GLUT_DOUBLE
if (gState.displayMode & GLUT_DOUBLE)
#define GLUT_WIND_IS_SINGLE(x) (((x) & GLUT_DOUBLE) == 0)
#define GLUT_WIND_IS_DOUBLE(x) (((x) & GLUT_DOUBLE) != 0)
glutInitDisplayMode(GLUT_RGB | GLUT_DEPTH | GLUT_DOUBLE);
glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGBA | GLUT_DEPTH);