CHAPTER 8
686
Interactive Features
TABLE 8.75 Field flags specific to button fields
BIT POSITION
NAME
MEANING
15
NoToggleToOff
(Radio buttons only)
If set, exactly one radio button must be selected at all
times; clicking the currently selected button has no effect. If clear, clicking
the selected button deselects it, leaving no button selected.
If set, the field is a set of radio buttons; if clear, the field is a check box.
This flag is meaningful only if the Pushbutton flag is clear.
If set, the field is a pushbutton that does not retain a permanent value.
(PDF 1.5)
If set, a group of radio buttons within a radio button field that
use the same value for the on state will turn on and off in unison; that is if
one is checked, they are all checked. If clear, the buttons are mutually ex-
clusive (the same behavior as HTML radio buttons).
16
17
26
Radio
Pushbutton
RadiosInUnison
Pushbuttons
The simplest type of field is a
pushbutton field,
which has a field type of
Btn
and
the Pushbutton flag (see Table 8.75) set. Because this type of button retains no
permanent value, it does not use the
V
and
DV
entries in the field dictionary (see
Check Boxes
A
check box field
represents one or more check boxes that toggle between two
states, on and off, when manipulated by the user with the mouse or keyboard. Its
field type is
Btn
and its Pushbutton and Radio flags (see Table 8.75) are both clear.
Each state can have a separate appearance, which is defined by an appearance
stream in the appearance dictionary of the field’s widget annotation (see Section
present, must be stored in the appearance dictionary under the name
Off
. The
recommended (but not required) name for the on state is
Yes
.
The
V
entry in the field dictionary (see Table 8.69 on page 675) holds a name ob-
ject representing the check box’s appearance state, which is used to select the ap-
propriate appearance from the appearance dictionary.