console-proxy/src/com/cloud/consoleproxy/ConsoleProxyClientBase.java - cloudstack - Git at Google

 package com.cloud.consoleproxy;

 import java.awt.Image;
 import java.awt.Rectangle;
 import java.util.List;

 import org.apache.log4j.Logger;

 import com.cloud.consoleproxy.util.TileInfo;
 import com.cloud.consoleproxy.util.TileTracker;
 import com.cloud.consoleproxy.vnc.FrameBufferCanvas;

 /**
  *
  * @author Kelven Yang
  *
  * ConsoleProxyClientBase implements a base console client class that can be extended to realize
  * an instance of specialized console protocol implementation, such as VNC or RDP
  *
  * It mainly implements the features needed by front-end AJAX viewer
  *
  */
 public abstract class ConsoleProxyClientBase implements ConsoleProxyClient, ConsoleProxyClientListener {
 	private static final Logger s_logger = Logger.getLogger(ConsoleProxyClientBase.class);

 	private static int s_nextClientId = 0;
 	protected int clientId = getNextClientId();

 	protected long ajaxSessionId = 0;

 	protected boolean dirtyFlag = false;
 	protected Object tileDirtyEvent = new Object();
 	protected TileTracker tracker;
 	protected AjaxFIFOImageCache ajaxImageCache = new AjaxFIFOImageCache(2);

 	protected String host;
 	protected int port;
 	protected String passwordParam;
 	protected String tag = "";
 	protected String ticket = "";
 	protected long createTime = System.currentTimeMillis();
 	protected long lastFrontEndActivityTime = System.currentTimeMillis();

 	protected boolean framebufferResized = false;
 	protected int resizedFramebufferWidth;
 	protected int resizedFramebufferHeight;

 	public ConsoleProxyClientBase() {
 		tracker = new TileTracker();
 		tracker.initTracking(64, 64, 800, 600);
 	}

 	//
 	// interface ConsoleProxyClient
 	//
 	@Override
 	public int getClientId() {
 		return clientId;
 	}

 	public abstract boolean isHostConnected();
 	public abstract boolean isFrontEndAlive();

 	@Override
 	public long getAjaxSessionId() {
 		return this.ajaxSessionId;
 	}

 	@Override
 	public AjaxFIFOImageCache getAjaxImageCache() {
 		return ajaxImageCache;
 	}

 	public Image getClientScaledImage(int width, int height) {
 		FrameBufferCanvas canvas = getFrameBufferCavas();
 		if(canvas != null)
 			return canvas.getFrameBufferScaledImage(width, height);

 		return null;
 	}

 	public abstract void sendClientRawKeyboardEvent(InputEventType event, int code, int modifiers);
 	public abstract void sendClientMouseEvent(InputEventType event, int x, int y, int code, int modifiers);

 	@Override
 	public long getClientCreateTime() {
 		return createTime;
 	}

 	@Override
 	public long getClientLastFrontEndActivityTime() {
 		return lastFrontEndActivityTime;
 	}

 	@Override
 	public String getClientHostAddress() {
 		return host;
 	}

 	@Override
 	public int getClientHostPort() {
 		return port;
 	}

 	@Override
 	public String getClientHostPassword() {
 		return passwordParam;
 	}

 	@Override
 	public String getClientTag() {
 		return tag;
 	}

 	@Override
 	public abstract void initClient(String clientHostAddress, int clientHostPort,
 		String clientHostPassword, String clientTag, String ticket);

 	@Override
 	public abstract void closeClient();

 	//
 	// interface FrameBufferEventListener
 	//
 	@Override
 	public void onFramebufferSizeChange(int w, int h) {
 		tracker.resize(w, h);

 		synchronized(this) {
 			framebufferResized = true;
 			resizedFramebufferWidth = w;
 			resizedFramebufferHeight = h;
 		}

 		signalTileDirtyEvent();
 	}

 	@Override
 	public void onFramebufferUpdate(int x, int y, int w, int h) {
 		if(s_logger.isTraceEnabled())
 			s_logger.trace("Frame buffer update {" + x + "," + y + "," + w + "," + h + "}");
 		tracker.invalidate(new Rectangle(x, y, w, h));

