You know that you can move the "main window" (= the controls) around with left mousebutton depressed.
If you have selected the feature ""Snap play window ...." and you play a movie in a window (as opposed to full screen) and then move the controls just underneath the movie-window, the controls will "stick" (as if glued) to the movie-window after which, if you move the controls, the movie window remains "glued" to the controls (and will also move as one whole together with the controls).
