<book xmlns:src="http://nwalsh.com/xmlns/litprog/fragment"
      xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
<bookinfo>
<title>XSL Library Template Reference</title>
<releaseinfo role="cvs">$Id: lib.xweb,v 1.1 2003/06/09 18:40:56 blackburst Exp $
</releaseinfo>
<corpauthor>DocBook Open Repository Team</corpauthor>
<copyright>
  <year>1999</year>
  <year>2000</year>
  <year>2001</year>
  <year>2002</year>
  <holder>Norman Walsh</holder>
</copyright>
</bookinfo>

<preface><title>Introduction</title>

<para>This is technical reference documentation for the DocBook XSL
Stylesheets; it documents (some of) the parameters, templates, and
other elements of the stylesheets.</para>

<para>This is not intended to be <quote>user</quote> documentation.
It is provided for developers writing customization layers for the
stylesheets, and for anyone who's interested in <quote>how it
works</quote>.</para>

<para>Although I am trying to be thorough, this documentation is known
to be incomplete. Don't forget to read the source, too :-)</para>

</preface>

<reference>
<title>General Library Templates</title>

<refentry id="dot.count">
<refnamediv>
<refname>dot.count</refname>
<refpurpose>Returns the number of <quote>.</quote> characters in a string</refpurpose>
</refnamediv>

<refsect1><title>Description</title>

<programlisting><src:fragment id='dot.count.frag'>
<xsl:template name="dot.count">
  <!-- Returns the number of "." characters in a string -->
  <xsl:param name="string"></xsl:param>
  <xsl:param name="count" select="0"/>
  <xsl:choose>
    <xsl:when test="contains($string, '.')">
      <xsl:call-template name="dot.count">
        <xsl:with-param name="string" select="substring-after($string, '.')"/>
        <xsl:with-param name="count" select="$count+1"/>
      </xsl:call-template>
    </xsl:when>
    <xsl:otherwise>
      <xsl:value-of select="$count"/>
    </xsl:otherwise>
  </xsl:choose>
</xsl:template>
</src:fragment></programlisting>

</refsect1>
</refentry>

<!-- ================================================================== -->

<refentry id="copy-string">
<refnamediv>
<refname>copy-string</refname>
<refpurpose>Returns <quote>count</quote> copies of a string</refpurpose>
</refnamediv>

<refsect1><title>Description</title>

<programlisting><src:fragment id='copy-string.frag'>
<xsl:template name="copy-string">
  <!-- returns 'count' copies of 'string' -->
  <xsl:param name="string"></xsl:param>
  <xsl:param name="count" select="0"/>
  <xsl:param name="result"></xsl:param>

  <xsl:choose>
    <xsl:when test="$count>0">
      <xsl:call-template name="copy-string">
        <xsl:with-param name="string" select="$string"/>
        <xsl:with-param name="count" select="$count - 1"/>
        <xsl:with-param name="result">
          <xsl:value-of select="$result"/>
          <xsl:value-of select="$string"/>
        </xsl:with-param>
      </xsl:call-template>
    </xsl:when>
    <xsl:otherwise>
      <xsl:value-of select="$result"/>
    </xsl:otherwise>
  </xsl:choose>
</xsl:template>
</src:fragment></programlisting>

</refsect1>
</refentry>

<!-- ====================================================================== -->

<refentry id="string.subst">
<refnamediv>
<refname>string.subst</refname>
<refpurpose>Substitute one text string for another in a string</refpurpose>
</refnamediv>

<refsect1><title>Description</title>

<para>The <function>string.subst</function> template replaces all
occurances of <parameter>target</parameter> in <parameter>string</parameter>
with <parameter>replacement</parameter> and returns the result.
</para>

<programlisting><src:fragment id='string.subst.frag'>
<xsl:template name="string.subst">
  <xsl:param name="string"></xsl:param>
  <xsl:param name="target"></xsl:param>
  <xsl:param name="replacement"></xsl:param>

