Set inlineVerticalFieldOfView to null for immersive sessions

components/script/dom/webidls/XRRenderState.webidl

@@ -14,6 +14,6 @@ dictionary XRRenderStateInit {
 [SecureContext, Exposed=Window, Pref="dom.webxr.enabled"] interface XRRenderState {
   readonly attribute double depthNear;
   readonly attribute double depthFar;
-  readonly attribute double inlineVerticalFieldOfView;
+  readonly attribute double? inlineVerticalFieldOfView;
   readonly attribute XRWebGLLayer? baseLayer;
 };

components/script/dom/xrrenderstate.rs

@@ -17,15 +17,15 @@ pub struct XRRenderState {
     reflector_: Reflector,
     depth_near: Cell<f64>,
     depth_far: Cell<f64>,
-    inline_vertical_fov: Cell<f64>,
+    inline_vertical_fov: Cell<Option<f64>>,
     layer: MutNullableDom<XRWebGLLayer>,
 }
 
 impl XRRenderState {
     pub fn new_inherited(
         depth_near: f64,
         depth_far: f64,
-        inline_vertical_fov: f64,
+        inline_vertical_fov: Option<f64>,
         layer: Option<&XRWebGLLayer>,
     ) -> XRRenderState {
         XRRenderState {
@@ -41,7 +41,7 @@ impl XRRenderState {
         global: &GlobalScope,
         depth_near: f64,
         depth_far: f64,
-        inline_vertical_fov: f64,
+        inline_vertical_fov: Option<f64>,
         layer: Option<&XRWebGLLayer>,
     ) -> DomRoot<XRRenderState> {
         reflect_dom_object(
@@ -73,7 +73,8 @@ impl XRRenderState {
         self.depth_far.set(depth)
     }
     pub fn set_inline_vertical_fov(&self, fov: f64) {
-        self.inline_vertical_fov.set(fov)
+        debug_assert!(self.inline_vertical_fov.get().is_some());
+        self.inline_vertical_fov.set(Some(fov))
     }
     pub fn set_layer(&self, layer: Option<&XRWebGLLayer>) {
         self.layer.set(layer)
@@ -92,8 +93,8 @@ impl XRRenderStateMethods for XRRenderState {
     }
 
     /// https://immersive-web.github.io/webxr/#dom-xrrenderstate-inlineverticalfieldofview
-    fn InlineVerticalFieldOfView(&self) -> Finite<f64> {
-        Finite::wrap(self.inline_vertical_fov.get())
+    fn GetInlineVerticalFieldOfView(&self) -> Option<Finite<f64>> {
+        self.inline_vertical_fov.get().map(Finite::wrap)
     }
 
     /// https://immersive-web.github.io/webxr/#dom-xrrenderstate-baselayer

components/script/dom/xrsession.rs

@@ -117,7 +117,12 @@ impl XRSession {
 
     pub fn new(global: &GlobalScope, session: Session, mode: XRSessionMode) -> DomRoot<XRSession> {
         use std::f64::consts::FRAC_PI_2;
-        let render_state = XRRenderState::new(global, 0.1, 1000.0, FRAC_PI_2, None);
+        let ivfov = if mode == XRSessionMode::Inline {
+            Some(FRAC_PI_2)
+        } else {
+            None
+        };
+        let render_state = XRRenderState::new(global, 0.1, 1000.0, ivfov, None);
         let input_sources = XRInputSourceArray::new(global);
         let ret = reflect_dom_object(
             Box::new(XRSession::new_inherited(
@@ -379,7 +384,10 @@ impl XRSession {
         let near = *render_state.DepthNear() as f32;
         let far = *render_state.DepthFar() as f32;
         clip_planes.update(near, far);
-        let top = *render_state.InlineVerticalFieldOfView() / 2.;
+        let top = *render_state
+            .GetInlineVerticalFieldOfView()
+            .expect("IVFOV should be non null for inline sessions") /
+            2.;
         let top = near * top.tan() as f32;
         let bottom = top;
         let left = top * size.width as f32 / size.height as f32;
@@ -454,7 +462,7 @@ impl XRSessionMethods for XRSession {
         }
 
         // Step 4:
-        if init.inlineVerticalFieldOfView.is_some() {
+        if init.inlineVerticalFieldOfView.is_some() && self.is_immersive() {
             return Err(Error::InvalidState);
         }