[meandmycode]

I'm dubious that a constraints system would ever be considered, CSS has so far had some strong goals around it's predictably on layout cost.. that said, Houdini layout proposal is the closest to your comment, offloading layout to an isolated js context https://github.com/w3c/css-houdini-drafts/blob/main/css-layo... .. but honestly flex and grid, plus other things like containment have solved so many things for folks now that there's just far less demand for improvement than the days before flex

[madeofpalk]

Oh man - I remember attending a CSS meetup in like 2014 at the Google offices in Sydney where someone from the CSS WG presented Houdini Layout. I would be surprised if that ever ships.