'Draw a glyph at
- *ox*, *oy*: position
- *facename*: One of the TeX face names
- *font_class*:
- *sym*: TeX symbol name or single character
- *fontsize*: fontsize in points
- *dpi*: The dpi to draw at.'

def render_glyph(self, ox, oy, facename, font_class, sym, fontsize, dpi):

    info = self._get_info(facename, font_class, sym, fontsize, dpi)
    (realpath, stat_key) = get_realpath_and_stat(info.font.fname)
    used_characters = self.used_characters.setdefault(stat_key, (realpath, set()))
    used_characters[1].add(info.num)
    self.mathtext_backend.render_glyph(ox, oy, info)
