private int?GetSeriesIndexOnPosition(double position, int headerSize, SeriesSizes series, int firstVisible)
{
if (position <= headerSize)
{
return(null);
}
int frozenSize = series.FrozenSize;
if (position <= headerSize + frozenSize)
{
return(series.GetFrozenIndexOnPosition((int)Math.Round(position - headerSize)));
}
return(series.GetScrollIndexOnPosition(
(int)Math.Round(position - headerSize - frozenSize) + series.GetPositionByScrollIndex(firstVisible)
) + series.FrozenCount);
}