code: def transform_cb(self, setting, value):
          
          self.make_callback('transform')
  
          # whence=0 because need to calculate new extents for proper
          # cutout for rotation (TODO: always make extents consider
          #  room for rotation)
          whence = 0
          self.redraw(whence=whence)
docs: Handle callback related to changes in transformations.