/*
 * Copyright (c) 1996-1999  Silicon Graphics, Inc.  All rights reserved.
 *
 * THE SOFTWARE IS PROVIDED "AS-IS" AND WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS, IMPLIED OR OTHERWISE, INCLUDING WITHOUT LIMITATION, ANY
 * WARRANTY OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
 *
 * IN NO EVENT SHALL SILICON GRAPHICS BE LIABLE FOR ANY SPECIAL, INCIDENTAL,
 * INDIRECT OR CONSEQUENTIAL DAMAGES OF ANY KIND, OR ANY DAMAGES WHATSOEVER
 * RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER OR NOT ADVISED OF THE
 * POSSIBILITY OF DAMAGE, AND ON ANY THEORY OF LIABILITY, ARISING OUT OF OR IN
 * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

/* input.c - open a window and clear the background.
 *	Set up a callback to handle ASCII keyboard input.
 *
 *	SPACE key		- generates a random background color
 *	Escape Key		- exit program
 */
#include <GL/glut.h>	/* includes gl.h, glu.h */

#include <stdlib.h>
#include <stdio.h>
#include <math.h>

/* Function Prototypes */

GLvoid initgfx( GLvoid );
GLvoid keyboard( GLubyte, GLint, GLint );
GLvoid drawScene( GLvoid );

void checkError( char * );
void printHelp( char * );

/* Global Definitions */

#define KEY_ESC	27	/* ascii value for the escape key */

/* Macro RANDOM() provides a consistent interface across both
 * IRIX and NT platforms to returns a random number between
 * 0.0 and 1.0.
 */

#define RANDOM()      ((double)rand()/RAND_MAX)

void
main( int argc, char *argv[] )
{
	GLsizei width, height;

	glutInit( &argc, argv );

	width = glutGet( GLUT_SCREEN_WIDTH ); 
	height = glutGet( GLUT_SCREEN_HEIGHT );
	glutInitWindowPosition( width / 4, height / 4 );
	glutInitWindowSize( width / 2, height / 2 );
	glutInitDisplayMode( GLUT_RGBA );
	glutCreateWindow( argv[0] );

	initgfx();

	glutKeyboardFunc( keyboard );
	glutDisplayFunc( drawScene ); 

	printHelp( argv[0] );

	glutMainLoop();
}

void printHelp( char *progname )
{
	fprintf(stdout, 
		"\n%s - demonstrates how to handle keyboard input\n\n"
		"SPACE Key	- generates a random background color\n"
		"Escape Key	- exit the program\n\n",
		progname);
}

GLvoid initgfx( GLvoid )
{
	/* set clear color to magenta */
	glClearColor( 1.0, 0.0, 1.0, 1.0 );
}

void checkError( char *label )
{
	GLenum error;
	while ( (error = glGetError()) != GL_NO_ERROR )
		printf( "%s: %s\n", label, gluErrorString(error) );
}

GLvoid keyboard( GLubyte key, GLint x, GLint y )
{
	switch (key) {
	case ' ':	/* SPACE key */
		/* generate a random background color */
		glClearColor( RANDOM(), RANDOM(), RANDOM(), 1.0 ); 
		glutPostRedisplay();
		break;
	case KEY_ESC:	/* Exit when the Escape key is pressed */
		exit(0);
	}
}

GLvoid drawScene( GLvoid )
{
	glClear( GL_COLOR_BUFFER_BIT );

	/* Do all your OpenGL rendering here */

	checkError( "drawScene" );
	glFlush();
}