replace arcto quads with a conic

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 "SkCubicClipper.h"
 #include "SkErrorInternals.h"
@@ skipping 1275 matching lines @@
     }
 
     SkScalar cosh = SkPoint::DotProduct(before, after);
     SkScalar sinh = SkPoint::CrossProduct(before, after);
 
     if (SkScalarNearlyZero(sinh)) {   // angle is too tight
         this->lineTo(x1, y1);
         return;
     }
 
-    SkScalar dist = SkScalarMulDiv(radius, SK_Scalar1 - cosh, sinh);
-    if (dist < 0) {
-        dist = -dist;
-    }
+    SkScalar dist = SkScalarAbs(SkScalarMulDiv(radius, SK_Scalar1 - cosh, sinh));
 
     SkScalar xx = x1 - SkScalarMul(dist, before.fX);
     SkScalar yy = y1 - SkScalarMul(dist, before.fY);
+#ifndef SK_SUPPORT_LEGACY_ARCTO
+    after.setLength(dist);
+    this->lineTo(xx, yy);
+    SkScalar weight = SkScalarSqrt(SK_ScalarHalf + cosh * SK_ScalarHalf);
+    this->conicTo(x1, y1, x1 + after.fX, y1 + after.fY, weight);
+#else
     SkRotationDirection arcDir;
 
     // now turn before/after into normals
     if (sinh > 0) {
         before.rotateCCW();
         after.rotateCCW();
         arcDir = kCW_SkRotationDirection;
     } else {
         before.rotateCW();
         after.rotateCW();
         arcDir = kCCW_SkRotationDirection;
     }
 
     SkMatrix    matrix;
     SkPoint     pts[kSkBuildQuadArcStorage];
 
     matrix.setScale(radius, radius);
     matrix.postTranslate(xx - SkScalarMul(radius, before.fX),
                          yy - SkScalarMul(radius, before.fY));
 
     int count = SkBuildQuadArc(before, after, arcDir, &matrix, pts);
 
     this->incReserve(count);
     // [xx,yy] == pts[0]
     this->lineTo(xx, yy);
     for (int i = 1; i < count; i += 2) {
         this->quadTo(pts[i], pts[i+1]);
     }
+#endif
 }
 
 ///////////////////////////////////////////////////////////////////////////////
 
 void SkPath::addPath(const SkPath& path, SkScalar dx, SkScalar dy, AddPathMode mode) {
     SkMatrix matrix;
 
     matrix.setTranslate(dx, dy);
     this->addPath(path, matrix, mode);
 }
@@ skipping 1743 matching lines @@
         }
     } while (!done);
     return SkToBool(tangents.count()) ^ isInverse;
 }
 
 int SkPath::ConvertConicToQuads(const SkPoint& p0, const SkPoint& p1, const SkPoint& p2,
                                 SkScalar w, SkPoint pts[], int pow2) {
     const SkConic conic(p0, p1, p2, w);
     return conic.chopIntoQuadsPOW2(pts, pow2);
 }