MRTK3 should expose a method to query if HoloLens 2 eye tracking is calibrated #11570

// Copyright (c) Microsoft Corporation.
// Licensed under the MIT License.

using System;
using UnityEngine;
using UnityEngine.Events;
#if WINDOWS_UWP
using Windows.Perception;
using Windows.Perception.People;
using Windows.Perception.Spatial;
using Windows.UI.Input.Spatial;
#endif

namespace Microsoft.MixedReality.Toolkit.Examples
{
    /// <summary>
    /// Checks whether the user is calibrated and prompts a notification to encourage the user to calibrate.
    /// </summary>
// TODO make sure this component menu is the same as other "input" things
    [AddComponentMenu("Scripts/MRTK/Input/EyeCalibrationChecker")]
    public class EyeCalibrationChecker : MonoBehaviour
    {
        [Tooltip("For testing purposes, you can manually assign whether the user is eye calibrated or not.")]
        [SerializeField]
        private bool editorTestUserIsCalibrated = true;

        public UnityEvent OnEyeCalibrationDetected;
        public UnityEvent OnNoEyeCalibrationDetected;

        private bool? prevCalibrationStatus = null;

        private void Update()
        {
            bool? calibrationStatus;

            if (Application.isEditor)
            {
                calibrationStatus = editorTestUserIsCalibrated;
            }
            else
            {
                calibrationStatus = CheckCalibrationStatus();
            }

            if (calibrationStatus.HasValue)
            {
                if (prevCalibrationStatus != calibrationStatus)
                {
                    if (!calibrationStatus.Value)
                    {
                        OnNoEyeCalibrationDetected.Invoke();
                    }
                    else
                    {
                        OnEyeCalibrationDetected.Invoke();
                    }
                    prevCalibrationStatus = calibrationStatus;
                }
            }
        }

        private bool CheckCalibrationStatus()
        {
#if WINDOWS_UWP

            if (MixedReality.OpenXR.PerceptionInterop.GetSceneCoordinateSystem(Pose.identity) is SpatialCoordinateSystem worldOrigin)
            {
                SpatialPointerPose pointerPose = SpatialPointerPose.TryGetAtTimestamp(worldOrigin, PerceptionTimestampHelper.FromHistoricalTargetTime(DateTimeOffset.Now));
                if (pointerPose != null)
                {
                    EyesPose eyes = pointerPose.Eyes;
                    if (eyes != null)
                    {
                        return eyes.IsCalibrationValid;
                    }
                }
            }
#endif // WINDOWS_UWP

            return true;
        }
    }
}

### Tasks
- [ ] Add an API to query if eye tracking is calibrated.
- [ ] Add usage of new API to Eye Gaze sample scene
- [ ] Add Unit Tests. Since Unit Tests will run on non-HL2s, tests should only validate behavior for non-HL2 devices.