Fix borrowed reference return in some callbacks

src/PyDrawable.cpp

@@ -10,10 +10,11 @@ static PyObject* PyDrawable_get_click(PyDrawableObject* self, void* closure)
         Py_RETURN_NONE;
 
     PyObject* ptr = self->data->click_callable->borrow();
-    if (ptr && ptr != Py_None)
+    if (ptr && ptr != Py_None) {
+        Py_INCREF(ptr);  // Return new reference, not borrowed
         return ptr;
-    else
+    }
-        Py_RETURN_NONE;
+    Py_RETURN_NONE;
 }
 
 // Click property setter

src/UIDrawable.cpp

@@ -259,10 +259,11 @@ PyObject* UIDrawable::get_click(PyObject* self, void* closure) {
             PyErr_SetString(PyExc_TypeError, "no idea how you did that; invalid UIDrawable derived instance for _get_click");
             return NULL;
     }
-    if (ptr && ptr != Py_None)
+    if (ptr && ptr != Py_None) {
+        Py_INCREF(ptr);  // Return new reference, not borrowed
         return ptr;
-    else
+    }
-        return Py_None;
+    Py_RETURN_NONE;
 }
 
 int UIDrawable::set_click(PyObject* self, PyObject* value, void* closure) {
@@ -1615,10 +1616,11 @@ PyObject* UIDrawable::get_on_enter(PyObject* self, void* closure) {
             PyErr_SetString(PyExc_TypeError, "Invalid UIDrawable derived instance for on_enter");
             return NULL;
     }
-    if (ptr && ptr != Py_None)
+    if (ptr && ptr != Py_None) {
+        Py_INCREF(ptr);  // Return new reference, not borrowed
         return ptr;
-    else
+    }
-        Py_RETURN_NONE;
+    Py_RETURN_NONE;
 }
 
 int UIDrawable::set_on_enter(PyObject* self, PyObject* value, void* closure) {
@@ -1698,10 +1700,11 @@ PyObject* UIDrawable::get_on_exit(PyObject* self, void* closure) {
             PyErr_SetString(PyExc_TypeError, "Invalid UIDrawable derived instance for on_exit");
             return NULL;
     }
-    if (ptr && ptr != Py_None)
+    if (ptr && ptr != Py_None) {
+        Py_INCREF(ptr);  // Return new reference, not borrowed
         return ptr;
-    else
+    }
-        Py_RETURN_NONE;
+    Py_RETURN_NONE;
 }
 
 int UIDrawable::set_on_exit(PyObject* self, PyObject* value, void* closure) {
@@ -1790,10 +1793,11 @@ PyObject* UIDrawable::get_on_move(PyObject* self, void* closure) {
             PyErr_SetString(PyExc_TypeError, "Invalid UIDrawable derived instance for on_move");
             return NULL;
     }
-    if (ptr && ptr != Py_None)
+    if (ptr && ptr != Py_None) {
+        Py_INCREF(ptr);  // Return new reference, not borrowed
         return ptr;
-    else
+    }
-        Py_RETURN_NONE;
+    Py_RETURN_NONE;
 }
 
