feat: playlist management, gapless playback, ReplayGain, Qobuz theme

Playlist management:
- Add/remove tracks from playlists via right-click context menu
- Create new playlists (right-click Playlists sidebar header)
- Delete playlists with confirmation dialog (right-click playlist item)
- Playlist view removes track immediately on delete (optimistic)
- Deleting currently-open playlist clears the track view

Gapless playback:
- Single long-running audio thread owns AudioOutput; CPAL stream stays
  open between tracks eliminating device teardown/startup gap
- Decode runs inline on the audio thread; command channel polled via
  try_recv() so Pause/Resume/Seek/Stop/Play all work without spawning
- New Play command arriving mid-decode is handled immediately,
  reusing the same audio output for zero-gap transition
- Position timer reduced from 500 ms to 50 ms for faster track-end detection
- URL/metadata prefetch: when gapless is enabled Qt pre-fetches the next
  track while the current one is still playing

ReplayGain:
- Toggled in Settings → Playback
- replaygain_track_gain (dB) from track audio_info converted to linear
  gain factor and applied per-sample alongside volume

Qobuz dark theme:
- Background #191919, base #141414, accent #FFB232 (yellow-orange)
- Selection highlight, slider fill, scrollbar hover all use #FFB232
- Links use Qobuz blue #46B3EE
- Hi-res H badges updated to #FFB232 (from #FFD700)
- Now-playing row uses #FFB232 (was Spotify green)
- QSS stylesheet for scrollbars, menus, inputs, buttons, groups

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

rust/include/qobuz_backend.h

@@ -30,7 +30,9 @@ enum QobuzEvent {
     EV_POSITION       = 16,
     EV_TRACK_URL_OK   = 17,
     EV_TRACK_URL_ERR  = 18,
-    EV_GENERIC_ERR    = 19,
+    EV_GENERIC_ERR      = 19,
+    EV_PLAYLIST_CREATED = 20,
+    EV_PLAYLIST_DELETED = 21,
 };
 
 // Callback signature
@@ -69,6 +71,16 @@ uint8_t  qobuz_backend_get_volume(const QobuzBackendOpaque *backend);
 int      qobuz_backend_get_state(const QobuzBackendOpaque *backend);
 int      qobuz_backend_take_track_finished(QobuzBackendOpaque *backend);
 
+// ReplayGain / Gapless
+void qobuz_backend_set_replaygain(QobuzBackendOpaque *backend, bool enabled);
+void qobuz_backend_prefetch_track(QobuzBackendOpaque *backend, int64_t track_id, int32_t format_id);
+
+// Playlist management
+void qobuz_backend_create_playlist(QobuzBackendOpaque *backend, const char *name);
+void qobuz_backend_delete_playlist(QobuzBackendOpaque *backend, int64_t playlist_id);
+void qobuz_backend_add_track_to_playlist(QobuzBackendOpaque *backend, int64_t playlist_id, int64_t track_id);
+void qobuz_backend_delete_track_from_playlist(QobuzBackendOpaque *backend, int64_t playlist_id, int64_t playlist_track_id);
+
 // Favorites modification
 void qobuz_backend_add_fav_track(QobuzBackendOpaque *backend, int64_t track_id);
 void qobuz_backend_remove_fav_track(QobuzBackendOpaque *backend, int64_t track_id);

rust/src/api/client.rs

@@ -89,6 +89,15 @@ impl QobuzClient {
         Ok(body)
     }
 
+    fn post_request(&self, method: &str) -> reqwest::RequestBuilder {
+        let mut builder = self.http.post(self.url(method));
+        builder = builder.query(&[("app_id", self.app_id.as_str())]);
+        if let Some(token) = &self.auth_token {
+            builder = builder.header("Authorization", format!("Bearer {}", token));
+        }
+        builder
+    }
+
     fn get_request(&self, method: &str) -> reqwest::RequestBuilder {
         let mut builder = self.http.get(self.url(method));
         builder = builder.query(&[("app_id", self.app_id.as_str())]);
@@ -329,6 +338,55 @@ impl QobuzClient {
         Ok(serde_json::from_value(body["artists"].clone())?)
     }
 
