## Copyright (C) 1996-2012 John W. Eaton
##
## 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
## <http://www.gnu.org/licenses/>.

## -*- texinfo -*-
## @deftypefn {Function File} {} meshc (@var{x}, @var{y}, @var{z})
## Plot a mesh and contour given matrices @var{x}, and @var{y} from
## @code{meshgrid} and a matrix @var{z} corresponding to the @var{x} and
## @var{y} coordinates of the mesh.  If @var{x} and @var{y} are vectors,
## then a typical vertex is (@var{x}(j), @var{y}(i), @var{z}(i,j)).  Thus,
## columns of @var{z} correspond to different @var{x} values and rows of
## @var{z} correspond to different @var{y} values.
## @seealso{meshgrid, mesh, contour}
## @end deftypefn

function h = meshc (varargin)

  if (! all (cellfun ("isreal", varargin)))
    error ("meshc: X, Y, Z, C arguments must be real");
  endif

  [hax, varargin, nargin] = __plt_get_axis_arg__ ("meshc", varargin{:});

  oldfig = ifelse (isempty (hax), [], get (0, "currentfigure"));
  unwind_protect
    hax = newplot (hax);

    htmp = surface (hax, varargin{:});

    ## FIXME - gnuplot does not support a filled surface and a
    ## non-filled contour.  3D filled patches are also not supported.
    ## Thus, the facecolor will be transparent for the gnuplot backend.
    set (htmp, "facecolor", "w");
    set (htmp, "edgecolor", "flat");

    if (! ishold ())
      set (hax, "view", [-37.5, 30],
                "xgrid", "on", "ygrid", "on", "zgrid", "on");
    endif

    drawnow ();

    zmin = get (hax, "zlim")(1);

    [~, htmp2] = __contour__ (hax, zmin, varargin{:});

    htmp = [htmp; htmp2];

  unwind_protect_cleanup
    if (! isempty (oldfig))
      set (0, "currentfigure", oldfig);
    endif
  end_unwind_protect

  if (nargout > 0)
    h = htmp;
  endif

endfunction