Add tn3270(no e) and fix animations

README.md

@@ -29,6 +29,11 @@ java -jar j3270.jar -s mainframe.example.com 992
 # Or using standard x3270 L: prefix
 java -jar j3270.jar L:mainframe.example.com:992
 
+# Connect via Plain TN3270 (Non-E)
+java -jar j3270.jar -P mainframe.example.com 23
+# Or using standard x3270 P: prefix
+java -jar j3270.jar P:mainframe.example.com:23
+
 # Connect with unverified/self-signed certificate verification bypass
 java -jar j3270.jar --tls --insecure mainframe.example.com 992
 
@@ -43,7 +48,7 @@ java -jar j3270.jar -c config.ini
 
 ## ✨ Features
 
-- **TN3270 & TN3270E Protocol Support**: RFC 2355 compliant state machine, negotiation, Device-Type query, and SSL/TLS encryption.
+- **TN3270 & TN3270E Protocol Support**: RFC 2355 compliant state machine, negotiation, Device-Type query, plain TN3270 fallback, and SSL/TLS encryption.
 - **SSL/TLS Security**:
   - Encrypted TN3270 over TLS connections on standard port `992` or custom ports.
   - Interactive certificate verification prompt for self-signed or untrusted certificates with fingerprint, subject, issuer, and validity inspection.
@@ -71,7 +76,7 @@ The project includes self-contained, portable build scripts:
 # Build executable JAR in 2 seconds:
 sh ./build_all.sh
 
-# Run all 48 automated unit tests in ~500ms:
+# Run all 56 automated unit tests in ~500ms:
 sh ./test_all.sh
 ```
 

j3270/src/main/java/org/pubvm/j3270/J3270App.java

@@ -34,6 +34,7 @@ public class J3270App extends JFrame implements ConnectionListener, ScreenUpdate
     private int lastPort = 23;
 
     private FileTransfer fileTransfer;
+    private final java.util.concurrent.atomic.AtomicBoolean screenUpdatePending = new java.util.concurrent.atomic.AtomicBoolean(false);
 
     public J3270App() {
         super("j3270 — Java TN3270 Terminal Emulator");
@@ -363,7 +364,9 @@ public class J3270App extends JFrame implements ConnectionListener, ScreenUpdate
 
     @Override
     public void onScreenUpdated() {
+        if (screenUpdatePending.compareAndSet(false, true)) {
             SwingUtilities.invokeLater(() -> {
+                screenUpdatePending.set(false);
                 // During an active file transfer, let the CUT/DFT handler drive
                 // keyboard state.  In x3270, ft_cut_data() runs before WCC
                 // keyboard-restore is applied — the keyboard stays locked for the
@@ -378,6 +381,7 @@ public class J3270App extends JFrame implements ConnectionListener, ScreenUpdate
                 statusBar.updateStatus();
             });
         }
+    }
 
     @Override
     public void onSoundAlarm() {
@@ -442,6 +446,7 @@ public class J3270App extends JFrame implements ConnectionListener, ScreenUpdate
         boolean debug = false;
         boolean cliTls = false;
         boolean cliNoVerifyCert = false;
+        Boolean cliTn3270e = null;
         org.lib3270j.graphics.GraphicsMode cliGraphicsMode = null;
         String configFile = null;
         java.util.List<String> remainingArgs = new java.util.ArrayList<>();
@@ -452,6 +457,10 @@ public class J3270App extends JFrame implements ConnectionListener, ScreenUpdate
                 cliTls = true;
             } else if ("--no-verify-cert".equals(args[i]) || "--insecure".equals(args[i]) || "-k".equals(args[i])) {
                 cliNoVerifyCert = true;
+            } else if ("--no-tn3270e".equals(args[i]) || "--plain-tn3270".equals(args[i]) || "--plain".equals(args[i]) || "-P".equals(args[i]) || "-p".equals(args[i]) || "--non-e".equals(args[i])) {
+                cliTn3270e = false;
+            } else if ("--tn3270e".equals(args[i])) {
+                cliTn3270e = true;
             } else if (args[i].startsWith("--graphics=")) {
                 cliGraphicsMode = org.lib3270j.graphics.GraphicsMode.fromString(args[i].substring(11));
             } else if (("--graphics".equals(args[i]) || "-g".equals(args[i])) && i + 1 < args.length && !args[i + 1].startsWith("-")) {
@@ -529,6 +538,7 @@ public class J3270App extends JFrame implements ConnectionListener, ScreenUpdate
 
         final boolean finalTls = cliTls;
         final boolean finalNoVerify = cliNoVerifyCert;
+        final Boolean finalTn3270e = cliTn3270e;
         final org.lib3270j.graphics.GraphicsMode finalGraphicsMode = cliGraphicsMode;
 
         SwingUtilities.invokeLater(() -> {
@@ -560,6 +570,9 @@ public class J3270App extends JFrame implements ConnectionListener, ScreenUpdate
                 if (finalNoVerify) {
                     config.setTlsVerifyCert(false);
                 }
+                if (finalTn3270e != null) {
+                    config.setTn3270eEnabled(finalTn3270e);
+                }
                 if (finalGraphicsMode != null) {
                     config.setGraphicsMode(finalGraphicsMode);
                 } else {
@@ -578,9 +591,11 @@ public class J3270App extends JFrame implements ConnectionListener, ScreenUpdate
                         int port = org.pubvm.j3270.config.Settings.getAutoConnectPort();
                         boolean tls = org.pubvm.j3270.config.Settings.getAutoConnectTls();
                         boolean verify = org.pubvm.j3270.config.Settings.getAutoConnectVerifyCert();
+                        boolean tn3270e = org.pubvm.j3270.config.Settings.getAutoConnectTn3270e();
                         if (host != null && !host.isEmpty()) {
                             ConnectionConfig config = new ConnectionConfig(host, port, TerminalModel.IBM_3279_4, tls);
                             config.setTlsVerifyCert(verify);
+                            config.setTn3270eEnabled(finalTn3270e != null ? finalTn3270e : tn3270e);
                             if (finalGraphicsMode != null) {
                                 config.setGraphicsMode(finalGraphicsMode);
                             } else {

j3270/src/main/java/org/pubvm/j3270/config/Settings.java

@@ -78,13 +78,21 @@ public class Settings {
         prefs.putBoolean("autoConnectVerifyCert", verify);
     }
 
+    public static boolean getAutoConnectTn3270e() {
+        return prefs.getBoolean("autoConnectTn3270e", true);
+    }
+
+    public static void setAutoConnectTn3270e(boolean tn3270e) {
+        prefs.putBoolean("autoConnectTn3270e", tn3270e);
+    }
+
     public static org.lib3270j.graphics.GraphicsMode getGraphicsMode() {
-        String modeStr = prefs.get("graphicsMode", org.lib3270j.graphics.GraphicsMode.NONE.name());
+        String modeStr = prefs.get("graphicsMode", org.lib3270j.graphics.GraphicsMode.BOTH.name());
         return org.lib3270j.graphics.GraphicsMode.fromString(modeStr);
     }
 
     public static void setGraphicsMode(org.lib3270j.graphics.GraphicsMode mode) {
-        prefs.put("graphicsMode", (mode != null ? mode : org.lib3270j.graphics.GraphicsMode.NONE).name());
+        prefs.put("graphicsMode", (mode != null ? mode : org.lib3270j.graphics.GraphicsMode.BOTH).name());
     }
 
     public static Color getColorOverride(int index, Color defaultColor) {
@@ -243,6 +251,11 @@ public class Settings {
                     case "tlsVerifyCert":
                         setAutoConnectVerifyCert(Boolean.parseBoolean(value));
                         break;
+                    case "autoConnectTn3270e":
+                    case "tn3270e":
+                    case "enableTn3270e":
+                        setAutoConnectTn3270e(Boolean.parseBoolean(value));
+                        break;
                     case "blockSelectMode": setBlockSelectMode(Boolean.parseBoolean(value)); break;
                     default:
                         log.warning("Unknown behavior/connection key: " + key);
@@ -309,6 +322,7 @@ public class Settings {
                 w.println("autoConnectPort = " + getAutoConnectPort());
                 w.println("autoConnectTls = " + getAutoConnectTls());
                 w.println("autoConnectVerifyCert = " + getAutoConnectVerifyCert());
+                w.println("autoConnectTn3270e = " + getAutoConnectTn3270e());
             }
