Simple presentation

components/script/dom/vrdisplay.rs

@@ -664,6 +664,35 @@ impl VRDisplay {
     }
 }
 
+// XR stuff
+// XXXManishearth eventually we should share as much logic as possible
+impl VRDisplay {
+    pub fn xr_present(&self, ctx: &WebGLRenderingContext) {
+        let layer_bounds = WebVRLayer::default();
+        self.xr.set(true);
+        if self.presenting.get() {
+            *self.layer.borrow_mut() = layer_bounds;
+            self.layer_ctx.set(Some(&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(Some(&ctx));
+            self.init_present();
+        }
+    }
+}
+
 // WebVR Spec: If the number of values in the leftBounds/rightBounds arrays
 // is not 0 or 4 for any of the passed layers the promise is rejected
 fn parse_bounds(src: &Option<Vec<Finite<f32>>>, dst: &mut [f32; 4]) -> Result<(), &'static str> {

components/script/dom/xr.rs

@@ -89,12 +89,15 @@ impl XRMethods for XR {
             },
         };
 
+        // XXXManishearth filter for displays which can_present
         if displays.is_empty() {
             promise.reject_error(Error::Security);
         }
 
         let session = XRSession::new(&self.global(), &displays[0]);
         promise.resolve_native(&session);
+        // whether or not we should initiate presentation is unclear
+        // https://github.com/immersive-web/webxr/issues/453
 
         promise
     }

components/script/dom/xrsession.rs

@@ -5,6 +5,8 @@
 use crate::dom::bindings::codegen::Bindings::XRBinding::XRSessionMode;
 use crate::dom::bindings::codegen::Bindings::XRSessionBinding;
 use crate::dom::bindings::codegen::Bindings::XRSessionBinding::XRSessionMethods;
+use crate::dom::bindings::codegen::Bindings::XRWebGLLayerBinding::XRWebGLLayerMethods;
+use crate::dom::bindings::inheritance::Castable;
 use crate::dom::bindings::num::Finite;
 use crate::dom::bindings::reflector::reflect_dom_object;
 use crate::dom::bindings::root::{Dom, DomRoot, MutNullableDom};
@@ -12,6 +14,7 @@ use crate::dom::eventtarget::EventTarget;
 use crate::dom::globalscope::GlobalScope;
 use crate::dom::vrdisplay::VRDisplay;
 use crate::dom::xrlayer::XRLayer;
+use crate::dom::xrwebgllayer::XRWebGLLayer;
 use dom_struct::dom_struct;
 use std::cell::Cell;
 
@@ -66,7 +69,14 @@ impl XRSessionMethods for XRSession {
     }
 
     fn SetBaseLayer(&self, layer: Option<&XRLayer>) {
-        self.base_layer.set(layer)
+        self.base_layer.set(layer);
+        if let Some(layer) = layer {
+            let layer = layer.downcast::<XRWebGLLayer>().unwrap();
+            self.display.xr_present(&layer.Context());
+        } else {
+            // steps unknown
+            // https://github.com/immersive-web/webxr/issues/453
+        }
     }
 
     fn GetBaseLayer(&self) -> Option<DomRoot<XRLayer>> {