Return the widget from initializeWidget instead of assigning a global

Element Call reached the widget API through a mutable module-level
binding, which every consumer imported directly. Nothing outside the app
shell needs it any more, so hand it back from initializeWidget and thread
it through: the initializer returns it, main passes it to App, and App
uses it to build the host bridge and to await the client the host is
lending us.

ClientContext's loadClient is now only about restoring or creating a
session of Element Call's own, since a widget's client arrives as a prop
like any other host's would.

Also fixes an early return added in the previous commit, which skipped
starting the analytics settings listener when a client was supplied. That
was harmless until now, but would have stopped analytics following the
user's choices in widget mode.

sdk/main.ts asked the host to close by hand; it now uses the bridge, which
also stops the transport as the app does.

sdk/main.ts

@@ -54,11 +54,7 @@ import { MediaDevices } from "../src/state/MediaDevices";
 import { E2eeType } from "../src/e2ee/e2eeType";
 import { currentAndPrev, TEXT_LK_TOPIC, tryMakeSticky } from "./helper";
 import { logger as rootLogger } from "matrix-js-sdk/lib/logger";
-import {
-  ElementWidgetActions,
-  widget as _widget,
-  initializeWidget,
-} from "../src/widget";
+import { initializeWidget } from "../src/widget";
 import { type Connection } from "../src/state/CallViewModel/remoteMembers/Connection";
 import { createWidgetHostBridge } from "../src/HostBridge";
 
@@ -110,8 +106,7 @@ export async function createMatrixRTCSdk(
   const scope = new ObservableScope();
 
   // widget client
-  initializeWidget(application, true);
-  const widget = _widget;
+  const widget = initializeWidget(application, true);
   if (!widget) throw Error("No widget. This webapp can only start as a widget");
   const client = await widget.client;
   const hostBridge = createWidgetHostBridge(widget);
@@ -294,18 +289,17 @@ export async function createMatrixRTCSdk(
       });
       await leaveResolver.promise;
       logger.info("send Unstick");
-      await widget.api
+      await hostBridge
         .setAlwaysOnScreen(false)
-        .catch((e) =>
-          logger.error(
-            "Failed to set call widget `alwaysOnScreen` to false",
-            e,
-          ),
+        .catch((e: unknown) =>
+          logger.error("Failed to set `alwaysOnScreen` to false", e),
         );
       logger.info("send Close");
-      await widget.api.transport
-        .send(ElementWidgetActions.Close, {})
-        .catch((e) => logger.error("Failed to send close action", e));
+      await hostBridge
+        .close?.()
+        .catch((e: unknown) =>
+          logger.error("Failed to ask the host to close", e),
+        );
     };
 
     // schedule close first and then leave (scope.end)

src/App.tsx

@@ -10,6 +10,7 @@ import { BrowserRouter, Route, useLocation, Routes } from "react-router-dom";
 import * as Sentry from "@sentry/react";
 import { TooltipProvider } from "@vector-im/compound-web";
 import { logger } from "matrix-js-sdk/lib/logger";
+import { type MatrixClient } from "matrix-js-sdk";
 import { I18nextProvider } from "react-i18next";
 
 import { HomePage } from "./home/HomePage";
@@ -19,7 +20,7 @@ import { RoomPage } from "./room/RoomPage";
 import { ClientProvider } from "./ClientContext";
 import { ErrorPage, LoadingPage } from "./FullScreenView";
 import { Initializer } from "./initializer";
-import { widget } from "./widget";
+import { type WidgetHelpers } from "./widget";
 import { useTheme } from "./useTheme";
 import { ProcessorProvider } from "./livekit/TrackProcessorContext";
 import { type AppViewModel } from "./state/AppViewModel";
@@ -81,9 +82,11 @@ const MaybeAppBar: FC<SimpleProviderProps> = ({ children }) => {
 
 interface Props {
   vm: AppViewModel;
+  /** A point of access to the widget API, if running as a widget. */
+  widget: WidgetHelpers | null;
 }
 
-export const App: FC<Props> = ({ vm }) => {
+export const App: FC<Props> = ({ vm, widget }) => {
   // The standalone build has no host; the widget build's host is the client it
   // is a widget of.
   const hostBridge = useInitial(() =>
@@ -100,26 +103,40 @@ export const App: FC<Props> = ({ vm }) => {
       .catch(logger.error);
   });
 
