hook up cmd queue to PlaybackManager

backend/app.go

@@ -377,9 +377,7 @@ func (a *App) LoadSavedPlayQueue() error {
 		return nil
 	}
 
-	if err := a.PlaybackManager.LoadTracks(queue.Tracks, Replace, false); err != nil {
+	a.PlaybackManager.LoadTracks(queue.Tracks, Replace, false)
-		return err
-	}
 	if queue.TrackIndex >= 0 && queue.TrackIndex < len(queue.Tracks) {
 		// TODO: This isn't ideal but doesn't seem to cause an audible play-for-a-split-second artifact
 		a.PlaybackManager.PlayTrackAt(queue.TrackIndex)

backend/ipc/server.go

@@ -9,16 +9,16 @@ import (
 )
 
 type PlaybackHandler interface {
-	PlayPause() error
+	PlayPause()
-	Stop() error
+	Stop()
-	Pause() error
+	Pause()
-	Continue() error
+	Continue()
-	SeekBackOrPrevious() error
+	SeekBackOrPrevious()
-	SeekNext() error
+	SeekNext()
-	SeekSeconds(float64) error
+	SeekSeconds(float64)
-	SeekBySeconds(float64) error
+	SeekBySeconds(float64)
 	Volume() int
-	SetVolume(int) error
+	SetVolume(int)
 }
 
 type IPCServer interface {
@@ -57,14 +57,12 @@ func (s *serverImpl) createHandler() http.Handler {
 		w.WriteHeader(http.StatusNotFound)
 		w.Write([]byte("The given path is not valid"))
 	})
-	m.HandleFunc(PingPath, s.makeSimpleEndpointHandler(func() error { return nil }))
+	m.HandleFunc(PingPath, s.makeSimpleEndpointHandler(func() {}))
-	m.HandleFunc(ShowPath, s.makeSimpleEndpointHandler(func() error {
+	m.HandleFunc(ShowPath, s.makeSimpleEndpointHandler(func() {
 		s.showFn()
-		return nil
 	}))
-	m.HandleFunc(QuitPath, s.makeSimpleEndpointHandler(func() error {
+	m.HandleFunc(QuitPath, s.makeSimpleEndpointHandler(func() {
 		s.quitFn()
-		return nil
 	}))
 	m.HandleFunc(PlayPath, s.makeSimpleEndpointHandler(s.pbHandler.Continue))
 	m.HandleFunc(PausePath, s.makeSimpleEndpointHandler(s.pbHandler.Pause))
@@ -77,7 +75,8 @@ func (s *serverImpl) createHandler() http.Handler {
 	m.HandleFunc(VolumePath, func(w http.ResponseWriter, r *http.Request) {
 		v := r.URL.Query().Get("v")
 		if vol, err := strconv.Atoi(v); err == nil {
-			s.writeSimpleResponse(w, s.pbHandler.SetVolume(vol))
+			s.pbHandler.SetVolume(vol)
+			s.writeOK(w)
 		} else {
 			s.writeErr(w, err)
 		}
@@ -85,31 +84,25 @@ func (s *serverImpl) createHandler() http.Handler {
 	return m
 }
 
-func (s *serverImpl) makeSimpleEndpointHandler(f func() error) func(http.ResponseWriter, *http.Request) {
+func (s *serverImpl) makeSimpleEndpointHandler(f func()) func(http.ResponseWriter, *http.Request) {
 	return func(w http.ResponseWriter, r *http.Request) {
-		s.writeSimpleResponse(w, f())
+		f()
+		s.writeOK(w)
 	}
 }
 
-func (s *serverImpl) makeFloatEndpointHandler(f func(float64) error, queryParam string) func(http.ResponseWriter, *http.Request) {
+func (s *serverImpl) makeFloatEndpointHandler(f func(float64), queryParam string) func(http.ResponseWriter, *http.Request) {
 	return func(w http.ResponseWriter, r *http.Request) {
 		v := r.URL.Query().Get(queryParam)
 		if val, err := strconv.ParseFloat(v, 64); err == nil {
-			s.writeSimpleResponse(w, f(val))
+			f(val)
+			s.writeOK(w)
 		} else {
 			s.writeErr(w, err)
 		}
 	}
 }
 
