experimenting with sessions and stuff like that.

Changes:
+ Login Panel
+ Some Kernel Booting stuff

src/main/java/com/rdesk/Main.java

@@ -1,103 +1,9 @@
 package com.rdesk;
 
-import com.rdesk.applications.entertainment.comic.Xkcd;
+import com.rdesk.applications.system.login.Login;
-import com.rdesk.applications.productivity.Calculator;
-import com.rdesk.applications.productivity.browsing.TabbedBrowser;
-import com.rdesk.applications.productivity.code.CodeDesk;
-import com.rdesk.applications.system.Exit;
-import com.rdesk.applications.productivity.Notes;
-import com.rdesk.applications.system.TaskManager;
-import com.rdesk.applications.system.filehaj.FileExplorerApp;
-import com.rdesk.applications.system.rsys.KbChanger;
-import com.rdesk.kernel.*;
-import com.rdesk.kernel.launcher.AppLauncher;
-
-import javax.swing.*;
 
 public class Main {
-
-    private static final boolean RUN_IN_FS = false;
-    private static final boolean USE_SYSDEFAULT_LAF = false;
-    private static final boolean USE_FLATLAF = false;
-    private static final boolean loadSettingsKernelFlag = true;
-
     public static void main(String[] args) {
-        SwingUtilities.invokeLater(Main::boot);
+        Login.main(args);
-    }
-
-    private static void boot() {
-        Kernel kernel = Kernel.get();
-        kernel.initSettings(loadSettingsKernelFlag);
-        kernel.boot();
-        JFrame frame = new JFrame("rDesk");
-
-        frame.setDefaultCloseOperation(JFrame.DO_NOTHING_ON_CLOSE);
-        frame.addWindowListener(new java.awt.event.WindowAdapter() {
-            @Override
-            public void windowClosing(java.awt.event.WindowEvent e) {
-                kernel.shutdown();
-            }
-        });
-
-        if (USE_FLATLAF) {
-            try {
-                UIManager.setLookAndFeel(
-                        "com.formdev.flatlaf.themes.FlatMacLightLaf"
-                );
-            } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
-                JOptionPane.showMessageDialog(
-                        null,
-                        ex.getMessage() + "@USE_FLATLAF"
-                );
-            }
-        }
-
-        if (USE_SYSDEFAULT_LAF) {
-            try {
-                UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
-            } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
-                JOptionPane.showMessageDialog(
-                        null,
-                        ex.getMessage() + "@USE_SYSDEFAULT_LAF"
-                );
-            }
-        }
-
-        if (RUN_IN_FS) {
-            frame.setUndecorated(true);
-            frame.setExtendedState(JFrame.MAXIMIZED_BOTH);
-        } else {
-            frame.setSize(1200, 800);
-            frame.setLocationRelativeTo(null);
-        }
-
-        JDesktopPane desktop = new JDesktopPane();
-        kernel.windows().attachDesktop(desktop);
-
-        AppLauncher launcher = new AppLauncher(kernel);
-
-        registerSystemApps(launcher);
-
-        JSplitPane split = new JSplitPane(JSplitPane.HORIZONTAL_SPLIT, launcher, desktop);
-        split.setDividerSize(0);
-        split.setEnabled(false);
-
-        frame.setContentPane(split);
-        frame.setVisible(true);
-    }
-
-    private static void registerSystemApps(AppLauncher launcher) {
-        // productivity
-        launcher.addApp(new Notes(), "Productivity");
-        launcher.addApp(new TabbedBrowser(), "Productivity");
-        launcher.addApp(new CodeDesk(), "Productivity");
-        launcher.addApp(new Calculator(), "Productivity");
-        // entertainment
-        launcher.addApp(new Xkcd(), "Entertainment");
-        // System apps
-        launcher.addApp(new Exit(),     "System");
-        launcher.addApp(new TaskManager(), "System");
-        launcher.addApp(new FileExplorerApp(), "System");
-        launcher.addApp(new KbChanger(), "System");
     }
 }

src/main/java/com/rdesk/applications/system/Exit.java

@@ -1,11 +1,13 @@
 package com.rdesk.applications.system;
 
