gdk-window-set-override-redirect (window override-redirect)

window -- a toplevel gdk-window object
override-redirect -- true if window should be override redirect

An override redirect window is not under the control of the window manager. This means it will not have a titlebar, will not be minimizable, etc. - it will be entirely under the control of the application. The window manager cannot see the override redirect window at all.

Override redirect should only be used for short-lived temporary windows, such as popup menus. gtk-menu uses an override redirect window in its implementation, for example.