#include <stdio.h>
#include <math.h>
#include <GL/glut.h>
#include <stdlib.h>
//Ukuran layar awal
int HEIGHT = 400;
int WIDTH  = 400;

//Batas koordinat
float X_MIN = -20.0;
float X_MAX =  20.0;
float Y_MIN = -20.0;
float Y_MAX =  20.0;

void grid()
{
     double i;

     glColor3f(0.3,0.3,0.3);
     glBegin(GL_LINES);
         for(i=0;i<X_MAX;i++)
         {
             glVertex2f(i,Y_MAX);
             glVertex2f(i,Y_MIN);
         }
         for(i=0;i>X_MIN;i--)
         {
             glVertex2f(i,Y_MAX);
             glVertex2f(i,Y_MIN);
         }
         for(i=0;i<Y_MAX;i++)
         {
             glVertex2f(Y_MAX,i);
             glVertex2f(Y_MIN,i);
         }
         for(i=0;i>Y_MIN;i--)
         {
             glVertex2f(Y_MAX,i);
             glVertex2f(Y_MIN,i);
         }
     glEnd();

     //Titik Pusat (0,0)
     glColor3f(1.0,1.0,1.0);
     glPointSize(5);
     glBegin(GL_POINTS);
         glVertex2f(0,0);
     glEnd();
}

void spike(int n,float size){
     float sudut=(2*3.14)/n;
     float x,y;
     int i;

     glPointSize(5);
     glLineWidth(2);

     for(i=0;i<n;i++){
         //glColor3f((float) i/n,(float) i/n,(float) i/n);
         glBegin(GL_LINES);
         x=sin(i*sudut) * size;
         y=cos(i*sudut) * size;
         glVertex2f(0.0,0.0);
         glVertex2f(x,y);
     }
     glEnd();
}

void bintang(int n,float size){
     float sudut=(2*3.14)/n;
     float x,y;
     int i;

     glPointSize(5);
     glLineWidth(2);

     glBegin(GL_LINE_LOOP);
     //verterx ganjil
     for(i=1;i<=n;i+=2){
         x=sin(i*sudut) * size;
         y=cos(i*sudut) * size;
         glVertex2f(x,y);
     }

     //vertex genap
     for(i=2;i<=n;i+=2){
         x=sin(i*sudut) * size;
         y=cos(i*sudut) * size;
         glVertex2f(x,y);
     }

     glEnd();
}

void draw_pixel(float x, float y) {

    glColor3f(1.0, 0.0, 0.0);
    glBegin(GL_POLYGON);
        glVertex2f(x, y);
        glVertex2f(x+1, y);
        glVertex2f(x+1, y+1);
        glVertex2f(x, y+1);
    glEnd();

}

void naive(int x1, int y1, int x2, int y2)
{
  int dx = x2 - x1;
  int dy = y2 - y1;

  draw_pixel(x1,y1);
  if(dx != 0) {
        float m = (float) dy / (float) dx;
        float b = y1 - m*x1;
        dx = (x2 > x1) ? 1 : -1;
        while (x1 != x2) {
              x1 += dx;
              y1 = (int)(m*x1 + b);
              draw_pixel(x1,y1);
        }
  }
}


void dda(int x1, int y1, int x2, int y2)
{
      int dy = y2 - y1;
      int dx = x2 - x1;
      float t = (float) 0.5;

      draw_pixel(x1,y1);
      if (abs(dx) > abs(dy)) {
         float m = (float) dy / (float) dx;
         t += y1;
         dx = (dx<0) ? -1 : 1;
         m *= dx;
         while (x1 != x2){
               x1 += dx;
                t += m;
               draw_pixel(x1, (int) t);
         }
      }
      else {
           float m = (float) dx / (float) dy;
           t += x1;
           dy = (dy<0) ? -1 : 1;
           m *= dy;
           while( y1 != y2) {
                  y1 += dy;
                  t += m;
                  draw_pixel((int)t,y1);
                  }
           }
}

void BresenhamLine (int x0,int y0,int xend, int yend,int color)
                  {   int dx,dy, incre_p1, incre_p2, p, x, y;
    dy=yend-y0, dx=xend-x0;
    incre_p1=2*dy, incre_p2=2* (dy-dx);
    x=x0, y=y0;
  p=2*dy-dx;
    drawpixel(x, y, color);
    while (x<x1)
    { if (p<0)       {x++, p+=incre_d1; }
     else               {x++, y++,p+=incre_d2;}
     drawpixel (x, y, color);
     }  /* while */
 } /* Bresenham */


void display(){
     glClear(GL_COLOR_BUFFER_BIT);
     grid();

     //spike(5,10);
     //bintang(5,10);
     //naive(0,0,5,5);

     glFlush();
}

void init()  {
 	 glClearColor( 0.0, 0.0, 0.0, 0.0);
     glMatrixMode(GL_PROJECTION);
     glLoadIdentity();
	 gluOrtho2D(X_MIN,X_MAX,Y_MIN,Y_MAX);
     glMatrixMode(GL_MODELVIEW);
}


int main( int  argc,  char  **argv)  {
  	glutInit( &argc, argv);
    glutInitWindowSize(WIDTH, HEIGHT);
  	glutInitWindowPosition(0, 0);
  	glutCreateWindow("Segi-N Beraturan");

 	glutDisplayFunc(display);


    glEnable(GL_POINT_SMOOTH);
    glEnable(GL_LINE_SMOOTH);
 	glEnable(GL_BLEND);                                              //memperhalus garis
    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);               // memperhalus garis

    init();
	glutMainLoop();
  	return 0;
}