bug: hyprpaper doesn't start when `graphical-session.target` is activated

[wuyoli]

Are you following the right branch?

• [X] My Nixpkgs and Home Manager versions are in sync

Is there an existing issue for this?

• [X] I have searched the existing issues

Issue description

hyprpaper doesn't start when graphical-session.target is activated. output of systemctl status:

$ systemctl status --user hyprpaper
○ hyprpaper.service - hyprpaper
     Loaded: loaded (/home/wuyoli/.config/systemd/user/hyprpaper.service; enabled; preset: enabled)
     Active: inactive (dead)
  Condition: start condition unmet at Thu 2024-07-11 19:48:27 CEST; 10min ago
             └─ ConditionEnvironment=WAYLAND_DISPLAY was not met

This started happening when I switched from sddm to lightdm by setting services.displayManager.enable = true; instead of services.displayManager.sddm.enable = true;.

Maintainer CC

@khaneliman @fufexan

System information

- system: `"x86_64-linux"`
 - host os: `Linux 6.8.12, NixOS, 24.11 (Vicuna), 24.11.20240703.9f4128e`
 - multi-user?: `yes`
 - sandbox: `yes`
 - version: `nix-env (Nix) 2.18.4`
 - nixpkgs: `/nix/store/dk2rpyb6ndvfbf19bkb2plcz5y3k8i5v-source`

[fufexan]

Right, because lightdm runs on X, not Wayland. Many people have had issues with lightdm, so it's recommended to use either sddm, gdm or greetd.