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Re: [css-device-adapt] Accepting semi-colons as a separator for meta-viewport

From: Rune Lillesveen <rune@opera.com>
Date: Fri, 21 Oct 2011 11:29:07 +0200
To: "Peter Beverloo" <beverloo@google.com>, "Tab Atkins Jr." <jackalmage@gmail.com>
Cc: www-style@w3.org
Message-ID: <op.v3o3atvy8isf1p@id-c1005.oslo.osa>
On Thu, 20 Oct 2011 23:36:34 +0200, Tab Atkins Jr. <jackalmage@gmail.com>  

> On Thu, Oct 20, 2011 at 10:12 AM, Peter Beverloo <beverloo@google.com>  
> wrote:
>> The CSS Device Adapt specification defines a parsing algorithm[1] for
>> the meta-element viewport content, which has been based on WebKit's
>> implementation that shipped with iOS4. This algorithm only accepts
>> commas as separators between properties.
>> In reality, web authors are using both commas as semi-colons. A wide
>> range of websites, including CNN[2], Flickr[3] and Reddit[4] depend on
>> this behavior, which has led at least Mozilla and Microsoft to
>> implement it and, in case of the latter, write about it[5].
>> I think the specification should adapt to reflect what authors are
>> doing. While it's unfortunate that the divergence between commas and
>> semi-colons happened, it's important for compatibility among mobile
>> browsers.
>> Thanks,
>> Peter
>> [1] http://dev.w3.org/csswg/css-device-adapt/#parsing-algorithm
>> [2] http://m.cnn.com
>> [3] http://m.flickr.com
>> [4] http://www.reddit.com/.compact (or http://m.reddit.com/)
>> [5]  
>> http://blogs.msdn.com/b/iemobile/archive/2010/11/22/the-ie-mobile-viewport-on-windows-phone-7.aspx
> Agreed that we should match current behavior, whatever it is.

There is no current behavior that matches all implementations. The current  
description matches Safari and Opera. If you add ';' as a valid separator,  
you'll probably describe Android WebKit and Fennec. I haven't analyzed  
those implementations in detail, so I don't know if there are other  
differences. The constraining procedure using the parsed values also  
differ, so it's not always easy to tell without looking at the source code.

> Hopefully by getting a single correct description of the necessary
> parsing algorithm we can get proper interop between everyone that
> prevents it from drifting further.

Depends on what you mean by a single correct description since the current  
implementations are not interoperable. You have to choose between one  
describing one of the existing implementations or choose an algorithm  
which matches neither.

Rune Lillesveen
Layout Group Manager
Core Technology Department
Opera Software ASA
Received on Friday, 21 October 2011 09:29:47 UTC

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