             w.println("blockSelectMode = " + getBlockSelectMode());
             w.println();

j3270/src/main/java/org/pubvm/j3270/ui/ConnectDialog.java

@@ -18,6 +18,7 @@ public class ConnectDialog extends JDialog {
     private JTextField luField;
     private JCheckBox tlsCheckBox;
     private JCheckBox verifyCertCheckBox;
+    private JCheckBox tn3270eCheckBox;
     private boolean confirmed;
     private ConnectionConfig result;
 
@@ -146,6 +147,17 @@ public class ConnectDialog extends JDialog {
         verifyCertCheckBox.setFocusPainted(false);
         mainPanel.add(verifyCertCheckBox, gbc);
 
+        // TN3270E Checkbox
+        gbc.gridx = 1;
+        gbc.gridy = 7;
+        tn3270eCheckBox = new JCheckBox("Enable TN3270E (Extended 3270)");
+        tn3270eCheckBox.setBackground(new Color(30, 30, 30));
+        tn3270eCheckBox.setForeground(fg);
+        tn3270eCheckBox.setFont(new Font(Font.SANS_SERIF, Font.PLAIN, 13));
+        tn3270eCheckBox.setSelected(org.pubvm.j3270.config.Settings.getAutoConnectTn3270e());
+        tn3270eCheckBox.setFocusPainted(false);
+        mainPanel.add(tn3270eCheckBox, gbc);
+
         // Buttons
         JPanel buttonPanel = new JPanel(new FlowLayout(FlowLayout.RIGHT));
         buttonPanel.setBackground(new Color(30, 30, 30));
@@ -169,7 +181,7 @@ public class ConnectDialog extends JDialog {
         buttonPanel.add(connectBtn);
 
         gbc.gridx = 0;
-        gbc.gridy = 7;
+        gbc.gridy = 8;
         gbc.gridwidth = 2;
         mainPanel.add(buttonPanel, gbc);
 
@@ -214,6 +226,7 @@ public class ConnectDialog extends JDialog {
         result.setGraphicsMode((org.lib3270j.graphics.GraphicsMode) graphicsCombo.getSelectedItem());
         result.setUseTls(tlsCheckBox.isSelected());
         result.setTlsVerifyCert(verifyCertCheckBox.isSelected());
+        result.setTn3270eEnabled(tn3270eCheckBox.isSelected());
         confirmed = true;
         dispose();
     }
@@ -243,4 +256,8 @@ public class ConnectDialog extends JDialog {
     public void setInitialVerifyCert(boolean verify) {
         verifyCertCheckBox.setSelected(verify);
     }
+
+    public void setInitialTn3270e(boolean tn3270e) {
+        tn3270eCheckBox.setSelected(tn3270e);
+    }
 }

j3270/src/main/java/org/pubvm/j3270/ui/TerminalPanel.java

@@ -22,6 +22,7 @@ public class TerminalPanel extends JPanel {
 
     // Font and cell dimensions
     private Font terminalFont;
+    private Font boldTerminalFont;
     private int cellWidth;
     private int cellHeight;
     private int fontAscent;
@@ -47,6 +48,14 @@ public class TerminalPanel extends JPanel {
 
     // ========== Selection / Copy-Paste state ==========
     private boolean blockSelectMode = false;
+
+    private static final String[] CHAR_STRINGS = new String[128];
+    static {
+        for (int i = 0; i < 128; i++) {
+            CHAR_STRINGS[i] = String.valueOf((char) i);
+        }
+    }
+    private static final Color CURSOR_COLOR = new Color(255, 255, 255, 180);
     private int selectionStartRow = -1, selectionStartCol = -1;
     private int selectionEndRow = -1, selectionEndCol = -1;
     private boolean isDragging = false;
@@ -779,6 +788,7 @@ public class TerminalPanel extends JPanel {
         cellHeight = fm.getHeight();
         fontAscent = fm.getAscent();
         fontDescent = fm.getDescent();
+        boldTerminalFont = terminalFont.deriveFont(Font.BOLD);
     }
 
     private void setupCursorBlink() {
@@ -818,6 +828,8 @@ public class TerminalPanel extends JPanel {
         Graphics2D g2 = (Graphics2D) g;
         g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
         g2.setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING, RenderingHints.VALUE_TEXT_ANTIALIAS_LCD_HRGB);
+        g2.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_NEAREST_NEIGHBOR);
+        g2.setRenderingHint(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_SPEED);
 
         // Clear entire panel with background color
         g2.setColor(bgColor);
@@ -828,8 +840,8 @@ public class TerminalPanel extends JPanel {
         int oy = getRenderOffsetY();
 
         ScreenBuffer sb = client.getScreenBuffer();
-        int rows = sb.getRows();
+        int rows = sb.getDisplayRows();
-        int cols = sb.getCols();
+        int cols = sb.getDisplayCols();
         boolean isColorModel = client.getConfig().getModel().isColor();
 
         // Track current field attribute for monochrome color decisions
@@ -839,7 +851,7 @@ public class TerminalPanel extends JPanel {
         for (int row = 0; row < rows; row++) {
             for (int col = 0; col < cols; col++) {
                 int baddr = row * cols + col;
-                ExtendedAttribute ea = sb.getCell(baddr);
+                ExtendedAttribute ea = sb.getDisplayCell(baddr);
 
                 int x = ox + col * cellWidth;
                 int y = oy + row * cellHeight;
@@ -854,10 +866,7 @@ public class TerminalPanel extends JPanel {
                 if (ea.isFieldAttribute()) {
                     currentFA = ea.fa;
                     currentFieldEa = ea;
-                    // Field attributes display as blanks
+                    // Selection highlight on field attribute cells
-                    g2.setColor(this.bgColor);
-                    g2.fillRect(x, y, cellWidth, cellHeight);
-                    // Selection highlight on field attribute cells too
                     if (isCellSelected(row, col)) {
                         g2.setColor(SELECTION_COLOR);
                         g2.fillRect(x, y, cellWidth, cellHeight);
@@ -892,12 +901,9 @@ public class TerminalPanel extends JPanel {
                 // Handle invisible fields (zero intensity / password fields)
                 // Modern UX: render '*' for typed characters so user sees length/digit count
                 if (faIsZero(currentFA & 0xFF)) {
-                    g2.setColor(this.bgColor);
-                    g2.fillRect(x, y, cellWidth, cellHeight);
-
                     char ch = ea.ucs4;
                     if (ch > 0x20 && ch != 0xFF) {
-                        Font f = bold ? terminalFont.deriveFont(Font.BOLD) : terminalFont;
+                        Font f = bold ? boldTerminalFont : terminalFont;
                         g2.setFont(f);
                         g2.setColor(fgColor);
                         g2.drawString("*", x, y + fontAscent);
@@ -917,9 +923,11 @@ public class TerminalPanel extends JPanel {
                     bgColor = tmp;
                 }
 
-                // Draw background
+                // Draw background only if different from default panel bgColor or if inverted
+                if (!bgColor.equals(this.bgColor) || reverse) {
                     g2.setColor(bgColor);
                     g2.fillRect(x, y, cellWidth, cellHeight);
+                }
 
                 // Draw character or Programmed Symbol
                 int cs = (ea.cs != 0) ? (ea.cs & 0xFF) : (currentFieldEa != null ? (currentFieldEa.cs & 0xFF) : 0);
@@ -927,23 +935,27 @@ public class TerminalPanel extends JPanel {
                 if (cs >= 0x40 && client.getProgramSymbolManager() != null) {
                     org.lib3270j.graphics.ProgramSymbolSet.SymbolSlot slot = client.getProgramSymbolManager().getSymbol(cs, ea.ec & 0xFF);
                     if (slot != null) {
-                        int[] rgb = slot.getRgbPixels(fgColor.getRGB(), bgColor.getRGB());
+                        java.awt.image.BufferedImage img = slot.getScaledImage(cellWidth, cellHeight, fgColor.getRGB(), bgColor.getRGB());
-                        java.awt.image.BufferedImage img = new java.awt.image.BufferedImage(slot.getWidth(), slot.getHeight(), java.awt.image.BufferedImage.TYPE_INT_ARGB);
+                        if (img != null) {
-                        img.setRGB(0, 0, slot.getWidth(), slot.getHeight(), rgb, 0, slot.getWidth());
+                            g2.drawImage(img, x, y, null);
-                        g2.drawImage(img, x, y, cellWidth, cellHeight, null);
                             drawnAsPs = true;
