- Renamed default theme to base

- Merged XSLT and AJAX -based themes
- Added automatic browser detection and mode selection
- Added automatic ajax-html page generation
- Added automatic XSLT theme header generation (no more window template modifications needed!)

svn changeset:187/svn branch:toolkit

src/com/itmill/toolkit/terminal/web/AjaxApplicationManager.java

@@ -114,7 +114,7 @@ public class AjaxApplicationManager implements Paintable.RepaintRequestListener,
         application.removeListener((Application.WindowDetachListener) this);
     }
 
-    public void handleXmlHttpRequest(HttpServletRequest request,
+    public void handleUidlRequest(HttpServletRequest request,
             HttpServletResponse response) throws IOException {
 
         boolean repaintAll = request.getParameter(GET_PARAM_REPAINT_ALL) != null;

src/com/itmill/toolkit/terminal/web/ApplicationServlet.java

@@ -52,7 +52,9 @@ import java.util.List;
 import java.util.Map;
 import java.util.Properties;
 import java.util.Set;
+import java.util.Stack;
 import java.util.StringTokenizer;
+import java.util.Vector;
 import java.util.WeakHashMap;
 
 import javax.servlet.ServletContext;
@@ -136,49 +138,49 @@ public class ApplicationServlet extends HttpServlet implements
 
 	private static final String PARAMETER_TRANSFORMER_CACHETIME = "TransformerCacheTime";
 
-	private static int DEFAULT_THEME_CACHETIME = 1000 * 60 * 60 * 24;
+	private static final int DEFAULT_THEME_CACHETIME = 1000 * 60 * 60 * 24;
 
-	private static int DEFAULT_BUFFER_SIZE = 32 * 1024;
+	private static final int DEFAULT_BUFFER_SIZE = 32 * 1024;
 
-	private static int DEFAULT_MAX_TRANSFORMERS = 1;
+	private static final int DEFAULT_MAX_TRANSFORMERS = 1;
 
-	private static int MAX_BUFFER_SIZE = 64 * 1024;
+	private static final int MAX_BUFFER_SIZE = 64 * 1024;
 
-	private static String SESSION_ATTR_VARMAP = "itmill-toolkit-varmap";
+	private static final String SESSION_ATTR_VARMAP = "itmill-toolkit-varmap";
 
-	static String SESSION_ATTR_CONTEXT = "itmill-toolkit-context";
+	private static final String SESSION_ATTR_CONTEXT = "itmill-toolkit-context";
 
-	static String SESSION_ATTR_APPS = "itmill-toolkit-apps";
+	protected static final String SESSION_ATTR_APPS = "itmill-toolkit-apps";
 
-	private static String SESSION_BINDING_LISTENER = "itmill-toolkit-bindinglistener";
+	private static final String SESSION_BINDING_LISTENER = "itmill-toolkit-bindinglistener";
 
 	// TODO Should default or base theme be the default?
-	private static String DEFAULT_THEME = "default";
+	protected static final String DEFAULT_THEME = "base";
 
-	private static String RESOURCE_URI = "/RES/";
+	private static final String RESOURCE_URI = "/RES/";
 
-	private static String AJAX_UIDL_URI = "/UIDL/";
+	private static final String AJAX_UIDL_URI = "/UIDL/";
 
-	private static String THEME_DIRECTORY_PATH = "WEB-INF/lib/themes/";
+	private static final String THEME_DIRECTORY_PATH = "WEB-INF/lib/themes/";
 
-	private static String THEME_LISTING_FILE = THEME_DIRECTORY_PATH
+	private static final String THEME_LISTING_FILE = THEME_DIRECTORY_PATH
 			+ "themes.txt";
 
-	private static String DEFAULT_THEME_JAR_PREFIX = "itmill-toolkit-themes";
+	private static final String DEFAULT_THEME_JAR_PREFIX = "itmill-toolkit-themes";
 
-	private static String DEFAULT_THEME_JAR = "WEB-INF/lib/"
+	private static final String DEFAULT_THEME_JAR = "WEB-INF/lib/"
 			+ DEFAULT_THEME_JAR_PREFIX + "-" + VERSION + ".jar";
 
-	private static String DEFAULT_THEME_TEMP_FILE_PREFIX = "ITMILL_TMP_";
+	private static final String DEFAULT_THEME_TEMP_FILE_PREFIX = "ITMILL_TMP_";
 
