import { default as React } from 'react';
/**
 * Observe element size changes for a given ref.
 * Falls back to returning `undefined` when ResizeObserver is unavailable.
 */
export declare function useResizeObserver<T extends HTMLElement>(ref: React.RefObject<T | null>, { box }: ResizeObserverOptions): {
    entry: ResizeObserverEntry | null;
    rect: DOMRect | undefined;
};