From 4a48ec98d02a2c1b409e1648e936abf1550e4a1b Mon Sep 17 00:00:00 2001
From: Lotus CI <ci@lotusguild.org>
Date: Sun, 20 Sep 2026 15:31:33 -0400
Subject: [PATCH] =?UTF-8?q?feat(lotus):=20io.lotus.set=5Faudio=5Foutput=20?=
 =?UTF-8?q?=E2=80=94=20host-driven=20output=20device=20switch=20(#119)?=
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The embed hides Element Call's footer, so its own output picker is out of
reach; the host's call bar now sends io.lotus.set_audio_output { deviceId }
and the fork applies it via mediaDevices.audioOutput.select(), answering
with io.lotus.audio_output_state { deviceId } on every change.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPmy3tPq869XDW4njjVaKA
---
 src/lotus/lotusActions.test.ts |  1 +
 src/lotus/lotusActions.ts      |  5 ++++
 src/lotus/lotusAudioOutput.ts  | 46 ++++++++++++++++++++++++++++++++++
 src/room/InCallView.tsx        |  7 ++++++
 4 files changed, 59 insertions(+)
 create mode 100644 src/lotus/lotusAudioOutput.ts

diff --git a/src/lotus/lotusActions.test.ts b/src/lotus/lotusActions.test.ts
index 787acce8..ce56bedb 100644
--- a/src/lotus/lotusActions.test.ts
+++ b/src/lotus/lotusActions.test.ts
@@ -26,6 +26,7 @@ describe("LotusWidgetActions", () => {
       LotusWidgetActions.SetQuality,
       LotusWidgetActions.Decorations,
       LotusWidgetActions.SetDeafen,
+      LotusWidgetActions.SetAudioOutput,
     ];
 
     expect(new Set(LOTUS_TO_WIDGET_ACTIONS)).toEqual(new Set(expectedToWidget));
diff --git a/src/lotus/lotusActions.ts b/src/lotus/lotusActions.ts
index 3e504664..7dd85df2 100644
--- a/src/lotus/lotusActions.ts
+++ b/src/lotus/lotusActions.ts
@@ -52,6 +52,10 @@ export enum LotusWidgetActions {
    * disconnect or in-call teardown, whichever comes first.
    */
   CallSummary = "io.lotus.call_summary",
+  /** toWidget: select the audio output device `{ deviceId }` (#119). */
+  SetAudioOutput = "io.lotus.set_audio_output",
+  /** fromWidget: the currently selected output `{ deviceId }` (#119). */
+  AudioOutputState = "io.lotus.audio_output_state",
 }
 
 /** toWidget Lotus actions that must be allow-listed in `initializeWidget`. */
@@ -61,4 +65,5 @@ export const LOTUS_TO_WIDGET_ACTIONS: LotusWidgetActions[] = [
   LotusWidgetActions.SetQuality,
   LotusWidgetActions.Decorations,
   LotusWidgetActions.SetDeafen,
+  LotusWidgetActions.SetAudioOutput,
 ];
diff --git a/src/lotus/lotusAudioOutput.ts b/src/lotus/lotusAudioOutput.ts
new file mode 100644
index 00000000..c114c9a9
--- /dev/null
+++ b/src/lotus/lotusAudioOutput.ts
@@ -0,0 +1,46 @@
+/*
+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 { logger } from "matrix-js-sdk/lib/logger";
+
+import { type MediaDevices } from "../state/MediaDevices";
+import { widget } from "../widget";
+import { LotusWidgetActions } from "./lotusActions";
+import { lotusSendToHost } from "./lotusWidget";
+
+/**
+ * [Gitea #119] Let the host switch the audio output device (headset ↔
+ * speakers) from its own call bar: `io.lotus.set_audio_output { deviceId }`
+ * selects the output; the fork answers each change (and the initial state)
+ * with `io.lotus.audio_output_state { deviceId, available: [{id,label}] }`.
+ * No effect unless the host sends the action. Returns a teardown function.
+ */
+export function startLotusAudioOutput(mediaDevices: MediaDevices): () => void {
+  const w = widget;
+  if (!w) return () => undefined;
+
+  const handler = (ev: CustomEvent<IWidgetApiRequest>): void => {
+    w.api.transport.reply(ev.detail, {});
+    const data = ev.detail.data as { deviceId?: string } | undefined;
+    if (typeof data?.deviceId !== "string") return;
+    logger.debug(`[lotus] set_audio_output: ${data.deviceId}`);
+    mediaDevices.audioOutput.select(data.deviceId);
+  };
+  w.lazyActions.on(LotusWidgetActions.SetAudioOutput, handler);
+
+  const sub = mediaDevices.audioOutput.selected$.subscribe((selected) => {
+    lotusSendToHost(LotusWidgetActions.AudioOutputState, {
+      deviceId: selected?.id ?? null,
+    });
+  });
+
+  return () => {
+    sub.unsubscribe();
+    w.lazyActions.off(LotusWidgetActions.SetAudioOutput, handler);
+  };
+}
diff --git a/src/room/InCallView.tsx b/src/room/InCallView.tsx
index 9d0d96c3..eef6f987 100644
--- a/src/room/InCallView.tsx
+++ b/src/room/InCallView.tsx
@@ -36,6 +36,7 @@ import { startLotusQuality } from "../lotus/lotusQuality";
 import { startLotusDecorations } from "../lotus/lotusDecorations";
 import { startLotusDenoise } from "../lotus/lotusDenoise";
 import { startLotusCallSummary } from "../lotus/lotusCallSummary";
+import { startLotusAudioOutput } from "../lotus/lotusAudioOutput";
 import { startLotusDeafen } from "../lotus/lotusDeafen";
 import styles from "./InCallView.module.css";
 import { GridTile } from "../tile/GridTile";
@@ -315,6 +316,12 @@ export const InCallView: FC<InCallViewProps> = ({
   // audio (and optionally screenshare audio) at the LiveKit source. No-op
   // unless the host sends the action.
   useEffect(() => startLotusDeafen(), []);
+  // [lotus #119] Let the host pick the audio output device from its call bar.
+  const lotusMediaDevices = useMediaDevices();
+  useEffect(
+    () => startLotusAudioOutput(lotusMediaDevices),
+    [lotusMediaDevices],
+  );
 
   const fatalCallError = useBehavior(vm.fatalError$);
   // Stop the rendering and throw for the error boundary