Re: [csswg-drafts] [css-values-5] issues with interpolation rules for calc-size() (#10220)

Ah, ok.  This is what happens when the spec gets written halfway through the implementation and I don't carefully reread all the bits I've already implemented before the spec existed.

That said, the behavior specified here behaves weirdly for percentages -- an animation between `100%` and `calc-size(fit-content)` possibly (though not clearly!) has percentageness at one endpoint of the animation, but doesn't have percentage-ness at any intermediate point nor at the other endpoint.  (Chromium code [has a `DCHECK()`](https://source.chromium.org/chromium/chromium/src/+/main:third_party/blink/renderer/core/animation/interpolable_length.cc;l=614-615;drc=39dd0ed2be3769779aa9019ef69ff9ba5bd09209) asserting that this doesn't happen, which is what led me to this issue in the first place.)

As to clarifying the sentence to be clearer, how about (ignoring any of the other issues):
> Some [`calc-size()`](https://drafts.csswg.org/css-values-5/#funcdef-calc-size) values can also be interpolated with a [`<length-percentage>`](https://drafts.csswg.org/css-values-4/#typedef-length-percentage) or an [`<intrinsic-size-keyword>`](https://drafts.csswg.org/css-values-5/#typedef-intrinsic-size-keyword).  To determine whether the values can interpolate and what the interpolation behavior is, treat the non-`calc-size()` value *value* as `calc-size(` *value* `)` and apply the rules above.

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Received on Tuesday, 16 April 2024 21:25:57 UTC