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_handlers.c

@@ -0,0 +1,170 @@
+/*
+ * $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 *****
+ */
+
+/** \file blender/python/intern/bpy_app_handlers.c
+ *  \ingroup pythonintern
+ */
+
+#include <Python.h>
+#include "BLI_utildefines.h"
+#include "BLI_callbacks.h"
+
+#include "RNA_types.h"
+#include "RNA_access.h"
+#include "bpy_rna.h"
+#include "bpy_app_handlers.h"
+
+void bpy_app_generic_callback(struct Main *main, struct ID *id, void *arg);
+
+static PyTypeObject BlenderAppCbType;
+
+static PyStructSequence_Field app_cb_info_fields[]= {
+	{(char *)"render_pre", NULL},
+	{(char *)"render_post", NULL},
+    {(char *)"load_pre", NULL},
+	{(char *)"load_post", NULL},
+    {(char *)"save_pre", NULL},
+	{(char *)"save_post", NULL},
+	{NULL}
+};
+
+static PyStructSequence_Desc app_cb_info_desc= {
+	(char *)"bpy.app.handlers",     /* name */
+	(char *)"This module contains callbacks",    /* doc */
+	app_cb_info_fields,    /* fields */
+	(sizeof(app_cb_info_fields)/sizeof(PyStructSequence_Field)) - 1
+};
+
+/*
+#if (BLI_CB_EVT_TOT != ((sizeof(app_cb_info_fields)/sizeof(PyStructSequence_Field))))
+#  error "Callbacks are out of sync"
+#endif
+*/
+
+static PyObject *py_cb_array[BLI_CB_EVT_TOT]= {0};
+
+static PyObject *make_app_cb_info(void)
+{
+	PyObject *app_cb_info;
+	int pos= 0;
+
+	app_cb_info= PyStructSequence_New(&BlenderAppCbType);
+	if (app_cb_info == NULL) {
+		return NULL;
+	}
+
+	for(pos= 0; pos < BLI_CB_EVT_TOT; pos++) {
+		if(app_cb_info_fields[pos].name == NULL) {
+			Py_FatalError("invalid callback slots 1");
+		}
+		PyStructSequence_SET_ITEM(app_cb_info, pos, (py_cb_array[pos]= PyList_New(0)));
+	}
+	if(app_cb_info_fields[pos].name != NULL) {
+		Py_FatalError("invalid callback slots 2");
+	}
+
+	return app_cb_info;
+}
+
+PyObject *BPY_app_handlers_struct(void)
+{
+	PyObject *ret;
+
+	PyStructSequence_InitType(&BlenderAppCbType, &app_cb_info_desc);
+
+	ret= make_app_cb_info();
+
+	/* prevent user from creating new instances */
+	BlenderAppCbType.tp_init= NULL;
+	BlenderAppCbType.tp_new= NULL;
+
+	/* assign the C callbacks */
+	if(ret) {
+		static bCallbackFuncStore funcstore_array[BLI_CB_EVT_TOT]= {{0}};
+		bCallbackFuncStore *funcstore;
+		int pos= 0;
+
+		for(pos= 0; pos < BLI_CB_EVT_TOT; pos++) {
+			funcstore= &funcstore_array[pos];
+			funcstore->func= bpy_app_generic_callback;
+			funcstore->alloc= 0;
+			funcstore->arg= SET_INT_IN_POINTER(pos);
+			BLI_add_cb(funcstore, pos);
+		}
+	}
+
+	return ret;
+}
+
+void BPY_app_handlers_reset(void)
+{
+	int pos= 0;
+
+	for(pos= 0; pos < BLI_CB_EVT_TOT; pos++) {
+		PyList_SetSlice(py_cb_array[pos], 0, PY_SSIZE_T_MAX, NULL);
+	}
+}
+
+/* the actual callback - not necessarily called from py */
+void bpy_app_generic_callback(struct Main *UNUSED(main), struct ID *id, void *arg)
+{
+	PyObject *cb_list= py_cb_array[GET_INT_FROM_POINTER(arg)];
+	Py_ssize_t cb_list_len;
+	if((cb_list_len= PyList_GET_SIZE(cb_list)) > 0) {
+		PyGILState_STATE gilstate= PyGILState_Ensure();
+
+		PyObject* args= PyTuple_New(1); // save python creating each call
+		PyObject* func;
+		PyObject* ret;
+		Py_ssize_t pos;
+
+		/* setup arguments */
+		if(id) {
+			PointerRNA id_ptr;
+			RNA_id_pointer_create(id, &id_ptr);
+			PyTuple_SET_ITEM(args, 0, pyrna_struct_CreatePyObject(&id_ptr));
+		}
+		else {
+			PyTuple_SET_ITEM(args, 0, Py_None);
+			Py_INCREF(Py_None);
+		}
+
+		// Iterate the list and run the callbacks
+		for (pos=0; pos < cb_list_len; pos++) {
+			func= PyList_GET_ITEM(cb_list, pos);
+			ret= PyObject_Call(func, args, NULL);
+			if (ret==NULL) {
+				PyErr_Print();
+				PyErr_Clear();
+			}
+			else {
+				Py_DECREF(ret);
+			}
+		}
+
+		Py_DECREF(args);
+
+		PyGILState_Release(gilstate);
+	}
+}