How to convert X Pixmap into GdkPixmap?

["Peter Zhelezniakov" <peter zhelezniakov gmail com>]

Hello Gtk gurus,

I have an X Display and an X Pixmap associated with that display, both
provided by a third-party library. I'd like to use the Pixmap in a GTK
program by wrapping it into a GdkPixmap structure. More specifically, i want
to use GTK's style functions (like gtk_paint_box) to draw to my Pixmap.

How do i do that? I guess i need to convert X Display into a GdkDisplay
first -- how? gdk_x11_lookup_xdisplay() gives me NULL -- is that correct?

Thanks!
Peter