code: def redo(self):
          
          if not self.gui_up:
              return
  
          self.clear_mask()
  
          image = self.fitsimage.get_image()
          if image is None:
              return
  
          n_obj = len(self._maskobjs)
          self.logger.debug('Displaying {0} masks'.format(n_obj))
          if n_obj == 0:
              return
  
          # Display info table
          self.recreate_toc()
  
          # Draw on canvas
          self.masktag = self.canvas.add(self.dc.CompoundObject(*self._maskobjs))
          self.fitsimage.redraw()
docs: Image or masks have changed. Clear and redraw.