Separate the display from the models on the python side, creating a BaseWidget class.

Conflicts:
	IPython/html/widgets/widget.py

IPython/html/widgets/widget.py

@@ -30,10 +30,13 b' from IPython.utils.py3compat import string_types'
 #-----------------------------------------------------------------------------
 # Classes
 #-----------------------------------------------------------------------------
-class Widget(LoggingConfigurable):
+
+class BaseWidget(LoggingConfigurable):
 
     # Shared declarations (Class level)
-    _keys = []
+    _keys = List(Unicode, help="List of keys comprising the state of the model.")
+    _children_attr = List(Unicode, help="List of keys of children objects of the model.")
+    _children_lists_attr = List(Unicode, help="List of keys containing lists of children objects of the model.")
     widget_construction_callback = None
 
     def on_widget_constructed(callback):
@@ -54,52 +57,24 b' class Widget(LoggingConfigurable):'
         registered in the frontend to create and sync this widget with.""")
     default_view_name = Unicode(help="""Default view registered in the frontend
         to use to represent the widget.""")
-    parent = Instance('IPython.html.widgets.widget.Widget')
-    visible = Bool(True, help="Whether or not the widget is visible.")
-
-    def _parent_changed(self, name, old, new):
-        if self._displayed:
-            raise Exception('Parent cannot be set because widget has been displayed.')
-        elif new == self:
-            raise Exception('Parent cannot be set to self.')
-        else:
-
-            # Parent/child association
-            if new is not None and not self in new._children:
-                new._children.append(self)
-            if old is not None and self in old._children:
-                old._children.remove(self)                
 
     # Private/protected declarations
     _property_lock = (None, None) # Last updated (key, value) from the front-end.  Prevents echo.
-    _css = Dict() # Internal CSS property dict
     _displayed = False
-   
+    _comm = None
     
     def __init__(self, **kwargs):
         """Public constructor
-
-        Parameters
-        ----------
-        parent : Widget instance (optional)
-            Widget that this widget instance is child of.  When the widget is
-            displayed in the frontend, it's corresponding view will be made
-            child of the parent's view if the parent's view exists already.  If
-            the parent's view is displayed, it will automatically display this 
-            widget's default view as it's child.  The default view can be set
-            via the default_view_name property.
         """
-        self._children = []
         self._display_callbacks = []
         self._msg_callbacks = []
-        super(Widget, self).__init__(**kwargs)
+        super(BaseWidget, self).__init__(**kwargs)
                 
         # Register after init to allow default values to be specified
-        self.on_trait_change(self._handle_property_changed, self.keys)
-
+        # TODO: register three different handlers, one for each list, and abstract out the common parts
+        self.on_trait_change(self._handle_property_changed, self.keys+self._children_attr+self._children_lists_attr)
         Widget._handle_widget_constructed(self)
         
-        
     def __del__(self):
         """Object disposal"""
         self.close()
@@ -113,12 +88,17 b' class Widget(LoggingConfigurable):'
     
     
     # Properties      
-    def _get_keys(self):
-        keys = ['visible', '_css']
+    @property
+    def keys(self):
+        keys = ['_children_attr', '_children_lists_attr']
         keys.extend(self._keys)
         return keys
-    keys = property(_get_keys)
     
+    @property
+    def comm(self):
+        if self._comm is None:
+            self._open_communication()
+        return self._comm
     
     # Event handlers
     def _handle_msg(self, msg):
@@ -179,7 +159,6 b' class Widget(LoggingConfigurable):'
             # Send new state to frontend
             self.send_state(key=name)
 
-
     def _handle_displayed(self, **kwargs):
         """Called when a view has been displayed for this widget instance
 
@@ -206,7 +185,6 b' class Widget(LoggingConfigurable):'
                 else:
                     handler(self, **kwargs)
     
-    
     # Public methods
     def send_state(self, key=None):
         """Sends the widget state, or a piece of it, to the frontend.
@@ -216,119 +194,43 b' class Widget(LoggingConfigurable):'
         key : unicode (optional)
             A single property's name to sync with the frontend.
         """
-        state = {}
-
-        # If a key is provided, just send the state of that key.
-        keys = []
-        if key is None:
-            keys.extend(self.keys)
-        else:
-            keys.append(key)
-        for key in self.keys:
-            try:
-                state[key] = getattr(self, key)
-            except Exception as e:
-                pass # Eat errors, nom nom nom
         self._send({"method": "update",
-                        "state": state})
+                    "state": self.get_state()})
 
-
-    def get_css(self, key, selector=""):
-        """Get a CSS property of the widget.  Note, this function does not 
-        actually request the CSS from the front-end;  Only properties that have 
-        been set with set_css can be read.
+    def get_state(self, key=None)
+        """Gets the widget state, or a piece of it.
 
