Or maybe the attached patch captures the goal of wxwidgets better (which they IMO don't succeed at).

I added gtk, opengl etc as native inputs instead of regular inputs because from the point of view of Python they are not direct inputs.

wxPython only requires gtk while building the extension because wxwidgets does #include <gtk/gtk.h> in their exported API (why...) - but after it's done it will not require it directly anymore and actually just require wxwidgets.

Of course, the gtk version of wxwidgets will still require gtk by itself.

That said, I still think it would be nicer if wxwidgets propagated gtk - since when you use wxwidgets, you also need to have gtk as well if wxwidgets was compiled for gtk - and the one deciding what wxwidgets is compiled for is the wxwidgets package. So it should go there...

What do you think?