MirOS Manual: assume_default_colors(3), default_colors(3), use_default_colors(3)


default_colors(3)   UNIX Programmer's Manual    default_colors(3)

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 back-
     ground, 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 implementa-
     tions, 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

MirOS BSD #10-current  Printed 03.04.2017                       1

default_colors(3)   UNIX Programmer's Manual    default_colors(3)

     painted to match the assumption. If your application does
     not use either use_default_colors() or
     assume_default_colors() ncurses will paint a white fore-
     ground (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(3) 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) pro-
     vides a background color which does not necessarily
     correspond to any of the ANSI colors. While a special ter-
     minfo 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

     These routines are specific to ncurses.  They were not sup-
     ported on Version 7, BSD or System V implementations.  It is
     recommended that any code depending on them be conditioned
     using NCURSES_VERSION.

SEE ALSO

     curs_color(3), ded(1).

AUTHOR

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

MirOS BSD #10-current  Printed 03.04.2017                       2

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