Document in widget packing that vaues must be JSON-able.

IPython/html/widgets/widget.py

@@ -1,437 +1,437 b''
 """Base Widget class.  Allows user to create widgets in the back-end that render
 in the IPython notebook front-end.
 """
 #-----------------------------------------------------------------------------
 # Copyright (c) 2013, the IPython Development Team.
 #
 # Distributed under the terms of the Modified BSD License.
 #
 # The full license is in the file COPYING.txt, distributed with this software.
 #-----------------------------------------------------------------------------
 
 #-----------------------------------------------------------------------------
 # Imports
 #-----------------------------------------------------------------------------
 from contextlib import contextmanager
 import inspect
 import types
 
 from IPython.kernel.comm import Comm
 from IPython.config import LoggingConfigurable
 from IPython.utils.traitlets import Unicode, Dict, Instance, Bool
 from IPython.utils.py3compat import string_types
 
 #-----------------------------------------------------------------------------
 # Classes
 #-----------------------------------------------------------------------------
 class Widget(LoggingConfigurable):
 
     #-------------------------------------------------------------------------
     # Class attributes
     #-------------------------------------------------------------------------
     widget_construction_callback = None
     widgets = {}
 
     def on_widget_constructed(callback):
         """Registers a callback to be called when a widget is constructed.  
 
         The callback must have the following signature:
         callback(widget)"""
         Widget.widget_construction_callback = callback
 
     def _call_widget_constructed(widget):
         """Class method, called when a widget is constructed."""
         if Widget.widget_construction_callback is not None and callable(Widget.widget_construction_callback):
             Widget.widget_construction_callback(widget)
 
     #-------------------------------------------------------------------------
     # Traits
     #-------------------------------------------------------------------------
     model_name = Unicode('WidgetModel', help="""Name of the backbone model 
         registered in the front-end to create and sync this widget with.""")
     view_name = Unicode(help="""Default view registered in the front-end
         to use to represent the widget.""", sync=True)
     _comm = Instance('IPython.kernel.comm.Comm')
 
     #-------------------------------------------------------------------------
     # (Con/de)structor
     #-------------------------------------------------------------------------    
     def __init__(self, **kwargs):
         """Public constructor"""
         self.closed = False
         self._property_lock = (None, None)
         self._display_callbacks = []
         self._msg_callbacks = []
         self._keys = None
         super(Widget, self).__init__(**kwargs)
 
         self.on_trait_change(self._handle_property_changed, self.keys)
         Widget._call_widget_constructed(self)
 
     def __del__(self):
         """Object disposal"""
         self.close()
 
     #-------------------------------------------------------------------------
     # Properties
     #-------------------------------------------------------------------------    
     @property
     def keys(self):
         """Gets a list of the traitlets that should be synced with the front-end."""
         if self._keys is None:
             self._keys = []
             for trait_name in self.trait_names():
                 if self.trait_metadata(trait_name, 'sync'):
                     self._keys.append(trait_name)
         return self._keys
 
     @property
     def comm(self):
         """Gets the Comm associated with this widget.
 
         If a Comm doesn't exist yet, a Comm will be created automagically."""
         if self._comm is None:
             # Create a comm.
             self._comm = Comm(target_name=self.model_name)
             self._comm.on_msg(self._handle_msg)
             self._comm.on_close(self._close)
             Widget.widgets[self.model_id] = self
 
             # first update
             self.send_state()
         return self._comm
     
     @property
     def model_id(self):
         """Gets the model id of this widget.
 
         If a Comm doesn't exist yet, a Comm will be created automagically."""
         return self.comm.comm_id
 
     #-------------------------------------------------------------------------
     # Methods
     #-------------------------------------------------------------------------    
     def close(self):
         """Close method.  
 
         Closes the widget which closes the underlying comm.
         When the comm is closed, all of the widget views are automatically
         removed from the front-end."""
         if not self.closed:
             self._comm.close() 
             self._close()
 
     def send_state(self, key=None):
         """Sends the widget state, or a piece of it, to the front-end.
 
