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