Backdrop requires _NET_WM_STATE_FOCUSED hint on X11
Submitted by John Lindgren
None of the ":backdrop" CSS selectors get used for unfocused/inactive windows if one uses a window manager such as xfwm4 or OpenBox instead of mutter. This bug, combined with the introduction of client-side decorations, means that the title bars for inactive windows still look exactly the same as the active window.
This is a major usability problem, since there is no longer any way to tell which window will respond if one starts typing.