default_colors(3X)default_colors(3X)NAME
use_default_colors, assume_default_colors - use terminal's
default colors
SYNOPSIS
#include <curses.h>
int use_default_colors(void);
int assume_default_colors(int fg, int bg);
DESCRIPTION
The use_default_colors() and assume_default_colors() func-
tions 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).
Applications that paint a colored background over the
whole screen 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 ls 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 setaf terminfo
capability to set the foreground color. Full-screen
applications that use default colors can achieve similar
visual effects.
The first function, 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.
The other, assume_default_colors() is a refinement which
tells which colors to paint for color pair 0. This func-
tion recognizes a special color number -1, which denotes
the default terminal color.
The following are equivalent:
use_default_colors();
assume_default_colors(-1,-1);
These are ncurses extensions. For other curses implemen-
tations, color number -1 does not mean anything, just as
for ncurses before a successful call of use_default_col-
ors() or assume_default_colors().
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 use_default_colors() or assume_default_col-
ors() ncurses will paint a white foreground (text) with
black background for color pair 0.
RETURN VALUE
These functions return the integer ERR upon failure and OK
on success. They will fail if either the terminal does
not support the orig_pair or orig_colors capability. If
the initialize_pair capability is found, this causes an
error as well.
NOTES
Associated with this extension, the init_pair(3X) function
accepts negative arguments to specify default foreground
or background colors.
PORTABILITY
These routines are specific to ncurses. They were not
supported on Version 7, BSD or System V implementations.
It is recommended that any code depending on them be con-
ditioned using NCURSES_VERSION.
SEE ALSOcurs_color(3X), ded(1).
AUTHOR
Thomas Dickey (from an analysis of the requirements for
color xterm for XFree86 3.1.2C, February 1996).
default_colors(3X)
