[css-color-5] Questions about color-adjust()

[weinig]

I have a few questions about the current CSS Color 5 color-adjust() function (https://drafts.csswg.org/css-color-5/#coloradjust), and thought perhaps throwing them in one issue would make sense. (if you would prefer I break these up, I'd be happy to).

1. What should the behavior be when no percentage is provided? In the current grammar, we have <percentage>?, which means the percentage can be elided. I am not sure this is useful, so perhaps we should just make it required.

2. What is the use of allowing the <color-adjuster> itself to optional. Seems like it should be required.

3. How does the hue modifier (e.g. shorter, longer, etc.), change the behavior of color adjusting? I had it in my mind that the modifier only had an effect on interpolation between two hues. Perhaps it isn't needed not that the adjusters are not used for color-mix()?

[svgeesus]

What should the behavior be when no percentage is provided?

I can't think of a useful default, so suggest the percentage be mandatory

What is the use of allowing the <color-adjuster> itself to optional

There can be more than one, but the grammar should be "one or more" not "zero or more"

How does the hue modifier (e.g. shorter, longer, etc.), change the behavior of color adjusting?

I think this got added when the modifiers were added to color-mix, perhaps without much thought, and that for a single color you just need a (signed) hue modifier.

[svgeesus]

I think this got added when the modifiers were added to color-mix, perhaps without much thought, and that for a single color you just need a (signed) hue modifier.

It looks like this was an inadvertent effect of simplifying color-mix, where it was originally defined but then got dropped.

I changed the parameter on color-adjust() to be a simple hue, and restored <hue-adjuster>? to color-mix.

[svgeesus]

Good points.

Percentages and color-adjuster are no longer optional. Color space is still optional, with LCH as the default.