Make round-caps line segments convex

src/core/SkStrokerPriv.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 "SkStrokerPriv.h"
 #include "SkGeometry.h"
 #include "SkPath.h"
 
 static void ButtCapper(SkPath* path, const SkPoint& pivot, const SkVector& normal,
                        const SkPoint& stop, SkPath*) {
     path->lineTo(stop.fX, stop.fY);
 }
 
 static void RoundCapper(SkPath* path, const SkPoint& pivot, const SkVector& normal,
                         const SkPoint& stop, SkPath*) {
     SkVector parallel;
     normal.rotateCW(&parallel);
 
     SkPoint projectedCenter = pivot + parallel;
 
-    path->conicTo(projectedCenter + normal, projectedCenter, SK_ScalarRoot2Over2);
-    path->conicTo(projectedCenter - normal, stop, SK_ScalarRoot2Over2);
+    path->conicTo(pivot + (parallel + normal) * 0.999, projectedCenter, SK_ScalarRoot2Over2);
+    path->conicTo(pivot + (parallel - normal) * 0.999, stop, SK_ScalarRoot2Over2);
 }
 
 static void SquareCapper(SkPath* path, const SkPoint& pivot, const SkVector& normal,
                          const SkPoint& stop, SkPath* otherPath) {
     SkVector parallel;
     normal.rotateCW(&parallel);
 
     if (otherPath) {
         path->setLastPt(pivot.fX + normal.fX + parallel.fX, pivot.fY + normal.fY + parallel.fY);
         path->lineTo(pivot.fX - normal.fX + parallel.fX, pivot.fY - normal.fY + parallel.fY);
@@ skipping 184 matching lines @@
 }
 
 SkStrokerPriv::JoinProc SkStrokerPriv::JoinFactory(SkPaint::Join join) {
     const SkStrokerPriv::JoinProc gJoiners[] = {
         MiterJoiner, RoundJoiner, BluntJoiner
     };
 
     SkASSERT((unsigned)join < SkPaint::kJoinCount);
     return gJoiners[join];
 }