Add a widget registry to make it easier to use custom widget factories.

enaml/qt/qt_widget_registry.py

@@ -0,0 +1,73 @@
+#------------------------------------------------------------------------------
+#  Copyright (c) 2012, Enthought, Inc.
+#  All rights reserved.
+#------------------------------------------------------------------------------
+from collections import defaultdict
+
+
+class QtWidgetRegistry(object):
+    """ A class for registering Qt widget factories.
+
+    This is a process-widget registry class. Interaction is done through
+    the two classmethods `register` and `lookup`.
+
+    """
+    #: Private storage for the widget factories.
+    _groups = defaultdict(dict)
+
+    @classmethod
+    def register(cls, name, factory, group='', strict=False):
+        """ Registery a widget factory.
+
+        Parameters
+        ----------
+        name : str
+            The name of the Enaml widget class which is implemented
+            by the class returned by the given factory.
+
+        factory : callable
+            A callable which takes no arguments and returns the class
+            which implements the widget.
+
+        group : str, optional
+            The widget group with which this factory is associated.
+            If not provided, the widget will be registered with the
+            default group.
+
+        strict : bool, optional
+            If True, attempting to register a factory for a widget
+            which is already registered will raise a ValueError.
+            The default is False.
+
+        """
+        thisgroup = cls._groups[group]
+        if strict and name in thisgroup:
+            msg = ('Factory already registered for the `%s` widget in the '
+                   '`%s` widget group.')
+            raise ValueError(msg % (name, group))
+        thisgroup[name] = factory
+
+    @classmethod
+    def lookup(cls, name, groups=None):
+        """ Lookup a widget factory.
+
+        Parameters
+        ----------
+        name : str
+            The name of the Enaml widget for which to lookup a factory.
+
+        groups : list of str, optional
+            The list of groups to check for a matching factory. The
+            groups are checked in order with the first match being
+            returned. If no match is found, None will be returned.
+            The default groups list contains the default group.
+
+        """
+        groups = groups or ['']
+        thesegroups = cls._groups
+        for group in groups:
+            if group in thesegroups:
+                thisgroup = thesegroups[group]
+                if name in thisgroup:
+                    return thisgroup[name]
+