-func (s *serverImpl) writeSimpleResponse(w http.ResponseWriter, err error) {
-	if err == nil {
-		s.writeOK(w)
-	} else {
-		s.writeErr(w, err)
-	}
-}
-
 func (s *serverImpl) writeOK(w http.ResponseWriter) (int, error) {
 	var r Response
 	b, err := json.Marshal(&r)

backend/mpris.go

@@ -150,46 +150,51 @@ func (m *MPRISHandler) SupportedMimeTypes() ([]string, error) {
 // OrgMprisMediaPlayer2PlayerAdapter implementation
 
 func (m *MPRISHandler) Next() error {
-	return m.pm.SeekNext()
+	m.pm.SeekNext()
+	return nil
 }
 
 func (m *MPRISHandler) Previous() error {
-	return m.pm.SeekBackOrPrevious()
+	m.pm.SeekBackOrPrevious()
+	return nil
 }
 
 func (m *MPRISHandler) Pause() error {
 	if m.pm.PlayerStatus().State == player.Playing {
-		return m.pm.PlayPause()
+		m.pm.PlayPause()
 	}
 	return nil
 }
 
 func (m *MPRISHandler) PlayPause() error {
-	return m.pm.PlayPause()
+	m.pm.PlayPause()
+	return nil
 }
 
 func (m *MPRISHandler) Stop() error {
-	return m.pm.Stop()
+	m.pm.Stop()
+	return nil
 }
 
 func (m *MPRISHandler) Play() error {
 	switch m.pm.PlayerStatus().State {
 	case player.Paused:
-		return m.pm.PlayPause()
+		m.pm.PlayPause()
 	case player.Stopped:
-		return m.pm.PlayFromBeginning()
+		m.pm.PlayFromBeginning()
 	}
 	return nil
 }
 
 func (m *MPRISHandler) Seek(offset types.Microseconds) error {
 	// MPRIS seek command is relative to current position
-	return m.pm.SeekBySeconds(microsecondsToSeconds(offset))
+	m.pm.SeekBySeconds(microsecondsToSeconds(offset))
+	return nil
 }
 
 func (m *MPRISHandler) SetPosition(trackId string, position types.Microseconds) error {
 	if m.curTrackPath == trackId {
-		return m.pm.SeekSeconds(microsecondsToSeconds(position))
+		m.pm.SeekSeconds(microsecondsToSeconds(position))
 	}
 	return nil
 }
@@ -297,7 +302,8 @@ func (m *MPRISHandler) Volume() (float64, error) {
 }
 
 func (m *MPRISHandler) SetVolume(v float64) error {
-	return m.pm.SetVolume(int(v * 100))
+	m.pm.SetVolume(int(v * 100))
+	return nil
 }
 
 func (m *MPRISHandler) Position() (int64, error) {

backend/playbackcommands.go

@@ -28,113 +28,120 @@ const (
 	cmdLoadRadioStation // arg: *mediaprovider.RadioStation, arg2: InsertQueueMode
 )
 
-type PlaybackCommand struct {
+type playbackCommand struct {
 	Type playbackCommandType
 	Arg  any
 	Arg2 any
 	Arg3 any
 }
 
-type CommandQueue struct {
+type playbackCommandQueue struct {
 	mutex        sync.Mutex
-	queue        []PlaybackCommand
+	queue        []playbackCommand
 	cmdAvailable *sync.Cond
-	nextChan     chan (PlaybackCommand)
+	nextChan     chan playbackCommand
 }
 
-func NewCommandQueue() *CommandQueue {
+func NewCommandQueue() *playbackCommandQueue {
-	c := &CommandQueue{}
+	c := &playbackCommandQueue{}
+	c.nextChan = make(chan playbackCommand)
 	c.cmdAvailable = sync.NewCond(&c.mutex)
 	go c.chanWriter()
 	return c
 }
 
