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#------------------------------------------------------------------------------
# Copyright (c) 2005, Enthought, Inc.
# All rights reserved.
#
# This software is provided without warranty under the terms of the BSD
# license included in enthought/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: David C. Morrill
# Original Date: 06/21/2002
#
# Symbols defined: TraitChangeNotifyWrapper
# UITraitChangeNotifyWrapper
# NewTraitChangeNotifyWrapper
# StaticAnyTraitChangeNotifyWrapper
# StaticTraitChangeNotifyWrapper
#
# Refactored into a separate module: 07/04/2003
#------------------------------------------------------------------------------
""" Defines the classes needed to implement and support the Traits change
notification mechanism.
"""
#-------------------------------------------------------------------------------
# Imports:
#-------------------------------------------------------------------------------
import weakref
import traceback
import sys
try:
# Requires Python 2.4:
from threading import local as thread_local
except:
thread_local = lambda: {}
from threading \
import Thread
from thread \
import get_ident
from types \
import MethodType
from trait_errors \
import TraitNotificationError
#-------------------------------------------------------------------------------
# Global Data:
#-------------------------------------------------------------------------------
# The thread ID for the user interface thread
ui_thread = -1
# The handler for notifications that must be run on the UI thread
ui_handler = None
#-------------------------------------------------------------------------------
# Sets up the user interface thread handler:
#-------------------------------------------------------------------------------
def set_ui_handler ( handler ):
""" Sets up the user interface thread handler.
"""
global ui_handler, ui_thread
ui_handler = handler
ui_thread = get_ident()
#-------------------------------------------------------------------------------
# 'NotificationExceptionHandlerState' class:
#-------------------------------------------------------------------------------
class NotificationExceptionHandlerState ( object ):
def __init__ ( self, handler, reraise_exceptions, locked ):
self.handler = handler
self.reraise_exceptions = reraise_exceptions
self.locked = locked
#-------------------------------------------------------------------------------
# 'NotificationExceptionHandler' class:
#-------------------------------------------------------------------------------
class NotificationExceptionHandler ( object ):
def __init__ ( self ):
self.traits_logger = None
self.main_thread = None
self.thread_local = thread_local()
#-- Private Methods ------------------------------------------------------------
def _push_handler ( self, handler = None, reraise_exceptions = False,
main = False, locked = False ):
""" Pushes a new traits notification exception handler onto the stack,
making it the new exception handler. Returns a
NotificationExceptionHandlerState object describing the previous
exception handler.
Parameters
----------
handler : handler
The new exception handler, which should be a callable or
None. If None (the default), then the default traits
notification exception handler is used. If *handler* is not
None, then it must be a callable which can accept four
arguments: object, trait_name, old_value, new_value.
reraise_exceptions : Boolean
Indicates whether exceptions should be reraised after the
exception handler has executed. If True, exceptions will be
re-raised after the specified handler has been executed.
The default value is False.
main : Boolean
Indicates whether the caller represents the main application
thread. If True, then the caller's exception handler is
made the default handler for any other threads that are
created. Note that a thread can explictly set its own exception
handler if desired. The *main* flag is provided to make it
easier to set a global application policy without having to
explicitly set it for each thread. The default value is
False.
locked : Boolean
Indicates whether further changes to the Traits notification
exception handler state should be allowed. If True, then
any subsequent calls to _push_handler() or _pop_handler() for
that thread will raise a TraitNotificationError. The default
value is False.
"""
handlers = self._get_handlers()
self._check_lock( handlers )
if handler is None:
handler = self._log_exception
handlers.append( NotificationExceptionHandlerState( handler,
reraise_exceptions, locked ) )
if main:
self.main_thread = handlers
return handlers[-2]
def _pop_handler ( self ):
""" Pops the traits notification exception handler stack, restoring
the exception handler in effect prior to the most recent
_push_handler() call. If the stack is empty or locked, a
TraitNotificationError exception is raised.
Note that each thread has its own independent stack. See the
description of the _push_handler() method for more information on
this.
"""
handlers = self._get_handlers()
self._check_lock( handlers )
if len( handlers ) > 1:
handlers.pop()
else:
raise TraitNotificationError(
'Attempted to pop an empty traits notification exception '
'handler stack.' )
def _handle_exception ( self, object, trait_name, old, new ):
""" Handles a traits notification exception using the handler defined
by the topmost stack entry for the corresponding thread.
