own patch [#27752] Python Callback (Scriptlink functionality)

Python:
 * adds bpy.app.handlers which contains lists, each for an event type:
   render_pre, render_post, load_pre, load_post, save_pre, save_post
 * each list item needs to be a callable object which takes 1 argument (the ID).
 * callbacks are cleared on file load.

Example:
 def MyFunc(scene): print("Callback:", data)
 bpy.app.handlers.render_post.append(MyFunc)

C:
 * This patch adds a generic C callback api which is currently only used by python.
 * Unlike python callbacks these are not cleared on file load.

source/blender/python/intern/bpy_app.c

@@ -30,6 +30,7 @@
 #include <Python.h>
 
 #include "bpy_app.h"
+#include "bpy_app_handlers.h"
 #include "bpy_driver.h"
 
 #include "BLI_path_util.h"
@@ -74,6 +75,9 @@ static PyStructSequence_Field app_info_fields[]= {
 	{(char *)"build_cxxflags", (char *)"C++ compiler flags"},
 	{(char *)"build_linkflags", (char *)"Binary linking flags"},
 	{(char *)"build_system", (char *)"Build system used"},
+
+	/* submodules */
+	{(char *)"handlers", (char *)"Application handler callbacks"},
 	{NULL}
 };
 
@@ -140,6 +144,8 @@ static PyObject *make_app_info(void)
 	SetStrItem("Unknown");
 #endif
 
+	SetObjItem(BPY_app_handlers_struct());
+
 #undef SetIntItem
 #undef SetStrItem
 #undef SetObjItem