In https://bugs.webkit.org/show_bug.cgi?id=220376 WebKit's UA stylesheet was tweaked to avoid mismatches between which <select> elements the UA stylesheet styles as a listbox and what the rendering engine decides is a listbox based on the rules specified in the HTML standard. But there's still a mismatch, for example if there's trailing whitespace or an infinite number of other attribute values that are parsed one way or the other for the size="" attribute. Chromium and Gecko instead support a UA-level-only pseudo-class that matches <select> elements that are listboxes, which solves the mismatch problem. In https://github.com/w3c/csswg-drafts/issues/7422 it's proposed that such a pseudo-class should be standardized and also exposed to author-level CSS, but the CSS WG is hesitant to standardize it because there are already many pseudo-classes and it's not clear if it solves a common problem for web developers. Nevertheless, I think a UA-level-only pseudo-class makes sense, and would improve WebKit's <select> rendering interop with Chromium and Gecko.
This seems reasonable. I think we could also add WPT for any interop issues?
Sure. I've opened a wpt PR for the spec's current default styles for <select> (which are incomplete) at https://github.com/web-platform-tests/wpt/pull/35801 I can add a test for this also, e.g. a reftest similar to: http://software.hixie.ch/utilities/js/live-dom-viewer/saved/10763
<rdar://problem/100521615>
(In reply to Simon Pieters (:zcorpan) from comment #2) > I can add a test for this also, e.g. a reftest similar to: > http://software.hixie.ch/utilities/js/live-dom-viewer/saved/10763 PR here: https://github.com/web-platform-tests/wpt/pull/36256
https://wpt.fyi/results/html/rendering/widgets/the-select-element?label=master&label=experimental&aligned=