modules/desktop: add fake UI for Helix

modules/desktop/default.nix

@@ -8,6 +8,7 @@ in {
     ./package-sets.nix
     ./nixpak-tricks.nix
     ./hidden-apps.nix
+    ./helix-desktop.nix
   ];
 
   services.xserver = {

modules/desktop/helix-desktop.nix

@@ -0,0 +1,58 @@
+{ pkgs, ... }:
+
+let
+  helixDesktop = pkgs.makeDesktopItem {
+    name = "net.privatevoid.HelixDesktop";
+    desktopName = "Helix";
+    comment = "Helix Editor";
+    mimeTypes = [
+      "text/plain"
+      "application/x-zerosize"
+      "inode/directory"
+    ];
+    inherit icon;
+    tryExec = "hx";
+    exec = ''${hxOpenHandler} %F'';
+  };
+
+  icon = pkgs.fetchurl {
+    name = "helix-logo.svg";
+    url = "https://raw.githubusercontent.com/helix-editor/helix/d1a4bd876b3ae646693c0905d7f29b636e2e5033/logo.svg";
+    sha256 = "sha256-1XBrlGbCfkfYhIZuQ9eDBgDoohup/gQ9VZynEerUqcY=";
+  };
+
+  hxOpenHandler = pkgs.writeShellScript "hx-open-handler" ''
+    isDir () { test -d "$1"; }
+    isFile () { test -f "$1"; }
+    findAnyDir () {
+      for f in "$@"; do
+        if test -d "$f"; then
+          echo "$f"
+          return 0
+        fi
+      done
+      return 1
+    }
+    if [[ "$#" == 0 ]]; then
+      exec blackbox -w "$HOME" -c hx
+    elif [[ "$#" == 1 ]]; then
+      isDir "$1" && exec blackbox -w "$1" -c "hx ."
+      isFile "$1" && exec blackbox -w "$(dirname "$1")" -c "hx '$1'"
+    else
+      firstDir="$(findAnyDir "$@")"
+      findAnyDirStatus="$?"
+      if [[ "$findAnyDirStatus" == 0 ]]; then
+        exec blackbox -w "$firstDir" -c "hx ."
+      else
+        # magic: find common base directory
+        workDir="$(dirname "$@" | sed -e 'N;s/^\(.*\).*\n\1.*$/\1\n\1/;D')"
+        args=("$@")
+        exec blackbox -w "$workDir" -c "hx ''${args[*]@Q}"
+      fi
+    fi
+  '';
+in
+
+{
+  environment.systemPackages = [ helixDesktop ];
+}