         Parameters
         ----------
-        key: unicode
-            CSS key
-        selector: unicode (optional)
-            JQuery selector used when the CSS key/value was set.
-        """
-        if selector in self._css and key in self._css[selector]:
-            return self._css[selector][key]
-        else:
-            return None
-
-
-    def set_css(self, *args, **kwargs):
-        """Set one or more CSS properties of the widget (shared among all of the 
-        views).  This function has two signatures:
-        - set_css(css_dict, [selector=''])
-        - set_css(key, value, [selector=''])
-
-        Parameters
-        ----------
-        css_dict : dict
-            CSS key/value pairs to apply
-        key: unicode
-            CSS key
-        value
-            CSS value
-        selector: unicode (optional)
-            JQuery selector to use to apply the CSS key/value.
+        key : unicode (optional)
+            A single property's name to get.
         """
-        selector = kwargs.get('selector', '')
+        state = {}
 
-        # Signature 1: set_css(css_dict, [selector=''])
-        if len(args) == 1:
-            if isinstance(args[0], dict):
-                for (key, value) in args[0].items():
-                    self.set_css(key, value, selector=selector)
+        # If a key is provided, just send the state of that key.
+        if key is None:
+            keys = self.keys[:]
+            children_attr = self._children_attr[:]
+            children_lists_attr = self._children_lists_attr[:]
             else:
-                raise Exception('css_dict must be a dict.')
-
-        # Signature 2: set_css(key, value, [selector=''])
-        elif len(args) == 2 or len(args) == 3:
-
-            # Selector can be a positional arg if it's the 3rd value
-            if len(args) == 3:
-                selector = args[2]
-            if selector not in self._css:
-                self._css[selector] = {}
-                
-            # Only update the property if it has changed.
-            key = args[0]
-            value = args[1]
-            if not (key in self._css[selector] and value in self._css[selector][key]):
-                self._css[selector][key] = value
-                self.send_state('_css') # Send new state to client.
+            keys = []
+            children_attr = []
+            children_lists_attr = []
+            if key in self._children_attr:
+                children_attr.append(key)
+            elif key in self._children_lists_attr:
+                children_lists_attr.append(key)
         else:
-            raise Exception('set_css only accepts 1-3 arguments')
-
-
-    def add_class(self, class_name, selector=""):
-        """Add class[es] to a DOM element
-
-        Parameters
-        ----------
-        class_name: unicode
-            Class name(s) to add to the DOM element(s).  Multiple class names 
-            must be space separated.
-        selector: unicode (optional)
-            JQuery selector to select the DOM element(s) that the class(es) will 
-            be added to.
-        """
-        self._send({"method": "add_class",
-                        "class_list": class_name,
-                        "selector": selector})
-
-
-    def remove_class(self, class_name, selector=""):
-        """Remove class[es] from a DOM element
-
-        Parameters
-        ----------
-        class_name: unicode
-            Class name(s) to remove from  the DOM element(s).  Multiple class 
-            names must be space separated.
-        selector: unicode (optional)
-            JQuery selector to select the DOM element(s) that the class(es) will 
-            be removed from.
-        """
-        self._send({"method": "remove_class",
-                        "class_list": class_name,
-                        "selector": selector})
+                keys.append(key)
+        for k in keys:
+            state[k] = getattr(self, k)
+        for k in children_attr:
+            # automatically create models on the browser side if they aren't already created
+            state[k] = getattr(self, k).comm.comm_id
+        for k in children_lists_attr:
+            # automatically create models on the browser side if they aren't already created
+            state[k] = [i.comm.comm_id for i in getattr(self, k)]
+        return state
 
 
     def send(self, content):
@@ -398,20 +300,9 b' class Widget(LoggingConfigurable):'
         self.send_state()
             
