feat(app): playback resolution divider (Full/Half/Quarter/Eighth)

The C++ viewer Playback Resolution menu, wired end to end: the radio in
the viewer context menu reflects and sets the PlaybackDivider config,
proxy_render_size renders the preview at 480/divider long edge, and
changing the divider invalidates the cached and in-flight preview
frames. This is the escape hatch for machines that cannot keep up with
playback (measured: a debug build of the worker pool reaches only 11
fps vs 152 fps in release on 1080p H.264, which no amount of
scheduling can make realtime).

src/menus/shared.rs

@@ -202,7 +202,7 @@ pub fn viewer_zoom_level_id(index: usize) -> usize {
 /// subtitle block the engine does not surface yet). Zoom / playback
 /// resolution / safe margins / waveform / FPS are placeholders until the
 /// viewer widget grows those controls.
-pub fn viewer_menu() -> Menu {
+pub fn viewer_menu(playback_divider: i64) -> Menu {
 	use crate::i18n::tr;
 	// Zoom: Fit + one entry per zoom level.
 	let mut zoom_items = vec![MenuItem::new(LOCAL_VIEWER_ZOOM_FIT, tr("viewer.context.zoom_fit"))];
@@ -213,12 +213,17 @@ pub fn viewer_menu() -> Menu {
 		));
 	}
 	// Playback resolution radio group.
+	// Playback Resolution radio group (the C++ `PlaybackDivider` config):
+	// the checked entry reflects the current divider.
 	let resolution_menu = Menu::new(vec![
-		MenuItem::new(LOCAL_VIEWER_RES_FULL, tr("viewer.context.res_full")).with_checked(true),
-		MenuItem::new(LOCAL_VIEWER_RES_HALF, tr("viewer.context.res_half")).with_checked(false),
+		MenuItem::new(LOCAL_VIEWER_RES_FULL, tr("viewer.context.res_full"))
+			.with_checked(playback_divider <= 1),
+		MenuItem::new(LOCAL_VIEWER_RES_HALF, tr("viewer.context.res_half"))
+			.with_checked(playback_divider == 2),
 		MenuItem::new(LOCAL_VIEWER_RES_QUARTER, tr("viewer.context.res_quarter"))
-			.with_checked(false),
-		MenuItem::new(LOCAL_VIEWER_RES_EIGHTH, tr("viewer.context.res_eighth")).with_checked(false),
+			.with_checked(playback_divider == 4),
+		MenuItem::new(LOCAL_VIEWER_RES_EIGHTH, tr("viewer.context.res_eighth"))
+			.with_checked(playback_divider >= 8),
 	]);
 	// Safe margins radio group.
 	let safe_menu = Menu::new(vec![
@@ -370,7 +375,7 @@ mod tests {
 	/// defaults each radio group to its first entry.
 	#[test]
 	fn viewer_menu_offers_every_zoom_level() {
-		let menu = viewer_menu();
+		let menu = viewer_menu(1);
 		let zoom = menu
 			.items
 			.iter()
@@ -389,7 +394,7 @@ mod tests {
 	/// (default) entry only.
 	#[test]
 	fn viewer_menu_radio_groups_default_to_the_first_entry() {
-		let menu = viewer_menu();
+		let menu = viewer_menu(1);
 		for label_key in [
 			"viewer.context.playback_resolution",
 			"viewer.context.safe_margins",
@@ -408,4 +413,20 @@ mod tests {
 			);
 		}
 	}
+
+	/// The resolution radio follows the current playback divider.
+	#[test]
+	fn viewer_menu_resolution_radio_follows_the_divider() {
+		let menu = viewer_menu(4);
+		let item = menu
+			.items
+			.iter()
+			.find(|item| item.label == crate::i18n::tr("viewer.context.playback_resolution"))
+			.expect("resolution submenu");
+		let sub = &item.submenu.as_ref().unwrap().items;
+		assert_eq!(sub[0].checked, Some(false), "full unchecked at /4");
+		assert_eq!(sub[1].checked, Some(false), "half unchecked at /4");
+		assert_eq!(sub[2].checked, Some(true), "quarter checked at /4");
+		assert_eq!(sub[3].checked, Some(false), "eighth unchecked at /4");
+	}
 }

src/oakui/engine.rs

@@ -740,6 +740,27 @@ pub trait AppEngine:
 		let _ = cx;
 	}
 
+	/// The playback resolution divider (the C++ viewer `Playback
+	/// Resolution ▸` menu / `PlaybackDivider` config): 1 = full preview
+	/// size, 2/4/8 = progressively smaller preview renders for machines
+	/// that cannot keep up. Preview-only; exports always render native.
+	fn playback_divider(&self) -> i64 {
+		oakcommon::configstore::ConfigStore::instance()
+			.get_int(None, "PlaybackDivider", 1)
+			.clamp(1, 8) as i64
+	}
+
+	/// Sets the playback resolution divider and invalidates the rendered
+	/// frames so the next pull re-renders at the new geometry.
+	fn set_playback_divider(&mut self, divider: i64, cx: &mut Context<Self>) {
+		oakcommon::configstore::ConfigStore::instance().set(
+			None,
+			"PlaybackDivider",
+			&divider.clamp(1, 8).to_string(),
+		);
+		let _ = cx;
+	}
+
 	/// The footage rows the proxy dialog's footage mode lists (every
 	/// footage node in the open project).
 	fn proxy_rows(&self) -> Vec<ProxyFootageRow> {

