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#include "nsISupports.idl"

/**
 * This interface is implemented by an object that wants
 * to observe an event corresponding to a topic.
 *
 * @status FROZEN
 */

[scriptable, uuid(DB242E01-E4D9-11d2-9DDE-000064657374)]
interface nsIObserver : nsISupports {

   /**
    * Observe will be called when there is a notification for the
    * topic |aTopic|.  This assumes that the object implementing
    * this interface has been registered with an observer service
    * such as the nsIObserverService. 
    *
    * If you expect multiple topics/subjects, the impl is 
    * responsible for filtering.
    *
    * You should not modify, add, remove, or enumerate 
    * notifications in the implemention of observe. 
    *
    * @param aSubject : Notification specific interface pointer.
    * @param aTopic   : The notification topic or subject.
    * @param aData    : Notification specific wide string.
    *                    subject event.
    */
    void observe( in nsISupports aSubject,
				  in string      aTopic,
				  in wstring     aData );

};