/* OpenGL erabiltzen duen programatxoa */
/* konpilatzeko gcc -lGL -lGLU -lglut agindua erabili behar da. */

#include <gl/glut.h>
#include <stdio.h>
#include <stdlib.h>

static float	 LOCAL_Red = 0.0f;

static void marraztu(void)
{
	glClear( GL_COLOR_BUFFER_BIT );

	glColor3f( 0.0f, 0.0f, 0.0f );
	glBegin( GL_POLYGON );
		glVertex3f( -0.3f, -0.3f, 0.0f );
		glVertex3f(  0.3f, -0.3f, 0.0f );
		glVertex3f(  0.3f,  0.3f, 0.0f );
		glVertex3f( -0.3f,  0.3f, 0.0f );
	glEnd();
	
	// Set state values that define properties that
	// will be assigned to future primitives
	glColor3f( LOCAL_Red, 1-LOCAL_Red, LOCAL_Red );
	glLineWidth( 10.0f );

	glBegin( GL_LINES );
		glVertex3f( -0.8f, -0.8f, 0.0f );
		glVertex3f(  0.8f,  0.8f, 0.0f );
	glEnd();

	glFlush();
}

// This function will be called whenever the user pushes one key
static void teklatua (unsigned char key, int x, int y)
{
	switch(key)
	{
	case 'r': 
		if ( LOCAL_Red > 0.01f ) LOCAL_Red -= 0.1f;
		printf ("red   : ");
		break;
	case 'R':
		if ( LOCAL_Red < 1.0f ) LOCAL_Red += 0.1f;
		printf ("red   : ");
		break;
	case 27:  // <ESC>
		exit( 0 );
		break;
	default:
		printf("%d %c\n", key, key );
	}

	printf ("(R = %f) (G = %f) (B = %f) \n", LOCAL_Red, 1-LOCAL_Red, LOCAL_Red );

	// The screen must be drawn to show the new values
	glutPostRedisplay();
}

int main(int argc, char** argv)
{

	printf("OpenGL erabiltzen duen programatxoa: r eta R teklen bidez kolorea aldatzen da\n");

	glutInit(&argc,argv);
	glutInitDisplayMode ( GLUT_RGB );
	glutInitWindowSize ( 500, 500 );
	glutInitWindowPosition ( 100, 100 );
	glutCreateWindow( "OpenGL leihoa" );

	glutDisplayFunc( marraztu );
	glutKeyboardFunc( teklatua );

	glClearColor( 0.0f, 0.0f, 0.7f, 1.0f );

	glutMainLoop();

	return 0;   
}