[vtkusers] altering a widgets response to mouse clicks

[Totte Karlsson]

Hello,
When using a boxwidget, pressing the left button and moving the mouse 
allow the user to rotate the widget,
while pressing the middle button and moving the mouse translates the widget.

How can I switch the behavior of those two buttons?
I.e. having the left button doing the translation and the middle button 
the rotation?

-tk