gioui.org@v0.6.1-0.20240506124620-7a9ce51988ce/io/event/event.go (about)

     1  // SPDX-License-Identifier: Unlicense OR MIT
     2  
     3  // Package event contains types for event handling.
     4  package event
     5  
     6  import (
     7  	"gioui.org/internal/ops"
     8  	"gioui.org/op"
     9  )
    10  
    11  // Tag is the stable identifier for an event handler.
    12  // For a handler h, the tag is typically &h.
    13  type Tag interface{}
    14  
    15  // Event is the marker interface for events.
    16  type Event interface {
    17  	ImplementsEvent()
    18  }
    19  
    20  // Filter represents a filter for [Event] types.
    21  type Filter interface {
    22  	ImplementsFilter()
    23  }
    24  
    25  // Op declares a tag for input routing at the current transformation
    26  // and clip area hierarchy. It panics if tag is nil.
    27  func Op(o *op.Ops, tag Tag) {
    28  	if tag == nil {
    29  		panic("Tag must be non-nil")
    30  	}
    31  	data := ops.Write1(&o.Internal, ops.TypeInputLen, tag)
    32  	data[0] = byte(ops.TypeInput)
    33  }