pixelpass/flake.nix

{
  description = "PixelPass — P2P screen sharing CLI over iroh";

  inputs = {
    # Same channel the hosts run (nixos-config tracks nixos-26.05). The capture
    # path talks to the live PipeWire daemon and the system PulseAudio server,
    # so the client libraries here should come from the same release the server
    # did.
    nixpkgs.url = "github:nixos/nixpkgs/nixos-26.05";

    # The Rust toolchain is pinned SEPARATELY from the system libraries, so a
    # nixpkgs bump cannot move the compiler under the lint gate. nixpkgs 26.05
    # ships 1.95.0; this crate was developed and verified on 1.97.1, and
    # peerspeak — the sibling project this one is built against — has a clippy
    # lint that differs between exactly those two versions. Keeping both repos
    # on one pinned compiler means a check that passes here passes there.
    #
    # This is the reproducible alternative to rustup: the same exact-version
    # control, but recorded in flake.lock, so a fresh clone resolves the
    # identical toolchain rather than whatever rustup fetches that day.
    rust-overlay = {
      url = "github:oxalica/rust-overlay";
      inputs.nixpkgs.follows = "nixpkgs";
    };
  };

  outputs =
    { nixpkgs, rust-overlay, ... }:
    let
      system = "x86_64-linux";
      pkgs = import nixpkgs {
        inherit system;
        overlays = [ rust-overlay.overlays.default ];
      };

      # Matches what CachyOS shipped (rust 1:1.97.1-1) and what peerspeak pins.
      # `default` is the rustup "default" profile — rustc, cargo, rust-std,
      # rustfmt and clippy — so those are NOT listed separately below. No
      # windows-gnu target here: pixelpass is Linux-only (portal/PipeWire/X11
      # capture), unlike peerspeak which has a Windows port.
      rustToolchain = pkgs.rust-bin.stable."1.97.1".default;

      # GStreamer is driven as a SUBPROCESS (gst-launch-1.0 / gst-inspect-1.0),
      # not linked — there is no gstreamer-sys in Cargo.lock. So these are PATH
      # dependencies at runtime rather than build inputs, and `deps.rs` refuses
      # to start a share if any are missing.
      gstPlugins = with pkgs; [
        gst_all_1.gstreamer # gst-launch-1.0 / gst-inspect-1.0
        gst_all_1.gst-plugins-base # videoscale (quality-preset downscale)
        gst_all_1.gst-plugins-good # pulsesrc, ximagesrc
        gst_all_1.gst-plugins-bad # h264parse, mpegtsmux, aacparse, vah264enc
        gst_all_1.gst-plugins-ugly # x264enc (software-encode fallback)
        gst_all_1.gst-libav # avenc_aac
        pipewire # pipewiresrc (Wayland capture; ships in this pkg)
      ];

      # Opened with dlopen by the optional `--gui` front end (eframe/egui_glow/
      # winit/glutin), never linked. Harmless for the default headless build.
      guiRuntimeLibs = with pkgs; [
        libGL
        libxkbcommon
        wayland
        libx11
        libxcursor
        libxrandr
        libxi
      ];
    in
    {
      devShells.${system}.default = pkgs.mkShell {
        nativeBuildInputs =
          [ rustToolchain ]
          ++ (with pkgs; [
            # Debian packaging (`cargo deb --no-build`). Build the binary
            # inside a Debian/Ubuntu distrobox first so it links that distro's
            # glibc — see the packaging notes in Cargo.toml.
            cargo-deb

            pkg-config

            # pipewire-sys, libspa-sys and libpulse-sys all generate bindings
            # with bindgen, which needs a real libclang at build time.
            clang
          ])
          ++ gstPlugins
          ++ [
            # The rest of what `deps::check_host_binaries` looks for.
            pkgs.pulseaudio # `pactl` (PipeWire stays the actual audio server)
            pkgs.mpv # the viewer-side player
            pkgs.xwininfo # the `--window` click-picker on X11

            # `--doctor` shells out to vainfo to confirm the VA-API H.264
            # ENCODE entrypoint really exists. Without it the report can only
            # say "vah264enc and a render node are present" and has to leave
            # hardware encode unconfirmed — which matters, because a GPU
            # missing that entrypoint produces no video at all under the
            # default encoder rather than failing loudly.
            pkgs.libva-utils
          ];

        buildInputs =
          with pkgs;
          [
            pipewire # pipewire-sys + libspa-sys
            libpulseaudio # libpulse-sys: --repair reads/unloads Pulse modules

            # x11rb is declared `default-features = false` here, which by itself
            # is pure Rust — but Cargo unifies features across the graph, and
            # arboard pulls x11rb with its `libxcb` feature on. That drags in
            # as-raw-xcb-connection and makes the final link need -lxcb. It is a
            # real link-time dependency of the binary, not an optional extra.
            libxcb
          ]
          ++ guiRuntimeLibs;

        # bindgen finds libclang through this variable specifically — having
        # clang on PATH is not sufficient.
        LIBCLANG_PATH = "${pkgs.llvmPackages.libclang.lib}/lib";

        # NixOS keeps every GStreamer plugin in its own store path, so
        # gst-launch-1.0 discovers them ONLY through this search path. Without
        # it, pixelpass's `gst-inspect-1.0 --exists pipewiresrc` preflight fails
        # even though the plugins are installed. Same reasoning as the
        # GST_PLUGIN_SYSTEM_PATH_1_0 block in nixos-config hosts/darp5.
        GST_PLUGIN_SYSTEM_PATH_1_0 = pkgs.lib.makeSearchPathOutput "lib" "lib/gstreamer-1.0" gstPlugins;

        LD_LIBRARY_PATH = pkgs.lib.makeLibraryPath guiRuntimeLibs;

        # Only greet an interactive shell. shellHook also runs under
        # `nix develop --command …`, where printing this would interleave the
        # banner with the command's own output (and corrupt it outright for
        # anything whose stdout is parsed, such as pixelpass's `--output json`).
        shellHook = ''
          if [ -t 1 ]; then
            echo "pixelpass — rustc $(rustc --version | cut -d' ' -f2) / cargo $(cargo --version | cut -d' ' -f2)"
            echo "  cargo build --release                 headless build (what peerspeak spawns)"
            echo "  cargo build --release --features gui  with the egui front end"
            echo "  cargo test                            unit + integration tests"
            echo "  ./target/debug/pixelpass --doctor     verify this machine can host"
            echo
            echo "GStreamer, pactl, mpv and xwininfo are on PATH in this shell, so"
            echo "capture works here without a system rebuild."
          fi
        '';
      };
    };
}