GDDM Tweaking

build.gradle

@@ -10,8 +10,10 @@ allprojects {
 subprojects {
     apply plugin: 'java'
 
-    sourceCompatibility = JavaVersion.VERSION_11
-    targetCompatibility = JavaVersion.VERSION_11
+    java {
+        sourceCompatibility = JavaVersion.VERSION_11
+        targetCompatibility = JavaVersion.VERSION_11
+    }
 
     test {
         useJUnitPlatform()

j3270/src/main/java/haus/nightmare/j3270/ui/SettingsDialog.java

@@ -453,7 +453,8 @@ public class SettingsDialog extends JDialog {
         JPanel main = new JPanel(new BorderLayout());
         
         String[] actions = {"ENTER", "TAB", "shift TAB", "UP", "DOWN", "LEFT", "RIGHT",
-            "HOME", "END", "PAGE_UP", "PAGE_DOWN", "ESCAPE", "INSERT", "DELETE", "BACK_SPACE", "CLEAR"};
+            "HOME", "END", "PAGE_UP", "PAGE_DOWN", "ESCAPE", "INSERT", "DELETE", "BACK_SPACE", "CLEAR",
+            "ERASE_INPUT", "NEWLINE", "DUP", "FIELD_MARK", "ATTN", "SYSREQ", "CURSEL"};
         
         keymapModel = new DefaultTableModel(new Object[]{"Action", "Key Binding"}, 0) {
             @Override
@@ -465,7 +466,14 @@ public class SettingsDialog extends JDialog {
         // Populate table from Settings or Defaults
         for(String act : actions) {
             String def = act;
-            if(def.equals("PAGE_UP")) def = "PAGE_UP"; // fallback example
+            if (def.equals("ERASE_INPUT")) def = "alt E";
+            else if (def.equals("NEWLINE")) def = "shift ENTER";
+            else if (def.equals("DUP")) def = "alt D";
+            else if (def.equals("FIELD_MARK")) def = "alt M";
+            else if (def.equals("ATTN")) def = "alt A";
+            else if (def.equals("SYSREQ")) def = "alt S";
+            else if (def.equals("CURSEL")) def = "alt Q";
+            else if (def.equals("CLEAR")) def = "alt C";
             String current = haus.nightmare.j3270.config.Settings.getKeyBinding(act, def);
             tempKeyBindings.put(act, current);
             keymapModel.addRow(new Object[]{act, current});

j3270/src/main/java/haus/nightmare/j3270/ui/TerminalPanel.java

@@ -163,10 +163,20 @@ public class TerminalPanel extends JPanel {
                     // IMPORTANT ARCHITECTURE NOTE:
                     // 1. In GDDM Graphic Cursor Mode (3179G / GOCA), mouse events represent graphic light-pen touches.
                     //    Text drag-selection is explicitly suppressed so blue selection boxes do not artifact over graphics.
-                    // 2. In Text Light Pen mode (Alt+L on 3270 formatted screens), clicks toggle selectable fields.
+                    // 2. In Text Light Pen / Selectable Field mode (per IBM Host On-Demand MouseMgr.java / PS3270.java),
+                    //    clicks on detectable fields (faIsSelectable) trigger field selection or cursor select.
                     // 3. In standard alphanumeric mode, click-drag selects text for copy-paste.
                     boolean isGraphic = client.getGocaDecoder() != null && client.getGocaDecoder().isGraphicsCursorActive();
-                    if (isGraphic || lightPenMode) {
+                    boolean isSelectableField = false;
+                    if (sb.isFormatted()) {
+                        int faPos = sb.findFieldAttribute(row * displayCols + col);
+                        if (faPos >= 0) {
+                            int fa = sb.getCell(faPos).fa & 0xFF;
+                            isSelectableField = haus.nightmare.lib3270j.protocol.DS3270Constants.faIsSelectable(fa) &&
+                                                !haus.nightmare.lib3270j.protocol.DS3270Constants.faIsZero(fa);
+                        }
+                    }
+                    if (isGraphic || lightPenMode || isSelectableField) {
                         clearSelection();
                     } else {
                         selectionStartRow = row;
@@ -259,10 +269,12 @@ public class TerminalPanel extends JPanel {
 
                             int gx = client.getGocaDecoder().getGraphicCursorX();
                             int gy = client.getGocaDecoder().getGraphicCursorY();
+                            int hitSeg = client.getGocaDecoder().findPickedSegment(gx, gy);
+                            int hitTag = client.getGocaDecoder().getSegmentTag(hitSeg);
                             int button = javax.swing.SwingUtilities.isRightMouseButton(e) ? 2 : 1;
                             System.err.println(String.format(
-                                "TerminalPanel.mouseReleased: mouse=(%d, %d) offset=(%d, %d) grid=(%dx%d) px=(%d, %d) goca=(%d, %d) btn=%d",
-                                e.getX(), e.getY(), ox, oy, gridW, gridH, px, py, gx, gy, button
+                                "TerminalPanel.mouseReleased: mouse=(%d, %d) offset=(%d, %d) grid=(%dx%d) px=(%d, %d) goca=(%d, %d) hitSeg=%d hitTag=%d btn=%d",
+                                e.getX(), e.getY(), ox, oy, gridW, gridH, px, py, gx, gy, hitSeg, hitTag, button
                             ));
 
                             client.getInputProcessor().sendGraphicMouseAid(
@@ -275,13 +287,34 @@ public class TerminalPanel extends JPanel {
                             return;
                         }
 
+                        // Automatic Light-Pen / Selectable Field detection on mouse click:
+                        // Per IBM Host On-Demand (MouseMgr.java / PS3270.java) and 3270 specifications:
+                        // If the clicked screen location belongs to a detectable field (faIsSelectable and not faIsZero),
+                        // automatically process light-pen / cursor selection (e.g. immediate selection, Enter, or toggling ? -> >).
+                        if (sb.isFormatted()) {
+                            int faPos = sb.findFieldAttribute(clickAddr);
+                            if (faPos >= 0) {
+                                int fa = sb.getCell(faPos).fa & 0xFF;
+                                if (haus.nightmare.lib3270j.protocol.DS3270Constants.faIsSelectable(fa) &&
+                                    !haus.nightmare.lib3270j.protocol.DS3270Constants.faIsZero(fa)) {
+                                    clearSelection();
+                                    if (client.lightPenSelect(clickAddr)) {
+                                        refreshScreen();
+                                        return;
+                                    }
+                                }
+                            }
+                        }
+
                         if (lightPenMode) {
                             clearSelection();
                             sb.setCursorAddress(clickAddr);
-                            boolean result = client.getInputProcessor().lightPenSelect(clickAddr);
+                            boolean result = client.lightPenSelect(clickAddr);
                             if (result) {
                                 refreshScreen();
                                 return;
+                            } else {
+                                Toolkit.getDefaultToolkit().beep();
                             }
                         }
 
@@ -608,6 +641,7 @@ public class TerminalPanel extends JPanel {
         bindKeyToMap(im, "FIELD_MARK", haus.nightmare.j3270.config.Settings.getKeyBinding("FIELD_MARK", "alt M"));
         bindKeyToMap(im, "ATTN", haus.nightmare.j3270.config.Settings.getKeyBinding("ATTN", "alt A"));
         bindKeyToMap(im, "SYSREQ", haus.nightmare.j3270.config.Settings.getKeyBinding("SYSREQ", "alt S"));
+        bindKeyToMap(im, "CURSEL", haus.nightmare.j3270.config.Settings.getKeyBinding("CURSEL", "alt Q"));
 
         // Copy/Paste bindings — Cmd+C / Cmd+V (macOS) or Ctrl+C / Ctrl+V (others)
         int shortcutMask = Toolkit.getDefaultToolkit().getMenuShortcutKeyMaskEx();
@@ -638,6 +672,7 @@ public class TerminalPanel extends JPanel {
         am.put("j3270-FIELD_MARK", createAction(this::handleFieldMark));
         am.put("j3270-ATTN", createAction(this::handleAttn));
         am.put("j3270-SYSREQ", createAction(this::handleSysReq));
+        am.put("j3270-CURSEL", createAction(this::handleCursorSelect));
 
         // Copy/Paste actions
         am.put("j3270-COPY", createAction(this::copySelection));
@@ -824,6 +859,17 @@ public class TerminalPanel extends JPanel {
         }
     }
 
+    private void handleCursorSelect() {
+        if (client != null && client.getConnectionState().isFullSession()) {
+            boolean selected = client.cursorSelect();
+            if (selected) {
+                refreshScreen();
+            } else {
+                Toolkit.getDefaultToolkit().beep();
+            }
+        }
+    }
+
     private void refreshScreen() {
         if (client != null) {
             client.getScreenBuffer().updateDisplaySnapshot();
@@ -930,8 +976,8 @@ public class TerminalPanel extends JPanel {
                 g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
                 g2.setRenderingHint(RenderingHints.KEY_FRACTIONALMETRICS, RenderingHints.VALUE_FRACTIONALMETRICS_ON);
 
-                int fontSize = (int) Math.round(ch * 0.95);
-                if (fontSize < 10) fontSize = 10;
+                int fontSize = Math.min((int) Math.round(ch * 0.82), (int) Math.round(cw * 1.45));
+                if (fontSize < 9) fontSize = 9;
                 Font f = (boldTerminalFont != null ? boldTerminalFont : terminalFont).deriveFont((float) fontSize);
                 g2.setFont(f);
                 FontMetrics fm = g2.getFontMetrics();
@@ -1137,10 +1183,11 @@ public class TerminalPanel extends JPanel {
                         Font f = bold ? boldTerminalFont : terminalFont;
                         g2.setFont(f);
                         g2.setColor(fgColor);
+                        int textY = y + fontAscent + Math.max(0, (cellHeight - (fontAscent + fontDescent)) / 2);
                         if (ch < 128) {
-                            g2.drawString(CHAR_STRINGS[ch], x, y + fontAscent);
+                            g2.drawString(CHAR_STRINGS[ch], x, textY);
                         } else {
-                            g2.drawString(String.valueOf(ch), x, y + fontAscent);
+                            g2.drawString(String.valueOf(ch), x, textY);
                         }
                     }
                 }
@@ -1148,8 +1195,8 @@ public class TerminalPanel extends JPanel {
                 // Draw underline
                 if (underline) {
                     g2.setColor(fgColor);
-                    g2.drawLine(x, y + cellHeight - fontDescent,
-                            x + cellWidth - 1, y + cellHeight - fontDescent);
+                    int ulY = Math.min(y + cellHeight - 1, y + fontAscent + Math.max(0, (cellHeight - (fontAscent + fontDescent)) / 2) + 2);
+                    g2.drawLine(x, ulY, x + cellWidth - 1, ulY);
                 }
 
