gesture: report one event at a time

Events are now delivered one at a time, and this change makes the
corresponding change to gestures.

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

gesture/gesture.go

@@ -173,9 +173,8 @@ func (c *Click) Pressed() bool {
 	return c.pressed
 }
 
-// Update state and return the click events.
+// Update state and return the next click events, if any.
-func (c *Click) Update(q input.Source) []ClickEvent {
+func (c *Click) Update(q input.Source) (ClickEvent, bool) {
-	var events []ClickEvent
 	for {
 		evt, ok := q.Event(c, pointer.Filter{Kinds: pointer.Press | pointer.Release | pointer.Enter | pointer.Leave})
 		if !ok {
@@ -192,9 +191,15 @@ func (c *Click) Update(q input.Source) []ClickEvent {
 			}
 			c.pressed = false
 			if !c.entered || c.hovered {
-				events = append(events, ClickEvent{Kind: KindClick, Position: e.Position.Round(), Source: e.Source, Modifiers: e.Modifiers, NumClicks: c.clicks})
+				return ClickEvent{
+					Kind:      KindClick,
+					Position:  e.Position.Round(),
+					Source:    e.Source,
+					Modifiers: e.Modifiers,
+					NumClicks: c.clicks,
+				}, true
 			} else {
-				events = append(events, ClickEvent{Kind: KindCancel})
+				return ClickEvent{Kind: KindCancel}, true
 			}
 		case pointer.Cancel:
 			wasPressed := c.pressed
@@ -202,7 +207,7 @@ func (c *Click) Update(q input.Source) []ClickEvent {
 			c.hovered = false
 			c.entered = false
 			if wasPressed {
-				events = append(events, ClickEvent{Kind: KindCancel})
+				return ClickEvent{Kind: KindCancel}, true
 			}
 		case pointer.Press:
 			if c.pressed {
@@ -224,7 +229,7 @@ func (c *Click) Update(q input.Source) []ClickEvent {
 				c.clicks = 1
 			}
 			c.clickedAt = e.Time
-			events = append(events, ClickEvent{Kind: KindPress, Position: e.Position.Round(), Source: e.Source, Modifiers: e.Modifiers, NumClicks: c.clicks})
+			return ClickEvent{Kind: KindPress, Position: e.Position.Round(), Source: e.Source, Modifiers: e.Modifiers, NumClicks: c.clicks}, true
 		case pointer.Leave:
 			if !c.pressed {
 				c.pid = e.PointerID
@@ -242,7 +247,7 @@ func (c *Click) Update(q input.Source) []ClickEvent {
 			}
 		}
 	}
-	return events
+	return ClickEvent{}, false
 }
 
 func (ClickEvent) ImplementsEvent() {}
@@ -364,9 +369,8 @@ func (d *Drag) Add(ops *op.Ops) {
 	event.InputOp(ops, d)
 }
 
-// Update state and return the drag events.
+// Update state and return the next drag event, if any.
-func (d *Drag) Update(cfg unit.Metric, q input.Source, axis Axis) []pointer.Event {
+func (d *Drag) Update(cfg unit.Metric, q input.Source, axis Axis) (pointer.Event, bool) {
-	var events []pointer.Event
 	for {
 		ev, ok := q.Event(d, pointer.Filter{Kinds: pointer.Press | pointer.Drag | pointer.Release})
 		if !ok {
@@ -416,10 +420,10 @@ func (d *Drag) Update(cfg unit.Metric, q input.Source, axis Axis) []pointer.Even
 			d.dragging = false
 		}
 
-		events = append(events, e)
+		return e, true
 	}
 
-	return events
+	return pointer.Event{}, false
 }
 
 // Dragging reports whether it is currently in use.

gesture/gesture_test.go

@@ -77,8 +77,16 @@ func TestMouseClicks(t *testing.T) {
 			r.Frame(&ops)
 			r.Queue(tc.events...)
 
-			events := click.Update(r.Source())
+			var clicks []ClickEvent
-			clicks := filterMouseClicks(events)
+			for {
+				ev, ok := click.Update(r.Source())
+				if !ok {
+					break
+				}
+				if ev.Kind == KindClick {
+					clicks = append(clicks, ev)
+				}
+			}
 			if got, want := len(clicks), len(tc.clicks); got != want {
 				t.Fatalf("got %d mouse clicks, expected %d", got, want)
 			}
@@ -108,13 +116,3 @@ func mouseClickEvents(times ...time.Duration) []event.Event {
 	}
 	return events
 }
-
-func filterMouseClicks(events []ClickEvent) []ClickEvent {
-	var clicks []ClickEvent
-	for _, ev := range events {
-		if ev.Kind == KindClick {
-			clicks = append(clicks, ev)
-		}
-	}
-	return clicks
-}

widget/button.go

@@ -116,7 +116,11 @@ func (b *Clickable) Update(gtx layout.Context) (Click, bool) {
 			NumClicks: c,
 		}, true
 	}
-	for _, e := range b.click.Update(gtx.Source) {
+	for {
+		e, ok := b.click.Update(gtx.Source)
+		if !ok {
+			break
+		}
 		switch e.Kind {
 		case gesture.KindClick:
 			if l := len(b.history); l > 0 {

