QMovie+QLabel plays GIFs too slowly in comparison to playing in browsers or other apps

Consider canonical use of QLabel with QMovie:

    QLabel label;
    QMovie movie("some-animated.gif");
    label.setMovie(&movie);
    movie.start();
    label.show();

It plays the GIF file but the animation is a bit slower than when the same GIF is played inside a browser or default Windows image viewer. It seems to be a bug in QMovie.

After a quick code inspection it seems that the scheduled delays between individual frames do not correctly account for time which the execution spends on displaying the frame or other overhead. To correctly display the playback, the delays between frames should be adjusted such that the cumulative frame delays should be equal to some real elapsed timer measurements.