@startuml
skinparam BackgroundColor F0F0F0

class gui::ItemNode
{
    gui::Item*
    int level
}

abstract class gui::ItemTree
{
    bool hasNext()
    gui::ItemNode getNext()
}

enum TraverseMode
{
    PreOrder
    PostOrder
}

class gui::DepthFirstItemTree
{
    DepthFirstItemTree(gui::Item *root, TraverseMode mode)
    bool hasNext()
    gui::ItemNode getNext()
}

gui::ItemTree <|-- gui::DepthFirstItemTree
gui::DepthFirstItemTree o-- TraverseMode

@enduml