pathops coincidence and security rewrite

Most changes stem from working on an examples bracketed
by #if DEBUG_UNDER_DEVELOPMENT  // tiger
These exposed many problems with coincident curves,
as well as errors throughout the code.

Fixing these errors also fixed a number of fuzzer-inspired
bug reports.

* Line/Curve Intersections
Check to see if the end of the line nearly intersects
the curve. This was a FIXME in the old code.

* Performance
Use a central chunk allocator.
Plumb the allocator into the global variable state
so that it can be shared. (Note that 'SkGlobalState'
is allocated on the stack and is visible to children
functions but not other threads.)

* Refactor
Let SkOpAngle grow up from a structure to a class.
Let SkCoincidentSpans grow up from a structure to a class.
Rename enum Alias to AliasMatch.

* Coincidence Rewrite
Add more debugging to coincidence detection.
Parallel debugging routines have read-only logic to report
the current coincidence state so that steps through the
logic can expose whether things got better or worse.

More functions can error-out and cause the pathops
engine to non-destructively exit.

* Accuracy
Remove code that adjusted point locations. Instead,
offset the curve part so that sorted curves all use
the same origin.
Reduce the size (and influence) of magic numbers.

* Testing
The debug suite with verify and the full release suite
./out/Debug/pathops_unittest -v -V
./out/Release/pathops_unittest -v -V -x
expose one error. That error is captured as cubics_d3.
This error exists in the checked in code as well.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2128633003

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2128633003

Review-Url: https://codereview.chromium.org/2128633003

1 files changed, 62 insertions, 14 deletions

diff --git a/tests/PathOpsDebug.cpp b/tests/PathOpsDebug.cpp
index 0f96ef4f88..7770b00c6a 100755
--- a/tests/PathOpsDebug.cpp
+++ b/tests/PathOpsDebug.cpp
@@ -50,6 +50,14 @@ void SkPathOpsDebug::WindingPrintf(int wind) {
 }
 #endif
 
+static void DumpID(int id) {
+    SkDebugf("} ");
+    if (id >= 0) {
+        SkDebugf("id=%d", id);
+    }
+    SkDebugf("\n");
+}
+
 void SkDConic::dump() const {
     dumpInner();
     SkDebugf("},\n");
@@ -57,7 +65,7 @@ void SkDConic::dump() const {
 
 void SkDConic::dumpID(int id) const {
     dumpInner();
-    SkDebugf("} id=%d\n", id);
+    DumpID(id);
 }
 
 void SkDConic::dumpInner() const {
@@ -73,7 +81,8 @@ void SkDCubic::dump() const {
 
 void SkDCubic::dumpID(int id) const {
     this->dumpInner();
-    SkDebugf("}} id=%d\n", id);
+    SkDebugf("}");
+    DumpID(id);
 }
 
 static inline bool double_is_NaN(double x) { return x != x; }
@@ -97,6 +106,10 @@ void SkDCubic::dumpInner() const {
     fPts[index].dump();
 }
 
+void SkDCurve::dump() const {
+    dumpID(-1);
+}
+
 void SkDCurve::dumpID(int id) const {
 #ifndef SK_RELEASE
     switch(fVerb) {
@@ -127,7 +140,8 @@ void SkDLine::dump() const {
 
 void SkDLine::dumpID(int id) const {
     this->dumpInner();
-    SkDebugf("}} id=%d\n", id);
+    SkDebugf("}");
+    DumpID(id);
 }
 
 void SkDLine::dumpInner() const {
@@ -168,7 +182,8 @@ void SkDQuad::dump() const {
 
 void SkDQuad::dumpID(int id) const {
     dumpInner();
-    SkDebugf("}} id=%d\n", id);
+    SkDebugf("}");
+    DumpID(id);
 }
 
 void SkDQuad::dumpInner() const {
@@ -787,6 +802,10 @@ const SkOpAngle* SkOpAngle::debugAngle(int id) const {
     return this->segment()->debugAngle(id);
 }
 
