If I write the following in a CSS stylesheet: @supports (display: contents) { display: contents; } WebKit will incorrectly claim to support `display: contents` and apply the styles inside that `@supports` block. As WebKit doesn't actually support this property, and instead falls back to `display: inline` which breaks many layouts dependent on `display: contents`, this feature query should not pass.
Could you please clarify which Safari version are you seeing this with? In particular, is this with shipping Safari/WebKit, STP or nightly builds?
Created attachment 333967 [details] Comparison of my test page between Firefox and Safari Yep, this bug affects the shipping version of Safari on both iOS and macOS. I've created a test case at https://low-organization.glitch.me/ that demonstrates the bug, as you can see in the attached screenshot.
Rhys, do you have a testcase? Seems like the glitch link expired. To me, it sounds like display: contents is not behaving as expected, because WebKit does actually support display: contents.
The relevant test site no longer exists. We can't take further action on this bug report.