default_colors 3x 2024-04-13 ncurses 6.5 Library calls

default_colors(3x)               Library calls              default_colors(3x)


       use_default_colors,  assume_default_colors  -  use  terminal's  default
       colors in curses


       #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 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.


       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.


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


       ded(1), curs_color(3x)

ncurses 6.5                       2024-04-13                default_colors(3x)