Changed children list to CTuple.

Also removed some unused refences in the widget code
and added support for tuples in the pack/unpack code.

IPython/html/widgets/widget.py

@@ -1,443 +1,443 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
 
 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')
     
     closed = Bool(False)
     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)
             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):
         """Private close - cleanup objects, registry entries"""
         del Widget.widgets[self.model_id]
         self._comm = None
         self.closed = True
 
     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 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:
                 value = self._unpack_widgets(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 _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.  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):
+        elif isinstance(x, (list, tuple)):
             return [self._pack_widgets(v) for v in x]
         elif isinstance(x, Widget):
             return x.model_id
         else:
             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):
+        elif isinstance(x, (list, tuple)):
             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 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, 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 not selector in self._css:
             self._css[selector] = {}
         my_css = self._css[selector]
         
         if value is None:
             css_dict = dict_or_key
         else:
             css_dict = {dict_or_key: value}
         
         for (key, value) in css_dict.items():
             if not (key in my_css and value == my_css[key]):
                 my_css[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):
+        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):
+        if isinstance(class_list, (list, tuple)):
             class_list = ' '.join(class_list)
 
         self.send({
             "msg_type"   : "remove_class",
             "class_list" : class_list,
             "selector"   : selector,
         })

IPython/html/widgets/widget_bool.py

@@ -1,34 +1,34 b''
 """BoolWidget class.  
 
 Represents a boolean using a widget.
 """
 #-----------------------------------------------------------------------------
 # 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 .widget import DOMWidget
-from IPython.utils.traitlets import Unicode, Bool, List
+from IPython.utils.traitlets import Unicode, Bool
 
 #-----------------------------------------------------------------------------
 # Classes
 #-----------------------------------------------------------------------------
 class _BoolWidget(DOMWidget):
     value = Bool(False, help="Bool value", sync=True)
     description = Unicode('', help="Description of the boolean (label).", sync=True) 
     disabled = Bool(False, help="Enable or disable user changes.", sync=True)
 
 
 class CheckboxWidget(_BoolWidget):
     _view_name = Unicode('CheckboxView', sync=True)
 
 
 class ToggleButtonWidget(_BoolWidget):
     _view_name = Unicode('ToggleButtonView', sync=True)
     
  No newline at end of file

IPython/html/widgets/widget_container.py

@@ -1,51 +1,51 b''
 """ContainerWidget class.  
 
 Represents a container that can be used to group other widgets.
 """
 #-----------------------------------------------------------------------------
 # 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 .widget import DOMWidget
-from IPython.utils.traitlets import Unicode, Bool, List, Instance
+from IPython.utils.traitlets import Unicode, CTuple, Instance
 
 #-----------------------------------------------------------------------------
 # Classes
 #-----------------------------------------------------------------------------
 class ContainerWidget(DOMWidget):
     _view_name = Unicode('ContainerView', sync=True)
 
     # Keys, all private and managed by helper methods.  Flexible box model
     # classes...
-    children = List(Instance(DOMWidget))
-    _children = List(Instance(DOMWidget), sync=True)
+    children = CTuple(Instance(DOMWidget))
+    _children = CTuple(Instance(DOMWidget), sync=True)
 
     def _children_changed(self, name, old, new):
         """Validate children list.
 
         Makes sure only one instance of any given model can exist in the 
         children list.
         An excellent post on uniqifiers is available at 
             http://www.peterbe.com/plog/uniqifiers-benchmark
         which provides the inspiration for using this implementation.  Below
         I've implemented the `f5` algorithm using Python comprehensions."""
         if new is not None and isinstance(new, list):
             seen = {}
             def add_item(i):
                 seen[i.model_id] = True
                 return i
             self._children = [add_item(i) for i in new if not i.model_id in seen]
 
 
 class PopupWidget(ContainerWidget):
     _view_name = Unicode('PopupView', sync=True)
     
     description = Unicode(sync=True)
     button_text = Unicode(sync=True)

IPython/html/widgets/widget_float.py

@@ -1,60 +1,60 b''
 """FloatWidget class.  
 
