Move the state layer onto the host bridge

MuteStates, CallViewModel and LocalMember reached the host through the
widget global. None of them are React components, so they take the bridge
as an explicit parameter: a constructor argument for MuteStates, a field
on CallViewModelOptions, and one on createLocalMembership$'s props.

src/state no longer refers to the widget API.

The conditionals around it mostly disappear: nullHostBridge's observables
are NEVER, so there is nothing to guard, and a request carries its own
reply rather than needing the transport and the original event.

CallViewModelWidget.test.ts drove hangup by emitting on the mocked
widget's action emitter, so it now injects a bridge instead, and checks
that the request is acknowledged.

sdk/main.ts

@@ -60,6 +60,7 @@ import {
   initializeWidget,
 } from "../src/widget";
 import { type Connection } from "../src/state/CallViewModel/remoteMembers/Connection";
+import { createWidgetHostBridge } from "../src/HostBridge";
 
 interface MatrixRTCSdk {
   /**
@@ -113,6 +114,7 @@ export async function createMatrixRTCSdk(
   const widget = _widget;
   if (!widget) throw Error("No widget. This webapp can only start as a widget");
   const client = await widget.client;
+  const hostBridge = createWidgetHostBridge(widget);
   logger.info("client created");
 
   // url params
@@ -132,10 +134,12 @@ export async function createMatrixRTCSdk(
     controlledAudioDevices,
     callIntent,
   });
-  const muteStates = new MuteStates(scope, mediaDevices, {
-    audioEnabled: false,
-    videoEnabled: false,
-  });
+  const muteStates = new MuteStates(
+    scope,
+    mediaDevices,
+    { audioEnabled: false, videoEnabled: false },
+    hostBridge,
+  );
 
   // call view model
   const callViewModel = createCallViewModel$(
@@ -146,6 +150,7 @@ export async function createMatrixRTCSdk(
     muteStates,
     {
       encryptionSystem: { kind: E2eeType.PER_PARTICIPANT },
+      hostBridge,
       controlledAudioDevices,
       callIntent,
     },

src/room/InCallView.tsx

@@ -29,6 +29,7 @@ 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";
 import { SettingsModal, defaultSettingsTab } from "../settings/SettingsModal";
@@ -116,6 +117,7 @@ export const ActiveCall: FC<ActiveCallProps> = (props) => {
     useState<ViewModel<DeveloperSettingsSnapshot> | null>(null);
 
   const urlParams = useUrlParams();
+  const hostBridge = useHostBridge();
   const mediaDevices = useMediaDevices();
   const trackProcessorState$ = useTrackProcessorObservable$();
   useEffect(() => {
@@ -141,6 +143,7 @@ export const ActiveCall: FC<ActiveCallProps> = (props) => {
       props.muteStates,
       {
         encryptionSystem: props.e2eeSystem,
+        hostBridge,
         autoLeaveWhenOthersLeft,
         waitForCallPickup: waitForCallPickup && sendNotificationType === "ring",
         matrixRTCMode$: matrixRTCModeSetting.value$,
@@ -171,6 +174,7 @@ export const ActiveCall: FC<ActiveCallProps> = (props) => {
     props.e2eeSystem,
     props.onLeft,
     urlParams,
+    hostBridge,
     mediaDevices,
     trackProcessorState$,
     props.client,

src/room/RoomPage.tsx

@@ -30,6 +30,7 @@ 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";
 import { E2eeType } from "../e2ee/e2eeType";
@@ -44,6 +45,7 @@ import { calculateInitialMuteState } from "../state/initialMuteState.ts";
 
 export const RoomPage: FC = (): ReactNode => {
   const urlParams = useUrlParams();
+  const hostBridge = useHostBridge();
   const { confineToRoom, preload, header, displayName, skipLobby } = urlParams;
   const { t } = useTranslation();
   const { roomAlias, roomId, viaServers } = useRoomIdentifier();
@@ -77,10 +79,11 @@ export const RoomPage: FC = (): ReactNode => {
           urlParams.callIntent,
           widget !== null,
         ),
+        hostBridge,
       ),
     );
     return (): void => scope.end();
-  }, [devices, urlParams]);
+  }, [devices, urlParams, hostBridge]);
 