+    // --- Playlist management ---
+
+    pub async fn create_playlist(&self, name: &str) -> Result<PlaylistDto> {
+        let resp = self
+            .post_request("playlist/create")
+            .form(&[("name", name), ("is_public", "false"), ("is_collaborative", "false")])
+            .send()
+            .await?;
+        let body = Self::check_response(resp).await?;
+        Ok(serde_json::from_value(body)?)
+    }
+
+    pub async fn add_track_to_playlist(&self, playlist_id: i64, track_id: i64) -> Result<()> {
+        let resp = self
+            .post_request("playlist/addTracks")
+            .form(&[
+                ("playlist_id", playlist_id.to_string()),
+                ("track_ids",   track_id.to_string()),
+                ("no_duplicate", "true".to_string()),
+            ])
+            .send()
+            .await?;
+        Self::check_response(resp).await?;
+        Ok(())
+    }
+
+    pub async fn delete_playlist(&self, playlist_id: i64) -> Result<()> {
+        let resp = self
+            .get_request("playlist/delete")
+            .query(&[("playlist_id", &playlist_id.to_string())])
+            .send()
+            .await?;
+        Self::check_response(resp).await?;
+        Ok(())
+    }
+
+    pub async fn delete_track_from_playlist(&self, playlist_id: i64, playlist_track_id: i64) -> Result<()> {
+        let resp = self
+            .post_request("playlist/deleteTracks")
+            .form(&[
+                ("playlist_id",        playlist_id.to_string()),
+                ("playlist_track_ids", playlist_track_id.to_string()),
+            ])
+            .send()
+            .await?;
+        Self::check_response(resp).await?;
+        Ok(())
+    }
+
     pub async fn add_fav_track(&self, track_id: i64) -> Result<()> {
         let resp = self
             .get_request("favorite/create")

rust/src/api/models.rs

@@ -48,6 +48,7 @@ pub struct TrackDto {
     pub title: Option<String>,
     pub duration: Option<i64>,
     pub track_number: Option<i32>,
+    pub playlist_track_id: Option<i64>,
     pub album: Option<AlbumDto>,
     pub performer: Option<ArtistDto>,
     pub composer: Option<ArtistDto>,

rust/src/lib.rs

@@ -75,12 +75,20 @@ pub type EventCallback = unsafe extern "C" fn(*mut c_void, c_int, *const c_char)
 
 // ---------- Backend ----------
 
+struct PrefetchedTrack {
+    track_id: i64,
+    track: api::models::TrackDto,
+    url: String,
+}
+
 struct BackendInner {
     client: Arc<Mutex<QobuzClient>>,
     player: Player,
     rt: Runtime,
     cb: EventCallback,
     ud: SendPtr,
+    replaygain_enabled: std::sync::Arc<std::sync::atomic::AtomicBool>,
+    prefetch: std::sync::Arc<tokio::sync::Mutex<Option<PrefetchedTrack>>>,
 }
 
 pub struct Backend(BackendInner);
@@ -121,6 +129,8 @@ pub unsafe extern "C" fn qobuz_backend_new(
         rt,
         cb: event_cb,
         ud: SendPtr(userdata),
+        replaygain_enabled: std::sync::Arc::new(std::sync::atomic::AtomicBool::new(false)),
+        prefetch: std::sync::Arc::new(tokio::sync::Mutex::new(None)),
     })))
 }
 
