// Program to demonstrate how to open a window size and position it properly

#include <stdlib.h>
#include <math.h>
#include <GL/glut.h>
int wide=300, high=300;   // Global Variables for Length and Width
int winX=40, winY=40;	  // X and Y positions for window
double radians, angle, velocity;
double dx, dy;
double vx, vy;
double time;
double dt = 0.05;
double a = 9.8;
double timestart=-10.0;
double timestop=10.0;
double x=0.0,y=0.0;
double clock=0.0;
double distanceup, distancefall;

//const double PI = 3.14159;

void drawAxis();

void drawAxis ()
{
   glColor3f(1.0, 0.0, 1.0);
   glBegin(GL_LINES);
      glVertex3f(0.0, -50.0, 0.0);
      glVertex3f(0.0, 400.0, 0.0);
      glVertex3f(-50.0, 0.0, 0.0);
      glVertex3f(800.0, 0.0, 0.0);
   glEnd();
}     


void DrawGraph()  // The Drawing Routine
{ 
    glColor3f(1.0, 1.0, 0.0);		// Set drawing color to yellow
    glBegin( GL_POINTS );		// Start drawing POINTS
    clock=clock+dt;
    x = x + dx;
    distanceup = distanceup + dy;
    distancefall = 0.5* a * clock*clock;
    y =  distanceup - distancefall;     // Calculate y value of parabola
    printf("x=%f, y=%f, t=%f, dx=%f, dy=%f, vx=%f,vy=%f\n",
			    x,y,time,dx,dy,vx,vy);
    glVertex3f(x, y, 0.0);      // Plot point at (x,y) z=0 in 2D
    glEnd();				// End drawing points
} 

void display(void)
{ /* clear all pixels */

   glClear(GL_COLOR_BUFFER_BIT);
   glColor3f(0.8900, 0.1500, 0.2100);  //alizarin_crimson see 
   glRectf(500.0,25.0,550.0,0.0);  // http://stevehollasch.com/cgindex/color/colors.txt
   drawAxis();
   DrawGraph();			// Call my Drawing Routine
   glFlush();  // Force writing all pending OpenGL actions to the screen.
   time = time + dt;
   glutSwapBuffers();
   if (x >800) dx = dx*-1;
   if (time <=timestop && y >=0 )
	glutPostRedisplay();
   
}

void keyboard(unsigned char key, int x, int y)
{
    if (key == (unsigned char) 27)   //Press 'Esc' key, with mouse on window, 
      exit(0);	                     // to exit
}


void myinit(void)
{ /* select clearing (background) color   */
   glClearColor(0.5, 0.5, 0.5, 0.0);     // These RGB values make gray
   
/* initialize viewing values */
   glMatrixMode(GL_PROJECTION);			// Select Matrix Mode
   glLoadIdentity();				// Provide Base Matrix 
   glOrtho(-50.0, 1000.0, -50.0, 500.0, -1.0, 1.0);   	// Set window dimensions
   glPointSize(5.0);
}

/* Declare initial window size, position, and display mode */

int main(int argc, char* argv[])
{  
   printf("Creating window %d pixels wide and %d pixels high", wide, high);
   printf(" at (%d,%d).\n", winX, winY);
   printf("Enter angle in degrees: ");
   scanf("%lf", &angle);
   radians = angle*M_PI/180.0;
   printf("Enter velocity in meters per sec (gravity acc = 9.8 m/sec^2): ");
   scanf("%lf", &velocity);
   vx = velocity*cos(radians);
   vy = velocity*sin(radians);
   dx = vx*dt;
   dy = vy*dt;
   distanceup=0.0;
   
   time = timestart;
   clock=0;
   glutInit(&argc, argv);   // Call glut's initialization routine
   glutInitDisplayMode(GLUT_DOUBLE|GLUT_RGB);	// Set Single Buffer, RGB Color
   glutInitWindowSize(wide, high);  	// Initialize window size
   glutInitWindowPosition(winX,winY); 	// Position window
   glutCreateWindow("My Window");	// Actually create window with title
   myinit();				// Call my initialization routine
   glutKeyboardFunc(keyboard);
   glutDisplayFunc(display);		// Call my display routine 
   glutMainLoop();			// Fall into glut's main event loop 
   return 0;
}