   useEffect(() => {
     // If we've finished loading, are not already authed and we've been given a display name as

src/state/CallViewModel/CallViewModel.ts

@@ -48,7 +48,6 @@ import {
   type RTCCallIntent,
   type RTCNotificationType,
 } from "matrix-js-sdk/lib/matrixrtc";
-import { type IWidgetApiRequest } from "matrix-widget-api";
 import { type CallMembershipIdentityParts } from "matrix-js-sdk/lib/matrixrtc/EncryptionManager";
 import { v4 as uuidv4 } from "uuid";
 import { type IMembershipManager } from "matrix-js-sdk/lib/matrixrtc/IMembershipManager";
@@ -89,7 +88,7 @@ import { MatrixKeyProvider } from "../../e2ee/matrixKeyProvider";
 import { type MuteStates } from "../MuteStates";
 import { HeaderStyle } from "../../UrlParams";
 import { type ProcessorState } from "../../livekit/TrackProcessorContext";
-import { ElementWidgetActions, widget } from "../../widget";
+import { type HostBridge, nullHostBridge } from "../../HostBridge";
 import {
   layoutShallowEquals,
   type Alignment,
@@ -173,6 +172,11 @@ import { type GridTileViewModel } from "../TileViewModel.ts";
 // callMembership -> rtcMembership
 export interface CallViewModelOptions {
   encryptionSystem: EncryptionSystem;
+  /**
+   * The application hosting Element Call, which can ask it to hang up and wants
+   * to know when the user joins or leaves. Defaults to no host.
+   */
+  hostBridge?: HostBridge;
   /**
    * Whether the app hosting Element Call controls the audio output devices,
    * rather than the browser. Defaults to false.
@@ -457,6 +461,7 @@ export function createCallViewModel$(
   // Defaults match what the URL parameters resolve to outside of widget mode,
   // so that callers which don't care (chiefly tests) behave as they always have.
   const {
+    hostBridge = nullHostBridge,
     controlledAudioDevices = false,
     header = HeaderStyle.Standard,
     showControls = true,
@@ -632,6 +637,7 @@ export function createCallViewModel$(
     localTransport$,
     roomId: matrixRoom.roomId,
     hideScreensharing,
+    hostBridge,
     logger: logger.getChild(`[${Date.now()}]`),
   });
 
@@ -923,24 +929,16 @@ export function createCallViewModel$(
 
   const userHangup$ = new Subject<void>();
 
-  const widgetHangup$ =
-    widget === null
-      ? NEVER
-      : (
-          fromEvent(
-            widget.lazyActions,
-            ElementWidgetActions.HangupCall,
-          ) as Observable<CustomEvent<IWidgetApiRequest>>
-        ).pipe(
-          tap((ev) => {
-            widget!.api.transport.reply(ev.detail, {});
-          }),
-        );
+  const hostHangup$ = hostBridge.hangUp$.pipe(
+    tap((request) => {
+      request.reply();
+    }),
+  );
 
   const leave$: Observable<"user" | "timeout" | "decline" | "allOthersLeft"> =
     merge(
       autoLeave$,
-      merge(userHangup$, widgetHangup$).pipe(map(() => "user" as const)),
+      merge(userHangup$, hostHangup$).pipe(map(() => "user" as const)),
     ).pipe(scope.share);
 
   const spotlightSpeaker$ = scope.behavior<UserMediaViewModel | undefined>(

src/state/CallViewModel/localMember/LocalMember.test.ts

@@ -52,6 +52,7 @@ import { ConnectionManagerData } from "../remoteMembers/ConnectionManager";
 import { ConnectionState, type Connection } from "../remoteMembers/Connection";
 import { type Publisher } from "./Publisher";
 import { initializeWidget } from "../../../widget";
+import { nullHostBridge } from "../../../HostBridge";
 import {
   type LocalTransport,
   type LocalTransportWithSFUConfig,
@@ -200,6 +201,7 @@ describe("LocalMembership", () => {
     },
     roomId: "!test-room-id:example.org",
     hideScreensharing: false,
+    hostBridge: nullHostBridge,
   };
 
   it("throws error on missing RTC config error", () => {

src/state/CallViewModel/localMember/LocalMember.ts

@@ -53,7 +53,7 @@ import {
   MembershipManagerError,
   UnknownCallError,
 } from "../../../utils/errors.ts";
-import { ElementWidgetActions, widget } from "../../../widget.ts";
+import { type HostBridge } from "../../../HostBridge.ts";
 
 import { PosthogAnalytics } from "../../../analytics/PosthogAnalytics.ts";
 import {
@@ -145,6 +145,8 @@ interface Props {
   >;
   /** Whether to hide the screen-sharing button. */
   hideScreensharing: boolean;
+  /** The application hosting Element Call, to be kept informed of join/leave. */
+  hostBridge: HostBridge;
   logger: Logger;
 }
 
