feat: implement event handlers for OpenXR events so that plugins can handle events without needing to modify bevy_mod_openxr

Signed-off-by: Schmarni <marnistromer@gmail.com>

crates/bevy_openxr/src/openxr/features/overlay.rs

@@ -1,12 +1,13 @@
 use std::{mem, ptr};
 
 use bevy::prelude::*;
-use openxr::sys;
+use openxr::{sys, Event};
 
 use crate::{
     next_chain::{OxrNextChainStructBase, OxrNextChainStructProvider},
     openxr::exts::OxrEnabledExtensions,
     openxr_session_available,
+    poll_events::{OxrEvent, OxrEventHandlerExt},
     session::{OxrSessionCreateNextChain, OxrSessionCreateNextProvider},
 };
 
@@ -20,6 +21,16 @@ impl Plugin for OxrOverlayPlugin {
             First,
             add_overlay_info_to_chain.run_if(openxr_session_available),
         );
+        app.add_oxr_event_handler(handle_overlay_event);
+    }
+}
+
+fn handle_overlay_event(event: In<OxrEvent>, mut writer: EventWriter<OxrOverlaySessionEvent>) {
+    if let Event::MainSessionVisibilityChangedEXTX(event) = unsafe { event.get() } {
+        writer.send(OxrOverlaySessionEvent::MainSessionVisibilityChanged {
+            visible: event.visible(),
+            flags: event.flags(),
+        });
     }
 }
 

crates/bevy_openxr/src/openxr/init.rs

@@ -18,6 +18,7 @@ use bevy::winit::UpdateMode;
 use bevy::winit::WinitSettings;
 use bevy_mod_xr::session::*;
 use openxr::Event;
+use openxr::EventDataBuffer;
 
 use crate::error::OxrError;
 use crate::features::overlay::OxrOverlaySessionEvent;
@@ -28,6 +29,8 @@ use crate::session::OxrSessionCreateNextChain;
 use crate::types::*;
 
 use super::exts::OxrEnabledExtensions;
+use super::poll_events::OxrEvent;
+use super::poll_events::OxrEventHandlerExt;
 
 pub fn session_started(started: Option<Res<OxrSessionStarted>>) -> bool {
     started.is_some_and(|started| started.0)
@@ -106,12 +109,7 @@ impl Plugin for OxrInitPlugin {
                         },
                         ExtractResourcePlugin::<OxrSessionStarted>::default(),
                     ))
-                    .add_systems(
-                        XrFirst,
-                        poll_events
-                            .in_set(XrHandleEvents::Poll)
-                            .run_if(not(state_equals(XrState::Unavailable))),
-                    )
+                    .add_oxr_event_handler(handle_events)
                     .add_systems(
                         XrFirst,
                         (
@@ -282,22 +280,14 @@ impl OxrInitPlugin {
 #[derive(Event, Clone, Copy, Debug, Default)]
 pub struct OxrInteractionProfileChanged;
 
-/// Polls any OpenXR events and handles them accordingly
-pub fn poll_events(
-    instance: Res<OxrInstance>,
+pub fn handle_events(
+    event: In<OxrEvent>,
     mut status: ResMut<XrState>,
     mut changed_event: EventWriter<XrStateChanged>,
     mut interaction_profile_changed_event: EventWriter<OxrInteractionProfileChanged>,
-    mut overlay_writer: Option<ResMut<Events<OxrOverlaySessionEvent>>>,
 ) {
-    let _span = info_span!("xr_poll_events");
-    let mut buffer = Default::default();
-    while let Some(event) = instance
-        .poll_event(&mut buffer)
-        .expect("Failed to poll event")
-    {
     use openxr::Event::*;
-        match event {
+    match unsafe { event.get() } {
         SessionStateChanged(state) => {
             use openxr::SessionState;
 
@@ -325,23 +315,12 @@ pub fn poll_events(
         }
         InstanceLossPending(_) => {}
         EventsLost(e) => warn!("lost {} XR events", e.lost_event_count()),
-            MainSessionVisibilityChangedEXTX(d) => {
-                if let Some(writer) = overlay_writer.as_mut() {
-                    writer.send(OxrOverlaySessionEvent::MainSessionVisibilityChanged {
-                        visible: d.visible(),
-                        flags: d.flags(),
-                    });
-                } else {
-                    warn!("Overlay Event Recieved without the OverlayPlugin being added!");
-                }
-            }
         // we might want to check if this is the correct session?
         Event::InteractionProfileChanged(_) => {
             interaction_profile_changed_event.send_default();
         }
         _ => {}
     }
-    }
 }
 
