String headerGetToolTip (int x) {
	if (resizeColumn != null) return null;
	int orderedIndex = computeColumnIntersect (x, 0);
	if (orderedIndex == -1) return null;
	CTableColumn[] orderedColumns = getOrderedColumns ();
	CTableColumn column = orderedColumns [orderedIndex];
	if (column.toolTipText == null) return null;

	/* no tooltip should appear if the hover is at a column resize opportunity */
	int columnX = column.getX ();
	if (orderedIndex > 0 && orderedColumns [orderedIndex - 1].resizable) {
		/* left column bound is resizable */
		if (x - columnX <= TOLLERANCE_COLUMNRESIZE) return null;
	}
	if (column.resizable) {
		/* right column bound is resizable */
		int columnRightX = columnX + column.width;
		if (columnRightX - x <= TOLLERANCE_COLUMNRESIZE) return null;
	}
	return removeMnemonics (column.toolTipText);
}