IPython/html/widgets/widget.py

"""Base Widget class.  Allows user to create widgets in the backend that render
in the IPython notebook frontend.
"""
#-----------------------------------------------------------------------------
# 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 copy import copy
from glob import glob
import uuid
import sys
import os
import inspect
import types

import IPython
from IPython.kernel.comm import Comm
from IPython.config import LoggingConfigurable
from IPython.utils.traitlets import Unicode, Dict, List, Instance, Bool
from IPython.display import Javascript, display
from IPython.utils.py3compat import string_types

#-----------------------------------------------------------------------------
# Classes
#-----------------------------------------------------------------------------
class Widget(LoggingConfigurable):

    # Shared declarations (Class level)
    _keys = []
    widget_construction_callback = None

    def on_widget_constructed(callback):
        """Class method, 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 _handle_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)

    

    # Public declarations (Instance level)
    target_name = Unicode('widget', help="""Name of the backbone model 
        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
   
    
    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)
                
        # Register after init to allow default values to be specified
        self.on_trait_change(self._handle_property_changed, self.keys)

        Widget._handle_widget_constructed(self)
        
        
    def __del__(self):
        """Object disposal"""
        self.close()
    

    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 frontend."""
        self._close_communication()
    
    
    # Properties      
    def _get_keys(self):
        keys = ['visible', '_css']
        keys.extend(self._keys)
        return keys
    keys = property(_get_keys)
    
    
    # Event handlers
    def _handle_msg(self, msg):
        """Called when a msg is recieved from the frontend"""
        data = msg['content']['data']
        method = data['method']

        # Handle backbone sync methods CREATE, PATCH, and UPDATE
        if method == 'backbone':
            if 'sync_method' in data and 'sync_data' in data:
                sync_method = data['sync_method']
                sync_data = data['sync_data']
                self._handle_recieve_state(sync_data) # handles all methods

        # Handle a custom msg from the front-end
        elif method == 'custom':
            if 'custom_content' in data:
                self._handle_custom_msg(data['custom_content'])


    def _handle_custom_msg(self, content):
        """Called when a custom msg is recieved."""
        for handler in self._msg_callbacks:
            if callable(handler):
                argspec = inspect.getargspec(handler)
                nargs = len(argspec[0])

                # Bound methods have an additional 'self' argument
                if isinstance(handler, types.MethodType):
                    nargs -= 1

                # Call the callback
                if nargs == 1:
                    handler(content)
                elif nargs == 2:
                    handler(self, content)
                else:
                    raise TypeError('Widget msg callback must ' \
                        'accept 1 or 2 arguments, not %d.' % nargs)
    
    
    def _handle_recieve_state(self, sync_data):
        """Called when a state is recieved from the frontend."""
        # Use _keys instead of keys - Don't get retrieve the css from the client side.
        for name in self._keys:
            if name in sync_data:
                try:
                    self._property_lock = (name, sync_data[name])
                    setattr(self, name, sync_data[name])
                finally:
                    self._property_lock = (None, None)
    
    
    def _handle_property_changed(self, name, old, new):
        """Called when a proeprty has been changed."""
        # Make sure this isn't information that the front-end just sent us.
        if self._property_lock[0] != name and self._property_lock[1] != new:
            # Send new state to frontend
            self.send_state(key=name)


    def _handle_displayed(self, view_name, parent=None):
        """Called when a view has been displayed for this widget instance

        Parameters
        ----------
        view_name: unicode
            Name of the view that was displayed.
        parent: Widget instance [optional]
            Widget that this widget should be displayed as a child of."""
        for handler in self._display_callbacks:
            if callable(handler):
                argspec = inspect.getargspec(handler)
                nargs = len(argspec[0])

                # Bound methods have an additional 'self' argument
                if isinstance(handler, types.MethodType):
                    nargs -= 1

                # Call the callback
                if nargs == 0:
                    handler()
                elif nargs == 1:
                    handler(self)
                elif nargs == 2:
                    handler(self, view_name)
                elif nargs == 3:
                    handler(self, view_name, parent)
                else:
                    raise TypeError('Widget display callback must ' \
                        'accept 0-2 arguments, not %d.' % nargs)
    
    
    # Public methods
    def send_state(self, key=None):
        """Sends the widget state, or a piece of it, to the frontend.

        Parameters
        ----------
        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})


    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})


    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",
                        "custom_content": content})


    def on_msg(self, callback, remove=False):
        """Register a callback for when a custom msg is recieved from the front-end

        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:
            self._msg_callbacks.append(callback)


    def on_displayed(self, callback, remove=False):
        """Register a callback to be called when the widget has been displayed

        Parameters
        ----------
        callback: method handler
            Can have a signature of:
            - callback()
            - callback(sender)
            - callback(sender, view_name)
            - callback(sender, view_name, parent)
        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:
            self._display_callbacks.append(callback)


    # Support methods
    def _repr_widget_(self, view_name=None):
        """Function that is called when `IPython.display.display` is called on
        the widget.

        Parameters
        ----------
        view_name: unicode (optional)
            View to display in the frontend.  Overrides default_view_name."""
        if not view_name:
            view_name = self.default_view_name
        
        # Create a communication.
        self._open_communication()
        
        # Make sure model is syncronized
        self.send_state()
            
        # Show view.
        if self.parent is None or self.parent._comm is None:
            self._send({"method": "display", "view_name": view_name})
            self._handle_displayed(view_name)
        else:
            self._send({"method": "display", 
                            "view_name": view_name,
                            "parent": self.parent._comm.comm_id})
            self._handle_displayed(view_name, self.parent)
        self._displayed = True

        # Now display children if any.
        for child in self._children:
            if child != self:
                child._repr_widget_()
        return None


    def _open_communication(self):
        """Opens a communication with the front-end."""
        # Create a comm.
        if not hasattr(self, '_comm') or self._comm is None:
            self._comm = Comm(target_name=self.target_name)
            self._comm.on_msg(self._handle_msg)
            self._comm.on_close(self._handle_close)


    def _handle_close(self):
        """Called when the comm is closed by the front-end."""
        self._close_communication()


    def _close_communication(self):
        """Closes a communication with the front-end."""
        if hasattr(self, '_comm') and self._comm is not None:
            self._comm.close()


    def _send(self, msg):
        """Sends a message to the model in the front-end"""
        if hasattr(self, '_comm') and self._comm is not None:
            self._comm.send(msg)
            return True
        else:
            return False