  <xsl:choose>
    <xsl:when test="contains($string, $target)">
      <xsl:variable name="rest">
        <xsl:call-template name="string.subst">
          <xsl:with-param name="string"
                          select="substring-after($string, $target)"/>
          <xsl:with-param name="target" select="$target"/>
          <xsl:with-param name="replacement" select="$replacement"/>
        </xsl:call-template>
      </xsl:variable>
      <xsl:value-of select="concat(substring-before($string, $target),
                                   $replacement,
                                   $rest)"/>
    </xsl:when>
    <xsl:otherwise>
      <xsl:value-of select="$string"/>
    </xsl:otherwise>
  </xsl:choose>
</xsl:template>
</src:fragment></programlisting>

</refsect1>
</refentry>

<!-- ================================================================== -->

<refentry id="xpointer.idref">
<refnamediv>
<refname>xpointer.idref</refname>
<refpurpose>Extract IDREF from an XPointer</refpurpose>
</refnamediv>

<refsect1><title>Description</title>

<para>The <function>xpointer.idref</function> template returns the
ID portion of an XPointer which is a pointer to an ID within the current
document, or the empty string if it is not.</para>
<para>In other words, <function>xpointer.idref</function> returns
<quote>foo</quote> when passed either <literal>#foo</literal>
or <literal>#xpointer(id('foo'))</literal>, otherwise it returns
the empty string.</para>

<programlisting><src:fragment id='xpointer.idref.frag'>
<xsl:template name="xpointer.idref">
  <xsl:param name="xpointer">http://...</xsl:param>
  <xsl:choose>
    <xsl:when test="starts-with($xpointer, '#xpointer(id(')">
      <xsl:variable name="rest" select="substring-after($xpointer, '#xpointer(id(')"/>
      <xsl:variable name="quote" select="substring($rest, 1, 1)"/>
      <xsl:value-of select="substring-before(substring-after($xpointer, $quote), $quote)"/>
    </xsl:when>
    <xsl:when test="starts-with($xpointer, '#')">
      <xsl:value-of select="substring-after($xpointer, '#')"/>
    </xsl:when>
    <!-- otherwise it's a pointer to some other document -->
  </xsl:choose>
</xsl:template>
</src:fragment></programlisting>

</refsect1>
</refentry>


<!-- ================================================================== -->

<refentry id="length-magnitude">
<refnamediv>
<refname>length-magnitude</refname>
<refpurpose>Return the unqualified dimension from a length specification</refpurpose>
</refnamediv>

<refsect1><title>Description</title>

<para>The <function>length-magnitude</function> template returns the
unqualified length ("20" for "20pt") from a dimension.
</para>

<programlisting><src:fragment id='length-magnitude.frag'>
<xsl:template name="length-magnitude">
  <xsl:param name="length" select="'0pt'"/>

  <xsl:choose>
    <xsl:when test="string-length($length) = 0"/>
    <xsl:when test="substring($length,1,1) = '0'
                    or substring($length,1,1) = '1'
                    or substring($length,1,1) = '2'
                    or substring($length,1,1) = '3'
                    or substring($length,1,1) = '4'
                    or substring($length,1,1) = '5'
                    or substring($length,1,1) = '6'
                    or substring($length,1,1) = '7'
                    or substring($length,1,1) = '8'
                    or substring($length,1,1) = '9'
                    or substring($length,1,1) = '.'">
      <xsl:value-of select="substring($length,1,1)"/>
      <xsl:call-template name="length-magnitude">
        <xsl:with-param name="length" select="substring($length,2)"/>
      </xsl:call-template>
    </xsl:when>
  </xsl:choose>
</xsl:template>
</src:fragment></programlisting>

</refsect1>
</refentry>

<!-- ================================================================== -->

<refentry id="length-units">
<refnamediv>
<refname>length-units</refname>
<refpurpose>Return the units from a length specification</refpurpose>
</refnamediv>

<refsect1><title>Description</title>

<para>The <function>length-units</function> template returns the
units ("pt" for "20pt") from a length. If no units are supplied on the
length, the <parameter>defauilt.units</parameter> are returned.</para>

<programlisting><src:fragment id='length-units.frag'>
<xsl:template name="length-units">
  <xsl:param name="length" select="'0pt'"/>
  <xsl:param name="default.units" select="'px'"/>
  <xsl:variable name="magnitude">
    <xsl:call-template name="length-magnitude">
      <xsl:with-param name="length" select="$length"/>
    </xsl:call-template>
  </xsl:variable>

  <xsl:variable name="units">
    <xsl:value-of select="substring($length, string-length($magnitude)+1)"/>
  </xsl:variable>

