[poppler] PDF with layers

[Pablo Rodríguez]

On 4/3/23 13:43, Valerio Messina wrote:
> HI,

Hi Valerio,

> I wanted to point out the lack of support for PDF layers in poppler.

Sorry, but I have just opened a PDF document from my computer with OCG
and evince-43.1 (+ poppler-22.08) opened it just fine.

Your statement is extremely broad and it might be false, since OCGs are
supported in poppler.

> It is a very important function for those who create PDFs for technical
> use.

Excuse me, but do you really think this is relevant for the fix?

> At the moment pdfunite/pdfseparate damage files by merging the
> layer contents on a single layer.

I totally agree with you, bugs suck. But merging or splitting files
isn’t modifying the sources (although the output contains glitches).

In the merge you provided at the GitLab report, OCGs aren‘t merged in a
single OCG.

What might be the case here is that OCGs from the second document are
simply being ignored.

Since you provided two documents with exactly the same OCG names, it is
impossible to see that OCGs from the second document are simply ignored
(not their content).

This explains the behavior you describe in your bug report.

> To date it seems that only open source app is Scribus that is able to
> produce PDF with layers through its internal library, while several
> programs rely on poppler and are not able to produce PDF with
> layers.

Again, this is too broad (Scribus being the only OSS to be able to
create OCGs) to be right (TeX is able to do it [even if it isn’t handy
for most people]).

Poppler is a intended to read PDF. I don‘t think is intended to write
PDF docs.

> thank you in advance,

Your bug report is five years old. poppler has too many users and very
few developers (not being one myself).

In your GitLab report, you mentioned you intended to implement “the
support for layers”.

If you allow me one more comment, please create two minimal files with
one OCG each and merge them and explains what happens in the issue at
GitLab.

It may take a while before a developer fixes the issue. poppler has too
many bugs for very few developers (again).

But if part of the issue you mention is guessing what is misbehaving in
poppler, this won’t help to speed up the potential fix.

Just in case it might help,

Pablo