Fix Scenes freeze and Languages up/down navigation

- VsmxInterpreter.interpretFunction: save/restore pc/exit/stack/callStates so
  re-entrant event firing (FireEventAnim, timers, movie callbacks) no longer
  truncates the outer script. This is what left ss_btn_mm without focus
  (Scenes appeared frozen: no selection, input ignored while audio continued).
- Add default geometric focus traversal for buttons with no direction handler:
  Controller.moveFocus picks the nearest visible focusable object. The PSP does
  this natively; English/Francais buttons have no onUp/onDown events in the RCO
  and relied on it.
- Track page visibility (BaseObject.displayed, set by PageObject.open/close) so
  traversal skips closed pages and collapsed (alpha 0) columns.
- Make BaseObject.trigger null-safe.

core/src/main/java/dev/quoije/umd/rco/object/BaseObject.java

@@ -30,6 +30,7 @@ public abstract class BaseObject extends BaseNativeObject implements IDisplay {
     protected Controller controller;
     private String name;
     private BaseNativeObject parent;
+    private boolean displayed;
 
     private Field[] getSortedFields() {
         Field[] fields = getClass().getFields();
@@ -140,8 +141,17 @@ public abstract class BaseObject extends BaseNativeObject implements IDisplay {
         return name;
     }
 
+    /** True while this object is part of an opened page's display list. */
+    public boolean isDisplayed() {
+        return displayed;
+    }
+
+    public void setDisplayed(boolean displayed) {
+        this.displayed = displayed;
+    }
+
     protected void trigger(EventType event) {
-        if (event.getEvent() != null && controller != null) {
+        if (event != null && event.getEvent() != null && controller != null) {
             controller.getInterpreter().interpretScript(getObject(), event.getEvent());
         }
     }

core/src/main/java/dev/quoije/umd/rco/object/ButtonObject.java

@@ -7,6 +7,7 @@ import dev.quoije.umd.rco.type.ImageType;
 import dev.quoije.umd.rco.type.IntType;
 import dev.quoije.umd.rco.type.TextType;
 import dev.quoije.umd.rco.vsmx.objects.BaseNativeObject;
+import dev.quoije.umd.rco.vsmx.objects.Controller;
 
 /** A button object. */
 public class ButtonObject extends BasePositionObject {
@@ -49,6 +50,14 @@ public class ButtonObject extends BasePositionObject {
         return focus.getImage();
     }
 
+    @Override
+    public void setController(Controller controller) {
+        super.setController(controller);
+        if (controller != null) {
+            controller.registerFocusable(this);
+        }
+    }
+
     @Override
     public void setFocus() {
         trigger(onFocusIn);
@@ -68,21 +77,37 @@ public class ButtonObject extends BasePositionObject {
 
     @Override
     public void onUp() {
+        if (onFocusUp != null && onFocusUp.getEvent() != null) {
             trigger(onFocusUp);
+        } else if (controller != null) {
+            controller.moveFocus(this, 0, 1);
+        }
     }
 
     @Override
     public void onDown() {
+        if (onFocusDown != null && onFocusDown.getEvent() != null) {
             trigger(onFocusDown);
+        } else if (controller != null) {
+            controller.moveFocus(this, 0, -1);
+        }
     }
 
     @Override
     public void onLeft() {
+        if (onFocusLeft != null && onFocusLeft.getEvent() != null) {
             trigger(onFocusLeft);
+        } else if (controller != null) {
+            controller.moveFocus(this, -1, 0);
+        }
     }
 