  <xsl:choose>
    <xsl:when test="$units = ''">
      <xsl:value-of select="$default.units"/>
    </xsl:when>
    <xsl:otherwise>
      <xsl:value-of select="$units"/>
    </xsl:otherwise>
  </xsl:choose>
</xsl:template>
</src:fragment></programlisting>

</refsect1>
</refentry>

<!-- ================================================================== -->

<refentry id="length-spec">
<refnamediv>
<refname>length-spec</refname>
<refpurpose>Return a fully qualified length specification</refpurpose>
</refnamediv>

<refsect1><title>Description</title>

<para>The <function>length-spec</function> template returns the
qualified length from a dimension. If an unqualified length is given,
the <parameter>default.units</parameter> will be added to it.
</para>

<programlisting><src:fragment id='length-spec.frag'>
<xsl:template name="length-spec">
  <xsl:param name="length" select="'0pt'"/>
  <xsl:param name="default.units" select="'px'"/>

  <xsl:variable name="magnitude">
    <xsl:call-template name="length-magnitude">
      <xsl:with-param name="length" select="$length"/>
    </xsl:call-template>
  </xsl:variable>

  <xsl:variable name="units">
    <xsl:value-of select="substring($length, string-length($magnitude)+1)"/>
  </xsl:variable>

  <xsl:value-of select="$magnitude"/>
  <xsl:choose>
    <xsl:when test="$units='cm'
                    or $units='mm'
                    or $units='in'
                    or $units='pt'
                    or $units='pc'
                    or $units='px'
                    or $units='em'">
      <xsl:value-of select="$units"/>
    </xsl:when>
    <xsl:when test="$units = ''">
      <xsl:value-of select="$default.units"/>
    </xsl:when>
    <xsl:otherwise>
      <xsl:message>
        <xsl:text>Unrecognized unit of measure: </xsl:text>
        <xsl:value-of select="$units"/>
        <xsl:text>.</xsl:text>
      </xsl:message>
    </xsl:otherwise>
  </xsl:choose>
</xsl:template>
</src:fragment></programlisting>

</refsect1>
</refentry>

<!-- ================================================================== -->

<refentry id="length-in-points">
<refnamediv>
<refname>length-in-points</refname>
<refpurpose>Returns the size, in points, of a specified length</refpurpose>
</refnamediv>

<refsect1><title>Description</title>

<para>The <function>length-in-points</function> template converts a length
specification to points and returns that value as an unqualified
number.
</para>

<caution>
<para>There is no way for the template to infer the size of an
<literal>em</literal>. It relies on the default <parameter>em.size</parameter>
which is initially <literal>10</literal> (for 10pt).</para>

<para>Similarly, converting pixesl to points relies on the
<parameter>pixels.per.inch</parameter> parameter which is initially
<literal>90</literal>.
</para>
</caution>

<programlisting><src:fragment id='length-in-points.frag'>
<xsl:template name="length-in-points">
  <xsl:param name="length" select="'0pt'"/>
  <xsl:param name="em.size" select="10"/>
  <xsl:param name="pixels.per.inch" select="90"/>

  <xsl:variable name="magnitude">
    <xsl:call-template name="length-magnitude">
      <xsl:with-param name="length" select="$length"/>
    </xsl:call-template>
  </xsl:variable>

  <xsl:variable name="units">
    <xsl:value-of select="substring($length, string-length($magnitude)+1)"/>
  </xsl:variable>

  <xsl:choose>
    <xsl:when test="$units = 'pt'">
      <xsl:value-of select="$magnitude"/>
    </xsl:when>
    <xsl:when test="$units = 'cm'">
      <xsl:value-of select="$magnitude div 2.54 * 72.0"/>
    </xsl:when>
    <xsl:when test="$units = 'mm'">
      <xsl:value-of select="$magnitude div 25.4 * 72.0"/>
    </xsl:when>
    <xsl:when test="$units = 'in'">
      <xsl:value-of select="$magnitude * 72.0"/>
    </xsl:when>
    <xsl:when test="$units = 'pc'">
      <xsl:value-of select="$magnitude * 12.0"/>
    </xsl:when>
    <xsl:when test="$units = 'px'">
      <xsl:value-of select="$magnitude div $pixels.per.inch * 72.0"/>
    </xsl:when>
    <xsl:when test="$units = 'em'">
      <xsl:value-of select="$magnitude * $em.size"/>
    </xsl:when>
    <xsl:otherwise>
      <xsl:message>
        <xsl:text>Unrecognized unit of measure: </xsl:text>
        <xsl:value-of select="$units"/>
        <xsl:text>.</xsl:text>
      </xsl:message>
    </xsl:otherwise>
  </xsl:choose>
</xsl:template>
</src:fragment></programlisting>

