Problem description:

when a user has a dual screen layout if the primary screen has no windows open but the secondary screen has, both the shutdown and unlock screen window appear in the second screen.

If the second screen is closed (common scenario - a TV) in both these cases the primary screen becomes dark and unusable. So the user in order to continue using the computer has to open the second screen and take the appropriate action.

Also is the user is unaware that the action prompt is in the second screen he may just cold restart his computer and think that GNOME crashed.

Reproduce:

Close all windows in your primary screen and leave one open in the secondary. Then leave the screen to go to sleep or try to bring up the shutdown dialog.

Solution:

Make the unlock and shutdown windows bind to the primary screen or make them movable Alt+F7 shortcut can be used in order to bring them over.