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;
  
  import org.opencms.gwt.client.util.CmsMediaQuery;
  
  import com.google.gwt.dom.client.Element;
  import com.google.gwt.user.client.ui.RootPanel;
  
  /**
   * Singleton class that evaluates, and keeps track of changes for, a fixed set of media queries and sets CSS classes
   * on the body element depending on which of the media queries match.
   */
  public class CmsMediaQueryRuleManager {
  
      /** The instance. */
      protected static CmsMediaQueryRuleManager instance;
  
      /**
       * Initializes the rules.
       */
      protected CmsMediaQueryRuleManager() {
  
          addRule("oc-touch-only", CmsCoreProvider.TOUCH_ONLY_RULE);
          addRule("oc-screensize-small", "(max-width: " + CmsWidthConstants.smallHigh() + ")");
          addRule(
              "oc-screensize-medium",
              "(min-width: "
                  + CmsWidthConstants.mediumLow()
                  + ") and (max-width: "
                  + CmsWidthConstants.mediumHigh()
                  + ")");
          addRule("oc-screensize-large", "(min-width: " + CmsWidthConstants.largeLow() + ")");
      }
  
      /**
       * Gets the instance.
       *
       * @return the instance
       */
      public static CmsMediaQueryRuleManager get() {
  
          if (instance == null) {
              instance = new CmsMediaQueryRuleManager();
          }
          return instance;
      }
  
      /** Initializes the manager and sets up the rules. */
      public static void initialize() {
  
          CmsMediaQueryRuleManager.get();
  
      }
  
      /**
       * Installs a new media query rule.
       *
       * @param cssClass the CSS class to add if the media query matches
       * @param mediaQueryText the text of the media query
       */
      public void addRule(String cssClass, String mediaQueryText) {
  
          CmsMediaQuery mediaQuery = CmsMediaQuery.parse(mediaQueryText);
          updateBodyClass(cssClass, mediaQuery.matches());
          mediaQuery.addListener(match -> {
              updateBodyClass(cssClass, match.booleanValue());
          });
      }
  
      /**
       * Adds or removes a CSS class from the body.
       *
       * @param cssClass the CSS class
       * @param enabled true if the class should be added, false to remove it
       */
      public void updateBodyClass(String cssClass, boolean enabled) {
  
          Element body = RootPanel.getBodyElement();
          if (enabled) {
              body.addClassName(cssClass);
          } else {
              body.removeClassName(cssClass);
          }
      }
  
  }
  