 int UIDrawable::set_on_move(PyObject* self, PyObject* value, void* closure) {

tests/regression/issue_callback_refcount_test.py

@@ -0,0 +1,157 @@
+#!/usr/bin/env python3
+"""Test for callback property reference counting fix.
+
+This test verifies that accessing callback properties (on_click, on_enter, etc.)
+returns correctly reference-counted objects, preventing use-after-free bugs.
+
+The bug: Callback getters were returning borrowed references instead of new
+references, causing objects to be freed prematurely when Python DECREFs them.
+"""
+import mcrfpy
+import sys
+import gc
+
+def test_callback_refcount():
+    """Test that callback getters return new references."""
+    errors = []
+
+    # Create a scene
+    scene = mcrfpy.Scene("test_callback_refcount")
+
+    # Test Frame
+    frame = mcrfpy.Frame(pos=(0, 0), size=(100, 100))
+
+    # Set a callback
+    def my_callback(pos, button, action):
+        pass
+
+    frame.on_click = my_callback
+
+    # Read the callback back multiple times
+    # If borrowing incorrectly, this could cause use-after-free
+    for i in range(10):
+        cb = frame.on_click
+        if cb is None:
+            errors.append(f"on_click returned None on iteration {i}")
+            break
+        if not callable(cb):
+            errors.append(f"on_click returned non-callable on iteration {i}: {type(cb)}")
+            break
+        # Explicitly delete to trigger any refcount issues
+        del cb
+        gc.collect()
+
+    # Final check - should still return the callback
+    final_cb = frame.on_click
+    if final_cb is None:
+        errors.append("on_click returned None after repeated access")
+    elif not callable(final_cb):
+        errors.append(f"on_click returned non-callable after repeated access: {type(final_cb)}")
+
+    # Test on_enter, on_exit, on_move
+    frame.on_enter = lambda pos, button, action: None
+    frame.on_exit = lambda pos, button, action: None
+    frame.on_move = lambda pos, button, action: None
+
+    for name in ['on_enter', 'on_exit', 'on_move']:
+        for i in range(5):
+            cb = getattr(frame, name)
+            if cb is None:
+                errors.append(f"{name} returned None on iteration {i}")
+                break
+            del cb
+        gc.collect()
+
+    return errors
+
+
+def test_grid_cell_callbacks():
+    """Test Grid cell callback getters (these were already correct)."""
+    errors = []
+
+    grid = mcrfpy.Grid(pos=(0, 0), size=(100, 100), grid_size=(5, 5),
+                       texture=mcrfpy.default_texture, zoom=1.0)
+
+    grid.on_cell_enter = lambda pos: None
+    grid.on_cell_exit = lambda pos: None
+    grid.on_cell_click = lambda pos: None
+
+    for name in ['on_cell_enter', 'on_cell_exit', 'on_cell_click']:
+        for i in range(5):
+            cb = getattr(grid, name)
+            if cb is None:
+                errors.append(f"{name} returned None on iteration {i}")
+                break
+            del cb
+        gc.collect()
+
+    return errors
+
+
+def test_subclass_callback():
+    """Test callback access on Python subclasses."""
+    errors = []
+
+    class MyFrame(mcrfpy.Frame):
+        pass
+
+    obj = MyFrame(pos=(0, 0), size=(100, 100))
+
+    # Set callback via property
+    obj.on_click = lambda pos, button, action: print("clicked")
+
+    # Read back multiple times
+    for i in range(5):
+        cb = obj.on_click
+        if cb is None:
+            errors.append(f"Subclass on_click returned None on iteration {i}")
+            break
+        if not callable(cb):
+            errors.append(f"Subclass on_click returned non-callable: {type(cb)}")
+            break
+        del cb
+        gc.collect()
+
+    return errors
+
+
+def run_tests():
+    """Run all callback refcount tests."""
+    all_errors = []
+
+    print("Testing callback property refcount...")
+    errors = test_callback_refcount()
+    if errors:
+        all_errors.extend(errors)
+        print(f"  FAIL: {len(errors)} errors")
+    else:
+        print("  PASS: on_click, on_enter, on_exit, on_move")
+
+    print("Testing Grid cell callbacks...")
+    errors = test_grid_cell_callbacks()
+    if errors:
+        all_errors.extend(errors)
+        print(f"  FAIL: {len(errors)} errors")
+    else:
+        print("  PASS: on_cell_enter, on_cell_exit, on_cell_click")
+
+    print("Testing subclass callbacks...")
+    errors = test_subclass_callback()
+    if errors:
+        all_errors.extend(errors)
+        print(f"  FAIL: {len(errors)} errors")
+    else:
+        print("  PASS: MyFrame(Frame) subclass")
+
+    if all_errors:
+        print(f"\nFAILED with {len(all_errors)} errors:")
+        for e in all_errors:
+            print(f"  - {e}")
+        sys.exit(1)
+    else:
+        print("\nAll callback refcount tests PASSED")
+        sys.exit(0)
+
+
+if __name__ == "__main__":
+    run_tests()