Bug 286403 – :has(:empty) still applied after the content is changed to not be empty

• Status: RESOLVED
• Resolution: FIXED
• Component: CSS

[Keavon]

Minimal reproduction:

Fiddle:
https://jsfiddle.net/5n1tb2sd/

HTML:
[<span>{<em></em>}</span>]

CSS:
span:has(em:empty) { color: red }

JS:
setTimeout(() => { document.querySelector("em").innerText = "no longer :empty so span shouldn't render this as red" }, 1000);

The expected behavior is that the curly brackets start out red for the first second, then the text appears (making <em> no longer :empty) and everything should become black. This works in Chrome and Firefox.

It is broken in Safari Version 18.1 (20619.2.8.11.10) which is the latest I can test through BrowserStack, it keeps the curly brackets and the added text red until I manage to force a repaint. Sometimes, merely opening dev tools causes it to repaint. Other times, I have to inspect the element and begin assigning it some CSS property or toggle an existing CSS property to force a repaint. To be clear, the red style is not applied to the <span> in dev tools, but it has been incorrectly painted red until the next repaint can be forced.

[Alexey Proskuryakov]

Resizing the window doesn't make the issue go away, so this is more than a repaint issue.

[Karl Dubost]

That seems related/similar to Bug 286047

[Radar WebKit Bug Importer]

<rdar://problem/143864358>

[Peter-Paul Koch]

I also encountered this bug and have more information as well as a simple test case and a workaround at https://quirksmode.org/browserbugs/safari-has-empty.html

Summary:
- y:has(x:empty) is checked for emptiness only one, between DOMContentLoaded and load.
- Emptiness is resolved incorrectly if element x is filled by a JavaScript onload AND the body  overflows the html vertically, but not horizontally.
- If this is the case AND element y has CSS lengths in viewport units AND element x is currently filled, resizing the window updates the styles of element y once.
- a special case applies if y has display: none; see page

I probably got some of the details wrong, but I'm fairly certain of the gist.

[Simon Fraser (smfr)]

*** Bug 311750 has been marked as a duplicate of this bug. ***

[Simon Fraser (smfr)]

Pull request: https://github.com/WebKit/WebKit/pull/62402

[Antti Koivisto]

Pull request: https://github.com/WebKit/WebKit/pull/62436

[EWS]

Committed 310932@main (cc50c7dd8a0c): <https://commits.webkit.org/310932@main>

Reviewed commits have been landed. Closing PR #62436 and removing active labels.

[EWS]

Committed 305413.653@safari-7624-branch (9679268f8b84): <https://commits.webkit.org/305413.653@safari-7624-branch>

Reviewed commits have been landed. Closing PR #4921 and removing active labels.