Function type for determining whether
column can be dropped in a particular spot (as determined by
In left to right locales,
prev_column is on the left of the potential drop spot, and
next_column is on the right. In
right to left mode, this is reversed. This function should return true if the spot is a valid drop spot.
Please note that returning true does not actually indicate that the column drop was made, but is meant only to
indicate a possible drop spot to the user.
The TreeViewColumn being dragged
A TreeViewColumn on one side of
A TreeViewColumn on the other side of