Although I've never ported it to Linux, the Faria ROM Editor is probably the best example of a fairly simple win32 app that I can share the src for with you [1].
That being said, win32 is old school. However, it is what I know well for non-web gui development.
My advise to you is to use the best tool kit for your preferred development platform and targeted user base. It probably isn't win32 or ncurses....
[1] https://www.ecoligames.com/svn/FariaEditor/