-func (c *CommandQueue) C() <-chan PlaybackCommand {
+func (c *playbackCommandQueue) C() <-chan playbackCommand {
 	return c.nextChan
 }
 
-func (c *CommandQueue) Stop() {
+func (c *playbackCommandQueue) Stop() {
 	c.filterCommandsAndAdd([]playbackCommandType{cmdContinue, cmdPause, cmdStop},
-		PlaybackCommand{Type: cmdStop})
+		playbackCommand{Type: cmdStop})
 }
 
-func (c *CommandQueue) Continue() {
+func (c *playbackCommandQueue) Continue() {
 	c.filterCommandsAndAdd([]playbackCommandType{cmdContinue, cmdPause, cmdStop},
-		PlaybackCommand{Type: cmdContinue})
+		playbackCommand{Type: cmdContinue})
 }
 
-func (c *CommandQueue) Pause() {
+func (c *playbackCommandQueue) Pause() {
 	c.filterCommandsAndAdd([]playbackCommandType{cmdContinue, cmdPause, cmdStop},
-		PlaybackCommand{Type: cmdPause})
+		playbackCommand{Type: cmdPause})
 }
 
-func (c *CommandQueue) StopAndClearPlayQueue() {
+func (c *playbackCommandQueue) PlayTrackAt(idx int) {
+	c.filterCommandsAndAdd([]playbackCommandType{cmdContinue, cmdPause, cmdStop, cmdPlayTrackAt},
+		playbackCommand{Type: cmdPlayTrackAt, Arg: idx})
+}
+
+func (c *playbackCommandQueue) StopAndClearPlayQueue() {
 	c.filterCommandsAndAdd([]playbackCommandType{cmdContinue, cmdPause, cmdStop, cmdStopAndClearPlayQueue},
-		PlaybackCommand{Type: cmdStopAndClearPlayQueue})
+		playbackCommand{Type: cmdStopAndClearPlayQueue})
 }
 
-func (c *CommandQueue) SetVolume(vol int) {
+func (c *playbackCommandQueue) SetVolume(vol int) {
 	c.filterCommandsAndAdd([]playbackCommandType{cmdVolume},
-		PlaybackCommand{Type: cmdVolume, Arg: vol})
+		playbackCommand{Type: cmdVolume, Arg: vol})
 }
 
-func (c *CommandQueue) SetLoopMode(mode LoopMode) {
+func (c *playbackCommandQueue) SetLoopMode(mode LoopMode) {
 	c.filterCommandsAndAdd([]playbackCommandType{cmdLoopMode},
-		PlaybackCommand{Type: cmdLoopMode, Arg: mode})
+		playbackCommand{Type: cmdLoopMode, Arg: mode})
 }
 
-func (c *CommandQueue) SeekSeconds(s float64) {
+func (c *playbackCommandQueue) SeekSeconds(s float64) {
 	c.filterCommandsAndAdd([]playbackCommandType{cmdSeekSeconds},
-		PlaybackCommand{Type: cmdSeekSeconds, Arg: s})
+		playbackCommand{Type: cmdSeekSeconds, Arg: s})
 }
 
-func (c *CommandQueue) SeekNext() {
+func (c *playbackCommandQueue) SeekNext() {
 	c.seekBackOrFwd(1)
 }
 
-func (c *CommandQueue) SeekBackOrPrevious() {
+func (c *playbackCommandQueue) SeekBackOrPrevious() {
 	c.seekBackOrFwd(-1)
 }
 
-func (c *CommandQueue) UpdatePlayQueue(items []mediaprovider.MediaItem) {
+func (c *playbackCommandQueue) UpdatePlayQueue(items []mediaprovider.MediaItem) {
 	c.filterCommandsAndAdd([]playbackCommandType{cmdUpdatePlayQueue},
-		PlaybackCommand{Type: cmdUpdatePlayQueue, Arg: items})
+		playbackCommand{Type: cmdUpdatePlayQueue, Arg: items})
 }
 
