ui/input: support single stepping through events

Change input.Events interface to return one event at a time until
the queue is empty.

Change text.Editor and gestures to match.

Re-add Editor.Submit while we're here; we don't want to enable
submit mode always.

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

ui/gesture/gestures.go

@@ -83,8 +83,12 @@ func (c *Click) Add(ops *ui.Ops) {
 
 func (c *Click) Update(q input.Events) []ClickEvent {
 	var events []ClickEvent
-	for _, e := range q.For(c) {
+	for {
-		e, ok := e.(pointer.Event)
+		evt, ok := q.Next(c)
+		if !ok {
+			break
+		}
+		e, ok := evt.(pointer.Event)
 		if !ok {
 			continue
 		}
@@ -135,8 +139,12 @@ func (s *Scroll) Update(cfg *ui.Config, q input.Events, axis Axis) int {
 		return 0
 	}
 	total := 0
-	for _, e := range q.For(s) {
+	for {
-		e, ok := e.(pointer.Event)
+		evt, ok := q.Next(s)
+		if !ok {
+			break
+		}
+		e, ok := evt.(pointer.Event)
 		if !ok {
 			continue
 		}

ui/input/input.go

@@ -7,7 +7,7 @@ package input
 // Events maps an event handler key to the events
 // available to the handler.
 type Events interface {
-	For(k Key) []Event
+	Next(k Key) (Event, bool)
 }
 
 // Key is the stable identifier for an event handler. For a handler h, the

ui/input/queue.go

@@ -19,8 +19,14 @@ type Queue struct {
 
 type handlerEvents map[Key][]Event
 
-func (q *Queue) For(k Key) []Event {
+func (q *Queue) Next(k Key) (Event, bool) {
-	return q.handlers[k]
+	events := q.handlers[k]
+	if len(events) == 0 {
+		return nil, false
+	}
+	e := events[0]
+	q.handlers[k] = events[1:]
+	return e, true
 }
 
 func (q *Queue) Frame(ops *ui.Ops) {

ui/text/editor.go

@@ -25,6 +25,7 @@ type Editor struct {
 	Face       Face
 	Alignment  Alignment
 	SingleLine bool
+	Submit     bool
 
 	oldCfg            ui.Config
 	blinkStart        time.Time
@@ -103,7 +104,11 @@ func (e *Editor) Next() (EditorEvent, bool) {
 		}
 	}
 	stop := (sdist > 0 && soff >= smax) || (sdist < 0 && soff <= smin)
-	for _, ke := range e.Inputs.For(e) {
+	for {
+		ke, ok := e.Inputs.Next(e)
+		if !ok {
+			break
+		}
 		e.blinkStart = e.Config.Now
 		switch ke := ke.(type) {
 		case key.Focus:
@@ -112,7 +117,7 @@ func (e *Editor) Next() (EditorEvent, bool) {
 			if !e.focused {
 				break
 			}
-			if ke.Name == key.NameReturn || ke.Name == key.NameEnter {
+			if e.Submit && (ke.Name == key.NameReturn || ke.Name == key.NameEnter) {
 				if !ke.Modifiers.Contain(key.ModShift) {
 					return Submit{}, true
 				}