BT: Mac OS X: Items are sometimes copied and sometimes moved in draggable icons example (regression)

Open the "draggableicons" example and drag icons around. In Qt 4.5, the icons would be copied if dragged into the opposite pane, but moved if they remained inside the current pane. In Qt 4.6 they will sometimes be copied and sometimes moved.

This can be seen by opening the example and dragging the sail boat in the left pane into a new location. The first time you do this, it will be copied and the second time it will be moved.