def transform_cb(self, setting, value):
        """Handle callback related to changes in transformations."""
        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)
Handle callback related to changes in transformations.