</refsect1>
</refentry>

<!-- ================================================================== -->

<refentry id="pi-attribute">
<refnamediv>
<refname>pi-attribute</refname>
<refpurpose>Extract a pseudo-attribute from a PI</refpurpose>
</refnamediv>

<refsect1><title>Description</title>

<para>The <function>pi-attribute</function> template extracts a pseudo-attribute
from a processing instruction. For example, given the PI
<quote><literal>&lt;?foo bar="1" baz='red'?&gt;</literal></quote>,</para>
<programlisting><![CDATA[<xsl:call-template name="pi-attribute">
  <xsl:with-param name="pis" select="processing-instruction('foo')"/>
  <xsl:with-param name="attribute" select="'baz'"/>
</xsl:call-template>]]></programlisting>
<para>will return <quote>red</quote>. This template returns the first matching
attribute that it finds. Presented with processing instructions that
contain badly formed pseudo-attributes (missing or unbalanced quotes,
for example), the template may silently return erroneous results.</para>

<programlisting><src:fragment id='pi-attribute.frag'>
<xsl:template name="pi-attribute">
  <xsl:param name="pis" select="processing-instruction('')"/>
  <xsl:param name="attribute">filename</xsl:param>
  <xsl:param name="count">1</xsl:param>

  <xsl:choose>
    <xsl:when test="$count>count($pis)">
      <!-- not found -->
    </xsl:when>
    <xsl:otherwise>
      <xsl:variable name="pi">
        <xsl:value-of select="$pis[$count]"/>
      </xsl:variable>
      <xsl:choose>
        <xsl:when test="contains($pi,concat(' ', $attribute, '='))">
          <xsl:variable name="rest" select="substring-after($pi,concat(' ', $attribute,'='))"/>
          <xsl:variable name="quote" select="substring($rest,1,1)"/>
          <xsl:value-of select="substring-before(substring($rest,2),$quote)"/>
        </xsl:when>
        <xsl:otherwise>
          <xsl:call-template name="pi-attribute">
            <xsl:with-param name="pis" select="$pis"/>
            <xsl:with-param name="attribute" select="$attribute"/>
            <xsl:with-param name="count" select="$count + 1"/>
          </xsl:call-template>
        </xsl:otherwise>
      </xsl:choose>
    </xsl:otherwise>
  </xsl:choose>
</xsl:template>
</src:fragment></programlisting>

</refsect1>
</refentry>

<!-- ================================================================== -->

<refentry id="lookup.key">
<refnamediv>
<refname>lookup.key</refname>
<refpurpose>Retrieve the value associated with a particular key in a table</refpurpose>
</refnamediv>

<refsect1><title>Description</title>

<para>Given a table of space-delimited key/value pairs,
the <function>lookup.key</function> template extracts the value associated
with a particular key.</para>

<programlisting><src:fragment id='lookup.key.frag'>
<xsl:template name="lookup.key">
  <xsl:param name="key" select="''"/>
  <xsl:param name="table" select="''"/>

  <xsl:if test="contains($table, ' ')">
    <xsl:choose>
      <xsl:when test="substring-before($table, ' ') = $key">
        <xsl:variable name="rest" select="substring-after($table, ' ')"/>
        <xsl:choose>
          <xsl:when test="contains($rest, ' ')">
            <xsl:value-of select="substring-before($rest, ' ')"/>
          </xsl:when>
          <xsl:otherwise>
            <xsl:value-of select="$rest"/>
          </xsl:otherwise>
        </xsl:choose>
      </xsl:when>
      <xsl:otherwise>
        <xsl:call-template name="lookup.key">
          <xsl:with-param name="key" select="$key"/>
          <xsl:with-param name="table"
                            select="substring-after(substring-after($table,' '), ' ')"/>
        </xsl:call-template>
      </xsl:otherwise>
    </xsl:choose>
  </xsl:if>
</xsl:template>
</src:fragment></programlisting>

