Issue #237 - Do not call onResize during setSize updater function in createNotifier

src/ResizeDetector.tsx

@@ -1,4 +1,12 @@
-import React, { PureComponent, isValidElement, cloneElement, createRef, ReactNode, ReactElement } from 'react';
+import React, {
+  PureComponent,
+  isValidElement,
+  cloneElement,
+  createRef,
+  ReactNode,
+  ReactElement,
+  MutableRefObject
+} from 'react';
 import { findDOMNode } from 'react-dom';
 
 import { patchResizeHandler, isFunction, isSSR, isDOMElement, createNotifier } from './utils';
@@ -13,6 +21,11 @@ class ResizeDetector<ElementT extends HTMLElement = HTMLElement> extends PureCom
   observableElement;
   resizeHandler;
   resizeObserver;
+  /**
+   * To access the current size in the ResizeObserver without having to recreate it each time size updates.
+   */
+  private readonly sizeRef: MutableRefObject<ReactResizeDetectorDimensions>;
+
   constructor(props: ResizeDetectorProps<ElementT>) {
     super(props);
 
@@ -22,6 +35,9 @@ class ResizeDetector<ElementT extends HTMLElement = HTMLElement> extends PureCom
       width: undefined,
       height: undefined
     };
+    this.sizeRef = {
+      current: this.state
+    };
 
     this.skipOnMount = skipOnMount;
     this.targetRef = createRef();
@@ -41,6 +57,7 @@ class ResizeDetector<ElementT extends HTMLElement = HTMLElement> extends PureCom
 
   componentDidUpdate(): void {
     this.attachObserver();
+    this.sizeRef.current = this.state;
   }
 
   componentWillUnmount(): void {
@@ -124,11 +141,7 @@ class ResizeDetector<ElementT extends HTMLElement = HTMLElement> extends PureCom
 
     if (!handleWidth && !handleHeight) return;
 
-    const notifyResize = createNotifier(
-      setStateFunc => this.setState(setStateFunc, () => onResize?.(this.state.width, this.state.height)),
-      handleWidth,
-      handleHeight
-    );
+    const notifyResize = createNotifier(onResize, this.sizeRef, this.setState.bind(this), handleWidth, handleHeight);
 
     entries.forEach(entry => {
       const { width, height } = (entry && entry.contentRect) || {};

src/useResizeDetector.ts

@@ -45,9 +45,13 @@ function useResizeDetector<T extends HTMLElement = any>({
 
   // this is a callback that will be called every time the ref is changed
   // we call setState inside to trigger rerender
+
   const onRefChange: OnRefChangeType = useCallback((node: T | null) => {
-    setRefElement(node);
-  }, []);
+    if (node !== refElement) {
+      setRefElement(node);
+    }
+  }, [refElement]);
+
   // adding `current` to make it compatible with useRef shape
   onRefChange.current = refElement;
 
@@ -60,6 +64,12 @@ function useResizeDetector<T extends HTMLElement = any>({
     };
   }, []);
 
+  /**
+   * To access the current size in the ResizeObserver without having to recreate it each time size updates.
+   */
+  const sizeRef = useRef(size);
+  sizeRef.current = size;
+
   useEffect(() => {
     if (!handleWidth && !handleHeight) return;
 
@@ -68,7 +78,7 @@ function useResizeDetector<T extends HTMLElement = any>({
       return;
     }
 
-    const notifyResize = createNotifier(setSize, handleWidth, handleHeight);
+    const notifyResize = createNotifier(onResize, sizeRef, setSize, handleWidth, handleHeight);
 
     const resizeCallback: ResizeObserverCallback = (entries: ResizeObserverEntry[]) => {
       if (!handleWidth && !handleHeight) return;
@@ -96,11 +106,7 @@ function useResizeDetector<T extends HTMLElement = any>({
       resizeObserver.disconnect();
       (resizeHandler.current as DebouncedFunc<ResizeObserverCallback>).cancel?.();
     };
-  }, [refreshMode, refreshRate, refreshOptions, handleWidth, handleHeight, observerOptions, refElement]);
-
-  useEffect(() => {
-    onResize?.(size.width, size.height);
-  }, [size]);
+  }, [refreshMode, refreshRate, refreshOptions, handleWidth, handleHeight, observerOptions, onResize, refElement]);
 
   return { ref: onRefChange, ...size };
 }

src/utils.ts

@@ -31,22 +31,27 @@ export const isDOMElement = (element: unknown): boolean =>
 
 export const createNotifier =
   (
+    onResize: Props['onResize'],
+    sizeRef: Readonly<React.MutableRefObject<ReactResizeDetectorDimensions>>,
     setSize: React.Dispatch<React.SetStateAction<ReactResizeDetectorDimensions>>,
     handleWidth: boolean,
     handleHeight: boolean
   ) =>
   ({ width, height }: ReactResizeDetectorDimensions): void => {
-    setSize(prev => {
-      if (prev.width === width && prev.height === height) {
-        // skip if dimensions haven't changed
-        return prev;
-      }
-
-      if ((prev.width === width && !handleHeight) || (prev.height === height && !handleWidth)) {
-        // process `handleHeight/handleWidth` props
-        return prev;
-      }
-
-      return { width, height };
-    });
+    const { current: prev } = sizeRef;
+
+    if (prev.width === width && prev.height === height) {
+      // skip if dimensions haven't changed
+      return;
+    }
+
+    if ((prev.width === width && !handleHeight) || (prev.height === height && !handleWidth)) {
+      // process `handleHeight/handleWidth` props
+      return;
+    }
+
+    onResize?.(width, height);
+
+    const newSize = { width, height };
+    setSize(newSize);
   };