Compatibility issues

[lammel-hub]

First of all: a fantastic job you are doing with this project - thank you!

Over time I have experienced different (small) glitches in importing and exporting files. In short some, added shapes from another tool have not been visible in pdf4qt, and sometimes the texts in pdf4qt do not show local characters in UTF8, but show correctly in other apps, e.g. okular.

My question is what level of compliance with ISO32000 is applied in pdf4qt development. Are you considering implementarions with strict compliance in mind, or best efforts?

[JakubMelka]

Hi @lammel-hub,

Thank you for the kind words — I really appreciate it!

Regarding ISO 32000 compliance: PDF4Qt targets best-effort compatibility with both PDF 1.7 (ISO 32000-1) and PDF 2.0 (ISO 32000-2), but it is not a strict-compliance implementation. Internally I maintain a conformance task list for PDF 2.0, and there are several documented gaps and partial implementations.

A few examples that are relevant to the issues you mentioned:

• Destinations / actions: some destination details are ignored (the viewer often jumps to a page but ignores position/fit hints).
• Fonts / text: some font types and behaviors are not fully supported yet (e.g., CID fonts, missing-width handling, text knockout). This can manifest as missing glyphs or incorrect display of some local characters.
• Color / graphics: some rendering features (overprint, halftones, separations) are not implemented or are approximated, which can affect appearance of certain imported shapes.

In other words, I aim for practical interoperability and render most documents correctly, but strict conformance to every requirement in ISO 32000 is not guaranteed.

If you can share a couple of small PDFs that demonstrate the missing shapes and UTF-8/local character issues, I can investigate whether they hit one of the known gaps or represent a bug that can be fixed.

Thanks again for the feedback and for using PDF4Qt!

Best regards,
Jakub

[lammel-hub]

@JakubMelka apologies for late reply. I had to dig through archives to find the file with the compatibility issues. It has been tested with Okular and other viewers (e.g. in-browser firefox and LibreOffice Draw) - and all of those render the text correctly.

When opening the file in PDF4QT vCiever or Editor I get the fie with ~ instead of the correct Ä and Å. in the bold headline. However: the other fonts that are less bold show the correct characters. The bottom line (also in bold with a URL is also with correct text).

Perhaps this can help you in identifying what could be the issue. PDF4QT is really great, this is the only glitch I have found in my use.

[JakubMelka]

Do you have font Sinkin Sans installed on your system?

[JakubMelka]

@lammel-hub, I have fixed it. In the next release, it will work.

[lammel-hub]

I do not have that font installed.

This is great news, thank you! 🙏🏻