+import com.rdesk.applications.system.login.Login;
 import com.rdesk.kernel.DesktopApp;
 import com.rdesk.kernel.Kernel;
 
 import javax.swing.*;
 import java.awt.*;
 import java.io.IOException;
+import java.awt.Window;
 
 public class Exit implements DesktopApp {
 
@@ -22,7 +24,7 @@ public class Exit implements DesktopApp {
     @Override
     public JInternalFrame createWindow(Kernel kernel) {
         JInternalFrame frame = new JInternalFrame("System Controls", true, true);
-        frame.setSize(350, 180);
+        frame.setSize(420, 240);
         frame.setResizable(false);
 
         JPanel mainPanel = new JPanel(new GridBagLayout());
@@ -30,7 +32,7 @@ public class Exit implements DesktopApp {
         GridBagConstraints gbc = new GridBagConstraints();
         gbc.gridwidth = GridBagConstraints.REMAINDER;
         gbc.fill = GridBagConstraints.HORIZONTAL;
-        gbc.insets = new Insets(5, 5, 5, 5);
+        gbc.insets = new Insets(6, 6, 6, 6);
 
         JLabel label = new JLabel("Choose an action:");
         label.setFont(label.getFont().deriveFont(Font.BOLD));
@@ -38,8 +40,11 @@ public class Exit implements DesktopApp {
 
         JButton shutdownButton = new JButton("Shutdown rDesk");
         JButton shutdownOS = new JButton("Shutdown Host OS");
+        JButton logoffButton = new JButton("Log off");
+
         shutdownButton.setFocusPainted(false);
         shutdownButton.addActionListener(e -> confirmAndShutdown(kernel, frame));
+
         shutdownOS.setFocusPainted(false);
         shutdownOS.addActionListener(e -> {
             try {
@@ -48,8 +53,38 @@ public class Exit implements DesktopApp {
                 throw new RuntimeException(ex);
             }
         });
+
+        logoffButton.setFocusPainted(false);
+
+        logoffButton.addActionListener(e -> {
+            int choice = JOptionPane.showConfirmDialog(
+                    frame,
+                    "Log off and return to the login screen?"
+                    + "This will end all running Tasks!",
+                    "Confirm Log off",
+                    JOptionPane.YES_NO_OPTION,
+                    JOptionPane.WARNING_MESSAGE
+            );
+            if (choice != JOptionPane.YES_OPTION) return;
+
+            SwingUtilities.invokeLater(() -> {
+                try {
+                    Login.main(null);
+                } catch (Exception ex) {
+                    JOptionPane.showMessageDialog(frame,
+                            "Failed to launch login screen: " + ex.getMessage(),
+                            "Error",
+                            JOptionPane.ERROR_MESSAGE);
+                    return;
+                }
+
+                kernel.logoff();
+            });
+        });
+
         mainPanel.add(shutdownButton, gbc);
         mainPanel.add(shutdownOS, gbc);
+        mainPanel.add(logoffButton, gbc);
 
         JButton cancelButton = new JButton("Cancel");
         cancelButton.setFocusPainted(false);
@@ -89,11 +124,11 @@ public class Exit implements DesktopApp {
                 "Are you sure? This will shutdown the Host OS",
                 JOptionPane.YES_NO_OPTION,
                 JOptionPane.WARNING_MESSAGE
-                );
+        );
 
         if (choice == JOptionPane.YES_OPTION) {
             frame.dispose();
-            performShutdownCmd(); // cause else the call wouldnt be called
+            performShutdownCmd();
             kernel.shutdown();
         }
     }
@@ -107,8 +142,8 @@ public class Exit implements DesktopApp {
                 JOptionPane.WARNING_MESSAGE
         );
         if (choice == JOptionPane.YES_OPTION) {
-            frame.dispose(); // close the confirmation window first
+            frame.dispose();
             kernel.shutdown();
         }
     }
-}
+}

