File containing mathML produces correct output but gives errors

[70ray]

My question is: since the output displays correctly in calibre epub viewer, why does ebookmaker give an error?

The original htm file contains a tagged equation. This does not display correctly in firefox because firefox does not support the <mlabeledtr> tag. Chromium does not display it correctly either. Nook ereader does not display the epub file correctly but I would not have expected it to.

Perhaps the answer is that MathML is not sufficiently well supported at present to be useful.

Link to folder containg htm, output.txt and epub:
https://www.dropbox.com/scl/fo/wxvd26ulbjovfqqxuk2y9/AP-845qvGgNVymg5-ZSSAng?rlkey=h7dvvply8eb2hby2en9zr2tim&st=r40yyoky&dl=0

I hope this link works, please let me know if it doesn't.

[eshellman]

some comments:

1. mlabeledtr is not included in the MathML subset "Suitable for browser implementation". So, our documentation should say it should not be used in PG books.
2. try including the baseline css sheet for user agents: https://www.w3.org/TR/mathml-core/#user-agent-stylesheet
   If this works, we can make an exception for using it in ebookmaker
3. I'll need to investigate the errors "The property "mathml" should be declared in the OPF file." That's likely an ebookmaker problem.
4. Currently, the math element is replaced using a provided image file for EPUB2 files, as EPUB2 does not support MathML. or the provided replacement text. I'm not sure why the math element is still there in the generated EPUB2

[70ray]

The background to this is that I am extending the m2svg tool. The present version takes a html file containing tex style math expressions and replaces them with links to svg images which it creates using mathjax nodejs functions. I believe Laura (lnatal) has used it on several occasions.
I am extending it to add options to use embedded svg or MathML also using mathjax functions.
The embedded svg works well and can use the \tag{} element which displays correctly even in an old NOOK ereader.
The MathML hit the problems mentioned above. The mlabeledtr is generated by the \tag{} markup, so it looks like this must be disallowed for the MathML option (as it is for the image option).
The xmlns is generated by the mathjax function. When I tried removing it to work around the elements from namespace "http://www.w3.org/1998/Math/MathML" are not allowed error the div not allowed here problem came up. As you pointed out the conversion to images for epub2 introduces divs which should not occur inside <p> markup. It would be nice if the image conversion could be done without using divs since display math expressions commonly occur inside paragraphs. Otherwise I could make the tool change all the <p> elements to divs with class=p as Alba T Ross suggested, but this seems very hacky.

[eshellman]

I think to make MathML really work, we'll need to have ebookmaker include some polyfill CSS, and a version of that for EPUB2. I imagine MathJax generates that to make mlabeledtr work. If that works, it will be easier to do that than to manage which elements are allowed or not allowed.

[eshellman]

As an ex-physicist, I'd love to see this work properly!

[70ray]

This page, (referring to mathjax used in a browser) indicates that mathjax can't itself display mathml any better that a browser does but uses it internally to generate svg or html/css output. So it seems we have to accept the limitations of mathml support in browsers.
The option providing best results seems to be embedded svg. But it results in a large file.
The nodejs functions of mathjax can also generate the html/css output that is one of the display options of mathjax and would probably result in a smaller file size, but to use it I think we would have to embed fonts in html which I understand is not acceptable.

[eshellman]

Currently, MathJax can render math in three ways:

• Using HTML and CSS to lay out the mathematics,
• Using Scalable Vector Graphics (SVG) to lay out the mathematics, or
  -As a serialized MathML string.

In principle, ebookmaker could be running MathJax to make html for EPUB2, SVG for HTML/HTML5, and MathML for the future.

But maybe that's aspirational. If we embed the TeX, it could be done in the future.

Doesn't MathML provide an element to wrap an image of the math (could be SVG) that ebookmaker could default to for now?

"large" files don't bother me. Embedded local fonts are already supported by ebookmaker, especially if we can subset them. What PG does NOT want is non-standard embedded fonts that are not strictly needed; they often need licensing review.

[70ray]

I'll try out the HTML and CSS option of MathJax.