can_change_color(3XCURSES)				  X/Open Curses Library Functions				can_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 ini-
       tializes 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 supports. 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, respectively. 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 number 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 information (1 to	COLOR_PAIRS-1).

       f	Is a pointer to the number of the foreground color (0 to COLORS-1) in pair.

       b	Is a pointer to the number of the background color (0 to COLORS-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 includ-
       ing 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	     |Standard			   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |Unsafe			   |
       +-----------------------------+-----------------------------+

SEE ALSO

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

SunOS 5.11							    5 Jun 2002						can_change_color(3XCURSES)