static final RangeThumbSelector _customRangeThumbSelector = (
    TextDirection textDirection,
    RangeValues values,
    double tapValue,
    Size thumbSize,
    Size trackSize,
    double dx,
  ) {
    final double start = (tapValue - values.start).abs();
    final double end = (tapValue - values.end).abs();
    return start < end ? Thumb.start : Thumb.end;
  };