Add addClass()/removeClass() utility functions

src/drawer.js

@@ -377,7 +377,7 @@ $.Drawer.prototype = {
         element.href    = "#/overlay/"+id;
     }
     element.id        = id;
-    element.className = element.className + " " + ( overlay.className ?
+    $.addClass( element, overlay.className ?
         overlay.className :
         "openseadragon-overlay"
     );

src/openseadragon.js

@@ -1025,6 +1025,48 @@ window.OpenSeadragon = window.OpenSeadragon || function( options ){
         },
 
 
+        /**
+         * Add the specified CSS class to the element if not present.
+         * @name $.addClass
+         * @function
+         * @param {Element|String} element
+         * @param {String} className
+         */
+        addClass: function( element, className ) {
+            element = $.getElement( element );
+
+            if ( ! element.className ) {
+                element.className = className;
+            } else if ( ( ' ' + element.className + ' ' ).
+                indexOf( ' ' + className + ' ' ) === -1 ) {
+                element.className += ' ' + className;
+            }
+        },
+
+
+        /**
+         * Remove the specified CSS class from the element.
+         * @name $.removeClass
+         * @function
+         * @param {Element|String} element
+         * @param {String} className
+         */
+        removeClass: function( element, className ) {
+            var oldClasses,
+                newClasses = [],
+                i;
+
+            element = $.getElement( element );
+            oldClasses = element.className.split( /\s+/ );
+            for ( i = 0; i < oldClasses.length; i++ ) {
+                if ( oldClasses[ i ] && oldClasses[ i ] !== className ) {
+                    newClasses.push( oldClasses[ i ] );
+                }
+            }
+            element.className = newClasses.join(' ');
+        },
+
+
         /**
          * Adds an event listener for the given element, eventName and handler.
          * @function

src/viewer.js

@@ -515,10 +515,7 @@ $.extend( $.Viewer.prototype, $.EventHandler.prototype, $.ControlDock.prototype,
 
                 //Make sure the user has some ability to style the toolbar based
                 //on the mode
-                this.toolbar.element.setAttribute( 
+                $.addClass( this.toolbar.element, 'fullpage' );
-                    'class',
-                    this.toolbar.element.className +" fullpage"
-                );
             }
             
             body.appendChild( this.element );
@@ -602,10 +599,7 @@ $.extend( $.Viewer.prototype, $.EventHandler.prototype, $.ControlDock.prototype,
 
                 //Make sure the user has some ability to style the toolbar based
                 //on the mode
-                this.toolbar.element.setAttribute( 
+                $.removeClass( this.toolbar.element, 'fullpage' );
-                    'class',
-                    this.toolbar.element.className.replace('fullpage','')
-                );
                 //this.toolbar.element.style.position = 'relative';
                 this.toolbar.parentNode.insertBefore( 
                     this.toolbar.element,