How to set screen resolution correctly in nixos as kvm guest os?

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context: I did a minimal install and installs xserver lightdm qtile as desktop environment. Running nixos as a guest os inside kvm.

I tried writing a service as follows in configuration.nix but get can’t open display.

      systemd.services.screensetter = {
		enable = true;
		description = "sets correct screen resolution";
		wantedBy = [ "multi-user.target"];
		# Add this line in your nixos configuration (E.G. the "configuration.nix" file or a module imported into it)
		# this allows you to use `xrandr` inside of scripts called by this service
		# https://www.reddit.com/r/NixOS/comments/w4fj6p/comment/ih1oa5e/?utm_source=reddit&utm_medium=web2x&context=3
		path = [ pkgs.xorg.xrandr ];

		unitConfig = {
			type = "simple";
		};

		serviceConfig = {
			ExecStart = "/home/<this_user>/.screenlayout/nixos-screenlayout.sh";
		};
	  };

then I tried spice-autorandr and that doesn’t work proper, sets a resolution bigger than my display’s native resolution.

services.spice-autorandr.enable = true;

finally after some trial and error I found a sketchy way to do it:

  services.xserver = {
    enable = true;
    windowManager.qtile.enable = true;
    displayManager.sessionCommands = ''
      xrandr --output Virtual-1 --primary --mode 1920x1080 --pos 0x0 --rotate normal
      xwallpaper --zoom ~/walls/jk.png
      xet r rate 200 35 &
    '';  
  };

now I wanted someone came up with a correct way to set screen resolution based on my arandr generated script