.\"	$NetBSD: curses_color.3,v 1.6 2003/06/26 10:00:24 wiz Exp $
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.Dd January 27, 2003
.Dt CURSES_COLOR 3
.Os
.Sh NAME
.Nm curses_color ,
.Nm has_colors ,
.Nm can_change_color ,
.Nm start_color ,
.Nm init_pair ,
.Nm pair_content ,
.Nm COLOR_PAIR ,
.Nm PAIR_NUMBER ,
.Nm init_color ,
.Nm color_content ,
.Nm no_color_video
.Nd curses color manipulation routines
.Sh LIBRARY
.Lb libcurses
.Sh SYNOPSIS
.In curses.h
.Ft bool
.Fn has_colors void
.Ft bool
.Fn can_change_color void
.Ft int
.Fn start_color void
.Ft int
.Fn init_pair "short pair" "short fore" "short back"
.Ft int
.Fn pair_content "short pair" "short *fore" "short *back"
.Ft int
.Fn COLOR_PAIR "int n"
.Ft int
.Fn PAIR_NUMBER "int val"
.Ft int
.Fn init_color "short color" "short red" "short green" "short blue"
.Ft int
.Fn color_content "short color" "short *red" "short *green" "short *blue"
.Ft attr_t
.Fn no_color_video void
.Pp
.Va extern int COLOR_PAIRS ;
.Pp
.Va extern int COLORS ;
.Sh DESCRIPTION
These functions manipulate color on terminals that support color attributes.
.Pp
The function
.Fn has_colors
indicates whether a terminal is capable of displaying color attributes.
It returns
.Dv TRUE
if the terminal is capable of displaying color attributes and
.Dv FALSE
otherwise.
.Pp
The function
.Fn can_change_color
indicates whether a terminal is capable of redefining colors.
It returns
.Dv TRUE
if colors can be redefined and
.Dv FALSE
if they can not.
.Pp
The function
.Fn start_color
initializes the curses color support on a terminal.
It must be called before any color manipulation functions are called on that
terminal.
The function initializes the eight basic colors (black, red, green, yellow,
blue, magenta, cyan and white) that are specified using the color macros
(such as
.Dv COLOR_BLACK )
defined in
.Em \*[Lt]curses.h\*[Gt] .
.Fn start_color
also initializes the global external variables
.Va COLORS
and
.Va COLOR_PAIRS .
.Va COLORS
defines the number of colors that the terminal supports and
.Va COLOR_PAIRS
defines the number of color-pairs that the terminal supports.
These color-pairs are initialized to white foreground on black background.
.Fn start_color
sets the colors on the terminal to the curses defaults of white
foreground on black background unless the functions
.Fn assume_default_colors
or
.Fn use_default_colors
have been called previously.
.Pp
The function
.Fn init_pair pair fore back
sets foreground color
.Fa fore
and background color
.Fa back
for color-pair number
.Fa pair .
.Pp
The function
.Fn pair_content pair *fore *back
stores the foreground and background color numbers of color-pair
.Fa pair
in the variables
.Fa fore
and
.Fa back ,
respectively.
.Pp
The macro
.Fn COLOR_PAIR n
gives the attribute value of color-pair number
.Fa n .
This is the value that is used to set the attribute of a character to this
color-pair.
For example,
.Dl attrset(COLOR_PAIR(2))
will display characters using color-pair 2.
.Pp
The macro
.Fn PAIR_NUMBER val
gives the color-pair number associated with the attribute value
.Fa val .
.Pp
The function
.Fn init_color color red green blue
sets the red, green and blue intensity components of color
.Fa color
to the values
.Fa red ,
.Fa green
and
.Fa blue ,
respectively.
The minimum intensity value is 0 and the maximum intensity value is 1000.
.Pp
The function
.Fn color_content color *red *green *blue
stores the red, green and blue intensity components of color
.Fa color
in the variables
.Fa red ,
.Fa green ,
and
.Fa blue ,
respectively.
.Pp
The function
.Fn no_color_video
returns those attributes that a terminal is unable to combine with color.
.Sh RETURN VALUES
The functions
.Fn start_color ,
.Fn init_pair ,
.Fn pair_content ,
.Fn init_color
and
.Fn color_content
return OK on success and ERR on failure.
.Sh SEE ALSO
.Xr curses_attributes 3 ,
.Xr curses_background 3 ,
.Xr curses_default_colors 3
.Sh STANDARDS
The
.Nx
Curses library complies with the X/Open Curses specification, part of the
Single Unix Specification.
.Pp
The function
.Fn no_color_video
is an extension to the X/Open Curses specification.
.Sh HISTORY
These functions first appeared in
.Nx 1.5 .
.Sh BUGS
Changing the background or foreground color of color-pair 0 has no effect.