Every menu has an associated pair of curses windows. The menu window displays any title and border associated with the window; the menu subwindow displays the items of the menu that are currently available for selection.
The first four functions get and set those windows. It is not
necessary to set either window; by default, the driver code uses
stdscr for both.
scale-menureturns the minimum size required for
the subwindow of menu.
set-menu-sub! will return one of the
E_POSTED if the menu has already been posted.