org.opencms.gwt.client.util.CmsStylesheetLoader Maven / Gradle / Ivy
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/*
* This library is part of OpenCms -
* the Open Source Content Management System
*
* Copyright (c) Alkacon Software GmbH & Co. KG (http://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: http://www.alkacon.com
*
* For further information about OpenCms, please see the
* project website: http://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 m_stylesheets;
/**
* Creates a new instance.
*
* @param stylesheets the list of stylesheets to load
* @param allLoadedCallback the callback to call when everything has been loaded
*/
public CmsStylesheetLoader(List stylesheets, Runnable allLoadedCallback) {
m_stylesheets = stylesheets;
m_loadCounter = 0;
m_allLoadedCallback = allLoadedCallback;
m_jsCallback = createJsCallback();
}
/**
* Checks the window.document for given style-sheet.
*
* @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.
*
* @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.
*/
private void callCallback() {
if (!m_callbackCalled) {
m_callbackCalled = true;
m_allLoadedCallback.run();
}
}
/**
* Checks if all stylesheets have been loaded.
*/
private void checkAllLoaded() {
if (m_loadCounter == m_stylesheets.size()) {
callCallback();
}
}
/**
* Creates the callback for the onload handlers of the link elements.
*
* @return the callback
*/
private native JavaScriptObject createJsCallback() /*-{
var self = this;
return function() {
[email protected]::onLoadCallback()();
}
}-*/;
/**
* The method which should be called by the onload handlers of the link elements.
*/
private void onLoadCallback() {
m_loadCounter += 1;
checkAllLoaded();
}
}