src/main/java/com/rdesk/applications/system/login/Handler.java

@@ -0,0 +1,126 @@
+
+package com.rdesk.applications.system.login;
+
+import com.google.gson.Gson;
+import com.google.gson.GsonBuilder;
+import com.google.gson.JsonArray;
+import com.google.gson.JsonElement;
+import com.google.gson.JsonParser;
+import com.google.gson.annotations.SerializedName;
+
+import javax.crypto.SecretKeyFactory;
+import javax.crypto.spec.PBEKeySpec;
+import java.awt.Window;
+import java.io.File;
+import java.io.FileReader;
+import java.io.FileWriter;
+import java.security.SecureRandom;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Base64;
+import java.util.List;
+
+public class Handler {
+    private static final String FILENAME = System.getProperty("user.home") + File.separator + "rsys_passwdstore.json";
+    private static final SecureRandom RNG = new SecureRandom();
+    private static final Gson GSON = new GsonBuilder().setPrettyPrinting().create();
+    private static final int SALT_LEN = 16;
+    private static final int KEY_LEN = 256; // bits
+    private static final int ITERATIONS = 200_000;
+    private static final String ALGO = "PBKDF2WithHmacSHA256";
+
+
+
+    public static boolean storeExists() {
+        return new File(FILENAME).exists();
+    }
+
+    public static UserRecord load() throws Exception {
+        File f = new File(FILENAME);
+        if (!f.exists()) return null;
+        try (FileReader fr = new FileReader(f)) {
+            return GSON.fromJson(fr, UserRecord.class);
+        }
+    }
+
+    public static void save(UserRecord u) throws Exception {
+        try (FileWriter fw = new FileWriter(FILENAME)) {
+            GSON.toJson(u, fw);
+        }
+    }
+
+    public static UserRecord createUser(String username, char[] password) throws Exception {
+        byte[] salt = new byte[SALT_LEN];
+        RNG.nextBytes(salt);
+        byte[] hash = pbkdf2(password, salt, ITERATIONS, KEY_LEN);
+        UserRecord u = new UserRecord();
+        u.username = username;
+        u.saltB64 = Base64.getEncoder().encodeToString(salt);
+        u.hashB64 = Base64.getEncoder().encodeToString(hash);
+        u.iterations = ITERATIONS;
+        return u;
+    }
+
+    public static boolean verifyPassword(char[] password, UserRecord stored) throws Exception {
+        byte[] salt = Base64.getDecoder().decode(stored.saltB64);
+        byte[] expected = Base64.getDecoder().decode(stored.hashB64);
+        byte[] computed = pbkdf2(password, salt, stored.iterations, expected.length * 8);
+        return slowEquals(expected, computed);
+    }
+
+    public static boolean verifyAndClose(Window window, char[] password, UserRecord stored) throws Exception {
+        try {
+            boolean ok = verifyPassword(password, stored);
+            if (ok && window != null) {
+                window.dispose();
+            }
+            return ok;
+        } finally {
+            clearPassword(password);
+        }
+    }
+
+    private static byte[] pbkdf2(char[] password, byte[] salt, int iterations, int keyLengthBits) throws Exception {
+        PBEKeySpec spec = new PBEKeySpec(password, salt, iterations, keyLengthBits);
+        SecretKeyFactory skf = SecretKeyFactory.getInstance(ALGO);
+        return skf.generateSecret(spec).getEncoded();
+    }
+
+    private static boolean slowEquals(byte[] a, byte[] b) {
+        if (a == null || b == null || a.length != b.length) return false;
+        int diff = 0;
+        for (int i = 0; i < a.length; i++) diff |= a[i] ^ b[i];
+        return diff == 0;
+    }
+
+    public static void clearPassword(char[] p) {
+        if (p == null) return;
+        Arrays.fill(p, (char) 0);
+    }
+
+    public static String[] listUsers() {
+        File f = new File(FILENAME);
+        if (!f.exists()) return new String[0];
+        try (FileReader fr = new FileReader(f)) {
+            JsonElement root = JsonParser.parseReader(fr);
+            List<String> users = new ArrayList<>();
+            if (root.isJsonArray()) {
+                JsonArray arr = root.getAsJsonArray();
+                for (JsonElement el : arr) {
+                    try {
+                        UserRecord ur = GSON.fromJson(el, UserRecord.class);
+                        if (ur != null && ur.username != null) users.add(ur.username);
+                    } catch (Throwable ignore) { /* skip malformed entry */ }
+                }
+            } else if (root.isJsonObject()) {
+                try {
+                    UserRecord ur = GSON.fromJson(root, UserRecord.class);
+                    if (ur != null && ur.username != null) users.add(ur.username);
+                } catch (Throwable ignore) { /* malformed object -> no users */ }
+            }
+            return users.toArray(new String[0]);
+        } catch (Exception e) {
+            return new String[0];
+        }
+    }
+}

