This guide provides an overview of Diazo theming in Plone versions 4.3 and higher.


In Plone versions 4.3 and higher you can edit your website theme through a web browser in Plone's site setup control panel. Only HTML, CSS and a little XML knowledge are required. This guide explains how to use this feature of Plone.

See introduction video to

What is a Diazo theme?

A "theme" makes a website (in this case, one powered by Plone) take on a particular look and feel.

Diazo (formerly known as XDV) is a technology that can be used to theme websites. It is not specific to Plone per se, but has been created by the Plone community and, as of Plone 4.3, provides the default way to apply a theme to a Plone site. You can learn more about Diazo at

Diazo themes may be a little different to themes you have created in other systems, and indeed to themes you may have created for earlier versions of Plone. A Diazo theme is really about transforming some content - in this case the output from "vanilla" Plone - into a different set of HTML markup by applying a set of rules to combine a static HTML mock-up of the end result you want with the dynamic content coming from Plone.

In comparison, the previous way to theme a Plone site (like the way many other content management systems are themed) relies on selectively overriding the templates and scripts that Plone uses to build a page with custom versions that produce different HTML markup. The latter approach can be more powerful, in some cases, but also requires much deeper knowledge of Plone's internals and command of server-side technologies such as Zope Page Templates and even Python. Diazo themes, by contrast, are easy to understand for web designers and non-developers alike.

A Diazo theme consists of three elements:

  1. One or more HTML mockups, also referred to as theme files, that represent the desired look and feel.

    These will contain placeholders for content that is to be provided by the Plone content management system. Mockups usually reference CSS, JavaScript and image files by relative path. The most common way to create a theme is to use desktop software like Dreamweaver or a text editor to create the relevant markup, styles and scripts, and test the theme locally in a web browser.

  2. The content that is being themed. In this case, that is the output from Plone.

  3. A rules file, which defines how the placeholders in the theme (i.e. the HTML mockup) should be replaced by relevant parts of the content.

The rules file uses XML syntax (similar to HTML). Here is a very simple example:

<?xml version="1.0" encoding="UTF-8"?>

    <theme href="theme.html" />

    <replace css:content-children="#content" css:theme-children="#main" />


Here, we are replacing the contents (child nodes) of a placeholder element with HTML id main in the theme file (theme.html, found in the same directory as the rules.xml file, as referenced by the <theme /> rule) with the contents (children) of the element with the HTML id content in the markup generated by Plone.

When this theme is applied, the result will look very much like the static HTML file theme.html (and its associated CSS, JavaScript and image files), except the placeholder identified by the node in the theme with id main will be filled by Plone's main content area.

Plone ships with an example theme called, appropriately, Example theme, which uses the venerable Twitter Bootstrap to build a simple yet functional theme exposing most of Plone's core functionality. Look at this example - in particular the rules.xml file - to learn more about how Diazo themes work.

Using the control panel

After installation of the Diazo theme support package in a Plone site, the Theming control panel will appear in Plone's Site setup.

The main tab of this control panel, Themes, will show all available themes, with buttons to activate/deactivate, modify, copy or delete each, as well as buttons to create new themes or bring up this help text.

Click on a theme preview image to open a preview of that theme in a new tab or window. The preview is navigable, but form submissions and some advanced features will not work.

Selecting a theme

To apply an existing theme, simply click the Activate button underneath the theme preview. The currently active theme will be highlighted in yellow. If you deactivate the currently active theme, no Diazo theme will be applied, i.e. "vanilla" Plone theming will apply.


The Theming control panel is never theemd, ensuring that you can always deactivate an errant theme that could render the control panel unusable. Thus, you may not see any difference immediately after enabling a theme. Simply navigate to another page in the Plone site, though, and you should see the theme applied.

Creating a new theme

New themes can be created in one of two ways:

  • Click the New theme button at the top of the Themes tab in the Theming control panel and enter a title and description in the form that appears. A bare-bones theme will be created, and you will be taken to the Modify theme screen (see below), where you can edit or create theme and rules files.
  • Click the Copy button underneath any existing theme and enter a title and description in the form that appears. A new theme will be created as a copy of the existing theme, and you will be taken to the Modify theme (see below), where you can edit or create theme and rules files.

