NAME

       StateVarView - state variable view base class

SYNOPSIS

       #include <Unidraw/stateview.h>

DESCRIPTION

       StateVarView  is  the base class for state variable views.  State variable views provide a
       graphical interface to examining and potentially modifying a state variable subject.   The
       StateVarView  base class is an abstract class derived from MonoScene.  Like MonoScene, the
       StateVarView class is  not  instantiated;  instead,  subclasses  add  state  and  behavior
       appropriate  for  displaying  and editing their subject.  Like other MonoScene subclasses,
       StateVarView subclasses use an interactor composition to define their appearance.

PUBLIC OPERATIONS

       virtual void Update()
              Update the state variable view in response to a  change  in  state  it  depends  on
              (typically  the  subject's).  This operation does not normally need redefinition if
              Init and Stale (described below) are redefined.

PROTECTED OPERATIONS

       StateVarView(StateVar*)
              Subclass constructors normally take an instance of the corresponding subject as  an
              argument.   The  base  class  constructor  automatically  attaches  the view to the
              subject.

       virtual void Init()
              Initialize the view based on information in the subject.  Subclasses redefine  this
              operation according to their semantics; it does nothing by default.

       virtual boolean Stale()
              Return  whether  the  view  is  in  any  way  inconsistent  with its subject.  This
              operation always returns true by default; subclasses can redefine it to make a more
              discerning decision.

SEE ALSO

       MonoScene(3I), StateVar(3U)