I was content with the Nouveau graphics drivers that Deepin uses by default, but yesterday decided to installed Nvidia drivers to see the difference.  I was shocked to find that whenever the mouse-pointer is moved over Dplayer when a video is playing, it almost grinds to a halt, with really jerky video.  No such problem occurs when VLC is playing the same video.

Also, according to the Nvidia configuration, Nvidia drivers are installed and working properly, even though System Settings -> Additional drivers list the installed Nvidia driver as "This driver is activated but not currently in use".  From what I've been able to find on the internet, this "..not currently in use" message is incorrect and a long-standing bug - ie. the Nvidia drivers are working, it's just the message that's wrong.

Is this poor playback problem normal for Dplayer?