Slow graphics

[Eliot Handelman <eliot@clarity.Princeton.EDU>]

Hello again,

We're running a big program with a graphic interface. On startup,
things run smoothly (the bulk of the program was ported from 
a Xerox machine running interlisp, and everyone is amazed at the
speedup under MACL). However after a while things begin to slow
down. Soon they get r-e-a-l-l-y slow, though all that's happening
is that graphic routines are getting called. It can happen that
the program gets stuck in the GC, with no chance of getting out.

First of all, I'd like to know whether it is reasonable to suppose
that we're running out of heap space? Our program was generating
volumes of bitmaps on the fly, but after taking care of this by either
reusing the bitmaps or explicitly disposing of them, I still don't see
much of a speedup.

One frequent client is PAINT-RECT, which I call with 4 arguments.
I have tried reserving a rectangle and stuffing that with the
arguments, but again this doesn't seem to have much of an effect.

I'd appreciate any stories of speedups that anyone might have, for
possible pointers to the right direction. I'm really stumped as
to what's going on.

Thanks for your help,

--eliot