                 // Draw selection highlight

lib3270j/src/main/java/haus/nightmare/lib3270j/Telnet3270Client.java

@@ -223,6 +223,10 @@ public class Telnet3270Client {
     public void sysReq()      { inputProcessor.sysReq(); }
     /** Reset (unlock keyboard). */  
     public void reset()       { inputProcessor.reset(); }
+    /** Trigger 3270 CURSR SEL (Cursor Select) key at current cursor position. */
+    public boolean cursorSelect() { return inputProcessor.cursorSelect(); }
+    /** Trigger Light Pen selection at the specified screen address. */
+    public boolean lightPenSelect(int address) { return inputProcessor.lightPenSelect(address); }
 
     public haus.nightmare.lib3270j.graphics.ProgramSymbolManager getProgramSymbolManager() {
         return dsProcessor.getProgramSymbolManager();

lib3270j/src/main/java/haus/nightmare/lib3270j/datastream/DataStreamProcessor.java

@@ -41,7 +41,7 @@ public class DataStreamProcessor {
 
     // Graphics & Programmed Symbols
     private final haus.nightmare.lib3270j.graphics.ProgramSymbolManager programSymbolManager = new haus.nightmare.lib3270j.graphics.ProgramSymbolManager();
-    private final haus.nightmare.lib3270j.graphics.GraphicsPlane graphicsPlane = new haus.nightmare.lib3270j.graphics.GraphicsPlane(800, 600);
+    private final haus.nightmare.lib3270j.graphics.GraphicsPlane graphicsPlane = new haus.nightmare.lib3270j.graphics.GraphicsPlane(720, 384);
     private final haus.nightmare.lib3270j.graphics.GocaDecoder gocaDecoder = new haus.nightmare.lib3270j.graphics.GocaDecoder(graphicsPlane);
     private final java.io.ByteArrayOutputStream gocaAccumulator = new java.io.ByteArrayOutputStream();
     private int currentGocaSubtype = 0;
@@ -832,9 +832,15 @@ public class DataStreamProcessor {
                                     programSymbolManager.loadps(psData);
                                 }
                                 break;
+                            case haus.nightmare.lib3270j.graphics.GocaConstants.SF_OBJDATA_SUB: { // 0x0F: Object Control / Data Unit
+                                // Per IBM HOD processDataunit(), 0x0F activates graphic cursor and initializes data unit
+                                log.info(String.format("SF 0x0F sub=0x0F (Data Unit Object Control len=%d): activating graphics cursor", fieldLen));
+                                gocaDecoder.setGraphicsCursorActive(true);
+                                notifyScreenUpdated();
+                                break;
+                            }
                             case haus.nightmare.lib3270j.graphics.GocaConstants.SF_OBJCNTL_SUB: // 0x11: Object Control (Procedure orders)
-                            case haus.nightmare.lib3270j.graphics.GocaConstants.SF_OBJPICT_SUB: // 0x10: Object Picture (Picture segments)
-                            case haus.nightmare.lib3270j.graphics.GocaConstants.SF_OBJDATA_SUB: { // 0x0F: Object Data (GOCA draw orders)
+                            case haus.nightmare.lib3270j.graphics.GocaConstants.SF_OBJPICT_SUB: { // 0x10: Object Picture (Picture segments)
                                 int flags = (fieldLen >= 6) ? (data[pos + 5] & 0xC0) : 0xC0;
                                 int orderOffset = (fieldLen >= 7) ? (pos + 7) : (pos + 4);
                                 int orderLen = Math.max(0, fieldLen - (orderOffset - pos));
@@ -847,6 +853,11 @@ public class DataStreamProcessor {
                                         sfSubId, fieldLen, flags, (orderOffset - pos), orderLen, hexDump.toString().trim()));
 
                                 graphicsPlane.setScreenDimensions(screen.getCols(), screen.getRows());
+                                int targetW = screen.getCols() * 9;
+                                int targetH = screen.getRows() * 16;
+                                if (graphicsPlane.getCanvasWidth() != targetW || graphicsPlane.getCanvasHeight() != targetH) {
+                                    graphicsPlane.resize(targetW, targetH);
+                                }
 
                                 if (flags == 0x80) { // SPAN_FIRST
                                     gocaAccumulator.reset();

lib3270j/src/main/java/haus/nightmare/lib3270j/datastream/QueryReplyBuilder.java

@@ -293,14 +293,36 @@ public class QueryReplyBuilder {
         out.write((Yr_3279_2 >> 16) & 0xFF);
         out.write((Yr_3279_2 >> 8) & 0xFF);
         out.write(Yr_3279_2 & 0xFF);
-        out.write(SW_3279_2);                // AW
-        out.write(SH_3279_2);                // AH
+        int charW = getCharWidth();
+        int charH = getCharHeight();
+        out.write(charW);                    // AW
+        out.write(charH);                    // AH
         int buf = maxCols * maxRows;
         out.write((buf >> 8) & 0xFF);        // buffer size high
         out.write(buf & 0xFF);               // buffer size low
         return out.toByteArray();
     }
 
+    public int getCharWidth() {
+        return SW_3279_2; // 9
+    }
+
+    public int getCharHeight() {
+        // ARCHITECTURAL NOTE ON 3179G GOCA VERTICAL ALIGNMENT & QUERY REPLIES:
+        // Why hardcoding SH = 12 (0x0C) in Character Sets & Usable Area failed in past iterations:
+        // When SDH/AH is declared as 12 (0x0C) in Query Reply, the mainframe host GDDM engine computes
+        // total presentation space as rows * 12 (e.g. 43 * 12 = 516 units, yMax = 257).
+        // GDDM then places the top menu bar at Row 1 (gy = 187..200).
+        // Meanwhile, the client emulator rendered into a 16-pitch grid (43 * 16 = 688 units, yMax = 343).
+        // On a 688-unit canvas, gy = 200 mapped to Row 9.2 (middle of the screen), leaving a massive void above.
+        // When the user clicked on the visual menu drawn at Row 9, the client emitted gy = 189 with cursor at Row 9,
+        // which GDDM rejected as outside its menu hit box (causing terminal alarm beeps).
+        //
+        // Solution: Declare SDH = 16 (0x10) when Vector Graphics is enabled (3179G standard), ensuring host GDDM
+        // and client GraphicsPlane share the exact same 16-pitch presentation space (720x688, yMax = 343).
+        return graphicsMode.isVectorGraphicsEnabled() ? 0x10 : SH_3279_2;
+    }
+
     private byte[] buildAlphaPartitions(int maxRows) {
         int bufSize = screen.getMaxCols() * screen.getMaxRows();
         ByteArrayOutputStream out = new ByteArrayOutputStream(4);
@@ -312,13 +334,16 @@ public class QueryReplyBuilder {
     }
 
     private byte[] buildCharsets() {
+        int charW = getCharWidth();
+        int charH = getCharHeight();
+
         if (graphicsMode.isProgrammedSymbolsEnabled()) {
             // Programmed Symbols mode (3279 PS with LoadPS 0x0A, flags1 = 0xA2 for GE + PS + CGCSGID)
             ByteArrayOutputStream out = new ByteArrayOutputStream(65);
             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)
+            out.write(charW); // SDW (9)
+            out.write(charH); // SDH (16 for 3179G, 12 for 3279-2)
             out.write(0x0a); // Load PS format types supported: Format 1 and Format 3
             out.write(0x00); // Load PS device type (high)
             out.write(0x00); // Load PS device type (low)
@@ -343,8 +368,8 @@ public class QueryReplyBuilder {
         ByteArrayOutputStream out = new ByteArrayOutputStream(23);
         out.write(0x82); // flags: GE, CGCSGID present
         out.write(0x00); // more flags
-        out.write(SW_3279_2); // SDW - default char width (9)
-        out.write(SH_3279_2); // SDH - default char height (12)
+        out.write(charW); // SDW - default char width (9)
+        out.write(charH); // SDH - default char height (16 for 3179G, 12 for 3279-2)
         out.write(0x00); // LoadPS format (0x00)
         out.write(0x00);
         out.write(0x00);

lib3270j/src/main/java/haus/nightmare/lib3270j/graphics/GddmCoordinateTransform.java

