Window Manager

Window Manager contains a sf::RenderWindow object on which we will be drawing our rendered images.
The object which is rendered is actually a sf::Sprite, which based on a sf::Texture, containing a sf::Image.

image to window pipeline

There can be a mismatch between the sprite and the window size (not the aspect ratios though because both determine the other factor of their dimension based on the aspect ratio).
We can scale the sprite up or down to fit in the window perfectly.

Sprite being scaled to the window

To find this scalar value, we are dividing either dimension of the window by the sprite.

float scalar = float(u_width) / img->getSize().x;

Rest of the display() function is pretty simple.

void Window_manager::display(const sf::Image* const img) {

    sf::Texture T_img;
    T_img.loadFromImage(*img);

    sf::Sprite S_img(T_img);

    float scalar = float(u_width) / img->getSize().x;
    S_img.scale(sf::Vector2f(scalar, scalar));

    // debug
    std::cout << "Img: " << img->getSize().x << "x" << img->getSize().y << std::endl;
    std::cout << "Window: " << u_width << "x" << u_height << std::endl;

    while(R_window.isOpen()) {

        sf::Event event;
        while (R_window.pollEvent(event)) {
            if(event.type == sf::Event::Closed)
                R_window.close();
        }

        R_window.clear(clr_bg_color);
        R_window.draw(S_img);
        R_window.display();
    }
}