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#------------------------------------------------------------------------------
# Copyright (c) 2005, Enthought, Inc.
# All rights reserved.
#
# This software is provided without warranty under the terms of the BSD
# license included in enthought/LICENSE.txt and may be redistributed only
# under the conditions described in the aforementioned license. The license
# is also available online at http://www.enthought.com/licenses/BSD.txt
# Thanks for using Enthought open source!
#
# Author: Enthought, Inc.
# Description: <Enthought pyface package component>
#------------------------------------------------------------------------------
""" A monitor for appearance and structural changes to a node. """
# Standard library imports.
import logging
# Enthought library imports.
from traits.api import Any, Event, HasTraits
# Local imports.
from .node_event import NodeEvent
# Create a logger for this module.
logger = logging.getLogger(__name__)
class NodeMonitor(HasTraits):
""" A monitor for appearance and structural changes to a node. """
#### 'NodeMonitor' interface ##############################################
# The node that we are monitoring.
node = Any
#### Events ####
# Fired when child nodes in the node that we are monitoring have changed in
# some way that affects their appearance but NOT their structure.
nodes_changed = Event(NodeEvent)
# Fired when child nodes have been inserted into the node that we are
# monitoring.
nodes_inserted = Event(NodeEvent)
# Fired when child nodes have been removed from the node that we are
# monitoring.
nodes_removed = Event(NodeEvent)
# Fired when child nodes have been replaced in the node that we are
# monitoring.
nodes_replaced = Event(NodeEvent)
# Fired when the structure of the node that we are monitoring has changed
# DRASTICALLY (i.e., we do not have enough information to make individual
# changes/inserts/removals).
structure_changed = Event(NodeEvent)
###########################################################################
# 'NodeMonitor' interface.
###########################################################################
#### public methods #######################################################
def start(self):
""" Start listening to changes to the node. """
if self.node.obj is not None:
self._setup_trait_change_handlers(self.node.obj)
return
def stop(self):
""" Stop listening to changes to the node. """
if self.node.obj is not None:
self._setup_trait_change_handlers(self.node.obj, remove=True)
return
def fire_nodes_changed(self, children=[]):
""" Fires the nodes changed event. """
self.nodes_changed = NodeEvent(node=self.node, children=children)
return
def fire_nodes_inserted(self, children, index=-1):
""" Fires the nodes inserted event.
If the index is -1 it means the nodes were appended.
fixme: The tree and model should probably have an 'appended' event.
"""
self.nodes_inserted = NodeEvent(
node=self.node, children=children, index=index
)
return
def fire_nodes_removed(self, children):
""" Fires the nodes removed event. """
self.nodes_removed = NodeEvent(node=self.node, children=children)
return
def fire_nodes_replaced(self, old_children, new_children):
""" Fires the nodes replaced event. """
self.nodes_replaced = NodeEvent(
node=self.node, old_children=old_children, children=new_children
)
return
def fire_structure_changed(self):
""" Fires the structure changed event. """
self.structure_changed = NodeEvent(node=self.node)
return
#### protected methods ####################################################
def _setup_trait_change_handlers(self, obj, remove=False):
""" Add or remove trait change handlers to/from a node. """
logger.debug('%s trait listeners on (%s) in NodeMonitor (%s)',
(remove and 'Removing' or 'Adding'), obj, self)
pass # derived classes should do something here!
return
#### EOF ######################################################################
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