composite structured graphic
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 supported 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.
- Picture(Graphic* = nil)
Construct a new picture, optionally supply a graphic from which to
copy an initial set of graphics 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.
- Graphic* graphic(UList*)
- UList* Elem(Iterator)
Convenience functions for extracting a graphic from a UList element
and a UList from an iterator.