->oppPtTStart();
         SkASSERT(startPtT->contains(oStartPtT));
-        SkASSERT(coin->fCoinPtTEnd->contains(coin->fOppPtTEnd));
+        SkASSERT(coin->coinPtTEnd()->contains(coin->oppPtTEnd()));
         const SkOpSpanBase* start = startPtT->span();
         const SkOpSpanBase* oStart = oStartPtT->span();
-        const SkOpSpanBase* end = coin->fCoinPtTEnd->span();
-        const SkOpSpanBase* oEnd = coin->fOppPtTEnd->span();
+        const SkOpSpanBase* end = coin->coinPtTEnd()->span();
+        const SkOpSpanBase* oEnd = coin->oppPtTEnd()->span();
+        FAIL_IF(oEnd->deleted());
         const SkOpSpanBase* test = start->upCast()->next();
-        const SkOpSpanBase* oTest = coin->fFlipped ? oStart->prev() : oStart->upCast()->next();
+        const SkOpSpanBase* oTest = coin->flipped() ? oStart->prev() : oStart->upCast()->next();
+        if (!oTest) {
+            return;
+        }
         while (test != end || oTest != oEnd) {
-            bool bumpTest = true;
-            bool bumpOTest = true;
-            if (!test->ptT()->contains(oTest->ptT())) {
+            if (!test->ptT()->contains(oTest->segment())
+                    || !oTest->ptT()->contains(start->segment())) {
                 // use t ranges to guess which one is missing
-                double startRange = coin->fCoinPtTEnd->fT - startPtT->fT;
+                double startRange = coin->coinPtTEnd()->fT - startPtT->fT;
+                FAIL_IF(!startRange);
                 double startPart = (test->t() - startPtT->fT) / startRange;
-                double oStartRange = coin->fOppPtTEnd->fT - oStartPtT->fT;
+                double oStartRange = coin->oppPtTEnd()->fT - oStartPtT->fT;
+                FAIL_IF(!oStartRange);
                 double oStartPart = (oTest->t() - oStartPtT->fT) / oStartRange;
-                if (startPart == oStartPart) {
-                    // data is corrupt
-                    log->record(kAddCorruptCoin_Glitch, id, start, oStart);
-                    break;
+                FAIL_IF(startPart == oStartPart);
+                bool startOver = false;
+                if (startPart < oStartPart)
+                        log->record(kAddExpandedCoin_Glitch, id,  // strange debug formatting lines up with original
+                                oStartPtT->fT + oStartRange * startPart, test);
+                        else log->record(kAddExpandedCoin_Glitch, id,
+                                startPtT->fT + startRange * oStartPart, oTest);
+                if (false) {
+                    SkASSERT(0);
+                    return;
                 }
-                if (startPart < oStartPart) {
-                    double newT = oStartPtT->fT + oStartRange * startPart;
-                    log->record(kAddExpandedCoin_Glitch, id, oStart, newT, test->pt());
-                    bumpOTest = false;
-                } else {
-                    double newT = startPtT->fT + startRange * oStartPart;
-                    log->record(kAddExpandedCoin_Glitch, id, start, newT, oTest->pt());
-                    bumpTest = false;
+                if (startOver) {
+                    test = start;
+                    oTest = oStart;
                 }
             }
-            if (bumpTest && test != end) {
+            if (test != end) {
                 test = test->upCast()->next();
             }
-            if (bumpOTest && oTest != oEnd) {
-                oTest = coin->fFlipped ? oTest->prev() : oTest->upCast()->next();
+            if (oTest != oEnd) {
+                oTest = coin->flipped() ? oTest->prev() : oTest->upCast()->next();
+                if (!oTest) {
+                    return;
+                }
             }
         }
-    } while ((coin = coin->fNext));
-}
-
-static void t_range(const SkOpPtT* overS, const SkOpPtT* overE, double tStart, double tEnd,
-        const SkOpPtT* coinPtTStart, const SkOpPtT* coinPtTEnd, double* coinTs, double* coinTe) {
-    double denom = overE->fT - overS->fT;
-    double start = 0 < denom ? tStart : tEnd;
-    double end = 0 < denom ? tEnd : tStart;
-    double sRatio = (start - overS->fT) / denom;
-    double eRatio = (end - overS->fT) / denom;
-    *coinTs = coinPtTStart->fT + (coinPtTEnd->fT - coinPtTStart->fT) * sRatio;
-    *coinTe = coinPtTStart->fT + (coinPtTEnd->fT - coinPtTStart->fT) * eRatio;
-}
-
-bool SkOpCoincidence::debugAddIfMissing(const SkCoincidentSpans* outer, const SkOpPtT* over1s,
-            const SkOpPtT* over1e) const {
-    const SkCoincidentSpans* check = this->fTop;
-    while (check) {
-        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 false;
-        }
-        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 false;
-        }
-        check = check->fNext;
+    } while ((coin = coin->next()));
+    return;
+}
+
+/* Commented-out lines keep this in sync with addIfMissing() */
+void SkOpCoincidence::debugAddIfMissing(const SkCoincidentSpans* outer, const SkOpPtT* over1s,
+            const SkOpPtT* over1e, const char* id, SkPathOpsDebug::GlitchLog* log) const {
+//     SkASSERT(fTop);
+    if (fTop && alreadyAdded(fTop, outer, over1s, over1e)) {  // in debug, fTop may be null
+        return;
     }
-    return true;
+    if (fHead && alreadyAdded(fHead, outer, over1s, over1e)) {
+        return;
+    }
+    log->record(kAddIfMissingCoin_Glitch, id, outer->coinPtTStart(), outer->coinPtTEnd(), over1s, over1e);
+    this->debugValidate();
+    return;
 }
 
