void MyWindow::MessageReceived(BMessage* message) { switch (message->what) { case 'FILE_OPEN': { // Handle the "Open File" menu item selection break; } case B_COPY: { // Handle the "Copy" menu item selection break; } // Add more cases for other menu items here } }In this example, the MessageReceived() function is called whenever a message is received by the window. The function uses a switch statement to determine which BMenuItem Message was sent, based on the message's "what" code. The code then handles the menu item selection appropriately. The BMenuItem Message is part of the BeOS/Haiku operating system's application framework library.