nsIDOMEventTarget Interface

 The nsIDOMEventTarget interface is the interface implemented by all
 event targets in the Document Object Model.

 For more information on this interface please see 
 http://www.w3.org/TR/DOM-Level-2-Events/

 @status FROZEN


 This method allows the registration of event listeners on the event target.
 If an EventListener is added to an EventTarget while it is processing an
 event, it will not be triggered by the current actions but may be 
 triggered during a later stage of event flow, such as the bubbling phase.
 
 If multiple identical EventListeners are registered on the same 
 EventTarget with the same parameters the duplicate instances are 
 discarded. They do not cause the EventListener to be called twice 
 and since they are discarded they do not need to be removed with the 
 removeEventListener method.

 @param   type The event type for which the user is registering
 @param   listener The listener parameter takes an interface 
                   implemented by the user which contains the methods 
                   to be called when the event occurs.
 @param   useCapture If true, useCapture indicates that the user 
                     wishes to initiate capture. After initiating 
                     capture, all events of the specified type will be 
                     dispatched to the registered EventListener before 
                     being dispatched to any EventTargets beneath them 
                     in the tree. Events which are bubbling upward 
                     through the tree will not trigger an 
                     EventListener designated to use capture.

void addEventListener(in DOMString type, in nsIDOMEventListener listener, in 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 EventTarget on which 
 dispatchEvent is called.

 @param   evt Specifies the event type, behavior, and contextual 
              information to be used in processing the event.
 @return  Indicates whether any of the listeners which handled the 
          event called preventDefault. If preventDefault was called 
          the value is false, else the value is true.
 @throws  UNSPECIFIED_EVENT_TYPE_ERR: Raised if the Event's type was 
              not specified by initializing the event before 
              dispatchEvent was called. Specification of the Event's 
              type as null or an empty string will also trigger this 
              exception.

boolean dispatchEvent(in nsIDOMEvent evt)

 This method allows the removal of event listeners from the event 
 target. If an EventListener is removed from an EventTarget while it 
 is processing an event, it will not be triggered by the current actions. 
 EventListeners can never be invoked after being removed.
 Calling removeEventListener with arguments which do not identify any 
 currently registered EventListener on the EventTarget has no effect.

 @param   type Specifies the event type of the EventListener being 
               removed.
 @param   listener The EventListener parameter indicates the 
                   EventListener to be removed.
 @param   useCapture Specifies whether the EventListener 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.

void removeEventListener(in DOMString type, in nsIDOMEventListener listener, in boolean useCapture)