Threads are Freezing my Window

[Kookies]

This is a function I'm using to spawn enemies, and I'm using sf::sleep to add a delay.

void spawn()
{
        sleep(seconds(2));
        if (count1 % 20 && count1 != 0)
        {
                enemies.push_back(Enemy(true, 500.0, 25.0, 50.0, 50.0, Color::Red));
        }
        else
        {
                enemies.push_back(Enemy(false, 100.0, 15.0, 50.0, 50.0, Color::White));
        }
        count1++;
}

I launch the thread from here:

Thread spawning(&spawn);
        spawning.launch();

But for some reason, the sleep in the thread affects my main loop and causes it to update every two seconds.

[Laurent]

If the Thread object is created within the main loop, it is destroyed in it as well, and the destructor of class Thread blocks until the thread's function has returned.

[Kookies]

So where should I create it?

[Laurent]

Outside the game loop. But then you'll have to change the logic of the spawn() function.

But... it makes no sense to run a thread just to make it wait. To do nothing during 2 seconds, you definitely don't need a thread. Just use a sf::Timer and call the spawn() function whenever it reaches 2 seconds.