W3C home > Mailing lists > Public > www-style@w3.org > April 2009

Re: Control over collapsing margins

From: David Hyatt <hyatt@apple.com>
Date: Wed, 22 Apr 2009 10:33:39 -0500
Cc: Niels Matthijs <niels.matthijs@internetarchitects.be>, www-style@w3.org
Message-id: <F1C1AE6B-881D-49CB-949E-D4FB37372932@apple.com>
To: "Tab Atkins Jr." <jackalmage@gmail.com>
On Apr 22, 2009, at 9:55 AM, Tab Atkins Jr. wrote:

> On Wed, Apr 22, 2009 at 5:27 AM, Niels Matthijs
> <niels.matthijs@internetarchitects.be> wrote:
>> Hi all,
>> I was reading up on collapsing margins as they've been causing me  
>> quite some trouble. Whenever a child element has a different  
>> background styling from its parent, collapsing margins are usually  
>> troublesome. The collapse is broken by padding and borders, but not  
>> by different style of background (which also indicates separation).
>> Rather than change the rules for collapsing, I wonder if it  
>> wouldn't be better to give css people the opportunity to manage  
>> them themselves if needed. In short, introduce a new property which  
>> can break the collapse when needed, because adding unneeded  
>> borders, paddings or overflows is really not the way to go.
>> Further explanations of my view can be found in the following  
>> article:
>> http://www.onderhond.com/blog/work/collapsing-margins-improvement
>> I apologize if this issue was already raised, but couldn't find any  
>> information about it.
> I know that a property to indicate that an element should form a block
> formatting context has been suggested before.  That would prevent
> margins from collapsing, as well as doing a few other things.  Would
> that be acceptable?
> I agree that the ability to stop margin collapsing at will would be
> occasionally useful.  I've had to hack around the problem with 1px
> padding or border before as well.
> ~TJ

These properties exist in WebKit.  I proposed them for standardization  
back when I implemented them and got a lukewarm response, so never  
followed up.  I'll propose them again now in case there is more  


Supported values are:
collapse - Do the collapse as normal.
separate - Don't collapse.
discard - Do the collapse and discard the entire result (this is  
actually how margins in table cells work for many HTML elements in  
quirks mode).

Received on Wednesday, 22 April 2009 15:34:23 UTC

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