Re: half-brackets in the Supplemental Punctuation block

From: Stephan Stiller <>
Date: Wed, 06 Jun 2012 17:11:48 -0700

Hi Philippe,

Thanks for your opinion. The examples I've just checked looked like
"zero-width or almost so" (Friedl) and "very narrow" (in a Japanese
dictionary, ISBN 978-4-7674-2315-9) to me. I am pretty sure I've seen
zero-width with either kana or romaji, just can't find a reference right
now. I think there are use instances. What "should" be done is also a
good question, and perhaps the answer isn't as obvious as I thought, but
these considerations make me wonder whether a font is really free to
make a choice about zero-width or not for any given Unicode symbol. If
not, I'm wondering whether Unicode could/should/does make that binary
decision. And in either case I'm wondering for /which/ characters in
Unicode zero-width is an option (or obligatory).


On 6/6/2012 4:52 PM, Philippe Verdy wrote:
> They are not supposed to be zero-width. But kerning may still reduce
> their width contextually, as long as there's no collision.
> For use in Japanese as mora indicators, given the size of glyphs used
> in Japanese (including Kanji characters) I don't think they should
> even be kerned with them, but should behave like the existing
> ideographic square quotation marks (and probably in this case, even
> their advance width would be extended to fit the alignment of
> ideographic squares, if they are used with an ideographic character
> encoded immmediately near them on their inner side, and aligned to the
> half-width box if their are used with an half-width character on their
> inner side.
> Fonts can contextually make these transformations of glyphs for Asian texts.
> Outside of these contexts, these characters should behave and be
> rendered like the usual [square brackets], with the same metrics and
> similar kerning rules. In monospaced fonts, these characters should
> advance by one cell and should be centered horizontally. They should
> also include an empty side-bearing gap between the horizontal stroke
> and the side of the cell (i.e. no connection/collision should be
> possible with characters encoded on the inner side, unless these
> characters are explicitly connecting outside of their own advance box,
> a basic macron diacritic not creating a collision because it already
> widdens the base character encoded with them to provide a minimum side
> bearing and no collision with surrounding glyphs; font authors and
> renderers will do their best to avoid these collisions and unexpected
> joinings)
> 2012/6/7 Stephan Stiller<>:
>> Hi,
>> I am excited to see the half-bracket symbols (U+2E22 -> U+2E25) in Unicode.
>> I've been waiting for them. I assume that they're meant for use cases such
>> as:
>> in certain Japanese dictionaries to indicate pitch accent (U+2E22 and U+2E23
>> would surround the high-register "mora")
>> for alternate quoting, such as Jeffrey Friedl's usage in his "Mastering
>> Regular Expressions" book to denote the beginning (U+2E22) and end (U+2E25)
>> of regexes
>> In both these two use cases that I'm aware of, the symbols are zero-width,
>> or casually indistinguishable from zero-width. Is there a place in the
>> standard to indicate that this is the recommended way for fonts to implement
>> these symbols?
Received on Wed Jun 06 2012 - 19:13:29 CDT

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