[Unicode]  Technical Reports
 

Proposed Draft Unicode Technical Report #50

Unicode Properties for Horizontal and Vertical Text Layout

Editor Eric Muller (emuller@adobe.com)
Date 2012-05-17
This Version http://www.unicode.org/reports/tr50/tr50-5.html
Previous Version n/a
Latest Version http://www.unicode.org/reports/tr50/
Latest Proposed Update http://www.unicode.org/reports/tr50/proposed.html
Revision 5

Summary

The Unicode code charts generally show characters in the orientation in which they appear in horizontal lines. However, there are a few exceptions, mostly for characters or scripts which are normally written in vertical lines. This report describes a property that documents that situation.

When text is presented in vertical lines, there are various conventions for the orientation of the characters with respect to the line. In many parts of the world, most characters are upright. In East Asia, Kanji and Kana characters are upright, Latin letters of acronyms are upright, while words and sentences in the Latin script are typically sideways. This report describes two Unicode character properties which can be used to determine a default orientation of characters in those two scenarios.

Status

This is a draft document which may be updated, replaced, or superseded by other documents at any time. Publication does not imply endorsement by the Unicode Consortium. This is not a stable document; it is inappropriate to cite this document as other than a work in progress.

A Unicode Technical Report (UTR) contains informative material. Conformance to the Unicode Standard does not imply conformance to any UTR. Other specifications, however, are free to make normative references to a UTR.

Please submit corrigenda and other comments with the online reporting form [Feedback]. Related information that is useful in understanding this document is found in References. For the latest version of the Unicode Standard see [Unicode]. For a list of current Unicode Technical Reports see [Reports]. For more information about versions of the Unicode Standard, see [Versions].

Contents


1 Editorial Warnings

The draft is currently structured around two properties, with values in the set V={R, U, T}. This is entirely equivalent to a single property with values in the set VxV. Going one step further, we can also give names to the values in VxV and use those names as the property values. Those are syntactic details which are easy to change as this draft progresses.

Another change that can be introduced is to have a level of indirection between the property values and the actual classes, and to bridge that indirection either via a simple mapping, or via rules (e.g. in the style of linebreak) or by some other machinery.

The motivation for the current choice is mostly to make the resulting orientation as clear as possible, and to delay the introduction of more complex machinery until a rationale is provided for doing so.

2 Introduction

The Unicode code charts generally show characters in the same orientation as in horizontal lines. However, there are a few exceptions, mostly for characters or scripts which are normally written in vertical lines; in those cases, the code charts show the characters in the same orientation as in vertical lines. Futhermore, those vertical characters and scripts are often rotated when displayed in horizontal lines; figure 1 shows an example of Mongolian text in horizontal lines, where the Mongolian characters are rotated 90 degree counter-clockwise with respect to the code charts. The property Horizontal Orientation documents that situation.

Figure 1. Mongalian text on horizontal lines

When text is displayed in vertical lines, there are various conventions for the orientation of the characters with respect to the line. In many parts of the world, most characters are upright, that is appear with the same orientation as in the code charts, as can be seen in figure 2. The property Stack Vertical Orientation documents the default orientation of characters in his scenario.

Figure 2. Western vertical text

In East Asia, Kanji and Kana characters are upright, Latin letters of acronyms are upright, while words and sentences in the Latin script are typically sideways, as can be seen in figure 3. The property Mixed Vertical Orientation documents the default orientation of characters in his scenario.

Figure 3. Japanese vertical text

3 Conformance

The properties and algorithms presented in this report are informative. The intent is to provide a reasonable determination of the orientation of characters which can be used in the absence of other information, but can be overridden by the context, such as markup in a document or preferences in a layout application. This default determination is based on the most common use of a character, but in no way implies that that character is used only in that way.

For more information on the conformance implications, see [Unicode], section 3.5, Properties, in particular the definition (D35) of an informative property.

4 Property values

The properties share the same set of values, which are given in table 1.

Table 1. Property Values

U characters which are displayed upright, with the same orientation as they appears in the code charts.
R characters which are displayed sideways, rotated 90 degrees clockwise compared to the code charts.
L characters which are displayed sideways, rotated 90 degrees counter-clockwise compared to the code charts.
T, Tu, Tr characters which are not just upright or sideways, but require a different glyph than in the code charts when used in vertical texts. In addition, Tu indicates that as a fallback, the character can be displayed with the code chart glyph upright; similarly, Tr indicates a possible fallback using the code chart glyph rotated 90 degrees clockwise.