@@ -341,35 +351,58 @@ pub unsafe extern "C" fn qobuz_backend_play_track(
     let format = Format::from_id(format_id);
     let cmd_tx = inner.player.cmd_tx.clone();
     let status = inner.player.status.clone();
+    let prefetch = inner.prefetch.clone();
+    let rg_enabled = inner.replaygain_enabled.clone();
 
     spawn(inner, async move {
-        // 1. Track metadata
-        let track = match client.lock().await.get_track(track_id).await {
-            Ok(t) => t,
-            Err(e) => { call_cb(cb, ud, EV_TRACK_URL_ERR, &err_json(&e.to_string())); return; }
+        // 1. Check prefetch cache first for zero-gap start
+        let cached = {
+            let mut lock = prefetch.lock().await;
+            if lock.as_ref().map(|p| p.track_id == track_id).unwrap_or(false) {
+                lock.take()
+            } else {
+                None
+            }
         };
 
-        // 2. Stream URL
-        let url_dto = match client.lock().await.get_track_url(track_id, format).await {
-            Ok(u) => u,
-            Err(e) => { call_cb(cb, ud, EV_TRACK_URL_ERR, &err_json(&e.to_string())); return; }
-        };
-        let url = match url_dto.url {
-            Some(u) => u,
-            None => { call_cb(cb, ud, EV_TRACK_URL_ERR, &err_json("no stream URL")); return; }
+        let (track, url) = if let Some(pf) = cached {
+            (pf.track, pf.url)
+        } else {
+            // Fetch track metadata
+            let track = match client.lock().await.get_track(track_id).await {
+                Ok(t) => t,
+                Err(e) => { call_cb(cb, ud, EV_TRACK_URL_ERR, &err_json(&e.to_string())); return; }
+            };
+            // Fetch stream URL
+            let url_dto = match client.lock().await.get_track_url(track_id, format).await {
+                Ok(u) => u,
+                Err(e) => { call_cb(cb, ud, EV_TRACK_URL_ERR, &err_json(&e.to_string())); return; }
+            };
+            let url = match url_dto.url {
+                Some(u) => u,
+                None => { call_cb(cb, ud, EV_TRACK_URL_ERR, &err_json("no stream URL")); return; }
+            };
+            (track, url)
         };
 
-        // 3. Notify track change
+        // 2. Notify track change
         if let Ok(j) = serde_json::to_string(&track) {
             call_cb(cb, ud, EV_TRACK_CHANGED, &j);
         }
 
+        // 3. Compute ReplayGain if enabled
+        let replaygain_db = if rg_enabled.load(std::sync::atomic::Ordering::Relaxed) {
+            track.audio_info.as_ref().and_then(|ai| ai.replaygain_track_gain)
+        } else {
+            None
+        };
+
         // 4. Update status + send play command
         *status.current_track.lock().unwrap() = Some(track.clone());
         if let Some(dur) = track.duration {
             status.duration_secs.store(dur as u64, std::sync::atomic::Ordering::Relaxed);
         }
-        let _ = cmd_tx.send(player::PlayerCommand::Play(player::TrackInfo { track, url, format }));
+        let _ = cmd_tx.send(player::PlayerCommand::Play(player::TrackInfo { track, url, format, replaygain_db }));
 
         // 5. State notification
         call_cb(cb, ud, EV_STATE_CHANGED, r#"{"state":"playing"}"#);
@@ -438,6 +471,41 @@ pub unsafe extern "C" fn qobuz_backend_take_track_finished(ptr: *mut Backend) ->
     if finished { 1 } else { 0 }
 }
 
