mmultiscripts spacing between children is too narrow

[samimaattaCelia]

Issue Summary

mmultiscripts children should have more spacing between them than what MathJax currently does (although I can't recall the proper values).

MathJax 4 output:

Firefox's native output:

Firefox's output is not necessarily the expected one, but there should at least some spacing between the children.

OS: Windows 11
Browser: Mozilla Firefox 153.0

Steps to Reproduce:

Use the code to render:

<math xmlns="http://www.w3.org/1998/Math/MathML">
    <mmultiscripts>
        <mi>A</mi>
        <mn>1</mn>
        <mn>2</mn>
        <mn>3</mn>
        <mn>4</mn>
        <mprescripts/>
        <mn>7</mn>
        <mn>300</mn>
        <mn>3</mn>
        <mn>700</mn>
    </mmultiscripts>
</math>

Technical details:

• MathJax Version: 4
• OS: Windows 11
• Browser: Mozilla Firefox 153.0

I am using the default MathJax configuration and loading MathJax via

<script src="https://cdn.jsdelivr.net/npm/mathjax@4/tex-mml-chtml.js" defer></script>

[dpvc]

The MathML3 specification on which MathJax is based is not explicit about the spacing to be used in a number of situations like this (though MathML4 and MathML-Core are much more specific about it). In any case, MathJax's output is based on TeX's spacing rules, not MathML's rules (unless you set the mmlSpacing option in the output section of the MathJax configuration).

For example, the result of

$$\tensor{T}{^1^2_3_4}$$
$$\tensor{T}{^{12}_{34}}$$

in LaTeX is:

and as you can see, there is no difference between the two forms (i.e., no extra space between the scripts in the upper formula). That is why MathJax implements mmultiscripts in this way.

The mmlSpacing option should introduce the space you are looking for, but doesn't. I will mark this as a feature request for inclusion in a future release.