give up if huge paths have unresolvable coincidence

This fuzzy test has enormous curves with coincidence runs that break numerics.
If the computed intersections identify that the span of coincidence has been deleted,
give up and return that the path op failed.

TBR=reed@google.com
BUG=597926
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1854333002

Review URL: https://codereview.chromium.org/1854333002

3 files changed, 13 insertions, 4 deletions

diff --git a/src/pathops/SkOpCoincidence.cpp b/src/pathops/SkOpCoincidence.cpp
index c0147bcfd9..130d1daff7 100755
--- a/src/pathops/SkOpCoincidence.cpp
+++ b/src/pathops/SkOpCoincidence.cpp
@@ -634,16 +634,22 @@ void SkOpCoincidence::fixUp(SkOpPtT* deleted, SkOpPtT* kept) {
 }
 
 /* this sets up the coincidence links in the segments when the coincidence crosses multiple spans */
-void SkOpCoincidence::mark() {
+bool SkOpCoincidence::mark() {
     SkCoincidentSpans* coin = fHead;
     if (!coin) {
-        return;
+        return true;
     }
     do {
         SkOpSpanBase* end = coin->fCoinPtTEnd->span();
+        if (end->deleted()) {
+          return false;
+        }
         SkOpSpanBase* oldEnd = end;
         SkOpSpan* start = coin->fCoinPtTStart->span()->starter(&end);
         SkOpSpanBase* oEnd = coin->fOppPtTEnd->span();
+        if (oEnd->deleted()) {
+          return false;
+        }
         SkOpSpanBase* oOldEnd = oEnd;
         SkOpSpanBase* oStart = coin->fOppPtTStart->span()->starter(&oEnd);
         bool flipped = (end == oldEnd) != (oEnd == oOldEnd);
@@ -668,6 +674,7 @@ void SkOpCoincidence::mark() {
             }
         } while (true);
     } while ((coin = coin->fNext));
+    return true;
 }
 
 bool SkOpCoincidence::overlap(const SkOpPtT* coin1s, const SkOpPtT* coin1e, 
diff --git a/src/pathops/SkOpCoincidence.h b/src/pathops/SkOpCoincidence.h
index 96bd21ac48..344866ff36 100644
--- a/src/pathops/SkOpCoincidence.h
+++ b/src/pathops/SkOpCoincidence.h
@@ -92,7 +92,7 @@ public:
         return !fHead;
     }
 
-    void mark();
+    bool mark();
 
 private:
     bool addIfMissing(const SkCoincidentSpans* outer, SkOpPtT* over1s, SkOpPtT* over1e,
diff --git a/src/pathops/SkPathOpsCommon.cpp b/src/pathops/SkPathOpsCommon.cpp
index 829f8a50d5..86a8cb0bef 100644
--- a/src/pathops/SkPathOpsCommon.cpp
+++ b/src/pathops/SkPathOpsCommon.cpp
@@ -494,7 +494,9 @@ bool HandleCoincidence(SkOpContourHead* contourList, SkOpCoincidence* coincidenc
     }
     DEBUG_COINCIDENCE_HEALTH(contourList, "expand2");
     // the expanded ranges may not align -- add the missing spans
-    coincidence->mark();  // mark spans of coincident segments as coincident
+    if (!coincidence->mark()) {  // mark spans of coincident segments as coincident
+        return false;
+    }
     DEBUG_COINCIDENCE_HEALTH(contourList, "mark1");
     // look for coincidence missed earlier
     if (missingCoincidence(contourList, coincidence, allocator)) {