add page template subclass providing overridable macros

git-svn-id: svn://svn.cy55.de/Zope3/src/cybertools/trunk@3958 fd906abe-77d9-0310-91a1-e0d9ade77398

browser/macro.py

@@ -0,0 +1,55 @@
+#
+#  Copyright (c) 2010 Helmut Merz helmutm@cy55.de
+#
+#  This program is free software; you can redistribute it and/or modify
+#  it under the terms of the GNU General Public License as published by
+#  the Free Software Foundation; either version 2 of the License, or
+#  (at your option) any later version.
+#
+#  This program is distributed in the hope that it will be useful,
+#  but WITHOUT ANY WARRANTY; without even the implied warranty of
+#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#  GNU General Public License for more details.
+#
+#  You should have received a copy of the GNU General Public License
+#  along with this program; if not, write to the Free Software
+#  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+#
+
+"""
+Wrapping ZPT macro templates for dynamic macro lookup.
+
+$Id$
+"""
+
+from zope.app.pagetemplate import ViewPageTemplateFile
+from zope.cachedescriptors.property import Lazy
+
+
+_not_found = object()
+
+
+class MacroTemplate(object):
+
+    def __init__(self, template, parent=None):
+        self.baseTemplate = template
+        self.parent = parent
+
+    @Lazy
+    def macros(self):
+        return Macros(self)
+
+
+class Macros(dict):
+
+    def __init__(self, template):
+        self.template = template
+
+    def __getitem__(self, key):
+        macro = self.template.baseTemplate.macros.get(key, _not_found)
+        if macro is _not_found:
+            parent = self.template.parent
+            if parent is None:
+                raise KeyError(key)
+            return parent.macros[key]
+        return macro