[csswg-drafts] Allow authors to configure a few settings from within CSS (CSS `@config`) (#9109)

bramus has just created a new issue for https://github.com/w3c/csswg-drafts:

== Allow authors to configure a few settings from within CSS (CSS `@config`) ==
_(This was originally presented during the lightning round at the 2023 F2F in Cupertino)_

This is a bit of controversial idea that has been lingering in the back of my mind. Basically, I’ve seen the need for authors to configure some things on a page, and it would be nice if they could do that from within CSS.

I am thinking of configuration settings like MPA View Transitions or other things that typically go into a meta tag. An example here is the switch to control the viewport resizing behavior when the virtual keyboard gets shown (see https://drafts.csswg.org/css-viewport/#interactive-widget-section)

I haven’t thought this entirely through *(insert chuckle by some of you here)* but am thinking of an `@config` at-rule for that. In it, you could put some things like the `interactive-widget` configuration.

```css
@config {
  interactive-widget: resize-viewport;
}
```

To make it a bit more controversial – because why not? – maybe it could also be extended to include some global rendering settings/switches? I am thinking of things like being able to choose the type of scrollbars, change where PosFixed should be laid out against, or maybe even crazy things like disabling margin collapsing entirely (:evil:)?

```css
@config {
  scrollbar-type: overlay;
  margin-collapse: off; 
  view-transitions: same-page, same-origin;
  interactive-widget: resize-viewport;
  fixed-pos: layout-viewport;
  …
}
```

There of course should be some requirements concerning this at-rule. Most values in it should only be set once, and cannot be changed on the fly. For example, you don’t want to change the scrollbar type during the lifetime of a page. Some descriptors otoh _might_ be eligible to being changed. I am thinking of the MPA view transitions settings. For that to work properly, the at-rule would need to be able to cascade.

I know something similar has been suggested in the past. There’s a `@css3` entry in the FAQ on the wiki – https://wiki.csswg.org/faq#versioning-css-fixing-design-mistakes

It was discarded at the time, but I think this might work in todays browsers;
- This here is not an all or nothing opt-in, but allows you to cherry pick what you want to change.
- No rulesets would go in this `@config` block, only config-descriptors.
- Authors have `at-rule()`, which allows them to sniff out support for certain config-descriptors

On the downside, I do definitely see that things like changing margin collapsing would but a burden on devs, as they would need to maintain two code paths for quite some time. Don’t let such a descriptor discard all possible other ones that might make more sense.

Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/9109 using your GitHub account


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Received on Tuesday, 25 July 2023 00:25:10 UTC