Add svg path arcto

include/core/SkPath.h

 /*
  * 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.
  */
 
 #ifndef SkPath_DEFINED
 #define SkPath_DEFINED
 
@@ skipping 481 matching lines @@
      */
     void arcTo(SkScalar x1, SkScalar y1, SkScalar x2, SkScalar y2, SkScalar radius);
 
     /** Append a line and arc to the current path. This is the same as the
         PostScript call "arct".
     */
     void arcTo(const SkPoint p1, const SkPoint p2, SkScalar radius) {
         this->arcTo(p1.fX, p1.fY, p2.fX, p2.fY, radius);
     }
 
+    /**
+     *  Append an elliptical arc from the current point in the format used by SVG.
+     *  The center of the ellipse is computed to satisfy the constraints below.
+     *
+     *  @param rx,ry The radii in the x and y directions respectively.
+     *  @param xAxisRotate The angle in degrees relative to the x-axis.
+     *  @param largeArc Determines whether the smallest (false) or largest (true) arc possible
+     *         is drawn.
+     *  @param sweep Determines if the arc should be swept in an anti-clockwise (false) or

[reed1, 2016/01/22 19:39:53]

Can we use Direction enum for sweep, rather than a bool?

[caryclark, 2016/01/22 22:14:00]

This is a dilemma. Note that Direction assigns 0 to CW and 1 to CCW, while SVG
has decided that a sweep of 0 is CCW and a sweep of 1 is CW. 

We can be consistent and require the caller to 'not' their sweep parameter, but
that sounds like a recipe to get it wrong every time.

What do you think?

[caryclark, 2016/01/23 12:53:34]

Made largeArc and sweep enums (Done.)

+     *         clockwise (true) direction.
+     *  @param x,y The destination coordinates.
+     */
+    void arcTo(SkScalar rx, SkScalar ry, SkScalar xAxisRotate, bool largeArc, bool sweep,
+               SkScalar x, SkScalar y);
+
+    void arcTo(const SkPoint r, SkScalar xAxisRotate, bool largeArc, bool sweep,
+               const SkPoint xy) {
+        this->arcTo(r.fX, r.fY, xAxisRotate, largeArc, sweep, xy.fX, xy.fY);
+    }
+
+    /** Same as arcTo format used by SVG, but the destination coordinate is relative to the
+     *  last point on this contour. If there is no previous point, then a
+     *  moveTo(0,0) is inserted automatically.
+     *
+     *  @param rx,ry The radii in the x and y directions respectively.
+     *  @param xAxisRotate The angle in degrees relative to the x-axis.
+     *  @param largeArc Determines whether the smallest (false) or largest (true) arc possible
+     *         is drawn.
+     *  @param sweep Determines if the arc should be swept in an anti-clockwise (false) or
+     *         clockwise (true) direction.
+     *  @param dx,dy The destination coordinates relative to the last point.
+     */
+    void rArcTo(SkScalar rx, SkScalar ry, SkScalar xAxisRotate, bool largeArc, bool sweep,
+               SkScalar dx, SkScalar dy);
+
     /** Close the current contour. If the current point is not equal to the
         first point of the contour, a line segment is automatically added.
     */
     void close();
 
     enum Direction {
         /** clockwise direction for adding closed contours */
         kCW_Direction,
         /** counter-clockwise direction for adding closed contours */
         kCCW_Direction,
@@ skipping 587 matching lines @@
 
     friend class SkAutoPathBoundsUpdate;
     friend class SkAutoDisableOvalCheck;
     friend class SkAutoDisableDirectionCheck;
     friend class SkBench_AddPathTest; // perf test reversePathTo
     friend class PathTest_Private; // unit test reversePathTo
     friend class ForceIsRRect_Private; // unit test isRRect
 };
 
 #endif