The black line is the drop shadow from the Unity Panel.
This bug is easily reproduced when right-clicking on a menu in a full-screen application. the context menu does not have to be the whole height of the screen, it just have its top drawn higher on the screen than the bottom of the Unity Panel.
The black line is the drop shadow from the Unity Panel.
This bug is easily reproduced when right-clicking on a menu in a full-screen application. the context menu does not have to be the whole height of the screen, it just have its top drawn higher on the screen than the bottom of the Unity Panel.