 		signalTileDirtyEvent();
 	}

 	//
 	// AJAX Image manipulation
 	//
 	public byte[] getFrameBufferJpeg() {
 		FrameBufferCanvas canvas = getFrameBufferCavas();
 		if(canvas != null)
 			return canvas.getFrameBufferJpeg();

 		return null;
 	}

 	public byte[] getTilesMergedJpeg(List<TileInfo> tileList, int tileWidth, int tileHeight) {
 		FrameBufferCanvas canvas = getFrameBufferCavas();
 		if(canvas != null)
 			return canvas.getTilesMergedJpeg(tileList, tileWidth, tileHeight);
 		return null;
 	}

 	private String prepareAjaxImage(List<TileInfo> tiles, boolean init) {
 		byte[] imgBits;
 		if(init)
 			imgBits = getFrameBufferJpeg();
 		else
 			imgBits = getTilesMergedJpeg(tiles, tracker.getTileWidth(), tracker.getTileHeight());

 		if(imgBits == null) {
 			s_logger.warn("Unable to generate jpeg image");
 		} else {
 			if(s_logger.isTraceEnabled())
 				s_logger.trace("Generated jpeg image size: " + imgBits.length);
 		}

 		int key = ajaxImageCache.putImage(imgBits);
 		StringBuffer sb = new StringBuffer("/ajaximg?host=");
 		sb.append(host).append("&port=").append(port).append("&sid=").append(passwordParam);
 		sb.append("&key=").append(key).append("&ts=").append(System.currentTimeMillis());
 		return sb.toString();
 	}

 	private String prepareAjaxSession(boolean init) {
 		if(init) {
 			synchronized(this) {
 				ajaxSessionId++;
 			}
 		}

 		StringBuffer sb = new StringBuffer();

 		sb.append("/ajax?host=").append(host).append("&port=").append(port);
 		sb.append("&sid=").append(passwordParam).append("&sess=").append(ajaxSessionId);
 		return sb.toString();
 	}

 	@Override
 	public String onAjaxClientKickoff() {
 		return "onKickoff();";
 	}

 	private boolean waitForViewerReady() {
 		long startTick = System.currentTimeMillis();
 		while(System.currentTimeMillis() - startTick < 5000) {
 			if(getFrameBufferCavas() != null)
 				return true;

 			try {
 				Thread.sleep(100);
 			} catch (InterruptedException e) {
 			}
 		}
 		return false;
 	}

 	private String onAjaxClientConnectFailed() {
 		return "<html><head></head><body><div id=\"main_panel\" tabindex=\"1\"><p>" +
 			"Unable to start console session as connection is refused by the machine you are accessing" +
 			"</p></div></body></html>";
 	}

 	@Override
 	public String onAjaxClientStart(String title, List<String> languages, String guest) {
 		updateFrontEndActivityTime();

 		if(!waitForViewerReady())
 			return onAjaxClientConnectFailed();

 		synchronized(this) {
 			ajaxSessionId++;
 			framebufferResized = false;
 		}

 		int tileWidth = tracker.getTileWidth();
 		int tileHeight = tracker.getTileHeight();
 		int width = tracker.getTrackWidth();
 		int height = tracker.getTrackHeight();

 		if(s_logger.isTraceEnabled())
 			s_logger.trace("Ajax client start, frame buffer w: " + width + ", " + height);

 		int retry = 0;
 		tracker.initCoverageTest();
 		while(!tracker.hasFullCoverage() && retry < 10) {
 			try {
 				Thread.sleep(1000);
 			} catch (InterruptedException e) {
 			}
 			retry++;
 		}

 		List<TileInfo> tiles = tracker.scan(true);
 		String imgUrl = prepareAjaxImage(tiles, true);
 		String updateUrl = prepareAjaxSession(true);

