## Copyright (C) 1996 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 2, 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.

## Author: jwe
## Modified: jc

function __plt__ (caller, varargin)

  global __pl
  strm = __pl_init;

  switch(caller)
    case ("plot")
      __pl.type(strm) = 0;
    case ("logx")
      __pl.type(strm) = 10;
    case ("logy")
      __pl.type(strm) = 20;
    case ("lgxy")
      __pl.type(strm) = 30;
    otherwise
      __pl.type(strm) = 0;
      error("__plt__: FIXME")
  endswitch

  if (!ishold)
    __pl.items(strm) = 1;
    __pl.lxm(strm) = __pl.lym(strm) = realmax;
    __pl.lxM(strm) = __pl.lyM(strm) = -realmax;
  endif

  if (nargin == 2)

    __plt1__ (varargin{1}, "");

  elseif (nargin > 2)

    hold_state = ishold;

    unwind_protect

      k = 1;
      x = varargin{k++};
      nargin = nargin - 2;
      x_set = 1;
      y_set = 0;

      ## Gather arguments, decode format, and plot lines.

      while (nargin-- > 0)

	fmt = "";
	new = varargin{k++};

	if (ischar (new))
	  if (! x_set)
	    error ("plot: no data to plot");
	  endif
	  fmt = new;
	  if (! y_set)
	    __plt1__ (x, fmt);
	  else
	    __plt2__ (x, y, fmt);
	  endif
	  hold on;
	  x_set = 0;
	  y_set = 0;
	elseif (x_set)
	  if (y_set)
	    __plt2__ (x, y, fmt);
	    hold on;
	    x = new;
	    y_set = 0;
	  else
	    y = new;
	    y_set = 1;
	  endif
	else
	  x = new;
	  x_set = 1;
	endif

      endwhile

      ## Handle last plot.

      if  (x_set)
	if (y_set)
	  __plt2__ (x, y, fmt);
	else
	  __plt1__ (x, fmt);
	endif
      endif

    unwind_protect_cleanup

      if (! hold_state)
        hold off;
      endif

    end_unwind_protect

  else

    msg = sprintf ("%s (x)\n", caller);
    msg = sprintf ("%s       %s (x, y)\n", msg, caller);
    msg = sprintf ("%s       %s (x2, y1, x2, y2)\n", msg, caller);
    msg = sprintf ("%s       %s (x, y, fmt)", msg, caller);
    usage (msg);

  endif

  __pl_plotit;

endfunction
