<refentry xmlns="http://docbook.org/ns/docbook"
          xmlns:xlink="http://www.w3.org/1999/xlink"
          xmlns:xi="http://www.w3.org/2001/XInclude"
          xmlns:src="http://nwalsh.com/xmlns/litprog/fragment"
          xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
          version="5.0" xml:id="custom.css.source">
  <refmeta>
    <refentrytitle>custom.css.source</refentrytitle>
    <refmiscinfo class="other" otherclass="datatype">string</refmiscinfo>
  </refmeta>
  <refnamediv>
    <refname>custom.css.source</refname>
    <refpurpose>Name of a custom CSS input file</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <src:fragment xml:id="custom.css.source.frag"><xsl:param name="custom.css.source"></xsl:param></src:fragment>
  </refsynopsisdiv>

  <refsection><info><title>Description</title></info>

<para>The <parameter>custom.css.source</parameter>
parameter enables you to add CSS styles to DocBook's
HTML output.</para>

<para>The parameter
specifies the name of a file containing custom
CSS styles.  The file must be a well-formed XML file that
consists of a single <tag>style</tag> root
element that contains CSS styles as its text content.
For example:</para>
<programlisting><![CDATA[<?xml version="1.0"?>
<style>
h2 {
  font-weight: bold;
  color: blue;
}
...
</style>
]]></programlisting>

<para>The filename specified by the parameter
should have a <literal>.xml</literal>
filename suffix, although that is not required.
The default value of this parameter is blank.</para>

<para>If <parameter>custom.css.source</parameter> is not blank, then
the stylesheet takes the following actions.
These actions take place regardless of the value of
the <parameter>make.clean.html</parameter> parameter.</para>

<orderedlist>
  <listitem>
    <para>The stylesheet uses the XSLT <literal>document()</literal>
    function to open the file specified by the parameter and
    load it into a variable.</para>
  </listitem>
  <listitem>
    <para>The stylesheet forms an output pathname consisting of the
    value of the <parameter>base.dir</parameter> parameter (if it is set)
    and the value of <parameter>custom.css.source</parameter>,
    with the <literal>.xml</literal> suffix stripped off.
    </para>
  </listitem>
  <listitem>
    <para>The stylesheet removes the <tag>style</tag>
    wrapper element and writes just the CSS text content to the output file.</para>
  </listitem>
  <listitem>
    <para>The stylesheet adds a <tag>link</tag> element to the
    HTML <tag>HEAD</tag> element to reference this external CSS stylesheet.
    For example:
    <programlisting>&lt;link rel="stylesheet" href="custom.css" type="text/css"&gt;
    </programlisting>
    </para>
  </listitem>
</orderedlist>


<para>If the <parameter>make.clean.html</parameter> parameter is nonzero
(the default is zero),
and if the <parameter>docbook.css.source</parameter> parameter
is not blank (the default is not blank),
then the stylesheet will also generate a default CSS file
and add a <tag>link</tag> tag to reference it.
The <tag>link</tag> to the custom CSS comes after the 
<tag>link</tag> to the default, so it should cascade properly
in most browsers.
If you do not want two <tag>link</tag> tags, and
instead want your custom CSS to import the default generated
CSS file, then do the following:
</para>

<orderedlist>
  <listitem>
    <para>Add a line like the following to your custom CSS source file:</para>
    <programlisting>@import url("docbook.css")
    </programlisting>
  </listitem>
  <listitem>
    <para>Set the <parameter>docbook.css.link</parameter> parameter 
    to zero. This will omit the <tag>link</tag> tag
    that references the default CSS file.</para>
  </listitem>
</orderedlist>

<para>If you set <parameter>make.clean.html</parameter> to nonzero but
you do not want the default CSS generated, then also set
the <parameter>docbook.css.source</parameter> parameter to blank.
Then no default CSS will be generated, and so
all CSS styles must come from your custom CSS file.</para>

<para>You can use the <parameter>generate.css.header</parameter>
parameter to instead write the CSS to each HTML <tag>HEAD</tag>
element in a <tag>style</tag> tag instead of an external CSS file.</para>

  </refsection>
</refentry>