of TeX patterns git-svn-id: https://svn.apache.org/repos/asf/xmlgraphics/fop/trunk@196734 13f79535-47bb-0310-9956-ffa450edef68

21 years ago · 41cf1c9083
--- a/src/documentation/content/xdocs/hyphenation.xml
+++ b/src/documentation/content/xdocs/hyphenation.xml
@@ -62,40 +62,79 @@ Please note that the "view" links reflect current CVS, and may be different than
    <title>Custom Hyphenation Support</title>
    <section id="custom-intro">
      <title>Introduction</title>
      <p>FOP uses an XML-based TeX-like hyphenation pattern scheme.
 However, because of <link href="#license-issues">licensing issues</link>, there are currently some significant holes in FOP's hyphenation support.
 The information in this section is intended to help you work around these limitations, if possible, add support for other languages, or enhance FOP's support of current languages.</p>
      <note>If you have access to hyphenation patterns that are licensed in an Apache-compatible way, or if you have made improvements to an existing FOP hyphenation pattern, or if you have created one from scratch, please consider contributing these to FOP so that they can benefit other FOP users as well. Please inquire on the <link href="maillist.html#fop-user">FOP User mailing list</link>.</note>
      <p>FOP uses Liang's hyphenation algorithm, well known from TeX. It needs
       language specific pattern and other data for operation.</p>
      <p>Because of <link href="#license-issues">licensing issues</link>,
       there are currently some significant holes in FOP's hyphenation support.
       The information in this section is intended to help you work around these
       limitations, if possible, add support for other languages, or enhance FOP's
       support of current languages.</p>
      <note>If you have access to hyphenation patterns that are licensed in an
       Apache-compatible way, or if you have made improvements to an existing FOP
       hyphenation pattern, or if you have created one from scratch, please
       consider contributing these to FOP so that they can benefit other FOP users
       as well. Please inquire on the <link href="maillist.html#fop-user">FOP User
       mailing list</link>.</note>
    </section>
    <section id="custom-license-issues">
      <title>License Issues</title>
      <p>Many of the hyphenation files distributed with TeX and its offspring are licenced under the <fork href="http://www.latex-project.org/lppl.html">LaTeX Project Public License (LPPL)</fork>, which prevents them from being distributed with Apache software.
 Although Apache FOP cannot redistribute hyphenation pattern files that do not conform with its license scheme, that does not necessarily prevent users from using such hyphenation patterns with FOP.
 However, it does place on the user the responsibility for determining whether the user can rightly use such hyphenation patterns under the hyphenation pattern license.</p>
      <warning>The user is responsible to settle license issues for hyphenation pattern files that are obtained from non-Apache sources.</warning>
      <p>Many of the hyphenation files distributed with TeX and its offspring are
       licenced under the <fork href="http://www.latex-project.org/lppl.html">LaTeX
       Project Public License (LPPL)</fork>, which prevents them from being
       distributed with Apache software. The LPPL puts restrictions on file names
       in redistributed derived works which we feel can't guarantee. Some
       hyphenation pattern files have other or additional restrictions, for
       example against use for commercial purposes.</p>
      <p>Although Apache FOP cannot redistribute hyphenation pattern files that do
       not conform with its license scheme, that does not necessarily prevent users
       from using such hyphenation patterns with FOP. However, it does place on
       the user the responsibility for determining whether the user can rightly use
       such hyphenation patterns under the hyphenation pattern license.</p>
      <warning>The user is responsible to settle license issues for hyphenation
       pattern files that are obtained from non-Apache sources.</warning>
    </section>
    <section id="custom-sources">
      <title>Sources of Custom Hyphenation Pattern Files</title>
      <p>The most important source of hyphenation pattern files is the <fork href="http://www.ctan.org/tex-archive/language/hyphenation/">CTAN TeX Archive</fork>.</p>
      <p>The most important source of hyphenation pattern files is the
       <fork href="http://www.ctan.org/tex-archive/language/hyphenation/">CTAN TeX
        Archive</fork>.</p>
    </section>
    <section id="custom-install">
      <title>Installing Custom Hyphenation Patterns</title>
      <p>To install custom a custom hyphenation pattern for use with FOP:</p>
      <ol>
        <li>Convert the TeX hyphenation pattern file to the FOP format. The FOP format is an xml file conforming to the DTD found at <code>{fop-dir}/src/hyph/hyphenation.dtd</code>.</li>
        <li>Name this new file following this schema: <code>languageCode_countryCode.xml</code>.
