BGE Python API

This changes how the BGE classes and Python work together, which hasnt changed since blender went opensource.
The main difference is PyObjectPlus - the base class for most game engine classes, no longer inherit from PyObject, and cannot be cast to a PyObject.

This has the advantage that the BGE does not have to keep 2 reference counts valid for C++ and Python.

Previously C++ classes would never be freed while python held a reference, however this reference could be problematic eg: a GameObject that isnt in a scene anymore should not be used by python, doing so could even crash blender in some cases.

Instead PyObjectPlus has a member "PyObject *m_proxy" which is lazily initialized when python needs it. m_proxy reference counts are managed by python, though it should never be freed while the C++ class exists since it holds a reference to avoid making and freeing it all the time.
When the C++ class is free'd it sets the m_proxy reference to NULL, If python accesses this variable it will raise a RuntimeError, (check the isValid attribute to see if its valid without raising an error).
- This replaces the m_zombie bool and IsZombie() tests added recently.

In python return values that used to be..
 return value->AddRef();
Are now
 return value->GetProxy();
or...
 return value->NewProxy(true); // true means python owns this C++ value which will be deleted when the PyObject is freed

source/gameengine/Ketsji/KXNetwork/KX_NetworkMessageSensor.cpp

@@ -235,9 +235,9 @@ PyObject* KX_NetworkMessageSensor::pyattr_get_bodies(void *self_v, const KX_PYAT
 {
 	KX_NetworkMessageSensor *self = static_cast<KX_NetworkMessageSensor*>(self_v);
 	if (self->m_BodyList) {
-		return ((PyObject*) self->m_BodyList->AddRef());
+		return self->m_BodyList->GetProxy();
 	} else {
-		return ((PyObject*) new CListValue());
+		return (new CListValue())->NewProxy(true);
 	}
 }
 
@@ -245,9 +245,9 @@ PyObject* KX_NetworkMessageSensor::pyattr_get_subjects(void *self_v, const KX_PY
 {
 	KX_NetworkMessageSensor *self = static_cast<KX_NetworkMessageSensor*>(self_v);
 	if (self->m_SubjectList) {
-		return ((PyObject*) self->m_SubjectList->AddRef());
+		return self->m_SubjectList->GetProxy();
 	} else {
-		return ((PyObject*) new CListValue());
+		return (new CListValue())->NewProxy(true);
 	}
 }
 
@@ -290,9 +290,9 @@ PyObject* KX_NetworkMessageSensor::PyGetBodies( PyObject* )
 {
 	ShowDeprecationWarning("getBodies()", "bodies");
 	if (m_BodyList) {
-		return ((PyObject*) m_BodyList->AddRef());
+		return m_BodyList->GetProxy();
 	} else {
-		return ((PyObject*) new CListValue());
+		return (new CListValue())->NewProxy(true);
 	}
 }
 
@@ -316,9 +316,9 @@ PyObject* KX_NetworkMessageSensor::PyGetSubjects( PyObject* )
 {
 	ShowDeprecationWarning("getSubjects()", "subjects");
 	if (m_SubjectList) {
-		return ((PyObject*) m_SubjectList->AddRef());
+		return m_SubjectList->GetProxy();
 	} else {
-		return ((PyObject*) new CListValue());
+		return (new CListValue())->NewProxy(true);
 	}
 }
 // <----- Deprecated