GTK equiv of XOpenDisplay?

[Lowell Smith <merick purdue edu>]

  I'm making a TV program that must make calls to XF86DGAQueryExtension,
and like most Xlib calls, I need to give it a Display variable.  Is there
anyway I can get this variable from the one GTK opens? It seems like a
waste to open a second, or is this indeed how I should do it.

Lowell Smith (begining Xlib/GTK programmer)
merick@purdue.edu