Untitled

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

sf::Color changeColor(sf::Color color, int &state, int speed = 10) {
    int red = color.r;
    int green = color.g;
    int blue = color.b;
    //std::cout << state << ' ' << red << ' ' << green << ' ' << blue << std::endl;
    switch(state) {
        case 0: {
            green += speed;
            if (green >= 255) {
                green = 255;
                state++;
            }
            break;
        }
        case 1: {
            red -= speed;
            if (red <= 0) {
                red = 0;
                state++;
            }
            break;
        }
        case 2: {
            blue += speed;
            if (blue >= 255) {
                blue = 255;
                state++;
            }
            break;
        }
        case 3: {
            green -= speed;
            if (green <= 0) {
                green = 0;
                state++;
            }
            break;
        }
        case 4: {
            red += speed;
            if (red >= 255) {
                red = 255;
                state++;
            }
            break;
        }
        case 5: {
            blue -= speed;
            if (blue <= 0) {
                blue = 0;
                state++;
            }
            break;
        }
        default: {
            state = 0;
        }

    }

    sf::Color newColor(red, green, blue);
    return newColor;
}

int main()
{
    int WINDOW_WIDTH = 800;
    int WINDOW_HEIGHT = 600;
    int RADIUS = 100;

    int red = 255;
    int green = 0;
    int blue = 0;
    int state = 0;
    int bgState = 3;

    sf::RenderWindow window(sf::VideoMode(WINDOW_WIDTH, WINDOW_HEIGHT), "AAAA");
    
    sf::Color circleColor(255, 0, 0);
    sf::Color bgColor(0, 255, 255);

    sf::CircleShape circle0(RADIUS);
    circle0.setFillColor(circleColor);
    circle0.setPosition(sf::Vector2f(WINDOW_WIDTH / 2 - RADIUS, WINDOW_HEIGHT / 2- RADIUS));
    
    window.setFramerateLimit(50);
    while (window.isOpen())
    {
        // check all the window's events that were triggered since the last iteration of the loop
        sf::Event event;
        while (window.pollEvent(event))
        {
            // "close requested" event: we close the window
            if (event.type == sf::Event::Closed)
                window.close();
        }

        circleColor = changeColor(circleColor, state);
        circle0.setFillColor(circleColor);

        bgColor = changeColor(bgColor, bgState, 25);

        // clear the window with black color
        window.clear(bgColor);
        window.draw(circle0);
        window.display();
    }
    return 0;
}