fix(client_openxr): 🐛 Fix crash on unsupported eye tracking permission on Pico (#2618)

Author: zmerp

alvr/client_openxr/src/extra_extensions/eye_gaze_interaction.rs

@@ -0,0 +1,35 @@
+use openxr::{self as xr, sys};
+use std::ptr;
+
+fn get_props<G, T>(session: &xr::Session<G>, system: xr::SystemId, default_struct: T) -> Option<T> {
+    let instance = session.instance();
+
+    let mut props = default_struct;
+    let mut system_properties = sys::SystemProperties::out((&mut props as *mut T).cast());
+    let result = unsafe {
+        (instance.fp().get_system_properties)(
+            instance.as_raw(),
+            system,
+            system_properties.as_mut_ptr(),
+        )
+    };
+    (result.into_raw() >= 0).then_some(props)
+}
+
+pub fn supports_eye_gaze_interaction<G>(session: &xr::Session<G>, system: xr::SystemId) -> bool {
+    if session.instance().exts().ext_eye_gaze_interaction.is_none() {
+        return false;
+    }
+
+    get_props(
+        session,
+        system,
+        sys::SystemEyeGazeInteractionPropertiesEXT {
+            ty: sys::SystemEyeGazeInteractionPropertiesEXT::TYPE,
+            next: ptr::null_mut(),
+            supports_eye_gaze_interaction: sys::FALSE,
+        },
+    )
+    .map(|props| props.supports_eye_gaze_interaction.into())
+    .unwrap_or(false)
+}

alvr/client_openxr/src/extra_extensions/mod.rs

@@ -1,4 +1,5 @@
 mod body_tracking_fb;
+mod eye_gaze_interaction;
 mod eye_tracking_social;
 mod face_tracking2_fb;
 mod facial_tracking_htc;
@@ -7,6 +8,7 @@ mod passthrough_fb;
 mod passthrough_htc;
 
 pub use body_tracking_fb::*;
+pub use eye_gaze_interaction::*;
 pub use eye_tracking_social::*;
 pub use face_tracking2_fb::*;
 pub use facial_tracking_htc::*;

alvr/client_openxr/src/interaction.rs

@@ -116,6 +116,7 @@ pub struct InteractionContext {
 impl InteractionContext {
     pub fn new(
         xr_session: xr::Session<xr::OpenGlEs>,
+        xr_system: xr::SystemId,
         platform: Platform,
         supports_multimodal: bool,
     ) -> Self {
@@ -270,9 +271,13 @@ impl InteractionContext {
             )
             .unwrap();
 
-        let combined_eyes_source = if xr_instance.exts().ext_eye_gaze_interaction.is_some()
-            && !platform.is_quest()
+        // Pico headsets require calling get_system_properties to test for extensions, because all
+        // extensions function pointers are available even if the feature is not supported by the
+        // hardware. The full checks are done in supports_eye_gaze_interaction. This is required
+        // to avoid a crash when requesting the EYE_TRACKING permission.
+        let combined_eyes_source = if !platform.is_quest()
             && !platform.is_vive()
+            && extra_extensions::supports_eye_gaze_interaction(&xr_session, xr_system)
         {
             #[cfg(target_os = "android")]
             if platform.is_pico() {

alvr/client_openxr/src/lib.rs

@@ -267,6 +267,7 @@ pub fn entry_point() {
 
         let interaction_context = Arc::new(RwLock::new(InteractionContext::new(
             xr_session.clone(),
+            xr_system,
             platform,
             exts.other
                 .contains(&META_SIMULTANEOUS_HANDS_AND_CONTROLLERS_EXTENSION_NAME.to_owned()),