-bool SkOpCoincidence::debugAddIfMissing(const SkOpPtT* over1s, const SkOpPtT* over1e,
-                      const SkOpPtT* over2s, const SkOpPtT* over2e, double tStart, double tEnd,
-        SkOpPtT* coinPtTStart, const SkOpPtT* coinPtTEnd,
-        SkOpPtT* oppPtTStart, const SkOpPtT* oppPtTEnd) const {
+/* Commented-out lines keep this in sync addIfMissing() */
+void SkOpCoincidence::debugAddIfMissing(const SkOpPtT* over1s, const SkOpPtT* over1e,
+        const SkOpPtT* over2s, const SkOpPtT* over2e, double tStart, double tEnd,
+        const SkOpPtT* coinPtTStart, const SkOpPtT* coinPtTEnd,
+        const SkOpPtT* oppPtTStart, const SkOpPtT* oppPtTEnd, const char* id, SkPathOpsDebug::GlitchLog* log) const {
     double coinTs, coinTe, oppTs, oppTe;
-    t_range(over1s, over1e, tStart, tEnd, coinPtTStart, coinPtTEnd, &coinTs, &coinTe);
-    t_range(over2s, over2e, tStart, tEnd, oppPtTStart, oppPtTEnd, &oppTs, &oppTe);
-    const SkOpSegment* coinSeg = coinPtTStart->segment();
-    const SkOpSegment* oppSeg = oppPtTStart->segment();
-    SkASSERT(coinSeg != oppSeg);
-    const SkCoincidentSpans* check = this->fTop;
-    ;
-    while (check) {
-        const SkOpSegment* checkCoinSeg = check->fCoinPtTStart->segment();
-        const SkOpSegment* checkOppSeg;
-        if (checkCoinSeg != coinSeg && checkCoinSeg != oppSeg) {
-            goto next;
-        }
-        checkOppSeg = check->fOppPtTStart->segment();
-        if (checkOppSeg != coinSeg && checkOppSeg != oppSeg) {
-            goto next;
-        }
-        {
-            int cTs = coinTs;
-            int cTe = coinTe;
-            int oTs = oppTs;
-            int oTe = oppTe;
-            if (checkCoinSeg != coinSeg) {
-                SkASSERT(checkOppSeg != oppSeg);
-                SkTSwap(cTs, oTs);
-                SkTSwap(cTe, oTe);
-            }
-            int tweenCount = (int) between(check->fCoinPtTStart->fT, cTs, check->fCoinPtTEnd->fT)
-                           + (int) between(check->fCoinPtTStart->fT, cTe, check->fCoinPtTEnd->fT)
-                           + (int) between(check->fOppPtTStart->fT, oTs, check->fOppPtTEnd->fT)
-                           + (int) between(check->fOppPtTStart->fT, oTe, check->fOppPtTEnd->fT);
-    //        SkASSERT(tweenCount == 0 || tweenCount == 4);
-            if (tweenCount) {
-                return true;
-            }
-        }
-next:
-        check = check->fNext;
+    TRange(over1s, over1e, tStart, tEnd, coinPtTStart, coinPtTEnd, &coinTs, &coinTe);
+    TRange(over2s, over2e, tStart, tEnd, oppPtTStart, oppPtTEnd, &oppTs, &oppTe);
+    bool swap = coinTs > coinTe;
+    if (swap) {
+        SkTSwap(coinTs, coinTe);
     }
     if ((over1s->fT < over1e->fT) != (over2s->fT < over2e->fT)) {
         SkTSwap(oppTs, oppTe);
     }
-    if (coinTs > coinTe) {
-        SkTSwap(coinTs, coinTe);
+    if (swap) {
         SkTSwap(oppTs, oppTe);
     }
-    bool cs = coinSeg->debugAddMissing(coinTs, oppSeg);
-    bool ce = coinSeg->debugAddMissing(coinTe, oppSeg);
-    if (cs == ce) {
-        return false;
+    const SkOpSegment* coinSeg = coinPtTStart->segment();
+    const SkOpSegment* oppSeg = oppPtTStart->segment();
+    if (coinSeg == oppSeg) {
+        return;
     }
-    return true;
+    return this->debugAddOrOverlap(coinSeg, oppSeg, coinTs, coinTe, oppTs, oppTe, id, log);
+}
+
+/* Commented-out lines keep this in sync addOrOverlap() */
+void SkOpCoincidence::debugAddOrOverlap(const SkOpSegment* coinSeg, const SkOpSegment* oppSeg,
+        double coinTs, double coinTe, double oppTs, double oppTe, const char* id, SkPathOpsDebug::GlitchLog* log) const {
+    SkTDArray<SkCoincidentSpans*> overlaps;
+    SkASSERT(!fTop);   // this is (correctly) reversed in addifMissing()
+    if (fTop && !this->checkOverlap(fTop, coinSeg, oppSeg, coinTs, coinTe, oppTs, oppTe, &overlaps)) {
+        return;
+    }
+    if (fHead && !this->checkOverlap(fHead, coinSeg, oppSeg, coinTs,
+            coinTe, oppTs, oppTe, &overlaps)) {
+        return;
+    }
+    const SkCoincidentSpans* overlap = overlaps.count() ? overlaps[0] : nullptr;
+    for (int index = 1; index < overlaps.count(); ++index) { // combine overlaps before continuing
+        const SkCoincidentSpans* test = overlaps[index];
+        if (overlap->coinPtTStart()->fT > test->coinPtTStart()->fT) {
+            log->record(kAddOrOverlap_Glitch, id, overlap, test->coinPtTStart());
+        }
+        if (overlap->coinPtTEnd()->fT < test->coinPtTEnd()->fT) {
+            log->record(kAddOrOverlap_Glitch, id, overlap, test->coinPtTEnd());
+        }
+        if (overlap->flipped()
+                ? overlap->oppPtTStart()->fT < test->oppPtTStart()->fT
+                : overlap->oppPtTStart()->fT > test->oppPtTStart()->fT) {
+            log->record(kAddOrOverlap_Glitch, id, overlap, test->oppPtTStart());
+        }
+        if (overlap->flipped()
+                ? overlap->oppPtTEnd()->fT > test->oppPtTEnd()->fT
+                : overlap->oppPtTEnd()->fT < test->oppPtTEnd()->fT) {
+            log->record(kAddOrOverlap_Glitch, id, overlap, test->oppPtTEnd());
+        }
+        if (!fHead) {
+            SkAssertResult(true);
+        }
+    }
+    const SkOpPtT* cs = coinSeg->existing(coinTs, oppSeg);
+    const SkOpPtT* ce = coinSeg->existing(coinTe, oppSeg);
+    if (overlap && cs && ce && overlap->contains(cs, ce)) {
+        return;
+    }
+    SkASSERT(cs != ce || !cs);
+    const SkOpPtT* os = oppSeg->existing(oppTs, coinSeg);
+    const SkOpPtT* oe = oppSeg->existing(oppTe, coinSeg);
+    if (overlap && os && oe && overlap->contains(os, oe)) {
+        return;
+    }
+    SkASSERT(true || !cs || !cs->deleted());
+    SkASSERT(true || !os || !os->deleted());
+    SkASSERT(true || !ce || !ce->deleted());
+    SkASSERT(true || !oe || !oe->deleted());
+    const SkOpPtT* csExisting = !cs ? coinSeg->existing(coinTs, nullptr) : nullptr;
+    const SkOpPtT* ceExisting = !ce ? coinSeg->existing(coinTe, nullptr) : nullptr;
+    if (csExisting && csExisting == ceExisting) {
+        return;
+    }
+    if (csExisting && (csExisting == ce || csExisting->contains(ceExisting ? ceExisting : ce))) {
+        return;
+    }
+    if (ceExisting && (ceExisting == cs || ceExisting->contains(csExisting ? csExisting : cs))) {
+        return;
+    }
+    const SkOpPtT* osExisting = !os ? oppSeg->existing(oppTs, nullptr) : nullptr;
+    const SkOpPtT* oeExisting = !oe ? oppSeg->existing(oppTe, nullptr) : nullptr;
+    if (osExisting && osExisting == oeExisting) {
+        return;
+    }
+    if (osExisting && (osExisting == oe || osExisting->contains(oeExisting ? oeExisting : oe))) {
+        return;
+    }
+    if (oeExisting && (oeExisting == os || oeExisting->contains(osExisting ? osExisting : os))) {
+        return;
+    }
+    bool csDeleted = false, osDeleted = false, ceDeleted = false,  oeDeleted = false;
+    this->debugValidate();
+    if (!cs || !os) {
+        if (!cs)
+            cs = coinSeg->debugAddT(coinTs, SkOpSegment::kNoAliasMatch, nullptr);
+        if (!os)
+            os = oppSeg->debugAddT(oppTs, SkOpSegment::kNoAliasMatch, nullptr);
+        if (cs && os) cs->span()->debugAddOppAndMerge(id, log, os->span(), &csDeleted, &osDeleted);
+//         cs = csWritable;

[herb_g, 2016/07/18 15:13:39]

You have a bunch of commented out code in this routine. Is it still needed?

