Fix GameCube poll thread shutdown and backoff

Reviewed-on: #54
Co-authored-by: Álex Román Núñez <eirexe@eirteam.moe>

src/input/gamecube/poll.rs

@@ -1,6 +1,8 @@
 use std::panic::{self, AssertUnwindSafe};
 use std::sync::atomic::{AtomicBool, Ordering};
 use std::sync::{Arc, Mutex};
+use std::thread::JoinHandle;
+use std::time::{Duration, Instant};
 
 use bevy::prelude::*;
 use gc_adapter_neo::{Controller, GcAdapter};
@@ -55,10 +57,11 @@ impl GcPortState {
 /// Shared, `Send + Sync` handle to the latest snapshot from the poll
 /// thread. Safe to store as an ordinary [`Resource`] (no `NonSend` needed)
 /// because the `GcAdapter` itself never leaves its thread.
-#[derive(Resource, Clone)]
+#[derive(Resource)]
 pub struct GcAdapterSnapshot {
     ports: Arc<Mutex<[GcPortState; 4]>>,
     shutdown: Arc<AtomicBool>,
+    poll_thread: Option<JoinHandle<()>>,
 }
 
 impl GcAdapterSnapshot {
@@ -69,12 +72,36 @@ impl GcAdapterSnapshot {
 
 impl Drop for GcAdapterSnapshot {
     fn drop(&mut self) {
-        // Only actually signals shutdown once the last clone (this resource
+        self.shutdown.store(true, Ordering::Release);
-        // is never cloned in practice, but be defensive) is dropped.
+
-        if Arc::strong_count(&self.shutdown) <= 1 {
+        if let Some(poll_thread) = self.poll_thread.take() {
-            self.shutdown.store(true, Ordering::Relaxed);
+            if let Err(payload) = poll_thread.join() {
+                error!(
+                    "GameCube Controller Adapter poll thread panicked during shutdown: {payload:?}"
+                );
             }
         }
+    }
+}
+
+const INITIAL_ERROR_BACKOFF: Duration = Duration::from_millis(1);
+const MAX_ERROR_BACKOFF: Duration = Duration::from_millis(100);
+
+fn next_error_backoff(backoff: Duration) -> Duration {
+    backoff.saturating_mul(2).min(MAX_ERROR_BACKOFF)
+}
+
+/// Wait for a retry while still allowing the owner to shut the poll thread down promptly.
+fn wait_for_retry(shutdown: &AtomicBool, delay: Duration) -> bool {
+    let deadline = Instant::now() + delay;
+    while !shutdown.load(Ordering::Acquire) {
+        let remaining = deadline.saturating_duration_since(Instant::now());
+        if remaining.is_zero() {
+            return true;
+        }
+        std::thread::sleep(remaining.min(Duration::from_millis(10)));
+    }
+    false
 }
 
 /// Connects to the first GameCube adapter found on the USB bus and starts
@@ -94,7 +121,7 @@ pub fn spawn_poll_thread() -> Result<GcAdapterSnapshot, gc_adapter_neo::UsbError
 
     let thread_ports = ports.clone();
     let thread_shutdown = shutdown.clone();
-    std::thread::Builder::new()
+    let poll_thread = std::thread::Builder::new()
         .name("gc-adapter-poll".into())
         .spawn(move || {
             // Flush whatever the adapter had buffered before we started
@@ -107,17 +134,27 @@ pub fn spawn_poll_thread() -> Result<GcAdapterSnapshot, gc_adapter_neo::UsbError
             let mut rate_window_start = std::time::Instant::now();
             #[cfg(debug_assertions)]
             let mut rate_window_count: u32 = 0;
+            let mut error_backoff = INITIAL_ERROR_BACKOFF;
 
-            while !thread_shutdown.load(Ordering::Relaxed) {
+            while !thread_shutdown.load(Ordering::Acquire) {
                 let result = panic::catch_unwind(AssertUnwindSafe(|| adapter.read_controllers()));
 
                 let controllers = match result {
-                    Ok(Ok(controllers)) => controllers,
+                    Ok(Ok(controllers)) => {
+                        error_backoff = INITIAL_ERROR_BACKOFF;
+                        controllers
+                    }
                     // Ignore this, for some reason we get a bunch of these when we start reading
                     Ok(Err(
                         gc_adapter_neo::AdapterError::Parse(_)
                         | gc_adapter_neo::AdapterError::ShortRead(_),
-                    )) => continue,
+                    )) => {
+                        if !wait_for_retry(&thread_shutdown, error_backoff) {
+                            break;
+                        }
+                        error_backoff = next_error_backoff(error_backoff);
+                        continue;
+                    }
                     Ok(Err(gc_adapter_neo::AdapterError::Usb(err))) => {
                         error!(
                             "GameCube Controller Adapter USB read failed ({err:?}); stopping \
@@ -160,5 +197,32 @@ pub fn spawn_poll_thread() -> Result<GcAdapterSnapshot, gc_adapter_neo::UsbError
         })
         .expect("failed to spawn gc-adapter poll thread");
 
