/* antialiasing.c   */

/* 
	Purpose: This program demonstrates line antialiasing.
*/

#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  */

/* Global variables */
GLfloat angle = 0.0;  /* how far is the line rotated? */

/* Functions */

void printHelp( void )
{
	fprintf(stdout,
		"Line antialiasing.\n\n"
		"r     - rotate line\n"
		"a     - toggle antialiasing\n"
		"Escape key    - exit the program\n\n");
}

GLvoid keyboard( GLubyte key, GLint x, GLint y)
{
    switch (key)
	{
    case KEY_ESC:   /* exit when escape key is pressed */
         exit(0);
	break;

	case 'a':
	case 'A':
	{
		static GLboolean blendOn = GL_TRUE;
		blendOn ? glEnable( GL_BLEND ) : glDisable( GL_BLEND );
		blendOn = !blendOn;
	}
	break;

    case 'r':
		angle += 2.0;
	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();
	}
}

GLvoid display( GLvoid )
{
	/* Do all your OpenGL rendering here */

	glClear( GL_COLOR_BUFFER_BIT );

	glLoadIdentity();
	glRotatef( angle, 0.0, 0.0, 1.0 );

	/* Draw a single line */
	glBegin(GL_LINES);
		glColor3f(1.0,0.25,0.25);
		glVertex2f( 0.0, 0.0 );
		glColor3f(0.5,0.5,0.0);
		glVertex2f( 1.0, 0.0 );
	glEnd();

	checkError( "display" );
	glFlush();
}

void init( void )
{
	glClearColor( 1.0, 1.0, 1.0, 1.0);
	glLineWidth(3.0);

	glEnable( GL_LINE_SMOOTH );
	glHint( GL_LINE_SMOOTH_HINT, GL_NICEST );
	glBlendFunc( GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA );
}

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

	glutInit( &argc, argv );

	glutInitDisplayMode( GLUT_SINGLE | GLUT_RGB );
	glutCreateWindow( argv[0] );

	printHelp( );

    glutKeyboardFunc( keyboard );
    glutSpecialFunc( specialkeys );

	glutDisplayFunc( display );

	init();

	glutMainLoop();

	return 0;
}