On Friday the initial batch of the monitor rework code landed into Mutter by Jonas. There is this GNOME bug report tracking the low-level monitor rework. In there Jonas explains, "This bug is a place holder for the progress related to moving all low level monitor logic (i.e. CRTC/connector/... things into mutter, hiding it behind a higher level configuration API). While the current API simply provides a getter and a setter for all KMS like state, the new will be placed a layer above, with a set of "monitors" that can be placed in "logical monitors". One will be able to rotate a logical monitor, set a scale, place multiple monitors inside one (i.e. mirroring)."
So far more than five dozen patches related to this initiative have landed with changes to monitor-manager, additions to the D-Bus API, expanded per-backend capabilities, and other API changes. This Mutter work should be settled by the GNOME 3.26 release in September. Stay tuned to Phoronix for more about the GNOME 3.26 features.