Metadata-Version: 1.0
Name: xdv
Version: 0.3
Summary: XDV implements a subset of Deliverance using a pure XSLT engine. With XDV, you
"compile" your theme and ruleset in one step, then use a superfast/simple
transform on each request thereafter. Alternatively, compile your theme during
development, check it into Subversion, and not touch XDV during deployment.
Home-page: UNKNOWN
Author: Paul Everitt, Laurence Rowe and Martin Aspeli.
Author-email: laurence@lrowe.co.uk
License: New BSD
Description: =============================
        XDV - XSLT Deliverance Engine
        =============================
        
        .. contents:: Contents
        
        Introduction
        ============
        
        XDV is an implementation of the `Deliverance`_ concept using pure XSLT. In
        short, it is a way to apply a style/theme contained in a static HTML web page
        (usually with related CSS, JavaScript and image resources) to a dynamic
        website created using any server-side technology.
        
        Consider a scenario where you have a dynamic website, to which you want to
        apply a theme built by a web designer. The web designer is not familiar with
        the technology behind the dynamic website, and so has supplied a "static HTML"
        version of the site. This consists of an HTML file with more-or-less semantic
        markup, one or more style sheets, and perhaps some other resources like
        images or JavaScript files.
        
        Using XDV, you could apply this theme to your dynamic website as follows:
        
        1. Identify the placeholders in the theme file that need to be replaced with
        dynamic elements. Ideally, these should be clearly identifiable, for
        example with a unique HTML ``id`` attribute.
        2. Identify the corresponding markup in the dynamic website. Then write a
        "replace" or "copy" rule using XDV's rules syntax that replaces the theme's
        static placeholder with the dynamic content.
        3. Identify markup in the dynamic website that should be copied wholesale into
        the theme. CSS and JavaScript links in the ``<head />`` are often treated
        this way. Write an XDV "append" or "prepend" rule to copy these elements
        over.
        4. Identify parts of the theme and/or dynamic website that are superfluous.
        Write an XDV "drop" rule to remove these elements.
        
        The rules file is written using a simple XML syntax. Elements in the theme
        and "content" (the dynamic website) can be identified using CSS3 or XPath
        selectors.
        
        Once you have a theme HTML file and a rules XML file, you compile these using
        the XDV compiler into a single XSLT file. You can then deploy this XSLT file
        with your application. An XSLT processor (such as mod_transform in Apache)
        will then transform the dynamic content from your website into the themed
        content your end users see. The transformation takes place on-the-fly for
        each request.
        
        Bear in mind that:
        
        * You never have to write, or even read, a line of XSLT (unless you want to).
        * The XSLT transformation that takes place for each request is very fast.
        * Static theme resources (like images, stylesheets or JavaScript files) can
        be served from a static webserver, which is normally much faster than
        serving them from a dynamic application.
        * You can leave the original theme HTML untouched, with makes it easier to
        re-use for other scenarios. For example, you can stitch two unrelated
        applications together by using a single theme file with separate rules
        files. This would result in two compiled XSLT files. You could use location
        match rules or similar techniques to choose which one to invoke for a given
        request.
        
        We will illustrate how to set up XDV for deployment below.
        
        Installation
        ============
        
        To install XDV, you should install the ``xdv`` egg. You can do that using
        ``easy_install``, ``pip`` or ``zc.buildout``. For example, using
        ``easy_install`` (ideally in a ``virtualenv``)::
        
        $ easy_install -U xdv
        
        If using ``zc.buildout``, you can use the following ``buildout.cfg`` as a
        starting point. This will ensure that the console scripts are installed,
        which is important if you need to execute the XDV compiler manually::
        
        [buildout]
        parts =
        xdv
        
        [xdv]
        recipe = zc.recipe.egg
        eggs = xdv
        
        Note that ``lxml`` is a dependency of ``xdv``, so you may need to install the
        libxml2 and libxslt development packages in order for it to build. On
        Debian/Ubuntu you can run::
        
        $ sudo apt-get install libxslt1-dev
        
        On some operating systems, notably Mac OS X, installing a "good" ``lxml`` egg
        can be problematic, due to a mismatch in the operating system versions of the
        ``libxml2`` and ``libxslt`` libraries that ``lxml`` uses. To get around that,
        you can compile a static ``lxml`` egg using the following buildout recipe::
        
        [buildout]
        # lxml should be first in the parts list
        parts =
        lxml
        xdv
        
        [lxml]
        recipe = z3c.recipe.staticlxml
        egg = lxml
        libxml2-url = http://xmlsoft.org/sources/libxml2-2.7.6.tar.gz
        libxslt-url = http://xmlsoft.org/sources/libxslt-1.1.26.tar.gz
        
        [xdv]
        recipe = zc.recipe.egg
        eggs = xdv
        
        Once installed, you should find ``xdvcompiler`` and ``xdvrun`` in your
        ``bin`` directory.
        
