IPython/html/widgets/widget.py

from copy import copy
import uuid
import sys

from IPython.kernel.comm import Comm
from IPython.config import LoggingConfigurable
from IPython.utils.traitlets import Unicode, Dict
from IPython.display import Javascript, display

class Widget(Comm):
    
    ### Public declarations
    target_name = Unicode('widget')
    view_name = Unicode()
    
    
    ### Private/protected declarations
    _keys = []
    _property_lock = False
    _parent = None
    _children = []
    _css = Dict()
    
    
    ### Public constructor
    def __init__(self, parent=None, **kwargs):
        super(Widget, self).__init__(**kwargs)
        
        self._children = []
        if parent is not None:
            parent._children.append(self)
        self._parent = parent

        # Send frontend type code.
        display(Javascript(data=self._get_backbone_js()))

        # Create a comm.
        self.comm = Comm(target_name=self.target_name)
        self.comm.on_msg(self._handle_msg)
        
        # Register after init to allow default values to be specified
        self.on_trait_change(self._handle_property_changed, self.keys)
        
        # Set initial properties on client model.
        self.send_state()
        
        
    def __del__(self):
        self.close()
    
    def close(self):
        self.comm.close()
        del self.comm
    
    
    ### Properties
    def _get_parent(self):
        return self._parent
    parent = property(_get_parent)
    
    
    def _get_children(self):
        return copy(self._children)
    children = property(_get_children)
    
    
    def _get_keys(self):
        keys = ['_css']
        keys.extend(self._keys)
        return keys
    keys = property(_get_keys)
    
    def _get_css(self, key, selector=""):
        if selector in self._css and key in self._css[selector]:
            return self._css[selector][key]
        else:
            return None
    def _set_css(self, value, key, selector=""):
        if selector not in self._css:
            self._css[selector] = {}
            
        # Only update the property if it has changed.
        if not (key in self._css[selector] and value in self._css[selector][key]):
            self._css[selector][key] = value
            self.send_state() # Send new state to client.
            
    css = property(_get_css, _set_css)
    
    
    ### Event handlers
    def _handle_msg(self, msg):
        
        # Handle backbone sync methods
        sync_method = msg['content']['data']['sync_method']
        sync_data = msg['content']['data']['sync_data']
        if sync_method.lower() in ['create', 'update']:
            self._handle_recieve_state(sync_data)
    
    
    def _handle_recieve_state(self, sync_data):
        self._property_lock = True
        try:
            
            # 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:
                    setattr(self, name, sync_data[name])
        finally:
            self._property_lock = False
    
    
    def _handle_property_changed(self, name, old, new):
        if not self._property_lock:
            # TODO: Validate properties.
            # Send new state to frontend
            self.send_state()
    
    
    ### Public methods
    def _repr_widget_(self):
        view_name = self.view_name
        if not view_name:
            view_name = self.target_name
            
        # Make sure model is syncronized
        self.send_state()
            
        # Show view.
        if self.parent is None:
            self.comm.send({"method": "show", "view_name": view_name})
        else:
            self.comm.send({"method": "show", 
                            "view_name": view_name,
                            "parent": self.parent.comm.comm_id})
        
        # Now show children if any.
        for child in self.children:
            child._repr_widget_()
        return self._get_backbone_js
            
    
    def send_state(self):
        state = {}
        for key in self.keys:
            try:
                state[key] = getattr(self, key)
            except Exception as e:
                pass # Eat errors, nom nom nom
        self.comm.send({"method": "update",
                   "state": state})
    
    ### Private methods
    def _get_backbone_js(self):
        return 'alert("woohoo!");'