Fix: Derivable drawable types participate in garbage collector cycle detection

tests/regression/subclass_callback_segfault_test.py

@@ -0,0 +1,87 @@
+#!/usr/bin/env python3
+"""Minimal reproduction of segfault when calling subclass method callback.
+
+The issue: When a Frame subclass assigns self.on_click = self._on_click,
+reading it back works but there's a segfault during cleanup.
+"""
+import mcrfpy
+import sys
+import gc
+
+class MyFrame(mcrfpy.Frame):
+    def __init__(self, **kwargs):
+        super().__init__(**kwargs)
+        self.on_click = self._on_click
+
+    def _on_click(self, pos, button, action):
+        print(f"Clicked at {pos}, button={button}, action={action}")
+
+
+def test_minimal():
+    """Minimal test case."""
+    print("Creating MyFrame...")
+    obj = MyFrame(pos=(100, 100), size=(100, 100))
+
+    print(f"Reading on_click: {obj.on_click}")
+    print(f"Type: {type(obj.on_click)}")
+
+    print("Attempting to call on_click...")
+    try:
+        obj.on_click((50, 50), "left", "start")
+        print("Call succeeded!")
+    except Exception as e:
+        print(f"Exception: {type(e).__name__}: {e}")
+
+    print("Clearing callback...")
+    obj.on_click = None
+
+    print("Deleting object...")
+    del obj
+
+    print("Running GC...")
+    gc.collect()
+
+    print("About to exit...")
+    sys.exit(0)
+
+
+def test_without_callback_clear():
+    """Test without clearing callback first."""
+    print("Creating MyFrame...")
+    obj = MyFrame(pos=(100, 100), size=(100, 100))
+
+    print("Calling...")
+    obj.on_click((50, 50), "left", "start")
+
+    print("Deleting without clearing callback...")
+    del obj
+    gc.collect()
+
+    print("About to exit...")
+    sys.exit(0)
+
+
+def test_added_to_scene():
+    """Test when added to scene."""
+    print("Creating scene and MyFrame...")
+    scene = mcrfpy.Scene("test")
+    obj = MyFrame(pos=(100, 100), size=(100, 100))
+    scene.children.append(obj)
+
+    print("Calling via scene.children[0]...")
+    scene.children[0].on_click((50, 50), "left", "start")
+
+    print("About to exit...")
+    sys.exit(0)
+
+
+if __name__ == "__main__":
+    # Try different scenarios
+    import sys
+    if len(sys.argv) > 1:
+        if sys.argv[1] == "2":
+            test_without_callback_clear()
+        elif sys.argv[1] == "3":
+            test_added_to_scene()
+    else:
+        test_minimal()