On Nov 3, 2006, at 10:09 PM, Rubber Chicken Software Co. wrote:
At 08:48 PM 11/3/2006, you wrote:
> As a usual VB user, all this seems funny to me in this day of age.
> VB seems very pre-emptive multi-tasking, whereas RB seems more like
> 16-Windows, where one thing MUST come after the other.
Not so. I think the problem here is that REALbasic uses cooperative
threads, and your dylib cannot cooperate with Rb.
Are there rules about that? Why can't it cooperate?
The question is how can it cooperate? The dylib code doesn't know
about Rb. All that Rb knows about the dylib is that you've declared
and called a function from it. Suspending execution of the library
function arbitrarily is, well, preemptive threading, and REALbasic
doesn't do that.
If you wrote the library, then it would be possible to reimplement
it so that it could
cooperate with Rb by breaking long tasks into a sequence of shorter
tasks that could be called from Rb in a loop, thus allowing the
runtime the opportunity to switch context.
That's like saying the earth can start revolving the other way. =)
Sure, that's nice to suggest (and thank you), but suppose I want
the dylib to do a whole task by itself? Splitting it up
unnecessarily gets RB involved in the process, which is exactly why
I want the dylib - to divest out of RB for a particular thing.
This seems like a typical thing - RB handles interface duties,
while a dylib handles things behind the scenes. It seems like a
natural encapsulation - RB handles user feedback, the dylib does
things and reports back to the RB interface on a timely basis.
Coding around technological issues (that should be addressed) is
sort of silly, as a concept.
How would you propose to address it? Any threading model will
require you to code around it, just as you must code around the
issues raised by the choice of memory management scheme in REALbasic
(note to GC advocates: you have to do it in Java as well).
OK, BTW, I found the solution to the question, although it brings
up another question. I put a App.DoEvents call in the callback
function; now everything seems A OK. (Thank you to Mars.) However,
the docs say that "using DoEvents in a GUI app will likely cause
instability." Will it in this case?
In any particular case, you'll have to try it to see.
Charles Yeomans
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