rendering code and api crate

crates/bevy_xr/Cargo.toml

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+[package]
+name = "bevy_xr"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+bevy.workspace = true

crates/bevy_xr/src/camera.rs

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+use bevy::app::{App, Plugin};
+use bevy::core_pipeline::core_3d::graph::Core3d;
+use bevy::core_pipeline::core_3d::Camera3d;
+use bevy::core_pipeline::tonemapping::{DebandDither, Tonemapping};
+use bevy::ecs::bundle::Bundle;
+use bevy::ecs::component::Component;
+use bevy::ecs::reflect::ReflectComponent;
+use bevy::math::{Mat4, Vec3A};
+use bevy::reflect::Reflect;
+use bevy::render::camera::{
+    Camera, CameraMainTextureUsages, CameraProjection, CameraProjectionPlugin, CameraRenderGraph,
+    Exposure,
+};
+use bevy::render::primitives::Frustum;
+use bevy::render::view::{ColorGrading, VisibleEntities};
+use bevy::transform::components::{GlobalTransform, Transform};
+
+pub struct XrCameraPlugin;
+
+impl Plugin for XrCameraPlugin {
+    fn build(&self, app: &mut App) {
+        app.add_plugins(CameraProjectionPlugin::<XrProjection>::default());
+    }
+}
+
+#[derive(Clone, Copy, Component, Reflect, Debug)]
+#[reflect(Component)]
+pub struct XrProjection {
+    pub projection_matrix: Mat4,
+    pub near: f32,
+    pub far: f32,
+}
+
+impl Default for XrProjection {
+    fn default() -> Self {
+        Self {
+            near: 0.1,
+            far: 1000.,
+            projection_matrix: Mat4::IDENTITY,
+        }
+    }
+}
+
+/// Marker component for an XR view. It is the backends responsibility to update this.
+#[derive(Clone, Copy, Component, Debug, Default)]
+pub struct XrView;
+
+impl CameraProjection for XrProjection {
+    fn get_projection_matrix(&self) -> Mat4 {
+        self.projection_matrix
+    }
+
+    fn update(&mut self, _width: f32, _height: f32) {}
+
+    fn far(&self) -> f32 {
+        self.far
+    }
+
+    // TODO calculate this properly
+    fn get_frustum_corners(&self, _z_near: f32, _z_far: f32) -> [Vec3A; 8] {
+        Default::default()
+    }
+}
+
+#[derive(Bundle)]
+pub struct XrCameraBundle {
+    pub camera: Camera,
+    pub camera_render_graph: CameraRenderGraph,
+    pub projection: XrProjection,
+    pub visible_entities: VisibleEntities,
+    pub frustum: Frustum,
+    pub transform: Transform,
+    pub global_transform: GlobalTransform,
+    pub camera_3d: Camera3d,
+    pub tonemapping: Tonemapping,
+    pub dither: DebandDither,
+    pub color_grading: ColorGrading,
+    pub exposure: Exposure,
+    pub main_texture_usages: CameraMainTextureUsages,
+    pub view: XrView,
+}
+
+impl Default for XrCameraBundle {
+    fn default() -> Self {
+        Self {
+            camera_render_graph: CameraRenderGraph::new(Core3d),
+            camera: Default::default(),
+            projection: Default::default(),
+            visible_entities: Default::default(),
+            frustum: Default::default(),
+            transform: Default::default(),
+            global_transform: Default::default(),
+            camera_3d: Default::default(),
+            tonemapping: Default::default(),
+            color_grading: Default::default(),
+            exposure: Default::default(),
+            main_texture_usages: Default::default(),
+            dither: DebandDither::Enabled,
+            view: XrView,
+        }
+    }
+}

crates/bevy_xr/src/lib.rs

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+pub mod camera;
+pub mod session;

crates/bevy_xr/src/session.rs

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+use bevy::app::{App, Plugin, PreUpdate};
+use bevy::ecs::event::{Event, EventReader, EventWriter};
+use bevy::ecs::system::Local;
+
+pub struct XrSessionPlugin;
+
+impl Plugin for XrSessionPlugin {
+    fn build(&self, app: &mut App) {
+        app.add_event::<CreateXrSession>()
+            .add_event::<BeginXrSession>()
+            .add_event::<EndXrSession>()
+            .add_event::<XrSessionState>()
+            .add_event::<XrInstanceCreated>()
+            .add_event::<XrInstanceDestroyed>()
+            .add_systems(PreUpdate, handle_xr_events);
+    }
+}
+
+pub fn handle_xr_events(
+    mut instance_created: EventReader<XrInstanceCreated>,
+    mut session_state: EventReader<XrSessionState>,
+    mut instance_destroyed: EventReader<XrInstanceDestroyed>,
+    mut create_session: EventWriter<CreateXrSession>,
+    mut begin_session: EventWriter<BeginXrSession>,
+    mut has_instance: Local<bool>,
+    mut local_session_state: Local<Option<XrSessionState>>,
+) {
+    // Don't do anything if no events recieved
+    if instance_created.is_empty() && instance_destroyed.is_empty() && session_state.is_empty() {
+        return;
+    }
+    if !instance_created.is_empty() {
+        *has_instance = true;
+        instance_created.clear();
+    }
+    if !instance_destroyed.is_empty() {
+        *has_instance = false;
+        instance_destroyed.clear();
+    }
+    for state in session_state.read() {
+        *local_session_state = Some(*state);
+    }
+    if *has_instance {
+        if local_session_state.is_none() {
+            create_session.send_default();
+        } else if matches!(*local_session_state, Some(XrSessionState::Ready)) {
+            begin_session.send_default();
+        }
+    }
+}
+
+/// Event sent to backends to create an XR session
+#[derive(Event, Clone, Copy, Default)]
+pub struct CreateXrSession;
+
+/// Event sent to backends to begin an XR session
+#[derive(Event, Clone, Copy, Default)]
+pub struct BeginXrSession;
+
+/// Event sent to backends to end an XR session.
+#[derive(Event, Clone, Copy, Default)]
+pub struct EndXrSession;
+
+// /// Event sent to backends to destroy an XR session.
+// #[derive(Event, Clone, Copy, Default)]
+// pub struct DestroyXrSession;
+
+/// Event sent from backends to inform the frontend of the session state.
+#[derive(Event, Clone, Copy)]
+pub enum XrSessionState {
+    /// The session is in an idle state. Either just created or stopped
+    Idle,
+    /// The session is ready. You may send a [`BeginXrSession`] event.
+    Ready,
+    /// The session is running.
+    Running,
+    /// The session is being stopped
+    Stopping,
+    /// The session is destroyed
+    Destroyed,
+}
+
+/// Event sent from backends to inform the frontend that the instance was created.
+#[derive(Event, Clone, Copy, Default)]
+pub struct XrInstanceCreated;
+
+/// Event sent from backends to inform the frontend that the instance was destroyed.
+#[derive(Event, Clone, Copy, Default)]
+pub struct XrInstanceDestroyed;