Comment by jerf

You can create UIs entirely out of composition. It's not even that hard, or that foreign per se. The problem you see there is a mismatch between Rust and GTK specifically, not GUIs in general. Of course, all the major GUIs are inheritance based, but I count that as less evidence than I might under other circumstances because GUI toolkits are multi-decade endeavors at the top end, and all the viable ones date to when inheritance was still the Law of the Land.