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curs_color(3)
NAME
curs_color, start_color, init_pair, init_color, has_colors,
can_change_color, color_content, pair_content, COLOR_PAIR, COLOR_PAIRS,
COLORS, PAIR_NUMBER - Curses color-manipulation routines and variables
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 );
int COLOR_PAIR(
int n );
int PAIR_NUMBER(
int value );
LIBRARY
Curses Library (libcurses)
STANDARDS
Interfaces documented on this reference page conform to industry standards
as follows:
start_color, init_pair, init_color, has_colors, can_change_color,
color_content, pair_content, COLOR_PAIR, PAIR_NUMBER: XCURSES4.2
Refer to the standards(5) reference page for more information about
industry standards and associated tags.
DESCRIPTION
The Curses library includes routines that manipulate color-on-color
alphanumeric terminals. To use these routines, applications must call
start_color, 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
characters are displayed). An application calls init_pair to initialize a
color-pair. After the color-pair is initialized, applications can call
COLOR_PAIR(n) to use color attributes.
If a terminal is capable of redefining colors, applications 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 application can change
the colors. The routine color_content allows an application to identify the
amounts of red, green, and blue components in an initialized color. The
routine pair_content allows the application 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
application uses colors, and before the application calls any other color
manipulation routine. It is good practice to call this routine right after
initscr. The start_color routine initializes eight basic colors (black,
red, green, yellow, blue, magenta, cyan, and white) and two global
variables (COLORS and COLOR_PAIRS, which respectively define the maximum
number of colors and color-pairs the terminal can support). The start_color
routine also restores the colors on the terminal to the values they had
when the terminal was turned on.
The init_pair routine changes the definition of a color-pair. This routine
takes three arguments that are identification numbers for the following:
· The color-pair to be changed
· The foreground color
· The background color
The value of the first argument must be between 1 and the smaller of either
63 or COLOR_PAIRS-1. The values 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 are changed to
the new definition.
The init_color routine changes the definition of a color. This routine
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,
respectively). The value of the first argument must be between 0 and
COLORS. (See the subsection 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, the routine 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; otherwise, the
routine 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. This routine requires
four arguments: the color number, and three addresses (of short data type)
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 which colors a given
color-pair consists of. This routine requires three arguments: the color-
pair number, and two addresses (of short data type) for storing the numbers
for the foreground and background colors. The value of the first argument
must be between 1 and the smaller of 63 or COLOR_PAIRS-1. The values that
are stored at the addresses pointed to by the second and third arguments
are between 0 and COLORS.
The COLOR_PAIR(n) macro returns the value of the color-pair whose number is
n. This value is the color attribute as it would be extracted from a
chtype variable. Conversely, the macro PAIR_NUMBER(value) returns the
number of the color-pair associated with the color attribute value.
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
NOTES
The header file <curses.h> automatically includes the header file
<stdio.h>.
Note that COLOR_PAIR and PAIR_NUMBER may be macros.
RETURN VALUES
The COLOR_PAIR, PAIR_NUMBER, can_change_color, and has_colors routines
return values as indicated in the DESCRIPTION section.
All other routines return ERR upon failure and OK upon successful
completion.
SEE ALSO
Functions: curses(3), curs_attr_get(3), curs_initscr(3)
Others: standards(5)
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