How do I strip out the boilerplate CSS from Quarto's ePub output?

[elsiehupp]

Description

Very simply, my issue is that Quarto puts the following at the top of every XHTML file in its ePub output, and I would like to be able to use an option in the project YAML to prevent it from appearing:

Details

  <style type="text/css">

  .callout {
    margin-top: 1em;
    margin-bottom: 1em;  
    border-radius: .25rem;
  }

  .callout.callout-style-simple { 
    padding: 0em 0.5em;
    border-left: solid #acacac .3rem;
    border-right: solid 1px silver;
    border-top: solid 1px silver;
    border-bottom: solid 1px silver;
    display: flex;
  }

  .callout.callout-style-default {
    border-left: solid #acacac .3rem;
    border-right: solid 1px silver;
    border-top: solid 1px silver;
    border-bottom: solid 1px silver;
  }

  .callout .callout-body-container {
    flex-grow: 1;
  }

  .callout.callout-style-simple .callout-body {
    font-size: 1rem;
    font-weight: 400;
  }

  .callout.callout-style-default .callout-body {
    font-size: 0.9rem;
    font-weight: 400;
  }

  .callout.callout-titled.callout-style-simple .callout-body {
    margin-top: 0.2em;
  }

  .callout:not(.callout-titled) .callout-body {
      display: flex;
  }

  .callout:not(.no-icon).callout-titled.callout-style-simple .callout-content {
    padding-left: 1.6em;
  }

  .callout.callout-titled .callout-header {
    padding-top: 0.2em;
    margin-bottom: -0.2em;
  }

  .callout.callout-titled .callout-title  p {
    margin-top: 0.5em;
    margin-bottom: 0.5em;
  }
    
  .callout.callout-titled.callout-style-simple .callout-content  p {
    margin-top: 0;
  }

  .callout.callout-titled.callout-style-default .callout-content  p {
    margin-top: 0.7em;
  }

  .callout.callout-style-simple div.callout-title {
    border-bottom: none;
    font-size: .9rem;
    font-weight: 600;
    opacity: 75%;
  }

  .callout.callout-style-default  div.callout-title {
    border-bottom: none;
    font-weight: 600;
    opacity: 85%;
    font-size: 0.9rem;
    padding-left: 0.5em;
    padding-right: 0.5em;
  }

  .callout.callout-style-default div.callout-content {
    padding-left: 0.5em;
    padding-right: 0.5em;
  }

  .callout.callout-style-simple .callout-icon::before {
    height: 1rem;
    width: 1rem;
    display: inline-block;
    content: "";
    background-repeat: no-repeat;
    background-size: 1rem 1rem;
  }

  .callout.callout-style-default .callout-icon::before {
    height: 0.9rem;
    width: 0.9rem;
    display: inline-block;
    content: "";
    background-repeat: no-repeat;
    background-size: 0.9rem 0.9rem;
  }

  .callout-title {
    display: flex
  }
    
  .callout-icon::before {
    margin-top: 1rem;
    padding-right: .5rem;
  }

  .callout.no-icon::before {
    display: none !important;
  }

  .callout.callout-titled .callout-body > .callout-content > :last-child {
    padding-bottom: 0.5rem;
    margin-bottom: 0;
  }

  .callout.callout-titled .callout-icon::before {
    margin-top: .5rem;
    padding-right: .5rem;
  }

  .callout:not(.callout-titled) .callout-icon::before {
    margin-top: 1rem;
    padding-right: .5rem;
  }

  /* Callout Types */

  div.callout-note {
    border-left-color: #4582ec !important;
  }

  div.callout-note .callout-icon::before {
    background-image: url('data:image/png;base64,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');
  }

  div.callout-note.callout-style-default .callout-title {
    background-color: #dae6fb
  }

  div.callout-important {
    border-left-color: #d9534f !important;
  }

  div.callout-important .callout-icon::before {
    background-image: url('data:image/png;base64,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');
  }

  div.callout-important.callout-style-default .callout-title {
    background-color: #f7dddc
  }

  div.callout-warning {
    border-left-color: #f0ad4e !important;
  }

  div.callout-warning .callout-icon::before {
    background-image: url('data:image/png;base64,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');
  }

  div.callout-warning.callout-style-default .callout-title {
    background-color: #fcefdc
  }

  div.callout-tip {
    border-left-color: #02b875 !important;
  }

  div.callout-tip .callout-icon::before {
    background-image: url('data:image/png;base64,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');
  }

  div.callout-tip.callout-style-default .callout-title {
    background-color: #ccf1e3
  }

  div.callout-caution {
    border-left-color: #fd7e14 !important;
  }

  div.callout-caution .callout-icon::before {
    background-image: url('data:image/png;base64,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');
  }

  div.callout-caution.callout-style-default .callout-title {
    background-color: #ffe5d0
  }

