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can_change_color(3XCURSEX/Open Curses Library Functican_change_color(3XCURSES)

NAME
       can_change_color,  color_content,  COLOR_PAIR,  has_colors, init_color,
       init_pair, pair_content, PAIR_NUMBER, start_color, COLOR_PAIRS,	COLORS
       - manipulate color information

SYNOPSIS
       cc [ flag... ] file... -I /usr/xpg4/include  -L	/usr/xpg4/lib \
	-R  /usr/xpg4/lib  -lcurses  [ library... ]

       c89 [ flag... ] file... -lcurses [ library... ]

       #include <curses.h>

       bool can_change_color(void);

       int color_content(short color, short *red, short *green, short *blue);

       int COLOR_PAIR(int n);

       bool has_colors(void);

       int init_color(short color, short red, short green, short blue);

       int init_pair(short pair, short f, short b);

       int pair_content(short pair, short *f, short *b);

       int PAIR_NUMBER(int value);

       int start_color(voidextern int COLOR_PAIRS;

       extern int COLORS;

DESCRIPTION
       These functions manipulate color on terminals that support color.

    Querying Capabilities
       The  has_colors()  function  indicates  whether the terminal is a color
       terminal. The can_change_color() function indicates whether the	termi‐
       nal is a color terminal on which colors can be redefined.

   Initialization
       The  start_color()  function must be called to enable use of colors and
       before any color manipulation function is called. The function initial‐
       izes  eight  basic  colors  (black,  red, green, yellow, blue, magenta,
       cyan, and white) that can be specified by the  color  macros  (such  as
       COLOR_BLACK)  defined  in  <curses.h>.  The initial appearance of these
       colors is unspecified.

       The function also initializes two global external variables:

	   o	  COLORS defines the number of colors that the	terminal  sup‐
		  ports.  See  Color Identification below. If COLORS is 0, the
		  terminal  does  not  support	redefinition  of  colors   and
		  can_change_color() will return FALSE.

	   o	  COLOR_PAIRS  defines	the maximum number of color-pairs that
		  the terminal supports. See User-defined Color Pairs below.

       The start_color() function also restores the colors on the terminal  to
       terminal-specific  initial  values.  The	 initial  background  color is
       assumed to be black for all terminals.

   Color Identification
       The init_color() function redefines color number	 color,	 on  terminals
       that  support  the  redefinition of colors, to have the red, green, and
       blue intensity components specified by red, green,  and	blue,  respec‐
       tively. Calling init_color() also changes all occurrences of the speci‐
       fied color on the screen to the new definition.

       The color_content() function identifies	the  intensity	components  of
       color number color. It stores the red, green, and blue intensity compo‐
       nents of this color in the addresses pointed  to	 by  red,  green,  and
       blue, respectively.

       For  both  functions, the color argument must be in the range from 0 to
       and including COLORS−1. Valid intensity value range from 0  (no	inten‐
       sity  component)	 up  to	 and including 1000 (maximum intensity in that
       component).

   User-defined Color Pairs
       Calling init_pair() defines or redefines color-pair number pair to have
       foreground  color f and background color b. Calling init_pair() changes
       any characters that were displayed in the color pair's  old  definition
       to the new definition and refreshes the screen.

       After  defining	the  color  pair,  the macro COLOR_PAIR(n) returns the
       value of color pair n. This value is the color attribute as it would be
       extracted  from	a  chtype.  Controversy, the macro COLOR_NUMBER(value)
       returns the color pair  number  associated  with	 the  color  attribute
       value.

       The  pair_content() retrieves the component colors of a color-pair num‐
       ber pair. It stores the foreground and background color numbers in  the
       variables pointed to by f and b, respectively.

       With  init_pair()  and  pair_content(),	the value of pair must be in a
       range from 0 to and including COLOR_PAIRS−1. Valid values for f	and  b
       are the range from 0 to and including COLORS−1.

PARAMETERS
       color	Is the number of the color for which to provide information (0
		to  COLORS−1).

       red	Is a pointer to the RGB value for the amount of red in color.

       green	Is a pointer to the RGB value  for  the	 amount	 of  green  in
		color.

       blue	Is a pointer to the RGB value for the amount of blue in color.

       n	Is the number of a color pair.

       pair	Is  the number of the color pair for which to provide informa‐
		tion (1 to  COLOR_PAIRS−1).

       f	Is a pointer to the number of the foreground color (0 to  COL‐
		ORS−1) in pair.

       b	Is  a pointer to the number of the background color (0 to COL‐
		ORS−1) in  pair.

       value	Is a color attribute value.

RETURN VALUES
       The has_colors() function returns TRUE if the terminal  can  manipulate
       colors. Otherwise, it returns FALSE.

       The  can_change_color() function returns TRUE if the terminal  supports
       colors and is able to change their definitions. Otherwise,  it  returns
       FALSE.

       Upon  successful	 completion, the other functions return OK. Otherwise,
       they return ERR.

ERRORS
       No errors are defined.

USAGE
       To use these functions, start_color() must  be  called,	usually	 right
       after initscr(3XCURSES).

       The  can_change_color()	and  has_colors() functions facilitate writing
       terminal-independent applications. For example, a  programmer  can  use
       them to decide whether to use color or some other video attribute.

       On  color terminals, a typical value of COLORS is 8 and the macros such
       as COLOR_BLACK return a value within the range from 0 to and  including
       7. However, applications cannot rely on this to be true.

ATTRIBUTES
       See attributes(5) for descriptions of the following attributes:

       ┌─────────────────────────────┬─────────────────────────────┐
       │      ATTRIBUTE TYPE	     │	    ATTRIBUTE VALUE	   │
       ├─────────────────────────────┼─────────────────────────────┤
       │Interface Stability	     │Committed			   │
       ├─────────────────────────────┼─────────────────────────────┤
       │MT-Level		     │Unsafe			   │
       ├─────────────────────────────┼─────────────────────────────┤
       │Standard		     │See standards(5).		   │
       └─────────────────────────────┴─────────────────────────────┘

SEE ALSO
       attroff(3XCURSES),	 delscreen(3XCURSES),	    initscr(3XCURSES),
       libcurses(3XCURSES), attributes(5), standards(5)

SunOS 5.11			  5 Jun 2002	    can_change_color(3XCURSES)
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