Re: Shaping Hangul text with U+115F and/or U+1160

From: Philippe Verdy <>
Date: Tue, 19 Mar 2013 01:19:00 +0100

It is the UCA that defines the concept of ignorable characters. And
the DUCET ("Default" UCET) that makes characters ignorable by default,
but this can still be tailored in specific collations).

Where did you see another confusive expression in TUS defining
"default ignorable" differently as being intended for rendering
purposes ?

If there's such a place it should be changed (and TUS should not
standardize what renderers should do, they have great flexibility as
long as this does not disrupt the text semantics 'too much", including
not rendering all possible semantic differences but rendering them in
contexts where confusion is not possible for readers in most used
locales and with common presentations used in that language and script

Many "zero-width" characters can in fact have a visible advance width
(e.g. the circumflex accent or macron above do have an inherent width
which may influence the advance width of a lowercase i below it, even
if in most common case they don't cause any additional advance width
above capitals). In other cases, that will in fact be kerned if
necessary (and if possible) into the characters on both sides,
provided they do not collide with them. The acute accent in Greek will
also be typically written on the left side of capitals, causing them
to move to the left, as of the acute accent had a non-zero width and
was a normal character...

2013/3/18 Richard Wordingham <>:
> On Mon, 18 Mar 2013 08:32:03 +0100
> Philippe Verdy <> wrote:
>> The "Default ignorable" property has nothing to do with rendering or
>> being zero-width, it's just a matter of collation (comparing strings
>> for similarity, for plain-text searches, or sorting them), it does not
>> necesarily mean that the character is zero-width (that's a rendering
>> property).
> "Default ignorable" is all about display and has nothing to do with
> collation. Perhaps you are confusing it with "completely ignorable".
> Completely ignorable characters are not completely ignorable; they can
> disrupt contractions.
> Richard.
Received on Mon Mar 18 2013 - 19:22:38 CDT

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