Diazo 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 -->
<after
    css:theme-children="#leftnav"
    css:content=".navitem"
    href="/@@extra-nav"
    />

The href attribute can be used with any rule apart from <drop /> and <strip />, and can reference any URL, for example to an existing browser view configured for your site. However, it is often desirable to generate some dynamic content specifically for the purpose of constructing a particular theme. In this scenario, you can use fragments.

Fragments are Zope Page Template files bundled with your theme. You can create them by adding a folder called fragments to your theme resource directory (i.e. the directory containing rules.xml), either through the web or on the filesystem, and creating one or more files with a .pt extension in this directory.

For example, you could create a file fragments/customnav.pt in your theme directory, containing:

<ul id="nav">
  <li tal:repeat="item context/@@folderListing">
    <img tal:replace="structure item/getIcon" />
    <span tal:replace="item/Title" tal:attributes="titile item/Description">Title</span>
  </li>
</ul>

This uses Zope Page Template TAL syntax (the same syntax you might use to create a template for a browser view if you are doing filesystem Python development, say) to generate some markup based on the attributes and helper views available relative to the current context.

The following variables are available to the page template used to build a fragment:

context

The context in which the fragment was looked up. This is usually either the portal root (when using an href with an absolute path, i.e. one starting with a /) or the current content object (when using an href with a relative path).

request

The request used to render the fragment. When using a fragment from the href of a rule, this is a clone of the request used to render the page, but with the path to the fragment view, not the original content object. Note that form parameters from the original request are not available in this request.

portal

The portal root object.

portal_url

The URL to the portal root.

You can learn more about Zope Page Template syntax here.

Fragment modules are Restricted Python Script modules bundled with your themes. Availability of methods is limited to specific fragment by naming the module after the fragment base name (with .py extension). Each module could contain any number Python function definitions, which are then made available as instance methods of the fragment view.

For example, you could create a file fragments/customnav.py in your theme directory, containing:

def getnav(self):
    return [{
        'Title': u'My title',
        'Description': u'My description',
        'getIcon': 'document_icon.png'
    }]

And call it in your fragment fragments/customnav.pt like a view method:

<ul id="nav">
  <li tal:repeat="item view/getnav">
    <img tal:replace="structure item/getIcon" />
    <span tal:replace="item/Title" tal:attributes="titile item/Description">Title</span>
  </li>
</ul>

Fragment methods are Restricted Python Script files bundled with your themes. Availability of methods is limited to specific fragment by prefixing the method filename with the fragment name. Each script should contain code for a single method and end by returning a value for the template.

For example, you could create a file fragments/customnav.getnav.py in your theme directory, containing:

return [{
    'Title': u'My title',
    'Description': u'My description',
    'getIcon': 'document_icon.png'
}]

And call it in your fragment fragments/customnav.pt like a view method:

<ul id="nav">
  <li tal:repeat="item view/getnav">
    <img tal:replace="structure item/getIcon" />
    <span tal:replace="item/Title" tal:attributes="titile item/Description">Title</span>
  </li>
</ul>

The following variables are available to the fragment method used to build a fragment:

self

The fragment view, which provides access to self.context, self.request and other available fragment methods similarly to filesystem browser views.

args

List of positional arguments for the method call. Fragment methods do not support Zope PythonScript's way of defining positional named arguments.

kwargs

Dictionary of keyword arguments for the method call. Fragment methods do not support Zope PythonScript's way of defining named keyword arguments.

context

The context in which the fragment was looked up. This is provided as tribute to Zope PythonScript.

container

The container for the context which the fragment was looked up. This is provided as tribute to Zope PythonScript.

traverse_subpath

An empty string. This is provided as tribute to Zope PythonScript.

The special @@theme-fragment view is used to render fragments. Before using it in your theme, you can test it directly in your browser by going to a URL like:

http://localhost:8080/Plone/@@theme-fragment/customnav

This will cause the fragment in fragments/customnav.pt to be rendered with the Plone site Plone running on localhost:8080 as its context. You can render fragments relative to any content object, by adjusting the URL.

Note: Fragments are only available for the currently active theme. When testing a fragment in the browser in this way, make sure the theme is enabled!

To use a fragment in a theme rule, use the href attribute with either an absolute or relative path. For example:

<replace css:theme="#navlist" css:content="#nav" href="/@@theme-fragment/customnav" />

will replace the element with id navlist in the theme with the element with id nav in the fragment generated by the fragments/customnav.pt template in the theme, rendered with the portal root as its context always (since the href is using an absolute path, i.e. one beginning with a /).

Similarly:

<replace css:theme="#navlist" css:content="#nav" href="@@theme-fragment/customnav" />

will do the same, but using the current content item as its context (i.e. the href is using a relative path).

Fragments can also be used as content views, by setting the layout-attribute of a content object to ++themefragment++name where name is the name of the fragment. Currently fragments cannot be configured to be visible in the display menu.

Note: Fragments are only available for the currently active theme. When using fragments in your content this way, make sure the theme is enabled!

Fragments, like theme HTML mockup files, are publicly accessible by default. Anyone with access to the site can construct a URL containing @@theme-fragment/<name> to render a given fragment.

Alernatively, more strict permissions can be defined per tile in theme manifest.cfg with syntax:

[theme:themefragments:permissions]
basename = zope2.View

However, regardless of the defined permissions, the page templates used to build fragments execute in a so-called Restricted Python environment. This means that the are executed as the current user (or Anonymous, if the current user is not logged in). Information (such as content items or their attributes) not accessible to the current user cannot be rendered, and may result in a 403 Forbidden error when rendering the fragment.

With plone.tiles, plone.app.tiles and plone.app.blocks installed this package provides an additional installation profile for Theme fragment tile, which can be used to place theme fragments as tiles.

More readable titles for theme fragments can be defined in theme manifest.cfg with:

[theme:themefragments:tiles]
basename = Display title

Where basename is the basename of fragment filename (the part before .pt).

Tiles can define their configuration schema using plone.supermodel XML in a fragment specific file having its matching filename ending with .xml instead of .pt.

It's also possible to specify fragment specific caching ruleset in manifest.cfg with:

[theme:themefragments:caching]
basename = plone.content.feed