Auto merge of #23159 - Manishearth:rigid-transforms, r=asajeffrey

Update XR code to use rigid transforms and new pose/transform stuff from the spec

This updates our XR code to use euclid's new [RigidTransform3D type](https://github.com/servo/euclid/pull/328), which is more efficent and convenient to work with.

It additionally brings us up to speed with the spec:

 - `XRViewerPose` was made a subclass of `XRPose` (https://github.com/immersive-web/webxr/pull/496)
 - `XRView.viewMatrix` was removed in favor of `XRRigidTransform.inverse.matrix` (https://github.com/immersive-web/webxr/pull/531)
 - `XRRigidTransform.inverse` is an attribute (https://github.com/immersive-web/webxr/pull/560)
 - `XRRigidTransform` now validates positions in its constructor (https://github.com/immersive-web/webxr/pull/568)

Furthermore, it adds support for `XRRigidTransform.matrix`.

While fixing this I also noticed that our view matrix code was incorrect, we calculated view matrices as `pose.to_column_major_array()`, whereas it *should* be `pose.inverse().to_row_major_array()` (since Euclid uses row vectors, whenever the spec says it wants a column major array we should use `.to_row_major_array()` since all web specs implicitly use column vectors). For 3DOF devices poses are mostly rotations anyway, so the effective transpose behaved _like_ an inversion, but was incorrect.

This PR gets rid of `view.viewMatrix` anyway, however I felt like I should mention this discrepancy, since otherwise the replacement of `view.viewMatrix` with `view.transform.inverse.matrix` doesn't make sense

r? @jdm

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1 files changed, 44 insertions, 0 deletions

diff --git a/components/script/dom/xrpose.rs b/components/script/dom/xrpose.rs
new file mode 100644
index 00000000000..9f8aec3a366
--- /dev/null
+++ b/components/script/dom/xrpose.rs
@@ -0,0 +1,44 @@
+/* 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::XRPoseBinding;
+use crate::dom::bindings::codegen::Bindings::XRPoseBinding::XRPoseMethods;
+use crate::dom::bindings::reflector::{reflect_dom_object, Reflector};
+use crate::dom::bindings::root::{Dom, DomRoot};
+use crate::dom::globalscope::GlobalScope;
+use crate::dom::xrrigidtransform::XRRigidTransform;
+use dom_struct::dom_struct;
+use euclid::RigidTransform3D;
+
+#[dom_struct]
+pub struct XRPose {
+    reflector_: Reflector,
+    transform: Dom<XRRigidTransform>,
+}
+
+impl XRPose {
+    pub fn new_inherited(transform: &XRRigidTransform) -> XRPose {
+        XRPose {
+            reflector_: Reflector::new(),
+            transform: Dom::from_ref(transform),
+        }
+    }
+
+    #[allow(unused)]
+    pub fn new(global: &GlobalScope, transform: RigidTransform3D<f64>) -> DomRoot<XRPose> {
+        let transform = XRRigidTransform::new(global, transform);
+        reflect_dom_object(
+            Box::new(XRPose::new_inherited(&transform)),
+            global,
+            XRPoseBinding::Wrap,
+        )
+    }
+}
+
+impl XRPoseMethods for XRPose {
+    /// https://immersive-web.github.io/webxr/#dom-xrpose-transform
+    fn Transform(&self) -> DomRoot<XRRigidTransform> {
+        DomRoot::from_ref(&self.transform)
+    }
+}