feat(keyboard): per-device layout for external keyboards

Add nomarchy.keyboard.devices ({ "<hyprctl-device-name>" = { layout; variant; }; })
generating Hyprland `device` blocks that override the session
nomarchy.keyboard.layout for a named keyboard -- e.g. an external board
that's physically a different layout than the laptop's built-in one.
Hyprland applies it whenever that device connects, so the external keyboard
"remembers" its layout the declarative way. A Waybar hyprland/language
indicator shows the active layout, placed only when more than one layout is
in play (a comma in the session layout, or any per-device override) so
single-layout bars stay clean.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

modules/home/hyprland.nix

@@ -150,6 +150,14 @@ in
         touchpad.natural_scroll = lib.mkDefault true;
       };
 
+      # Per-device keyboard layouts (nomarchy.keyboard.devices): each
+      # overrides the session kb_layout for one named keyboard — e.g. an
+      # external board that's physically a different layout than the laptop's
+      # built-in one. Hyprland applies them whenever the device connects.
+      device = lib.mapAttrsToList
+        (name: d: { inherit name; kb_layout = d.layout; kb_variant = d.variant; })
+        config.nomarchy.keyboard.devices;
+
       # dwindle:pseudotile was removed in Hyprland 0.55 (the `pseudo`
       # dispatcher still exists); setting it aborts config parsing.
       dwindle.preserve_split = lib.mkDefault true;

modules/home/options.nix

@@ -96,6 +96,33 @@ in
       description = "XKB variant for the Hyprland session.";
     };
 
+    keyboard.devices = lib.mkOption {
+      type = lib.types.attrsOf (lib.types.submodule {
+        options = {
+          layout = lib.mkOption {
+            type = lib.types.str;
+            description = "XKB layout for this specific keyboard.";
+          };
+          variant = lib.mkOption {
+            type = lib.types.str;
+            default = "";
+            description = "XKB variant for this keyboard.";
+          };
+        };
+      });
+      default = { };
+      example = lib.literalExpression ''{ "keychron-keychron-k2" = { layout = "de"; }; }'';
+      description = ''
+        Per-device keyboard layout. The key is the device name from
+        `hyprctl devices` (lower-case, hyphenated). Each entry generates a
+        Hyprland `device` block that overrides the session-wide
+        nomarchy.keyboard.layout for that keyboard only — e.g. an external
+        keyboard that's physically a different layout than the laptop's
+        built-in one. Hyprland applies it automatically whenever that
+        keyboard is connected.
+      '';
+    };
+
     package = lib.mkOption {
       type = lib.types.package;
       default = pkgs.nomarchy-theme-sync;

modules/home/waybar.nix

@@ -12,6 +12,12 @@
 let
   t = config.nomarchy.theme;
 
+  # Show the active-keyboard-layout indicator only when more than one layout
+  # is in play — multiple session layouts (comma-separated) or per-device
+  # overrides (nomarchy.keyboard.devices) — so single-layout bars stay clean.
+  showLanguage = lib.hasInfix "," config.nomarchy.keyboard.layout
+    || config.nomarchy.keyboard.devices != { };
+
   # Power-profile indicator (power-profiles-daemon). Both scripts self-
   # gate: they exit silently unless this is a laptop (a battery is
   # present) running PPD, so the module hides itself on desktops and
@@ -70,7 +76,9 @@ let
 
     modules-left = [ "hyprland/workspaces" "hyprland/window" ];
     modules-center = [ "clock" ];
-    modules-right = [ "tray" "pulseaudio" "network" "cpu" "memory" "custom/powerprofile" "battery" "custom/notification" ];
+    modules-right = [ "tray" "pulseaudio" "network" "cpu" "memory" "custom/powerprofile" ]
+      ++ lib.optional showLanguage "hyprland/language"
+      ++ [ "battery" "custom/notification" ];
 
     "hyprland/workspaces" = {
       format = "{icon}";
@@ -88,6 +96,13 @@ let
       tooltip-format = "<tt><small>{calendar}</small></tt>";
     };
 
+    # Active keyboard layout (per focused device) — only placed in
+    # modules-right when showLanguage (see above).
+    "hyprland/language" = {
+      format = "󰌌 {short}";
+      tooltip = false;
+    };
+
     pulseaudio = {
       format = "{icon} {volume}%";
       format-muted = "󰝟";
@@ -193,7 +208,7 @@ let
       font-weight: bold;
     }
 
-    #tray, #pulseaudio, #network, #cpu, #memory, #custom-powerprofile, #battery, #custom-notification {
+    #tray, #pulseaudio, #network, #cpu, #memory, #custom-powerprofile, #language, #battery, #custom-notification {
       color: @subtext;
       padding: 0 10px;
     }