gdk_window_foreign_new returns NULL

[jacktm <jacktm o2 pl>]

Hello.

I'm working on a big project and I have to use
gdk_window_foreign_new function in it. It doesn't work
and always returns NULL. I've checked if I can use
it in a small application - just to see how does it work,
but unfortunately it doesn't work for me.  I attached
as simple test as I could do (just a tutorial program
+ call to gdk_window_foreign_new). What's wrong?
What should I do to make it work?

Thanks,
    Jack