.\"***************************************************************************
-.\" Copyright (c) 1998,2000 Free Software Foundation, Inc. *
+.\" Copyright (c) 1998-2005,2009 Free Software Foundation, Inc. *
.\" *
.\" Permission is hereby granted, free of charge, to any person obtaining a *
.\" copy of this software and associated documentation files (the *
.\" authorization. *
.\"***************************************************************************
.\"
-.\" $Id: curs_color.3x,v 1.15 2000/07/08 11:59:51 tom Exp $
+.\" $Id: curs_color.3x,v 1.29 2009/01/24 23:10:02 tom Exp $
.TH curs_color 3X ""
+.na
+.hy 0
.SH NAME
\fBstart_color\fR,
\fBinit_pair\fR,
\fBcolor_content\fR,
\fBpair_content\fR,
\fBCOLOR_PAIR\fR - \fBcurses\fR color manipulation routines
+.ad
+.hy
.SH SYNOPSIS
\fB# include <curses.h>\fR
.br
programmer initializes a color-pair with the routine \fBinit_pair\fR. After it
has been initialized, \fBCOLOR_PAIR\fR(\fIn\fR), a macro defined in
\fB<curses.h>\fR, can be used as a new video attribute.
-
+.PP
If a terminal is capable of redefining colors, the programmer can use the
routine \fBinit_color\fR to change the definition of a color. The routines
\fBhas_colors\fR and \fBcan_change_color\fR return \fBTRUE\fR or \fBFALSE\fR,
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.
-
+.PP
The \fBinit_pair\fR 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.
.TP 5
-
The value of the first argument
-must be between \fB1\fR and \fBCOLOR_PAIRS-1\fR.
+must be between \fB1\fR and \fBCOLOR_PAIRS-1\fR,
+except that if default colors are used (see \fBuse_default_colors\fP)
+the upper limit is adjusted to allow for extra pairs which use
+a default color in foreground and/or background.
.TP 5
-
The value of the second and
-third arguments must be between 0 and \fBCOLORS\fR (the 0 color pair is wired
-to white on black and cannot be changed).
+third arguments must be between 0 and \fBCOLORS\fR.
+Color pair 0 is assumed to be white on black,
+but is actually whatever the terminal implements before color is initialized.
+It cannot be modified by the application.
.PP
If the color-pair was previously
-initialized, the screen is refreshed and all occurrences of that color-pair is
-changed to the new definition.
-
+initialized, the screen is refreshed and all occurrences of that color-pair
+are changed to the new definition.
+.PP
As an extension, ncurses allows you to set color pair 0 via
the \fBassume_default_colors\fR routine, or to specify the use of
default colors (color number \fB-1\fR) if you first invoke the
\fBuse_default_colors\fR routine.
-
+.PP
The \fBinit_color\fR 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
must be a value between 0 and 1000. When \fBinit_color\fR is used, all
occurrences of that color on the screen immediately change to the new
definition.
-
+.PP
The \fBhas_colors\fR routine requires no arguments. It returns \fBTRUE\fR if
the terminal can manipulate colors; otherwise, it returns \fBFALSE\fR. 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.
-
+.PP
The \fBcan_change_color\fR routine requires no arguments. It returns
\fBTRUE\fR if the terminal supports colors and can change their definitions;
other, it returns \fBFALSE\fR. This routine facilitates writing
terminal-independent programs.
-
+.PP
The \fBcolor_content\fR 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 \fBshort\fRs for storing
\fBCOLORS\fR. 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).
-
+.PP
The \fBpair_content\fR 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 \fBshort\fRs for storing the foreground and the
In \fB<curses.h>\fR the following macros are defined. These are the default
colors. \fBcurses\fR also assumes that \fBCOLOR_BLACK\fR is the default
background color for all terminals.
-
+.PP
.nf
\fBCOLOR_BLACK\fR
\fBCOLOR_RED\fR
.SH RETURN VALUE
The routines \fBcan_change_color()\fR and \fBhas_colors()\fR return \fBTRUE\fR
or \fBFALSE\fR.
-
+.PP
All other routines return the integer \fBERR\fR upon failure and an \fBOK\fR
(SVr4 specifies only "an integer value other than \fBERR\fR") upon successful
completion.
+.PP
+X/Open defines no error conditions.
+This implementation will return \fBERR\fR 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 \fBinit_color\fP 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 secondary functions such as \fBinit_pair\fP
+if \fBstart_color\fP was not called.
+.RS
+.TP 5
+\fBinit_color\fP
+returns an error if the terminal does not support
+this feature, e.g., if the \fIinitialize_color\fP capability is absent
+from the terminal description.
+.TP 5
+\fBstart_color\fP
+returns an error
+If the color table cannot be allocated.
+.RE
.SH NOTES
In the \fIncurses\fR implementation, there is a separate color activation flag,
color palette, color pairs table, and associated COLORS and COLOR_PAIRS counts
for each screen; the \fBstart_color\fR 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.
-
+.PP
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 \fBcurs_bkgd\fR(3X).
-
+.PP
Several caveats apply on 386 and 486 machines with VGA-compatible graphics:
.TP 5
-
.PP
The assumption that \fBCOLOR_BLACK\fR is the default
background color for all terminals can be modified using the
-\fBassume_default_colors\fP extension,
-..
+\fBassume_default_colors\fP extension.
+.PP
+This implementation checks the pointers,
+e.g., for the values returned by
+\fBcolor_content\fP and \fBpair_content\fP,
+and will treat those as optional parameters when null.
.SH SEE ALSO
\fBcurses\fR(3X),
\fBcurs_initscr\fR(3X),
\fBcurs_attr\fR(3X),
-\fBdft_fgbg\fR(3X)
+\fBdefault_colors\fR(3X)
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