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386
CHAPTER 4 Graphics
The remaining discussion in this section applies only to viewer applications. Such
applications should examine the AS array for usage application dictionaries that
have an Event of type View. For each one found, the groups listed in its OCGs ar-
ray should be adjusted as described in “Usage and Usage Application Dictionar-
ies” on page 380.
Subsequently, the document is ready for interactive viewing by a user. Whenever
there is a change to a factor that the usage application dictionaries with event type
View depend on (such as zoom level), the corresponding dictionaries should be
reapplied.
The user may manipulate optional content group states manually or by triggering
SetOCGState actions (see “Set-OCG-State Actions” on page 667) by, for example,
clicking links or bookmarks. Manual changes override the states that were set au-
tomatically. The states of these groups remain overridden and are not readjusted
based on usage application dictionaries with event type View as long as the docu-
ment is open (or until the user reverts the document to its original state).
When a document is printed by a viewer application, usage application dictionar-
ies with an event type Print are applied over the current states of optional content
groups. These changes persist only for the duration of the print operation; then
all groups revert to their prior states.
Similarly, when a document is exported to an earlier version of PDF or other for-
mat that does not support optional content, usage application dictionaries with
an event type Export are applied over the current states of optional content
groups. Changes persist only for the duration of the export operation; then all
groups revert to their prior states.
Note: Although the event types Print and Export have identically named counter-
parts that are usage categories, the corresponding usage application dictionaries are
permitted to specify that other categories may be applied.
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