Debugging xdg-open

[Felix Natter]

hello,

I am the author of a "freeplane" debian package, and the problem is that
for a user, it runs successfully from a terminal, but not from a file
manager (rightclick->run_as I think).

Now I would like to debug this (possibly using xdg-open):

- $ file bugreports.mm 
  bugreports.mm: Freeplane document

- $ xdg-open bugreports.mm 
Opening "bugreports.mm" with LibreOffice Writer  (text/x-troff-mm)
(even though Freeplane is listed first in right-click dialog in
 nautilus)

--> Is there another way to debug this? Will "Terminal=true" in a
desktop file work? Do I need to run a command after I modify
/usr/share/applications/freeplane.desktop?

Thanks and Best Regards,
-- 
Felix Natter