/*
 * BufferCanvas
 * 
 * Version 1.1 - Java 1.1 compatible
 *
 * Dec 10 2001
 * 
 * Copyright 2001 David Joiner and the Shodor Education Foundation
 */
import java.awt.*; 
 
/**
 * BufferCanvas is a canvas with double buffering
 */
public abstract class BufferCanvas extends Canvas {

    /*
     * Member variables
     */

    protected Image im;
    protected Graphics buf=null;
    protected int imWidth=100;
    protected int imHeight=20;
    private boolean clearScreen=true;

    /*
     * Constructors
     */
     
    public BufferCanvas () {
        super();
        
        checkSize();
    }

    /*
     * Painting methods
     */
     
    public void update(Graphics g) {
        // check to see if the component has been implemented or resized
        if (checkSize()) {
            repaintBuffer();
        }
        if (!paintingBuffer) {
            g.drawImage(im,0,0,this);
        } else {
            repaint(2);
        }
    }
    
    boolean paintingBuffer = false;
    
    public abstract void paintBuffer(Graphics buf);
    
    public void repaintBuffer() {
        if (buf != null) {
            paintingBuffer = true;
            if(clearScreen) {
                Color fgColor = buf.getColor();
                buf.setColor(getBackground());
                buf.fillRect(0,0,imWidth,imHeight);
                buf.setColor(fgColor);
            }
            paintBuffer(buf);
            paintingBuffer = false;
            repaint();
        }
    }
    
    public void paint(Graphics g) {
        update(g);
    }
            
    public boolean checkSize() {
        // check to see if size data has changed and that it is usable
        Dimension size=getSize();
        if (imWidth==size.width && imHeight==size.height) {
            if (size.height>0 && size.width>0 && buf==null) {
                imWidth = size.width;
                imHeight = size.height;
                readyBuffer();
                return true;
            } else {
                return false;
            }
        } else {
            if (size.height>0 && size.width>0) {
                imWidth = size.width;
                imHeight = size.height;
                readyBuffer();
                return true;
            } else {
                return false;
            }
        }
    }
    
    public int getWidth() {
        return getSize().width;
    }
    
    public int getHeight() {
        return getSize().height;
    }

    public void readyBuffer() {
        if (buf!=null) buf.dispose();
        im=createImage(imWidth,imHeight);
        buf=im.getGraphics();
        repaint();
    }
    
    public void thickLine(Graphics g, int x1,int y1,int x2,int y2) {
        g.drawLine(x1,y1,x2,y2);
        g.drawLine(x1+1,y1,x2+1,y2);
        g.drawLine(x1,y1+1,x2,y2+1);
        g.drawLine(x1-1,y1,x2-1,y2);
        g.drawLine(x1,y1-1,x2,y2-1);
    }
}