Include thread replies in message previews (#10631)

* Include thread replies to message previews

* Extend tests

* Fix type issue

* Use currentColor for thread icon

* Fix long room name overflow

* Update snapshots

* Fix preview

* Fix typing issue

* Fix type issues

* Tweak thread reply detection

* Extend tests

* Fix type issue

* Fix test

src/components/views/rooms/RoomTileSubtitle.tsx

@@ -0,0 +1,71 @@
+/*
+Copyright 2023 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.
+*/
+
+import React from "react";
+import classNames from "classnames";
+
+import { MessagePreview } from "../../../stores/room-list/MessagePreviewStore";
+import { Call } from "../../../models/Call";
+import { RoomTileCallSummary } from "./RoomTileCallSummary";
+import { VoiceBroadcastRoomSubtitle } from "../../../voice-broadcast";
+import { Icon as ThreadIcon } from "../../../../res/img/compound/thread-16px.svg";
+
+interface Props {
+    call: Call | null;
+    hasLiveVoiceBroadcast: boolean;
+    messagePreview: MessagePreview | null;
+    roomId: string;
+    showMessagePreview: boolean;
+}
+
+const messagePreviewId = (roomId: string): string => `mx_RoomTile_messagePreview_${roomId}`;
+
+export const RoomTileSubtitle: React.FC<Props> = ({
+    call,
+    hasLiveVoiceBroadcast,
+    messagePreview,
+    roomId,
+    showMessagePreview,
+}) => {
+    if (call) {
+        return (
+            <div className="mx_RoomTile_subtitle">
+                <RoomTileCallSummary call={call} />
+            </div>
+        );
+    }
+
+    if (hasLiveVoiceBroadcast) {
+        return <VoiceBroadcastRoomSubtitle />;
+    }
+
+    if (showMessagePreview && messagePreview) {
+        const className = classNames("mx_RoomTile_subtitle", {
+            "mx_RoomTile_subtitle--thread-reply": messagePreview.isThreadReply,
+        });
+
+        const icon = messagePreview.isThreadReply ? <ThreadIcon className="mx_Icon mx_Icon_16" /> : null;
+
+        return (
+            <div className={className} id={messagePreviewId(roomId)} title={messagePreview.text}>
+                {icon}
+                <span className="mx_RoomTile_subtitle_text">{messagePreview.text}</span>
+            </div>
+        );
+    }
+
+    return null;
+};