[vtkusers] vtkInteractorStyleTrackballCamera renders unnecessarily

[Christoph Kolb]

Hi All,

In several events defined in vtkInteractorStyleTrackballCamera which are 
rerendering the scene (zooming, panning...), an additional render call 
is issued within StopState() at the end of an Interaction.
For example if the mouseWheelEvent is processed, the 3D scene is zoomed 
for one step but two consecutive render calls are started. There seems 
to be no difference between both renderings.
Can you please explain the need for the rendering in StopState()? Is it 
possible to avoid the second rendering without subclassing the 
vtkInteractorStyle?

Thank you for your help!

Regards
Christoph