                         }
                     }
+                }
 
                 if (!drawnAsPs) {
                     char ch = ea.ucs4;
                     if (ch > 0x20 && ch != 0xFF) {
-                        Font f = bold ? terminalFont.deriveFont(Font.BOLD) : terminalFont;
+                        Font f = bold ? boldTerminalFont : terminalFont;
                         g2.setFont(f);
                         g2.setColor(fgColor);
+                        if (ch < 128) {
+                            g2.drawString(CHAR_STRINGS[ch], x, y + fontAscent);
+                        } else {
                             g2.drawString(String.valueOf(ch), x, y + fontAscent);
                         }
                     }
+                }
 
                 // Draw underline
                 if (underline) {
@@ -975,13 +987,13 @@ public class TerminalPanel extends JPanel {
 
         // Draw cursor
         if (cursorVisible && client.getConnectionState().isFullSession()) {
-            int curAddr = sb.getCursorAddress();
+            int curAddr = sb.getDisplayCursorAddress();
             int curRow = curAddr / cols;
             int curCol = curAddr % cols;
             int cx = ox + curCol * cellWidth;
             int cy = oy + curRow * cellHeight;
 
-            g2.setColor(new Color(255, 255, 255, 180));
+            g2.setColor(CURSOR_COLOR);
             g2.setXORMode(bgColor);
             g2.fillRect(cx, cy, cellWidth, cellHeight);
             g2.setPaintMode();

lib3270j/src/main/java/org/lib3270j/ConnectionConfig.java

@@ -17,7 +17,8 @@ public class ConnectionConfig {
     private int connectTimeoutMs = 15000;
     private int nopIntervalSeconds = 0;
     private String terminalName = null; // override terminal type string
-    private org.lib3270j.graphics.GraphicsMode graphicsMode = org.lib3270j.graphics.GraphicsMode.NONE;
+    private boolean tn3270eEnabled = true;
+    private org.lib3270j.graphics.GraphicsMode graphicsMode = org.lib3270j.graphics.GraphicsMode.BOTH;
 
     public ConnectionConfig() {}
 
@@ -66,6 +67,9 @@ public class ConnectionConfig {
     public boolean isTlsVerifyCert()          { return tlsVerifyCert; }
     public void setTlsVerifyCert(boolean verify) { this.tlsVerifyCert = verify; }
 
+    public boolean isTn3270eEnabled()         { return tn3270eEnabled; }
+    public void setTn3270eEnabled(boolean enabled) { this.tn3270eEnabled = enabled; }
+
     public org.lib3270j.tls.TlsCertificateVerifier getCertificateVerifier() { return certificateVerifier; }
     public void setCertificateVerifier(org.lib3270j.tls.TlsCertificateVerifier verifier) { this.certificateVerifier = verifier; }
 
@@ -87,8 +91,8 @@ public class ConnectionConfig {
     public void setTerminalName(String name)  { this.terminalName = name; }
 
     /**
-     * Parse a host connection string which may include prefixes for TLS (e.g. "L:host:port", "ssl:host:port", "y:host:port")
+     * Parse a host connection string which may include prefixes for TLS (e.g. "L:host:port", "ssl:host:port", "y:host:port"),
-     * or standard "host:port" formats.
+     * plain TN3270 (e.g. "P:host:port", "plain:host:port", "non-e:host:port"), or standard "host:port" formats.
      */
     public static ConnectionConfig parseHostString(String hostStr, int defaultPort, TerminalModel defaultModel) {
         if (hostStr == null || hostStr.trim().isEmpty()) {
@@ -96,17 +100,35 @@ public class ConnectionConfig {
         }
         String s = hostStr.trim();
         boolean tls = false;
+        boolean tn3270e = true;
 
-        // Check TLS prefixes
+        // Parse chained x3270-style prefixes (e.g. "L:P:host:port" or "P:host:port")
-        if (s.startsWith("L:") || s.startsWith("l:")) {
+        boolean prefixFound = true;
-            tls = true;
+        while (prefixFound) {
-            s = s.substring(2);
+            prefixFound = false;
-        } else if (s.startsWith("Y:") || s.startsWith("y:")) {
+            if (s.startsWith("L:") || s.startsWith("l:") || s.startsWith("Y:") || s.startsWith("y:")) {
                 tls = true;
                 s = s.substring(2);
+                prefixFound = true;
             } else if (s.toLowerCase().startsWith("ssl:") || s.toLowerCase().startsWith("tls:")) {
                 tls = true;
                 s = s.substring(4);
+                prefixFound = true;
+            } else if (s.startsWith("N:") || s.startsWith("n:") || s.toLowerCase().startsWith("notls:") || s.toLowerCase().startsWith("nossl:")) {
+                tls = false;
+                int colon = s.indexOf(':');
+                s = s.substring(colon + 1);
+                prefixFound = true;
+            } else if (s.startsWith("P:") || s.startsWith("p:")) {
+                tn3270e = false;
+                s = s.substring(2);
+                prefixFound = true;
+            } else if (s.toLowerCase().startsWith("plain:") || s.toLowerCase().startsWith("non-e:")) {
+                tn3270e = false;
+                int colon = s.indexOf(':');
+                s = s.substring(colon + 1);
+                prefixFound = true;
+            }
         }
 
         String host = s;
@@ -133,6 +155,7 @@ public class ConnectionConfig {
 
         ConnectionConfig config = new ConnectionConfig(host, port, defaultModel != null ? defaultModel : TerminalModel.IBM_3279_4);
         config.setUseTls(tls);
+        config.setTn3270eEnabled(tn3270e);
         return config;
     }
 

lib3270j/src/main/java/org/lib3270j/datastream/DataStreamProcessor.java

@@ -9,6 +9,7 @@ import static org.lib3270j.protocol.DS3270Constants.*;
 import java.io.ByteArrayOutputStream;
 import java.util.List;
 import java.util.concurrent.CopyOnWriteArrayList;
+import java.util.logging.Level;
 import java.util.logging.Logger;
 
 /**
@@ -105,16 +106,24 @@ public class DataStreamProcessor {
             return;
 
         int cmd = data[offset] & 0xFF;
-        log.info(">>> CMD: " + commandName(cmd) + " (0x" + String.format("%02x", cmd) + ") " + length + " bytes");
+        synchronized (screen.getRenderLock()) {
+            if (log.isLoggable(Level.FINE)) {
+                log.fine(">>> CMD: " + commandName(cmd) + " (0x" + String.format("%02x", cmd) + ") " + length + " bytes");
+            }
 
             switch (cmd) {
                 case CMD_W:
                 case SNA_CMD_W:
+                    programSymbolManager.commitStagedSymbols();
                     processWrite(data, offset, length, false);
                     break;
                 case CMD_EW:
                 case SNA_CMD_EW:
-                log.info(">>> ERASE/WRITE: clearing screen (default size)"); {
+                    programSymbolManager.commitStagedSymbols();
+                    if (log.isLoggable(Level.FINE)) {
+                        log.fine(">>> ERASE/WRITE: clearing screen (default size)");
+                    }
+                    {
                         int oldRows = screen.getRows();
                         int oldCols = screen.getCols();
                         screen.erase(false);
@@ -127,7 +136,11 @@ public class DataStreamProcessor {
                     break;
                 case CMD_EWA:
                 case SNA_CMD_EWA:
-                log.info(">>> ERASE/WRITE ALTERNATE: clearing screen (alt size)"); {
+                    programSymbolManager.commitStagedSymbols();
+                    if (log.isLoggable(Level.FINE)) {
+                        log.fine(">>> ERASE/WRITE ALTERNATE: clearing screen (alt size)");
+                    }
+                    {
                         int oldRows = screen.getRows();
                         int oldCols = screen.getCols();
                         screen.erase(true);
@@ -140,18 +153,22 @@ public class DataStreamProcessor {
                     break;
                 case CMD_RB:
                 case SNA_CMD_RB:
+                    programSymbolManager.commitStagedSymbols();
                     processReadBuffer();
                     break;
