[vtkusers] Identifying which button is pressed

[Paul Albee]

Hi All,
   I'm using the vtkImagePlaneWidget in Tcl, and need to capture the 
pick position only when the left mouse button is pressed. Currently I 
cannot figure out how to tell which button was pressed when I have an 
observer set for StartInteractionEvent for a vtkImagePlaneWidget. Any 
suggestions would be appreciated.

Thanks,
Paul Albee