Uploading an existing theme

Themes can be distributed as Zip files, containing the HTML mockup and rules file. To download an existing theme, click the Download button underneath the theme on the Themes tab of the Theming control panel.

To upload such a Zip file into another site, use the Upload Zip file button on the Themes tab of the Theming control panel. You can choose whether or not to replace any existing theme with the same name (based on the name of the top-level directory contained within the Zip file).

You can also upload a Zip file of a static HTML mockup that does not contain a rules file, such as a design provided by a Plone-agnostic web designer.

In this case, a basic rules.xml file will be added for you to start building up a theme from using the Modify theme screen (see below). The generated rules file will assume the main HTML mockup file is called index.html, but you can change this in rules.xml.

Once you have successfully uploaded a theme Zip file, you will be taken to the Modify theme screen (see below), where you can edit or create theme files.

Hint: If you get an error message like "The uploaded file does not contain a valid theme archive", this usually means that you have uploaded a Zip file that contains multiple files and folders, rather than a single top level folder with all the theme resources in it. This could happen if you compressed a theme or HTML mockup by adding its files and folders directly a Zip archive, rather than compressing the directory in which they were found. To fix this, simply unzip the archive on your computer into a new directory, move up a level, and compress this directory on its own into a new Zip file, which you can then upload.

Modifying the theme

You can modify a theme by clicking Modify theme underneath a theme in the Themes tab of the Theming control panel. This screen is also launched automatically when you create or upload a new theme.

Note: Only themes created or uploaded through the Theming control panel can be modified through Plone. Themes installed by third-party add-ons or distributed on the filesystem cannot, although changes made on the filesystem will be reflected immediately if Zope is running in debug mode. To modify a filesystem theme, you can copy it to a new in-Plone theme by clicking the Copy button underneath the theme in the Theming control panel.

The Modify theme screen initially shows a file manager, with a file tree on the left and an editor on the right. Click on a file in the file tree to open an editor or preview: HTML, CSS, JavaScript and other text files can be edited directly through the editor. Other files (e.g. images) will be rendered as a preview.


The advanced editor with syntax highlighting is not available in Microsoft Internet Explorer.

Click New folder to create a new folder. You can also right-click on a folder in the file tree to bring up this action.

Click New file to create a new text file. You can also right-click on a folder in the file tree to bring up this action.

Click Upload file to upload a file from your computer. You can also right-click on a folder in the file tree to bring up this action.

Click Preview theme to preview the theme as it will be applied with the mockup and rules as currently saved. The preview is navigable, but forms and certain advanced features will not work.

To save the file currently being edited, click the Save file button, or use the keyboard shortcut Ctrl+S (Windows/Linux) or Cmd+S (Mac).

To rename or delete a file or folder, right-click on it in the file tree and select the appropriate action.

The theme inspector

The theme inspector provides an advanced interface for discovering and building up the rules of a Diazo theme. It can be launched by clicking the Show inspectors button on the Modify theme screen for in-Plone themes, or by clicking the Inspect theme button underneath a filesystem theme on the Themes tab of the Theming control panel.

The theme inspector consists of two panels:

  • The HTML mockup. If there are several HTML files in the theme, you can switch between them using the drop-down list underneath the HTML mockup panel.
  • The Unthemed content. This shows Plone without any theme applied.

Either panel can be maximised by clicking the arrows icon at the top right of either.

The HTML mockups and Unthemed content panels can be switch to source view, showing their underlying HTML markup, by clicking the tags icon at the top right of either.

As you hover over elements in the HTML mockup or Unthemed content panels, you will see:

  • An outline showing the element under the cursor.
  • A CSS or XPath selector in the status bar at the bottom if the panel which would uniquely identify this element in a Diazo rule.

