[css-multicol-2][css-scroll-snap] Snapping to column boxes

[fantasai]

It's been brought up a few times before, most recently in #5911, that it would be useful to set snapping controls on the individual columns of a multi-column element to enable, for example, using multicol as a pagination mechanism with snapping between "pages".

The most straightforward way to do this would be to add a pseudo-element (e.g. ::column or ::nth-column(An+B) that represents each column. It could initially accept only the properties in css-scroll-snap, though we'll likely want to extend it to accept other properties in the future as well.

Thoughts?

p.s. With a generic name like that, though, we'll have to contend with also the question of whether to extend this to grid tracks, flex lines, and/or table rows and columns. (It's not so necessary to have this feature there, because they typically have elements we can snap to instead.)

[rachelandrew]

Yes, very much a fan of this, the scrolling to a column thing has been mentioned to me a number of times. I like the approach of adding a pseudo-element as that could potentially enable a few other things people want to do.

In terms of extending this to grid tracks and so on, perhaps this is two separate things. One is adding to multicol a pseudo-element so we can target a particular column box, the second is to add the snapping to a identified column/track/flex line.