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Re: bolder/lighter defintion

From: Chris Lilley <chris@w3.org>
Date: Mon, 25 May 2009 18:56:21 +0200
Message-ID: <1786271055.20090525185621@w3.org>
To: Zack Weinberg <zweinberg@mozilla.com>
CC: Thomas Phinney <tphinney@cal.berkeley.edu>, W3C Emailing list for WWW Style <www-style@w3.org>
On Monday, May 18, 2009, 8:06:06 PM, Zack wrote:

ZW> Thomas Phinney <tphinney@cal.berkeley.edu> wrote:

>> > The CSS font-weight property does not take arbitrary numeric values,
>> > only "nice even 100s".

>> Why? That seems like yet another way of ensuring that different UAs
>> get different results with the same CSS+fonts.

ZW> My understanding is that CSS contemplates nine possible font weights,
ZW> which happen to be assigned the ordered sequence of labels 100,
ZW> 200, ... 900. 

That is correct, and at the time of writing it was asserted that fonts used only multiples of 100. However, in practice, they use other values as well.


ZW>  These don't (as far as I know) line up neatly with the
ZW> weight properties in any font format, 

The 100..900 values in CSS2 were directly modelled on those in TT/OT.

ZW> so there has to be some mapping
ZW> established by the UA.  There are guidelines for that mapping in the
ZW> spec, but it may not be possible to nail things down perfectly.

There are guidelines for the mapping in the CSS2 spec, which look well and good until a close reading shows that they are just an example and not actually testable. 

CSS3 Fonts responds to that by pulling even the suggested mapping. I don't think that is a good idea. It makes the spec less testable and implementations will have an undesired point of variation. 

I would prefer to see the mapping made normative.



-- 
 Chris Lilley                    mailto:chris@w3.org
 Technical Director, Interaction Domain
 W3C Graphics Activity Lead
 Co-Chair, W3C Hypertext CG
Received on Monday, 25 May 2009 16:56:50 GMT

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