1 files changed, 64 insertions, 0 deletions

diff --git a/components/script/dom/xrrigidtransform.rs b/components/script/dom/xrrigidtransform.rs
index 3f726475517..ad7cbe7543b 100644
--- a/components/script/dom/xrrigidtransform.rs
+++ b/components/script/dom/xrrigidtransform.rs
@@ -3,6 +3,7 @@
  * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
 
 use crate::dom::bindings::codegen::Bindings::DOMPointBinding::DOMPointInit;
+use crate::dom::bindings::codegen::Bindings::DOMPointReadOnlyBinding::DOMPointReadOnlyBinding::DOMPointReadOnlyMethods;
 use crate::dom::bindings::codegen::Bindings::XRRigidTransformBinding;
 use crate::dom::bindings::codegen::Bindings::XRRigidTransformBinding::XRRigidTransformMethods;
 use crate::dom::bindings::error::Fallible;
@@ -12,12 +13,17 @@ use crate::dom::bindings::root::{Dom, DomRoot};
 use crate::dom::dompointreadonly::DOMPointReadOnly;
 use crate::dom::window::Window;
 use dom_struct::dom_struct;
+use euclid::{Rotation3D, Transform3D};
 
 #[dom_struct]
 pub struct XRRigidTransform {
     reflector_: Reflector,
     position: Dom<DOMPointReadOnly>,
     orientation: Dom<DOMPointReadOnly>,
+    #[ignore_malloc_size_of = "defined in euclid"]
+    translate: Transform3D<f64>,
+    #[ignore_malloc_size_of = "defined in euclid"]
+    rotate: Rotation3D<f64>,
 }
 
 impl XRRigidTransform {
@@ -25,10 +31,23 @@ impl XRRigidTransform {
         position: &DOMPointReadOnly,
         orientation: &DOMPointReadOnly,
     ) -> XRRigidTransform {
+        let translate = Transform3D::create_translation(
+            position.X() as f64,
+            position.Y() as f64,
+            position.Z() as f64,
+        );
+        let rotate = Rotation3D::unit_quaternion(
+            orientation.X() as f64,
+            orientation.Y() as f64,
+            orientation.Z() as f64,
+            orientation.W() as f64,
+        );
         XRRigidTransform {
             reflector_: Reflector::new(),
             position: Dom::from_ref(position),
             orientation: Dom::from_ref(orientation),
+            translate,
+            rotate,
         }
     }
 
@@ -65,6 +84,7 @@ impl XRRigidTransform {
     ) -> Fallible<DomRoot<Self>> {
         let global = window.global();
         let position = DOMPointReadOnly::new_from_init(&global, &position);
+        // XXXManishearth normalize this
         let orientation = DOMPointReadOnly::new_from_init(&global, &orientation);
         Ok(XRRigidTransform::new(window, &position, &orientation))
     }
@@ -79,4 +99,48 @@ impl XRRigidTransformMethods for XRRigidTransform {
     fn Orientation(&self) -> DomRoot<DOMPointReadOnly> {
         DomRoot::from_ref(&self.orientation)
     }
+    // https://immersive-web.github.io/webxr/#dom-xrrigidtransform-inverse
+    fn Inverse(&self) -> DomRoot<XRRigidTransform> {
+        // An XRRigidTransform is a rotation and a translation,
+        // i.e. T * R
+        //
+        // Its inverse is (T * R)^-1
+        //    = R^-1 * T^-1
+        //    = R^-1 * T^-1 * (R * R^-1)
+        //    = (R^-1 * T^-1 * R) * R^-1
+        //    = T' * R^-1
+        //    = T' * R'
+        //
+        //  (R^-1 * T^-1 * R) is a translation matrix, and R^-1 is a
+        //  rotation matrix, so we can use these in the new rigid transform
+        let r_1 = self.rotate.inverse();
+        let t_1 = self
+            .translate
+            .inverse()
+            .expect("translation matrices should be invertible");
+        let t_p = r_1
+            .to_transform()
+            .post_mul(&t_1)
+            .post_mul(&self.rotate.to_transform());
+
+        let global = self.global();
+        let position =
+            DOMPointReadOnly::new(&global, t_p.m41.into(), t_p.m42.into(), t_p.m43.into(), 1.);
+        let orientation = DOMPointReadOnly::new(
+            &global,
+            r_1.i.into(),
+            r_1.j.into(),
+            r_1.k.into(),
+            r_1.r.into(),
+        );
+        XRRigidTransform::new(global.as_window(), &position, &orientation)
+    }
+}
+
+impl XRRigidTransform {
+    pub fn matrix(&self) -> Transform3D<f64> {
+        // Spec says the orientation applies first,
+        // so post-multiply (?)
+        self.translate.post_mul(&self.rotate.to_transform())
+    }
 }