modules/home/users/crumb/niri.nix

@@ -9,14 +9,6 @@ in {
       type = lib.types.nullOr lib.types.path;
       default = config.stylix.image;
     };
-    # xwayland-satellite implements rootless Xwayland in a separate application,
-    # without the host compositor's involvement. It makes X11 windows appear as
-    # normal windows, just like a native Xwayland integration. While it is still
-    # somewhat experimental, it handles a lot of applications correctly, like
-    # Steam, games and Discord.
-    xwayland-satellite.enable =
-      lib.mkEnableOption "xwayland-satellite starting with Niri"
-        // { default = true; };
     polkit.enable =
       lib.mkEnableOption "Niri/Gnome Polkit" // { default = true; };
     swaylock.enable =
@@ -67,26 +59,17 @@ in {
     stylix.targets.swaylock.enable = cfg.swaylock.enable;
 
     services.polkit-gnome.enable = cfg.polkit.enable;
+    sydnix.xwayland-satellite.enable = lib.mkDefault true;
 
     # File-picker.
     home.packages = [ pkgs.nautilus ];
 
-    systemd.user.services.xwayland-satellite =
-      lib.mkIf cfg.xwayland-satellite.enable {
-        Service.ExecStart =
-          ["${pkgs.xwayland-satellite}/bin/xwayland-satellite"];
-        Unit.After = ["niri.service"];
-        Unit.PartOf = ["niri.service"];
-        Install.WantedBy = ["niri.service"];
-      };
-
     programs.niri = {
       settings = {
         # Activates some Nixpkgs patches to help run Electron applications under
         # Wayland.
 	environment = {
 	  NIXOS_OZONE_WL = "1";
-	  DISPLAY = ":0";
 	  XDG_CURRENT_DESKTOP = "niri";
 	  QT_QPA_PLATFORM = "wayland";
 	  ELECTRON_OZONE_PLATFORM_HINT = "auto";

modules/home/xwayland-satellite.nix

@@ -0,0 +1,38 @@
+{ config, lib, pkgs, ... }:
+
+let cfg = config.sydnix.xwayland-satellite;
+in {
+  options.sydnix.xwayland-satellite = {
+    # xwayland-satellite implements rootless Xwayland in a separate
+    # application, without the host compositor's involvement. It makes
+    # X11 windows appear as normal windows, just like a native
+    # Xwayland integration. While it is still somewhat experimental,
+    # it handles a lot of applications correctly, like Steam, games
+    # and Discord.
+    enable = lib.mkEnableOption "XWayland outside your Wayland";
+  };
+
+  config = lib.mkIf cfg.enable {
+    systemd.user.services.xwayland-satellite =
+      let xwayland-satellite =
+        pkgs.xwayland-satellite.override { withSystemd = true; };
+      in {
+        Unit = {
+          Description = "Xwayland outside your Wayland";
+          BindsTo = [ "graphical-session.target" ];
+          PartOf = [ "graphical-session.target" ];
+          After = [ "graphical-session.target" ];
+          Requisite = [ "graphical-session.target" ];
+        };
+        Service = {
+          Type = "notify";
+          NotifyAccess = "all";
+          ExecStart = lib.getExe xwayland-satellite;
+          StandardOutput = "journal";
+          ExecStartPost = "systemctl --user set-environment DISPLAY=:0";
+          ExecStop = "systemctl --user unset-environment DISPLAY";
+        };
+        Install.WantedBy = [ "graphical-session.target" ];
+      };
+  };
+}

modules/nixos/dank-material-shell.nix

@@ -12,6 +12,13 @@ in {
       enableDynamicTheming = false;
     };
 
+    # Start after xwayland-satellite, if possible.  So DMS can start
+    # with the DISPLAY env var set.
+    systemd.user.services.dms = {
+      wants = ["xwayland-satellite.service"];
+      after = ["xwayland-satellite.service"];
+    };
+
     services.displayManager.dms-greeter = {
       enable = true;
       compositor.name = assert config.sydnix.niri.enable; "niri";