[vtkusers] WHY dragging the window triggers the render?

[Marius S Giurgi]

Can someone enlighten me, please? and tell me WHY is it that whenever I 
drag the window around it triggers the rendering pipeline update? Not 
only that it is useless, consuming CPU resources, but it is also slow, 
especially whenever there's a volume rendering involved, as it takes a 
long time to recompute the ray-casting. Thus moving the window aside 
it's no longer a trivial (quick) task. I'm not sure if this happens on 
other platforms but it certainly does on Mac OS X.

is this a bug? is it supposed to happen like it does?

marius