double poor_stretched_font_rep::get_left_slope (string s) { return base->get_left_slope (s) / factor; }
double poor_bbb_font_rep::get_left_slope (string s) { return base->get_left_slope (s); }
double poor_distorted_font_rep::get_left_slope (string s) { return base->get_left_slope (s); }
double text_box_rep::left_slope () { return fn->get_left_slope (str); }