[css-fonts-4] Clarify maximum number of <feature-value-names> in character-variant()

[cdoublev]

There it says 2:

The character-variant() property value allows two values and styleset() allows an unlimited number.

https://drafts.csswg.org/css-fonts-4/#multi-value-features

But in other places, it says unlimited.

character-variant(<feature-value-name>#): Enables display of specific character variants [...]

https://drafts.csswg.org/css-fonts-4/#character-variant

Example 66:

p {
  font-variant: discretionary-ligatures
    character-variant(leo-B, leo-M, leo-N, leo-T, leo-U);
}

https://drafts.csswg.org/css-fonts-4/#ex-byzantine-variants

Chrome/FF (at least) accept an unlimited number.

[svgeesus]

I don't understand where "allows two values" comes from, it seems clearly wrong.

[svgeesus]

Aha, I think this is a mixing up of character-variant property and @character-variant:

When two values are listed, the first value indicates the feature used and the second the value passed for that feature. If more than two values are assigned to a given name, a syntax error occurs and the entire feature value definition is ignored.

So the fix is "The @character-variant font feature value allows either one or two values"

[svgeesus]

Looks like this was my mistake when the text was moved from Fonts 3 (which did not use bikeshed) to Fonts 4.

[cdoublev]

The text in CSS Fonts 3 was the same. I do not know how to access the old CVS repo to further investigate the initial intent, but I also think that declaration values in @character-variant should match <integer>{2}; the number of arguments in character-variant() is unlimited (there is no character-variant property, Bikeshed outputs character-variant() from 'character-variant').

[svgeesus]

character-variant is a value of the font-variant-alternates property.

I'm about to push an edit which hopefully clears things up.

[svgeesus]

@cdoublev please take a look

[cdoublev]

Looks good to me, thank you! So it should be character-variant(<feature-value-name>#{2})?

I was waiting for Tab and Simon answers on how to represent font feature value rules in a production. But now w3c/webref can scrap these rule definitions, I think. In this #9114 (comment), I suggested using definition tables, but I am not sure how it could work with these rules. I will keep an eye on this issue.

[cdoublev]

So it should be character-variant(#{2})?

Nevermind! Time to sleep.

[cdoublev]

I am sorry because I should have take a look at your changes earlier in the day, and this sentence seems confusing to me:

The character-variant() property value and the @character-variant descriptor allow two values, which enables a feature (from the first value) and sets it to a given (second) value.

character-variant() definitely allows more than two values.

I think it should be something like this:

The character-variant() property value enables the features defined by the @character-variant descriptor declarations whose names are specified as its arguments. @character-variant declaration values allow two values, which enables a feature (from the first value) and sets it to a given (second) value.

[cdoublev]

I also would like to clarify the expected output when declaring a feature for @character-variant with more than two values. Should it be valid but ignored? Or invalid and discarded?

edit:

Never mind, I did not see this further above:

A syntax error within a font feature value declaration makes the declaration invalid and ignored, but does not invalidate the font feature value block it occurs in.