Stop asking whether Element Call is a widget

The remaining reads of the widget global were all asking one of two
different questions, so they get two different answers.

The app shell — the auth hooks, automatic guest registration, the group
call loader's diagnostic and the initial mute state — wants to know
whether Element Call was launched as a widget. That is a property of the
URL it was launched with, so expose the isWidget that computeUrlParams
already computed internally, documented as being for shell use only.

The call interface — whether to offer the profile settings tab — wants to
know something about its host, so it asks the bridge. A host that can
dismiss Element Call owns the user's account, so their profile is not ours
to edit; this reuses the close capability as a proxy, with a TODO
alongside the others.

ClientContext also takes supportsReactions from the bridge rather than
checking four widget capabilities itself, which removes widgetApi from
InitResult — a field that was always null outside widget mode.

Note this changes behaviour for a malformed widget URL: one carrying a
widget ID and parent URL but missing the room, user, device or base URL
would previously have fallen back to registering a guest user, and will
now not.

src/ClientContext.tsx

@@ -21,9 +21,9 @@ import { logger } from "matrix-js-sdk/lib/logger";
 import { type ISyncStateData, type SyncState } from "matrix-js-sdk/lib/sync";
 import { ClientEvent, type MatrixClient } from "matrix-js-sdk";
 
-import type { WidgetApi } from "matrix-widget-api";
 import { ErrorPage } from "./FullScreenView";
 import { widget } from "./widget";
+import { useHostBridge } from "./HostBridge";
 import {
   PosthogAnalytics,
   RegistrationType,
@@ -138,6 +138,7 @@ interface Props {
 
 export const ClientProvider: FC<Props> = ({ children }) => {
   const navigate = useNavigate();
+  const hostBridge = useHostBridge();
 
   // null = signed out, undefined = loading
   const [initClientState, setInitClientState] = useState<
@@ -201,7 +202,6 @@ export const ClientProvider: FC<Props> = ({ children }) => {
 
       saveSession(session);
       setInitClientState({
-        widgetApi: null,
         client,
         passwordlessUser: session.passwordlessUser,
       });
@@ -307,36 +307,16 @@ export const ClientProvider: FC<Props> = ({ children }) => {
       initClientState.client.on(ClientEvent.Sync, onSync);
     }
 
-    if (initClientState.widgetApi) {
-      const reactSend = initClientState.widgetApi.hasCapability(
-        "org.matrix.msc2762.send.event:m.reaction",
-      );
-      const redactSend = initClientState.widgetApi.hasCapability(
-        "org.matrix.msc2762.send.event:m.room.redaction",
-      );
-      const reactRcv = initClientState.widgetApi.hasCapability(
-        "org.matrix.msc2762.receive.event:m.reaction",
-      );
-      const redactRcv = initClientState.widgetApi.hasCapability(
-        "org.matrix.msc2762.receive.event:m.room.redaction",
-      );
-
-      if (!reactSend || !reactRcv || !redactSend || !redactRcv) {
-        logger.warn("Widget does not support reactions");
-        setSupportsReactions(false);
-      } else {
-        setSupportsReactions(true);
-      }
-    } else {
-      setSupportsReactions(true);
-    }
+    if (!hostBridge.supportsReactions)
+      logger.warn("The host does not permit reactions");
+    setSupportsReactions(hostBridge.supportsReactions);
 
     return (): void => {
       if (initClientState.client) {
         initClientState.client.removeListener(ClientEvent.Sync, onSync);
       }
     };
-  }, [initClientState, onSync]);
+  }, [initClientState, onSync, hostBridge]);
 
   if (alreadyOpenedErr) {
     return <ErrorPage error={alreadyOpenedErr} />;
@@ -346,7 +326,6 @@ export const ClientProvider: FC<Props> = ({ children }) => {
 };
 
 export type InitResult = {
-  widgetApi: WidgetApi | null;
   client: MatrixClient;
   passwordlessUser: boolean;
 };
@@ -357,7 +336,6 @@ async function loadClient(): Promise<InitResult | null> {
     logger.log("Using a matryoshka client");
     const client = await widget.client;
     return {
-      widgetApi: widget.api,
       client,
       passwordlessUser: false,
     };

src/UrlParams.ts

@@ -59,6 +59,17 @@ export interface UrlProperties {
   // Widget api related params
   widgetId: string | null;
   parentUrl: string | null;
+  /**
+   * Whether Element Call was started as a widget of a Matrix client, which is
+   * to say whether it was given a widget ID and a parent to talk to.
+   *
+   * Only meaningful to the standalone and widget builds, which own the URL —
+   * so use it for decisions that belong to the app shell, such as whether
+   * Element Call is responsible for authenticating the user. Anything the call
+   * interface itself needs to know about its host should come from the host
+   * bridge instead.
+   */
+  isWidget: boolean;
   /**
    * Anything about what room we're pointed to should be from useRoomIdentifier which
    * parses the path and resolves alias with respect to the default server name, however
@@ -448,6 +459,7 @@ export const computeUrlParams = (search = "", hash = ""): UrlParams => {
   const properties: UrlProperties = {
     widgetId,
     parentUrl,
+    isWidget,
     // NB. we don't validate roomId here as we do in getRoomIdentifierFromUrl:
     // what would we do if it were invalid? If the widget API says that's what
     // the room ID is, then that's what it is.

