Heads up.

The IFile refactoring requieres a new field/widget
for the subobject Mime in the IFile.contents field.

I decide to add a SchemaWidget (Iinput) which can handle 
subobjects like the ObjectWidget does. 
See the difference to ObjectWidget described below.

Start adding a schema input widget.
The schema input widget allowes to define a interface and a factory id.
The factory is used for storing the attributes given form the schema.
This powerfull field is used for defining fields of subobjects with 
the schema of the subobject. We will use this in the IFile.contents field.

I think in a long therm we ca replace the IObject field and ObjectWidget
with this new field/widget. This pattern supports all requiered declaration
in the interface/schema where the Object field requieres a separate view 
for rendering subwidgets with additional CustomWidgetFacotires.
The factory in the SchemaWidget is aquiered via the registred IFactory
of a content type. "getUtility(IFactory, factoryId)".

browser/__init__.py

@@ -29,6 +29,9 @@
 from zope.app.form.browser.textwidgets import DateDisplayWidget
 from zope.app.form.browser.textwidgets import BytesDisplayWidget
 
+# Widgets for schema-based fields
+from zope.app.form.browser.schemawidgets import SchemaWidget
+
 # Widgets for file-based fields
 from zope.app.form.browser.filewidgets import FileWidget
 from zope.app.form.browser.filewidgets import MimeWidget

browser/configure.zcml

@@ -144,6 +144,14 @@
       permission="zope.Public"
       />
 
+  <view
+      type="zope.publisher.interfaces.browser.IBrowserRequest"
+      for="zope.schema.interfaces.ISchema"
+      provides="zope.app.form.interfaces.IInputWidget"
+      factory=".SchemaWidget"
+      permission="zope.Public"
+      />
+
   <view
       type="zope.publisher.interfaces.browser.IBrowserRequest"
       for="zope.schema.interfaces.IMime"

browser/filewidgets.py

@@ -22,12 +22,37 @@
 
 from zope.app.form.interfaces import IInputWidget, ConversionError
 from zope.app.form.browser.widget import SimpleInputWidget, renderElement
+from zope.app.form import InputWidget
+from zope.app.form.browser.widget import BrowserWidget
 from zope.app.form.browser.textwidgets import BytesWidget
 from zope.app.form.browser.widget import DisplayWidget
 from zope.app.form.browser.textwidgets import escape
+from zope.app.pagetemplate.viewpagetemplatefile import ViewPageTemplateFile
 
 
-class MimeWidget(SimpleInputWidget):
+# dependency
+from zope.app.file.file import Mime
+
+# used from ObjectWidget
+from zope.schema import getFieldNamesInOrder
+from zope.app.form.utility import setUpEditWidgets, applyWidgetsChanges
+
+
+
+
+class MimeWidgetView:
+
+    template = ViewPageTemplateFile('mimewidget.pt')
+
+    def __init__(self, context, request):
+        self.context = context
+        self.request = request
+
+    def __call__(self):
+        return self.template()
+
+
+class MimeWidget(BrowserWidget, InputWidget):
     """MimeWidget renders the subwidgets for the interface IMime.
     
