16226 2012-03-04 10:55:11 +0000 Margin collapsing: Clarify Note in 8.3.1 to use computed values of properties 2012-12-04 00:51:17 +0000 1 1 1 Unclassified CSS CSS Level 2 unspecified All Windows 3.1 NEW P2 normal --- 1 antonsforums bert public-css-bugzilla oldest_to_newest 64990 0 antonsforums 2012-03-04 10:55:11 +0000 Reported by Anton Prowse 8.3.1 says, in the long Note: # - The bottom margin of an in-flow block box with a 'height' # of 'auto' and a 'min-height' of zero collapses with its # last in-flow block-level child's bottom margin if the box # has no bottom padding and no bottom border and the child's # bottom margin does not collapse with a top margin that has # clearance. # - A box's own margins collapse if the 'min-height' property # is zero, and it has neither top or bottom borders nor top # or bottom padding, and it has a 'height' of either 0 or # 'auto', and it does not contain a line box, and all of its # in-flow children's margins (if any) collapse. The values in question of the 'height' and 'min-height' properties are *computed* values, but this is not clear in the prose. Now, the spec often fails to be explicit about values being computed values, and this part of 8.3.1 is just a Note, and the normative prose in 8.3.1 (of which the Note is just a summary of consequences) is explicit in its use of computed values. So this bug does not have especially high importance. However, the distinction of whether it's the used value or the computed value of 'height' used in 8.3.1 is important to the application of 'min-height' and 'max-height' in 10.7, and so clarifying the Note above would remove a potential, albeit small, source of confusion. 64991 1 antonsforums 2012-03-04 10:58:03 +0000 Conversation begins: http://lists.w3.org/Archives/Public/www-style/2012Feb/1153.html Bug description: http://lists.w3.org/Archives/Public/www-style/2012Feb/1342.html (penultimate part) 64992 2 antonsforums 2012-03-04 10:59:16 +0000 See Bug 15746 and Bug 15745 which describe another issues with the note mentioned. 64993 3 antonsforums 2012-03-04 11:02:16 +0000 Proposal: Replace: # - The bottom margin of an in-flow block box with a 'height' # of 'auto' and a 'min-height' of zero collapses with its # last in-flow block-level child's bottom margin if the box # has no bottom padding and no bottom border and the child's # bottom margin does not collapse with a top margin that has # clearance. # - A box's own margins collapse if the 'min-height' property # is zero, and it has neither top or bottom borders nor top # or bottom padding, and it has a 'height' of either 0 or # 'auto', and it does not contain a line box, and all of its # in-flow children's margins (if any) collapse. with: | - The bottom margin of an in-flow block box with a computed | 'height' of 'auto' and a computed 'min-height' of zero | collapses with its last in-flow block-level child's bottom | margin if the box has no bottom padding and no bottom | border and the child's bottom margin does not collapse | with a top margin that has clearance. | - A box's own margins collapse if it has a computed | 'min-height' of zero, and it has neither top or bottom | borders nor top or bottom padding, and it has a computed | 'height' of either 0 or 'auto', and it does not contain a | line box, and all of its in-flow children's margins (if | any) collapse.