def _handle_double_click(self, event):
        """ Double click with left mouse button focuses the state and toggles the collapse status"""
        if event.get_button()[1] == 1:  # Left mouse button
            path_info = self.tree_view.get_path_at_pos(int(event.x), int(event.y))
            if path_info:  # Valid entry was clicked on
                path = path_info[0]
                iter = self.tree_store.get_iter(path)
                state_model = self.tree_store.get_value(iter, self.MODEL_STORAGE_ID)

                # Set focus to StateModel
                selection = self._selected_sm_model.selection
                selection.focus = state_model

                # Toggle collapse status if applicable for this kind of state
                if self.view.row_expanded(path):
                    self.view.collapse_row(path)
                else:
                    if isinstance(state_model, ContainerStateModel) or \
                                    isinstance(state_model, LibraryStateModel) and self.show_content(state_model):
                        self.view.expand_to_path(path)