Test OpenGL Line (Works only from 0° to -45°)

#include <windows.h>
#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <GL/glut.h>

int Xo, Xf;
int Yo, Yf;

int H, W;
int yL = 10;
void ConfigureWindow(int newW, int newH);
void OnResizeWindow(int width, int height);
void OnRender(void);
void init();

void init(void)
{
    Xo = 0;
    Xf = 0;
    Yo = 0;
    Yf = 0;
    glClearColor(0.0, 0.0, 0.0, 0.0); //parametros: rojo, amarillo y azul, el cuarto es el parametro alpha
    glShadeModel(GL_FLAT);
    glColor3f(1.0, 1.0, 1.0);
}
void OnMouse(int button, int state, int x, int y)
{
    if (button == GLUT_LEFT_BUTTON)
    {
        if (state == GLUT_DOWN)
        {
            Xo = x;
            Yo = y;
        }
    }
}

void OnMouseMove(int x, int y)
{
    Xf = x;
    Yf = y;

    glutPostRedisplay();
}

void pantalla(){

    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();

    glColor4f(1.0f, 1.0f, 0.0f, 1.0f);
    glBegin(GL_POINTS);
    int dx, dy, dE, dNE, d, x, y;
    dx = Xf - Xo;
    dy = Yf - Yo;

    x = Xo;
    y = Yo;
/////////////////
    if(x < Xf)
    {
            d = -2 * dy + dx;
            dE = 2 * dy - dx;
            dNE = 2 * (dy - dx);
            //dE < 0 && dNE >0
            while (x < Xf)

        {
            if (d <= 0){
                d = d + dE;
                x++;
            }
            else{
                d = d + dNE;
                x++;
                y++;
            }
            glVertex2i(x, y);

        }
        glEnd();
    }
//////////
 else if (y < Yf)
 {
            d = -dy + 2*dx;
            dE = (3/2)*dy + 1;
            dNE = (3/2)*dy;
            //dE < 0 && dNE >0
            while (x < Xf)

        {
            if (d <= 0){
                d = d + dE;
                y++;
            }
            else{
                d = d + dNE;
                x++;
                y++;
            }
            glVertex2i(x, y);
        }
        glEnd();
    }
 ////////////////
}
void ConfigureWindow(int newW, int newH)
{
    glViewport(0, 0, newW, newH);

    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluOrtho2D(0, newW, newH, 0);
}

void OnResizeWindow(int width, int height)
{
    ConfigureWindow(width, height);

    W = width;
    H = height;
}

void OnRender(void)
{
    glClear(GL_COLOR_BUFFER_BIT);
    ConfigureWindow(W, H);
    pantalla();

    glutSwapBuffers();
}
void reshape(int w, int h)

{
    glViewport(0, 0, (GLsizei)w, (GLsizei)h);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho(-10.0, 10.0, -10.0, 10, -10.0, 10.0);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();

}

int main(int argc, char **argv){
    H = 500;
    W = 500;
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_RGBA | GLUT_DOUBLE);
    glutCreateWindow("Línea");
    glutReshapeWindow(W, H);
    glutDisplayFunc(OnRender);
    glutReshapeFunc(OnResizeWindow);
    glutMouseFunc(OnMouse);
    glutMotionFunc(OnMouseMove);
    glutMainLoop();
    return 0;
}