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#!/usr/bin/python
#
# Urwid signal dispatching
# Copyright (C) 2004-2009 Ian Ward
#
# This library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2.1 of the License, or (at your option) any later version.
#
# This library 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
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with this library; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
#
# Urwid web site: http://excess.org/urwid/
class MetaSignals(type):
"""
register the list of signals in the class varable signals,
including signals in superclasses.
"""
def __init__(cls, name, bases, d):
signals = d.get("signals", [])
for superclass in cls.__bases__:
signals.extend(getattr(superclass, 'signals', []))
signals = dict([(x,None) for x in signals]).keys()
d["signals"] = signals
register_signal(cls, signals)
super(MetaSignals, cls).__init__(name, bases, d)
def setdefaultattr(obj, name, value):
# like dict.setdefault() for object attributes
if hasattr(obj, name):
return getattr(obj, name)
setattr(obj, name, value)
return value
class Signals(object):
_signal_attr = '_urwid_signals' # attribute to attach to signal senders
def __init__(self):
self._supported = {}
def register(self, sig_cls, signals):
"""
Available as:
urwid.regsiter_signal(sig_cls, signals)
sig_class -- the class of an object that will be sending signals
signals -- a list of signals that may be sent, typically each
signal is represented by a string
This function must be called for a class before connecting any
signal callbacks or emiting any signals from that class' objects
"""
self._supported[sig_cls] = signals
def connect(self, obj, name, callback, user_arg=None):
"""
Available as:
urwid.connect_signal(obj, name, callback, user_arg=None)
obj -- the object sending a signal
name -- the name of the signal, typically a string
callback -- the function to call when that signal is sent
user_arg -- optional additional argument to callback, if None
no arguments will be added
When a matching signal is sent, callback will be called with
all the positional parameters sent with the signal. If user_arg
is not None it will be sent added to the end of the positional
parameters sent to callback.
"""
sig_cls = obj.__class__
if not name in self._supported.get(sig_cls, []):
raise NameError, "No such signal %r for object %r" % \
(name, obj)
d = setdefaultattr(obj, self._signal_attr, {})
d.setdefault(name, []).append((callback, user_arg))
def disconnect(self, obj, name, callback, user_arg=None):
"""
Available as:
urwid.disconnect_signal(obj, name, callback, user_arg=None)
This function will remove a callback from the list connected
to a signal with connect_signal().
"""
d = setdefaultattr(obj, self._signal_attr, {})
if name not in d:
return
if (callback, user_arg) not in d[name]:
return
d[name].remove((callback, user_arg))
def emit(self, obj, name, *args):
"""
Available as:
urwid.emit_signal(obj, name, *args)
obj -- the object sending a signal
name -- the name of the signal, typically a string
*args -- zero or more positional arguments to pass to the signal
callback functions
This function calls each of the callbacks connected to this signal
with the args arguments as positional parameters.
This function returns True if any of the callbacks returned True.
"""
result = False
d = getattr(obj, self._signal_attr, {})
for callback, user_arg in d.get(name, []):
args_copy = args
if user_arg is not None:
args_copy = args + (user_arg,)
result |= bool(callback(*args_copy))
return result
_signals = Signals()
emit_signal = _signals.emit
register_signal = _signals.register
connect_signal = _signals.connect
disconnect_signal = _signals.disconnect