>I dont know how vfp window was created.Maybe its original definition blocks the maximized undocking.its an old story ...
>What i experiment is that a window created with the API CreateWindowEx have the same behavior as all windows
>and can be docked or undocked when maximized.
>you have a working example in http://www.news2news.com/vfp/index.php?example=50
>you can make this window as top level in dwExStyle.for this see :
> https://msdn.microsoft.com/en-us/library/windows/desktop/ms632600%28v=vs.85%29.aspx?f=255&MSPPError=-2147217396
>and test.it can be docked or undocked as expected in my Windows10.


Thank you.
I think with BindEvent to OS messages,
we can do the job.