Path: utzoo!attcan!utgpu!watmath!iuvax!rutgers!apple!apple.com!goldman
From: goldman@apple.com (Phil Goldman)
Newsgroups: comp.sys.mac.programmer
Subject: Re: MultiFinder rationing background update events?
Message-ID: <3420@internal.Apple.COM>
Date: 9 Aug 89 08:20:38 GMT
References: <5181@umd5.umd.edu>
Organization: Apple Computer
Lines: 26

In article <5181@umd5.umd.edu> zben@umd5.umd.edu (Ben Cranston) writes:
> behavior.  Some small part of the updating (perhaps a few tens of 
separate
> update events) actually get done, then drawing suddenly ceases.  If I 
then
> uncover more of the window, another small piece of the drawing is done, 
etc.
> My application is far too simple to explain this behavior.
> 
> The only explanation I can think of is some MF heuristic must be coming 
into
> play.

Yes.  The problem is that many apps will simply not update their windows 
in certain situations.  Therefore, since context switching is relatively 
expensive, MultiFinder provides a maximum number of tries that it will 
give an app to update in the background.  The number of tries allowed was 
chosen as to be large enough so that legitimate updating could occur in 
pieces; I believe the number is somewhere around 50.

If you find that you must do more than a few pieces then you should do 
exactly what you mentioned in your posting:  Clear the update and keep 
your own region.  To do this you will have to be a background app too.

-Phil Goldman
Apple Computer