Note that the orientation is described with respect to the appearance in the code charts.

Currently, there are no code points with Horizontal Orientation property value L, T, Tu or Tr; there are no code points with Stacked and Mixed Orientation property value L.

5 Properties

The Horizontal Orientation (short name ho) property is intented to be used for horizontal lines.

The Stacked Vertical Orientation (short name svo) property is intended to be used for vertical lines in those parts of the world where characters are mostly upright.

The Mixed Vertical Orientation (short name mvo) property is intended to be used for vertical lines in East Asia, and more specifically in Japan, China and Korea.

The scope of these properties is limited by the scope of Unicode itself. For example, Unicode does not support directly the representation of texts and inscriptions using Egyptian Hieroglyphs. Instead, Unicode provides characters intended for use when writing about such texts or inscriptions, or for use in conjunction with a markup system such as the Manuel de Codage. While the properties are defined for Egyptian Hieroglyphs, they are meaningful only for occurrences of these characters in discursive texts; when the characters are used with markup, the markup controls the orientation. See [Unicode], section 14.8 for a more complete discussion of the scope of Egyptian Hieroglyph characters.

5.1 Grapheme Clusters

As in all matters of typography, the interesting unit of text is not the character, but a grapheme cluster: it does not make sense to use a base character upright and a combining mark attached to it sideways.

It is expected that the client of the properties defined here will select a notion of grapheme cluster, and is interested in obtaining an orientation for the cluster as a whole.

A possible choice for the notion of grapheme cluster is either that of legacy grapheme cluster or that of extended grapheme cluster, as defined in [UAX29].

The orientation for a grapheme cluster as a whole is then determined by taking the orientation of the first character in the cluster, with the following exceptions:

5.2 Resulting orientation

The properties are intended to provide only a default orientation, rather than to handle correctly all situations. It is expected by when used in the context of a markup system, the user will be able to 1) have some control over which property is used and 2) specify an explicit orientation. For example, one could have an attribute orientation with possible values auto, 0, 90, 180 and 270; when the value of the attribute is not auto, the explicit orientation is used; when the value is auto, the property values are used.

The property values, if used, are intended to be used directly.

There is actually one character for which a contextual determination would be useful and reliable: U+00AE ® REGISTERED SIGN, which can occur both following terms in kanji/kana and following terms in Latin. An occurrence of ® should be assigned the same class as the character it follows. Others? Enough to warrant the complexity of contextual rules?

There are other cases where the character is used routinely in both Japanese and Western contexts: quotation marks are a good example. While contextual determination would be useful, it's probably the case that it's not going to be reliable.

6 Tailorings

To facilitate tailorings, this reports identifies sets of characters which behave similarly, and for which it can useful to tailor the orientation as a group.

6.1 The brackets

This set contains brackets, which while they appear rotated, are commonly implemented as if they were transformed.

Table 2. The brackets set

00AB
00BB
201C..201F
2039..203A
2045..2046
3008..3011
3014..301B
FE59..FE5E
FF08..FF09
FF3B
FF3D
FF5B
FF5D
FF5F..FF60
FF62..FF63

6.2 The arrows

This set contains arrows.

Table 3. The arrows set

2190..21FF
261A..261F
2794
2798..27AF
27B1..27BE
27F0..27FF
2900..297F
2B00..2B11
2B30..2B4C
FFE9..FFEC

7 Glyphs Changes for Vertical Orientation

Table 4 provides representative glyphs for the horizontal and vertical appearance of characters with the property value T.

Add glyphs for all the entries: 301F, 332C, FF61, FF64, 1F200, 1F201, halfwidth small kanas. Some glyphs (2018, 2019) may not be correct.

Recently, the brackets have been made T, because they have a slightly different position in their box between horizontal and vertical. It is arguable whether characters for which the difference is only a slight position adjustments should be included in T.

