Thanks. It is a lot more clear to me. My app is not integrated with gnome, but using it made it works immediately
I think that those recommendations should be in the same page as the (freeplane example)[Java applications] . I get to that page from Desktop applications looking for Java Swing and never saw the gtk2/gtk3 explanation. A lot of java developers will go to the freeplane page at first look how to package.
I love to see how snaps evolve.