001/*
002 * This library is part of OpenCms -
003 * the Open Source Content Management System
004 *
005 * Copyright (c) Alkacon Software GmbH & Co. KG (http://www.alkacon.com)
006 *
007 * This library is free software; you can redistribute it and/or
008 * modify it under the terms of the GNU Lesser General Public
009 * License as published by the Free Software Foundation; either
010 * version 2.1 of the License, or (at your option) any later version.
011 *
012 * This library is distributed in the hope that it will be useful,
013 * but WITHOUT ANY WARRANTY; without even the implied warranty of
014 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
015 * Lesser General Public License for more details.
016 *
017 * For further information about Alkacon Software, please see the
018 * company website: http://www.alkacon.com
019 *
020 * For further information about OpenCms, please see the
021 * project website: http://www.opencms.org
022 *
023 * You should have received a copy of the GNU Lesser General Public
024 * License along with this library; if not, write to the Free Software
025 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
026 */
027
028package org.opencms.gwt.client.ui;
029
030import com.google.gwt.user.client.ui.Composite;
031import com.google.gwt.user.client.ui.FlowPanel;
032import com.google.gwt.user.client.ui.Widget;
033
034/**
035 * Widget which wraps another widget, which will only be appended to the DOM if the wrapper's
036 * <code>widget()</code> method is called.<p>
037 *
038 * @param <W> the type of the widget to wrap
039 *
040 * @since 8.0.0
041 */
042public class CmsLazyWidgetWrapper<W extends Widget> extends Composite {
043
044    /** The wrapper panel. */
045    private FlowPanel m_panel;
046
047    /** The wrapped widget. */
048    private W m_widget;
049
050    /**
051     * Creates a new instance.<p>
052     *
053     * @param widget the widget to wrap
054     */
055    public CmsLazyWidgetWrapper(W widget) {
056
057        m_panel = new FlowPanel();
058        initWidget(m_panel);
059        m_widget = widget;
060    }
061
062    /**
063     * Returns the wrapped widget and attaches it to the DOM if necessary.<p>
064     *
065     * @return the wrapped widget
066     */
067    public W widget() {
068
069        if (m_widget.getParent() == null) {
070            m_panel.add(m_widget);
071        }
072        return m_widget;
073    }
074
075}