                 case CMD_RM:
                 case SNA_CMD_RM:
+                    programSymbolManager.commitStagedSymbols();
                     processReadModified(false);
                     break;
                 case CMD_RMA:
                 case SNA_CMD_RMA:
+                    programSymbolManager.commitStagedSymbols();
                     processReadModified(true);
                     break;
                 case CMD_EAU:
                 case SNA_CMD_EAU:
+                    programSymbolManager.commitStagedSymbols();
                     log.info(">>> EAU: erasing all unprotected fields");
                     screen.eraseAllUnprotected();
                     break;
@@ -170,9 +187,11 @@ public class DataStreamProcessor {
             // Translate EBCDIC to Unicode for display
             screen.translateToUnicode();
             screen.markAllChanged();
+            screen.updateDisplaySnapshot();
+        }
 
         // Debug: dump non-empty screen lines
-        if (cmd == SNA_CMD_EWA || cmd == CMD_EWA || cmd == SNA_CMD_EW || cmd == CMD_EW) {
+        if (log.isLoggable(Level.FINE) && (cmd == SNA_CMD_EWA || cmd == CMD_EWA || cmd == SNA_CMD_EW || cmd == CMD_EW)) {
             int r = screen.getRows();
             int c = screen.getCols();
             StringBuilder dump = new StringBuilder();
@@ -205,7 +224,7 @@ public class DataStreamProcessor {
                 }
             }
             if (dump.length() > 0) {
-                log.info("Screen content after " + commandName(cmd) + ":\n" + dump.toString());
+                log.fine("Screen content after " + commandName(cmd) + ":\n" + dump.toString());
             }
         }
     }
@@ -798,7 +817,6 @@ public class DataStreamProcessor {
                         byte[] psData = new byte[fieldLen - 3];
                         System.arraycopy(data, pos + 3, psData, 0, psData.length);
                         programSymbolManager.loadps(psData);
-                        notifyScreenUpdated();
                     }
                     break;
                 case org.lib3270j.graphics.GocaConstants.SF_LOADPS: { // 0x0F: 2-byte Structured Field prefix
@@ -810,7 +828,6 @@ public class DataStreamProcessor {
                                     byte[] psData = new byte[fieldLen - 4];
                                     System.arraycopy(data, pos + 4, psData, 0, psData.length);
                                     programSymbolManager.loadps(psData);
-                                    notifyScreenUpdated();
                                 }
                                 break;
                             case org.lib3270j.graphics.GocaConstants.SF_OBJCNTL_SUB: // 0x11: Object Control (Procedure orders)

lib3270j/src/main/java/org/lib3270j/datastream/QueryReplyBuilder.java

@@ -22,7 +22,7 @@ public class QueryReplyBuilder {
     private static final int Yr_3279_2 = 0x0002006f;
 
     private final ScreenBuffer screen;
-    private GraphicsMode graphicsMode = GraphicsMode.NONE;
+    private GraphicsMode graphicsMode = GraphicsMode.BOTH;
 
     // Base query reply codes (text mode)
     private static final int[] SUPPORTED_QR_BASE = {
@@ -313,9 +313,9 @@ public class QueryReplyBuilder {
 
     private byte[] buildCharsets() {
         if (graphicsMode.isProgrammedSymbolsEnabled()) {
-            // Programmed Symbols mode (3279 PS with LoadPS 0x0A)
+            // Programmed Symbols mode (3279 PS with LoadPS 0x0A, flags1 = 0xA2 for GE + PS + CGCSGID)
             ByteArrayOutputStream out = new ByteArrayOutputStream(65);
-            out.write(0x82); // flags: GE, CGCSGID present
+            out.write(0xa2); // flags: GE (0x80), PS/Loadable Charsets (0x20), CGCSGID present (0x02)
             out.write(0x00); // more flags
             out.write(SW_3279_2); // SDW (9)
             out.write(SH_3279_2); // SDH (12)
@@ -328,14 +328,14 @@ public class QueryReplyBuilder {
             out.write(0x00); out.write(0x10); out.write(0x00); out.write(0x02); out.write(0xb9); out.write(0x00); out.write(0x25);
             // Descriptor 2 (SET 1): APL/GE character set
             out.write(0x01); out.write(0x00); out.write(0xf1); out.write(0x03); out.write(0xc3); out.write(0x01); out.write(0x36);
-            // Loadable Single-Plane PS Sets (PSA, PSB: Slots 2, 3)
+            // Loadable Single-Plane PS Sets (PSA, PSB: Slots 2, 3) - Flags = 0x80 (Loadable, single plane)
             out.write(0x02); out.write(0x80); out.write(0x40); out.write(0x00); out.write(0x00); out.write(0x00); out.write(0x00);
             out.write(0x03); out.write(0x80); out.write(0x41); out.write(0x00); out.write(0x00); out.write(0x00); out.write(0x00);
-            // Loadable Triple-Plane PS Sets (PSC, PSD, PSE, PSF: Slots 4, 5, 6, 7)
+            // Loadable Triple-Plane PS Sets (PSC, PSD, PSE, PSF: Slots 4, 5, 6, 7) - Flags = 0xC0 (0x80 Loadable | 0x40 Triple-plane)
-            out.write(0x04); out.write(0x80); out.write(0x42); out.write(0x00); out.write(0x00); out.write(0x00); out.write(0x00);
+            out.write(0x04); out.write(0xc0); out.write(0x42); out.write(0x00); out.write(0x00); out.write(0x00); out.write(0x00);
-            out.write(0x05); out.write(0x80); out.write(0x43); out.write(0x00); out.write(0x00); out.write(0x00); out.write(0x00);
+            out.write(0x05); out.write(0xc0); out.write(0x43); out.write(0x00); out.write(0x00); out.write(0x00); out.write(0x00);
-            out.write(0x06); out.write(0x80); out.write(0x44); out.write(0x00); out.write(0x00); out.write(0x00); out.write(0x00);
+            out.write(0x06); out.write(0xc0); out.write(0x44); out.write(0x00); out.write(0x00); out.write(0x00); out.write(0x00);
-            out.write(0x07); out.write(0x80); out.write(0x45); out.write(0x00); out.write(0x00); out.write(0x00); out.write(0x00);
+            out.write(0x07); out.write(0xc0); out.write(0x45); out.write(0x00); out.write(0x00); out.write(0x00); out.write(0x00);
             return out.toByteArray();
         }
 

lib3270j/src/main/java/org/lib3270j/graphics/ProgramSymbolManager.java

@@ -17,12 +17,31 @@ public class ProgramSymbolManager {
     public static final int NUMBER_TRIPLE_PLANE_PS_SETS = 4; // RWS 4..7 (Sets 2..5)
     public static final int NUMBER_GRAPHICS_SYMBOL_SETS = 4; // RWS 8..11 (Sets 6..9)
 
+    private int defaultCellWidth = 9;
+    private int defaultCellHeight = 12; // Standard IBM 3279 PS Slot Default Height (SDH = 0x0C = 12)
+
+    public void setDefaultCellDimensions(int width, int height) {
+        this.defaultCellWidth = (width > 0) ? width : 9;
+        this.defaultCellHeight = (height > 0) ? height : 12;
+    }
+
+    public int getDefaultCellWidth() {
+        return defaultCellWidth;
+    }
+
+    public int getDefaultCellHeight() {
+        return defaultCellHeight;
+    }
+
     private final ProgramSymbolSet[] sets = new ProgramSymbolSet[NUMBER_SYMBOL_SETS];
+    private final ProgramSymbolSet[] stagingSets = new ProgramSymbolSet[NUMBER_SYMBOL_SETS];
+    private final ProgramSymbolSet[] lcidMap = new ProgramSymbolSet[256];
 
     public ProgramSymbolManager() {
         for (int i = 0; i < NUMBER_SYMBOL_SETS; i++) {
             boolean isTriple = (i >= NUMBER_SINGLE_PLANE_PS_SETS && i < NUMBER_SINGLE_PLANE_PS_SETS + NUMBER_TRIPLE_PLANE_PS_SETS);
             sets[i] = new ProgramSymbolSet(isTriple);
+            stagingSets[i] = new ProgramSymbolSet(isTriple);
         }
     }
 
@@ -30,32 +49,67 @@ public class ProgramSymbolManager {
      * Resets all symbol sets.
      */
     public synchronized void clearAll() {
-        for (ProgramSymbolSet set : sets) {
+        Arrays.fill(lcidMap, null);
-            set.clear();
+        for (int i = 0; i < NUMBER_SYMBOL_SETS; i++) {
-            set.setLcid(0);
+            sets[i].clear();
+            sets[i].setLcid(0);
+            stagingSets[i].clear();
+            stagingSets[i].setLcid(0);
+        }
+    }
+
+    /**
+     * Commits all staged multi-plane symbol sets to the active presentation sets atomically.
