Qt: glitch when seeking: buffering should be shown only after a given timeout
If the seek is fast, but not too fast, you can see the buffering bar on top of the seek bar for less than few ms. This doesn't occur when the seek is long or when the seek is superfast (and the buffering events are not even processed).
Suggestion: emit that->q_func()->bufferingChanged( new_buffering );
should be delayed with a small timer, like around 500ms. If the player takes less than 500ms to seek, the buffering won't be shown.