  </style>
  <style type="text/css">
    /* Figure formatting */
    .quarto-layout-panel>figure>figcaption,
    .quarto-layout-panel>.panel-caption {
      margin-top: 10pt;
    }

    .quarto-layout-row {
      display: flex;
      align-items: flex-start;
    }

    .quarto-layout-valign-top {
      align-items: flex-start;
    }

    .quarto-layout-valign-bottom {
      align-items: flex-end;
    }

    .quarto-layout-valign-center {
      align-items: center;
    }

    .quarto-layout-cell {
      position: relative;
      margin-right: 20px;
    }

    .quarto-layout-cell:last-child {
      margin-right: 0;
    }

    .quarto-layout-cell figure,
    .quarto-layout-cell>p {
      margin: 0.2em;
    }

    .quarto-layout-cell .html-widget {
      width: 100% !important;
    }

    .quarto-layout-cell div figure p {
      margin: 0;
    }

    .quarto-layout-cell figure {
      display: inline-block;
      margin-inline-start: 0;
      margin-inline-end: 0;
    }

    .quarto-layout-cell table {
      display: inline-table;
    }

    .quarto-layout-cell-subref figcaption {
      font-style: italic;
      text-align: center;
    }

    .quarto-figure>figure {
      width: 100%;
    }

    .quarto-figure-left>figure>p {
      text-align: left;
    }

    .quarto-figure-center>figure>p {
      text-align: center;
    }

    .quarto-figure-right>figure>p {
      text-align: right;
    }

    figure>p:empty {
      display: none;
    }

    figure>p:first-child {
      margin-top: 0;
      margin-bottom: 0;
    }

    figure>figcaption {
      margin-top: 0.5em;
    }

    figcaption {
      font-size: 0.8em;
    }

    details {
      margin-bottom: 1em;
    }

    details[show] {
      margin-bottom: 0;
    }

    .quarto-unresolved-ref {
      font-weight: 600;
    }

    .quarto-cover-image {
      float: right;
      margin-left: 30px;
    }

    .cell-output-display {
      overflow-x: scroll;
    }

    .hidden {
      display: none;
    }
  </style>

There does not seem to be a way to do so, which is to say this might actually be a feature request, in which case this discussion can be recategorized, but I don't actually know up front.

FWIW I have already used Quarto's YAML to specify a custom CSS file, and the CSS file I have specified is empty. I could still very easily use this currently empty CSS file to add back any of the boilerplate CSS rules as necessary.

To recast this as a bug: it's unclear to me why these CSS rules appear in the XHTML headers and not in external CSS.

(It would be nice, though, if the boilerplate CSS, both from whatever CSS file may or may not be included by default and from the headers, appeared in the Quarto documentation, to make it easier to reference when borrowing from it.)

[mcanouil]

This CSS is needed for Quarto's features to properly work.
Removing it means to remove the features:

• Basic figure layout styles
• Caption formatting
• Callout styling
• Table overflow handling
• Other EPUB-specific formatting

If you really wish to remove that, a post-render script is the solution right now.

• https://github.com/quarto-dev/quarto-cli/blob/main/src/resources/formats/epub/styles.html
• https://github.com/quarto-dev/quarto-cli/blob/main/src/resources/formats/html/styles-callout.html

[elsiehupp]

I get that this CSS is necessary for certain Quarto features to work.

The thing is just that the Quarto project I am currently working on is somewhat unusual in that it is a humanities project, not a STEM-related project, so I AFAIK don't actually need any of the features supported by this CSS.

Perhaps one option for addressing this could be Quarto checking each source QMD file to see if it actually needs the CSS in question and then including it only if necessary.

Or, alternately, the boilerplate CSS could be included from an external CSS file rather than appearing in the header of every single XHTML file in the ePub.

I have literally no idea where to start with the post-render script. Do you have any links for templates I might use?

(Again, it could be nice if excluding the boilerplate CSS from the ePub could be as simple as an option in the project YAML.)

[mcanouil]

See https://quarto.org/docs/projects/scripts.html#pre-and-post-render.
You already know the structure of your files. You need to write a script to delete the lines you don't want in them.

minimal: true and theme: none could probably be extended from HTML to EPUB.

---

EPUB is configured to be self-contained because readers usually have limited CSS support to read external resources.

This approach ensures maximum compatibility across the diverse ecosystem of EPUB reading devices and applications, from dedicated e-readers to mobile apps and desktop software.

[elsiehupp]

I know how to write Python. What I don't know is how to actually use Python from scratch in this particular instance, hence asking if you could point me to someone else's Python scripts that at the very least already deal with Quarto's ePub output post-render.

[elsiehupp]

Extending minimal: true and theme: none from HTML to EPUB would probably be quite helpful, though!

(I mean, having a more robust set of theme options for EPUB more generally could be nice, but EPUB readers usually override a lot of things anyway, so it's probably a question of a only really a handful of CSS rules.)