Add a viewer typed reference space

components/script/dom/xrreferencespace.rs

@@ -10,9 +10,7 @@ use crate::dom::bindings::reflector::{reflect_dom_object, DomObject};
 use crate::dom::bindings::root::{Dom, DomRoot};
 use crate::dom::globalscope::GlobalScope;
 use crate::dom::xrrigidtransform::XRRigidTransform;
-use crate::dom::xrsession::{
-    cast_transform, cast_transform_to_pose, ApiPose, ApiRigidTransform, XRSession,
-};
+use crate::dom::xrsession::{cast_transform, ApiPose, ApiRigidTransform, ApiViewerPose, XRSession};
 use crate::dom::xrspace::XRSpace;
 use dom_struct::dom_struct;
 use euclid::{TypedRigidTransform3D, TypedVector3D};
@@ -82,7 +80,7 @@ impl XRReferenceSpace {
     ///
     /// This is equivalent to `get_pose(self).inverse() * get_pose(viewerSpace)` (in column vector notation),
     /// however we specialize it to be efficient
-    pub fn get_viewer_pose(&self, base_pose: &Frame) -> ApiRigidTransform {
+    pub fn get_viewer_pose(&self, base_pose: &Frame) -> ApiViewerPose {
         let pose = self.get_unoffset_viewer_pose(base_pose);
 
         // This may change, see https://github.com/immersive-web/webxr/issues/567
@@ -100,8 +98,8 @@ impl XRReferenceSpace {
     /// Gets pose of the viewer with respect to this space
     ///
     /// Does not apply originOffset, use get_viewer_pose instead if you need it
-    pub fn get_unoffset_viewer_pose(&self, base_pose: &Frame) -> ApiRigidTransform {
-        let viewer_pose = cast_transform(base_pose.transform);
+    pub fn get_unoffset_viewer_pose(&self, base_pose: &Frame) -> ApiViewerPose {
+        let viewer_pose: ApiViewerPose = cast_transform(base_pose.transform);
         // all math is in column-vector notation
         // we use the following equation to verify correctness here:
         // get_viewer_pose(space) = get_pose(space).inverse() * get_pose(viewer_space)
@@ -164,7 +162,7 @@ impl XRReferenceSpace {
                 // the floor-level space is 2m below the eye-level space, which is (0, 0, 0)
                 TypedVector3D::new(0., -2., 0.).into()
             },
-            XRReferenceSpaceType::Viewer => cast_transform_to_pose(base_pose.transform),
+            XRReferenceSpaceType::Viewer => cast_transform(base_pose.transform),
             _ => unimplemented!(),
         }
     }

components/script/dom/xrsession.rs

@@ -276,17 +276,14 @@ impl XRSessionMethods for XRSession {
 pub struct ApiSpace;
 // The pose of an object in native-space. Should never be exposed.
 pub type ApiPose = TypedRigidTransform3D<f32, ApiSpace, webxr_api::Native>;
+// The pose of the viewer in some api-space.
+pub type ApiViewerPose = TypedRigidTransform3D<f32, webxr_api::Viewer, ApiSpace>;
 // A transform between objects in some API-space
 pub type ApiRigidTransform = TypedRigidTransform3D<f32, ApiSpace, ApiSpace>;
 
 #[allow(unsafe_code)]
-pub fn cast_transform_to_pose<T>(
-    transform: TypedRigidTransform3D<f32, T, webxr_api::Native>,
-) -> ApiPose {
-    unsafe { mem::transmute(transform) }
-}
-
-#[allow(unsafe_code)]
-pub fn cast_transform<T, U>(transform: TypedRigidTransform3D<f32, T, U>) -> ApiRigidTransform {
+pub fn cast_transform<T, U, V, W>(
+    transform: TypedRigidTransform3D<f32, T, U>,
+) -> TypedRigidTransform3D<f32, V, W> {
     unsafe { mem::transmute(transform) }
 }

components/script/dom/xrview.rs

@@ -9,7 +9,7 @@ use crate::dom::bindings::root::{Dom, DomRoot};
 use crate::dom::globalscope::GlobalScope;
 use crate::dom::vrframedata::create_typed_array;
 use crate::dom::xrrigidtransform::XRRigidTransform;
-use crate::dom::xrsession::{cast_transform, ApiRigidTransform, XRSession};
+use crate::dom::xrsession::{cast_transform, ApiViewerPose, XRSession};
 use dom_struct::dom_struct;
 use js::jsapi::{Heap, JSContext, JSObject};
 use std::ptr::NonNull;
@@ -45,13 +45,16 @@ impl XRView {
         session: &XRSession,
         view: &View<V>,
         eye: XREye,
-        pose: &ApiRigidTransform,
+        pose: &ApiViewerPose,
     ) -> DomRoot<XRView> {
         // XXXManishearth compute and cache projection matrices on the Display
-        let offset = cast_transform(view.transform);
 
-        let transform = pose.post_mul(&offset.into());
-        let transform = XRRigidTransform::new(global, transform);
+        // this transform is the pose of the viewer in the eye space, i.e. it is the transform
+        // from the viewer space to the eye space. We invert it to get the pose of the eye in the viewer space.
+        let offset = view.transform.inverse();
+
+        let transform = pose.pre_mul(&offset);
+        let transform = XRRigidTransform::new(global, cast_transform(transform));
 
         let ret = reflect_dom_object(
             Box::new(XRView::new_inherited(session, &transform, eye)),

components/script/dom/xrviewerpose.rs

@@ -10,7 +10,7 @@ use crate::dom::bindings::root::DomRoot;
 use crate::dom::globalscope::GlobalScope;
 use crate::dom::xrpose::XRPose;
 use crate::dom::xrrigidtransform::XRRigidTransform;
-use crate::dom::xrsession::{ApiRigidTransform, XRSession};
+use crate::dom::xrsession::{cast_transform, ApiViewerPose, XRSession};
 use crate::dom::xrview::XRView;
 use dom_struct::dom_struct;
 use js::conversions::ToJSValConvertible;
@@ -37,7 +37,7 @@ impl XRViewerPose {
     pub fn new(
         global: &GlobalScope,
         session: &XRSession,
-        pose: ApiRigidTransform,
+        pose: ApiViewerPose,
     ) -> DomRoot<XRViewerPose> {
         rooted_vec!(let mut views);
         session.with_session(|s| match s.views() {
@@ -49,7 +49,7 @@ impl XRViewerPose {
                 views.push(XRView::new(global, session, &right, XREye::Right, &pose));
             },
         });
-        let transform = XRRigidTransform::new(global, pose);
+        let transform = XRRigidTransform::new(global, cast_transform(pose));
         let pose = reflect_dom_object(
             Box::new(XRViewerPose::new_inherited(&transform)),
             global,