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Re: [CSS21] last edition: pity

From: Giovanni Campagna <scampa.giovanni@gmail.com>
Date: Sun, 10 May 2009 19:55:21 +0200
Message-ID: <65307430905101055u4f084051q7f3719eb73118087@mail.gmail.com>
To: Bert Bos <bert@w3.org>
Cc: www-style@w3.org
2009/5/7 Bert Bos <bert@w3.org>:
> [...]
>
>> 4. 15 Fonts,
>>     15.6 Font boldness : the 'font-weight' property:
>>       'bolder' selects the next weight that is assigned to a font
>> that is darker than the inherited one.
>>     following sentence removed:
>>       If there is no such weight, it simply results in the next
>> darker numerical value (and the font remains unchanged), unless the
>> inherited value was '900' in which case the resulting weight is also
>> '900'.
>>     [similar in 'lighter']
>>     following paragraph added:
>>       Note: A set of nested elements that mix 'bolder' and 'lighter'
>> will give unpredictable results depending on the UA, OS, and font
>> availability. This behavior will be more precisely defined in CSS3.
>>
>>     - changing _defined_ behaviour to _undefined_ is not an
>> improvement. - css3 reference nonsence.
>>       (imo: if someone tries to turn css2 specification into
>>       'css3 todo list' - shoot, don't talk)
>>     - the weight metric is independent from font[family].
>>       as value of independent metric, 'bolder' SHOULD result next
>> numerical value.
>>       futher - as a hack for non-perfect world - it MAY (or MAY NOT)
>>       yield to next available font's weight.
>>       what was unclean here? why you killing primary objectives of
>>       property/value, leaving only hack description?
>
> Imagine four nested elements, from outside to inside they have
>
>    font-weight: normal
>    font-weight: bolder
>    font-weight: bolder
>    font-weight: lighter
>
> The old spec said the computed value of the innermost is "one of the
> legal number values combined with one or more of the relative
> values (bolder or lighter)." But does that mean
>
>    400 + bolder + bolder + lighter
> or
>    400 + bolder
> or
>    400 + 1 * lighter + 2 * bolder?
>
> That makes a difference. Assume a font with weights 400 (normal)
> and 900 (extra bold). A UA that does the first will end up at 400,
> while a UA that does the second will choose 900.

Bolder is min(inherit + 100,900) and the computed value is a number:
you solve the issue without complicating with the computed value. Bold
computes to 700, normal and initial to 400. Lighter to max(inherit -
100,100).

> The text about taking the next available weight or the next
> numerical value if there is no next weight available dates from
> the old CSS2 REC, and assumed that the computed value was a number.
> But it didn't define what happened for elements with more than one
> font family, so it's likely that taking the next numerical value
> isn't actually a good idea.

The font matching algorithm is in CSS3 Fonts, and
1) assumes a numerical weight
2) should work the same for bolder/ligther or explicit numbers
As usual, first you find the computed values, then the used values
(that require knowing the font metrics and availability) for
rendering.

> Maybe we will find a good solution before we progress CSS 2.1 to
> Recommendation. That's currently issue 111[3]. But maybe we won't
> and leave the algorithm undefined in CSS 2.1.
>
> [3] http://wiki.csswg.org/spec/css2.1#issue-111
>
>
>
> Bert
> --
>  Bert Bos                                ( W 3 C ) http://www.w3.org/
>  http://www.w3.org/people/bos                               W3C/ERCIM
>  bert@w3.org                             2004 Rt des Lucioles / BP 93
>  +33 (0)4 92 38 76 92            06902 Sophia Antipolis Cedex, France
>
>

Giovanni
Received on Sunday, 10 May 2009 17:56:04 GMT

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