Fix some features not being configurable via features (#10276)

src/settings/controllers/MatrixClientBackedController.ts

@@ -0,0 +1,52 @@
+/*
+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 { MatrixClient } from "matrix-js-sdk/src/client";
+
+import SettingController from "./SettingController";
+
+// Dev note: This whole class exists in the event someone logs out and back in - we want
+// to make sure the right MatrixClient is listening for changes.
+
+/**
+ * Represents the base class for settings controllers which need access to a MatrixClient.
+ * This class performs no logic and should be overridden.
+ */
+export default abstract class MatrixClientBackedController extends SettingController {
+    private static _matrixClient: MatrixClient;
+    private static instances: MatrixClientBackedController[] = [];
+
+    public static set matrixClient(client: MatrixClient) {
+        const oldClient = MatrixClientBackedController._matrixClient;
+        MatrixClientBackedController._matrixClient = client;
+
+        for (const instance of MatrixClientBackedController.instances) {
+            instance.initMatrixClient(oldClient, client);
+        }
+    }
+
+    protected constructor() {
+        super();
+
+        MatrixClientBackedController.instances.push(this);
+    }
+
+    public get client(): MatrixClient {
+        return MatrixClientBackedController._matrixClient;
+    }
+
+    protected abstract initMatrixClient(oldClient: MatrixClient, newClient: MatrixClient): void;
+}