PyAPI: Store PyInstances for ID's

This means once an ID is created,
it will keep using the same PyObject instance.

This has some advantages:
- Avoids unnecessary re-creation of instances on UI poll / redraw.
- Accessing free'd ID's gives an exception instead of crashing.
  (long standing annoyance!, though this only applies to ID's
   and not yet other data that uses the ID's - vertices for eg).
- Allows using instance comparison (a little faster).

Note that the instances won't be kept between undo.

1 files changed, 12 insertions, 0 deletions

diff --git a/source/blender/makesrna/intern/rna_ID.c b/source/blender/makesrna/intern/rna_ID.c
index 3d162137bd1..1c6172ef667 100644
--- a/source/blender/makesrna/intern/rna_ID.c
+++ b/source/blender/makesrna/intern/rna_ID.c
@@ -394,6 +394,14 @@ static void rna_ID_animation_data_free(ID *id, Main *bmain)
 	DEG_relations_tag_update(bmain);
 }
 
+#ifdef WITH_PYTHON
+void **rna_ID_instance(PointerRNA *ptr)
+{
+	ID *id = (ID *)ptr->data;
+	return &id->py_instance;
+}
+#endif
+
 static void rna_IDPArray_begin(CollectionPropertyIterator *iter, PointerRNA *ptr)
 {
 	IDProperty *prop = (IDProperty *)ptr->data;
@@ -1071,6 +1079,10 @@ static void rna_def_ID(BlenderRNA *brna)
 	                                "Tag the ID to update its display data, "
 	                                "e.g. when calling :class:`bpy.types.Scene.update`");
 	RNA_def_enum_flag(func, "refresh", update_flag_items, 0, "", "Type of updates to perform");
+
+#ifdef WITH_PYTHON
+	RNA_def_struct_register_funcs(srna, NULL, NULL, "rna_ID_instance");
+#endif
 }
 
 static void rna_def_library(BlenderRNA *brna)