Moving rows within a tree, or between trees sharing a mime type.
Readonly
Carries the dragged ids. Convention: application/vnd.code.tree.<viewid>.
application/vnd.code.tree.<viewid>
Called after a drop with the dragged items' ids, because ids are what reliably survive the drag's serialisation. Redrawing is the handler's job.
Moving rows within a tree, or between trees sharing a mime type.