ncurses 5.1

[ncurses.git] / man / dft_fgbg.3x

diff --git a/man/dft_fgbg.3x b/man/dft_fgbg.3x
index 2461256857b818ed270e39961e743b2c09d68a8b..eedde7c3bbe5028a9c61f4492ae613621d6ae53f 100644 (file)
--- a/man/dft_fgbg.3x
+++ b/man/dft_fgbg.3x
@@ -1,5 +1,5 @@
 .\"***************************************************************************
-.\" Copyright (c) 1998 Free Software Foundation, Inc.                        *
+.\" Copyright (c) 1998,1999,2000 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            *
@@ -26,35 +26,84 @@
 .\" authorization.                                                           *
 .\"***************************************************************************
 .\"
-.\" Author: Thomas E. Dickey <dickey@clark.net> 1997
+.\" Author: Thomas E. Dickey <dickey@clark.net> 1997,1999
 .\"
-.\" $Id: dft_fgbg.3x,v 1.6 1998/03/14 23:43:15 tom Exp $
+.\" $Id: dft_fgbg.3x,v 1.12 2000/07/04 22:31:56 tom Exp $
 .TH use_default_colors 3X ""
 .SH NAME
-\fBdft_fgbg\fR \- use terminal's default colors
+\fBdft_fgbg\fR:
+\fBuse_default_colors\fR,
+\fBassume_default_colors\fR \- use terminal's default colors
 ..
 .SH SYNOPSIS
 \fB#include <curses.h>\fP
 
 \fBint use_default_colors(void);\fP
+.br
+\fBint assume_default_colors(int fg, int bg);\fP
 ..
 .SH DESCRIPTION
-This is an extension to the curses library.
-It is used with terminals that support ISO 6429 color, or equivalent.
+The
+.I use_default_colors()
+and
+.I assume_default_colors()
+functions are extensions to the curses library.
+They are used with terminals that support ISO 6429 color, or equivalent.
 These terminals allow the application to reset color to an unspecified
 default value (e.g., with SGR 39 or SGR 49).
-Because they are designed to support this, their design usually includes
-features to change the default foreground or background colors so that
-they do not match the assumption in XSI curses of white on black.
 .PP
 Applications that paint a colored background over the whole screen
-are not adversely impacted by this type of terminal design.
-However, there are applications that are designed to work with
-the default background.
+do not take advantage of SGR 39 and SGR 49.
+Some applications are designed to work with the default background,
+using colors only for text.
+For example, there are several implementations of the \fBls\fP program
+which use colors to denote different file types or permissions.
+These "color ls" programs do not necessarily modify the background color,
+typically using only the \fIsetaf\fP terminfo capability to set the
+foreground color.
+Full-screen applications that use default colors can achieve similar
+visual effects.
+.PP
+The first function,
+.I use_default_colors()
+tells the curses library to assign terminal default
+foreground/background colors to color number -1. So init_pair(x,COLOR_RED,-1)
+will initialize pair x as red on default background and init_pair(x,-1,COLOR_BLUE) will
+initialize pair x as default foreground on blue.
+.PP
+The other,
+.I assume_default_colors()
+is a refinement which tells which colors to paint for color pair 0.
+This function recognizes a special color number -1,
+which denotes the default terminal color.
+.PP
+The following are equivalent:
+.RS
+.br
+.I use_default_colors();
+.br
+.I assume_default_colors(-1,-1);
+.RE
+.PP
+These are ncurses extensions.
+For other curses implementations, color
+number -1 does not mean anything, just as for ncurses before a
+successful call of \fIuse_default_colors()\fP or \fIassume_default_colors()\fP.
+.PP
+Other curses implementations do not allow an application to modify color pair 0.
+They assume that the background is COLOR_BLACK,
+but do not ensure that the color pair 0 is painted to match the
+assumption.
+If your application does not use either
+.I use_default_colors()
+or
+.I assume_default_colors()
+ncurses will paint a white foreground (text) with black background
+for color pair 0.
 ..
 .SH RETURN VALUE
-The function returns the integer \fBERR\fP upon failure and \fBOK\fP on success.
-It will fail if either the terminal does not support
+These functions return the integer \fBERR\fP upon failure and \fBOK\fP on success.
+They will fail if either the terminal does not support
 the \fIorig_pair\fP or \fIorig_colors\fP capability.
 If the \fIinitialize_pair\fP capability is found, this causes an
 error as well.