Fix UniformCollection owner validity check (closes #272)

UniformCollection accessor methods checked the raw collection pointer
but never checked if the owning object was still alive. Changed owner
field from weak_ptr<UIDrawable> to weak_ptr<void> (type-erased) so
both UIDrawable and UIEntity owners can be tracked. Set owner in both
get_uniforms() paths. All accessors now check owner.lock() before
dereferencing the raw collection pointer.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/PyUniformCollection.cpp

@@ -151,7 +151,7 @@ PyObject* PyUniformCollectionType::repr(PyObject* obj) {
     PyUniformCollectionObject* self = (PyUniformCollectionObject*)obj;
     std::ostringstream ss;
     ss << "<UniformCollection";
-    if (self->collection) {
+    if (self->owner.lock() && self->collection) {
         auto names = self->collection->getNames();
         ss << " [";
         for (size_t i = 0; i < names.size(); ++i) {
@@ -166,15 +166,15 @@ PyObject* PyUniformCollectionType::repr(PyObject* obj) {
 
 Py_ssize_t PyUniformCollectionType::mp_length(PyObject* obj) {
     PyUniformCollectionObject* self = (PyUniformCollectionObject*)obj;
-    if (!self->collection) return 0;
+    if (!self->owner.lock() || !self->collection) return 0;
     return static_cast<Py_ssize_t>(self->collection->getNames().size());
 }
 
 PyObject* PyUniformCollectionType::mp_subscript(PyObject* obj, PyObject* key) {
     PyUniformCollectionObject* self = (PyUniformCollectionObject*)obj;
 
-    if (!self->collection) {
+    if (!self->owner.lock() || !self->collection) {
-        PyErr_SetString(PyExc_RuntimeError, "UniformCollection is not valid");
+        PyErr_SetString(PyExc_RuntimeError, "UniformCollection is not valid (owner destroyed)");
         return NULL;
     }
 
@@ -239,8 +239,8 @@ PyObject* PyUniformCollectionType::mp_subscript(PyObject* obj, PyObject* key) {
 int PyUniformCollectionType::mp_ass_subscript(PyObject* obj, PyObject* key, PyObject* value) {
     PyUniformCollectionObject* self = (PyUniformCollectionObject*)obj;
 
-    if (!self->collection) {
+    if (!self->owner.lock() || !self->collection) {
-        PyErr_SetString(PyExc_RuntimeError, "UniformCollection is not valid");
+        PyErr_SetString(PyExc_RuntimeError, "UniformCollection is not valid (owner destroyed)");
         return -1;
     }
 
@@ -330,7 +330,7 @@ int PyUniformCollectionType::mp_ass_subscript(PyObject* obj, PyObject* key, PyOb
 int PyUniformCollectionType::sq_contains(PyObject* obj, PyObject* key) {
     PyUniformCollectionObject* self = (PyUniformCollectionObject*)obj;
 
-    if (!self->collection) return 0;
+    if (!self->owner.lock() || !self->collection) return 0;
 
     if (!PyUnicode_Check(key)) return 0;
 
@@ -339,7 +339,7 @@ int PyUniformCollectionType::sq_contains(PyObject* obj, PyObject* key) {
 }
 
 PyObject* PyUniformCollectionType::keys(PyUniformCollectionObject* self, PyObject* Py_UNUSED(ignored)) {
-    if (!self->collection) {
+    if (!self->owner.lock() || !self->collection) {
         return PyList_New(0);
     }
 
@@ -352,7 +352,7 @@ PyObject* PyUniformCollectionType::keys(PyUniformCollectionObject* self, PyObjec
 }
 
 PyObject* PyUniformCollectionType::values(PyUniformCollectionObject* self, PyObject* Py_UNUSED(ignored)) {
-    if (!self->collection) {
+    if (!self->owner.lock() || !self->collection) {
         return PyList_New(0);
     }
 
@@ -372,7 +372,7 @@ PyObject* PyUniformCollectionType::values(PyUniformCollectionObject* self, PyObj
 }
 
 PyObject* PyUniformCollectionType::items(PyUniformCollectionObject* self, PyObject* Py_UNUSED(ignored)) {
-    if (!self->collection) {
+    if (!self->owner.lock() || !self->collection) {
         return PyList_New(0);
     }
 
@@ -395,7 +395,7 @@ PyObject* PyUniformCollectionType::items(PyUniformCollectionObject* self, PyObje
 }
 
 PyObject* PyUniformCollectionType::clear(PyUniformCollectionObject* self, PyObject* Py_UNUSED(ignored)) {
-    if (self->collection) {
+    if (self->owner.lock() && self->collection) {
         auto names = self->collection->getNames();
         for (const auto& name : names) {
             self->collection->remove(name);

src/PyUniformCollection.h

@@ -83,8 +83,8 @@ private:
 // Python object structure for UniformCollection
 typedef struct {
     PyObject_HEAD
-    UniformCollection* collection;  // Owned by UIDrawable, not by this object
+    UniformCollection* collection;  // Owned by UIDrawable/UIEntity, not by this object
-    std::weak_ptr<UIDrawable> owner;  // For checking validity
+    std::weak_ptr<void> owner;  // Type-erased weak ref for validity checking
     PyObject* weakreflist;
 } PyUniformCollectionObject;
 

src/UIDrawable.cpp

@@ -41,6 +41,28 @@ static UIDrawable* extractDrawable(PyObject* self, PyObjectsEnum objtype) {
     }
 }
 
+// Helper to extract shared_ptr<UIDrawable> for ownership tracking
+static std::shared_ptr<UIDrawable> extractDrawableShared(PyObject* self, PyObjectsEnum objtype) {
+    switch (objtype) {
+        case PyObjectsEnum::UIFRAME:
+            return ((PyUIFrameObject*)self)->data;
+        case PyObjectsEnum::UICAPTION:
+            return ((PyUICaptionObject*)self)->data;
+        case PyObjectsEnum::UISPRITE:
+            return ((PyUISpriteObject*)self)->data;
+        case PyObjectsEnum::UIGRID:
+            return ((PyUIGridObject*)self)->data;
+        case PyObjectsEnum::UILINE:
+            return ((PyUILineObject*)self)->data;
+        case PyObjectsEnum::UICIRCLE:
+            return ((PyUICircleObject*)self)->data;
+        case PyObjectsEnum::UIARC:
+            return ((PyUIArcObject*)self)->data;
+        default:
+            return nullptr;
+    }
+}
+
 UIDrawable::UIDrawable() : position(0.0f, 0.0f) { click_callable = NULL;  }
 
 UIDrawable::UIDrawable(const UIDrawable& other)
@@ -1271,7 +1293,7 @@ PyObject* UIDrawable::get_uniforms(PyObject* self, void* closure) {
 
     collection->collection = drawable->uniforms.get();
     collection->weakreflist = NULL;
-    // Note: owner weak_ptr could be set here if we had access to shared_ptr
+    collection->owner = extractDrawableShared(self, objtype);
 
     return (PyObject*)collection;
 }

src/UIEntityPyMethods.h

@@ -140,6 +140,7 @@ static PyObject* UIEntity_get_uniforms(PyUIEntityObject* self, void* closure)
 
     // The collection is owned by the sprite, we just provide a view
     uniforms_obj->collection = self->data->sprite.uniforms.get();
+    uniforms_obj->owner = self->data;  // Entity shared_ptr keeps collection alive
     uniforms_obj->weakreflist = NULL;
 
     return (PyObject*)uniforms_obj;