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

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Signed-off-by: Sebastien Binet <s@sbinet.org>
This commit is contained in:
Sebastien Binet
2020-11-11 15:05:47 +00:00
committed by Elias Naur
parent 7de8ce51a5
commit 7eb32360e5
8 changed files with 145 additions and 3 deletions
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gpu/stroke.go
+45
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@@ -423,6 +423,10 @@ 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) {
if sty.Miter > 0 {
strokePathMiterJoin(sty, rhs, lhs, hw, pivot, n0, n1, r0, r1)
return
}
switch sty.Join {
case clip.BevelJoin:
strokePathBevelJoin(rhs, lhs, hw, pivot, n0, n1, r0, r1)
@@ -464,6 +468,47 @@ func strokePathRoundJoin(rhs, lhs *strokeQuads, hw float32, pivot, n0, n1 f32.Po
}
}
func strokePathMiterJoin(sty clip.StrokeStyle, rhs, lhs *strokeQuads, hw float32, pivot, n0, n1 f32.Point, r0, r1 float32) {
if n0 == n1.Mul(-1) {
strokePathBevelJoin(rhs, lhs, hw, pivot, n0, n1, r0, r1)
return
}
// This is to handle nearly linear joints that would be clipped otherwise.
limit := math.Max(float64(sty.Miter), 1.001)
cw := dotPt(rot90CW(n0), n1) >= 0.0
if cw {
// hw is used to calculate |R|.
// When running CW, n0 and n1 point the other way,
// so the sign of r0 and r1 is negated.
hw = -hw
}
hw64 := float64(hw)
cos := math.Sqrt(0.5 * (1 + float64(cosPt(n0, n1))))
d := hw64 / cos
if math.Abs(limit*hw64) < math.Abs(d) {
sty.Miter = 0 // Set miter to zero to disable the miter joint.
strokePathJoin(sty, rhs, lhs, hw, pivot, n0, n1, r0, r1)
return
}
mid := pivot.Add(normPt(n0.Add(n1), float32(d)))
rp := pivot.Add(n1)
lp := pivot.Sub(n1)
switch {
case cw:
// Path bends to the right, ie. CW.
lhs.lineTo(mid)
default:
// Path bends to the left, ie. CCW.
rhs.lineTo(mid)
}
rhs.lineTo(rp)
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 {