If i play a video and toggle fullscreen a frame from the part is quickly showed.
Like if you have a video with red colors in the beginning and green at the end, when you play the red part and toggle fullscreen on and off and then skip to the green part and just when you toggle fullscreen on... a frame from the red part is quickly showned before the toggle is completed.
Like it saves one frame from the last time fullscreen was enabled and displayes it just for a short glimse the next time you toggle fullscreen on.