@marp-team/marp-core

The core of Marp converter.

In order to use on Marp tools, we have extended from the slide deck framework Marpit. You can use the practical Markdown syntax, advanced features, and official themes.

Usage

We provide Marp class, that is inherited from Marpit.

import Marp from '@marp-team/marp-core'

// Convert Markdown slide deck into HTML and CSS
const marp = new Marp()
const { html, css } = marp.render('# Hello, marp-core!')

Features

We will only explain features extended in marp-core. Please refer to @marp-team/marpit repository if you want to know the basic feature of Marpit framework.

Marp Markdown

Marp Markdown is based on Marpit and CommonMark, and there are these additional features:

• Marpit
  • Enable inline SVG mode and loose YAML parsing by default.

• CommonMark
  • For security reason, HTML tag only allows <br /> by default.
  • Support table and strikethrough syntax, based on GitHub Flavored Markdown.
  • Line breaks in paragraph will convert to <br> tag.
  • Auto convert URL like text into hyperlink.

Built-in official themes

We provide bulit-in official themes for Marp. See more details in themes.

Default	Gaia	Uncover
<!-- theme: default -->	<!-- theme: gaia -->	<!-- theme: uncover -->

size global directive

Do you want a traditional 4:3 slide size? We've added the support of size global directive only for Marp Core. Our extended theming system can use 960x720 slide in built-in themes easier: size: 4:3.

---
theme: gaia
size: 4:3
---

# A traditional 4:3 slide

If you want to use more size presets in your theme, you have to define @size metadata(s) in theme CSS. Learn in the document of theme metadata for Marp Core.

Theme author does not have to worry an unintended design being used with unexpected slide size because user only can use pre-defined presets by author.

Emoji support

Emoji shortcode (like :smile:) and Unicode emoji 😄 will convert into the SVG vector image provided by twemoji . It could render emoji with high resolution.

Math typesetting

We have Pandoc's Markdown style math typesetting support. Surround your formula by $...$ to render math as inline, and $$...$$ to render as block.

Markdown	Rendered slide
Render inline math such as $ax^2+bc+c$. $$ I_{xx}=\int\int_Ry^2f(x,y)\cdot{}dydx $$ $$ f(x) = \int_{-\infty}^\infty \hat f(\xi)\,e^{2 \pi i \xi x} \,d\xi $$

You can choose using library for math from KaTeX and MathJax in math global directive (or JS constructor option). By default, we prefer KaTeX for compatibility and performance, but MathJax has better rendering and syntax support than KaTeX.

math global directive

Through math global directive, Marp Core is supporting to declare math library that will be used within current Markdown.

Set katex or mathjax in the math global directive like this:

---
# Declare to use MathJax in this Markdown
math: mathjax
---

$$
\begin{align}
x &= 1+1 \tag{1} \\
  &= 2
\end{align}
$$

If not declared, Marp Core will use the default library to render math (KaTeX in v2).

We may change the default in the future and would break existing slides, so recommend to declare the library whenever to use math typesetting.

⚠️ The declaration of math library is given priority over math JS constructor option, but you cannot turn on again via math global directive if disabled math typesetting by the constructor.

Auto-scaling features

Auto-scaling is available only if enabled Marpit's inlineSVG mode and defined @auto-scaling metadata in an using theme CSS.

/*
 * @theme enable-all-auto-scaling
 * @auto-scaling true
 */

Marp Core's scaling features will be realized by manipulating the original DOM to use inline SVG. So the theme author must take care of updated DOM in styling. Refer to the source code of offical themes.

@auto-scaling meta can also pick the favorite features to enable by using keyword(s).

/*
 * @theme enable-auto-scaling-for-fitting-header-and-math
 * @auto-scaling fittingHeader,math
 */

⚠️ In the math block and the code block, Marp Core won't detect whether they actually protrude from the slide. It might not work scaling correctly when there are many elements in a slide.

Fitting header

When the headings contains <!-- fit --> comment, the size of headings will resize to fit onto the slide size.

# <!-- fit --> Fitting header

This syntax is similar to Deckset's [fit] keyword, but we use HTML comment to hide a fit keyword on Markdown rendered as document.

ℹ️ @auto-scaling fittingHeader is a keyword of the @auto-scaling meta to enable fitting header.

KaTeX Math block

We can scale-down the viewing size of KaTeX math block (surrounded by $$) to fit a slide automatically.

Traditional rendering	Auto-scaling

ℹ️ @auto-scaling math is a keyword of the @auto-scaling meta to enable math block scaling.

