op/clip: add absolute Path.ArcTo for completeness

Signed-off-by: Elias Naur <mail@eliasnaur.com>

op/clip/clip.go

@@ -297,14 +297,12 @@ func (p *Path) QuadTo(ctrl, to f32.Point) {
 	p.expand(to)
 }
 
-// Arc adds an elliptical arc to the path. The implied ellipse is defined
+// ArcTo adds an elliptical arc to the path. The implied ellipse is defined
 // by its focus points f1 and f2.
 // The arc starts in the current point and ends angle radians along the ellipse boundary.
 // The sign of angle determines the direction; positive being counter-clockwise,
 // negative clockwise.
-func (p *Path) Arc(f1, f2 f32.Point, angle float32) {
+func (p *Path) ArcTo(f1, f2 f32.Point, angle float32) {
-	f1 = f1.Add(p.pen)
-	f2 = f2.Add(p.pen)
 	const segments = 16
 	m := stroke.ArcTransform(p.pen, f1, f2, angle, segments)
 
@@ -317,6 +315,13 @@ func (p *Path) Arc(f1, f2 f32.Point, angle float32) {
 	}
 }
 
+// Arc is like ArcTo where f1 and f2 are relative to the current position.
+func (p *Path) Arc(f1, f2 f32.Point, angle float32) {
+	f1 = f1.Add(p.pen)
+	f2 = f2.Add(p.pen)
+	p.ArcTo(f1, f2, angle)
+}
+
 // Cube records a cubic Bézier from the pen through
 // two control points ending in to.
 func (p *Path) Cube(ctrl0, ctrl1, to f32.Point) {