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Re: bolder/lighter defintion

From: John Daggett <jdaggett@mozilla.com>
Date: Tue, 23 Mar 2010 19:11:48 -0700 (PDT)
To: fantasai <fantasai.lists@inkedblade.net>
Cc: www-style <www-style@w3.org>
Message-ID: <51400715.20463.1269396708444.JavaMail.root@cm-mail03.mozilla.org>

fantasai wrote:

> The problem with this proposal is that it doesn't roundtrip very well.
> If I start at 300 and go bolder, then lighter, I don't get back to my
> start: I get 100 instead of 300. The same is true of many other start
> points. It might not make a difference in a font with few weights, but
> in a font with all weights available, it's likely to be noticeable.

No, you've missed how bolder/lighter works, the inherited weight is
first mapped to an existing weight and *then* bolder/lighter is applied.
So for a family with weights 100, 400, 700, and 900, round tripping
works just fine.  A font weight of 300 will map to a lighter weight,
namely 100 (using the "fill in the holes" algorithm).  Relative weights
of bolder, then lighter map back to the original 100.  This means that
'600' maps to 700 and '600 bolder' maps to 900, not 700 also.

The reason for clamping the scale to 100/400/700/900 is so that the
bolder/lighter steps are always distinct if weights exist.  It's often
very hard to distinguish weights like 400 and 500 or 500 and 600. 
Authors who want finer grained control can use specific weight values.

This was discussed during the March 2009 F2F in Tokyo.  

Received on Wednesday, 24 March 2010 02:12:21 UTC

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