io/input: permit FocusCmd to explicitly set the focus to any tag

If the client asks for the focus to be set to a tag, allow it. There is a
check at the end of Router.Frame that clears the focus if the tag turns
out to fail the requirements (visible and has asked for FocusEvents).

The change simplifies the logic for determining whether a command can
be executed immediately.

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

io/input/key.go

@@ -281,11 +281,6 @@ func keyFilterMatch(f key.Filter, e key.Event) bool {
 }
 
 func (q *keyQueue) Focus(handlers map[event.Tag]*handler, state keyState, focus event.Tag) (keyState, []taggedEvent) {
-	if focus != nil {
-		if h, exists := handlers[focus]; !exists || !h.filter.key.focusable || !h.key.visible {
-			focus = nil
-		}
-	}
 	if focus == state.focus {
 		return state, nil
 	}

io/input/key_test.go

@@ -62,6 +62,10 @@ func TestKeyStacked(t *testing.T) {
 	ops := new(op.Ops)
 	r := new(Router)
 
+	for i := range handlers {
+		assertKeyEvent(t, events(r, &handlers[i], key.FocusFilter{}), false)
+	}
+
 	event.InputOp(ops, &handlers[0])
 	r.Source().Execute(key.FocusCmd{})
 	r.Source().Execute(key.SoftKeyboardCmd{Show: false})
@@ -71,10 +75,6 @@ func TestKeyStacked(t *testing.T) {
 	r.Source().Execute(key.SoftKeyboardCmd{Show: true})
 	event.InputOp(ops, &handlers[3])
 
-	for i := range handlers {
-		assertKeyEvent(t, events(r, &handlers[i], key.FocusFilter{}), false)
-	}
-
 	r.Frame(ops)
 
 	assertKeyEvent(t, events(r, &handlers[1], key.FocusFilter{}), true)
@@ -101,14 +101,6 @@ func TestKeyRemoveFocus(t *testing.T) {
 	ops := new(op.Ops)
 	r := new(Router)
 
-	// New InputOp with Focus and Keyboard:
-	event.InputOp(ops, &handlers[0])
-	r.Source().Execute(key.FocusCmd{Tag: &handlers[0]})
-	r.Source().Execute(key.SoftKeyboardCmd{Show: true})
-
-	// New InputOp without any focus:
-	event.InputOp(ops, &handlers[1])
-
 	filters := []event.Filter{
 		key.FocusFilter{},
 		key.Filter{Name: key.NameTab, Required: key.ModShortcut},
@@ -116,6 +108,13 @@ func TestKeyRemoveFocus(t *testing.T) {
 	for i := range handlers {
 		assertKeyEvent(t, events(r, &handlers[i], filters...), false)
 	}
+	// New InputOp with Focus and Keyboard:
+	event.InputOp(ops, &handlers[0])
+	r.Source().Execute(key.FocusCmd{Tag: &handlers[0]})
+	r.Source().Execute(key.SoftKeyboardCmd{Show: true})
+
+	// New InputOp without any focus:
+	event.InputOp(ops, &handlers[1])
 
 	r.Frame(ops)
 
@@ -180,6 +179,10 @@ func TestKeyFocusedInvisible(t *testing.T) {
 	ops := new(op.Ops)
 	r := new(Router)
 
+	for i := range handlers {
+		assertKeyEvent(t, events(r, &handlers[i], key.FocusFilter{}), false)
+	}
+
 	// Set new InputOp with focus:
 	r.Source().Execute(key.FocusCmd{Tag: &handlers[0]})
 	event.InputOp(ops, &handlers[0])
@@ -188,10 +191,6 @@ func TestKeyFocusedInvisible(t *testing.T) {
 	// Set new InputOp without focus:
 	event.InputOp(ops, &handlers[1])
 
