Re: Missing items to make Cairo ready

[Han-Wen Nienhuys]

On Thu, Dec 29, 2022 at 1:53 AM Jean Abou Samra <jean@abou-samra.fr> wrote:
>
> Hi,
>
> I have just opened issues for the missing features of
> the Cairo backend that I am aware of.
>
> https://gitlab.com/lilypond/lilypond/-/issues/6500
> https://gitlab.com/lilypond/lilypond/-/issues/6501
> https://gitlab.com/lilypond/lilypond/-/issues/6502
> https://gitlab.com/lilypond/lilypond/-/issues/6503
> https://gitlab.com/lilypond/lilypond/-/issues/6504
>
> Are there any others?

I've read through the discussion you started here, but IMO we're too
fixated on backward compatibility, which is unfortunate because the PS
-> GS -> PDF route was never thought through carefully. We started
dumping PostScript because we were going through TeX before, and
creating PDF at the time involved .tex => .dvi => .ps  => .pdf (with
.eps included into .dvi for graphics).  However, at the time, PDF
rather than PS was already the common format for print documents. We
were also lazy, and didn't want to bother learning how to dump PDF
directly.

PNG images will always be clunky for embedding line art, so it can't
be the recommended solution. What makes most sense for users? Other
illustration programs also can't process EPS (for the same reasons we
don't), so how do those programs embed line art? What is the preferred
format for logos today? SVG? AI? PDF?

Given the sorry state of the SVG backend, and the niche quality of the
output-attributes feature, we could be justified to drop the SVG
backend rather than implementing attributes in Cairo-SVG (although it
sounds like a straightforward extension to Cairo).

Regarding versioning: the 1.x to 2.x transition was motivated by
radical syntax changes that necessitated converting and 'manually'
verifying the .ly files. Since Cairo vs. Ghostscript doesn't affect
the semantics of .ly files, I think we can continue the 2.x version
number. As a practical example, page layout was introduced in 2.4, and
direct to PostScript only became default in 2.6; both changes are much
more invasive than what we are discussing here.


> I ask this because we are at an early point in the
> 2.26 release cycle, which could potentially be ideal
> to get testing for "Cairo by default" if it were
> ready, but it isn't yet.
>
> Best,
> Jean
>


--
Han-Wen Nienhuys - hanwenn@gmail.com - http://www.xs4all.nl/~hanwen