[css-colors-5] Minor syntax problems

[cdoublev]

1. <color> is missing <color-mix()>.

2. <cmyk-component> is missing none (also applies to the <alpha-value> of device-cmyk()).

All color functions (with the exception of those using the legacy color syntax) allow any of their components to be specified as none.

https://drafts.csswg.org/css-color-4/#missing

3. <custom-params> should define a list of whitespace (vs. comma) separated parameters (+ instead of #).

4. <rectangular-color-space> is defined in CSS Color 4 with a wider range of values than in CSS Color 5.

[LeaVerou]

2. <cmyk-component> is missing none (also applies to the <alpha-value> of device-cmyk()).

At this point, we should probably define tokens for color components and use those instead of repeating them in component definitions, which is error prone.

I.e.:

<color-component-percentage>: <percentage> | none
<color-component-number>: <number> | <percentage> | none
<color-component-angle>: <angle> | <percentage> | none

Legacy ones can probably stay as-is.

Agreed to all other remarks as well. Would you like to send a PR for 1, 3, 4 or should I (or @svgeesus) make the changes?

4. <rectangular-color-space> is defined in CSS Color 4 with a wider range of values than in CSS Color 5.

These kinds of things crop up so frequently that I'm starting to think Bikeshed needs some kind of templating/abstraction mechanism. Thoughts, @tabatkins ?

[cdoublev]

Would you like to send a PR for 1, 3, 4 or should I (or @svgeesus) make the changes?

Please do the changes. Productions for each color channel do not make the syntax more readable (imo) but it is less error prone, indeed.

lab() = lab( <color-component-number>
      <color-component-number>
      <color-component-number>
      [ / <color-component-alpha> ]? )

lab() = lab( [<percentage> | <number> | none]
      [ <percentage> | <number> | none]
      [ <percentage> | <number> | none]
      [ / [<alpha-value> | none] ]? )

[svgeesus]

Thanks, fixed!

[cdoublev]

Nit:

- device-cmyk() = device-cmyk( <cmyk-component>{4} [ / <alpha-value> | none ]? )
+ device-cmyk() = device-cmyk( <cmyk-component>{4} [ / [ <alpha-value> | none ] ]? )

Also, this is not strictly related but would be helpful:

- device-cmyk() = device-cmyk( <cmyk-component>{4} [ / [ <alpha-value> | none ] ]? )
+ device-cmyk() = <legacy-device-cmyk-syntax> | <modern-device-cmyk-syntax>
+ <legacy-device-cmyk-syntax> = device-cmyk( <number>#{4} , <alpha-value>? ) |
+                               device-cmyk( <percentage>#{4} , <alpha-value>? ) |
+ <modern-device-cmyk-syntax> = device-cmyk( <cmyk-component>{4} [ / [ <alpha-value> | none ] ]? )
  <cmyk-component> = <number> | <percentage> | none

However I am not sure its legacy syntax should allow <percentage>.

[svgeesus]

However I am not sure its legacy syntax should allow .

The legacy syntax, which was implemented in some CSS to PDF tools, did not allow percentage for the color components (and did not allow alpha at all, in fact).