Greek unicode letters not rendered in pdf output

[peteole]

Bug description

Using unicode letters and rendering to pdf results in the letters bein omitted (on manjaro linux, vscode). Setting

mainfont: Times New Roman

lets me render unicode in the main text flow, but not in code blocks. Also this option results in an error when run on my system because the font is not installed. This is not the best UX. This should just work without user interaction.
See this example:

---
title: "test"
jupyter: julia-1.8
---

```{julia}
α=3
```

α is a great constant.

---

The output is

Checklist

• Please include a minimal, fully reproducible example in a single .qmd file? Please provide the whole file rather than the snippet you believe is causing the issue.
• Please format your issue so it is easier for us to read the bug report.
• Please document the RStudio IDE version you're running (if applicable), by providing the value displayed in the "About RStudio" main menu dialog?
• Please document the operating system you're running. If on Linux, please provide the specific distribution.

[cscheid]

Thanks for the report. I don't know how we could proceed without user interaction when fonts is not installed. When latex packages are missing, we automatically install them. But in the case of missing fonts, there's no standard repository.

[cscheid]

In the meantime, I've found that the following front matter will make it so that Unicode symbols such as alpha, etc will generally work on PDF output:

format:
  pdf:
    monofont: "DejaVu Sans Mono"
    mainfont: "Times New Roman"

Naturally, you'll need to install DejaVu Sans Mono.

[peteole]

One part of the issue is handling missing fonts. Maybe it makes sense to just package the default font with quarto?
The other part of the issue is that by default greek letters are not displayed. Should we maybe change the default font or at least provide a more clear error/warning? And what can I do to display greek letters in code blocks?

[cscheid]

The default font is installed, but Computer Modern does not have unicode symbols. We could try to scan the document for code points that are missing, but coming up with a font that handles those correctly is a generally hard problem (especially since Unicode continues to add new code points over time). I think this is a limitation of LaTeX in general that we won't be able to solve with quarto.

I do agree that we should better document this Unicode limitation!

[capnrefsmmat]

Would it be worth bundling a font like STIX Two, which is built by technical publishers to include all the characters and symbols they might conceivably need?

It probably doesn't include a full set of emoji, for instance, but it includes Latin, Greek, and Cyrillic, plus diacritics and technical symbols.