大家好，请帮我看一下这个opengl 中点画线法为什么画不出来

[观重青]

#include<stdlib.h>
#include<GL/glut.h>

void myinit(void)
{
	glClearColor(1.0,1.0,1.0,0.0);
	glColor3f(1.0,0.0,0.0);
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	gluOrtho2D(0.0,500.0,0.0,500.0);
	glMatrixMode(GL_MODELVIEW);
}

void MidpointLine(int x0,int y0,int x1,int y1)
{
	int a,b,d1,d2,d,x,y;
	a=y0-y1,b=x1-x0,d=2*a+b;
	d1=2*a,d2=2*(a+b);
	x=x0,y=y0;
	while(x<x1)
	{
		if(d<0)
		{
			x++,y++,d+=d2;
		}
		else
		{
			x++,d+=d2;
		}
}
}

void display(void)
{
	glClear(GL_COLOR_BUFFER_BIT);
	MidpointLine(200,200,2000,2000);
	glFlush();
}
  
int main(int argc, char** argv)  
{ 
    glutInit(&argc,argv);  
    glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB);
    glutInitWindowSize(500,500);
    glutInitWindowPosition(0,0); 
    glutCreateWindow("中点画线法"); 
    glutDisplayFunc(display);
    myinit(); 
    glutMainLoop(); 
}  

[headache_]

MidpointLine()里面的画点函数呢？ while(x<x1) { if(d<0) { x++,y++,d+=d2; } else { x++,d+=d2; } glVertex2f(x, y); //加个这个 }

[十面矛盾]

void MidPointLine(int x1, int y1, int x2, int y2) { int a, b, dt1, dt2, d, x, y; a = y1 - y2; b = x2 - x1; d = 2*a + b; dt1 = a + b + a + b; dt2 = a + a; x = x1; y = y1; glColor3f(1.0f, 0.0f, 0.0f); glBegin(GL_POINTS); glVertex2i(x, y); glEnd(); while (x < x2) { if (d < 0) { x++; y++; d += dt1; } else { x++; d += dt2; } glBegin(GL_POINTS); glVertex2i(x, y); glEnd(); } }