mirror of
https://git.sr.ht/~eliasnaur/gio
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Elias Naur
101 lines
2.9 KiB
Go
101 lines
2.9 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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var p Path
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p.Begin(ops)
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p.Move(rr.Rect.Min)
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roundRect(&p, rr.Rect.Size(), rr.SE, rr.SW, rr.NW, rr.NE)
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return p.End()
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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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// Border represents the clip area of a rectangular border.
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type Border struct {
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// Rect is the bounds of the border.
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Rect f32.Rectangle
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Width float32
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// The corner radii.
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SE, SW, NW, NE float32
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}
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func (b Border) op(ops *op.Ops) Op {
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var p Path
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p.Begin(ops)
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w := b.Width
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// Outer outline.
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r := b.Rect
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p.Move(r.Min)
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end := roundRect(&p, r.Size(), b.SE, b.SW, b.NW, b.NE)
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// Inner outline
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r = b.Rect
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r.Min.X += w
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r.Min.Y += w
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r.Max.X -= w
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r.Max.Y -= w
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p.Move(r.Min.Sub(end))
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roundRectRev(&p, r.Size(), b.SE-w, b.SW-w, b.NW-w, b.NE-w)
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return p.End()
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}
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// Add the border clip.
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func (rr Border) Add(ops *op.Ops) {
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rr.op(ops).Add(ops)
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}
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// roundRect adds the outline of a rectangle with rounded corners to a
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// path.
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func roundRect(p *Path, size f32.Point, se, sw, nw, ne float32) f32.Point {
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// https://pomax.github.io/bezierinfo/#circles_cubic.
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w, h := size.X, size.Y
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const c = 0.55228475 // 4*(sqrt(2)-1)/3
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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.pen
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}
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// roundRectRev is like roundRect but counter-clockwise.
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func roundRectRev(p *Path, size f32.Point, se, sw, nw, ne float32) {
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w, h := size.X, size.Y
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const c = 0.55228475
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p.Move(f32.Point{X: 0, Y: h - sw})
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p.Cube(f32.Point{X: 0, Y: sw * c}, f32.Point{X: sw - sw*c, Y: sw}, f32.Point{X: sw, Y: sw}) // SW
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p.Line(f32.Point{X: -se + w - sw, Y: 0})
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p.Cube(f32.Point{X: se * c, Y: 0}, f32.Point{X: se, Y: -se + se*c}, f32.Point{X: se, Y: -se}) // SE
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p.Line(f32.Point{X: 0, Y: ne - h + se})
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p.Cube(f32.Point{X: 0, Y: -ne * c}, f32.Point{X: -ne + ne*c, Y: -ne}, f32.Point{X: -ne, Y: -ne}) // NE
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p.Line(f32.Point{X: -w + ne + nw, Y: 0})
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p.Cube(f32.Point{X: -nw * c, Y: 0}, f32.Point{X: -nw, Y: nw - nw*c}, f32.Point{X: -nw, Y: nw}) // NW
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}
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