event.go raw

   1  // SPDX-License-Identifier: Unlicense OR MIT
   2  
   3  /*
   4  Package event contains the types for event handling.
   5  
   6  The Queue interface is the protocol for receiving external events.
   7  
   8  For example:
   9  
  10  	var queue event.Queue = ...
  11  
  12  	for _, e := range queue.Events(h) {
  13  		switch e.(type) {
  14  			...
  15  		}
  16  	}
  17  
  18  In general, handlers must be declared before events become
  19  available. Other packages such as pointer and key provide
  20  the means for declaring handlers for specific event types.
  21  
  22  The following example declares a handler ready for key input:
  23  
  24  	import github.com/p9c/p9/pkg/gel/gio/io/key
  25  
  26  	ops := new(op.Ops)
  27  	var h *Handler = ...
  28  	key.InputOp{Tag: h}.Add(ops)
  29  
  30  */
  31  package event
  32  
  33  // Queue maps an event handler key to the events
  34  // available to the handler.
  35  type Queue interface {
  36  	// Events returns the available events for an
  37  	// event handler tag.
  38  	Events(t Tag) []Event
  39  }
  40  
  41  // Tag is the stable identifier for an event handler.
  42  // For a handler h, the tag is typically &h.
  43  type Tag interface{}
  44  
  45  // Event is the marker interface for events.
  46  type Event interface {
  47  	ImplementsEvent()
  48  }
  49