Basic syntax¶

A Diazo theme consists of a static HTML page (referred to as the “theme”) and a rules file, conventionally called rules.xml.

The rules file contains an XML document that is is rooted in a tag called <rules />:

<rules
    xmlns="http://namespaces.plone.org/diazo"
    xmlns:css="http://namespaces.plone.org/diazo/css"
    xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

       ...

</rules>

Here we have defined three namespaces: the default namespace is used for rules and XPath selectors. The css namespace is used for CSS3 selectors. These are functionally equivalent to the XPath selectors. 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. The xsl namespace is used if you want to add inline XSLT directives for fine-grained control. We will come to that later in this guide.

Diazo 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.

Rule directives¶

The following directives are allowed inside the <rules /> element in the rules file:

`<theme />`¶

Used to specify the theme file. For example:

<theme href="theme.html" />

Relative paths are resolved relative to the rules.xml file. For http/https urls, the --network switch must be supplied to the diazocompiler or diazorun program.

The following attributes are allowed:

href (required): A reference to the theme HTML file, as either a relative or absolute URL.
if: Used to specify an arbitrary condition that must be true for this theme reference to be used. More on this in the section on using multiple themes later in this guide.
if-path: Used to specify a URL path segment that must be matched by the current request for this theme reference to be used. More on this in the section on using multiple themes later in this guide.
if-content or css:if-content: Used to specify an element that must be present in the content for this theme reference to be used. More on this in the section on using multiple themes later in this guide.

`<notheme />`¶

Used to turn off all theming in certain conditions. For example:

<theme href="theme.html" />
<notheme css:if-content="body.rawpage" />

Multiple <notheme /> elements may be used. If the condition on any of them is true, the theme will be omitted. That is, they are logically or’d together.

One or more of the following attributes are required:

if: Used to specify an arbitrary condition for when to omit the theme.
if-path: Used to specify a URL path segment that must be matched by the current request for the theme to be omitted.
if-content or css:if-content: Used to specify an element that must be present in the content for the theme to be omitted.

If more than one attribute is used, the condition of all must be true for the directive to take effect. That is, they are logically and’ed together.

`<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.

The following attributes are allowed:

theme or theme-children or css:theme or css:theme-children (required)

Used to specify the node(s) in the theme that is to be replaced. When using theme-children, all elements inside the tag that matches the XPath or CSS expression will be replaced, but the matched tag itself will remain intact.

content or content-children or css:content or css:content-children (required)

Used to specify the node in the content that is to replace the matched node(s) in the theme. When using content-children, all elements inside the tag that matches the XPath or CSS expression will be used, but the matched tag itself will be left out.

attributes

If you want to replace attributes instead of tags, you can use the attributes attribute to provide a space-separated list of attributes that should be replaced on the matched theme node(s). For example, with attributes="class" the class attribute on the matched theme node(s) will be replaced by the class attribute of the matched content node(s).

Note: As with <replace /> rules working on tags, if the named attribute(s) do not exist on the both the theme and content nodes, nothing will happen. If you want to copy attributes regardless of whether they exist on the theme node(s) or not, you can use <copy /> instead.

Using attributes="class id", the class and id attributes will be replaced.

As a special case, you can write attributes="*" to drop all attributes on the matched theme node and copy over all attributes from the matched content node.

Note: You should not use theme-children or content-children or their CSS equivalents when using attributes.

See also <merge />, <copy /> and <drop />

method

If you have any <drop /> or other rules that manipulate the content, and you do not want that manipulation to be taken into account when performing this replacement, you can add method="raw" to the <replace /> rule.

if

Used to specify an arbitrary condition for when to perform the replacement.

if-path

Used to specify a URL path segment that must be matched by the current request for the replacement to be performed

if-content or css:if-content

Used to specify an element that must be present in the content for the replacement to be performed.

For more advanced usage of <replace>, see Modifying the theme on the fly and Modifying the content on the fly.

`<before />` and `<after />`¶

These are equivalent to <replace /> except that the node(s) matched in the content are inserted before or after the node(s) matched in the theme, respectively. 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" />

To insert the box immediately inside the #content node, before any of its existing children, we could do:

<before css:theme-children="#content" css:content="#info-box" />

<before /> and <after /> have the same required and optional attributes as <replace />, except for attributes, which is not supported.

`<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: and -children equivalents), but not both:

<drop css:content="#portal-content .about-box" />
<replace css:theme-children="#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.

