python support for defining region drawing callbacks, while not directly related to operators, this means python can now make operators that draw in the 3D viewport interactively.

nicer then 2.4x space handelers because you can register draw handelers to draw pre/post 3d space or in pixel space.

source/blender/python/intern/bpy_rna_callback.h

@@ -0,0 +1,29 @@
+/**
+ * $Id:
+ *
+ * ***** BEGIN GPL LICENSE BLOCK *****
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ * Contributor(s): Campbell Barton
+ *
+ * ***** END GPL LICENSE BLOCK *****
+ */
+
+struct BPy_StructRNA;
+struct PyObject;
+
+struct PyObject *pyrna_callback_add(struct BPy_StructRNA *self, struct PyObject *args);
+struct PyObject *pyrna_callback_remove(struct BPy_StructRNA *self, struct PyObject *args);