oxr/st: add oxr/state tracker stubs for XR_ANDROID_face_tracking

Part-of: <https://gitlab.freedesktop.org/monado/monado/-/merge_requests/2605>

src/xrt/state_trackers/oxr/CMakeLists.txt

···
 	target_sources(st_oxr PRIVATE oxr_api_body_tracking.c oxr_body_tracking.c)
 endif()
 
+if(XRT_FEATURE_OPENXR_FACE_TRACKING_ANDROID)
+	target_sources(st_oxr PRIVATE oxr_api_face_tracking_android.c oxr_face_tracking_android.c)
+endif()
+
 if(XRT_FEATURE_OPENXR_FACIAL_TRACKING_HTC)
 	target_sources(st_oxr PRIVATE oxr_api_face_tracking_htc.c oxr_face_tracking_htc.c)
 endif()

src/xrt/state_trackers/oxr/oxr_api_face_tracking_android.c

···
+// Copyright 2025, Collabora, Ltd.
+// SPDX-License-Identifier: BSL-1.0
+/*!
+ * @file
+ * @brief Android face tracking related API entrypoint functions.
+ * @author Korcan Hussein <[e-mail]>
+ * @ingroup oxr_api
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "util/u_trace_marker.h"
+
+#include "oxr_objects.h"
+#include "oxr_logger.h"
+
+#include "oxr_api_funcs.h"
+#include "oxr_api_verify.h"
+#include "oxr_handle.h"
+
+XRAPI_ATTR XrResult XRAPI_CALL
+oxr_xrCreateFaceTrackerANDROID(XrSession session,
+                               const XrFaceTrackerCreateInfoANDROID *createInfo,
+                               XrFaceTrackerANDROID *faceTracker)
+{
+	OXR_TRACE_MARKER();
+	struct oxr_logger log;
+	struct oxr_session *sess = NULL;
+	OXR_VERIFY_SESSION_AND_INIT_LOG(&log, session, sess, "xrCreateFaceTrackerANDROID");
+	OXR_VERIFY_SESSION_NOT_LOST(&log, sess);
+	OXR_VERIFY_EXTENSION(&log, sess->sys->inst, ANDROID_face_tracking);
+	OXR_VERIFY_ARG_TYPE_AND_NOT_NULL(&log, createInfo, XR_TYPE_FACE_TRACKER_CREATE_INFO_ANDROID);
+	return oxr_face_tracker_android_create(&log, sess, createInfo, faceTracker);
+}
+
+XRAPI_ATTR XrResult XRAPI_CALL
+oxr_xrDestroyFaceTrackerANDROID(XrFaceTrackerANDROID facialTracker)
+{
+	OXR_TRACE_MARKER();
+	struct oxr_logger log;
+	struct oxr_face_tracker_android *face_tracker_android = NULL;
+	OXR_VERIFY_FACE_TRACKER_ANDROID_AND_INIT_LOG(&log, facialTracker, face_tracker_android,
+	                                             "xrDestroyFaceTrackerANDROID");
+	return oxr_handle_destroy(&log, &face_tracker_android->handle);
+}
+
+XRAPI_ATTR XrResult XRAPI_CALL
+oxr_xrGetFaceStateANDROID(XrFaceTrackerANDROID faceTracker,
+                          const XrFaceStateGetInfoANDROID *getInfo,
+                          XrFaceStateANDROID *faceStateOutput)
+{
+	OXR_TRACE_MARKER();
+	struct oxr_logger log;
+	struct oxr_face_tracker_android *face_tracker_android = NULL;
+	OXR_VERIFY_FACE_TRACKER_ANDROID_AND_INIT_LOG(&log, faceTracker, face_tracker_android, "xrGetFaceStateANDROID");
+	OXR_VERIFY_SESSION_NOT_LOST(&log, face_tracker_android->sess);
+	OXR_VERIFY_ARG_NOT_NULL(&log, face_tracker_android->xdev);
+	OXR_VERIFY_ARG_TYPE_AND_NOT_NULL(&log, getInfo, XR_TYPE_FACE_STATE_GET_INFO_ANDROID);
+	OXR_VERIFY_ARG_TYPE_AND_NOT_NULL(&log, faceStateOutput, XR_TYPE_FACE_STATE_ANDROID);
+	OXR_VERIFY_ARG_TIME_NOT_ZERO(&log, getInfo->time);
+	OXR_VERIFY_TWO_CALL_ARRAY(&log, faceStateOutput->parametersCapacityInput,
+	                          (&faceStateOutput->parametersCountOutput), faceStateOutput->parameters);
+	OXR_VERIFY_TWO_CALL_ARRAY(&log, faceStateOutput->regionConfidencesCapacityInput,
+	                          (&faceStateOutput->regionConfidencesCountOutput), faceStateOutput->regionConfidences);
+	return oxr_get_face_state_android(&log, face_tracker_android, getInfo, faceStateOutput);
+}
+
+XRAPI_ATTR XrResult XRAPI_CALL
+oxr_xrGetFaceCalibrationStateANDROID(XrFaceTrackerANDROID faceTracker, XrBool32 *faceIsCalibratedOutput)
+{
+	OXR_TRACE_MARKER();
+	struct oxr_logger log;
+	struct oxr_face_tracker_android *face_tracker_android = NULL;
+	OXR_VERIFY_FACE_TRACKER_ANDROID_AND_INIT_LOG(&log, faceTracker, face_tracker_android,
+	                                             "xrGetFaceCalibrationStateANDROID");
+	OXR_VERIFY_SESSION_NOT_LOST(&log, face_tracker_android->sess);
+	OXR_VERIFY_ARG_NOT_NULL(&log, face_tracker_android->xdev);
+	OXR_VERIFY_ARG_NOT_NULL(&log, faceIsCalibratedOutput);
+	return oxr_get_face_calibration_state_android(&log, face_tracker_android, faceIsCalibratedOutput);
+}