+// ---------- ReplayGain / Gapless ----------
+
+#[no_mangle]
+pub unsafe extern "C" fn qobuz_backend_set_replaygain(ptr: *mut Backend, enabled: bool) {
+    (*ptr).0.replaygain_enabled.store(enabled, std::sync::atomic::Ordering::Relaxed);
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn qobuz_backend_prefetch_track(
+    ptr: *mut Backend,
+    track_id: i64,
+    format_id: i32,
+) {
+    let inner  = &(*ptr).0;
+    let client = inner.client.clone();
+    let prefetch = inner.prefetch.clone();
+    let format = Format::from_id(format_id);
+
+    spawn(inner, async move {
+        let track = match client.lock().await.get_track(track_id).await {
+            Ok(t) => t,
+            Err(_) => return,
+        };
+        let url_dto = match client.lock().await.get_track_url(track_id, format).await {
+            Ok(u) => u,
+            Err(_) => return,
+        };
+        let url = match url_dto.url {
+            Some(u) => u,
+            None => return,
+        };
+        *prefetch.lock().await = Some(PrefetchedTrack { track_id, track, url });
+    });
+}
+
 // ---------- Favorites modification ----------
 
 #[no_mangle]
@@ -489,3 +557,68 @@ pub unsafe extern "C" fn qobuz_backend_remove_fav_album(ptr: *mut Backend, album
         }
     });
 }
+
+// ---------- Playlist management ----------
+
+pub const EV_PLAYLIST_CREATED: c_int = 20;
+pub const EV_PLAYLIST_DELETED: c_int = 21;
+
+#[no_mangle]
+pub unsafe extern "C" fn qobuz_backend_create_playlist(ptr: *mut Backend, name: *const c_char) {
+    let inner = &(*ptr).0;
+    let name  = CStr::from_ptr(name).to_string_lossy().into_owned();
+    let client = inner.client.clone();
+    let cb = inner.cb; let ud = inner.ud;
+    spawn(inner, async move {
+        match client.lock().await.create_playlist(&name).await {
+            Ok(p)  => call_cb(cb, ud, EV_PLAYLIST_CREATED, &serde_json::to_string(&p).unwrap_or_default()),
+            Err(e) => call_cb(cb, ud, EV_GENERIC_ERR, &err_json(&e.to_string())),
+        }
+    });
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn qobuz_backend_delete_playlist(ptr: *mut Backend, playlist_id: i64) {
+    let inner  = &(*ptr).0;
+    let client = inner.client.clone();
+    let cb = inner.cb; let ud = inner.ud;
+    spawn(inner, async move {
+        match client.lock().await.delete_playlist(playlist_id).await {
+            Ok(()) => call_cb(cb, ud, EV_PLAYLIST_DELETED,
+                &serde_json::json!({"playlist_id": playlist_id}).to_string()),
+            Err(e) => call_cb(cb, ud, EV_GENERIC_ERR, &err_json(&e.to_string())),
+        }
+    });
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn qobuz_backend_add_track_to_playlist(
+    ptr: *mut Backend,
+    playlist_id: i64,
+    track_id: i64,
+) {
+    let inner  = &(*ptr).0;
+    let client = inner.client.clone();
+    let cb = inner.cb; let ud = inner.ud;
+    spawn(inner, async move {
+        if let Err(e) = client.lock().await.add_track_to_playlist(playlist_id, track_id).await {
+            call_cb(cb, ud, EV_GENERIC_ERR, &err_json(&e.to_string()));
+        }
+    });
+}
+
+#[no_mangle]
+pub unsafe extern "C" fn qobuz_backend_delete_track_from_playlist(
+    ptr: *mut Backend,
+    playlist_id: i64,
+    playlist_track_id: i64,
+) {
+    let inner  = &(*ptr).0;
+    let client = inner.client.clone();
+    let cb = inner.cb; let ud = inner.ud;
+    spawn(inner, async move {
+        if let Err(e) = client.lock().await.delete_track_from_playlist(playlist_id, playlist_track_id).await {
+            call_cb(cb, ud, EV_GENERIC_ERR, &err_json(&e.to_string()));
+        }
+    });
+}

rust/src/player/decoder.rs

@@ -15,7 +15,7 @@ use symphonia::core::{
     units::Time,
 };
 
-use crate::player::{output::AudioOutput, PlayerStatus};
+use super::{output::AudioOutput, PlayerCommand, PlayerStatus, TrackInfo};
 
