[pmarreck]

> the implicit global state and, in particular, the fact that it's very difficult and error-prone to make applications that interact with OpenGL from multiple threads

These things are obviously related.

From my work in OO langs, I believe it is possible to wrap OO code in functional code to some degree without rewriting, assuming that global references can be intercepted and resolved to local ones somehow, and that the state reference that encompasses all the globals is an immutable data struct