[css-color-5] Only hsl and hwb have channel values as percentages in RCS

[romainmenke]

I was going over the list of changes in css-color-5 and I noticed that only hsl and hwb have channel keywords in RCS that have percentage values.

Both however also allow number values as regular arguments.
In css-color-5 these are both valid and equal :

• hwb(90deg 25% 25%)
• hwb(90deg 25 25)

@svgeesus is there a reason not to give the channel keywords the number type?
That would make these two color functions more consistent with every other color function.

• https://drafts.csswg.org/css-color-5/#relative-HSL
• https://drafts.csswg.org/css-color-5/#relative-HWB

[svgeesus]

No, it looks like just a failure on my part to update all affected parts of the spec. This edit changed

They are <<number>>s or <<percentage>>s

to

They are <<number>>s

but only for relative color() not for other color functions.

You are right that hsl() and hwb() were changed to always allow number or percentage, and the CSS WG resolution was that channel keywords should resolve to <number>.

• RESOLVED: keywords with multiple specified types result in number

@tabatkins had pointed out that channel keywords were still using percentage for HWB, and I stated that this was correct because that predated the resolution (which was made on the call that same day).

And the spec was even changed elsewhere to refer to these being number for HSL and HWB, see this edit, as part of #8322.

So I should fix that, for consistency. Thanks for your careful review!

[svgeesus]

Also from the intro to RCS;

The channel keywords return a <number>; if they were originally specified as a <percentage> or an <angle>, that <percentage> is resolved to a <number> and the <angle> is resolved to a <number> of degrees (which is the canonical unit) in the range [0, 360].

[svgeesus]

Relevant tests to check:

• parsing/color-valid-relative-color.html
• parsing/color-invalid-relative-color.html

Add subtests with calc(), to check correct types used, on:

• HSL hue
• HSL L and S
• HWB hue
• HWB W and B
• LCH hue
• Oklch hue

[romainmenke]

One more :)

csswg-drafts/css-color-5/Overview.bs

Line 1417 in 70622d0

* <dfn value for="oklch()">h</dfn> is an <<angle>>

[svgeesus]

Thanks!

[romainmenke]

Thank you for these edits and clarifications 🙇

[svgeesus]

(Leaving the issue open so I don't forget about the need for testcase review and supplementation)

[romainmenke]

I've added a few tests that should also cover this issue : web-platform-tests/wpt#43931

[svgeesus]

Cheers, I just approved them.

[svgeesus]

The spec is now correct and the tests are updated, so I believe this can be closed.