Widgets that a GUI toolkit should have for Emacs.

[Vincenzo Pupillo]

Ciao,
for another project I am working on (low priority at the moment) I have 
started to write a small cross platform GUI Toolkit (for SDL 3 which has not 
yet been released).
In the future, if I can adopt an open license (probably MIT or zlib), I would 
like to be able to try using it with Emacs. So I wanted to ask if you could 
tell me what are the minimum requirements and widgets that are essential for 
Emacs.

Thanks

Vincenzo