[BUG] MathJax 3 Line Break Bug - Support MathJax 2 and/or 4

[battaglia01]

Describe the bug

MathJax 3 has a well-known line break bug which causes line breaks not to work:

$$
a = 1 \\
b = 2 \\
c = 3 \\
d = 4
$$

looks like this with the new MathJax 3:

It should look like this:

Solution

This was working in MathJax 2. Many people haven't upgraded to MathJax 3 as a result of this bug. Even Jupyter didn't upgrade to MathJax 3 for a long time because of this.

I would suggest letting the user choose different MathJax versions - it would be great if we could go back to MathJax 2.

Or, the new MathJax 4 should be released any day now - they're a few weeks behind.

[battaglia01]

I note that if you set the "MathJax V3 Script Src" to the 4.0.0 beta:

https://cdn.jsdelivr.net/npm/mathjax@4.0.0-beta.3/tex-mml-chtml.js

then this works again.

I am not sure if MathJax 4 is backwards compatible with MathJax 3 in every way but it seems to work so far. I'd suggest supporting this version officially.

[yuriever]

I think this should not be considered as a bug. MathJax is designed to be as similar as LaTeX.

In LaTeX the standard multiline equation is the align environment with & and \\. $$ or equation* should not be used to display multiline equations.

In MathJax 3 align environment has been supported long ago.

[battaglia01]

No, that is not correct. MathJax was designed to support line breaks with \\ even though they aren't in LaTeX. MathJax 3 broke this but planned to reimplement it, and now they have with MathJax 4. Again, this is a well known issue that has been talked about extensively.