-  const content = loaded ? (
-    <ClientProvider>
-      <MediaDevicesContext value={vm.mediaDevices}>
-        <ProcessorProvider>
-          <Sentry.ErrorBoundary
-            fallback={(error) => <ErrorPage error={error} />}
-          >
-            <Routes>
-              <SentryRoute path="/" element={<HomePage />} />
-              <SentryRoute path="/login" element={<LoginPage />} />
-              <SentryRoute path="/register" element={<RegisterPage />} />
-              <SentryRoute path="*" element={<RoomPage />} />
-            </Routes>
-          </Sentry.ErrorBoundary>
-        </ProcessorProvider>
-      </MediaDevicesContext>
-    </ClientProvider>
-  ) : (
-    <LoadingPage />
+  // As a widget, the client comes from the host over the widget API. Standalone,
+  // Element Call finds one itself, so there is nothing to wait for here.
+  const [widgetClient, setWidgetClient] = useState<MatrixClient | undefined>(
+    undefined,
   );
+  useEffect(() => {
+    if (widget === null) return;
+    widget.client
+      .then(setWidgetClient)
+      .catch((e) => logger.error("Failed to obtain the host's client", e));
+  }, [widget]);
+  const clientReady = widget === null || widgetClient !== undefined;
+
+  const content =
+    loaded && clientReady ? (
+      <ClientProvider client={widgetClient}>
+        <MediaDevicesContext value={vm.mediaDevices}>
+          <ProcessorProvider>
+            <Sentry.ErrorBoundary
+              fallback={(error) => <ErrorPage error={error} />}
+            >
+              <Routes>
+                <SentryRoute path="/" element={<HomePage />} />
+                <SentryRoute path="/login" element={<LoginPage />} />
+                <SentryRoute path="/register" element={<RegisterPage />} />
+                <SentryRoute path="*" element={<RoomPage />} />
+              </Routes>
+            </Sentry.ErrorBoundary>
+          </ProcessorProvider>
+        </MediaDevicesContext>
+      </ClientProvider>
+    ) : (
+      <LoadingPage />
+    );
 
   return (
     <I18nextProvider i18n={i18n}>

src/ClientContext.tsx

@@ -22,7 +22,6 @@ import { type ISyncStateData, type SyncState } from "matrix-js-sdk/lib/sync";
 import { ClientEvent, type MatrixClient } from "matrix-js-sdk";
 
 import { ErrorPage } from "./FullScreenView";
-import { widget } from "./widget";
 import { useHostBridge } from "./HostBridge";
 import {
   PosthogAnalytics,
@@ -163,7 +162,12 @@ export const ClientProvider: FC<Props> = ({ children, client }) => {
 
   const initializing = useRef(false);
   useEffect(() => {
-    if (client !== undefined) return;
+    if (client !== undefined) {
+      // Nothing to load, but analytics still need to follow the user's choices.
+      if (PosthogAnalytics.instance.isEnabled())
+        PosthogAnalytics.instance.startListeningToSettingsChanges();
+      return;
+    }
     // In case the component is mounted, unmounted, and remounted quickly (as
     // React does in strict mode), we need to make sure not to doubly initialize
     // the client.
@@ -246,9 +250,9 @@ export const ClientProvider: FC<Props> = ({ children, client }) => {
   // To protect against multiple sessions writing to the same storage
   // simultaneously, we send a broadcast message that shuts down all other
   // running instances of the app. Element Call only has storage of its own to
-  // protect when it created the session itself; given a client, or running as a
-  // widget, it is mostly stateless.
-  const ownsSession = client === undefined && widget === null;
+  // protect when it created the session itself; given a client — by a host, or
+  // over the widget API — it is mostly stateless.
+  const ownsSession = client === undefined;
   useEffect(() => {
     if (ownsSession) loadChannel?.postMessage({});
   }, [ownsSession]);
@@ -349,19 +353,13 @@ export type InitResult = {
   passwordlessUser: boolean;
 };
 