 Represents an unbounded float using a widget.
 """
 #-----------------------------------------------------------------------------
 # 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 .widget import DOMWidget
-from IPython.utils.traitlets import Unicode, CFloat, Bool, List, Enum
+from IPython.utils.traitlets import Unicode, CFloat, Bool, Enum
 
 #-----------------------------------------------------------------------------
 # Classes
 #-----------------------------------------------------------------------------
 class _FloatWidget(DOMWidget):
     value = CFloat(0.0, help="Float value", sync=True) 
     disabled = Bool(False, help="Enable or disable user changes", sync=True)
     description = Unicode(help="Description of the value this widget represents", sync=True)
 
 
 class _BoundedFloatWidget(_FloatWidget):
     max = CFloat(100.0, help="Max value", sync=True)
     min = CFloat(0.0, help="Min value", sync=True)
     step = CFloat(0.1, help="Minimum step that the value can take (ignored by some views)", sync=True)
 
     def __init__(self, *pargs, **kwargs):
         """Constructor"""
         DOMWidget.__init__(self, *pargs, **kwargs)
         self.on_trait_change(self._validate, ['value', 'min', 'max'])
 
     def _validate(self, name, old, new):
         """Validate value, max, min."""
         if self.min > new or new > self.max:
             self.value = min(max(new, self.min), self.max)
 
 
 class FloatTextWidget(_FloatWidget):
     _view_name = Unicode('FloatTextView', sync=True)
 
 
 class BoundedFloatTextWidget(_BoundedFloatWidget):
     _view_name = Unicode('FloatTextView', sync=True)
 
 
 class FloatSliderWidget(_BoundedFloatWidget):
     _view_name = Unicode('FloatSliderView', sync=True)
     orientation = Enum([u'horizontal', u'vertical'], u'horizontal', 
         help="Vertical or horizontal.", sync=True)
     readout = Bool(True, help="Display the current value of the slider next to it.", sync=True)
 
 
 class FloatProgressWidget(_BoundedFloatWidget):
     _view_name = Unicode('ProgressView', sync=True)

IPython/html/widgets/widget_int.py

@@ -1,60 +1,60 b''
 """IntWidget class.  
 
 Represents an unbounded int using a widget.
 """
 #-----------------------------------------------------------------------------
 # 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 .widget import DOMWidget
-from IPython.utils.traitlets import Unicode, CInt, Bool, List, Enum
+from IPython.utils.traitlets import Unicode, CInt, Bool, Enum
 
 #-----------------------------------------------------------------------------
 # Classes
 #-----------------------------------------------------------------------------
 class _IntWidget(DOMWidget):
     value = CInt(0, help="Int value", sync=True) 
     disabled = Bool(False, help="Enable or disable user changes", sync=True)
     description = Unicode(help="Description of the value this widget represents", sync=True)
 
 
 class _BoundedIntWidget(_IntWidget):
     step = CInt(1, help="Minimum step that the value can take (ignored by some views)", sync=True)
     max = CInt(100, help="Max value", sync=True)
     min = CInt(0, help="Min value", sync=True)
 
     def __init__(self, *pargs, **kwargs):
         """Constructor"""
         DOMWidget.__init__(self, *pargs, **kwargs)
         self.on_trait_change(self._validate, ['value', 'min', 'max'])
 
     def _validate(self, name, old, new):
         """Validate value, max, min."""
         if self.min > new or new > self.max:
             self.value = min(max(new, self.min), self.max)
 
 
 class IntTextWidget(_IntWidget):
     _view_name = Unicode('IntTextView', sync=True)
 
 
 class BoundedIntTextWidget(_BoundedIntWidget):
     _view_name = Unicode('IntTextView', sync=True)
 
 
 class IntSliderWidget(_BoundedIntWidget):
     _view_name = Unicode('IntSliderView', sync=True)
     orientation = Enum([u'horizontal', u'vertical'], u'horizontal', 
         help="Vertical or horizontal.", sync=True)
     readout = Bool(True, help="Display the current value of the slider next to it.", sync=True)
 
 
 class IntProgressWidget(_BoundedIntWidget):
     _view_name = Unicode('ProgressView', sync=True)

IPython/html/widgets/widget_selectioncontainer.py

@@ -1,58 +1,58 b''
 """SelectionContainerWidget class.  
 
