freeglut

#include <iostream>
#include <gl/glut.h>

using namespace std;

struct Point {
    int x;
    int y;
};

//

#define VERTEX_COUNT 5

Point points[VERTEX_COUNT] = {
        103, 273,
        516, 273,
        184, 32,
        308, 452,
        439, 32
};

//

void draw_dda(Point p1, Point p2) {
    GLfloat dx = p2.x - p1.x;
    GLfloat dy = p2.y - p1.y;

    GLfloat x1 = p1.x;
    GLfloat y1 = p1.y;

    GLfloat step = 0;

    if(abs(dx) > abs(dy)) {
        step = abs(dx);
    } else {
        step = abs(dy);
    }

    GLfloat xInc = dx/step;
    GLfloat yInc = dy/step;

    for(float i = 1; i <= step; i++) {
        glVertex2i(x1, y1);
        x1 += xInc;
        y1 += yInc;
    }
}

void init() {
    glClearColor(1.0, 1.0, 1.0, 0.0);
    glColor3f(0.0f, 0.0f, 0.0f);
    gluOrtho2D(0.0, 640.0, 0.0, 480.0);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glPointSize(1.0f);
}

void display() {
    glClear(GL_COLOR_BUFFER_BIT);
    glBegin(GL_POINTS);
    Point stPoint = points[0];

    for(int i = 1; i < VERTEX_COUNT; i++) {
        draw_dda(stPoint, points[i]);
        stPoint = points[i];
    }
    draw_dda(stPoint, points[0]);

    glEnd();
    glFlush();
}

int main(int argc, char** argv) {
    glutInit(&argc, argv);
    glutInitWindowPosition(400, 200);
    glutInitWindowSize(640, 480);
    glutInitDisplayMode(GLUT_SINGLE|GLUT_RGB);
    glutCreateWindow("OpenGL");
    init();
    glutDisplayFunc(display);
    glutMainLoop();
    return 0;
}