"""
excp_class, excp = sys.exc_info()[:2]
handler_info = self._get_handlers()[-1]
handler_info.handler( object, trait_name, old, new )
if (handler_info.reraise_exceptions or
isinstance( excp, TraitNotificationError )):
raise excp
def _get_handlers ( self ):
""" Returns the handler stack associated with the currently executing
thread.
"""
thread_local = self.thread_local
if isinstance( thread_local, dict ):
id = get_ident()
handlers = thread_local.get( id )
else:
handlers = getattr( thread_local, 'handlers', None )
if handlers is None:
if self.main_thread is not None:
handler = self.main_thread[-1]
else:
handler = NotificationExceptionHandlerState(
self._log_exception, False, False )
handlers = [ handler ]
if isinstance( thread_local, dict ):
thread_local[ id ] = handlers
else:
thread_local.handlers = handlers
return handlers
def _check_lock ( self, handlers ):
""" Raises an exception if the specified handler stack is locked.
"""
if handlers[-1].locked:
raise TraitNotificationError(
'The traits notification exception handler is locked. '
'No changes are allowed.' )
#---------------------------------------------------------------------------
# This method defines the default notification exception handling
# behavior of traits. However, it can be completely overridden by pushing
# a new handler using the '_push_handler' method.
#
# It logs any exceptions generated in a trait notification handler.
#---------------------------------------------------------------------------
def _log_exception ( self, object, trait_name, old, new ):
""" Logs any exceptions generated in a trait notification handler.
"""
# When the stack depth is too great, the logger can't always log the
# message. Make sure that it goes to the console at a minimum:
excp_class, excp = sys.exc_info()[:2]
if ((excp_class is RuntimeError) and
(excp.args[0] == 'maximum recursion depth exceeded')):
sys.__stderr__.write( 'Exception occurred in traits notification '
'handler for object: %s, trait: %s, old value: %s, '
'new value: %s.\n%s\n' % ( object, trait_name, old, new,
''.join( traceback.format_exception( *sys.exc_info() ) ) ) )
logger = self.traits_logger
if logger is None:
import logging
self.traits_logger = logger = logging.getLogger(
'enthought.traits' )
handler = logging.StreamHandler()
handler.setFormatter( logging.Formatter( '%(message)s' ) )
logger.addHandler( handler )
print ('Exception occurred in traits notification handler.\n'
'Please check the log file for details.')
try:
logger.exception(
'Exception occurred in traits notification handler for '
'object: %s, trait: %s, old value: %s, new value: %s' %
( object, trait_name, old, new ) )
except Exception:
# Ignore anything we can't log the above way:
pass
#-------------------------------------------------------------------------------
# Traits global notification exception handler:
#-------------------------------------------------------------------------------
notification_exception_handler = NotificationExceptionHandler()
push_exception_handler = notification_exception_handler._push_handler
pop_exception_handler = notification_exception_handler._pop_handler
handle_exception = notification_exception_handler._handle_exception
#-------------------------------------------------------------------------------
# 'StaticAnyTraitChangeNotifyWrapper' class:
#-------------------------------------------------------------------------------
class StaticAnyTraitChangeNotifyWrapper:
def __init__ ( self, handler ):
self.handler = handler
self.__call__ = getattr( self, 'call_%d' %
handler.func_code.co_argcount )
def equals ( self, handler ):
return False
def call_0 ( self, object, trait_name, old, new ):
try:
self.handler()
except:
handle_exception( object, trait_name, old, new )
def call_1 ( self, object, trait_name, old, new ):
try:
self.handler( object )
except:
handle_exception( object, trait_name, old, new )
def call_2 ( self, object, trait_name, old, new ):
try:
self.handler( object, trait_name )
except:
handle_exception( object, trait_name, old, new )
def call_3 ( self, object, trait_name, old, new ):
try:
self.handler( object, trait_name, new )
except:
handle_exception( object, trait_name, old, new )
def call_4 ( self, object, trait_name, old, new ):
try:
self.handler( object, trait_name, old, new )
except:
handle_exception( object, trait_name, old, new )
#-------------------------------------------------------------------------------
# 'StaticTraitChangeNotifyWrapper' class:
#-------------------------------------------------------------------------------
class StaticTraitChangeNotifyWrapper:
def __init__ ( self, handler ):
self.handler = handler
