# screencast-receiver.service — autostart for the receiver.
#
# This file is a template: scripts/install-receiver.sh substitutes
# __SC_RECEIVER_BIN__ and __SC_RECEIVER_USER__ before installing it to
# /etc/systemd/system/screencast-receiver.service.
#
# Display environments:
#
# 1. Headless console (SDL renders via KMSDRM): works as installed. The
#    configured User needs access to /dev/dri and the input devices; the
#    install script adds it to the video/render/input groups.
#
# 2. Graphical session (Wayland or X11 desktop with autologin): uncomment
#    the Environment lines in [Service] and adjust them to the session
#    owner (XDG_RUNTIME_DIR usually lives in /run/user/1000).

[Unit]
Description=Screencast receiver (H.264 over RTP/UDP)
Wants=network-online.target
After=network-online.target avahi-daemon.service
# Give slow-booting boards (and desktop sessions that start late) a chance;
# systemd's default limit would give up after 5 fast failures.
StartLimitIntervalSec=30
StartLimitBurst=10

[Service]
Type=simple
User=__SC_RECEIVER_USER__
# SDL's KMSDRM backend wants a tty. The service gets its OWN virtual
# terminal: systemd must acquire the controlling terminal before exec, and
# acquiring one that another session owns (tty1: getty, console autologin,
# or a desktop) blocks the start FOREVER in a pre-exec placeholder process
# (systemctl status shows the main PID as "(screencast)"). tty7 is free on
# stock systems; tty1 keeps the console login.
ExecStartPre=-/usr/bin/chvt 7
ExecStart=__SC_RECEIVER_BIN__ --receive
StandardInput=tty
TTYPath=/dev/tty7
# SIGTERM (systemctl stop) shuts the receiver down gracefully, which
# withdraws its mDNS announcement. Never SIGKILL it; the systemd default
# KillMode escalates only after the graceful timeout.
KillSignal=SIGTERM
TimeoutStopSec=10
Restart=on-failure
RestartSec=3
NoNewPrivileges=true
PrivateTmp=true

# Graphical session: uncomment and adjust to the session owner.
#Environment=XDG_RUNTIME_DIR=/run/user/1000
#Environment=WAYLAND_DISPLAY=wayland-0
#Environment=DISPLAY=:0

[Install]
WantedBy=multi-user.target

# Headless console recipe (no window manager needed — SDL renders directly
# to the kernel via KMSDRM):
#   * Raspberry Pi OS Lite, no desktop enabled (a running compositor would
#     hold the DRM master and the receiver could not take it)
#   * no console autologin needed: the service owns tty7 and switches to it
#     at boot; Ctrl+Alt+F1 returns to the console login, Ctrl+Alt+F7 to the
#     screencast
#   * disable console blanking: add consoleblank=0 to
#     /boot/firmware/cmdline.txt