overlay + library: the preloader working on glass, album names that land on the right self-titled record, and covers warmed before you scroll to them

src-tauri/src/diagnostics.rs

@@ -6,6 +6,7 @@
 //! Process figures aggregate the WHOLE process tree: the WebView2 children
 //! do the actual rendering, so app.exe alone would tell a comforting lie.
 
+use std::collections::HashMap;
 use std::sync::{Arc, Mutex};
 use std::time::Instant;
 
@@ -27,6 +28,48 @@ struct Inner {
     /// StreamProgress — the overlay must read download truth at the source,
     /// not the UI store's window-activity-gated mirror.
     current_stream: Option<(u64, Arc<StreamProgress>)>,
+    /// On-deck pre-buffer transfers by transfer id, mirrored from the
+    /// download event stream (those updates are otherwise swallowed — no
+    /// player, no Downloads view). The Instant is set when the transfer
+    /// reaches a terminal state, so finished rows linger long enough to be
+    /// seen and then fall off.
+    preloads: HashMap<u64, (PreloadDl, Option<Instant>)>,
+}
+
+/// One on-deck transfer as the overlay sees it.
+#[derive(Serialize, Clone)]
+#[serde(rename_all = "camelCase")]
+pub struct PreloadDl {
+    pub username: String,
+    /// Full remote path — the frontend matches queue rows by this.
+    pub path: String,
+    pub state: String,
+    /// Remote queue position, when the peer reported one.
+    pub place: Option<u32>,
+    pub received: u64,
+    pub total: u64,
+    pub speed_bps: u64,
+}
+
+/// Called from the download event stream for every preload update.
+pub fn note_preload(app: &tauri::AppHandle, id: u64, dl: PreloadDl, terminal: bool) {
+    if let Some(state) = app.try_state::<DiagState>() {
+        let finished = if terminal { Some(Instant::now()) } else { None };
+        state
+            .0
+            .lock()
+            .expect("diag lock")
+            .preloads
+            .insert(id, (dl, finished));
+    }
+}
+
+/// Called when a play path takes the transfer over: it is the CURRENT
+/// track's stream from here on (note_stream reports it), not an on-deck row.
+pub fn retire_preload(app: &tauri::AppHandle, id: u64) {
+    if let Some(state) = app.try_state::<DiagState>() {
+        state.0.lock().expect("diag lock").preloads.remove(&id);
+    }
 }
 
 /// Called by the play paths: this track streams from a peer.
@@ -51,6 +94,7 @@ pub fn init(app: &tauri::AppHandle) {
         gpu: GpuCounter::open(),
         started: Instant::now(),
         current_stream: None,
+        preloads: HashMap::new(),
     })));
 }
 
@@ -98,6 +142,9 @@ pub struct DebugStats {
     pub preview_volume: Option<f32>,
     /// The active preview clip's loudness-normalization gain in dB.
     pub preview_norm_db: Option<f32>,
+    /// On-deck pre-buffer transfers, in arrival order (finished rows linger
+    /// ~15s so a completion is visible before it drops off).
+    pub preload_dl: Vec<PreloadDl>,
 }
 
 #[tauri::command]
@@ -167,6 +214,18 @@ pub fn debug_stats(app: tauri::AppHandle, state: State<'_, DiagState>) -> DebugS
     let tree_u32: Vec<u32> = tree.iter().map(|p| p.as_u32()).collect();
     let gpu_sample = inner.gpu.as_mut().and_then(|g| g.sample(&tree_u32));
 
+    // On-deck transfers: drop terminal rows after they've been visible a
+    // while, then report the rest in arrival (transfer-id) order.
+    inner
+        .preloads
+        .retain(|_, v| v.1.is_none_or(|t| t.elapsed().as_secs() < 15));
+    let mut preload_ids: Vec<u64> = inner.preloads.keys().copied().collect();
+    preload_ids.sort_unstable();
+    let preload_dl: Vec<PreloadDl> = preload_ids
+        .iter()
+        .filter_map(|id| inner.preloads.get(id).map(|(dl, _)| dl.clone()))
+        .collect();
+
     DebugStats {
         cpu_process,
         cpu_system: inner.sys.global_cpu_usage(),
@@ -201,6 +260,7 @@ pub fn debug_stats(app: tauri::AppHandle, state: State<'_, DiagState>) -> DebugS
         main_fade_gain: app
             .try_state::<crate::playback::PlayerState>()
             .map(|p| p.player.fade_gain()),
+        preload_dl,
     }
 }