Presenter: Live Capture + Relay + Remote Annotation

At its core, Presenter bridges desktop capture to remote viewers. The Electron PC app captures the desktop (or individual windows), compresses video with hardware encoders (NVIDIA NVENC, Intel QSV, or software fallback), and routes frames either to an embedded in-process hub or to a Docker-hosted relay server. The viewer side is a PWA that runs on iPad or web browsers, connected over WebSocket, receiving video frames and broadcasting annotation strokes (pen, arrow, text, image) back to all participants in real time.

The architecture is built around three deployment modes. Local mode pairs a single iPad directly to the PC via QR code—zero external infrastructure. Embedded mode spins up a lightweight Node.js hub inside the Electron process itself, so viewers on the local network can connect without Docker. External hub mode connects to a remote Docker container, supporting multiple rooms and member rosters, ideal for large streams or VPS deployment. All three modes use the same CBOR protocol and can be switched at runtime.

The system's centerpiece is a transparent overlay window on Windows that floats the toolbar and annotation UI over the live desktop without obscuring what's being presented. This required solving multiple DirectComposition, DWM cloak, and opacity bugs specific to Chromium on Win11. The native addon (C++, presenter_stream.node) handles OS-level capture, GPU composition, encoder probing, and cursor tracking; the renderer coordinates layers, annotations, recording, and stream dispatch. MP4 muxing happens in the main process to avoid starving the renderer's audio pump.