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#Copyright (c) 2006 Simon Wittber
#
#Permission is hereby granted, free of charge, to any person
#obtaining a copy of this software and associated documentation files
#(the "Software"), to deal in the Software without restriction,
#including without limitation the rights to use, copy, modify, merge,
#publish, distribute, sublicense, and/or sell copies of the Software,
#and to permit persons to whom the Software is furnished to do so,
#subject to the following conditions:
#
#The above copyright notice and this permission notice shall be
#included in all copies or substantial portions of the Software.
#
#THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
#EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
#MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
#NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
#BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
#ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
#CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
#SOFTWARE.
"""
A simple event/signal dispatcher.
"""
import weakref
from collections import deque
def call_with_keywords(func, *args, **kw):
"""
Call a function with allowed keywords only.
"""
return func(*args, **dict([i for i in kw.items() if i[0] in func.func_code.co_varnames]))
class Dispatcher(object):
"""
A simple event dispatcher.
"""
def __init__(self):
self.events = {}
self.stacks = {}
def subscribe(self, func, name, static=False):
"""
Subscribe a callable to an event. Keeps a weakref to func.
"""
if static:
print func
callable = func.im_func
obj = func
function = lambda kw: call_with_keywords(callable, obj, **kw)
else:
if hasattr(func, 'im_self'):
obj = weakref.proxy(func.im_self)
callable = func.im_func
function = lambda kw: call_with_keywords(callable, obj, **kw)
function.ref = weakref.ref(func.im_self, lambda x: self.events[name].remove(function))
else:
callable = weakref.proxy(func)
function = lambda kw: call_with_keywords(callable, **kw)
function.ref = weakref.ref(func, lambda x: self.events[name].remove(function))
try:
self.events[name].append(function)
except KeyError:
self.events[name] = [function]
except AttributeError:
raise RuntimeError("Cannot subscribe to a captured event. %s is currently captured by %s." % (name,self.events[name][0]))
return function
def capture(self, func, name):
"""
Bind a callable exclusively to an event.
"""
try:
handlers = self.events[name]
except KeyError:
handlers = []
self.stacks.setdefault(name, deque()).appendleft(handlers)
function = lambda kw: call_with_keywords(func, **kw)
self.events[name] = (function,)
return function
def release(self, func, name):
"""
Release a captured event.
"""
if func is not self.events[name][0]:
raise RuntimeError("A callable bound to %s was released out of sequence." % name)
handlers = self.stacks[name].popleft()
self.events[name] = handlers
def unsubscribe(self, func, name):
"""
Unsubscribe a callable from an event.
"""
try:
self.events[name].remove(func)
except ValueError:
pass
def post(self, _event_identity, **kw):
"""
Post an event, which is dispatched to all callables which are subscribed to that event.
"""
try:
events = self.events[_event_identity]
except KeyError:
return tuple()
else:
return tuple((i(kw) for i in events))
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