# File vtk/gtk/GtkVTKRenderWindowInteractor.rb, line 171
    def OnButtonDown(self, wid, event)
        """Mouse button pressed."""
        m = self.get_pointer
        ctrl, shift = self._GetCtrlShift(event)
        self._Iren.SetEventInformationFlipY(m[0], m[1], ctrl, shift,
                                            chr(0), 0, nil)
        button = event.button
        if button == 3
            self._Iren.RightButtonPressEvent
            return gtk.TRUE
        end
    end