Click on an element or press Enter whilst hovering oveer an element to select it. The most recently selected element in each panel is shown in the bottom right of the relevant status bar.

Press Esc whilst hovering over an element to select its parent. This is useful when trying to select "invisible" container elements. Press Enter to save this selection.

The contents of the HTML mockup or (more commonly) Unthemed content panels can be navigated, for example to get to a content page that requires specific theme rules, by disabling the inspector. Use the toggle switches at the bottom right of the relevant panel to enable or disable the selector.

The rule builder

Click the Build rule button near the top of the Modify theme or Inspect theme screen to launch an interactive rule building wizard. You will be asked which type of rule to build, and then prompted to select the relevant elements in the HTML mockup and/or Unthemed content panels as required. By default, this will use any saved selections, unless you untick the Use selected elements box on the first page if the wizard.

Once the wizard completes, you will be shown the generated rule. You can edit this if you wish. If you click Insert, the newly generated rule will be inserted into the rules.xml editor at or near your current cursor position. You can move it around or edit it further as you wish.

Click Preview theme to preview the theme in a new tab or window. Don't forget to save the rules.xml file if you have made changes.

Note: In readonly mode, you can build rules and inspect the HTML mockup and theme, but not change the rules.xml file. In this case, the Insert button of the rule builder (see below) will not be available either.


The ability to insert rules from the Build rule wizard is not available in Microsoft Internet Explorer, although you will be given the option to copy the rule to the clipboard when using this browser.

Advanced settings

The Theming control panel also contains a tab named Advanced settings. Here be dragons.

The Advanced setings tab is divided into two areas. The first, Theme details, contains the underlying settings that are modified when a theme is applied from the Themes control panel. These are:

  • Whether or not Diazo themes are enabled at all.
  • The path to the rules file, conventionally called rules.xml, either relative to the Plone site root or as an absolute path to an external server.
  • The prefix to apply when turning relative paths in themes (e.g. references to images in an <img /> tag's src attribute) into absolute ones at rendering time.
  • The HTML DOCTYPE to apply to the rendered output, if different to the default XHTML 1.0 Transitional`.
  • Whether or not to allow theme resources (likes rules.xml) to be read from the network. Disabling this gives a modest performance boost.
  • A list of host names for which a theme is never applied. Most commonly, this contains, allowing you to view an unthemed site through and a themed one at http://localhost:8080 during development, say.
  • A list of theme parameters and the TALES expressions to generate them (see below).

The second, Theme base, controls the presentation of the unthemed content, and apply even if no Diazo theme is being applied. These are the settings that used to be found in the Themes control panel in previous versions of Plone.


The remainder of this guide contains reference materials useful for theme builders.

Deploying and testing themes

To build and test a theme, you must first create a static HTML mockup of the look and feel you want, and then build a rules file to describe how Plone's content maps to the placeholders in this mockup.

The mockup can be created anywhere using whatever tool you feel most comfortable building web pages in. To simplify integration with Plone, you are recommended to make sure it uses relative links for resources like CSS, JavaScript and image files, so that it will render properly when opened in a web browser from a local file. Plone will convert these relative links to the appropriate absolute paths automatically, ensuring the theme works no matter which URL the user is viewing when the theme is applied to a Plone site.

There are several ways to get the theme into Plone:

  1. On the filesystem

    If you used an installer or a standard "buildout" to set up your Plone site, you should have a directory called resources in the root of your Plone installation (this is created using the resources option to the buildout recipe plone.recipe.zope2instance. See for more details.)

    You can find (or create) a theme directory inside this directory, which is used to contain themes. Each theme needs its own directory with a unique name. Create one (e.g. resources/theme/mytheme) and put your HTML files and any references resources inside this directory. You can use subdirectories if you wish, but it is recommended to keep the basic theme HTML files at the top of the theme directory.

