scrollBy method

@override bool scrollBy(int delta)

Scrolls by a delta. Returns true if the offset changed.

Implementation

@override
bool scrollBy(int delta) {
  if (delta == 0) return false;
  final before = _offset;
  final next = (_offset + delta).clamp(0, maxOffset);
  if (next == _offset) {
    _traceScroll(
      'widget_scroll.scrollBy noop '
      'delta=$delta offset=$before max=$maxOffset',
    );
    return false;
  }
  _offset = next;
  _notifyListeners();
  _traceScroll(
    'widget_scroll.scrollBy '
    'delta=$delta from=$before to=$_offset max=$maxOffset',
  );
  return true;
}