#include <GL/glut.h>
//we're going to build the main function of our application. 
//The main function will perform the required initializations and start the event processing loop. 
//All the functions in GLUT have the prefix glut, 
//and those which perform some kind of initialization have the prefix glutInit. 

void renderScene(void);

void main(int argc, char **argv) {
	//The first thing you must do is call the function glutInit. It initializes GLUT library.
	//use the same parameters as those to main()
	glutInit(&argc, argv);

	//2. Define the display mode using the function glutInitDisplayMode(unsigned int mode)
	// mode -> specifies the display mode (a Bollean combination of possible predefined values in GLUT: color mode, number and type of buffers)
	// (1) color model constants include: GLUT_RGBA (default) or GLUT_RGB or GLUT_INDEX
	// (2) number of buffers: GLUT_SINGLE or GLUT_DOUBLE
	// (3) other particular set of buffers: GLUT_DEPTH, GLUT_ACCUM, GLUT_STENCIL...
	//  check detailed explanations at:
    //  http://pyopengl.sourceforge.net/documentation/manual/glutInitDisplayMode.3GLUT.html
	// just OR all parameters you want here
	glutInitDisplayMode(GLUT_SINGLE | GLUT_RGBA);


	//3. Define our window
	//3.1. Establish the window's position, i.e. its top left corner. 
	//In order to do this we use the function glutInitWindowPosition. 
	//void glutInitWindowPosition(int x, int y); 
	// x-> number of pixels from the left of the screen
	// y-> number of pixels from the top of the screen
	glutInitWindowPosition(100,100);


	//3.2. Choose the window size, using the function glutInitWindowSize(int width, int height).
	// width -> the width of the window, height -> the height of the window
	glutInitWindowSize(640,480);

		
	//3.3 After these settings, we can create the window with a title
	glutCreateWindow("Hello World");

	//4. Assign a function responsible for the rendering (register a callback)
	//void glutDisplayFunc(void (*func)(void));
	// func -> the name of the function to be called when the window needs to be redrawn (should not be NULL)
	glutDisplayFunc(renderScene);
	
	//Finally, get in the application event processing loop
	// GLUT provides a function that gets the application in a never ending loop, 
	// always waiting for the next event to process
	glutMainLoop();
}

void renderScene(void) {
	glClear(GL_COLOR_BUFFER_BIT);
	glBegin(GL_TRIANGLES);
		glVertex3f(-0.5,-0.5,0.0);
		glVertex3f(0.5,0.0,0.0);
		glVertex3f(0.0,0.5,0.0);
	glEnd();
	glFlush();
}