--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/pyams_utils/context.py	Wed Dec 05 12:45:56 2018 +0100
@@ -0,0 +1,56 @@
+#
+# 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
+
+# import packages
+
+
+class ContextSelector(object):
+    """Interface based context selector
+
+    This selector can be used as a subscriber predicate to define
+    an interface that the context must support for the event to be applied:
+
+    .. code-block:: python
+
+        from pyams_utils.interfaces.site import ISiteRoot
+
+        @subscriber(IObjectModifiedEvent, context_selector=ISiteRoot)
+        def siteroot_modified_event_handler(event):
+            '''This is an event handler for an ISiteRoot object modification event'''
+    """
+
+    def __init__(self, ifaces, config):
+        if not isinstance(ifaces, (list, tuple, set)):
+            ifaces = (ifaces,)
+        self.interfaces = ifaces
+
+    def text(self):
+        return 'context_selector = %s' % str(self.interfaces)
+
+    phash = text
+
+    def __call__(self, event):
+        for intf in self.interfaces:
+            try:
+                if intf.providedBy(event.object):
+                    return True
+            except (AttributeError, TypeError):
+                if isinstance(event.object, intf):
+                    return True
+        return False