On 24.03.2009, at 22:37, Andreas Raab wrote:

> Chris Muller wrote:
>> (3.9 Morphic).  With Maui I occassionally get World lockups due to  
>> the
>> UI process waiting for the #next of the deferredUIMessages, which is
>> empty.
>> Specifically, the freeze, when it occurs, is always in
>> WorldState>>#runStepMethodsIn:.  There's a while loop to process
>> messages in the queue:
>> 	"Dispatch deferred messages while maintaing rudimentary UI  
>> responsiveness."
>> 	[i < numItems and: [(Time millisecondsSince: stamp) < limit]]
>> 		whileTrue: [queue next value. i := i + 1].
>
> This is plain wrong. I don't know what the rationale of the change  
> was but you'll have much better success if you change this to e.g.,
>
> 	queue := self class deferredUIMessages.
> 	[(msg := queue nextOrNil) == nil] whileFalse: [
> 		msg value.
> 	].
>
> The reason why the original version is wrong is that there is  
> absolutely no assurance that some Morph won't call World doOneCycle  
> which would re-enter the above loop, pull out all of the events and  
> leave the original caller hanging; just as you report.


FWIW, the 3.8 method looked like this:

	[queue isEmpty] whileFalse: [queue next value].

- Bert -