'Returns True if all the characters in text have glyphs in this font.'

@same_thread
def supports_text(self, text, has_non_printable_chars=True):

    if (not isinstance(text, unicode)):
        raise TypeError((u'%r    is    not    a    unicode    object' % text))
    if has_non_printable_chars:
        from calibre.utils.fonts.utils import get_printable_characters
        text = get_printable_characters(text)
    chars = tuple(frozenset(map(ord, text)))
    return self.face.supports_text(chars)
