From dd57f5c1f5daf4da4d6f8e21fc51e15d99e4d838 Mon Sep 17 00:00:00 2001
From: Sebastien Binet <binet@cern.ch>
Date: Wed, 26 Apr 2023 16:54:12 +0200
Subject: [PATCH] stroke: add ArcTo

Signed-off-by: Sebastien Binet <binet@cern.ch>
---
 stroke/clip_test.go                |  28 ++++++++++++++++++++++++++++
 stroke/refs/TestStrokedPathArc.png | Bin 0 -> 2165 bytes
 stroke/stroke.go                   |  14 ++++++++++++++
 3 files changed, 42 insertions(+)
 create mode 100644 stroke/refs/TestStrokedPathArc.png

diff --git a/stroke/clip_test.go b/stroke/clip_test.go
index 6277941..9ce6abb 100644
--- a/stroke/clip_test.go
+++ b/stroke/clip_test.go
@@ -327,6 +327,34 @@ func TestStrokedPathBalloon(t *testing.T) {
 	})
 }
 
+func TestStrokedPathArc(t *testing.T) {
+	run(t, func(o *op.Ops) {
+		p := Path{
+			Segments: []Segment{
+				MoveTo(f32.Pt(0, 65)),
+				LineTo(f32.Pt(20, 65)),
+				ArcTo(f32.Pt(70, 65), +math.Pi/3),
+				LineTo(f32.Pt(70, 65)),
+				LineTo(f32.Pt(20, 65)),
+				ArcTo(f32.Pt(70, 65), -math.Pi/2),
+				LineTo(f32.Pt(70, 65)),
+			},
+		}
+		cl := Stroke{
+			Path:  p,
+			Width: 2.83,
+			Cap:   RoundCap,
+			Join:  RoundJoin,
+		}.Op(o).Push(o)
+		paint.Fill(o, red)
+		cl.Pop()
+	}, func(r result) {
+		r.expect(0, 0, transparent)
+		r.expect(70, 65, colornames.Red)
+		r.expect(35, 65, colornames.Red)
+	})
+}
+
 var fruit = Path{
 	Segments: []Segment{
 		MoveTo(f32.Pt(10, 50)),
diff --git a/stroke/refs/TestStrokedPathArc.png b/stroke/refs/TestStrokedPathArc.png
new file mode 100644
index 0000000000000000000000000000000000000000..e1a64034873896c44251896b942ac6cbbc767b4a
GIT binary patch
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diff --git a/stroke/stroke.go b/stroke/stroke.go
index 9902359..59c870e 100644
--- a/stroke/stroke.go
+++ b/stroke/stroke.go
@@ -48,6 +48,7 @@ const (
 	segOpLineTo
 	segOpQuadTo
 	segOpCubeTo
+	segOpArcTo
 )
 
 // StrokeCap describes the head or tail of a stroked path.
@@ -124,6 +125,15 @@ func CubeTo(ctrl0, ctrl1, end f32.Point) Segment {
 	return s
 }
 
+func ArcTo(center f32.Point, angle float32) Segment {
+	s := Segment{
+		op: segOpArcTo,
+	}
+	s.args[0] = center
+	s.args[1].X = angle
+	return s
+}
+
 // Op returns a clip operation that approximates stroke.
 func (s Stroke) Op(ops *op.Ops) clip.Op {
 	if len(s.Path.Segments) == 0 {
@@ -152,6 +162,10 @@ func (s Stroke) Op(ops *op.Ops) clip.Op {
 		case segOpCubeTo:
 			contour = append(contour, stroke.Segment{stroke.Point(pen), stroke.Point(seg.args[0]), stroke.Point(seg.args[1]), stroke.Point(seg.args[2])})
 			pen = seg.args[2]
+		case segOpArcTo:
+			out := stroke.ArcSegment(stroke.Point(pen), stroke.Point(seg.args[0]), seg.args[1].X)
+			contour = append(contour, out)
+			pen = f32.Point(out.End)
 		}
 	}
 	if len(contour) > 0 {
-- 
2.45.2