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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