core: kv lang introduce ids attribute in line with the discussion on

kivy/lang.py

@@ -464,6 +464,7 @@
 from kivy import kivy_data_dir, require
 from kivy.lib.debug import make_traceback
 import kivy.metrics as metrics
+from weakref import ref
 
 
 trace = Logger.trace
@@ -1264,6 +1265,17 @@ def _apply_rule(self, widget, rule, rootrule, template_ctx=None):
         # if we got an id, put it in the root rule for a later global usage
         if rule.id:
             rctx['ids'][rule.id] = widget
+            # set id name as a attribute for root widget so one can in python
+            # code simply access root_widget.id_name
+            _ids = dict(rctx['ids'])
+            _root = _ids.pop('root')
+            _new_ids = _root.ids
+            for _key in _ids.keys():
+                if _ids[_key] == _root:
+                    # skip on self
+                    continue
+                _new_ids[_key] = ref(_ids[_key])
+            _root.ids = _new_ids
 
         # first, ensure that the widget have all the properties used in
         # the rule if not, they will be created as ObjectProperty.

kivy/properties.pyx

@@ -234,9 +234,11 @@ cdef class Property:
 
     :Parameters:
         `errorhandler`: callable
-            If set, must take a single argument and return a valid substitute value
+            If set, must take a single argument and return a valid substitute
+            value
         `errorvalue`: object
-            If set, will replace an invalid property value (overrides errorhandler)
+            If set, will replace an invalid property value (overrides
+            errorhandler)
 
     .. versionchanged:: 1.4.2
         Parameters errorhandler and errorvalue added
@@ -601,8 +603,28 @@ class ObservableDict(dict):
         self.obj = largs[1]
         super(ObservableDict, self).__init__(*largs[2:])
 
+    def __getattr__(self, attr):
+        try:
+            return self.__getitem__(attr)
+        except KeyError:
+            try:
+                return super(ObservableDict, self).__getattr__(attr)
+            except AttributeError:
+                raise KeyError(attr)
+
+    def __setattr__(self, attr, value):
+        if attr in ('prop', 'obj'):
+            super(ObservableDict, self).__setattr__(attr, value)
+            return
+        self.__setitem__(attr, value)
+
     def __setitem__(self, key, value):
-        dict.__setitem__(self, key, value)
+        if value is None:
+            # remove attribute if value is None
+            # is this really needed?
+            self.__delitem__(key)
+        else:
+            dict.__setitem__(self, key, value)
         observable_dict_dispatch(self)
 
     def __delitem__(self, key):

kivy/uix/widget.py

@@ -82,7 +82,7 @@ def callback_pos(instance, value):
 from kivy.factory import Factory
 from kivy.properties import NumericProperty, StringProperty, \
         AliasProperty, ReferenceListProperty, ObjectProperty, \
-        ListProperty
+        ListProperty, DictProperty
 from kivy.graphics import Canvas
 from kivy.base import EventLoop
 from kivy.lang import Builder
@@ -564,6 +564,16 @@ def set_center_y(self, value):
     dict.
     '''
 
+    ids = DictProperty({})
+    '''This is a Dictionary of id's defined in your kv language. This will only
+    be populated if you use id's in your kv language code.
+
+    .. versionadded:: 1.6.0
+
+    :data:`ids` is a :class:`~kivy.properties.DictProperty`, defaults to a empty
+    dict {}.
+    '''
+
     opacity = NumericProperty(1.0)
     '''Opacity of the widget and all the children.