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Re: [csswg-drafts] [css-text] Add new CSS text-transform values for math (#3745)

From: Frédéric Wang via GitHub <sysbot+gh@w3.org>
Date: Tue, 26 Mar 2019 06:02:11 +0000
To: public-css-archive@w3.org
Message-ID: <issue_comment.created-476487297-1553580129-sysbot+gh@w3.org>
Exposing 𝕸, as "M" rather than "mathematical bold fraktur capital M" is wrong. It's very common in math text to use the same letter with different "style" to convey different meanings, so we really want all users to be able to distinguish them. That was the rationale for proposing these new characters to the Unicode standard and the reason why they were accepted. Arguably, people who rely on these in social networks for purely stylistic purpose are doing misappropriate use, they should rather keep the original ASCII letters with a different font (which as said above is not easy/possible in social networks).

This text-transform proposal is based on the MathML @mathvariant attribute. Originally, the idea for this MathML attribute was to help systems that do not support non-BMP characters very well while still trying to preserve the semantic. It turned out that it is also useful for bottom-to-top LaTeX-to-MathML converters (e.g. fast ones generated LALR parsers) or other MathML generators. The MathML CG has been discussing deprecating/removing this attribute (since it actually duplicates direct use of transformed character) but unfortunately it seems it is still widely used ( https://github.com/mathml-refresh/mathml/issues/77 ). Hence we still need one implementation.

For browser implementation, experience has shown that we want to implement mathvariant by relying on CSS inheritance (rather than implementing a MathML-specific inheritance like in WebKit or older Gecko versions) and to do the character transform at the same place as text-transform (otherwise we get limited and hacky support like in WebKit or older Gecko versions). Since WebKit (and Chromium?) does not have this notion of "internal" CSS property and since text-transform is very similar, this proposal tries to rely on this existing support to make implementation easy.

To make things more complicate, there is this "math-auto" value to render variables with a math italic (that is visually different from CSS italic) and is provided by math fonts in the math italic unicode range. This is instrumental to get beautiful rendering of math equations but does not really convey semantics, so should not be exposed to assistive technologies so the spec should probably mention it. Authors won't use the transformed characters in that case.

I guess in any case the spec should be amended to say how the characters are exposed to assistive technologies. math and Asian examples mentioned  above suggests it could depend on text-transform values.

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Received on Tuesday, 26 March 2019 06:02:14 UTC

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