/// <summary>
        /// Helper to get a string from a tracked device property
        /// </summary>
        public static Result<string, ETrackedPropertyError> TrackedDeviceString(this CVRSystem hmd, int trackedDeviceIndex, ETrackedDeviceProperty prop)
        {
            if (hmd == null) throw new ArgumentNullException(nameof(hmd));
            if (trackedDeviceIndex < 0 || trackedDeviceIndex > OpenVR.k_unMaxTrackedDeviceCount) throw new ArgumentOutOfRangeException(nameof(trackedDeviceIndex));

            ETrackedPropertyError err = ETrackedPropertyError.TrackedProp_Success;
            uint requiredBufferLen = hmd.GetStringTrackedDeviceProperty((uint)trackedDeviceIndex, prop, null, 0, ref err);
            if (err != ETrackedPropertyError.TrackedProp_BufferTooSmall) return Result<string, ETrackedPropertyError>.Err(err);
            if (requiredBufferLen == 0) return "";

            var pchBuffer = new StringBuilder((int)requiredBufferLen);
            requiredBufferLen = hmd.GetStringTrackedDeviceProperty((uint)trackedDeviceIndex, prop, pchBuffer, requiredBufferLen, ref err);
            if (err != ETrackedPropertyError.TrackedProp_Success) return Result<string, ETrackedPropertyError>.Err(err);
            return pchBuffer.ToString();
        }

	public abstract bool GetBoolTrackedDeviceProperty(uint unDeviceIndex,ETrackedDeviceProperty prop,ref ETrackedPropertyError pError);

 private string GetStringProperty(ETrackedDeviceProperty prop)
 {
     ETrackedPropertyError eTrackedPropertyError = ETrackedPropertyError.TrackedProp_Success;
     uint stringTrackedDeviceProperty = this.hmd.GetStringTrackedDeviceProperty(0u, prop, null, 0u, ref eTrackedPropertyError);
     if (stringTrackedDeviceProperty > 1u)
     {
         StringBuilder stringBuilder = new StringBuilder((int)stringTrackedDeviceProperty);
         this.hmd.GetStringTrackedDeviceProperty(0u, prop, stringBuilder, stringTrackedDeviceProperty, ref eTrackedPropertyError);
         return stringBuilder.ToString();
     }
     return (eTrackedPropertyError == ETrackedPropertyError.TrackedProp_Success) ? "<unknown>" : eTrackedPropertyError.ToString();
 }

	public override HmdMatrix34_t GetMatrix34TrackedDeviceProperty(uint unDeviceIndex,ETrackedDeviceProperty prop,ref ETrackedPropertyError pError)
	{
		CheckIfUsable();
		HmdMatrix34_t result = VRNativeEntrypoints.VR_IVRSystem_GetMatrix34TrackedDeviceProperty(m_pVRSystem,unDeviceIndex,prop,ref pError);
		return result;
	}

	internal static extern uint VR_IVRSystem_GetStringTrackedDeviceProperty(IntPtr instancePtr, uint unDeviceIndex, ETrackedDeviceProperty prop, System.Text.StringBuilder pchValue, uint unBufferSize, ref ETrackedPropertyError pError);

	internal static extern ulong VR_IVRSystem_GetUint64TrackedDeviceProperty(IntPtr instancePtr, uint unDeviceIndex, ETrackedDeviceProperty prop, ref ETrackedPropertyError pError);

	public abstract uint GetStringTrackedDeviceProperty(uint unDeviceIndex,ETrackedDeviceProperty prop,System.Text.StringBuilder pchValue,uint unBufferSize,ref ETrackedPropertyError pError);

	public abstract ulong GetUint64TrackedDeviceProperty(uint unDeviceIndex,ETrackedDeviceProperty prop,ref ETrackedPropertyError pError);

	public float GetFloatTrackedDeviceProperty(uint unDeviceIndex,ETrackedDeviceProperty prop,ref ETrackedPropertyError pError)
	{
		float result = FnTable.GetFloatTrackedDeviceProperty(unDeviceIndex,prop,ref pError);
		return result;
	}

	public bool GetBoolTrackedDeviceProperty(uint unDeviceIndex,ETrackedDeviceProperty prop,ref ETrackedPropertyError pError)
	{
		bool result = FnTable.GetBoolTrackedDeviceProperty(unDeviceIndex,prop,ref pError);
		return result;
	}

 public static IEnumerable<string> TrackedDeviceStrings(this CVRSystem hmd, ETrackedDeviceProperty prop)
 {
     if (hmd == null) throw new ArgumentNullException(nameof(hmd));
     return DeviceIndexes.Select(i => hmd.TrackedDeviceString(i, prop)).WhereSuccess();
 }

 //convenience wrap with logging
 private static bool GetFloatProperty(uint device, ETrackedDeviceProperty property, ref float outputValue)
 {
     ETrackedPropertyError pError = 0;
     var val = m_vrSystem.GetFloatTrackedDeviceProperty(device, ETrackedDeviceProperty.Prop_UserIpdMeters_Float, ref pError);
     if (pError == ETrackedPropertyError.TrackedProp_Success)
     {
         outputValue = val;
         return true;
     }
     Log.WriteLine("ERROR  GetFloatTrackedDeviceProperty(" + device + "," + property + "," + outputValue + ") returned  error " + pError);
     return false;
 }

 public Result<string, ETrackedPropertyError> DeviceInfo(int deviceIndex, ETrackedDeviceProperty prop)
     => hmd.TrackedDeviceString(deviceIndex, ETrackedDeviceProperty.Prop_RenderModelName_String);

	public abstract float GetFloatTrackedDeviceProperty(uint unDeviceIndex,ETrackedDeviceProperty prop,ref ETrackedPropertyError pError);

	public int GetInt32TrackedDeviceProperty(uint unDeviceIndex,ETrackedDeviceProperty prop,ref ETrackedPropertyError pError)
	{
		int result = FnTable.GetInt32TrackedDeviceProperty(unDeviceIndex,prop,ref pError);
		return result;
	}

	public abstract int GetInt32TrackedDeviceProperty(uint unDeviceIndex,ETrackedDeviceProperty prop,ref ETrackedPropertyError pError);

	public ulong GetUint64TrackedDeviceProperty(uint unDeviceIndex,ETrackedDeviceProperty prop,ref ETrackedPropertyError pError)
	{
		ulong result = FnTable.GetUint64TrackedDeviceProperty(unDeviceIndex,prop,ref pError);
		return result;
	}

	public HmdMatrix34_t GetMatrix34TrackedDeviceProperty(uint unDeviceIndex,ETrackedDeviceProperty prop,ref ETrackedPropertyError pError)
	{
		HmdMatrix34_t result = FnTable.GetMatrix34TrackedDeviceProperty(unDeviceIndex,prop,ref pError);
		return result;
	}

	internal static extern float VR_IVRSystem_GetFloatTrackedDeviceProperty(IntPtr instancePtr, uint unDeviceIndex, ETrackedDeviceProperty prop, ref ETrackedPropertyError pError);

	public uint GetStringTrackedDeviceProperty(uint unDeviceIndex,ETrackedDeviceProperty prop,System.Text.StringBuilder pchValue,uint unBufferSize,ref ETrackedPropertyError pError)
	{
		uint result = FnTable.GetStringTrackedDeviceProperty(unDeviceIndex,prop,pchValue,unBufferSize,ref pError);
		return result;
	}