mirror of
https://git.sr.ht/~eliasnaur/gio
synced 2026-07-01 15:45:38 +00:00
Elias Naur
110 lines
3.3 KiB
Go
110 lines
3.3 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 are registered with SourceOps, data targets with TargetOps.
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// - A data source receives a RequestEvent when a transfer is initiated.
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// It must respond with an OfferOp.
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// - The target receives a DataEvent when transferring to it. It must close
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// the event data 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/internal/ops"
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"gioui.org/io/event"
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"gioui.org/op"
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)
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// SourceOp registers a tag as a data source for a MIME type.
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// Use multiple SourceOps if a tag supports multiple types.
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type SourceOp struct {
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Tag event.Tag
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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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// TargetOp registers a tag as a data target.
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// Use multiple TargetOps if a tag supports multiple types.
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type TargetOp struct {
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Tag event.Tag
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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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// OfferOp is used by data sources as a response to a RequestEvent.
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type OfferOp 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 (op SourceOp) Add(o *op.Ops) {
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data := ops.Write2(&o.Internal, ops.TypeSourceLen, op.Tag, op.Type)
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data[0] = byte(ops.TypeSource)
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}
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func (op TargetOp) Add(o *op.Ops) {
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data := ops.Write2(&o.Internal, ops.TypeTargetLen, op.Tag, op.Type)
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data[0] = byte(ops.TypeTarget)
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}
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// Add the offer to the list of operations.
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// It panics if the Data field is not set.
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func (op OfferOp) Add(o *op.Ops) {
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if op.Data == nil {
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panic("invalid nil data in OfferOp")
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}
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data := ops.Write3(&o.Internal, ops.TypeOfferLen, op.Tag, op.Type, op.Data)
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data[0] = byte(ops.TypeOffer)
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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 OfferOp.
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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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