.\"***************************************************************************
-.\" Copyright (c) 1998-2001,2002 Free Software Foundation, Inc. *
+.\" Copyright (c) 1998-2010,2015 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 1.19 2002/02/16 22:38:32 tom Exp $
+.\" $Id: curs_color.3x,v 1.40 2015/12/05 20:09:42 tom Exp $
.TH curs_color 3X ""
+.ie \n(.g .ds `` \(lq
+.el .ds `` ``
+.ie \n(.g .ds '' \(rq
+.el .ds '' ''
+.de bP
+.IP \(bu 4
+..
+.ds n 5
+.na
+.hy 0
.SH NAME
\fBstart_color\fR,
\fBinit_pair\fR,
\fBcan_change_color\fR,
\fBcolor_content\fR,
\fBpair_content\fR,
-\fBCOLOR_PAIR\fR - \fBcurses\fR color manipulation routines
+\fBCOLOR_PAIR\fR \- \fBcurses\fR color manipulation routines
+.ad
+.hy
.SH SYNOPSIS
\fB# include <curses.h>\fR
-.br
+.sp
\fBint start_color(void);\fR
.br
\fBint init_pair(short pair, short f, short b);\fR
.br
\fBint pair_content(short pair, short *f, short *b);\fR
.br
+\fBint COLOR_PAIR(int n);\fR
+.br
.SH DESCRIPTION
.SS Overview
-\fBcurses\fR support color attributes on terminals with that capability. To
-use these routines \fBstart_color\fR must be called, usually right after
-\fBinitscr\fR. Colors are always used in pairs (referred to as color-pairs).
+\fBcurses\fR supports color attributes on terminals with that capability.
+To use these routines \fBstart_color\fR must be called, usually right after
+\fBinitscr\fR.
+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 displayed). A
-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
+color (for the blank field on which the characters are displayed).
+A 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,
+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,
depending on whether the terminal has color capabilities and whether the
-programmer can change the colors. The routine \fBcolor_content\fR allows a
+programmer can change the colors.
+The routine \fBcolor_content\fR allows a
programmer to extract the amounts of red, green, and blue components in an
-initialized color. The routine \fBpair_content\fR allows a programmer to find
+initialized color.
+The routine \fBpair_content\fR allows a programmer to find
out how a given color-pair is currently defined.
+.SS Color Rendering
+The \fBcurses\fP library combines these inputs to produce the
+actual foreground and background colors shown on the screen:
+.bP
+per-character video attributes (e.g., via \fBwaddch\fP),
+.bP
+the window attribute (e.g., by \fBwattrset\fP), and
+.bP
+the background character (e.g., \fBwbkgdset\fP).
+.PP
+Per-character and window attributes are usually set by a parameter containing
+video attributes including a \fBCOLOR_PAIR\fP value.
+Some functions such as \fBwattr_set\fP use a separate parameter which
+is the color pair number.
+.PP
+The background character is a special case: it includes a character value,
+just as if it were passed to \fBwaddch\fP.
+.PP
+The \fBcurses\fP library does the actual work of combining these color
+pairs in an internal function called from \fBwaddch\fP:
+.bP
+If the parameter passed to \fBwaddch\fP is \fIblank\fP,
+and it uses the special color pair 0,
+.RS
+.bP
+\fBcurses\fP next checks the window attribute.
+.bP
+If the window attribute does not use color pair 0,
+\fBcurses\fP uses the color pair from the window attribute.
+.bP
+Otherwise, \fBcurses\fP uses the background character.
+.RE
+.bP
+If the parameter passed to \fBwaddch\fP is \fInot blank\fP,
+or it does not use the special color pair 0,
+\fBcurses\fP prefers the color pair from the parameter,
+if it is nonzero.
+Otherwise, it tries the window attribute next, and finally the
+background character.
+.PP
+Some \fBcurses\fP functions such as \fBwprintw\fP call \fBwaddch\fP.
+Those do not combine its parameter with a color pair.
+Consequently those calls use only the window attribute or
+the background character.
.SS Routine Descriptions
-The \fBstart_color\fR routine requires no arguments. It must be
-called if the programmer wants to use colors, and before any other
-color manipulation routine is called. It is good practice to call
-this routine right after \fBinitscr\fR. \fBstart_color\fR initializes
-eight basic colors (black, red, green, yellow, blue, magenta, cyan,
-and white), and two global variables, \fBCOLORS\fR and
+The \fBstart_color\fR routine requires no arguments.
+It must be called if the programmer wants to use colors, and before any other
+color manipulation routine is called.
+It is good practice to call this routine right after \fBinitscr\fR.
+\fBstart_color\fR does this:
+.bP
+It initializes two global variables, \fBCOLORS\fR and
\fBCOLOR_PAIRS\fR (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 \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
+and color-pairs the terminal can support).
+.bP
+It initializes the special color pair \fB0\fP to the default foreground
+and background colors.
+No other color pairs are initialized.
+.bP
+It restores the colors on the terminal to the values
+they had when the terminal was just turned on.
+.bP
+If the terminal supports the \fBinitc\fP (\fBinitialize_color\fP) capability,
+\fBstart_color\fP
+initializes its internal table representing the
+red, green and blue components of the color palette.
