"""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 from IPython.core.getipython import get_ipython from IPython.kernel.comm import Comm from IPython.config import LoggingConfigurable from IPython.utils.traitlets import Unicode, Dict, Instance, Bool, List, Tuple, Int from IPython.utils.py3compat import string_types #----------------------------------------------------------------------------- # Classes #----------------------------------------------------------------------------- class CallbackDispatcher(LoggingConfigurable): """A structure for registering and running callbacks""" callbacks = List() def __call__(self, *args, **kwargs): """Call all of the registered callbacks.""" value = None for callback in self.callbacks: try: local_value = callback(*args, **kwargs) except Exception as e: ip = get_ipython() if ip is None: self.log.warn("Exception in callback %s: %s", callback, e, exc_info=True) else: ip.showtraceback() else: value = local_value if local_value is not None else value return value def register_callback(self, callback, remove=False): """(Un)Register a callback Parameters ---------- callback: method handle Method to be registered or unregistered. remove=False: bool Whether to unregister the callback.""" # (Un)Register the callback. if remove and callback in self.callbacks: self.callbacks.remove(callback) elif not remove and callback not in self.callbacks: self.callbacks.append(callback) def _show_traceback(method): """decorator for showing tracebacks in IPython""" def m(self, *args, **kwargs): try: return(method(self, *args, **kwargs)) except Exception as e: ip = get_ipython() if ip is None: self.log.warn("Exception in widget method %s: %s", method, e, exc_info=True) else: ip.showtraceback() return m class Widget(LoggingConfigurable): #------------------------------------------------------------------------- # Class attributes #------------------------------------------------------------------------- _widget_construction_callback = None widgets = {} @staticmethod 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 @staticmethod def _call_widget_constructed(widget): """Static 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') msg_throttle = Int(3, sync=True, help="""Maximum number of msgs the front-end can send before receiving an idle msg from the back-end.""") keys = List() def _keys_default(self): return [name for name in self.traits(sync=True)] _property_lock = Tuple((None, None)) _display_callbacks = Instance(CallbackDispatcher, ()) _msg_callbacks = Instance(CallbackDispatcher, ()) #------------------------------------------------------------------------- # (Con/de)structor #------------------------------------------------------------------------- def __init__(self, **kwargs): """Public constructor""" 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 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) 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 underlying comm. When the comm is closed, all of the widget views are automatically removed from the front-end.""" if self._comm is not None: Widget.widgets.pop(self.model_id, None) self._comm.close() self._comm = None 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] state = {} for k in keys: f = self.trait_metadata(k, 'to_json') if f is None: f = self._trait_to_json value = getattr(self, k) state[k] = f(value) return state 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 receive callback. Parameters ---------- callback: callable callback will be passed two arguments when a message arrives:: callback(widget, content) remove: bool True if the callback should be unregistered.""" self._msg_callbacks.register_callback(callback, remove=remove) def on_displayed(self, callback, remove=False): """(Un)Register a widget displayed callback. Parameters ---------- callback: method handler Must have a signature of:: callback(widget, **kwargs) kwargs from display are passed through without modification. remove: bool True if the callback should be unregistered.""" self._display_callbacks.register_callback(callback, remove=remove) #------------------------------------------------------------------------- # Support methods #------------------------------------------------------------------------- @contextmanager def _lock_property(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] # Event handlers @_show_traceback 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: f = self.trait_metadata(name, 'from_json') if f is None: f = self._trait_from_json value = f(sync_data[name]) with self._lock_property(name, value): setattr(self, name, value) def _handle_custom_msg(self, content): """Called when a custom msg is received.""" self._msg_callbacks(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""" self._display_callbacks(self, **kwargs) def _trait_to_json(self, x): """Convert a trait value to json Traverse lists/tuples and dicts and serialize their values as well. Replace any widgets with their model_id """ if isinstance(x, dict): return {k: self._trait_to_json(v) for k, v in x.items()} elif isinstance(x, (list, tuple)): return [self._trait_to_json(v) for v in x] elif isinstance(x, Widget): return "IPY_MODEL_" + x.model_id else: return x # Value must be JSON-able def _trait_from_json(self, x): """Convert json values to objects Replace any strings representing valid model id values to Widget references. """ if isinstance(x, dict): return {k: self._trait_from_json(v) for k, v in x.items()} elif isinstance(x, (list, tuple)): return [self._trait_from_json(v) for v in x] elif isinstance(x, string_types) and x.startswith('IPY_MODEL_') and x[10:] in Widget.widgets: # we want to support having child widgets at any level in a hierarchy # trusting that a widget UUID will not appear out in the wild return 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 the widget is visible.", sync=True) _css = List(sync=True) # Internal CSS property list: (selector, key, value) 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, dict_or_key, value=None, selector=''): """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, kwarg only) 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). """ if value is None: css_dict = dict_or_key else: css_dict = {dict_or_key: value} for (key, value) in css_dict.items(): # First remove the selector/key pair from the css list if it exists. # Then add the selector/key pair and new value to the bottom of the # list. self._css = [x for x in self._css if not (x[0]==selector and x[1]==key)] self._css += [(selector, key, value)] self.send_state('_css') 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, tuple)): 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, tuple)): class_list = ' '.join(class_list) self.send({ "msg_type" : "remove_class", "class_list" : class_list, "selector" : selector, })