curs_color(S)

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

Syntax

cc ... -lcurses

# 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(S) provides routines that manipulate color on color alphanumeric terminals. To use these routines a program must call start_color(S), usually right after initscr(S).

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(S). After it has been initialized, COLOR_PAIRn), 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(S) to change the definition of a color.

The routines has_colors(S) and can_change_color(S) return TRUE or FALSE, depending on whether the terminal has color capabilities and whether the programmer can change the colors. The routine color_content(S) allows a programmer to identify the amounts of red, green, and blue components in an initialized color. The routine pair_content(S) tells a programmer 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 the smaller of 63 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 are 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 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, 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 short s 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 the colors a given color-pair. It requires three arguments: the color-pair number and two addresses of short s for storing the foreground and the background color numbers. The value of the first argument must be between 1 and 63 or COLOR_PAIRS-1, whichever is less. The values 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 on failure and OK on successful completion.

Warning

The header file curses.h automatically includes the header files stdio.h and unctrl.h.

Files

/usr/lib/libcurses.a: the library

Standards conformance

start_color(S), init_pair(S), init_color(S), has_colors(S), can_change_color(S), color_content(S), and pair_content(S) are not part of any currently supported standard; they were developed by UNIX System Laboratories, Inc. and are maintained by The SCO Group.