Re: the *precise* definition of 1em
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
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