#include <GL/gl.h>
#include <GL/glu.h>
#include <glut.h>
#include <stdio.h>
#include <malloc.h>

/* you may need to locate glut.h on your computer and change the path accordingly.
 * It is most likely in ~/include or ~include/GL.
 */

/* the viewport is 500x500 with the origin at (0,0) */
#define WINDOW_SIZE 500

static int startX, startY, endX, endY;

void init(void) 
{
   glClearColor (0.0, 0.0, 0.0, 0.0);
}

void display(void)
{
	glClear (GL_COLOR_BUFFER_BIT);   

	glColor3f(1.0,1.0,1.0);

	printf("line = <%d, %d> -> <%d, %d>\n", startX, startY, endX, endY);
	glBegin(GL_LINES);
		glVertex2i(startX, startY);
		glVertex2i(endX, endY);
	glEnd();

	glFlush ();
}
int motionX=0;
int motionY=0;
int Ctrl=0;
void motion(int x, int y)
{
	printf("motion = <%d, %d>\n", x, WINDOW_SIZE-y);
}
void keyboard(unsigned char key, int x, int y)
{

	printf("key down = %c\n", key);

	switch(key){
		case 'q':
			exit(0);
			break;
		default:
			break;
	}

}

void keyup(unsigned char key, int x, int y)
{
	printf("key up = %c\n", key);

}
void mouse(int button, int state, int x, int y)
{
	switch (button) {
		case GLUT_LEFT_BUTTON:
			if (state == GLUT_DOWN) {
				printf("mouse down = <%d, %d>\n", x, WINDOW_SIZE - y);
				startX = x;
				startY = WINDOW_SIZE - y;
			}
			else {
				printf("mouse up = <%d, %d>\n", x, WINDOW_SIZE - y);
				endX = x;
				endY = WINDOW_SIZE - y;
				glutPostRedisplay();
			}
			break;
		default:
			break;
   }

}
void reshape (int w, int h)
{
   glViewport (0, 0, (GLsizei) w, (GLsizei) h); 
   glMatrixMode (GL_PROJECTION);
   glLoadIdentity ();

   glFrustum (-1.0, 1.0, -1.0, 1.0, 1.5, 500.0); // 3d

   glMatrixMode (GL_MODELVIEW);
   glLoadIdentity();

   /* assume a square window of size WINDOW_SIZE */
   gluLookAt (WINDOW_SIZE/2.0, WINDOW_SIZE/2.0, 3.0*(WINDOW_SIZE)/4.0, WINDOW_SIZE/2.0, WINDOW_SIZE/2.0, 0.0, 0.0, 1.0, 0.0);

}

int main(int argc, char** argv)
{
   glutInit(&argc, argv);
   glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB);
   glutInitWindowSize (WINDOW_SIZE, WINDOW_SIZE); 
   glutInitWindowPosition (100, 100);
   glutCreateWindow (argv[0]);
   
   init ();

   glutDisplayFunc(display); 
   glutReshapeFunc(reshape);
   glutMouseFunc(mouse);
   glutMotionFunc(motion);
   glutKeyboardFunc(keyboard);
   glutKeyboardUpFunc(keyup);
   glutMainLoop();
   return 0;
}