LXQt has wrong/invalid defaults

[wamserma]

Issue description

LXQt has invalid default default settings, giving it a black-on-black theme, e.g. the clock in the panel is not readable (black font on black bg) and the background image is missing.
(default points to /nix/store/w2xzdhvlq9bz4kd6s298gjy6dlssdq37-lxqt-build-tools-0.6.0/share/lxqt/themes/frost/lxqt-origami-light.png while it should be sth matching /nix/store/*-lxqt-themes-0.14.0/share/lxqt/themes/frost/lxqt-origami-light.png)
Further, Themes are not listed and changing the panel theme has no effect.

The issue reminds of https://bugs.launchpad.net/ubuntu/+source/lxqt-session/+bug/1781392 though I am not knowledgeable enough to confirm this.

Steps to reproduce

configuration.nix:

  # Enable the LXQt Desktop Environment.
   services.xserver.displayManager.sddm.enable = true;
   services.xserver.desktopManager.lxqt.enable = true;
   services.xserver.autorun = true;

lxqt.lxqt-themes is listed in environment.systemPackages

Technical details

Please run nix run nixpkgs.nix-info -c nix-info -m and paste the result.

• system: "x86_64-linux"
• host os: Linux 4.19.76, NixOS, 19.09beta606.3ba0d9f75cc (Loris)
• multi-user?: yes
• sandbox: yes
• version: nix-env (Nix) 2.3
• channels(root): "nixos-19.09beta606.3ba0d9f75cc, unstable-20.03pre194293.2436c27541b"
• channels(user): ""
• nixpkgs: /nix/var/nix/profiles/per-user/root/channels/nixos

[worldofpeace]

Known issue @wamserma, see #65482 (just forgot to report it 😅)

[wamserma]

Ah, I only searched for open PRs..
Let's also Cross-Ref #65399 here.

[wamserma]

Fixed the wallpaper, panel/theme issue still applies (LXQt 0.15.0)

[tpwrules]

Have you discovered a way to fix this? The issue also applies using lightdm.

[romildo]

I would like to ask maintainers of the Qt libraries in nixpkgs to take a look at this issue, if possible. Maybe they can help in fixing this issue, which exists since LXQt was changed to use qt5's mkDerivation (#65482).

cc @ttuegel @periklis @bkchr @qknight @doronbehar @FRidh