std::cerr << "gtk_math_view_expose_event " << std::endl;
gtk_math_view_expose_event(GtkWidget* widget,			   GdkEventExpose* event){  g_return_val_if_fail(widget != NULL, FALSE);  g_return_val_if_fail(event != NULL, FALSE);  g_return_val_if_fail(GTK_IS_MATH_VIEW(widget), FALSE);  GtkMathView* math_view = GTK_MATH_VIEW(widget);  std::cerr << "gtk_math_view_expose_event " << std::endl;  update_widget(math_view, event->area.x, event->area.y, event->area.width, event->area.height);  return FALSE;}