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                                                       787
            SECTION 9.4                                                       Alternate Presentations



            ble 3.28) contains a name tree that maps name strings to the alternate presenta-
            tions available for the document.

            Note: Since PDF viewers are not required to support alternate presentations, au-
            thors of documents containing alternate presentations should define the files such
            that something useful and meaningful can be displayed and printed. For example, if
            the document contains an alternate presentation slideshow of a sequence of photo-
            graphs, the photographs should be viewable in a static form by viewers that are not
            capable of playing the slideshow.

            As of PDF 1.5, the only type of alternate presentation is a slideshow. Slideshows
            are typically invoked by means of JavaScript actions (see “JavaScript Actions” on
            page 709”) initiated by user action on an interactive form element (see Section
            8.6, “Interactive Forms”). Implementation note 155 in Appendix H describes Ac-
            robat’s implementation of slideshows.

            The following table shows the entries in a slideshow dictionary.

                                 TABLE 9.32 Entries in a slideshow dictionary
KEY              TYPE         VALUE

Type             name         (Required; PDF 1.4) The type of PDF object that this dictionary describes; must be
                              SlideShow for a slideshow dictionary.

Subtype          name         (Required; PDF 1.4) The subtype of the PDF object that this dictionary describes;
                              must be Embedded for a slideshow dictionary.

Resources        name tree    (Required; PDF 1.4) A name tree that maps name strings to objects referenced by
                              the alternate presentation.
                              Note: Even though PDF treats the strings in the name tree as strings without a speci-
                              fied encoding, the slideshow interprets them as UTF-8 encoded Unicode.

StartResource    byte string (Required; PDF 1.4) A byte string that must match one of the strings in the Re-
                             sources entry. It defines the root object for the slideshow presentation.


            The Resources name tree represents a virtual file system to the slideshow. It asso-
            ciates strings (“file names”) with PDF objects that represent resources used by the
            slideshow. For example, a root stream might reference a file name, which would
            be looked up in the Resources name tree, and the corresponding object would be
            loaded as the file. (This virtual file system is flat; that is, there is no way to refer-
            ence subfolders.)

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