4.10.1 The basics of color

Life seems dull with no colors. Curses has a nice mechanism to handle colors. Let’s get into the thick of things with a small program.

#!/usr/bin/guile
!#
(use-modules (ncurses curses))

(define stdscr (initscr))
(if (has-colors?)
    (begin
      (start-color!)
      (init-pair! 1 COLOR_GREEN COLOR_YELLOW)
      (attr-on! stdscr (logior A_BOLD (color-pair 1)))
      (addstr stdscr "Voila!! In color...")
      (refresh stdscr)
      (sleep 3)
      (endwin)
      0)
    (begin
      (endwin)
      (display "Your terminal does not support color")
      1))

As you can see, to start using color, you should first call start-color!. After that you can use color capabilities of your terminal. To find out whether a terminal has color capabilities or not, you can use has-colors?, which returns #f if the terminal does not support color.

Curses initializes all the color support for the terminal when start-color! is called. Usually, a color terminal will have at least eight colors available that can be accessed by constants like COLOR_BLACK, etc. Now to actually start using colors, you have to define pairs. Colors are always used in pairs. That means you have to use the function init-pair! to define the foreground and background for the pair number you give. After that, that pair number can be used as a normal attribute with the color-pair procedure. This may seem to be cumbersome at first.

The following colors are defined. You can use these as parameters for the various color functions.

1. COLOR_BLACK
2. COLOR_RED
3. COLOR_GREEN
4. COLOR_YELLOW
5. COLOR_BLUE
6. COLOR_MAGENTA
7. COLOR_CYAN
8. COLOR_WHITE