         Parameters
         ----------
         key : unicode (optional)
             A single property's name to sync with the front-end.
         """
         self._send({
             "method" : "update",
             "state"  : self.get_state()
         })
 
     def get_state(self, key=None):
         """Gets the widget state, or a piece of it.
 
         Parameters
         ----------
         key : unicode (optional)
             A single property's name to get.
         """
         keys = self.keys if key is None else [key]
         return {k: self._pack_widgets(getattr(self, k)) for k in keys} 
 
     def send(self, content):
         """Sends a custom msg to the widget model in the front-end.
 
         Parameters
         ----------
         content : dict
             Content of the message to send.
         """
         self._send({"method": "custom", "content": content})
 
     def on_msg(self, callback, remove=False):
         """(Un)Register a custom msg recieve callback.
 
         Parameters
         ----------
         callback: method handler
             Can have a signature of:
             - callback(content)
             - callback(sender, content)
         remove: bool
             True if the callback should be unregistered."""
         if remove and callback in self._msg_callbacks:
             self._msg_callbacks.remove(callback)
         elif not remove and not callback in self._msg_callbacks:
             if callable(callback):
                 argspec = inspect.getargspec(callback)
                 nargs = len(argspec[0])
 
                 # Bound methods have an additional 'self' argument
                 if isinstance(callback, types.MethodType):
                     nargs -= 1
 
                 # Call the callback
                 if nargs == 1:
                     self._msg_callbacks.append(lambda sender, content: callback(content))
                 elif nargs == 2:
                     self._msg_callbacks.append(callback)
                 else:
                     raise TypeError('Widget msg callback must ' \
                         'accept 1 or 2 arguments, not %d.' % nargs)
             else:
                 raise Exception('Callback must be callable.')
 
     def on_displayed(self, callback, remove=False):
         """(Un)Register a widget displayed callback.
 
         Parameters
         ----------
         callback: method handler
             Can have a signature of:
             - callback(sender, **kwargs)
               kwargs from display call passed through without modification.
         remove: bool
             True if the callback should be unregistered."""
         if remove and callback in self._display_callbacks:
             self._display_callbacks.remove(callback)
         elif not remove and not callback in self._display_callbacks:
             if callable(handler):
                 self._display_callbacks.append(callback)
             else:
                 raise Exception('Callback must be callable.')
 
     #-------------------------------------------------------------------------
     # Support methods
     #-------------------------------------------------------------------------
     @contextmanager
     def _property_lock(self, key, value):
         """Lock a property-value pair.
 
         NOTE: This, in addition to the single lock for all state changes, is 
         flawed.  In the future we may want to look into buffering state changes 
         back to the front-end."""
         self._property_lock = (key, value)
         try:
             yield
         finally:
             self._property_lock = (None, None)
 
     def _should_send_property(self, key, value):
         """Check the property lock (property_lock)"""
         return key != self._property_lock[0] or \
         value != self._property_lock[1]
     
     def _close(self):
         """Unsafe close"""
         del Widget.widgets[self.model_id]
         self._comm = None
         self.closed = True
 
     # Event handlers
     def _handle_msg(self, msg):
         """Called when a msg is received from the front-end"""
         data = msg['content']['data']
         method = data['method']
         if not method in ['backbone', 'custom']:
             self.log.error('Unknown front-end to back-end widget msg with method "%s"' % method)
 
         # Handle backbone sync methods CREATE, PATCH, and UPDATE all in one.
         if method == 'backbone' and 'sync_data' in data:
             sync_data = data['sync_data']
             self._handle_receive_state(sync_data) # handles all methods
 
