mirror of
https://git.sr.ht/~eliasnaur/gio
synced 2026-07-01 15:45:38 +00:00
Elias Naur
ce9bcee62b
Context keeps the current Constraints and Dimensions so the layout
function scopes don't have to.
With
ctx := new(layout.Context)
a label with margins and alignment goes from
return al.Layout(ops, cs, func(cs layout.Constraints) layout.Dimensions {
in := layout.Inset{...}
return in.Layout(c, ops, cs, func(cs layout.Constraints) layout.Dimensions {
return text.Label{...}.Layout(ops, cs)
})
})
to
al.Layout(ops, ctx, func() {
in := layout.Inset{...}
in.Layout(c, ops, ctx, func() {
text.Label{...}.Layout(ops, ctx)
})
})
It was a difficult trade-off between the verbose functional approach
and the shorter but more complex Context.
Signed-off-by: Elias Naur <mail@eliasnaur.com>
55 lines
1.3 KiB
Go
55 lines
1.3 KiB
Go
// SPDX-License-Identifier: Unlicense OR MIT
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// Package widget implements common widgets.
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package widget
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import (
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"image"
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"gioui.org/ui"
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"gioui.org/ui/f32"
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"gioui.org/ui/layout"
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"gioui.org/ui/paint"
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)
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// Image is a widget that displays an image.
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type Image struct {
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// Src is the image to display.
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Src image.Image
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// Rect is the source rectangle.
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Rect image.Rectangle
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// Scale is the ratio of image pixels to
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// device pixels. If zero, a scale that
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// makes the image appear at approximately
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// 72 DPI is used.
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Scale float32
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}
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func (im Image) Layout(c ui.Config, ops *ui.Ops, ctx *layout.Context) {
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size := im.Src.Bounds()
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wf, hf := float32(size.Dx()), float32(size.Dy())
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var w, h int
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if im.Scale == 0 {
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const dpPrPx = 160 / 72
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w, h = c.Px(ui.Dp(wf*dpPrPx)), c.Px(ui.Dp(hf*dpPrPx))
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} else {
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w, h = int(wf*im.Scale+.5), int(hf*im.Scale+.5)
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}
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cs := ctx.Constraints
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d := image.Point{X: cs.Width.Constrain(w), Y: cs.Height.Constrain(h)}
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aspect := float32(w) / float32(h)
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dw, dh := float32(d.X), float32(d.Y)
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dAspect := dw / dh
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if aspect < dAspect {
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d.X = int(dh*aspect + 0.5)
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} else {
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d.Y = int(dw/aspect + 0.5)
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}
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dr := f32.Rectangle{
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Max: f32.Point{X: float32(d.X), Y: float32(d.Y)},
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}
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paint.ImageOp{Src: im.Src, Rect: im.Rect}.Add(ops)
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paint.PaintOp{Rect: dr}.Add(ops)
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ctx.Dimensions = layout.Dimensions{Size: d, Baseline: d.Y}
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}
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