 The country code is optional, and should be used only if needed. For example:
        <li>Convert the TeX hyphenation pattern file to the FOP format. The FOP
         format is an xml file conforming to the DTD found at
         <code>{fop-dir}/src/hyph/hyphenation.dtd</code>.</li>
        <li>Name this new file following this schema:
         <code>languageCode_countryCode.xml</code>. The country code is
          optional, and should be used only if needed. For example:
          <ul>
            <li><code>en_US.xml</code> would be the file name for an American English hyphenation pattern.</li>
            <li><code>it.xml</code> would be the file name for an Italian hyphenation pattern.</li>
            <li><code>en_US.xml</code> would be the file name for American
             English hyphenation patterns.</li>
            <li><code>it.xml</code> would be the file name for Italian
             hyphenation patterns.</li>
          </ul>
 The language and country codes must match the XSL-FO input, which follows <link href="http://www.ics.uci.edu/pub/ietf/http/related/iso639.txt">ISO 639</link> (languages) and
 <link href="http://www.ics.uci.edu/pub/ietf/http/related/iso3166.txt">ISO 3166</link> (countries).
 NOTE: The ISO 639/ISO 3166 convention is that language names are written in lower case, while country codes are written in upper case.</li>
        <li>There are two ways to make the FOP-compatible hyphenation pattern file accessible to FOP:
          The language and country codes must match the XSL-FO input, which
          follows <link href="http://www.ics.uci.edu/pub/ietf/http/related/iso639.txt">ISO
          639</link> (languages) and <link href="http://www.ics.uci.edu/pub/ietf/http/related/iso3166.txt">ISO
          3166</link> (countries). NOTE: The ISO 639/ISO 3166 convention is that
          language names are written in lower case, while country codes are written
          in upper case. FOP does not check whether the language and country specified
          in the FO source are actually from the current standard, but it relies
          on it being two letter strings in a few places. So you can make up your
          own codes for custom hyphenation patterns, but they should be two
          letter strings too (patches for proper handling extensions are welcome)</li>
        <li>There are two ways to make the FOP-compatible hyphenation pattern file
         accessible to FOP:
          <ul>
            <li>Place the FOP-compatible hyphenation pattern file into the directory {fop-dir}/src/hyph and rebuild FOP. The file will be picked up and added to fop.jar.</li>
            <li>Put the file into a directory of your choice and configure FOP to look for custom patterns in this directory, by setting the <link href="configuration.html#hyphenation-dir">&lt;hyphenation-dir&gt; configuration option</link>.</li>
            <li>Place the FOP-compatible hyphenation pattern file into the
             directory {fop-dir}/src/hyph and rebuild FOP. The file will be picked
             up and added to fop.jar.</li>
            <li>Put the file into a directory of your choice and configure FOP to
             look for custom patterns in this directory, by setting the
             <link href="configuration.html#hyphenation-dir">&lt;hyphenation-dir&gt;
              configuration option</link>.</li>
          </ul>
        </li>
      </ol>
@@ -103,28 +142,74 @@ NOTE: The ISO 639/ISO 3166 convention is that language names are written in lowe
  </section>
  <section id="patterns">
    <title>Hyphenation Patterns</title>
    <p>If you would like to build your own hyphenation pattern files, or modify existing ones, this section will help you understand how to do so. Even when creating a pattern file from scratch, it may be beneficial to start with an existing file and modify it. See <link href="#std">Standard Hyphenation Support</link> or the source distribution (src/hyph) for examples. Here is a brief explanation of the contents of FOP's hyphenation patterns:</p>
    <warning>The remaining content of this section should be considered "draft" quality. It was drafted from theoretical literature, and has not been tested against actual FOP behavior. It may contain errors or omissions. Do not rely on these instructions without testing everything stated here. If you use these instructions, please provide feedback on the <link href="maillist.html#fop-user">FOP User mailing list</link>, either confirming their accuracy, or raising specific problems that we can address.</warning>
    <p>If you would like to build your own hyphenation pattern files, or modify
     existing ones, this section will help you understand how to do so. Even
     when creating a pattern file from scratch, it may be beneficial to start
     with an existing file and modify it. See <link href="#std">Standard
     Hyphenation Support</link> or the source distribution (src/hyph) for
     examples. Here is a brief explanation of the contents of FOP's hyphenation
     patterns:</p>
    <warning>The remaining content of this section should be considered "draft"
     quality. It was drafted from theoretical literature, and has not been
     tested against actual FOP behavior. It may contain errors or omissions.
