Fullscreen leaves zombie window open on macOS

[JonnyPtn]

Subject of the issue

on macOS if you make a window fullscreen then go back to windowed, there will be a zombie window left open with nothing rendered to it

Your environment

• macOS Mojave
• Latest master (have reproduced as far back as 2.3)
• Xcode 10.2

Steps to reproduce

Simply make the window fullscreen then windowed again

#include <SFML/Graphics.hpp>

int main()
{
    sf::RenderWindow window(sf::VideoMode(1280, 720), "Minimal, complete and verifiable example");
    window.setFramerateLimit(60);

    while (window.isOpen())
    {
        sf::Event event;
        while (window.pollEvent(event))
        {
            if (event.type == sf::Event::Closed)
                window.close();
            if (event.type == sf::Event::KeyPressed)
            {
                static bool fullscreen = true;
                window.create(sf::VideoMode(1280,720), "Non-zombie window", fullscreen ? sf::Style::Fullscreen : sf::Style::Default);
                fullscreen = !fullscreen;
            }
        }

        window.clear();
        window.display();
    }
}

Expected behavior

There should only ever be one window

Actual behavior

After returning from fullscreen to windowed, there is a zombie window left behind

Notes

The zombie window seems to have the size/title of the window before going fullscreen (i.e. in the example code above it will have the original title from when it was created, not the new one)

This doesn't seem to be cumulative, i.e. if I continue to toggle full screen it won't create further windows

I tested just recreating the window without going fullscreen, and there is no issue, so it is somehow related to going fullscreen

[chusloj]

@JonnyPtn Looking through old posts to SFML forums voicing the same concerns as you, sf::Style::Fullscreen doesn't seem to be the way to directly change a window to fullscreen based on OSX's definition of fullscreen anymore (changing to a different window separate from the desktop). Now, the best approximation is to use sf::VideoMode::getFullscreenModes(). I haven't looked into this issue too extensively, but from what I know this is because of how OSX is set up and how interfacing with OS capabilities such as fullscreen is much easier with DirectX on Windows.

As for your code, a simple work-around would be to use sf::VideoMode::getFulscreenModes() to use the most appropriate video mode provided by that function:

#include <SFML/Graphics.hpp>

int main()
{
    sf::RenderWindow window(sf::VideoMode(1280, 720), "Minimal, complete and verifiable example");
    window.setFramerateLimit(60);
    
    static bool fullscreen = true;

    while (window.isOpen())
    {
        sf::Event event;
        while (window.pollEvent(event))
        {
            if (event.type == sf::Event::Closed)
                window.close();
            if (event.type == sf::Event::KeyPressed)
            {
                window.create(fullscreen ? sf::VideoMode::getFullscreenModes()[0] : sf::VideoMode(1280, 720), "Non-zombie window");
                fullscreen = !fullscreen;
            }
        }

        window.clear();
        window.display();
    }
}

---

Also:

Your Environment

OSX Big Sur
SFML 2.5

When running your code, I receive the following message:

The requested video mode is not available, switching to a valid mode

[eXpl0it3r]

@JonnyPtn / @chusloj could you give #1814 a try?
I'm unable to reproduce the mentioned issue on Big Sur

[eXpl0it3r]

If this wasn't fixed by the mentioned PR, feel free to reopen the issue. As said, I can't reproduce it.