########################################################################
##
## Copyright (C) 2017-2021 The Octave Project Developers
##
## See the file COPYRIGHT.md in the top-level directory of this
## distribution or <https://octave.org/copyright/>.
##
## This file is part of Octave.
##
## Octave is free software: you can redistribute it and/or modify it
## under the terms of the GNU General Public License as published by
## the Free Software Foundation, either version 3 of the License, or
## (at your option) any later version.
##
## Octave is distributed in the hope that it will be useful, but
## WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
## GNU General Public License for more details.
##
## You should have received a copy of the GNU General Public License
## along with Octave; see the file COPYING.  If not, see
## <https://www.gnu.org/licenses/>.
##
########################################################################

## -*- texinfo -*-
## @deftypefn {} {@var{h} =} groot ()
## Return a handle to the root graphics object.
##
## The root graphics object is the ultimate parent of all graphics objects.
##
## In addition, the root object contains information about the graphics
## system as a whole such as the @code{ScreenSize}.  Use @w{@code{get (groot)}}
## to find out what information is available.
##
## Defaults for the graphic system as a whole are specified by setting
## properties of the root graphics object that begin with @qcode{"Default"}.
## For example, to set the default font for all text objects to FreeSans use
##
## @example
## set (groot, "DefaultTextFontName", "FreeSans")
## @end example
##
## Default properties can be deleted by using @code{set} with the special
## property value of @qcode{"remove"}.  To undo the default font assignment
## above use
##
## @example
## set (groot, "DefaultTextFontName", "remove")
## @end example
##
## Programming Note: The root graphics object is identified by the special
## handle value of 0.  At some point this unique value may change, but code can
## be made resistant to future changes by using @code{groot} which is
## guaranteed to always return the root graphics object.
## @seealso{gcf, gca, get, set}
## @end deftypefn

function h = groot ()

  if (nargin != 0)
    print_usage ();
  endif

  h = 0;

endfunction


%!assert (groot (), 0)

## Test input validation
%!error groot (1)