Feature - broadcast for live presentation

[niemes]

Live slide broadcasting / Present any deck online

Bento is really good, I'd been searching for a while for a PowerPoint alternative that handles presentations well, and the single-file format is what finally won me over. The one thing missing to fully replace PowerPoint Live / Prezi / Excalidraw presentations for me was presenting a deck online, live.

Since Bento already has the collab sync worker, I built a live broadcast feature on top of it. I'd love your feedback on whether it fits the project's direction before opening a PR.

What it does

• Broadcast toggle in speaker view — one button arms the broadcast; the popup shows a shareable link and the live viewer count.
• "Save broadcast copy…" in the Share menu — exports a standalone viewer file that boots into a locked present-follow mode. It follows the presenter's show slide-for-slide, transitions and morphs included, because it runs the real renderer on its own copy of the document.
• Hosted link — when the deck carries a hosting URL (Document properties), the speaker popup shows a full link (host/file?room=) so you share a URL instead of the file.
• Navigation, laser pointer, and black screen sync in real time. Viewers need no account, no write access, no collab keys.

Design highlights — I believe (after digging the contribution.md) these match Bento's philosophy

• The relay stays blind: the nav channel carries only a slide number (plus laser/black control), never content. The relay never holds a document, consistent with the existing ciphertext-only collab design. (Laser needed some rework to be properly synced)
• No account system: the room is derived from the presenter's signing key; the relay pins that key per room (trust-on-first-use). The only backend change is the existing worker.
• Write is impossible: control frames are ECDSA-signed and verified by the relay; the broadcast copy carries no keys.
• Format stays additive: collab.broadcast is an optional field — old files open unchanged.
• The broadcast copy is a plaintext file share, the same trust model as "Save read-only copy…".

Implementation state

It's fully implemented and tested: a relay control-frame test suite (unsigned/forged/member-key frames dropped, replay order, presence, rate limiting), the single-file build, and a verified two-tab browser flow. The worker change needs a wrangler deploy for enforcement, ofcourse. I needed this feature for my own projects and think could be a useful for a lot of people.

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Does this fit with the direction of the project? I'd love to hear your thoughts.
I can open the PR if you're open to it.

Cheers!

[nyblnet]

Thanks, this looks really cool. Since you seem to have already working code, please submit a PR and we can see how to best merge it in. Generally speaking, the biggest consideration I have is to ensure the core runtime remains small.

[fyn93]

Live demo: https://cnb.cool/Black_Myth_wukong/next-ppt

same idea！ we have a runable version for chinese, run on a platform called https://cnb.cool, which run by Tencent.
maybe you can try , i‘ll be happy if there is any discussion or colleboration.