+/**
+ * Restores or creates a session of Element Call's own. Only reached when no
+ * client was supplied for it to use.
+ */
 async function loadClient(): Promise<InitResult | null> {
-  if (widget) {
-    // We're inside a widget, so let's engage *matryoshka mode*
-    logger.log("Using a matryoshka client");
-    const client = await widget.client;
-    return {
-      client,
-      passwordlessUser: false,
-    };
-  } else {
-    const { initSPA } = await import("./utils/spa");
-    return initSPA(loadSession, clearSession);
-  }
+  const { initSPA } = await import("./utils/spa");
+  return initSPA(loadSession, clearSession);
 }
 
 export interface Session {

src/initializer.tsx

@@ -32,7 +32,7 @@ import { Config } from "./config/Config";
 import { seedSettingsFromConfig } from "./settings/settings";
 import { platform } from "./Platform";
 import { isFailure } from "./utils/fetch";
-import { initializeWidget } from "./widget";
+import { initializeWidget, type WidgetHelpers } from "./widget";
 import { enableExtendedLivekitLogs } from "./settings/settings.ts";
 import {
   type AnalyticsConfig,
@@ -155,8 +155,8 @@ export class Initializer {
     return !!Initializer.internalInstance?.isInitialized;
   }
 
-  public static async initBeforeReact(): Promise<void> {
-    initializeWidget();
+  public static async initBeforeReact(): Promise<WidgetHelpers | null> {
+    const widget = initializeWidget();
 
     const polyfills: Promise<unknown>[] = [];
     if (shouldPolyfillSegmenter()) {
@@ -243,6 +243,8 @@ export class Initializer {
     });
 
     window.setLKLogLevel = setLKLogLevel;
+
+    return widget;
   }
 
   public static init(): Promise<void> | null {

src/main.tsx

@@ -49,7 +49,7 @@ if (fatalError !== null) {
 }
 
 Initializer.initBeforeReact()
-  .then(() => {
+  .then((widget) => {
     const { controlledAudioDevices, callIntent } = getUrlParams();
     root.render(
       <StrictMode>
@@ -60,6 +60,7 @@ Initializer.initBeforeReact()
               callIntent,
             })
           }
+          widget={widget}
         />
       </StrictMode>,
     );

src/widget.test.ts

@@ -9,7 +9,7 @@ import { describe, expect, vi, it, beforeEach } from "vitest";
 import { createRoomWidgetClient, EventType } from "matrix-js-sdk";
 
 import { getUrlParams } from "./UrlParams";
-import { initializeWidget, widget } from "./widget";
+import { initializeWidget } from "./widget";
 import { Config } from "./config/Config";
 import { ElementCallReactionEventType } from "./reactions";
 
@@ -42,7 +42,7 @@ beforeEach(() => {
 
 describe("widget", () => {
   it("should create an embedded client with the correct params", () => {
-    initializeWidget("ANYRTCAPP");
+    const widget = initializeWidget("ANYRTCAPP");
 
     expect(getUrlParams()).toStrictEqual({
       widgetId: "id",

src/widget.ts

@@ -58,21 +58,21 @@ export interface WidgetHelpers {
 }
 
 /**
- * A point of access to the widget API, if the app is running as a widget. This
- * is initialized with `initializeWidget`. This should happen at the top level because the widget messaging
- * needs to be set up ASAP on load to ensure it doesn't miss any requests.
- */
-export let widget: WidgetHelpers | null = null;
-
-/**
- * Should be called as soon as possible on app start. (In the initilizer before react)
+ * Connects to the widget API, if Element Call is running as a widget.
+ *
+ * Should be called as soon as possible on app start (in the initializer, before
+ * React), because the widget messaging needs to be set up ASAP on load to
+ * ensure it doesn't miss any requests.
+ *
+ * @returns A point of access to the widget API, or null if Element Call is not
+ *   running as a widget.
  */
 // this needs to be a seperate call and cannot be done on import to allow us to spy on methods in here before
 // execution.
 export const initializeWidget = (
   rtcApplication: string = "m.call",
   sendRoomEvents = false,
-): void => {
+): WidgetHelpers | null => {
   try {
     const {
       widgetId,
@@ -202,14 +202,14 @@ export const initializeWidget = (
         return client;
       };
 
-      widget = { api, lazyActions, client: clientPromise() };
+      return { api, lazyActions, client: clientPromise() };
     } else {
       if (import.meta.env.MODE !== "test")
         logger.info("No widget API available");
-      widget = null;
+      return null;
     }
   } catch (e) {
     logger.warn("Continuing without the widget API", e);
-    widget = null;
+    return null;
   }
 };