/*  
   grid1.c  
   draws a white filled rectangle on a black background  
  
   Laura Toma 
*/ 
 
 
#include <stdlib.h> 
#include <stdio.h> 
#include <math.h> 
#include <assert.h> 
#ifdef __APPLE__ 
#include <GLUT/glut.h> 
#else 
#include <GL/glut.h> 
#endif 
 
 
int nrows = 472;  
int ncols = 391; 
 
float pos[3] = {0,0,0};  
 
 
/* forward declarations of functions */ 
void display(void); 
void keypress(unsigned char key, int x, int y); 
 
 
int main(int argc, char** argv) { 
 
  /* open a window */ 
  glutInit(&argc, argv); 
  glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB | GLUT_DEPTH); 
  glutInitWindowSize(500, 500); 
  glutInitWindowPosition(100,100); 
  glutCreateWindow(argv[0]); 
 
  /* OpenGL init */ 
  glClearColor(0, 0, 0, 0);   /* set background color black*/ 
  glColor3f(1.0,1.0,1.0);   /* set draw color white */ 
 
  /* callback functions */ 
  glutDisplayFunc(display);  
  glutKeyboardFunc(keypress); 
 
  glEnable(GL_DEPTH_TEST); //not necessary in 2D 
 
  /* event handler */  
  glutMainLoop();       
  return 0; 
} 

void display(void) { 
  //clear the screen, need t oclear also teh depth buffer  
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);  
 
  glMatrixMode(GL_MODELVIEW);  
 
  glLoadIdentity(); //clear the matrix 
 
  /* the default GL window is [-1,1]x[-1,1] with the origin in the 
     center the points are in the range (0,0) to (ncols,nrows), so 
     they need to be mapped to [-1,1]x [-1,1] */ 
 
  //this make sit square, and we don;t want that  
  //glScalef(2.0/ncols, 2.0/nrows, 1.0);   
 
  //pick the maximum of (nrows, ncols) and scale with it  
  //glScalef(2.0/nrows, 2.0/nrows, 1.0);   
  glScalef(1.5/nrows, 1.5/nrows, 1.0);   
 
 /* our grid is in upper right quadrant, so we need to shift it to get 
  it centered */ 
  glTranslatef(-ncols/2.0, -nrows/2.0, 0);  
 
  //user translation  
  glTranslatef(pos[0], pos[1], pos[2]); 
 
 
  /* draw grid boundary polygon. we are rendering in the space [0,0] x 
     [ncols, nrows] */ 
  glPolygonMode(GL_FRONT_AND_BACK, GL_FILL); 
  glBegin(GL_POLYGON); 
  glVertex2f(0,0); 
  glVertex2f(0,nrows); 
  glVertex2f(ncols, nrows); 
  glVertex2f(ncols, 0); 
  glEnd(); 
 
 
  
  /* execute the drawing commands */ 
  glFlush(); 
} 
 
void keypress(unsigned char key, int x, int y) { 
  switch(key) { 
  case 'q': 
    exit(0); 
    break; 
 
  case 'l': 
    pos[0] -= 5;  //move left 5 cols  
    glutPostRedisplay();  
    break;  
     
  case 'r':  
    pos[0] += 5; //move right 5 cols  
    glutPostRedisplay();  
    break; 
  
  case 'u':  
    pos[1] += 5; //move up 5 rows  
    glutPostRedisplay();  
    break;  
     
  case 'd':  
    pos[1] -= 5; //move down 5 rows  
    glutPostRedisplay();  
    break;  
  } 
}