flatpak: refactor as home module to fix themes and fonts

Signed-off-by: Myned <dev@bjork.tech>

flake.in.nix

@@ -140,7 +140,6 @@
                     inputs.arion.nixosModules.arion
                     inputs.disko.nixosModules.disko
                     inputs.fw-fanctrl.nixosModules.default
-                    inputs.nix-flatpak.nixosModules.nix-flatpak
                   ];
 
                   home-manager.users.${config.custom.username}.imports = [

options/custom/services/flatpak.nix

@@ -11,6 +11,21 @@ in {
   options.custom.services.flatpak.enable = mkOption {default = false;};
 
   config = mkIf cfg.enable {
+    services.flatpak.enable = true;
+
+    #!! Only takes effect if /usr/* shares do not exist
+    # Nixpkgs workaround requires packages in the global environment
+    # https://github.com/NixOS/nixpkgs/pull/262462
+    environment.systemPackages =
+      config.fonts.packages
+      ++ [
+        config.home-manager.users.${config.custom.username}.gtk.cursorTheme.package
+        config.home-manager.users.${config.custom.username}.gtk.iconTheme.package
+      ];
+
+    home-manager.users.${config.custom.username} = {
+      imports = [inputs.nix-flatpak.homeManagerModules.nix-flatpak];
+
       # https://wiki.nixos.org/wiki/Flatpak
       # https://github.com/gmodena/nix-flatpak
       services.flatpak = {
@@ -18,7 +33,7 @@ in {
         uninstallUnmanaged = true; # Immutable flatpaks
         update.auto.enable = true; # Auto update flatpaks weekly
 
-      #!! Installation occurs in background as a oneshot service
+        #!! Installation occurs during activation
         #?? flatpak search NAME
         packages =
           optionals config.custom.default [
@@ -30,13 +45,18 @@ in {
           ++ optionals config.custom.full [
             "app.drey.Biblioteca"
           ];
-    };
 
-    # Theme packages must be installed system-wide for flatpaks
-    environment.systemPackages = with pkgs; [
-      adw-gtk3
-      google-cursor
-      papirus-icon-theme
+        # https://github.com/gmodena/nix-flatpak?tab=readme-ov-file#overrides
+        overrides.global = {
+          Context.filesystems = [
+            "xdg-config/gtk-3.0:ro"
+            "xdg-config/gtk-4.0:ro"
+
+            # HACK: Globally allow access to /nix/store for symlinked themes
+            "/nix/store:ro"
           ];
         };
+      };
+    };
+  };
 }