Toggle css class and use css content for anchor

css/ol.css

@@ -52,6 +52,13 @@
   text-decoration: none;
   width: 22px;
 }
+a.ol-full-screen-false:after {
+  content: "\2194";
+}
+a.ol-full-screen-true:after {
+  content: "\00d7";
+}
+
 .ol-full-screen div {
   border-radius: 2px;
 }

src/ol/control/fullscreencontrol.js

@@ -3,6 +3,7 @@ goog.provide('ol.control.FullScreen');
 goog.require('goog.asserts');
 goog.require('goog.dom');
 goog.require('goog.dom.TagName');
+goog.require('goog.dom.classes');
 goog.require('goog.dom.fullscreen');
 goog.require('goog.events');
 goog.require('goog.events.EventType');
@@ -20,16 +21,23 @@ ol.control.FullScreen = function(opt_options) {
 
   var options = goog.isDef(opt_options) ? opt_options : {};
 
+  /**
+   * @private
+   * @type {string}
+   */
+  this.cssClassName_ = 'ol-full-screen';
+
   var aElement = goog.dom.createDom(goog.dom.TagName.A, {
-    'href': '#fullScreen'
-  }, '\u00d7');
+    'href': '#fullScreen',
+    'class': this.cssClassName_ + '-' + goog.dom.fullscreen.isFullScreen()
+  });
   goog.events.listen(aElement, [
     goog.events.EventType.CLICK,
     goog.events.EventType.TOUCHEND
   ], this.handleClick_, false, this);
 
   var element = goog.dom.createDom(goog.dom.TagName.DIV, {
-    'class': 'ol-full-screen ' + ol.css.CLASS_UNSELECTABLE
+    'class': this.cssClassName_ + ' ' + ol.css.CLASS_UNSELECTABLE
   }, aElement);
 
   goog.base(this, {
@@ -61,11 +69,16 @@ ol.control.FullScreen.prototype.handleClick_ = function(browserEvent) {
   if (!goog.dom.fullscreen.isSupported()) {
     return;
   }
+  var opened = this.cssClassName_ + '-true';
+  var closed = this.cssClassName_ + '-false';
+  var anchor = goog.dom.getFirstElementChild(this.element);
   if (goog.dom.fullscreen.isFullScreen()) {
+    goog.dom.classes.swap(anchor, opened, closed);
     goog.dom.fullscreen.exitFullScreen();
   } else {
     var element = map.getTarget();
     goog.asserts.assert(!goog.isNull(element));
+    goog.dom.classes.swap(anchor, closed, opened);
     if (this.keys_) {
       goog.dom.fullscreen.requestFullScreenWithKeys(element);
     } else {