#include <OpenGL/gl.h>
#include <OpenGL/glu.h>
#include <GLUT/glut.h>

#define WINDOW_WIDTH	640
#define WINDOW_HEIGHT	480

int gl_init(GLvoid) {
	glShadeModel(GL_SMOOTH);

	glClearColor(0.0f, 0.0f, 0.0f, 0.0f);

	glClearDepth(1.0f);
	glEnable(GL_DEPTH_TEST);
	glDepthFunc(GL_LEQUAL);

	glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);

	return 0;
}

int gl_scene_draw(GLvoid) {
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
	glLoadIdentity();

	glTranslatef(-1.5f, 0.0f, -6.0f);

	glBegin(GL_TRIANGLES);
		glVertex3f( 0.0f,  1.0f, 0.0f);
		glVertex3f(-1.0f, -1.0f, 0.0f);
		glVertex3f( 1.0f, -1.0f, 0.0f);
	glEnd();

	glTranslatef(3.0f, 0.0f, 0.0f);

	glBegin(GL_QUADS);
		glVertex3f(-1.0f,  1.0f, 0.0f);
		glVertex3f( 1.0f,  1.0f, 0.0f);
		glVertex3f( 1.0f, -1.0f, 0.0f);
		glVertex3f(-1.0f, -1.0f, 0.0f);
	glEnd();

	return 0;
}

GLvoid gl_scene_scale(GLsizei width, GLsizei height) {
	if(height == 0) height = 1;

	glViewport(0, 0, width, height);

	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();

	gluPerspective(45.0f,(GLfloat)width/(GLfloat)height,0.1f,100.0f);

	glMatrixMode(GL_MODELVIEW);
	glLoadIdentity();
}

int main(int argc, char** argv) {
	glutInit(&argc, argv);
	glutInitDisplayMode (GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
	glutInitWindowSize (WINDOW_WIDTH, WINDOW_HEIGHT);
	glutInitWindowPosition (100, 100);
	glutCreateWindow(argv[0]);

	gl_init();

	glutDisplayFunc(gl_scene_draw);
	glutReshapeFunc(gl_scene_scale);

	glutMainLoop();

	return 0;
}