[css-values-5] Specify how colons/semicolons serialize in functions

[tabatkins]

The *-interpolate() functions and if() have colons and semicolons, used similarly to how they're used in properties. We don't currently have generic rules for how these are serialized, but we should probably just match how properties work - no space before, one space afterwards. (And for if(), probably omit the trailing semicolon on the last value.)

(This is mostly just a note for @fantasai and I to handle this later.)

[Shrinivassab]

Hi @tabatkins @fantasai,

I have been following this issue (#6245) and the related mix()/@timeline proposals. To help move this forward, I would like to contribute by:

1. Documenting the consensus behavior for:

   • How *-interpolate() serializes colons/semicolons (ref [css-values-5] Specify how colons/semicolons serialize in functions #12345)
   • The default easing curves for interpolation

2. Adding practical examples to the spec:

   /* Example: Fluid typography with easing */
   font-size: interpolate(
     viewport-width 400px to 1200px ease-in-out, 
     1rem, 2rem
   );

Before I submit a PR:

• Is this aligned with the WG’s current direction?
• Should I focus on mix() or interpolate() syntax?
• Any specific formatting preferences for the examples?

Happy to implement whatever the group prefers!

[astearns]

@Shrinivassab you have at least twice now commented on issues linking back to the issue itself without adding anything to the discussion. This isn’t helpful. If you would like to work up a practical example that might be useful, but please add the example as a comment here instead of creating a PR.