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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | NOTES | PORTABILITY | SEE ALSO | AUTHOR | COLOPHON |
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default_colors(3X) default_colors(3X)
use_default_colors, assume_default_colors - use terminal's default
colors
#include <curses.h>
int use_default_colors(void);
int assume_default_colors(int fg, int bg);
The use_default_colors and 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).
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 function 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 implementations,
color number -1 does not mean anything, just as for ncurses before
a successful call of use_default_colors 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_colors ncurses will paint a
white foreground (text) with black background for color pair 0.
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 not found, this causes an error as well.
Associated with this extension, the init_pair function accepts
negative arguments to specify default foreground or background
colors.
The use_default_colors function was added to support ded. This is
a full-screen application which uses curses to manage only part of
the screen. The bottom portion of the screen, which is of
adjustable size, is left uncolored to display the results from
shell commands. The top portion of the screen colors filenames
using a scheme like the “color ls” programs. Attempting to manage
the background color of the screen for this application would give
unsatisfactory results for a variety of reasons. This extension
was devised after noting that color xterm (and similar programs)
provides a background color which does not necessarily correspond
to any of the ANSI colors. While a special terminfo entry could
be constructed using nine colors, there was no mechanism provided
within curses to account for the related orig_pair and
back_color_erase capabilities.
The assume_default_colors function was added to solve a different
problem: support for applications which would use environment
variables and other configuration to bypass curses' notion of the
terminal's default colors, setting specific values.
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 conditioned using
NCURSES_VERSION.
ded(1), curs_color(3X).
Thomas Dickey (from an analysis of the requirements for color
xterm for XFree86 3.1.2C, February 1996).
This page is part of the ncurses (new curses) project.
Information about the project can be found at
⟨https://www.gnu.org/software/ncurses/ncurses.html⟩. If you have a
bug report for this manual page, send it to
bug-ncurses-request@gnu.org. This page was obtained from the
project's upstream Git mirror of the CVS repository
⟨https://github.com/mirror/ncurses.git⟩ on 2025-02-02. (At that
time, the date of the most recent commit that was found in the
repository was 2023-03-12.) If you discover any rendering
problems in this HTML version of the page, or you believe there is
a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
man-pages@man7.org
default_colors(3X)
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HTML rendering created 2025-02-02 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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