[css-color-5] Nested relative colors

[cdoublev]

3. Relative Color Syntax does not define whether nested relative colors are allowed, eg. hsl(from rgb(from var(--brand-yellow) calc(r - 100) g b) h calc(s - 10%) l), and I do not see any example of this in the spec.

Is it fine to assume that this is allowed and that you will later define a maximum of 32 level of nestings, like for math functions?

#3462 addressed maximum parentheses (function and simple block) nestings but only resolved on defining a minimum for calculations.

[svgeesus]

Ah, I see the problem. The RCS productions in CSS Color 5 are linking to the definition of <color> in CSS Color 4 (which does not include RCS).

Yes, if <color> includes rgb() and

rgb( [ from <color> ]? [ <number> | <percentage> | none]{3} 
     [ / [<alpha-value> | none] ]?  )

then nesting is possible (and intended).

We haven't yet discussed a limit on the degree of nesting.

[LeaVerou]

Yeah, RCS, as well as things like color-mix() or contrast-color() all produce <color> values, so any <color> value could use them.

[svgeesus]

c17a10d