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CHAPTER 8 Interactive Features
TABLE 8.68 Signature flags
BIT POSITION NAME MEANING
1 SignaturesExist If set, the document contains at least one signature field. This flag allows a
viewer application to enable user interface items (such as menu items or
pushbuttons) related to signature processing without having to scan the
entire document for the presence of signature fields.
2 AppendOnly If set, the document contains signatures that may be invalidated if the file
is saved (written) in a way that alters its previous contents, as opposed to
an incremental update. Merely updating the file by appending new infor-
mation to the end of the previous version is safe (see Section G.6, “Up-
dating Example”). Viewer applications can use this flag to present a user
requesting a full save with an additional alert box warning that signatures
will be invalidated and requiring explicit confirmation before continuing
with the operation.
8.6.2 Field Dictionaries
Each field in a document’s interactive form is defined by a field dictionary, which
must be an indirect object. The field dictionaries may be organized hierarchically
into one or more tree structures. Many field attributes are inheritable, meaning
that if they are not explicitly specified for a given field, their values are taken from
those of its parent in the field hierarchy. Such inheritable attributes are designated
as such in the tables below. The designation (Required; inheritable) means that an
attribute must be defined for every field, whether explicitly in its own field dictio-
nary or by inheritance from an ancestor in the hierarchy. Table 8.69 shows those
entries that are common to all field dictionaries, regardless of type. Entries that
pertain only to a particular type of field are described in the relevant sections be-
low.
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