forked from joejulian/gio
Egon Elbre
21ef492cc9
color.RGBA has two problems with regards to using it. First the color values need to be premultiplied, whereas most APIs have non-premultiplied values. This is mainly to preserve color components with low alpha values. Second there are two ways to premultiply with sRGB. One is to premultiply after sRGB conversion, the other is before. This makes using the API more confusing. Using color.NRGBA in sRGB makes it align with CSS.e Signed-off-by: Egon Elbre <egonelbre@gmail.com>
82 lines
1.6 KiB
Go
82 lines
1.6 KiB
Go
// SPDX-License-Identifier: Unlicense OR MIT
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package material
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import (
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"image"
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"image/color"
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"math"
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"time"
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"gioui.org/f32"
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"gioui.org/layout"
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"gioui.org/op"
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"gioui.org/op/clip"
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"gioui.org/op/paint"
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"gioui.org/unit"
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)
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type LoaderStyle struct {
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Color color.NRGBA
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}
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func Loader(th *Theme) LoaderStyle {
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return LoaderStyle{
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Color: th.Color.Primary,
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}
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}
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func (l LoaderStyle) Layout(gtx layout.Context) layout.Dimensions {
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diam := gtx.Constraints.Min.X
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if minY := gtx.Constraints.Min.Y; minY > diam {
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diam = minY
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}
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if diam == 0 {
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diam = gtx.Px(unit.Dp(24))
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}
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sz := gtx.Constraints.Constrain(image.Pt(diam, diam))
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radius := float64(sz.X) * .5
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defer op.Push(gtx.Ops).Pop()
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op.Offset(f32.Pt(float32(radius), float32(radius))).Add(gtx.Ops)
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dt := (time.Duration(gtx.Now.UnixNano()) % (time.Second)).Seconds()
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startAngle := dt * math.Pi * 2
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endAngle := startAngle + math.Pi*1.5
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clipLoader(gtx.Ops, startAngle, endAngle, radius)
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paint.ColorOp{
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Color: l.Color,
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}.Add(gtx.Ops)
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op.Offset(f32.Pt(-float32(radius), -float32(radius))).Add(gtx.Ops)
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paint.PaintOp{}.Add(gtx.Ops)
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op.InvalidateOp{}.Add(gtx.Ops)
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return layout.Dimensions{
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Size: sz,
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}
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}
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func clipLoader(ops *op.Ops, startAngle, endAngle, radius float64) {
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const thickness = .25
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var (
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width = float32(radius * thickness)
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delta = float32(endAngle - startAngle)
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vy, vx = math.Sincos(startAngle)
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pen = f32.Pt(float32(vx), float32(vy)).Mul(float32(radius))
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center = f32.Pt(0, 0).Sub(pen)
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style = clip.StrokeStyle{
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Cap: clip.FlatCap,
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}
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p clip.Path
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)
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p.Begin(ops)
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p.Move(pen)
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p.Arc(center, center, delta)
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p.Stroke(width, style).Add(ops)
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}
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