PDF not generated when using render_js=True

[sebascert]

I'm attempting to generate a PDF of cp-algorithms, this is my fork.
When I don't use the render_js option every math expression is printed literally "$math$", but when I attempt to use it it outputs a pdf with a single page and the text in the image.

This is the output of mkdocs build:

(cmd)╰$ mkdocs build
INFO    -  git-committers plugin DISABLED
INFO    -  [macros] - No default module `main` found
INFO    -  git-committers: loading authors cache file
INFO    -  git-committers: saving authors cache file
INFO    -  [macros] - Config variables: ['extra', 'config',
           'environment', 'plugin', 'git', 'analytics', 'macros', 'filters',
           'filters_builtin']
INFO    -  [macros] - Config macros: ['context', 'macros_info', 'now',
           'fix_url']
INFO    -  [macros] - Config filters: ['pretty', 'relative_url']
INFO    -  Cleaning site directory
INFO    -  Building documentation to directory:
           /home/yoaquin/projects/cp-algorithms/public
INFO    -  Doc file 'algebra/discrete-log.md' contains a link
           'phi-function.md#toc-tgt-2', but the doc 'algebra/phi-function.md'
           does not contain an anchor '#toc-tgt-2'.
INFO    -  Number headings up to level 3.
INFO    -  Generate a table of contents up to heading level 2.
INFO    -  Generate a cover page with "default_cover.html.j2".
INFO    -  Converting <img> alignment(workaround).
INFO    -  Rendering on `Headless Chrome`(execute JS).
INFO    -  Rendering for PDF.
INFO    -  Output a PDF to
           "/home/yoaquin/projects/cp-algorithms/public/pdf/document.pdf".
INFO    -  Converting 166 articles to PDF took 45.2s
INFO    -  Documentation built in 65.08 seconds

I tested opening the PDF with multiple PDF viewers and all show the same, and I tested my headless chrome as in this guide, and it works fine, the output also shows.

[sebascert]

It seems to me that the output pdf it's simply the output from chrome when its attempting to read a file it can't find, I've also tried to see some logs with:

plugins:
  - to-pdf:
      verbose: true
      debug_html: true

but there seems to be no error, Is there any other way I could look for logs or errors?

[domWalters]

Out of interest, what is your OS?

[sebascert]

What do you mean out of interest? and I'm in Ubuntu 24.04.2, any more details I could provide?

[domWalters]

I had a previous issue which sounds similar to this where my PDF was just a Web error message. It was related to restrictions with Web browsers installed using snap not getting write access to the tmp directory.

With debug_html on you should get a terminal dump of the HTML that gets turned into the PDF.

Can you provide that HTML?

[sebascert]

mkdocs config

---
plugins:
  - to-pdf:
      enabled: !ENV [MKDOCS_ENABLE_TO_PDF, False]
      render_js: true
      headless_chrome_path: chromium-browser
      debug_html: true

Command for debug.html:

export MKDOCS_ENABLE_TO_PDF=True && mkdocs build > debug.html

The debug.html

debug_html.json

I uploaded it as a json as gh wouldn't allow me to submit an html file.

[sebascert]

I just tested and indeed my browser is installed via snap:

$ snap list | grep 'chromium'
chromium    138.0.7204.100  3199    latest/stable   canonical** -

I tried to dump the html of /tmp/test.pdf and I got an html page with the
same browser error, and this logged error:

$ chromium-browser --headless --disable-gpu --dump-dom file:///tmp/test.pdf > test.html
Fontconfig error: Cannot load default config file

But I think is not because it cannot read from /tmp, because when I open said
pdf in chrome it loads without issues, it may be due to the font config it's
missing.

[sebascert]

In the end I just used google-chrome installation with .deb instead of snap,
and it worked fine. Thank you for pointing me to the issue, are you interested
in documenting this error?

[domWalters]

Nice to hear that you got it working with a workaround.

Lets leave this open.

I can see the problem; there's a tempfile used in the headless chrome code:

https://github.com/domWalters/mkdocs-to-pdf/blob/develop/src/mkdocs_to_pdf/drivers/headless_chrome.py#L24

I fixed this on another branch when I hit this problem ages ago, but the feature I was using on that branch has not been merged.

---

Tasks for Me

• Change tempfile to generate in the site directory
• Actually detect that this error has happened and crash the build step with a decent error message

[sebascert]

Thank you for your help

[matusdrobuliak66]

Workaround solved for me ✔️

Thanks @sebascert @domWalters for you help, I had the same issue, this solve it for me:

sudo snap remove --purge chromium

wget https://dl.google.com/linux/direct/google-chrome-stable_current_amd64.deb
sudo apt install ./google-chrome-stable_current_amd64.deb

Testing with google-chrome-stable --headless --disable-gpu --dump-dom https://google.com works ✔️

Now I have just adjusted the mkdocs.yaml file

plugins:
  - to-pdf:
      render_js: true
      headless_chrome_path: google-chrome-stable