import { ElementRef, OnDestroy, OnInit } from '@angular/core';
import { Observable } from 'rxjs';
import { _RxVirtualViewObserver } from './model';
import * as i0 from "@angular/core";
/**
 * The RxVirtualViewObserver directive observes the virtual view and emits a boolean value indicating whether the virtual view is visible.
 * This is the container for the RxVirtualView directives.
 *
 * This is a mandatory directive for the RxVirtualView directives to work.
 *
 * @example
 * ```html
 * <div rxVirtualViewObserver>
 *   <div rxVirtualView>
 *     <div *rxVirtualViewContent>Virtual View 1</div>
 *     <div *rxVirtualViewPlaceholder>Loading...</div>
 *   </div>
 * </div>
 * ```
 *
 * @developerPreview
 */
export declare class RxVirtualViewObserver extends _RxVirtualViewObserver implements OnInit, OnDestroy {
    #private;
    /**
     * The root element to observe.
     *
     * If not provided, the root element is the element that the directive is attached to.
     */
    root: import("@angular/core").InputSignal<HTMLElement | ElementRef<any>>;
    /**
     * The root margin to observe.
     *
     * This is useful when you want to observe the virtual view in a specific area of the root element.
     */
    rootMargin: import("@angular/core").InputSignal<string>;
    /**
     * The threshold to observe.
     *
     * If you want to observe the virtual view when it is partially visible, you can set the threshold to a number between 0 and 1.
     *
     * For example, if you set the threshold to 0.5, the virtual view will be observed when it is half visible.
     */
    threshold: import("@angular/core").InputSignal<number | number[]>;
    ngOnInit(): void;
    ngOnDestroy(): void;
    /**
     * Hide all the virtual views.
     *
     * This is useful when you want to hide all the virtual views when the user cannot see them.
     *
     * For example, when the user opens a modal, you can hide all the virtual views to improve performance.
     *
     * **IMPORTANT:**
     *
     * Don't forget to call `showAllVisible()` when you want to show the virtual views again.
     */
    hideAll(): void;
    /**
     * Show all the virtual views that are currently visible.
     *
     * This needs to be called if `hideAll()` was called before.
     */
    showAllVisible(): void;
    observeElementVisibility(virtualView: HTMLElement): Observable<boolean>;
    observeElementSize(element: Element, options?: ResizeObserverOptions): Observable<ResizeObserverEntry>;
    static ɵfac: i0.ɵɵFactoryDeclaration<RxVirtualViewObserver, never>;
    static ɵdir: i0.ɵɵDirectiveDeclaration<RxVirtualViewObserver, "[rxVirtualViewObserver]", never, { "root": { "alias": "root"; "required": false; "isSignal": true; }; "rootMargin": { "alias": "rootMargin"; "required": false; "isSignal": true; }; "threshold": { "alias": "threshold"; "required": false; "isSignal": true; }; }, {}, never, never, true, never>;
}