Comment 28 for bug 1307545

I did the same tests for trusty: The behavior is basically the same, only the xfce4-power-manager/logind-handle-lid-switch xfconf-key is handled oppositional (probably due to http://git.xfce.org/xfce/xfce4-power-manager/commit/?id=f62e82256cb2a45b4f044b7d603017952f7dd63e).

Let's try to summarize all findings:
trusty case 1)
    xfce4-power-manager/logind-handle-lid-switch = true
    -> blank-screen bug with light-locker
    -> debug trace: xfpm_manager_inhibit_sleep_systemd(): [...] handle-lid-switch
    a) lid close action: nothing -> result: nothing
    b) lid close action: lock -> result: suspend + lock + blank bug

trusty case 2)
    xfce4-power-manager/logind-handle-lid-switch = false
    -> light-locker works
    -> debug trace: xfpm_manager_inhibit_sleep_systemd(): [...]
    a) lid close action: nothing -> result: suspend + lock
    b) lid close action: lock -> result: suspend + lock

utopic case 1)
    xfce4-power-manager/logind-handle-lid-switch = true
    -> light-locker works
    -> debug trace: xfpm_manager_inhibit_sleep_systemd(): [...]
    a) lid close action: nothing -> result: suspend + lock
    b) lid close action: lock -> result: suspend + lock

utopic case 2)
    xfce4-power-manager/logind-handle-lid-switch = false
    -> blank-screen bug with light-locker
    -> debug trace: xfpm_manager_inhibit_sleep_systemd(): [...] handle-lid-switch
    a) lid close action: nothing -> result: nothing
    b) lid close action: lock -> result: suspend + lock + blank bug