diff -r 000000000000 -r bb4aabe07487 src/pyams_skin/skin.py
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/pyams_skin/skin.py	Thu Feb 19 10:59:00 2015 +0100
@@ -0,0 +1,100 @@
+#
+# Copyright (c) 2008-2015 Thierry Florac <tflorac AT ulthar.net>
+# All Rights Reserved.
+#
+# This software is subject to the provisions of the Zope Public License,
+# Version 2.1 (ZPL).  A copy of the ZPL should accompany this distribution.
+# THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
+# WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+# WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
+# FOR A PARTICULAR PURPOSE.
+#
+
+__docformat__ = 'restructuredtext'
+
+# import standard library
+
+# import interfaces
+from pyams_skin.interfaces import ISkin, ISkinnable, IUserSkinnable, SkinChangedEvent
+from pyams_skin.layer import IBaseLayer, IPyAMSLayer
+from pyams_utils.interfaces.site import ISiteRoot
+from zope.traversing.interfaces import IBeforeTraverseEvent
+
+# import packages
+from pyams_utils.registry import utility_config
+from pyramid.events import subscriber
+from pyramid.threadlocal import get_current_request
+from pyramid_zope_request import PyramidPublisherRequest
+from zope.interface import implementer, directlyProvidedBy, directlyProvides
+from zope.schema.fieldproperty import FieldProperty
+
+from pyams_skin import _
+
+
+@utility_config(name='PyAMS default skin', provides=ISkin)
+class PyAMSSkin(object):
+    """PyAMS default skin"""
+
+    label = _("Default PyAMS skin")
+    layer = IPyAMSLayer
+
+
+@implementer(ISkinnable)
+class SkinnableContent(object):
+    """Skinnable content base class"""
+
+    def get_skin(self):
+        """Get current skin"""
+        raise NotImplementedError("SkinnableContent subclasses must implement `get_skin` method")
+
+
+@implementer(IUserSkinnable)
+class UserSkinnableContent(SkinnableContent):
+    """User skinnable content base class"""
+
+    skin = FieldProperty(IUserSkinnable['skin'])
+
+    def get_skin(self, request=None):
+        skin = self.skin
+        if skin is not None:
+            if request is None:
+                request = get_current_request()
+            return request.registry.queryUtility(ISkin, skin)
+
+
+@subscriber(IBeforeTraverseEvent, context_selector=ISkinnable)
+def handle_content_skin(event):
+    """Apply skin when traversing skinnable object"""
+    request = event.request
+    skin = event.object.get_skin(request)
+    if skin is not None:
+        apply_skin(request, skin)
+
+
+@subscriber(IBeforeTraverseEvent, context_selector=ISiteRoot)
+def handle_root_skin(event):
+    """Apply skin when traversing site root"""
+    if not ISkinnable.providedBy(event.object):
+        apply_skin(event.request, PyAMSSkin)
+
+
+def apply_skin(request, skin):
+    """Apply given skin to request"""
+
+    def _apply(request, skin):
+        ifaces = [iface for iface in directlyProvidedBy(request)
+                  if not issubclass(iface, IBaseLayer)]
+        # Add the new skin.
+        if isinstance(skin, str):
+            skin = request.registry.queryUtility(ISkin, skin)
+        if skin is not None:
+            ifaces.append(skin.layer)
+            directlyProvides(request, *ifaces)
+
+    _apply(request, skin)
+    if isinstance(request, PyramidPublisherRequest):
+        request = request._request
+        _apply(request, skin)
+    else:
+        request.registry.notify(SkinChangedEvent(request))
+        request.annotations['__skin__'] = skin