package com.ericgiguere.j2mebook.utils;

import com.sun.kjava.Graphics;

/**
 * Utility class for drawing circles using the Palm user interface
 * classes included with the CLDC reference implementation.  No
 * floating point is required.  This code is taken from
 * Leen Ammeraal's book "Computer Graphics for Java Programmers",
 * published in 1999 by John Wiley & Sons, ISBN 0471981427.
 * For more information, see the book, or else consult any good
 * graphics textbook (or search the web!) for an explanation of
 * Bresenham's algorithm for drawing circles, of which this is
 * an adaptation.
 */

public final class Circle
//***********************
{
    /**
     * Draws a single point by drawing a line starting and
     * ending at the same coordinates.
     *
     * @param g the Graphics object to draw with.
     * @param x the x-coordinate of the point.
     * @param y the y-coordinate of the point.
     */

    private static void putPixel( Graphics g, int x, int y ){
	g.drawLine( x, y, x, y, g.PLAIN );
    }

    /**
     * Draws a circle centered at the given point and with
     * the given radius.
     *
     * @param g  the Graphics object to draw with.
     * @param xC the x-coordinate of the circle's center point.
     * @param yC the y-coordinate of the circle's center point.
     * @param r  the circle's radius.
     */

    public static void draw( Graphics g, int xC, int yC, int r ){
	int x=0, y=r, u=1, v=2*r-1, E=0;
	while( x < y ){
	    putPixel( g, xC+x, yC+y );
	    putPixel( g, xC+y, yC-x );
	    putPixel( g, xC-x, yC-y );
	    putPixel( g, xC-y, yC+x );
	    x++; E += u; u+= 2;
	    if( v < 2 * E ) { y--; E -= v; v -= 2; }
	    if( x > y ) break;
	    putPixel( g, xC+y, yC+x );
	    putPixel( g, xC+x, yC-y );
	    putPixel( g, xC-y, yC-x );
	    putPixel( g, xC-x, yC+y );
	}
    }
}