Can't get speechSynthesizer:didFinishSpeaking: to run on OS X

[Ivan Andrus]

I would like to add GNUstep/Cocoa speech synthesis to my local copy of emacs.  
I know this is an GNUstep/OS X only feature and that it will probably never 
make it into emacs.  I also know about emacspeak and such, but I just want 
something very simple to play around with.

So far I can start and stop speech, but I have been unable to get the 
didFinishSpeaking callback to work.  I have implemented an ObjC class (in 
nsfns.m) which implements

- (void)speechSynthesizer:(NSSpeechSynthesizer *)sender 
didFinishSpeaking:(BOOL)success 

and I have set an instance as a delegate to an NSSpeechSynthesizer object, but 
it never fires.  If I call it manually as

[[speech_synthesizer delegate] speechSynthesizer: speech_synthesizer 
didFinishSpeaking: YES];

it works, so I don't think there is a problem with the callback, or the 
delegate.  I read at 
http://lists.apple.com/archives/cocoa-dev/2009/Feb/msg00624.html
that asynchronous callbacks rely on the runloop.  I think Emacs.app does some 
weird things with the runloop, so my question is, what must I do to get this to 
work?  Is it even possible?  Does Emacs.app even use the runloop?  Is it worth 
the effort?  I'm not an expert in either Cocoa/GNUstep or emacs development.

I can send the code if it's helpful, but I thought someone might know offhand 
what the problem is and and could point me in the right direction to fix it.

Thanks,
Ivan