docs: def on_widget__motion_notify_event(self, widget, event):
          '''
          Called when mouse pointer is moved within drawing area.
  
  
          .. versionchanged:: 0.11
              Do not trigger `route-electrode-added` event if `ALT` key is
              pressed.
          '''
          if self.canvas is None:
              # Canvas has not been initialized.  Nothing to do.
              return
          elif event.is_hint:
              pointer = event.window.get_pointer()
              x, y, mod_type = pointer
          else:
              x = event.x
              y = event.y
          shape = self.canvas.find_shape(x, y)
  
          # Grab focus to [enable notification on key press/release events][1].
          #
          # [1]: http://mailman.daa.com.au/cgi-bin/pipermail/pygtk/2003-August/005770.html
          self.widget.grab_focus()
  
          if shape != self.last_hovered:
              if self.last_hovered is not None:
                  # Leaving shape
                  self.emit('electrode-mouseout', {'electrode_id':
                                                   self.last_hovered,
                                                   'event': event.copy()})
                  self.last_hovered = None
              elif shape is not None:
                  # Entering shape
                  self.last_hovered = shape
  
                  if self._route is not None:
                      if self._route.append(shape) and not (event.get_state() &
                                                            gtk.gdk.MOD1_MASK):
                          # `<Alt>` key was not held down.
                          self.emit('route-electrode-added', shape)
  
                  self.emit('electrode-mouseover', {'electrode_id':
                                                    self.last_hovered,
                                                    'event': event.copy()})