[caryclark, 2016/07/18 15:55:49]

See reply above.

+//         os = osWritable;
+        if ((ce && ce->deleted()) || (oe && oe->deleted())) {
+            return;
+        }
+    }
+    if (!ce || !oe) {
+        if (!ce)
+            ce = coinSeg->debugAddT(coinTe, SkOpSegment::kNoAliasMatch, nullptr);
+        if (!oe)
+            oe = oppSeg->debugAddT(oppTe, SkOpSegment::kNoAliasMatch, nullptr);
+        if (ce && oe) ce->span()->debugAddOppAndMerge(id, log, oe->span(), &ceDeleted, &oeDeleted);
+//         ce = ceWritable;
+//         oe = oeWritable;
+    }
+    this->debugValidate();
+    if (csDeleted || osDeleted || ceDeleted || oeDeleted) {
+        return;
+    }
+    if (!cs || !ce || cs->contains(ce) || !os || !oe || os->contains(oe)) {
+        return;
+    }
+//     bool result = true;
+    if (overlap) {
+        if (overlap->coinPtTStart()->segment() == coinSeg) {
+                log->record(kAddMissingExtend_Glitch, id, coinSeg, coinTs, coinTe, oppSeg, oppTs, oppTe);
+        } else {
+            if (oppTs > oppTe) {
+                SkTSwap(coinTs, coinTe);
+                SkTSwap(oppTs, oppTe);
+            }
+            log->record(kAddMissingExtend_Glitch, id, oppSeg, oppTs, oppTe, coinSeg, coinTs, coinTe);
+        }
+#if DEBUG_COINCIDENCE_VERBOSE
+//         if (result) {
+//             overlap->debugShow();
+//         }
+#endif
+    } else {
+        log->record(kAddMissingCoin_Glitch, id, coinSeg, coinTs, coinTe, oppSeg, oppTs, oppTe);
+#if DEBUG_COINCIDENCE_VERBOSE
+//         fHead->debugShow();
+#endif
+    }
+    this->debugValidate();
+    return;
 }
 
