[vtkusers] Change viewport during runtime

[mailing-list at gmx.de]

Hey,

I'm using vtkImageViewer2 and want to change the viewport. Setting the
size with vtkImageViewer->GetRenderer()->SetViewPort(....) for the
first time is not the problem but if I want to change it later
my program is crashing.
I tied DrawOff setting the size and DrawOn, Disable and Enable
the interaction too but without any success.

In a normal OpenGL application a don't have this problem
and being able to change the viewport without crashing
the program but I guess this happen because of the 
running rendering loop.

So maybe someone has a hint or good advice how to solve this
problem.

Thanks in advanced

Frank