Picture - composite structured graphic

SYNOPSIS

       #include <Unidraw/Graphic/picture.h>

DESCRIPTION

       A  Picture  defines  a  composition of graphic objects.  A
       picture has its own graphics state, which it  concatenates
       with  its  children's  state  when  it is drawn or erased.
       Picture adopts the default  concatenation  semantics  sup-
       ported  by  the Graphic base class: The picture's graphics
       state effectively overrides its children's  so  that  they
       are drawn with the picture's state information substituted
       for their own.  A child's attribute is used only when  the
       picture  does  not  already  define  it.   Moreover,  each
       child's transformer is  postmultiplied  by  the  picture's
       transformer  when  the picture is drawn; thus children are
       drawn relative to the picture's coordinate system.

PUBLIC OPERATIONS

       Picture(Graphic* = nil)
              Construct  a  new  picture,  optionally  supply   a
              graphic from which to copy an initial set of graph-
              ics state.  Picture is derived from FullGraphic and
              therefore defines a full set of graphics state.

       virtual ~Picture()
              The   picture  deletes  its  children  when  it  is
              deleted.

       boolean IsEmpty()
              Picture defines IsEmpty in addition to the standard
              Graphic  child  traversal  operations  to provide a
              convenient way to check  if  the  picture  has  any
              children.

PROTECTED OPERATIONS

       Graphic* graphic(UList*)
       UList* Elem(Iterator)
              Convenience functions for extracting a graphic from
              a UList element and a UList from an iterator.

SEE ALSO

       Graphic(3U),  Iterator(3U),  Transformer(3I),   UList(3U),
       pspaint(3U)