fix integration with undo/redo

Lib/idlelib/linenumbers.py

@@ -105,10 +105,15 @@ def __init__(self, editwin):
  self.sidebar_text.bind(event_name,
  lambda event, event_name=event_name:
  self.redirect_event(event, event_name))
- self.end_line_delegator = EndLineDelegator(self.update_sidebar_text)
  end = get_end(self.text)
  self.update_sidebar_text(end)
- self.editwin.per.insertfilter(self.end_line_delegator)
+
+ end_line_delegator = EndLineDelegator(self.update_sidebar_text)
+ # Insert the delegator after the undo delegator, so that line numbers
+ # are properly updated after undo and redo actions.
+ end_line_delegator.delegate = self.editwin.undo.delegate
+ self.editwin.undo.delegate = end_line_delegator
+
  # self.state = idleConf.GetOption('extensions', 'LineNumber', 'visible',
  # type='bool')
  self.state = True # TODO: Read config