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.util;
  
  import java.util.List;
  
  import com.google.gwt.core.client.JavaScriptObject;
  import com.google.gwt.user.client.Timer;
  
  /**
   * Helper class to append a stylesheet link to the head of the current page and run a callback when everything has been loaded.
   */
  public class CmsStylesheetLoader {
  
      /** The callback that should be called when everything has been loaded. */
      private Runnable m_allLoadedCallback;
  
      /** Indicates whether the all-loaded callback has already been called. */
      private boolean m_callbackCalled;
  
      /** The callback for the onload handlers of the stylesheets. */
      private JavaScriptObject m_jsCallback;
  
      /** The number of stylesheets that have been already loaded. */
      private int m_loadCounter;
  
      /** The list of stylesheets to load. */
      private List<String> m_stylesheets;
  
      /**
       * Creates a new instance.<p>
       *
       * @param stylesheets the list of stylesheets to load
       * @param allLoadedCallback the callback to call when everything has been loaded
       */
      public CmsStylesheetLoader(List<String> stylesheets, Runnable allLoadedCallback) {
  
          m_stylesheets = stylesheets;
          m_loadCounter = 0;
          m_allLoadedCallback = allLoadedCallback;
  
          m_jsCallback = createJsCallback();
      }
  
      /**
       * Checks the window.document for given style-sheet.<p>
       *
       * @param styleSheetLink the style-sheet link
       * @return true if the stylesheet is already present
       */
      private static native boolean checkStylesheet(String styleSheetLink)/*-{
          var styles = $wnd.document.styleSheets;
          for (var i = 0; i < styles.length; i++) {
              if (styles[i].href != null
                      && styles[i].href.indexOf(styleSheetLink) >= 0) {
                  // style-sheet is present
                  return true;
              }
          }
          return false;
      }-*/;
  
      /**
       * Starts the loading process and creates a timer that sets of the callback after a given tiime if it hasn't already been triggered.
       *
       * @param timeout number of milliseconds after which the callback should be called if it hasn't already been
       */
      public void loadWithTimeout(int timeout) {
  
          for (String stylesheet : m_stylesheets) {
              boolean alreadyLoaded = checkStylesheet(stylesheet);
              if (alreadyLoaded) {
                  m_loadCounter += 1;
              } else {
                  appendStylesheet(stylesheet, m_jsCallback);
              }
          }
          checkAllLoaded();
          if (timeout > 0) {
              Timer timer = new Timer() {
  
                  @SuppressWarnings("synthetic-access")
                  @Override
                  public void run() {
  
                      callCallback();
                  }
              };
  
              timer.schedule(timeout);
          }
      }
  
      /**
       * Appends a stylesheet to the page head.<p>
       *
       * @param stylesheet the stylesheet link
       * @param callback the load handler for the stylesheet link element
       */
      private native void appendStylesheet(String stylesheet, JavaScriptObject callback) /*-{
          var headID = $wnd.document.getElementsByTagName("head")[0];
          var cssNode = $wnd.document.createElement('link');
          cssNode.type = 'text/css';
          cssNode.rel = 'stylesheet';
          cssNode.href = stylesheet;
          headID.appendChild(cssNode, callback);
          cssNode.addEventListener("load", callback);
      }-*/;
  
      /**
       * Calls the callback if it hasn't already been triggered.<p>
       */
      private void callCallback() {
  
          if (!m_callbackCalled) {
              m_callbackCalled = true;
              m_allLoadedCallback.run();
          }
      }
  
      /**
       * Checks if all stylesheets have been loaded.<p>
       */
      private void checkAllLoaded() {
  
          if (m_loadCounter == m_stylesheets.size()) {
              callCallback();
          }
      }
  
      /**
       * Creates the callback for the onload handlers of the link elements.<p>
       *
       * @return the callback
       */
      private native JavaScriptObject createJsCallback() /*-{
          var self = this;
          return function() {
              self.@org.opencms.gwt.client.util.CmsStylesheetLoader::onLoadCallback()();
          }
      }-*/;
  
      /**
       * The method which should be called by the onload handlers of the link elements.<p>
       */
      private void onLoadCallback() {
  
          m_loadCounter += 1;
          checkAllLoaded();
      }
  
  }
  