Add Nix Flake (#77)

* Add Nix Flake

Co-authored-by: Bryce Berger <bryce.z.berger@gmail.com>

* Describe nix flake in readme

* Add `niri-config` to build source list

* Add maintainer info

Add comment at top to indicate the Nix Flake file
is community maintained.

* Clarify Nix/NixOS README instructions

* Shorten Nix/NixOS build instructions

Co-authored-by: Ivan Molodetskikh <yalterz@gmail.com>

* Move NixOS installation instruction to "Tip" section

---------

Co-authored-by: Bryce Berger <bryce.z.berger@gmail.com>
Co-authored-by: Ivan Molodetskikh <yalterz@gmail.com>

4 files changed, 254 insertions, 1 deletions

diff --git a/.gitignore b/.gitignore
index ea8c4bf7..d787b706 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1 +1,2 @@
 /target
+/result
diff --git a/README.md b/README.md
index 1f49ae76..77436afb 100644
--- a/README.md
+++ b/README.md
@@ -36,7 +36,7 @@ When a monitor disconnects, its workspaces will move to another monitor, but upo
 > [!TIP]
 > For Fedora users, there's a COPR with built and packaged niri: https://copr.fedorainfracloud.org/coprs/yalter/niri/
 >
-> NixOS users, check out https://github.com/sodiboo/niri-flake
+> For NixOS users, check out https://github.com/sodiboo/niri-flake
 
 First, install the dependencies for your distribution.
 
@@ -57,6 +57,16 @@ First, install the dependencies for your distribution.
 
 Next, build niri with `cargo build --release`.
 
+### NixOS/Nix
+
+We have a community-maintained flake which provides a devshell with required dependencies. Use `nix build` to build niri, and then run `./results/bin/niri`.
+    
+If you're not on NixOS, you may need [NixGL](https://github.com/nix-community/nixGL) to run the resulting binary:
+
+```
+nix run --impure github:guibou/nixGL -- ./results/bin/niri
+```
+
 ## Installation
 
