/*
 * 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.
 */

/* lookat.c - use input from the keyboard to control the viewpoint
 *
 *	F1 key		- print help information
 *	Left Arrow Key	- move the reference point to the left
 *	Right Arrow Key	- move the reference point to the right
 *	Up Arrow Key	- move the reference point up
 *	Down Arrow Key	- move the reference point down
 *	Escape key 	- exit the program
 */

#include <GL/glut.h>	/* includes gl.h, glu.h */
#include <math.h>
#include <stdio.h>	/* for printf */

#include "axes.h"
#include "shapes.h"

/*  Function Prototypes  */

GLvoid  initgfx( GLvoid );
GLvoid  drawScene( GLvoid );
GLvoid  reshape( GLsizei, GLsizei );
GLvoid  keyboard( GLubyte, GLint, GLint );
GLvoid  specialkeys( GLint, GLint, GLint );

void printHelp( char * );

/* Global Definitions */

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

/* Global Variables */

static GLdouble		xRef = 0.0, yRef = 0.0;

static char *progname;

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

	glutInit( &argc, argv );

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

	initgfx();

	glutKeyboardFunc( keyboard );
	glutSpecialFunc( specialkeys );
	glutReshapeFunc( reshape );
	glutDisplayFunc( drawScene ); 

	progname = argv[0];
	printHelp( progname );

	glutMainLoop();
}

void
printHelp( char *progname )
{
	fprintf(stdout, "\n%s - uses keyboard input to control the "
		"location of the reference point point\n\n"
		"F1 Key			- print Help information\n"
		"Left Arrow Key		- move reference point to the left\n"
		"Right Arrow Key	- move reference point to the right\n"
		"Up Arrow Key		- move reference point up\n"
		"Down Arrow Key		- move reference point down\n"
		"Escape Key		- exit the program\n\n",
		progname);
}

GLvoid
initgfx( GLvoid )
{
	glClearColor( 0.0, 0.0, 0.0, 1.0 );
	glShadeModel( GL_FLAT );
	glEnable( GL_DEPTH_TEST );
}

GLvoid
reshape( GLsizei width, GLsizei height )
{
	GLdouble	aspect;

	glViewport( 0, 0, width, height );

	aspect = (GLdouble) width / (GLdouble) height;

	glMatrixMode( GL_PROJECTION );
	glLoadIdentity();
	gluPerspective( 45.0, aspect, 1.0, 20.0 );
	glMatrixMode( GL_MODELVIEW );
}

GLvoid 
keyboard( GLubyte key, GLint x, GLint y )
{
	switch (key) {
	case KEY_ESC:	/* Exit when the Escape key is pressed */
		exit(0);
	}
}

GLvoid 
specialkeys( GLint key, GLint x, GLint y )
{
	switch (key) {
	case GLUT_KEY_F1:	/* print Help */
		printHelp( progname );
		break;

	case GLUT_KEY_LEFT:	/* move reference point to the left */
		xRef -= 0.5;
		if (xRef < -4.0) xRef = -4.0;
		glutPostRedisplay();
 		break;

	case GLUT_KEY_RIGHT:	/* move reference point to the right */
		xRef += 0.5;
		if (xRef > 4.0) xRef = 4.0;
		glutPostRedisplay();
		break;

	case GLUT_KEY_UP:	/* move reference point up */
		yRef += 0.5;
		if (yRef > 3.0) yRef = 3.0;
		glutPostRedisplay();
		break;

	case GLUT_KEY_DOWN:	/* move reference point down */
		yRef -= 0.5;
		if (yRef < -3.0) yRef = -3.0;
		glutPostRedisplay();
		break;
	}
}

GLvoid
drawScene( GLvoid )
{
	static GLfloat	upperArmColor[] = { 1.0f, 0.0f, 0.0f };
	static GLfloat	lowerArmColor[] = { 0.8f, 0.5f, 0.5f };

	glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );

	glPushMatrix();

		/* Move the reference point */
		gluLookAt( 0.0, 0.0, 8.0, xRef, yRef, 0.0, 0.0, 1.0, 0.0 );

		XYaxes();

		/* Draw the shoulder at the new origin */
		glTranslatef( 1.0f, 0.0f, 0.0f ); 
    		glColor3fv( upperArmColor );
		WireBox( 2.0, 0.4, 1.0 );

		/* Draw the lower arm at the end of the upper arm and 
	 	 * rotate it 45 degrees */
		glTranslatef( 1.0f, 0.0f, 0.0f );
		glRotatef( 45.0f, 0.0f, 0.0f, 1.0f );
		glTranslatef( 1.0f, 0.0f, 0.0f );
    		glColor3fv( lowerArmColor );
		WireBox( 2.0, 0.4, 1.0 );
	glPopMatrix();

	glutSwapBuffers();
}