The important part is...

So yeah, my native code can now communicate with the Java App :)
Yea!

The way do do this is to call any method of

 com.hymerfania.mandelbrotbridge.UpperDeck 

from within the switch block of

MandelbrotLib::EventMachine::processEvent

Right now I have merely hard-coded a call to

 UpperDeck.helloWorld(String message)

But I could register listeners on UpperDeck, and propagate events out from there.

I'll wait on that, because I don't what I want to transmit out of the DLL, or who will want to listen.