-func (c *CommandQueue) RemoveItemsFromQueue(idxs []int) {
+func (c *playbackCommandQueue) RemoveItemsFromQueue(idxs []int) {
 	c.mutex.Lock()
-	defer c.mutex.Unlock()
+	c.queue = append(c.queue, playbackCommand{
-	c.queue = append(c.queue, PlaybackCommand{
 		Type: cmdRemoveTracksFromQueue,
 		Arg:  idxs,
 	})
+	c.mutex.Unlock()
+	c.cmdAvailable.Signal()
 }
 
-func (c *CommandQueue) LoadRadioStation(radio *mediaprovider.RadioStation, insertMode InsertQueueMode) {
+func (c *playbackCommandQueue) LoadRadioStation(radio *mediaprovider.RadioStation, insertMode InsertQueueMode) {
 	c.mutex.Lock()
-	defer c.mutex.Unlock()
+	c.queue = append(c.queue, playbackCommand{
-	c.queue = append(c.queue, PlaybackCommand{
 		Type: cmdLoadRadioStation,
 		Arg:  radio,
 		Arg2: insertMode,
 	})
+	c.mutex.Unlock()
+	c.cmdAvailable.Signal()
 }
 
-func (c *CommandQueue) LoadItems(items []mediaprovider.MediaItem, insertQueueMode InsertQueueMode, shuffle bool) {
+func (c *playbackCommandQueue) LoadItems(items []mediaprovider.MediaItem, insertQueueMode InsertQueueMode, shuffle bool) {
 	c.mutex.Lock()
-	defer c.mutex.Unlock()
+	c.queue = append(c.queue, playbackCommand{
-	c.queue = append(c.queue, PlaybackCommand{
 		Type: cmdLoadItems,
 		Arg:  items,
 		Arg2: insertQueueMode,
 		Arg3: shuffle,
 	})
+	c.mutex.Unlock()
+	c.cmdAvailable.Signal()
 }
 
-func (c *CommandQueue) filterCommandsAndAdd(excludeTypes []playbackCommandType, command PlaybackCommand) {
+func (c *playbackCommandQueue) filterCommandsAndAdd(excludeTypes []playbackCommandType, command playbackCommand) {
 	c.mutex.Lock()
-	defer c.mutex.Unlock()
-
 	j := 0
 	for _, cmd := range c.queue {
 		if slices.Contains(excludeTypes, cmd.Type) {
@@ -145,12 +152,12 @@ func (c *CommandQueue) filterCommandsAndAdd(excludeTypes []playbackCommandType,
 	}
 	c.queue = c.queue[:j]
 	c.queue = append(c.queue, command)
+	c.mutex.Unlock()
+	c.cmdAvailable.Signal()
 }
 
-func (c *CommandQueue) seekBackOrFwd(direction int) {
+func (c *playbackCommandQueue) seekBackOrFwd(direction int) {
 	c.mutex.Lock()
-	defer c.mutex.Unlock()
-
 	j := 0
 	n := 0
 	for _, cmd := range c.queue {
@@ -162,12 +169,14 @@ func (c *CommandQueue) seekBackOrFwd(direction int) {
 		}
 	}
 	c.queue = c.queue[:j]
-	c.queue = append(c.queue, PlaybackCommand{
+	c.queue = append(c.queue, playbackCommand{
 		Type: cmdSeekFwdBackN,
 		Arg:  n + direction})
+	c.mutex.Unlock()
+	c.cmdAvailable.Signal()
 }
 
-func (c *CommandQueue) chanWriter() {
+func (c *playbackCommandQueue) chanWriter() {
 	for {
 		c.mutex.Lock()
 		for len(c.queue) == 0 {

backend/playbackmanager.go

@@ -2,7 +2,6 @@ package backend
 
 import (
 	"context"
-	"errors"
 	"log"
 	"math/rand"
 
