User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:48.0) Gecko/20100101 Firefox/48.0 Build ID: 20160413030239 Steps to reproduce: Open testcase. Actual results: Firefox freezes. Expected results: Firefox should not freeze. Pushlog: https://hg.mozilla.org/integration/mozilla-inbound/pushloghtml?fromchange=3baed5c339e31188949641cb7bc7178a71070718&tochange=52c0128aff10f4c50ae3ab34c64cef8844497942

Yeah, I suspected this might happen in bug 1260655 comment 11 but couldn't find a test case to produce it. We'll need to make display not animatable.

MozReview-Commit-ID: HOVHXfoFv5l

MozReview-Commit-ID: HOVHXfoFv5l

Regarding the spec status of this, in bug 1064937 we're going to do an investigation into which properties are animatable in different implementations, send the list to www-style, then update all the CSS specs to indicate which properties are never animatable vs properties that are animatable using 'discrete' animation. See, in particular, bug 1064937 comment 4. In discussion with Google, however, we agree at least that we shouldn't animate CSS animation/transition properties and 'display'. With regards to 'display', it is problematic for at least CSS animations and CSS transitions since it performs playback control there. In discussion with Google earlier in the year they were concerned that it was problematic even for just script-generated animations. I think it's simplest to just disallow 'display' everywhere for now. If it proves possible and desirable to allow it for script-generated animations we can remove the restriction then.

Comment on attachment 8741582 [details] [diff] [review] Don't allow animation of 'display' property Review of attachment 8741582 [details] [diff] [review]: ----------------------------------------------------------------- Please make sure to file a bug on the specs to prevent animation of display.

(In reply to Cameron McCormack (:heycam) from comment #6) > Comment on attachment 8741582 [details] [diff] [review] > Don't allow animation of 'display' property > > Review of attachment 8741582 [details] [diff] [review]: > ----------------------------------------------------------------- > > Please make sure to file a bug on the specs to prevent animation of display. Unfortunately, we don't have a concept of 'not animatable' vs 'discrete animation' in CSS yet. CSS simply has 'Animatable: no' which is ambiguous as to which it means. So the spec bug is basically [1] where I need to go and change all CSS specs from using 'Animatable' to 'Animation type' and introduce the 'none' and 'discrete' types. I've added a note to that issue to make sure 'display' gets the 'none' animation type for this. [1] https://github.com/w3c/csswg-drafts/issues/72

Thanks, sounds good.

I reproduced the initial issue on old Nightly (build ID: 20160413030239). I verified that the issue is fixed using Firefox-48.0b5 on Windows 10 x64, Ubuntu 14.04 x32, Mac 10.11.

Thanks Cipri for testing! Changing tracking flag for 48 to verified and closing this bug as Verified Fixed.