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 displayed).  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  pro-
       grammer	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  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 COLOR_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 actu-
	    ally whatever the terminal implements before color is initialized.	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 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 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; oth-
       er, 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  re-
       quires  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  ad-
       dresses 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 col-
       or-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  back-
       ground 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.

       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  sec-
       ondary functions such as init_pair if start_color was not called.

	      init_color
		   returns  an	error  if  the terminal does not support this feature, 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
       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 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  exten-
       sion.

       This  implementation checks the pointers, e.g., for the values returned by color_content and pair_content, and will treat those as optional
       parameters when null.

SEE ALSO

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

																    curs_color(3X)