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trait_notifiers.py

#-------------------------------------------------------------------------------
#
#  Define the classes needed to implement and support the trait change
#  notification mechanism.
#
#  Written by: David C. Morrill
#
#  Original Date:                         06/21/2002
#  Rewritten as a C-based type extension: 06/21/2004
#
#  Refactored into a separate module: 07/04/2003
#
#  Symbols defined: TraitChangeNotifyWrapper
#                   StaticAnyTraitChangeNotifyWrapper
#                   StaticTraitChangeNotifyWrapper
#
#  (c) Copyright 2002, 2003 by Enthought, Inc.
#
#-------------------------------------------------------------------------------

#-------------------------------------------------------------------------------
#  Imports:
#-------------------------------------------------------------------------------

import weakref

from types import MethodType

#-------------------------------------------------------------------------------
#  Log any exceptions generated in a trait notification handler:
#-------------------------------------------------------------------------------

traits_logger = None

def log_exception ( ):
    global traits_logger
    
    if traits_logger is None:
        import logging
        traits_logger = logging.getLogger( 'enthought.traits' )
        handler       = logging.StreamHandler()
        handler.setFormatter( logging.Formatter( '%(message)s' ) )
        traits_logger.addHandler( handler )
        
    traits_logger.exception( 'Exception occurred in traits notification '
                             'handler' )
        
#-------------------------------------------------------------------------------
#  '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:
            log_exception()
                                 
    def call_1 ( self, object, trait_name, old, new ):
        try:
            self.handler( object )
        except:
            log_exception()
                                 
    def call_2 ( self, object, trait_name, old, new ):
        try:
            self.handler( object, trait_name )
        except:
            log_exception()
                                 
    def call_3 ( self, object, trait_name, old, new ):
        try:
            self.handler( object, trait_name, new )
        except:
            log_exception()
                                 
    def call_4 ( self, object, trait_name, old, new ):
        try:
            self.handler( object, trait_name, old, new )
        except:
            log_exception()
          
#-------------------------------------------------------------------------------
#  '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:
            log_exception()
                                 
    def call_1 ( self, object, trait_name, old, new ):
        try:
            self.handler( object )
        except:
            log_exception()
                                 
    def call_2 ( self, object, trait_name, old, new ):
        try:
            self.handler( object, new )
        except:
            log_exception()
                                 
    def call_3 ( self, object, trait_name, old, new ):
        try:
            self.handler( object, old, new )
        except:
            log_exception()
                                 
    def call_4 ( self, object, trait_name, old, new ):
        try:
            self.handler( object, trait_name, old, new )
        except:
            log_exception()      

#-------------------------------------------------------------------------------
#  '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 )
       
   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.handler()
       except:
          log_exception()
                                
   def call_1 ( self, object, trait_name, old, new ):
       try:
          self.handler( new )
       except:
          log_exception()
                                
   def call_2 ( self, object, trait_name, old, new ):
       try:
          self.handler( trait_name, new )
       except:
          log_exception()
                                
   def call_3 ( self, object, trait_name, old, new ):
       try:
          self.handler( object, trait_name, new )
       except:
          log_exception()
                                
   def call_4 ( self, object, trait_name, old, new ):
       try:
          self.handler( object, trait_name, old, new )
       except:
          log_exception()
                                
   def rebind_call_0 ( self, object, trait_name, old, new ):
       try:
          getattr( self.object(), self.name )()
       except:
          log_exception()
                                
   def rebind_call_1 ( self, object, trait_name, old, new ):
       try:
          getattr( self.object(), self.name )( new )
       except:
          log_exception()
                                
   def rebind_call_2 ( self, object, trait_name, old, new ):
       try:
          getattr( self.object(), self.name )( trait_name, new )
       except:
          log_exception()
                                
   def rebind_call_3 ( self, object, trait_name, old, new ):
       try:
          getattr( self.object(), self.name )( object, trait_name, new )
       except:
          log_exception()
                                
   def rebind_call_4 ( self, object, trait_name, old, new ):
       try:
          getattr( self.object(), self.name )( object, trait_name, old, new )
       except:
          log_exception()


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