        Rules file syntax
        =================
        
        The rules file, conventionally called ``rules.xml``, is rooted in a tag
        called ``<rules />``::
        
        <?xml version="1.0" encoding="UTF-8"?>
        <rules xmlns="http://namespaces.plone.org/xdv"
        xmlns:css="http://namespaces.plone.org/xdv+css">
        
        ...
        
        </rules>
        
        Here we have defined two namespaces: the default namespace is used for rules
        and XPath selectors. The ``css`` namespace is used for CSS3 selectors. These
        are functionally equivalent. In fact, CSS selectors are replaced by the
        equivalent XPath selector during the pre-processing step of the compiler.
        Thus, they have no performance impact.
        
        XDV supports complex CSS3 and XPath selectors, including things like the
        ``nth-child`` pseudo-selector. You are advised to consult a good reference
        if you are new to XPath and/or CSS3.
        
        The following elements are allowed inside the ``<rules />`` element:
        
        ``<replace />``
        ---------------
        
        Used to replace an element in the theme entirely with an element in the
        content. For example::
        
        <replace theme="/html/head/title" content="/html/head/title"/>
        
        The (near-)equivalent using CSS selectors would be::
        
        <replace css:theme="title" css:content="title"/>
        
        The result of either is that the ``<title />`` element in the theme is
        replaced with the ``<title />`` element in the (dynamic) content.
        
        ``<copy />``
        ------------
        
        Used to replace the contents of a placeholder tag with a tag from the
        theme. For example::
        
        <copy css:theme="#main" css:content="#portal-content > *" />
        
        This would replace any placeholder content inside the element with id
        ``main`` in the theme with all children of the element with id
        ``portal-content`` in the content. The usual reason for using ``<copy />``
        instead of ``<replace />``, is that the theme has CSS styles or other
        behaviour attached to the target element (with id ``main`` in this case).
        
        ``<append />`` and ``<prepend />``
        ----------------------------------
        
        Used to copy elements from the content into an element in the theme,
        leaving existing content in place. ``<append />`` places the matched
        content directly before the closing tag in the theme; ``<prepend />`` places
        it directly after the opening tag. For example::
        
        <append theme="/html/head" content="/html/head/link" />
        
        This will copy all ``<link />`` elements in the head of the content into
        the theme.
        
        As a special case, you can copy individual *attributes* from a content
        element to an element in the theme using ``<prepend />``::
        
        <prepend theme="/html/body" content="/html/body/@class" />
        
        This would copy the ``class`` attribute of the ``<body />`` element in
        the content into the theme (replacing an existing attribute with the
        same name if there is one).
        
        ``<before />`` and ``<after />``
        --------------------------------
        
        These are equivalent to ``<append />`` and ``<prepend />``, but place
        the matched content before or after the matched theme element, rather
        than immediately inside it. For example:
        
        <before css:theme="#content" css:content="#info-box" />
        
        This would place the element with id ``info-box`` from the content
        immediately before the element with id ``content`` in the theme. If we
        wanted the box below the content instead, we could do::
        
        <after css:theme="#content" css:content="#info-box" />
        
        ``<drop />``
        ------------
        
        Used to drop elements from the theme or the content. This is the only
        element that accepts either ``theme`` or ``content`` attributes (or their
        ``css:`` equivalents), but not both::
        
        <drop css:content="#portal-content .about-box" />
        <copy css:theme="#content" css:content="#portal-content > *" />
        
        This would copy all children of the element with id ``portal-content`` in
        the theme  into the element with id ``content`` in the theme, but only
        after removing any element with class ``about-box`` inside the content
        element first. Similarly::
        
        <drop theme="/html/head/base" />
        
        Would drop the ``<base />`` tag from the head of the theme.
        
