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// SPDX-License-Identifier: Unlicense OR MIT
package clip
import (
"image"
"math"
"gioui.org/f32"
"gioui.org/internal/ops"
"gioui.org/op"
)
// Rect represents the clip area of a pixel-aligned rectangle.
type Rect image.Rectangle
// Op returns the op for the rectangle.
func (r Rect) Op() Op {
return Op{
outline: true,
path: r.Path(),
}
}
// Push the clip operation on the clip stack.
func (r Rect) Push(ops *op.Ops) Stack {
return r.Op().Push(ops)
}
// Path returns the PathSpec for the rectangle.
func (r Rect) Path() PathSpec {
return PathSpec{
shape: ops.Rect,
bounds: image.Rectangle(r),
}
}
// UniformRRect returns an RRect with all corner radii set to the
// provided radius.
func UniformRRect(rect f32.Rectangle, radius float32) RRect {
return RRect{
Rect: rect,
SE: radius,
SW: radius,
NE: radius,
NW: radius,
}
}
// RRect represents the clip area of a rectangle with rounded
// corners.
//
// Specify a square with corner radii equal to half the square size to
// construct a circular clip area.
type RRect struct {
Rect f32.Rectangle
// The corner radii.
SE, SW, NW, NE float32
}
// Op returns the op for the rounded rectangle.
func (rr RRect) Op(ops *op.Ops) Op {
if rr.SE == 0 && rr.SW == 0 && rr.NW == 0 && rr.NE == 0 {
r := image.Rectangle{
Min: image.Point{X: int(rr.Rect.Min.X), Y: int(rr.Rect.Min.Y)},
Max: image.Point{X: int(rr.Rect.Max.X), Y: int(rr.Rect.Max.Y)},
}
// Only use Rect if rr is pixel-aligned, as Rect is guaranteed to be.
if fPt(r.Min) == rr.Rect.Min && fPt(r.Max) == rr.Rect.Max {
return Rect(r).Op()
}
}
return Outline{Path: rr.Path(ops)}.Op()
}
// Push the rectangle clip on the clip stack.
func (rr RRect) Push(ops *op.Ops) Stack {
return rr.Op(ops).Push(ops)
}
// Path returns the PathSpec for the rounded rectangle.
func (rr RRect) Path(ops *op.Ops) PathSpec {
var p Path
p.Begin(ops)
// 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()
}
// Ellipse represents the largest axis-aligned ellipse that
// is contained in its bounds.
type Ellipse f32.Rectangle
// Op returns the op for the filled ellipse.
func (e Ellipse) Op(ops *op.Ops) Op {
return Outline{Path: e.Path(ops)}.Op()
}
// Push the filled ellipse clip op on the clip stack.
func (e Ellipse) Push(ops *op.Ops) Stack {
return e.Op(ops).Push(ops)
}
// Path constructs a path for the ellipse.
func (e Ellipse) Path(o *op.Ops) PathSpec {
bounds := f32.Rectangle(e)
if bounds.Dx() == 0 || bounds.Dy() == 0 {
return PathSpec{shape: ops.Rect}
}
var p Path
p.Begin(o)
center := bounds.Max.Add(bounds.Min).Mul(.5)
diam := bounds.Dx()
r := diam * .5
// We'll model the ellipse as a circle scaled in the Y
// direction.
scale := bounds.Dy() / diam
// https://pomax.github.io/bezierinfo/#circles_cubic.
const q = 4 * (math.Sqrt2 - 1) / 3
curve := r * q
top := f32.Point{X: center.X, Y: center.Y - r*scale}
p.MoveTo(top)
p.CubeTo(
f32.Point{X: center.X + curve, Y: center.Y - r*scale},
f32.Point{X: center.X + r, Y: center.Y - curve*scale},
f32.Point{X: center.X + r, Y: center.Y},
)
p.CubeTo(
f32.Point{X: center.X + r, Y: center.Y + curve*scale},
f32.Point{X: center.X + curve, Y: center.Y + r*scale},
f32.Point{X: center.X, Y: center.Y + r*scale},
)
p.CubeTo(
f32.Point{X: center.X - curve, Y: center.Y + r*scale},
f32.Point{X: center.X - r, Y: center.Y + curve*scale},
f32.Point{X: center.X - r, Y: center.Y},
)
p.CubeTo(
f32.Point{X: center.X - r, Y: center.Y - curve*scale},
f32.Point{X: center.X - curve, Y: center.Y - r*scale},
top,
)
ellipse := p.End()
ellipse.shape = ops.Ellipse
return ellipse
}
func fPt(p image.Point) f32.Point {
return f32.Point{
X: float32(p.X), Y: float32(p.Y),
}
}
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