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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
[email protected]. This page was obtained from the
project's upstream Git mirror of the CVS repository
⟨https://github.com/mirror/ncurses.git⟩ on 2024-06-14. (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
[email protected]
default_colors(3X)
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HTML rendering created 2024-06-26 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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