t</tt> is the horizontal distance from the
      current pen position to the leftmost border of the glyph bitmap, while
      <tt>bitmap_top</tt> is the vertical distance from the pen position (on
      the baseline) to the topmost border of the glyph bitmap.  <em>It is
      positive to indicate an upwards distance</em>.</p>

      <p>The next section will give more details on the contents of a glyph
      slot and how to access specific glyph information (including
      metrics).</p>

      <h4>
        