 /// First 512 KiB of stream kept in memory to support backward seeks during probing.
 const HEAD_SIZE: usize = 512 * 1024;
@@ -127,13 +127,22 @@ impl MediaSource for HttpStreamSource {
     }
 }
 
-/// Stream and decode audio from `url`. Runs on a dedicated OS thread.
-pub fn play_track(
+/// Decode and play `url` inline on the calling thread (the player loop).
+///
+/// `audio_output` is reused across calls if the sample rate and channel count match,
+/// keeping the CPAL stream open between tracks for gapless playback.
+///
+/// Returns:
+/// - `Ok(Some(TrackInfo))` — a new Play command arrived; start that track next.
+/// - `Ok(None)`            — track finished naturally or was stopped.
+/// - `Err(_)`              — unrecoverable playback error.
+pub fn play_track_inline(
     url: &str,
     status: &PlayerStatus,
-    stop: &Arc<AtomicBool>,
     paused: &Arc<AtomicBool>,
-) -> Result<()> {
+    audio_output: &mut Option<AudioOutput>,
+    cmd_rx: &std::sync::mpsc::Receiver<PlayerCommand>,
+) -> Result<Option<TrackInfo>> {
     let response = reqwest::blocking::get(url)?;
     let content_length = response.content_length();
     let source = HttpStreamSource::new(response, content_length);
@@ -160,19 +169,91 @@ pub fn play_track(
         .make(&track.codec_params, &DecoderOptions::default())
         .map_err(|e| anyhow::anyhow!("decoder init failed: {e}"))?;
 
-    let mut audio_output = AudioOutput::try_open(sample_rate, channels)?;
-
-    loop {
-        if stop.load(Ordering::SeqCst) {
-            break;
+    // Reuse existing audio output if format matches; rebuild only on format change.
+    if let Some(ao) = audio_output.as_ref() {
+        if ao.sample_rate != sample_rate || ao.channels != channels {
+            *audio_output = None; // will be recreated below
         }
-        while paused.load(Ordering::SeqCst) {
-            std::thread::sleep(std::time::Duration::from_millis(50));
-            if stop.load(Ordering::SeqCst) {
-                return Ok(());
+    }
+    if audio_output.is_none() {
+        *audio_output = Some(AudioOutput::try_open(sample_rate, channels)?);
+    }
+    let ao = audio_output.as_mut().unwrap();
+
+    let mut stopped = false;
+    let mut next_track: Option<TrackInfo> = None;
+
+    'decode: loop {
+        // Non-blocking command check — handle Pause/Resume/Seek/Stop/Play
+        loop {
+            match cmd_rx.try_recv() {
+                Ok(PlayerCommand::Pause) => {
+                    paused.store(true, Ordering::SeqCst);
+                    *status.state.lock().unwrap() = super::PlayerState::Paused;
+                }
+                Ok(PlayerCommand::Resume) => {
+                    paused.store(false, Ordering::SeqCst);
+                    *status.state.lock().unwrap() = super::PlayerState::Playing;
+                }
+                Ok(PlayerCommand::Seek(s)) => {
+                    status.seek_target_secs.store(s, Ordering::Relaxed);
+                    status.seek_requested.load(Ordering::SeqCst); // read-side fence
+                    status.seek_requested.store(true, Ordering::SeqCst);
+                }
+                Ok(PlayerCommand::SetVolume(v)) => {
+                    status.volume.store(v, Ordering::Relaxed);
+                }
+                Ok(PlayerCommand::Stop) => {
+                    paused.store(false, Ordering::SeqCst);
+                    *status.state.lock().unwrap() = super::PlayerState::Idle;
+                    *status.current_track.lock().unwrap() = None;
+                    status.position_secs.store(0, Ordering::Relaxed);
+                    status.duration_secs.store(0, Ordering::Relaxed);
+                    stopped = true;
+                    break 'decode;
+                }
+                Ok(PlayerCommand::Play(info)) => {
+                    // New track requested — stop current and return it
+                    next_track = Some(info);
+                    break 'decode;
+                }
+                Err(std::sync::mpsc::TryRecvError::Empty) => break,
+                Err(std::sync::mpsc::TryRecvError::Disconnected) => {
+                    stopped = true;
+                    break 'decode;
+                }
             }
         }
 