@@ -13,7 +12,8 @@ import (
 // A high-level MediaProvider-aware playback engine, serves as an
 // intermediary between the frontend and various Player backends.
 type PlaybackManager struct {
-	engine *playbackEngine
+	engine   *playbackEngine
+	cmdQueue *playbackCommandQueue
 }
 
 func NewPlaybackManager(
@@ -23,9 +23,14 @@ func NewPlaybackManager(
 	scrobbleCfg *ScrobbleConfig,
 	transcodeCfg *TranscodingConfig,
 ) *PlaybackManager {
-	return &PlaybackManager{
+	e := NewPlaybackEngine(ctx, s, p, scrobbleCfg, transcodeCfg)
-		engine: NewPlaybackEngine(ctx, s, p, scrobbleCfg, transcodeCfg),
+	q := NewCommandQueue()
+	pm := &PlaybackManager{
+		engine:   e,
+		cmdQueue: q,
 	}
+	go pm.runCmdQueue(ctx)
+	return pm
 }
 
 func (p *PlaybackManager) CurrentPlayer() player.BasePlayer {
@@ -106,7 +111,8 @@ func (p *PlaybackManager) LoadAlbum(albumID string, insertQueueMode InsertQueueM
 	if err != nil {
 		return err
 	}
-	return p.LoadTracks(album.Tracks, insertQueueMode, shuffle)
+	p.LoadTracks(album.Tracks, insertQueueMode, shuffle)
+	return nil
 }
 
 // Loads the specified playlist into the play queue.
@@ -115,26 +121,28 @@ func (p *PlaybackManager) LoadPlaylist(playlistID string, insertQueueMode Insert
 	if err != nil {
 		return err
 	}
-	return p.LoadTracks(playlist.Tracks, insertQueueMode, shuffle)
+	p.LoadTracks(playlist.Tracks, insertQueueMode, shuffle)
+	return nil
 }
 
 // Load tracks into the play queue.
 // If replacing the current queue (!appendToQueue), playback will be stopped.
-func (p *PlaybackManager) LoadTracks(tracks []*mediaprovider.Track, insertQueueMode InsertQueueMode, shuffle bool) error {
+func (p *PlaybackManager) LoadTracks(tracks []*mediaprovider.Track, insertQueueMode InsertQueueMode, shuffle bool) {
-	return p.engine.LoadTracks(tracks, insertQueueMode, shuffle)
+	items := copyTrackSliceToMediaItemSlice(tracks)
+	p.cmdQueue.LoadItems(items, insertQueueMode, shuffle)
 }
 
 // Load items into the play queue.
 // If replacing the current queue (!appendToQueue), playback will be stopped.
-func (p *PlaybackManager) LoadItems(items []mediaprovider.MediaItem, insertQueueMode InsertQueueMode, shuffle bool) error {
+func (p *PlaybackManager) LoadItems(items []mediaprovider.MediaItem, insertQueueMode InsertQueueMode, shuffle bool) {
-	return p.engine.LoadItems(items, insertQueueMode, shuffle)
+	p.cmdQueue.LoadItems(items, insertQueueMode, shuffle)
 }
 
 // Replaces the play queue with the given set of tracks.
 // Does not stop playback if the currently playing track is in the new queue,
 // but updates the now playing index to point to the first instance of the track in the new queue.
-func (p *PlaybackManager) UpdatePlayQueue(items []mediaprovider.MediaItem) error {
+func (p *PlaybackManager) UpdatePlayQueue(items []mediaprovider.MediaItem) {
-	return p.engine.UpdatePlayQueue(items)
+	p.cmdQueue.UpdatePlayQueue(items)
 }
 
 func (p *PlaybackManager) PlayAlbum(albumID string, firstTrack int, shuffle bool) error {
@@ -144,7 +152,8 @@ func (p *PlaybackManager) PlayAlbum(albumID string, firstTrack int, shuffle bool
 	if p.engine.replayGainCfg.Mode == ReplayGainAuto {
 		p.SetReplayGainMode(player.ReplayGainAlbum)
 	}
-	return p.PlayTrackAt(firstTrack)
+	p.PlayTrackAt(firstTrack)
+	return nil
 }
 
