The issue here, whether using GTK or SDL, is Sopwith uses old versions of these libraries. SDL 1.2 and GTK 2 (probably). Neither of those libraries maintain backward compatibility. Both were pretty much designed to make application developers re-write large chunks of code.
So the way forward is, ideally, to port Sopwith to SDL 2 (the GTK port was dropped years ago as being basically unmaintainable). The trick is someone needs to find enough time to learn the newer SDL 2 library and re-write the Sopwith code to match. I might end up doing this, but it's way down my priority list at the moment, especially since the current version still runs okay in most environments. In short: the fix is conceptually easy (re-write for SDL 2), it's just going to be time consuming.
