Support WebXR devices with main thread affinity

components/compositing/compositor.rs

@@ -182,6 +182,9 @@ pub struct IOCompositor<Window: WindowMethods + ?Sized> {
     /// Some VR displays want to be sent a heartbeat from the main thread.
     webvr_heartbeats: Vec<Box<dyn WebVRMainThreadHeartbeat>>,
 
+    /// Some XR devices want to run on the main thread.
+    pub webxr_main_thread: webxr_api::MainThreadRegistry,
+
     /// Map of the pending paint metrics per layout thread.
     /// The layout thread for each specific pipeline expects the compositor to
     /// paint frames with specific given IDs (epoch). Once the compositor paints
@@ -314,6 +317,7 @@ impl<Window: WindowMethods + ?Sized> IOCompositor<Window> {
             webrender_document: state.webrender_document,
             webrender_api: state.webrender_api,
             webvr_heartbeats: state.webvr_heartbeats,
+            webxr_main_thread: state.webxr_main_thread,
             pending_paint_metrics: HashMap::new(),
             cursor: Cursor::None,
             output_file,
@@ -999,7 +1003,10 @@ impl<Window: WindowMethods + ?Sized> IOCompositor<Window> {
                 pipeline_ids.push(*pipeline_id);
             }
         }
-        let animation_state = if pipeline_ids.is_empty() && !self.webvr_heartbeats_racing() {
+        let animation_state = if pipeline_ids.is_empty() &&
+            !self.webvr_heartbeats_racing() &&
+            !self.webxr_main_thread.running()
+        {
             windowing::AnimationState::Idle
         } else {
             windowing::AnimationState::Animating
@@ -1456,6 +1463,9 @@ impl<Window: WindowMethods + ?Sized> IOCompositor<Window> {
             webvr_heartbeat.heartbeat();
         }
 
+        // Run the WebXR main thread
+        self.webxr_main_thread.run_one_frame();
+
         if !self.pending_scroll_zoom_events.is_empty() && !self.waiting_for_results_of_scroll {
             self.process_pending_scroll_events()
         }

components/compositing/compositor_thread.rs

@@ -155,4 +155,5 @@ pub struct InitialCompositorState {
     pub webrender_document: webrender_api::DocumentId,
     pub webrender_api: webrender_api::RenderApi,
     pub webvr_heartbeats: Vec<Box<dyn WebVRMainThreadHeartbeat>>,
+    pub webxr_main_thread: webxr_api::MainThreadRegistry,
 }

components/compositing/windowing.rs

@@ -178,7 +178,7 @@ pub trait EmbedderMethods {
     }
 
     /// Register services with a WebXR Registry.
-    fn register_webxr(&mut self, _: &mut webxr_api::Registry) {}
+    fn register_webxr(&mut self, _: &mut webxr_api::MainThreadRegistry) {}
 }
 
 #[derive(Clone, Copy, Debug)]

components/servo/lib.rs

@@ -292,10 +292,10 @@ where
 
         // For the moment, we enable use both the webxr crate and the rust-webvr crate,
         // but we are migrating over to just using webxr.
-        let mut webxr_registry =
-            webxr_api::Registry::new().expect("Failed to create WebXR device registry");
+        let mut webxr_main_thread =
+            webxr_api::MainThreadRegistry::new().expect("Failed to create WebXR device registry");
         if pref!(dom.webvr.enabled) || pref!(dom.webxr.enabled) {
-            embedder.register_webxr(&mut webxr_registry);
+            embedder.register_webxr(&mut webxr_main_thread);
         }
 
         let mut webvr_heartbeats = Vec::new();
@@ -332,7 +332,7 @@ where
             webrender_api_sender,
             window.gl(),
             webvr_services,
-            webxr_registry,
+            webxr_main_thread.registry(),
             player_context,
         );
 
@@ -359,6 +359,7 @@ where
                 webrender_document,
                 webrender_api,
                 webvr_heartbeats,
+                webxr_main_thread,
             },
             opts.output_file.clone(),
             opts.is_running_problem_test,