_gtkButtonSwitchCBactivate gets the current state (on or off) of a ButtonSwitch object.
The used GTK+ version should be 3.x or above, otherwise the object will not be created and nil will be always returned.
This function should be never called ! You should call _gtkWidgetCBmouse
with flag CB_MOUSE_PRESSED instead and next ask the state of the ButtonSwitch
by _gtkButtonSwitchGet.
Another way is to call _gtkWidgetCB with
"notify::active" as signal name (experimental).