xournal: add desktop file and mime info

Fixes #20510.

The application now appears in system menus, and Konqueror now suggests
opening .xoj files with Xournal. Other file browsers should as well.

pkgs/applications/graphics/xournal/default.nix

@@ -1,4 +1,4 @@
-{ stdenv, fetchurl
+{ stdenv, fetchurl, makeDesktopItem
 , ghostscript, atk, gtk2, glib, fontconfig, freetype
 , libgnomecanvas, libgnomeprint, libgnomeprintui
 , pango, libX11, xproto, zlib, poppler
@@ -21,6 +21,32 @@ stdenv.mkDerivation rec {
 
   NIX_LDFLAGS = [ "-lX11" "-lz" ];
 
+  desktopItem = makeDesktopItem {
+    name = name;
+    exec = "xournal";
+    icon = "xournal";
+    desktopName = "Xournal";
+    comment = meta.description;
+    categories = "Office;Graphics;";
+    mimeType = "application/pdf;application/x-xoj";
+    genericName = "PDF Editor";
+  };
+
+  postInstall=''
+      mkdir --parents $out/share/mime/packages
+      cat << EOF > $out/share/mime/packages/xournal.xml
+      <mime-info xmlns='http://www.freedesktop.org/standards/shared-mime-info'>
+         <mime-type type="application/x-xoj">
+          <comment>Xournal Document</comment>
+          <glob pattern="*.xoj"/>
+         </mime-type>
+      </mime-info>
+      EOF
+      cp --recursive ${desktopItem}/share/applications $out/share
+      mkdir --parents $out/share/icons
+      cp $out/share/xournal/pixmaps/xournal.png $out/share/icons
+  '';
+
   meta = {
     homepage = http://xournal.sourceforge.net/;
     description = "Note-taking application (supposes stylus)";