Function width 

pub fn width(c: char) -> usize

Available on crate feature width only.

Returns an estimate of the worst-case display width in milli-m’s (thousandths of the the width of an m character).

For example, width('m') returns 1000 and width('\u{FDFD}') returns 10300 (wouldn’t you like to know if your user’s text is 10.3X longer per character than you might have expected?).

Precision is not necessarily 1 milli-m (currently, it is 100 milli-m’s).