+     */
+    public synchronized void commitStagedSymbols() {
+        for (int i = 0; i < NUMBER_SYMBOL_SETS; i++) {
+            int lcid = stagingSets[i].getLcid();
+            if (lcid > 0) {
+                ProgramSymbolSet staged = stagingSets[i];
+                ProgramSymbolSet active = sets[i];
+                active.setLcid(lcid);
+                for (int slot = 0; slot < ProgramSymbolSet.NUM_SLOTS; slot++) {
+                    active.setSlot(slot, staged.getSlot(slot));
+                }
+                if (lcid < 256) {
+                    lcidMap[lcid] = active;
+                }
+            }
         }
     }
 
     /**
      * Retrieves the symbol set corresponding to a given LCID (0x40 - 0xFE).
      */
-    public synchronized ProgramSymbolSet getSymbolSet(int lcid) {
+    public ProgramSymbolSet getSymbolSet(int lcid) {
-        if (lcid <= 0) {
+        if (lcid <= 0 || lcid >= 256) {
             return null;
         }
-        for (ProgramSymbolSet set : sets) {
+        ProgramSymbolSet set = lcidMap[lcid];
-            if (set.getLcid() == lcid) {
+        if (set == null) {
+            for (ProgramSymbolSet s : stagingSets) {
+                if (s.getLcid() == lcid) return s;
+            }
+        }
         return set;
     }
-        }
-        return null;
-    }
 
     /**
      * Retrieves a specific symbol glyph by LCID and character code point (0x40 - 0xFE).
      */
-    public synchronized ProgramSymbolSet.SymbolSlot getSymbol(int lcid, int codePoint) {
+    public ProgramSymbolSet.SymbolSlot getSymbol(int lcid, int codePoint) {
-        ProgramSymbolSet set = getSymbolSet(lcid);
+        if (lcid <= 0 || lcid >= 256) {
+            return null;
+        }
+        ProgramSymbolSet set = lcidMap[lcid];
+        if (set == null) {
+            for (ProgramSymbolSet s : stagingSets) {
+                if (s.getLcid() == lcid) {
+                    set = s;
+                    break;
+                }
+            }
+        }
         if (set == null) {
             return null;
         }
@@ -98,12 +152,12 @@ public class ProgramSymbolManager {
                 return;
         }
 
-        ProgramSymbolSet set = sets[setIndex];
         boolean isTriplePlane = (rws >= 4 && rws <= 7);
+        ProgramSymbolSet set = isTriplePlane ? stagingSets[setIndex] : sets[setIndex];
 
         int extHeaderLen = 0;
-        int cellWidth = 9;
+        int cellWidth = defaultCellWidth;
-        int cellHeight = 16;
+        int cellHeight = defaultCellHeight;
         int colorPlane = 0; // 0 = all planes, 1 = Red, 2 = Green, 4 = Blue
 
         if (hasExtHeader && data.length > 4) {
@@ -121,10 +175,10 @@ public class ProgramSymbolManager {
             }
         }
 
-        if (clearAll) {
-            set.clear();
-        }
         set.setLcid(lcid);
+        if (!isTriplePlane && lcid > 0 && lcid < 256) {
+            lcidMap[lcid] = set;
+        }
 
         int offset = 4 + (hasExtHeader ? extHeaderLen : 0);
         int remaining = data.length - offset;
@@ -142,12 +196,10 @@ public class ProgramSymbolManager {
         }
 
         while (remaining >= bytesPerSymbol && codeIndex < ProgramSymbolSet.NUM_SLOTS) {
-            byte[] pixelData;
+            byte[] pixelData = new byte[cellWidth * cellHeight];
             ProgramSymbolSet.SymbolSlot existing = set.getSlot(codeIndex);
-            if (existing != null && existing.getWidth() == cellWidth && existing.getHeight() == cellHeight) {
+            if (!clearAll && existing != null && existing.getWidth() == cellWidth && existing.getHeight() == cellHeight) {
-                pixelData = existing.getPixelData();
+                System.arraycopy(existing.getPixelData(), 0, pixelData, 0, Math.min(existing.getPixelData().length, pixelData.length));
-            } else {
-                pixelData = new byte[cellWidth * cellHeight];
             }
 
             if (loadFormat == 1) {
@@ -163,10 +215,18 @@ public class ProgramSymbolManager {
             remaining -= bytesPerSymbol;
         }
 
-        logger.info(String.format("LOADPS: Loaded PS Set LCID=0x%02X (RWS=%d, %s, %dx%d, %d glyphs)",
+        if (clearAll) {
+            for (int i = codeIndex; i < ProgramSymbolSet.NUM_SLOTS; i++) {
+                set.clearSlot(i);
+            }
+        }
+
+        if (logger.isLoggable(Level.FINE)) {
+            logger.fine(String.format("LOADPS: Loaded PS Set LCID=0x%02X (RWS=%d, %s, %dx%d, %d glyphs)",
                     lcid, rws, isTriplePlane ? "Triple-Plane" : "Single-Plane",
                     cellWidth, cellHeight, codeIndex - ((startCodePoint >= 0x40) ? (startCodePoint - 0x40) : startCodePoint)));
         }
+    }
 
     /**
      * Unpacks Format 1 (9x16) symbol slice bit-pattern.

lib3270j/src/main/java/org/lib3270j/graphics/ProgramSymbolSet.java

@@ -64,6 +64,12 @@ public class ProgramSymbolSet {
         private int[] cachedRgbArray;
         private int cachedFgRgb = -1;
         private int cachedBgRgb = -1;
+        private java.awt.image.BufferedImage cachedImage;
+        private java.awt.image.BufferedImage cachedScaledImage;
+        private int cachedTargetW = 0;
+        private int cachedTargetH = 0;
+        private int cachedScaledFgRgb = -1;
+        private int cachedScaledBgRgb = -1;
 
         public SymbolSlot(int width, int height, byte[] pixelData, boolean isTriplePlane) {
             this.width = width > 0 ? width : 9;
@@ -88,6 +94,61 @@ public class ProgramSymbolSet {
             return isTriplePlane;
         }
 
+        /**
+         * Returns an image scaled directly to target dimensions (cellWidth x cellHeight).
+         * Enables unscaled 1:1 hardware blitting in Java2D.
+         */
+        public synchronized java.awt.image.BufferedImage getScaledImage(int targetW, int targetH, int fgArgb, int bgArgb) {
+            if (targetW <= 0 || targetH <= 0) {
+                return getImage(fgArgb, bgArgb);
+            }
+            if (targetW == width && targetH == height) {
+                return getImage(fgArgb, bgArgb);
+            }
+            if (cachedScaledImage != null && cachedTargetW == targetW && cachedTargetH == targetH
+                    && cachedScaledFgRgb == fgArgb && cachedScaledBgRgb == bgArgb) {
+                return cachedScaledImage;
+            }
+            int[] srcRgb = getRgbPixels(fgArgb, bgArgb);
+            java.awt.image.BufferedImage scaled = new java.awt.image.BufferedImage(targetW, targetH, java.awt.image.BufferedImage.TYPE_INT_ARGB);
+            int[] dstRgb = ((java.awt.image.DataBufferInt) scaled.getRaster().getDataBuffer()).getData();
+
+            for (int dy = 0; dy < targetH; dy++) {
+                int sy = dy * height / targetH;
+                int srcRowOffset = sy * width;
+                int dstRowOffset = dy * targetW;
+                for (int dx = 0; dx < targetW; dx++) {
+                    int sx = dx * width / targetW;
+                    dstRgb[dstRowOffset + dx] = srcRgb[srcRowOffset + sx];
+                }
+            }
+
+            this.cachedScaledImage = scaled;
+            this.cachedTargetW = targetW;
+            this.cachedTargetH = targetH;
+            this.cachedScaledFgRgb = fgArgb;
+            this.cachedScaledBgRgb = bgArgb;
+            return scaled;
+        }
+
+        /**
+         * Computes and returns the cached BufferedImage for this symbol glyph.
+         * Eliminates per-cell heap allocations during high frame rate rendering.
