Widget annotation kid of radio button field seems to be treated as field dictionary rather than annotation dictionary

[a20dev]

For the attached file, I get these unexpected errors from verapdf-arlington 1.29.78:

• FieldBtnRadio shall not contain entries except AA, DA, DV, FT, Ff, Kids, Opt, Parent, Q, T, TM, TU, V ( FieldBtnRadio contains entry(ies) F)
• Entry Ff with type Bitmask in Field shall satisfy special case: fn:Eval(fn:BitsClear(4, 32))
• Entry DA in FieldBtnRadio is required (Entry DA in FieldBtnRadio is missing)
• Field shall not contain entries except AA, Ff, Kids, Parent, T, TM, TU (Field contains entry(ies) F,V,FT)

Apparently, the entries of the Kids array of the field dictionary are interpreted as field dictionaries rather than annotation dictionaries. However, 12.7.5.2.4 of ISO 32000-2:2020 says:

The Kids entry in the radio button field’s field dictionary [...] holds an array of widget annotations representing the individual buttons in the set.

r3.pdf

[MaximPlusov]

@a20dev There are several different issues. I fixed one of them. The latest version verapdf-arlington 1.29.79 contains only 2 deviations:

• FieldBtnRadio shall not contain entries except AA, DA, DV, FT, Ff, Kids, Opt, Parent, Q, T, TM, TU, V ( FieldBtnRadio contains entry(ies) F)
• Entry DA in FieldBtnRadio is required (Entry DA in FieldBtnRadio is missing)

Both errors about object 11 0, which is the radio button field:

It seems that these errors are detected correctly according arlington pdf model: the field contains the extra entry F and the entry DA is missing.

[a20dev]

Thanks for the fix!

About the F entry: true. F belongs into the annotation dictionary. I don't know why Adobe Acrobat put it into the field dictionary.

About missing DA: DA is required for "all fields containing variable text". Ah, I remember: it's still open what a "field containing variable text" is, see pdf-association/pdf-issues#323. My private definition for now is that fields whose V entry is of type string contain variable text. The V entry of radio buttons is of type name. Also, for radio buttons, the appearance of a radio button is known in advance (it's one of the two streams in /AP/N), so "the field may contain text whose value is not known until viewing time" of 12.7.4.3 does not apply. I guess we'll have to wait for a resolution of that issue.