     Do not rely on these instructions without testing everything stated here.
     If you use these instructions, please provide feedback on the
     <link href="maillist.html#fop-user">FOP User mailing list</link>, either
     confirming their accuracy, or raising specific problems that we can
     address.</warning>
    <ul>
      <li>The root of the pattern file is the &lt;hyphenation-info> element.</li>
      <li>&lt;hyphen-char> is self-explanatory: its attribute "value" contains the default character to be used for hyphenating this language. For English, this is the hyphen "-".</li>
      <li>&lt;hyphen-char>: its attribute "value" contains the character signalling
       a hyphen in the &lt;exceptions> section. It has nothing to do with the
       hyphenation character used in FOP, use the XSLFO hyphenation-character
       property for defining the hyphenation character there. At some points
       a dash U+002D is hardwired in the code, so you'd better use this too
       (patches to rectify the situation are welcome). There is no default,
       if you declare exceptions with hyphenations, you must declare the
       hyphen-char too.</li>
      <li>&lt;hyphen-min> contains two attributes:
        <ul>
          <li>before: the minimum number of characters in a word allowed to exist on a line immediately preceding a hyphenated word-break.</li>
          <li>after: the minimum number of characters in a word allowed to exist on a line immediately after a hyphenated word-break.</li>
          <li>before: the minimum number of characters in a word allowed to exist
           on a line immediately preceding a hyphenated word-break.</li>
          <li>after: the minimum number of characters in a word allowed to exist
           on a line immediately after a hyphenated word-break.</li>
        </ul>
        This element is unused and not even read. It should be considered a
        documentation for parameters used during pattern generation.
      </li>
      <li>&lt;classes> contains whitespace-separated character sets.
 The members of each set should be treated as equivalent for purposes of hyphenation.
 The English patterns, for example, include sets such as "aA" and "bB" to indicate that lower case characters should be treated as equivalent to uppercase characters for purposes of computing potential hyphenation breaks.</li>
      <li>&lt;exceptions> contains whitespace-separated words, each of which has either explicit hyphen characters to denote acceptable breakage points, or no hyphen characters, to indicate that this word should never be hyphenated.
 Exceptions override the patterns described below.</li>
      <li>&lt;patterns> includes whitespace-separated patterns, which are what drive most hyphenation decisions.
