[vtkusers] expose slowness under X windows

[John Hunter]

I am experiencing an irritating expose problem that has me stumped.
The problem is occurring on a redhat linux 9 desktop with XFree86
4.3.0. I don't experience it on a windows XP platform though both
machines are similarly equipped (processor, memory, video card).

I have a renderer with approx 200 sphere actors.  When the render
window overlaps another (non vtk) window on the desktop and I click
back and forth between the windows (generating expose events) the
repaints are very slow.  It seems to become worse the more actors
there are in the renderer.  If the windows do not overlap, clicking
back and forth between them doesn't create any slow paints.

I don't think it's simply a matter of inadequate hardware, since I can
interact with the objects (pan, zoom, rotate) with no perceptible lag
caused by the Render calls.  It's only on the expose events that I
encounter the problem.

I'll include a bit of platform specific information below.  If anyone
has any suggestions about how I can fix this, I'd appreciate it.  My
hardware should be more than adequate to handle the scenes I am
rendering, but this expose problem is making my desktop virtually
unusable as I try and go back and forth between dialog boxes and the
render window - it can take several seconds to repaint the desktop.
I'll include a toy example below, which replicates the expose problem.
It's not as severe as in my actual code, perhaps because I have more
actors in my actual code, but it's apparent.

Test script

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Test data for script (some xyz coords)

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Platform info:

Intel(R) Pentium(R) 4 CPU 3.00GHz with nvidia card

hunter:~/python/projects/eegtools/test> uname -a
Linux hunter.paradise.lost 2.4.20-8smp #1 SMP Thu Mar 13 17:45:54 EST 2003 i686
i686 i386 GNU/Linux


XFree86 Version 4.3.0 - These are the modules XFree loaded - no errors
reported:

  bitmap, pcidata, dbe, extmod, fbdevhw, glx, record, freetype, type1,
  dri, drm, nvidia, mouse, vgahw, ddc, fb, ramdac