Add support for set_formspec_prepend in main menu (#8611)

src/gui/guiEngine.cpp

@@ -389,6 +389,15 @@ void GUIEngine::cloudPostProcess()
 	}
 }
 
+/******************************************************************************/
+void GUIEngine::setFormspecPrepend(const std::string &fs)
+{
+	if (m_menu) {
+		m_menu->setFormspecPrepend(fs);
+	}
+}
+
+
 /******************************************************************************/
 void GUIEngine::drawBackground(video::IVideoDriver *driver)
 {
@@ -610,4 +619,3 @@ unsigned int GUIEngine::queueAsync(const std::string &serialized_func,
 {
 	return m_script->queueAsync(serialized_func, serialized_params);
 }
-

src/gui/guiEngine.h

@@ -221,6 +221,8 @@ private:
 	/** script basefolder */
 	std::string              m_scriptdir = "";
 
+	void setFormspecPrepend(const std::string &fs);
+
 	/**
 	 * draw background layer
 	 * @param driver to use for drawing