[luatex] Bug: When nesting Form XObject reference in <box>, \pdfxform resources {<resources>} <box> -> missing user-provided <resources>

[Alexander Grahn]

On Mon, Mar 19, 2018 at 01:17:11PM +0100, Hans Hagen wrote:
>On 3/19/2018 12:58 PM, Alexander Grahn wrote:
>> On 3/19/2018 11:52 AM, Hans Hagen wrote:
>>> On 3/19/2018 11:20 AM, Alexander Grahn wrote:
>>>> Dear all,
>>>>
>>>> it seems that I discovered a bug in connection with nested Form XObjects
>>>> (pdftex built-in \pdfxform) that occurs in pdfTeX as well as in LuaTeX.
>>>>
>>>> The \pdfxform built-in provides the optional `resources {<resources>}'
>>>> argument, as in
>>>>
>>>>     \pdfxform resources {<resources>} <box>
>>>>
>>>> , in order to allow the user to insert additional entries in the /Resources
>>>> dictionary of the Form XObject to be produced from box register <box>.
>>>>
>>>> This works as advertised for ordinary box content (1st \pdfxform in the code
>>>> below), but as soon as another Form XObject is referenced inside <box>, the
>>>> `resources {...}' argument is ignored and user-provided <resources> are missing
>>>> in the generated PDF code (2nd \pdfxform).
>>>>
>>>> Here is a minimal example for pdfTeX and LuaTeX for demonstration. The PDF
>>>> object numbers mentioned in the comments are different in the PDF output from
>>>> LuaTeX.
>>>>
>>>> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
>>>> % Bug: When nesting Form XObject reference in <box>,
>>>> %      \pdfxform resources {<resources>} <box>
>>>> %      --> missing user-provided <resources>
>>>>
>>>> \input luatex85.sty
>>>>
>>>> \pdfcompresslevel=0
>>>> \pdfobjcompresslevel=0
>>>>
>>>> \setbox0=\hbox{World}
>>>> \edef\wrldwd{\the\wd0}
>>>>
>>>> \pdfxform
>>>> attr {}
>>>> resources {/Properties <</Key1 (Val1)>>} % OK
>>>> 0
>>>>
>>>> %nesting Form XObject reference
>>>> \setbox0=\hbox{Hello \hbox to \wrldwd {\pdfrefxform\pdflastxform\hss}!}
>>>>
>>>> \pdfxform
>>>> attr {}
>>>> % /Properties <<...>> missing in /Resources dict (object `8 0'), ref'ed in
>>>> resources {/Properties <</Key2 (Val2)>>}%       Form XObject (object `2 0')
>>>> 0
>>>>
>>>> \pdfrefxform\pdflastxform
>>>>
>>>> \bye
>>>> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
>>>
>>> there is no nesting stack kept there ...
>>>
>>> \immediate\pdfxform ...
>>>
>>> works ok
>>>
>>> Hans
>> 
>> That is strange, as for `attr {...}' such a stack apparently exists.
>> `resources {...}' should behave in the same way.
>
>resources are more complex as they also need to merge with others ... 
>it's something we will ook into but don't expect changes too soon as 
>we're in texlive code freeze mode

Thank you, Hans, a lot for taking this into consideration!

Kind regards,
Alexander