 		StringBuffer sbTileSequence = new StringBuffer();
 		int i = 0;
 		for(TileInfo tile : tiles) {
 			sbTileSequence.append("[").append(tile.getRow()).append(",").append(tile.getCol()).append("]");
 			if(i < tiles.size() - 1)
 				sbTileSequence.append(",");

 			i++;
 		}

 		return getAjaxViewerPageContent(sbTileSequence.toString(), imgUrl,
 			updateUrl, width, height, tileWidth, tileHeight, title,
 			ConsoleProxy.keyboardType == ConsoleProxy.KEYBOARD_RAW,
 			languages, guest);
 	}

 	private String getAjaxViewerPageContent(String tileSequence, String imgUrl, String updateUrl, int width,
 		int height, int tileWidth, int tileHeight, String title, boolean rawKeyboard, List<String> languages, String guest) {

 		StringBuffer sbLanguages = new StringBuffer("");
 		if(languages != null) {
 			for(String lang : languages) {
 				if(sbLanguages.length() > 0) {
 					sbLanguages.append(",");
 				}
 				sbLanguages.append(lang);
 			}
 		}

 		String[] content = new String[] {
 			"<html>",
 			"<head>",
 			"<script type=\"text/javascript\" language=\"javascript\" src=\"/resource/js/jquery.js\"></script>",
 			"<script type=\"text/javascript\" language=\"javascript\" src=\"/resource/js/cloud.logger.js\"></script>",
 			"<script type=\"text/javascript\" language=\"javascript\" src=\"/resource/js/ajaxviewer.js\"></script>",
 			"<script type=\"text/javascript\" language=\"javascript\" src=\"/resource/js/handler.js\"></script>",
 			"<link rel=\"stylesheet\" type=\"text/css\" href=\"/resource/css/ajaxviewer.css\"></link>",
 			"<link rel=\"stylesheet\" type=\"text/css\" href=\"/resource/css/logger.css\"></link>",
 			"<title>" + title + "</title>",
 			"</head>",
 			"<body>",
 			"<div id=\"toolbar\">",
 			"<ul>",
 				"<li>",
 					"<a href=\"#\" cmd=\"sendCtrlAltDel\">",
 						"<span><img align=\"left\" src=\"/resource/images/cad.gif\" alt=\"Ctrl-Alt-Del\" />Ctrl-Alt-Del</span>",
 					"</a>",
 				"</li>",
 				"<li>",
 					"<a href=\"#\" cmd=\"sendCtrlEsc\">",
 						"<span><img align=\"left\" src=\"/resource/images/winlog.png\" alt=\"Ctrl-Esc\" style=\"width:16px;height:16px\"/>Ctrl-Esc</span>",
 					"</a>",
 				"</li>",

 				"<li class=\"pulldown\">",
 					"<a href=\"#\">",
 						"<span><img align=\"left\" src=\"/resource/images/winlog.png\" alt=\"Keyboard\" style=\"width:16px;height:16px\"/>Keyboard</span>",
 					"</a>",
 					"<ul>",
 		    			"<li><a href=\"#\" cmd=\"keyboard_us\"><span>Standard (US) keyboard</span></a></li>",
 		    			"<li><a href=\"#\" cmd=\"keyboard_jp\"><span>Japanese keyboard</span></a></li>",
 					"</ul>",
 				"</li>",
 			"</ul>",
 			"<span id=\"light\" class=\"dark\" cmd=\"toggle_logwin\"></span>",
 			"</div>",
 			"<div id=\"main_panel\" tabindex=\"1\"></div>",
 			"<script language=\"javascript\">",
 			"var acceptLanguages = '" + sbLanguages.toString() + "';",
 			"var tileMap = [ " + tileSequence + " ];",
 			"var ajaxViewer = new AjaxViewer('main_panel', '" + imgUrl + "', '" + updateUrl + "', tileMap, ",
 				String.valueOf(width) + ", " + String.valueOf(height) + ", " + String.valueOf(tileWidth) + ", " + String.valueOf(tileHeight) + ");",

 			"$(function() {",
 				"ajaxViewer.start();",
 			"});",

 			"</script>",
 			"</body>",
 			"</html>"
 		};

