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The hand-rolled std::format strings embedded literal newline and Unicode characters via C++ universal character name escapes (\u23f8, \u2014, \u25b6, \n), which the compiler converts to actual control characters in the output. Raw newlines inside JSON strings are invalid, so waybar's parser failed and displayed the raw JSON text instead of the widget. Build the status line with nlohmann::json, which escapes everything correctly.
screen_cast
A native Linux peer-to-peer screencast application.
- Send your desktop or a window to another Linux machine.
- Receive a stream and render it in a window.
- Discover receivers on the LAN via mDNS/Avahi; negotiate sessions with JSON signaling; stream H.264 over RTP/UDP.
Built with C++20, Meson, PipeWire, FFmpeg, and SDL3.
Quick start
Requirements:
- C++20 compiler with
<format>(GCC 13+, Clang 18+) - Meson >= 0.63, Ninja
- FFmpeg development packages (
libavcodec,libavutil,libswscale) - SDL3 development package (
sdl3) - nlohmann JSON (
nlohmann_json) and Avahi client (avahi-client) - For the sender only: PipeWire dev (
libpipewire-0.3) and libportal
Build and run tests:
meson setup build
meson compile -C build
meson test -C build --print-errorlogs
Stream between two machines:
screencast --receive # machine A: announces itself, opens a window
screencast --send # machine B: discovers A, negotiates, streams
See docs/RUNBOOK.md for all modes, flags, and validation procedures.
Receiver on a small ARM board (e.g. Raspberry Pi Zero 2 W)
The receiver does not need the sender's PipeWire/portal capture stack. On the board, run:
sudo ./scripts/install-receiver.sh
screencast --receive
The script installs the dependencies, builds a receiver-only binary
(-Dsender=false), runs the test suite, and installs to /usr/local/bin
(override with SC_RECEIVER_INSTALL_DIR). It needs Raspberry Pi OS Trixie
or newer (GCC 13+ for C++20 <format>), builds SDL3 from source when the
distribution does not package it, and enables avahi-daemon. It also
installs and enables a systemd service so the receiver starts at boot —
systemctl status screencast-receiver to check on it.
Performance note: decoding is software H.264; on very small boards expect smooth playback for modest resolutions and reduced frame rates at high resolutions. Hardware decode is planned for Phase 7. On a headless console the receiver runs fullscreen automatically with aspect-preserving letterboxing.
Architecture
See docs/ARCHITECTURE.md for module boundaries and design rules.
Roadmap
Development is split into phases in docs/PHASES.md.
Current phase: Phase 7 — Resilience and polish.
License
MIT — see LICENSE (to be added).