-	private static String SERVER_COMMAND_PARAM = "SERVER_COMMANDS";
+	private static final String SERVER_COMMAND_PARAM = "SERVER_COMMANDS";
 
-	private static int SERVER_COMMAND_STREAM_MAINTAIN_PERIOD = 15000;
+	private static final int SERVER_COMMAND_STREAM_MAINTAIN_PERIOD = 15000;
 
-	private static int SERVER_COMMAND_HEADER_PADDING = 2000;
+	private static final int SERVER_COMMAND_HEADER_PADDING = 2000;
 
 	// Maximum delay between request for an user to be considered active (in ms)
-	private static long ACTIVE_USER_REQUEST_INTERVAL = 1000 * 45;
+	private static final long ACTIVE_USER_REQUEST_INTERVAL = 1000 * 45;
 
 	// Private fields
 	private Class applicationClass;
@@ -499,15 +501,9 @@ public class ApplicationServlet extends HttpServlet implements
 		HttpVariableMap variableMap = null;
 		OutputStream out = response.getOutputStream();
 		HashSet currentlyDirtyWindowsForThisApplication = new HashSet();
-		WebApplicationContext appContext = null;
 		Application application = null;
 		try {
 
-			// If the resource path is unassigned, initialize it
-			if (resourcePath == null)
-				resourcePath = request.getContextPath()
-						+ request.getServletPath() + RESOURCE_URI;
-
 			// Handle resource requests
 			if (handleResourceRequest(request, response))
 				return;
@@ -523,19 +519,15 @@ public class ApplicationServlet extends HttpServlet implements
 			if (application == null)
 				application = createApplication(request);
 
-			// Is this a download request from application
-			DownloadStream download = null;
+			// Set the last application request date
+			applicationToLastRequestDate.put(application, new Date());
 
 			// Invoke context transaction listeners
-			if (application != null) {
-				appContext = (WebApplicationContext) application.getContext();
-			}
-			if (appContext != null) {
-				appContext.startTransaction(application, request);
-			}
+			((WebApplicationContext) application.getContext())
+					.startTransaction(application, request);
 
-			// Set the last application request date
-			applicationToLastRequestDate.put(application, new Date());
+			// Is this a download request from application
+			DownloadStream download = null;
 
 			// The rest of the process is synchronized with the application
 			// in order to guarantee that no parallel variable handling is
@@ -546,7 +538,7 @@ public class ApplicationServlet extends HttpServlet implements
 				String resourceId = request.getPathInfo();
 				if (resourceId != null && resourceId.startsWith(AJAX_UIDL_URI)) {
 
-					getApplicationManager(application).handleXmlHttpRequest(
+					getApplicationManager(application).handleUidlRequest(
 							request, response);
 
 					return;
@@ -594,6 +586,7 @@ public class ApplicationServlet extends HttpServlet implements
 											window, t));
 						}
 					}
+
 					// Remove application if it has stopped
 					if (!application.isRunning()) {
 						endApplication(request, response, application);
@@ -634,34 +627,128 @@ public class ApplicationServlet extends HttpServlet implements
 						window.setTerminal(terminalType);
 					}
 