 		StringBuffer sb = new StringBuffer();
 		for(int i = 0; i < content.length; i++)
 			sb.append(content[i]);

 		return sb.toString();
 	}

 	public String onAjaxClientDisconnected() {
 		return "onDisconnect();";
 	}

 	@Override
 	public String onAjaxClientUpdate() {
 		updateFrontEndActivityTime();
 		if(!waitForViewerReady())
 			return onAjaxClientDisconnected();

 		synchronized(tileDirtyEvent) {
 			if(!dirtyFlag) {
 				try {
 					tileDirtyEvent.wait(3000);
 				} catch(InterruptedException e) {
 				}
 			}
 		}

 		boolean doResize = false;
 		synchronized(this) {
 			if(framebufferResized) {
 				framebufferResized = false;
 				doResize = true;
 			}
 		}

 		List<TileInfo> tiles;

 		if(doResize)
 			tiles = tracker.scan(true);
 		else
 			tiles = tracker.scan(false);
 		dirtyFlag = false;

 		String imgUrl = prepareAjaxImage(tiles, false);
 		StringBuffer sbTileSequence = new StringBuffer();
 		int i = 0;
 		for(TileInfo tile : tiles) {
 			sbTileSequence.append("[").append(tile.getRow()).append(",").append(tile.getCol()).append("]");
 			if(i < tiles.size() - 1)
 				sbTileSequence.append(",");

 			i++;
 		}

 		return getAjaxViewerUpdatePageContent(sbTileSequence.toString(), imgUrl, doResize,
 			resizedFramebufferWidth, resizedFramebufferHeight,
 			tracker.getTileWidth(), tracker.getTileHeight());
 	}

 	private String getAjaxViewerUpdatePageContent(String tileSequence, String imgUrl, boolean resized, int width,
 		int height, int tileWidth, int tileHeight) {

 		String[] content = new String[] {
 			"tileMap = [ " + tileSequence + " ];",
 			resized ? "ajaxViewer.resize('main_panel', " + width + ", " + height + " , " + tileWidth + ", " + tileHeight + ");" : "",
 			"ajaxViewer.refresh('" + imgUrl + "', tileMap, false);"
 		};

 		StringBuffer sb = new StringBuffer();
 		for(int i = 0; i < content.length; i++)
 			sb.append(content[i]);

 		return sb.toString();
 	}

 	//
 	// Helpers
 	//
 	private synchronized static int getNextClientId() {
 		return ++s_nextClientId;
 	}

 	private void signalTileDirtyEvent() {
 		synchronized(tileDirtyEvent) {
 			dirtyFlag = true;
 			tileDirtyEvent.notifyAll();
 		}
 	}

 	public void updateFrontEndActivityTime() {
 		lastFrontEndActivityTime = System.currentTimeMillis();
 	}

 	protected abstract FrameBufferCanvas getFrameBufferCavas();
 }
	package com.cloud.consoleproxy;

	import java.awt.Image;
	import java.awt.Rectangle;
	import java.util.List;

	import org.apache.log4j.Logger;

	import com.cloud.consoleproxy.util.TileInfo;
	import com.cloud.consoleproxy.util.TileTracker;
	import com.cloud.consoleproxy.vnc.FrameBufferCanvas;

	/**
	*
	* @author Kelven Yang
	*
	* ConsoleProxyClientBase implements a base console client class that can be extended to realize
	* an instance of specialized console protocol implementation, such as VNC or RDP
	*
	* It mainly implements the features needed by front-end AJAX viewer
	*
	*/
	public abstract class ConsoleProxyClientBase implements ConsoleProxyClient, ConsoleProxyClientListener {
	private static final Logger s_logger = Logger.getLogger(ConsoleProxyClientBase.class);

	private static int s_nextClientId = 0;
	protected int clientId = getNextClientId();

	protected long ajaxSessionId = 0;

	protected boolean dirtyFlag = false;
	protected Object tileDirtyEvent = new Object();
	protected TileTracker tracker;
	protected AjaxFIFOImageCache ajaxImageCache = new AjaxFIFOImageCache(2);

	protected String host;
	protected int port;
	protected String passwordParam;
	protected String tag = "";
	protected String ticket = "";
	protected long createTime = System.currentTimeMillis();
	protected long lastFrontEndActivityTime = System.currentTimeMillis();

	protected boolean framebufferResized = false;
	protected int resizedFramebufferWidth;
	protected int resizedFramebufferHeight;

	public ConsoleProxyClientBase() {
	tracker = new TileTracker();
	tracker.initTracking(64, 64, 800, 600);
	}