+         */
+        public synchronized java.awt.image.BufferedImage getImage(int fgArgb, int bgArgb) {
+            if (cachedImage != null && cachedFgRgb == fgArgb && cachedBgRgb == bgArgb) {
+                return cachedImage;
+            }
+            int[] rgb = getRgbPixels(fgArgb, bgArgb);
+            java.awt.image.BufferedImage img = new java.awt.image.BufferedImage(width, height, java.awt.image.BufferedImage.TYPE_INT_ARGB);
+            int[] imgData = ((java.awt.image.DataBufferInt) img.getRaster().getDataBuffer()).getData();
+            System.arraycopy(rgb, 0, imgData, 0, rgb.length);
+            this.cachedImage = img;
+            this.cachedFgRgb = fgArgb;
+            this.cachedBgRgb = bgArgb;
+            return img;
+        }
+
         /**
          * Computes and returns the 32-bit ARGB pixel array for this symbol.
          * The returned array has length (width * height).

lib3270j/src/main/java/org/lib3270j/screen/ScreenBuffer.java

@@ -36,8 +36,12 @@ public class ScreenBuffer {
     private byte defaultGr = 0x00;
     private byte defaultCs = 0x00;
     private byte defaultIc = 0x00;
-
     private final EbcdicTranslator translator;
+    private final Object renderLock = new Object();
+
+    public Object getRenderLock() {
+        return renderLock;
+    }
 
     public ScreenBuffer(TerminalModel model, EbcdicTranslator translator) {
         this.translator = translator;
@@ -79,6 +83,50 @@ public class ScreenBuffer {
         return buffer[addr];
     }
 
+    private ExtendedAttribute[] displaySnapshot;
+    private int displayRows;
+    private int displayCols;
+    private int displayCursorAddress;
+
+    /**
+     * Atomically creates a snapshot of the current presentation buffer for tear-free rendering.
+     * Takes ~2 microseconds and eliminates mutual thread contention with the UI thread.
+     */
+    public synchronized void updateDisplaySnapshot() {
+        int size = rows * cols;
+        if (displaySnapshot == null || displaySnapshot.length < size) {
+            displaySnapshot = new ExtendedAttribute[size];
+            for (int i = 0; i < size; i++) {
+                displaySnapshot[i] = new ExtendedAttribute();
+            }
+        }
+        for (int i = 0; i < size; i++) {
+            displaySnapshot[i].copyFrom(buffer[i]);
+        }
+        this.displayRows = rows;
+        this.displayCols = cols;
+        this.displayCursorAddress = cursorAddress;
+    }
+
+    public synchronized ExtendedAttribute getDisplayCell(int addr) {
+        if (displaySnapshot == null || addr < 0 || addr >= displayRows * displayCols) {
+            return getCell(addr);
+        }
+        return displaySnapshot[addr];
+    }
+
+    public synchronized int getDisplayRows() {
+        return displayRows > 0 ? displayRows : rows;
+    }
+
+    public synchronized int getDisplayCols() {
+        return displayCols > 0 ? displayCols : cols;
+    }
+
+    public synchronized int getDisplayCursorAddress() {
+        return displayRows > 0 ? displayCursorAddress : cursorAddress;
+    }
+
     // ========== Dimension accessors ==========
     public int getRows()       { return rows; }
     public int getCols()       { return cols; }

lib3270j/src/main/java/org/lib3270j/telnet/TelnetConnection.java

@@ -149,9 +149,7 @@ public class TelnetConnection {
                         log.fine("RCVD " + n + " bytes: " + formatHex(buf, 0, n));
                     }
                     try {
-                        for (int i = 0; i < n; i++) {
+                        fsm.feedBytes(buf, 0, n);
-                            fsm.feedByte(buf[i] & 0xFF);
-                        }
                         fsm.endOfNetworkData();
                     } catch (Throwable t) {
                         log.log(Level.SEVERE, "Exception processing incoming data stream", t);

lib3270j/src/main/java/org/lib3270j/telnet/TelnetFSM.java

@@ -58,6 +58,7 @@ public class TelnetFSM {
     private int eXmitSeq;
     private int responseRequired = RSF_NO_RESPONSE;
     private boolean deferredWillTtype;
+    private boolean tn3270eDeviceTypeSent;
 
     // Connection references
     private TelnetConnection connection;
@@ -103,6 +104,7 @@ public class TelnetFSM {
         java.util.Arrays.fill(hisOpts, false);
         java.util.Arrays.fill(eFuncs, false);
         tn3270eNegotiated = false;
+        tn3270eDeviceTypeSent = false;
         tn3270eSubmode = TN3270ESubmode.UNBOUND;
         tn3270eBound = false;
         eXmitSeq = 0;
@@ -118,6 +120,37 @@ public class TelnetFSM {
         changeState(ConnectionState.TELNET_PENDING);
     }
 
+    /**
+     * Feed a bulk buffer of bytes from the network into the FSM.
+     */
+    public void feedBytes(byte[] buf, int offset, int len) {
+        int end = offset + len;
+        int i = offset;
+        while (i < end) {
+            if (state == TNS_DATA) {
+                int start = i;
+                while (i < end && (buf[i] & 0xFF) != IAC) {
+                    i++;
+                }
+                if (i > start) {
+                    if (connectionState == ConnectionState.TELNET_PENDING) {
+                        changeState(ConnectionState.CONNECTED_NVT);
+                    }
+                    if (connectionState.is3270() || connectionState.isTn3270e() || connectionState == ConnectionState.TELNET_PENDING) {
+                        ibuf.write(buf, start, i - start);
+                    }
+                }
+                if (i < end) {
+                    state = TNS_IAC;
+                    i++;
+                }
+            } else {
+                feedByte(buf[i] & 0xFF);
+                i++;
+            }
+        }
+    }
+
     /**
      * Feed a single byte from the network into the FSM.
      */
@@ -172,8 +205,8 @@ public class TelnetFSM {
             changeState(ConnectionState.CONNECTED_NVT);
         }
 
-        // Accumulate data for 3270, TN3270E (including SSCP-LU and unbound states)
+        // Accumulate data for 3270, TN3270E (including SSCP-LU and unbound states, and pending)
-        if (connectionState.is3270() || connectionState.isTn3270e()) {
+        if (connectionState.is3270() || connectionState.isTn3270e() || connectionState == ConnectionState.TELNET_PENDING) {
             ibuf.write(c);
         }
         // NVT data would go to NVT processor (not implemented in initial version)
@@ -189,7 +222,7 @@ public class TelnetFSM {
                 break;
             case EOR: // End of record — process accumulated 3270 data
                 log.fine("RCVD EOR");
-                if (connectionState.is3270() || connectionState.isTn3270e()) {
+                if (connectionState.is3270() || connectionState.isTn3270e() || connectionState == ConnectionState.TELNET_PENDING) {
                     processEndOfRecord();
                 }
                 ibuf.reset();
@@ -235,7 +268,9 @@ public class TelnetFSM {
                 break;
 
             case TELOPT_TN3270E:
-                if (!hisOpts[opt]) {
+                if (!config.isTn3270eEnabled()) {
+                    sendCommand(DONT, opt);
+                } else if (!hisOpts[opt]) {
                     hisOpts[opt] = true;
                     sendCommand(DO, opt);
                 }
@@ -278,7 +313,7 @@ public class TelnetFSM {
             case TELOPT_TTYPE:
                 if (!myOpts[opt]) {
                     myOpts[opt] = true;
-                    if (hisOpts[TELOPT_TN3270E]) {
+                    if (config.isTn3270eEnabled() && hisOpts[TELOPT_TN3270E]) {
                         // Defer TTYPE response until TN3270E negotiation completes
                         deferredWillTtype = true;
                     } else {
@@ -288,11 +323,16 @@ public class TelnetFSM {
                 break;
 
             case TELOPT_TN3270E:
-                if (!myOpts[opt]) {
+                if (!config.isTn3270eEnabled()) {
+                    sendCommand(WONT, opt);
+                } else if (!myOpts[opt]) {
                     myOpts[opt] = true;
                     sendCommand(WILL, opt);
                     // Start TN3270E sub-negotiation: send device type request
+                    if (!tn3270eDeviceTypeSent) {
                         sendTN3270EDeviceTypeRequest();
+                        tn3270eDeviceTypeSent = true;
+                    }
                 }
                 break;
 
@@ -428,7 +468,10 @@ public class TelnetFSM {
         switch (op) {
             case OP_SEND:
                 // Host asks us to send device-type request
+                if (!tn3270eDeviceTypeSent) {
                     sendTN3270EDeviceTypeRequest();
+                    tn3270eDeviceTypeSent = true;
+                }
                 break;
 
             case OP_DEVICE_TYPE:
@@ -488,14 +531,19 @@ public class TelnetFSM {
             pos++;
         }
 
+        // Check if REJECT
         if (pos < data.length && (data[pos] & 0xFF) == OP_REJECT) {
-            // Rejection
             pos++;
-            int reason = -1;
+            int reason = (pos < data.length) ? (data[pos] & 0xFF) : REASON_UNSUPPORTED_REQ;
-            if (pos < data.length && (data[pos] & 0xFF) == OP_REASON) {
+            if (reason == REASON_INV_DEVICE_TYPE || reason == REASON_UNSUPPORTED_REQ) {
-                pos++;
+                // Try fallback model 2 if we were requesting something else
-                if (pos < data.length) {
+                if (config.getModel() != TerminalModel.IBM_3278_2 &&
-                    reason = data[pos] & 0xFF;
+                    config.getModel() != TerminalModel.IBM_3279_2) {
+                    log.warning("TN3270E device-type rejected (" +
+                        TN3270EConstants.reasonName(reason) + "), retrying with IBM-3278-2");
+                    config.setModel(TerminalModel.IBM_3278_2);
+                    sendTN3270EDeviceTypeRequest();
+                    return;
                 }
             }
             log.warning("TN3270E device-type rejected: " + TN3270EConstants.reasonName(reason));
@@ -563,33 +611,86 @@ public class TelnetFSM {
         log.info("SENT SB TN3270E FUNCTIONS REQUEST " + funcNames + " SE");
     }
 
-    private void handleTN3270EFunctions(byte[] data) {
+    private void sendTN3270EFunctionsIs() {
-        // Parse: TN3270E FUNCTIONS IS [func...]
