message popups from worker thread

[Alan Mazer <alan s mazer jpl nasa gov>]

Hi.  I need some advice because I think I might be missing something simple!

I have an app with a worker thread.  The app is doing real-time image 
display and plotting with data from an attached science instrument.

Occasionally the worker thread will detect an error which the user needs 
to know about.  Previously I had the worker thread creating 
MessageDialogs for these messages but I realized that I should probably 
be using a dispatcher instead.

I noticed two things when I switched, first that plotting and image 
display now stop when there's an error until the dialog is dismissed, 
and more importantly, that if the user doesn't acknowledge the dialog 
immediately and another dialog pops up, the entire application freezes.  
Presumably, overlapped calls to a dispatcher are a big no no (which 
makes sense).

What's the best way to approach this?  I'd like image display and 
plotting to continue which messages are up, and I especially need a way 
to pop up an indefinite number of message dialogs, not from the worker 
thread, without the app freezing.

-- Alan