Theme suffixes

Theme suffixes

So as I read the various implementations for the widgets, I notice that we inject content around, and inside, elements and add various ui-* classes. What do the single lettered suffixes at the end of ui-* class names mean?

For example, I've seen classes that end in "-a", "-c", and "-f". I guess an example would be "ui-btn-up-f".

- Kin