XGetXCBConnection - get the XCB connection for an Xlib Display
   #include <X11/Xlib-xcb.h>
xcb_connection_t *XGetXCBConnection(Display *dpy);
  - dpy
- Specifies the connection to the X server.
The XGetXCBConnection function returns the XCB connection associated with
  an Xlib Display. Clients can use this XCB connection with functions from the
  XCB library, just as they would with an XCB connection created with XCB.
  Callers of this function must link to libX11-xcb and a version of Xlib built
  with XCB support.
XOpenDisplay(3), XSetEventQueueOwner(3),
Xlib - C Language X Interface