        Order of rule execution
        -----------------------
        
        In most cases, you should not care too much about the inner workings of the
        XDV compiler. However, it can sometimes be useful to understand the order
        in which rules are applied.
        
        1. ``<before />`` rules are always executed first.
        2. ``<drop />`` rules are executed next.
        3. ``<replace />`` rules are executed next, provided no ``<drop />`` rule was
        applied to the same theme node.
        4. ``<prepend />``, ``<copy />`` and ``<append />`` rules execute next,
        provided no ``<replace />`` rule was applied to the same theme node.
        5. ``<after />`` rules are executed last.
        
        Behaviour if theme or content is not matched
        --------------------------------------------
        
        If a rule does not match the theme (whether or not it matches the content),
        it is silently ignored.
        
        If a ``<replace />`` rule matches the theme, but not the content, the matched
        element will be dropped in the theme::
        
        <replace css:theme="#header" content="#header-element" />
        
        Here, if the element with id ``header-element`` is not found in the content,
        the placeholder with id ``header`` in the theme is removed.
        
        Similarly, the contents of a theme node matched with a ``<copy />`` rule will
        be dropped if there is no matching content. Another way to think of this is
        that if no content node is matched, XDV uses an empty nodeset when copying or
        replacing.
        
        If you want the placeholder to stay put in the case of a missing content node,
        you can make this a conditional rule::
        
        <replace css:theme="#header" content="#header-element" if-content="" />
        
        See below for more details on conditional rules.
        
        Advanced usage
        --------------
        
        The simple rules above should suffice for most use cases. However, there are
        a few more advanced tools at your disposal, should you need them.
        
        Conditional rules
        ~~~~~~~~~~~~~~~~~
        
        Sometimes, it is useful to apply a rule only if a given element appears or
        does not appear in the markup. The ``if-content`` attribute can be used with
        any rule to make it conditional.
        
        ``if-content`` should be set an XPath expression. You can also use
        ``css:if-content`` with a CSS3 expression. If the expression matches a node
        in the content, the rule will be applied::
        
        <copy css:theme="#portlets" css:content=".portlet"/>
        <drop css:theme="#portlet-wrapper" if-content="not(//*[@class='portlet'])"/>
        
        This will copy all elements with class ``portlet`` into the ``portlets``
        element. If there are no matching elements in the content we drop the
        ``portlet-wrapper`` element, which is presumably superfluous.
        
        Here is another example using CSS selectors::
        
        <copy css:theme="#header" css:content="#header-box > *"
        css:if-content="#personal-bar"/>
        
        This will copy the children of the element with id ``header-box`` in the
        content into the element with id ``header`` in the theme, so long as an
        element with id ``personal-bar`` also appears somewhere in the content.
        
        Above, we also saw the special case of an empty ``if-content`` (which also
        works with an empty ``css:if-content``). This is a shortcut that means "use
        the expression in the ``content`` or ``css:content``` attribute as the
        condition". Hence the following two rules are equivalent::
        
        <copy css:theme="#header" css:content="#header-box > *"
        css:if-content="#header-box > *"/>
        <copy css:theme="#header" css:content="#header-box > *"
        css:if-content=""/>
        
        If multiple rules of the same type match the same theme node but have
        different ``if-content`` expressions, they will be combined as an
        if..else if...else block::
        
        <copy theme="/html/body/h1" content="/html/body/h1/text()"
        if-content="/html/body/h1"/>
        <copy theme="/html/body/h1" content="//h1[@id='first-heading']/text()"
        if-content="//h1[@id='first-heading']"/>
        <copy theme="/html/body/h1" content="/html/head/title/text()" />
        
        These rules all attempt to fill the text in the ``<h1 />`` inside the body.
        The first rule looks for a similar ``<h1 />`` tag and uses its text. If that
        doesn't match, the second rule looks for any ``<h1 />`` with id
        ``first-heading``, and uses its text. If that doesn't match either, the
        final rule will be used as a fallback (since it has no ``if-content``),
        taking the contents of the ``<title />`` tag in the head of the content
        document.
        
