CairoMakie: Allow restricting PDF version

[barucden]

Description

This PR allows users to restrict the version of an output PDF like this:

fig = Figure()
ax = Axis(fig[1, 1])
x = range(0, 10, length=100)
y = sin.(x)
save("version_1-4.pdf", fig, pdf_version="1.4")
save("version_1-7.pdf", fig, pdf_version="1.7")

shell> file version_1-4.pdf
version_1-4.pdf: PDF document, version 1.4, 1 page(s)

shell> file version_1-7.pdf
version_1-7.pdf: PDF document, version 1.7

This feature was discussed on Discourse (and also earlier)

Type of change

• New feature (non-breaking change which adds functionality)

Checklist

• Added an entry in CHANGELOG.md (for new features and breaking changes)
• Added or changed relevant sections in the documentation
• Added unit tests for new algorithms, conversion methods, etc.

I need guidance regarding documentation (where to best put this) and testing (I am not sure how to check a PDF's version in Julia).

Also I was thinking that the CAIRO_PDF_VERSION_* constants together with restrict_pdf_version! should perhaps go to Cairo.jl. What do you think?

[barucden]

I have added an entry to changelog and documented the new config option.

[asinghvi17]

Looks good to me!

[barucden]

Rebased to resolve new conflicts

[barucden]

The error is not related imho:

GLMakie/Normals of a Cat.png: Test Failed at /home/runner/work/Makie.jl/Makie.jl/ReferenceTests/src/runtests.jl:117
  Expression: score <= threshold
   Evaluated: 0.5715945363044739 <= 0.05

[barucden]

CI's green ✅ Thank you, Simon.

[barucden]

Rebased to fix conflicts.

[jkrumbiegel]

would be simpler to type the v with the enum here, then you don't need yet another check. I'd guess you don't even have to manually convert it to Int32 in the ccall

[barucden]

I would like to move restrict_pdf_version! to Cairo.jl eventually, where they stick to numerical constants instead of enums, so I'd prefer to keep the argument as Integer.

You are right that the manual conversion in the ccall is not needed. I removed it.