</refsect1>
</refentry>

<!-- ================================================================== -->

<refentry id="xpath.location">
<refnamediv>
<refname>xpath.location</refname>
<refpurpose>Calculate the XPath child-sequence to the current node</refpurpose>
</refnamediv>

<refsect1><title>Description</title>

<para>The <function>xpath.location</function> template calculates the
absolute path from the root of the tree to the current element node.
</para>

<programlisting><src:fragment id='xpath.location.frag'>
<xsl:template name="xpath.location">
  <xsl:param name="node" select="."/>
  <xsl:param name="path" select="''"/>

  <xsl:variable name="next.path">
    <xsl:value-of select="local-name($node)"/>
    <xsl:if test="$path != ''">/</xsl:if>
    <xsl:value-of select="$path"/>
  </xsl:variable>

  <xsl:choose>
    <xsl:when test="$node/parent::*">
      <xsl:call-template name="xpath.location">
        <xsl:with-param name="node" select="$node/parent::*"/>
        <xsl:with-param name="path" select="$next.path"/>
      </xsl:call-template>
    </xsl:when>
    <xsl:otherwise>
      <xsl:text>/</xsl:text>
      <xsl:value-of select="$next.path"/>
    </xsl:otherwise>
  </xsl:choose>
</xsl:template>
</src:fragment></programlisting>

</refsect1>
</refentry>

<!-- ================================================================== -->

<refentry id="comment-escape-string">
<refnamediv>
<refname>comment-escape-string</refname>
<refpurpose>Prepare a string for inclusion in an XML comment</refpurpose>
</refnamediv>

<refsect1><title>Description</title>

<para>The <function>comment-escape-string</function> template returns a string
that has been transformed so that it can safely be output as an XML comment.
Internal occurrences of "--" will be replaced with "- -" and a leading and/or
trailing space will be added to the string, if necessary.</para>

<programlisting><src:fragment id='comment-escape-string'>
<xsl:template name="comment-escape-string">
  <xsl:param name="string" select="''"/>

  <xsl:if test="starts-with($string, '-')">
    <xsl:text> </xsl:text>
  </xsl:if>

  <xsl:call-template name="comment-escape-string.recursive">
    <xsl:with-param name="string" select="$string"/>
  </xsl:call-template>

  <xsl:if test="substring($string, string-length($string), 1) = '-'">
    <xsl:text> </xsl:text>
  </xsl:if>
</xsl:template>
</src:fragment></programlisting>

</refsect1>
</refentry>

<refentry id="comment-escape-string.recursive">
<refnamediv>
<refname>comment-escape-string.recursive</refname>
<refpurpose>Internal function used by comment-escape-string</refpurpose>
</refnamediv>

<refsect1><title>Description</title>

<para>The <function>comment-escape-string.recursive</function> template is used
by <function>comment-escape-string</function>.</para>

<programlisting><src:fragment id="comment-escape-string.recursive">
<xsl:template name="comment-escape-string.recursive">
  <xsl:param name="string" select="''"/>
  <xsl:choose>
    <xsl:when test="contains($string, '--')">
      <xsl:value-of select="substring-before($string, '--')"/>
      <xsl:value-of select="'- -'"/>
      <xsl:call-template name="comment-escape-string.recursive">
        <xsl:with-param name="string" select="substring-after($string, '--')"/>
      </xsl:call-template>
    </xsl:when>
    <xsl:otherwise>
      <xsl:value-of select="$string"/>
    </xsl:otherwise>
  </xsl:choose>
</xsl:template>
</src:fragment></programlisting>
</refsect1>
</refentry>

</reference>

<reference>
<title>Relative URI Functions</title>

<partintro><title>Introduction</title>

<para>These functions manipulate relative URI references.</para>

<para>The following assumptions must hold true:</para>

<orderedlist>
<listitem>
<para>All URIs are relative.</para>
</listitem>
<listitem>
<para>No URI contains the <quote><literal>../</literal></quote> sequence
which would effectively move <quote>up</quote> the hierarchy.</para>
</listitem>
</orderedlist>