src/xrt/state_trackers/oxr/oxr_api_funcs.h

···
 oxr_xrCancelFutureEXT(XrInstance instance, const XrFutureCancelInfoEXT *cancelInfo);
 #endif
 
+/*
+ *
+ * oxr_api_face_tracking_android.c
+ *
+ */
+
+#ifdef OXR_HAVE_ANDROID_face_tracking
+XRAPI_ATTR XrResult XRAPI_CALL
+oxr_xrCreateFaceTrackerANDROID(XrSession session,
+                               const XrFaceTrackerCreateInfoANDROID *createInfo,
+                               XrFaceTrackerANDROID *faceTracker);
+
+XRAPI_ATTR XrResult XRAPI_CALL
+oxr_xrDestroyFaceTrackerANDROID(XrFaceTrackerANDROID facialTracker);
+
+XRAPI_ATTR XrResult XRAPI_CALL
+oxr_xrGetFaceStateANDROID(XrFaceTrackerANDROID faceTracker,
+                          const XrFaceStateGetInfoANDROID *getInfo,
+                          XrFaceStateANDROID *faceStateOutput);
+
+XRAPI_ATTR XrResult XRAPI_CALL
+oxr_xrGetFaceCalibrationStateANDROID(XrFaceTrackerANDROID faceTracker, XrBool32 *faceIsCalibratedOutput);
+#endif
+
 /*!
  * @}
  */

src/xrt/state_trackers/oxr/oxr_api_negotiate.c

···
 	ENTRY_IF_EXT(xrCancelFutureEXT, EXT_future);
 #endif // OXR_HAVE_EXT_future
 
+#ifdef OXR_HAVE_ANDROID_face_tracking
+	ENTRY_IF_EXT(xrCreateFaceTrackerANDROID, ANDROID_face_tracking);
+	ENTRY_IF_EXT(xrDestroyFaceTrackerANDROID, ANDROID_face_tracking);
+	ENTRY_IF_EXT(xrGetFaceCalibrationStateANDROID, ANDROID_face_tracking);
+	ENTRY_IF_EXT(xrGetFaceStateANDROID, ANDROID_face_tracking);
+#endif
+
 #ifdef OXR_HAVE_KHR_extended_struct_name_lengths
 	ENTRY_IF_EXT(xrStructureTypeToString2KHR, KHR_extended_struct_name_lengths);
 #endif // OXR_HAVE_KHR_extended_struct_name_lengths

src/xrt/state_trackers/oxr/oxr_api_verify.h

···
 #define OXR_VERIFY_FUTURE_AND_INIT_LOG(log, thing, new_thing, name) \
 	OXR_VERIFY_AND_SET_AND_INIT(log, thing, new_thing, oxr_future_ext, FUTURE, name, new_thing->inst); \
 	OXR_VERIFY_FUTURE_VALID(log, new_thing)
+#define OXR_VERIFY_FACE_TRACKER_ANDROID_AND_INIT_LOG(log, thing, new_thing, name) \
+	OXR_VERIFY_AND_SET_AND_INIT(log, thing, new_thing, oxr_face_tracker_android, FTRACKER, name, new_thing->sess->sys->inst)
 // clang-format on
 
