content: /*
   * This library is part of OpenCms -
   * the Open Source Content Management System
   *
   * Copyright (c) Alkacon Software GmbH & Co. KG (https://www.alkacon.com)
   *
   * This library is free software; you can redistribute it and/or
   * modify it under the terms of the GNU Lesser General Public
   * License as published by the Free Software Foundation; either
   * version 2.1 of the License, or (at your option) any later version.
   *
   * This library is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
   * Lesser General Public License for more details.
   *
   * For further information about Alkacon Software, please see the
   * company website: https://www.alkacon.com
   *
   * For further information about OpenCms, please see the
   * project website: https://www.opencms.org
   *
   * You should have received a copy of the GNU Lesser General Public
   * License along with this library; if not, write to the Free Software
   * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
   */
  
  package org.opencms.gwt.client.ui.tree;
  
  import org.opencms.gwt.client.Messages;
  import org.opencms.gwt.client.ui.input.CmsCheckBox;
  
  import com.google.gwt.user.client.ui.Label;
  import com.google.gwt.user.client.ui.Widget;
  
  /**
   * Tree item for lazily loaded list trees.<p>
   *
   * @since 8.0.0
   */
  public class CmsLazyTreeItem extends CmsTreeItem {
  
      /** Enum for indicating the load state of a tree item. */
      public enum LoadState {
  
          /** children have been loaded. */
          LOADED,
  
          /** loading children. */
          LOADING,
  
          /** children haven't been loaded. */
          UNLOADED;
      }
  
      /**
       * Helper tree item which displays a "loading" message.<p>
       */
      protected class LoadingItem extends CmsTreeItem {
  
          /**
           * Constructs a new instance.<p>
           */
          public LoadingItem() {
  
              super(true, new Label(Messages.get().key(Messages.GUI_LOADING_0)));
          }
      }
  
      /** The loading item. */
      private LoadingItem m_loadingItem = new LoadingItem();
  
      /** The load state of this tree item. */
      private LoadState m_loadState = LoadState.UNLOADED;
  
      /** Flag to show a load item while children are being loaded. */
      private boolean m_useLoadItem;
  
      /**
       * Constructs a new lazy tree item with a main widget and a check box.<p>
       *
       * @param checkbox the check box
       * @param widget the main widget
       * @param useLoadItem <code>true</code> to show a load item while children are being loaded
       */
      public CmsLazyTreeItem(CmsCheckBox checkbox, Widget widget, boolean useLoadItem) {
  
          super(true, checkbox, widget);
          m_useLoadItem = useLoadItem;
      }
  
      /**
       * Constructs a new lazy tree item with a main widget.<p>
       *
       * @param widget the main widget
       * @param useLoadItem <code>true</code> to show a load item while children are being loaded
       */
      public CmsLazyTreeItem(Widget widget, boolean useLoadItem) {
  
          super(true, widget);
          m_useLoadItem = useLoadItem;
      }
  
      /**
       * Gets the load state of the tree item.<p>
       *
       * @return a load state
       */
      public LoadState getLoadState() {
  
          return m_loadState;
      }
  
      /**
       * Returns if tree item children have been loaded.<p>
       *
       * @return <code>true</code> if tree item children have been loaded
       */
      public boolean isLoaded() {
  
          return LoadState.LOADED == m_loadState;
      }
  
      /**
       * This method should be called when the item's children have finished loading.<p>
       */
      public void onFinishLoading() {
  
          m_loadState = LoadState.LOADED;
          if (m_useLoadItem) {
              m_loadingItem.removeFromParent();
          }
          onChangeChildren();
      }
  
      /**
       * This method is called when the tree item's children start being loaded.<p>
       */
      public void onStartLoading() {
  
          m_loadState = LoadState.LOADING;
          if (m_useLoadItem) {
              addChild(m_loadingItem);
          }
      }
  
      /**
       * @see org.opencms.gwt.client.ui.tree.CmsTreeItem#onChangeChildren()
       */
      @Override
      protected void onChangeChildren() {
  
          if (m_loadState == LoadState.LOADED) {
              super.onChangeChildren();
          }
      }
  
  }
  