+// Extra commented-out lines keep this in sync with addMissing()
+/* detects overlaps of different coincident runs on same segment */
+/* does not detect overlaps for pairs without any segments in common */
+// returns true if caller should loop again
 void SkOpCoincidence::debugAddMissing(const char* id, SkPathOpsDebug::GlitchLog* log) const {
     const SkCoincidentSpans* outer = fHead;
     if (!outer) {
         return;
     }
+    // bool added = false;
+    // fTop = outer;
+    // fHead = nullptr;
     do {
     // addifmissing can modify the list that this is walking
     // save head so that walker can iterate over old data unperturbed
     // addifmissing adds 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());
+        const SkOpSegment* outerCoin = outer->coinPtTStart()->segment();
+        const SkOpSegment* outerOpp = outer->oppPtTStart()->segment();
+        if (outerCoin->done() || outerOpp->done()) {
+            continue;
+        }
         const SkCoincidentSpans* inner = outer;
-        while ((inner = inner->fNext)) {
+        while ((inner = inner->next())) {
+            this->debugValidate();
             double overS, overE;
-            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->debugAddIfMissing(outer->fCoinPtTStart, outer->fCoinPtTEnd,
-                        inner->fCoinPtTStart, inner->fCoinPtTEnd, overS, overE,
-                        outer->fOppPtTStart, outer->fOppPtTEnd,
-                        inner->fOppPtTStart, inner->fOppPtTEnd)) {
-                    log->record(kAddMissingCoin_Glitch, id, outer, inner->fCoinPtTStart);
+            const SkOpSegment* innerCoin = inner->coinPtTStart()->segment();
+            const SkOpSegment* innerOpp = inner->oppPtTStart()->segment();
+            if (innerCoin->done() || innerOpp->done()) {
+                continue;
+            }
+            if (outerCoin == innerCoin) {
+                if (outerOpp != innerOpp
+                        && this->overlap(outer->coinPtTStart(), outer->coinPtTEnd(),
+                        inner->coinPtTStart(), inner->coinPtTEnd(), &overS, &overE)) {
+                    this->debugAddIfMissing(outer->coinPtTStart(), outer->coinPtTEnd(),
+                            inner->coinPtTStart(), inner->coinPtTEnd(), overS, overE,
+                            outer->oppPtTStart(), outer->oppPtTEnd(),
+                            inner->oppPtTStart(), inner->oppPtTEnd(), id, log);
                 }
-            } else if (outerCoin == innerOpp
-                    && this->overlap(outer->fCoinPtTStart, outer->fCoinPtTEnd,
-                    inner->fOppPtTStart, inner->fOppPtTEnd, &overS, &overE)) {
-                if (this->debugAddIfMissing(outer->fCoinPtTStart, outer->fCoinPtTEnd,
-                        inner->fOppPtTStart, inner->fOppPtTEnd, overS, overE,
-                        outer->fOppPtTStart, outer->fOppPtTEnd,
-                        inner->fCoinPtTStart, inner->fCoinPtTEnd)) {
-                    log->record(kAddMissingCoin_Glitch, id, outer, inner->fOppPtTStart);
+            } else if (outerCoin == innerOpp) {
+                if (outerOpp != innerCoin
+                        && this->overlap(outer->coinPtTStart(), outer->coinPtTEnd(),
+                        inner->oppPtTStart(), inner->oppPtTEnd(), &overS, &overE)) {
+                    this->debugAddIfMissing(outer->coinPtTStart(), outer->coinPtTEnd(),
+                            inner->oppPtTStart(), inner->oppPtTEnd(), overS, overE,
+                            outer->oppPtTStart(), outer->oppPtTEnd(),
+                            inner->coinPtTStart(), inner->coinPtTEnd(), id, log);
                 }
-            } else if (outerOpp == innerCoin
-                    && this->overlap(outer->fOppPtTStart, outer->fOppPtTEnd,
-                    inner->fCoinPtTStart, inner->fCoinPtTEnd, &overS, &overE)) {
-                if (this->debugAddIfMissing(outer->fOppPtTStart, outer->fOppPtTEnd,
-                        inner->fCoinPtTStart, inner->fCoinPtTEnd, overS, overE,
-                        outer->fCoinPtTStart, outer->fCoinPtTEnd,
-                        inner->fOppPtTStart, inner->fOppPtTEnd)) {
-                    log->record(kAddMissingCoin_Glitch, id, outer, inner->fCoinPtTStart);
+            } else if (outerOpp == innerCoin) {
+                SkASSERT(outerCoin != innerOpp);
+                if (this->overlap(outer->oppPtTStart(), outer->oppPtTEnd(),
+                        inner->coinPtTStart(), inner->coinPtTEnd(), &overS, &overE)) {
+                    this->debugAddIfMissing(outer->oppPtTStart(), outer->oppPtTEnd(),
+                            inner->coinPtTStart(), inner->coinPtTEnd(), overS, overE,
+                            outer->coinPtTStart(), outer->coinPtTEnd(),
+                            inner->oppPtTStart(), inner->oppPtTEnd(), id, log);
                 }
-            } else if (outerOpp == innerOpp
-                    && this->overlap(outer->fOppPtTStart, outer->fOppPtTEnd,
-                    inner->fOppPtTStart, inner->fOppPtTEnd, &overS, &overE)) {
-                if (this->debugAddIfMissing(outer->fOppPtTStart, outer->fOppPtTEnd,
-                        inner->fOppPtTStart, inner->fOppPtTEnd, overS, overE,
-                        outer->fCoinPtTStart, outer->fCoinPtTEnd,
-                        inner->fCoinPtTStart, inner->fCoinPtTEnd)) {
-                    log->record(kAddMissingCoin_Glitch, id, outer, inner->fOppPtTStart);
-                }
-            } 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
-                const SkOpPtT* testS = outer->fCoinPtTStart->debugContains(innerCoin);
-                const SkOpPtT* testE = outer->fCoinPtTEnd->debugContains(innerCoin);
-                if (testS && testS->fT >= inner->fCoinPtTStart->fT
-                        && testE && testE->fT <= inner->fCoinPtTEnd->fT
-                        && this->testForCoincidence(outer, testS, testE)) {
-                    if (this->debugAddIfMissing(outer, testS, testE)) {
-                        log->record(kAddMissingCoin_Glitch, id, outer, testS, testE);
-                    }
-                } else {
-                    testS = inner->fCoinPtTStart->debugContains(outerCoin);
-                    testE = inner->fCoinPtTEnd->debugContains(outerCoin);
-                    if (testS && testS->fT >= outer->fCoinPtTStart->fT
-                            && testE && testE->fT <= outer->fCoinPtTEnd->fT
-                            && this->testForCoincidence(inner, testS, testE)) {
-                        if (this->debugAddIfMissing(inner, testS, testE)) {
-                            log->record(kAddMissingCoin_Glitch, id, inner, testS, testE);
-                        }
-                    }
+            } else if (outerOpp == innerOpp) {
+                SkASSERT(outerCoin != innerCoin);
+                if (this->overlap(outer->oppPtTStart(), outer->oppPtTEnd(),
+                        inner->oppPtTStart(), inner->oppPtTEnd(), &overS, &overE)) {
+                    this->debugAddIfMissing(outer->oppPtTStart(), outer->oppPtTEnd(),
+                            inner->oppPtTStart(), inner->oppPtTEnd(), overS, overE,
+                            outer->coinPtTStart(), outer->coinPtTEnd(),
+                            inner->coinPtTStart(), inner->coinPtTEnd(), id, log);
                 }
             }
+            this->debugValidate();
+        }
+    } while ((outer = outer->next()));
+    // this->restoreHead();
+    return;
+}
+
+// Commented-out lines keep this in sync with release()
+void SkOpCoincidence::debugRelease(const char* id, SkPathOpsDebug::GlitchLog* log, const SkOpSegment* deleted) const {
+    const SkCoincidentSpans* coin = fHead;
+    if (!coin) {
+        return;
+    }
+    do {
+        if (coin->coinPtTStart()->segment() == deleted
+                || coin->coinPtTEnd()->segment() == deleted
+                || coin->oppPtTStart()->segment() == deleted
+                || coin->oppPtTEnd()->segment() == deleted) {
+            log->record(kReleasedSpan_Glitch, id, coin);
+        }
+    } while ((coin = coin->next()));
+}
+
+// Commented-out lines keep this in sync with reorder()
+// iterate through all coincident pairs, looking for ranges greater than 1
+// if found, see if the opposite pair can match it -- which may require
+// reordering the ptT pairs
+void SkOpCoincidence::debugReorder(const char* id, SkPathOpsDebug::GlitchLog* log) const {
+    const SkCoincidentSpans* coin = fHead;
+    if (!coin) {
+        return;
+    }
+    do {
+        // most commonly, concidence are one span long; check for that first
+        int intervals = coin->spanCount();
+        if (intervals = 1) {
+#if DEBUG_COINCIDENCE_VERBOSE
+            // SkASSERT(!coin->debugExpand(nullptr, nullptr));
+#endif
+            continue;
+        }
+        coin->debugExpand(id, log);
+        if (coin->spanCount() <= 0) {
+            return;
         }
-    } while ((outer = outer->fNext));
+        // check to see if every span in coin has a mate in opp
+        const SkOpSpan* start = coin->coinPtTStart()->span()->upCast();
+        bool flipped = coin->flipped();
+        const SkOpSpanBase* oppStartBase = coin->oppPtTStart()->span();
+        const SkOpSpan* oppStart = flipped ? oppStartBase->prev() : oppStartBase->upCast();
+        SkDebugf("", start, oppStart);
+    } while ((coin = coin->next()));
+    return;
 }
 
+// Commented-out lines keep this in sync with expand()
+// expand the range by checking adjacent spans for coincidence
 bool SkOpCoincidence::debugExpand(const char* id, SkPathOpsDebug::GlitchLog* log) const {
     const SkCoincidentSpans* coin = fHead;
     if (!coin) {
@@ -1352,109 +1671,296 @@ bool SkOpCoincidence::debugExpand(const char* id, SkPathOpsDebug::GlitchLog* log
     }
     bool expanded = false;
     do {
-        const SkOpSpan* start = coin->fCoinPtTStart->span()->upCast();
-        const SkOpSpanBase* end = coin->fCoinPtTEnd->span();
-        const SkOpSegment* segment = coin->fCoinPtTStart->segment();
-        const SkOpSegment* oppSegment = coin->fOppPtTStart->segment();
-        const SkOpSpan* prev = start->prev();
-        if (prev && prev->debugContains(oppSegment)) {
-            double midT = (prev->t() + start->t()) / 2;
-            if (segment->isClose(midT, oppSegment)) {
-                log->record(kExpandCoin_Glitch, id, coin, prev);
-            }
-        }
-        SkOpSpanBase* next = end->final() ? nullptr : end->upCast()->next();
-        if (next && next->debugContains(oppSegment)) {
-            double midT = (end->t() + next->t()) / 2;
-            if (segment->isClose(midT, oppSegment)) {
-                log->record(kExpandCoin_Glitch, id, coin, next);
-            }
+        if (coin->debugExpand(id, log)) {
+            // check to see if multiple spans expanded so they are now identical
+            const SkCoincidentSpans* test = fHead;
+            do {
+                if (coin == test) {
+                    continue;
+                }
+                if (coin->coinPtTStart() == test->coinPtTStart()
+                        && coin->oppPtTStart() == test->oppPtTStart()) {
+                    if (log) log->record(kExpandCoin_Glitch, id, fHead, test->coinPtTStart());
+                    break;
+                }
+            } while ((test = test->next()));
+            expanded = true;
         }
-    } while ((coin = coin->fNext));
+    } while ((coin = coin->next()));
     return expanded;
 }
 
