void gdk_window_set_override_redirect ( GdkWindow* window, gboolean override_redirect )
An override redirect window is not under the control of the window manager. This means it won’t have a titlebar, won’t be minimizable, etc. - it will be entirely under the control of the application. The window manager can’t see the override redirect window at all.
Override redirect should only be used for short-lived temporary
windows, such as popup menus.
GtkMenu uses an override redirect
window in its implementation, for example.