PyAPI Mathutils Vector callbacks, referencing other PyObjects rather then thin wrapping vectors which is crash prone.

in short, vectors can work as if they are thin wrapped but not crash blender if the original data is removed.

* RNA vector's return Mathutils vector types.
* BGE vectors for GameObject's localPosition, worldPosition, localPosition, localScale, worldScale, localInertia.
* Comment USE_MATHUTILS define to disable returning vectors.

Example...

* 2.49... *
 loc = gameOb.worldPosition
 loc[1] = 0
 gameOb.worldPosition = loc

* With vectors... *
 gameOb.worldPosition[1] = 0


* But this wont crash... *
 loc = gameOb.worldPosition
 gameOb.endObject()
 loc[1] = 0 # will raise an error that the objects removed.

This breaks games which assume return values are lists.

Will add this to eulers, matrix and quaternion types later.

source/blender/python/intern/bpy_rna.c

@@ -39,6 +39,64 @@
 #include "BKE_global.h" /* evil G.* */
 #include "BKE_report.h"
 
+#define USE_MATHUTILS
+
+#ifdef USE_MATHUTILS
+#include "../generic/Mathutils.h" /* so we can have mathutils callbacks */
+
+static int mathutils_rna_vector_cb_index= -1; /* index for our callbacks */
+
+static int mathutils_rna_vector_check(PyObject *user)
+{
+	return ((BPy_PropertyRNA *)user)->prop?1:0;
+}
+
+static int mathutils_rna_vector_get(BPy_PropertyRNA *self, int subtype, float *vec_from)
+{
+	if(self->prop==NULL)
+		return 0;
+	
+	RNA_property_float_get_array(&self->ptr, self->prop, vec_from);
+	return 1;
+}
+
+static int mathutils_rna_vector_set(BPy_PropertyRNA *self, int subtype, float *vec_to)
+{
+	if(self->prop==NULL)
+		return 0;
+
+	RNA_property_float_set_array(&self->ptr, self->prop, vec_to);
+	return 1;
+}
+
+static int mathutils_rna_vector_get_index(BPy_PropertyRNA *self, int subtype, float *vec_from, int index)
+{
+	if(self->prop==NULL)
+		return 0;
+	
+	vec_from[index]= RNA_property_float_get_index(&self->ptr, self->prop, index);
+	return 1;
+}
+
+static int mathutils_rna_vector_set_index(BPy_PropertyRNA *self, int subtype, float *vec_to, int index)
+{
+	if(self->prop==NULL)
+		return 0;
+
+	RNA_property_float_set_index(&self->ptr, self->prop, index, vec_to[index]);
+	return 1;
+}
+
+Mathutils_Callback mathutils_rna_vector_cb = {
+	mathutils_rna_vector_check,
+	mathutils_rna_vector_get,
+	mathutils_rna_vector_set,
+	mathutils_rna_vector_get_index,
+	mathutils_rna_vector_set_index
+};
+
+#endif
+
 static int pyrna_struct_compare( BPy_StructRNA * a, BPy_StructRNA * b )
 {
 	return (a->ptr.data==b->ptr.data) ? 0 : -1;
@@ -144,7 +202,22 @@ PyObject * pyrna_prop_to_py(PointerRNA *ptr, PropertyRNA *prop)
 
 	if (len > 0) {
 		/* resolve the array from a new pytype */
-		return pyrna_prop_CreatePyObject(ptr, prop);
+		PyObject *ret = pyrna_prop_CreatePyObject(ptr, prop);
+		
+#ifdef USE_MATHUTILS
+		/* return a mathutils vector where possible */
+		if(	RNA_property_type(prop)==PROP_FLOAT &&
+			RNA_property_subtype(prop)==PROP_VECTOR &&
+			len>=2 && len <= 4 )
+		{
+			PyObject *vec_cb= newVectorObject_cb(ret, len, mathutils_rna_vector_cb_index, 0);
+			Py_DECREF(ret); /* the vector owns now */
+			
+			ret= vec_cb; /* return the vector instead */
+		}
+#endif
+		
+		return ret;
 	}
 	
 	/* see if we can coorce into a python type - PropertyType */
@@ -1674,6 +1747,10 @@ PyObject *BPY_rna_module( void )
 {
 	PointerRNA ptr;
 	
+#ifdef USE_MATHUTILS // register mathutils callbacks, ok to run more then once.
+	mathutils_rna_vector_cb_index= Mathutils_RegisterCallback(&mathutils_rna_vector_cb);
+#endif
+	
 	/* This can't be set in the pytype struct because some compilers complain */
 	pyrna_prop_Type.tp_getattro = PyObject_GenericGetAttr; 
 	pyrna_prop_Type.tp_setattro = PyObject_GenericSetAttr;