-					// Find theme and initialize TransformerType
-					UIDLTransformerType transformerType = null;
-					if (window.getTheme() != null) {
-						Theme activeTheme;
-						if ((activeTheme = this.themeSource
-								.getThemeByName(window.getTheme())) != null) {
-							transformerType = new UIDLTransformerType(
-									terminalType, activeTheme);
-						} else {
-							Log
-									.info("Theme named '"
-											+ window.getTheme()
-											+ "' not found. Using system default theme.");
+					// Find theme
+					Theme theme = themeSource
+							.getThemeByName(window.getTheme() != null ? window
+									.getTheme() : DEFAULT_THEME);
+					if (theme == null)
+						throw new ServletException("Default theme (named '"
+								+ DEFAULT_THEME + "') can not be found");
+
+					// If UIDL rendering mode is preferred, a page for it is
+					// rendered
+					String renderingMode = theme.getPreferredMode(terminalType,
+							themeSource);
+					if (Theme.MODE_UIDL.equals(renderingMode)) {
+						response.setContentType("text/html");
+						BufferedWriter page = new BufferedWriter(
+								new OutputStreamWriter(out));
+
+						page
+								.write("<!DOCTYPE html PUBLIC \"-//W3C//DTD XHTML 1.0 Transitional//EN\" "
+										+ "\"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd\">\n");
+
+						page.write("<html><head>\n<title>"
+								+ window.getCaption() + "</title>\n");
+
+						Theme t = theme;
+						Vector themes = new Vector();
+						themes.add(t);
+						while (t.getParent() != null) {
+							String parentName = t.getParent();
+							t = themeSource.getThemeByName(parentName);
+							themes.add(t);
 						}
-					}
+						for (int k=themes.size()-1; k>=0; k--) {
+							t = (Theme) themes.get(k);
+							Collection files = t.getFileNames(terminalType,
+									Theme.MODE_UIDL);
+							for (Iterator i = files.iterator(); i.hasNext();) {
+								String file = (String) i.next();
+								if (file.endsWith(".css"))
+									page
+											.write("<link rel=\"stylesheet\" href=\""
+													+ getResourceLocation(t
+															.getName(),
+															new ThemeResource(
+																	file))
+													+ "\" type=\"text/css\" />\n");
+								else if (file.endsWith(".js"))
+									page
+											.write("<script src=\""
+													+ getResourceLocation(t
+															.getName(),
+															new ThemeResource(
+																	file))
+													+ "\" type=\"text/javascript\"></script>\n");
+							}
+
+						}
+
+						page.write("</head><body>\n");
 
-					// Use default theme if selected theme was not found.
-					if (transformerType == null) {
-						Theme defaultTheme = this.themeSource
-								.getThemeByName(ApplicationServlet.DEFAULT_THEME);
-						if (defaultTheme == null) {
-							throw new ServletException(
-									"Default theme not found in the specified theme source(s).");
+						page
+								.write("<div id=\"ajax-wait\"><div>Loading...</div></div>\n");
+
+						page.write("<div id=\"ajax-window\"></div>\n");
+
+						page.write("<script language=\"JavaScript\">\n");
+						page
+								.write("var client = new ITMillToolkitClient("
+										+ "document.getElementById('ajax-window'),"
+										+ "\""
+										+ getApplicationUrl(request)
+										+ "/UIDL/"
+										+ "\",\""
+										+ resourcePath +  ((Theme)themes.get(themes.size()-1)).getName() + "/"
+										
+										+ "client/\",document.getElementById('ajax-wait'));\n");
+
+						// TODO Should we also show debug information?
+						/*
+						 * var debug =
+						 * document.location.href.split("debug=")[1]; if (debug &&
+						 * debug.split("&")[0] == "1") client.debugEnabled =
+						 * true;
+						 */
+
+						for (int k=themes.size()-1; k>=0; k--) {
+							t = (Theme) themes.get(k);
+							String themeObjName = t.getName() + "Theme";
+							themeObjName = themeObjName.substring(0,1).toUpperCase() + themeObjName.substring(1);
+							page
+							.write(" (new "+themeObjName+"(\"" + resourcePath + ((Theme)themes.get(k)).getName()  + "/\")).registerTo(client);\n");
 						}
-						transformerType = new UIDLTransformerType(terminalType,
-								defaultTheme);
+						 
+						page.write("client.start();\n");
+
+						page.write("</script>\n");
+
+						page.write("</body></html>\n");
+						page.close();
+
+						return;
+					}
+
+					// If other than XSLT or UIDL mode is requested
+					if (!Theme.MODE_XSLT.equals(renderingMode)) {
+						// TODO More informal message should be given is browser
+						// is not supported
+						response.setContentType("text/html");
+						BufferedWriter page = new BufferedWriter(
+								new OutputStreamWriter(out));
+						page.write("<html><head></head><body>");
+						page.write("Unsupported browser.");
+						page.write("</body></html>");
+						page.close();
+
+						return;
 					}
 
+					// Initialize Transformer
+					UIDLTransformerType transformerType = new UIDLTransformerType(
+							terminalType, theme);
+
 					transformer = this.transformerFactory
 							.getTransformer(transformerType);
 
@@ -769,9 +856,9 @@ public class ApplicationServlet extends HttpServlet implements
 				transformerFactory.releaseTransformer(transformer);
 
