During Drag and Drop operations it is possible that a user may wish to drop the
subject of the operation on a region of a scrollable GUI control that is
not currently visible to the user.
In such situations it is desirable that the GUI control detect this and
institute a scroll operation in order to make obscured region(s) visible to
the user. This feature is known as autoscrolling.
If a GUI control is both an active DropTarget and is also scrollable,
it can receive notifications of autoscrolling gestures by the user from
the Drag and Drop system by implementing this interface.
An autoscrolling gesture is initiated by the user by keeping the drag
cursor motionless with a border region of the Component, referred to as
the "autoscrolling region", for a predefined period of time, this will
result in repeated scroll requests to the Component until the drag Cursor
resumes its motion.
