Keep content when switching between rich text and plain text mode

src/components/views/rooms/MessageComposer.tsx

@@ -60,6 +60,7 @@ import {
 } from '../../../voice-broadcast';
 import { SendWysiwygComposer, sendMessage } from './wysiwyg_composer/';
 import { MatrixClientProps, withMatrixClientHOC } from '../../../contexts/MatrixClientContext';
+import { htmlToPlainText } from '../../../utils/room/htmlToPlaintext';
 
 let instanceCount = 0;
 
@@ -102,6 +103,7 @@ interface IState {
     showVoiceBroadcastButton: boolean;
     isWysiwygLabEnabled: boolean;
     isRichTextEnabled: boolean;
+    initialComposerContent: string;
 }
 
 export class MessageComposer extends React.Component<IProps, IState> {
@@ -138,6 +140,7 @@ export class MessageComposer extends React.Component<IProps, IState> {
             showVoiceBroadcastButton: SettingsStore.getValue(Features.VoiceBroadcast),
             isWysiwygLabEnabled: SettingsStore.getValue<boolean>("feature_wysiwyg_composer"),
             isRichTextEnabled: true,
+            initialComposerContent: '',
         };
 
         this.instanceId = instanceCount++;
@@ -355,6 +358,10 @@ export class MessageComposer extends React.Component<IProps, IState> {
     private onRichTextToggle = () => {
         this.setState(state => ({
             isRichTextEnabled: !state.isRichTextEnabled,
+            initialComposerContent: !state.isRichTextEnabled ?
+                state.composerContent :
+                // TODO when available use rust model plain text
+                htmlToPlainText(state.composerContent),
         }));
     };
 
@@ -434,6 +441,7 @@ export class MessageComposer extends React.Component<IProps, IState> {
                         onChange={this.onWysiwygChange}
                         onSend={this.sendMessage}
                         isRichTextEnabled={this.state.isRichTextEnabled}
+                        initialContent={this.state.initialComposerContent}
                     />,
                 );
             } else {

src/components/views/rooms/wysiwyg_composer/SendWysiwygComposer.tsx

@@ -34,6 +34,7 @@ const Content = forwardRef<HTMLElement, ContentProps>(
 );
 
 interface SendWysiwygComposerProps {
+    initialContent: string;
     isRichTextEnabled: boolean;
     disabled?: boolean;
     onChange: (content: string) => void;

src/components/views/rooms/wysiwyg_composer/components/PlainTextComposer.tsx

@@ -14,11 +14,11 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import React, { MutableRefObject, ReactNode } from 'react';
+import React, { MutableRefObject, ReactNode, useEffect } from 'react';
+
 import { useComposerFunctions } from '../hooks/useComposerFunctions';
 import { usePlainTextListeners } from '../hooks/usePlainTextListeners';
 import { ComposerFunctions } from '../types';
-
 import { Editor } from "./Editor";
 
 interface PlainTextComposerProps {
@@ -33,12 +33,20 @@ interface PlainTextComposerProps {
     ) => ReactNode;
 }
 
-export function PlainTextComposer({ className, disabled, onSend, onChange, children }: PlainTextComposerProps) {
+export function PlainTextComposer({
-   const {ref, onInput, onPaste, onKeyDown} = usePlainTextListeners(onChange, onSend)
+    className, disabled, onSend, onChange, children, initialContent }: PlainTextComposerProps,
-   const composerFunctions = useComposerFunctions(ref)
+) {
+    const { ref, onInput, onPaste, onKeyDown } = usePlainTextListeners(onChange, onSend);
+    const composerFunctions = useComposerFunctions(ref);
+
+    useEffect(() => {
+        if (ref.current) {
+            ref.current.innerText = initialContent;
+        }
+    }, [ref, initialContent]);
 
     return <div className={className} onInput={onInput} onPaste={onPaste} onKeyDown={onKeyDown}>
         <Editor ref={ref} disabled={disabled} />
-        {children?.(ref, composerFunctions)}
+        { children?.(ref, composerFunctions) }
     </div>;
 }

src/components/views/rooms/wysiwyg_composer/utils/createMessageContent.ts

@@ -20,6 +20,7 @@ import { htmlSerializeFromMdIfNeeded } from "../../../../../editor/serialize";
 import SettingsStore from "../../../../../settings/SettingsStore";
 import { RoomPermalinkCreator } from "../../../../../utils/permalinks/Permalinks";
 import { addReplyToMessageContent } from "../../../../../utils/Reply";
+import { htmlToPlainText } from "../../../../../utils/room/htmlToPlaintext";
 
 // Merges favouring the given relation
 function attachRelation(content: IContent, relation?: IEventRelation): void {
@@ -50,10 +51,6 @@ function getTextReplyFallback(mxEvent: MatrixEvent): string {
     return "";
 }
 
-function htmlToPlainText(html: string) {
-    return new DOMParser().parseFromString(html, 'text/html').documentElement.textContent;
-}
-
 interface CreateMessageContentParams {
     relation?: IEventRelation;
     replyToEvent?: MatrixEvent;

src/utils/room/htmlToPlaintext.ts

@@ -0,0 +1,19 @@
+/*
+Copyright 2022 The Matrix.org Foundation C.I.C.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+export function htmlToPlainText(html: string) {
+    return new DOMParser().parseFromString(html, 'text/html').documentElement.textContent;
+}