
Listing 2

poly(nverts, poly_list)
int nverts, *poly_list[];
{
  int i;
  
  /* 
    see if vertices list is closed
    and close it if not 
  */
  if (poly_list[0] != poly_list[(nverts*2)-2] ||
      poly_list[1] != poly_list[(nverts*2)-1])
    {
      poly_list[(nverts*2)+0] = poly_list[0];
      poly_list[(nverts*2)+1] = poly_list[1];
      nverts++;
    }
  
  /* 
    invert the Y axis of each vertice in list 
  */
  for (i=0; i < nverts; i++)
    poly_list[(i * 2)+1] = ydots-poly_list[(i * 2)+1];
  
  /* 
    then draw it 
  */
  if (filling)
    fill_polygon_a(nverts,poly_list);
  else
    draw_polyline(nverts,poly_list);
}
