Add Nix flake and development shell (#645)

README.md

@@ -201,6 +201,28 @@ time.
 
 The CMake source root is the repository root.
 
+### Building on NixOS
+
+A development shell provides Clang, CMake, Ninja, Qt 6, the Vulkan headers, and the SDL2 backend
+libraries. Enter it and configure exactly as on other Linux distributions; the shell exports
+`CMAKE_PREFIX_PATH` and `QT_PLUGIN_PATH`, so the `-DCMAKE_PREFIX_PATH="$Qt6_DIR"` argument is not
+needed:
+
+```bash
+nix-shell # or: nix develop
+git submodule update --init --recursive
+
+cmake -S . -B _Build/linux -G Ninja -DCMAKE_BUILD_TYPE=Release \
+  -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++
+
+cmake --build _Build/linux --target launcher --parallel
+cmake --install _Build/linux --prefix _Build/linux/install
+```
+
+The configure step downloads the FFmpeg prebuilts and the `xbyak`/`zydis` sources, so it needs
+network access; a fully sandboxed `nix build` would require vendoring those inputs. A Vulkan 1.3
+driver must be available at runtime (on NixOS, `hardware.graphics.enable = true`).
+
 ### Building on macOS
 
 macOS builds target x86-64 and run under Rosetta 2 on Apple Silicon, so the PS5's x86-64 game

flake.lock

@@ -0,0 +1,27 @@
+{
+  "nodes": {
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1789426278,
+        "narHash": "sha256-GnotcvKtbTMnoVx6G4E7ZdUX6487Dky74dqq3pU7iRk=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "efe6f071ede9d21c37462d2d6682d5e670099684",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "nixos-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "nixpkgs": "nixpkgs"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}

flake.nix

@@ -0,0 +1,20 @@
+{
+  description = "KytyPS5 development shell";
+
+  inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+
+  outputs = { self, nixpkgs }:
+    let
+      systems = [ "x86_64-linux" ];
+      forAllSystems = nixpkgs.lib.genAttrs systems;
+    in
+    {
+      devShells = forAllSystems (system:
+        let
+          pkgs = import nixpkgs { inherit system; };
+        in
+        {
+          default = import ./nix/devshell.nix { inherit pkgs; };
+        });
+    };
+}

nix/devshell.nix

@@ -0,0 +1,84 @@
+{ pkgs }:
+
+let
+  # Build-time dependencies. Every -dev package the bundled SDL2 probes for must
+  # be listed here, otherwise SDL2 quietly drops the audio/Wayland/udev backends.
+  buildDeps = with pkgs; [
+    qt6.qtbase # Concurrent, Network, Widgets (launcher)
+    vulkan-headers
+    vulkan-loader
+    vulkan-tools
+    vulkan-validation-layers
+    libglvnd
+    # X11 / input
+    libX11
+    libXcursor
+    libXext
+    libXfixes
+    libXi
+    libXrandr
+    libXScrnSaver
+    libxkbcommon
+    # Wayland
+    wayland
+    wayland-protocols
+    libdecor
+    # audio + device/dbus
+    alsa-lib
+    libpulseaudio
+    systemd # libudev
+    dbus
+  ];
+
+  # Libraries the built binaries need at runtime.
+  runtimeLibs = with pkgs; [
+    stdenv.cc.cc.lib # libstdc++ / libgcc_s
+    libgcc.lib
+    qt6.qtbase # libQt6Concurrent/Network/Widgets
+    vulkan-loader
+    libglvnd
+    alsa-lib
+    libpulseaudio
+    libX11
+    libXcursor
+    libXext
+    libXfixes
+    libXi
+    libXrandr
+    libXScrnSaver
+    libxkbcommon
+    wayland
+    libdecor
+    systemd
+    dbus
+  ];
+in
+pkgs.mkShell {
+  name = "kytyps5";
+
+  nativeBuildInputs = with pkgs; [
+    clang
+    lld
+    cmake
+    ninja
+    pkg-config
+    git
+    glslang # provides glslangValidator for the bundled shaders
+  ];
+
+  buildInputs = buildDeps;
+
+  shellHook = ''
+    export CMAKE_PREFIX_PATH="${pkgs.qt6.qtbase}:''${CMAKE_PREFIX_PATH:-}"
+    export QT_PLUGIN_PATH="${pkgs.qt6.qtbase}/lib/qt-6/plugins:${pkgs.qt6.qtbase}/lib/qt6/plugins:''${QT_PLUGIN_PATH:-}"
+    export LD_LIBRARY_PATH="${pkgs.lib.makeLibraryPath runtimeLibs}:''${LD_LIBRARY_PATH:-}"
+
+    if [ -z "''${KYTY_SHELL_QUIET:-}" ]; then
+      echo "KytyPS5 dev shell"
+      echo "  cmake -S . -B _Build/linux -G Ninja -DCMAKE_BUILD_TYPE=Release \\"
+      echo "    -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++"
+      echo "  cmake --build _Build/linux --target launcher --parallel"
+      echo "  cmake --install _Build/linux --prefix _Build/linux/install"
+    fi
+  '';
+}

shell.nix

@@ -0,0 +1,4 @@
+let
+  pkgs = import <nixpkgs> { };
+in
+import ./nix/devshell.nix { inherit pkgs; }