Migrating a large application to Qt. I have a Window CDialog that I want to host inside a QWidget

How to achieve that? QWinHost doesn't seem appropriate as that seems to require subclassing and modification of a native Windows app event loop which doesn't seem useful.

No I cannot re-implement that dialog in Qt in short order - it will take months of work as it has 10 custom CWnd children not of which are in any way trivial (the smallest is around 3k of code).