src/auth/useInteractiveRegistration.ts

@@ -17,7 +17,7 @@ import { logger } from "matrix-js-sdk/lib/logger";
 import { initClient } from "../utils/matrix";
 import { type Session } from "../ClientContext";
 import { Config } from "../config/Config";
-import { widget } from "../widget";
+import { useUrlParams } from "../UrlParams";
 
 export const useInteractiveRegistration = (
   oldClient?: MatrixClient,
@@ -32,6 +32,7 @@ export const useInteractiveRegistration = (
     passwordlessUser: boolean,
   ) => Promise<[MatrixClient, Session]>;
 } => {
+  const { isWidget } = useUrlParams();
   const [privacyPolicyUrl, setPrivacyPolicyUrl] = useState<string | undefined>(
     undefined,
   );
@@ -47,7 +48,7 @@ export const useInteractiveRegistration = (
   }
 
   useEffect(() => {
-    if (widget) return;
+    if (isWidget) return;
     // An empty registerRequest is used to get the privacy policy and recaptcha key.
     authClient.current!.registerRequest({}).catch((error) => {
       setPrivacyPolicyUrl(
@@ -55,7 +56,7 @@ export const useInteractiveRegistration = (
       );
       setRecaptchaKey(error.data?.params["m.login.recaptcha"]?.public_key);
     });
-  }, []);
+  }, [isWidget]);
 
   const register = useCallback(
     async (

src/auth/useRegisterPasswordlessUser.ts

@@ -12,7 +12,7 @@ import { useClient } from "../ClientContext";
 import { useInteractiveRegistration } from "../auth/useInteractiveRegistration";
 import { generateRandomName } from "../auth/generateRandomName";
 import { useRecaptcha } from "../auth/useRecaptcha";
-import { widget } from "../widget";
+import { useUrlParams } from "../UrlParams";
 
 interface UseRegisterPasswordlessUserType {
   privacyPolicyUrl?: string;
@@ -22,6 +22,7 @@ interface UseRegisterPasswordlessUserType {
 
 export function useRegisterPasswordlessUser(): UseRegisterPasswordlessUserType {
   const { setClient } = useClient();
+  const { isWidget } = useUrlParams();
   const { privacyPolicyUrl, recaptchaKey, register } =
     useInteractiveRegistration();
   const { execute, reset, recaptchaId } = useRecaptcha(recaptchaKey);
@@ -31,7 +32,7 @@ export function useRegisterPasswordlessUser(): UseRegisterPasswordlessUserType {
       if (!setClient) {
         throw new Error("No client context");
       }
-      if (widget) {
+      if (isWidget) {
         throw new Error(
           "Registration was skipped: We should never try to register password-less user in embedded mode.",
         );
@@ -53,7 +54,7 @@ export function useRegisterPasswordlessUser(): UseRegisterPasswordlessUserType {
         throw e;
       }
     },
-    [execute, reset, register, setClient],
+    [execute, reset, register, setClient, isWidget],
   );
 
   return { privacyPolicyUrl, registerPasswordlessUser, recaptchaId };

src/room/InCallView.tsx

@@ -28,7 +28,6 @@ import { useTranslation } from "react-i18next";
 import { Header, LeftNav, RightNav, RoomHeaderInfo } from "../Header";
 import { HeaderStyle, useUrlParams } from "../UrlParams";
 import { useCallViewKeyboardShortcuts } from "../useCallViewKeyboardShortcuts";
-import { widget } from "../widget";
 import { useHostBridge } from "../HostBridge.ts";
 import styles from "./InCallView.module.css";
 import { GridTile } from "../tile/GridTile";
@@ -251,6 +250,7 @@ export const InCallView: FC<InCallViewProps> = ({
 }) => {
   const logger = rootLogger.getChild("[InCallView]");
   const { t } = useTranslation();
+  const hostBridge = useHostBridge();
   const { sendReaction, toggleRaisedHand } = useReactionsSender();
 
   useWakeLock();
@@ -334,14 +334,17 @@ export const InCallView: FC<InCallViewProps> = ({
 
   const openProfile = useMemo(
     () =>
-      // Profile settings are unavailable in widget mode
-      widget === null
+      // A host that can dismiss us is a host that owns the user's account, so
+      // their profile is not ours to edit.
+      // TODO: another use of the close capability as a proxy — see the note in
+      // GroupCallView.
+      hostBridge.close === undefined
         ? (): void => {
             setSettingsTab("profile");
             setSettingsOpen(true);
           }
         : null,
-    [setSettingsTab, setSettingsOpen],
+    [setSettingsTab, setSettingsOpen, hostBridge],
   );
 
