sway: refactor with a wrapper

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;
+}