treat backwards quads as not convex

src/core/SkPath.cpp

 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkBuffer.h"
 #include "SkErrorInternals.h"
 #include "SkGeometry.h"
@@ skipping 2111 matching lines @@
 
     return kStraight_DirChange;
 }
 
 // only valid for a single contour
 struct Convexicator {
     Convexicator()
     : fPtCount(0)
     , fConvexity(SkPath::kConvex_Convexity)
     , fDirection(SkPath::kUnknown_Direction)
-    , fIsFinite(true) {
+    , fIsFinite(true)
+    , fIsCurve(false) {
         fExpectedDir = kInvalid_DirChange;
         // warnings
         fLastPt.set(0, 0);
         fCurrPt.set(0, 0);
         fLastVec.set(0, 0);
         fFirstVec.set(0, 0);
 
         fDx = fDy = 0;
         fSx = fSy = kValueNeverReturnedBySign;
     }
@@ skipping 43 matching lines @@
     void close() {
         if (fPtCount > 2) {
             this->addVec(fFirstVec);
         }
     }
 
     bool isFinite() const {
         return fIsFinite;
     }
 
+    void setCurve(bool isCurve) {
+        fIsCurve = isCurve;
+    }
+
 private:
     void addVec(const SkVector& vec) {
         SkASSERT(vec.fX || vec.fY);
         DirChange dir = direction_change(fLastPt, fCurrPt, fLastVec, vec);
         switch (dir) {
             case kLeft_DirChange:       // fall through
             case kRight_DirChange:
                 if (kInvalid_DirChange == fExpectedDir) {
                     fExpectedDir = dir;
                     fDirection = (kRight_DirChange == dir) ? SkPath::kCW_Direction
                                                            : SkPath::kCCW_Direction;
                 } else if (dir != fExpectedDir) {
                     fConvexity = SkPath::kConcave_Convexity;
                     fDirection = SkPath::kUnknown_Direction;
                 }
                 fLastVec = vec;
                 break;
             case kStraight_DirChange:
                 break;
             case kBackwards_DirChange:
+                if (fIsCurve) {
+                    fConvexity = SkPath::kConcave_Convexity;
+                    fDirection = SkPath::kUnknown_Direction;
+                }
                 fLastVec = vec;
                 break;
             case kInvalid_DirChange:
                 SkFAIL("Use of invalid direction change flag");
                 break;
         }
     }
 
     SkPoint             fLastPt;
     SkPoint             fCurrPt;
     // fLastVec does not necessarily start at fLastPt. We only advance it when the cross product
     // value with the current vec is deemed to be of a significant value.
     SkVector            fLastVec, fFirstVec;
     int                 fPtCount;   // non-degenerate points
     DirChange           fExpectedDir;
     SkPath::Convexity   fConvexity;
     SkPath::Direction   fDirection;
     int                 fDx, fDy, fSx, fSy;
     bool                fIsFinite;
+    bool                fIsCurve;
 };
 
 SkPath::Convexity SkPath::internalGetConvexity() const {
     SkASSERT(kUnknown_Convexity == fConvexity);
     SkPoint         pts[4];
     SkPath::Verb    verb;
     SkPath::Iter    iter(*this, true);
 
     int             contourCount = 0;
     int             count;
     Convexicator    state;
 
     if (!isFinite()) {
         return kUnknown_Convexity;
     }
     while ((verb = iter.next(pts)) != SkPath::kDone_Verb) {
         switch (verb) {
             case kMove_Verb:
                 if (++contourCount > 1) {
                     fConvexity = kConcave_Convexity;
                     return kConcave_Convexity;
                 }
                 pts[1] = pts[0];
+                // fall through
+            case kLine_Verb:
                 count = 1;
+                state.setCurve(false);
                 break;
-            case kLine_Verb: count = 1; break;
-            case kQuad_Verb: count = 2; break;
-            case kConic_Verb: count = 2; break;
-            case kCubic_Verb: count = 3; break;
+            case kQuad_Verb:
+                // fall through
+            case kConic_Verb:
+                // fall through
+            case kCubic_Verb:
+                count = 2 + (kCubic_Verb == verb);
+                // As an additional enhancement, this could set curve true only
+                // if the curve is nonlinear
+                state.setCurve(true);
+                break;
             case kClose_Verb:
+                state.setCurve(false);
                 state.close();
                 count = 0;
                 break;
             default:
                 SkDEBUGFAIL("bad verb");
                 fConvexity = kConcave_Convexity;
                 return kConcave_Convexity;
         }
 
         for (int i = 1; i <= count; i++) {
@@ skipping 517 matching lines @@
     switch (this->getFillType()) {
         case SkPath::kEvenOdd_FillType:
         case SkPath::kInverseEvenOdd_FillType:
             w &= 1;
             break;
         default:
             break;
     }
     return SkToBool(w);
 }