Parent window for other GtkWindow-s

["Atanas Atanasov" <thenasko gmail com>]

I have a set of GtkWindow-s and I would like to enclose them in a
single frame - something very similar to the MDI interface. What
widget can I use for the parent frame / window? It is important that
the child windows will appear inside the parent window and one will
not see them outside its border.

Atanas