feat(tracker): compile with midi support only when CGO is available

Also add the midi context to the VSTI, so VSTI can use MIDI if they
wish so.

cmd/midi_cgo.go

@@ -0,0 +1,12 @@
+//go:build cgo
+
+package cmd
+
+import (
+	"github.com/vsariola/sointu/tracker"
+	"github.com/vsariola/sointu/tracker/gomidi"
+)
+
+func NewMidiContext(broker *tracker.Broker) tracker.MIDIContext {
+	return gomidi.NewContext(broker)
+}

cmd/midi_not_cgo.go

@@ -0,0 +1,12 @@
+//go:build !cgo
+
+package cmd
+
+import (
+	"github.com/vsariola/sointu/tracker"
+)
+
+func NewMidiContext(broker *tracker.Broker) tracker.MIDIContext {
+	// with no cgo, we cannot use MIDI, so return a null context
+	return tracker.NullMIDIContext{}
+}

cmd/sointu-track/main.go

@@ -16,7 +16,6 @@ import (
 	"github.com/vsariola/sointu/oto"
 	"github.com/vsariola/sointu/tracker"
 	"github.com/vsariola/sointu/tracker/gioui"
-	"github.com/vsariola/sointu/tracker/gomidi"
 )
 
 var cpuprofile = flag.String("cpuprofile", "", "write cpu profile to `file`")
@@ -47,7 +46,7 @@ func main() {
 		recoveryFile = filepath.Join(configDir, "Sointu", "sointu-track-recovery")
 	}
 	broker := tracker.NewBroker()
-	midiContext := gomidi.NewContext(broker)
+	midiContext := cmd.NewMidiContext(broker)
 	defer midiContext.Close()
 	midiContext.TryToOpenBy(*defaultMidiInput, *firstMidiInput)
 	model := tracker.NewModel(broker, cmd.MainSynther, midiContext, recoveryFile)
@@ -65,7 +64,7 @@ func main() {
 
 	trackerUi := gioui.NewTracker(model)
 	audioCloser := audioContext.Play(func(buf sointu.AudioBuffer) error {
-		player.Process(buf, midiContext)
+		player.Process(buf, tracker.NullPlayerProcessContext{})
 		return nil
 	})
 

cmd/sointu-vsti/main.go

@@ -24,16 +24,8 @@ type (
 		eventIndex int
 		host       vst2.Host
 	}
-
-	NullMIDIContext struct{}
 )
 
-func (m NullMIDIContext) InputDevices(yield func(tracker.MIDIDevice) bool) {}
-
-func (m NullMIDIContext) Close() {}
-
-func (m NullMIDIContext) HasDeviceOpen() bool { return false }
-
 func (c *VSTIProcessContext) BPM() (bpm float64, ok bool) {
 	timeInfo := c.host.GetTimeInfo(vst2.TempoValid)
 	if timeInfo == nil || timeInfo.Flags&vst2.TempoValid == 0 || timeInfo.Tempo == 0 {
@@ -54,7 +46,7 @@ func init() {
 			recoveryFile = filepath.Join(configDir, "sointu", "sointu-vsti-recovery-"+hex.EncodeToString(randBytes))
 		}
 		broker := tracker.NewBroker()
-		model := tracker.NewModel(broker, cmd.MainSynther, NullMIDIContext{}, recoveryFile)
+		model := tracker.NewModel(broker, cmd.MainSynther, cmd.NewMidiContext(broker), recoveryFile)
 		player := tracker.NewPlayer(broker, cmd.MainSynther)
 		detector := tracker.NewDetector(broker)
 		go detector.Run()

tracker/model.go

@@ -117,8 +117,11 @@ type (
 		InputDevices(yield func(MIDIDevice) bool)
 		Close()
 		HasDeviceOpen() bool
+		TryToOpenBy(name string, first bool)
 	}
 
+	NullMIDIContext struct{}
+
 	MIDIDevice interface {
 		String() string
 		Open() error
@@ -385,6 +388,11 @@ func (d *modelData) Copy() modelData {
 	return ret
 }
 
+func (m NullMIDIContext) InputDevices(yield func(MIDIDevice) bool) {}
+func (m NullMIDIContext) Close()                                   {}
+func (m NullMIDIContext) HasDeviceOpen() bool                      { return false }
+func (m NullMIDIContext) TryToOpenBy(name string, first bool)      {}
+
 func (m *Model) resetSong() {
 	m.d.Song = defaultSong.Copy()
 	for _, instr := range m.d.Song.Patch {

tracker/model_test.go

@@ -13,18 +13,10 @@ import (
 
 type NullContext struct{}
 
-func (NullContext) FinishBlock(frame int) {}
-
 func (NullContext) BPM() (bpm float64, ok bool) {
 	return 0, false
 }
 
-func (NullContext) InputDevices(yield func(tracker.MIDIDevice) bool) {}
-
-func (NullContext) HasDeviceOpen() bool { return false }
-
-func (NullContext) Close() {}
-
 type modelFuzzState struct {
 	model     *tracker.Model
 	clipboard []byte
@@ -261,7 +253,7 @@ func FuzzModel(f *testing.F) {
 		reader := bytes.NewReader(slice)
 		synther := vm.GoSynther{}
 		broker := tracker.NewBroker()
-		model := tracker.NewModel(broker, synther, NullContext{}, "")
+		model := tracker.NewModel(broker, synther, tracker.NullMIDIContext{}, "")
 		player := tracker.NewPlayer(broker, synther)
 		buf := make([][2]float32, 2048)
 		closeChan := make(chan struct{})

tracker/player.go

@@ -51,6 +51,8 @@ type (
 		BPM() (bpm float64, ok bool)
 	}
 
+	NullPlayerProcessContext struct{}
+
 	// NoteEvent describes triggering or releasing of a note. The timestamps are
 	// in frames, and relative to the clock of the event source. Different
 	// sources can use different clocks. Player tries to adjust the timestamps
@@ -200,6 +202,10 @@ func (p *Player) advanceRow() {
 	p.send(nil) // just send volume and song row information
 }
 
+func (p NullPlayerProcessContext) BPM() (bpm float64, ok bool) {
+	return 0, false // no BPM available
+}
+
 func (p *Player) processMessages(context PlayerProcessContext) {
 loop:
 	for { // process new message