From e571187361ec9af1db8fba9050c23ec10db677f4 Mon Sep 17 00:00:00 2001
From: Adam Soltys <adam@coinos.io>
Date: Mon, 19 Oct 2026 00:01:52 -0700
Subject: Screen sharing. In a call: Share screen in the call's bar (where the
 browser can — desktops) puts your screen in your camera's place, or into the
 call if your camera's off; Stop sharing, or the browser's own, brings the
 camera back or stops the picture, and the other side's view follows (a
 picture that stops coming is hidden). Live: Share screen / Back to camera on
 the broadcast bar switches without stopping the stream; the browser's Stop
 sharing goes back to the camera instead of ending it, and a cancelled screen
 picker leaves the camera going.
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Content-Transfer-Encoding: 8bit

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_013ZDf1cyCQLkfjftYhymZAg
---
 src/calls.js | 60 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 58 insertions(+), 2 deletions(-)

(limited to 'src/calls.js')

diff --git a/src/calls.js b/src/calls.js
index 366b00d..8ff32e9 100644
--- a/src/calls.js
+++ b/src/calls.js
@@ -89,6 +89,7 @@ export function createCalls(env) {
 
   function stopMedia(c) {
     for (const s of [c.local]) if (s) for (const t of s.getTracks()) { try { t.stop(); } catch {} }
+    for (const t of [c.cam, c.screen]) if (t) { try { t.stop(); } catch {} } // the camera set aside while sharing
     try { c.pc && c.pc.close(); } catch {}
   }
   function end(reason, c = call) {
@@ -111,7 +112,12 @@ export function createCalls(env) {
     const pc = new PC({ iceServers: await env.iceServers(), bundlePolicy: 'max-bundle', iceCandidatePoolSize: 2 });
     c.pc = pc;
     c.remote = new MediaStream();
-    pc.ontrack = (e) => { for (const t of (e.streams[0] || { getTracks: () => [e.track] }).getTracks()) if (!c.remote.getTracks().includes(t)) c.remote.addTrack(t); changed(); };
+    pc.ontrack = (e) => {
+      for (const t of (e.streams[0] || { getTracks: () => [e.track] }).getTracks()) if (!c.remote.getTracks().includes(t)) c.remote.addTrack(t);
+      // a picture that stops coming (they stopped sharing, camera and all) mutes
+      e.track.onmute = e.track.onunmute = changed;
+      changed();
+    };
     c.trickle = env.trickle ? env.trickle() !== false : true;
     c.sent = [];
     pc.onicecandidate = (e) => {
@@ -285,6 +291,56 @@ export function createCalls(env) {
     await c.pc.setLocalDescription(await c.pc.createOffer());
     await sendFor(c, CALL.RENEGOTIATE, c.peer, c.pc.localDescription.sdp);
   }
+  // Your screen in the call: in the camera's place if it's on (a swap, no new
+  // offer), else into the video slot by a renegotiation, as addVideo does.
+  // Stopping — here or from the browser's own Stop sharing — brings the
+  // camera back if it was on, else stops sending a picture.
+  async function shareScreen() {
+    const c = call;
+    if (!c || c.state !== 'connected' || !c.pc || c.sharing) return;
+    let track;
+    try { track = (await env.media('screen')).getVideoTracks()[0]; } catch { return; }
+    if (!track) return;
+    if (call !== c || c.state !== 'connected') { track.stop(); return; }
+    try { track.contentHint = 'detail'; } catch {}
+    const cam = c.local.getVideoTracks()[0] || null;
+    Object.assign(c, { sharing: true, screen: track, cam });
+    c.local = new MediaStream([...c.local.getAudioTracks(), track]);
+    let renego = false;
+    const sender = c.pc.getSenders().find((x) => x.track && x.track.kind === 'video');
+    if (sender) await sender.replaceTrack(track);
+    else {
+      const tr = c.pc.getTransceivers().find((x) => !x.stopped && !x.sender.track && x.receiver.track && x.receiver.track.kind === 'video');
+      if (tr) { await tr.sender.replaceTrack(track); if (tr.direction !== 'sendrecv') { tr.direction = 'sendrecv'; renego = true; } }
+      else { c.pc.addTrack(track, c.local); renego = true; }
+    }
+    c.type = 'video';
+    track.onended = () => { if (call === c && c.screen === track) stopShare(); };
+    changed();
+    if (renego) await renegotiate(c).catch(() => {});
+  }
+  async function stopShare() {
+    const c = call;
+    if (!c || !c.sharing) return;
+    const track = c.screen, cam = c.cam;
+    Object.assign(c, { sharing: false, screen: null, cam: null });
+    try { track.stop(); } catch {}
+    if (!c.pc || c.state === 'ended') return;
+    const sender = c.pc.getSenders().find((x) => x.track === track);
+    if (cam && cam.readyState === 'live') {
+      if (sender) await sender.replaceTrack(cam).catch(() => {});
+      c.local = new MediaStream([...c.local.getAudioTracks(), cam]);
+      changed();
+      return;
+    }
+    c.local = new MediaStream(c.local.getAudioTracks());
+    changed();
+    if (sender) {
+      await sender.replaceTrack(null).catch(() => {});
+      const tr = c.pc.getTransceivers().find((x) => x.sender === sender);
+      if (tr && !tr.stopped) { tr.direction = 'recvonly'; await renegotiate(c).catch(() => {}); }
+    }
+  }
   // the other camera: the sender's track swapped, no new offer needed
   async function flip() {
     const c = call;
@@ -401,7 +457,7 @@ export function createCalls(env) {
 
   return {
     get call() { return call; },
-    start, accept, reject, hangup, setMuted, setCamOff, flip, addVideo, handle,
+    start, accept, reject, hangup, setMuted, setCamOff, flip, addVideo, shareScreen, stopShare, handle,
     // a sign-out or account switch: whatever was going on ends here
     stop() { if (call && call.state !== 'ended') hangup(); call = null; early.clear(); },
   };
-- 
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