import { SingleSubject } from '../types/signal';
import { BalVisibilityObserver } from './visibility.interfaces';
export declare class BalVisibilitySubject extends SingleSubject<BalVisibilityObserver> {
    private listener?;
    private debouncedNotify;
    constructor();
    attach(observer: BalVisibilityObserver): void;
    detach(): void;
}
