hidden=until-found HTML attribute and beforematch event

[josepharhar]

Request for Mozilla Position on an Emerging Web Specification

• Specification Title: hidden=until-found HTML attribute and beforematch event
• Specification or proposal URL: Add hidden=until-found HTML attribute and beforematch event whatwg/html#7475
• Caniuse.com URL (optional):
• Bugzilla URL (optional):
• Mozillians who can provide input (optional): @emilio

Other information

• whatwg/html issue: Proposal: beforematch event and hidden=until-found attribute whatwg/html#6040
• Explainer: https://github.com/WICG/display-locking/blob/main/explainers/hidden-content-explainer.md
• This was originally proposed as the beforematch event and the content-visibility:hidden-matchable CSS property, but was changed to an HTML attribute due to feedback from the CSSWG.
• This is very similar to the auto-expanding details feature, but is a more generic version that can be used outside of details elements: Auto-expanding details elements #578

[annevk]

Thanks for raising this @josepharhar!

As mentioned, this is very similar to auto-expanding details elements which we're supportive of. It's just now something that all elements can make use of.

I suggest we mark this worth prototyping as well, sans dashboard entry.