Tag an item nearest to coordinates. If more than one item is at the same
closest distance (e.g. two items overlap the point), then the top-most
of these items (the last one in the display list) is used. If radius is
specified, then it must be a non-negative value. Any item closer than
halo to the point is considered to overlap it.
Tag an item nearest to coordinates. If more than one item is at the same closest distance (e.g. two items overlap the point), then the top-most of these items (the last one in the display list) is used. If radius is specified, then it must be a non-negative value. Any item closer than halo to the point is considered to overlap it.