-void SkOpCoincidence::debugFixAligned(const char* id, SkPathOpsDebug::GlitchLog* log) const {
+// Commented-out lines keep this in sync with removeCollapsed()
+void SkOpCoincidence::debugRemoveCollapsed(const char* id, SkPathOpsDebug::GlitchLog* log) const {
     const SkCoincidentSpans* coin = fHead;
     if (!coin) {
         return;
     }
+    // SkCoincidentSpans** priorPtr = &fHead;
     do {
-        if (coin->fCoinPtTStart->deleted()) {
-            log->record(kDeletedCoin_Glitch, id, coin, coin->fCoinPtTStart);
-        }
-        if (coin->fCoinPtTEnd->deleted()) {
-            log->record(kDeletedCoin_Glitch, id, coin, coin->fCoinPtTEnd);
-        }
-        if (coin->fOppPtTStart->deleted()) {
-            log->record(kDeletedCoin_Glitch, id, coin, coin->fOppPtTStart);
+        if (coin->coinPtTStart() == coin->coinPtTEnd()) {
+            return;
         }
-        if (coin->fOppPtTEnd->deleted()) {
-            log->record(kDeletedCoin_Glitch, id, coin, coin->fOppPtTEnd);
+        if (coin->oppPtTStart() == coin->oppPtTEnd()) {
+            return;
         }
-    } while ((coin = coin->fNext));
-    coin = fHead;
-    do {
-        if (coin->fCoinPtTStart->collapsed(coin->fCoinPtTEnd)) {
-            log->record(kCollapsedCoin_Glitch, id, coin, coin->fCoinPtTStart);
+        if (coin->coinPtTStart()->collapsed(coin->coinPtTEnd())) {
+            log->record(kCollapsedCoin_Glitch, id, coin);
+//             continue;
         }
-        if (coin->fOppPtTStart->collapsed(coin->fOppPtTEnd)) {
-            log->record(kCollapsedCoin_Glitch, id, coin, coin->fOppPtTStart);
+        if (coin->oppPtTStart()->collapsed(coin->oppPtTEnd())) {
+            log->record(kCollapsedCoin_Glitch, id, coin, coin);
+//             continue;
         }
-    } while ((coin = coin->fNext));
+        // priorPtr = &coin->nextPtr();
+    } while ((coin = coin->next()));
+    return;
 }
 
+// Commented-out lines keep this in sync with mark()
+/* this sets up the coincidence links in the segments when the coincidence crosses multiple spans */
 void SkOpCoincidence::debugMark(const char* id, SkPathOpsDebug::GlitchLog* log) const {
     const SkCoincidentSpans* coin = fHead;
     if (!coin) {
         return;
     }
     do {
-        const SkOpSpanBase* end = coin->fCoinPtTEnd->span();
-        const SkOpSpanBase* oldEnd = end;
-        const SkOpSpan* start = coin->fCoinPtTStart->span()->debugStarter(&end);
-        const SkOpSpanBase* oEnd = coin->fOppPtTEnd->span();
-        const SkOpSpanBase* oOldEnd = oEnd;
-        const SkOpSpanBase* oStart = coin->fOppPtTStart->span()->debugStarter(&oEnd);
-        bool flipped = (end == oldEnd) != (oEnd == oOldEnd);
+        const SkOpSpan* start = coin->coinPtTStartWritable()->span()->upCast();
+//         SkASSERT(start->deleted());
+        const SkOpSpanBase* end = coin->coinPtTEndWritable()->span();
+//         SkASSERT(end->deleted());
+        const SkOpSpanBase* oStart = coin->oppPtTStartWritable()->span();
+//         SkASSERT(oStart->deleted());
+        const SkOpSpanBase* oEnd = coin->oppPtTEndWritable()->span();
+//         SkASSERT(oEnd->deleted());
+        bool flipped = coin->flipped();
         if (flipped) {
             SkTSwap(oStart, oEnd);
         }
+        /* coin and opp spans may not match up. Mark the ends, and then let the interior
+           get marked as many times as the spans allow */
+        start->debugInsertCoincidence(id, log, oStart->upCast());
+        end->debugInsertCoinEnd(id, log, oEnd);
+        const SkOpSegment* segment = start->segment();
+        const SkOpSegment* oSegment = oStart->segment();
         const SkOpSpanBase* next = start;
         const SkOpSpanBase* oNext = oStart;
-        do {
-            next = next->upCast()->next();
-            oNext = flipped ? oNext->prev() : oNext->upCast()->next();
-            if (next == end || oNext == oEnd) {
-                break;
+        while ((next = next->upCast()->next()) != end) {
+            if (next->upCast()->debugInsertCoincidence(id, log, oSegment, flipped), false) {
+                return;
             }
-            if (!next->containsCoinEnd(oNext)) {
-                log->record(kMarkCoinEnd_Glitch, id, next, oNext);
+        }
+        while ((oNext = oNext->upCast()->next()) != oEnd) {
+            if (oNext->upCast()->debugInsertCoincidence(id, log, segment, flipped), false) {
+                return;
             }
-            const SkOpSpan* nextSpan = next->upCast();
-            const SkOpSpan* oNextSpan = oNext->upCast();
-            if (!nextSpan->containsCoincidence(oNextSpan)) {
-                log->record(kMarkCoinInsert_Glitch, id, nextSpan, oNextSpan);
+        }
+    } while ((coin = coin->next()));
+    return;
+}
+#endif
+
+#if DEBUG_COINCIDENCE_VERBOSE
+// Commented-out lines keep this in sync with markCollapsed()
+void SkOpCoincidence::debugMarkCollapsed(const char* id, SkPathOpsDebug::GlitchLog* log, const SkCoincidentSpans* coin, const SkOpPtT* test) const {
+    while (coin) {
+        if (coin->collapsed(test)) {
+            if (zero_or_one(coin->coinPtTStart()->fT) && zero_or_one(coin->coinPtTEnd()->fT)) {
+                log->record(kCollapsedCoin_Glitch, id, coin);
             }
-        } while (true);
-    } while ((coin = coin->fNext));
+            if (zero_or_one(coin->oppPtTStart()->fT) && zero_or_one(coin->oppPtTEnd()->fT)) {
+                log->record(kCollapsedCoin_Glitch, id, coin);
+            }
+        }
+        coin = coin->next();
+    }
+}
+
+// Commented-out lines keep this in sync with markCollapsed()
+void SkOpCoincidence::debugMarkCollapsed(const char* id, SkPathOpsDebug::GlitchLog* log, const SkOpPtT* test) const {
+    this->debugMarkCollapsed(id, log, fHead, test);
+    this->debugMarkCollapsed(id, log, fTop, test);
 }
 #endif
 
