The more complicated mode is the Childframe mode which also needs QextMdiChildArea as application-internal desktop (background widget) and QextMdiChildFrm as emulated toplevel-window frame for MDI child views for attached view state.
Additionally there are some minor, internally used helper classes. They are QextMdiTaskBarButton that provides the special button type of the MDI view taskbar, some customer event classes (sometimes used to break the function call stack to avoid circular method calls) and some iterator classes for abstract handling of internally used data.