bug: gtk.theme option assumes theme is used for GTK2, GTK3 and GTK4

[knokelmaat]

Are you following the right branch?

• My Nixpkgs and Home Manager versions are in sync

Is there an existing issue for this?

• I have searched the existing issues

Issue description

Description

I use adw-gtk3 theme for GTK3 to make it look more like the modern libadwaita applications.

I've been having some issues with visual errors in my GTK4 theming and narrowed the issue down to how home-manager implements GTK theming.
The documentation is all over the place (at points only mentioning GTK 2 and GTK 3), while in reality it also configures the theme for GTK 4:

home-manager/modules/misc/gtk.nix

Lines 111 to 113 in ffe2d07

	options = {
	gtk = {
	enable = mkEnableOption "GTK 2/3 configuration";

home-manager/modules/misc/gtk.nix

Lines 286 to 289 in ffe2d07

	xdg.configFile."gtk-4.0/settings.ini".text =
	toGtk3Ini { Settings = gtkIni // cfg4.extraConfig; };
	xdg.configFile."gtk-4.0/gtk.css" = mkIf (gtk4Css != "") { text = gtk4Css; };

Here, home-manager makes two assumptions that are in my opinion incorrect:

1. The user wants to use the same theme for GTK 2, GTK 3 and GTK 4
2. The supplied themes supports all 3 GKT versions

Solution

Either removing support for GTK 4, or giving the user the option to decide what GTK versions should be using what themes.

Maintainer CC

@rycee,

System information

- system: `"x86_64-linux"`
 - host os: `Linux 6.6.52, NixOS, 24.11 (Vicuna), 24.11.20240923.30439d9`
 - multi-user?: `yes`
 - sandbox: `yes`
 - version: `nix-env (Nix) 2.18.7`
 - channels(root): `"nixos-24.05"`
 - nixpkgs: `/nix/store/p2hby44a0qzrnd1vxcpcgfav6160rmcv-source`