Because dragging is implemented as a simulated 1x1 block selection,
there's no way to pick out and drag a single item when multiple items
overlap.
Currently the drag hotkey handler checks to see how many items are
under the mouse, let's the user select one via a popup menu if there
are more than one, and then throws that info away because it sets up a
1x1 block selection. The block selection finds all all items under the
cursor, and you end up dragging them all instead of the item you
wanted.
This patch fixes that in the block selection code by checking if this
is currently a simulated drag (block command == drag and current
item != null) and returning the currently selected item, rather than
testing everything under the cursor and returning multiple items. This
seemed like the most straight-forward way to fix the issue and still
keep dragging as a simulated block selection.
