This parameter, when inserted into a port, causes the port to display data
available for the actor to read.
It assumes that the port is an input port.
Otherwise, it returns an empty string. It is a singleton, and it's
name is always _showInfo, regardless of what name argument is specified to the constructor.
Note that the display is not automatically updated. Use an instance of RepaintController
in your model to cause the display to be updated, or use MonitorReceiverContents.
Add a listener to be notified when the value of this settable
object changes. An implementation of this method should ignore
the call if the specified listener is already on the list of
listeners. In other words, it should not be possible for the
same listener to be notified twice of a value update.
Get the expression currently used by this variable. The expression
is either the value set by setExpression(), or a string representation
of the value set by setToken(), or an empty string if no value
has been set.
Get the visibility of this Settable, as set by setVisibility().
If setVisibility() has not been called, then implementations of
this interface should return some default, not null, indicating
user-level visibility. The returned value is one of the static
instances of the Visibility inner class.
Set the value of the attribute by giving some expression.
In some implementations, the listeners and the container will
be notified immediately. However, some implementations may
defer notification until validate() is called.
Set the visibility of this Settable. The argument should be one
of the static public instances of the inner class Visibility.
This is enforced by making it impossible to construct instances
of this inner class outside this interface definition.
If this method is not called, then implementations of
this interface should return some default, not null.
Check the validity of the expression set in setExpression().
Implementations of this method should notify the container
by calling attributeChanged(), unless the container has already
been notified in setExpression(). They should also notify any
registered value listeners if they have not already been notified.
If any other instances of Settable are validated as a side effect,
then an implementation should return a Collection containing those
instances. This can be used by the caller to avoid validating those
again. The list may contain this instance of Settable.