EditScopePlugValueWidget : Add Refresh menu item

This allows the user to get explicit feedback about ContextTracker updates in the unlikely event that they are slow enough to not be done before the menu is accessed. I've deliberately only shown the BusyWidget when the user "opts in" via a refresh as I think most updates are going to be so rapid that it would flicker annoyingly for them.

python/GafferUI/EditScopeUI.py

@@ -127,6 +127,8 @@ def __init__( self, plug, **kw ) :
 			with GafferUI.ListContainer( GafferUI.ListContainer.Orientation.Horizontal, spacing = 4 ) :
 				GafferUI.Spacer( imath.V2i( 4, 1 ), imath.V2i( 4, 1 ) )
 				GafferUI.Label( "Edit Scope" )
+				self.__busyWidget = GafferUI.BusyWidget( size = 18 )
+				self.__busyWidget.setVisible( False )
 				self.__menuButton = GafferUI.MenuButton(
 					"",
 					menu = GafferUI.Menu( Gaffer.WeakMethod( self.__menuDefinition ) ),
@@ -247,6 +249,7 @@ def __editScopeMetadataChanged( self, editScope, key, reason ) :
 	def __contextTrackerChanged( self, contextTracker ) :
 
 		self.__updateMenuButton()
+		self.__busyWidget.setVisible( False )
 
 	def __editScope( self ) :
 
@@ -409,13 +412,24 @@ def addToMenuHierarchy( editScope, root ) :
 			result.update( self.__buildMenu( result, category, currentEditScope ) )
 
 
+		if self.__contextTracker.updatePending() :
+			result.append( "/__RefreshDivider__", { "divider" : True } )
+			result.append( "/Refresh", { "command" : Gaffer.WeakMethod( self.__refreshMenu ) } )
+
 		result.append( "/__NoneDivider__", { "divider" : True } )
 		result.append(
 			"/None", { "command" : functools.partial( self.getPlug().setInput, None ) },
 		)
 
 		return result
 
+	def __refreshMenu( self ) :
+
+		if self.__contextTracker.updatePending() :
+			# An update will already be in progress so we just show our busy
+			# widget until it is done.
+			self.__busyWidget.setVisible( True )
+
 	def __navigationMenuDefinition( self ) :
 
 		result = IECore.MenuDefinition()