Make MathML attributes ASCII case-insensitive

[fred-wang]

This is a follow-up of #22 ; we decided to follow HTML/CSS which treat things as ASCII case-insensitive. Concretely, ftp://ftp.unicode.org/Public/UNIDATA/CaseFolding.txt has this line:

017F; C; 0073; # LATIN SMALL LETTER LONG S

which means that falſe is case-insensitively equal to false. However, it is not ASCII case-insensitively equal to false (only a-z <-> A-Z equivalence are considered in that case).

Currently, the MathML Core spec just says "case-insensitive".

Note: for CSS colors, I reported w3c/csswg-drafts#4599

[fred-wang]

I did a quick check and for the MathML-specific definitions, I only see case-insensitive against strings with ASCII letters and dashes. So the only difference would be for "LATIN SMALL LETTER LONG S", "KELVIN SIGN" and maybe a few "LATIN SMALL LIGATURE" (e.g. double-STruck). Unlikely for "LATIN CAPITAL LETTER I WITH DOT ABOVE" if the Turkish rule is used. See w3c/csswg-drafts#4599 (comment)

[NSoiffer]

That's a good catch. I'm pretty sure we all agree that we only mean ASCII case-insensitivity. I suggest we add the following to the spec, which is a slight rewording from the HTML spec:

Many strings in the HTML and CSS syntax (e.g. the names of elements and their attributes) are case-insensitive, but only for ASCII upper alphas and ASCII lower alphas. For convenience, in this specification this is just referred to as "case-insensitive".

I suggest this goes into Appendix G.1: Document Conventions.

[fred-wang]

I would prefer to be explicit everywhere and use "ASCII case-insensitive" with a link to https://infra.spec.whatwg.org/#ascii-case-insensitive ; this seems to be what the HTML and CSS specifications do (or how they would be fixed it e.g. w3c/csswg-drafts#4599 (comment)). I'm sure if we just keep case-insensitive as it is now, people will easily not read the appendix. We should also avoid duplicating definition from HTML5 as it was mentioned in another issue.

[fred-wang]

Consensus from 2019/12/16: Move to ASCII case-insensitiveness

[fred-wang]

These are the attributes, with the behavior changes that will require tests:

• boolean attributes: Behavior change for falSe.
• dir: No behavior change.
• mathvariant: Behavior change for e.g. double-StrucK
• display: Behavior change for blocK.
• form: Behavior change for poStfix.
• notation: Behavior change for e.g. updiagonalStriKe
• frame: Behavior change for e.g. daShed

Other attributes rely on CSS ( https://mathml-refresh.github.io/mathml-core/#types-for-mathml-attribute-values ) so nothing is changed here (although tests can always be added).