        Including external content
        ~~~~~~~~~~~~~~~~~~~~~~~~~~
        
        Normally, the ``content`` attribute of any rule selects nodes from the
        response being returned by the underlying dynamic web server. However, it is
        possible to include content from a different URL using the ``href`` attribute
        on any rule (other than ``<drop />``). For example::
        
        <append css:theme="#left-column" css:content="#portlet" href="/extra.html"/>
        
        This will resolve the URL ``/extra.html``, look for an element with id
        ``portlet`` and then append to to the element with id ``left-column`` in the
        theme.
        
        The inclusion can happen in one of three ways:
        
        * Using the XSLT ``document()`` function. This is the default, but it can
        be explicitly specified by adding an attribute ``method="document"`` to the
        rule element. Whether this is able to resolve the URL depends on how and
        where the compiled XSLT is being executed::
        
        <append css:theme="#left-column" css:content="#portlet"
        href="/extra.html" method="document" />
        
        * Via a Server Side Include directive. This can be specified by setting the
        ``method`` attribute to ``ssi``::
        
        <append css:theme="#left-column" css:content="#portlet"
        href="/extra.html" method="ssi"/>
        
        The output will look something like this::
        
        <!--# include wait="yes" virtual="/extra.html?;filter_xpath=//*[@id%20=%20'portlet']" -->
        
        This SSI instruction would need to be processed by a fronting web server
        such as Apache or nginx. Also note the ``;filter_xpath`` query string
        parameter. Since we are deferring resolution of the referenced document
        until SSI processing takes place (i.e. after the compiled XDV XSLT transform
        has executed), we need to ask the SSI processor to filter out elements in
        the included file that we are not interested in. This requires specific
        configuration. An example for nginx is included below.
        
        For simple SSI includes of a whole document, you may omit the ``content``
        selector from the rule::
        
        <append css:theme="#left-column" href="/extra.html" method="ssi"/>
        
        The output then renders like this::
        
        <!--# include wait="yes" virtual="/extra.html" -->
        
        * Via an Edge Side Includes directive. This can be specified by setting the
        ``method`` attribute to ``esi``::
        
        <append css:theme="#left-column" css:content="#portlet"
        href="/extra.html" method="esi"/>
        
        The output is similar to that for the SSI mode::
        
        <esi:include src="/extra.html?;filter_xpath=//*[@id%20=%20'portlet']"></esi:include>
        
        Again, the directive would need to be processed by a fronting server, such
        as Varnish. Chances are an ESI-aware cache server would not support
        arbitrary XPath filtering. If the referenced file is served by a dynamic
        web server, it may be able to inspect the ``;filter_xpath`` parameter and
        return a tailored response. Otherwise, if a server that can be made aware
        of this is placed in-between the cache server and the underlying web server,
        that server can perform the necessary filtering.
        
        For simple ESI includes of a whole document, you may omit the ``content``
        selector from the rule::
        
        <append css:theme="#left-column" href="/extra.html" method="esi"/>
        
        The output then renders like this::
        
        <esi:include src="/extra.html"></esi:include>
        
        Modifying the theme on the fly
        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
        
        Sometimes, the theme is almost perfect, but cannot be modified, for example
        because it is being served from a remote location that you do not have access
        to, or because it is shared with other applications.
        
        XDV allows you to modify the theme using "inline" markup in the rules file.
        You can think of this as a rule where the matched ``content`` is explicitly
        stated in the rules file, rather than pulled from the response being styled.
        
        For example::
        
        <xdv:rules
        xmlns:xdv="http://namespaces.plone.org/xdv"
        xmlns:css="http://namespaces.plone.org/xdv+css"
        xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
        >
        
        <xdv:append theme="/html/head">
        <style type="text/css">
        /* From the rules */
        body > h1 { color: red; }
        </style>
        </xdv:append>
        
        </xdv:rules>
        
        Notice how we have placed the rules in an explicit ``xdv`` namespace, so that
        we can write the "inline" HTML without a namespace prefix.
        
        In the example above, the ``<append />`` rule will copy the ``<style />``
        attribute and its contents into the ``<head />`` of the theme. Similar rules
        can be constructed for ``<copy />``, ``<replace />``, ``<prepend />``,
        ``<before />`` or ``<after />``.
        
