Feat: background head-preload for sample libraries

src/main.rs

@@ -1,7 +1,7 @@
 mod app;
-mod init;
 mod commands;
 mod engine;
+mod init;
 mod input;
 mod midi;
 mod model;
@@ -118,6 +118,11 @@ fn main() -> io::Result<()> {
 
             audio_sample_pos.store(0, Ordering::Relaxed);
 
+            let preload_entries: Vec<(String, std::path::PathBuf)> = restart_samples
+                .iter()
+                .map(|e| (e.name.clone(), e.path.clone()))
+                .collect();
+
             match build_stream(
                 &new_config,
                 new_audio_rx,
@@ -127,7 +132,7 @@ fn main() -> io::Result<()> {
                 restart_samples,
                 Arc::clone(&audio_sample_pos),
             ) {
-                Ok((new_stream, info, new_analysis)) => {
+                Ok((new_stream, info, new_analysis, registry)) => {
                     _stream = Some(new_stream);
                     _analysis_handle = Some(new_analysis);
                     app.audio.config.sample_rate = info.sample_rate;
@@ -135,7 +140,18 @@ fn main() -> io::Result<()> {
                     app.audio.config.channels = info.channels;
                     sample_rate_shared.store(info.sample_rate as u32, Ordering::Relaxed);
                     app.audio.error = None;
+                    app.audio.sample_registry = Some(Arc::clone(&registry));
                     app.ui.set_status("Audio restarted".to_string());
+
+                    if !preload_entries.is_empty() {
+                        let sr = info.sample_rate;
+                        std::thread::Builder::new()
+                            .name("sample-preload".into())
+                            .spawn(move || {
+                                init::preload_sample_heads(preload_entries, sr, &registry);
+                            })
+                            .expect("failed to spawn preload thread");
+                    }
                 }
                 Err(e) => {
                     app.audio.error = Some(e.clone());