feat(lotus): io.lotus.screenshare_notice — window closed, no frames, sharing alone (#39)

Watches the local screenshare publication and tells the host, once per
share each: the MediaStreamTrack ended (window closed), it has been muted
(no frames — minimised/occluded window) for 15 s, or 30 min of sharing
with nobody else in the call. Detection only; the host renders the
notices. LiveKit already unpublishes an ended share, so nothing lingers.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPmy3tPq869XDW4njjVaKA

src/lotus/lotusScreenshareWatch.test.ts

@@ -0,0 +1,154 @@
+/*
+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 { RoomEvent, Track } from "livekit-client";
+import { BehaviorSubject } from "rxjs";
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
+
+import { type CallViewModel } from "../state/CallViewModel/CallViewModel";
+import {
+  ALONE_MS,
+  NO_FRAMES_MS,
+  startLotusScreenshareWatch,
+} from "./lotusScreenshareWatch";
+
+const sent: unknown[] = [];
+vi.mock("../widget", () => ({ widget: { api: {} } }));
+vi.mock("./lotusWidget", () => ({
+  lotusSendToHost: (action: string, data: unknown): boolean => {
+    sent.push({ action, data });
+    return true;
+  },
+}));
+
+class FakeTrack extends EventTarget {}
+
+const makeRoom = (): {
+  room: Record<string, unknown>;
+  emit: (event: string, ...args: unknown[]) => void;
+  remote: Map<string, unknown>;
+} => {
+  const handlers = new Map<string, ((...args: unknown[]) => void)[]>();
+  const remote = new Map<string, unknown>();
+  const room = {
+    remoteParticipants: remote,
+    localParticipant: { trackPublications: new Map() },
+    on: (event: string, h: (...args: unknown[]) => void): void => {
+      handlers.set(event, [...(handlers.get(event) ?? []), h]);
+    },
+    off: (event: string, h: (...args: unknown[]) => void): void => {
+      handlers.set(
+        event,
+        (handlers.get(event) ?? []).filter((x) => x !== h),
+      );
+    },
+  };
+  return {
+    room,
+    remote,
+    emit: (event, ...args): void => {
+      (handlers.get(event) ?? []).forEach((h) => h(...args));
+    },
+  };
+};
+
+describe("startLotusScreenshareWatch", () => {
+  let clock = 0;
+  beforeEach(() => {
+    sent.length = 0;
+    clock = 1_000_000;
+    vi.useFakeTimers();
+  });
+  afterEach(() => vi.useRealTimers());
+
+  const start = (): ReturnType<typeof makeRoom> & { stop: () => void } => {
+    const fake = makeRoom();
+    const connections = new BehaviorSubject({
+      getConnections: () => [{ livekitRoom: fake.room }],
+    });
+    const stop = startLotusScreenshareWatch(
+      { allConnections$: connections } as unknown as CallViewModel,
+      () => clock,
+    );
+    return { ...fake, stop };
+  };
+
+  it("reports a share whose track ended", () => {
+    const { emit, stop } = start();
+    const mst = new FakeTrack();
+    emit(RoomEvent.LocalTrackPublished, {
+      source: Track.Source.ScreenShare,
+      track: { mediaStreamTrack: mst },
+    });
+    mst.dispatchEvent(new Event("ended"));
+    expect(sent).toEqual([
+      { action: "io.lotus.screenshare_notice", data: { kind: "ended" } },
+    ]);
+    stop();
+  });
+
+  it("reports no frames after a sustained mute, once, and not after an unmute", () => {
+    const { emit, stop } = start();
+    const mst = new FakeTrack();
+    emit(RoomEvent.LocalTrackPublished, {
+      source: Track.Source.ScreenShare,
+      track: { mediaStreamTrack: mst },
+    });
+    mst.dispatchEvent(new Event("mute"));
+    vi.advanceTimersByTime(NO_FRAMES_MS / 2);
+    mst.dispatchEvent(new Event("unmute"));
+    vi.advanceTimersByTime(NO_FRAMES_MS);
+    expect(sent).toEqual([]);
+    mst.dispatchEvent(new Event("mute"));
+    vi.advanceTimersByTime(NO_FRAMES_MS);
+    mst.dispatchEvent(new Event("mute"));
+    vi.advanceTimersByTime(NO_FRAMES_MS);
+    expect(sent).toEqual([
+      { action: "io.lotus.screenshare_notice", data: { kind: "no-frames" } },
+    ]);
+    stop();
+  });
+
+  it("nudges after 30 min of sharing with nobody else, never while others are present", () => {
+    const { emit, remote, stop } = start();
+    emit(RoomEvent.LocalTrackPublished, {
+      source: Track.Source.ScreenShare,
+      track: { mediaStreamTrack: new FakeTrack() },
+    });
+    remote.set("bob", {});
+    clock += ALONE_MS + 60_000;
+    vi.advanceTimersByTime(60_000);
+    expect(sent).toEqual([]);
+    remote.clear();
+    vi.advanceTimersByTime(60_000);
+    vi.advanceTimersByTime(60_000);
+    expect(sent).toEqual([
+      { action: "io.lotus.screenshare_notice", data: { kind: "alone" } },
+    ]);
+    stop();
+  });
+
+  it("ignores non-screenshare publications and stops watching on unpublish", () => {
+    const { emit, stop } = start();
+    const cam = new FakeTrack();
+    emit(RoomEvent.LocalTrackPublished, {
+      source: Track.Source.Camera,
+      track: { mediaStreamTrack: cam },
+    });
+    cam.dispatchEvent(new Event("ended"));
+    const share = new FakeTrack();
+    const pub = {
+      source: Track.Source.ScreenShare,
+      track: { mediaStreamTrack: share },
+    };
+    emit(RoomEvent.LocalTrackPublished, pub);
+    emit(RoomEvent.LocalTrackUnpublished, pub);
+    share.dispatchEvent(new Event("ended"));
+    expect(sent).toEqual([]);
+    stop();
+  });
+});