XGrabServer, XUngrabServer - grab the server
int XGrabServer(Display *display);
int XUngrabServer(Display *display);
  - display
- Specifies the connection to the X server.
The XGrabServer function disables processing of requests and close downs
  on all other connections than the one this request arrived on. You should not
  grab the X server any more than is absolutely necessary.The XUngrabServer function restarts processing of requests
    and close downs on other connections. You should avoid grabbing the X server
    as much as possible.
XGrabButton(3), XGrabKey(3), XGrabKeyboard(3), XGrabPointer(3)
Xlib - C Language X Interface