+        ByteArrayOutputStream out = new ByteArrayOutputStream();
-        int pos = 2; // Skip TN3270E, FUNCTIONS
+        out.write(IAC);
+        out.write(SB);
+        out.write(TELOPT_TN3270E);
+        out.write(OP_FUNCTIONS);
+        out.write(OP_IS);
 
-        if (pos < data.length && (data[pos] & 0xFF) == OP_IS) {
+        StringBuilder funcNames = new StringBuilder();
-            pos++; // Skip IS
+        for (int i = 0; i < eFuncs.length; i++) {
+            if (eFuncs[i]) {
+                out.write(i);
+                if (funcNames.length() > 0) funcNames.append(" ");
+                funcNames.append(TN3270EConstants.functionName(i));
+            }
         }
 
-        // The remaining bytes are the agreed-upon functions
+        out.write(IAC);
-        java.util.Arrays.fill(eFuncs, false);
+        out.write(SE);
-        StringBuilder funcNames = new StringBuilder();
+        sendBytes(out.toByteArray());
+        log.info("SENT SB TN3270E FUNCTIONS IS " + funcNames + " SE");
+    }
+
+    private void handleTN3270EFunctions(byte[] data) {
+        // Parse: TN3270E FUNCTIONS REQUEST [func...] or TN3270E FUNCTIONS IS [func...]
+        int pos = 1;
+        boolean isRequest = false;
+
+        while (pos < data.length) {
+            int b = data[pos] & 0xFF;
+            if (b == OP_FUNCTIONS) {
+                pos++;
+            } else if (b == OP_REQUEST) {
+                isRequest = true;
+                pos++;
+                break;
+            } else if (b == OP_IS) {
+                isRequest = false;
+                pos++;
+                break;
+            } else {
+                pos++;
+            }
+        }
+
+        // The remaining bytes are the proposed/agreed functions
+        boolean[] hostFuncs = new boolean[8];
         while (pos < data.length) {
             int func = data[pos] & 0xFF;
             if (func <= FUNC_SNA_SENSE) {
-                eFuncs[func] = true;
+                hostFuncs[func] = true;
-                if (funcNames.length() > 0) funcNames.append(" ");
-                funcNames.append(TN3270EConstants.functionName(func));
             }
             pos++;
         }
 
+        if (isRequest) {
+            // Host sent FUNCTIONS REQUEST -> We reply with FUNCTIONS IS (intersection of functions)
+            for (int i = 0; i < eFuncs.length; i++) {
+                eFuncs[i] = eFuncs[i] && hostFuncs[i];
+            }
+            sendTN3270EFunctionsIs();
+        } else {
+            // Host sent FUNCTIONS IS -> Accept host's agreed function list
+            for (int i = 0; i < eFuncs.length; i++) {
+                eFuncs[i] = hostFuncs[i];
+            }
+        }
+
         tn3270eNegotiated = true;
-        log.info("TN3270E functions IS: " + funcNames);
+        log.info("TN3270E functions negotiated: " + getNegotiatedFunctionNames());
         log.info("TN3270E negotiation complete");
 
-        // Move to CONNECTED_UNBOUND or CONNECTED_SSCP
+        // RFC 2355: If BIND-IMAGE function is not negotiated, the emulation session is considered
+        // to be bound immediately upon completion of the FUNCTIONS negotiation.
+        if (eFuncs[FUNC_BIND_IMAGE]) {
             changeState(ConnectionState.CONNECTED_UNBOUND);
+        } else {
+            changeState(ConnectionState.CONNECTED_TN3270E);
+            tn3270eSubmode = TN3270ESubmode.E_3270;
+        }
 
         // Notify listeners
         for (ConnectionListener l : connectionListeners) {
@@ -597,12 +698,29 @@ public class TelnetFSM {
         }
     }
 
+    private String getNegotiatedFunctionNames() {
+        StringBuilder sb = new StringBuilder();
+        for (int i = 0; i < eFuncs.length; i++) {
+            if (eFuncs[i]) {
+                if (sb.length() > 0) sb.append(" ");
+                sb.append(TN3270EConstants.functionName(i));
+            }
+        }
+        return sb.length() > 0 ? sb.toString() : "<none>";
+    }
+
     // ========== End of Record processing ==========
 
     private void processEndOfRecord() {
         byte[] data = ibuf.toByteArray();
+        ibuf.reset();
         if (data.length == 0) return;
 
+        if (connectionState == ConnectionState.TELNET_PENDING && !tn3270eNegotiated) {
+            log.info("Received EOR during TELNET_PENDING - transitioning to plain TN3270 mode");
+            changeState(ConnectionState.CONNECTED_3270);
+        }
+
         if (tn3270eNegotiated) {
             // TN3270E mode: data starts with 5-byte header
             processTN3270ERecord(data);
@@ -701,11 +819,11 @@ public class TelnetFSM {
                                 bindRa = screenBuffer.getMaxRows();
                                 bindCa = screenBuffer.getMaxCols();
                                 break;
-                            case 0x7e:
+                            case 0x7E:
                                 // Both default and alternate = specified values
                                 bindRa = bindRd; bindCa = bindCd;
                                 break;
-                            case 0x7f:
+                            case 0x7F:
                                 // Default and alternate are both specified separately
                                 bindRa = data[EH_SIZE + BIND_OFF_RA] & 0xFF;
                                 bindCa = data[EH_SIZE + BIND_OFF_CA] & 0xFF;
@@ -767,7 +885,20 @@ public class TelnetFSM {
                 break;
 
             default:
+                // Check if the host sent a raw 3270 data stream (e.g. 0xF5 EraseWrite, 0x7E EW Alternate, 0xF1 Write, etc.)
+                // This happens when the server ignores or drops TN3270E framing and speaks plain 3270 data stream.