    You will also need a rules file called rules.xml inside this directory. If you haven't got one yet, start with an empty one:

<?xml version="1.0" encoding="UTF-8"?>

    <theme href="theme.html" />
    <replace css:content-children="#content" css:theme-children="#main" />


Provided you are running Zope in debug mode (e.g. you start it up with bin/instance fg), changes to the theme and rules should take effect immediately. You can preview or enable the theme through the Themes control panel, and then iteratively modify the rules.xml file or the theme mockup as you wish.

  1. Through the web

    If you prefer (or do not have filesystem access), you can create themes entirely through the Plone control panel, either by duplicating an existing theme, or starting from scratch with a near-empty theme.

    See the instructions on using the control panel above for more details.

    Once a theme has been created, you can modify it through the Theming control panel. See above for more details.

  2. As a zip file

    Themes can be downloaded from Plone as Zip files, which can then be uploaded into other sites.

    See the instructions on using the control panel above for more details.

    In fact, you can create valid theme zip archives by compressing a theme directory on the filesystem using a standard compression tool such as 7-Zip or Winzip (for Windows) or the built-in Compress action in the Mac OS X Finder. Just make sure you compress exactly one folder that contains all the theme files and the rules.xml file. (Do not compress the contents of the folder directly: when unpacked, the zip file should produce exactly one folder which in turn contains all the relevant files).

  3. In a Python package (programmers only)

    If you are creating a Python package containing Plone customisations that you intend to install into your site, you can let it register a theme for installation into the site.

    To do this, place a directory called e.g. theme at the top of the package, next to the Zope configure.zcml file, and add a <plone:static /> declaration to the configure.zcml file:

        <plone:static name="mytheme" directory="theme" type="theme" />

    Notice the declaration of the plone namespace at the root <configure /> element. Place the theme files and the rules.xml file into the theme directory.

    If your package has a GenericSetup profile, you can automatically enable the theme upon installation of this profile by adding a theme.xml file in the profiles/default directory, containing e.g.:


The manifest file

It is possible to give additional information about a theme by placing a file called manifest.cfg next to the rules.xml file at the top of a theme directory.

This file may look like this:

title = My theme
description = A test theme
rules =
prefix = /some/prefix
doctype = <!DOCTYPE html>
preview = preview.png
enabled-bundles = mybundle
disabled-bundles = plone
development-css = /++theme++barceloneta/less/barceloneta.plone.less
production-css = /++theme++barceloneta/less/barceloneta-compiled.css
development-js = /++theme++barceloneta/barceloneta.js
production-js = /++theme++barceloneta/barceloneta.min.js
tinymce-content-css = /++theme++barceloneta/tinymce-styles.css

As shown here, the manifest file can be used to provide a more user friendly title and a longer description for the theme, for use in the control panel. Only the [theme] header is required - all other keys are optional.

Manifest settings:

to use a different rule file name than rules.xml (you should provide a URL or relative path).

To change the absolute path prefix (see Advanced settings), use:

prefix = /some/prefix

To employ a DOCTYPE in the themed content other than XHTML 1.0 Transitional, add e.g.:

doctype = <!DOCTYPE html>

To provide a user-friendly preview of your theme in the Theming control panel. Here, preview.png is an image file relative to the location of the manifest.cfg file:

preview = preview.png
Bundles that will automatically be enabled when a theme is activated
Bundles that will automatically be disabled when a theme is activated
CSS to automatically include when in development mode and theme is active
JavaScript file to automatically include when in development mode when theme is active
CSS to automatically include when theme is active and in production mode
JavaScript to automatically include when theme is active and in production mode
CSS file tinymce should load to apply styles to content inside the editor
CSS file tinymce should load to provide additionally automatically detected drop-down styles in the editor

Extensions to the Diazo theming engine can add support for additional blocks of configurable parameters.

Rules syntax

The following is a short summary of the Diazo rules syntax. See for more details and further examples.


Each rule is represented by an XML tag that operates on one or more HTML elements in the content and/or theme. The elements to operate on are indicated using attributes of the rules known as selectors.

The easiest way to select elements is to use a CSS expression selector, such as css:content="#content" or css:theme="#main .content". Any valid CSS 3 expression (including pseudo-selectors like :first-child may be used.