 func (p *PlaybackManager) PlayPlaylist(playlistID string, firstTrack int, shuffle bool) error {
@@ -154,7 +163,8 @@ func (p *PlaybackManager) PlayPlaylist(playlistID string, firstTrack int, shuffl
 	if p.engine.replayGainCfg.Mode == ReplayGainAuto {
 		p.SetReplayGainMode(player.ReplayGainTrack)
 	}
-	return p.PlayTrackAt(firstTrack)
+	p.PlayTrackAt(firstTrack)
+	return nil
 }
 
 func (p *PlaybackManager) PlayTrack(trackID string) error {
@@ -166,13 +176,14 @@ func (p *PlaybackManager) PlayTrack(trackID string) error {
 	if p.engine.replayGainCfg.Mode == ReplayGainAuto {
 		p.SetReplayGainMode(player.ReplayGainTrack)
 	}
-	return p.PlayFromBeginning()
+	p.PlayFromBeginning()
+	return nil
 }
 
 func (p *PlaybackManager) ShuffleArtistAlbums(artistID string) {
 	artist, err := p.engine.sm.Server.GetArtist(artistID)
 	if err != nil {
-		log.Printf(err.Error())
+		log.Printf("failed to get artist: %v\n", err)
 		return
 	}
 	if len(artist.Albums) == 0 {
@@ -196,7 +207,7 @@ func (p *PlaybackManager) ShuffleArtistAlbums(artistID string) {
 func (p *PlaybackManager) PlayArtistDiscography(artistID string, shuffleTracks bool) {
 	tr, err := p.engine.sm.Server.GetArtistTracks(artistID)
 	if err != nil {
-		log.Printf(err.Error())
+		log.Printf("failed to get artist tracks: %v\n", err)
 		return
 	}
 	p.LoadTracks(tr, Replace, shuffleTracks)
@@ -210,12 +221,12 @@ func (p *PlaybackManager) PlayArtistDiscography(artistID string, shuffleTracks b
 	p.PlayFromBeginning()
 }
 
-func (p *PlaybackManager) PlayFromBeginning() error {
+func (p *PlaybackManager) PlayFromBeginning() {
-	return p.engine.PlayTrackAt(0)
+	p.cmdQueue.PlayTrackAt(0)
 }
 
-func (p *PlaybackManager) PlayTrackAt(idx int) error {
+func (p *PlaybackManager) PlayTrackAt(idx int) {
-	return p.engine.PlayTrackAt(idx)
+	p.cmdQueue.PlayTrackAt(idx)
 }
 
 func (p *PlaybackManager) PlayRandomSongs(genreName string) {
@@ -231,12 +242,12 @@ func (p *PlaybackManager) PlaySimilarSongs(id string) {
 }
 
 func (p *PlaybackManager) LoadRadioStation(station *mediaprovider.RadioStation, queueMode InsertQueueMode) {
-	p.engine.LoadRadioStation(station, queueMode)
+	p.cmdQueue.LoadRadioStation(station, queueMode)
 }
 
-func (p *PlaybackManager) PlayRadioStation(station *mediaprovider.RadioStation) error {
+func (p *PlaybackManager) PlayRadioStation(station *mediaprovider.RadioStation) {
 	p.LoadRadioStation(station, Replace)
-	return p.PlayFromBeginning()
+	p.PlayFromBeginning()
 }
 
 func (p *PlaybackManager) fetchAndPlayTracks(fetchFn func() ([]*mediaprovider.Track, error)) {
@@ -268,12 +279,12 @@ func (p *PlaybackManager) OnTrackRatingChanged(id string, rating int) {
 }
 
 func (p *PlaybackManager) RemoveTracksFromQueue(idxs []int) {
-	p.engine.RemoveTracksFromQueue(idxs)
+	p.cmdQueue.RemoveItemsFromQueue(idxs)
 }
 
