[Cuis] Curious drawing performance issue

[Phil (list)]

I noticed a while back that something appeared to be going on with Cuis
drawing performance (at idle on my system Morphic consumes ~20% of VM
CPU *miniumum* according to ProcessBrowser) and this seems to give an
indication of what it's currently costing in drawing performance...

After seeing the Squeak 5.0 announcement, I was curious to see roughly
how much of a speed boost we might be able to expect from Spur down the
road.  So I decided to look at BouncingAtomsMorph to try to get a rough
apples-to-apples comparison and was quite surprised: Spur was faster,
but it was too much faster.  So I dropped back to Squeak 4.5 and it also
performs much, much better than the Cuis version on the same VM.   Here
are the numbers I'm seeing using BouncingAtomsMorph with roughly
comparable (i.e. eyeballed) morph sizes and atom count set to 5000:
Squeak 5.0 (Spur VM from all-in-one download): 29-31 fps
Squeak 4.5 (Cog VM 15.25.3390): 24-26 fps
Cuis 2440 (Cog VM 15.25.3390): 6-8 fps

Granted BouncingAtomsMorph is not 100% identical from a source code
standpoint but it's not nearly different enough where I'd expect that
sort of difference.  Is this a platform-specific issue (I'm on Linux) or
are others noticing drawing issues as well?