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[css3-mediaqueries] Re: Media queries using relative units

From: Maciej Stachowiak <mjs@apple.com>
Date: Wed, 16 May 2012 16:11:26 -0700
Cc: www-style list <www-style@w3.org>
Message-id: <6B7A0CCC-ABF4-42A8-955C-AE2F4AD5E891@apple.com>
To: Hugh Guiney <hugh.guiney@gmail.com>

On May 16, 2012, at 3:53 PM, Hugh Guiney <hugh.guiney@gmail.com> wrote:

> Not sure if this is already on your radar, but if you're working on
> relative-unit MQ parsing in WebKit, it would be awesome to see a fix
> for this bug along with it. :)
> https://bugs.webkit.org/show_bug.cgi?id=41063

By my reading of the Media Queries spec (in particular the statement below), this bug is invalid. The em unit used for media queries should be based on the initial value of font-size, which should not be affected by a user zoom operation. But I'm not a CSS expert so I might be misunderstanding. Clarification from folks who know more about media queries would be welcome.

Regards,
Maciej

> 
> On Wed, May 16, 2012 at 4:54 PM, Maciej Stachowiak <mjs@apple.com> wrote:
>> 
>> 
>> My mistake, this is defined in the Units section:
>> 
>> "Relative units in media queries are based on the initial value, which means that units are never based on results of declarations. For example, in HTML, the ‘em’ unit is relative to the initial value of ‘font-size’."
>> 
>>  - Maciej
>> 
>> On May 16, 2012, at 1:42 PM, Maciej Stachowiak <mjs@apple.com> wrote:
>> 
>>> 
>>> How are media queries using relative units supposed to be computed? The draft says:
>>> 
>>> "The ‘em’ value is relative to the initial value of ‘font-size’."
>>> <http://www.w3.org/TR/css3-mediaqueries/#width>
>>> 
>>> However, this statement is contained in an example. So it's not clear if this is meant to be a normative requirement or a fact that happens to be true for some other (non-obvious) reason, and it's not clear if it applies to all uses of relative units or only the specific example.
>>> 
>>> Regards,
>>> Maciej
>>> 
>>> 
>> 
>> 
> 
Received on Wednesday, 16 May 2012 23:11:52 GMT

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