desktop: add shell ui selector

dotfiles/lib/bin/desktop_shell_ui

@@ -0,0 +1,93 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+state_file="${IM_DESKTOP_SHELL_UI_STATE:-${XDG_STATE_HOME:-$HOME/.local/state}/imalison/desktop-shell-ui}"
+default_shell_ui="${IM_HYPRLAND_SHELL_UI:-taffybar}"
+
+normalize_shell_ui() {
+  case "${1:-}" in
+    noctalia)
+      printf '%s\n' "noctalia"
+      ;;
+    taffybar|rofi)
+      printf '%s\n' "taffybar"
+      ;;
+    *)
+      return 1
+      ;;
+  esac
+}
+
+current_shell_ui() {
+  local configured=""
+
+  if [[ -r "$state_file" ]]; then
+    IFS= read -r configured < "$state_file" || true
+  fi
+
+  normalize_shell_ui "$configured" 2>/dev/null \
+    || normalize_shell_ui "$default_shell_ui" 2>/dev/null \
+    || printf '%s\n' "taffybar"
+}
+
+write_shell_ui() {
+  local shell_ui="$1"
+  mkdir -p "$(dirname "$state_file")"
+  printf '%s\n' "$shell_ui" > "$state_file"
+}
+
+apply_shell_ui() {
+  local shell_ui="$1"
+
+  export IM_HYPRLAND_SHELL_UI="$shell_ui"
+  systemctl --user import-environment IM_HYPRLAND_SHELL_UI 2>/dev/null || true
+
+  case "$shell_ui" in
+    noctalia)
+      systemctl --user stop taffybar.service 2>/dev/null || true
+      systemctl --user reset-failed taffybar.service 2>/dev/null || true
+      systemctl --user start noctalia-shell.service
+      ;;
+    taffybar)
+      systemctl --user stop noctalia-shell.service 2>/dev/null || true
+      systemctl --user reset-failed noctalia-shell.service 2>/dev/null || true
+      systemctl --user start taffybar.service
+      ;;
+  esac
+}
+
+set_shell_ui() {
+  local shell_ui
+  shell_ui="$(normalize_shell_ui "${1:-}")" || {
+    echo "usage: desktop_shell_ui set {taffybar|noctalia}" >&2
+    exit 2
+  }
+
+  write_shell_ui "$shell_ui"
+  apply_shell_ui "$shell_ui"
+}
+
+case "${1:-current}" in
+  current)
+    current_shell_ui
+    ;;
+  set)
+    set_shell_ui "${2:-}"
+    ;;
+  toggle)
+    case "$(current_shell_ui)" in
+      noctalia) set_shell_ui taffybar ;;
+      *) set_shell_ui noctalia ;;
+    esac
+    ;;
+  apply)
+    apply_shell_ui "$(current_shell_ui)"
+    ;;
+  exec-condition)
+    [[ "$(current_shell_ui)" == "$(normalize_shell_ui "${2:-}")" ]]
+    ;;
+  *)
+    echo "usage: desktop_shell_ui {current|set|toggle|apply|exec-condition}" >&2
+    exit 2
+    ;;
+esac

nixos/desktop.nix

@@ -6,7 +6,19 @@
   makeEnable,
   ...
 }:
-makeEnable config "myModules.desktop" true {
+let
+  cfg = config.myModules.desktop;
+  desktopShellUi = pkgs.writeShellApplication {
+    name = "desktop_shell_ui";
+    runtimeInputs = [
+      pkgs.coreutils
+      pkgs.systemd
+    ];
+    text = ''
+      exec ${../dotfiles/lib/bin/desktop_shell_ui} "$@"
+    '';
+  };
+  enabledModule = makeEnable config "myModules.desktop" true {
   services.greenclip.enable = true;
   imports = [
     ./fonts.nix
@@ -40,8 +52,11 @@ makeEnable config "myModules.desktop" true {
     enable = true;
   };
 
-  # This is for the benefit of VSCODE running natively in wayland
+  environment.sessionVariables = {
-  environment.sessionVariables.NIXOS_OZONE_WL = "1";
+    # This is for the benefit of VSCODE running natively in wayland
+    NIXOS_OZONE_WL = "1";
+    IM_HYPRLAND_SHELL_UI = cfg.shellUi;
+  };
 
   system.activationScripts.playwrightChromeCompat.text = lib.optionalString (pkgs.stdenv.hostPlatform.system == "x86_64-linux") ''
     # Playwright's Chrome channel lookup expects the FHS path below.
@@ -87,6 +102,8 @@ makeEnable config "myModules.desktop" true {
 
   environment.systemPackages = with pkgs;
     [
+      desktopShellUi
+
       # Appearance
       adwaita-icon-theme
       hicolor-icon-theme
@@ -169,4 +186,18 @@ makeEnable config "myModules.desktop" true {
         ]
       else []
     );
+  };
+in
+enabledModule
+// {
+  options = lib.recursiveUpdate enabledModule.options {
+    myModules.desktop.shellUi = lib.mkOption {
+      type = lib.types.enum [ "noctalia" "taffybar" ];
+      default = "taffybar";
+      description = ''
+        Desktop shell UI used by Hyprland-oriented bindings. This controls
+        the active shell service and Hyprland launcher/window picker dispatch.
+      '';
+    };
+  };
 }