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curs_color(3X)                                                  curs_color(3X)

NAME
       start_color, init_pair, init_color, has_colors, can_change_color,
       color_content, pair_content, COLOR_PAIR - 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 support color attributes on terminals with that capability.  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 blank 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 as a new video attribute.

       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 extract 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.  For portable
       applications:

       -    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.  Color pair 0 is assumed to be white on black, but is
            actually whatever the terminal implements before color is
            initialized.  It cannot be modified by the application.

       If the color-pair was previously initialized, the screen is refreshed
       and all occurrences of that color-pair are changed to the new
       definition.

       As an extension, ncurses allows you to set color pair 0 via the
       assume_default_colors routine, or to specify the use of default colors
       (color number -1) if you first invoke the use_default_colors routine.

       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 programmers 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 programmers 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 VALUE
       The routines can_change_color() and has_colors() return TRUE or FALSE.

       All other routines return the integer ERR upon failure and an OK (SVr4
       specifies only "an integer value other than ERR") upon successful
       completion.

       X/Open defines no error conditions.  This implementation will return
       ERR on attempts to use color values outside the range 0 to COLORS-1
       (except for the default colors extension), or use color pairs outside
       the range 0 to COLOR_PAIR-1.  Color values used in init_color must be
       in the range 0 to 1000.  An error is returned from all functions if the
       terminal has not been initialized.  An error is returned from secondary
       functions such as init_pair if start_color was not called.

              init_color
                   returns an error if the terminal does not support this
                   feature, e.g., if the initialize_color capability is absent
                   from the terminal description.

              start_color
                   returns an error If the color table cannot be allocated.

NOTES
       In the ncurses implementation, there is a separate color activation
       flag, color palette, color pairs table, and associated COLORS and
       COLOR_PAIRS counts for each screen; the start_color function only
       affects the current screen.  The SVr4/XSI interface is not really
       designed with this in mind, and historical implementations may use a
       single shared color palette.

       Note that setting an implicit background color via a color pair affects
       only character cells that a character write operation explicitly
       touches.  To change the background color used when parts of a window
       are blanked by erasing or scrolling operations, see curs_bkgd(3X).

       Several caveats apply on 386 and 486 machines with VGA-compatible
       graphics:

       -    COLOR_YELLOW is actually brown.  To get yellow, use COLOR_YELLOW
            combined with the A_BOLD attribute.

       -    The A_BLINK attribute should in theory cause the background to go
            bright.  This often fails to work, and even some cards for which
            it mostly works (such as the Paradise and compatibles) do the
            wrong thing when you try to set a bright "yellow" background (you
            get a blinking yellow foreground instead).

       -    Color RGB values are not settable.

PORTABILITY
       This implementation satisfies XSI Curses's minimum maximums for COLORS
       and COLOR_PAIRS.

       The init_pair routine accepts negative values of foreground and
       background color to support the use_default_colors extension, but only
       if that routine has been first invoked.

       The assumption that COLOR_BLACK is the default background color for all
       terminals can be modified using the assume_default_colors extension.

       This implementation checks the pointers, e.g., for the values returned
       by color_content and pair_content, and will treat those as optional
       parameters when null.

SEE ALSO
       curses(3X), curs_initscr(3X), curs_attr(3X), default_colors(3X)

                                                                curs_color(3X)

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | NOTES | PORTABILITY | SEE ALSO

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