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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 dis-played). displayed).
       played).  A  programmer  initializes  a  color-pair  with  the  routine
       init_pair.   After  it has been initialized, COLOR_PAIR(n), a macro de-fined defined
       fined in <curses.h>, can be used as a new video attribute.  If a termi-nal terminal
       nal is capable of redefining colors, the programmer can use the routine
       init_color to change the definition of a color.  The routines  has_col-ors has_colors
       ors 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 manipu-lation manipulation
       lation 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 COL-OR_PAIRS-1. COLOR_PAIRS-1.
            OR_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 ac-tually actually
            tually whatever the terminal implements before color  is  initial-ized. initialized.
            ized.  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  defini-tion. definition.
       tion.   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 re-turns returns
       turns 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 facil-itates facilitates
       itates writing terminal-independent programs.  The  color_content  rou-tine routine
       tine  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  col-or. color.
       or.  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 com-ponent). component).
       ponent).  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  com-pletion. completion.
       pletion.

       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 fea-ture, feature,
                   ture, 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  COL-OR_PAIRS COLOR_PAIRS
       OR_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 opera-tion operation
       tion 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 VGAcompatible
       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 back-ground background
       ground 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 pa-rameters parameters
       rameters when null.

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



                                                                curs_color(3X)