App: Add class CleanupProcess to allow to free resources when closing the application

src/App/Application.cpp

@@ -84,6 +84,7 @@
 
 #include "Annotation.h"
 #include "Application.h"
+#include "CleanupProcess.h"
 #include "ComplexGeoData.h"
 #include "DocumentObjectFileIncluded.h"
 #include "DocumentObjectGroup.h"
@@ -1699,6 +1700,8 @@ void Application::destruct()
     cleanupUnits();
 #endif
 
+    CleanupProcess::callCleanup();
+
     // not initialized or double destruct!
     assert(_pcSingleton);
     delete _pcSingleton;

src/App/CMakeLists.txt

@@ -271,6 +271,7 @@ SET(FreeCADApp_CPP_SRCS
     ApplicationPy.cpp
     AutoTransaction.cpp
     Branding.cpp
+    CleanupProcess.cpp
     Color.cpp
     ColorModel.cpp
     ComplexGeoData.cpp
@@ -296,6 +297,7 @@ SET(FreeCADApp_HPP_SRCS
     Application.h
     AutoTransaction.h
     Branding.h
+    CleanupProcess.h
     Color.h
     ColorModel.h
     ComplexGeoData.h

src/App/CleanupProcess.cpp

@@ -0,0 +1,47 @@
+// SPDX-License-Identifier: LGPL-2.1-or-later
+
+/***************************************************************************
+ *   Copyright (c) 2024 Werner Mayer <wmayer[at]users.sourceforge.net>     *
+ *                                                                         *
+ *   This file is part of FreeCAD.                                         *
+ *                                                                         *
+ *   FreeCAD is free software: you can redistribute it and/or modify it    *
+ *   under the terms of the GNU Lesser General Public License as           *
+ *   published by the Free Software Foundation, either version 2.1 of the  *
+ *   License, or (at your option) any later version.                       *
+ *                                                                         *
+ *   FreeCAD 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      *
+ *   Lesser General Public License for more details.                       *
+ *                                                                         *
+ *   You should have received a copy of the GNU Lesser General Public      *
+ *   License along with FreeCAD. If not, see                               *
+ *   <https://www.gnu.org/licenses/>.                                      *
+ *                                                                         *
+ **************************************************************************/
+
+#include "PreCompiled.h"
+#include <list>
+
+#include "CleanupProcess.h"
+
+
+using namespace App;
+
+namespace
+{
+    static std::list<std::function<void()>> cleanup_funcs;  // NOLINT
+}
+
+void CleanupProcess::registerCleanup(const std::function<void()>& func)
+{
+    cleanup_funcs.push_back(func);
+}
+
+void CleanupProcess::callCleanup()
+{
+    for (const auto& func : cleanup_funcs) {
+        func();
+    }
+}

src/App/CleanupProcess.h

@@ -0,0 +1,57 @@
+// SPDX-License-Identifier: LGPL-2.1-or-later
+
+/***************************************************************************
+ *   Copyright (c) 2024 Werner Mayer <wmayer[at]users.sourceforge.net>     *
+ *                                                                         *
+ *   This file is part of FreeCAD.                                         *
+ *                                                                         *
+ *   FreeCAD is free software: you can redistribute it and/or modify it    *
+ *   under the terms of the GNU Lesser General Public License as           *
+ *   published by the Free Software Foundation, either version 2.1 of the  *
+ *   License, or (at your option) any later version.                       *
+ *                                                                         *
+ *   FreeCAD 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      *
+ *   Lesser General Public License for more details.                       *
+ *                                                                         *
+ *   You should have received a copy of the GNU Lesser General Public      *
+ *   License along with FreeCAD. If not, see                               *
+ *   <https://www.gnu.org/licenses/>.                                      *
+ *                                                                         *
+ **************************************************************************/
+
+#ifndef APP_CLEANUPPROCESS_H
+#define APP_CLEANUPPROCESS_H
+
+#include <functional>
+#include <FCGlobal.h>
+
+namespace App
+{
+
+/*!
+ * \brief The CleanupProcess class
+ */
+class AppExport CleanupProcess
+{
+public:
+    /*!
+     * \brief registerCleanup
+     * \param func
+     * This adds a callback function that will be called when the application
+     * is about to be shut down.
+     * @note A callback function is only about to free resources. Accessing
+     * stuff of the application like parameter groups should be avoided.
+     */
+    static void registerCleanup(const std::function<void()>& func);
+    /*!
+     * \brief callCleanup
+     * Calls the functions that are registered with \a registerCleanup.
+     */
+    static void callCleanup();
+};
+
+}
+
+#endif  // APP_CLEANUPPROCESS_H