Re: [csswg-drafts] [css-grid] Interpolate repeat() (#3503)

Yup, this is unspecified and should be fixed. My intuitions:

> ```
> repeat(2, 2fr 30px)
> repeat(2, 3fr 40px)
> ```

This should definitely interpolate. Same N, contained track list is same length and item-wise interpolable, everything's A-OK.

> ```
> repeat(2, 2fr 30px)
> repeat(4, 40px)
> ```

I could go either way. Fine with this being interpolable in theory (same lengths *once expanded*, expanded track list is item-wise interpolable), but I'd also be fine being simple here and saying no if it would cause implementation difficulties. I'm generally in favor of keeping interpolation simple and obvious if possible, which leans me toward saying "no", and requiring authors to write the second as `repeat(2, 40px 40px)` if they want it to interpolate.

> ```
> repeat(auto-fill, 10px)
> repeat(auto-fill, 20px)
> ```

I think these should interpolate, going from `10px` to `20px`. Yes, the number of tracks can change, but I think that's fine? Track-number determination doesn't happen until used-value time, so interpolation doesn't need to care about it. Leaning on my "should be simple and obvious", these definitely *look like* they're compatible with each other.

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So all in all, the rule I lean towards is "first argument must be identical, second argument must be interpolable as a computed track list; else discrete". So that's yes on Example 1, no on Example 2, and yes on Example 3.

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Received on Friday, 11 January 2019 20:07:19 UTC