@@ -165,6 +167,7 @@ interface Props {
  * @param props.matrixRTCSession The matrix RTC session to join.
  * @param props.roomId The room ID used as the call identifier in analytics events.
  * @param props.hideScreensharing Whether to hide the screen-sharing button.
+ * @param props.hostBridge The application hosting Element Call.
  * @returns
  *  - publisher: The handle to create tracks and publish them to the room.
  *  - connected$: the current connection state. Including matrix server and livekit server connection. (only considering the livekit server we are using for our own media publication)
@@ -184,6 +187,7 @@ export const createLocalMembership$ = ({
   matrixRTCSession,
   roomId,
   hideScreensharing,
+  hostBridge,
 }: Props): {
   /**
    * This request to start audio and video tracks.
@@ -576,29 +580,24 @@ export const createLocalMembership$ = ({
       }
     });
 
-  // inform the widget about the connect and disconnect intent from the user.
+  // inform the host about the connect and disconnect intent from the user.
   scope
     .behavior(joinAndPublishRequested$.pipe(pairwise(), scope.bind()), [
       undefined,
       joinAndPublishRequested$.value,
     ])
     .subscribe(([prev, current]) => {
-      if (!widget) return;
       // JOIN prev=false (was left) => current-true (now joiend)
       if (!prev && current) {
-        widget.api.transport
-          .send(ElementWidgetActions.JoinCall, {})
-          .catch((e) => {
-            logger.error("Failed to send join action", e);
-          });
+        hostBridge.notifyJoined().catch((e) => {
+          logger.error("Failed to notify the host that we joined", e);
+        });
       }
       // LEAVE prev=false (was joined) => current-true (now left)
       if (prev && !current) {
-        widget.api.transport
-          .send(ElementWidgetActions.HangupCall, {})
-          .catch((e) => {
-            logger.error("Failed to send hangup action", e);
-          });
+        hostBridge.notifyHungUp().catch((e) => {
+          logger.error("Failed to notify the host that we hung up", e);
+        });
       }
     });
 
@@ -845,7 +844,7 @@ interface EnterRTCSessionOptions {
  * @param options - `encryptMedia`: Whether to encrypt media. `matrixRTCMode`: The
  *   Matrix RTC mode to use. `sendNotificationType`: Whether and what kind of
  *   notification to send on join. `callIntent`: The kind of call being placed.
- * @throws If the widget could not send ElementWidgetActions.JoinCall action.
+ * @throws If the host could not be told that we are joining.
  */
 // Exported for unit testing
 export function enterRTCSession(

src/state/CallViewModelWidget.test.ts

@@ -6,39 +6,31 @@ Please see LICENSE in the repository root for full details.
 */
 
 import { it, vi, expect } from "vitest";
-import EventEmitter from "events";
+import { Subject } from "rxjs";
 
 // import * as ComponentsCore from "@livekit/components-core";
 import { withCallViewModel } from "./CallViewModel/CallViewModelTestUtils.ts";
 import { type CallViewModel } from "./CallViewModel/CallViewModel.ts";
 import { constant } from "./Behavior.ts";
 import { aliceParticipant, localRtcMember } from "../utils/test-fixtures.ts";
-import { ElementWidgetActions, widget } from "../widget.ts";
+import {
+  type HostBridge,
+  type HostRequest,
+  nullHostBridge,
+} from "../HostBridge.ts";
 import { E2eeType } from "../e2ee/e2eeType.ts";
 import { MatrixRTCMode } from "../config/ConfigOptions.ts";
 
 vi.mock("@livekit/components-core", { spy: true });
 
