@rc-component/resize-observer/es/useResizeObserver.js

Resize observer for React

import * as React from 'react';
import { observe, unobserve } from "./utils/observerUtil";
import { useEvent } from '@rc-component/util';
export default function useResizeObserver(enabled, getTarget, onDelayResize, onSyncResize) {
  // ============================= Size =============================
  const sizeRef = React.useRef({
    width: -1,
    height: -1,
    offsetWidth: -1,
    offsetHeight: -1
  });

  // =========================== Observe ============================

  // Handler
  const onInternalResize = useEvent(target => {
    const {
      width,
      height
    } = target.getBoundingClientRect();
    const {
      offsetWidth,
      offsetHeight
    } = target;

    /**
     * Resize observer trigger when content size changed.
     * In most case we just care about element size,
     * let's use `boundary` instead of `contentRect` here to avoid shaking.
     */
    const fixedWidth = Math.floor(width);
    const fixedHeight = Math.floor(height);
    if (sizeRef.current.width !== fixedWidth || sizeRef.current.height !== fixedHeight || sizeRef.current.offsetWidth !== offsetWidth || sizeRef.current.offsetHeight !== offsetHeight) {
      const size = {
        width: fixedWidth,
        height: fixedHeight,
        offsetWidth,
        offsetHeight
      };
      sizeRef.current = size;

      // IE is strange, right?
      const mergedOffsetWidth = offsetWidth === Math.round(width) ? width : offsetWidth;
      const mergedOffsetHeight = offsetHeight === Math.round(height) ? height : offsetHeight;
      const sizeInfo = {
        ...size,
        offsetWidth: mergedOffsetWidth,
        offsetHeight: mergedOffsetHeight
      };

      // Call the callback immediately, let the caller decide whether to defer
      // onResize(sizeInfo, target);
      onSyncResize?.(sizeInfo, target);

      // defer the callback but not defer to next frame
      Promise.resolve().then(() => {
        onDelayResize?.(sizeInfo, target);
      });
    }
  });

  // Dynamic observe
  const isFuncTarget = typeof getTarget === 'function';
  const funcTargetIdRef = React.useRef(0);
  React.useEffect(() => {
    const target = isFuncTarget ? getTarget() : getTarget;
    if (target && enabled) {
      observe(target, onInternalResize);
    } else if (enabled && isFuncTarget) {
      funcTargetIdRef.current += 1;
    }
    return () => {
      if (target) {
        unobserve(target, onInternalResize);
      }
    };
  }, [enabled,
  // If function target resolves after a parent render, the bumped ref value
  // lets the next render re-run this effect without watching the function identity.
  isFuncTarget ? funcTargetIdRef.current : getTarget]);
}