OpenGL实现中点划线法

#include "GL/glut.h"
#include "stdio.h"
#include "math.h"
 
int xs, ys, xe, ye;
 
void MidpointLine(int x0, int y0, int x1, int y1)
{
 if((x0 != x1) && (y0 != y1))
 {
 int a, b, deltal, delta2, d, x, y;
 a = y0 - y1;
 b = x1 - x0;
 d = 2 * a + b;
 deltal = 2 * a;
 delta2 = 2 * (a + b);
 x = x0;
 y = y0;
 glVertex2i(x, y);
 while(x