nix: add overlay, remove flake-parts, and other changes

Most of the changes are heavily inspired by the structure of Niri's
flake.nix.
- add overlay
- add formatter for nix
- remove flake-parts
- use rust-overlay only for the dev shell. end users can set `inputs.rust-overlay.follows = ""` to skip downloading it.
- add rust-analyzer and rust-src extensions in the dev shell
- filter the source in order to reduce rebuilds
- support all Linux systems that the nixpkgs flake exposes
- override VERGEN_GIT_DESCRIBE to include the git rev as well
- remove `clangStdenv` from the dev shell.  I'm not sure what purpose it served. If the intention was faster linking with lld, then it's not needed anymore, now that lld has become the default linker in rust 1.90.0.

.gitignore

@@ -1 +1,2 @@
 /target
+/result

flake.lock

@@ -1,23 +1,5 @@
 {
   "nodes": {
-    "flake-utils": {
-      "inputs": {
-        "systems": "systems"
-      },
-      "locked": {
-        "lastModified": 1731533236,
-        "narHash": "sha256-l0KFg5HjrsfsO/JpG+r7fRrqm12kzFHyUHqHCVpMMbI=",
-        "owner": "numtide",
-        "repo": "flake-utils",
-        "rev": "11707dc2f618dd54ca8739b309ec4fc024de578b",
-        "type": "github"
-      },
-      "original": {
-        "owner": "numtide",
-        "repo": "flake-utils",
-        "type": "github"
-      }
-    },
     "nixpkgs": {
       "locked": {
         "lastModified": 1764522689,
@@ -36,7 +18,6 @@
     },
     "root": {
       "inputs": {
-        "flake-utils": "flake-utils",
         "nixpkgs": "nixpkgs",
         "rust-overlay": "rust-overlay"
       }
@@ -60,21 +41,6 @@
         "repo": "rust-overlay",
         "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",

flake.nix

@@ -1,46 +1,60 @@
 {
+  description = "Xwayland outside your Wayland";
+
   inputs = {
     nixpkgs.url = "github:NixOS/nixpkgs/nixos-25.11";
-    flake-utils.url = "github:numtide/flake-utils";
+
+    # NOTE: This is not necessary for end users
+    # You can omit it with `inputs.rust-overlay.follows = ""`
     rust-overlay = {
       url = "github:oxalica/rust-overlay";
       inputs.nixpkgs.follows = "nixpkgs";
     };
   };
 
-  outputs = { self, nixpkgs, rust-overlay, flake-utils }:
+  outputs =
-    let systems = [ "x86_64-linux" "aarch64-linux" ];
+    {
-    in flake-utils.lib.eachSystem systems (system:
+      self,
+      nixpkgs,
+      rust-overlay,
+    }:
     let
-        overlays = [ (import rust-overlay) ];
-        pkgs = import nixpkgs { inherit system overlays; };
-
       cargoToml = builtins.fromTOML (builtins.readFile ./Cargo.toml);
       cargoPackageVersion = cargoToml.package.version;
-
       commitHash = self.shortRev or self.dirtyShortRev or "unknown";
 
+      xwayland-satellite-package =
+        {
+          lib,
+          rustPlatform,
+          pkg-config,
+          makeBinaryWrapper,
+          libxcb,
+          xcb-util-cursor,
+          xwayland,
+          withSystemd ? true,
+        }:
+        rustPlatform.buildRustPackage (finalAttrs: {
+          pname = "xwayland-satellite";
           version = "${cargoPackageVersion}-${commitHash}";
 
-        buildXwaylandSatellite =
+          src = lib.fileset.toSource {
-          { lib
+            root = ./.;
-          , rustPlatform
+            fileset = lib.fileset.unions [
-          , pkg-config
+              ./OpenSans-Regular.ttf
-          , makeBinaryWrapper
+              ./build.rs
-          , libxcb
+              ./macros
-          , xcb-util-cursor
+              ./testwl
-          , xwayland
+              ./wl_drm
-          , withSystemd ? true
+              ./resources
-          }:
+              ./src
-
+              ./Cargo.toml
-          rustPlatform.buildRustPackage rec {
+              ./Cargo.lock
-            pname = "xwayland-satellite";
+            ];
-            inherit version;
+          };
-
-            src = self;
 
           cargoLock = {
-              lockFile = "${src}/Cargo.lock";
+            lockFile = ./Cargo.lock;
             allowBuiltinFetchGit = true;
           };
 
