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Elias Naur
d572aa23ac
The pixel-aligned Rect is more efficient and easier to use in the common case of layout clipping. Signed-off-by: Elias Naur <mail@eliasnaur.com>
52 lines
1.5 KiB
Go
52 lines
1.5 KiB
Go
// SPDX-License-Identifier: Unlicense OR MIT
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package clip
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import (
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"gioui.org/f32"
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"gioui.org/op"
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)
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// RRect represents the clip area of a rectangle with rounded
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// corners.
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//
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// Specify a square with corner radii equal to half the square size to
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// construct a circular clip area.
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type RRect struct {
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Rect f32.Rectangle
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// The corner radii.
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SE, SW, NW, NE float32
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}
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// op returns the op for the rectangle.
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func (rr RRect) op(ops *op.Ops) Op {
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return roundRect(ops, rr.Rect, rr.SE, rr.SW, rr.NW, rr.NE)
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}
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// Add the rectangle clip.
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func (rr RRect) Add(ops *op.Ops) {
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rr.op(ops).Add(ops)
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}
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// roundRect returns the clip area of a rectangle with rounded
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// corners defined by their radii.
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func roundRect(ops *op.Ops, r f32.Rectangle, se, sw, nw, ne float32) Op {
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size := r.Size()
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// https://pomax.github.io/bezierinfo/#circles_cubic.
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w, h := float32(size.X), float32(size.Y)
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const c = 0.55228475 // 4*(sqrt(2)-1)/3
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var p Path
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p.Begin(ops)
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p.Move(r.Min)
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p.Move(f32.Point{X: w, Y: h - se})
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p.Cube(f32.Point{X: 0, Y: se * c}, f32.Point{X: -se + se*c, Y: se}, f32.Point{X: -se, Y: se}) // SE
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p.Line(f32.Point{X: sw - w + se, Y: 0})
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p.Cube(f32.Point{X: -sw * c, Y: 0}, f32.Point{X: -sw, Y: -sw + sw*c}, f32.Point{X: -sw, Y: -sw}) // SW
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p.Line(f32.Point{X: 0, Y: nw - h + sw})
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p.Cube(f32.Point{X: 0, Y: -nw * c}, f32.Point{X: nw - nw*c, Y: -nw}, f32.Point{X: nw, Y: -nw}) // NW
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p.Line(f32.Point{X: w - ne - nw, Y: 0})
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p.Cube(f32.Point{X: ne * c, Y: 0}, f32.Point{X: ne, Y: ne - ne*c}, f32.Point{X: ne, Y: ne}) // NE
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return p.End()
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}
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