         # Handle a custom msg from the front-end
         elif method == 'custom':
             if 'content' in data:
                 self._handle_custom_msg(data['content'])
 
     def _handle_receive_state(self, sync_data):
         """Called when a state is received from the front-end."""
         for name in self.keys:
             if name in sync_data:
                 value = self._unpack_widgets(sync_data[name])
                 with self._property_lock(name, value):
                     setattr(self, name, value)
 
     def _handle_custom_msg(self, content):
         """Called when a custom msg is received."""
         for handler in self._msg_callbacks:
             handler(self, content)
 
     def _handle_property_changed(self, name, old, new):
         """Called when a property has been changed."""
         # Make sure this isn't information that the front-end just sent us.
         if self._should_send_property(name, new):
             # Send new state to front-end
             self.send_state(key=name)
 
     def _handle_displayed(self, **kwargs):
         """Called when a view has been displayed for this widget instance"""
         for handler in self._display_callbacks:
             handler(self, **kwargs)
 
     def _pack_widgets(self, x):
         """Recursively converts all widget instances to model id strings.
 
         Children widgets will be stored and transmitted to the front-end by 
-        their model ids."""
+        their model ids.  Return value must be JSON-able."""
         if isinstance(x, dict):
             return {k: self._pack_widgets(v) for k, v in x.items()}
         elif isinstance(x, list):
             return [self._pack_widgets(v) for v in x]
         elif isinstance(x, Widget):
             return x.model_id
         else:
-            return x
+            return x # Value must be JSON-able
 
     def _unpack_widgets(self, x):
         """Recursively converts all model id strings to widget instances.
 
         Children widgets will be stored and transmitted to the front-end by 
         their model ids."""
         if isinstance(x, dict):
             return {k: self._unpack_widgets(v) for k, v in x.items()}
         elif isinstance(x, list):
             return [self._unpack_widgets(v) for v in x]
         elif isinstance(x, string_types):
             return x if x not in Widget.widgets else Widget.widgets[x]
         else:
             return x
 
     def _ipython_display_(self, **kwargs):
         """Called when `IPython.display.display` is called on the widget."""
         # Show view.  By sending a display message, the comm is opened and the
         # initial state is sent.
         self._send({"method": "display"})
         self._handle_displayed(**kwargs)
 
     def _send(self, msg):
         """Sends a message to the model in the front-end."""
         self.comm.send(msg)
 
 
 class DOMWidget(Widget):
     visible = Bool(True, help="Whether or not the widget is visible.", sync=True)
     _css = Dict(sync=True) # Internal CSS property dict
 
     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.
 
         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.  If no selector 
             is provided, an empty selector is used.  An empty selector makes the 
             front-end try to apply the css to a default element.  The default
             element is an attribute unique to each view, which is a DOM element
             of the view that should be styled with common CSS (see 
             `$el_to_style` in the Javascript code).
         """
         selector = kwargs.get('selector', '')
         if not selector in self._css:
             self._css[selector] = {}
             
         # Signature 1: set_css(css_dict, selector='')
         if len(args) == 1:
             if isinstance(args[0], dict):
                 for (key, value) in args[0].items():
                     if not (key in self._css[selector] and value == self._css[selector][key]):
                         self._css[selector][key] = value
                 self.send_state('_css')
             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 == 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_names, selector=""):
         """Add class[es] to a DOM element.
 
         Parameters
         ----------
         class_names: unicode or list
             Class name(s) to add to the DOM element(s).
         selector: unicode (optional)
             JQuery selector to select the DOM element(s) that the class(es) will
             be added to.
         """
         class_list = class_names
         if isinstance(class_list, list):
             class_list = ' '.join(class_list)
 
         self.send({
             "msg_type"   : "add_class",
             "class_list" : class_list,
             "selector"   : selector
         })
 
     def remove_class(self, class_names, selector=""):
         """Remove class[es] from a DOM element.
 
         Parameters
         ----------
         class_names: unicode or list
             Class name(s) to remove from  the DOM element(s).
         selector: unicode (optional)
             JQuery selector to select the DOM element(s) that the class(es) will
             be removed from.
         """
         class_list = class_names
         if isinstance(class_list, list):
             class_list = ' '.join(class_list)
 
         self.send({
             "msg_type"   : "remove_class",
             "class_list" : class_list,
             "selector"   : selector,
         })