A display area can have a number of associated inline areas
called attachment areas.
These are illustrated in Figure 14, Attachment
Areas which shows
the use of sidelines and graphics as attachment areas on either side of the
display area.
NOTE 40
Attachment areas are used for sidelines, line numbers, and marginalia.
Each attachment area is positioned relative to a point on the
display area's
box called the attachment point for the attachment area.
The attachment point may be different for each of the attachment areas
of the display area. An attachment point lies on an edge of the
display area that is parallel
to the placement direction.
There is a specification for each
attachment area that indicates which such edge of the display area it is
attached to. Each attachment area has an alignment
point and is positioned so that the attachment area's alignment
point is at the same position in the placement direction as the
corresponding attachment point on the display area.
Each attachment area has a specified
separation from the display area. If the attachment point is on
the edge that is
at the start in the direction determined by the writing-mode, then the
separation
is the distance in that direction from the attachment area's
alignment point to the attachment point, and the attachment area's
alignment point is its escapement point. If the attachment point
is on the edge that is at the end in the direction determined by the
writing-mode, then
the separation is the distance in that direction from the
attachment point to attachment area's alignment point, and the
attachment area's alignment point is its position point.
NOTE 41
A negative value for the separation means that the attachment
point is inside the display area.