[Libreoffice-bugs] [Bug 126207] New: Export signature line as PDF signature field

[bugzilla-daemon at bugs.documentfoundation.org]

https://bugs.documentfoundation.org/show_bug.cgi?id=126207

            Bug ID: 126207
           Summary: Export signature line as PDF signature field
           Product: LibreOffice
           Version: unspecified
          Hardware: All
                OS: All
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: medium
         Component: Printing and PDF export
          Assignee: libreoffice-bugs at lists.freedesktop.org
          Reporter: gellert.gyuris at gmail.com

Description:
Signature line should be exported as visible PDF signature field when "Create
PDF form" option is enabled.

Steps to Reproduce:
1. Open attached "Signature line example (signed).odt". There is a filled
signature line.
2. Export it to PDF with "Create PDF form" option enabled and sign the PDF on
Export.
3. Exported signature line is just a drawing object, not a PDF signature field.

Actual Results:
As Miklós Vajna explained in 117109#c2 currently LibreOffice on PDF exporting
(or PDF signing) place signature widget on first page as 0×0 sized object.

Expected Results:
Signature line should be exported as PDF signature field:

1. Export as PDF > Create PDF form option disabled
Keep current behavior.
Example: "Signature line example (signed).pdf"

2. Export as PDF > Create PDF form option enabled and signature line is signed
(and on export Digital Signatures are filled)
- Replace the signature line with a real PDF signature field
- fill it with a PNG replacement of current appearance 
- and place it on the same place and same dimension.
Example: "Signature line example (signed) (with option Create PDF form).pdf"
Currently all form elements are exported as PDF annotations. This is the
expected result. But signature line is a simple draw object. It should be a PDF
annotation, or as Miklós write a PDF widget.

3. Export as PDF > Create PDF form option enabled and signature line is empty
(and PDF isn’t signed)
Replace the signature line with an empty PDF signature line. This can be filled
out in a PDF editor like Acrobat Reader.
This is a missed function. There is only 2 FOSS implementation in LaTeX: eform
(https://ctan.org/pkg/eforms) and digsig
(http://home.htp-tel.de/lottermose2/tex/dist/digsig.sty)
Examples:
- "Empty signature line example (empty).pdf" – This file is originally created
in LibreOffice and PDF signature field is added in Adobe Acrobat.
- "Empty signature line example (empty) (signed in Adobe Reader)" – Previous
example signed in Adobe Reader.
- "digsig.pdf" and "eform.pdf" – These files are created with LaTeX and contain
only one empty PDF signature field. See them with Adobe Reader. 

4. PDF signing:
Keep current behavior - there is no signature line.

And a closing comment. If the signature line is filled (document is signed) why
we need to add signature details again on PDF export? This should be
automatically _and unchangeable_ while the document is unmodified. I think in
the current behavior someone can sign the document and someone else can export
to PDF with another key... In this case the signed key and the displayed key is
different. Am I correct?


Reproducible: Always


User Profile Reset: No



Additional Info:
According to #119017 and #117109

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