Cocos2d-x 3.2. When user clicks "close" button or presses Cmd+Q, this code snippet shows a message asking user to confirm the game exit. Particular this code is used on mac desktop versions, but I guess the glfwSetWindowCloseCallback can be used on other desktop platforms too. Things can be changed on later versions of cocos2d-x.

AppDelegate.cpp

/*

Cocos2d-x 3.2

When user clicks "close" button or presses Cmd+Q, this code snippet shows a message asking user to confirm the game exit.
Particular this code is used on mac desktop versions, but I guess the glfwSetWindowCloseCallback can be used on other desktop platforms too.
Things can be changed on later versions of cocos2d-x.

*/

bool AppDelegate::applicationDidFinishLaunching() {
      // initialize director
    auto director = Director::getInstance();
    auto glview = director->getOpenGLView();
    //...
    
#if CC_TARGET_PLATFORM == CC_PLATFORM_MAC
    
    //auto window = (dynamic_cast<GLViewImpl *>(glview))->getWindow(); // dirty variant for cocos2d-x 3.4
    auto window = glView->getWindow();
    glfwSetWindowCloseCallback(window, [](GLFWwindow* window){
        
        auto alert = [[NSAlert alloc] init];
        [alert addButtonWithTitle:@"Yes"];
        [alert addButtonWithTitle:@"No"];
        [alert setMessageText:@"Exit the game?"];
        [alert setInformativeText:@"Do you really want to exit the game?"];
        [alert setAlertStyle:NSWarningAlertStyle];
        
        if ([alert runModal] != NSAlertFirstButtonReturn) {
            glfwSetWindowShouldClose(window, GL_FALSE);
        }
    });
#endif

    //...
    // run
    director->runWithScene(scene);

    return true;
}