Sure, you need to wrap it in C, but there is also `cfltk` that is maintained and used in Rust bindings. Btw., the difference in memory usage is huge with GTK4. FLTK hello world is ~10M, GTK3 is ~15M, GTK4 is 40M! With Cairo rendering, it's about 30M, but still a lot.

GTK4 memory usage is ludicrous

ah neat, I wasn't aware that cfltk was already used by rust.

There is cflt and Freebasic FLTK