self.__call__ = getattr( self, 'call_%d' %
handler.func_code.co_argcount )
def equals ( self, handler ):
return False
def call_0 ( self, object, trait_name, old, new ):
try:
self.handler()
except:
handle_exception( object, trait_name, old, new )
def call_1 ( self, object, trait_name, old, new ):
try:
self.handler( object )
except:
handle_exception( object, trait_name, old, new )
def call_2 ( self, object, trait_name, old, new ):
try:
self.handler( object, new )
except:
handle_exception( object, trait_name, old, new )
def call_3 ( self, object, trait_name, old, new ):
try:
self.handler( object, old, new )
except:
handle_exception( object, trait_name, old, new )
def call_4 ( self, object, trait_name, old, new ):
try:
self.handler( object, trait_name, old, new )
except:
handle_exception( object, trait_name, old, new )
#-------------------------------------------------------------------------------
# 'TraitChangeNotifyWrapper' class:
#-------------------------------------------------------------------------------
class TraitChangeNotifyWrapper:
def __init__ ( self, handler, owner ):
func = handler
if type( handler ) is MethodType:
func = handler.im_func
object = handler.im_self
if object is not None:
self.object = weakref.ref( object, self.listener_deleted )
self.name = handler.__name__
self.owner = owner
self.__call__ = getattr( self, 'rebind_call_%d' %
(func.func_code.co_argcount - 1) )
return
self.name = None
self.handler = handler
self.__call__ = getattr( self, 'call_%d' %
handler.func_code.co_argcount )
# NOTE: This method is normally the only one that needs to be overridden in
# a subclass to implement the subclass's dispatch mechanism:
def dispatch ( self, handler, *args ):
handler( *args )
def equals ( self, handler ):
if handler is self:
return True
if (type( handler ) is MethodType) and (handler.im_self is not None):
return ((handler.__name__ == self.name) and
(handler.im_self is self.object()))
return ((self.name is None) and (handler == self.handler))
def listener_deleted ( self, ref ):
self.owner.remove( self )
self.object = self.owner = None
def dispose ( self ):
self.object = None
def call_0 ( self, object, trait_name, old, new ):
try:
self.dispatch( self.handler )
except:
handle_exception( object, trait_name, old, new )
def call_1 ( self, object, trait_name, old, new ):
try:
self.dispatch( self.handler, new )
except:
handle_exception( object, trait_name, old, new )
def call_2 ( self, object, trait_name, old, new ):
try:
self.dispatch( self.handler, trait_name, new )
except:
handle_exception( object, trait_name, old, new )
def call_3 ( self, object, trait_name, old, new ):
try:
self.dispatch( self.handler, object, trait_name, new )
except:
handle_exception( object, trait_name, old, new )
def call_4 ( self, object, trait_name, old, new ):
try:
self.dispatch( self.handler, object, trait_name, old, new )
except:
handle_exception( object, trait_name, old, new )
def rebind_call_0 ( self, object, trait_name, old, new ):
try:
self.dispatch( getattr( self.object(), self.name ) )
except:
handle_exception( object, trait_name, old, new )
def rebind_call_1 ( self, object, trait_name, old, new ):
try:
self.dispatch( getattr( self.object(), self.name ), new )
except:
handle_exception( object, trait_name, old, new )
def rebind_call_2 ( self, object, trait_name, old, new ):
try:
self.dispatch( getattr( self.object(), self.name ),
trait_name, new )
except:
handle_exception( object, trait_name, old, new )
def rebind_call_3 ( self, object, trait_name, old, new ):
try:
self.dispatch( getattr( self.object(), self.name ),
object, trait_name, new )
except:
handle_exception( object, trait_name, old, new )
def rebind_call_4 ( self, object, trait_name, old, new ):
try:
self.dispatch( getattr( self.object(), self.name ),
object, trait_name, old, new )
except:
handle_exception( object, trait_name, old, new )
#-------------------------------------------------------------------------------
# 'UITraitChangeNotifyUIWrapper' class:
#-------------------------------------------------------------------------------
class UITraitChangeNotifyWrapper ( TraitChangeNotifyWrapper ):
def dispatch ( self, handler, *args ):
if get_ident() == ui_thread:
handler( *args )
else:
ui_handler( handler, *args )
#-------------------------------------------------------------------------------
# 'NewTraitChangeNotifyWrapper' class:
#-------------------------------------------------------------------------------
class NewTraitChangeNotifyWrapper ( TraitChangeNotifyWrapper ):
def dispatch ( self, handler, *args ):
Thread( target = handler, args = args ).start()
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