There is a weird window on my desktop that is not going away. It happens occasionally, I think it is triggered by mouse action:
This window does not belong to any application. Window icons are blanked out as well:
It appears on all desktops, I have no idea what this is doing. The bar belongs to an application (close, minimize, expand). Below that, the transparent border with shadow occupies the entire screen. It sits on top of every thing else. Mouse actions are working as if it wasn't there, like a window that is non-active, yet sits on top of other windows. I am using Ubuntu 16.04
- how do I trigger this behaviour?
- what is its purpose?
Edit: It disappeared from its own. I think it was because the system went into sleep.