Retain cursor if an unsupported cursor is used

[eXpl0it3r]

Description

While testing #1688, I ran into random crashes and after a while I realized that the switch-case construct didn't cover all cursor types - as documented - which then lead to random crashes when picking the unsupported cursors.

Tasks

• Tested on macOS

How to test this PR?

You can use this example that counts through all the cursor types and will crash with master right now.

#include <iostream>
#include <SFML/Graphics.hpp>

int main()
{
    auto window = sf::RenderWindow{{800, 600, 32}, "SFML Window"};
    window.setFramerateLimit(60);

    auto cursor = sf::Cursor{};

    auto start = sf::Cursor::Arrow;
    auto current = sf::Cursor::Arrow;
    auto end = sf::Cursor::NotAllowed;

    cursor.loadFromSystem(current);
    window.setMouseCursor(cursor);
    std::cout << "New cursor type: " << current << "\n";

    while (window.isOpen())
    {
        for (auto event = sf::Event{}; window.pollEvent(event);)
        {
            if (event.type == sf::Event::Closed)
            {
                window.close();
                return 0;
            }

            if ((event.type == sf::Event::KeyPressed))
            {
                switch (event.key.code)
                {
                    case sf::Keyboard::Escape:
                    {
                        window.close();
                        return 0;
                    }
                    case sf::Keyboard::Up:
                        if(current < end)
                        {
                            current = static_cast<sf::Cursor::Type>(current + 1);
                            cursor.loadFromSystem(current);
                            window.setMouseCursor(cursor);
                            std::cout << "New cursor type: " << current << "\n";
                        }
                        break;
                    case sf::Keyboard::Down:
                        if(current > start)
                        {
                            current = static_cast<sf::Cursor::Type>(current - 1);
                            cursor.loadFromSystem(current);
                            window.setMouseCursor(cursor);
                            std::cout << "New cursor type: " << current << "\n";
                        }
                        break;
                }
            }
        }


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

[eXpl0it3r]

If I understand the memory model of Obj-C correctly, this is not guaranteed to work, as the release at the top of the function, will allow the releasing of the cursor immediately, so one wouldn't be able to retain it here.

[JonnyPtn]

Yeah, I think the correct approach here is to set the member to nil after releasing it, as if it's deallocated we end up with a dangly pointer, have got a PR incoming

[eXpl0it3r]

Superseded by #1736