Table 4. Glyph Changes for Vertical Orientation

character H V
U+2018 LEFT SINGLE QUOTATION MARK
U+2019 RIGHT SINGLE QUOTATION MARK
U+3001 IDEOGRAPHIC COMMA
U+3002 IDEOGRAPHIC STOP
U+301C WAVE DASH
U+301D REVERSED DOUBLE PRIME QUOTATION MARK
U+301E DOUBLE PRIME QUOTATION MARK
U+301F LOW DOUBLE PRIME QUOTATION MARK
U+30FC KATAKANA-HIRAGANA PROLONGED SOUND MARK
U+3041 HIRAGANA LETTER SMALL A
U+3043 HIRAGANA LETTER SMALL I
U+3045 HIRAGANA LETTER SMALL U
U+3047 HIRAGANA LETTER SMALL E
U+3049 HIRAGANA LETTER SMALL O
U+3063 HIRAGANA LETTER SMALL TU
U+3083 HIRAGANA LETTER SMALL YA
U+3085 HIRAGANA LETTER SMALL YU
U+3087 HIRAGANA LETTER SMALL YO
U+308E HIRAGANA LETTER SMALL WA
U+3095 HIRAGANA LETTER SMALL KA
U+3096 HIRAGANA LETTER SMALL KE
U+30A1 KATAKANA LETTER SMALL A
U+30A3 KATAKANA LETTER SMALL I
U+30A5 KATAKANA LETTER SMALL U
U+30A7 KATAKANA LETTER SMALL E
U+30A9 KATAKANA LETTER SMALL O
U+30C3 KATAKANA LETTER SMALL TU
U+30E3 KATAKANA LETTER SMALL YA
U+30E5 KATAKANA LETTER SMALL YU
U+30E7 KATAKANA LETTER SMALL YO
U+30EE KATAKANA LETTER SMALL WA
U+30F5 KATAKANA LETTER SMALL KA
U+30F6 KATAKANA LETTER SMALL KE
U+31F0 KATAKANA LETTER SMALL KU
U+31F1 KATAKANA LETTER SMALL SI
U+31F2 KATAKANA LETTER SMALL SU
U+31F3 KATAKANA LETTER SMALL TO
U+31F4 KATAKANA LETTER SMALL NU
U+31F5 KATAKANA LETTER SMALL HA
U+31F6 KATAKANA LETTER SMALL HI
U+31F7 KATAKANA LETTER SMALL HU
U+31F8 KATAKANA LETTER SMALL HE
U+31F9 KATAKANA LETTER SMALL HO
U+31FA KATAKANA LETTER SMALL MU
U+31FB KATAKANA LETTER SMALL RA
U+31FC KATAKANA LETTER SMALL RI
U+31FD KATAKANA LETTER SMALL RU
U+31FE KATAKANA LETTER SMALL RE
U+31FF KATAKANA LETTER SMALL RO
U+3300 SQUARE APAATO
U+3301 SQUARE ARUHUA
U+3302 SQUARE ANPEA
U+3303 SQUARE AARU
U+3304 SQUARE ININGU
U+3305 SQUARE INTI
U+3306 SQUARE UON
U+3307 SQUARE ESUKUUDO
U+3308 SQUARE EEKAA
U+3309 SQUARE ONSU
U+330A SQUARE OOMU
U+330B SQUARE KAIRI
U+330C SQUARE KARATTO
U+330D SQUARE KARORII
U+330E SQUARE GARON
U+330F SQUARE GANMA
U+3310 SQUARE GIGA
U+3311 SQUARE GINII
U+3312 SQUARE KYURII
U+3313 SQUARE GIRUDAA
U+3314 SQUARE KIRO
U+3315 SQUARE KIROGURAMU
U+3316 SQUARE KIROMEETORU
U+3317 SQUARE KIROWATTO
U+3318 SQUARE GURAMU
U+3319 SQUARE GURAMUTON
U+331A SQUARE KURUZEIRO
U+331B SQUARE KUROONE
U+331C SQUARE KEESU
U+331D SQUARE KORUNA
U+331E SQUARE KOOPO
U+331F SQUARE SAIKURU
U+3320 SQUARE SANTIIMU
U+3321 SQUARE SIRINGU
U+3322 SQUARE SENTI
U+3323 SQUARE SENTO
U+3324 SQUARE DAASU
U+3325 SQUARE DESI
U+3326 SQUARE DORU
U+3327 SQUARE TON
U+3328 SQUARE NANO
U+3329 SQUARE NOTTO
U+332A SQUARE HAITU
U+332B SQUARE PAASENTO
U+332C SQUARE PAATU
U+332D SQUARE BAARERU
U+332E SQUARE PIASUTORU
U+332F SQUARE PIKURU
U+3330 SQUARE PIKO
U+3331 SQUARE BIRU
U+3332 SQUARE HUARADDO
U+3333 SQUARE HUIITO
U+3334 SQUARE BUSSYERU
U+3335 SQUARE HURAN
U+3336 SQUARE HEKUTAARU
U+3337 SQUARE PESO
U+3338 SQUARE PENIHI
U+3339 SQUARE HERUTU
U+333A SQUARE PENSU
U+333B SQUARE PEEZI
U+333C SQUARE BEETA
U+333D SQUARE POINTO
U+333E SQUARE BORUTO
U+333F SQUARE HON
U+3340 SQUARE PONDO
U+3341 SQUARE HOORU
U+3342 SQUARE HOON
U+3343 SQUARE MAIKURO
U+3344 SQUARE MAIRU
U+3345 SQUARE MAHHA
U+3346 SQUARE MARUKU
U+3347 SQUARE MANSYON
U+3348 SQUARE MIKURON
U+3349 SQUARE MIRI
U+334A SQUARE MIRIBAARU
U+334B SQUARE MEGA
U+334C SQUARE MEGATON
U+334D SQUARE MEETORU
U+334E SQUARE YAADO
U+334F SQUARE YAARU
U+3350 SQUARE YUAN
U+3351 SQUARE RITTORU
U+3352 SQUARE RIRA
U+3353 SQUARE RUPII
U+3354 SQUARE RUUBURU
U+3355 SQUARE REMU
U+3356 SQUARE RENTOGEN
U+3357 SQUARE WATTO
U+337B SQUARE ERA NAME HEISEI
U+337C SQUARE ERA NAME SYOUWA
U+337D SQUARE ERA NAME TAISYOU
U+337E SQUARE ERA NAME MEIZI
U+337F SQUARE CORPORATION
U+FF61 HALFWIDTH IDEOGRAPHIC FULL STOP
U+FF64 HALFWIDTH IDEOGRAPHIC COMMA
U+FF67 HALFWIDTH KATAKANA LETTER SMALL A
U+FF68 HALFWIDTH KATAKANA LETTER SMALL I
U+FF69 HALFWIDTH KATAKANA LETTER SMALL U
U+FF6A HALFWIDTH KATAKANA LETTER SMALL E
U+FF6B HALFWIDTH KATAKANA LETTER SMALL O
U+FF6C HALFWIDTH KATAKANA LETTER SMALL YA
U+FF6D HALFWIDTH KATAKANA LETTER SMALL YU
U+FF6E HALFWIDTH KATAKANA LETTER SMALL YO
U+FF6F HALFWIDTH KATAKANA LETTER SMALL TU
U+1F200 SQUARE HIRAGANA HOKA
U+1F201 SQUARED KATAKANA KOKO

