Extending the Verbatim Rendering
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## Extending the Verbatim Rendering

### Dblatex Specific Options

There are few attributes or options specific to dblatex to render verbatim blocks:

- The `role` attribute of `screen`, `programlisting`, and `literallayout` can take the following special values:

  wrap

    The verbatim lines can break and wrap when they are longer than the available width. It is the default behaviour.

  overflow

    The verbatim lines never break and go into the margin when they are too long.

  scale

    The verbatim block is automatically scaled so that the longuest line fits in the available page width. This feature is activated only when role is set to this value and when the parameter `literal.extensions` is not set to 0.

- The parameter `literal.role` can be used to set the default role to apply. By default the value is an empty string.

- The parameter `literal.class` can be used to set the default `literallayout` class when no class attribute is given. By default the value is `monospaced`.

### Formatting embedded elements

The programlisting and screen environments are supported by dblatex, but the implementation is rather conservative, that is, most of the elements embedded in such environments are not rendered like in normal environment (e.g. bold, enphasis, etc.). Only the contained text is printed out. For the elements whose rendering is lost, dblatex prints out a warning message.

For example, let's compile the following programlisting fragment:

    <programlisting>

    zone <replaceable>zone_name</replaceable>
    <optional><replaceable>class</replaceable></optional> {
        type delegation-only;
    };

    </programlisting>

dblatex warns that the `optional` and `replaceable` elements are not supported (i.e. not rendered) in the programlisting:

    $ dblatex progfrag.xml
    Build the book set list...
    Build the listings...
    XSLT stylesheets DocBook - LaTeX 2e (devel)
    ===================================================
    Warning: the root element is not an article nor a book
    Warning: programlisting wrapped with article
    replaceable not supported in programlisting or screen
    optional not supported in programlisting or screen
    replaceable not supported in programlisting or screen
    replaceable not supported in programlisting or screen
    optional not supported in programlisting or screen
    replaceable not supported in programlisting or screen
    ...

If you want those elements be formatted in bold, or italic you need to override the templates used in `latex.programlisting` mode, as follow:

    <xsl:template match="replaceable|optional" mode="latex.programlisting">
       <xsl:param name="co-tagin" select="'&lt;:'"/>
       <xsl:param name="rnode" select="/"/>
       <xsl:param name="probe" select="0"/>

       <xsl:call-template name="verbatim.boldseq">
         <xsl:with-param name="co-tagin" select="$co-tagin"/>
         <xsl:with-param name="rnode" select="$rnode"/>
         <xsl:with-param name="probe" select="$probe"/>
       </xsl:call-template>
    </xsl:template>

| These parameters are required in `latex.programlisting` mode.
| The predefined template makes bold the verbatim text of the element.

If formatting setup is not enough, you can also render these elements as if they were in a normal environment. To do this, you need to override the templates used in `latex.programlisting` mode, as follow:

    <xsl:template match="replaceable|optional" mode="latex.programlisting">
       <xsl:param name="co-tagin" select="'&lt;:'"/>
       <xsl:param name="rnode" select="/"/>
       <xsl:param name="probe" select="0"/>

       <xsl:call-template name="verbatim.embed">
         <xsl:with-param name="co-tagin" select="$co-tagin"/>
         <xsl:with-param name="rnode" select="$rnode"/>
         <xsl:with-param name="probe" select="$probe"/>
       </xsl:call-template>
    </xsl:template>

| To enable the normal mode rendering within a verbatim environment, call the verbatim.embed template, and pass the mandatory parameters.

### Creating a new Verbatim Environment

dblatex heavily relies upon the listing latex package to display the `screen`, `programlisting`, and `literallayout` blocks.

The global listing setup can be overwritten with `literal.layout.options` but the user can also provide its own listing environment to use instead of the default environment, by using the following procedure:

1. Create the new listing environment in a customized latex style, like the following example. It is required that the environment name starts with the string `"lst"`. If not, dblatex raises an error because it cannot recognize it as a special verbatim environment.

       %%
       %% This style is derivated from the db2latex one
       %%
       \NeedsTeXFormat{LaTeX2e}
       \ProvidesPackage{mystyle}[2012/02/03 My DocBook Style]

       %% Just use the original package and pass the options
       \RequirePackageWithOptions{db2latex}

       %% New listing environment doing what I want
       \lstnewenvironment{lstblock}[1][]
         {\lstset{numbers=left,numberstyle=\tiny,float,#1}}
         {}

2. Specify to dblatex the listing environment name through the `literal.environment` parameter, either on the command line or with a user XSL stylesheet.

       $ dblatex -s mystyle.sty -P literal.environment=lstblock file.xml

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