[csswg-drafts] [css-color-5] color-mix() spec incorrectly states that is ok to specify a <hue-adjuster> (though has no effect) for rectangular color spaces (#6831)

weinig has just created a new issue for https://github.com/w3c/csswg-drafts:

== [css-color-5] color-mix() spec incorrectly states that is ok to specify a <hue-adjuster> (though has no effect) for rectangular color spaces ==
In step 2 of the post normalization `color-mix()` algorithm (see https://drafts.csswg.org/css-color-5/#color-mix), the spec states:

> Colors are then interpolated in the specified color space, as described in CSS Color 4 § 13 Interpolation. If the specified color space is a cylindrical-polar-color space, then the <hue-adjuster> controls the interpolation of hue, as described in CSS Color 4 § 13.3 Hue interpolation. If no `<hue-adjuster>` is specified, it is as if shorter had been specified. If the specified colorspace is a rectangular-orthogonal-color space, then specifying a <hue-adjuster> is not an error, but has no effect.

(The issue with `<hue-adjuster>` now being called `<hue-interpolation-method>` has been separately files as https://github.com/w3c/csswg-drafts/issues/6830.)

According to the grammar for `<color-interpolation-method>`, https://drafts.csswg.org/css-color/#color-interpolation-method, a `<hue-interpolation-method>` is only valid following a  `<polar-color-space>`. 


```
<rectangular-color-space>` = srgb | lab | oklab | xyz | xyz-d50 | xyz-d65
<polar-color-space> = hsl | hwb | lch | oklch
<hue-interpolation-method> = [ shorter | longer | increasing | decreasing | specified ] hue
<color-interpolation-method> = in [ <rectangular-color-space> | <polar-color-space> <hue-interpolation-method>? ]
```

Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/6831 using your GitHub account


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Received on Saturday, 27 November 2021 18:28:32 UTC