Making Components Theme Specific

You may want to make components only available for your particular theme. To do this you will need an interface.

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:

      name="[your namespace].[your presentation viewlet]"
      class=".[your viewlet module].[your viewlet class]"

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

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/ or configure.zcml

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