Rework how X session is started

hm/frobar/default.nix

@@ -1,4 +1,4 @@
-{ pkgs ? import <nixpkgs> { config = { }; overlays = [ ]; } }:
+{ pkgs ? import <nixpkgs> { config = { }; overlays = [ ]; }, ... }:
 # Tried using pyproject.nix but mpd2 dependency wouldn't resolve,
 # is called pyton-mpd2 on PyPi but mpd2 in nixpkgs.
 let
@@ -6,6 +6,7 @@ let
     pname = "frobar";
     version = "2.0";
 
+    runtimeInputs = with pkgs; [ lemonbar-xft wirelesstools ];
     propagatedBuildInputs = with pkgs.python3Packages; [
       coloredlogs
       notmuch
@@ -15,21 +16,33 @@ let
       pulsectl
       pyinotify
     ];
+    makeWrapperArgs = [ "--prefix PATH : ${pkgs.lib.makeBinPath (with pkgs; [ lemonbar-xft wirelesstools ])}" ];
 
     src = ./.;
   };
-  frobar_launcher = pkgs.writeShellApplication
-    {
-      name = "frobar_launcher";
-      runtimeInputs = with pkgs; [ lemonbar-xft wirelesstools ];
-      text = ''
-        pidfile=$XDG_RUNTIME_DIR/frobar/$DISPLAY.pid
-        ${pkgs.coreutils}/bin/mkdir -p "$(${pkgs.coreutils}/bin/dirname "$pidfile")"
-        ([ -f "$pidfile" ] && ${pkgs.procps}/bin/kill "$(<"$pidfile")") || true
-        ${frobar}/bin/frobar & disown
-        echo $! > "$pidfile"
-      '';
-    };
 in
-frobar_launcher
-# TODO Connection with i3 is lost sometimes, more often than with Arch?
+{
+  config = {
+    xsession.windowManager.i3.config.bars = [ ];
+    programs.autorandr.hooks.postswitch = {
+      frobar = "${pkgs.systemd}/bin/systemctl --user restart frobar";
+    };
+    systemd.user.services.frobar = {
+      Unit = {
+        Description = "frobar";
+        After = [ "graphical-session-pre.target" ];
+        PartOf = [ "graphical-session.target" ];
+      };
+
+      Service = {
+        # Wait for i3 to start. Can't use ExecStartPre because otherwise it blocks graphical-session.target, and there's nothing i3/systemd
+        # TODO Do that better
+        ExecStart = ''${pkgs.bash}/bin/bash -c "while ! ${pkgs.i3}/bin/i3-msg; do ${pkgs.coreutils}/bin/sleep 1; done; ${frobar}/bin/frobar"''; 
+      };
+
+      Install = { WantedBy = [ "graphical-session.target" ]; };
+    };
+  };
+}
+# TODO Connection with i3 is lost on start sometimes, more often than with Arch?
+# TODO Restore ability to build frobar with nix-build