The following attributes are allowed:

theme or theme-children or css:theme or css:theme-children

Used to specify the node(s) in the theme that is to be dropped. When using theme-children, all elements inside the tag that matches the XPath or CSS expression will be dropped, but the matched tag itself will remain intact.

content or content-children or css:content or css:content-children

Used to specify the node(s) in the content that is to be dropped. When using content-children, all elements inside the tag that matches the XPath or CSS expression will be dropped, but the matched tag itself will remain intact.

attributes

If you want to drop attributes instead of whole tags, you can use the attributes attribute to provide a space-separated list of attributes that should be dropped on the matched theme node(s). For example, with attributes="class" the class attribute will be dropped from the matched node(s). Using attributes="class id", the class and id attributes will both be dropped.

As a special case, you can write attributes="*" to drop all attributes on the matched theme node.

Note: You should not use theme-children or content-children or their CSS equivalents when using attributes.

`<strip />`¶

Used to strip a tag from the theme or content, leaving its children intact. You can think of this as the inverse of <drop /> with theme-children or content-children. For example:

<strip css:theme="#content" />

This will remove the element with id content, leaving in place all its children.

Similarly:

<strip css:content="#main-area .wrapper" />
<replace css:theme="#content-area" css:content="#main-area" />

This will replace the theme’s element with the id content-area with the element in the content that has the id main-area, but will strip out any nested tags with the CSS class wrapper found inside #main-area.

<strip /> uses the same attributes and semantics as <drop />.

`<merge />`¶

Used to merge the values of attributes in the content with attributes with the same name in the theme. This is mainly useful for merging CSS classes:

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

If the theme has the following body tag:

<body class="alpha beta">

and the content has:

<body class="delta gamma">

then the result will be:

<body class="alpha beta delta gamma">

The following attributes are allowed:

attributes (required): A space-separated list of attributes to merge. A given attribute must exist on both the theme and the content nodes for the rule to have any effect.
theme or css:theme (required): The theme node(s) to merge the attribute value(s) with.
content (required): The content node(s) to merge the attribute value(s) from.
separator: The separator to use when merging attributes. The default is to use a space. Use separator="" to merge with no separator.
if: Used to specify an arbitrary condition for when to perform the merge.
if-path: Used to specify a URL path segment that must be matched by the current request for the merge to be performed
if-content or css:if-content: Used to specify an element that must be present in the content for the merge to be performed.

`<copy />`¶

Used to copy an attribute from a node in the content to a node in the theme. Unlike <replace />, <copy /> will work even if the attribute does not exist on the target theme node. If it does exist, it will be replaced. For example:

<copy attributes="class" css:theme="body" css:content="body"/>

The following attributes are allowed:

theme or css:theme (required)

Used to specify the node(s) in the theme where the attribute should be copied.

content or css:content (required)

Used to specify the node(s) in the content from which the attribute should be copied.

attributes (required)

A space-separated list of attributes that should be copied to the theme.

As a special case, you can write attributes="*" to drop all attributes on the matched theme node and copy over all attributes from the matched content node.

if

Used to specify an arbitrary condition for when to perform the copy.

if-path

Used to specify a URL path segment that must be matched by the current request for the copy to be performed

if-content or css:if-content

Used to specify an element that must be present in the content for the copy to be performed.

Order of rule execution¶

In most cases, you should not care too much about the inner workings of the Diazo compiler. However, it can sometimes be useful to understand the order in which rules are applied.

<before /> rules using theme (but not theme-children) are always executed first.
<drop /> rules are executed next.
<replace /> rules using theme (but not theme-children) are executed next, provided no <drop /> rule was applied to the same theme node or method="raw" was used.
<strip /> rules are executed next. Note that <strip /> rules do not prevent other rules from firing, even if the content or theme node is going to be stripped.
Rules that operate on attributes.
<before /> and <replace /> and <after /> rules using theme-children execute next, provided no <replace /> rule using theme was applied to the same theme node previously.
<after /> rules using theme (but not theme-children) 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, Diazo 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 the next section for more details on conditional rules.

Basic syntax¶

Rule directives¶

<theme />¶

<notheme />¶

<replace />¶

<before /> and <after />¶

<drop />¶

<strip />¶

<merge />¶

<copy />¶

Order of rule execution¶

Behaviour if theme or content is not matched¶

`<theme />`¶

`<notheme />`¶

`<replace />`¶

`<before />` and `<after />`¶

`<drop />`¶

`<strip />`¶

`<merge />`¶

`<copy />`¶