Files
gio/widget/material/progressbar.go
T
Egon Elbre 21ef492cc9 all: use color.NRGBA in public API
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>
2020-11-19 11:30:11 +01:00

73 lines
1.6 KiB
Go

// SPDX-License-Identifier: Unlicense OR MIT
package material
import (
"image"
"image/color"
"gioui.org/f32"
"gioui.org/internal/f32color"
"gioui.org/layout"
"gioui.org/op/clip"
"gioui.org/op/paint"
"gioui.org/unit"
)
type ProgressBarStyle struct {
Color color.NRGBA
Progress int
}
func ProgressBar(th *Theme, progress int) ProgressBarStyle {
return ProgressBarStyle{
Progress: progress,
Color: th.Color.Primary,
}
}
func (p ProgressBarStyle) Layout(gtx layout.Context) layout.Dimensions {
shader := func(width float32, color color.NRGBA) layout.Dimensions {
maxHeight := unit.Dp(4)
rr := float32(gtx.Px(unit.Dp(2)))
d := image.Point{X: int(width), Y: gtx.Px(maxHeight)}
clip.RRect{
Rect: f32.Rectangle{Max: f32.Point{X: width, Y: float32(gtx.Px(maxHeight))}},
NE: rr, NW: rr, SE: rr, SW: rr,
}.Add(gtx.Ops)
paint.ColorOp{Color: color}.Add(gtx.Ops)
paint.PaintOp{}.Add(gtx.Ops)
return layout.Dimensions{Size: d}
}
progress := p.Progress
if progress > 100 {
progress = 100
} else if progress < 0 {
progress = 0
}
progressBarWidth := float32(gtx.Constraints.Max.X)
return layout.Stack{Alignment: layout.W}.Layout(gtx,
layout.Stacked(func(gtx layout.Context) layout.Dimensions {
// Use a transparent equivalent of progress color.
bgCol := f32color.MulAlpha(p.Color, 150)
return shader(progressBarWidth, bgCol)
}),
layout.Stacked(func(gtx layout.Context) layout.Dimensions {
fillWidth := (progressBarWidth / 100) * float32(progress)
fillColor := p.Color
if gtx.Queue == nil {
fillColor = f32color.MulAlpha(fillColor, 200)
}
return shader(fillWidth, fillColor)
}),
)
}