        It is even possible to insert XSLT instructions into the compiled theme in
        this manner. Having declared the ``xsl`` namespace as shown above, we can do
        something like this::
        
        <xdv:replace css:theme="#details">
        <dl id="details">
        <xsl:for-each css:select="table#details > tr">
        <dt><xsl:copy-of select="td[1]/text()"/></dt>
        <dd><xsl:copy-of select="td[2]/node()"/></dd>
        </xsl:for-each>
        </dl>
        </xdv:replace>
        
        Note that css expressions are converted to "placeless" XPath expressions,
        so ``css:select="table#details > tr"`` converts to
        ``select="//table[@id='details]/tr"``. This means it would not be possible to
        use ``css:select="td:first-child > *"`` as you want a relative selector here.
        You can, of course, just use a manual XPath in a ``select`` attribute instead.
        
        Inline XSL directives
        ~~~~~~~~~~~~~~~~~~~~~
        
        You may supply inline XSL directives in the rules to tweak the final output,
        for instance to strip space from the output document use::
        
        <rules xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
        
        <xsl:strip-space elements="*" />
        
        </rules>
        
        Note: this may effect the rendering of the page on the browser.
        
        To use a strict doctype::
        
        <xsl:output
        doctype-public="-//W3C//DTD XHTML 1.0 Strict//EN"
        doctype-system="http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"/>
        
        XInclude
        ~~~~~~~~
        
        You may wish to re-use elements of your rules file across multiple themes.
        This is particularly useful if you have multiple variations on the same theme
        used to style different pages on a particular website.
        
        Rules files may be included using the XInclude protocol.
        
        Inclusions use standard XInclude syntax. For example::
        
        <rules
        xmlns="http://namespaces.plone.org/xdv"
        xmlns:css="http://namespaces.plone.org/xdv+css"
        xmlns:xi="http://www.w3.org/2001/XInclude">
        
        <xi:include href="standard-rules.xml" />
        
        </rules>
        
        Compilation
        ===========
        
        Once you have written your rules file, you need to compile it to an XSLT for
        deployment. In some cases, you may have an application server that does this
        on the fly, e.g. if you are using the ``collective.xdv`` package with Plone.
        For deployment to a web server like Apache or nginx, however, you will need
        to perform this step manually.
        
        The easiest way to invoke the XDV compiler is via the ``xdvcompiler`` command
        line script which is installed with the ``xdv`` egg. To see its help output,
        do::
        
        $ bin/xdvcompiler --help
        
        To run the compiler with ``rules.xml`` operating on ``theme.html``::
        
        $ bin/xdvcompiler rules.xml theme.html
        
        This will print the compiled XSLT file to the standard output. You can save
        it to a file instead using::
        
        $ bin/xdvcompiler -o theme.xsl rules.xml theme.html
        
        The following command line options are available:
        
        * Use ``-p`` to pretty-print the output for improved readability. There is a
        risk that this could alter rendering in the browser, though, as browsers
        are sensitive to some kinds of whitespace.
        * Use ``-a`` to set an absolute prefix - see below.
        * Use ``-i`` to set the default external file inclusion mode to one of
        ``document``, ``ssi`` or ``esi``.
        * Use ``--trace`` to output trace logging during the compilation step. This
        can be helpful in debugging rules.
        
        Check the output of the ``--help`` option for more details.
        
        Absolute prefix
        ---------------
        
        The compiler can be passed an "absolute prefix". This is a string that will be
        prefixed to any *relative* URL referenced an image, link or stylesheet in the
        theme HTML file, before the theme is passed to the compiler. This allows a
        theme to be written so that it can be opened and views standalone on the
        filesystem, even if at runtime its static resources are going to be served
        from some other location.
        
        For example, say the theme is written with relative URLs for images and
        external resources, such as ``<img src="images/foo.jpg" />``. When the
        compiled theme is applied to a live site, this is unlikely to work for
        any URL other than a sibling of the ``images`` folder.
        
