Add audio device switching UI

internal/mixer/mixer.go

@@ -31,10 +31,15 @@ var (
 	defaultAllow     = sdl.AUDIO_ALLOW_ANY_CHANGE
 
 	refreshCacheCallback func()
+
+	persistConfigCallback func(*db.AppConfig) error
 )
 
 // Init initializes SDL audio + SDL_mixer. Safe to call multiple times.
-func Init(cfg *db.AppConfig, onUpdate func()) error {
+// persistConfig persists the given config (used to save the selected audio
+// device across restarts); it may be nil, in which case device selections are
+// not saved.
+func Init(cfg *db.AppConfig, onUpdate func(), persistConfig func(*db.AppConfig) error) error {
 	mu.Lock()
 	defer mu.Unlock()
 	if inited {
@@ -42,6 +47,7 @@ func Init(cfg *db.AppConfig, onUpdate func()) error {
 	}
 
 	refreshCacheCallback = onUpdate
+	persistConfigCallback = persistConfig
 
 	if err := sdl.InitSubSystem(sdl.INIT_AUDIO); err != nil {
 		return fmt.Errorf("SDL audio init failed: %w", err)
@@ -52,9 +58,20 @@ func Init(cfg *db.AppConfig, onUpdate func()) error {
 		logger.Error("Failed to initialize MP3/OGG support: %v", err)
 	}
 
+	// A stored "default" (the first-run seed) is the system default.
 	deviceName := cfg.SelectedAudioDevice
-	if deviceName == "default" {
+	if deviceName == "" || deviceName == "default" {
 		deviceName = ""
+	} else {
+		// Honor a persisted device selection by resolving it against the
+		// currently enumerated devices, falling back to the system default if
+		// it is no longer present.
+		if resolved, ok := resolvePreferredDevice(deviceName); ok {
+			deviceName = resolved
+		} else {
+			logger.Warning("Selected audio device %q not found; using system default", cfg.SelectedAudioDevice)
+			deviceName = ""
+		}
 	}
 	if err := openDeviceLocked(deviceName); err != nil {
 		sdl.QuitSubSystem(sdl.INIT_AUDIO)
@@ -178,7 +195,10 @@ func IsPlaying() bool {
 	return mix.PlayingMusic()
 }
 
-// SetVolume sets the SDL_mixer music volume to level (0.0–1.0).
+// SetVolume sets the SDL_mixer music volume to level (0.0–1.0), mapped onto
+// SDL_mixer's 0–128 scale (mix.MAX_VOLUME). This is relative to the OS audio
+// sink, which the kiosk shell pins to 100%, so in-app volume is 0–100% of the
+// sink output.
 func SetVolume(level float64) error {
 	if level < 0 || level > 1 {
 		return fmt.Errorf("volume must be between 0.0 and 1.0, got %f", level)
@@ -204,23 +224,6 @@ func ConvertVolume(volPerc int) float64 {
 	return float64(volPerc) / 100.0
 }
 
-// ListDevices returns the list of available output device names (from core SDL).
-func ListDevices() []string {
-	mu.Lock()
-	defer mu.Unlock()
-	n := sdl.GetNumAudioDevices(false)
-	if n <= 0 {
-		return nil
-	}
-	out := make([]string, 0, n)
-	for i := 0; i < n; i++ {
-		if name := sdl.GetAudioDeviceName(i, false); name != "" {
-			out = append(out, name)
-		}
-	}
-	return out
-}
-
 // CurrentDevice returns the last requested/opened device name ("" means default).
 func CurrentDevice() string {
 	return deviceName
@@ -265,6 +268,14 @@ func SwitchDevice(newName string, cfg *db.AppConfig) error {
 	}
 
 	if cfg != nil {
+		// Persist whatever device is actually open (openDeviceLocked falls
+		// back to the system default if the requested name cannot be opened).
+		cfg.SelectedAudioDevice = CurrentDevice()
+		if persistConfigCallback != nil {
+			if err := persistConfigCallback(cfg); err != nil {
+				logger.Error("Failed to persist audio device selection: %v", err)
+			}
+		}
 		currentVolume = cfg.SavedVolume
 		v := int(math.Round(cfg.SavedVolume * float64(mix.MAX_VOLUME)))
 		mix.VolumeMusic(v)