XGetXCBConnection - get the XCB connection for an Xlib Display

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.

       XGetXCBConnection - get the XCB connection for an Xlib Display

XOpenDisplay(3), XSetEventQueueOwner(3),
       Xlib-CLanguageXInterface

X Version 11                                      libX11 1.8.12                             XGetXCBConnection(3)

               #include <X11/Xlib-xcb.h>

       xcb_connection_t *XGetXCBConnection(Display *dpy);