 // Stop playback and clear the play queue.
 func (p *PlaybackManager) StopAndClearPlayQueue() {
-	p.engine.StopAndClearPlayQueue()
+	p.cmdQueue.StopAndClearPlayQueue()
 }
 
 func (p *PlaybackManager) SetReplayGainOptions(config ReplayGainConfig) {
@@ -289,17 +300,16 @@ func (p *PlaybackManager) SetReplayGainMode(mode player.ReplayGainMode) {
 func (p *PlaybackManager) SetNextLoopMode() {
 	switch p.engine.loopMode {
 	case LoopNone:
-		p.engine.SetLoopMode(LoopAll)
+		p.cmdQueue.SetLoopMode(LoopAll)
 	case LoopAll:
-		p.engine.SetLoopMode(LoopOne)
+		p.cmdQueue.SetLoopMode(LoopOne)
 	case LoopOne:
-		p.engine.SetLoopMode(LoopNone)
+		p.cmdQueue.SetLoopMode(LoopNone)
-
 	}
 }
 
 func (p *PlaybackManager) SetLoopMode(loopMode LoopMode) {
-	p.engine.SetLoopMode(loopMode)
+	p.cmdQueue.SetLoopMode(loopMode)
 }
 
 func (p *PlaybackManager) GetLoopMode() LoopMode {
@@ -310,29 +320,29 @@ func (p *PlaybackManager) PlayerStatus() player.Status {
 	return p.engine.PlayerStatus()
 }
 
-func (p *PlaybackManager) SetVolume(vol int) error {
+func (p *PlaybackManager) SetVolume(vol int) {
-	return p.engine.SetVolume(vol)
+	p.cmdQueue.SetVolume(vol)
 }
 
 func (p *PlaybackManager) Volume() int {
 	return p.engine.CurrentPlayer().GetVolume()
 }
 
-func (p *PlaybackManager) SeekNext() error {
+func (p *PlaybackManager) SeekNext() {
-	return p.engine.SeekNext()
+	p.cmdQueue.SeekNext()
 }
 
-func (p *PlaybackManager) SeekBackOrPrevious() error {
+func (p *PlaybackManager) SeekBackOrPrevious() {
-	return p.engine.SeekBackOrPrevious()
+	p.cmdQueue.SeekBackOrPrevious()
 }
 
 // Seek to given absolute position in the current track by seconds.
-func (p *PlaybackManager) SeekSeconds(sec float64) error {
+func (p *PlaybackManager) SeekSeconds(sec float64) {
-	return p.engine.SeekSeconds(sec)
+	p.cmdQueue.SeekSeconds(sec)
 }
 
 // Seek by given relative position in the current track by seconds.
-func (p *PlaybackManager) SeekBySeconds(sec float64) error {
+func (p *PlaybackManager) SeekBySeconds(sec float64) {
 	status := p.engine.PlayerStatus()
 	target := status.TimePos + sec
 	if target < 0 {
@@ -340,40 +350,79 @@ func (p *PlaybackManager) SeekBySeconds(sec float64) error {
 	} else if target > status.Duration {
 		target = status.Duration
 	}
-	return p.engine.SeekSeconds(target)
+	p.cmdQueue.SeekSeconds(target)
 }
 
 // Seek to a fractional position in the current track [0..1]
-func (p *PlaybackManager) SeekFraction(fraction float64) error {
+func (p *PlaybackManager) SeekFraction(fraction float64) {
 	if fraction < 0 {
 		fraction = 0
 	} else if fraction > 1 {
 		fraction = 1
 	}
 	target := p.engine.curTrackDuration * fraction
-	return p.engine.SeekSeconds(target)
+	p.cmdQueue.SeekSeconds(target)
 }
 
-func (p *PlaybackManager) Stop() error {
+func (p *PlaybackManager) Stop() {
-	return p.engine.Stop()
+	p.cmdQueue.Stop()
 }
 
-func (p *PlaybackManager) Pause() error {
+func (p *PlaybackManager) Pause() {
-	return p.engine.Pause()
+	p.cmdQueue.Pause()
 }
 
-func (p *PlaybackManager) Continue() error {
+func (p *PlaybackManager) Continue() {
-	return p.engine.Continue()
+	p.cmdQueue.Continue()
 }
 
