void headerOnMouseUp (Event event) {
	if (resizeColumn == null) return;	/* not resizing a column */

	/* remove the resize line */
	GC gc = new GC (this);
	redraw (resizeColumnX - 1, 0, 1, clientArea.height, false);
	gc.dispose ();

	int newWidth = resizeColumnX - resizeColumn.getX ();
	if (newWidth != resizeColumn.width) {
		setCursor (null);
		updateColumnWidth (resizeColumn, newWidth);
	}
	resizeColumnX = -1;
	resizeColumn = null;
}