     The widget also extracts the filename and the fileupload to the session. 
@@ -38,7 +63,115 @@ class MimeWidget(SimpleInputWidget):
     ObjectWidget implementation in 
     'zope.app.form.browser.objectwidget.ObjectWidget'.
     """
-    pass
+
+    implements(IInputWidget)
+
+    _object = None      # the object value (from setRenderedValue & request)
+    _request_parsed = False
+
+    def __init__(self, context, request, **kw):
+        super(MimeWidget, self).__init__(context, request)
+
+        # define view that renders the widget
+        self.view = MimeWidgetView(self, request)
+
+        # factory used to create content that this widget (field)
+        # represents
+        self.factory = Mime
+
+        # handle foo_widget specs being passed in
+        self.names = getFieldNamesInOrder(self.context.schema)
+        for k, v in kw.items():
+            if k.endswith('_widget'):
+                setattr(self, k, v)
+
+        # set up my subwidgets
+        self._setUpEditWidgets()
+
+    def setPrefix(self, prefix):
+        super(ObjectWidget, self).setPrefix(prefix)
+        self._setUpEditWidgets()
+
+    def _setUpEditWidgets(self):
+        # subwidgets need a new name
+        setUpEditWidgets(self, self.context.schema, source=self.context,
+                         prefix=self.name, names=self.names, 
+                         context=self.context)
+
+    def __call__(self):
+        return self.view()
+
+    def legendTitle(self):
+        return self.context.title or self.context.__name__
+
+    def getSubWidget(self, name):
+        return getattr(self, '%s_widget' % name)
+
+    def subwidgets(self):
+        return [self.getSubWidget(name) for name in self.names]
+
+    def hidden(self):
+        """Render the list as hidden fields."""
+        result = []
+        for name in self.names:
+            result.append(getSubwidget(name).hidden())
+        return "".join(result)
+
+    def getInputValue(self):
+        """Return converted and validated widget data.
+
+        The value for this field will be represented as an `ObjectStorage`
+        instance which holds the subfield values as attributes. It will
+        need to be converted by higher-level code into some more useful
+        object (note that the default EditView calls `applyChanges`, which
+        does this).
+        """
+        content = self.factory()
+        for name in self.names:
+            setattr(content, name, self.getSubWidget(name).getInputValue())
+        return content
+
+    def applyChanges(self, content):
+        field = self.context
+
+        # create our new object value
+        value = field.query(content, None)
+        if value is None:
+            # TODO: ObjectCreatedEvent here would be nice
+            value = self.factory()
+
+        # apply sub changes, see if there *are* any changes
+        # TODO: ObjectModifiedEvent here would be nice
+        changes = applyWidgetsChanges(self, field.schema, target=value,
+                                      names=self.names)
+
+        # if there's changes, then store the new value on the content
+        if changes:
+            field.set(content, value)
+
+        return changes
+
+    def hasInput(self):
+        """Is there input data for the field
+
+        Return ``True`` if there is data and ``False`` otherwise.
+        """
+        for name in self.names:
+            if self.getSubWidget(name).hasInput():
+                return True
+        return False
+
+    def setRenderedValue(self, value):
+        """Set the default data for the widget.
+
+        The given value should be used even if the user has entered
+        data.
+        """
+        # re-call setupwidgets with the content
+        self._setUpEditWidgets()
+        for name in self.names:
+            self.getSubWidget(name).setRenderedValue(getattr(value, name, None))
+
 
 
 class MimeDataWidget(SimpleInputWidget):

browser/mimewidget.pt

@@ -0,0 +1,6 @@
+<fieldset>
+  <legend tal:content="context/legendTitle">The Legend</legend>
+  <tal:block repeat="widget context/subwidgets">
+    <metal:block use-macro="context/@@form_macros/widget_row" />
+  </tal:block>
+</fieldset>

browser/schemawidget.pt

@@ -0,0 +1,6 @@
+<fieldset>
+  <legend tal:content="context/legendTitle">The Legend</legend>
+  <tal:block repeat="widget context/subwidgets">
+    <metal:block use-macro="context/@@form_macros/widget_row" />
+  </tal:block>
+</fieldset>

