CHAPTER 8
696
Interactive Features
Filling in (signing) the signature field entails updating at least the
V
entry and
usually also the
AP
entry of the associated widget annotation. Exporting a signa-
ture field typically exports the
T
,
V
, and
AP
entries.
Like any other field, a signature field may actually be described by a widget anno-
tation dictionary containing entries pertaining to an annotation as well as a field
(see “Widget Annotations” on page 640). The annotation rectangle (
Rect
) in such
a dictionary gives the position of the field on its page. Signature fields that are not
intended to be visible should have an annotation rectangle that has zero height
and width.
The appearance dictionary (
AP
) of a signature field’s widget annotation defines
the field’s visual appearance on the page (see Section 8.4.4, “Appearance
is in the technical note
Digital Signature Appearances
(see the Bibliography).
TABLE 8.81 Additional entries specific to a signature field
KEY
TYPE
VALUE
Lock
dictionary
(Optional; must be an indirect reference; PDF 1.5)
A
signature field lock dictionary
that
specifies a set of form fields to be locked when this signature field is signed. Table 8.82
lists the entries in this dictionary.
(Optional; must be an indirect reference; PDF 1.5)
A
seed value dictionary
(see Table
plied to this field.
SV
dictionary
The value of the
SV
entry in the field dictionary is a seed value dictionary whose
entries (see Table 8.83
)
provide constraining information that is to be used at the
time the signature is applied.
Its
Ff
entry specifies whether the other entries in the
dictionary are required to be honored or whether they are merely recommenda-
tions.
Note:
The seed value dictionary may include seed values for private entries belong-
ing to multiple handlers. A given handler should use only those entries that are per-
tinent to itself and ignore the others.