 			// Notify transaction end
-			if (appContext != null && application != null) {
-				appContext.endTransaction(application, request);
-			}
+			if (application != null)
+				((WebApplicationContext) application.getContext())
+						.endTransaction(application, request);
 
 			// Clean the function library state for this thread
 			// for security reasons
@@ -988,6 +1075,11 @@ public class ApplicationServlet extends HttpServlet implements
 	private boolean handleResourceRequest(HttpServletRequest request,
 			HttpServletResponse response) throws ServletException {
 
+		// If the resource path is unassigned, initialize it
+		if (resourcePath == null)
+			resourcePath = request.getContextPath() + request.getServletPath()
+					+ RESOURCE_URI;
+
 		String resourceId = request.getPathInfo();
 
 		// Check if this really is a resource request

src/com/itmill/toolkit/terminal/web/CollectionThemeSource.java

@@ -1,30 +1,30 @@
 /* *************************************************************************
  
-                               IT Mill Toolkit 
+ IT Mill Toolkit 
 
-               Development of Browser User Intarfaces Made Easy
+ Development of Browser User Intarfaces Made Easy
 
-                    Copyright (C) 2000-2006 IT Mill Ltd
-                     
-   *************************************************************************
+ Copyright (C) 2000-2006 IT Mill Ltd
+ 
+ *************************************************************************
 
-   This product is distributed under commercial license that can be found
-   from the product package on license/license.txt. Use of this product might 
-   require purchasing a commercial license from IT Mill Ltd. For guidelines 
-   on usage, see license/licensing-guidelines.html
+ This product is distributed under commercial license that can be found
+ from the product package on license/license.txt. Use of this product might 
+ require purchasing a commercial license from IT Mill Ltd. For guidelines 
+ on usage, see license/licensing-guidelines.html
 
-   *************************************************************************
-   
-   For more information, contact:
-   
-   IT Mill Ltd                           phone: +358 2 4802 7180
-   Ruukinkatu 2-4                        fax:   +358 2 4802 7181
-   20540, Turku                          email:  info@itmill.com
-   Finland                               company www: www.itmill.com
-   
-   Primary source for information and releases: www.itmill.com
+ *************************************************************************
+ 
+ For more information, contact:
+ 
+ IT Mill Ltd                           phone: +358 2 4802 7180
+ Ruukinkatu 2-4                        fax:   +358 2 4802 7181
+ 20540, Turku                          email:  info@itmill.com
+ Finland                               company www: www.itmill.com
+ 
+ Primary source for information and releases: www.itmill.com
 
-   ********************************************************************** */
+ ********************************************************************** */
 
 package com.itmill.toolkit.terminal.web;
 
@@ -34,12 +34,15 @@ import java.util.Iterator;
 import java.util.LinkedList;
 import java.util.List;
 
-/** Theme source for consisting of collection of other theme sources.
- * This class is used to implement the retrieval of themes
- * from multiple sources. Also this class implements the inheritance 
- * of themes by first retrieving the relevant parent theme information.
+/**
+ * Theme source for consisting of collection of other theme sources. This class
+ * is used to implement the retrieval of themes from multiple sources. Also this
+ * class implements the inheritance of themes by first retrieving the relevant
+ * parent theme information.
+ * 
  * @author IT Mill Ltd.
- * @version @VERSION@
+ * @version
+ * @VERSION@
  * @since 3.0
  */
 public class CollectionThemeSource implements ThemeSource {
@@ -54,10 +57,11 @@ public class CollectionThemeSource implements ThemeSource {
 	}
 
 	/**
-	 * @see com.itmill.toolkit.terminal.web.ThemeSource#getXSLStreams(Theme, WebBrowser)
+	 * @see com.itmill.toolkit.terminal.web.ThemeSource#getXSLStreams(Theme,
+	 *      WebBrowser)
 	 */
 	public Collection getXSLStreams(Theme theme, WebBrowser type)
-		throws ThemeException {
+			throws ThemeException {
 		Collection xslFiles = new LinkedList();
 