+const SkOpCoincidence* SkOpAngle::debugCoincidence() const {
+    return this->segment()->debugCoincidence();
+}
+
 SkOpContour* SkOpAngle::debugContour(int id) {
     return this->segment()->debugContour(id);
 }
@@ -925,6 +944,10 @@ SkOpContour* SkOpPtT::debugContour(int id) {
     return this->span()->debugContour(id);
 }
 
+const SkOpCoincidence* SkOpPtT::debugCoincidence() const {
+    return this->span()->debugCoincidence();
+}
+
 const SkOpPtT* SkOpPtT::debugPtT(int id) const {
     return this->span()->debugPtT(id);
 }
@@ -964,7 +987,8 @@ void SkOpPtT::dumpAll() const {
 }
 
 void SkOpPtT::dumpBase() const {
-    SkDebugf(" t=%1.9g pt=(%1.9g,%1.9g)%s%s", this->fT, this->fPt.fX, this->fPt.fY,
+    SkDebugf(" t=%1.9g pt=(%1.9g,%1.9g)%s%s%s", this->fT, this->fPt.fX, this->fPt.fY,
+            this->fCoincident ? " coin" : "",
             this->fDuplicatePt ? " dup" : "", this->fDeleted ? " deleted" : "");
 }
 
@@ -972,6 +996,10 @@ const SkOpAngle* SkOpSpanBase::debugAngle(int id) const {
     return this->segment()->debugAngle(id);
 }
 
+const SkOpCoincidence* SkOpSpanBase::debugCoincidence() const {
+    return this->segment()->debugCoincidence();
+}
+
 SkOpContour* SkOpSpanBase::debugContour(int id) {
     return this->segment()->debugContour(id);
 }
@@ -989,15 +1017,19 @@ const SkOpSpanBase* SkOpSpanBase::debugSpan(int id) const {
 }
 
 void SkOpSpanBase::dump() const {
-    this->dumpAll();
-    SkDebugf("\n");
+    this->dumpHead();
+    this->fPtT.dump();
 }
 
-void SkOpSpanBase::dumpAll() const {
+void SkOpSpanBase::dumpHead() const {
     SkDebugf("%.*s", contour()->debugIndent(), "        ");
     SkDebugf("seg=%d span=%d", this->segment()->debugID(), this->debugID());
     this->dumpBase();
     SkDebugf("\n");
+}
+
+void SkOpSpanBase::dumpAll() const {
+    this->dumpHead();
     this->fPtT.dumpAll();
 }
 
@@ -1008,6 +1040,11 @@ void SkOpSpanBase::dumpBase() const {
     if (this->fChased) {
         SkDebugf(" chased");
     }
+#ifdef SK_DEBUG
+    if (this->fDeleted) {
+        SkDebugf(" deleted");
+    }
+#endif
     if (!this->final()) {
         this->upCast()->dumpSpan();
     }
@@ -1069,6 +1106,11 @@ const SkOpAngle* SkOpSegment::debugAngle(int id) const {
     return this->contour()->debugAngle(id);
 }
 
+
+const SkOpCoincidence* SkOpSegment::debugCoincidence() const {
+    return this->contour()->debugCoincidence();
+}
+
 SkOpContour* SkOpSegment::debugContour(int id) {
     return this->contour()->debugContour(id);
 }
@@ -1188,20 +1230,26 @@ void SkOpCoincidence::dump() const {
     SkCoincidentSpans* span = fHead;
     while (span) {
         span->dump();
-        span = span->fNext;
+        span = span->next();
     }
     if (!fTop || fHead == fTop) {
         return;
     }
     SkDebugf("top:\n");
     span = fTop;
-    if (fHead) {
-        span->dump();
-        return;
-    }
+    int count = 0;
     while (span) {
         span->dump();
-        span = span->fNext;
+        span = span->next();
+        SkCoincidentSpans* check = fTop;
+        ++count;
+        for (int index = 0; index < count; ++index) {
+            if (span == check) {
+                SkDebugf("(loops to #%d)\n", index);
+                return;
+            }
+            check = check->next();
+        }
     }
 }