Handle doom emacs theme

hm-modules/theme/default.nix

@@ -30,15 +30,21 @@ let
 
   availableVariants = concatStringsSep " " (attrNames themeVariants);
 
+  # variant:doomtheme pairs consumed by the theme-switch script's
+  # best-effort Doom Emacs hook (see ./theme-switch.sh).
+  doomThemeMap = concatStringsSep " "
+    (mapAttrsToList (variant: theme: "${variant}:${theme}") cfg.doomThemes);
+
   # Userspace theme switcher: activates a pre-built Home Manager
   # specialisation generation. No sudo, no OS rebuild — just runs the
   # specialisation's activation script in the base HM generation.
   #
   # The script logic lives in ./theme-switch.sh (plain shell, no Nix
-  # escaping); we only inject the two config-derived values it needs.
+  # escaping); we only inject the config-derived values it needs.
   theme-switch = pkgs.writeShellScriptBin "theme-switch" ''
     baseVariant="${baseVariant}"
     availableVariants="${availableVariants}"
+    doomThemes="${doomThemeMap}"
     ${builtins.readFile ./theme-switch.sh}
   '';
 
@@ -67,6 +73,28 @@ in {
       default = builtinThemes;
       description = "Available themes with dark and light variants";
     };
+
+    doomThemes = mkOption {
+      type = types.attrsOf types.str;
+      default = {
+        gruvbox-dark = "doom-gruvbox";
+        gruvbox-light = "doom-one-light";
+        catppuccin-dark = "doom-one";
+        catppuccin-light = "doom-one-light";
+      };
+      description = ''
+        Mapping from theme variant name (e.g. "gruvbox-dark") to the Doom
+        Emacs theme symbol (e.g. "doom-gruvbox") that theme-switch will
+        live-load via emacsclient when switching to that variant. Variants
+        absent from this map are left unchanged in Emacs.
+
+        Only themes actually installed in Doom will load; the defaults use
+        themes bundled with doom-themes (so they work out of the box, though
+        catppuccin variants fall back to generic dark/light). For accurate
+        catppuccin colours, install the `catppuccin-theme` Emacs package and
+        map the variants to `catppuccin-mocha` / `catppuccin-latte`.
+      '';
+    };
   };
 
   config = mkIf cfg.enable (

hm-modules/theme/theme-switch.sh

@@ -1,18 +1,22 @@
 # shellcheck shell=bash
 # theme-switch — activate a pre-built Home Manager specialisation.
 #
-# Expects two variables to be injected by the Nix wrapper:
+# Expects these variables to be injected by the Nix wrapper:
 #   baseVariant        the variant that is the generation itself (not a
 #                      specialisation), activated via `$gen/activate`.
 #   availableVariants  space-separated list of all variant names (help text).
+#   doomThemes         optional space-separated `variant:doomtheme` pairs for
+#                      the best-effort Doom Emacs live-switch (may be empty).
 #
 # Standalone usage for testing:
 #   baseVariant=gruvbox-dark \
 #   availableVariants="gruvbox-dark gruvbox-light catppuccin-dark catppuccin-light" \
+#   doomThemes="gruvbox-dark:doom-gruvbox" \
 #   bash theme-switch.sh <variant>
 
 : "${baseVariant:?theme-switch: baseVariant not set}"
 : "${availableVariants:?theme-switch: availableVariants not set}"
+: "${doomThemes:=}"
 set -euo pipefail
 
 variant="${1:-}"
@@ -74,4 +78,26 @@ if [ ! -x "$activate" ]; then
 fi
 
 echo "Switching theme to $variant..."
+
+# Best-effort: live-switch the running Doom Emacs daemon too. No config
+# files are touched; if the daemon isn't running or emacsclient isn't
+# installed (e.g. on a server), this is silently skipped. A theme symbol
+# that isn't installed in Doom makes emacsclient return non-zero, which we
+# also treat as skip.
+doom_theme=""
+if [ -n "$doomThemes" ]; then
+  for pair in $doomThemes; do
+    case "$pair" in
+      "${variant}":*) doom_theme="${pair#*:}"; break ;;
+    esac
+  done
+fi
+if [ -n "$doom_theme" ] && command -v emacsclient >/dev/null 2>&1; then
+  if emacsclient --eval "(progn (mapc (function disable-theme) custom-enabled-themes) (load-theme (quote ${doom_theme}) t))" >/dev/null 2>&1; then
+    echo "Doom: ${doom_theme}"
+  else
+    echo "note: Doom theme switch skipped (daemon not running or '${doom_theme}' not installed)" >&2
+  fi
+fi
+
 exec "$activate"