-	for i := range handlers {
-		assertKeyEvent(t, events(r, &handlers[i], key.FocusFilter{}), false)
-	}
-
 	r.Frame(ops)
 
 	assertKeyEvent(t, events(r, &handlers[0], key.FocusFilter{}), true)

io/input/router.go

@@ -112,9 +112,7 @@ type SemanticID uint
 type handler struct {
 	// active tracks whether the handler was active in the current
 	// frame. Router deletes state belonging to inactive handlers during Frame.
-	active bool
-	// old is true iff the handler was aded in a previous frame.
-	old     bool
+	active  bool
 	pointer pointerHandler
 	key     keyHandler
 	// filter the handler has asked for through event handling
@@ -279,7 +277,6 @@ func (q *Router) Frame(frame *op.Ops) {
 			delete(q.handlers, k)
 		} else {
 			h.active = false
-			h.old = true
 		}
 	}
 	q.executeCommands()
@@ -381,22 +378,14 @@ func (q *Router) processEvent(e event.Event) bool {
 }
 
 func (q *Router) execute(c Command) {
-	// The command can be executed immediately if:
-	//
-	// - event delivery is not frozen, and
-	// - the influencing tag and event receivers were all seen
-	//   in the previous frame, and
-	// - no event receiver has completed their event handling.
+	// The command can be executed immediately if event delivery is not frozen, and
+	// no event receiver has completed their event handling.
 	if !q.deferring {
-		tag, ch := q.executeCommand(c)
+		ch := q.executeCommand(c)
 		immediate := true
-		if tag != nil {
-			h, ok := q.handlers[tag]
-			immediate = immediate && ok && h.old
-		}
 		for _, e := range ch.events {
 			h, ok := q.handlers[e.tag]
-			immediate = immediate && ok && h.old && !h.processedFilter.Matches(e.event)
+			immediate = immediate && (!ok || !h.processedFilter.Matches(e.event))
 		}
 		if immediate {
 			// Hold on to the remaining events for state replay.
@@ -434,7 +423,7 @@ func (q *Router) lastState() inputState {
 
 func (q *Router) executeCommands() {
 	for _, c := range q.commands {
-		_, ch := q.executeCommand(c)
+		ch := q.executeCommand(c)
 		q.changeState(nil, ch.state, ch.events)
 	}
 	q.commands = nil
@@ -442,31 +431,25 @@ func (q *Router) executeCommands() {
 
 // executeCommand the command and return the resulting state change along with the
 // tag the state change depended on, if any.
-func (q *Router) executeCommand(c Command) (event.Tag, stateChange) {
+func (q *Router) executeCommand(c Command) stateChange {
 	state := q.state()
 	var evts []taggedEvent
-	var tag event.Tag
 	switch req := c.(type) {
 	case key.SelectionCmd:
-		tag = req.Tag
 		state.keyState = q.key.queue.setSelection(state.keyState, req)
 	case key.FocusCmd:
-		tag = req.Tag
 		state.keyState, evts = q.key.queue.Focus(q.handlers, state.keyState, req.Tag)
 	case key.SoftKeyboardCmd:
 		state.keyState = state.keyState.softKeyboard(req.Show)
 	case key.SnippetCmd:
-		tag = req.Tag
 		state.keyState = q.key.queue.setSnippet(state.keyState, req)
 	case transfer.OfferCmd:
-		tag = req.Tag
 		state.pointerState, evts = q.pointer.queue.offerData(q.handlers, state.pointerState, req)
 	case clipboard.WriteCmd:
 		q.cqueue.ProcessWriteClipboard(req)
 	case clipboard.ReadCmd:
 		state.clipboardState = q.cqueue.ProcessReadClipboard(state.clipboardState, req.Tag)
 	case pointer.GrabCmd:
-		tag = req.Tag
 		state.pointerState, evts = q.pointer.queue.grab(state.pointerState, req)
 	case op.InvalidateCmd:
 		if !q.wakeup || req.At.Before(q.wakeupTime) {
@@ -474,7 +457,7 @@ func (q *Router) executeCommand(c Command) (event.Tag, stateChange) {
 			q.wakeupTime = req.At
 		}
 	}
-	return tag, stateChange{state: state, events: evts}
+	return stateChange{state: state, events: evts}
 }
 
 func (q *Router) changeState(e event.Event, state inputState, evts []taggedEvent) bool {