Making Components Theme Specific

As components come into being as soon as Zope starts up and reads the .zcml files, they are available for every Plone site you have in a Zope instance. You might not want this to happen.

A Theme Interface

You can specify that your components are available only for your theme with a marker interface and a layer attribute in ZCML. Here's a rewired version of the presentation viewlet:

<browser:viewlet
      name="[your namespace].[your presentation viewlet]"
      for="Products.ATContentTypes.interface.IATDocument"
      manager="plone.app.layout.viewlets.interfaces.IAboveContentBody"
      class=".[your viewlet module].[your viewlet class]"
      layer=".interfaces.IThemeSpecific"
      permission="zope2.View"
      />

Note: Don't confuse the layer attribute with a skin layer. Here, layer refers to the whole theme rather than just one slice of it.

There are two methods for creating a theme interface:

Using plone.theme

In Plone 3.0, plone.theme is used:

• A marker interface is defined in [your theme package]/browser/interfaces.py:

from plone.theme.interfaces import IDefaultPloneLayer

class IThemeSpecific(IDefaultPloneLayer):
    """Marker interface that defines a Zope 3 browser layer.    """

• and this is registered in ZCML in [your theme package]/browser/configure.zcml

<interface
        interface=".interfaces.IThemeSpecific"
        type="zope.publisher.interfaces.browser.IBrowserSkinType"
        name="[your skin name]"
        />

Note: [your skin name] crops up here; refer back to the skins section if you are wondering what this is.

Using plone.browserlayer

In Plone 3.1, plone.browserlayer is available to you.

• Create your interface (e.g. in [your theme package]/browser/interfaces.py)

from zope.interface import Interface
    class IThemeSpecific(Interface):
        """A layer specific to my product        """

• Register this in the configuration (in [your theme package]/profiles/default/browserlayer.xml):

<layers>
 <layer name="[your skin name]"
   interface="[your namespace].[your theme name].browser.interfaces.IThemeSpecific"
 />
</layers>

If you generate your file system product or egg using the plone3_theme paster template, then the basics will be done for you (using the plone.theme method), you will simply need to track down the interface to find its name. Look in

• [your theme package]/browser/interfaces.py or configure.zcml

and you should find it with the name IThemeSpecific. When you refer to it, use its path

layer=".interfaces.IThemeSpecific"