refac: use resize observer instead mutation observer in order to resize iframe

frontend/apps/remark42/app/components/auth/auth.hooks.ts

@@ -76,11 +76,11 @@ export function useDropdown(disableClosing?: boolean) {
 
     handleChangeIframeSize(dropdownElement);
 
-    const observer = new MutationObserver(() => {
+    const observer = new ResizeObserver(() => {
       handleChangeIframeSize(dropdownElement);
     });
 
-    observer.observe(dropdownElement, { attributes: true, childList: true, subtree: true });
+    observer.observe(dropdownElement);
 
     return () => {
       document.body.style.removeProperty('min-height');

frontend/apps/remark42/app/components/comment-form/comment-form.tsx

@@ -19,7 +19,6 @@ import { SubscribeByRSS } from './__subscribe-by-rss';
 import { MarkdownToolbar } from './markdown-toolbar';
 import { TextExpander } from './text-expander';
 import { updatePersistedComments, getPersistedComment, removePersistedComment } from './comment-form.persist';
-import { updateIframeHeight } from 'utils/post-message';
 
 export type Props = {
   id: string;
@@ -453,7 +452,6 @@ export class CommentForm extends Component<Props, State> {
               disabled={isDisabled}
               autofocus={!!autofocus}
               spellcheck={true}
-              onResize={updateIframeHeight}
             />
           </TextExpander>
           {charactersLeft < 100 && <span className="comment-form__counter">{charactersLeft}</span>}

frontend/apps/remark42/app/components/root/root.tsx

@@ -1,5 +1,5 @@
 import { h, Component, Fragment } from 'preact';
-import { useEffect, useRef } from 'preact/hooks';
+import { useEffect } from 'preact/hooks';
 import { useSelector } from 'react-redux';
 import b from 'bem-react-helper';
 import { IntlShape, useIntl, FormattedMessage, defineMessages } from 'react-intl';
@@ -36,12 +36,19 @@ import { ConnectedComment as Comment } from 'components/comment/connected-commen
 import { uploadImage, getPreview } from 'common/api';
 import { isUserAnonymous } from 'utils/isUserAnonymous';
 import { bindActions } from 'utils/actionBinder';
-import { postMessageToParent, parseMessage, updateIframeHeight } from 'utils/post-message';
+import { postMessageToParent, parseMessage } from 'utils/post-message';
 import { useActions } from 'hooks/useAction';
 import { setCollapse } from 'store/thread/actions';
 
 import styles from './root.module.css';
 
+/**
+ * Sends size of the iframe to parent window
+ */
+export function updateIframeHeight() {
+  postMessageToParent({ height: document.body.offsetHeight });
+}
+
 const mapStateToProps = (state: StoreState) => ({
   sort: state.comments.sort,
   isCommentsLoading: state.comments.isFetching,
@@ -294,33 +301,12 @@ interface CommentsProps {
   showMore(): void;
 }
 function Comments({ isLoading, topComments, commentsShown, showMore }: CommentsProps) {
-  const rootRef = useRef<HTMLDivElement>(null);
-
-  useEffect(() => {
-    if (!rootRef.current) {
-      return;
-    }
-
-    updateIframeHeight();
-    // TODO: throttle updates
-    const observer = new MutationObserver(() => {
-      // a hacky way to force iframe height update when new image is rendered and loaded
-      rootRef.current?.querySelectorAll('img').forEach((img) => {
-        img.addEventListener('load', updateIframeHeight);
-      });
-    });
-
-    observer.observe(rootRef.current, { attributes: true, childList: true, subtree: true });
-
-    return () => observer.disconnect();
-  }, []);
-
   const renderComments =
     IS_MOBILE && commentsShown < topComments.length ? topComments.slice(0, commentsShown) : topComments;
   const isShowMoreButtonVisible = IS_MOBILE && commentsShown < topComments.length;
 
   return (
-    <div className="root__threads" role="list" ref={rootRef}>
+    <div className="root__threads" role="list">
       {isLoading ? (
         <Preloader className="root__preloader" />
       ) : (
@@ -358,6 +344,14 @@ export function ConnectedRoot() {
   const props = useSelector(mapStateToProps);
   const actions = useActions(boundActions);
 
+  useEffect(() => {
+    const observer = new ResizeObserver(updateIframeHeight);
+
+    updateIframeHeight();
+    observer.observe(document.body);
+    return () => observer.disconnect();
+  }, []);
+
   if (!window.remark_config) {
     throw new Error('Remark42: Config object is undefined');
   }

frontend/apps/remark42/app/components/textarea-autosize.tsx

@@ -5,40 +5,33 @@ import { useEffect, useRef } from 'preact/hooks';
 function autoResize(textarea: HTMLTextAreaElement, onResize?: () => void) {
   textarea.style.height = '';
   textarea.style.height = `${textarea.scrollHeight}px`;
-  // Call on rezie callback after textarea height is changed
-  if (onResize) {
-    window.requestAnimationFrame(onResize);
-  }
 }
 
 type Props = Omit<JSX.HTMLAttributes<HTMLTextAreaElement>, 'onInput'> & {
   onInput?(evt: JSX.TargetedEvent<HTMLTextAreaElement, Event>): void;
-  onResize?(): void;
 };
 
-export const TextareaAutosize = forwardRef<HTMLTextAreaElement, Props>(
-  ({ onInput, value, onResize, ...props }, externalRef) => {
-    const localRef = useRef<HTMLTextAreaElement>(null);
-    const ref = externalRef || localRef;
+export const TextareaAutosize = forwardRef<HTMLTextAreaElement, Props>(({ onInput, value, ...props }, externalRef) => {
+  const localRef = useRef<HTMLTextAreaElement>(null);
+  const ref = externalRef || localRef;
 
-    const handleInput: JSX.GenericEventHandler<HTMLTextAreaElement> = (evt) => {
-      if (!ref.current) {
-        return;
-      }
+  const handleInput: JSX.GenericEventHandler<HTMLTextAreaElement> = (evt) => {
+    if (!ref.current) {
+      return;
+    }
 
-      if (onInput) {
-        return onInput(evt);
-      }
+    if (onInput) {
+      return onInput(evt);
+    }
 
-      autoResize(ref.current, onResize);
-    };
+    autoResize(ref.current);
+  };
 
-    useEffect(() => {
-      if (ref.current) {
-        autoResize(ref.current, onResize);
-      }
-    }, [onResize, value, ref]);
+  useEffect(() => {
+    if (ref.current) {
+      autoResize(ref.current);
+    }
+  }, [value, ref]);
 
-    return <textarea {...props} data-testid={props.id} onInput={handleInput} value={value} ref={ref} />;
-  }
-);
+  return <textarea {...props} data-testid={props.id} onInput={handleInput} value={value} ref={ref} />;
+});

frontend/apps/remark42/app/utils/post-message.ts

@@ -61,10 +61,3 @@ export function parseMessage({ data }: MessageEvent): AllMessages {
 
   return data as AllMessages;
 }
-
-/**
- * Sends size of the iframe to parent window
- */
-export function updateIframeHeight() {
-  postMessageToParent({ height: document.body.offsetHeight });
-}