browser/schemawidgets.py

@@ -0,0 +1,157 @@
+##############################################################################
+#
+# Copyright (c) 2004 Zope Corporation and Contributors.
+# 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.
+#
+##############################################################################
+"""Browser widgets for text-like data
+
+$Id: objectwidget.py 26748 2004-07-24 05:51:58Z pruggera $
+"""
+__docformat__ = 'restructuredtext'
+
+from zope.interface import implements
+from zope.schema import getFieldNamesInOrder
+from zope.component.interfaces import IFactory
+
+from zope.app.zapi import queryUtility
+from zope.app.form.interfaces import IInputWidget
+from zope.app.form import InputWidget
+from zope.app.form.browser.widget import BrowserWidget
+from zope.app.form.utility import setUpEditWidgets, applyWidgetsChanges
+from zope.app.pagetemplate.viewpagetemplatefile import ViewPageTemplateFile
+
+
+class SchemaWidgetView:
+
+    template = ViewPageTemplateFile('schemawidget.pt')
+
+    def __init__(self, context, request):
+        self.context = context
+        self.request = request
+
+    def __call__(self):
+        return self.template()
+
+
+class SchemaWidget(BrowserWidget, InputWidget):
+    """A widget over an Interface that contains Fields."""
+
+    implements(IInputWidget)
+
+    _object = None      # the object value (from setRenderedValue & request)
+    _request_parsed = False
+
+    def __init__(self, context, request, **kw):
+        super(SchemaWidget, self).__init__(context, request)
+
+        # define view that renders the widget
+        self.view = SchemaWidgetView(self, request)
+
+        # factory used to create content that this widget (field)
+        # represents, we get the factory id of a content type declared
+        # in the schema field
+        factoryId = self.context.factoryId
+        self.factory = queryUtility(IFactory, factoryId)
+
+        # handle foo_widget specs being passed in
+        self.names = getFieldNamesInOrder(self.context.schema)
+        for k, v in kw.items():
+            if k.endswith('_widget'):
+                setattr(self, k, v)
+
+        # set up my subwidgets
+        self._setUpEditWidgets()
+
+    def setPrefix(self, prefix):
+        super(SchemaWidget, self).setPrefix(prefix)
+        self._setUpEditWidgets()
+
+    def _setUpEditWidgets(self):
+        # subwidgets need a new name
+        setUpEditWidgets(self, self.context.schema, source=self.context,
+                         prefix=self.name, names=self.names, 
+                         context=self.context)
+
+    def __call__(self):
+        return self.view()
+
+    def legendTitle(self):
+        return self.context.title or self.context.__name__
+
+    def getSubWidget(self, name):
+        return getattr(self, '%s_widget' % name)
+
+    def subwidgets(self):
+        return [self.getSubWidget(name) for name in self.names]
+
+    def hidden(self):
+        """Render the list as hidden fields."""
+        result = []
+        for name in self.names:
+            result.append(getSubwidget(name).hidden())
+        return "".join(result)
+
+    def getInputValue(self):
+        """Return converted and validated widget data.
+
+        The value for this field will be represented as an `ObjectStorage`
+        instance which holds the subfield values as attributes. It will
+        need to be converted by higher-level code into some more useful
+        object (note that the default EditView calls `applyChanges`, which
+        does this).
+        """
+        content = self.factory()
+        for name in self.names:
+            setattr(content, name, self.getSubWidget(name).getInputValue())
+        return content
+
+    def applyChanges(self, content):
+        field = self.context
+
+        # create our new object value
+        value = field.query(content, None)
+        if value is None:
+            # TODO: ObjectCreatedEvent here would be nice
+            value = self.factory()
+
+        # apply sub changes, see if there *are* any changes
+        # TODO: ObjectModifiedEvent here would be nice
+        changes = applyWidgetsChanges(self, field.schema, target=value,
+                                      names=self.names)
+
+        # if there's changes, then store the new value on the content
+        if changes:
+            field.set(content, value)
+
+        return changes
+
+    def hasInput(self):
+        """Is there input data for the field
+
+        Return ``True`` if there is data and ``False`` otherwise.
+        """
+        for name in self.names:
+            if self.getSubWidget(name).hasInput():
+                return True
+        return False
+
+    def setRenderedValue(self, value):
+        """Set the default data for the widget.
+
+        The given value should be used even if the user has entered
+        data.
+        """
+        # re-call setupwidgets with the content
+        self._setUpEditWidgets()
+        for name in self.names:
+            self.getSubWidget(name).setRenderedValue(getattr(value, name, None))
+
+