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Re: bolder/lighter defintion

From: John Daggett <jdaggett@mozilla.com>
Date: Wed, 24 Mar 2010 01:02:00 -0700 (PDT)
To: fantasai <fantasai.lists@inkedblade.net>
Cc: www-style <www-style@w3.org>, Thomas Phinney <tphinney@cal.berkeley.edu>
Message-ID: <844820558.22312.1269417720912.JavaMail.root@cm-mail03.mozilla.org>

fantasai wrote:

>> I think I mentioned before, one limitation of this table is that it
>> only handles values in even 100s, when real-world fonts sometimes use
>> in-between numbers. Notably (but not only) some fonts from Adobe.
> 
> I would expect the UA to map the actual font weights to the CSS scale,
> essentially treating the CSS scale as arbitrary keywords.

Precisely.  

And user agents typically rely on platform-level API's
that "interpret" the font weight.  The font weight that Thomas is
referring to is the weight in the OS/2 table of OpenType fonts.  The
weight model of CSS is based on this:

  http://www.microsoft.com/typography/otspec/OS2.htm#wtc

Unfortunately, fonts often swizzle this value around to avoid problems
with the Windows GDI API.  The problem there is that if the desired
weight when rendering a line of text is 200 or greater than the OS/2
weight value, GDI applies fake bolding.  So an app that specifies a
normal text rendering with a weight of 400 would cause GDI to fake
bold any font with a weight value less than or equal to 200.  Adobe
ships fonts that *should* have a weight of 100 with a weight of 250
instead to avoid this problem.

Here's what the Helvetica Neue family looks like in Font Folio 11:

   Helvetica Neue LT Std
     250 - Thin
     275 - Ultra Light
     300 - Light
     400 - Roman
     500 - Medium
     700 - Bold
     750 - Heavy
     900 - Black
     
Mac OSX 10.5 ships with a version of this family containing these
weight values instead:

   Helvetica Neue
     100 - UltraLight
     300 - Light
     400 - Regular
     700 - Bold
     900 - Black (only condensed)
   
Maybe because of the weight-value swizzling that Adobe does with
their fonts, Apple considers the OS/2 weight unreliable and for
lighter weights it sniffs the style name to try and adjust the weight
value.
Received on Wednesday, 24 March 2010 08:02:34 GMT

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