Extend branding options (#18804)

src/Main/MainGui.cpp

@@ -173,8 +173,7 @@ int main(int argc, char** argv)
     App::Application::Config()["SplashWarningColor"] = "#CA333B";
     App::Application::Config()["SplashInfoColor"] = "#000000";
     App::Application::Config()["SplashInfoPosition"] = "6,75";
-
-    QGuiApplication::setDesktopFileName(QStringLiteral("org.freecad.FreeCAD"));
+    App::Application::Config()["DesktopFileName"] = "org.freecad.FreeCAD";
 
     try {
         // Init phase ===========================================================
@@ -189,6 +188,10 @@ int main(int argc, char** argv)
 #else
         App::Application::init(argc, argv);
 #endif
+        // to set window icon on wayland, the desktop file has to be available to the compositor
+        QGuiApplication::setDesktopFileName(
+            QString::fromLatin1(App::Application::Config()["DesktopFileName"].c_str()));
+
 #if defined(_MSC_VER)
         // create a dump file when the application crashes
         std::string dmpfile = App::Application::getUserAppDataDir();