        Let's say the theme's static resources are served from a simple web server
        and made available under the directory ``/static``. In this case, we can
        set an absolute prefix of ``/static``. This will modify the ``<img />`` tag
        in the compiled theme so that it becomes an absolute path that will work for
        any URL: ``<img src="/static/images/foo.jpg"`` />
        
        Testing the compiled theme
        --------------------------
        
        To test the compiled theme, you can apply it to a static file representing
        the content. The easiest way to do this is via the ``xdvrun`` script::
        
        $ bin/xdvrun theme.xsl content.html
        
        This will print the output to the standard output. You can save it to a file
        instead with::
        
        $ bin/xdvrun -o output.html theme.xsl content.html
        
        For testing, you can also compile and run the theme in one go, by using the
        ``-r`` (rules) and ``-t`` (theme) arguments to ``xdvrun``::
        
        $ bin/xdvrun -o output.html -r rules.xml -t theme.html content.html
        
        To see the built-in help for this command, run::
        
        $ bin/xdvrun --help
        
        Compiling the theme in Python code
        ----------------------------------
        
        You can run the XDV compiler from Python code using the following helper
        function::
        
        >>> from xdv.compiler import compile_theme
        
        This method takes the following arguments:
        
        * ``rules`` is the rules file, given either as a file name or a string with
        the file contents.
        * ``theme`` is the theme file, given either as a file name or a string with
        the file contents
        * ``extra`` is an optional XSLT file with XDV extensions, given as a URI
        (depracated, use inline xsl in the rules instead)
        * ``css``   can be set to False to disable CSS syntax support (providing a
        moderate speed gain)
        * ``xinclude`` can be set to ``False`` to enable XInclude support (at a
        moderate speed cost). If enabled, XInclude syntax can be used to split the
        rules file into multiple, re-usable fragments.
        * ``absolute_prefix`` can be set an string to be used as the "absolute prefix"
        for relative URLs - see above.
        * ``update`` can be set to ``False`` to disable the automatic update support
        for the old Deliverance 0.2 namespace (for a moderate speed gain)
        * ``trace`` can be set to True to enable compiler trace information
        * ``includemode`` can be set to 'document', 'esi' or 'ssi' to change the way
        in which includes are processed
        * ``parser`` can be set to an lxml parser instance; the default is an
        HTMLParser
        * ``compiler_parser``` can be set to an lxml parser instance; the default is a
        XMLParser
        * ``rules_parser`` can be set to an lxml parser instance; the default is a
        XMLParse.
        
        The parser parameters may be used to add custom resolvers for external content
        if required. See the `lxml <http://codespeak.net/lxml>`_ documentation for
        details.
        
        ``compile_theme()`` returns an XSLT document in ``lxml``'s ``ElementTree``
        format. To set up a transform representing the theme and rules, you can do::
        
        from lxml import etree
        from xdv.compiler import compile_theme
        
        absolute_prefix = "/static"
        
        rules = "rules.xml"
        theme = "theme.html"
        
        compiled_theme = compile_theme(rules, theme,
        absolute_prefix=absolute_prefix)
        
        transform = etree.XSLT(compiled_theme)
        
        You can now use this transformation::
        
        content = etree.parse(some_content)
        transformed = transform(content)
        
        output = etree.tostring(transformed)
        
        Please see the ``lxml`` documentation for more details.
        
        Deployment
        ==========
        
        Before it can be used, the deployed theme needs to be deployed to a proxying
        web server which can apply the XSLT to the response coming back from another
        web application.
        
        In theory, any XSLT processor will do. In practice, however, most websites
        do not produce 100% well-formed XML (i.e. they do not conform to the XHTML
        "strict" doctype). For this reason, it is normally necessary to use an XSLT
        processor that will parse the content using a more lenient parser with some
        knowledge of HTML. libxml2, the most popular XML processing library on Linux
        and similar operating systems, contains such a parser.
        
        Plone
        -----
        
        If you are working with Plone, the easiest way to use XDV is via the
        `collective.xdv <http://pypi.python.org/pypi/collective.xdv>`_ add-on. This
        provides a control panel for configuring the XDV rules file, theme and
        other options, and hooks into a transformation chain that executes after
        Plone has rendered the final page to apply the XDV transform.
        
        Even if you intend to deploy the compiled theme to another web server,
        ``collective.xdv`` is a useful development tool: so long as Zope is in
        "development mode", it will re-compile the theme on the fly, allowing you
        to make changes to theme and rules on the fly. It also provides some tools
        for packaging up your theme and deploying it to different sites.
        
        WSGI
        ----
        
        If you are using a WSGI stack, you can use the `dv.xdvserver
        <http://pypi.python.org/pypi/dv.xdvserver>`_ middleware to apply an XDV
        theme. This supports all the core XDV options, and can be configured to
        either re-compile the theme on the fly (useful for development), or compile
        it only once (useful for deployment.)
        
