pathops: Split loop type cubics only when there is a self-intersection.

src/pathops/SkPathOpsCubic.cpp

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 #include "SkGeometry.h"
 #include "SkLineParameters.h"
 #include "SkPathOpsConic.h"
 #include "SkPathOpsCubic.h"
@@ skipping 222 matching lines @@
     SkScalar d[3];
     SkCubicType cubicType = SkClassifyCubic(pointsPtr, d);
     if (cubicType == kLoop_SkCubicType) {
         // crib code from gpu path utils that finds t values where loop self-intersects
         // use it to find mid of t values which should be a friendly place to chop
         SkScalar tempSqrt = SkScalarSqrt(4.f * d[0] * d[2] - 3.f * d[1] * d[1]);
         SkScalar ls = d[1] - tempSqrt;
         SkScalar lt = 2.f * d[0];
         SkScalar ms = d[1] + tempSqrt;
         SkScalar mt = 2.f * d[0];
-        if (between(0, ls, lt) || between(0, ms, mt)) {
+        if (roughly_between(0, ls, lt) && roughly_between(0, ms, mt)) {
             ls = ls / lt;
             ms = ms / mt;
-            SkScalar smaller = SkTMax(0.f, SkTMin(ls, ms));
-            SkScalar larger = SkTMin(1.f, SkTMax(ls, ms));
-            *t = (smaller + larger) / 2;
+            SkASSERT(roughly_between(0, ls, 1) && roughly_between(0, ms, 1));
+            *t = (ls + ms) / 2;
+            SkASSERT(roughly_between(0, *t, 1));
             return *t > 0 && *t < 1;
         }
     } else if (kSerpentine_SkCubicType == cubicType || kCusp_SkCubicType == cubicType) {
         SkDCubic cubic;
         cubic.set(pointsPtr);
         double inflectionTs[2];
         int infTCount = cubic.findInflections(inflectionTs);
         if (infTCount == 2) {
             double maxCurvature[3];
             int roots = cubic.findMaxCurvature(maxCurvature);
@@ skipping 430 matching lines @@
     for (int index = 0; index < roots; ++index) {
         double t = startT + (endT - startT) * extremeTs[index];
         SkDPoint mid = dCurve.ptAtT(t);
         if (topPt->fY > mid.fY || (topPt->fY == mid.fY && topPt->fX > mid.fX)) {
             topT = t;
             *topPt = mid;
         }
     }
     return topT;
 }