4.2 Interactive sessions and guile-ncurses-shell

If you would like to try out these functions interactively by typing them into the scheme shell, instead of typing them and running them as scripts, the program guile-ncurses-shell can be used. The problem with interactive Guile sessions using curses is that you are typing into the same screen that curses is trying to manage, which leads to confusing results. The program guile-ncurses-shell, which must be run on X, starts an interactive guile session and creates and xterm that will be managed by curses. The results of the curses function calls will appear in the xterm, instead of in the screen where the interactive guile session occurs.

Here we’ll try four functions: initscr sets up the screen, addstr writes a string to the screen, refresh redraws the screen, and endwin frees the screen.

Upon initialization guile-ncurses-shell automatically calls these functions.

(use-modules (ncurses curses))
(define %guile-ncurses-shell-stdscr (initscr))

It loads the ncurses module; initializes the screen; and saves the returned ncurses screen structure in the variable %guile-ncurses-shell-stdscr. Thus, you do not need to call (initscr) in your interactive session when you use guile-ncurses-shell.

The first thing you want to do is to redefine the name of the standard window to something more reasonable.

(define win %guile-ncurses-shell-stdscr)

To check and see if the guile-ncurses-shell is working, you can write a string onto the created xterm.

(addstr win "hello, world!")
(refresh win)

The guile-ncurses-shell communicates with the xterm using a read port and a write port. If, for some obscure reason, you need to access the read or write port directly, they are stored in the variables %guile-ncurses-shell-read-port and %guile-ncurses-shell-write-port.

When exiting an interactive session, by C-D for example, guile-ncurses-shell automatically calls (endwin), so you do not need to call that yourself.