ExtendMarkdown Plugin

A simple extension of the Rainlab.Blog plugin for October CMS allowing for user defined extensions to Markdown input, as well as a way to protect certain constructions from October's built-in Markdown interpreter, thus allowing for example MathJax and Markdown to play nice with each other.

Background

The excellent Rainlab.Blog plugin uses Markdown formatting of posts. Unfortunately the built-in Markdown interpreter Parsedown interferes with the standard MathJax library for typesetting matematical formulas using LaTeX syntax. While Parsedown seems to handle some MathJax constructions properly, the parser often produces output that causes MathJax rendering to fail.

For example: in a blog post containing text like

    The equation $x_{n+2} - 5x_{n+1} + 6x_{n} = 0$.

Parsedown sees the _ as italic markers, and produces the following HTML code

    <p>The equation $x<em>{n+2} - 5x</em>{n+1} + 6x_{n} = 0$.</p>

The incorrectly inserted <em> tags destroys the LaTeX markup and thus MathJax fails to typeset the formulas properly.

Solution

The ExtendMarkdown plugin provides a simple, reasonable clean solution allowing the user to create a number of replacement "rules", protecting certain input from the Parsedown interpreter. These rules will be applied everytime a blog post is saved.

Also, the plugin can be used to add extra shortcuts for commonly used markup.

By default, the plugin comes with the following rules

Rules protecting input from the Parsedown interpreter:

Input start tag	Input close tag	Output start tag	Output close tag
$	$	$	$
$$	$$	$$	$$
\begin{equation}	\end{equation}	\begin{equation}	\end{equation}
\begin{align}	\end{align}	\begin{align}	\end{align}

Additional markup shortcuts

Input start tag	Input close tag	Output start tag	Output close tag
@@	@@	<strong class="text-primary">	</strong>

The plugin provides a backend interface for modifying and adding additional rules as needed.

Live MathJax updates when previewing a blog post in the backend

If you write a lot of MathJax heavy blog posts, you probably want to render the MathJax markup, also in the backend preview.

To do this, install the Mossadal.MathJax plugin.