Auto merge of #22528 - Manishearth:webxr, r=jdm,MortimerGoro

Preliminary WebXR support

This implements just enough WebXR to display to 3DOF devices in
immersive mode only.

Couple missing things:

 - [ ] Handling reference spaces (even if just supporting eye-level spaces)
 - [x] Spec links
 - [ ] We enter immersive mode when baseLayer is set, but it seems like
we're supposed to do this when requestSession is called (https://github.com/immersive-web/webxr/issues/453)
 - [ ] VR/XR should block less (https://github.com/servo/servo/issues/22505)
 - [x] More pref-gating
 - [x] `views` is a method instead of an attribute because we don't support FrozenArray

<s>Once I add spec links and pref gating</s> this can be landed as-is for further experimentation.

r? @jdm @MortimerGoro

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1 files changed, 83 insertions, 0 deletions

diff --git a/components/script/dom/xrview.rs b/components/script/dom/xrview.rs
new file mode 100644
index 00000000000..55975e5d8a0
--- /dev/null
+++ b/components/script/dom/xrview.rs
@@ -0,0 +1,83 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+use crate::dom::bindings::codegen::Bindings::XRViewBinding;
+use crate::dom::bindings::codegen::Bindings::XRViewBinding::{XREye, XRViewMethods};
+use crate::dom::bindings::reflector::{reflect_dom_object, Reflector};
+use crate::dom::bindings::root::{Dom, DomRoot};
+use crate::dom::globalscope::GlobalScope;
+use crate::dom::vrframedata::create_typed_array;
+use crate::dom::xrsession::XRSession;
+use dom_struct::dom_struct;
+use js::jsapi::{Heap, JSContext, JSObject};
+use std::ptr::NonNull;
+use webvr_traits::WebVRFrameData;
+
+#[dom_struct]
+pub struct XRView {
+    reflector_: Reflector,
+    session: Dom<XRSession>,
+    eye: XREye,
+    proj: Heap<*mut JSObject>,
+    view: Heap<*mut JSObject>,
+}
+
+impl XRView {
+    fn new_inherited(session: &XRSession, eye: XREye) -> XRView {
+        XRView {
+            reflector_: Reflector::new(),
+            session: Dom::from_ref(session),
+            eye,
+            proj: Heap::default(),
+            view: Heap::default(),
+        }
+    }
+
+    pub fn new(
+        global: &GlobalScope,
+        session: &XRSession,
+        eye: XREye,
+        data: &WebVRFrameData,
+    ) -> DomRoot<XRView> {
+        let ret = reflect_dom_object(
+            Box::new(XRView::new_inherited(session, eye)),
+            global,
+            XRViewBinding::Wrap,
+        );
+
+        let (proj, view) = if eye == XREye::Left {
+            (&data.left_projection_matrix, &data.left_view_matrix)
+        } else {
+            (&data.right_projection_matrix, &data.right_view_matrix)
+        };
+
+        let cx = global.get_cx();
+        create_typed_array(cx, proj, &ret.proj);
+        create_typed_array(cx, view, &ret.view);
+        ret
+    }
+
+    pub fn session(&self) -> &XRSession {
+        &self.session
+    }
+}
+
+impl XRViewMethods for XRView {
+    /// https://immersive-web.github.io/webxr/#dom-xrview-eye
+    fn Eye(&self) -> XREye {
+        self.eye
+    }
+
+    #[allow(unsafe_code)]
+    /// https://immersive-web.github.io/webxr/#dom-xrview-projectionmatrix
+    unsafe fn ProjectionMatrix(&self, _cx: *mut JSContext) -> NonNull<JSObject> {
+        NonNull::new(self.proj.get()).unwrap()
+    }
+
+    #[allow(unsafe_code)]
+    /// https://immersive-web.github.io/webxr/#dom-xrview-projectionmatrix
+    unsafe fn ViewMatrix(&self, _cx: *mut JSContext) -> NonNull<JSObject> {
+        NonNull::new(self.view.get()).unwrap()
+    }
+}