Plone Content icons for Archetypes and Dexterity

01 April 2014

Due to the slow move from Archetypes to Dexterity, I have been dealing with a lot of sites recently that contain both Archetypes and Dexterity content types mixed together. For the most part this works fine, but there are a few places where you find yourself writing different code depending on which type of object you have at any one time.

A perfect example of this came up recently; when trying to list objects within a folder that were from both types. The problem came when trying to show icons for these objects. In Archetypes, you could simply do:


This would return you an object which implements IContentIcon, on which you would usually call the html_tag method. This would give you a fully formed img tag which you could put straight into a template. With dexterity, this is now deprecated.

The difference with dexterity is that in an Archetypes definition of a content type, you would define a content_icon property:

<property name="content_icon">MyType.gif</property>

where as in dexterity, we now define an icon expression:

<property name="icon_expr">string:++resource++my.package/images/my_type.png</property>

The former is assumed to be in a skins folder, the latter is an expression containing the path to the image.

The fix here involves using the portal types tool and this handy function from CMFCore called ‘createExprContext’:

from Products.CMFCore.Expression import createExprContext  

portal_types_tool = api.portal.get_tool('portal_types')
type_info = portal_types_tool.getTypeInfo(portal_type)
icon_ob = type_info.getIconExprObject()
portal = api.portal.get()
exp_context = createExprContext(
portal, portal, portal)
return icon_ob(exp_context)

This will return an absolute path to the icon in the context of the portal. This can then be used in tal for either archetypes or dexterity.