+void SkCoincidentSpans::debugShow() const {
+    SkDebugf("%s - id=%d t=%1.9g tEnd=%1.9g\n", __FUNCTION__,
+            coinPtTStart()->segment()->debugID(),
+            coinPtTStart()->fT, coinPtTEnd()->fT);
+    SkDebugf("%s + id=%d t=%1.9g tEnd=%1.9g\n", __FUNCTION__,
+            oppPtTStart()->segment()->debugID(),
+            oppPtTStart()->fT, oppPtTEnd()->fT);
+}
+
 void SkOpCoincidence::debugShowCoincidence() const {
-    SkCoincidentSpans* span = fHead;
+#if DEBUG_COINCIDENCE
+    const SkCoincidentSpans* span = fHead;
     while (span) {
-        SkDebugf("%s - id=%d t=%1.9g tEnd=%1.9g\n", __FUNCTION__,
-                span->fCoinPtTStart->segment()->debugID(),
-                span->fCoinPtTStart->fT, span->fCoinPtTEnd->fT);
-        SkDebugf("%s + id=%d t=%1.9g tEnd=%1.9g\n", __FUNCTION__,
-                span->fOppPtTStart->segment()->debugID(),
-                span->fOppPtTStart->fT, span->fOppPtTEnd->fT);
-        span = span->fNext;
+        span->debugShow();
+        span = span->next();
     }
+#endif
 }
 
 #if DEBUG_COINCIDENCE
+static void DebugValidate(const SkOpSpanBase* next, const SkOpSpanBase* end,
+        double oStart, double oEnd, const SkOpSegment* oSegment,
+        const char* id, SkPathOpsDebug::GlitchLog* log) {
+    SkASSERT(next != end);
+    SkASSERT(!next->contains(end) || log);
+    if (next->t() > end->t()) {
+        SkTSwap(next, end);
+    }
+    do {
+        const SkOpPtT* ptT = next->ptT();
+        int index = 0;
+        bool somethingBetween;
+        do {
+            ++index;
+            ptT = ptT->next();
+            const SkOpPtT* checkPtT = next->ptT();
+            if (ptT == checkPtT) {
+                break;
+            }
+            bool looped = false;
+            for (int check = 0; check < index; ++check) {
+                if ((looped = checkPtT == ptT)) {
+                    break;
+                }
+                checkPtT = checkPtT->next();
+            }
+            if (looped) {
+                SkASSERT(0);
+                break;
+            }
+            if (ptT->deleted()) {
+                continue;
+            }
+            if (ptT->segment() != oSegment) {
+                continue;
+            }
+            somethingBetween |= between(oStart, ptT->fT, oEnd);
+        } while (true);
+        SkASSERT(somethingBetween);
+    } while (next != end && (next = next->upCast()->next()));
+}
+
+static void DebugCheckOverlap(const SkCoincidentSpans* test, const SkCoincidentSpans* list,
+        const char* id, SkPathOpsDebug::GlitchLog* log) {
+    if (!list) {
+        return;
+    }
+    const SkOpSegment* coinSeg = test->coinPtTStart()->segment();
+    SkASSERT(coinSeg == test->coinPtTEnd()->segment());
+    const SkOpSegment* oppSeg = test->oppPtTStart()->segment();
+    SkASSERT(oppSeg == test->oppPtTEnd()->segment());
+    SkASSERT(coinSeg != test->oppPtTStart()->segment());
+    SkDEBUGCODE(double tcs = test->coinPtTStart()->fT);
+    SkASSERT(between(0, tcs, 1));
+    SkDEBUGCODE(double tce = test->coinPtTEnd()->fT);
+    SkASSERT(between(0, tce, 1));
+    SkASSERT(tcs < tce);
+    double tos = test->oppPtTStart()->fT;
+    SkASSERT(between(0, tos, 1));
+    double toe = test->oppPtTEnd()->fT;
+    SkASSERT(between(0, toe, 1));
+    SkASSERT(tos != toe);
+    if (tos > toe) {
+        SkTSwap(tos, toe);
+    }
+    do {
+        double lcs, lce, los, loe;
+        if (coinSeg == list->coinPtTStart()->segment()) {
+            if (oppSeg != list->oppPtTStart()->segment()) {
+                continue;
+            }
+            lcs = list->coinPtTStart()->fT;
+            lce = list->coinPtTEnd()->fT;
+            los = list->oppPtTStart()->fT;
+            loe = list->oppPtTEnd()->fT;
+            if (los > loe) {
+                SkTSwap(los, loe);
+            }
+        } else if (coinSeg == list->oppPtTStart()->segment()) {
+            if (oppSeg != list->coinPtTStart()->segment()) {
+                continue;
+            }
+            lcs = list->oppPtTStart()->fT;
+            lce = list->oppPtTEnd()->fT;
+            if (lcs > lce) {
+                SkTSwap(lcs, lce);
+            }
+            los = list->coinPtTStart()->fT;
+            loe = list->coinPtTEnd()->fT;
+        } else {
+            continue;
+        }
+        SkASSERT(tce < lcs || lce < tcs);
+        SkASSERT(toe < los || loe < tos);
+    } while ((list = list->next()));
+}
+
+
+static void DebugCheckOverlapTop(const SkCoincidentSpans* head, const SkCoincidentSpans* opt,
+        const char* id, SkPathOpsDebug::GlitchLog* log) {
+    // check for overlapping coincident spans
+    const SkCoincidentSpans* test = head;
+    while (test) {
+        const SkCoincidentSpans* next = test->next();
+        DebugCheckOverlap(test, next, id, log);
+        DebugCheckOverlap(test, opt, id, log);
+        test = next;
+    }
+}
+
+#if DEBUG_COINCIDENCE_VERBOSE
+void SkOpCoincidence::debugCheckOverlap(const char* id, SkPathOpsDebug::GlitchLog* log) const {
+    DebugCheckOverlapTop(fHead, fTop, id, log);
+    DebugCheckOverlapTop(fTop, nullptr, id, log);
+}
+#endif
+
+static void DebugValidate(const SkCoincidentSpans* head, const SkCoincidentSpans* opt,
+        const char* id, SkPathOpsDebug::GlitchLog* log) {
+    // look for pts inside coincident spans that are not inside the opposite spans
+    const SkCoincidentSpans* coin = head;
+    while (coin) {
+        SkASSERT(SkOpCoincidence::Ordered(coin->coinPtTStart()->segment(),
+                coin->oppPtTStart()->segment()));
+        SkASSERT(coin->coinPtTStart()->span()->ptT() == coin->coinPtTStart());
+        SkASSERT(coin->coinPtTEnd()->span()->ptT() == coin->coinPtTEnd());
+        SkASSERT(coin->oppPtTStart()->span()->ptT() == coin->oppPtTStart());
+        SkASSERT(coin->oppPtTEnd()->span()->ptT() == coin->oppPtTEnd());
+        DebugValidate(coin->coinPtTStart()->span(), coin->coinPtTEnd()->span(),
+                coin->oppPtTStart()->fT, coin->oppPtTEnd()->fT, coin->oppPtTStart()->segment(),
+                id, log);
+        DebugValidate(coin->oppPtTStart()->span(), coin->oppPtTEnd()->span(),
+                coin->coinPtTStart()->fT, coin->coinPtTEnd()->fT, coin->coinPtTStart()->segment(),
+                id, log);
+        coin = coin->next();
+    }
+    DebugCheckOverlapTop(head, opt, id, log);
+}
+#endif
+
+void SkOpCoincidence::debugValidate() const {
+#if DEBUG_COINCIDENCE
+ //   if (fGlobalState->debugCheckHealth()) {
+//        return;
+//    }
+    DebugValidate(fHead, fTop, nullptr, nullptr);
+    DebugValidate(fTop, nullptr, nullptr, nullptr);
+#endif
+}
+
+#if DEBUG_COINCIDENCE_VERBOSE
+void SkOpCoincidence::debugCheckValid(const char* id, SkPathOpsDebug::GlitchLog* log) const {
+    DebugValidate(fHead, fTop, id, log);
+    DebugValidate(fTop, nullptr, id, log);
+}
+#endif
+
+#if DEBUG_COINCIDENCE_VERBOSE
 void SkOpContour::debugCheckHealth(const char* id, SkPathOpsDebug::GlitchLog* log) const {
     const SkOpSegment* segment = &fHead;
     do {
@@ -1462,16 +1968,36 @@ void SkOpContour::debugCheckHealth(const char* id, SkPathOpsDebug::GlitchLog* lo
     } while ((segment = segment->next()));
 }
 
