- 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>
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 UTC