-vi.mock("../widget", () => ({
-  ElementWidgetActions: {
-    HangupCall: "HangupCall",
-    // Add other actions if needed
-  },
-  widget: {
-    api: {
-      transport: {
-        send: vi.fn().mockResolvedValue(undefined),
-        reply: vi.fn().mockResolvedValue(undefined),
-      },
-    },
-    lazyActions: new EventEmitter(),
-  },
-}));
-
 it.each([[MatrixRTCMode.Compatibility], [MatrixRTCMode.Matrix_2_0]])(
-  "expect leave when ElementWidgetActions.HangupCall is called (%s mode)",
+  "expect leave when the host asks us to hang up (%s mode)",
   async (mode) => {
     const pr = Promise.withResolvers<string>();
+    const hangUp$ = new Subject<HostRequest<Record<string, never>>>();
+    const hostBridge: HostBridge = { ...nullHostBridge, hangUp$ };
+    const reply = vi.fn();
+
     withCallViewModel(mode)(
       {
         remoteParticipants$: constant([aliceParticipant]),
@@ -49,25 +41,17 @@ it.each([[MatrixRTCMode.Compatibility], [MatrixRTCMode.Matrix_2_0]])(
           pr.resolve(s);
         });
 
-        widget!.lazyActions!.emit(
-          ElementWidgetActions.HangupCall,
-          new CustomEvent(ElementWidgetActions.HangupCall, {
-            detail: {
-              action: "im.vector.hangup",
-              api: "toWidget",
-              data: {},
-              requestId: "widgetapi-1761237395918",
-              widgetId: "mrUjS9T6uKUOWHMxXvLbSv0F",
-            },
-          }),
-        );
+        hangUp$.next({ data: {}, reply });
       },
       {
         encryptionSystem: { kind: E2eeType.PER_PARTICIPANT },
+        hostBridge,
       },
     );
 
     const source = await pr.promise;
     expect(source).toBe("user");
+    // The host expects to hear back that we acted on its request
+    expect(reply).toHaveBeenCalledOnce();
   },
 );

src/state/MuteStates.test.ts

@@ -9,6 +9,7 @@ import { afterEach, beforeEach, describe, expect, test, vi } from "vitest";
 import { BehaviorSubject } from "rxjs";
 import { logger } from "matrix-js-sdk/lib/logger";
 
+import { nullHostBridge } from "../HostBridge";
 import { MuteStates, MuteState } from "./MuteStates";
 import {
   type AudioOutputDeviceLabel,
@@ -228,10 +229,12 @@ describe("MuteStates", () => {
       videoInput: aVideoInput(),
       // other devices are not relevant for this test
     });
-    const muteStates = new MuteStates(testScope, mediaDevices, {
-      audioEnabled: false,
-      videoEnabled: false,
-    });
+    const muteStates = new MuteStates(
+      testScope,
+      mediaDevices,
+      { audioEnabled: false, videoEnabled: false },
+      nullHostBridge,
+    );
 
     let latestSyncedState: boolean | null = null;
     muteStates.video.setHandler(async (enabled: boolean): Promise<boolean> => {

src/state/MuteStates.ts

@@ -6,14 +6,12 @@ SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
 Please see LICENSE in the repository root for full details.
 */
 
-import { type IWidgetApiRequest } from "matrix-widget-api";
 import { logger } from "matrix-js-sdk/lib/logger";
 import {
   BehaviorSubject,
   combineLatest,
   distinctUntilChanged,
   firstValueFrom,
-  fromEvent,
   map,
   merge,
   Observable,
@@ -24,7 +22,7 @@ import {
 } from "rxjs";
 
 import { type MediaDevices, type MediaDevice } from "../state/MediaDevices";
-import { ElementWidgetActions, widget } from "../widget";
+import { type DeviceMuteState, type HostBridge } from "../HostBridge";
 import { type ObservableScope } from "./ObservableScope";
 import { type Behavior, constant } from "./Behavior";
 
