text: ##########################################################################
  #
  #  Copyright (c) 2016, Image Engine Design Inc. All rights reserved.
  #
  #  Redistribution and use in source and binary forms, with or without
  #  modification, are permitted provided that the following conditions are
  #  met:
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  #        copyright notice, this list of conditions and the following
  #        disclaimer.
  #
  #      * Redistributions in binary form must reproduce the above
  #        copyright notice, this list of conditions and the following
  #        disclaimer in the documentation and/or other materials provided with
  #        the distribution.
  #
  #      * Neither the name of John Haddon nor the names of
  #        any other contributors to this software may be used to endorse or
  #        promote products derived from this software without specific prior
  #        written permission.
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  #  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
  #  IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
  #  THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  #  PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
  #  CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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  #  PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
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  #  SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  #
  ##########################################################################
  
  from __future__ import with_statement
  
  import Gaffer
  import GafferUI
  
  ## PlugValueWidget suitable for incrementing a plug to trigger a refresh
  # of nodes which access the filesystem.
  class RefreshPlugValueWidget( GafferUI.PlugValueWidget ) :
  
  	def __init__( self, plug, **kw ) :
  
  		self.__button = GafferUI.Button( image = "refresh.png", hasFrame = False )
  
  		GafferUI.PlugValueWidget.__init__( self, self.__button, plug, **kw )
  
  		self.__clickedConnection = self.__button.clickedSignal().connect( Gaffer.WeakMethod( self.__clicked ) )
  
  	def _updateFromPlug( self ) :
  
  		pass
  
  	def __clicked( self, widget ) :
  
  		# Deliberately not making this undoable, as once we've refreshed
  		# a loaded file, there's no going back.
  		self.getPlug().setValue( self.getPlug().getValue() + 1 )
  