wire up editor component (somewhat hacky)

src/components/structures/MessagePanel.js

@@ -450,9 +450,14 @@ module.exports = React.createClass({
 
     _getTilesForEvent: function(prevEvent, mxEv, last) {
         const EventTile = sdk.getComponent('rooms.EventTile');
+        const MessageEditor = sdk.getComponent('elements.MessageEditor');
         const DateSeparator = sdk.getComponent('messages.DateSeparator');
         const ret = [];
 
+        if (this.props.editEvent && this.props.editEvent.getId() === mxEv.getId()) {
+            return [<MessageEditor key={mxEv.getId()} event={mxEv} />];
+        }
+
         // is this a continuation of the previous message?
         let continuation = false;
 

src/components/structures/TimelinePanel.js

@@ -402,6 +402,9 @@ const TimelinePanel = React.createClass({
         if (payload.action === 'ignore_state_changed') {
             this.forceUpdate();
         }
+        if (payload.action === "edit_event") {
+            this.setState({editEvent: payload.event});
+        }
     },
 
     onRoomTimeline: function(ev, room, toStartOfTimeline, removed, data) {
@@ -1244,6 +1247,7 @@ const TimelinePanel = React.createClass({
                 tileShape={this.props.tileShape}
                 resizeNotifier={this.props.resizeNotifier}
                 getRelationsForEvent={this.getRelationsForEvent}
+                editEvent={this.state.editEvent}
             />
         );
     },

src/components/views/elements/MessageEditor.js

@@ -0,0 +1,56 @@
+/*
+Copyright 2019 New Vector Ltd
+
+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.
+*/
+import React from 'react';
+import sdk from '../../../index';
+import {_t} from '../../../languageHandler';
+import PropTypes from 'prop-types';
+import dis from '../../../dispatcher';
+import {MatrixEvent, MatrixClient} from 'matrix-js-sdk';
+
+export default class MessageEditor extends React.Component {
+    static propTypes = {
+        // the latest event in this chain of replies
+        event: PropTypes.instanceOf(MatrixEvent).isRequired,
+        // called when the ReplyThread contents has changed, including EventTiles thereof
+        // onHeightChanged: PropTypes.func.isRequired,
+    };
+
+    static contextTypes = {
+        matrixClient: PropTypes.instanceOf(MatrixClient).isRequired,
+    };
+
+    constructor(props, context) {
+        super(props, context);
+        this.state = {};
+        this._onCancelClicked = this._onCancelClicked.bind(this);
+    }
+
+    _onCancelClicked() {
+        dis.dispatch({action: "edit_event", event: null});
+    }
+
+    render() {
+        const AccessibleButton = sdk.getComponent('elements.AccessibleButton');
+        return <div className="mx_MessageEditor">
+                <div className="editor" contentEditable="true">
+                    {this.props.event.getContent().body}
+                </div>
+                <div className="buttons">
+                    <AccessibleButton onClick={this._onCancelClicked}>{_t("Cancel")}</AccessibleButton>
+                </div>
+            </div>;
+    }
+}

src/components/views/messages/MessageActionBar.js

@@ -58,6 +58,13 @@ export default class MessageActionBar extends React.PureComponent {
         });
     }
 
+    onEditClick = (ev) => {
+        dis.dispatch({
+            action: 'edit_event',
+            event: this.props.mxEvent,
+        });
+    }
+
     onOptionsClick = (ev) => {
         const MessageContextMenu = sdk.getComponent('context_menus.MessageContextMenu');
         const buttonRect = ev.target.getBoundingClientRect();
@@ -128,6 +135,7 @@ export default class MessageActionBar extends React.PureComponent {
         let agreeDimensionReactionButtons;
         let likeDimensionReactionButtons;
         let replyButton;
+        let editButton;
 
         if (isContentActionable(this.props.mxEvent)) {
             agreeDimensionReactionButtons = this.renderAgreeDimension();
@@ -136,12 +144,17 @@ export default class MessageActionBar extends React.PureComponent {
                 title={_t("Reply")}
                 onClick={this.onReplyClick}
             />;
+            editButton = <span className="mx_MessageActionBar_maskButton mx_MessageActionBar_editButton"
+                title={_t("Edit")}
+                onClick={this.onEditClick}
+            />;
         }
 
         return <div className="mx_MessageActionBar">
             {agreeDimensionReactionButtons}
             {likeDimensionReactionButtons}
             {replyButton}
+            {editButton}
             <span className="mx_MessageActionBar_maskButton mx_MessageActionBar_optionsButton"
                 title={_t("Options")}
                 onClick={this.onOptionsClick}