Add support for loading user-defined CSS stylesheet

[agoose77]

Users often want to define custom styling (CSS, SCSS, or SASS) for their site. This allows them to do lightweight theming without needing to create an entirely new theme. It also allows authors to make page-specific styling for certain UI components etc.

Proposal

We should allow users to:

• Define custom CSS for their MyST sites.
• Allow users to write this as SCSS or SASS, including the use of variables.
• Ideally, allow for this either on a per-page basis (e.g. page metadata), or a project wide basis (e.g. myst.yml)

Inspiration

1. Point to an (S)CSS file from myst.yml. here's how sphinx does this
2. Add CSS directly to a page via HTML in the markdown (e.g. <style> tags)
3. Add CSS via frontmatter on the page or in myst.yml (e.g. a key like site.style: <scss rules to add to the page or the website>)

Related

• Support custom CSS classes for blocks of content mystmd#857 would allow users to add classes that could be styled with this CSS
• Expose raw html / allowDangerousHtml to the MyST CLI mystmd#1040 would allow people to add style directly to a page
• Hugo transpiling SCSS docs)
• Quarto support for SASS variables.

Tasks and updates

• Automatically include e.g. myst-theme.scss

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[choldgraf]

I added a few ideas for how this could look from a user's perspective to the top comment

[AlexEMG]

That would be a great feature!

[cboettig]

Looking forward to this! In addition to CSS, it might be nice to be able to support SASS / SCSS transpiling into CSS. SASS supports things like variable definitions and many users may find it easier to write SASS than raw CSS (or modify any of the many scss themes). Other popular static site generators, like Hugo, have supported SCSS transpile on the fly for a while now (https://gohugo.io/hugo-pipes/transpile-sass-to-css/), and quarto supports SASS variables as well https://quarto.org/docs/output-formats/html-themes.html#sass-variables.

[choldgraf]

thanks for this @cboettig - I've included your links into the top comment of the issue and cleaned it up a bit

[sbooeshaghi]

Hi, I'd like to voice my support for adding the ability to reference raw HTML files in the myst.yml file. This would be valuable for my use case:

I maintain a tool documentation site (https://pachterlab.github.io/seqspec/) and have custom HTML content on a separate site (https://www.sina.bio/seqspec-builder/regions.html). I'd like to embed this custom content at a specific path on the main site (e.g., https://pachterlab.github.io/seqspec/regions.html).

The custom HTML contains an auto-generated table from a database, describing file format features documented on the main site. Colocalizing the docs and examples via MyST would improve user experience.

Ideally, I'd like to reference HTML files in the myst.yml file like this:

  toc:
    # Auto-generated by `myst init --write-toc`
    - file: README.md
    - file: docs/INSTALLATION.md
    - file: docs/UNIFORM.md
    - title: Examples # <-- requested additional feature
      children:
      - file: docs/regions.html
      - file: docs/reads.html
      - file: docs/assays.html
    - title: Documentation
      children:
      - file: docs/SEQSPEC_FILE.md
      - file: docs/SEQSPEC_TOOL.md
      - file: docs/SPECIFICATION.md
    - title: Tutorials
      children:
      - file: docs/TUTORIAL_SIMPLE.md
      - file: docs/TUTORIAL_COMPLEX.md
      - file: docs/USING_SEQSPEC.ipynb
      - file: docs/SEQ_PRIMER.md
    - file: docs/CONTRIBUTING.md
    - file: docs/CHANGELOG.md

This feature would significantly enhance my workflow and improve documentation integration.

[rowanc1]

This is super cool work @sbooeshaghi, thanks for sharing!