Have emoji working in sphinx latexpdf xelatex generated content, titles and code

Question

How to have emojis in sphinx latexpdf xelatex generated for:

• content ? OK
• titles ? KO
• code ? KO

Below a sphinx to illustrate emoji in latexpdf:

$ sphinx-quickstart --no-batchfile --no-sep -p test_emoj -l en -a me -v 1.0 -q
$ cd test_emoj; tree
├── _build
├── conf.py
├── index.rst
├── Makefile
├── NotoColorEmoji.ttf
├── _static
└── _templates

add some content:

$ vim index.rst
$ cat index.rst 
=========
test_emoj
=========

Hello space 
==============

Space  and hammer .

.. code::

  ✔ app 8 layers [⣿⣿⣿]  Pulled
$

Set latex_engine and article xelatex:

echo "latex_engine ='xelatex'"  >> conf.py
echo "latex_theme='howto'"  >> conf.py

HTML emoji are ok

$ make html 
...
$ 

latexpdf with xelatex engine have no emoji:

$ make latexpdf 
...
$ evince _build/latex/test_emoj.pdf 

with setmainfont get get some emoji (B&W and only in content):

$ echo 'latex_elements = {"preamble": r"\setmainfont{Symbola}"}' >> conf.py
$ make latexpdf 
...
$ evince _build/latex/test_emoj.pdf 

The corresponding latex code expose that font for section does not know about emoji, neither font define for sphinxVerbatim::

$ vim _build/latex/test_emoj.tex
...
\section{Hello space }
\label{\detokenize{index:hello-space}}
\sphinxAtStartPar
Space , hammer  and ⣿

\begin{sphinxVerbatim}[commandchars=\\\{\}]
\(\pmb{\checkmark}\) app 8 layers [⣿⣿⣿]  Pulled
\end{sphinxVerbatim}
...

The latex log file expose that in code:: latex look for emoji in FreeMono.otf and in title latex look for emoji in FreeSansBold.otf:

$ grep '^Missi' _build/latex/test_emoj.log 
Missing character: There is no  (U+1F680) in font [FreeSansBold.otf]/OT:script
Missing character: There is no ⣿ (U+28FF) in font [FreeMono.otf]/OT:script=latn
Missing character: There is no ⣿ (U+28FF) in font [FreeMono.otf]/OT:script=latn
Missing character: There is no ⣿ (U+28FF) in font [FreeMono.otf]/OT:script=latn
$

To see which one of my fonts has the ⣿.

$ java -jar /usr/share/texlive/texmf-dist/scripts/albatross/albatross.jar --detailed ⣿

On my unbuntu 22.04 the below fonts have the ⣿ character:

/usr/share/fonts/truetype/ancient-scripts/Symbola_hint.ttf
/usr/share/fonts/truetype/dejavu/DejaVuSans-Bold.ttf
/usr/share/fonts/truetype/dejavu/DejaVuSans-BoldOblique.ttf
/usr/share/fonts/truetype/dejavu/DejaVuSans-Oblique.ttf
/usr/share/fonts/truetype/dejavu/DejaVuSans.ttf
/usr/share/fonts/truetype/dejavu/DejaVuSansCondensed-Bold.ttf
/usr/share/fonts/truetype/dejavu/DejaVuSansCondensed.ttf
/usr/share/fonts/truetype/dejavu/DejaVuSerif
/usr/share/fonts/truetype/noto/NotoSansSymbols2-Regular.ttf

Beyond the

"Have emoji working in sphinx latexpdf xelatex generated content, titles and code"

question, I wonder why:

• how \setmainfont can have both Symbola and FreeSerif values in tex file, I expect to have only one mainfont, idealy to define Symbola as a fall back font in case characters are not found in the FreeSerif "mainfont":

    $ grep setmainfont _build/latex/test_emoj.tex 
    \setmainfont{FreeSerif}[
    \setmainfont{Symbola}
    $
  

• is there a way to have color emoji ?

Note: Sphinx doc to configure latex, here so#497403 they talk about Noto Color Emoji but nothing on having emojis in title and code.