-void SkOpContour::debugMissingCoincidence(const char* id, SkPathOpsDebug::GlitchLog* log,
-        const SkOpCoincidence* coincidence) const {
+// commmented-out lines keep this aligned with missingCoincidence()
+void SkOpContour::debugMissingCoincidence(const char* id, SkPathOpsDebug::GlitchLog* log) const {
+//    SkASSERT(fCount > 0);
     const SkOpSegment* segment = &fHead;
+//    bool result = false;
     do {
-        segment->debugMissingCoincidence(id, log, coincidence);
-    } while ((segment = segment->next()));
+        if (fState->angleCoincidence()) {
+// #if DEBUG_ANGLE
+//          segment->debugCheckAngleCoin();
+// #endif
+        } else if (segment->debugMissingCoincidence(id, log), false) {
+//          result = true;
+// see FIXME in missingCoincidence()
+//
+//
+//
+    //      continue;
+        }
+        segment = segment->next();
+    } while (segment);
+    return;
 }
 #endif
 
 void SkOpSegment::debugValidate() const {
+#if DEBUG_COINCIDENCE
+    if (this->globalState()->debugCheckHealth()) {
+        return;
+    }
+#endif
 #if DEBUG_VALIDATE
     const SkOpSpanBase* span = &fHead;
     double lastT = -1;
@@ -1500,56 +2026,47 @@ void SkOpSegment::debugValidate() const {
 #endif
 }
 
-bool SkOpSpanBase::debugAlignedEnd(double t, const SkPoint& pt) const {
-    SkASSERT(zero_or_one(t));
-    const SkOpSegment* segment = this->segment();
-    SkASSERT(t ? segment->lastPt() == pt : segment->pts()[0] == pt);
-    if (!debugAlignedInner()) {
-          return false;
-    }
-    if ((t ? segment->lastPt() : segment->pts()[0]) != pt) {
-        return false;
+#if DEBUG_COINCIDENCE_VERBOSE
+// Commented-out lines keep this in sync with addOppAndMerge()
+// If the added points envelop adjacent spans, merge them in.
+void SkOpSpanBase::debugAddOppAndMerge(const char* id, SkPathOpsDebug::GlitchLog* log, const SkOpSpanBase* opp, bool* spanDeleted, bool* oppDeleted) const {
+    if (this->ptT()->debugAddOpp(opp->ptT())) {
+        this->debugCheckForCollapsedCoincidence(id, log);
     }
-    const SkOpPtT* ptT = &this->fPtT;
-    SkASSERT(t == ptT->fT);
-    SkASSERT(pt == ptT->fPt);
-    const SkOpPtT* test = ptT, * stopPtT = ptT;
-    while ((test = test->next()) != stopPtT) {
-        const SkOpSegment* other = test->segment();
-        if (other == this->segment()) {
-            continue;
-        }
-        if (!zero_or_one(test->fT)) {
-            continue;
-        }
-        if ((test->fT ? other->lastPt() : other->pts()[0]) != pt) {
-            return false;
-        }
+    // compute bounds of points in span
+    SkPathOpsBounds bounds;
+    bounds.set(SK_ScalarMax, SK_ScalarMax, SK_ScalarMin, SK_ScalarMin);
+    const SkOpPtT* head = this->ptT();
+    const SkOpPtT* nextPt = head;
+    do {
+        bounds.add(nextPt->fPt);
+    } while ((nextPt = nextPt->next()) != head);
+    if (!bounds.width() && !bounds.height()) {
+        return;
     }
-    return this->fAligned;
+    this->debugMergeContained(id, log, bounds, spanDeleted);
+    opp->debugMergeContained(id, log, bounds, oppDeleted);
 }
 
-bool SkOpSpanBase::debugAlignedInner() const {
-    // force the spans to share points and t values
-    const SkOpPtT* ptT = &this->fPtT, * stopPtT = ptT;
-    const SkPoint& pt = ptT->fPt;
+// Commented-out lines keep this in sync with checkForCollapsedCoincidence()
+void SkOpSpanBase::debugCheckForCollapsedCoincidence(const char* id, SkPathOpsDebug::GlitchLog* log) const {
+    const SkOpCoincidence* coins = this->globalState()->coincidence();
+    if (coins->isEmpty()) {
+        return;
+    }
+// the insert above may have put both ends of a coincident run in the same span
+// for each coincident ptT in loop; see if its opposite in is also in the loop
+// this implementation is the motivation for marking that a ptT is referenced by a coincident span
+    const SkOpPtT* head = this->ptT();
+    const SkOpPtT* test = head;
     do {
-        if (ptT->fPt != pt) {
-            return false;
+        if (!test->coincident()) {
+            continue;
         }
-        const SkOpSpanBase* span = ptT->span();
-        const SkOpPtT* test = ptT;
-        do {
-            if ((test = test->next()) == stopPtT) {
-                break;
-            }
-            if (span == test->span() && !span->segment()->ptsDisjoint(*ptT, *test)) {
-                return false;
-            }
-        } while (true);
-    } while ((ptT = ptT->next()) != stopPtT);
-    return true;
+        coins->debugMarkCollapsed(id, log, test);
+    } while ((test = test->next()) != head);
 }
+#endif
 
 bool SkOpSpanBase::debugCoinEndLoopCheck() const {
     int loop = 0;
@@ -1574,16 +2091,57 @@ bool SkOpSpanBase::debugCoinEndLoopCheck() const {
     return true;
 }
 