src/main/java/com/rdesk/applications/system/login/Login.java

@@ -0,0 +1,267 @@
+package com.rdesk.applications.system.login;
+
+import com.rdesk.kernel.BootMgr;
+
+import javax.swing.*;
+import java.awt.*;
+import java.awt.event.ActionEvent;
+import java.awt.image.BufferedImage;
+import java.util.logging.Logger;
+
+public class Login {
+    private JFrame frame;
+    private JComboBox<String> userCombo;
+    private JTextField userFieldFallback;
+    private JPasswordField passField;
+    private JLabel statusLabel;
+    private UserRecord stored;
+    private JButton loginBtn;
+    private JButton closeBtn;
+
+    public static void main(String[] args) {
+        SwingUtilities.invokeLater(() -> {
+            try {
+                new Login().start();
+            } catch (Exception e) {
+                JOptionPane.showMessageDialog(null, e);
+                System.exit(1);
+            }
+        });
+    }
+
+    private void start() throws Exception {
+        log("start(): checking store existence");
+        if (!Handler.storeExists()) {
+            showCreateUserDialog();
+        }
+        stored = Handler.load();
+        log("start(): loaded user record: " + (stored != null ? stored.username : "null"));
+        buildAndShowGui();
+    }
+
+    private void buildAndShowGui() {
+        log("buildAndShowGui(): building GUI");
+        frame = new JFrame("rDesk Login");
+        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
+        frame.setResizable(false);
+
+        Image icon = createImageFromSwingIcon(UIManager.getIcon("FileView.computerIcon"));
+        if (icon != null) frame.setIconImage(icon);
+
+        JPanel panel = new JPanel(new GridBagLayout());
+        GridBagConstraints c = new GridBagConstraints();
+        c.insets = new Insets(6, 6, 6, 6);
+        c.anchor = GridBagConstraints.WEST;
+        c.fill = GridBagConstraints.HORIZONTAL;
+
+        int row = 0;
+
+        if (icon != null) {
+            JLabel iconLabel = new JLabel(new ImageIcon(icon.getScaledInstance(64, 64, Image.SCALE_SMOOTH)));
+            GridBagConstraints ic = (GridBagConstraints) c.clone();
+            ic.gridx = 0;
+            ic.gridy = row;
+            ic.gridheight = 2;
+            ic.anchor = GridBagConstraints.CENTER;
+            panel.add(iconLabel, ic);
+        }
+
+        int colOffset = (icon != null) ? 1 : 0;
+
+        c.gridx = colOffset;
+        c.gridy = row;
+        c.gridwidth = 1;
+        panel.add(new JLabel("Username:"), c);
+
+        c.gridx = colOffset + 1;
+        c.gridy = row++;
+        c.weightx = 1.0;
+        String[] users = fetchUserList();
+        if (users.length > 0) {
+            userCombo = new JComboBox<>(users);
+            userCombo.setEditable(false);
+            userCombo.setPreferredSize(new Dimension(160, 24));
+            panel.add(userCombo, c);
+        } else {
+            userFieldFallback = new JTextField(16);
+            userFieldFallback.setPreferredSize(new Dimension(160, 24));
+            panel.add(userFieldFallback, c);
+        }
+
+        c.gridx = colOffset;
+        c.gridy = row;
+        c.weightx = 0;
+        panel.add(new JLabel("Password:"), c);
+
+        c.gridx = colOffset + 1;
+        c.gridy = row++;
+        c.weightx = 1.0;
+        passField = new JPasswordField(16);
+        passField.setPreferredSize(new Dimension(160, 24));
+        panel.add(passField, c);
+
+        closeBtn = new JButton("Close");
+        closeBtn.addActionListener(e -> frame.dispose());
+        loginBtn = new JButton("Login");
+        loginBtn.addActionListener(e -> onLogin());
+
+        c.gridx = colOffset;
+        c.gridy = row;
+        c.gridwidth = 1;
+        c.weightx = 0.5;
+        c.fill = GridBagConstraints.HORIZONTAL;
+        panel.add(closeBtn, c);
+
+        c.gridx = colOffset + 1;
+        c.gridy = row++;
+        c.weightx = 0.5;
+        panel.add(loginBtn, c);
+
+        statusLabel = new JLabel(" ");
+        statusLabel.setForeground(Color.BLUE);
+        c.gridx = colOffset;
+        c.gridy = row;
+        c.gridwidth = 2;
+        c.weightx = 1.0;
+        c.fill = GridBagConstraints.HORIZONTAL;
+        panel.add(statusLabel, c);
+
+        frame.getContentPane().add(panel);
+        frame.getRootPane().setDefaultButton(loginBtn);
+
+        passField.addActionListener(e -> onLogin());
+        if (userFieldFallback != null) userFieldFallback.addActionListener(e -> onLogin());
+        if (userCombo != null) {
+            userCombo.getInputMap(JComponent.WHEN_FOCUSED).put(KeyStroke.getKeyStroke("ENTER"), "login");
+            userCombo.getActionMap().put("login", new AbstractAction() {
+                @Override public void actionPerformed(ActionEvent e) { onLogin(); }
+            });
+        }
+
+        frame.pack();
+        Dimension total = frame.getContentPane().getSize();
+        int gap = 12;
+        int buttonWidth = Math.max(90, (total.width - gap) / 2);
+        closeBtn.setPreferredSize(new Dimension(buttonWidth, 28));
