import { Observable, OperatorFunction } from 'rxjs';
/**
 * @description
 *
 * This function returns the zone un-patched API for the a specific Browser API.
 * If no target is passed the window is used instead
 *
 * @param name - The name of the API to check.
 * @param target - The target to get un-patched API from.
 * @return {Function} - The zone un-patched API in question.
 *
 */
export declare function getZoneUnPatchedApi<N extends keyof (Window & typeof globalThis)>(name: N): (Window & typeof globalThis)[N];
export declare function getZoneUnPatchedApi<T extends object, N extends keyof T>(target: T, name: N): T[N];
export declare function unpatchedMicroTask(): Observable<void>;
export declare function unpatchedScroll(el: EventTarget): Observable<void>;
/**
 * @description
 *
 * calculates the correct scrollTop value in which the rx-virtual-scroll-viewport
 * is actually visible
 */
export declare function parseScrollTopBoundaries(scrollTop: number, offset: number, contentSize: number, containerSize: number): {
    scrollTopWithOutOffset: number;
    scrollTopAfterOffset: number;
    scrollTop: number;
};
/**
 * @description
 *
 * Calculates the visible size of the rx-virtual-scroll-viewport container. It
 * accounts for the fact that the viewport can partially or fully be out of viewport because
 * static contents that are living between the boundaries of rx-virtual-scroll-viewport
 * and its scrollable element.
 */
export declare function calculateVisibleContainerSize(containerSize: number, scrollTopWithOutOffset: number, scrollTopAfterOffset: number): number;
/**
 * This operator maps an Observable out of a static value or an Observable.
 *
 */
export declare function coerceObservable<T>(): OperatorFunction<Observable<T | null | undefined> | T | null | undefined, Observable<T | null | undefined>>;