Function replace_range 

pub fn replace_range(
    value: &str,
    state: &TextEditState,
    start: usize,
    end: usize,
    text: &str,
    now: f32,
) -> (String, TextEditState)

Replace an EXPLICIT [start, end) range — the primitive behind EditController::replace_range, independent of wherever the caret currently is. Never coalesces (a programmatic edit is its own event).