Please notice that the math block rendered by MathJax would always be scaled-down and cannot control whether scale via metadata.

Code block

Several themes also can scale-down the viewing size of the code block to fit a slide.

Traditional rendering	Auto-scaling

These features means that the contents on a slide are not cropped, and not shown unnecessary scrollbars in code.

ℹ️ @auto-scaling code is a keyword of the @auto-scaling meta to enable code block scaling.

uncover theme has disabled code block scaling because we use elastic style that has not compatible with it.

Constructor options

You can customize a behavior of Marp parser by passing an options object to the constructor. You can also pass together with Marpit constructor options.

ℹ️ Marpit's markdown option is accepted only object options because of always using CommonMark.

const marp = new Marp({
  // marp-core constructor options
  html: true,
  emoji: {
    shortcode: true,
    unicode: false,
    twemoji: {
      base: '/resources/twemoji/',
    },
  },
  math: 'mathjax',
  minifyCSS: true,
  script: {
    source: 'cdn',
    nonce: 'xxxxxxxxxxxxxxx',
  },

  // It can be included Marpit constructor options
  looseYAML: false,
  markdown: {
    breaks: false,
  },
})

html: boolean | object

Setting whether to render raw HTML in Markdown. It's an alias to markdown.html (markdown-it option) but has additional feature about HTML allowlist.

• true: The all HTML will be allowed.
• false: All HTML except supported in Marpit Markdown will be disallowed.

By passing object, you can set the allowlist to specify allowed tags and attributes.

// Specify tag name as key, and attributes to allow as string array.
{
  a: ['href', 'target'],
  br: [],
}

// You may use custom attribute sanitizer by passing object.
{
  img: {
    src: (value) => (value.startsWith('https://') ? value : '')
  }
}

Marp core allows only <br> tag by default, that is defined in Marp.html.

Whatever any option is selected, <!-- HTML comment --> and <style> tag are always parsed for directives / tweaking style.

emoji: object

Setting about emoji conversions.

• shortcode: boolean | "twemoji"
  • By setting false, it does not convert any emoji shortcodes.
  • By setting true, it converts emoji shortcodes into Unicode emoji. :dog: → 🐶
  • By setting "twemoji" string, it converts into twemoji vector image. :dog: → (default)

• unicode: boolean | "twemoji"
  • It can convert Unicode emoji into twemoji when setting "twemoji". 🐶 → (default)
  • If you not want this aggressive conversion, please set false.

• twemoji: object
  • base: string - It is corresponded to twemoji's base option. By default, marp-core will use online emoji images through MaxCDN (twemoji's default).
  • ext: "svg" | "png" - Setting the file type of twemoji images. (svg by default)

For developers: When you setting unicode option as true, Markdown parser will convert Unicode emoji into tokens internally. The rendering result is same as in false.

math: boolean | "katex" | "mathjax" | object

Enable or disable math typesetting syntax and math global directive.

You can choose the default library for math by passing "katex" (default) or "mathjax", and modify more settings by passing an object of sub-options.

• lib: "katex" | "mathjax"
  • Choose the default library for math typesetting. (katex by default)

• katexOption: object
  • Options that will be passed to KaTeX. Please refer to KaTeX document.

• katexFontPath: string | false
  • By default, Marp Core will use online web-font resources through jsDelivr CDN. You have to set path to fonts directory if you want to use local resources. If you set false, we will not manipulate the path (Use KaTeX's original path: fonts/KaTeX_***-***.woff2).

minifyCSS: boolean

Enable or disable minification for rendered CSS. true by default.

script: boolean | object

Setting about an injected helper script for the browser context. This script is necessary for applying WebKit polyfill and rendering auto-scaled elements correctly.

• true: Inject the inline helper script into after the last of slides. (default)
• false: Not inject helper script. Developer must execute a helper script manually, exported in @marp-team/marp-core/browser. Requires bundler such as webpack. It's suitable to the fully-controlled tool such as Marp Web.

You can control details of behavior by passing object.

• source: string - Choose the kind of script.
  • inline: Inject the inline script. It would work correctly also in the environment that there is not network. (default)
  • cdn: Inject script referred through jsDelivr CDN. It's better choice on the restricted environment by CSP.

• nonce: string - Set nonce attribute of <script>.

Contributing

Are you interested in contributing? Please see CONTRIBUTING.md and the common contributing guideline for Marp team.

Author

Managed by @marp-team.

• Yuki Hattori (@yhatt)

License

This package releases under the MIT License.