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# (C) Copyright 2005-2023 Enthought, Inc., Austin, TX
# All rights reserved.
#
# This software is provided without warranty under the terms of the BSD
# license included in 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>
import logging
from pyface.action.action import Action
from traits.api import Any, Str, observe, Undefined
# Logging.
logger = logging.getLogger(__name__)
class ListeningAction(Action):
""" An Action that listens and makes a callback to an object.
"""
# ListeningAction interface ----------------------------------------------
#: The (extended) name of the method to call. By default, the on_perform
#: function will be called with the event.
method = Str()
#: The (extended) name of the attribute that determines whether the action
#: is enabled. By default, the action is always enabled when an object is
#: set.
enabled_name = Str()
#: The (extended) name of the attribute that determines whether the action
#: is visible. By default, the action is always visible.
visible_name = Str()
#: The object to which the names above apply.
object = Any()
# -------------------------------------------------------------------------
# 'Action' interface.
# -------------------------------------------------------------------------
def destroy(self):
""" Called when the action is no longer required.
Removes all the task listeners.
"""
if self.object:
if self.enabled_name:
self.object.observe(
self._enabled_update, self.enabled_name, remove=True
)
if self.visible_name:
self.object.observe(
self._visible_update, self.visible_name, remove=True
)
def perform(self, event=None):
""" Call the appropriate function.
This looks for a method to call based on the extended method name
stored in the :py:attr:`method` trait. If the method is empty, then
this follows the usual Action method resolution.
"""
if self.method != "":
method = self._get_attr(self.object, self.method)
if method:
method()
else:
super().perform(event)
# -------------------------------------------------------------------------
# Protected interface.
# -------------------------------------------------------------------------
def _get_attr(self, obj, name, default=None):
""" Perform an extended look up of a dotted name. """
try:
for attr in name.split("."):
# Perform the access in the Trait name style: if the object is
# None, assume it simply hasn't been initialized and don't show
# the warning.
if obj is None:
return default
else:
obj = getattr(obj, attr)
except AttributeError:
logger.error("Did not find name %r on %r" % (attr, obj))
return default
return obj
# Trait change handlers --------------------------------------------------
@observe('enabled_name')
def _enabled_name_updated(self, event):
old, new = event.old, event.new
obj = self.object
if obj is not None:
if old:
obj.observe(self._enabled_update, old, remove=True)
if new:
obj.observe(self._enabled_update, new)
self._enabled_update()
@observe('visible_name')
def _visible_name_updated(self, event):
old, new = event.old, event.new
obj = self.object
if obj is not None:
if old:
obj.observe(self._visible_update, old, remove=True)
if new:
obj.observe(self._visible_update, new)
self._visible_update()
@observe('object')
def _object_updated(self, event):
old, new = event.old, event.new
for kind in ("enabled", "visible"):
method = getattr(self, "_%s_update" % kind)
name = getattr(self, "%s_name" % kind)
if name:
if old and old is not Undefined:
old.observe(method, name, remove=True)
if new:
new.observe(method, name)
method()
def _enabled_update(self, event=None):
if self.enabled_name:
if self.object:
self.enabled = bool(
self._get_attr(self.object, self.enabled_name, False)
)
else:
self.enabled = False
else:
self.enabled = bool(self.object)
def _visible_update(self, event=None):
if self.visible_name:
if self.object:
self.visible = bool(
self._get_attr(self.object, self.visible_name, False)
)
else:
self.visible = False
else:
self.visible = True
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