 		// Add parent theme XSL
@@ -74,17 +78,16 @@ public class CollectionThemeSource implements ThemeSource {
 	}
 
 	private Collection getParentXSLStreams(Theme theme, WebBrowser type)
-		throws ThemeException {
+			throws ThemeException {
 		Collection xslFiles = new LinkedList();
-		Collection parents = theme.getParentThemes();
-		for (Iterator i = parents.iterator(); i.hasNext();) {
-			String name = (String) i.next();
-			Theme parent = this.getThemeByName(name);
+		String parentName = theme.getParent();
+		if (parentName != null) {
+			Theme parent = this.getThemeByName(parentName);
 			if (parent != null) {
 				xslFiles.addAll(this.getXSLStreams(parent, type));
 			} else {
 				throw new ThemeSource.ThemeException(
-					"Parent theme not found for name: " + name);
+						"Parent theme not found for name: " + parentName);
 			}
 		}
 		return xslFiles;
@@ -112,7 +115,7 @@ public class CollectionThemeSource implements ThemeSource {
 		int delim = resourceId.indexOf("/");
 		String subResourceId = "";
 		String themeName = "";
-		if (delim >=0 && delim < resourceId.length() - 1) {
+		if (delim >= 0 && delim < resourceId.length() - 1) {
 			subResourceId = resourceId.substring(delim + 1);
 			themeName = resourceId.substring(0, delim);
 		}
@@ -122,8 +125,9 @@ public class CollectionThemeSource implements ThemeSource {
 		if (themeName.length() > 0) {
 			Theme t = this.getThemeByName(themeName);
 			if (t != null) {
-				themes.add(t.getName());
-				addAllParents(themes, t);
+				themes.add(themeName);
+				if (t.getParent() != null)
+					themes.add(t.getParent());
 			}
 		}
 
@@ -134,8 +138,8 @@ public class CollectionThemeSource implements ThemeSource {
 			// Search all sources
 			for (Iterator i = this.sources.iterator(); i.hasNext();) {
 				try {
-					InputStream in =
-						((ThemeSource) i.next()).getResource(resource);
+					InputStream in = ((ThemeSource) i.next())
+							.getResource(resource);
 					if (in != null)
 						return in;
 				} catch (ThemeException e) {
@@ -144,26 +148,8 @@ public class CollectionThemeSource implements ThemeSource {
 			}
 		}
 
-		throw new ThemeException(
-			"Theme resource not found:"
-				+ subResourceId
-				+ " in themes "
-				+ themes);
-	}
-	/** Recusrivelu get list of parent themes in inheritace order.
-	 *  
-	 * @param t Theme which parents should be listed
-	 * @return Collection of themes in inheritance order.
-	 */
-	private void addAllParents(List list, Theme t) {
-		if (t == null)
-			return;
-
-		List parents = t.getParentThemes();
-		list.addAll(parents);
-		for (Iterator i = parents.iterator(); i.hasNext();) {
-			addAllParents(list, this.getThemeByName((String) i.next()));
-		}
+		throw new ThemeException("Theme resource not found:" + subResourceId
+				+ " in themes " + themes);
 	}
 
 	/**
@@ -190,8 +176,11 @@ public class CollectionThemeSource implements ThemeSource {
 		return null;
 	}
 
-	/**Add new theme source to this collection.
-	 * @param source Theme source to be added.
+	/**
+	 * Add new theme source to this collection.
+	 * 
+	 * @param source
+	 *            Theme source to be added.
 	 */
 	public void add(ThemeSource source) {
 		this.sources.add(source);

src/com/itmill/toolkit/terminal/web/Theme.java

@@ -172,8 +172,8 @@ public class Theme extends DefaultHandler {
 	/** Author of the theme. */
 	private Author author;
 
-	/** List of parent themes */
-	private List parentThemes = new LinkedList();
+	/** Name of the theme, which this theme extends */
+	private String parentTheme = null;
 
 	/** Fileset of included XSL files. */
 	private Fileset files = null;
@@ -234,26 +234,30 @@ public class Theme extends DefaultHandler {
 	 * Get the preferred operating mode supported by this theme for given
 	 * terminal.
 	 */
-	public String getPreferredMode(WebBrowser terminal) {
+	public String getPreferredMode(WebBrowser terminal, ThemeSource themeSource) {
 