@@ -0,0 +1,206 @@
+package haus.nightmare.lib3270j.graphics;
+
+import java.awt.Point;
+
+/**
+ * Dedicated scaling layer for IBM 3179G / GDDM GOCA graphics presentation space.
+ * Matches IBM Host On-Demand (HODTransform.java, PS3179G.java, HODInput.java).
+ *
+ * <p>Coordinate System Architecture:
+ * <ul>
+ *   <li>GOCA Presentation Space: Centered at (0, 0).
+ *       X ranges [-xMax .. +xMax] where width = cols * defaultCharWidth (defsx = 9).
+ *       Y ranges [-yMax .. +yMax] where height = rows * defaultCharHeight (defsy = 16 or 12).
+ *       (+Y is UP, -Y is DOWN, +X is RIGHT, -X is LEFT).</li>
+ *   <li>Base Presentation Space (px, py): Unsigned top-left origin (0, 0).
+ *       px = gx + xMax (ranges 0 .. totalWidth).
+ *       py = yMax - gy (ranges 0 .. totalHeight).</li>
+ *   <li>Display Screen / Window Space (sx, sy): Physical Swing pixel coordinates relative
+ *       to terminal character grid rendering offset (ox, oy).
+ *       sx = ox + (int) Math.round(px * transformX).
+ *       sy = oy + (int) Math.round(py * transformY).
+ *       where transformX = cellWidth / defaultCharWidth, transformY = cellHeight / defaultCharHeight.</li>
+ * </ul>
+ *
+ * <p>Why simple fixed pixel scaling or hardcoded multipliers failed in past iterations:
+ * <ul>
+ *   <li><b>Failure Mode 1</b>: Hardcoding totalHeight = rows * 12 caused coordinate truncation in 43-row mode (Model 4),
+ *       capping yMax at 257 instead of 343 and making the top menu / EXIT button unreachable.</li>
+ *   <li><b>Failure Mode 2</b>: Hardcoding totalHeight = rows * 16 without viewport alignment resulted in yMax = 343.
+ *       In ADMDRAW, GDDM defines the entire active drawing area between y = -169 and y = +200 (~370 units total height).
+ *       Mapping this into a 688-high canvas placed the top menu at Row 9.2 (middle of the screen) with a large blank void above,
+ *       and clicking the visual menu emitted gy = 224 (missing the [187..200] menu bounding box).</li>
+ *   <li><b>Failure Mode 3</b>: Intermediate raster buffering (e.g. fixed 800x600 canvas stretched to gridW x gridH)
+ *       introduced rounding artifacts in bidirectional coordinate conversion (unmapX/unmapY).</li>
+ *   <li><b>Failure Mode 4</b>: Overlapping dropdown menus (FILE, DRAW, TRANSFORM) lingering simultaneously when
+ *       segment retention/clearing was decoupled from GDDM's segment lifecycle.</li>
+ * </ul>
+ */
+public class GddmCoordinateTransform {
+
+    public static final int DEFAULT_CHAR_WIDTH = 9;   // defsx: 3179G standard character cell width
+    public static final int DEFAULT_CHAR_HEIGHT_16 = 16; // defsy: 3179G standard character cell height
+    public static final int DEFAULT_CHAR_HEIGHT_12 = 12; // defsy: 3279-2 alternate character cell height
+
+    private int defaultCharWidth = DEFAULT_CHAR_WIDTH;
+    private int defaultCharHeight = DEFAULT_CHAR_HEIGHT_16;
+
+    private int screenCols = 80;
+    private int screenRows = 24;
+
+    private double transformX = 1.0;
+    private double transformY = 1.0;
+
+    public GddmCoordinateTransform() {
+        this(80, 24, DEFAULT_CHAR_WIDTH, DEFAULT_CHAR_HEIGHT_16);
+    }
+
+    public GddmCoordinateTransform(int screenCols, int screenRows) {
+        this(screenCols, screenRows, DEFAULT_CHAR_WIDTH, DEFAULT_CHAR_HEIGHT_16);
+    }
+
+    public GddmCoordinateTransform(int screenCols, int screenRows, int defCharWidth, int defCharHeight) {
+        this.screenCols = screenCols > 0 ? screenCols : 80;
+        this.screenRows = screenRows > 0 ? screenRows : 24;
+        this.defaultCharWidth = defCharWidth > 0 ? defCharWidth : DEFAULT_CHAR_WIDTH;
+        this.defaultCharHeight = defCharHeight > 0 ? defCharHeight : DEFAULT_CHAR_HEIGHT_16;
+    }
+
+    /**
+     * Updates screen grid and cell dimensions from UI.
+     *
+     * @param cellWidth  Width of a character cell in Swing pixels
+     * @param cellHeight Height of a character cell in Swing pixels
+     */
+    public void updateDisplayMetrics(int cellWidth, int cellHeight) {
+        if (cellWidth > 0 && defaultCharWidth > 0) {
+            this.transformX = (double) cellWidth / (double) defaultCharWidth;
+        }
+        if (cellHeight > 0 && defaultCharHeight > 0) {
+            this.transformY = (double) cellHeight / (double) defaultCharHeight;
+        }
+    }
+
+    public void setScreenDimensions(int cols, int rows) {
+        if (cols > 0) this.screenCols = cols;
+        if (rows > 0) this.screenRows = rows;
+    }
+
+    public void setDefaultCharMetrics(int defWidth, int defHeight) {
+        if (defWidth > 0) this.defaultCharWidth = defWidth;
+        if (defHeight > 0) this.defaultCharHeight = defHeight;
+    }
+
+    public int getTotalWidth() {
+        return screenCols * defaultCharWidth;
+    }
+
+    public int getTotalHeight() {
+        return screenRows * defaultCharHeight;
+    }
+
+    public int getXMax() {
+        int totalW = getTotalWidth();
+        return (totalW - 1) / 2 + (totalW - 1) % 2;
+    }
+
+    public int getYMax() {
+        int totalH = getTotalHeight();
+        return (totalH - 1) / 2;
+    }
+
+    public double getTransformX() {
+        return transformX;
+    }
+
+    public double getTransformY() {
+        return transformY;
+    }
+
+    public int getDefaultCharWidth() {
+        return defaultCharWidth;
+    }
+
+    public int getDefaultCharHeight() {
+        return defaultCharHeight;
+    }
+
+    /**
+     * Converts a GOCA signed coordinate (gx, gy) to base presentation space coordinate (px, py).
+     */
+    public Point gocaToBase(int gx, int gy) {
+        int px = gx + getXMax();
+        int py = getYMax() - gy;
+        return new Point(px, py);
+    }
+
+    /**
+     * Converts a base presentation space coordinate (px, py) to GOCA signed coordinate (gx, gy).
+     */
+    public Point baseToGoca(int px, int py) {
+        int gx = px - getXMax();
+        int gy = getYMax() - py;
+        return new Point(gx, gy);
+    }
+
+    /**
+     * Converts a GOCA signed coordinate (gx, gy) directly to Swing screen pixel coordinate (sx, sy).
+     */
+    public Point gocaToScreenPixel(int gx, int gy, int ox, int oy, int cellWidth, int cellHeight) {
+        updateDisplayMetrics(cellWidth, cellHeight);
+        int px = gx + getXMax();
+        int py = getYMax() - gy;
+        int sx = ox + (int) Math.round(px * transformX);
+        int sy = oy + (int) Math.round(py * transformY);
+        return new Point(sx, sy);
+    }
+
+    /**
+     * Converts a mouse click in Swing screen coordinates (mouseX, mouseY) directly to GOCA signed coordinate (gx, gy).
+     * Matches HODInput.getHODInput:
+     *   x = mouseX / transformX
+     *   y = mouseY / transformY
+     *   gx = x - xMax
+     *   gy = yMax - y
+     */
+    public Point screenPixelToGoca(int mouseX, int mouseY, int ox, int oy, int cellWidth, int cellHeight) {
+        updateDisplayMetrics(cellWidth, cellHeight);
+        double relX = mouseX - ox;
+        double relY = mouseY - oy;
+
+        int px = (transformX > 0) ? (int) Math.round(relX / transformX) : (int) relX;
+        int py = (transformY > 0) ? (int) Math.round(relY / transformY) : (int) relY;
+
+        int gx = px - getXMax();
+        int gy = getYMax() - py;
+        return new Point(gx, gy);
+    }
+
+    /**
+     * Maps GOCA (gx, gy) to fixed canvas buffer dimensions (canvasWidth, canvasHeight).
+     */
+    public Point gocaToCanvasPixel(int gx, int gy, int canvasWidth, int canvasHeight) {
+        int totalW = getTotalWidth();
+        int totalH = getTotalHeight();
+        int xMax = getXMax();
+        int yMax = getYMax();
+
+        int px = (int) Math.round((double) (gx + xMax) * canvasWidth / (totalW > 0 ? totalW : 1));
+        int py = (int) Math.round((double) (yMax - gy) * canvasHeight / (totalH > 0 ? totalH : 1));
+        return new Point(px, py);
+    }
+
+    /**
+     * Maps fixed canvas buffer pixel (canvasX, canvasY) to GOCA (gx, gy).
+     */
+    public Point canvasPixelToGoca(int canvasX, int canvasY, int canvasWidth, int canvasHeight) {
+        int totalW = getTotalWidth();
+        int totalH = getTotalHeight();
+        int xMax = getXMax();
+        int yMax = getYMax();
+
+        int nx = (int) Math.round((double) canvasX * totalW / (canvasWidth > 0 ? canvasWidth : 1));
+        int ny = (int) Math.round((double) canvasY * totalH / (canvasHeight > 0 ? canvasHeight : 1));
+        return new Point(nx - xMax, yMax - ny);
+    }
+}

lib3270j/src/main/java/haus/nightmare/lib3270j/graphics/GocaDecoder.java

@@ -164,7 +164,7 @@ public class GocaDecoder {
         for (int i = activeSegmentsInOrder.size() - 1; i >= 0; i--) {
             SegmentBounds sb = activeSegmentsInOrder.get(i);
             if (sb.contains(gx, gy, 25)) {
-                System.err.println(String.format(
+                logger.info(String.format(
                     "findPickedSegment: goca=(%d, %d) HIT segId=%d bounds=[%d..%d, %d..%d] tag=%d",
                     gx, gy, sb.segId, sb.minX, sb.maxX, sb.minY, sb.maxY, sb.tag
                 ));
@@ -173,14 +173,14 @@ public class GocaDecoder {
         }
         for (SegmentBounds sb : segmentBoundsMap.values()) {
             if (sb.contains(gx, gy, 25)) {
-                System.err.println(String.format(
+                logger.info(String.format(
                     "findPickedSegment (fallback): goca=(%d, %d) HIT segId=%d bounds=[%d..%d, %d..%d] tag=%d",
                     gx, gy, sb.segId, sb.minX, sb.maxX, sb.minY, sb.maxY, sb.tag
                 ));
                 return sb.segId;
             }
         }
-        System.err.println(String.format("findPickedSegment: goca=(%d, %d) NO HIT (defaulting to 0/canvas)", gx, gy));
+        logger.info(String.format("findPickedSegment: goca=(%d, %d) NO HIT (defaulting to 0/canvas)", gx, gy));
         return 0;
     }
 
@@ -436,7 +436,7 @@ public class GocaDecoder {
                     if (currentSegId != 0) {
                         SegmentBounds sb = segmentBoundsMap.get(currentSegId);
                         if (sb != null) {
-                            System.err.println(String.format(
+                            logger.info(String.format(
                                 "GocaDecoder: ENDSEGM segId=%d bounds=[%d..%d, %d..%d] tag=%d",
                                 sb.segId, sb.minX, sb.maxX, sb.minY, sb.maxY, sb.tag
                             ));
@@ -805,12 +805,17 @@ public class GocaDecoder {
                     idx += 2;
                     break;
                 }
-                case GocaConstants.P_ERASE: { // 0x0A: Erase Graphics Presentation Space
+                case GocaConstants.P_ERASE: { // 0x0A: Erase Graphics Presentation Space (HODEraseGraphicsPlane)
                     plane.clear();
                     resetAttributes();
                     curX = 0;
                     curY = 0;
                     activeSegmentsInOrder.clear();
+                    segmentBoundsMap.clear();
+                    segmentStore.clear();
+                    segmentOrderList.clear();
+                    chainedTargets.clear();
+                    logger.info("GOCA P_ERASE: erased graphics presentation space and cleared segment stores");
                     idx += 2;
                     break;
                 }
@@ -818,55 +823,15 @@ public class GocaDecoder {
                     idx += 12;
                     break;
                 }
-                case GocaConstants.P_SCUDEF: { // 0x21: Drawing Process Control / Segment Execute
-                    if (idx + 5 < end) {
-                        int pLen = data[idx + 1] & 0xFF;
-                        if (pLen >= 6) {
-                            int flags0 = data[idx + 2] & 0xFF;
-                            int flags1 = data[idx + 3] & 0xFF;
-                            int startSeg = ((data[idx + 4] & 0xFF) << 8) | (data[idx + 5] & 0xFF);
-                            int endSeg = (idx + 7 < end) ? (((data[idx + 6] & 0xFF) << 8) | (data[idx + 7] & 0xFF)) : startSeg;
-                            logger.info(String.format("GOCA P_SCUDEF: flags0=0x%02x flags1=0x%02x startSeg=%d endSeg=%d",
-                                flags0, flags1, startSeg, endSeg));
-                            // Redraw all stored base segments not in dynamic range [startSeg..endSeg]
-                            for (int segId : segmentOrderList) {
-                                if (segId < startSeg || segId > endSeg) {
-                                    if (!chainedTargets.contains(segId)) {
-                                        byte[] segBytes = segmentStore.get(segId);
-                                        if (segBytes != null) {
-                                            int savedSegId = currentSegId;
-                                            currentSegId = segId;
-                                            SegmentBounds sb = segmentBoundsMap.computeIfAbsent(segId, SegmentBounds::new);
-                                            activeSegmentsInOrder.remove(sb);
-                                            activeSegmentsInOrder.add(sb);
-                                            callDepth++;
-                                            decodeStreamDirect(segBytes, 0, segBytes.length);
-                                            callDepth--;
-                                            currentSegId = savedSegId;
-                                        }
-                                    }
-                                }
-                            }
-
-                            for (int s = startSeg; s <= endSeg; s++) {
-                                byte[] segBytes = segmentStore.get(s);
-                                if (segBytes != null) {
-                                    int savedSegId = currentSegId;
-                                    currentSegId = s;
-                                    SegmentBounds sb = segmentBoundsMap.computeIfAbsent(s, SegmentBounds::new);
-                                    activeSegmentsInOrder.remove(sb);
-                                    activeSegmentsInOrder.add(sb);
-                                    callDepth++;
-                                    decodeStreamDirect(segBytes, 0, segBytes.length);
-                                    callDepth--;
-                                    currentSegId = savedSegId;
-                                }
-                            }
-                        }
-                    }
+                case GocaConstants.P_SCUDEF: { // 0x21: Set Current Defaults (HODCurrentDefaults)
+                    // Note: Per IBM 3179G / HOD architecture, 0x21 sets default drawing attributes (color, line, pattern).
+                    // It is NOT an executive segment redraw order. A prior attempt treated 0x21 as an invented
+                    // P_SCUDEF segment redraw loop, which caused old dropdown menus and segments to be repeatedly
+                    // repainted on top of the screen, creating ghost artifacts and stale bounding boxes.
                     if (idx + 1 < end) {
-                        int len = (data[idx + 1] & 0xFF) + 2;
-                        idx += len;
+                        int pLen = data[idx + 1] & 0xFF;
+                        logger.fine(String.format("GOCA Set Current Defaults (0x21): len=%d", pLen));
+                        idx += pLen + 2;
                     } else {
                         idx++;
                     }
@@ -1302,9 +1267,9 @@ public class GocaDecoder {
         int textLen = end - pos;
         if (textLen <= 0) return;
 
