useGridDimensions.ts

import { useLayoutEffect, useState } from 'react';
import { flushSync } from 'react-dom';

export function useGridDimensions({
  gridRef
}: {
  gridRef: React.RefObject<HTMLDivElement | null>;
}) {
  const [inlineSize, setInlineSize] = useState(1);
  const [blockSize, setBlockSize] = useState(1);

  useLayoutEffect(() => {
    const { ResizeObserver } = window;

    // don't break in Node.js (SSR), jsdom, and browsers that don't support ResizeObserver
    // eslint-disable-next-line @typescript-eslint/no-unnecessary-condition
    if (ResizeObserver == null) return;

    const { clientWidth, clientHeight } = gridRef.current!;

    setInlineSize(clientWidth);
    setBlockSize(clientHeight);

    const resizeObserver = new ResizeObserver((entries) => {
      const size = entries[0].contentBoxSize[0];

      // we use flushSync here to avoid flashing scrollbars
      flushSync(() => {
        setInlineSize(size.inlineSize);
        setBlockSize(size.blockSize);
      });
    });
    resizeObserver.observe(gridRef.current!);

    return () => {
      resizeObserver.disconnect();
    };
  }, [gridRef]);

  return [inlineSize, blockSize] as const;
}