Return a function taking a text string value and returns |True| if
        that text fits in this fitter when rendered at *point_size*. Used as
        predicate for _break_line()

def _fits_in_width_predicate(self, point_size):
        """
        Return a function taking a text string value and returns |True| if
        that text fits in this fitter when rendered at *point_size*. Used as
        predicate for _break_line()
        """
        def predicate(line):
            """
            Return |True| if *line* fits in this fitter when rendered at
            *point_size*.
            """
            cx = _rendered_size(line.text, point_size, self._font_file)[0]
            return cx <= self._width

        return predicate