Provided by: ncurses-doc_6.2-0ubuntu2_all bug


       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:

       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

       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.


       color(3NCURSES), ded(1).


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