//********************************************************************************/
// OpenGL program illustartes: animation, interaction.
//
// OpenGL program that draws a square centered at the orign
// and spins it around the origin
// keyboard calback to speed up and speed down the rotation
// qiit with q/Q

// File: spinSquare.cpp
// Date: 9/24/2006
/*********************************************************************************/
#include<stdio.h>
#include<GL/glut.h>
#include <math.h>
#include <stdlib.h>


// modeling constants
#define PI               3.141592

// globals
GLdouble theta = 0;          // rotation angle 
GLsizei wnd_w = 500;         // display window width 
GLsizei wnd_h = 500;         // display window height
GLfloat spin_speed = PI/180; // inceremt for angle in  rad


//prototypes
void help();                           //print instructions
void myinit();                         // OpenGL init
void display();                        // display callback
void myreshape(GLsizei, GLsizei);      // reshape callback
void update_angle();                    // idle callback
void control_speed(GLubyte, GLint, GLint);   // keyboard callback

/****************/
/***** MAIN *****/
/****************/
int main(int argc, char **argv)
{
	glutInit(&argc, argv);
	glutInitDisplayMode(GLUT_DOUBLE|GLUT_RGB);
	glutInitWindowSize(wnd_w,wnd_h);
	glutInitWindowPosition(0,0);
	glutCreateWindow("spinning square, speed control with menu");
	
	myinit();
	
	// register callbacks
	glutDisplayFunc(display);
    glutReshapeFunc(myreshape);
	glutIdleFunc(update_angle);
	glutKeyboardFunc(control_speed);
		
	glutMainLoop();

	return 0;
}
/********************************/
/***** FUNCTION DEFINITIONS *****/
/********************************/

/******************************************************************************/
// Print instructions
/******************************************************************************/
void help()
{
	printf("Spin the square");
	printf("   To speed up press s\n   To slow down press d\n   Press q to quit\n");

}
/*********************************************************************************/
// OpenGL init
/*********************************************************************************/
void myinit()
{
	help();
	glClearColor(0.0,0.0,0.0,1.0);  // white

   	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	gluOrtho2D(-2, 2, -2, 2); // origin at center of 4x4 clip window
	glMatrixMode(GL_MODELVIEW);
	
}


/*********************************************************************************/
// display callback
/*********************************************************************************/
void display()
{
    glClear(GL_COLOR_BUFFER_BIT);
	
	
	glBegin(GL_POLYGON);
	  glColor3f(1.0, 0.0, 0.0);
	  glVertex2d(cos(theta), sin(theta));
	  glColor3f(0.0, 0.1, 0.0);
	  glVertex2d(-sin(theta), cos(theta));
	  glColor3f(1.0, 0.0, 1.0);
	  glVertex2d(-cos(theta), -sin(theta));
	  glColor3f(1.0, 1.0, 0.0);
	  glVertex2d(sin(theta), -cos(theta));
	glEnd();
	  
   glutSwapBuffers();
   
}
/*********************************************************************************/
// window events (reshape) callback.
// keeps the viewport aspect ratio 1, so drawings do not get distorted
/*********************************************************************************/
void myreshape(GLsizei w, GLsizei h)
{
	wnd_w = w; wnd_h = h;
    
	if (h < w)
		w=h;

	// adjust viewport (to preserve the original aspect ratio), and clear.
	glViewport(0, 0, w, w); 
   
	glutPostRedisplay();
	
}

/*********************************************************************************/
// idle callback updates rotation angle for spinning 
/*********************************************************************************/
void update_angle(void)
{	
	theta += spin_speed;

	if (theta>360) theta-=360;
	
	glutPostRedisplay();
}

/*****************************************************************************/
// keyboard callback increase spead, decrease spid or quit
/*****************************************************************************/

void control_speed(GLubyte key, GLint x, GLint y)
{
	switch (key) {
		case('q'):  
	    case('Q'): exit (0); break;
		case('s'):
        case( 'S'): spin_speed *=2; break;
		case( 'd'):
        case( 'D'): spin_speed /= 2;
	}
    
	  	 	
    glutPostRedisplay( );
}