mirror of
https://git.sr.ht/~eliasnaur/gio
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Elias Naur
3af01a3f43
Change the definition of Widget from the implicit
type Widget func()
to the explicit functional
type Widget func(gtx layout.Context) layout.Dimensions
The advantages are numerous:
- Clearer connection between the incoming context and the output dimensions.
- Returning the Dimensions are impossible to omit.
- Contexts passed by value, so its fields can be exported
and freely mutated by the program.
The only disadvantage is the longer function literals and the many "returns".
What tipped the scales in favour of the explicit Widget variant is that type
aliases can dramatically shorten the literals:
type (
C = layout.Context
D = layout.Dimensions
)
widget := func(gtx C) D {
...
}
Note that the aliases are not part of the Gio API and it is up to each user
whether they want to use them.
Finally the Go proposal for lightweight function literals,
https://github.com/golang/go/issues/21498, may remove the disadvantage
completely in future.
Context becomes a plain struct with only public fields, and its Reset is
replaced by a NewContext convenience constructor.
Signed-off-by: Elias Naur <mail@eliasnaur.com>
88 lines
2.0 KiB
Go
88 lines
2.0 KiB
Go
// SPDX-License-Identifier: Unlicense OR MIT
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package widget
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import (
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"image"
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"time"
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"gioui.org/f32"
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"gioui.org/gesture"
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"gioui.org/io/pointer"
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"gioui.org/layout"
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"gioui.org/op"
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)
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// Clickable represents a clickable area.
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type Clickable struct {
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click gesture.Click
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// clicks tracks the number of unreported clicks.
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clicks int
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history []Click
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}
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// Click represents a past click.
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type Click struct {
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Position f32.Point
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Time time.Time
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}
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// Clicked calls Update and reports whether the button was
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// clicked since the last call. Multiple clicks result in Clicked
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// returning true once per click.
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func (b *Clickable) Clicked(gtx layout.Context) bool {
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b.Update(gtx)
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if b.clicks > 0 {
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b.clicks--
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if b.clicks > 0 {
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// Ensure timely delivery of remaining clicks.
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op.InvalidateOp{}.Add(gtx.Ops)
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}
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return true
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}
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return false
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}
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// History is the past clicks useful for drawing click markers.
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// Clicks are retained for a short duration (about a second).
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func (b *Clickable) History() []Click {
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return b.history
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}
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func (b *Clickable) Layout(gtx layout.Context) layout.Dimensions {
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// Flush clicks from before the previous frame.
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b.Update(gtx)
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var st op.StackOp
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st.Push(gtx.Ops)
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pointer.Rect(image.Rectangle{Max: gtx.Constraints.Min}).Add(gtx.Ops)
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b.click.Add(gtx.Ops)
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st.Pop()
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for len(b.history) > 0 {
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c := b.history[0]
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if gtx.Now().Sub(c.Time) < 1*time.Second {
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break
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}
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n := copy(b.history, b.history[1:])
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b.history = b.history[:n]
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}
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return layout.Dimensions{Size: gtx.Constraints.Min}
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}
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// Update the button state by processing events. The underlying
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// gesture events are returned for use beyond what Clicked offers.
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func (b *Clickable) Update(gtx layout.Context) []gesture.ClickEvent {
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evts := b.click.Events(gtx)
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for _, e := range evts {
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switch e.Type {
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case gesture.TypeClick:
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b.clicks++
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case gesture.TypePress:
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b.history = append(b.history, Click{
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Position: e.Position,
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Time: gtx.Now(),
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})
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}
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}
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return evts
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}
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