-        // IBM 3279 vector graphics base cell is 9x12
+        // IBM 3179G vector graphics base cell is 9x16
         double cw = charWidth > 0 ? ((double) charWidth * plane.getCanvasWidth() / (plane.getScreenCols() * 9.0)) : 10.0;
-        double ch = charHeight > 0 ? ((double) charHeight * plane.getCanvasHeight() / (plane.getScreenRows() * 12.0)) : 14.0;
+        double ch = charHeight > 0 ? ((double) charHeight * plane.getCanvasHeight() / (plane.getScreenRows() * 16.0)) : 14.0;
 
         int totalW = textLen * (charWidth > 0 ? charWidth : 9);
         int totalH = (charHeight > 0 ? charHeight : 14);

lib3270j/src/main/java/haus/nightmare/lib3270j/graphics/GraphicInputBuilder.java

@@ -6,13 +6,18 @@ package haus.nightmare.lib3270j.graphics;
  */
 public class GraphicInputBuilder {
 
-    // 56-byte template mask from IBM Host On-Demand (HODInput.java)
+    // 56-byte template mask from IBM Host On-Demand (HODInput.java).
+    // Note on Structured Field Length (bytes 0-1):
+    // IBM HOD sets bytes 0-1 to 0x00 0x34 (52 decimal). In 3270 GOCA architecture,
+    // the Data Unit Object Control payload is 52 bytes. Overwriting this with 0x00 0x38 (56)
+    // causes the host's 3270 inbound structured field decoder to misalign the trailing AID byte
+    // (0x7D) and cursor address by 4 bytes, causing host GDDM to reject the click with an alarm beep.
     private static final byte[] MASK = new byte[] {
-        0x00, 0x38, 0x0F, 0x0F, 0x00, (byte) 0xC0, 0x00, 0x40,
+        0x00, 0x34, 0x0F, 0x0F, 0x00, (byte) 0xC0, 0x00, 0x40,
         0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
         0x23, 0x00, 0x23, 0x00, 0x00, 0x00, 0x1F, 0x01,
-        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-        0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00,
+        0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x04,
+        0x00, 0x04, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00,
         0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
         0x00, 0x00, 0x00, 0x00, 0x00, 0x00, (byte) 0x80, 0x00
     };
@@ -30,16 +35,17 @@ public class GraphicInputBuilder {
      */
     public static byte[] buildGraphicInput(int gocaX, int gocaY, int buttonOrAidCode,
                                           boolean isMouseAction, boolean isShift, boolean isCtrl) {
-        return buildGraphicInput(gocaX, gocaY, buttonOrAidCode, isMouseAction, isShift, isCtrl, 0, 0);
+        return buildGraphicInput(gocaX, gocaY, 0, 0, buttonOrAidCode, isMouseAction, isShift, isCtrl);
     }
 
     /**
-     * Builds the 56-byte Graphic Input Structured Field with picked segment ID and correlation tag.
+     * Builds the 56-byte Graphic Input Structured Field with picked segment ID and correlation tag (legacy overload).
+     * Note: Per IBM HOD / 3179G architecture, pick correlation is evaluated host-side by GDDM using (gx, gy).
      */
     public static byte[] buildGraphicInput(int gocaX, int gocaY, int buttonOrAidCode,
                                           boolean isMouseAction, boolean isShift, boolean isCtrl,
                                           int pickedSegId, int pickTag) {
-        return buildGraphicInput(gocaX, gocaY, 0, 0, buttonOrAidCode, isMouseAction, isShift, isCtrl, pickedSegId, pickTag);
+        return buildGraphicInput(gocaX, gocaY, 0, 0, buttonOrAidCode, isMouseAction, isShift, isCtrl);
     }
 
     /**
@@ -48,20 +54,22 @@ public class GraphicInputBuilder {
     public static byte[] buildGraphicInput(int gocaX, int gocaY, int row, int col, int buttonOrAidCode,
                                           boolean isMouseAction, boolean isShift, boolean isCtrl,
                                           int pickedSegId, int pickTag) {
+        return buildGraphicInput(gocaX, gocaY, row, col, buttonOrAidCode, isMouseAction, isShift, isCtrl);
+    }
+
+    /**
+     * Builds the 56-byte Graphic Input Structured Field matching IBM Host On-Demand (HODInput.java).
+     */
+    public static byte[] buildGraphicInput(int gocaX, int gocaY, int row, int col, int buttonOrAidCode,
+                                          boolean isMouseAction, boolean isShift, boolean isCtrl) {
         byte[] sf = new byte[MASK.length];
         System.arraycopy(MASK, 0, sf, 0, MASK.length);
 
-        // Byte 0-1: Structured Field Length (56 bytes)
-        sf[0] = (byte) ((MASK.length >> 8) & 0xFF);
-        sf[1] = (byte) (MASK.length & 0xFF);
+        // Bytes 0-1: Structured Field Length (0x0034 = 52 decimal per IBM HODInput.java / GOCA architecture).
+        // Preserved from MASK; do not overwrite with MASK.length (56).
 
-        // Bytes 16-19: Cursor Row & Column
-        if (row > 0 || col > 0) {
-            sf[16] = (byte) (row & 0xFF);
-            sf[17] = (byte) (col & 0xFF);
-            sf[18] = (byte) (row & 0xFF);
-            sf[19] = (byte) (col & 0xFF);
-        }
+        // Bytes 16-19: Device correlation class descriptor (0x23, 0x00, 0x23, 0x00)
+        // Note: Preserved from MASK per IBM Host On-Demand (HODInput.java); do not overwrite with row/col.
 
         // Byte 24-25: GOCA X coordinate (signed 16-bit big-endian)
         sf[24] = (byte) ((gocaX >> 8) & 0xFF);
@@ -72,15 +80,15 @@ public class GraphicInputBuilder {
         sf[27] = (byte) (gocaY & 0xFF);
 
         if (isMouseAction) {
-            // Byte 28-31: Picked Segment ID (4 bytes big-endian)
-            sf[28] = (byte) ((pickedSegId >> 24) & 0xFF);
-            sf[29] = (byte) ((pickedSegId >> 16) & 0xFF);
-            sf[30] = (byte) ((pickedSegId >> 8) & 0xFF);
-            sf[31] = (byte) (pickedSegId & 0xFF);
+            // Byte 28-31: Fixed mouse trigger class constant (0x00000004 per IBM HODInput.java)
+            sf[28] = 0x00;
+            sf[29] = 0x00;
+            sf[30] = 0x00;
+            sf[31] = 0x04;
 
-            // Byte 32-33: Pick Tag / Correlation (2 bytes big-endian)
-            sf[32] = (byte) ((pickTag >> 8) & 0xFF);
-            sf[33] = (byte) (pickTag & 0xFF);
+            // Byte 32-33: Fixed mouse correlation class constant (0x0004 per IBM HODInput.java)
+            sf[32] = 0x00;
+            sf[33] = 0x04;
 
             sf[34] = isShift ? (byte) 0x80 : (isCtrl ? (byte) 0x40 : 0x00);
             sf[35] = (byte) (buttonOrAidCode == 2 ? 0x02 : 0x01); // Button 1 = Pick, Button 2 = Action

lib3270j/src/main/java/haus/nightmare/lib3270j/graphics/GraphicsPlane.java

@@ -36,14 +36,14 @@ public class GraphicsPlane {
         {-1, -1, -1, -1, -1, -1, -1, -1}                      // 16: Solid
     };
 
-    private int canvasWidth = 800;
-    private int canvasHeight = 600;
+    // 3179G Presentation Space metrics: 9x16 cell pitch (720x384 for Model 2, 720x688 for Model 4)
+    private int screenCols = 80;
+    private int screenRows = 24;
+    private int canvasWidth = 720;
+    private int canvasHeight = 384;
     private int[] rgbBuffer;
     private boolean hasContent = false;
     private long updateCount = 0;
-
-    private int screenCols = 80;
-    private int screenRows = 24;
     private ProgramSymbolManager programSymbolManager;
 
     public void setProgramSymbolManager(ProgramSymbolManager psm) {
@@ -115,6 +115,7 @@ public class GraphicsPlane {
     public synchronized void setScreenDimensions(int cols, int rows) {
         this.screenCols = cols > 0 ? cols : 80;
         this.screenRows = rows > 0 ? rows : 24;
+        this.transform.setScreenDimensions(this.screenCols, this.screenRows);
     }
 
     public int getScreenCols() {
@@ -125,14 +126,53 @@ public class GraphicsPlane {
         return screenRows;
     }
 
+    // Dedicated GDDM coordinate transformation scaling layer (matching IBM HODTransform)
+    private final GddmCoordinateTransform transform = new GddmCoordinateTransform();
+
+    public GddmCoordinateTransform getTransform() {
+        return transform;
+    }
+
     public int getTotalWidth() {
         int cols = screenCols > 0 ? screenCols : 80;
         return cols * 9;
     }
 
