lotus(#4): focus-participant spotlight via widget action

Adds io.lotus.focus_participant (toWidget): the host can pin a participant
to the spotlight by Matrix user id (or clear with userId:null), via a
manual override injected into CallViewModel.spotlightSpeaker$. Replaces
cinny's fragile DOM .click() tile-selector focus hack. Extracts the action
enum into lotusActions.ts (no circular import) and allow-lists Lotus
toWidget actions in initializeWidget. Additive: no-op unless the host
sends the action.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/lotus/lotusActions.ts

@@ -0,0 +1,26 @@
+/*
+Copyright 2026 Lotus Guild
+
+SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
+Please see LICENSE in the repository root for full details.
+*/
+
+/**
+ * Custom widget actions exchanged between the Lotus host (cinny) and this fork.
+ * Kept dependency-free so both `widget.ts` and `lotus/*` can import it without
+ * a circular dependency.
+ */
+export enum LotusWidgetActions {
+  /** fromWidget: in-call per-participant speaking / mute state. */
+  CallState = "io.lotus.call_state",
+  /** toWidget: pin/spotlight (or clear, with userId=null) a participant. */
+  FocusParticipant = "io.lotus.focus_participant",
+  /** toWidget: mix an audio clip into the local published mic track. */
+  InjectAudio = "io.lotus.inject_audio",
+}
+
+/** toWidget Lotus actions that must be allow-listed in `initializeWidget`. */
+export const LOTUS_TO_WIDGET_ACTIONS: LotusWidgetActions[] = [
+  LotusWidgetActions.FocusParticipant,
+  LotusWidgetActions.InjectAudio,
+];

src/lotus/lotusFocus.ts

@@ -0,0 +1,38 @@
+/*
+Copyright 2026 Lotus Guild
+
+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 { type CallViewModel } from "../state/CallViewModel/CallViewModel";
+import { widget } from "../widget";
+import { LotusWidgetActions } from "./lotusActions";
+
+/**
+ * Handle the host's `io.lotus.focus_participant` toWidget action (#4): pin a
+ * participant to the spotlight by Matrix user id, or clear it with
+ * `{ userId: null }`. This replaces cinny's old DOM `.click()` tile-selector
+ * hack with a real, layout-aware spotlight override.
+ *
+ * No effect unless the host actually sends the action, so registering the
+ * handler whenever we're a widget is safe. Returns a teardown function.
+ */
+export function startLotusFocus(vm: CallViewModel): () => void {
+  const w = widget;
+  if (!w) return () => undefined;
+
+  const handler = (ev: CustomEvent<IWidgetApiRequest>): void => {
+    // Always reply so the host transport doesn't time out.
+    void w.api.transport.reply(ev.detail, {});
+    const data = ev.detail.data as { userId?: unknown } | undefined;
+    const userId = typeof data?.userId === "string" ? data.userId : null;
+    vm.setManualSpotlight(userId);
+  };
+
+  w.lazyActions.on(LotusWidgetActions.FocusParticipant, handler);
+  return () =>
+    w.lazyActions.off(LotusWidgetActions.FocusParticipant, handler);
+}

src/lotus/lotusWidget.ts

@@ -17,16 +17,9 @@ Please see LICENSE in the repository root for full details.
 import { logger } from "matrix-js-sdk/lib/logger";
 
 import { widget } from "../widget";
+import { LotusWidgetActions } from "./lotusActions";
 
-/** Custom widget actions used between the Lotus host and this fork. */
+export { LotusWidgetActions } from "./lotusActions";
-export enum LotusWidgetActions {
-  /** fromWidget: in-call per-participant speaking / mute state. */
-  CallState = "io.lotus.call_state",
-  /** toWidget: pin/spotlight (or clear) a participant. */
-  FocusParticipant = "io.lotus.focus_participant",
-  /** toWidget: mix an audio clip into the local published mic track. */
-  InjectAudio = "io.lotus.inject_audio",
-}
 
 let cachedParams: URLSearchParams | undefined;
 

