Comment 12 for bug 1258170

More complete example with a valid XID (but doesn't make a difference):

xvfb-run python -c 'from gi.repository import Gdk, GdkX11; display = GdkX11.X11Display(); print("display:", display); rw = Gdk.get_default_root_window(); print("rootwin:", rw); xid = rw.get_xid(); print("xid:", xid); fd = GdkX11.X11Window.foreign_new_for_display(display, xid); print("foreign:", fd); origin = fd.get_origin(); print("origin:", origin)'