W3C home > Mailing lists > Public > www-style@w3.org > July 2012

Re: [css3-box] padding: auto

From: Tab Atkins Jr. <jackalmage@gmail.com>
Date: Mon, 16 Jul 2012 16:15:24 -0700
Message-ID: <CAAWBYDC1RzJrhGQWn5eB5VedtH3OENd-FEk8_iztK+7WP9ezCg@mail.gmail.com>
To: Lea Verou <leaverou@gmail.com>
Cc: www-style list <www-style@w3.org>
On Mon, Jul 16, 2012 at 4:07 PM, Lea Verou <leaverou@gmail.com> wrote:
> A common visual design pattern that has emerged in the past few years is the
> content area having a fixed width, with the background extending to cover
> the entire viewport width. Here is a quick list of websites doing this:
> http://lesscss.org/
> http://www.opera.com/
> http://www.mozilla.org/
> http://www.kaleidoscopeapp.com/
> http://daneden.me/type/
> http://www.alfredapp.com/
> http://grabaperch.com/
> http://twostepmedia.co.uk/jsquery/
> http://whiteboard.is/
>
> For given viewport dimensions, this could be done by adjusting the left &
> right padding to be equal to (viewport width - width) / 2. However,
> viewports are not fixed, and therefore authors almost always resort to using
> a wrapper element for the content, with fixed dimensions and margin: auto,
> and assign the background to its parent element. calc() enables this to be
> expressed in pure CSS with something along the lines of:
> width: 20em;
> padding: calc(50vw - 20em / 2);
>
> This is certainly an improvement, but still suboptimal. Not only it’s not
> very readable, but the width needs to be duplicated or assigned to a
> variable to keep the code DRY. Given that this is not an isolated case, but
> an incredibly common pattern, I believe it should be addressed by something
> more straightforward.
>
> Basically, what’s needed is an `auto` value for padding, that makes it
> behave as `auto` does for margin. In the latest ED there *is* a new `auto`
> value allowed for the padding properties [1], but the way it’s supposed to
> work is not explained anywhere.
>
> [1]: http://dev.w3.org/csswg/css3-box/#the-padding-properties

An alternative way to do this would be to have a way to opt-in to
<body>'s special handling, where its background gets hoisted to the
canvas.  That's how you achieve this effect when you're not varying
the background within the page.

~TJ
Received on Monday, 16 July 2012 23:16:11 GMT

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