serves state information of objects which can be connected to
controllers (e.g., toolbox controllers).
Each state change is to be broadcast to all registered
status listeners. The first notification should be performed
synchronously from XDispatch::addStatusListener ;
if not, controllers may flicker. State listener must be aware of this
synchronous notification.
The state consists of enabled/disabled and a short descriptive text
of the function (e.g., "undo insert character"). It is to be broadcast
whenever this state changes or the controller should re-get the value
for the URL to which it is connected. Additionally, a context-switch-event
is to be broadcast whenever the object may be out of scope,
to force the state listener to requery the XDispatch .