Bevy UI example does not exit when window is closed.

[DGriffin91]

Bevy version

Bevy Main 7dcfaae

What you did

• cargo run --example ui
• Close the window

What went wrong

When closing the window, the bevy app continues to run even after the window is closed.

Additional information

Seems to be related to using WinitSettings::desktop_app(). If I comment this out the app exits as expected.

[spkjp]

It happens only for ReactiveLowPower, because it never sees the winit_state.low_power_event that is emitted in response to WindowEvent::CloseRequested.

bevy/crates/bevy_winit/src/lib.rs

Lines 602 to 611 in 7dcfaae

	let update = if winit_state.active {
	let windows = app.world.resource::<Windows>();
	let focused = windows.iter().any(|w| w.is_focused());
	match winit_config.update_mode(focused) {
	UpdateMode::Continuous | UpdateMode::Reactive { .. } => true,
	UpdateMode::ReactiveLowPower { .. } => {
	winit_state.low_power_event
	|| winit_state.redraw_request_sent
	|| winit_state.timeout_reached
	}

Therefore update is false and nothing happens.

The root cause seems to be that the window is removed here

bevy/crates/bevy_winit/src/lib.rs

Lines 225 to 232 in 7dcfaae

	if !removed_windows.is_empty() {
	for id in removed_windows {
	// Close the OS window. (The `Drop` impl actually closes the window)
	let _ = winit_windows.remove_window(id);
	// Clean up our own data structures
	windows.remove(id);
	window_close_events.send(WindowClosed { id });
	}

before the event loop can handle the low_power_event and thus bails out early as it cannot find a window:

bevy/crates/bevy_winit/src/lib.rs

Lines 375 to 385 in 7dcfaae

	let window_id =
	if let Some(window_id) = winit_windows.get_window_id(winit_window_id) {
	window_id
	} else {
	warn!(
	"Skipped event for unknown winit Window Id {:?}",
	winit_window_id
	);
	return;
	};

This workaround seems to work for me, but it feels like a hack and not robust enough. There's probably a cleaner solution as the event loop just needs to run for the low_power_event before the windows are cleared.

diff --git a/crates/bevy_winit/src/lib.rs b/crates/bevy_winit/src/lib.rs
index 135ad332..47bf9882 100644
--- a/crates/bevy_winit/src/lib.rs
+++ b/crates/bevy_winit/src/lib.rs
@@ -331,6 +331,7 @@ pub fn winit_runner_with(mut app: App) {
         .0;
     let mut app_exit_event_reader = ManualEventReader::<AppExit>::default();
     let mut redraw_event_reader = ManualEventReader::<RequestRedraw>::default();
+    let mut window_closed_reader = ManualEventReader::<WindowClosed>::default();
     let mut winit_state = WinitPersistentState::default();
     app.world
         .insert_non_send_resource(event_loop.create_proxy());
@@ -608,6 +609,13 @@ pub fn winit_runner_with(mut app: App) {
                             winit_state.low_power_event
                                 || winit_state.redraw_request_sent
                                 || winit_state.timeout_reached
+                                || app
+                                    .world
+                                    .get_resource::<Events<WindowClosed>>()
+                                    .and_then(|window_closed_events| {
+                                        window_closed_reader.iter(window_closed_events).last()
+                                    })
+                                    .is_some()
                         }
                     }
                 } else {