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 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

       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  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

       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.

AUTHORS

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

SEE ALSO

       ded(1), color(3NCURSES)

ncurses 6.4                                        2023-12-16                           default_colors(3NCURSES)