Private Use areas - Vertical Text

via Unicode unicode at
Tue Aug 28 23:04:31 CDT 2018

Dear Richard and Peter,

apologies for the lack of clarity. Let me try to explain below.

On 2018-08-29 01:13, WORDINGHAM RICHARD via Unicode wrote:
>> On 27 August 2018 at 15:22 Peter Constable via Unicode
>> <unicode at> wrote:
>> Layout engines that support CJK vertical layout do not rely on the
>> 'vert' feature to rotate glyphs for CJK ideographs, but rather
>> rotate the glyph 90° and switch to using vertical glyph metrics.
>> The 'vert' feature is used to substitute vertical alternate glyphs
>> as needed, such as for punctuation that isn't automatically rotated
>> (and would probably need a differently-positioned alternate in any
>> case).
>> Cf. UAX 50.
> There have been some pretty confused statements. I believe the
> observed problem is that PUA characters for Zhuang CJK ideographs get
> rotated when displayed vertically rather than left-to-right.

Yes, as Richard says when CJK Zhuang text is displayed vertically whilst 
the Zhuang characters in Unicode remain upright, but those with PUA 
codepoints are rotated 90°. This is because the PUA characters are 
treated like English text, which are correctly rotated 90°. The 
orientation of the CJK characters in this case appears to depend on 
which block they belong to. As Peter points out this does not seem to 
match UAX 50.

> Unicode is doing what it can in this matter:
> (a) Zhuang PUA characters are being made individually obsolete.

Yes and No. Whilst a thousand Zhuang characters have been enocoded and 
two thousand have been submitted via IRG, however the number of PUA 
Zhuang characters is about the same or increasing. In 2006 when started 
just under 6k PUA points were used, presently there are over 8k, over 6k 
of which have not been submitted, and the earliest any future 
submissions can be encoded is 2026. That being said the number of more 
common Zhuang characters needing PUA support is coming down. So whilst 
individual characters are being resolved, the need for PUA Zhuang 
characters remains, and will so for decades to come.

> (b) By default, PUA characters have the value of
> Vertical_orientation=upright as do CJK ideographs.

Noted above.


> For CJK ideographs, it is not clear to me when the vert feature (if
> present) would be applied.  Is it only for some codepoints (vo=tu), or
> is it for all that the engine expects to be displayed 'upright' in
> vertical text?  The vrtr feature (if present) would be applied when
> glyphs are to be rotated.  Is it for all such glyphs, or only those
> for which rotation is expected to be inadequate (vo=tr)?  It seems
> that feature vrt2 is to be applied to all glyphs; perhaps rotation is
> the default behaviour when there is no look-up value for a glyph that
> the engine expects to be rotated.  The truly difficult case would be
> when there is no attempt to apply a look-up - possibly vrtr would not
> apply to /p{vo=r}.
> I would expect that defining the lookup vrt2 or vrtr to map Zhuang
> glyphs to themselves (or something prerotated) would cure the problem.
>  This would not work for sequences of Zhuang ideographs treated as RTL
> text - but that is unlikely to happen.
> Richard.

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