build(packaging): add the Arch package, systemd unit and gamescope config

The PKGBUILD builds from the surrounding source tree (makepkg's -flto is
disabled because it breaks the libspa-sys C shim). The user unit and the
env example ship the intended deployment, and gamescope-tv.conf documents the
gamescope session it is meant to run against.

contrib/PKGBUILD

@@ -0,0 +1,64 @@
+# Arch Linux package built from this source tree (the directory above this PKGBUILD).
+#
+#   cd contrib && makepkg -si
+
+pkgname=gamescope-hyperhdr
+pkgver=0.1.0
+pkgrel=1
+pkgdesc="Feeds gamescope's PipeWire picture, downscaled by gamescope, to HyperHDR's flatbuffers server"
+arch=('x86_64' 'aarch64')
+license=('MIT')
+depends=('libpipewire' 'libgcc' 'glibc')
+makedepends=('cargo' 'clang' 'pkgconf')
+optdepends=('wireplumber: links the capture stream to the gamescope node')
+# makepkg's -flto turns libspa-sys' C shim into LTO bytecode that the Rust link step cannot
+# resolve (undefined spa_*_libspa_rs symbols).
+options=('!lto')
+
+_tree() {
+  realpath "$startdir/.."
+}
+
+pkgver() {
+  sed -n 's/^version = "\(.*\)"$/\1/p' "$(_tree)/Cargo.toml" | head -n1
+}
+
+prepare() {
+  rm -rf "$srcdir/$pkgname"
+  mkdir -p "$srcdir/$pkgname"
+  cp -a "$(_tree)"/{Cargo.toml,Cargo.lock,src,tests,examples,schema} "$srcdir/$pkgname/"
+
+  cd "$srcdir/$pkgname"
+  export RUSTUP_TOOLCHAIN=stable
+  cargo fetch --locked --target "$(rustc -vV | sed -n 's/host: //p')"
+}
+
+build() {
+  cd "$srcdir/$pkgname"
+  export RUSTUP_TOOLCHAIN=stable
+  # Outside the copied tree, so rebuilds stay incremental.
+  export CARGO_TARGET_DIR="$srcdir/target"
+  cargo build --frozen --release --bin gamescope-hyperhdr
+}
+
+check() {
+  cd "$srcdir/$pkgname"
+  export RUSTUP_TOOLCHAIN=stable
+  export CARGO_TARGET_DIR="$srcdir/target"
+  cargo test --frozen --release
+}
+
+package() {
+  local tree
+  tree="$(_tree)"
+  install -Dm755 "$srcdir/target/release/gamescope-hyperhdr" "$pkgdir/usr/bin/gamescope-hyperhdr"
+  install -Dm644 "$tree/contrib/systemd/gamescope-hyperhdr.service" \
+    "$pkgdir/usr/lib/systemd/user/gamescope-hyperhdr.service"
+  install -Dm644 "$tree/contrib/gamescope-hyperhdr.env.example" \
+    "$pkgdir/usr/share/doc/$pkgname/gamescope-hyperhdr.env.example"
+  install -Dm644 "$tree/contrib/systemd/gamescope-tv.conf" \
+    "$pkgdir/usr/share/doc/$pkgname/gamescope-tv.conf"
+  install -Dm644 "$tree/README.md" "$pkgdir/usr/share/doc/$pkgname/README.md"
+  install -Dm644 "$tree/LICENSE" "$pkgdir/usr/share/licenses/$pkgname/LICENSE"
+  install -Dm644 "$tree/schema/NOTICE" "$pkgdir/usr/share/licenses/$pkgname/NOTICE.HyperHDR"
+}

contrib/gamescope-hyperhdr.env.example

@@ -0,0 +1,23 @@
+# ~/.config/gamescope-hyperhdr/env — every flag can also be set here.
+
+# HyperHDR host (required)
+GSHDR_HOST=192.168.1.50
+#GSHDR_PORT=19400
+
+# Must be lower (= more important) than the USB grabber's priority (240)
+#GSHDR_PRIORITY=150
+#GSHDR_ORIGIN=gamescope
+
+# Frame size sent to HyperHDR and CPU supersampling factor (gamescope renders SIZE x N)
+#GSHDR_SIZE=320x180
+#GSHDR_SUPERSAMPLE=1
+
+#GSHDR_MAX_FPS=30
+#GSHDR_KEEPALIVE_MS=1000
+# Clear the priority after this many seconds without new frames (0 = off)
+#GSHDR_IDLE_CLEAR_SECS=0
+
+# node.name of the gamescope PipeWire node
+#GSHDR_TARGET=gamescope
+
+#RUST_LOG=info

contrib/systemd/gamescope-hyperhdr.service

@@ -0,0 +1,25 @@
+# User unit for gamescope-hyperhdr. The Arch package installs it into /usr/lib/systemd/user;
+# for a manual install copy it to ~/.config/systemd/user. It runs as the user of the PipeWire
+# session and waits for the gamescope node, so it can simply stay enabled. To run it only
+# together with gamescope-tv.service, add the gamescope-tv.conf drop-in.
+[Unit]
+Description=gamescope → HyperHDR ambilight feed
+After=pipewire.service wireplumber.service
+Wants=pipewire.service
+
+[Service]
+Type=simple
+# System-wide settings, overridden by the per-user file.
+EnvironmentFile=-/etc/gamescope-hyperhdr.env
+EnvironmentFile=-%h/.config/gamescope-hyperhdr/env
+# No absolute path: systemd searches /usr/local/bin and /usr/bin, which covers both the package
+# and a manual install.
+ExecStart=gamescope-hyperhdr
+Restart=on-failure
+RestartSec=2
+# Exit code 2 is a configuration error (e.g. GSHDR_HOST not set); restarting will not help.
+RestartPreventExitStatus=2
+NoNewPrivileges=yes
+
+[Install]
+WantedBy=default.target

contrib/systemd/gamescope-tv.conf

@@ -0,0 +1,13 @@
+# Drop-in for gamescope-hyperhdr.service: run the feed only together with gamescope-tv.service,
+# starting with it and stopping when it stops.
+#
+#   install -Dm644 gamescope-tv.conf ~/.config/systemd/user/gamescope-hyperhdr.service.d/gamescope-tv.conf
+#   systemctl --user daemon-reload
+#   systemctl --user add-wants gamescope-tv.service gamescope-hyperhdr.service
+#
+# The Arch package ships this file as /usr/share/doc/gamescope-hyperhdr/gamescope-tv.conf.
+# add-wants makes gamescope-tv.service pull the feed in. Do not also `enable` the feed:
+# BindsTo= would then start gamescope-tv.service whenever the feed starts.
+[Unit]
+BindsTo=gamescope-tv.service
+After=gamescope-tv.service