Bug 182816 – `@supports (display: contents)` feature query in CSS incorrectly passes

• Component: CSS
• Status: RESOLVED INVALID

[Rhys Powell]

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.

[Alexey Proskuryakov]

Could you please clarify which Safari version are you seeing this with? In particular, is this with shipping Safari/WebKit, STP or nightly builds?

[Rhys Powell]

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.

[Tim Nguyen (:ntim)]

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.

[Brent Fulgham]

The relevant test site no longer exists. We can't take further action on this bug report.