Unicode Technical Note #22

Robust Vertical Text Layout

Version	1
Authors	Elika J. Etemad
Date	April 25, 2005
This Version	http://www.unicode.org/notes/tn22/tn22-1.html
Previous Version	n/a
Latest Version	http://www.unicode.org/notes/tn22/

Summary

As cross-cultural written communication increases, the technology underlying that communication needs to handle the intersection of their layout conventions. Vertical text is the traditional mode of text layout for many East Asian writing systems. It is also used for effects such as vertical headers in horizontal layout. However, few formatting systems today can do true vertical text layout, and most of those can only handle common scripts in right-to-left columns. Methods for typesetting left-to-right columns or uncommon script combinations such as Mongolian and Arabic thus often involve unwieldy BIDI overrides and delicate glyph rendering tweaks. These workarounds are awkward and can break the portability of the underlying text. The model outlined in this paper uses the intrinsic properties of the characters and an expansion of Unicode's logic to lay out the text without these hacks. Such a system can scale to gracefully handle any combination of scripts, can correctly lay out text with any combination of styling properties, and can integrate well with the layered Unicode + Markup + Styling design of semantically-tagged documents on the Web. This paper focuses on methods for automatically handling character ordering, shaping, and glyph orientation switches when typesetting lesser-known scripts and unusual script combinations in vertical layout, without reworking existing horizontal layout algorithms or adding script-specific new modules.

Status

This document is a Unicode Technical Note. It is supplied purely for informational purposes and publication does not imply any endorsement by the Unicode Consortium. For general information on Unicode Technical Notes, see http://www.unicode.org/notes/.

Contents

The body of this note is contained in the file "RobustVerticalLayout.pdf".

© 2005 Elika J. Etemad. This publication is protected by copyright, and permission must be obtained from the author and Unicode, Inc. prior to any reproduction, modification, or other use not permitted by the Terms of Use.

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