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gpu,op/clip: implement stroked paths with round joins

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Signed-off-by: Sebastien Binet <s@sbinet.org>
This commit is contained in:
Sebastien Binet
2020-11-11 12:57:17 +00:00
committed by Elias Naur
parent f3f32ed7aa
commit 700cec440e
7 changed files with 90 additions and 9 deletions
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gpu/gpu.go
+2 -1
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@@ -162,7 +162,8 @@ func (op *clipOp) decode(data []byte) {
bounds: layout.FRect(r),
width: math.Float32frombits(bo.Uint32(data[17:])),
style: clip.StrokeStyle{
Cap: clip.StrokeCap(data[21]),
Cap: clip.StrokeCap(data[21]),
Join: clip.StrokeJoin(data[22]),
},
}
}
gpu/stroke.go
+38 -2
View File
@@ -51,7 +51,7 @@ func (qs *strokeQuads) pen() f32.Point {
}
func (qs *strokeQuads) lineTo(pt f32.Point) {
end := (*qs)[len(*qs)-1].quad.To
end := qs.pen()
*qs = append(*qs, strokeQuad{
quad: ops.Quad{
From: end,
@@ -273,6 +273,13 @@ func strokePathNorm(p0, p1, p2 f32.Point, t, d float32) f32.Point {
func rot90CW(p f32.Point) f32.Point { return f32.Pt(+p.Y, -p.X) }
func rot90CCW(p f32.Point) f32.Point { return f32.Pt(-p.Y, +p.X) }
// cosPt returns the cosine of the opening angle between p and q.
func cosPt(p, q f32.Point) float32 {
np := math.Hypot(float64(p.X), float64(p.Y))
nq := math.Hypot(float64(q.X), float64(q.Y))
return dotPt(p, q) / float32(np*nq)
}
func normPt(p f32.Point, l float32) f32.Point {
d := math.Hypot(float64(p.X), float64(p.Y))
l64 := float64(l)
@@ -416,7 +423,14 @@ func quadBezierSplit(p0, p1, p2 f32.Point, t float32) (f32.Point, f32.Point, f32
// strokePathJoin joins the two paths rhs and lhs, according to the provided
// stroke style sty.
func strokePathJoin(sty clip.StrokeStyle, rhs, lhs *strokeQuads, hw float32, pivot, n0, n1 f32.Point, r0, r1 float32) {
strokePathBevelJoin(rhs, lhs, hw, pivot, n0, n1, r0, r1)
switch sty.Join {
case clip.BevelJoin:
strokePathBevelJoin(rhs, lhs, hw, pivot, n0, n1, r0, r1)
case clip.RoundJoin:
strokePathRoundJoin(rhs, lhs, hw, pivot, n0, n1, r0, r1)
default:
panic("impossible")
}
}
func strokePathBevelJoin(rhs, lhs *strokeQuads, hw float32, pivot, n0, n1 f32.Point, r0, r1 float32) {
@@ -428,6 +442,28 @@ func strokePathBevelJoin(rhs, lhs *strokeQuads, hw float32, pivot, n0, n1 f32.Po
lhs.lineTo(lp)
}
func strokePathRoundJoin(rhs, lhs *strokeQuads, hw float32, pivot, n0, n1 f32.Point, r0, r1 float32) {
rp := pivot.Add(n1)
lp := pivot.Sub(n1)
cw := dotPt(rot90CW(n0), n1) >= 0.0
switch {
case cw:
// Path bends to the right, ie. CW (or 180 degree turn).
c := pivot.Sub(lhs.pen())
angle := -math.Acos(float64(cosPt(n0, n1)))
lhs.arc(c, c, float32(angle))
lhs.lineTo(lp) // Add a line to accomodate for rounding errors.
rhs.lineTo(rp)
default:
// Path bends to the left, ie. CCW.
angle := math.Acos(float64(cosPt(n0, n1)))
c := pivot.Sub(rhs.pen())
rhs.arc(c, c, float32(angle))
rhs.lineTo(rp) // Add a line to accomodate for rounding errors.
lhs.lineTo(lp)
}
}
// strokePathCap caps the provided path qs, according to the provided stroke style sty.
func strokePathCap(sty clip.StrokeStyle, qs *strokeQuads, hw float32, pivot, n0 f32.Point) {
switch sty.Cap {