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                                                     672
           CHAPTER 8                                                            Interactive Features



           Each field in a document’s interactive form is defined by a field dictionary (see
           Section 8.6.2, “Field Dictionaries”). For purposes of definition and naming, the
           fields can be organized hierarchically and can inherit attributes from their an-
           cestors in the field hierarchy. A field’s children in the hierarchy may also include
           widget annotations (see “Widget Annotations” on page 640) that define its ap-
           pearance on the page. A field whose children are widget annotations is called a
           terminal field.

           As a convenience, when a field has only a single associated widget annotation, the
           contents of the field dictionary and the annotation dictionary (Section 8.4.1, “An-
           notation Dictionaries”) may be merged into a single dictionary containing entries
           that pertain to both a field and an annotation. (This presents no ambiguity, since
           the contents of the two kinds of dictionaries do not conflict.) If such an object de-
           fines an appearance stream, the appearance must be consistent with the object’s
           current value as a field.

           Note: Fields containing text whose contents are not known in advance may need to
           construct their appearance streams dynamically instead of defining them statically
           in an appearance dictionary; see “Variable Text” on page 677.


  8.6.1 Interactive Form Dictionary

           The contents and properties of a document’s interactive form are defined by an
           interactive form dictionary that is referenced from the AcroForm entry in the doc-
           ument catalog (see Section 3.6.1, “Document Catalog”). Table 8.67 shows the
           contents of this dictionary.

                             TABLE 8.67 Entries in the interactive form dictionary
KEY                  TYPE                VALUE

Fields               array               (Required) An array of references to the document’s root fields (those
                                         with no ancestors in the field hierarchy).

NeedAppearances      boolean             (Optional) A flag specifying whether to construct appearance streams
                                         and appearance dictionaries for all widget annotations in the docu-
                                         ment (see “Variable Text” on page 677). Default value: false.

SigFlags             integer             (Optional; PDF 1.3) A set of flags specifying various document-level
                                         characteristics related to signature fields (see Table 8.68, below, and
                                         “Signature Fields” on page 695). Default value: 0.

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