         # Show view.
-        if self.parent is None or self.parent._comm is None:
             self._send({"method": "display", "view_name": view_name})
-        else:
-            self._send({"method": "display", 
-                            "view_name": view_name,
-                            "parent": self.parent._comm.comm_id})
-        self._handle_displayed(**kwargs)
         self._displayed = True
-
-        # Now display children if any.
-        for child in self._children:
-            if child != self:
-                child._repr_widget_()
-        return None
+        self._handle_displayed(**kwargs)
 
 
     def _open_communication(self):
@@ -434,8 +325,121 b' class Widget(LoggingConfigurable):'
 
     def _send(self, msg):
         """Sends a message to the model in the front-end"""
-        if hasattr(self, '_comm') and self._comm is not None:
+        if self._comm is not None:
             self._comm.send(msg)
             return True
         else:
             return False
+
+class Widget(BaseWidget):
+
+    _children = List(Instance('IPython.html.widgets.widget.Widget'))
+    _children_lists_attr = List(Unicode, ['_children'])
+    visible = Bool(True, help="Whether or not the widget is visible.")
+
+    # Private/protected declarations
+    _css = Dict() # Internal CSS property dict
+
+    # Properties
+    @property
+    def keys(self):
+        keys = ['visible', '_css']
+        keys.extend(super(Widget, self).keys)
+        return keys
+
+    def get_css(self, key, selector=""):
+        """Get a CSS property of the widget.  Note, this function does not
+        actually request the CSS from the front-end;  Only properties that have
+        been set with set_css can be read.
+
+        Parameters
+        ----------
+        key: unicode
+            CSS key
+        selector: unicode (optional)
+            JQuery selector used when the CSS key/value was set.
+        """
+        if selector in self._css and key in self._css[selector]:
+            return self._css[selector][key]
+        else:
+            return None
+
+
+    def set_css(self, *args, **kwargs):
+        """Set one or more CSS properties of the widget (shared among all of the
+        views).  This function has two signatures:
+        - set_css(css_dict, [selector=''])
+        - set_css(key, value, [selector=''])
+
+        Parameters
+        ----------
+        css_dict : dict
+            CSS key/value pairs to apply
+        key: unicode
+            CSS key
+        value
+            CSS value
+        selector: unicode (optional)
+            JQuery selector to use to apply the CSS key/value.
+        """
+        selector = kwargs.get('selector', '')
+
+        # Signature 1: set_css(css_dict, [selector=''])
+        if len(args) == 1:
+            if isinstance(args[0], dict):
+                for (key, value) in args[0].items():
+                    self.set_css(key, value, selector=selector)
+            else:
+                raise Exception('css_dict must be a dict.')
+
+        # Signature 2: set_css(key, value, [selector=''])
+        elif len(args) == 2 or len(args) == 3:
+
+            # Selector can be a positional arg if it's the 3rd value
+            if len(args) == 3:
+                selector = args[2]
+            if selector not in self._css:
+                self._css[selector] = {}
+
+            # Only update the property if it has changed.
+            key = args[0]
+            value = args[1]
+            if not (key in self._css[selector] and value in self._css[selector][key]):
+                self._css[selector][key] = value
+                self.send_state('_css') # Send new state to client.
+        else:
+            raise Exception('set_css only accepts 1-3 arguments')
+
+
+    def add_class(self, class_name, selector=""):
+        """Add class[es] to a DOM element
+
+        Parameters
+        ----------
+        class_name: unicode
+            Class name(s) to add to the DOM element(s).  Multiple class names
+            must be space separated.
+        selector: unicode (optional)
+            JQuery selector to select the DOM element(s) that the class(es) will
+            be added to.
+        """
+        self._send({"method": "add_class",
+                        "class_list": class_name,
+                        "selector": selector})
+
+
+    def remove_class(self, class_name, selector=""):
+        """Remove class[es] from a DOM element
+
+        Parameters
+        ----------
+        class_name: unicode
+            Class name(s) to remove from  the DOM element(s).  Multiple class
+            names must be space separated.
+        selector: unicode (optional)
+            JQuery selector to select the DOM element(s) that the class(es) will
+            be removed from.
+        """
+        self._send({"method": "remove_class",
+                        "class_list": class_name,
+                        "selector": selector})