requested to merge asturmlechner/qtwayland:asturmlechner/QTBUG-112161-mimedata-drags into kde/5.15
It's possible for clients to perform a drag and drop operation within their own client without any mimeData. A user can directly access the original drag.
On wayland without any mimedata it's impossible for a client to accept a drag as the mechansim involved is to either select a given mimedata entry or an empty string. Within Qt we always accept the first format if we accept a drag.
When dragging within our own window we also start a wayland drag so will receive a cancel event from the compositor if the compositor doesn't believe the client has accepted the drag.
This patch provides a dummy mimedata entry so that something can be accepted.