I think speeding long lists is important enough that more than just
trivial changes will be considered. 

It seems the QuadTrees are a general solution that could be used without
adding any constraints, just some complexity. It might be worth
considering.

You mentioned a performance penalty in building the tree. Did you
measure how significant it is? Does it slow down or speed up opening a
changesorter with lots of updates, for example?

More generally, what does it do to the macrobenchmarks?

Daniel

Eddie Cottongim <cottonsqueak at earthlink.net> wrote:
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> We've talked quite a bit about working on speeding scrolling in lists and
> scrollpanes.
> 
> One thing that Andreas, myself and others have found is that by caching
> TransformMorph's localSubmorphBounds, you can get a fairly nice improvement
> in scrolling speed for lists and scrollpanes. This seems to be a safe and
> simple change.
> 
> I hope that this enhancement is simple enough that it can be accepted and
> provide some immediate benefit to users on PDAs and slower machines. On
> larger lists, you should see 20-50% improvement in scrolling. Hopefully
> later we'll get something really smooth, but this helps for now.
> 
> Andreas sent essentially the same code to the list a while back. If you'd
> rather use his, thats fine with me, just let one of us know and it can be
> reposted as an [ENH].
> 
> Eddie
> 
> >From the preamble:
> 
> "Cache the value of localSubmorphBounds, as suggested by Andreas, myself and
> others.
> 
> Adds the iVar localBounds to do this.
> Value is computed lazily by the localSubmorphBounds method and cached. It is
> invalidated when layoutChanged it received.
> 
> Class comment is changed to reflect this addition.
> 
> Should yield 20-50% speedup in scrolling speed depending on the number of
> submorphs of the TransformMorph."
> 
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