How can I render AsciiMath expressions in both inline and display style with MathJax 3?

[Frank Illenberger]

By default, MathJax3 is rendering AsciiMath expressions in inline style. In my project, I need AsciiMath expressions also in display style. As a start, I tried to achieve this by subclassing FindAsciiMath:

class MyFindAsciiMath extends MathJax._.input.asciimath.FindAsciiMath.FindAsciiMath {
  getPatterns() {
    let options = this.options
    let starts = []
    this.end = {}
    options['delimiters'].forEach((delims) => this.addPattern(starts, delims, true))
    this.start = new RegExp(starts.join('|'), 'g')
    this.hasPatterns = (starts.length > 0)
  }
}

Here I set the 3rd parameter of addPattern to true to switch it to display mode. But this only results in the mjx-assistive-mml element getting a block display attribute but the expression is still rendered inline. Is there a way to achieve this with MathJax3? In MathJax2 this used to work with postfilterHooks.

Many thanks.

[Davide Cervone]

The current AsciiMath input jax is really the v2 one pasted into MathJax v3 with some shims and glue functions, and it really needs to be made into a proper input jax for v3.  It's on the to-do list, but other things have taken priority.  It turns out that the display parameter doesn't actually work properly, as you have noticed.

Here is a configuration that will do what is needed:

<script>

MathJax = {

  loader: {load: ['input/asciimath', 'output/chtml']},

  asciimath: {

    delimiters: [['``','``'], ['`','`']]

  },

  startup: {

    ready() {

      const {AsciiMath} = MathJax._.input.asciimath_ts;

      Object.assign(AsciiMath.prototype, {

        _compile: AsciiMath.prototype.compile,

        compile(math, document) {

          math.display = (math.start?.delim === '``');

          const result = this._compile(math, document);

          const mstyle = result.childNodes[0].childNodes.pop();

          mstyle.childNodes.forEach(child => result.appendChild(child));

          if (math.display) {

            result.attributes.set('display', 'block');

          }

          return result;

        }

      });

      MathJax.startup.defaultReady();

    }

  }

};

</script>

<script src="https://cdn.jsdelivr.net/npm/mathjax@3/es5/startup.js"></script>

Here, we configure AsciiMath to use two different delimiters (the order matters), and hijack the AsciiMath compile() method to handle our needed display mode.  We remove the top-level mstyle element that AsciiMath adds to set the displaystyle, and set the math element's display attribute to block for display mode (leaving it unset for in-line math, since that is the default).  This makes displayed math be a displayed equation as well as typesetting in display style.  If you want it to remain an in-line expression but using display style rules, change

            result.attributes.set('display', 'block');

to

            result.attributes.set('displaystyle', 'true');

instead.

I think this should do what you are looking for.

Davide

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[Frank Illenberger]

Thank you very much!

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