[okular] [Bug 470128] New: Saving document with resized text creates huge memory footprint

[bugzilla_noreply at kde.org]

https://bugs.kde.org/show_bug.cgi?id=470128

            Bug ID: 470128
           Summary: Saving document with resized text creates huge memory
                    footprint
    Classification: Applications
           Product: okular
           Version: unspecified
          Platform: Other
                OS: Linux
            Status: REPORTED
          Severity: normal
          Priority: NOR
         Component: PDF backend
          Assignee: okular-devel at kde.org
          Reporter: dorla.hutch at gmail.com
  Target Milestone: ---

This issue haunts me for a longer time and I'd like to share it with you.

When I browse my PDF and I add an annotation to the slides or form, sometimes
the selected font size is too small or large. When I resize the text (same for
annotated text inside a box) and save it, it will not only take a long time but
the size of the PDF will get huge, more than 100MiB are added during saving!
Going from 2 MiB to 103MiB! This is like saving a high-resolution image for
every character in the alphabet. This memory waste is added to each affected
document.

This does not happen if the font size is not changed.

There are significant problems

- It cannot be undone!! Saving after removing the change that inflated the file
will not help. The only way to regain the previous size is to scrap the
document with all annotations and redownload the original one, creating new
annotations.
- file becomes too large for emails, uploading or submission with size
restrictions
- it wastes a lot of memory for no good reason
- it's the size of a large or long compressed video

If the issue cannot be fixed, there are some intermediate but weak solutions:

- export + import of annotations between documents (it should work at least for
equal documents)
- if the problem occurs, warn users and let them cancel the saving process
- allow changes made by saving to be undone completely

Version: Flathub, installed via Software Center on Ubuntu 20.04.3 LTS.

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