Event Interceptors

Though org.zkoss.zk.ui.util.EventInterceptor is designed to allow developer to intercept how an event is processed, you could use it as callback to know how long it takes to process an event. The event processing time can be calculated by subtracting the time between org.zkoss.zk.ui.util.EventInterceptor#beforeProcessEvent(org.zkoss.zk.ui.event.Event) and org.zkoss.zk.ui.util.EventInterceptor#afterProcessEvent(org.zkoss.zk.ui.event.Event)

Once implemented, you could register it by specifying the following in WEB-INF/zk.xml (assume the class is called foo.MyEventMeter):

<zk>
    <listener>
        <listener-class>foo.MyEventMeter</listener-class>
    </listener>
</zk>