 fn init_xr_session(

crates/bevy_openxr/src/openxr/mod.rs

@@ -9,6 +9,7 @@ use bevy::{
 use bevy_mod_xr::session::XrSessionPlugin;
 use bevy_mod_xr::{camera::XrCameraPlugin, session::XrState};
 use init::OxrInitPlugin;
+use poll_events::{OxrEventHandlers, OxrEventsPlugin};
 use render::OxrRenderPlugin;
 use resources::OxrInstance;
 use session::OxrSession;
@@ -35,6 +36,7 @@ pub mod resources;
 pub mod session;
 pub mod spaces;
 pub mod types;
+pub mod poll_events;
 
 /// A [`Condition`](bevy::ecs::schedule::Condition) system that says if the OpenXR session is available.
 pub fn openxr_session_available(
@@ -60,6 +62,7 @@ pub fn add_xr_plugins<G: PluginGroup>(plugins: G) -> PluginGroupBuilder {
         // .disable::<PipelinedRenderingPlugin>()
         .add_before::<RenderPlugin, _>(XrSessionPlugin { auto_handle: true })
         .add_before::<RenderPlugin, _>(OxrInitPlugin::default())
+        .add(OxrEventsPlugin)
         .add(OxrReferenceSpacePlugin::default())
         .add(OxrRenderPlugin)
         .add(OxrPassthroughPlugin)

crates/bevy_openxr/src/openxr/poll_events.rs

@@ -0,0 +1,80 @@
+use std::mem;
+
+use bevy::{ecs::system::SystemId, prelude::*};
+use bevy_mod_xr::session::{XrFirst, XrHandleEvents};
+use openxr::{Event, EventDataBuffer};
+
+pub struct OxrEventsPlugin;
+
+impl Plugin for OxrEventsPlugin {
+    fn build(&self, app: &mut App) {
+        app.init_resource::<OxrEventHandlers>();
+        app.add_systems(
+            XrFirst,
+            poll_events
+                .in_set(XrHandleEvents::Poll)
+                .run_if(openxr_session_available),
+        );
+    }
+}
+/// Polls any OpenXR events and handles them accordingly
+pub fn poll_events(world: &mut World) {
+    let _span = info_span!("xr_poll_events");
+    let instance = world.resource::<OxrInstance>().clone();
+    let handlers = world.remove_resource::<OxrEventHandlers>().unwrap();
+    let mut buffer = EventDataBuffer::default();
+    while let Some(event) = instance
+        .poll_event(&mut buffer)
+        .expect("Failed to poll event")
+    {
+        for handler in handlers.handlers.iter() {
+            if let Err(err) = world.run_system_with_input::<_, ()>(*handler, OxrEvent::new(event)) {
+                error!("error when running oxr event handler: {err}");
+            };
+        }
+    }
+    world.insert_resource(handlers);
+}
+
+use super::{openxr_session_available, resources::OxrInstance};
+#[derive(Resource, Debug, Default)]
+pub struct OxrEventHandlers {
+    pub handlers: Vec<OxrEventHandler>,
+}
+pub type OxrEventHandler = SystemId<OxrEvent, ()>;
+
+pub struct OxrEvent {
+    event: Event<'static>,
+}
+
+impl OxrEvent {
+    pub(crate) fn new<'a>(event: Event<'a>) -> Self {
+        Self {
+            event: unsafe { mem::transmute::<Event<'a>, Event<'static>>(event) },
+        }
+    }
+    /// # Safety
+    /// The event is only valid for the duration of the poll event callback,
+    /// don't Store the [Event] anywhere!!
+    #[allow(clippy::needless_lifetimes)]
+    pub unsafe fn get<'a>(&'a self) -> Event<'a> {
+        self.event
+    }
+}
+pub trait OxrEventHandlerExt {
+    fn add_oxr_event_handler<M>(
+        &mut self,
+        system: impl IntoSystem<OxrEvent, (), M> + 'static,
+    ) -> &mut Self;
+}
+impl OxrEventHandlerExt for App {
+    fn add_oxr_event_handler<M>(&mut self, system: impl IntoSystem<OxrEvent, (), M> + 'static) -> &mut Self {
+        self.init_resource::<OxrEventHandlers>();
+        let id = self.register_system(system);
+        self.world_mut()
+            .resource_mut::<OxrEventHandlers>()
+            .handlers
+            .push(id);
+        self
+    }
+}