Use DejaVu fonts in PDF builds

[mortenpi]

DejaVu Sans Mono seems to be available out of the box on Linux (at least on Ubuntu), so no need to worry about installing it on the Docker image etc. It provides good Unicode coverage in my experience -- this is the fallback font on Ubuntu and I have not noticed any missing symbols. From a font quality perspective, I don't actually see much difference between it and Roboto Mono.

Fix #803. Once downstreamed will fix JuliaLang/julia#31048.

[mortenpi]

I also changed the sans-serif font to DejaVu Sans, since Lato is missing a lot of the necessary Unicode characters too. I would say that it looks good enough and my current feeling is that decent Unicode coverage is more important than having the most beautiful font.

Here is an example of the main manual compiled with the DejaVu fonts: TheJuliaLanguage.pdf

Just a note for future: Tex, unfortunately, does not seem to support fallback fonts (i.e. that if a particular character is missing, it would render it from a different font). The closest you have is ucharclasses for XeTeX, but it has two issues: (1) we are using LuaTex and it's XeTeX-only, and (2) it only allows setting different fonts for classes of characters but does not provide fallbacks for individual characters.

[mortenpi]

DejaVu Sans Mono does not render the ⊻ symbol, so I actually created our homebrew fallback system for this case. Instances of that character get replaced by the \unicodeveebar command in the TeX source, which then renders it DejaVu Sans instead.

In principle, this is pretty easily extensible to other missing Unicode characters as well, should they come up.

Here is an example build which shows off all the Unicode characters reported in #803: Unicodetest.pdf

@fredrikekre Any thoughts about this hack?

[Ronneesley]

Hello @mortenpi,

I noticed that in PDF manual version 1.2, some characters aren't appearing, like:

Function composition and piping

The symbol: ∘

(sqrt ∘ +)(3, 6)

Repeated Evaluation: Loops

The symbol: ∈

for s ∈ ["foo","bar","baz"]
     println(s)
end

Is it resolved? Why new manual's version doesn't include the solution? Thanks.

[mortenpi]

The 1.2.0 manual was still built with an older Documenter, so it did not have these fixes. With the latest Documenter, they render fine:

We could potentially backport JuliaLang/julia#32376 to 1.2.1. Otherwise, 1.3.0 will definitely have this fixed.