b140e7fbeb
In order to go back in monitor configurations, save them to a history. The history is implemented as a max 3 element long queue, where newly set configurations are pushed to the head, and old are popped from the tail. The difference between using a single previous config reference and a queue is that we can now remember the configuration used prior to a D-Bus triggered configuration when the user discarded the configuration. This will later be used to restore a previous configuration when a laptop lid is opened. https://bugzilla.gnome.org/show_bug.cgi?id=777732