sway: refactor with a wrapper

nixos/modules/programs/sway.nix

@@ -4,27 +4,32 @@ with lib;
 
 let
   cfg = config.programs.sway;
-  swayPackage = pkgs.sway;
 
-  swayWrapped = pkgs.writeShellScriptBin "sway" ''
-    set -o errexit
+  wrapperOptions = types.submodule {
+    options =
+      let
+        mkWrapperFeature  = default: description: mkOption {
+          type = types.bool;
+          inherit default;
+          example = !default;
+          description = "Whether to make use of the ${description}";
+        };
+      in {
+        base = mkWrapperFeature true ''
+          base wrapper to execute extra session commands and prepend a
+          dbus-run-session to the sway command.
+        '';
+        gtk = mkWrapperFeature false ''
+          wrapGAppsHook wrapper to execute sway with required environment
+          variables for GTK applications.
+        '';
+    };
+  };
 
-    if [ ! "$_SWAY_WRAPPER_ALREADY_EXECUTED" ]; then
-      export _SWAY_WRAPPER_ALREADY_EXECUTED=1
-      ${cfg.extraSessionCommands}
-    fi
-
-    if [ "$DBUS_SESSION_BUS_ADDRESS" ]; then
-      export DBUS_SESSION_BUS_ADDRESS
-      exec ${swayPackage}/bin/sway "$@"
-    else
-      exec ${pkgs.dbus}/bin/dbus-run-session ${swayPackage}/bin/sway "$@"
-    fi
-  '';
-  swayJoined = pkgs.symlinkJoin {
-    name = "sway-joined";
-    paths = [ swayWrapped swayPackage ];
-    passthru.providedSessions = [ "sway" ];
+  swayPackage = pkgs.sway.override {
+    extraSessionCommands = cfg.extraSessionCommands;
+    withBaseWrapper = cfg.wrapperFeatures.base;
+    withGtkWrapper = cfg.wrapperFeatures.gtk;
   };
 in {
   options.programs.sway = {
@@ -36,6 +41,15 @@ in {
       Please have a look at the "extraSessionCommands" example for running
       programs natively under Wayland'';
 
+    wrapperFeatures = mkOption {
+      type = wrapperOptions;
+      default = { };
+      example = { gtk = true; };
+      description = ''
+        Attribute set of features to enable in the wrapper.
+      '';
+    };
+
     extraSessionCommands = mkOption {
       type = types.lines;
       default = "";
@@ -56,7 +70,7 @@ in {
     extraPackages = mkOption {
       type = with types; listOf package;
       default = with pkgs; [
-        swaylock swayidle swaybg
+        swaylock swayidle
         xwayland rxvt_unicode dmenu
       ];
       defaultText = literalExample ''
@@ -76,8 +90,17 @@ in {
   };
 
   config = mkIf cfg.enable {
+    assertions = [
+      {
+        assertion = cfg.extraSessionCommands != "" -> cfg.wrapperFeatures.base;
+        message = ''
+          The extraSessionCommands for Sway will not be run if
+          wrapperFeatures.base is disabled.
+        '';
+      }
+    ];
     environment = {
-      systemPackages = [ swayJoined ] ++ cfg.extraPackages;
+      systemPackages = [ swayPackage ] ++ cfg.extraPackages;
       etc = {
         "sway/config".source = mkOptionDefault "${swayPackage}/etc/sway/config";
         #"sway/security.d".source = mkOptionDefault "${swayPackage}/etc/sway/security.d/";
@@ -89,7 +112,7 @@ in {
     fonts.enableDefaultFonts = mkDefault true;
     programs.dconf.enable = mkDefault true;
     # To make a Sway session available if a display manager like SDDM is enabled:
-    services.xserver.displayManager.sessionPackages = [ swayJoined ];
+    services.xserver.displayManager.sessionPackages = [ swayPackage ];
   };
 
   meta.maintainers = with lib.maintainers; [ gnidorah primeos colemickens ];

pkgs/applications/window-managers/sway/default.nix

@@ -3,11 +3,11 @@
 , pkgconfig, scdoc
 , wayland, libxkbcommon, pcre, json_c, dbus, libevdev
 , pango, cairo, libinput, libcap, pam, gdk-pixbuf
-, wlroots, wayland-protocols, swaybg
+, wlroots, wayland-protocols
 }:
 
 stdenv.mkDerivation rec {
-  pname = "sway";
+  pname = "sway-unwrapped";
   version = "1.2";
 
   src = fetchFromGitHub {
@@ -22,7 +22,9 @@ stdenv.mkDerivation rec {
     ./load-configuration-from-etc.patch
   ];
 
