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
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.
This page is part of the ncurses (new curses) project. Information
about the project can be found at
⟨https://www.gnu.org/software/ncurses/ncurses.html⟩. If you have a
bug report for this manual page, send it to
firstname.lastname@example.org. This page was obtained from the
project's upstream Git mirror of the CVS repository
⟨git://ncurses.scripts.mit.edu/ncurses.git⟩ on 2017-03-13. If you
discover any rendering problems in this HTML version of the page, or
you believe there is a better or more up-to-date source for the page,
or you have corrections or improvements to the information in this
COLOPHON (which is not part of the original manual page), send a mail