Emit events from DeviceListenerCurrentDevice instead of delegating to DeviceListener (#32451)

* Emit events from DeviceListenerCurrentDevice instead of delegating to DeviceListener

* Make CurrentDeviceEvents a const enum

* Break out event emitting into its own class so the instance can be persistent

src/components/views/settings/tabs/user/EncryptionUserSettingsTab.tsx

@@ -24,7 +24,7 @@ import { RecoveryPanelOutOfSync } from "../../encryption/RecoveryPanelOutOfSync"
 import { useTypedEventEmitterState } from "../../../../../hooks/useEventEmitter";
 import { KeyStoragePanel } from "../../encryption/KeyStoragePanel";
 import { DeleteKeyStoragePanel } from "../../encryption/DeleteKeyStoragePanel";
-import { DeviceListener, DeviceListenerEvents, type DeviceState } from "../../../../../device-listener";
+import { DeviceListener, CurrentDeviceEvents, type DeviceState } from "../../../../../device-listener";
 import { useKeyStoragePanelViewModel } from "../../../../viewmodels/settings/encryption/KeyStoragePanelViewModel";
 
 /**
@@ -64,8 +64,8 @@ export function EncryptionUserSettingsTab({ initialState = "main" }: Readonly<Pr
     const [state, setState] = useState<State>(initialState);
 
     const deviceState = useTypedEventEmitterState(
-        DeviceListener.sharedInstance(),
+        DeviceListener.sharedInstance().currentDeviceChangedEmitter,
-        DeviceListenerEvents.DeviceState,
+        CurrentDeviceEvents.DeviceStateChanged,
         (state?: DeviceState): DeviceState => {
             return state ?? DeviceListener.sharedInstance().getDeviceState();
         },

src/device-listener/CurrentDeviceChangedEmitter.ts

@@ -0,0 +1,36 @@
+/*
+Copyright 2026 Element Creations Ltd.
+
+SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only OR LicenseRef-Element-Commercial
+Please see LICENSE files in the repository root for full details.
+*/
+
+import { TypedEventEmitter } from "matrix-js-sdk/src/matrix";
+
+import { type DeviceState } from ".";
+
+/**
+ * The events emitted when the {@link DeviceState} of the current device
+ * changes.
+ */
+export const enum CurrentDeviceEvents {
+    DeviceStateChanged = "device_state",
+}
+
+/**
+ * You must provide one of these if you listen to {@link CurrentDeviceEvents}
+ * emitted by {@link DeviceListenerCurrentDevice}. It specifies how to handle
+ * each type of event.
+ */
+type EventHandlerMap = {
+    [CurrentDeviceEvents.DeviceStateChanged]: (state: DeviceState) => void;
+};
+
+/**
+ * Emits events when the current device changes state.
+ */
+export class CurrentDeviceChangedEmitter extends TypedEventEmitter<CurrentDeviceEvents, EventHandlerMap> {
+    public onStateChanged(newState: DeviceState): void {
+        this.emit(CurrentDeviceEvents.DeviceStateChanged, newState);
+    }
+}

src/device-listener/DeviceListener.ts

@@ -7,7 +7,7 @@ SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only OR LicenseRef-Element-Com
 Please see LICENSE files in the repository root for full details.
 */
 
-import { type MatrixClient, ClientStoppedError, TypedEventEmitter } from "matrix-js-sdk/src/matrix";
+import { type MatrixClient, ClientStoppedError } from "matrix-js-sdk/src/matrix";
 import { logger as baseLogger, LogSpan } from "matrix-js-sdk/src/logger";
 import { type CryptoSessionStateChange } from "@matrix-org/analytics-events/types/typescript/CryptoSessionStateChange";
 import { secureRandomString } from "matrix-js-sdk/src/randomstring";
@@ -20,22 +20,16 @@ import SdkConfig from "../SdkConfig";
 import PlatformPeg from "../PlatformPeg";
 import { recordClientInformation, removeClientInformation } from "../utils/device/clientInformation";
 import SettingsStore, { type CallbackFn } from "../settings/SettingsStore";
-import { DeviceListenerOtherDevices, DeviceListenerCurrentDevice, type DeviceState } from ".";
+import {
+    DeviceListenerOtherDevices,
+    DeviceListenerCurrentDevice,
+    type DeviceState,
+    CurrentDeviceChangedEmitter,
+} from ".";
 
 const logger = baseLogger.getChild("DeviceListener:");
 
-/**
+export class DeviceListener {
- * The events emitted by {@link DeviceListener}
- */
-export enum DeviceListenerEvents {
-    DeviceState = "device_state",
-}
-
-type EventHandlerMap = {
-    [DeviceListenerEvents.DeviceState]: (state: DeviceState) => void;
-};
-
-export class DeviceListener extends TypedEventEmitter<DeviceListenerEvents, EventHandlerMap> {
     private dispatcherRef?: string;
 
     /**
@@ -44,11 +38,34 @@ export class DeviceListener extends TypedEventEmitter<DeviceListenerEvents, Even
      */
     public otherDevices?: DeviceListenerOtherDevices;
 
-    /** All the information about whether this device's encrypytion is OK. Only
+    /**
-     * set if `running` is true, otherwise undefined.
+     * All the information about whether this device's encrypytion is OK.
+     *
+     * Defined after {@link DeviceListener.start} has been called, before {@link
+     * DeviceListener.stop} is called.
      */
     public currentDevice?: DeviceListenerCurrentDevice;
 
+    /**
+     * Emits `CurrentDeviceEvents` events when the state
+     * of the current device changes.
+     *
+     * @example
+     * ```ts
+     * const deviceState = useTypedEventEmitterState(
+     *     DeviceListener.sharedInstance().currentDeviceChangedEmitter,
+     *     CurrentDeviceEvents.DeviceStateChanged,
+     *     (state?: DeviceState): DeviceState => {
+     *         return state ?? DeviceListener.sharedInstance().getDeviceState();
+     *     },
+     * );
+     * ```
+     *
+     * Now `deviceState` will reflect the state of the current device and
+     * trigger an update when it changes.
+     */
+    public currentDeviceChangedEmitter = new CurrentDeviceChangedEmitter();
+
     private running = false;
     // The client with which the instance is running. Only set if `running` is true, otherwise undefined.
     private client?: MatrixClient;

src/device-listener/DeviceListenerCurrentDevice.ts

@@ -18,7 +18,7 @@ import {
     ClientEvent,
 } from "matrix-js-sdk/src/matrix";
 
-import { type DeviceListener, type DeviceState, DeviceListenerEvents } from ".";
+import { type DeviceListener, type DeviceState } from ".";
 import {
     hideToast as hideSetupEncryptionToast,
     showToast as showSetupEncryptionToast,
@@ -263,7 +263,7 @@ export class DeviceListenerCurrentDevice {
     private async setDeviceState(newState: DeviceState, logSpan: LogSpan): Promise<void> {
         this.deviceState = newState;
 
-        this.deviceListener.emit(DeviceListenerEvents.DeviceState, newState);
+        this.deviceListener.currentDeviceChangedEmitter.onStateChanged(newState);
 
         if (newState === "ok" || this.dismissedThisDeviceToast) {
             hideSetupEncryptionToast();

src/device-listener/index.ts

@@ -5,6 +5,7 @@ SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only OR LicenseRef-Element-Com
 Please see LICENSE files in the repository root for full details.
 */
 
+export * from "./CurrentDeviceChangedEmitter";
 export * from "./DeviceListener";
 export * from "./DeviceListenerCurrentDevice";
 export * from "./DeviceListenerOtherDevices";