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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).	 A  programmer	initializes  a	color-pair  with  the  routine
       init_pair.   After  it has been initialized, COLOR_PAIR(n), a macro de‐
       fined 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.  For portable ap‐
       plications:

       -    The value of the  first  argument  must  be	 between  1  and  COL‐
	    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  whatever  the terminal implements before color is initial‐
	    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.

       As an extension, ncurses allows you to set color pair  0	 via  the  as‐
       sume_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 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 ad‐
       dresses 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.

       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, 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	 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 touch‐
       es.  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	 back‐
       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 when null.

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

								curs_color(3X)
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