+    /**
+     * Total vertical presentation space units.
+     *
+     * <p>Historical / Architecture Note for Future Iterations:
+     * <ul>
+     *   <li><b>Failed Approach 1 (Hardcoded 12-pitch / rows * 12)</b>:
+     *       Used 516 units (yMax = 257) on 43-row screen. Caused upper coordinate truncation;
+     *       menus at gy > 257 were clipped and mathematically impossible to pick.</li>
+     *   <li><b>Failed Approach 2 (Hardcoded 16-pitch / rows * 16 without viewport alignment)</b>:
+     *       Used 688 units (yMax = 343). Visual rendering was shifted downward by ~50 pixels relative
+     *       to GDDM's internal picture space viewport, causing clicks at Row 7 to emit gy = 226
+     *       which missed the GDDM menu hit box and caused terminal alarm beeps.</li>
+     *   <li><b>Failed Approach 3 (Overwriting Graphic Input SF bytes 16-19 with row/col)</b>:
+     *       Overwrote device correlation descriptor 0x00230023, causing GDDM Structured Field
+     *       parser to reject inbound correlation packets as malformed.</li>
+     *   <li><b>Failed Approach 4 (Misinterpreting Procedure Order 0x21 as Segment Redraw loop)</b>:
+     *       Order 0x21 is HODCurrentDefaults (Set Current Defaults), not an executive redraw loop.
+     *       Treating 0x21 as segment execution caused previous menu frames and stored segments
+     *       to be repeatedly repainted over active screens, leaving behind visual ghost artifacts.</li>
+     *   <li><b>Failed Approach 5 (Static yMax=343 scaling vs GDDM ADMDRAW Viewport bounds)</b>:
+     *       In ADMDRAW, GDDM defines the graphics presentation space between y = -169 (canvas bottom)
+     *       and y = +200 (top menu bar), with total height ~370 units. Mapping this into a static
+     *       yMax = 343 (688 total height) renders the top menu at Row 9.2 (middle of the screen) with
+     *       a large vertical void above it, and clicking the visual menu sends gy = 224 which misses
+     *       the [187..200] menu bounding box. Furthermore, multiple dropdown menus (FILE, DRAW, TRANSFORM)
+     *       overlapped simultaneously because segment retention and clearing was decoupled from GDDM's
+     *       actual viewport state.</li>
+     *   <li><b>Solution Path</b>: Use {@link GddmCoordinateTransform} for dynamic display and aspect
+     *       scaling, ensuring host Query Reply metrics (SDH/AH) and GDDM Picture Space Window
+     *       orders are synchronized with client-side mouse transformation.</li>
+     * </ul>
+     */
     public int getTotalHeight() {
         int rows = screenRows > 0 ? screenRows : 24;
-        return rows * 12;
+        return rows * 16;
     }
 
     public int getXMax() {
@@ -158,7 +198,7 @@ public class GraphicsPlane {
 
     /**
      * Maps a 3179G / GOCA signed coordinate (centered at screen midpoint, bottom-up) to canvas pixel Y (top-down) as a double.
-     * IBM 3179G / HOD presentation space coordinate range is [-yMax .. +yMax] (height = rows * 12).
+     * IBM 3179G / HOD presentation space coordinate range is [-yMax .. +yMax] (height = rows * 16).
      */
     public double mapYDouble(double gocaY) {
         int totalH = getTotalHeight();
@@ -555,8 +595,19 @@ public class GraphicsPlane {
         int fill = (fillColorArgb != 0) ? fillColorArgb : GocaConstants.GOCA_COLORS[0];
         int bg = bgColorArgb;
 
-        boolean isTransparentBlack = (fill == GocaConstants.GOCA_COLORS[8] || (fill & 0x00FFFFFF) == 0) && (bgMix != GocaConstants.MIX_OVER);
-        if (pattern != GocaConstants.PT_EMPTY && (pattern != 0 || !drawBoundary) && !isTransparentBlack) {
+        // ARCHITECTURAL NOTE ON GOCA BACKGROUND MIX & BLACK AREA FILLING:
+        // In GOCA (GA23-0059 / SC31-6805), Color 0 / 8 is the default background/neutral color (Black).
+        // Background Mix (GSBMX / bgMix):
+        //   - bgMix == 0 or 2 (BMX_DEFAULT / BMX_LEAVE): Leave destination unchanged (Transparent).
+        //     Fills with default background color (Black) under BMX_LEAVE are transparent and must NOT overwrite pixels.
+        //     (e.g. ADMOPSLA slide preview selection boxes, where GDDM draws hollow frames with bgMix = 0).
+        //   - bgMix == 5 or 1 (BMX_OVER / OVERPAINT): Overwrite background pixels with background color (Opaque).
+        //     Fills with Black under BMX_OVER are explicit erasure rectangles used to erase closed menus and dialogs
+        //     (e.g. ADMDRAW menu erasure, where GDDM explicitly issues GSBMX 5 before the black fill).
+        boolean isTransparentBlack = ((fill & 0x00FFFFFF) == 0) &&
+                                     (bgMix == GocaConstants.MIX_DEFAULT || bgMix == GocaConstants.MIX_LEAVE || bgMix == 0);
+
+        if (!isTransparentBlack && pattern != GocaConstants.PT_EMPTY && (pattern != 0 || !drawBoundary)) {
             // Find polygon vertical bounds across all points
             int minY = py[0];
             int maxY = py[0];

lib3270j/src/main/java/haus/nightmare/lib3270j/input/InputProcessor.java

@@ -244,7 +244,43 @@ public class InputProcessor {
             return;
         }
 
-        // Enter, PF keys, PA keys: send AID + optional PID + cursor address + modified field data
+        if (aidCode == AID_SELECT) {
+            // 3270 Selector Pen / Light Pen Immediate Selection (AID 0x7E):
+            // Per IBM 3270 Data Stream Architecture (GA23-0059) and IBM Host On-Demand (DS3270.sendAid lines 727-1019):
+            // The inbound data stream consists of:
+            // 1. AID byte (0x7E)
+            // 2. Cursor address (2 bytes)
+            // 3. For each field with MDT=1:
+            //    - SBA order (0x11)
+            //    - Designator character address (faAddr + 1)
+            // CRITICAL: NO FIELD CHARACTER DATA IS TRANSMITTED FOR AID_SELECT!
+            // Sending character data in an AID_SELECT stream violates 3270 protocol and causes the host to reject the selection.
+            ByteArrayOutputStream out = new ByteArrayOutputStream();
+            out.write(AID_SELECT);
+
+            byte[] caddr = encodeAddress(screen.getCursorAddress(), screen.getRows(), screen.getCols());
+            out.write(caddr[0] & 0xFF);
+            out.write(caddr[1] & 0xFF);
+
+            if (screen.isFormatted()) {
+                int size = screen.getRows() * screen.getCols();
+                for (int i = 0; i < size; i++) {
+                    ExtendedAttribute ea = screen.getCell(i);
+                    if (ea.isFieldAttribute() && faIsModified(ea.fa & 0xFF)) {
+                        int designatorAddr = (i + 1) % size;
+                        out.write(ORDER_SBA);
+                        byte[] addr = encodeAddress(designatorAddr, screen.getRows(), screen.getCols());
+                        out.write(addr[0] & 0xFF);
+                        out.write(addr[1] & 0xFF);
+                    }
+                }
+            }
+
+            sendAidResponse(out.toByteArray());
+            return;
+        }
+
+        // Enter, PF keys: send AID + optional PID + cursor address + modified field data
         ByteArrayOutputStream out = new ByteArrayOutputStream();
 
         out.write(aidCode);
@@ -298,7 +334,7 @@ public class InputProcessor {
         sendAidResponse(out.toByteArray());
     }
 
-    private void sendAidResponse(byte[] data) {
+    protected void sendAidResponse(byte[] data) {
         if (fsm != null && fsm.getConnectionState() != null && fsm.getConnectionState().isSscp()) {
             fsm.sendSscpLuData(data);
         } else if (fsm != null) {
@@ -307,10 +343,10 @@ public class InputProcessor {
     }
 
     /**
-     * Transmit a mouse / light-pen graphic input AID matching IBM Host On-Demand PS3179G.
+     * Transmit a mouse / light-pen graphic input AID matching IBM Host On-Demand PS3179G and DS3270.
      */
     public void sendGraphicMouseAid(int aidCode, int button, boolean isShift, boolean isCtrl) {
-        if (fsm == null || !fsm.getConnectionState().isFullSession()) {
+        if (fsm != null && fsm.getConnectionState() != null && !fsm.getConnectionState().isFullSession()) {
             return;
         }
         if (isKeyboardLocked()) {
@@ -322,8 +358,6 @@ public class InputProcessor {
         if (gocaDecoder != null && gocaDecoder.isGraphicsCursorActive()) {
             int gx = gocaDecoder.getGraphicCursorX();
             int gy = gocaDecoder.getGraphicCursorY();
-            int pickedSeg = gocaDecoder.findPickedSegment(gx, gy);
-            int pickTag = gocaDecoder.getSegmentTag(pickedSeg);
             int cursorAddr = screen != null ? screen.getCursorAddress() : 0;
             int cols = (screen != null && screen.getCols() > 0) ? screen.getCols() : 80;
             int row = cursorAddr / cols;
@@ -340,16 +374,53 @@ public class InputProcessor {
             }
 
             byte[] sf = haus.nightmare.lib3270j.graphics.GraphicInputBuilder.buildGraphicInput(
-                gx, gy, row, col, button, true, isShift, isCtrl, pickedSeg, pickTag
+                gx, gy, row, col, button, true, isShift, isCtrl
             );
-            System.err.println(String.format(
-                "sendGraphicMouseAid: goca=(%d, %d) row=%d col=%d pickedSeg=%d pickTag=%d btn=%d shift=%b ctrl=%b",
-                gx, gy, row, col, pickedSeg, pickTag, button, isShift, isCtrl
+
+            StringBuilder sfHex = new StringBuilder();
+            for (byte b : sf) {
+                sfHex.append(String.format("%02X ", b & 0xFF));
+            }
+            log.info(String.format(
+                "sendGraphicMouseAid: goca=(%d, %d) row=%d col=%d btn=%d shift=%b ctrl=%b SF_HEX=[%s]",
+                gx, gy, row, col, button, isShift, isCtrl, sfHex.toString().trim()
             ));
+
+            // Structured Field AID (0x88) + 56-byte Graphic Input SF
             out.write(AID_SF);
             try {
                 out.write(sf);
             } catch (java.io.IOException ignored) {}
+
+            // Trailing AID + cursor address + modified fields matching HOD DS3270.sendMouseAid
+            out.write(aidCode);
+            byte[] caddr = encodeAddress(screen.getCursorAddress(), screen.getRows(), screen.getCols());
+            out.write(caddr[0] & 0xFF);
+            out.write(caddr[1] & 0xFF);
+
+            if (screen.isFormatted()) {
+                int size = screen.getRows() * screen.getCols();
+                for (int i = 0; i < size; i++) {
+                    ExtendedAttribute ea = screen.getCell(i);
+                    if (ea.isFieldAttribute() && faIsModified(ea.fa & 0xFF)) {
+                        int fieldStart = (i + 1) % size;
+                        out.write(ORDER_SBA);
+                        byte[] addr = encodeAddress(fieldStart, screen.getRows(), screen.getCols());
+                        out.write(addr[0] & 0xFF);
+                        out.write(addr[1] & 0xFF);
+
+                        int pos = fieldStart;
+                        while (!screen.getCell(pos).isFieldAttribute()) {
+                            int b = screen.getCell(pos).ec & 0xFF;
+                            if (b != 0x00) {
+                                out.write(b);
+                            }
+                            pos = (pos + 1) % size;
+                            if (pos == fieldStart) break;
+                        }
+                    }
+                }
+            }
         } else {
             out.write(aidCode);
             byte[] caddr = encodeAddress(screen.getCursorAddress(), screen.getRows(), screen.getCols());
@@ -363,11 +434,11 @@ public class InputProcessor {
     // ========== Cursor movement ==========
 
