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                                                   649
         SECTION 8.5                                                                      Actions



         tion. In PDF 1.4, the document catalog dictionary (see Section 3.6.1, “Document
         Catalog”) may also contain an AA entry for trigger events affecting the document
         as a whole. Tables 8.44 to 8.47 show the contents of this type of dictionary. (See
         implementation notes 98 and 99 in Appendix H.)

         PDF 1.5 introduces four trigger events to support multimedia presentations:

         • The PO and PC entries have a similar function to the O and C entries in the page
             object’s additional-actions dictionary (see Table 8.45). However, associating
             these triggers with annotations allows annotation objects to be self-contained
             and greatly simplifies authoring. For example, annotations containing such ac-
             tions can be copied or moved between pages without requiring page open/close
             actions to be changed.
         • The PV and PI entries allow a distinction between pages that are open and pages
             that are visible. At any one time, only a single page is considered open in the
             viewer application, while more than one page may be visible, depending on the
             page layout.

         Note: For these trigger events, the values of the flags specified by the annotation’s F
         entry (see Section 8.4.2, “Annotation Flags”) have no bearing on whether a given
         trigger event occurs.

                    TABLE 8.44 Entries in an annotation’s additional-actions dictionary
KEY   TYPE             VALUE

E     dictionary       (Optional; PDF 1.2) An action to be performed when the cursor enters the annotation’s
                       active area.

X     dictionary       (Optional; PDF 1.2) An action to be performed when the cursor exits the annotation’s
                       active area.

D     dictionary       (Optional; PDF 1.2) An action to be performed when the mouse button is pressed
                       inside the annotation’s active area. (The name D stands for “down.”)

U     dictionary       (Optional; PDF 1.2) An action to be performed when the mouse button is released
                       inside the annotation’s active area. (The name U stands for “up.”)
                       Note: For backward compatibility, the A entry in an annotation dictionary, if present,
                       takes precedence over this entry (see Table 8.15 on page 606).

Fo    dictionary       (Optional; PDF 1.2; widget annotations only) An action to be performed when the
                       annotation receives the input focus.

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