Revert "move to single crate for webxr and openxr"

This reverts commit 5e769ef52b.

crates/bevy_xr/src/session.rs

@@ -0,0 +1,127 @@
+use std::sync::{Arc, RwLock};
+
+use bevy::prelude::*;
+
+pub struct XrSessionPlugin;
+
+impl Plugin for XrSessionPlugin {
+    fn build(&self, app: &mut App) {
+        app.add_event::<CreateXrSession>()
+            .add_event::<DestroyXrSession>()
+            .add_event::<BeginXrSession>()
+            .add_event::<EndXrSession>()
+            .add_systems(
+                PreUpdate,
+                handle_session.run_if(resource_exists::<XrSharedStatus>),
+            );
+    }
+}
+
+#[derive(Resource, Clone)]
+pub struct XrSharedStatus(Arc<RwLock<XrStatus>>);
+
+impl XrSharedStatus {
+    pub fn new(status: XrStatus) -> Self {
+        Self(Arc::new(RwLock::new(status)))
+    }
+
+    pub fn get(&self) -> XrStatus {
+        *self.0.read().unwrap()
+    }
+
+    pub fn set(&self, status: XrStatus) {
+        *self.0.write().unwrap() = status;
+    }
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+#[repr(u8)]
+pub enum XrStatus {
+    /// An XR session is not available here
+    Unavailable,
+    /// An XR session is available and ready to be created with a [`CreateXrSession`] event.
+    Available,
+    /// An XR session is created but not ready to begin.
+    Idle,
+    /// An XR session has been created and is ready to start rendering with a [`BeginXrSession`] event, or
+    Ready,
+    /// The XR session is running and can be stopped with an [`EndXrSession`] event.
+    Running,
+    /// The XR session is in the process of being stopped.
+    Stopping,
+    /// The XR session is in the process of being destroyed
+    Exiting,
+}
+
+pub fn handle_session(
+    status: Res<XrSharedStatus>,
+    mut previous_status: Local<Option<XrStatus>>,
+    mut create_session: EventWriter<CreateXrSession>,
+    mut begin_session: EventWriter<BeginXrSession>,
+    mut end_session: EventWriter<EndXrSession>,
+    mut destroy_session: EventWriter<DestroyXrSession>,
+) {
+    let current_status = status.get();
+    if *previous_status != Some(current_status) {
+        match current_status {
+            XrStatus::Unavailable => {}
+            XrStatus::Available => {
+                create_session.send_default();
+            }
+            XrStatus::Idle => {}
+            XrStatus::Ready => {
+                begin_session.send_default();
+            }
+            XrStatus::Running => {}
+            XrStatus::Stopping => {
+                end_session.send_default();
+            }
+            XrStatus::Exiting => {
+                destroy_session.send_default();
+            }
+        }
+    }
+    *previous_status = Some(current_status);
+}
+
+/// A [`Condition`](bevy::ecs::schedule::Condition) system that says if the XR session is available. Returns true as long as [`XrStatus`] exists and isn't [`Unavailable`](XrStatus::Unavailable).
+pub fn session_available(status: Option<Res<XrSharedStatus>>) -> bool {
+    status.is_some_and(|s| s.get() != XrStatus::Unavailable)
+}
+
+/// A [`Condition`](bevy::ecs::schedule::Condition) system that says if the XR session is ready or running
+pub fn session_created(status: Option<Res<XrSharedStatus>>) -> bool {
+    matches!(
+        status.as_deref().map(XrSharedStatus::get),
+        Some(XrStatus::Ready | XrStatus::Running)
+    )
+}
+
+/// A [`Condition`](bevy::ecs::schedule::Condition) system that says if the XR session is running
+pub fn session_running(status: Option<Res<XrSharedStatus>>) -> bool {
+    matches!(
+        status.as_deref().map(XrSharedStatus::get),
+        Some(XrStatus::Running)
+    )
+}
+
+/// A function that returns a [`Condition`](bevy::ecs::schedule::Condition) system that says if an the [`XrStatus`] is in a specific state
+pub fn status_equals(status: XrStatus) -> impl FnMut(Option<Res<XrSharedStatus>>) -> bool {
+    move |state: Option<Res<XrSharedStatus>>| state.is_some_and(|s| s.get() == status)
+}
+
+/// Event sent to backends to create an XR session. Should only be called in the [`XrStatus::Available`] state.
+#[derive(Event, Clone, Copy, Default)]
+pub struct CreateXrSession;
+
+/// Event sent to the backends to destroy an XR session.
+#[derive(Event, Clone, Copy, Default)]
+pub struct DestroyXrSession;
+
+/// Event sent to backends to begin an XR session. Should only be called in the [`XrStatus::Ready`] state.
+#[derive(Event, Clone, Copy, Default)]
+pub struct BeginXrSession;
+
+/// Event sent to backends to end an XR session. Should only be called in the [`XrStatus::Running`] state.
+#[derive(Event, Clone, Copy, Default)]
+pub struct EndXrSession;