GVUpdater  -  updates  GraphicViews structure to match its
       subject

SYNOPSIS

       #include <Unidraw/Components/gvupdater.h>

DESCRIPTION

       GVUpdater is an  implementation  class  that  GraphicViews
       uses  to  keep its state and structure consistent with its
       GraphicComps subject.  GVUpdater  ensures  that  subject's
       immediate  children  are identical to the view's in number
       and graphics state attributes. It also  ensures  that  the
       root  GraphicViews  and  GraphicComps  themselves have the
       same graphics state.  GVUpdater does not  ensure  that  it
       will detect and update changes made to deeper child nodes.

PUBLIC OPERATIONS

       GVUpdater(GraphicView*)
              The constructor takes the GraphicView that it  will
              be  updating  as  a  parameter and stores it in the
              protected member _gv.  Normally,  GraphicViews  are
              the only objects that will instantiate GVUpdater.

       virtual void Update()
              Update  the  GraphicView to make it consistent with
              its subject.

PROTECTED OPERATIONS

       void UpdateStructure()
       void UpdateState()
              The Update procedure takes  place  in  two  stages.
              The  subject's and view's structures are reconciled
              first  by  UpdateStructure,  and  then  the  view's
              graphic state is changed to match the subjects with
              UpdateState.

       void AddDamage(Graphic*)
       void IncurDamage(Graphic*)
       void Unselect(GraphicView*)
       virtual void Add(GraphicView*)
       virtual void Append(GraphicView*)
       virtual void InsertBefore(Iterator, GraphicView*)
        virtual void Remove(Iterator&)
       virtual void DeleteView(Iterator&)
              GVUpdater is a friend of GraphicViews.  These  con-
              venience  operations  provide  an  interface to the
              corresponding protected GraphicViews operations.

       virtual ClassId ViewCategory()
              Returns the view category (see  classes(3U))  GVUp-
              dater  will  use  to instantiate views of subjects.
              ViewCategory returns COMPONENT_VIEW by default.

       GraphicComp(3U), GraphicView(3U), classes(3U)