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# Copyright (C) 2009, Tutorius.org
# Copyright (C) 2009, Vincent Vinet <vince.vinet@gmail.com>
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
import logging
logger = logging.getLogger("filters")
from sugar.tutorius import properties
class EventFilter(properties.TPropContainer):
"""
Base class for an event filter
"""
def __init__(self, next_state=None):
"""
Constructor.
@param next_state name of the next state
"""
super(EventFilter, self).__init__()
self._callback = None
def install_handlers(self, callback, **kwargs):
"""
install_handlers is called for eventfilters to setup all
necessary event handlers to be able to catch the desired
event.
@param callback the callback function that will be called
with the event filter as an argument when the event is catched
and validated.
@param **kwargs unused by this handler for now, allows subclasses
to receive information about the context when installing
Subclasses must call this super method to setup the callback if they
feel like cooperating
"""
self._callback = callback
def remove_handlers(self):
"""
remove_handlers is called when a state is done so that all
event filters can cleanup any handlers they have installed
This function will also clear the callback function so that any
leftover handler that is triggered will not be able to change the
application state.
subclasses must call this super method to cleanup the callback if they
collaborate and use this classe's do_callback()
"""
self._callback = None
def do_callback(self, *args, **kwargs):
"""
Default callback function that calls the event filter callback
with the event filter as only argument.
"""
if self._callback:
self._callback(self)
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