+        loginBtn.setPreferredSize(new Dimension(buttonWidth, 28));
+        frame.pack();
+
+        frame.setLocationRelativeTo(null);
+        frame.setVisible(true);
+        log("buildAndShowGui(): GUI visible");
+    }
+
+    private Image createImageFromSwingIcon(Icon icon) {
+        if (icon == null) return null;
+        int w = Math.max(1, icon.getIconWidth());
+        int h = Math.max(1, icon.getIconHeight());
+        BufferedImage img = new BufferedImage(w, h, BufferedImage.TYPE_INT_ARGB);
+        Graphics2D g = img.createGraphics();
+        try {
+            icon.paintIcon(null, g, 0, 0);
+        } finally {
+            g.dispose();
+        }
+        return img;
+    }
+
+    private void onLogin() {
+        String userAttempt = (userCombo != null)
+                ? String.valueOf(userCombo.getSelectedItem()).trim()
+                : userFieldFallback.getText().trim();
+        char[] passAttempt = passField.getPassword();
+
+        log("onLogin(): attempt for user='" + userAttempt + "'");
+
+        if (stored == null) {
+            statusLabel.setText("No user record found.");
+            Handler.clearPassword(passAttempt);
+            return;
+        }
+
+        if (!stored.username.equals(userAttempt)) {
+            statusLabel.setText("Invalid username or password.");
+            Handler.clearPassword(passAttempt);
+            return;
+        }
+
+        try {
+            boolean ok = Handler.verifyAndClose(frame, passAttempt, stored);
+            if (ok) {
+                log("onLogin(): authentication successful for user='" + userAttempt + "'");
+                statusLabel.setText(" ");
+                SwingUtilities.invokeLater(() -> {
+                    new SwingWorker<Void, Void>() {
+                        @Override protected Void doInBackground() {
+                            try {
+                                BootMgr.launchOrShow();
+                                log("[Login]: BootManager.launchOrShow() completed");
+                            } catch (Exception e) {
+                                log("onLogin(): BootManager error: " + e.getMessage());
+                            }
+                            return null;
+                        }
+                    }.execute();
+                });
+            } else {
+                statusLabel.setText("Invalid username or password.");
+                log("onLogin(): password verification failed for user='" + userAttempt + "'");
+            }
+        } catch (Exception ex) {
+            ex.printStackTrace();
+            statusLabel.setText("Error during verification.");
+            log("onLogin(): exception during verification: " + ex.getMessage());
+        } finally {
+            Handler.clearPassword(passAttempt);
+            passField.setText("");
+        }
+    }
+
+    private void showCreateUserDialog() throws Exception {
+        log("showCreateUserDialog(): creating user dialog");
+        JPanel p = new JPanel(new GridLayout(3,2,6,6));
+        JTextField user = new JTextField(16);
+        JPasswordField pass = new JPasswordField(16);
+        JPasswordField pass2 = new JPasswordField(16);
+        p.add(new JLabel("Username:")); p.add(user);
+        p.add(new JLabel("Password:")); p.add(pass);
+        p.add(new JLabel("Confirm:")); p.add(pass2);
+
+        int res = JOptionPane.showConfirmDialog(null, p, "Create User", JOptionPane.OK_CANCEL_OPTION, JOptionPane.PLAIN_MESSAGE);
+        if (res != JOptionPane.OK_OPTION) {
+            log("showCreateUserDialog(): user cancelled creation, exiting");
+            System.exit(0);
+        }
+        if (!String.valueOf(pass.getPassword()).equals(String.valueOf(pass2.getPassword()))) {
+            JOptionPane.showMessageDialog(null, "Passwords do not match.", "Error", JOptionPane.ERROR_MESSAGE);
+            log("showCreateUserDialog(): passwords did not match");
+            showCreateUserDialog();
+            return;
+        }
+        UserRecord u = Handler.createUser(user.getText().trim(), pass.getPassword());
+        Handler.save(u);
+        log("showCreateUserDialog(): created and saved user '" + u.username + "'");
+        JOptionPane.showMessageDialog(null, "User created.", "Success", JOptionPane.INFORMATION_MESSAGE);
+    }
+
+    private String[] fetchUserList() {
+        try {
+            log("fetchUserList(): attempting to retrieve user list from Handler");
+            String[] users = Handler.listUsers();
+            if (users == null || users.length == 0) {
+                if (stored != null) {
+                    return new String[]{stored.username};
+                }
+                return new String[0];
+            }
+            return users;
+        } catch (Exception t) {
+            if (stored != null) return new String[]{stored.username};
+            return new String[0];
+        }
+    }
+
+    private void log(String msg) {
+        System.out.println("[Login]: " + msg);
+    }
+}

