User-Agent: Mozilla/5.0 (Windows NT 5.2; WOW64; rv:2.2a1pre) Gecko/20110402 Firefox/4.2a1pre
I presume that the ancient behaviour was okay. See following test:
Created attachment 523831 [details]
z-index with transform
Created attachment 523832 [details]
z-index without transform
Any value other than ‘none’ for the transform results in the creation of both a
stacking context and a containing block.
so the behavior you see is correct as far as I can tell.
Er, wrong resolution.
Okay, the behavior of Presto is similar, but Gecko 1.9.x et Webkit are a behavior different.
It is strange to see like that with floating ojects.
Oups, sorry, it's only with Webkit.
I filed https://bugs.webkit.org/show_bug.cgi?id=57730
I think that creating a stacking context is not enough for z-index to apply. For example, z-index does not apply to an element with opacity:0.5 but position:static.
OK. Note that Opera, IE9, and we all apply z-index to transformed content (presumably because the spec says it needs to act like position:relative).
I guess we should see where the discussion on www-style ends up.