<para>If these assumptions do not hold, the results are unpredictable.</para>

</partintro>

<refentry id="count.uri.path.depth">
<refnamediv>
<refname>count.uri.path.depth</refname>
<refpurpose>Count the number of path components in a relative URI</refpurpose>
</refnamediv>

<refsect1><title>Description</title>

<para>This function counts the number of path components in a relative URI.</para>

<programlisting><src:fragment id='count.uri.path.depth.frag'>
<xsl:template name="count.uri.path.depth">
  <xsl:param name="filename" select="''"/>
  <xsl:param name="count" select="0"/>

  <xsl:choose>
    <xsl:when test="contains($filename, '/')">
      <xsl:call-template name="count.uri.path.depth">
        <xsl:with-param name="filename" select="substring-after($filename, '/')"/>
        <xsl:with-param name="count" select="$count + 1"/>
      </xsl:call-template>
    </xsl:when>
    <xsl:otherwise>
      <xsl:value-of select="$count"/>
    </xsl:otherwise>
  </xsl:choose>
</xsl:template>
</src:fragment></programlisting>

</refsect1>
</refentry>

<refentry id="trim.common.uri.paths">
<refnamediv>
<refname>trim.common.uri.paths</refname>
<refpurpose>Trim common leading path components from a relative URI</refpurpose>
</refnamediv>

<refsect1><title>Description</title>

<para>This function trims common leading path components from a relative URI.</para>

<programlisting><src:fragment id='trim.common.uri.paths.frag'>
<xsl:template name="trim.common.uri.paths">
  <xsl:param name="uriA" select="''"/>
  <xsl:param name="uriB" select="''"/>
  <xsl:param name="return" select="'A'"/>

  <xsl:choose>
    <xsl:when test="contains($uriA, '/') and contains($uriB, '/')
                    and substring-before($uriA, '/') = substring-before($uriB, '/')">
      <xsl:call-template name="trim.common.uri.paths">
        <xsl:with-param name="uriA" select="substring-after($uriA, '/')"/>
        <xsl:with-param name="uriB" select="substring-after($uriB, '/')"/>
        <xsl:with-param name="return" select="$return"/>
      </xsl:call-template>
    </xsl:when>
    <xsl:otherwise>
      <xsl:choose>
        <xsl:when test="$return = 'A'">
          <xsl:value-of select="$uriA"/>
        </xsl:when>
        <xsl:otherwise>
          <xsl:value-of select="$uriB"/>
        </xsl:otherwise>
      </xsl:choose>
    </xsl:otherwise>
  </xsl:choose>
</xsl:template>
</src:fragment></programlisting>

</refsect1>
</refentry>

</reference>

<appendix><title>The Stylesheet</title>

<para>The <filename>lib.xsl</filename> stylesheet is just a wrapper
around these functions.</para>

<src:fragment id="top" mundane-result-prefixes="xsl">

<!-- ********************************************************************
     $Id: lib.xweb,v 1.1 2003/06/09 18:40:56 blackburst Exp $
     ********************************************************************

     This file is part of the XSL DocBook Stylesheet distribution.
     See ../README or http://nwalsh.com/docbook/xsl/ for copyright
     and other information.

     This module implements DTD-independent functions

     ******************************************************************** -->

<xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
                xmlns:src="http://nwalsh.com/xmlns/litprog/fragment"
                exclude-result-prefixes="src"
                version='1.0'>

<src:fragref linkend="dot.count.frag"/>
<src:fragref linkend="copy-string.frag"/>
<src:fragref linkend="string.subst.frag"/>
<src:fragref linkend="xpointer.idref.frag"/>
<src:fragref linkend="length-magnitude.frag"/>
<src:fragref linkend="length-units.frag"/>
<src:fragref linkend="length-spec.frag"/>
<src:fragref linkend="length-in-points.frag"/>
<src:fragref linkend="pi-attribute.frag"/>
<src:fragref linkend="lookup.key.frag"/>
<src:fragref linkend="xpath.location.frag"/>
<src:fragref linkend="comment-escape-string"/>
<src:fragref linkend="comment-escape-string.recursive"/>
<src:fragref linkend="count.uri.path.depth.frag"/>
<src:fragref linkend="trim.common.uri.paths.frag"/>

</xsl:stylesheet>
</src:fragment>

</appendix>
</book>