     @Override
     public void onRight() {
+        if (onFocusRight != null && onFocusRight.getEvent() != null) {
             trigger(onFocusRight);
+        } else if (controller != null) {
+            controller.moveFocus(this, 1, 0);
+        }
     }
 }

core/src/main/java/dev/quoije/umd/rco/object/PageObject.java

@@ -35,6 +35,7 @@ public class PageObject extends BaseObject {
         VsmxBaseObject children = object.getPropertyValue(Resource.childrenName);
         for (String childName : children.getPropertyNames()) {
             VsmxBaseObject child = children.getPropertyValue(childName);
+            setDisplayed(child, true);
             display.add(child);
             display(child);
         }
@@ -47,11 +48,18 @@ public class PageObject extends BaseObject {
         VsmxBaseObject children = object.getPropertyValue(Resource.childrenName);
         for (String childName : children.getPropertyNames()) {
             VsmxBaseObject child = children.getPropertyValue(childName);
+            setDisplayed(child, false);
             display.remove(child);
             hide(child);
         }
     }
 
+    private static void setDisplayed(VsmxBaseObject object, boolean displayed) {
+        if (object instanceof VsmxNativeObject nativeObject && nativeObject.getObject() instanceof BaseObject baseObject) {
+            baseObject.setDisplayed(displayed);
+        }
+    }
+
     private BasePositionObject getFirstButton(VsmxBaseObject object) {
         if (!object.hasPropertyValue(Resource.childrenName)) {
             return null;

core/src/main/java/dev/quoije/umd/rco/object/UButtonObject.java

@@ -6,6 +6,7 @@ import dev.quoije.umd.rco.type.EventType;
 import dev.quoije.umd.rco.type.ImageType;
 import dev.quoije.umd.rco.type.IntType;
 import dev.quoije.umd.rco.vsmx.objects.BaseNativeObject;
+import dev.quoije.umd.rco.vsmx.objects.Controller;
 
 /** A user button object (navigation with onLeft/onRight/onUp/onDown events). */
 public class UButtonObject extends BasePositionObject {
@@ -39,6 +40,14 @@ public class UButtonObject extends BasePositionObject {
         onDisplayUpdated();
     }
 
+    @Override
+    public void setController(Controller controller) {
+        super.setController(controller);
+        if (controller != null) {
+            controller.registerFocusable(this);
+        }
+    }
+
     @Override
     public void setFocus() {
         trigger(onFocusIn);
@@ -58,21 +67,37 @@ public class UButtonObject extends BasePositionObject {
 
     @Override
     public void onUp() {
+        if (onUp != null && onUp.getEvent() != null) {
             trigger(onUp);
+        } else if (controller != null) {
+            controller.moveFocus(this, 0, 1);
+        }
     }
 
     @Override
     public void onDown() {
+        if (onDown != null && onDown.getEvent() != null) {
             trigger(onDown);
+        } else if (controller != null) {
+            controller.moveFocus(this, 0, -1);
+        }
     }
 
     @Override
     public void onLeft() {
+        if (onLeft != null && onLeft.getEvent() != null) {
             trigger(onLeft);
+        } else if (controller != null) {
+            controller.moveFocus(this, -1, 0);
+        }
     }
 
     @Override
     public void onRight() {
+        if (onRight != null && onRight.getEvent() != null) {
             trigger(onRight);
+        } else if (controller != null) {
+            controller.moveFocus(this, 1, 0);
+        }
     }
 }

core/src/main/java/dev/quoije/umd/rco/vsmx/interpreter/VsmxInterpreter.java

@@ -498,6 +498,19 @@ public final class VsmxInterpreter {
 
     /** Interprets a function body in a fresh call frame. */
     public synchronized void interpretFunction(VsmxFunction function, VsmxBaseObject object, VsmxBaseObject[] arguments) {
+        // This entry point can be invoked re-entrantly (FireEventAnim, timers,
+        // movie callbacks all run from inside an already-running script), so the
+        // outer execution state must be preserved and restored. Without this,
+        // the inner RETURN would set {@code exit} and truncate the outer script.
+        int savedPc = pc;
+        boolean savedExit = exit;
+        Deque<VsmxBaseObject> savedStack = stack;
+        Deque<VsmxCallState> savedCallStates = callStates;
+        VsmxCallState savedCallState = callState;
+
+        callStates = new ArrayDeque<>();
+        stack = null;
+        callState = null;
         pushCallState(object, function.getLocalVars(), false, true);
         for (int i = 1; i <= function.getArgs(); i++) {
             if (arguments == null || i > arguments.length) {
@@ -508,6 +521,12 @@ public final class VsmxInterpreter {
         }
         pc = function.getStartLine();
         interpret();
+
+        pc = savedPc;
+        exit = savedExit;
+        stack = savedStack;
+        callStates = savedCallStates;
+        callState = savedCallState;
     }
 
