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default_colors(3X)					    default_colors(3X)

       use_default_colors, assume_default_colors - use terminal's default col-

       #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	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 de-
       signed 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  as-
       sign  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 de-
       fault 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:

       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 as-
       sume_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 necessar-
       ily correspond to any of	the ANSI colors.  While	a special terminfo en-
       try could be constructed	using nine colors, there was no	mechanism pro-
       vided  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.

       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.

       curs_color(3X), ded(1).

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



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