/* extra6a.c  */


/* 
	Purpose:	This program constructs a simple robot arm that can be rotated at 
				the elbow and wrist. 
				It displays the angles at the foot of the screen. 
*/



#ifdef __APPLE__
#include <GLUT/glut.h>
#else
#include <GL/glut.h>
#endif

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

#define KEY_ESC 27      /* glut doesn't define this one */


/* Global Constants and Variables */

static GLfloat mEangle;  /* elbow angle */
static GLfloat mSangle;  /* shoulder angle */
static GLfloat mWangle;  /* wrist angle */

static const GLfloat mSegmentLength = 2.0;  /* length of robot arm segments */   
static const GLsizei mStatusBarHeight = 25;   /* height of box that we write the angle info in */


void printHelp( void )
{
	fprintf(stdout,
		"\nRobot Arm\n\n"
    "Escape key - exit the program\n\n"
    "s - rotate the shoulder\n"
    "e - rotate the elbow\n"
    "w - rotate the wrist\n");
}

GLvoid keyboard( GLubyte key, GLint x, GLint y)
{
	switch (key) 
	{

 	case KEY_ESC:   /* exit when escape key is pressed */
		exit(0);
    break;
  
	case 'e':
	case 'E':
		mEangle += 2.0;
		if (mEangle > 360.0) mEangle -= 360.0;
	break;

	case 's':
	case 'S':
		mSangle += 2.0;
		if (mSangle > 360.0) mSangle -= 360.0;
	break;

	case 'w':
	case 'W':
		mWangle += 2.0;
		if (mWangle > 360.0) mWangle -= 360.0;
	break;

  }
	glutPostRedisplay();
}


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


GLvoid checkError( const char* const label )
{
	GLenum error;

	error = glGetError();
	while ( GL_NO_ERROR != error )
	{
		fprintf( stderr,"%s: %s\n", label, gluErrorString(error) );
		error = glGetError();
	}
}

void reshape(GLint width, GLint height)
{
	GLdouble aspect;

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

	/* We still want the output to cover the whole window */
	glViewport(0, 0, width, height);

	glMatrixMode( GL_PROJECTION );
	glLoadIdentity();

	/* Get the viewing volume set up to match the aspect ratio of the viewport */
	if (width > height)
	{
		glOrtho(-6 * aspect, 6 * aspect, -6, 6, -2, 2);
	}
	else
	{
		glOrtho(-6, 6, -6 / aspect, 6 / aspect, -2, 2);
	}

	glMatrixMode( GL_MODELVIEW );
} 


void displayStr(char *str, GLfloat x, GLfloat y)
{
  /* choose what font we wish to use */
	void* fontName = GLUT_BITMAP_HELVETICA_18;
 
  unsigned int index = 0;

  /* where do we want the text to go */
  glRasterPos2f(x, y);

  /* Display the string on the screen */
  while (str[index] != 0  && index < 1000)
	{
		glutBitmapCharacter(fontName, str[index]);  
    ++index;
	}	
  
}

GLvoid drawSegment( GLvoid )
{
	glPushMatrix();
		glScalef(mSegmentLength, 0.2, 0.2);
		glutWireCube(1.0);		
	glPopMatrix();
}

GLvoid display( GLvoid )
{
	GLsizei ww;
	GLsizei wh;
	char str[255];

	ww = glutGet( GLUT_WINDOW_WIDTH );
	wh = glutGet( GLUT_WINDOW_HEIGHT );  


	/* Main view of robot arm */
	glViewport(0.0, mStatusBarHeight, ww, wh-mStatusBarHeight);

	glClear(GL_COLOR_BUFFER_BIT);

	glPushMatrix();

		/* Draw the elbow to shoulder segment */
		glRotatef(mSangle, 0.0, 0.0, 1.0);
		glTranslatef(mSegmentLength/2, 0.0, 0.0);
		drawSegment();

		/* Draw the wrist to elbow segment */		
		glTranslatef(mSegmentLength/2, 0.0, 0.0);
		glRotatef(mEangle, 0.0, 0.0, 1.0);
		glTranslatef(mSegmentLength/2, 0.0, 0.0);
		drawSegment();

		/* Draw the wrist to fingers segment */
		glTranslatef(mSegmentLength/2, 0.0, 0.0);
		glRotatef(mWangle, 0.0, 0.0, 1.0);
		glTranslatef(mSegmentLength/2, 0.0, 0.0);
		drawSegment();

	glPopMatrix();

	glViewport(0.0, 0.0, ww, mStatusBarHeight);

	sprintf(str, "s: %f\t e:  %f\t w: %f", mSangle, mEangle, mWangle);
	displayStr(str, -6, 0);

	checkError( "display" );

	glFlush();

}


void init( void )
{
	glClearColor( 1.0, 1.0, 1.0, 1.0);
	glColor3f(1.0,0.0,0.0);
	glLineWidth(3.0);
}


int main( int argc, char *argv[] )
{
	glutInit( &argc, argv );
	glutInitDisplayMode( GLUT_SINGLE | GLUT_RGB );
	glutCreateWindow( argv[0] );

	init();
     
	glutKeyboardFunc( keyboard );
	glutSpecialFunc( specialkeys );
	glutReshapeFunc( reshape );
	glutDisplayFunc( display ); 

	printHelp( );

	glutMainLoop();

	return 0;
}