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OpenDarwin 7.2.1 - man page for curs_color (opendarwin section 3X)

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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_con-
       tent, 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  charac-
       ters)  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  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  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  capa-
       bilities  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  ini-
       tialized  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 vari-
       ables, 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 back-
       ground 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 (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 are changed to the new definition.

       As an extension, ncurses allows you to set color pair 0 via the assume_default_colors rou-
       tine,  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  COL-
       ORS.   (See the section Colors for the default color index.)  Each of the last three argu-
       ments 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 manipu-
       late colors; otherwise, it returns FALSE.  This routine facilitates writing terminal-inde-
       pendent	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  sup-
       ports  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  argu-
       ments 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.

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  sup-
       port 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,

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

										   curs_color(3X)
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