forked from joejulian/gio
Elias Naur
75314fcee2
With the introduction of filters, it is now possible to have one tag per widget by convention. Note that gestures still have their own tags, for disambiguation. Signed-off-by: Elias Naur <mail@eliasnaur.com>
89 lines
1.9 KiB
Go
89 lines
1.9 KiB
Go
package widget
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import (
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"io"
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"gioui.org/f32"
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"gioui.org/gesture"
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"gioui.org/io/event"
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"gioui.org/io/pointer"
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"gioui.org/io/transfer"
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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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)
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// Draggable makes a widget draggable.
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type Draggable struct {
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// Type contains the MIME type and matches transfer.SourceOp.
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Type string
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drag gesture.Drag
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click f32.Point
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pos f32.Point
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}
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func (d *Draggable) Layout(gtx layout.Context, w, drag layout.Widget) layout.Dimensions {
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if !gtx.Enabled() {
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return w(gtx)
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}
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dims := w(gtx)
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stack := clip.Rect{Max: dims.Size}.Push(gtx.Ops)
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d.drag.Add(gtx.Ops)
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event.InputOp(gtx.Ops, d)
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stack.Pop()
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if drag != nil && d.drag.Pressed() {
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rec := op.Record(gtx.Ops)
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op.Offset(d.pos.Round()).Add(gtx.Ops)
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drag(gtx)
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op.Defer(gtx.Ops, rec.Stop())
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}
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return dims
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}
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// Dragging returns whether d is being dragged.
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func (d *Draggable) Dragging() bool {
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return d.drag.Dragging()
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}
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// Update the draggable and returns the MIME type for which the Draggable was
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// requested to offer data, if any
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func (d *Draggable) Update(gtx layout.Context) (mime string, requested bool) {
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pos := d.pos
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for _, ev := range d.drag.Update(gtx.Metric, gtx.Source, gesture.Both) {
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switch ev.Kind {
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case pointer.Press:
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d.click = ev.Position
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pos = f32.Point{}
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case pointer.Drag, pointer.Release:
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pos = ev.Position.Sub(d.click)
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}
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}
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d.pos = pos
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for {
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e, ok := gtx.Event(d, transfer.SourceFilter{Type: d.Type})
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if !ok {
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break
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}
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if e, ok := e.(transfer.RequestEvent); ok {
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return e.Type, true
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}
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}
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return "", false
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}
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// Offer the data ready for a drop. Must be called after being Requested.
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// The mime must be one in the requested list.
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func (d *Draggable) Offer(gtx layout.Context, mime string, data io.ReadCloser) {
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gtx.Execute(transfer.OfferCmd{Tag: d, Type: mime, Data: data})
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}
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// Pos returns the drag position relative to its initial click position.
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func (d *Draggable) Pos() f32.Point {
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return d.pos
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}
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