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+## Copyright (C) 2005, 2006, 2007 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} {} drawnow ()
+## Update and display the current graphics.
+##
+## Octave automatically calls drawnow just before printing a prompt,
+## when @code{sleep} or @code{pause} is called, or while waiting for
+## command-line input.
+## @end deftypefn
+
+## Author: jwe
+
+function gnuplot_drawnow (h, term, file, mono, debug_file)
+
+  if (nargin < 4)
+    mono = false;
+  endif
+
+  if (nargin >= 3 && nargin <= 5)
+    f = __get__ (h);
+    plot_stream = [];
+    fid = [];
+    unwind_protect
+      [plot_stream, enhanced] = open_gnuplot_stream ([], term, file);
+      __go_draw_figure__ (f, plot_stream, enhanced, mono);
+      if (nargin == 5)
+        fid = fopen (debug_file, "wb");
+        enhanced = init_plot_stream (fid, [], term, file);
+        __go_draw_figure__ (f, fid, enhanced, mono);
+      endif
+    unwind_protect_cleanup
+      if (! isempty (plot_stream))
+        pclose (plot_stream);
+      endif
+      if (! isempty (fid))
+        fclose (fid);
+      endif
+    end_unwind_protect
+  elseif (nargin == 1)
+    f = __get__ (h);
+    plot_stream = f.__plot_stream__;
+    if (isempty (plot_stream))
+      [plot_stream, enhanced] = open_gnuplot_stream (h);
+      set (h, "__enhanced__", enhanced);
+    else
+      enhanced = f.__enhanced__;
+    endif
+    __go_draw_figure__ (f, plot_stream, enhanced, mono);
+  else
+    print_usage ();
+  endif
+
+endfunction
+
+function [plot_stream, enhanced] = open_gnuplot_stream (h, varargin)
+
+  cmd = gnuplot_binary ();
+
+  plot_stream = popen (cmd, "w");
+
+  if (plot_stream < 0)
+    error ("drawnow: failed to open connection to gnuplot");
+  else
+
+    if (! isempty (h))
+      set (h, "__plot_stream__", plot_stream);
+    endif
+
+    enhanced = init_plot_stream (plot_stream, h, varargin{:});
+
+  endif
+
+endfunction
+
+function enhanced = init_plot_stream (plot_stream, h, term, file)
+
+  if (nargin == 4)
+    enhanced = enhanced_term (term);
+    if (! isempty (term))
+      if (enhanced)
+	fprintf (plot_stream, "set terminal %s enhanced;\n", term);
+      else
+	fprintf (plot_stream, "set terminal %s;\n", term);
+      endif
+    endif
+    if (! isempty (file))
+      fprintf (plot_stream, "set output \"%s\";\n", file);
+    endif
+  else
+
+    ## Guess the terminal type.
+    term = getenv ("GNUTERM");
+    if (isempty (term))
+      if (! isempty (getenv ("DISPLAY")))
+	term = "x11";
+      elseif (! isunix ())
+	term = "windows";
+      else
+	## This should really be checking for os x before setting
+	## the terminal type to aqua, but nobody will notice because
+	## every other unix will be using x11 and windows will be
+	## using windows.  Those diehards still running octave from
+	## a linux console know how to set the GNUTERM variable.
+	term = "aqua";
+      endif
+    endif
+
+    enhanced = enhanced_term (term);
+    if (enhanced)
+      enh_str = "enhanced";
+    else
+      enh_str = "";
+    endif
+
+    ## If no 'h' (why not?) then open the terminal as Figure 0.
+    if (isempty (h))
+      h = 0;
+    endif
+
+    if (strcmp (term, "x11"))
+      fprintf (plot_stream, "set terminal x11 %s title \"Figure %d\"\n",
+	       enh_str, h);
+    elseif (strcmp (term, "aqua"))
+      ## Aqua doesn't understand the 'title' option despite what the
+      ## gnuplot 4.2 documentation says.
+      fprintf (plot_stream, "set terminal aqua %d %s\n", h, enh_str);
+    elseif (strcmp (term, "wxt"))
+      fprintf (plot_stream, "set terminal wxt %s title \"Figure %d\"\n", 
+	       enh_str, h);
+
+    elseif (enhanced)
+      fprintf (plot_stream, "set terminal %s %s\n", term, enh_str);
+    endif
+    ## gnuplot will pick up the GNUTERM environment variable itself
+    ## so no need to set the terminal type if not also setting the
+    ## figure title or enhanced mode.
+
+  endif
+
+endfunction
+
+function have_enhanced = enhanced_term (term)
+  persistent enhanced_terminals;
+
+  if (isempty (enhanced_terminals))
+    ## Don't include pstex, pslatex or epslatex here as the TeX commands
+    ## should not be interpreted in that case.
+    if (compare_versions (__gnuplot_version__ (), "4.0", ">"))
+      enhanced_terminals = {"aqua", "dumb", "png", "jpeg", "gif", "pm", ...
+	                    "windows", "wxt", "svg", "postscript", "x11", "pdf"};
+    else 
+      enhanced_terminals = {"x11", "postscript"};
+    endif
+  endif
+
+  term = tolower (term);
+
+  have_enhanced = false;
+  for i = 1 : length (enhanced_terminals)
+    t = enhanced_terminals{i};
+    if (strncmp (term, t, min (length (term), length (t))))
+      have_enhanced = true;
+      break;
+    endif
+  endfor
+endfunction