As reported on webcompat.com, the animated submenus on nderf.org are broken on nightly; only a sliver of them draws (just the box-shadow, I believe). They work on stable channel (and other browsers), but not on nightly. I'm not sure what the problem is, or if it's indeed just one problem. Mozregression kept giving me differing (and useless) results, with the only one that seemed potentially related pointing at bug 1274962. As such I'm filing a fresh bug with a reduced test-case. One must hover their mouse over the text "Outer", then the text "Inner 1", then the inner menu ought to animate in. Note that removing the left:100% in the test-case fixes things, as does removing other bits of the transforms.

Bug 1274962 was fixed recently, but this testcase is still not rendering properly. However, I do note that now when I disable this rule, things work: .container3d { transform-style:preserve-3d } Note that I've tried this on several systems, including Linux and OSX and with HWA off.

This bug is still occurring for me on today's nightly; can you recommend someone who could take a look at it, :jet?

Bug 1274962 landed 1 year ago, so it's not that one if the bug doesn't appear in the Release channel. Miko: can you help narrow this down to the right regressing bug?

I am getting the regression on both FF53 and Nightly, on Windows 10 and OSX. We actually have two different bugs here. One is incorrect rendering of the second submenu, and the other one is erratic hit testing. The behavior of hit testing seems to change depending on if the submenu is opened by hovering over the text or the bullet. This regression seems to be at least partially caused by the changes in bug 1313753. I tried backing out the changeset for that bug, and that seems to fix the rendering problems. Thinker, do you have any idea what might be causing this?

I think it is duplication of bug 1358102. I would try to spend a bit time on it in following days.