     /**
-     * Simulate a Text Light Pen selection.
+     * Simulate a Text Light Pen selection at the specified screen address.
+     * Conforms to IBM 3270 / Host On-Demand PS3270 processCurSelKey specifications.
      */
     public boolean lightPenSelect(int address) {
         if (screen == null || !screen.isFormatted()) {
-            System.out.println("LP: screen null or unformatted");
             return false;
         }
         int size = screen.getRows() * screen.getCols();
@@ -375,15 +446,13 @@ public class InputProcessor {
         address = ((address % size) + size) % size;
         int faPos = screen.findFieldAttribute(address);
         if (faPos < 0) {
-            System.out.println("LP: no FA found for addr=" + address);
             return false;
         }
 
         ExtendedAttribute faCell = screen.getCell(faPos);
         int fa = faCell.fa & 0xFF;
-        System.out.println("LP: addr=" + address + " faPos=" + faPos + " fa=0x" + String.format("%02X", fa) 
-            + " selectable=" + haus.nightmare.lib3270j.protocol.DS3270Constants.faIsSelectable(fa));
-        if (!haus.nightmare.lib3270j.protocol.DS3270Constants.faIsSelectable(fa)) {
+        if (!haus.nightmare.lib3270j.protocol.DS3270Constants.faIsSelectable(fa) ||
+            haus.nightmare.lib3270j.protocol.DS3270Constants.faIsZero(fa)) {
             return false;
         }
 
@@ -392,33 +461,52 @@ public class InputProcessor {
         int ebcdic = desCell.ec & 0xFF;
         char ascii = (char) desCell.ucs4;
 
-        screen.setCursorAddress(designatorPos);
+        // Set cursor to the clicked/selected position matching HOD / 3270 standards
+        screen.setCursorAddress(address);
 
-        if (ebcdic == 0x00 || ebcdic == 0x40 || ascii == ' ' || ascii == 0 || (ebcdic != 0x50 && ascii != '&' && ebcdic != 0x6F && ascii != '?' && ebcdic != 0x6E && ascii != '>')) {
-            faCell.fa |= haus.nightmare.lib3270j.protocol.DS3270Constants.FA_MODIFY;
-            sendAid(haus.nightmare.lib3270j.protocol.DS3270Constants.AID_SELECT);
-            return true;
-        } else if (ebcdic == 0x50 || ascii == '&') {
-            faCell.fa |= haus.nightmare.lib3270j.protocol.DS3270Constants.FA_MODIFY;
-            sendAid(haus.nightmare.lib3270j.protocol.DS3270Constants.AID_ENTER);
-            return true;
-        } else if (ebcdic == 0x6F || ascii == '?') {
-            desCell.ec = (byte) 0x6E;
-            desCell.ucs4 = '>';
-            faCell.fa |= haus.nightmare.lib3270j.protocol.DS3270Constants.FA_MODIFY;
-            screen.updateDisplaySnapshot();
-            return true;
-        } else if (ebcdic == 0x6E || ascii == '>') {
-            desCell.ec = (byte) 0x6F;
-            desCell.ucs4 = '?';
-            faCell.fa &= ~haus.nightmare.lib3270j.protocol.DS3270Constants.FA_MODIFY;
-            screen.updateDisplaySnapshot();
-            return true;
-        } else {
+        // Immediate Selection (Space or Null) -> AID_SELECT (0x7E)
+        if (ebcdic == 0x00 || ebcdic == 0x40 || ascii == ' ' || ascii == 0 || ascii == '\u3000') {
             faCell.fa |= haus.nightmare.lib3270j.protocol.DS3270Constants.FA_MODIFY;
             sendAid(haus.nightmare.lib3270j.protocol.DS3270Constants.AID_SELECT);
             return true;
         }
+        // Enter Immediate (&) -> AID_ENTER (0x7D)
+        else if (ebcdic == 0x50 || ascii == '&' || ascii == '\uFF06') {
+            faCell.fa |= haus.nightmare.lib3270j.protocol.DS3270Constants.FA_MODIFY;
+            sendAid(haus.nightmare.lib3270j.protocol.DS3270Constants.AID_ENTER);
+            return true;
+        }
+        // Deferred Selection (? -> >)
+        else if (ebcdic == 0x6F || ascii == '?' || ascii == '\uFF1F') {
+            desCell.ec = (byte) 0x6E;
+            desCell.ucs4 = '>';
+            faCell.fa |= haus.nightmare.lib3270j.protocol.DS3270Constants.FA_MODIFY;
+            screen.markAllChanged();
+            screen.updateDisplaySnapshot();
+            return true;
+        }
+        // Deferred Deselection (> -> ?)
+        else if (ebcdic == 0x6E || ascii == '>' || ascii == '\uFF1E') {
+            desCell.ec = (byte) 0x6F;
+            desCell.ucs4 = '?';
+            faCell.fa &= ~haus.nightmare.lib3270j.protocol.DS3270Constants.FA_MODIFY;
+            screen.markAllChanged();
+            screen.updateDisplaySnapshot();
+            return true;
+        }
+        // Any other character is an invalid designator and cannot be selected
+        else {
+            return false;
+        }
+    }
+
+    /**
+     * Simulate the 3270 CURSR SEL (Cursor Select) key at the current cursor position.
+     * Equivalent to processCurSelKey in IBM Host On-Demand PS3270.
+     */
+    public boolean cursorSelect() {
+        if (screen == null) return false;
+        return lightPenSelect(screen.getCursorAddress());
     }
 
     public void cursorUp() {

lib3270j/src/test/java/haus/nightmare/lib3270j/datastream/QueryReplyBuilderTest.java

@@ -132,11 +132,15 @@ public class QueryReplyBuilderTest {
         assertEquals(0x81, replies[3] & 0xFF);
         assertEquals(QR_DDM, replies[4] & 0xFF);
 
-        // Second SF should be Usable Area
+        // Second SF should be Usable Area: 23 bytes (4 bytes header + 19 bytes payload)
         int pos2 = 1 + len1;
         int len2 = ((replies[pos2] & 0xFF) << 8) | (replies[pos2 + 1] & 0xFF);
+        assertEquals(23, len2);
         assertEquals(0x81, replies[pos2 + 2] & 0xFF);
         assertEquals(QR_USABLE_AREA, replies[pos2 + 3] & 0xFF);
+        // Offset 0x15 (21 in SF payload = pos2 + 21): Buffer size high
+        int bufSize = ((replies[pos2 + 21] & 0xFF) << 8) | (replies[pos2 + 22] & 0xFF);
+        assertEquals(80 * 43, bufSize);
     }
 
     @Test

lib3270j/src/test/java/haus/nightmare/lib3270j/ft/FTDftTest.java

@@ -0,0 +1,190 @@
+package haus.nightmare.lib3270j.ft;
+
+import haus.nightmare.lib3270j.charset.EbcdicTranslator;
+import haus.nightmare.lib3270j.input.InputProcessor;
+import haus.nightmare.lib3270j.screen.ScreenBuffer;
+import haus.nightmare.lib3270j.TerminalModel;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.File;
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+public class FTDftTest {
+
+    private EbcdicTranslator translator;
+    private ScreenBuffer screen;
+    private InputProcessor input;
+    private TestListener listener;
+    private FTDft dft;
+    private FTConfig config;
+
+    private static class TestListener implements FTDft.FTDftListener {
+        boolean dftRunningCalled = false;
+        boolean completeCalled = false;
+        boolean abortCalled = false;
+        String completeMsg = null;
+        String abortMsg = null;
+        long bytesTransferred = 0;
+        FTConstants.FTState state = FTConstants.FTState.RUNNING;
+        FTConfig config;
+
+        @Override
+        public void onDftRunning() {
+            dftRunningCalled = true;
+        }
+
+        @Override
+        public void onTransferComplete(String errorMessage) {
+            completeCalled = true;
+            completeMsg = errorMessage;
+        }
+
+        @Override
+        public void onTransferAborted(String errorMessage) {
+            abortCalled = true;
+            abortMsg = errorMessage;
+        }
+
+        @Override
+        public void onBytesTransferred(long bytes) {
+            bytesTransferred = bytes;
+        }
+
+        @Override
+        public FTConstants.FTState getCurrentState() {
+            return state;
+        }
+
+        @Override
+        public void setState(FTConstants.FTState state) {
+            this.state = state;
+        }
+
+        @Override
+        public FTConfig getConfig() {
+            return config;
+        }
+
+        @Override
+        public File getLocalFile() {
+            return null;
+        }
+    }
+
+    @BeforeEach
+    public void setUp() {
+        translator = new EbcdicTranslator();
+        screen = new ScreenBuffer(TerminalModel.IBM_3279_4, translator);
+        input = new InputProcessor(screen, translator, null);
+        listener = new TestListener();
+        config = new FTConfig();
+        config.setDirection(FTConfig.Direction.RECEIVE);
+        config.setTransferMode(FTConfig.TransferMode.BINARY);
+        listener.config = config;
+
+        dft = new FTDft(input, translator, listener);
+    }
+
+    @Test
+    public void testOpenMessageStreamAsciiAndHandleTrans14Error() {
+        ByteArrayOutputStream outStream = new ByteArrayOutputStream();
+        dft.initTransfer(null, outStream);
+
+        // 1. Simulate TR_OPEN_REQ with ASCII "FT:MSG" matching j3270.log:
+        // SF length = 0x0023, SF type = 0xD0, Request code = 0x0012, stream name "FT:MSG " at offset 28
+        byte[] openReq = new byte[] {
+            0x00, 0x23, (byte) 0xD0, 0x00, 0x12, 0x01, 0x06, 0x01, 0x01, 0x04,
+            0x03, 0x0a, 0x0a, 0x00, 0x00, 0x00, 0x00, 0x11, 0x01, 0x01,
+            0x00, 0x50, 0x05, 0x52, 0x03, (byte) 0xF0, 0x03, 0x09,
+            0x46, 0x54, 0x3A, 0x4D, 0x53, 0x47, 0x20 // "FT:MSG "
+        };
+
+        dft.processStructuredField(openReq, 0, openReq.length);
+
+        // Should NOT trigger onDftRunning because it's a message stream
+        assertFalse(listener.dftRunningCalled);
+
+        // 2. Simulate TR_DATA_INSERT on the message stream with "TRANS14   Error reading file from host: ..."
+        String errorMsg = "TRANS14   Error reading file from host: file format invalid";
+        byte[] msgBytes = errorMsg.getBytes(StandardCharsets.ISO_8859_1);
+        int totalPayloadLen = msgBytes.length + 5;
+
+        ByteArrayOutputStream sfOut = new ByteArrayOutputStream();
+        sfOut.write(0); sfOut.write(0); // placeholder length
+        sfOut.write(0xD0); // SF_TRANSFER_DATA
+        sfOut.write((FTConstants.TR_DATA_INSERT >> 8) & 0xFF);
+        sfOut.write(FTConstants.TR_DATA_INSERT & 0xFF);
+        sfOut.write((FTConstants.TR_NOT_COMPRESSED >> 8) & 0xFF);
+        sfOut.write(FTConstants.TR_NOT_COMPRESSED & 0xFF);
+        sfOut.write(FTConstants.TR_BEGIN_DATA);
+        sfOut.write((totalPayloadLen >> 8) & 0xFF);
+        sfOut.write(totalPayloadLen & 0xFF);
+        sfOut.write(msgBytes, 0, msgBytes.length);
+
+        byte[] insertData = sfOut.toByteArray();
+        int sfLen = insertData.length;
+        insertData[0] = (byte) ((sfLen >> 8) & 0xFF);
+        insertData[1] = (byte) (sfLen & 0xFF);
+
+        dft.processStructuredField(insertData, 0, insertData.length);
+
+        // Verify that onTransferAborted was called with the error message
+        assertTrue(listener.abortCalled, "onTransferAborted should be called for TRANS14 error");
+        assertNotNull(listener.abortMsg);
+        assertTrue(listener.abortMsg.contains("TRANS14"));
+        assertFalse(listener.completeCalled, "onTransferComplete should NOT be called for an error");
+
+        // Verify that the error message was NOT written to the destination file stream!
+        assertEquals(0, outStream.size(), "Error message should not be written to destination file");
+    }
+
+    @Test
+    public void testOpenDataStreamAndWriteData() {
+        ByteArrayOutputStream outStream = new ByteArrayOutputStream();
+        dft.initTransfer(null, outStream);
+
+        // 1. Simulate TR_OPEN_REQ with ASCII "FT:DATA"
+        byte[] openReq = new byte[] {
+            0x00, 0x23, (byte) 0xD0, 0x00, 0x12, 0x01, 0x06, 0x01, 0x01, 0x04,
+            0x03, 0x0a, 0x0a, 0x00, 0x00, 0x00, 0x00, 0x11, 0x01, 0x01,
+            0x00, 0x50, 0x05, 0x52, 0x03, (byte) 0xF0, 0x03, 0x09,
+            0x46, 0x54, 0x3A, 0x44, 0x41, 0x54, 0x41 // "FT:DATA"
+        };
+
+        dft.processStructuredField(openReq, 0, openReq.length);
+        assertTrue(listener.dftRunningCalled, "onDftRunning should be called for file data stream");
+
+        // 2. Simulate TR_DATA_INSERT with binary file payload
+        byte[] fileData = new byte[] { 0x25, 0x50, 0x44, 0x46, 0x2D, 0x31, 0x2E, 0x34 }; // "%PDF-1.4"
+        int totalPayloadLen = fileData.length + 5;
+
+        ByteArrayOutputStream sfOut = new ByteArrayOutputStream();
+        sfOut.write(0); sfOut.write(0);
+        sfOut.write(0xD0);
+        sfOut.write((FTConstants.TR_DATA_INSERT >> 8) & 0xFF);
+        sfOut.write(FTConstants.TR_DATA_INSERT & 0xFF);
+        sfOut.write((FTConstants.TR_NOT_COMPRESSED >> 8) & 0xFF);
+        sfOut.write(FTConstants.TR_NOT_COMPRESSED & 0xFF);
+        sfOut.write(FTConstants.TR_BEGIN_DATA);
+        sfOut.write((totalPayloadLen >> 8) & 0xFF);
+        sfOut.write(totalPayloadLen & 0xFF);
+        sfOut.write(fileData, 0, fileData.length);
+
+        byte[] insertData = sfOut.toByteArray();
+        int sfLen = insertData.length;
+        insertData[0] = (byte) ((sfLen >> 8) & 0xFF);
+        insertData[1] = (byte) (sfLen & 0xFF);
+
+        dft.processStructuredField(insertData, 0, insertData.length);
+
+        // Data must be written to file stream
+        assertArrayEquals(fileData, outStream.toByteArray());
+        assertEquals(8, listener.bytesTransferred);
+    }
+}

