procedure eve_only_window                   
!
! When there is more than one window on the screen, this procedure will
! use ber$main_window to overlay lines 1-22 with a new window mapped to
! the current buffer.  The procedure eve_noonly.tpu will unmap this
! window, restoring the original multi-window screen.
! EVE_SPLIT_WINDOW will refuse to split the window created by this procedure,
! but will invoke EVE_NOONLY instead.
!
if eve$x_number_of_windows = 1 then
  message("Only one window on screen");
  return;
endif;       

if ber$main_window  = '' then ! Create the window
 ber$main_window := create_window(1,22,ON);
endif;

if current_window = ber$main_window then
  message("Already using only window; use NOONLY to remove it");
  return;
endif;

 ber$old_window := current_window;
 map(ber$main_window,current_buffer);
 eve$set_status_line(ber$main_window);
 update(ber$main_window);

endprocedure;