        It is also possible to use this with the Paste ``proxy`` middleware to
        create a standalone XDV proxy for any site. See the `dv.xdvserver`_
        documentation for details.
        
        nginx
        -----
        
        To deploy an XDV theme to the `nginx <http://nginx.org>`_ web server, you
        will need to compile nginx with a special version of the XSLT module that
        can (optionally) use the HTML parser from libxml2.
        
        In the future, the necessary patches to enable HTML mode parsing will
        hopefully be part of the standard nginx distribution. In the meantime,
        they are maintained in the `html-xslt <http://code.google.com/p/html-xslt/>`_
        project.
        
        Using a properly patched nginx, you can configure it with XSLT support like
        so::
        
        $ ./configure --with-http_xslt_module
        
        If you are using zc.buildout and would like to build nginx, you can start
        with the following example::
        
        [buildout]
        parts =
        ...
        nginx
        
        ...
        
        [nginx]
        recipe = zc.recipe.cmmi
        url = http://html-xslt.googlecode.com/files/nginx-0.7.65-html-xslt-2.tar.gz
        extra_options =
        --conf-path=${buildout:directory}/etc/nginx.conf
        --sbin-path=${buildout:directory}/bin
        --error-log-path=${buildout:directory}/var/log/nginx-error.log
        --http-log-path=${buildout:directory}/var/log/nginx-access.log
        --pid-path=${buildout:directory}/var/nginx.pid
        --lock-path=${buildout:directory}/var/nginx.lock
        --with-http_stub_status_module
        --with-http_xslt_module
        
        If libxml2 or libxslt are installed in a non-standard location you may need to
        supply the ``--with-libxml2=<path>`` and ``--with-libxslt=<path>`` options.
        This requires that you set an appropriate ``LD_LIBRARY_PATH`` (Linux / BSD) or
        ``DYLD_LIBRARY_PATH`` (Mac OS X) environment variable when running nginx.
        
        For theming a static site, enable the XSLT transform in the nginx
        configuration as follows::
        
        location / {
        xslt_stylesheet /path/to/compiled-theme.xsl;
        xslt_html_parser on;
        xslt_types text/html;
        }
        
        nginx may also be configured as a transforming proxy server::
        
        location / {
        xslt_stylesheet /path/to/compiled-theme.xsl;
        xslt_html_parser on;
        xslt_types text/html;
        rewrite ^(.*)$ /VirtualHostBase/http/localhost/Plone/VirtualHostRoot$1 break;
        proxy_pass http://127.0.0.1:8080;
        proxy_set_header Host $host;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-XDV "true";
        proxy_set_header Accept-Encoding "";
        }
        
        Removing the Accept-Encoding header is sometimes necessary to prevent the
        backend server compressing the response (and preventing transformation). The
        response may be compressed in nginx by setting ``gzip on;`` - see the `gzip
        module documentation <http://wiki.nginx.org/NginxHttpGzipModule>`_ for
        details.
        
        In this example an X-XDV header was set so the backend server may choose to
        serve different different CSS resources.
        
        Including external content
        ~~~~~~~~~~~~~~~~~~~~~~~~~~
        
        As an event based server, it is not practical to add ``document()`` support to
        the nginx XSLT module for in-transform inclusion. Instead, external content is
        included through SSI in a sub-request. The SSI sub-request includes a query
        string parameter to indicate which parts of the resultant document to include,
        called ``;filter_xpath`` - see above for a full example. The configuration
        below uses this parameter to apply a filter::
        
        worker_processes  1;
        events {
        worker_connections  1024;
        }
        http {
        include mime.types;
        gzip on;
        server {
        listen 80;
        server_name localhost;
        root html;
        
