Re: [Swingosc-devel] "failed to start" message

[James H. <jam...@gm...>]

>
> hmmm,
>
> updatelistener per se is very robust and first 100% correct, i have it all over the place in my live instrument. so if there is a bug it must be somewhere outside of it, maybe a missed registration or a race condition, or....?
>
> at the moment i don't have time to look into it (also since i never witnessed this problem), but will keep it in my mind. if you have a startup sequence that reproduces the problem (without relying on extra quarks), i could see if i find the issue.
>
>    

Arghhh... I think I found it. SwingOSC is a subclass of Model, which 
doesn't include the fix that was made to Object:changed to avoid 
iterating over a collection from which items might be removed.

     changed { arg what ... moreArgs;
         dependants.do({ arg item;
             item.update(this, what, *moreArgs);
         });
     }

The only thing about my startup sequence that I can find is that I use 
SwingOSC.default.waitForBoot in my startup file, which calls 
doWhenBooted. SwingOSC:boot also calls doWhenBooted -- so there's a pair 
of UpdateListeners. I'm almost certain what's happening is that one of 
these listeners fires and removes itself from the dependents collection, 
which then modifies the collection so that the iterator never touches 
the other listener.

I'll do some more testing by changing the method to read 
dependants.copy.do (to match Object:changed).

CC: sc-dev, so I can rant about the continued existence of Model. I can 
see that it's there to improve performance of dependent notifications 
over Object's dependantsDictionary -- but, because supercollider doesn't 
have multiple inheritance, subclassing Model means that you can't 
subclass anything else at the same time. So nobody uses Model, with the 
side effect here that an important fix to the dependency protocol in 
Object never made it over to Model, and it wasn't discovered for 
probably a couple of years.

Mental note -- SC4 cleanup -- remove Model.
hjh


-- 

James Harkins /// dewdrop world
jam...@de...
http://www.dewdrop-world.net

"Come said the Muse,
Sing me a song no poet has yet chanted,
Sing me the universal." -- Whitman

blog: http://www.dewdrop-world.net/words
audio clips: http://www.dewdrop-world.net/audio
more audio: http://soundcloud.com/dewdrop_world/tracks