src/main/java/com/rdesk/applications/system/login/UserRecord.java

@@ -0,0 +1,10 @@
+package com.rdesk.applications.system.login;
+
+import com.google.gson.annotations.SerializedName;
+
+public class UserRecord {
+    @SerializedName("username") public String username;
+    @SerializedName("salt_b64") public String saltB64;
+    @SerializedName("hash_b64") public String hashB64;
+    @SerializedName("iterations") public int iterations;
+}

src/main/java/com/rdesk/kernel/BootMgr.java

@@ -0,0 +1,40 @@
+package com.rdesk.kernel;
+
+import javax.swing.*;
+import java.awt.*;
+
+public final class BootMgr {
+    private static JFrame desktopFrame;
+    private BootMgr() {}
+
+    public static synchronized void launchOrShow() {
+        if (desktopFrame == null) {
+            JFrame f = BootProc.boot();
+            if (f != null) desktopFrame = f;
+            else {
+                desktopFrame = new JFrame();
+                desktopFrame.setContentPane(f);
+                desktopFrame.pack();
+            }
+            desktopFrame.setVisible(true);
+            desktopFrame.toFront();
+        } else {
+            if (!desktopFrame.isVisible()) desktopFrame.setVisible(true);
+            desktopFrame.toFront();
+            desktopFrame.requestFocus();
+        }
+    }
+
+    public static synchronized void hideDesktopOnLogout() {
+        if (desktopFrame != null) {
+            desktopFrame.setVisible(false);
+        }
+    }
+
+    public static synchronized void disposeDesktop() {
+        if (desktopFrame != null) {
+            desktopFrame.dispose();
+            desktopFrame = null;
+        }
+    }
+}

