feat: midi note input for the tracker

tracker/gioui/tracker.go

@@ -35,6 +35,7 @@ type (
 		BottomHorizontalSplit *Split
 		VerticalSplit         *Split
 		KeyPlaying            map[key.Name]tracker.NoteID
+		MidiNotePlaying       []byte
 		PopupAlert            *PopupAlert
 
 		SaveChangesDialog *Dialog
@@ -77,6 +78,7 @@ func NewTracker(model *tracker.Model) *Tracker {
 		VerticalSplit:         &Split{Axis: layout.Vertical},
 
 		KeyPlaying:        make(map[key.Name]tracker.NoteID),
+		MidiNotePlaying:   make([]byte, 0, 32),
 		SaveChangesDialog: NewDialog(model.SaveSong(), model.DiscardSong(), model.Cancel()),
 		WaveTypeDialog:    NewDialog(model.ExportInt16(), model.ExportFloat(), model.Cancel()),
 		InstrumentEditor:  NewInstrumentEditor(model),
@@ -306,3 +308,46 @@ func (t *Tracker) layoutTop(gtx layout.Context) layout.Dimensions {
 		},
 	)
 }
+
+/// Event Handling (for UI updates when playing etc.)
+
+func (t *Tracker) ProcessMessage(msg interface{}) {
+	switch msg.(type) {
+	case tracker.StartPlayMsg:
+		fmt.Println("Tracker received StartPlayMsg")
+	case tracker.RecordingMsg:
+		fmt.Println("Tracker received RecordingMsg")
+	default:
+		break
+	}
+}
+
+func (t *Tracker) ProcessEvent(event tracker.MIDINoteEvent) {
+	// MIDINoteEvent can be only NoteOn / NoteOff, i.e. its On field
+	if event.On {
+		t.addToMidiNotePlaying(event.Note)
+	} else {
+		t.removeFromMidiNotePlaying(event.Note)
+	}
+	t.TrackEditor.HandleMidiInput(t)
+}
+
+func (t *Tracker) addToMidiNotePlaying(note byte) {
+	for _, n := range t.MidiNotePlaying {
+		if n == note {
+			return
+		}
+	}
+	t.MidiNotePlaying = append(t.MidiNotePlaying, note)
+}
+
+func (t *Tracker) removeFromMidiNotePlaying(note byte) {
+	for i, n := range t.MidiNotePlaying {
+		if n == note {
+			t.MidiNotePlaying = append(
+				t.MidiNotePlaying[:i],
+				t.MidiNotePlaying[i+1:]...,
+			)
+		}
+	}
+}