src/org/w3c/dom/events/EventTarget.java

/*
 * Copyright (c) 2000 World Wide Web Consortium,
 * (Massachusetts Institute of Technology, Institut National de
 * Recherche en Informatique et en Automatique, Keio University). All
 * Rights Reserved. This program is distributed under the W3C's Software
 * Intellectual Property License. This program is distributed in the
 * hope that it will be useful, but WITHOUT ANY WARRANTY; without even
 * the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
 * PURPOSE. See W3C License http://www.w3.org/Consortium/Legal/ for more
 * details.
 */

package org.w3c.dom.events;

/**
 *  The <code>EventTarget</code> interface is implemented by all 
 * <code>Nodes</code> in  an implementation which supports the DOM Event 
 * Model.  The interface allows registration and removal of 
 * <code>EventListeners</code> on an <code>EventTarget</code> and dispatch of 
 * events to that <code>EventTarget</code> .
 * @since DOM Level 2
 */
public interface EventTarget {
    /**
     *  This method allows the registration of event listeners on the event 
     * target.  If an <code>EventListener</code> is added to an 
     * <code>EventTarget</code> which is  currently processing an event the 
     * new listener will not be triggered by the current event. 
     * <br> If multiple identical <code>EventListener</code> s are registered 
     * on the same <code>EventTarget</code> with the same parameters the 
     * duplicate instances are discarded. They do not cause the 
     * <code>EventListener</code> to be called twice and since they are  
     * discarded they do not need to be removed with the 
     * <code>removeEventListener</code> method. 
     * @param type  The event type for which the user is registering
     * @param listener  The <code>listener</code> parameter takes an interface 
     *   implemented by the user which contains the methods to be called when 
     *   the event occurs.
     * @param useCapture  If true, <code>useCapture</code> indicates that the 
     *   user wishes to initiate capture.  After initiating capture, all 
     *   events of the specified type will be  dispatched to the registered 
     *   <code>EventListener</code> before being dispatched to any 
     *   <code>EventTargets</code> beneath them in the tree.  Events which 
     *   are bubbling upward through the tree will not trigger an 
     *   <code>EventListener</code> designated to use capture.
     */
    public void addEventListener(String type, 
                                 EventListener listener, 
                                 boolean useCapture);

    /**
     *  This method allows the removal of event listeners from the event 
     * target.  If an <code>EventListener</code> is removed from an 
     * <code>EventTarget</code> while it is  processing an event, it will 
     * complete its current actions but will not be triggered again during 
     * any later stages of event flow.
     * <br> If an <code>EventListener</code> is removed from an 
     * <code>EventTarget</code> which is  currently processing an event the 
     * removed listener will still be triggered by the current event.
     * <br> Calling <code>removeEventListener</code> with arguments which do 
     * not identify any currently registered <code>EventListener</code> on 
     * the <code>EventTarget</code> has no effect.
     * @param type  Specifies the event type of the <code>EventListener</code> 
     *   being removed. 
     * @param listener  The <code>EventListener</code> parameter indicates the 
     *   <code>EventListener</code> to be removed. 
     * @param useCapture  Specifies whether the <code>EventListener</code> 
     *   being removed was registered as a capturing listener or not.  If a 
     *   listener was registered twice, one with capture and one without, 
     *   each must be removed separately.  Removal of a capturing listener 
     *   does not affect a non-capturing version of the same listener, and 
     *   vice versa. 
     */
    public void removeEventListener(String type, 
                                    EventListener listener, 
                                    boolean useCapture);

    /**
     *  This method allows the dispatch of events into the implementations 
     * event model.  Events dispatched in this manner will have the same 
     * capturing and bubbling behavior as events dispatched directly by the 
     * implementation.  The target of the event is the 
     * <code>EventTarget</code> on which <code>dispatchEvent</code> is called.
     *  
     * @param evt  Specifies the event type, behavior, and contextual 
     *   information to be used in processing the event.
     * @return  The return value of <code>dispatchEvent</code> indicates 
     *   whether any of the listeners which handled the event called 
     *   <code>preventDefault</code> .  If <code>preventDefault</code> was 
     *   called the value is false, else the value is true. 
     * @exception EventException
     *    UNSPECIFIED_EVENT_TYPE_ERR: Raised if the <code>Event</code> 's 
     *   type was not specified by initializing the event before 
     *   <code>dispatchEvent</code> was called. Specification of the 
     *   <code>Event</code> 's type as <code>null</code> or an empty string 
     *   will also trigger this exception.
     */
    public boolean dispatchEvent(Event evt)
                                 throws EventException;

}