sketcher2/src/com/jotuntech/sketcher/common/Canvas.java

package com.jotuntech.sketcher.common;

import java.awt.Image;
import java.awt.image.ImageObserver;
import java.util.LinkedHashSet;
import java.util.Set;

import javax.swing.event.ChangeEvent;
import javax.swing.event.ChangeListener;

public class Canvas implements ImageObserver {
	private int width, height;
	private TwoWayHashMap<Integer, Layer> layerMap;
	private Set<ImageObserver> observers;
	private volatile boolean drawing;

	public Canvas(int width, int height) {
		this.drawing = false;

		this.width = width;
		this.height = height;

		this.layerMap = new TwoWayHashMap<Integer, Layer>();

		this.observers = new LinkedHashSet<ImageObserver>();

		getLayerMap().addChangeListener(new ChangeListener() {
			public void stateChanged(ChangeEvent e) {
				addImageObserverToLayers();
			}
		});
	}

	public int getWidth() {
		return width;
	}

	public int getHeight() {
		return height;
	}

	public TwoWayHashMap<Integer, Layer> getLayerMap() {
		return layerMap;
	}

	public void addImageObserver(ImageObserver observer) {
		observers.add(observer);
	}

	public Set<ImageObserver> getImageObservers() {
		return observers;
	}

	public ImageObserver getImageObserver() {
		return this;
	}

	private void addImageObserverToLayers() {
		for(Layer l : getLayerMap().values()) {
			l.addImageObserver(this);
		}
	}

	public boolean imageUpdate(Image img, int infoflags, int x, int y, int width, int height) {
		for(ImageObserver o : observers) {
			o.imageUpdate(img, infoflags, x, y, width, height);
		}
		return true;
	}

	public void setDrawing(boolean drawing) {
		this.drawing = drawing;
	}

	public boolean isDrawing() {
		return drawing;
	}
}