Add android.permission.EYE_TRACKING_FINE request

Author: keveleigh

org.mixedrealitytoolkit.input/Interactors/Gaze/GazeInteractor.cs

@@ -5,6 +5,10 @@
 using UnityEngine;
 using UnityEngine.XR.Interaction.Toolkit.Interactors;
 
+#if UNITY_ANDROID && !UNITY_EDITOR
+using UnityEngine.Android;
+#endif
+
 namespace MixedReality.Toolkit.Input
 {
     /// <summary>
@@ -25,7 +29,7 @@ public class GazeInteractor :
         /// interaction mode manager and is assigned an interaction mode. This GameObject represents the group that this interactor belongs to.
         /// </summary>
         /// <remarks>
-        /// This will default to the GameObject that this attached to a parent <see cref="TrackedPoseDriver"/>.
+        /// This will default to the GameObject that this attached to a parent <see cref="UnityEngine.InputSystem.XR.TrackedPoseDriver"/>.
         /// </remarks>
         public GameObject ModeManagedRoot
         {
@@ -41,5 +45,48 @@ public GameObject GetModeManagedController()
             // interaction mode manager is used instead.
             return forceDeprecatedInput ? null : ModeManagedRoot;
         }
+
+#if UNITY_ANDROID && !UNITY_EDITOR
+        protected override void Start()
+        {
+            base.Start();
+
+            if (!Permission.HasUserAuthorizedPermission(EyeTrackingPermission))
+            {
+                PermissionCallbacks callbacks = new();
+                callbacks.PermissionDenied += OnPermissionDenied;
+                callbacks.PermissionGranted += OnPermissionGranted;
+
+                Permission.RequestUserPermission(EyeTrackingPermission, callbacks);
+                Debug.Log($"MRTK is requesting {EyeTrackingPermission}.");
+            }
+            else
+            {
+                Debug.Log($"{EyeTrackingPermission} already granted for MRTK.");
+            }
+        }
+
+        private const string EyeTrackingPermission = "android.permission.EYE_TRACKING_FINE";
+
+        void OnPermissionDenied(string permission)
+        {
+            if (permission == EyeTrackingPermission)
+            {
+                Debug.Log($"{EyeTrackingPermission} denied or not needed on this runtime" +
+#if UNITY_OPENXR_PRESENT
+                    $" ({UnityEngine.XR.OpenXR.OpenXRRuntime.name})" +
+#endif
+                    ". MRTK eye gaze tracking may not work as expected.");
+            }
+        }
+
+        void OnPermissionGranted(string permission)
+        {
+            if (permission == EyeTrackingPermission)
+            {
+                Debug.Log($"{EyeTrackingPermission} newly granted for MRTK.");
+            }
+        }
+#endif // UNITY_ANDROID && !UNITY_EDITOR
     }
 }