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color_content(3)

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
       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.  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
       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 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
       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  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,

SEE ALSO

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

								curs_color(3X)

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