 The recommended way to install and run niri is as a standalone desktop session.
diff --git a/flake.lock b/flake.lock
new file mode 100644
index 00000000..bdf52d54
--- /dev/null
+++ b/flake.lock
@@ -0,0 +1,138 @@
+{
+  "nodes": {
+    "crane": {
+      "inputs": {
+        "nixpkgs": [
+          "nixpkgs"
+        ]
+      },
+      "locked": {
+        "lastModified": 1702918879,
+        "narHash": "sha256-tWJqzajIvYcaRWxn+cLUB9L9Pv4dQ3Bfit/YjU5ze3g=",
+        "owner": "ipetkov",
+        "repo": "crane",
+        "rev": "7195c00c272fdd92fc74e7d5a0a2844b9fadb2fb",
+        "type": "github"
+      },
+      "original": {
+        "owner": "ipetkov",
+        "repo": "crane",
+        "type": "github"
+      }
+    },
+    "fenix": {
+      "inputs": {
+        "nixpkgs": [
+          "nixpkgs"
+        ],
+        "rust-analyzer-src": "rust-analyzer-src"
+      },
+      "locked": {
+        "lastModified": 1701411808,
+        "narHash": "sha256-K8QDx8UgbvGdENuvPvcsCXcd8brd55OkRDFLBT7xUVY=",
+        "owner": "nix-community",
+        "repo": "fenix",
+        "rev": "3776d0e2a30184cc6a0ba20fb86dc6df5b41fccd",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-community",
+        "ref": "monthly",
+        "repo": "fenix",
+        "type": "github"
+      }
+    },
+    "flake-utils": {
+      "inputs": {
+        "systems": "systems"
+      },
+      "locked": {
+        "lastModified": 1701680307,
+        "narHash": "sha256-kAuep2h5ajznlPMD9rnQyffWG8EM/C73lejGofXvdM8=",
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "rev": "4022d587cbbfd70fe950c1e2083a02621806a725",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "flake-utils",
+        "type": "github"
+      }
+    },
+    "nix-filter": {
+      "locked": {
+        "lastModified": 1701697642,
+        "narHash": "sha256-L217WytWZHSY8GW9Gx1A64OnNctbuDbfslaTEofXXRw=",
+        "owner": "numtide",
+        "repo": "nix-filter",
+        "rev": "c843418ecfd0344ecb85844b082ff5675e02c443",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "nix-filter",
+        "type": "github"
+      }
+    },
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1702900294,
+        "narHash": "sha256-pt7sSoJYNw3n8YtXw0Z/Nnr6/PfY2YrjDvqboErXnRM=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "886c9aee6ca9324e127f9c2c4e6f68c2641c8256",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "nixpkgs-unstable",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "crane": "crane",
+        "fenix": "fenix",
+        "flake-utils": "flake-utils",
+        "nix-filter": "nix-filter",
+        "nixpkgs": "nixpkgs"
+      }
+    },
+    "rust-analyzer-src": {
+      "flake": false,
+      "locked": {
+        "lastModified": 1701372675,
+        "narHash": "sha256-MSHhnAoLjJuoPxzsTzBOzNhjhlCTHPs4nvkPAZVV1eY=",
+        "owner": "rust-lang",
+        "repo": "rust-analyzer",
+        "rev": "c9d189d1375e59a6c9b4d62fdede94ade001f6ee",
+        "type": "github"
+      },
+      "original": {
+        "owner": "rust-lang",
+        "ref": "nightly",
+        "repo": "rust-analyzer",
+        "type": "github"
+      }
+    },
+    "systems": {
+      "locked": {
+        "lastModified": 1681028828,
+        "narHash": "sha256-Vy1rq5AaRuLzOxct8nz4T6wlgyUR7zLU309k9mBC768=",
+        "owner": "nix-systems",
+        "repo": "default",
+        "rev": "da67096a3b9bf56a91d16901293e51ba5b49a27e",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-systems",
+        "repo": "default",
+        "type": "github"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}
diff --git a/flake.nix b/flake.nix
new file mode 100644
index 00000000..3dd31050
--- /dev/null
+++ b/flake.nix
@@ -0,0 +1,104 @@
+# This flake file is community maintained
+# Maintainers:
+#   Bill Sun (github/billksun)
+{
+  description = "Niri: A scrollable-tiling Wayland compositor.";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
+    crane = {
+      url = "github:ipetkov/crane";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
+    flake-utils.url = "github:numtide/flake-utils";
+    nix-filter.url = "github:numtide/nix-filter";
+    fenix = {
+      url = "github:nix-community/fenix/monthly";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
+  };
+
+  outputs = {
+    self,
+    nixpkgs,
+    crane,
+    nix-filter,
+    flake-utils,
+    fenix,
+    ...
+  }: let
+    systems = ["aarch64-linux" "x86_64-linux"];
+  in
+    flake-utils.lib.eachSystem systems (
+      system: let
+        pkgs = nixpkgs.legacyPackages.${system};
+        toolchain = fenix.packages.${system}.complete.toolchain;
+        craneLib = crane.lib.${system}.overrideToolchain toolchain;
+
+        craneArgs = {
+          pname = "niri";
+          version = self.rev or "dirty";
+
+          src = nix-filter.lib.filter {
+            root = ./.;
+            include = [
+              ./src
+              ./niri-config
+              ./Cargo.toml
+              ./Cargo.lock
+              ./resources
+            ];
+          };
+
+          nativeBuildInputs = with pkgs; [
+            pkg-config
+            autoPatchelfHook
+            clang
+          ];
+
+          buildInputs = with pkgs; [
+            wayland
+            systemd # For libudev
+            seatd # For libseat
+            libxkbcommon
+            libinput
+            mesa # For libgbm
+            fontconfig
+            stdenv.cc.cc.lib
+            pipewire
+          ];
+
+          runtimeDependencies = with pkgs; [
+            wayland
+            mesa
+            libglvnd # For libEGL
+          ];
+
+          LIBCLANG_PATH = "${pkgs.libclang.lib}/lib";
+        };
+
+        cargoArtifacts = craneLib.buildDepsOnly craneArgs;
+        niri = craneLib.buildPackage (craneArgs // {inherit cargoArtifacts;});
+      in {
+        formatter = pkgs.alejandra;
+
+        checks.niri = niri;
+        packages.default = niri;
+
+        devShells.default = pkgs.mkShell.override {stdenv = pkgs.clangStdenv;} {
+          inherit (niri) nativeBuildInputs buildInputs LIBCLANG_PATH;
+          packages = niri.runtimeDependencies;
+
+          # Force linking to libEGL, which is always dlopen()ed, and to
+          # libwayland-client, which is always dlopen()ed except by the
+          # obscure winit backend.
+          RUSTFLAGS = map (a: "-C link-arg=${a}") [
+            "-Wl,--push-state,--no-as-needed"
+            "-lEGL"
+            "-lwayland-client"
+            "-Wl,--pop-state"
+          ];
+        };
+      }
+    );
+}