	//
	// interface ConsoleProxyClient
	//
	@Override
	public int getClientId() {
	return clientId;
	}

	public abstract boolean isHostConnected();
	public abstract boolean isFrontEndAlive();

	@Override
	public long getAjaxSessionId() {
	return this.ajaxSessionId;
	}

	@Override
	public AjaxFIFOImageCache getAjaxImageCache() {
	return ajaxImageCache;
	}

	public Image getClientScaledImage(int width, int height) {
	FrameBufferCanvas canvas = getFrameBufferCavas();
	if(canvas != null)
	return canvas.getFrameBufferScaledImage(width, height);

	return null;
	}

	public abstract void sendClientRawKeyboardEvent(InputEventType event, int code, int modifiers);
	public abstract void sendClientMouseEvent(InputEventType event, int x, int y, int code, int modifiers);

	@Override
	public long getClientCreateTime() {
	return createTime;
	}

	@Override
	public long getClientLastFrontEndActivityTime() {
	return lastFrontEndActivityTime;
	}

	@Override
	public String getClientHostAddress() {
	return host;
	}

	@Override
	public int getClientHostPort() {
	return port;
	}

	@Override
	public String getClientHostPassword() {
	return passwordParam;
	}

	@Override
	public String getClientTag() {
	return tag;
	}

	@Override
	public abstract void initClient(String clientHostAddress, int clientHostPort,
	String clientHostPassword, String clientTag, String ticket);

	@Override
	public abstract void closeClient();

	//
	// interface FrameBufferEventListener
	//
	@Override
	public void onFramebufferSizeChange(int w, int h) {
	tracker.resize(w, h);

	synchronized(this) {
	framebufferResized = true;
	resizedFramebufferWidth = w;
	resizedFramebufferHeight = h;
	}

	signalTileDirtyEvent();
	}

	@Override
	public void onFramebufferUpdate(int x, int y, int w, int h) {
	if(s_logger.isTraceEnabled())
	s_logger.trace("Frame buffer update {" + x + "," + y + "," + w + "," + h + "}");
	tracker.invalidate(new Rectangle(x, y, w, h));

	signalTileDirtyEvent();
	}

	//
	// AJAX Image manipulation
	//
	public byte[] getFrameBufferJpeg() {
	FrameBufferCanvas canvas = getFrameBufferCavas();
	if(canvas != null)
	return canvas.getFrameBufferJpeg();

	return null;
	}

	public byte[] getTilesMergedJpeg(List<TileInfo> tileList, int tileWidth, int tileHeight) {
	FrameBufferCanvas canvas = getFrameBufferCavas();
	if(canvas != null)
	return canvas.getTilesMergedJpeg(tileList, tileWidth, tileHeight);
	return null;
	}

	private String prepareAjaxImage(List<TileInfo> tiles, boolean init) {
	byte[] imgBits;
	if(init)
	imgBits = getFrameBufferJpeg();
	else
	imgBits = getTilesMergedJpeg(tiles, tracker.getTileWidth(), tracker.getTileHeight());

	if(imgBits == null) {
	s_logger.warn("Unable to generate jpeg image");
	} else {
	if(s_logger.isTraceEnabled())
	s_logger.trace("Generated jpeg image size: " + imgBits.length);
	}

	int key = ajaxImageCache.putImage(imgBits);
	StringBuffer sb = new StringBuffer("/ajaximg?host=");
	sb.append(host).append("&port=").append(port).append("&sid=").append(passwordParam);
	sb.append("&key=").append(key).append("&ts=").append(System.currentTimeMillis());
	return sb.toString();
	}

	private String prepareAjaxSession(boolean init) {
	if(init) {
	synchronized(this) {
	ajaxSessionId++;
	}
	}

	StringBuffer sb = new StringBuffer();

	sb.append("/ajax?host=").append(host).append("&port=").append(port);
	sb.append("&sid=").append(passwordParam).append("&sess=").append(ajaxSessionId);
	return sb.toString();
	}