-func (p *PlaybackManager) PlayPause() error {
+func (p *PlaybackManager) PlayPause() {
 	switch p.engine.PlayerStatus().State {
 	case player.Playing:
-		return p.engine.Pause()
+		p.Pause()
 	case player.Paused:
-		return p.engine.Continue()
+		p.Continue()
 	case player.Stopped:
-		return p.engine.PlayTrackAt(0)
+		p.PlayTrackAt(0)
+	}
+}
+
+func (p *PlaybackManager) runCmdQueue(ctx context.Context) {
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		case c := <-p.cmdQueue.C():
+			switch c.Type {
+			case cmdStop:
+				p.engine.Stop()
+			case cmdContinue:
+				p.engine.Continue()
+			case cmdPause:
+				p.engine.Pause()
+			case cmdPlayTrackAt:
+				p.engine.PlayTrackAt(c.Arg.(int))
+			case cmdSeekSeconds:
+				p.engine.SeekSeconds(c.Arg.(float64))
+			case cmdSeekFwdBackN:
+				log.Println("TODO")
+			case cmdVolume:
+				p.engine.SetVolume(c.Arg.(int))
+			case cmdLoopMode:
+				p.engine.SetLoopMode(c.Arg.(LoopMode))
+			case cmdStopAndClearPlayQueue:
+				p.engine.StopAndClearPlayQueue()
+			case cmdUpdatePlayQueue:
+				p.engine.UpdatePlayQueue(c.Arg.([]mediaprovider.MediaItem))
+			case cmdRemoveTracksFromQueue:
+				p.engine.RemoveTracksFromQueue(c.Arg.([]int))
+			case cmdLoadItems:
+				p.engine.LoadItems(
+					c.Arg.([]mediaprovider.MediaItem),
+					c.Arg2.(InsertQueueMode),
+					c.Arg3.(bool),
+				)
+			}
+		}
 	}
-	return errors.New("unreached - invalid player state")
 }

ui/bottompanel.go

@@ -106,7 +106,7 @@ func NewBottomPanel(pm *backend.PlaybackManager, im *backend.ImageManager, contr
 	pm.OnLoopModeChange(bp.AuxControls.SetLoopMode)
 	pm.OnVolumeChange(bp.AuxControls.VolumeControl.SetVolume)
 	bp.AuxControls.VolumeControl.OnSetVolume = func(v int) {
-		_ = pm.SetVolume(v)
+		pm.SetVolume(v)
 	}
 	bp.AuxControls.OnChangeLoopMode(func() {
 		pm.SetNextLoopMode()

ui/controller/connectactions.go

@@ -158,7 +158,7 @@ func (c *Controller) ConnectPlayQueuelistActions(list *widgets.PlayQueueList) {
 	}
 	list.OnAddToPlaylist = c.DoAddTracksToPlaylistWorkflow
 	list.OnPlayItemAt = func(tracknum int) {
-		_ = c.App.PlaybackManager.PlayTrackAt(tracknum)
+		c.App.PlaybackManager.PlayTrackAt(tracknum)
 	}
 	list.OnShowArtistPage = func(artistID string) {
 		c.NavigateTo(ArtistRoute(artistID))

ui/mainwindow.go

@@ -241,13 +241,13 @@ func (m *MainWindow) SetupSystemTrayMenu(appName string, fyneApp fyne.App) {
 	if desk, ok := fyneApp.(desktop.App); ok {
 		menu := fyne.NewMenu(appName,
 			fyne.NewMenuItem(fmt.Sprintf("%s/%s", lang.L("Play"), lang.L("Pause")), func() {
-				_ = m.App.PlaybackManager.PlayPause()
+				m.App.PlaybackManager.PlayPause()
 			}),
 			fyne.NewMenuItem(lang.L("Previous"), func() {
-				_ = m.App.PlaybackManager.SeekBackOrPrevious()
+				m.App.PlaybackManager.SeekBackOrPrevious()
 			}),
 			fyne.NewMenuItem(lang.L("Next"), func() {
-				_ = m.App.PlaybackManager.SeekNext()
+				m.App.PlaybackManager.SeekNext()
 			}),
 			fyne.NewMenuItemSeparator(),
 			fyne.NewMenuItem(lang.L("Volume")+" +10%", func() {