From: Jukka K. Korpela (jkorpela@cs.tut.fi)
Date: Sat Apr 19 2008 - 14:14:35 CDT
Asmus Freytag wrote:
> It's a deliberate limitation of Unicode conformance that it focuses
> its requirements on the *identity* of the character, not on the finer
> points of typography. In other words, the conformance seeks to ensure
> that writers know which characters to use to designate a combination
> of base and mark, and receivers know when they receive the data, which
> combination was intended.
That's the big picture, but there's still the question how poor the
rendering can be. For example, if "overprinting" implementation makes a
diacritic practically unrecognizable, is it conformant? What if it is
_barely_ recognizable, which means that it is not recognizable to many
people?
I don't think there are any fixed rules. The Unicode Standard says, more
or less, that you must not render an "A" as a "B", but in a world of
confusables, that's not very exact, and it's not really presented as a
conformance requirement, as far as I can see.
Diacritics themselves are confusable (think about caron vs. breve), and
their rendering is a further complication. A perfectly legible diacritic
can become mysterious when rendered in a wrong position. I think the
bottom line is that conformance requirements cannot deal with such
issues. Rather, we can judge pragmatically that _in a given context_
some rendering is so poor that it is unnacceptable, wrong - not as a
matter of conformance to the Unicode Standard but other requirements.
For example, in a context where diacritic marks frequently appear on
uppercase letters, the "overprinting" approach seems to be just _wrong_,
whereas in a more typical situation, it's just poor quality, or, at
times, acceptable quality.
Jukka K. Korpela ("Yucca")
http://www.cs.tut.fi/~jkorpela/
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