RE: [css3-backgrounds] Should a non-zero border-radius create a new stacking context ?

What complexity would have been added for authors by creating new stacking contexts for overflow != visible ?

I'd argue the latter is what is actually expected by most, especially so when overflow == hidden. Having outside elements layer underneath the children of an element with overflow:hidden - never mind clipped children - is neither easy to explain nor is it common practice.

Not sure what we mean by 'reasonable behavior'. Reasonable for authors or implementors ?

From: [] on behalf of Robert O'Callahan []
Sent: Monday, November 22, 2010 2:52 PM
To: Sylvain Galineau
Cc: Brad Kemper;
Subject: Re: [css3-backgrounds] Should a non-zero border-radius create a new stacking context ?

On Tue, Nov 23, 2010 at 9:57 AM, Sylvain Galineau <<>> wrote:

I disagree that this adds complexity for authors; we can't argue that creating a stacking context for overflow != visible would have simplified things *and* that doing so in some cases makes them unacceptably harder. Especially when existing, heavily-used properties already do this.

Forcing stacking contexts for overflow != visible would have simplified things for implementors, and added complexity for authors. (Although I claim that special-casing border-radius + overflow-not-visible is more surprising than just special-casing overflow-not-visible.)

If the side effects of creating a new stacking context is so likely to break pages then opacity and transforms are equally problematic for authors. If so I'd like to see evidence that working around this is a common issue for authors; I'm not claiming such evidence does not exist btw. Pointers definitely welcome.

I do not claim that forcing a stacking context for border-radius + overflow-not-visible is likely to break existing pages.

 In the absence of said evidence, a cogent argument as to why taking this kind of risk is acceptable in some cases but not others - opacity is very heavily used, at least as much as border-radius if not more so - would be most helpful.

As I explained above, AFAIK the primary reason for making opacity < 1 force a stacking context is that it's impossible to define reasonable behavior otherwise. This is not a problem for border-radius + overflow-not-visible.

"Now the Bereans were of more noble character than the Thessalonians, for they received the message with great eagerness and examined the Scriptures every day to see if what Paul said was true." [Acts 17:11]

Received on Tuesday, 23 November 2010 02:03:44 UTC