@Override
	public Point getToolTipLocation(MouseEvent event) {
		int x = event.getX();
		Column column = overColumn(x);
		if (column != null) {
			Row row = overRow(event.getY());
			if (row != null) {
				Rectangle bounds = getCellBounds(row, column);
				return new Point(x, bounds.y + bounds.height);
			}
		}
		return null;
	}