 #define OXR_VERIFY_INSTANCE_NOT_NULL(log, arg, new_arg) OXR_VERIFY_SET(log, arg, new_arg, oxr_instance, INSTANCE);

src/xrt/state_trackers/oxr/oxr_face_tracking_android.c

···
+// Copyright 2025, Collabora, Ltd.
+// SPDX-License-Identifier: BSL-1.0
+/*!
+ * @file
+ * @brief Android face tracking related API entrypoint functions.
+ * @author Korcan Hussein <[e-mail]>
+ * @ingroup oxr_main
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "oxr_objects.h"
+#include "oxr_logger.h"
+#include "oxr_handle.h"
+
+static XrResult
+oxr_face_tracker_android_destroy_cb(struct oxr_logger *log, struct oxr_handle_base *hb)
+{
+	struct oxr_face_tracker_android *face_tracker_android = (struct oxr_face_tracker_android *)hb;
+	free(face_tracker_android);
+	return XR_SUCCESS;
+}
+
+XrResult
+oxr_face_tracker_android_create(struct oxr_logger *log,
+                                struct oxr_session *sess,
+                                const XrFaceTrackerCreateInfoANDROID *createInfo,
+                                XrFaceTrackerANDROID *faceTracker)
+{
+	return oxr_session_success_result(sess);
+}
+
+XrResult
+oxr_get_face_state_android(struct oxr_logger *log,
+                           struct oxr_face_tracker_android *facial_tracker_android,
+                           const XrFaceStateGetInfoANDROID *getInfo,
+                           XrFaceStateANDROID *faceStateOutput)
+{
+
+	return oxr_session_success_result(facial_tracker_android->sess);
+}
+
+XrResult
+oxr_get_face_calibration_state_android(struct oxr_logger *log,
+                                       struct oxr_face_tracker_android *facial_tracker_android,
+                                       XrBool32 *faceIsCalibratedOutput)
+{
+	return oxr_session_success_result(facial_tracker_android->sess);
+}

src/xrt/state_trackers/oxr/oxr_objects.h

···
 struct oxr_action_set_ref;
 struct oxr_action_ref;
 struct oxr_hand_tracker;
+struct oxr_face_tracker_android;
 struct oxr_facial_tracker_htc;
 struct oxr_face_tracker2_fb;
 struct oxr_body_tracker_fb;
···
 	return XRT_CAST_PTR_TO_OXR_HANDLE(XrFaceTracker2FB, face_tracker2_fb);
 }
 #endif
+
+#ifdef OXR_HAVE_ANDROID_face_tracking
+/*!
+ * To go back to a OpenXR object.
+ *
+ * @relates oxr_facial_tracker_htc
+ */
+static inline XrFaceTrackerANDROID
+oxr_face_tracker_android_to_openxr(struct oxr_face_tracker_android *face_tracker_android)
+{
+	return XRT_CAST_PTR_TO_OXR_HANDLE(XrFaceTrackerANDROID, face_tracker_android);
+}
+#endif
+
 /*!
  *
  * @name oxr_input.c
···
 XrResult
 oxr_event_push_XrEventDataUserPresenceChangedEXT(struct oxr_logger *log, struct oxr_session *sess, bool isUserPresent);
 #endif // OXR_HAVE_EXT_user_presence
+
+#ifdef OXR_HAVE_ANDROID_face_tracking
+/*!
+ * Android specific Facial tracker.
+ *
+ * Parent type/handle is @ref oxr_instance
+ *
+ *
+ * @obj{XrFaceTrackerANDROID}
+ * @extends oxr_handle_base
+ */
+struct oxr_face_tracker_android
+{
+	//! Common structure for things referred to by OpenXR handles.
+	struct oxr_handle_base handle;
+
+	//! Owner of this face tracker.
+	struct oxr_session *sess;
+
+	//! xrt_device backing this face tracker
+	struct xrt_device *xdev;
+};
+
+XrResult
+oxr_face_tracker_android_create(struct oxr_logger *log,
+                                struct oxr_session *sess,
+                                const XrFaceTrackerCreateInfoANDROID *createInfo,
+                                XrFaceTrackerANDROID *faceTracker);
+
+XrResult
+oxr_get_face_state_android(struct oxr_logger *log,
+                           struct oxr_face_tracker_android *facial_tracker_android,
+                           const XrFaceStateGetInfoANDROID *getInfo,
+                           XrFaceStateANDROID *faceStateOutput);
+
+XrResult
+oxr_get_face_calibration_state_android(struct oxr_logger *log,
+                                       struct oxr_face_tracker_android *facial_tracker_android,
+                                       XrBool32 *faceIsCalibratedOutput);
+#endif // OXR_HAVE_ANDROID_face_tracking
 
 /*!
  * @}