The standard selectors, css:theme and css:content, operate on the element(s) that are matched. If you want to operate on the children of the matched element instead, use css:theme-children="..." or css:content-children="..." instead.

If you cannot construct a suitable CSS 3 expression, you can use XPath expressions such as content="/head/link" or theme="//div[@id='main']" (note the lack of a css: prefix when using XPath expressions). The two approaches are equivalent, and you can mix and match freely, but you cannot have e.g. both a css:theme and a theme attribute on a single rule. To operate on children of a node selected with an XPath expression, use theme-children="..." or content-children="...".

You can learn more about XPath at


By default, every rule is executed, though rules that do not match any elements will of course do nothing. You can make a rule, set of rules or theme reference (see below) conditional upon an element appearing in the content by adding an attribute to the rule like css:if-content="#some-element" (to use an XPath expression instead, drop the css: prefix). If no elements match the expression, the rule is ignored.

Tip: if a <replace /> rule matches an element in the theme but not in the content, the theme node will be dropped (replaced with nothing). If you do not want this behavior and you are unsure if the content will contain the relevant element(s), you can use css:if-content conditional rule. Since this is a common scenario, there is a shortcut: css:if-content="" means "use the expression from the css:content attribute".

Similarly, you can construct a condition based on the path of the current request by using an attribute like if-path="/news" (note that there is no css:if-path ). If the path starts with a slash, it will match from the root of the Plone site. If it ends with a slash, it will match to the end of the URL. You can set an absolute path by using a leading and a trailing slash.

Finally, you can use arbitrary XPath expressions against any defined variable using an attribute like if="$host = 'localhost'" . By default, the variables url , scheme , host and base are available, representing the current URL. Themes may define additional variables in their manifests.

Available rules

The various rule types are summarized below.


Wraps a set of rules. Must be used as the root element of the rules file. Nested <rules /> can be used with a condition to apply a single condition to a set of rules.

When used as the root element of the rules file, the various XML namespaces must be declared:

theme and notheme
<theme href="theme.html" />
<theme href="news.html" if-path="/news" />
<notheme if="$host = ''" />

Choose the theme file to be used. The href is a path relative to the rules file. If multiple <theme /> elements are present, at most one may be given without a condition. The first theme with a condition that is true will be used, with the unconditional theme, if any, used as a fallback.

<notheme /> can be used to specify a condition under which no theme should be used. <notheme /> takes precedence over <theme />.

Tip: To ensure you do not accidentally style non-Plone pages, add a condition like css:if-content="#visual-portal-wrapper" to the last theme listed, and do not have any unconditional themes.


Replaces the matched element(s) in the theme with the matched element(s) from the content.

before and after


Inserts the matched element(s) from the content before or after the matched element(s) in the theme. By using theme-children , you can insert the matched content element(s) as the first (prepend) or last (append) element(s) inside the matched theme element(s).

drop and strip
<drop css:content=".documentByLine" />
<drop theme="/head/link" />
<drop css:theme="#content *" attributes="onclick onmouseup" />

<strip css:content="#parent-fieldname-text" />

Remove element(s) from the theme or content. Note that unlike most other rules, a <drop /> or <strip /> rule can operate on the theme or content , but not both. <drop /> removes the matched element(s) and any children, whereas <strip /> removes the matched element(s), but leaves any children in place.

<drop /> may be given a whitespace-separated list of attributes to drop. In this case, the matched element(s) themselves will not be removed. Use attributes="*" to drop all attributes.

merge and copy


These rules operate on attributes. <merge /> will add the contents of the named attribute(s) in the theme to the value(s) of any existing attributes with the same name(s) in the content, separated by whitespace. It is mainly used to merge CSS classes.

<copy /> will copy attributes from the matched element(s) in the content to the matched element(s) in the theme, fully replacing any attributes with the same name that may already be in the theme.

The attributes attribute can contain a whitespace-separated list of attributes, or the special value * to operate on all attributes of the matched element.

