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Nifty GUI is a Java Library that supports the building of interactive user interfaces for games or similar applications. It utilizes OpenGL for rendering and it can be easily integrated into many rendering systems. The configuration of the GUI is stored in xml files with little supporting Java code. In short Nifty helps you to layout stuff, display it in a cool way and interact with it :)

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package org.bushe.swing.event.annotation;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

import org.bushe.swing.event.EventService;
import org.bushe.swing.event.EventServiceLocator;
import org.bushe.swing.event.ThreadSafeEventService;

/**
 * An Annotation for adding VetoListener subscriptions to EventService Events.
 * 
 * This annotation simplifies much of the repetitive boilerplate used for adding veto listeners
 * (which in EventBus 2.0 will be called VetoSubscribers, thus this annotation name difference)
 * to EventService Events.  Example:
 * 

 * 
 * public class MyAppController {
 *   public MyAppController {
 *       AnnotationProcessor.process(this);//this line can be avoided with a compile-time tool or an Aspect
 *   }
 *   @EventSubscriber(eventClass=AppAppClosingEvent.class)
 *   public void onAppClosingEvent(AppClosingEvent appClosingEvent) {
 *      //close connections, close windows
 *   }
 * }
 *
 * public class MyDocumentController {
 *   @VetoSubscriber(eventClass=AppAppClosingEvent.class)
 *   public boolean ensureDocumentIsSaved(AppAppClosingEvent appClosingEvent) {
 *      if (docHasUnsavedChanges()) {
 *         boolean answer = MyModalDialog.show("Are you sure you want to close and lose your changes?");
 *         if (answer == StandardButtonValues.Cancel) {
 *            //stop processing this event
 *            return true;
 *         }
 *      }
 *      //It's OK to close
 *      return false;
 *   }
 * }
 * 
 */
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface VetoSubscriber {
   /** The class to subscribe to, if not specified, a subscription is created for the type of the method parameter. */
   public abstract Class eventClass() default UseTheClassOfTheAnnotatedMethodsParameter.class;

   /** Determines the order in which this veto subscriber is called, default is FIFO.*/
   public abstract int priority() default 0;

   /** Whether or not to subscribe to the exact class or a class hierarchy, defaults to class hierarchy (false). */
   public abstract boolean exact() default false;

   /** Whether to subscribe weakly or strongly. */
   public abstract ReferenceStrength referenceStrength() default ReferenceStrength.WEAK;

   /** The event service to subscribe to, default to the EventServiceLocator.SERVICE_NAME_EVENT_BUS. */
   public abstract String eventServiceName() default EventServiceLocator.SERVICE_NAME_EVENT_BUS;

   /**
    * Whether or not to autocreate the event service if it doesn't exist on subscription, default is true. If the
    * service needs to be created, it must have a default constructor.
    */
   public abstract Class autoCreateEventServiceClass() default ThreadSafeEventService.class;
}