Use async VR presentation code for XRSession

components/script/dom/vrdisplay.rs

@@ -347,8 +347,9 @@ impl VRDisplayMethods for VRDisplay {
             },
         };
 
-        self.request_present(layer_bounds, Some(&layer_ctx),
-                             promise.clone(), |p| p.resolve_native(&()));
+        self.request_present(layer_bounds, Some(&layer_ctx), Some(promise.clone()), |p| {
+            p.resolve_native(&())
+        });
         promise
     }
 
@@ -437,15 +438,20 @@ impl VRDisplay {
         }
     }
 
-    pub fn request_present<F>(&self, layer_bounds: WebVRLayer,
-                              ctx: Option<&WebGLRenderingContext>,
-                              promise: Rc<Promise>, resolve: F)
-        where F: FnOnce(Rc<Promise>) + Send + 'static {
+    pub fn request_present<F>(
+        &self,
+        layer_bounds: WebVRLayer,
+        ctx: Option<&WebGLRenderingContext>,
+        promise: Option<Rc<Promise>>,
+        resolve: F,
+    ) where
+        F: FnOnce(Rc<Promise>) + Send + 'static,
+    {
         // WebVR spec: Repeat calls while already presenting will update the VRLayers being displayed.
         if self.presenting.get() {
             *self.layer.borrow_mut() = layer_bounds;
             self.layer_ctx.set(ctx);
-            resolve(promise);
+            promise.map(resolve);
             return;
         }
 
@@ -458,7 +464,7 @@ impl VRDisplay {
                 sender,
             ))
             .unwrap();
-        let promise = TrustedPromise::new(promise);
+        let promise = promise.map(TrustedPromise::new);
         let this = Trusted::new(self);
         let ctx = ctx.map(|c| Trusted::new(c));
         let global = self.global();
@@ -471,23 +477,22 @@ impl VRDisplay {
             let _ = task_source.queue_with_canceller(
                 task!(vr_presenting: move || {
                     let this = this.root();
-                    let promise = promise.root();
+                    let promise = promise.map(|p| p.root());
                     let ctx = ctx.map(|c| c.root());
                     match recv {
                         Ok(()) => {
                             *this.layer.borrow_mut() = layer_bounds;
                             this.layer_ctx.set(ctx.as_ref().map(|c| &**c));
                             this.init_present();
-                            resolve(promise);
+                            promise.map(resolve);
                         },
                         Err(e) => {
-                            promise.reject_native(&e);
+                            promise.map(|p| p.reject_native(&e));
                         },
                     }
                 }),
                 &canceller,
             );
-
         });
     }
 
@@ -715,30 +720,19 @@ impl VRDisplay {
 // XR stuff
 // XXXManishearth eventually we should share as much logic as possible
 impl VRDisplay {
-    pub fn xr_present(&self, session: &XRSession, ctx: Option<&WebGLRenderingContext>) {
+    pub fn xr_present(
+        &self,
+        session: &XRSession,
+        ctx: Option<&WebGLRenderingContext>,
+        promise: Option<Rc<Promise>>,
+    ) {
         let layer_bounds = WebVRLayer::default();
         self.xr_session.set(Some(session));
-        if self.presenting.get() {
-            *self.layer.borrow_mut() = layer_bounds;
-            self.layer_ctx.set(ctx);
-            return;
-        }
-
-        // Request Present
-        let (sender, receiver) = ipc::channel(self.global().time_profiler_chan().clone()).unwrap();
-        self.webvr_thread()
-            .send(WebVRMsg::RequestPresent(
-                self.global().pipeline_id(),
-                self.display.borrow().display_id,
-                sender,
-            ))
-            .unwrap();
-
-        if let Ok(()) = receiver.recv().unwrap() {
-            *self.layer.borrow_mut() = layer_bounds;
-            self.layer_ctx.set(ctx);
-            self.init_present();
-        }
+        let session = Trusted::new(session);
+        self.request_present(layer_bounds, ctx, promise, move |p| {
+            let session = session.root();
+            p.resolve_native(&session);
+        });
     }
 
     pub fn xr_raf(&self, callback: Rc<XRFrameRequestCallback>) -> u32 {

components/script/dom/xr.rs

@@ -95,9 +95,7 @@ impl XRMethods for XR {
         }
 
         let session = XRSession::new(&self.global(), &displays[0]);
-        // XXXManishearth we should actually xr_present() here instead of
-        // in XRSession::new, and resolve a promise based on it
-        promise.resolve_native(&session);
+        session.xr_present(promise.clone());
         promise
     }
 }

components/script/dom/xrsession.rs

@@ -14,6 +14,7 @@ use crate::dom::bindings::reflector::reflect_dom_object;
 use crate::dom::bindings::root::{Dom, DomRoot, MutNullableDom};
 use crate::dom::eventtarget::EventTarget;
 use crate::dom::globalscope::GlobalScope;
+use crate::dom::promise::Promise;
 use crate::dom::vrdisplay::VRDisplay;
 use crate::dom::xrlayer::XRLayer;
 use crate::dom::xrwebgllayer::XRWebGLLayer;
@@ -37,13 +38,15 @@ impl XRSession {
     }
 
     pub fn new(global: &GlobalScope, display: &VRDisplay) -> DomRoot<XRSession> {
-        let ret = reflect_dom_object(
+        reflect_dom_object(
             Box::new(XRSession::new_inherited(display)),
             global,
             XRSessionBinding::Wrap,
-        );
-        ret.display.xr_present(&ret, None);
-        ret
+        )
+    }
+
+    pub fn xr_present(&self, p: Rc<Promise>) {
+        self.display.xr_present(self, None, Some(p));
     }
 }
 
@@ -78,7 +81,7 @@ impl XRSessionMethods for XRSession {
         self.base_layer.set(layer);
         if let Some(layer) = layer {
             let layer = layer.downcast::<XRWebGLLayer>().unwrap();
-            self.display.xr_present(&self, Some(&layer.Context()));
+            self.display.xr_present(&self, Some(&layer.Context()), None);
         } else {
             // steps unknown
             // https://github.com/immersive-web/webxr/issues/453