Advanced modification

Instead of selecting markup to insert into the theme from the content, you can place markup directly into the rules file, as child nodes of the relevant rule element:

<after css:theme="head">
    <style type="text/css">
        body > h1 { color: red; }

This also works on the content, allowing you to modify it on the fly before any rules are applied:

<replace css:content="#portal-searchbox input.searchButton">
    <button type="submit">
        <img src="images/search.png" alt="Search" />

In addition to including static HTML in this manner, you can use XSLT instructions that operate on the content. You can even use css: selectors directly in the XSLT.:

<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>

Rules may operate on content that is fetched from somewhere other than the current page being rendered by Plone, by using the href attribute to specify a path of a resource relative to the root of the Plone site:

<!-- Pull in extra navigation from a browser view on the Plone site root -->

Theme parameters

It is possible to pass arbitrary parameters to your theme, which can be referenced as variables in XPath expressions. Parameters can be set in Plone's theming control panel, and may be imported from a manifest.cfg file.

For example, you could have a parameter mode that could be set to the string live or test. In your rules, you could do something like this to insert a warning when you are on the test server:

<before css:theme-children="body" if="$mode = 'test'">
    <span class="warning">Warning: This is the test server</span>

You could even use the parameter value directly, e.g.:

<before css:theme-children="body">
    <span class="info">This is the <xsl:value-of select="$mode" /> server</span>

The following parameters are always available to Plone themes:

The scheme portion of the inbound URL, usually http or https.
The hostname in the inbound URL.
The path segment of the inbound URL. This will not include any virtual hosting tokens, i.e. it is the path the end user sees.
The Zope base url (the BASE1 request variable).

You can add additional parameters through the control panel, using TALES expressions. Parameters are listed on the Advanced tab, one per line, in the form <name> = <expression>.

For example, if you want to avoid theming any pages that are loaded by Plone' overlays, you can make use of the ajax_load request parameter that they set. Your rules file might include:

<notheme if="$ajax_load" />

To add this parameter as well as the mode parameter outlined earlier, you could add the following in the control panel:

ajax_load = python: request.form.get('ajax_load')
mode = string: test

The right hand side is a TALES expression. It must evaluate to a string, integer, float, boolean or None: lists, dicts and objects are not supported. python:, string: and path expressions work as they do in Zope Page Templates.

The following variables are available when constructing these TALES expressions:

The context of the current request, usually a content object.
The current request.
The portal root object.
The @@plone_context_state view, from which you can look up additional values such as the context's URL or default view.
The @@plone_portal_state view, form which you can look up additional values such as the navigation root URL or whether or not the current user is logged in.

See for details about the @@plone_context_state and @@plone_portal_state views.

Theme parameters are usually integral to a theme, and will therefore be set based on a theme's manifest when a theme is imported or enabled. This is done using the [theme:parameters] section in the manifest.cfg file. For example:

title = My theme
description = A test theme

ajax_load = python: request.form.get('ajax_load')
mode = string: test

Theme debugging

When Zope is in development mode (e.g. running in the foreground in a console with bin/instance fg), the theme will be re-compiled on each request. In non-development mode, it is compiled once when first accessed, and then only re-compiled the control panel values are changed.

Also, in development mode, it is possible to temporarily disable the theme by appending a query string parameter For example:


Finally, you can get an overlay containing your rules, annotated with how many times the conditions matched both the theme and the document. Green means the condition matched, red means it didn't. The entire rule tag will be green (i.e. it had an effect) so long as all conditions within are green.

To enable this, append diazo.debug=1. For example:


The parameter is ignored in non-development mode.