+.IP
+The components depend on whether the terminal uses
+CGA (aka "ANSI") or
+HLS (i.e., the \fBhls\fP (\fBhue_lightness_saturation\fP) capability is set).
+The table is initialized first for eight basic colors
+(black, red, green, yellow, blue, magenta, cyan, and white),
+and after that (if the terminal supports more than eight colors)
+the components are initialized to \fB1000\fP.
+.IP
+\fBstart_color\fP does not attempt to set the terminal's color palette
+to match its built-in table.
+An application may use \fBinit_color\fP to alter the internal table
+along with the terminal's color.
+.PP
+These limits apply to color values and color pairs.
+Values outside these limits are not legal, and may result in a runtime error:
+.bP
+\fBCOLORS\fP corresponds to the terminal database's \fBmax_colors\fP capability,
+which is typically a signed 16-bit integer (see \fBterminfo\fR(\*n)).
+.bP
+color values are expected to be in the range \fB0\fP to \fBCOLORS\-1\fP,
+inclusive (including \fB0\fP and \fBCOLORS\-1\fP).
+.bP
+a special color value \fB\-1\fP is used in certain extended functions
+to denote the \fIdefault color\fP (see \fBuse_default_colors\fP).
+.bP
+\fBCOLOR_PAIRS\fP corresponds to the terminal database's \fBmax_pairs\fP capability,
+which is typically a signed 16-bit integer (see \fBterminfo\fR(\*n)).
+.bP
+legal color pair values are in the range \fB1\fP to \fBCOLOR_PAIRS\-1\fP,
+inclusive.
+.bP
+color pair \fB0\fP is special; it denotes \*(``no color\*(''.
+.IP
+Color pair \fB0\fP 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
+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.
For portable applications:
-.TP 5
--
-The value of the first argument
-must be between \fB1\fR and \fBCOLOR_PAIRS-1\fR.
-.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).
+.bP
+The first argument must be a legal color pair value.
+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.
+.bP
+The second and third arguments must be legal color values.
.PP
-If the color-pair was previously
-initialized, the screen is refreshed and all occurrences of that color-pair
+If the color-pair was previously initialized,
+the screen is refreshed and all occurrences of that color-pair
are changed to the new definition.
-
-As an extension, ncurses allows you to set color pair 0 via
+.PP
+As an extension, ncurses allows you to set color pair \fB0\fP 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
+default colors (color number \fB\-1\fR) if you first invoke the
\fBuse_default_colors\fR routine.
-
-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
-argument must be between \fB0\fR and \fBCOLORS\fR. (See the section
-\fBColors\fR for the default color index.) Each of the last three arguments
-must be a value between 0 and 1000. When \fBinit_color\fR is used, all
+.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 first argument must be a legal color value;
+default colors are not allowed here.
+(See the section \fBColors\fR for the default color index.)
+Each of the last three arguments
+must be a value in the range \fB0\fP through \fB1000\fP.
+When \fBinit_color\fR is used, all
occurrences of that color on the screen immediately change to the new
definition.
-
-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.
-
-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 \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
+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
the information about the amounts of red, green, and blue components in the
-given color. The value of the first argument must be between 0 and
-\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).
-
+given color.
+The first argument must be a legal color value, i.e.,
+\fB0\fP through \fBCOLORS\-1\fP, inclusive.
+The values that are stored at the addresses pointed to by the
+last three arguments are in the range
+\fB0\fP (no component) through \fB1000\fP (maximum amount of component), inclusive.
+.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
+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
-background color numbers. The value of the first argument must be between 1
-and \fBCOLOR_PAIRS-1\fR. The values that are stored at the addresses pointed
-to by the second and third arguments are between 0 and \fBCOLORS\fR.
+background color numbers.
+The first argument must be a legal color value,
+i.e., in the range \fB1\fP through \fBCOLOR_PAIRS\-1\fR, inclusive.
+The values that are stored at the addresses pointed
+to by the second and third arguments are in the
+range \fB0\fP through \fBCOLORS\fR, inclusive.
.SS Colors
-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
+In \fB<curses.h>\fR the following macros are defined.
+These are the standard colors (ISO-6429).
+\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 \fB0\fP to COLORS\-1
+(except for the default colors extension),
+or use color pairs outside the range \fB0\fP to \fBCOLOR_PAIRS\-1\fP.
+Color values used in \fBinit_color\fP must be in the range \fB0\fP to \fB1000\fP.
+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 3
+.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
+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
+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
--
-COLOR_YELLOW is actually brown. To get yellow, use COLOR_YELLOW combined with
-the \fBA_BOLD\fR attribute.
-.TP 5
--
-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
+.bP
+COLOR_YELLOW is actually brown.
+To get yellow, use COLOR_YELLOW combined with the \fBA_BOLD\fR attribute.
+.bP
+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).
-.TP 5
--
+.bP
Color RGB values are not settable.
.SH PORTABILITY
This implementation satisfies XSI Curses's minimum maximums
.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),
+\fBcurs_variables\fR(3X),
\fBdefault_colors\fR(3X)
-.\"#
-.\"# The following sets edit modes for GNU EMACS
-.\"# Local Variables:
-.\"# mode:nroff
-.\"# fill-column:79
-.\"# End:
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