 The characters in these patterns are explained as follows:
      <li>&lt;classes> contains whitespace-separated character sets. The members
       of each set should be treated as equivalent for purposes of hyphenation,
       usually upper and lower case of the same character. The first character
       of the set is the canonical character, the patterns and exceptions
       should only contain these canonical representation characters (except
       digits for weight, the period (.) as word delimiter in the patterns and
       the hyphen char in exceptions, of course).</li>
      <li>&lt;exceptions> contains whitespace-separated words, each of which
       has either explicit hyphen characters to denote acceptable breakage
       points, or no hyphen characters, to indicate that this word should
       never be hyphenated, or contain explicit &lt;hyp> elements for specifying
       changes of spelling due to hyphenation (like backen -> bak-ken or
       Stoffarbe -> Stoff-farbe in the old german spelling). Exceptions override
       the patterns described below. Explicit &lt;hyp> declarations don't work
       yet (patches welcome). Exceptions are generally a bit brittle, test
       carefully.</li>
      <li>&lt;patterns> includes whitespace-separated patterns, which are what
       drive most hyphenation decisions. The characters in these patterns are
       explained as follows:
        <ul>
          <li>non-numeric characters represent characters in a sub-word to be evaluated</li>
          <li>the period character (.) represents a word boundary, i.e. either the beginning or ending of a word</li>
          <li>numeric characters represent a scoring system for indicating the acceptability of a hyphen in this location. Only odd numbers represent an acceptable location for a hyphen, with 5 being most desirable, and 1 being least desirable. Even numbers indicate an unacceptable location, with zero (implied when there is no number present) being unacceptable, and 4 being extremely unacceptable.</li>
          <li>non-numeric characters represent characters in a sub-word to be
           evaluated</li>
          <li>the period character (.) represents a word boundary, i.e. either
           the beginning or ending of a word</li>
          <li>numeric characters represent a scoring system for indicating the
           acceptability of a hyphen in this location. Odd numbers represent an
           acceptable location for a hyphen, with higher values overriding lower
           inhibiting values. Even numbers indicate an unacceptable location, with
           higher values overriding lower values indicating an acceptable position.
           A value of zero (inhibiting) is implied when there is no number present.
           Generally patterns are constructed so that valuse greater than 4 are rare.
           Due to a bug currently patterns with values of 8 and greater don't
           have an effect, so don't wonder.</li>
        </ul>
        Here are some examples from the English patterns file:
        <ul>
@@ -134,7 +219,32 @@ The characters in these patterns are explained as follows:
        Note that the algorithm that uses this data searches for each of the word's substrings in the patterns, and chooses the <em>highest</em> value found for letter combination.
      </li>
    </ul>
    <note>An open-source utility called patgen is available on many Unix/Linux distributions to assist in creating pattern files from dictionaries. Consult man pages or the www for details.</note>
    <p>If you want to convert a TeX hyphenation pattern file, you have to undo
     the TeX encoding for non-ASCII text. FOP uses Unicode, and the patterns
     must be proper Unicode too. You should be aware of the XML encoding issues,
     preferably use a good Unicode editor.</p>
    <p>Note that FOP does not do Unicode character normalization. If you use
     combining chars for accents and other character decorations, you must
     declare character classes for them, and use the same sequence of base character
     and combining marks in the XSLFO source, otherwise the pattern wouldn't match.
     Fortunately, Unicode provides precomposed characters for all important cases
     in common languages, until now nobody run seriously into this issue. Some dead
     languages and dialects, especially ancient ones, may pose a real problem
     though.</p>
    <p>If you want to generate your own patterns, an open-source utility called
     patgen is available on many Unix/Linux distributions and every TeX
     distribution which can be used to assist in
     creating pattern files from dictionaries. Pattern creation for languages like
     english or german is an art. If you can, read Frank Liang's original paper
     "Word Hy-phen-a-tion by Com-pu-ter" (yes, with hyphens). It is not available
     online. The original patgen.web source, included in the TeX source distributions,
     contains valuable comments, unfortunately technical details obscure often the
     high level issues. Another important source is
     <fork href="http://www.ctan.org/tex-archive/systems/knuth/tex/texbook.tex">The
     TeX Book</fork>, appendix H (either read the TeX source, or run it through
     TeX to typeset it). Secondary articles, for example the works by Petr Sojka,
     may alos give some much needed insigth into problems arising in automated
     hyphenation.</note>
  </section>
  </body>
 </document>