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>
111 lines
2.4 KiB
Go
111 lines
2.4 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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"gioui.org/f32"
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"gioui.org/internal/f32color"
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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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"gioui.org/widget"
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)
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// Slider is for selecting a value in a range.
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func Slider(th *Theme, float *widget.Float, min, max float32) SliderStyle {
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return SliderStyle{
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Min: min,
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Max: max,
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Color: th.Color.Primary,
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Float: float,
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}
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}
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type SliderStyle struct {
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Min, Max float32
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Color color.NRGBA
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Float *widget.Float
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}
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func (s SliderStyle) Layout(gtx layout.Context) layout.Dimensions {
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thumbRadiusInt := gtx.Px(unit.Dp(6))
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trackWidth := float32(gtx.Px(unit.Dp(2)))
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thumbRadius := float32(thumbRadiusInt)
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halfWidthInt := 2 * thumbRadiusInt
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halfWidth := float32(halfWidthInt)
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size := gtx.Constraints.Min
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// Keep a minimum length so that the track is always visible.
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minLength := halfWidthInt + 3*thumbRadiusInt + halfWidthInt
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if size.X < minLength {
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size.X = minLength
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}
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size.Y = 2 * halfWidthInt
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st := op.Push(gtx.Ops)
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op.Offset(f32.Pt(halfWidth, 0)).Add(gtx.Ops)
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gtx.Constraints.Min = image.Pt(size.X-2*halfWidthInt, size.Y)
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s.Float.Layout(gtx, halfWidthInt, s.Min, s.Max)
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thumbPos := halfWidth + s.Float.Pos()
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st.Pop()
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color := s.Color
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if gtx.Queue == nil {
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color = f32color.MulAlpha(color, 150)
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}
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// Draw track before thumb.
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st = op.Push(gtx.Ops)
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track := f32.Rectangle{
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Min: f32.Point{
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X: halfWidth,
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Y: halfWidth - trackWidth/2,
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},
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Max: f32.Point{
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X: thumbPos,
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Y: halfWidth + trackWidth/2,
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},
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}
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clip.RRect{Rect: track}.Add(gtx.Ops)
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paint.ColorOp{Color: color}.Add(gtx.Ops)
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paint.PaintOp{}.Add(gtx.Ops)
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st.Pop()
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// Draw track after thumb.
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st = op.Push(gtx.Ops)
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track.Min.X = thumbPos
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track.Max.X = float32(size.X) - halfWidth
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clip.RRect{Rect: track}.Add(gtx.Ops)
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paint.ColorOp{Color: f32color.MulAlpha(color, 96)}.Add(gtx.Ops)
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paint.PaintOp{}.Add(gtx.Ops)
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st.Pop()
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// Draw thumb.
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st = op.Push(gtx.Ops)
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thumb := f32.Rectangle{
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Min: f32.Point{
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X: thumbPos - thumbRadius,
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Y: halfWidth - thumbRadius,
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},
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Max: f32.Point{
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X: thumbPos + thumbRadius,
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Y: halfWidth + thumbRadius,
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},
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}
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rr := thumbRadius
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clip.RRect{
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Rect: thumb,
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NE: rr, NW: rr, SE: rr, SW: rr,
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}.Add(gtx.Ops)
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paint.ColorOp{Color: color}.Add(gtx.Ops)
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paint.PaintOp{}.Add(gtx.Ops)
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st.Pop()
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return layout.Dimensions{Size: size}
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}
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