XFCE: Screens sometimes display hours-old graphics
 

Slackware 14.2, xfce 4.12. I've got two physical screens, and four workspaces. As I work through the day, I'll get a very specific graphical glitch - sometimes the wrong workspace will display spontaneously. If I switch out of the buggy one, into a working one, and back, the workspace will work again (for a while - minutes usually, before it appears again). Also, if I move the mouse, or type, the glitchy part will be replaced with the correct one, as if refreshing that location on the monitor causes XFCE to realize that it's displaying the wrong thing.

This gets progressively worse over the course of a day. When I power off, power on the machine, the buggy workspace is fixed.

Today, I noticed that the erroneous workspace displayed is several hours old (the clock icon is wrong). It's also consistent - it's not a current alternative workspace that is being switched to, but a specific one from some snapshot in the past.

Anyone have suggestions for debugging? Or even a command that would somehow refresh XFCE without me having to relog and close windows?

Sounds like the graphics card is showing stale video-ram for some reason.

Does swapping to a console and back with: ctrl-alt-f1, ctrl-alt-f7 restore the correct screen image?

You might also want to see whether it helps if you turn off compositing in the xfce window manager settings (I think that's where the option is, but its been a while since I've used xfce) and see whether that helps.

Things like this are almost always a video driver bug. Other than playing with the various video options to see if you can avoid the issue, or updating drivers/kernel in the hope that it goes away there's not much one can do in this situation.