from preamble:

"Change Set:		InvalidationOptimization-nk
Date:			24 September 2003
Author:			Ned Konz

This CS skips invalidation of rectangles whose width or height is 0.

This eliminates huge amounts of unnecessary redrawing (much of it out of
bounds!!) with PluggableListMorphs.

You can see the difference by doing this before and after you load this
CS:

* open a browser.
* Bring up a halo on the class category list's listmorph.
* inspect the morph
* turn on the debugShowDamage preference
* evaluate this in the inspector:
   model changed: (self getListSelector)

"!
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