We should support at least appearance auto and none, which are aliases that override -webkit-appearance.
FYI: Chrome is going to ship 'appearance' property soon.
FYI https://bugs.chromium.org/p/chromium/issues/detail?id=963551 is now fixed and looks like it's targeting M84 (reaching stable mid-July per https://www.chromestatus.com/features/schedule )
I think trying to coordinate on the timing on this can reduce compat problems, and allow for clearer messaging to web developers to start using unprefixed appearance.
Issue for Gecko: https://bugzilla.mozilla.org/show_bug.cgi?id=1620467
(In reply to Simon Pieters from comment #4)
> Issue for Gecko: https://bugzilla.mozilla.org/show_bug.cgi?id=1620467
FYI this landed last week, and so will make it to release for Firefox 80.
> We should support at least appearance auto and none, which are aliases that override -webkit-appearance.
We already support none; we should however probably add support (to -webkit-appearance) for auto as this is the one value we don't already support.
IIRC, this probably means moving the current -webkit-appearance into an internal property (which defines which appearance is _actually_ used, including which widget) and then we can start iterating from there.
The spec is getting close to done now, and wpt tests exist.
+ various tests in https://wpt.live/css/css-ui/
`<progress>` and `<meter>` might be changed in the spec, see https://github.com/w3c/csswg-drafts/pull/6537#issuecomment-931716364
'-webkit-appearance` was unprefixed in https://bugs.webkit.org/show_bug.cgi?id=231534.