feat(tracker): rework the MIDI input and note event handling

tracker/gioui/keyboard.go

@@ -0,0 +1,58 @@
+package gioui
+
+import (
+	"time"
+
+	"github.com/vsariola/sointu/tracker"
+)
+
+type (
+	// Keyboard is used to associate the keys of a keyboard (e.g. computer or a
+	// MIDI keyboard) to currently playing notes. You can use any type T to
+	// identify each key; T should be a comparable type.
+	Keyboard[T comparable] struct {
+		broker  *tracker.Broker
+		pressed map[T]tracker.NoteEvent
+	}
+)
+
+func MakeKeyboard[T comparable](broker *tracker.Broker) Keyboard[T] {
+	return Keyboard[T]{
+		broker:  broker,
+		pressed: make(map[T]tracker.NoteEvent),
+	}
+}
+
+func (t *Keyboard[T]) Press(key T, ev tracker.NoteEvent) {
+	if _, ok := t.pressed[key]; ok {
+		return // already playing a note with this key, do not send a new event
+	}
+	t.Release(key) // unset any previous note
+	if ev.Note > 1 {
+		ev.Source = t // set the source to this keyboard
+		ev.On = true
+		ev.Timestamp = t.now()
+		if tracker.TrySend(t.broker.ToPlayer, any(ev)) {
+			t.pressed[key] = ev
+		}
+	}
+}
+
+func (t *Keyboard[T]) Release(key T) {
+	if ev, ok := t.pressed[key]; ok {
+		ev.Timestamp = t.now()
+		ev.On = false // the pressed contains the event we need to send to release the note
+		tracker.TrySend(t.broker.ToPlayer, any(ev))
+		delete(t.pressed, key)
+	}
+}
+
+func (t *Keyboard[T]) ReleaseAll() {
+	for key := range t.pressed {
+		t.Release(key)
+	}
+}
+
+func (t *Keyboard[T]) now() int64 {
+	return time.Now().UnixMilli() * 441 / 10 // convert to 44100Hz frames
+}