Fix the missing desktop file

nix/fg42.nix

@@ -67,6 +67,8 @@ let
   paths = map (x: "${x}/bin/") (lib.lists.flatten runtimeBins);
   pathsStr = lib.strings.concatStrings (lib.strings.intersperse ":" paths);
 
+  mimes = import ./mimes.nix;
+
 in stdenv.mkDerivation (final: rec {
   inherit version;
   pname = "fg42";
@@ -77,20 +79,6 @@ in stdenv.mkDerivation (final: rec {
     exec = "${placeholder "out"}/bin/fg42 %F";
     comment = "Emacs Editor for advance users";
   };
-  #   [Desktop Entry]
-  #   Encoding=UTF-8
-  #   Name=FG42
-  #   GenericName=FG42
-  #   Comment=
-  #   MimeType=text/x-makefile;text/x-c++hdr;text/x-c++src;text/x-java;application/x-shellscript;text/x-c;text/x-c++;text/x-ruby;text/x-python;text/x-clojure;text/css;text/html;text/x-javascript;
-  #   Type=Application
-  #   Terminal=false
-  #   Categories=Development;TextEditor;
-  #   StartupWMClass=FG42
-  #   Exec=
-  #   Icon=fg42
-  #   Version=${version}
-  # '';
 
   src = srcDir;
   outputs = [ "out" ];
@@ -98,12 +86,29 @@ in stdenv.mkDerivation (final: rec {
   buildPhase = ''
     LISPDIR=$out/share/fg42/
     mkdir -p $out/bin
+    mkdir -p $out/share/applications/
     install -d $LISPDIR
 
     cp -rv ${src}/lisp/ $LISPDIR
     cp -rv ${src}/share $out/
     cp -rv ${src}/snippets $LISPDIR/snippets
 
+    cat >> $out/share/applications/FG42.desktop << EOF
+    [Desktop Entry]
+    Encoding=UTF-8
+    Name=FG42
+    GenericName=FG42
+    Comment=The nix base Emacs bundle for advance users
+    MimeType=${mimes.mimeTypes}
+    Type=Application
+    Terminal=false
+    Categories=Development;TextEditor;
+    StartupWMClass=FG42
+    Exec=${placeholder "out"}/bin/fg42
+    Icon=fg42
+    Version=${version}
+    EOF
+
     runHook preBuild
 
     cd $LISPDIR

nix/mimes.nix

@@ -0,0 +1,34 @@
+# Fg42 - Emacs Editor for advance users
+#
+# Copyright (c) 2010-2024 Sameer Rahmani <lxsameer@gnu.org>
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, version 2.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+rec {
+  types = [
+    "text/x-makefile"
+    "text/x-c++hdr"
+    "text/x-c++src"
+    "text/x-java"
+    "application/x-shellscript"
+    "text/x-c"
+    "text/x-c++"
+    "text/x-ruby"
+    "text/x-python"
+    "text/x-clojure"
+    "text/css"
+    "text/html"
+    "text/x-javascript"
+  ];
+
+  mimeTypes = builtins.concatStringsSep ";" types;
+}