Commonly used rules

The following recipes illustrate rules commonly used in building Plone themes:

To copy the page title:

<replace css:theme="title" css:content="title" />

To copy the <base /> tag (necessary for Plone's links to work):

<replace css:theme="base" css:content="base" />

If there is no <base /> tag in the theme, you can do:

<before css:theme-children="head" css:content="base" />

To drop all styles and JavaScript resources from the theme and copy them from Plone's portal_css tool instead:

<!-- Drop styles in the head - these are added back by including them from Plone -->
<drop theme="/html/head/link" />
<drop theme="/html/head/style" />

<!-- Pull in Plone CSS -->
<after theme-children="/html/head" content="/html/head/link | /html/head/style" />

To copy Plone's JavaScript resources:

<!-- Pull in Plone CSS -->
<after theme-children="/html/head" content="/html/head/script" />

To copy the class of the <body /> tag (necessary for certain Plone JavaScript functions and styles to work properly):

<!-- Body -->
<merge attributes="class" css:theme="body" css:content="body" />

Advanced: Using portal_css to manage your CSS

Plone's "resource registries", including the portal_css tool, can be used to manage CSS stylesheets. This offers several advantages over simply linking to your stylesheets in the template, such as:

  • Detailed control over the ordering of stylesheets
  • Merging of stylesheets to reduce the number of downloads required to render your page
  • On-the-fly stylesheet compression (e.g. whitespace removal)
  • The ability to include or exclude a stylesheet based on an expression

It is usually desirable (and sometimes completely necessary) to leave the theme file untouched, but you can still use portal_css to manage your stylesheets. The trick is to:

  • Register your theme's styles with Plone's portal_css tool (this is normally best done when you ship a theme in a Python package - there is currently no way to automate this for a theme imported from a Zip file or created through the web)
  • Drop the theme's styles with a rule, and then * Include all styles from Plone

For example, you could add the following rules:

<drop theme="/html/head/link" />
<drop theme="/html/head/style" />

<!-- Pull in Plone CSS -->
<after theme-children="/html/head" content="/html/head/link | /html/head/style" />

The use of an "or" expression for the content in the after /> rule means that the relative ordering of link and style elements is maintained.

To register stylesheets upon product installation using GenericSetup, use the cssregistry.xml import step in your GenericSetup profiles/default directory:

<?xml version="1.0"?>
<object name="portal_css">

 <!-- Set conditions on stylesheets we don't want to pull in -->
     expression="not:request/HTTP_X_THEME_ENABLED | nothing"

 <!-- Add new stylesheets -->
 <stylesheet title="" authenticated="False" cacheable="True"
    compression="safe" conditionalcomment="" cookable="True" enabled="on"
    expression="request/HTTP_X_THEME_ENABLED | nothing"
    id="++theme++my.theme/css/styles.css" media="" rel="stylesheet"


There is one important caveat, however. Your stylesheet may include relative URL references of the following form:

background-image: url(../images/bg.jpg);

If your stylesheet lives in a resource directory (e.g. it is registered in portal_css with the id ++theme++my.theme/css/styles.css), this will work fine so long as the registry (and Zope) is in debug mode. The relative URL will be resolved by the browser to ++theme++my.theme/images/bg.jpg.

However, you may find that the relative URL breaks when the registry is put into production mode. This is because resource merging also changes the URL of the stylesheet to be something like:


To correct for this, you must set the applyPrefix flag to true when installing your CSS resource using cssregistry.xml. There is a corresponding flag in the portal_css user interface.

It is sometimes useful to show some of Plone's CSS in the styled site. You can achieve this by using an Diazo <after /> rule or similar to copy the CSS from Plone's generated <head /> into the theme. You can use the portal_css tool to turn off the style sheets you do not want.

However, if you also want the site to be usable in non-themed mode (e.g. on a separate URL), you may want to have a larger set of styles enabled when Diazo is not used. To make this easier, you can use the following expressions as conditions in the portal_css tool (and portal_javascripts if relevant), in portal_actions, in page templates, and other places that use TAL expression syntax:

request/HTTP_X_THEME_ENABLED | nothing

This expression will return True if Diazo is currently enabled, in which case an HTTP header "X-Theme-Enabled" will be set.

If you later deploy the theme to a fronting web server such as nginx, you can set the same request header there to get the same effect, even if is uninstalled.


not: request/HTTP_X_THEME_ENABLED | nothing

to 'hide' a style sheet from the themed site.