var draw_taxiways = func(group, apt, lod) {     # TODO: the LOD arg isn't stricly needed here, 
                                                # the layer is a conventional canvas group, so it can access its map 
                                                # parent and just read the "range" property to do LOD handling
    group.set("z-index",-100) # HACK: we need to encapsulate this
         .set("stroke", "none");
    # var group = group.createChild("group", "apt-"~apt.id); #FIXME: we don't need to use two nested groups for each taxiway - performance?
    # group = group.createChild("group", "taxiways");
     # print("drawing taxiways for:", apt.id);
    # Taxiways drawn first so the runways and parking positions end up on top.

    # Preallocate all paths at once to gain some speed
    var taxi_paths = group.createChildren("path", size(apt.taxiways));
    var i = 0;
    foreach(var taxi; apt.taxiways)
    {
      var clr = SURFACECOLORS[taxi.surface];
      if (clr == nil) { clr = SURFACECOLORS[0]};

      var txi = Runway.new(taxi);
      var beg1 = txi.pointOffCenterline(0,  0.5 * taxi.width);
      var beg2 = txi.pointOffCenterline(0, -0.5 * taxi.width);
      var end1 = txi.pointOffCenterline(taxi.length,  0.5 * taxi.width);
      var end2 = txi.pointOffCenterline(taxi.length, -0.5 * taxi.width);

      taxi_paths[i].setColorFill(clr.r, clr.g, clr.b)
                   .setDataGeo
                   (
                     [ canvas.Path.VG_MOVE_TO,
                       canvas.Path.VG_LINE_TO,
                       canvas.Path.VG_LINE_TO,
                       canvas.Path.VG_LINE_TO,
                       canvas.Path.VG_CLOSE_PATH ],
                     [ beg1[0], beg1[1],
                       beg2[0], beg2[1],
                       end2[0], end2[1],
                       end1[0], end1[1] ]
                   );
      i += 1;
    }
}