/* Columns.java{{IS_NOTE	Purpose:			Description:			History:		Tue Oct 25 16:00:29     2005, Created by tomyeh}}IS_NOTECopyright (C) 2005 Potix Corporation. All Rights Reserved.{{IS_RIGHT	This program is distributed under GPL Version 2.0 in the hope that	it will be useful, but WITHOUT ANY WARRANTY.}}IS_RIGHT*/package org.zkoss.zul;import org.zkoss.zk.ui.Component;import org.zkoss.zk.ui.UiException;import org.zkoss.zul.impl.HeadersElement;/** * Defines the columns of a grid. * Each child of a columns element should be a {@link Column} element. * * @author tomyeh */public class Columns extends HeadersElement {	/** Returns the grid that it belongs to.	 * <p>It is the same as {@link #getParent}.	 */	public Grid getGrid() {		return (Grid)getParent();	}		//-- Component --//	public void setParent(Component parent) {		if (parent != null && !(parent instanceof Grid))			throw new UiException("Unsupported parent for columns: "+parent);		super.setParent(parent);	}	public boolean setVisible(boolean visible) {		final boolean vis = super.setVisible(visible);		final Grid grid = getGrid();		if (grid != null)			grid.invalidate();		return vis;	}		public boolean insertBefore(Component child, Component insertBefore) {		if (!(child instanceof Column))			throw new UiException("Unsupported child for columns: "+child);		return super.insertBefore(child, insertBefore);	}}