jxxcarlson/elm-markdown

The aim of this Markdown library is to provide a pure Elm implementation of Markdown which offers a small set of optional extensions:

• Standard: the usual thing
• Extended: strike-though text, tables, and Poetry and Verbatim blocks, better image handling
• ExtendedMath: like Extended, but math formulas written in TeX/LaTeX, eg., This **is** a test: $a^2 + b^2 = c^2$ are properly rendered.

How to use it

For simple applications, use the Markdown.Elm and Markdown.Option modules, as in this example:

sourceText = "This **is** a test."
Markdown.Render.toHtml Standard sourceText
    |> Html.map MarkdownMsg

To render mathematical text, do something like this:

sourceText = "Use $a^2 + b^2 = c^2$."
Markdown.Render.toHtml ExtendedMath sourceText 
    |> Html.map MarkdownMsg

The Markdown.Option module exports ExtendedMath while Markdown.Render exposes MarkdownMsg. For the ExtendedMath option, take a look at ./Editor/simplest/ in the source code to see what to do. You will need some Javascript, incuding MathJax 3. Here is a direct linkd .

Editor demos

There are three versions of the demo: ./editor/simplest/, ./editor/simple/, and editor/fancy. The second and third include extra bells, whistles and optimizations that are useful for interactive editing environments and documents with a lot of mathematics.

See markdown.minilatex.app for the latest version the fancy demo.

NOTE: This package is still evolving relatively rapidly. I regret publishing so many updates, but I am using it in several apps, and this is the only way I know how to encapsulate the complexity, work with the CI build systems, and keep my sanity

Installing the Demo

$ cd to ./app-demo-fancy

$ npm install

$ npm start

Style

The style used by the library is entirely determined by the definitions of the CSS classes that you refer to in your index.html. The ones used for the demo app are found in ./app-demo/assets/style.css and ./app-demo-fancy/assets/style.css You can easily reconfigure the CSS to satsify your own esthetics.

Markdown extensions

I am trying to be conservative about extensions to Markdown. However, there are two that I thought important enough to add: tables, poetry blocks and verbatim text. Poetry blocks are are like quotation blocks, except that they begin with ">>" instead of ">". Line endings are respected in poetry blocks. Verbatim blocks are like code blocks, except that they are set off by four backticks instead of three. No syntax coloring is applied to verbatim blocks.

Images

The usual ![My favorite image](imageUrl) does the usual thing, with the image scaled to 100% of the width. You can also say ![My favorite image::left](imageUrl) or ![My favorite image::right](imageUrl) to float the image left or right at 40% width. The widths are defined in style.css.

Advanced Usage: AST

If you wish to write your own renderer, or do other fancy things, you will want to produce and manpulate the AST:

Markdown.Parse.toMDBlockTree : Version 
       -> Option -> Document -> Tree MDBlock

where Version is an integer and Document is a type alias for String.
This is also useful if you wish to transform the abstract syntax tree before rendering it. The Version parameter may be set to zero if you do not have to worry about updated thd ids of rendered elements in an interactive editing environment.

Editor

The fancy demo app now uses pure Elm text editor. It is very much a work in progress.

Bugs and whatnot

Please write me at [email protected] or post an issue on the Github repository regarding bugs or anything else. I will steer this library towards the Commonmark spec to the greatest extent possible by the method of successive approximations

Recent Changes

• Greatly simplified the API. Now there are just three exported modules, Markdown.Option, Markdown.Render, and Markdown.Parse. The latter is needed only in advanced applications.

• Changed the return type of the rendering functions, e.g., toHtml : Option -> String -> Html msg becomes toHtml : Option -> String -> Html MarkdownMsg. This change makes the rendered text "active," e.g., can respond to clicks. See next item.

• Added sourceMap : Tree MDBlockWithId -> BiDict String String in the Markdown.Parse module as a hook for host programs to implement bidrectional sync of source and rendered text.

Thanks

Thanks to Folkert de Vries and Luke Westby. A shout-out to Folkert for an optimiztaion of the pure text rendering (10 x speedup).