/*******************************************************************************
 * Copyright (c) 2005, 2008 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
module org.eclipse.core.databinding.observable.IObservable;

import java.lang.all;

/**
 * An object with state that allows to listen for state changes.
 * 
 * <p>
 * Implementations must not manage listeners themselves, listener management
 * must be delegated to a private instance of type {@link ChangeSupport} if it
 * is not inherited from {@link AbstractObservable}.
 * </p>
 * 
 * @noextend This interface is not intended to be extended by clients.
 * @noimplement This interface is not intended to be implemented by clients.
 *              Clients should instead subclass one of the classes in the
 *              framework that implement this interface. Note that direct
 *              implementers of this interface outside of the framework will be
 *              broken in future releases when methods are added to this
 *              interface.
 * 
 * @since 1.0
 * 
 */
public interface IObservable {

    /**
     * Returns the realm for this observable. Unless otherwise specified,
     * getters and setters must be accessed from within this realm. Listeners
     * will be within this realm when they receive events from this observable.
     * <p>
     * Because observables can only be accessed from within one realm, and they
     * always fire events on that realm, their state can be observed in an
     * incremental way. It is always safe to call getters of an observable from
     * within a change listener attached to that observable.
     * </p>
     * 
     * @return the realm
     */
    public Realm getRealm();

    /**
     * Adds the given change listener to the list of change listeners. Change
     * listeners are notified about changes of the state of this observable in a
     * generic way, without specifying the change that happened. To get the
     * changed state, a change listener needs to query for the current state of
     * this observable.
     * 
     * @param listener
     */
    public void addChangeListener(IChangeListener listener);

    /**
     * Removes the given change listener from the list of change listeners. Has
     * no effect if the given listener is not registered as a change listener.
     * 
     * @param listener
     */
    public void removeChangeListener(IChangeListener listener);

    /**
     * Adds the given stale listener to the list of stale listeners. Stale
     * listeners are notified when an observable object becomes stale, not when
     * is becomes non-stale.
     * 
     * @param listener
     * 
     * @see #isStale()
     */
    public void addStaleListener(IStaleListener listener);

    /**
     * Removes the given stale listener from the list of stale listeners. Has no
     * effect if the given listener is not registered as a stale listener.
     * 
     * @param listener
     */
    public void removeStaleListener(IStaleListener listener);

    /**
     * Returns whether the state of this observable is stale and is expected to
     * change soon. A non-stale observable that becomes stale will notify its
     * stale listeners. A stale object that becomes non-stale does so by
     * changing its state and notifying its change listeners, it does <b>not</b>
     * notify its stale listeners about becoming non-stale. Clients that do not
     * expect asynchronous changes may ignore staleness of observable objects.
     * 
     * @return true if this observable's state is stale and will change soon.
     * 
     * @TrackedGetter - implementers must call
     *                {@link ObservableTracker#getterCalledcast(IObservable)}.
     */
    public bool isStale();

    /**
     * Disposes of this observable object, removing all listeners registered
     * with this object, and all listeners this object might have registered on
     * other objects.
     */
    public void dispose();
}