fix(audio): read the device id instead of its description on macOS

CHANGELOG.md

@@ -53,6 +53,8 @@
 
 - **Radio falls back to station information for blank titles**: empty or dash-only ICY titles no longer blank the playbar subtitle or the artist sent to media integrations ([#820](https://github.com/LargeModGames/spotatui/issues/820)).
 
+- **No more random audio dropouts on macOS USB outputs** while local files, Subsonic or YouTube tracks play: the once-a-second check for a changed default output device rebuilt two CoreAudio units each time, which made USB devices glitch. It now reads the device's stable id instead ([#928](https://github.com/LargeModGames/spotatui/issues/928)).
+
 - **The page no longer scrolls past the player bar when a list has explicit songs** in the desktop app and the browser GUI: the hidden screen-reader text next to each E badge had no anchor, so it stretched the document below the window and the whole page could scroll into empty space. The text is now anchored and clipped, so only the panels inside the page scroll ([#878](https://github.com/LargeModGames/spotatui/issues/878)).
 
 - **Escape dismisses the announcement popup** in the terminal: the popup said `[Press ENTER or ESC to dismiss]`, but Esc did nothing because the global escape handler swallowed it before the popup's own handler ran; Esc now dismisses the current announcement and shows the next one, like Enter ([#871](https://github.com/LargeModGames/spotatui/issues/871)).

src/infra/audio/player.rs

@@ -30,7 +30,7 @@
 //! `DeviceNotAvailable`. It cannot notice the far more common case: the OS
 //! moving its **default output** somewhere else — headphones unplugged, AirPods
 //! back in their case — which leaves the stream happily bound to a device
-//! nobody is listening to. So the sink also remembers which device it opened
+//! nobody is listening to. So the sink also remembers its device's id,
 //! and [`device_lost`](LocalPlayer::device_lost) compares that against the
 //! current default.
 //!
@@ -95,7 +95,7 @@ pub struct LocalPlayer {
   stage_transition: Mutex<()>,
 }
 
-/// One default-output read, keyed on the name the sink opened so a swapped
+/// One default-output read, keyed on the opened device's id so a swapped
 /// sink is never answered from the old sink's cache.
 struct DeviceCheck {
   checked_at: Instant,
@@ -132,9 +132,10 @@ struct Sink {
   _keepalive: mpsc::Sender<()>,
   /// Raised by our cpal error callback when the device is *removed*.
   lost: Arc<AtomicBool>,
-  /// The device this sink was opened on, as cpal names it, so a default-output
-  /// change can be spotted (see module docs). `None` when the name could not be
-  /// read, which only disables the comparison — never fakes a change.
+  /// The key identifying the device this sink was opened on (id on macOS,
+  /// name elsewhere - see `device_key`), so a default-output change can be
+  /// spotted (see module docs). `None` when the key could not be read, which
+  /// only disables the comparison — never fakes a change.
   device_name: Option<String>,
 }
 
@@ -157,7 +158,7 @@ const AUDIO_THREAD_CEILING: Duration = Duration::from_secs(90);
 const DEVICE_OPEN_TIMEOUT: Duration = Duration::from_secs(5);
 
 /// How often [`LocalPlayer::device_lost`] re-reads the default output device.
-/// The tick asks on every frame, and the read is a full device enumeration.
+/// The tick asks on every frame, and the read talks to the OS's audio APIs.
 const DEVICE_CHECK_INTERVAL: Duration = Duration::from_secs(1);
 
