Add filter results count and explore prompt

src/components/views/rooms/RoomListNumResults.tsx

@@ -0,0 +1,41 @@
+/*
+Copyright 2020 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, {useState} from "react";
+
+import { _t } from "../../../languageHandler";
+import RoomListStore, { LISTS_UPDATE_EVENT } from "../../../stores/room-list/RoomListStore";
+import {useEventEmitter} from "../../../hooks/useEventEmitter";
+
+const RoomListNumResults: React.FC = () => {
+    const [count, setCount] = useState<number>(null);
+    useEventEmitter(RoomListStore.instance, LISTS_UPDATE_EVENT, () => {
+        if (RoomListStore.instance.getFirstNameFilterCondition()) {
+            const numRooms = Object.values(RoomListStore.instance.orderedLists).flat(1).length;
+            setCount(numRooms);
+        } else {
+            setCount(null);
+        }
+    });
+
+    if (typeof count !== "number") return null;
+
+    return <div className="mx_LeftPanel_roomListFilterCount">
+        {_t("%(count)s results", { count })}
+    </div>;
+};
+
+export default RoomListNumResults;