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                                         689
SECTION 8.6                                                             Interactive Forms



most one button in the on state at any given time; selecting any of the buttons au-
tomatically deselects all the others.

Note: An exception occurs when multiple radio buttons in a field have the same on
state and the RadiosInUnison flag is set. In that case, turning on one of the buttons
turns on all of them.

The field type is Btn, the Pushbutton flag (see Table 8.75 on page 686) is clear, and
the Radio flag is set. This type of button field has an additional flag, NoToggle-
ToOff, which specifies, if set, that exactly one of the radio buttons must be select-
ed at all times. In this case, clicking the currently selected button has no effect; if
the NoToggleToOff flag is clear, clicking the selected button deselects it, leaving
no button selected.

The Kids entry in the radio button field’s field dictionary (see Table 8.69 on page
675) holds an array of widget annotations representing the individual buttons in
the set. The parent field’s V entry holds a name object corresponding to the ap-
pearance state of whichever child field is currently in the on state; the default val-
ue for this entry is Off. Example 8.17 shows the object definitions for a set of radio
buttons.

Example 8.17

   10 0 obj                                      % Radio button field
      << /FT /Btn
         /Ff …                                   % … Radio flag = 1, Pushbutton = 0 …
         /T ( Credit card )
         /V /MasterCard
         /Kids [ 11 0 R
                  12 0 R
                ]
      >>
   endobj

   11 0 obj                                      % First radio button
      << /Parent 10 0 R
         /AS /MasterCard
         /AP << /N << /MasterCard 8 0 R
                        /Off 9 0 R
                     >>
              >>
      >>
   endobj

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