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RE: [css3-fonts] font-size-adjust auto issue (was: Comments on CSS3 Fonts Module LC)

From: Levantovsky, Vladimir <Vladimir.Levantovsky@monotype.com>
Date: Mon, 19 Aug 2013 13:57:00 +0000
To: John Daggett <jdaggett@mozilla.com>
CC: W3C Style <www-style@w3.org>
Message-ID: <79E5B05BFEBAF5418BCB714B43F4419923DFA2C3@wob-mail-01>
On Monday, August 19, 2013 2:29 AM John Daggett wrote:
> 
> When the author specifies an explicit value for 'font-size-adjust',
> they specify one that matches the first font, such that if the first
> font is around, no adjustment will occur. In the case that it doesn't
> exist, the font size is adjusted so that the fallback fonts match the
> x-height of Verdana at the originally specified font size.  This is
> what Example 3 and Figure 19 show.
> 
> When the author specifies 'auto', *no* font in a given font list
> defined by 'font-family' affects the calculation of the aspect value
> used:
> 
> # Behaves just like <number>, except the number used is the aspect
> # value calculated by user agents for the first font in the list of
> # fonts defined for the initial value of the ‘font-family’ property.
> 

Yes, this is exactly how I understood it and this is why I raised an objection to having the value <auto> defined for 'font-size-adjust' property. Authors who know what they're doing and who know exactly what they want to achieve will use <number> to define the value of the property, but I am afraid that many will be mislead by <auto> definition that promises to "behave just like a <number>" but, in fact, does nothing useful for them. This is exactly the reason I suggested to get rid of <auto> and allow the value to be defined either as <number> or <none>.

> In CSS the term "initial value" means the value of a property when
> there's no explicit definition provided on a given page.  For
> 'font-family' the "Initial" field is defined as "depends on user
> agent" [1]. It's typically defined by user agents to be whatever the
> default serif or sans-serif face is on the platform.
> 
> Ex:
> 
>   font-family:      Verdana, Zapfino, Futura, Times;
>   font-size-adjust: auto;
> 
> The aspect value for 'auto' on OSX is typically that of Times and on
> Windows it's often the aspect value of Times New Roman.  The aspect
> value of Verdana or Zapfino (an irrational number?) has *no* affect on
> that calculation.
> 

So, one will never see the kind of adjustment illustrated by Fig. 19 when using <auto> - why bother having it defined for this property in the first place?

Thank you,
Vlad

> Regards,
> 
> John Daggett
> 
> [1] http://dev.w3.org/csswg/css-fonts/#font-family-prop


Received on Monday, 19 August 2013 13:57:26 UTC

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