/**
 * Hook that uses `ResizeObserver` to access an element's size every time it updates.
 * @private
 * @param onResize callback fired with the element's new dimensions on every resize.
 * @returns a callback ref that needs to be set on the element, and a ResizeObserver instance.
 *
 * @example
 * const onResize = React.useCallback((size) => console.log(size), []);
 * const [ref] = useResizeObserver(onResize);
 * ...
 * return <div ref={ref}>...</div>;
 */
export declare const useResizeObserver: <T extends HTMLElement>(onResize: (size: DOMRectReadOnly) => void) => readonly [(element: T | null | undefined) => void, ResizeObserver | undefined];