[desktop] Declaratively sets dark-mode options

home-manager/features/hyprland.nix

@@ -27,6 +27,9 @@
         "swayidle -w before-sleep hyprlock"
         "swayosd-server"
         "systemctl --user start hyprpolkitagent"
+
+        "gsettings set org.gnome.desktop.interface color-scheme \"prefer-dark\""
+        "gsettings set org.gnome.desktop.interface gtk-theme \"Adwaita-dark\""
       ];
 
       env = [

home-manager/features/linux-desktop.nix

@@ -20,6 +20,7 @@
     hyprpolkitagent # Privilege managent
     gnome-keyring # Secret management
     glib # for Gnome/GTK settings
+    gsettings-desktop-schemas # So that we can access gnome settings
     xdg-desktop-portal-hyprland
     xdg-desktop-portal-gtk # GTK backend for XDG components like pickers
     grim # Screenshot provider
@@ -29,6 +30,7 @@
     wirelesstools
     waypaper # Wallpaper switcher
     phinger-cursors # Mouse cursors
+
   ];
 
   # Hint for electron apps to use wayland
@@ -54,6 +56,14 @@
     };
   };
 
+  # This is where the real magic happens to tell the applications to prefer
+  # dark mode.  For example, Element reads from this setting.
+  dconf.settings = {
+    "org/gnome/desktop/interface" = {
+      color-scheme = "prefer-dark";
+    };
+  };
+
   # QT theming
   qt = {
     enable = true;