refactor: Use property setter pattern for parent assignment

Instead of separate getParent()/setParent()/removeFromParent() methods,
the parent property now supports the Pythonic getter/setter pattern:
- child.parent       # Get parent (or None)
- child.parent = f   # Set parent (adds to f.children)
- child.parent = None # Remove from parent

This matches the existing pattern used by the click property callback.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/UIBase.h

@@ -165,10 +165,11 @@ static int UIDrawable_set_opacity(T* self, PyObject* value, void* closure)
 // #122 & #102: Macro for parent/global_position properties (requires closure with type enum)
 // These need the PyObjectsEnum value in closure, so they're added separately in each class
 #define UIDRAWABLE_PARENT_GETSETTERS(type_enum) \
-    {"parent", (getter)UIDrawable::get_parent, NULL, \
+    {"parent", (getter)UIDrawable::get_parent, (setter)UIDrawable::set_parent, \
      MCRF_PROPERTY(parent, \
-         "Parent drawable (read-only). " \
-         "Returns the parent Frame/Grid if nested, or None if at scene level." \
+         "Parent drawable. " \
+         "Get: Returns the parent Frame/Grid if nested, or None if at scene level. " \
+         "Set: Assign a Frame/Grid to reparent, or None to remove from parent." \
      ), (void*)type_enum}, \
     {"global_position", (getter)UIDrawable::get_global_pos, NULL, \
      MCRF_PROPERTY(global_position, \

src/UIDrawable.cpp

@@ -848,6 +848,87 @@ PyObject* UIDrawable::get_parent(PyObject* self, void* closure) {
     return obj;
 }
 
+// Python API - set parent drawable (or None to remove from parent)
+int UIDrawable::set_parent(PyObject* self, PyObject* value, void* closure) {
+    PyObjectsEnum objtype = static_cast<PyObjectsEnum>(reinterpret_cast<long>(closure));
+    std::shared_ptr<UIDrawable> drawable = nullptr;
+
+    // Get the shared_ptr for self
+    switch (objtype) {
+        case PyObjectsEnum::UIFRAME:
+            drawable = ((PyUIFrameObject*)self)->data;
+            break;
+        case PyObjectsEnum::UICAPTION:
+            drawable = ((PyUICaptionObject*)self)->data;
+            break;
+        case PyObjectsEnum::UISPRITE:
+            drawable = ((PyUISpriteObject*)self)->data;
+            break;
+        case PyObjectsEnum::UIGRID:
+            drawable = ((PyUIGridObject*)self)->data;
+            break;
+        case PyObjectsEnum::UILINE:
+            drawable = ((PyUILineObject*)self)->data;
+            break;
+        case PyObjectsEnum::UICIRCLE:
+            drawable = ((PyUICircleObject*)self)->data;
+            break;
+        case PyObjectsEnum::UIARC:
+            drawable = ((PyUIArcObject*)self)->data;
+            break;
+        default:
+            PyErr_SetString(PyExc_TypeError, "Invalid UIDrawable derived instance");
+            return -1;
+    }
+
+    // Handle None - remove from parent
+    if (value == Py_None) {
+        drawable->removeFromParent();
+        return 0;
+    }
+
+    // Value must be a Frame or Grid (things with children collections)
+    // Check if it's a Frame
+    PyTypeObject* frame_type = (PyTypeObject*)PyObject_GetAttrString(McRFPy_API::mcrf_module, "Frame");
+    PyTypeObject* grid_type = (PyTypeObject*)PyObject_GetAttrString(McRFPy_API::mcrf_module, "Grid");
+
+    bool is_frame = frame_type && PyObject_IsInstance(value, (PyObject*)frame_type);
+    bool is_grid = grid_type && PyObject_IsInstance(value, (PyObject*)grid_type);
+
+    Py_XDECREF(frame_type);
+    Py_XDECREF(grid_type);
+
+    if (!is_frame && !is_grid) {
+        PyErr_SetString(PyExc_TypeError, "parent must be a Frame, Grid, or None");
+        return -1;
+    }
+
+    // Remove from old parent first
+    drawable->removeFromParent();
+
+    // Get the new parent's children collection and append
+    std::shared_ptr<std::vector<std::shared_ptr<UIDrawable>>>* children_ptr = nullptr;
+    std::shared_ptr<UIDrawable> new_parent = nullptr;
+
+    if (is_frame) {
+        auto frame = ((PyUIFrameObject*)value)->data;
+        children_ptr = &frame->children;
+        new_parent = frame;
+    } else if (is_grid) {
+        auto grid = ((PyUIGridObject*)value)->data;
+        children_ptr = &grid->children;
+        new_parent = grid;
+    }
+
+    if (children_ptr && *children_ptr) {
+        // Add to new parent's children
+        (*children_ptr)->push_back(drawable);
+        drawable->setParent(new_parent);
+    }
+
+    return 0;
+}
+
 // Python API - get global position (read-only)
 PyObject* UIDrawable::get_global_pos(PyObject* self, void* closure) {
     PyObjectsEnum objtype = static_cast<PyObjectsEnum>(reinterpret_cast<long>(closure));