src/oakui/real.rs

@@ -1231,8 +1231,12 @@ impl RealEngine {
 	fn proxy_render_size(&self) -> Option<(i32, i32)> {
 		let info = self.sequence_info.as_ref()?;
 		let (w, h) = (info.format.width.max(1), info.format.height.max(1));
-		const MAX_LONG_EDGE: u32 = 480;
-		let scale = MAX_LONG_EDGE as f64 / w.max(h) as f64;
+		// The playback resolution divider (the C++ viewer `Playback
+		// Resolution ▸` menu): render the preview at 480/divider long edge
+		// so slower machines (or debug builds) can still play in real time.
+		let divider = self.playback_divider().max(1) as u32;
+		let max_long_edge = 480 / divider;
+		let scale = max_long_edge as f64 / w.max(h) as f64;
 		let width = ((w as f64 * scale).round() as u32).max(2);
 		let height = ((h as f64 * scale).round() as u32).max(2);
 		Some((width as i32, height as i32))
@@ -4007,6 +4011,18 @@ impl AppEngine for RealEngine {
 		self.invalidate_preview_frames(cx);
 	}
 
+	/// Sets the playback resolution divider (the viewer `Playback
+	/// Resolution ▸` menu): the preview geometry changes, so every cached
+	/// and in-flight preview frame is stale.
+	fn set_playback_divider(&mut self, divider: i64, cx: &mut Context<Self>) {
+		oakcommon::configstore::ConfigStore::instance().set(
+			None,
+			"PlaybackDivider",
+			&divider.clamp(1, 8).to_string(),
+		);
+		self.invalidate_preview_frames(cx);
+	}
+
 	fn proxy_rows(&self) -> Vec<super::engine::ProxyFootageRow> {
 		let Some(project) = self.project.as_ref() else {
 			return Vec::new();

src/panels/program_viewer.rs

@@ -146,9 +146,21 @@ impl<E: AppEngine> ProgramViewerPanel<E> {
 		}
 	}
 
-	/// Handles the viewer's local (non-registry) context-menu items — all
-	/// placeholders until the viewer widget grows the matching controls.
-	fn on_local_menu_item(&mut self, item: usize, _cx: &mut Context<Self>) {
+	/// Handles the viewer's local (non-registry) context-menu items.
+	fn on_local_menu_item(&mut self, item: usize, cx: &mut Context<Self>) {
+		use crate::menus::shared as shared_menu;
+		let divider = match item {
+			shared_menu::LOCAL_VIEWER_RES_FULL => Some(1),
+			shared_menu::LOCAL_VIEWER_RES_HALF => Some(2),
+			shared_menu::LOCAL_VIEWER_RES_QUARTER => Some(4),
+			shared_menu::LOCAL_VIEWER_RES_EIGHTH => Some(8),
+			_ => None,
+		};
+		if let Some(divider) = divider {
+			let engine = self.engine.clone();
+			engine.update(cx, |engine, cx| engine.set_playback_divider(divider, cx));
+			return;
+		}
 		println!("[program viewer] context-menu item {item} (not implemented yet)");
 	}
 
@@ -309,8 +321,12 @@ impl<E: AppEngine> Render for ProgramViewerPanel<E> {
 			// the panel opens the shared viewer menu here.
 			.on_mouse_down(MouseButton::Right, {
 				cx.listener(|this, event: &gpui::MouseDownEvent, _window, cx| {
-					this.context_menu
-						.show(event.position, crate::menus::shared::viewer_menu(), cx);
+					let divider = this.engine.read(cx).playback_divider();
+					this.context_menu.show(
+						event.position,
+						crate::menus::shared::viewer_menu(divider),
+						cx,
+					);
 				})
 			})
 			.child(

src/panels/source_viewer.rs

@@ -80,9 +80,21 @@ impl<E: AppEngine> SourceViewerPanel<E> {
 		}
 	}
 
-	/// Handles the viewer's local (non-registry) context-menu items — all
-	/// placeholders until the viewer widget grows the matching controls.
-	fn on_local_menu_item(&mut self, item: usize, _cx: &mut Context<Self>) {
+	/// Handles the viewer's local (non-registry) context-menu items.
+	fn on_local_menu_item(&mut self, item: usize, cx: &mut Context<Self>) {
+		use crate::menus::shared as shared_menu;
+		let divider = match item {
+			shared_menu::LOCAL_VIEWER_RES_FULL => Some(1),
+			shared_menu::LOCAL_VIEWER_RES_HALF => Some(2),
+			shared_menu::LOCAL_VIEWER_RES_QUARTER => Some(4),
+			shared_menu::LOCAL_VIEWER_RES_EIGHTH => Some(8),
+			_ => None,
+		};
+		if let Some(divider) = divider {
+			let engine = self.engine.clone();
+			engine.update(cx, |engine, cx| engine.set_playback_divider(divider, cx));
+			return;
+		}
 		println!("[source viewer] context-menu item {item} (not implemented yet)");
 	}
 
@@ -142,8 +154,12 @@ impl<E: AppEngine> Render for SourceViewerPanel<E> {
 			// the panel opens the shared viewer menu here.
 			.on_mouse_down(MouseButton::Right, {
 				cx.listener(|this, event: &gpui::MouseDownEvent, _window, cx| {
-					this.context_menu
-						.show(event.position, crate::menus::shared::viewer_menu(), cx);
+					let divider = this.engine.read(cx).playback_divider();
+					this.context_menu.show(
+						event.position,
+						crate::menus::shared::viewer_menu(divider),
+						cx,
+					);
 				})
 			})
 			.child(