#include<iostream>
#include<math.h>
using namespace std;

#include<GL\glut.h>

void lineDDA (int x1, int y1,  int x2, int y2);
void init (void);
void Display (void);
void setPixel(int x, int y);

void main (int argc, char** argv) {
	glutInit(&argc, argv);
	glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
	glutInitWindowPosition(0, 0);
	glutInitWindowSize(640, 480); //set Display window
	glutCreateWindow("Homework Line DDA Program");
	init();
	glutDisplayFunc(Display);
	glutMainLoop();
}

void init (void) {
	glClearColor(1.0, 1.0, 1.0, 0.0);
	glMatrixMode(GL_PROJECTION);
	gluOrtho2D(0.0, 400.0, 0.0, 300.0);
}

void lineDDA (int x1, int y1,  int x2, int y2)  {
	float m = (float)  (y2-y1)/(x2-x1);
	if (m <= 1) {
		setPixel(x1, y1);
		float y = y1;
		for (int i =x1; i <= x2; i++) {
			y += m;
			setPixel(i, (int)y);
		}
	} else if (m > 1) {
		float x = 0;
		for (int i = y1; i <= y2; i++) {
			x += (1/m);
			setPixel(x, i);
		}
	} else if (m < 1 && -1 <= m) {
		float y = 0;
		for (int i =x1; i <= x2; i++) {
			y -= m;
			setPixel(i, (int)y);
		}
	} else if (m > 1 && (-1/m) <= m) {
		float x = 0;
			for (int i = y1; i <= y2; i++) {
			x -= (1/m);
			setPixel(x, i);
		}
	}
}

void setPixel(int x, int y) {
	cout<<"x:"<<x << " y: "<< y <<endl;
	glBegin(GL_POINTS);
		glVertex2i(x, y);
	glEnd();
}

void Display (void) {
	glClear(GL_COLOR_BUFFER_BIT);
	glColor3f(1.0, 0.0, 0.0);

	lineDDA(48, 152, 400, 400);
	lineDDA(0, 53, 600, 461);
	lineDDA(100, 23, 550, 202);

	glFlush();
}