# coding: utf-8
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"""This module provides a simple generic notification system."""
from __future__ import absolute_import, division, unicode_literals
__authors__ = ["T. Vincent"]
__license__ = "MIT"
__date__ = "25/07/2016"
import logging
from silx.utils.weakref import WeakList
_logger = logging.getLogger(__name__)
# Notifier ####################################################################
[docs]class Notifier(object):
"""Base class for object with notification mechanism."""
def __init__(self):
self._listeners = WeakList()
[docs] def addListener(self, listener):
"""Register a listener.
Adding an already registered listener has no effect.
:param callable listener: The function or method to register.
"""
if listener not in self._listeners:
self._listeners.append(listener)
else:
_logger.warning('Ignoring addition of an already registered listener')
[docs] def removeListener(self, listener):
"""Remove a previously registered listener.
:param callable listener: The function or method to unregister.
"""
try:
self._listeners.remove(listener)
except ValueError:
_logger.warn('Trying to remove a listener that is not registered')
[docs] def notify(self, *args, **kwargs):
"""Notify all registered listeners with the given parameters.
Listeners are called directly in this method.
Listeners are called in the order they were registered.
"""
for listener in self._listeners:
listener(self, *args, **kwargs)
[docs]def notifyProperty(attrName, copy=False, converter=None, doc=None):
"""Create a property that adds notification to an attribute.
:param str attrName: The name of the attribute to wrap.
:param bool copy: Whether to return a copy of the attribute
or not (the default).
:param converter: Function converting input value to appropriate type
This function takes a single argument and return the
converted value.
It can be used to perform some asserts.
:param str doc: The docstring of the property
:return: A property with getter and setter
"""
if copy:
def getter(self):
return getattr(self, attrName).copy()
else:
def getter(self):
return getattr(self, attrName)
if converter is None:
def setter(self, value):
if getattr(self, attrName) != value:
setattr(self, attrName, value)
self.notify()
else:
def setter(self, value):
value = converter(value)
if getattr(self, attrName) != value:
setattr(self, attrName, value)
self.notify()
return property(getter, setter, doc=doc)
[docs]class HookList(list):
"""List with hooks before and after modification."""
def __init__(self, iterable):
super(HookList, self).__init__(iterable)
self._listWasChangedHook('__init__', iterable)
def _listWillChangeHook(self, methodName, *args, **kwargs):
"""To override. Called before modifying the list.
This method is called with the name of the method called to
modify the list and its parameters.
"""
pass
def _listWasChangedHook(self, methodName, *args, **kwargs):
"""To override. Called after modifying the list.
This method is called with the name of the method called to
modify the list and its parameters.
"""
pass
# Wrapping methods that modify the list
def _wrapper(self, methodName, *args, **kwargs):
"""Generic wrapper of list methods calling the hooks."""
self._listWillChangeHook(methodName, *args, **kwargs)
result = getattr(super(HookList, self),
methodName)(*args, **kwargs)
self._listWasChangedHook(methodName, *args, **kwargs)
return result
# Add methods
def __iadd__(self, *args, **kwargs):
return self._wrapper('__iadd__', *args, **kwargs)
def __imul__(self, *args, **kwargs):
return self._wrapper('__imul__', *args, **kwargs)
def append(self, *args, **kwargs):
return self._wrapper('append', *args, **kwargs)
def extend(self, *args, **kwargs):
return self._wrapper('extend', *args, **kwargs)
def insert(self, *args, **kwargs):
return self._wrapper('insert', *args, **kwargs)
# Remove methods
def __delitem__(self, *args, **kwargs):
return self._wrapper('__delitem__', *args, **kwargs)
def __delslice__(self, *args, **kwargs):
return self._wrapper('__delslice__', *args, **kwargs)
def remove(self, *args, **kwargs):
return self._wrapper('remove', *args, **kwargs)
def pop(self, *args, **kwargs):
return self._wrapper('pop', *args, **kwargs)
# Set methods
def __setitem__(self, *args, **kwargs):
return self._wrapper('__setitem__', *args, **kwargs)
def __setslice__(self, *args, **kwargs):
return self._wrapper('__setslice__', *args, **kwargs)
# In place methods
def sort(self, *args, **kwargs):
return self._wrapper('sort', *args, **kwargs)
def reverse(self, *args, **kwargs):
return self._wrapper('reverse', *args, **kwargs)
[docs]class NotifierList(HookList, Notifier):
"""List of Notifiers with notification mechanism.
This class registers itself as a listener of the list items.
The default listener method forward notification from list items
to the listeners of the list.
"""
def __init__(self, iterable=()):
Notifier.__init__(self)
HookList.__init__(self, iterable)
def _listWillChangeHook(self, methodName, *args, **kwargs):
for item in self:
item.removeListener(self._notified)
def _listWasChangedHook(self, methodName, *args, **kwargs):
for item in self:
item.addListener(self._notified)
self.notify()
def _notified(self, source, *args, **kwargs):
"""Default listener forwarding list item changes to its listeners."""
# Avoid infinite recursion if the list is listening itself
if source is not self:
self.notify(*args, **kwargs)
