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

Hi Philippe,

thanks for your reply.
I was confused by http://www.unicode.org/faq/unsup_char.html , which states
> All default-ignorable characters should be rendered as completely invisible (and non advancing, i.e. "zero width"), if not explicitly supported in rendering.
Do I understand correctly that, if the choseong filler is used when
there's no leading consonnent before a medial vowel, it should be
rendered as visible; otherwise become non-advancing
(similarly, if the jungseong filler is used to replace a missing
medial or final vowel, it should be rendered as visible; otherwise
become non-advancing) ?
i.e. <U+115F>, or <U+1161, U+1160>, or <U+115F, U+112B> -- should the
fillers be rendered as non-advancing?

regards,
Konstantin

2013/3/18 Philippe Verdy <verdy_p_at_wanadoo.fr>:
> 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).
>
> Characters that are "default ignorable" may still have an effect on
> cluster boundaries used when editing texts, if you count manually the
> number of zero-width characters (by pressng the left or right arrow
> fnction keys.) As long as the rendering is correct, editors may allow
> you to place insertion points between them.
>
> U+115F is the choseong filler (used when there's no leading consonnent
> to place before a medial vowel), U+1160 is the jungseong filler (used
> to replace a missing medial or final vowel).
>
> You're right when saying that there should be two clusters in
> <U+115F, U+1161>, <U+112B, U+1160>
> - The first one is a isolated vowel A, it should become spacing but
> U+115F is just used as an invisible holder for the vowel,
> - The second one is an isolated consonnant KAPYEOUNPIEUP, and the
> U+1160 filler will remain invisible except that it iis used here so
> that it explicitly terminates the cluster if it was followed by a
> leading consonnant or dirctly by a "defective" vovel.
>
> But the U+115F and U+1160 Hangul fillfers remain default ignorable in
> collation. And there's no bug about this.
>
> 2013/3/18 Konstantin Ritt <ritt.ks_at_gmail.com>:
>> 2013/3/18 Konstantin Ritt <ritt.ks_at_gmail.com>:
>>> The user reports Korean text rendering issue with any modern Hangul
>>> font when U+115F and U+1160 are handled like default_ignorable code
>>> points.
>>> [quote]With input string "U+115F U+1161 U+112B U+1160", we get three
>>> zero-width glyphs instead of two; this is wrong.[/quote]
>>> I did check some Hangul font and found that either U+115F or U+1160
>>> zero-advances, not both. When handling them like default ignorable,
>>> the rendered text seems to lack some advancing.
>>> Since I know nothing about Korean typography, I'd like to ask here:
>>> what is the reason for U+115F and U+1160 to be default ignorables and
>>> shouldn't that be revised?
Received on Mon Mar 18 2013 - 10:39:02 CDT