/**
* Is called only for the root element in order to dispatch GVT
* events to the DOM.
*/
public static void addGVTListener(BridgeContext ctx, Document doc) {
UserAgent ua = ctx.getUserAgent();
if (ua != null) {
EventDispatcher dispatcher = ua.getEventDispatcher();
if (dispatcher != null) {
final Listener listener = new Listener(ctx, ua);
dispatcher.addGraphicsNodeMouseListener(listener);
dispatcher.addGraphicsNodeMouseWheelListener(listener);
dispatcher.addGraphicsNodeKeyListener(listener);