@Override
	public String getToolTipText(MouseEvent event) {
		Column column = overColumn(event.getX());
		if (column != null) {
			Row row = overRow(event.getY());
			if (row != null) {
				return column.getRowCell(row).getToolTipText(event, getCellBounds(row, column), row, column);
			}
		}
		return super.getToolTipText(event);
	}