t surface.  In this example, it takes a pointer to a
          FT_Bitmap descriptor and the position of its top-left corner as
          arguments.</p>
        </li>

        <li>
          <p>The value of <tt>slot-&gt;bitmap_top</tt> is positive for an
          <em>upwards</em> vertical distance.  Assuming that the coordinates
          taken by <tt>my_draw_bitmap</tt> use the opposite convention
          (increasing&nbsp;Y corresponds to downwards scanlines), we
          subtract it from <tt>pen_y</tt>