src/UIDrawable.h

@@ -95,6 +95,7 @@ public:
 
     // Python API for parent/global_position
     static PyObject* get_parent(PyObject* self, void* closure);
+    static int set_parent(PyObject* self, PyObject* value, void* closure);
     static PyObject* get_global_pos(PyObject* self, void* closure);
     
     // New properties for Phase 1

tests/unit/test_parent_child_system.py

@@ -186,6 +186,67 @@ def test_all_drawable_types():
     print("  - All drawable types: PASS")
 
 
+def test_parent_setter():
+    """Test parent property setter (assign parent directly)"""
+    print("Testing parent setter...")
+
+    mcrfpy.createScene("test7")
+    ui = mcrfpy.sceneUI("test7")
+
+    # Create parent frame and child
+    parent = mcrfpy.Frame(pos=(100, 100), size=(200, 200))
+    child = mcrfpy.Caption(text="Child", pos=(10, 10))
+    ui.append(parent)
+
+    # Child has no parent initially
+    assert child.parent is None, "Child should have no parent initially"
+
+    # Set parent via property assignment
+    child.parent = parent
+    assert child.parent is not None, "Child should have parent after assignment"
+    assert len(parent.children) == 1, f"Parent should have 1 child, has {len(parent.children)}"
+
+    # Verify global position updates
+    global_pos = child.global_position
+    assert global_pos.x == 110.0, f"Global X should be 110, got {global_pos.x}"
+    assert global_pos.y == 110.0, f"Global Y should be 110, got {global_pos.y}"
+
+    # Set parent to None to remove
+    child.parent = None
+    assert child.parent is None, "Child should have no parent after setting None"
+    assert len(parent.children) == 0, f"Parent should have 0 children, has {len(parent.children)}"
+
+    print("  - Parent setter: PASS")
+
+
+def test_reparenting_via_setter():
+    """Test moving a child from one parent to another via setter"""
+    print("Testing reparenting via setter...")
+
+    mcrfpy.createScene("test8")
+    ui = mcrfpy.sceneUI("test8")
+
+    parent1 = mcrfpy.Frame(pos=(0, 0), size=(100, 100))
+    parent2 = mcrfpy.Frame(pos=(200, 200), size=(100, 100))
+    child = mcrfpy.Sprite(pos=(5, 5))
+
+    ui.append(parent1)
+    ui.append(parent2)
+
+    # Add to first parent via setter
+    child.parent = parent1
+    assert len(parent1.children) == 1, "Parent1 should have 1 child"
+    assert len(parent2.children) == 0, "Parent2 should have 0 children"
+
+    # Move to second parent via setter (should auto-remove from parent1)
+    child.parent = parent2
+    assert len(parent1.children) == 0, f"Parent1 should have 0 children after reparent, has {len(parent1.children)}"
+    assert len(parent2.children) == 1, f"Parent2 should have 1 child after reparent, has {len(parent2.children)}"
+    assert child.global_position.x == 205.0, f"Global X should be 205, got {child.global_position.x}"
+
+    print("  - Reparenting via setter: PASS")
+
+
 if __name__ == "__main__":
     try:
         test_parent_property()
@@ -194,6 +255,8 @@ if __name__ == "__main__":
         test_remove_clears_parent()
         test_scene_level_elements()
         test_all_drawable_types()
+        test_parent_setter()
+        test_reparenting_via_setter()
 
         print("\n=== All tests passed! ===")
         sys.exit(0)