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op/clip: use absolute coordinates in RRect

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This avoids issues with floating point drift.

Signed-off-by: Egon Elbre <egonelbre@gmail.com>
This commit is contained in:
Egon Elbre
2021-03-13 16:22:20 +02:00
committed by Elias Naur
parent b9f2e0fb41
commit d994d092ae
1 changed files with 40 additions and 31 deletions
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op/clip/shapes.go
+40 -31
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@@ -51,15 +51,44 @@ type RRect struct {
// Op returns the op for the rounded rectangle.
func (rr RRect) Op(ops *op.Ops) Op {
return Outline{Path: rr.path(ops)}.Op()
}
// path returns the path spec for the rounded rectangle.
func (rr RRect) path(ops *op.Ops) PathSpec {
var p Path
p.Begin(ops)
p.Move(rr.Rect.Min)
roundRect(&p, rr.Rect.Size(), rr.SE, rr.SW, rr.NW, rr.NE)
p.Close()
return Outline{
Path: p.End(),
}.Op()
// https://pomax.github.io/bezierinfo/#circles_cubic.
const q = 4 * (math.Sqrt2 - 1) / 3
const iq = 1 - q
se, sw, nw, ne := rr.SE, rr.SW, rr.NW, rr.NE
w, n, e, s := rr.Rect.Min.X, rr.Rect.Min.Y, rr.Rect.Max.X, rr.Rect.Max.Y
p.MoveTo(f32.Point{X: w + nw, Y: n})
p.LineTo(f32.Point{X: e - ne, Y: n}) // N
p.CubeTo( // NE
f32.Point{X: e - ne*iq, Y: n},
f32.Point{X: e, Y: n + ne*iq},
f32.Point{X: e, Y: n + ne})
p.LineTo(f32.Point{X: e, Y: s - se}) // E
p.CubeTo( // SE
f32.Point{X: e, Y: s - se*iq},
f32.Point{X: e - se*iq, Y: s},
f32.Point{X: e - se, Y: s})
p.LineTo(f32.Point{X: w + sw, Y: s}) // S
p.CubeTo( // SW
f32.Point{X: w + sw*iq, Y: s},
f32.Point{X: w, Y: s - sw*iq},
f32.Point{X: w, Y: s - sw})
p.LineTo(f32.Point{X: w, Y: n + nw}) // W
p.CubeTo( // NW
f32.Point{X: w, Y: n + nw*iq},
f32.Point{X: w + nw*iq, Y: n},
f32.Point{X: w + nw, Y: n})
return p.End()
}
// Add the rectangle clip.
@@ -82,14 +111,11 @@ type Border struct {
// stroked line that traces the border rectangle, optionally with rounded
// corners and dashes.
func (b Border) Op(ops *op.Ops) Op {
var p Path
p.Begin(ops)
p.Move(b.Rect.Min)
roundRect(&p, b.Rect.Size(), b.SE, b.SW, b.NW, b.NE)
p.Close()
return Stroke{
Path: p.End(),
Path: RRect{
Rect: b.Rect,
SE: b.SE, SW: b.SW, NW: b.NW, NE: b.NE,
}.path(ops),
Style: StrokeStyle{
Width: b.Width,
},
@@ -122,7 +148,7 @@ func (c Circle) path(ops *op.Ops) PathSpec {
r := c.Radius
// https://pomax.github.io/bezierinfo/#circles_cubic.
const q = 4 * (math.Sqrt2 - 1) / 3 // 4*(sqrt(2)-1)/3
const q = 4 * (math.Sqrt2 - 1) / 3
curve := r * q
top := f32.Point{X: center.X, Y: center.Y - r}
@@ -150,20 +176,3 @@ func (c Circle) path(ops *op.Ops) PathSpec {
)
return p.End()
}
// roundRect adds the outline of a rectangle with rounded corners to a
// path.
func roundRect(p *Path, size f32.Point, se, sw, nw, ne float32) {
// https://pomax.github.io/bezierinfo/#circles_cubic.
w, h := size.X, size.Y
const c = 0.55228475 // 4*(sqrt(2)-1)/3
p.Move(f32.Point{X: w, Y: h - se})
p.Cube(f32.Point{X: 0, Y: se * c}, f32.Point{X: -se + se*c, Y: se}, f32.Point{X: -se, Y: se}) // SE
p.Line(f32.Point{X: sw - w + se, Y: 0})
p.Cube(f32.Point{X: -sw * c, Y: 0}, f32.Point{X: -sw, Y: -sw + sw*c}, f32.Point{X: -sw, Y: -sw}) // SW
p.Line(f32.Point{X: 0, Y: nw - h + sw})
p.Cube(f32.Point{X: 0, Y: -nw * c}, f32.Point{X: nw - nw*c, Y: -nw}, f32.Point{X: nw, Y: -nw}) // NW
p.Line(f32.Point{X: w - ne - nw, Y: 0})
p.Cube(f32.Point{X: ne * c, Y: 0}, f32.Point{X: ne, Y: ne - ne*c}, f32.Point{X: ne, Y: ne}) // NE
p.Line(f32.Point{X: 0, Y: -(ne - h + se)})
}