-  nativeBuildInputs = [ pkgconfig meson ninja scdoc makeWrapper ];
+  nativeBuildInputs = [
+    pkgconfig meson ninja scdoc
+  ];
 
   buildInputs = [
     wayland libxkbcommon pcre json_c dbus libevdev
@@ -37,10 +39,6 @@ stdenv.mkDerivation rec {
     "-Dtray=enabled" "-Dman-pages=enabled"
   ];
 
-  postInstall = ''
-    wrapProgram $out/bin/sway --prefix PATH : "${swaybg}/bin"
-  '';
-
   meta = with stdenv.lib; {
     description = "i3-compatible tiling Wayland compositor";
     homepage    = https://swaywm.org;

pkgs/applications/window-managers/sway/wrapper.nix

@@ -0,0 +1,50 @@
+{ lib, stdenv
+, sway-unwrapped, swaybg
+, makeWrapper, symlinkJoin, writeShellScriptBin
+, withBaseWrapper ? true, extraSessionCommands ? "", dbus
+, withGtkWrapper ? false, wrapGAppsHook, gdk-pixbuf
+}:
+
+assert extraSessionCommands != "" -> withBaseWrapper;
+
+with lib;
+
+let
+  baseWrapper = writeShellScriptBin "sway" ''
+     set -o errexit
+     if [ ! "$_SWAY_WRAPPER_ALREADY_EXECUTED" ]; then
+       export _SWAY_WRAPPER_ALREADY_EXECUTED=1
+       ${extraSessionCommands}
+     fi
+     if [ "$DBUS_SESSION_BUS_ADDRESS" ]; then
+       export DBUS_SESSION_BUS_ADDRESS
+       exec ${sway-unwrapped}/bin/sway "$@"
+     else
+       exec ${dbus}/bin/dbus-run-session ${sway-unwrapped}/bin/sway "$@"
+     fi
+   '';
+in symlinkJoin {
+  name = "sway-${sway-unwrapped.version}";
+
+  paths = (optional withBaseWrapper baseWrapper)
+    ++ [ sway-unwrapped ];
+
+  nativeBuildInputs = [ makeWrapper ]
+    ++ (optional withGtkWrapper wrapGAppsHook);
+
+  buildInputs = optional withGtkWrapper gdk-pixbuf;
+
+  postBuild = ''
+    # We want to run wrapProgram manually to only wrap sway and add swaybg:
+    export dontWrapGApps=true
+    ${optionalString withGtkWrapper "wrapGAppsHook"}
+    wrapProgram $out/bin/sway \
+      --prefix PATH : "${swaybg}/bin" ${optionalString withGtkWrapper ''\
+        "''${gappsWrapperArgs[@]}"
+      ''}
+  '';
+
+  passthru.providedSessions = [ "sway" ];
+
+  inherit (sway-unwrapped) meta;
+}

pkgs/top-level/all-packages.nix

@@ -19373,7 +19373,8 @@ in
 
   wlroots = callPackage ../development/libraries/wlroots { };
 
-  sway = callPackage ../applications/window-managers/sway { };
+  sway-unwrapped = callPackage ../applications/window-managers/sway { };
+  sway = callPackage ../applications/window-managers/sway/wrapper.nix { };
   swaybg = callPackage ../applications/window-managers/sway/bg.nix { };
   swayidle = callPackage ../applications/window-managers/sway/idle.nix { };
   swaylock = callPackage ../applications/window-managers/sway/lock.nix { };