new file mode 100644
--- /dev/null
+++ b/scripts/plot/private/__add_datasource__.m
@@ -0,0 +1,55 @@
+## Copyright (C) 2008, 2009 David Bateman
+##
+## 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} {@var{newargs} =} __add_datasource__ (@var{fcn}, @var{h}, @var{data}, @var{varargin})
+## Undocumented internal function.
+## @end deftypefn
+
+function newargs = __add_datasource__ (fcn, h, data, varargin)
+
+  if (nargin < 3)
+    error ("internal error");
+  endif
+
+  if (ischar (data))
+    data = {data};
+  endif
+
+  for i = 1 : numel (data)
+    addproperty (strcat (data{i}, "datasource"), h, "string", "");
+  endfor
+
+  i = 0;
+  newargs = {};
+  while (i < numel (varargin))
+    arg = varargin{++i};
+    if (i != numel(varargin) && ischar (arg)
+	&& length (arg) > 9 && strcmpi (arg(end-9:end), "datasource"))
+      arg = tolower (arg);
+      val = varargin{++i};
+      if (ischar (val))
+	set (h, arg, val);
+      else
+	error ("%s: expecting data source to be a string", fcn);
+      endif
+    else
+      newargs{end + 1} = arg;
+    endif
+  endwhile
+endfunction