Wait to startup mcg until xmonad has gotten a little further

This is a quick'n'dirty workaround for
xmonad/xmonad#422. Hopefully a better answer
shows up there someday.

pattern/audio.nix

@@ -36,11 +36,26 @@ in
     XDG_RUNTIME_DIR = "/run/user/${builtins.toString config.snow.user.uid}";
   };
 
+  systemd.user.targets = {
+    # This xmonad target just exists as a workaround for
+    # https://github.com/xmonad/xmonad/issues/422.
+    # See shared/xmonad/xmonad.hs for where this target gets triggered.
+    "xmonad" = {
+      enable = true;
+      partOf = [ "graphical-session.target" ];
+    };
+  };
   systemd.user.services = {
     "mcg" = {
       enable = true;
-      wantedBy = [ "graphical-session.target" ];
-      partOf = [ "graphical-session.target" ];
+
+      # We can't use graphical-session because of
+      # https://github.com/xmonad/xmonad/issues/422.
+      # wantedBy = [ "graphical-session.target" ];
+      # partOf = [ "graphical-session.target" ];
+      wantedBy = [ "xmonad.target" ];
+      partOf = [ "xmonad.target" ];
+
       serviceConfig = {
         ExecStart = "${mcg}/bin/mcg";
       };

shared/xmonad/xmonad.hs

@@ -163,6 +163,11 @@ isNotInfixOf a b = not (a `isInfixOf` b)
 main = do
     dirs <- getDirectories
     let conf = docks $ ewmh desktopConfig {
+        -- Trigger the xmonad.target target. This really shouldn't be
+        -- necessary, but we're using it as a workaround for
+        -- https://github.com/xmonad/xmonad/issues/422. See pattern/audio.nix
+        -- for details.
+        startupHook = spawn "systemctl --user start xmonad.target",
         manageHook = manageDocks <+> manageSpawn <+> windowPlacement <+> manageHook desktopConfig,
         handleEventHook = handleEventHook def <+> Hacks.windowedFullscreenFixEventHook <+> swallowEventHook (className =? "Alacritty" <&&> fmap ( "xmonad-no-swallow" `isNotInfixOf`) title) (return True),
         layoutHook = myLayout,