+        // Spin while paused, but keep checking for commands
+        while paused.load(Ordering::SeqCst) {
+            std::thread::sleep(std::time::Duration::from_millis(10));
+            // Still check for Stop/Play while paused
+            match cmd_rx.try_recv() {
+                Ok(PlayerCommand::Resume) => {
+                    paused.store(false, Ordering::SeqCst);
+                    *status.state.lock().unwrap() = super::PlayerState::Playing;
+                }
+                Ok(PlayerCommand::Stop) => {
+                    paused.store(false, Ordering::SeqCst);
+                    stopped = true;
+                    break;
+                }
+                Ok(PlayerCommand::Play(info)) => {
+                    paused.store(false, Ordering::SeqCst);
+                    next_track = Some(info);
+                    break 'decode;
+                }
+                Ok(PlayerCommand::SetVolume(v)) => {
+                    status.volume.store(v, Ordering::Relaxed);
+                }
+                _ => {}
+            }
+            if stopped { break 'decode; }
+        }
+        if stopped { break; }
+
+        // Handle seek
         if status.seek_requested.load(Ordering::SeqCst) {
             status.seek_requested.store(false, Ordering::SeqCst);
             let target = status.seek_target_secs.load(Ordering::Relaxed);
@@ -190,8 +271,10 @@ pub fn play_track(
 
         let packet = match format.next_packet() {
             Ok(p) => p,
-            Err(SymphoniaError::IoError(e)) if e.kind() == std::io::ErrorKind::UnexpectedEof => {
-                break;
+            Err(SymphoniaError::IoError(e))
+                if e.kind() == std::io::ErrorKind::UnexpectedEof =>
+            {
+                break; // natural end of track
             }
             Err(SymphoniaError::ResetRequired) => {
                 decoder.reset();
@@ -205,13 +288,16 @@ pub fn play_track(
         }
 
         if let Some(ts) = packet.ts().checked_div(sample_rate as u64) {
-            status.position_secs.store(ts, std::sync::atomic::Ordering::Relaxed);
+            status.position_secs.store(ts, Ordering::Relaxed);
         }
 
         match decoder.decode(&packet) {
             Ok(decoded) => {
                 let volume = status.volume.load(Ordering::Relaxed) as f32 / 100.0;
-                audio_output.write(decoded, volume, stop)?;
+                let rg = *status.replaygain_gain.lock().unwrap();
+                // Use a stop flag tied to new-track-incoming so write doesn't block
+                let dummy_stop = Arc::new(AtomicBool::new(false));
+                ao.write(decoded, (volume * rg).min(1.0), &dummy_stop)?;
             }
             Err(SymphoniaError::IoError(_)) => break,
             Err(SymphoniaError::DecodeError(e)) => eprintln!("decode error: {e}"),
@@ -219,5 +305,10 @@ pub fn play_track(
         }
     }
 
-    Ok(())
+    if stopped {
+        // On explicit stop, drop the audio output to silence immediately
+        *audio_output = None;
+    }
+
+    Ok(next_track)
 }

rust/src/player/mod.rs

@@ -24,6 +24,8 @@ pub struct TrackInfo {
     pub track: TrackDto,
     pub url: String,
     pub format: Format,
+    /// ReplayGain track gain in dB, if enabled and available.
+    pub replaygain_db: Option<f64>,
 }
 
