refactor(tracker): harmonize naming and use iterators in MIDI

using iterators requires go 1.23

cmd/sointu-track/main.go

@@ -54,8 +54,8 @@ func main() {
 		recoveryFile = filepath.Join(configDir, "Sointu", "sointu-track-recovery")
 	}
 	model, player := tracker.NewModelPlayer(cmd.MainSynther, recoveryFile)
-	model.MIDI = gomidi.CreateContext()
+	model.MIDI = gomidi.NewContext()
-	defer model.MIDI.DestroyContext()
+	defer model.MIDI.Close()
 	if a := flag.Args(); len(a) > 0 {
 		f, err := os.Open(a[0])
 		if err == nil {

go.mod

@@ -1,6 +1,6 @@
 module github.com/vsariola/sointu
 
-go 1.22.2
+go 1.23
 
 require (
 	gioui.org v0.7.1

tracker/action.go

@@ -445,11 +445,14 @@ func (m *Model) Cancel() Action      { return Allow(func() { m.dialog = NoDialog
 func (m *Model) Export() Action      { return Allow(func() { m.dialog = Export }) }
 func (m *Model) ExportFloat() Action { return Allow(func() { m.dialog = ExportFloatExplorer }) }
 func (m *Model) ExportInt16() Action { return Allow(func() { m.dialog = ExportInt16Explorer }) }
-func (m *Model) SelectMidiInput(item MIDIDevicer) Action {
+func (m *Model) SelectMidiInput(item MIDIDevice) Action {
 	return Allow(func() {
-		if !m.MIDI.OpenInputDevice(item) {
+		if err := item.Open(); err != nil {
-			message := fmt.Sprintf("Could not open MIDI device %s\n", item)
+			message := fmt.Sprintf("Could not open MIDI device: %s", item)
 			m.Alerts().Add(message, Error)
+		} else {
+			message := fmt.Sprintf("Opened MIDI device: %s", item)
+			m.Alerts().Add(message, Info)
 		}
 	})
 }

tracker/gomidi/midi.go

@@ -1,8 +1,8 @@
 package gomidi
 
 import (
+	"errors"
 	"fmt"
-	"time"
 
 	"github.com/vsariola/sointu/tracker"
 	"gitlab.com/gomidi/midi/v2"
@@ -11,105 +11,111 @@ import (
 )
 
 type (
-	MIDIContext struct {
+	RTMIDIContext struct {
-		driver          *rtmididrv.Driver
+		driver    *rtmididrv.Driver
-		inputAvailable  bool
+		currentIn drivers.In
-		driverAvailable bool
+		events    chan midi.Message
-		currentIn       MIDIDevicer
+	}
-		events          chan midi.Message
+
+	RTMIDIDevice struct {
+		context *RTMIDIContext
+		in      drivers.In
 	}
-	MIDIDevicer drivers.In
 )
 
-func (m *MIDIContext) ListInputDevices() <-chan tracker.MIDIDevicer {
+func (m *RTMIDIContext) ListInputDevices() func(yield func(tracker.MIDIDevice) bool) {
-
+	return func(yield func(tracker.MIDIDevice) bool) {
-	ins, err := m.driver.Ins()
+		if m.driver == nil {
-	channel := make(chan tracker.MIDIDevicer, len(ins))
+			return
-	if err != nil {
-		m.driver.Close()
-		m.driverAvailable = false
-		return nil
-	}
-	go func() {
-		for i := 0; i < len(ins); i++ {
-			channel <- ins[i].(MIDIDevicer)
 		}
-		close(channel)
+		ins, err := m.driver.Ins()
-	}()
+		if err != nil {
-	return channel
+			return
+		}
+		for i := 0; i < len(ins); i++ {
+			device := RTMIDIDevice{context: m, in: ins[i]}
+			if !yield(device) {
+				break
+			}
+		}
+	}
 }
 
 // Open the driver.
-func CreateContext() *MIDIContext {
+func NewContext() *RTMIDIContext {
-	m := MIDIContext{}
+	m := RTMIDIContext{events: make(chan midi.Message, 1024)}
-	var err error
+	// there's not much we can do if this fails, so just use m.driver = nil to
-	m.driver, err = rtmididrv.New()
+	// indicate no driver available
-	m.driverAvailable = err == nil
+	m.driver, _ = rtmididrv.New()
-	if m.driverAvailable {
-		m.events = make(chan midi.Message)
-	}
 	return &m
 }
 