 		// If no supported modes are declared, then we use parents preferred
 		// mode
-		if (parentThemes != null && parentThemes.size() > 0
-				&& supportedModes.keySet().isEmpty())
-			return ((Theme) parentThemes.get(0)).getPreferredMode(terminal);
-
+		if (parentTheme != null
+				&& supportedModes.keySet().isEmpty()) {
+			Theme parent = themeSource.getThemeByName(parentTheme);
+			if (parent == null)
+				throw new IllegalStateException("Parent theme '"+parentTheme+"' is not found for theme '"+getName()+"'.");
+			return parent.getPreferredMode(terminal, themeSource);
+		}
+		
 		// Iterate and test the modes in order
 		for (Iterator i = supportedModes.keySet().iterator(); i.hasNext();) {
 			String mode = (String) i.next();
-			if (supportsMode(mode, terminal))
+			if (supportsMode(mode, terminal,themeSource))
 				return mode;
 		}
 
-		return MODE_FALLBACK;
+		return null;
 	}
 
 	/** Tests if this theme suppors given mode */
-	public boolean supportsMode(String mode, WebBrowser terminal) {
+	public boolean supportsMode(String mode, WebBrowser terminal, ThemeSource themeSource) {
 
 		// Theme must explicitly support the given mode
 		RequirementCollection rc = (RequirementCollection) supportedModes
@@ -262,9 +266,13 @@ public class Theme extends DefaultHandler {
 			return false;
 
 		// All parents must also support the mode
-		for (Iterator i = parentThemes.iterator(); i.hasNext();)
-			if (!((Theme) i.next()).supportsMode(mode, terminal))
-				return false;
+		if (parentTheme != null) {
+			Theme parent = themeSource.getThemeByName(parentTheme);
+			if (parent == null)
+				throw new IllegalStateException("Parent theme '"+parentTheme+"' is not found for theme '"+getName()+"'.");
+			if(!parent.supportsMode(mode, terminal, themeSource))
+			return false;
+		}
 
 		return true;
 	}
@@ -324,7 +332,9 @@ public class Theme extends DefaultHandler {
 			if (this.name.equals(themeName))
 				throw new IllegalArgumentException("Theme " + this.name
 						+ " extends itself.");
-			this.parentThemes.add(themeName);
+			if (parentTheme != null)
+				throw new IllegalArgumentException("Only one extends statement is allowed");
+			this.parentTheme = themeName;
 		} else if (TAG_FILE.equals(qName)) {
 			File f = new File(atts.getValue(ATTR_NAME));
 			if (this.openFilesets.isEmpty()) {
@@ -437,6 +447,11 @@ public class Theme extends DefaultHandler {
 			this.modesListCurrentlyOpen = false;
 		} else if (TAG_MODE.equals(qName)) {
 			this.currentlyOpenMode = null;
+		} else if (TAG_OR.equals(qName) || TAG_AND.equals(qName)) {
+			RequirementCollection r = (RequirementCollection) openRequirements.pop();
+			if (openRequirements.size() < 1)
+				throw new IllegalStateException();
+			((RequirementCollection)openRequirements.peek()).addRequirement(r);
 		}
 	}
 
@@ -532,8 +547,8 @@ public class Theme extends DefaultHandler {
 	 * @see java.lang.Object#toString()
 	 */
 	public String toString() {
-		return this.name + " author=[" + this.author + "]" + " inherits="
-				+ parentThemes + "]" + " files={"
+		return this.name + " author='" + this.author + "'" + (parentTheme != null ? " inherits='"
+				+ parentTheme + "'" : "" )+ " files={"
 				+ (files != null ? files.toString() : "null") + "}";
 	}
 
@@ -1082,13 +1097,11 @@ public class Theme extends DefaultHandler {
 	}
 
 	/**
-	 * Returns the list of parent themes of this theme. Returns list of all
-	 * inherited themes in the inheritance order.
+	 * Returns the name of the parent theme.
 	 * 
-	 * @return List of parent theme instances.
 	 */
-	public List getParentThemes() {
-		return parentThemes;
+	public String getParent() {
+		return parentTheme;
 	}
 
 	/** Get theme description */

src/com/itmill/toolkit/terminal/web/WebBrowser.java

@@ -100,7 +100,7 @@ public class WebBrowser implements Terminal {
 	 * @return Name of the terminal window
 	 */
 	public String getDefaultTheme() {
-		return "default";
+		return ApplicationServlet.DEFAULT_THEME;
 	}
 
 	/** Get the name and version of the web browser application.