Abstract electron settings properly to avoid boilerplate-hell (#22491)

* Remove unused method `BasePlatform::screenCaptureErrorString`

* Extract SeshatIndexManager into its own file

* Improve platform typescripting

* Consolidate IPC call promisification into IPCManager

* Abstract electron settings properly to avoid boilerplate-hell

* i18n

* Iterate PR

src/vector/platform/IPCManager.ts

@@ -0,0 +1,70 @@
+/*
+Copyright 2022 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 { defer, IDeferred } from 'matrix-js-sdk/src/utils';
+import { logger } from "matrix-js-sdk/src/logger";
+
+import { ElectronChannel } from "../../@types/global";
+
+const electron = window.electron;
+
+interface IPCPayload {
+    id?: number;
+    error?: string;
+    reply?: any;
+}
+
+export class IPCManager {
+    private pendingIpcCalls: { [ipcCallId: number]: IDeferred<any> } = {};
+    private nextIpcCallId = 0;
+
+    public constructor(
+        private readonly sendChannel: ElectronChannel = "ipcCall",
+        private readonly recvChannel: ElectronChannel = "ipcReply",
+    ) {
+        electron.on(this.recvChannel, this.onIpcReply);
+    }
+
+    public async call(name: string, ...args: any[]): Promise<any> {
+        // TODO this should be moved into the preload.js file.
+        const ipcCallId = ++this.nextIpcCallId;
+        const deferred = defer<any>();
+        this.pendingIpcCalls[ipcCallId] = deferred;
+        // Maybe add a timeout to these? Probably not necessary.
+        window.electron.send(this.sendChannel, { id: ipcCallId, name, args });
+        return deferred.promise;
+    }
+
+    private onIpcReply = (ev: {}, payload: IPCPayload): void => {
+        if (payload.id === undefined) {
+            logger.warn("Ignoring IPC reply with no ID");
+            return;
+        }
+
+        if (this.pendingIpcCalls[payload.id] === undefined) {
+            logger.warn("Unknown IPC payload ID: " + payload.id);
+            return;
+        }
+
+        const callbacks = this.pendingIpcCalls[payload.id];
+        delete this.pendingIpcCalls[payload.id];
+        if (payload.error) {
+            callbacks.reject(payload.error);
+        } else {
+            callbacks.resolve(payload.reply);
+        }
+    };
+}