VarjoNativeInterface.cs

using Microsoft.Extensions.Logging;
using System;
using System.IO;
using System.Reflection;
using System.Runtime.InteropServices;
using System.Text;

namespace VRCFTVarjoModule
{
    class VarjoNativeInterface
    {
        private IntPtr _session;
        protected GazeData gazeData;
        protected EyeMeasurements eyeMeasurements;
        protected ILogger Logger;

        #region Lifetime methods (Init, Update, Teardown)
        public bool Initialize(ILogger loggerInstance, bool use200Hz = false)
        {
            Logger = loggerInstance;

            if (!VarjoAvailable())
            {
                Logger.LogError("Varjo headset isn't detected");
                return false;
            }
            if (LoadLibrary())
            {
                _session = varjo_SessionInit();
                if (_session == IntPtr.Zero)
                {
                    return false;
                }
                if (!varjo_IsGazeAllowed(_session))
                {
                    Logger.LogError("Gaze tracking is not allowed! Please enable it in the Varjo Base!");
                    return false;
                }

                // Prep the Init Parameters first
                GazeParameter frequency = new GazeParameter(VarjoGazeParameterKey.OutputFrequency);
                if (use200Hz)
                {
                    // Don't set a fixed 200Hz tracking rate here, or otherwise the module breaks on 100Hz ET headsets
                    // Instead use maximum supported
                    frequency.value = GazeOutputFrequency.MaximumSupported;
                }
                else
                {
                    frequency.value = GazeOutputFrequency.Frequency100Hz;
                }
                GazeParameter[] parameters = {
                    frequency
                };

                varjo_GazeInitWithParameters(_session, parameters, parameters.Length);

                varjo_SyncProperties(_session);

                return true;
            }
            return false;
        }

        public void Teardown()
        {
            varjo_SessionShutDown(_session);
        }

        /// <summary>
        /// Get's the newest Data from the SDK and stores it internally
        /// </summary>
        /// <returns>true when the data fetching was successful</returns>
        public bool Update()
        {
            if (_session == IntPtr.Zero)
                return false;

            // Get's GazeData and EyeMeasurements from the Varjo SDK
            // Return value states whether or not the request was successful (true = has Data; false = Error occured)
            bool hasData = varjo_GetGazeData(_session, out gazeData, out eyeMeasurements);

            if (!hasData)
                Logger.LogWarning("Error while getting Gaze Data");

            return hasData;
        }
        #endregion

        #region Public Getters
        public GazeData GetGazeData()
        {
            return gazeData;
        }

        public EyeMeasurements GetEyeMeasurements()
        {
            return eyeMeasurements;
        }

        public string GetHMDName()
        {
            int bufferSize = varjo_GetPropertyStringSize(_session, VarjoPropertyKey.HMDProductName);
            StringBuilder buffer = new StringBuilder(bufferSize);
            varjo_GetPropertyString(_session, VarjoPropertyKey.HMDProductName, buffer, bufferSize);

            return buffer.ToString();
        }

        public string GetVBVersion()
        {
            string returnVal = "";
            try
            {
                IntPtr versionPtr = varjo_GetVersionString();
                string version = Marshal.PtrToStringAnsi(versionPtr);
                if (version != null)
                {
                    returnVal = version;
                }
            }
            catch { }
            return returnVal;
        }
        #endregion

        #region Internal helper methods
        private bool LoadLibrary()
        {
            var path = Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location) + "\\TrackingLibs\\VarjoLib.dll";
            if (path == null)
            {
                Logger.LogError(string.Concat("Couldn't extract the library ", path));
                return false;
            }
            if (LoadLibrary(path) == IntPtr.Zero)
            {
                Logger.LogError(string.Concat("Unable to load library ", path));
                return false;
            }
            Logger.LogInformation(string.Concat("Loaded library ", path));
            return true;
        }

        private static bool VarjoAvailable()
        {
            // totally not how the official Varjo library works under the hood
            return File.Exists("\\\\.\\pipe\\Varjo\\InfoService");
        }
        #endregion

        #region DllImports
        [DllImport("kernel32", CharSet = CharSet.Unicode, ExactSpelling = false, SetLastError = true)]
        private static extern IntPtr LoadLibrary(string lpFileName);

        [DllImport("VarjoLib", CharSet = CharSet.Auto)]
        private static extern bool varjo_IsAvailable();

        [DllImport("VarjoLib", CharSet = CharSet.Auto)]
        private static extern IntPtr varjo_SessionInit();

        [DllImport("VarjoLib", CharSet = CharSet.Auto)]
        private static extern void varjo_SessionShutDown(IntPtr session);

        [DllImport("VarjoLib", CharSet = CharSet.Auto)]
        private static extern void varjo_GazeInit(IntPtr session);

        [DllImport("VarjoLib", CharSet = CharSet.Auto)]
        private static extern void varjo_GazeInitWithParameters(IntPtr session, [In, Out] GazeParameter[] parameters, int parameterCount);

        [DllImport("VarjoLib", CharSet = CharSet.Auto)]
        private static extern int varjo_GetError(IntPtr session);

        [DllImport("VarjoLib", CharSet = CharSet.Auto)]
        private static extern string varjo_GetErrorDesc(int errorCode);

        [DllImport("VarjoLib", CharSet = CharSet.Auto)]
        private static extern bool varjo_IsGazeAllowed(IntPtr session);

        [DllImport("VarjoLib", CharSet = CharSet.Auto)]
        private static extern bool varjo_IsGazeCalibrated(IntPtr session);

        [DllImport("VarjoLib", CharSet = CharSet.Auto)]
        private static extern GazeData varjo_GetGaze(IntPtr session);

        [DllImport("VarjoLib", CharSet = CharSet.Auto)]
        private static extern bool varjo_GetGazeData(IntPtr session, out GazeData gaze, out EyeMeasurements eyeMeasurements);

        [DllImport("VarjoLib", CharSet = CharSet.Auto)]
        private static extern void varjo_RequestGazeCalibration(IntPtr session);

        [DllImport("VarjoLib", CharSet = CharSet.Auto)]
        private static extern bool varjo_GetPropertyBool(IntPtr session, VarjoPropertyKey propertyKey);

        [DllImport("VarjoLib", CharSet = CharSet.Auto)]
        private static extern int varjo_GetPropertyInt(IntPtr session, VarjoPropertyKey propertyKey);

        [DllImport("VarjoLib", CharSet = CharSet.Ansi)]
        private static extern void varjo_GetPropertyString(IntPtr session, VarjoPropertyKey propertyKey, StringBuilder buffer, int bufferSize);

        [DllImport("VarjoLib", CharSet = CharSet.Auto)]
        private static extern int varjo_GetPropertyStringSize(IntPtr session, VarjoPropertyKey propertyKey);

        [DllImport("VarjoLib", CharSet = CharSet.Auto)]
        private static extern IntPtr varjo_GetVersionString();

        [DllImport("VarjoLib", CharSet = CharSet.Auto)]
        private static extern void varjo_SyncProperties(IntPtr session);
        #endregion

    }
}