curs_color(3X) curs_color(3X)
NAME
curs_color: start_color, init_pair, init_color, has_colors,
can_change_color, color_content, pair_content - curses color
manipulation routines
SYNOPSIS
# include <curses.h>
int start_color(void);
int init_pair(short pair, short f, short b);
int init_color(short color, short r, short g, short b);
bool has_colors(void);
bool can_change_color(void);
int color_content(short color, short *r, short *g, short *b);
int pair_content(short pair, short *f, short *b);
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. 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 charac-
ters 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 ter-
minal 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 glo-
bal 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-
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curs_color(3X) curs_color(3X)
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 attri-
bute.
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
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curs_color(3X) curs_color(3X)
the default background color for all terminals.
COLOR_BLACK
COLOR_RED
COLOR_GREEN
COLOR_YELLOW
COLOR_BLUE
COLOR_MAGENTA
COLOR_CYAN
COLOR_WHITE
RETURN VALUE
All routines that return an integer return ERR upon failure
and OK upon successful completion.
NOTES
The header file <curses.h> automatically includes the header
files <stdio.h> and <unctrl.h>.
SEE ALSO
curses(3X), curs_initscr(3X), curs_attr(3X).
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