lib3270j/src/test/java/haus/nightmare/lib3270j/graphics/GddmCoordinateTransformTest.java

@@ -0,0 +1,43 @@
+package haus.nightmare.lib3270j.graphics;
+
+import org.junit.jupiter.api.Test;
+import java.awt.Point;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+public class GddmCoordinateTransformTest {
+
+    @Test
+    public void testModel4PresentationSpaceMetrics() {
+        GddmCoordinateTransform transform = new GddmCoordinateTransform(80, 43, 9, 16);
+
+        assertEquals(720, transform.getTotalWidth());
+        assertEquals(688, transform.getTotalHeight());
+        assertEquals(360, transform.getXMax());
+        assertEquals(343, transform.getYMax());
+
+        // Screen center (0, 0)
+        Point baseCenter = transform.gocaToBase(0, 0);
+        assertEquals(360, baseCenter.x);
+        assertEquals(343, baseCenter.y);
+        assertEquals(new Point(0, 0), transform.baseToGoca(360, 343));
+
+        // Bidirectional screen pixel transformation
+        // Cell width = 10, Cell height = 20, Offset = (100, 50)
+        int ox = 100, oy = 50, cw = 10, ch = 20;
+        Point screenPt = transform.gocaToScreenPixel(0, 0, ox, oy, cw, ch);
+        Point roundtripGoca = transform.screenPixelToGoca(screenPt.x, screenPt.y, ox, oy, cw, ch);
+        assertEquals(0, roundtripGoca.x);
+        assertEquals(0, roundtripGoca.y);
+    }
+
+    @Test
+    public void testModel2PresentationSpaceMetrics() {
+        GddmCoordinateTransform transform = new GddmCoordinateTransform(80, 24, 9, 16);
+
+        assertEquals(720, transform.getTotalWidth());
+        assertEquals(384, transform.getTotalHeight());
+        assertEquals(360, transform.getXMax());
+        assertEquals(191, transform.getYMax());
+    }
+}

lib3270j/src/test/java/haus/nightmare/lib3270j/graphics/GocaDecoderTest.java

@@ -221,6 +221,12 @@ public class GocaDecoderTest {
         GraphicsPlane plane = new GraphicsPlane(1000, 750);
         plane.setScreenDimensions(80, 43);
 
+        // Standard IBM 3179G 43-row presentation space (80*9 = 720 wide, 43*16 = 688 high)
+        assertEquals(720, plane.getTotalWidth());
+        assertEquals(688, plane.getTotalHeight());
+        assertEquals(360, plane.getXMax());
+        assertEquals(343, plane.getYMax());
+
         // Screen center (0, 0) should map to canvas center
         assertEquals(500, plane.mapX(0));
         assertEquals(374, plane.mapY(0));
@@ -240,6 +246,13 @@ public class GocaDecoderTest {
         assertEquals(0, plane.unmapY(plane.mapY(0)));
         assertEquals(100, plane.unmapY(plane.mapY(100)));
         assertEquals(-200, plane.unmapY(plane.mapY(-200)));
+
+        // Standard IBM 3179G Model 2 (24-row) presentation space (24*16 = 384 high, yMax = 191)
+        plane.setScreenDimensions(80, 24);
+        assertEquals(720, plane.getTotalWidth());
+        assertEquals(384, plane.getTotalHeight());
+        assertEquals(360, plane.getXMax());
+        assertEquals(191, plane.getYMax());
     }
 
     @Test
@@ -735,8 +748,9 @@ public class GocaDecoderTest {
         out.write(0x00); out.write(20); out.write(0x00); out.write(40);
         out.write(GocaConstants.G_GEAR);
 
-        // 4. Draw White slide boundary frame (Color set to 8/Black before GBAR, GSCOL White inside GBAR)
+        // 4. Draw White slide boundary frame (Color set to 8/Black before GBAR, Pattern 15/Empty, GSCOL White inside GBAR)
         out.write(GocaConstants.G_GSCOL); out.write(0x08); // Black (background)
+        out.write(GocaConstants.G_GSPT);  out.write(0x0F); // Empty pattern (transparent interior)
         out.write(GocaConstants.G_GBAR);  out.write(0x80);
         out.write(GocaConstants.G_GSCOL); out.write(0x07); // White line color
         out.write(GocaConstants.G_GSLT);  out.write(GocaConstants.LT_DOT); // Dotted line

lib3270j/src/test/java/haus/nightmare/lib3270j/input/InputProcessorTest.java

@@ -138,7 +138,7 @@ public class InputProcessorTest {
         byte[] sf = haus.nightmare.lib3270j.graphics.GraphicInputBuilder.buildGraphicInput(100, -50, AID_ENTER, false, false, false);
         assertEquals(56, sf.length);
         assertEquals(0x00, sf[0]);
-        assertEquals(0x38, sf[1]); // Length = 56 bytes (0x0038)
+        assertEquals(0x34, sf[1]); // Length = 52 bytes (0x0034) matching IBM HODInput.java
         assertEquals(0x0F, sf[2]); // SF ID = 0x0F
         assertEquals(0x0F, sf[3]); // SF ID = 0x0F
 
@@ -154,38 +154,170 @@ public class InputProcessorTest {
         assertEquals((byte) 0xFF, sf[34]);
         assertEquals((byte) AID_ENTER, sf[35]);
 
-        // Mouse Button 1 with picked segment 2 and tag 5
+        // Mouse Button 1 matching HODInput.java (0x04 trigger constants and 0x23 correlation descriptor)
         byte[] sfMouse = haus.nightmare.lib3270j.graphics.GraphicInputBuilder.buildGraphicInput(
-            294, 192, 1, true, false, false, 2, 5
+            294, 192, 1, true, false, false
         );
         assertEquals(56, sfMouse.length);
         assertEquals(0x00, sfMouse[0]);
-        assertEquals(0x38, sfMouse[1]);
+        assertEquals(0x34, sfMouse[1]); // Length = 52 bytes (0x0034) matching IBM HODInput.java
+        assertEquals(0x23, sfMouse[16]);
+        assertEquals(0x00, sfMouse[17]);
+        assertEquals(0x23, sfMouse[18]);
+        assertEquals(0x00, sfMouse[19]);
         int mx = (sfMouse[24] << 8) | (sfMouse[25] & 0xFF);
         int my = (sfMouse[26] << 8) | (sfMouse[27] & 0xFF);
         assertEquals(294, (short) mx);
         assertEquals(192, (short) my);
-        int segId = ((sfMouse[28] & 0xFF) << 24) | ((sfMouse[29] & 0xFF) << 16) |
-                    ((sfMouse[30] & 0xFF) << 8)  | (sfMouse[31] & 0xFF);
-        assertEquals(2, segId);
-        int tag = ((sfMouse[32] & 0xFF) << 8) | (sfMouse[33] & 0xFF);
-        assertEquals(5, tag);
+        assertEquals(0x00, sfMouse[28]);
+        assertEquals(0x00, sfMouse[29]);
+        assertEquals(0x00, sfMouse[30]);
+        assertEquals(0x04, sfMouse[31]); // Mouse trigger class constant (0x04)
+        assertEquals(0x00, sfMouse[32]);
+        assertEquals(0x04, sfMouse[33]); // Mouse correlation class constant (0x04)
         assertEquals(0x00, sfMouse[34]);
         assertEquals(0x01, sfMouse[35]); // Button 1
 
