wrapping a C style delegate

[Nicholas Wilson via Digitalmars-d-learn]

I want to wrap:

ErrorEnum function(Struct* s, void function(Struct*, ErrorEnum 
status, void *userData) callback, void *userData, uint flags);

as a member of a wrapping struct

struct Mystruct
{
    Struct* s; // wrapped

      ErrorEnum addCallback(void delegate(Struct*, ErrorEnum 
status))
      {
          //...
      }
}


How do I wrap that?