[cairo] New PDF features

[Guillaume Ayoub]

Hello,

I would like to thank you for the new features added in 1.15.x
versions, especially the ones related to PDF generation. I really like
the new API and find it very useful.

I've implemented most of (all?) these features in CairoCFFI [1], a
Python binding of Cairo, and things seem to work very well.

After trying to use these features in WeasyPrint [2], I have two
questions:

- I've tried to add internal hyperlinks using the "rect=[x x x x]
page=x pos=[x x]" syntax. It works when the target is on a previous
page or on the same page as the link, but it's broken when the target
is on a page that has not been created yet. Is it a known limitation, a
bug, or did I miss something about the way the feature works?

- All PDF metadata can now be changed except from "/Producer" that is
fixed to "cairo xxx (http://cairographics.org)". Would it be possible
to make this string editable, or at least let users add something
before/after this string? I can even provide a patch if needed :).

Thanks a lot,

[1] https://cairocffi.readthedocs.io/
[2] https://weasyprint.org/

[Guillaume Ayoub]

Le sam. 4 août 2018 à 22:21, Guillaume Ayoub

Post by Guillaume Ayoub
Hello,
[
]
- I've tried to add internal hyperlinks using the "rect=[x x x x]
page=x pos=[x x]" syntax. It works when the target is on a previous
page or on the same page as the link, but it's broken when the target
is on a page that has not been created yet. Is it a known limitation,
a bug, or did I miss something about the way the feature works?

After reading the source, it's a bug (or a big undocumented
limitation). I think that it should be fixed before 1.16.0.

Links are added to the PDF while the document is being created. When a
link's target is on a page that's not been added yet, an explicit check
on the page number discards the link creation (in
cairo_pdf_interchange_write_explicit_dest).

A solution would be to add links at the end of the document creation,
just as it's done for other objects in
_cairo_pdf_interchange_write_document_objects.

I can try to provide a patch, but it would probably be better from
people knowing cairo (and C :p).

Post by Guillaume Ayoub
- All PDF metadata can now be changed except from "/Producer" that is
fixed to "cairo xxx (http://cairographics.org)". Would it be possible
to make this string editable, or at least let users add something
before/after this string? I can even provide a patch if needed :).

I've sent a patch, comments welcome!