Add pointing UIWorker example

The voice LLM delegates to a ReplyToolMixin UIWorker that scrolls offscreen
items into view and highlights the phones it names — exercising the scroll_to /
highlight UI commands and the [offscreen] state tag.

examples/multi-worker/ui-worker/pointing/client/main.js

@@ -0,0 +1,170 @@
+/**
+ * Pointing — vanilla JS client.
+ *
+ * Builds on the hello-snapshot wiring (PipecatClient +
+ * managed snapshot streaming + bot audio sink) and adds two command
+ * handlers: ``scroll_to`` and ``highlight``. Both resolve the target
+ * element via ``findElementByRef`` (the snapshot ref system the
+ * walker assigns) and act on the live DOM node.
+ *
+ * The React SDK ships ``useDefaultScrollToHandler`` and
+ * ``useDefaultHighlightHandler`` that do this same work in hooks.
+ * Vanilla apps subscribe to ``RTVIEvent.UICommand`` and filter by
+ * command name.
+ */
+
+import {
+  PipecatClient,
+  RTVIEvent,
+  findElementByRef,
+} from "@pipecat-ai/client-js";
+import { SmallWebRTCTransport } from "@pipecat-ai/small-webrtc-transport";
+
+const BOT_URL = "http://localhost:7860/api/offer";
+
+const connectButton = document.getElementById("connect");
+const status = document.getElementById("status");
+const botAudio = document.getElementById("bot-audio");
+
+let client;
+let unsubscribes = [];
+
+function setStatus(text, autoHideMs = 0) {
+  status.textContent = text;
+  status.dataset.show = text ? "1" : "0";
+  if (text && autoHideMs > 0) {
+    setTimeout(() => {
+      if (status.textContent === text) status.dataset.show = "0";
+    }, autoHideMs);
+  }
+}
+
+/**
+ * Resolve a payload that carries either ``ref`` (snapshot id) or
+ * ``target_id`` (DOM element id). Match what the standard React
+ * handlers do: prefer ref, fall back to target_id.
+ */
+function resolveTarget(payload) {
+  if (payload?.ref) {
+    const el = findElementByRef(payload.ref);
+    if (el) return el;
+  }
+  if (payload?.target_id) {
+    return document.getElementById(payload.target_id);
+  }
+  return null;
+}
+
+function handleScrollTo(payload) {
+  const el = resolveTarget(payload);
+  if (!el) return;
+  const behavior =
+    payload?.behavior === "instant" || payload?.behavior === "smooth"
+      ? payload.behavior
+      : "smooth";
+  el.scrollIntoView({ behavior, block: "center", inline: "nearest" });
+}
+
+function handleHighlight(payload) {
+  const el = resolveTarget(payload);
+  if (!el) return;
+  // The page CSS defines ``.ui-highlight`` as a keyframe pulse —
+  // scale + glow + tint, settling back. The animation duration is
+  // driven by the ``--highlight-duration`` CSS variable so the
+  // server-supplied ``duration_ms`` actually controls it.
+  const duration = payload?.duration_ms ?? 1500;
+  el.style.setProperty("--highlight-duration", `${duration}ms`);
+  // Re-trigger the animation cleanly if a previous highlight is
+  // still running on this element.
+  el.classList.remove("ui-highlight");
+  void el.offsetWidth; // force reflow so removing + re-adding restarts
+  el.classList.add("ui-highlight");
+  setTimeout(() => {
+    el.classList.remove("ui-highlight");
+    el.style.removeProperty("--highlight-duration");
+  }, duration);
+}
+
+function onUICommand(command, handler) {
+  const listener = (data) => {
+    if (data.command !== command) return;
+    handler(data.payload);
+  };
+  client.on(RTVIEvent.UICommand, listener);
+  return () => client.off(RTVIEvent.UICommand, listener);
+}
+
+async function connect() {
+  connectButton.disabled = true;
+  setStatus("Connecting…");
+
+  client = new PipecatClient({
+    transport: new SmallWebRTCTransport(),
+    enableMic: true,
+    enableCam: false,
+  });
+
+  client.on(RTVIEvent.BotConnected, () => setStatus("Bot connected", 1500));
+  client.on(RTVIEvent.Disconnected, () => {
+    setStatus("Disconnected", 2000);
+    connectButton.dataset.state = "";
+    connectButton.textContent = "Connect";
+    connectButton.disabled = false;
+    teardownUI();
+  });
+
+  // Pipe the bot's audio track into the <audio> sink.
+  client.on(RTVIEvent.TrackStarted, (track, participant) => {
+    if (track.kind !== "audio") return;
+    if (participant?.local) return;
+    botAudio.srcObject = new MediaStream([track]);
+  });
+
+  unsubscribes = [
+    onUICommand("scroll_to", handleScrollTo),
+    onUICommand("highlight", handleHighlight),
+  ];
+
+  try {
+    await client.connect({ webrtcUrl: BOT_URL });
+    client.startUISnapshotStream();
+    connectButton.dataset.state = "connected";
+    connectButton.textContent = "Disconnect";
+    connectButton.disabled = false;
+    setStatus("Connected. Try: 'where's the Pixel 9?'", 4000);
+  } catch (err) {
+    console.error("Connect failed:", err);
+    setStatus(`Connect failed: ${err.message ?? err}`, 4000);
+    teardownUI();
+    connectButton.disabled = false;
+  }
+}
+
+async function disconnect() {
+  connectButton.disabled = true;
+  setStatus("Disconnecting…");
+  try {
+    await client?.disconnect();
+  } finally {
+    teardownUI();
+    connectButton.dataset.state = "";
+    connectButton.textContent = "Connect";
+    connectButton.disabled = false;
+  }
+}
+
+function teardownUI() {
+  client?.stopUISnapshotStream();
+  unsubscribes.forEach((unsubscribe) => unsubscribe());
+  unsubscribes = [];
+  if (botAudio.srcObject) botAudio.srcObject = null;
+  client = undefined;
+}
+
+connectButton.addEventListener("click", () => {
+  if (connectButton.dataset.state === "connected") {
+    disconnect();
+  } else {
+    connect();
+  }
+});