%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% +   line label plotting utility; plot element groups in region;
%                                  colorize, offset
define p_groups ()
  {
  variable xlo, xhi;
  variable ii, nbright=50;

  if (_NARGS == 3) nbright = ();
  xhi = ();
  xlo = ();

  % ISIS pre-defined colors:
  % red=2, green=3, blue=4, purple=6, yellow=7, orange=8, grey=15
  % Define some additional colors (done by experiment) :

  variable light_blue=5, bluegreen=10, periwinkle=11,
           violet=12, magenta=13, slategray=14;

  variable p_elems = [Fe, Ar, O, Si, Mg, Ne, S, Ca, Ni, Al];

  variable p_color =
       [green, light_blue, magenta, orange, purple, red, bluegreen,
           periwinkle, violet, grey];

  variable p_top = [0.8, 0.75, 0.70, 0.65, 0.60, 0.55, 0.50, 0.45, 0.425, 0.40];

  variable p_bot = p_top - 0.1;

  variable grp = brightest(nbright, where( wl(xlo,xhi) ) );
  variable s = line_label_default_style();
  variable egrp;

  for (ii=0; ii<length(p_elems); ii++)
    {
     egrp = pick_el(grp, p_elems[ii]);
     if (egrp[0] != -1)
      {
      s.top_frac = p_top[ii];
      s.bottom_frac = p_bot[ii];
      plot_group([egrp], p_color[ii], s);
      }
    } % endfor p_elems.

   % label any other elements, ions in the region:
   plot_group(brightest(5, where( wl(xlo,xhi)  and not (el_ion(p_elems)))), slategray);
  }
%-