There is no way to know if the option as been passed when argument is optionnal.

Pending having bug 588989 not crash, I don't find any way to check of said option has been set.

  Glib::ustring search;
  Glib::OptionEntry entry;
  entry.set_long_name("search");
  entry.set_flags(Glib::OptionEntry::FLAG_OPTIONAL_ARG);
  entry.set_description("Open the search all notes window with the search text.");
  options.add_entry(entry, search);


In the above case, if --search is passed, "search" will be empty, like if --search was NOT passed.