        # Decide if we need to filter
        if ($args ~ "^(.*);filter_xpath=(.*)$") {
        set $newargs $1;
        set $filter_xpath $2;
        # rewrite args to avoid looping
        rewrite    ^(.*)$    /_include$1?$newargs?;
        }
        
        location @include500 { return 500; }
        location @include404 { return 404; }
        
        location ^~ /_include {
        # Restrict _include (but not ?;filter_xpath=) to subrequests
        internal;
        error_page 404 = @include404;
        # Cache page fragments in Varnish for 1h when using ESI mode
        expires 1h;
        # Proxy
        rewrite    ^/_include(.*)$    $1    break;
        proxy_pass http://127.0.0.1:80;
        # Protect against infinite loops
        proxy_set_header X-Loop 1$http_X_Loop; # unary count
        proxy_set_header Accept-Encoding "";
        error_page 500 = @include500;
        if ($http_X_Loop ~ "11111") {
        return 500;
        }
        # Filter by xpath
        xslt_stylesheet filter.xsl
        xpath=$filter_xpath
        ;
        xslt_html_parser on;
        xslt_types text/html;
        }
        
        location / {
        xslt_stylesheet theme.xsl;
        xslt_html_parser on;
        xslt_types text/html;
        ssi on; # Not required in ESI mode
        }
        }
        }
        
        In this example the sub-request is set to loop back on itself, so the include
        is taken from a themed page. ``filter.xsl`` (in the lib/xdv directory) and
        ``theme.xsl`` should both be placed in the same directory as ``nginx.conf``.
        
        An example buildout is available in ``nginx.cfg`` in this package.
        
        Varnish
        -------
        
        To enable ESI in Varnish simply add the following to your VCL file::
        
        sub vcl_fetch {
        if (obj.http.Content-Type ~ "text/html") {
        esi;
        }
        }
        
        An example buildout is available in ``varnish.cfg``.
        
        Apache
        ------
        
        XDV currently requires a version of mod_transform with html parsing support
        and a disabled mod_depends. The latest patched versions may be downloaded from
        the `html-xslt project page <http://code.google.com/p/html-xslt/>`_.
        
        As well as the libxml2 and libxslt development packages, you will require
        libapreq2 and the Apache development pacakges::
        
        $ sudo apt-get install libxslt1-dev libapache2-mod-apreq2 libapreq2-dev \
        > apache2-threaded-dev
        
        Install mod_depends then mod_transform using the standard procedure::
        
        $ ./configure
        $ make
        $ sudo make install
        
        An example virtual host configuration is shown below::
        
        NameVirtualHost *
        LoadModule depends_module /usr/lib/apache2/modules/mod_depends.so
        LoadModule transform_module /usr/lib/apache2/modules/mod_transform.so
        <VirtualHost *>
        
        FilterDeclare THEME
        FilterProvider THEME XSLT resp=Content-Type $text/html
        
        TransformOptions +ApacheFS +HTML
        TransformSet /theme.xsl
        TransformCache /theme.xsl /etc/apache2/theme.xsl
        
        <LocationMatch "/">
        FilterChain THEME
        </LocationMatch>
        
        </VirtualHost>
        
        The +ApacheFS directive enables XSLT ``document()`` inclusion.
        
        Unfortunately it is not possible to theme error responses (such as a 404 Not
        Found page) with Apache as these do not pass through the filter chain.
        
        .. _Deliverance: http://deliveranceproject.org/
        
        
        Changelog
        =========
        
        0.3 - 2010-05-29
        ----------------
        
        * Added access control defaults, xdv.utils.AC_READ_NET, xdv.utils.AC_READ_FILE
        
        0.3rc2 - 2010-05-25
        -------------------
        
        Note: the current lxml Windows binaries are unable to load files over the
        network.
        
        * Fixed bug resolving the rules files while use a network theme.
        [elro]
        
        0.3rc1 - 2010-05-23
        -------------------
        
        * Nested <rules> are now allowed, so you can simply::
        
        ``<xi:include href="standard-rules.xml" />``
        
        [elro]
        
        * XInclude processing is now enabled by default
        [elro]
        
        * XSL directives inlined in the rules file are now supported (e.g.
        <xsl:strip-space elements="*" />). With the inline XSL support, there should
        now be no need for extra.xsl.
        [elro]
        
        * libxml2 quotes CR characters on output, causing Firefox to insert extra
        blank lines in ``<pre>`` blocks. As HTTP specified CRLF line endings for
        form this was a problem for us. This is now caught by the compiled XSL.
        [elro]
        
        * Support for including complete fragment documents with SSI/ESI.
        [elro]
        
        * A bug on namespace upgrade is fixed, but you should update your namespace to
        http://namespaces.plone.org/xdv anyway.
        [elro]
        
        * First release candidate.
        [elro]
        
Platform: UNKNOWN
