Hello,

Currently MathML attributes mathvariant, displaystyle and scriptlevel [1] [2] are implemented in WebKit using custom "style resolution" and "one-glyph rendering" inside the MathML layout code [3] [4] [5]. These features involve text rendering and interaction with CSS font-size, so it is difficult to implement them properly and completely that way. There are known bugs and missing features right now (e.g. mathvariant transform only applies to one-character strings, automatic displaystyle/scriptlevel does not work with fractions, etc)

Hi,

An update on this, we have been discussing these and new properties with the CSSWG:

https://github.com/w3c/csswg-drafts/issues/5384

The math-depth / math-style CSS properties are being implemented in Chromium and renamed/exposed/tweaked in Gecko:

https://mathml-refresh.github.io/mathml-core/#the-math-style-property

https://mathml-refresh.github.io/mathml-core/#the-math-script-level-property

So it makes sense to implement them in WebKit (it seems we still don't have a "intent to" mechanism, but people can follow https://bugs.webkit.org/show_bug.cgi?id=195797).

The CSSWG is fine with a new text-transform value for automatic italic but using it for other values is controversial (see https://github.com/w3c/csswg-drafts/issues/3775). So if we want to preserve backward compatibility and fix existing bugs with mathvariant, we should probably re-implement it using an internal math-transform property (like what Gecko does) which according to our previous discussion is nowadays possible in WebKit.

-- 
Frédéric Wang