gEDA-dev: PCB rendering performance

[der Mouse]

I hope nobody has been putting many brain cycles into the PCB rendering
slowness I mentioned a little while back.  Quite by coincidence, I
found very compelling evidence that the problem isn't in PCB, not even
if my HID counts as part of "PCB".

I was trying to track down another problem.  Specifically, if I display
tut1.pcb with the "whole board" zoom setting of 510 and it's fine, set
zoom to 100 and it draws a small part, as expected, then the machine
crashes.  (I hasten to add, I do not consider this PCB's fault.  No
matter _how_ buggy it may be, it shouldn't be able to do that; it's
running with no access to /dev/mem or any such thing that could justify
a crash.)

While trying to figure out what's with the crash, I ran PCB under a
very simple server+mterm+twm session instead of my usual full-fledged X
session.  The redraw that has usually taken some 45-60 seconds
completed in maybe one or two seconds.

The really bizarre thing is, when I try it now under my usual session,
it is a little slower, but still only maybe two to three seconds.
There's a delay of about five seconds before it starts drawing, and
that might be worth looking at, but until I figure out WTF is going on
with this graphics replot speed bizarrity I don't think there's any
point in even thinking about other speed issues.  I'm trying to imagine
what possible relevant difference there could be between a freshly
booted machine and one that's been up for a while.

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