-    Ok(GcAdapterSnapshot { ports, shutdown })
+    Ok(GcAdapterSnapshot {
+        ports,
+        shutdown,
+        poll_thread: Some(poll_thread),
+    })
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn error_backoff_is_capped() {
+        let mut backoff = INITIAL_ERROR_BACKOFF;
+        for _ in 0..16 {
+            backoff = next_error_backoff(backoff);
+        }
+
+        assert_eq!(backoff, MAX_ERROR_BACKOFF);
+        assert_eq!(next_error_backoff(MAX_ERROR_BACKOFF), MAX_ERROR_BACKOFF);
+    }
+
+    #[test]
+    fn retry_wait_stops_when_shutdown_is_requested() {
+        let shutdown = AtomicBool::new(true);
+
+        assert!(!wait_for_retry(&shutdown, Duration::from_secs(1)));
+    }
 }

src/menus/character_select/mod.rs

@@ -241,7 +241,7 @@ pub fn copy_cursor_transform_to_token(
     character_boxes: Query<(&CharacterBox, &ComputedNode, &UiGlobalTransform)>,
     match_config: Res<MenuMatchConfig>,
     cursors: Query<&UiGlobalTransform, With<FGMenuCursor>>,
-    cam: Single<&Camera, With<IsDefaultUiCamera>>,
+    cam: Single<&Camera>,
     ui_scale: Res<UiScale>,
 ) -> Result {
     let camera = cam.into_inner();

src/menus/cursor.rs

@@ -181,7 +181,7 @@ pub fn cursor_input(
 }
 
 pub fn update_cursor_transform(
-    camera: Single<&Camera, With<IsDefaultUiCamera>>,
+    camera: Single<&Camera>,
     query: Query<(&mut Node, &PointerLocation), With<FGMenuCursor>>,
     ui_scale: Res<UiScale>,
 ) {

src/menus/mod.rs

@@ -25,6 +25,8 @@ pub mod style;
 
 #[derive(Component, Clone, Default)]
 pub struct MenuMarker {}
+#[derive(Component, Clone, Default)]
+pub struct MenuCameraMarker {}
 
 pub struct MenuPlugin;
 
@@ -38,6 +40,7 @@ pub fn wrap_menu(menu: impl Scene) -> impl Scene {
     bsn! {
         #MenuRoot
         MenuMarker
+        Transform
         Node {
             width: percent(100),
             height: percent(100),
@@ -46,6 +49,11 @@ pub fn wrap_menu(menu: impl Scene) -> impl Scene {
             flex_direction: FlexDirection::Column,
         }
         Children [
+            (
+                #MenuCamera
+                Camera
+                Camera2d
+            ),
             (
                 #MenuContainer
                 Node {
@@ -65,15 +73,18 @@ pub fn wrap_menu(menu: impl Scene) -> impl Scene {
 
 pub fn despawn_menu(
     existing_menu: Option<Single<Entity, With<MenuMarker>>>,
+    existing_menu_camera: Option<Single<Entity, With<MenuCameraMarker>>>,
     mut commands: Commands,
 ) {
     if let Some(entity) = existing_menu {
         commands
             .entity(entity.into_inner())
-            .remove::<Camera2d>()
-            .remove::<Camera>()
             .despawn();
     }
+
+    if let Some(menu_cam) = existing_menu_camera {
+        commands.entity(*menu_cam).despawn();
+    }
 }
 
 pub fn spawn_menu(
@@ -84,8 +95,6 @@ pub fn spawn_menu(
     if let Some(entity) = existing_menu {
         commands
             .entity(entity.into_inner())
-            .remove::<Camera2d>()
-            .remove::<Camera>()
             .despawn();
     }
     commands.queue_spawn_scene(wrap_menu(menu));
@@ -113,16 +122,7 @@ impl Plugin for MenuPlugin {
     fn build(&self, app: &mut App) {
         app.add_systems(
             OnEnter(AppState::MainMenu),
-            (build_menu::<MainMenu>, |mut commands: Commands| {
+            build_menu::<MainMenu>,
-                commands.spawn((Camera2d, IsDefaultUiCamera));
-                commands.spawn((
-                    Camera2d,
-                    Camera {
-                        order: 1,
-                        ..default()
-                    },
-                ));
-            }),
         )
         .add_message::<character_select::PlayerSlotAssigned>()
         .init_resource::<navigation::UINavigationActionState>()