curs_color(3X)                                     curs_color(3X)

NAME
       start_color,     init_pair,     init_color,    has_colors,
       can_change_color,  color_content,  pair_content  -  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 charac-
       ters are displayed).  A programmer  initializes  a  color-
       pair  with  the routine init_pair.  After it has been ini-
       tialized, 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 pro-
       grammer can use the routine init_color to change the defi-
       nition   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.  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
       (the 0 color pair is wired to white on black and cannot be
       changed).   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 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  com-
       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 argu-
       ments 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.

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 back-
       ground 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  maxi-
       mums for COLORS and COLOR_PAIRS.

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

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

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