 #[derive(Debug, Clone, PartialEq)]
@@ -47,6 +49,8 @@ pub struct PlayerStatus {
     /// Set by the player loop when a seek command arrives; cleared by the decode thread.
     pub seek_requested: Arc<AtomicBool>,
     pub seek_target_secs: Arc<AtomicU64>,
+    /// Linear gain factor to apply (1.0 = unity). Updated each time a new track starts.
+    pub replaygain_gain: Arc<std::sync::Mutex<f32>>,
 }
 
 impl PlayerStatus {
@@ -60,6 +64,7 @@ impl PlayerStatus {
             track_finished: Arc::new(AtomicBool::new(false)),
             seek_requested: Arc::new(AtomicBool::new(false)),
             seek_target_secs: Arc::new(AtomicU64::new(0)),
+            replaygain_gain: Arc::new(std::sync::Mutex::new(1.0)),
         }
     }
 
@@ -106,10 +111,6 @@ impl Player {
         self.cmd_tx.send(cmd).ok();
     }
 
-    pub fn play_track(&self, track: TrackDto, url: String, format: Format) {
-        self.send(PlayerCommand::Play(TrackInfo { track, url, format }));
-    }
-
     pub fn pause(&self) {
         self.send(PlayerCommand::Pause);
     }
@@ -133,68 +134,77 @@ impl Player {
     }
 }
 
+/// The player loop runs on a single dedicated OS thread.
+/// It owns the `AudioOutput` locally so there are no Send constraints.
+/// Decoding is performed inline; the command channel is polled via try_recv
+/// inside the decode loop to handle Pause/Resume/Seek/Stop/Play without
+/// tearng down and re-opening the audio device between tracks.
 fn player_loop(rx: std::sync::mpsc::Receiver<PlayerCommand>, status: PlayerStatus) {
-    let mut stop_flag = Arc::new(AtomicBool::new(true));
+    use std::sync::mpsc::RecvTimeoutError;
+
+    let mut audio_output: Option<output::AudioOutput> = None;
     let paused = Arc::new(AtomicBool::new(false));
+    // pending_info holds a Play command that interrupted an ongoing decode
+    let mut pending_info: Option<TrackInfo> = None;
 
-    loop {
-        match rx.recv_timeout(Duration::from_millis(100)) {
-            Ok(cmd) => match cmd {
-                PlayerCommand::Play(info) => {
-                    stop_flag.store(true, Ordering::SeqCst);
-                    stop_flag = Arc::new(AtomicBool::new(false));
-                    paused.store(false, Ordering::SeqCst);
-
-                    *status.state.lock().unwrap() = PlayerState::Playing;
-                    *status.current_track.lock().unwrap() = Some(info.track.clone());
-                    if let Some(dur) = info.track.duration {
-                        status.duration_secs.store(dur as u64, Ordering::Relaxed);
+    'outer: loop {
+        // Wait for a Play command (or use one that was interrupted)
+        let info = if let Some(p) = pending_info.take() {
+            p
+        } else {
+            loop {
+                match rx.recv_timeout(Duration::from_millis(100)) {
+                    Ok(PlayerCommand::Play(info)) => break info,
+                    Ok(PlayerCommand::Stop) => {
+                        audio_output = None;
+                        paused.store(false, Ordering::SeqCst);
+                        *status.state.lock().unwrap() = PlayerState::Idle;
+                        *status.current_track.lock().unwrap() = None;
+                        status.position_secs.store(0, Ordering::Relaxed);
+                        status.duration_secs.store(0, Ordering::Relaxed);
                     }
-                    status.position_secs.store(0, Ordering::Relaxed);
+                    Ok(PlayerCommand::SetVolume(v)) => {
+                        status.volume.store(v, Ordering::Relaxed);
+                    }
+                    Ok(PlayerCommand::Seek(s)) => {
+                        status.seek_target_secs.store(s, Ordering::Relaxed);
+                        status.seek_requested.store(true, Ordering::SeqCst);
+                    }
+                    Ok(_) => {} // Pause/Resume ignored when idle
+                    Err(RecvTimeoutError::Timeout) => {}
+                    Err(RecvTimeoutError::Disconnected) => break 'outer,
+                }
+            }
+        };
 
