double red, double green, double blue);
void graph_free(struct graph *bg);
+typedef void (*graph_axis_unit_change_callback)(struct graph *g, int power_of_ten);
+void graph_x_axis_unit_change_notify(struct graph *g, graph_axis_unit_change_callback f);
+void graph_y_axis_unit_change_notify(struct graph *g, graph_axis_unit_change_callback f);
#endif