src/main/java/com/rdesk/kernel/BootProc.java

@@ -0,0 +1,109 @@
+package com.rdesk.kernel;
+
+import com.rdesk.applications.entertainment.comic.Xkcd;
+import com.rdesk.applications.productivity.Calculator;
+import com.rdesk.applications.productivity.Notes;
+import com.rdesk.applications.productivity.browsing.TabbedBrowser;
+import com.rdesk.applications.productivity.code.CodeDesk;
+import com.rdesk.applications.system.Exit;
+import com.rdesk.applications.system.TaskManager;
+import com.rdesk.applications.system.filehaj.FileExplorerApp;
+import com.rdesk.applications.system.rsys.KbChanger;
+import com.rdesk.kernel.launcher.AppLauncher;
+
+import javax.swing.*;
+
+public class BootProc {
+    private static final boolean RUN_IN_FS = true;
+    private static final boolean USE_SYSDEFAULT_LAF = false;
+    private static final boolean USE_FLATLAF = false;
+    private static final boolean loadSettingsKernelFlag = true;
+
+    private static JFrame mainFrame;
+    private static JDesktopPane desktopPane;
+
+    public static synchronized JFrame boot() {
+        if (mainFrame != null) {
+            if (!mainFrame.isVisible()) mainFrame.setVisible(true);
+            mainFrame.toFront();
+            mainFrame.requestFocus();
+            return mainFrame;
+        }
+
+        Kernel kernel = Kernel.get();
+        kernel.initSettings(loadSettingsKernelFlag);
+        kernel.boot();
+
+        mainFrame = new JFrame("rDesk");
+        mainFrame.setDefaultCloseOperation(JFrame.DO_NOTHING_ON_CLOSE);
+        mainFrame.addWindowListener(new java.awt.event.WindowAdapter() {
+            @Override
+            public void windowClosing(java.awt.event.WindowEvent e) {
+                kernel.shutdown();
+            }
+        });
+
+        if (USE_FLATLAF) {
+            try {
+                UIManager.setLookAndFeel("com.formdev.flatlaf.themes.FlatMacLightLaf");
+            } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
+                JOptionPane.showMessageDialog(null, ex.getMessage() + "@USE_FLATLAF");
+            }
+        }
+
+        if (USE_SYSDEFAULT_LAF) {
+            try {
+                UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
+            } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
+                JOptionPane.showMessageDialog(null, ex.getMessage() + "@USE_SYSDEFAULT_LAF");
+            }
+        }
+
+        if (RUN_IN_FS) {
+            mainFrame.setUndecorated(true);
+            mainFrame.setExtendedState(JFrame.MAXIMIZED_BOTH);
+        } else {
+            mainFrame.setSize(1200, 800);
+            mainFrame.setLocationRelativeTo(null);
+        }
+
+        desktopPane = new JDesktopPane();
+        kernel.windows().attachDesktop(desktopPane);
+        kernel.attachFrame(mainFrame);
+
+        AppLauncher launcher = new AppLauncher(kernel);
+        registerSystemApps(launcher);
+
+        JSplitPane split = new JSplitPane(JSplitPane.HORIZONTAL_SPLIT, launcher, desktopPane);
+        split.setDividerSize(0);
+        split.setEnabled(false);
+
+        mainFrame.setContentPane(split);
+        mainFrame.setVisible(true);
+
+        return mainFrame;
+    }
+
+    public static synchronized JFrame getMainFrame() {
+        return mainFrame;
+    }
+
+    public static synchronized JDesktopPane getDesktopPane() {
+        return desktopPane;
+    }
+
+    private static void registerSystemApps(AppLauncher launcher) {
+        // productivity
+        launcher.addApp(new Notes(), "Productivity");
+        launcher.addApp(new TabbedBrowser(), "Productivity");
+        launcher.addApp(new CodeDesk(), "Productivity");
+        launcher.addApp(new Calculator(), "Productivity");
+        // entertainment
+        launcher.addApp(new Xkcd(), "Entertainment");
+        // System apps
+        launcher.addApp(new Exit(), "System");
+        launcher.addApp(new TaskManager(), "System");
+        launcher.addApp(new FileExplorerApp(), "System");
+        launcher.addApp(new KbChanger(), "System");
+    }
+}

src/main/java/com/rdesk/kernel/Kernel.java

@@ -64,6 +64,14 @@ public class Kernel {
         this.desktopFrame = frame;
     }
 
+
+    public void logoff() {
+        if (running) SwingUtilities.invokeLater(() -> {
+            desktopFrame.setVisible(false);
+        });
+    }
+
+
     public void shutdown() {
         if (!running) return;