feat(gpui): audio scrub while dragging the playhead

apps/desktop-gpui/src/assets.rs

@@ -167,6 +167,7 @@ const ICONS: &[(&str, &[u8])] = assets!("icons":
     "ratio.svg",
     "refresh-cw.svg",
     "rotate-ccw.svg",
+    "volume-2.svg",
     "volume-x.svg",
     "gem.svg",
     "sliders-horizontal.svg",

apps/desktop-gpui/src/editor_window.rs

@@ -203,6 +203,8 @@ impl EditorVerticalLayout {
     }
 }
 
+/// Length of each audio-scrub slice; the next one replaces what is left.
+const SCRUB_SLICE_SECS: f64 = 0.09;
 const PRESETS_MENU_WIDTH: f32 = 288.;
 const PRESET_SUBMENU_WIDTH: f32 = 208.;
 const PRESET_SUBMENU_HEIGHT: f32 = 5. * 32. + 4. * 2. + 8.;
@@ -1367,6 +1369,12 @@ pub struct EditorWindow {
     /// Kept alive for the window's lifetime: dropping the last `Arc` is what
     /// tears the decoders down, and `dispose()` on close does it explicitly.
     pub(crate) instance: Option<Arc<EditorInstance>>,
+    /// Audio scrub: a slice request is in flight, and the newest position
+    /// asked for meanwhile (played once it lands).
+    /// The toolbar's speaker toggle ([`crate::store::audio_scrub_enabled`]).
+    audio_scrub: bool,
+    scrub_audio_busy: bool,
+    scrub_audio_next: Option<f64>,
     focus: FocusHandle,
 
     // -- Transport ----------------------------------------------------------
@@ -2070,6 +2078,9 @@ impl EditorWindow {
             total: 0.0,
             transport: None,
             scrub: None,
+            audio_scrub: crate::store::audio_scrub_enabled(),
+            scrub_audio_busy: false,
+            scrub_audio_next: None,
             stats: None,
             play_mark: None,
             timeline: TimelineModel::default(),
@@ -3989,6 +4000,7 @@ impl EditorWindow {
             // `applyScrub()` runs immediately on mousedown.
             self.scrub = Some(Scrub::Ruler);
             self.seek_to_time(time, cx);
+            self.scrub_audio_at(time, cx);
         } else {
             self.scrub = Some(Scrub::Press { time });
         }
@@ -4017,6 +4029,41 @@ impl EditorWindow {
         // in-flight work when it sees a newer instruction
         // (`editor_instance.rs:563-575`).
         self.scrub_to_time(time, cx);
+        self.scrub_audio_at(time, cx);
+    }
+
+    /// Audio scrub: while the ruler is dragged with playback stopped, play a
+    /// short slice of the mix under the playhead. One request at a time; the
+    /// newest position waits and plays next, spaced by about a slice so they
+    /// run back to back.
+    fn scrub_audio_at(&mut self, time: f64, cx: &mut Context<Self>) {
+        if self.playing || !self.audio_scrub {
+            return;
+        }
+        if self.scrub_audio_busy {
+            self.scrub_audio_next = Some(time);
+            return;
+        }
+        let Some(instance) = self.instance.clone() else {
+            return;
+        };
+        self.scrub_audio_busy = true;
+        let slice = gpui_tokio::Tokio::spawn(cx, async move {
+            instance.scrub_audio(time, SCRUB_SLICE_SECS).await;
+        });
+        cx.spawn(async move |this, cx| {
+            let _ = slice.await;
+            cx.background_executor()
+                .timer(Duration::from_millis(60))
+                .await;
+            let _ = this.update(cx, |this, cx| {
+                this.scrub_audio_busy = false;
+                if let Some(next) = this.scrub_audio_next.take() {
+                    this.scrub_audio_at(next, cx);
+                }
+            });
+        })
+        .detach();
     }
 
     /// The **timeline's own** mouseup, the one the source registers on
@@ -10538,6 +10585,31 @@ impl EditorWindow {
                                 )),
                             ),
                     )
+                    .child(
+                        ui::EditorButton::plain(&theme, "transport-audio-scrub")
+                            .left_icon(if self.audio_scrub {
+                                "icons/volume-2.svg"
+                            } else {
+                                "icons/volume-x.svg"
+                            })
+                            .tooltip(
+                                &theme,
+                                if self.audio_scrub {
+                                    "Audio while scrubbing: on"
+                                } else {
+                                    "Audio while scrubbing: off"
+                                },
+                            )
+                            .pressed(self.audio_scrub)
+                            .on_click(cx.listener(|this, _, window, cx| {
+                                this.audio_scrub = !this.audio_scrub;
+                                if !crate::store::set_audio_scrub_enabled(this.audio_scrub) {
+                                    tracing::warn!("could not save the audio scrub preference");
+                                }
+                                cx.notify();
+                                window.refresh();
+                            })),
+                    )
                     .child(self.header_divider())
                     // `IconCapZoomOut` -> `updateZoom(zoom * 1.1,
                     // playbackTime)`; `IconCapZoomIn` -> `zoom / 1.1`

apps/desktop-gpui/src/store.rs

@@ -1096,6 +1096,20 @@ pub fn set_studio_sound_defaults(enabled: bool, isolation: cap_project::VoiceIso
     section.insert("isolation".into(), serde_json::to_value(isolation).unwrap());
     set_store_value(AUDIO_ENHANCEMENT, Value::Object(section))
 }
+/// Editor preferences that belong to the user rather than a project.
+pub const EDITOR_PREFERENCES: &str = "editor_preferences";
+pub const AUDIO_SCRUB_KEY: &str = "audioScrub";
+
+/// Whether dragging the playhead on the ruler plays the audio under it.
+/// Defaults on; the timeline toolbar's speaker toggle writes it.
+pub fn audio_scrub_enabled() -> bool {
+    bool_at(&store_section(EDITOR_PREFERENCES), AUDIO_SCRUB_KEY, true)
+}
+
+pub fn set_audio_scrub_enabled(enabled: bool) -> bool {
+    set_store_setting(EDITOR_PREFERENCES, AUDIO_SCRUB_KEY, Value::Bool(enabled))
+}
+
 /// `RecordingSettingsStore::KEY` (`src-tauri/src/recording_settings.rs:37`) --
 /// the section the tray's Select Mode submenu reads and writes.
 pub const RECORDING_SETTINGS: &str = "recording_settings";