default_colors(3x) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | NOTES | PORTABILITY | SEE ALSO | AUTHOR | COLOPHON

default_colors(3X)                                    default_colors(3X)

NAME         top

       use_default_colors, assume_default_colors - use terminal's
       default colors

SYNOPSIS         top

       #include <curses.h>

       int use_default_colors(void);
       int assume_default_colors(int fg, int bg);

DESCRIPTION         top

       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.

RETURN VALUE         top

       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.

NOTES         top

       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.

PORTABILITY         top

       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.

SEE ALSO         top

       ded(1), curs_color(3X).

AUTHOR         top

       Thomas Dickey (from an analysis of the requirements for color
       xterm for XFree86 3.1.2C, February 1996).

COLOPHON         top

       This page is part of the ncurses (new curses) project.
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                                                      default_colors(3X)