#include <stdlib.h>
#include <GL/glut.h>

#define X 300
#define Y 300
float color[3] = {0.5,0.5,0.5};

void setColor(int i){
  switch (i){
  case 0:
    color[0]=1.0;
    color[1]=0.0;
    color[2]=0.0;
    break;
  case 1:
    color[0]=0.0;
    color[1]=1.0;
    color[2]=0.0;
    break;
  case 2:
    color[0]=0.0;
    color[1]=0.0;
    color[2]=1.0;
    break;
  case 3:
    color[0]=0.0;
    color[1]=0.0;
    color[2]=0.0;
    break;
  case 4:
    color[0]=1.0;
    color[1]=1.0;
    color[2]=1.0;
    break;
  default: break;
  }
}
void init(){
  //set the background color to black (RGBA)
  glClearColor(0.0,0.0,0.0,0.0);
  //Make a menu (pass in the func name, the func takes an int)
  glutCreateMenu(setColor);
  //add entries (char *,int)
  glutAddMenuEntry("Red",0);
  glutAddMenuEntry("Green",1);
  glutAddMenuEntry("Blue",2);
  glutAddMenuEntry("Black",3);
  glutAddMenuEntry("White",4);
  //make the menu show up upon right mouse button (hold down)
  glutAttachMenu(GLUT_RIGHT_BUTTON);
}
void display(){
  glClear(GL_COLOR_BUFFER_BIT);
  glBegin(GL_POINTS);
  //put the real work in between here
  for (int i=0;i<50;i++){
    glColor3f((float)i*1.0/(float)50,1.0,0.0);
    glVertex2i(10+i,20+i);
  }
  //
  glEnd();
  glFlush();
}
void mouse(int button, int state, int x, int y){
  y = Y - y;	//this converts coordinates properly
  switch(button){
  case GLUT_LEFT_BUTTON:
    if (state==GLUT_DOWN){
      glBegin(GL_POINTS);
      //3fv takes an array of 3 floats
      glColor3fv(color);
      glVertex2i(x,y);
      glEnd();
      glFlush();
    }break;
  default:break;
  }
}
void keyboard(unsigned char key, int x, int y){
  y = Y - y;	//this also converts coordinates properly
  switch (key){
  case 'q':case 'Q':
    exit(0);
    break;
  case ' ':
    glBegin(GL_POINTS);
    glColor3f(1.0,1.0,1.0);
    glVertex2i(x,y);
    glEnd();
    glFlush();
    break;
  default:
    display();
  }
   }
int main (int argc,char **argv){
  glutInit(&argc,argv);
  glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
  glutInitWindowSize(X,Y);	//your window size
  glutInitWindowPosition(100,100);//your window position
  glutCreateWindow(argv[0]);	//your window name
  glOrtho(0,X-1,0,Y-1,-1,1);	//the coords that will show up in your window
  init();
  glutDisplayFunc(display);
  glutMouseFunc(mouse);
  glutKeyboardFunc(keyboard);
  glutMainLoop();		//note: this will NEVER return.
  return 0;
}