ui: add package input for merged input

To avoid passing a queue type for each kind of input (pointer, key),
introduce package input for mapping a handler key to all input events.

Future input sources can be added without changes to programs, and
as an added bonus, event ordering is preserved across input sources.

Signed-off-by: Elias Naur <mail@eliasnaur.com>

ui/key/key.go

@@ -16,14 +16,6 @@ type OpHideInput struct{}
 
 type Key interface{}
 
-type Events interface {
-	For(k Key) []Event
-}
-
-type Event interface {
-	isKeyEvent()
-}
-
 type Focus struct {
 	Focus bool
 }
@@ -93,9 +85,9 @@ func (h OpHideInput) Add(o *ui.Ops) {
 	o.Write(data)
 }
 
-func (Edit) ImplementsEvent()  {}
-func (Chord) ImplementsEvent() {}
-func (Focus) ImplementsEvent() {}
-func (Edit) isKeyEvent()       {}
-func (Chord) isKeyEvent()      {}
-func (Focus) isKeyEvent()      {}
+func (Edit) ImplementsEvent()       {}
+func (Chord) ImplementsEvent()      {}
+func (Focus) ImplementsEvent()      {}
+func (Edit) ImplementsInputEvent()  {}
+func (Chord) ImplementsInputEvent() {}
+func (Focus) ImplementsInputEvent() {}