 /// The spacing between reopen attempts, and how many are made before the
@@ -269,15 +270,15 @@ impl LocalPlayer {
   /// us, or the OS quietly moved its default output elsewhere and nobody did.
   pub fn device_lost(&self) -> bool {
     // Read the sink's answer and release its lock: the default-output read
-    // below enumerates devices, and the render path waits on this mutex.
+    // below queries the OS, and the render path waits on this mutex.
     let (removed, opened) = {
       let sink = self.sink.lock().unwrap();
       (sink.lost.load(Ordering::Relaxed), sink.device_name.clone())
     };
     if removed {
       return true;
     }
-    // Only a name read successfully on *both* sides is evidence: a missing one
+    // Only an id read successfully on *both* sides is evidence: a missing one
     // means "cannot tell", which must not read as "changed" — mid-switch there
     // is briefly no default device at all, and tearing playback down for that
     // would be worse than the silence this exists to catch.
@@ -290,7 +291,7 @@ impl LocalPlayer {
         return cached.moved;
       }
     }
-    let moved = default_output_name().is_some_and(|current| current != opened);
+    let moved = default_output_key().is_some_and(|current| current != opened);
     *check = Some(DeviceCheck {
       checked_at: Instant::now(),
       opened,
@@ -619,7 +620,7 @@ fn open_sink() -> Result<Sink> {
   let device = rodio::cpal::default_host()
     .default_output_device()
     .context("no audio output device available")?;
-  let device_name = device_name(&device);
+  let device_key = device_key(&device);
 
   let lost = Arc::new(AtomicBool::new(false));
   let on_error = {
@@ -683,25 +684,38 @@ fn open_sink() -> Result<Sink> {
     player: Arc::new(player),
     _keepalive: keepalive_tx,
     lost,
-    device_name,
+    device_name: device_key,
   })
 }
 
-/// A device's name as cpal reports it. `None` when it cannot be read — the
-/// caller must treat that as "cannot tell", never as a change.
-fn device_name(device: &rodio::Device) -> Option<String> {
+/// What identifies the device for the default-output comparison.
+///
+/// On macOS the id is read: `description()` builds two AudioUnits through its
+/// config queries, and re-reading it every check churns the device enough to
+/// glitch USB outputs, while `id()` is a plain property read. Everywhere else
+/// the name is kept: cpal's WASAPI `id()` leaks the COM string it copies on
+/// every call, which a once-a-second poll would turn into a steady leak.
+#[cfg(target_os = "macos")]
+fn device_key(device: &rodio::Device) -> Option<String> {
+  use rodio::DeviceTrait;
+  device.id().ok().map(|id| id.to_string())
+}
+
+/// Non-macOS: the description works and carries no per-read side effect.
+#[cfg(not(target_os = "macos"))]
+fn device_key(device: &rodio::Device) -> Option<String> {
   use rodio::DeviceTrait;
   device.description().ok().map(|d| d.name().to_string())
 }
 
-/// The name of the output device the OS currently calls its default, which is
-/// what a sink opened earlier is compared against.
-fn default_output_name() -> Option<String> {
+/// The identifying key of the output device the OS currently calls its
+/// default, which is what a sink opened earlier is compared against.
+fn default_output_key() -> Option<String> {
   use rodio::cpal::traits::HostTrait;
   rodio::cpal::default_host()
     .default_output_device()
     .as_ref()
-    .and_then(device_name)
+    .and_then(device_key)
 }
 
 // ---------------------------------------------------------------------------
@@ -846,19 +860,19 @@ mod tests {
       "a sink freshly opened on the current default is not lost"
     );
 
-    // Stand in for the OS switching away: the sink names a device that is no
-    // longer the default.
+    // Stand in for the OS switching away: the sink holds the id of a device
+    // that is no longer the default.
     player.sink.lock().unwrap().device_name = Some("a device that went away".to_string());
     assert!(
       player.device_lost(),
       "a default that moved is a lost device"
     );
 
-    // A name we could not read means "cannot tell", never "changed": mid-switch
+    // An id we could not read means "cannot tell", never "changed": mid-switch
     // there is briefly no default at all, and tearing playback down for that
     // would be worse than the silence this exists to catch.
     player.sink.lock().unwrap().device_name = None;
-    assert!(!player.device_lost(), "an unreadable name is not evidence");
+    assert!(!player.device_lost(), "an unreadable id is not evidence");
 
     player.reopen().expect("reopen on the default device");
     assert!(