	@Override
	public String onAjaxClientKickoff() {
	return "onKickoff();";
	}

	private boolean waitForViewerReady() {
	long startTick = System.currentTimeMillis();
	while(System.currentTimeMillis() - startTick < 5000) {
	if(getFrameBufferCavas() != null)
	return true;

	try {
	Thread.sleep(100);
	} catch (InterruptedException e) {
	}
	}
	return false;
	}

	private String onAjaxClientConnectFailed() {
	return "<html><head></head><body><div id=\"main_panel\" tabindex=\"1\"><p>" +
	"Unable to start console session as connection is refused by the machine you are accessing" +
	"</p></div></body></html>";
	}

	@Override
	public String onAjaxClientStart(String title, List<String> languages, String guest) {
	updateFrontEndActivityTime();

	if(!waitForViewerReady())
	return onAjaxClientConnectFailed();

	synchronized(this) {
	ajaxSessionId++;
	framebufferResized = false;
	}

	int tileWidth = tracker.getTileWidth();
	int tileHeight = tracker.getTileHeight();
	int width = tracker.getTrackWidth();
	int height = tracker.getTrackHeight();

	if(s_logger.isTraceEnabled())
	s_logger.trace("Ajax client start, frame buffer w: " + width + ", " + height);

	int retry = 0;
	tracker.initCoverageTest();
	while(!tracker.hasFullCoverage() && retry < 10) {
	try {
	Thread.sleep(1000);
	} catch (InterruptedException e) {
	}
	retry++;
	}

	List<TileInfo> tiles = tracker.scan(true);
	String imgUrl = prepareAjaxImage(tiles, true);
	String updateUrl = prepareAjaxSession(true);

	StringBuffer sbTileSequence = new StringBuffer();
	int i = 0;
	for(TileInfo tile : tiles) {
	sbTileSequence.append("[").append(tile.getRow()).append(",").append(tile.getCol()).append("]");
	if(i < tiles.size() - 1)
	sbTileSequence.append(",");

	i++;
	}

	return getAjaxViewerPageContent(sbTileSequence.toString(), imgUrl,
	updateUrl, width, height, tileWidth, tileHeight, title,
	ConsoleProxy.keyboardType == ConsoleProxy.KEYBOARD_RAW,
	languages, guest);
	}

	private String getAjaxViewerPageContent(String tileSequence, String imgUrl, String updateUrl, int width,
	int height, int tileWidth, int tileHeight, String title, boolean rawKeyboard, List<String> languages, String guest) {

	StringBuffer sbLanguages = new StringBuffer("");
	if(languages != null) {
	for(String lang : languages) {
	if(sbLanguages.length() > 0) {
	sbLanguages.append(",");
	}
	sbLanguages.append(lang);
	}
	}

	String[] content = new String[] {
	"<html>",
	"<head>",
	"<script type=\"text/javascript\" language=\"javascript\" src=\"/resource/js/jquery.js\"></script>",
	"<script type=\"text/javascript\" language=\"javascript\" src=\"/resource/js/cloud.logger.js\"></script>",
	"<script type=\"text/javascript\" language=\"javascript\" src=\"/resource/js/ajaxviewer.js\"></script>",
	"<script type=\"text/javascript\" language=\"javascript\" src=\"/resource/js/handler.js\"></script>",
	"<link rel=\"stylesheet\" type=\"text/css\" href=\"/resource/css/ajaxviewer.css\"></link>",
	"<link rel=\"stylesheet\" type=\"text/css\" href=\"/resource/css/logger.css\"></link>",
	"<title>" + title + "</title>",
	"</head>",
	"<body>",
	"<div id=\"toolbar\">",
	"<ul>",
	"<li>",
	"<a href=\"#\" cmd=\"sendCtrlAltDel\">",
	"<span><img align=\"left\" src=\"/resource/images/cad.gif\" alt=\"Ctrl-Alt-Del\" />Ctrl-Alt-Del</span>",
	"</a>",
	"</li>",
	"<li>",
	"<a href=\"#\" cmd=\"sendCtrlEsc\">",
	"<span><img align=\"left\" src=\"/resource/images/winlog.png\" alt=\"Ctrl-Esc\" style=\"width:16px;height:16px\"/>Ctrl-Esc</span>",
	"</a>",
	"</li>",