+                if (dataType == 0xF5 || dataType == 0x7E || dataType == 0xF1 || dataType == 0x6F ||
+                    dataType == 0x6E || dataType == 0xF2 || dataType == 0xF6 || dataType == 0x05 ||
+                    dataType == 0x0D || dataType == 0x01 || (data.length >= 2 && (data[0] & 0xFF) == 0x11)) {
+                    log.warning("Received plain 3270 command (0x" + Integer.toHexString(dataType) +
+                                ") in TN3270E mode — automatically switching to plain TN3270 mode");
+                    tn3270eNegotiated = false;
+                    changeState(ConnectionState.CONNECTED_3270);
+                    dsProcessor.processRecord(data, 0, data.length, true);
+                    notifyScreenUpdate();
+                } else {
                     log.info("Unhandled TN3270E data type: " + dataType);
+                }
                 break;
         }
     }
@@ -790,7 +921,7 @@ public class TelnetFSM {
         if (connectionState != ConnectionState.TELNET_PENDING) return;
 
         // For TN3270E, we wait for TN3270E negotiation to complete
-        if (myOpts[TELOPT_TN3270E] && hisOpts[TELOPT_TN3270E]) {
+        if (config.isTn3270eEnabled() && myOpts[TELOPT_TN3270E] && hisOpts[TELOPT_TN3270E]) {
             return; // TN3270E in progress
         }
 

lib3270j/src/test/java/org/lib3270j/datastream/QueryReplyBuilderTest.java

@@ -15,8 +15,27 @@ public class QueryReplyBuilderTest {
     private final QueryReplyBuilder qrBuilder = new QueryReplyBuilder(screen);
 
     @Test
-    public void testBuildAllQueryRepliesDefaultNone() {
+    public void testBuildAllQueryRepliesDefaultBoth() {
-        assertEquals(GraphicsMode.NONE, qrBuilder.getGraphicsMode());
+        assertEquals(GraphicsMode.BOTH, qrBuilder.getGraphicsMode());
+        byte[] replies = qrBuilder.buildAllQueryReplies(80, 43, 80 * 43);
+        assertNotNull(replies);
+        assertTrue(replies.length > 0);
+        assertEquals((byte) AID_SF, replies[0]);
+
+        // In GraphicsMode.BOTH, Vector Graphics QR 0xB0 must be present
+        boolean hasB0 = false;
+        for (int i = 0; i < replies.length - 3; i++) {
+            if ((replies[i] & 0xFF) == 0x81 && (replies[i + 1] & 0xFF) == QR_GRAPHICS) {
+                hasB0 = true;
+                break;
+            }
+        }
+        assertTrue(hasB0);
+    }
+
+    @Test
+    public void testBuildAllQueryRepliesExplicitNone() {
+        qrBuilder.setGraphicsMode(GraphicsMode.NONE);
         byte[] replies = qrBuilder.buildAllQueryReplies(80, 43, 80 * 43);
         assertNotNull(replies);
         assertTrue(replies.length > 0);
@@ -156,4 +175,61 @@ public class QueryReplyBuilderTest {
         assertEquals(80, altCols);
         assertEquals(43, altRows);
     }
+
+    @Test
+    public void testProgrammedSymbolsDescriptorsSingleAndTriplePlane() {
+        qrBuilder.setGraphicsMode(GraphicsMode.PROGRAMMED_SYMBOLS);
+        byte[] requested = new byte[] { (byte) QR_CHARSETS };
+        byte[] replies = qrBuilder.buildQueryReplies(requested, 80, 43, 80 * 43);
+
+        assertNotNull(replies);
+        int offset = -1;
+        for (int i = 0; i < replies.length - 3; i++) {
+            if ((replies[i] & 0xFF) == 0x81 && (replies[i + 1] & 0xFF) == QR_CHARSETS) {
+                offset = i + 2;
+                break;
+            }
+        }
+        assertTrue(offset >= 0, "QR_CHARSETS must be present");
+
+        // QR_CHARSETS payload structure:
+        // Flags (2 bytes), SDW (1 byte), SDH (1 byte), Form (1 byte), DevType (2 bytes), Res (1 byte), DL (1 byte)
+        // DL is at offset + 8, and is 7 bytes per descriptor.
+        int dl = replies[offset + 8] & 0xFF;
+        assertEquals(7, dl);
+
+        int descOffset = offset + 9;
+
+        // Descriptor 1: SET 0 (Base) -> flags 0x10
+        assertEquals(0x00, replies[descOffset] & 0xFF);
+        assertEquals(0x10, replies[descOffset + 1] & 0xFF);
+
+        // Descriptor 2: SET 1 (APL) -> flags 0x00
+        assertEquals(0x01, replies[descOffset + 7] & 0xFF);
+        assertEquals(0x00, replies[descOffset + 7 + 1] & 0xFF);
+
+        // Descriptor 3: PSA (Single plane) -> flags 0x80 (Loadable, single-plane)
+        assertEquals(0x02, replies[descOffset + 14] & 0xFF);
+        assertEquals(0x80, replies[descOffset + 14 + 1] & 0xFF);
+
+        // Descriptor 4: PSB (Single plane) -> flags 0x80 (Loadable, single-plane)
+        assertEquals(0x03, replies[descOffset + 21] & 0xFF);
+        assertEquals(0x80, replies[descOffset + 21 + 1] & 0xFF);
+
+        // Descriptor 5: PSC (Triple plane) -> flags 0xC0 (Loadable | Triple-plane)
+        assertEquals(0x04, replies[descOffset + 28] & 0xFF);
+        assertEquals(0xC0, replies[descOffset + 28 + 1] & 0xFF);
+
+        // Descriptor 6: PSD (Triple plane) -> flags 0xC0 (Loadable | Triple-plane)
+        assertEquals(0x05, replies[descOffset + 35] & 0xFF);
+        assertEquals(0xC0, replies[descOffset + 35 + 1] & 0xFF);
+
+        // Descriptor 7: PSE (Triple plane) -> flags 0xC0 (Loadable | Triple-plane)
+        assertEquals(0x06, replies[descOffset + 42] & 0xFF);
+        assertEquals(0xC0, replies[descOffset + 42 + 1] & 0xFF);
+
+        // Descriptor 8: PSF (Triple plane) -> flags 0xC0 (Loadable | Triple-plane)
+        assertEquals(0x07, replies[descOffset + 49] & 0xFF);
+        assertEquals(0xC0, replies[descOffset + 49 + 1] & 0xFF);
+    }
 }

lib3270j/src/test/java/org/lib3270j/graphics/GraphicsModeTest.java

@@ -46,11 +46,11 @@ public class GraphicsModeTest {
     @Test
     public void testConnectionConfigDefault() {
         ConnectionConfig config = new ConnectionConfig();
-        assertEquals(GraphicsMode.NONE, config.getGraphicsMode());
-
-        config.setGraphicsMode(GraphicsMode.BOTH);
         assertEquals(GraphicsMode.BOTH, config.getGraphicsMode());
 
+        config.setGraphicsMode(GraphicsMode.NONE);
+        assertEquals(GraphicsMode.NONE, config.getGraphicsMode());
+
         config.setGraphicsMode(null);
         assertEquals(GraphicsMode.NONE, config.getGraphicsMode());
     }

lib3270j/src/test/java/org/lib3270j/graphics/ProgramSymbolManagerTest.java

@@ -51,7 +51,7 @@ public class ProgramSymbolManagerTest {
         ProgramSymbolSet.SymbolSlot slot = manager.getSymbol(0x40, 0x41);
         assertNotNull(slot);
         assertEquals(9, slot.getWidth());
-        assertEquals(16, slot.getHeight());
+        assertEquals(12, slot.getHeight());
         assertFalse(slot.isTriplePlane());
 
         // Verify pixel data (Row 0 Col 0 is 1)
@@ -64,10 +64,33 @@ public class ProgramSymbolManagerTest {
         int bg = 0xFF000000; // Black
         int[] rgb = slot.getRgbPixels(fg, bg);
         assertNotNull(rgb);
-        assertEquals(9 * 16, rgb.length);
+        assertEquals(9 * 12, rgb.length);
         assertEquals(fg, rgb[0]); // Row 0 Col 0 pixel should be foreground Green
     }
 
+    @Test
+    public void testExplicitCellDimensions() {
+        ProgramSymbolManager manager = new ProgramSymbolManager();
+        manager.setDefaultCellDimensions(9, 16);
+
+        byte[] payload = new byte[4 + 18];
+        payload[0] = 0x01; // Format 1
+        payload[1] = 0x40; // LCID 0x40
+        payload[2] = 0x41; // Code point 0x41
+        payload[3] = 0x02; // RWS 2
+        payload[4] = (byte) 0x80;
+        payload[5] = (byte) 0x00;
+        for (int r = 0; r < 16; r++) {
+            payload[6 + r] = (byte) 0xFF;
+        }
+
+        manager.loadps(payload);
+        ProgramSymbolSet.SymbolSlot slot = manager.getSymbol(0x40, 0x41);
+        assertNotNull(slot);
+        assertEquals(9, slot.getWidth());
+        assertEquals(16, slot.getHeight());
+    }
+
     @Test
     public void testTriplePlaneMultiColorComposite() {
         ProgramSymbolManager manager = new ProgramSymbolManager();