 Represents a multipage container that can be used to group other widgets into
 pages.
 """
 #-----------------------------------------------------------------------------
 # 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 .widget_container import ContainerWidget
-from IPython.utils.traitlets import Unicode, Dict, CInt, List, Instance
+from IPython.utils.traitlets import Unicode, Dict, CInt
 
 #-----------------------------------------------------------------------------
 # Classes
 #-----------------------------------------------------------------------------
 class _SelectionContainerWidget(ContainerWidget):
     _titles = Dict(help="Titles of the pages", sync=True)
     selected_index = CInt(0, sync=True)
 
     # Public methods
     def set_title(self, index, title):
         """Sets the title of a container page.
 
         Parameters
         ----------
         index : int
             Index of the container page
         title : unicode
             New title"""
         self._titles[index] = title
         self.send_state('_titles')
 
     def get_title(self, index):
         """Gets the title of a container pages.
 
         Parameters
         ----------
         index : int
             Index of the container page"""
         if index in self._titles:
             return self._titles[index]
         else:
             return None
 
 
 class AccordionWidget(_SelectionContainerWidget):
     _view_name = Unicode('AccordionView', sync=True)
 
 
 class TabWidget(_SelectionContainerWidget):
     _view_name = Unicode('TabView', sync=True)

IPython/html/widgets/widget_string.py

@@ -1,72 +1,72 b''
 """StringWidget class.  
 
 Represents a unicode string using a widget.
 """
 #-----------------------------------------------------------------------------
 # 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 .widget import DOMWidget, CallbackDispatcher
-from IPython.utils.traitlets import Unicode, Bool, List
+from IPython.utils.traitlets import Unicode, Bool
 
 #-----------------------------------------------------------------------------
 # Classes
 #-----------------------------------------------------------------------------
 class _StringWidget(DOMWidget):
     value = Unicode(help="String value", sync=True)
     disabled = Bool(False, help="Enable or disable user changes", sync=True)
     description = Unicode(help="Description of the value this widget represents", sync=True)
 
 
 class HTMLWidget(_StringWidget):
     _view_name = Unicode('HTMLView', sync=True)
 
 
 class LatexWidget(_StringWidget):
     _view_name = Unicode('LatexView', sync=True)
 
 
 class TextareaWidget(_StringWidget):
     _view_name = Unicode('TextareaView', sync=True)
 
     def scroll_to_bottom(self):
         self.send({"method": "scroll_to_bottom"})
 
 
 class TextWidget(_StringWidget):
     _view_name = Unicode('TextView', sync=True)
 
     def __init__(self, **kwargs):
         super(TextWidget, self).__init__(**kwargs)
         self._submission_callbacks = CallbackDispatcher()
         self.on_msg(self._handle_string_msg)
 
     def _handle_string_msg(self, _, content):
         """Handle a msg from the front-end.
 
         Parameters
         ----------
         content: dict
             Content of the msg."""
         if content.get('event', '') == 'submit':
             self._submission_callbacks(self)
 
     def on_submit(self, callback, remove=False):
         """(Un)Register a callback to handle text submission.
 
         Triggered when the user clicks enter.
 
         Parameters
         ----------
         callback: callable
             Will be called with exactly one argument: the Widget instance
         remove: bool (optional)
             Whether to unregister the callback"""
         self._submission_callbacks.register_callback(callback, remove=remove)