> Very special case.

It's not so special if you want to execute an image processing operation on a 
multi core machine and wait for the result in the main thread, something like 
(pseudo code):


StartThreads(GetNumberOfProcessors);
WaitForThreads;

> Freezing GUI is not acceptable.

[...]

> I would like to know for sure: do I have to do Canvas.Lock or such the
> lock is unnecessary?

Then you have to use locking.






-- 
Jens Gruschel
http://www.pegtop.net