8 Data File

The data file, in UCD syntax.

To help during the review, a slightly more readable version is available.

U+2016 ‖ DOUBLE VERTICAL LINE; JRLEQ classifies this character as cl-19 ideographic; typically, this is a clue that it is upright; also, JIS 0213:2000 does not give a vertical variant. On the other hand, it seems that 'vert' often presents it sideways. Which is right? Could it be that font vendors have been influenced by U+30A0 ゠ KATAKANA-HIRAGANA DOUBLE HYPHEN?

Acknowledgments

Please let me know if I forgot your name or you prefer a different spelling/etc.

Thanks to the reviewers: Julie Allen, Ken Lunde, Nat McCully, Ken Whistler, Taro Yamamoto, htakenaka, John Cowan, Fantasai, Asmus Freytag, Van Anderson, Ishi Koji, sikeda, Shinyu Murakami, Tokushige Kobayashi, Addison Phillips, Martin Dürst, the W3C Internationalization Core Working Group, the W3C I18N Interest group, the W3C CSS Working group, Michael Everson, John Daggett, Laurentiu Iancu, Dwayne Robinson.

References

[JLREQ] Requirements for Japanese Text layout, W3C Working Group Note
[Errata] Updates and Errata

http://www.unicode.org/errata
[Feedback] http://www.unicode.org/reporting.html

For reporting errors and requesting information online.
[Reports] Unicode Technical Reports

http://www.unicode.org/reports/

For information on the status and development process for technical reports, and for a list of technical reports.
[UAX29] UAX #29: Unicode Text Segmentation

http://www.unicode.org/reports/tr29/
[Unicode] The Unicode Standard, Version 6.1.0, defined by: The Unicode Standard, Version 6.1.0 (Mountain View, CA: The Unicode Consortium, 2012. ISBN 978-1-936213-02-3)

http://www.unicode.org/versions/Unicode6.1.0
[Versions] Versions of the Unicode Standard

http://www.unicode.org/versions/

For details on the precise contents of each version of the Unicode Standard, and how to cite them.

Modifications

This section indicates the changes introduced by each revision.

Revision 5

Revision 4

Revision 3

Revision 2

Revision 1