I don't agree with this change. Based on the code, it looks like there should be an enumeration of cell_types somewhere, a button should have a cell_type, and

I don't agree with this change. Based on the code, it looks like there should be an enumeration of cell_types somewhere, a button should have a cell_type, and then there's a map from cell_type to construction_fn (or a polymorphic set of classes to serve as the map.) Metaprogramming is something you do when you can't do it easily in the usual way. If a dispatch table or inheritance takes care of something, use the existing language features instead of building your own. (EDIT: On examination, there already is a RowType, and the pull request is a lot closer to my suggestion than I first thought, so mostly ignore this.)