@@ -56,24 +70,25 @@
           ];
 
           buildNoDefaultFeatures = true;
-            buildFeatures = lib.optionals withSystemd [ "systemd" ];
+          buildFeatures = lib.optional withSystemd "systemd";
 
-            postPatch = ''
+          doCheck = false;
-              substituteInPlace resources/xwayland-satellite.service \
-                --replace-fail '/usr/local/bin' "$out/bin"
-            '';
 
-            postInstall = lib.optionalString withSystemd ''
+          env.VERGEN_GIT_DESCRIBE = finalAttrs.version;
+
+          postInstall = ''
+            wrapProgram $out/bin/xwayland-satellite \
+              --prefix PATH : "${lib.makeBinPath [ xwayland ]}"
+          ''
+          + lib.optionalString withSystemd ''
             install -Dm0644 resources/xwayland-satellite.service -t $out/lib/systemd/user
           '';
 
-            postFixup = ''
+          postFixup = lib.optionalString withSystemd ''
-              wrapProgram $out/bin/xwayland-satellite \
+            substituteInPlace $out/lib/systemd/user/xwayland-satellite.service \
-                --prefix PATH : "${lib.makeBinPath [ xwayland ]}"
+              --replace-fail /usr/local/bin $out/bin
           '';
 
-            doCheck = false;
-
           meta = with lib; {
             description = "Xwayland outside your Wayland";
             homepage = "https://github.com/Supreeeme/xwayland-satellite";
@@ -81,26 +96,60 @@
             mainProgram = "xwayland-satellite";
             platforms = platforms.linux;
           };
-          };
+        });
 
-        xwayland-satellite = pkgs.callPackage buildXwaylandSatellite { };
+      inherit (nixpkgs) lib;
+
+      # Support all Linux systems that the nixpkgs flake exposes
+      systems = lib.intersectLists lib.systems.flakeExposed lib.platforms.linux;
+
+      forAllSystems = lib.genAttrs systems;
+      nixpkgsFor = forAllSystems (system: nixpkgs.legacyPackages.${system});
     in
     {
-        devShell = (pkgs.mkShell.override { stdenv = pkgs.clangStdenv; }) {
+      devShells = forAllSystems (
-          buildInputs = with pkgs; [
+        system:
-            rustPlatform.bindgenHook
+        let
-            rust-bin.stable.latest.default
+          pkgs = nixpkgsFor.${system};
-            pkg-config
+          rust-bin = rust-overlay.lib.mkRustBin { } pkgs;
-
+          inherit (self.packages.${system}) xwayland-satellite;
-            xcb-util-cursor
+        in
-            xorg.libxcb
+        {
-            xwayland
+          default = pkgs.mkShell {
+            packages = [
+              (rust-bin.stable.latest.default.override {
+                extensions = [
+                  "rust-analyzer"
+                  "rust-src"
+                ];
+              })
             ];
-        };
 
-        packages = {
+            nativeBuildInputs = [
-          xwayland-satellite = xwayland-satellite;
+              pkgs.rustPlatform.bindgenHook
-          default = xwayland-satellite;
+              pkgs.pkg-config
+              pkgs.makeBinaryWrapper
+            ];
+            buildInputs = xwayland-satellite.buildInputs ++ [ pkgs.xwayland ];
+          };
+        }
+      );
+
+      formatter = forAllSystems (system: nixpkgsFor.${system}.nixfmt);
+
+      packages = forAllSystems (
+        system:
+        let
+          xwayland-satellite = nixpkgsFor.${system}.callPackage xwayland-satellite-package { };
+        in
+        {
+          inherit xwayland-satellite;
+          default = xwayland-satellite;
+        }
+      );
+
+      overlays.default = final: _: {
+        xwayland-satellite = final.callPackage xwayland-satellite-package { };
+      };
     };
-      });
 }