OPengl运行时窗口一闪而过，为毛啊?代码如下：

class GLintPoint
{
public:
GLint x,y;
};

class Point2
{
public :
float x,y;
void set(float dx, float dy)
{
x = dx;
y = dy;
}

void set(Point2 &p)
{
    x = p.x;
    y = p.y;
}

Point2(float xx, float yy)
{
    x = xx,
        y= yy;
}

Point2(){ x=y=0;}

};

Point2 currPos;
Point2 CP;

void moveTo(Point2 p)
{
CP.set(p);
}

void lineTo(Point2 p)
{
glBegin(GL_LINES);
glVertex2f(CP.x,CP.y);
glVertex2f(p.x,p.y);
glEnd();
glFlush( );
CP.set(p);
}

void myInit(void)
{
glClear(GL_COLOR_BUFFER_BIT);
glClearColor(1.0, 0.0, 0.0, 0.0);
glColor3f(0.0, 0.0, 1.0);
}

void rosette(int N, float radius)
{
Point2 * pointlist = new Point2[N];
GLfloat theta = (2.0f * 3.1415926536)/N;
for(int c = 0; c<N; c++)
{
pointlist[c].set(radius * sin(theta * c),radius * cos(theta * c));
}

for(int i = 0; i<N; i++)
{
    for(int j = 0; j<N; j++)
    {
        moveTo(pointlist[i]);
        lineTo(pointlist[j]);
    }
}

}

void render()
{
glClear(GL_COLOR_BUFFER_BIT);
glViewport(10, 10, 640, 480);
rosette(5, 0.66f);
glFlush();
}

void main(int argc, char ** argv)
{
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glutInitWindowSize(640,480);
glutDisplayFunc(render);
myInit();
glutMainLoop();
}

http://zhidao.baidu.com/link?url=7CovDzHbZpoKjtsDYLIpkcrXswEbfNGZqUJbB4Sav48YweeT42eUd93eZaSSW_KYD2gDIVMlk3Jf3HR-3pTcGq
http://blog.csdn.net/hippig/article/details/8568388