Hello Nick Polyak,
You say that:
"I do not see any problem with WPF allowing a popup to cover a screen. If a software engineer does not make it do it, it will not do it."
What I meant with my previous reply is that we need to use popups internally in the current implementation of the DragDrop to draw the drag arrows and cues but we cannot do this due to the large popups bug.
You can run the attached project and see that large popups indeed cannot be created.
We expect that will be able to come up with a different implementation of the DragDrop but until then I cannot offer a workaround.
At the time being for drag-drop across different windows I can only suggest using the built-in WPF DragDrop.
the Telerik team
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