finish method
void
finish()
Finishes the current bar line with a trailing newline (no-op when disabled
or nothing was drawn since the last finish). Resets state so the bar can be
reused across successive transfers, e.g. a long-running watch.
Implementation
void finish() {
if (_enabled && _dirty) _out.write('\n');
_dirty = false;
_lastLen = 0;
}