/**
 * Merges an external ref with an internal ref object.
 * Handles both callback refs and ref objects.
 *
 * @param internalRef - The internal ref object to update
 * @param externalRef - The external ref from props (can be callback or ref object)
 * @returns A callback ref that updates both refs
 *
 * @example
 * ```tsx
 * const MyComponent = ({ ref, ...props }: MyComponentProps) => {
 *   const internalRef = useRef<HTMLDivElement>(null);
 *   const mergedRef = useMergedRef(internalRef, ref);
 *
 *   return <div ref={mergedRef} {...props} />;
 * };
 * ```
 */
export declare const useMergedRef: <T extends Element>(internalRef: React.RefObject<T | null>, externalRef?: React.Ref<T> | null) => (node: T | null) => void;