Thanks! Worked like a charm with accumulating the time.
But now I have to solve a way to make the alpha-value change for the image based on the time given. I tried with Sprite::SetColor(); before, it didn't really do anything....
I had like this to try it but the display didn't change:
sf::Sprite sprite;
sf::Color color;
for(int i = 255; i >= 0; i--) {
color.a = i;
sprite.SetColor(color);
// And then I drew it to the display
}
Ow yeah, sorry, It's off-topic. But my solution to this was to use Image(Color(0, 0, 0, 35)) instead. But that ends up with that I can't change the color.
** EDIT **
Never mind, I fixed it