Can't drop files to IShellView when FWF_DESKTOP flag set

I implemented an IShellBrowser to host an IShellView object. And I set the FWF_DESKTOP flag when I call IShellView::CreateViewWindow. After IShellView::UIActivate, the view window its created cannot accept user drop files on it, but can drag to other explorer Window. I tried to obtain an IDropTarget via IShellFolder::CreateViewObject, and RegisterDragDrop to the view window, it works. But when I drag file from explorer to it, no dragging image displayed(it seems like old style D&D), and I also can't drag and drop items in same window. If I CreateViewWindow with FWF_NONE, 开发者_运维知识库all fine. But....why?

How can I make Drag & Drop work properly when I specify FWF_DESKTOP?

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The desktop view might have some special handling, even MSDN says:

This value applies only to the desktop view and is not used for typical Shell folders.

Why do you think you need the FWF_DESKTOP flag?