-bool SkOpSpanBase::debugContains(const SkOpSegment* segment) const {
-    const SkOpPtT* start = &fPtT;
-    const SkOpPtT* walk = start;
-    while ((walk = walk->next()) != start) {
-        if (walk->segment() == segment) {
-            return true;
+#if DEBUG_COINCIDENCE_VERBOSE
+// Commented-out lines keep this in sync with insertCoinEnd()
+void SkOpSpanBase::debugInsertCoinEnd(const char* id, SkPathOpsDebug::GlitchLog* log, const SkOpSpanBase* coin) const {
+    if (containsCoinEnd(coin)) {
+//         SkASSERT(coin->containsCoinEnd(this));
+        return;
+    }
+    debugValidate();
+//     SkASSERT(this != coin);
+    log->record(kMarkCoinEnd_Glitch, id, this, coin);
+//     coin->fCoinEnd = this->fCoinEnd;
+//     this->fCoinEnd = coinNext;
+    debugValidate();
+}
+
+// Commented-out lines keep this in sync with mergeContained()
+void SkOpSpanBase::debugMergeContained(const char* id, SkPathOpsDebug::GlitchLog* log, const SkPathOpsBounds& bounds, bool* deleted) const {
+    // while adjacent spans' points are contained by the bounds, merge them
+    const SkOpSpanBase* prev = this;
+    const SkOpSegment* seg = this->segment();
+    while ((prev = prev->prev()) && bounds.contains(prev->pt()) && !seg->ptsDisjoint(prev, this)) {
+        if (prev->prev()) {
+            log->record(kMergeContained_Glitch, id, this, prev);
+        } else if (this->final()) {
+            log->record(kMergeContained_Glitch, id, this, prev);
+            // return;
+        } else {
+            log->record(kMergeContained_Glitch, id, prev, this);
         }
     }
-    return false;
+    const SkOpSpanBase* current = this;
+    const SkOpSpanBase* next = this;
+    while (next->upCastable() && (next = next->upCast()->next())
+            && bounds.contains(next->pt()) && !seg->ptsDisjoint(this, next)) {
+        if (!current->prev() && next->final()) {
+            log->record(kMergeContained_Glitch, id, next, current);
+            current = next;
+        }
+        if (current->prev()) {
+            log->record(kMergeContained_Glitch, id, next, current);
+            current = next;
+        } else {
+            log->record(kMergeContained_Glitch, id, next, current);
+            current = next;
+        }
+    }
+#if DEBUG_COINCIDENCE
+    // this->globalState()->coincidence()->debugValidate();
+#endif
 }
+#endif
 
 const SkOpSpan* SkOpSpanBase::debugStarter(SkOpSpanBase const** endPtr) const {
     const SkOpSpanBase* end = *endPtr;
@@ -1599,6 +2157,11 @@ const SkOpSpan* SkOpSpanBase::debugStarter(SkOpSpanBase const** endPtr) const {
 }
 
 void SkOpSpanBase::debugValidate() const {
+#if DEBUG_COINCIDENCE
+    if (this->globalState()->debugCheckHealth()) {
+        return;
+    }
+#endif
 #if DEBUG_VALIDATE
     const SkOpPtT* ptT = &fPtT;
     SkASSERT(ptT->span() == this);
@@ -1643,6 +2206,39 @@ bool SkOpSpan::debugCoinLoopCheck() const {
     return true;
 }
 
+#if DEBUG_COINCIDENCE_VERBOSE
+// Commented-out lines keep this in sync with insertCoincidence() in header
+void SkOpSpan::debugInsertCoincidence(const char* id, SkPathOpsDebug::GlitchLog* log, const SkOpSpan* coin) const {
+    if (containsCoincidence(coin)) {
+//         SkASSERT(coin->containsCoincidence(this));
+        return;
+    }
+    debugValidate();
+//     SkASSERT(this != coin);
+    log->record(kMarkCoinStart_Glitch, id, this, coin);
+//     coin->fCoincident = this->fCoincident;
+//     this->fCoincident = coinNext;
+    debugValidate();
+}
+
+// Commented-out lines keep this in sync with insertCoincidence()
+void SkOpSpan::debugInsertCoincidence(const char* id, SkPathOpsDebug::GlitchLog* log, const SkOpSegment* segment, bool flipped) const {
+    if (this->containsCoincidence(segment)) {
+        return;
+    }
+    const SkOpPtT* next = &fPtT;
+    while ((next = next->next()) != &fPtT) {
+        if (next->segment() == segment) {
+            log->record(kMarkCoinInsert_Glitch, id, flipped ? next->span()->prev() : next->span());
+            return;
+        }
+    }
+#if DEBUG_COINCIDENCE
+    log->record(kMarkCoinMissing_Glitch, id, segment, this);
+#endif
+}
+#endif
+
 // called only by test code
 int SkIntersections::debugCoincidentUsed() const {
     if (!fIsCoincident[0]) {
@@ -1667,6 +2263,27 @@ int SkIntersections::debugCoincidentUsed() const {
 
 #include "SkOpContour.h"
 
+// Commented-out lines keep this in sync with addOpp()
+bool SkOpPtT::debugAddOpp(const SkOpPtT* opp) const {
+    // find the fOpp ptr to opp
+    const SkOpPtT* oppPrev = opp->fNext;
+    if (oppPrev == this) {
+        return false;
+    }
+    while (oppPrev->fNext != opp) {
+        oppPrev = oppPrev->fNext;
+        if (oppPrev == this) {
+            return false;
+        }
+    }
+//    const SkOpPtT* oldNext = this->fNext;
+    SkASSERT(this != opp);
+//    this->fNext = opp;
+//    SkASSERT(oppPrev != oldNext);
+//    oppPrev->fNext = oldNext;
+    return true;
+}
+
 bool SkOpPtT::debugContains(const SkOpPtT* check) const {
     SkASSERT(this != check);
     const SkOpPtT* ptT = this;
@@ -1736,6 +2353,11 @@ int SkOpPtT::debugLoopLimit(bool report) const {
 }
 
 void SkOpPtT::debugValidate() const {
+#if DEBUG_COINCIDENCE
+    if (this->globalState()->debugCheckHealth()) {
+        return;
+    }
+#endif
 #if DEBUG_VALIDATE
     SkOpGlobalState::Phase phase = contour()->globalState()->phase();
     if (phase == SkOpGlobalState::kIntersecting