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


See attributes(7) for descriptions of the following attributes:


+---------------+-----------------+
|ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+---------------+-----------------+
|MT-Level | Unsafe |
+---------------+-----------------+

SEE ALSO


curs_attr(3CURSES), curs_initscr(3CURSES), curses(3CURSES), attributes(7)

NOTES


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


December 31, 1996 CURS_COLOR(3CURSES)