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Using TeX hyphenation patterns in OpenOffice.org

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This document describes how to properly convert TeX hyphenation patterns for OpenOffice.org and other software projects using the Hyphen hyphenation library.

  • Written by Martin Srebotnjak.
  • Some portions of text contributed by László Németh and Mojca Miklavec.
  • Version: 1.1 (July 24, 2010).

Introduction

OpenOffice.org uses Hyphen, part of the Hunspell project, as its hyphenation engine.

The hyphenation files are represented by two files:

  • the patterns file (a text file with all the patterns and extra hyphenation rules; hyph_xx_YY.dic) and
  • the readme file (a text file with all the credits and licensing information; README_hyph_xx_YY.txt).

The language descriptor xx_YY is an actual ISO-code, you can look it up in the following table: http://wiki.services.openoffice.org/wiki/Languages

From OpenOffice.org 3.0 onwards the hyphenation patterns are packed as an OpenOffice.org extension, usually as a part of a dictionary language pack (with a spell-checking dictionary for the same language and, optionally, a thesaurus). Here is a list of available dictionary language packs: http://extensions.services.openoffice.org/en/dictionaries

Using TeX patterns

Hyphen (and OpenOffice.org) can use TeX hyphenation patters for hyphenation, which is great, because TeX patterns are available for more than 50 different languages.

But because of differences between TeX hyphenation and Hyphen the TeX hyphenation patterns must be first converted. If conversion is not applied, several issues can surface:

  • not all TeX patterns will work in OpenOffice.org - which means that TeX patterns will perform substandardly in OpenOffice.org;
  • if code-page is not set correctly the TeX patterns can behave erratically in OpenOffice.org;

Conversion of TeX patterns

The following conversion process must be followed step-by-step:

1. Download up-to-date TeX hyphenation patterns

Tex hyphenation repository contains up-to-date TeX hyphenation patterns. They are located here:

http://tug.org/svn/texhyphen/trunk/hyph-utf8/tex/generic/hyph-utf8/patterns/txt/

Example: for Slovenian language one would download file hyph-sl.pat.txt from the SVN repository.

2. Convert TeX hyphenation patterns file into proper character set

Recent Hyphen version of OpenOffice.org 3 has a problem with UTF-8 encoded hyphenation patterns: it misses the first hyphenation break point in special circumstances (in LEFTHYPHENMIN positions before letters with diacritics, eg. "zaživeti" where the "zaži" does not get split). Consider the conversion of your UTF-8 encoded TeX patterns to ISO-8859-X code-pages (or KOI8-R).

Example: Slovenian language uses ISO-8859-2 code-page, so one would open the UTF-8 file in a code-page savvy text editor, then convert and save it as an ISO-8859-2 coded text.

3. Run the substrings.pl conversion script

Hyphen library (based on libhnj from Raph Levien) uses a time optimized implementation of the original Liang's algorithm of TeX, and substring.pl conversion is a requirement of this implementation. You can download the latest version of substrings.pl conversion script from the Hyphen repository. At the time of writing this was:

http://sourceforge.net/projects/hunspell/files/Hyphen/2.5/hyphen-2.5.tar.gz/download

The script has the following parameters: the input file name, the output file name, the code-page setting (ISO8859-1, ISO8859-2, ..., ISO8859-10, KOI8-R) and the LEFTHYPHENMIN and RIGHTHYPHEMIN values that define the minimum left and right length of hyphenated words.

Example: for Slovenian the ISO-8859-2 code page is used, left and right hyphenmin values are 2. So one would use:

./substrings.pl hyph-sl.pat.txt hyph_sl_SI.dic ISO8859-2 2 2

Warning: note how ISO8859-2 is used and not ISO-8859-2! Remember to omit the first hyphen in the ISO codepage name!

4. Add hyphenation rules for special characters

Special characters (apostrophe, hyphen, in version 3.2.0 n-dash and m-dash ...) are word characters in OpenOffice.org, but not boundary characters in the hyphenation of OpenOffice.org which is an incompatibility with the TeX boundary hyphenation patterns. It results in potentially bad hyphenation for words with hyphens and other special characters. Please consider adding the following lines at the end of the converted hyphenation patterns file (hyph_xx_YY.dic):

8-8
8a8-8
8b8-8
8c8-8
...
-a8
-b8
-c8
...
8'8
8a8'8
8b8'8
8c8'8
...
'a8
'b8
'c8
...

Note: "..." represents all missing lines for other characters of your alphabet.

For words with apostrophes OpenOffice.org calculates bad hyphen limits. Add the following lines before your patterns to fix this calculation:

1'.
NEXTLEVEL

English hyphenation patterns use an extended version to handle the words ending with "'s" and "'t" correctly, too:

1'.
1's./'=s,1,2
1't./'=t,1,2
NEXTLEVEL

With UTF-8 patterns, you can fix the hyphen limits for the typographical apostrophes, too:

1'.
1’.
NEXTLEVEL
8'8
8a8'8
8b8'8
8c8'8
...
'a8
'b8
'c8
...
8’8
8a8’8
8b8’8
8c8’8
...
’a8
’b8
’c8
...

Note: Hyphen 2.7 (it hasn't been integrated yet) supports a better method to handle this kind of hyphenation. See NOHYPHEN feature in README.compound.

5. Create/update the appropriate readme file

The readme file contains the credits (author of the patterns, other collaborators...) and licensing information.

Official TeX hyphenation patterns are released under the GNU Lesser General Public License (LGPL) which makes them appropriate for inclusion into OpenOffice.org.

If you use TeX hyphenation patterns from other sources remember to check and mention the license they are available under in the readme file.

The hyphenation patterns to be included in the official OpenOffice.org builds must also include the filled-in http://external.openoffice.org/ form data.

6. Create/update an OpenOffice.org dictionary extension

Package the converted hyphenation patterns in a new (or update the existing) OpenOffice.org extension and upload it to the OpenOffice.org extension repository.

Before uploading try extensively if it works properly with different versions of OpenOffice.org.

If the patterns perform well and the patterns are licensed under LGPL, the patterns could eventually make it into the official releases of OpenOffice.org.

For further details see Extensions development.

Future fixes

Hyphen 2.5 has already fixed the problem with the UTF-8 encoded patterns for platforms with external Hyphen libraries. The integration of Hyphen 2.5 is planned in OpenOffice.org 3.4. You can limit your UTF-8 encoded hyphenation patterns for OpenOffice.org 3.4 by adding the following lines to the distribution.xml of your extension:

    <dependencies>
        <OpenOffice.org-minimal-version value="3.4" d:name="OpenOffice.org 3.4" />
    </dependencies>

This will allow older versions of OpenOffice.org to use the older, non-UTF-8 version of your extension.

Conclusion

Since Hyphen engine is used also by other open-source software projects (as are the OpenOffice.org hyphenation patterns files), following these instructions will provide correct patterns for programs like Scribus, KOffice etc.


See Also



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