[css-fonts][css-conditional] Case of font-technology feature queries.

[svgeesus]

Context: I'm about to harmonize the syntax used in CSS Fonts 4 @font-face src to that used in CSS Conditional 4 feature queries. Currently the former uses color(COLRv1) while the latter uses color-colrv1.

font-technology feature queries are (I believe) ascii-case-insensitive.

For those which are defined by OpenType table names (where case is significant), should the examples

1. use the casing from the OpenType specification (which is what the relevant section of CSS Fonts 4 currently does ) - for example sbix, CBDT
2. use consistent lower case (which is what the relevant section of CSS Conditional 4 currently does) - for example color-sbix, color-cbdt

I'm tending towards the latter, with the move to hyphenated rather than functional form.

@LeaVerou @fantasai @litherum @drott

[drott]

No strong opinion. I personally don't always exactly remember the OpenType case for all of them anyway, and perhaps lowercase makes the examples less confusing, so going with lowercase sounds fine to me.

[LeaVerou]

Very slightly tending towards lowercase, as it's more consistent with the rest of CSS, even though it's less consistent with OpenType.

[Lorp]

I believe there is little danger of uppercase table tags being reused in lowercase (unlike, say, variable axis names when they become registered). So Chris’s suggestion sounds safe. Lowercase table names are simply reserved by Apple.

[tabatkins]

As these will be language-defined keywords, they should definitely be ASCII case-insensitive. How we write them in the spec doesn't matter too much, but I also lean towards consistent lowercase (the only place I violate that in my specs is the NaN keyword, which is spelled consistently with that casing across so many contexts).

Are there any OpenType keywords where case actually distinguishes things, or is it just that they have a particular defined casing?

[svgeesus]

I'm not aware of any tag which conflicts with another one if both are uppercased.

Unless an Apple-reserved one became standardized without a name change.

[svgeesus]

OK lets go for all-lowercase

[khaledhosny]

FWIW, AAT has feat table and Graphite has Feat table.

[svgeesus]

Thanks, @khaledhosny ! Great example.

Although so far, we don't use that table name in the font-technology strings, so it won't be a problem.

(We do allow differentiating between OpenType, AAT and Graphite layout, though).

[yisibl]

I prefer lowercase, which is consistent with other parts of CSS. And many CSS developers are not clear about the case of table names in OpenType.