-        // Mouse Button 2 (Action) with no segment (0)
+        // Mouse Button 2 (Action) with Shift modifier
         byte[] sfMouse2 = haus.nightmare.lib3270j.graphics.GraphicInputBuilder.buildGraphicInput(
-            0, 0, 2, true, true, false, 0, 0
+            0, 0, 2, true, true, false
         );
-        int segId2 = ((sfMouse2[28] & 0xFF) << 24) | ((sfMouse2[29] & 0xFF) << 16) |
-                     ((sfMouse2[30] & 0xFF) << 8)  | (sfMouse2[31] & 0xFF);
-        assertEquals(0, segId2);
-        int tag2 = ((sfMouse2[32] & 0xFF) << 8) | (sfMouse2[33] & 0xFF);
-        assertEquals(0, tag2);
+        assertEquals(0x23, sfMouse2[16]);
+        assertEquals(0x00, sfMouse2[17]);
+        assertEquals(0x23, sfMouse2[18]);
+        assertEquals(0x00, sfMouse2[19]);
+        assertEquals(0x04, sfMouse2[31]);
+        assertEquals(0x04, sfMouse2[33]);
         assertEquals((byte) 0x80, sfMouse2[34]); // Shift modifier
         assertEquals(0x02, sfMouse2[35]); // Button 2
     }
 
+    @Test
+    public void testLightPenSelectImmediateSpace() {
+        screen.erase(false);
+        // Field attribute at pos 0: unprotected, intensified selectable (0x08)
+        screen.setCellFA(0, (byte) (FA_PRINTABLE | FA_INT_HIGH_SEL));
+        // Designator character at pos 1: space (immediate select)
+        screen.getCell(1).ec = 0x40;
+        screen.getCell(1).ucs4 = ' ';
+        screen.getCell(2).ec = (byte) 0xC1;
+        screen.getCell(2).ucs4 = 'A';
+
+        java.util.concurrent.atomic.AtomicInteger sentAid = new java.util.concurrent.atomic.AtomicInteger(-1);
+        InputProcessor input = new InputProcessor(screen, translator, null) {
+            @Override
+            public void sendAid(int aidCode) {
+                sentAid.set(aidCode);
+            }
+        };
+
+        boolean result = input.lightPenSelect(2);
+        assertTrue(result);
+        assertEquals(AID_SELECT, sentAid.get());
+        assertTrue((screen.getCell(0).fa & FA_MODIFY) != 0);
+        assertEquals(2, screen.getCursorAddress());
+    }
+
+    @Test
+    public void testLightPenSelectEnterImmediateAmpersand() {
+        screen.erase(false);
+        // Field attribute at pos 0: normal detectable (0x04)
+        screen.setCellFA(0, (byte) (FA_PRINTABLE | FA_INT_NORM_SEL));
+        // Designator character at pos 1: '&' (enter immediate)
+        screen.getCell(1).ec = 0x50;
+        screen.getCell(1).ucs4 = '&';
+
+        java.util.concurrent.atomic.AtomicInteger sentAid = new java.util.concurrent.atomic.AtomicInteger(-1);
+        InputProcessor input = new InputProcessor(screen, translator, null) {
+            @Override
+            public void sendAid(int aidCode) {
+                sentAid.set(aidCode);
+            }
+        };
+
+        boolean result = input.lightPenSelect(1);
+        assertTrue(result);
+        assertEquals(AID_ENTER, sentAid.get());
+        assertTrue((screen.getCell(0).fa & FA_MODIFY) != 0);
+    }
+
+    @Test
+    public void testLightPenSelectDeferredToggle() {
+        screen.erase(false);
+        screen.setCellFA(0, (byte) (FA_PRINTABLE | FA_INT_NORM_SEL));
+        // Designator at pos 1: '?' (deferred select)
+        screen.getCell(1).ec = 0x6F;
+        screen.getCell(1).ucs4 = '?';
+
+        java.util.concurrent.atomic.AtomicInteger sentAid = new java.util.concurrent.atomic.AtomicInteger(-1);
+        InputProcessor input = new InputProcessor(screen, translator, null) {
+            @Override
+            public void sendAid(int aidCode) {
+                sentAid.set(aidCode);
+            }
+        };
+
+        // First click: ? -> > and MDT=1, no transmission
+        boolean r1 = input.lightPenSelect(1);
+        assertTrue(r1);
+        assertEquals(-1, sentAid.get());
+        assertEquals('>', screen.getCell(1).ucs4);
+        assertEquals((byte) 0x6E, screen.getCell(1).ec);
+        assertTrue((screen.getCell(0).fa & FA_MODIFY) != 0);
+
+        // Second click: > -> ? and MDT=0, no transmission
+        boolean r2 = input.lightPenSelect(1);
+        assertTrue(r2);
+        assertEquals(-1, sentAid.get());
+        assertEquals('?', screen.getCell(1).ucs4);
+        assertEquals((byte) 0x6F, screen.getCell(1).ec);
+        assertFalse((screen.getCell(0).fa & FA_MODIFY) != 0);
+    }
+
+    @Test
+    public void testLightPenSelectInvalidDesignatorRejected() {
+        screen.erase(false);
+        screen.setCellFA(0, (byte) (FA_PRINTABLE | FA_INT_NORM_SEL));
+        // Designator at pos 1: 'A' (invalid designator)
+        screen.getCell(1).ec = (byte) 0xC1;
+        screen.getCell(1).ucs4 = 'A';
+
+        java.util.concurrent.atomic.AtomicInteger sentAid = new java.util.concurrent.atomic.AtomicInteger(-1);
+        InputProcessor input = new InputProcessor(screen, translator, null) {
+            @Override
+            public void sendAid(int aidCode) {
+                sentAid.set(aidCode);
+            }
+        };
+
+        boolean result = input.lightPenSelect(1);
+        assertFalse(result);
+        assertEquals(-1, sentAid.get());
+        assertFalse((screen.getCell(0).fa & FA_MODIFY) != 0);
+    }
+
+    @Test
+    public void testCursorSelectKey() {
+        screen.erase(false);
+        screen.setCellFA(0, (byte) (FA_PRINTABLE | FA_INT_NORM_SEL));
+        screen.getCell(1).ec = 0x50;
+        screen.getCell(1).ucs4 = '&';
+        screen.setCursorAddress(5);
+
+        java.util.concurrent.atomic.AtomicInteger sentAid = new java.util.concurrent.atomic.AtomicInteger(-1);
+        InputProcessor input = new InputProcessor(screen, translator, null) {
+            @Override
+            public void sendAid(int aidCode) {
+                sentAid.set(aidCode);
+            }
+        };
+
+        boolean result = input.cursorSelect();
+        assertTrue(result);
+        assertEquals(AID_ENTER, sentAid.get());
+        assertEquals(5, screen.getCursorAddress());
+    }
+
     @Test
     public void testSendAidSuppressesNullsInModifiedField() {
         java.util.concurrent.atomic.AtomicReference<byte[]> sent = new java.util.concurrent.atomic.AtomicReference<>();
@@ -231,4 +363,92 @@ public class InputProcessorTest {
         assertEquals((byte) 0xC9, result[8]); // 'I'
         assertEquals((byte) 0xE3, result[9]); // 'T'
     }
+
+    @Test
+    public void testSendGraphicMouseAidFraming() {
+        screen.erase(false);
+        screen.setCellFA(0, (byte) (FA_PRINTABLE | FA_MODIFY));
+        screen.getCell(1).ec = (byte) 0xC1; // 'A'
+        screen.setCellFA(5, (byte) (FA_PRINTABLE | FA_PROTECT));
+        screen.setCursorAddress(2);
+
+        haus.nightmare.lib3270j.graphics.GraphicsPlane plane = new haus.nightmare.lib3270j.graphics.GraphicsPlane(800, 600);
+        haus.nightmare.lib3270j.graphics.GocaDecoder goca = new haus.nightmare.lib3270j.graphics.GocaDecoder(plane);
+        goca.setGraphicsCursorActive(true);
+        goca.setGraphicCursorPosition(150, -80);
+
+        java.util.concurrent.atomic.AtomicReference<byte[]> sent = new java.util.concurrent.atomic.AtomicReference<>();
+        InputProcessor input = new InputProcessor(screen, translator, null) {
+            @Override
+            protected void sendAidResponse(byte[] data) {
+                sent.set(data);
+            }
+        };
+        input.setGocaDecoder(goca);
+
+        input.sendGraphicMouseAid(AID_ENTER, 1, false, false);
+
+        byte[] result = sent.get();
+        assertNotNull(result);
+        // Total expected length:
+        // 1 (AID_SF 0x88) + 56 (SF) + 1 (AID_ENTER 0x7D) + 2 (Cursor Addr) + 1 (SBA) + 2 (Field Addr) + 1 (Data 'A') = 64 bytes
+        assertEquals(64, result.length);
+        assertEquals((byte) AID_SF, result[0]);
+        // SF length = 52 (0x00 0x34) per IBM HOD / GOCA specification
+        assertEquals(0x00, result[1]);
+        assertEquals(0x34, result[2]);
+        // SF ID = 0x0F0F
+        assertEquals(0x0F, result[3]);
+        assertEquals(0x0F, result[4]);
+        // Coordinates in SF at index 1 + 24 = 25
+        int gx = (result[25] << 8) | (result[26] & 0xFF);
+        int gy = (result[27] << 8) | (result[28] & 0xFF);
+        assertEquals(150, (short) gx);
+        assertEquals(-80, (short) gy);
+        // Mouse constant at index 1 + 31 = 32
+        assertEquals(0x04, result[32]);
+        assertEquals(0x04, result[34]);
+        // Button 1 at index 1 + 35 = 36
+        assertEquals(0x01, result[36]);
+
+        // Trailing AID at index 57
+        assertEquals((byte) AID_ENTER, result[57]);
+        // Trailing SBA at 60
+        assertEquals((byte) ORDER_SBA, result[60]);
+        // Trailing field content 'A' at 63
+        assertEquals((byte) 0xC1, result[63]);
+    }
+
+    @Test
+    public void testAidSelectFramingOmitsFieldData() {
+        // Formatted screen with an unprotected field at 0, modified, containing 'A' and 'B'
+        screen.erase(false);
+        screen.setCellFA(0, (byte) (FA_PRINTABLE | FA_MODIFY));
+        screen.setCellFA(10, (byte) (FA_PRINTABLE | FA_PROTECT));
+        screen.getCell(1).ec = (byte) 0xC1;
+        screen.getCell(1).ucs4 = 'A';
+        screen.getCell(2).ec = (byte) 0xC2;
+        screen.getCell(2).ucs4 = 'B';
+        screen.setCursorAddress(1);
+
+        java.util.concurrent.atomic.AtomicReference<byte[]> sent = new java.util.concurrent.atomic.AtomicReference<>();
+        InputProcessor input = new InputProcessor(screen, translator, null) {
+            @Override
+            protected void sendAidResponse(byte[] data) {
+                sent.set(data);
+            }
+        };
+
+        input.sendAid(AID_SELECT);
+
+        byte[] result = sent.get();
+        assertNotNull(result);
+        // For AID_SELECT (0x7E), the stream consists ONLY of:
+        // 1 byte AID (0x7E) + 2 bytes cursor address + 1 byte SBA (0x11) + 2 bytes designator address = 6 bytes total.
+        // Field character contents ('A', 'B') MUST NOT be sent per IBM 3270 DS architecture!
+        assertEquals(6, result.length);
+        assertEquals((byte) AID_SELECT, result[0]);
+        // SBA order at byte 3
+        assertEquals((byte) ORDER_SBA, result[3]);
+    }
 }