Should `text-decoration-thickness: auto` and `from-font` round to device pixels and ensure >= 1px?

[Loirooriol]

https://drafts.csswg.org/css-text-decor-4/#text-decoration-thickness-property says this for lengths and percentages:

The UA should round the actual value to the nearest integer device pixel, and ensure it is at least one device pixel.

However, I don't see anything similar for auto nor from-font.

In servo this means that the thickness can get below 1px and not be painted: servo/servo#29668

I think it would be good to do that for all values, not just lengths and percentages.

L3 doesn't have text-decoration-thickness and leaves it up to the UA, but could also round to >= 1device pixels.

[Loirooriol]

Also, other than rounding thickness to device pixels, should it also be positioned in device pixels, so that it properly lines up with the pixel grid?

[emilio]

I think we just resolved this in #12696

[Loirooriol]

Yes, @fantasai reopen and add your Agenda+ back if there was something missing.