widget/dnd.go

@@ -53,7 +53,11 @@ func (d *Draggable) Dragging() bool {
 // requested to offer data, if any
 func (d *Draggable) Update(gtx layout.Context) (mime string, requested bool) {
 	pos := d.pos
-	for _, ev := range d.drag.Update(gtx.Metric, gtx.Source, gesture.Both) {
+	for {
+		ev, ok := d.drag.Update(gtx.Metric, gtx.Source, gesture.Both)
+		if !ok {
+			break
+		}
 		switch ev.Kind {
 		case pointer.Press:
 			d.click = ev.Position

widget/editor.go

@@ -316,10 +316,18 @@ func (e *Editor) processPointer(gtx layout.Context) {
 
 func (e *Editor) clickDragEvents(gtx layout.Context) []event.Event {
 	var combinedEvents []event.Event
-	for _, evt := range e.clicker.Update(gtx.Source) {
+	for {
+		evt, ok := e.clicker.Update(gtx.Source)
+		if !ok {
+			break
+		}
 		combinedEvents = append(combinedEvents, evt)
 	}
-	for _, evt := range e.dragger.Update(gtx.Metric, gtx.Source, gesture.Both) {
+	for {
+		evt, ok := e.dragger.Update(gtx.Metric, gtx.Source, gesture.Both)
+		if !ok {
+			break
+		}
 		combinedEvents = append(combinedEvents, evt)
 	}
 	return combinedEvents

widget/enum.go

@@ -47,7 +47,11 @@ func (e *Enum) Update(gtx layout.Context) bool {
 	e.hovering = false
 	changed := false
 	for _, state := range e.keys {
-		for _, ev := range state.click.Update(gtx.Source) {
+		for {
+			ev, ok := state.click.Update(gtx.Source)
+			if !ok {
+				break
+			}
 			switch ev.Kind {
 			case gesture.KindPress:
 				if ev.Source == pointer.Mouse {

widget/float.go

@@ -48,7 +48,11 @@ func (f *Float) Layout(gtx layout.Context, axis layout.Axis, pointerMargin unit.
 // The range of f is set by the minimum constraints main axis value.
 func (f *Float) Update(gtx layout.Context) bool {
 	changed := false
-	for _, e := range f.drag.Update(gtx.Metric, gtx.Source, gesture.Axis(f.axis)) {
+	for {
+		e, ok := f.drag.Update(gtx.Metric, gtx.Source, gesture.Axis(f.axis))
+		if !ok {
+			break
+		}
 		if f.length > 0 && (e.Kind == pointer.Press || e.Kind == pointer.Drag) {
 			pos := e.Position.X
 			if f.axis == layout.Vertical {

widget/list.go

@@ -61,7 +61,11 @@ func (s *Scrollbar) Update(gtx layout.Context, axis layout.Axis, viewportStart,
 	}
 
 	// Jump to a click in the track.
-	for _, event := range s.track.Update(gtx.Source) {
+	for {
+		event, ok := s.track.Update(gtx.Source)
+		if !ok {
+			break
+		}
 		if event.Kind != gesture.KindClick ||
 			event.Modifiers != key.Modifiers(0) ||
 			event.NumClicks > 1 {
@@ -80,7 +84,11 @@ func (s *Scrollbar) Update(gtx layout.Context, axis layout.Axis, viewportStart,
 	}
 
 	// Offset to account for any drags.
-	for _, event := range s.drag.Update(gtx.Metric, gtx.Source, gesture.Axis(axis)) {
+	for {
+		event, ok := s.drag.Update(gtx.Metric, gtx.Source, gesture.Axis(axis))
+		if !ok {
+			break
+		}
 		switch event.Kind {
 		case pointer.Drag:
 		case pointer.Release, pointer.Cancel:
@@ -136,7 +144,11 @@ func (s *Scrollbar) Update(gtx layout.Context, axis layout.Axis, viewportStart,
 
 	// Process events from the indicator so that hover is
 	// detected properly.
-	_ = s.indicator.Update(gtx.Source)
+	for {
+		if _, ok := s.indicator.Update(gtx.Source); !ok {
+			break
+		}
+	}
 }
 
 // AddTrack configures the track click listener for the scrollbar to use

widget/selectable.go

@@ -283,10 +283,18 @@ func (e *Selectable) processPointer(gtx layout.Context) {
 
 func (e *Selectable) clickDragEvents(gtx layout.Context) []event.Event {
 	var combinedEvents []event.Event
-	for _, evt := range e.clicker.Update(gtx.Source) {
+	for {
+		evt, ok := e.clicker.Update(gtx.Source)
+		if !ok {
+			break
+		}
 		combinedEvents = append(combinedEvents, evt)
 	}
-	for _, evt := range e.dragger.Update(gtx.Metric, gtx.Source, gesture.Both) {
+	for {
+		evt, ok := e.dragger.Update(gtx.Metric, gtx.Source, gesture.Both)
+		if !ok {
+			break
+		}
 		combinedEvents = append(combinedEvents, evt)
 	}
 	return combinedEvents