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 sub-
       ject.  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 sub-
              ject'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)