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)

Unidraw                                           6 August 1990                                 StateVarView(3U)