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

Re: Control over collapsing margins

From: Giovanni Campagna <scampa.giovanni@gmail.com>
Date: Tue, 28 Apr 2009 15:36:14 +0200
Message-ID: <65307430904280636o2696538bs1170bc63b1ca7e6@mail.gmail.com>
To: Niels Matthijs <niels.matthijs@internetarchitects.be>
Cc: Anton Prowse <prowse@moonhenge.net>, www-style@w3.org
2009/4/28 Niels Matthijs <niels.matthijs@internetarchitects.be>:
> -----Original Message-----
> From: www-style-request@w3.org [mailto:www-style-request@w3.org] On
> Behalf Of Anton Prowse
> Sent: 23 April 2009 14:57
> To: www-style@w3.org
> Cc: www-style@w3.org
> Subject: Re: Control over collapsing margins
>> We really need some concrete real-world examples and detailed
> use-cases
>> in order to assess the best way forward.  Trouble is, although I've
>> needed to suppress margin collapsing lots of times, I struggle to
>> remember now the exact reason and so I can't propose any use-cases off
>> the top of my head. I would guess many others are in the same boat;
> this
>> issue tends to be very situation-specific.
>> Cheers,
>> Anton Prowse
>> http://dev.moonhenge.net
> The real world examples are quite simple. Whenever you have a visual box
> only separated by background color (fe, body bg is black, box bg is
> #666) the intended results fails when elements within the visual box are
> positioned using margins.
> body {background:#000;}
> body .box {background:#666; margin:1em;}
> body .box>* {margin:1em;}
> html example here:
> http://users.telenet.be/onderhond/collapsing_margins.html
> This is probably a problem I run into every project. It is of course
> highly dependent on your way of coding, but like I said earlier, margins
> are really the way to go if you want to achieve flexible css code.

For the moment, you can go with overflow:auto on the .box, to make it
a BFC and avoid margin-collapsing. You just need to set height always
to auto (to avoid overflow).
In the future, I think that something similar to hasLayout (to create
arbitrary BFCs) should be introduced.

Floats are still a problem, but if you're visually distinguishing the
box from its parent, probably you want floats inside it. On the other
hand, setting a "layout-mode:block-formatting-context" should help in
many float-based layouts (when you're struggling with backgrounds that
don't extend to the bottom of the highest float)

> I know this problem isn't all that flashy or cool as SVG graphics or any
> other nifty css 3 feature, but it seems that we would actually benefit
> from a more solid base than excessive css 3 features while we can't even
> control our margins.
> Greets,
> Niels Matthijs
Received on Tuesday, 28 April 2009 13:36:55 UTC

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