src/room/InCallView.tsx

@@ -30,6 +30,7 @@ import { HeaderStyle, useUrlParams } from "../UrlParams";
 import { useCallViewKeyboardShortcuts } from "../useCallViewKeyboardShortcuts";
 import { widget } from "../widget";
 import { startLotusCallState } from "../lotus/lotusCallState";
+import { startLotusFocus } from "../lotus/lotusFocus";
 import styles from "./InCallView.module.css";
 import { GridTile } from "../tile/GridTile";
 import { SettingsModal, defaultSettingsTab } from "../settings/SettingsModal";
@@ -283,6 +284,9 @@ export const InCallView: FC<InCallViewProps> = ({
   // [lotus] Stream per-participant speaking/mute state to the host (cinny) over
   // the widget API when opted in via lotusCallState=1. No-op otherwise.
   useEffect(() => startLotusCallState(vm), [vm]);
+  // [lotus] Handle the host's io.lotus.focus_participant action to pin a
+  // participant to the spotlight (#4). No-op unless the host sends it.
+  useEffect(() => startLotusFocus(vm), [vm]);
 
   const fatalCallError = useBehavior(vm.fatalError$);
   // Stop the rendering and throw for the error boundary

src/state/CallViewModel/CallViewModel.ts

@@ -255,6 +255,11 @@ export interface CallViewModel {
    * Callback to toggle screen sharing. If null, screen sharing is not possible.
    */
   toggleScreenSharing: (() => void) | null;
+  /**
+   * [lotus] Pin a participant to the spotlight by Matrix user id (#4
+   * focus-participant). Pass null to clear and restore speaker-follows.
+   */
+  setManualSpotlight: (userId: string | null) => void;
   /**
    * Whether we are sharing our screen.
    */
@@ -897,7 +902,7 @@ export function createCallViewModel$(
       merge(userHangup$, widgetHangup$).pipe(map(() => "user" as const)),
     ).pipe(scope.share);
 
-  const spotlightSpeaker$ = scope.behavior<UserMediaViewModel | undefined>(
+  const autoSpotlightSpeaker$ = scope.behavior<UserMediaViewModel | undefined>(
     userMedia$.pipe(
       switchMap((mediaItems) =>
         mediaItems.length === 0
@@ -933,6 +938,29 @@ export function createCallViewModel$(
     ),
   );
 
+  // [lotus] Manual spotlight override (#4 focus-participant widget action).
+  // When set to a userId still present in the call, that participant is
+  // spotlighted instead of the auto-selected active speaker; null restores the
+  // default speaker-follows behaviour. Defaults to null, so without the host
+  // using io.lotus.focus_participant this is a no-op.
+  const manualSpotlightUserId$ = new BehaviorSubject<string | null>(null);
+  const spotlightSpeaker$ = scope.behavior<UserMediaViewModel | undefined>(
+    combineLatest([
+      autoSpotlightSpeaker$,
+      manualSpotlightUserId$,
+      userMedia$,
+    ]).pipe(
+      map(([auto, manualUserId, mediaItems]) => {
+        if (manualUserId !== null) {
+          const pinned = mediaItems.find((m) => m.userId === manualUserId);
+          if (pinned) return pinned;
+        }
+        return auto;
+      }),
+    ),
+    undefined,
+  );
+
   const grid$ = scope.behavior<UserMediaViewModel[]>(
     userMedia$.pipe(
       switchMap((mediaItems) => {
@@ -1699,6 +1727,8 @@ export function createCallViewModel$(
     join: localMembership.requestJoinAndPublish,
     leave: localMembership.requestDisconnect,
     toggleScreenSharing: toggleScreenSharing,
+    setManualSpotlight: (userId: string | null): void =>
+      manualSpotlightUserId$.next(userId),
     sharingScreen$: sharingScreen$,
 
     tapScreen: (): void => screenTap$.next(),

src/widget.ts

@@ -22,6 +22,7 @@ import { LazyEventEmitter } from "./LazyEventEmitter";
 import { getUrlParams } from "./UrlParams";
 import { Config } from "./config/Config";
 import { ElementCallReactionEventType } from "./reactions";
+import { LOTUS_TO_WIDGET_ACTIONS } from "./lotus/lotusActions";
 
 // Subset of the actions in element-web
 export enum ElementWidgetActions {
@@ -103,6 +104,8 @@ export const initializeWidget = (
         ElementWidgetActions.JoinCall,
         ElementWidgetActions.HangupCall,
         ElementWidgetActions.DeviceMute,
+        // [lotus] custom toWidget actions handled by the fork (focus, audio-inject)
+        ...LOTUS_TO_WIDGET_ACTIONS,
       ].forEach((action) => {
         api.on(`action:${action}`, (ev: CustomEvent<IWidgetApiRequest>) => {
           ev.preventDefault();