Adding a custom view for the content — Plone Documentation v4.3

The browser layer concept¶

A browser layer is a concept introduced by Zope Component Architecture (Zope 3), and which can be used in Plone. It is useful for registering views and resources (images, CSS, JS) for the site, in a way that they can override default elements (which are implicitly registered for the default browser layer) or be overriden when needed, even through the ZMI. A browser layer is similar in purpose to a CMF skin layer, but is implemented differently.

To add a browser layer to your product, you need 3 steps:

Define the marker interface for the browser layer (for example, example.archetype.interfaces.IInstantMessageSpecific.)
Add an XML file in your extension profile named browserlayer.xml providing the browser layer settings to the site. (This step is covered later as part of the various product setup details.)
Register (using ZCML) your browser views, templates and resources.

For more about browser layer techniques, check this tutorial.

Defining the browser layer interface¶

Add a marker interface for the browser layer (in interfaces.py):

                        from plone.theme.interfaces import IDefaultPloneLayer

class IInstantMessageSpecific(IDefaultPloneLayer):
    """Marker interface that defines a Zope 3 skin layer for this product.
    """

Adding and registering the browser template¶

To provide a custom view template for your content type, you need a page template called instantmessage.pt in the browser/ directory, and a ZCML declaration in the configure.zcml to associate the template to the IInstantMessageSpecific Zope 3 skin layer.

                        <configure xmlns="http://namespaces.zope.org/zope"
    xmlns:browser="http://namespaces.zope.org/browser"
    i18n_domain="example.archetype" >
    <browser:page
        for="example.archetype.interfaces.IInstantMessage"
        layer="example.archetype.interfaces.IInstantMessageSpecific"
        name="instantmessage_view"
        template="instantmessage.pt"
        permission="zope2.View"
        />
</configure>

                      

Here is the example template code:

                        <html metal:use-macro="here/main_template/macros/master"
      i18n:domain="plone" >
<body>

<div metal:fill-slot="main"
     tal:define="priority here/getPriority;
                 priority_color python:(priority == 'high' and 'red') or (priority == 'low' and 'green') or ''" >

        <h1 tal:content="context/Title"
            tal:attributes="style string:color:$priority_color" >
          Title
        </h1>

        <p tal:content="structure here/getBody" />

        <div class="documentByLine">
          Message by <span tal:content="context/Creator" />
          with <strong tal:content="priority" /> priority.
          -
          <span tal:replace="python:here.toLocalizedTime(context.CreationDate(),long_format=1)" />
        </div>

</div>

</body>
</html>

                      

Python notes:

The new methods we use on the content object (getPriority, getBody, etc), called the “accessors”, are generated by Archetypes as part of its internal mechanisms, based on the field definition in the content schema; so if the field is called ‘priority’, there is a generated method called ‘getPriority’ responsible to return the stored value on the object. Note that the code of the method is not available somewhere for modification ; “generated” here means it is available in the server’s memory, within Archetypes engine’s registries, when the Zope server has started.

After the product installation step, which we still have to discuss (see later), Plone should be able to find this template and use it as the content object’s default view when you invoke the content’s URL.

Adding a custom view for the content¶

The browser layer concept¶

Defining the browser layer interface¶

Adding and registering the browser template¶