def _position_cb(self, unused_pipeline, unused_position):
        if not self.__source_uses_keyframes():
            return
        for prop in ["posx", "posy", "width", "height"]:
            self.__update_spin_btn(prop)
        # Keep the overlay stack in sync with the spin buttons values
        self.app.gui.editor.viewer.overlay_stack.update(self.source)