 // Open an input device while closing the currently open if necessary.
-func (m *MIDIContext) OpenInputDevice(in tracker.MIDIDevicer) bool {
+func (m RTMIDIDevice) Open() error {
-	fmt.Printf("Opening midi device %s\n.", in)
+	if m.context.currentIn == m.in {
-	if m.driverAvailable {
+		return nil
-		if m.currentIn == in {
-			return false
-		}
-		if m.inputAvailable && m.currentIn.IsOpen() {
-			m.currentIn.Close()
-		}
-		m.currentIn = in.(MIDIDevicer)
-		m.currentIn.Open()
-		_, err := midi.ListenTo(m.currentIn, m.HandleMessage)
-		if err != nil {
-			m.inputAvailable = false
-			return false
-		}
 	}
-	return true
+	if m.context.driver == nil {
+		return errors.New("no driver available")
+	}
+	if m.context.currentIn != nil && m.context.currentIn.IsOpen() {
+		m.context.currentIn.Close()
+	}
+	m.context.currentIn = m.in
+	err := m.in.Open()
+	if err != nil {
+		m.context.currentIn = nil
+		return fmt.Errorf("opening MIDI input failed: %W", err)
+	}
+	_, err = midi.ListenTo(m.in, m.context.HandleMessage)
+	if err != nil {
+		m.in.Close()
+		m.context.currentIn = nil
+	}
+	return nil
 }
 
-func (m *MIDIContext) HandleMessage(msg midi.Message, timestampms int32) {
+func (d RTMIDIDevice) String() string {
-	go func() {
+	return d.in.String()
-		m.events <- msg
-		time.Sleep(time.Nanosecond)
-	}()
 }
 
-func (c *MIDIContext) NextEvent() (event tracker.MIDINoteEvent, ok bool) {
+func (m *RTMIDIContext) HandleMessage(msg midi.Message, timestampms int32) {
+	select {
+	case m.events <- msg: // if the channel is full, just drop the message
+	default:
+	}
+}
+
+func (c *RTMIDIContext) NextEvent() (event tracker.MIDINoteEvent, ok bool) {
 	select {
 	case msg := <-c.events:
-		{
+		var channel uint8
-			var channel uint8
+		var velocity uint8
-			var velocity uint8
+		var key uint8
-			var key uint8
+		if msg.GetNoteOn(&channel, &key, &velocity) {
-			var controller uint8
+			return tracker.MIDINoteEvent{Frame: 0, On: true, Channel: int(channel), Note: key}, true
-			var value uint8
+		} else if msg.GetNoteOff(&channel, &key, &velocity) {
-			if msg.GetNoteOn(&channel, &key, &velocity) {
+			return tracker.MIDINoteEvent{Frame: 0, On: false, Channel: int(channel), Note: key}, true
-				return tracker.MIDINoteEvent{Frame: 0, On: true, Channel: int(channel), Note: key}, true
-			} else if msg.GetNoteOff(&channel, &key, &velocity) {
-				return tracker.MIDINoteEvent{Frame: 0, On: false, Channel: int(channel), Note: key}, true
-			} else if msg.GetControlChange(&channel, &controller, &value) {
-				fmt.Printf("CC @ Channel: %d, Controller: %d, Value: %d\n", channel, controller, value)
-			} else {
-				fmt.Printf("Unhandled MIDI message: %s\n", msg)
-			}
 		}
+		// TODO: handle control messages with something like:
+		// if msg.GetControlChange(&channel, &controller, &value) {
+		//	....
 	default:
 		// Note (@LeStahL): This empty select case is needed to make the implementation non-blocking.
 	}
 	return tracker.MIDINoteEvent{}, false
 }
 
-func (c *MIDIContext) BPM() (bpm float64, ok bool) {
+func (c *RTMIDIContext) BPM() (bpm float64, ok bool) {
 	return 0, false
 }
 
-func (c *MIDIContext) DestroyContext() {
+func (c *RTMIDIContext) Close() {
-	close(c.events)
+	if c.driver == nil {
-	c.currentIn.Close()
+		return
+	}
+	if c.currentIn != nil && c.currentIn.IsOpen() {
+		c.currentIn.Close()
+	}
 	c.driver.Close()
 }

tracker/model.go

@@ -76,7 +76,7 @@ type (
 		PlayerMessages chan PlayerMsg
 		modelMessages  chan<- interface{}
 
-		MIDI MIDIContexter
+		MIDI MIDIContext
 	}
 
 	// Cursor identifies a row and a track in a song score.
@@ -123,16 +123,15 @@ type (
 
 	Dialog int
 
-	MIDIContexter interface {
+	MIDIContext interface {
-		ListInputDevices() <-chan MIDIDevicer
+		ListInputDevices() func(yield func(MIDIDevice) bool)
-		OpenInputDevice(item MIDIDevicer) bool
+		Close()
-		DestroyContext()
+		PlayerProcessContext
-		BPM() (bpm float64, ok bool)
-		NextEvent() (event MIDINoteEvent, ok bool)
 	}
 
-	MIDIDevicer interface {
+	MIDIDevice interface {
 		String() string
+		Open() error
 	}
 )