pub fn shift_after(runs: &mut [FormatRun], threshold: u32, delta: i32)Expand description
Shift the byte offsets of every run whose byte_start >= threshold
by delta. Used after a text insert/delete to keep downstream runs
in sync with the new block text. Runs strictly before the threshold
are unaffected; runs that straddle the threshold are left alone
(the caller should have spliced them first).
Panics in debug mode if delta would underflow a run’s offset.