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                                                   669
      SECTION 8.5                                                                            Actions




                     TABLE 8.64 Additional entries specific to a rendition action
KEY    TYPE           VALUE

S      name           (Required) The type of action that this dictionary describes; must be Rendition for a
                      rendition action.

R      dictionary     (Required when OP is present with a value of 0 or 4; otherwise optional) A rendition ob-
                      ject (see Section 9.1.2, “Renditions”).

AN     dictionary     (Required if OP is present with a value of 0, 1, 2, 3 or 4; otherwise optional) An indirect
                      reference to a screen annotation (see “Screen Annotations” on page 639).

OP     integer        (Required if JS is not present; otherwise optional) The operation to perform when the
                      action is triggered. Valid values are:
                         0    If no rendition is associated with the annotation specified by AN, play the ren-
                              dition specified by R, associating it with the annotation. If a rendition is al-
                              ready associated with the annotation, it is stopped, and the new rendition is
                              associated with the annotation.
                         1    Stop any rendition being played in association with the annotation specified
                              by AN, and remove the association. If no rendition is being played, there is no
                              effect.
                         2    Pause any rendition being played in association with the annotation specified
                              by AN. If no rendition is being played, there is no effect.
                         3    Resume any rendition being played in association with the annotation speci-
                              fied by AN. If no rendition is being played or the rendition is not paused, there
                              is no effect.
                         4    Play the rendition specified by R, associating it with the annotation specified
                              by AN. If a rendition is already associated with the annotation, resume the
                              rendition if it is paused; otherwise, do nothing.

JS     text string    (Required if OP is not present; otherwise optional) A text string or stream containing a
       or stream      JavaScript script to be executed when the action is triggered.

      Either the JS entry or the OP entry must be present. If both are present, OP is con-
      sidered a fallback to be executed if the viewer application is unable to execute
      JavaScripts. If OP has an unrecognized value and there is no JS entry, the action is
      invalid.

      In some situations, a pause (OP value of 2) or resume (OP value of 3) operation may
      not make sense (for example, for a JPEG image) or the player may not support it. In
      such cases, the user should be notified of the failure to perform the operation.

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