Feat: rework audio sample library viewer

src/views/render.rs

@@ -170,12 +170,49 @@ fn render_side_panel(frame: &mut Frame, app: &App, area: Rect) {
     let focused = app.panel.focus == PanelFocus::Side;
     match &app.panel.side {
         Some(SidePanel::SampleBrowser(state)) => {
+            let [tree_area, preview_area] =
+                Layout::vertical([Constraint::Fill(1), Constraint::Length(6)]).areas(area);
+
             let entries = state.entries();
             SampleBrowser::new(&entries, state.cursor)
                 .scroll_offset(state.scroll_offset)
                 .search(&state.search_query, state.search_active)
                 .focused(focused)
-                .render(frame, area);
+                .render(frame, tree_area);
+
+            if let Some(sample) = state
+                .sample_key()
+                .and_then(|key| app.audio.sample_registry.as_ref()?.get(&key))
+                .filter(|s| s.frame_count >= s.total_frames)
+            {
+                use crate::widgets::Waveform;
+                use std::cell::RefCell;
+                thread_local! {
+                    static MONO_BUF: RefCell<Vec<f32>> = const { RefCell::new(Vec::new()) };
+                }
+
+                let [wave_area, info_area] =
+                    Layout::vertical([Constraint::Fill(1), Constraint::Length(1)])
+                        .areas(preview_area);
+
+                MONO_BUF.with(|buf| {
+                    let mut buf = buf.borrow_mut();
+                    let channels = sample.channels as usize;
+                    let frame_count = sample.frame_count as usize;
+                    buf.clear();
+                    buf.reserve(frame_count);
+                    for i in 0..frame_count {
+                        buf.push(sample.frames[i * channels]);
+                    }
+                    frame.render_widget(Waveform::new(&buf), wave_area);
+                });
+
+                let duration = sample.total_frames as f32 / app.audio.config.sample_rate;
+                let ch_label = if sample.channels == 1 { "mono" } else { "stereo" };
+                let info = Paragraph::new(format!(" {duration:.1}s · {ch_label}"))
+                    .style(Style::new().fg(theme::get().ui.text_dim));
+                frame.render_widget(info, info_area);
+            }
         }
         None => {}
     }