io,app: route all unhandled key events to the topmost handler

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

app/window.go

@@ -937,6 +937,11 @@ func (w *Window) processEvent(d driver, e event.Event) bool {
 				handled = false
 			}
 		}
+		// As a sepcial case, the top-most input handler receives all unhandled
+		// events.
+		if e, ok := e.(key.Event); ok && !handled {
+			handled = w.queue.q.QueueTopmost(e)
+		}
 		w.updateCursor(d)
 		return handled
 	}

io/key/key.go

@@ -30,6 +30,8 @@ type InputOp struct {
 	Hint InputHint
 	// Keys is the set of keys Tag can handle. That is, Tag will only
 	// receive an Event if its key and modifiers are accepted by Keys.Contains.
+	// As a special case, the topmost (first added) InputOp handler receives all
+	// unhandled events.
 	Keys Set
 }
 

io/router/router.go

@@ -134,7 +134,26 @@ func (q *Router) Frame(frame *op.Ops) {
 	}
 }
 
-// Queue an event and report whether at least one handler had an event queued.
+// Queue key events to the topmost handler.
+func (q *Router) QueueTopmost(events ...key.Event) bool {
+	var topmost event.Tag
+	pq := &q.pointer.queue
+	for _, h := range pq.hitTree {
+		if h.ktag != nil {
+			topmost = h.ktag
+			break
+		}
+	}
+	if topmost == nil {
+		return false
+	}
+	for _, e := range events {
+		q.handlers.Add(topmost, e)
+	}
+	return q.handlers.HadEvents()
+}
+
+// Queue events and report whether at least one handler had an event queued.
 func (q *Router) Queue(events ...event.Event) bool {
 	for _, e := range events {
 		switch e := e.(type) {