Simple Mouse Wheel support for GWT

source : http://www.bigbold.com/snippets/user/sligowaths

public interface MouseWheelListener {
public void onMouseWheelUp(int intensity);
public void onMouseWheelDown(int intensity);
}

public class MouseWheel {
private MouseWheel(Element e, MouseWheelListener listener) {
attachMouseWheelListener(e, listener);
}

/**
* Sets a MouseWheelListener to a given Element
*/

public static void setMouseWheelListener(Element e, MouseWheelListener listener) {
new MouseWheel(e, listener);
}

/**
* This method is used by FF
* @param event
*/

private static native void dispatchMouseWheelEvent(JavaScriptObject event) /*-{
@br.com.example.client.util.MouseWheel::dispatchMouseWheelEvent(Lcom/google/gwt/core/client/JavaScriptObject;Lbr/com/example/client/util/MouseWheelListener;)(event, this.__mousewheellistener);
}-*/;

/**
* This method is used by IE and FF
* Part of this method was retrieved from http://adomas.org/notes/mouse-wheel.html
*
* @param event
* @param listener
*/

private static native void dispatchMouseWheelEvent(JavaScriptObject event, MouseWheelListener listener) /*-{
if (!event) event = $wnd.event; // For IE

var delta = 0;
if (event.wheelDelta) // IE case, delta is multiple of 120
delta = event.wheelDelta / 120;
else if (event.detail ) // Mozilla case
delta = -event.detail / 3; // different sign and multiple of 3

if ( delta > 0 ) {
listener.@br.com.example.client.util.MouseWheelListener::onMouseWheelUp(I)(delta);
} else {
listener.@br.com.example.client.util.MouseWheelListener::onMouseWheelDown(I)(-delta);
}
}-*/;

private native void attachMouseWheelListener(Element e, MouseWheelListener listener) /*-{
e.__mousewheellistener = listener;
// for FF
if (e.addEventListener) {
e.addEventListener('DOMMouseScroll', @br.com.example.client.util.MouseWheel::dispatchMouseWheelEvent(Lcom/google/gwt/core/client/JavaScriptObject;), false);
return;
}
// for IE
e.onmousewheel = function(event) {
@br.com.example.client.util.MouseWheel::dispatchMouseWheelEvent (Lcom/google/gwt/core/client/JavaScriptObject;Lbr/com/example/client/util/MouseWheelListener;)(event, this.__mousewheellistener);
}
}-*/;
}

And here is how to use it:
MouseWheel.setMouseWheelListener(RootPanel.get("slot2").getElement(), new MouseWheelListener() {
public void onMouseWheelUp(int intensity) {
Window.alert("up.. " + intensity);
}

public void onMouseWheelDown(int intensity) {
Window.alert("down..." + intensity);
}
});

Remember to replace my hardcoded package name (br.com.example) for your own..