import { AfterViewInit, ElementRef, EventEmitter, NgZone, OnDestroy } from '@angular/core';
import * as i0 from "@angular/core";
export declare class ObserverViewDirective implements AfterViewInit, OnDestroy {
    private element;
    private readonly ngZone;
    observerRoot?: HTMLElement;
    observerRootMargin?: string;
    readonly observeVisible: EventEmitter<boolean>;
    private observer;
    private previousRation;
    private frameId;
    constructor(element: ElementRef, ngZone: NgZone);
    ngAfterViewInit(): void;
    ngOnDestroy(): void;
    private observeChange;
    static ɵfac: i0.ɵɵFactoryDeclaration<ObserverViewDirective, never>;
    static ɵdir: i0.ɵɵDirectiveDeclaration<ObserverViewDirective, "[observerView]", never, { "observerRoot": "observerRoot"; "observerRootMargin": "observerRootMargin"; }, { "observeVisible": "observeVisible"; }, never>;
}
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