Tribblix: manual page: curs

CURS_COLOR(3CURSES) Curses Library Functions CURS_COLOR(3CURSES)

NAME

curs_color, start_color, init_pair, init_color, has_colors,
can_change_color, color_content, pair_content - curses color
manipulation functions

SYNOPSIS

cc [ flag ... ] file ... -lcurses [ library ... ]
#include <curses.h>

int start_color(void);

int init_pair(short pair, short fg, short bg);

int init_color(short color, short red, short green, short blue);

bool has_colors(void);

bool can_change_color(void);

int color_content(short color, short *redp, short *greenp, short *bluep);

int pair_content(short pair, short *fgp, short *bgp);

DESCRIPTION

Overview

curses provides routines that manipulate color on color alphanumeric
terminals. To use these routines start_color() must be called,
usually right after initscr(). See curs_initscr(3CURSES). Colors are
always used in pairs (referred to as color-pairs). A color-pair
consists of a foreground color (for characters) and a background
color (for the field on which the characters are displayed). A
programmer initializes a color-pair with the routine init_pair. After
it has been initialized, COLOR_PAIR(n), a macro defined in
<curses.h>, can be used in the same ways other video attributes can
be used. If a terminal is capable of redefining colors, the
programmer can use the routine init_color() to change the definition
of a color. The routines has_colors() and can_change_color() return
TRUE or FALSE, depending on whether the terminal has color
capabilities and whether the programmer can change the colors. The
routine color_content() allows a programmer to identify the amounts
of red, green, and blue components in an initialized color. The
routine pair_content() allows a programmer to find out how a given
color-pair is currently defined.

Routine Descriptions

The start_color() routine requires no arguments. It must be called if
the programmer wants to use colors, and before any other color
manipulation routine is called. It is good practice to call this
routine right after initscr(). start_color() initializes eight basic
colors (black, red, green, yellow, blue, magenta, cyan, and white),
and two global variables, COLORS and COLOR_PAIRS (respectively
defining the maximum number of colors and color-pairs the terminal
can support). It also restores the colors on the terminal to the
values they had when the terminal was just turned on.

The init_pair() routine changes the definition of a color-pair. It
takes three arguments: the number of the color-pair to be changed,
the foreground color number, and the background color number. The
value of the first argument must be between 1 and COLOR_PAIRS-1. The
value of the second and third arguments must be between 0 and COLORS.
If the color-pair was previously initialized, the screen is refreshed
and all occurrences of that color-pair is changed to the new
definition.

The init_color() routine changes the definition of a color. It takes
four arguments: the number of the color to be changed followed by
three RGB values (for the amounts of red, green, and blue
components). The value of the first argument must be between 0 and
COLORS. (See the section Colors for the default color index.) Each of
the last three arguments must be a value between 0 and 1000. When
init_color() is used, all occurrences of that color on the screen
immediately change to the new definition.

The has_colors() routine requires no arguments. It returns TRUE if
the terminal can manipulate colors; otherwise, it returns FALSE. This
routine facilitates writing terminal-independent programs. For
example, a programmer can use it to decide whether to use color or
some other video attribute.

The can_change_color() routine requires no arguments. It returns TRUE
if the terminal supports colors and can change their definitions;
other, it returns FALSE. This routine facilitates writing terminal-
independent programs.

The color_content() routine gives users a way to find the intensity
of the red, green, and blue (RGB) components in a color. It requires
four arguments: the color number, and three addresses of shorts for
storing the information about the amounts of red, green, and blue
components in the given color. The value of the first argument must
be between 0 and COLORS. The values that are stored at the addresses
pointed to by the last three arguments are between 0 (no component)
and 1000 (maximum amount of component).

The pair_content() routine allows users to find out what colors a
given color-pair consists of. It requires three arguments: the color-
pair number, and two addresses of shorts for storing the foreground
and the background color numbers. The value of the first argument
must be between 1 and COLOR_PAIRS-1. The values that are stored at
the addresses pointed to by the second and third arguments are
between 0 and COLORS.

Colors

In <curses.h> the following macros are defined. These are the default
colors. curses also assumes that COLOR_BLACK is the default
background color for all terminals.

COLOR_BLACK
COLOR_RED
COLOR_GREEN
COLOR_YELLOW
COLOR_BLUE
COLOR_MAGENTA
COLOR_CYAN
COLOR_WHITE

RETURN VALUES

All routines that return an integer return ERR upon failure and OK
upon successful completion.

ATTRIBUTES

NOTES

The header <curses.h> automatically includes the headers <stdio.h>
and <unctrl.h>.

December 31, 1996 CURS_COLOR(3CURSES)