   const [headerRef, headerBounds] = useMeasure();

src/room/RoomPage.tsx

@@ -29,7 +29,6 @@ import { GroupCallView } from "./GroupCallView";
 import { useRoomIdentifier, useUrlParams } from "../UrlParams";
 import { useRegisterPasswordlessUser } from "../auth/useRegisterPasswordlessUser";
 import { HomePage } from "../home/HomePage";
-import { widget } from "../widget";
 import { useHostBridge } from "../HostBridge.ts";
 import { CallTerminatedMessage, useLoadGroupCall } from "./useLoadGroupCall";
 import { LobbyView } from "./LobbyView";
@@ -77,7 +76,7 @@ export const RoomPage: FC = (): ReactNode => {
         calculateInitialMuteState(
           urlParams.skipLobby,
           urlParams.callIntent,
-          widget !== null,
+          urlParams.isWidget,
         ),
         hostBridge,
       ),
@@ -88,7 +87,7 @@ export const RoomPage: FC = (): ReactNode => {
   useEffect(() => {
     // If we've finished loading, are not already authed and we've been given a display name as
     // a URL param, automatically register a passwordless user
-    if (!loading && !authenticated && displayName && !widget) {
+    if (!loading && !authenticated && displayName && !urlParams.isWidget) {
       setIsRegistering(true);
       registerPasswordlessUser(displayName)
         .catch((e) => {
@@ -102,6 +101,7 @@ export const RoomPage: FC = (): ReactNode => {
     loading,
     authenticated,
     displayName,
+    urlParams.isWidget,
     setIsRegistering,
     registerPasswordlessUser,
   ]);

src/room/useLoadGroupCall.ts

@@ -34,7 +34,7 @@ import {
   EndCallIcon,
 } from "@vector-im/compound-design-tokens/assets/web/icons";
 
-import { widget } from "../widget";
+import { useUrlParams } from "../UrlParams";
 
 export type GroupCallLoaded = {
   kind: "loaded";
@@ -132,6 +132,7 @@ export const useLoadGroupCall = (
   const [state, setState] = useState<GroupCallStatus>({ kind: "loading" });
   const activeRoom = useRef<Room | undefined>(undefined);
   const { t } = useTranslation();
+  const { isWidget } = useUrlParams();
 
   const bannedError = useCallback(
     (): CallTerminatedMessage =>
@@ -249,7 +250,7 @@ export const useLoadGroupCall = (
           // room already joined so we are done here already.
           return room!;
         }
-        if (widget)
+        if (isWidget)
           // in widget mode we never should reach this point. (getRoom should return the room.)
           throw new Error(
             "Room not found. The widget-api did not pass over the relevant room events/information.",
@@ -373,6 +374,7 @@ export const useLoadGroupCall = (
   }, [
     bannedError,
     client,
+    isWidget,
     knockRejectError,
     removeNoticeError,
     roomIdOrAlias,

src/settings/SettingsModal.tsx

@@ -18,7 +18,7 @@ import { ProfileSettingsTab } from "./ProfileSettingsTab";
 import { FeedbackSettingsTab } from "./FeedbackSettingsTab";
 import { iosDeviceMenu$ } from "../state/MediaDevices";
 import { useMediaDevices } from "../MediaDevicesContext";
-import { widget } from "../widget";
+import { useHostBridge } from "../HostBridge";
 import {
   useSetting,
   soundEffectVolume as soundEffectVolumeSetting,
@@ -123,6 +123,7 @@ export const SettingsModal: FC<Props> = ({
   // On EC, we decided that it is less confusing for the user if they see those options in the output section
   // rather than the input section.
   const { controlledAudioDevices } = useUrlParams();
+  const hostBridge = useHostBridge();
   // If we are on iOS we will show a button to open the native audio device picker.
   const iosDeviceMenu = useBehavior(iosDeviceMenu$);
 
@@ -234,7 +235,9 @@ export const SettingsModal: FC<Props> = ({
   };
 
   const tabs = [audioTab, videoTab];
-  if (widget === null) tabs.push(profileTab);
+  // A host that can dismiss us is a host that owns the user's account, so their
+  // profile is not ours to edit.
+  if (hostBridge.close === undefined) tabs.push(profileTab);
   tabs.push(preferencesTab);
   if (isRageshakeAvailable || import.meta.env.VITE_PACKAGE === "full") {
     // for full package we want to show the analytics consent checkbox

src/utils/spa.ts

@@ -40,7 +40,6 @@ export async function initSPA(
     try {
       const client = await initClient(initClientParams, true);
       return {
-        widgetApi: null,
         client,
         passwordlessUser,
       };