/* -*- Mode: IDL; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
 *
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "nsISupports.idl"
interface nsIObserver;

/**
 * This interface lets you monitor how long the user has been 'idle',
 * i.e. not used their mouse or keyboard. You can get the idle time directly,
 * but in most cases you will want to register an observer for a predefined
 * interval. The observer will get an 'idle' notification when the user is idle
 * for that interval (or longer), and receive a 'back' notification when the
 * user starts using their computer again.
 */

[scriptable, uuid(cc52f19a-63ae-4a1c-9cc3-e79eace0b471)]
interface nsIIdleService : nsISupports
{
    /**
     * The amount of time in milliseconds that has passed
     * since the last user activity.
     *
     * If we do not have a valid idle time to report, 0 is returned
     * (this can happen if the user never interacted with the browser
     * at all, and if we are also unable to poll for idle time manually).
     */
    readonly attribute unsigned long idleTime;

    /**
     * Add an observer to be notified when the user idles for some period of
     * time, and when they get back from that.
     *
     * @param observer the observer to be notified
     * @param time the amount of time in seconds the user should be idle before
     *             the observer should be notified.
     *
     * @note
     * The subject of the notification the observer will get is always the
     * nsIIdleService itself.
     * When the user goes idle, the observer topic is "idle" and when they get
     * back, the observer topic is "back".
     * The data param for the notification contains the current user idle time.
     *
     * @note
     * You can add the same observer twice.
     * @note
     * Most implementations need to poll the OS for idle info themselves,
     * meaning your notifications could arrive with a delay up to the length
     * of the polling interval in that implementation.
     * Current implementations use a delay of 5 seconds.
     */
    void addIdleObserver(in nsIObserver observer, in unsigned long time);

    /**
     * Remove an observer registered with addIdleObserver.
     * @param observer the observer that needs to be removed.
     * @param time the amount of time they were listening for.
     * @note
     * Removing an observer will remove it once, for the idle time you specify. 
     * If you have added an observer multiple times, you will need to remove it
     * just as many times.
     */
    void removeIdleObserver(in nsIObserver observer, in unsigned long time);
};

