17130 2012-05-21 10:46:30 +0000 Margin collapsing: clarify the transitivity 2012-12-04 00:54:31 +0000 1 1 1 Unclassified CSS CSS Level 2 unspecified PC Windows 3.1 NEW P2 normal --- 1 antonsforums bert public-css-bugzilla oldest_to_newest 67946 0 antonsforums 2012-05-21 10:46:30 +0000 Reported by Anton Prowse 8.3.1 says: # In CSS, the adjoining margins of two or more boxes (which might or # might not be siblings) can combine to form a single margin. Margins # that combine this way are said to collapse, and the resulting # combined margin is called a collapsed margin. # # Adjoining vertical margins collapse, except: # [omitted cases] # A collapsed margin is considered adjoining to another margin if any # of its component margins is adjoining to that margin. # # Note. Adjoining margins can be generated by elements that are not # related as siblings or ancestors. This recently-rewritten text has made a clear distinction between adjointness and margin collapsing, employing the former as a tool to define the latter. This was a good idea, but it doesn't quite achieve its goals: there still remains some vagueness about whether either concept is transitive. Note there doesn't seem to be any particular advantage in making adjointness transitive, and the disadvantage is that it becomes a less useful tool for defining collapsing since it becomes too similar to collapsing. (8.3.1 is a pretty hard section to word satisfactorily, so the more useful the tool, the better.) I propose we make it clearer that adjointness is non-transitive and collapsing is transitive. Conversation begins: Bug description: http://lists.w3.org/Archives/Public/www-style/2012Mar/0057.html