-                    let status_c = status.clone();
-                    let stop_c = stop_flag.clone();
-                    let paused_c = paused.clone();
+        // Compute ReplayGain factor
+        let rg_factor = info.replaygain_db
+            .map(|db| 10f32.powf(db as f32 / 20.0))
+            .unwrap_or(1.0);
+        *status.replaygain_gain.lock().unwrap() = rg_factor;
 
-                    std::thread::spawn(move || {
-                        match decoder::play_track(&info.url, &status_c, &stop_c, &paused_c) {
-                            Ok(()) => {
-                                if !stop_c.load(Ordering::SeqCst) {
-                                    *status_c.state.lock().unwrap() = PlayerState::Idle;
-                                    status_c.track_finished.store(true, Ordering::SeqCst);
-                                }
-                            }
-                            Err(e) => {
-                                eprintln!("playback error: {e}");
-                                *status_c.state.lock().unwrap() =
-                                    PlayerState::Error(e.to_string());
-                            }
-                        }
-                    });
-                }
-                PlayerCommand::Pause => {
-                    paused.store(true, Ordering::SeqCst);
-                    *status.state.lock().unwrap() = PlayerState::Paused;
-                }
-                PlayerCommand::Resume => {
-                    paused.store(false, Ordering::SeqCst);
-                    *status.state.lock().unwrap() = PlayerState::Playing;
-                }
-                PlayerCommand::Stop => {
-                    stop_flag.store(true, Ordering::SeqCst);
-                    *status.state.lock().unwrap() = PlayerState::Idle;
-                    *status.current_track.lock().unwrap() = None;
-                    status.position_secs.store(0, Ordering::Relaxed);
-                    status.duration_secs.store(0, Ordering::Relaxed);
-                }
-                PlayerCommand::SetVolume(_) => {}
-                PlayerCommand::Seek(secs) => {
-                    status.seek_target_secs.store(secs, Ordering::Relaxed);
-                    status.seek_requested.store(true, Ordering::SeqCst);
-                }
-            },
-            Err(std::sync::mpsc::RecvTimeoutError::Timeout) => {}
-            Err(std::sync::mpsc::RecvTimeoutError::Disconnected) => break,
+        *status.state.lock().unwrap() = PlayerState::Playing;
+        *status.current_track.lock().unwrap() = Some(info.track.clone());
+        if let Some(dur) = info.track.duration {
+            status.duration_secs.store(dur as u64, Ordering::Relaxed);
+        }
+        status.position_secs.store(0, Ordering::Relaxed);
+        paused.store(false, Ordering::SeqCst);
+
+        match decoder::play_track_inline(&info.url, &status, &paused, &mut audio_output, &rx) {
+            Ok(Some(next_info)) => {
+                // Interrupted by a new Play — loop immediately with reused audio output
+                pending_info = Some(next_info);
+            }
+            Ok(None) => {
+                // Track finished naturally
+                *status.state.lock().unwrap() = PlayerState::Idle;
+                status.track_finished.store(true, Ordering::SeqCst);
+            }
+            Err(e) => {
+                eprintln!("playback error: {e}");
+                *status.state.lock().unwrap() = PlayerState::Error(e.to_string());
+            }
         }
     }
 }

rust/src/player/output.rs

@@ -15,6 +15,8 @@ const RING_BUFFER_SIZE: usize = 32 * 1024;
 pub struct AudioOutput {
     ring_buf_producer: rb::Producer<f32>,
     _stream: cpal::Stream,
+    pub sample_rate: u32,
+    pub channels: usize,
 }
 
 impl AudioOutput {
@@ -50,6 +52,8 @@ impl AudioOutput {
         Ok(Self {
             ring_buf_producer: producer,
             _stream: stream,
+            sample_rate,
+            channels,
         })
     }