Function truncate_mode 

pub fn truncate_mode(
    s: &str,
    length: usize,
    tail: &str,
    mode: WidthMode,
    eaw_wide: bool,
) -> String

Width-mode variant of truncate.

mode and eaw_wide control grapheme width calculation. If the input already fits, it is returned unchanged; otherwise the visible prefix is shortened enough to fit tail, and trailing escape sequences are still copied.