type Cleanup = () => void;
/**
 * Tracks interaction with the app without treating an open/backgrounded tab as
 * proof that somebody is still present.
 */
export declare class UserActivityTracker {
    private readonly now;
    private readonly isAppVisible;
    private lastActivityAt;
    constructor(now?: () => number, isAppVisible?: () => boolean);
    getLastActivityAt(): number;
    recordActivity(at?: number): boolean;
    /**
     * Attach activity listeners to either the main app window or a same-origin
     * embedded editor window. The returned cleanup is safe to call repeatedly.
     */
    attachWindow(targetWindow: Window): Cleanup;
    private isTopDocumentHidden;
}
declare const userActivityTracker: UserActivityTracker;
export { userActivityTracker };
export default userActivityTracker;