refactor(home/linux/desktop): home/linux/desktop => home/linux/gui

home/linux/gui/i3/options/default.nix

@@ -0,0 +1,3 @@
+{mylib, ...}: {
+  imports = mylib.scanPaths ./.;
+}

home/linux/gui/i3/options/nvidia.nix

@@ -0,0 +1,27 @@
+{
+  config,
+  lib,
+  ...
+}:
+with lib; let
+  cfg = config.modules.desktop.i3;
+in {
+  options.modules.desktop.i3 = {
+    nvidia = mkEnableOption "whether nvidia GPU is used";
+  };
+
+  config = mkIf (cfg.enable && cfg.nvidia) (
+    let
+      env = {
+        "LIBVA_DRIVER_NAME" = "nvidia";
+        "GBM_BACKEND" = "nvidia-drm";
+        "__GLX_VENDOR_LIBRARY_NAME" = "nvidia";
+      };
+    in {
+      # environment set for systemd's user session
+      systemd.user.sessionVariables = env;
+      # environment set at user login
+      home.sessionVariables = env;
+    }
+  );
+}