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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 - 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).	  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  rou‐
       tines  has_colors  and can_change_color return TRUE or FALSE, depending
       on whether the terminal has color capabilities and whether the program‐
       mer can change the colors.  The routine color_content allows a program‐
       mer 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 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 fore‐
       ground 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 occur‐
       rences 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 rou‐
       tine 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-indepen‐
       dent 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  com‐
       ponents	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 com‐
       pletion.

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 com‐
       bined 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 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)

								curs_color(3X)
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