Re: Missing items to make Cairo ready

[Jean Abou Samra]

Le 29/12/2022 à 11:53, Jonas Hahnfeld a écrit :
> On Thu, 2022-12-29 at 01:53 +0100, Jean Abou Samra 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?
> In my understanding (please correct me if I get this wrong), the
> elephant in the room is that we _cannot_ support a number of features /
> markup commands in Cairo, or at least a significant subset of how some
> of them are used today: \epsfile and \postscript will only work with
> Cairo if you produce a Postscript file, but not in the "default" modes
> of outputting PDFs and PNGs.


Yes. To my knowledge, they are the only ones, though.

Here is an idea. We already have a working EPS → PNG
conversion through GS. With
https://gitlab.com/lilypond/lilypond/-/merge_requests/1787
Cairo supports PNG images. So, to support \epsfile
and \postscript, we can convert and embed as PNG.
Of course, this means we cannot drop Ghostscript,
but we're not going to do it anytime soon anyway.
The Cairo backend needs to be the default for some time
before the old PS backend is dropped.

It means we can separate the moment we switch to Cairo
by default while keeping GS and the old backend, and
the moment where we drop those. The *second* one is the
moment where users will really need to have converted
their EPS images to PNG.

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