ion misses glyphs if glyph names are
      non-standard.  For some fonts, including symbol fonts and (older)
      fonts for Asian scripts, no Unicode emulation is possible at all.</p>

      <p>We will describe later how to look for specific charmaps in a face.
      For now, we will assume that the face contains at least a Unicode
      charmap that was selected during a call to <tt>FT_New_Face</tt>.  To
      convert a Unicode character code to a font glyph index, we use
      <tt>FT_Get_Char_Index</tt>,