[CSS21] further explanation of Issue 225

Issue 225 concerns the auto height calculation rules in 10.6.3, which 
are flawed in respect of margin collapsing.

The issue was closed since the WG couldn't see what the problem was. 
Looking at my original post [1] for this Issue, I realize that my 
description was faulty; sorry about that.

Specifically, in the last paragraph, I claimed that the spec was wrong 
due to the second sentence, but my explanation was muddled.  I should 
have said:

"Without this edit the spec is wrong – specifically, in the second 
sentence – since the parent element in question might have overflow 
other than visible (for example) and have a first child with positive 
top margin height."

Such a case is intended to fall under the second sentence but doesn't 
because the parent need not have a positive top padding or border; the 
fact that it's a BFC alone is enough to prevent margin collapsing 
between its own top margin and its first child's top margin.

I continue to claim that the spec should simply refer to the generic 
situation in which margin collapsing is prevented, rather than get 
bogged down in the specific situations that cause that to occur – which 
are adequately explained elsewhere.

However, that said, this issue has in fact been superseded by 
http://lists.w3.org/Archives/Public/www-style/2011Feb/0492.html, as-yet 
unfiled.

Cheers,
Anton Prowse
http://dev.moonhenge.net

Received on Tuesday, 15 March 2011 22:03:36 UTC