public void RegisterCallback(AnalogCallback callback)
 {
     Start(); // make sure the interface is initialized.
     if (null == analogCallbacks)
     {
         analogCallbacks   = callback;
         rawAnalogCallback = new OSVR.ClientKit.AnalogCallback(AnalogCb);
         iface.registerCallback(rawAnalogCallback, System.IntPtr.Zero);
     }
     else
     {
         analogCallbacks += callback;
     }
 }
 public void RegisterCallback(AnalogCallback callback)
 {
     Start(); // make sure the interface is initialized.
     if (null == analogCallbacks)
     {
         analogCallbacks = callback;
         rawAnalogCallback = new OSVR.ClientKit.AnalogCallback(AnalogCb);
         iface.registerCallback(rawAnalogCallback, System.IntPtr.Zero);
     }
     else
     {
         analogCallbacks += callback;
     }
 }