[css-grid-1] Define computed value of grid-template-rows/columns

[fantasai]

The computed value of grid-template-rows/columns is somewhat handwavy. It's not exposed by getComputedStyle() since that returns the resolved value, but we should be more precise here so that it's clear e.g. minmax(auto, auto) [] 4px can interpolate with auto 10px.

[fantasai]

So I checked in changes to clarify this, currently the spec says

the keyword none or a list, alternating each item as either a (potentially empty) list of identifiers or a minmax() or repeat() notation, representing each <track-size> as a minmax() notation and each <length-percentage> computed

It needs some follow-up to clarify that the computation nests into repeat(), and that there is a name list at both the start and end of each track listing (at the top level and within each repeat).

Gonna file a separate issue on interpolation.

[tabatkins]

Agenda+ to confirm that our edits are good.

[fantasai]

Filed #3201 on interpolation.

[css-meeting-bot]

The CSS Working Group just discussed Define computed value of grid-template-rows/columns, and agreed to the following:

• RESOLVED: Accept this edit: https://github.com/w3c/csswg-drafts/commit/63a1d65afa5997a56b210c1cbddccdb2603ecec9

The full IRC log of that discussion

<dael> Topic: Define computed value of grid-template-rows/columns
<dael> github: https://github.com//issues/3154#issuecomment-428002686
<dael> fantasai: As part of fix computed values I noticed this. Wanted to cross check witht he group this seemed reasonable
<dael> fantasai: Current ED says [reads]
<astearns> https://github.com/w3c/csswg-drafts/commit/63a1d65afa5997a56b210c1cbddccdb2603ecec9
<dael> fantasai: What this means is no distinction in computed value of 50px and minmax(50px)50px. functionally same so shouldn't be a distinction
<fantasai> minmax(50px,50px)
<dael> astearns: Any idea about what's impl?
<dael> fantasai: Didn't check
<dael> fantasai: It's hard to check because gCS is the used value for these prop so can't retrive computed value
<dael> fantasai: Main check would be animating between. Not sure animation is well supported
<dael> fantasai: This would clarify
<dael> rego: I think animations aren't working on any mpl yet so hard to check
<dael> astearns: I like the clarification and seems reasonable to me. Haven't thought through implications for animations
<dael> fantasai: What this does is makes it as likely as possible to animate between 2 values so that functionally same values compute to each other. Everything matchs so values that mean the same are represented same.
<dael> fantasai: Additional magic we might want for animating, but that's issue #3201. Computed value that's best we can do to make animation as easy as can be
<dael> astearns: Other comments?
<dael> astearns: Concerns?
<dael> emilio: Can test be written? All this is tricky and to get interop tests would be best
<dael> fantasai: Tests would be for animation and this is not being animated as far as I know. Be we can write tests
<dael> astearns: When someone impl animations for these properties tests will need to be written
<emilio> yeah, fair enough
<dael> astearns: Concern or objection on taking this edit: https://github.com/w3c/csswg-drafts/commit/63a1d65afa5997a56b210c1cbddccdb2603ecec9 ?
<dael> RESOLVED: Accept this edit: https://github.com/w3c/csswg-drafts/commit/63a1d65afa5997a56b210c1cbddccdb2603ecec9
<fantasai> https://github.com//issues/3201
<dael> fantasai: Issue #3201 is looking for impl feedback