'When the size calculation of the trees is changed.'

def update_size_calc(self):

    if (self.model is not None):
        with self._prevent_commit():
            self.grid.clear()
            self._draw_trees()
            if (self.selected_tree_index != (-1)):
                self.grid_items[self.selected_tree_index].setSelected(True)
            self.update_depth()
