# default_colors 3x

    default_colors(3x)                                          default_colors(3x)

## NAME

           use_default_colors, assume_default_colors - use terminal's default col-
           ors

## 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 functions  are  exten-
           sions 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  fore-
           ground  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 col-
           ors  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 success-
           ful 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

           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

           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 necessar-
           ily 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 prob-
           lem: 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  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

           curs_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)