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Elias Naur
ef8171b971
Instead of having to supply the predicates for event filtering at the
time of layout, the new Filter type allows widgets to filter at the time
of calling Source.Events. There is then only the need for a single input
op type, in package event.
Filters most importantly allow the use of one tag for several event types,
and we can define that a widget w has &w as its primary tag, by convention.
This allows the replacement of per-widget Focus methods with direct uses
of FocusCmd{&w}, and the later addition of Source.Focused(&w) queries.
Note that the TestCursor test needed restructuring to avoid its use of
InputOps.
Signed-off-by: Elias Naur <mail@eliasnaur.com>
92 lines
3.0 KiB
Go
92 lines
3.0 KiB
Go
// Package transfer contains operations and events for brokering data transfers.
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//
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// The transfer protocol is as follows:
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//
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// - Data sources use [SourceFilter] to receive an [InitiateEvent] when a drag
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// is initiated, and an [RequestEvent] for each initiation of a data transfer.
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// Sources respond to requests with [OfferCmd].
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// - Data targets use [TargetFilter] to receive an [DataEvent] for receiving data.
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// The target must close the data event after use.
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//
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// When a user initiates a pointer-guided drag and drop transfer, the
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// source as well as all potential targets receive an InitiateEvent.
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// Potential targets are targets with at least one MIME type in common
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// with the source. When a drag gesture completes, a CancelEvent is sent
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// to the source and all potential targets.
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//
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// Note that the RequestEvent is sent to the source upon drop.
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package transfer
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import (
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"io"
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"gioui.org/io/event"
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)
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// OfferCmd is used by data sources as a response to a RequestEvent.
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type OfferCmd struct {
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Tag event.Tag
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// Type is the MIME type of Data.
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// It must be the Type from the corresponding RequestEvent.
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Type string
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// Data contains the offered data. It is closed when the
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// transfer is complete or cancelled.
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// Data must be kept valid until closed, and it may be used from
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// a goroutine separate from the one processing the frame.
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Data io.ReadCloser
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}
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func (OfferCmd) ImplementsCommand() {}
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// SourceFilter filters for any [RequestEvent] that match a MIME type
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// as well as [InitiateEvent] and [CancelEvent].
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// Use multiple filters to offer multiple types.
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type SourceFilter struct {
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// Type is the MIME type supported by this source.
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Type string
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}
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// TargetFilter filters for any [DataEvent] whose type matches a MIME type
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// as well as [CancelEvent]. Use multiple filters to accept multiple types.
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type TargetFilter struct {
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// Type is the MIME type accepted by this target.
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Type string
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}
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// RequestEvent requests data from a data source. The source must
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// respond with an OfferCmd.
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type RequestEvent struct {
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// Type is the first matched type between the source and the target.
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Type string
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}
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func (RequestEvent) ImplementsEvent() {}
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// InitiateEvent is sent to a data source when a drag-and-drop
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// transfer gesture is initiated.
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//
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// Potential data targets also receive the event.
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type InitiateEvent struct{}
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func (InitiateEvent) ImplementsEvent() {}
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// CancelEvent is sent to data sources and targets to cancel the
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// effects of an InitiateEvent.
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type CancelEvent struct{}
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func (CancelEvent) ImplementsEvent() {}
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// DataEvent is sent to the target receiving the transfer.
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type DataEvent struct {
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// Type is the MIME type of Data.
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Type string
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// Open returns the transfer data. It is only valid to call Open in the frame
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// the DataEvent is received. The caller must close the return value after use.
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Open func() io.ReadCloser
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}
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func (DataEvent) ImplementsEvent() {}
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func (SourceFilter) ImplementsFilter() {}
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func (TargetFilter) ImplementsFilter() {}
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