# File vtk/tk/vtkTkRenderWindowInteractor.rb, line 214
  def MiddleButtonPressEvent(event, ctrl, shift)
    @Iren.SetEventInformationFlipY(event.x, event.y, ctrl,
                                   shift, 0.chr, 0, nil)
    @Iren.MiddleButtonPressEvent
    if  !@FocusOnEnter
      _GrabFocus
    end
  end