     /** Interprets a script event handler by name (e.g. "script:/main/onPush"). */

core/src/main/java/dev/quoije/umd/rco/vsmx/objects/Controller.java

@@ -10,6 +10,9 @@ import dev.quoije.umd.rco.vsmx.interpreter.VsmxNativeObject;
 import dev.quoije.umd.rco.vsmx.interpreter.VsmxNull;
 import dev.quoije.umd.rco.vsmx.interpreter.VsmxString;
 
+import java.util.ArrayList;
+import java.util.List;
+
 /** The controller native object: input focus and resource management. */
 public class Controller extends BaseNativeObject {
 
@@ -20,6 +23,7 @@ public class Controller extends BaseNativeObject {
     private VsmxBaseObject userData;
     private String resource;
     private BasePositionObject focus;
+    private final List<BasePositionObject> focusables = new ArrayList<>();
 
     public static VsmxNativeObject create(VsmxInterpreter interpreter, MenuHost menuHost, String resource) {
         Controller controller = new Controller(interpreter, menuHost);
@@ -79,6 +83,63 @@ public class Controller extends BaseNativeObject {
         return focus;
     }
 
+    /** Registers a focusable object so default (geometric) focus traversal can reach it. */
+    public void registerFocusable(BasePositionObject object) {
+        synchronized (focusables) {
+            if (!focusables.contains(object)) {
+                focusables.add(object);
+            }
+        }
+    }
+
+    /**
+     * Moves focus to the nearest visible, focusable object in the given direction
+     * when a button has no script handler for that direction. {@code dx}/{@code dy}
+     * use the framebuffer coordinate system (+X right, +Y up).
+     */
+    public void moveFocus(BasePositionObject from, int dx, int dy) {
+        int fromX = from.getX() + from.getWidth() / 2;
+        int fromY = from.getY() + from.getHeight() / 2;
+
+        BasePositionObject best = null;
+        double bestScore = Double.MAX_VALUE;
+        synchronized (focusables) {
+            for (BasePositionObject candidate : focusables) {
+                if (candidate == from || !candidate.isDisplayed() || candidate.getAlpha() <= 0f
+                        || candidate.getImage() == null) {
+                    continue;
+                }
+                int candidateX = candidate.getX() + candidate.getWidth() / 2;
+                int candidateY = candidate.getY() + candidate.getHeight() / 2;
+                int offsetX = candidateX - fromX;
+                int offsetY = candidateY - fromY;
+                if (dy < 0 && offsetY >= 0) {
+                    continue;
+                }
+                if (dy > 0 && offsetY <= 0) {
+                    continue;
+                }
+                if (dx < 0 && offsetX >= 0) {
+                    continue;
+                }
+                if (dx > 0 && offsetX <= 0) {
+                    continue;
+                }
+                double primary = dx != 0 ? java.lang.Math.abs(offsetX) : java.lang.Math.abs(offsetY);
+                double secondary = dx != 0 ? java.lang.Math.abs(offsetY) : java.lang.Math.abs(offsetX);
+                double score = primary * 10 + secondary;
+                if (score < bestScore) {
+                    bestScore = score;
+                    best = candidate;
+                }
+            }
+        }
+
+        if (best != null) {
+            best.setFocus();
+        }
+    }
+
     public void onUp() {
         if (focus != null) {
             focus.onUp();