home: wm: use explicit 'enable' options

This is so that I can explicitly enable them if I were to use Wayland
and Sway, given that they should be compatible with both environment.

This also means that putting them in `/home/x/` would a misnomer... Will
revisit this if and when I try out Wayland and sway...

home/wm/default.nix

@@ -1,4 +1,13 @@
-{ lib, ... }:
+{ config, lib, ... }:
+let
+  mkRelatedOption = description: relatedWMs:
+    let
+      isActivatedWm = wm: config.my.home.wm.windowManager == wm;
+    in
+    (lib.mkEnableOption description) // {
+      default = builtins.any isActivatedWm relatedWMs;
+    };
+in
 {
   imports = [
     ./i3.nix
@@ -13,5 +22,13 @@
       example = "i3";
       description = "Which window manager to use for home session";
     };
+
+    i3bar = {
+      enable = mkRelatedOption "i3bar configuration" [ "i3" ];
+    };
+
+    rofi = {
+      enable = mkRelatedOption "rofi menu" [ "i3" ];
+    };
   };
 }

home/wm/i3bar.nix

@@ -1,9 +1,9 @@
 { config, lib, pkgs, ... }:
 let
-  isEnabled = config.my.home.wm.windowManager == "i3";
+  cfg = config.my.home.wm.i3bar;
 in
 {
-  config = lib.mkIf isEnabled {
+  config = lib.mkIf cfg.enable {
     home.packages = with pkgs; [
       alsaUtils # Used by `sound` block
       lm_sensors # Used by `temperature` block

home/wm/rofi.nix

@@ -1,9 +1,9 @@
 { config, lib, pkgs, ... }:
 let
-  isEnabled = config.my.home.wm.windowManager == "i3";
+  cfg = config.my.home.wm.rofi;
 in
 {
-  config = lib.mkIf isEnabled {
+  config = lib.mkIf cfg.enable {
     programs.rofi = {
       enable = true;