enhancement proposition: add nix support

[MixedOne]

Hello,
I'd be more than happy to see nix pkg support added. I would do it myself, unfortunately I don't have enough domain knowledge.
examples:
- https://github.com/NixOS/nixpkgs/blob/nixos-24.05/pkgs/data/themes/chili-sddm/default.nix
- https://github.com/MarianArlt/sddm-chili
- https://github.com/Zhaith-Izaliel/sddm-sugar-candy-nix/blob/master/nix/default.nix

I tried to figure it out by myself but even dry-run throws errors
(I'm using below pkgs:
gst_all_1.gst-libav
libsForQt5.phonon
libsForQt5.phonon-backend-gstreamer
gst_all_1.gst-plugins-good
libsForQt5.qt5.qtquickcontrols
libsForQt5.qt5.qtgraphicaleffects
libsForQt5.qt5.qtmultimedia
kdePackages.qtmultimedia
ffmpeg for the below execution)
cmd: sddm-greeter-qt6 --test-mode --theme aerial-sddm-theme

Loading file:aerial-sddm-theme/Main.qml...
file:///home/MixedOne/playground/sddm-themes/aerial-sddm-theme/Main.qml:157:5: MediaPlayer is not a type 
         property MediaPlayer currentPlayer: mediaplayer1 
         ^
file:///home/MixedOne/playground/sddm-themes/aerial-sddm-theme/Main.qml:157:5: MediaPlayer is not a type 
         property MediaPlayer currentPlayer: mediaplayer1 
         ^
Fallback to embedded theme

(...)

Fallback to embedded theme
file:///nix/store/cd4038059sm99vag858akf6dd5x5xpk9-sddm-unwrapped-0.21.0/lib/qt-6/qml/SddmComponents/LayoutBox.qml:35:5: QML Connections: Implicitly defined onFoo properties in Connections are deprecated. Use this syntax instead: function onFoo(<arguments>) { ... }
file:///nix/store/cd4038059sm99vag858akf6dd5x5xpk9-sddm-unwrapped-0.21.0/lib/qt-6/qml/SddmComponents/ComboBox.qml:105:9: QML Image: Cannot open: file:///nix/store/cd4038059sm99vag858akf6dd5x5xpk9-sddm-unwrapped-0.21.0/lib/qt-6/qml/SddmComponents/angle-down.png
file:///nix/store/cd4038059sm99vag858akf6dd5x5xpk9-sddm-unwrapped-0.21.0/lib/qt-6/qml/SddmComponents/ComboBox.qml:105:9: QML Image: Cannot open: file:///nix/store/cd4038059sm99vag858akf6dd5x5xpk9-sddm-unwrapped-0.21.0/lib/qt-6/qml/SddmComponents/angle-down.png
qrc:/theme/Main.qml:41:5: QML Connections: Implicitly defined onFoo properties in Connections are deprecated. Use this syntax instead: function onFoo(<arguments>) { ... }
Adding view for "DP-1" QRect(1920,1120 3413x1440)
file:///nix/store/cd4038059sm99vag858akf6dd5x5xpk9-sddm-unwrapped-0.21.0/lib/qt-6/qml/SddmComponents/ComboBox.qml:105:9: QML Image: Cannot open: file:///nix/store/cd4038059sm99vag858akf6dd5x5xpk9-sddm-unwrapped-0.21.0/lib/qt-6/qml/SddmComponents/angle-down.png
file:///nix/store/cd4038059sm99vag858akf6dd5x5xpk9-sddm-unwrapped-0.21.0/lib/qt-6/qml/SddmComponents/ComboBox.qml:105:9: QML Image: Cannot open: file:///nix/store/cd4038059sm99vag858akf6dd5x5xpk9-sddm-unwrapped-0.21.0/lib/qt-6/qml/SddmComponents/angle-down.png
file:///nix/store/cd4038059sm99vag858akf6dd5x5xpk9-sddm-unwrapped-0.21.0/lib/qt-6/qml/SddmComponents/ComboBox.qml:105:9: QML Image: Cannot open: file:///nix/store/cd4038059sm99vag858akf6dd5x5xpk9-sddm-unwrapped-0.21.0/lib/qt-6/qml/SddmComponents/angle-down.png
file:///nix/store/cd4038059sm99vag858akf6dd5x5xpk9-sddm-unwrapped-0.21.0/lib/qt-6/qml/SddmComponents/ComboBox.qml:105:9: QML Image: Cannot open: file:///nix/store/cd4038059sm99vag858akf6dd5x5xpk9-sddm-unwrapped-0.21.0/lib/qt-6/qml/SddmComponents/angle-down.png
file:///nix/store/cd4038059sm99vag858akf6dd5x5xpk9-sddm-unwrapped-0.21.0/lib/qt-6/qml/SddmComponents/ComboBox.qml:105:9: QML Image: Cannot open: file:///nix/store/cd4038059sm99vag858akf6dd5x5xpk9-sddm-unwrapped-0.21.0/lib/qt-6/qml/SddmComponents/angle-down.png
file:///nix/store/cd4038059sm99vag858akf6dd5x5xpk9-sddm-unwrapped-0.21.0/lib/qt-6/qml/SddmComponents/ComboBox.qml:105:9: QML Image: Cannot open: file:///nix/store/cd4038059sm99vag858akf6dd5x5xpk9-sddm-unwrapped-0.21.0/lib/qt-6/qml/SddmComponents/angle-down.png
qt.qml.context: file:///nix/store/cd4038059sm99vag858akf6dd5x5xpk9-sddm-unwrapped-0.21.0/lib/qt-6/qml/SddmComponents/PictureBox.qml:106:13 Parameter "event" is not declared. Injection of parameters into signal handlers is deprecated. Use JavaScript functions with formal parameters instead.

[3ximus]

Hello, I have no plans nor interest in adding this as a nix package since I don't use it.

However from at the errors, someone else reported some issue regarding running the theme in test-mode on sddm-0.21.0 #49. So try setting the theme and go to the login screen to see if it works perhaps.
I guess the theme would need some updates to work with qt-6 but I don't really care to do it...
Pull requests are welcome if you're interested.
Cheers