[okular] [Bug 496369] New: Saving PDF form data multiples times, increases PDF size (possible leak / not removing previous form data)

[Andrew Rembrandt]

https://bugs.kde.org/show_bug.cgi?id=496369

            Bug ID: 496369
           Summary: Saving PDF form data multiples times, increases PDF
                    size (possible leak / not removing previous form data)
    Classification: Applications
           Product: okular
           Version: 24.08.3
          Platform: Arch Linux
                OS: Linux
            Status: REPORTED
          Severity: normal
          Priority: NOR
         Component: PDF backend
          Assignee: okular-devel at kde.org
          Reporter: public at rembrandt.dev
  Target Milestone: ---

Created attachment 175875
  --> https://bugs.kde.org/attachment.cgi?id=175875&action=edit
Blank form with no saves

SUMMARY
I have a PDF with 2 large text box forms (it's contains a large amount of form
text - addendum for a legal contract).
It increased in size from 400kB (including embedded form fonts) to 18MB after
approximately 20-30 edits of form data and 20-30 saves.
At first, I thought this might be a bug with embedded fonts being duplicated,
but after checking, there was only 5 or so fonts in the PDF, not >20. 

Unfortunately, I can't publicly share that PDF (happy to privately if you
wish).
However, I created a test PDF which I reproduced the problem after 50 saves of
form data in Okular.

STEPS TO REPRODUCE
1. Record PDF file size
2. Click Show Forms
3. Pasting a ‘large’ amount of text in the form, e.g. from:
https://www.lipsum.com/feed/html
4. Save
5. Record PDF file size (~44KB)
6. Make a minor modification (e.g. remove a character / add a new line or
space)
7. Save
8. Repeat the previous 2 steps 50 times
9. Record PDF file size (~730KB)


OBSERVED RESULT
File size increases each save, until it reaches 730KB after 50 times.

EXPECTED RESULT
File size remains approximately 44K, similar in size to the first save.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Arch linux kernel 6.11.8 x64, last full system update
2024-11-15
KDE Plasma Version: 6.2.3
KDE Frameworks Version: 6.8.0
Qt Version: 6.8.0
Poppler: 24.11.0-2

ADDITIONAL INFORMATION
Many thanks for the amazing project work all - the KDE Project is amazing.

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