	"<li class=\"pulldown\">",
	"<a href=\"#\">",
	"<span><img align=\"left\" src=\"/resource/images/winlog.png\" alt=\"Keyboard\" style=\"width:16px;height:16px\"/>Keyboard</span>",
	"</a>",
	"<ul>",
	"<li><a href=\"#\" cmd=\"keyboard_us\"><span>Standard (US) keyboard</span></a></li>",
	"<li><a href=\"#\" cmd=\"keyboard_jp\"><span>Japanese keyboard</span></a></li>",
	"</ul>",
	"</li>",
	"</ul>",
	"<span id=\"light\" class=\"dark\" cmd=\"toggle_logwin\"></span>",
	"</div>",
	"<div id=\"main_panel\" tabindex=\"1\"></div>",
	"<script language=\"javascript\">",
	"var acceptLanguages = '" + sbLanguages.toString() + "';",
	"var tileMap = [ " + tileSequence + " ];",
	"var ajaxViewer = new AjaxViewer('main_panel', '" + imgUrl + "', '" + updateUrl + "', tileMap, ",
	String.valueOf(width) + ", " + String.valueOf(height) + ", " + String.valueOf(tileWidth) + ", " + String.valueOf(tileHeight) + ");",

	"$(function() {",
	"ajaxViewer.start();",
	"});",

	"</script>",
	"</body>",
	"</html>"
	};

	StringBuffer sb = new StringBuffer();
	for(int i = 0; i < content.length; i++)
	sb.append(content[i]);

	return sb.toString();
	}

	public String onAjaxClientDisconnected() {
	return "onDisconnect();";
	}

	@Override
	public String onAjaxClientUpdate() {
	updateFrontEndActivityTime();
	if(!waitForViewerReady())
	return onAjaxClientDisconnected();

	synchronized(tileDirtyEvent) {
	if(!dirtyFlag) {
	try {
	tileDirtyEvent.wait(3000);
	} catch(InterruptedException e) {
	}
	}
	}

	boolean doResize = false;
	synchronized(this) {
	if(framebufferResized) {
	framebufferResized = false;
	doResize = true;
	}
	}

	List<TileInfo> tiles;

	if(doResize)
	tiles = tracker.scan(true);
	else
	tiles = tracker.scan(false);
	dirtyFlag = false;

	String imgUrl = prepareAjaxImage(tiles, false);
	StringBuffer sbTileSequence = new StringBuffer();
	int i = 0;
	for(TileInfo tile : tiles) {
	sbTileSequence.append("[").append(tile.getRow()).append(",").append(tile.getCol()).append("]");
	if(i < tiles.size() - 1)
	sbTileSequence.append(",");

	i++;
	}

	return getAjaxViewerUpdatePageContent(sbTileSequence.toString(), imgUrl, doResize,
	resizedFramebufferWidth, resizedFramebufferHeight,
	tracker.getTileWidth(), tracker.getTileHeight());
	}

	private String getAjaxViewerUpdatePageContent(String tileSequence, String imgUrl, boolean resized, int width,
	int height, int tileWidth, int tileHeight) {

	String[] content = new String[] {
	"tileMap = [ " + tileSequence + " ];",
	resized ? "ajaxViewer.resize('main_panel', " + width + ", " + height + " , " + tileWidth + ", " + tileHeight + ");" : "",
	"ajaxViewer.refresh('" + imgUrl + "', tileMap, false);"
	};

	StringBuffer sb = new StringBuffer();
	for(int i = 0; i < content.length; i++)
	sb.append(content[i]);

	return sb.toString();
	}

	//
	// Helpers
	//
	private synchronized static int getNextClientId() {
	return ++s_nextClientId;
	}

	private void signalTileDirtyEvent() {
	synchronized(tileDirtyEvent) {
	dirtyFlag = true;
	tileDirtyEvent.notifyAll();
	}
	}

	public void updateFrontEndActivityTime() {
	lastFrontEndActivityTime = System.currentTimeMillis();
	}

	protected abstract FrameBufferCanvas getFrameBufferCavas();
	}