As seen in the screenshot, the area will hold artefacts of what ever is put over it. I cant access x+- buttons.
In this instance, I had been running google chrome and browsing reddit. I was watching fullscreen video before and the shading of this rectangle were present though video was being rendered correctly in it. In 3D games it is a black rectangle, no rendering in it.
I am running nvidia g210 card with the experimental 310 drivers.