@@ -216,58 +214,51 @@ export class MuteStates {
       audioEnabled: boolean;
       videoEnabled: boolean;
     },
+    hostBridge: HostBridge,
   ) {
-    if (widget !== null) {
-      // Sync our mute states with the hosting client
-      const widgetApiState$ = combineLatest(
-        [this.audio.enabled$, this.video.enabled$],
-        (audio, video) => ({ audio_enabled: audio, video_enabled: video }),
-      );
-      widgetApiState$.pipe(this.scope.bind()).subscribe((state) => {
-        widget!.api.transport
-          .send(ElementWidgetActions.DeviceMute, state)
-          .catch((e) =>
-            logger.warn("Could not send DeviceMute action to widget", e),
-          );
-      });
+    // Keep the host informed of our mute state
+    const muteState$ = combineLatest(
+      [this.audio.enabled$, this.video.enabled$],
+      (audio, video): DeviceMuteState => ({
+        audio_enabled: audio,
+        video_enabled: video,
+      }),
+    );
+    muteState$.pipe(this.scope.bind()).subscribe((state) => {
+      hostBridge
+        .notifyDeviceMute(state)
+        .catch((e) => logger.warn("Could not send mute state to the host", e));
+    });
 
-      // Also sync the hosting client's mute states back with ours
-      const muteActions$ = fromEvent(
-        widget.lazyActions,
-        ElementWidgetActions.DeviceMute,
-      ) as Observable<CustomEvent<IWidgetApiRequest>>;
-      muteActions$
-        .pipe(
-          withLatestFrom(
-            widgetApiState$,
-            this.audio.setEnabled$,
-            this.video.setEnabled$,
-          ),
-          this.scope.bind(),
-        )
-        .subscribe(([ev, state, setAudioEnabled, setVideoEnabled]) => {
-          // First copy the current state into our new state
-          const newState = { ...state };
-          // Update new state if there are any requested changes from the widget
-          // action in `ev.detail.data`.
-          if (
-            ev.detail.data.audio_enabled != null &&
-            typeof ev.detail.data.audio_enabled === "boolean" &&
-            setAudioEnabled !== null
-          ) {
-            newState.audio_enabled = ev.detail.data.audio_enabled;
-            setAudioEnabled(newState.audio_enabled);
-          }
-          if (
-            ev.detail.data.video_enabled != null &&
-            typeof ev.detail.data.video_enabled === "boolean" &&
-            setVideoEnabled !== null
-          ) {
-            newState.video_enabled = ev.detail.data.video_enabled;
-            setVideoEnabled(newState.video_enabled);
-          }
-          widget!.api.transport.reply(ev.detail, newState);
-        });
-    }
+    // And apply the changes the host asks for
+    hostBridge.deviceMute$
+      .pipe(
+        withLatestFrom(
+          muteState$,
+          this.audio.setEnabled$,
+          this.video.setEnabled$,
+        ),
+        this.scope.bind(),
+      )
+      .subscribe(([request, state, setAudioEnabled, setVideoEnabled]) => {
+        // First copy the current state into our new state
+        const newState = { ...state };
+        // Then apply whichever changes the host asked for
+        if (
+          typeof request.data.audio_enabled === "boolean" &&
+          setAudioEnabled !== null
+        ) {
+          newState.audio_enabled = request.data.audio_enabled;
+          setAudioEnabled(newState.audio_enabled);
+        }
+        if (
+          typeof request.data.video_enabled === "boolean" &&
+          setVideoEnabled !== null
+        ) {
+          newState.video_enabled = request.data.video_enabled;
+          setVideoEnabled(newState.video_enabled);
+        }
+        request.reply(newState);
+      });
   }
 }

src/utils/test.ts

@@ -63,6 +63,7 @@ import { type MediaDevices } from "../state/MediaDevices";
 import { type Behavior, constant } from "../state/Behavior";
 import { ObservableScope } from "../state/ObservableScope";
 import { MuteStates } from "../state/MuteStates";
+import { nullHostBridge } from "../HostBridge";
 import {
   createLocalUserMedia,
   type LocalUserMediaViewModel,
@@ -577,10 +578,12 @@ export function mockMuteStates(
   joined$: Observable<boolean> = of(true),
 ): MuteStates {
   const observableScope = new ObservableScope();
-  return new MuteStates(observableScope, mockMediaDevices({}), {
-    audioEnabled: false,
-    videoEnabled: false,
-  });
+  return new MuteStates(
+    observableScope,
+    mockMediaDevices({}),
+    { audioEnabled: false, videoEnabled: false },
+    nullHostBridge,
+  );
 }
 
 export class MockConnection extends Connection {