? MDI depreciated

[Brendan]

This is probably a question better suited for a wxPython or MSDN
newsgroup.  What OS are you referring to?  What GUI toolkit are you
using?

Microsoft's office on Windows has moved to a model where every document
has its own toolbar, menubar, and taskbar entry.  Windows developers
tend to mimic MS Office, so many are also moving to this model. Mac
apps have never had MDI.