Back in the days of Delphi, that was trivial. The description of the GUI itself was kept separate (I believe in binary files?) and you basically only used code

Back in the days of Delphi, that was trivial. The description of the GUI itself was kept separate (I believe in binary files?) and you basically only used code for interaction/changes. A lot of quite complex apps were written in it before Microsoft and their own stupid decisions basically killed them off.