CHAPTER 8
614
Interactive Features
TABLE 8.19 Entries in an appearance dictionary
KEY
TYPE
VALUE
N
R
stream or dictionary
stream or dictionary
stream or dictionary
(Required)
The annotation’s normal appearance.
(Optional)
The annotation’s rollover appearance. Default value: the value of
the
N
entry.
(Optional)
The annotation’s down appearance. Default value: the value of the
N
entry.
D
Each entry in the appearance dictionary may contain either a single appearance
stream or an
appearance subdictionary.
In the latter case, the subdictionary de-
fines multiple appearance streams corresponding to different
appearance states
of
the annotation.
For example, an annotation representing an interactive check box might have two
appearance states named
On
and
Off
. Its appearance dictionary might be defined
as
/AP << /N << /On
/Off
>>
/D << /On
/Off
>>
>>
formXObject
1
formXObject
2
formXObject
3
formXObject
4
where
formXObject
1
and
formXObject
2
define the check box’s normal appearance
in its checked and unchecked states, and
formXObject
3
and
formXObject
4
provide
visual feedback, such as emboldening its outline, when the user clicks it. (No
R
entry is defined because no special appearance is needed when the user moves
the cursor over the check box without pressing the mouse button.) The choice be-
tween the checked and unchecked appearance states is determined by the
AS
en-
try in the annotation dictionary (see Table 8.15 on page 606).
Note:
Some of the standard PDF annotation types, such as movie annotations—as
well as all custom annotation types defined by third parties—are implemented
through plug-in extensions. If the plug-in for a particular annotation type is not
available, PDF viewer applications should display the annotation with its normal
(
N
) appearance. Viewer applications should also attempt to provide reasonable be-