[css-fonts] @font-palette-values rule has no object model

[svgeesus]

https://drafts.csswg.org/css-fonts-4/#font-palette-values

This rule needs an enumeration added, for example

partial interface CSSRule {
  const unsigned short FONT_PALETTE_VALUES_RULE = 15;
}

and a definition of the interface, something like:

interface CSSFontPaletteValuesRule : CSSRule {
  attribute CSSOMString fontFamily;
  attribute CSSOMString basePalette;
  attribute CSSOMRGBColor integer;
}

???? No idea how in WebIDL to declare an unbounded set of descriptors whose names are the set of integers. Would that be a map?

Nor how to declare that it is <color> not just the DOM 2 CSS RGBColor.

Also, those are really bad descriptor names, overly generic.

[tabatkins]

No idea how in WebIDL to declare an unbounded set of descriptors whose names are the set of integers. Would that be a map?

Best way is to make the interface maplike, yeah, so you'd do palette.set(1, "red").

[litherum]

3009d53

[tabatkins]

(Comment left on commit.)

[svgeesus]

@tabatkins you said

This should definitely not be using the old DOM 2 Style classes. Make it just take a CSSOMString, with a manually-defined set() method that checks that it [=CSS/parses=] as a CSS value, and throws a TypeError if not.

Sounds like you know exactly what you want, but we aren't sure and this issue is languishing. Care to gives us something copy-pastable?

[tabatkins]

The "old DOM 2 Style class" I was referring to was CSSOMRGBColor; that interface is long obsolete and should never be used for anything. Just drop it from the signature.

Then just define the error handling properly: use [=CSS/parse=] to parse it as a <color>, and if it returns failure, throw a SyntaxError.

[svgeesus]

@tabatkins this was assigned to you my @litherum because, although you left hints on what needed to be done, neither of us was totally sure. Could uou make further comments so we can land the PR ?

[tabatkins]

My last comment is exactly what you need to do.

CSSOMRGBColor; that interface is long obsolete and should never be used for anything. Just drop it from the signature.

and

use [=CSS/parse=] to parse it as a <color>, and if it returns failure, throw a SyntaxError.

rather than the existing vague "parsed as a solid color" wording. Plus it should throw on a parse error, not just return undefined and do nothing.

[svgeesus]

I wasn't sure how to add to the interface to make it throw.