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Re: the *precise* definition of 1em

From: Hakon Lie <howcome@w3.org>
Date: Wed, 23 Jul 1997 00:38:08 +0200 (MET DST)
Message-Id: <199707222238.AAA09044@online.no>
To: "Joel N. Weber II" <devnull@gnu.ai.mit.edu>
Cc: www-style@w3.org
Joel N. Weber II writes:

 >    What's the percentage variation that can be
 >    considered an approximation and not an abomination? I suspect it's
 >    subjective. Some readers will see .5 pt variations as annoying,
 >    especially if off-sized fonts are of a different family.
 > 
 > The CSS1 spec allows up to a 20% variation from what the user specified.
 > However, it is possible for a UA to make this configurable.
 > My understanding is that a UA can conform to the spec as long as it
 > will never use a font which is more than a 20% difference from the
 > user-specified size.  So if a UA usings 10% or 5% or 0%, that's fine.

The margin of tolerance is UA-dependent, but the spec suggests 20% for
bitmapped fonts. I'd say you could go beyond 20 percent if needed and
you shouldn'd necessarily wait for user configuration before doing so.
We're in a hazy area of the spec and implementation experience is much
appreciated.

Regards,

-h&kon

H      k   o   n      W   i   u   m       L   i   e
howcome@w3.org   W o r l d   Wide  W e b  Consortium
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Received on Tuesday, 22 July 1997 18:38:14 GMT

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