Challenges with Quarto and Julia unicode π

[GregVernon]

Description

I've been struggling the past several days getting my Quarto document to quarto render to PDF -- it works fine to quarto preview. The issue seems to boil down to my use of the character π in some Julia code blocks -- I really want these to render as π (e.g., 2π, 3π/2 ) rather than pi (e.g., 2*pi, 3*pi/2). The specific code-block looks like this:

```{julia}
#| output: false
f = sin( x )
g = sin( x )
L2 = integrate( f * g, ( x, 0 // 1, 2π ); symbolic = true, detailed = false )

And my _quarto.yml contains the following for the PDF spec:

pdf:
    pdf-engine: xelatex
    latex-auto-install: true
    latex-clean: true
    latex-tinytex: false
    keep-tex: true
    documentclass: scrreprt
    include-in-header:
      text: |
        \usepackage{amsmath}
        \usepackage{amssymb}
        \usepackage{mathpazo}
        \usepackage{mathtools}
        \usepackage{bm}
        \usepackage{breqn}
        \newcommand{\Real}{\mathbb{R}}
        \newcommand{\Inner}[2]{\left\langle #1, #2 \right\rangle}
        \newcommand{\Vector}[1]{\mathbf{\mathit{#1}}}
        \newcommand{\Matrix}[1]{\boldsymbol{\mathrm{#1}}}
        \newcommand{\ChangeBasisOp}[2]{\Matrix{R}_{\tiny{\Matrix{#1} \rightarrow \Matrix{#2}}}}

Note that I've got my own installation of TexLive 2024 -- though I've also tried using the "Quarto-recommended" TinyTex installation. I've installed TexLive (as well as MikTex) to try to have more control over the distro.

If I try to use the above approach I get an error:

Rendering PDF
running xelatex - 1
  This is XeTeX, Version 3.141592653-2.6-0.999996 (TeX Live 2024) (preloaded format=xelatex)
   restricted \write18 enabled.
  entering extended mode

updating tlmgr

updating existing packages
ERROR: 
compilation failed- error
Undefined control sequence.
<recently read> \

l.228

Which appears to be because inline math using $\math \stuff \here$ delimiters gets translated to \( \math \stuff \here \)

What I wrote in the .qmd file

As a simple example of this, let us imagine that we have some function, $f(x)$, that we wish to integrate over the domain $[2, 7]$.

Quarto-generated index.tex:

As a simple example of this, let us imagine that we have some function, \(f(x)\), that we wish to integrate over the domain \([2, 7]\).

Which is incompatible with the Quarto-generated preamble that uses unicode-math:

\ifPDFTeX
  \usepackage[T1]{fontenc}
  \usepackage[utf8]{inputenc}
  \usepackage{textcomp} % provide euro and other symbols
\else % if luatex or xetex
  \usepackage{unicode-math}  % THIS
  \defaultfontfeatures{Scale=MatchLowercase}  % THIS
  \defaultfontfeatures[\rmfamily]{Ligatures=TeX,Scale=1}  % THIS
\fi

Specifically, if I comment out the % THIS lines, then the document compiles - but leaves empty spaces in place of π.

Also note that if I replace all instances of π with pi (incl. necessary operators such as *), and use the pdflatex engine then everything works as expected:

Rendering PDF
running pdflatex - 1
  This is pdfTeX, Version 3.141592653-2.6-1.40.26 (TeX Live 2024) (preloaded format=pdflatex)
   restricted \write18 enabled.
  entering extended mode

running pdflatex - 2
  This is pdfTeX, Version 3.141592653-2.6-1.40.26 (TeX Live 2024) (preloaded format=pdflatex)
   restricted \write18 enabled.
  entering extended mode

running pdflatex - 3
  This is pdfTeX, Version 3.141592653-2.6-1.40.26 (TeX Live 2024) (preloaded format=pdflatex)
   restricted \write18 enabled.
  entering extended mode
  
Output created: _book\index.html

But, of course, if I use the π characters, then pdflatex fails due to:

ERROR: 
compilation failed- error
LaTeX Error: Unicode character π (U+03C0) not set up for use with LaTeX.

Any thoughts?

[mcanouil]

You need to use/set a font that allows such characters.
If the font does not support Unicode then you have an error.

[GregVernon]

I've tried that, via:

pdf:
    mainfont: "Times New Roman"
    monofont: "JuliaMono"
    # other options

Which gives me errors like Cannot find JuliaMono.mf:

running xelatex - 1
  This is XeTeX, Version 3.141592653-2.6-0.999996 (TeX Live 2024) (preloaded format=xelatex)
   restricted \write18 enabled.
  entering extended mode

  kpathsea: Running mktextfm JuliaMono

  The command name is C:\texlive\2024\bin\windows\mktextfm
  name = JuliaMono, rootname = JuliaMono, pointsize =
  mktexmf: empty or non-existent rootfile!

  kpathsea: Running mktexmf JuliaMono.mf

  The command name is C:\texlive\2024\bin\windows\mktexmf
  Cannot find JuliaMono.mf.
  kpathsea: Appending font creation commands to missfont.log.

updating tlmgr

updating existing packages
finding package for JuliaMono
finding package for mktextfm
> 1 package to install
> installing texlive-scripts (1 of 1)
  This is XeTeX, Version 3.141592653-2.6-0.999996 (TeX Live 2024) (preloaded format=xelatex)
   restricted \write18 enabled.
  entering extended mode

  kpathsea: Running mktextfm JuliaMono

  The command name is C:\texlive\2024\bin\windows\mktextfm
  name = JuliaMono, rootname = JuliaMono, pointsize =
  mktexmf: empty or non-existent rootfile!

  kpathsea: Running mktexmf JuliaMono.mf

  The command name is C:\texlive\2024\bin\windows\mktexmf
  Cannot find JuliaMono.mf.
  kpathsea: Appending font creation commands to missfont.log.

finding package for JuliaMono
finding package for mktextfm
ERROR: 
compilation failed- package installation error
Package fontspec Error:
(fontspec)                The font "JuliaMono" cannot be found; this may be
(fontspec)                but usually is not a fontspec bug. Either there is
(fontspec)                a typo in the font name/file, the font is not
(fontspec)                installed (correctly), or there is a bug in the
(fontspec)                underlying font loading engine (XeTeX/luaotfload).

For immediate help type H <return>.
 ...

l.27 \fi

Note that JuliaMono is installed on my system (Windows 11) (and obviously Times New Roman is installed):

If I grab a font with unicode support from fc-list > fonts.txt the issue remains that I still have to copy index.tex to Overleaf, as well as the index_files directory that contains rendered artifacts (plots etc.), so that I can comment-out those unicode-math commands from the auto-generated preamble.

[GregVernon]

As I've been digging in deeper -- the root-cause appears to be the use of the breqn package -- it's what's resulting in the use of \( in inline equations to trigger Undefined control sequence issues. Everything else is a red-herring.